Research On Optimization Of Control Strategy Of Single-phase PWM Rectifier

PWM rectifier is a device that can "green" transform electric energy.It has the advantages of unit power factor operation,small current harmonic,stable DC voltage and bidirectional energy flow.It has been widely used in marine electric propulsion,electric locomotive traction,new energy power generation and other fields,and has achieved good economic and social benefits.With the rapid development of power quality control technology,the requirement for higher performance of static and dynamic power rectifier is put forward.Therefore,it is very important to study the control strategy of single-phase PWM rectifier.In order to improve the dynamic response speed,reduce the current harmonic content and ensure the stability of DC voltage,this paper mainly studies the optimization of control strategy.First,analyze the topological structure and working mode of the single-phase PWM rectifier,and establish the mathematical model of the main circuit of the rectifier in the two-phase stationary coordinate system and the rotating coordinate system.Since the single-phase system has only one degree of freedom,four methods for constructing virtual quadrature components are summarized and analyzed,and the advantages and disadvantages of each method are compared and analyzed.On this basis,design and calculate the main circuit parameters including AC-side inductance and DC-side capacitance,and analyze the basic principles of single-phase SPWM and single-phase SVPWM modulation techniques,and build a simulation model with dual closed-loop control for comparison and simulation.The result shows that the current waveform of the SVPWM modulation method is smooth and the harmonics are small,which is closer to unity power factor.Secondly,the power mathematical model of the single-phase PWM rectifier is calculated based on the single-phase instantaneous power theory,and a direct power control algorithm with power feedforward decoupling is proposed.On this basis,the principle of direct power control strategy based on traditional voltage outer-loop control is analyzed in detail.In order to improve the dynamic response speed of single-phase rectifier system,a direct power control strategy based on capacitive energy storage outer-loop control is proposed.Two simulation models of different outer-loop control algorithms are built.The simulation results of the two show that the single-phase PWM rectifier can work normally under the two control algorithms,the AC-side can achieve unit power factor approximately.And the dynamic performance and anti-interference ability of the capacitive energy storage outer loop control system are better than traditional voltage outer loop control.Third,based on the model reference adaptive method,it is proposed to construct a single-phase PWM rectifier without grid-side voltage sensor control system.Based on the analysis of the basic theory and method classification,the system active and reactive power mathematical models in the reference model and the adjustable model are established respectively,and the grid-side voltage amplitude and angular frequency are estimated by adjusting the adaptive law.Combine the power feedforward decoupling direct power control algorithm to build a complete single-phase grid side voltage sensorless control system,and build a complete system simulation model for simulation verification,in the case of grid-side voltage amplitude mutation,frequency mutation and phase mutation,the control system can realize the tracking of the grid-side voltage signal.Finally,this paper builds a low-power experiment platform with DSP as the control core to verify the voltage and current double closed-loop control algorithm of the single-phase PWM rectifier.