Feasibility Study of Using Modified Single-Phase Wireless Power Transfer System for Three-Phases Motor Driving

Conventional integration of Wireless Power Transmission (WPT) system with electric motor drive system seems not to be a desirable solution in some aspects like reliability, economic, sizing and numbers of power conversion. This is because of using two independent sets of switching converters at the primary and secondary side of WPT system as well as isolating DC link between these two systems. The primary sets act as high-frequency amplifier and the secondary one converts the induced power to low frequency one to feed the motor. These drawbacks will be more dominant even in three-phases motor drive applications. In this paper, a modified nine-switches topology is proposed in the secondary side of WPT system which is using high-frequency AC link voltage and converting it directly to three-phases low-frequency one to supply three-phases motor. This is carried out without using any rectification circuit and DC link as interface. Despite the lower cost of this system, it is also capable of direct drive of the motor from the primary side of WPT system. Unlike the conventional topology, the topology proposed in this paper has less switches as well as lower voltage oscillation with the same performance. Some quantified comparisons have been done in both theory and simulation which shows the superiority of the proposed system.

I. Introduction

Wireless power transfer systems are more and more evaluated for static and dynamic supply of future electric vehicles and in-motion systems [1]. Most of such these systems are employed for single-phase power transfer [2], [3]. In general, in these systems for feeding the AC loads, first, the AC power is transferred to the secondary side through a rectifier system and an inverter in the primary side and as well as through a magnetic coupling. This power is converted to DC power in the secondary side by a rectifier system, and finally by a driver inverter on the secondary, the AC power required by the load is provided. Therefore, the dc-links, which include dc electrolyte capacitors with a high degrade factor, isolate the grid from the WPT system and isolate the WPT system from the motor drive [4, 5]. According to abovementioned, two sets of power conversion together with the DC capacitor for DC/AC at the primary and AC/DC in secondary side is needed for WPT system [6]. Accordingly, the reliability and economic aspect of the system weaken. So, reducing one power conversion with its associated elements especially in secondary side may cope with the mentioned drawbacks. In this way, direct driving of electric motor can be possible only through the primary side of WPT system. Depending on the motor type, different wireless motor drive methods have been introduced. For direct wireless DC motor drive, higher numbers of secondary winding are needed to meet the required power, which makes the system more expensive. In return, for AC motors, wireless driving is possible by using less circuit components that enhance economic feasibility [7]. For wireless drive of a three-phase reluctance motor, three secondary windings with different resonant frequencies are used [8]. The similar method is used for driving several DC motors in robot at the same time by means of specific interval pattern for feeding power [9]. wireless drive can be also applied to servo motors and switched reluctance ones where they need the position feedback to rotate at any time [10, 11]. Depending on the position of the rotor, the associated coil of such these motors will be energized from one of the secondary winding with a unique resonant frequency [12, 13]. In this method, for a certain part of a whole period, the switching frequency of the primary inverter is the same as each secondary winding’s with different resonant frequency. A new single phase wireless motor drive has been proposed in [14] by removing secondary side driver and DC link and only via primary side inverter. The proposed method has been extended to three-phases wireless motor drive in [15] by giving solution about the probable issues associated with three-phases system. However, the converter used in [15] suffers from large numbers of bidirectional switches. So, achieving the topology with the same performance and lower switches number for direct wireless drive of three-phase electric motors are recommended.