A strategy for the implementation of the output impedance in single-phase inverters connected in parallel with droop control for uninterruptible power supply applications is proposed in this study. The proposal allows the load current to be distributed in proportion to the power capacity of the inverters connected in parallel, by establishing the magnitude and phase of the output impedance at the fundamental frequency and its harmonics, when the voltage control is performed through odd harmonic repetitive controllers. This is accomplished through the design of an output impedance profile based on the transfer function of a second-order high-pass filter and a virtual impedance loop. The proposal achieves a correct operation of the droop control strategy and the proper sharing of the harmonics of the non-linear load current between the inverters connected in parallel, obtaining reduced values of individual harmonic content and harmonic distortion in the output voltage with reduced processing requirements. The validity of the proposal is verified through a 2 kVA experimental prototype, considering the requirements of the international quality standards IEC62040-3 and IEC61000-2-2, in terms of output voltage regulation, individual harmonic content, and harmonic distortion for inverters operating both in islanded-mode and in parallel.

中文翻译：

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具有重复控制和下垂控制的单相逆变器中输出阻抗的实现

本研究提出了一种在不间断电源应用中与下降控制并联连接的单相逆变器中实现输出阻抗的策略。当通过奇次谐波重复执行电压控制时，通过确定基频及其谐波处输出阻抗的大小和相位，该建议允许负载电流与并联连接的逆变器的功率容量成比例地分配。控制器。这是通过基于二阶高通滤波器和虚拟阻抗环路的传递函数设计输出阻抗曲线来实现的。该建议实现了下垂控制策略的正确操作，并且在并联连接的逆变器之间实现了非线性负载电流的谐波的正确共享，从而降低了单个谐波含量的值和输出电压中的谐波失真，从而降低了处理要求。考虑到国际质量标准IEC62040-3和IEC61000-2-2的要求，该建议的有效性通过2 kVA实验原型进行了验证，包括输出电压调节，单个谐波含量和同时运行这两个逆变器的谐波失真在孤岛模式下并排运行。