Voltage Droop Control in Power Flow Solutions
Saurav Mohapatra, Senior Software Engineer, Powerworld Corporation
In steady state power flow models, renewable generation plants (like solar and wind) are often modeled as multiple generators linked to a point of interconnection (POI) through a network of equivalent feeders and transformers. In a real power system, a plant like this is setup to collectively regulate the voltage at the POI by following a Q-V characteristic curve that varies the reactive power arriving at the POI as a function of voltage at the POI. However, traditional power flow software did not have a way to model this type of voltage control, as generators could only be configured to have a voltage set-point. In the summer of 2019, PowerWorld Simulator version 21 introduced a new software feature, termed as Voltage Droop Control, which now allows this type of control to be modeled in power flow solutions. While this behavior has been modeled in transient stability software for many years, it is a new concept in steady state power flow solutions.

This presentation will go through the need for having a Voltage Droop Control algorithm in a power flow solution, and explain how it overcomes the limitations of a traditional generator software model. Examples will be discussed to show how this feature allows for voltage droops and a voltage dead-band to be incorporated into steady state voltage regulation. It will include a demonstration to illustrate how the reactive power output of a renewable plant (i.e., a group of generators) can proportionately adjust to varying voltage conditions, and ultimately better simulate the actual operation of these plants.