Multi-load Wireless Power Transfer Research Articles

A Hybrid-Frequency-Based Multi-Load Wireless Power Transfer System With Constant Current or Voltage Outputs

A Hybrid-Frequency-Based Multi-Load Wireless Power Transfer System With Constant Current or Voltage Outputs

Magnetically coupled resonant multi-frequency and multi-load wireless power transfer system with load-isolation

Magnetically coupled resonant multi-frequency and multi-load wireless power transfer system with load-isolation

Modular Stacked Multiport Wireless Energy Interconnection System With Virtual AC Bus and Its Power Flow Control Strategy

This article proposes a modular stacked multiport wireless energy interconnection (WEI) system with a virtual ac bus for multisource and multiload wireless power transfer (WPT) applications, which has the following advantages. 1) It can serve as an interface for WPT among multiple sources and loads. 2) Bipolar coils are adopted to eliminate the undesired cross-coupling among multiple coils, which simplifies the complexity of system modeling and power flow control. 3) The relay coil with constant current characteristics is introduced as a virtual ac bus, from which the derived multicoil structure provides the bidirectional channel for power transfer between any two ports. 4) System applicability and scalability are greatly enhanced due to the modularization of coils, power converters, and compensation circuits. For power flow control, the hybrid phase-shifted control method matched with the WEI system is applied, in which the power flow direction is determined by the external phase-shifted angles between ports, whereas the power values are regulated by the internal phase-shifted angles. Furthermore, the peak value of the current of the virtual ac bus, as an intermediate control variable, is controlled to be constant; thus, distributed control can be further realized. Finally, a four-port experimental prototype was built and experiments were carried out under different operating conditions. The efficiency curves and loss distribution, as well as the tolerance analysis of coil misalignments, are given. From the experimental results, the effectiveness of the proposed system architecture and its power flow control strategy is verified.

Multiload Wireless Power Transfer System With Constant Output Power and Efficiency

For a multiload wireless power transfer (WPT) system, it has always been a challenge to maintain constant output power with constant efficiency for each load when the coupling conditions change. Besides, the unbalanced power distribution and cross-coupling among loads are also the key issues. In order to solve these problems, a novel multiload WPT system combining the parity-time (PT) symmetry principle and time-sharing control strategy is proposed. First, the multiload PT-symmetric WPT (PT-WPT) system with single natural resonant frequency is modeled and analyzed based on the circuit model. Then, a multiload PT-WPT system with time-sharing control strategy is constructed by adding a controllable resonant capacitor array at the transmitter. The time-sharing control strategy is realized by periodically turning <small>on</small>&#x002F;<small>off</small> a controllable resonant capacitor selectively, which enables a single transmitter to supply power to multiple loads with different natural resonant frequencies, and each load realizes PT transmission characteristics. Further, using the time-sharing control strategy, the power distribution among multiple loads is realized by only controlling the duty cycle of each load. Finally, two dual-load PT-WPT experiments are designed and carried out. Experimental results show that each load can maintain constant output power with constant transfer efficiency about 90&#x0025; in a wide coupling range, and realize power distribution at desired values simultaneously.

A Multiload Wireless Power Transfer System With Concentrated Magnetic Field for AUV Cluster System

In this article, a multiload wireless power transfer (WPT) system is proposed for the power supply of autonomous underwater vehicle (AUV) cluster system. The segmented arc solenoid transmitter coil is designed to generate the concentrated magnetic field. The adjacent transmitter coils are reversely wound to form the strengthened magnetic field, which can improve the coupling between the transmitter and the receiver. The proposed coil structure is verified via finite element analysis based on ANSYS Maxwell. The transfer performance is analyzed and it is found that the transfer efficiency can be maximized against the voltage gain under the two-receiver case, which can also be extended to multiple-receiver case. An <i>LCC&#x2013;LCC</i> compensated multiload WPT prototype was established and the experimental results verified the theoretical analysis and simulations. The output power of each receiver and the system efficiency can reach 500 W and 90&#x0025; under the different angles between any two receivers.

Parity–Time Symmetric Model and Analysis for Stable Multi-Load Wireless Power Transfer

A noticeable challenge for a multi-load wireless power transfer system is to achieve stable power transfer under a dynamic change in coupling conditions. It was proposed that the parity–time symmetric wireless power transfer (PT-WPT) system can achieve stable output efficiency for a single receiver when tuned at the purely real eigenfrequency. However, in the case of higher order, PT symmetric systems usually cannot maintain the real eigenfrequency. To address the issue, a high-order PT-WPT model was established using coupled mode theory (CMT) theory in this paper, and the eigenfrequency of the multi-load PT-WPT system was analyzed. Here, we propose that, theoretically, the system can work at the purely real eigenfrequency by impedance matching. The transfer efficiency of the multi-load PT-WPT system when the system works at the real eigenfrequency was analyzed. The results of the numerical simulation show that the multi load PT-WPT system can maintain stable output efficiency under a dynamic change in coupling conditions. In the long run, our work provides a new possibility for the stable transmission of the multi-load wireless power transfer system.

Multiphase Direct AC Wireless Power Transfer System: Comparative Proposals Using Frequency and Amplitude Modulations

Using multiload wireless power transfer (WPT) systems to supply power to multiple receivers with a single transmitter is an interesting topic. However, previous studies are all based on a dc–dc WPT system. If the loads demand ac power, additional dc–ac inverters need to be implemented, which increases the system complexity and cost. This article addresses two direct ac WPT systems that can regulate the ac power of multiple phases or loads independently, using frequency modulation and amplitude modulation (AM), respectively. The proposed WPT systems can directly control the ac power of multiple loads through the transmitter side, without any power converter at the receiver side. A typical application of the proposed system is for powering a three-phase load in a rotational object, e.g., three-phase motors in articulated robots or in-wheel motors. To demonstrate the feasibility of the proposed WPT systems, simulation and experiment studies of a wireless three-phase power transfer are presented. The results suggest that AM is a more advantageous solution to a direct ac WPT system. A power-loss breakdown analysis is presented to suggest future steps of efficiency improvement.

Long‐distance wireless power transfer system powering multiple loads with constant voltage outputs using S‐SP compensation

This paper proposes a long-distance multi-load wireless power transfer (WPT) system with a constant voltage (CV) output for each load. A repeater unit consisting of two bipolar repeater coils is designed to power the load. Multiple repeater units are placed in a line and the power can be transferred from one unit to the next. Each repeater unit corresponds to one load and multiple loads can be powered simultaneously. The two repeater coils in the same repeater unit are placed perpendicularly to eliminate the magnetic coupling between them. In each repeater unit, a compensation capacitor is placed in series with the transmitting coil while two extra compensation capacitors form a series-parallel (SP) structure for the receiving coil. When neglecting the coil's parasitic resistance, the CV characteristics can be obtained, which enables the independent and flexible power control of each load. Moreover, the influence of the parasitic resistances on the system performance is analysed. Such a system is especially suitable for powering the gate drivers in a high-voltage converter where multiple insulated gate bipolar transistors (IGBTs) are connected in series. An experimental setup with six loads is constructed to validate the proposed system. The maximum system efficiency can reach 88.1%.

Analysis, Design, and Implementation of Junction Temperature Fluctuation Tracking Suppression Strategy for SiC MOSFETs in Wireless High-Power Transfer

In order to improve system reliability and reduce device thermal fatigue failure in multiload wireless power transfer (WPT) systems for electric vehicles, the implementation of the junction temperature fluctuation suppression strategy for SiC MOSFETs is necessary. However, current methods are relatively lacking, and active thermal management has not been used in WPT systems. In this article, the relationship between circuit parameters and junction temperature of SiC MOSFET is analyzed. In particular, a junction temperature fluctuation tracking suppression strategy for SiC MOSFETs is proposed, which consists of a coarse and a fine adjustment stage. As for the former, a shunt capacitor bank switching method is implemented. In order to compensate for the coarse adjustment defects in the small adjustment range and poor effect, in fine adjustment stage, a changing driving voltage method is used. Finally, a 5-kW multiload WPT system is built for verification. Experimental results show that the proposed strategy has obvious effect on the suppression of junction temperature fluctuation and keeps temperature near the target temperature. Benefiting from this, the maximum 13.9 °C junction temperature fluctuation is completely eliminated when the power fluctuations are within 36.1% of the rated power, and the heat load of each SiC MOSFET can be independently adjusted.

Circuit Model and Analysis of Multi-Load Wireless Power Transfer System Based on Parity-Time Symmetry

In the multi-load wireless power transfer (WPT) system, the output power and transfer efficiency will drop significantly with the change of distance between transmitter and receiver. Power distribution among multiple loads is also a major challenge. In order to solve these problems, a novel multi-load WPT system based on parity–time symmetry (PT-WPT) is proposed in this paper. Firstly, the multi-load PT-WPT system is modeled based on the circuit model. Then, the transmission characteristics of the multi-load PT-WPT system are analyzed. It is found that constant output power with constant transfer efficiency can be maintained against the variation of coupling coefficient, and the power distribution relationship among loads is only related to the coupling coefficient. Further, power distribution under different coupling situations is analyzed in detail to meet different power demands. Finally, taking a dual-load PT-WPT system as an example, the system parameters are designed and the circuit simulation is carried out. The simulation results are consistent with the theoretical analysis, which shows that PT symmetry can be applied to the multi-load WPT system to achieve constant output power, constant transfer efficiency, and power distribution simultaneously.

The Design and Optimization of a Wireless Power Transfer System Allowing Random Access for Multiple Loads

As is common in multi-load wireless power transfer (WPT) systems based on series–series compensation topology, the power received by loads and the efficiency of the process are highly sensitive to changes in the number of loads. To guarantee that the power supplied to a load remains stable when other loads access or leave the system, we propose an improved multi-load system for WPT. The new system uses an LCC/S topology (based on inductor–capacitor–inductor or LCL topology) to keep the power received by the loads stable. By comparing two scenarios (ideal and real models based on LCC/S topology), we aim to eliminate cross-coupling between receiving coils by connecting compensating capacitors in series on the receiving side. In this way, the stability of the power received by loads is further improved. Moreover, a method of optimizing control over the efficiency is proposed based on the effect on the overall efficiency of impedance and number of loads. This allows us to optimize the overall efficiency of the system. Finally, a system to verify our theoretical analysis is established and used to show the validity and effectiveness of the proposed system.