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This paper aims to analyze the frequency characteristics of wireless power transfer (WPT) systems with relay resonators in terms of the power delivered to the load and system efficiency. Based on the analytical results, system parameters can be optimized to achieve maximum power transfer and higher system efficiency.

Based on Kirchhoff’s voltage law equations, WPT systems with relay resonators are described by the coupled linear second-order differential equations. Splitting frequencies are estimated by using the matrix theory. In addition, critical coupling conditions are demonstrated based on discriminant analysis.

It was found that multi-maximum values exist for the power delivered to the load and total system efficiency owing to multiple eigenfrequencies of the system. Also, frequency conditions of maximum power transfer and system efficiency, as well as their critical coupling conditions, were quantitatively estimated.

During our analytical process, we assume that quality factors of resonators in the system are high and the crossing coupling between resonators is negligible.

In previous works, the exact analysis of frequency characteristics is limited to WPT systems with two resonators. The appealing feature of this work lies in its ability to present a simplified analytical method with negligible approximation errors for WPT systems with relay resonators.

The purpose of this paper is to study the wireless power transfer (WPT) system that always achieves the maximum output power at a fixed angular frequency using the dynamic impedance compensation and also the maximum transfer efficiency.

An efficient topology of the WPT system is proposed which states that the functions of the relay are transformed into the functions of the compensator in the three-coil WPT system.

Increasing the ratio of the frequency detuning factor of the compensator relative to the frequency detuning factor of the compensator also causes the curves of the normalized output power and the transfer efficiency to move toward the high frequency direction.

The scheme of the dynamic compensation for the WPT using a compensator is convenient to obtain the dynamic impedance compensation by adding or removing the capacitances or inductances from the compensator.

The functions of the relay are transformed into the functions of the compensator in the three-coil WPT system.

The impedance compensation approaches have been adopted to achieve the maximum output power and transfer efficiency in many magnetic coupling resonance wireless power transfer projects. However, it remains a challenge to obtain the constant output power and transfer efficiency in a fixed-frequency mode during variations in transfer distance and orientation of the coils. In this paper, using two series transmitting coils to achieve the constant output power and transfer efficiency is used.

First, the circuit model is established and transfer characteristics are studied. Second, using the two series transmitting coils to achieve the constant output power and transfer efficiency is investigated. Finally, the experimental system is designed; it can optimize the transfer performances by itself; the constant output power and transfer efficiency are achieved in the fixed-frequency mode.

When the receiving coil moves between the two series transmitting coils, the tolerance of the output power and transfer efficiency is less than 5 per cent.

When a receiving coil is placed between the two series transmitting coils, there are space limits. The receiving coil only shifts between the two transmitting coils.

However, the rail guide vehicle may achieve constant output power and transfer efficiency when it moves on the rail guide. So, this topology may provide a practical solution.

In this research, the three-coil MCR-WPT system including two series transmitting coils is presented. In a fixed-frequency mode, the constant output power and transfer efficiency is achieved in experiments during variations in transfer distance and orientation of the coils. The fluctuation of the output power and transfer efficiency is less than 5 per cent.

The purpose of this paper is to model and analyze energy transfer through near‐field resonant coupling for high power light‐emitting diode (HPLED) illumination, with the intention to increase the appreciation and use of the coupled mode theory (CMT) other than the usual equivalent circuit method.

The CMT is extensively used to analyze the wireless energy transfer system because of its generality, simplicity, accuracy and intuitive understanding of near‐field resonant energy coupling mechanism.

The CMT forms a general way to model and analyze the non‐radiative magnetic resonant coupling systems. It is suitable not only for low frequency coupling but also for high frequency (of million‐Hertz) in which the circuit parameters are not easily obtained. Optimal coupling condition corresponding to the maximum power transfer is identified based on the CMT, and the multiple limit cycle phenomenon caused by the nonlinear nature of the HPLED is also described on the CMT model.

This paper takes advantages of CMT, i.e. generality, simplicity, accuracy and intuitive understanding to analyze the near‐field resonant energy coupling system. Key characteristics of the systems are explored based on the CMT, not the usual equivalent circuit method. The influence of nonlinear nature of the high power LED on energy transfer is also investigated. This work seeks a more general way than conventional equivalent circuit method to model and analyze the resonant magnetic system and the results obtained could facilitate better understanding of the resonant magnetic coupling mechanism and optimal design of the near‐field energy transfer system.

This paper aims to present a new wireless power transfer technique using capacitive coupling. The capacitive power transfer (CPT) system has been introduced as an attractive alternative to the traditional inductive coupling method. The CPT offers benefits such as simple topology, fewer components, better electromagnetic interference (EMI) performance and robustness to surrounding metallic elements.

A class-E inverter together with and without inductor capacitor (LC) matching circuit has been utilised in this work because of its ability to perform the DC-to-AC inversion efficiently with significant reduction in switching losses. The validity of the proposed concept has been verified by conducting a laboratory experiment of the CPT system.

The performances for both systems are analysed and evaluated. A 9.7 W output power is generated through a combined interface [printed circuit board (PCB) plate] capacitance of 2.82 nF at an operating frequency of 1 MHz, with 97 per cent efficiency for 0.25 mm coupling gap distance.

An efficient CPT system with class-E LC matching topology is proposed in this paper. With this topology, the zero-voltage switching can be achieved even if the load is different by properly designing the LC matching transformation circuit.

The purpose of this paper is to design and realize a high gain power amplifier (PA) with low output back-off power using the InGaP/GaAs HBT process for WCDMA applications from 1.85 to 1.91 GHz.

A three stages cascaded PA is designed which observes a high power gain. A 100 mA of quiescent current helps the PA to operate efficiently. The final stage device dimension has been selected diligently in order to deliver a high output power. The inter-stage match between the driver and main stage has been designed to provide maximum power transfer. The output matching network is constructed to deliver a high linear output power which meets the WCDMA adjacent channel leakage ratio (ACLR) requirement of −33 dBc close to the 1 dB gain compression point.

With the cascaded topology, a maximum 31.3 dB of gain is achieved at 1.9 GHz. S11 of less than −18 dB is achieved across the operating frequency band. The maximum output power is indicated to be 32.7 dBm. An ACLR of −33 dBc is achieved at maximum linear output power of 31 dBm.

The designed PA is an excellent candidate to be employed in the WCDMA transmitter chain without the aid of additional driver amplifier and linearization circuits.

In this work, a fully integrated GaAs HBT PA has been implemented which is capable to operate linearly close to its 1 dB gain compression point.

In most maximum power point tracking (MPPT) methods described in the literature, the optimal operating point of the PV systems is estimated by linear approximations. These approximations can reduce considerably the performances of the PV systems. This paper seeks to provide comparative analyses of different MPPT methods used in photovoltaic (PV) systems and proposes a new approach that uses a nonlinear expression of the optimal voltage in combination with perturbation and observation (P&O) methods.

First, an analytical model for determining the nonlinear PV optimal operating point is detailed and each equation is explained. Second, a combination of the new method with P&O method is proposed to reduce the PV losses.

The simulation results showed that the approach improves clearly the tracking efficiency of the maximum power available at the PV modules output. The implementation of this new method will improve PV systems energy production rate and its long‐term storage in hydrogen form.

The simulation results showed that the new approach improves the MPP's tracking efficiency of the PV system on average at 92 percent. The implementation of the developed approach in a PV system with hydrogen storage increased the energy transfer from PV modules to the electrolyzer.

This paper proposes a new approach to determine the maximum power point (MPP) from the measurement of the open circuit voltage of PV modules. A nonlinear expression of the optimal voltage was developed and is used in combination with P&O methods. The proposed approach largely improves the performance of the MPP tracking of the PV systems.

Power quality issues highly affect the secure and economic operations of the power system. Although numerous methodologies are reported in the literature, flexible alternating current transmission system (FACTS) devices play a primary role. However, the FACTS devices require optimal location and sizing to perform the power quality enhancement effectively and in a cost efficient manner. This paper aims to attain the maximum power quality improvements in IEEE 30 and IEEE 57 test bus systems.

This paper contributes the adaptive whale optimization algorithm (AWOA) algorithm to solve the power quality issues under deregulated sector, which enhances available transfer capability, maintains voltage stability, minimizes loss and mitigates congestions.

Through the performance analysis, the convergence of the final fitness of AWOA algorithm is 5 per cent better than artificial bee colony (ABC), 3.79 per cent better than genetic algorithm (GA), 2,081 per cent better than particle swarm optimization (PSO) and fire fly (FF) and 2.56 per cent better than whale optimization algorithm (WOA) algorithms at 400 per cent load condition for IEEE 30 test bus system, and the fitness convergence of AWOA algorithm for IEEE 57 test bus system is 4.44, 4.86, 5.49, 7.52 and 9.66 per cent better than FF, ABC, WOA, PSO and GA, respectively.

This paper presents a technique for minimizing the power quality problems using AWOA algorithm. This is the first work to use WOA-based optimization for the power quality improvements.

The purpose of this study is to show in power-voltage curve, a unique maximum power point (MPP) is existed which has the maximum power.

This paper presents a MPP tracker algorithm for a standalone system includes DC-DC buck converter and battery storage.

By using this algorithm, the maximum available power is achieved and simultaneously, the battery is charged and also protected against overcharge and discharge. The operation of the proposed algorithm is evaluated in with Proteus software to be sure that it can be implemented in microcontroller in reality.

The simulations results show that the proposed algorithm is able to detect the MPP under different irradiations. Moreover, the battery is charged during the day by PV and protected against overcharge and discharge.

The purpose of this research paper is to explore the possibility to enhance the power transfer from piezoelectric energy harvester (PEH) source to the load. As the proposed gyrator-induced voltage flip technique (GIVFT) does not require bulky components such as physical inductors, it is easily realizable in small integrated circuits (IC) package thereby offering performance benefits, reducing area overhead and providing cost benefits for constrained self-powered autonomous Internet-of-Things (IoT) applications.

This paper presents an inductorless interface circuit for PEH. The proposed technique is called GIVFT and is demonstrated using active elements. The authors use gyrator to induce voltage flip at the output side of PEH to enhance the charge extraction from PEH. The proposed technique uses the current-voltage (I-V) relationship of gyrator to get appropriate phasor response necessary to induce the voltage flip at the output of PEH to gain power transfer enhancement at the load.

The experimental results show the efficacy of the GIVFT realization for enhanced power extraction. The authors have compared their proposed design with popular earlier reported interface circuits. Experimentally measured performance improvement is 1.86×higher than the baseline comparison of full-wave bridge rectifier circuit. The authors demonstrated a voltage flip using GIVFT to gain power transfer improvement in piezoelectric energy harvesting.

To the best of the authors’ knowledge, pertaining to the field of PEH, this is the first reported GIVFT based on the I-V relationship of the gyrator. The proposed approach could be useful for constrained self-powered autonomous IoT applications, and it could be of importance in guiding the design of new interface circuits for PEH.