Virtual synchronous generator with active damping

A control system for controlling a power generating unit, the power generating unit comprises a power source, a machine side converter, a line side converter, a DC link electrically connected to an output of the machine side converter and an input of the grid side converter, and filter inductors and filter capacitors arranged at the output of the power generating unit, the control system is arranged to perform an operation, comprising:

• obtaining capacitor voltage signals in a measurement frame by measuring capacitor voltages of one or more of the filter capacitors;
• determining a virtual synchronous machine rotational speed and/or a synchronous machine angle, where the derivative of the synchronous machine rotational speed is indicative of a deviation between a power reference for a desired power output of the power generating unit and a grid power supplied by the power generating unit to the output combined with a damping power;
• providing a voltage magnitude reference for the desired reactive power to be generated by the line side converter;
• optionally, transforming the capacitor voltage signals from the measurement frame into a target frame to generate transformed capacitor voltage signals;
• filtering the capacitor voltage signals, or the transformed capacitor voltage signals, with a compensation filter into filtered capacitor voltage signals, where the compensation filter s designed to reduce a magnitude of an impedance peak and/or shift the impedance peak, where the impedance peak is present in an impedance characteristic of the output of the power generating unit;
• and
• determining a filter compensated voltage reference by combining the voltage magnitude reference, or a transformation thereof, with the filtered capacitor voltage signals.

A system, comprising:

• a wind turbine, comprising:
• a tower;
• a nacelle;
• a generator disposed on the nacelle;
• and
• a rotor extending from the generator and having a plurality of blades disposed on a distal end thereof;
• a power generating unit, comprising:
• the generator;
• a machine side converter;
• a line side converter;
• a DC link electrically connected to an output of the machine side converter and an input of the grid side converter;
• a plurality of filter inductors and filter capacitors arranged at an output of the generator;
• and
• a control system for controlling the power generating unit according to an operation, comprising:
• obtaining first capacitor voltage signals in a first measurement frame by measuring capacitor voltages of one or more of the filter capacitors;
• determining a virtual synchronous machine rotational speed and/or a synchronous machine angle, where the derivative of the synchronous machine rotational speed is indicative of a deviation between a power reference for a desired power output of the power generating unit and a grid power supplied by the power generating unit to the output combined with a damping power;
• providing a voltage magnitude reference for the desired reactive power to be generated by the line side converter;
• filtering the first capacitor voltage signals with a compensation filter into filtered capacitor voltage signals, where the compensation filter is designed to reduce a magnitude of an impedance peak and/or shift the impedance peak, where the impedance peak is present in an impedance characteristic of the output of the power generating unit;
• and
• determining a first filter compensated voltage reference by combining the voltage magnitude reference, or a transformation thereof, with the first filtered capacitor voltage signals.