Capacitance Voltage Imbalance Mechanism and Modulation Control of Cascade H Bridge

This paper analyzes the capacitor voltage imbalance mechanism of cascaded H-bridge and proposes one-dimensional and two-dimensional modulation strategies of cascaded H-bridge topology. The research shows that the selection of different modulation points determines the energy distribution among the bridges in the H-bridge cascade topology. According to the two-dimensional modulation control simulation of the cascade rectifier stage, the position of the modulation point can be adjusted to change the size of the DC side capacitor voltage. When the active energy absorbed by two cascaded H-bridges is coupled with each other, increasing the active energy absorption of either bridge will lead to the reduction of the active energy absorbed by the other bridge. Therefore, during the operation of the rectifier stage, the relevant controller can be designed to achieve the stability of the rectifier stage system without a power frequency transformer according to the regulation principle of the modulation point.