• International Journal of CAD/CAM
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• v.7 no.1
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• pp.11-20
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• 2007

A topology optimization methodology, named "smooth boundary topology optimization," is proposed to overcome the shortcomings of cell-based methods. Material boundary is represented by B-spline curves and their control points are considered as design variables. The design is improved by either creating a hole or moving control points. To determine which is more beneficial, a selection criterion is defined. Once determined to create a hole, it is represented by a new B-spline and recognized as a new boundary. Because the proposed method deals with the control points of B-spline as design variables, their total number is much smaller than cell-based methods and it ensures smooth boundaries. Differences between our method and level set method are also discussed. It is shown that our method is a natural way of obtaining smooth boundary topology design effectively combining computer graphics technique and design sensitivity analysis.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.5 no.2
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• pp.108-113
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• 2005

This paper suggests a control method for an efficient topology/parameter evolution in a bond graph-based GP design framework that automatically synthesizes designs for multi-domain, lumped parameter dynamic systems. We adopt a hierarchical breeding control mechanism with fitness-level-dependent differences to obtain better balancing of topology/parameter search - biased toward topological changes at low fitness levels, and toward parameter changes at high fitness levels. As a testbed for this approach in bond graph synthesis, an eigenvalue assignment problem, which is to find bond graph models exhibiting minimal distance errors from target sets of eigenvalues, was tested and showed improved performance for various sets of eigenvalues.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.5
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• pp.431-437
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• 2022

This study proposes a converter that makes battery charging, discharging, and zero voltage control possible. The proposed topology consists of an LLC converter and a half-bridge inverter, and all power semiconductor devices are applied Si-MOSFETs. The topology is designed with an LLC switching frequency of 100 kHz, a half-bridge inverter switching frequency of 50 kHz, and a battery voltage of 5 V. The advantages of the charging/discharging operation of the 5 V battery voltage and the zero voltage control of the battery are verified. In addition, by using a two-stage topology, the battery can be charged, discharged through current control, and discharged to zero voltage. With the proposed topology, the current can be maintained even when the battery voltage drops to zero.

• ETRI Journal
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• v.30 no.2
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• pp.341-343
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• 2008

This letter presents an angular minimum spanning tree (AMST) algorithm for topology control in multi-hop wireless ad hoc networks. The AMST algorithm builds up an MST for every angular sector of a given degree around each node to determine optimal transmission power for connecting to its neighbors. We demonstrate that AMST preserves both local and network-wide connectivity. It also improves robustness to link failure and mitigates transmission power waste.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.1311-1318
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• 2015

This paper introduces a novel topology and an effective control strategy for a shunt hybrid power filter (SHPF) to simultaneously compensate harmonic currents and reactive power. The proposed SHPF topology is composed of an LC passive filter tuned to the 7^th harmonic frequency and a small-rated active filter connected in parallel with the inductor L_pf of the LC passive filter. Together with the SHPF topology, we also propose a control strategy, which consists of a proportional-integral (PI) controller for DC-link voltage regulation and a PI plus repetitive current controller, in order to compensate both the harmonic current and the reactive power without the need for additional hardware. Thanks to the effectiveness of the proposed control scheme, the supply current is sufficiently compensated to be sinusoidal and in-phase with the supply voltage, regardless of the distorted and phase lagging of the load current. The effectiveness of the proposed SHPF topology and control strategy is verified by simulated and experimental results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.7B
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• pp.488-501
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• 2008

Convergence of various wireless systems can be cost effectively achieved through enhancement of existing technology. The emergence of Wireless Mesh Network (WMN) entails the interoperability and interconnection of various wireless technologies in one single system. Furthermore, WMN can be implemented with multi-radio and multi-channel enhancement. A multi-radio, multi-channel wireless mesh network could greatly improve certain networking performance metrics. In this research, two approaches namely, clustering and topology control mechanisms are integrated with multi-radio multi-channel wireless mesh network. A Clustering and Topology Control Algorithm (CTCA)is presented that would prolong network lifetime of the client nodes and maintain connectivity of the routers.

• Journal of Power Electronics
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• v.16 no.5
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• pp.1743-1751
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• 2016

The increasing demand for high voltage DC grids resulting from the continuous installation of offshore wind farms in the North Sea has led to the concept of multi-terminal direct current (MTDC) grids, which face some challenges. Power (current) flow control is a challenge that must be addressed to realize a reliable operation of MTDC grids. This paper presents a reduced switch count topology of a current flow controller (CFC) for power flow and current limiting applications in MTDC grids. A simple control system based on hysteresis band current control is proposed for the CFC. The theory of operation and control of the CFC are demonstrated. The key features of the proposed controller, including cable current balancing, cable current limiting, and current nulling, are illustrated. An MTDC grid is simulated using MATLAB/SIMULINK software to evaluate the steady state and dynamic performance of the proposed CFC topology. Furthermore, a low power prototype is built for a CFC to experimentally validate its performance using rapid control prototyping. Simulation and experimental studies indicate the fast dynamic response and precise results of the proposed topology. Furthermore, the proposed controller offers a real solution for power flow challenges in MTDC grids.

• Journal of Power Electronics
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• v.15 no.4
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• pp.910-919
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• 2015

The use of a PV grid-connected inverter with non-isolated topology and without a transformer is good for improving conversion efficiency; however, this inverter has become increasingly complicated for eliminating leakage current. To simplify the complicated architecture of traditional three-level dual buck inverters, a new dual Buck three-level PV grid-connected inverter topology is proposed. In the proposed topology, the voltage on the grounding stray capacitor is clamped by large input capacitors and is equal to half of the bus voltage; thus, leakage current can be eliminated. Unlike in the traditional topology, the current in the proposed topology passes through few elements and does not flow through the body diodes of MOSFET switches, resulting in increased efficiency. Additionally, a multi-loop control method that includes voltage-balancing control is proposed and analyzed. Both simulation and experimental results are demonstrated to verify the proposed structure and control method.

• Steel and Composite Structures
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• v.39 no.5
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• pp.511-528
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• 2021

There are recently some advances in solving numerically topology optimization problems for large-scaled trusses based on ground structure approach. A disadvantage of this approach is that the final design usually includes many bars, which is difficult to be produced in practice. One of efficient tools is a so-called filter scheme for the ground structure to reduce this difficulty and determine several distinct bars. In detail, this technique is valuable for practical uses because unnecessary bars are filtered out from the ground structure to obtain a well-defined structure during the topology optimization process, while it still guarantees the global equilibrium condition. This process, however, leads to a singular system of equilibrium equations. In this case, the minimization of least squares with Tikhonov regularization is adopted. In this paper, a proposed algorithm in controlling optimal Tikhonov parameter is considered in combination with the filter scheme due to its crucial role in obtaining solution to remove numerical singularity and saving computational time by using sparse matrix, which means that the discrete optimal topology solutions depend on choosing the Tikhonov parameter efficiently. Several numerical examples are investigated to demonstrate the efficiency of the filter parameter control algorithm in terms of the large-scaled optimal topology designs.

• Proceedings of the KIEE Conference
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• 2006.07d
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• pp.2122-2123
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• 2006

본 논문에서는 멀티 홈 패킷 무선통신 네트워크를 위한 An Energy-efficient Topology Control 을 제안한다. 센서 네트워크의 기본적인 형태에 따라 네트워크 망의 구성 방식은 큰 차이를 가져온다. 현재 센서 네트워크의 topology control 의 많은 부분에서는 clustering을 이용하여 센서 네트워크의 lifetime 을 연장시키는 연구가 진행 되고 있다. 그러나 cluster 로의 노드의 연합과 분리는 네트워크 topology 의 안정성을 혼란시킬 뿐만 아니라, BS(Base Station)가 시스템의 외부에 존재하는 경우 더 적합한 방식이라고 볼 수 있다. 본 논문에서는 BS 가 시스템의 내부에 존재하는 경우에 대한 sensor network의 lifetime 을 연장시키는 방안에 대해 제안 하고 있다. 이러한 시스템의 경우 BS에 가까운 지역일수록 Black-hole effect 가 발생할 가능성이 증가하게 되고 이는 네트워크의 수명을 단축시키게 된다. 따라서 노드의 energy를 균등하게 사용 함 으로서 lifetime을 연장 하는 on-demand 방식의 topology control을 제시하고 이를 시뮬레이션으로 확인하였다.