基于架空线传输的风电柔直并网系统容易发生瞬时直流故障,利用风机内部配置的储能单元消纳故障期间的不平衡功率是一种有效解决方案.然而,现有文献未考虑各个储能单元之间的剩余容量差异,将风电场等值为单台风机进行研究,这容易造成剩余容量较小的储能单元过载,而剩余容量较大的储能单元仍有富余的储能能力未被利用,从而导致故障期间功率不平衡.针对上述问题,本文提出一种基于风电场储能优化控制的直流故障穿越协调控制策略.该策略将荷电状态(State of Charge,SOC)方差作为定量描述储能单元剩余容量差异程度的指标,并以SOC方差下降率最大作为目标函数,将非故障极换流站转带后的剩余不平衡功率优化分配给各个风机内部的储能单元,在保证故障期间系统功率平衡的同时,缩小各储能单元之间的剩余容量的差异.在PSCAD/EMTDC仿真平台上搭建模型将所提出的储能功率优化分配方案与传统平均分配方案进行对比.结果表明,储能功率优化分配方案充分发挥了储能系统的功率消纳能力,提高了系统直流故障穿越能力.
DC fault ride-through of MMC-HVDC-connected wind farm via optimized energy storage control
The Modular Multilevel Converter-based High Voltage Direct Current(MMC-HVDC)overhead line transmission scheme is susceptible to instantaneous DC faults,and utilizing the Energy Storage Units(ESUs)in-stalled within each wind turbine to absorb unbalanced power during faults is an effective solution.However,existing literature often considers the wind farm as a single Wind Generator(WG),neglecting the differences in residual ca-pacities among individual ESUs.This approach easily leads to overloading of ESUs with smaller residual capacities,while those with larger residual capacity still have unutilized reserve capacities,resulting in power imbalance during faults.To address these issues,this paper proposes a coordinated control strategy for DC fault ride-through based on optimized control of ESUs within WGs.The strategy adopts the variance of the State of Charge(SOC)as an indica-tor to quantitatively describe the differences in residual capacities of ESUs,and takes the maximum decline rate of SOC variance as the objective function.The residual unbalanced power after the conversion of non-fault pole convert-er station is optimally allocated to the ESUs within individual WGs,so as to reduce the differences of residual capac-ities while ensuring the power balance of the system during faults.A model is developed on the PSCAD/EMTDC simulation platform to compare the proposed optimized power allocation scheme with the traditional average alloca-tion scheme.The results show that the optimized allocation scheme fully utilizes the power absorption capacities of ESUs,thereby improving the DC fault ride-through capability of the system.
wind powerflexible DC transmissionenergy storageDC fault ride-through
万方数据
维普
