• Journal of the Korean Society for Precision Engineering
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• v.25 no.11
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• pp.73-82
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• 2008

A dynamic model of reducer for generating facility of electric pourer having bevel gear pair and planetary gear train is developed by lumped method. The model accounts for the shaft and bearing flexibilities, gyroscopic effects and the force couplings among the transverse and torsion motions due to gearing. Vibration/noise analysis as well as strength of bevel gear pair and planetary gear train are considered. Exciting forces of high reducer for generating facility of electric power areconsidered as the mass unbalance of the rotors, misalignment and a function of gear transmission error. A Campbell diagram, in which the excitation sources caused by the mass unbalance of the rotors, misalignment and the transmitted errors of the gearing are considered, shows that, at the operating speed, there are not critical speed.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.565-568
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• 2001

A novel control scheme compensating for source voltage unbalance and harmonic current for series active power filters is proposed, where the references for voltage unbalance and current harmonic and phase angle is derived from the positive sequence component of the source voltage obtained simply through digital all-pass filters, which makes the whole control algorithm simpler than other methods using p-q theory. In addition, the harmonic component of source current is compensated by harmonic component of load voltage and therefore fundamental component of source current is considered as separated terms for the control issue. The validity of the proposed scheme has been verified by experimental results.

• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.15-16
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• 2015

According to 2014 fire statistical yearbook in the National Fire Data System, a main cause of fire is electrical fire except carelessness fire. Joint/contact badness is the one of the main cause of electrical fire. Furthermore, power relays which are used in electric panel board, motor control center and automation controller, are main element of automation system in the industry field. Overload, voltage unbalance and open-phase due to joint/contact badness of terminal make electric accidents or electrical fires. In order to prevent joint/contact badness of terminal, this paper proposes a sensing circuit of chattering, tracking, arc current, voltage unbalance and open-phase etc. Some experimental tests of the proposed apparatus confirm practicality and validity of the theoretical results.

• Journal of Power Electronics
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• v.8 no.1
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• pp.10-22
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• 2008

The wind-driven doubly fed induction generator (DFIG) is currently under pressure to be more grid-compatible. The main concern is the fault ride-through (FRT) requirement to keep the generator connected to the grid during faults. In response to this, the paper introduces a novel model and new control scheme for the DFIG. The model provides a means of direct stator power control and considers the stator transients. On the basis of the derived model, a robust linear quadratic (LQ) controller is synthesized. The control law has proportional and integral actions and takes account of one sample delay in the input owing to the microprocessor's execution time. Further, the influence of the grid voltage imperfection is mitigated using frequency shaped cost functional method. Compensation of the rotor current pulsations is proposed to improve the FRT capability as well as the generator performance under grid voltage unbalance. As a consequence, the control system can achieve i) fast direct power control without instability risk, ii) alleviation of the problems associated with the DFIG operation under unbalanced grid voltage, and iii) high probability of successful grid FRT. The effectiveness of the proposed solution is confirmed through simulation studies on 2MW DFIG.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.6
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• pp.511-521
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• 2014

This study proposes an electric vehicle (EV) smart panel board and its control method on the basis of charging scheduling. The proposed system consists of batteries, a three-phase battery charger, three single-phase inverters, transfer switches for electric power distribution, and a controller. The three-phase battery charger usually charges the batteries at midnight when electric rates are cheap and in light load. When the electric power consumption of the EV standard chargers connected to one phase of the power line is relatively large or when a blackout occurs, the electric power stored in the battery is supplied by discharging through the inverters to the EV standard chargers. As a result, the value of peak load and the charging electric power quantity supplied from a utility grid are reduced, and the current unbalance is improved. The usefulness of the proposed system is confirmed through simulations, experiments, and case studies.

• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.2
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• pp.158-165
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• 2012

In this paper, the test bed using three-phase PWM converter connected with single phase inverter in series is set up to configure an active AC electric load. Since the two topologies, three-phase PWM converter and single-phase inverter, can be operated bidirectionally, the system not only re-generates surplus power to grid but also prevents power dissipation. However, the construction of system has a drawback. That is, ripple components two times of inverter operation frequency occur at DC-Link due to cascade connection, it can be cause of three phase unbalance Since the operational characteristic of the active AC electric load, the power frequency entered into the electric load can be varied, and the ripple of DC-Link is changed as well. In this paper, the three-phase PWM converter using a variable notch filter is proposed, and the reduction of three-phase current unbalance is presented. the validity of the proposed PWM converter using a variable notch filter is verified by the simulation and experimental results.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.172-176
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• 2001

In this paper, a new detection algorithm of faulted voltages under the unbalanced condition and a control algorithm of the instantaneous voltage sag corrector (IVSC) are proposed. To quantify the unbalance under fault conditions, the voltages are decomposed into two balanced three-phase systems using the symmetrical components of positive and negative sequence voltages, which is defined by magnitude factor (MF) and unbalance factor (UF). New control algorithm based on MF and UF values for instantaneous voltage compensation are proposed and verified through the PSCAD/EMTDC simulation and experimental results.

• Journal of Power Electronics
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• v.16 no.3
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• pp.946-959
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• 2016

A novel Virtual Space Vector (VSV) modulation strategy for complete control of potential neutral point (NP) issues is proposed in this paper. The neutral point potential balancing problems of multi-level converters, which include elimination of low frequency oscillations and self-balancing for NP dc unbalance, are investigated first. Then a set of improved virtual space vectors with dynamic adjustment factors are introduced and a multi-objective optimization algorithm which aims to optimize these adjustment factors is presented in this paper. The improved virtual space vectors and the multi-objective optimization algorithm constitute the novel Virtual Space Vector modulation. The proposed novel Virtual Space Vector modulation can simultaneously recover NP dc unbalance and eliminate low frequency oscillations of the neutral point. Experiment results show that the proposed strategy has excellent performance, and that both of the neutral point potential issues can be solved.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.5
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• pp.266-274
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• 2004

This paper presents a scheme for the interconnection of dispersed generator systems(DGs) based on load .unbalance and load model in composite distribution systems. Groups of each individual load model consist of residential, industrial, commercial, official and agricultural load. The unbalance is involved with many single-phase line segment. . Voltage profile improvement and system loss minimization by installation of DGs depend greatly on how they are placed and operated in the distribution systems. So, DGs can reduce distribution real power losses and replace large-scale generators if they are placed appropriately in the distribution systems. The main idea of solving fuzzy goal programming is to transform the original objective function and constraints into the equivalent multi-objectives functions with fuzzy sets to evaluate their imprecise nature for the criterion of power loss minimization, the number or total capacity of DGs and the bus voltage deviation, and then solve the problem using genetic algorithm. The method proposed is applied to IEEE 13 bus and 34 bus test systems to demonstrate its effectiveness.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.1
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• pp.27-36
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• 2007

This paper proposes a current control scheme of the PWM converters under nonideal source voltage conditions such as unbalance and distortion. For the distorted source voltage, the harmonic current controllers are introduced to the conventional current controller. These control loops can eliminate the 5th and 7th order harmonics which are hardly to be done by using filters. For the unbalanced source voltage, a negative sequence current controller is introduced either to reduce the DC-link voltage ripples or to eliminate the source current unbalance. Experimental results show the validity of the proposed control scheme.