Double-sided LCC Compensation Research Articles

An Integrated Double-Sided LCC Compensation Based Dual-Frequency Compatible WPT System with Constant-Current Output and ZVS Operation

This article presents an integrated double-sided inductance and double capacitances (DS-LCC) compensation based dual-frequency compatible wireless power transfer (WPT) system. A cascaded single-phase multi-frequency inverter (CSMI) is constructed to generate the independent dual-frequency power transfer signals. In order to achieve the load-independent constant-current output (CCO) at two frequencies, an integrated DS-LCC compensated topology is reconstructed. By configuring the frequency-selective resonating compensation (FSRC) network in the primary side, the power transfer signals at two frequencies can be superimposed into a single transmitting coil, reducing the cost and volume of the system. Furthermore, to implement zero-voltage switching (ZVS) of the CSMI throughout the entire power range, a general parameter design method of the proposed system is also introduced. A 1.5-kW experimental prototype is built to validate the practicability of the presented dual-frequency compatible WPT System. The system can supply power to different loads at two frequencies simultaneously with CCO and ZVS properties. The peak efficiency reaches 91.75% at a 1.2-kW output power.

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

Purpose This 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/approach The 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. Findings In 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/value In 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.

Constant-Voltage and Constant-Current Controls of the Inductive Power Transfer System for Electric Vehicles Based on Full-Bridge Synchronous Rectification

When an inductive power transfer (IPT) system conducts wireless charging for electric cars, the coupling coefficient between the coils is easily affected by fluctuations in the external environment. With frequent changes in the battery load impedance, it is difficult for the IPT system to achieve constant-voltage and constant-current (CVCC) controls. A CVCC control method is proposed for the IPT system that has a double-sided LCC compensation structure based on full-bridge synchronous rectification. The proposed method achieved good dynamic stability and was able to effectively switch between the output current and voltage of the system by adjusting only the duty cycle of the switch on the secondary side of the rectification bridge. As a result, the system efficiency was improved. The output characteristics of the double-sided LCC compensation structure was derived and the conduction condition with zero voltage was analyzed by using four switches through two conduction time series of the rectifier circuit. Then, the output voltage of the synchronized rectifier was derived. The hardware implementation of the full-bridge controllable rectifier was described in detail. Finally, a MATLAB/Simulink 2018a simulation model was developed and applied to an 11 kW prototype to analyze and validate the design. The results showed that the designed system had good CVCC output characteristics and could maintain constant output under certain coupling offsets. Compared with semi synchronous rectification methods, the proposed method had a higher efficiency, which was 95.6% at the rated load.

Magnetic Field Mitigation in Dynamic Wireless Power Transfer Systems by Double Sided LCC Compensation

Magnetic Field Mitigation in Dynamic Wireless Power Transfer Systems by Double Sided LCC Compensation

Double-Sided LCC Compensation Network and Its Tuning Method for Wireless Power Transfer for EV charging

Abstract: This research explores a double-sided LCC compensation network's utilization in an inductively coupled wireless power transfer (WPT) system for electric car charging applications and its wireless power transfer tuning procedure (WPT). A wireless power transmission system is offered with a double-sided LCC compensating network. The compensation circuit is crucial because it may be used to adjust the system's resonance frequency, lower reactive power in the power electronics converter, and boost the efficiency and capability of transferred power. The proposed architecture and its tuning technique allow the system to operate at a constant switching frequency since the resonant frequency is unaffected by the coupling coefficient between the two coils and is also independent of the load status. Also, it has been discovered that the corrected receiving coil inductance is a useful tuning parameter for ensuring the primary side zero voltage switching (ZVS) operation.

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 Multirelay Wireless Power Transfer System With Double-Sided LCC Compensation Network for Online Monitoring Equipment

A multirelay wireless power transfer (WPT) system with the double-sided inductor-capacitor-capacitor (LCC) compensation network for the online monitoring equipment on the high-voltage transmission line is proposed. Constant-voltage (CV) or constant-current (CC) output characteristics is achieved. The proposed topology does not use ferrite materials, and the LCC compensation networks are only utilized at the transmitter and the receiver. Each relay coil is only connected in series with one compensation capacitor. Three working modes are proposed according to the resonance conditions of Tx compensation network, Rx compensation network, and compensating capacitances of relay coils. CC and CV output characteristics in each mode are analyzed and compared by simulation in terms of system output attenuation with load changes and frequency sensitivity. The parameter design process is given. A six-coil experimental prototype is built to validate the correctness and feasibility of the theoretical analysis.

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.

Coils and Compensation Circuit Design Reduces Power Pulsation and Optimizes Transfer Efficiency in the Dynamic Wireless Charging System for Electric Vehicles

This paper presents a method of designing coils and compensation circuits to reduce output power pulsation, optimize transfer efficiency for electric vehicle dynamic wireless charging systems. The transmission lane is modularly designed. Each module has three short-track transmitter coils that are placed closely together along the moving track of the receiver and connected to a single inverter. The designs of the transmitter and receiver coils are analyzed by finite element analysis to reduce the variation of the coupling coefficient. Then the coupling coefficient is analyzed to identify the characteristics of the dynamic wireless charging lane. The double-sided LCC compensation circuit is designed according to the optimum load value to obtain maximum transfer efficiency. The SIC devices are used to improve the efficiency of the 85 kHz resonant inverter. A 1.5 kW dynamic charging system prototype is constructed. Experimental results show that the average system efficiency of 89.5% is obtained, and the output power pulse rate is ±9.5% in the dynamic charging process.

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.

A multi-objective-based parametric design method for WPT systems with double-sided LCC compensation network

A multi-objective-based parametric design method for WPT systems with double-sided LCC compensation network

Sensitivity analysis of wireless power transmission

The compensation networks that realize constant current/constant voltage in the wireless power transfer are high-order resonant networks, and there are multiple resonance frequency points to achieve load-independent constant current/constant voltage output. However, the output characteristics of wireless power transfer based on high-order resonant networks are extremely susceptible to the effects of resonant network parameters. Therefore, the analysis of the resonance point of the wireless power transfer is helpful to select the appropriate resonance frequency point and achieve stable output. This article analyzes the resonance conditions of the double-sided LCC compensation network and then gives a parameter design method to achieve load-independent CC/CV output characteristics under ZPA conditions. The effects of the resonant network’s primary/secondary series compensation capacitor parameters on the resonance point and output characteristics of the wireless power transfer system are analyzed. Finally, the correctness of the parameter design of the resonance network and the accuracy of the theoretical analysis are verified.

Modelling and improvement of oscillation problem in a double-sided LCC compensation network for electric vehicle wireless power transfer

The double-sided LCC compensation network shows high performances in electric vehicle wireless power transfer (EV WPT) applications owing to its constant output current, low voltage stress and other good characteristics. In order to achieve full power and high-efficiency energy transmission within the specified range of coupling and battery voltage, a controlled rectification scheme became a trend in EVs manufacturers and standards. However, a current oscillation problem emerges in a double-sided LCC system when employing a circulating current control method for the controlled rectifier. This paper proposes a mechanism to understand the oscillation phenomenon caused by the inter-harmonics and a positive feedback scheme. The amplification effect of circuit admittance is believed to be the key cause of the inter-harmonics. Therefore, an oscillation improvement is proposed in this paper by adding an inductor and a capacitor to the secondary LCC network, minimizing the admittance amplification effect. A comprehensive simulation and experimental validations under different rectifier duty cycles, coupling positions and load resistances, confirmed the effectiveness of the proposed method. Interestingly, the optimized system expanded the safe operating region and reduced the oscillating operating points from 18 to 8 out of the 27 possible conditions. • This paper clearly reveals the cause of current oscillation in an EV-WPT system. • Interharmonics were grabbed and analyzed in an LCC-LCC circuit for the first time. • Additional LC is first introduced into the system, suppressing oscillation greatly.

Sensitivity Analysis and Parameter Optimization of Inductive Power Transfer

There are several resonance frequencies points in the high-order resonant network to realize constant current/constant voltage output, but the disturbance of the resonant network parameters will affect the output characteristics of the system. Therefore, selecting the appropriate resonant frequency is necessary to achieve stable output characteristics of wireless power transmission. This paper analyzes the influence of sensitivity of the double-sided LCC compensation network parameters on resonance point and output characteristics. Moreover, this paper proposes a design method to realize load-independent constant current and constant voltage output under two ZPA frequencies, and the resonance parameters are optimized for the realization of ZVS. Under constant current and constant voltage output resonant points, the transmission efficiency of the double-sided LCC IPT system reaches 88.9% and 88.5%, respectively.

New Integrated Tripolar Pad Using Double-Sided LCC Compensation for Wireless Power Transfer

In this paper, a new integrated tripolar pad using double-sided LCC compensation is proposed and then based on the circuit characteristic, which is analyzed in detail, the introduced system is simulated and investigated. The tripolar pad utilizes three decoupled coils and shows a promising tolerance against rotational displacements and consequently provides a convenience for the user to park the vehicle. Due to compensator coils, the double-sided method of compensation is more massive than the other methods. Here, the authors offer a scheme to make the wireless power transfer system more compact by integrating the compensation inductors with the main couplers. In order to locate the best place to embed the compensator coils, the flux density between the couplers is analyzed. Additionally, it is shown that since the pad is composed of multiple coils, there are some undesired mutual inductances that should be designed for the least possible values. The behaviors of the proposed pad are analyzed and thoroughly discussed based on four different displacements. In order to validate the theoretical results, a 500 W wireless power transfer is fabricated and tested at 85 kHz for the proposed double-sided LCC compensation. The simulation and experimental results show the performance of the proposed structure.

Constant-Voltage and Constant-Current Output Using P-CLCL Compensation Circuit for Single-Switch Inductive Power Transfer

The characteristic of constant-current output (CCO) and constant-voltage output (CVO) on full-bridge topology can be realized by using a traditional double-sided LCC compensation network. The switching from CCO mode to CVO mode can be realized by switching the operating frequency in CCO mode ( f CC) to the operating frequency in CVO mode ( f CV). However, the operating frequency is generally high, the value of L P, L S, and M in the loosely coupled transformer will have a significant influence on the operating frequency of the circuit, which makes it difficult to carry out a long-distance transmission at a lower operating frequency, otherwise, the self-inductance of the coils will be high, even though it is used to transfer low-power. Therefore, in this article, a novel P- CLCL compensation topology based on a single-switching circuit (SSC) is proposed to address these problems. The switching from CCO to CVO can also be realized by changing the operating frequency from f CC to f CV, and a relatively lower operating frequency and a relatively farther transmission distance than full-bridge topology are realized. The calculation method of circuit parameters, implementation of zero-voltage-switching, sensitivity analysis, and load-independent output are discussed. Finally, the simulation and experiment are carried out to verify the correctness of the analysis.

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.