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This paper introduces a combination of two proposed efficiency improvement techniques for a microinverter with current mode control zero-voltage switching output stages. The first technique is dynamic dead-time optimization wherein pulse width modulation dead times are dynamically adjusted as a function of load current. The second method is advanced phase skipping control which maximizes inverter efficiency by controlling power on individual phases depending on the available input power from the photovoltaic source. Neither of the techniques requires any additional circuit components and both can be easily implemented in digital controller firmware. The two techniques were designed and implemented in a 400-W three-phase microinverter prototype. The experimental results validate the theoretical analysis of these techniques and demonstrate that a significant efficiency improvement can be achieved by combining the two proposed control techniques. [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]

In this paper, a new isolated high step-up dc–dc converter is proposed based on the quasi-switched-boost network. The proposed converter has the following features: 1) continuous input current; 2) reduced turn ratio of the isolated transformer; 3) increased reliability, as it can operate in either short-circuit mode or open-circuit mode without causing damage to the power converter; and 4) unchanged primary and secondary voltage waveforms of the transformer, although the shoot-through duty cycle is variable. Compared to the quasi-Z-source-based isolated dc–dc converter, the proposed converter uses fewer passive components. The operating principles, analysis, parameter design guideline, and comparison with the quasi-Z-source-based isolated dc–dc converter are presented. A 450 W prototype is built to test the proposed converter. The proposed converter is applicable for distributed power generation applications where a varying low dc input voltage is converted to a high stabilized dc output voltage with a galvanic separation requirement. [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]

This paper proposes a new configuration for static ground power unit (GPU) based on the novel 25-level hybrid active neutral-point-clamped (HANPC) converter. The superiority of the proposed converter, as compared with conventional and other suggested multilevel converters, is significant decreasing the number of switches and minimizing the number of flying capacitors (FC) in converter. This improvement is possible by using suggested low-voltage submodule converter to the ANPC converter and proposed modulation method. This results in reduction of the size and cost of converter and makes it more feasible and reliable. Applying the active voltage balancing method for FC in the proposed HANPC converter guaranties fast charging and voltage-level regulation of FC without using balance booster circuit. Improving output voltage spectrum leads to inductance reduction of output L–C filter which enhances static GPU performance. The simulation and experimental results verify the validity and feasibility of the proposed converter. [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]

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 harmonic elimination technique based on a three-level dodecagonal space vector structure for open-end winding induction motor (IM) drives with a single-dc supply. Advantages of dodecagonal space vector switching and multilevel inverters are achieved with a single-dc supply. A dc supply-fed three-level flying capacitor (FC) inverter feeds active power to one end of the IM winding terminals and H-bridge connected capacitors eliminate fifth- and seventh-order harmonics from the other end. A pulsewidth modulation (PWM) technique is developed to switch the three-level dodecagonal space vectors and simultaneously control the H-bridge capacitors at 0.1445V\text{dc}. The fifth- and seventh-order harmonics are eliminated for the full modulation range of the three-level FC inverter, including the extreme 6-step operation. An increase in the linear modulation range has been achieved, resulting in improved dc bus utilization. Harmonic elimination is achieved by increasing switching frequency of the low-voltage capacitor connected H-bridge inverter; thus, switching frequency for the high-voltage dc supply-fed FC inverter is not increased. Using the proposed scheme, the instantaneous phase voltage never exceeds \frac23V\text{dc} (maximum phase voltage applied for hexagonal space vector structure) for which the machine windings are rated. Additionally, the proposed inverter has also been shown to operate for field oriented control of the open-end winding IM drive. [ABSTRACT FROM AUTHOR]

In this paper, a novel four-phase interleaved high step-down converter is presented. The proposed converter can provide an extremely high step-down voltage conversion ratio within a moderate duty cycle. There are four main advantages of the proposed converter. First, the blocking capacitors can store energy as usual. Therefore, they are used as voltage sources to reduce the input voltage as well as to reduce the switch voltage stresses. Second, due to the charge balance of the dc blocking capacitors, the converter possesses an automatic uniform current sharing characteristic of the interleaved phases without adopting any extra circuitry. Third, due to the phase shift between the interleaved phases, the architecture provides a low output current ripple. Fourth, the number of phases can be expanded or reduced to any even phases; therefore, the converter has a wide range of applications. Finally, the operating principles and analysis of this architecture are given, and an experimental prototype is also provided to verify the effectiveness of the proposed converter. [ABSTRACT FROM PUBLISHER]

The model predictive control has an ability to achieve multiple control objectives for a modular multilevel converter. This approach has high computational complexity and causes the unwanted switching's leading to a higher ripple in output current and harmonic distortion in output voltage and current waveforms. To solve the issues of computational burden and unwanted switchings, this paper proposes a dual-stage model predictive control approach for a modular multilevel converter. In this approach, the primary objectives are evaluated in first stage corresponding to the redundancy of voltage vectors, while the secondary objectives are evaluated in second stage corresponding to the submodule redundancy. Therefore, the computational burden is significantly minimized without affecting the dynamic response. In addition, a discrete-time model of modular multilevel converter incorporating the common-mode voltage is proposed. The simulation and experimental studies are conducted on a three-phase modular multilevel converter to verify the dynamic and steady-state performance of the proposed approach. The performance comparison between the proposed and conventional model predictive control approach is also presented. [ABSTRACT FROM PUBLISHER]

This paper provides a characterizationr analysis for the voltage balance of modular cascaded converter in a medium-voltage direct-current distribution grid. Specifically, voltage stability and traditional auxiliary resistor solution are analyzed from the theoretical level. On this basis, a minimum voltage tracking balance (MVTB) control based on a switched resistor is proposed. The voltage balance during startup and normal locked processes can be adjusted effectively by MVTB control. Moreover, the resistor does not need to absorb power continuously; instead, it is just switched into operation for a while when a difference occurs, and the power loss can be decreased after the system recovers to a steady state. Finally, experimental results verify the effectiveness of the MVTB control. [ABSTRACT FROM PUBLISHER]

This paper presents a control scheme based on the predictive control theory and Petri nets (PNs) formalism to control a flying capacitor multilevel converter. The proposed scheme takes advantage of the benefits offered by the finite control set-model predictive control (FCS-MPC) methodology and the versatility of PNs to regulate the capacitor voltages and output current, simultaneously. The inclusion of PNs allows us to simplify the control scheme. A first PN is used to select, from a subset of switching states, the switching state that accomplishes both control objectives. This approach reduces the computational burden if compared with a typical predictive control scheme. Furthermore, a PN-based prediction scheme is used to predict the capacitor voltages. This prediction scheme uses only measurements of output voltage and current, which reduces the number of required sensors. This approach allows us to implement the internal capacitor voltages control independently if a multileg configuration is needed. The scheme is experimentally validated in a five-level flying capacitor multilevel converter. [ABSTRACT FROM PUBLISHER]

In this paper, an efficient zero-voltage-switching (ZVS) synchronous buck converter with extended duty cycle and low-current ripple is proposed for voltage regulator module (VRM) applications. By combining series capacitor and coupled inductors, operating duty cycle is extended considerably. Also, soft switching condition for all switches is provided without any auxiliary circuit and as a result, overall efficiency is improved. In addition, by complementary operation of the main switches of the interleaved modules, the resulting output current ripple is reduced. The converter operating modes are discussed and experimental results are presented to verify the theoretical analysis. [ABSTRACT FROM PUBLISHER]

In this paper, a simple control method of the half-bridge (HB) LLC converter with one additional switch and capacitor in the primary side is proposed for wide-input-voltage applications with the hold-up time conditions. At nominal input, since the proposed method enables the HB LLC converter to operate with large transformer magnetizing inductance, it can reduce the conduction and switch turn-off losses in the primary side, which makes it highly efficient. On the other hand, during the hold-up time, since the proposed method increases the resonant capacitance by turning on one additional switch, the HB LLC converter can obtain high-voltage gain. To confirm the validity of the HB LLC converter with the proposed method, a 325–385 V input and 56 V/350 W output laboratory prototype is built and tested. [ABSTRACT FROM PUBLISHER]

The majority of the industrial motor drive systems are equipped with the conventional line-commutated front-end rectifiers and being one of the main sources of harmonics in the power line. While a parallel combination of these drive units elevates current quality issues, a proper arrangement of them can lead to the cancellation of specific harmonics. This paper proposes a new cost-effective harmonic mitigation solution for multidrive systems using a predictive pulse pattern current modulation control strategy. The proposed technique applies suitable interaction among parallel drive units at the rectification stage to synthesize sinusoidal input currents. The input voltage sensing is avoided in order to minimize the number of required sensors, and the grid synchronization also has been implemented based on a common phase-locked loop (PLL) using the dc-link capacitor voltage ripple. Experimental results validate the effectiveness of the proposed strategy. [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]

In this paper, an improved model predictive control (MPC) of the modular multilevel converter (MMC) with reduced computational burden is proposed. A mathematical model of the MMC system based on the sum and difference of arm voltages are derived. Instead of determining the switching state of individual submodule (SM), the voltage levels of MMC are considered as control options based on the assumption that the SM capacitor voltages are well balanced. The further reduction of calculation effort is realized by using the tolerance band of capacitor voltages. The proposed MPC has a hierarchical structure. The cost function taking into account the ac-side current control, circulating current elimination and arm energy balancing is presented. The optimal voltage level, selected by the cost function, provides the voltage reference for the pulse width modulation modulator. The SM capacitor voltage balancing is done using a separate control loop. The proposed control strategy is investigated using an MMC high-voltage direct current system with 200 SMs in each arm in real-time simulation and hardware-in-the-loop tests. The performance of proposed method is verified by both steady-state and transient-state operations. [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]

This paper suggests a high-efficiency portable welding machine based on full-bridge converter with input-series-output-parallel (ISOP)-connected single transformer. Link voltage balance problem is theoretically analyzed according to deviations of transformer leakage inductances and transformer turns-ratios and simple voltage-balancing circuit using flying capacitor is introduced to remove this problem. Also, active-snubbing method is also proposed to improve overall efficiency by recovering parasitic resonant energy and regulating the voltage stress of rectifiers to the level that schottky diodes are available. The feasibility of the proposed structure has been verified with 17.5-kW welding machine with 60-kHz switching frequency. [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]

Phase-shifted carrier modulation is an industry standard in its application to multilevel H-bridge converters. The major advantage of this scheme over level-shifted and space vector modulation schemes is its inherent ability to evenly distribute losses between semiconductor devices. However, phase-shifted schemes suffer from harmonic degradation when operated at the low carrier frequencies required in high-power high-level number applications. This paper develops a model predictive modulation (MPM) scheme that achieves superior harmonic performance, compared to phase-shifted modulation, while ensuring equal semiconductor loss distribution. With respect to complete-enumeration-based predictive techniques, the proposed modulation significantly reduces the number of times the system cost function is evaluated. Reducing the number of calculations by several orders of magnitude ensures computational feasibility. Simulation and experimental results are presented, which confirm correct operation of the modulation strategy. [ABSTRACT FROM PUBLISHER]

This paper presents the new implementation of the finite control states set model predictive control (FS-MPC) applied to three-level four-leg flying capacitor converter (FCC) operating as a shunt active power filter (SAPF). The three main issues regarding the algorithm development are described and the solutions are proposed. The first is addressed to modeling of the four-wire system, which for simplification is based on wire-to-wire voltage equations. The second relates to the control of FCC by MPC, i.e., a proper interpretation of the FCC switching states and control of flying capacitor (FC) voltages, which was moved from the prediction loop. Finally, the system restriction regarding undesirable switching states’ transitions is explained and the solution is presented. The control performance was tested in the simulation model in MATLAB–Simulink and validated experimentally by measurements on the 10-kVA FCC laboratory setup. [ABSTRACT FROM PUBLISHER]

A new resonant converter having low voltage stress and nearly constant efficiency against line variation for high- and wide-input-voltage applications is presented in this paper. It is similar to a three-level zero-voltage-switching pulsewidth modulation converter (TL ZVS PWMC) with two flying capacitors. In the proposed converter, however, two flying capacitors are used as the resonant capacitors, and the output voltage regulation is achieved by frequency modulation. The main advantages of the proposed converter are that, since the sum of the voltages of two resonant capacitors is constant and is equal to half of the input voltage, the voltage across each switch clamps to half of the input voltage and keeps the balance. Moreover, all main switches and rectifier diodes are softly switched under full-line and full-load conditions, and high efficiency can be constantly achieved over a wide input voltage range. These advantages solve the drawbacks on TL ZVS PWMCs. The features, operation principles, and relevant analysis results over a wide input voltage range of the proposed converter are presented in this paper. The validity of this study is confirmed by the experimental results of a prototype converter with 400–600-V input, 48-V/10-A output, and 200-kHz resonant frequency. The experimental results show that the maximum efficiency of the proposed converter is 95.08% under a full-load and a 600-V input and slightly varies across the 400–600-V input voltage range. [ABSTRACT FROM AUTHOR]

In this paper, an integrated double buck–boost (IDBB) converter is proposed as a high-power-factor offline power supply for power-LED lamps. The IDBB converter features just one controlled switch and two inductors and is able to supply a solid-state lamp from the mains, providing high power factor and good efficiency. In this paper, the IDBB converter is analyzed, and a design methodology is proposed. It is demonstrated that, with a careful design of the converter, the filter capacitances can be made small enough so that film capacitors may be used. In this way, the converter mean time between failures can be made as high as that of the solid-state lamp. A design example for a 70-W converter supplied from a 230 V/50 Hz mains for street lighting applications is shown. Finally, experimental results from a laboratory prototype are also presented. [ABSTRACT FROM AUTHOR]

First, the limitations of the conventional interleaved boost converters in high-step-up and high-output-voltage applications are addressed in this paper. Then, a general derivation law of the nonisolated converters from their isolated counterparts is proposed and studied to give a universal solution for high-performance topology deduction. By employing the direct energy transfer concept, a family of nonisolated high-step-up interleaved boost converters is originated to make the turns ratio of a built-in transformer as another design freedom for the voltage gain extension. The derived converters have the advantages of large voltage conversion ratio, low power switch voltage stress, small input current ripple, and zero-voltage-switching soft-switching performance. The steady-state operation of the derived converter is analyzed, and the circuit performance is summarized to explore its advantages in the high-step-up, high-output-voltage, and large-current conversion systems. Finally, a 1-kW prototype with 40-V input and 380-V output voltages is implemented and tested to show the effectiveness of the derived converters. One of the main contributions of this paper is that a clear picture is made on the universal derivation law to generate high-step-up and high-performance dc/dc converters. [ABSTRACT FROM PUBLISHER]

The matrix converter can be used in a wide range of applications. Nevertheless, it does not yet represent a sufficiently mature option for industrialization. In order to resolve this problem, this paper examines the hardware of the matrix converter and identifies all the circuits that should be included in this. It also quantifies the operating conditions and provides practical guidelines for the step-by-step design of a matrix converter. These considerations are validated with experimental results. In this way, it can be said that this paper represents a step forward toward the development of reliable matrix converters for real applications. [ABSTRACT FROM AUTHOR]

This paper proposes a novel family of cascade three-level (TL) ac–ac direct converters based on ac switch cells, which transfer unsteady high ac voltage with distortion into regulated sinusoidal voltage with low total harmonic distortion (THD). The topological family includes buck TL–boost, buck–boost TL, and buck TL–boost TL modes. In order to achieve a reliable TL ac–ac conversion, a double transient voltage feedback control strategy of the output voltage and the voltage across the flying capacitor is introduced in this paper. A 500-VA 220-V \pm10% 50-Hz ac/220-V 50-Hz ac prototype is presented with the experimental results to prove that the converters have four improved advantages simultaneously, including lower voltage across power switches, bidirectional power flow, low THD of output voltage, and higher input power factor. [ABSTRACT FROM AUTHOR]

This paper investigates the buck–boost dc–dc converter and the energy transmission techniques in this kind of converter. In this paper, the critical inductance between the continuous conduction and discontinuous conduction modes are determined. In addition, the critical inductance equation between the complete inductor supply mode and incomplete inductor supply mode are calculated. The energy transmission technique and the output voltage ripple (OVR) of a buck–boost converter are analyzed in a specific range of the load and input voltage. The relations between the maximum OVR (MOVR) and the converter component parameters are deduced, and the minimum inductance value is calculated to ensure the MOVR minimization. Experimental and simulation results are used to prove the validity of the presented theoretical subjects. [ABSTRACT FROM AUTHOR]

This paper proposes a new space-vector pulsewidth modulation (SV-PWM) strategy for a three-level neutral point clamped inverter. The presented SV-PWM strategy makes it possible to control the neutral point voltage by optimum choice of switch sequence for any position and length of output voltage vector. The proposed solution takes into consideration the unbalance of the dc-link voltages. It also analyzes the influence of vector sequences on the predicted unbalance of the dc-link voltage. The solution allows selecting optimum vectors and their on-time durations in order to reduce quickly the dc-link voltage unbalance. The calculation of the space vector area proposed in this paper takes into consideration voltage unbalance and its influence on the length and position of vectors. The proposed approach assures properly generating the voltage output vectors, even in the case of the existing large voltage unbalance in the dc-link. The results of the experimental investigation of the proposed modulation strategy are presented in this paper. [ABSTRACT FROM PUBLISHER]

Multilevel power electronic converters have gained popularity in high-power applications due to their lower switch voltage stress and modularity. Cascaded H-bridge converters are a promising breed of multilevel converters which generally require several separate dc voltage sources. By utilizing the redundant switching states, it is possible to replace the separate dc voltage sources with capacitors and keep only the one with the highest voltage level. Redundancy in the charge and discharge modes of the capacitors is assumed to be adequate for their voltage regulation. However, the effects of the output current of the converter as well as the time duration of the redundant switching states have been neglected. In this paper, the impacts of the connected load to the cascaded H-bridge converter as well as the switching angles on the voltage regulation of the capacitors are studied. This paper proves that voltage regulation is only attainable in a much limited operating conditions that it was originally reported. In addition, based on the analysis of the converter, a simplified formula is found which can be used to find those modulation indices that regulate the voltage of the capacitor. This formula can be used in harmonic minimization problems while capacitor voltage regulation is ensured. Simulation and laboratory results are provided to confirm the analysis. [ABSTRACT FROM PUBLISHER]

In this paper, a direct ac–dc power electronic converter topology is proposed for efficient and optimum energy harvesting from low-voltage microgenerators. The converter utilizes the bidirectional current-conduction capability of MOSFETs to avoid the use of a front-end bridge rectifier. It is operated in discontinuous conduction mode and offers a resistive load to the microgenerator. Detailed analysis and modeling of the converter is presented. In such low-power applications, the power consumption of gate drive and control circuits should be minimal. In this paper, they are specifically designed to consume very low power. A suitable startup circuit and auxiliary dc supply circuit is proposed for the implementation of the converter. A low-voltage microgenerator is used to verify the performance and operation of the converter and the gate drive circuits. [ABSTRACT FROM AUTHOR]

This paper introduces a new magnetically coupled single-switch nonisolated dc–dc converter with a high-voltage gain. The topology utilizes magnetic coupling for boosting its output voltage, but unlike other converters with coupled magnetics, its voltage gain is increased by reducing its magnetic turns ratio. The name “Trans-inverse (Tx−1)” is thus used for representing this inverse operating principle of the converter. The converter draws a continuous current from the source and is, hence, suitable for many types of renewable sources. Its leakage energy from the coupled magnetics has further been recycled and transferred to the load by an integrated regenerative snubber circuit. Its inclusion of dc-current-blocking capacitors has also helped to prevent core saturation, which, together with other performance features, has been verified experimentally. [ABSTRACT FROM PUBLISHER]

In this paper, a cascaded H-Bridge (CHB)-multilevel converter (MC)-based photovoltaic (PV) system with no voltage or current sensors at the dc-side is proposed. Eliminating the dc-side sensors simplifies the hardware, leading to lower cost and higher reliability of the PV system. A novel scheme estimating the capacitors’ voltages from the ac output voltage of the inverter is developed. The scheme allows replacing all dc-side voltage sensors by a single-voltage sensor at the ac-side of the converter. Furthermore, the dc current sensors, conventionally required for the maximum power point tracking (MPPT), are also eliminated. Instead, the outputs from the capacitors’ voltage control systems are utilized for the MPPT. The effectiveness of the proposed dc-side sensorless system is experimentally demonstrated on a 2-kW single-phase seven-level CHB converter-based PV system. [ABSTRACT FROM PUBLISHER]

This paper presents a new dual-switch control structure for an ac/dc noninverting cascaded buck–boost power factor correction converter. The proposed converter operates at a discontinuous capacitor voltage mode providing an inherent high-power factor and a zero voltage turn-off switching. Additionally, the proposed control structure enables for a nondistorted sinusoidal current for a wide range of output voltage levels. Unlike the conventional methods, a mode detector is not required and consequently there is no hard transition between buck and boost modes. Although both converter switches are controlled, only one feedback control loop is required to obtain the desired power flow at a unity power factor. The principle of operation, theoretical analysis, simulation, and experimental results of a 1.6-kW prototype grid-connected converter are presented. The results confirmed the validity of the proposed system under various operating conditions. [ABSTRACT FROM PUBLISHER]

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]

Compared with constant duty cycle-controlled discontinuous conduction mode (DCM) boost power factor (PF) correction (PFC) converter, constant duty cycle-controlled quadratic DCM–DCM boost PFC converter features with much lower second-order line frequency output voltage ripple, and however, it suffers from low PF. To increase PF of quadratic DCM–DCM boost PFC converter, a variable duty cycle control technique for quadratic DCM–DCM boost PFC converter is presented in this paper. An approximation equivalent for the variable duty cycle is employed to simplify the implementation circuit. The corresponding expressions of PF and output voltage ripple are analyzed. For input voltage range of 100–240 Vac, quadratic DCM–DCM boost PFC converter with variable duty cycle control benefits with very high PF, and tradeoff between PF and output voltage ripple of this converter is analyzed. Experimental results from 100-W prototypes are given to verify the theoretical analysis. [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]

Modular multilevel converter (MMC) is a promising new topology for high-voltage applications. The MMC is made of several identical submodules. For proper operation, each submodule can be considered as a controlled voltage source where capacitor’s voltage should be maintained at a certain level. Besides, the minimization of the circulating current, which does not flow to the load, is crucial for achieving stable and efficient operation of the MMC. The interrelations among the load current, circulating current, and capacitor voltages complicate the MMC control. This paper aims to achieve stable and balanced voltage and current control with reduced circulating current in various operating conditions. The proposed control uses weighted model predictive control based on a normalized cost function to select the inverter switching patterns, which control the load current, while minimizing voltage fluctuation and circulating current. The weighting factors were selected based on minimizing the load-current total harmonic distortion (THD) and circulating current. The analysis is conducted on a low-power case study of single-phase four-cells MMC with possible extension to higher number of cells. The low-power three-level prototype is designed and built to validate this proposed method. Theoretical analysis, simulation, and experimental results are presented and compared. Parameter sensitivity analysis was also conducted. They all confirm the effectiveness of the proposed control method. [ABSTRACT FROM PUBLISHER]

In recent years, modular multilevel converters (MMCs) are very popular in medium/high-voltage motor drive systems and high-voltage direct-current (HVDC) applications. The conventional model predictive control (MPC) strategies for the MMC are not practical due to their substantial calculation requirements, especially under high number of voltage levels. To solve this problem, a fast MPC strategy combined with a submodule (SM)-voltage sorting balancing method is proposed based on the discrete mathematical model derived for the MMC in this paper. By optimizing the implementation of the control objectives and simplifying the rolling optimization, the proposed strategy is simpler to expand to a system with larger number of SMs, with the amount of calculation reduced and the advantages of the conventional MPC algorithm reserved. In addition, the proposed control can minimize the $dv/dt$ of the output voltages. Both steady-state and transient performances are evaluated by a down-scaled three-phase MMC prototype under various experimental conditions, which validates the proposed fast MPC strategy. [ABSTRACT FROM PUBLISHER]

The flying capacitor multilevel inverter (FCMLI) is one of the well-known structures of multilevel inverters having attracted considerable attention because of its merits. In spite of its many advantages, it has some limitations such as high volume and complicated control method because of its bulky capacitors and their voltage balancing requirement. Moreover, the high number of power semiconductors required makes this structure susceptible to failure. To increase the ratio of the number of levels to the number of components, an uneven distribution of capacitor voltages has been suggested in previous reports; however, this approach complicates the control method. Up to now, almost all presented methods suffer from high computational load and/or structure-dependent algorithm. In this paper, a simple state-based and structure-independent method is proposed for capacitor voltage regulation. The proposed method is straightforward and can perform online computation of switching sequences in a computationally efficient manner without any need for stored information or look-up tables. The method is conveniently extendible to any number of cells and levels in an FCMLI structure with arbitrary dc link voltage distribution schemes. Simulation and experimental results show the effectiveness and simplicity of this method. [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 common grounded Z-source dc–dc converter with high voltage gain is proposed for photovoltaic (PV) applications, which require a relatively high output–input voltage conversion ratio. Compared with the traditional Z-source dc–dc converter, the proposed converter, which employs a conventional Z-source network, can obtain higher voltage gain and provide the common ground for the input and output without any additional components, which results in low cost and small size. Moreover, the proposed converter features low voltage stresses of the switch and diodes. Therefore, the efficiency and reliability of the proposed converter can be improved. The operating principle, parameters design, and comparison with other converters are analyzed. Simulation and experimental results are given to verify the aforementioned characteristics and theoretical analysis of the proposed converter. [ABSTRACT FROM PUBLISHER]

Renewable sources like solar photovoltaic (PV) and fuel cell stack are preferred to be operated at low voltages. For applications such as grid-tied systems, this necessitates high voltage boosting resulting in efficiency reduction. To handle this issue, this paper proposes a novel high voltage gain, high-efficiency dc–dc converter based on coupled inductor, intermediate capacitor, and leakage energy recovery scheme. The input energy acquired from the source is first stored in the magnetic field of coupled inductor and intermediate capacitor in a lossless manner. In subsequent stages, it is passed on to the output section for load consumption. A passive clamp network around the primary inductor ensures the recovery of energy trapped in the leakage inductance, leading to drastic improvement in the voltage gain and efficiency of the system. Exorbitant duty cycle values are not required for high voltage gain, which prevents problems such as diode reverse recovery. Presence of a passive clamp network causes reduced voltage stress on the switch. This enables the use of low voltage rating switch (with low “on-state” resistance), improving the overall efficiency of the system. Analytical details of the proposed converter and its hardware results are included. [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]

A four-level open-end winding induction motor (OEWIM) drive is known to suffer from two perennial problems. One is the problem of zero-sequence currentin the motor phases, which is caused by the existence of zero-sequence voltage in them. The other is the overcharging of the dc-link capacitor of theinverter operated with lower dc-link voltage by its counterpart operated with a higher dc-link voltage. This paper investigates the applicability of aspecial variant of space vector pulse width modulation (SVPWM) scheme for a recently proposed power circuit configuration, in which arectifier–inverter combination is nested within the conventional two-level inverter configuration to achieve four-level inversion. This PWM schemeis named as the sample-averaged zero-sequence elimination (SAZE) SVPWM scheme, wherein the zero sequence voltage is suppressed in each sampling timeperiod in the average sense. Both of the aforementioned problems encountered in this drive are successfully overcome for this power circuit configurationby resorting to the proposed SVPWM strategy. [ABSTRACT FROM PUBLISHER]