抑制燃料电池单相逆变系统低频纹波的波形控制方法

Waveform Control Method for Mitigation the Low-frequency Current Ripple in the Fuel Cell Single Phase Inverter System

燃料电池单相交流供电系统中,负载所需两倍于输出电压频率的脉动功率将通过直流侧辐射到燃料电池,从而导致燃料电池输出能量的波动,降低燃料电池系统的能量转化效率,威胁其安全运行,严重影响燃料电池的寿命和稳定性。针对燃料电池分布式发电和电动汽车等单相交流供电系统,采用差分式逆变结构,提出抑制燃料电池输出侧低频电流纹波的有源控制方法——波形控制方法。该方法通过分别控制两支差分电容电压的方式为交流侧提供负载所需要的脉动功率,而平均功率则由直流侧电源提供,有效抑制了燃料电池输出的低频电流纹波。该方法在不增加硬件成本的条件下,保证输出电压质量的同时有效抑制燃料电池输出低频电流纹波。对波形控制方法进行详细的理论分析,并且选取合适的设计参数,从稳态和大范围负载输出动态两方面进行仿真和实验,结果验证了所提出方法的可行性和有效性。该方法可以推广到级联变换器间的解耦研究与应用。

Fuel-cell power systems comprising single-phase DC/AC inverters draw low-frequency AC ripple currents at twice the output frequency from the fuel cell. Such a 100/120 Hz ripple current may create instability in the fuel cell system, lower its efficiency, and shorten the lifetime of fuel cell stack. This paper presented a waveform control method that can mitigate such a low-frequency ripple current being drawn from the fuel cell, while the AC power Distributed Power Generation System or the Electric Vehicle Power Supply system delivers AC power to the load through a differential inverter. It is possible that with the proposed solution, the pulsation component of the output AC power will be supplied mainly by the two output capacitors of the differential inverter while the average DC output power is supplied by the fuel cell, without any extra hardware. Theoretical analysis, simulation, and experimental results were provided to explain the operation and show the steady state and dynamic performance with wide range load of the approach. Results validate that the proposed solution can achieve significant mitigation of the current ripple as well as high quality output voltage without extra hardware.