Double-sided LCC Compensation Topology Research Articles

The power control and efficiency optimization strategy of dynamic wireless charging system for multiple electric vehicles

PurposeThis study aims to solve the problem that both the speed and the required driving power of electric vehicles (EVs) will change during the dynamic wireless charging (DWC) process, making it difficult to charge EVs with a constant power considering the overall efficiency of DWC system, the numbers of EVs and the power supply capacity. Therefore, this paper proposes the power control and efficiency optimization strategies for multiple EVs.Design/methodology/approachThe wireless power charging system for multiple loads with a structure of double-sided LCC compensation topology is established. The expressions of optimal transmission efficiency and optimal equivalent impedance are derived. Taking the Tesla Model 3 as an example, a method to determine the number of EVs allowed by one transmitter coil and the overall charging power is proposed considering EV speed, power supply capacity, safe braking distance and overall efficiency. Then, the power control strategy, which can adapt to the changes of EV speed and the efficiency optimization strategy under different numbers of EVs are proposed.FindingsIn this paper, a method to determine the numbers of EVs allowed by one transmitter coil and the overall charging power is proposed considering EVs speed, power supply capacity, safe braking distance and overall efficiency. The accuracy of the charging power is good enough and the overall efficiency reaches a maximum of 91.79% when the load resistance changes from 5Ω to 20Ω.Originality/valueIn this paper, the power control and efficiency optimization strategy of DWC system for multiple EVs are proposed. Specifically, a method of designing the number of EVs and charging power allowed by one transmitter coil considering the factors of EV speed, power supply capacity, safe braking distance and overall efficiency is designed. The overall efficiency of the experiment reaches a maximum of 91.79% after adopting the optimization strategy.

Design of Inductive Power Transfer Charging System with Weak Coupling Coefficient

Inductive power transfer (IPT) technology is used in various applications owing to its safety features, robust environmental adaptability, and convenience. In some special applications, the charging pads are required to be as compact as possible to accommodate practical spatial requirements, and even size requirements dictate that the diameter of the charging pad matches the air gap. However, such requirements bring about a decrease in the transmission efficiency, power, and tolerance to misalignment of the system. In this paper, by comparing a double-sided inductor–capacitor–capacitor (LCC), double-sided inductor–capacitor–inductor (LCL), series–series (SS), and inductor–capacitor–capacitor–series (LCC-S) compensation topologies in IPT systems, we identified a double-sided LCC compensation topology that is suitable for weak coupling coefficients. Furthermore, this study modeled and simulated the typical parameters of coreless coils in circular power pads, such as the number of coil layers, turns, wire diameter, and wire spacing, to enhance the mutual inductance of the magnetic coupler during misalignment and long-distance transmission. A wireless charging system with 640 W output power was built, and the experimental results show that a maximum dc-dc efficiency of over 86% is achieved across a 200 mm air gap when the circular power pad with a diameter of 200 mm is well aligned. The experimental results show that using a suitable compensation topology and optimizing the charging pad parameters enables efficient IPT system operation when the coupling coefficient is 0.02.

Inductive Wireless Power Transfer Systems for Low-Voltage and High-Current Electric Mobility Applications: Review and Design Example

Along with the technology boom regarding electric vehicles such as lithium-ion batteries, electric motors, and plug-in charging systems, inductive power transfer (IPT) systems have gained more attention from academia and industry in recent years. This article presents a review of the state-of-the-art development of IPT systems, with a focus on low-voltage and high-current electric mobility applications. The fundamental theory, compensation topologies, magnetic coupling structures, power electronic architectures, and control methods are discussed and further considered in terms of several aspects, including efficiency, coil misalignments, and output regulation capability. A 3D finite element software (Ansys Maxwell) is used to validate the magnetic coupler performance. In addition, a 2.5 kW 400/48 V IPT system is proposed to address the challenges of low-voltage and high-current wireless charging systems. In this design, an asymmetrical double-sided LCC compensation topology and a passive current balancing method are proposed to provide excellent current sharing capability in the dual-receiver structures under both resonant component mismatch and misalignment conditions. Finally, the performance of the proposed method is verified by MATLAB/PSIM simulation results.

A Unique Design Approach of Double-Sided LCC Compensated IPT System for Misalignment-Tolerant Characteristic

For double-sided LCC compensation topology, it is not easy to maintain the output current and output voltage constant over the variation of coupling coefficient and load. Consequently, in this article, a unique design approach is presented. With the presented method, whether during a constant current output procedure or constant voltage output procedure, the resonant frequency maintains constant and cannot be affected by the coupling coefficient and load condition. In addition, the transmission gain is kept constant in different misalignment by the phase shift modulation. Zero voltage switching with the minimum reactive current can be implemented by the switch-controlled capacitor (SCC) regardless of the coupling coefficient and owing to the constant phasor of the current flowing the SCC, the control system of SCC is greatly simplified. Finally, a 60 W prototype is designed to verify the validity of the theoretical analysis. From the results of the experiment, when the coupling coefficient range is between 0.13 and 0.2, the fluctuation factors of output current and output voltage are only 0.5% and 1.0%, respectively.

Analyses of charging power and performance in electric vehicles using Fuzzy Type-II approach

Nowadays, there is a need for charging electric vehicles (EVs) wirelessly, since it provides a more convenient, reliable, and safer charging option for the EV customers. A wireless charging system using a double-sided LCC compensation topology is proven to be highly efficient. In this paper, considering the importance of wireless charging of electric vehicles, using a circuit equivalent to the wireless power Transfer (WPT) system, the behavior of electric vehicles in the power grid only in technical analysis is investigated. Accordingly, two different scenarios have been used in modeling and simulation. In the first scenario, the charge of electric vehicles was controlled using an [Formula: see text] controller to stabilize the charging frequency. The model predictive control (MPC) controller was used to identify the optimum power factor for electric vehicles and determine the optimal power values and efficiency. In the second scenario, a two-way AC-DC converter was designed using a Fuzzy type-II controller under uncertainty to provide precise control over the vehicle charge exchange in terms of voltage, current, and stage of control (SOC). So, type-II fuzzy controller is used to control the process of charging and discharging vehicles. The results show that the final efficiency is 0.98, and the power will be 1480 W.

Wireless Charging Concave Coil Design for UAVs

This paper proposes an orthogonal concave coupling mechanism based on wireless charging for unmanned aerial vehicles (UAVs); the original edge adopts a concave transmitting coil. So as not to occupy the gimbal position at the receiving end, the receiving coil is installed on the landing gear of the UAV perpendicular to the transmitting coil to form an orthogonal coupling magnetic field. This study conducted a finite element simulation of the coupling mechanism using Ansys Maxwell to test the mechanism’s coupling capability and anti-offset performance. The spatial distribution of the system’s magnetic field was constrained, and the magnetic flux leakage of the system was reduced by optimizing the transmitter structure. The system employed a double-sided LCC compensation topology network and used wireless communication to achieve constant voltage/constant current closed-loop control. Finally, the experimental platform was built, and the results show that the system output power was able to reach 960 W with 85.7% efficiency, and could realize the closed-loop control of charging with 48 V constant voltage and 20 A constant current. The system has the advantages of being small in size, lightweight (290 g) and easy to install, and the receiver device has strong resistance to offset.

Integrated Double-Sided LCC Compensation Topology for an Electric Vehicle Wireless Charging System

Wireless power transfer (WPT) is a necessary solution for removal of high power cables (direct electrical contact) that provides safer charging solution, waterproof and dust-proof capability, sterile environment application, etc. The double-sided LCC (DSLCC) compensation topology offers a high efficient Electric Vehicle (EV) wireless charging operations. Due to the number of elements utilized in DSLCC, it requires large space. In order to reduce the space and cost, class-E converters are utilized to design a low power wireless charging system. Class E converters have such benefits as less components, high reliability, and soft switching. Thus, to have a compact efficient Wireless Charging System (WCS) by reducing the space occupancy of DSLCC, an integrated DSLCC based wireless charging system for low power applications is proposed. This method was realized by utilizing the MATLAB simulation and achieved more than 90% of efficiency for 1 kW system with 85 kHz frequency.

The Charging Control and Efficiency Optimization Strategy for WPT System Based on Secondary Side Controllable Rectifier

The equivalent resistance of the battery will change during charging in practical applications, so it is difficult to design a wireless power transfer (WPT) system with accurate constant current (CC) and constant voltage (CV) output characteristics. In addition, the WPT system efficiency is also affected by the change of equivalent resistance. Therefore, this paper studies the charging control and efficiency optimization strategy for the WPT system with dynamic loads. The WPT system with a structure of double-sided LCC compensation topology and containing controllable rectifier circuit at the secondary side is established, and the working process of full-bridge controllable rectifier circuit is analyzed. Then the output characteristics of the WPT system are analyzed. The expressions of the optimal transmission efficiency and the optimal equivalent impedance of the full-bridge rectifier are derived. The relationships between the equivalent impedance of the capacitor-filtered full-bridge controllable rectifier circuit and the phase shift angle, the charging current and the phase shift angle are also obtained. In this paper, the CC and CV charging strategies based on phase shift control of controllable rectifier circuit and efficiency optimization strategy based on dynamic equivalent impedance matching are proposed, which can improve the WPT system transmission efficiency while realizing CC and CV charging. Finally, the effectiveness of the proposed control strategy is verified by simulation and experiment. The WPT system realizes CC charging mode and CV charging mode in turn when the load resistance changes from $5~\Omega $ to $30~\Omega $ , and the overall efficiency is up to 90.71% at the transmission distance of 15cm.

Modeling and Control of Double-Sided LCC Compensation Topology with Semi-Bridgeless Active Rectifier for Inductive Power Transfer System

This paper proposes the modeling and design of a controller for an inductive power transfer (IPT) system with a semi-bridgeless active rectifier (S-BAR). This system consists of a double-sided Inductor-Capacitor-Capacitor (LCC) compensation network and an S-BAR, and maintains a constant output voltage under load variation through the operation of the rectifier switches. Accurate modeling is essential to design a controller with good performance. However, most of the researches on S-BAR have focused on the control scheme for the rectifier switches and steady-state analysis. Therefore, modeling based on the extended describing function is proposed for an accurate dynamic analysis of an IPT system with an S-BAR. Detailed mathematical analyses of the large-signal model, steady-state operating solution, and small-signal model are provided. Nonlinear large-signal equivalent circuit and linearized small-signal equivalent circuit are presented for intuitive understanding. In addition, worst case condition is selected under various load conditions and a controller design process is provided. To demonstrate the effectiveness of the proposed modeling, experimental results using a 100 W prototype are presented.

Implementation of the Constant Current and Constant Voltage Charge of Inductive Power Transfer Systems With the Double-Sided LCC Compensation Topology for Electric Vehicle Battery Charge Applications

When compared to plugged-in chargers, inductive power transfer (IPT) methods for electric vehicle (EV) battery chargers have several benefits, such as greater convenience and higher safety. In an EV, the battery is an indispensable component, and lithium-ion batteries are identified as the most competitive candidate to be used in EVs due to their high power density, long cycle life, and better safety. In order to charge lithium-ion batteries, constant current/constant voltage (CC/CV) is often adopted for high-efficiency charging and sufficient protection. However, it is not easy to design an IPT battery charger that can charge the batteries with a CC/CV charge due to the wide range of load variations, because it requires a wide range of variation in its operating frequency, duty, or phase-shift. Furthermore, zero phase angle (ZPA) condition for the primary inverter cannot be achieved over the entire charge process without the help of additional switches and related driver circuits to transform the topology. This paper proposes a design method that makes it possible to implement the CC/CV mode charge with minimum frequency variation during the entire charge process by using the load-independent characteristics of an IPT system under the ZPA condition without any additional switches. A theoretical analysis is presented to provide the appropriate procedure to design the double-sided LCC compensation tank which can achieve both CC and CV mode charge under ZPA condition at two different resonant frequencies. As a consequence, the proposed method is advantageous in that the efficiency of compensation tank is very high due to achieving the perfect resonant operation during the entire charge process. A 6.6-kW prototype charger has been implemented to demonstrate the feasibility and validity of the proposed method. A maximum efficiency of 96.1% has been achieved with a 200-mm airgap at 6.6 kW during the CC mode charge.

A Novel Integration Method for a Bipolar Receiver Pad Using <italic>LCC</italic> Compensation Topology for Wireless Power Transfer

A bipolar pad (BPP) is the newcomer magnetic structure of inductive power transfer (IPT). This pad has a better performance in the lateral misalignment compared to the other single-sided pads such as double-D pad (DDP). Also, it has less amount of copper compared to the double-D quadrature pad. Double-sided LCC compensation topology is an efficient way to compensate the IPT contrasted with the other compensation types. However, due to the utilization of compensation inductances, the system volume is larger than the other formats. Thus, to have a compact compensation method, these inductances are integrated into the main coils, considering the effects of the coils on each other. In this paper, for the first time, compensation of a BPP with novel integrated inductances of the LCC compensation method is introduced. This integration is analyzed and its effects are optimized to an insignificant rate with three-dimensional finite element analysis tool ANSYS MAXWELL. Also, the primary compensation is changed to a series method to decrease the number of compensation components and assess the effects of this variation on the circuit. Finally, DDP transmitter and BPP receiver with integrated double-sided LCC compensation topology are prototyped to verify the analytical results.

A Rotation-Resilient Wireless Charging System for Lightweight Autonomous Underwater Vehicles

This paper presents a rotation-resilient wireless charging system with a reversely wound receiver that supports efficient charging for lightweight autonomous underwater vehicles. By employing a two-part reversely wound receiver coil structure, the total mutual inductance of the proposed coil structure remains relatively constant when rotational misalignment between the transmitter and receiver coils occurs, thereby ensuring wireless charging power is nearly continuous during rotational misalignment. Finite element analysis was performed with ANSYS Maxwell to verify the proposed coil structure. Double-sided LCC compensation topology was applied and circuit analysis was conducted via a mesh current method. A prototype of the rotation-resilient wireless charging system with the proposed coil structure was built and tested. Experimental results are well-matched to simulations, demonstrating that the system can deliver 745 Watts at a dc-dc efficiency of 86.19% when the system is fully aligned, and efficient under worst-case rotational misalignment.

S/CLC Compensation Topology Analysis and Circular Coil Design for Wireless Power Transfer

Wireless power transfer (WPT) has drawn a lot of attention due to its inherent advantages and great potential in various applications. This paper proposes a novel compensation topology composed of one compensation inductor and three compensation capacitors. The newly proposed compensation topology, named as S/CLC, provides the advantages of constant voltage output and easy achievement of zero phase angle and zero voltage switching. It is also free from the constraints imposed by the loosely coupled transformer (LCT) parameters. All the above-mentioned merits are theoretically analyzed and verified by simulation and experiment. Compared to double-sided LCC compensation topology, S/CLC compensation topology needs less compensation components, meaning lower cost, smaller size, higher power density, and greater potential in practical applications. The optimization of a circular pad is conducted as well since the properties of the LCT have a significant impact on the performance of a WPT system. A circular pad is manufactured in terms of the conclusions obtained from the optimization. The coupling coefficient Circular pad design, constant voltage output (CVO), wireless power transfer (WPT), zero phase angle (ZPA), zero voltage switching (ZVS).of the circular pad is quite appealing, demonstrating the validity of the optimization.

A New Integration Method for an Electric Vehicle Wireless Charging System Using LCC Compensation Topology: Analysis and Design

There is a need for charging electric vehicles (EVs) wirelessly since it provides a more convenient, reliable, and safer charging option for EV customers. A wireless charging system using a double-sided LCC compensation topology is proven to be highly efficient; however, the large volume induced by the compensation coils is a drawback. In order to make the system more compact, this paper proposes a new method to integrate the compensated coil into the main coil structure. With the proposed method, not only is the system more compact, but also the extra coupling effects resulting from the integration are either eliminated or minimized to a negligible level. Three-dimensional finite-element analysis tool ANSYS MAXWELL is employed to optimize the integrated coils, and detailed design procedures on improving system efficiency are also given in this paper. The wireless charging system with the proposed integration method is able to transfer 3.0 kW with 95.5% efficiency (overall dc to dc) at an air gap of 150 mm.

Comparison Study on SS and Double-Sided LCC Compensation Topologies for EV/PHEV Wireless Chargers

This paper compares the characteristics of the series–series and double-sided Inductor-Capacitor-Capacitor (LCC) compensation topologies for electric vehicle (EV) wireless chargers. Both the well-tuned and mistuned topologies for the two compensation methods are analyzed in detail. The mistuning considered here is mainly caused by the variations of the relative position between the primary and secondary sides. The output power displacements caused by mistuning are compared for both compensation topologies, as well as the impacts of the load variations on the performances of the mistuned topologies. The voltage and current stresses on components are also studied. The comparative result shows that the double-sided LCC compensation topology is less sensitive to mistuning. A double-sided LCC-compensated EV wireless charger system with up to 7.7-kW output power is built to verify the analysis results. A peak efficiency of 96% from dc power source to battery load is achieved.

Compact and Efficient Bipolar Coupler for Wireless Power Chargers: Design and Analysis

Compactness and efficiency are the two basic considerations of the wireless battery chargers for electric vehicles (EVs) and plug-in hybrid EVs. The double-sided LCC compensation topology for wireless power transfer (WPT) has been proved to be one of the efficient solutions lately. However, with the increase of the numbers of compensation components, the volume of the system may become larger, which makes it less attractive. To improve the compactness, a bipolar coupler structure with a compensation-integrated feature is proposed. The inductors of the LCC compensation networks are designed as planar-type and attached to the power-transferring main coils. Extra space and magnetic cores for the compensated inductors outside of the coupler are saved. The cost is that extra couplings between the compensated coils (inductors) and the main coils are induced. To validate the feasibility, the proposed coupler is modeled and investigated by 3-D finite-element analysis tool first. The positioning of the compensated coils, the range of the extra couplings, and the tolerance to misalignment are studied. This is followed by the circuit modeling and characteristic analysis of the proposed WPT topology based on the fundamental harmonic approximation. At last, a 600 mm × 600 mm with a nominal 150-mm-gap wireless charger prototype, operated at a resonant frequency of 95 kHz and a rated power of 5.6 kW has been built and tested. A peak efficiency of 95.36% from a dc power source to the battery load is achieved at rated operation condition.