Photovoltaic (PV) power generation, as one important part of renewable energy, has been greatly developed in recent years. The stability of PV inverters is very important for the normal operation of PV systems. However, most PV systems, especially the large PV plants, locate in rural areas. The corresponding equivalent grid impedance is rather large and easy to lead to stability problems of grid-connected inverters and many researches have been done focusing on the stability problems. In this study, a survey of stability problems of PV inverters on weak grid condition is given. The stability problems are mainly divided into two parts, i.e. the control loops instability and inverter output voltage instability. The control loops cover the current loop and dc voltage loop. The output voltage instability refers to the voltage phasors relationship and the application of reactive power compensation. The non-linear parts of inverter dead-time, digital control delay, and phase-locked loop are explored. Future trends and challenges are given.

中文翻译：

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弱电网中光伏逆变器的稳定性问题综述

近年来，作为可再生能源的重要组成部分的光伏（PV）发电得到了极大的发展。光伏逆变器的稳定性对于光伏系统的正常运行非常重要。但是，大多数光伏系统，尤其是大型光伏电站都位于农村地区。相应的等效电网阻抗相当大，容易导致并网逆变器的稳定性问题，并且针对稳定性问题进行了许多研究。本文对弱电网条件下光伏逆变器的稳定性问题进行了研究。稳定性问题主要分为两部分，即控制回路不稳定和逆变器输出电压不稳定。控制回路涵盖电流回路和直流电压回路。输出电压的不稳定性是指电压相量的关系和无功补偿的应用。探索了逆变器死区时间，数字控制延迟和锁相环的非线性部分。给出了未来的趋势和挑战。