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The modular multilevel converter (MMC) is a favored topology in the industry, but its reliability is at risk with an increase in the number of sub-modules (SMs) due to a rise in switching components. The essential need for maintaining capacitor voltage balance in each arm leads to increased complexity and cost, as numerous voltage sensors are required. This study introduces an innovative approach to minimize the number of voltage sensors by employing an enhanced algorithm for open-circuit fault detection in switches. The proposed scheme organizes each arm into groups, each containing two SMs and one voltage sensor, aiming to reduce the overall sensor count. A novel fault detection mechanism is presented, identifying open-circuit faults by comparing group output voltages in healthy and defective conditions. The capacitor voltage estimation algorithm in the sensor reduction scheme is noted for its simplicity compared to other methods. The effectiveness of these methods is validated through simulations and experimental implementations across diverse scenarios, affirming their reliability. [ABSTRACT FROM AUTHOR]

This paper propose a high gain non-isolated DC-DC converter using coupled inductor at input stage and capacitor voltage multiplier cell (VMC) at the output stage. The input coupled inductor is responsible for ripple reduction and the output capacitor multiplier cells are intended to improve the voltage gain. The use of VMC reduces the voltage stress across the power converter switches and facilitates to exploit low rated switches. It will reduce the conduction, switching losses and improve the converter efficiency. The charge balance between the blocking capacitor helps to achieve uniform current sharing in each phase of interleaving operation. The projected DC-DC converter is highly recommended for fuel cell application due to the low input current ripple and high gain. The mathematical model and simulation analysis has been conducted in detailed to validate the converter topology. The converter characteristics have been compared with the high conversion ratio DC-DC converter. [ABSTRACT FROM AUTHOR]

The non-inverting buck boost (NIBB) converter has attracted significant attention in recent years, as it shares ground between input and output, and the voltage stress of switches is lower. In order to investigate the differences between NIBB and conventional buck boost converters, a comprehensive comparison and analysis of these two converters were conducted in terms of their operation principles, which includes multi-mode control strategy and dual-edge modulation here, and also the characteristics of switches and passive components in the two converters were analysed. The results show that NIBB is better than conventional buck boost circuit in these aspects of electrical stress, power loss, cost, passive component volume, and so on. Two prototypes for the two converters with 10 kW/20 kHz were designed and simulated, respectively, for verifying the results. Analytical and simulated results confirmed the conclusions. [ABSTRACT FROM AUTHOR]

Highlights • Presenting a multi-input DC-DC converter for utilizing in hybrid applications. • Providing a unidirectional input port, a bidirectional port and an output port. • Presenting performance evaluation and good comparable results. Abstract This paper proposes a non-isolated high step-up multi-input DC-DC converter for utilizing in hybrid applications. This converter provides the interfaces between input power sources, energy storage devices and load. The resonant auxiliary circuit used in the proposed converter provides soft switching condition for the main switches as well as charging the storage device which has caused considerable improvement in the converter efficiency. This converter uses only three switches to control the power absorbed from a unidirectional input, the power absorbed or stored in the bidirectional port and also the power transmitted to load while provides soft switching condition of all semiconductor devices. Thus, the number of switches applied is same as conventional hard switched converters for this purpose. This converter shares only one inductor between all inputs, so the volume is reduced. Various converter operating modes are discussed and design considerations are presented. Finally, to validate the theoretical analysis, a prototype of the proposed converter is implemented for a 400 V output voltage at 200 W. [ABSTRACT FROM AUTHOR]

Summary: This work proposes the conception of a nonisolated direct current (DC)‐DC buck‐boost converter employing the three‐state switching cell. Similarly to interleaving, it is possible to achieve higher power levels than that regarding the classical buck‐boost converter, but prominent advantages over the interleaved approach result, ie, the input current is continuous for duty ratios higher than 0.5; good current sharing is achieved without the need of special control schemes; and the active switches are connected to the same reference node as the input voltage source, as there is no need to use isolated drive circuitry. A thorough quantitative and qualitative analysis is carried for the entire range of the duty cycle D, considering that the proposed converter presents distinct behaviors for D < 0.5 and D > 0.5. An experimental prototype is developed and evaluated, while the results are discussed in detail. A direct current (DC) to direct current buck‐boost converter based on the three‐state switching cell is presented. The topology is adequate for high‐power, high‐current applications, with significant advantages if compared with similar approaches, eg, nonpulsating input current and good current sharing without the need of dedicated control techniques. [ABSTRACT FROM AUTHOR]

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

Impedance source inverters (ISIs) are gaining attention due to features such as single-stage conversion, buck-boost capability, and inherent shoot-through protection. To maintain the required ac output voltage, typically ISIs are operated at a higher dc-link voltage due to constrained modulation index. This also increases voltage stress across capacitors and switches of the converter. This voltage stress is approximately double compared to that of voltage source inverter with preboost stage (Boost-VSI). To mitigate this problem, a new pulsewidth modulation (PWM) scheme for the active-front-end based ISIs (AFE-ISIs) is proposed. The proposed scheme enables the ISIs to produce high ac gain with lower voltage stress across the capacitor and switches. In other words, the proposed scheme blends the advantages of Boost-VSI into ISIs. With the new PWM scheme, there are also reductions in output voltage total harmonic distortion, switching frequency ripple in the inductor current, and power loss in the converter. A prototype of the current-fed switched inverter, an AFE-ISI, is designed, and the proposed PWM scheme is implemented. Experimental results obtained are in accordance with the proposed theory and show that the voltage stress has reduced from 325 V to 203 V for an ac output of 110 V. [ABSTRACT FROM AUTHOR]

Highlights • The converter applies one auxiliary switch to create soft switching condition. • The proposed converter has simple structure and its control circuit remains PWM. • The converter has high voltage gain without using any transformer in its structure. • All switches have low current stress due to use of interleaved structure. • The converter is a proper selection for PV application due to its high efficiency. Abstract This paper presents a high step-up fully soft switching interleaved Sheppard-Taylor converter to be used in PV applications. The proposed converter utilizes only one auxiliary switch to create the soft switching conditions for all semiconductor devices. The converter has a simple structure, and its control circuit remains PWM. Moreover, the auxiliary switch is not located in the main power path; therefore, the conduction losses are decreased, and the overall efficiency is improved. Besides, the rate of the auxiliary switch current will be very low. On the other hand, the proposed converter has a high-voltage gain. Furthermore, all switches and other circuit elements have low current stress due to the interleaved structure in the proposed converter. The guidelines for the design consideration are presented. A 250 W, 25–250 V laboratory prototype operating at 100 kHz is implemented to verify the performance of the converter and an efficiency of 96% at full load can be achieved. [ABSTRACT FROM AUTHOR]

The study introduces a bidirectional dc-dc converter with current- and voltage-fed (VF) ports that features soft switching in both buck and boost operating modes. The converter can be used for integration of low-voltage DC sources, such as batteries into a dc bus of considerably higher voltage or a dc link of a grid side inverter. Zero current switching, assisted with the leakage inductance of the isolation transformer, can be achieved at the current-fed side along with zero voltage switching of the VF side, assisted by snubber or intrinsic capacitances of the transistors. Soft switching can be maintained over a wide range of voltage and power levels, regardless of the energy transfer direction. Converter operation is described and theoretical findings were verified with experimental results obtained by means of a 300 W prototype operating at a switching frequency of 100 kHz and designed for integration of a 24 V battery into 400 V dc bus. The converter proposed is compared in terms of efficiency to other competing soft-switching full-bridge topologies implemented with the same components. [ABSTRACT FROM AUTHOR]

A high-efficiency multimode battery charger with an adaptive supply voltage (ASV) control scheme is presented in this paper. The proposed battery charger includes a charging circuit and a dc–dc buck converter. The charging circuit automatically switches among trickle current (TC), constant-current (CC), and constant-voltage (CV) modes corresponding to the battery voltage while the buck converter with ASV control generates an ASV to closely track the battery voltage, leading to significant reduction in the power loss of the charging circuit. To further enhance the efficiency of the battery charger, zero-current detection and nonswitching control schemes are employed to decrease the power consumption of the buck converter in TC and CV modes. The battery charger was implemented with a 0.35- μm CMOS 2P4M process. The experimental results are shown to verify the theoretical analysis of the proposed charger. The maximum efficiency of the overall system is 88.3%, and the maximum efficiency improvement between the proposed charger and the conventional linear charger with fixed supply voltage is up to 11.6%. [ABSTRACT FROM AUTHOR]

This paper proposes a single-stage, high power-factor light-emitting diode (LED) driver with a self-excited control scheme for the power switches. The self-excited mechanism is accomplished by fetching the driving voltages from a center-tapped transformer. The frequency of the driving voltages is exactly the same as the resonant frequency of the resonant converter, thus synchronizing the resonant frequency with the switching frequency and achieving zero-voltage switching (ZVS) and zero-current switching (ZCS) of power switches. The circuit topology is mainly composed of a half-bridge LC resonant converter, along with a boost-type power-factor corrector (PFC) to fulfill the single-stage structure, meaning that the presented LED driver possesses high power-factor features and low switching loss. Finally, a 40 W prototype circuit is implemented and tested, and the experimental results exhibit a satisfactory performance. [ABSTRACT FROM AUTHOR]

The alternate arm converter (AAC) is an emerging fault-tolerant multilevel converter topology from the same family of multilevel converters as the modular multilevel converter (MMC). Due to the alternate operation of the converter arms, energy balancing in the AAC is not continuous, but restricted to small time intervals. This paper develops a gradient-based current control and energy-balancing method for the AAC. The proposed strategy enforces the dynamic limits on the redundant submodules (SMs) during the overlap period and allocates effectively the maximum available number of redundant SMs to control the circulating current. The choice of the gradient as the circulating current control parameter improves the energy regulation capability of the AAC, and the enforcement of dynamic limitations avoids distortions of the output voltage. Results from an AAC-based HVDC converter model derived from the CIGRE benchmark MMC system demonstrate that the proposed strategy delivers improved energy control and balancing with good harmonic performance compared to existing current control methods for the AAC while also maintaining zero-current switching of the director switches of the AAC arms. [ABSTRACT FROM AUTHOR]

This paper presents an isolated bidirectional interleaved converter with minimum active switches to achieve high conversion ratio. The proposed converter has symmetric structure for easy control, and incorporates two coupled inductors for galvanic isolation and high voltage ratio achievement. A dual-inductor-capacitor-diode (LCD) snubber with common resonant inductor at low-voltage side is in charge of leakage energy recycling for efficiency improvement. In addition, the converter can obtain interleaved terminal current at low-voltage side for lowering current ripples, no matter in boost mode or buck mode. Finally, a 400-W prototype is built for validation, where the experimental results indicate that the highest efficiencies in boost and buck modes are 95.5% and 95.4%, respectively. [ABSTRACT FROM PUBLISHER]

All-GaN-integrated cascode heterojunction field effect transistors were designed and fabricated for power switching applications. A threshold voltage of +2 V was achieved using a fluorine treatment and a metal–insulator–semiconductor gate structure on the enhancement mode part. The cascode device exhibited an output current of 300 mA/mm by matching the current drivability of both enhancement and depletion mode parts. The optimization was achieved by shifting the threshold voltage of the depletion mode section to a more negative value with the addition of a dielectric layer under the gate. The switching performance of the cascode was compared to the equivalent GaN enhancement-mode-only device by measuring the hard switching speed at 200 V under an inductive load in a double pulse tester. For the first time, we demonstrate the switching speed advantage of the cascode over equivalent GaN enhancement-mode-only devices, due to the reduced Miller-effect and the unique switching mechanisms. These observations suggest that practical power switches at high power and high switching frequency will benefit as part of an integrated cascode configuration. [ABSTRACT FROM AUTHOR]

An asymmetric three-level neutral point diode clamped converter for switched reluctance motor drives is proposed in this paper. The modulation method, the dc-link voltage balancing algorithm, and the current control scheme of this converter are presented. The proposed three-level converter is compared with the conventional two-level asymmetric half-bridge converter in terms of cost, current ripple, noise, and power losses. Compared to the conventional two-level converter, the proposed three-level converter has much lower current ripple, lower noise, and higher efficiency. The effectiveness of the proposed converter is verified by both simulation and experimental results. [ABSTRACT FROM AUTHOR]

The demand of miniaturization of power systems has accelerated the research on high-switching-frequency power converters. A flyback converter in resonant mode that features low switching losses, less transformer losses, and low switching noise at high switching frequency is investigated in this paper as an alternative to a conventional quasi-resonant (QR) flyback topology to increase power density. In order to find a compromise between magnet size, electromagnetic interference (EMI), and efficiency, the concept utilizes the resonant behavior between transformer leakage inductance and snubber capacitor to achieve near-zero-voltage switching at both turn-on and turn-off of the primary switch, low core loss due to a continuous transformer magnetizing current, and reduced EMI due to low di/dt and dv/dt values. Meanwhile, the concept uses the regenerative snubber to recycle the transformer leakage energy with two snubber diodes and one snubber capacitor. The proposed concept has been validated on a 340-kHz 65-W prototype. Compared to the conventional QR flyback converter operating at the same switching frequency, the proposed concept has 2% efficiency improvement and better EMI performance. [ABSTRACT FROM AUTHOR]

This paper presents two hybrid six-phase machine drive systems. The topologies are considered to be hybrid because two three-phase groups of the machine are fed by different types of converters. The purpose of these topologies is to be alternative configurations, being midway between the conventional six-leg two-level (2L) inverter, composed of 12 switches, and more complex structures, such as the six-leg three-level neutral point clamped (3L-NPC) inverter, composed of 24 switches and 12 clamping diodes, or the conventional 12-leg dual inverter, composed of 24 switches. One of the hybrid topologies is composed of 18 switches and the other is composed of 18 switches and 6 clamping diodes. A comparative study of harmonic distortion, semiconductor losses, and machine torque ripple is performed. Compared with the conventional 2L inverter, the proposed systems provide better performance in terms of harmonic distortion, overall semiconductor losses, and machine torque ripple and are less complex than dual and NPC inverters. Pulse width modulation (PWM) strategy is discussed and simulated. A modification in PWM strategy of the hybrid configurations is performed in order to obtain similar torque ripple to the cases when dual and 3L-NPC converters are used, even with lower number of semiconductor devices. Experimental results are also presented in order to validate the PWM strategy. [ABSTRACT FROM AUTHOR]

To interface generation sources and loads to four-wire distribution networks it is important to use power converters and modulation methods, which provide high performance, flexibility, and reliability. To achieve these goals, this paper proposes a simple and efficient space vector modulation (SVM) algorithm in $\alpha \beta \gamma$ coordinates for neutral point clamped (NPC) converters. The proposed SVM method reduces a 3-D ($\alpha \beta \gamma$) search amongst modulating vectors into a simple 2-D ( $\alpha \beta$) problem. Moreover, the algorithm provides full utilization of the dc-link voltage and full utilization of the redundant vectors, and it can be applied to any other four-leg converter topology. The proposed SVM has been successfully validated using a 6-kW three-level four-leg NPC converter, achieving control over the voltages of the dc-link capacitors and a simple definition of the switching patterns for shaping the frequency spectrum. [ABSTRACT FROM AUTHOR]

A single-stage three-level isolated ac/dc power factor correction (PFC) converter for high dc-link voltage low- power application with increased efficiency is presented in this paper. For achieving this, both ac/dc and dc/dc stages are effectively integrated. The efficiency is increased by the method of synchronous rectification. Using this method, all the switches are shared. The bus voltage regulation and output voltage regulation can be achieved without introducing additional switches with the proposed converter and switching scheme. Two independent PI controllers are used for this. This converter is used for low voltage applications such as laptop chargers, mobile chargers, lamps, etc. [ABSTRACT FROM AUTHOR]

In recent years, fault tolerance has gained a growing interest from the scientific community, particularly in DC/DC converters. Generally, fault-tolerance refers to a fault-tolerant topology and/or control for power converters. In this paper, a floating interleaved boost converter (FIBC) is used in order to meet the fuel cell requirements, particularly in terms of input current ripple reduction and reliability. In DC/DC converters, power switches are ranked as the most fragile components. The most common failures in power switches are open-circuit faults (OCFs), gating faults and short-circuit faults (SCFs). The loss of one leg in case of OCF or SCF (considering that the faulty leg is isolated before damaging the system) leads up to the drastic increase of the fuel cell current ripple and consequently fuel cell lifespan reduction. The purpose of this paper is to present a fast and efficient power switch open-circuit fault detection algorithm and fault-tolerant control (FTC). The performances of the developed fault detection algorithm and FTC are validated by carrying out experimental tests between a proton exchange membrane fuel cell and a FIBC topology. The experimental results demonstrate the ability of the developed FTC to reduce drastically the fuel cell current ripple while improving the fuel cell lifespan. [ABSTRACT FROM AUTHOR]

The traditional critical conduction mode (CRM) flyback PFC converter with constant on-time control strategy usually suffers low power factor (PF) and high total harmonic distortion (THD) due to the nonsinusoidal input current waveform. In order to solve this problem, an improved variable on-time control strategy for the CRM flyback PFC converter is proposed in this letter. A simple analog divider circuit consisting of an operational amplifier, two signal switches, and an RC filter is proposed to modulate the turn-on time of the primary switch, and the PF and THD of the CRM flyback PFC converter can be evidently improved. The theoretical analysis is presented and the experiment results verify the advantages of the proposed control scheme. [ABSTRACT FROM PUBLISHER]

This paper describes a novel modeling approach for self-oscillating resonant power converters operating under a control method based on the variable structure of the system (VSS). Using a fundamental harmonic approximation, the link between control and switching frequency in steady state is found to be accurately described by an affine function that depends on the load. Besides, this link has been extended in order to characterize the control-to-switching frequency dynamics, resulting in a novel small-signal continuous-time model. The resulting control-to-switching frequency transfer function can be appended to the well-known models for frequency modulation, in order to obtain a complete control-to-output system. The new model exposes that the dynamics of the converter under the VSS-based control approach presents advantages with respect to the conventional methods as frequency modulation: 1) reduced dc gain variation for uncertain loads and 2) improved phase margin at high frequencies. The dynamic modeling is complemented with the design of a controller for regulating the output voltage of a parallel resonant converter, whose performance and robustness are compared with the standard frequency modulation. Numerical simulations and experimental results confirm and verify the analytical derivations. [ABSTRACT FROM AUTHOR]

Hybrid cascaded multilevel inverters have been recognised as an important alternative in the medium-voltage inverter market due to their high-quality output and outstanding availability. To optimise the performance of voltage-source converters, modulation technologies have attracted more and more attention. With conventional modulation technologies, the switches within a cell are not utilised at a uniform switching frequency, which is not benefit for reliability and modularity. To solve this problem, a modified hybrid modulation strategy based on unipolar frequency doubling is proposed for H-bridge hybrid cascaded inverters. The equivalence of different multilevel carrier-based modulation strategies is revealed and corresponding implement methods are provided. Based on the equivalent hybrid modulation strategy, a modified hybrid modulation strategy is presented by using unipolar frequency doubling. Compared with the conventional modulation strategies, the proposed strategy makes a more uniform use of the switches within a cell. The proposed strategy keeps the output quality and efficiency while the maximum switching frequency is decreased by half. The strategy has been successfully substantiated by the simulation and experimental results of a seven-level hybrid cascaded inverter. [ABSTRACT FROM AUTHOR]

This study presents a novel single-switch high step-up dc–dc converter employing a quasi-resonant operation with high efficiency and low ripple continuous input current characteristics. In order to achieve a high voltage gain, a combination of coupled inductor and switched capacitor techniques is used in the proposed dc–dc converter. Moreover, utilising a series resonance capacitor with the leakage inductance of the coupled inductor leads to a resonant circuit. Subsequently, by employing a quasi-resonant operation, the switching loss of the proposed dc–dc converter has been reduced significantly. Operational analysis, mathematical derivation, component voltage and current ratings are well demonstrated in this study. Finally, the performance of the proposed circuit is evaluated through a 200 W laboratory prototype with 25 V input voltage and 400 V output voltage. The maximum efficiency achieved at full load is 96.4%. [ABSTRACT FROM AUTHOR]

Nine-switch dual-output inverter stage two-stage matrix converter (NS-TSMC) has been widely applied in dual AC motors drive system, while it has the shortcoming of low voltage transfer ratio. Based on the NS-TSMC, a modified topology, named as series Z-source and nine-switch dual-output inverter stage two-stage matrix converter (ZS-NS-TSMC), is proposed, in which the series Z-source network is connected between the rectifier stage and nine-switch dual-output inverter stage (NS-DOI). In the presented topology, a brief shoot-through vector is employed, which can improve the voltage transfer ratio. Other advantages of the series Z-source network, such as low voltage stress of Z-source capacitor, zero dead-time of NS-DOI and limiting inrush current at startup, are discussed in the study. Furthermore, the dual space vector modulation is presented, which can achieve the merits of unity input power factor, sinusoidal input and outputs. Besides, the sinusoidal outputs, the capability of boosting voltage and adjustable output voltage amplitude are also discussed by the mathematical proof. Finally, an experimental prototype is set up based on the controllers of TMS320F28069 (DSP) and EPM570 (CPLD), the results of which verify the feasibility and desired advantages of the proposed topology and modulation strategy. [ABSTRACT FROM AUTHOR]

This paper presents a fault-tolerant configuration for the modular multilevel converter (MMC). The procedure is able to detect faults in voltage sensors and semiconductor switching devices, and it can reconfigure the system so that it can keep on operating. Both switch and sensor faults can be detected by comparing the output voltage of a set of submodules (SMs), which is measured by a so-called supervisory sensor, with two calculated reference voltages. Faults in the supervisory sensors are also considered. Sensor faults are overcome by using a measuring technique based on estimates that are periodically updated with the voltage measurements of the supervisory sensors. Additional SMs are included in the arms so that the MMC can bypass a faulty SM and continue operating without affecting the output voltage of the phase-leg. Experimental results obtained from a low-power MMC prototype are presented in order to demonstrate the effectiveness of the proposed techniques. [ABSTRACT FROM AUTHOR]

In this paper, a regulated output Buck-Boost DC–DC converter is designed and simulated for photovoltaic energy system. The presented Buck-Boost converter has two power switches; moreover, its output voltage is regulated to a constant value regardless of its input. In the presented work, the Buck-Boost is used as a second converter after a Single-Ended Primary-Inductance Converter (SEPIC) that is controlled with a maximum power point tracking technique (MPPT); Incremental Conductance MPPT algorithm is chosen to be used because of its simplicity and easy implementation. The Buck-Boost converter is controlled in a way to have a suitable output voltage by introducing the right duty cycle of the pulse width modulation signals that control the switches of the converter. The proposed configuration of Buck-Boost converter has been simulated in Matlab/Simulink environment; the simulation results show that it is a good choice to take in order to maintain the output voltage constant while ensuring a good energy transfer. [ABSTRACT FROM AUTHOR]

Static power converters have various applications, such as static ground power units (GPUs) for airplanes. This study proposes a new configuration of a static GPU based on a novel nine-level flying capacitor h-bridge active-neutralpoint-clamped (FCHB_ANPC) converter. The main advantages of the proposed converter in comparison with conventional nine-level ANPC converter are decreasing the number of switches and flying capacitors (FCs) in the proposed converter, doubling the output voltage level of a traditional ANPC converter and reduction of output L-C filter sizes which results in significant improvement in GPU dynamic performances. This progress is achieved by utilising the proposed FCHB converter to an ANPC converter and using the suggested modulation method. This leads to diminish the size and cost and enhance the feasibility and reliability of the converter. Applying the proposed modulation method for FCs in the FCHB_ANPC converter guaranties self-balancing and voltage level regulation of FCs without using closed-loop control. Improved output voltage spectrum leads to inductance reduction of output L-C filter which enhances static GPU performance. The simulation and experimental results demonstrate the validity and feasibility of the proposed converter and the modulation method under various operating conditions. [ABSTRACT FROM AUTHOR]

This paper proposes a novel zero-current-switching series resonant high-voltage DC-DC converter with reduced component count. The series resonant inverter in the proposed topology has two power switches (insulated-gate bipolar transistors, IGBTs), two resonant capacitors, and only one high-voltage transformer (HVT) with center-tapped primary windings. The power switches are connected in the form of a half-bridge network. The leakage inductances of the transformer's primary windings together with the resonant capacitors form two series resonant circuits. The series resonant circuits are fed alternately by operating the power switches with interleaved half switching cycle. The secondary winding of the HVT is connected to a bridge rectifier circuit to rectify the secondary voltage. The converter operates in the discontinuous conduction mode (DCM) and its output voltage is regulated by pulse frequency modulation. Therefore, all the power switches turn on and off at the zero-current switching condition. The main features of the proposed converter are its lower core loss, lower cost, and smaller size compared to previously proposed double series resonant high voltage DC-DC converters. The experimental results of a 130-W prototype of the proposed converter are presented. The results confirm the excellent operation and performance of the converter. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

The alternate arm converter and hybrid cascaded multilevel converter are two promising hybrid multi-level converters for long-distance overhead-line-based high-voltageDCtransmission systems. This article first outlines the basic topologies, mathematical equations, and switching patterns of both the alternate arm converter and hybrid cascaded multi-level converter; the initial required number of H-bridge cells in the wave-shaping circuits and series-connected insulated-gate bipolar transistors in the director switches of the alternate arm and hybrid cascaded multi-level converters are calculated. Then considering the operational characteristics, including the transient voltage stresses, the over-insulated-gate bipolar transistor and diode reliability of the individual semiconductor device in the alternate arm and hybrid cascaded multi-level converters are initialized. Further, the reliability analysis of the two hybrid multi-level converters is carried out, and the optimal redundancy configuration method of wave-shaping circuits and director switches is proposed and calculated by the first-order differences of the three-dimensional surfaces, in which an objective function is established that reconciles reliability and investment of hybrid multi-level converters. Finally, numerical calculations successfully validated the effectiveness of the proposed redundancy configuration method. [ABSTRACT FROM AUTHOR]

Reduced part count multilevel inverters (RPC-MLIs), an emerging technology for grid interfacing applications of renewable energy sources. RPC-MLIs overcome the limitations of conventional two-level and classical multilevel inverters (NPC, FC and CHB) by the use of reduced part counts for generation of same number of levels in the output. Focus of this paper is on to present review of the RPC-MLIs for researchers and engineers and classification of all the topologies. RPC-MLIs are compared considering its circuit complexity and performance. The comparison exposes advantages and disadvantages of topologies, as well as a wide spectrum for future research. This paper also draws the most potential topology in the field of grid integrated applications. Promising topology is simulated here under the same load and input source condition using real time simulator. [ABSTRACT FROM AUTHOR]

LLCL filter has been proven to introduce more filtering at the converter switching frequency, while using smaller passive components. However, like other higher order filters, it introduces resonance to the grid when used with a grid converter. Its stability and robustness are also affected by grid impedance variations, making its design more challenging. To address these concerns, a new parameter design method for the LLCL filter has been formulated in this paper, which when enforced, guarantees robust and stable grid current control regardless of how the grid conditions change. It is thus an enhanced method even with no damping added to the grid converter. The method has been applied to the development of an LLCL filter for testing in the laboratory with a 5-kW, 400-V, and 50-Hz grid converter. The method can also be applied to the lower order LCL filter with only a slight modification needed. [ABSTRACT FROM AUTHOR]

A novel soft-switching PWM three-level (TL) dc–dc converter with two added secondary switches is proposed. The proposed converter has following good features: four primary switches sustain half of the input voltage; the primary circuit is simpler and more compact due to only one flying capacitor with smaller current stress is required to clamp off state voltage of the primary switches; the secondary rectified voltage before the output filter is a TL waveform, which significantly reduces the requirement of the output and input filters; all primary switches can obtain ZVS in wide load range. Furthermore, less conduction loss is added. The added secondary switches can obtain zero-current switching independent of the load current. The proposed converter can be extended to higher voltage level easily due to simpler and more compact primary structure. In addition, the presented converter is also well suitable for high-input dc interfaces with independent controllable multioutput ports. The operation principle, soft switching characteristics, and some important analyzes are presented in this paper. The proposed converter is verified by the experimental results from a 10-kW prototype. [ABSTRACT FROM AUTHOR]

This paper presents a simple but precise model of phase-shifted full bridge zero-voltage switching (PSFB ZVS) converter by introducing an effective duty ratio. The resonant states of PSFB ZVS converter are fully considered in the derivation of effective duty ratio, which results in a model with high precision. According to the proposed model, the output voltage of PSFB ZVS converter is not determined by duty ratio but by the phase shift, which is different from traditional models, and is verified by simulation and experiment. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

In series-connected battery systems, typically, separate converters for intramodule balancing bidirectional connection to a load and charging from an external power source are employed. In this paper, an integrated reconfigurable converter for high-voltage series-connected battery storage systems is proposed. The main advantage of the proposed converter is that it can be reconfigured to operate in different operating modes: feeding the load from the battery system, feeding the load from a backup power source, regenerative mode, intramodule balancing mode, and charging mode. Unlike conventional systems, the proposed topology shares the semiconductor devices and an inductor among the different operating modes which makes it compact. The proposed converter exhibits redundant modes which together with a backup mode increase its reliability. Additionally, the proposed topology minimizes stress on the batteries during the charging/discharging cycles. A scaled down experimental prototype of the proposed converter is implemented for a five-module battery system to verify its viability and demonstrate all operating modes. [ABSTRACT FROM PUBLISHER]

This paper proposes and evaluates an active voltage-balancing method for stacked multicell converters (SMCs) using phase-shifted pulse width modulation. The method is easy to implement and can be applied to SMCs with any number of levels. The proposed method balances the voltages of the capacitors by modifying the duty cycle of each switch of the SMC using a proportional controller. The direction of the output current and the crossed effect among the duty cycles of the switches is considered and used to improve capacitor voltage balance. The performance of the proposed voltage-balancing method is verified experimentally for different loads, such as linear and nonlinear loads, and under transient conditions. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel circulating-current control strategy applied in back-to-back parallel three-phase converters with individual dc links for permanent magnet synchronous motor (PMSM) drives. First, the zero-sequence circulating current and the cross current paths in the whole parallel system are analyzed. Then, the models of an n-paralleled subsystem with individual dc links in both the three-phase stationary coordinates and the synchronous rotating coordinates are built up, which explores the fundamental mechanism of circulating current. Based on the analysis, a novel control strategy can suppress the circulating current at the motor side. The control system consists of two main loops in the d-axis, q-axis, and zero-axis, which are defined in this paper as sum control and difference control. The proposed control strategy effectively suppresses the circulating current in both steady-state and transient operations. The zero-sequence circulating current is greatly reduced by the difference control on the zero-axis. In addition, the bandwidth of the controllers is greatly improved, especially when the current-sharing inductance is much smaller than the stator inductance. Finally, with a PMSM load, the simulation and experiment results are presented to verify the theoretical analysis and proposed control strategy. [ABSTRACT FROM PUBLISHER]

This paper presents an analytical method to evaluate pertinent data of the resonant capacitive switching converter, especially the voltage gain and power efficiency. Instead of long transient simulation time, the proposed model uses frequency decomposition to speed-up computation. This method is valid for N-phase operation, and extends the recently published studies on this promising topology outside zero-current/voltage switching conditions. Thanks to this tractable expression, we also reveal the intrinsic efficiencies over the voltage gain of two- and three-phase structures working at the resonant frequency in step-down operation. These results help to gain better understanding of multiphase operation, and encourage additional studies to use the full capability offered by the resonant-switched capacitor converter especially for power on-chip integration. [ABSTRACT FROM AUTHOR]

Resonant power conversion is a key enabling technology for many high-performance and high-efficiency systems. Induction heating is an example of such systems, which outperforms conventional heating technologies, leading to a wide spectrum of industrial, domestic, and medical applications. In order to ensure the proper operation of the resonant converter, accurate converter operation monitoring techniques are required. This paper proposes an effective monitoring technique based on the measurement of the resonant capacitor voltage. The proposed monitoring system provides essential information regarding the output power, soft-switching conditions, and input voltage, while featuring a cost-effective implementation. The proposed technique is validated through an FPGA-controlled resonant power converter applied to induction heating, proving the feasibility of this proposal. [ABSTRACT FROM AUTHOR]

With the advancement of material science, various smart materials with intrinsic capacitive property are emerging. The high-voltage (HV) power electronics converters with bidirectional energy flow functionality for supplying the capacitive load are highly demanded. A switching cycle-based analytical model of an HV bidirectional converter driving capacitive load is beneficial in thoroughly understanding the operational behavior, investigating the energy efficiency, and optimizing the design. In this paper, an HV bidirectional flyback converter for capacitive load is generally discussed in terms of configuration and working principle. Considering the parasitic elements as well as the core loss effect, the converter is modeled with analytical formulas for one switching cycle. The comparison between the model-based calculation results and prototype experiments-based measurement results are used to validate the analytical model. [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel transformer-less direct current (dc) converter that features low switch voltage stress and automatic uniform current sharing. An interleaved four-phase voltage divider operating from a 400 V dc bus is used to achieve a high step-down conversion ratio with a moderate duty ratio. Based on the capacitive voltage division, the proposed converter achieves two major objectives, i.e., increased voltage conversion ratio, due to energy storage in the blocking capacitors, and reduced voltage stress of active switches and diodes. As a result, the proposed converter permits the use of lower voltage rating MOSFETs to reduce both switching and conduction losses, thereby improving the overall efficiency. In addition, due to the charge balance of the capacitors, the proposed converter enables automatic uniform current sharing of the interleaved phases without adding extra circuitry or complex control methods. The operation principles and performance analyses of the proposed converter are presented, and its effectiveness is verified by a 500 W output power prototype circuit that converts 400 V input voltage into 24 V output voltage. [ABSTRACT FROM AUTHOR]

This paper introduces the application of a switched-diode-capacitor voltage accumulator (SDCVA) on conventional boost converter. This study aims to obtain two different kinds of multi-input step-up converters with high voltage gains, low component stresses, low ripples, simple control, and high conversion efficiencies: one is based on the parallel SDCVA and the other based on the serial SDCVA. The double-input step-up converter based on the parallel SDCVA and the double-input step-up converter based on the serial SDCVA are, respectively, taken as an example to do theoretical analysis, including operating principles and performance analyses when they work individually and simultaneously. The two proposed converters are implemented with a voltage closed-loop control at the switching frequency of 30 kHz. Experimental results obtained from the implemented prototypes are provided to validate the feasibility and effectiveness of the proposed converters. [ABSTRACT FROM AUTHOR]

This paper proposed an online optimizing duty cycle control approach for three-phase active-front-end rectifiers, aiming to obtain the optimal control actions under different operating conditions. Similar to finite-control set model predictive control strategy, a cost function previously constructed based on the desired control performance is adopted here, which is essential for the solving process of the optimizing problem. On the other hand, differently, with respect to the proposed strategy, duty cycle signals are optimized, instead of possible switching states. The determination of optimal duty cycles is made by predicting the effect of duty cycles on instantaneous current variations and minimizing the cost function. Due to the adoption of behavior prediction, the proposed controller inherits the excellent dynamic characteristics of predictive controllers. Moreover, the application of optimal duty cycles determined by cost function minimization automatically ensures optimum operations of converters within each sampling period. Improved transient and steady-state features of the proposed strategy are confirmed by experimental validations and in-depth comparisons with linear controllers, deadbeat predictive controllers, and finite-control set model predictive control strategies. [ABSTRACT FROM PUBLISHER]

Current-fed DC–DC converter has received a lot of attention recently for the fuel cell power source applications. This is due to its attractive features, such as low input current ripple, high voltage conversion ratio and high efficiency. Unfortunately, a high voltage stress across the switches and hard switching is the main drawback of the current-fed topologies. Therefore, an active clamp circuit is often implemented to suppress any voltage overshoot across the switches and achieving zero-voltage switching. In this paper, based on detailed analysis on the converter performance it was found that parasitic elements of the converter can have a large impact on promising features of current-fed converters with an active clamp. This has not been reported in the literature. It has been shown through an in-depth analysis on the converter that particularly during the switch overlap period the parasitic elements create undesirable oscillations leading to additional circulating energy that adds to the conduction losses of the converter. It also results in voltage ringing across the clamp switch, oscillations in the current through the clamp circuit and high voltages across the bridge switches, even when the switches are conducting. Based on this finding a number of modifications have been proposed and these have been verified by thorough simulation and experiment. [ABSTRACT FROM AUTHOR]

The interconnection of basic switching converters to increase power handling capabilities in dc applications has been widely reported in technical literature. This study presents a family of switching step-up dc-dc converters based on the principle of reduced redundant power processing (R²P²). This principle states that the power transfer from input port and output port on interconnected converters is reduced when a non-cascading connection is used. As shown in this study, the principle R²P² is useful for developing new converters. These have wide conversion ratios and quadratic dependence with respect to the duty ratio. In this study, the voltage conversion ratios, average models and steadystate operating conditions for proposed converters are derived, which are verified by experimental results. [ABSTRACT FROM AUTHOR]

Multilevel inverters (MLI) are extensively used in various fields and industrial applications. This study proposes a simple algorithm for detection and identification of switch faults in insulated gate bipolar transistors (IGBTs) of multilevel inverter feeding an induction motor drive. The effects on the system for switch shorted are more severe than the switch opened if no protective action is taken in time. A fast and novel fault identifier designed in this study is used not only for switch short fault but also for switch open fault by analysing the performance of MLI drive system using wavelet based multi-resolution analysis (MRA). On occurrence of switch fault in inverter, the fault information appears in the signals in frequency region resulting in variation in the details of level of wavelet transform (WT). The instant of variation in the WT is correlated with the instant of fault. The voltage and current signals from the experimental setup were used as input for wavelet analysis to develop suitable feature vector that will act as signature to discriminate faulty system from healthy one. The experimental prototype of five level diode clamped multilevel inverter feeding an induction motor has been implemented to validate the fault analysis with simulated result. [ABSTRACT FROM AUTHOR]

Time-sharing switching (TSS) techniques are usually utilised in multiple-input converters (MICs) to manage power sharing among inputs as well as output-voltage regulation. The two most-commonly-used TSS schemes in practical MIC applications are trailing-edge modulation (TEM) and interleaved dual-edge modulation (IDEM), both of which containing abundant significant information on conduction sequence. Steady-state analysis and computation help understand MICs' behaviour, being of high significance in both principal and practical researches. This study exhibits a general and exact methodology for computing and synthesising analytical expressions in a steady state of any kind of MIC topology, based upon analysis of segmented waveforms of common inductor current and output capacitor voltage. The derivation results are of high accuracy and generality, applicable for scenarios with arbitrary number of inputs in either continuous conduction mode or discontinuous conduction mode, and applied by either TEM-based or IDEM-based TSS schemes. Analytical and derivation details are addressed to the issues of multiple-input buck converters, along with general procedures established for other MICs topologies, for example, multiple-input buck-boost converters and multiple-input single-ended primary-inductor converters. Case study on a dual-input buck converter prototype, considering power dissipations and voltage drops on its components, is put forward for theoretical verification. [ABSTRACT FROM AUTHOR]

Rigorous analysis and design of the current control loop in voltage source converters (VSCs) requires an accurate modeling. The loop behavior can be significantly influenced by the VSC working conditions. To consider such effect, converter losses should be included in the model, which can be done by means of an equivalent series resistance. This paper proposes a method to identify the VSC equivalent loss resistance for the proper tuning of the current control loop. It is based on analysis of the closed-loop transient response provided by a synchronous proportional-integral current controller, according to the internal model principle. The method gives a set of loss resistance values linked to working conditions, which can be used to improve the tuning of the current controllers, either by online adaptation of the controller gains or by open-loop adaptive adjustment of them according to prestored data. The developed identification procedure is tested in the laboratory at different specifications of power level and switching frequency. [ABSTRACT FROM AUTHOR]