• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.10
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• pp.1458-1464
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• 2013

This paper proposed a new real time catenary impedance estimation technique using synchronized power data from the measured data of operating vehicle and substation for catenary protective relay and fault locator setting. This paper presented estimation equation of catenary impedance using synchronized power data between substation and vehicle of AT feeding system for the performance verification of the proposed technique. Also AC feeding system is modeled through power analysis program and performance was verified through simulation according to various load changes. We verified that average 2.38%(distance equivalent 23.8 m) error appeared between the proposed estimation equation of catenary impedance and power analysis program simulation output in no connection double track system between up track and down track. Furthermore, We confirmed that estimation error is bigger depending on the increasing the distance from substation and vehicle impedance using only using vehicle current when calculating vehicle impedance in connection double track system between up track and down track. But, We confirmed that the proposed technique estimated accurately catenary impedance regardless of vehicle impedance and distance from substation.

• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1049-1053
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• 1999

It is important to measuring and monitoring about state vectors of power system for precise operation control. All state vectors cannot be measured because it is economically disadvantageous, so that some state vectors are determined using state estimator. Determination of observability is a important precondition of power system state estimation because state estimation can be performed when given power system is observable. Recently as time-synchronization technique progress, using the PMU(Phasor Measurement Unit), state vector can be measured directly so that voltage phasor and current phasor measurements can be used for power system estimation. In this paper, observability algorithm is proposed to determinate the observability with real/reactive injection power measurements and real/reactive lineflow power measurements of existing measurement system and with phasor measurements of PMU. The jacobian matrix is newly composed for state estimation with measurements of added PMU, and state estimation is performed with least square estimatior. Comparison between state estimation result of existing measurement system and that of measurement system added PMU is presented.

• Journal of the Korea Society of Computer and Information
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• v.25 no.5
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• pp.65-72
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• 2020

To improve the performance of D2D power control algorithm proposed in the previous work, three modified D2D power control algorithms are proposed to compensate the channel estimation error. Then, we evaluate the performance of three modified D2D power control algorithms in the channel estimation error environment. In real channel environment, the channel estimation is not perfect. To that end, the impact of imperfect channel estimation on the D2D power control algorithm, which was developed with the assumption of perfect channel estimation, has been analyzed in the previous work. Three modified D2D power control algorithms are based on 1) Retransmission, 2) SIR Margin, and 3) Retransmission and SIR Margin. Simulation results show that the Retransmission and SIR Margin approach shows best performance in the sense of the transmit power consumption and the latency.

• Journal of Power Electronics
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• v.10 no.3
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• pp.293-299
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• 2010

In this paper, a single-phase PFC (Power Factor Correction) dual boost converter based on input voltage estimation is studied for DC inverter air conditioner. It is focused on improving input power factor and power quality to satisfy the recent harmonic current regulation standards. Furthermore the input voltage estimation is introduced for price competitive products. A low cost and reasonable control system is implemented using a specified high-speed 32-bit microprocessor. Their effectiveness are verified through theoretical analysis and experiments.

• Journal of Electrical Engineering and Technology
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• v.3 no.4
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• pp.451-459
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• 2008

Accurate load modeling is essential for power system static and dynamic analysis. By the nature of the problem of parameter estimation for power system load modeling using actual measurements, multiple local optimal solutions may exist and local methods can be trapped in a local optimal solution giving possibly poor performance. In this paper, Trust-Tech, a novel methodology for global optimization, is applied to tackle the multiple local optimal solutions issue in measurement-based power system load modeling. Multiple sets of parameter values of a composite load model are obtained using Trust-Tech in a deterministic manner. Numerical studies indicate that Trust-Tech along with conventional local methods can be successfully applied to power system load model parameter estimation in measurement-based approaches.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.2
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• pp.152-159
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• 2015

In a weak grid condition, the precise grid impedance estimation is essential to guaranteeing the high performance current control and power transfer for a grid-connected inverter. This study proposes a precise estimation method for grid impedance by PQ variations by employing the variation method of reference currents. The operation principle of grid impedance estimation is fully presented, and the negative impact of the phase locked loop is analyzed. Estimation error by a synchronization angle in the park's transformation using the phase locked loop is derived. As a result, the variation method of reference currents for accurate estimation is introduced. The validation of the proposed method is verified through several simulation results and experiments based on a 2-kW voltage source inverter prototype.

• Journal of Communications and Networks
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• v.14 no.3
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• pp.237-242
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• 2012

One of the major problems for accurate channel estimation in power line communication systems is impulsive noise. Traditional channel estimation algorithms are based on the assumption of Gaussian noise, or the need to locate the positions of impulsive noise. The algorithms may lose optimality when impulsive noise exists in the channel, or if the location estimation of impulsive noise is inaccurate. In the present paper, an effective channel estimation algorithm based on a robust cost function is proposed to mitigate impulsive noise. The proposed method can provide a closed-form solution, and the application of robust estimation theory enables the proposed method to be free from localization of impulsive noise and thus can guarantee that the proposed method has better performance. Simulations verified the proposed algorithm.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.369-372
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• 1999

In this paper, we propose a new method for power estimation in nodes of multi-level combinational circuits and describe its application to the extraction of common expressions for low power design. It is assumed that each node is implemented as a complex gate and the capacitance and the switching activity of the nodes are considered in the power estimation. Extracting common expressions which is accomplished mostly by the extraction of kernels, can be transformed to the problem of rectangle covering. We describe how the newly proposed estimation method can be applied to the rectangle covering problem and show the experimental results with comparisons to the results of SIS-1.2.

• International Journal of Internet, Broadcasting and Communication
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• v.12 no.4
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• pp.18-25
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• 2020

In the fifth generation (5G) and beyond 5G (B5G) mobile communication, non-orthogonal multiple access (NOMA) has attracted great attention due to higher spectral efficiency and massive connectivity. We investigate the impacts of the channel estimation errors on the bit-error rate (BER) of NOMA, especially with the single-user decoding (SUD) receiver, which does not perform successive interference cancellation (SIC), in contrast to the conventional SIC NOMA scheme. First, an analytical expression of the BER for SUD NOMA with channel estimation errors is derived. Then, it is demonstrated that the BER performance degrades severely up to the power allocation less than about 20%. Additionally, we show that for the fixed power allocation of 10% in such power allocation range, the signal-to-noise (SNR) loss owing to channel estimation errors is about 5 dB. As a consequence, the channel estimation error should be considered for the design of the SUD NOMA scheme.

• Proceedings of the KIEE Conference
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• 2008.11a
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• pp.261-263
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• 2008

In power systems operation, state estimation takes an important role in security control. For the state estimation problem, the weighted least squares(WLS) method and the fast decoupled method have been widely used at present. But these algorithms have disadvantage of converging local optimal solution. In these days, a modern heuristic optimization method such as Particle Swarm Optimization(PSO), are introduced to overcome the problems of classical optimization. In this paper, we proposed particle swarm optimization (PSO) to search an optimal solution of state estimation in power systems. To demonstrate the usefulness of the proposed method, PSO algorithm was tested in the IEEE-57 bus systems. From the simulation results, we can find that the PSO algorithm is applicable for power system state estimation.