This paper presents the design and implementation of a laboratory grid simulator which is used to test the grid-connected devices according to the strict standards. Three-phase four-leg inverter with direct voltage control in Natural Frame is adopted in this grid simulator, which significantly reduces the computing and realizing complexities. Proportional and resonant controller is utilized to regulate the output voltage. Furthermore, various feedback variables in the inner control loop are discussed and compared. The capacitor current feedback was identified to guarantee better stability and power quality. Experimental results verify the functionality and performances of the designed grid simulator.
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