The simulation for pumped storage machine withstanding excess torque in motor mode

Pumped storage machine (PSM) can operate in both generator and motor modes compared with conventional hydro generators. So PSM should be capable of withstanding the impact of power system disturbance in generator mode and possess special operating ability in motor mode. IEC60034-1:2004 "Rotating electrical machines-Rating and performance" prescribe that polyphase synchronous (salient pole) motor shall be capable of withstanding a 50%excess torque for 15 seconds without falling out of synchronism, the excitation being maintained at the value corresponding to rated load. When automatic excitation is used, the limits of torque shall be the same values with the excitation equipment operating under normal conditions. This item has been emphasized and written into contract by customers of PSM. It is also an important performance and needs to be evaluated in initial electrical calculation in order to optimize the design for PSM. To know the operating behavior of PSM withstanding excess torque, the dynamic process of system should be numeric simulated and analyzed. In this paper, the state equations of PSM are given and simulation model including machine, main transformer, transmission lines, infinite bus, automatic voltage regulator and mechanical shafting system is set up. Taking a 286 MVA PSM as a calculation example, the dynamic process of momentary excess torque for motor mode is simulated. Some main variable curves such as voltage, current, electromagnetic torque and power angle etc. are obtained. Furthermore, according to a mass of simulations, the key parameters affecting the ability of momentary excess torque are presented, which can provide references for design engineers.