| With the development of controllable power industry,PWM rectifier has become a research hotspot in the field of green power conversion technology because of its high efficiency and energy feedback.In the actual operation of the power grid,due to the load asymmetry and other reasons,the power grid is often in an unbalanced state;While the existing PWM rectifier system design,mostly in the balance of power state,lead to system performance degradation,a variety of characteristic and noncharacteristic harmonics will lead to increase the loss,and even burn out the electronic equipment.In this paper,the control strategy of PWM rectifier is studied under the unbalanced grid conditions.Firstly,the topology,working principle and mathematical model of the threephase PWM rectifier are analyzed in detail under the ideal Grid condition.Then,considering the actual operating state of the grid,the characteristics of the PWM rectifier under unbalanced grid voltage are analyzed in detail,based on this,the control strategy and method of PWM rectifier under unbalanced grid voltage are studied.PI control strategy and algorithm of unbalanced network voltage PWM rectifier based on RBF neural network are proposed,and the system modeling and simulation analysis by MATLAB/Simulink.The simulation results show that the stability of DC side voltage of PWM rectifier can be effectively improved,and the harmonic content and ripple amplitude can be significantly reduced.Secondly,in order to save the system cost,the control strategy of the PWM rectifier without grid pressure is studied,based on the analysis of the virtual flux of the PWM rectifier,the method of estimating the unbalanced grid voltage is derived by combining the electromagnetic relationship.The simulation results show the effectiveness and feasibility of the proposed method.Finally,starting from the whole system,the main circuit parameter design of the control system is analyzed,and the simulation model of the control system is designed in detail. |
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