PFC Cuk Converter-Fed BLDC Motor Drive
This project deals with a power factor correction (PFC)-based Cuk converter-fed brushless dc motor (BLDC) drive as a cost-effective solution for low-power applications. The speed of the BLDC motor is controlled by varying the dc-bus voltage of a voltage source inverter (VSI) which uses a low frequency switching of VSI (electronic commutation of the BLDC motor) for low switching losses. A diode bridge rectifier followed by a Cuk converter working in a discontinuous conduction mode (DCM) is used for control of dc-link voltage with unity power factor at ac mains.
The BLDC motor is a three-phase synchronous motor consisting of a stator having a three-phase concentrated windings and a rotor having permanent magnets. It does not have mechanical brushes and commutator assembly; hence, wear and tear of the brushes and sparking issues as in case of conventional dc machines are eliminated in BLDC motor and thus it has low EMI problems. This motor is also referred as an electronically commutated motor since an electronic commutation based on the Hall-effect rotor position signals is used rather than a mechanical commutation. There is a requirement of an improved power quality (PQ) as per the international PQ standard IEC 61000-3-2 which recommends a high power factor (PF) and low total harmonic distortion (THD) of ac mains current for Class-A applications which includes many household equipments. The conventional scheme of a BLDC motor fed by a diode bridge rectifier (DBR) and a high value of dc-link capacitor draws a nonsinusoidal current, from ac mains which is rich in harmonics such that the THD of supply current is as high as 65%, which results in PF as low as 0.8.
The proposed drive system has shown satisfactory results in all aspects and is a recommended solution for low-power BLDC motor drives. A detailed comparison of all modes of operation has been presented on the basis of feasibility in design and the cost constraint in the development of such drive for low-power applications. Finally, a best suited mode of the Cuk converter with output inductor current operating in the DICM has been selected for experimental verifications.
The speed of the BLDC motor drive has been controlled by varying the dc-link voltage of VSI, which allows the VSI to operate in the fundamental frequency switching mode for reduced switching losses. Four different modes of the Cuk converter operating in the CCM and DCM have been explored for the development of the BLDC motor drive with unity PF at ac mains.
TOOLS AND SOFTWARE USED:
- MP LAB
Vashist Bist, Student Member, IEEE, and Bhim Singh, Fellow, IEEE, “PFC Cuk Converter-Fed BLDC Motor Drive”, IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 30, NO. 2, FEBRUARY 2015.