7 - Study of control strategies of power electronics during faults in microgrids

Abstract

This chapter has firstly summarized the instantaneous power theory and its extension for the purpose of controlling voltage source inverters under unbalanced faults. Regarding the converters operating in grid-connected mode to feed a certain amount of active and reactive power to the microgrid, two groups of control strategies, namely flexible oscillating power control and flexible positive- and negative-sequence power control are reviewed together with the design of inner current controllers and converter current limitation methods. For the autonomous operation of the microgrid, the control of a voltage source inverter operating under an islanded mode to provide voltage amplitude and frequency references is briefly reviewed. To improve the short-circuit performance of such an inverter under unbalanced fault, the negative-sequence current control loop is implemented. This chapter is finally supported by the application of different control strategies in a typical microgrid setting followed by discussions on microgrid protection.