• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.258-259
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• 2012

This paper proposes a new control strategy to eliminate the harmonic components of stator current for stand-alone DFIG system feeding non-linear loads. In this method, the LSC operates as an active filter which is controlled by employing a proportional-integral and a resonant controller. And also, the stator current is used as the feedback signal for the compensator instead of the load current, so that the additional current sensor at the load side can be removed. The experiment is verified to validate the effectiveness of the proposed compensating method.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.660-662
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• 2001

This paper describes the problems generated with the use of PWM ASDs with induction motors. The major effect of harmonic voltages and currents in induction motors is increased the heating due to iron and copper losses at harmonic frequencies. The harmonic components thus affect the motor efficiency and developed the torque. In order to investigate the effect of harmonics which is caused by using of nonlinear load at the low voltage system, we set up simple load system and measured the voltage and current. Measurement results show that additional operation of induction motor at the parallel bus in using nonlinear load such as ASD is helpful to the reduction of harmonic current.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.8
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• pp.54-62
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• 2006

Voltage unbalance will be generated by the load unbalance operation such as combination operation of single & three phase load and current unbalance will be more severe by the deteriorated voltage quality. Under the these unbalance conditions, all power electronic converters used in different types of electronic systems can increase harmonic disturbances by injecting harmonic currents directly into the feeder grid of three phase 4-wire. Harmonic current may cause torque to decrease. it may also overheat or become noisy and torque oscillation in the rotor can lead to mechanical resonance and vibration. This paper presents a scheme on the characteristics of induction motor under the combination of linear & non-linear loads at the three phase 4-wire power distribution system by the unbalance and harmonic components. It was able to confirm that the number of torque pulsation decreased and torque ripple values increased by the harmonics that reduction was difficult by five harmonics filters at additional driving time of single-phase non-linear load.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.9
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• pp.1626-1631
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• 2016

Generally, the low-voltage customer has been used with a linear load and nonlinear load in the 3-phase 4-wire distribution system. Linear load has usually configured the resistance and inductance, current phase is slower than the voltage phase, so power factor is low. It is required for the power factor correction device prior to the phase of the current than the voltage. The capacitor is connected in parallel to the load in order to ensure a low power factor. Power converter such as an inverter is a typical non-linear load. Non-linear load generates harmonic currents in the energy conversion process. Many electrical equipment may be adversely affected by the harmonic current. There, passive or active filter have been used to reduce these harmonics current. Passive filter consisting of inductor and capacitor generates a reactive power. According to the combination of filter inductor and capacitor, reactive power can be adjusted. In this paper, we analyzed how the combination of inductor and capacitor affects the overall power factor by simulation and measurement.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.52 no.3
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• pp.100-106
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• 2003

The increasing application of power electronic equipment in industrial field has led to a growing concern for harmonic distortion and the resulting impacts on system equipment and operations. Harmonic currents are generated by the operation of nonlinear loads and equipment on the power system. These are more increased by unbalance voltage of electrical distribution power systems. This paper describes harmonics characteristics generated by varying of nonlinear load at the PCC under the voltage unbalance.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.3
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• pp.257-262
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• 2009

Capacitor is basically used for the power-factor compensation and sometimes as the passive filter to reduce harmonics of nonlinear load. Since the impedance of capacitor is inversely proportional to the frequency. The harmonic current may result in the problems of voltage distortion and resonance. Capacitor has easily fall under by two harmonic components, a nonlinear load and a distorted utility voltage. The amplified harmonic current and voltage may damage power capacitor. Hence the pre-investigation of harmonic is needed before designing and application the power factor for reducing fault rate. In this paper, we analyzed that voltage and current with harmonics components act on the capacitor under the resonance condition. we concluded that both voltage and current harmonics have an bad effect on the capacitor and current harmonics is a bitter rather than effect by voltage harmonics.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.83-84
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• 2011

This paper presents an analysis and a novel strategy for a doubly fed induction generator (DFIG) based wind energy conversion system under unbalanced grid voltage and non-linear load conditions. A proportional-resonant (PR) current controller is applied in both grid side converter (GSC) and rotor side converter (RSC). The RSC is controlled to mitigate the stator active power and the rotor current oscillations at double supply frequency under unbalanced grid voltage while the GSC is controlled to mitigate ripples in the dc-link voltage and compensate harmonic components of the network current. Simulation results using Psim simulation program are presented for a 2 MW DFIG to confirm the effectiveness of the proposed control strategy.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.1
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• pp.1-8
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• 2009

Recently, application of non-linear load is gradually increased. Non-linear load produces harmonic components of current during the energy conversion transition. Passive filter is used for reducing of harmonics in the user power systems. This filter, which is composed of capacitor and reactor, frequently get out of order by electrical stress. There are voltage and current increase when capacitor and reactor are applied in the user's filter systems. If increased voltage and current is above stipulated values, they have severely an influences on the life of capacitor and reactor. This paper describes that the voltage and current of capacitor used for filter is within the limits of allowable values, but reactor is beyond the limits and reveals spike voltage. Therefore this phenomenon brings about premature fault of reactor and capacitor.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.4
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• pp.370-376
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• 2008

Power capacitors is widely used for power factor correction and component of passive filter in the user power systems. Recently, application of non-linear load is gradually increased. Non-linear load produces harmonic components of current. There are series resonance and parallel resonance when capacitors are applied in the user electrical application. If this harmonic component matches resonance, voltage and current is magnified and has severely an influences on capacitor. This paper purposes a new method for the magnitude of voltage and current by the frequency scan analysis without equivalent circuit for the actual circuit at the resonance condition.

• Journal of Power Electronics
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• v.5 no.2
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• pp.109-119
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• 2005

This paper deals with the performance analysis of static compensator (STATCOM) based voltage regulator for self­excited induction generators (SEIGs) supplying balanced/unbalanced and linear/ non-linear loads. In practice, most of the loads are linear. But the presence of non-linear loads in some applications injects harmonics into the generating system. Because an SEIG is a weak isolated system, these harmonics have a great effect on its performance. Additionally, SEIG's offer poor voltage regulation and require an adjustable reactive power source to maintain a constant terminal voltage under a varying load. A three-phase insulated gate bipolar transistor (IGBT) based current controlled voltage source inverter (CC- VSI) known as STATCOM is used for harmonic elimination. It also provides the required reactive power an SEIG needs to maintain a constant terminal voltage under varying loads. A dynamic model of an SEIG-STATCOM system with the ability to simulate varying loads has been developed using a stationary d-q axes reference frame. This enables us to predict the behavior of the system under transient conditions. The simulated results show that by using a STATCOM based voltage regulator the SEIG terminal voltage can be maintained constant and free from harmonics under linear/non linear and balanced/unbalanced loads.