Performance Analysis of an Inductive Contactless Power Transfer System

An inductive power transfer (IPT) system usually consists of four parts: an AC-DC power factor correction (PFC) converter, a high frequency DC-AC inverter, a compensation network comprising a loosely coupled transformer (LCT) and the resonant capacitors, and a rectification output circuit. Due to the relative large air gap, the magnetic coupling coefficient of the IPT system is poor, different from the closely-coupled IPT systems. As a result, the efficiency of the IPT system is always a main concern for different applications. To ensure high power transfer efficiency, these IPT systems should have high tolerance for different gap variation and horizontal misalignment conditions. In this paper, some design considerations to reduce gap and misalignment effects for the IPT system is proposed. By using finite element analysis (FEA) simulation method, the performance of different transmitter and receiver coil dimensions are compared. In order to validate the performance of the proposed design considerations, a hardware prototype is built and the corresponding experiments are carried out. The experimental results shows that the LCT prototype could maintain coupling coefficient between 0.237∼0.212 within 40 mm horizontal misalignment.

The inductively coupled power transfer technology (ICPT) is a new power transmission technology, which can transmit electric energy without physical connection. With the advantages of safety and convenience, it has been applied in portable electronic products, medical devices, and high-power transmission. In space engineering, the electric energy generated by solar panels needs to be transmitted to the spacecraft through brushes. Brushes are costly because of the high requirement, and the ICPT instead of brushes is proposed in this paper. A rotating loosely coupled transformer is designed that can transmit electric energy steadily and reliably. This paper studies the compensation network, the influence of coupling coefficient (k), compensation capacitance ratio (α), and quality factor (Q) on compensation characteristics. A prototype of ICPT system is built, which includes the selection of topology of main circuit, the design of driving circuit, shaping circuit, and the selection of original and secondary compensation network parameters. Finally, the performance test of the prototype is carried out. The experimental results show that the prototype of ICPT system can transmit electric energy stably and reliably.

Although the demand for high-power inductive power transfer (IPT) systems is on the rise, implementation of such IPT systems using low-cost semiconductor devices has been a challenge. This study presents a new IPT topology that facilitates easy integration of multiple IPT modules, which are made of low cost and freely available semiconductor components, to cater for high-power applications. An intermediate circuit, comprising an inductor-capacitor-inductor resonant network, serves as a contactless interface through which the modules of primary and secondary (pick-up) systems can be either series or parallel integrated. Inductor coils of the intermediate circuit and both primary and pick-up systems are magnetically coupled to allow for contactless power transfer. The proposed topology is parallel compensated to minimise its var requirement, and both the direction and amount of power flow are controlled by phase and/or magnitude modulation of voltages generated by primary and pick-up side converters. Theoretical analysis, together with simulations and experimental evidence of integrating four prototype bi-directional IPT systems to cater for 1.8 kW demand, is presented to show that the proposed new IPT topology is suitable for high-power applications, and flexible for both bi-directional and uni-directional contactless power transfer.

Contactless power transfer is expected to be applied to many applications since it is convenience and safety. Inductive power transfer (IPT) is a kind of contactless power transfer schemes uses two coils. These coils are inductively coupled and power is transferred from primary coil to secondary coil when high frequency (a few tens of kHz) AC power supplies to primary coil. In many applications using IPT, received AC power is converted to DC power and then the power is charged to battery. Thus, two functions which are rectification and regulating voltage or current are required on the receiver (secondary) side. In this study, one of two types (buck type and boost type) of DC-DC converter connected to diode rectifier were applied to IPT system, and characteristics of each type were compared by experiments. As a result of the experiments, it was found that both rectifiers have two functions which are rectification and regulating voltage or current. It was also found that boost type is better in terms of regulation capability and of efficiency of resonant circuit.

SummaryRectifier load in inductive power transfer system has nonlinear characteristics. However, the traditional analysis method equates it to a pure resistor, which leads to a certain deviation between the theoretical analysis and the actual circuit. This will reduce the accuracy of the inductive power transfer (IPT) system model and affect the soft switching operation of the inverter. In this paper, the IPT system with S‐type topology on the secondary side is studied. Firstly, the resistance–inductance characteristics of the rectifier load are analyzed by simulation, and then a second‐order circuit response model is established to solve the time‐domain expression of voltage and current. Then, the fundamental component of voltage and current is extracted by Fourier transform to calculate the impedance value of the rectifier load, and the mathematical calculation model of the rectifier load is established. On this basis, the influence of the inductive component of the rectifier load on the input impedance of the IPT system is analyzed. Then, a parameter design method for zero voltage switching is proposed for S‐S and LCC‐S topologies. Finally, an experimental platform of S‐S and LCC‐S IPT system is built. The correctness and effectiveness of the theoretical analysis and the proposed parameter design method are verified by experiments.

The charging power is being augmented to enhance the ease of electric automobiles. Nonetheless, high‐power charging may lead to significant and apparent issues with battery heat production. Consequently, a prominent research concern is achieving an optimal equilibrium between rapid charging and preserving battery performance. An LCLC‐compensated combination inductive and capacitive wireless power transfer (COMPT) system for battery charging is a novel system in this work. Inductive and capacitive power transfer (IPT and CPT) systems are combined in the circuit design. A detailed analysis of the combined circuit architecture’s working principle clarifies the link between circuit parameters and system power. For inductive and capacitive coupling design, finite‐element analysis is used. The connector plate equivalent circuit model will be created for 100 kW. Design and implementation of the COMPPT system will demonstrate combined inductive and capacitive coupling. Both the inductive and capacitive couplers are 500 mm × 500 mm. Many air gaps are investigated for each coupler, ranging from 150 to 750 mm. Combining IPT and CPT systems yields COMPT’s output power. The prototype will generate 95.46 kW of power with 95.7% efficiency at a 1‐MHz switching frequency and operate better under misalignment than the IPT System. The inductive‐capacitive combination COMPT technology may be suitable for electric battery charging. The special environmental conditions that affect energy transfer, such as heat, rain, snow, and other important major environmental factors that affect energy transfer this research examines several lithium‐ion, lead‐acid, and nickel‐metal hydride batteries, using experiments to analyze the impact of pulse charging and constant current charging on battery performance. A suggested assessment methodology assesses the viability of various charging techniques, including rapid charging for power batteries, based on charging duration, rechargeable capacity, temperature variations while charging, and battery life degradation during cyclic charging.

This paper presents a method for finding the optimum load resistance that maximizes the power efficiency of a tuned-resonant inductive power transfer (IPT) system. In this method, the equivalent AC circuit of the IPT system is transformed to match the topology of a reference ladder prototype. This simplifies the design problem, because the ladder prototype offers intuitive and accurate closed-form approximations for the optimum load resistance and maximum power efficiency. The process is graphical in the sense that manipulations and transformations are made directly on the circuit diagram. Compared to traditional circuit analysis, the ladder prototype approach does not entail complicated systems of equations or matrix manipulations. We show the utility of our method by designing a practical IPT system.

An inductive power transfer (IPT) system usually consists of four parts: an ac–dc power factor correction (PFC) converter, a high-frequency dc–ac inverter, a compensation network comprising a loosely coupled transformer (LCT) and the resonant capacitors, and a rectification output circuit. Due to the relatively large air gap, the magnetic coupling coefficient of the IPT system is significantly lower than that with tightly coupled transformer. As a result, the efficiency of the IPT system is always a main concern for applications with possible gap variation or misalignment condition. To ensure high power transfer efficiency, these IPT systems should have high tolerance for different gap variation and horizontal misalignment conditions. In this paper, the effect of coupling coefficient deviation to compensation network efficiency is analyzed, and design considerations to reduce gap and misalignment effects for the IPT system are proposed. By using finite-element analysis simulation method, the performance of different transmitter and receiver coil dimensions is compared. In order to validate the performance of the proposed design considerations, a 100-W hardware prototype with two sets of LCT is built and the corresponding experiments are carried out. As compared to the symmetrical LCT architecture, the proposed asymmetrical LCT prototype improves the coupling coefficient reduction from 68% to 28% when the gap varies from 6 to 20 mm and from 89% to 31% when the misalignment ranges from 0 to 50 mm. Therefore, the efficiency deviation for the asymmetrical LCT is maintained within 3.5% over the entire tested gap variation and misalignment ranges.

The efficiency of an inductive power transfer (IPT) system is greatly affected by lateral misalignment between the transmitter and receiver coils. This study proposes a hexagonal arrangement of multi-coil configuration IPT system to improve misalignment tolerance while maintaining the transfer efficiency. Key parameters including equivalent self and mutual inductance of various coil connections are examined. The magnetic characteristics including flux distribution and density, and mutual inductance are simulated using COMSOL Multiphysics software package. Experimental results of the proposed multi-coil IPT system are given and compared with the conventional two-coil IPT system. Simulation and experimental results have shown that the proposed multi-transmitter coil configuration can increase misalignment tolerance compared with conventional system.

A dynamic inductive power transfer (IPT) system is a safe and convenient solution to address the issues related to the limited battery capacity and travel distance of electric vehicles (EVs). In recent years, practical aspects of dynamic IPT systems have been investigated to advance various IPT technologies from laboratories to roadways. This paper suggests a configuration to mitigate some of the installation and maintenance concerns of IPT roadways by proposing a switchable inductively coupled connector. Besides providing galvanic isolation, the inductively coupled connector helps maintain a constant and load-independent current in the primary coupler. Moreover, each primary coupler is connected to a common H-bridge through a single DC switch minimizing the number of components required to energize each coupler independently. A mathematical analysis and simulation results have been provided to validate a scaled 3.3kW prototype IPT system employing the proposed configuration.

Modeling position uncertainty of networked autonomous underwater vehicles

In present days, wireless power transfer systems are more popular for its application like wireless charging devices such as cell phones, laptops, electric vehicles, underwater vehicles and medical devices. In an inductively coupled battery charging system, for better power transfer capability, a high efficiency and attaining required power level, compensation is required. This paper focused on designing and analysis of series-series (S-S) compensation topologies to minimize impedance and increase efficiency of Inductive wireless power transfer (IWPT) of electric vehicle (EV) battery charging systems. First, the designing formulas are derived for S-S compensated Inductive power transfer (IPT) system from that bifurcation issue, gain, dual side control and maximum efficiency conditions are achieved. Based on formulas, equivalent electrical circuits parameters are calculated for designing a 1.5 kW output power and the resonance frequency 85 kHz. The results convey that the maximum efficiency and zero power angle (ZPA) are achieved. A simulation system is made in the MATLAB/SIMULINK, from which performance of the system results are verified.

This paper presents a novel approach for simultaneous inductive power transfer (IPT) and communication in one system. The communication part is using the coupled pair of coils of the IPT system as transmitting medium. The proposed architecture is applicable to new and existing IPT systems with operating frequencies above 100 kHz. The challenge is to enable robust and reliable communication in the noisy environment of the power transfer. High reliability is necessary as it shall transmit sensor data error free. For example, this data link can be used for closed-loop operation of the IPT system. Through its fully digital implementation it can be quickly adapted for various other applications. It will be shown that a reliable communication system with joint power transfer and continuous data transmission over the same pair of coupling coils can be realised. Even during high power transfers it features a robust communication channel with outstanding signal to noise ratio and advantageous error vector magnitude. For proof of concept the key performance values of the proposed communication architecture are measured in a 20W IPT system.

The IPT system has been studied for underwater applications such as autonomous underwater vehicles (AUVs) and subsea sensors. However, it rarely comparatively shows the performance of the IPT system in air, freshwater, and seawater. Based on the fore‐mentioned research background, this paper presents a survey of the properties of the IPT system in different mediums. Here, a 100 W power‐level experimental IPT prototype is built and tested. The resonant frequency is set at 300 kHz with a gap range from 10 to 190 mm. The comparison is focused on the efficiency, mutual inductance, coupling coefficient, coil resistance, and quality factor of the IPT system. The IPT system is placed in air, freshwater, and seawater with the same settings. What's more, the magnetic fields of coupling coils in air, freshwater, and seawater are presented in this paper. This paper could be acted as a reference to optimize the IPT system and facilitate future IPT research for underwater applications by analysing the performance of the IPT system in different mediums. The 3D Ansys Maxwell simulation of the IPT system is also given here to study the magnetic fields.

This article studies magnetic forces between transmitter (Tx) and receiver (Rx) coils in an inductive power transfer (IPT) system aiming to use those forces to align the coils and, consequently, improve power transfer. Due to its popularity, the analysis is conducted on a series–series compensated IPT system with planar spiral coils. The proposed method utilizes the bifurcation operation mode of the system and unloaded resonating receiver to maximize attractive force between magnetic couplers. Three-dimensional finite-element method simulations indicate that high-power IPT systems can develop enough attractive force to align coils even under nominal current. Regardless of the coil shape, e.g., spiral or Double-D (DD), the attractive forces tend to align the coils. Hence, a smart charging station can be devised based on self-aligning capability. Furthermore, this article proposes a mechanical structure to facilitate the attractive lateral force for the alignment of high power applications, i.e., wireless fast-charging stations. The forces are analyzed, modeled, and simulated for a 100-kW IPT system with an operating frequency of 20 kHz, while the self-aligning capability is experimentally verified on a downscale 11-kW prototype.