Research On PWM Rectifiers Based On Deadbeat Control

Because of its sinusoidal ac current waveform, high power factor, and energy feedback ability, the PWM rectifier truly realizes "green power conversion". PWM rectifiers usually adop the voltage and current double closed-loop control strategy, in which the current loop is the key factor to the control performance. Aiming at the defects of the traditional double closed-loop PI control strategy, this thesis comes up with a deadbeat current control strategy.Firstly, the defects of the conventional double closed-loop PI control strategy are analyzed:PI control is sensitive to the system parameter variations, its anti-disturbance is weak, and it has the slow dynamic response. A deadbeat current control scheme for three-phase voltage source PWM rectifier is presented in order to improve the conventional PI control scheme, which is sensitive to system parameters. This scheme has the characteristics of the fast current tracking, good disturbance resistance, and easy digital realization.Secondly, this thesis analyzes the principle of the deadbeat control, establishes the mathematical model of three-phase voltage source PWM rectifier, and then deduces the discrete mathematical model of the deadbeat control. Predicted current control based on the phase lock function is proposed to realize the current deadbeat control. On this basis, the deadbeat control of double closed-loop control system is designed, the voltage loop with PI control and the current loop with a deadbeat control algorithm. The principle of space vector pulse width modulation is described. A simplified SVPWM algorithm is proposed on this basis. The simulation model of the deadbeat control is established in the MATLAB/Simulink environment, and it is simulated under rectifier and inverter operations. The waveforms are obtained under steady state and dynamic state, which we can see from that the deadbeat control can keep output voltage constant, current sinusoidal, and energy feedback. Simulation results verify the correctness of the theoretical analysis and the feasibility of the control system.Finally, for PWM rectifiers easy to be digitalized, the hardware and software of the deadbeat control of the PWM rectifier are studied and designed, with TMS320F2812 DSP chip as a controller. Schematic principle diagrams and PCB diagrams of the hardware circuit system are designed. In CCS integrated environment, software is designed and debugged. A experimental platform of control system is built up and relevant experiments are carried out. Experimental results further verify the feasibility of the deadbeat current control strategy.