Showing papers on "Topology (electrical circuits) published in 2012"
TL;DR: A new topology with a reversing-voltage component is proposed to improve the multilevel performance by compensating the disadvantages mentioned and the overall cost and complexity are greatly reduced particularly for higher output voltage levels.
Abstract: Multilevel inverters have been widely accepted for high-power high-voltage applications. Their performance is highly superior to that of conventional two-level inverters due to reduced harmonic distortion, lower electromagnetic interference, and higher dc link voltages. However, it has some disadvantages such as increased number of components, complex pulsewidth modulation control method, and voltage-balancing problem. In this paper, a new topology with a reversing-voltage component is proposed to improve the multilevel performance by compensating the disadvantages mentioned. This topology requires fewer components compared to existing inverters (particularly in higher levels) and requires fewer carrier signals and gate drives. Therefore, the overall cost and complexity are greatly reduced particularly for higher output voltage levels. Finally, a prototype of the seven-level proposed topology is built and tested to show the performance of the inverter by experimental results.
397 citations
TL;DR: The LLCL filter as mentioned in this paper inserts a small inductor in the branch loop of the capacitor in the traditional LCL filter to compose a series resonant circuit at the switching frequency, which attenuates the switching-frequency current ripple components much better than an LCL filtering.
Abstract: This paper presents a new topology of higher order power filter for grid-tied voltage-source inverters, named the LLCL filter, which inserts a small inductor in the branch loop of the capacitor in the traditional LCL filter to compose a series resonant circuit at the switching frequency. Particularly, it can attenuate the switching-frequency current ripple components much better than an LCL filter, leading to a decrease in the total inductance and volume. Furthermore, by decreasing the inductance of a grid-side inductor, it raises the characteristic resonance frequency, which is beneficial to the inverter system control. The parameter design criteria of the proposed LLCL filter is also introduced. The comparative analysis and discussions regarding the traditional LCL filter and the proposed LLCL filter have been presented and evaluated through experiment on a 1.8-kW-single-phase grid-tied inverter prototype.
350 citations
TL;DR: In this article, a generalized mode analysis is presented that provides highly accurate prediction on resonant current and voltage behavior and dc gain characteristic, and an approximation method is developed to estimate the peak gain point, which is useful in LLC design.
Abstract: With the advantage of achieving zero voltage switching for a wide input voltage range, the LLC resonant topology has become increasingly popular for use in high power density and high-efficiency power converter applications. However, when the LLC converter is applied to wide input voltage range applications, the widely used fundamental harmonic approximation is incapable of guiding the design due to its inaccuracy. Thus an accurate LLC converter model is desired. In this paper, a generalized mode analysis is presented that provides highly accurate prediction on resonant current and voltage behavior and dc gain characteristic. Also, because operation modes are affected by load, frequency, and gain conditions, the boundaries and distribution of modes are discussed and illustrated. Based on the mode analysis, an approximation method is developed to estimate the peak gain point, which is useful in LLC design. This approximation demonstrates high accuracy within the simulation results. An experimental prototype is built to verify the analysis.
337 citations
TL;DR: It is proved that second-order consensus can be reached if the general algebraic connectivity of the communication topology is larger than a threshold value and the mobile agents communicate with their neighbors frequently enough as the network evolves.
Abstract: The problem of second-order consensus is investigated in this paper for a class of multi-agent systems with a fixed directed topology and communication constraints where each agent is assumed to share information only with its neighbors on some disconnected time intervals. A novel consensus protocol designed based on synchronous intermittent local information feedback is proposed to coordinate the states of agents to converge to second-order consensus under a fixed strongly connected topology, which is then extended to the case where the communication topology contains a directed spanning tree. By using tools from algebraic graph theory and Lyapunov control approach, it is proved that second-order consensus can be reached if the general algebraic connectivity of the communication topology is larger than a threshold value and the mobile agents communicate with their neighbors frequently enough as the network evolves. Finally, a numerical example is simulated to verify the theoretical analysis. Copyright © 2011 John Wiley & Sons, Ltd.
304 citations
TL;DR: Two basic traction electric drive systems of electric/hybrid vehicles are presented and evaluated, with a special focus on the efficiency analysis of the main drive components efficiency, including the global drive efficiency, presented in the form of efficiency maps.
Abstract: One of the most important research topics in drive train topologies applied to electric/hybrid vehicles is the efficiency analysis of the power train components, including the global drive efficiency. In this paper, two basic traction electric drive systems of electric/hybrid vehicles are presented and evaluated, with a special focus on the efficiency analysis. The first topology comprises a traditional pulsewidth-modulation (PWM) battery-powered inverter, whereas in the second topology, the battery is connected to a bidirectional dc-dc converter, which supplies the inverter. Furthermore, a variable-voltage control technique applied to this second topology is presented, which allows for the improvement of the drive overall performance. Some simulation results are presented, considering both topologies and a permanent-magnet synchronous motor (PMSM). An even more detailed analysis is performed through the experimental validation. Particular attention is given to the evaluation of the main drive components efficiency, including the global drive efficiency, presented in the form of efficiency maps. Other parameters such as motor voltage distortion and power factor are also considered. In addition, the comparison of the two topologies takes into account the drive operation under the motoring and regenerative-braking modes.
261 citations
TL;DR: The results demonstrate that the phase shifted semi-bridgeless PFC boost converter is ideally suited for automotive level I residential charging applications in North America, where the typical supply is limited to 120 V and 1.44 kVA.
Abstract: As a key component of a plug-in hybrid electric vehicle (PHEV) charger system, the front-end ac-dc converter must achieve high efficiency and power density. This paper presents a topology survey evaluating topologies for use in front end ac-dc converters for PHEV battery chargers. The topology survey is focused on several boost power factor corrected converters, which offer high efficiency, high power factor, high density, and low cost. Experimental results are presented and interpreted for five prototype converters, converting universal ac input voltage to 400 V dc. The results demonstrate that the phase shifted semi-bridgeless PFC boost converter is ideally suited for automotive level I residential charging applications in North America, where the typical supply is limited to 120 V and 1.44 kVA or 1.92 kVA. For automotive level II residential charging applications in North America and Europe the bridgeless interleaved PFC boost converter is an ideal topology candidate for typical supplies of 240 V, with power levels of 3.3 kW, 5 kW, and 6.6 kW.
245 citations
Cray1
TL;DR: This paper presents the architecture of the Cray Cascade system, a distributed memory system based on the Dragonfly network topology, and describes a set of advanced features supporting both mainstream high performance computing applications and emerging global address space programing models.
Abstract: Higher global bandwidth requirement for many applications and lower network cost have motivated the use of the Dragonfly network topology for high performance computing systems. In this paper we present the architecture of the Cray Cascade system, a distributed memory system based on the Dragonfly [1] network topology. We describe the structure of the system, its Dragonfly network and the routing algorithms. We describe a set of advanced features supporting both mainstream high performance computing applications and emerging global address space programing models. We present a combination of performance results from prototype systems and simulation data for large systems. We demonstrate the value of the Dragonfly topology and the benefits obtained through extensive use of adaptive routing.
223 citations
TL;DR: An improved three-level grid-connected inverter is proposed based on the NPCTLI and the dual-buck half-bridge inverter (DBHBI), and which avoids the shoot-through problem and is referred to as split-inductor NP CTLI (SI-NPCTLI).
Abstract: Characterized by low leakage current and low voltage stress of the power device, a neutral point clamped three-level inverter (NPCTLI) is suitable for a transformerless photovoltaic (PV) grid-connected system. Unfortunately, the shoot-through problem of bridge legs still exists in an NPCTLI, so its operation reliability is degraded. An improved three-level grid-connected inverter is proposed based on the NPCTLI and the dual-buck half-bridge inverter (DBHBI), and which avoids the shoot-through problem. The proposed topology guarantees no switching-frequency common-mode voltage and no shoot-through risk. Furthermore, the freewheeling diode of bridge legs of the DBHBI can be removed taking into consideration the unity power factor of grid current, and a straightforward topology is thus derived. The new topology is referred to as split-inductor NPCTLI (SI-NPCTLI). The operation mode, common-mode characteristic, and control strategy are analyzed. Finally, both the simulation and the experimental results of a 1-kW SI-NPCTLI prototype verify the analysis.
195 citations
TL;DR: In this paper, a three-phase, five-level inverter topology with a single-dc source is presented by cascading a 3-level flying capacitor inverter with a flying H-bridge power cell in each phase.
Abstract: In this paper, a new three-phase, five-level inverter topology with a single-dc source is presented. The proposed topology is obtained by cascading a three-level flying capacitor inverter with a flying H-bridge power cell in each phase. This topology has redundant switching states for generating different pole voltages. By selecting appropriate switching states, the capacitor voltages can be balanced instantaneously (as compared to the fundamental) in any direction of the current, irrespective of the load power factor. Another important feature of this topology is that if any H-bridge fails, it can be bypassed and the configuration can still operate as a three-level inverter at its full power rating. This feature improves the reliability of the circuit. A 3-kW induction motor is run with the proposed topology for the full modulation range. The effectiveness of the capacitor balancing algorithm is tested for the full range of speed and during the sudden acceleration of the motor.
188 citations
TL;DR: In this article, a new multilevel converter topology was introduced, which can synthesise all possible additive and subtractive combinations of input DC levels in the output voltage waveform with fewer power electronic switches.
Abstract: This study introduces a new multilevel converter topology, which can synthesise all possible additive and subtractive combinations of input DC levels in the output voltage waveform with fewer power electronic switches. An appropriate modulation scheme has also been proposed for low switching frequency operation of the proposed topology. As compared with the classic multilevel topologies, the proposed topology results in reduction of the number of switches and conduction losses. The operation and performance of the proposed multilevel converter has been ascertained through simulations and verified experimentally for single-phase nine-level multilevel inverter. Moreover, a 15-level inverter with asymmetric source configuration has been also investigated for charge balance control using the proposed modulation scheme. The same has been verified experimentally for effective balanced power delivery.
185 citations
TL;DR: A mixed integer linear programming model is developed to optimize the physical topology of IP over WDM networks with the objective of minimizing the network total power consumption and the results show that optimizing the physicalTopology increases the utilization of the renewable energy sources.
Abstract: The energy consumption of information and communications technology networks is increasing rapidly as a result of the Internet expansion in reach and capacity. In this paper, we investigate energy-efficient physical topologies for backbone IP over wavelength-division multiplexing (WDM) networks. We develop a mixed integer linear programming model to optimize the physical topology of IP over WDM networks with the objective of minimizing the network total power consumption. We consider the National Science Foundation network topology and compare its energy consumption with the energy consumption of optimized physical topologies under different IP over WDM approaches and nodal degree constraints. We study the physical topology optimization under a symmetric full-mesh connectivity traffic matrix and an asymmetric traffic demand, where data centers create a hot node scenario in the network. We also investigate the power savings obtained by deploying topologies that eliminate the need for IP routers, including a full-mesh topology and a star topology. Simulation results show that the full-mesh and star topologies result in significant power savings of 95% and 92%, respectively. Furthermore, the optimization of the physical topology is investigated considering the presence of renewable energy sources in the network. The results show that optimizing the physical topology increases the utilization of the renewable energy sources.
TL;DR: In this paper, a cascaded dc/dc converter based on a boost chopper is proposed, where the converters' parameters and the arrangement of the PV cells are variable parameters.
Abstract: The integration of photovoltaic (PV) modules in buildings causes problems with shadows that can strongly reduce the energy produced by these systems. Moreover, most PV modules are designed for stand-alone applications that have output voltage adapted to lead batteries. Indeed, this historical sizing of PV modules can be discussed in the case of grid-connected systems. In this paper, a cascaded dc/dc converter based on boost chopper is proposed. First, the advantages and the limits of this topology will be shown. Second, this topology will be optimized to maximize the efficiency or minimize the volume. The originality of this optimization is that the converters' parameters and the arrangement of the PV cells are variable parameters. Indeed, the optimization is done on the entire system. To realize these optimizations, semiempiric models of losses and volumes of different components of a boost chopper were developed. The optimization uses a successive quadratic programming algorithm. Considering the optimization results over the whole range of the specifications, a flexible solution is developed and experimental results are presented. Finally, optimized topologies connected to several PV are evaluated at different situations of typical shadows.
TL;DR: The main significance of the generator topology is that the relative position of the magnets, copper, and steels has been chosen so that there are no magnetic attraction forces between a stator and a permanent-magnet translator.
Abstract: A linear-generator topology is proposed for wave-energy applications. The main significance of the generator topology is that the relative position of the magnets, copper, and steels has been chosen so that there are no magnetic attraction forces between a stator and a permanent-magnet (PM) translator. The lack of magnetic forces and the modular nature of the generator topology make the manufacture and assembly of the generator easier than a conventional iron-cored PM linear generator. Analytical modeling techniques are described with a genetic-algorithm optimization method. The proposed topology is implemented to an Archimedes-wave-swing wave-energy converter. A 50-kW prototype has been built to prove the concept, and the no-load- and load-test results are presented.
TL;DR: A systematic framework to analyze the global pinning-controllability of general complex networks with or without time-delay based on the properties of M-matrices and directed spanning trees and the roles of network nodes in the pinning control is presented.
Abstract: This paper presents a systematic framework to analyze the global pinning-controllability of general complex networks with or without time-delay based on the properties of M-matrices and directed spanning trees Some stability criteria are established to guarantee that a network can be globally asymptotically pinned to a homogenous state By partitioning the interaction diagraph into a minimum number of components, a selective pinning scheme for a complex network with arbitrary topology is proposed to determine the number and the locations of the pinned nodes In particular, this paper deeply investigates the roles of network nodes in the pinning control, including what kind of nodes should be pinned and what kind of nodes may be left unpinned Numerical simulations are given to verify the theoretical analysis
TL;DR: In this article, a modified full-bridge inverter topology to reduce the dc-side leakage current as well as to mitigate the ac-side common-mode electromagnetic interference noise is presented.
Abstract: The leakage current in grid-interface converter systems presents a considerable issue in regard to safety and efficiency. The full-bridge inverter is a well-accepted topology in single-phase power conversion applications. The high-frequency pulsewidth modulation (PWM) modulation schemes are normally applied to the full-bridge topology for smaller ac filter size, which, however, generates a high-frequency dc-side leakage current, resulting in an enormous negative impact on dc components, such as photovoltaic panels and energy storage elements. In this paper, a modified full-bridge inverter topology to reduce the dc-side leakage current as well as to mitigate the ac-side common-mode electromagnetic interference noise is presented. Several considerations are discussed, such as the PWM modulation and filter design. Compared to the other existing methods, the proposed solution provides a reliable performance for bidirectional operation, minimum additional components, low cost, and a simple design process.
TL;DR: A new 16-phase interleaved bidirectional dc/dc converter is developed featuring smaller input/output filters, faster dynamic response and lower device stress than conventional designs, for hybrid vehicle applications.
Abstract: A new 16-phase interleaved bidirectional dc/dc converter is developed featuring smaller input/output filters, faster dynamic response and lower device stress than conventional designs, for hybrid vehicle applications. The converter is connected between the ultracapacitor (UC) pack and the battery pack in a multisource energy storage system of a hybrid vehicle. Typically, multiphase interleaved converters require a current control loop in each phase to avoid imbalanced current between phases. This increases system cost and control complexity. In this paper, in order to minimize imbalance currents and remove the current control loop in each phase, the converter is designed to operate in discontinuous conduction mode (DCM). The high current ripple associated with DCM operation is then alleviated by interleaving. The design, construction, and testing of an experimental hardware prototype is presented, with the test results included. Finally, a novel soft switch topology for DCM operation is proposed for future research, to achieve zero-voltage switching (ZVS), or zero-current switching (ZCS) in all transitions.
01 Sep 2012
TL;DR: In this paper, a fully decoupled current control which allows an independent input, output, and internal balancing current control is presented to equalize the energy stored in the nine converter arms, including average, horizontal, vertical and diagonal balancing control loops.
Abstract: The Modular Multilevel Matrix Converter (M3C) is a Modular Multilevel Converter topology which is suitable for high power low speed drive applications. This paper presents a fully decoupled current control which allows an independent input, output and internal balancing current control. To equalize the energy stored in the nine converter arms, an energy and balancing control is presented which includes average, horizontal, vertical and diagonal balancing control loops. Simulation results are used to verify the function of the M3C together with an induction motor drive system. Additionally, the proper function of the recently constructed arm PCB working as single phase multilevel STATCOM is presented. This PCB will be used for each arm in the laboratory prototype of the M3C in the near future.
16 Jan 2012
TL;DR: The main approach relies on approximating the measurements as normal distributed random variables, and applying the maximum likelihood principle, and an alternative based on support vectors is discussed.
Abstract: We consider here the problem of detecting changes in the status of switching devices, circuit breakers in particular, in distribution networks. The lack of measurements in distribution networks compared to transmission networks is the main challenge of this problem. Using expected values of power consumption, and their variance, we are able to quickly calculate the confidence level of identifying the correct topology, or the current status of switching devices, using any given configuration of real time measurements. This allows to compare between different configurations in order to select the optimal one. The main approach we propose relies on approximating the measurements as normal distributed random variables, and applying the maximum likelihood principle. We also discuss an alternative based on support vectors. Results are demonstrated using the IEEE 123 buses distribution test case.
TL;DR: In this paper, the authors proposed a new topology based on the non-insulated dc voltage sources for multilevel inverter with reduced number of switching devices, which can be easily extended to a desired number of voltage levels.
Abstract: Multilevel inverters have an important portion in power processing in power systems. These inverters have some inherent advantages such as ability to operate with high power and voltage, improved output waveform quality and flexibility which make them attractive and more popular. This study proposes a new topology based on the non-insulated dc voltage sources for multilevel inverter with reduced number of switching devices. As a result, it reduces control complexity and gate driver circuits. The proposed topology is a general topology which can be easily extended to a desired number of voltage levels. All of the desired output voltage levels (both odd and even) can be achieved using the proposed topology. The validity of the proposed multilevel inverter is verified with both computer simulation and experimental results from a 15-level laboratory prototype.
TL;DR: In this paper, an innovative design methodology that optimizes the weighted efficiency of a single-phase, single-stage flyback inverter for ac-photovoltaic (PV) module applications is proposed.
Abstract: An innovative design methodology that optimizes the weighted efficiency of a single-phase, single-stage flyback inverter for ac-photovoltaic (PV) module applications is proposed. This novel approach combines the essential advantages of the flyback topology with high-efficiency design in the direction of a reliable, cost-effective, and high-performance PV system. The proposed methodology focuses exclusively on choosing the inverter design parameters, taking into consideration the PV module characteristics and the topology operation constraints. In order to meet this goal, an analytical losses calculation should be performed. Since the problem is complicated, special effort is given to manipulate the equations and variables in such a way to minimize the number of parameters. The proposed methodology is also verified experimentally.
TL;DR: A formation control algorithm is proposed which makes the nonlinear multi-agent systems converge to a desired formation by constructing an appropriate Lyapunov functional and utilising linear matrix inequality (LMI) method.
Abstract: In this article, two kinds of leader-following formation control problems for second-order nonlinear multi-agent systems are investigated, that is, the cases with fixed topology and with switching topology. For the former, by constructing an appropriate Lyapunov functional and utilising linear matrix inequality (LMI) method, we propose a formation control algorithm which makes the nonlinear multi-agent systems converge to a desired formation. In addition, a formation control algorithm is also developed for coupled double-integrators with a constant reference velocity. Then we extend these results to the case when the interaction topology is switching. Numerical simulations are presented finally to demonstrate the effectiveness of the proposed results.
TL;DR: In this paper, the authors presented optimized very high performance CMOS slow-wave shielded CPW transmission lines (S-CPW TLines), which were used to realize a 60 GHz bandpass filter, with T-junctions and open stubs.
Abstract: This paper presents optimized very high performance CMOS slow-wave shielded CPW transmission lines (S-CPW TLines). They are used to realize a 60-GHz bandpass filter, with T-junctions and open stubs. Owing to a strong slow-wave effect, the longitudinal length of the S-CPW is reduced by a factor up to 2.6 compared to a classical microstrip topology in the same technology. Moreover, the quality factor of the realized S-CPWs reaches 43 at 60 GHz, which is about two times higher than the microstrip one and corresponds to the state of the art concerning S-CPW TLines with moderate width. For a proof of concept of complex passive device realization, two millimeter-wave filters working at 60 GHz based on dual-behavior-resonator filters have been designed with these S-CPWs and measured up to 110 GHz. The measured insertion loss for the first-order (respectively, second-order) filter is -2.6 dB (respectively, -4.1 dB). The comparison with a classical microstrip topology and the state-of-the-art CMOS filter results highlights the very good performance of the realized filters in terms of unloaded quality factor. It also shows the potential of S-CPW TLines for the design of high-performance complex CMOS passive devices.
01 Jul 2012
TL;DR: A channel assignment algorithm named as DPSO-CA which is based on the discrete particle swarm optimization and can be used to find the approximate optimized solution is formulated and it is shown that the algorithm can be easily extended to the case with uneven traffic load in the network.
Abstract: The wireless mesh network is a new emerging broadband technology providing the last-mile Internet access for mobile users by exploiting the advantage of multiple radios and multiple channels. The throughput improvement of the network relies heavily on the utilizing the orthogonal channels. However, an improper channel assignment scheme may lead to network partition or links failure. In this paper we consider the assignment strategy with topology preservation by organizing the mesh nodes with available channels, and aim at minimizing the co-channel interference in the network. The channel assignment with the topology preservation is proved to be NP-hard and to find the optimized solution in polynomial time is impossible. We have formulated a channel assignment algorithm named as DPSO-CA which is based on the discrete particle swarm optimization and can be used to find the approximate optimized solution. We have shown that our algorithm can be easily extended to the case with uneven traffic load in the network. The impact of radio utilization during the channel assignment process is discussed too. Extensive simulation results have demonstrated that our algorithm has good performance in both dense and sparse networks compared with related works.
TL;DR: In this paper, the inverse Watkins-Johnson (IWJ) topology is proposed to achieve robust electromagnetic interference noise immunity, which is achieved by allowing shoot through of the inverter leg switches.
Abstract: A Z-source inverter (ZSI) uses an L-C impedance network between the source and the voltage source inverter (VSI). It has the property of stepping down or stepping up the input voltage, as a result, the output can be either higher or lower than the input voltage as per requirement. This topology also possesses robust electromagnetic interference noise immunity, which is achieved by allowing shoot through of the inverter leg switches. This letter proposes an inverter circuit based on the inverse Watkins-Johnson (IWJ) topology that can achieve similar advantages as that of a ZSI. The proposed circuit requires two switches and one pair of an LC filter apart from the VSI. The systematic development of this inverter topology is described starting from the basic IWJ circuit. Steady-state analysis and implementation of the proposed topology are also described. The pulse width modulation control strategy of the inverter is explained. An experimental prototype is used to validate the proposed circuit.
TL;DR: In this paper, a relatively simple space vector modulation (SVM) algorithm, based on the already well-understood five-phase two-level drive SVM method, is developed.
Abstract: Open-end winding three-phase variable speed drives with dual-inverter supply have been extensively investigated for various applications, including series hybrid powertrains and propulsion motors. The topology is simple to realize while offering a higher number of switching states without the need for capacitor voltage balancing algorithms, when compared to the standard multilevel converters. This paper extends the open-end winding concept to a five-phase drive. A relatively simple space-vector modulation (SVM) algorithm, based on the already well-understood five-phase two-level drive SVM method, is developed. The proposed modulation technique has the advantage of being straightforward to implement and, like its two-level counterpart, is able to generate output voltages with minimum low-order harmonic content. The method generates up to 17-level output phase voltage and, therefore, offers superior harmonic performance when compared to the two-level five-phase modulation. The developed scheme is verified via detailed simulations and experiments, using a five-phase induction machine operating under open-loop V/f control.
TL;DR: A novel interleaved boost converter with zero-voltage switching (ZVS) and zero-current switching ( ZCS) characteristics is proposed in this paper and by establishing the common soft-switching module, the soft- Switching interleaves converter can greatly reduce the size and cost.
Abstract: A novel interleaved boost converter with zero-voltage switching (ZVS) and zero-current switching (ZCS) characteristics is proposed in this paper. By using the interleaved approach, this topology not only decreases the current stress of the main circuit device but also reduces the ripple of the input current and output voltage. Moreover, by establishing the common soft-switching module, the soft-switching interleaved converter can greatly reduce the size and cost. The main switches can achieve the characteristics of ZVS and ZCS simultaneously to reduce the switching loss and improve the efficiency with a wide range of load. This topology has two operational conditions depending on the situation of the duty cycle. A driving circuit is designed for the proposed topology to determine the two conditions automatically. The operational principle, theoretical analysis, and design method of the proposed converter are presented. Finally, simulations and experimental results are used to verify the feasibility and exactness of the proposed converter.
TL;DR: This paper investigates different modulation strategies applied to RMC for offshore wind farms, focused on efficiency improvement of the entire convention system and shows that current source operation with space vector modulation presents minimum losses at nominal wind velocity.
Abstract: Reduced matrix converter (RMC) is a convenient topology for offshore wind farm due to its potential to reduce the size and weight of the converter, to improve the reliability by removing the electrolytic capacitor, and to increase the efficiency inherent to less stages of conversion. Moreover, it is a very flexible topology which permits different types of operation with a simpler modulation compared with conventional three-phase matrix converter. This paper investigates different modulation strategies applied to RMC for offshore wind farms, focused on efficiency improvement of the entire convention system. Simulation results using a detailed loss model for high-power level are presented. Four cases are investigated according to the modulation strategies (space vector modulation and carrier-based modulation) and the operation principle (current source converter or voltage source converter). Losses in the clamp circuit are also calculated. Different wind velocities are considered in the simulations. Results show that current source operation with space vector modulation presents minimum losses at nominal wind velocity. This operation is suitable for series connection of offshore wind farms which has been reported as the most efficient alternative from the grid losses point of view.
TL;DR: In this paper, the authors proposed tractable transmission topology control policies, which employ sensitivity information readily available from the economic generation dispatch (ED) to select candidate lines to change status while maintaining system connectivity.
Abstract: The standard economic generation dispatch (ED) minimizes generation costs subject to transmission constraints, where the status of each line, i.e., open or closed, is fixed. Recent research shows that, by optimally dispatching the network topology along with generation resources, significant congestion costs may be avoided. Optimal topology control, i.e., appropriate changes of transmission-line status, for real-sized power networks requires the solution of a computationally intractable mixed-integer linear program; however, it appears that much of the cost savings may be attained by changing the status of just a few lines. This paper proposes tractable transmission topology control policies, which employ sensitivity information readily available from the ED to select candidate lines to change status while maintaining system connectivity. Implementation on the IEEE 118-bus test system found that our best performing policy captured an average of 96% of the potential cost savings. Moreover, the limited computational effort required suggests that these policies could be employed in real-system operations.
TL;DR: Using tools from graph theory and nonnegative matrix theory, particularly the product properties of row-stochastic matrices from an infinite set, it is shown that essentially the same result as that for the synchronous discrete-time system holds in the face of asynchronous setting.
Abstract: This paper is concerned with the asynchronous consensus problem of discrete-time second-order multi-agent system under dynamically changing communication topology, in which the asynchrony means that each agent detects the neighbors' state information to update its state information by its own clock. It is not assumed that the agents' clocks are synchronized. Nor is it assumed that the time sequence over which each agent update its state information is evenly spaced. By using tools from graph theory and nonnegative matrix theory, particularly the product properties of row-stochastic matrices from an infinite set, we finally show that essentially the same result as that for the synchronous discrete-time system holds in the face of asynchronous setting. This generalizes the existing result to a very general case.
TL;DR: An analytical model and an exhaustive optimization procedure for finding the minimum active mass subject to certain performance specifications are developed for the novel linear air-cored topology and first test results from a 1 kW experimental machine confirm the feasibility of implementing the novel topology on a small scale.
Abstract: Direct drive wave energy converters are attractive due to the elimination of intermediate mechanical power conversion stages. Longitudinal flux (LF) linear generators with iron-cored stators have so far been dominant in experimental direct drive WECs, but suffer from high bearing loads and unwanted end effects. A novel linear air-cored topology is presented in this paper which eliminates most of the end effects associated with LF iron-cored machines as well as the attraction forces between iron-cored stators and magnet translators. The attraction forces between the opposing sides of the translators of double-sided air-cored machines are also ideally eliminated. An analytical model and an exhaustive optimization procedure for finding the minimum active mass subject to certain performance specifications are developed for the novel topology. Finite element analysis is used to verify and further analyze the model. First test results from a 1 kW experimental machine correspond well with designed values and confirm the feasibility of implementing the novel topology on a small scale.