Power generation device

A power generation device comprising:

• a variable speed generator motor or a variable speed generator in which a secondary side DC-excited plunge pole type rotor rotates at a variable speed and a primary stator is connected to a commercial power system via a frequency converter;
• and
• a pump turbine or a water turbine directly connected to a rotor of the variable speed generator motor or the variable speed generator and configured to drive the rotor during a power generation operation and to be driven by the rotor during a pumping operation, wherein
• the power generation device is configured to:
• perform, in the power generation operation, speed control by providing a speed control command calculated based on a deviation between a rotational speed of the rotor and a rotational speed command by a rotational speed control device including a proportional control element, an integral control element, and a differential control element to the pump turbine or the water turbine, the pump turbine or the water turbine being a motor, and
• perform power control by providing a power output command to the variable speed generator motor or the variable speed generator, and wherein
• in cases that the variable speed generator motor or the variable speed generator is operated at a variable speed, and that an output of the pump turbine or the water turbine due to an increase in a decreasing rate of a rotational speed at a sudden increase in load from a partial load in a total head to a maximum output in a power plant with respect to a rotational speed command value corresponding to a maximum output is insufficient for a power output equivalent in a vicinity of a fully opened guide vane opening and the rotational speed decreases,
• the power generation device is configured to:
• stop an increase in a generator motor output command or a generator output command for a certain period of time;
• and
• cancel the stop of the increase in the generator motor output command or the generator output command after the rotational speed is increased until the output of the pump turbine or the water turbine is equal to or higher than a maximum power output including electric machine losses of the variable speed generator motor or the variable speed generator and the frequency converter as well as a DC excitation device.