Optimal Idling Control Strategy For Three-port Full-bridge Converters

As the energy crisis and environmental pollution have been aggravated, new energy and newenergy vehicles have been spilt into public view. As effective solutions, they are researched by lots ofscholars. The power supply systems of new energy and new energy vehicles are used to put the newenergy sources, the traditional energy sources, the energy storage units and the load together. Insteadof several separate DC/DC converters, the power supply systems adopt a multi-port DC/DC converter,which can not only simplify the system structure but also reduce the cost. In some operationconditions, the port connected to the energy storage unit may quit from the system, leaving this idlingport at zero power. Though keeping out of the drive signal for the MOSFETs in the idling port, thepower will continue to go through the body diodes of MOSFETs. As a result, an active controlstrategy should be introduced to solve this problem.Take three-port full-bridge converter as the research object. At first, the power transfercharacteristics and soft-switching ranges of the converter are analyzed under both phase-shift controland phase-shift plus PWM control. Based on this, the operation mode with one port power flow atzero is researched in detailed. Under phase-shift control, voltage and current close-loops and dualvoltage close-loops are used. According to different close-loops control, soft switching ranges and theconduction losses are given. Under dual voltage close-loops control, the voltage of the idling port islimited by the power of the converter. The converter cannot realize zero-voltage-switching (ZVS)within the wide input voltage and power range under the voltage and current close-loops control,resulting in a low efficiency. With the analyses of soft-switching range and conduction losses underphase-shift plus PWM control, the optimal idling control strategy was proposed to ensure the switchesrealizing ZVS and the conduction losses to be minimum within the wide input voltage and powerrange. Finally, a1kW simulation model and two1kW prototype converters have been built to verifythe theoretical analyses.