Study On Var Compensation System Based On Fast Response Magnetic Controlled Reactor

With the rapid development of national economy and fast growth of electricity demand, improving power supply standard and to provide safe, reliable and top-quality electric power is becoming a very important work. The use of traditional perceptual load(such as asynchronous motors) and modern power electronic equipment consumes reactive power and reduces power factor, thereby brings many problems such as voltage sharp fluctuation and high-order harmonic. Traditional reactive-load compensation technique can not meet the needs of power transmission and research of new type methods is more and more imperative. Magnetic-valve controlled reactor(MCR) has good prospects for development in dynamic reactive power compensation area because of many advantages such as reliable structure, low power loss, small harmonic and smoothing capacity adjustment with the development of electric power transmission. However, the response time of MCR is between 200 ms and 300 ms because of the structure.Slow response time will reduce grid stability and increase the probability of the system oscillation. It is a meaningful work to research methods to enhance the response speed.First of all, in this paper the background and the significance of the research is introduced and several common methods of reactive power compensation is analyzed in brief. Then, the mathematic model and equivalent circuit of MCR is established based on the analysis of the structure and working principle, and the expression of volt-ampere characteristic, control characteristic and response characteristic is obtained. The response time of MCR is slower than other reactive power compensating mode, which will decrease the stability of power grid and increase probability of system oscillation. The paper proves that capacitor discharge is the most useful way by comparing three methods to reduce the MCR’s response time. Fast excitation system of MCR is designed and the working mode is described in detail,which taking the boost chopping circuit as center. The models of conventional MCR and fast response MCR are built by MATLAB/Simulink and simulation results show correctness of theory.A VAR compensation control system based on fast response MCR is designed, which is centered upon DSP(TMS320F2812).The hardware construction, key algorithm and software constitution of the control system are explained in detail. The part of hardware construction includes the design of the main control board and display board, the implementation of the synchronizing signal circuit and sample conditioning circuit and the drive circuit of thyristor and IGBT. The part of key algorithm includes fast fourier-transform algorithm(FFT), rational interpolation method for building the relationship between the loop-current and control angle and open-loop control strategy for fast response MCR. The part of software constitution includes the main program flow chart, synchronous signal flow chart, sampling flow chart and fast response function flow chart.Finally, the prototype of MCR(380V/25kVA) with high speed excitation circuit is produced and the experiments are made. The results of experiment show that the reactive power compensation system based on fast response MCR has good performance and can satisfied the practice requirement, and provide reference for the construction.