多逆变器并联系统环流分析及抑制方法

Circulating Current Analysis and Suppression Method for Multi-inverter Parallel System

多逆变器并联可以提高系统的功率等级和可靠性,已在大功率的逆变器上得到广泛应用。但逆变器并联存在因载波相位不一致引起的环流问题,会增加系统的损耗。本文首先分析了环流产生的机理,通过对逆变器输出电压进行双傅里叶分析,推导出载波相位差与环流之间的关系表达式,并得到环流开关分量的特性。然后,在分析的基础上提出了一种载波相位补偿的控制策略,该策略能有效改善对开关环流的控制能力,对因载波相位不一致产生的环流起到显著抑制效果。采用PI控制电压外环、无差拍控制电流内环的双闭环控制策略,保证了逆变器系统的正常稳定运行。最后,仿真结果验证了本文所提出的控制策略的有效性和可行性。

Multiple inverters in parallel operation can improve the power level and reliability of the system,thus theyare widely applied to high power inverters. However,the inconsistencies due to carrier phase-shift will increase the sys-tem loss. First,the generation mechanism of circulating current is analyzed,the expression of the relationship betweenthe carrier shifted phase and circulating current is formulated according to the double Fourier transform on the outputvoltage of inverters,and the characteristics of switching components in circulating current are obtained. Then,based onthe above analysis,a control strategy of carrier-phase compensation is proposed to inhibit the circulating current causedby the carrier phase difference,which can effectively improve the control capability of the switching frequency circulat-ing current. The dual-loop control strategy,which uses PI controller for the outer voltage and deadbeat control for the in-ner current,can ensure the normal and stable operation of the inverter system. Finally,the simulation results verify theeffectiveness and feasibility of the proposed control strategy.