面向光伏并网的动态容性补偿器及其优化控制

Dynamic Capacitive Compensator for Photovoltaic Connection and Its Optimal Control

光伏经逆变器接入弱电网时,容性补偿对于增强逆变器功率传输能力与并网稳定性具有重要意义。为解决传统容性补偿装置性能与成本之间的矛盾,提出一种动态容性补偿器。首先,根据接入静止无功发生器的光伏并网系统在dq坐标系下的基频等效电路模型,分析了容性补偿对其功率传输能力的影响。其次,介绍了动态容性补偿器(dynamic capacitive compensator,DCC)电路拓扑与工作原理,并综合考虑负载与线路阻抗的无功消耗,提出瞬时无功与电压下垂调节相结合的无功指令电流计算方法,基于此给出了晶闸管投切电容器控制策略。同时,针对DCC特殊结构带来的LC串联谐振问题,提出了LC支路电流反馈的有源阻尼优化控制策略和反馈参数设计方法。最后,仿真与实验结果验证了DCC拓扑与优化控制策略的有效性。

When photovoltaic power is connected to a weak grid via an inverter, the capacitive compensation is of great significance for enhancing the power transmission capacity of the inverter and the stability of the grid connection. In order to solve the contradiction between the performance and the cost of the traditional capacitive compensation device, a type of dynamic capacitive compensator is proposed. First, according to the fundamental frequency equivalent circuit model of the photovoltaic grid-connected system connected to the static var generator in the dq coordinate system, the influence of capacitive compensation on its power transmission capability is analyzed. Secondly, the topology and working principle of the dynamic capacitive compensator(DCC) circuit are introduced.considering the reactive power consumption of load and line impedance comprehensively, the reactive power command current calculation combining the instantaneous reactive power with the voltage droop adjustment is proposed. Based on this,the thyristor switching capacitor control strategy is given. At the same time, for the LC series resonance problem caused by the special structure of DCC, the active damping optimization control strategy and the feedback parameter design method of the LC branch current feedback are proposed. Finally,simulation and experimental results verify the effectiveness of the DCC topology and the optimized control strategy.