Strategy Research On The Direct Power Control Of Three-phase Voltage Source PWM Rectifier

With the remarkable development of power and electronic technologies and people's growing attention to energy conservation, power and electronic equipments are getting more attention for its highly efficient and practical. Rectifiers are widely used in various fields for their merits such as low harmonic pollution and operation with unity power factor. The most important factor in affecting each performance index is the control system strategy that the system adopts. Therefore in recent years, study on rectifier control strategy is becoming a key research direction for scholars in all countries, and among all the control strategies, Direct Power Control(DPC) is outstanding and receives much concern for it boasts fast track power, fast dynamic response, high power factor and easily applicable structure.Most DPC systems contain two controlling units: direct voltage outer control and instantaneous power inner-loop controller. In traditional Voltage Oriented Direct Power Control(VO-DPC) system, the instantaneous power inner-loop controller usually adopts switching vector table and lag power loop comparator, which will result in unstable switch frequency and lag of control in the whole system. This paper proposes a Model Predictive Direct Power Control(MP-DPC) strategy in order to solve these problems. This strategy uses model predicative controller to take the place of power lag loop comparator to enhance the speed of control. Meanwhile, such control strategy is integrated with Space Vector Pulse Modulation(SVPWM) to modulate and control voltage space vector with the average voltage vector as the basic vector of the whole control process, which simplifies the structure of DPC system and lowers the difficulty of design.This paper proceeds from the main circuit topology of three-phase voltage source PWM rectifier and analyzes from two aspects: math model and instantaneous power theory. Later it analyzes the topologies of two strategies: VO-DPC and MP-DPC, studies design methods and builds math models. In the end, in MATLAB simulation software, it employs simulink environment to build VO-DPC and MP-DPC models and through comparison and analysis of the simulation experiment results of the two control strategies, this paper proves that the control effect of MP-DPC exceeds that of VO-DPC.