• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.11C
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• pp.1067-1075
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• 2009

In this paper, we propose an adaptive companding scheme to effectively reduce PAPR (Peak-to-Average Power Ratio) of the OFDM (Orthogonal Frequency Division Multiplexing) signals, while considering both complexity and BER (Bit Error Rate) performance of systems. The proposed scheme adaptively alters the compression function in the transmitter and the expanding function in the receiver to simultaneously take into account the BER performance and the PAPR reduction. In this paper, we also measure in-band and out-of-band spectra of the proposed scheme, and observe the BER performance after applying the filtering to reduce the out-of-band radiation. As compared to the conventional companding algorithm, simulation results reveal that the proposed scheme achieves more reliable BER performance in all the cases of with and without the filtering, and has a good spectrum characteristic with effective PAPR reduction.

• Journal of IKEEE
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• v.25 no.2
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• pp.388-398
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• 2021

This paper proposes a particle swarm optimization (PSO)-based peak shaving scheme using energy storage system (ESS) for electricity tariff reduction. The proposed scheme compares the actual load with the estimated load consumption, calculates the additional output power that the ESS needs to discharge additionally to reduce peak load, and adds the input. In addition, in order to compensate for the additional power, the process of allocating power to the determined point is performed, and an optimization that minimizes the average of the load expected at the active power allocations using PSO so that the allocated value does not affect the peak load. To investigated the performance of the proposed scheme, case study of small and large load prediction errors was conducted by reflecting actual load data and load prediction algorithm. As a result, when the proposed scheme is performed with the ESS charge and discharge control to reduce electricity tariff, even when the load prediction error is large, the peak load is successfully reduced, and the peak load reduction effect of 17.8% and electricity tariff reduction effect of 6.02% is shown.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.1
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• pp.12-18
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• 2014

In this paper, a new peak-to-average power ratio (PAPR) reduction method for spatial modulation(SM) is presented. By using the matrix with all non-zero elements to precode the signals before transmitting, the transmit power is scattered over all transmit antennas for achieving the goal of PAPR reduction. If this matrix is also an unitary matrix, the distribution of transmit power over transmit antennas will be uniform and it also could retain the characteristic of avoiding inter channel interference (ICI) due to the orthogonality of unitary matrix. In case of a non-ideal amplifier, the proposed method can produce a considerable improvement that increases with a number of transmit antennas in performance. Furthermore, the new scheme achieves an identical performance with conventional one in the case of ideal amplifier.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.8
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• pp.1496-1503
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• 2009

The United Nations Framework Convention on Climate Change (UNFCCC) is an international environmental treaty to stabilize greenhouse gas concentrations in the atmosphere. In order to fulfil the commitments of the countries in an economically efficient way, the UNFCCC adapted the emission trading scheme in the Kyoto Protocol. If the UNFCCC's scheme is enforced in the country, considerable changes in electric power industry are expected due to the imposed greenhouse gas emission reduction. This paper proposes a game theoretic model of the case when generation companies participate in both competitive electricity market and emission market simultaneously. The model is designed such that generation companies select strategically between power quantity and greenhouse gas reduction to maximize their profits in both markets. Demand function and Environmental Welfare of emission trading market is proposed in this model. From the simulation results using the proposed model the impact of the emission trading on generation companies seems very severe in case that the emission prices are significantly high.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.31 no.11
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• pp.133-140
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• 1982

In recent years, a number of thyristor-controlled shunt compensators have been used in industrial and utility systems for phase balancing, power-factor correction and flicker reduction. This paper describes a simple and basic control scheme and circuits for shunt compensator with a fixed capacitor and thyristor-controlled reactor. Feedforward-control scheme is applied, and compensating currents are computed from the symmetrical components of the disturbed system. A 8 bit microprocessor is used for the computation of the compensating currents as well as for the measurements of the symmetric components. A 3-phase 1 KVA compensator is developed and a good reduction of the unbalance factor of the power source is achieved using it.

• Journal of Power Electronics
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• v.7 no.3
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• pp.257-264
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• 2007

Active power filters can be cost-effective for use in practical systems with the insertion of a few passive elements in shunt or series configuration. The resulting hybrid filters can be designed to provide dominant lower order harmonic elimination and reactive power support by the passive elements so that the burden on the active filter counterpart is reduced. In this paper, the rate reduction in the shunt active filter is estimated when it is connected in parallel with suitable passive tuned harmonic filters. The active filtering system is based on an appropriate control scheme. The simulation and the experimental results of the shunt active filter, along with the estimated value of reduction in rating, show that the hybrid shunt filtering system is quite effective in compensating for the harmonics and reactive power, in addition to being cost-effective.

• 제어로봇시스템학회:학술대회논문집
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• 1988.10a
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• pp.154-159
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• 1988

In this paper, a hyperstable cascade control scheme for servo drive systems is proposed to reduce the chattering, which is an undesirable property in discontinuously controlled systems. First, a discontinuously controlled hyperstable MRAC scheme is designed with respect to PI speed control system using only output variables, and then a linear position controller is cascaded. It is shown that the above system is asymptotically stable and the chattering is greatly reduced at a constant speed provided that the disturbance torque satisfies a certain condition.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.2C
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• pp.203-209
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• 2010

In this paper, we propose a new selected mapping (SLM) scheme for reducing peak to average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals modulated with quadrature amplitude modulation (QAM), called amplitude and phase variant SLM (APSLM). Contrary to the conventional SLM which rotates the phases of QAM symbols in the frequency domain, the proposed scheme changes the magnitudes as well as the phases of QAM symbols by applying binary sequences to the binary data sequence before mapped to QAM symbols. Simulation results show that the proposed scheme has better PAPR reduction performance than the conventional SLM scheme for the QAM modulated OFDM signals, especially for the small number of subcarriers.

• Journal of Power System Engineering
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• v.8 no.3
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• pp.23-29
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• 2004

In this paper, a finite element formulation using dynamic-explicit time integration scheme is used for numerical analysis of Hydro-forming processes. The lumping scheme is employed for the diagonal mass matrix and dynamic explicit formulation. Hydro-forming process for auto-body panel forming is analyzed by using dynamic-explicit finite element method. Further, the simulated results of the Hydro-forming processes are shown and discussed. Its application is being increased especially in the automotive industrial area for the cost reduction, weight saving, and improvement of strength.

• Journal of Power Electronics
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• v.16 no.6
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• pp.2067-2075
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• 2016

Cascaded H-bridge multilevel inverters are currently used because it enables the integration of various sources, such as batteries, ultracapacitors, photovoltaic array and fuel cells in a single system. Conventional modulation schemes for multilevel inverters have concentrated mainly on the generation of a low harmonic output voltage, which results in less effective utilization of connected sources. Less effective utilization leads to a difference in the charging/discharging of sources, causing unsteady voltages over a long period of operation and a reduction in the lifetime of the sources. Hence, a charge balance control scheme has to be incorporated along with the modulation scheme to overcome these issues. In this paper, a new approach for charge balancing in symmetric cascaded H-bridge multilevel inverter that enables almost 100% charge balancing of sources is presented. The proposed method achieves charge balancing without any additional stages or complex circuit or considerable computational requirement. The validity of the proposed method is verified through simulation and experiments.