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Showing papers on "Topology (electrical circuits) published in 2015"


Journal ArticleDOI
Siqi Li1, Weihan Li1, Junjun Deng1, Trong Duy Nguyen1, Chunting Chris Mi1 
TL;DR: With the proposed topology and its tuning method, the resonant frequency is irrelevant with the coupling coefficient between the two coils and is also independent of the load condition, which means that the system can work at a constant switching frequency.
Abstract: This paper proposes a double-sided LCC compensation network and its tuning method for wireless power transfer (WPT). With the proposed topology and its tuning method, the resonant frequency is irrelevant with the coupling coefficient between the two coils and is also independent of the load condition, which means that the system can work at a constant switching frequency. Analysis in frequency domain is given to show the characteristics of the proposed method. We also propose a method to tune the network to realize zero voltage switching (ZVS) for the Primary-side switches. Simulation and experimental results verified analysis and validity of the proposed compensation network and the tuning method. A wireless charging system with output power of up to 7.7 kW for electric vehicles was built, and 96% efficiency from dc power source to battery load is achieved.

768 citations


Journal ArticleDOI
TL;DR: Reduction in the number of power switches, driver circuits, and dc voltage sources is the advantage of the developed single-phase cascaded multilevel inverter, and the installation space and cost of the inverter are reduced.
Abstract: In this paper, a new single-phase cascaded multilevel inverter is proposed. This inverter is comprised of a series connection of the proposed basic unit and is able to only generate positive levels at the output. Therefore, an H-bridge is added to the proposed inverter. This inverter is called the developed cascaded multilevel inverter. In order to generate all voltage levels (even and odd) at the output, four different algorithms are proposed to determine the magnitude of dc voltage sources. Reduction in the number of power switches, driver circuits, and dc voltage sources is the advantage of the developed single-phase cascaded multilevel inverter. As a result, the installation space and cost of the inverter are reduced. These features are obtained by the comparison of the conventional cascaded multilevel inverters with the proposed cascaded topology. The ability of the proposed inverter to generate all voltage levels (even and odd) is reconfirmed by using the experimental results of a 15-level inverter.

444 citations


Journal ArticleDOI
TL;DR: In this paper, a hybrid modular multilevel converter (MMC) which combines full-bridge submodules (FBSM) and half-branch sub-modules (HBSM), which has the same dc fault blocking capability but uses fewer power devices hence has lower power losses, is presented.
Abstract: This paper presents a hybrid modular multilevel converter (MMC), which combines full-bridge submodules (FBSM) and half-bridge submodules (HBSM). Compared with the FBSM-based MMC, the proposed topology has the same dc fault blocking capability but uses fewer power devices hence has lower power losses. To increase power transmission capability of the proposed hybrid MMC, negative voltage states of the FBSMs are adopted to extend the output voltage range. The optimal ratio of FBSMs and HBSMs, and the number of FBSMs generating a negative voltage state are calculated to ensure successful dc fault blocking and capacitor voltage balancing. Equivalent circuits of each arm consisting of two individual voltage sources are proposed and two-stage selecting and sorting algorithms for ensuring capacitor voltage balancing are developed. Comparative studies for different circuit configurations show excellent performance balance for the proposed hybrid MMC, when considering dc fault blocking capability, power losses, and device utilization. Experimental results during normal operation and dc fault conditions demonstrate feasibility and validity the proposed hybrid MMC.

361 citations


Journal ArticleDOI
TL;DR: Topology optimized architectures are designed and printed with programmable Poisson's ratios ranging from -0.8 to 0.8 over large deformations of 20% or more.
Abstract: Topology optimized architectures are designed and printed with programmable Poisson's ratios ranging from -0.8 to 0.8 over large deformations of 20% or more.

359 citations


Journal ArticleDOI
TL;DR: This paper provides as a guide and quick reference for researchers and practicing engineers in deciding which control and modulation method to consider for an application in a given topology at a certain power level, switching frequency and demanded dynamic response.
Abstract: Impedance-source networks cover the entire spectrum of electric power conversion applications (dc-dc, dc-ac, ac-dc, ac-ac) controlled and modulated by different modulation strategies to generate the desired dc or ac voltage and current at the output. A comprehensive review of various impedance-source-network-based power converters has been covered in a previous paper and main topologies were discussed from an application point of view. Now Part II provides a comprehensive review of the most popular control and modulation strategies for impedance-source network-based power converters/inverters. These methods are compared in terms of theoretical complexity and performance, when applied to the respective switching topologies. Further, this paper provides as a guide and quick reference for researchers and practicing engineers in deciding which control and modulation method to consider for an application in a given topology at a certain power level, switching frequency and demanded dynamic response.

310 citations


Journal ArticleDOI
TL;DR: The Consensus Constrained TOPology prediction (CCTOP; http://cctop.hu) server is a web-based application providing transmembrane topology prediction that showed superior performance to existing approaches.
Abstract: The Consensus Constrained TOPology prediction (CCTOP; http://cctop.enzim.ttk.mta.hu) server is a web-based application providing transmembrane topology prediction. In addition to utilizing 10 different state-of-the-art topology prediction methods, the CCTOP server incorporates topology information from existing experimental and computational sources available in the PDBTM, TOPDB and TOPDOM databases using the probabilistic framework of hidden Markov model. The server provides the option to precede the topology prediction with signal peptide prediction and transmembrane-globular protein discrimination. The initial result can be recalculated by (de)selecting any of the prediction methods or mapped experiments or by adding user specified constraints. CCTOP showed superior performance to existing approaches. The reliability of each prediction is also calculated, which correlates with the accuracy of the per protein topology prediction. The prediction results and the collected experimental information are visualized on the CCTOP home page and can be downloaded in XML format. Programmable access of the CCTOP server is also available, and an example of client-side script is provided.

306 citations


Journal ArticleDOI
TL;DR: The proposed topology will reduce the size of the additional coil and make the system more compact with extremely high efficiency and three categories of operation modes are presented and analyzed.
Abstract: This paper presents an integrated $LCC$ compensation topology for electric vehicle/plug-in hybrid electric vehicle wireless chargers. The effect of the coupling between the additional coil and the main coil on the $LCC$ compensation topology is studied. The proposed topology will reduce the size of the additional coil and make the system more compact with extremely high efficiency. The basic characteristics of the proposed topology are analyzed based on fundamental harmonic approximation. Furthermore, based on the steady-state model, three categories of operation modes are presented and analyzed. In order to realize zero-voltage switching, the series capacitor $C_{2} $ on the secondary side is tuned. A numerical method is used to analyze the impact of different values of $\Delta C_{2}$ on the turnoff current, and the best value of $C_{2}$ is chosen to build a prototype to verify the analysis.

260 citations


Journal ArticleDOI
TL;DR: In this article, a holistic control system for a modular multilevel converter (MMC) to feed variable-speed drives is presented, which ensures a dynamic balancing of the energies in the cells of the MMC at minimum necessary internal currents over the complete frequency range.
Abstract: The modular multilevel converter (MMC) is an upcoming topology for high-power drive applications especially in the medium voltage range. This paper presents the design process of a holistic control system for a MMC to feed variable-speed drives. First, the design of the current control for the independent adjustment of several current components is derived from the analysis of the equivalent circuits. Second, the current and voltage components for balancing the energies in the arms of the MMC are identified systematically by the investigation of the transformed arm power components. These fundamentals lead to the design of the cascaded control structure, which allows the balancing task in the whole operating range of a three-phase machine. The control system ensures a dynamic balancing of the energies in the cells of the MMC at minimum necessary internal currents over the complete frequency range. Simultaneously, all other circulating current components are avoided to minimize current stress and additional voltage pulsations. The performance of the control system is finally validated by measurements on a low-voltage MMC prototype, which feeds a field-oriented controlled induction machine.

230 citations


Journal ArticleDOI
TL;DR: In this article, a direct cell-to-cell battery equalizer based on quasi-resonant LC converter (QRLCC) and boost dc-dc converter (BDDC) is proposed.
Abstract: In conventional equalizers, the facts of bulky size and high cost are widespread. Particularly, the zero-switching loss and zero-voltage gap (ZVG) between cells are difficult to implement due to the high-frequency hard switching and the voltage drop across power devices. To overcome these difficulties, a direct cell-to-cell battery equalizer based on quasi-resonant LC converter (QRLCC) and boost dc-dc converter (BDDC) is proposed. The QRLCC is employed to gain zero-current switching, leading to a reduction of power losses. The BDDC is employed to enhance the equalization voltage gap for large balancing current and ZVG between cells. Moreover, through controlling the duty cycle of the BDDC, the topology can online adaptively regulate the equalization current according to the voltage difference, which not only effectively prevents overequalization but also abridges the overall balancing time. Instead of a dedicated equalizer for each cell, only one balancing converter is employed and shared by all cells, reducing the size and implementation cost. Simulation and experimental results show the proposed scheme exhibits outstanding balancing performance, and the energy conversion efficiency is higher than 98%. The validity of the proposed equalizer is further verified by a quantitative and systematic comparison with the existing active balancing methods.

227 citations


Journal ArticleDOI
TL;DR: The average number of connections per branch provides a measure of connectivity that is almost completely independent of the topology, and the extension of topological concepts to 3-dimensions is discussed.

214 citations


Journal ArticleDOI
TL;DR: In this paper, the authors show that resonant and soft-charging operations of SC converters are closely related, and a technique will be proposed, which achieves either operation by adding a single inductor to existing SC topologies.
Abstract: Traditionally, switched-capacitor (SC) converters have suffered from high transient currents, which limit both the efficiency and power density of such converters. Soft-charging operation can be employed to eliminate the current transients and greatly improve the power density of SC converters. In this approach, a second-stage magnetic converter is cascaded with the SC stage to act as a controlled current load. Another approach is to use resonant SC converters with zero-current switching. This paper shows that resonant and soft-charging operations of SC converters are closely related, and a technique will be proposed, which achieves either operation by adding a single inductor to existing SC topologies. In addition, since most preexisting resonant or soft-charging SC converters were devised in an ad-hoc manner, this paper formulates an analytical method that can determine whether an existing conventional SC converter topology is compatible with the proposed approach. A number of common SC topologies are analyzed, including Dickson, series-parallel, ladder, Fibonacci, and doubler configurations. Through comparison to simulated results, as well as experimental work, the proposed method is validated and a family of high-performance SC converters is obtained.

Journal ArticleDOI
TL;DR: In this paper, the authors examined two primary power supply architectures being predominantly used for wireless electric vehicle (EV) charging, namely the series LC (SLC) resonant and the hybrid series-parallel (LCL ) resonant full-bridge inverter topologies.
Abstract: This paper examines two of the primary power supply architectures being predominantly used for wireless electric vehicle (EV) charging, namely the series LC (SLC) resonant and the hybrid series–parallel ( LCL ) resonant full-bridge inverter topologies. The study of both of these topologies is presented in the context of designing a 3-kW primary-side controlled stationary wireless EV charger with nominal operating parameters of 30-kHz center frequency, a range of coupling in the neighborhood of 0.18–0.26, and a parallel secondary pick-up with partial series coil compensation. A comparison of both architectures is made in terms of their design methodology, physical size, cost, complexity, and efficiency. It is found that the SLC architecture is 2.45% less costly than the LCL topology. On the other hand, it is observed that the LCL architecture achieves almost 10% higher peak efficiency at rated load and minimum coupling. The study also showed that the SLC topology suffers from poor light load efficiency, while the LCL topology maintains very high efficiency over its full range of coupling and loading. The study also revealed that the capacitor voltage stress is significantly higher in the SLC topology. Finally, it is also shown that the control complexity of the SLC architecture is higher than that of the LCL architecture because of its sensitivity to changes in the reflected secondary impedance, which result in loss of constant current source and ZVS operation unless a suitable combination of parameters are modulated by the closed-loop controller.

Proceedings ArticleDOI
27 Aug 2015
TL;DR: An overview of vehicular platoon control techniques from networked control perspective is presented, which naturally decomposes a platoon into four interrelated components, i.e., 1) node dynamics (ND), 2) information flow topology (IFT), 3) distributed controller (DC) and, 4) geometry formation (GF).
Abstract: The platooning of autonomous ground vehicles has potential to largely benefit the road traffic, including enhancing highway safety, improving traffic utility and reducing fuel consumption. The main goal of platoon control is to ensure all the vehicles in the same group to move at consensual speed while maintaining desired spaces between adjacent vehicles. This paper presents an overview of vehicular platoon control techniques from networked control perspective, which naturally decomposes a platoon into four interrelated components, i.e., 1) node dynamics (ND), 2) information flow topology (IFT), 3) distributed controller (DC) and, 4) geometry formation (GF). Under the four-component framework, existing literature are categorized and analyzed according to their technical features. Three main performance metrics, i.e. string stability, stability margin and coherence behavior, are also discussed.

Journal ArticleDOI
TL;DR: In this paper, a bipolar coupler structure with a compensation-integrated feature is proposed to improve the compactness of the battery chargers for electric vehicles (EVs) and plug-in hybrid EVs.
Abstract: Compactness and efficiency are the two basic considerations of the wireless battery chargers for electric vehicles (EVs) and plug-in hybrid EVs. The double-sided LCC compensation topology for wireless power transfer (WPT) has been proved to be one of the efficient solutions lately. However, with the increase of the numbers of compensation components, the volume of the system may become larger, which makes it less attractive. To improve the compactness, a bipolar coupler structure with a compensation-integrated feature is proposed. The inductors of the LCC compensation networks are designed as planar-type and attached to the power-transferring main coils. Extra space and magnetic cores for the compensated inductors outside of the coupler are saved. The cost is that extra couplings between the compensated coils (inductors) and the main coils are induced. To validate the feasibility, the proposed coupler is modeled and investigated by 3-D finite-element analysis tool first. The positioning of the compensated coils, the range of the extra couplings, and the tolerance to misalignment are studied. This is followed by the circuit modeling and characteristic analysis of the proposed WPT topology based on the fundamental harmonic approximation. At last, a 600 mm × 600 mm with a nominal 150-mm-gap wireless charger prototype, operated at a resonant frequency of 95 kHz and a rated power of 5.6 kW has been built and tested. A peak efficiency of 95.36% from a dc power source to the battery load is achieved at rated operation condition.

Book
01 Jan 2015
TL;DR: In this paper, a transistor-level, design-intensive overview of high speed and high frequency monolithic integrated circuits for wireless and broadband systems from 2 GHz to 200 GHz is presented.
Abstract: A transistor-level, design-intensive overview of high speed and high frequency monolithic integrated circuits for wireless and broadband systems from 2 GHz to 200 GHz, this comprehensive text covers high-speed, RF, mm-wave and optical fiber circuits using nanoscale CMOS, SiGe BiCMOS and III-V technologies. Step-by-step design methodologies, end-of-chapter problems and practical simulation and design projects are provided, making this an ideal resource for senior undergraduate and graduate courses in circuit design. With an emphasis on device-circuit topology interaction and optimization, it gives circuit designers and students alike an in-depth understanding of device structures and process limitations affecting circuit performance.

Journal ArticleDOI
Tianyang Jiang1, Junming Zhang1, Xinke Wu1, Kuang Sheng1, Yousheng Wang1 
TL;DR: With the proposed new control scheme, the power flow direction and output power of the proposed converter can be changed automatically and continuously, which is attractive for energy storage systems to balance the energy and to keep the dc-bus voltage constant.
Abstract: This paper proposes an improved bidirectional LLC resonant topology with a new control scheme. All the switches in the proposed topology can achieve soft switching. Compared with traditional isolated bidirectional dc-dc converters such as dual active bridge converter, the reverse energy and turn-off loss are reduced dramatically, and the conversion efficiency can be much improved. With the proposed new control scheme, the power flow direction and output power of the proposed converter can be changed automatically and continuously, which is attractive for energy storage systems to balance the energy and to keep the dc-bus voltage constant. Performance of the proposed circuit is validated by the experimental results from a 1-kW prototype. Over 97% efficiency is achieved at full load condition based on the prototype.

Journal ArticleDOI
TL;DR: In this paper, a modular multilevel series/parallel converter that allows switching modules dynamically not only in series, as in the traditional modular multi-level converter (M2C), but also in parallel is presented.
Abstract: This paper introduces a novel modular multilevel series/parallel converter that allows switching modules dynamically not only in series, as in the traditional modular multilevel converter (M2C), but also in parallel. As in M2C, the semiconductor voltages do not exceed the module capacitor voltage for any module state. While the new topology is a generalization of M2C and could, therefore, be operated identically to it, the additional states provide degrees of freedom that the controller can dynamically employ to achieve several advantages. Whereas in M2C many modules are bypassed if the instantaneous converter voltage is lower than the system's peak voltage, the parallel connectivity enables these modules to contribute to the current load, thus reducing conduction losses. In addition, the parallel configuration of modules can be used for balancing the modules' state of charge (SOC). The parallelization losses are moderate or negligible, dependent on the switching rate. Since the parallel connection of capacitors can ensure balancing, it enables stable operation of a multilevel converter without the need for monitoring the module SOCs. While such economical control hardware may be appropriate for low-power systems, we also present more sophisticated control that uses the additional degrees of freedom to minimize losses. Finally, we point to further extensions of the circuit topology to multipole module connectivity that could enable additional functionality and applications.

Journal ArticleDOI
TL;DR: In this paper, a fault-tolerant single-phase five-level inverter configuration is proposed for photovoltaic (PV) generation systems, which is constructed by using a half-bridge two-level, a three-level diode clamp inverter, and a bidirectional switch.
Abstract: In this paper, a fault-tolerant single-phase five-level inverter configuration is proposed for photovoltaic (PV) generation systems. Conventional two-level inverters are popularly used in PV applications, but these inverters provide the output voltage with considerable harmonic content. One of the efficient ways to improve the power quality of PV generation systems is to replace a two-level inverter with a multilevel inverter. Conventional multilevel inverters reduce total harmonic distortion and filter requirements effectively, but it has limitations in terms of reliability due to increased device count and capacitor voltage balancing issues. Therefore, a fault-tolerant single-phase five-level inverter is presented, which is constructed by using a half-bridge two-level inverter, a three-level diode clamp inverter, and a bidirectional switch. The proposed inverter topology can tolerate the system faults due to failure of the source and/or switching devices with least modification in the switching combinations. It has less number of switching devices compared to conventional five-level inverters. The topology also has the energy-balancing capability between sources which helps in reducing uneven charge of batteries in case of partial shading or hotspots on one side of the PV panels. The proposed system under normal and faulty condition is simulated in MATLAB/Simulink environment, and results are verified with a laboratory prototype.

Journal ArticleDOI
TL;DR: In this article, the authors present some of the recent trends in the development of multi-input and multi-output DC-DC converters, their operational principles, merits and demerits are studied.
Abstract: Power electronics DC–DC converters are being widely used in various applications like hybrid energy systems, hybrid vehicles, aerospace, satellite applications and portable electronics devices. In the recent past, a lot of research and development has been carried out to enhance the reliability, efficiency, modularity and cost effectiveness of these converters. A number of new topologies have been proposed and new characteristics of power conversion have been defined. DC–DC converters have made a successful transition from single input–single output to multiinput–multioutput converters. These converters are now able to interface different level inputs and combine their advantages to feed the different level of outputs. Research is continued to bring down the cost and reduce the number of components while keeping the continuous improvement in the areas like reliability and efficiency of the overall system. The study of different multiinput DC–DC converter topologies suggests that there is no single topology which can handle the entire goals of cost, reliability, flexibility, efficiency and modularity single handed. This paper presents some of the recent trends in the development of multiinput and multioutput DC–DC converters. Methods to synthesize multiinput converters, their operational principles, merits and demerits are studied.

Journal ArticleDOI
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.

Journal ArticleDOI
TL;DR: In this paper, the effects of inner and outer open-switch faults of the neutral point-clamped (NPC) rectifier and inverter of a back-to-back converter were analyzed.
Abstract: In wind turbine generation (WTG) systems, a back-to-back converter with a neutral-point-clamped (NPC) topology is widely used because this topology has more advantages than a conventional two-level topology, particularly when operating at high power. There are 12 switches in the NPC topology. An open-switch fault in the NPC rectifier of the back-to-back converter leads to the distortion of the input current and torque vibration in the system. Additionally, an open-switch fault in the NPC inverter of the back-to-back converter causes the distortion of the output current. Furthermore, the WTG system can break down in the worst case scenario. To improve the reliability of WTG systems, an open-switch fault detection method for back-to-back converters using the NPC topology is required. This study analyzes effects of inner and outer open-switch faults of the NPC rectifier and inverter and describes a novel open-switch fault detection method for all possible open-switch faults in the back-to-back converter.

Patent
21 Oct 2015
TL;DR: In this article, a system for receiving topology information from a plurality of waveguide systems or other transmission devices is described, where the topology is used to identify one or more transmission media available to each waveguide system for transmitting or receiving electromagnetic waves.
Abstract: Aspects of the subject disclosure may include, for example, a system for receiving topology information from a plurality of waveguide systems or other transmission devices, the topology information identifying one or more transmission media available to each waveguide system for transmitting or receiving electromagnetic waves, and updating a topology of a communication system from the topology information provided by the plurality of waveguide systems. Other embodiments are disclosed.

Journal ArticleDOI
TL;DR: In this article, a capacitor voltage-balancing method for the 5L-ANPC converter, including the voltage balancing of dc-link capacitors and flying capacitors, is presented.
Abstract: Five-level active neutral-point clamped (5L-ANPC) converter is an attractive topology for high-power medium-voltage motor drives. This paper presents a capacitor voltage-balancing method for the 5L-ANPC converter, including the voltage balancing of dc-link capacitors and flying capacitors. In order to ensure that the series-connected or high-voltage switches of the 5L-ANPC converter are operated at fundamental frequency and the other switches are operated at a constant switching frequency, phase-shifted pulse width modulation is used to control this converter. The relationship between the average neutral-point current and zero-sequence voltage is investigated, and an optimum zero-sequence voltage is calculated to regulate the neutral-point potential. The voltage across the flying capacitor is also regulated by adjusting the switching duty cycles of two PWM signals, which varies the operation time of redundant switching states in each switching period. Simulation and experimental results are presented to verify the validity of this method.

Journal ArticleDOI
TL;DR: It is proven that the proposed topology is able to reduce the leakage current without sacrificing the overall performance of the system.
Abstract: Recently, reduced common-mode voltage (CMV) pulsewidth modulation (RCMV-PWM) methods have been proposed to reduce the leakage current in three-phase transformerless photovoltaic (PV) systems. However, most of these studies only focus on leakage current elimination and neglect the overall performance of the PV systems on issues such as cost, voltage linearity, dc-link current ripples, and harmonic distortion. In this paper, a three-phase transformerless inverter, adapted from the single-phase H5 topology, is investigated. Since the H5 topology has been conventionally developed for a single-phase system, its adaptation to the three-phase system requires the development of corresponding three-phase modulation techniques. Hence, modulation techniques are proposed based on conventional PWM. The performances of the proposed PWM, in terms of CMV, leakage current, voltage linearity, output current ripples, dc-link current ripples, and harmonic distortion are studied and discussed via simulation and experiment. It is proven that the proposed topology is able reduce the leakage current without sacrificing the overall performance of the system.

Journal ArticleDOI
TL;DR: In this article, a series connected double sub module (SDSM) is designed and dc link fault current blocking capability is realized without tripping ac circuit breaker, so MMC-HVDC with this improved topology can immediately rebuild dc link voltage and resume power transmission.
Abstract: The high voltage direct current transmission system based on modular multilevel converter (MMC-HVDC) technology is now studied and used widely. But traditional half bridge topology of sub module (HBSM) of MMC can't block dc link fault current because of the freewheeling effect of diodes. In order to solve this problem, firstly, this paper improves HBSM topology, a series connected double sub module (SDSM) is designed and dc link fault current blocking capability is realized without tripping ac circuit breaker, so MMC-HVDC with this improved topology can immediately rebuild dc link voltage and resume power transmission. Secondly, the self starting and fault disposing procedure are also designed. At last, simulations in the software PSCAD/EMTDC are carried out to verify its effectiveness and feasibility.

Proceedings ArticleDOI
07 Jun 2015
TL;DR: This paper proposes a coarse to fine optimization technique that speeds up inference in terms of the number of updates by an order of magnitude and significantly outperforms the baselines in the segmentation metrics and achieves the lowest error on the stereo task.
Abstract: In this paper, we tackle the problem of unsupervised segmentation in the form of superpixels. Our main emphasis is on speed and accuracy. We build on [31] to define the problem as a boundary and topology preserving Markov random field. We propose a coarse to fine optimization technique that speeds up inference in terms of the number of updates by an order of magnitude. Our approach is shown to outperform [31] while employing a single iteration. We evaluate and compare our approach to state-of-the-art superpixel algorithms on the BSD and KITTI benchmarks. Our approach significantly outperforms the baselines in the segmentation metrics and achieves the lowest error on the stereo task.

Journal ArticleDOI
TL;DR: A multilevel inverter for generating 17 voltage levels using a three-level flying capacitor inverter and cascaded H-bridge modules with floating capacitors has been proposed in this article.
Abstract: A multilevel inverter for generating 17 voltage levels using a three-level flying capacitor inverter and cascaded H-bridge modules with floating capacitors has been proposed. Various aspects of the proposed inverter like capacitor voltage balancing have been presented in the present paper. Experimental results are presented to study the performance of the proposed converter. The stability of the capacitor balancing algorithm has been verified both during transients and steady-state operation. All the capacitors in this circuit can be balanced instantaneously by using one of the pole voltage combinations. Another advantage of this topology is its ability to generate all the voltages from a single dc-link power supply which enables back-to-back operation of converter. Also, the proposed inverter can be operated at all load power factors and modulation indices. Additional advantage is, if one of the H-bridges fail, the inverter can still be operated at full load with reduced number of levels. This configuration has very low dv/dt and common-mode voltage variation.

Journal ArticleDOI
TL;DR: In this paper, the authors compared how a dc fault affects a multiterminal dc (MTdc) network depending on the HVDC transmission system topology and proposed a six-step methodology for the selection of the necessary dc fault protection measures.
Abstract: This paper compares how a dc fault affects a multiterminal dc (MTdc) network depending on the HVDC transmission system topology. To this end, a six-step methodology is proposed for the selection of the necessary dc fault protection measures. The network consists of four voltage-source converters converters radially connected. The converters natural fault response to a dc fault for the different topologies is studied using dynamic simulation models. For clearing of the dc faults, four different dc breaker technologies are compared based on their fault interruption time, together with a current direction fault detection method. If necessary, the converters are reinforced with limiting reactors to decrease the peak value and rate of rise of the fault currents providing sufficient time for the breakers to isolate the fault without interrupting the MTdc network operation. The study shows that the symmetric monopolar topology is least affected by dc contingencies. Considering bipolar topologies, the bipolar with metallic return exhibits better fault response compared to the one with ground return. Topologies with ground or metallic return require full semiconductor or hybrid breakers with reactors to successfully isolate a dc fault.

Journal ArticleDOI
TL;DR: In this paper, the harmonic filter for a three-level neutral-point-clamped (NPC) grid interface converter is designed with good filtering performance and small component size.
Abstract: The harmonic filter for a three-level neutral-point-clamped (NPC) grid interface converter is designed in this paper with good filtering performance and small component size. LCL topology is selected because of the attenuation and size tradeoff. The design of the inverter-side inductor L 1 is emphasized due to its cost. A detailed inductor current ripple analysis is given based on the space vector modulation. The analysis derives the inductor volt-second and the maximum current ripple equation in line cycle. It also reveals the switching cycle current ripple distribution over a line cycle, with the consideration of power factor. The total system loss is calculated with different ripple current. Inductor L 1 is determined by the loss and size tradeoff. Also the capacitor- and grid-side inductor L 2 is designed based on attenuation requirement. Different damping circuits for LCL filter are compared and investigated in detail. The filter design is verified by both simulation and 200-kVA three-level NPC converter hardware.

Journal ArticleDOI
TL;DR: A family of single-input-multiple-output (SIMO) dc-dc converter topologies, which can provide one step-up and multiple step-down outputs, which has been presented and results show that the proposed converter has very good cross-regulation to step load change as well as dynamic reference change in either output.
Abstract: This paper presents a family of single-input–multiple-output (SIMO) dc–dc converter topologies, which can provide one step-up and multiple step-down outputs. These topologies are synthesized by replacing the control switch of a boost converter topology with series-connected switches and using the additional switch nodes to generate step-down dc outputs. Compared with separate converters, these topologies utilize a lower number of switches and are more reliable due to their inherent shoot-through protection. Analysis shows that the topologies exhibit similar dynamic behavior as individual buck and boost converters. Hence, the control system methodology is the same as that of separate converters, with each output being precisely regulated. The behavior of these converters has been illustrated in this paper using the integrated dual-output converter (IDOC), which has a step-up and a step-down output. The steady-state characteristics and dynamic behavior of the converter have been studied. An analog closed-loop control system for the converter has been described for regulation of both the outputs. The operating principles have been experimentally validated using a 120-W prototype. Results show that the proposed converter has very good cross-regulation to step load change as well as dynamic reference change in either output. The measured efficiencies of the IDOC prototype are around 90%.