Based on the voltage type PWM AC/DC/AC conversion, the parameter selection of energy-storage filtering capacitors in DC side of the inverter is a key factor for stable operation. This paper aiming at the DC capacitor is selected that has certain inaccuracy, according to the rectifier filter and SPWM pulse width modulation inverter principle to studied the steady state filter capacitor charge and discharge waveforms and the inverter voltage relationship between the DC side and the AC side. A mathematical model of charging and discharging the capacitor ripple voltage between three-phase power supply voltage deviation is established.Proposed the capacitance parameter selection method based on the three-phase power supply voltage deviation. This paper respectively gives the appropriate analysis and calculations of filter capacitance when three phase and single phase uncontrolled rectifier circuit provides dc power. And through simulation and experimental verification of the DC filter capacitor energy storage method for determining the validity of arguments.