Study About Static Synchronous Compensator (STATCOM) Based On Hybrid Cascaded Multilevel Inverter

In recent years, since the multilevel inverter can reduce the voltage resistance of switching devices, save the multiple transformers and improve the quality of output waveform, it has been a hot topic in the engineering research on STATCOM. As an innovation technology in multilevel inverter, the hybrid cascaded multilevel inverter has been placed in an important position in the application research on STATCOM.In this paper, the 2H/3H hybrid multilevel inverter is proposed as the main circuit topology of STATCOM. The working principle of this main circuit topology is specialized. For application in reactive power compensation, stair-waveform EPWM modulation is deeply researched to control the 2H/3H hybrid cascaded multilevel inverter. This modulation method can achieve waveform with high quality using low switching frequency.The simulation software Simplorer is used to simulate the hybrid cascaded STATCOM based on 2H/3H hybrid cascaded multilevel inverter. The simulation results show that the hybrid STATCOM has a good output waveform and it can successfully compensate the reactive power in the system.Basing on the theoretical analysis and simulation research, the hardware and software of the hybrid STATCOM are designed. The hardware circuit uses two ARM7 embeded chips as the core, including power grid synchronous signal generating circuit, data acquisition unit, drive circuit, main control unit and main circuit. The software is consisted of data acquisition software and main control software, responsible for A / D sampling, reactive current count and the output of PWM signals. The development of the software is based on ADS1.2.Basing on the design of the hybrid cascaded STATCOM, an experiment prototype is made. After the debugging, the prototype is used in the reactive power compensation experiment. The experiment results show that the prototype can compensate the reactive power and track reactive current changes in the system. Compared with traditional STATCOM, the 2H/3H hybrid cascaded STATCOM has advantages on installation costs, quality of output waveform and switching frequency.