考虑转供与重构协同的多端柔性互联配电网供电恢复策略

Optimal Power Restoration Strategy for Multi-Terminal Flexible Interconnected Distribution Networks Based on Flexible Interconnection Device and Network Reconfiguration

柔性互联装置(FID)实现配电网不同馈线之间的柔性互联,可实现故障后配电网的快速恢复供电。该文以含直流网络的四端柔性互联配电网为研究对象,提出基于FID和网络重构的多端柔性互联配电网两阶段供电恢复策略。首先,在分析FID运行模式工作原理的基础上,提出了故障快速转供的FID平滑控制结构和考虑开关同期并网控制虚拟同步发电机(VSG)控制策略,支撑故障后第一阶段FID的快速供电恢复;然后,通过建立和求解考虑联络开关和FID容量限制的全局优化模型得出FID与网络重构相结合的第二阶段供电恢复策略,更大限度地恢复失电负荷;最后,利用PSCAD/MTDC仿真软件搭建了一个58节点四端含直流网络的柔性配电系统进行仿真验证。结果表明,所述供电恢复策略不仅能实现部分负荷的不停电转供,还能够通过网络重构大幅提高负荷恢复水平。

With the developments of the"dual carbon"goal and accelerated energy transformation,a high proportion of new energy and large-scale new load integration,as well as the widespread application of flexible power electronic equipment,have put forward higher requirements for the morphology,structure,operation control,and power quality of the existing distribution network.Flexible interconnection device(FID)enables flexible interconnection between different feeders in the distribution network,enabling rapid restoration of power supply after faults.At present,the power recovery strategy for FID is to directly provide the control strategy for the corresponding scenario,operating status of the FID,and the final operating status of various switches.There is little research on the coordinated control of multi terminal FIDs,support for power supply recovery control strategies,dynamic process of power supply recovery in distribution networks based on FIDs,and collaborative cooperation between FIDs and various mechanical switches.To address these issues,this paper takes the four-terminal flexible interconnection distribution network with DC network as the case study,and proposes a two-stage power supply restoration strategy for multi-terminal flexible interconnection distribution network based on FID and network reconfiguration.Firstly,based on the operation principle of FID,the smoothing control structure for FID with fast power transfer under fault conditions,and the VSG control strategy considering the switching simultaneous grid connection control,are proposed to support the fast power supply restoration in the first stage after a fault.Then,a second-stage power restoration strategy combining FID and network reconfiguration is derived by building and solving a global optimization model considering contact switching and FID capacity limitation,which restores the lost loads to a larger extent.Finally,a 58-node four-terminal flexible distribution system with DC network is constructed by using PSCAD/MTDC simulation software for simulation verification.The results showed that through the proposed two-stage fault recovery strategy,the important load of the fault network was increased by 0.05%after optimization,and the general load was improved by 9.61%after optimization.The total recovery situation was improved by 7.07%.This fully demonstrates the effectiveness of the proposed method.The following conclusions can be obtained from this paper.(1)The proposed two-stage power restoration strategy combining FID and network reconfiguration can not only support seamless power transfer of lost loads,but also realize a wider range of lost loads restoration.(2)The proposed fault smooth switching control with mode switching can smoothly and quickly complete the power restoration after a fault occurs,and guarantee the non-stop transfer of some loads.(3)The proposed VSG control strategy considering synchronous grid connection of switches can effectively avoid the inrush current at the instant of switch closure when switching from off-grid to grid-connected operation after fault removal,and also avoid the inrush current generated by frequent switching of the contact switches under power during the optimization phase of network reconfiguration.The two-stage recovery strategy proposed in this paper can achieve a wider range of fault recovery,but the focus of this paper is on the recovery strategy and process,and it does not involve the study of how to make use of the active regulation capability of FID to achieve the detailed continuous state transfer and action sequence of near-zero-power switching of the contact switch,which will be studied in detail in our future work.