Research On Direct Power Control Strategy Of PWM Rectifier Under Unbalanced Voltage

With the rapid development of power electronics converters,more and more converters have been widely used in the national economy and society.However,the traditional phase-controlled rectifier circuits not only bring a lot of reactive power into the grid,but also bring great harmonic pollution to the grid.In this paper,after analyzing the danger and harmfulness of the phase-controlled rectifier circuits,the advantages and characteristics of PWM rectifier are pointed out.Then,the research status of PWM rectifier is introduced from three aspects: topological structure of PWM rectifier,control strategy and PWM rectifier control strategy under unbalanced conditions.The problems and research directions of PWM rectifier are pointed out.In this paper,the basic principle of PWM rectifier is introduced firstly.Starting from the classification and topology of PWM rectifier,this paper introduces the topologies of the voltage source,the current source rectifier,single-phase and three-phase PWM rectifiers in detail.The advantages and disadvantages of topologies abovementioned are analyzed.In this paper,the vector relation and four-quadrant operation of the rectifier under steady-state condition are described,and the derivation of the mathematical model of the PWM rectifier is given.Secondly,the basic working principle of traditional direct power control of PWM rectifier is introduced.The calculation and deduction of the instantaneous power of PWM rectifier are introduced in different coordinate systems.And the working principle of each module for direct power control is given.In order to solve the problems of high power ripple and current harmonics in conventional DPC,the existing literatures have proposed some methods to reduce power ripple.However,these methods are usually complicated and increase the calculation burden of the system.This paper proposed a novel and effective method to obtain the duty ratio based on the conventional duty ratio modulation methods.And the switching table of the conventional DPC is optimized simultaneous.The proposed schemes are able to reduce the power ripple and total harmonic distortion while reduce the computational burden.Simulations validate the effectiveness of the proposed schemes in this paper.