LCC Compensation Research Articles

Small-Signal Model of an Inductive Power Transfer System Using LCC–LCC Compensation

The LCC–LCC compensation is widely used in the inductive power transfer systems. However, there is no simple and accurate small-signal equivalent circuit model for this resonant converter. Based on the extended describing function method, this article proposed a full-order (17th-order) equivalent circuit model to accurately predict the small-signal behaviors. For simplification, the full-order model is gradually simplified to a ninth-order model and finally to a fifth-order model. The input to output transfer function are analytically derived for the first time. Both simulation and experimental results are presented to justify the effectiveness of the model, and the model is accurate up to one-fifth of the switching frequency.

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.

A Strong Misalignment Tolerance Dual-Channel Coupler for Wireless Power Transfer System

In order to improve the transmission performance of the wireless power transfer (WPT) system under misaligned conditions, a novel type of dual-channel DDP type transmitter coil is proposed inspired by the traditional LCC compensation circuit and DD coil. The proposed DDP coil is a combination of DD coil and P coil, which jointly establishes the main flux for magnetic coupling and power transmission. At the same time, the P coil also acts as the resonant inductor of the LCC compensation circuit of the WPT system. When the system parameters are well designed, we can achieve relatively more stable output current during the offset of the primary and secondary sides. Experimental results indicate that when the misalignment varies from 0 m to 0.15 m, the output current variation range is 2.92 A to 3.68 A, the current fluctuation rate is 11.5%. Compared with the traditional DD coil with LCC topology, the proposed dual-channel transmitter DDP coil shows better performance in misalignment tolerance.

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.

Wireless charging system for electric bicycle application

This paper presents a design of the wireless charging system for e-byke applications. The double-side LCC compensation circuit is used to achieve high efficiency and reduce the volt-ampere rating. A new constant current/voltage (CC/CV) charging control method at the transmitter side is proposed to avoid dual side wireless communication. This paper also presents a simple method of estimating both the coupling coefficient and load impedance only from the transmitter side. A wireless charging system of 2.5kW is built. Error in the CC/CV charging mode is 3.3% and 1.12%, respectively. System efficiency reaches 92.1% in CC charging mode.

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.

Simultaneous Wireless Power Transfer and Full-Duplex Communication With a Single Coupling Interface

A method to achieve simultaneous wireless power transfer and full-duplex communication with a pair of coupling coils is proposed in this article. A double-side LCC compensation topology for power transfer is adopted, while the data transfer channel is constituted by a four resonance dual-rejection structure. In the process of power transfer and full-duplex communication, from the view of data transmitting and receiving, the data transmitting/receiving circuits on one side can not only transmit/receive the desired data carriers but also block the interference data carriers, and from the view of power transfer, the rated power transfer can be realized with little influence. Moreover, the parameter design method of the proposed system is given. Besides, the interference between the power wave and data carriers and the crosstalk between the data carriers are analyzed. Finally, an experimental prototype is built, which achieves an output power of 600 W and a data transmission rate of 80 kbps.

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.

Wireless power transfer system design for electric vehicle dynamic charging application

This paper proposes and demonstrates a wireless power transfer system design for electric vehicle dynamic charging applications. The dynamic wireless charging (DWC) lane is designed for modularly. Each module has three shorttrack transmitter coils that are placed closely together and connected to a single inverter to reduce the number of inverters. The magnetic coupler design is analyzed and optimized by finite element analysis (FEA) to reduce the output power variation during dynamic charging. The LCC compensation circuit is designed according to the optimal load value to obtain maximum efficiency. The SIC devices are used to improve the efficiency of the high-frequency resonant inverter. A 1.5 kW dynamic charging system prototype is constructed. Experimental results show that the output power variation of 9.5% and the average efficiency of 89.5% are obtained in the moving condition.

A Design Method to Implement ZVS for Electric Vehicle Wireless Charging System With Double-Side LCC Compensation

In this article, the zero voltage switching (ZVS) of the inverter in the electric vehicle wireless charging system is realized through the parameter optimization design of compensation components, which is conducive to the high efficient operation of the system. The effects of the parameter adjustment of each compensation component on the input impedance angle and output current of the double-side LCC compensation topology were analyzed under the conditions of different output voltages and coupling coefficients, which provides a basis for the component optimization design of the inverter ZVS realization. The quantitative relationship between the optimized component parameter and the soft switching implementation conditions was analyzed. Then, a specific parameter design method was proposed, according to the results analyzed earlier. At last, the effectiveness of the proposed method was verified by a 3.3-kW wireless charging system prototype. Experimental results show that the optimized system is always able to achieve soft switching, the system efficiency is up to 95.2% at the rated power, and it is higher than 93% even under the condition where the coupling coefficient and output voltage are both reduced by half.

Monte-Carlo Analysis of the Influence of the Electrical Component Tolerances on the Behavior of Series-Series- and LCC-Compensated IPT Systems

The use of compensation networks increases the power transfer capability of inductive power transfer (IPT) systems in the battery charging process of electric vehicles (EVs). Among the proposed topologies, the Series-Series (SS) and the LCC networks are currently in widespread use in wireless battery chargers based on IPT systems. This paper focuses on the study of the behavior of both compensation topologies when they are detuned due to the tolerances of their components. To compare their performances, a Monte-Carlo analysis was carried out using Simulink and MATLAB. The tolerance values, assigned independently to each component, fall within a [ − 20 , 20] % range according to a normal distribution. Histograms and scatter plots were used for comparison purposes. The analysis reveals that the LCC network allows a tighter control over the currents that flow through the magnetic coupler coils. Moreover, it was found that the increments in those currents can be limited to some extent by selecting capacitors featuring low tolerance values in the LCC compensation. Nevertheless, the SS network remains an appropriate choice if size and cost are essential constraints in a given design.

Compensation Parameters Optimization of Wireless Power Transfer for Electric Vehicles

For wireless charging of electric vehicles (EVs), increasing the output power level is particularly important. In this paper, the purpose of improving the output power while maintaining optimal transmission efficiency is achieved by optimizing the parameters of the compensation topology under the premise that the coupled coils of the system does not need to be redesigned. The series-series (SS) and hybrid-series-parallel (LCC, composed by an inductor and two capacitors) compensation topology are studied. The influence factors of load resistance to achieve optimal efficiency, the influence of LCC compensation parameters on the power output level, and the influence of parameter changes on system safety are analyzed. Theorical results show that by rationally designing the LCC compensation parameters, larger output power and optimal transfer efficiency can be achieved under different load resistance by adjusting the inductances of the primary and secondary compensation circuits. The output power of the optimized system with adjusted LCC compensation topology is increased by 64.2% with 89.8% transfer efficiency under 50 ohms load in experiments. The correctness and feasibility of this parameter design method are verified by both theorical and experimental results.

An Efficiency Optimization-Based Asymmetric Tuning Method of Double-Sided LCC Compensated WPT System for Electric Vehicles

Compensation topologies play an essential role in wireless power transfer systems for electric vehicles. Specifically, the double-sided LCC compensated (DS- LCC ) topology has been widely adopted, owing to its inherent advantages, such as load-independent constant current (CC) output, low sensitivity to load variation, and high freedom in parameter design. However, large resonant devices in the DS- LCC topology lower the system efficiency and increase the complexity of optimal parameter tuning. Therefore, in this article, the parameters of the DS- LCC compensation topology are reconfigured by adjusting the ratios of its two compensation inductances without changing the specified system-level parameters, such as the loosely coupled transformer, operating frequency, and specified CC outputs. The system performance under each case is analyzed and compared in detail, based on which, an asymmetric parameter-design method is proposed to optimize the system efficiency. To verify the reasonability of the proposed tuning method, a 6.6-kW experimental prototype is configured, and comparative experiments are conducted. The experimental results indicate that, compared with the conventional method, the proposed parameter-tuning method improves the system efficiency under overall load conditions, especially under light loads.

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.

Null-Coupled Magnetic Integration for EV Wireless Power Transfer System

Wireless power transfer (WPT) for electrical vehicles (EV) has become increasingly popular because it is safe and convenient. Double-sided inductor–capacitor–capacitor ( LCC ) compensation network is suitable for WPT systems. A more compact structure can be realized by integrating the magnetic components in the LCC compensation network into the power-transferring coils. Based on the earlier study that double D (DD) coil and unipolar coil couple zero power, two types of null-coupled magnetic integrated structures are proposed. A feasible structure is chosen by analyzing the characteristics of these two structures. The impacts of the extra couplings due to magnetic integration are modeled and analyzed. Results show that the magnetic integration slightly changes the coil currents, transferred power, and power factor but the variations can be reduced by properly designing the coils. The proposed structure and analysis are validated by experiments on a prototype.

CLL/S Detuned compensation network for electric vehicles wireless charging application

<span lang="EN-GB">An electric vehicle (EV) can be charged wirelessly through an inductively coupled power transfer system where the system resonates the inductive coupling coil at the operating frequency by means of a compensation network. However, the resonant behaviour implies overcurrent in the inverter MOSFETs during uncoupled and high load resistor conditions, which affect to the inverter MOSFETs failure whenever the current exceeds their maximum current rating. Therefore, this paper presents a CLL/S detuned compensation network for EV wireless charging application to limit the inverter current during the uncoupled state and open circuit load conditions. The proposed compensation consists of a series capacitor and parallel inductor at the primary side and series capacitor at the secondary side. By using Kirchhoff Voltage Law (KVL) analysis, the primary side is detuned to inductive behaviour to ensure zero voltage switching (ZVS), and the secondary side remains at natural resonant tuning. From the simulation analysis, the slight increase of the parallel inductor value at the primary side can limit of the inverter current at uncoupled and high load resistor conditions. The proposed system also offers higher efficiency than the series-series detuned compensation and slightly lower than the double-sided LCC compensation network at different coupling factor.</span>

High-Order Compensated Wireless Power Transfer for Dimmable Metal Halide Lamps

A high-order compensated wireless power transfer (WPT) system is proposed and implemented for dimmable metal halide (MH) lamps without using any ignitor or ballast. Possessing high ignition voltage and constant current output, the LCC - LC compensated WPT is identified to be more competent for MH lamps as compared with the four basic compensation networks as well as the double-sided LCC compensation networks. Meanwhile, dimming control and power stabilization are achieved by the phase-shift modulation, and the multilayer multitype coil is newly proposed to enhance the tolerance of varying coupling coefficients. For exemplification, a wireless dimmable MH lamp operating at 400 kHz has been designed and prototyped. Particularly, the system can tolerate coil deviation up to 20 cm and dim the lamp down to 30% of standard illuminance with the merit of acoustic resonance free. Both theoretical and experimental results are given to validate the feasibility of the proposed system.

An LCC-Compensated Multiple-Frequency Wireless Motor System

In this paper, a novel kind of wireless motors, namely, the LCC -compensated wireless switched reluctance motor, is proposed and implemented. The definite advantages are that there is no power converter at the motor side and particularly no switched-capacitor array at the transmitter side to realize the multiple-frequency operation. The key is to develop an LCC compensation involving an inductor and two capacitors (the so-called LCC ) for a multiple-frequency wireless power transfer system. As a result, only one transmitter is needed to targetedly feed three receivers, which directly energize the three phase windings of the motor. Particularly, there is no need to control switched capacitors to change the resonant frequency of the transmitter. Meanwhile, the burst firing control method is employed to realize the speed control. Both calculation and experimental results are presented to validate the feasibility of the proposed system. In the system prototype, the transmission distance can reach up to 150 mm and the transmission efficiency can be achieved up to 80%.

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.