Rectangular spiral coils are easier to implement in wireless power transfer (WPT) applications than circular spirals. Despite this fact, research into mutual coupling between rectangular spiral coils is insufficient. In this study, a new analytical model of mutual coupling is proposed, which converts a complex multi-turn rectangular spiral coil into a single-turn rectangular coil, simplifying calculation of the self- and mutual inductances. The mutual coupling between two different arbitrarily sized rectangular spiral coils with lateral misalignment and the rectangular cross-sections can be described accurately using this model. A series of experiments is carried out, the results of which agree well with the results of calculations. Finally, the effect of the number of turns in a coil on the coupling coefficient is discussed in order to determine the recommended number of turns. This research provides an effective tool for the design of a WPT system.

Hysteretic comparators are often used to implement sliding-mode controllers or other type of discontinuous regulators for power switching converters. Their design is usually performed analogically yielding robust and fast controllers that can even allow converter operation with high values of duty cycle. A new analogue implementation based on a low-cost microcontroller is described in this study showing the mentioned advantages plus the flexibility of a programmable digital system. The proposed comparator employs some microcontroller peripherals without consuming execution time of the control algorithm and without requiring interruption management. It provides variable hysteresis width to obtain constant switching frequency in sliding-mode strategies and can be used in any type of hard switching converter. The dynamic performance of the method is verified experimentally in a boost converter-based rectifier with power factor correction and output voltage regulation in one single stage. The boost converter operates in sliding mode with constant switching frequency and results in a total harmonic distortion of the input current <1%.

Recently, switched-inductor Z-source inverters (SL-ZSIs) have been reported to achieve high-voltage gain and good power inversion operation at low shoot-through duty ratio D as compared to conventional ZSI. As the SL-ZSIs have high passive component count, weight, volume and losses of the system increases that lead to reduction in efficiency. To address the issues of conventional ZSI and SL-ZSIs, two single-phase switched LC (SLC)-ZSIs (Type 1 SLC-ZSI and Type 2 SLC-ZSI) are proposed in this study to achieve high-voltage gains at low values of D with lower passive component count as compared to SL-ZSIs. At low values of D, modulation index M approaches to higher values which results into improved AC output at reduced harmonic distortion. Due to low passive component count in the proposed inverters, weight, volume and losses decreases resulting into increase in efficiency. The proposed inverters can be used in various DC–AC and DC–DC power conversions in renewable energy applications due to their high-voltage gain, better immunity to EMI noise and higher reliability. The detailed steady-state analysis of the two proposed SLC-ZSIs is given in this study. Scaled down experimentation has been carried out to verify the performance of the proposed inverters.

Open end winding induction motor (OEWIM) drives are better alternate for multi-level inverter fed induction motor drives. OEWIM drives can be used in industries and electric vehicles but they entail ripple-free torque. Predictive torque control (PTC) strategy offers high dynamic performance and lesser ripple in torque, flux when compared with direct torque control. Classical PTC involves high switching frequencies and empirical methods to select weighting factors. The selection and tuning of weighting factors are cumbersome. In this article, a new normalised weighted sum model (WSM) based PTC of four-level inverter fed OEWIM is introduced to curtail torque, flux ripples, switching frequency and enhance the selection of weighting factors. The proposed algorithm uses multi-objective cost function and the optimisation of cost function is performed by using normalised WSM. The normalisation of individual cost function simplifies the selection of weighting factors to select optimal voltage vector. As a result, the proposed PTC offers all the features of classical PTC and overcomes the difficulties involved in classical PTC. Simulation and experimental studies are performed on dual inverter fed OEWIM with four-level inversion. The effectiveness of proposed algorithm is verified by comparing proposed PTC algorithm with classical PTC algorithm.

This study presents a soft-switching converter for direct current microgrid applications. The studied converter includes n cells of the hybrid full-bridge converter with primary-series–secondary-parallel connection for high-voltage input and large current output applications. Thus, the voltage stress of power switches and the current stress of rectifier diodes are decreased. Therefore, the low-voltage stress and low conduction resistance of power metal–oxide–semiconductor field-effect transistors are utilised in the studied converter to reduce conduction losses on power switches. The flying capacitors are connected between each circuit cell to prevent voltage unbalance on input split capacitors. On each circuit cell, a full-bridge converter with an additional half-bridge circuit is employed to achieve low circulating current losses, less output inductance and a wide range of zero-voltage switching. Finally, the studied converter with 1800 W rated power is constructed and tested to verify the theoretical analysis.

Here, applying the coupled inductor and the capacitor to the isolated light-emitting diode (LED) driving circuit is studied, and hence an isolated two-channel LED driver featuring automatic current balance and zero dc magnetising inductance current is presented. In the proposed LED driver, each winding of the transformer has a capacitor connected in series. Therefore, the dc magnetising inductance current is zero, and hence the entire core B–H curve loop can be utilised, which can lower the core size. Moreover, due to the capacitor on the secondary side, the LED currents can be balanced naturally. The two-channel isolated LED driver can be extended to a multi-channel LED driver without increasing the output voltage. Therefore, the duty cycle of the multi-channel LED driver is determined by the sum of the voltages of two LED strings. Finally, the detailed theoretical analyses and experimental results are provided to verify the feasibility and effectiveness of the proposed LED driver.

Modular multilevel converters (MMC) have proven to be a viable candidate for high-voltage direct current transmission systems. Here, asymmetric modular multilevel converters (A-MMC) are introduced wherein each series connected module has two half-bridge (HB) submodules, with asymmetric voltage rating. Compared to conventional symmetric MMCs, such systems offer the following benefits: (i) generation of four distinct voltage levels using one module; (ii) 33% lesser semiconductor and gate drive requirement; (iii) higher system efficiency; (iv) reduction in overall cost and size. A hybrid pulse-width modulation technique generates optimised switching pulses of the A-MMC. A novel voltage balancing algorithm is proposed to stabilise each asymmetric HB submodule at the rated voltage. Circulating current control is implemented to suppress the dominant second harmonic in the arm currents of the A-MMC. Detailed simulations in MATLAB/Simulink are performed to validate the operation and control. A quantitative and qualitative comparison with conventional MMCs is also presented in terms of the converter losses, output voltage/current total harmonic distortion, capacitor ripple voltages, circulating currents etc.

In this study, two new structures of single-phase hybrid multilevel inverter are proposed for both symmetrical and asymmetrical configurations that can be employed in drives and control of electrical machines and connection of renewable energy sources. The proposed configuration uses a less number of semiconductor devices and DC sources as compared with conventional and newly developed topologies which lead to a reduction in cost and installation area. The proposed topology poses a vital advantage of self-voltage balancing of its capacitor voltage regardless of load type, load dynamics and modulation index. Also, the proposed topology is expanded in a cascaded fashion which reduces the complexity and improves the performance significantly. A wide range of comparison is done with conventional and newly developed topologies to show the superior performance of proposed topologies regarding a total number of switches and DC sources. The multi-carrier pulse-width modulation strategy is adopted for generating switching pulses for respective switches. A laboratory prototype is developed for testing the performance of the proposed topology for 9-level and 17-level inverters.

A novel non-isolated high step-up high-power DC–DC converter based on coupled inductor (CI) and voltage multiplier cell (VMC) for renewable energy DC microgrids is presented in this study. A hybrid combination of three-phase interleaved boost converter with three CIs is chosen to reduce the current ripple at the input and meet the high-power requirement. Three VMCs connected at the secondary side of the CIs serve as gain extension cells. The voltage stress experienced by the switches is only a fraction of the output voltage as the gain extension is mainly achieved at the secondary side of CIs. Practical results obtained from the proposed converter which operated from a 60 V input and provided an output voltage of 1.1 kV while delivering 3 kW of output power prove the correctness of the design details and validate the proposed concept.

In this study, first, a new definition is proposed for the state of the boost converter. In this approach, the state is defined based on the relative value of two successive samples of the output voltage with respect to the reference voltage. Then a finite-state-machine (FSM) model, which takes into account the possible variations of the input voltage and load resistance, is proposed. This model is discrete-time and represents the evolution of states implicitly based on the events like load and input voltage variation. One advantage of this model is that it is valid both in continuous conduction mode and discontinuous conduction mode. At the next step, a voltage-mode controller, which can regulate the output voltage at the presence of load and input voltage variations, is proposed. Stability of the resulting closed-loop system is studied using the FSM model and the discrete-time Lyapunov method. Simulations and experimental results are presented.

Electric components in numerous applications (particularly wind generation) are not straightforwardly accessible for monitoring. Therefore, the monitoring and protection through voltage/current measurement may not be dependable since the current value passes numerous segments to reach the observing element. Accordingly, finding an unusual phenomenon of a specific element is difficult. To resolve this issue, using transmitted electromagnetic field of an element for wide area condition monitoring is proposed. It is planned to diagnose and locate short-circuit in induction generator drive such as interturn, intercoil and terminal-to-turn failures. The frequency characteristics of the propagated field is then utilized for finding the short-circuit. The theoretical foundation that relate the behavior of each elements to their frequency response is analyzed and used. To utilize the derived technique for different practical circumstances, two distinctive methods are used for locating the short-circuit. As the experimental test of major fault cases could destruct the winding, the full three-dimensional finite element analysis is used in these cases and some are verified experimentally through the wide area communication. Identifying the areas of partial faults Prevents the whole winding failure prior to a massive destruction, which is costly especially for cases in inaccessible situations such as offshore wind towers.

Nowadays, low power factor (PF) is a serious problem that has gained more importance in power electronics area. In this study, a unity PF control (UPC) strategy for boundary conduction mode (BCM) buck–buck/boost PF correction converter is proposed. The proposed control strategy can achieve high PF and low total harmonic distortion by utilising the input and output voltages to modulate the on-time of both buck and buck/boost switches. The operating principles and comparative analysis of BCM buck–buck/boost converter with conventional non-UPC and UPC are analysed. For verifying the effectiveness of the proposed control strategy, the experimental verifications are carried out from a 100 W universal input prototype.

This study proposes a generalised double line voltage synthesis strategy for 3 × N matrix converter. This strategy is simple without segment partitions and combinations, and it can be easily extended to any number of output phases. In order to gain the maximum VTR, the input line-to-line voltages and the ‘source key’ are selected reasonably, according to the polarity of the input and output phase voltages which have maximum absolute value. The relationships between input and output voltages are obtained and the general expressions of duty ratios are derived. Further, input currents are analysed when input voltages are balanced or unbalanced. In addition, this study also proposes an innovative arrangement of switching sequence, which makes the relationship of duty ratios only one fixed case. This strategy reduces the complexity of control algorithm and inherits the advantage of traditional method. Desired output voltages are realised under both balanced and unbalanced input voltages. The feasibility and effectiveness of the proposed strategy are validated through the experimental results of 3 × 3 MC and 3 × 5 MC.

This study presents a novel high conversion gain converter with a tightly coupled-inductor-inverse for distributed generation system, where high conversion gain is regularly required. The new converter utilises coupled-inductor-inverse network for high conversion gain applications that is not presently comparable with the existing coupled inductor-based high conversion gain converters. The new converter has a unique feature that the voltage gain is lifted by reducing the turns ratio of the coupled inductor. Subsequently, the diode–capacitor circuit is introduced to primarily recycle the leakage energy, and secondly help to boost the output voltage. This study depicts the main waveforms of the proposed converter and the relevant derivation of the operation principle. The theoretical analysis is verified by the experimental waveforms based on a prototype circuit rated 400 W output power.

The significant reduction in switch count of symmetrical/asymmetrical reduced switch count multilevel inverters (RSC-MLI) topologies has modified the operation of inverter such that the conventional carrier-based pulse width modulation (PWM) schemes such as level-shifted PWM and phase-shifted PWM can no more realise them. To control these RSC-MLI topologies, reduced carrier PWM schemes with modified switching logic gained more prominence. These schemes involve suitable logical expressions to realise the switching states of the inverter. However, these logical expressions vary with topological arrangement and number of levels. Moreover, these schemes produce high total harmonic distortion (THD) in line-voltages. Therefore, to improve the line-voltage THD and generalise the switching logic, a modified reduced carrier PWM scheme with unified logical expressions is presented here. The proposed PWM scheme is directly valid for any topology and can be easily scalable to any number of levels in the inverters. To validate the implementation of the proposed PWM to control any RSC-MLI, experimental studies of various asymmetrical RSC-MLI topologies with the proposed PWM scheme are carried out. Further, to verify the superiority of the proposed scheme in terms of THD, complexity, scalability, and computation burden, its performance is compared with carrier-based PWM schemes reported in the literature.

This study presents a 17-level inverter-based induction motor drive for high-resolution multilevel voltage space-vector (SV) generation. The proposed topology consists of a three-level inverter and a seven-level inverter connected to an open-end winding induction machine. The two inverters are powered by two unequal DC supplies, resulting in a low component count, with just 12 switches and three floating capacitors per phase. The voltage SVs applied by the two inverters are chosen to eliminate circulating power flow and prevent DC bus overcharging. In addition, the switching states of both inverters are chosen in order to keep voltages of all floating capacitors well-controlled. Since the capacitors voltages are controlled using the phase currents, additional pre-charging circuitry is not required. A modulation scheme using level-shifted carriers has also been developed, which can be used with both V/f control and d–q control. The high-voltage inverter has a low effective switching frequency and the low-voltage inverter has a high effective switching frequency, reducing the switching loss. The included results of steady-state and transient testing of an experimental prototype demonstrate that the proposed scheme is suited for industrial drives and traction applications.

A line-modulation-based flux-weakening control is proposed for surface-mounted permanent-magnet synchronous machines. To evaluate the average dc bus voltage utilisation, the maximum line-modulation-ratio, which cannot be >1, is defined. If the maximum line-modulation-ratio is equal to 1, the voltage capacity of voltage-source-inverter is fully utilised, which means the dc bus voltage utilisation has been maximised. Without special declarations, the overmodulation scheme is not utilised in this study. The line modulation is employed in the proposed flux-weakening control, in which the average dc bus voltage utilisation can be maximised by regulating the maximum line-modulation-ratio to 1. Compared with the conventional flux-weakening control, the proposed one is simpler and its copper loss can be reduced. The reason is that the proposed flux-weakening control employs the line modulation while the conventional flux-weakening control usually adopts the space vector pulse width modulation. The effectiveness of the proposed flux-weakening control is verified by experimental results.

Although hysteresis band current control is an easy to implement and robust control method for industrial power electronics converters, it has also some disadvantages like variable and high switching frequency causing high switching losses. In this study, a novel adaptive fuzzy hysteresis band current control system is proposed by making use of fuzzy expressions of both hybrid active power filter (HAPF) current and integral of its harmonic components to reduce the switching losses of three-phase three-wire two-level HAPF. To reach this aim, a relation between switching frequency and integral of filter current harmonic components is formulised and used for defining a fuzzy hysteresis band. Moreover, the magnitude of the instantaneous current switched is also correlated to the switching losses; in this way, its fuzzy expression is also used for defining hysteresis band. Those fuzzy expressions are then utilised to constitute a dynamically changing hysteresis bandwidth. The proposed control system is finally optimised using EMTDC/PSCAD simulation environment and implemented in the field. The implemented HAPF system has been shown to successfully suppress all the interharmonic and harmonic current components produced by a steel melting facility occupying three induction melting furnaces and it has provided around 9% reduction in overall losses.

A two switch three-phase power factor correction SEPIC converter with coupled inductor operating in discontinuous current mode is presented. The switches voltage stress in this converter is related to peak of phase voltage instead of line voltage. Also, applying coupled inductor technique, not only reduces number of the magnetic cores but also with suitable design of coupling coefficient, input current ripple cancellation is achieved, so smaller inductor size can be used as input inductance. Thus, the proposed converter only applies three magnetic cores and <5% THD is achieved with the proposed converter in a wide range of load and input voltage variations. Input phases are decoupled so converter can keep unity power factor even under unbalanced input source. Operating modes of the proposed converter is explained, and its input impedance is determined. It is verified that input impedance is pure resistive. The mathematical analysis and design procedure are discussed. Design example and experimental results from 400 W prototype with 220 V line to natural input RMS phase voltage and with 400 V output voltage operating at 40 kHz are presented to verify theoretical analysis.

A novel differentiation phase locked loop (dPLL)-based control technique is used for control of a three-phase hybrid wind–solar grid connected inverter (HWS-GCI) with a capacitor-supported DC link. The DC link is simultaneously interfaced to a solar photovoltaic and permanent magnet brushless DC wind generator via unidirectional DC–DC converters, in a two-stage topology, to channelise excess power generation to the grid, thus increasing the energy conversion capability. In addition, the HWS-GCI is used as a distribution static compensator to enhance the dynamic performance of the system, by the use of a novel harmonics isolation control algorithm based on differentiation and variable coefficient proportional–integral–derivative controller. The algorithm possesses fast dynamic response and preserves the mutual relationship of the three-phase currents, allowing the accurate detection of load side or source side phase unbalancing. A comparison of the proposed technique with previously known methods is provided to establish the competency of the algorithm. The experimental performance validation under non-linear load unbalancing and sudden changes in solar insolation and power generated by a wind generator are considered using the real-time implementation platform.