Showing papers on "Topology (electrical circuits) published in 2005"

Design and analysis of an MST-based topology control algorithm

Abstract: In this paper, we present a minimum spanning tree (MST)-based algorithm, called local minimum spanning tree (LMST), for topology control in wireless multihop networks. In this algorithm, each node builds its LMST independently and only keeps on-tree nodes that are one-hop away as its neighbors in the final topology. We analytically prove several important properties of LMST: 1) the topology derived under LMST preserves the network connectivity; 2) the node degree of any node in the resulting topology is bounded by 6; and 3) the topology can be transformed into one with bidirectional links (without impairing the network connectivity) after removal of all unidirectional links. Simulation results show that LMST can increase the network capacity as well as reduce the energy consumption.

Local area network of serial intelligent cells

Abstract: A serial intelligent cell (SIC) and a connection topology for local area networks using Electrically-conducting media. A local area network can be configured from a plurality of SIC's interconnected so that all communications between two adjacent SIC's is both point-to-point and bidirectional. Each SIC can be connected to one or more other SIC's to allow redundant communication paths. Communications in different areas of a SIC network are independent of one another, so that, unlike current bus topology and star topology, there is no fundamental limit on the size or extent of a SIC network. Each SIC can optionally be connected to one or more data terminals, computers, telephones, sensors, actuators, etc., to facilitate interconnectivity among such devices. Networks according to the present invention can be configured for a variety of applications, including a local telephone system, remote computer bus extender, multiplexers, PABX/PBX functionality, security systems, and local broadcasting services. The network can use dedicated wiring, as well as existing wiring as the in-house telephone or electrical wiring.

Sufficient Conditions for Fast Switching Synchronization in Time Varying Network Topologies

Abstract: In previous work, empirical evidence indicated that a time-varying network could propagate sufficient information to allow synchronization of the sometimes coupled oscillators, despite an instantaneously disconnected topology. We prove here that if the network of oscillators synchronizes for the static time-average of the topology, then the network will synchronize with the time-varying topology if the time-average is achieved sufficiently fast. Fast switching, fast on the time-scale of the coupled oscillators, overcomes the descychnronizing decoherence suggested by disconnected instantaneous networks. This result agrees in spirit with that of where empirical evidence suggested that a moving averaged graph Laplacian could be used in the master-stability function analysis. A new fast switching stability criterion here-in gives sufficiency of a fast-switching network leading to synchronization. Although this sufficient condition appears to be very conservative, it provides new insights about the requirements for synchronization when the network topology is time-varying. In particular, it can be shown that networks of oscillators can synchronize even if at every point in time the frozen-time network topology is insufficiently connected to achieve synchronization.

Softrouter separate control network

Abstract: An embodiment of the exemplary SoftRouter architecture includes two physically separate networks, a control plane network and a data plane network. The data plane network is one physical network for the data traffic, while the control plane network is another physical network for the control traffic. The topology of the data plane network is made up of interconnected forwarding elements (FEs). The topology of the control plane network is made up interconnected control elements (CEs). This physical independence of the control plane network from the data plane network provides for a secure mechanism to communicate among the CEs in the control plane network. In addition, this physical independence provides improved reliability and improved scalability, when compared to the traditional router architecture, where control plane message are in-band with the data plane.

Approximate distributed Kalman filtering in sensor networks with quantifiable performance

Abstract: We analyze the performance of an approximate distributed Kalman filter proposed in recent work on distributed coordination. This approach to distributed estimation is novel in that it admits a systematic analysis of its performance as various network quantities such as connection density, topology, and bandwidth are varied. Our main contribution is a frequency-domain characterization of the distributed estimator's steady-state performance; this is quantified in terms of a special matrix associated with the connection topology called the graph Laplacian, and also the rate of message exchange between immediate neighbors in the communication network.

Bridgeless PFC implementation using one cycle control technique

Abstract: Conventional boost PFC suffers from the high conduction loss in the input rectifier-bridge. Higher efficiency can be achieved by using the bridgeless boost topology. This new circuit has issues such as voltage sensing, current sensing and EMI noise. In this paper, one cycle control technique is used to solve the issues of the voltage sensing and current sensing. Experimental results show efficiency improvement and EMI performance

Interference-aware topology control for wireless sensor networks

Abstract: Topology control has been well studied in wireless ad hoc networks. However, only a few topology control methods (e.g. (1)) take into account the low interference as a goal of the methods. Some researchers tried to indirectly reduce the interference by reducing the transmission power or by devising low degree topologies, but none of those protocols can guarantee low interference. In this paper we present several algorithms to construct network topologies such that the maximum (or average) link (or nodal) interference of the topology is either minimized or approximately minimized. The algorithms and definitions introduced in this paper are not based on any geometry information about the nodes and they work for any graph models of wireless communication. The theoretical results are corroborated by simulation studies.

Topological hole detection in wireless sensor networks and its applications

Abstract: The identification of holes in a wireless sensor network is of primary interest since the breakdown of sensor nodes in a larger area often indicates one of the special events to be monitored by the network in the first place (e.g. outbreak of a fire, destruction by an earthquakes etc.). This task of identifying holes is especially challenging since typical wireless sensor networks consist of lightweight, low-capability nodes that are unaware of their geographic location.But there is also a secondary interest in detecting holes in a network: recently routing schemes have been proposed that do not assume knowledge of the geographic location of the network nodes but rather perform routing decisions based on the topology of the communication graph. Holes are salient features of the topology of a communication graph.In the first part of this paper we propose a simple distributed procedure to identify nodes near the boundary of the sensor field as well as near hole boundaries. Our hole detection algorithm is based purely on the topology of the communication graph, i.e. the only information available is which nodes can communicate with each other. In the second part of this paper we illustrate the secondary interest of our hole detection procedure using several examples.

A multilevel inverter system for an induction motor with open-end windings

Abstract: In this paper, a multilevel inverter system for an open-end winding induction motor drive is described. Multilevel inversion is achieved by feeding an open-end winding induction motor with two two-level inverters in cascade (equivalent to a three-level inverter) from one end and a single two-level inverter from the other end of the motor. The combined inverter system with open-end winding induction motor produces voltage space-vector locations identical to a six-level inverter. A total of 512 space-vector combinations are available in the proposed scheme, distributed over 91 space-vector locations. The proposed inverter drive scheme is capable of producing a multilevel pulsewidth-modulation (PWM) waveform for the phase voltage ranging from a two-level waveform to a six-level waveform depending on the modulation range. A space-vector PWM scheme for the proposed drive is implemented using a 1.5-kW induction motor with open-end winding structure.

Control channel based MAC-layer configuration, routing and situation awareness for cognitive radio networks

Abstract: In a cognitive radio (CR) network, MAC-layer configuration involves determining a common set of channels to facilitate communication among participating nodes. Further, the availability of multiple channels and frequent channel switches add to the complexity of route selection. Knowledge of the global network topology can be used to solve the above-described problems. In this paper, we propose a distributed algorithm for gathering global network topology information for a CR network. We outline approaches that utilize the gathered topology information for MAC-layer configuration and efficient routing of packets. In addition, situation awareness is achieved by sharing the physical location information among the nodes in the network. The proposed algorithm determines the global network topology in O(N2 ) timeslots, where N is the maximum number of nodes deployed. With 80 available channels for communication, the algorithm terminates within 0.8 second

Circuit topology and the evolution of robustness in two-gene circadian oscillators

Abstract: Many parameters driving the behavior of biochemical circuits vary extensively and are thus not fine-tuned. Therefore, the topology of such circuits (the who-interacts-with-whom) is key to understanding their central properties. I here explore several hundred different topologies of a simple biochemical model of circadian oscillations to ask two questions: Do different circuits differ dramatically in their robustness to parameter change? If so, can a process of gradual molecular evolution find highly robust topologies when starting from less robust topologies? I find that the distribution of robustness among different circuit topologies is highly skewed: Most show low robustness, whereas very few topologies are highly robust. To address the second evolutionary question, I define a topology graph, each of whose nodes corresponds to one circuit topology that shows circadian oscillations. Two nodes in this graph are connected if they differ by only one regulatory interaction within the circuit. For the circadian oscillator I study, most topologies are connected in this graph, making evolutionary transitions from low to high robustness easy. A similar approach has been used to study the evolution of robustness in biological macromolecules, with similar results. This suggests that the same principles govern the evolution of robustness on different levels of biological organization. The regulatory interlocking of several oscillating gene products in biological circadian oscillators may exist because it provides robustness.

Multi-input bidirectional DC-DC converter combining DC-link and magnetic-coupling for fuel cell systems

Abstract: This paper presents a new multi-input bidirectional dc-dc converter which connects a fuel cell, storage and load by a combination of a dc-link and magnetic-coupling. A boost-dual-half-bridge and a bidirectional direct-connected switching cell are used. The topology is simple and only needs six power switches. The load and the sources are galvanically isolated. Furthermore, the proposed converter draws/injects smooth current from the fuel cell and the supercapacitor. The system is suitable for medium-power applications where simple topology, autonomous operation, compact packaging, and low cost are required. Different control schemes to manage power flow are proposed and compared. Simulation and experimental results that verify the effectiveness of the topology and its control scheme are presented. Moreover, it is shown that the idea of combining the dc-link and magnetic-coupling can be further developed to a general topology for multi-port bidirectional dc-dc converters.

Reconstructing biological networks using conditional correlation analysis

Abstract: Motivation: One of the present challenges in biological research is the organization of the data originating from high-throughput technologies. One way in which this information can be organized is in the form of networks of influences, physical or statistical, between cellular components. We propose an experimental method for probing biological networks, analyzing the resulting data and reconstructing the network architecture. Methods: We use networks of known topology consisting of nodes (genes), directed edges (gene--gene interactions) and a dynamics for the genes' mRNA concentrations in terms of the gene--gene interactions. We proposed a network reconstruction algorithm based on the conditional correlation of the mRNA equilibrium concentration between two genes given that one of them was knocked down. Using simulated gene expression data on networks of known connectivity, we investigated how the reconstruction error is affected by noise, network topology, size, sparseness and dynamic parameters. Results: Errors arise from correlation between nodes connected through intermediate nodes (false positives) and when the correlation between two directly connected nodes is obscured by noise, non-linearity or multiple inputs to the target node (false negatives). Two critical components of the method are as follows: (1) the choice of an optimal correlation threshold for predicting connections and (2) the reduction of errors arising from indirect connections (for which a novel algorithm is proposed). With these improvements, we can reconstruct networks with the topology of the transcriptional regulatory network in Escherichia coli with a reasonably low error rate. Contact: gustavo@us.ibm.com Supplementary information: Available from our website: www.research.ibm.com/FunGen

A multilevel converter topology with fault-tolerant ability

Abstract: A new topology with fault-tolerant ability that improves the reliability of multilevel converters is proposed. This new topology is developed through analysis of different power device's failure modes. With the proposed scheme, the function of the power stage can be maintained even part of it fails. Its fault-tolerant ability results from the redundant nature of the multiswitching-state topology and from control signal modification. Furthermore, it balances the voltage levels automatically without any assistance from other circuits. The validity of the proposed scheme is confirmed by experiments in a five-level single-phase inverter prototype.

Cooperative routing in wireless networks

Abstract: The joint problem of transmission-side diversity and routing in wireless networks is studied. It is assumed that each node in the network is equipped with a single omni-directional antenna and multiple nodes are allowed to coordinate their transmissions to achieve transmission-side diversity. The problem of finding the minimum energy route under this setting is formulated. Analytical asymptotic results are obtained for lower bounds on the resulting energy savings for both a regular line network topology and a grid network topology. For a regular line topology, it is possible to achieve energy savings of 39%. For a grid topology, it is possible to achieve energy savings of 56%. For arbitrary networks, we develop heuristics with polynomial complexity which result in average energy savings of 30% – 50% based on simulations.

A two-output series-resonant inverter for induction-heating cooking appliances

Abstract: Multiple-burner induction-heating cooking appliances are suitable for using multiple-output inverters. Some common approaches use several single-output inverters or a single-output inverter multiplexing the loads along the time periodically. By specifying a two-output series-resonant high-frequency inverter, a new inverter is obtained fulfilling the requirements. The synthesized converter can be considered as a two-output extension of a full-bridge topology. It allows the control of the two outputs, simultaneously and independently, up to their rated powers saving component count compared with the two-converter solution and providing a higher utilization of electronics. To verify theoretical predictions, the proposed converter is designed and tested experimentally in an induction-heating appliance prototype. A fixed-frequency control strategy is digitally implemented with good final performances for the application, including ZVS operation for active devices and a quick heating function. Although the work is focused on low-power induction heating, it can be probably useful for other power electronic applications.

Photovoltaic DC-to-AC power converter and control method

Abstract: An apparatus and method of control for converting DC (direct current) power from a solar photovoltaic source to AC (alternating current) power. A novel DC-to-AC power converter topology and a novel control method are disclosed. This combination of topology and control are very well suited for photovoltaic microinverter applications. Also, a novel variant of this control method is illustrated with a number of known photovoltaic DC-to-AC power converter topologies. The primary function of both control methods is to seek the maximum power point (MPP) of the photovoltaic source with novel, iterative, perturb and observe control algorithms. The control portion of this invention discloses two related control methods, both an improvement over prior art by having greatly improved stability, dynamic response and accuracy.

A simple space vector PWM scheme to operate a three-level NPC inverter at high modulation index including over-modulation region, with neutral point balancing

Abstract: Multilevel inverters are being increasingly used for high-power medium-voltage applications. Three-level neutral point clamped (NPC) topology is most widely used topology of multilevel inverters. However, at higher modulation index, particularly in over-modulation region, the neutral point fluctuation deteriorates the performance of the inverter. Furthermore, operating the inverter at lower modulation index implies that it is operated at lower voltages only, and the installed DC link capacity is not fully utilized. This paper proposes a simple space vector PWM scheme for operating a three-level NPC inverter at higher modulation indices including over-modulation region, with neutral point balancing. Experimental results are provided.

A family of high power density unregulated bus converters

Abstract: This paper begins by reviewing current bus converters and exploring their limitations. Next, a family of inductor-less bus converters is proposed to overcome the limitations. In the new bus converters, magnetizing current is used to achieve zero-voltage-switching (ZVS) turn-on for all switches. The resonant concept is used to achieve nearly zero-current-switching (ZCS) turn-off for the primary switches and no body diode loss for the synchronous rectifiers (SRs). Meanwhile, the self-driven method can be easily applied to save drive loss of SRs. Based on these concepts, a full-bridge bus converter is built in the quarter-brick size to verify the analysis. The experimental results indicate that it can achieve 95.5% efficiency at 500-W, 12-V/45-A output. Compared with industry products, this topology can dramatically increase the power density. These concepts are also applied to nonisolated dc/dc converters. As an example, a resonant Buck converter is proposed and experimentally demonstrated.

Localized topology control algorithms for heterogeneous wireless networks

Abstract: Most existing topology control algorithms assume homogeneous wireless networks with uniform maximal transmission power, and cannot be directly applied to heterogeneous wireless networks where the maximal transmission power of each node may be different. We present two localized topology control algorithms for heterogeneous networks: Directed Relative Neighborhood Graph (DRNG) and Directed Local Spanning Subgraph (DLSS). In both algorithms, each node independently builds its neighbor set by adjusting the transmission power, and defines the network topology by using only local information. We prove that: 1) both DRNG and DLSS can preserve network connectivity; 2) the out-degree of any node in the resulting topology generated by DRNG or DLSS is bounded by a constant; and 3) DRNG and DLSS can preserve network bi-directionality. Simulation results indicate that DRNG and DLSS significantly outperform existing topology control algorithms for heterogeneous networks in several aspects.

Compact, frequency-agile, absorptive bandstop filters

Abstract: Two absorptive bandstop filter circuit topologies are introduced. The preferred topology is analyzed and its advantages over traditional approaches quantified. A corresponding varactor-tuned microstrip absorptive bandstop filter is described and its unique ability to maintain its attenuation while tuning across a broad frequency range using only resonant frequency tuning is demonstrated.

A 1mW current-reuse CMOS differential LC-VCO with low phase noise

Abstract: An LC-VCO with halt of the power dissipation of a that of the conventional topology is presented. The LC-VCO replaces one of the NMOSFET of the conventional differential LC-VCO with a PMOSFET. The operational principles and design guidelines of the proposed topology are reported. The proposed LC-VCO is implemented in a 0.18 /spl mu/m CMOS technology for 2GHz applications and measurements show phase noise is -103dBc/Hz at 100kHz offset while dissipating 1mW from a 1.25V supply.

Current-source converter based STATCOM: modeling and control

Abstract: STATCOM is a FACTS controller that is used in power systems to regulate the line voltage, enhance the power transmission capacity and extend the transient stability margin. STATCOM is conventionally realized by a voltage-source converter; however, being a current injection device, its performance can be improved when realized by a current-source converter (CSC) that can generate a controllable current directly at its output terminals. In this paper, a STATCOM based on the current-source converter topology is proposed. The nonlinear model of the current-source converter, which is the source of the difficulties in the controller design, has been modified to a linear model through a novel modeling technique. The proposed modeling technique is not based on the linearization of a set of nonlinear equations around an operating point. Instead, the power balance equation and a nonlinear input transformation are used to derive a linear model independent of the operating point. This model acts as the basis for the design of a decoupled state-feedback controller. The proposed STATCOM has been simulated using the PSCAD/EMTDC package. The simulation results show that a CSC-based STATCOM can result in excellent current and voltage waveforms as well as very short response time while operating at a low switching frequency. This makes the proposed scheme suitable for high power applications.

Small-signal and signal-flow-graph modeling of switched Z-source impedance network

Abstract: The Z-source inverter is a recently proposed converter topology that uses a unique X-shaped impedance network on its dc side for achieving both voltage-buck and boost capabilities. In the process of designing control schemes for the Z-source inverter, knowledge of the transfer function representing its unique dc impedance network is essential. Toward this end, this letter presents dynamic small-signal modeling of the Z-source impedance network using perturbed mathematical analysis and a signal-flow graph with parasitic components taken into consideration. In particular, the developed average control-to-output model reveals the presence of a right-hand-plane zero in the network transfer function, whose trajectories with variations in network parameters can be studied using classical root-locus analyses. Using the graphical signal-flow modeling approach, various disturbance-to-output transfer functions can also be derived with their parameter sensitivity similarly studied. Lastly, simulation and experimental results are presented for verifying the dynamic phenomena identified in this letter.

Transformerless, load adaptive speed controller

Abstract: The invention in one embodiment is an improved variable speed engine/generator set with an integrated power conditioning system and control method including load shedding to generate high quality AC power with improved fuel efficiency and reduced emissions. The variable speed generator control scheme allows for load adaptive speed control of engine and generator field. The transformerless power inverter topology and control method provides the necessary output frequency, voltage and/or current waveform regulation, harmonic distortion rejection, and provides for single phase, or unbalanced loading.

Design aspects of bearingless slice motors

Abstract: The complexity of a bearingless motor offers a multitude of freedoms in constructive design because different motor setups may have nearly the same dynamic behavior, and may differ only slightly in some operation characteristic. However, the mechanical setup often has a very strong impact on the power inverter topology and the volt-ampere requirements, thereby affecting the system costs significantly. This paper focuses on design aspects of bearingless slice motors with permanent magnet excitation, and presents a methodical evaluation approach based on performance indexes.

Optimal Control of the Boost dc-dc Converter

Abstract: This paper extends the recently introduced approach for modelling and solving the optimal control problem of fixed frequency switch-mode dc-dc converters using hybrid system methodologies to the boost circuit topology, including parasitic elements. The concept of the ν-resolution model is employed to capture the hybrid nature of these circuits. As the resulting equations are nonlinear, two models are formulated, one featuring additional piecewise affine approximations of the nonlinearities and another nonlinear model that retains the nonlinearities in the related system description. An optimal control problem is formulated and solved online for both cases. Simulation results are provided to compare the outcomes of these approaches.

Analysis of a High-Power-Factor Electronic Ballast for High Brightness Light Emitting Diodes

Abstract: This paper analyzes the performance of a high-power-factor AC-DC converter for the supply of high-brightness light emitting diodes (HBLEDs). The considered topology is a D2 one (i.e. a topology that, working in continuous conduction mode, has a voltage conversion ratio that is a function of the duty-cycle squared), working in one of its possible discontinuous modes. No line-frequency energy storage element is used so that the LED current is pulsating at twice the line frequency, with a small high-frequency ripple on top. The impact of such pulsating current supply on LED optical performance and reliability is also evaluated by comparison with standard DC current supply

A Technology-Aware and Energy-Oriented Topology Exploration for On-Chip Networks

Abstract: As packet-switching interconnection networks replace buses and dedicated wires to become the standard on-chip interconnection fabric, reducing their power consumption has been identified to be a major design challenge. Network topologies have high impact on network power consumption. Technology scaling is another important factor that affects network power since each new technology changes semiconductor physical properties. As shown in this paper, these two aspects need to be considered synergistically. In this paper, we characterize the impact of process technologies on network energy for a range of topologies, starting from 2-dimensional meshes/tori, to variants of meshes/tori that incorporate higher dimensions, multiple hierarchies and express channels. We present a method which uses an analytical model to predict the most energy-efficient topology based on network size and architecture parameters for future technologies. Our model is validated against cycle-accurate network power simulation and shown to arrive at the same predictions. We also show how our method can be applied to actual parallel benchmarks with a case study. We see this work as a starting point for defining a roadmap of future on-chip networks.