Multi-dimensional Performance Evaluation of High-voltage Multilevel Converters for Medium-voltage Energy Storage: From Three-level to Five-level

With the DC bus voltage of energy storage converters increasing from 1500 V to 2 kV and above, multilevel converters have become a key development direction for next-generation grid-connected energy storage converters due to their low device voltage stress and high output power quality. However, existing grid-connected energy storage converters are mainly based on two- or three-level topologies and silicon(Si) devices, facing bottlenecks such as difficulty in voltage elevation, high losses, and large size. Moreover, the impact of higher-level topologies and silicon carbide(SiC) devices on energy storage grid-connected systems remains unclear. Therefore, a multidimensional performance study on three- to five-level converters for medium-voltage energy storage systems is conducted. It systematically clarifies the multidimensional performance characteristics, such as output harmonics, loss distribution, capacitor voltage balance, and common-mode voltage of three-, four-, and five-level topologies under grid-forming operating conditions. Furthermore, it comparatively analyzes the influence of SiC versus Si devices on the loss and efficiency of multilevel converters, providing theoretical support for the construction of a new generation of high-efficiency, high-performance, medium-voltage, large-capacity energy storage converters.