基于级联式多电平变换器的静止无功补偿器拓扑研究

Topology Research of Static Reactive Compensator Based on Cascade Multilevel Converter

电力系统实时无功补偿对提升电能质量至关重要,传统的无功功率补偿常采用大容量的电抗器、电容器,体积大、重量大、效率低。静止无功补偿器采用全控开关器件构成,具有可控,动态响应速度快,损耗低,效率高的优点。以单相H桥为级联单位串联而成的级联式多电平变换器可通过对各个H桥进行移相控制,输出多电平波形,提高输出电压正弦度,降低谐波含量,减小滤波器的体积,且具有扩展性强,适应性强,实现容易等优点。介绍了级联式多电平变换器的拓扑与工作原理及适用于该变换器的基于三角载波移相技术的PWM调制策略,通过降低开关管的开关频率,提高系统的效率。最后搭建了仿真模型验证了该拓扑与调制策略的有效性。

Real-time reactive power compensation of a power system is very important to improve power quality.The traditional reactive power compensation often uses large-capacity reactors and capacitors,which are large in volume,heavy in weight and low in efficiency.The static reactive compensator is composed of fully controlled switching devices,which has the advantages of controllable,fast dynamic response,low loss and high efficiency.The cascaded multilevel converter,which takes single-phase H bridge as the cascaded unit in series,can output multilevel waveform,improve the sinusoidal degree of output voltage,reduce the harmonic content,and reduce the volume of filter through phase shifting control of each H bridge.Moreover,it has the advantages of strong scalability,strong adaptability and easy implementation.This paper introduces the topology and working principle of cascade multilevel converter.Then the PWM modulation strategy based on the triangle carrier phase shifting technology is introduced to reduce the switching frequency of the switching tube and improve the efficiency of the system.Finally,a simulation model is built to verify the effectiveness of the topology and modulation strategy.