• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.379-384
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• 2000

The reactive and harmonic current components of dc loads can be compensated by the three-phase hybrid power filter (HPF) system. After compensation, the resulting current has sinusoidal and in-phase components with the source voltage. The HPF system is constructed by an active filter and passive filters. The passive filter reduce the 5th and 7th harmonic of the load current. The active filter compensates the remainder of the load current. Using the HPF system, a low cost harmonic compensator can be made. Performance of the HPF system is verified through simulation,

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.6
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• pp.330-335
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• 1999

This paper proposed the p-q-r coordinate system where the instantaneous active power p, and the two instantaneous reactive powers qq, qr were defined. The three power components are linearly independent, so the compensation for the two instantaneous reactive powers leads to control the two components of the current space vector. With the theory, the neutral current of a three-phase four-wire system can be eliminated by only compensating the instantaneous reactive power using no energy storge element.

• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.1
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• pp.8-13
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• 2012

DSTATCOM is active filter that reduces nonlinear and unbalanced currents. Researches about DSTATCOM are mainly divided two parts, one is the reference value calculation of compensation current depending on the calculation of the load-side average active power and dc-link capacitor average voltage, the other part is actual current control depending on the reference value of compensation current. This paper proposes a calculation of dc-link capacitor average voltage ripple voltage extraction instead of conventional method using LPF. The utility of the proposed algorithm is verified through the theoretical analysis and the experiment under unbalance loads and non-linear load.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.1
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• pp.65-73
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• 2007

This paper presents an on-line correction method of current measurement errors for a pure-integration-based flux estimation down to 1-Hz stator frequency. An observer-based approach is taken as one possible solution of eliminating the dc offset and the negative sequence component of unbalanced gains in the synchronous coordinate. At the same time, the positive sequence component estimation is performed by creating an error signal between a motor model reference and an estimated q-axis rotor flux established by a permanent magnet (PM) in the synchronous coordinate. The compensator utilizes a PI controller that controls the error signal to zero. The proposed technique further contains a residual error compensator to completely eliminate miscellaneous disturbances in the estimated flux. The developed algorithm has been implemented on a 1.1-kW permanent magnet synchronous motor (PMSM) drive to confirm the effectiveness of the proposed scheme.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.356-361
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• 2005

In this paper, a new scheme of current programmed control for three phase PWM AC-AC converter is presented. Compared to duty-ratio voltage control, current programmed control has several advantages such as reduction of system order and inherent current protection. By considering only the magnitude components, the same scheme in the DC-DC converter can be extended to the three phase PWM AC-AC converter. Sensing the output voltage and the inductor current, an error signal will be generated by comparing the output voltage magnitude with a reference value. Then the error signal will be processed by a PI compensator to generate the current command. The converter switches will the change the state by a periodic clock pulse or at the instants when the inductor current magnitude reaches the current command. As an example case, the buck converter is treated. The converter analysis is carried out by applying the complex DQ circuit transformation to obtain basic physical insight into the converter operation and to establish some important characteristic equations for control purpose. The simulation with Simplorer shows the validity of the proposed scheme and the experimental results support the verification of the design.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.1
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• pp.19-30
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• 2015

A static synchronous compensator (STATCOM) applied to rapidly changing, highly unbalanced loads such as electric arc furnaces (EAFs), requires both positive-sequence and negative-sequence current control, which indicates fast response characteristics and can be controlled independently. Furthermore, a delta-connected STATCOM with cascaded H-bridge configuration accompanying multiple separate DC-sides, should have high performance zero-sequence current control to suppress a phase-to-phase imbalance in DC-side voltages when compensating for unbalanced load. In this paper, actual EAF data is analyzed to reflect on the design of current controllers and a pioneering zero-sequence current controller with a superb transient performance is devised, which generates an imaginary -axis component from the presumed response of forwarded reference. Via simulation and experiments, the performance of the positive, negative, and zero-sequence current control of a cascaded H-bridge STATCOM for EAF is verified.

• Progress in Superconductivity and Cryogenics
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• v.6 no.2
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• pp.29-34
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• 2004

The linear type flux pump aims to compensate a little bit decremental persistent current of the HTS magnet in NMR and MRI spectrometers. The flux pump mainly consists of DC bias coil, 3-phase AC coil and Nb foil. The persistent current in closed superconductive circuit can be easily adjusted by the 3-phase AC current, its frequency and the DC bias current. In the experiment, it has been investigated that the flux pump can effectively charge the current in the load coil of 543 mH for various frequencies in 18 minutes under the DC bias of 10 A and the AC of 5 $A_{rms}$. The maximum magnitudes of pumping current and load magnet voltage are 0.72 A/min and 20 ㎷, respectively. Based on simulation results by the FEM are proved to nearly agree with experimental ones.

• Journal of Power Electronics
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• v.8 no.3
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• pp.259-267
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• 2008

Power quality improvement in a three-phase four-wire system is achieved using a new topology of DSTATCOM (distribution static compensator) consisting of a star/delta transformer with a tertiary winding and a three-leg VSC (voltage source converter). This new topology of DSTATCOM is proposed for power factor correction or voltage regulation along with harmonic elimination, load balancing and neutral current compensation. A tertiary winding is introduced in each phase for a delta connected secondary in addition to the star-star windings and this delta connected winding is responsible for neutral current compensation. The dynamic performance of the proposed DSTATCOM system is demonstrated using MATLAB with its Simulink and Power System Blockset (PSB) toolboxes under varying loads. The capacitor supported DC bus of the DSTATCOM is regulated to the reference voltage under varying loads.

• Proceedings of the KIEE Conference
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• 1988.11a
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• pp.269-272
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• 1988

This paper introduces a method to reduce the reactive power required by electronic converters. The instantaeous reactive power is calculated and compensated by the current controlled PWH voltage source converter connected parallel between the power lines and the converter. A high performance current control technique which is based on the current deviation vector is used for the PWM converter as compensator of reactive power. Accurate compensation of the reactive power and t control system ensuring fast response to the sudden change of loaf are attained. The converter structure and control scheme are discussed. Simulation of the system is performed.

• Proceedings of the KIEE Conference
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• 1989.11a
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• pp.305-309
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• 1989

This paper presents a simple method to compensate reactive/harmonic current components in power lines, with voltage type current controlled converter. The method proposed differs from conventional methods in that it does not rely on explict evaluation of active power. Instead, the closed-loop control of the do link voltage of the compensator plays a major role in adjusting the compensation current. It is shown that the system can be modelled as a simple linear system, which facilitates th analytical approach to the system characteristics. The dynamic performances are examined through the digital simulation and some aspects on the controller design are discussed. Experimental results showed good agreement with the anticipate performance