Since the invention of direct torque control (DTC) in later 1980s for alternating current (AC) motor drives, it has undergone many modifications to improve the control strategy. This study provides a comprehensive review of recent advancements of DTC of induction motor (IM) for the past one decade. Strategies adopted to improve the performance of DTC based on switching table, constant switching frequency operation, intelligent control, sensorless control and predictive control are extensively discussed with its key results and algorithms.

This study presents a simple ultra-low standby power control analogue circuit for home appliances using an AC power relay and charge capacitor for the gating delay of metal–oxide–semiconductor field-effect transistor (MOSFET) to control the power relay. In the standby mode, the AC power is fully disconnected by the relay to the home appliance, and connected by the user input action. To make sure there is enough time for the SMPS and the main MCU initialization, a simple charge capacitor and parallel connected sustaining signal are proposed. The capacitor saves the power during the user input action, and discharges to sustain the gating of MOSFET up to the SMPS activation. After start-up the SMPS and main MCU of home appliance, user input can be detected by the main MCU of home appliance, and the main MCU produces the sustain signal to keep the turn-on state. In the turn-off operation, the main MCU cuts off the sustaining signal by detecting of the user input signal. After the user input action to turn-off the power, the main AC power can be disconnected after the discharging of capacitor. The operating modes and power consumptions are analysed in the simulation and experimental results.

A new cascaded multilevel inverter (MLI) is presented with the aim of utilising lesser number of switches, better modularity and reduced voltage stress. The new structure configured under symmetric and asymmetric mode, produces all odd and even voltage levels. This structure comprises semi-half-bridge cells connected in series with crisscross switches to generate any target level for synthesising the sinusoidal output voltage waveform. In extension to the proposed topology, subinverters derived from the proposed MLI are cascaded with an objective to produce more voltage levels with reduced standing voltage. Compared with the cascading H-bridge topology, the proposed MLI and the extended version uses lesser number of semi-conductor switches. The MATLAB R2013b-based simulation results along with the experimental results validate the proposed topology.

This study introduces a soft-switching non-isolated bidirectional DC–DC converter with high voltage conversion ratio and low voltage stress across semiconductor devices. The presented topology is well suited for high step-up/step-down applications. By integrating coupled inductors and switched capacitors techniques, a high step-up/step-down voltage gain is achieved. Active clamp circuits are employed in both high step-up and high step-down operating states to recycle the leakage inductance energy and realise zero-voltage-switching condition for all switches to mitigate the switching losses and improve efficiency. Also, the reverse recovery problem of the body diodes is completely alleviated owing to zero-current-switching performance. The operation principles and theoretical analysis of proposed converter are presented in details. Finally, the experimental results of a 200 W prototype circuit are provided to confirm the validity of the proposed topology.

Two new pulse width modulation (PWM) methods are proposed for a dual two-level inverter (DTLI) fed open-end winding induction motor drive for complete elimination of zero sequence voltage (ZSV), enabling the DTLI drive to be powered from a single DC power supply only. One of the PWM methods is carefully devised and uses a single inverter only to be switched at all instants of time and dwell times of that switching inverter are derived by applying a simple volt-second balance principle, for ZSV elimination. The second PWM method involves switching of both the inverters, for ZSV elimination in the DTLI. While the dwell times of first inverter are derived using the concept of ‘effective-time’, whereas dwell times of the second inverter are obtained by thoughtfully exploiting the notion of ‘phase-shift’. Additionally, torque ripple performance of the open-end winding induction motor is theoretically analysed; ripple content is quantified to compare the performance of the proposed PWM methods. Finally, a typical PWM variant that results in the least torque ripple in the induction motor is recommended. All the envisaged ZSV elimination PWM methods and its variants are simple to implement and are first analysed, simulated and experimentally verified.

Reliability is an important requirement for a grid-connected photovoltaic (PV) system in remote military-secured areas, which are difficult to access for system maintenance. However, the reliability of the PV system is reduced by the use of electrolytic capacitors in inverters. Active power decoupling (APD) topologies eliminate the need for these capacitors by using an additional decoupling circuit. However, the vulnerability of switching devices to failure is another reason for reduced reliability of inverters, which is not addressed in these topologies. Several fault-tolerant topologies are proposed in literature to address this limitation. However, these topologies use electrolytic capacitors in dc-link, which affects the overall reliability of inverter. To address these limitations, a fault-tolerant strategy is proposed in this study. In the proposed strategy, a conventional APD topology is used along with an electrolytic capacitor in the dc-link. The lifetime of the capacitor is improved using the decoupling circuit of the APD topology. In this regard, a switching strategy is proposed, using which the current flowing through dc-link capacitor is reduced. Furthermore, in the event of a device fault, the topology continues to function like the conventional H-bridge inverter. The operation of proposed strategy is validated through simulation and experimental studies.

This study is focused on studying a resonant current converter for the electrical supply of dielectric barrier discharge devices. To understand the impact of parasitic capacitances and incorporate them into the design of an optimised power supply, this approach theoretically analyses a boost-based resonant converter, considering switch capacitance and analysing the impact of the transformer turns ratio on the system's electrical efficiency. The theoretical loss analysis shows a considerable variation in efficiency for different transformer turns ratios (between 38 and 90%). At low turns ratios, most of the losses are caused by switching, whereas at high turns ratios, the conduction losses outweigh the switching losses. The impact of the transformer stray capacitance is analysed via simulation and the optimised converter is used for the experimental validation of the theoretical study.

In this study, the analysis of a three-coil wireless power transfer (WPT) system, which can be divided into source, communication and load circuits, is discussed in details. Among the three-coil WPT systems features, it is demonstrated, for instance, that maximum efficiency () and maximum power transferred to the load (P _3MAX) do not depend on the load resistance, neither on the mutual inductance between communication and load coils. In fact, it is shown that and P _3MAX depend only on source and communication circuits parameters. Practical results are also presented, showing good agreement with the developed theory and validating the proposed analysis.

The reliability and lifespan of micro-inverters are two significant features of AC-module photovoltaic systems. One of the most effective methods to enhance the reliability and life duration of micro-inverters is achieved by substituting their electrolytic power decoupling capacitor with the film capacitors. In this study, a new DC/AC inverter based on an isolated single-ended primary-inductance converter with an active clamp power decoupling is introduced. The proposed converter has no electrolytic capacitor which results in long lifetime and high reliability. Moreover, the inverter has simple structure and low number of semiconductor switches which improve the efficiency and make it cost effective. The sufficient stepping up ability for output voltage without increasing turns ratio excessively, non-pulsating input current, and appropriate isolation make the proposed micro-inverter a proper choice for grid-connected applications. The converter operating modes are discussed and design considerations are presented. Finally, experimental results of the implemented prototype validate aforementioned features and performance of the proposed micro-inverter.

Multilevel inverters are one of the preferred choices in medium-voltage and high-power applications in the recent past. Active neutral-point-clamped (ANPC) inverter is the most popular topology, especially in the class of five-level (5L) inverters. In this study, a nine-level topology with improved output waveform quality is proposed based on ameliorating the 5L ANPC inverter with least modifications. The addition of only two switches operating at line frequency to the conventional 5L ANPC inverter while maintaining an identical precursor part count is the proposed modification. A logic form equation-based active voltage balancing scheme that is independent of load current and power factor is developed to regulate the flying capacitor voltage at the reference value. The operating principle, salient features, and the developed control scheme are comprehensively detailed. The operation of the proposed inverter considering a grid integrated case is simulated in MATLAB/Simulink, and the results corresponding to steady-state and dynamic conditions are presented. The benefits of the proposed topology are elucidated by comparing it with other classic topologies considering various prominent viewpoints. This comparison has illustrated the proposed topology's distinctive characteristics and profound advantages. The performance validation, feasibility, and practicability of the proposed inverter are established through the experimental results obtained from a laboratory-scale prototype.

Driver of a low-profile organic light-emitting diode (OLED) luminary due to space constraints uses a planar inductor with ferrite layers to realise desired inductive properties. This study presents the analysis of usage of ferrite layers with single-coil and double-coil windings in the OLED driver. The model based on magnetic circuits is used to analyse the inductance and the quality factor. The influence of the winding dimensions and the ferrite layers is analysed. The analysis is verified by electromagnetic simulations and measurements. The results of vector network analyser measurements show that the double-coil design has the maximum inductance ∼80% and maximum quality factor ∼10% larger than the single-coil design. The measurements of the planar inductors in the OLED driver show that the best-case single-coil and double-coil inductors have a similar efficiency, but the double-coil inductor has a 35% smaller current ripple which leads to better EMC performance of the driver. It is concluded that it is sufficient that the ferrite layer covers the inductor, i.e. it does not have to be much larger than the inductor to achieve good performance.

The effect of sampling frequency on digital sinusoidal pulse width modulated (SPWM) output of phase-shifted carrier-based multilevel voltage source inverter (VSI) and the characteristics of output voltage and load current has been discussed here. The generalised equation of digitally controlled phase-shifted carrier-based multilevel VSI output voltage is derived using double Fourier integral solution. The Jacobi–Anger expansion has been used to obtain the integral solution. Time-domain analysis has been used to establish the relation between sampling frequency, carrier frequency, and fundamental frequency, at different modulation indices for n-level VSI. The load current of VSI is stepped in nature due to stepped variation in the output of the digital SPWM. Therefore, the low-frequency harmonic components closer to the fundamental frequency appear in the frequency spectrum. The variation of total harmonic distortion with respect to multisampling factor (sampling to carrier frequency ratio) has been discussed at different modulation indices for multicarrier-based multilevel inverter. The analytical results are verified through simulation and laboratory experimental results.

High harmonics in supply currents of three-phase controlled/uncontrolled converters are creating many problems to the power system and customers at point of common coupling. Third harmonic current injection technique is an excellent option for harmonic reduction of these converters. Minimum total harmonic distortion (THD) for any firing angle of controlled converter is function in phase-angle and amplitude of harmonic injection current that can be controlled by single-phase controlled converter and boost converter, respectively. A novel scheme with three bidirectional switches and single-phase controlled converter to circulate the injection current to supply currents has been introduced. This novel scheme is compared to the state-of-the-art system using zigzag transformer. A novel mathematical analysis showing the optimum values for components on the harmonic injection path at minimum THD and the corresponding efficiency for the proposed scheme and state-of-the-art scheme is introduced. Two lab prototypes for these two schemes have been implemented, discussed, and compared to show the benefits of using the new proposed scheme. The results show the superiority of the new proposed scheme.

This study proposes a model predictive stator current control (MPSCC) strategy of doubly fed induction generator (DFIG) under unbalanced grid voltage conditions. Sinusoidal and balanced stator currents injected into the power grid can be ensured due to the direct control of stator currents rather than rotor currents. Model predictive control instead of traditional vector control is adopted, which can increase the current loop bandwidth and obtain faster dynamic responses. Conventional resonant regulators such as second-order generalised integrators or second-order vector integrators that are usually used to eliminate unbalanced components in stator currents can also be avoided. Moreover, both extractions of negative sequence components in rotor or stator currents and calculation of commanded rotor current are avoided, which simplifies the control scheme. The proposed MPSCC strategy can also implement the grid connection by introducing the virtual stator currents without any changes in the control scheme. Finally, experimental results based on a 1 kW lab DFIG system are provided to validate the effectiveness of the proposed control strategy.

This study aims to present a two-output three-level series-resonant inverter together with an implementation and experiments for an induction melting application. A three-level circuit is applied for each branch of inverter in order to decrease the voltage stress on switching devices. A phase-shifted pulse-width modulation (PSPWM) with variable frequency control is applied for providing and maintaining a zero-voltage switching condition over a wide load range. In addition, the PSPWM could provide symmetrical output voltage and current waveforms that result in decreasing the THD _v and THD _i of output waveforms and harmonic losses of high-frequency transformer cores comparing to other PWM schemes. Finally, the prototype was designed, built, and tested to verify the consistency between the experimental results and theories of the proposed inverter.

Here, a non-isolated-based single-stage integrated bidirectional converter has been proposed for plug-in electric vehicles, which has the capability to achieve all modes of vehicle operation, i.e. plug-in charging, propulsion, and regenerative braking. This integrated converter has improved efficiency of 2–2.5% in propulsion boost and regenerative braking buck modes over existing non-isolated integrated converters which leads to a long run of vehicle and saves the electricity usages. Despite the proposed converter has two inductors, the size of the second inductor is approximately reduced by 35–40% compared with single-inductor converters. A detailed loss analysis of the proposed converter is investigated in propulsion boost and regenerative buck modes. Further, the design considerations of passive components are presented to achieve continuous conduction operation in each mode as well as low capacitor voltage ripple. Experimental results confirm the effectiveness of the proposed converter.

This study presents a light emitting diode driver circuit topology based on a full-bridge configuration with dimming control. It is more suitable for high power lighting loads. The proposed configuration has advantages of zero-voltage switching, reduced component count and high efficiency. It can power multiple lighting loads. Operation of the proposed circuit configuration is explained in detail and it is validated through simulated and experimental results on the 145 W experimental prototype with dimming control.

In this study, the discrete-time model is used to analyse a constant on-time one-cycle controlled boost converter operating in continuous conduction mode. Then, it derives the critical boundary between continuous conduction mode and discontinuous conduction mode. In terms of Newton–Raphson methodology, the numerical solutions of fixed points are obtained. Thereafter, the stability of closed-loop boost converter is analysed based on its Jacobian matrix. It remarks that a couple of conjugate multipliers of Jacobian matrix of the system cross the unit circle gradually with constant on-time value increasing, while the step-up power stage moves from period-1 state into Neimark–Sacker bifurcation. Based on the stability analysis, an additional current loop is developed to improve the control for extending the stable region. Finally, simulation and experimental results well validate the theoretical analysis.

The authors report on a large area, fully screen-printed transistors, using nanostructured silicon as the active material. The transistors are produced by simple screen printing processes under ambient conditions without the need for post-processing steps. The devices can be operated as two-way switches both with a direct or alternating current (AC). The authors demonstrated the operation of the devices printed on flexible substrates (office paper 80 g/m²) using silver as the conductive electrodes and highly doped p-type nanostructured silicon as the active layer. A method of switching sinusoidal AC using a single printed transistor is demonstrated at a frequency of 50 Hz at ambient condition. The silicon used as active materials, present domains, and blocks at a microscopic level, with an electric behaviour similar to one of the varistor-like components used as surge suppressors. So, unlike conventional transistors which rely on electric field modulation or charge injection, these AC switches operate by activation transport of charge carriers in the active silicon layer. Switching AC is achieved by applying a signal to the base which results in a change of the current's direction from between the collector and base to between the base and emitter.

This study presents a general control strategy for active power filters derived from the current-shaping principle previously employed in shunt active filters. The generalisation introduced here and denoted as voltage–current shaping control, exploits the symmetry between the possible wave-shaping solutions, and can be applied to shunt, series, and more complex networks of active filters. Moreover, the proposed generalisation allows the synthesis of specific control schemes with a reduced number of sensors. The relevant properties of the proposed schemes in the application of harmonic mitigation are determined. Further, a discussion of the integration of multiple quasi-resonant schemes is presented. Using this approach, it is possible to fine-tune the mitigation of specific components in the harmonic profile from the voltages or currents in the circuit. Experimental results obtained from using a 1 kVA prototype are presented to support the proposed generalisation.

For a wide dc input voltage range of photovoltaic (PV) array, a two-stage grid-connected inverter that allows input voltage regulation is required. This study proposes a topology with time-sharing synchronous modulation in which energy transmission paths, wheeling branches and switching losses for high-frequency switches are optimised to achieve efficiency improvement. The small-signal model of proposed topology is analysed in detail. A hybrid current control strategy based on frequency-amplitude domain analysis is presented. To solve further transitional problem on boost–buck mode switching, the controller uses a carrier-overlapping pulse-width modulation (PWM)-based generator. Then, the effectiveness of the proposed topology and the control strategy under different experimental conditions are verified. Experimental results indicate hybrid current control strategy promotes current waveform quality and the burrs and oscillations in transition between buck mode and boost mode can be reduced.

The present work introduces the concept of classical reactive power (Q)-based model reference adaptive system (MRAS) for the speed estimation and control of low-cost BDFR motor drive. The reasons behind such choice for this drive's control are: (i) MRAS-based controllers can inherently take care of the machine parameter variations which had been a challenging issue with the other available sensorless speed estimation strategies and (ii) the employment of Q as a functional candidate inevitably makes the formulation immune to the variations in stator resistance. The experimental assessment, in this respect, confirms these claims. Furthermore, the analytical validation of Popov's hyperstability criteria on the proposed controller, confirms the drive's overall stability within the investigated speed control range. The speed control performance is examined in MATLAB/Simulink. The simulation results are further validated by a real-time implementation using dSPACE-1103-based 1.6 kW BDFR machine prototype.

DC-link current is an important parameter for selection and design of DC-link capacitor or battery. Considering the AC current ripple, this study introduced a general DC-link current real-time prediction method for three-phase two-level voltage inverters (three-phase 2L-VSI) using the pulse width modulation. Compared with the traditional analysis which just takes AC average current into consideration, the time-domain comparison and spectral analysis of DC-link current have been studied. Meanwhile, accurate calculation of RMS current on the DC-link capacitor has been provided. Simulation results and experimental results are provided to support the analysis and proposed method.

Considering that so far all studies regarding multiphase drives fault tolerance performance have been carried out making use of conventional two-level inverters, this study discusses the fault tolerance performance of a six-phase drive system based on a dual inverter under single-, two-, or three-phase open-circuit fault. Aiming applications where simplicity and low computation efforts are required and fast dynamic response is not imperative, an open-loop volts/hertz (V/f) compensation strategy is discussed in order to keep the rated operation even after the occurrence of the fault, assuring the maintenance of sinusoidal flux. The six-phase machine mathematical model after the fault is detailed and utilised to elaborate the compensation strategy. Simulation and experimental results show the validity of the discussed solution and its feasibility.

This study presents the development, design and performance analysis of a multistring bidirectional solar inverter connected to the grid (BSICG). An algorithm for the independent global maximum power tracking was both developed and implemented, which produced a system immune to non-uniform irradiation conditions with the aim of applying such on DC (direct current) microgrids connected to a conventional AC (alternating current) grid on the BSICG, which is characterised by bidirectional power flow management. The main advantage of this proposal is thus highlighted as the stabilisation of the voltage on the DC bus even when confronted with irradiance intermittencies from photovoltaic solar energy. All theories are presented and corroborated through experimental results obtained from a 2.0 kW prototype.