Redesign of common dc-link capacitors for dual-three phase machine drive system based on PWM sequence reorder

Abstract

The dual three phase machine drive system with the common dc-link capacitors has been widely used in many industrial applications due to the advantages such as small stallion volume, reduced cost and flexibility. The large ripple current caused by the pulse width modulation (PWM) switching has to be reduced by choosing the large capacitor, while the bulky dc-link capacitor is still the main drawback for the improvement of power density. Therefore, this paper proposes a common dc-link capacitors reduced design method for dual three phase machine drives system with the proposed PWM sequence reorder aiming at the cost, volume and lifetime. First, the derived dc-link current expression are given according to the phase current and average current. Secondly, the PWM sequence reorder method on two inverters is used to reduce the dc-link capacitors switching frequency harmonics. Finally, the design principle of the new capacitors is proposed considering the cost, volume, lifetime. The results show that the lifetime of the capacitors with the proposed reorder PWM method can be extended significantly. The experiment results are given to verify the effectively of the proposed method. The results could provide a good guideline for the dual-three phase drive system design with low cost and high reliability.

Keywords

• Common dc-link capacitor
• Dual three phase drive
• Carrier phase shift