Three-level neutral-point-clamped quasi-Z-source inverter with reduced Z-source capacitor voltage
01 Feb 2017-Electronics Letters (The Institution of Engineering and Technology)-Vol. 53, Iss: 3, pp 185-187
TL;DR: In this article, a new three-level neutral-point-clamped quasi-Z-source inverter topology is proposed to reduce the Z-source network capacitance voltage stress and inhibit the start inrush current.
Abstract: A new three-level neutral-point-clamped quasi-Z-source inverter topology is proposed. The topology can effectively reduce the Z-source network capacitor voltage stress and inhibit the start inrush current, thus low-voltage capacitors can be selected to reduce the volume and cost of the inverter. In addition, the changed structure will not affect the boost ability and all existing modulation methods can be used directly. The proposed topology is validated by simulations.
Citations
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TL;DR: A closed-loop control of the ac load voltage in the fuel-cell or photovoltaic applications based on the proposed inverter is realized, in order to supply a desired voltage to the critical load in islanding mode of a microgrid.
Abstract: This paper presents the topology and modulation technique of a three-phase three-level modified Z-source neutral-point-clamped (MZS-NPC) inverter, which combines a modified Z-source impedance network and a three-phase three-level NPC inverter. The boost factor of the proposed MZS-NPC inverter is twice as high as the three existing representative topologies combing an impedance network with a three-level NPC inverter. A modulation scheme for the proposed topology, based on a maximum boost control method, is designed to achieve the maximum voltage gain with simple implementation and to balance the dc-link neutral-point voltage. A closed-loop control of the ac load voltage in the fuel-cell or photovoltaic applications based on the proposed inverter is realized, in order to supply a desired voltage to the critical load in islanding mode of a microgrid. The boosting ability and operation validity of the proposed topology and modulation technique are demonstrated with simulation and experimental results.
32 citations
Cites background from "Three-level neutral-point-clamped q..."
...A three-level NPC-qZSI topology proposed in [25] can reduce the capacitor voltage stress....
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27 Sep 2018
TL;DR: Eleven Z-source topologies are analyzed in terms of boost capacity, inductance start-up current, capacitance stress and economy, and two kinds of promising topologies were gotten.
Abstract: This paper does some theoretical analysis and simulation studies on the most common topologies of Z-source inverter. As we all know, the traditional Z-source inverter has some problems, such as the voltage of the capacitor which belongs to this topology is higher and there is a startup shock, which caused researchers proposed a variety of improved Z-source topologies to solve these problems. Some of these topologies can increase boost capacity, and some can reduce the capacitor voltage. However, these topologies can improve only part of the problems of the traditional Z-source inverter, which leads to that the users are hard to choose which topologies. Faced with this situation, eleven Z-source topologies are analyzed in terms of boost capacity, inductance start-up current, capacitance stress and economy in this paper. Finally, two kinds of promising topologies were gotten.
25 citations
Cites background from "Three-level neutral-point-clamped q..."
...Meanwhile, some improved Z-source topologies can reduce the capacitor voltage and reduce the start-up shock, but this kind of topology can not completely improve the boost capacity of the inverter [12-13]....
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TL;DR: In this article, an improved version of maximum boost control (MBC) via appropriate modification in the conventional space vector pulse width modulation of three-level ZSI (3L-ZSI) is proposed.
Abstract: The maximum boost control (MBC) technique of voltage boosting offers the highest output voltage gain among other boost control techniques of Z -source inverter (ZSI). But, this technique suffers from the major drawback of sixth fundamental frequency (6thF1) ripple components of the impedance network inductor current. Due to this, the size/cost of the impedance network increases, which limits the practical applications of MBC. This article proposes an improved version of MBC via appropriate modification in the conventional space vector pulse width modulation of three-level ZSI (3L-ZSI). The improved MBC eliminates the problem of the 6thF1 impedance network inductor current ripple of 3L-ZSI without affecting its input/output gain and switching stress across power switches as compared to the existing MBC. Also, two new improved reduced common-mode voltage (RCMV) switching patterns have been proposed. As compared to the existing ones, the proposed RCMV switching patterns of 3L-ZSI offers reduced size of the impedance network while limiting the common-mode voltage magnitude to one-sixth of the available dc-link voltage. The above-mentioned findings have been successfully validated using theoretical analysis, simulation, and experimental results.
16 citations
TL;DR: The quantitative and qualitative analysis shows that a higher voltage gain can be achieved in the discontinuous current mode as compared to the continuous current mode, and the proposed converter is validated experimentally in both the modes and for different modulation techniques.
Abstract: An interesting feature of a Z-source inverter is to provide buck–boost ability in a single stage. However, this concept is most popular in the conventional inverters. In a few multilevel inverters (MLIs), Z-source is utilized to have higher gain along with retaining the advantages of an MLI such as better electromagnetic interference compatibility, low harmonic distortion, etc. However, the potential of the Z-source concept is not fully exploited in MLIs. To widen the feasibility of the Z-source concept in the MLI, a modular MLI is considered. In this article, a generalized switched inductor cell is selected as a Z-source network for integration, however, other Z-source networks such as quasi-boost network, quasi-switched boost network, two winding coupled inductor network, three winding coupled inductor network, etc., may be used in place of a switched inductor cell. The quantitative and qualitative analysis is done for the proposed converter in both the continuous current mode and discontinuous current mode. The analysis shows that a higher voltage gain can be achieved in the discontinuous current mode as compared to the continuous current mode. To control the proposed converter, two new modulation techniques are proposed, i.e., full shoot through and upper shoot through/lower shoot through. Finally, the proposed converter is validated experimentally in both the modes and for different modulation techniques.
15 citations
Additional excerpts
...proposed a new quasi-Z-source-based MLI [18]....
[...]
TL;DR: In this paper, the authors presented a PV tied Z-NPC-MLI grid connected system with a unique hysteresis current control SVPWM (HSVM) strategy with neutral point balancing control and direct current control in the inverter input side.
Abstract: The Photo-voltaic (PV) tied Z-source Neutral-point clamped multilevel inverter (Z-NPC-MLI) is used in solar grid connected applications due to its single stage conversion and better performance. Though the Z source inverters adaptation is accepted in grid connected technology, the need for suitable controller and PWM scheme are necessary to meet out the performance such as shoot through switching, neutral point balancing, and harmonic reduction. The space vector pulse width modulation (SVPWM) strategy is a prominent modulation technique for Z-source NPC-MLIs due to the flexibility to select the appropriate voltage vector. Previous publications have shown the control of a Z-source MLI using the SVPWM with and without modification of shoot through switching. However, the current controller (CC) based SVPWM is not matured, which is the most essential consideration for the grid connected inverter to provide neutral point balancing, shoot through control for low harmonic distortion and a high quality current. With all these aims, this paper presents a PV tied Z-NPC-MLI grid connected system with a unique hysteresis current control SVPWM (HSVM) strategy with neutral point (NP) balancing control and direct current control in the inverter input side. Also, the proposed HSVM is assuring the grid connection with high quality voltage and current waveforms. This CC based SVPWM for Z-NPC MLI has been validated through simulation and FPGA based experimental investigations. The results are confirmed the feasibility and reliability of the proposed HSVM for the PV tie grid connected Z- Source NPC-MLI.
15 citations
References
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TL;DR: The Z-source converter employs a unique impedance network to couple the converter main circuit to the power source, thus providing unique features that cannot be obtained in the traditional voltage-source (or voltage-fed) and current-source converters where a capacitor and inductor are used, respectively.
Abstract: This paper presents an impedance-source (or impedance-fed) power converter (abbreviated as Z-source converter) and its control method for implementing DC-to-AC, AC-to-DC, AC-to-AC, and DC-to-DC power conversion. The Z-source converter employs a unique impedance network (or circuit) to couple the converter main circuit to the power source, thus providing unique features that cannot be obtained in the traditional voltage-source (or voltage-fed) and current-source (or current-fed) converters where a capacitor and inductor are used, respectively. The Z-source converter overcomes the conceptual and theoretical barriers and limitations of the traditional voltage-source converter (abbreviated as V-source converter) and current-source converter (abbreviated as I-source converter) and provides a novel power conversion concept. The Z-source concept can be applied to all DC-to-AC, AC-to-DC, AC-to-AC, and DC-to-DC power conversion. To describe the operating principle and control, this paper focuses on an example: a Z-source inverter for DC-AC power conversion needed in fuel cell applications. Simulation and experimental results are presented to demonstrate the new features.
2,851 citations
TL;DR: In this paper, the authors presented the design and control of two three-level Z-source inverters, whose output voltage can be stepped down or up using only a single LC impedance network connected between the dc input source and either a neutral-point-clamped (NPC) or dc-link cascaded inverter circuitry.
Abstract: Three-level Z-source inverters are recent single-stage topological solutions proposed for buck-boost energy conversion with all favorable advantages of three-level switching retained. Despite their effectiveness in achieving voltage buck-boost conversion, existing three-level Z-source inverters use two LC impedance networks and two isolated dc sources, which can significantly increase the overall system cost and require a more complex modulator for balancing the network inductive voltage boosting. Offering a number of less costly alternatives, this letter presents the design and control of two three-level Z-source inverters, whose output voltage can be stepped down or up using only a single LC impedance network connected between the dc input source and either a neutral-point-clamped (NPC) or dc-link cascaded inverter circuitry. Through careful design of their modulation scheme, both inverters can function with the minimum of six device commutations per half carrier cycle (similar to that needed by a traditional buck three-level NPC inverter), while producing the correct volt-sec average and inductive voltage boosting at their ac output terminals. Physically, the designed modulation scheme can conveniently be implemented using a generic "alternative phase opposition disposition" carrier-based modulator with the appropriate triplen offset and time advance/delay added. The designed inverters, having a reduced passive component count, are lastly tested in simulation and experimentally using a laboratory prototype with the captured results presented in a later section of the letter
198 citations
TL;DR: In this paper, a three-level neutral-point-clamped quasi-Z-source inverter is proposed for single-stage buck-boost multilevel inverters.
Abstract: This study presents a novel three-level neutral-point-clamped quasi-Z-source inverter in the single-stage buck-boost multilevel inverter family. The topology was derived by combining the properties of the quasi-Z-source network with those of a three-level neutral point clamped inverter. It features such advantages as low voltage stress of the switches, single-stage buck-boost power conversion, continuous input current, short-circuit withstandability and low total harmonic distortion of the output voltage and current. The authors present a steady state analysis of the topology along with a special modulation technique to distribute shoot-through states during the whole fundamental period. Component design guidelines for a single-phase case study system are described. All the findings have been confirmed by simulations and experiments. The topology could be recommended for applications requiring continuous input current, high input voltage gain and enhanced quality of the output voltage.
149 citations
01 Aug 2006
TL;DR: In this paper, two three-level cascaded Z-source inverters, whose output voltage can be stepped down or up unlike a traditional buck 3-level inverter, are proposed.
Abstract: This paper presents the development of two three-level cascaded Z-source inverters, whose output voltage can be stepped down or up unlike a traditional buck three-level inverter. The proposed inverters are designed using two three-phase voltage-source inverter bridges, supplied by two uniquely designed Z-source impedance networks. These three-phase bridges can either be cascaded at their dc sides to form a dc-link-cascaded Z-source inverter or at their ac outputs using single-phase transformers to form a dual Z-source inverter. The dc-link-cascaded inverter has the advantages of not using any clamping diodes and transformers, but does not have redundant switching states within a phase leg for equalizing switching losses among the power devices. This constraint limits the modulation options for the dc-link-cascaded inverter, and indeed, it can only be controlled using the modified carrier disposition technique with appropriate ldquoZ-source shoot-throughrdquo states inserted for achieving balanced voltage boosting and optimal ldquonearest-three-vectorsrdquo switching. On the other hand, the dual Z-source inverter with transformer isolation can be controlled using different modulation approaches due to the presence of redundant switching states within a phase leg. Particularly, using a modified phase-shifted-carrier (PSC) scheme with shoot-through states inserted, it is shown that the dual inverter can be implemented using only a single Z-source network, while still achieving the correct volt-sec average and switching loss equalization. This represents a significant reduction in cost, and can more than compensate for the slightly degraded spectral characteristics of the PSC scheme. To verify the theoretical concepts discussed, experimental testing has been performed with the captured results presented in a later section of the paper.
104 citations
TL;DR: In this paper, an improved Z-source inverter topology is proposed to reduce the voltage stress and resonance between the Z-capacitors and Z-inductors.
Abstract: This paper proposes an improved Z-source inverter topology. Compared to previous Z-source inverter topology, it can reduce the Z-source capacitor voltage stress greatly, and has an inherent limitation to inrush current. The control strategy is exactly the same as the previous one, so all existing control strategies can be used directly. Soft-start strategy is also proposed to avoid the inrush current and resonance between the Z-capacitors and the Z-inductors. Comparison between the proposed and previous topologies is also presented. Analysis, simulation, and experimental results are presented to demonstrate the new features of the improved topology.
95 citations