Proportional harmonic current sharing among inverters is desired in ac microgrid with nonlinear loads. Usually, virtual impedance is emulated to achieve good harmonic current sharing at the cost of increased harmonic voltage distortion in the system. Existing schemes overcome this issue by communicating voltage and/or current values among inverters, thereby requiring significant data exchange. Further, some of them suffer from single point of failure because of their centralized architecture. This article proposes a distributed controller, which emulates harmonic voltage sources in addition to the virtual impedance, thereby reducing voltage distortion in the system. Furthermore, the proposed scheme reduces congestion in the communication network, as compared to the existing communication-based methods, as only two bits per harmonic frequency is communicated among inverters. The effect of virtual impedance on the stability of the system is investigated. Additionally, the impact of communication delay on the current sharing error is studied in this article. Finally, the proposed technique is validated through simulation and experimentation on a scaled-down laboratory prototype.

中文翻译：

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交流微电网的分布式控制谐波虚拟阻抗环


在具有非线性负载的交流微电网中，需要在逆变器之间进行比例谐波电流共享。通常，通过仿真虚拟阻抗来实现良好的谐波电流共享，但代价是增加系统中的谐波电压失真。现有方案通过在逆变器之间传送电压和/或电流值来克服这个问题，从而需要大量的数据交换。此外，其中一些由于其集中式架构而遭受单点故障。本文提出了一种分布式控制器，除了虚拟阻抗之外还模拟谐波电压源，从而减少系统中的电压失真。此外，与现有的基于通信的方法相比，所提出的方案减少了通信网络中的拥塞，因为每个谐波频率仅在逆变器之间通信两位。研究了虚拟阻抗对系统稳定性的影响。此外，本文还研究了通信延迟对均流误差的影响。最后，通过在缩小的实验室原型上进行模拟和实验来验证所提出的技术。