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The increased penetration of photovoltaic (PV) systems in different applications with critical loads such as in medical applications, industrial control systems, and telecommunications has highlighted pressing needs to address reliability and service continuity. Recently, distributed maximum power point tracking architectures, based on dc–dc converters, are being used increasingly in PV systems. Nevertheless, dc–dc converters are one of the important failure sources in a PV system. Since the semiconductor switches are one of the most critical elements in these converters, a fast switch fault detection method (FDM) is a mandatory step to guarantee the service continuity of these systems. This paper proposes a very fast FDM based on the shape of the inductor current associated to fault-tolerant (FT) operation for boost converter used in PV systems. By implementing fault diagnosis and reconfiguration strategies on a single field-programmable gate array target, both types of switch failure (open- and short-circuit faults) can be detected, identified and handled in real time. The FDM uses the signal provided by the current sensor dedicated to the control of the system. Consequently, no additional sensor is required. The proposed FT topology is based on a redundant switch. The results of hardware-in-the-loop and experimental tests, which all confirm the excellent performances of the proposed approach, are presented and discussed. The obtained results show that a switch fault can be detected in less than one switching period, typically around 100 ms in medium power applications, by the proposed FDM. [ABSTRACT FROM PUBLISHER]

This paper proposes a new topology for a three-phase open-delta connection ac–ac converter based on the switched capacitor principle. The topology employs only capacitors and switches in the power stage, which can provide high efficiency and power density. It operates in open loop with constant values for the gain, duty cycle, and frequency. The converter is bidirectional and thus it can step-down or step-up the output voltages. A 3.5-kW prototype was built, tested and used to verify the theoretical analysis for resistive, inductive, and nonlinear loads. The efficiency of the topology is around 93% in nominal load and the power density is 1.178 kW/kg. [ABSTRACT FROM PUBLISHER]

According to the requirement of fuel cell generation system, this paper presents a new single-stage and boost-voltage grid-connected inverter, as well as the signal modulation diagram in a line cycle. In the proposed inverter, one of the bridge legs is shared with a boost converter. The boost inductor current is designed in discontinuous conduction mode, which can effectively decrease low-frequency current ripple (LFCR) in the output current of the fuel cell. The switching modes of the proposed inverter are analyzed in positive and negative half line cycles, respectively. The LFCR in the output current of the fuel cell is analyzed, from which the design principle of the boost voltage inductor is obtained. The per-unit current values of the shared switches and the loss of the whole system are derived and compared with those of the conventional inverter. Experimental verifications are presented to verify the theoretical analysis. [ABSTRACT FROM PUBLISHER]

This paper presents a comparative evaluation of silicon carbide power devices for the domestic induction heating (IH) application, which currently has a major industrial, economic and social impact. The compared technologies include MOSFETs, normally on and normally off JFETs, as well as BJTs. These devices have been compared according to different figure-of-merit evaluating conduction and switching performance, efficiency, impact of temperature, as well as other driving and protection issues. To perform the proposed evaluation, a versatile test platform has been developed. As a result of this study, several differential features are identified and discussed, taking into account the pursued induction heating application. [ABSTRACT FROM PUBLISHER]

In photovoltaic (PV) grid-connected generation system, the key focus is how to expand the generation range of the PV array and enhance the total efficiency of the system. This paper originally derived expressions of the total loss and grid current total harmonics distortions of cascaded inverter and H-bridge inverter under the conditions of variable output voltage and power of the PV array. It is proved that, compared with the H-bridge inverter, the operation range of the cascaded inverter is wider, whereas the total loss is larger. Furthermore, a novel online variable topology-type grid-connected inverter is proposed. A bidirectional power switch is introduced into the conventional cascaded inverter to connect the negative terminals of the PV arrays. When the output voltages of the PV arrays are lower, the proposed inverter works under cascaded inverter mode to obtain wider generation range. When the output voltages of the PV arrays are higher, the proposed inverter is transformed into equivalent H-bridge inverter mode to reduce the total loss. Thus, wider generation range and higher efficiency are both implemented. Specific demonstration of the proposed inverter based on five-level cascaded inverter is presented. The detailed experimental results verify the accuracy and feasibility of the theoretical analysis and the proposed inverter topology. [ABSTRACT FROM PUBLISHER]

This paper proposes novel multilevel ac/dc/ac converters with reduced number of semiconductor devices to achieve light weight, efficiency, and better input current quality. The proposed three-phase front-end bidirectional five-level (5L) rectifier and rear-end 5L inverter are constructed based on multiple-pole multilevel diode-clamped (M2DCC) approach, which consist a total number of 24 diode components clamped. Based on the M2DCC concept, the number of switching devices can be further reduced to construct a new unidirectional front-end rectifier (M2SCR). Comparative studies are conducted to analyze the performances of the two proposed front-end rectifiers with supportive mathematical derivations. Experimental prototypes have proven the feasibility of the proposed ac/dc/ac configurations. Results obtained show that low current harmonic distortions of 5% and high power factor of 0.99 are achieved with small input inductors despite low-switching-frequency operation at 1 kHz. [ABSTRACT FROM PUBLISHER]

High step-up ratio dc–dc converters with megawatt ratings are of interest in wind turbine interfaces and high-voltage direct-current systems. This paper presents a modular multilevel dc–dc converter based on the standard boost converter topology but with the normal single switches replaced by a number of capacitor-clamped submodules. The converter is operated in resonant mode with resonance between submodule capacitors and the arm inductor. A phase-shifted switching arrangement is applied such that there is a constant number, i.e., $N$, of submodules supporting the high voltage at a time. In this operation mode, the step-up ratio is dependent on the number of submodules and the inductor charging ratio. The converter exhibits scalability without using a transformer and is capable of bidirectional power flow. An application example of a wind turbine interface with a 10 : 1 conversion ratio is demonstrated in simulation. The experimental verification of the concept using a lab-scale prototype is provided. [ABSTRACT FROM PUBLISHER]

Single-phase voltage source transformerless inverters have been developed for many years and have been successful commercial applications in the distributed photovoltaic (PV) grid-connected systems. Moreover, many advanced industrial topologies and recent innovations have been published in the last few years. The objective of this paper is to classify and review these recent contributions to establish the present state of the art and trends of the transformerless inverters. This can provide a comprehensive and insightful overview of this technology. First, the generation mechanism of leakage current is investigated to divide the transformerless inverters into asymmetrical inductor-based and symmetrical inductor-based groups. Then, the concepts of dc-based and ac-based decoupling networks are proposed to not only cover the published symmetrical inductor-based topologies but also offer an innovative strategy to derive advanced inverters. Furthermore, the transformation principle between the dc-based and ac-based topologies is explored to make a clear picture on the general law and framework for the recent advances and future trend in this area. Finally, a family of clamped highly efficient and reliable inverter concept transformerless inverters is derived and tested to offer some excellent candidates for next-generation high-efficiency and cost-effective PV grid-tie inverters. [ABSTRACT FROM PUBLISHER]

A hybrid switched-capacitor/interleaved boost converter able to provide a high voltage gain and to cancel the input current ripple at a preselected duty cycle was recently presented in the literature. This paper extends that work by proposing an optimized switching strategy for operating conditions at other values of duty cycle. The switching strategy effect on the converter's voltage gain and input current ripple is quantified and compared against the performance under the conventional switching strategy. The approach is validated in the laboratory through hardware prototyping. [ABSTRACT FROM PUBLISHER]

This paper analyzes the interleaved boost with coupled inductors (IBCI) converter, which is an isolated topology that is suitable for high step-up applications. Two main contributions are given: an exhaustive steady-state analysis and an accurate small-signal model. The former allows for deriving a closed-form noniterative design procedure for the power-stage active and passive components. In addition, it reveals an interesting equivalence with an apparently different converter, i.e., the single active bridge. Subsequently, the IBCI converter dynamic behavior is investigated, deriving a nonlinear average model that, under small-signal approximation, can be linearized around a given operating point and used for feedback controller design. A single photovoltaic module interface converter, rated for 300-W output power, is considered as a case study to validate the analysis outcome and the design procedure. Both are fully validated by measurements taken on the laboratory prototype. [ABSTRACT FROM PUBLISHER]

A photovoltaic (PV)-based stand-alone power system is usually used to manage the energy supplied from several power sources such as PV solar arrays and battery and deliver a continuous power to the users in an appropriate form. Traditionally, three different dc/dc converters would have been used. To reduce the cost and improve the power density of the power system, an integrated solution of PV isolated dc/dc three-port converter (TPC) is proposed in this paper. Zero current switching can be achieved for all main diodes and MOSFETs to improve the efficiency, and a continuous input current of solar array is maintained by adding a magnetic switch derived from a fourth winding of the half-bridge transformer. Based on the energy-balancing part formed by boost, the control methods for the single module to realize maximum power point tracking (MPPT), battery charge control, and main bus regulation are proposed. The power system control method for multimodules in parallel is also derived, and the operation of the TPC power system can be transited between conductance mode and MPPT mode automatically. Finally, the experimental results verify that the proposed TPC, together with the proposed control method, meets the requirements of a high-power-density stand-alone PV-battery power system. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel multiple-input bidirectional dc–dc power converter to interface more than two dc sources of different voltage levels. This finds applications in hybrid electric/fuel cell vehicles (FCVs), where different dc sources of unequal voltage levels need to be connected with bidirectional power flow capability. The converter can be used to operate in both the buck and boost modes with bidirectional power control. It is also possible to independently control power flow between any two sources when more than two sources are actively transferring power in either directions. The operation, analysis, and design of the converter are presented with different modes of power transfer. The proposed converter is demonstrated for FCV application using real-time hardware-in-the-loop system. Experimental results for a 5-kW system are presented, validating the theoretical analysis. [ABSTRACT FROM PUBLISHER]

Existing bridgeless boost (BLB) converter with soft switching utilize more than two active switches and extra resonant networks. In this paper, a new zero-current-switching BLB rectifier with high power factor (PF) using only two active switches is proposed. The proposed BLB converter is based on a totem-pole BLB (TPBLB) configuration, which allows the current to flow from high side to low side and vice versa during resonance. Hence, no auxiliary active switch is needed to provide soft switching for all semiconductor devices. The soft switching also reduces the body diode reverse recovery problem, hence allowing the TPBLB to operate in continuous conduction mode. Standard components are used to prove that the proposed converter is working with an acceptable performance compared with other BLB converters with soft switching. In order to achieve smooth input current waveform, high PF, and wide soft-switching operations, a pulsewidth modulation controller is proposed and developed, which combines a conventional PF correction average current mode controller with several logic gates and a phase detector. A detailed analysis of the converter operation and control is presented. Design considerations and parameter values calculations are given. An experimental prototype is developed and tested to verify the converter performance. [ABSTRACT FROM PUBLISHER]

Recently, the interest in offshore wind farms has been significantly increased because of the stronger and more stable winds at sea, which will lead to a higher power production. DC/DC power conversion solutions are becoming more popular for fulfilling the growing challenges in the high-voltage (HV) dc-connected offshore wind power industry. This paper presents several multilevel modular dc/dc conversion systems based on the capacitor-clamped (CC) module concept for high-power offshore wind energy applications. Two types of the CC modules, namely, the double-switch (DS) module and the switchless (SL) module, are discussed. A soft-switching technique is adopted to achieve minimal switching losses and the maximum system efficiency. Theoretical analysis is carried out for the $2n+1$-level cascaded configurations based on the CC modules. The inherent interleaving property of the proposed configurations effectively reduces the output voltage ripple without adding extra components. A cascaded hybrid topology is developed by the combination of DS and SL modules. The proposed hybrid topology achieves higher efficiency and lower component count. The cascaded hybrid approach is evaluated in terms of the power device count, reliability, and efficiency against other HV dc/dc topologies to demonstrate its advantage for HVDC-connected offshore wind farms. The experimental results of two 5-kW prototype CC converters are presented to validate the theoretical analysis and principles as well as attest the feasibility of the proposed topologies. [ABSTRACT FROM PUBLISHER]

A high-voltage tapped-inductor buck converter utilizing a novel autonomous high-voltage valve is presented in this paper. Its application as auxiliary power supply for high-power cascaded-converter submodules is discussed, followed by a presentation of the most challenging problems in designing a low-power high-voltage step-down converter. The TI-buck converter topology is analyzed, which together with the novel autonomous high-voltage valve overcomes most of the problems. Analytical expressions describing the operation as well as circuit simulations are presented. Finally, an experimental evaluation of a 3-kV 70-W prototype converter utilizing the proposed autonomous high-voltage valve with series-connected super-junction MOSFETs is presented. [ABSTRACT FROM PUBLISHER]

This paper presents a capacitor voltage balancing control applicable to any multilevel dc–ac converter formed by a single set of series-connected capacitors implementing the dc link and semiconductor devices, such as the diode-clamped topology. The control is defined for any number of dc-link voltage levels and converter legs (for single-phase and multiphase systems), guaranteeing the capacitor voltage control for any modulation index value and load (from idle mode to full power). The associated control loop small-signal transfer function is presented, from which optimum compensator design guidelines are derived. The improvement in control performance is verified through simulation and experiments comparing with a previous balancing control strategy in a four-level three-phase dc–ac conversion system. The satisfactory control performance is also verified through simulation in a four-level five-phase dc–ac conversion system. [ABSTRACT FROM PUBLISHER]

Automotive embedded electronic systems have been increasing in power and complexity and, therefore, more advanced power electronic converters are necessary in these vehicles. Several dual-voltage (42 V/14 V) bidirectional converter architectures have been proposed for automotive systems in recent years. However, most of them have low efficiency or are based in series and parallel configurations with large number of semiconductors and magnetics devices. Therefore, in this paper, we propose a bidirectional high-efficiency converter with lower number of components. This converter was created by merging a switched-capacitor converter and a conventional bidirectional converter, resulting in a hybrid topology. The voltage across the semiconductors of the proposed converter is equal to half of the highest voltage source value. Furthermore, the topology is composed of only one inductor to control the power flow between the two voltage sources. To verify all the mentioned features, a prototype was implemented experimentally, reaching a maximum efficiency of 97.5%. [ABSTRACT FROM PUBLISHER]

This paper presents a circuit structure with a novel inverter that is applicable to arc welding machines. The output rectifier configuration adopts the current doubler rectifier with two coupled inductors. The proposed inverter topology can keep the energy stored in the coupled inductor until the next commutation interval. Moreover, the conduction loss will be lower, which improve the conversion efficiency of the arc welding machine. The operation principle, control circuit, and inverter design example are also described in detail. Experimental results demonstrate the feasibility and efficiency of the proposed inverter topology. [ABSTRACT FROM PUBLISHER]

A switched boost inverter (SBI) can replace a $Z$-source inverter (ZSI) in low-power applications because it has one less $LC$ pair than the ZSI. This paper presents a class of quasi-SBIs (qSBIs) that offers several advantages when compared with a conventional SBI, including reducing the voltage stress on the capacitor, increasing the boost voltage factor, and improving input current profiles. Operating principles, steady-state analysis, and comparisons with conventional inverters are presented. A prototype based on a TMS320F28335 digital signal processor is built to verify the operating principle of the proposed qSBIs. [ABSTRACT FROM PUBLISHER]

Three-level topologies are widely used in back-to-back converters of wind turbine generation (WTG) systems. In comparison with a conventional two-level topology, three-level topologies have more advantages, particularly for the high power. Neutral-point clamped (NPC) and T-type are typical three-level topologies. An open-switch fault of a three-level rectifier that is connected to a permanent-magnet synchronous generator (PMSG) leads to the current distortion and torque vibration in WTG systems. Furthermore, WTG systems can break down in the worst case. Therefore, a tolerance control for open-switch faults is required to improve the reliability of WTG systems. WTG systems by applying the tolerance control can be stopped safely and prevent additional problems. Depending on the situation, it can keep the operation of WTG systems under open-switch fault. The effects of outer open-switch faults of three-level rectifiers are analyzed by considering PMSG specifications in this paper. Moreover, a tolerance control for outer open-switch faults of the NPC and T-type three-level rectifiers are proposed with existing tolerance controls for inner open-switch faults. The proposed tolerance control is to inject the exact $d$-axis current value to eliminate current distortion. The simulation and experiment are conducted to prove the feasibility of the proposed tolerance control and to identify its performance. [ABSTRACT FROM PUBLISHER]

In this paper, a new single-phase cascaded multilevel inverter is proposed. This inverter is comprised of a series connection of the proposed basic unit and is able to only generate positive levels at the output. Therefore, an H-bridge is added to the proposed inverter. This inverter is called the developed cascaded multilevel inverter. In order to generate all voltage levels (even and odd) at the output, four different algorithms are proposed to determine the magnitude of dc voltage sources. Reduction in the number of power switches, driver circuits, and dc voltage sources is the advantage of the developed single-phase cascaded multilevel inverter. As a result, the installation space and cost of the inverter are reduced. These features are obtained by the comparison of the conventional cascaded multilevel inverters with the proposed cascaded topology. The ability of the proposed inverter to generate all voltage levels (even and odd) is reconfirmed by using the experimental results of a 15-level inverter. [ABSTRACT FROM PUBLISHER]

Dynamic voltage restorer (DVR) is a definitive solution toward compensation of voltage sag with phase jump. Conventional DVR topologies, however, have dc links and two-stage power conversions. This increases its size, cost, and associated losses. Therefore, topologies without the dc link, mitigating sag by utilizing direct ac–ac converters, are preferable over the conventional ones. As no storage device is employed, compensation by these topologies is limited only by the voltages at the point of common coupling that is feeding the converters. In this paper, a direct-ac–ac-converter-based topology fed with line voltages is proposed. The arrangement provides increased range of compensation in terms of magnitude and phase angle correction. Detailed simulations have been carried out in MATLAB to compare the capability of the proposed topology with other similar topologies. Experimental results are presented to validate the capability of the topology to compensate various sags. [ABSTRACT FROM PUBLISHER]

This paper presents input-series–output-parallel (ISOP) configuration for single-phase front-end buck rectifiers (BRs). The configuration is especially suitable for traction applications, where the complete rectification system needs to withstand high ac voltages and supply medium-power loads. The primary rectification module of the proposed configuration is based on pulsewidth-modulated BR (current source inverter topology). The desired isolation, mandatory for ISOP connection, is provided at the dc stage through a medium-frequency/high-frequency transformer. Equal power sharing by modules is achieved from the ac side through input voltage and current sharing. The proposed control scheme is configured using two loops. While the outer loop regulates the output dc voltage and active wave shaping of the source current, the inner loop ensures stable voltage sharing. The performance of the proposed ISOP configuration is verified using numerical simulation. Experimental verification is achieved through a 2-kW grid-connected laboratory prototype. [ABSTRACT FROM PUBLISHER]

One of the most important power quality issues is related to current harmonics generated by nonlinear loads such as diode and thyristor front-end rectifiers. Well-established solutions to overcome this problem, such as active power filters (APFs), have the required high power rating components as a major disadvantage. An alternative, called hybrid power filter (HPF), mixes low power rating active filters with passive filters. Unfortunately, many of these HPF topologies have, as a common disadvantage, a great number of passive components and/or transformers. Based on this fact, new concepts of HPFs, consisting of small-rated inverters and $LC$ filters, have been introduced with wide acceptance. The advantage comes from the fact that these HPFs are connected to the grid without any matching transformer. Recently, some topologies based on dual-converter configurations have been shown to be very attractive, where the APF (or HPF) must deal with highly nonlinear loads with high values of $di/dt$ and supplying the reactive power together with harmonic compensation. On the other hand, the drawback of dual converters is the high number of switch devices. Therefore, this paper proposes a transformerless HPF based on a new six-switch two-leg inverter with an enhanced harmonic compensation capability. Aside from presenting a reduced number of switches when compared with dual topologies, the proposed solution is capable of providing fully compensation even for loads with high harmonic content. Experimental results are presented for an HPF inverter prototype in order to demonstrate that the harmonic compensation performance meets the IEEE 519 standard. [ABSTRACT FROM PUBLISHER]

This paper presents a bidirectional current-fed parallel resonant push–pull inverter (CFPRPI) for contactless energy conversions. In conventional CFPRPIs, each switch is in series with a blocking diode. Direct zero voltage switching (ZVS) is proposed to remove the series blocking diodes for higher efficiency and boosting ratio. In addition, the modified inverter has bidirectional power flow capability when these blocking diodes are omitted. Resonant tuning of the system is investigated by using a phase-locked loop and a new self-oscillating switching technique (SST). By using the new SST, the inverter has direct ZVS in a wide range of operating frequencies, which is necessary for inductively coupled power transfer systems. Finally, a laboratory prototype with an input voltage of 12 V and a maximum output power of 60 W has been implemented. [ABSTRACT FROM PUBLISHER]

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

This paper presents the analysis and design of a very high-voltage-gain single-stage boost converter operating at the boundary between continuous conduction mode (CCM) and discontinuous conduction mode (DCM). The converter is supplied by a 12-V car battery and attains 1200 V with a voltage gain of 100. The use of a hysteretic comparator in the control loop precludes the risk of modulator saturation and facilitates the operation at the mentioned boundary. Sliding-mode control theory is applied to analyze the dynamic behavior of the switching regulator and to establish the system stability conditions. The performance of the converter is investigated using silicon carbide (SiC) devices for the power switch realization. LED-based efficient lighting systems can be a promising application of the proposed system. [ABSTRACT FROM PUBLISHER]

This paper presents a novel combined-synchronous-rectifier high-frequency-link (CSR-HFL) inverter. Three types of conventional HFL inverters are analyzed and their performance is summarized. According to one of the conventional HFL inverters, i.e., cycloconverter-type HFL (CHFL) inverter, a combined rectifier topology is deduced. To prevent a shorted circuit, two additional switches are used in the new topology. The operation mode of the CSR-HFL inverter is analyzed and the mathematical relationships are given. The difference and correlation, and advantages and disadvantages, are analyzed between the CSR-HFL inverter and the conventional HFL inverter. The relevant grid-connected inverter, ac/ac converter, and full-wave CSR-HFL inverter are also given. The experimental results verify that the proposed CSR-HFL inverter has excellent performance and high efficiency. [ABSTRACT FROM PUBLISHER]

In this paper, a new single-phase cascaded multilevel inverter based on novel H-bridge units is proposed. In order to generate all voltage levels (even and odd) at the output, nine different algorithms are proposed to determine the magnitudes of dc voltage sources. Then, the proposed algorithms are compared to investigate their advantages and disadvantages. This topology is able to increase the number of output voltage levels by using a lower number of power electronic devices such as switches, power diodes, driver circuits, and dc voltage sources that lead to reduction in installation space and cost of the inverter. In addition, in the proposed cascaded multilevel inverter, not only the number of required power electronic devices is reduced, but also the amount of the blocked voltage by switches, and the number of different voltage amplitudes of the used sources is decreased. These features are some of the most important advantages of the proposed topology. These features are obtained via the comparison of the proposed topology and its proposed algorithms with the conventional cascaded multilevel inverters that have been presented in the literatures. The operation and performances of the proposed topology with its presented algorithms in generating all voltage levels have been verified by using the experimental results of a 49-level single-phase inverter. [ABSTRACT FROM PUBLISHER]

This paper presents a dc–dc boost converter with high voltage gain based on the three-state switching cell for split-capacitor neutral-point-clamped inverters. The proposed converter is analyzed considering the operation in continuous conduction mode and duty cycle higher than 0.5, which corresponds to overlapping mode. The main characteristics of the topology are operation at high switching frequency, whereas the input inductor is designed for twice such frequency; in order to minimize weight and volume, the voltage stress across the switches is lower than half of the output voltage and naturally clamped by one output capacitor, allowing the use of MOSFET transistors with reduced intrinsic on-resistance; the input current presents small ripple; the output voltage can be further stepped up by increasing the transformer turns ratio without compromising the voltage stress across the switches; and the output voltage is naturally balanced, thus making the converter suitable for supplying split-capacitor inverters. Several topologies where a high voltage step-up is possible are initially investigated in the literature. Then, the principle of operation and experimental results for a 1-kW prototype are presented to validate the theoretical analysis and demonstrate the converter performance. [ABSTRACT FROM PUBLISHER]

The objective of this paper is to propose a new inverter topology for a multilevel voltage output. This topology is designed based on a switched capacitor (SC) technique, and the number of output levels is determined by the number of SC cells. Only one dc voltage source is needed, and the problem of capacitor voltage balancing is avoided as well. This structure is not only very simple and easy to be extended to a higher level, but also its gate driver circuits are simplified because the number of active switches is reduced. The operational principle of this inverter and the targeted modulation strategies are presented, and power losses are investigated. Finally, the performance of the proposed multilevel inverter is evaluated with the experimental results of an 11-level prototype inverter. [ABSTRACT FROM PUBLISHER]

This paper illustrates the design and an experimental test of a line-fed solid-state lamp driver based on the asymmetrical half-bridge flyback converter. Its favorable characteristics, in terms of soft-switching range and circuit complexity, allow the converter to operate at variable switching frequency in the range of 300–450 kHz, supplying 6 W to the load with good efficiency. The considered lamp is made up of five series-connected high-power light-emitting diodes (Cree XR-E) and is supplied with 350-mA closed-loop-regulated constant current. While presenting similar complexity and overall efficiency with respect to a conventional driver, due to an original feedforward control technique that allows shrinking the input filter capacitor, the proposed circuit allows a significant volume reduction and consequent power density improvement. [ABSTRACT FROM PUBLISHER]

Low leakage current and high efficiency are two key indexes for the transformerless photovoltaic (PV) grid-connected inverter. The transformerless inverter topologies have superior efficiency owing to saving the transformer, but their switches are still on a hard-switching state at present. This paper presents a novel zero-voltage transition (ZVT) concept for the full-bridge transformerless PV grid-connected inverter topologies. The zero-voltage turn-on and turnoff of the high-frequency main switches and the zero-current turn-on of the auxiliary switches, as well as the zero-voltage turn-on and turnoff of the antiparallel diodes of the line-frequency switches, are realized by introducing two resonant tanks. Take ZVT-H6-I for example. The operation principle, soft-switching conditions, duty cycle restriction, and parameter design rule of the resonant tank are analyzed in detail. Finally, the validity of the ZVT concept is verified by a ZVT-H6-I prototype rated at 100 kHz and 1 kW. [ABSTRACT FROM PUBLISHER]

In this paper, novel topologies for symmetric, asymmetric, and cascade switched-diode multilevel converter are proposed, which can produce many levels with minimum number of power electronic switches, gate driver circuits, power diodes, and dc voltage sources. The number of required power electronic switches against required voltage levels is a very important factor in designing of multilevel converter, because switches define the reliability, circuit size, cost, installation area, and control complexity. For asymmetric and cascade converter, new algorithms for determination of dc voltage sources values are presented. To produce maximum number of levels at the output voltage, the proposed cascade topology is optimized for different goals, such as the minimization of the number of power electronic switches, gate driver circuits, power diodes, dc voltage sources, and blocking voltage on switches. Comparison of the results of various multilevel converters will be investigated to reflect the merits of the presented topologies. The operations of the proposed multilevel converters have been analyzed with the experimental and simulation results for different topologies. Verification of the analytical results is done using MATLAB simulation. [ABSTRACT FROM PUBLISHER]

In this paper, two new topologies are proposed for multilevel inverters. The proposed topologies consist of a combination of the conventional series and the switched capacitor inverter units. The proposed topologies reduce the number of switches and isolated dc voltage sources, the variety of the dc voltage source values, and the size and cost of the system in comparison with the conventional topologies. In addition, the proposed topologies can double the input voltage without a transformer. There is no need for complicated methods to balance the capacitor voltage. The simulation and experimental results of single-phase 25- and 17-level inverters are given to prove the correct operation of the proposed topologies. [ABSTRACT FROM PUBLISHER]

High-boost dc-ac inverters are used in solar photovoltaic (PV), fuel cell, wind energy, and uninterruptible power supply systems. High step-up and step-down capabilities and shoot-through immunity are some of the desired properties of an inverter for a reliable, versatile, and low-distortion ac inversion. The recently developed Z-source inverter (ZSI) possesses these qualities. However, the realization of ZSI comes at a cost of higher passive component count as it needs two sets of passive filters. A switched boost inverter (SBI) has similar properties as ZSI, and it has one L\-C pair less compared to ZSI, but its gain is less than ZSI. This paper proposes the current-fed switched inverter (CFSI) which combines the high-gain property of ZSI and low passive component count of SBI. The proposed inverter uses only one L\-C filter and three switches apart from the inverter structure. The inverter topology is based on current-fed dc/dc topology. Steady-state analysis of the inverter is presented to establish the relation between the dc input and the ac output. A pulse width modulation (PWM) control strategy is devised for the proposed inverter. An experimental prototype is built to validate the proposed inverter circuit in both buck and boost modes of operation. A 353-V dc-link and a 127 V (rms) ac are obtained from a 35.3-V dc input to demonstrate the boost mode of operation. A 200-V dc-link and a 10.5-V (rms) ac are obtained from a 37.8-V dc input to verify the buck mode of operation of CFSI. [ABSTRACT FROM PUBLISHER]

This paper presents a single-phase transformerless grid-connected photovoltaic converter based on two cascaded full bridges with different dc-link voltages. The converter can synthesize up to nine voltage levels with a single dc bus, since one of the full bridges is supplied by a flying capacitor. The multilevel output reduces harmonic distortion and electromagnetic interference. A suitable switching strategy is employed to regulate the flying-capacitor voltage, improve the efficiency (most devices switch at the grid frequency), and minimize the common-mode leakage current with the help of a novel dedicated circuit (transient circuit). Simulations and experiments confirm the feasibility and good performance of the proposed converter. [ABSTRACT FROM PUBLISHER]

In this paper, a new general cascaded multilevel inverter using developed H-bridges is proposed. The proposed topology requires a lesser number of dc voltage sources and power switches and consists of lower blocking voltage on switches, which results in decreased complexity and total cost of the inverter. These abilities obtained within comparing the proposed topology with the conventional topologies from aforementioned points of view. Moreover, a new algorithm to determine the magnitude of dc voltage sources is proposed. The performance and functional accuracy of the proposed topology using the new algorithm in generating all voltage levels for a 31-level inverter are confirmed by simulation and experimental results. [ABSTRACT FROM PUBLISHER]

This paper presents a multilevel inverter that has been conceptualized to reduce component count, particularly for a large number of output levels. It comprises floating input dc sources alternately connected in opposite polarities with one another through power switches. Each input dc level appears in the stepped load voltage either individually or in additive combinations with other input levels. This approach results in reduced number of power switches as compared to classical topologies. The working principle of the proposed topology is demonstrated with the help of a single-phase five-level inverter. The topology is investigated through simulations and validated experimentally on a laboratory prototype. An exhaustive comparison of the proposed topology is made against the classical cascaded H-bridge topology. [ABSTRACT FROM PUBLISHER]

In this paper, a model predictive control strategy is adapted to the cascaded H-bridge (CHB) multilevel rectifier. The proposed control scheme aims to keep the sinusoidal input current in phase with the supply voltage and to achieve independent voltage regulation of the H-bridge cells. To do so, the switches are directly manipulated without the need of a modulator. Furthermore, since all the possible switching combinations are taken into account, the controller exhibits favorable performance not only under nominal conditions but also under asymmetrical voltage potentials and unbalanced loads. Finally, a short horizon is employed in order to ensure robustness; this way, the required computational effort remains reasonable, making it possible to implement the algorithm in a real-time system. Experimental results obtained from a two-cell CHB rectifier are presented in order to demonstrate the performance of the proposed approach. [ABSTRACT FROM PUBLISHER]

This paper proposes a simple capacitor clamped current-sharing circuit including linear and loop types according to the connection of capacitors for multistring light-emitting diodes (LEDs). The proposed circuit employs interleaved turn-on switches and multicapacitor charge conservation to solve the current imbalance problem caused by voltage drop tolerance and the negative temperature coefficient of LEDs. The operating principle and parameter design of the topologies are analyzed in detail. Based on this analysis, a three-string current-sharing topology has been validated by experiments. Experimental waveforms show that the proposed circuit does not only have good effect on current sharing while the effect is not affected by individual LED short but also has the advantages of low voltage stress, nonmagnetic components, ease of integration, and simple control. [ABSTRACT FROM PUBLISHER]

This paper considers mainly the leader-following consensus for multiple agents with general linear system dynamics under switching topologies. Three different settings are systematically considered. We first consider the setting that the underlying interaction topologies switch arbitrarily among the possible weakly connected digraphs and then extend it to a more general setting that the weak connectivity of the interaction topologies is kept for some disconnected time intervals with short length due to the communication constraints among agents. Exponentially, consensus control is proved to be achieved, and the convergence rate can be specified as well for both settings in spite of the relaxed conditions on the system dynamics of each individual agent which even allow that each agent has exponentially unstable mode, while for the last case where the weak connectivity is only maintained on the joint of the interaction topologies, consensus control is proved to be achieved when the system matrix of each individual agent satisfies certain stability conditions. [ABSTRACT FROM PUBLISHER]

A systematic method for deriving multiport converters (MPCs) from the full bridge (FB) converter (FBC) and bidirectional dc–dc converters (BDCs) is proposed in this paper through sharing the parasitized switching legs by the BDCs and the FBC. By employing the proposed method, families of FB and BDC-based MPCs (FB-BDC-MPCs), including some existing ones, are developed for renewable generation systems with the merits of simple topology, reduced devices, and single-stage power conversion. Voltage regulations between any two ports can be achieved by employing pulsewidth modulation and phase-angle-shift control scheme. Furthermore, zero-voltage switching for all the switches can be realized in the proposed FB-BDC-MPCs. A typical four-port converter developed by the proposed method, named buck/boost four-port converter (BB-FPC), is analyzed in detail as an example in terms of operation principles, design considerations, and control strategy. Experiments have been carried out on a 500-W prototype of BB-FPC, which demonstrate the feasibility and effectiveness of the proposed topology derivation method. [ABSTRACT FROM AUTHOR]

This paper presents the use of a high-performance boundary controller for the full-bridge zero-voltage-switching topology. An enhanced dynamic response is obtained by employing the natural switching surface (SS), which is thoroughly derived in the normalized geometrical domain. The advantages of the normalization are the simple graphical representation, the generality for any combination of parameters, and the mathematical simplicity. Recently, nonisolated basic topologies have benefited from advancements in boundary control. The analysis and derivation in this work bring the benefit of outstanding dynamic performance to this isolated topology. As demonstrated in this work, the relationship between the leakage and output filter inductances makes the formulation of the natural trajectories for isolated converters possible. The resulting SS provides an excellent dynamic response during start-up, reference change, and sudden output loading conditions. Experimental results are presented to illustrate the characteristics and advantages of the control scheme and the converter operation with fixed switching frequency. [ABSTRACT FROM AUTHOR]

Reliability and availability levels are crucial aspects for assessing the economic viability of wind energy conversion systems. Therefore, fault-tolerant systems can make a valuable contribution. This paper presents a fault-tolerant permanent-magnet synchronous generator (PMSG) drive employing new direct control techniques. For postfault operation, a direct power control (DPC) of a four-switch three-phase converter and a direct torque control of a three-switch three-phase rectifier are proposed. Switching tables are theoretically formulated for both control techniques. Two alternative tables are obtained for the DPC of the grid-side converter, permitting the choice between implementation simplicity and enhanced performance. All necessary reconfigurations to handle open-circuit faults are triggered by a reliable fault diagnostic method, which has a low computational demand, without requiring additional measurements. Experimental results are presented, demonstrating the feasibility of the proposed fault-tolerant PMSG drive. [ABSTRACT FROM AUTHOR]

In this paper, a new fifth-order boost point of load converter is proposed, and then, a digital controller is designed using a Tchebyshev polynomial approach. The proposed converter has a reduced source ripple current together with a better boosting capability at lower duty ratios. Discrete-time models of the converter are formulated and then used in the identification of the direct digital controller stabilizing region. These discrete-time transfer functions are transformed into a Tchebyshev representation, consisting of converter control-to-output and controller transfer functions, which are then used to ascertain the existence of a stabilizing controller, and if stabilization is possible, then the entire set of gains is constructively determined. Using this method, the controller gain range is obtained as a set of inequalities in two variables for a fixed third variable. By sweeping the third variable over its entire range, the complete stabilizing sets are obtained. Within these ranges, the optimal digital controller parameters are obtained through a constrained optimization problem using a genetic algorithm. An integral time absolute error performance index is used in the optimization. A 30-W, 12- to 28-V, and 100-kHz laboratory prototype closed-loop converter has been developed and then tested, both as a simulation and experimentally, for its voltage regulation capability against source and load perturbations. Both the simulated and experimental results confirm the effectiveness of the proposed design. [ABSTRACT FROM PUBLISHER]

This paper discusses the operation of a multiphase system, which is aimed at both variable-speed drive and generating (e.g., wind energy) applications, using back-to-back converter structure with dual three-phase machine-side converters. In the studied topology, an asymmetrical six-phase induction machine is controlled using two three-phase two-level voltage source converters connected in series to form a cascaded dc link. The suggested configuration is analyzed, and a method for dc-link midpoint voltage balancing is developed. Voltage balancing is based on the use of additional degrees of freedom that exist in multiphase machines and represents entirely new utilization of these degrees. The validity of the topology and its control is verified by simulation and experimental results on a laboratory-scale prototype, thus proving that it is possible to achieve satisfactory dc-link voltage control under various operating scenarios. [ABSTRACT FROM PUBLISHER]

This paper presents an analytical design method for the dc collector systems of offshore wind farms and proposes an improved topology to overcome the limitations of the conventional series–parallel (SP) topology. During a severe failure in the SP topology, bypassing the faulty units imposes overvoltage on fault-free units and leads to the disconnection of the series branch from the collector system. By providing auxiliary connection paths, the suggested topology reduces the overvoltage of the units and hence maintains fault-free units operational following a severe failure. Hence, the efficiency of a wind farm increases considerably upon any failure occurrence. To show the merits of the suggested topology, the captured power during a failure has been calculated and fairly compared with that of the conventional SP topology, considering the excess cost of the suggested topology due to additional connection paths. To investigate the performances of both topologies and their feasibility, a collector system including 12 wind turbine generators has been simulated in time domain software environment. Then, various failure scenarios have been investigated to evaluate the transient behavior of the dc collector system following slight and severe failures. The study results reveal the feasibility of the proposed topology as a promising structure for future dc collector systems. [ABSTRACT FROM PUBLISHER]

This paper unifies the underlying concepts of all basic single-switch, two-state, dc-to-dc voltage-sourced converters, by duality, as generic related current and voltage-sourced converters. By using ac and dc circuit theory, the three basic converters can be transformed to yield all known transfer functions and realizes a proliferation of 33 topologies, three being previously unidentified topologies with unique characteristics. The circuit based systematic unifying approach offers new insight and an alternative interpretation to the origin of the 33 topologies including the Zeta, Cuk, \pmLuo, CSC, Landsman, and Sepic converters. Converter time-domain simulations and corresponding practical results of the three new topologies extol and culminate the concepts and analysis presented. [ABSTRACT FROM PUBLISHER]

This paper proposes the pulsewidth modulation (PWM) strategy of Z-source inverters (ZSIs) with minimum inductor current ripple. In existing PWM strategy with single-phase shoot-through, the shoot-through time interval is divided into six equal parts, therefore the three phase legs bear the equal shoot-through time interval. In this manner, the allotment and arrangement of the shoot-through state is easy to realize, but the inductor current ripple is not optimized. This causes to use relatively large inductors. In the proposed PWM strategy, the shoot-through time intervals of three phase legs are calculated and rearranged according to the active state and zero state time intervals to achieve the minimum current ripple across the Z-source inductor, while maintaining the same total shoot-through time interval. The principle of the proposed PWM strategy is analyzed in detail, and the comparison of current ripple under the traditional and proposed PWM strategy is given. Simulation and experimental results on the series ZSI are shown to verify the analysis. [ABSTRACT FROM PUBLISHER]