The Study Of Three Phase Boost Type PWM Inverters Based On Direct Power Control Strategy

Nowadays, with the pollution of the environment and increasing depletion of energy, it’sparticularly important to develop and use renewable energy. Three phase inverter as theutilization of new energy, energy conversion devices, is one of the people focuses of the study.PWM inverter with low harmonics of the grid-side current, unity power factor, etc.. The maincontent of this paper is to conduct a in-depth study about direct power control system inthree-phase boost type PWM inverter.In this paper, the historical development and the current research of the inverters, and thecontrol method of modern inverter technology were described. The mathematical models ofthree-phase boost type PWM inverter, respectively, are established with the analysis ofinverter topology and working principle in the three-phase static coordinate system, thetwo-phase stationary coordinate system and two-phase synchronous rotating coordinatesystem.The paper mainly studied direct voltage oriented power control strategy (VO-DPC) andvirtual flux oriented direct power control strategy (VFO-DPC) for three-phase boost typePWM inverter. This paper introduce the definition and calculation of the instantaneous power,describe the theoretical basis of the direct power control system, and analyses VO-DPCsystem architecture. Fundamentals of structuring switch table are analyzed detailedly.Improved method on the basis of the original switching table enhance the regulatory role ofthe instantaneous reactive power.The value of the virtual flux is calculated by the DC voltage, line-side current and theinverter switching vector. Further, instantaneous active power and instantaneous reactivepower is obtained. Integrator initial value problem is solved, when virtual flux observer isconstructed. The structure and working principle of the VFO-DPC system is analyzeddetailedly. The main circuit parameters of PWM inverter are also designed.Finally, in the simulation environment of MATLAB/SIMULINK，the models of directpower control system of three-phase boost type PWM inverter have been established to verifyvoltage oriented direct power control system and virtual flux-oriented direct power controlsystem. The results show that the VO-DPC system has the advantages of high power factor,low current distortion rate, as well as simple algorithms and system structures; VFO-of DPC system can still achieve the same effect with VO-of DPC system without AC voltage sensor.