This study suggests a novel ultra-step-up dc–dc converter with low normalised voltage stress across the power devices. The proposed converter incorporates the conventional boost converter with a self-lift circuit and charge pump concept and utilises a voltage multiplier cell at the output side. In the input side, two inductors are magnetised during the switch on-time. During the switch off-time, the stored energy in these inductors, charge pump capacitor and input source, is delivered to the load. Accordingly, the proposed converter is capable of providing high voltage gains with a small duty cycle. Besides, the voltage stress across the power devices is low. Therefore, the MOSFET switch with low R _DS-on and devices with reduced nominal voltage can be used which in turn reduces the conduction and turn-on losses. The analysis of the voltage and current stresses is accomplished. The circuit performance is compared with other solutions in the literature in terms of voltage gain and normalised voltage stress of the semiconductors. Eventually, to validate the theoretical analysis, the experimental results are given.

Flexible interconnection switch (FIS) is a power electronic device applied to electrical distribution system to realise the flexible control of power flow. Due to the fact that the reliability of FIS tends to be influenced by its operating conditions and dynamic characteristics during its actual operation, it is of significance to characterise the effects of loadings on reliability of FIS. Therefore, an improved reliability model of FIS is proposed, considering the state uncertainty of current and voltage loadings. First, the structural reliability model of modular multilevel converter (MMC) is established. Next, in view of the uncertainty of source and load in distribution network, Monte Carlo simulation is used to deal with the random current loadings, thus the equivalent reliability model of insulated gate bipolar transistor module is built. Then, considering the arm's voltage loading sharing mechanism, a state-dependent arm reliability model is built. Finally, an eight-state reliability model for the entire FIS is developed, and Markov-based analytical method is used to solve it. With the standard test system as well as the actual project in Hangzhou are taken as the testing systems, the reliability indices of FIS are calculated and compared with the field data. The numerical results validate the validity of the proposed model.

In this study, a quadratic-based transformerless high step-down DC-DC buck converter is presented. There are two switching patterns applied to the switches. Through the first switching pattern, the proposed converter provides a constant step-down voltage conversion ratio for the whole ranges of duty cycles. On the other hand, by using an interleaved switching pattern for the proposed converter the input voltage will be divided equally between the primary capacitors, as a result, low voltage stress will be across the semiconductor components. This feature allows the designer to select switches and diodes with lower voltage ratings. However, with the interleaved switching pattern, the converter will have two different voltage conversion ratios for duty cycles larger and less than 0.5. Furthermore, the proposed converter is capable of providing a high range of currents without applying extremely narrow duty ratios. Theoretical analysis is provided in this study. To show the merits of the proposed converter, it is compared with other similar recently presented converters. A 430 W prototype of the proposed converter with 600 V/20 V is implemented and experimental results are presented and compared with the theoretical ones.

This document studies torque degradation of an internal permanent magnet motor due to an incorrect rotor angle measurement when low rotor angle resolution sensors are used. The performance of the control with different rotor angle resolution is also analysed to determine the torque error due to the use of an incorrect synchronous rotating reference system. To address torque degradation due to the low resolution of Hall sensors, a new method of estimating the rotor angle is proposed that incorporates the information from Hall sensors. In this way, good resolution is achieved, allowing the machine to be controlled over a wide speed range even with rated torque. This method is validated through simulations and real experiments.

This study proposes a practical control strategy of passivity based control (PBC) of the power conversion system (PCS) used in the energy storage system. First, the differential equations based on the Kirchhoff voltage and current laws are listed in the study, and the mathematical model in Euler–Lagrange form is also given. On the basis of the PBC theory, the system passivity of the PCS is demonstrated, the implementation of differential equations based on the damping injection principle is deduced, and simulation results in SIMULINK are also given. The PBC strategy has the advantages of high stability globally in a nonlinear system, and strong robustness to the system parameters deviation and external interference. Finally, a PCS prototype of 10 kW, which is made up of ac–dc converter and dc–dc converter, is built and the experimental results verify the correctness and effectivity of the proposed solution.

This paper proposes three new direct power control (DPC) algorithms which minimise the variation of the common mode voltage (CMV) provided by a transformerless grid-connected three-level neutral point clamped (3L-NPC) inverter. The proposed techniques make use of three reduced switching tables designed with the aim to control the active and reactive powers and to minimise the variation of the CMV. The first switching table uses large, medium and zero vectors of the space vector diagram; it is therefore named large medium zero vectors DPC. The second table uses the medium and zero vectors. It is referred to as medium zero vectors DPC. The third one namely medium vectors DPC, uses only medium vectors. Numerical simulations and experimental tests carried out on a laboratory prototype of the 3L-NPC inverter confirm the feasibility and effectiveness of the proposed algorithms.

A high-gain single-stage three-phase coupled-inductor diode-assisted boost inverter (CL-DABI) is presented for energy applications. A new scheme has been proposed which is simple, has less number of energy storage components and uses non-shoot-through pulse-width modulation (PWM) techniques such as sine-wave PWM and space vector modulation to get the maximum gain from a low-voltage dc source. During simulation and hardware implementation, it was observed that the SPWM method resulted in a lower conversion rate and higher device stress. To improve the shortcomings, extended sine-wave PWM (ESPWM) method is proposed to achieve high gain without compromising the conversion efficiency and putting devices under stress. Mathematical analysis, simulations results and experimental verifications are presented here. Hardware results prove the validity of the proposed CL-DABI with ESPWM by achieving high intermediate dc gain, excellent dc–ac coupling, less device stress, comparable power quality and smaller size.

This study presents a control system to track the sinusoidal ripple current (SRC) of lithium (Li)-ion batteries. In this method, a combination of a DC and a sinusoidal ripple current is injected to the battery. By choosing the appropriate frequency, the minimum AC impedance of the battery is obtained. This study, the impact of temperature has been considered as a protection criterion in the proposed charge algorithm, also a state-space model of the charger system has been developed, and finally a pole placement controller has been proposed to control charging current. To evaluate the design, a laboratory setup has been implemented to obtain experimental results from a 1 kW Li-ion battery pack. Also, simulations have been carried out by Simulink/MATLAB. The proposed pole placement control method for tracking of SRC and the optimal frequency detection algorithm have been designed and tested on a practical 10 Ah Li iron phosphate battery pack in different charge modes. In addition, results of the conventional proportional–integrator (PI) controller have been compared with the proposed controller. Both simulation and experimental results show the effectiveness of the proposed algorithm and control system to track SRC reference current in all frequencies.

An integrated soft switching cell and clamp circuit suitable for interleaved high-step-up converters with coupled inductors is proposed in this study. This cell is applied to an interleaved boost converter with winding cross-coupled inductors and series capacitors. The main contribution of the study is presenting a simple auxiliary circuit which provides soft switching condition and acts as a clamp circuit. In addition, only one auxiliary circuit is utilised for both phases of the proposed converter in order to absorb the energy of the leakage inductances and achieve fully soft switching condition. To verify the theoretical analysis and the operation of the proposed converter, a 300 W prototype converter with 24–380 V conversion ratio is implemented.

In this study, a sensorless hybrid control scheme for brushless direct current (BLDC) motors for use in multirotor aerial vehicles is introduced. In such applications, the control scheme must satisfy high-performance demands for a wide range of rotor speeds and must be robust to motor parameter uncertainties and measurement noise. The proposed controller combines field-oriented control (FOC) and direct torque control (DTC) techniques to take benefit of the advantages offered by each of these techniques individually. Simulation results demonstrate the effectiveness of the proposed control scheme over a wide range of rotor speeds as well as good robustness against parameter uncertainties within for inductance and for resistance parameters. The proposed hybrid controller is robust also against noise in voltage and current measurements. In order to verify the results from simulation, the proposed hybrid controller is implemented in hardware using the TI C2000 Piccolo Launchpad and TI BOOSTXL-DRV8305EVM BoosterPack. Testing is done with a Bull Running motor typically used in aerial drones. Testing experiments demonstrate that the hybrid controller reduces the rotor speed ripple when compared to DTC while operating in steady-state mode and decreases the response time to desired speed changes when compared to FOC.

This study proposes a modified modulated model predictive control (MMPC) scheme to control an open-end winding induction motor drive using an asymmetric source dual inverter with one floating bridge. The control algorithm uses a modulation algorithm within the cost function optimisation scheme to avoid variable switching frequency. The voltage of the floating capacitor is regulated utilising predefined redundant switching sequences as well as the voltage vector location is identified to improve calculation time. The proposed MMPC scheme enhances the output performance with comparison to the model predictive control scheme. Experimental results are presented to verify theory and simulation results.

DC distributed power systems (DPSs) have attained much attention because of its characteristics of high efficiency, high power density and flexible configuration. However, when converters are interconnected in a system, adverse interactions may occur due to the converter sensitivity to the external impedance, these interactions may degrade converters transient performance or cause stability issues. Currently, research mainly focuses on DPS with a DC voltage bus, including stability analysis and approaches to improve system stability. This study is to establish stability criteria for DPS with a DC current bus. Firstly, basic current type DC/DC converters and their small signal models are introduced. Then, the current bus DPS is derived, discussed, and the stability criteria are obtained by using two-port small signal model. The proposed criteria are verified by comparing the results of theoretical calculations and simulations. Finally, an experimental prototype is built to validate the theoretical analysis and simulation.

This study studies a two-input boost DC/DC converter with high-output voltage gain. The presented converter has several advantages such as high step-up capability, continuous input current, bidirectional power flow from one of the ports, and its simple and low-cost structure. The presented converter can achieve a high-output voltage gain without using a coupled inductor or a transformer in its structure. Coupled inductors can cause voltage spikes on the main power switch, so active/passive clamp circuits are additionally required to eliminate the voltage spikes. The continuous input current of the presented converter makes it suitable for renewable energy sources such as photovoltaic panels and fuel cells.‏ An energy storage source such as a battery pack can be used in the presented converter. Charging and discharging of the energy storage source is possible using the presented converter. Pulsating charging current of the battery can improve the lifetime of the battery. In addition, discharging of the battery can be done without any constraints in the duty cycles. The thorough analysis and design of the proposed converter are discussed. A 300 W prototype of the presented converter is also used to verify the feasibility and proper operation of the converter.

Multilevel inverters (MLIs) are rapidly acquiring techno-economic feasibility for both high-power and medium-power applications. Increased number of power switches has been cited as one of the most important limitations of MLIs; and to overcome it, a whole new class of MLI topologies has come up. These topologies are commonly called ‘reduced device count’ MLIs (RDC-MLIs). As the number of controlled switches is significantly reduced in RDC-MLIs, the redundant states are also reduced. Hence, the possibility of fault tolerant operation is severely affected. This study looks at the possibility of imparting fault-tolerant characteristics to RDC-MLIs. In this study, some of the recently proposed RDC-MLI topologies are first analysed for the possibility of fault tolerant operation in the case of ‘any single switch open-circuit fault (ASSOF)’. Thereafter, an optimal addition of power switch is proposed which enables fault tolerant operation in the event of ASSOF. Furthermore, these modified RDC-MLIs are verified under normal and faulty conditions using software simulations and experimental set-ups and these results are presented.

The paper presents a new transformer-less step-up multilevel inverter structure with a single DC source. The concept was based on cascaded connection of bipolar T-type 5-level modules. Proper charging and discharging of capacitors across the load in prearranged time durations would make a nearly sinusoidal staircase voltage. The output voltage amplitude was several times greater than the DC input depending on the number of modules and charging mode of the capacitors. Multiplying the input voltage, self-balancing, generating bipolar voltage waveform, easy circuit expansion and considerably low THD (Total Harmonic Distortion) were found to be the advantages of the proposed topology. The paper also adds operating principle, simulation and experimental results of a 29-level prototype based on the presented inverter structure.

Highly reliable operation at high temperatures is required for next-generation power modules in electric vehicles. We propose a joining concept involving nickel–tin (Ni–Sn) double solid–liquid interdiffusion with an aluminium (Al) sheet (Ni–Sn DSLID/Al), which enables the production of modules with high thermal reliability. The use of Ni–Sn DSLID/Al joint as bonding layers for a large thermal coefficient mismatch [silicon (Si) chip: 3.9 × 10⁻⁶ K⁻¹, copper electrode plate: 16.5 × 10⁻⁶ K⁻¹] effectively decreased the compressive stress to 250 MPa in the Si chip, compared with that of a conventional Ni–Sn SLID joint (500 MPa) after joining. Moreover, the stress was relaxed when heating to 200°C during thermal cycling (from −40 to 200°C), due to the plastic and creep deformations of the inserted Al sheet. In addition, Ni–Sn DSLID/Al joint suppressed crack propagation during thermal cycling and exhibited higher thermal durability than Ni–Sn SLID and Sn–10% antimony solder joints up to 500 cycles, due to the higher resistances of the plastic and creep deformations of the inserted Al sheet. The present concept demonstrates great potential for use in fabricating joints for next-generation power modules.

This study proposes an interleaved multi-level power converter (IMPC) for a battery energy storage system. The proposed IMPC is composed of two power-electronic legs. The first power-electronic leg is an interleaved multi-level leg that contains eight power-electronic switches. Four power-electronic switches constitute a two-phase interleaved switch set and these are switched in a high-frequency interleaved pulse-width modulation. The other four power-electronic switches constitute a level-selection switch set that determines the dc bus voltage for the two-phase interleaved switch set according to the magnitude of the utility voltage. The second power-electronic leg is the low-frequency switching leg, which is composed of two power-electronic switches. Since the proposed IMPC integrates the performances of the multi-level power converter and interleaved power converter, the effective switching frequency is twice the practical switching frequency and the output voltage has five voltage levels. The ripple of the output current is significantly attenuated and the power capacity of the output filter is reduced. The proposed IMPC can also be used to adjust the real and the reactive power flows, in order to control the charging/discharging of battery sets and to compensate for the reactive power. A hardware prototype is developed to verify the performance of the proposed IMPC.

To realise a soft-switching inverter with a simple structure, high-efficiency and low-voltage stress, a novel resonant DC-link three-phase soft-switching inverter and its load adaptive commutation control are proposed in this study. Without two bulk capacitors and coupled inductors in the commutation circuit, the analysis and calculation of the inverter are simplified. Main switches of the inverter can achieve zero-voltage zero-current turn-on and pseudo zero-voltage turn-off, and commutation switches can achieve pseudo zero-current turn-on and pseudo zero-voltage turn-off. In addition, compared with the fixed time control, the load adaptive commutation control can dynamically regulate the switching points of commutation switches in each switching period and improve the efficiency of the inverter and the DC-link voltage utilisation rate. The main switches and commutation switches have the same and fixed switching frequency, and the voltage stress of them is equal to the input DC voltage. The load adaptive commutation control, the soft-switching resonant process and the design method of inverter resonant parameters are analysed in this study. A 10 kW prototype is designed to verify the feasibility of the inverter.

This study proposed a hybrid periodic carrier frequency modulation (HPCFM) technique based on the modified space vector pulse-width modulation (SVPWM) for two-level three-phase voltage source inverters to eliminate the PWM noise. Owing to PWM technique and switching losses considerations, ear-piercing high-frequency acoustic noise from motor is common. The proposed HPCFM technique is able to remove the high-frequency unpleasant acoustic noise more effectively than conventional PCFM with lower switching losses and shorter frequency range. In addition, the PWM harmonics in phase voltage and phase current are reduced significantly. Furthermore, the HPCFM method is simple to implement and does not employ additional circuits in drive system. The effectiveness of the proposed approach has been confirmed by detailed experimental results.

The cascade connection of two dc–dc switching converters for constant power supply is studied. The source converter is of boost type while the load converter is of buck type. The natural unstable behaviour of the cascade connection for both on and off states of the boost converter is counteracted by a sliding-mode control strategy that combines unstable trajectories to generate a stable one for the regulated boost converter dynamics. Experimental results using an electronic load to emulate a buck converter-based constant power load are in good agreement with the theoretical predictions. A similar agreement is later obtained when a buck converter with a dynamic behaviour close to an instantaneous constant power load is employed instead of the electronic load.

In this study, a new non-isolated DC–DC cuk–boost converter structure with high voltage gain is proposed. The presented topology is composed of boost and cuk converters, which in comparison with the traditional boost and cuk converter have low output voltage ripple and high voltage gain. Operation of diodes and switches of the proposed converter under zero voltage switching and zero current switching can play an important role in reducing circuit losses. Due to the output structure of this converter, it can be used as a symmetrical power supply. The proposed converter has two input power supplies, which can deliver power to load simultaneously. Simulation of the proposed converter is done by SIMULINK/MATLAB software. Finally, a prototype is established in the lab, and the experimental results are given to verify the correctness of the analysis.

Model predictive control (MPC) strategies have been frequently studied in recent years. To reduce the common-mode voltage (CMV) as well as the current total harmonic distortions (THDs) of the 2-level voltage sources (2L-VSIs), a new MPC strategy is proposed in this study considering both the dead-time and the one-step delay effects. First, the reference voltage vector (VV) prediction based MPC strategy is utilised as it is simple and accurate. Next, the VV preselection strategy is studied in detail to remove the CMV spikes. The effects of the dead time on the CMV are analysed, and an improved VV preselection strategy is presented to reduce the CMV spikes. Then, the one-step delay effects are also analysed, and further improvements are made to completely remove the CMV spikes. Moreover, the maximum variation of the current during one control period is studied in-depth to provide a solid theory foundation for dividing the current sector more accurately. As the six non-zero VVs of the 2L-VSI are fully used in the proposed method, not only the CMV but also the current THDs are reduced. Finally, comparative simulation and experimental studies are carried out to validate the effectiveness of the proposed method.

This paper deals with power quality problems encountered in weak AC microgrids and solutions for mitigation. A power electronic converter can be used as an effective power quality conditioner to compensate non-idealities in currents drawn from the grid. A power quality conditioner consisting of three power converters connected to a common DC link is analysed. One of these converters acts as an active power filter for removing unwanted harmonics in grid currents feeding a non-linear load. The other two converters instead remove the harmonics from the voltage at the terminals of a sensitive load. The control of the shunt converter is designed to be fast enough for power quality servicing but also has a fast disturbance rejection capability. Simulation and experimental results validating the concept are provided along with obtained total harmonic distortion improvements.

This study presents a switching frequency adjustment technique that helps widen the input voltage range of a current mode DC–DC converter. Conventional current-mode switching converters suffer the minimum on/off time restrictions that limit the input-to-output conversion ratio. This work introduces an additional regulation loop on top of an existing converter that regulates the switching period when the minimum on/off time limit is approached. Compared with a converter with fixed switching frequency, the proposed approach allows the free-running switching to be set without being limited by the minimum on/off time. A boost topology with output voltage of 24 V was built based on the proposed approach, and the measured valid input voltage range was extended from 8–16 to 3–21 V by the proposed scheme under 1 MHz preset frequency. Since the slope-compensation current, the inductor size, and the output capacitor are all optimised at 1 MHz and is not limited by the minimum on/off time which may lower the switching frequency of a conventional converter down to 450 kHz, the measured maximum available output current and the typical output voltage ripple under 12 V input achieved 1.57 A and 57 mV, respectively.

This study aims to investigate the correlation between inverter non-linearity and modulation technique selection in a dual three-phase induction machine (D3IM) drives. Even though vector space decomposition (VSD) technique is in the literature perceived as the most suited and well-adapted control strategy for D3IM, herein conducted analysis has established that VSD vector selection principle together with inverter non-linearity effects can lead to a significant decrease in the performance of a driven machine. It is demonstrated that by changing vector selection principle, the influence of the mentioned inverter limitations could be reduced without any major negative influence on other important aspects that determine technique suitability for the use in D3IM drives. The experimental results gathered from two separate test stations undoubtedly show the mutual impact of the inverter non-linearity and vector selection strategy on the drive overall performance.

Cascaded multilevel inverters (MLIs) have been proposed that utilise transformers in the basic unit. The proposed inverters primarily serve to step up the input voltages in addition to using lower number of components in comparison to traditional MLIs. In order to generate all voltage levels (even and odd) at the output, three different algorithms are proposed to determine the magnitude of DC voltage sources and transformer turn ratios. Also, the basic inverter unit was further developed and two new flexible MLI structures have been obtained. The developed structures increase the input voltage with no need for an additional boost converter. A reduction in the number of power switches, the peak inverse voltage, and the number of DC voltage sources are other advantages of the proposed topologies. Also, a simple cost model was developed and the dimensionless cost coefficient was determined. The overall cost of the proposed MLIs was compared to the similar MLIs from the literature. It was shown that the proposed MLI decrease the overall cost of the system if the cost coefficient is selected appropriately. To verify the performance of the proposed topologies simulated by the mathematical model; several lab-scale inverters were built and tested and good agreement was achieved.

Differential-drive cross-coupled (DDCC) rectifier is an important type of rectifier for radio-frequency energy harvesting. In this study, the analytical model of a DDCC rectifier is derived. With this model, optimisation procedures for most power-efficient rectifiers are derived. The model is verified extensively with Spectre simulations using the more complicated BSIM transistor model. Simulation results are further verified with measurements from reported rectifier designs. This study shows that DDCC rectifiers with the efficiency of 80.7% could ideally be achieved with −30 dBm sensitivity following the optimisation procedures introduced in this work.

A direct torque control (DTC) strategy of five-phase permanent magnet synchronous motor (PMSM) is proposed in this study. The proposed DTC scheme uses five-phase inverter to output basic voltage vector or discrete synthesised voltage vectors in one control period to realise the direct control of torque and flux on the fundamental and third harmonic planes simultaneously, and then realise the third harmonic current injection to enhance the load capacity. In order to realise the third harmonic current injection with maximum torque outputting and minimum peak of stator current, the maximum torque per ampere (MTPA) scheme is proposed in which the minimum copper loss and the same phase relation between fundamental and third harmonic currents are taken as the constraint conditions, and the amplitude of the fundamental and third harmonic fluxes and the optimal torque distribution ratio are derived in MTPA. A TMS320F2812-based digital controller is adopted as a core to construct the DTC experimental platform of the five-phase PMSM with 800 W rated power. The results of experiment and simulation show that the proposed DTC strategy can improve the maximum load torque of the motor, reduce the flux density of the stator and improve the core utilisation rate of the stator.

This study presents types 1 and 2 hybrid converters with reduced power circuit complexity compared with the mixed cell modular multilevel converter (MC-MMC). The type 1 converter is formed by replacing the director switches of the alternate arm converter by high-voltage (HV) half-bridge (HB) cells rated for half of the dc-link voltage. Also, it resembles special case of MC-MMC, where the entire HB cells of each arm are lumped into a single HV HB cell, with both capacitors of the half- and full-bridge cells are exposed to fundamental current as in the conventional MMC. The upper and lower arms of the type 2 converter resemble a front-to-front connection of two three-phase hybrid cascaded two-level converters, where the cell capacitors of the three-phase two-level converters that act as director switches do not experience fundamental currents. Therefore, the type 2 converter offers compact design compared with type 1 converter and the MC-MMC. The technical viabilities of the proposed hybrid converters are assessed using simulations, with both converters modelled in MATLAB–Simulink using electromagnetic transient simulation approach, considering normal and transient conditions. Experimental results obtained from single-phase type 1 converter confirm the practical viability of the proposed converters.

In this study, a novel non-linear sliding-mode controller with a boundary layer solution and a redefined sliding manifold is proposed for a bidirectional converter utilised in plug-in electric vehicles. The proposed method employs a Lyapunov function to formulate the stability condition of the non-linear controller. The proposed switching regime and control strategy enforce a pseudo-resistive relation at the input terminals of the converter to ensure the unity power factor in power conversion. The input resistance of the converter is regulated and controlled to positive and negative values to facilitate both grid-to-vehicle and vehicle-to-grid features, respectively. Simulation and experimental results are provided to evaluate performance of the proposed modelling and feedback control scheme.