| The three-phase 6-pulse and 12-pulse rectifiers are widely used in various kinds situation because high efficient,high responsibility and simple construction.The harmonic current of the rectifiers distort the voltage of power gird,affect most of electrical installations,as well as measurement equipment,even relay protection device.What's more,there is significant influence to the grid harmonic power flow when the power of three-phase rectifiers are injected and the contribution of each voltage harmonic to each harmonic power is nonnegligible.Therefore,deeply study the harmonic analytical calculation mothed of three-phase rectifiers and establish harmonic power model of three-phase rectifiers are significant.The main content of this paper is as follows:(1)The operating principle of AC in continuous and discontinuous of three-phase 6-pulse uncontrolled rectifier load is analyzed.The time-domain AC expression of three-phase 6-pulse rectifier load is obtained through establish the current and voltage balance equations,and then the frequency-domain harmonic model of three-phase 6-pulse rectifier load is proposed.A parameters estimate method of equivalent circuit of three-phase 6-pulse rectifier load is proposed based on measurement data of AC side.(2)The operating principle of phase-control three-phase 12-pulse rectifier in series circuit and parallel circuit with isolation transformer are analyzed.The frequency-domain harmonic Coupled admittance matrix is established respectively under positive sequence voltage and negative sequence voltage.Furthermore,the frequency-domain harmonic analytical model of phase-control 12-pulse rectifier under unbalanced voltage is established.This model has taken fully consideration of non-ideal grid voltage,transfer the time-domain nonlinear characteristic of series and parallel 12-pulse rectifier into frequency-domain linear admittance matrix,which capable illustrate the relationship between each harmonic current and each terminal harmonic voltage.(3)The frequency-domain harmonic admittance matrix of three-phase rectifier loads are studied,and proposed harmonic power model with the same form.Take three-phase 6 pulse uncontrolled rectifier as an example,combine with the parameter estimate method and frequency-domain harmonic coupled matrix,the harmonic power model of three-phase 6 pulse uncontrolled rectifier is established.Furthermore,the characteristic of harmonic model is analyzed and a simplified model has been proposed.(4)Build simulation models of three-phase 6-pulse and 12-pulse rectifier in Matlab/Simulink,and harmonic coupled admittance matrix models proposed in this paper are verified.An experiment plant of three-phase 6-pulse rectifier is build.The parameter estimate method is verified and scope of application of full harmonic power model and simplified harmonic power model are verified through experiment and simulation in Matlab/Simulink. |
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