Variation Of Coupling Coefficient Research Articles

A robust parity‐time‐symmetric hybrid wireless power transfer system with extended coupling range

SummaryInductive power transmission (IPT) and capacitive power transmission (CPT) are currently the two main wireless power transfer technologies. Hybrid power transmission (HPT) systems that combine IPT and CPT can improve transmission performance and are more attractive for some charging applications such as electric bicycles (e‐bikes). However, HPT systems are more sensitive to parameter variations, and the coupling mechanism is prone to misalignment during wireless charging. Therefore, achieving stable output power and constant transfer efficiency over a wide range of coupling coefficient variations is still a major challenge for HPT systems. In this work, the parity–time (PT) symmetry theory is applied to an SS‐type HPT system, and a circuit model of the PT‐based HPT system is developed by using coupling capacitance and coupling inductance. The effect of connecting the plates to the homonymous end or heteronymous end of the coupling coils on the PT symmetry range of the HPT system is discussed. It is found that the heteronymous end connection of the coils can effectively increase the range of constant output power and stable transfer efficiency. Finally, a prototype is built to verify the feasibility and effectiveness of the proposed PT‐based HPT system. The transfer power and efficiency remain constant in the PT‐symmetric range, and the inductive and capacitive coupling coefficients are smaller compared to IPT and CPT systems with the same parameters.

Novel FR4‐based low loss reconfigurable filter with four operating modes using movable transmission lines

AbstractIn the letter, a novel reconfigurable filter using movable transmission lines is proposed. The filter is based on substrate‐integrated‐suspended‐line structure with two inner layers, fabricated on low‐cost FR4 substrate. The suspension line and the cavity are completely covered by copper. The suspension line could be freely moved in the air cavity. In the novel structure, the coupled lines have a variable coupling coefficient. With the movements of two transmission lines, the filter has four operating modes and can be tuned, with low insertion loss of less than 0.45 dB, showing promising properties.

A Control Strategy for Achieving Constant Voltage Output with an Extensive ZVS Operating Range in Bidirectional Wireless EV Charging Systems

Variations in the coupling coefficient of loosely coupled transformers and dynamic loads have a significant impact on the overall performance of bidirectional inductive power transfer (BIPT) systems. However, a wide range of load and coupling coefficient variations are common in the actual charging process, which may cause the converter on both sides to operate in a hard switching state, resulting in switching noise, reduced efficiency, and potential safety concerns. In this paper, a triple-phase-shift control (TPSC) strategy is proposed to study the zero-voltage switching (ZVS) operating range and constant-voltage output (CVO) characteristics of the double-side-LCC (DS-LCC) topology. To ensure a CVO over the wide range of coupling coefficient variations, a dual-phase-shift control is introduced for AC voltage matching. Based on this, the third phase-shift angle control between the converters on both sides is introduced to ensure the ZVS realization. Meanwhile, the time-domain model is developed to analyze the rationality of the proposed third phase-shift angle and the ZVS operating range. Finally, the effectiveness of the proposed TPSC strategy is validated through a 1.5 kW experimental prototype with an air gap of 100–150 mm.

Primary-Frequency-Tuning and Secondary-Impedance-Matching IPT Converter With Programmable Constant Power Output and Optimal Efficiency Tracking Against Variation of Coupling Coefficient

Primary-Frequency-Tuning and Secondary-Impedance-Matching IPT Converter With Programmable Constant Power Output and Optimal Efficiency Tracking Against Variation of Coupling Coefficient

A Fast and structurally simple control scheme based on a fuzzy supervisory approach for wireless power transfer systems

AbstractWireless power transfer (WPT) is a promising technology and has attracted many researchers’ attention due to its inherent advantages such as reliability, safety, flexibility, and low maintenance costs. For WPT systems, the output voltage varies according to the variable loads and the coupling coefficient conditions, affecting system stability and efficiency. In this regard, this study is concerned with the tracking control problem of WPT systems based on fuzzy supervisory proportional–integral (PI) controller and a phase shift modulation technique, which is for the first time proposed by this paper. By introducing appropriate fuzzy rules, the proposed control scheme not only can track the desired output voltage but also has better robust behaviour to deal with the problem of variations of circuit elements and coupling coefficients. That is, the proposed fuzzy supervisory PI control scheme can perform better than the traditional PI controller. Analysis of the designed control method and simulation results validate the superiority of the proposed method over the traditional PI controller in all conditions, which can make it a suitable choice for the applications of electric vehicle charging systems. The analysis is supported by experimental measurements.

Influence of ambient pressure and laser energy on the plasma dynamics and parameters of laser-irradiated polyvinyl chloride

The dependence of propulsion performance generated by laser ablation of polyvinyl chloride on laser energy and pressure is investigated using Q-switched Nd: YAG laser with the wavelength of 1064 nm. When the pressure is decreased, the impulse and coupling coefficient rise first and then decline. Such a trend is also reflected in the variation of coupling coefficient with laser energy in the whole pressure range. However, the change in impulse with laser energy at atmospheric pressure is not completely consistent with that at low pressure levels. The dynamic behavior and duration of plasma plume are considered to be the factors for the difference in propulsion performance. By capturing the fast exposure images of plume, the separation at atmospheric pressure and severe expansion accompanied by rapid quenching in near vacuum are observed. Moreover, the plasma plume lasts longer time at high pressures. It is ascribed to the higher electron temperature, which promotes background gas to excite and ionize. Since the electron density increases with the improvement of laser energy and pressure, the absorption of electrons to laser energy becomes stronger through the inverse bremsstrahlung mechanism. Accordingly, the shielding effect of plasma is enhanced, causing the weak laser-target interaction. The result is that the crater depth and ablative mass increase with decreasing pressure. This work is important for understanding the energy conversion mechanism and optimizing the laser propulsion performance.

Wireless Charging System with Three Arc-Transmitting Coils for Autonomous Underwater Vehicle

To enhance the misalignment tolerance of the coupling device of the autonomous underwater vehicle wireless charging system, this paper proposes a magnetic coupling device with strong misalignment tolerance. Through the Ansys Maxwell finite element analysis software, it is concluded that, under the dislocation state of the proposed magnetic coupling device, the magnetic field is mainly distributed near the shell wall of the autonomous underwater vehicle. The coupling coefficient change range under the rolling dislocation state is 0.35~0.83, the axial dislocation coupling coefficient fluctuation range is 0.79~0.83, and the radial dislocation coupling coefficient variation range is 0.48~0.83. We design and calculate the compensation network in a wireless charging system and obtain the calculation method of the compensation network. A prototype of that wireless charging system containing arc-emitting coils applied to the AUV has been made, which transfers 48 W power with an efficiency of 87.3%.

A Dual-Frequency-Detuning Method for Improving the Coupling Tolerance of Wireless Power Transfer

This letter proposes a dual-frequency-detuning method for wireless power transfer systems to gain a smooth power profile in large coupling variation ranges. The application of the detuning method in the dual-frequency resonant network is explored to adjust the equivalent impedance of each frequency channel at different coupling conditions. Accordingly, the proposed method can freely regulate the voltage gain and output power curves even under a square-wave voltage excitation with high-order harmonic components. By designing the system properly, both the fundamental and 3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> frequency channels alternately serve as the main power transfer channel under strong and weak coupling conditions, so less power fluctuation over a large coupling variation is realized. A 130W prototype is developed, and the experimental results show that the maximum power fluctuation is less than 6.8% against coupling coefficient variations from 0.35 to 0.74.

Variable Coupling Coefficient Integrated Inductor for Hybrid Energy Source Systems

Variable Coupling Coefficient Integrated Inductor for Hybrid Energy Source Systems

A Position-Insensitive Nonlinear Inductive Power Transfer System Employing Saturable Inductor

Most of the practical inductive power transfer (IPT) systems are the ones with variable coupling coefficients and loads. The output voltage, current and power are affected by the variation in coupling coefficient and load. In this paper, a novel approach based on a nonlinear resonator is proposed to obtain stable output voltage, which is independent of coupling coefficient and load variation. First, the theory and properties of nonlinear resonators are analyzed by Duffing equation. Then, a nonlinear IPT system with a magnetic saturation inductor is proposed, and the saturable inductor modeling and its effect on system performance are further studied. Finally, the experimental prototype is built to validate the effectiveness of the nonlinear IPT system. The experimental results show that when the coupling coefficient varies from 0.32 to 0.24 and the load resistance varies from 80Ω to 120Ω, the system works in a nonlinear state, the output voltage ripple is 1.77%, and the overall efficiency of the system is not less than 82.60%. The experimental results are basically consistent with the theoretical analysis. The novel design approach improves the output voltage stability with respect to position misalignment and load variation, and the bandwidth of the system is also enhanced.

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.

Modeling and Control of Dynamic Wireless Power Transfer System for Electric Vehicle charger application

This paper proposes a nonlinear state-space model for a dynamic wireless power transfer system (DWPT). The DWPT system comprises emitter coils supplied by DC/AC converters, with a phase angle control to achieve maximum power transfer. The power receiver coil is connected to a full bridge diode rectifier followed by an equivalent load resistance. To emulate the dynamic movement property of WPT, the coupling factors between the emitter and receiver coils are set to be variable and depend on the movement of the power receiver alongside the power emitter coils. The control has been successfully demonstrated under variable coupling coefficients to achieve maximum power transfer. Such improvement maintains the power and voltage across the load during transient states.

Performance characteristics of single Bragg grating fiber under various filter impulse functions and grating filter profiles

Abstract This work has demonstrated the performance characteristics of single Bragg grating fiber under various filter impulse functions and grating filter profiles. Single fiber Bragg grating (FBG) power propagation, grating index change, coupling coefficient and apodization variations versus grating length variations is demonstrated at the central wavelength of 1550 nm by using both Hamming, Blackman impulse filter function and Hamming, Blackman grating profile. As well as the single FBG power spectrum, delay, dispersion, transmittivity/reflectivity are simulated and clarified against wavelength variations using both Hamming, Blackman impulse filter function and Hamming, Blackman grating profile. The Hamming impulse function filter and Hamming grating profile have clarified better performance than Blackman impulse function filter and Blackman grating profile.

A wireless power transfer system based on quasi‐parity–time symmetry with gain–loss ratio modulation

SummaryWireless power transfer (WPT) systems based on parity–time (PT) symmetry can realize robust power transfer against the fluctuation of distance. There is an exceptional point (EP) that partitions the PT‐symmetric and PT‐broken phase, and it is nonadjustable at the conventional system with unity gain–loss ratio unless changing circuit parameters, which limits the improvement of its transfer performance. This paper proposed a novel quasi‐PT‐WPT system based on gain–loss ratio modulation. The proposed system can operate under different gain–loss condition with constant transfer power and efficiency regardless of coupling coefficient variation at the PT‐symmetric phase, which can enhance either the maximum transfer efficiency or distance alternatively. The proposed system consists of a nonlinear gain with adjustable gain–loss ratio to enable the transfer performance control, which is implemented by the virtual impedance. Experimental results verified the correctness of the theoretic analysis and implied the inherent contradiction between the transfer efficiency and distance.

A Unipolar-Duty-Cycle Hybrid Control Strategy of Series–Series Compensated IPT System for Constant-Current Output and Efficiency Optimization

Based on the unipolar-duty-cycle (UDC) modulation technique, this article presents a hybrid control strategy for a series–series compensated inductive power transfer (IPT) system. By adjusting the duty cycle and the operating frequency, zero-voltage switching (ZVS) and constant-current output (CCO) can be achieved with varying coupling coefficients and load. Furthermore, as the proposed strategy enables the IPT system to lower the frequency of operation, it provides higher efficiency in the overall output power range than the conventional variable-frequency control methods. The basic principle of the UDC control strategy and its characteristics are introduced, and the system performance under UDC is analyzed and compared with the performance achieved by conventional control methods. Based on this, the UDC closed-loop control scheme, which combines PI control and hysteresis control, is proposed for the dynamic tracking of the ZVS and the CCO under a wide range of coupling coefficients and load. To validate the practicability of the proposed control strategy, a 500-W experimental prototype is configured. The simulation and experimental results indicate that the proposed scheme can stably and accurately track the ZVS and the CCO under varying parameter conditions, and it significantly improves the system efficiency. Especially, the system efficiency is improved by approximately 1.75% under light-load conditions as compared with that of the conventional control method. In addition, since the proposed method employs only one control loop, the cost and complexity of the IPT system are reduced.

Widening the Operating Range of a Wireless Charging System Using Tapped Transmitter Winding and Bifrequency Pulse Train Control

In this article, a subharmonics switching technique named bifrequency pulse train (BF-PT) control for wireless battery charging system with tapped transmitter (Tx) winding is proposed to regulate the output power against the variation of load and coupling coefficient. The tapped Tx winding is spilt into two subwindings: subwinding I is connected to the inverter while subwinding II is in open circuit. The charging current and charging voltage can be acquired by measuring the induced current of subwinding I and the induced voltage of subwinding II, respectively, without dual-side communication. BF-PT control, which contains high- and low-frequency pulse trains, can achieve zero voltage switching over a wide operating range. The high- and low-frequency pulse trains are uniformly distributed to suppress the winding current oscillation and to minimize the output voltage ripple. When the coupling becomes weaker and/or light-load conditions, the switches are operated at the subharmonics frequency to further reduce the average switching frequency of the system. To verify the validity of the proposed method, a wireless charging system with 72 V/3 A output is fabricated. The experimental results confirmed that the proposed method is able to maintain constant current and constant voltage output regardless of the load and coupling variations.

Tracking and Dynamic Tuning of a Wireless Powered Endoscopic Capsule

This work presents an inductive wireless power transfer system for powering an endoscopy capsule supplying energy to power electronic devices allocated inside a capsule of ≈26.1 mm × 9 mm. A receiver with three coils in quadrature with dimensions of ≈9 mm × 9 mm × 10 mm is located inside the capsule, moving freely inside a transmitter coil with 380 mm diameter through translations and revolutions. The proposed system tracks the variations of the equivalent magnetic coupling coefficient compensating misalignments between the transmitter and receiver coils. The power on the load is estimated and optimized from the transmitter, and the tracking control is performed by actuating on a capacitance in the matching network and on the voltage source frequency. The proposed system can prevent load overheating by limiting the power via adjusting of the magnitude of voltage source . Experimental results with uncertainties analysis reveal that, even at low magnetic coupling coefficients k ranging from (1.7 × 10, 3.5 × 10), the power on the load can be held within the range of 100–130 mW. These results are achieved with any position of the capsule in the space, limited by the diameter of the transmitter coil and height of 200 mm when adjusting the series capacitance of the transmitter in the range (17.4, 19.4) pF and the frequency of the power source in the range (802.1, 809.5) kHz.

Position-Independent Constant Current or Constant Voltage Wireless Electric Vehicles Charging System Without Dual-Side Communication and DC–DC Converter

In this article, a robust wireless power transfer (WPT) system considering a wide variation in load resistance and coupling coefficient is proposed for electric vehicles charging. Here, a new implementation of the parity-time (PT)-symmetric circuit using a phase synchronization method is presented, in which a power-adjustable negative resistor is constructed only by a single-stage inverter. Moreover, based on the PT-symmetric circuit, a control strategy that does not require dual-side communication and extra dc–dc converters is developed for battery charging. Theoretical analysis shows that constant current (CC) and constant voltage (CV) outputs independent of load and position can be achieved, and the charging mode can be switched automatically. A scaled-down prototype with an 8-A charging current and a 120-V charging voltage is built to verify the feasibility of the proposed method. Experimental results demonstrate that within the transfer distance of 10–25 cm, the CC/CV outputs can be maintained during the charging process.

Bidirectional Q-Z-Source DC Circuit Breaker

In this article, a novel Z-source dc circuit breaker topology with a Q-shaped impedance network (Q-Z-source circuit breaker) is presented. The new topology has a better performance and is more resilient properties than those of the recently published O-Z-source circuit breaker. The new Q-Z topology provides bidirectional protection but only requires one semiconductor switch in its current path during normal operation, leading to a simpler and smaller physical structure and a lower conduction penalty. It also drastically improves the sensitivity issue on the magnetic coupling coefficient that manifests in the existing O-Z-source circuit breaker. In a realistic, practical application with a nonideal magnetic coupling coefficient, the new topology requires a smaller capacitance that can be translated into lower weight and/or lower cost. Detailed mathematical models are built to analyze and compare the short-circuit fault responses of a variable coupling coefficient. The bidirectional snubber circuit and its connection to the Q-Z topology are discussed for achieving faster fault clearing. Finally, a prototype is built in the laboratory to verify the theoretical analysis and improved performance of the proposed bidirectional Q-Z-source dc circuit breaker.

Constant Voltage Charging and Maximum Efficiency Tracking for WPT Systems Employing Dual-Side Control Scheme

The wireless power transfer (WPT) system has been gradually integrated into our daily applications due to its advantages of security, esthetics, and convenience. Generally, for a complete WPT system, two main goals need to be achieved: one is the constant voltage (CV) output and the other is the highest possible transfer efficiency. However, the highest possible transfer efficiency is difficult to achieve when the WPT system maintains the CV output against the time-varying load resistance and coupling coefficient. In this article, a new dual-side control scheme that employs transmitter-side high-frequency inverter (HFI) and receiver-side semi-active rectifier (SAR) is proposed to simultaneously achieve the CV output and maximum efficiency tracking (MET) control regardless of the variable load resistance and coupling coefficient. It is proved that the system can obtain the maximum transfer efficiency when the derivative of <inline-formula> <tex-math notation="LaTeX">$\sin (\alpha /2)$ </tex-math></inline-formula> with <inline-formula> <tex-math notation="LaTeX">$\sin (\beta /2)$ </tex-math></inline-formula> is a specific constant, which is determined by self-resistances of transceiver coils and system input and output dc voltage. In the above derivative, <inline-formula> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> are phase shift angles of the HFI and SAR, respectively. The CV output is maintained by adjusting <inline-formula> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>, while the MET control is performed by continuously adjusting <inline-formula> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula>. A confirmatory experimental setup with the charging voltage of 72 V is built, and the experimental results fully prove the correctness and effectiveness of the proposed scheme.