A testing platform for distribution grid with multiple grid-connected converters

Distributed renewable energy generation units with medium-voltage distribution grid integration are considered as the most effective utilization manner because of low cost. However, the medium-voltage level (typically reach to 50 kV) brings safety risks in the experimental debugging process of new circuit topologies and algorithms for medium-voltage interface converters if directly in a full-scale power environment at the beginning. The scale-down testing platform has brought many merits for the analysis and test of medium-voltage distribution grid with multiple grid-connected converters. Unfortunately, due to the lack of proper base value selection method for DC side parameters of DC/AC type converter, such a scale-down model is still unavailable till now. The theoretical reason is that presented quasi-per-unit models for DC/AC type converters resulted in the missing of physical meaning for DC side variables. In order to solve the problem, this paper proposes a novel DC side base value selection method based on the rules that the voltage relationship of DC/AC converter's two sides complies with the AC `transformer' principle, and their current relationship satisfies the `power conservation' principle, and the detail calculation procedure of the scale-down model parameters is listed. These contributions provide the bedrock for performing the analysis and test of new circuit topologies and algorithms for the medium-voltage interface converters.