Research On The Application Of STATCOM In The Asymmetric Distribution System

In the power system distribution network,the transmission of power can appear the loss of reactive power and active power,which brings the system such as the uneven distribution of power flow,the quality of power and so on.Therefore,the ability to quickly and accurately compensate the reactive power of the distribution network is the key to maintain its stability and safe operation.Its stability is of great significance to the balance of power flow and the problem of power quality.As a kind of advanced dynamic compensation equipment,the static synchronous compensator(STATCOM)makes up for the shortcomings of the limitation of the application range of the traditional equipment and the longer time of compensation.This paper mainly studies the main circuit and control strategy of STATCOM in distribution system.Firstly,the development and research status of reactive power compensation technology are reviewed,and the characteristics of STATCOM and other reactive power compensation equipment are introduced.In the second chapter,the compensation parameters of the general passive three-phase four wire system are analyzed and calculated,and a constant power numerical approximation algorithm is proposed,which can find the optimal compensation parameters according to the constant active power before and after the compensation.In the third chapter,the mathematical model of the three-phase four wire STATCOM main circuit topology is established,and the selection method of STATCOM device operating parameters is discussed.In the fourth chapter,in view of the shortcomings of the traditional PI control compensation method,the signal control precision is not high and the speed of compensation is slow,a characteristic harmonic feedforward compensation method is proposed.On the basis of the PI control compensation method,the voltage feedforward compensation link of the system is replaced by the characteristic harmonic feedforward compensation link.This method uses the generalized coordinate transformation method to realize the selective detection of the characteristic harmonics,and reconstructs the PWM modulation wave by the way of the characteristic harmonic injection,thus improving the tracking control precision and the response speed.Finally,the experimental simulation of STATCOM unbalancedcompensation is carried out by Matlab/Simulink,and the control method proposed in this paper is compared with the simulation results of the traditional PI control method,and the feasibility and superiority of the proposed characteristic harmonic feedforward compensation method is verified.