Lý thuyết điện & an toànElectrical theory & safety · BàiLesson 2/6
Power Electronics in Inverters
Trong bàiOn this page
Solar Knowledge HubĐiện tử công suất trong biến tầnPower electronics in the inverter
Biến tần là bộ não biến điện một chiều thành xoay chiều dùng được, nhờ đóng cắt bán dẫn hàng chục nghìn lần mỗi giây.The inverter is the brain that turns DC into usable AC, by switching semiconductors tens of thousands of times per second.
| Linh kiệnDevice | Tên chân (VN)Pins (VI) | Tên chân (EN)Pins (EN) |
|---|---|---|
| MOSFETMOSFET | Cổng · Máng · NguồnCổng · Máng · Nguồn | Gate · Drain · SourceGate · Drain · Source |
| IGBTIGBT | Cổng · Cực thu · Cực phátCổng · Cực thu · Cực phát | Gate · Collector · EmitterGate · Collector · Emitter |
Infographic gốc ghép IGBT với bộ chân của MOSFET. IGBT không có chân Drain/Source: mà là Gate/Collector/Emitter.The original infographic gave IGBT the MOSFET’s pins. IGBT has no Drain/Source: it is Gate/Collector/Emitter.
Vì sao biến tần này đắt hơn dù cùng công suất? Đáng nói là chất lượng và số lượng MPPT cùng dải điện áp làm việc, nhiều MPPT, dải rộng giúp khai thác tốt khi mái nhiều hướng hoặc bị che bóng.Why is this inverter pricier at equal power? Often the number and quality of MPPTs and voltage range: more trackers handle multi-orientation or partly-shaded roofs better.
The inverter converts DC electricity from solar panels and battery storage into usable AC, and it accomplishes this through power electronics. This document opens up the inverter to examine its internal building blocks, from switching devices to maximum power point tracking, giving technicians and sales consultants enough understanding to read a schematic and explain inverter quality to customers.
For: technicians who want to understand inverter architecture, newcomers who need the MPPT concept, and sales staff who need to articulate what an inverter actually does.
Quick Summary
Inverters are built on two foundations: Ohm’s law and power principles covered in document 01-01, and the technique of rapidly switching semiconductor devices. Switching tens of thousands of times per second allows voltage to be shaped and converted with high efficiency.
Current flows through a chain of blocks. A DC-DC converter steps voltage up or down, a maximum power point tracker continuously finds the optimal operating point of the panel, and then the inverter stage converts DC to AC.
The two most common switching device families are MOSFETs and IGBTs. They have different pin names, and confusing these pin names is a common documentation error worth avoiding.
Switching Is the Key
An inverter does not generate energy. It only reshapes an existing energy flow. It does this with high efficiency by switching current on and off extremely rapidly through semiconductor devices, rather than impeding current with resistors that generate substantial heat. By adjusting the ratio of on-time to off-time, the inverter controls the average voltage and constructs an AC waveform.
This technique is called pulse width modulation. It is the reason a modern inverter achieves conversion efficiency of around 97 to over 98 percent, with the remainder lost as heat in the devices and circuitry.
The Internal Block Chain of an Inverter
Current from the solar panels passes through a processing chain before reaching the load or the grid. A DC-DC converter steps voltage up or down: the step-up type is called a boost converter and the step-down type is called a buck converter. A maximum power point tracker continuously sweeps to keep the panel operating at the point that delivers the greatest power output. The inverter stage uses switching devices to convert DC into AC for the load or for grid tie-in. In a hybrid inverter, an intelligent controller coordinates power from the solar panels, battery storage, grid, and load in real time.
The maximum power point tracker deserves further discussion because it directly affects energy yield. A panel’s optimal voltage and current shift continuously with irradiance and temperature. The tracker locates this optimal point many times per second, ensuring the panel always delivers the highest power possible under current conditions.
When a customer asks why one inverter costs more than another of the same rated power, one compelling point is the quality and number of maximum power point trackers, together with the operating voltage range. More trackers and a wider range allow better harvest when a roof has multiple orientations or is partially shaded.
MOSFETs and IGBTs: Do Not Confuse the Pin Names
The two common switching device families are MOSFETs and IGBTs, chosen according to operating voltage and switching frequency. The critical distinction is that they carry different pin names. A MOSFET has three pins called gate, drain, and source. An IGBT has three pins called gate, collector, and emitter.
This is an important correction, because the original infographic paired IGBT with the MOSFET pin names. A symbol drawn as a MOSFET labelled gate, drain, source is correct, but labelling that same symbol as an IGBT is wrong. In technical documentation, using the correct pin names for the correct device type is a small detail that reflects accuracy.
In practice, MOSFETs are typically used on the low-voltage, high-switching-frequency side, while IGBTs excel on the high-voltage, high-current side. Many inverters combine both families in different stages. When reading a schematic or a service manual, correctly identifying the device type allows you to look up the right voltage and current ratings.
Inverter block-chain architecture, the roles of buck/boost converters, and MPPT are per TYCORUN and the Wikipedia article on MPPT. Switching principles and pulse width modulation are per inverter manufacturer documentation. MOSFET pin names (gate, drain, source) and IGBT pin names (gate, collector, emitter) are per Electronics Tutorials and Infineon: this is the correction relative to the original source. The conversion efficiency range of 97 to over 98 percent is discussed in depth in Chapter 04 on inverters.