Analysis and Control of Voltage Stability in Offshore Wind Systems Under Small Disturbances

This paper proposes an analysis of voltage stability under small disturbances following the integration of an offshore wind farm into a real power system, considering various load and generation scenarios under both normal and post-disturbance conditions. This study utilizes the southern region equivalent system, simulated with Anarede software version 11.7.2, an offshore wind farm with a maximum capacity of 2010 MW. This wind farm is modeled as a PQ bus, operating at partial (50%) and full (100%) generation levels. Three power factor scenarios are examined: resistive, capacitive, and inductive. Submodule 2.3 of the Brazilian National System Operator guidelines states that the base case operating conditions are considered voltage insecurity. Resistive and capacitive power factor operation improved voltage stability margins but resulted in overvoltage on several buses. Conversely, inductive power factor operation led to reduced stability margins and undervoltages at buses near the wind farm. Contingency analysis further revealed stability margins below security limits. Static Var Compensators were installed at critical buses to mitigate these effects, successfully eliminating the initial overvoltage and undervoltage. Modeling as PQ buses does not guarantee stability, making compensators essential for the safe integration of offshore wind generation in Brazilian test systems.