MCSPWM Multilevel Inverter for Grid-forming New Energy Generation System

Grid-forming new energy generation system has the merits of system inertia and voltage support, which improves energy usage and system stabilization by using the complementation of all kinds of energy. In this system, multilevel inverters play an important role. In this paper, a novel switched capacitor 9-level inverter was proposed, with high-frequency multi-carrier sinusoidal pulse width modulation (MCSPWM) strategy, which owns comprehensively good performances of switches amount, voltage stress of power switches, boosting ability, and control difficulty. The operation principle and the suppression method of capacitor charging current was analyzed. The prototype of switched capacitor 9-level inverter was developed based on the design. Experimental results verify that, under the high-frequency modulation strategy, the presented inverter has double output voltages and bi-directional power flow. Automatic voltage balance of the switched capacitors is achieved. Voltage stress of the power switches is limited to the input voltage Uin, and ripple voltage peak value of the switching capacitors is less than 2 V. The proposed switched capacitor 9-level inverter has a good application prospect in grid-forming new energy generation system. © 2024 Science Press. All rights reserved.