• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1259-1261
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• 1999

The paper proposes a simple method to calculate the portion of real power losses allocated to individual loads. The method is implemented by loss distribution factors, and analyses the share of loads in transmission line losses. Effectiveness of the algorithm is verified by a computer simulation. The results can be used to compute the cost of ancillary services under deregulated environment in electric power industries.

• Progress in Superconductivity and Cryogenics
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• v.16 no.4
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• pp.57-61
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• 2014

Output fluctuation which is generated in wind power farm can hinder stability of total power system. The electric energy storage (EES) reduces unstable output, and superconducting magnetic energy storage (SMES) of various EESs has the proper performance for output compensation of wind power farm since it charges and discharges large scale power quickly with high efficiency. However, because of the change of current within SMES, the electromagnetic losses occur in the process of output compensation. In this paper, the thermal effect of the losses that occur in SMES system while compensating in wind power farm is analyzed. The output analysis of wind power farm is processed by numerical analysis, and the losses of SMES system is analyzed by 3D finite element analysis (FEA) simulation tool.

• Journal of Power Electronics
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• v.17 no.4
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• pp.1097-1108
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• 2017

Accurate calculation of the conduction and switching losses of a power electronic converter is required to achieve the efficiency of the converter. Such calculation is also useful for computing the junction temperature of the switches. A few models have been developed in the articles for calculating the switching energy losses during switching transitions for the given values of switched voltage and switched current. In this study, these models are comprehensively reviewed and investigated for the first time for ease of comparison among them. These models are used for calculating the average amount of switching power losses. However, some points and details should be considered in utilizing these models when switched current or switched voltage presents time-variant and alternative quantity. Therefore, an applicable technique is proposed in details to use these models under the above-mentioned conditions. A proper switching loss model and the presented technique are used to establish a new and fast method for obtaining the average switching power losses in any type of power electronic converters. The accuracy of the proposed method is evaluated by comprehensive simulation studies and experimental results.

• Journal of Power Electronics
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• v.15 no.3
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• pp.702-711
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• 2015

In this paper, an effective carrier-based modulation (CBM) strategy to reduce the switching losses for indirect matrix converters (IMCs) is presented. The discontinuous pulse width modulation method is applied to decrease the switching numbers in one carrier cycle, and an optimum offset voltage is selected to avoid commutations of the high output phase currents. By decreasing the switching numbers along with avoiding commutation of the high currents, the proposed CBM strategy significantly reduces the switching losses in IMCs. In addition, the proposed CBM strategy is independent of load conditions, such as load power and power factor, and it has good performance in terms of the input/output waveforms. Simulation and experimental results are provided to verify the effectiveness of the proposed CBM strategy.

• Journal of Electrical Engineering and Technology
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• v.2 no.2
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• pp.194-200
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• 2007

The deregulation problem has recently attracted attentions in a competitive electric power market, where the cost must be earmarked fairly and precisely for the customers and the Independent Power Producers (IPPs) as well. Transmission loss is an one of several important factors that determines power transmission cost. Because the cost caused by transmission losses is about $3{\sim}5%$, it is important to allocate transmission losses into each bus in a power system. This paper presents the new algorithm to allocate transmission losses based on an integration method using the loss sensitivity. It provides the buswise incremental transmission losses through the calculation of load ratios considering the transaction strategy of an overall system. The performance of the proposed algorithm is evaluated by the case studies carried out on the WSCC 9-bus and IEEE 14-bus systems.

• Journal of Electrical Engineering and Technology
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• v.12 no.1
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• pp.173-181
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• 2017

In this paper, the bifurcation criteria for inductive power transfer (IPT) systems is suggested considering the inductive power pad losses. The bifurcation criteria for series-series (SS) and series-parallel (SP) topologies are derived in terms of the main parameters of the IPT system. For deriving precise criteria, power pad resistance is obtained by copper loss calculation and core loss analysis. Utilizing the suggested criteria, possibility of bifurcation occurrence can be predicted in the design process. In order to verify the proposed criteria, 50 W IPT laboratory prototype is fabricated and the feasibilities of the switching frequency and AC load resistance shift to escape from bifurcation are identified.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.4
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• pp.299-305
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• 2005

The work described in this paper is to investigate the additional iron losses and consequent temperatures in core ends of a turbo-generator wound with high voltage cables. Electromagnetic calculations are made with 3D FE models, which include the lamination material with anisotropic properties both in magnetic permeability and electric conductivity. The models also include the geometry of the stator teeth and eventually the axial steps designated to reduce the core end losses. The 3D model of the rotor consists of field windings with straight in-slot parts and end windings. The thermal models are simplified into two dimensions and include the heat sources dumped from the 3D electromagnetic solutions. The influences of power factor on additional iron losses are studied for this cable wound machine and conventional machines. The calculation results show that the additional iron losses can be reduced to about $15\%$ by introducing some small steps around the airgap corner of core ends.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.3
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• pp.251-256
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• 2001

Bi-2223 tapes have been developed for low-field power applications at liquid nitrogen temperature. When the Bi-2223 tapes are used in an application such as a power transmission cable or a power transformer, they are supplied with an AC transport current simultaneously. AC loss taking into account such real applications is a crucial issue for power applications fo the Bi-2223 tapes to be feasible. In this paper, the transport losses for different AC current levels and arrangements of the neighboring tapes have been measured in a 1./5 m long Bi-2223 tape. The significant increase of the transport losses due to neighboring tape's AC currents is observed. An increase of the transport losses caused by a decrease of the Bi-2223 tape's critical current is a minor effect. The measured trasprot losses could not be explained by a dynamic resistance loss based on DC voltage-current characteristics in combination with the neighboring tape's AC currents.The trasport losses do not depend on the frequency of the neighboring tape's AC currents but is arrangements in the range of small current especially.

• Proceedings of the KIEE Conference
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• 2001.11b
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• pp.96-100
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• 2001

Bi-2223 tapes have been developed for low-field power applications at liquid nitrogen temperature. When the Bi-2223 tapes are used in an application such as a power transmission cable or a power transformer, they are supplied with an AC transport current and exposed to an external magnetic field generated by neighboring tape's AC currents simultaneously. AC loss taking into account such real applications is a crucial issue for power applications of the Bi-2223 tapes to be feasible. In this paper, the transport losses for different AC current levels and arrangements of the neighboring tapes have been measured in a 1.5 m long Bi-2223 tape. The significant increase of the transport losses due to neighboring tape's AC currents is observed. An increase of the transport losses caused by a decrease of the Bi-2223 tape's critical current is a minor effect. The measured transport losses could not be explained by a dynamic resistance loss based on DC voltage-current characteristics in combination with the neighboring tape's AC currents. The transport losses do not depend on the frequency of the neighboring tape's AC currents but its arrangements in the range of small current especially.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.1
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• pp.34-41
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• 2016

This study investigates transformer losses caused by current harmonics. Electrical transformers are designed to work under sinusoidal voltage and current waves at a rated frequency. Recently, various nonlinear loads, such as power electronic converters, are connected to a power system; these converters generate current harmonics. Current harmonics increase power loss in transformers, which results in several problems, including temperature increase of the transformer and insulation damage. These problems will eventually shorten the operational life of the transformer. In this study, different types of losses caused by current harmonics in three-phase transformers are studied under linear and nonlinear load conditions. Linear loads are simulated and experimented on using pure resistance load, whereas nonlinear loads are simulated and experimented on using a three-phase twelve-pulse thyristor full-bridge rectifier. The different types of losses in three-phase transformers are evaluated analytically through the experimental result and simulation in PSiM.