考虑架构灵活重构的混合式贯通牵引供电装置应急管控与故障恢复策略

Emergency Control and Fault Recovery Strategy of Hybrid Advanced Traction Power Supply Device Considering Flexible Reconfiguration

基于牵引变压器与两相交流输入至单相交流输出(两相-单相)变换单元的混合式贯通牵引供电系统(HATPSS)凭借其设备利用率高、改造成本低等优势而受到关注。然而,两相-单相变换单元作为系统中的薄弱环节,其任意端口故障会导致系统出现负序电流与功率缺失等问题,严重者将引发整个贯通系统失稳。此外,受HATPSS供电架构特殊性及其控制目标多样性的影响,传统牵引系统冗余备用方案与应急管控技术适用性差等问题突出。鉴于此,该文针对两相-单相变换单元的输入/输出端故障工况,综合考虑牵引站中既有设备应急管控潜能与两相-单相变换单元控制自由度的特点,分别提出面向HATPSS的应急管控与故障恢复策略。仅通过牵引变压器、联络开关、两相-单相变换单元等系统既有装置间的协同配合,实现在不同故障工况下HATPSS额定功率运行与负序电流抑制。最后,仿真与实验验证了在不同工况下该文所提应急管控策略的可行性与有效性。

With the rapid development of electrified railways in China,neutral sections and power quality problems have affected the daily operation of the traction power supply system.Fortunately,the advanced traction power supply system based on power electronics technology provides an opportunity to solve the above problems.The new hybrid advanced traction power supply system(HATPSS),based on the traction transformer and two-phase to single-phase(2AC-AC)converter,is gaining traction due to its high equipment utilization and low-cost advantages.However,as a weak link in HATPSS,the 2AC-AC converter can cause problems under port faults,such as negative sequence currents,power loss,and even system instability.In addition,due to the particularity of the HATPSS architecture and the diversity of control objectives,the traditional redundant backup scheme and emergency management have poor applicability.Therefore,considering the existing equipment's emergency operation potential and the 2AC-AC converter's topological advantages,the emergency management and control and fault recovery strategies are proposed respectively under the input/output fault conditions of the 2AC-AC converter.First,according to different fault locations and operation characteristics in the 2AC-AC converter,the fault type can be divided into two conditions:type I-output portγfault,typeⅡ-input portαorβfault.Under typeⅠ-output portγfault,the uαof the traction transformer’s secondary side can be connected to the traction network to ensure power supply for the traction load.Then,by controlling the power flow between portαand portβ,the two-phase power of the secondary side can be balanced to suppress the negative-sequence current.Under typeⅡ-input portαorβfault,the uαor uβcan be connected to the traction network according to the fault location of the input port to ensure power supply for the traction load.Adjusting the output power of portγallows for suppressing negative sequence currents.The fault recovery strategy is initiated once the faulty port is repaired,and the HATPSS returns to healthy operation.During the process of emergency control and fault recovery,the rated power operation of HATPSS and negative sequence current suppression are realized through coordinating the existing devices of the system,such as traction transformer,grid-connected switch,two-phase-single-phase converter,and healthy traction station.To further verify the feasibility and effectiveness of the proposed emergency control and fault recovery strategies,a 20 MW simulation model and 6 kW experimental platform of HATPSS are built.Finally,the following conclusions can be drawn from the simulation and experimental analysis:(1)The proposed emergency control strategies are realized using resources,such as contact switches,traction transformers,and 2AC-AC converters,without additional hardware investment cost.(2)Under input or output faults,the fault traction station's 100%output power supply can be ensured to improve the reliability of HATPSS effectively.(3)During the process of emergency operation and fault recovery,the fault traction station remains connected to the network,and only a transient negative-sequence current is on the power grid side,effectively improving the system's power quality.The proposed emergency control idea can also be applied to modular multilevel and high-frequency isolation architectures.