Widely existing circuit topologies and inverter control strategies for photovoltaic (PV) systems allow customer flexibility but also introduce different kinds of interharmonics into the grid. A complete understanding of interharmonics from PV systems, with reasons behind their origin, remains needed. In addition, the time-varying nature of interharmonics and the potential impacts on other equipment are yet to be understood. In this paper, laboratory and field measurements of seven different inverter types at multiple locations are presented. A comprehensive analysis is performed to understand the existence, persistence, and propagation of interharmonics in PV systems on the dc side as well as grid side for different power levels. The origins of the interharmonics are established with experimental evidence and through a comparative analysis. A rural low voltage six customer network, with two different impedance profiles caused by the installation of PV, is considered to show the potential impact on customer voltage. To address the time-varying nature of interharmonics, a sliding window ESPRIT method is preferred over fast fourier transform (FFT)-based methods.

中文翻译：

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不同类型并网光伏逆变器系统中的时变间谐波

现有的用于光伏 (PV) 系统的广泛现有电路拓扑和逆变器控制策略允许客户灵活使用，但也会将不同类型的间谐波引入电网。仍然需要全面了解光伏系统的间谐波及其起源背后的原因。此外，间谐波的时变特性以及对其他设备的潜在影响尚待了解。在本文中，介绍了在多个位置对七种不同逆变器类型进行的实验室和现场测量。执行综合分析以了解不同功率水平的直流侧和电网侧光伏系统中间谐波的存在、持续和传播。间谐波的起源是通过实验证据和比较分析确定的。一个农村低压六客户网络，由于安装光伏而具有两种不同的阻抗曲线，被认为显示了对客户电压的潜在影响。为了解决间谐波随时间变化的问题，滑动窗口 ESPRIT 方法优于基于快速傅立叶变换 (FFT) 的方法。