Wireless power transfer (WPT) technology makes it possible to supply power through an air-gap, without the need for current-carrying wires. One important technique of WPT technology is magnetic resonant coupling (MRC) WPT. Based on the advantages of MRC WPT, such as safety and high power transfer efficiency over a long transmit distance, there are many possible applications of MRC WPT. This study provides a comprehensive, state-of-the-art review of the MRC WPT technology and wireless charging for electric vehicle (EV). A comparative overview of MRC WPT system design which includes a detailed description of the prototypes, schematics, compensation circuit topologies (impedance matching), and international charging standards. In addition, this study provides an overview of wireless EV charging including the static wireless EV charging and the dynamic wireless EV charging, which focuses on the coil design, power transfer efficiency, and current research achievement in the literature.

Matrix converters are a well-known class of direct AC–AC power converter topologies that can be used in applications, where compact volume and low weight are necessary. For good performance, special attention should be paid to the control scheme used for these converters. The model predictive control strategy is a promising, straightforward and flexible choice for controlling various different matrix converter topologies. This work provides a comprehensive study and detailed classification of several predictive control methods and techniques, discussing special capabilities they each add to the operation and control scheme for different matrix converter topologies. This study also considers the issues regarding the implementation of model predictive control strategies for matrix converters. This survey and comparison are intended to be a useful guide for solving the related drawbacks of each topology and to enable the application of this control scheme for matrix converters in practical applications.

All switching power converters are characterised by inevitable switching actions with relevant interference emissions. The voltage and current transients of power metal oxide semiconductor field effect transistor (MOSFET)/insulated-gate bipolar transistor are the main sources in switching power converters for both conducted and radiated emissions. In this study, a promising electromagnetic interference (EMI) mitigation method combining the closed-loop gate drive method and the chaotic switching frequency modulation technique is demonstrated for switching power converters. A chaotic pulse-width modulation waveform with Gaussian S-shape switching transients was proposed to achieve remarkable reduced EMI generation at all frequencies. Spectral characteristics of this new switching waveform were investigated by the power spectral density to verify the feasibility of reduced EMI generation. A closed-loop gate controller was presented to shape the switching transients of power MOSFET into the proposed switching waveform. Circuit tests were carried out in both simulations and experiments. The results validated that the proposed method could achieve remarkable EMI mitigation in switching power converters.

In this study, a switched Z-source inverter with a new suitable control method is proposed that is called the series modified switched boost inverter (SM-SBI). In addition, the generalised proposed control method is presented. Furthermore, in order to show the effect of the other control methods on the operation of SM-SBI, the operation of the proposed inverter is presented using two other control methods. In order to analyse precisely, each of these three switching methods is completely introduced and then the operation of SM-SBI in these three switching methods is thoroughly stated. In addition, equivalent circuits of the SM-SBI during these control methods are presented. The voltage and current equations of all elements in the proposed structure based on the three switching methods are derived. In addition, the power loss analysis of SM-SBI is presented too. In order to show the effect of used control methods on the other conventional structures, a comprehensive comparison between the proposed inverter and the other switched step-up inverters is shown by applying these three switching methods. In the end, in order to confirm theoretical analyses, the simulation results by using PSCAD/EMTDC software are presented as well as the experimental results.

The modular multilevel converter (MMC) is an attractive option for high-voltage direct-current (HVDC) transmission applications. The dc line short-circuit fault is one of the key challenges for the HVDC system. In this study, a thyristor-based MMC with current interruption capability is proposed, where the IGBT with anti-parallel thyristor is employed to realise current interruption with the advantages of the simple circuit configuration and less number of power electronic devices. Also, the protection scheme for the thyristor-based MMC HVDC system under dc lines short-circuit faults is also proposed, where the fault current can be quickly interrupted by the thyristor-based MMC. The proposed thyristor-based MMC HVDC system is not necessary to be disconnected with the ac grid during the dc-line fault, where the MMC can continue operating and can be used for reactive power regulation before the fault is cleared, and therefore improves the system performance. The simulation and experimental studies are conducted, and the results verify the effectiveness of the proposed thyristor-based MMC and control scheme.

In this study, a new approach based on adaptive dynamic programming (ADP) is proposed to control single-phase uninterruptible power supply inverters. The control scheme uses a single function approximator, called critic, to evaluate the optimal cost and determine the optimal switching. After offline training of the critic, which is a function of system states and elapsed time, the resulting optimal weights are used in online control, to get a smooth output AC voltage in a feedback form. Simulations show the desirable performance of this controller with linear and non-linear loads and its relative robustness to parameter uncertainty and disturbances. Furthermore, the proposed controller is upgraded so that the inverter is suitable for single-phase variable frequency drives. Finally, as one of the few studies in the field of ADP, the proposed controllers are implemented on a physical prototype to show the performance in practise.

Model predictive control (MPC) has emerged as a real alternative for the control of different topologies of power converters. In particular, MPC has been successfully applied in matrix converters, significantly reducing the difficulty of control compared with classical techniques. In this study, a predictive voltage control strategy for a four-leg indirect matrix converter is proposed. The idea is based on the discrete minimisation of a cost function in order to select the best vector state of the power converter to be applied in the next sampling instant. Experimental results are presented to validate the proposal under several operating points.

This study is research upon the over-potential of Li-iron batteries. By performing many cycles of charging–discharging experiments under controlled ambient temperature, adjusted depth-of-discharge, and discharging current rates, the dynamic voltage variation data is collected. A model based on the cubic over-potential differential equation is proposed. This model is able to predict the gradually prolonged time-constant dynamics of the battery loaded voltages with fewer parameters. By this way, a set of procedures is also proposed to adjust the parameters as the battery ages. The experimental result is used to verify the feasibility of this model. Even for the aged batteries, the prediction error is small and the result is satisfactory.

A novel high step-up DC–DC converter with coupled inductors has been proposed. The proposed topology includes two coupled inductors, four capacitors, four diodes, and two metal–oxide–semiconductor field-effect transistors. Two coupled inductors charge in parallel when the switches are on and discharge in series when switches are off. Additionally, for absorbing the energy of stray inductance, a regenerative snubber is used. In this way, the duty cycle of the power switches can vary in a wider range and the voltage gain is higher in comparison to most of the other coupled-inductor-based converters. The effectiveness of the proposed converter has been verified by various simulation and experimental results.

The systems consisting of multiple DC–DC converters with input-series output-parallel (ISOP) connection are widely used in high-power applications. In the ISOP connection, the total input voltage and output current should be divided equally between the converters. However, in order to achieve this purpose, a proper control scheme should be used. This study proposes two control schemes: (i) output current feedback (OCF) and (ii) input voltage feedback (IVF). Based on the power balance, in the IVF scheme, the total output current, and in the OCF scheme, the total input voltage are divided automatically between the converters, and there is no need to use an extra control loop. The IVF and the OCF control schemes consist of two control loops: a common output voltage regulator (OVR) loop and individual input voltage sharing loops in the IVF scheme or individual output current sharing loops in the OCF scheme. The proposed control scheme can effectively improve the stability and dynamic characteristics of system. Finally, both the results of the simulation and laboratory prototype of an ISOP system consisting two forward converters have verified the performance of the IVF and OCF control schemes.

On the grid side, the half-bridge topology of the microinverter is of interest for solar rooftop applications because of its high efficiency, low component count, and cost-effectiveness. However, it has an inherent double-line frequency ripple voltage on the dc-link, which causes the injection of a third-order harmonic current when the voltage control loop is closed. Furthermore, in practice, different average voltages or different capacitances of the two capacitors at the dc-link produce a second-order harmonic current that flows into the grid. In this paper, the analytical details of these harmonics are comprehensively described, and a simple and effective low-cost technique using the cascaded connection of two modified notch filters is proposed in the voltage control loop to mitigate their effects. The simulation and experimental results of a 300 W microinverter indicate that the proposed filters represent an effective low-cost solution and perform well in accordance with the IEEE 1547 standard, even if the capacitances at the dc-link are mismatched by 20%. Besides, the prototype is tested when occurring of the changing +1% of the line frequency, or appearing of the distorted waveform of grid voltage with the composition of 6% of fifth-order harmonic.

Non-linear rectifier loads usually cause heavy distortion in the output voltage of single-phase inverters due to pulsating charging current of the rectifier direct current link capacitor. In this article, a predictive load current-based digital feedforward (PCFF) compensation method is proposed to decrease the inverter voltage distortion associated with the pulsating load current. PCFF control scheme works along with the basic inverter control structure that consists of a repetitive controller and a synchronous reference frame PI controller. The PCFF method further improves the single-phase inverter performance by enhancing its compensation dynamics. The simulation and experimental results show that the proposed control strategy can effectively reduce the total harmonics distortion of the inverter voltage and improve the output voltage quality.

This study proposes a novel pulse width modulation (PWM) algorithm to mitigate the common mode voltage (CMV) in a multi-level voltage source inverter feeding an electric machine. Dead-time effect frequently prevents the CMV not to reach zero in several switching periods. Then the electromagnetic interference noise is generated and causes bearing failure and overvoltage stress on winding insulations. The proposed strategy compensates the dead-time effect that alleviates the high-amplitude rectangular pulses with extreme range of variations during high-frequency switching transitions. The existing PWM methods reduce the CMV to however by utilising the presented approach, CMV can be reduced to zero. However, the total harmonic distortion will be increased 0.3% at fundamental current harmonic rather than conventional state PWM method, which could be neglected. Simulation results and efficiency analysis imply on worthy performance of the proposed strategy to eliminate the CMV.

This study proposes a topology of wind energy conversion system based on hexagonal modular multilevel converter (H-MMC), which can connect the wind turbine and the AC grid with one stage conversion. It has the advantages of low power losses, low ripple of capacitor voltage and transformer-less grid connection. The operation principle of the proposed topology is analysed in detail. Then, the positive and negative sequence control method is proposed to eliminate the second harmonics in the output power of H-MMC under asymmetrical grid faults. The double proportional resonant (PR) controller is proposed to track arm current references without steady error. The effectiveness of the proposed topology and its control method are verified by simulations and hardware in loop tests.

This study proposes a simple mixed droop- v / f control strategy for the master inverter of a microgrid to achieve seamless mode transfer between grid-connected and autonomous islanding modes. The proposed control utilises (i) a modified droop control in grid-connected mode to achieve seamless transfer from grid-connected mode to islanding mode in case of intentional and unintentional islanding events, and (ii) v / f control in islanding mode, which is realised by simply reducing the droop coefficient to zero gradually after islanding, to provide voltage and frequency references to the slave inverters. Pre-synchronisation on the voltage and frequency between microgrid and utility grid is used for the reconnection of them in a seamless manner. The rationale and detailed design of the system with the proposed control strategy are elaborated, after which its effectiveness is proved by simulations and experiments.

Combining low-voltage power sources with loads that require high-voltage levels is a challenge, especially for power devices above 500 W. In this context, this study presents a new dc–dc high-gain converter using coupled inductors. The new converter uses only one switch and output capacitors with low values. It also allows the use of energy from the leakage inductors and enables the input current to operate in the continuous mode. The experimental concept validation was carried out in a prototype of 1 kW with an input voltage between 48 and 96 V and an output voltage of 800 V. The results obtained were coherent, with no significant semiconductor over-voltage and high efficiency was achieved for a wide power range.

Virtual synchronous generator (VSG) controlled grid-tied converters could increase power overshoot and oscillation if real power reference disturbance (PRD) occurs. Existing VSG methods can mitigate the power oscillations, but they may reduce the supporting capability of grid contingency. To cope with the issue, a modified virtual inertia control method of VSG strategy is proposed. The proposed modified VSG method introduces two frequencies of point of common coupling into the virtual inertia control. The estimated frequency is used to mitigate the power oscillations and the measured frequency aims to provide extra power supporting. The formulated parameters design principles are given according to the transient characteristics. Stability analysis of power and frequency response is carried out to evaluate the proposed method. Besides, the transient power and frequency response of the PRD case and grid-frequency disturbance (GFD) case are studied. The power overshoot of the proposed modified VSG method decreases by 52.5% under the PRD case and the power support peak increases by 34.3% under the GFD case. Experimental results show that the transient performance of the proposed modified VSG controlled grid-tied converters is improved.

Modular multilevel converter (MMC) is widely used in medium- and high-voltage applications, but there are large capacitor voltage ripples on the sub-modules (SMs) when applied to low-speed applications, such as wind generator system. The method based on the injection of common-mode voltage and high-frequency current is the most effective solution at present, but it will bring new problems. To solve these problems, a modified MMC is proposed in this study. Firstly, coupled inductors and LC resonance circuit are adopted as the power transfer channel between the upper arm and lower arm of the MMC, to eliminate the low-frequency voltage ripple. The theoretical analysis and design guideline of the coupled inductors and LC resonance circuit are discussed in detail before the explanation of SM voltage fluctuation suppression method. Secondly, an improved voltage fluctuation suppression method, named limited compensation method, is presented to replace the conventional full compensation method to decrease the magnitude of injected high-frequency current, thereby reducing the current ratings of power devices, size of inductors, and the cost of system. In the end, MATLAB/SIMULINK simulations and a 2 kW down-scaled prototype are performed to validate the effectiveness of the proposed solution and its control scheme.

In saliency-based sensorless methods, the amplitude of the injected voltage cannot be reduced to levels below its specified value because of the reasonable signal required for the noise ratio. Increasing the injection signal amplitude increases not only the acoustic noise and high-frequency (HF) losses, but also the total harmonic distortion (THD) of the output voltage and current ripples. A new pulsating semi-impulse signal injection method based on the current sensing technique is proposed for the sensorless control of interior permanent magnet synchronous motors (IPMSMs). The proposed method aims to control the motor speed and reduce some problems due to the HF signal injection involving acoustic noise, HF losses and THD of the output voltage. Taking into account the premium injection angle, these problems are reduced significantly as compared to those in conventional square-wave methods. Hence, the proposed method increases the sensorless driver efficiency and its application scope. The effectiveness of the proposed method is then confirmed with computer simulation and experimental tests. Experimental comparisons at the same injection frequency and injection effective voltage show that the performance of the proposed method is beneficial. All experiments were performed on a IPMSM with V-shaped PMs which is used in a refrigerator compressor.

The major concern with renewable sources of energy, feeding the distributed power generation system, is the power quality, reliability and efficiency of the system. This study proposes a novel topology comprising single-phase, seven-level, grid-connected photovoltaic-fed (PV) inverters in parallel. An important expediency of connecting multilevel inverters (MLIs) in parallel is that the failure of any source or the MLI module itself will never stop the overall generation, leading to improved efficiency and reliability of the system. This study also incorporates a novel controller comprising of two DC and an AC controller that independently controls the DC-link voltage of PV system and AC-side voltage so as to inject a pure sinusoidal current at unity power factor into the grid. Also, the AC controller discussed here is self-synchronising, i.e. aloof of phase-locked loop. The power mismatch problem that basically arises due to partial shading conditions in PV system has also been discussed. The MATLAB/Simulink-based proposed two seven-level grid-connected inverters in parallel are modelled and simulation results are presented. An experimental prototype of the PV-fed grid-connected system comprising two seven-level inverters in parallel is developed and tested to validate the simulation results.

This study deals with a two-stage photovoltaic (PV) array-fed irrigation pump using a synchronous reluctance (SynREL) motor drive. In this scheme, a boost converter is utilised for harvesting maximum available power from a PV array through an incremental conductance-based maximum power point tracking algorithm. Here, it feeds power to a voltage source inverter through a DC-link capacitor. The prime objective of the proposed system is to provide water supply for domestic and irrigation purposes; therefore, to avoid complexity and for increased reliability, the speed/position sensor is eliminated. A speed/position observer is utilised for the estimation of angular position of SynREL motor. A PV feed-forward term is used to estimate the reference speed, which aids in enhancing the transient behaviour of proposed system. Moreover, the control is inherently resistant to the ageing-related variation in pump's constant. The applicability of proposed water pumping system is verified through test results, recorded on a developed prototype in the laboratory under varying atmospheric conditions.

In this study, a sensorless vector control for the rotor-tied doubly fed induction generator (RDFIG) is proposed in the grid-connected mode. The proposed sensorless vector control method includes a slip speed/angle estimator which is based on the association of the high-order sliding mode observer (HOSMO) with a phase-locked loop (PLL). In addition, an extensive comparison between the PLL-based HOSMO estimator and the PLL-based second-order sliding mode observer (SMO) estimator is also presented. The Lyapunov stability criterion is used to determine both observer gains to allow their convergence in finite time. Both the proposed HOSMO and the SMO use the three-phase stator current and back-electromotive force (EMF) as state variables which enable the start of the estimation even before the machine is connected to the grid. The proposed HOSMO takes into account the dynamics of the back-EMF space vector. The PLL is used to extract the estimated slip speed/angle from the estimated back-EMF. The performance of the proposed sensorless vector control strategy is validated experimentally with a 5.5-kW custom-designed RDFIG on a test bench based on the National Instrument (NI) PXIe-8115 real-time controller.

An improved selective harmonic elimination-pulse width modulation (SHE-PWM) scheme has been proposed for a three-phase seven-level cascaded H-bridge (CHB) inverter that enhances the power utilisation capability of the inverter by sharing the desired amount of power among the H-bridge cells and also eliminates both 5th- and 7th-order harmonic components from the inverter output voltage maintaining the desired fundamental voltage component for a wide range of modulation index. Compared to conventional SHE-PWM, this scheme introduces two additional switching in the first cell, while the second and the third cells are switched at advanced switching angles. The differential search algorithm (DSA) technique has been applied to solve the proposed SHE-PWM scheme, and it exhibited comparatively better performance than the algorithm based on genetic algorithm, BEE algorithm and particle swarm optimisation. The effectiveness of the proposed scheme has been verified by both simulation and experimental study on a seven-level CHB inverter. Finally, the proposed scheme has been applied to the closed-loop constant V/f control of the induction motor drive application. It has been established that the proposed scheme is independent of the load power factor angle, and it improved the power conversion efficiency of the conventional SHE-PWM scheme.

This study presents a fault detection and isolation (FDI) method for open-circuit faults (OCFs) in the switching devices of a grid-connected neutral-point-clamped (NPC) inverter for photovoltaic (PV) applications. The proposed methodology addresses the fault diagnosis problem by a combined model-based and data processing perspective to study single and simultaneous faults in the NPC inverter. For the model-based scheme, a bank of sliding-mode proportional–integral observers is suggested to estimate the fault profiles under an additive model. Thus, from the estimated fault profiles, and by performing a directional residual evaluation in a fixed reference frame, single and simultaneous fault scenarios can be isolated in the NPC inverter. However, for some fault classes, there is some ambiguity by just the model-based approach that is overcome by employing the average line currents to construct extra fault signatures. The proposed FDI scheme only requires the measurements of line currents and grid voltages in the diagnosis media and can isolate single OCFs and simultaneous OCFs in the order or lower than a fundamental period of the grid frequency. Our new FDI methodology is validated through experimental data from a practical PV system in a closed-loop grid-connected NPC inverter under single and simultaneous OCF conditions.

The influence of the silicon carbide (SiC) technology in terms of volume, weight, efficiency, and cost in a 225 kW DC–DC railway converter is detailed in this study. Three different power modules technologies have been used: ‘traditional’ silicon-based power modules, SiC-hybrid modules, and the newest full-SiC power modules available in the market. An experimental comparison of the SiC-hybrid and full-SiC modules is presented, showing their switching waveforms compared with those of the original Si modules. The highest speeds obtained by the SiC technology make the use of the traditional power module packages impossible employing Si technology. Hence, the first full-SiC modules available in the market are offered in low current ratings, requiring the complete redesign of the power converter to take advantage of the capabilities of the full-SiC modules. The railway power converter under study in this work is nowadays used to regenerate the braking energy in a DC 750 V tram with some catenary-free areas. As a final result, a full-SiC version of converter is achieved.

In this research, voltage regulation of a DC–DC buck converter is realised via the ripple-free deadbeat control (RFDBC) with the equivalent input disturbance observer (EIDO). A small-signal state-space model is constructed for the RFDBC design of a converter. Faced with mismatched models, unknown parameter perturbation, and time-varying voltage source and load demands, augmented disturbance state is constructed and extended state observer is utilised to estimate this augmented model accurately. Based on this model, EIDO is proposed to evaluate the equivalent input disturbance affecting on the input channel. Disturbance compensation is analysed in theory, and the simulation model of the proposed EIDO-based RFDBC is created to illustrate the control performance in MATLAB/Simulink. Finally, a LabVIEW-based FPGA experimental rig is set up for the voltage regulation of a DC–DC buck converter. Two other controllers, RFDBC without EIDO and active disturbance rejection control are also designed for performance comparison. The performance comparison result of transient tracking indicates the outstanding characteristics of the proposed controller.

This study proposes a new quasi-discrete approach to modelling the permanent magnet synchronous motor (PMSM). The quasi-discrete modelling reflects the impact of continuous rotor movement, which takes place during a control cycle, on the shape of motor current waveforms. This provides much improvement in current modelling accuracy under inverter low switching-to-fundamental frequency operation. The proposed approach may be used in predictive control to compute current at forthcoming instants or in classical control to improve precision of determining mean current feedback. The superior accuracy of the quasi-discrete model is confirmed by simulation and experiment for an exemplary PMSM drive operating at inverter switching frequency of 5 kHz and fundamental frequency reaching 400 Hz.

Single-inductor–multiple-output (SIMO) light-emitting-diode (LED) drivers are attractive, practical solutions for lighting applications. An SIMO LED driver is usually constructed with conventional voltage-source-mode dc–dc converters. Current-source-mode (CSM) converters, though being highly suited for current driving, are less studied. Simple control, low cost and independent dimming function are among the advantages of CSM SIMO converters. The limiting factors of CSM SIMO converters, however, include the relatively low efficiency and the restricted number of outputs under low-frequency pulse-width modulation (PWM) dimming control. In this study, an adaptive current bus technique to the CSM SIMO converter is applied. Results show that a significant improvement in efficiency can be achieved. The low-frequency PWM dimming method is also analysed and redesigned. Also, we compare the voltage stress in the CSM SIMO converter with traditional input-series-connected structure. Results show that the CSM SIMO converter achieves a high-voltage step-down ratio without the use of transformers. This study presents detailed analysis and experimental results of the CSM SIMO converter with adaptive current bus.

To characterise the grid-connected inverter with strong robustness against grid impedance, this study proposes an integrated design approach of LCL-type filter and controller parameters. In the approach, the inherent relation between LCL-type filter and controller in regarding to inverter robustness is revealed and utilised to realise the optimised match between LCL-type-filter parameters and controller parameters. To facilitate the analysis of stability and robustness, a parameter normalisation scheme is also proposed. With the scheme, relevant normalisation parameters can be designed succinctly according to the required stability and robustness. Additionally, the LCL-type parameter and controller parameter can be achieved immediately by restoring normalisation parameters. Based on the approach parameter constraints and design guidelines for robust grid-connected inverter design are also derived in the study to facilitate its application in practice. The proposed inverter design method can guarantee the inverter stability and robustness simultaneously without needing the complicated iterative computations, which cannot be avoided for conventional design methods. Simulation and experimental results are presented to validate the performance and demonstrate the merits of the integrated design method.

This study proposes a step-down converter based on the non-synchronous series-capacitor buck converter. Instead of the regular capacitor of the series topology, the Valley-Fill capacitor-diode structure is inserted in order to extend the step-down conversion ratio of the converter from D/2 to D/3, which leads to a gain ranging from 0 to 1/6, since the maximum allowed duty cycle is D = 0.5. The power stage employs only two active switches, five diodes, two capacitors and two inductors. The study investigates the mechanism of the Valley-Fill structure, analyses the pulse width modulation stages during a switching period, theoretically derives the gain considering ideal and non-ideal components, characterises the current distribution for the inductors and the voltage and current stresses among the power semiconductors and capacitors of the power stage. The proposed topology will be qualitatively and quantitatively compared to state-of-the-art step-down converters with similar gain. The study includes simulation and experimental results for a 300 V/12 V prototype up to 100 W of power and operating at 100 kHz switching frequency.