Revisiting the French Secondary Voltage Regulation and Assessing its Dynamic Behavior with Dynaωo

Voltage regulation in France relies on cascaded primary and secondary automatic controls. The former is achieved through Automatic Voltage Regulators (AVR) implemented in most power generation units to regulate their terminal voltage within a few seconds. The reference signals of these local controllers are updated by distributed Secondary Voltage Regulators (SVR) that compute per-unit reactive power levels for each control zone to regulate, within a few minutes, the voltage of a specific bus (the pilot bus). This level is translated into AVR voltage references by individual Reactive Power Control Loops (RPCL). This cascaded structure restricts the dynamics of the SVR which is set to be slower than the RPCLs. Moreover, the currently implemented SVR exhibits a non-minimum phase behavior that tends to slow down the voltage recovery following disturbances. In search for an improvement of the SVR dynamic response while taking advantage of the digitization of the grid, RTE, the French Transmission System Operator (TSO), is revisiting its control law. In this work, the positive impact that a new SVR could have on the voltage dynamics of the French network is demonstrated. The simulations are made with Dynaωo, the open-source hybrid Modelica/C++ suite of simulation tools used at RTE for voltage stability studies.