| Abstract |
Power electronic traction transformer (PETT) is an emerging technology for traction applications. LLCresonant converter is an attractive option for isolated DC/DC stage because of its high efficiency.However, there will be inevitable twice-line frequency ripple on the resonant current due to the singlephasepower fluctuation. On the other hand, parameter mismatch between modules can result in powerimbalance. Both phenomena reduce the system capacity and efficiency. In this paper, a small signalmodel of LLC resonant converter is derived, and then the converter transfer function and powercharacteristic can be obtained. By analyzing the magnitude diagram of the transfer function, upper limitof secondary DC bus capacitor can be observed. And from power characteristic, the difference betweenprimary side and secondary side voltage determines the power flow. Thus, a power balance strategybased on the single phase d-q vector control of cascaded rectifier is proposed. Power balance can beachieved by regulating primary side DC bus voltages to slightly different values. |
