IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 57, NO. 9, SEPTEMBER 2010 3181 Contactless Energy Transfer System With FPGA-Controlled Resonant Converter Artur J. Moradewicz and Marian P. Kazmierkowski, Fellow, IEEE Abstract—Power supply based on an inductive coupled contact- less energy transfer system is presented in this paper. The energy is transferred using a rotatable transformer and a power electronic converter. To minimize total losses of the system, a series resonant compensation circuit is applied assuring zero-current switching condition for insulated-gate bipolar transistors. The analytical ex- pression of the transfer dc voltage gain is presented and discussed. The novelty of the system lies in the application of a fully digital field-programmable-gate-array-based controller and a protection system. The resonant frequency is adjusted by a primary peak current regulator. Some simulation and experimental results illus- trating the operation of the developed 3-kW 60-kHz laboratory prototype are given. Although the presented power supply with a rotatable transformer is constructed mainly for robotics and manipulators, the described design and control methodology has general validity and can be applied for a wide class of contactless power supply with core or coreless transformers. Index Terms—Contactless energy transfer (CET) of electrical energy, contactless power supply, field-programmable gate array (FPGA) controls, series resonance converter. I. I NTRODUCTION R ECENTLY, in power supply systems of mobile devices and vehicles, a strong tendency for the use of contactless energy transfer (CET) systems has been observed. The CET systems allow elimination of cables, rails, slip rings, plugs, and sockets, resulting in extended maintenance-free operation and increased reliability and safety (no sparkling, ruggedness against dust, and aggressive environmental conditions). There- fore, the CET systems are used in such critical applications as in aerospace [29], [30], transportation [5], [12], [16], [17], [22], [23], biomedicine [3], [10], robotics [7], [24], industrial automation [1], [27], battery charging [9], [11], [28], [32], etc. Fig. 1 shows a general classification of the CET systems. As “medium” for CET systems, electromagnetic waves, including light [15] and acoustic waves (ultrasonic) [10], as well as electric field [1], [19], can be used. In the most popular appli- cations, the core of CET systems is the inductive or capacitive coupling between power source and load, and high-switching- frequency power electronic converter for energy flow control. Manuscript received August 27, 2009; revised November 16, 2009 and January 26, 2010; accepted March 23, 2010. Date of current version August 11, 2010. A. J. Moradewicz is with the Laboratory of Numerical Control, Department of Electric Drives, Electrotechnical Institute (IEL), 04-703 Warsaw, Poland (e-mail: a.moradewicz@iel.waw.pl). M. P. Kazmierkowski is with the Institute of Control and Industrial Elec- tronics, Warsaw University of Technology, 00-662 Warsaw, Poland (e-mail: mpk@isep.pw.edu.pl). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TIE.2010.2051395 Fig. 1. Classification of CET systems. The capacitive coupling is used in the low-power range [1], [19], whereas the inductive coupling allows transferring power from a few milliwatts [3], [27] throughout several kilowatts [5], [9], [26], [32] up to hundreds of kilowatts [7], [12], [14], [21]–[23]. Because of the high switching frequency (f sw ≥ 20 kHz) used in CET power electronic converters, most of the re- ported systems have been built in hardware technology [3], [5], [9], [21]–[23], [29]–[32]. Therefore, the implemented control and protection methods were characteristic for hardware-based approach. However, more sophisticated and flexible methods could be implemented only in digital signal processors or programmable circuits like the field-programmable gate array (FPGA). This paper is an extended version of [25] and reports on a newly developed inductive CET system with a rotatable transformer and an insulated-gate bipolar transistor (IGBT)- based resonant converter. In contrast to the hardware-based solution presented in [7], this paper describes a fully digital system, including a primary peak current regulator, for resonant converter control and protection implemented in an FPGA circuit. In comparison with [25], this paper is extended by the selection guidelines of the compensation method for a resonant circuit, as well as transformer modeling and design. Among the important features of the developed CET system are the following: 1) high total efficiency (93%) due to careful design of all system components; 2) operation of high-switching-frequency IGBT-based resonant converter at zero-current switching (ZCS) conditions; 3) low-cost single-board FPGA-based controller; 4) reliable and fast operation; 5) robustness to magnetic coupling factor changes of the main circuit. 0278-0046/$26.00 © 2010 IEEE