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To support the development of high-frequency ac microgrids in terms of compact design, high-voltage gain and low total harmonic distortion (THD), a buck–boost dual-leg-integrated step-up inverter is proposed in this paper. The inverter is formed by integrating a buck–boost converter into a conventional single-phase full-bridge inverter by sharing the upper switch and the body diode of the lower switch in both bridge-legs. Consequently, the component count is significantly reduced over the step-up inverter counterparts. In addition, to address the drawbacks of hybrid modulation methods adopted by existing dual-leg-integrated inverters, such as double-variable control, and high THD of output voltage/current at high input voltage and heavy load conditions, unipolar frequency doubling sinusoidal pulse width modulation scheme is adopted in this inverter. As a result, the modulation ratio M becomes the only control variable to regulate the output voltage/current and the control is simplified. The THD of the proposed inverter output can remain low throughout the entire input voltage range and load power range. This paper presents the topology derivation procedure, operation principle, and steady-state characteristics of the proposed inverter. To validate the effectiveness of theory, experimental results of a 400 W hardware prototype, where the output voltage frequency is at 500 Hz, are reported. [ABSTRACT FROM PUBLISHER]

This paper presents a new four-quadrant (4Q) boost-type converter with the use of active virtual ground (AVG) technology. The presented topology can step up the ac grid voltage to a regulated dc voltage under a stable bidirectional current flow and support the power transmission in either real power or reactive power delivery. With the use of the proposed modulation method, only two high-frequency switches are required through the 4Q operation. Under a full-bridge converter structure, an efficient system can be guaranteed. Also, benefiting from the AVG technology, an LCL filter is formed at the system input over the 4Q operation. Both magnitude of leakage current and grid current ripple are also minimized to a small value. Thus, a high-efficiency and low-noise 4Q converter is guaranteed. The presented topology is successfully implemented on a 750 VA prototype and the performance is experimentally verified on it, which shows good agreement with the theoretical knowledge. [ABSTRACT FROM AUTHOR]

Aimed at the problem that the auxiliary commutation circuit (ACC) of auxiliary resonant commutated pole (ARCP) inverters has a high loss in commutation processes, this paper presents a novel modulation strategy with shunt dead time based on a double ARCP (DARCP) inverter. In comparison with the original modulation strategy, this modulation strategy cannot only achieve soft switching for all switches, but also avoid the superposition of resonance current and load current at commutation moments in double ACCs (DACCs) and make the maximum current through DACCs approximately equal to load current in commutation processes. So, the circulating current loss in DACCs and the current stress of auxiliary switches can be effectively reduced. According to the equivalent circuits in different operation modes under the novel modulation strategy, this paper analyzes the operation principle, soft-switching implementation condition, and optimal parameter design procedure of the DARCP inverter. Finally, a 10-kW–16-kHz DARCP inverter prototype with insulated gate bipolar transistor-based switches is built. Experimental results are given to demonstrate the validity and features of the DARCP inverter under the novel modulation strategy. [ABSTRACT FROM AUTHOR]

A variable switching frequency space vector modulation control method is proposed in this paper. It is used to achieve zero-voltage switching (ZVS) for two parallel 180° interleaved three-phase grid-connected voltage-source inverters at unity power factor. A wide range of ZVS can be achieved without any additional sensor, auxiliary circuit, or current zero-crossing detection circuit. The carrier wave frequency is easy to be calculated and updated with digital control. The current ripple is precisely predicted and controlled to minimize unnecessary circulation loss. The high current ripple at the inverter side can be considerably canceled by the parallel interleaved configuration. LCL filter is used to further attenuate the current ripple and improve the power quality at the grid side. The switching loss can be significantly reduced especially by using a wide bandgap device with low turn-off loss. The power density is greatly improved owing to the high switching frequency and low component parameters of the filter. A 4.5-kW simulation and experimental prototype interfacing 400 V dc with a three-phase 110-V ac grid is developed to verify the performance of the proposed control strategy. [ABSTRACT FROM AUTHOR]

This paper proposes a switching strategy for the Z-source inverter (ZSI), which has unequal short-through intervals to reduce the current ripple in the inductor of its impedance source. A size reduction of the inductor of the ZSI is one of the important issues in improving the power density of the ZSI, and the inductor current ripple reduction is required to achieve it. The proposed method can reduce the inductor current ripple by 27.8% compared with the conventional method that has equal short-through intervals without increasing the number of inverter switching. The proposed operation and ripple reduction were confirmed in experiments with a 3-kW-class laboratory prototype. Its result agreed to the calculated results, and it was confirmed that there is no increase in circuit losses caused by the application of the proposed method. [ABSTRACT FROM AUTHOR]

A new space vector modulation, i.e., ZSVM3, for three-phase quasi-Z-source rectifier (qZSR) is proposed. All switches in the three-phase bridge can be turned on and turned off with zero current or zero voltage using the proposed ZSVM3 with no auxiliary circuit. The current through the inductors of the quasi-Z-source network operates in a boundary conduction mode or discontinuous conduction mode to achieve all freewheeling diodes turned off with zero-current switching (ZCS). At the same time, the switch in the quasi-Z-source network can be turned on with ZCS. Besides, the voltage stress of all switches is equal to dc-link voltage. The operation principle of the qZSR is analyzed in detail, and the calculated value of the quasi-Z-source inductor is given. The proposed theory in this paper is verified by a 2-kW prototype. [ABSTRACT FROM PUBLISHER]

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

This paper describes novel single-phase solutions with increased inverter voltage levels derived by means of a nonstandard inverter configuration and impedance source networks. Operation principles based on special modulation techniques are presented. Detailed component design guidelines along with simulation and experimental verification are also provided. Possible application fields are discussed, as well as advantages and disadvantages. Finally, future studies are addressed for the new solutions. [ABSTRACT FROM PUBLISHER]

The conventional current-source inverter has two major problems: unidirectional power flow and voltage boost operation, which make it impossible to be used in many applications, such as hybrid electric vehicles and general-purpose variable-speed motor drives. Z-source inverters (ZSIs) can solve both problems. Quasi-ZSIs (qZSIs) were recently proposed as an important improvement to traditional ZSIs. Besides the advantages inherited from ZSIs, qZSIs also have several of their own merits. This paper presents a comprehensive study on the new features of current-fed qZSI, including the advantageous buck–boost function, improved reliability, reduced passive component ratings, and unique regeneration capability. The current-fed qZSIs are bidirectional with an additional diode, unlike the voltage-fed ZSI that needs a switch to achieve bidirectional power flow. A modified space vector pulse-width-modulation method is proposed, and the available operating regions for motoring and regeneration operation are analyzed in this paper. Since the current-fed qZSI has the same operation as the current-fed ZSI, many results of this paper are also applicable to the current-fed ZSI. A reverse-blocking insulated-gate bipolar-transistor-based current-fed qZSI prototype was developed in the laboratory. Simulation and experimental results are shown to verify the theoretical analysis. [ABSTRACT FROM PUBLISHER]

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

This paper proposes a new topology named the active-switched-capacitor/switched-inductor quasi-Z -source inverter (ASC/SL-qZSI), which is based on a traditional qZSI topology. Compared to other qZSI-based topologies under the same operating conditions, the proposed ASC/SL-qZSI provides higher boost ability, requires fewer passive components such as inductors and capacitors, and achieves lower voltage stress across the switching devices of the main inverter. Another advantage of the topology is its expandability. If a higher boosting rate is required, additional cells can easily be cascaded at the impedance network by adding one inductor and three diodes. Both the simulation studies and the experimental results obtained from a prototype built in the laboratory validate proper operation and performance of the proposed ASC/SL-qZSI. [ABSTRACT FROM AUTHOR]

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

The quasi-Z-source cascaded multilevel inverter (qZS-CMI) presented many advantages over conventional CMI when applied in photovoltaic (PV) power systems. For example, qZS-CMI provides the balanced dc-link voltage and voltage boost ability, saves one-third modules, etc. However, current research studies only disclosed control of single-phase qZS-CMI-based PV power systems, and there was no literature related to control of three-phase qZS-CMI-based PV power systems. In this paper, for the first time, three-phase qZS-CMI's control is proposed and demonstrated for application to PV power systems. The models of PV-panel-fed qZS H-bridge module and qZS-CMI-based PV power system are built to accurately design control algorithms for each module and the whole system. The proposed control method includes the distributed maximum power point tracking for each module, dc-link peak voltage balance control for all modules, and grid-tie control for the whole system; moreover, a new multilevel space vector modulation method is proposed for the three-phase qZS-CMI. Simulation and experimental results on a test bench with a three-phase seven-level qZS-CMI-based PV power system verify the proposed control and modulation methods. [ABSTRACT FROM PUBLISHER]

The voltage range of a renewable energy source, such as the photovoltaic cell, is influenced by the environment, light, temperature, and so on. The power conditioning system should adapt to the wide input voltage and have buck–boost ability. Based on the structure of the “ac/ac unit,” this paper presents a novel active buck–boost inverter (ABI) topology suitable for wide-range input, which can realize buck–boost conversion in a quasi-single-stage inverter. The ac/ac unit composed of active switches is utilized to perform voltage boost without introducing additional passive elements, which is in favor to the system power density and efficiency. Operational analysis in buck and boost modes are presented, and the modulation strategy applied in the ABI is also developed. Simulation and experimental results are presented to verify the operational principle and its modulation strategy. [ABSTRACT FROM PUBLISHER]

This paper presents a novel direct current-fed interleaved phase-modulated single-phase unfolding inverter for fuel-cell applications. Two active-clamped zero-voltage switching current-fed half-bridge isolated converters are interleaved in parallel input and series output configuration. Phase modulation is proposed to control these two converter cells, which generate a rectified sinusoidal pattern at the dc link. A simple H-bridge unfolding dc–ac inversion is used to produce single-phase sine voltage at line frequency switching using square-wave control. This not only simplifies the inversion stage in terms of modulation but also reduces the switching losses. Direct front-end current-fed based unfolding inverter is not reported in literature yet. Detailed analysis and design of the proposed direct current-fed single-phase unfolding inverter has been presented. Simulation waveforms using PSIM 9.0.4 are given to verify the presented analysis and design. Experimental results on a laboratory prototype rated at 200 W are demonstrated to support the investigation, to validate the accuracy of the proposed analysis and design, and to test the performance. [ABSTRACT FROM PUBLISHER]

In this paper, a multilevel current-source inverter (MCSI) topology is analyzed. The issue of constructing a novel modular single-rating inductor MCSI is explored, taking advantage of the features of field-programmable gate arrays (FPGA) for control and gate signal generation. The proposed topology is built with identical modules where all inductors carry the same amount of current, simplifying the construction and operation of industrial applications with higher efficiency. A new state-machine approach, which is easy to implement in an FPGA, and a proper implementation of the phase-shifted carrier sinusoidal pulse width modulation (PSC-SPWM) allow both current balance in all modules and effective switching-frequency minimization. The performance of the MSCI proposed is simulated with Matlab and is verified by constructing a prototype. [ABSTRACT FROM PUBLISHER]

In this paper, a novel single-phase five-level inverter is proposed using coupled inductors. This inverter can output five-level voltage with only one dc source. No split of the dc voltage capacitor is needed, totally avoiding the voltage balancing problem in conventional multilevel inverters. The level of the output voltage is only half of the dc-link voltage in all conditions, leading to much reduced dv/dt . This inverter is based on the widely used three-arm power module and the voltage stresses on all the power switches are the same, making it very easy to construct. Operation mechanism of this inverter is analyzed and the possible switching patterns are investigated. Based on these analyses, a novel optimized modulation scheme is presented. With this modulation method, no dc components exist in the inductor currents, which is very helpful for minimization of the inductors. Simulation and experimental results show the validity of the proposed inverter together with the optimized modulation scheme. [ABSTRACT FROM AUTHOR]

This paper proposes a bidirectional buck-boost cascade inverter and presents its modeling and control methods. The proposed inverter can be seen as the cascade of a buck converter and a boost converter, both with bipolar outputs. The buck stage maintains the main inductor current and the boost stage controls the output voltage to track a given reference. With detailed analysis, the switching function model is established, which reveals that the inverter has an extra control freedom for achieving high performance. Then, the averaged model for control is given and thereby the buck-boost capability is proven. Afterward, utilizing the feedforward compensation technique, a decoupled control scheme is designed. A new modulation strategy is also proposed to minimize the dead time effect. By simulations and experiments, it is verified that the proposed system possesses the following features: 1) bidirectional operation with bipolar buck-boost output voltage; 2) reduced output distortion due to advanced modulation minimizing the dead time effect; 3) reduced size and weight with only one main energy storage component; 4) decoupled linear controller design; and 5) good steady-state and dynamic performance including wide operation range, strong robustness to load and input voltage variations, fast dynamic response, and excellent overload protection. [ABSTRACT FROM AUTHOR]

A novel switched-capacitor inverter is proposed. The proposed inverter outputs larger voltage than the input voltage by switching the capacitors in series and in parallel. The maximum output voltage is determined by the number of the capacitors. The proposed inverter, which does not need any inductors, can be smaller than a conventional two-stage unit which consists of a boost converter and an inverter bridge. Its output harmonics are reduced compared to a conventional voltage source single phase full bridge inverter. In this paper, the circuit configuration, the theoretical operation, the simulation results with MATLAB/SIMULINK, and the experimental results are shown. The experimental results accorded with the theoretical calculation and the simulation results. [ABSTRACT FROM PUBLISHER]

This paper extends the impedance-source (Z-source) inverters concept to the transformer-based Z-source (trans-Z-source) inverters. The original Z-source inverter (ZSI) employs an impedance network of two inductors and two capacitors connected in a special arrangement to interface the dc source and the inverter bridge. It has buck and boost function that cannot be achieved by traditional voltage-source inverters and current-source inverters. In the proposed four trans-Z-source inverters, all the impedance networks consist of a transformer and one capacitor. While maintaining the main features of the previously presented Z-source network, the new networks exhibit some unique advantages, such as the increased voltage gain and reduced voltage stress in the voltage-fed trans-ZSIs and the expanded motoring operation range in the current-fed trans-ZSIs, when the turns ratio of the transformer windings is over 1. Simulation and experimental results of the voltage-fed and the current-fed trans-ZSIs are provided to verify the analysis. [ABSTRACT FROM AUTHOR]