• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.9
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• pp.1706-1713
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• 2009

In this paper, a parallel operation algorithm for high power PEMFC generation systems is proposed. According to increasing the capacity of fuel cell systems with several fuel cell stacks, the different dynamic characteristics of each fuel cell stack effect on imbalance of load sharing and current distribution, so that a robust parallel operation algorithm is desired. Therefore, a power-sharing technique is developed and explained in order to design an optimal distributed PEMFC generation system. In addition, an optimal controller design procedure for the proposed parallel operation algorithm is introduced, along with informative simulations and experimental results.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.6
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• pp.738-744
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• 2018

This paper proposes a low cost hot swap operation circuit of a parallel operation power supply for servers. Hot swap function for server power system is essential in 24 hour operation system such as internet data center, server, factory and etc. Server power supplies used in internet data centers have two or more parallel operations with the hot swap operation. However, the cost of the power supply is high because the controller IC for hot swap operation is very expensive. Therefore, this paper proposes a parallel-operated power supply with a low-cost hot swap controller for servers. The proposed system can operate hot swap function by using discrete devices and reduce the cost by more than 50%. A 1.2kW prototype system is implemented to verify the proposed low cost hot swap controller.

• Proceedings of the KIPE Conference
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• 1996.06a
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• pp.56-59
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• 1996

In this paper, we developed a micro-stepping drive circuit of step motor and proposed software algorithm for parallel operation of step motors drived by micro-stepping circuit. Also, we implemented a parallel operation controller with a 16-bit micro-controller.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.8
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• pp.509-513
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• 2000

This paper deals with the parallel operation of space vector PWM for large capacity inverter system. To enlarge the capacity of inverter system and to reduce the current ripples on inverter output side, two or more inverters are operated in parallel. In this paper, a new parallel operation strategy which minimizes the harmonic distortion of the output stage is described. The proposed method is developed on the basis of the space-vector PWM in order to increase the linearly controllable voltage range. With the help of the proposed voltage synthesis method, the total harmonic distortion of the output stage can be greatly reduced in compared with that of conventional method with sinusoidal PWM or that of the single inverter operation case. The experimental results with reduced scale test show the feasibility of the proposed voltage synthesis method.

• Journal of Power Electronics
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• v.13 no.3
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• pp.437-446
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• 2013

This paper proposes a design scheme for an LCL-filter used for the three-parallel operation of the power converters in high-capacity wind turbines. The designs of the power devices and grid connected filter are difficult due to the high level voltages and currents in huge-capacity wind turbines. To solve these problem, this paper presents three-parallel operation and LCL-filter design techniques optimized by parallel operation. Furthermore, the design of an inverter side inductance of the LCL-filter is discussed in detail considering the switching modulation method. Simulation and experimental results demonstrate the validity of the designed filter and wind turbines.

• Proceedings of the KIPE Conference
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• 2002.11a
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• pp.158-162
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• 2002

The parallel operation system of multiple UPS(Uninterruptible Power Supply) is used to increase power capacity of the system or to secure higher reliability at critical loads. In the parallel operation of the two UPSs, the load sharing control to maintain the current balance between them is a matter of consequence. In this paper, a highly precise load sharing controller is proposed and implemented for the parallel operation system of two UPSs. After that, a good performance of the proposed method is verified by simulation in the parallel operation system with two UPSs.

• Special Issue of the Society of Naval Architects of Korea
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• 2009.09a
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• pp.97-106
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• 2009

Many production methods are tried to enhance the productivity efficiency. Parallel connected floating cranes are one of the examples to lift mega-blocks quickly and efficiently. However, a general operation manual to operate parallel connected floating cranes and a method to consider risks during lifting operation are not confirmed. And if each floating crane is operated by itself, it is very hard to cooperate. Therefore, Synchronized operation system is installed to control parallel connected floating cranes simultaneously and to be informed of each floating cranes data. And weighting factor is calculated by considering all hazards during the operation and the general operation manual is confirmed based on the factor. This paper introduces the procedure for lifting operations by parallel Connected Floating Cranes using synchronized operation system, and its applications to lifting operation of a heavy cargo such as barge lifting test, floating dock installation and 900 ton goliath crane replacement operation, etc.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.3
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• pp.256-262
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• 2013

In the large system such DC distribution for building, the method that a number of modules converters operation in parallel is commonly used. When parallel operation, circulating current is directly related to the loss of the entire system. Accordingly, each module to share the same current is the most important for the safety of the power system. In this paper, control method for reducing circulating current in parallel operation is proposed. furthermore response and operation of steady-state with parallel system was verified by simulation and experiment results.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.4
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• pp.88-95
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• 2013

A new droop control method which can be applied to 3-phase 4-wire uninterruptible power supply is proposed in this paper. The droop control method for parallel operation is very attractive one as UPS parallel operation can be carried out without any data communication devices provided among UPS systems connected, but it reportedly shows a PnP(plug-and-play) problem. A basic reason why a circulating current could flow among parallel-connected UPS systems is clearly investigated as well when droop-controlled-ups systems are operated in the manner of PnP. The proposed algorithm is deduced from the investigated result and is basically structured to keep a balanced frequency and balanced voltage profile against power variation. This paper shows that balanced parallel operation of droop control method can be obtained under unbalanced load as well as balanced load conditions when PnP operation is needed and load change occurs.

• Journal of Electrical Engineering and Technology
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• v.8 no.1
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• pp.106-109
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• 2013

It is desirable and advantageous to feed parallel propulsion with induction motors by a single voltage source inverter. However, effects of deviation of the wheel diameters on motor current, rotor speed and torque should be also considered for parallel operation. In order to understand the behavior and characteristics, a simple simulation model is developed by using a commercial Matlab Simulink. From the results, it is clear to manage the diameter deviation of the wheels which are connected to traction motors.