Research Of Digital Controlled 400Hz Three-Phase Four-Wire High Power Factor PWM Converter

Three phase high power factor PWM converter is widely used with the rapid development of SVG, FACTS, HVDC, UPS and new energy. This paper designed a 3kW digital controlled 400Hz three-phase four-wire high power factor PWM converter covers main circuit parameters design, main circuit modeling, current controller design in d-q-0 synchronous system, output voltage balance control, drive and protection circuit design.The input current of PWM converter should be controlled as well as the output voltage to make it sinusoidal and in phase with its input voltage to realize high power factor input. Traditional PI controller has static error problem for AC signals and this problem is more serious when the fundamental frequency is 400Hz. In this paper current controller is designed in d-q-0 synchronous rotation system to achieve zero static error control.In three-phase four-wire topology, two capacitors are series connected as the output filter, and there midpoint is connected to the neutral wire of the system. So the output voltage may imbalance due to load imbalance or DC disturbance in modulated signals. Voltage balance outer loop in series with neutral current inner loop control strategy is proposed in this paper to realize output voltage balance and make the converter suitable for half-bridge inverter and other loads.TMS320F2812 digital signal processor produced by Texas Instruments is selected as the actuator of control method. Analog sampling and protection are implemented by hardware.A 3kW prototype is built and tested under various load conditions at the end of this paper to verify the validity and feasibility of the control method.