Research On PWM Rectifier Technology Of Wide Speed Vehicle Generator

With the increase in demand for fire control, communication, anti-terrorism and the development of power electronic technology, more and more electrical equipment is installed in special vehicles. Therefore, it is very meaningful to develop a controller which can improve the utilization rate and increase the power density of the generator. In this paper, from the perspective of power factor, a three-phase six switch PWM rectifier is used to improve the power factor of the existing generator and solve the problem of regulating voltage in the condition of variable speed.The first, the working principle of PWM rectifier is presented, and its mathematical model in different coordinate system is derived. According to the mathematical model of PWM rectifier in the d-q coordinate system, this paper chooses the voltage and current double closed-loop control strategy based on voltage feedforward and current decoupling. Voltage feedforward can restrain voltage fluctuation interference, current loop decoupling can realize the d-q axis independent control.The next, the application scheme of PWM rectifier in power generator is discussed in detail. Due to the back EMF of the winding is not measurable, this paper emphatically introduces the sliding mode variable structure observer(SMO) theory, its construction method and filtering method. The SMO can extract the back EMF of the motor winding from the generator terminal voltage and current, the robustness and accuracy is very well.Then, the hardware and software of whole generator PWM rectifier system is designed according to the previous theoretical analysis. Based on Altera's FPGA chip as the control core, this paper designs system circuit, driving circuit, sampling circuit and communication circuit, etc.. The part of software, this paper mainly introduces the main program, the SMO program, PI program, SVPWM program, protection program and host computer program.Finally, a test prototype is built, and a number of experiments are completed on the test platform. The experimental result verifies its feasibility of the algorithm.