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This paper presents a multilevel step-up dc/dc converter for dc-grid-based offshore wind energy conversion applications. The main features of the proposed multilevel converter are as follows: 1) the voltage stress of the power devices can be reduced, making it suitable for high-voltage applications; 2) the boost inductor can be reduced significantly, leading to the outstanding dynamic performance; and 3) high-voltage gain can be obtained and thus is well-suited for high-gain applications. Theoretical analysis was carried out for a four-level step-up converter, based on which, the converter can be extended to any arbitrary number of levels. The proposed four-level converter was verified by a simulation and evaluated by comparing with a conventional multilevel dc/dc converter in terms of the component stress and power device count. The developed topology was implemented on a 2-kW prototype converter to evaluate its feasibility. [ABSTRACT FROM AUTHOR]

The five-phase coupled-inductor inverter is a newly proposed option for three-level five-phase inverter drives. This paper comprehensively analyzes the inverter including the coupled-inductor current, current stress on the dc-link capacitors, and a comparison of these performance aspects using three pulse width modulation (PWM) strategies. Mathematical derivations of the inverter currents and the associated current stress reveal that the current stress is not only influenced by the choice of modulation strategy, as in the neutral-point-clamped topology, but also by the value of coupled inductance; furthermore, the choice of the modulation strategy impacts the core loss of the coupled inductors. Three carrier-based PWM methods are considered: sinusoidal PWM (SPWM), and two methods with the common-mode voltage reduction (referred to as CMVR1 and CMVR2) for the five-phase coupled-inductor inverter. CMVR2 is shown to be the best solution if common-mode voltage reduction is required. The analysis demonstrates that SPWM performs better with respect to current stress and inverter losses, therefore is the preferable modulating strategy for the five-phase coupled-inductor inverter if common-mode voltage reduction is not required. The analysis is verified by simulations and experiments. [ABSTRACT FROM AUTHOR]

This paper proposes a novel high step-up nonisolated single switch dc–dc converter suitable for regulating dc bus in various microsources especially for photovoltaic (PV) sources. Quadratic boost and switched-capacitor technique are used as primary and secondary circuits, respectively. A coupled inductor is applied to make a connection between them, so a high dc voltage gain is achieved. High efficiency is yield where voltage stress on active switch is alleviated by clamped capacitor; consequently, smaller \rmR\rm{DS(ON)} for power switch is required. On the other hand, input current of the proposed converter is continued, hence stress on the input source is reduced. The operating principles and steady-state analyses are discussed in detail for both continuous and discontinuous conduction modes. Also, the boundary condition is computed. To verify the performance of the proposed converter and theoretical calculations, a 250-W prototype converter is implemented with an input voltage of 24 V and an output voltage of 400 V designed especially for PV sources in continuous conduction mode operation. Finally, simulation results are confirmed by experimental results; maximum efficiency is occurred at 150 W and full-load efficiency is 92.96%. [ABSTRACT FROM AUTHOR]

This paper proposes a new three-phase modular multilevel inverter (MMLI). The proposed inverter consists of repeated modular primary cells that are connected in series configuration. Therefore, the proposed topology can be extended to get more output voltage levels by adding additional cells without increasing voltage stresses across power switches. Both sinusoidal pulsewidth modulation (SPWM) and staircase modulation are successfully applied to the proposed inverter. The proposed inverter features many advantages such as reduced number of semiconductor power switches, driver circuits, dc-voltage sources, simplified control algorithm, and reduced voltage stresses across the switches independent of output voltage level. Furthermore, the performance of the proposed inverter is studied under both open-loop and closed-loop operations for highly inductive load. Beside the obtained simulation results, a laboratory prototype has been carried out and tested to verify the control techniques and performances of the topology. Simulation and experimental results are compared together to highlight the similarity and consistence of them. [ABSTRACT FROM AUTHOR]

The reduced capability of multilevel converters with more than one intermediate node to balance the dc-link capacitors voltage, as well as the lack of standard modulation methods to improve their balancing performance, makes these converter topologies unattractive for real power applications. This is especially true when the load demands active power. One of these topologies is the five-level multipoint clamped (5L-MPC) converter. The back-to-back (B2B) configuration of two 5L-MPC converters and the use of a space vector modulation (SVM) that exploits the voltage balancing capability of the redundant switching vectors extend the operation conditions range in which a proper voltage balance can be achieved. However, if practical modulation restrictions are considered (limitation of voltage steps, dead times, switching losses, etc.), the voltage balance cannot be achieved for all operation conditions. In this paper, an SVM which takes into account practical restrictions is proposed. In order to guarantee the voltage balance at any operation condition, the grid-side rectifier exchanges reactive power with the grid-side LCL filter. Thus, the voltage balance of the dc-link is guaranteed while a unity grid-side power factor is achieved. The proposed modulation scheme and the voltage balancing strategy are experimentally validated in a 6.6 kV 1.5 MW 5L-MPC B2B converter. [ABSTRACT FROM AUTHOR]

This paper presents a closed-loop space vector modulation (SVM)-based sliding mode controller (SMC) for a three-level grid-connected neutral point clamped (3L-NPC) inverter. The nonlinear SMC based on Gao's reaching law has been designed to control the grid current and inject desired amount of active and reactive power into the network. Due to using single dc source at the NPC inverter dc bus, neutral point voltage is controlled through redundant switching states and instantaneous dc voltage feedback integrated into SVM technique. Meanwhile, there is no external voltage controller involved, thus no associated fine tuning issues are existed. The performance of the proposed hybrid controller to inject a desired active/reactive power to the grid is investigated through external perturbations such as change in the line current amplitude/phase shift, ac voltage fluctuation, as well as dc voltage variation. Full converter state-space model was developed and simulated. Experimental results are provided to verify the fast dynamic performance, low content of line current THD%, and good voltage balancing of dc bus capacitors of the NPC inverter. [ABSTRACT FROM AUTHOR]

A new cascade topology for multilevel converter is introduced in this paper which comprises series connection of several submultilevel units. To determine the magnitudes of the dc sources, two new methods are described. The proposed topology is optimized to generate any levels with minimum number of components and peak voltage on switches. The presented topology can be used in high-voltage applications due to using the switches with low voltage rating. To indicate the merits of the proposed structure, comparison studies are provided with other topologies in terms of the number of elements and peak voltage on switches. The comparison results prove that the presented cascade multilevel converter requires fewer components. Moreover, it is shown that the total peak voltage on switches in the proposed topology is less than other structures. Experimental work is presented to demonstrate the performance of the presented multilevel converter. [ABSTRACT FROM PUBLISHER]

A family of dc–dc converters based on impedance source dc–dc converters is presented. The scheme of the proposed family is that the switch of impedance source dc–dc converters is moved forward. The derived topologies are suitable for high-voltage step-up ratio. Compared to the typical impedance source dc–dc converters, the presented topology dramatically reduces the voltage stresses on the power semiconductor devices. In addition, the passive lossless clamped circuit is introduced into the proposed family to restrict the peak voltage of the main switch. This paper presents an analysis of the converter and results from a prototype converter to validate the topology's performance. [ABSTRACT FROM AUTHOR]

Multiterminal converters eliminate using several single-input-single-output converters and simplify their topologies and reduce their cost. In this paper, a new family of multi-input converters based on three switches leg is introduced. Inputs of the proposed converters are similar and they are topologically interchangeable and have boost or buck operation modes. The proposed converter has one output that operates as an inverter. Here, all operating modes of the proposed converters and their effects on each other are investigated, in details. Also, an appropriate switching technique for the converters is given. A detailed comparison between conventional and proposed two-input converters is also presented. A two-input, one-output prototype converter has been implemented to validate the given analyses and to verify the proposed converter's performance. The experimental results are in good agreement with the theoretical and simulated analyses. [ABSTRACT FROM AUTHOR]

In this paper, a novel topology of six-level inverters for a medium-voltage high-power applications is proposed, which consists of inner flying-capacitor inverter (FCI) units and outer two-level inverter units. The proposed topology can reduce the number of devices, components, and isolated sources compared with the existing ones in the case of the same number of output voltage steps, which result in a reduction of the size and weight of the inverters. Also, the total power loss of the proposed topology is lower than that of the diode-clamped inverter (DCI) and FCI. Besides, the estimated cost of the proposed topology is about 60.5% and 81.3% compared with the DCI and FCI, respectively. In addition, the modulation technique and the control strategy for the dc-link capacitor and flying-capacitor voltages are developed for the proposed topology. The effectiveness of the proposed six-level inverter for the medium-voltage applications has been verified by simulation results. Also, the feasibility of the proposed inverter has been proved by experimental results for the prototype at the laboratory. [ABSTRACT FROM AUTHOR]

This paper presents a finite-control-set model predictive control (FCS-MPC) for grid-tied packed U cells (PUC) multilevel inverter (MLI). The system under study consists of a single-phase 3-cells PUC inverter connected to the grid through filtering inductor. The proposed competitive topology allows the generation of 7-level output voltage with reduction of passive and active components compared to the conventional MLIs. The aim of the proposed FCS-MPC technique is to achieve, under various operating conditions, grid-tied current injection with unity power factor and low total harmonic distortion while balancing the capacitor voltage. Parameters’ sensitivity analysis was also conducted. The study is conducted on a low-power case study single-phase 3-cells PUC inverter and with possible extension to higher number of cells. Theoretical analysis, simulation, and experimental results are presented and compared. [ABSTRACT FROM AUTHOR]

In this paper, a novel cascaded seven-level inverter topology with a single input source integrating switched-capacitor techniques is presented. Compared with the traditional cascade multilevel inverter, the proposed topology replaces all the separate dc sources with capacitors, leaving only one H-bridge cell with a real dc voltage source and only adds two charging switches. The capacitor charging circuit contains only power switches, so that the capacitor charging time is independent of the load. The capacitor voltage can be controlled at a desired level without complex voltage control algorithm and only use the most common carrier phase-shifted sinusoidal pulse width modulation strategy. The operation principle and the charging–discharging characteristic analysis are discussed in detail. A 1-kW experimental prototype is built and tested to verify the feasibility and effectiveness of the proposed topology. [ABSTRACT FROM AUTHOR]

This paper presents a new E-type module for asymmetrical multilevel inverters (MLIs) with reduced components. Each module produces 13 levels with four unequal dc sources and 10 switches. The design of the proposed module makes some preferable features with a better quality than similar modules such as the low number of semiconductors and dc sources and low switching frequency. Also, this module is able to create a negative level without any additional circuit such as an H-bridge, which causes reduction of voltage stress on switches. Cascade connection of the proposed structure leads to a modular topology with more levels and higher voltages. Selective harmonics elimination pulse width modulation (SHE-PWM) scheme is used to achieve high-quality output voltage with lower harmonics. MATLAB simulations and practical results are presented to validate the proposed module good performance. Module output voltage satisfies harmonics standard (IEEE519) without any filter in output. [ABSTRACT FROM AUTHOR]

A new single-phase \uppi-\texttype 5-level inverter using 3-terminal switch-network (3TSN) is proposed in this paper. The topology is considered as a variant of T-type 3-level structure or dual-buck inverter with coupled inductors. This new inverter is suitable for multilevel power inversion with low dc-bus voltage. The merit of the proposed topology is to apply only four active power switches to achieve 5-level operation. Other benefits include double frequency operation of output inductor and equal division of the current that flows through power switches and filter inductor. Hence, it leads to high efficiency and low harmonics. These characteristics allow improvement of losses distribution and volume reduction of output filter inductor. The operation scenario with sinusoidal pulsewidth modulation (SPWM) is described in details. Meanwhile, the magnetic analysis and design are studied and discussed. Finally, a prototype is built to verify the theoretical analysis and demonstrate the benefits of the proposed topology. [ABSTRACT FROM AUTHOR]

In this paper, the control performances of a modular power converter for a three-phase switched reluctance machine (SRM) are analyzed and improved. The converter is implemented by a dual and a six-pack IGBT module, and the phase windings of the SRM are Y-connected and bipolar excited. The performances of the existing control method for this converter are evaluated by simulation and compared with those for the traditional asymmetric half-bridge converter, and the drawbacks, such as big torque ripple and small average torque, are presented. With the new operating modes of phase branch, namely magnetization, freewheeling, and demagnetization, improved basic control methods are proposed, which can effectively enhance the performances, flexibility, and applicability of the converter. Furthermore, the direct instantaneous torque control, which can reduce the torque ripple, is realized with the converter as well. Several simulations and experiments under different working conditions are carried out to verify the performances of the improved control methods. [ABSTRACT FROM PUBLISHER]

A bidirectional converter (BDC) is essential in applications where energy storage devices are involved. Such applications include transportation, battery less uninterruptible power system, flywheel energy storage systems, etc. Bidirectional power flow through buck and boost modes of operation along with high power density and efficiency is important requirement of such systems. This paper presents a new BDC topology using a combination of fast turn-off SCR and insulated-gate bipolar transistor with a novel control logic implementation to achieve zero switching losses through zero voltage transition and zero current transition techniques. The proposed scheme ensures zero switching power loss (ZSPL) for both buck and boost modes of operation of the BDC. The scheme is simple and achieves ZSPL during both turn-on and turn-off of the devices resulting in improved efficiency and reduced electromagnetic interference problems. The basic principle of operation, analysis, and design procedure are presented for both voltage buck and boost modes of operation of the proposed BDC topology. A design example is presented. Limitations of the system are highlighted. Experimental and simulation results obtained on a 4 kW, 340 V input prototype with a switching frequency of 15.4 kHz are presented to verify the design. [ABSTRACT FROM PUBLISHER]

To improve the reliability of the matrix converter (MC), a fault diagnosis method to identify a single open-switch fault is proposed in this paper. The introduced fault diagnosis method is based on finite control set-model predictive control (FCS-MPC), which employs a time-discrete model of the MC topology and a cost function to select the best switching state for the next sampling period. The proposed fault diagnosis method is realized by monitoring the load currents and judging the switching state to locate the faulty switch. Compared to the conventional modulation strategies such as carrier-based modulation method, indirect space vector modulation, and optimum Alesina–Venturini, the FCS-MPC has known and unchanged switching state in a sampling period. It is simpler to diagnose the exact location of the open switch in MC with FCS-MPC. To achieve better quality of the output current under single open-switch fault conditions without any redundant hardware, a fault tolerant strategy based on predictive control is also studied. The fault tolerant strategy is to select the most appropriate switching state associated with the remaining normal switches of the MC. Experiment results are presented to show the feasibility and effectiveness of the proposed fault diagnosis method and fault tolerant strategy. [ABSTRACT FROM PUBLISHER]

This paper presents a new configuration for integrated on-board battery chargers of electric vehicles (EVs) incorporating symmetrical six-phase machines. The configuration proposes an exclusive utilization of a nine-switch converter (NSC) along with the machine windings during both propulsion and charging of EVs. The proposed configuration has the advantage of employing a reduced number of components in both the EV (on-board) and charging station (off-board), with the privilege of avoiding machine electromagnetic torque production during charging/vehicle-to-grid (V2G) mode of operation. During charging/V2G mode, the NSC is turned into a conventional three-phase pulse width modulation rectifier and is directly connected to the three-phase mains through the machine windings. Conventional three-phase transformers can be employed for galvanic isolation. Switching between propulsion and charging modes is carried out using a simple hardware reconfiguration. Control schemes for both propulsion and charging/V2G modes are elaborated, along with the principles of operation of the NSC. Experimental results are provided to validate the theoretical deductions for the different operating modes. [ABSTRACT FROM PUBLISHER]

In recent years, model predictive control (MPC) has been successfully used for the control of power electronics converters with different topologies and for different applications. MPC offers many advantages over more traditional control techniques such as the ability to avoid cascaded control loops, easy inclusion of constraint, and fast transient response. On the other hand, the controller computational burden increases exponentially with the system complexity and may result in an unfeasible realization on modern digital control boards. This paper proposes a novel distributed MPC (DMPC), which is able to achieve the same performance of the classical MPC while reducing the computational requirements of its implementation. The proposed control approach is tested on a ac/ac converter in a back-to-back configuration used for power flow management. Simulation results are provided and validated through experimental testing in several operating conditions. [ABSTRACT FROM PUBLISHER]

This paper presents a new family of buck type power factor corrector rectifiers that operates in continuous-conduction mode (CCM) and generates a multilevel voltage waveform at the input. Due to CCM operation, commonly used ac-side capacitive filter and dc-side inductive filter are removed from the proposed modified packed U-cell rectifier structure. Dual dc output terminals are provided to have a five-level voltage waveform at the input points of the rectifier where it is supplied by a grid via a line inductor. Producing different voltage levels reduces the voltage harmonics which affects the grid current harmonic contents directly. Low switching frequency of the proposed rectifier is a distinguished characteristic among other buck type rectifiers that reduces switching losses and any high switching frequency related issues, significantly. The proposed transformerless, reduced filter, and multilevel rectifier topology has been investigated experimentally to validate the good dynamic performance in generating and regulating dual 125-V dc outputs terminals as telecommunication boards feeders or industrial battery chargers under various situation including change in the loads and change in the main grid voltage amplitude. [ABSTRACT FROM PUBLISHER]

This paper presents a new formulation of a finite control set model-predictive control (FCS-MPC) algorithm, allowing to determine the best commutation instant in order to optimize the converter current tracking. This algorithm, mixing properties of FCS-MPC method and time resolution related to pulse width modulation schemes, is illustrated in a parallel flying capacitor converter. The parallel association of classical commutation cells is a good solution for increasing the output current driven by the converters, while the standard semiconductor technology is used. The control strategy used with this type of connection must be able to ensure not only a good distribution of the output current among the different legs, but also the balancing of the floating capacitor voltages. [ABSTRACT FROM PUBLISHER]

A converter system for high-power applications, connected to a medium-voltage network using a step-up transformer, is presented in this paper. The converter-side winding of the transformer is configured as an open-end, and both the ends of the windings are fed from two different converter groups. Each converter group comprises of two parallel voltage-source converters (VSCs), whose carrier signals are interleaved to improve the harmonic quality of the resultant switched output voltage of that converter group. However, an additional inductive component is required to suppress the circulating current that flows between the parallel-interleaved VSCs. An integrated inductor is proposed, which suppresses the circulating current in both the converter groups. In addition, the functionality of the line filter inductor is also integrated. Flux in various parts of the integrated inductor is analyzed, and a design procedure is also described. The volume and the losses of the proposed solution are compared with that of the state-of-the-art solution. The control of the proposed converter system is also discussed. The analysis has been verified by the simulation and experimental results. [ABSTRACT FROM PUBLISHER]

In conventional dc–dc converters with synchronous rectifiers, hard-switching operation of the main switch and reverse-recovery problem of the synchronous switch result in degraded performance. In order to avoid these two undesired shortcomings, employing a coupled inductor is a simple yet effective solution. Apart from the improved soft-switching characteristic, low component count is also achieved since only a coupled winding and a series auxiliary diode are added. In this paper, a general zero-voltage-switching (ZVS) topology with a coupled inductor is proposed and based on which, a family of ZVS synchronous buck, boost, and buck–boost converters is readily obtained. For each fundamental dc–dc converter, several viable ZVS topologies evolve, among which an optimum topology can be chosen according to the different requirement in practical engineering applications. To help the topology selection, generalized analysis and individual comparison are also undertaken. In addition, design consideration is illustrated and experiment results are provided to validate converter effectiveness. Furthermore, thanks to its generality, the topology derivation and generalized analysis can be easily extended to various synchronous dc–dc converters. [ABSTRACT FROM PUBLISHER]

For cascaded multilevel inverter topologies with a single dc supply, closed-loop capacitor voltage control is necessary for proper operation. This paper presents zero and reduced common-mode voltage (CMV) operation of a hybrid cascaded multilevel inverter with predictive capacitor voltage control. Each phase of the inverter is realized by cascading two- three-level flying capacitor inverters with a half-bridge module in between. For the presented inverter topology, there are redundant switching states for each inverter voltage levels. By using these switching state redundancies, for every sampling instant, a cost function is evaluated based on the predicted capacitor voltages for each phase. The switching state that minimizes cost function is treated as the best and is switched for that sampling instant. The inverter operates with zero CMV for a modulation index upto 86%. For modulation indices from 86% to 96%, the inverter can operate with reduced CMV magnitude (Vdc/18) and reduced CMV switching frequency using the new space-vector pulsewidth modulation (SVPWM) presented herein. As a result, the linear modulation range is increased to 96% as compared to 86% for zero CMV operation. Simulation and experimental results are presented for the inverter topology for various steady state and transient operating conditions by running an induction motor drive with open loop $V/f$ control scheme. [ABSTRACT FROM PUBLISHER]

This paper presents a novel topology for a direct ac–ac power converter, called as the “three-to- k” phase matrix converter. The input to the proposed matrix converter configuration is a three-phase fixed voltage and a fixed frequency supply from the grid. The output is a variable voltage and variable frequency ac supply of any number of phases (k phase). However, the discussion is limited here for a k that is equal to odd number of phases. As an example, a “three-to-five” phase matrix converter is utilized for discussion and analysis. This paper also proposes two pulsewidth modulation (PWM) control techniques for the general topology of the “three-to- k” phase matrix converter. This is based on the so-called direct duty ratio PWM (DPWM). In one presented technique, the output voltage is limited to one half of the input voltage. For the other proposed scheme, the output voltage is enhanced to 78.86% of the input voltage. The proposed control algorithm is validated using simulation and an experimental approach. [ABSTRACT FROM AUTHOR]

In this paper, a model-predictive control (MPC) has been designed and implemented on the packed U-cell (PUC) inverter, which has one isolated dc source and one capacitor as an auxiliary dc link. The MPC is designed to regulate the capacitor voltage at the desired magnitude to have seven voltage levels at the output of the inverter. Since grid-connected application is targeted by this application, the inverter should be capable of supplying requested amount of active and reactive power at the point of common coupling (PCC) as well. Therefore, MPC should also consider the line-current control to monitor the exchange of reactive power with the grid while injecting appropriate active power at low total harmonic distortion (THD). Various experimental tests including change in dc-source voltage, active power variation, and operation at different power factor (PF) have been performed on a laboratory prototype to validate the good performance obtained by the proposed MPC. The dynamic performance of the controller during sudden changes in dc capacitor voltage, supply current, and PF demonstrates the fast and accurate response and the superior operation of the proposed controller. [ABSTRACT FROM PUBLISHER]

In this paper, the predictive power control with active damping function is proposed for matrix converter (MC). In every sampling period, the values of load active power pL, load reactive power qL, and input reactive power qi at the period after next are predicted. The best switching state is selected based on the minimum cost function g for the next sampling time interval, where $g$ is the sum of the absolute errors between the reference and the predicted values. Since pL, qL, and qi are equally important for MC control, their weighting factors are fixed at 1, rather than being adjusted empirically. On this basis, a novel active damping control strategy is realized by modifying the reference values of load active power and input reactive power. By applying the active damping function, the input filter resonances which are liable to be excited by predictive control are effectively suppressed. Experimental results have verified the feasibility and validity of the proposed strategy. [ABSTRACT FROM PUBLISHER]

This paper presents a model predictive control (MPC) scheme for quasi-Z-source (qZS) three-phase four-leg inverter. In order to cope with the drawbacks of traditional voltage source inverters (VSIs), a qZS three-phase four-leg inverter topology is proposed. This topology features a wide range of voltage gain which is suitable for applications in renewable energy-based power systems, where the output of the renewable energy sources varies widely with operating conditions such as wind speed, temperature, and solar irradiation. To improve the capability of the controller, an MPC scheme is used which implements a discrete-time model of the system. The controller handles each phase current independently, which adds flexibility to the system. Simulation and experimental studies verify the performances of the proposed control strategy under balanced and unbalanced load conditions as well as single-phase open-circuit fault condition. [ABSTRACT FROM PUBLISHER]

The aim of this paper is to present a new structure for switched-capacitor multilevel inverters (SCMLIs) which can generate a great number of voltage levels with optimum number of components for both symmetric and asymmetric values of dc-voltage sources. The proposed topology consists of a new switched-capacitor dc/dc converter (SCC) that has boost ability and can charge capacitors as self-balancing by using the proposed binary asymmetrical algorithm and series–parallel conversion of power supply. The proposed SCC unit is used in new configuration as a submultilevel inverter (SMLI) and then, these proposed SMLIs are cascaded together and create a new cascaded multilevel inverter (MLI) topology that is able to increase the number of output voltage levels remarkably without using any full H-bridge cell and also can pass the reverse current for inductive loads. In this case, two half-bridge modules besides two additional switches are employed in each of SMLI units instead of using a full H-bridge cell that contribute to reduce the number of involved components in the current path, value of blocked voltage, the variety of isolated dc-voltage sources, and as a result, the overall cost by less number of switches in comparison with other presented topologies. The validity of the proposed SCMLI has been carried out by several simulation and experimental results. [ABSTRACT FROM PUBLISHER]

In this paper, a new topology for half-bridge switched boost inverter (HB-SBI) is proposed. The proposed half-bridge inverter uses more active elements rather than capacitors and inductors in comparison with the conventional half-bridge Z-source inverter with two Z-networks, which results in reduction of weight, size, and cost. Moreover, the proposed inverter has the capability of eliminating inverter leg short-circuit issues and is able to further increase the output voltage level in comparison with its conventional types. Generating zero-level output voltage is also another advantage of this topology. Based on theoretical calculations, the steady-state and small-signal analysis of the proposed topology in different operating modes are performed and the ripple of inductors’ current and capacitors’ voltage are also calculated. A comprehensive comparison is also made between the proposed inverter and the conventional types. Finally, the experimental results are provided to reconfirm the performance of the proposed inverter. [ABSTRACT FROM PUBLISHER]

This paper presents a resilient framework for fault-tolerant operation in modular multilevel converters (MMCs) to facilitate normal operation under internal and external fault conditions. This framework is realized by designing and implementing a supervisory algorithm and a postfault restoration scheme. The supervisory algorithm includes monitoring and decision-making units to detect and identify faults by analyzing the circulating current and submodule capacitor voltages in a very short time. The postfault restoration scheme is proposed to immediately replace the faulty submodule with the redundant healthy one. The restoration is achieved by virtue of a multilevel modular capacitor-clamped dc/dc converter (MMCCC), which is redundantly aggregated to each arm of the MMC. This design effectively guarantees smooth mode transition and handles the failure of multiple submodules in a short time interval. In addition, a modified modulation scheme is presented to ensure submodule capacitor voltage balancing of the MMC without implementing any additional hardware. Fast fault identification, a fully modular structure, and robust postfault restoration are the main features of the proposed framework. Digital time-domain simulation studies are conducted on a 21-level MMC to confirm the effectiveness and resilience of the proposed fault-tolerant framework during internal and external faults. Furthermore, the proposed framework is implemented in the FPGA-based RT-LAB real-time simulator platform to validate its resilience in a hardware-in-the-loop setup. [ABSTRACT FROM PUBLISHER]

In this paper, a new inverter topology is proposed for generating a multilevel dodecagonal voltage space vector structure for open-end winding induction motor (IM) using a single dc source. Dodecagonal voltage space vector structure eliminates fifth- and seventh-order harmonic voltages from phase voltage output and hence eliminates the fifth- and seventh-order harmonic currents through the motor leading to removal of the dominant sixth-order torque ripple generation in the motor over the entire modulation range. Multilevel space vector structure generates output voltage with better THD and low dv/dt. In the proposed topology, two three-level inverters drive an open-end winding IM, one inverter from each side. DC-link of primary inverter is from a dc source which delivers the entire active power, whereas the secondary inverter dc-link is maintained by a capacitor, which is self balanced during the inverter operation. The PWM scheme implemented ensures low switching frequency for primary inverter. Secondary inverter operates at a small dc-link voltage. Hence, switching losses are small for both primary and secondary inverters. Experimental results show the elimination of fifth- and seventh-order harmonic voltages over the entire modulation range, validating effectiveness of the proposed multilevel inverter scheme. [ABSTRACT FROM PUBLISHER]

High-power and high-voltage gain dc–dc converters are key to high-voltage direct current (HVDC) power transmission for offshore wind power. This paper presents an isolated ultra-high step-up dc–dc converter in matrix transformer configuration. A flyback-forward converter is adopted as the power cell and the secondary side matrix connection is introduced to increase the power level and to improve fault tolerance. Because of the modular structure of the converter, the stress on the switching devices is decreased and so is the transformer size. The proposed topology can be operated in column interleaved modes, row interleaved modes, and hybrid working modes in order to deal with the varying energy from the wind farm. Furthermore, fault-tolerant operation is also realized in several fault scenarios. A 400-W dc–dc converter with four cells is developed and experimentally tested to validate the proposed technique, which can be applied to high-power high-voltage dc power transmission. [ABSTRACT FROM AUTHOR]

This paper presents a boost-multilevel inverter design with integrated battery energy storage system for standalone application. The inverter consists of modular switched-battery cells and a full-bridge. It is multifunctional and has two modes of operation: 1) the charging mode, which charges the battery bank and 2) the inverter mode, which supplies ac power to the load. This inverter topology requires significantly less power switches compared to conventional topology such as cascaded H-bridge multilevel inverter, leading to reduced size/cost and improved reliability. To selectively eliminate low-order harmonics and control the desired fundamental component, nonlinear system equations are represented in fitness function through the manipulation of modulation index and the genetic algorithm (GA) is employed to find the optimum switching angles. A seven-level inverter prototype is implemented and experimental results are provided to verify the feasibility of the proposed inverter design. [ABSTRACT FROM AUTHOR]

This paper investigates the problem of distributed \mathcalH\infty filtering for a class of discrete-time Markov jump Lur’e systems over sensor networks with stochastic switching topologies. As a first effort, the redundant channels are considered to use in the data transmission to strive against the fragility of networks commonly configured by a single channel in the communication networks subject to quantization and randomly occurring packet dropouts. By constructing a Lur’e-type Lyapunov function interconnected with a cone-bounded nonlinearity, the filtering performance analysis for the underlying systems is carried out first. Then, a new class of distributed filters, which can be used to reflect the mismatching characteristic of modes jumping between the target plants and the proposed filters, is designed such that the filtering error system is stochastically stable and achieves a prescribed average \mathcalH\infty performance index. A numerical example is provided to show the effectiveness of the proposed filtering scheme. [ABSTRACT FROM PUBLISHER]

Multilevel inverters are gaining more attention in ac drive application due to their many attractive features. In the case of conventional neutral-point-clamped (NPC) or flying capacitor multilevel inverter configurations, active switches are connected in series to produce multilevel output voltage waveform. Therefore, if any one switch fails, the entire configuration has to be shut down; this will reduce the reliability of the system. A dual three-level inverter configuration for induction motor drive is proposed in this paper to improve reliability of the system. This topology is developed by feeding four-pole induction motor stator winding with four conventional two-level inverter modules. A level-shifted carrier-based third harmonic injection pulsewidth-modulation technique is used to produce the gating signals for the proposed configuration. By providing proper phase shift between carrier waves, multilevel voltage waveform is produced across the total motor phase winding, and first center band harmonics are also canceled. Thereby, the torque ripple will be considerably reduced compared with conventional NPC five-level inverter-driven induction motor drive. Finite-element analysis (FEA) is used to estimate the torque ripple when induction motor is supplied by the proposed configuration and conventional five-level NPC inverter configuration to show the effectiveness of the proposed converter. The proposed configuration is simulated using MATLAB/Simulink and experimentally verified using a laboratory prototype with a 5-hp four-pole induction motor drive. [ABSTRACT FROM PUBLISHER]

This paper proposes a new approach for the analysis of consensus of multi-agent systems subject to time-varying delayed control inputs and switching topology. The main contribution is a condition for consensus for a networked system based on linear matrix inequalities that takes into account the joint effect of time-varying delays and switching network topology. Topology changes are modeled using Markov jumps with uncertain rates of transitions. A practical example is shown to illustrate the main result in various scenarios. [ABSTRACT FROM PUBLISHER]

Distributed maximum power point tracking (MPPT) photovoltaic (PV) systems have drawn increased attention since the inhomogeneous irradiance on PV modules can significantly deteriorate the effectiveness of solar energy harvest. To address the issue, this paper focuses on developing a highly efficient submodule integrated converter (subMIC), which is connected across each submodule of a PV panel. Gallium nitride (GaN) field-effect transistors are utilized in the synchronous buck converter topology to achieve high conversion efficiency and reduced size. A converter prototype, which is digitally controlled using a microcontroller for MPPT, is developed and tested, considering various irradiation conditions. The peak efficiency of the proposed GaN-based subMIC is measured to be higher than 99% at 400-kHz switching frequency, whereas the accuracy of MPPT is above 99% considering low-power conditions. [ABSTRACT FROM PUBLISHER]

In this paper, a novel grid-connected high step-up inverter is proposed. The topology is composed of two stages. The first stage is a single-switch high step-up dc–dc converter with bipolar outputs, and the second stage is a conventional half-bridge dc–ac grid-connected inverter. Negative grounding of the photovoltaic (PV) module has resulted in elimination of unwanted ground leakage currents in the PV system. Simple structure, employing few semiconductor switches, simple control, and high efficiency are the features of the proposed topology. Theoretical analysis and principal operation of the circuit are discussed. An experimental prototype is implemented to verify the performance of the proposed inverter. The experimental results confirm the aforementioned features and the theoretical analysis of the converter operation. [ABSTRACT FROM PUBLISHER]

This paper proposes a new topology for an enhanced-boost Z-source inverter (ZSI) with combined two Z-impedance networks. By two Z-impedance networks and low shoot-through duty cycle, the proposed inverter produces high output voltage gain. In traditional ZSIs for high boosting voltage, a low modulation index is required; hence, under these conditions, the output voltage will have low quality with high total harmonic distortion. Compared with the conventional high-boost ZSI topologies, the proposed inverter uses shorter shoot-through duration and a larger modulation index to improve the output waveform quality. Comparison between the proposed topology and previously proposed schemes, in terms of inductor numbers, voltage and current stresses on elements, sizes of inductors and capacitors, efficiency, and switching device product (SDP) factors of diodes, is made, and the results verify the priority of the proposed topology. The operating principle of the proposed topology is analyzed in detail. Both simulation and experimental results verify the high performance of the proposed inverter. [ABSTRACT FROM PUBLISHER]

Carrier-based pulsewidth-modulation (CBPWM) techniques are popular due to their simplicity, and have been widely researched for various three-phase inverter configurations. In this paper, two CBPWM techniques are proposed to reduce the common-mode (CM) voltage generated by the five-phase inverter. The five-phase inverters have more flexibility in reducing the CM voltage than their three-phase counterparts because they have more phase legs, hence finer control over the star-point voltage of the load. Two methods are proposed for the conventional two-level five-phase inverter to reduce the CM voltage; one utilizing adjacent modulating waveforms and the other utilizing nonadjacent modulating waveforms. The coupled inductor inverter (CII) uses coupled inductors to generate multilevel outputs. As the volt-second balance must be maintained across each coupled inductor, direct application of the proposed methods on the CII inverter will result in overcurrents in the coupled inductors. Hence, the proposed methods are further improved to ensure the volt-second integral over each switching period is zero. Moreover, the two proposed methods are designed to reduce switching events and prevent unexpected states occurring during the switching transitions. The performance and the switching strategy of both methods are verified by both simulations and experiments on a prototype of five-phase CII. [ABSTRACT FROM AUTHOR]

This paper proposes an indirect matrix converter (IMC) topology to supply a five-phase load directly from three-phase ac power sources without bulky electrolytic capacitors and explains its operating principle. Using the emerging topology, which combines the five-leg inverter into the rectifier stage of the conventional IMC, the three-to-five-phase IMC topology reduces the number of power switches and results in a simpler commutation compared with the conventional three-to-five-phase direct matrix converter. In addition, a simple approach to realize the carrier-based pulsewidth modulation (CBPWM) method for a three-to-five-phase IMC is presented, and the proposed CBPWM method is analyzed based on the space-vector approach. As a result, the IMC with the proposed CBPWM method can be more easily implemented compared with IMCs with the space-vector PWM method. A three-to-five-phase IMC control platform is realized by coordinating a TMS320F28335 DSP (Texas Instruments) with an EPM7128SLC84-15 field-programmable gate array (Altera). The simulation and experimental results are provided to verify the effectiveness of the CBPWM strategy. [ABSTRACT FROM AUTHOR]

A novel complementary phase disposition pulsewidth modulation method for the modular multilevel converter (MMC) with a limited number of submodules is proposed in this paper. Compared with the previous works, more practical issues have been considered, and the corresponding solutions have been provided. First, a new preset PWM signal mapping sequence and an improved virtual loop mapping (VLM) are used in the modulation. This method not only achieves a favorable capacitor voltage balance in the symmetry system but lowers the switching frequency of MMC's devices. Second, to further reduce the switching frequency, the unbalance margin of capacitor voltages is adopted to achieve the switching between the VLM and the selective VLM (SVLM). Moreover, the system robustness has been improved by considering the situation of symmetry losing, like cell fails; in these cases, the capacitor voltages of the upper and lower arms are balanced through the collaboration of the SVLM and the reconfigurable VLM. Finally, the effectiveness of the proposed method has been verified with simulation and experimental studies. [ABSTRACT FROM AUTHOR]

The Vienna rectifier, which is a nongenerative-boost type rectifier, is used in many applications such as telecommunication systems and wind turbine systems. The Vienna rectifier has a special operating requirement. Many switching methods considering this requirement were proposed. These methods generally take into account the Vienna rectifier's operation with the unity power factor because the Vienna rectifier aims to provide the power to the load. However, as the applications for the Vienna rectifier are diversified, control requirements have been suggested, including the dc-link voltage balance control and the novel control under severely unbalanced grids. In this paper, we propose a carrier-based pulse-width modulation (CB-PWM) method for Vienna rectifier operation with a variable power factor. The proposed CB-PWM method adds the compensation voltage to the three-phase reference voltages, depending on the power factor, to maintain the sinusoidal input currents of the Vienna rectifier. The performance and effectiveness of the proposed CB-PWM method are verified by simulation and experiment. [ABSTRACT FROM AUTHOR]

This paper presents a high-efficiency multilevel flying-capacitor (FC) dc/dc power conversion with a lower passive component rating and power device count for distributed renewable energy systems. A resonant technique is adopted for the proposed dc/dc converter to achieve zero-current switching (ZCS) for all switches. Theoretical analysis is carried out for the proposed quintuple topology with three active switches. The proposed converter is evaluated to the conventional FC converter, in terms of the component rating and count, to highlight its advantages with respect to the power density and cost. The experimental results of a 1-kW prototype FC converter are presented to validate the theoretical analysis and principles, as well as attest the feasibility of the proposed topologies. [ABSTRACT FROM PUBLISHER]

In this paper, a fault-tolerant single-phase five-level inverter configuration is proposed for photovoltaic (PV) generation systems. Conventional two-level inverters are popularly used in PV applications, but these inverters provide the output voltage with considerable harmonic content. One of the efficient ways to improve the power quality of PV generation systems is to replace a two-level inverter with a multilevel inverter. Conventional multilevel inverters reduce total harmonic distortion and filter requirements effectively, but it has limitations in terms of reliability due to increased device count and capacitor voltage balancing issues. Therefore, a fault-tolerant single-phase five-level inverter is presented, which is constructed by using a half-bridge two-level inverter, a three-level diode clamp inverter, and a bidirectional switch. The proposed inverter topology can tolerate the system faults due to failure of the source and/or switching devices with least modification in the switching combinations. It has less number of switching devices compared to conventional five-level inverters. The topology also has the energy-balancing capability between sources which helps in reducing uneven charge of batteries in case of partial shading or hotspots on one side of the PV panels. The proposed system under normal and faulty condition is simulated in MATLAB/Simulink environment, and results are verified with a laboratory prototype. [ABSTRACT FROM PUBLISHER]

This paper focuses on the galvanically isolated quasi-Z-source dc–dc converter with a novel zero voltage and zero current switching technique. The unique feature of the impedance network lies in combining the buck–boost operation capability with the short- and open-circuit immunity of transistors; at the same time, it can perform zero voltage and zero current switching on the primary side. The boundary conduction mode of the current in the second inductor of the quasi-Z-source network was used along with snubber capacitors in the two out of four transistors and a special control algorithm to achieve full zero-switching operation of the inverter. Simulation and experimental results prove the discussed ideas. Possible modifications of the algorithm and future applications are also described. [ABSTRACT FROM PUBLISHER]

In this paper, a pulsewidth modulation (PWM) plus secondary-side phase-shift (SSPS) controlled full-bridge three-port converter (FB-TPC) is proposed for a renewable power system, which is derived by integrating two interleaved buck/boost circuits (IBBC) and a SSPS full-bridge converter (FBC), to interface the energy source, energy storage element, and output load simultaneously. The two switching legs are shared by the IBBC and FBC, which improves the active devices sharing ratio and power density. With PWM plus SSPS control scheme, decoupled power control can be realized and the converter can achieve wide input voltage range power conversion. In addition, zero-voltage switching (ZVS) of both the primary and secondary switches are achieved in a wide range. Furthermore, the circulating current can be greatly eliminated, which helps to reduce conduction losses. Moreover, the voltage stresses on the secondary rectifier are effectively suppressed since the power switches and diodes are clamped to output voltage. The operation principles, output characteristics, ZVS performances, and control strategy are analyzed in detail. Experimental results of a 600-W prototype are provided to verify the effectiveness and the advantages of the proposed converter. [ABSTRACT FROM PUBLISHER]

In this paper, an advanced configuration for a symmetric multilevel voltage source inverter is proposed. The authority of the proposed inverter versus the conventional cascaded H-bridge inverter and those most recently introduced is verified with provided comparisons. The proposed inverter is able to generate the desired voltage levels using a lower number of circuit devices, including power semiconductor switches and related gate driver circuits of switches. As a result, the total cost is considerably reduced, and the control scheme gets simpler. Moreover, the reduced amount of on-state switches in the suggested configuration decreases voltage drops. Furthermore, power losses are diminished. The given simulation results confirm the feasibility of the proposed configuration. To approve the practicability of the proposed inverter, a prototype of the proposed topology has been implemented. Finally, simulation and experimental results are compared, and the provided comparison shows that the obtained results are in good agreement. [ABSTRACT FROM PUBLISHER]

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