为提高电压质量,降低线路损耗,在考虑光伏出力随机波动和负荷预测误差的基础上,提出了低压配电网无功补偿分散配置的鲁棒优化模型。模型以配电台区总网损最小为目标,采用不确定集描述负荷功率以及影响光伏出力的光照强度和温度等不确定变量,约束条件包括了节点电压的上下限和无功补偿容量的上下限,以及补偿装置安装点总数的限制。利用变形的S型函数近似逼近符号函数以实现对模型中不可导函数的光滑化,并通过双层优化方法将含不确定变量的鲁棒优化模型转化为双层确定性优化模型进行交替求解,最后采用内点法优化求解确定性优化模型以得到分散无功补偿鲁棒优化配置方案。通过对某个实际低压配电网台区进行分析计算,结果表明所提出的分散无功补偿配置鲁棒优化方法得到的补偿方案能够满足光伏出力和负荷在其波动区间内任意变化时所有节点的电压均在合格范围内,具有良好的工程实用性。
In order to improve voltage quality and reduce line loss, a robust optimization model of distributed reactive power compensation for low voltage(LV) distribution network is proposed, considering random fluctuation of photovoltaic(PV) output and forecasting error of load power. In this model, objective is to minimize total power loss of distribution network, with uncertain variables of load power, light intensity and temperature affecting PV output discribed as uncertain set. Its constraints include upper and lower limits of node voltage and reactive power compensation capacity, and limit of total number of installed compensation devices. A deformed S-function is used to approximate symbolic function to smooth non-differentiable function in the model. Bi-level optimization method is used to transform robust optimization model with uncertain variables to bi-level deterministic optimization model, which is solved alternately. Finally, interior point method is adopted to solve the deterministic model to obtain robust optimal allocation scheme of reactive power compensation. Analysis of a real LV distribution network demonstrates that the obtained robust optimal allocation scheme of reactive power compensation can ensure all node voltage qualified no matter how LV output and load power changes in their own fluctuation interval, so the scheme is more applicable in engineering.