考虑新能源波动区间的交直流配电网下垂斜率鲁棒优化方法

Robust Optimization Method for Droop Slopes in AC/DC Distribution Network Considering Fluctuation Interval of Renewable Energy Source

为应对交直流配电网中新能源出力的不确定性,以交直流混合配电网电压源型变流器(VSC)为研究对象,提出了考虑新能源波动区间的交直流配电网VSC下垂斜率鲁棒优化方法。该方法在保证系统鲁棒安全的前提下最小化期望场景的网损,并采用列和约束生成算法进行求解。在下垂控制中,提出V 2ac-P和V 2ac-Q双下垂控制,在保证线性反馈下垂特性的前提下,将模型的子问题转化为混合整数二阶锥规划问题。此外,为提高子问题二阶锥松弛的精确性,提出了支路损耗限值策略,通过求解支路损耗最优潮流模型,确定每次迭代过程中各支路可能的最大损耗,并在子问题中以此为约束对支路电流进行限值。数值仿真结果表明,提出的优化方法可以以微小的经济代价显著提高系统的鲁棒安全性。支路损耗限值策略能有效提高二阶锥松弛的精确性,从而增强子问题对于极端场景的优化能力。

In order to deal with the uncertainty of the output power of renewable energy sources(RESs),this paper proposes a robust optimization method for voltage source converter(VSC) droop slopes in AC/DC distribution networks considering fluctuation interval of RESs.The proposed method aims to minimize the network loss in expect scenarios while ensuring the system robust security.The optimization model is solved by the column-and-constraint generation(CCG) algorithm.Besides,V2 ac-P and V2 ac-Q dual droop controls are proposed in the droop control schemes to guarantee the linear feedback characteristic,and therefore the sub-problem could be transformed into a mixed-integer second-order cone programming(MI-SOCP) problem.Furthermore,to improve the accuracy of second-order cone relaxation in the sub-problem,a branch loss limit strategy is designed.By solving the branch loss optimal power flow model,the maximum possible branch loss is pre-identified,and a series of branch current limit constraints are added to the sub-problem to restrain the feasible range of the branch current.Numerical simulation results suggest that the proposed optimization method can significantly improve the system robust security with little extra economic cost.The branch loss limit strategy can effectively improve the accuracy of the second-order cone relaxation.And it can enhance the optimization ability of subproblems in extreme scenarios.