Abstract: In view of problem of large volume of DC capacitor of high voltage inverter cascaded in H-bridge type, a kind of control strategy to minimize DC capacitance by injecting the third-order harmonic into fundamental modulation signal was proposed. The DC capacitor voltage ripple was reduced because part of the low-order harmonic of DC capacitor current was equivalently converted to high-order harmonic when the total modulation index remained the same. The relationship of harmonic content of DC capacitor current and the third-order harmonic injection amount was derived, and the expression of the maximum third-order harmonic injection amount under different power factors was presented. Matlab/Simulink simulation results show that the DC capacitance achieves 24.2% reduction under typical load with 0.85 power factor, which verifies feasibility and effectiveness of the control strategy.