Power Conversion Research Of Parallel DC/DC Converters

With the advance and development in technology, Bi-directional DC/DC Converter (BDC) has been used more and more widely. BDC is the two-quadrant operating DC/DC converter, it can achieve the transmission of energy in either direction and have wide application prospects. Because of the need for high-power loads, the research of parallel DC/DC converters are increasing. In the parallel system, current-sharing control must be introduced to balance current distribution. Current-sharing technique has become one of key techniques in the parallel system.Based on present situation, this dissertation proposed parallel BDC topology. By using the rational control strategy, the parallel BDC can achieve two-way flow of energy and sharing of current. In the reference literatures, four topologies of non-isolated BDC as well as common current-sharing methods were analysed and compared in detail. Finally, bidirectional Buck/Boost converter and automatic current-sharing policy were selected in this design. Based on the detailed work analysis of the bi-directional Buck/Boost converter, the control method and components parameters were setted according to the design requirements.By using the MATLAB simulation software, Buck converter, Boost converter, single-module BDC as well as parallel BDC simulation models were established, and it achieved the simulation of three-loop control for parallel system. The simulation results were compared with non-current-sharing control method. The results showed that the power can flow in either direction and the current sharing effect was better, so it verified that the theoretical analysis and calculations were right. It provided simulation experience for the application of the parallel BDC.Finally, the control circuit of hardware and software design were completed. Hardware circuits included voltage sampling circuit, current sampling conversion circuit, protection circuit and driver circuit. Software design focused on the overall design ideas, digital PID control theory and digital current-sharing method and so on. The paper concluded with a brief anti-disturbing design of the system.