电网电压不平衡下燃料电池并网逆变器功率控制

Power Control of Grid-connected Inverter for Fuel Cell under Unbalanced Grid Voltage

基于参考指令变更的三相并网逆变器功率控制方法,通过调节影响功率波动的参考指令内的谐波分量可以实现逆变器电流质量和功率波动间协调控制,但不能实现三相电压不平衡下负序交流分量的无静差调整。针对此问题,提出了三相电压不平衡下燃料电池三相并网逆变器功率控制方法,构建了燃料电池三相并网逆变器电路拓扑结构。在此基础上采用无锁相环直接功率控制方法,采用全通滤波器对并网逆变器电路中的电压和电流基波分量进行90°相移,消除2倍频的负序交流分量,实现并网逆变器有功功率和无功功率的有效控制。仿真结果证明,所提方法控制的并网逆变器进网电流谐波含量为0.33%,输出电流正弦度较高,电网电压不平衡状态下仍能坚持对电流进行控制。该方法功率控制效果好,具有较强的安全性。

Using the power control method for a three-phase grid-connected inverter based on changes in reference instruction,the coordinated control of current quality and power fluctuations of the inverter can be realized by adjusting harmonic components in the reference instruction that affect power fluctuations.However,the non-static adjustment of the negative-sequence AC component under three-phase voltage imbalance cannot be realized.To solve this problem,a power control method for the three-phase grid-connected inverter for fuel cell under three-phase voltage imbalance is proposed,and the inverter’s circuit topology is obtained.On this basis,a direct power control method without phase-locked loop is adopted.The voltage and current fundamental components in the grid-connected inverter circuit are shifted by 90°using an all-pass filter to eliminate the negative-sequence AC component with 2-fold frequency,thus realizing an effective control of active and reactive power of the grid-connected inverter.Simulation results show that the harmonic content of current in the grid-connected inverter controlled by the proposed method is 0.33%,the sine degree of output current is higher,and the current can still be controlled under grid voltage imbalance.Owing to its satisfying power control effect,the proposed method has advantages in security.