DC Voltage Control of the DC Micro-grid for Super High Quality Distribution

DC micro-grid is a novel super high quality electric power system. The power is transmitted through dc distribution line and converted to required ac or dc voltages by converters placed near loads. Those load side converters do not need transformers by choosing proper dc distribution voltage (plusmn170 V). The dc power line is composed of 3 wires: +170 V line, neutral line and -170 V line. The distribution voltages have to be balanced to keep high quality power supplying. In this paper, a voltage balancer for dc distribution are proposed and studied. Computer simulation results demonstrated that dc micro-grid was able to supply both ac and dc power to loads simultaneously and stably by 3-wire dc distribution line and load side converters. In addition, another voltage balancer (dc/dc converter type) is also proposed and studied in the last section.