A New Receiver-Side Integrated Regulator With Phase Shift Control Strategy For Wireless Power Transfer System

The efficiency of a multiphase wireless power transfer (WPT) system varies with the size and position of loads. Based on the traditional WPT system, the efficiency improvement of three-phase WPT system under load variation was studied. A three–phase shift control (PSC) strategy is proposed. Mathematical formula of optimal resistance is deduced and the optimal phase shift angles (PSA) for maximum efficiency are presented in the three-phase WPT system. Through the analysis of the electromagnetic model of the system, the optimal phase angle at which the load maintains optimum efficiency at different locations is deriving. A three-phase WPT phase experimental platform based on PSC is built. Verify the validity and correctness of PSC strategy. Simulation and experimental results show that the efficiency of the receiving coil can be increased by 10−15% after the phase is adjusted at different positions. The proposed three-phase phase shift control strategy has a guiding and reference significance for subsequent related research.

This paper presents a two-coil reconfigurable wireless power transfer (WPT) system topology in order to optimize transmission efficiency under different transmission distance (DIS) and lateral misalignment (MIS) conditions. The reconfigurable WPT system includes one transmitter (Tx) side and one receiver (Rx) side but it could switch between different circuit configurations (which are made up of different values of series and shunt capacitors) at Tx side and/or Rx side. Design guidelines of the two-coil reconfigurable WPT system are devised based on an equivalent circuit model. A proof of concept prototype with three different adaptive configurations at Tx side and one configuration at Rx side is built and experimentally compared with conventional two-coil WPT system. Results show that when the system is perfectly aligned, the reconfigurable system improves the transmission efficiency by up to 20%. When system is laterally misaligned, the transmission efficiency is improved by up to 19%.

A wireless power transfer (WPT) system via magnetic resonance coupling method is attracting attention to high convenience. A WPT system has problems such as power transmitting loss and output voltage fluctuation due to the change in the coupling coefficient and the load state. In previous method, sliding mode control system as a tracking controller considering nonlinearity and uncertainty has been proposed, but the output of this control system had bias and chattering. This paper proposes operator-based nonlinear sliding mode control system to reduce chattering and bias simultaneously for a WPT system using buck converter. First, the model of the WPT system using rectifier and buck converter is explained and dynamics formulas are derived. Next, the proposed operator-based nonlinear sliding mode control system design for the WPT system is described and tracking performance is confirmed. Finally, the result of simulation of constant voltage control and comparison with the previous method is shown.

The magnetic fields (MF) generated in close proximity to high power wireless power transfer (WPT) systems generally exceed exposure limits and might also violate basic restrictions (BR). However, there are as yet no available standards describing methods to measure the MF generated by WPT systems. In this study, a new method for demonstration of compliance with the BR in the close proximity to sources at frequencies from 3 kHz to 10 MHz is proposed. This approach mitigates overestimation by incident field assessment in strong field gradients close to WPT systems. The spatial peak MF amplitude and gradient generated by WPT systems are measured with a field gradient probe at the closest location to the source. The induced fields and absorbed power are then calculated on the basis of specific transformation functions for testing of compliance with the BR of all international safety guidelines.

A Wireless Power Transfer (WPT) system, known for its contactless power delivery, is extensively used for power supply in spacecraft applications. Achieving efficient and stable power transfer necessitates the integration of DC/DC converters on both the primary and secondary sides of WPT systems for power conversion and control. Traditional efficiency optimization methods primarily focus on impedance matching within the wireless power resonance network, often neglecting the overall efficiency optimization of multi-stage DC-DC and WPT systems. This oversight results in suboptimal overall system efficiency despite optimal efficiency in the wireless transmission segment. Additionally, the time-varying nature of mutual inductance and load parameters during power transmission in WPT systems presents challenges for maximum efficiency tracking and power control. This paper introduces a multi-level coordinated control efficiency optimization method for WPT systems utilizing the particle swarm optimization (PSO) algorithm. This method takes into account the transmission losses across all power conversion units within the WPT system, establishing a mathematical model for the joint optimization of overall system transmission efficiency and power. The PSO algorithm is then employed to solve this optimization model using estimated mutual inductance and load values. By adjusting the DC/DC converters on both sides, the method ensures optimal overall system efficiency and consistent power transmission. Experimental results indicate that under varying load and mutual inductance conditions, a Series–Series (SS) compensated WPT system using this method achieves a 200 W power output with maximum efficiency tracking, a power output error of 0.63%, and an average transmission efficiency of 86.2%. This demonstrates superior power transmission stability and higher efficiency compared to traditional impedance matching methods.

Many researches have been carried out by previous researchers to get better performance of a wireless power transfer (WPT) system. This research uses a partitioned shielding made of metallic material to protect WPT system from electromagnetic interference (EMI). Also, a shielding material is connected to ground, so that it can reduce occurrence of stray/parasitic capacitance between electrodes of electronic components. Both the electromagnetic interference and the stray/parasitic capacitance can deteriorate performance of WPT system. In this research, the WPT system works at voltage 14.7V, frequency 56,298 Hz, distance coil to coil is 0 till 5 cm. The efficiency of WPT system is achieved until 14.9 % (without shielding) and until 17.9% (with partitioned shielding).

In wireless power transfer (WPT) systems, magnetically coupled wireless power transfer has become a major research focus due to its advantages such as long transmission distance, strong tolerance to misalignment, and high power transfer capability. It is also widely applied in vehicle wireless power transfer systems. From the perspective of practical engineering applications, this paper investigates the problem of system parameter variations caused by changes in inductance and load, in combination with magnetically coupled structures. During actual system operation, misalignment of the coupling mechanism leads to variations in mutual inductance, while the load resistance may also fluctuate. These parameter changes result in alterations to the overall output characteristics of the system, which are detrimental to stable system operation. Moreover, adopting a dual-side communication control strategy is susceptible to interference from the system’s power circuitry. To address these issues, this paper proposes a novel state variable modeling method and designs a state observer based on the extended Kalman filter (EKF) algorithm to estimate the secondary-side parameters, thereby enabling observation of the voltage across the load at the receiver side. The state observer is configured with two operating modes to monitor variations in mutual inductance and load resistance. The observer outputs are compared with the actual load-side voltage, and the effectiveness of the proposed state observer is verified.

It is well known that the power transfer efficiency (PTE) of a two-coil wireless power transfer (WPT) system is maximized at critical coupling under fixed system parameters. However, the two-coil WPT system is critical-coupled with a relatively short distance between the coils. To overcome the problem, a multicoil WPT system has been studied. In this paper, we review the impedance characteristics of the critical-coupled two-coil WPT system and reveal that the conventional three-coil WPT system cannot have the same impedance characteristics as critical coupling. Based on the impedance matching conditions with critical coupling of the two-coil WPT system, we propose a design method of a three-coil WPT system in which the free resonant frequencies of all resonators are changed. The proposed design method is successfully implemented at the operating frequency of 6.78 MHz. The experimental results are in good agreement with the simulated PTEs and show that by changing the free resonant frequencies, a higher PTE can be effectively achieved in comparison to the conventional two-coil and thee-coil WPT systems.

In previous researches, an operator-based sliding mode control design to achieve high power transfer efficiency of a wireless power transfer (WPT) system via magnetic resonance coupling were shown. However, it is difficult to reduce the steady-state error by using SMC-based tracking controller. In this paper, an operator-based integral sliding mode control method is adopted to reduce the steady-state error in the WPT system. Moreover, high power efficiency should be achieved in the WPT system by using an impedance matching control. The effectiveness of the proposed method is verified by simulation results.

The wireless power transfer (WPT) system based on parity-time (PT) symmetry has the advantages of robustness, stable, and efficient power transmission. However, the region of PT symmetry is limited, which cannot satisfy some practical requirements. Multiple transmitting coils have been shown to improve the misalignment tolerance of WPT systems. Towards this end, a parity-time-symmetric-based WPT (PT-based WPT) system with double-transmitting coil is presented in this article. First, an approximate equivalent circuit model of this PT-based WPT system was developed. Second, compared with the conventional single transmitting coil PT-based WPT system, the proposed system expands the PT symmetry region and provides higher output power and transmission efficiency. Furthermore, the mutual inductance between two transmitting coils can be designed to meet the requirements of different scenarios, which improves the freedom of system design. Finally, a 30 W prototype is designed to evaluate the proposed WPT system. Experimental results show that the critical coupling coefficient is reduced by about 12.5% at <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sub> = 0.51, which implies a longer transmission distance. Moreover, the maximum output voltage fluctuation in the strongly coupled region is only 3.5%, while the transfer efficiency is approximately constant, which implies stable and efficient power transfer.

The wireless power transfer (WPT) system for LED TVs could be adapted to transfer power to specific locations in luxury residences. However, at a resonant frequency, the output power of the WPT system is only able to provide maximum power at only a set distance. This article presents the adaption of mutual impedance for maximum power point tracking (MPPT) to vary the distance for LED TVs using the WPT system. To adapt the mutual impedance, the frequencies and the resonator capacitances are tuned to the required distance. In the experiment, the WPT system was loaded with a 30W LED TV and the input was through a full-bridge inverter to enable the input voltage and frequency to be varied. The computer simulation and the actual experiment on MPPT for the LED TV WPT system closely correlate. The result shows that when the LED TV WPT system input was 6.66 V, 3.01 kHz, C 16.8 F, the maximum output power was 30.1 W was achieved at a distance of only 10 cm. Significantly, when using the frequencies and resonator capacitances according to the mutual impedance adaption as proposed in this article, the LED TV WPT output power reached peak power at distances varying between 0-60 cm distances.

A highly efficient wireless power transfer (WPT) system is required in many applications to replace the conventional wired system. The high temperature superconducting (HTS) wires are examined in a WPT system to increase the power-transfer efficiency (PTE) as compared with the conventional copper/Litz conductor. The HTS conductors are naturally can produce higher amount of magnetic field with high induced voltage to the receiving coil. Moreover, the WPT systems are prone to misalignment, which can cause sudden variation in the induced voltage and lead to rapid damage of the resonant capacitors connected in the circuit. Hence, the protection or elimination of resonant capacitor is required to increase the longevity of WPT system, but both the adoptions will operate the system in nonresonance mode. The absence of resonance phenomena in the WPT system will drastically reduce the PTE and correspondingly the future commercialization. This paper proposes an open bifilar spiral coils based self-resonant WPT method without using resonant capacitors at both the sides. The mathematical modeling and circuit simulation of the proposed system is performed by designing the transmitter coil using HTS wire and the receiver with copper coil. The three-dimensional modeling and finite element simulation of the proposed system is performed to analyze the current density at different coupling distances between the coil. Furthermore, the experimental results show the PTE of 49.8% under critical coupling with the resonant frequency of 25 kHz.

Dual-band coil modules facilitate efficient access to distinct-band, high-power, or rapid-charging wireless power transfer (WPT) systems. However, they do not function efficiently when the frequency ratio between two operating frequencies is large. To overcome this problem, we propose enhanced dual-band coil modules that adopt repeaters in the WPT system. We present a circuit-based analysis of repeaters in various dual-band coil modules compared with those in a single-band WPT system. The analytical results provide a design methodology applicable to diverse types of dual-band coil modules with a repeater in the WPT system. Our experimental results are consistent with the circuit-based analysis: coil power transfer efficiencies of 55% at 200 kHz and 74% at 6.78 MHz were obtained concurrently in the dual-band WPT system with a dual-band repeater. This paper reduced the application constraint of dual-band coil modules and facilitated the realization and application of multiband WPT systems.

The magnetic coupling of a practical wireless power transfer (WPT) system is greatly influenced by the variations in the alignment of the magnetic couplers. For a given coupling range, a WPT system is expected to output the required rated power with a given load. However, this requirement cannot be easily met by the widely adopted series–series or inductor–capacitor–capacitor compensation topologies in a conventional two-resonator WPT system. This article proposes a design methodology for three-resonator WPT systems to achieve a constant output power in a wide coupling range. The basic characteristics of the three-resonator WPT system are reviewed and the proposed design methodology is presented in detail. A 3.3-kW three-resonator WPT prototype is designed and built, achieving nearly constant output in the given misalignment range. The measured dc–dc efficiency of the prototype reaches 94.47 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> at the rated power.

Polyphase wireless power transfer (WPT) systems can achieve much higher surface power densities (kW/m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>) and specific power levels (kW/kg) compared to the conventional circular single phase WPT systems. Therefore, polyphase WPT systems can reduce the size, weight, volume, and cost of the WPT systems and can simplify the electric vehicle integration with less demand for space. This study presents the high-performance and compact 100-kW WPT development using polyphase electromagnetic coupling coils with rotating magnetic fields.