Abstract: A method for suppressing a direct current-link (DC-Link) capacitor current ripple (CCR) of a coupled three-level inverter (TLI), including: dividing space vector diagram regions of coupled TLI based on value range of virtual voltage vector duty cycle distribution factor; determining, based on amplitude, phase angle, and three-phase output current of reference voltage vector, sector and region in which reference voltage vector is located; then selecting nearest one virtual voltage vector and two basic voltage vectors, to calculate duty cycles thereof, respectively; designing a controller, updating duty cycle distribution factor of small vector based on sector and region in which reference voltage vector is located, set value of voltage difference across DC-Link capacitors, and actual value of voltage difference across DC-Link capacitors; and designing switching sequence based on updated small vector duty cycle and sector and region in which reference voltage vector is located.

Abstract: The present invention provides a method for cooperatively suppressing a common-mode voltage and current harmonics of coupled three-level inverters, comprising: based on amplitude and phase angle of reference voltage vector, determining sector and region in which the reference voltage vector is located; selecting four basic voltage vectors with low common-mode voltage amplitudes to synthesize the reference voltage vector; writing volt-second balance equation based on selected basic voltage vectors, and calculating duty cycles thereof; and based on sector and region in which reference voltage vector is located, set value of voltage difference across capacitors on direct current side, and actual value of voltage difference across capacitors on direct current side, (1) updating duty cycles of basic voltage vectors, to realize separate control of capacitor voltage; and (2) designing and converting switching sequence into PWM drive signal of power switch, to control the coupled three-level inverter to operate.