Impact of Plant Level Voltage Control of Large-Scale Inverter Based Generators on Long-Term Voltage Stability

Long-term voltage instability has been the trigger of major system collapses. Since its main causes were identified, many System Integrity Protection Schemes (SIPSs) have been proposed for systems that are dominated by Synchronous Generators (SGs). With the increased replacement of SGs by Inverter Based Generators (IBGs), the effectiveness of traditional SIPSs needs to be assessed. This paper investigates the impact of IBGs on long-term voltage stability focusing on the plant level voltage control. The IEEE system for voltage stability (the Nordic test system) is used for this purpose. It is concluded that the plant level voltage control can improve the long-term voltage stability when combined with a SIPS and a proper reactive power limitation. Despite what could be assumed, a high reactive power injection is not always the appropriate course of action to avoid voltage collapse in cases where it comes along with a considerable active power reduction by IBGs.