Grid connected converters as reactive power ancillary service providers: Technical analysis for minimum required DC-link voltage

Providing solutions for reactive power compensation next to reactive loads is beneficial for the efficiency of the overall grid system. The main reactive power compensation solutions are based on passive VAR generators (like capacitor banks) or active VAR generators (like static VAR generators). Extra use of VAR generators can be avoided by providing reactive power through renewable energy systems or loads, which are connected to the grid through Grid connected Converters (GcCs). In fact, GcCs can be controlled so that, in addition to their main control task, they realize an additional reactive power ancillary service. In this context, this paper investigates the achievement of reactive power ancillary service using three-phase GcCs and presents a detailed analysis regarding the determination of the minimal required DC-link voltage level for proper operation of GcCs as reactive power ancillary service providers. This analysis is done under both steady-state and transient conditions. Several simulation and experimental results are presented to confirm the validity of the obtained analytical results.