Boost Three-Effective-Vector Current Control Scheme for a Brushless DC Motor With Novel Five-Switch Three-Phase Topology

This paper presents a boost five-switch three-phase (BFSTP) topology in brushless dc motor (BLDCM) drives by combining a four-switch three-phase (FSTP) inverter and a boost circuit together. In BLDCM drives, load and speed ranges are greatly restricted when the conventional FSTP inverter is employed, especially in the cases of solar power and battery, where power supply voltage is lower than the rated voltage of motor. Based on the novel topology, a boost three-effective-vector (BTEV) scheme is also presented. With the proposed BTEV scheme, two functions are realized. First, the voltage across the capacitors on the side of dc link is boosted by inserting shoot-through vectors in Modes V and VI, thus widening the speed and load ranges under low power supply voltage. Second, by taking the advantages of two adjusting vectors, possible distortion of currents caused by phase C back-EMF is restrained by employing a three-effective-vector scheme in Modes I and IV. The proposed BFSTP topology has a compact structure and a small size. Moreover, the BTEV current control scheme is easy to implement and needs no complex calculation involved in conventional vector control. The effectiveness of the proposed BFSTP topology and the BTEV scheme is validated through experiment.