Long-distance power transmission makes a large-scale centralized photovoltaic (PV) power plant (CPPP) integrated into a weak power grid with a low short circuit ratio. Under this condition, small fluctuations in PV power are likely to cause significant fluctuations in system-wide voltage. To overcome this problem, a novel CPPP Volt-Var control (VVC) strategy is proposed. Unlike the conventional VVC strategy achieved in a centralized manner, the realization of the proposed VVC is mainly based on decentralized communication. The control framework for the proposed VVC has two tiers. In the upper-tier “optimal control”, a distributed VVC optimization model is formulated. Analysis target cascading (ATC) and alternating direction method of multipliers (ADMM) are combined to provide 15-minute-ahead optimal VVC scheduling, considering voltage deviation and active power losses together. In the lower tier “emergency control”, local droop control is applied to respond to the unexpected voltage deviation in real time. The final simulation results indicate that the proposed VVC strategy has good performances on the algorithm convergence in the upper tier and the control stability in the lower tier. The entire two-stage VVC could effectively maintain the system-wide voltage within the safe range and perform well on active power losses reduction, without the central controller.

中文翻译：

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基于分散通信的大型集中式光伏电站两级伏无功控制策略


长距离电力传输使得大型集中式光伏电站（CPPP）能够以较低的短路比融入弱电网。在这种情况下，光伏发电的微小波动就可能引起全系统电压的大幅波动。为了克服这个问题，提出了一种新颖的 CPPP 伏特-无功控制（VVC）策略。与传统的以中心化方式实现的VVC策略不同，所提出的VVC的实现主要基于去中心化通信。拟议的 VVC 控制框架有两层。在上层“最优控制”中，制定了分布式VVC优化模型。分析目标级联（ATC）和乘法器交替方向法（ADMM）相结合，提供提前15分钟的最优VVC调度，同时考虑电压偏差和有功功率损耗。在下层“紧急控制”中，采用本地下垂控制来实时响应意外的电压偏差。最终仿真结果表明，所提出的VVC策略在上层算法收敛性和下层控制稳定性方面具有良好的性能。整个两级VVC可以有效地将全系统电压维持在安全范围内，并且在减少有功功率损耗方面表现良好，无需中央控制器。