Research On A Three Phase Bidirectional PWM Converter

The three-phase bidirectional PWM converter owns such features as constant output, running under unit power factor and feedback of power into the power networks, so it is widely used in the situation which need feed back the energy into the power networks and eliminating electric harmonics. The principle of power flow and control strategy without line voltage sensors are researched in this paper.First of all,the operation principle of PWM converter is introduced in detail.Low frequency models and high frequency models are set up in ABC coordinate,α-βcoordinate and d-q coordinate respectively.Based on analsis of the direction of power flow,the space control strategy based on d-q coordinate is presented,the design principles of control loop is presented also.A new control strategy without line voltage sensors is proposed,which the line voltage can be estimated by the line current, switch signal and DC voltage. All the control strategies are simulated in Matlab software.The simulated results verify the analysis. Finally, a 1kW prototype based on DSP is build and the design methods of hardware circuit and software program are presented. The experimental results based on this prototype verify the analysis.