Distributed Generation Grid-Connected Converter Testing Device Based on Cascaded H-Bridge Topology

This paper presents the configuration, control, and implementation of a testing device to check the reliability of a high-voltage high-power distributed generation (DG) grid-connected converter. The device employs the cascaded H-bridge topology and generates abnormal voltages (AVs), i.e., voltage amplitude-frequency deviation, voltage fluctuation, and voltage unbalance that are associated with a typical power grid. A unified rms value feedback control (URFC) in the stationary frame (SF) is adopted, which has the advantages of a higher precision, an easier selection of controller parameters, and a higher reliability, compared with other existing control approaches in either synchronous reference frame or SF. The feasibility and effectiveness of the proposed design concept of a DG grid-connected converter testing device (DGCTD) are validated by the real-world industrial field experiments performed on the "35 kV-6 MW testing device," under both no-load and load conditions.