Stability Boundaries for Offshore Wind Park Distributed Voltage Control

In order to identify mechanisms causing slow reactive power oscillations observed in an existing offshore wind power plant (WPP), and be able to avoid similar events in the future, voltage control is studied in this brief for a plant with a static synchronous compensator, type-4 wind turbines, and a park pilot control. Using data from the actual WPP, all stabilizing subsystem voltage proportional-integral controller parameters are first characterized based on their Hurwitz signature. Inner loop current control is then designed using internal mode control principles, and guidelines for feedforward filter design are given to obtain required disturbance rejection properties. This brief contributes by providing analytical relations between power plant control, droop, sampling time, electrical parameters, and voltage control characteristics, and by assessing frequencies and damping of reactive power modes over a realistic envelope of electrical impedances and control parameters.