Design and Implementation of a Three-Phase DC-AC Converter for Microgrids Based on Renewable Energy Sources

This paper proposes a three phase DC AC converter for autonomous microgrids based on renewable energy sources. The microgrid topology offer simple control characteristics, where the AC link does not need a complex voltage controller strategy. The DC AC converter (three phase inverter) generates output voltages with very low THD for any type of load. To obtain the before mentioned characteristics for the inverter, this work propose an internal model principle based controller structure in synchronous dq frame, with a reduced sampling and number of poles. With this structure, is possible to considerably improve the stability and dynamic system response, and mainly, the saturation of the low frequency insulating transformer is avoided. Also in this paper, is proposed a straightforward design methodology for the discrete internal model based controller. In order to validate the proposed digital controller structure, the design methodology and to demonstrate the steady state and transient performance, experimental results are presented from a 15kVA SVPWM modulated three-phase inverter, fully controlled by a DSC dsPIC30F4011.