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In this paper, a Phase-shift-modulated (PS) Resonant Two-switch Boosting Switched-capacitor Converter (RTBSC) and its modulation map are proposed. Compared with the traditional RTBSC, all diodes are replaced by active switches and then phase-shift modulation is applied. The advantages of the modified topology are obtained as follow. 1) The voltage gain can be regulated efficiently either below or above the nominal value even at light-load condition, making it suitable for applications with voltage fluctuations; 2) The conduction loss is reduced by replacing all diodes in RTBSC with low turn-on resistance transistors, especially for high-order and high-gain configuration; 3) All switches achieve the zero-voltage-switching (ZVS) turn-on operation; 4) The soft-charging property smooths the current profile. Aside from the topology modification, a comprehensive analysis of operation principle, voltage gain, component stress and ZVS region is given. On the basis, a modulation map with the optimal operation region is proposed. It provides a guideline to operate and design such converters in the target gain range, low component stress and ZVS region, making up for the lack of modulation map and design guideline in aforementioned literatures. A 120W prototype with low-voltage side 43-60V and high-voltage side 150V was designed to verify the above analyses.

This brief proposes a low voltage ultra-low power 10-bit 100-MS/s successive approximation register (SAR) analog-to-digital converter (ADC). To overcome the performance degradation due to the signal-related current fluctuation under lower supply voltage, an adaptive-biasing comparator with current self-compensation (CSC) technique is proposed to obtain a constant working current, reducing the minimum supply voltage from 0.7V in conventional ADCs to 0.55V. Since full-scale range shrinks with the supply voltage, voltage undershoot in power rail caused by capacitor digital-to-analog converter (C-DAC) deteriorates effective-number-of-bits (ENOB). Conventional solutions involve enhanced regulators and large decoupling capacitors, which cost remarkable power dissipation and large chip area. This brief presents a pulse-injection undershoot compensation technique which reduces the DAC-related supply fluctuation from a typical 15mV to 1.8mV, and improves the ENOB by 0.4 bit. The prototype was fabricated in TSMC 28nm HPC CMOS technology. The proposed SAR ADC achieves an SNDR of 54.7dB and an SFDR of 68dB with the power consumption of 0.16mW under 0.55V supply voltage, a figure of merit (FoM) of 3.6-fJ/conversion-step is achieved. The chip area of the ADC core is 130μm×225μm.

This paper studies the coordinated use of smart inverters with legacy voltage regulating devices to help increase the energy savings from conservation voltage reduction (CVR) in distribution systems with high photovoltaic penetration. Two voltage optimization algorithms are developed to evaluate the CVR benefit by considering two types of smart inverter functions: aggregated reactive power control and autonomous volt/VAR control. In each algorithm, smart inverters are coordinately controlled with the operation of legacy voltage regulating devices including load tap changers and capacitor banks. Both algorithms are tested on representative utility distribution system models. Simulation results demonstrate that the proposed algorithms can achieve around 1.8-3.6% energy savings when only using legacy voltage regulating devices and an additional 0.3-0.9% when adding smart inverters.

The steep voltage slopes of today’s wide-bandgap (WBG), fast-switching power semiconductors — like SiC and GaN — lead amongst other challenges to reflection on long cables and thereby overvoltage at inductive loads. To enable the use of these inverters with motors without specially reinforced insulation the voltage slopes need to be slowed down. This article presents a new low-loss countermeasure, which involves the parallel connection of two half-bridges via an interphase transformer. For this one half-bridge is delayed relative to the other one by a delay tuned to a resonant circuit. Undesired DC components in the cross-current of the interphase transformer occur due to non-idealities in the voltage symmetry. The subsequent DC magnetization ultimately can cause the core to saturate. The paper describes the effects due to inaccurate timings and the aspects to keep in mind when dimensioning the magnetic core. Also, this article describes an approach to deal with the undesired current components using a closed-loop control. For that, a special differential-mode shunt is used which enables a dedicated measurement of the cross-current mean value and mitigates the influence of the switching frequency. Finally, the controller concept is presented. The controller is implemented and verified on a 500 kVA SiC inverter test bench.

Conventionally, single phase shift control technique is used, for dual active bridge (DAB) which works efficiently at unity voltage conversion ratio and full load. However, when there is mismatch between primary voltage and reflected secondary voltage on primary side at light load, its efficiency reduces because of increased current stress and circulating power. Moreover, due to single control variable, its power flow controllability is confined. In this paper, isolated bi-directional T-type multilevel dual active bridge dc-dc converter topology is presented. It has five level voltages on both the primary and secondary side of high frequency transformer, which reduces the current stress and circulating power over wide operating range. It also has five control variables which gives extra edge for enhancing power flow controllability. Comparative analysis reveals that the proposed converter has high efficiency over wide operating range, due to reduced circulating power and current stress. Performance of the proposed T- type multilevel dual active bridge DC-DC converter topology has been verified via simulation in MATLAB.

The present day ever escalating power demand moves the operating point ofthe distribution networks in the vicinity of the voltage stability boundaries.Any small reactive power unbalance between the generation and demandmay trigger voltage instability, which makes the voltage magnitude to fallslowly until a rapid change occurs. This paper presents an adaptive dragonflyoptimization based method for placement of shunt capacitor banks witha view of improving the voltage stability besides enhancing the voltageprofile and lowering the network losses. Simulation results on 33 and 69-node distribution networks exhibit the greater performances of the suggestedalgorithm.

Battery power has been a popular choice of delivering DC power to many portable RF systems including wireless sensor nodes/internet of Everything (IoE). An autonomously powered RF system of the orders of 100’s of µwatts is becoming increasingly popular in recent times because of integrated solutions in energy harvesting. The minimum sensitivity of an RF energy harvester and the targeted deliverable output voltage for a specific load resistance are dictated by threshold voltage of transistors used and reverse leakage of such transistors. A detailed look into the architectures of rectifiers can help tackle design problems in the RF-DC conversion process. So in this work we focused on the design of integrated RF energy harvesting by studying four important architectures of RF-DC converters. To achieve a fair comparison between these architectures, a matching network operating at 0.8 MHz is designed and applied for simulation. All of these converters are tested in LT-SPICE XVII using the same designed matching network and the rectifiers are implemented in 180 nm CMOS technology.

Pulsed electric field disinfection is an effective non-thermal water disinfection technology. Compared to conventional disinfection techniques, PEF inactivation has several advantages including no by-products. In this context, the use of silver ions in conjunction with a reverse osmosis filtration system has been proposed as a safe and cost-effective treatment approach that can be used in a point of use technologies. This system contains two silver meshes as electrodes inside a reverse osmosis membrane with the application of a pulsed electric field on it as a disinfection method, After conducting chemical and physical tests of the water samples before and after the treatment system, it was noticed that most of these characteristics were significantly affected by increasing the number of electrical impulses and the intensity of the applied voltage as a result of the increase in the ionization process of silver in water.

In General, a larger number of experimental data would be required for optimizing the performance efficiency of the electrodes in solid oxide fuel cells (SOFC), as it was likely to involve many complex chemical and physical reactions. Therefore, in this study, we have attempted the artificial intelligence (AI) technique for analyzing the performance of the anode and cathode electrodes of SOFC under various key parameters that normally influences the efficiency of the electrodes. Since the cost of SOFC elements is expensive, computational trials with the aid of AI would not only be curtailing the preparation cost but also ensures less time consumption. Among the variety of AI methods available in the literature, the Support Vector Machine (SVM) appears to be one of the excellent and effective machine learning techniques. Hence, we have developed a SVM model and predicted the maximum current density and power density of Nickel oxide-samarium-doped ceria (NiO-SDC) composite anode and La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) cathode electrodes of SOFC. The input parameters such as stack temperature, supply voltage were supplied to the SVM model and obtained maximum current density and power density as output and it decides the working performance of the electrodes. We have also predicted that the maximum current density and power density of 1160 mA cm2 and 225 mW cm2 respectively at 800 °C. To validate the results as predicted from SVM, we have experimented using Yttrium stabilized zirconia electrolyte-supported single cell with our prepared NiO-SDC anode and LSCF cathode which exhibited a maximum current and power density of 1170 mA cm2 and 227 mW cm2 at 800 °C using H2 as fuel. It has been found that that the theoretical predicted data current and power densities of the electrodes from the SVM approach reasonably agrees well with the experimental results.

This paper introduces a new active-neutral-point clamped (ANPC) seven-level inverter with a switched-capacitor technique. The introduced inverter generates a seven-level ac output voltage with a maximum voltage-boosting gain of 1.5. Also, a simple modulation technique was proposed, where the capacitors voltages are naturally balanced by the series-parallel connection of the input voltage source. Compared with seven-level inverter topologies, the proposed topology is simpler and its control system does not requires sensors or balancing circuits to stabilize the dc-link voltages. Additionally, the dc-link voltage requirement is reduced by 33.33%, eliminating the need for an intermediate dc-boosting stage and making the introduced inverter a good candidate for applications such as photovoltaic panels and full-cells systems, both characterized by a low input voltage. The operation and performance of the proposed topology is validated through simulation and experimental results.

The most important variables to consider in the design of antennas for RFED applications and effective communications are low cost, low profile, and reduced size. The dipole antenna, often known as a dipole aerial, is the most basic and widely used type of antenna. Among other antennas, this is one of the most straightforward antenna layouts. It may be achieved by applying a sinusoidal voltage differential between two thin metallic rods. The dipole antenna is a particularly important type of RF antenna that is frequently used for radio transmission and reception. For many types of antennas, this antenna can be employed as a radiating or driving element. This Dipole antenna may be used in the radio frequency spectrum sections HF, VHF and UHF. The major advantage of a dipole antenna is that it can serve as both a broadcast transmitter and receiver. So, to obtain the most crucial factors, we'll design an antenna in COMSOL Multi Physics and display the results as Radiation patterns.

This paper investigates a single-phase multilevel dc-ac converter composed of four series/parallel-connected H-bridges with floating capacitors. System model, pulse-width modulation (PWM) strategies, and a control strategy have been presented. An important variable is the control of the dc-links voltages in the floating capacitor. Thus, an individual balancing of dc-links voltages using auxiliary variables and redundant voltage vectors are shown in this work for different dc-link voltage ratios. Simulations and experimental results with several power levels show how the operating characteristics.

In this work, a multi-level 42-sided polygonal space vector structure (SVS) for suppression of lower order harmonics for Open-End Induction Motor(OEIM) drive applications is proposed. The proposed power circuit topology consists of two inverters feeding an OEIM from either side. The main inverter fed with a single DC link providing active power for motoring operation is switched at low switching frequency. The secondary inverter fed with a capacitive supply is switched at high frequency to suppress lower order harmonics upto 39th order, up to the base speed of operation allowing maximum utilization of the DC link. The advantages of lower order harmonic suppression in motor phase voltage, for polygonal space vector structures are combined with multi-level inverter topology. This offers various advantages like multilevel operation with low inverter switching for the main power delivery inverter and harmonic suppression throughout the modulation range. The low switching frequency primary inverter generates low order harmonics. The harmonics are suppressed by the capacitor fed secondary inverter which supplies only reactive power for suppression of lower order harmonics in motor phase voltage. Use of a single DC link facilitates four-quadrant operation of the inverter.

Accurate and timely fault diagnosis of the rotating rectifier for a wound-rotor synchronous starter/generator is of great importance to improve system reliability. In the generation mode of the system, there is one idle stator winding of the main exciter. The terminal voltage characteristic of the idle stator winding is analyzed, and a novel fault diagnosis method for the rotating rectifier in the generation mode of the system is proposed. In this method, two feature voltages, namely, the maximum peak voltage and any other peak voltage of the idle stator winding terminal voltage are extracted through voltage sequence reconstruction to calculate the feature ratio for fault detection. The corresponding rotor position obtained by an inherent position sensor where the maximum peak voltage occurs is collected to determine the faulty diode location. The experimental results verify the feasibility and effectiveness of the proposed fault diagnosis method.

Multilevel topologies with SiC devices for medium voltage (MV) motor drive have advantages to reduce the harmonics and device voltage stress as well as to increase the efficiency. However, with the application of SiC devices, the reflected wave phenomenon still happens in multilevel motor drive due to its high dv/dt, resulting in overvoltage at motor terminals. This paper proposed a T-type circuit based active reflected wave canceller (ARWC) to suppress the overvoltage of a M-level motor drives with reduced voltage rating of Vdc/(M-1). A coupled inductor is applied to isolate the ARWC output and the main inverter. In addition, the coupled inductor is designed with a small resistor to allow low current flowing into ARWC. The proposed ARWC configuration can be applied for general multilevel topologies. A 3-level ANPC converter with 3.3 kV SiC device is built in the laboratory. A 1.2 kV SiC module is applied in the proposed ARWC. The experimental results at 1.6 kV Vdc and 16 A (RMS) load current with and without proposed ARWC are provided and compared to verify the validity of proposed method.

This article brings forward a phase-disposition pulse width modulation enabled model predictive control (PDPWM-MPC) for a nine-level inner-interleaved hybrid multilevel converter (9L-IHMC). Firstly, three layers of virtual space vector diagrams (VSVD) are established based on the sign patterns of the original and virtual reference vectors in the abcframe, respectively, to achieve the phase-disposition pulse width modulation (PD-PWM) in a non-independent three-phase way. Then, three adjacent virtual vectors in the third-layer VSVD, together with their optimized duty cycles, are applied to guarantee the optimal current tracking. Finally, through the use of the duty cycle alternation approach, dc-link and floating capacitors voltages are balanced and circulating currents are mitigated as well. The proposed PDPWM-MPC can not only enable the decoupling of the low-and high-frequency stages in the 9L-IHMC, but also reduce both output current ripples and computational burden. In addition, it can achieve a constant equivalent switching frequency and address the disproportion of power losses associated with the PD-PWM. Both simulations and experiments on a silicon carbide device-based prototype substantiate the effectiveness of the proposed control strategy.

A switching state selection scheme for a five level stacked multilevel inverter for open end winding motor drive is presented in this work. Using the proposed scheme, converter can be operated with a single DC supply and with zero common mode voltage. In addition, the switching transition of high voltage switches occurs at zero voltage conditions. The degree of freedom provided by the redundant switching states and voltage vectors of the inverter topology is utilised to design the modulation scheme. The proposed switching state selection leads to inherent capacitor balancing without using any extra sensors and fundamental frequency switching of the high voltage switches of the topology. The modulation scheme uses triangular carrier comparison and hence avoids the complexity of sub-sector identification and dwell time calculation. Half wave symmetry in output waveforms is ensured by maintaining synchronous sampling with constant samples per fundamental cycle. The inverter topology and the effectiveness of state selection scheme is experimentally validated on an open end winding induction motor drive and experimental results showing steady state and dynamic operation are presented.

In this paper, a non-isolated dc-dc high step-up converter with passive switched-inductor-capacitor network is proposed, which is applicable for the required high gain voltage low power applications, such as battery-powered LED lighting systems and high-intensity mobile discharge lamps. The proposed circuit can produce higher gain voltage with small duty cycle, which decreases the voltage stress and conduction power loss on the active switches. In contrast to other non-isolated dc converters, by using the same or analogous number of passive/active components in circuit topology, the proposed topology has lower voltage stresses across capacitors and diodes, lower inductor current stresses. Therefore, the efficiency and reliability of the circuit topology can be ameliorated. The theoretical principle, parameter design guideline, small-signal dynamic analysis, power loss analysis and performance comparison with other dc-dc non-isolated converters have been implemented. Finally, a 200 W experimental setup is built and tested with an input dc voltage of 36V–60V and an output voltage of 200V to validate the aforementioned merits of the proposed circuit.

The drive to miniaturize power electronics motivates investigation into alternative passive component technologies such as piezoelectrics, which offer fundamentally higher power density and efficiency capabilities at small scales compared to magnetics. Piezoelectric transformers (PTs) have seen application in dc-dc converters, but these designs typically require additional magnetics for competitive efficiency. In this work, we systematically enumerate isolated and non-isolated dc-dc converter topologies and switching sequences capable of efficiently utilizing PTs as their only energy storage components. The proposed switching sequences maintain high-efficiency behaviors (e.g., zero voltage switching (ZVS), all-positive instantaneous power transfer, and minimal charge circulation) across wide voltage gain and load ranges. We present techniques for deriving these switching sequences’ ZVS regions, estimating PT efficiency, and solving for periodic steady state switching times; these offer insights for comparing and implementing design options. We then verify our analyses in a 180-500 V experimental prototype based on a commercially-available PT, which demonstrates significant efficiency gain through a proposed implementation.

The demand for high-density, high-efficiency bi-directional battery chargers is driven by the fast development of energy storage system in renewable energy system, micro-grid, and transportation electrification. Isolated dc-dc converter that interfaces a battery with a variable voltage range is one of the critical components. Input-parallel output-series (IPOS) partial power (PP) converter is considered a promising high-efficiency, high density solution because only a fraction of power is processed via multi-stage converters to regulate the output voltage. However, due to the tight coupling between two dc transformers (DCXs), the design of PP converter is complicated. To solve this issue, a design procedure for a bi-directional soft-switching resonant type PP converter is proposed. In the parameters design part, a decoupled design method is proposed to simplify the DCXs design. With this method, two DCXs can be designed separately, and the typical optimization method can be easily applied. As for the hardware design part, to minimize the ac loop inductance and resistance, a 2-directions (2-D) flux cancelation method and an “intra-leaving” winding structure are proposed for circuit layout and high-frequency transformer to obtain high operation efficiency and power density. Finally, the whole design procedure is verified by an 18 kW rated, 25 kW peak, prototype operating at 500 kHz. The realized PP converter features a peak efficiency of 98. 8% and a power density of 142 W/in3. This article is accompanied by two videos demonstrating the dynamic voltage regulation test and the efficiency measurement.

AC-type flying capacitor concept has been proposed for current source converter (CSC) topologies recently, which offers unique merits over traditional CSCs, such as lower dv/dt with improved DC-link voltage quality as well as flexible common-mode voltage (CMV) control. To cope with main-stream three-phase industrial applications, the three-phase flying-capacitor-clamped CSC (FCC-CSC) is introduced and extensively investigated in this paper for the first time. A novel space vector modulation (SVM) is proposed, featuring a modular design process, active flying capacitor voltage control, and CMV suppression. The detailed commutation principles and the capacitor clamping voltage influence under different switching states are comprehensively addressed. Then, the redundant switching states are optimized to fulfill the multiple targets simultaneously. Simulation and experimental results are performed to demonstrate the superior dc-link power quality and CMV performance compared to traditional three-phase CSC topology.

Impedance-source inverters with coupled inductors can provide much higher voltage gains, but occasionally at the expense of discontinuous input currents and large voltage spikes at their dc-links. The former is caused by absence of inductances at their inputs, while the latter is due to unintentional interruptions of leakage currents through their coupled inductors. These problems have now been solved here by a new family of dual-winding impedance-source inverters (DW-ISIs). Each DW-ISI can recycle leakage energy from its two windings to a few clamping capacitors, which in turn help to prevent voltage spikes. This, together with the presence of an inductance for smoothing its input current, renders the family of DW-ISIs to be highly effective, while not compromising voltage and current stresses when compared to other precedent inverters. In addition, to simplify the circuit analysis, a reactive component elimination method has been proposed in this paper. Simulation and experimental results have confirmed the validity of the proposed topologies.

A Phase-shifted full-bridge (PSFB) converter is widely used in various applications due to its soft-switching characteristics. However, one of the recognized shortcomings of the PSFB converter is that it cannot simultaneously have a wide soft switching range and a small secondary-side duty cycle loss. The shortcoming hinders the high frequency and high efficiency of the converter. In this paper, the change of the energy demand of the converter on the external series inductor with input voltage and load is analyzed. On this basis, a variable saturation inductor with controllable energy is proposed to meet the energy demand and solve the problem of core heating. The controllable change characteristics of the inductor energy are studied directly instead of the controllable change of the inductance value. By adjusting the inductor energy, the PSFB can not only achieve soft switching under light loads, but also reduce duty cycle loss under heavy loads. Theoretical analysis and experimental verification are carried out on the soft switching and duty cycle loss of the converter. Since the transformer ratio can be increased due to the smaller duty cycle loss. The efficiency of the converter can be further improved.

High voltage/high power capacitor chargers are primarily interested in many industrial applications. Resonant converters have been a proper choice in such applications because of their advantages. However, the performance of the resonant converter is highly affected by the parasitic elements of the high voltage/high power transformer. Also, short circuit condition is a frequent event in high voltage applications, so that the resonant converter should be robust against the short circuit condition. This paper presents a novel LCCL resonant converter with current source characteristics used as a high voltage capacitor charger. The proposed resonant converter eliminates the undesirable effect of the stray capacitance in high voltage devices and is robust against the short circuit condition inherently. It also provides a semi-trapezoidal resonant current wave which produces a lower crest factor. Furthermore, a frequency-sweep operation is applied, which has advantages in reducing the resonant current's peak value and the resonant network's size. Simulation results show a satisfactory performance of the proposed resonant converter. Moreover, experimental results confirm the effectiveness of the proposed resonant converter in the application of capacitor charging.

DC-field excited modular variable flux reluctance machines (VFRM) have passive salient-pole rotor, which makes it suitable for high-speed applications. In addition, independent stator winding eliminates the electrical, magnetic, and thermal coupling among phases, improving its reliability. However, fault-tolerant operation is still required to improve its output capability under post fault. Hence, the performance under winding open-circuit faults is analyzed and the fault-tolerant control strategy is presented to increase the output capacity in this paper. Firstly, the DC-rectified output voltages and power of the VFRM under both normal and open-circuit faults are derived. Then, phase angle control (PAC) strategy of the fault-tolerant operation for a 12-slot-14-rotor-pole (12s14r) modular VFRM is proposed, where the control sequence is optimized to achieve the maximum output power of the generation system. Compared with the classical fault-tolerant method, a higher applicability of the proposed method in terms of the types of fault-tolerant operations can be achieved. The electromagnetic properties, including the armature current and the capacity of electrical power output are analyzed with finite element analysis. The effectiveness and feasibility of the proposed fault-topology and control strategy are verified by the 12s14r VFRM prototype in normal, fault and fault-tolerant operation.

This paper proposes a high step-up dc-dc converter with a continuous input current which is suitable for sustainable energy systems. A three-winding coupled inductor, two power switches, three diodes, and three capacitors are utilized to perform the functions of active switched inductor and switched capacitor. By charging the two primary windings in parallel, and discharging the two primary windings in series to the intermediate capacitor and the output, the conversion ratio can be further improved with lower voltage stresses and current stresses on its power switches. In addition, the energy stored in the leakage inductance is recycled to reduce the voltage spikes of the power switches. Eventually, a laboratory prototype with an input voltage of 36 V - 48 V, and output voltage of 400 V - 600 V with a rated power of 600 W is implemented to validate the correctness and effectiveness of the theoretical analyses. The maximum efficiency and full load efficiency are 97 % and 96.2 %, respectively.

This article describes design, operation and experimental testing of a mechanical DC CB (Circuit Breaker) with parallel capacitors. The topology resembles hybrid DC CB but there are possible advantages in the costs since the main semiconductor valve is replaced with capacitors and in performance since this breaker inserts counter voltage earlier. A detailed PSCAD model is employed to support DC CB design and to analyse operating principles. A 5 kV, 2 kA hardware demonstrator with 1.5 ms disconnector opening time is developed in the university laboratory. The test results demonstrate successful breaking of DC currents, with the measured time for insertion of capacitor voltage of around 290 s. Further experimental analysis evaluates stresses on the key components, optimal timing for opening of LCS (Load Commutation Switch) and the margins for successful current interruption.

Ultra-high voltage fast vacuum circuit breakers (FVCBs) could benefit a power system by promoting transient stability. This paper presents the design and verification of a prototype 363-kV/5000-A 63-kA multiple-break FVCB. The prototype consists of two parallel-connected circuit branches in each phase. Each branch comprises three breaking units. The breaking unit, arranged on a 330-kV-class insulating platform, is a double-break FVCB driven by two independent electromagnetic repulsion actuators. The breaking units include a specially designed 40.5-kV vacuum interrupter (VI) with an extended ceramic envelope and optimized contact contours. A 4.0-nF grading capacitor is connected in parallel with each break to achieve a uniform stressed voltage distribution across the break. The prototype performs controlled switching of short-circuit current with an arcing time of 2.0 ms. The feasibility of the 363-kV FVCB is verified by a dielectric test on one break of the prototype and a series of tests on a single-phase prototype. The tests include controlled switching of a short-circuit current in a short arcing time under different transient recovery voltages following test duties T100s(b) and T100a, short-time withstand current and peak withstand current tests, a temperature rise test, and an electromagnetic compatibility tes

A non-isolated bidirectional DC-DC converter is proposed for energy storage systems in this paper. The proposed converter is composed of three active switches, two synchronous rectifiers, two clamping capacitors and two inductors. The proposed converter has advantages of being a simple structure, a fewer number of components, a common ground, lower voltage stress, and wide voltage gain range. Compared with the conventional buck converters, the novel converter triples the effective duty cycle and lowers voltage stresses across the active switches. A 300 W/500 kHz GaN-based experimental prototype is built and tested to verify the correctness and validity, demonstrating a peak efficiency of 94.54% in step-down mode and a peak efficiency of 94.88% in step-up mode.

In this paper, a method of simultaneous sensorless rotor position and torque estimation is proposed for interior permanent magnet synchronous machines at standstill and low speed. The proposed method estimates the torque using high frequency inductances identified from the current variations due to high frequency square wave voltage injections in the estimated dq-axeswhich are simultaneously used for sensorless rotor position estimation. The proposed method is not dependent on the fundamental model and has taken the cross-coupling effect into consideration, allowing for low cost and fast torque estimation at standstill and low speed. Both simulations and experiments are carried out to verify the effectiveness of the proposed method.

A hybrid excitation generator is proposed as a brushless solution for aircraft low-voltage DC power system applications. This topology distinguishes itself from the commonly used electrically excited generator in aircraft power systems, because it features an open-circuit voltage without field current. This feature is an advantage but it also includes a risk. As a too high open-circuit voltage has detrimental influences on the generation system, the limitation of this open-circuit voltage needs to be guaranteed at all times. The key design parameters, such as the slot-pole combination, stack length, and number of turns of the armature winding, are determined to make sure that generators meet the open-circuit voltage limitation. These key design parameters influence also the inductance characteristics of the generator and put consequences on the load characteristics thereby. Therefore, this paper also analyzes the load and short-circuit characteristics of these hybrid excitation generators as function of these parameters. Theoretical deduction and simulation are conducted to reveal the influence law of the parameters on the performance of the hybrid excitation generator under the limitation of open-circuit voltage. A 12300rpm 12kW prototype is developed. The experiments verify the analysis and show the hybrid excitation generator is appropriate for aircraft applications.

The insulation impedance monitoring methods such as capacitance/dissipation factor (C/DF) monitoring methods have been proposed for the online stator insulation condition monitoring. By measuring the insulation leakage currents and the phase-to-ground voltages, the groundwall and phase-to-phase insulation impedances can be calculated in frequency domain. In the existing methods, the calculation is based on the assumption that the differential mode phase-to-ground voltage decreases linearly along the stator winding and no phase angle deviation is considered. However, the phase angles of the induced electromagnetic forces in stator winding in different slots depend on the slot positions. The assumption in the existing methods neglects this phase deviation and causes errors in the monitoring results. In order to eliminate this effect, the effect of the phase angle deviation on monitoring results is analyzed in this paper. Its dependency on the turn number, the winding configuration and the frequency of the selected monitoring signals is studied. A compensation method is proposed and the compensation coefficients are calculated for different winding cases for the demonstration purpose. The online experimental results prove that the accuracy of the online monitoring results is improved after the compensation.

This paper proposes an intensive study for common-mode voltage (CMV) elimination/reduction in a five-level dual T-type multilevel converter (5LDT-MLC) drive. An advanced and fast model predictive control (MPC) approach is developed for CMV reduction (CMVR) and CMV elimination (CMVE) based on preselection of the switching states (SS). In addition, the proposed approach considers the torque control and the capacitor balancing of the proposed drive as essential aspects of MLC drives. A detailed study for the impact of the converter SS on the CMV is presented. The main features of the proposed MPC approach are reducing the complexity of the cost-function, the tuning burden of the weighting factors, and the computation time by more than 80% compared to conventional MPC techniques. A hardware implementation based on Silicon Carbide (SiC) T-type MLC is built. The experimental results demonstrate the effectiveness of the proposed MPC approach to mitigate/eliminate the CMV along with achieving the torque command and balancing the DC link capacitors. Unlike conventional CMVR techniques, the proposed approach reduces the CMV by 75% of its normal values without jeopardizing the harmonic contents, drive efficiency, and flux as well as torque ripples.

Solid-state transformers can be applied in the AC/DC hybrid distribution network. The reliability and power density of a solid-state transformer is significantly influenced by the insulation design of the isolated DC-DC converter and, in particular, its medium-voltage medium-frequency transformer. This paper proposes an insulation design method for the medium-voltage medium-frequency transformer. A novel insulation structure is adopted to reduce the volume and improve the heat dissipation performance. Optimization of insulation distance parameters is performed based on finite element method simulations. The proposed method is applied to a 60 kVA/10 kHz transformer, and the simulation results verify the improved performances with the proposed insulation design method. A prototype is developed according to the proposed scheme, and the experimental results of a DC-DC converter and the partial discharge and applied voltage tests are presented.

The basic structure and generalization of two cascaded transformer multilevel inverters (CTMIs) are proposed in this paper. Such configurations are based on cascaded symmetrical transformers coupled to two-level (2L) legs and three-level (3L) neutral-point clamped (NPC) legs. One configuration has a shared 2L leg, connected to all transformers. The other configuration consists of multiple shared legs, where each is connected between two transformers. A modulation technique is also presented that allows only one leg of the proposed inverters operates at high frequency, while all other legs operate at low frequency. Compared to three conventional CTMIs, the proposed structures can produce more output voltage levels using a smaller number of switches and transformers, offering a better power quality, less weight, volume, and cost of the system. Moreover, the proposed inverters offer a natural balancing property that can self-regulate the dc-link capacitor voltages. Simulation and experimental results are presented in order to demonstrate the performance and feasibility of the proposed configurations.

A triple-port solid state transformer (TP-SST) topology based on the combination of modular multilevel converter (MMC) and resonant push-pull converter (RP2C) is proposed in this paper. For an MMC-based SST, large size capacitor caused by fluctuating power and voltage imbalance of MMC sub-modules (SMs) are two important problems. Based on a simple open-loop control scheme, the RP2C based high frequency links (HFL) are characterized by a voltage source with fixed conversion ratio and low impedance, and then can form a power free-coupling channel between SMs and realize the automatic balance of capacitors voltage. Moreover, the fluctuating power can cancel each other based on their three-phase symmetry, which obviously reduces the capacitance size, and the 2nd-order harmonic circulating current of the arms could be eliminated at the same time, greatly simplifying the control of system. In this paper, the working principle of TP-SST are described, and the methods of HFL realizing SM voltage ripple elimination and self-balancing are analyzed in detail. In addition, a comparison with traditional SST in efficiency and cost is presented. Finally, simulation and experimental results verify the correctness and effectiveness of the proposed topology scheme.

The galvanic isolation of solid-state transformers (SSTs) is typically realized with a medium-frequency (MF) magnetic-core transformer (MCT). Previous demonstrations indicate that achieving highly power dense and lightweight MCTs imposes several challenges on the design because of stringent requirements related to insulation and cooling. This work investigates the achievable efficiency of an optimized 166kW / 7 kV air-core transformer (ACT), which is a core part of a DC Transformer (DCX), i.e., an unregulated DC-DC SST with a voltage scaling defined by the transformer turns ratio. The ACT features relatively low complexity of the construction, comparably high coupling values, and high efficiency. Modeling, optimization, and construction of the realized ACT are explained and guidelines regarding insulation, cooling, and shielding of the magnetic stray flux are discussed in detail. Furthermore, the prototype is experimentally validated to demonstrate its full functionality. In the investigated DCX, which is based on a series resonant converter (SRC) topology, the realized ACT is found to achieve a full-load efficiency of 99.5% and an unprecedented gravimetric power density of 16.5 kW/kg. With the use of 10 kV SiC MOSFETs, the complete DCX is estimated to reach an efficiency of 99% at 166kW output power.

In this paper, a robust wireless power transfer (WPT) system considering a wide variation in load resistance and coupling coefficient is proposed for electric vehicles (EVs) charging. Here, a new implementation of the parity-time(PT)-symmetric circuit using a phase synchronization method is presented, in which a power-adjustable negative resistor is constructed only by a single-stage inverter. Moreover, based on the PT-symmetric circuit, a control strategy that does not require dual-side communication and extra dc-dc converters is developed for battery charging. Theoretical analysis shows that constant current (CC) and constant voltage (CV) outputs independent of load and position can be achieved, and the charging mode can be switched automatically. A scaled-down prototype with an 8 A charging current and a 120 V charging voltage is built to verify the feasibility of the proposed method. Experimental results demonstrate that within the transfer distance of 10-25 cm, the CC/CV outputs can be maintained during the charging process.

A three-level bidirectional AC-DC converter with H8 topology is proposed to combine the advantages of both neutral-point clamped and flying-capacitor three-level converters for medium voltage AC-DC solid-state transformer applications. The innovative H8 converter features self-balanced capacitor voltage, common-mode voltage elimination, and small capacitance of the flying capacitors. The proposed carrier-based modulation enables the H8 converter to operate under both active and reactive power conditions. A 10 kVA AC-DC converter prototype with 1.7 kV SiC MOSFETs and 3.3 kV SiC diodes verifies the feasibility and advantages of the proposed topology and the modulation method. The capacitance of the flying capacitors in the H8 converter is reduced by 45 times compared to that of the flying-capacitor converters. The H8 converter efficiency is tested up to 99% at 2 kV DC voltage. The proposed H8 converter is suitable for the next-generation PV inverter, grid-forming inverter, MV fast charger, and SST applications.

Following the continuous development of wide bandgap (WBG) devices and multilevel converter technology, medium voltage (MV) active front ends (AFEs) are becoming promising in future high-power-density and high-power applications. However, the cost issue is one of the major drawbacks, which stops the WBG devices from being widely applied in high-power areas. This paper proposes a silicon carbide (SiC) and silicon (Si) hybrid five-level unidirectional rectifier. It requires only four SiC MOSFETs with relatively low blocking voltage and four Si diodes. Meanwhile, by adding snubber capacitors, all the Si devices are with low-speed switching, and the voltage stresses of fast SiC MOSFETs are minimized. In this paper, operational analysis and carrier-based phase-disposition PWM scheme for this circuit are discussed in detail. The capacitor voltage balancing and unity power factor are both realized. Simulation and scaled-down experimental results are demonstrated to verify the proposed rectifier. Furthermore, the comparison of the hybrid five-level rectifiers is given to show the advantages of the proposed rectifier in terms of voltage stress, efficiency, and cost.

Multiphase electric drives offer attractive advantages over conventional three-phase systems. Some of the benefits are shared by all multiphase configurations, but the performance can be highly affected by the specific location of the stator windings. While the asymmetrical configuration has been traditionally a popular choice, the symmetrical disposition in even-phase machines has a main advantage: it is possible to generate - voltages without any contribution in different x-y subspaces. This work explains and demonstrates this feature for the general case of distributed-winding symmetrical n-phase machines, with n being an even number. Fortunately, direct controllers can benefit from this characteristic by exclusively selecting voltage states with only - voltage production. To illustrate this capability, a finite-control-set model predictive control (FCS-MPC) using these special voltage states is also suggested in this work for symmetrical six-phase electric drives. This approach provides a greater simplicity and much less current distortion than in standard FCS-MPC for the asymmetrical configuration. Comparative experimental results confirm the minimal x-y injection of symmetrical configurations thanks to the proposed control actions (i.e., voltage states).

The field-winding-induced voltage pulsation in the doubly salient brushless DC (DSBLDC) generator leads to the field current ripple and challenges the DC power supply for the field winding. In this paper, a new DSBLDC generator with stator-damper winding is proposed to reduce the induced voltage in the DC field winding. The stator-damper winding configuration is illustrated. The winding self-inductance and coupling characteristics are investigated. The influence of the allocation and dimension of the damper winding on the induced voltage suppression, as well as the power generation performance is comparatively analyzed. A prototype of the stator-damper-winding DSBLDC generator is designed and developed. The experimental results show that the induced voltage of the field winding is reduced by more than 90%, while the output power is nearly close to that of the conventional DSBLDC generator.

This paper presents a partial-power post-regulated LLC resonant converter. In the proposed topology, the input power is first transferred to the secondary side of the transformer through the LLC-DCX converter to achieve galvanic isolation and voltage conversion functions. Then, most of the power is directly transmitted to the load side, and only a small portion of the power is converted to the output side by the partial-power processing converter (PPC). Therefore, unlike the two-stage solution, the converter proposed in this paper achieves output voltage regulation while minimizing the efficiency loss caused by the two-stage conversion. The operating principle of the proposed converter is analyzed, and the system prototype is constructed. Experimental result validates the correctness of the analysis and proves the feasibility of the proposed converter.

The brushless doubly fed motor (BDFM) shows great potential for use in large medium-voltage adjustable-speed drive (ASD) systems due to its high reliability and cost benefits of a partially rated low-voltage power electronics converter. However, undesired performance caused by rich useless space-harmonics restrict the application of the BDFM in medium-voltage high-power ASD systems. In this paper, a medium-voltage wound rotor BDFM consisting of specially designed stator and rotor windings is developed. Firstly, the wound rotor with unequal turns and unequal pitches is designed and then compared with a nested loop counterpart. In addition, a 10 kV single-layer winding with shifted slot number in the stator is proposed to further reduce the space-harmonics by equivalent pitched effect. The finite element model of the BDFM is established to analyze electromagnetic performance and the influence of magnetic slot wedges. A lumped parameter thermal model is developed to quickly evaluate the average temperature rise of the proposed prototype. Field tests of driving a circulation water pump in a steel rolling mill were conducted to validate the feasibility of the proposed scheme.

In this paper, a new triple-switch triple-mode (TS-TM) high step-up DC-DC converter has been proposed. The proposed converter consists of three switches, four diodes, two magnetically coupled inductors, and three capacitors. This converter can provide a high voltage conversion ratio with high power efficiency and low voltage stress across the power semiconductor components. Due to the low voltage stresses of the power semiconductors and implementing the coupled inductors technique, the proposed converter is a low-cost and high-efficient structure in comparison to the other similar TS-TM structures. In order to clarify the advantages of the proposed converter, the required mathematical calculations and comparison results with similar converters are presented. Also, a novel TS-TM with transformer (TS-TMTR) has been proposed to overcome the electromagnetic interface (EMI) problems. Furthermore, a 500W experimental prototype is built and its performance with different values of duty cycles has been tested to prove the claimed features of the proposed converter. 94.5% maximum power efficiency of the assembled prototype has been obtained at 260W output power.

Automotive applications demand high efficiency, good reliability, and a wide operating speed range within limited DC bus voltage constraints. In this paper, a zero degree displacement dual three-phase PMSM is derived from an original 3-phase PMSM to enhance the power rating as well as the operating speed range. The proposed topology can be used as an alternative to the conventional configuration of three-phase PMSM with a bidirectional DC-DC converter for electric vehicles. Even though the commonly used dual three-phase PMSM with split-phase winding eliminates the sixth harmonic torque pulsation, a large circulating current is generated during six-step operation, which results in additional stator copper loss. In this paper, six-step operation of the symmetric dual three-phase PMSM with zero degree winding displacement is proposed to achieve maximum inverter utilisation. Both harmonic circulating current and torque pulsation were observed to be within satisfactory levels using this configuration. A changeover algorithm is also proposed to enable a smooth transition between closed-loop current vector control during low and medium speed operation to open-loop six-step voltage angle control for high speed operation. The performance of the proposed method is experimentally validated on a 3kW dual three-phase PMSM drive.

Recently, inverters with a common ac and dc ground are gaining significant interest due to their zero common-mode voltage that made them particularly attractive for the solar photovoltaic application. However, the dc source current of the existing topologies is discontinuous, and their voltage gains are limited. This article proposes a novel common-ground-type boost inverter that achieves continuous dc source current with significantly enhanced dynamic voltage gain. It consists of one boost inductor, four capacitors, nine power MOSFETs, and two power diodes. Voltage boosting and generation of nine-level ac voltage are achieved concurrently within a single-stage operation. The operation of the proposed CGT-9L-BI inverter is analyzed. Simulation and experimental results are presented for validation.

This paper proposes a traveling wave based scheme for wye-connected shunt capacitor bank protection. The proposed method provides high sensitivity and fast response, assisting in mitigating capacitor damage during internal cascading failure. The available protection schemes for capacitor bank use RMS values of voltage and current phasors for trip decision. Threshold selection is required in these methods which needs accurate estimation of equivalent capacitance of the bank. In addition, phasor being estimated from one-cycle running data window, such a method is slow. The proposed traveling wave based method identifies an internal fault in case of opposite polarities of traveling waves seen in the terminal voltage and current signals of the faulted phase. If the mid-point tapping is available in capacitor bank, the faulted half can be identified using the traveling wave of tap voltage. The magnitude of the traveling wave in terminal voltage reveals the number of failed capacitor elements. Such information assists in expediting maintenance. The performance of the proposed method is tested using PSCAD/EMTDC simulation data for various situations, including internal short circuit, external, and identical faults in the shunt capacitor bank. Comparative analysis highlights its higher sensitivity and better accuracy in comparison to available protection methods.

This paper presents a ground breaking traction drive for fuel cell powered light rail vehicles based on a multilevel cascade converter with H-bridge cells. The converter provides dc-ac power conversion with unique buck-boost capability to compensate for the variation of fuel cell terminal voltage with the load power. In comparison to a conventional boost inverter, based on the cascade connection of a boost dc-dc converter and a voltage source inverter, the proposed converter has the significant benefits of much smaller inductor size, lower dc side current ripple, and multilevel voltage waveforms at the ac output. This paper presents the converter modelling and design of the boost inductor and sub-module capacitors, taking into account the full speed range of the motor. The concept has been fully validated on a bespoke experimental prototype driving a small induction motor, showing the suitability of the proposed converter as a traction drive for hydrogen-powered rail vehicles.

Reliable and affordable AC/AC power conversion plays a key role in supplying various electrical equipment. Among the options available, direct matrix converter (DMC) outperforms its counterparts (e.g. AC/DC/AC), in terms of lifespan and compactness, due to its omission of fragile and bulky dc-link capacitors. However, most off-the-shelf DMC modules suffer from high input current spikes, which if unresolved, can noticeably increase current stresses and lower efficiency. Origin of the spikes and a mechanism for reducing them are hence studied in the paper, before developing a low-cost SiC-Si hybrid module for implementing DMC reliably and compactly. The developed module consists of 18 Si insulated gate bipolar transistors (IGBTs) and 18 SiC junction barrier Schottky (JBS) diodes connected in a common-collector structure. The improved reverse recovery property of the SiC JBS diodes then permits the hybrid module to operate with mitigated current spikes. To demonstrate, the hybrid module has been fabricated, tested and compared with two counterparts in terms of their input current spikes and power losses over different output voltages and switching frequencies. Experimental results have proven the expected performances of the hybrid DMC module, which collectively, can accelerate large-scale emergence of small all-semiconductor drives for industrial pumps, cooling and refrigeration systems, and others widely needed in developing economies.