三相负荷平衡的光伏逆变器与充电桩协调优化控制策略

Load Balancing With PV Inverters and EV Chargers in Unbalanced Distribution Grids

摘要:

平衡的三相四线制或五线制低压配电网能夠显著增加对分布式电源、电动汽车的接纳能力。大量光伏发电、电动汽车接入低压配电网可能导致网损大幅增加,三相不平衡加剧,配变过载,电压越限,威胁配电网的安全、经济运行。针对已有的负荷平衡方法代价高、适应性低的不足,从将重载相负荷转移至轻载相的基本原理出发,提出了在配电网中配置多副公共直流母线,设计了两种将位置相近、从不同相接入的光伏逆变器、充电桩直流侧连接至此共同直流母线的具有不同结构与造价的方案。构建了光伏逆变器、充电桩协调优化控制的线性约束混合整数二次规划的模型。模型的目标函数能够兼顾降损与平衡负荷。采用实际71节点低压配电系统仿真计算,与无序充电及经典方法进行了对比,验证了所提方法计算速度快,能夠满足在线运行的要求,具有完全平衡三相负荷,降低网损,削峰填谷,改善供电电压质量等优越性能。#$NL关键词: 光伏发电；电动汽车；配电网；协调优化控制；三相不平衡

Abstract:

Balanced three-phase four-wire or five-wire distribution grids can host significant more photovoltaic generators (PV) and electric vihicles (EV). A large amount of EV and PV connected to low voltage distribution grids may aggravate three-phase imbalance, increase the network losses, overload the distribution transformers and deteriorate the voltages, threatening the safe and cost effective operation of distribution grids. The current load balancing methods are too expensive or can not fully balance the three-phase load. In this paper, two schemes that the DC sides of adjacent single phase PV inverterts and EV chargers are coonected to a common DC bus to transfer load from highly load phase to less loaded phase are proposed. Based on this two schemes, two modelsSofSco-scheduling PV inverters and EV chargers to minimize network losses with load balancing taken into account are formulated. The proposed method are compared with the uncoordinated charging scenarios and the classic method which aim at minimizing the three-phase load variance. The proposed optimization is evaluated using an actual 213-bus case as the test system. Results are promising with the proposed method having good convergence under time-ef?cient calculations while providing optimization of power losses and load balance, lower load variance, and improvement of voltage pro?les versus the uncoordinated scenarios and classic method.