Bidirectional Wireless Power Transfer System Research Articles

Medium-Duty Delivery Truck Integrated Bidirectional Wireless Power Transfer System With Grid and Stationary Energy Storage System Connectivity

Medium-Duty Delivery Truck Integrated Bidirectional Wireless Power Transfer System With Grid and Stationary Energy Storage System Connectivity

DAB-Based Bidirectional Wireless Power Transfer System with LCC-S Compensation Network under Grid-Connected Application

To realize two-way power transfer without physical connections under a grid-connected application, bidirectional wireless power transfer (BDWPT) is introduced. This paper proposes an LCC-S compensated BDWPT system based on dual-active-bridge (DAB) topology with the minimum component counts. LCC-S is designed to be a constant voltage (CV) network. To obtain the power transmission characteristics of the system, a mathematical model based on the fundamental harmonic approximation (FHA) method is established, and the result shows that the direction and amount of transfer power can be controlled by changing the magnitude of output voltages of either/both side of H-bridges. The reactive power of the system can be controlled to be zero when the output voltages of two H-bridges are in the same phase. Compared with DAB-based BDWPT systems with constant current (CC) compensation networks, the proposed structure has better transfer power regulation capability and easier control of the direction of power flow. A 1.1 kW experimental prototype is built in the laboratory to verify the characteristics of the proposed system. The results indicate that the power transfer characteristics of the proposed BDWPT system match its mathematical derivation results based on the FHA model.

An I/Q Phase Detection-Based Harmonic- Insensitive Phase Synchronization Method for Bidirectional Wireless Power Transfer System

An I/Q Phase Detection-Based Harmonic- Insensitive Phase Synchronization Method for Bidirectional Wireless Power Transfer System

Real-Time Hardware Emulation of Microgrid Forming Wireless Power Transfer Systems

The prevalence of wireless charging approaches has manifested a grid-supporting potential which can be evaluated by hardware-based methodologies. In this work, real-time emulation of a bidirectional wireless power transfer (WPT) system capable of DC microgrid formation is investigated on the field-programmable gate array (FPGA). Following a detailed analysis of the transfer characteristics of the dual-active bridge with a series-compensated resonant tank in between, a unified control scheme utilizing a phase-shift strategy is proposed for a flexible voltage or current regulation, thereby enabling the DC microgrid-forming capability. Electromagnetic transient modeling is then carried out so that an accurate digital emulation platform is feasible for prototyping. The fact that the WPT has a high frequency compels a small computation step size, which poses a dramatic challenge to real-time execution. A partition-iteration approach is therefore proposed for matrix dimension reduction which ultimately results in an alleviated processing burden. In the meantime, the parallelism of configurable logic blocks and the pipelined architecture of the FPGA are explored to achieve a low hardware latency. The analytical models, as well as the proposed control method, are validated experimentally, and then real-time hardware emulation of a DC microgrid consisting of WPT systems is performed for an integration study.

Research on a soft-start method for LCC-LCC compensated bidirectional wireless power transfer system

The increased popularity of electric vehicles and the pursuit of user convenience makes bidirectional wireless power transfer (BWPT) an attractive technology for charging batteries. To improve the transmission efficiency of BWPT and limit the external radiated magnetic field, it is necessary to ensure the zero-voltage switching (ZVS) operation of the converter on the transmitter-side and limit the transient start-up current of the inverter when the system is working. To solve this problem, this paper proposes a soft-start modulation strategy based on an H-bridge inverter on the transmitter-side. First, the circular characteristics of dual LCC compensation topology are analysed based on an equivalent circuit. Secondly, according to the characteristics of the input impedance angle and current of the transmitter-side, a soft-start control method combining frequency and phase shift control is proposed. Finally, the feasibility of the proposed soft-start modulation strategy is verified on a prototype.

A Bidirectional Wireless Power Transfer System with Integrated Near-Field Communication for E-Vehicles

This paper presents the design of a bidirectional wireless power and information transfer system. The wireless information transfer is based on near-field technology, utilizing communication coils integrated into power transfer coils. Compared with conventional far-field-based communication methods (e.g., Bluetooth and WLAN), the proposed near-field-based communication method provides a peer-to-peer feature, as well as lower latency, which enables the simple paring of a transmitter and a receiver for power transfer and the real-time updating of control parameters. Using the established communication, control parameters are transmitted from one side of the system to another side, and the co-control of the inverter and the active rectifier is realized. In addition, this work innovatively presents the communication-signal-based synchronization of an inverter and a rectifier, which requires no AC current sensing in the power path and no complex algorithm for stabilization, unlike conventional current-based synchronization methods. The proposed information and power transfer system was measured under different operating conditions, including aligned and misaligned positions, operating points with different charging powers, and forward and reverse power transfer. The results show that the presented prototype allows a bidirectional power transfer of up to 1.2 kW, and efficiency above 90% for the power ranges from 0.6 kW to 1.2 kW was obtained. Furthermore, the integrated communication is robust to the crosstalk from the power transfer and misalignment, and a zero BER (bit error rate) and ultra-low latency of 15.36 µs are achieved. The presented work thus provides a novel solution to the synchronization and real-time co-control of an active rectifier and an inverter in a wireless power transfer system, utilizing integrated near-field-based communication.

A Hybrid Modulation Strategy for LCC–LCC Compensated Bidirectional Wireless Power Transfer System to Achieve High Efficiency in the Whole Operating Range

A hybrid modulation strategy is proposed for the LCC-LCC compensated bidirectional wireless power transfer system (LCC-BWPT), which aims to boost the efficiencies in the whole operating range. The basic operating modes of LCC-BWPT with the hybrid modulation strategy are analyzed, and the unified discrete-time model is then established based on the full-mode operation, which can accurately describe the state variables under all operating modes. Based on the model, the criteria for optimal operation are put forward in consideration of three working processes of LCC-BWPT, i.e., the constant current (CC) charging process, the constant voltage (CV) charging process, and the CC discharging process. The optimal control variables in three working processes are derived respectively, which realize full zero-voltage switching (ZVS) operation and minimize the reactive current. On this basis, an optimal modulation strategy featuring high efficiency performance is proposed for LCC-BWPT. Besides, a control method independent of the real-time wireless communication is developed for LCC-BWPT with the optimal modulation strategy. Finally, a 1.2kW prototype is applied, and experimental results verify the effectiveness of the proposed optimal modulation strategy, where the efficiencies are improved in the whole operating range.

The Effect of Cross-Coupling on the Dynamic Performance of a Dual Phase Shift Controlled BiWPT System

In a bidirectional wireless power transfer (BiWPT) system, dual phase-shift (DPS) control is used to maintain the optimal efficiency at constant output power over varying misalignment. The presence of multiple control and output variables in DPS control creates cross-coupling between transmitter and receiver side, making BiWPT a multiple-input multiple-output (MIMO) system. Due to cross coupling, any change in control variable in one side of the BiWPT system will affect the output of the same side as well as output and control input in the other side. This results in an uncertain dynamic behaviour of the output response. The cross-coupling effect has not been adequately researched in the literature. Hence, this paper presents an accurate dynamic model using a generalized state-space averaging approach (GSSA) and an extended describing function (EDF) method for a multivariable control of the S-S compensated BiWPT system. This model is used to derive the system’s relative gain array (RGA), which is used to study the effect of cross-coupling terms on the output variables. A 1 kW S-S compensated BiWPT experimental set-up is used to validate the effect of cross-coupling on the dynamic behavior of the system by comparing DPS and single phase-shift (SPS) controlled experimental waveforms. The steady-state and transient behavior of the BiWPT system has also been investigated with simulation and experimental results.

High-efficiency bidirectional resonant WPT system for electric vehicles

<p>The wireless power transfer (WPT) system has become popular given its safety and flexibility in electric vehicle (EVs) charging applications. Due to the increasing number of EVs, vehicle to grid (V2G) can be implemented in the future in which a bidirectional WPT is one of the key features. A high-efficiency bidirectional resonant WPT system is studied and implemented in this study. Besides bidirectional capability, single stage and regulated output voltage are other features of this work. It is done by using the variable frequency control without sacrificing efficiency and conforming to the typical frequency range of the WPT system for EVs application. The analysis of the series-series compensated WPT is presented, followed by the design consideration of the developed bidirectional WPT system. At last, the implementation and experimental results for a 3 kW laboratory prototype are also presented to show the validity and the feasibility of the proposed scheme. A 96.8% efficiency at a 210-mm gap and a 95% efficiency at a 250-mm gap can be achieved under a rated power condition.</p>

Bidirectional Wireless Power Transfer System for Electric Vehicle

Bidirectional Wireless Power Transfer System for Electric Vehicle

Control Strategy for a Bidirectional Wireless Power Transfer System With Vehicle to Home Functionality

Control Strategy for a Bidirectional Wireless Power Transfer System With Vehicle to Home Functionality

Efficiency Optimization of LCC-S Compensated Multiple-Receiver Bidirectional WPT System for Stackers in Automated Storage and Retrieval Systems

In automated storage and retrieval systems (ASRS), adopting wireless power transfer (WPT) technology is an available way to avoid the drawbacks of the contact power supply system for multiple stackers. When stackers are dropping goods, it is meaningful to recycle the power generated by the motors and feedback to the other stackers or the ground power supply for improving the overall efficiency of ASRS. This article proposes a bidirectional WPT (BD-WPT) system for multiple receivers. Based on the values of transmission power and the power flow directions of receivers, a general model of the BD-WPT system is established with identifying the system operation modes and their boundaries. To achieve flexible switching among different operation modes and adapt the required transmission power with maximum efficiency point tracking (MEPT), a control strategy of the BD-WPT system is proposed. In the 2-kW experimental prototype built, the power demands can be met in real time, and the power fed back by the stackers can be supplied to other loads or recycled by the ground power supply with good dynamic performance. Compared with the system without MEPT, the efficiency of the proposed system is improved by 26.7% at most, and the maximum efficiency achieves 96.4%.

Review on Power Flow Evaluation of Grid Connected Bidirectional Wireless Power Transfer for EV System

Wireless Power Transfer (WPT) for Electric Vehicle (EV) battery charging application is one of the key upcoming technologies. The possibility of using EVs to transfer power back to the grid, utilizing the concept of Bidirectional Wireless Power Transfer (BD-WPT) is extensively being explored. The effect of integration of EV on grid is also of concern. This paper presents analysis of complete grid integrated BD-WPT system for controlling power transfer between grid and EV battery, along-with ensuring Unity Power Factor (UPF) at grid side. Mathematical model of each component in the system is presented which is then used to design vehicle and grid side controllers for achieving desired output. Concepts stated analytically are validated by simulation in MATLAB (Simulink).

Bidirectional LCC–LCC-Compensated 20-kW Wireless Power Transfer System for Medium-Duty Vehicle Charging

This article presents the design and demonstration of a bidirectional 20-kW wireless charging system (WCS) with a significantly large air gap (11 in) and asymmetrical input-output voltage levels. Analytical and experimental sensitivity analyses of the WCS resonant tank were conducted to verify the optimal operating region under the load and frequency variation. The inverter and rectifier were designed with switching components, the charging pads were designed with double-D (DD) coils, and the tuning networks were designed with an LCC - LCC tuning circuit. The grid and vehicle side tuning circuits were designed separately to achieve a ~1:2 gain for the asymmetrical input (800 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dc</sub> ) and output (350 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dc</sub> ) voltages. The proposed WCS was designed, simulated, and tested to verify the efficiency, power transfer capacity, and sensitivity under load variation. The experimental results show that, at 20-kW output power, the achieved grid-to-vehicle dc - dc efficiency was 96.1%, and the vehicle-to-grid dc - dc efficiency was 96.2%. The proposed system is the largest-air gap bidirectional WCS with the highest efficiency and power density.

Design Consideration of Bidirectional Wireless Power Transfer and Full-Duplex Communication System via a Shared Inductive Channel

Communication between the primary and secondary sides is pivotal to the wireless power transfer (WPT) system. The system control commands and feedback information need simultaneous wireless information and power transfer (SWIPT). In this paper, a FSK-based SWIPT system with full-duplex communication via a shared channel is provided. Considering the complexity of the coupling relationship in this kind of full-duplex SWIPT system, this paper proposes an analysis method based on the transmission channel, studies the crosstalk between the power channel and the information channel, and between the forward and reverse transfer of information. A design method of full-duplex communication SWIPT system based on shared coupling channels is provided. A 60 W SWIPT prototype with a full-duplex communication rate of 20 kbps is built to verify the proposed method.

Design of a Bidirectional Wireless Power Transfer System for Vehicle-to-Home Applications

Energy storage plays a fundamental role in balancing the power fluctuations induced by the distributed generation of renewable energy sources. In this scenario, electric vehicles can strongly contribute to exchange power with the grid through their on-board batteries. When the vehicle is parked, the battery can be discharged, injecting active power into the grid, provided that its state of charge will be restored before vehicle utilization. This paper presents a comprehensive step-by-step design of a wireless charger for a Vehicle-to-Home application. The design procedure begins from the constraints disposed by the Italian reference technical rules for Low Voltage utilities and by the standard SAE J2954 for Wireless Power Transfer for electric vehicles. The selection of the output power of the battery is followed by the power sizing of each stage of the bidirectional wireless charger.

An Energy Injection Method to Improve Power Transfer Capability of Bidirectional WPT System With Multiple Pickups

Track wireless power transfer (WPT) systems are increasingly used for monorail robots, industrial transportation, etc. Conventionally, the track WPT system's primary power supply is designed to be equal or higher than the total running pickups’ rated power. However, in practice, some of the pickups may transiently require more power than their normal operating state. It is not cost effective to increase the power rating of the primary source for the transient case. Hence, this article proposes a method to strengthen the track's power transfer capability by reversely injecting energy from available online pickups to the transiently over-rated one. A bioperation mode is proposed, which includes both the normal operation and the strengthening operation. A bidirectional pickup topology is used, and the equivalent circuit is analyzed accounting the bioperation mode. In addition, a synchronization method of the primary and reverse injection pickups is proposed. A criterion to determine the boundary of the reverse energy injection is also presented. By detecting the peak current, this energy injection method can be practically implemented and the proposed method is verified through the experimental results.

Constant Output-Voltage Design for Bi-Directional Wireless Power Transfer System with Multiple Stages

For the application of wireless power transfer (WPT) technology in a robot (like the snake robot), the power is supposed to be transferred to each device across multiple robot joints. This paper proposes a multi-stage bi-directional WPT (MB-WPT) system that not only provides power to multiple loads but also increases the power transfer distance. Besides, the last stage can charge for the preceding stages by reverse power transfer. The constant output voltage can be achieved whether the power is transmitted in a forward or reverse direction, and different output voltages for each stage can be achieved to satisfy the respective voltage requirement through the parameter design method. The validity of the theoretical analysis and the feasibility of the system are verified by experiments.

A Direct Three-Phase AC–AC Matrix Converter-Based Wireless Power Transfer System for Electric Vehicles

For the bidirectional wireless power transfer system of electric vehicles, the topology proposed in this paper includes a direct three-phase AC–AC matrix converter as the pre-stage main circuit, a bilateral inductor–capacitor–capacitor–inductor (LCCL) as the resonance compensation network, and a full-bridge converter as the latter stage circuit. According to the characteristics of the system topology, a new control strategy is proposed based on the de-re-coupling method. The control principle of the coordination work of the scheme is expounded, and the corresponding switch combination logic is designed. According to the three-phase voltage amplitude relationship at different stages, combined with the resonant frequency, the switch arms of the matrix converter are alternately controlled separately. The number of switching operations is reduced, the system efficiency and safety are improved, and the full range of soft switching operations of the converter is realized. The theoretical analysis of the bilateral LCCL resonance compensation network is carried out, and its constant voltage/current output characteristic and high power factor transmission characteristic are obtained. Finally, the effectiveness and feasibility of the bidirectional wireless power transfer system for electric vehicles proposed in this paper are verified by simulation analysis.

A Bidirectional Wireless Power Transfer System Control Strategy Independent of Real-Time Wireless Communication

For the bidirectional wireless power transfer (BWPT) technology, the phase synchronization between the transmitting and receiving converters is very essential and difficult to achieve by wireless communication between two sides because the delay and data transfer interval of wireless communication severely influence the control performance. This article proposes a novel control strategy for BWPT, which can achieve the phase synchronization and maximum efficiency point tracking independent of the real-time wireless communication. To solve the overshoot and oscillation problem incurred by the proposed control strategy and the nature of the system itself, the dynamics of a series-series compensated BWPT system is then analyzed and a small-signal model of this system is derived based on the generalized state space averaging and extended describing function methods. Using the small-signal model, a BWPT control system based on the proposed control strategy is designed and optimized. The validity of the proposed strategy and the performance of the control system are verified experimentally using a 3.3-kW prototype system.