Research And Design Of Key Technology For Cascade H Bridge Static Synchronous Compensator

In recent years with the development of science and technology and economy, such as electrified railway, the iron and steel smelting and other nonlinear or impact loads increase rapidly in our country, cause voltage distortion of the distribution network increase,power quality decline and power loss increase. The large-scale construction of photovoltaic, wind power and other new energy power generation easy to cause the system to access point of distribution network of large amplitude disturbance. This would require a large number of dynamic reactive power to support the voltage stability.In order to solve the problem, it’s necessary to increase the dynamic reactive power compensation equipment. Static synchronous compensator(STATCOM) with the superiority of wide compensation scope, fast response, compensation function diversification and small occupation area is replacing the traditional reactive power compensation device(SVC) etc. Static synchronous compensator is a research hotspot in the field of reactive power compensation with the broad application prospect. This dissertation is mainly concerned with the design and implementation of the whole system and control strategy of static synchronous compensator and DC capacitor voltage balance control technology. The author’s main result of the research contents and contributions are outlined as follows:1. The topological structure and modulation technology for static synchronous compensator have been studied. Analysis of the common multilevel converter topologies and modulation technology, we select H bridge cascade multilevel structure star connection and carrier phase shifted pulse width modulation technology(CPS-SPWM).2. The control strategy of static synchronous compensator and DC capacitor voltage balance control technology have been studied. Firstly, put forward the improvement of overall system control strategy, through the inverse Park transform to optimize it in the generation of modulation signals based on the feed forward decoupling control. Then through the hierarchical control thinking, by using the method of pure active voltage vector to balance each capacitor. Finally verified by Matlab /Sinulink simulation, the simulation result show that good control effect and effective and without the balancecontrol contract, balance control achieved obvious control effect.3. The circuit of hardware and software system is designed. The hardware mainly concern signal sampling and conditioning circuit, DSP and FPGA control circuit. Write the software of STATCOM system and introduces the working process of the software.4. The type and parameters of the main circuit of STATCOM system device have been studied. Verified and correctness and feasibility of the hardware and software design by building a small voltage experiment model.