为保证工业生产和居民用电对电能质量和供电可靠性的高要求，配电网不停电合环负荷转供的研究具有重要意义。目前配电网合环通常需要借助额外的装置，存在经济性较差等问题，近年来，基于多交流端口电力电子变压器的研究逐渐得到关注并已实际应用，针对该应用场景以及不停电合环负荷转供需求，可基于电力电子变压器不同端口的控制实现柔性合环，拓展其应用功能。文中提出了基于多交流端口级联型电力电子变压器(multiple-AC-ports cascaded H-bridge type power electronic transformer, MAC-CHB-PET)的交流柔性合环方案。文章介绍了MAC-CHB-PET的结构；分析了合环冲击电流和合环稳态电流产生的内在机理，并根据选取的特征因素提出了一种基于MAC-CHB-PET合环调节的功率指令值计算方法；进而提出了不停电负荷转供的交流柔性合环方案，基于MAC-CHB-PET采用两个交流端口有功功率和无功功率的协调控制进行交流母线电压调节，实现交流柔性合环；最后建立仿真模型，验证了所提出交流柔性合环方案的可行性。
英文摘要:
The research on uninterrupted loop-closing load transfer in distribution network is of great significance to ensure the high requirements for power quality and supply reliability in industrial production and residential electricity. At present, the loop-closing of the distribution network usually requires the use of additional devices, which has problems such as poor economic efficiency. In recent years, the research on power electronic transformers based on multiple-AC-ports has gradually attracted attention and has been put into practical application. For this application scenario and the demand for uninterrupted loop-closing load transfer, flexible loop-closing can be achieved based on the control of different ports of power electronic transformers to expand its application functions. This paper proposes an AC flexible loop-closing scheme based on the multiple-AC-ports cascaded H-bridge type power electronic transformer (MAC-CHB-PET). The structure of MAC-CHB-PET is analyzed. The internal mechanism of the impulse current and steady-state current generated during loop-closing are analyzed, and a power command value calculation method based on MAC-CHB-PET loop-closing regulation is proposed based on the selected characteristic factors. Furthermore, the AC flexible loop-closing scheme for uninterrupted load transfer is proposed, based on MAC-CHB-PET, which adopts coordinated control of active and reactive power at two AC ports to regulate the AC bus voltage and achieve AC flexible loop-closing. A simulation model is established to verify the feasibility of the proposed AC flexible loop-closing scheme.