• Journal of Korea Multimedia Society
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• v.21 no.5
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• pp.592-598
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• 2018

In wireless sensor networks where there is no centralized base station, each node has limited transmission range and the multi-hop routing for transmitting data to the destination is the one of the important technical issues. In particular, the wireless sensor network is not powered by external power source but operates by its own battery, so it is required to maximize the network life through efficient use of energy. To balance the power consumption, the residual power based adaptive power control is required in routing protocol. In this paper, we propose a routing protocol that prolongs the network lifetime by balancing the power consumption among the nodes by controlling the transmit power according to the residual power. We evaluate the proposed routing protocol using extensive simulation, and the results show that the proposed routing scheme can balance the power consumption and prolong network lifetime.

• Journal of Power Electronics
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• v.8 no.1
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• pp.81-90
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• 2008

This paper presents an investigation of a voltage and frequency controller for an isolated asynchronous generator (IAG) driven. by a wind turbine and supplying 3-phase 4-wire loads to the isolated areas where a grid is not accessible. The control strategy is based on the indirect current control of the VSC (voltage source converter) using the frequency PI controller. The proposed controller consists of three single-phase IGBT (Insulated Gate Bipolar Junction Transistor) based VSC, which are connected to each phase of the IAG through three single phase transformers and a battery at their DC link. The controller has the capability of controlling reactive and active powers to regulate the magnitude and frequency of the generated voltage, harmonic elimination, load balancing and neutral current compensation. The proposed isolated system is modeled and simulated in MATLAB using Simulink and PSB (Power System Block-set) toolboxes to verify the performance of the controller.

• Journal of Power Electronics
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• v.18 no.4
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• pp.1223-1234
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• 2018

In this paper, a new three-port multidirectional DC-DC converter is proposed for integrating an energy storage system (ESS) to a bipolar DC microgrid (BPDCMG). The proposed converter provides a voltage-balancing function for the BPDCMG and adjusts the charge of the ESS. Thanks to the multi-functional operation of the proposed converter, the conversion stages of the system are reduced. In addition, the efficiency and weight of the system are improved. Therefore, this converter has a significant capability when it comes to use in portable BPDCMGs such as electric DC ships. The converter modes are analyzed and small-signal models of the converter in each of the independent modes are extracted. Finally, comprehensive simulation studies are carried out and a BPDCMG laboratory prototype is implemented in order to verify the performance of the proposed voltage balancer using the burst mode control scheme.

• Proceedings of the Korean Information Science Society Conference
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• 2002.10e
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• pp.40-42
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• 2002

이동 애드혹 네트워크의 경우, 이동 노드들은 자신의 데이터를 처리하는 기능 이외에 다른 노드의 데이터를 전달하는 기능을 하게 된다. 이러한 기능을 수행하기 위하여 노드는 더 많은 에너지를 소비하게 되므로, 에너지 소비량이나 에너지 균형과 같은 에너지 관련문제가 중요한 관심 분야로 조명되고 있다. 이에 관련된 연구들은 최적으로 에너지 균형을이루는 경로를 찾기 위한 방법에 관한 것이었다. 그러나 기존의 연구들은 데이터 통신 중간의 에너지 균형에 대해서는 고려하지 않고 있으며, 본 논문에서는 이 문제를 해결하기 위해노드 경고 알고리즘 (NOAL)을 제안한다. NOAL에서, 데이터를 전달하는 중간 노드들은 자신의 에너지 보유량을 검사하여 기준 값 이하일 경우, 자신의 에너지 정보를 다른 노드들에게 알리게 된다 이는 다른 노드들로부터 자신에게 더 이상의 데이터를 보내지 않도록 하며,자신은 데이터 전달에 의한 에너지 소모량을 줄일 수 있다. 본 논문에서는 NOAL을 이용하여 LEAR with NOAL (LENOAL) 을 제안한다. 실험을 통해서 결과를 산출했으며, 본 논문에서 제시한 알고리즘이 에너지 균형을 21-36% 정도 향상시킬 수 있음을 보여준다.

• The Journal of Korea Robotics Society
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• v.9 no.4
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• pp.250-257
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• 2014

In this paper, a new mobile robot, so called a rollerbot, is presented, which has single body and rugby-ball shaped roller wheel. A rollerbot has single point contact on ground and low energy consumption in motion because of the reduced friction. By changing center of mass using a balancing weight, a rollerbot is able to get steering force. The vertical position of mass center of the rollerbot in this paper is designed to lie inside radius of the roller wheel, so that to have stable equilibrium position. Thus, the posture and the steering control of the rollerbot can be easily done by changing the center of mass. Kinematics of the rollerbot is derived by transformation of differential motion in this paper.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.05a
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• pp.649-651
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• 2018

Since the ubiquitous sensor network is not connected to external power source and operated by its own battery, it is required to maximize the network life using the efficient energy utilization. In a conventional hop count based routing protocol, most sensor nodes are designed with a constant transmission power. In this paper, we propose a routing protocol that prolongs the network lifetime by balancing the power consumption among the nodes by controlling the transmit power according to the residual power of the nodes, and compared the performance of the proposed routing protocol through computer simulations.

• Journal of Power Electronics
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• v.9 no.3
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• pp.472-480
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• 2009

In this paper, a charge equalization converter with parallel-connected primary windings of transformers is proposed. The proposed work effectively balances the voltage among Lithium-Ion battery cells despite each battery cell has low voltage gap compared with its state of charge (SOC). The principle of the proposed work is that the equalizing energy from all battery strings moves to the lowest voltage battery through the isolated dc/dc converter controlled by the corresponding solid state relay switch. For this research a prototype of four Lithium-Ion battery cells is optimally designed and implemented, and experimental results show that the proposed method has excellent cell balancing performance.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.3
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• pp.175-180
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• 2008

Flow quantity to supply to a coil in floor heating system is important to achieve comfortable indoor air condition in the winter season. The hot water header is used to distribute the water into the coil. Experimental study has been performed using the water header that have 5 branches consisted of flow control valves and automatic shut-off valves. Each branch line connected it with X-L pipe. Experimental tests accomplished it to investigate the flow distribution characteristics of the hot water header. Experimental results show that the selection of the pump head and differential pressure are very important to save running energy of the system, and high differential pressure needs more friction loss in the case of suitable differential pressure for balancing of the header.

• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.639-643
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• 2003

We are interested in this paper on the control of an electromechanical system consisting of a doubly-fed induction generator(DFIG), driven by a prime mover that can supply or extract mechanical power, e.g., a flywheel inertia, and an induction motor(IM). The stator of the Induction machine is connected to the stator of the generator whose rotor voltage is regulated by a bidirectional converter. The main interest of this configuration is that it permits a bidirectional power flow between the motor, which may operate in regenerative mode, and the generator We propose a passivity-based controller to regulate the motor mechanical speed. Since this kind of controllers achieve stabilization via energy balancing, regulation of the power flow in the system is naturally incorporated. Simulation results are presented to illustrate the main points of our paper.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.10A
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• pp.1671-1683
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• 2001

무선 ad-hoc 네트워크 환경에서 이동 호스트의 에너지는 중요한 요소로 간주된다. 무선 ad-hoc 네트워크에서는 이동 호스트들이 라우팅 역할을 수행해야 하므로 네트워크 구조와 노드들의 위치에 따라 각 노드들의 라우팅 역할수해에 필요한 에너지의 양에 차이가 있게 된다. 즉, 메시지가 자주 전송되는 경로에 있는 노드들은 라우팅 역할을 수행하면서 많은 에너지를 소비하게 되고, 메시지가 적게 전송되는 경로에 있는 노드들은 상대적으로 적은 에너지를 소비하게 된다. 본 논문에서는 에너지가 적은 노드의 라우팅 역할을 에너지가 많은 노드로 전이시켜 에너지가 적은 노드의 라우팅 에너지 소비를 줄이는 기법을 제안한다. 본 제안 기법에서는 특정 노드의 라우팅 역할을 다른 노드로 전이할 때 부가적인 지역 메시지의 송수신이 필요하게 되어 전이 프로토콜에 참여하는 노드들의 에너지 소비가 전체적으로 증가될 수 있다. 하지만, 이 기법은 전체 시스템에 존재하는 노드들의 에너지 양을 균등화시킴으로서 라우팅으로 인한 에너지 소비가 많은 노드의 수명을 연장시킬 수 있게 하여, 상대적으로 많은 노드들이 라우팅에 오랫동안 참여할 수 있게 하고 시스템의 성능과 수명을 향상시킬 수 있게 한다.