Topology Modification And Power Optimized Control For Push-Pull Dual Active Bridge Converter

Push pull bi-directional DC-DC converter has the advantages of simple control,less power switches and low cost.It is widely used in new energy generation system to connect energy storage device and voltage bus to improve the operation stability of the whole micro grid.In push-pull bidirectional DC-DC converters with half-bridge topology,the push-pull forward circuit can minimize the number of switches and effectively suppress the voltage spikes at both ends of the power switches.However,the soft switching and circulating current performance for conventional push-pull dual active bridge(DAB)converter with half-bridge structure is limited,and the problem of hard switching is obvious under light load.To solve these problems,in this thesis,two MOSFET are added to the high voltage side of the conventional half-bridge type push-pull dual active bridge converter and the extended phase shift(EPS)control is adopted to enlarge the zero-voltage switching(ZVS)range.In addition,an optimized control law is also proposed to minimize the RMS current at the high voltage side of the converter.Compared with the control scheme before optimization,the optimized control scheme can reduce the effective value of current when transmitting the same power,so as to reduce the loss.Finally,the simulation results based on PSIM and experimental results are used to verify the above theoretical analysis.These results show that the converter can realize ZVS of all power devices under a wide voltage range,which is suitable for the field of new energy power generation with input or output voltage variation.44 Figures,6 Tables,60 References...