两级式双向DC/DC变换器的电流纹波抑制

Current Ripple Suppression of Two-stage Bidirectional DC/DC Converter

双向DC/DC变换器作为储能电池和直流母线的桥梁,电流纹波问题越来越受到关注。首先分析了双向DC/DC变换器中输入电流纹波来源。由于并网使得输入输出功率不平衡,直流母线上存在二次脉动,若控制上无法有效调节母线电压的脉动,则输入电流会含有二次纹波。而当数字控制的精度不够时,每一次调节都会产生较大的量化误差,该量化误差会造成输入电流中的数字化纹波。针对上述问题,建立了小信号模型并对纹波进行了量化计算,提出了比例积分微分谐振(PIDR)控制并应用了高分辨率脉宽调制(PWM)技术。分析了LLC谐振变换器在并网软启时结电容过大导致的能量反灌问题,搭建s域模型,定量分析了开关管寄生电容对变换器的电压电流的影响,并选用结电容更小的SiC金属-氧化物半导体场效应晶体管(MOSFET)解决了该问题。最后搭建了一台2 kW的双向DC/DC变换器,验证了分析和所提策略的有效性。

Bidirectional DC/DC converter,as a bridge between energy storage battery and DC bus,the current ripple problem is attracting more and more attention.The source of input current ripple in bidirectional DC/DC converter is analyzed.Because of the grid-connection,the input power is inequal to the output power,and there is secondary ripple in the bus voltage.Without proper regulation,there is secondary ripple in the input current.When the accuracy of digital control is not enough,each adjustment will produce a large quantization error,which will cause the input current in the digital ripple.A small signal model is built to calculate the current ripple theoretically.The proportion integral differential resonant(PIDR)control is proposed and the high resolution pulse width modulation(PWM)technique is applied to reduce current ripple.Secondly,the energy backfilling problem caused by the large junction capacitance of LLC resonant converter in the soft startup of grid-connected converter is analyzed.The s-domain model is built to quantitatively analyze the influence of parasitic switching tube capacitance on the voltage and current of the converter,and the SiC metal-oxide-semiconductor field-effect transistor(MOSFET)with smaller junction capacitance is selected to solve this problem.Finally,a 2 kW bidirectional DC/DC converter is built to verify the effectiveness of the analysis and the proposed strategy.