Esearch On The Technology Of Multilevel Inverter And Its Application In STATCOM

In recent years, with the new generation of power electronics device, to promote the rapid development of multilevel inverter, and it also makes people have higher demands on power quality. It is now a hot topic on How to better improve the utilization of power and improve the quality of electricity, reduce the reactive power in the circuit. The harm of reactive power for power supply network is obvious to all, it is not only Destroy the stability of power system, which will lead to the safe operation of the system coefficient become lower, but also can cause low power factor in industrial power, The increased cost of electricity, This is a problem that how to dynamically test the reactive power and give it the real-time compensation in power grid which need to solve.In this paper, starting from the reactive power, to understand the causes、harm of reactive power as well as the necessity of reactive power compensation, then introduces the common topological structure of multilevel inverter, compared the advantages and disadvantages of them, Thus put forward the most suitable for the multilevel structure of STATCOM:Cascaded H bridge type multilevel STATCOM. Interpretation of the H bridge cascade ways, analyses its r advantages than othe multilevel inverter topology and its own shortcomings. This article further introduces multilevel STATCOM that composed of this cascade mode, introduce the basic principle of Cascade multilevel inverter STATCOM and PWM modulation method,,choose the control method which is suitable for STATCOM by comparing all kinds of modulation mode. To understand the STATCOM system effect in reactive compensation,use the Matlab to simulate it. To obtain optimal parameters when the system is running, by changing the parameters of the load and the voltage to observe dynamic compensation performance of STATCOM device, Proposed system scheme optimization Based on the problems arising from the simulation.Finally a brief introduction to the hardware part of the system, the main control system is composed of DSP and FPGA together dynamic testing in the grid voltage current signal by DSP, and to processing it, then produce PWM pulse transmitted to the FPGA, again produced three-phase PWM pulse by FPGA to phase shift PWM processing. to compensate reactive power by control the inverter circuit to produce need compensation current in the power grid.