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Multiphase variable-speed drives and generation systems (systems with more than three phases) have become one of the mainstream research areas during the last decade. The main driving forces are the specific applications, predominantly related to the green agenda, such as electric and hybrid electric vehicles (EVs), locomotive traction, ship propulsion, “more-electric” aircraft, remote offshore wind farms for electric energy generation, and general high-power industrial applications. As a result, produced body of significant work is substantial, making it impossible to review all the major developments in a single paper. This paper therefore surveys the recent progress in two specific areas associated with multiphase systems, namely power electronic supply control and innovative ways of using the additional degrees of freedom in multiphase machines for various nontraditional purposes. [ABSTRACT FROM AUTHOR]

Power electronics is a fast-developing technology within the electrical engineering field. This paper presents the results and experiences gained from applying design-oriented project-based learning to switch-mode power supply design in a power electronics course at the Technical University of Denmark (DTU). Project-based learning (PBL) is known to be a motivating problem-centered teaching method that not only places students at the core of teaching and learning activities but also gives them the ability to transfer their acquired scientific knowledge into industrial practice. Students choose a specification to implement from various power converter application projects, such as a fuel cell power conditioning converter, a light-emitting diode (LED) driver or a battery charger. The students select the topology, design magnetic components, calculate input/output filters and design closed-loop controllers necessary to fulfill the requirements listed in the chosen specification and thus meet the project's goals. This paper presents the course teaching plan and teaching methods, assessment method and student feedback. [ABSTRACT FROM PUBLISHER]

This paper describes a dc-link voltage control method of a single-phase back-to-back cascaded H-bridge inverter (SBCI) for a medium-voltage motor drive system. The main advantage of the SBCI topology over the conventional regenerative cascaded H-bridge topology with a three-phase active front-end (AFE) is a simple system structure, which is composed of an input transformer, a power cell, a current sensor, etc. However, the challenging points of the SBCI are larger voltage ripple in the dc-link capacitor and imbalance of dc-link voltages of each phase. The asymmetric dc-link voltage of each power cells could cause unstable operation such as over-modulation due to the lack of the dc-link voltage of a particular phase and result in over-voltage or under-voltage faults. In this paper, the control strategy of the dc-link voltage for the SBCI that uses the negative-sequence voltage of the converter is described. The proposed control method is verified with a computer simulation whose target is a 6.6-kV–1.25-MW medium-voltage drive system. Also, through the experimental setup with the prototype SBCI whose power rating is 16.2 kVA, the dc-link voltage of each AFE has been controlled within a 0.5% error of its reference value at the full load. [ABSTRACT FROM AUTHOR]

Some electrified vehicles, for example the Toyota Prius, integrate a dc–dc converter between the battery pack and the traction inverter to increase the powertrain efficiency. However, adding this extra converter adversely affects the cost and power density of the powertrain due to the additional components, such as the switches and the inductor, that are expensive and heavy in high-power converters. The concept of the multi-source inverter was previously introduced as an alternative solution to reduce the power rating of the dc–dc converter while keeping similar powertrain performance. In this paper, the implementation of the multi-source inverter in a hybrid power-split powertrain is discussed. The operating modes during both dc–ac and ac–dc conversions are detailed and a prototype is experimentally tested with a load. New control strategies of the proposed powertrain show that three out of five operating modes bring new opportunities in terms of battery charging and power rating reduction of the dc–dc converter. A vehicle-level simulation model is developed in MATLAB/Simulink to quantify the benefits of the proposed topology. Simulations are performed for four drive cycles to compare the power profile of the dc–dc converter of the suggested powertrain with the Toyota Prius. The average power transferred by the dc–dc converter can be reduced by up to 25 $\%$ in most drive cycles tested. [ABSTRACT FROM AUTHOR]

A modular multilevel converter (MMC) is regarded as a promising topology in high-voltage direct current systems. However, the MMC consists of numerous submodules (SMs) and switching devices, which lead to a considerable switching loss, and increased cost and size of the heat sink. To mitigate these issues, this paper presents a novel modulation method composed of fundamental frequency modulation (FFM) and multicarrier-based sinusoidal pulsewidth modulation schemes. The main purpose of this modulation method is the reduction of switching loss while maintaining good harmonic performance. However, the FFM scheme leads to the unbalanced capacitor voltage of each SM in the MMC. Accordingly, this paper additionally proposes the rotation method and selective voltage balancing control for SMs to ensure effective performance of the method. Simulation and experimental results verify the effectiveness and performance of the proposed modulation scheme through switching loss and spectral analyses. [ABSTRACT FROM AUTHOR]

Multioutput converters with single input source are currently studied as an alternative to conventional dc–dc topologies in order to improve power density in low-power multiload applications. This paper reviews three different ways in which a boost topology can be customized to supply multiple outputs. The first way uses a charge-sharing approach using individual switches to distribute inductor energy to different capacitors. The second method of creating a multiport converter (MPC) combines two converters with similar front end to generate two outputs using only one controlled switch. Using this method, a boost converter can be combined with single–ended primary–inductor converter (SEPIC), Cuk, and current source converter topologies. The third method uses time multiplexing of switches to produce two regulated ports and is referred to as switched-boost action. This method uses relatively less number of switches and allows regulation and control of all the outputs. Practical utility of switched-boost action based MPC is reported in this paper. This switched-boost MPC is applied to a renewable power converter system to interface a solar panel, a battery, and home loads to produce a 12-V and a 48-V bus. The 12-V bus is interfaced to battery and capable of optimally charging the battery in constant current–constant voltage (CC-CV) mode. The converter is demonstrated to operate with solar panel as it supplies a 12-V battery and a 48-V load bus. When the solar power is not available, the converter automatically goes into a mode in which the 12-V battery supplies the loads on the 48-V bus. [ABSTRACT FROM AUTHOR]

This paper proposes a new bidirectional resonant dc–dc converter suitable for wide voltage gain range applications (e.g., energy storage systems). The proposed converter overcomes the narrow voltage gain range of conventional resonant dc–dc converters, and meanwhile achieves high efficiency throughout the wide range of operation voltage. It is achieved by configuring a full-bridge mode and a half-bridge mode operation during each switching cycle. A fixed-frequency phase-shift control scheme is proposed and the normalized voltage gain can be always from 0.5 to 1, regardless of the load. The transformer root-mean-square (rms) currents in both the forward and reverse power flow directions have a small variation with respect to the voltage gain, which is beneficial to the conduction losses reduction throughout a wide voltage range. Moreover, the power devices are soft-switched for minimum switching losses. The operation principles and characteristics of the proposed converter are firstly analyzed in this paper. Then the analytical solutions for the voltage gain, soft-switching, and rms currents are derived, which facilitates the parameters design and optimization. Finally, the proposed topology and analysis are verified with experimental results obtained from a 1-kW converter prototype. [ABSTRACT FROM PUBLISHER]

This paper presents a hybrid seven-level converter based on T-type converter and H-bridge cascaded suitable for low-voltage and high-power-density applications. The operation principles and conduction paths are analyzed comprehensively. Voltage balance control of the floating capacitors is the key point of this paper. Mathematical expressions of capacitor voltage balance conditions are deduced based on sinusoidal pulse width modulation (SPWM). The results show that floating capacitor voltages are only balanced when the modulation index is below 0.82 under SPWM. In order to enlarge the modulation index ensuring the capacitor voltage balance, space vector modulation (SVM) is also applied to regulate floating capacitor voltages taking advantage of redundant switching vectors. Meanwhile, in SVM, there are no additional control requirements for the capacitor voltage. Taken both SPWM and SVM into consideration, the limit to the range of operation for this seven-level converter is presented, which is a function of the modulation index and the power factor. The merit of dc voltage utilization improvement in this topology is also analyzed based on simulation results. Simulations and experimental results under different modulation index and RL load are presented to verify the modulation strategies illustrated in this paper. [ABSTRACT FROM PUBLISHER]

An extended-duty-ratio (EDR) boost converter is studied extensively in this paper for high voltage gain applications with a wide input (and/or output) voltage range. The EDR is a unique combination of an interleaved, multiphase boost converter and switched capacitor configuration that achieves high voltage gain with significantly lower switch voltage stress and switching losses compared to conventional high-gain solutions. Most of the switches in the multiphase EDR experience only a fixed fraction of the output voltage ($1/M, 2/M$ , etc., where $M$ is the number of phases). Through extensive analysis over a wide operating range, it is shown here that the EDR boost converter has inherent current sharing among the phases only in a limited range of duty ratio— $(M-1)/M \leq D \leq 1$. As the duty ratio reduces beyond this range as required in wide input voltage applications, inherent current sharing property is lost. In this paper, techniques to ensure current sharing under all operating zones without requiring current sensors are presented. Instead of having equal duty ratio for each phase, it is adjusted for each phase according to the operating region of the converter. Extensive analysis is presented to derive the required duty ratio changes for the different phases. The proposed concept is validated with experimental results from a 250 W, 3-phase EDR boost, and GaN-based hardware prototype. [ABSTRACT FROM AUTHOR]

This paper presents the performance analysis and comparison of two types of bidirectional dc–dc converters—cascaded buck–boost capacitor in the middle and cascaded buck–boost inductor in the middle for use in plug-in electric and hybrid electric vehicles. The comparison of the two converters is based on device requirements, rating of switches and components, control strategy, and performance. Each of the converter topologies has some advantages over the other in certain aspects. Efficiency analysis has been carried out for specific scenarios in vehicle applications. The simulation and experimental results are provided for both converter types. [ABSTRACT FROM PUBLISHER]

This paper presents an asymmetrical cascaded multilevel inverter based on a five-level transistor-clamped H-bridge power cell. A two-cell configuration with a dc link voltage ratio of 4 : 1 is presented. The modulation method is based on the fundamental frequency switching. An analysis of the inverter output voltage and harmonics is presented. Injection of the third harmonic voltage as to maximize the output voltage and the issue of the inverse power flow or regeneration in the low-voltage cell are presented. The prototype of the proposed inverter was built, and its functionality was verified through experimental results. [ABSTRACT FROM AUTHOR]

Phase-shift full-bridge (PSFB) converter is a widely used topology for high-efficiency and high-power applications, thanks to low voltage/current stress of all components and zero-voltage-switching operation of primary mosfets. The critical drawback of the PSFB converter is hard-switching characteristics of primary mosfets at a very light load, which causes severe thermal explosion and extremely high input power consumption, especially with the latest super-junction mosfet. To minimize the switching loss of the PSFB converter at a very light load, a new optimal dead-time control scheme with burst-mode operation is proposed in this paper and its validity is verified experimentally with the implemented 2.2-kW server power supply unit. [ABSTRACT FROM AUTHOR]

Fault-tolerant permanent magnet synchronous generator (PMSG) drives for wind turbine applications play a major role in improving reliability and availability levels, since power converters are very prone to fail. In this paper, a fault-tolerant converter with the ability to handle power switch open-circuit faults is addressed. The main concern of the proposed converter topology is the minimization of the hardware requirements, leading to a low increase of the system cost. First, the employed fault diagnostic technique does not require additional measurements, nor high computational effort. Secondly, the circuit topology reconfiguration implies a minimum number of extra components as well as minimal oversizing of the standard ones. Accordingly, a four-switch three-phase converter with the dc bus midpoint connected to the transformer neutral point and a three-switch three-phase rectifier are adopted for post-fault operation of the grid- and PMSG-side converters, respectively. Vector control strategies are proposed for both converters under analysis, focusing the issues of capacitor voltages balancing and torque ripple minimization. The performance of the proposed fault-tolerant PMSG drive is analyzed by means of experimental results. [ABSTRACT FROM PUBLISHER]

This paper introduces a novel five-level nested neutral point piloted (NNPP) converter and analyzes the operating principle of five-level NNPP converter. This paper presents a novel space vector pulse width modulation (SVPWM) algorithm based on gh coordinate for five-level NNPP converter. First, the common-mode voltage is reduced by choosing the appropriate redundant switching states. After that, the floating-capacitor voltage balance control strategy is presented. The appropriate switch combinations of each phase are determined by the control requirements of floating-capacitor voltages respectively and the hardware mapping method of the switching states is presented. Furthermore, the neutral-point voltage balance control strategy is presented. In order to balance the dc-link capacitor voltages, the seven-segment switching sequence is selected according to the control requirements of dc-link capacitor voltages and the neutral-point voltage regulatory factor is introduced to regulate the durations of the redundant switching states in a switching cycle. Finally, the validity of the novel SVPWM algorithm with decoupling control strategies of floating-capacitor voltages and dc-link capacitor voltages is verified by the experimental results of five-level NNPP converter under steady-state and dynamic conditions. [ABSTRACT FROM AUTHOR]

A new static synchronous compensator (STATCOM) based on the diode-clamped modular multilevel converter (DCM2 C) is proposed in this paper. In this converter topology, the capacitor voltage is clamped by using a low power rating diode in each submodule. The quantity of voltage sensors is significantly reduced and is free from the number of voltage levels. Furthermore, the voltage balancing control method becomes very simple and the capacitor voltage balance speed is fast. Based on the structure of modular multilevel converter, the DCM2C-STATCOM has the capability of Var compensation and negative-sequence current compensation. The topology characteristics and compensation control method of DCM2C-STATCOM are investigated in this paper. Experimental results obtained from a laboratory prototype validate that the capacitor voltage of the proposed DCM2C-STATCOM can be well balanced and the Var and negative-sequence current compensations are effective. [ABSTRACT FROM AUTHOR]

In this paper, a new structure for symmetric and cascade multilevel converter is presented. This structure requires the least power electronic components, gate driver circuits, power diode, and dc voltage source. The number of output levels is high. Reduction of the number of power electronic switches against voltage levels is an important factor in multilevel converters due to safety in switches, circuit size, cost, installation area, and complexity in control. To maximize the number of output level in the proposed optimized structure in order to attain different goals, such as reduction of stress on switches, the result of comparing the proposed structure and other structures present. The proposed method is robust against the switching faults in multilevel converter for dc source and the equipment. The simulation and experimental results presented in this paper show the performance of the proposed method. [ABSTRACT FROM AUTHOR]

The large number of semiconductors typically implemented in multilevel converters generates large stray inductances in their commutation loops. As a consequence, high-voltage overshoots appear in the semiconductors during commutation which may limit the operation of the converter. The paper analyzes these overvoltages in the five-level active neutral-point-clamped (5L­ANPC) converter, one of the most popular five level converters and employed by ABB in its ACS­2000 drive. Experimental results show overvoltages almost three times higher than those corresponding to a two-level converter. In order to overcome this problem, the paper presents a new 5L­ANPC with the same characteristics (number of semiconductors, output waveform, switching frequency, efficiency, etc.), but with smaller overvoltages. This is achieved by adding some small capacitors to the busbar that behave like lossless snubbers but with a much simpler implementation. The experimental results illustrate the working principle of these capacitors and demonstrate the reduction of the overvoltages. As a result, the new converter can reach a higher output current or speed-up the commutations reducing, therefore, the losses and increasing the efficiency compared with the previous 5L­ANPC. [ABSTRACT FROM AUTHOR]

In several electrical dc–ac power conversions, the ac output voltage is higher than the input voltage. If a voltage-source inverter (VSI) is used, then an additional dc–dc boosting stage is required to overcome the step-down VSI limitations. Recently, several impedance source converters are gaining higher attentions [1], [2], as they are able to provide buck-boost capability in a single conversion stage. This paper proposes the merging of the boost stage and the VSI stage in a single stage dc–ac power conversion, denoted as split-source inverter (SSI). The proposed topology requires the same number of active switches of the VSI, three additional diodes, and the same eight states of a conventional space-vector modulation. It also shows some merits compared to Z-source inverters, especially in terms of reduced switch voltage stress for voltage gains higher than 1.15. This paper presents the analysis of the SSI and compares different modulation schemes. Moreover, it presents a modified modulation scheme to eliminate the low frequency ripple in the input current and the voltage across the inverter bridge. The proposed analysis has been verified by simulation and experimental results on a 2.0-kW prototype. [ABSTRACT FROM PUBLISHER]

This paper proposes an electronic driver for public lighting systems. The input stage is based on the integration of two flyback converters with different polarities, in order to avoid the use of the input diode bridge rectifying stage. The output stage is a boost converter with an output current control. The proposed circuit is introduced and analyzed, and a design example for a 50-W light-emitting diode lamp is presented. The most relevant simulation and experimental results are also shown, in order to validate the idea. A comparison in terms of efficiency for the input stage is carried out between the proposed topology and the conventional flyback converter, showing an efficiency enhancement in the proposed converter. However, the most important advantage of the proposed converter is outlined in the final part of this paper. This advantage comes from the avoidance of the input diode bridge, thus enabling the bidirectional power flow at the input stage. Therefore, the topology can be used to deliver energy into the power grid. In recent lighting applications, the use of micro renewable generators in lighting points has made the use of special electronics to handle the energy flows in the ballast necessary. The present topology is an alternative to standard bidirectional input stages. [ABSTRACT FROM AUTHOR]

This paper discussed an active-bridge-active-clamp (ABAC) topology that is suitable for highpower more-electric-aircraft applications. Though conventional modulation techniques can be applied to ABAC converters, they present drawbacks, such as increased low-voltage (LV) current ripple and limited power transfer capability. To address these problems, a phase-shift-modulation (PSM) scheme is proposed to provide clean dc terminal current at the LV side while maintaining high power transfer capability and efficiency in a wide operating range. The proposed PSM has a complete switching harmonics cancellation on the LV terminals independent of the operating conditions. This results in high quality power without any ac components, thus minimizing passive filtering. In addition, when terminal voltages vary from their nominal values, the proposed PSM can improve the maximum power transfer capability of the ABAC converter compared to the conventional approach. The theoretical claims are validated by both simulation and experimental results on a 10-kW 270-V/28-V ABAC converter. [ABSTRACT FROM AUTHOR]

In this paper, a systematic and analytical study of non-isolated topologies belonging to the family of reduced redundant power processing (R2P2) converters is presented. Based on this study, all the non-isolated R2P2 topologies that can be implemented in reality are derived. Detailed examples clarify all possible cases of this analysis. In addition to this, the voltage ratio and the efficiency for each one of the R2P2 configurations are calculated, being further illustrated with examples. A comparison among configurations is also discussed with criteria the high step-up voltage gain and efficiency, aiming for high-power applications. One of these R2P2 converters is selected for further examination, as the most suitable for such applications. The theoretical analysis, as well as the calculations of the step-up voltage ratio and efficiency of the selected converter, is compared to experimental results conducted on a 2-kW laboratory prototype designed to operate in various step-up voltage ratios and in a high-power range, proving the effectiveness of the proposed investigation. [ABSTRACT FROM AUTHOR]

In this paper, a new class of bidirectional partial-resonance power converters is presented. The proposed family can be configured to interface single- or multi-port dc, single- or multi-phase ac systems at input-side and/or output-side. The proposed family offers a very modular structure, which can lead to cost reduction from a common designed module. In this converter, which accomplishes power conversion in a single stage, a small inductor placed in series with the input and output switch-bridges forms the link. This small link inductor is responsible for transferring power between different ports of the system. The proposed topologies can operate in buck, boost, and buck–boost modes of operation to step up and/or step down the voltage. In buck–boost mode of operation, the converter is controlled such that the power is entirely transferred through the link inductor; whereas, in buck or boost modes of operation only a fraction of the power is transferred through the link inductor, and the remaining power is directly transferred from input phases to the output phases. Galvanic isolation, which is typically a prominent factor contributing to power density of a converter, can be provided by means of a compact and lightweight single-phase high-frequency transformer added to the link. In comparison with earlier generations of partial-resonance inductive-link power converters, in the proposed converter, the level of link peak current and consequently power-loss, as well as voltage and current stress of switches are dramatically decreased. A very small film capacitor can be placed in parallel with the link inductor to facilitate zero-voltage-switching (ZVS) operation for all the switches/diodes. Apart from increasing the overall efficiency, minimized dv/dt stress and improvement in power density are achieved by adding the link capacitor. The proposed converter employs four-quadrant switches, i.e., bidirectional-conducting bidirectional-blocking switches, and charges the link inductor in both positive and negative directions in each cycle. In view of this, better utilization of the link inductor and lower total harmonic distortion (THD) are offered. Furthermore, two distinct switching algorithms are developed for the proposed family of converters. In this paper, the detailed behavior of the proposed family is investigated analytically, and simulation and experimental results are presented to evaluate the performance and effectiveness of the proposed converter. A low-power proof-of-concept prototype with input voltage of 59 V/161 V, load voltage of 178 V/73.5 V, maximum switching frequency of 4.9 kHz/3.65 kHz at 215 W/450 W in a step-up/step-down operation is considered for the experimental verification. [ABSTRACT FROM AUTHOR]

This paper proposes a high-frequency isolated dc/dc converter, whose switching frequency is 20 MHz. Meanwhile, the switch voltage stress is reduced based on optimal switch impedance. In the proposed converter, the switch can operate in ZVS condition, which can help to reduce the switching loss. A mathematical model of the proposed high frequency converter is built, which provides an effective design method for the system parameters. Meanwhile, the design method for PCB air-core transformer has been proposed and depicted. To verify the feasibility of the proposed converter and mathematic model, a 10 W prototype is built. [ABSTRACT FROM AUTHOR]

This paper proposes a capacitor voltage regulation method for the dual converter with a floating bridge for aerospace applications. This topology has previously been reported, but with a constrained voltage utilization factor due to the need for capacitor voltage regulations. In this paper, the effect of switching states on the voltage variation of capacitor is quantitatively modeled and an enhanced space vector modulation scheme with current feedback is proposed to achieve an active control of the floating capacitor voltages. This proposed method also allows further exploitation and utilization of converter voltage. The relationship between the allowed modulation index of dual converter and load power factor is obtained and expressed using a fitted polynomial equation. The advantages of the proposed method include boosted voltage utilization and superior performance in term of capacitor voltage balance. These advantages have been proven through simulation and experimental results on RL loads as well as with an open-end winding induction motor. The proposed modulation scheme can boost the converter voltage utilization by at least 10% while achieving full four-level operation. More importantly, the higher available voltage allows extending the constant torque region of the motor, the further beginning of field weakening operation could be postponed. [ABSTRACT FROM AUTHOR]

This paper presents a generalized topology for multilevel converters based on flying capacitor multicell structure. The proposed topology consists of two modular high-frequency (HF) and low-frequency (LF) sections or cells. The HF cells consist of flying capacitors and semiconductor switches operating at carrier frequency. The LF cells consist of dc sources and semiconductor switches operating at line frequency and its multiples. The proposed topology can be implemented with arbitrary number HF and LF cells. An important advantage of the proposed topology is its reduced components when compared to other multilevel converter topologies in the same family. Another interesting feature is the relatively low blocking voltage requirement for HF switches, making it an attractive choice for high-power applications. A modulating algorithm is devised to generate the gating pulses for the HF and LF cells using phase-shifted carrier-based pulsewidth modulation. As a particular case, the operation of a 25-level topology is explained by the help of illustrating waveforms. A comprehensive comparative study is presented to illustrate the advantages of the proposed topology in terms of the number of components and other performance criteria. Various simulations are carried out to verify the operation of the proposed topology at different operating conditions. The theoretical analysis is experimentally verified using a scaled-down laboratory setup. [ABSTRACT FROM AUTHOR]

A trinary multilevel converter uses a few heterogeneous H-bridge submodules (SMs) to synthesize an output voltage with multiple levels. Two major limitations of this converter are that it needs multiple dc sources and it cannot operate under pulsewidth modulation (PWM). This paper addresses these limitations by adding a low-voltage H-bridge SM to this converter and proposing a new switching algorithm. The resulting PWM-based asymmetric cascaded H-bridge converter uses only one dc source and synthesizes a high-quality output voltage. This improved converter can be a potential choice for real and reactive power support in power system applications. This paper also proposes methods for stability analysis and design of this converter. Experimental case studies evaluate the performance of the proposed converter for both standalone and grid-connected modes of operation. [ABSTRACT FROM AUTHOR]

A single-stage three-phase ac–ac converter benefiting from a high-frequency alternating link voltage is proposed in this paper. In this converter, a very small film capacitor can transfer the energy from the input to the output, owing to the high-frequency alternating voltage of the link. This eliminates the need for large electrolytic capacitors that are typically used in dc-link ac–ac converters. Moreover, a compact high-frequency transformer at the link can replace the bulky low-frequency transformers, in case isolation is required. These features increase the power density as well as reliability of the proposed converter in comparison with the conventional dc-link converters. The number of required switches in the proposed converter is 12, which is less than the number of switches needed in matrix converters, leading to lower switching and conduction losses. Despite being single-stage, the proposed ac–ac converter is capable of both stepping up and stepping down the voltage and also frequency transformation. This eliminates the need for using cascaded power converters. In this paper, the operation principles of the proposed ac–ac converter are investigated, and variable switching frequency and fixed switching frequency control methods for operating this converter are introduced. The performance of the converter is verified through simulation and experiment. [ABSTRACT FROM AUTHOR]

In this paper, a new structure for a nonisolated boost dc–dc converter is proposed. The proposed converter generates higher voltage gain than some conventional nonisolated boost dc–dc converters. In this paper, the voltage and current equations of the elements and voltage gain in continuous conduction mode and discontinuous conduction mode are extracted. Then, the critical inductance converter is extracted and the current stresses in the switches are calculated. To achieve high voltage gain, a generalized structure based on the proposed structure generates for dc–dc converters. Meanwhile, the root mean square current relations of devices are obtained for an extended structure. Finally, the results of PSCAD/EMTDC software and laboratory prototype are used to reconfirm theoretical concept. [ABSTRACT FROM AUTHOR]

Modular multilevel converters (MMCs) represent an emerging topology in medium-voltage (MV) and high-voltage applications. But for MV variable-speed motor drives, the MMC faces the challenge of large capacitor voltage ripple at low speeds. Delightfully, a hybrid MMC (HMMC) has proved to be potential in MV motor drives, since this topology has a lower capacitor voltage ripple and does not introduce any common voltage to the motor. This paper proposed a method to decrease the average capacitor voltage of the HMMC, which can effectively drive the motor at very low speeds without significantly increasing the submodule (SM) capacitance. Moreover, the selection of average capacitor voltage and the dimension of the SM capacitance are presented. Simulation and experimental results verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper presents a deadbeat-based method for the single-inductor multiple-input multiple-output (SI-MIMO) dc–dc converter. By solving the cross regulation problem of the SI-MIMO dc–dc converter, the proposed method is capable of achieving the input current regulation (ICR) and the output voltage regulation (OVR) simultaneously. Moreover, the output current observers are adopted to replace the output current sensors, which are required by the conventional model based methods for dc–dc converters. The proposed control approaches including ICR and OVR are discussed in detail. To verify the effectiveness of the proposed deadbeat-based method, simulation runs and experiments are conducted on the single-inductor dual-input dual-output buck converter simulation platform and hardware prototype, respectively. The simulation and experimental results are analyzed in detail, and the comparison with the previous works is conducted. [ABSTRACT FROM AUTHOR]

In this paper, in response to the open-circuit fault scenario in the grid-side converter (GSC) of doubly fed induction generator-based wind turbines (DFIG-WTs), a fault-tolerant four-switch three-phase (FSTP) topology-based GSC is studied. Compared with other switch-level fault-tolerant converter topologies, fewer switches, less switching and conduction losses, and simpler converter structure are derived. A simplified space vector pulse width modulation (SVPWM) technique is proposed to improve the output current quality and reduce the computational complexity in the control process. Unified expressions of duty ratios for the two remaining healthy bridge arms are obtained. In addition, the three-phase unbalance phenomenon caused by the capacitive impedance in the faulty phase is analyzed from the ac point of view, and a current distortion compensation scheme is illustrated. Furthermore, a dc-bus voltage deviation suppression strategy is proposed to maximize the dc-bus voltage utilization rate and mitigate the damage to the dc-link capacitors. Simulations are carried out in MATLAB/Simulink2017a to demonstrate the validity of the proposed SVPWM technique and compensation schemes in FSTP GSC for a 1.5-MW grid-connected DFIG-WT when different working conditions are considered. [ABSTRACT FROM AUTHOR]

Switching power supplies are sources of noise for sensitive circuits. Converters should comply with electromagnetic compatibility (EMC) rules so that the electromagnetic interference (EMI) caused by switching cannot interfere with the normal operation of adjacent circuits and also the converter itself. The produced interference can be in the form of conduction or radiation. In this paper, some techniques are used in switching converters to suppress EMI with emphasis on the conduction form. EMI analysis and evaluation of a conventional flyback converter and a proposed zero-current transition (ZCT) flyback converter is achieved by simulation and experimental results. In addition to evaluating some EMI suppression techniques, the main objective of this paper is to improve EMI in the topology design stage. The operating modes of the improved ZCT flyback are discussed. In addition to the efficiency improvement, the amount of EMI reduction of this ZCT flyback and the effectiveness of some EMI reduction techniques are shown by practical implementation. [ABSTRACT FROM AUTHOR]

Dual active bridge (DAB) based converters offer the benefit of smaller volume due to high-frequency isolation and controllability of active power flow, making them attractive for various applications, such as renewable energy generation, plug-in hybrid vehicles, and distribution systems. This paper presents a novel converter topology along with a modulation strategy for a DAB-based three-phase ac to dc converter. The major benefits are single-stage conversion, no unreliable intermediate dc-link capacitor, reduced number of switches, i.e., only two active switches on the ac side, simple control scheme, open-loop unity power factor operation, bidirectional power flow, and partial soft-switching. This paper presents the analysis of all the operating modes of the converter, resulting in the analytical estimation of power transfer and rms winding current and investigation of soft-switching conditions for the power devices. Simulation and experimental results have been presented to demonstrate the advantages of the proposed technique and accuracy of the analysis.1 [ABSTRACT FROM AUTHOR]

In this paper, a new cascaded multilevel inverter is proposed. For the proposed inverter, two different algorithms to determine the magnitude of the dc voltage sources are proposed. Then, in order to generate maximum numbers of output voltage levels by using a constant number of power switches and/or dc voltage sources, several optimum structures of the proposed inverter are obtained. In comparison with the conventional cascaded multilevel inverters, the proposed inverter is able to generate a high number of output voltage levels by using a lower number of power electronic devices such as power switches, driver circuits, power diodes, and dc voltage sources. In addition, the low amount of blocked voltage by switches is another advantage of the proposed inverter. The accuracy performance of the proposed inverter in generating the positive and negative voltage levels is verified through the experimental results on a 61-level inverter. [ABSTRACT FROM PUBLISHER]

Conventionally, the converter of switched reluctance motor (SRM) is fed by the uncontrollable diode bridge rectifier (DBR), which leads to a low grid-side power factor (PF) and high current total harmonic distortion (THD). In this paper, an alternative solution for the grid-connected high-speed SRM drive system with improved PF is proposed. In the proposed drive system, the three-level active front end (AFE) is connected in cascade with the midpoint converter for SRM operation. A centralized strategy, which controls the AFE and SRM together, is proposed to govern the motor speed and grid-side PF by regulating the real power and reactive power of the system, respectively. Specifically, the real power, reactive power, and the voltage balancing of split capacitors are controlled by the model predictive directed power control (MP-DPC) algorithm, which significantly reduces the control complexity and guarantees the fast dynamic response. Consequently, satisfying speed regulation, high PF, low current THD, and bi-directional power-transfer capability are achieved. An idea-proofed testbench is constructed in laboratory, and the applicability of the proposed drive system is verified by a series of experimental results. [ABSTRACT FROM AUTHOR]

This paper introduces a versatile control scheme for unidirectional ac–dc boost converters for the purpose of mitigating grid power quality. Since most power factor correction circuits available in the commercial market utilize unidirectional ac–dc boost converter topologies, this is an almost no-cost solution for compensating harmonic current and reactive power in residential applications. Harmonic current and reactive power compensation methods in the unidirectional ac–dc boost converter are investigated. The additional focus of this paper is to quantify the input current distortions by the unidirectional ac–dc boost converter used for supplying not only active power to the load but also reactive power. Due to input current distortions, the amount of reactive power injected from an individual converter to the grid should be restricted. Experimental results are presented to validate the effectiveness of the proposed control method. [ABSTRACT FROM AUTHOR]

In a photovoltaic (PV)- or fuel-cell-based grid-connected power system, a high step-up dc–dc converter is required to boost the low voltage of a PV or fuel cell to a relatively high bus voltage for the downstream dc–ac grid-connected inverter. To integrate the advantages of the high voltage gain of a switched-capacitor (SC) converter and excellent output regulation of a switching-mode dc–dc converter, a method of combining the two types of converters is proposed in this paper. The basic idea is that when the switch is turned on, the inductor is charged, and the capacitors are connected in series to supply the load, and when the switch is turned off, the inductor releases energy to charge multiple capacitors in parallel, whose voltages are controlled by a pulsewidth modulation technique. Thus, a high voltage gain of the dc–dc converter can be obtained with good regulation. Based on this principle, a series of new topologies are derived, and the operating principles and voltage gains of the proposed converters are analyzed. Finally, the design of the proposed converter is given, and the experiment results are provided to verify the theoretical analysis. [ABSTRACT FROM PUBLISHER]

This paper presents a high-frequency, digitally controlled high-brightness LED driver for automotive applications with fast dimming capabilities. The power converter is based on the magnetically coupled Ćuk topology and employs a single, off-the-shelf SMT mutual inductor. The proposed digital control technique exploits the inherent stabilizing effect of magnetic coupling, and combines it with a dedicated duty cycle feedforward technique for step-reference response enhancement during the dimming operation. No direct sensing of the LED string current is performed, bypassing the disadvantage of the Ćuk topology of having an inverted output polarity. Furthermore, the magnetically coupled Ćuk topology is a single-switch solution and it provides inherent filtering of the input and output currents without introducing the additional magnetic elements, strongly reducing the total required capacitance and maintaining the small form-factor required in the automotive environment. This paper discusses the theoretical and practical development of the proposed controller. Experimental tests on a 40-W, 1-A, 500-kHz prototype indicate a 0- to 1-A current rise time in the tens of microseconds time frame with excellent damping characteristics and regulation accuracy. [ABSTRACT FROM AUTHOR]

Traditional seven-level active neutral-point-clamped (ANPC-7L) converters suffer from the problems of dynamic voltage balancing in series switches and multilevel voltage jumping of phase output voltage during switching states transition. This paper presents a novel ANPC-7L topology with auxiliary commutating branches and elaborates on its commutating strategies. The presented topology and its commutating strategies completely resolve the two problems mentioned above. The validity of the presented topology and its commutating strategies are verified by experimental results from a 380 V/5 kW ANPC-7L converter. [ABSTRACT FROM AUTHOR]

This paper presents the active capacitor voltage-balancing (ACVB) methods based on the dynamic model for a five-level nested neutral-point piloted (NNPP) converter using hybrid carrier modulation. The traditional hybrid carrier modulation provides natural voltage balancing of floating capacitors and dc-link capacitors. First, the natural voltage-balancing ability under steady-state and ideal conditions is theoretically proved. However, there are accumulated errors and deviations of capacitor voltages in practical applications, especially under dynamic conditions. In order to address the accumulated errors and deviations of capacitor voltages, the dynamic models of floating-capacitor voltages and neutral-point voltage are established. Moreover, the ACVB method based on the dynamic model of the neutral-point voltage is proposed by injecting the zero-sequence voltage. And the ACVB method based on the dynamic model of floating-capacitor voltages is proposed by introducing the adjustment variables. The proposed ACVB methods have the advantages of simple formula, definite physical meaning, and high accuracy. Furthermore, the output voltage quality and current quality are evaluated in term of total harmonic distortion and the effect of model parameter mismatch on the proposed ACVB methods is presented. Finally, the comparative simulation and experimental results verify the correctness of the proposed ACVB methods based on the dynamic model under different conditions. [ABSTRACT FROM AUTHOR]

This paper presents a breaker arrangement concept, the multiline breaker (MLB), for the protection of multiterminal high voltage dc (MTdc) networks. Based on the design of a hybrid breaker, the MLB is an economically attractive solution for the protection of multiple dc lines in nodal connection using a single main breaker path. By using commutation units, the MLB directs the fault current through the main breaker in a unidirectional way, irrespective of the fault location. Hence, this study presents the design requirements for the MLB, regarding both hardware and control, and evaluates its operation within a grid. For this reason, a four-terminal half-bridge multilevel modular converters-based MTdc grid in radial configuration was used and pole-to-ground dc fault conditions were investigated. The dc fault response of the grid with one MLB at the central node is compared to the respective response of the grid when one hybrid breaker is employed at each dc line. The simulations show that the MLB is feasible and that the overall MTdc grid fault response for the two protection systems is very similar. As a result, the design advantages of the MLB make it a promising solution for the dc fault isolation in MTdc grids. [ABSTRACT FROM AUTHOR]

In order to increase the output voltage levels and reduce the isolated dc sources, a symmetrical hybrid nine-level inverter for high-speed motor drive applications is presented in this paper. Each phase of this inverter is composed of a five-level dc/dc converter cell and an H-bridge cell. The dc/dc converter is operated at high frequency with low-voltage devices and the H-bridge is operated at fundamental frequency with high-voltage devices. The three phases are connected to a common dc-link and each drives an isolated winding of an open-winding motor. The operating principles and modulation method are introduced. A detailed analysis of the average currents through the flying capacitor and neutral point of the dc-link is presented and a capacitor voltage balancing method based on phase-shifted pulse-width modulation is proposed. Simulation and experimental results are presented to demonstrate the feasibility of this topology and control method. [ABSTRACT FROM PUBLISHER]

Boost-derived hybrid converter (BDHC) is a single-stage converter that produces both dc and ac output voltages. The operation of BDHC under continuous conduction mode is satisfactory. However, the nonzero discontinuous conduction mode (NZ-DCM) and standalone ac operation restrict the stable operation of the converter. To mitigate these limitations, modified BDHC (MBDHC) is proposed in this paper. The main idea behind these changes is to redeem NZ-DCM by forced continuous conduction mode (FCM). The adverse effect of NZ-DCM in a BDHC is analyzed in terms of ac output voltage total harmonic distortion, and dc output voltage ripple. This analysis is further extended for MBDHC to highlight the benefits of FCM. Moreover, for hybrid loads, the efficiency of MBDHC is compared with its counterpart BDHC and cascaded boost inverter. [ABSTRACT FROM PUBLISHER]

This paper investigates the utilization of two different six-leg configurations of single-phase to three-phase converters. One of the topologies is transformerless and the other is transformer based. The studied converters allow feeding the load voltage with sinusoidal voltages with constant amplitude and frequency, and to operate with sinusoidal grid current with high power factor. The system model and pulse-width modulation techniques for one of the topologies are given. Control strategies for both topologies are provided. The studied topologies are compared with the conventional in terms of dc-link specification, voltages harmonic distortions, semiconductor losses, and other characteristics. Simulation and experimental results are provided to illustrate the operation of the systems. [ABSTRACT FROM PUBLISHER]

This paper presents a generalized multilevel direct power control (ML-DPC) scheme for grid-connected multilevel power converters. The proposed method extends the original DPC operating principle by considering only the closest subset of two-level voltage vectors to the present switching state. The implementation of this principle requires the power derivatives for feedback, which can present numerical problems when applied experimentally, mainly due to high measurement noise sensitivity. Therefore, a derivative estimator is proposed based on the converter-grid model in the synchronous reference frame. In addition, a virtual flux observer is developed to achieve synchronization and improve robustness in the presence of grid voltage harmonics. The proposed method is applicable to any multilevel converter topology of any number of levels. In this paper, simulations and experimental results are presented for a seven-level cascaded H-bridge converter. [ABSTRACT FROM AUTHOR]

Increasing energy demand and growth of wind generation have significantly increased the stress on the electric grid. The low investment in transmission infrastructure necessitates adoption of methods for efficient use of existing resources. Power converter-based FACTS devices, capable of dynamic power-flow control, have been the preferred solution to maximize utilization of existing infrastructure, but implementation of traditional FACTS solutions at transmission level voltages is complex and cost prohibitive. This paper proposes a power router (PR) for dynamic power-flow control in a meshed network. The proposed PR is realized by augmenting a transformer with a fractionally rated back-to-back converter. The main advantages of the proposed converter are the fractional converter rating and reduced low-frequency transformer requirement compared to the traditional FACTS solutions. This paper outlines the proposed PR topology, control range, controller design and demonstrates the functionality through simulation and experimental results. [ABSTRACT FROM AUTHOR]

This paper presents a theoretical harmonic analysis of phase disposition (PD) and phase-shifted carrier pulse-width modulation strategies for modular multilevel converters (MMCs). It is shown that when these strategies are implemented on a per MMC arm basis, their spectral performances converge because of cancellation of odd carrier sideband groups between each phase leg's arms. An improved PD modulation strategy is then presented that uses a single PD modulator for the entire phase leg, followed by a state machine decoder that evenly distributes switching pulses to all submodules across the phase leg upper and lower arms to balance the distribution of submodule commutation events. The resulting strategy achieves optimum phase leg PD spectral performance and also achieves natural voltage balancing of the MMC submodules. All theoretical findings are supported by simulation and experimental results obtained using a five-level MMC prototype. [ABSTRACT FROM AUTHOR]

An efficient power converter system plays a significant role in the design of battery charging systems for electric vehicles (EVs). In this paper, a new zero-voltage and zero-current switching (ZVZCS) full-bridge dc–dc converter is proposed to reduce the power conversion losses. The proposed converter incorporates a new asymmetrical pulse width modulation (APWM) gating technique for the dc–dc conversion stage in the battery charging system. The proposed dc–dc converter topology achieves zero-voltage switching (ZVS) for all the active switches and near zero-current switching (ZCS) for low-side active switches throughout the charging range of the battery. The proposed APWM technique can reduce the switching and conduction losses compared to the conventional phase-shift modulation (PSM) gating technique. The auxiliary inductance required to ensure ZVS with APWM can also be reduced compared to PSM. Analysis, design, and implementation of the proposed APWM ZVZCS full-bridge dc-dc converter are discussed in this paper. A 100-kHz 1.2-kW laboratory prototype is developed and the experimental results are presented. The results validate the analysis and performance of the proposed converter. [ABSTRACT FROM AUTHOR]

The modular multilevel converter (MMC or M2C) is an emerging attractive multilevel topology for medium-voltage high-power applications. The capacitor voltage balancing control and the improvement of output current rating are two challenging issues of MMC. This paper proposed a new parallel-connected diode-clamped M2C (DCM2C), in which each arm consists of two parallel-connected clusters. In this topology, the capacitor voltages can be balanced automatically without any balancing control algorithms. Theoretically, no voltage sensors are needed to measure the capacitor voltages theoretically. Thus, the control of the converter can be simplified greatly. With a simple current-sharing control, an equal current distribution can be achieved between the two clusters. Furthermore, an extended parallel-DCM2C is proposed for larger current applications, and the corresponding current-sharing control method is developed. Experimental results validated the voltage self-balancing capability of parallel-DCM2C and the effectiveness of the proposed current-sharing control. [ABSTRACT FROM PUBLISHER]

This paper presents a method for generating a multilevel dodecagonal voltage space vector structure using a single dc source for induction motor drives. Multilevel dodecagonal structure combines the advantages of both multilevel and dodecagonal structures, and hence, generates low dv/dt phase voltage along with the elimination of fifth- and seventh-order harmonics over the entire modulation range. This eliminates low-order harmonic currents and prevents the generation of sixth-order torque ripple in the motor. The topology used requires only one dc source making four-quadrant operation of the drive system simpler compared to previously proposed multilevel topologies generating dodecagonal space vector structures. The topology used consists of a three-level flying capacitor (FC) inverter cascaded with a capacitor fed H-bridge. The FC inverter operates at a lower switching frequency and the low-order harmonics are eliminated by the switching action of the cascaded H-bridge inverter. The capacitors in the cascaded H-bridge modules are maintained at a substantially smaller voltage compared to the dc-link voltage and are inherently balanced during the pulsewidth modulation operation. This results in low switching loss, in the FC inverter as well as in the cascaded H-bridge inverter. Experimental results are included to validate the operation of the topology and modulation scheme presented in this paper. [ABSTRACT FROM AUTHOR]