Connecting Solar to the Grid is Harder Than You Think
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- Äas pĆidĂĄn 15. 04. 2024
- A lot of the interesting challenges with renewables are happening behind the scenes.
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Weâre in the growing pains stage right now, working out the bugs that these new types of energy generation create, but if you pay attention to whatâs happening in the industry, itâs mostly good news. A lot of people from all sides of the industry are working really hard on these engineering challenges so that weâll soon come out with a more reliable, sustainable, and resilient grid on the other end.
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why title the video this way? why not reflect a more bold, "we can do it" mentality in the video title? idk, it just feels like sowing doubt instead of portraying the challenges we face in a practical, realistic way.
Oh snap ... I've never thought of distributed generation solar increasing rocof. It's a lose lose situation for grid tied solar. The next Gen nat gas turbines (GE and Siemens) seem really cool, and a good mitigation for this issue
Hey! Solar interconnections are what I do for a living! Always great videos on the power grid. You reflect the info very accurately!
I wish you had a media mail shipping option for your book. Iâm only a few hours away in DFW, and the cheapest shipping option right now is over $12.
O-scopes everywhere are jealous of the hard hat you provide to protect yours.
In early 2025, the Baltic states in North-Eastern Europe are set to disconnect their grid from the Russian power grid, and connect up with European power grid instead. This might sound like it's simply some sort of resynchronization task, however the reality is much more complicated, requiring the Baltic states to build out a fair bit of extra infrastructure and take on the task of maintaining grid frequency where before, Russia would have been doing so. This might make for an interesting video.
They better hurry up
I live at a junction between two power companies' service areas, and they have the ability, in an emergency, to connect one to the other, but there is the catch that there has to be a transformer, there, because the operating voltages don't match - and there's no synchronization, and there's a meter to measure the power that crosses junction.
Should've been done years ago tbh
@@kenbrown2808 Brazil has the same issue, along with Japan, and built HVDC systems that are both frequency changing, and bidirectional, so that power can flow either way, along with changing the frequency of that power to suit the local grids as well.
â@@personzorz why? đ
I work as a lineman in northern EU, and an interesting effect we've noticed with solar is that sometimes the inverters won't disconnect from the grid during a power outage. We've ran into this when doing service work on pad-mount transformers, when we open the switch to de-energize the transformer supplying a neighborhood (in our case an average of 150 households/transformer) with a lot of solar, on rare occasions it will remain energized, backfed from the households solar production. This happens because in the right conditions the solar panels will produce the same amount of power as the households consume, so there's no current flow through the transformer. So, when we open the switch - as far as the inverters are concerned nothing changes, so they remain on and backfeed the grid. It usually doesn't last very long since when the balance shifts they'll disconnect but you could still get a nasty surprise if you're not careful.
Ah now this is technically illegal, all devices that back feed to the grid must have anti-islanding devices fitted. Well in France and the UK. When I worked for RTe (french transmission operator) there was talk of taking some people to court etc about this issue. The same goes for houses fitted with a gen, it must separate from the grid when the grid goes down.
Woah, that's an interesting fault. I've never heard / thought about this exact configuration, but yeah, they would stay on as long as that configuration remains stable...
@@matthewmaxwell-burton4549 Yeah we have the same here but the issue is them not being able to tell if the grid went down, as long as the flow stays balanced at least
>lineman
Lying American. We do not have lineman, as we do not install our lines above ground like savages.
I learned today that new installation of a grid-interactive inverter must: have ability to throttle the power and also be able to shutdown the Inverter power and control the scheduling of when the power is used/delivered and the quantity on command from the utility. I imagine the direct command & control will tend to resolve this accidental self-supporting meta-stable microgrid situation.
I worked at a factory that ran 24/7 and consumed megawatts of power. We were looking for backup power solutions. The problem was the few seconds backup generators take to start. There were "batteries" that consisted of carbon fiber flywheels in a vacuum spinning at 500,000 RPM. They could deliver 100% output (multiple megawatts) within 10 cycles, and for up to 10 seconds - enough time to start a generator kept in warm stand-by. Perhaps technology like this is what we need to stabilize the grid.
The UK is spending billions in building flywheels to pick up the janky electricity from solar and wind and add a modicum of control to it.
Or we could just use nuclear đ€·ââïž
There are a lot of companies looking into grid scale flywheel energy storage. It's a valuable option and one I could stand to learn more about. But I think the biggest problem with any **grid scale** energy storage solution is cost. I'd love to see a practical engineering deep dive into grid scale storage and fly wheels.
I understand that flywheels are already used by various utilities for this sort of purpose, providing inertia at a moment's notice. Wikipedia at least says that there are grid-connected flywheels in New York, Germany, and Ontario. Would be nice to see more about how these sort of utilities work!
Yeah, I am hardly an expert, I just remembered the Capex research I did for that project a decade ago. The thing with flywheels is stored energy goes up linearly with mass, but squared with rotational speed. So a 1 pound carbon fiber disk spinning at half a million RPM can potentially store more energy than a multi ton wheel spinning standard generator speeds like 1800 RPM.
Chances are people in the industry know much more about the details than I do, but occasionally good ideas slip through the cracks.
Flywheel storage solutions are interesting. I work on mission critical power systems, and most of the time a battery based UPS is used. For certain loads, especially at a factory where there are huge motors flywheel based solutions can be better
"Everything is a smoke machine if you operate it wrong enough."
I'm an engineer for a utility-scale solar developer and this is a fantastic summary of the challenges we face and design for.
My issue with solar: all we are doing is tearing down forests to build them⊠lets destroy more habitat so we can build solar power, yay!⊠looking at you australia
Tree clearing is expensive, slow, and complex. Itâs a last resort and doesnât represent the typical project (at least here in the US).
Just out of curiosity do batteries help "clean up" the power from solar? I've heard one issue is the power they put out can sometimes be "dirty" and cause issues. I'm thinking of solar at home but I've heard those systems can sometimes cause issues for peoples neighbors. I'm not sure with the inverters that people put in along with a battery backup can sorta smooth everything out so the power being output is clean. From this video it seems like the inverter might actually be the issue. As a side note would flywheel storage being added to larger renewable systems help with this or is that still needing to go through the inverter? The flywheel system might not be actually used for storage but it could just smooth out the output? Seems like wind might not have the same issue though since the turbine itself almost acts like a flywheel.
@@pin65371 Batteries basically use the same inverters as PV. Either literally the same inverters (if DC coupled) or models that were likely derived from PV inverters (if AC coupled). Either way, I disagree that the output from PV facilities is "dirty". As the video mentions, it can output a perfect 60hz using electronics alone. They can also be called upon to inject or absorb VARs to help strengthen the grid. The real issue is that renewables are intermittent which can make load balancing challenging for grid operators. Batteries definitely help with this, as they can help firm or smooth the output of the plant to avoid fluctuations. I've never heard of flywheels being used alongside PV, but some companies are looking at alternatives to batteries, such as hydrogen electrolyzers to "store" energy as hydrogen.
@goldenhate6649 âThat is far from what we commonly do in the US at least for my EPC. Additionally when there are protected areas or wildlife we often have to have a dedicated biologist on site. SWPP is also huge to ensure runoff does not cause problems for thr surrounding area.
the final project for one of my classes was to design a solar installation for a factory, we had to calculate power usage from power bills, design a capacitor bank for power factor correction, find out how many panels, in what arrangement, and at what angle and distance from each other they had to be installed, pick an MPPT and inverter, and design a battery bank.
i couldn't finish in time, it was a nightmare, but at least it taught me that people way underestimate how much work goes into installing solar
Anyone who has tried to design their own solar panels and inverter setup for their home knows that its a complex process that has you reading datasheets for the panels and the manuals for the inverter!
â@@tlangdon12I ordered a kit online in 2017, 20 Astro Energy 310W modules, DC optimizers, and a Solaredge SE6000A-US-U inverter, Iron Ridge XR100 racking, and connected it all. I got a Bosh D-Tect 150 to help me hit the rafters through the roof with the 5 inch stainless lag screws holding the flash feet. Making 4.47kw right now. It's all tested by UL. There was a little paperwork to get permits, and pass inspection. Your backfeed breaker has to go in the bottom because the solar adds to the amount of power you can pull out of the pannel, and you don't want it to add that to grid power and exceed the capacity of the bus bar. If you put it in a subpannel, same thing, and it needs to be in the bottom of the main pannel. It's not a beginner project, but totally doable if you are motivated.
Complexity varies. I just pluged microinverter to grid and screwd panels to frame and done. Nothing complex on simple house system. Not a single thought about power factor correction. Its how complex do you want or need to make it.
Wait, what? Was this a school or uni project? Because this is definitely too much work for the former...
@@TheMightyZwom Almost certainly a university project, you would be happy to learn about solar power at all at some schools.
Connecting it to the grid is easy.
Making it not explode when it does is the problem.
I think making anything not explode when it explodes is problematic.
Or being fried.
Anything renewable is a PITA to connect to the grid outside hydro because of the insane variability of the power output.
Or in other words:
"Everything can be connected to the grid at least once"
You can technically connect anything to the grid for a few milliseconds.
Iâm so happy the idea that âmagic smokeâ is what makes electronics work, is so ubiquitous.
Magic smoke isn't what makes it work, it's what happens when it doesn't work. Something underneath blows up, "guess it was magic."
@@nathanpeterson5609Electronics work because magic smoke is added to some rocks in the factory. When the magic smoke gets out, the electronics stop working.
â@@nathanpeterson5609Nah, if you actually know how electronics work, especially modern small ones, you'd be blown away how much of a miracle that things work at all.
Beyond walking in a knifes edge, you're walking on an edge literally hundred if atoms thin.
So many insignificant things can make it all go haywire, our maths are amazing
I'm a retired EE, and the sight of magic smoke got me into it decades ago. Still release some, in my hobby time, now.
Don't let the smoke out!
The Odessa event was (edit: contributed to) by a particular phenomenon called Cessation, which is not an unexpected behavior of nebulous algorithms. Designers put it in intentionally to protect the hardware without violating the grid rules at the time, which say when a disturbance happens, you must keep your output breaker closed to help the system (low voltage ride-through.) But there were no requirements that your unit continue to output (real) power. Solar units therefore would drop their power output to nearly 0 to protect the hardware from harmonics generated by the panels trying to push power into a disturbed grid. There was also an automatic timeout on this cessation where the panel would not ramp up until the disturbance had passed for some time. This was often baked into the hardware and many farm owners didn't even know the behavior existed.
6:30 this explanation would have benefitted a lot from showing a raw PWM signal, then showing a capacitor low-pass filter wipe across it to smooth it out
This reads like a case of a disconnect between the objectives of the people writing the grid connection rules and the people implementing them?
@@rowanjones3476 eh, it was more a case of hardware designers not being aware of WHY particular requirements exist. They met the letter of the law while violating the spirit of it.
@@marshallc6215 As a hardware designer, this kind of thing drives me nuts. We're always having to go back to product managers and ask WHY they want things on our boards. But I understand not everyone feels like they have that ability, or perhaps are jaded after being told "just build it to the spec and quit bugging me!"
The key thing here is that the inverter has to push real power. If all you needed was a "sine wave" then you could produce one with a DAC and a simple capacitor-based filter. The problem is that a DAC is a resistive device and can't actually push any real power (it would melt into a pile of sludge in milliseconds if it tried), so the sine wave is useless for inverter purposes.
For the same reason, using e.g. a transistor type of circuit to amplify such a loe-poert sine wave won't work because the transistor is a diode-like device and the voltage difference is dissipated as heat. The transistor can't actually amplify a DC input and produce a ton of power on the output that looks like a sine wave either. It would instantly melt.
Same thing for a PWM signal. The PWM signal itself can drive FET gates, and the FETs are what switch the real power from the DC or rectified source. But a capacitor on that output won't produce a sine wave, it will just melt (more or less instantly) because it is essentially short-circuiting the FETs. Again its an issue of the power flow. A capacitor that isn't doing any work won't melt, but in this case the capacitor is doing a massive amount of work and the FETs are basically pushing incredible currents into and out of it because it kinda looks like a short to the FETs (hundreds of amps.... 1000VA for each real 1W of power).
So the only way to really produce a real sine wave with the desired amount of power is with magnetic components... inductors and transformers. The PWM can drive the FETs, the FETs run the real power through an inductor to convert the medium-frequency PWM signal into a voltage, and that runs through a transformer to produce the desired output AC voltage. The inductor and the transformer both filter what is essentially a huge HF mess of square and sawtooth waves into something close to a pure sine wave and a single capacitor on the output gets rid of remaining HF artifacts.
-Matt
@@junkerzn7312 Are they just like variable output buck convertors then?
I am a test engineer for high power frequency converters and be build our "VSD"'s not only for grid injectors like wind turbines (exactly like in the video), but also for applications where you would not suspect them. Is is for example sometimes easier to let a water turbine run at a non-constant speed and run all that power through a VSD, which constantly synchronizes to the grid, than try to maintain a constant speed with the turbine. The are also used as a soft starter for these very big motors and sometimes, they can even reverse the flow of energy to pump water back up into a lake for example. We are talking from 500kW to 100MW here.
Great video!
This was interesting. I was a nuclear trained submarine officer and served on an improved LA class sub for 3 years. Going through the nuclear training pipeline, you learn a lot of this stuff. In fact, the crude demonstration in the video of a drill turning an AC generator is something we had two: the "ships service motor generator" (SSMG -- everything needs an abbreviation), which were approximately the size of a midsize vehicle. They converted power back and forth from the AC to DC bus, where the DC bus was powered by **VERY LARGE** lead-acid batteries in the bottom of the sub. Very interesting stuff. The control room ("Maneuvering") had the panel for managing the electrical buses, and the operators manually would synchronize various bus frequencies ("slow, in the fast direction" for the incoming bus, and throw the switch for the breaker at approximately the 10/11 o'clock position to shut the breaker at 12). Depended on the operator -- not automatic. I believe newer subs use a solid state inverter system and not the SSMGs now. Anyone really interested in hands on, great education in this sort of stuff, either as enlisted or officer, join the Navy and go to Nuclear Power School and get to a ship. I wasn't an engineer in college, but you more or less become one working the engine room of a nuclear submarine.
That's really cool, thanks for sharing!
i get seasick :/
I taught NNPS when it was in Orlando. After that, I designed and built the electric plant trainers based on the S5W (Bluefish, et. al.) plant used in NFAS back in the late 80's. Modeling the SSMG was one of the more challenging things I've ever done as an engineer. I used capacitor charging curves to emulate the starting surges that occur when the resistor sequence is pulled as the rotor speed comes up. The ships battery was a 3 D-Cell actual battery pack, that was literally charged and discharged from the op amps of the model. Overall that project was the best engineering task I ever undertook, and got a Westinghouse Signature award for the work. But they wouldn't promote me ahead of "years in grade" ( just like the military!) so I quit. And BTW both Bettis and KAPL were absolutely bursting with "engineers" that couldn't design a resistor divider.....but they wrote beautiful reports to be sent along to Navsea-08 to impress them with how much was being accomplished. đź
@@jeffferguson4632 Oh, that's neat! I was one of the last classes through Orlando NNPS in 1997. Your comment about the resistors in the SSMG startup is memorable. The DC startup on those machines caused the biggest transients on the electrical panel -- always something to watch when that happened. Plus, I recall a teachable moment about good engineering practice when we restarted an SSMG (following routine maintenance) while in an unusual electrical lineup. That's quite a thing to have been involved in the engineering of. They worked well from my perspective.
I was involved in the early design of the Moored Training Ship setup in Charleston....when the simulator was located in the trailer. You wouldn't believe the arguments we had about putting a "head" in the trailer. If you went to MTS Charleston and bitched everytime you had to go back to the building to take a leak....well...I tried.
power electronics engineer here: Good video. I do have a few additional thoughts, though:
1. You said a home PV system cannot provide power during a blackout. At the end of the video you talk about grid forming inverters being able to support e.g. a backstart or island grids. The good news is: Those systems do exist for home PV applications. They are usually more expensive, but can supply power during a blackout. (There are different types being able to do different things exactly - I'm not going into details.)
2. One problem not addressed in the video (or maybe I missed it?) is the fact that mechanical generators can provide high short circuit currents that will trip breakers (not the ones in your house, the large ones being part of the power grid). Since fault currents have always been high in the past (something like 10x the maximum normal current), circuit breakers were designed to not only handle them, but also require them for fault detection. But: Inverters don't deliver such high surge currents, even if they stay active during the fault event. They generally limit their own output current. While a mechanical generator can survive a current surge into the grid, a - for example - PV inverter couldn't (hence the current limiting). This is different from fault ride through (FRT) and is an additional problem. IMHO the solution to this is more modern protective equipment that will detect faults differently and trip not only during high current surges.
3. What you're showing at 6:06 is NOT pulse width modulation (PWM)! This is (kind of) what a multi-level inverter's output voltage could look like. A PWM still only has two voltages: plus and minus dc voltage (in the case of a two level inverter, that is), but switches between them rapidly, so that the resulting voltage resembles a sine-wave after filtering.
Grid operators usually don't want solar supplying power during a blackout. At best it complicates the process of reconnecting power, and at worst it makes cutting power for servicing very difficult.
The problem with demonstrating PWM is that the fundamental frequency of the modulator is usually off into the hundreds of kilohertz, but the frequency of the final output is in the tens of hertz. This makes is it impossible to show both parts at the same time, The levels of zoom are just too far apart. I think showing that off would have made the video too complicated for its intended audience. Also, he didn't say that what he was showing was PWM anyway. He said that it was multilevel output, although I'll grant you that describing PWM as being just like multilevel but with more switching doesn't really make any sense. And, the way that he describes it sounds a lot more like pulse density modulation, which is quite rare, as far as I can tell, but, in my opinion is easier to explain than PWM. PWM is just way more common, probably because it's a bit more simple in how the algorithm that drives it works.
I mean, if you know all this stuff youâre watching this mostly for entertainment purposes anyway. If you donât know this stuff, thatâs outside of the scope of this video. I like these videos because they give a broad overview of a subject.
1. He said "most" residential solar systems can't provide power during a blackout, which is true. You need a Tesla Powerwall, a Generac battery/inverter system, etc. to have both the storage and the grid-forming inverter to do that, and you need an automatic transfer switch to prevent you from energizing the grid during a blackout.
3. He specifically said this was from a "cheap" inverter (i.e. "modified" sine wave), not from a PWM inverter. There are multi-level PWM circuits. In fact, all 2-level 3-phase PWM inverters (which is most of those described in the video) are effectively 3-level because of the 3-phases. A 3-level 3-phase inverter is effectively 5-level.
@@vylbird8014 A system providing your house with backup power during a blackout does not provide power to the grid! That would be a different thing.
I learned all about MPPT while shopping for solar charge controllers. No tutorial I found actually showed the same panel in different conditions, they just said that the MPP changes. Your test results were nice to see, and helped with understanding. Thanks!
Power grid automation and protection are the industry I work in (R&D at Schweitzer Engineering Laboratories). This is one of the really pressing and interesting challenges which modern grid operators are dealing with. Wind and solar both add quite a few challenges when it comes to grid stability, but the economics are such that they are going to continue to become a larger piece of the puzzle moving forward, so we have to continue learning how to protect and regulate our evolving power grid. This was a very nicely produced video which strikes a good balance of talking about the challenges and reasons why power production still is going in this direction.
You work at SEL!! How cool
@@SeeNickView I think so. I love getting to work with the talented team of engineers I support, and really appreciate working for a company which has such strong values (and really tries to live them). I really appreciate how much emphasis there is on doing the best we can to always do right by our suppliers, employees, and customers. And getting to work on some really cool products and help solve fascinating puzzles is just icing on the cake.
This helps me to appreciate what is going on inside my off grid solar system controller. Cooling fans spooling up and down in proportion to the amount of sun juice coming from the panels, amp meters on battery management units counting out the juice coming and going to keep me connected, comfortable, and conserving in an independent way. Super technology and we are gleaning the results of a massive effort. Thanks for being the one who explains the mega-systems under construction today.
Fun fact about the frequency. Microwave ovens usually use grid frequency to keep clock in time. That's why microwave ovens' clock never stays on time, at least very long. Where I live the clock ticks ever so slightly too fast, because our grid provides slightly over 50Hz power, but MWO still ticks on one second every 50 oscillations.
We have a 60hz grid and the operators actually average out the frequency by making sure there is 60hz*60sec*60min*24hours of cycles per day. Over time the number of cycles is about spot on, so our grid-based time keeping stays spot on over time, even if it varies a tiny bit throughout the day. Short of a power-outage throwing that all out the window, the only time I adjust the clocks is evil daylight-savings.
Yeah, the 50 Hz in Europe may vary a bit, but the frequency target is actually biased such that the summed cycle offset tends towards zero. There was an issue a couple years back when a dispute between Kosovo and Serbia resulted in underproduction and a prolonged lowered grid frequency. The noticeable effect of this was that frequency-tied clocks were running 6 minutes late. They regained this time over the following months though, as designed.
In my experience, there's 2 reasons a frequency-tied clock can get a permanent offset: 1) Your local area was islanded and the grid frequency was shifted to trip solar inverters. The change may be as much as 2%, resulting in clocks rapidly gaining time. 2) A simple blackout: No grid means no cycles.
@@AlexandervanGessel My microwave oven has been being running fast since we bought it over a year ago. It's not much, like 1-4 minutes a month, but never runs late.
I'm not sure if the Kosovo-Serbian situation affected us, we are in Nordpool and AFAIK we use almost exclusively our own electricity, and import rest from Sweden. I can be wrong 'tho
@@TheSanpletext Well, I'm referring to the central Europe synchronous grid (which stretches from Morocco through continental Europe to Turkey). While Norway, Sweden and Finland are members of ENTSO-E, they have their own separate synchronous grid, which includes parts of Denmark. Maybe the frequency is less controlled there?
It sure is difficult. But engineering is transformative-no matter what field or area you're in.
Nicely said.
Yeah nice one, morning after Barbie
I'm a consultant electrical engineer for many large US utility companies. There is no plan at any level by anyone for a zero carbon electrical grid.
A dive into grid forming inverters would be an interesting future video.
I work in power generation ( a good portion of my work is in the renewable sector). Solar farms present a unique challenge in the fact that there is no inertia behind the power production. A regular power plant ( gas or steam turbine) has an effect almost of a synchronous condenser ( a small power reserve). Inverter based generation doesnât provide that. Which can be weird once you start getting into crazy demand days.
Most inverters used on the grid are whatâs called voltage source inverters, meaning that the dc voltage MUST always be higher than the inverter AC output voltage. This is to ensure the inverter can âpumpâ power out to the grid.
From a dispatch standpoint , most solar farms are not dispatched, they produce what they produce to the grid.
The ac voltage that gets exported to the grid is a relatively stable voltage regardless of the dc production, although the power flow will adjust with dc production. There is very little tolerances when it comes to grid tied systems.
Most solar inverters and battery storage inverters ( again utility scale) are the exact same equipment. They can be configured for each operation. Almost all inverters from the major manufacturers, are capable of grid forming, which means they can start with no grid reference. These units can be paralleled to create a backbone to which thermal generation can actually sync to.
Basically the more solar farms that pop up, the more battery storage systems will be needed.
All utility scale inverters have some sort or primary, secondary, and reserve frequency response algorithms built in. Theyâll just convert this mismatch into heat ( vars).
Let me know if you have any questions. I can provide clear explanations on anything else. đ
How big is the battery required for grid-forming? I'm guessing not by much, as it's essentially used as giant capacitor. Perhaps supercapacitor can be used instead?
@@hanifarroisimukhlis5989 they arenât usually separate pieces of equipment. A battery storage facility has 2 electrical measurements.
Power: expressed in megawatts, which is the amount of real time power that can be produced.
Energy: expressed in MwH, or how long it can âgenerateâ
The black start BESS systems Iâm currently working on are in the range of 3-5 megawatt systems, with 20MwH of capacity. So it can discharge at full capacity (5MW) for 4 hours.
You need capacity and power for a black start to work, usually black starting the transmission grid takes time, even if successful the first attempt. Youâre looking at a minimum of 3 hours to restoration depending on what caused the grid collapse
I was waiting to hear "spinning inertia". This whole subject came up when i did my degree back in 2017 and the exact predictions of a semi-blackout.
No grid tie inverter I have ever worked with works without "grid reference". Id est, without the 50hz reference point they cannot output. What century are you from?
I work in Scada for an EPC, those are good points. Would have liked him to dive a bit deeper. Seemed most of the video presented a challenge that none of our jobs usually face (the grid following). All of my jobs have PFR
Audio nerd here and you stole the words out of my mouth with that inverter explanation when I thought "That just sounds like the way pulse width modulation works."
Same here! I saw the stair-step waves and thought, "Digital audio!" I never realized inverters are basically 'digitizing' the power to make it into A/C.
Though normally solar inverters are horrid RF noise generators, as most of them really do not have enough filtering, and often enough the connection methods used are not the best from a RF noise point of view. You really need a lot more filtering to reduce harmonics, and such filters at power are both heavy, expensive and tend to run somewhat hot, losing power in the noise by dissipating as heat in the inductors and capacitors. No way to work it with smaller power, though you can reduce emitted noise quite a lot simply by connecting grounds correctly, and using properly RF bonded steel conduits for the cables, and a local RF functional ground as well. But most will not install that, as it adds a lot of cost to the system for little perceived improvement.
Reminded of my first time finding out what PWM is. Had to change the cooling fan motor on Lincoln and I thought it was broke. It wasn't. It was turning at whatever speed it needed to. Once I got it hot it went 100% full blast. Then I found out it was PWM and explained it to the owner, he thought it was broke because it wasn't turning as fast as he thought it should.
MPPT: Am I a joke to you?
@@cjc363636âstair steppedâ waves do not exist in digital audio. That is a myth and misrepresentation.
It's amazing how much smarter the grid is becoming all the time. To think - a hundred and fifty years ago all we wanted was electric lights that could withstand a lot of variability and now we have all this delicate machinery in our homes that could be thrown off by a few volts at the wrong time.
Depends, most DC items use a switch mode power supply, which are very forgiving. They're rated (usually) 100-240v 50-60hz, so anything near or within that range will be just fine. The most sensitive common item will be things like compressors and other motors
Actually more of the "smart" devices are problematic for the grid during brownouts, not the other way around. Switching power supplies will try to draw the same amount of power regardless of the input voltage. Normally if the grid sags, motors and basic resistive loads will draw less power and it can stabilize, but too many adaptive loads will pull ever more current as the voltage drops.
You should watch the video again, we're not talking about voltage but frequency. It's frequency which keeps the balance of active power in check. Voltage regulation is less critical than frequency.
@@Chopper153 it's possible for a video to inspire other thoughts in people, you know? The delicate nature of our modern electronics contrasting with both the complexity of the grid and how much it has had to evolved since it was first being built.
Most of it shouldn't even require the power it does, but alas, the Internet of Things.
I've worked in the inverter and battery world for 20+ years. This was a well produced overview of inverter technology
Matt, Greg from Alaska here. Hope things are going well. Talked to Lones every few years :-) maybe heâs the only old OB tech left. Anyway, take care of yourself,
@solarwind907 hey old friend! Good to hear from you. Lones retired and living island and boat life. Take good care. M
@@mattjames7272 if you run into Lones, give him my best,
Another old, now resolved problem with PV inverters was that in case of an over or underfrequency (I'm going with overfrequency for now), not just one or a couple inverters starting dropping their power but every single inverter connected to the grid. In the early days the power reductions level were hard set which led to situations where an overfrequency triggered thousand of inverters at once to drop their output, causing a sudden drop in the frequency, which then again led all the inverters to ramp back up, causing a fast over and underfrequency swinging, where the overfrequency swinging also led to wind turbines being shut down in the thousands, making the problem even worse
oh man, you gotta make sure the magic smoke stays INSIDE the equipment!
Smoke is a process indicator; fire is a fail.
Frequency reserve response (FRR) is the holdback. Hydro units shine in this area given they have the largest rotating mass. When an event is triggered the MW setpoint will be released and the governor will respond by either picking up or dropping load (the event can be over or under frequency).
This is brilliant. I work for a large utility company (although I am in IT), and I love this video.
It's even harder when power companies like PECO don't know how to: read solar schematics, inspect a customer's transformer size accurately, or keep to their own scheduled appointments. We've had panels sitting on a customer roof for 4 months because of the incompetence (maybe even greed) of the power companies. Meanwhile, this customer could have been 100% off the grid and feeding excess back into the grid which desperately needs the extra power!
Well, you have to look at it from the perspective of the power company. Being forced to purchase electricity from every customer with a system is not a good deal for them in any way. Even if you set aside the fact that having numerous producers whcih you have very little control over complicates operating your system and makes it more expensive, just the purchase alone (separate from the operational complications) is a raw deal. The power company is required to purchase the electricity at rates based on their retail rates. Here's the thing though, those retail rates are a combination of generation costs and the power company's transmission and distribution costs. Building, operating and maintaining the infrastructure that delivers the electricity to the customer's home is a significant cost. 50% is a common figure, but I'm sure that it varies depending on the situation. Regardless, the price you pay at your meter is partly the cost to generate that electricity, and partly the cost to get that electricity from the generator to your house. Requiring the power company to purchase electricity you generate at that same (or similar) price means that they are paying way more than the generation cost for essentially additional generation capacity, while ignoring the cost to them to distribute "your" power to other customers. So given that, it's understandable that power companies aren't thrilled to be required to enter into agreements that just cost them money, and understandably aren't leaping immediately to the opportunity to lose more money.
How can one be 100% off the grid and yet feeding excess into the grid?
I work in Utility Scale Renewable energy, and we also need to ensure grid relaibility for LVRT, HVRT, Harmonics, Frequency etc. This episode quite nicely shared the challenges of large scale renewables.
But aren't the big inverters (+100kW) doing all of that already on their own? At least the ones from SMA and Huawei do.
Great video! I work in utility solar and you did a great job explaining the complicated challenges we face.
I worked for a utility company a while back and I have to say this is an incredibly well written video
What are your thoughts of using natural gas plants as an in-between for power plant replacement in the near future?
@@Mcfunface that's ok for filling in the gaps right now while long duration storage is developed. But we have a lot of simple cycle capacity throughout the US so I'm skeptical of the need to build out a whole bunch more.
Really what's needed more than new gas plants is better transmission between ISOs/RTOs and a simplified process for getting lines approved and built
I was camping just the other day and my friend who works for GE was telling me about synchronous condensers. Interesting that this video comes out the next day. Was hoping to hear a bit more in depth about how we manage, at least outside of inverters.
I work at a Public Utility District along the Columbia River in the Pacific Northwest. We are also a Balancing Authority for WECC. There are many systems that are always being monitored but load and it's effect on the frequency impacted by that demand is closely correlated and adjusted by adding or removing generation capability on the grid.
From what I recall, in the early days of home solar. There was the issue of these small systems de stabilizing the relatively small Hawaiian grid that all home solar was ordered off the grid until things got figured out.
There was a problem with too many producers on the same local wire pushing the voltage too high, which was fixed by requiring inverters to stop feeding above a certain voltage. I don't think they orderered anything off the grid.
Another great video Grady. I've worked in the inverter industry for over 25 years and this video has taken all the complicated technology and simplified it to the point that a larger audience can gain knowledge. I'll be using this video as a supplement to the training material I've created. Well done sir!
Another exceptional piece of work, Grady. Iâm proud to be a patron of your channel. My Father-in-love was head load dispatcher for PECO back in the day (retired before Y2K) and Iâve shared this installment with him. I am sure he will enjoy it. Blessings, my friend. Keep up the great work!
1900s: "The future has flying cars!"
2024: "We _almost_ have, a power grid... still working out the bugs..."
To be fair, it's just as well we didn't get flying cars. A fair percentage of the population really shouldn't even be trusted with the normal kind.
Way oversimplified theory vs. real engineering that has to be tested to the utmost.
We have a real power grid
Helicopters are just flying cars, so.
@@Duiker36 I wouldn't like to try to fly one using my car-driving knowledge. ;-)
Afaik in Germany you are required according to vde-ar-n-4105-2018 "Therefore, in the future, newly constructed generating plants must support the grid in case of disruptions."
That would mean more complex and expensive power conversion equipment, but it's what's needed so it can come out of the corner as more than a niche player.
@@seekingthelovethatgodmeans7648 Ehhh, not really: at worst you need a small battery about 20% as expensive as the solar panels themselves, and that's for a much higher level of capability than the regulation mandates. Those mandates are basically all just controller/brain requirements, which may have some effect on what sensing circuits the inverter needs to feel the grid, but nothing that actually handles power.
That's the beauty: the normal inverter already needs to have all that power conversion circuity just to feed a reasonable sine into the grid when the sun shines.
âDisconnecting customers to reduce demandâ is a odd formulation for rolling blackout.
Sounds like something the idiotic german government would say while 10% of its population has no power because they didnât get enough solar power
Well, I'd guess everyone unterstands the explanation and that is what counted for the video, I guess.
Maybe he should've said "consumption" instead of "demand" or something.
Rolling blackouts and under frequency load shedding are two different schemes. Both reduce demand, in the only way possible by reducing connected loads, but for totally different reasons. Rolling blackouts are planned when projected generation can't meet demand and rolling reserves. Under frequency load shed is the last ditch effort to prevent an instantaneous, unplanned grid collapse. Also "demand" is the industry term for power use.
@@inothome Doesn't that under frequency load shedding also count as a rolling blackout if it takes the form of blacking out different areas sequentially?
The joy of crating those videos certainly does come across, and seeing someone who's excited to talk about stuff they like makes watching that much better :)
I found this super interesting! Usually you only hear about the problems with new technologies, especially when there's a powerful political lobby against them. So I was under the impression that renewables are an unqualified negative for grid stability and that we'd need flywheels or something if we get rid of too many turbine-based power plants. And I don't live in an anti-renewable bubble mind you!
So thank you for teaching me that these new types of power plants aren't better or worse, they're _different_ and we need to learn how to integrate them well into our existing infrastructure while it is changing at a very fast pace. This seems to be a big challenge to engineers and regulators alike, but one that does not seem to be beyond their abilities. Well, not beyond that of the engineers at least.
In Toronto, you can either connect it to a battery, or the grid, but not both. They won't let you use an automatic switch so that you can sell your solar power when the grid is working, but then use your solar power during a blackout.
You get grid tied inverters with battery now, that will charge the battery as priority with solar input, and excess will be fed back via grid tie, and after dark they will run off battery to a point, then leave the battery and run off grid till morning, when they use the solar to charge the battery again. Manage your power use and you really can be a net exporter, never actually drawing power in from the grid.
Utilities increasingly make it difficult to sell power back for any meaningful gain. Solar panels can still make sense, but one really has to run the numbers carefully. Assume worst case scenario for uptime and maintenance. Panels can last decades, but many components won't and are consumables that need to be periodically replaced. To put it another way, figure whatever a solar panel company is promising is fantasy and budget accordingly. As in 10 years payback at most. If it's longer than that, likely best to wait it out for now.
@@SeanBZA Yep, I have one of those from Fronius. It's also blackstart capable if the battery is emtpy but the sun comes up and it controls the grid disconnect automatically, so when the grid is flaky it goes into island mode and when the grid is back and stable for a while, it switches over to the grid again. Not seamlessly, there are about 10 seconds pause in between, but that's fine, honestly.
@@ronbennett7885 I hit breakeven after about 7.5 years. Helps to drive and heat with the electricity. Also, my country has almost the highest prices for electricity in the world, currently paying about 0.32âŹ/kWh.
@@ronbennett7885 There are a couple of issues here. First, often solar panels are producing power when there is excess in the system, so it not valuable. But if folks do get high feed-in tariffs or net metering schemes, you essential have poorer people paying for rich folks having solar systems. Third, people scream bloody-murder about having to pay for grid connection fees when they are using little or no power. But someone needs to pay for the grid.
Thanks for the excellent video as usual. This is a side of renewables that is seldom talked about outside of engineering circles so I am very happy to see such a good video on the topic. I have a clear memory of my 2nd year power systems class where we were shown a demonstration of how nicely "spinny things" stabilise the frequency when demand increases.
now that 2nd year class is probably tenth year :)
One of the better videos I have seen in a long time. You take a simple sounding project, like adding solar to the grid, and clearly explain many of the subtle problems that come up. I am going to use this video as a prime example of how simple projects can grow into complex problems. Thanks for all the hard work.
Great job considering your world of Civil Engineering is quite a bit different wheelhouse than my world of Electrical Engineering. The depth that you dove into the EE aspects of power is very much appreciated by your entire audience, regardless of their profession.
the other reason home solar arrays typically shut down is because they are not allowed to remain connected to the grid in a power outage, and it's easier to shut down the array, than to have able to disconnect from the grid and operate as a standalone system.
Especially if the inverter connects in parallel with the grid, it's impossible for it to isolate itself. A smarter inverter MIGHT be able to do so.
It's a function of money. This technology already exists, it's just not practical for an individual homeowner
@@thedude5040 a standalone system pretty much has to have a sizable battery bank and be able to manage production based on the battery bank. and have an air gap transfer switch to disconnect from the grid. doable, but people haven't started asking for it in enough numbers to inspire manufacturers to go there.
@kenbrown2808 why invest $30-50k for this kind of setup when a $600 gasoline generator with a 5 gallon gasoline can does the same thing.
@@thedude5040 it's not going to cost that much MORE than the grid connected system. and a 5 gallon gasoline can is good for about 8 hours, depending on the generator.
Great stuff!
Got a solar install here (in Ireland) which allows for off-grid usage during outages though there is some downtime in the switchover as it has to completely disconnect from the grid to operate. Still a useful option if you can get it.
How does the solar function after sunset? Do you have battery backup?
@@johntex105 Yep, though we haven't yet had a night time outage.
Yay! I love it when another one of your videos pops up on my feed! Thanks for sharing.
4:37 .. These are still popular today ..
There are several, single to three, "rotary phase converter" companies, and the old "Redline" 12 volt DC to 20 volt AC "rotary converter" is still used today.
All that spinning mass is the stored energy to get through transient events. On an airplane I worked on there was a motor generator to both get a particular DC voltage an aftermarket system needed AND it also ensured clean, stable output even if the input AC was interrupted briefly.
An NC (Asheville?) TV station was said to have had a flywheel 'buffer' between the mains grid and the on-site diesel generator. That way, when grid mains were lost, the switchover was not a blackout / brownout event. The spinning flywheel buffed out the transition. Sorry, but I don't remember the call letters. I'd heard this from TV engineers back in the 80s/90s.
I know of a few new factories here in Austria that use two separate power grids. One classical AC, the second one DC to use the electricity from the solar panels on the roof directly.
Where are they located, which companies?
It's interesting that, DC-sources are causing people to start thinking outside the AC box, and start looking at using the DC directly (pun intended). The simplification it creates has benefits.
I've wondered when DC end to end would start happening (even if in small scale), given that more and more loads either use DC (lighting, electronics), or in principle could just as well use DC or AC, while there's increasing generation that's inherently DC (solar). As an aside, AC is responsible for much loss in the grid (for the same reason that transformers work... induction). More and more long distance transmission lines are DC. So the chain is sometimes DC generation, DC for part of the transmission, and DC loads. I've read that some companies are working on fully DC grid designs. I doubt that it'll become the norm in my lifetime, but I wonder when the benefit of transformers won't be sufficient to justify AC, if DC grid technology gets sufficiently good someday.
@@bearcubdaycare one of the problems is, DC doesn't work well over longer distances, not without some seriously big cables. but if you were going to do certain dedicated things, like say a direct PV connection to an electric hot water heater, then it might not matter as much.
It tickles me to think of fancy new Austrian factories working on basically the same principle as the old camper trailer I used to have (which had an external AC connection for the aircon, appliances, and wall outlets, but ran all the lighting off an internal 12V DC circuit powered by a car battery). ;)
Your videos on grid and power are my favorites. I practically drop everything to watch them. Love your book too!
its practical to drop things? ok if not carrying a cup of cofee i suppose ;)
Most excellent episode - bite-sized chunk presented in a most digestible way. Thank you.
An enlightening video. Really shines a light on the topic in a way any sun of a gun can understand.
Ah, I was wondering why we had a power cut... when we had a power cut. Figured there was something about our solar configuration that meant it couldn't work as the sole power source for the house.
Grady did not cover another reason solar systems turn off when there is no utility. If your solar system is feeding power into a utility that the power company has turned off for repairs then you are energising cable plant that is expected to be de-energised. This can be dangous to linemen. Remember transformers work both directions.
There are three kinds of solar systems. Off grid, make power all the time, can't be connected to the grid cause it doesn't sync. Grid tie, which does sync to the grid, but when the grid shuts off, it MUST shut off, both because lineman don't want to get zapped, and because you will never own equipment powerful enough to carry the whole neighborhood. The third is a hybrid, which can do both, because it automatically disconnects from the grid, and then turns on(often with multiple pieces of equipment). Tesla has a system. They used to have a Tesla gateway, which was the switch that disconnected you from the grid, and let the powerwall know it can turn on. They might have built that functionality into the Powerwall 3, not sure, but their new setup isn't approved everywhere yet. Enphase has a system. SolArk sells a hybrid inverter. Point is, if you want your system to do it all, you have to design it that way, and pay for the parts. I just have a grid tie from 2017, but I want to eventually be able to do it all.
Grady, good video. Couple of things. I installed my first grid forming inverter 30 years ago and they have been around for much longer than that. Most Utility engineers are just learning this. People who lived off grid with Solar and/or wind plus batteries and an inverter have known about this for a long time.
Companies like Sol-Ark, Outback Power and Midnite Solar sell high-quality inverters. You can buy today and combine with a battery bank to either buy from or sell power to your local utility.
Another thing, your video makes solar, wind, and inverters sound dangerous. If we donât stop burning fossil fuels ASAP, we will see many more of the catastrophic climate events experienced in the last few years. Iâm talking about the massive fires in Canada and California, droughts, hurricanes etc. costing billions of dollars every year. Soon we will have these catastrophic events occurring concurrently. insurance companies will go bankrupt. If we wind up in a situation with 8 billion people on earth and only the resources for 4 billion, itâs not going to be pretty.
There is no sane choice except to vastly increase the amount of solar, wind and energy storage connected to the grid ASAP.
you are an exceptional educator. Thank you very much,
Blown away by the details in your videos. You explain it all so well.
You nailed this subject. I will be sending this video anytime I have to explain how grid frequency stability works.
5:31 I audibly laughed when those skwigli lines poped up. Is there a schematic of that cursed thing by any chance?
Should send it to Big Clive to tear apart and show how it (barely) works!
I learned a lot about the power grid from this video. The graphics were super helpful to conceptualize. It was also telling to see the choppy waveform of cheap AC inverters. Better than a square wave, but not by much!
Such an informative video regarding the constraints of renewable sources in grid systems. Well done Sir!
Just started to explore Grid-tired solar system. This video came a a good time. I was discussing with our Solar vendor about having the inverter continue powering thru a grid outages... and the Solis smart inverter could not do it. Yup, knew of MPPT, and how Solar Generation is not as smooth as most people think that it is, passing clouds could drop the generation just like that, and it will cycle thru generation at Peak and trough...not an easy task, trying to do power generation, and still have to follow the grid's frequency and voltages.
What ever you choose, choose hybrid inverter with un-balanced output with some batterys.
Nice video.
You did a great job of explaining a very complex topic!
Been trying to understand grid inertia for a long time. Thank you
It's interesting to think about how solar and distributed inverters could be used to provide half-cycle ride through and power factor adjustments. Seems like just changing our thinking we could use these to our advantage.
you mean from profit based thinking to solution based thinking?
@@kenbrown2808 One does not exclude the other. You provide a solution and make a profit. That's capitalistic 101.
@@huckleberryfinn6578 no, that's economics 101. capitalism 101 is "a dollar in the hand is better than two in the future"
@@huckleberryfinn6578 That's Adam Smith air-quote "capitalism". It relies on this underlying assumption that the best solution will always be the most profitable. It doesn't take a Nobel laureate to figure out that assumption just is not the case.
PG&E is a classic example. Much of their infrastructure is decades past its rated service life. But upgrading and replacing it cuts into profit, so instead they cut power to their customers and burn down the countryside whenever there's a light breeze.
If you care to educate yourself on some of the thicker weeds, you should look up concepts such as price elasticity of demand and hydraulic despotism. These two principles are the Achilles heel of capitalist ideology.
This was mentioned, just briefly, in the video - some inverters can provide what I think he called 'virtual inertia'. Either boosting the front of the sine wave or loading it down if the frequency drops or peaks.
We might need a video on the FSK Bridge
Fantastic video! Each resource type has its own advantages, and this highlights how they work together.
Great video, thanks! Keep making more about the grid!
Maybe someday we'll have cheap thyristors that allow abundant high voltage DC transmission
Highly unlikely. We've reached the end of Moore's law, so silicon fabrication technology isn't going to get much cheaper.
@@Shaker626 , grid level semiconductors are not using shrinking to improve economies of scale. They're much larger due to the power they're handling, so Moore's law has little impact either way.
@@JimBob1937 The wafer production backend is a big chunk of the cost of those chips (their fabrication is not as expensive, however). Moore's law was the main driver for making wafers cheaper, which is not very likely to proceed at the same rate. It's unlikely that power transistors will get much cheaper than they are now with the IGBT.
@@Shaker626 Moore's law is for scaling down transistor, not efficiency/power density.
@@Shaker626 , wafer production is based on growing a cylinder from a seed crystal and then slicing and polishing it up into a set of wafers. This has no connection to Moore's Law. Moore's Law is more about shrinking down the transistors via smaller and smaller interconnect technology and better and better photolithography (most recently EUV, due to the shorter frequency giving better detail resolve). This in turn ither allowed for an increase in transistors per fixed area of the wafer, or for less wafer area for a fixed number of transistors. This allowed the wafers to be better utilized. However, grid level semiconductors are not concerned with size as much as power handling. Nothing of Moore's law directly affects them, since it isn't an area they're concerned with.
We had a similar disturbance happen in the UK a few years ago, and it triggered the catchily named "Accelerated Loss of Mains Change Programme"
Thank you! This helped me understand MPPT more.
I've also heard about the problem of voltage rise near solar installations- as solar panels doesn't use the concept of power angle like generators, the only way they can inject energy into the grid is by increasing the voltage a little bit. This is fine for a few panels, but in residential areas having large number of installations, each panel has to up their voltage, resulting in significant rise in voltage in lines in the vicinity.
Mostly because the grid was designed as one way, you would need to have a lot more automatic on line tap changers in the residential suburbs to counter this, as they typically are only used in the larger local distribution network for the primary incoming transformers. Local uses mostly off line tap changers, set, locked and left as you cannot change them energised. Automatic tap changers in areas with lots of solar will help, but the expense for the utility is not warranted, seeing as it is not power they are able to bill for easily, and thus low on the priority list to implement. Residential inverters are programmed not to exceed peak line voltage, so the power loss is purely on the solar household side, not the utility side.
Usually there are certain limits to this effect, so that PV inverters will lower power to prevent the voltage from rising too much. In addition, there are actually concepts to counter the effect by drawing reactive power (lowering the cos(phi) of the current injected in the grid) at the same time. I don't know if they are implementet in current PV systems, though.
I dunno about "significant", but your surmise is wrong... grid-tied inverters do use power angle like generators. They push phase, not voltage. But that does have two side-effects which do cause the voltage to rise.
(1) The homes are burning less energy from the grid, the lighter loads mean higher voltages.
(2) The exported energy has to go somewhere and since it isn't going to frequency that leaves only voltage. Even though the inverters are pushing phase, there will be some voltage rise on the whole circuit as the energy smooths out over distance.
But again, "significant" ? Its possible but exceedingly rare, and it will still be in-spec since the grid-tied inverters trip-off if the voltage goes out of spec.
A very real problem is that voltage rises in residential voltages feed-backwards through the pole AND substation transformers which multiply it back up to transmission voltage levels. And even when these rises are within specifications, the multiplication on the way back, if the backfeed gets all the way to the substation, can cause the transmission line voltage to go out of spec.
This is easily rectified but requires a transformer upgrade at the substation (basically to a modern transformer with two-way sensing and automatic tap control). Fortunately, though, this sort of situation only occurs with a very small number of circuits, so mostly problems develop because utilities are blowing smoke and purposefully letting them get out of control to try to convince politicians to slow solar installations down.
-Matt
pulse width modulation does not produce step like waveform, as it name suggest it changes the off/on pulse length and uses a low pass filter to smooth out the wave. what you have looks like a DAC, which may not be suitable for high power and are more expensive.
Its not a DAC. You can't DAC an AC output at significant amounts of power... DACs are resistive devices so the inverter would basically melt, more or less instantly. And it's not the PWM either. Modified sine wave inverters work mostly by pumping two capacitors with two somewhat out-of-phase square waves and getting an additive effect. That is what creates the step pattern.
Pure sine wave inverters work by running a square wave into a transformer/inductor circuit and using the magnetic effects to turn that into an almost real sine wave. Then a simple filter stage to turn that into something very very close to a pure sine wave.
You can't do non-resistive voltage regulation of any kind without some sort of magnetic component or electric field component (or both). A capacitor, for example. And you can't really get anything resembling an actual sine wave without using something with a magnetic component (either an inductor or a transformer or both).
-Matt
â@@junkerzn7312 Ehhh, you can use capacitors and switches to provide enough intermediate taps from where you can then afford to resistive DAC a pure sine wave, without any magnetics. And still at over 95% efficiency. Though you'll want to use tiny inductance to resonate some of the oscillating currents in the arrangement to not loose so much energy during the switch transitions, as the efficient capacitors are expensive so you want to switch fast so you need less of them. That's why you'd in practice need a tiny bit of inductance to get >98% efficiency from such a system.
Fantastic Video. Grady... you really should add a link to the black start video in the description for this one! Maybe even at the end credits. There is a strong connection here.
Great video. You reminded me of how much I'd forgotten about the topic.
Solar is excellent for future-built homes. You add DC outlets (or USB ones) designed specifically for electronic devices, power tool battery chargers, or electric cars so you can directly power them without having to invert it to AC and back again.
I think this would work well. Look at RV's, the have 12 volt, 120 volt, and gas systems, why not our home and work places. lights and electronics could all be DC.
I like the concept in that most electronic devices, if you look at the little wall adapters for them, run off of 5VDC or 12VDC. Its a whole lot more efficient to buck-down a modest DC voltage then to convert to AC and then back to DC. But there are some warts.
The biggest wart is a safety concern. You can't use AC breakers with DC voltages and you also have a problem with ARCing when wires break that you don't have with AC (because with AC the current crosses zero 120 times a second). So even though we can have in-house DC wiring, its a bit more dangerous when faults develop as the wiring ages.
As such, I think DC circuits are an interesting concept, but amperages would have to be severely limited and electronically controlled., possibly with an insulation resistance check as part of the safety device requirement.
I think something like .... well, for house wiring you don't really want 12V. You want something like POE+ (power over ethernet) which is an actively negotiated protocol which also actively checks available wire pairs continuously. It runs at roughly 56VDC. Almost impossible for POE+ to cause any sort of fire. It is typically limited to roughly 60W over four pair which is barely 15W per wire pair (0.35A or so per wire pair). There is also POE++ which supports higher wattages by using higher voltages.
-Matt
I'm still waiting on reasonably priced DC breakers to actually use that (not at my home, because I don't have a good place to put solar), particularly actually for a mini-split AC/heat pump.
@@junkerzn7312 Modern AC breakers actually have substantial DC capacity (and rating!), it's just that you can't really handle more than 60V with a single contact MCB.
There are low voltage DC standards in place currently for e.g. iirc a bipolar +-125V system without locking connectors, and an iirc about 380V system with locking connectors that's been deployed in data centers for a while now (their DC is their battery backup bank; they skip the inverter of their UPS).
@@namibjDerEchte Well, I've got like four different brands of DC MCBs in front of me and the unpolarized ones are typically rated to around 110VDC and the polarized ones up to roughly 250VDC, I think I have one PUFA here somewhere with a 1000VDC rating.
Generally speaking, the DC MCBs with higher ratings tend to be polarized. The DC MCBs with lower ratings tend not to be. But this is an area that get DIYers into trouble all the time. Either they buy polarzied breakers and don't hook them up properly, or they buy polarized breakers and don't realize that they can't be used in a battery circuit where current can flow both ways (charging and discharging). OR they buy a non-name breaker and just assume it is polarized or unpolarized from the markings, not realizing that most polarity markings are completely meaningless as a "tell" on the type of breaker.
Most AC breakers do not have DC ratings and definitely cannot be used in DC systems. Not sure where that came from. Expensive high-end breakers will often have both AC and DC ratings but most run-of-the-mill breakers that people buy... those almost never do. The construction is too different.
Typical AC breakers use relatively large GAPs to break ARCs for example. And also often don't have arc extinguishers. But that method relies on the current crossing 0A 120 times a second (AC waveform). DC with a breaker like that will build a lot more carbon up on every trip until the breaker fails and fails to break the ARC, then catch on fire,
Typical DC MCBs use narrow gaps and walk the current up to the ARC extinguisher. That can be done both polarized and unpolarized. Polarized breakers can walk the current more quickly and more reliably and tend to have higher voltage ratings. Unpolarized breakers still walk the current away from the contacts but don't have magnets near the contact point forcing it to walk faster. But being unpolarized, they can break current going in either direction.
-Matt
Good job Explaining â€â€
I wanted to watch this because my favorite presentation at a data conference a few years ago was from an electrical engineer from Dominion Power (my power company). He started with a bit of an overview of electricity and went on to show how his team was monitoring fluctuations in order to enable the power company to better handle the increasing domestic solar installations. But you covered a different angle! Interesting information!
also, i loved that talk so much that i asked several other ppl if they liked it as much - they all couldnt follow his intro overview at all - I guess the 2 years I spent as an EE major were good for something.
I work on photovoltaics and batteries directly, but it's really cool to see the other side, on how people work on installation and application. Thanks for this!
Rome wasn't built in a day neither was grid.
Correct but it won't be rebuilt fast enough to keep up with demand either.....so....no more ev mandates or rolling blackouts
Texas being unreliable is not a surprise but renewable energy is hardy a root cause, it's the transition that's probably the problem. Here in Denmark we have the highest amount of wind energy and we have the 2nd most stable energy grid in the world behind Norway.
Right! And not just the transition, but the way Texas (and most of America) handles that transition. In America it's all about maximizing profit rather than maximizing reliability, so corners get cut and grid equipment gets manufactured by "the lowest bidder". A few places in the US have municipal (owned by the public) utilities and these are almost universally more reliable and cheaper, even with a very high renewable portfolio.
The problem with renewables in the US is that in a lot of areas of the US air conditioning is needed during the hot summers which run normally until around 8pm. The problem is solar and wind shut off around 6-7pm during the peak power consumption from around 4-8pm which is the reason why renewables are causing headaches for the US grid. Having a major power generation system shut off during the peak of power consumption is not a good mix.
Texas is a world leader in wind and solar generation. Our economy is growing so fast that it's almost impossible to build power generation sources fast enough to keep up with demand created by this growth. When you also factor in our extreme heat in the summer, when our wind production is typically at its lowest point. This can cause problems.
That statistic has nothing to do with frequency stability in Denmark, since the rotational inertia that maintains it comes from increasingly parasitic use of interconnection with turbine generators throughout the rest of Europe.
The electricity in Denmark is also insanely expensive.
I used to work for a Utility level inverter manufacturer and our California customers often opted for the Ride Though board. They allowed the units to keep running for a couple minutes while the grid went through a black out (happened often back then). Fun times!
Great video and channel!
Glad I found you! Keep it up!
It's always crazy to me just how much Texa's grid is privatized and how often that causes issues.
Some of it is just for safety, but 90% of the problem with solar in my state is political - the utilities have complete control of the legislature and the laws are punishing for anyone who isnât them
This gives you an opportunity. You can get retired panels and connect them to an off grid load. In Phoenix I would put retired solar on the roof and connect it to a mini split for free air-conditioning
@@TimHayward Great use of solar.
For profit utility grids are terribly inefficient, from a customer value perspective.
â@@TimHaywardRetired panels? Never heard of it, but now I'm definitely curious!
Why do they Retire them? Do they need some type of maintenance?
Where do I find these?
Really interesting video. Thanks Grady!
Love your lessons, making a complicated system easier to understand, many thanks for doing these.
Our south african eskom would shock you...
đyeah totally....
engineering rarely scales âeasilyâ which is why i like the idea of homes that arenât grid tied and are self sustaining at least in power. someday weâll get there.
I absolutely loved the way you explained some tough concepts with great level of detail in a simple manner. Congrats on a fantastic content as usual. đ
Great video! Loved the detailed explanation, but in an understandable fashion!
My parents are retired and totally OFF GRID in a brand new home and they don't have to contend with all this choppy inverter feedback-to-the-grid nonsense at all. They get a cleaner AC sine wave from their wall outlets than I do in the suburbs, 25m from the distribution box!
If you own solar DO NOT sell your electricity back to the companies for mere pennies. STORE it in a battery and enjoy totally FREE electricity!
With good battery management you'll get 20 years out of them.
Interesting, what size/type system do your parents have and what was the cost? Thank you
20 years from a lead acid is a pipe dream.
@@Bacongrease00 hahaha... No way I'd suggest lead acid.. they're only good for a few cycles.
@@subliminalvibes typically hundreds of cycles depending on depth of discharge but none the less they donât seem to last much beyond 4-6 years before loosing along of capacity. They also are sensitive to temperature. I believe one manufacturer states for every 13F above 77f you can expect a 50% reduction in life.
@@Bacongrease00 again, I'd never consider them. đđ
Thanks very much for making a video on this really interesting and important topic!
This is an absolutely amazing video. It manages to summarize the most critical and complicated problems of power grids, in the most intuitive way!
This topic came up in a recent standards meeting I was at. You did a great job covering the high level overview. If you have more details on the power industry I would love to hear it.
A comprehnsive and simple and yet technically correct explanation of the complicated aspects of connecting renewable energy to the grid.
7:02 Awesome explanation. I've always wondered why many grid tied solar kits were useless during power outages.
Super awesome to finally get one about my field
With a grid tied inverter, increasing or decreasing the voltage will just push or pull VARs from the network. It is actually shifting the phase of the inverter ahead of the network that will push power out.