Impedance Matching for VSC–HVDC and Energy Storage Damping Controllers

The small-disturbance electromechanical dynamics of a power system can be translated to an equivalent circuit model with inductances and capacitances. Damping control of active power in proportion to local frequency as with a voltage source converter (VSC)–HVdc link or energy storage then corresponds to introducing a resistor in the circuit model. This letter shows that impedance matching can be used to select resistor value and, equivalently, damping controller gain, that gives maximum damping ratio. It is also shown how the concept is employed without a circuit model.