Cascaded conversion system and voltage-sharing control method thereof

The invention provides a cascaded conversion system and a voltage-sharing control method thereof. The cascaded conversion system comprises a plurality of cascaded conversion circuits. Each conversion circuit comprises a direct current side capacitor, a switch unit and a control unit. The direct current side capacitors of the plurality of conversion circuits are electrically connected in series. In any conversion circuit, the switch unit is connected in parallel with the direct current side capacitor and comprises a plurality of bridge arms, and each bridge arm comprises a first switch and a second switch. And the control unit is used for controlling the switch in the switch unit according to the voltage on the direct-current side capacitor. The control unit controls the first switches and the second switches to be switched on alternately, all the first switches are switched on and switched off synchronously, and all the second switches are switched on and switched off synchronously, so that voltages on the mu