考虑配电网电能质量改善的分布式光伏优化调度方法

针对配电网中存在的电压越限、谐波畸变、三相不平衡等问题,从综合改善多电能质量问题的角度出发,研究了一种配电网分布式光伏优化调度模型及其求解方法。首先,分析了分布式光伏并网逆变器进行无功功率、谐波电流及不平衡功率补偿的控制方案;在此基础上,以可调度分布式光伏的三相功率及谐波电流输出为控制变量,基于配电网三相基波及谐波潮流方程,建立了最小化网络损耗、不平衡电压以及谐波电压的最优潮流模型;然后,提出了一种潮流计算与优化计算交替迭代的两阶段优化求解算法,对非凸非线性的最优潮流模型进行变量削减,并将其转换为凸二次约束二次规划模型从而实现高效求解;最后,通过一个162节点三相配电网进行算例分析,结果表明,根据最优潮流模型结果对分布式光伏进行调度后,配电网谐波畸变、三相不平衡以及电压越限问题得到了有效改善,且两阶段优化求解算法的计算效率也满足配电网调度时间要求,验证了所提分布式光伏优化调度方法在改善配电网电能质量方面的有效性。

Optimal Scheduling Method for Distributed Photovoltaic Generation in Distribution Network Considering Power Quality Improvement

Aiming at the problems of voltage violation, harmonic distortion and three-phase imbalance in distribution network, this paper studies the optimal scheduling model and its solution algorithm of distributed photovoltaic generation in distribution network from the perspective of comprehensively improving power quality. Firstly, the control scheme of reactive power, harmonic current and unbalanced power compensation of the grid-connected inverter of distributed photovoltaic generation is analyzed. On this basis, taking the three-phase power and harmonic current output of schedulable distributed photovoltaic generation as control variables, combined with the three-phase fundamental and harmonic power flow equations of distribution network, an optimal power flow model considering the improvement of power quality is established. Then, a two-stage optimization algorithm with alternating iteration of power flow calculation and optimization calculation is proposed to reduce the variables of the nonconvex nonlinear optimal power flow model and convert it into a convex quadratic constrained quadratic programming model, so as to achieve efficient solution. Finally, a case study is carried out on a 162-node three-phase distribution network. The results show that, after the scheduling of distributed photovoltaic generation according to the solution of optimal power flow model, the problems of harmonic distortion, three-phase imbalance and voltage violation of distribution network have been effectively improved, and the computational efficiency of the two-stage optimization algorithm also meets the distribution network scheduling requirements, which verifies the effectiveness of the proposed optimal scheduling method for distributed photovoltaic generation in improving the power quality of distribution network.