Research On Three Phase PWM Converter Based On Fuzzy-PI Control

Nowadays the energy conservation has become the mainstream in the world. However, the energy efficiency in our country is low, especially in the motor system which accounted for more than 70% of the electricity consumption. Therefore, energy-saving of motor system is very important. In the occasion of four-quadrant operation, the traditional general inverter based on traditional diode rectifier, not only wasting a lot of energy, but would also bring potentially dangerous and severe harmonics pollution to the power grid. The new PWM could stratify the requirement of bidirectional power flow. And it reduces pollution of harmonics, brings high performance and power factor.Firstly, the principle of a three-phase PWM rectifier is analyzed. Through the circuit Vectors steady equations of the system are established. Through those equations, this paper analyzes the steady-state characteristics and the regulative relationship of main parameters in the system. These analyses provide a theoretical basis for design of the parameters of the rectifier.Then article describes the differential equations of three-phase voltage source rectifier. By Park transformation, mathematical model is established under the d-q rotating coordinate system. Based on the double closed-loop control strategy, the parameters of PI controller are design through simulation. By establishing Simulink model and simulation, the feasibility of the theoretical design method in the rectifier system is verified. In addition, the paper also elaborate on the principle and the improved algorithm of the space vector pulse width modulation(SVPWM) which could effectively broaden the scope of system parameters and steady-state operating range.Finally, this paper presents the structure and principles of fuzzy control strategy. The fuzzy-PI fuzzy controller which combines the fuzzy control and traditional PI-controller is used in the voltage outer loop. Through the system characteristics analysis and simulation, designing and building a Simulink model of the system. The feasibility that the fuzzy-PI controller could improve system performance is showed in multiple cases of simulation.