统一潮流控制器用串联变压器设计

The Design of Series Transformer Applied in the Unified Power-Flow Controller

串联变压器作为统一潮流控制器(UPFC)系统中的关键设备,承担着换流器与交流系统交换功率的重要作用,一方面需要匹配交流系统电压与换流器直流电压,另一方面在电气结构上实现交流系统与换流器的隔离。UPFC用串联变压器在电气结构上不同于常规电力变压器,其一次侧绕组(线路侧绕组)分相接入三相线路,变压器一次侧绕组每相的首尾端拆开,经6个端口接入线路;二次侧绕组(阀侧绕组)与换流器连接,采用常规的星型或者角型接法。串联变压器的绕组需要具备承受系统短路电流的能力,同时需要具备持续一定时间的4倍过激磁耐受能力,对变压器的电气、结构等方面的设计提出了严酷的要求。文中结合南京220 k V西环网统一潮流控制器工程,分析了串联变压器的运行工况,以此为基础提出了串联变压器的关键设备参数,并对其恶劣工况下的耐受能力进行了仿真验证。

As the key equipment in the UPFC, the series transformer plays an important role in the power transmission between the convertor and the AC system. The voltage of the transformer should match the AC system voltage with the DC voltage of the convertor on one hand; on the other hand the transformer can provide the electrical insolation between AC and convertor. The electrical structure of the series transformer is different with the normal one. The primary wings of the series transformer are connected in the lines in split-phase with 6 terminals and the secondary ones are connected to the convertor with the connection of star or delta. The wings of the series transformer should be capable to withstand the short-circuit current of the power system; and the equipment should also be able to withstand four times of over-excitation capacity within certain time, which require a lot to the electric and structure of the transformer. The operation conditions of the series transformer of Nanjing UPFC project have been analyzed. Based on the analysis the key parameters for the series transformer are recommended, and the tolerance conditions of the series transformer have been simulated in the end.