Research On Normalized Model Of Single-phase PWM Rectifier And Its DC-ripple Control Strategy

With the advantages of bidirectional energy flow and high power factor,single-phase voltage source PWM rectifier(VSR)is widely used in various single-phase grid-connected devices,including clean energy power generation system and power compensation device.There are many control strategies have been put forward by experts and scholars at home and abroad in order to obtain better performance.Among these control strategies,the control strategy based on the rotating coordinate system has been widely used because it can control the active and reactive components independently.However,it's essential for such control strategies to fabricate the current and voltage components that are orthogonal to the grid current and grid voltage.What's more,the algorithm of this kind of control strategy is sophisticated.Owing to the defect of single-phase VSR itself,harmonic component of twice the grid frequency inevitably exists in the output DC bus.The second harmonic component seriously affects the dynamic and steady-state performance of the rectifier system,reduces the power density of the system,which may cause grid-connected current distortion in serious cases.To solve the above problems,this paper takes the classical vector control strategy of single-phase VSR as the research object.Firstly,the mathematical model of single-phase VSR in rotating coordinates is transformed into static coordinates by means of equivalent transformation of control structure.The normalized model of virtual current control strategy of single-phase VSR in static coordinates is constructed,and the differences between the model and traditional PR control model is analyzed.Meanwhile,the virtual current control strategy based on the normalized model is optimized,while the controller parameter allocation criteria are proposed to optimize the dynamic and steady-state performance of the system.The simulation and hardware experiment platform is built to verify the feasibility of the model and algorithm from the practical point of view.Secondly,aiming at the problem of secondary ripple of DC bus,the second harmonic is compensated by shunt active power filter in this paper.When it comes to the compensation circuit,Lyapunov theory is adopted in this paper to design voltage and current controllers,in order to ensure the stability of the DC side voltage of the compensation circuit and the accurate tracking of the second harmonic current by the compensation inductance.The DC bus voltage fluctuation is suppressed by injecting secondary ripple through the compensation circuit.A simulation model is built in Matlab/Simulink to verify the accuracy of the theoretical analysis.Last but not least,there is an elaboration about the hardware circuit design of singlephase VSR and the realization of control strategy in DSP chip at the end.