Double fed synchronous generator motor
A double fed synchronous generator motor which is coupled to a reversible pump-turbine and operated while switched to a power generating operation mode or a pumping operation mode, is equipped with a controller for controlling the double fed synchronous generator motor so that power output from the double fed synchronous generator motor is coincident with an instruction value and the rotating speed is set between upper and lower limit values of the rotating speed by changing exciting current. In the power generating operation mode, the lower limit value of the rotating speed is varied by active power output from the double fed synchronous generator motor, and when the active power is small, the lower limit value of the rotating speed is set to a smaller value than that when the active power is large.
1. A double fed synchronous generator motor which is coupled to a reversible pump-turbine and operated while switched to a power generating operation mode or a pumping operation mode, comprising a controller for controlling the double fed synchronous generator motor so that power output from the double fed synchronous generator motor is coincident with an instruction value and the rotating speed is set between upper and lower limit values of the rotating speed by changing exciting current, wherein in the power generating operation mode, the lower limit value of the rotating speed is varied by active power output from the double fed synchronous generator motor, and when the active power is small, the lower limit value of the rotating speed is set to a smaller value than that when the active power is large.
2. The double fed synchronous generator motor according to claim 1 , wherein in the power generating operation mode, the lower limit value of the rotating speed is varied on the basis of reactive power by large excitation current output from the double fed synchronous generator motor, and when the reactive power by large excitation current is small, the lower limit value of the rotating speed is set to a value smaller than that when the reactive power by large excitation current is large.
3. The double fed synchronous generator motor according to claim 1 , wherein in the power generating operation mode, the lower limit value of the rotating speed is varied on the basis of a lagging power factor of power output from the double fed synchronous generator motor, and when the lagging power factor is large, the lower limit value of the rotating speed is set to a value smaller than that when the lagging power factor is small.
4. The double fed synchronous generator motor according to claim 1 , wherein in the power generating operation mode, the lower limit value of the rotating speed is varied on the basis of exciting current, and when the exciting current is small, the lower limit value of the rotating speed is set to a value smaller than that when the exciting current is large.
5. The double fed synchronous generator motor according to claim 1 , wherein the controller controls the rotating speed so that the rotating speed is coincident with the target value, and in the power generating operation mode, the target value is set to be larger than the lower limit value of the rotating speed by only a predetermined value.
6. The double fed synchronous generator motor according to claim 1 , wherein in a pumping operation mode, the lower limit value of the rotating speed is varied on the basis of active power input to the double fed synchronous generator motor, and when the active power is small, the lower limit value of the rotating speed is set to a value smaller than that when the active power is large.
7. The double fed synchronous generator motor according to claim 6 , wherein in the pumping operation mode, the lower limit value of the rotating speed is varied on the basis of reactive power by large excitation current input to the double fed synchronous generator motor, and when the reactive power by large excitation current is small, the lower limit value of the rotating speed is set to a value smaller than that when the reactive power by large excitation current is large.
8. The double fed synchronous generator motor according to claim 6 , wherein in the pumping operation mode, the lower limit value of the rotating speed is varied on the basis of a lagging power factor of power input to the double fed synchronous generator motor, and when the lagging power factor is large, the lower limit value of the rotating speed is set to a value smaller than that when the lagging power factor is small.
9. The double fed synchronous generator motor according to claim 6 , herein in the pumping operation mode, the lower limit value of the rotating speed is varied on the basis of exciting current, and when the exciting current is small, the lower limit value of the rotating speed is set to a value smaller than that when the exciting current is large.