Voltage control in renewable plants

Voltage droop control is an essential function of the PPC, that enables the power plant to automatically regulate its reactive power output in response to deviations in grid voltage. This functionality plays an important role in supporting grid voltage stability by providing an appropriate reactive power response to voltage.

voltage control in RE

Figure - Voltage Droop Characteristics of the PPC During over-voltage events, the plant absorbs reactive power from the grid and support voltage regulation. On the other hand, during under-voltage events, the plant tries to supply extra amount of reactive power, subject to the available reactive power reserve and operating limits, to help restore grid voltage. The change in reactive power (ΔQ), calculated based on the measured voltage deviation and predefined droop characteristic. This is provided as an input to the reactive power control block along with the existing reactive power setpoint. The reactive power control block combines these inputs to determine the revised reactive power reference, ensuring an appropriate response to grid voltage variations while maintaining the plant's operating constraints. Voltage droop is determined by a configurable droop coefficient, typically ranging from 1% to 10%, which specifies the sensitivity of the reactive power response to voltage variations. For example, a 3% droop setting corresponds to a voltage deviation of ±0.03 pu to achieve a 100% change in the available reactive power reserve.