With ever-increasing concerns on health and environmental safety, there is a fast-growing interest in new technologies for medical devices and applications. Particularly, wireless power transfer (WPT) technology provides reliable and convenient power charging for implant medical devices without additional surgery. For those WPT medical systems, the width of the human body restricts the charging distance, while the specific absorption rate (SAR) standard limits the intensity of the electromagnetic field. In order to develop a high-efficient charging strategy for medical implants, the key factors of transmission distance, coil structure, resonant frequency, etc. are paid special attention. In this paper, a comprehensive overview of near-field WPT technologies in medical devices is presented and discussed. Also, future development is discussed for the prediction of different devices when embedded in various locations of the human body. Moreover, the key issues including power transfer efficiency and output power are addressed and analyzed. All concerning characteristics of WPT links for medical usage are elaborated and discussed. Thus, this review provides an in-depth investigation and the whole map for WPT technologies applied in medical applications.

Most of the existing one-to-multiple wireless power transfer (OWPT) systems are single-channel one-to-multiple wireless power transfer (SOWPT) systems. They only utilize one power channel to charge multiple receivers. In this paper, a novel multi-channel one-to-multiple wireless power transfer (MOWPT) system is proposed, which can deliver power to different receivers simultaneously with separately power channels. In the proposed MOWPT system, the composited compensation topology is utilized to build multiple power channels, which possess totally variou resonant frequencies and nearly do not affect each other. Compared to those existing SOWPT systems, the power of receivers of the proposed MOWPT system can be simply and separately controlled by changing the duty cycles of the inverters without a complex control method and extra DC-DC converters. In order to analyze the performances of the proposed MOWPT system, a 0-LC MOWPT system, which utilizes the air-transformers to provide multiple power supplies of different frequencies, is modeled and analyzed in detail. Moreover, based on the analysis results, a corresponding parameter design method is proposed to simplify the design procedure of this MOWPT system. Finally, an experimental prototype is built up to verify the performances of the proposed MOWPT system and the parameter design method.

Open-winding (OW) PMSM could obtain the higher bus voltage utilization and more robustness against the component damage and faults. However, the additional torque ripples and THD caused by zero-sequence current would limit the further applications of OW-PMSM. In this paper, a novel model predictive two-target current control (MPTCC) scheme is presented to deal with such problem through model predictive control (MPC) concept. Firstly, a basic model predictive current control (MPCC) is proposed to deal with the torque production in fundamental components. Then, another modified cost function is proposed to provide more precise voltage vectors in torque production. After that, the deadbeat predictive control concept is proposed to calculate the required voltage vectors in zero-sequence loop. It needs to be mentioned that the limitation of inverter is analyzed. And the real-time judgement is proposed to assess the performance of MPTCC in some work conditions. Finally, both simulation and experiments have been both applied to assess the performances of proposed control scheme. Comparing with those existing q-axis current injection methods and modified SVPWM technologies, the proposed control scheme could eliminate the torque ripple and THD at the same time and thus possess the better performances

This paper is to present the design, analysis and verification of a new hybrid wireless power transfer (HWPT) system, which has a space-saving coupler structure. The key of the design is to simplify two coupling capacitor plates into one single frame-shaped plate at each side. Then, the coupling coil for inductive power transfer (IPT) is embedded into the metal frame to form a compact hybrid coupler. Meanwhile, the coupling polarity between the coils is specified to realize the superposition of the inductive and capacitive coupling. As a result, the proposed HWPT system can offer a good comprise of efficiency promotion and a space-saving coupler structure simultaneously. To illustrate the system working principle, the equivalent circuit model is firstly derived. Then, a detailed analysis is conducted in terms of the reflected impedance. Consequently, the mechanism of the efficiency promotion can be clearly explained. Finally, a prototype is constructed with experiments, which validates the effectiveness of the proposed HWPT system. Results show that an efficiency increase of 14% over the pure IPT is obtained at 35 cm distance. Moreover, the effects of varying the resonant frequency are also carried out to instruct the practical system design.

The additional harmonic currents in multiphase permanent magnet synchronous motors (PMSMs) have been widely discussed and suppressed by the virtual vectors (VVs). However, the concept of VVs would result in an increasing in the switching frequency and losing the controllability in the harmonic subspace. In this article, a novel direct modulation pattern control (DMPC) method is proposed to provide the further discussion on the lower switching frequency and the better harmonic current suppression. First, a deadbeat control concept is applied to calculate the reference voltage vectors in torque production. In dual three-phase PMSM, there are several switching patterns which could generate the reference voltage vector. The designs of these switching patterns are determined according to the demand. In fact, two design concepts under the structure of DMPC is proposed. One is called the low switching frequency design. The control sets of this design is several switching patterns with only one switching signal. Another is called the low THD design. The control sets of this design is two switching patterns with opposite harmonic voltage vectors. Second, the influence of these different switching patterns in the xy currents is optimized by a cost function. Actually, there are two types of cost function. One is a multiobjective cost function, which is designed to regulate both the amplitude of switching patterns and suppress the xy currents. Another is derived from the first cost function that regulates only the xy currents. The amplitude is determined directly in the voltage vector calculation. Finally, the experimental results show a good performance of these control strategies, in terms of the αβ currents production, the xy currents and the switching frequency reduction.

Model predictive control (MPC) schemes applied in multiphase permanent magnet synchronous motors (PMSMs) should provide the precise torque output and suppress the harmonic currents at the same time. Then, the trade-off between precise torque output and harmonic currents suppression is inevitable in the finite control set MPC (FCS-MPC). To provide an alternative to this problem, this article presents a new extension strategy of FCS-MPC applied in multiphase PMSMs. The novelty of this article includes two parts. First, the control sets are extended from the candidate voltage vectors to the candidate modulation patterns. These modulation patterns consist of switching signals with specific rules. The second one is the new cost function which realizes the harmonic current suppression with the modulation patterns selection. Two groups of modulation patterns are developed to assess the performance of this structure. The first group is called “semi-controlled modulation pattern” which could provide the precise voltage vectors in the $\alpha \beta $ subspace. The second group is called “fundamental torque-controlled modulation pattern” which could further suppress the harmonic currents. These two groups of modulation patterns could realize the required performance with a much lower switching frequency (SW). Moreover, the parameter mismatches in the harmonic subspace caused by the uncertainties of the system and errors in the parameter values are also compensated in the proposed MPC. Finally, the comparative experiments show the performance differences between two modulation patterns and those existing controllers.