It consists of main circuit, control circuit and detection circuit. The main circuit is composed of three parts: the parallel part, the series part and the filter energy storage capacitor Cd of the DC part. The parallel part is composed of a low-pass filter and a three-phase PWM switching rectifier. The switching rectifier is actually a three-phase voltage inverter. Its main function is to provide rectified DC power for the single-phase compensation inverter in the series part. Keep the voltage on the DC capacitor Cd constant. The DC capacitor Cd plays the role of filtering and energy storage. There are two purposes of using a three-phase switching rectifier. One is to keep the mains input power factor cosφ=1, and to make the input current waveform close to sinusoidal, so as to reduce the pollution to the mains; The reactive energy in the inverter load can be fed back to the mains power supply, improving the efficiency of the compensator. In addition, if the energy storage battery is connected in parallel with the DC capacitor Cd, when the mains fails, the three-phase PWM switching rectifier switches to the inverter state to work, and can be used as an online UPS for a short time. If a part of the control circuit is added, the three-phase voltage inverter can be used as a reactive power compensator or an active filter to filter out the harmonics in the load current. The series part is composed of three single-phase full-bridge inverters and their output transformers (that is, compensation transformers), whose function is to compensate for the high and low changes of the mains voltage, three-phase asymmetry, harmonics, flicker, etc.; There are two reasons why the series part uses three single-phase inverters and output transformers. It is also asymmetrical and must be compensated independently with unconnected single-phase inverters. Second, it can also improve the reliability of the three-phase four-wire power supply. In case one phase fails, the other two phases can continue to supply power. The three single-phase inverters can also work in both directions. When the mains voltage us is equal to the nominal reference voltage, the three single-phase inverters are converted from the compensation state of the inverter to the switching rectification state to the DC capacitor Cd or The battery supplies power to ensure the normal operation of the three-phase voltage inverter in the parallel circuit. In this way, the three-phase AC regulated power supply becomes a user power integrated regulato
