The Research On Three-phase Voltage-type PWM Rectifiers Based On Predictive Power Control With Virtual Flux

With the energy shortage and environmental pollution worsening,the utilization of new energy is gradually becoming the focus attention of the world.Therefore,the three-phase voltage-type PWM rectifier has been widely used in the field of new energy especially the wind power.However,most of the three-phase voltage-type PWM rectifiers applying currently have many problems such as low anti-interference ability,serious harmonic pollution and also need multiple sensors which not only increase system cost but also affect system's stability.In this paper,a new virtual flux oriented direct power control(VF-DPC)strategy is proposed of which the control strategy and virtual flux observer are improved,so that the problems arising in traditional methods are solved and the system can operate reliable and stable.Firstly,the paper analyzes the main circuit topology and working principle of the three-phase voltage-type PWM rectifier,then establishes its mathematical models in stationary coordinate system,the two-phase stationary coordinate system and the two-phase synchronous rotating coordinate system and all of these work laid the theoretical foundation in depth research of direct power control of three-phase voltage-type PWM rectifiers.Secondly,the paper compares the direct power control strategy on virtual flux oriented and on voltage oriented,finally chooses the first one for its low cost and well stability.Then it analyzes the traditional flux observer and the flux observer consists of the first-order low pass filter,and builds its simulation model in MATLAB.The simulation results verify the accuracy of the control strategy propose before.On the basis of the theoretical research,the paper combines the predictive control technology and a new virtual flux observer and then proposes a predictive direct power control based on new virtual flux observer.The new control strategy solves the problem of the system slow dynamic response as well as the unfixed frequency of power switching devices so that the design of filter inductor in network side becomes easy.The results of simulation and experiment both show that the improved control strategy realizes a better dynamic performance and steady operating performance.Finally,a three-phase voltage-type PWM Rectifier test system platform is built of which the main circuit hardware system and control system are detailed introduced.The digital signal processor TMS320F2808 DSP is used as a control unit in the control strategy proposed in the paper.The experiment results verify the rightness of the control strategy for the three-phase voltage-type PWM rectifier proposed in this paper in theory and the usefulness in project.