Frequency changing actuation in pump operation of the pumped storage hydropower units is a systematic problem, induced due to the main connection and high voltage synchronization. Theoretically, the key point to insure the success of unit start is the control of the SFC output current, the increase method of the excitation current during the actuation, selection of the transformer's iron core and the control schemes of the monitoring system. In short, a successful start can be assured only if a good coordination is obtained of the relationship of different equipment. This is already approved in the Shisanling pumped storage hydropower station. There is a history of the synchronization mode. The Japanese Hongkawa pumped storage hydropower station is the first one in the world to adopted high voltage synchronization and frequency change actuation, the main reason of which was difficult to manufacture a breaker at the exit of the generators which had then large load and required phase changing. Nevertheless, their practice has approved that if necessary measures are taken such a synchronization and connection mode is feasible, except for the more complicated control techniques. The Shisanling station has, through trial operation, obtained a success, but there are still two aspects requiring further study:1. An in-depth analysis is impossible at present to observe the percentage of shunting for the main transformer due to limited conditions. But it is a subject for the future. 2. Because the main transformer has not been put into operation for an enough long time, the phenomenon of residula magnetism is not outstanding, and that is why to emphasize a strict monitoring to it in the future, to insure a smooth starting actuation by SFC in pump mode.
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