• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.1984-1989
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• 2008

A powered system with fuel cell is regarded as a high current and low voltage source. Effects of the loads on the electrical power source are important to optimize the integrated power system. The design parameters of the system should be chosen by taking into account the characteristics of the fuel cell, so the costs of the power system at given operating conditions can be reduced. Furthermore, the dynamics characteristic of the system is crucial to acquire performance in applications, particularly interactions between loads and the fuel cell system. Currently, no integrated simulation has been approached to analyze interrelated effects. Therefore, the dynamic models of power conversion system with a PEM fuel cell that includes the PEM fuel cell stack, DC/DC converter and associated controls is developed. Electric lads for the system are derived by using a power theory that separates a load current into active, reactive, distortion or a mixed current component. Dependency of the DC capacitor on the loads are analyzed.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2011년도 추계학술대회
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• pp.249-250
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• 2011

In DC Power Distribution System(DC PDS), a bus voltage instability is occurred by multiple parallel loads. The Voltage Bus Conditioner(VBC) is used to mitigate the DC bus voltage transient. An adaptive controller of the VBC is designed and the simulation result of the controller is verified by PSIM simulation package for the proposed control technique.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 추계학술대회 논문집 전력기술부문
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• pp.472-475
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• 2008

A DC distributed power system(DPS) has many loads with varied functions. In particular, there may be large pulsed toads with short duty ratio, which can affect the normal operation of other loads. In this paper, a bi-directional converts with inductive storage is used as a DC bus conditioner to damp voltage transients on the bus. In addition, the constant frequency hysteresis control technique for a DC bus conditioner is presented. A simple and fast prediction of the hysteresis band-width is implemented by the phase-lock loop control, keeping constant switching frequency. This technique offers the excellent dynamic response in load or parameter variation. The control performance is illustrated by simulated results with the SABER package. The proposed hysteresis control results in the shortest and the smallest excursions.

• 전기학회논문지
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• 제64권6호
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• pp.864-871
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• 2015

Recently, one of the main research on the power distribution system is the microgrid. The microgrid is a combination of power sources and loads, which is controllable and has separable connection. The main objective of microgrid is the deployment of the renewable clean energy and the enhancement of load-side reliability. The modern power sources and loads have DC I/O interfaces, which is the major advantage of DC microgrid compared to the conventional AC grid. The components in the microgrid have diverse features, so there is need of proper coordination control. For achieving economic feature, the active power of renewable energy resources is regarded as major control parameter and the whole operation modes of DC microgrid are defined, and the proper operations of each component are described. From the inherent characteristics of DC, there are two control variables: voltage and active power. Through analysis of operation modes, it is possible to determine exact control objectives and optimized voltage & power control strategy in each mode. Because of consideration of whole operation modes, regardless of the number and capacity of components, this coordination control method can be used without modification. This paper defines operation mode of DC microgrid with several DC sources and suggests economic and efficient coordinated control methods. Simulation with PSCAD proves effectiveness.

• 전력전자학회논문지
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• 제15권3호
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• pp.207-217
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• 2010

현재 디지털 제품의 사용의 증가로 제품 내부의 DC 전원의 사용이 증가하는 가운데 시스템의 구동전압을 공급하기 위해 기기내부에 장착된 AC/DC컨버터로 인한 입력전류의 역률저하 및 고조파 증가, 그리고 AC/DC 컨버터에서 발생하는 변환 손실 등의 문제가 발생한다. 하이브리드 배전시스템은 기존의 AC부하(전동기 부하 및 변압기 부하)와 DC 부하(컴퓨터, TV, LED조명)에 AC 와 DC 전원을 동시에 공급하며, 직류출력 전원(신재생에너지 및 배터리뱅크)과 상용전원에서 전력을 공급받아 사용자에게 DC 및 AC 전력을 공급해주는 시스템으로 상용전원의 효율을 향상시키고 신재생에너지의 사용 편의성을 올리며 가정에 AC와 DC를 동시에 공급하는데 주목적이 있다. 본 논문을 통해 DC 및 AC 동시 배전을 위해 기존 교류부하의 직류특성에 관한 연구를 하며, 하이브리드 배전의 적절한 DC 전압레벨을 선정한다.

• 전기학회논문지
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• 제62권7호
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• pp.943-949
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• 2013

Recently, an electric vehicle (EV) has been become a huge issue in the automotive industry. The EV has many electrical units: electric motors, batteries, converters, etc. The DC distribution power system (DPS) is essential for the EV. The DC DPS offers many advantages. However, multiple loads in the DC DPS may affect the severe instability on the DC bus voltage. Therefore, a voltage bus conditioner (VBC) may use the DC DPS. The VBC is used to mitigate the voltage transient on the bus. Thus, a suitable control technique should be selected for the VBC. In this research, Current controller with fixed switching frequency is designed and applied for the VBC. The DC DPS consist of both a resistor load and a boost converter load. The load variations cause the instability of the DC DPS. This instability is mitigated by the VBC. The simulation results by Matlab simulink and experimental results are presented for validating the proposed VBC and designed control technique.

• 조명전기설비학회논문지
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• 제29권4호
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• pp.54-61
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• 2015

Recently, DC-based power system is being paid attention as the solution for energy efficiency. As the example, HVDC (High Voltage DC) transmission system is utilized in the real power system. On the other hand, researches on LVDC (Low Voltage DC) distribution system, which are including digital loads, are not enough. In this paper, reliability in LVDC distribution system is analyzed according to the specific characteristics such as the arrangement of DC/DC converters and the number of poles. Furthermore, power quality is also taken account of since LVDC distribution system includes multiple sensitive loads and electric power converters. In order to achieve this, LVDC distribution systems are modeled using ElectroMagnetic Transient Program (EMTP) and both the minimal cut-set method and Customer Interruption Cost (CIC) are used in the reliability analysis.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.110-112
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• 2007

Output voltage waves of a DC/AC inverter system are likely to be distorted if variable loads e.g. motors or rectifiers exist in the output terminal. This paper designs a disturbance observer-based PI controller for a single-phase inverter system that is robust against load changes. In this paper, we regard the output voltage changes due to various loads as disturbances of the control system, Then we design a disturbance observer for estimation of the disturbances caused by the load current and any other error sources (such as parameter uncertainties and model mismatches etc.). In order to test the performance of the proposed control law, simulation studies are carried out for a single-phase inverter system using SimPowerSystems of Matlab Simulink. Compared to a simple PI control, the disturbance observer-based controller shows enhanced performance in transient responses for step load changes.

• 대한전기학회논문지:시스템및제어부문D
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• 제50권3호
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• pp.107-113
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• 2001

This paper deals with speed control of DC servo motor using a PID controller with a gain tuning based on a Back-Propagation(BP) Learning Algorithm. Conventionally a PID controller has been used in the industrial control. But a PID controller should produce suitable parameters for each system. Also, variables of the PID controller should be changed according to environments, disturbances and loads. In this paper described by a experiment that contained a method using a PID controller with a gain tuning based on a Back-Propagation(BP) Learning Algorithm, we developed speed characteristics of a DC servo motor on variable loads. The parameters of the controller are determined by neural network performed on on-line system after training the neural network on off-line system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 추계학술대회 논문집 학회본부
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• pp.323-325
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• 1996

The design of Intelligent Energy Saving Power System Controller (IESPSC) for Telecom DC power plants is proposed and presented in this paper. From the past experience. rectifiers for Telecom DC power plants have been operated inefficiently at light loads. IESPSC offers "novel load sharing" approach based on the knowledge of each unit's efficiency of paralleled rectifiers. Neural networks is used for identifying each rectifier's efficiency characteristic curve corresponding to load currents, which is in turn utilized to produce a system efficiency close to the maximum under all operating conditions. In addition, by limiting the number of operating units to the minimum while maintaining high efficiency at the determined loads, a drastic savings in operating cost can be achieved.