Performance optimization of LC bi-directional inductive power transfer system

Bi-directional Inductive Power Transfer (IPT) systems allow contactless power transfer between two sides and across an air-gap, through weak magnetic coupling. These systems essentially constitute high order resonant circuit and their complexity increases with increasing number of pick-ups. A mathematical model which provides an insight into the behaviour of bi-directional IPT systems with multiple pick-ups would therefore be invaluable at design stage. This paper develops a multivariable dynamic model for bi-directional IPT system with multiple pick-ups. A 1.5 kW bi-directional IPT system with 3 pick-ups is simulated in PLECS and the results are presented with comparisons to demonstrate the validity of the proposed model. Results of the simulation indicate that the proposed model accurately predicts the behaviour of bi-directional IPT system with multiple pick-ups and can therefore be used as a valuable tool for both dynamic analysis and controller design.

Bi-directional Inductive Power Transfer (IPT) systems facilitate contactless power transfer between two sides and across an air-gap, through weak magnetic coupling. These systems constitute a 6th order resonant circuit and, as such, are difficult to design and control. A mathematical model which provides an insight into the behaviour of bi-directional IPT systems would therefore be invaluable at design stage. This paper presents a dynamic model through which the behaviour of bi-directional IPT systems can be accurately predicted. A 1.5 kW bi-directional IPT system is simulated in PLECS, and results are presented with comparisons to demonstrate the validity of the dynamic model. Results indicate that the proposed model accurately predicts the dynamics of the bi-directional IPT system and can therefore be used as a valuable tool for both transient analysis and controller design.

Matrix converter (MC) based grid connected bi-directional inductive power transfer (BD-IPT) systems are preferable for numerous applications such as electric vehicle (EV) charging and vehicle-to-grid (V2G) systems due to their single-stage grid integration as opposed to two-stage grid integration of conventional BD-IPT systems. However MC based BD-IPT systems essentially produce harmonics which can have adverse effects on power quality of the utility grid. This paper presents a new control technique, through which the grid side harmonic distortion of MC based BD-IPT systems can be improved. A theoretical analysis is presented with simulations to show that the proposed approach is viable, and results suggest that the presented technique improves the power quality of the system significantly by minimizing the grid side harmonic distortion.

Mobility, continuity and safety are crucial in charging and discharging system of electric vehicles (EV) in smart grid applications. Bidirectional inductive wireless power transfer (BIWPT) system is ideal choice for these services. With accurate and efficient system models in hand, the circuit designers can predict and optimize the system performance. In this paper, an accurate, intuitive, and comprehensive steady-state theoretical model is proposed and implemented in MatLab environment. This model is generalized and can be used for any magnetic design of BIWPT system with the same compensation topology. The model is able to predict the system currents, voltages, power, power factor and equivalent impedance. The proposed model is used to evaluate two different designs for LCL compensation topology based on impedance frequency response analysis. Also, general considerations for the filters design parameters are stated and verified in this paper. A Simulink MatLab model for 1 kW BIWPT system is built to verify the proposed theoretical analysis.

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.

Depletion of fossil fuels and growing concerns about climate change have resulted in an increasing trend towards the use of sustainable technologies such as electric vehicles (EVs). As a result, effective means of charging EVs and managing EVs has become one of the most researched topics in the past few years. Among the many solutions proposed, inductive power transfer (IPT) systems, especially bi-directional IPT systems, are gaining popularity as an effective method to wirelessly interface EVs with the utility grid for charging as well as dynamic demand management. To enable wide spread use of bi-directional IPT technology for interfacing EVs with the gird essentially requires low cost and efficient magnetic couplers. As such, this paper investigates three new low cost magnetic designs, as alternatives to commonly used circular couplers. The proposed designs along with a standard circular coupler with similar ratings are modeled and simulated on JMAG studio to compare the performance. Based on the simulation data and experimental results gathered from a prototype implementation, the most effective design that yields a good coupling for the lowest cost has been identified as a possible solution for magnetic couplers used in bi-directional IPT systems.

Bidirectional Inductive Power Transfer (BD-IPT) is a promising technology that plays a significant role in specific scenarios such as vehicle-to-grid/home/vehicle systems. However, the BD-IPT system requires frequency synchronization between primary and secondary sides. Some researchers utilize a dedicated wireless communication interface to get the synchronization tracking information. But this solution will increase the cost and complexity while decrease the robustness and universality of the system. Therefore, this paper proposes a synthesizer PLL based frequency tracking technique for the BD-IPT system without adopting any communications. Specifically, the proposed controller includes two closed-loops, which decide and calculate the details of the active power, respectively. A proposed synthesizer PLL, which includes the phase detector, low-pass filter and voltage-controlled oscillator, is designed to generate an accurate synchronization signal. Also, the entire system operates in a zero-voltage switching (ZVS) state to achieve the high efficiency. Finally, a 120 W experimental prototype is built to verify the correctness feasibility of the whole system.

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.

For Inductive Power Transfer (IPT) system, the bi-directional power transfer mode is designed for energy feedback from receiver to transmitter. It will be helpful to improve system efficiency in high power application. In order to realize power flow from low voltage side to high voltage side, the paper gives voltage gain analysis method. On the basis, aiming at the power flow control, the paper proposes a dynamical control method. Based on switching between energy injection and free-running mode, the there is no needed of additional auxiliary circuit. As the control method is only based on logistical computing, the control method is simple and easy for implementation. Finally, simulation and experimental results verify the control method.

In recent years, a number of bidirectional inductive power transfer systems (BD-IPT) suitable for wireless grid integration of electric vehicles have been developed. These developments have been fueled by the enhanced efficiency and spatial tolerance offered by BD-IPT systems. A typical BD-IPT system utilizes two synchronized full-bridge converters operating at fixed duty cycles to drive the primary and secondary magnetic couplers. However, in order to cater for a wide range of loading conditions, additional circuitry is employed at the expense of cost and power density. As an alternative solution, this paper proposes a novel power converter, named a boost active bridge (BAB), to replace the full-bridge converters. The BAB topology caters to a wide range of loading conditions without the need for any extra switching devices. A comprehensive mathematical model that predicts steady-state currents, voltages, and power transfer is presented to highlight the operating principles of the BAB technology. Experimental results obtained from a 3.5-kW prototype show a nearly constant efficiency under all loading conditions, validating the viability of the proposed BAB topology.

For bidirectional inductive wireless power transfer systems, zero voltage switching (ZVS) of switching devices and system efficiency are always the keys to research. In this paper, the efficiency of the bidirectional dual-LCC compensation topology is firstly modelled, and the optimal bilateral modulation strategy is quantitatively derived. Then, a half-bridge modulation method under light load conditions is proposed. Compared with the full-bridge modulation strategy, the operating efficiency of the system is further improved. Finally, a 3.3 kW two-way wireless power transfer system simulation model is built in MATLAB. Compared with the full-bridge triple-phase-shift modulation strategy, it is proved that the half-bridge modulation scheme proposed in this paper has higher energy transfer efficiency under light load conditions.

In bidirectional inductive power transfer (BIPT) systems, phase synchronization loop that keeps the secondary-side excitation voltage synchronized with the current is essential for stable power transmission. However, the characteristic of control object in the synchronization loop can vary due to the variation of the operating point parameters (OPPs), which can lead to loop instability. In this article, the transfer functions of the control object and the phase detector in the phase synchronization loop are derived. The influence of the variation of OPPs on the transfer function of the control object is analyzed. The transfer function is mainly affected by one zero that is sensitive to the OPPs and can shift into low-frequency region, while the other poles and zeros are at high frequencies and have less influence. The phase synchronization controller is designed considering the variation of OPPs to ensure the stability of the system in a wide range of OPPs. The sensitivity of the loop to the OPPs is analyzed. Frequency response results from simulation and experiment have verified the correctness of the model, and the stability of the loop. Steady-state and transient experiments prove the stable steady-state performance and fast transient response of the system.

Bidirectional inductive power transfer (BIPT) allows power to be transferred bidirectionally between two electrical systems. In BIPT systems, phase synchronization of the AC port excitation voltage with the resonant current is essential for a stable transmission of power, which requires the detection of the phase difference between the fundamental components of the voltage and current, which is the fundamental power angle. To detect the fundamental power angle, this paper proposes a quadrature phase detection based fundamental power angle acquisition method with multi-level staircase signal as multiplicand. By using the multi-level staircase signal with eliminated low order harmonics, the phase detection error caused by the resonant current harmonics can be reduced. The basic characteristics of the BIPT system as well as the working principle of the quadrature phase detection method are introduced. The impact of harmonics on the fundamental power angle detection result is analyzed. The low order harmonics elimination parameters of the multi-level staircase signal are calculated. And the method to implement the multiplication of the resonant current with the equivalent multi-level staircase signal without using any multiplier, is proposed. Simulations are performed with the proposed method under various conditions, which show the improvement of the accuracy of the phase detection result with the proposed method.

In this paper, a compensation network analysis, and a design method for bidirectional power transfer of an inductive power transfer (IPT) converter for electric vehicles (EVs) are proposed. Through the analysis of input and output characteristics of compensation networks, a topology that enables stable bidirectional operation with respect to the coupling coefficient and load is selected. The system is designed with the selected topology and experimental verification is performed with simulation and 6.6 kW IPT converter prototype to confirm stable bidirectional power transfer.

Demand for supplying contactless or wireless power for various applications, ranging from low-power biomedical implants to high-power battery charging systems, is on the rise. Inductive power transfer (IPT) is a well recognized technique through which power can be transferred from one system to another with no physical contacts. This paper presents a novel bidirectional IPT system, which is particularly suitable for applications such as plug-in electric vehicles (EVs) and vehicle-to-grid (V2G) systems, where two-way power transfer is advantageous. The proposed IPT system facilitates simultaneous and controlled charging or discharging of multiple EVs through loose magnetic coupling and without any physical connections. A mathematical model is presented to show that both the amount and direction of power flow between EVs or multiple systems can be controlled through either phase or/and magnitude modulation of voltages generated by converters of each system. The validity of the concept is verified by theoretical analysis, simulations, and experimental results of a 1.5-kW prototype bidirectional IPT system with a 4-cm air gap. Results indicate that the proposed system is an ideal power interface for efficient and contactless integration of multiple hybrid or EVs into typical power networks.