A single-source switched-capacitor multilevel inverter for magnetic coupling wireless power transfer systems

This paper proposes a single-source switched-capacitor multilevel inverter for magnetic coupling wireless power transfer (MC-WPT) systems. The proposed inverter consists of one DC source, two half bridges, and novel extensible I-type switched-capacitor modules. It can generate a staircase waveform voltage with higher amplitude and lower total harmonic distortion, and the voltage stress of all power switches is equal to the DC input voltage, so high output power can be obtained by power switches with low voltage capacity. Compared with the existing multilevel inverters, the proposed inverter requires a less number of power switches and energy storage components to generate the same number of voltage levels, which means better voltage boost ability. Moreover, it can achieve self-voltage balancing of switched capacitors easily without balancing circuit or control algorithm. The topology, operating principle, output voltage, and self-voltage balancing ability of the proposed inverter are analyzed, and the comparison with the existing multilevel inverters is presented. The modulation strategy and value of the switched capacitor are designed, and the soft switching state and power loss are analyzed and calculated. Finally, an experimental setup of a 1-kW MC-WPT system is implemented to verify the correctness of the theoretical analysis and the feasibility and superiority of the proposed inverter.