System and method for mitigating overvoltage on a DC link of a power converter

A method for mitigating overvoltage on a DC link of a power converter of an electrical power system connected to a power grid caused by transients on the power grid, the method comprising:

• receiving a voltage feedback signal from the DC link;
• determining a power going into the DC link of the power converter;
• receiving an active power feedback from a rotor-side converter of the power converter;
• receiving an active power feedback from a line-side converter of the power converter;
• determining a difference between the active power feedback from the rotor-side converter and the active power feedback from the line-side converter, the difference representing the power going into the DC link;
• receiving a DC capacitance from the DC link;
• predicting a future voltage value on the DC link as a function of the difference between the active power feedback from the rotor-side converter and the active power feedback from the line-side converter, the voltage feedback signal, and the DC capacitance;
• and,
• controlling the electrical power system based on the future voltage value.

A wind turbine power system connected to a power grid, the wind turbine power system comprising:

• a doubly-fed asynchronous generator (DFAG) comprising a rotor and a stator, the DFAG connected to the power grid;
• a power converter comprising a rotor-side converter electrically coupled to a line-side converter via a DC link;
• and,
• a controller communicatively coupled to the DFAG and the power converter, the controller configured to perform a plurality of operations, the plurality of operations comprising:
• receiving a voltage feedback signal from the DC link for a predetermined time period;
• determining a rate of change of the voltage feedback signal during the predetermined time period by processing the voltage feedback signal via a differential element, the differential element comprising a washout filter and a low-pass filter;
• and,
• predicting a future voltage value on the DC link by summing the voltage feedback signal and the rate of change of the voltage feedback signal;
• and,
• controlling the electrical power system based on the future voltage value.