• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.30 no.3
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• pp.130-142
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• 2018

We use heat pumps with thermal storage system to reduce peak usage of electric power during winters and summers. A heat pump stores thermal energy in a thermal storage tank during the night, to meet load requirements during the day. This system stabilizes the supply and demand of electric power; moreover by utilizing the inexpensive midnight electric power, thus making it cost effective. In this study, we propose a system wherein the thermal storage tank and heat pump are modeled using the TRNSYS, whereas the control simulations are performed by (i) conventional control methods (i.e., thermal storage priority method and heat pump priority method); (ii) region control method, which operates at the optimal part load ratio of the heat pump; (iii) load response control method, which minimizes operating cost responding to load; and (iv) dynamic programming method, which runs the system by following the minimum cost path. We observed that the electricity cost using the region control method, load response control approach, and dynamic programing method was lower compared to using conventional control techniques. According to the annual simulation results, the electricity cost utilizing the load response control method is 43% and 4.4% lower than those obtained by the conventional techniques. We can note that the result related to the power cost was similar to that obtained by the dynamic programming method based on the load prediction. We can, therefore, conclude that the load response control method turned out to be more advantageous when compared to the conventional techniques regarding power consumption and electricity costs.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.10
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• pp.399-409
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• 2006

This paper presents a novel method for satisfying the thermal comfort of indoor environment and reducing the summer peak demand power by minimizing the power consumption for an Air-conditioner within a space. Korea Electric Power Corporation (KEPCO) use the fixed duty cycle control method regardless of the indoor thermal environment. However, this method has disadvantages that energy saving depends on the set-point value of the Air-Conditioner and direct load control (DLC) has no net effects on Air-conditioners if the appliance has a lower operating cycle than the fixed duty cycle. In this paper, the variable duty cycle control method is proposed in order to compensate the weakness of conventional fixed duty cycle control method and improve the satisfaction of residents and the reduction of peak demand. The proposed method estimates the predict mean vote (PMV) at the next step with predicted temperature and humidity using the back propagation neural network model. It is possible to reduce the energy consumption by maintaining the Air-conditioner's OFF state when the PMV lies in the thermal comfort range. To verify the effectiveness of the proposed variable duty cycle control method, the case study is performed using the historical data on Sep. 7th, 2001 acquired at a classroom in Seoul and the obtained results are compared with the fixed duty cycle control method.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.1084-1087
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• 1993

The importance of reliable electric power has increased rapidly with the proliferation of sophisticated communication systems, computers and critical surgical operations and it considered as one of the most important issues which must be reflected on initial engineering for construction. In this connection, this paper describes the basic conception of peak shaving and cogeneration which are widely used to control the electric power supply recently.

• Journal of the Korean Society of Industry Convergence
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• v.21 no.5
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• pp.207-217
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• 2018

Recently, the importance of energy demand management, particularly peak load control, has been increasing due to the policy changes of the Second Energy Basic Plan. Even though the installation of distributed generation systems such as Photovoltaic and energy storage systems (ESS) are encouraged, high initial installation costs make it difficult to expand their supply. In this study, the power consumption of a university building was measured in real time and the measured power consumption data was used to calculate the optimal installation capacity of the Photovoltaic and ESS, respectively. In order to calculate the optimal capacity, it is necessary to analyze the operation methods of the Photovoltaic and ESS while considering the KEPCO electricity billing system, power consumption patterns of the building, installation costs of the Photovoltaic and ESS, estimated savings on electric charges, and life time. In this study, the power consumption of the university building with a daily power consumption of approximately 200kWh and a peak power of approximately 20kW was measured per minute. An economic analysis conducted using these measured data showed that the optimal capacity was approximately 30kW for Photovoltaic and approximately 7kWh for ESS.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.4
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• pp.278-287
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• 2009

Plug-in hybrid electric vehicle (PHEV) with capability of being recharged from the power-grid will reduce oil consumption. Also, the PHEV will affect the utility operations by adding additional electricity demand for charging. In this research, the power-grid impact by demand of PHEV charging is presented and the optimal charging control strategy for utility operators is proposed with simulated data. The penetration of PHEV is assumed to be 50% in the circumstances of Korean passenger car market and Korean power-grid market limitedly. To obtain smooth load shape and utilize the surplus electricity in power-grid at midnight and dawn, the peak of charging demand should be controlled to be located before 4:00 a.m., and the time slot which can supply the electricity power to PHEV should be allowed between 1:00 a.m.$\sim$7:00 a.m.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.149-151
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• 2005

Recently, power supply-demand instability due to the dramatic increase in power usage suchas air-conditioning load at summertime has brought forecasts of decrease in power supply capability. Therefore improving the load factor through systematic load management, in other words, Direct Load Control became necessary. Direct Load Control(DLC) system is kind of a load management program for stabilization of electric power supply-demand. It's purpose is limiting the demand of the demand side selected at peak load or other time periods. The paper presented a Design of Direct Load Controller for control the amount of power demand in demand side. The proposed Controller is cheaper and has ability of storing more power data than pre-existing device.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.5
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• pp.730-737
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• 2016

Electric utilities may face new threats with increase in electric vehicles (EVs) in the personal automobile market. The peak demand will increase which may stress the distribution network equipment. The focus of this paper is on an adaptive control of smart household appliances by using an intelligent load management system (ILMS). The main objectives are to accomplish consumer needs and prevent overloading of power grid. The stress from the network is released by limiting the peak demand of a house when it exceeds a certain point. In the proposed strategy, for each smart appliance, the customers will set its order/rank according to their own preferences and then system will control the household loads intelligently for consumer reliability. The load order can be changed at any time by the customer. The difference between the set and actual value for each load's specific parameter will help the utility to estimate the acceptance of this intelligent load management system by the customers.

• Journal of Power Electronics
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• v.10 no.3
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• pp.328-333
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• 2010

A photovoltaic power conditioning system (PV PCS) that contains single-phase dc/ac inverters tends to draw an ac ripple current at twice the output frequency. Such a ripple current perturbs the operating points of solar cells continuously and it may reduce the efficiency of the current based maximum power point tracking technique (CMPPT). In this paper, the ripple current generation in a dc link and boost inductor is analyzed using the ac equivalent circuit of a dc/dc boost converter. A new feed-forward ripple current compensation method to incorporate a current control loop into a dc/dc converter for ripple reduction is proposed. The proposed feed-forward compensation method is verified by simulation and experimental results. These results show a 41.8 % reduction in the peak-to peak ac ripple. In addition, the dc/ac inverter control system uses an automatic voltage regulation (AVR) function to mitigate the ac ripple voltage effect in the dc link. A 3kW PV PCS prototype has been built and its experimental results are given to verify the effectiveness of the proposed method.

• Proceedings of the KIEE Conference
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• summer
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• pp.1260-1262
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• 2004

Direct Load Control(DLC) system is a load management program for stablization of electric power supply-demand. It is a series of acts limiting the demand of selected demand side at peak load or other time periods. Recently, power supply-demand instability due to dramatic increase in power usage such as summertime air-conditioning load has brought forecasts of decrease in power supply capability. Therefore heightening the load factor through systematic load management, in other words, Direct Load Control became necessary. By examining the composition and operation of the DLC system, this paper provides conceptional understanding of the DLC system and help in system research.

• Proceedings of the KIEE Conference
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• 1989.11a
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• pp.250-253
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• 1989

As the necessity of increasing the midnight base load is extensively increased, electric power companies have to increase the demand of midnight electrical power by lowering the electrical charge rate at midnight. One of the most widely used midnight equipments is the heat Storage type's electrical boiler. A Single chip microprocessor controller for the heat-storage type's electrical boiler is developed. This controller call reduce the undesirable peak load at the begining of midnight (i.e.11 P.M.) time band by using backward load control method. Futhermore, this controller enables reservation of heat storge and the effective heating control the field test has been done by use the boiler for 66$m^2$ with the heater of 21KW quality.