Control and Design of a Boost-Based Electrolytic Capacitor-Less Single-Phase-Input Drive

Abstract

Adjustable-speed drives with single-phase input require a power factor correction front-end, usually implemented by a boost converter, to reduce the current distortion from the uncontrolled rectifier; this stage is then followed by a three-phase inverter. Bulky electrolytic capacitors are used to limit the direct current voltage ripple resulting from the rectification of the single-phase input. This leads to increased system size and shorter lifetime. In this work, the usual boost front-end is exploited to actively control the DC link voltage ripple while limiting the input current distortion and, hence, the power factor, even if not reaching unity. However, Power Factor is greatly improved with respect to the uncontrolled rectifier alone. This approach permits one to reduce the required capacitance, allowing the substitution of the electrolytic capacitor with a long-life low-equivalent-series-resistance film one. A control targeting capacitor voltage level, ripple, and boost inductor peak current is presented, together with practical design models. The synergic control of the boost front-end and of the machine drive is presented as well. The resulting converter is tested with resistive load and permanent-magnet synchronous machine drive, highlighting the advantages and limits of the proposed solution.

Keywords

• capacitor-less drive
• single-phase inverter
• adjustable-speed drive
• boost converter
• power factor correction
• synchronous motor drives