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Photovoltaic (PV) is a promising way to meet the increasing global energy demand due to its sustainability, efficiency, and cost-effectiveness. For the wide-scale adoption of PV systems, converters with reliable input sources, stable control strategies and appropriate modulation techniques must be designed. In the literature, various modulation techniques have been developed that help to boost the voltage of the PV modules by implementing shoot-through (ST) in which the upper and lower switches of an inverter conduct simultaneously and short-circuit occurs. Various optimised modulation techniques have been implemented to enhance its performance. Among those, the quasi-Z-source inverter (qZSI) has attracted much attention due to its ability to achieve higher conversion ratios for grid-connected PV applications. In this paper, a detailed comparison of the modulation schemes for the qZSI PV systems has been done to understand the trade-off and select the most suitable approach. Upon the selection of the space vector modulation with unique switching sequences and rearranging upper ST and lower ST states, the inverter can achieve ST with reduced switching losses. Furthermore, a 600 VA three-phase grid-connected system utilizing a three-level neutral-point-clamped qZSI topology is modulated and simulated. It has been demonstrated that the constant boost control offers good performance in terms of reduced voltage stresses on switches, lower total harmonic distortion, and hence, higher efficiency.

Summary: This paper presents a new high voltage gain quasi Z‐source inverter consisting of a switched‐inductor unit. A coupled inductor including three windings is utilized in structure of the switched inductor in a way to increase voltage gain effectively. In addition, the configuration includes an active switch with low number of components that has positive effects on voltage gain and two of its components recycles stored energy of the coupled inductor similar to a clamp circuit. The converter boosts voltage appropriately in low shoot‐through duty cycles and transfers power with a continuous input current, leading to a reduction in losses, requiring smaller output filter and improving the efficiency. Also, the converter can operate in high modulation index for similar voltage gains compared to the other works which improves quality of outputs. Low number of components and fewer cores for inductors are considered during the design of the converter, causing some superiorities for it in comparisons. In addition, the presented converter has appropriate condition from the viewpoint of voltage stress on its diodes. To validate quality of the converter performance, a 240‐W prototype is prepared that converts 35‐ to 60‐V DC to three‐phase sinusoidal voltages where effective voltage of each phase is equal to 110 V. [ABSTRACT FROM AUTHOR]

Background and Objectives: The H-bridge (HB) driver design with high efficiency is one of the most challenging issues in power systems that drive AC/DC loads. HB driver circuit based upon complementary MOSFET type used as a driving system of DC motor, power converters, and battery charger for electrical vehicles. In Driving DC motors, dead-time (DT) generation has been considered a major factor such as preventive power line short-circuits (shoot-through) over high and low-side MOSFETs. In this paper, the HB driver is designed for linear actuators with consideration for the prevention of shoot-through. Methods: The propagation delay of logic gates are used to postpone the arrival gate drive signal for high/low side MOSFETs resulting in short circuit elimination on the DC source. Results: As mentioned, logic gates' propagation delay by their values causes interruption between the high and low-side power switches gate drive signal resulting in shoot-through elimination. Although the existence of DT influences the performance of the rotational speed and output torque of a DC motor by increasing the distortion and pulse interval, Linear actuators due to low-velocity linear motion do not require the PWM control, therefore DT has no substantial effect on driver performance. Conclusion: Simulation and experimental results validate the method proposed in this paper. According to the specifications of the circuit designed in this paper, for loads that do not need rotational speed control, logic gates with proper propagation delay can be chosen to eliminate short circuits in complementary MOS switches without requiring DT compensation methods. [ABSTRACT FROM AUTHOR]

Summary: In this paper, a new combined impedance‐source network inverter (CISI) with high voltage gain in low duty cycle is presented. With common ground between the input source and the inverter bridge and a continuous input current, the proposed converter is a suitable choice for renewable energy applications. The duty cycle of the inverter switches is low, leading to a reduction in losses and improving the efficiency. Also, due to the small duty cycle, the modulation index can be increased, and as a result, the quality of output voltages and currents is greatly improved. The proposed circuit has no switch in the input impedance network, and the number of components is reasonable compared to other works. Another advantage of the proposed converter is the low voltage stress on its capacitors and diodes. The proposed circuit is designed and tested at 180 W. The experimental results and the calculated values are close to each other, verifying the accuracy of the analysis. [ABSTRACT FROM AUTHOR]

This paper proposes a new PWM technique for a reduced-component-count active impedance network (RCC-AIN) three-level inverter to maximize the input/output (I/O) voltage gain. Although the max boost control (MBC) technique offers the same I/O voltage gain, it suffers from the drawback of low-frequency (LF) ripples of the source current. In contrast, the proposed PWM technique is a combination of improved MBC (IMBC) and a new switching state pattern that eliminates this drawback and offers up to 79% reduction in the peak-to-peak ripple value of the source current while maintaining the same I/O voltage gain as MBC. The cumulative sum of ripple components is used to find the exact maximum and minimum peaks of the source current over the fundamental period. The proposed switching pattern doubles the switching frequency of a boosting switch to limit the current spikes of capacitors during state change-over. The RCC-AIN topology was analyzed in various voltage-boosting techniques, and the proposed PWM technique utilizes the full potential of the RCC-AIN topology in a better way. The findings have been verified using theoretical calculations, simulation, and experimental results.

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Low voltage stress on the impedance source network devices is the main reason for the advent of DC-linked type quasi-switched boost inverters (DqSBIs). However, the DqSBI has become less attractive due to its low voltage gain. This paper presents a novel PWM control strategy for the DqSBI and its comparative performance evaluation to the conventional inverters. The modified PWM control strategy based DqSBI improves the voltage gain and reduces the conduction loss and the inductor current ripple. Circuit analysis and comparison study between the DqSBI, the quasi-Z-source inverters, and the two-stage inverter with a boost DC-DC converter are presented. 1-kVA three-phase inverter prototypes were set up to compare and evaluate the performance of the DqSBI with the improved PWM method for voltage gains of 0.85 to 1.6. The measured efficiency and total harmonic distortion (THD) values are also presented.

A grid-tied, single stage, three phase, PV system provides higher efficiency than a two-stage PV system. This paper presents a three-phase, single stage, grid-connected PV system with MPPT and reactive power injection capability into the grid using modified capacitor assisted extended boost quasi Z-source inverter (MCAEB q-ZSI) as the grid-tied PV inverter. The adaptability of the inverter for irradiance changes and the boost factor control with its shoot-through duty ratio adjustment made it highly recommended for the grid system. The shoot-through control technique like maximum constant boost control with a third harmonic injection enhances the performance of the inverter by reducing the low order ripples and voltage stress. The fuzzy voltage controller is proposed with the capacitor linearization algorithm to regulate the DC-link voltage. The current approach uses a fuzzy controller to control the real and the reactive power injection into the grid. The performance evaluation of the fuzzy and PI grid controller is carried out for the constant irradiance condition and from the investigation, parameters like boost factor (B), the shoot-through duty ratio(Ds), real power (P), reactive power (Q), power factor and harmonics in the current injection are determined. A laboratory setup of the PV powered grid system is implemented, tested and validated with the simulation results. ABSTRAK: Dalam sistem fotovoltaik (PV) yang bersambung dengan satu peringkat, satu sistem elektronik kuasa yang mempunyai keuntungan dan kecekapan yang tinggi diperlukan untuk menginterupasi dengan utiliti tersebut. Dalam makalah ini, kapasitor yang diubah suai dibantu oleh pemacu kuadratik Z-source yang dilanjutkan (MCAEB q-ZSI) bertindak sebagai unit interfacing antara PV dan grid. Penyesuaian penyongsang untuk perubahan sinaran dan kawalan faktor rangsangan dengan pelarasan nisbah tugas menembak membuatnya sangat disyorkan untuk sistem grid. Teknik kawalan menembak seperti kawalan rangsangan berterusan maksimum dengan suntikan harmonik ketiga meningkatkan prestasi penyongsang dengan mengurangkan aruhan pesanan rendah dan tekanan voltan. Pendekatan semasa menggunakan pengawal kabur untuk mengawal suntikan kuasa sebenar dan reaktif ke grid. Penilaian prestasi pengawal grid fuzzy dan PI dilakukan untuk keadaan iradiasi malar dan dari penyiasatan, parameter seperti faktor rangsangan (B), nisbah tugas menembak (Ds), kuasa nyata (P), kuasa reaktif Q), faktor kuasa dan harmonik dalam suntikan semasa ditentukan.

In this paper, a new topology for cascaded multilevel inverter based on quasi-Z-source converter is proposed. In the proposed topology the magnitude of output DC voltage is not limited to the sum of magnitude of DC voltage sources. Moreover, the reliability of the circuit due to capability of short circuit by Z-source network is increased. The quasi-Z- source converter in different modes is analyzed and the voltage gain is obtained. Also, the values of quasi-Z-source network components are designed. In the proposed topology, the number of DC voltage sources, the number of switches, installation area and cost in comparison with conventional multilevel inverters are significantly reduced. Three algorithms to determine the magnitude of DC voltage sources are proposed. Then the optimal structures for the minimum number of switches and DC voltage sources to generate the maximum voltage levels are presented. Moreover, the control method for the proposed topology is described. To verify the performance of the proposed topology, simulation and experimental results of proposed topology are presented.

SUMMARY In this paper, a high efficiency quasi‐Z‐source inverter with a single high‐frequency switch is proposed to achieve a high efficiency and more compact topology. The converter utilizes a single high‐speed GaN FET. In the proposed converter, four switches operate with low frequency sinusoidal pulse width modulation while the fifth switch short circuits the inverter switch‐legs with a high switching frequency and prepares the shoot‐through current path. The operation of the fifth switch in high switching frequency helps the inverter to operate with modulation index equal to unity. Also, the impedance network operates in high switching frequency, which makes it possible to decrease the components' size. The operation principles, efficiency, and switches' losses of the proposed converter are investigated analytically. A comparison between theoretical and simulation results is performed to validate the theoretical description of the inverter. To validate the well‐behavior of the inverter under various operation modes, the performance of the proposed converter is examined under different types of load. Moreover, loss breakdown and efficiency comparisons are utilized to show improvements with respect to the conventional inverter. The performance of the converter has been examined and validated through a 300 W prototype of the inverter. [ABSTRACT FROM AUTHOR]

The soft-switching buck inverter, which is mainly applied to solve the contradictions between the switching frequency and the shoot-through problem along with the dead-time effect, is proposed in this paper. A detailed analysis of the relationship between the range of the duty ratio to realize soft-switching as well as the additional voltage stress and the current stress is conducted. In addition, a 1 kW prototype is designed and established. Results of simulations and experiments verify the validity of the theoretical analysis. Furthermore, the proposed soft-switching buck inverter has a strong practical significance in situations where medium and high power outputs are required. [ABSTRACT FROM AUTHOR]

In this paper, a novel impedance network referred to as a high-gain switched-coupled-inductor quasi-Z-source network (hgSCL-qZSN) is presented. The proposed topology employs a two-winding switched-coupled-inductor and a switched-capacitor in the impedance network, which offers a higher voltage boost capability when compared to most of the existing ZS-based topologies. In addition, the proposed SCL-qZSN has a low peak magnetizing current, which leads to a smaller core volume. This, in turn, reduces costs as well as core/winding losses. Moreover, to produce higher voltage gains, the presented hgSCL-qZSN requires lower winding turn ratios and shoot-through (ST) ratios, which leads to lower voltage stresses on the passive and active components. A detailed theoretical analysis of the proposed topology is presented in this paper, followed by a number of experimental results. [ABSTRACT FROM AUTHOR]

During the short-circuit fault of a two-level bridge converter based on silicon carbide (SiC) metal–oxide–semiconductor field-effect transistors (MOSFETs), the SiC MOSFETs may fail within a few microseconds without short-circuit protection. The short-circuit protection of SiC MOSFETs is an essential feature for improving the reliability of converters. This study proposes an improved short-circuit protection method for medium-voltage SiC MOSFETs subjected to shoot-through conditions. In the protection method, the gate–source voltage of the SiC MOSFETs in a half bridge is detected to determine whether a shoot-through short circuit occurs or not. A desaturation protection circuit based on VDS measurement for a short circuit is also designed for overcurrent. The protection circuit's validity is verified by the experimental results. Compared with conventional commercial driver integrated circuits, the proposed method can detect and turn off SiC MOSFETs in 0.2 μs under the shoot-through condition. Desaturation protection can be completed in 0.5 μs when overcurrent occurs. [ABSTRACT FROM AUTHOR]

The family of DC-DC q-ZSCs is extended from two to three classes and four to six members. All the members were analyzed based on efficient duty ratio range (RDeff) and general duty ratio range (RDgen). Findings showed that similar to the traditional buck-boost converter (BBC), each of the topologies is theoretically capable of inverted buck-boost (BB) operation for the RDgen with additional advantages but differed according to class in how the gains are achieved. The new topologies have advantages of BB capability at the RDeff, continuous and operable duty ratio range with unity gain at D = 0.5 contrary to existing topologies where undefined or zero gain is produced. Potential applications of each class were discussed with suitable topologies for applications such as fuel cells, photovoltaic, uninterruptible power supply (UPS), hybrid energy storage and load levelling systems identified. [ABSTRACT FROM AUTHOR]

In this paper, an embedded half-bridge Z-source inverter based on gamma structure is proposed. In contrast with the classical half-bridge inverter, the proposed inverter can generate zero voltage levels in output. High voltage gain and low voltage stress on capacitors are the main advantages of the proposed converter. The value of the boost factor in the proposed structure is increased by changing both the shoot-through (ST) duty cycle and turns ratio of the transformer. The operating principle of the proposed converter in four operating modes is presented. We also calculate the critical inductance and compare the proposed converter with conventional topologies. In addition, power loss and THD analysis are presented. Finally, PSCAD/EMTDC software is used to verify the correct operation of the proposed inverter and the experimental results.

A new modulation strategy has been introduced in this paper in order to enhance the boost factor for the three-level quasi-switched boost T-type inverter (3L-qSBT2I). Under this approach, the component rating of power devices is significantly decreased. Moreover, the use of a larger boost factor produces a smaller shoot-through current. This benefit leads to reducing the conduction loss significantly. Furthermore, the neutral voltage unbalance is also considered. The duty cycle of two active switches of a quasi-switched boost (qSB) network is redetermined based on actual capacitor voltages to recovery balance condition. Noted that the boost factor will not be affected by the proposed capacitor voltage balance strategy. The proposed method is taken into account to be compared with other previous studies. The operation principle and overall control strategy for this configuration are also detailed. The simulation and experiment are implemented with the help of PSIM software and laboratory prototype to demonstrate the accuracy of this strategy.

In this paper, a new topology for cascaded multilevel inverter based on quasi-Zsource converter is proposed. In the proposed topology the magnitude of output DC voltage is not limited to the sum of magnitude of DC voltage sources. Moreover, the reliability of the circuit due to capability of short circuit by Z-source network is increased. The quasi-Zsource converter in different modes is analyzed and the voltage gain is obtained. Also, the values of quasi-Z-source network components are designed. In the proposed topology, the number of DC voltage sources, the number of switches, installation area and cost in comparison with conventional multilevel inverters are significantly reduced. Three algorithms to determine the magnitude of DC voltage sources are proposed. Then the optimal structures for the minimum number of switches and DC voltage sources to generate the maximum voltage levels are presented. Moreover, the control method for the proposed topology is described. To verify the performance of the proposed topology, simulation and experimental results of proposed topology are presented. [ABSTRACT FROM AUTHOR]

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

In this paper, a developed structure for DC–DC quasi-Z-source (QZS) converters is proposed. First, the proposed two-stage structure is presented and analyzed. Then, the proposed structure is extended to n stages and its relations are calculated. Compared with other conventional structures, the proposed structure has higher voltage gain and higher reliability. The proposed topology is suitable for high power applications. To have the correct performance of conventional QZS converter, all impedance network elements must be intact. In the case of small failure in one of the elements, the operation of the whole system is disrupted. The proposed structure has high reliability because when one stage fails, the fault management system separates that stage from the other stages and the remaining stages continue to transmit power. In this paper, in addition to analyzing the operation of the proposed converter in different operating modes, calculations of voltage gain, voltage stresses across capacitors and reliability analysis are also presented. Reliability is calculated according to well-known Markov model. Moreover, a comprehensive comparison in terms of voltage gain and reliability is made between the proposed converter and the other conventional structures. Also, the rating values of inductors and capacitors are designed. Finally, experimental and simulation results are presented by using power system computer-aided design (PSCAD) software to verify the theories. [ABSTRACT FROM AUTHOR]

Summary: In this paper, 2 types of half‐bridge quasi‐Z‐source inverters with detailed analysis are proposed. Unlike the classical half‐bridge inverter, both types of proposed half‐bridge inverters can generate zero voltage level in output. Moreover, lack of continuous input current in conventional half‐bridge inverters is resolved by the second type of proposed inverters. One of the important advantages of proposed inverters is using the 1 impedance network only with 2 capacitors and 2 inductors; whereas, most of the half‐bridge Z‐source inverters have more than 1 impedance network or use additional semiconductor elements. In this paper, operation principles of proposed inverters in different operating modes are discussed. Then, design considerations and calculation of critical Inductance in boundary conditions between 2 different states are provided. Next, power circuit of general topology with multiple DC sources and derivation of subcircuits are proposed. Finally, to verify validity of derived equations, simulation results using PSCAD/EMTDC software and experimental results are provided. In this paper, 2 types of half‐bridge quasi‐Z‐source inverters with detailed analysis are proposed. Unlike the classical half‐bridge inverter, both types of proposed half‐bridge inverters can generate zero voltage level in output. Moreover, lack of continuous input current in conventional half‐bridge inverters is resolved by the second type of proposed inverters. One of the important advantages of proposed inverters is using the 1 impedance network only with 2 capacitors and 2 inductors. [ABSTRACT FROM AUTHOR]

Summary: This paper presents a new topology of the input current continuous switch boost inverter (ICCSBI) and a perturbation observation with hysteresis comparator method. Because the traditional inverter needs to join the dead time to avoid short circuit, the dead time will cause distortion of the output current. And the traditional inverter is not suitable for photovoltaic power generation because it is a buck converter. The ICCSBI structure improves the booster circuit, which refers to the Z‐source inverter. It can get higher voltage than traditional inverter. Meanwhile, the ICCSBI not only retains the advantages of the Z‐source inverter but also reduces the number of passive components. In addition, the hysteresis band comparator is added to the perturbation observation method to make the system better robustness at the maximum power point of the photovoltaic system. In the photovoltaic system, to ensure the output current stable, the current control method is added to the ICCSBI. Finial, the experimental results are presented to demonstrate the new topology and control method. The input current continuous switch boost inverter has high voltage gain. The control strategy does not need to add dead time. This control strategy can avoid short circuit problem caused by dead time too short. The maximum power point tracking is more accurate and stable at the maximum power point. [ABSTRACT FROM AUTHOR]

Abstract The paper presents an alternative scheme using fuzzy logic methodology to control a grid-connected photovoltaic system through ZSI using MCBC method. The system model and control are implemented using MATLAB-SIMULINK simulation toolbox. In view of control, Fuzzy Logic Controllers (FLCs) are designed to enhance the system stability. To ensure a unity power factor operation, the inverter modulation index is controlled to manage the phase current of the grid. Also, the control in the shoot-through ratio controls the output voltage of the PV array, so the maximum power (MP) is extracted. The simulation results using FLCs are compared with others obtained using Proportional Integral (PI) controllers. This is under the same normal operating and transient conditions which are irradiation variation, three-phase short circuit fault at point of connection and voltage variation of the grid. The simulation results of FLCs achieve supplementary enhancement of the system stability over various operating conditions. [ABSTRACT FROM AUTHOR]

In this paper, a new topology for boost Z-source inverterbased on switched-inductor cell is proposed. The operating modes of the proposed inverter are analyzed and also a suitable control method to generate the trigger signals of the inverter is presented. Having a common earth between the input source and inverter and capability to generate a higher voltage gain by using lower amounts of the duty cycles are some advantages of the proposed Z-source inverter. Comparison of the proposed inverter with conventional Z-source inverters is presented from different points of the view. Finally, the accuracy performance of the proposed inverter is reconfirmed through the simulation results in EMTDC/PSCAD software program.

In recent years, the three-level T-Type inverter has been considered the best choice for many low and medium power applications. Nevertheless, this topology is known as a buck converter. Therefore, in this paper, a new topology incorporating the dc-link type quasi-switched boost network with the traditional three-level T-type inverter is proposed to overcome the limit of traditional three-level T-Type inverter. The space vector pulse width modulation scheme is considered to control this topology, which provides some benefits such as enhancing modulation index and reducing the magnitude of common-mode voltage. For this scheme, the zero, medium, and large vectors are utilized to generate the output voltage. The shoot-through state which is adopted by turning on all power switches of inverter leg is inserted into zero vector to boost the dc-link voltage. As a result, there is no distortion at the output waveform. The control signal of intermediate network power switches is also detailed to improve the boost factor and voltage gain. As a result, the voltage stress on power devices like capacitors, diodes, and switches is decreased significantly. To demonstrate the outstanding of proposed structure and its control strategy, some comparisons between the proposed method and other ones are performed. Simulation and experimental prototype results are conducted to verify the accuracy of the theory and effectiveness of the inverter.

This paper proposes a new single-phase single-stage switched-boost inverter with four switches. Like the quasi-Z-source inverter and quasi-switched boost inverter (qSBI), the proposed inverter has the main features as continuous input current, buck/boost voltage with single-stage conversion, and shoot-through immunity. Compared to the qSBI, the proposed inverter uses one more capacitor and one less switch. This paper presents the operating principles, pulse-width modulation control strategy, parameter design guidelines, and simulation results for the proposed inverter. To verify the performance of the proposed inverter, an 800-W prototype was built with an 110 V/50 Hz output voltage in stand-alone and grid-connected modes. The simulation and experimental results matched those of the theoretical analysis. [ABSTRACT FROM AUTHOR]

Several single-stage topologies have been introduced since kicking off the three-phase Z-source inverter (ZSI), and among these topologies, the quasi-ZSI (qZSI) is the most common one due to its simple structure and continuous input current. Furthermore, different modulation strategies, utilizing multiple reference signals, have been developed as well. However, prior art modulation methods have some demerits, such as the complexity of generating the gate signals, the increased number of switch commutations with continuous commutation at high current level during the entire fundamental cycle, and the multiple commutations at a time. Hence, this paper proposes two modified space vector modulation strategies, aimed at the reduction of the qZSI number of switch commutations at high current level for shorter periods during the fundamental cycle, i.e., reducing the switching loss, simplifying the generation of the gate signals by utilizing only three reference signals, and achieving a single-switch commutation at a time. These modulation strategies are analyzed and compared to the conventional ones, where a reduced-scale 1-kVA three-phase qZSI is designed and simulated using these different modulation strategies. Finally, the 1-kVA three-phase qZSI is implemented experimentally to validate the performance of the proposed modulation strategies and verify the reported analysis. [ABSTRACT FROM PUBLISHER]

The simple boost control (SBC) method is usually used to control the shoot-through state in a single-phase single-stage quasi-switched boost inverter (qSBI). This paper proposes a new pulse-width modulation (PWM) control scheme to improve the modulation index for the qSBI. The advantages of the proposed method for the qSBI over the conventional SBC method are as follows: 1) the modulation index is larger; 2) the voltage stress on the capacitor, diodes, and switches is reduced significantly; 3) the high-frequency peak-to-peak inductor current and capacitor voltage ripples are smaller; 4) the shoot-through current is lower; and 5) the efficiency is higher. The operating principles and circuit analysis for the proposed PWM control scheme are shown. To verify the performance of the proposed PWM control method, a 400W prototype was built with a 110 V/50 Hz output voltage. The experimental results matched those of the theoretical analysis. [ABSTRACT FROM PUBLISHER]

Nine-switch inverter with two sets of three-phase outputs is an improved topology proposed in place of the 12-switch back-to-back converters and has therefore attracted much attention in recent years. This inverter can be used with two conventional pulse width modulation approaches: different frequency and the constant frequency. One disadvantage of using this modulation method is the possibility of short-circuits in the legs (shoot-through), which decreases the reliability of converter and system. This paper presents a new modulation technique, in which switching pulses of nine-switch inverter are produced by not only the original carrier signals but also through two auxiliary carrier signals. In this method, adjustable three-phase voltages are produced in the inverter’s terminals, and so there is no possibility of any shoot-through in the inverter’s legs. The suggested reliable modulation approach does not rely on any information about the load polarity, as switching is performed by a simple and reliable algorithm. The result is the considerably better waveform quality of the output voltages in comparison with other methods. To verify the analysis, an experimental platform based on DSP is built. The simulation and experimental results are given to demonstrate the effectiveness and feasibility of this new approach. [ABSTRACT FROM AUTHOR]

In this paper, a new topology for cascaded multilevel inverters based on quasi Z-source converter is proposed. In the proposed topology, the magnitude of output voltage is not limited to dc voltage source, while the magnitude of output voltage of conventional cascaded multilevel inverters is limited to dc voltage source. In the proposed topology, the magnitude of output voltage can be increased by controlling the duty cycle of shoot-through (ST) state, transformer turn ratio, and the number of switched inductors in the Z-source network. As a result, there is no need for extra dc-dc converter. In the proposed topology, the total harmonic distortion (THD) is decreased in comparison with the conventional Z-source inverters. The proposed topology directly delivers power from a power source to load. In addition, in the proposed basic unit, higher voltage gain is achieved in higher modulation index which is an advantage for the proposed base unit. The performance of the proposed topology is verified by the experimental results of five-level single-phase inverter. [ABSTRACT FROM AUTHOR]

A double closed-loop control structure of a three-phase voltage-type PWM rectifier is designed by using the control strategy of feed-forward decoupling. At the same time, the three-phase PWM rectifier for high power can lead to the bridge shoot-through because of external or other electromagnetic interference, which is possible to burn the IGBT. In order to solve the problem an improved scheme of three-phase PWM rectifier is proposed in this paper, in which a diode is added to the circuit and then a loop between the output capacitor and the IGBT of shoot-through arm can not be formed, when the bridge arm is straight through, to ensure the IGBT is not threatened. The simulation results of the three-phase PWM rectifier and the improved three-phase PWM rectifier are verified by Matlab simulation. The superiority of the improved three-phase PWM rectifier is verified. The experimental prototype shows that the designed system is feasible. [ABSTRACT FROM AUTHOR]

Este trabalho apresenta o cálculo dos esforços de corrente nos semicondutores do inversor fonte Z trifásico operando com a modulação Boost Simples. O inversor fonte Z possui uma malha de impedância conhecida como malha Z, que possibilita realizar as funções CC-CC elevador e CC-CA em um único estágio. Por possuir essa característica, este conversor se torna uma opção interessante em aplicações com células fotovoltaicas. Serão apresentadas as etapas de operação e as equações que regem o funcionamento do inversor operando com a modulação Boost Simples para que se possa entender o desenvolvimento do equacionamento dos valores médio e eficaz nos semicondutores. A etapa Boost é definida por uma nova etapa conhecida como shoot-through, em que os semicondutores do mesmo braço conduzem simultaneamente. Esta característica altera profundamente o comportamento das correntes, exigindo um cálculo complexo dos esforços. Para validar os cálculos, os resultados teóricos são comparados com os resultados obtidos na simulação, assim como os dados experimentais.

This paper presents a three-phase multilevel quasi-Z-source inverter (qZSI) topology operating in normal and fault-tolerant operation mode. This structure is composed by two symmetrical quasi-Z-source networks and a three-phase T-type inverter. Besides the intrinsic advantages of multilevel voltage source inverters, the proposed structure is also characterized by their semiconductor fault tolerance capability. This feature is only obtained through changes on the modulation scheme after the semiconductor fault and does not require additional extra-phase legs or collective switching states. In certain fault types, the reduction of the output power capacity will be compensated by the boost characteristic of the qZSI. The fault-tolerant behavior of the proposed topology is demonstrated by several simulation results of the converter in normal and fault condition. To validate the characteristics of this multilevel qZSI, an experimental prototype was also built to experimentally confirm the results. [ABSTRACT FROM PUBLISHER]