• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.7
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• pp.966-973
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• 2012

In microgrid demonstration site, distributed generations can make bidirectional power flows on the system. If an accident occurs, the fault current from the inverter based distributed generation is small. However, the conventional protection scheme in distribution network is designed to operate at high fault current. This means that the traditional protection of distribution network is no longer applicable and new protection methods must be developed. In this paper, for two cases, algorithms for protection coordination of demonstration site is proposed and verified through PSCAD/EMTDC simulation. In first case, protection devices are assumed to have the abilities of directional relaying and communication. In second case, protection devices do not have those abilities. Proposed protection coordination algorithms detect the fault locations and protect the microgrid fairly well.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.1
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• pp.111-119
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• 2022

This paper is about power transfer between heterogeneous systems in zero-energy buildings. Currently, electricity used in buildings, from renewable energy generation power in buildings, consists of alternating current networks. In order to use electricity, alternating current must be converted to direct current, which typically results in a loss of 10%. In order to solve this problem, research is needed to reduce power loss as much as possible by implementing both a DC network and an AC network in a zero-energy building. Therefore, in this paper, an inter-link converter capable of bidirectional power transfer between DC and AC networks applied to zero-energy buildings is developed. The structure of the inter-link converter to be developed was proposed and its feasibility was verified through simulations and experiments.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.10
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• pp.1949-1954
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• 2016

Smart grid technology can be called grid techniques to improve the efficiency of the electric power by exchanging bidirectional information of electric power with real-time between electric power suppliers and consumers. Recently, the solar power generation system is being applied actively. However the solar power system has several problems leading to reduce overall electricity generation, because the difficult of the diagnosis and the solar power system failure such as PV(PhotoVoltaics) and inverter. In order to build an efficient smart grid, a stable electric power energy requirements capture and management and early fault detection is essentially required in solar power generation system. In this paper, it is designed to monitor the operating status of the solar power monitoring system from a remote location through a RS-485 or TCP/IP communication module to monitoring the output of solar power energy and abnormal phenomenon, to developing the measurement module and to transfer measured data.

• Journal of the Korean Solar Energy Society
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• v.26 no.2
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• pp.69-77
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• 2006

Photovoltaic is an attractive technology to remote power applications, because of its reliability, low maintenance, and zero fuel requirements. In this paper represents residential PV system based on BESS(battery energy storage system) for managing the electric power, a pattern of daily operation considering the load characteristics of the house, the generation characteristics of PV power, and utility power leveling. For apply to control algorithm, we consider the load on monthly power consumption trend and daily usage pattern. As for the control of the proposed system, to increase the conversion efficiency of the PV power, bidirectional converter is used for MPPT and SPWM inverter. An experimental system is implemented, and some experimental results are provided to demonstrate the effectiveness of the proposed system.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.625-628
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• 1996

Recent power converting system for an electric train has characteristics of a complex electromechanical system, which includes VVVF inverter, bidirectional converter, ac motor and controller and etc. So in order to analysis its dynamic characteristics reliably, a powerful and flexible simulation technique is needed. Concerned with this respect, because the Simulink has a veriety of powerful functions and analysis tools not available in conventional power electronics simulation packages, it can be effectively applied to the simulation of the power converting system. In this paper, a schematically similar model for an electric train power converting system is derived on the Simulink Window, based on the Dynamic Node Technique, and several simulations have been implemented with the model. With the simulation results, the characteristics of the power converting system and the easeness of the proposed Simulink-based simulation technique could be verified clearly.

• Journal of Electrical Engineering and Technology
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• v.6 no.1
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• pp.67-75
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• 2011

The development of electric vehicle power electronics system control, composed of DC-AC inverters and DC-DC converters, attract much research interest in the modern industry. A DC-AC inverter supplies the high-power motor torques of the propulsion system and utility loads of electric vehicles, whereas a DC-DC converter supplies the conventional low-power and low-voltage loads. However, the need for high-power bidirectional DC-DC converters in future electric vehicles has led to the development of many new topologies of DC-DC converters. The nonlinear control of power converters is an active research area in the field of power electronics. This paper focuses on the use of the fuzzy sliding mode strategy as a control strategy for buck-boost DC-DC converter power supplies in electric vehicles. The proposed fuzzy controller specifies changes in control signals based on the surface and knowledge on surface changes to satisfy the sliding mode stability and attraction conditions. The performance of the proposed fuzzy sliding controller is compared to that of the classical sliding mode controller. The satisfactory simulation results show the efficiency of the proposed control law, which reduces the chattering phenomenon. Moreover, the obtained results prove the robustness of the proposed control law against variations in load resistance and input voltage in the studied converter.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.11
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• pp.561-568
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• 2005

This paper proposes a method that distributes the load power and stores the regenerated energy for a hoist-load system using the supercapacitor, an energy storage device. The crane, which is a representative hoist-load system, operates in two modes. The first is the hoist-up mode in which the load container is lifted up: the maximum power is required at the end of acceleration. The second is the hoist-down mode in which the load container is lifted down; the regenerated energy is wasted by the resistor In this paper, the supercapacitor stores the regenerated energy in the hoist-down operation and supplies the peak power demand in the hoist-up operation. The same structure as the commercially available three-phase inverter is proposed as a bidirectional do-dc converter to charge and discharge the supercapacitor. A power control algorithm is proposed to optimize the load sharing between the generator and the supercapacitor. Using the proposed method, it is effected that the generator size can be cut down to one third of the original one; it leads to the reduction of the fuel consumption, noise and air pollution. Simulation and experimental results verify the effectiveness of the Proposed method.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.2B no.3
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• pp.133-139
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• 2002

In this paper, a prototype of an active auxiliary quasi-resonant DC link (QRDCL) snubber assisted voltage source bidirectional power converter (AC to DC and DC to AC) operating at zero voltage soft-switching (BVS) PWM nlode is presented for a Battery Energy Storage System (BESS). The operating principle of this QRDCL circuit and multifunctional control-based converter system, including PWM inverter mode in which energy flows from the battery bank to the three-phase utility-grid in addition to an active PWM converter mode in which energy flows from the utility-grid to the battery banks are described respectively by the control implementation on the basis of d-q coordinate plane transformation. The multifunctional operation characteristics of this three-phase ZVS PWM bi-directional converter with QRDCL is demonstrated fer a BESS under the power conditioning and processing schemes of energy supply mode and energy storage mode, and compared with a conventional three-phase hard switching PWM bi-directional converter for a BESS. The effectiveness of the three-phase ZVS PWM hi-directional converter with QRDCL is proven via the simulation analysis.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.36-38
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• 2018

중요부하를 가지고 있는 계통연계 인버터는 계통과의 연결이 끊길 경우 중요부하에 안정적인 전압공급을 위하여 끊김 없는 모드전환 동작이 요구된다. 기존 인버터는 계통연계 시 전류제어모드, 독립운전 시에는 전압제어모드로 운전을 한다. 그래서 모드전환 시 제어기절체로 인한 출력전압에 심각한 과도상태가 발생할 수 있으며 단독운전 검출 전에도 불안정한 전압을 부하에 공급하게 되어 중요부하에 큰 손상을 입힐 수 있다. 본 논문에서는 LCL필터 뿐만 아니라 LC필터 구조에서도 적용이 가능하며, 양방향 운전 시 자율적인 모드전환이 가능한 계통연계 인버터의 모드전환 기법을 제안한다. 제안된 알고리즘은 5kW 시작품을 제작하여 타당성을 검증하였다.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.1
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• pp.91-98
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• 2012

Climate change and other pollutions make a huge demand of environment friendly and high efficient motors especially Brushless DC (BLDC) motors. Generally, bidirectional energized BLDC motors are used widely; however, inverter devices used in the driver put fear of being effected by noise. This paper proposes unidirectional energized BLDC motor which utilizes asymmetrical H-bridge circuit as the driver circuit. The Minato motor is one of the pioneers in unidirectional energized system. The use of bar magnets in the rotor is one of the biggest disadvantages of the motor. We proposed using tabular magnets. The paper compares the power consumption and efficiency of the Minato motor and the proposed motor. During high speed rotation, undesirable armature current is generated that has a deceleration characteristic. This current lowers the motor's efficiency. In this paper, we propose the solutions and show comparison through equations of the copper loss ratio for the Minato and our proposed motors. The third motor, which has the highest efficiency, was discovered during examination of the equations.