基于HPWM调制的级联H桥型多功能串联补偿器的研究

Research on cascaded H⁃bridge multifunctional series compensator based on HPWM

公用电网欠发达地区的铁路电力电源有时直接利用牵引变电27.5 kV电源,并通过变压器向铁路配电所提供10 kV电源。这样的供电方式存在电压波动大、谐波含量高等严重的电能质量问题,对供电负荷影响巨大。基于此,提出一种基于混合脉宽调制(HPWM)的级联H桥型串联补偿器。该串联补偿拓扑通过采用基波电压控制和谐波电压、电流控制的混合控制策略,同时结合低频和高频优化混合调制方法,在不影响THD的情况下,降低了总开关频率且提高了10 kV侧电能质量。所提拓扑及方法不仅能够实现负载基波和谐波电压的补偿,而且在10 kV侧电压正常或波动时均能够对负载产生的谐波电流进行隔离。同时,基于控制目标对调制信号进行了优化分配,采用HPWM调制在保证较高质量多电平输出波形的同时有利于降低开关损耗。最后,仿真验证了理论分析的正确性。

Sometimes,the power supply of 27.5 kV traction substation will be directly used for railway power supply in areas with less developed public power grid,and transformers are used to provide 10 kV power supply to railway distribution station.Such a power supply mode has poor power quality,for example,large voltage fluctuation and high harmonic content,which has great influence on power supply load.In view of this,a cascade H⁃bridge series compensator based on hybrid pulse width modulation(HPWM)is proposed.By adopting fundamental wave voltage control and a hybrid control strategy of harmonic voltage&current control,and combining the hybrid modulation method of low frequency and high frequency optimization,the series compensation topology reduces the total switching frequency and improves the power quality of 10 kV side without affecting THD.The proposed topology and method can not only realize the fundamental wave and harmonic voltage compensation of the load,but also isolate the harmonic current generated by the load when the 10 kV side voltage is normal or fluctuating.The modulation signals are subjected to optimal distribution based on the control target.The HPWM is beneficial to reducing switching loss while ensuring high quality multilevel output waveform.The simulation has verified the correctness of the theoretical analysis.