An inverter is a device that converts direct current (DC) to alternating current (AC) to meet the power demand of an AC load. According to the topology, inverters can be divided into high frequency inverters and power frequency inverters.

High frequency inverter

Since the high-frequency inverter adopts the high-frequency magnetic core material with small volume and light weight, the power density of the circuit is greatly improved, so that the no-load loss of the inverter power supply is small, and the inverter efficiency is improved. Usually, the high frequency inverter used in small and medium PVS, its peak conversion efficiency can reach more than 90%.

Power frequency inverter

The power frequency inverter first inverts the DC power into power frequency low-voltage AC power, and then boosts it into 220V, 50Hz AC power for the load through the power frequency transformer.

Its advantage is that the structure is simple, and various protection functions can be realized at lower voltages. Because there is a power frequency transformer between the inverter power supply and the load, the inverter runs stably, reliably, with strong overload capacity and shock resistance, and can suppress the high-order harmonic components in the waveform. However, power frequency transformers are also bulky and expensive, and their efficiency is relatively low. The rated load efficiency of small power frequency inverters produced at the current level generally does not exceed 90%. At the same time, because the iron loss of the power frequency transformer is basically unchanged when operating under full load and light load, so it operates under light load. The no-load loss is larger and the efficiency is lower.

Weight comparison of high frequency inverter and power frequency inverter

The power frequency inverter of the same power inverter is much heavier than the high frequency inverter. The high frequency inverter is small in size, light in weight, high in efficiency and low in no-load load, but cannot be connected to a full-load inductive load, and Poor overload capability.

Comparison of working principles of high frequency inverter and power frequency inverter

The high-frequency inverter circuit is more complicated, and the high-frequency inverter is usually composed of IGBT high-frequency rectifier, battery converter, inverter and bypass. The IGBT can be turned on and off by controlling the drive applied to the gate. The switching frequency of the IGBT rectifier is usually several kilohertz to tens of kilohertz, even as high as hundreds of kilohertz, which is much higher than the power frequency inverter. Therefore it is called a high frequency inverter.

The power frequency inverter is designed based on the traditional analog circuit principle and consists of a thyristor (SCR) rectifier, an IGBT inverter, a bypass and a power frequency step-up isolation transformer. Because the working frequency of the rectifier and the transformer are both the power frequency of 50Hz, as the name suggests, it is called the power frequency inverter.

Comparison of Conversion Efficiency of High Frequency Inverter and Power Frequency Inverter

The power frequency inverter does not have the high conversion efficiency of the high frequency inverter, because the complicated hardware analog circuit is programmed into the microprocessor, and the operation of the inverter is controlled by a software program. In addition to the size reduction of the high-frequency inverter, the conversion efficiency is also improved.