Inside the LVYUAN 3 kW Hybrid Inverter: A Teardown and Circuit Analysis
イチケン / ICHIKEN
Solar power conditioners for Japanese homes are usually associated with brands like Omron, Nichicon, and Tesla. Huawei is a major name for industrial installations. The unit in this video is different. It is an LVYUAN hybrid inverter that has become popular with people building their own solar setups on a budget. It is called a "hybrid" inverter because it can work with storage batteries as well as solar panels.
This first installment takes the unit apart, reverse-engineers its main circuit, and explains how a hybrid inverter of this type typically operates. The presenter says several times that they have not yet tested this particular unit's actual behavior. That is planned for later videos. Their provisional verdict is that the design looks reasonable for fully off-grid use. When it is connected to the grid, they consider it a "gray area" product.
Why self-consumption now beats selling power
A power conditioner converts the DC output of solar panels into AC. In a typical household, that power is either sold to the utility or sent into the home's distribution board for the household's own use. Under the old feed-in tariff (FIT), purchase prices were around 40 yen per kWh, so selling any surplus made economic sense.
The presenter explains that purchase prices have since fallen to about 15 yen per kWh. Buying electricity still costs around 40 yen per kWh, depending on the utility. Given that gap, they argue it is now smarter not to sell at all. Instead, generated power can be stored in batteries and consumed entirely at home.
The hybrid inverter concept
The LVYUAN product is built around this idea. It is not meant to sell electricity. All generated power goes to self-consumption or storage. The presenter notes that some other companies' products are exceptions. As an example, they cite Tesla's Powerwall, a hybrid inverter that can sell power. DIY-oriented hybrid inverters like this one generally do not sell power. The presenter says the product has been well received in recent years by people who want their own solar systems, because of soaring electricity prices and instability in the energy situation.
Pure self-consumption without batteries has two problems:
- Daytime surplus is wasted. When daytime generation exceeds household use, the panels' capacity cannot be fully used.
- Night and early morning need the grid. The panels produce nothing then, so power must be bought.
Adding batteries addresses both problems. Daytime generation either charges the battery or supplies the home, and the battery covers consumption at night. Only when the battery is empty does the home buy power from the grid again.
Specifications and their limits
The label reads "3,000W single-phase two-wire hybrid inverter," and the side panel lists the specs. The unit carries the PSE mark. The presenter picked out several limitations:
- 3 kW capacity. This likely won't cover peak household demand, so the owner may end up buying from the grid fairly often.
- 100 V output only, no 200 V. IH cooking heaters, EcoCute water heaters, and larger room air conditioners run on 200 V. For a home that relies on them, the presenter calls the specs tough. For a household without such heavy loads, it is not a problem.
- 108 V maximum panel open-circuit voltage. Typical power conditioners accept up to about 500 V.
- 24 V battery voltage. This is low, so the presenter expects high currents throughout the circuit and doubts that overall efficiency is high.
Opening the case: fans, filters, and relays
The presenter notes that the unit shown had already been disassembled and reassembled for filming, so it differs slightly from its factory state. For example, a plastic insulating film was originally fitted inside. The internal wiring runs back and forth quite a bit.
There are two cooling fans, and they exhaust air from the bottom of the unit. The presenter questions this choice. Heat rises, so placing fans at the top and exhausting from there should give better heat removal. They ask viewers what they think of the design.
The AC input and output terminals have rather bulky filters. The presenter reasons that these block noise, since powerful power electronics sit inside. Because the unit has PSE certification, its conducted and radiated noise should be below regulatory limits, though they did not measure it.
With the input filter removed, six relays are visible below the AC input. By switching these on and off, the unit decides whether it is connected to the grid and whether power goes to home consumption. A current transformer sits in the same section. A single plug-in board serves as the control board.
Power stages and an unusual heatsink terminal
The power semiconductors under the largest heatsink form the single-phase inverter and related power-conversion circuitry. Another section handles the battery input. The smallest heatsink belongs to the circuit connected to the solar panels.
The presenter finds the solar section particularly interesting. The panel's positive lead goes into the printed circuit board. The negative lead connects to the heatsink that cools the power semiconductors, so the heatsink itself serves as a terminal. Current flows from the heatsink into the semiconductor, so that one device has no insulating sheet, unlike the others.
Electrolytic capacitors
In circuits handling this much power, the presenter says the first parts to fail are probably either the power semiconductors or the electrolytic capacitors. They checked the capacitor makers and found two: AiSHi and JiangHai. Both are very popular. According to the presenter, AiSHi capacitors are often used in electric cars and similar applications. JiangHai capacitors are common in industrial equipment, and the company holds a very strong position in China.
The transcribed schematic
The presenter traced out the main circuit. They omitted sensors, some transistors, and auxiliary power supplies, and annotated each capacitor's rated voltage so viewers can see roughly what voltage each node runs at. The layout is:
- "GRID & Filter": the AC input from the grid.
- AC-OUT-L and AC-OUT-N: nearby outputs going to the home's distribution board.
- Right side: the solar panel connection.
- Below it: the battery terminals.
The unit has to manage current flowing to and from the grid-side inverter, the solar panels, and the battery, so there is a lot to control. The main blocks are:
- A single-phase inverter.
- A bidirectional converter.
- A circuit resembling a full-bridge push-pull converter.
- A buck converter for the solar panels, with a backflow-prevention switch.
The PV− node is the heatsink terminal seen earlier. The battery path also has a 150 A fuse.
For the explanation that follows, the presenter simplifies the design into three blocks:
- AC/DC: the single-phase inverter.
- DC/DC: the bidirectional converter and push-pull converter.
- DC/DC: the buck converter on the solar side.
They stress that what follows describes typical hybrid inverter operation, not verified behavior of this LVYUAN unit.
Solar charging and MPPT
Solar panels only supply power, never absorb it. Their output passes through the buck converter toward the push-pull converter. To start simply, the presenter assumes the push-pull stage is stopped, so the panels charge only the battery.
In this mode, controlling the buck converter's inductor current sets the battery charging current. The same inductor current also drives MPPT (maximum power point tracking), the control method that tries to draw as much power as possible from the panels. The disassembled unit naturally has MPPT. The inductor current is proportional to the panel current. As it rises, panel voltage falls, and the controller adjusts the current to keep tracking the point of maximum power. The controller therefore has to watch the state of both the panels and the battery.
In a typical charge cycle, when the battery's state of charge (SOC) is low, the buck converter limits current to avoid overcurrenting the battery. Avoiding overcurrent takes priority here, so the unit may not draw maximum power from the panels. As SOC rises, charging moves from constant-current to constant-voltage. This pure battery-charging scenario corresponds, for example, to a sunny day when the home uses no electricity, so nothing to the left of the buck stage runs. When the home is consuming power, the other stages run and the behavior differs somewhat.
The middle converters: day and night scenarios
The push-pull-like converter and the bidirectional converter have two jobs. Working with the single-phase inverter, they either deliver power from the right-hand side (panels and battery) to the home, or draw power from the grid to charge the battery. The presenter explains this by comparing times with and without sun.
With sun and household use:
- Light use: the panels charge the battery and supply the home at the same time.
- Heavier use: the panels and the battery together supply the home.
- Heavier still: grid purchases may be added on top.
At night: there is no solar generation, so the question is what to do with the battery.
- If the battery has enough charge, it discharges to supply the home.
- Once it is empty, the presenter thinks the typical behavior is for the battery to sit idle until the sun returns, while the home buys only the electricity it uses.
- Alternatively, the unit can buy extra power to charge the battery. This may make sense where late-night electricity is cheap.
The presenter cautions against overnight charging, though. If the next day is sunny enough for the panels alone to supply the home and recharge the battery, buying power at night to charge it is not very economical. The right mode depends on how the owner wants to use the battery. In many cases, they think the most economical approach is to charge from the sun by day and use the stored energy at night.
The single-phase inverter and the reverse-flow problem
The presenter calls this part of the operation especially important. Ordinary hybrid inverters can export power without any problem, but this LVYUAN product is not JET certified. As the presenter explains it, the unit can be physically connected to the grid, but you cannot sign a grid-interconnection contract with a utility. That means it must never cause reverse power flow into the grid. As a result, the household load and the inverter's own input and output must be monitored at all times.
When the inverter is idle, for example at night with an empty battery, grid power simply bypasses the hybrid inverter and flows to the home. When the inverter is running, it works with the circuits to its right to draw power from the panels or battery. An inductor on the inverter controls the current flowing in and out.
As the inverter outputs more current, it covers more of the home's usage, and grid purchases shrink. If inverter output exactly matched household consumption, the home would buy nothing and be fully self-sufficient. In reality, household current fluctuates constantly. A normal hybrid inverter can let current flow back to the grid at that point, but this product must not. The presenter therefore expects it to keep a margin. The current measured at CT2 should stay a little higher than at CT1, meaning the home always buys a small amount of power. They do not yet know how large that margin is on the LVYUAN unit.
The schematic also shows that the circuitry itself is configured so that reverse current can flow. Preventing it depends entirely on control of the relays and the single-phase inverter, which makes that control critical.
The presenter also points out a trade-off. Compared with a JET-certified hybrid inverter that allows reverse flow, this unit cannot sell power, so the owner may not get the full potential out of the panels. They plan to confirm the actual behavior experimentally later.
Anti-islanding and independent operation
The presenter could not tell whether the unit has an anti-islanding function. Islanding is when the grid goes down but the inverter stays connected and keeps outputting voltage onto the lines. Utility workers repairing the outage could then get a shock from wires they expect to be dead. So a grid-tied inverter must automatically disconnect when it detects an outage. Ideally, it would then switch into independent (stand-alone) operation mode.
The relay section makes both anti-islanding and independent operation possible in circuit terms. What the presenter doesn't know is whether the control firmware actually implements them. The instruction manual describes a UPS mode that supplies power from the battery, which suggests something similar to anti-islanding protection is present. The presenter has not confirmed this through testing.
Their conclusion here is that, when connected to the grid, the product sits in a somewhat gray area. For fully off-grid use with no grid connection at all, it looks fine.
Verdict so far and what comes next
The presenter admits they took the unit completely apart before testing it, so operational tests are no longer possible with this sample. They invite anyone from LVYUAN or SRNE who sees the video to get in touch.
Their assessment so far covers three points:
- Circuit design: fine for people who want to be fully self-sufficient off-grid with solar panels and batteries.
- Cooling: the airflow pushes heat out from the top down rather than letting it rise and escape upward. Because of this, the presenter suspects some components may have a shortened lifespan.
- Grid protection: the unit is not JET certified and its circuit is configured to allow reverse current, so they consider it a gray area.
How the unit actually handles reverse-flow prevention and grid disconnection remains open. The presenter plans to address it in a future video.
This video is brought to you courtesy of JLCPCB. Hello. Today's video is a teardown of a solar power conditioner. Here is the power conditioner.
When it comes to solar power conditioners, Huawei is strong in industrial applications. Omron, Nichicon, and Tesla are among the most famous for home use in Japan. The power conditioner we will be looking at is popular with those trying to build their own solar power system on the cheap. Unlike normal power conditioners, it can also be combined with storage batteries, so it is called a hybrid inverter.
Today, we're going to take this hybrid inverter apart and check what is inside. We will also verify its operation in the next and subsequent videos. But first, here is today's sponsor. Go ahead.
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First, let's briefly look at the role of power conditioners. Basically, a power conditioner is a device that converts the DC power output from solar panels into AC power. In an average household, you can earn income by selling the electricity you generate, or connect outlets from the distribution board and allocate the power for your own consumption. For the portion of electricity generated in excess of on-site consumption, it is basically more economical to sell it.
Feed-in tariffs used to be about 40 yen per kWh, so it made sense to sell the electricity. But recently, the purchase price has dropped to about 15 yen. Electricity costs about 40 yen per kWh, depending on the power company. Therefore, storing the generated electricity in batteries and consuming it all ourselves, instead of selling it, is becoming a wise use of the money.
What about the hybrid inverter we will be looking at? Basically, the concept is to consume all the electricity generated in-house or store it, without selling electricity. There are exceptions among other companies' products when it comes to selling electricity, but systems you build yourself with a hybrid inverter like this basically don't seem to sell power. In the past few years, due to soaring electricity prices and instability in the energy situation, the product has been quite well received by people who want to build their own solar power system.
The area enclosed by the dotted line here is the hybrid inverter. The regular power conditioner was selling power, but in this case, no electricity is sold. Whenever solar power is being generated, it is all for private consumption. However, if the electricity generated during the daytime exceeds on-site consumption, you cannot take full advantage of the solar panels' generation capacity. Also, electricity cannot be generated at night and early in the morning, so eventually it becomes necessary to purchase power from the grid.
To solve these problems, storage batteries are usually used together with the system. The electricity generated by the panels during the daytime can either be stored in batteries or used for self-consumption. At night, when sunlight is not available, discharge from the storage battery covers private consumption. During hours when the sun is not shining, if all the energy in the batteries is also used up, power is purchased from the grid as before. Because they use both solar power and storage batteries in this way, they are called hybrid inverters.
Whether LVYUAN's hybrid inverter behaves like this, I don't know, because I haven't verified its operation this time. We'll see in the next video. Does that mean companies other than LVYUAN aren't producing hybrid inverters? No. These days, many power conditioner manufacturers produce hybrid inverters that can be used in combination with storage batteries. For example, Tesla's Powerwall is a hybrid inverter that can actually sell electricity.
We will look at the hybrid inverter we purchased. It looks like this is read as LVYUAN. It is a 3,000 W single-phase, two-wire hybrid inverter. If you look on the side, you'll see the specifications. It looks like it does have PSE certification.
This hybrid inverter has a capacity of 3 kW. It probably cannot cover peak power for self-consumption, so power will likely be purchased from the grid more often. The output voltage is 100 V, with no 200 V output. Induction cooking heaters, Eco-Cute water heaters, and larger room air conditioners run on 200 V, so these specifications are limiting. Conversely, if you do not use such high-power appliances, there is no problem.
The output voltage is low to begin with. The maximum open-circuit voltage of the solar panels is also 108 V. Typical power conditioners often allow up to about 500 V here. The battery voltage is also low, at 24 V. The current flowing through the entire circuit is likely to be high, so the overall efficiency does not seem high.
From here, we'll disassemble it to see what's inside. It opens like this. This was already disassembled and then reassembled for filming, so it is slightly different from the product's original state. For example, this plastic film for insulation was originally included.
If you look inside, you'll see that the wiring goes back and forth quite a bit. There are two cooling fans here. If you take a closer look, they exhaust air from underneath the main unit. Heat basically goes up, so putting a fan on top and exhausting air from there would seem to provide better heat removal. For some reason, they are attached to the bottom. What do you think of this design?
These are the AC input and output terminals. They are equipped with rather bulky filters. There is some pretty powerful power electronics circuitry inside, so these prevent noise from traveling along the leads and escaping outside. I didn't actually check it this time, but it has PSE certification, so conducted and radiated noise should be below regulatory limits.
We will look at the entire circuit in a little more detail. First, here is the input circuit. When the filter is removed, it looks like this. It has quite a substantial input filter. Below the filter on the AC input are relays like this. Six are used. Turning these relays on and off determines whether it is connected to the power grid and whether power is used at home, among other things. There is also a current transformer in this section.
There is a single board inserted here. This is a control board. We have power semiconductors in this area, forming a single-phase inverter and other power conversion circuits. It has a rather bulky heat sink. The circuit in this area is the battery input circuit. Here, with the smallest heat sink, is the circuit connected to the solar panel.
The circuit for this solar panel section is quite interesting. The positive terminal goes into the printed circuit board. The negative terminal is connected to the heat sink that cools the power semiconductors. Using the heat sink itself as a terminal is quite an interesting design. To pass current from the heat sink through the power semiconductor, only this power semiconductor has no insulation sheet attached.
We will take a quick look at the passive components used. In circuits that handle such high power, the first thing to break is probably either a power semiconductor or an electrolytic capacitor. I was curious about the manufacturers of the electrolytic capacitors used, so let's look. Electrolytic capacitors from these two companies were used: AiSHi and Jianghai. Both are very popular. AiSHi capacitors are often used in electric cars and such. Jianghai is an electrolytic capacitor manufacturer whose products are very commonly used in industrial applications. Jianghai, for example, has a very strong position in China.
Next, we will look at the schematic. Here is the main circuit section I traced out. There are sensors, other transistors, power supplies, and so on that are not shown here; they have been omitted. I have written the capacitors' rated voltages so you can see roughly what voltage each node operates at.
The part marked "GRID & Filter" is the AC input. AC-OUT-L and AC-OUT-N are located right near it. These are the outputs connected to the distribution board in the house. On the right side of the circuit is the part connected to the solar panel. Below that are the battery connection terminals. Since it is a hybrid inverter, it controls the current flowing to the inverter, the solar panel current, and the current flowing through the battery. It is a circuit with lots of things to control.
Let's see what circuits it consists of. This part is a single-phase inverter. This is the bidirectional converter. Here is a circuit that looks like a full-bridge push-pull converter. This is the buck converter for the solar panels. The solar panel section is equipped with a reverse-current prevention switch. PV- here is the part connected to the heat sink you just saw. It also had a 150 A fuse in the battery section.
I would now like to explain the actual operation of a hybrid inverter. It is difficult to explain using this circuit, so I will use a further simplified circuit. Corresponding to the circuit I mentioned earlier, here is the power grid, this line connects to the house, and here are the solar panel and battery. This AC/DC block is the single-phase inverter. The DC/DC part represents the bidirectional converter and full-bridge push-pull converter. The DC/DC block here is the buck converter.
I haven't checked whether LVYUAN's hybrid inverter actually operates as I am about to describe. This is an explanation of typical hybrid inverter operation.
First, we will look at the solar power generation part and battery charging and discharging, which are the easiest to understand. Solar panels basically only operate in the direction of supplying power. The power from the solar panels goes through a buck converter to a push-pull converter. Let's assume for now that this push-pull converter has stopped operating. We will look at a mode that charges only the battery.
Basically, controlling the current flowing through this inductor controls the battery charging current. The inductor current is also involved in the solar panels' MPPT control. MPPT is a control method that tries to draw as much power as possible from the solar panels. Naturally, the hybrid inverter I disassembled today also uses MPPT control.
The current flowing through this inductor is proportional to the current flowing through the solar panels. As the inductor current increases, the panel voltage decreases like this. Basically, we continuously track the point where maximum power can be extracted from the panel. The buck converter here controls the inductor current to do that.
For this circuit to work properly, it needs to monitor the state of both the solar panels and the battery. In typical charging operation, when the battery's SOC is low, MPPT control is performed along with current control of the buck converter to avoid excessive battery current. However, avoiding excessive battery current takes priority, so it may not draw maximum power from the solar panels. As the battery's SOC increases and the constant-current charging mode finishes, the battery is charged at a constant voltage.
For example, during the daytime when the sun is shining, if you use no electricity at home, the circuit to the left here does not run at all, and power from the solar panels charges the batteries. If there is on-site consumption, this part of the circuit operates, so it works a little differently.
Next, we will look at this middle circuit: the push-pull converter-like circuit here and the bidirectional converter circuit. This circuit has two roles. In coordination with the single-phase inverter on the left, it draws power for home use from the circuit on the right. It also works with the single-phase inverter to draw power from the grid to charge the batteries.
To understand this operation, it is helpful to consider cases with and without sunlight. First, consider when the sun is shining and electricity is being used at home. In this case, power from the solar panels can charge the batteries while also providing electricity for self-consumption. If more power is consumed at home, power from both the panels and the battery can cover that consumption. If household consumption increases further, there is also the possibility of purchasing power from the grid in addition to using solar panel and battery power.
Next, let's consider nighttime. There is no solar power generation at night, so we need to think about what to do with the battery power. If the battery has sufficient remaining power, you will want it to provide power for home use. This is the mode in which the battery discharges. What happens when the battery runs out? I think the usual operation is for the battery to do nothing until the sun comes up again, while purchasing only the electricity needed for home use.
You can also purchase additional electricity, beyond what is used in the house, to charge the battery. You may use this mode in areas where late-night electricity is less expensive. However, if the weather is fine the following day and solar panel power alone can cover household consumption and charge the battery, buying power at night to charge the battery is not very economical. Operation depends on how you want to use the battery. In many cases, I think the most economical approach is to charge the battery with sunlight during the day and use the stored power at home at night.
Next, we will look at the operation of the single-phase inverter. This part is quite important. Although normal hybrid inverters do not have this problem, the LVYUAN product disassembled here is not JET certified. Therefore, it can be connected to the power grid, but you cannot enter into a grid-interconnection contract with a power company. That means you cannot cause reverse power flow. The power used in the house and the inverter's input and output power must be monitored at all times. Let's see how it works.
First, what is the situation when this inverter is not operating? It could be nighttime, with no electricity generated by the solar panels and no battery charge remaining. Let's say you are using electricity at home. Power flows from the grid to the house. The hybrid inverter itself does not operate; power bypasses it.
Next is the case where the single-phase inverter operates, drawing power from the solar panels or battery. The inverter and the circuit to its right work together. The single-phase inverter actually has an inductor here, which controls the current flowing into and out of it.
First, let's consider current flowing out of the single-phase inverter. Since the hybrid inverter supplies electricity used in the house, the power purchased from the grid decreases. Suppose the inverter outputs even more current, until household electricity use exactly matches the power drawn from the hybrid inverter. Then you are not buying power from the grid and are completely self-sufficient in electricity.
The electricity actually used at home—in this case, the current—fluctuates all the time. With a normal hybrid inverter, you can allow reverse current flow.
The LVYUAN product we are looking at must not feed power back into the grid. Therefore, it needs a little margin for power fluctuations in actual home use. In a nutshell, the current flowing in CT2 needs to be greater than the current flowing in CT1. In other words, you're going to have to buy a little bit of electricity. But how much electricity is being purchased in this situation with LVYUAN's hybrid inverter is not known. I haven't verified it this time.
You can see the circuit in this section. The circuitry is configured to allow reverse power flow. Therefore, the control of the relays and single-phase inverter here will be very important. Let me repeat that: the product we disassembled this time is not JET certified. It can be connected to the power grid, but it is not possible to make a contract for grid connection and reverse power flow. Compared to a typical JET-certified hybrid inverter capable of reverse power flow, since electricity cannot be sold, we may not be able to make the most of the solar panels' potential.
I haven't experimented with it this time and would like to confirm at a later date, but it is unclear whether this product has an anti-islanding function. Islanding is when the power grid is out of power, but the inverter remains connected to it and continues to output voltage. In this state, power company workers who come to fix the blackout could receive an electric shock if they touch the wires. Therefore, the ability to automatically disconnect from the power grid if a power failure is detected is essential.
Ideally, if a power outage is detected, I'd like to see it disconnect from the power grid and go into independent operation mode. In terms of circuitry, there is a relay in this part of the circuit, so anti-islanding and independent operation are possible. I'm just not sure whether that is implemented in the control system. The instruction manual says there is a UPS mode that provides power from the battery. So something similar to an anti-islanding function seems to be implemented. I have not actually checked the operation of the system, so I don't know this time.
In any case, when connecting to the power grid, this is going to be a bit of a gray area product. The product looks fine for completely off-grid use, without any connection to the power grid. We have completely disassembled the product before verifying its operation, so operation verification is no longer possible. If anyone from LVYUAN or SRNE sees this video, please contact me!
Today, I've disassembled and explained a hybrid inverter. For those who want to be self-sufficient in electricity, completely off-grid with solar panels and storage batteries, I thought the product was fine in terms of circuitry. Just looking at the cooling structure, though, there are some areas that seem to have a bit of a short lifespan. The airflow doesn't let heat escape from the bottom to the top; it lets it escape from the top down. The components seem to have a short lifespan in that regard.
On the other hand, this product is not JET certified. Also, the circuit is configured to allow reverse power flow. In terms of grid protection, I thought it was a gray area product. We will be making a video in the future to verify the operation of this part of the system.
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