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Active magnetic bearing is a core technology for high-speed rotational machines. Power electronics converter as the active magnetic bearing drive is the actuation unit and its topology highly impacts the performance of the bearing system. This paper introduces the progress of topology of active magnetic bearing drive. The initial topology of an H-bridge does not sufficiently utilize the power electronics devices. The topology with half-bridge and shared phase-leg has been proposed as the fundamental topology. In this paper, two approaches of novel magnetic bearing drive topology modification have been developed on the basis of the fundamental topology. In the first approach, central phase-leg for multiaxis magnetic bearing drive can be further shared and the power electronic devices can be globally optimized in the whole system. Further, a topology with current in the reverse direction can reduce the central phase-leg current rating and power losses. In the second approach, fault-tolerant magnetic bearing drive topology has been developed on the basis of the fundamental topology, too. It can ride-through the open-circuit fault of power electronics switch-in operation and keep levitation for the magnetic bearing. The series work of novel topologies can improve the performance of an active magnetic bearing system in application. [ABSTRACT FROM AUTHOR]

In this paper, a single-inductor dual-output (SIDO) dc–dc converter is proposed. The significant feature of the proposed converter is feeding a constant power load in low-voltage side (LVS) port, where even feeding a variable load at LVS does not have any cross regulation to high-voltage side port with the desired approximation. Magnificently, both merits are obtained in open-loop manner, which is an outstanding characteristic in comparison with that of the existed converters. In this paper, soft commutation and soft switching of switches and diodes are investigated along with the aforementioned main novelty. Moreover, detailed theoretical analyses of the proposed SIDO dc–dc converter in continuous conduction mode are presented besides the comparisons with some other structures. Finally, theoretical analyses are verified through a 1500 W experimental prototype results. [ABSTRACT FROM AUTHOR]

In this paper, a series-capacitor-based interleaving buck power factor correction (PFC) converter is proposed, the intermediate energy storage capacitance of which is operated at discontinuous capacitor voltage mode (DCVM), and automatic power factor (PF) correction for this converter is obtained. Moreover, the voltage across the series capacitor of the proposed PFC converter is clamped at the input voltage, and thus peak voltage stress existed in the traditional DCVM buck PFC could be relieved. By effectively regulating the charge/discharge time for the series capacitor, ultrahigh step-down conversion ratio of the proposed converter is achieved, the conversion ratio of which is independent of the duty cycle and only related to the switching frequency and circuit parameters. Therefore, high PF can be obtained due to very narrow deadtime of the input current. Meanwhile, the proposed PFC converter can realize the soft turn-on of part power switch and soft turn-off of part power diodes. In addition, comparing with the traditional discontinuous inductor current mode PFC, the input current of the proposed PFC converter is continuous so that the peak value and root-mean-square value of input current can be reduced. The operational principle, performance analysis, and parameter design principle are given in this paper. The analysis results show that the PF and total harmonic distortion are also independent of the duty cycle. Finally, a 220-Vac input, 60 W/15 V output experimental prototype is built to verify the validity of the theoretical analysis. [ABSTRACT FROM AUTHOR]

Reduced switch active phase converters (APC) are cost-effective solutions for running three-phase loads from single-phase grids. This paper proposes a novel auxiliary-capacitor-based APC (AC-APC) for this application. The combination of the topological location of the auxiliary capacitor and the control of the AC-APC reduces current stress on the semiconductor devices. In this paper, a selection criterion for the optimal auxiliary capacitor value is formulated to reduce the device currents in such a way that the overall efficiency is enhanced. This paper presents a comparative analysis of converter volt-ampere (VA) rating and device power loss for conventional H-bridge active front-end and inverter-based topology, APC, and AC-APC. To evaluate the efficacy of the proposed AC-APC, an experimental study is conducted on the APC and the AC-APC feeding a 3-hp three-phase induction motor. At a full load of $\text{2.5}\,\text{kW}$ and $\text{0.8 } \text{power factor}$ , the measured maximum efficiency of the AC-APC is $2\%$ higher than that of the APC. Analytical evaluation of converter currents and device power loss are in close agreement with experimental observations. [ABSTRACT FROM AUTHOR]

This paper presents a novel insulated gate bipolar transistor (IGBT) behavioral model on the field programmable gate array (FPGA), which is suitable for the real-time simulation of fast transients in power electronics circuits. In this model, the static and dynamic behaviors of the IGBT switch are described and modeled separately. The static IGBT model is represented by the saturation region of output characteristic and is a part of the circuit network model. The dynamic IGBT model is combined with the static one to describe the fast switching transient behaviors by using the IGBT equivalent circuit model. The presented dynamic model in this paper does not involve any iterative solving algorithm and can be designed with highly pipelined structures on FPGA. Therefore, the IGBT switching transient waveforms can be generated precisely with a 5 ns resolution. The proposed model is tested with two cases—a four-phase floating interleaved boost converter and a three-phase five-level modular multilevel converter. The effectiveness and accuracy of the model are validated by comparing the real-time simulation results with offline simulation software. [ABSTRACT FROM AUTHOR]

This paper proposes a visible light communication (VLC) system consisting of a single-stage buck–boost power factor correction converter operating in the discontinuous conduction mode with dimming capability. Additionally, this paper proposes the on–off M-frequency shift keying modulation for the VLC system. This modulation allows for the transmission of more than a single bit for each switching period without affecting the dimming characteristics of the light-emitting diode luminaire. The design of the whole system is discussed in detail, including both transmitter and receiver modules. A 20-W laboratory prototype was built in order to verify the proposed modulation scheme. The experimental evaluation showed a good performance of the transmitter, which was able to perform simultaneously the desired functions, namely power factor correction, dimming, and data transmission. The receiver also achieved the desired performance with a low bit error rate (BER). The results showed that the proposed system was able to transfer data between emitter and receiver with a bit rate of 1.11 Mb/s at a frequency of up to 375 kHz over a distance of 10 m, and with a BER lower than $10^{-3}$ under the influence of external lighting sources with illuminance levels up to 500 lx. [ABSTRACT FROM AUTHOR]

The extra-LC auxiliary-resonant-snubber-based converter (ELCARSC), as a soft-switching converter, has the advantages of low switching loss, low electromagnetic interference noise, and low-output distortion caused by the dead-time effect. However, the dead-time effect is still the main problem in a high-precision application. Besides, the traditional control and compensation methods rely on the accuracy of the circuit parameters, especially the junction capacitance, thus resulting in compensation error. Therefore, this paper proposed a novel high-precision control method through modulating the initial resonant current to eliminate the dead-time effect of ELCARSC. The method does not need complicated online calculation and reduces the dependence on the accuracy of the circuit parameters, especially the influence of the junction capacitances of the switches. In this paper, the dead-time effect of the ELCARSC is analyzed. The output voltage error with the conventional variable-timing control method is analyzed. Subsequently, the proposed modulated initial resonant current control is introduced. Finally, a prototype was developed that verified the effectiveness of the control method. The quality of the output current and voltage is improved by utilizing the proposed control method. However, the peak current of the auxiliary switch is increased. [ABSTRACT FROM AUTHOR]

This paper presents research results of voltage gain number control methods of a power electronic resonant zero-current switching dc–dc switched-capacitor (SC) voltage multiplier (SCVM) in a topology with fault tolerance capability (FSCVM). The converters operated under the basic switching patterns are constant-voltage-gain dc–dc series-parallel resonant SC converters. However, this paper presents a method for the output voltage regulation by a special switching strategy. A variable voltage gain is made possible by selecting the number of active switching cells, using an appropriate control method. This creates a set of voltage ratio ranges. In addition, the proposed topology and method of control enable a fault-tolerant operation of the FSCVM under various failures of the device. The paper presents an analysis of the concept, simulation results and an experimental verification in a three-cell FSCVM dc–dc resonant boost converter operating at a 200-watt charge. Issues regarding the selection of components related to the problem of inrush currents that can occur during the voltage ratio increase are also analyzed in this paper, and the design for low inrush currents is demonstrated. [ABSTRACT FROM AUTHOR]

This paper proposes a new developed switched-capacitor converter to achieve high-voltage pulses with adjustable voltage level and frequency. The proposed topology generates repetitive high-voltage pulses by using low-voltage power supply with reduced number of components, including power semiconductors and capacitor. Therefore, a converter based on switched-capacitor units with high voltage gain and high efficiency can be achieved. Operation principles and design steps of the converter as well as comparative study with conventional converters are described in this paper. Finally, simulation and experimental results of a two-stage structure of the proposed circuit validate the operation principles and features of this topology. [ABSTRACT FROM AUTHOR]

Induction motor drives operated with a low ratio of the switching frequency to the fundamental frequency (i.e., pulse number) are prone to have high magnitudes of low-order torque harmonics. This paper proposes a method to analytically evaluate the harmonic torque spectrum based on the pulsewidth-modulated voltage waveforms for low pulse number operation. The predicted torque harmonic spectra for different pulsewidth-modulated waveforms are validated through simulations and experiments. This paper also reports optimal switching angles to minimize the total rms value of torque harmonics of order 6, 12, 18 $,\dots,$ $6(N-1)$ , considering the number of switching angles per quarter ($N$) to be 4 and 5. Compared to sine triangle pulsewidth modulation and selective harmonic elimination pulsewidth modulation with the same pulse number, the proposed optimal switching angles significantly reduce the total rms value of all harmonic torques of order lower than $6N$. Extensive simulation and experimental results on a 3.7-kW induction motor drive are presented to demonstrate the superior performance of the proposed optimal pulsewidth modulation. [ABSTRACT FROM AUTHOR]

In this paper, a new nonisolated high step-down dc–dc converter with ultrahigh step-down conversion ratio is proposed. Advantages of the proposed converter are high step-down ratio, extended duty cycle, reduced switching losses by a converter operation under zero-voltage switching (ZVS) conditions, reduced reverse reco-very losses of diodes by achieved zero-current switching turn-off condition, and reduced voltage spikes by the inherent active-clamping structure of the converter. In this converter, series capacitors and coupled inductors have been used in power path to achieve the low voltage gain and extended duty cycle. By the inherent active-clamping structure of the proposed converter, the leakage inductance energy is totally recovered in the output; therefore, the high voltage spike across the semiconductor devices is suppressed. The switches of the proposed converter can operate under ZVS conditions, which cause reduced switching losses and improved efficiency. In this paper, the converter operating modes are discussed, and a prototype circuit is implemented. Experimental results are presented to verify the theoretical analysis. [ABSTRACT FROM AUTHOR]

This paper presents a uniform control strategy for the bidirectional ac/dc interlinking converter (BIC) in hierarchical controlled hybrid microgrid. The uniform control strategy unifies different control structures for multifunctional BIC in terms of power management, ac and dc voltage support. With the unified control structure, various triggering mechanisms for BIC mode-switch are not compulsory in response to the relevant scenario changes in the power network. Therefore, the negative consequences, such as unsmooth transition and system collapse due to the inaccurate or slower mode switch, can be avoided. Moreover, the uniform control strategy is also applicable for the hierarchical controlled hybrid microgrid, whose control architecture is typically comprised of the centralized and decentralized levels. This enables the communication fault ride-through capability and the impact from the communication failures can thus be mitigated. To sum up the above two features, the proposed control strategy is able to provide a smooth operation for the BIC without control mode switch in the event of unintentional scenario changes in power or communication network. To verify the validity of the proposed uniform control strategy, the controller hardware-in-the-loop experimental results have been provided in this paper. [ABSTRACT FROM PUBLISHER]

The nine-switch converter is a multiport converter having two three-phase terminals and a dc-link, just like a 12-switch back-to-back (BTB) converter, but with 25% reduction of active switch count. However, the reduction from 12-switch to 9-switch may not always be an efficient choice considering losses in the switches. Only the load–source combination for the ac–ac common frequency mode and the source–source combination for the ac–dc different frequency (ac–dc DF) mode have been reported, so far, to yield relatively lower loss for the nine-switch converter. This paper shows that the nine-switch converter can have relatively lower loss even with a load–source combination, instead of only source–source combination in its ac–dc DF mode—when the upper terminal is connected to a dc load and the lower terminal is connected to an ac source. Mathematical proof is presented with derivation of the particular operating parameters for which the nine-switch converter will have comparatively lower losses. The analysis is validated with simulation and experimental results of a 1-kW system. Finally, the benchmark of the application criteria of the nine-switch converter for having lower conduction loss than the BTB converter is updated in this paper. [ABSTRACT FROM AUTHOR]

For power converters with inductive loads, a freewheeling path is needed for the current due to reactive power. The MOSFET synchronous rectification (SR) is widely used to reduce the conduction loss during the freewheeling period. Due to the wide band gap of silicon carbide (SiC), the intrinsic body diode of SiC MOSFET exhibits a high voltage drop. Hence, an antiparallel SiC Schottky diode is normally implemented to eliminate its conduction. However, the external SiC Schottky diode is not fully utilized as it only works during the dead time. In this paper, the hard-switching SR is investigated in an SiC three-phase inverter and compared with a conventional inverter using freewheeling diode (FWD). An improved power loss model for the two inverters has been developed. It is found that the inverter using SR has higher efficiency due to the smaller switching loss. A 7-kW prototype of SiC three-phase inverter is built, which achieves a peak efficiency of 98.8% ($\pm$ 0.15%) and 98.5% ($\pm$ 0.15%) at 40 kHz using SR and FWD, respectively. This paper confirms that the SiC MOSFET is an ideal candidate for the SR. [ABSTRACT FROM PUBLISHER]

This paper presents three unidirectional step-up ac–dc converter topologies with voltage multiplication on their outputs. The first topology is the hybrid boost rectifier and the other two are novel bridgeless structures, all based on the integration of boost rectifier and the ladder switched-capacitor (SC) cell. The new hybrid structures provide high voltage gain with low voltage stress across the switches, high-power factor, and output voltage regulation. This paper presents the principle of operation, steady-state and dynamic analysis, design methodology, and experimental verification. A different approach is also presented for the design methodology of the SC cell and for the analysis of its influence on the dynamic model. Three 1000-W prototypes with a 220-V input voltage, 800-V output voltage, and 100-kHz switching frequency were designed to corroborate the theoretical study. The best efficiency was 97.1$\%$ in the proposed bridgeless versions and the voltage stress across the switches stands around 400 V. Furthermore, a comparison between the proposed structures and previous topologies is also presented. [ABSTRACT FROM PUBLISHER]

This paper proposes an analytical design procedure for the LLCL and the LCCL filters for grid integration of high-power voltage-source converters. The low switching frequency and stringent limits on grid-injected harmonics in high-power applications lead to large smoothing filters. In order to reduce the size and weight, high-order filters are already proposed and wise design procedures with the main goal of minimizing the overall filter size are being suggested. In this paper, the parameters of the LLCL and the LCCL filters are designed in the per-unit system to satisfy the requirements on the injected grid current and at the same time minimize the overall filter size through minimizing the total energy stored in the filter components. The experimental results of a downscaled laboratory prototype with a low switching frequency prove the effectiveness of the proposed design procedure. [ABSTRACT FROM PUBLISHER]

The selective harmonic current mitigation pulsewidth modulation (SHCM-PWM) technique can be used in cascaded multilevel converters to extend the harmonic reduction spectrum, reduce the coupling inductance and increase the efficiency. The offline SHCM-PWM technique has small number of switching transitions as its switching angles can only change once in a fundamental cycle and relatively long time delays because it uses FFT. As a result, its dynamic response has a lot to desire. As it will be proven in this paper, in four-quadrant power converters, to have a good transient dynamic response, both active and reactive power must be controlled at least two times in a fundamental cycle. In this paper, a hybrid modulation technique is introduced. The proposed technique uses SHCM-PWM under steady state and phase-shift PWM (PSPWM) under transient. In addition, in order to extend the modulation index range and ensure that SHCM-PWM can process four-quadrant active and reactive power, the constraints of the switching angles for the SHCM-PWM are modified. Simulations and experiments are conducted on a seven-level cascaded H-bridge converter to verify the proposed technique. [ABSTRACT FROM PUBLISHER]

Circuit analysis and design criteria of a two-phase bidirectional converter with high voltage gain are presented in this paper. The operating principle of the forward or reverse mode is similar to that of the conventional buck or boost converter. Compared with the conventional converter, the switch stresses can be reduced significantly depending on the operating region of the voltage ratio in the two-phase converter. The power losses can also be reduced due to the use of low-voltage rating switches. The derivate converters are discussed to demonstrate the advantages of the proposed topology. A 200 W/1 MHz two-phase prototype converter with gallium nitride (GaN) devices is built and tested to verify the feasibility. [ABSTRACT FROM AUTHOR]

This paper proposes the use of an artificial neural network (ANN) for solving one of the ongoing research challenges in finite set-model predictive control (FS-MPC) of power electronics converters, i.e., the automated selection of weighting factors in cost function. The first step in this approach is to simulate a detailed converter circuit model or run experiments numerous times using different weighting factor combinations. The key performance metrics [e.g., average switching frequency ($f_{{\rm sw}}$) of the converter, total harmonic distortion, etc.] are extracted from each simulation. This data is then used to train the ANN, which serves as a surrogate model of the converter that can provide fast and accurate estimates of the performance metrics for any weighting factor combination. Consequently, any arbitrary user-defined fitness function that combines the output metrics can be defined and the weighting factor combinations that optimize the given function can be explicitly found. The proposed methodology was verified on a practical weighting factor design problem in FS-MPC regulated voltage source converter for uninterruptible power supply system. Designed weighting factors for two exemplary fitness functions turned out to be robust to load variations and to yield close to expected performance when applied both to detailed simulation model (less than 3% error) and to experimental test bed (less than 10% error). [ABSTRACT FROM AUTHOR]

This paper presents a novel switch current stress reduction technique for a single switch boost-flyback high step up dc–dc converter. Coupled inductor-based converters do not have a sufficiently higher inductance value of their windings. This creates current surge during transient and steady state, which in turn increases current stress at main switch. To compensate this difficulty in coupled inductor-based boost flyback converter, an inductor–diode parallel combination has been connected in series with the switch. This technique increases the effective inductance of the coupled inductor primary winding during switch turn-on operation and helps to reduce current stress. Steady-state operating principle with the proposed technique is analyzed in continuous conduction mode. The current reduction technique is discussed with a proper mathematical derivation. To verify theoretical findings, simulation study is carried out in MATLAB/Simulink R2014b. Finally, a laboratory-based 40-W prototype converter is designed to show the effectiveness of the proposed switch current reduction technique. [ABSTRACT FROM AUTHOR]

The efficiency of multiterminal dc (MTDC) grid simulation decreases with an expansion of its scale and the inclusion of accurate component models. Thus, the variable time-stepping scheme is proposed in this paper to expedite the electromagnetic transient computation. A number of criteria are proposed to evaluate the time-step and regulate it dynamically during simulation. Meanwhile, as the accuracy of results is heavily reliant on the switch model in the modular multilevel converter, the nonlinear behavioral model with a greater accuracy is proposed in addition to the classic ideal model, and their corresponding variable time-stepping schemes are analyzed. Circuit partitioning is effective in accelerating the MTDC grid simulation via fine-grained separation of nonlinearities. A subsequent large number of identical circuits enabled a massively parallel implementation on the graphics processing unit, which achieved a remarkable speedup over the CPU-based implementation. The inclusion of variable time-stepping schemes eventually makes the simulation of MTDC grid with highly detailed nonlinear switch models feasible. The results are validated by commercial device-level and system-level simulation tools. [ABSTRACT FROM AUTHOR]

In this paper, a new soft-switching bridgeless single-phase power factor correction converter is introduced and analyzed. Employing an auxiliary flyback circuit, existing dead angle in the input current is eliminated while softswitching is achieved. The flyback converter processes only small amount of output power. Therefore, conduction losses of its bridge diode and semiconductor devices are low. Also, the auxiliary flyback converter provides soft-switching condition for buck switches. All semiconductors are turned on and off under soft-switching condition. In addition to reduction of switching losses, diode's reverse-recovery problems are eliminated due to soft-switching condition. The proposed approach takes advantage of operating under discontinuous conduction mode to shape the input current into sinusoidal form inherently. Experimental results are reported for a 120-W prototype at 110 Vrms input and 48-V output. The results demonstrate efficiency of 93% at nominal load condition. Furthermore, the input current harmonics fulfill IEC61000-3-2 (Class D) standard as well. [ABSTRACT FROM AUTHOR]

A new transformerless bidirectional buck-boost converter is proposed in this paper. The proposed converter has a simple circuit structure, low component count, low voltage stress on the power transistors, and a wide voltage gain range. This makes it applicable in the energy storage charge/discharge systems, such as electric vehicles (EV), microgrids and nanogrids with energy storage units, and uninterruptible power supplies. In addition, synchronous rectification between the complementary transistors is employed to improve the converter efficiency. A comprehensive analysis of the steady-state operation, small-signal model, component parameters design, and efficiency analysis of the proposed converter operating in a continuous conduction mode is given. Finally, a 1.6-kW scaled-down prototype was built using Silicon Carbide MOSFETS to validate the effectiveness and feasibility of the proposed converter. [ABSTRACT FROM AUTHOR]

In this paper, a novel noncoupled inductor high voltage gain single-ended primary-inductor converter (SEPIC) is presented. The proposed converter has various advantages, such as lower voltage stress on the switches, noninverting output voltage, high efficiency, and high voltage gain. Also, the introduced converter has a continuous input current which makes it suitable for renewable energy and fuel cell applications. Moreover, high voltage gain is achieved without using any transformer and coupled inductor, thus there is not any voltage overshoot for the switches during the turn-off process. This effect allows low conduction losses by using lower voltage rating switches and also additional clamping circuit is not needed. The control system of the presented converter is simple and the converter can be easily controlled in continuous conduction mode mode operation. Because, the gating pulses for both of the switches are the same and wide output voltage range is achieved only by changing the duty cycle. Furthermore, the number of the components compared to the other noncoupled inductor, SEPIC-based converters which provide near voltage gain to the proposed converter, is reduced. The detailed operation of the introduced converter and design considerations are discussed. Experimental results are presented to verify the performance of the proposed dc–dc converter. [ABSTRACT FROM AUTHOR]

This paper presents an approach for dealing with the control of five-level, diode-clamped rectifiers. The control of such converters is challenging, as voltage balancing among capacitors is not a trivial task. Some of the existing approaches that cope with this problem use specific modifications of one of the traditional modulation techniques, such as using redundant vectors in space vector modulation (SVM). The main feature of the proposed technique is that part of the modulation is considered in the system equations and, in this way, the voltage balance can be solved designing a specific controller for this problem. As a result, several levels are used within a switching period. Furthermore, it is shown that the proposed approach hardly affects the control of active and reactive powers and total dc-link voltage in such a way that the well-known direct power control can be applied. As a consequence, the resultant modulation stage is simpler than other techniques based on, e.g., SVM. The effectiveness and good performance of the system under the proposed control approach are validated by both simulation and experimental results. [ABSTRACT FROM AUTHOR]

In this paper, a cooperative triple-phase-shift (CTPS) control for the isolated dual active bridge dc–dc converter is proposed first to eliminate the dual-dc side flow back currents. Furthermore, the current characteristics of the proposed CTPS control with the main variable (the primary side inner phase shift) tuned in two different regions are derived in detail and compared with each other. The tuning region of the main variable with the optimal current characteristics is finally determined based on the comparison results. As a result, the current stress is reduced and the efficiency is enhanced. The detailed experimental results of CTPS control verify its validity and practicability. The advantages of CTPS control are also highlighted by comparing it with some conventional phase shift controls. [ABSTRACT FROM AUTHOR]

Thanks to the favorable advantage of low cost, integrated three-port dc–dc converters with reduced switches have attracted extensive attention. In order to provide more new topologies, this paper aims to propose a programmable topology derivation method, which effectively simplifies the cumbersome process of the conventional combination method. Instead of the manual connection and examination, the proposed alternative can quickly and rigorously derive multiple viable integrated three-port dc–dc topologies from a great number of possible connections with the aid of computer program. Besides, generalized analysis is also accomplished, with which performance characteristics of all derived converters are simultaneously obtained and then a comprehensive comparison can be easily conducted to select a preferred one for the practical application. Finally, an example-specific application with one input and two outputs is given, with topology selection, design, and experimental results demonstrated in detail. [ABSTRACT FROM AUTHOR]

Power converter is critical but prone to be failure in switched reluctance motor (SRM) drives. The open- and short-circuit fault characteristics of freewheeling diode in asymmetric bridge power converter are analyzed in details. Based on logic judgment, four online fault diagnostic methods with digital phase current analysis of power converter are proposed in this paper. The fault features are extracted by analyzing the relationship between chopping signal and the current information from some special positions. The four fault diagnostic methods are carried out according to the current obtained by detecting dc bus current and the lower freewheeling bus current, the chopped bus current, the upper excitation bus current and lower freewheeling bus current, the lower excitation bus current, and dc bus current, respectively. Comparisons between the four diagnostic methods are conducted. Simulations and experiments on a 12/8 SRM validate the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

Synchronous rectification (SR) is one of the well-known methods to reduce the conduction losses by replacing the power diodes. The control of SR requires the phase information of the device current. In this paper, a novel extended harmonics approximation modeling approach is introduced for CLLC resonant converters to estimate the phase of its secondary side current accurately. Conventionally, the first harmonic approximation (FHA) is used to model any resonant converter; however, FHA works more accurately near the resonant frequency operation. But in case of a set of unmatched LC tank parameters in the primary and secondary side of a CLLC converter, there is no uniquely defined resonant frequency, which reduces the accuracy of the FHA model. Unlike FHA-based approach, our proposed modeling considers the effects of other odd order harmonics present in the square wave voltage waveform towards determining the zero-crossing instant or phase information of the resonant currents. The proposed concept is verified through experimental results obtained at 3.3-kW load condition, and the converter efficiency is improved by 1.8% with the proposed phase tracking technique, compared to FHA modeling approach. [ABSTRACT FROM AUTHOR]

Cascaded H-bridge (CHB) is a promising topology for medium-voltage high-power applications. CHB consists of low-power H-bridge modules in each phase, and these modules are connected in a cascade manner to achieve multilevel operation. However, CHB requires a phase-shifting transformer with multiple secondary windings to generate an isolated dc source for each module, and this requirement increases the overall system cost. In this paper, a series connection of low-power modules is employed to realize a new power converter called a series-connected multilevel converter. Each phase of the proposed topology requires a single isolated dc source. Hence, the required number of secondary windings is considerably reduced. This approach also minimizes the complexity and cost of the overall system. The operation of the proposed topology is presented by using three-level neutral point clamped modules in each phase. Model predictive control (MPC) is employed to control the dc-bus capacitor voltage and output currents of the proposed topology. A discrete-time mathematical model of the proposed topology is also developed to predict the future behavior of control variables. The performance of the proposed topology with MPC is verified through MATLAB simulations and a scaled-down laboratory prototype. [ABSTRACT FROM AUTHOR]

Switching-linear hybrid envelope tracking (SLH ET) power supplies can achieve both high efficiency and high bandwidth. However, the switching frequency is often required to be far higher than or at least equal to the envelope bandwidth. With the modulation methods advance, the increasing envelope bandwidth may lead to a too high switching frequency to implement. This paper proposes an SLH ET power supply, consisting of a multilevel converter and a linear amplifier connected in series. Based on the multicell configuration of the multilevel converter, a pulse edge independent distribution method is proposed, which can break the control pulses for the multilevel converter into independent rising and falling edges, and rebuild them with new sequences. It can not only reduce the switching frequency to 1/n (n ∊ N) of the envelope bandwidth but also extend the pulsewidths to provide a more reliable and effective driving for high bandwidth applications. A prototype for 2 MHz sine-wave tracking, with 7–27-V output voltage and 90-W peak output power, is fabricated and tested. It is also verified by a 5- and a 10-MHz bandwidth communication envelope. The experimental results validate the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, a fully soft-switched bidirectional dc–dc converter is proposed. All semiconductor devices are soft switched, while its control circuit remains pulsewidth modulated. This condition is achieved only by one auxiliary switch. So, the proposed topology has less complexity in comparison with other similar structures. The energy conversion through the proposed topology during buck and boost modes is highly efficient due to achieved soft-switching condition. The auxiliary circuit operates once during each switching cycle. The converter is analyzed and a 250-W laboratory prototype of the proposed converter is constructed. The experimental results are presented that confirm the theoretical analysis. [ABSTRACT FROM AUTHOR]

This paper proposes a light, flexible, and yet reliable multiparametric estimation algorithm for grid-connected voltage-source-converter-based systems. This approach combines the nonlinear least squares (NLSQ) fitting algorithm and the steady-state extended harmonic domain (EHD) model to take into account the harmonic effects. The EHD model is used to take advantage of the harmonic content of the electrical signals to provide robustness and improved performance to the NLSQ estimation methodology. In addition, this harmonic formulation reduces the necessity of synchronized measurements. Details of the implementation are provided by an experimental case study, in which the grid equivalent (Thevenin voltage, inductance, and resistance), the ac-side filter (inductance and resistance), and the converter switching and conduction loss resistance are accurately estimated for three different operating conditions. [ABSTRACT FROM AUTHOR]

This paper proposes two coupled-inductors-based Z-source networks, called the modified series and tapped switched-coupled-inductors quasi-Z-source networks (mSSCL-qZSN and mTSCL-qZSN, respectively). These networks offer high voltage gains with less-than-unity winding turn ratios $(n < {\text{1)}}$ , resulting in a reduced inductive element size. Other advantages include a less number of active components and their lower ratings and a higher efficiency. In addition, a lower magnetic core size is required for the proposed ZSNs due to the lower peak magnetizing current. The performance principles and detailed comparative analysis are provided and confirmed through experiments on a 200-W dc–dc converter. [ABSTRACT FROM AUTHOR]

Discrete-time control of power converters without modulation blocks have been considered in recent times in modern high-performance electromechanical drives, particularly with the appearance of model predictive control in its finite set version. The shortcomings produced by the fixed discretization of time used in this kind of control systems has been analyzed, and several methods have been put forward to deal with them. Most of the alternatives increase the complexity of the controller introducing different analytical modulation methods. However, a variable sampling time can be a simpler and more natural solution, at the expense of using a less-known paradigm for implementation. This paper introduces a new control approach based on a model of the system as in predictive controllers but using variable sampling time. It can be applied to modern power converters and drives, including conventional three-phase or advanced multiphase ones. Experimental results are provided to test the ability of the controller using a five-phase induction motor drive as a case example. [ABSTRACT FROM AUTHOR]

In this paper, a model predictive control (MPC) based on optimal switching sequences (OSSs) for a single-phase grid-connected full-bridge neutral-point-clampled (NPC) power converter is presented. The predictive control algorithm is formulated in terms of OSSs, which was originally proposed to govern three-phase power converters. In this paper, the OSS concept is extended to control single-phase power converters. The proposed MPC algorithm belongs to the continuous control set MPC and is able to provide fixed switching frequency while handling system constraints. The proposed algorithm has been experimentally tested in an NPC power converter prototype. Experimental results show the desired fixed switching behavior in the steady-state condition and the intrinsic fast dynamic provided by MPC during transients. Furthermore, the test outcomes demonstrate the robustness of the proposed controller under large system parameter deviations. [ABSTRACT FROM AUTHOR]

This paper presents a three-phase open-end winding induction motor drive. The drive consists of a three-phase induction machine with open stator phase windings and dual-bridge inverter supplied from a single dc voltage source. To achieve multilevel output voltage waveforms, a floating capacitor bank is used for the second of the dual bridges. The capacitor voltage is regulated using redundant switching states at half of the main dc-link voltage. This particular voltage ratio (2:1) is used to create a multilevel output voltage waveform with three levels. A modified modulation scheme is used to improve the waveform quality of this dual inverter. This paper also compares the losses in the dual-inverter system in contrast with a single-sided three-level neutral point clamped converter. Finally, detailed simulation and experimental results are presented for the motor drive operating as an open-loop v /f controlled motor drive and as a closed-loop field-oriented motor controller. [ABSTRACT FROM PUBLISHER]

Ensuring electrification of remote locations continues to be a major challenge for power engineers. To deal with the effect of intermittent nature of wind, this paper presents the design and implementation of a composite sliding mode controller (CSMC) for a battery energy storage (BES) supported solar photovoltaic (PV)–wind hybrid system in a remote location. This control technique comprises of a soft-switching sliding-mode observer (SS-SMO) and a nonsingular terminal sliding mode controller (NTSMC). The SS-SMO is used to observe the disturbances, whereas the NTSMC is used as a speed controller. The chattering problem caused by the conventional sliding mode controller is alleviated by replacing the conventional signum switching function with the smooth hyperbolic tangent function in disturbance observer loop. The fast and finite time convergence NTSMC based speed controller along with the SS-SMO based disturbance rejection unit, serves the benefits of CSMC. This technique exhibits robustness against model uncertainties and external disturbances. Moreover, the complexity of the system is reduced by replacing the mechanical speed and position sensors with parameter estimation. A double-stage configuration using a dc/dc boost converter is adopted for a PV system. A comparative analysis is presented between the proposed and conventional techniques. A prototype of the hybrid system is developed in the laboratory with permanent magnet synchronous generator. The CSMC-based controller with disturbance rejection ability is implemented to harvest peak wind power. A perturb and observe maximum power point tracking technique is adopted to harvest peak solar power. A voltage control technique is adopted to maintain the voltage at the point of common coupling. [ABSTRACT FROM AUTHOR]

In this paper, a high step up converter consisting of an integrated quadratic-boost converter and a voltage doubler is proposed. The integration of the quadratic-boost converter makes the system easier to lift up its voltage gain through slightly increasing the duty ratio of the single switch. The voltage doubler further increases the voltage gain of the system as the turn ratio rises. The voltage stresses on the switch and the diodes are decreased for such cascaded topology. Different operation modes are analyzed and mathematical analysis of the converter is presented in detail. The leakage inductance contributes to realizing zero current switching of the diodes in the second boost stage and the doubler and the energy can be recycled to the load. A 38-W prototype is built to work as a vehicle LED driver. Experiments are conducted to verify the advantages of the proposed converter and the efficiency is 90% at the nominal operating point. [ABSTRACT FROM AUTHOR]

In recent years, modular multilevel converter (MMC) is considered for medium-voltage variable speed drives (VSD) due to its modularity and higher reliability. However, the major drawback of the MMC-based VSD is the higher capacitor ripple voltage at lower operating speeds. In literature, this ripple voltage is reduced by injecting a high-frequency circulating current into each arm. This additional circulating current increases the overall current rating of the devices, inductors, and capacitors. Alternatively, the capacitor ripple voltage can be reduced at the lower output frequency by reducing the dc-bus voltage. This paper proposes a new configuration using a multipulse diode-bridge rectifier to reduce the dc-bus voltage when the drive is operated at lower speeds. Therefore, the capacitor ripple voltage decreases without injecting any circulating current. In addition, a new technique is proposed to maintain the peak-to-peak value of the submodule capacitor ripple voltage constant at near-zero speed. The proposed converter with 24-pulse rectifier configuration is simulated in MATLAB/Simulink, and the experimental validation is carried out on a prototype with 12-pulse rectifier. [ABSTRACT FROM AUTHOR]

In this paper, a new modified single-switch single-ended primary inductor converter (MS2-SEPIC)-based high step-up dc–dc converter is presented. The proposed topology uses the coupled-inductor (CL) technique and a voltage tripler rectifier, which results in a high voltage gain for the converter. Here, the switching loss has been reduced significantly owing to the quasi-resonance operation of the circuit created by the leakage inductance of the CL along with circuit capacitors. The operational principles and steady-state analysis are discussed. Experimental results based on a 100 W laboratory prototype verify the validity of theoretical analysis. [ABSTRACT FROM AUTHOR]

When the selected harmonic elimination pulsewidth modulation (SHEPWM) is adopted to three-level neutral-point-clamped converters to reduce the switching frequency, the neutral-point potential (NPP) problem becomes more severe compared with other modulations. It is because there is no degree of freedom for SHEPWM to control the NPP. SHEPWM realizes a better harmonic performance by calculating the switching angles offline based on harmonic requirements. Since it is harsh to solve the angles online, we cannot change the angles to control the NPP. Aiming at the low-frequency NPP fluctuation minimum, a novel current harmonic minimum method based on the optimal third-order/ninth-order harmonic is proposed in this paper. The optimal third-order/ninth-order harmonic is derived based on the relationships among the third-order/ninth-order harmonic and the NPP. They can be utilized to realize the low-frequency NPP fluctuation minimum without changing any switching angle online. Moreover, some comparisons, such as the solution ranges, weighted total harmonic distortion, the initial value of iteration calculation, show that the proposed method has a good output performance. Finally, the experimental results are given to verify the validity of the proposed method. [ABSTRACT FROM AUTHOR]

A 1-MHz-modified single-ended primary-inductor converter (SEPIC) circuit is presented in this paper as an LED driver for automotive headlights. On the basis of traditional SEPIC, only a diode and two capacitors are added; therefore, the circuit structure is relatively simple and the volume is relatively small. High step-up capability is obtained with moderate duty cycle. Compared with traditional step-up circuit such as boost, low-voltage stress is gained which is beneficial to device selection. Zero-voltage switching is achieved at the same time to reduce switching loss. Planar inductors are used with the advantages of low profile and good thermal characteristic. Operational principle and parameters design process are introduced in detail. A 36-W prototype has been designed to demonstrate theoretical analysis. Obtained efficiency was up to 90.91% at full load. [ABSTRACT FROM AUTHOR]

Switched-capacitor converter (SCC) featuring high efficiency and power density has attracted industry interest, but weak output voltage regulation hinders its application. This paper presents an optimized phase-shift (PS) control strategy for a bridge modular SCC, utilized in energy storage system, to obtain continuous conversion ratio and high-efficiency operation. By employing a small inductor as current buffer, the control strategy could be implemented to regulate output voltage conveniently with excellent steady and dynamic performance in step-down mode as well as step-up mode. Most importantly, the high-efficiency operation mechanism never reported before is revealed here. Correspondingly, the active circumfluence could be controlled through optimizing the range of PS time, which will avoid the loss in circuit self. Meanwhile, the soft-switching conditions of all the switches are comprehensively analyzed and soft-switching operations are achieved according to the logic timing control of the power devices, improving efficiency further. Finally, the prototype of the proposed converter was built and the experimental results validated the principle and features of the conversion method. [ABSTRACT FROM AUTHOR]

In this paper, a novel buck–boost converter with low electric stress on components and negative output voltage is proposed. The operational principle, steady-state analysis, and small-signal modeling of the proposed buck–boost converter in continuous conduction mode are presented. Comparisons among another five buck–boost converters and the proposed buck–boost converter are presented. It is found that the proposed converter's voltage gain is smaller than the other converters’ in step-down mode. Also, based upon the comparisons among the same kind and same number of components, the voltage and current stresses on the power switch of the proposed buck–boost converter are less than or equal to those of the comparative converters, and the voltage stress on the charge pump capacitor and the switching device power rating of the proposed buck–boost converter are always lower than those of other comparative converters. The efficiency of the proposed buck–boost converter is highest among those converters having the same number of elements. These advantages make component selection for the proposed converter much easier, and it can be used directly in applications needing a negative voltage source. Finally, simulation results and circuit experiments are given for validating the effectiveness of the proposed buck–boost converter. [ABSTRACT FROM AUTHOR]

In this paper, a sequence switching control (SSC) scheme based on an auxiliary parallel inductor is proposed to improve the transient performance of buck converters. The proposed SSC scheme introduces a small controlled inductor in parallel with the output inductor, so as to increase the inductor-current slew rate when it is activated during a load transient. Furthermore, an “n+ 1” sequence switching strategy is proposed to control the auxiliary parallel inductor. The proposed scheme divides the transient event inton+ 1 periods. In the formernperiods, the same small output voltage deviations are designed, while in the last period, a smaller deviation is done for a smooth transition from the transient to the steady state. The switching sequence is derived applying the capacitor–charge balance principle for each ofn+ 1 periods. For a given buck converter in the experiment, the settling time and the output voltage deviation of the proposed SSC scheme enhance more than 50% and 67%, respectively, over those of the time-optimal control for a 3-A load step. [ABSTRACT FROM AUTHOR]

DC-link current ripple is one of the important factors for operating the current-source converter. In practice, the dc-link current ripple can be reduced by increasing the switching frequency or inductance. However, it may result in the higher switching losses, larger size, or higher cost. In order to deal with this problem, the inherent limitation of the conventional solution is discussed in this paper. The time-domain equation of the dc-link current is established for the first time. And then, a new space vector control strategy is proposed to reduce the ripple with no need of increasing the switching frequency or inductance. The space vector is divided into 12 sectors, where the dc-link current ripple can be effectively reduced by the optimal vector sequence. Finally, the proposed method is implemented on the TMS320F28335DSP + XC3400FPGA digital control hardware platform. The experimental results verify the effectiveness of the proposed strategy. [ABSTRACT FROM AUTHOR]

Conventional two-level as well as multilevel voltage-source-inverter topologies with a hexagonal voltage-space vector structure generate low-order harmonics in the machine terminal voltages when operated beyond the linear modulation range in variable speed drive application. Progressing from hexagonal to a higher sided polygonal voltage-space-vector structure (VSVS) suppresses significant low-order harmonics throughout the modulation range. In addition, the linear modulation range will also be enhanced very near to the base speed. In this paper, for the first time, the generation of a multilevel 24-sided VSVS using a single dc source for induction-motor drives is proposed. A cascaded topology with a dc-source-fed flying-capacitor inverter and two low-voltage capacitor-fed H-bridge cells forms the power circuit. The features and advantages of the proposed scheme are validated through experimental results and discussions. [ABSTRACT FROM AUTHOR]

In this paper, a new control strategy for single-inductor multiple-output (SIMO) converters is proposed. The strategy is based on the hybrid control scheme. Switched linear equations of the converter are used in the design procedure. As a result, the cross regulation is suppressed inherently. A minimum dwell-time constraint is considered to suppress the switching loss and electromagnetic interference. The proposed scheme can control both minimum phase and nonminimum phase SIMO converters. It will be shown that the system is robust to input voltage and load variations. In order to compare the results, a recent pulsewidth-modulation-based control system is considered. Performance of the system is evaluated by a number of simulations and experiments. [ABSTRACT FROM AUTHOR]

In this paper, a new method is applied to predict the average value of the phase currents of a two-level voltage source converter. The method uses a suitable model of the converter, the modulation method, and the measurement. The samples given by the analog-to-digital converter (ADC) are used to predict the time progress of the currents in every switching cycle and then calculate its average. This allows removal of the delay introduced by filtering and avoids aliasing in the measurements. The average prediction is contrasted with the pulsewidth modulation (PWM) synchronous sampling method and the sigma-delta ADC with a moving average filter. Applied to a load observer, the method effectively reduces its estimation error. The findings are verified experimentally. [ABSTRACT FROM AUTHOR]