Investigation on full bridge inductively coupled power transfer system

To date inductively coupled power transfer (ICPT) systems have already found many practical applications including battery charging pads. In fact, current charging platforms tend to largely support only one- or two-dimensional planar movement in load. This paper proposes a new concept of extending the aspect ratios of the operating power transfer volume of ICPT systems to support arbitrary three dimensional load movements with respect to the primary coils. This is done by use of modern finite element method analysis software to propose the primary and secondary magnetic structures of such an ICPT system. Firstly, two primary magnetic structures are proposed based on contrasting modes of operation and different field directions. This includes a single-phase and multi-phase current model. Next, a secondary magnetic structure is customized to be compatible with both primary structures. The resulting system is shown to produce a 3D power transfer volume for battery cell charging applications.

Inductive coupled power transfer (ICPT) is an emerging technology that may create new applications for wireless power charging. However, low efficiency is one of the main obstructing factors for promoting this technology. In this paper, a method of resonant frequency optimization based on resonant current calculation at the secondary side of the system is proposed to achieve higher efficiency. In order to research the influences of resonant frequency on system efficiency, the resonant current of the secondary side circuit is calculated, from which the phase shift angle between resonant current and voltage, and the conduction angle of diodes of rectifier can be obtained. Furthermore, a set of simulations are performed to find the optimized resonant frequency relationship between output power and the resonant current amplitude, because the copper loss and core loss of a loosely coupled transformer are all positively associated with resonant current. Finally, a 1.6 kW ICPT system is built and tested to verify the effectiveness of the proposed system. The results prove that the optimized resonant frequency can achieve a system efficiency of 92.5%, when that of a conventional system with a resonant frequency equal to the working frequency is 92%.

In this paper, the generalized model of an inductively coupled power transfer (ICPT) system, which could transfer power efficiently, is built to predict the output power and voltage of the system. The basic concept and structure of ICPT systems is described and a current source push-pull resonant converter for ICPT is presented, and some characteristics of the ICPT system are discussed. The equivalent circuit model is built with mutual inductance concept. Based on this model, equations are obtained to calculate the output power, voltage and resonant frequency, which are verified by experimental results. A brief loss analysis based on Steinmetz equation is given to explain the difference between the predicted and measured values, which are verified by experimental results to make the model more accurate.

As battery-electric vehicle technology advances as a viable alternative to internal combustion engine vehicles, consumer acceptance becomes a critical factor for the future of these vehicles, with driving range and vehicle cost being the preeminent parameters of concern. Unique to battery-electric vehicles is the direct inverse relationship between these parameters. Battery pack costs often account for over one half of the vehicle cost, with the vehicle range determined by the capacity (and thus cost) of the battery pack as well. An increase in vehicle range would therefore result in a significant increase in battery pack cost, and vice versa. In addition, the relationship between overall vehicle mass and total range further inversely couples vehicle cost and range. It is apparent then that a fundamental trade-off will always exist between the two parameters, unless an additional factor is added to decouple the direct relationship between them. This paper presents results of an analytical investigation of the aforementioned relationships unique to battery-electric vehicles and proposes inductively coupled power transfer (ICPT) as a potential solution and decoupling method for the vehicle range –1 vehicle cost relationship. The proposed inductively coupled power transfer (ICPT) system was found to be very effective by allowing the battery pack size to be reduced by up to 48%.

In motor drives supplied through wireless power transfer (WPT) systems, a high frequency inverter and a low frequency one are commonly used in the primary and secondary sides of the system respectively. This arrangement causes reduced reliability and efficiency, and high cost. In this paper, a single inverter in the primary side drives an induction motor without an extra inverter in the secondary side. This is achieved by using a simple AC/AC chopper in the secondary side as a voltage demodulator. The performance of proposed wireless motor drive under a closed-loop V/ f motor control system is verified by simulation using MATLAB/SIMULINK.

In the existing pieces of literature about the three-coil wireless power transfer (WPT) system, a three-coil structure is proposed to increase the efficiency compared to the two-coil WPT system. The cross-coupling among three coils, compensation capacitor of the repeating coil (RPC) and the rectified load are considered incompletely. The circuit model of a three-coil WPT system with rectified load is developed by taking the cross-coupling of all coils and the compensation capacitor of RPC into consideration in this paper. The relationship among system efficiency, compensation level, and rectifier load is deduced. The detailed mathematical analysis and compensation capacitor selection of RPC are investigated to improve the system efficiency. An experimental study demonstrates that the selected compensation capacitor of RPC achieves a higher efficiency than resonant compensation in a three-coil WPT system with different cross-coupling conditions and rectifier load conditions. System efficiency is promoted from 73.9% (resonant compensation capacitor for RPC) to 84.2% (selected compensation capacitor for RPC).

In this article, a self-tuning <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC/LCC</i> wireless power transfer system based on switch-controlled capacitors is proposed to maintain a high power factor on the primary inverter side and fixed output power on the secondary side against self or mutual inductance variation of the magnetic coupler. The PI control on the primary side and the method of gradient descent on the secondary side are proposed based on the proposed normalized mistuned <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC/LCC</i> circuit model. Only two switch-controlled capacitors on each primary and secondary side are used to implement the control scheme without the Wi-Fi communication or parameter identification. A 3 kW experiment setup was built in the lab and two different magnetic shields, namely ferrite and nanocrystalline, were tested on the secondary pad. According to the experiment results, the proposed system is proven to be able to maintain a high power factor (>0.9) and the desired dc output power against 52% mutual inductance variation and 12% self-inductance variation of the secondary pad. The proposed system can be applied as a wireless charger for electric vehicles or a high-power wireless charger test bench.

A study on renewed perspectives of electrified road for wireless power transfer of electric vehicles

This paper presents a new electromagnetic coupling mechanism called pot coil focusing on improving the inductively coupled power transfer (ICPT) system with limited transmission distance and range. Pot coil allows pick-up coil in electromagnetic field to move at larger range and ensure the output power remains unchanged. The contrast for the magnetic flux intensity distribution of pot coil and conventional spiral coil is brought out by using Ansoft Maxwell, a kind of 3D finite element analysis software. The simulation results demonstrate that pot coil increases energy transmission distance and promotes equilibrium of magnetic circuit. Finally, the experiment results prove the validity of the theory analysis.

The output power of a wireless power transfer (WPT) system varies with load and coupling factor of the inductively coupled coils. This paper presents a method to control the output power of primary side LCC and secondary side series tuned WPT system using information of primary side variables. In this approach, a secondary side control system or secondary side sensors are not needed. Detailed mathematical derivations are given to identify and justify the suitable primary side variable that accomplishes the desired purpose without the need of any secondary side communications. Simulation results presented validate the proposed scheme.

Inductively Coupled Power Transfer (ICPT) systems are designed to deliver power efficiently from a stationary primary source to movable secondary loads over air gaps via magnetic coupling. Present vehicle chargers are wired. Corrosion of connectors is a very serious problem. Frequent replacement and maintenance are needed for proper operation. For charging different vehicles with different battery voltages we have to modify the charger to suit the battery voltages that will affect the charger efficiency. This work proposes a design for practical electric vehicle charger suitable for any power vehicles (two wheelers, four wheelers, heavy motor). LCPT vehicle chargers are wireless and there is no contact problems and maintenance so it is a maintenance free charger. LCPT can charge different vehicles with different battery voltages without making any changes in the charger so the efficiency does not affect. Only the number of turns of the pickup coil (secondary coil) has to be adjusted at the time of manufacturing of the vehicles. This same concept can be used in traction system by neglecting the battery.

With the extensive applications of magnetically coupled resonant wireless power transfer (WPT), improving the power transfer efficiency (PTE) of WPT systems is critical. Magnetic metamaterials (MTMs) can effectively improve the PTE. However, currently the design of MTMs is mainly based on microwave or optical theory, and their applicability in low-frequency WPT systems needs to be further explored. In this paper, a fast and effective method for the design and optimization of low-frequency MTM is provided. Firstly, based on circuit theory and mutual inductance calculation, the PTE of WPT systems is concluded in an equation that concerns the position of a 2-D MTM slab and compensation capacitance of MTM unit coils. Two WPT systems with large differences in coil size of the transmitter (Tx) and receiver (Rx) and the same size are considered. In addition, a directly separating variables method is proposed to optimize the MTM slab position and the compensation capacitance of unit coils to maximize PTE when the MTM slab position changes axially between Tx and Rx. It is found that the optimal MTM slab positions for the two systems are remarkably different, and the PTE impressively presents a capacitance splitting phenomenon with the change of compensation capacitance. Finally, two MTM-enhanced WPT systems are established to verify the theoretical calculation. The experiments show that the maximum PTE is significantly increased by 144&#x0025; and 31&#x0025; respectively by adopting optimized compensation capacitance compared with that without MTM for the two systems with different or same transceiver coil size.

This paper presents a power unit for use in the primary side of 3 kW rated inductive charging system. The objective is the design of 3 kW rated primary sides which are compatible to 20 kW rated secondary side receiving units inside electric vehicles. The motivation arises from the consideration that 3 kW and 20 kW charging stations should be kept compatible. Compatible especially in the way that vehicles with 20 kW rated receiving units should be able to use 3 kW charging stations. The basis for the design of the 3 kW system is a series-compensated secondary receiving coil without an additional DC/DC-converter stage between a B4 rectifier and battery with a rated power of 20 kW. The absence of a DC/DC stage allows lower weight and installation space in the vehicle, but the possibility for impedance matching is missing. The system behavior is investigated analytically, so that all currents and voltages, as well as the reactive power in both compensation networks can be calculated depending on the given systems parameter, such as the inductance of the secondary coil, the coupling factor, the operation frequency and the transferred power. It is shown that the operation point with the lowest reactive power, and thus least losses in the coils and compensation capacitors, strongly depends on the design of the receiving unit. Since the receiving unit is designed for a transferred power of 20 kW, an operation with 3 kW will result in a significantly lower efficiency. Therefore a solution is presented, to shift the ideal operation point of the secondary side system from 20 kW to a much lower value. That way, the 3 kW system is able to operate very close to the shifted ideal operation point.

Dynamic load will deviate primary side and secondary side of the system from the resonant state and lead to reducing of the power transmission efficiency rapidly. Detuning of the secondary side circuit due to changes in load inductance or capacitance lead to circuit's resonant frequency changes. Detuning of the primary side circuit due to the secondary side load change, Under the effect of the mutual inductance, resulting in the change of primary side inductance or capacitance, so it makes the primary resonant frequency change. At the same time, theoretical studies shown that there are many resonant frequency in the primary circuit.

Contactless power transfer (CPT) systems with primary series and secondary parallel capacitors (SP topology) are useful for charging electric vehicles. However, SP topology is not suitable for bidirectional power transfer. This paper introduces a novel SPL topology for bidirectional CPT systems that is realized by adding an inductor and an inverter to the SP topology. The 3 kW and 160 mm gap bidirectional test results show that the efficiency of G2V is 92.5%, and the efficiency of V2G is 93.4%, which are approximately equal to the efficiency of the unidirectional SP topology system of 93.1%.