Bidirectional Inductive Power Transfer System Research Articles

Optimal event‐triggered control for wireless power transfer system in electric vehicles

AbstractThis study focuses on stabilizing a bidirectional inductive wireless power transfer (WPT) system using an event‐triggered approach. It is only assumed the inductor currents on both the primary and pickup sides are measurable, and they are sent synchronously to the controller via a digital channel. To estimate the unmeasured states and maintain plant stability, a full‐order state observer and an observer‐based controller have been developed. The control parameters are optimized through a genetic algorithm to achieve the desired output response. An emulation methodology is then applied to create an output‐based event‐triggering condition. This condition ensures the stability of the closed‐loop system even in the presence of communication constraints. To prevent Zeno sampling, a minimal time interval between two transmissions is enforced using time‐regularization techniques. Furthermore, the performance of the event‐triggered controller is enhanced by solving a linear matrix inequality condition, which further reduces the number of transmission instances. The methodology offers a systematic and optimal design for the bidirectional inductive WPT system. It eliminates the need for manual tuning of control parameters, which is particularly beneficial given the system's complex nature. To address both continuous‐time and discrete‐time dynamics, the entire system is represented as a hybrid dynamical system, making it more intuitive for networked control systems. The efficiency of this approach is assessed through numerical simulations of a WPT system, demonstrating its effectiveness. The results show that the average intertransmission interval has been increased from 0.0799 to 0.1782 s, that is, the proposed event‐triggering strategy reduced the number of transmissions to more than 50% compared with conventional periodic sampling.

A Control Strategy for Achieving Constant Voltage Output with an Extensive ZVS Operating Range in Bidirectional Wireless EV Charging Systems

Variations in the coupling coefficient of loosely coupled transformers and dynamic loads have a significant impact on the overall performance of bidirectional inductive power transfer (BIPT) systems. However, a wide range of load and coupling coefficient variations are common in the actual charging process, which may cause the converter on both sides to operate in a hard switching state, resulting in switching noise, reduced efficiency, and potential safety concerns. In this paper, a triple-phase-shift control (TPSC) strategy is proposed to study the zero-voltage switching (ZVS) operating range and constant-voltage output (CVO) characteristics of the double-side-LCC (DS-LCC) topology. To ensure a CVO over the wide range of coupling coefficient variations, a dual-phase-shift control is introduced for AC voltage matching. Based on this, the third phase-shift angle control between the converters on both sides is introduced to ensure the ZVS realization. Meanwhile, the time-domain model is developed to analyze the rationality of the proposed third phase-shift angle and the ZVS operating range. Finally, the effectiveness of the proposed TPSC strategy is validated through a 1.5 kW experimental prototype with an air gap of 100–150 mm.

Fuzzy Logic Controlled Pulse Density Modulation Technique for Bidirectional Inductive Power Transfer Systems

Fuzzy Logic Controlled Pulse Density Modulation Technique for Bidirectional Inductive Power Transfer Systems

State-Space Based Universal Time-Domain Model for Voltage-Fed Bidirectional IPT Systems

Conventional time-domain model of bidirectional inductive power transfer (BIPT) systems highly rely on specific compensation network and lacks universality. To address this issue, we propose a universal time-domain model for voltage-fed BIPT systems. The proposed state-space model applies to all compensation networks and resonant parameters, The input of the state space consists of the output voltage of the H-bridge. While the voltage combinations of the H-bridge are adaptive to different phase shift conditions. Based on the circuit analysis and by solving the state equations, analytical expressions for the state variables can be obtained. The time-domain analytical model is piecewise and accurately predicts the coil currents and capacitor voltages under all fundamental modulation schemes and compensation topologies. The simulation and experimental results of different compensation topologies and modulation strategies are presented, verifying the effectiveness of the proposed model. Compared with commercial software, the computation burden is obviously alleviated. The simulation is accelerated by 64 times than Simulink and 10 times than Psim.

A Triple Phase Shift Control Method for Bidirectional Inductive Power Transfer (BIPT) Systems with Fully-compensated Series-Series (SS) Topology

A Triple Phase Shift Control Method for Bidirectional Inductive Power Transfer (BIPT) Systems with Fully-compensated Series-Series (SS) Topology

Decoupled State-Plane Analysis of Series–Series Compensated Bidirectional IPT Systems

Decoupled State-Plane Analysis of Series–Series Compensated Bidirectional IPT Systems

Bidirectional inductive underwater wireless power transfer converter with variable structure

The undersea sensor networks have an important function in marine resource exploration. To prolong the lifetime of the sensor networks, a bidirectional inductive underwater wireless power transfer (BI-UWPT) system with variable structure is proposed. With the proposed system, the autonomous underwater vehicle (AUV) could receive energy from the undersea docking station and transmit energy to the undersea sensor networks. The two full bridge topologies and the SS compensation networks are adopted in the system to achieve the bidirectional power transfer. To achieve bidirectional energy transmission of different power levels, two different operating frequencies and variable compensation capacitors are employed by the AUV. The system mathematical model is also presented. To verify the theoretical analysis, a 432 W simulation model when the AUV receiving electric energy and a 96 W simulation model when the AUV transmitting electric energy are constructed, respectively. The theoretical analysis is verified by the simulation results. Simulation results show that the variable compensation networks can obtain high transfer efficiency of the BI-UWPT system.

Power Factor Corrector Control Strategies of a Bidirectional Wireless Battery Charger With an Unfolding Active Rectifier

In this article, two power factor corrector (PFC) control strategies for a bidirectional inductive power transfer (IPT) system are proposed. These control strategies are presented for a novel power circuit without input and output interfaces for a wireless electric vehicle battery charger application. This compact topology comprises: unfolding rectifier, primary resonant bridge, and secondary-side active rectification. Two PFC controls are described in detail: a primary-side PFC control, performed in the primary resonant bridge; and a secondary-side PFC control, implemented in the secondary-side active rectification stage. Both strategies are based on a duty-cycle control operating close to the resonance frequency, integrating different functionalities, i.e., PFC, current shaping (CS), and power control on a single control strategy. We analyze each control strategy, evaluating them for different operating points of the charging process. The performance of the wireless charger applying both control strategies is evaluated in terms of power losses, power factor, harmonic distortion, and bifurcation. Additionally, the theoretical results are validated using a GaN-based experimental prototype. The presented analysis and experimental results clearly identify the advantages and limitations of each control strategy leaving no doubt about their usefulness for the future IPT systems.

A Versatile Unified Model for Inductive Power Transfer (IPT) Systems

Efficient and cost-effective inductive power transfer (IPT) systems essentially require reactive power compensation networks. To select and design compensation networks best suited to meet the specific requirements of any particular application, the modeling and investigation of each type of compensation are required. Traditional approaches using separate models for each compensation type are repetitive and inefficient. Therefore, this article proposes a novel unified model for IPT systems that can be easily adapted to investigate the suitability of any type of compensation network. It is applicable to the design of uni-, or bidirectional IPT systems. Its utility is apparent from the ease with which it can be used to evaluate key performance indicators of IPT systems that are affected by compensation network design. The proposed unified model is benchmarked against experimental results from already published work, highlighting its benefits and verifying its accuracy.

Research on Synchronous Phase Shift Control Strategy of Bilateral Converter in Bidirectional Inductive Power Transfer System

Research on Synchronous Phase Shift Control Strategy of Bilateral Converter in Bidirectional Inductive Power Transfer System

Control Scheme of a Bidirectional Inductive Power Transfer System for Electric Vehicles Integrated into the Grid

Inductive power transfer (IPT) systems have become a very effective technology when charging the batteries of electric vehicles (EVs), with numerous research works devoted to this field in recent years. In the battery charging process, the EV consumes energy from the grid, and this concept is called Grid-to-Vehicle (G2V). Nevertheless, the EV can also be used to inject part of the energy stored in the battery into the grid, according to the so-called Vehicle-to-Grid (V2G) scheme. This bidirectional feature can be applied to a better development of distributed generation systems, thus improving the integration of EVs into the grid (including IPT-powered EVs). Over the past few years, some works have begun to pay attention to bidirectional IPT systems applied to EVs, focusing on aspects such as the compensation topology, the design of the magnetic coupler or the power electronic configuration. Nevertheless, the design of the control system has not been extensively studied. This paper is focused on the design of a control system applied to a bidirectional IPT charger, which can operate in both the G2V and V2G modes. The procedure design of the control system is thoroughly explained and classical control techniques are applied to tailor the control scheme. One of the advantages of the proposed control scheme is the robustness when there is a mismatch between the coupling factor used in the model and the real value. Moreover, the control system can be used to limit the peak value of the primary side current when this value increases, thus protecting the IPT system. Simulation results obtained with PSCADTM/EMTDCTM show the good performance of the overall system when working in both G2V and V2G modes, while experimental results validate the control system behavior in the G2V mode.

Dual-Side Asymmetrical Voltage-Cancelation Control for Bidirectional Inductive Power Transfer Systems

Bidirectional inductive power transfer (BIPT) systems for electric vehicles allow power exchange between grid and vehicle. To achieve high transfer efficiency under a wide range of transmission power, this article proposes a dual-side asymmetrical voltage-cancelation (AVC) control technique. With the proposed dual-side AVC control, the adjustment of the fundamental component amplitude of the excitation voltage, the maintenance of a large phase angle between excitation voltages as well as zero-voltage switching (ZVS) of the power switches, and the optimization of the resonant tank power transfer efficiency can be achieved simultaneously. The basic characteristics and the conditions for maximum transfer efficiency of the resonant tank are derived. The control scheme for the overall system including the control of the primary-side and secondary-side full bridges is proposed, which considers both efficiency optimization and ZVS operation of all switches. The ZVS range of the proposed dual-side AVC control technique is presented. Experiments are performed with dual-phase-shift, triple-phase-shift, and the proposed dual-side AVC control technique, which show that the BIPT system with the proposed dual-side AVC control technique achieves a higher efficiency over the others in a wide range of transmission power.

Primary-Side Parameter Estimation Method for Bidirectional Inductive Power Transfer Systems

This letter proposes a novel primary-side parameter estimation method for bidirectional inductive power transfer (BD-IPT) systems. This method can estimate mutual inductance at startup and monitor secondary-side phasor information continuously during operation. The proposed method can be used to simplify existing optimal control methods in BD-IPT systems by providing necessary feedback information without a wireless communication link. Besides, it helps to implement new control methods to further improve system performance. A current decoupling concept is utilized to estimate both the mutual inductance and secondary phasor information. A circuit model based on the superposition principle is presented to describe the current decoupling concept. The validity and accuracy of the proposed estimation method are demonstrated using the measured results of a 1-kW prototype BD-IPT system.

A Single-Stage Bidirectional Inductive Power Transfer System With Closed-Loop Current Control Strategy

A conventional two-stage topology that consists of a dc/ac converter, a dc-link, and two ac/dc converter is being used as wireless charging of electric vehicles (EVs). However, the conventional topology contains more conversion stages with a bulky dc-link capacitor, and implementation of control strategies is not easy to transfer power from the primary coil to pickup coil or vice versa. A single-stage, inductive power transfer (IPT) system with a simple control strategy is needed to reduce the conversion stages and to increase the reliability of the system. This article proposes a control strategy for a single-stage conversion topology that is easy to implement and more importantly can achieve unity power factor (UPF) using a single controller. The experimental validation of single-stage conversion topology and steady-state analysis with series–series (SS) compensation scheme is presented in this article. A fixed angle of ±90° in between the output phase of the converters is achieved without estimating any power or current parameters. A hardware prototype working at a lower watt rating is analyzed, and the validation of the proposed system for 3.7-kVA rating as per the international standard is simulated. Furthermore, transient response is also observed to verify the closed-loop control scheme of battery current.

An Optimal Multivariable Control Strategy for Inductive Power Transfer Systems to Improve Efficiency

Efficiency of wireless power transfer systems, based on inductive power transfer (IPT) technology, suffers significantly due to coil misalignment and load variations. Although numerous control strategies have been proposed in the past to improve the efficiency under these conditions, a technique that utilizes all freedoms of control simultaneously to maximize efficiency is yet to be reported. This article therefore proposes a multivariable control strategy that uses the optimal combination of all control variables to maximize the efficiency of IPT systems when regulating power and even under large coil misalignments and load variations. The article presents a comprehensive mathematical model, describing the underlying theory of the proposed optimal control philosophy, and investigates the performance and limitations of the proposed technique under wide range of operating conditions. To demonstrate the improvement in performance, theoretical results are presented in comparison to those obtained from a 1-kW prototype bidirectional IPT system, and also benchmarking against conventional control techniques. Results convincingly indicate that the proposed optimal control strategy regulates power at maximum efficiency despite large coil misalignments and load variations.

A Wireless EV Charging Topology With Integrated Energy Storage

This article presents a wireless power transfer topology based on inductive power transfer (IPT) with integrated supercapacitor (SC) energy storage. The proposed topology is suitable for dynamic charging of electric vehicles (EVs), where pulses of energy must be processed without placing excessive strain on the utility grid or the EV battery. This topology extends the functionality of a typical LCL- tuned bidirectional IPT system by adding the ability to store energy in an SC in a controlled manner. Operation of the system is described in terms of the switching patterns and control variables required to transfer energy between the input, output, and the SCs. A mathematical model that predicts the overall transfer of power between the input, output, and SCs is presented along with experimental results at a nominal power level of 3.8 kW to validate the model and the topology under a variety of typical operating conditions.

A Digital Phase Synchronization Method for Bidirectional Inductive Power Transfer

Bidirectional inductive power transfer (BIPT) systems are of particular interest for electrical vehicles for their enabling power to exchange between grid and vehicle. In BIPT systems, it is critical to keep the voltage phasors of the primary-side and secondary-side converters synchronized to regulate the power flow. In this article, the basic operation and steady-state characteristics of the BIPT system are introduced. A phase synchronization method for BIPT systems, which does not require any communication between primary- and secondary-side controllers or complicated hardware, is proposed in this article. To assist the design of the synchronization controller, the large-signal model and small-signal model of the BIPT system are derived. Based on the derived model of the system, the controller design for the phase synchronization method is proposed, considering the coupling between the synchronization controller and the BIPT main circuit and the clock frequency deviation between the primary-side and secondary-side controllers. The parameter sensitivity of the proposed method is analyzed. The large-signal and small-signal models are verified through simulations. And the experimental verification of the phase synchronization method shows that the BIPT system with the proposed phase synchronization method has a fast transient response as well as a stable steady-state performance.

A Consideration on Maximum Efficiency of Resonant Circuit of Inductive Power Transfer System with Soft-Switching Operation

By using bi-directional inductive power transfer (IPT) systems as battery chargers for electric vehicles (EVs), battery charging operations become convenient and safe. However, IPT systems have problems such as occurrences of much electromagnetic noise and power loss because the converters of IPT systems are driven in high frequency by tens of kHz. To solve these problems, there is a case where the soft-switching technique needs to be applied to the converters of IPT systems. However, in soft-switching operation, the power factor of the resonant circuit becomes lower, resulting in a lower resonant circuit efficiency. In previous works, when the soft-switching technique was applied to the converters, the resonant circuit had not always been able to be operated with high efficiency because the influence caused by soft-switching operation had not been considered. For this reason, there was a case where the efficiency of the overall system with soft-switching operation became lower than the efficiency in hard-switching operation. Therefore, in this paper, the influence on the efficiency of the resonant circuit caused by the soft-switching operation is clarified by the theoretical analysis and experiments; then, the guideline for improving the efficiency of IPT systems is shown. As a result, in the experiments, it could be understood that the efficiency of the overall system with soft-switching operation becomes higher than the efficiency in hard-switching operation when the operating point of the resonant circuit was close to the requirement guideline, which is shown by using the primary-side voltage and the secondary-side voltage of the resonant circuit. Therefore, it is suggested that the efficiency of IPT systems could be improved by properly regulating the primary-side direct current (DC) voltage.

A Control Strategy for Efficiency Optimization and Wide ZVS Operation Range in Bidirectional Inductive Power Transfer System

The efficiency of bidirectional inductive power transfer (BIPT) systems is strongly dependent on the load. Besides, the soft-switching operation of power switches is critical to high-frequency converter in the BIPT systems. In this paper, a triple-phase-shift (TPS) control strategy is proposed to achieve load matching while realizing zero voltage switching (ZVS) for all power switches within the entire power range. The load matching condition of the BIPT system with double-sided LCC compensation network is analyzed. And a dual side phase shift control is proposed to adjust power flow while realizing load matching. To realize ZVS operation, the third phase shift between primary and secondary side is introduced as an extra control variable. A time domain model of double-sided LCC compensation network is established to analyze the ZVS range. With the proposed TPS control, wide ZVS operation range of the system can be achieved while maintaining load matching. At last, a scale down prototype of 1 kW BIPT system is developed. The experimental results show good agreement with theoretical analysis, all switches realize ZVS within the entire power range and a peak efficiency of 94.83% is achieved.

A Push–Pull Parallel Resonant Converter-Based Bidirectional IPT System

Bidirectional inductive power transfer (BD-IPT) systems facilitate wireless grid integration of electric vehicles to offer vehicle-to-grid (V2G) services. This paper presents a novel push–pull parallel resonant converter-based BD-IPT system to provide a more efficient and cost-effective solution to wireless V2G technologies. The proposed system integrates the functionality of bulky passive elements into a double-D type magnetic coupler to achieve high power density. A phase-delay control technique is proposed to reduce the startup transients as well as to regulate bidirectional power flow between the primary and secondary sides of the push–pull converters. A zero-voltage switching zone is identified to maintain safe operation of the system. Both the operating principles and control philosophy of the converters are described, and a detailed mathematical analysis is presented. The effectiveness of the proposed system is verified by building a 3.3-kW prototype system. The experimental results show that the peak power transfer efficiency reaches 96.5%, and the efficiency remains high under a wide range of operating conditions.