Why is inverter cut off voltage so high? - Page 1
Forum section: electronics / general

author: Marco
author_rank: Super Contributor
timestamp: August 22, 2024, 12:24:20 pm
content: The power companies in my country are getting desperate to deal with excessive rooftop solar and unwanted currents on the distribution grid.Why didn't government mandate the cut off voltages for inverters be substantially lower than the max voltage power companies have to maintain? The power companies have to maintain <253 same as the inverters.If the inverters had to cut off at say 243V they could just change the tap on a local transformer as a way to regulate rooftop solar. It would not be popular, but at least they'd have it in their toolbox.

author: Siwastaja
author_rank: Super Contributor
timestamp: August 22, 2024, 01:42:43 pm
content: Because on grid-level, maintaining balance of production and consumption is not based on voltage, as the grid is very low-impedance.High voltage is alast mile problem, absolutely nothing to do with nation-wide balance of production and consumption. So if inverters started to cut off at lower voltage, many inverters would cut off when there is still demand for the generated power in the grid. The only reason for voltage limit is to avoid causing damage by overvoltage, which again would be a localized problem.

author: tszaboo
author_rank: Super Contributor
timestamp: August 22, 2024, 01:49:50 pm
content: Please don't believe the bullshit that those companies are feeding you.Repeat after me: There is no such thing as too much solar generation.If there would be, then the voltage increases, and the inverters shut off. As you already seen it, every inverter sold in the EU, by law, cannot output voltages that are higher than the maximum specifications for the grid. You cannot overload the grid with too much solar. What you can do is, hurt their bottom line. This costs them money. And that's why they started this nonsense explanation that there is too much solar. They lie to you for money, it's that simple.And now politicians and the ACM and the people without solar started believing them and mobbing us with extra costs. Oh and the lobbying. They had zero issues fixing the price for 1 EUR/KWh, when diesel generators were cheaper than buying electricity from them, and now their profits are bad.

author: Marco
author_rank: Super Contributor
timestamp: August 22, 2024, 02:05:53 pm
content: Quote from: Siwastaja on August 22, 2024, 01:42:43 pmThey now have zero control over currents from inverters except letting voltage rise above 253V, which they are not allowed to do intentionally ... but I have my doubts, they almost certainly do it on the sly with regulators looking the other way if they don't abuse it too much.I don't like these unspoken rules, better just handle it in the open. Which they could, if inverters had 5% headroom instead of the full 10% the powercompanies have.

author: Marco
author_rank: Super Contributor
timestamp: August 22, 2024, 02:17:20 pm
content: Quote from: tszaboo on August 22, 2024, 01:49:50 pmAs far as I know they have service level agreements which disallow voltage to go over 10% too, regardless of small generators ... so they would be breaking their contract if they do this structurally.What caused me to question this is the plan in Zeeland to pay people with rooftop solar to turn it off. As I said, desperate.

author: tszaboo
author_rank: Super Contributor
timestamp: August 22, 2024, 02:26:08 pm
content: Quote from: Marco on August 22, 2024, 02:17:20 pmThe same 10% as inverters. There is nothing magical here, a power plant cannot output more, an inverter cannot output more.What breaks my mind is this:We have net metering. It's a subsidy. It's the elected government making a decision that they are going to support the people with solar panels to advance green transition. Subsidies by definition mean that whoever is using it, it's going to be cheaper, and for other people it's going to be more expensive.So with this declared, unelected electricity companies, all of them at the same time decide that they are going to charge people with solar panels money. Because it makes electricity more expensive for everyone else, and it's unfair. Guess what, that's the whole point of a subsidy.So an elected government made a decision, that a unelected cartel of energy companies unmade. All of them at the same time. And the orders for solar installations are down 95% since last year. And the electricity price came down by drumroll, 1.5 cents for everyone else. I guess they couldn't afford that 1.5 cents to save the environment. Meanwhile we have 13.5 cent tax on KWh, and VAT on top of that (because of course tax on tax).

author: Marco
author_rank: Super Contributor
timestamp: August 22, 2024, 02:50:54 pm
content: A powerplant is under their control, when they want less current on a leg of the high voltage distribution network they can modulate the power of two or more plants in different locations to do so.Needing to break their service level agreements to control rooftop solar is a problem.

author: tszaboo
author_rank: Super Contributor
timestamp: August 22, 2024, 02:59:55 pm
content: Quote from: Marco on August 22, 2024, 02:50:54 pmDo you think that's happening?

author: Marco
author_rank: Super Contributor
timestamp: August 22, 2024, 03:55:55 pm
content: Quote from: tszaboo on August 22, 2024, 02:59:55 pmThey payment scheme in Zeeland shows they are both desperate to control rooftop solar and to avoid doing so through excessive voltage.Basically most PV on sunny days is flowing to the Randstad industry, there is as of yet sufficient demand but the grid wasn't designed for current flowing that way. Long term we need more batteries and intermittent hydrogen generation, but for now they need to prevent overloading the grid.

author: tszaboo
author_rank: Super Contributor
timestamp: August 22, 2024, 04:17:24 pm
content: Quote from: Marco on August 22, 2024, 03:55:55 pmRight, so how exactly this overload happens? Like which parameter is overloaded?Because the cables are not zero impedance, and they are designed to operate with a high voltage transformer on one end, and load on the other. The transformer being the higher voltage. So the typical setpoint (ratio) for this transformer is higher than nominal voltage. When houses start feeding back electricity, the voltage increases further. Finally the houses closer to the transformer will be able to generate electricity, the ones further away will shut down their inverters. So where is the overload? Do we get to see sparks?I especially love when they talk about that the grid cannot handle more consumers because it's overloaded with solar. Producers. So somehow electricity flowing in one direction is overloading the wires that can't handle the other direction? Does this make any sense to you?

author: Marco
author_rank: Super Contributor
timestamp: August 22, 2024, 04:25:59 pm
content: In the extreme, sagging cables and boiling transformer oil. Traditional production was near consumption, not power from the whole country flowing to the Randstad.Obviously they can just allow voltage to rise above 253V but I suspect they are contractually obligated not to do so. Hence the desperation.

author: tszaboo
author_rank: Super Contributor
timestamp: August 22, 2024, 04:50:07 pm
content: Quote from: Marco on August 22, 2024, 04:25:59 pmBut do you understand Kirchoff's current law?There is no such thing as too much generation. And if the voltage is already high at the power plant, the inverters see even higher voltage when they generate. It's not the same everywhere it's a dynamic system with resistances in between.And the only way to direct current from places is when there is a voltage difference. It follows the same laws as your regular circuit. How would you get sagging cable? That cable is designed to carry more current from the power plant to the consumer (by the high voltage transformer turns ratio and nominal voltage), and the consumers are limited by this impedance (and the firmware of the inverter) of how much electricity they can feed back.The situation they are talking about is impossible.What is possible is that they are obligated to buy electricity back when the price is negative. And that costs them money. And they lie to you.

author: nctnico
author_rank: Super Contributor
timestamp: August 22, 2024, 04:53:35 pm
content: Quote from: tszaboo on August 22, 2024, 01:49:50 pmNo, but there is something like a congested grid which can't bring amount of electricity generated to places where it is needed.

author: tszaboo
author_rank: Super Contributor
timestamp: August 22, 2024, 05:01:57 pm
content: Quote from: nctnico on August 22, 2024, 04:53:35 pmTrue, which is something that is under their control since the mainline is under variable voltage control.So it's quite possible that a consumer is fed by a fossil power plant and inverters are shut down other parts of the country.Yet this is not an overload.

author: tszaboo
author_rank: Super Contributor
timestamp: August 22, 2024, 05:07:51 pm
content: Actually this is a software and organizational problem. DSOs if they would be a little smarter, they would sell the solar generation on the day ahead market, not the spot market. At least more of it. Then they would receive a few cents for the electricy instead of costing a few cents. But instead they are making it the consumers trouble.

author: nctnico
author_rank: Super Contributor
timestamp: August 22, 2024, 05:22:53 pm
content: Quote from: tszaboo on August 22, 2024, 05:01:57 pmIt is an overload. You have X transport capacity and Y to transport. If Y exceeds X, you need to limit Y. There is no argueing around that. You can't make a powerline transport twice its rating by making the voltage a few percent higher.

author: tszaboo
author_rank: Super Contributor
timestamp: August 22, 2024, 05:30:55 pm
content: Quote from: nctnico on August 22, 2024, 05:22:53 pmOverload by too much consumption is possible and off topic. Overload because too much generation, is not possible, because the voltage increases and the inverters switch off. Voltage increases because the feed line has a resistance, and the feed line is designed to handle the voltage difference. QED.It's the equivalent of saying: I've put too much current into a resistor, without increasing the voltage, and it overloaded.

author: Siwastaja
author_rank: Super Contributor
timestamp: August 22, 2024, 06:14:36 pm
content: Oh, this was another nutjob word salad thread after all. Nice. We didn't have too many already.

author: Marco
author_rank: Super Contributor
timestamp: August 22, 2024, 06:18:53 pm
content: Quote from: tszaboo on August 22, 2024, 04:50:07 pmTransformer taps are not static. If voltage in Zeeland is 253V, they can change the tap to have it generate a higher voltage on the high voltage side to push current to the Randstad and lower the mains voltage in Zeeland. They can overpower the resistance of the wires. Obviously they won't do that to the point of failure, but not doing that means letting the voltage in Zeeland getting too high and breaking their contractual obligations.

author: tszaboo
author_rank: Super Contributor
timestamp: August 22, 2024, 06:26:34 pm
content: Quote from: Marco on August 22, 2024, 06:18:53 pmOf course they are not going to overload the grid intentionally.How does the voltage get too high? The inverters are limited to 253V, the transformer cannot be 253V because Ohm's law. If that's also 253V there is no current. It has to be lower.

author: Marco
author_rank: Super Contributor
timestamp: August 22, 2024, 06:29:02 pm
content: Quote from: tszaboo on August 22, 2024, 06:26:34 pmThat is already too high, they can't just run at the edge ... hence the desperation and trying to pay customers to take their PV offline.

author: tszaboo
author_rank: Super Contributor
timestamp: August 22, 2024, 06:31:05 pm
content: Quote from: Marco on August 22, 2024, 06:29:02 pmSure they can. It's within specifications for everything. So is reducing the output of the inverter.What they dont like is paying negative prices.

author: Marco
author_rank: Super Contributor
timestamp: August 22, 2024, 06:35:15 pm
content: If they were allowed to just turn off (most of) the inverters by running the mains voltage near 253, they could do that for free ... yet they are paying people to turn them off instead.Why do you think they are doing that?

author: tszaboo
author_rank: Super Contributor
timestamp: August 22, 2024, 06:39:34 pm
content: Quote from: Marco on August 22, 2024, 06:35:15 pmCan you please post a reference for this?

author: Marco
author_rank: Super Contributor
timestamp: August 22, 2024, 07:15:38 pm
content: https://tweakers.net/nieuws/225662/stedin-en-eneco-vragen-huishoudens-in-zeeland-om-zonnepanelen-uit-te-zetten.html

author: tszaboo
author_rank: Super Contributor
timestamp: August 22, 2024, 07:47:28 pm
content: Quote from: Marco on August 22, 2024, 07:15:38 pmQuoteTranslation:QuoteOnce again, how is this possible? Electricity is not a liquid or gas, it doesn't have pressure, and obeys Kirchoff law. It's not a bucket.Your question was: why don't they do it if they can? Because they cannot. This is Eneco and Stedin, they are responsible for billing. They are also obliged to pay you if you generate electricity. The grid is operated by Enexis. They probably asked Enexis to increase the voltage, who has zero incentive to do so, because they are getting a flat fee for delivery.No indication on what is overloaded. No blackouts or any failures in this record breaking summer.Also, they are going to compensate 40c/KWh based on... not generated electricity? How does this actually work?And here is an article talking about how all this amount of extra charge might be illegal:https://tweakers.net/nieuws/225436/acm-gaat-extra-onderzoek-doen-naar-kosten-en-vergoedingen-van-zonnestroom.htmlLet me ask you this. They point at solar panels as scapegoats, and started charging ~20-30 EUR for 2 million households with solar every month. That's ~600 MEUR a year. You see some inventive to lie about this?

author: Simon
author_rank: Unknown
timestamp: August 22, 2024, 08:19:35 pm
content: Quote from: tszaboo on August 22, 2024, 02:26:08 pmwhat the hell are you waffling on about? I don't know about your country but in mine you get paid 15p/kWh of export and they sell it for 30p/kWh, we have to pay for our own solar panels, I don't see the subsidee. The only clever thing I can do is use my battery, charge it at night for 7.5p/kWh and then I can use it during the day instead of paying 30p/kWh.Inverters are current sources that follow the grid voltage, it's all really simle, it just works, no conspiracy to see here.

author: nctnico
author_rank: Super Contributor
timestamp: August 22, 2024, 08:56:21 pm
content: In the Netherlands there is a lot of turmoil about solar panels at the moment. There are a few things at play:1) The government promised that people would get the same price per kWh they provide to the grid as they would pay per kWh for as long as they use more than deliver to the grid. Call it a 'kWh per kWh subsidy'. The government and energy companies pay for this as a form of subsidies to motivate people to get solar panels.1a) If people deliver more to the grid, the energy companies would pay a certain amount to the people for the energy. Typically this wasn't a large amount.1b) This arrangement would originally end by 2025. Then it got changed to a gradual changeover period between 2025 and 2031 (IIRC). However the latest plan from the new parliament is to stop this kWh for kWh subsidy per 2027.1c) The number of solar panels on homes is far greater than projected; the amount of energy produced is 3 times higher than expected / planned for. The 'kWh for kWh subsidy' should have been stopped in 2021 but this date got shoved around several times.2) Energy companies have found a loop-hole where they can charge people for supplying the grid with energy. A feed-in tariff. At the same time the electricity prices have been lowered. So people get less from the 'kWh for kWh subsidy' and must pay to feed into the grid. The effect is that solar panels have a much longer ROI than they used to have and what people planned for.2a) Once the 'kWh for kWh subsidy' stops, the feed-in tariffs are supposed to dissapear.2b) For example: I pay 21ct per kWh but I get 12ct per kWh I deliver to the grid (if I would supply more to the grid than I consume). However, I have to pay a 240 euro/year feed-in tariff based on the amount of electricity I supply to the grid. Even my relatively cheap DIY solar system went from a ROI of 2 years to 5 years. And the 5 years number is low due to the massive payback I got in 2022 which paid for 1/3rd of the install. People who paid full price for a similar installation I have, are looking at an ROI of 10 years instead of 5 years.3) The Dutch electricity grid is seriously congested in many places. At the level that new homes and companies can't get grid connections due to shortage and at other places renewable energy can't be fed into the grid. Some companies are actually running on diesel generators in order to have electricity. This is all because the government body which gouverns investments in the electricity grid choose to ignore specialists telling them in 2008 the electricity grid would become seriously congested in 15 years. So nothing happened to expand the grid for 15 years while the need for expansion was obvious all this time.3a) This grid congestion leads to all kinds of creative solutions in order to keep the grid manageable. Appearantly in some regions people are asked to turn their solar panels off and being compensated for not supplying energy. It is like paying a wedding band NOT to play but here we are.However, none of this has to do with inverter cut-off voltages.

author: tszaboo
author_rank: Super Contributor
timestamp: August 22, 2024, 10:26:27 pm
content: Quote from: Simon on August 22, 2024, 08:19:35 pmYou have different rules.We have net metering, it's the law. Yet they made some illegal changes, every single electricity provider at the same time to charge people with solar panels. Some per KWh you feed back, some a flat fee per month.Also, sale price of excess electricity went from ~25 cent/kwh to 3 cent in 3 years.

author: coppercone2
author_rank: Super Contributor
timestamp: August 23, 2024, 01:23:56 am
content: I can tell you one thing about US power companies, its serious nepotism. Meaning its in your interest to question them because its all in the family. Its literary run by like male heirs lolif you work there they seriously expect your kids to work there too

author: Simon
author_rank: Unknown
timestamp: August 23, 2024, 06:40:47 am
content: Quote from: tszaboo on August 22, 2024, 10:26:27 pmOh no, nearly the same rules. When we started you got 60p/kWh for everything you generated even if you used it, that was over subscribed and it then came down to 1.6p/kWh for new installs. I got in at my last house with 4p/kWh. They paid for what we exported at 6p/kWh so you got a 4p bonus for using your own and 10p for net export.That is all over now and it is net metering of export at around 15p/kWh, my supplier gives me 16.5p as I also buy from them.

author: tszaboo
author_rank: Super Contributor
timestamp: August 23, 2024, 07:37:31 am
content: Quote from: Simon on August 23, 2024, 06:40:47 amNot nearly. I also get charged for export now. You heard that right.And that's not the point. The point is they are legally required to do net metering.And now solar panels are apparently responsible for everything. Lack of capacity on the supply (!), high prices, probably also world hunger and WW2.

author: Simon
author_rank: Unknown
timestamp: August 23, 2024, 01:26:06 pm
content: lots of governments made mistakes. In the UK they offered 60p when the buying cost to the consumer was 15p or less and this was for what you generated. Naturally anyone with money to invest jumped on it and in later years it became evident that they had not budgeted for the amount of people that would take it up. So they cut that bit to 1.6p and introduced the export tariff along side it and now it is export only.The reason there are all of these devices that for example dump electricity into heating water to stop you from exporting was for these wealthy people who not withanding getting 4x the actual value of the electricity sought to make sure that none of it was exported. Where they could heat water at 1/4 the price with gas they instead heated the water with electricity they were paid for, meanwhile the grid was being run by gas fired power stations.So companies like myenergy who claim to make green energy products are just a bunch of liars fueled by the money of the middle class that even when paid 4x what something is worth still won't supply it.

author: Marco
author_rank: Super Contributor
timestamp: August 23, 2024, 03:00:12 pm
content: Quote from: nctnico on August 22, 2024, 08:56:21 pmIt is the method of last resort to turn off otherwise uncontrolled small generators when there is too much power for consumption&transport.If the cut off voltages were lower it could have been used as a more routine way to add control, now if they want automated control it will become a very expensive retrofit.

author: tszaboo
author_rank: Super Contributor
timestamp: August 23, 2024, 03:03:59 pm
content: Quote from: Simon on August 23, 2024, 01:26:06 pmVery true. I heard stories of Spanish people running diesel generators in their basement overnight because it was worth it.Or the other end, Hungary introduced an extra tax on solar panels because they have to be disposed at some point.There are two things I'm a bit upset about. One is the lying about the technology, that is apparently so abundant and believable, that even engineers repeat these.In 2017 in Belgium I was working at a company that was monitoring solar panel installations, and trading green certificates. We were actively monitoring the "too much production" issue and conceded that abut 5% of our customers were effected, about 50 EUR/year loss of their production. We also worked on the mathematics and physics behind the grid. The idea behind it was that we could (with external communication) force inverters to generate some (the correct amount ) reactive power into the grid, that provides a very cheap way to compensate the reactive currents of large industrial installations.We were also running some projects that would time the usage to the generation, with estimated 3% capacity savings nation wide. Doesn't sound like much, but that's a cost of a power plant right there.Anyway, that's when an university professor showed the mathematics, on how "too much solar" is impossible. It's more complicated, but the basics are really just Ohm's law, with more current there is more voltage.Anyway, fast forward some time, Belgian government cuts incentive for solar power and re-introduces it for coal power. Their policies (and the bad management of that company) ultimately put us out of business. So I have an axe to grind about bad policies and lying about solar.

author: Simon
author_rank: Unknown
timestamp: August 23, 2024, 04:25:54 pm
content: You are talking about the smart grid. Having made an utter mess of "smart" meters governments have still not learnt and are letting private businesses battle it out to see who wins rather than just set up a committee and get a technical standard hammered out so that companies large and small can offer their products and ideas and things move faster without a single company monopoly.I have in fact wondered about setting inverters to output slightly more than a power factor of 1 to help balance the grid. Obviously this cannot be the sole solution or we are back to having much more current flow on the grid than the wiring can take but distributed generators that supply a power factor over unity would be manageable locally and lots of local systems being better balanced would make a big difference to the main grid backbone.

author: johansen
author_rank: Super Contributor
timestamp: August 23, 2024, 04:49:13 pm
content: Quote from: Simon on August 23, 2024, 04:25:54 pmprogramming in a fixed power factor of 1.05 or 1.1 only offsets the amount of capacitors needed to compensate, it doesn't do anything else.where i live, 100KVA capacitors can occasionally be seen on power poles, to cancel out the inductance of the powerline, or reduce the amps a little due to say, 0.9 powerfactor of homes these days (probably used to be worse) . 100 kva is only 10 amps at 12700 volts or 22uf (granted actual values are different as there are three capacitors at 7200v line to ground. those capacitors last decades, and have very, very low losses.my guess is, a solar farm at 100% amperer output delivering 1.5 power factor (ltes say the solar energy input is at 70% and the current is at 100% so that's 70% reactive power plus 70% real power means 100% amps output..lets say you run the solar farm at 100% current all the time regardless of solar incident energy. What is the cost to the inverter's life? lets assume power flow stays positive at all times (it would be 2% negative, at night to offset losses of reactive power production.) -the solar operator is going to want to get paid for the 2% reduced production caused by the increased losses in the inverters.my guess is, its not worth it.now, if the utility has control over the inverter's power factor.. it will help with short term voltage control (due to the inductance of the transmission line and the varying load in the nearby location).. but it will not control the power or the frequency, as the solar farms are always delivering 100% of what they can, unless they are contractually or actively limited by the grid operator "somehow".in otherwords, the dynamic power factor control may be able to be used to increase the life of tap changers... but that's about it.that.. "somehow" is the problem and the solution. everyone wants to make the most amount of money possible, but the grid demand is fixed, unless dynamic price lowering can increase consumption.

author: johansen
author_rank: Super Contributor
timestamp: August 23, 2024, 05:08:50 pm
content: Quote from: Marco on August 22, 2024, 12:24:20 pmthis can work for controlling micro grids, when the frequency is fixed by a central fixed battery inverter, and when you can tolerate a much wider swing in voltage.the power grid isn't controlled by voltage its controlled by very complicated agreements between power producers as to who is going to generate x amount based on y price. and they all mutually work to keep the frequency constant, although there could be bad behavior by certain producers intentionally to destabilize the grid but i think they would quickly lose money trying that.there is no massive battery to keep the frequency fixed, so if power in>power out, frequency rises. voltage doesn't always rise or fall. voltage can fall and current increases while the frequency increases and total power increases.in america, perhaps not now but 10 years ago, half of the power grid's load was induction motors over 100 hp. as more and more loads switch to VFD driven machines, the load will stay constant regardless of the grid voltage, or frequency (within 10% limits)a direct online induction motor: when the voltage rises, current goes down.. power factor goes up, which means the generators don't need as much excitation to produce the same power. its a closely regulated dynamic problem that is not intrinsically stable. when the frequency rises, the load increases. significantly. as in 1% increase in frequency is a 3% increase in load for most large pumps. the effect of that is a significant stabilizer.a 230v motor may draw 12.5 amps full load at 87% power factor at 93% efficiency. when the voltage drops to 208, that motor will draw 15 amps at around 83% power factor and 89% efficiency.as much less of the power grid is resistive loads, which decrease in current as voltage goes down, and much more of the grid is fixed power loads due to all the electronic drives.. the grid is going to become less and less stable.

author: Marco
author_rank: Super Contributor
timestamp: August 23, 2024, 05:16:07 pm
content: Rooftop solar for the moment isn't controlled at all, except for by voltage ... and adding any other sort of control is expensive.

author: nctnico
author_rank: Super Contributor
timestamp: August 23, 2024, 05:19:47 pm
content: Quote from: tszaboo on August 23, 2024, 03:03:59 pmI'm missing one important element in this story: does the grid have the capacity to transport the electricity where it needs to go? If you look closely at your electricity bill, you'll see a significant amount of money goes into transport costs already; for a household the transport costs can be 50%. IOW: it makes no sense to transport electricity far away if that means the transport costs are going to dominate the price per kWh.

author: Simon
author_rank: Unknown
timestamp: August 23, 2024, 05:25:08 pm
content: correct, micro generation is actually quite good. If you distribute generation to match consumption there is little transport, but this is hard work which is why there will always be a grid but with plenty of distributed generation the effective capacity of the current infrastructure is extended.

author: Zero999
author_rank: Super Contributor
timestamp: August 23, 2024, 05:36:57 pm
content: Quote from: Marco on August 22, 2024, 12:24:20 pmBecause they would get a huge number of returns, as it's very common for the mains to be a higher voltage than 243V. Where I work, the mains voltage regularly exceeds 253V, so this would be unacceptable.

author: Simon
author_rank: Unknown
timestamp: August 23, 2024, 05:53:34 pm
content: Quote from: Zero999 on August 23, 2024, 05:36:57 pmIt's what some dick head at myenergy did with the zappi, in the end mine was replaced. The fuckheads based everything on 230V totally ignoring that much of the country is still on 240V substations. Why on earth we would turn everything down I don't know, I prefer my extra 5%, it means 5% less current required so less than 95% of the usual power transfer losses. My old house was easily at 254V overnight. where I am now is a fairly stable 230V

author: tszaboo
author_rank: Super Contributor
timestamp: August 23, 2024, 06:03:25 pm
content: Quote from: nctnico on August 23, 2024, 05:19:47 pmIf it doestn't the voltage goes up and the generation stops.But you have to look at the two issues separately. The grid needs improvement anyway, because our load went up because of electric cars. Having more generation capacity is never bad. Worst case is that you cannot utilize the capacity and inverters are switched off because of that.When I look at the electricity bill, I think it's 3 cent/KWh is the grid, 13.5 cent taxes, and 9 cent is the electricity price.What you are talking about is the fixed costs: leasing you the smart meter (quite a scam), operating the network, making sure they walk away with 1.2 billion EUR profit for 2022 (Enexis) and then complain that they have to spend money on the network. I genuinely don't know why the DSOs are a for profit organization.

author: Zero999
author_rank: Super Contributor
timestamp: August 23, 2024, 06:59:53 pm
content: Quote from: Simon on August 23, 2024, 05:53:34 pmIt depends, sometimes a slightly higher voltage is better, sometimes not i.e. when it's powering a linear regulator, which is the case for most LED lamps.

author: Siwastaja
author_rank: Super Contributor
timestamp: August 24, 2024, 10:09:55 am
content: Quote from: Marco on August 23, 2024, 05:16:07 pmIt is also controlled by frequency.QuoteCompared to the expense of solar installation itself, not that much, but of course, what is "expensive" is subjective. But so far, there has been no need, and despite monthly nutjob panic threads on eevblog forum, nothing bad has happened even though some kind of disaster or collapse has been "just right around the corner" for years.

author: nctnico
author_rank: Super Contributor
timestamp: August 24, 2024, 10:14:40 am
content: Quote from: Siwastaja on August 24, 2024, 10:09:55 amIt means adding a couple of hundred euro of installation costs (hardware, wiring, configuration). And operating & maintaining the control system at the energy grid's end isn't free either. So there are extra one-time costs and recurring costs and all eat into the ROI of the solar panels.

author: Siwastaja
author_rank: Super Contributor
timestamp: August 24, 2024, 10:38:47 am
content: Quote from: nctnico on August 24, 2024, 10:14:40 amThat's right; including the biggest cost item (at least here), namely sales, it's even more than just a couple of hundred. Our box for example could control solar inverters (just that currently we justmonitorPV-only inverters, andcontrolbattery hybrid inverters), but it does cost something to install and operate. People are happily buying it, and paying us a smallish annual fee for the service, because it allows increase of solar self use by controlling their loads, too. It pays back for itself and shortens the ROI actually in most customer cases. In those where it does not, we don't recommend buying it.So far we don't control anything based on grid operator input (control based on customer's own needs is still the primary way to operate as it produces direct cost savings to customer) but this would be under discussion sometime in the future. Though, then again, the priority order is obvious: if there are any loads to turn on, this is done before reducing PV production.But sure, we already have some negative priced hours. For example, right now, -0.01€/kWh. Add transmission fee (e.g. 0.08€/kWh) and it makes a lot of sense to self-use that energy instead of turning the inverter off.Luckily, or almost magically, Finnish governments have somehow forgot to ruin the PV market. No subsidies, no weird artificial pricing models.

author: Someone
author_rank: Super Contributor
timestamp: August 24, 2024, 11:01:24 am
content: Quote from: nctnico on August 24, 2024, 10:14:40 amComplete bollocks, what is needed to be added to current residential inverters that would cost that much?https://www.eevblog.com/forum/renewable-energy/stability-of-grids-with-a-high-percentage-of-asynchronous-sourcing/msg5580399/#msg5580399Stability and control can be had for zero hardware cost, just some software and administrative changes. Only if the grid was 100% residential solar inverters (obviously impractical and never going to happen) would any overlaid control channel beyond frequency be needed, and thats only IF there was a desire to maintain long term frequency accuracy (which few grids around the world bother with).Or is this going to become another of your throwaway inflammatory "points" which are entirely misleading without the corner case framing and unbelievable conditionals you do not include.

author: Siwastaja
author_rank: Super Contributor
timestamp: August 24, 2024, 11:05:20 am
content: Quote from: Someone on August 24, 2024, 11:01:24 amnctnico is building on the premise that somehow these control devices would need to be retrofitted on existing inverters. It's an interesting scenario to discuss, but let's indeed remember that there is no basis for the idea that any of this would benecessary. Even if there was some sort of magical point after which there is too much PV and it needs some new type of control, this additional control would then apply to new installs.As for centralized remote control, many of the inverters actually installed here are already internet-connected, in the cloud services of the Chinese manufacturers. The WiFi connectivity stick costs some tens of euros extra. This is so that installers can remotely monitor the performance or fault codes of the inverter if the customer has any problems or calls back.

author: Someone
author_rank: Super Contributor
timestamp: August 24, 2024, 11:33:59 am
content: Quote from: Siwastaja on August 24, 2024, 11:05:20 amSeems like the usual not saying what they actually mean and leaving a standalone misleading claim that is likely to be taken out of context. Especially when you go back to the full quote that started the tower:Quote from: Marco on August 23, 2024, 05:16:07 pmVoltage and frequency are both controlling current (residential and almost all commercial) rooftop solar. Adding some finesse with a droop control would be trivial software change, and what should be relatively non-controversial administrative change.

author: Siwastaja
author_rank: Super Contributor
timestamp: August 24, 2024, 11:48:14 am
content: Quote from: Someone on August 24, 2024, 11:33:59 amHaving gone through the control parameter / modbus listings of the all popular (most cheap Chinese) inverters sold within 2-3 last years, it seems they are pretty capable to be programmed in most kinds of frequency/voltage control curves one could imagine. So for new units, all that is needed is an administrative decision of the exact parameters that are desirable, and manufacturer will most definitely program them as default settings for the given country code, free of cost as part of their normal operation.If anyone wants to update the old units on the field with new parameters, for which I don't see much reason to, a reprogramming modbus dongle supporting the 10 most common inverter models can be easily done and then a service technician can just go, plug it, reprogram and leave in 5 minutes.But currently, pretty crudely set on/off limits based on frequency and voltage seem to work quite fine.

author: nctnico
author_rank: Super Contributor
timestamp: August 24, 2024, 01:22:52 pm
content: Quote from: Someone on August 24, 2024, 11:01:24 amOver here you need to pay someone to get work done. So someone has to come over, install an extra interface box to add control to the inverter, bring wiring from the inverter to the distribution panel to measure the current between home & grid, configure the system, check whether it is working locally and has connection to the grid operator. And then someone needs to monitor the system at the grid operator's end. Unless someone works for free, this easely adds up to a couple of hundred euro in workmanship alone. And this has nothing to do with grid stability but the case where solar panels produce too much energy for the grid to handle (and with 'the grid' I mean the section of the grid that is affected by having excess energy). And despite you thinking voltage & frequency can be used to control solar inverters, this isn't the case for the situation what started this topic. The grid operator in this case is looking at way to shutdown solar inverters remotely.Just some example on how labour intensive it is to install extra boxes & infrastructure in people's homes: When I got glass fiber installed, it took 3 people 45 minutes to get the job done. And all they did was feed in the fiber through the crawl space, mount a box in the utility closet and splice fibers together. Including travel time, planning & making appointments, this adds up to large amounts of money just in labour alone. Similar story when I had remote monitoring on district heating installed. It took the guy close to an hour even though I already prepared a mains outlet. Otherwise he would have had to install that as well.Edit: come to think of it: frequency control can never work in a country or continent wide interconnected grid as the frequency would need to be adjusted grid wide. This while controlling production & consumption are bound to locations needing a local control method. With frequency control, one part of the grid would need to go higher and one part would need to go lower. It just won't work. So what is left are remote control or voltage.

author: Siwastaja
author_rank: Super Contributor
timestamp: August 24, 2024, 06:40:52 pm
content: Quote from: nctnico on August 24, 2024, 01:22:52 pmNo, no oneneedsto come over. If you want extra features, then you will pay for them, obviously. It is very highly unlikely that anyone would force you to buy a box you describe. Burden of proof for that idea is on you.

author: nctnico
author_rank: Super Contributor
timestamp: August 24, 2024, 06:52:14 pm
content: Quote from: Siwastaja on August 24, 2024, 06:40:52 pmWell, I needed to have a smart meter installed. And more recently a joule meter for district heating. I need neither but the energy supplier mandated these and I'm sure I'm paying for these boxes!

author: Siwastaja
author_rank: Super Contributor
timestamp: August 24, 2024, 07:03:29 pm
content: Quote from: nctnico on August 24, 2024, 06:52:14 pmAnd I have had a water meter replaced and indeed we customers are paying the bill!Indeed, there is nothing weird or surprising on these devices, metering electricity, heat, water, gas etc. has been there since these consumables have been sold, and sure the consumer is paying the bill finally. And these metering devices have a technical lifetime so they are replaced every now and then.However, there is still no proof for the claim that existing PV installations need a control box you describe. Sure, if such need arises, I would agree that the end user finally pays it as part ofsomething, but so far it's quite a far-fetched idea. OP's delirium is not a proof of anything.One thing is sure, if a utility arranges an addition of a box or meter swap, it's going to be a very efficient operation. I know this is at least the case with electricity meters here. It happens every 10-20 years and the time per customer is extremely short.

author: tszaboo
author_rank: Super Contributor
timestamp: August 24, 2024, 09:41:27 pm
content: Quote from: Someone on August 24, 2024, 11:01:24 amI worked on a device like that. It was a DIN rail mounted Linux computer, with GSM module. That's completely unnecessary and very expensive for what it needs to do. Since it's DIN rail, and RS485/Modbus port is not plug and play, an electrician has to go on site to install it. The issue with WIFI is that commissioning is very unreliable because firewall settings, changing modems, and so on. Constant ringing phones of the customer service. So someone going on site, installing a whatever, opening the inverter to bring out some cables... Few hundred EUR is a good estimate.Or you can rely on customers maintaining the wifi connection over 25 years. And then the inverter needs to open TCP communication because ports are closed on routers.Someone should go back in time and mandate a powerline communication protocol for the inverters.

author: nctnico
author_rank: Super Contributor
timestamp: August 24, 2024, 10:22:27 pm
content: All devices that need communication with utility operators use a mobile link. They are not going to rely on infrastructure that may or may not be available at the customer.

author: Someone
author_rank: Super Contributor
timestamp: August 24, 2024, 10:26:55 pm
content: Quote from: nctnico on August 24, 2024, 06:52:14 pmA smart meter, ORLY. So in that case you already have a precision current meter. Which makes this layers of bullshit:Quote from: nctnico on August 24, 2024, 01:22:52 pmQuote from: nctnico on August 24, 2024, 01:22:52 pmJust like the grid operators control existing loads and generators, by frequency.Quote from: nctnico on August 24, 2024, 01:22:52 pmThis is more of your unstated requirements. IF you insist on long term integral error approaching zero, that is trivially handled by directing other (already remotely controllable) generators or loads to change their set points and slowly drift the frequency average back. It does not require every single participant to be centrally controlled or directed. Which I have already clearly stated in this thread, and in the previous threads:Quote from: Someone on August 24, 2024, 11:01:24 amOr are you now trying to claim transmission congestion must be solved by adding centralised control to ALL small generators? Because you just make bold claims that are unexplained and impossible to understand their framing. It is unlikely that residential rooftop solar will ever reach the share of production that would mandate it to have such intelligence and complexity at every single instance. Given smart meters (usually) have zigbee for bidirectional communication to/from the distribution/grid operator most of the infrastructure is already in place for all these nice-to-have things, at trivial incremental (or real) cost.

author: Someone
author_rank: Super Contributor
timestamp: August 24, 2024, 10:35:13 pm
content: Quote from: tszaboo on August 24, 2024, 09:41:27 pmAgree that additional box(es) and configuration, communication, maintenance, etc would be uneconomic. Which is why I keep pointing out that is the wrong solution, and it is not the only way co-ordinated control can be added to small scale generation.What do most solar installs already have? A box with the DC->mains inverter, and a smart meter. Between those two units they already have the collection of hardware, compute, and communication resources needed to solve the problems of inertia, FCAS, dispatch, etc. What's missing is the incentive to make that mass-market where the administrative+software costs then disappear into some trivial amount due to the volume.

author: tszaboo
author_rank: Super Contributor
timestamp: August 25, 2024, 11:40:15 am
content: Quote from: Someone on August 24, 2024, 10:35:13 pmThey do have that, at least here almost everyone has smart meters. The inverters are only connected to Wifi, so it's not really reliable. That aside, I think you are trying to solve the wrong problem.The issue we see is that too much solar power is sold on the spot market. The price of electricity is either positive or negative on the spot market.More solar should be sold on the day-ahead market. The price is almost never negative on the day-ahead market. And when it does, it's good, incentivizes to install energy storage.Also utility scale solar, and wind can very effectively react to changes in the daily weather. And they can do that without shutting down small scale solar installations with overvoltage. I see wind generators regularly shut down, because there is an even cheaper source of electricity. Issue is that they still seem to be profitable to operate because (unlike home owners) they receive subsidy even with negative prices. So they sell electricity because they receive ~150 EUR/MWh because it's green. They are going to sell at -10c/kWh because there is stil lprofit in that. Again, bad regulation.We also started having dynamic contracts, where electricity is priced on the hourly rate. People can charge their cars for next to nothing who have these contracts and smart charger.

author: Marco
author_rank: Super Contributor
timestamp: August 25, 2024, 02:04:16 pm
content: Quote from: Someone on August 24, 2024, 11:33:59 amAs far as I know there is no cross EU standard for power frequency control and even if there was you can't use it to control local power, which is what is needed. Frequency control is for the traditional system without large local imbalances by design.You need power voltage control, so you can "just" change local taps on the distribution transformers, or direct remote control.QuoteExcept for all the ones not internet connected, from bankrupt companies and no longer for sale (for enough money they will modify them, but it will take money) and there is the problem of interaction with storage systems.

author: nctnico
author_rank: Super Contributor
timestamp: August 25, 2024, 02:14:11 pm
content: Quote from: Marco on August 25, 2024, 02:04:16 pmAgreed. Country / continent wide electricity grids are like a bunch of barrels filled with water connected by tubes. A barrel being emptied or filled quicker (both conditions can happen at the same time in different places!) than the tubes can keep up with to equalise water levels, needs a local solution because it is a local problem.

author: Siwastaja
author_rank: Super Contributor
timestamp: August 25, 2024, 06:28:06 pm
content: Of course countries have different pricing models because transmission links between countries are limited. Sometimes even within countries, e.g. in Northern Sweden there is often nearly excess generation, all of which can't be transferred to Southern Sweden, therefore two pricing regions for the Nordpool market for a single country, and the 1000MW (or so) link with Northern Finland being directed into Finland most of the time, at least during winter.This is allnormal, not some kind of new catastrophic problem, and it actually has not much to do with PV at all, even less with household generated PV. Improving the weakest links of grid, including those between countries, would be a pretty sane thing to do as that would enable even better use of renewables when there is excess.But nctnico would make an excellent clickbait journalist, for whom every normal thing is some kind of huge problem.And I'm sure the "solution" to these "problems" is hydrogen and solar roadways.

author: Marco
author_rank: Super Contributor
timestamp: August 25, 2024, 07:43:59 pm
content: It's enough of a problem for pilot schemes to pay people to take their rooftop PV offline in my country ... so it's a real problem in my country, they don't hand out money out of charity.A problem caused by poor planning no doubt, but a problem all the same.

author: Someone
author_rank: Super Contributor
timestamp: August 25, 2024, 10:44:35 pm
content: Quote from: tszaboo on August 25, 2024, 11:40:15 amI'm trying to solve the wrong problem? You and nctnico are walking off into the hills arguing there is an (unreasonable) cost to retrofit existing installs. Took us a while to actually add all these conditions which are not part of what was said initially.Siwastaja and I keep pointing out that this is not some extreme cost for future installs, there is no significant problem or challenge to adding these (allegedly necessary) functions going forward.

author: Someone
author_rank: Super Contributor
timestamp: August 25, 2024, 11:06:25 pm
content: Quote from: Marco on August 25, 2024, 02:04:16 pmJoining in with the backwards looking crowd?Frequency control, albeit an abrupt and clunky one just like the voltage limits, is already in place. Or are you trying to claim that inverters will free run out in frequency? That does not solve local control to combat congestion, but it does exist.Lets go back to your original question:Quote from: Marco on August 22, 2024, 12:24:20 pmTap changers are rarely on small enough segments to adequately tame residential solar so I doubt it is as simple as you say. One way to look at this problem is that the grid was designed around end consumers never producing. Adding production equal to worst case consumption would need a doubling of the transmission infrastructure on those legs/segments.Why is the residential inverter cutoff right up against the maximum? To ensure that as much solar as possible enters the grid. This is by design. Who should pay for the extra infrastructure these new generators are requiring? I'd say that should be on the people adding this new requirement but for sure that created noise by the people who want to continue with their free ride and profit.In theory transmission operators/owners were supposed to have limited solar installs to what could be adequately supported. In Australia people were denied permits to install solar as the congestion was already too high.Going forwardthis can be addressed by having inverters participate in the grid like the larger generators do, rather than their dumb "pour it all out until maximum voltage or frequency is reached" control law they currently employ. Droop control is a good start, and then add in adjustable set points on a granular basis (right down to the individual unit) and all these "problems" are gone.Adding tap changers around the network, vs mandating smart meter and inverter pairs talk to each other. I'm pretty sure which one of those is cheaper. Why keep trying to add more complexity and hardware to the system when the functionality is already sitting there unused.There is no need for internet connection, smart meters already provide the two way back haul and is within/controlled by the distribution operator. That just needs a standard and mandated power control connection/interface with inverters. Doesn't matter if companies go bankrupt if the access is standardised (and not through some proprietary server).

author: nctnico
author_rank: Super Contributor
timestamp: August 25, 2024, 11:12:35 pm
content: Quote from: Someone on August 25, 2024, 11:06:25 pmKeep on dreaming for the next decade. Meanwhile the real world is going for solutions which are actually achievable within the timeframe the solutions are needed. For now that is turning solar inverters off manually. Next step is adding a box to do it remotely. Likely this is a simple remote controlled relay which disconnects the circuit the solar inverter is on.

author: Someone
author_rank: Super Contributor
timestamp: August 25, 2024, 11:23:17 pm
content: Quote from: nctnico on August 25, 2024, 11:12:35 pmOk, then stop complaining about the cost being pushed onto you as the owner of the generator.We already have the standards in place for the majority of this, it is not some big leap.

author: Marco
author_rank: Super Contributor
timestamp: August 26, 2024, 01:15:58 am
content: Hmmm, Solar Edge seems to have support for voltage dependent power regulation in their newer inverters.Is that just forward looking, or are there some countries which require it? An alternative to tap changing would be fast adjustable tank circuits to drop voltage.

author: johansen
author_rank: Super Contributor
timestamp: August 26, 2024, 05:05:28 pm
content: Quote from: Marco on August 26, 2024, 01:15:58 amplease explain how that works, and how much it costs.

author: Marco
author_rank: Super Contributor
timestamp: August 26, 2024, 06:56:16 pm
content: https://www.ausgrid.com.au/About-Us/Future-Grid/Innovation-Portfolio/STATCOM-Low-Voltage-RegulationCost, no idea.

author: Marco
author_rank: Super Contributor
timestamp: August 27, 2024, 11:38:51 am
content: Oh, I see. Australia has already mandated volt watt control since 2020.That explains why it is in the inverters and why Australia is experimenting with statcoms on the low voltage level, though they are a bit coy about the fact it can be used for gradual curtailment.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: September 05, 2024, 09:03:51 pm
content: Quote from: Marco on August 22, 2024, 12:24:20 pmThe problem in the Netherlands started some 20 or 30 years ago. Somewhere in between privatisation and government meddling investment in the distribution part of the grid got left behind. And as a result there are now a bunch of locations where there simply is not enough capacity to handle the amount of energy pumped into the grid. So as a result, whenever there are moments that there is more solar power then the local grid can handle, they just let the voltage be pushed upward until the enough of the solar installations reach the maximum allowed limit and turn themselves off.And at the moment, I don't know how much factories we have that can make new transformers and high voltage pylons, but I assume production capacity is limited. I would vote to sent to Ukraine whatever stuff they need to keep up a grid that is somewhat working, compared with putting some extra money into the pockets of people here who are rich enough already. Even if that stuff gets bombed into smithereens in a few months.

author: Siwastaja
author_rank: Super Contributor
timestamp: September 06, 2024, 08:27:03 am
content: Quote from: Doctorandus_P on September 05, 2024, 09:03:51 pmThe technical problem is the historical asymmetry being replaced with modern symmetry. It was tempting (and obvious) to save cost on copper or improvement work by just changing to higher transformer tap when neighborhoods started to consume more; as long as zero consumption voltage is below legal maximum, everything is fine, and this gives more margin for voltage drop while still staying above legal minimum at full load.But with introduction of PV, zero-load voltage cannot be biased at maximum, otherwise production drops out during combination of high production and low use.The solution to this is normal management of things. It sounds like you have a chaos in place. Here this problem is nearly absent due to two things:1) even the last mile is probably better maintained and lower impedance, so tap switching for higher voltages did not go too far,2) authorities / grid operators have decent idea of the status of the grid, including the last distribution piece, so they deny permits completely, or give permit to a smaller system if there is already too much PV locallySolution to inverters dropping out due to overvoltage is,1) Improve distribution when it is economically viable to do so: e.g., if a renovation is scheduled in near future anyway, if power quality is poor anyway (as it is often the case, inverters dropping out being just the final straw), and if the work is not overly expensive at that location2) When improvements are overly expensive, do not give permits to large PV systems. You can still pretty safely let people install say 3-4 kWp system on their roofs, the popular size some 5-10 years ago, great because it is easier to self-use this power and self-use is more valuable. Small string inverters are still available, and cheap, you don't have to do a 10kWp system just because that's the trend.3) Mandating volt-watt control would be a good idea as it responds more softly, and most importantly, fairly so that it's not always just one poor guy who's inverter drops out first.

author: tszaboo
author_rank: Super Contributor
timestamp: September 07, 2024, 09:37:43 am
content: So in an effort to gather some data I started plotting the line voltage measured by the inverter. 2 days ago we had a sunny day, my system was working at 75% of it's nameplate capacity. The voltage peak for the day was 245V. Yesterday, the inverter had very little work, 1/3rd of nameplate, the same peak was 238V. While I was checking the settings, I noticed that "Power limit" is reported, which might be interesting to look at as well. In any case, since we are already in September, I don't think that we will see clipping of power this year.