The Study Of H-bridges Cascaded Active Power Filter

Nowadays, the application of power electronic technology is increasing widely. However, it also brings serious harmonics pollution and causes serious harm to the safe operation of power grid. Active power filter (APF) is used to alleviate harmonic pollution. In high voltage and high power applications, the working voltage of power switching devices and switching frequency are often contradictory. Carrier phase shifted technique (CPS-SPWM) and cascaded H-bridge multilevel technology can solve this problem.This paper introduces the basic principle of carrier phase shifted (SPWM) technique, the technique of output voltage waveform and frequency characteristics. The cascaded H-bridge multi-level converter has many advantages such as the same H-bridge unit to perform availably the modularized design, the least component amount, achieving high output voltage by low-voltage devices. CPS-SPWM is applied to the H-bridge cascade multi-level converter, because it has a perfect prospect in APF and power converter.In this paper, the cascaded H-bridge multilevel inverter acts as the main circuit of a shunt active power filter. This paper introduces the method of harmonic detection based on instantaneous reactive power theory and its derivative algorithm. It also introduces the current tracking strategy and the voltage stability of the DC side. And it establishes the simulation model in MATLAB to verify results.The experimental device based on the cascaded H-bridge of carrier phase shifted SPWM technique for multilevel converter is designed in this paper. This paper introduces the design process of main parameters of the experiment device and experimental device is still in further research.