Start-up Mode Analysis And Typical Failure Study Of Static Frequency Converter In Large Pumped Storage Power Station

As China economic growing,power demand is rising with the grid capacity increasing.More and more mega-kilowatt class generator units come onto the grid,once single unit accident occurs,it will cause great impact on power grid.To improve the power supply quality and reliability continuously,it is necessary to build a quick start-stop power plant to play a role of peak load shifting and emergency standby for power grid.At present,building pumped storage units is one of the best way to solve this problem.Huizhou pumped storage power station is a large pumped storage power station with one-time investment in China.There is a Static Frequency Converter(SFC)respectively in plant A and B of Huizhou pumped storage power station.Each SFCsystem can be used for 4 units one by one when it starts in pump mode,which is connected to each unit through the 18 kVstarting bus.The unit of pumped storage power station is a reversible pump-turbine generator unit,which can be used as either a generator or a pump.There are usually two modes for pump starting mode,including static variable frequency starting and back-to-back starting.When SFCsystem works,firstly alternating current(AC)of 50 Hz from the grid is send to the bridge(Silicon controlled rectifier bridge)which outputs direct current(DC)through input step-down transformer,and then it converts DC to a rising AC of 0-50 Hz gradually with bridge inverter,and the it is transferred to the corresponding unit trough output step-up transformer,output switch,output reactor and generatrix,eventually the rotor would be accelerated gradually by magnetic field with rising frequency.When the unit speed reaches the rated speed and meets the synchronization condition,the unit is combined to the grid through after the unit circuit breaker switching on.The process of starting Condenser-Pump condition of a unit using SFCsystem is successful.Then the SFCsystem quits operation and waits for a starting command of the next unit.Static variable frequency startup mode is widely used in pumped storage now,because there are so many advantages,such as smaller impact onto power grid,smaller harm to the generator and quick startup reliably.Therefore,this study is of the theoretical and practical significance by using the static variable frequency startup mode in the pump-turbine generator set.