Variable speed pumping systems

A variable speed pumping system comprising:

• a generator motor including a frequency converter and a primary side synchronously connected to a commercial power system although a rotor rotates at a variable speed;
• and
• a pump turbine directly connected to the rotor of the generator motor and configured to drive the generator motor in a power generation mode and to be driven by the generator motor in a pumping mode,
• wherein the variable speed pumping system is configured to, in the pumping mode, input to a power controller a value obtained by subtracting an actual power input from a value obtained by adding a power input command to a power control correction signal calculated by a power control correction signal generator based on a deviation between a rotational speed of the rotor and a rotational speed command calculated based on the power input command and supply a power command to the generator motor to perform power control, and
• the power control correction signal generator is configured to add a value obtained by multiplying a signal based on a difference between the power input command and an actual power input measured by a power detector in the pumping mode by a constant gain to a signal based on the deviation and input the added value to an integration control element to generate the power control correction signal based on an output signal of the integration control element.