MMC换流阀最优三次谐波注入方法研究

损耗是衡量柔性直流输电系统性能的关键指标之一。对调制波叠加三次谐波可以提高换流阀直流电压利用率,还可以增大换流阀的冗余度,提高可靠性。推导了叠加三次谐波后换流阀的损耗计算公式,详细分析了三次谐波叠加率对换流阀损耗的影响。计算结果表明,随着三次谐波叠加率的增大,换流阀损耗逐渐降低,但是此时的冗余度与损耗并不是最优值,因此通过遗传算法对损耗与冗余度进行了优化配置以兼顾损耗与冗余度。结果表明:当三次谐波叠加量达到24.3%时的时候损耗与冗余度取得性能平衡,此时总损耗为1.485%,冗余度为12.7%。

Optimal Method of Third Harmonic Injection to MMC Value

The loss of the converter valve is one of the key indexes to evaluate the VSC HVDC transmission system.In this paper,in order to improve the availability of VSC HVDC converter valve,the three harmonic wave is injected to the modular wave.By this way,the redundancy degree of the converter valve can be improved.The formula of the losses of converter valve is obtained under this way.The impact of the three harmonic superposition rate on the losses of converter valve is discussed in detail.Example results show that the losses of converter valve are reduced with the increase of three harmonic superposition rate.But the redundancy degree and losses is not enough good at this time.So we get the optimal allocation between redundancy degree and losses by genetic algorithm.The results show that when the three harmonic superposition rate reaches 24.3%when the losses and redundancy get performance balance,then the total loss is 1.485%and redundancy degree is 12.7%.