Robust Control And Analysis Of Single-phase PWM Rectifier Based On Parameter Uncertainty

The single-phase pulse width modulation(PWM)rectifier is widely used in the traction drive system of high-speed train because of its advantages of high power factor,low harmonic content and the bidirectional flowing of energy.The operation environment of the traction drive system is very complex,and there are many faults due to the aging,overloading and improper operation of devices,as well as in the long term electromagnetic interference and electromechanical stress.So the working performance of the rectifier system in this harsh environment has become an important link to determine the safe and stable operation of the train.It is of great theoretical and practical significance to study the control strategy of the rectifier to improve the robustness of the system on the basis of guaranteeing the dynamic performance in normal operation.In this paper,the generalized internal model control strategy of single-phase PWM rectifier is studied and designed.The details are as follows:Firstly,the topology and operation principle of single-phase PWM rectifiers are discussed,and the mathematical model in static and rotating coordinates is deduced based on the circuit equations.There are two commonly used methods to construct the virtual coordinate system,and the control principle of traditional current decoupling control strategy in dq axis is also described in this paper.At the same time,after using the coordinate transformation method of SOGI-PLL,operation principle of linear quadratic regulator(LQR)is introduced,so the robust performance of the controller is deduced,and the single-phase PWM rectifier control system based on LQR is designed.Secondly,aiming at the shortcomings of LQR controller and traditional robust control in practical application,the generalized internal model control(GIMC)theory is introduced,and there are differences and connections between generalized internal model control,internal model control and Youla controller parameterization.The design method of generalized internal model controller is introduced in detail,and then the single-phase PWM rectifier control system based on GIMC is designed with LQR controller and predict current controller as nominal controller.Then,the performance of the nominal system and the robust control system under parameter uncertainties are analyzed.System based on the predictive current control,after the reference current is decoupled,it can be regarded as two identical SISO system.Calculating the amplitude-frequency response characteristics can obtain the performance of the system under the parameter uncertainty.The MIMO system based on the the LQR controller,its robustness can be analyzed using the structured singular value.Finally,the stability of the designed control structure is deduced and analyzed in detail,and the performance of the generalized internal model controller is compared and analyzed by computer simulation.The simulation results show that: in the single-phase PWM rectifier system based on generalized internal model control structure,the nominal performance determined by nominal controller can be obtained in normal operation.When there is a certain range of model perturbations or external perturbations in the system,the robust controller will operate to keep the DC output voltage and the grid side unit power factor constant.It can be obtained that this control strategy improves the robustness of the system based on not affecting the dynamic performance of the system in normal operation.