Research On Predictive Direct Power Control For Three-phase Voltage-Type PWM Rectifiers

With the development of economy,there is an increasing need of convertor device to be used in modern industry,includ ing high frequency switching power supply,transduer and so on.Most of these devices use rectifier to produce dc voltage.The conventional method takes uncontrolled rectifier or phase controlled rectifier as rectifier link which inject harmonic currents and reactive power to the grid.At the same time,with the development of power electronics,more non-liner loads are injected into grid and it bring about increasingly serious harmonic pollution.Therefore,all kinds of new technology which are based on PWM are introduced to the power conversion device.The new technology can effectively reduce the harmonic pollution,and has been widely used.The control strategy of the three-phase voltage type PWM rectifier is as the objective to study.Depended on the topological structure of three-phase voltage-type source rectifier,the paper described the operation principle and mathematical model in static three-phase coordinates,static two-phase coordinates and rotary two-phase coordinates.Then this paper produced the concept of instantaneous power and described calculation method of instantaneous power.According to the literature of the existing the control of three-phase voltage-type source rectifier is divided into three types:vector control,direct power control based on switching table,direct power control based on space vector modulation.Respectively,a brief introduction of the three kinds of control strategy and the important modules are analyzed in detail.At the same time building simulation models of the three kinds of control strategies.Through the simulation results which are analyzed in theory and simulation analysis,it is concluded that the advantages and disadvantages of the three control strategies.According to the classification of predictive direct power,this paper focuses on the model predictive direct power control and deadbeat predictive direct power control.Firstly,based on the traditional model predictive control theory this paper put forward a new model predictive direct power control which is no complexity in the method and also is no restriction to indicating the required average voltage vector of the convertor at the beginning of each switching period.Secondly,because digital the practical implementation needs discrete-time intervals,the systematic sampling and algorithm can not be instantaneous and time delay is unavoidable.At the same time,after the disappearance of the instantaneous active and reactive power controller error,the appropriate control vector can not be more effectively selected.This paper respectively introduces the delay compensation and repetitive control to optimize the predictive direct power control system(the model predictive direct power control and the deadbeat predictive direct power control).A comparative study by numerical simulation of the proposed modified predictive direct power control,conventional predictive direct power control based direct power control for three phase PWM rectifier using MATLAB/Simulink,and a simulation analysis is carried out.At the same time,research on parameter mismatch of system performance under the condition of different control strategies and a simulation analysis were carried out.Based on the above simulation results,it is concluded that proposed modified predictive direct power control have much better steady-state performance and dynamic performance than predictive direct power control.Finally,a digital signal processor(TMS320F2812DSP)as the control center of the three-phase voltage-type PWM rectifiers for hardware and software design is carried out and the proposed method was validated.