Current‐limiting Universal Droop Controller

Abstract

Power electronic converters are known to be vulnerable to excessive over‐currents. This chapter presents a current‐limiting universal droop controller to operate a grid‐connected inverter under both normal and faulty grid conditions. The system consists of a single‐phase inverter connected to the grid via an LCL filter. The chapter focuses on the design of the virtual resistance to obtain the desired current‐limiting property. In contrast to existing current‐limiting approaches, the current limitation is achieved without external limiters, additional switches or monitoring devices. Furthermore, this function is independent of grid voltage and frequency variations, achieving desired control performance under grid faults as well. The chapter also presents extensive experimental results to verify the droop function of the controller and its current‐limiting capability under normal and faulty grid conditions.