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ABSTRACT The output AC side voltage of traditional full‐bridge inverter is lower than the input DC side voltage, which is limited in low‐voltage power generation. The conventional boost circuit and the modified boost circuit structure are effectively combined, thus putting forward a kind of no leakage current of single‐phase single‐stage booster inverter. The inverter has the characteristics of common ground, which can suppress the leakage current from the structure and avoid the problem of shoot‐through and improve the reliability of the system. The working mode, modulation strategy, and steady‐state performance of the proposed circuit structure are analyzed in detail. Finally, a 250‐W experimental prototype is designed in the laboratory, and the experimental results verify the feasibility and superiority of the proposed inverter. [ABSTRACT FROM AUTHOR]

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]

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]

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]

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]

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]

The series Z-source network, an expansion of the popular concept of the Z-source dc link, was originally proposed for boosting the output voltage of power electronic inverters. In this paper, that idea is extended on a three-phase indirect matrix converter. The converter is based on the ultrasparse matrix topology characterized by the minimum number of semiconductor switches. The series Z-source network is placed between the three-switch input rectifier stage and the six-switch output inverter stage in either the positive or the negative rail. A brief shoot-through state produces the voltage boost. An optimal pulsewidth modulation (PWM) technique is developed for higher boosting capability of the converter and minimization of switching losses. A comparison is made between the matrix converters employing series and conventional cascade Z-source networks. The inrush current and Z-source capacitor's voltage are reduced in the series Z-source matrix converter. Furthermore, the fast Fourier transform analysis of the output current of the converters suggests superiority of the series Z-source matrix converter over the cascaded Z-source matrix converter. [ABSTRACT FROM PUBLISHER]

This paper deals with the impedance source (Z-source) multiphase inverter, where the maximum constant boost control method is studied and analyzed in the general case of number of phases. On the other side the impact of the modulation index and the number of phases on the duty cycle shoot-through and on the gain of the output voltage ranges is presented. To validate advantages of the Z-source multiphase inverter, the proposed topology and the maximum constant boost control are implemented in simulation and in real time experimentation with Z-source five phase inverter. The output voltage is applied to two parallel loads, a five phase resistive load and a five phase induction machine. [ABSTRACT FROM AUTHOR]

In traditional Z-source inverter (ZSI) fed induction motor drives, the Z-source capacitor voltage and the motor terminal voltage are controlled by the shoot-through duty ratio and the modulation index, respectively. Modified voltage space vector has been proposed to improve motor terminal voltage control with effective DC boost in the DC link. For the same shootthrough duty ratio, modified voltage space vector provides better voltage boost in the DC link with reduced harmonics in the load side than the traditional voltage space vector. This paper presents an integrated control technique to minimise the electromagnetic torque ripples in the rotor of the ZSI-fed induction motor drives using modified voltage space vector. To improve the stability of the overall drive system, the motor terminal voltage alone is sensed instead of sensing the Z-source capacitor voltage and motor terminal voltage independently. This provides a single-stage controller for motor drive systems. The proposed induction motor drive system provides a better ride-through capability during voltage sags, better line harmonic profile, and minimisation of the torque ripples in the rotor. The proposed control technique is simulated using MATLAB/Simulink software, and analysis and experimental results have been presented to validate them. [ABSTRACT FROM AUTHOR]

In traditional control strategies, with three state transitions three equal interval shoot-through states can be added immediately adjacent to the active states per switching cycle for modulation of three-phase three-wire three-two leg Z-source inverters. The Z-source capacitor voltage is controlled by the shoot-through duty ratio and the output voltage is controlled by the modulation index, respectively. Modified space vector modulated (MSVM) control provides better AC output control with effective DC boost, but still it has two-stage controllers. The algorithm presented in this paper provides a modified voltage space vector with single-stage control having one degree of freedom with improved AC output voltage control and reduced harmonic profile. The simulation has been performed in Matlab/Simulink and the relative simulation results with traditional control method have been presented to validate the proposed algorithm. The integrated control algorithm using modified voltage space vector is presented in this paper and experimentally verified with Z-source inverter prototype in the laboratory. [ABSTRACT FROM AUTHOR]

In traditional Z-source inverter (ZSI) fed induction motor drives, the Z-source capacitor voltage and the motor terminal voltage are controlled by the shoot-through duty ratio and the modulation index, respectively. Modified voltage space vector has been proposed to improve motor terminal voltage control with effective DC boost in the DC link. For the same shootthrough duty ratio, modified voltage space vector provides better voltage boost in the DC link with reduced harmonics in the load side than the traditional voltage space vector. This paper presents an integrated control technique to minimise the electromagnetic torque ripples in the rotor of the ZSI-fed induction motor drives using modified voltage space vector. To improve the stability of the overall drive system, the motor terminal voltage alone is sensed instead of sensing the Z-source capacitor voltage and motor terminal voltage independently. This provides a single-stage controller for motor drive systems. The proposed induction motor drive system provides a better ride-through capability during voltage sags, better line harmonic profile, and minimisation of the torque ripples in the rotor. The proposed control technique is simulated using MATLAB/Simulink software, and analysis and experimental results have been presented to validate them. [ABSTRACT FROM AUTHOR]

This paper presents a new topology of uninterruptible power supply (UPS) by using a Z-source inverter, where a symmetrical LC network is employed to couple the main power circuit of an inverter to a battery bank. With this new topology, the proposed UPS can maintain the desired ac output voltage at the significant voltage drop of the battery bank with high efficiency, low harmonics, fast response, and good steady-state performance in comparison with traditional UPSs. The simulation and experimental results of a 3.kW UPS with the new topology confirm its validity. [ABSTRACT FROM AUTHOR]

We identified a failure mode in a two stage dc/ac converter, comprising a high-frequency dc/ac inverter followed by an ac/ac cycloconverter, both operating at the same switching frequency. The failure-mode is a short-circuit condition, which is a combined effect of the reverse recovery of the MOSFET body diode and simultaneous spurious turn-on of the bidirectional switches of the cycloconverter, owing to a significantly high dv/dt (>2 × 108 V/ns). A high dv/dt causes appreciable current to flow through the gate-to-drain (Miller) capacitance, thereby producing a significant amount of voltage drop across the external gate resistance. Consequently, the gate-to-source voltage of the power MOSFET may exceed the threshold voltage of the device, which turns the device on. We explain the mechanism for the dv/dt-related gate turn-on and present experimental results to validate the explanation. We also demonstrate, how a two-fold increase in the value of external gate resistance of the inverter switches (to reduce the dv/dt applied to the cycloconverter) reduces the periodicity of the short-circuit condition. [ABSTRACT FROM AUTHOR]

The zeta inverter has been used for single-phase grid-tied applications. For its use of energy storage systems, this paper proposes the bidirectional operation scheme of the grid-tied zeta inverter. A shoot-through switching state is introduced, providing reliable bidirectional operation modes. A shoot-through duty cycle is utilized for the bidirectional grid current control of the inverter. The grid current is bidirectionally controlled by the shoot-through duty cycle, which enables the inverter to operate with seamless change of operation modes. Over the state-of-the art techniques using flyback and Cuk inverter topologies, the grid-tied zeta inverter using the proposed operation scheme provides advantages of high efficiency, low cost, and high reliability. The operation principle is presented by describing the operation mode and control method for the grid-tied zeta inverter. A 500 W prototype has been built and tested to verify its operation principle. [ABSTRACT FROM AUTHOR]

In this paper, the performance of a new Z-source inverter (ZSI)-based single-stage power conditioning system (PCS) is analyzed for a standalone photovoltaic (PV) power generation system. The proposed ZSI-based PCS includes two main parts: one is the input from PV units and the other is the ZSI. In this work, a new topology, termed the switched inductor-assisted strong boost ZSI (SL-SBZSI), is introduced for improving the performance of the PCS. The proposed topology shows high boosting capability during the voltage sag in PV units due to variations in solar irradiation and temperature. Another key advantage is the reduced capacitor voltage stress and semiconductor switch voltage stress of the inverter bridge, which ultimately minimizes the size and cost of the single-stage PCS. The proposed ZSI topology falls under the doubly grounded category of inverter by sharing the common ground between the input and output. This is an additional feature that can minimize the leakage current of PV units at the ac output end. The operational principles, detailed mathematical modeling, and characteristics of the proposed SL-SBZSI for a standalone photovoltaic (PV) power generation system is presented in this paper for analyzing performance. The simulation results, which are performed in MATLAB/Simulink, demonstrate the improved performance of the proposed SL-SBZSI for the standalone PV system. The performance of the proposed topology is also evaluated through an experimental validation on a laboratory-based PV system. [ABSTRACT FROM AUTHOR]