Topology (electrical circuits)

About: Topology (electrical circuits) is a research topic. Over the lifetime, 33316 publications have been published within this topic receiving 397651 citations. The topic is also known as: topology.

Structural controllability of multi-agent systems

Abstract: In this paper, the controllability problem for multi-agent systems is investigated. In particular, the case of a single leader under a fixed topology is considered. In contrast to the existing literature on this topic, we assume that the graph is weighted and we may freely assign the weights. Under this setup, the system is controllable if one may find a set of weights so as to satisfy the classical controllability rank condition. It turns out that this controllability notation purely depends on the topology of the communication scheme, and the multi-agent system is controllable if and only if the graph is connected. Moreover, some simulation results and numerical examples are presented to illustrate the approach.

Automatic completion and evaluation of road networks

Abstract: Road networks automatically extracted from digital imagery are in general incomplete and fragmented. Completeness and topology of the extracted network can be improved by the use of the global network structure which is a result of the function of roads as part of the transport network. This is especially – but not exclusively – important for the extraction of roads from imagery with low resolution (e.g., ground pixel size 1 m) because only little local evidence for roads can be extracted from those images. In this paper, an approach is described for the completion of incompletely extracted road networks. The completion is done by generating link hypotheses between points on the network which are likely to be connected based on the network characteristics. The proposed link hypotheses are verified based on the image data. A quantitative evaluation of the achieved improvements is given. New developments presented in this paper are the generation of link hypotheses between different connected components of the extracted road network and the introduction of measures for the evaluation of the network topology and connectivity. Results of the improved completion scheme are presented and evaluated based on the introduced measures. The results show the feasibility of the presented completion approach as well as its limitations. Major advantages of the completion of road networks are the improved network topology and connectivity of the extraction result. The new measures prove to be very useful for the evaluation of network topology and connectivity.

A general technique for derivation of average current mode control laws for single-phase power-factor-correction circuits without input voltage sensing

Abstract: This paper presents a general technique to derive average current mode control (CMC) laws without input voltage sensing to achieve high power factor for single-phase topologies operating in continuous conduction mode (CCM). The control laws are derived based on the steady-state input-output voltage relationships and the CCM large-signal averaged pulsewidth modulation (PWM)-switch model. Using this methodology, average CMC laws with linear PWM waveforms are discovered for commonly used single-phase power stage topologies such as boost, flyback, SEPIC, and buck/boost. Conventional three-loop-controlled average CMC converters can now be controlled with a two-loop architecture. Hardware results for a boost power factor correction (PFC) and simulation results for flyback, SEPIC, and buck/boost topologies verify operation. The small-signal models of the current loop and voltage loop are derived for the boost topology and are used for control loop design. Input current harmonic distortion measurements demonstrate improved performance compared to the conventional three-loop control technique.

Design and Implementation of Two-Layer Compact Wideband Butler Matrices in SIW Technology for Ku-Band Applications

Abstract: The design and realization of a novel wideband two-layer 4 × 4 Butler matrix in substrate integrated waveguide (SIW) technology are addressed. The two-layer SIW design is exploited through a two-fold enhancement approach. The two-layer topology is first explored in a simple matrix layout with minimum number of components. A space saving design is then proposed making optimum use of the two-layer topology and the SIW technology leading to a significant size reduction. A two-level, low-loss, wideband SIW transition is designed and optimized using its equivalent circuit model. The two corresponding Butler matrix prototypes are optimized, fabricated and measured. Measured and simulated results are in good agreement. Isolation characteristics better than -15 dB with input reflection levels lower than - 12 dB are experimentally validated over 24% frequency bandwidth centered at 12.5 GHz. Measured transmission magnitudes and phases exhibit good dispersive characteristics of 1 dB, around an average value of -6.8 dB, and 10° with respect to the theoretical phase values, respectively, over the entire frequency band. The impact of the measured transmission phases and magnitudes on the radiation pattern of a 4-element antenna array is also investigated.

Cascaded H-Bridge Multilevel PV Topology for Alleviation of Per-Phase Power Imbalances and Reduction of Second Harmonic Voltage Ripple

Abstract: The cascaded H-bridge (CHB) topology is ideal for implementing large-scale converters for photovoltaic (PV) applications. The improved quality of output voltage waveforms, high efficiency due to transformer-less connection, and ability to employ multiple instances of a maximum power point tracking (MPPT) algorithm are just some advantages. An important disadvantage is the required over-rating to ensure balanced three-phase currents at times of unequal PV generation. Unequal generation occurs due to shading, temperature inhomogeneity, faulty H-bridges, etc. Capacitor voltage balancing under such conditions requires zero-sequence voltage injection which increases the required number of series connected H-bridges. However, leakage current and safety requirements often dictate a need for isolation between PV arrays and the cascaded converter. Therefore, this paper proposes a converter topology that avoids the cost of extra series connected H-bridges by extending the function of dc–dc converters that provide isolation. Second harmonic power oscillations seen in typical cascaded topologies can also be eliminated or reduced through use of the proposed topology. Simulation and experimental results are presented that confirm correct operation of the proposed approach.