5L-ANPC逆变器输出电压谐波解析计算方法

Analytical Calculation Method of Output Voltage Harmonics for 5L-ANPC Inverter

光伏系统谐波影响传统低压配电系统的故障特征,对光伏系统谐波特征的有效解析是对电力电子设备高渗透率低压网络故障检测的基础。针对五电平有源中点箝位型(5L-ANPC)逆变器在电网中的应用,提出一种载波移相调制下输出电压谐波的解析计算方法。首先将5L-ANPC逆变器等效为电容箝位型三电平级联逆变器,然后进一步等效为两电平H桥级联逆变器。根据叠加关系及两电平输出电压谐波的解析表达式,推导出5L-ANPC逆变器输出电压谐波的解析表达式。仿真与实验验证结果表明,所提计算方法能够准确表征逆变器的输出谐波,该方法可为多电平变换器的输出滤波器设计提供理论依据。

The harmonics of photovoltaic system affect the fault characteristics of traditional low-voltage distribution system,the effective analysis of the harmonic characteristics of photovoltaic system is the basis of fault detection for high permeability low voltage network of power electronic equipment.Aiming at the application of five level active-neutral-point-clamped(5L-ANPC)inverter in power grid,an analytical calculation method of output voltage harmonics under carrier phase-shift modulation is proposed.Firstly,the 5L-ANPC inverter is equivalent to a capacitor clamped three-level cascade inverter,which is further equivalent to a two-level H-bridge cascade inverter.According to the su-perposition relation and the analytical expression of two-level output voltage harmonics,the output voltage harmonics analytical expression of the 5L-ANPC inverter is derived.The simulation and experimental results show that the prop-osed method can accurately represent the output harmonics of the inverter.This method can also provide theoretical basis for the design of output filter of multilevel converter.