Research on a back-to-back cascaded h-bridge four-quadrant five-level converter

In order to raise the voltage level, eliminate the line-frequency transformers, reduce the size/cost of the converter, and make bi-directional power flow available, a back-to-back cascaded H-bridge four-quadrant five-level converter was proposed. Five-level output voltages can be realized, which can enlarge the capacity of the system with low rating voltage devices. The equalization circuit and legal switching states of the converter are presented. Moreover, the capacitor voltage balancing algorithm is built, a five-level three-phase experiment system is established, and the results validate the proposed topology and algorithm. The capacitor voltages can be maintained as constant, the power factor on the input side is as high as 1, and the converter can output five-level voltages. Also, the four-quadrant experiment is carried out, which validates the bi-directional power flow capability.