Variable Damping Control And Application Of PWM Rectifiers

The PWM rectifier has a lot of advantages compared with the traditional rectifier in performance, it is widely used in modern power electronic devices and an effective way to power pollution control. The three-phase PWM rectifier is a nonlinear and strong coupling complex system, although a variety of linear control theory has been very mature, can not meet the requirements of more fast and more accurate. In recent years, various nonlinear control method development and application to PWM rectifier, so that the performance of rectifier is greatly improved. Nonlinear control methods such as fuzzy control, intelligent control, based on passivity control methods have their advantages and disadvantages. To improve the performance of system, some methods improved and several methods mixed.In this paper, variable damping and sliding mode control were added into the port controlled Hamiltonian method to study the performance of the rectifier.Firstly, the model of PWM rectifier of resistive load are respectively established in abc coordinate and dq coordinate. The port controlled Hamiltonian method used and the controller of PWM rectifier is designed by using interconnection and damping assignment, and it changes damper by the tracking-differentiator to realize the variable damping control.Secondly, the three-phase PWM rectifier system is seen as a switching system. The injection damper of system switched between different damping value according to switching laws in all kinds of disturbance, and the realization of PWM rectifier switching control.Thirdly, sliding-mode control method and port controlled Hamiltonian method are combined to control the rectifier. The sliding-mode variable structure algorithm used in outer loop, and the sliding surface is constructed by the error and derivative of output voltage. The port controlled Hamiltonian method used in inner loop, and the controller is designed by interconnection and damping assignment. The sliding-mode and port controlled Hamiltonian control is realized.Fourthly, the inverter and the motor of back-to-back AC drive system are considered as a load of rectifier. To achieve the four quadrant work of motor, the rectifier is controlled by port controlled Hamiltonian method and the motor side is controlled by vector control method. The changes of voltage in DC side of rectifier and the power flow are studied.The above control methods are simulated in Matlab/Simulink, which show that the methods can realize PWM rectifier DC side voltage stability, unity power factor operation and has good dynamic and static response under various disturbances, and achieve control requirements.