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The hybrid-series-converter-(HSC) has enhanced operating modulation-index-(MI) range as compared to the parallel-hybrid-converter-(PHC). However, the HSC is underutilized when employed for high-voltage-direct-current-(HVDC) applications, HSC-HVDC. The parallel-chain-links-(PCLs) of HSC-HVDC generate fixed voltage and the series-chain-links(SCLs) of HSC-HVDC serves only as voltage wave-shaping circuit and does not increasing the output voltage levels. Thus, energy storage requirement of HSC-HVDC is higher than PHC. The switches of HSC-HVDC undergo forced commutation and increase losses. This paper intends to extract all the advantages inherent with the HSC and utilize it to its maximum capability by operating it as a static-compensator-(STATCOM), HSCSTATCOM. The proposed HSC-STATCOM requires lesser switching devices, capacitors besides having reduced energy storage requirements and zero-voltage-switching-(ZVS) nature. A new capacitor voltage control technique during unbalanced grid conditions is also proposed in this paper. The operating principle of the proposed STATCOM and proposed control technique is validated using different simulation case studies.

This paper investigates the dynamic characteristics of AC microgrids in the presence of Constant Power Loads or Constant Power Sources (CPL/CPS). This dynamic characteristic is useful for understanding how AC microgrids behave in different operating points. If the dynamic characteristic is not desired, microgrids’ components can be tuned or proper approaches can be adopted to improve it. In this paper, the input impedances of a non-ideal CPL/CPS is mathematically derived through vigorous modeling. Moreover, the closed-loop output impedance of a distributed energy resource regulating the microgrid voltage is modelled. A unifying approach is adopted to transfer impedances of AC microgrid components to the same coordinate in order to utilize impedance-based stability analysis to assess the dynamic characteristics of AC microgrids in different operating points. Finally, simulation results are provided to validate findings.

This paper focuses on the multi-circuit HVDC transmission system which can localize DC line faults. The conventional method requires to shutdown and restart the wind power plants after the DC line faults, resulting in the long-term suspension of the power plants. This paper proposes a control sequence for enabling continuous operation of wind power plants under DC line faults in the multi-circuit HVDC transmission system. The proposed method reduces the power outage after the DC line faults. Simulation results demonstrate that the proposed method enables continuous operation of the wind power plants and reduces the power outage to 0.2 seconds.

This paper expands a previous study regarding application of modular variable filter inductor in a cascaded H-bridge low-capacitance StatCom (LC-StatCom). In this paper, the benefit of having such a filter to expand the operating capability of the LC-StatCom into the inductive region is demonstrated. A comparison between the modular filter inductor and thyristor bypassed series inductor solutions is performed through derivation of analytic expressions. The added capacity to operate in the inductive region is also validated via experimental results.

Due to easy implementation and fast dynamic response, deadbeat predictive current control (DPCC) has been got wide attention for permanent magnet synchronous machine (PMSM) drives. In order to further enhance DPCC performance, it is meaningful to compensate the voltage distortion caused by inverter nonlinearity. In this paper, an internal model control (IMC) is employed to constitute a voltage distortion estimator. In addition, the DPCC with the voltage distortion estimator is proposed. Compared with other compensation methods, the proposed method can be utilized for different PMSM speed and dc-bus voltage conditions. To verify the effectiveness of the proposed method, experimental results are carried out in this paper.

Mission profiles are widely used for the reliability analysis of power converters. Typically, to assess the converter reliability, long-term (e.g., one year) mission profiles are adopted, and it is assumed that the profiles will be repeated in future years. However, due to mission profile uncertainties, the assumption can introduce considerable errors in the estimated reliability. In this paper, the errors introduced by the above assumption are studied in detail. Furthermore, to tackle this challenge, the paper proposes using the Generative Adversarial Networks (GAN) to generate unique mission profile scenarios that capture the temporal and probabilistic properties of the real profiles. In this regard, the effectiveness of using the GAN-generated profiles to improve the accuracy of the estimated reliability is demonstrated.

Solid-State transformers (SST) consist of isolated bidirectional DC-DC Converters as a link between the Active Front End (AFE) and the DC-AC converter to adjust the voltage across the two DC links. Dual-Bridge Series Resonant Converter (SRCDAB) is one of the promising topologies for such applications. In this paper, the design methodology for SRC-DAB is explained for wide-input voltage range which can be used in universal voltage SSTs across global LV grids. The converter operates using Single Phase Shift (SPS) modulation scheme with a constant and unique switching frequency for different grid connections. The practical methodology of selecting the switching frequency, transformer turns ratio and resonant tank parameters for minimum peak semiconductor losses for the complete input voltage range has been described in this paper. The converter is designed to provide constant power output of 50 kW at 750 V for an input voltage range of 300-800 V. An experimental 10 kW prototype is shown.

A novel long distance multi-coil wireless power transfer (WPT) system with constant voltage (CV) output characteristic is designed and optimized in this paper. The CV output multi-coil WPT system mathematical model is systematically analyzed and summarized, and the system operating frequency can be calculating by this model. Through state deconstruction analysis, this paper has analyzed the distance between adjacent coils on the transmission efficiency of WPT system at a long distance. Finally, the experimental results are consistent with the theoretical analysis, and the maximum transmission efficiency is 54.2% under the transmission distance of 1.1 m.

More Electric Aircraft’ (MEA) is a trend for medium and long haul airliners, in which all functions except propulsion are powered by engine-driven electrical generators. Power systems for MEA are in the process of rapid development. Constant Power Loads (CPL) pose a big challenge for power system stability. This paper proposes a concept of a MEA power system with a common DC bus, where power sharing between generators is achieved without droop or explicit communication. The paper shows how a coordinated response can be achieved by multiple DC-DC converters under PI current control, based on the local current measurements only. It utilises advanced control concepts, including feedforward and multiple degrees-of-freedom design. The paper demonstrates stability of the proposed power system with respect to any load type, including CPL. The findings of the paper are validated by detailed simulations and preliminary experimental results.

This paper formulates a discontinuous modulation (DM) technique for cascaded H-bridge (CHB) static compensators (StatComs) with star configuration. In the CHB StatComs, capacitor voltage (CV) oscillations cannot be disregarded when using relatively small dc-link capacitors. For this reason, in this paper, DM is achieved by injecting a zero-sequence voltage (ZSV) that takes into account the inherent CV oscillations. Then, the coupling that exists between the CV waveforms and the injected ZSV is analyzed. Particularly, the steady-state reference signals for the CHB StatCom operated discontinuously are analytically calculated. The practicability of the proposed DM technique is verified experimentally.

3-Level Voltage Source Inverters (3L-VSI) have emerged as effective approach to achieve high efficiency and better harmonic distortion performance. As a State-of-Art (SoA), two types of carrier arrangement methods are used for carrier-based pulse width modulation (PWM), namely, phase disposition (PD) and alternate phase opposite disposition (APOD). PD PWM gives better performance in terms of current quality and Total Harmonic Distortion (THD) whereas, APOD PWM is more effective for suppression of Common-Mode Voltage (CMV) with the expense of increased THD. In this paper, a novel Quasi-reference PWM method for 3L-VSIs is presented which results in low CMV as that of the APOD along with the reduced THD. The proposed method can be considered as a distinct trade-off between the two SoA methods, which maintains the merits of both. This paper presents the detail analysis and experimental verification of the proposed PWM technique.

This paper analyzes the torque equation of an interior permanent-magnet synchronous machine (IPMSM), including magnetic saturation, spatial harmonics, and the variation of the magnetic energy. Based on the analysis, a torque-sensorless method is proposed to identify an IPMSM’s torque map. Since magnetic energy cannot be measured in the experiment, its effect on the torque is indirectly considered using the gradient to dq-currents. In this paper, the torque gradient is formularized with the flux-linkage map; it is verified by finite element analysis (FEA). With the formularized torque gradient, the proposed method reconstructs IPMSM’s torque map through the gradient theorem. Experiments veify the proposed method’s effectiveness.

This paper introduces a common-mode voltage reduction method based on zero-sequence voltage injection for a back-to-back three-level NPC converter. A detailed analysis in the following paper will show that the amplitude of common-mode voltage in this converter is related to the rising and falling edges of six-phase output voltage pulses, and it is reflected by pulse widths of output voltages in the waveform. When the pulse widths of six-phase output voltages meet a certain relationship, the common-mode voltage will output a higher amplitude. By injecting zero-sequence voltage, widths of output voltage pulses can be changed. According to this principle, a dual-side zerosequence voltage injection method is proposed to change output voltage pulse widths and decrease the common-mode voltage amplitude. Simulation and experimental results show that the proposed method is effective, it can reduce the common-mode voltage to 1/6 of the DC-link voltage in the back-to-back three-level NPC converter.

This paper proposes a four-port AC/DC-DC/AC converter composed of a half-bridge converter and a full-bridge converter replacing their inductive filters by means of a transformer. The power balance between the ports is achieved through both duty-cycles and the phase angle between the voltages applied by these bridges. The analysis of the converter was accomplished by using the superposition principle allowing to define different modes of operation. Furthermore, a control strategy is proposed for an application of the converter and in order to corroborate the theoretical analysis, simulation and experimental results are introduced. Finally, the performance of the converter is assessed as a function of the delivered power.

Thomson Coil Actuator (TCA) has gained increased research interests in recent years due to the fast response as well as manageable losses. Therefore, this paper presents the design and analysis results of a single and double fixed coils TCA. The actuator is developed as a part of an extra fast medium voltage hybrid DC Circuit Breaker (CB) for DC modern grids. The design analysis for the single fixed coil TCA highlights the challenges that the actuator may experience with higher excitation voltage. Furthermore, a double-sided TCA version has been designed and compared to the single fixed coil one demonstrating the essential advantages that the double-sided version has. In addition, other design aspects such as mechanical and thermal analysis have been studied and presented in order to guarantee higher reliability of the actuator during its operation. Also, a comparison of the TCA vs. a conventional solenoid-based actuator will be presented.

The magnetic flux valve (MFV) is a novel electromagnetic device for controlling the magnetic flux in magnetic circuits. Due to the corner effect, when a control voltage is applied on the MFV, the electric field around the corners of the MFV is much larger than that in the center of the MFV. Therefore, the corner effect of electric field should be considered in the insulation design of the MFV. To minimize the impact of the corner effect on the MFV, this paper first reviewed the MFV’s structure and working principle, analyzed the corner effect of the electric field of the MFV, and then proposed four design options to study the impact of the corner effect on the MFV. The four design options were numerically simulated with the finite element method in Ansys Maxwell. Based on the simulation results, the best design option with the minimum corner effect is determined for the MFV.

The three-phase four-leg four-wire (3P4L4W) three-level (3L) inverter, constituted by three 3L phase-legs and a fourth two-level (2L) phase-leg, is capable of feeding both balanced and unbalanced loads. In this paper, a closed-loop common-mode (CM) load-voltage control incorporated decoupled modulation scheme (CL-DMS), which combines the advantage of the three-dimensional space-vector modulation (3D-SVM) with the closed-loop control for the CM part in the load voltages and the advantage of the carrier-based modulation scheme with the low complexity for implementation, is proposed for the 3P4L4W3L inverter. In doing so, the 3L phase-legs are modulated to attain both the voltage balancing control for the split dc-bus voltages and the closed-loop control for the differential-mode (DM) load voltages, whereas the fourth leg is independently modulated to realize the closed-loop control for the CM load voltage. The proposed work has been verified on a 10-kVA 3P4L4W3L inverter. The experimental results show that the proposed decoupling modulation scheme benefits the 3P4LW3L inverter with well-balanced split dc-bus voltages and well-balanced load voltages with low total-harmonic-distortion (THD) for both balanced and unbalanced loads.

Synchronous rectification (SR) is widely adopted for low-voltage high-current applications to improve efficiency. However, most SR researches focus on low power levels at hundreds or several kilowatts, and there is yet any attempt to extend SR to tens of kilowatts. This paper presents the design and experimental results of a full-bridge SR using ON-Semi NCP4305 SR IC at 20kW for 48V data center application.

In this paper, a novel constant current control method, with improved dynamic performance over the conventional PI method, is proposed for the CLLC converter. We proposed a state trajectory model for the CLLC converter. Based on the proposed the state trajectory analysis, a novel dead-band based control method with improved dynamic performance is proposed. The effectiveness of the proposed method was verified by experimental results. The response time was hugely reduced (less than 50% of the PI method) and no overshoot was detected.

This paper presents a novel solution for the parallel operation of gradient power amplifiers to drive the gradient coil within magnetic resonance imaging system. A total-current feedback algorithm collaborating with a current-sharing algorithm, also with a small magnetic core ensure tight load sharing without large coupling reactor. The control bandwidth has not to be compromised, resulting in fast, smooth and high fidelity performance. Experimental results verify the effectiveness.

Droop control is a commonly used method for load current sharing between the converters in DC microgrid applications. In droop control, the current sharing performance gets degraded due to the resistance of the cables and other non-idealities. Secondary control approaches are typically used along with droop control to achieve accurate current sharing among the converters. However, secondary control methods can result in the converter steady-state output voltages exceeding the design or permissible voltage limits. In this paper, a tertiary control method is proposed to ensure that the converter steady-state output voltages remain within the safe bounds under all operating conditions. The proposed tertiary control loop gets activated when any of the converter output voltages exceed the permissible limit, and modifies the current sharing ratio to ensure that the converter steady-state output voltages are bounded. The proposed tertiary control approach is verified using extensive switching circuit simulations. Further, a hardware-based experimental DC microgrid test-bench is used to validate the effectiveness of the proposed tertiary droop control.

High frequency multiresonant electronic ballasts have been widely used into fluorescent lamps because it can obviously prolong the life of fluorescent lamps. In this paper, a passive integrated passive unit with the flexible multi-layer foil (FMLF) integration technique is proposed to improve the power density of the high frequency multiresonant electronic ballast. Furthermore, the construction, flux analysis and parameter design of the integrated unit are demonstrated in detail. Finally, a simulation model based on Maxwell/Ansoft and a prototype for a 68W-23.5kHz multiresonant converter electronic ballast are established to verify the feasibility of the proposed idea.

Extreme events such as faults, cyber-physical attacks, and natural disasters have a widespread impact on the electrical system infrastructure, leading to extensive power outages or blackouts. These events can cause temporary or permanent damages to the power systems and seriously compromise the system’s resiliency. A quick restoration strategy for the systems’ critical loads after extreme events is crucial to ensure resilient operation. This paper presents a fast load restoration (LR) approach for multi-agent-system-based networked DC microgrid systems with distributed energy resources. The overall restoration problem is designed with a weighted sum optimization technique that consists of operational costs, load pickup costs, and optimum power-flow-related costs. It was solved in a distributed manner by applying Alternating Direction Method of Multipliers (ADMM) algorithm through multi-agent communications. The effectiveness of the developed LR technique is verified by applying it to a networked MG system of 4 single-bus DC MGs.

The asymmetric half-bridge converters are usually used for the switched-reluctance motor (SRM) drive. The current tracking speed and the current ripple are dependent on the switch-bus voltage. The larger the switch-bus voltage is, the faster the current tracking speed is, but the larger the steady-state current ripple is. In this paper, the bidirectional voltage-multiplier front-end converter (BVMFEC) with two switch-bus voltage level is proposed to meet the requirement of the current tracking speed and the current ripple. Single current sensor and single voltage sensor are used to control the BVMFEC-fed SRM drive. The proposed converter and SRM drive is demonstrated by the provided simulation results and the experimental results.

In high-speed machines, the AC copper loss is a serious issue that can't be neglected. In this paper, two new transposition technologies for both single coil and series coils are proposed. With the help of specific winding formers, the proposed transposition technologies can be achieved in engineering for random-wound windings without loss of slot filling factor. The technologies are used in a 200 kW 54000 rpm high-speed permanent magnet synchronous machine (PMSM). The simulation results show that the suppression effect of the proposed transposition technologies on the AC loss is very significant and the copper loss can be reduced by up to 92% at 1800Hz. Finally, experiments are carried out on the stator of the 200 kW 54000 rpm PMSM to validation the effectiveness of the proposed transposition technologies.

This paper has developed a static synchronous compensator (STATCOM) based on the open-DC modular multilevel converter (MMC) which has one more degree of freedom than the cascaded H-bridge converter to deal with the unbalanced grid conditions. In addition to the negative sequence current and the zero sequence voltage, the DC circulating current is also available in the open-DC MMC so that there are three control freedoms for addressing the unbalanced grid conditions. The corresponding control scheme is thus designed, and the laboratory test results are provided as well to validate the proposed control scheme.

In electric vehicles, power consumption and a wide speed range with high motors power are essential. Permanent magnet (PM) motors exhibit high capacity and efficiency. However, the flux-weakening control technique may cause significant iron and copper losses and high harmonic iron losses to decrease the back-EMF at high-speed. This paper proposes a variable-magnetization technique for PM in the interior permanent magnet (IPM) motor by a field due to the small magnetization current to achieve variable back-EMF and describes the proposed IPM motor using its technique produces high power over a wide speed range. Our results indicate that the proposed PM motor can vary the de- and re-magnetization and achieve compatibility between a wide variable back-EMF range and a small magnetization current. Furthermore, our analysis results confirm that the proposed IPM motor can produce high torque over a wide speed range by varying the magnetization state of PM.

In this paper, a problem of huge voltage overshoots (V OVERSHOOT ) of VDS in GaN FETs, which rarely happens during an automatic search of optimum gate driving parameters in a digital gate driving (DGD), is clarified for the first time, and a solution to avoid the problem is proposed. The highest V OVERSHOOT in 165k measurements, where parameters of 6-bit DGD IC in 6 time slots in 3.3-ns time intervals are randomly changed in the turn-off of GaN FET at 20 V and 10 A, is 27.6 V, which is 115% larger than the conventional single-step gate driving (CSG) and is almost equal to the maximum rated voltage of the GaNFET. To solve the problem, a safe and fast search method of optimum parameters for DGD is proposed, which achieved 61% reduction of the switching loss and 59% reduction of V OVERSHOOT compared with CSG.

The influences of on-resistances and parasitic elements on the static current sharing of N-paralleled discrete silicon carbide (SiC) MOSFETs are analyzed in this paper. First of all, the limitation of self-balancing effect of MOSFETs caused by the positive temperature dependent on-resistance is quantitatively analyzed. From a statistical analysis, the current sharing distribution according to the spread of on-resistances is presented, which helps to screen the proper devices based on the current sharing requirement. Furthermore, a general circuit model is proposed to analyze the effect of inevitable circuit parasitic elements on current sharing with a given current slew rate. With the recursive circuit model, current imbalance contributed by parasitic resistances and inductances can be separately calculated, which can be used to guide the hardware design to improve current sharing in a real converter. The theoretical analysis is verified by experimental results.

This paper presents a new modeling and analysis approach to address the small-signal stability issues among interconnected grid-forming (GFM) inverters. A novel phasor domain “power impedance” model is developed to capture the terminal characteristics of GFM inverters. Based on the developed models, a sum-type impedance stability criterion is proposed to analyze the power oscillations between GFM Inverters. The developed models are validated with EMT simulations and the stability analysis results using the proposed stability criterion can match both EMT simulations and eigenvalue analysis. In addition, the application of the developed model can be extended to the stability analysis of large-scale power system with high penetration of GFM inverters.

In this paper, a novel fault diagnosis scheme has been proposed to detect and identify the occurrences of open-switch failures at the four-level active neutral-point-clamped (4L-ANPC) inverter. This technique is developed based on two inherent voltage parameters which are effective to detect and identify the critical faulty devices. An auxiliary balancing circuit is also selected and applied to support the inverter operation during fault occurrence and prevent further failures at other devices. The effectiveness of the proposed scheme has been verified by simulation results.

In wireless charging applications, multiple phases of the inverter can be paralleled to enhance the power level. Even though the same pulse-width modulated signals are applied for the corresponding switches, there can still be phase differences in the driving pulses which directly turn on/off the switches, due to the inconsistency in the switch parameters or driving circuits. The different driving pulses can result in large circulating currents, which decrease the power level. Current balancing techniques can be adopted to solve this issue. This paper proposes a passive current balancing method for wireless charging. Compared with the existing method, the proposed method can reduce the number of coupled inductors by half and balance every two sources to achieve good current balancing performance. Experimental results have validated the effectiveness of the proposed method.

The penetration of distributed generation (DG) into the electricity supply mix has increased at the distribution level. The DG size is typically smaller than that of centralized power plants, and thereby the DG is generally decentralized. Thus, this has complicated DG's connection requirements in the grid codes worldwide and brought difficulties in deploying renewable generation. Thus, the paradigm shift at the distribution level brought the concept of microgrids (MG) to reduce the DG's effect on a whole power system. Due to the significant growth of the DG, there has been a need for a methodology to manage MGs to operate MGs optimally and reduce system impact. This paper proposes an optimal separation method of a distribution network consisting of multiple MGs to enable the MGs to respond to unexpected disturbances optimally. To achieve this, the authors enhance a conventional MG-partitioning algorithm by considering supply-demand balance and the minimum number of dispatchable generators in individual MGs. The proposed algorithm's performance was tested using a modified IEEE 33-bus radial distribution system and indicates that the proposed algorithm gains more advantages than the original k-way partitioning scheme.

Compared to the traditional isolated bidirectional DC-DC converters (IBDC), the parallel-resonant isolated bidirectional DC-DC converter (PR-IBDC) has many benefits, such as high efficiency, low current ripple and high voltage gain. In this paper, a passive integrated unit with the flexible multi-layer foil (FMLF) integration technique is proposed to improve the power density of the PR-IBDC since many passive components are used in this converter for power conversion. Furthermore, the construction, flux analysis and parameter design of the proposed integrated unit are introduced in detail. Finally, a prototype and a simulation model based on Maxwell/Ansoft are built for a lkW-200kHz PR-IBDC to prove the validity of the proposed idea.

Due to high efficiency and bidirectional capability, unregulated CLLC converters have significant potential for the DC transformer and chargers with two stages, where the switching frequency is designed to be fixed at resonance. However, the actual resonant frequency may drift from the designed value because of resonant tank component tolerances, temperature, and aging. This leads to a decrease in efficiency for unregulated CLLC converters with a fixed frequency. To solve these issues, a bidirectional resonant frequency tracking method is proposed for CLLC converters in this paper. Based on the analysis of input and output impedance, a unique feature is discovered that no matter how resonant tank parameters deviate, the switching frequencies harvesting maximum efficiency are identical for bidirectional operations. To track this global optimal switching frequency, the proposed method adopts a voltage edges-based sensing technique, so the bidirectional tracking is realized and costly current sensors of conventional methods are eliminated. It is lower cost and robust against noise. Experimental results show that bidirectional fast-tracking and efficiency improvement are achieved for parameter deviation conditions.

The alternate arm converter (AAC) is being considered as a potential alternative for MMC in HVDC applications because of lower energy storage requirement and dc-fault tolerant capability. However, to achieve energy balancing over wide range of operating modulation indices, it requires a dedicated controller that needs to exchange the unbalanced energies between the upper and lower arms of each phase-leg to achieve the balancing of its SMs capacitor voltages. In this paper, a new control scheme is proposed for AAC to balance its SMs capacitor voltages. The proposed scheme is based on the constant overlap-time and the magnitude of current during overlap-time is varied depending on the operating modulation index and power-factor. As the overlap-time is kept constant in the proposed control scheme, the operation of AAC can be extended to higher modulation range without increasing the number of SMs per arm. A detailed analysis of arm energy in AAC is presented to determine the required magnitude of current to be injected during the overlap for energy balancing. The efficacy of the analysis and the control scheme is verified using simulation and experimental studies on a scaled down laboratory prototype.

One possibility for onboard electricity generation in a hybrid vehicle is a free piston engine incorporating an integrated linear generator. This paper presents the modelling and development of the linear engine generator concept, where a linear electrical machine is physically integrated within a free piston engine. Details and results of a multi-physics simulation of this concept are given, with a focus on the design of the electric machine. It is shown that a short translator design can result in the highest power density. This also gives the opportunity for integrating the electric machine physically within the compressor. Details of a prototype demonstrator of the resulting generator-compressor are given.

A synchronous rectification increases efficiency and mitigates thermal issues by replacing the diodes with switching devices. For this reason, a number of studies carried out the implementation of synchronous rectification for resonant converters. However, a thorough investigation on optimized synchronous rectification of Class-E resonant rectifier for a wide range of load was not addressed in previous works. This paper proposes a design and control method of synchronous Class-E resonant rectifier with comprehensive analysis. The switch ON and OFF analysis is developed based on the operating characteristics and mathematical equation of the synchronous rectifier for a wide range of loads. The optimum duty ratio is analytically investigated, and the proposed tracking algorithm ensures the optimum operation of synchronous rectification. As a result, the proposed method minimizes the switching and the diode conduction loss of the rectifier. For verification, a prototype of a 40 W resonant converter is implemented. The experimental result confirms the validity of the analysis and the control method with a fast dynamic response for all ranges of load.

Common-Ground (CG)-type multilevel inverters exhibit some interesting features in removing the concern of ground leakage current and improving the overall efficiency of the system within a single power processing stage. In this paper, a new reduced-switch count five-level (5L)-CG-based inverter is proposed, which offers a step-up voltage boosting property and can be extended to the three-phase systems whilst maintaining its CG-feature. The circuit descriptions, comparative study and the relevant measurement results for both the single and three-phase systems are presented to verify the feasibility of the proposed topology.

Schottky diodes have little to no reverse recovery charge due to the lack of a PN junction or associated minority carriers. However, commercial Schottky diodes incorporate a PN junction guard ring under the electrode edge. At high currents, conduction through the guard ring structure can occur, injecting minority carriers and increasing reverse recovery charge. This behavior can lead to adverse circuit effects and increased loss, especially in high frequency dc-dc converters. Moreover, this effect is little-discussed in technical literature, not captured in datasheet provided values, and not typically incorporated into manufacture provided simulation models. This paper provides an open source and low-cost diode recovery test circuit and uses it to evaluate a selection of small-signal Schottky diodes and rectifiers. In several of the diodes, we find a significant increase in the recovery charge at high currents, characteristic of the PN junction guard ring’s conduction.

This paper presents a comparison of optimized tooth-coil-winding modular permanent-magnet synchronous machines (TCW-MPMSMs) with H-shape and U-shape stator segments for fault-tolerance applications. Four optimization objectives are studied by means of a Particle-Swarm-Optimization (PSO) based routine: maximum rated torque, minimum torque ripple, maximum efficiency, and minimum mutual inductance. Two 22-pole and 24-slot TCW-MPMSMs with H-shape and U-shape stator cores were evaluated and optimized aiming to optimize each objective. From the results, it was found that U-shape machines are suitable for high-torque and low-mutual-inductance requirements, crucial in fault-tolerant applications, whilst H-shape machines offer low ripple torque and slightly lower performance indices for fault-tolerance applications.

In the medium-voltage cascaded Photovoltaic (PV) converter, output of converter modules may differ due to tolerance of PV panels and operation conditions such as temperature and irradiance. The power imbalance problem among the converter modules will results in certain converter module over-modulated. Reactive power control (RPC) scheme is a newly emerging way to ensure the normal operation of the cascaded PV converters under imbalance conditions. However, the existing discussions of the RPC scheme have not yet penetrated into the detailed calculation and the optimization of RPC scheme. In this paper, the method to minimize the reactive power, i.e. minimize the conduction power losses caused by the reactive power injecting is discussed in detail. Based on the analysis, a detailed RPC scheme is proposed. The proposed scheme enhances the adaptability of the RPC scheme while minimizing the injected reactive power. Finally, a prototype was built and the experimental results validate the proposed scheme.

The ON-OFF controlled very high frequency Class E dc-dc converter has been widely investigated for achieving high power density and high fast dynamic response. However, the ON-OFF controlled converter is not able to limit the converter output current in the event of the overload or short-circuit fault, bringing the converter with the potential risk of overcurrent damage. To solve this problem, this paper proposes a current limiting scheme for the ON-OFF controlled converter, with which, a current regulator is added to limit the converter output current in presence of the overload or short-circuit fault without impacting the converter’s normal operation. Experimental results have been provided to verify the feasibility of the proposed current limiting scheme for a 30 MHz,10W ON-OFF controlled Class E dc-dc converter.

Fast charging is an enabling technique for the large-scale penetration of electric vehicles. However, the pursuit of utmost charging speed risks the violation of critical physical limits companied by the unexpected thermal/stress buildup and side reactions. Motivated by this, this paper proposes a multi-physics constrained fast charging strategy of the lithium-ion battery (LIB). In particular, a novel stress-coupled electrochemical model is established to describe the mechanical-electro-thermal dynamics of the lithium-ion battery (LIB). Based on this, A stress-and thermal-limited fast charging method is proposed based on the model predictive control (MPC) method. Comparative results show that the proposed charging strategy can improve the charging speed of LIB while fulfill the thermal and mechanical tolerance, which promise a favorable thermal safety and longevity.

In this paper, a new level shifted pulse-width modulation (LSPWM) method utilizing the suggested intermodulated floating carrier signals is proposed for the nine-level packed U-cell (PUC9) converter. In the proposed inter-modulated floating carrier LSPWM (IFC-LSPWM) technique, six floating carrier signals are modulated between the main eight level shifted fixed carriers to achieve active voltage balancing of the auxiliary capacitors. Hence, the staircase nine-level output voltage is generated by employing eight fixed level-shifted PWM carrier signals whereas six inter-modulated floating carrier signals provide voltage balancing of the auxiliary capacitors. Therefore, the proposed IFC-LSPWM method does not require any logic gates or comparison loops to provide voltage balancing of the auxiliary capacitors. Moreover, constant switching frequency operation and the reduced values of the auxiliary capacitors are obtained by employing the proposed IFC-LSPWM. The proposed IFC-LSPWM method is applied to the three-phase PUC9 converter. The provided experimental results verify the viability and performance of the proposed IFC-LSPWM method.

Intermittent renewable solar photovoltaic (PV) sources cause reliability and power quality issues in the power system. To alleviate these issues, flexible power point tracking (FPPT) algorithms were introduced. The secant-based FPPT algorithm does not require tuning of any parameter, making it a reliable control algorithm whose performance remains unaffected even after PV modules degradation. This paper focuses on the calculation of initial parameters and the implementation of the secant method-based FPPT algorithm considering PV panel degradation. Simulation and experimental comparisons are made between a conventional FPPT algorithm based on adaptive voltage step-based perturb and observe (P&O) method and the secant method-based algorithm during normal and degraded panel state of operation.

This paper presents a general method to extract dominant device model parameters for analyzing the current imbalance of parallel-connected Silicon Carbide (SiC) metal-oxide-semiconductor field-effect-transistors (MOSFETs). The proposed method is based on a sensitivity-based analytical equation, referred to as N-devices forward propagation of variance (NFPV). Using NFPV, we can accurately and efficiently calculate the energy loss variation as the function of model parameters and their correlations of the N-paralleled devices. The NFPV enables us to quantify contributions of each model parameter to the energy loss variation due to the current imbalance. Experimental results using measured current-voltage characteristics of SiC MOSFETs demonstrate that the proposed method efficiently found the two most important model parameters, with which the energy loss variation is reproduced.

Grid-connected inverters are widely used in the renewable energy such as PV and wind power grid-connected systems. However, actual application results show output power of inverters has an impact on the stability when the system is weak grid. To overcome the stability problem, some control strategies have been proposed. However, few control strategies take into account dynamic response of the system. Moreover, some may cause degradation of dynamic performance like the adaptive control that the PLL bandwidth is reduced to improve system stability. Hence, this paper proposes a new control strategy, which is based on the conventional PLL structure. PLL bandwidth is increased under the proposed strategy when the output power is increased in weak grids. Further, the proposed control strategy enables fast dynamic response of PLL. Moreover, the system can operate stably in the entire output power range. Experiment results are presented to demonstrate the effectiveness of the proposed method.

Synchronous PI current regulators are the preferred option for the current control of ac electric drives. The controller tuning requires knowledge of machine parameters that can change during normal operation, e.g. due to saturation and temperature variations, leading to changes in the current regulator dynamic response. This paper proposes the use of high-frequency signal injection (HFI) for parameter identification. This will enable online adaptation of the current regulator gains, eventually making their response robust against parameter variations.

A pole changing motor can operate in a dual pole configuration for high torque during low-speed operation with a higher pole configuration and an enhanced constant power speed region at higher speeds with a lower pole configuration. In these motors, electronic pole changing is accomplished by changing the currents in certain windings by using an inverter. Although pole-changing transition on the fly has been explored in literature, the specifics as to when a pole change is required is yet to be established. This paper discusses the control of a 4-pole/2-pole induction motor where the controller initiates a pole change from one pole configuration to another to minimize the power loss of the motor when the operating region overlaps for the two pole configurations. Results from Simulink based on parameters extracted from Motor-CAD are provided to validate the control method. The pole changing control results demonstrate a smooth torque transition while minimizing the motor loss. The open loop experimental results are also given.