A Power Distribution Control Strategy Between Energy Storage Elements and Capacitors for Cascaded Multilevel Inverter With Hybrid Energy Sources

The key technology of a cascaded multilevel inverter with hybrid energy sources lies in the power distribution among different chains. A power distribution control strategy between the energy storage elements and the capacitors is proposed to achieve fault tolerant control. In the cascaded multilevel inverter with hybrid energy sources, the chains with energy storage elements can operate in four quadrants, while the chains with capacitors can only operate in two quadrants. With the proposed control method, the active power distribution is realized by active voltage vector superposition, and the reactive power distribution is achieved by initial operation point selection. This enhances both the system reliability and availability while enabling continuous operation in four quadrants. Meanwhile, the stable operation region and the range of the initial operating point have been derived by the vector analysis to avoid over-modulation. An experimental prototype based on a single-phase link with two series chains has been built in the laboratory. The simulation and experimental results are provided to demonstrate the effectiveness of the proposed control method.