Research On Grid Voltage Sensorless Control Strategies For PWM Rectifier

Modern power electronic technology has been widely used in power and other industries. The PWM rectifier with the advantages of high power factor, bi-directional energy flow and no power "pollution", has became real "green power conversion" technology.the "green power conversion". Therefore, focus on green environmental protection today, the research on PWM rectifier has become one of the hot topics in the field of power electronics.Firstly, the topology of the PWM rectifier is given, the working principle of threephase voltage type PWM rectifier is analyzed in theory, established the mathematical model of PWM rectifier in three kinds of coordinate system. On this basis, analysis of the voltage oriented control strategy without net pressure sensor, method for estimation of AC voltage is given, and explains its advantages and disadvantages; According to the similarity of the features of PWM rectifier topology and AC motor, and introduces the concept of virtual flux, according to the state of the switch of DC bus voltage, alternating current and rectifier estimate virtual flux estimation, the grid voltage angle through the virtual grid flux, so as to achieve the purpose of a AC voltage. In order to effectively overcome the traditional integral initial value problem of virtual flux observer, based on the analysis of advantages and disadvantages of the traditional virtual flux observer, a new virtual flux observer is proposed, voltage sensorless control strategy gives the virtual grid flux oriented, the realization of the PWM rectifier AC voltage sensorless control. The simulation verified the feasibility of the model for virtual flux observer and effectiveness.Then,combined with the definition of instantaneous power, analyzed the principle of direct power control, and the application of a new virtual flux observer research on PWM rectifier direct power control, put forward the non pressure sensor network direct power control strategy based on virtual flux orientation. The simulation results show that: Under the condition of grid voltage sensorless, the system has better control effect of instantaneous power.Finally, the control system of PWM rectifier is designed, mainly including the selection of parameters in the main circuit, the design of control system of double closed loop, SVPWM modulation algorithm etc.