基于动态调节下垂曲线的光伏逆变器两阶段协调控制策略

Two-stage Voltage Coordinated Control Strategy of Photovoltaic Inverter Based on Dynamic Adjustable Droop Control Curve

在分布式光伏高渗透的有源配电网中,常规集中、局部电压控制已无法经济有效地解决电压越限、波动问题。为此提出光伏逆变器集中-局部电压两阶段控制策略,局部控制曲线采用多曲线节点灵活可调的改进无功-电压(Q-V)下垂曲线。集中控制阶段以电压控制成本与电压越限条件风险价值的加权和最小为目标函数,利用分布鲁棒优化算法和模型预测控制算法考虑光伏出力预测不确定性,对各光伏逆变器的有功功率削减量参考值和Q-V下垂曲线进行分钟级全局优化设置和调节;局部控制阶段根据Q-V下垂曲线和实时测量的节点电压,动态调整光伏逆变器无功出力。采用改进的IEEE 37节点配电系统进行仿真,结果表明:所提控制策略不仅能够集中、最优地协调各光伏逆变器的有功功率削减量和无功出力,避免电压越限,还能在局部控制阶段利用集中优化后的Q-V下垂曲线使电压波动降低40.56%,满足配电网运营商对电压控制经济性和鲁棒性的不同需求。

In the active distribution networks penetrated by a proliferation of distributed photovoltaic(PV),traditional central and local voltage control can’t solve the voltage fluctuation problem economically and effectively.Therefore,this paper proposes a two-stage voltage control strategy for PV inverters.The local control curve adopts flexible and adjustable improved volt-var(Q-V)droop control curve.The central control stage takes the weighted sum of voltage control cost and the conditional value at risk(CVaR)of voltage violations as the objective function,uses the distributionally robust optimization algorithm and the model predictive control algorithm to consider PV prediction uncertainty,and performs minute-level global collaborative optimization of each PV inverter’s curtailed active power reference and adjustable nodes of the proposed Q-V droop control curve.The local control stage dynamically adjusts the reactive power output based on the Q-V droop control curve and the real-time measured local voltage.Simulation results of the modified IEEE 37 bus distribution system show that the proposed control strategy can not only centrally optimize the coordination of the curtailed active power and reactive power output of each PV inverter to avoid voltage violations but also utilize the centrally optimized Q-V droop curve in the local control stage to reduce voltage fluctuations by 40.56%,meeting different economy and robustness requirements of the distribution network operators for voltage control.