Deye PV microinverters lack a safety relay (EU) - Page 1
Forum section: electronics / general

author: madires
author_rank: Super Contributor
timestamp: July 19, 2023, 09:04:48 am
content: RelayGate: Deye Solar Microinverters Lack Essential Part (https://www.heise.de/news/RelayGate-Deye-Solar-Microinverters-Lack-Essential-Part-9220307.html)TL;DR:- they got their microinverters certified with the required safety relay- sold tons of microinverters without the relay (more profit, 400k+ inverters sold in Germany)- someone opened an inverter and noticed, others checked too- big oopsie

author: Marco
author_rank: Super Contributor
timestamp: July 19, 2023, 10:05:16 am
content: Pre-bankruptcy trickery incoming, regulators need to immediately freeze their assets and warehouse stock.PS. Deye's explanation is so much bullshit, they knew they needed redundant disconnect and doubling up on active switches is hardly an option. Relays are the only real option.

author: fourtytwo42
author_rank: Super Contributor
timestamp: July 19, 2023, 10:11:41 am
content: Interesting but not unusual, many times I have disassembled noisy (from an EMC perspective) power supplies and found the grid side EMC filter components missing and bridged out even though they carry CE labels.

author: madires
author_rank: Super Contributor
timestamp: July 20, 2023, 01:26:41 pm
content: Anker also (MI60 inverters):Balcony power plant manufacturer reacts: First inverter replacement begins (https://samagame.com/en/live/balcony-power-plant-manufacturer-reacts-first-inverter-replacement-begins/)

author: Kleinstein
author_rank: Super Contributor
timestamp: July 20, 2023, 04:39:23 pm
content: AFAIK the extra relay is not required in all EU countries, though it looks like in Germany the relay is required. The pictures of the internals show a signnificant filter capacitance on the intermediate voltage level and thus they should need some extra method to turn off - just the semiconductors is not enough there. In most cases they turn off OK and nothing happens, but I see 2 scenarios where the more software based mechanism can fail:1) during / after grid down a voltage transient damages semiconductors of the inverter and this way connects the charged filter capacitor (e.g. some 10-100 µF) to the grid side.2) after disconnection a strong ESD even damages the semiconductors and this way connect the filter capacitors that still hold charge for quite some time after disconnect.The main problem seems to be a large Chinese company that seem to be willing to fix the problem (exchance or deliver extra relay boxes) - this time is does not look like the disapear or bankrupt if get caught scheme. Not taking the regulations seriously also happend to a German car manufacturer.Hardware with EMI filtering removed in later versions can be an issue. There could also be legit cases with the space for extra filtering included just in case or some version and they may meet the limits also with the reduced filter version. If they produce EMI problems and have the filter not populated this is of cause suspicous and a lower cost version should not have the CE lable removed as well.

author: Marco
author_rank: Super Contributor
timestamp: July 20, 2023, 05:33:41 pm
content: Quote from: Kleinstein on July 20, 2023, 04:39:23 pmEN 50549-1 requires single fault tolerance for the disconnect, would it count if you used inverting/SEPIC/Cuk for the boost circuit with an inactive boost circuit being one isolation and the inverter the other?With a normal boost circuit I don't see how you could get away without the relays.

author: switchabl
author_rank: Frequent Contributor
timestamp: July 20, 2023, 06:23:06 pm
content: If there is indeed a requirement to "disconnect" that strongly suggests a relay to me (but I don't have the standard).However, as far as I can tell, EN 50549-1 is not a harmonised standard, so it's not directly relevant to CE and enforcing it would still be a matter of national implementation.

author: uer166
author_rank: Super Contributor
timestamp: July 20, 2023, 07:32:52 pm
content: Usually a device that provides isolation in a normative sense is defined per some standard. I don't believe any kind of silicon can do it, and if you use a Sepic, it'll have to use caps that are rated as such (e.g. Y-caps for both forward and return).Usually the base standard will call out a specific relay, breaker, contactor, or switch standards that are acceptable for isolation.

author: f4eru
author_rank: Super Contributor
timestamp: July 20, 2023, 09:46:14 pm
content: This norm should be updated.Mandating relays is a nightmare, they are long term unreliable stuff that really needs to be phased out.the new version should limit itself to just a single failure resistant disabling, like everywhere in the machine directive.I have had, on a product in qty 20k/y, a relay contact consistently failing after a few months because of outgassing of a nearby plastic was contaminating the contacts....and a bunch of other random failures....in a safety impacted application.....

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 21, 2023, 02:45:28 am
content: If it's to disconnect in case a power semiconductor fails shorted, wouldn't a fuse do that automatically?

author: f4eru
author_rank: Super Contributor
timestamp: July 21, 2023, 06:13:40 am
content: Nope, it is for guaranteeing to stop in case of loss of mains.it's old style.

author: Kleinstein
author_rank: Super Contributor
timestamp: July 21, 2023, 06:24:44 am
content: Quote from: NiHaoMike on July 21, 2023, 02:45:28 amIn many cases yes, but not necessary when this happen just in the moment or after the mains connection is lost. The fuse would than need 2 failed semiconductors or a short on the output side.The moment when the grid connection is lost has a somewhat increased risk that there are voltage spikes, e.g. a spike from the grid side may cause a GFI to open.Under normal conditions the relay should not open or close under load. So I see no reason for the relay to wear out, even in decades of use. It is only of the relay is poorly build or choosen that it may be an issue. The same signal that detect the loss of grid connection will open the realy and stop the inverter circuit. Here the electronic part should stop before the realy actually opens. The main reason is to make sure the mains part is safely isolated from the energy stored in the intermediate voltage (e.g. some 400 V) capacitors. For fixed istallations I would have no real problem for allowing a little longer to get a reliable discharge of the capacitor(s) instead of the relay. For the plug in types this may not be fast enough.Those small plug in PV installation are a stupid idea anyway: they produce not much energy as they often work at poor locations and the costs are relatively high for the rather low power. The only reason why they may in some cases are profitable is because of the billing system, not because of the real value they provide. Shifting money from one person to the other could be done more efficiently with less EMI and safty risks.

author: Marco
author_rank: Super Contributor
timestamp: July 21, 2023, 06:29:13 am
content: Quote from: f4eru on July 20, 2023, 09:46:14 pmHow are high voltage reed relays supposed to degrade? The contacts are hermetically sealed, the coil is potted, outside of failure modes it never switches current.

author: Kleinstein
author_rank: Super Contributor
timestamp: July 21, 2023, 06:38:14 am
content: This are not reed realys, but more "normal" (still seem to need some safety rating) relays.

author: f4eru
author_rank: Super Contributor
timestamp: July 21, 2023, 06:39:41 am
content: QuoteReed relays cannot cut the required spikes and powerQuoteYou seem to have no experience with reliability of relays in series products

author: Siwastaja
author_rank: Super Contributor
timestamp: July 21, 2023, 06:53:50 am
content: Besides, relays have the same failure mode as semiconductors, fail as short circuit. So just saying "relay is good" is cargo cult engineering. The relay has to be specifically engineered and well tested to provide the safety, even in presence of worst case currents and voltages. Exactly the same applies to semiconductor solutions!Now admittedly designing a reliable and safe semiconductor disconnect and proving it is more difficult - but not impossible. But in the end it might end up more expensive than the relay.

author: Marco
author_rank: Super Contributor
timestamp: July 21, 2023, 07:04:47 am
content: Quote from: f4eru on July 21, 2023, 06:39:41 amThat's just a question of money. You can buy anything in a hermetically sealed package if you pay.

author: Marco
author_rank: Super Contributor
timestamp: July 21, 2023, 07:10:58 am
content: Quote from: Siwastaja on July 21, 2023, 06:53:50 amIf it's to be redundant resistance is also a factor.

author: f4eru
author_rank: Super Contributor
timestamp: July 21, 2023, 07:23:21 am
content: Quote from: Marco on July 21, 2023, 07:04:47 amNope. Why do you think most power relays are NOT sealed ?It is because sealing also confines the outgassing and particles emanations of the sparking contacts, and contaminates the contact insulation, mechanical bearing surfaces and coils with abrasive conductive dust and other gassy nastyness, compromising the relay on the medium term...Sometimes, a sealed relay can fail faster than the same unsealed.

author: Marco
author_rank: Super Contributor
timestamp: July 21, 2023, 07:34:29 am
content: But how is that relevant in this particular situation? It's zero current switching under normal conditions. Apart from the temperature, it's ideal condition.Given the no single point of failure standard and size of the market, you'd expect purpose designed relays for consumer grid attached generators instead of having to rely on stuff made for appliances.

author: f4eru
author_rank: Super Contributor
timestamp: July 21, 2023, 07:45:00 am
content: Quote from: Marco on July 21, 2023, 06:29:13 amThe list of possible failures is very very long.It is a really big mistake to take relays as a simple coil'n'switch.Relay reliability and switching dynamics are a really very complex topic, also depending a lot on the environment, especially the source and load transient response and impedances.Even high end sealed HV relays fail, an example :https://www.spcd.space/proceedings/2018/1st%20Day/Lessons%20Learned%20and%20In-flight%20Experiences/Presentation/05.%20Relays%20Failures.pdfWhat is crazy is that even ESA could identify a root cause only for half of the observed relay failuresAnd they put in real means to try to get to the bottom of the rabbit hole.Quote from: Marco on July 21, 2023, 06:29:13 amWrong. An AC disconnect relay switches current on every cycle (1-5 per day in a solar inverter)The X and Y-capacitors will be charged by a high inrush current on every switch closing, typically a microsecond scale spike of 300A if the switch closes on the max AC peak.That erodes contacts, especially fine contacts that would not be engineered for high currents.If a DC-link cap is also charged at that moment, it becomes approx 100x worse.The effects, lifetime, and failures can never be fully validated and guaranteed, because of the random variation in cable length and inductance on the AC network, among others like mounting angle affecting spark rising......

author: Marco
author_rank: Super Contributor
timestamp: July 21, 2023, 09:02:30 am
content: Or you just switch on zero crossing.

author: madires
author_rank: Super Contributor
timestamp: July 21, 2023, 09:23:32 am
content: AFAIK, two contactors/relays in series are required. But for low power inverters it's tolerated when the switching bridge also does the job of one safety relay.

author: f4eru
author_rank: Super Contributor
timestamp: July 21, 2023, 09:24:45 am
content: Yep. Just another new can of worms.in short: nice try, but does not work either, because closing/opening time can vary over lifetime.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 21, 2023, 09:45:00 am
content: Quote from: Marco on July 21, 2023, 07:10:58 amRelays have a lot more resistance than people seem to assume, because the metal contacts can handle high temperatures and relays are large and thus have significant surface area for cooling. With a semiconductor solution, unless you want to design in a metal heatsink (no one wants, it's expensive and you need to think about mounting), you have to engineer it for less resistance than the relay solution.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 21, 2023, 09:47:34 am
content: Quote from: Marco on July 21, 2023, 07:34:29 amIt is well known that relays which switch rarely under load develop significantly higher contact resistance. Just right amount of sparking cleans the contacts. Too much and contacts wear, too little and they oxidize on their own.

author: Marco
author_rank: Super Contributor
timestamp: July 21, 2023, 09:53:20 am
content: Which goes back to making them hermetic, where there is a wallet there is a way.

author: f4eru
author_rank: Super Contributor
timestamp: July 21, 2023, 10:02:06 am
content: again: sealing does not work for power relays, due to self-contamination of the fumes released by the sparks (ozone, metal particles, etc...)Relays are like ICE engines:a complex system that is about fit for purpose since 160 years, but we did never kink out all the random failure modes (we still find new ones, high end or not), and is slowly going towards widespread obsolescence.Every time we make improvements, there are new modes of failure around the corner.

author: Uunoctium
author_rank: Frequent Contributor
timestamp: July 21, 2023, 10:16:04 am
content: Deye yesterday released an official statement on their homepage on that issue:In accordance with regulator (BNetzA) Deye urgent recommends users to disconnect these converters until a solution is certified.https://de.deyeinverter.com/news/company-news/aktuelle-information-zum-mikrowechselrichter-deye-sun600g3eu230-vor-bergehende-beh-rdlich-angeordnete-netztrennung.html

author: Uunoctium
author_rank: Frequent Contributor
timestamp: July 21, 2023, 10:24:02 am
content: At that page the second image shows internal of the affected converter(s).At upper right corner an current compensated choke was inserted instead of two 1pole relay.https://www.pv-magazine.de/2023/07/17/normenverstoss-bei-balkonsolar-mikrowechselrichtern-von-deye-fehlt-schutz-relais/Relay type is Hongfa HF115 acc to certificatehttps://www.hongfa.com/Product/Item/355

author: f4eru
author_rank: Super Contributor
timestamp: July 21, 2023, 10:31:20 am
content: It is really good to see them taking responsibility and getting towards a solutionThis affects all the legislative improvements that usergroups push for the light schuko-fed-in "balkonsolar" type PV installations.Now next step for the industry would be to update the norm to allow relaisless disabling.

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 21, 2023, 01:18:41 pm
content: The high current relays used in EV batteries are sealed with some special gas mixture, most obvious downside is the relatively high cost.Quote from: Kleinstein on July 21, 2023, 06:24:44 amIt looks like in that inverter design, the big capacitors are on the other side of the transformer and so the energy stored at high voltage would be relatively small.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 21, 2023, 02:22:40 pm
content: Quote from: f4eru on July 21, 2023, 10:31:20 amWithout reading that standard (but having some general idea about how standards work), I'm 95% sure it does not mandate the use of mechanical relay. Additionally, even if standard mandates it, remember that standards are not legal requirements; their existence is only so that if manufacturer demonstrates their product adheres to standard, then it will adhere to the law (and in case of harmonized standards, the laws of every EU member state), simplifying the process. Law itself is more generic, while standards describethe usual, tried and testedways of doing something. This means, if a given standard seemingly prevents a superior way of doing something, you can always deviate, that just requires even more rigorous proof. This is actually pretty common in innovative technology, because obviously a standard exists only after a certain way of doing something becomes mainstream. Before that happens, a designer has to find similar enough standards for some parts, and just prove their compliance to law without citing any standard for some novel parts.

author: Uunoctium
author_rank: Frequent Contributor
timestamp: July 21, 2023, 02:38:22 pm
content: It seems, there is no transformer in that design. The four big cores are storage chokes. Each 3,5µH and in my view they are belonging to primary step up converters to gerenate the intermediate voltage. H-bridge at output - done. So, how do they isolate panel inputs from mains?

author: Siwastaja
author_rank: Super Contributor
timestamp: July 21, 2023, 02:43:24 pm
content: Quote from: Uunoctium on July 21, 2023, 02:38:22 pmSolar inverters (string or micro) almost never isolate the panels from mains. That is not required, adds a lot of cost and reduces efficiency.

author: Jeroen3
author_rank: Super Contributor
timestamp: July 21, 2023, 03:07:36 pm
content: Yeah, it was funny viewing the german from balkonkraftwerk fuming from rage in his video.Though, the regulations are more complicated. For compliance the inverter doesn't need to have a relay. The installation must have. For the grid code.This is in basically all of Europe. Here they mandate a "scheider" or separator. Transistors are not a separator. Thus big inverters use a contactor for that. Space enough.Now I'm not sure if the regulation specific for inverters specifies any different, but that isn't a VDE, it would be an IEC.Microinverters cannot use any mechanical relays due to their IP rating and wide temperature range. It's not going to happen, there are no off the shelf relays for this use case.The worst part of this is Deye intentionally putting such relay inside the inverter, completing VDE 4105 certification, then removing the relay.They could just as well have validated the inverter without the relay with a stipulation that external automatic separator would be required.But they would have lost their edge to their competitor...Enphase for example sells the q-relay in europe which provides isolation in abnormal grid states.The q-relay also provides DC leakage current protection mandatory for PV systems. Even though Enphase uses isolation transformers, turning the changes of Dc fault to negligible..Most big inverter include DC leakage protection inside. (if they don't do this right you get theEaseesituation)I'm not sure if Deye has DC-leakage protection. If they don't users may need to install a pricey type B rcd.This isn't VDE 4105 I think, but at least in our installation code NEN 1010 derived from IEC 60364.Bottom line, they shouldn't have done this to Germans. It probably wouldn't have been a big issue in any other country.But Germans... they love their VDE.

author: bdunham7
author_rank: Super Contributor
timestamp: July 21, 2023, 03:10:49 pm
content: Quote from: Siwastaja on July 21, 2023, 02:22:40 pmI'm not intimately familiar with EU regulations and law, but I doubt legislators are going to write laws with detailed technical requirements. In jurisdictions I am initimately familiar with, this usually involves simply adopting a standard. Additional requirements and details relating to inspection and enforcement may be added, often by administrative authorities empowered by an enabling law. So most of the time you cannot deviate unless the relevant authority has some legal leeway to do so. Construction and fire protection are areas where you aren't going to get much wiggle room.QuoteI'd prefer mine isolated, thank you! I can't speak for all manufacturers, but Enphase inverters are all isolated by design and are 97%+ efficient. I'm not sure if this exempts them from some other requirements like the disconnect relay, but the standards that seem to be implicated are mentioned in this letter. I think proper isolation probably solves a few problems, one being that you really don't need a disconnect relay--even if they are mandated in certain areas.https://enphase.com/download/rcd-manufacturer-statement

author: f4eru
author_rank: Super Contributor
timestamp: July 24, 2023, 08:49:06 pm
content: Quote from: Siwastaja on July 21, 2023, 02:22:40 pmsomething something something ... physical disconnection.try to do that without a relayThe standard is outdated, and makes the inverters respecting it unnecessarily uncompetitive ....

author: bdunham7
author_rank: Super Contributor
timestamp: July 24, 2023, 09:02:36 pm
content: Quote from: f4eru on July 24, 2023, 08:49:06 pmIt's especially stupid when applied to inverters that have a HF transformer for isolation and I'd argue that the transformerisa physical disconnection. Sadly that view has not prevailed and EU customers are stuck with a less-reliable system that protects them against nothing.

author: Phoenix
author_rank: Frequent Contributor
timestamp: July 25, 2023, 04:27:08 am
content: I no longer have access to the standards as I've been out of the grid connect converter area for a little while now, so I could be out of date... but I will add a few things.VDE 4105 requires that either the device itself or installation has an "Interface Switch" that is triggered by the "Network and System protection (NS protection)".For the integrated switch case, all the inverter standards I am familiar with (IEC62109 series, AS4777 series, EN 50438, VDE4105), have essentially the same requirement for redundant disconnects:1. For isolated inverters - single mechanical disconnect and the semiconductor bridge2. For non-isolated inverters - dual redundant mechanical disconnectsIn both cases the integrity of the relays needs to be monitored, if they are stuck closed the converter can not operate.You can read some test reports to get an idea of what everyone is doing, and what the standards require without having them on hand:VDE4105An isolated microinverter with integrated NS protection (single 2 pole relay):https://www.photovoltaikforum.com/core/attachment/93544-envertech-vde-ar-n-4105-testreport-pdf/A non-isolated string inverter with dual relays operated by dual microcontrollers:https://solar-distribution.baywa-re.de/out/media/9-SUN2000_-_M2_SUN2000-8_10_12_15_17_20_M0_M2__VDE-AR-N_4105_Report_BV_Eng_2020.04.22.pdfEN 50438A non-isolated string inverter with dual relayshttps://voltaconsolar.com/DOWNLOAD-FILES/Hybrid%20Inverters/VOLTASOLAR%20SUPER%204KW%20PV170207N030_4K_EN50438_2013%20report_0.pdfsee section 4.6.3 regarding testing single relay defect and "shutdown device".An example of a stand alone network switch:https://www.dold.com/media/pdf/95/3d/77/RP9810_en.pdfQuote from: bdunham7The HF transformer is considered in the switch requirements - with a transformer only a single mechanical disconnect is required. It's not just EU; the requirements are basically equivalent in every place I am familiar. They key missing here is redundancy... the transformer has no redundancy as a physical disconnection.Quote from: SiwastajaEvery commercial micro-inverter I am aware of is isolated. Maybe I missed the evidence that the Deye was not isolated, but the construction looks 100% isolated to me (based on the linked youtube video - probably flyback). Thus they would only need a single relay per pole. I am not sure if microinverters MUST be isolated to meet IEC62109 as the PV side could be considered DVC-A (like SELV) and require isolation to the mains at DVC-C (hazardous) - I would need to read the standard again to confirm. It would be interesting if anyone can link a non-isolated microinverter.String inverters are largely non-isolated now - for obvious efficiency and cost reasons.

author: Jeroen3
author_rank: Super Contributor
timestamp: July 25, 2023, 07:23:08 am
content: I don't know, but VDE is quite clear about what it should have.Quote from: VDE 4105 (2011) (google translated)Dutch grid code (actual law) also uses the word "separator", imho mosfets are not a "separator".Quote from: bdunham7 on July 21, 2023, 03:10:49 pmYou'd be surprised how much technical details, limits and maths is defined in energy laws. A harmonised european synchronous grid must require this I think.

author: nctnico
author_rank: Super Contributor
timestamp: July 25, 2023, 09:36:57 pm
content: Quote from: madires on July 19, 2023, 09:04:48 amAFAIK this is pretty common. For the Enphase microinverters you'll also need an external relay box between the microinverters and the grid connection in order to comply with regulations.

author: nctnico
author_rank: Super Contributor
timestamp: July 25, 2023, 09:48:48 pm
content: Quote from: Siwastaja on July 21, 2023, 02:22:40 pmIn most cases they actually are legal requirements. Just look at laws that define building codes which then refer to electrical and other safety standards as being mandatory for compliance.

author: Phoenix
author_rank: Frequent Contributor
timestamp: July 26, 2023, 04:11:32 am
content: Quote from: nctnico on July 25, 2023, 09:36:57 pmThe difference here is that Enphase got their system certified with the external switch unit which communicates with each microinverter. Deye would need to under-go recompliance and prove the arrangement with external switch is acceptable.