• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.4
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• pp.256-262
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• 2021

Six-phase motors can be used in industrial applications, such as an electric vehicle, due to their high reliability and low current magnitude per phase. An asymmetrical PMSM with two sets of three-phase windings is a commonly used structure for six-phase motors, with each winding set demonstrating a phase difference of 30°. Although the asymmetrical PMSM presents low torque ripples, its dynamic torque response deteriorates due to coupled components in the two three-phase windings. The decoupled VSD control is applied to eliminate the coupling effect. Load ratio control of two inverters for the six-phase PMSM is proposed in this study. DQ currents are controlled on the basis of two synchronous reference frames, and the six-phase drive system can be changed to a three-phase drive system when one inverter presents fault conditions. The operation and effectiveness of the proposed algorithm is verified through simulation and experiments. The six-phase drive system is transferred to a three-phase drive system by changing the current reference of the second DQ reference frame. Moreover, control of both torque and speed exhibits satisfactory performance before and after the mode change.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.2B no.3
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• pp.115-124
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• 2002

This paper presents an active auxiliary edge-resonant DC link snubber with a ringing surge damper and a three-phase voltage source type zero voltage soft-switching inverter with the resonat snubber treated here for the AC servo motor driver applications. The operation of the active auxiliary edge-resonant DC link snubber circuit with PWM voltage is described, together with the practical design method to select its circuit parameters. The three-phase voltage source type soft-switching inverter with a single edge-resonant DC link snubber treated here is evaluated and discussed for the small-scale permanent magnet (PM) type-AC servo motor driver from an experimental point of view. In addition to these, the AC motor stator current and its motor speed response for the proposed three-phase soft-switching inverter employing Intelligent Power Module(IPM) based on IGBTS are compared with those of the conventional three-phase hard-switching inverter using IPM. The practical effectiveness of the three-phase soft-switching inverter-fed permanent magnet type AC motor speed tracking servo driver is proven on the basis of the common mode current in a novel type three-phase soft-switching inverter-fed AC motor side and the conductive noise on the mains terminal interface voltage as compared with those of the conventional three-phase hard-switching inverter-fed permanent magnet type AC servo motor driver for the speed tracking applications.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.11
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• pp.1560-1565
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• 2013

This paper proposes the control method for compensating for unbalanced grid current and reducing a total harmonic distortion (THD) of the grid current at the three-phase grid-connected inverter systems under unbalancd and distorted grid voltage conditions. The THD of the grid current caused by grid voltage harmonics is derived by considering the phase delay and magnitude attenuation due to the hardware low-pass filter (LPF). The Cauchy-Schwarz inequality theory is used in order to search more easily for a minimum point of THD. Both the gain and angle of a compensation voltage at the minimum point of THD of the grid current are derived. The negative-sequence components in the three-phase unbalanced grid voltage are cancelled in order to achieve the balanced grid current. The simulation and experimental results show the validity of the proposed control methods.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.4
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• pp.343-350
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• 2016

Generally, the average phase current is sampled at the midpoint of a PWM signal for the vector control of an AC motor. The three-phase current can also be reconstructed from a DC-link shunt resistor by sampling the shunt voltage during the active vectors of the SVPWM. However, the reconstructed current is different from the average current because of the deviation of the sampling point from the midpoint of the PWM signal. This paper proposes an algorithm to estimate the average current from the reconstructed current in a single-shunt inverter. The proposed method is derived from the phase current slopes based on switching states and corresponding switching time. In addition, the proposed method is generalized for all the six sectors of the space vector hexagon. The validity of the proposed algorithm is verified with simulations and experiments.

• Journal of Electrical Engineering and information Science
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• v.2 no.4
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• pp.86-91
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• 1997

A method of detecting the three phase currents for a voltage-fed pusle width modulated(PWM) inverter is proposed, where only one current sensor is utilized on the dc-link. The proposed method has the constant sampling time by employing he modified space-vector PWM technique which generates the rearranged switching pattern to detect a phase current from ad dc-link current. Experimental results show that eh proposed scheme provides a very good detection method of three phase currents without phase current sensors. This method is very simple and has small detection errors.

• Journal of Power Electronics
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• v.18 no.3
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• pp.871-878
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• 2018

In this paper, the conducted EMI reduction performances of active feed-forward current-sensing current-actuation (CSCA) and voltage-sensing current-actuation (VSCA) filters for a three-phase induction motor drive system are evaluated by experiments. For comparison purposes, the conducted EMI (CM emission, DM emission and total emission) of a three-phase induction motor drive with a conventional CM choke, a conventional CM choke in series with an active VSCA filter, and an active CSCA filter (where the CM choke was modified and used as a sensing current transformer) were compared to the case of a system without any filter inserted. Experimental results show that the active CSCA and VSCA filters can improve the CM reduction performance of the conventional CM choke by about 5 dB especially at low-frequencies. However, for DM comparisons, it shows that there is no different between cases with and without filters inserted.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.209-212
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• 1999

We studied the operating properties of resistive and inductive SFCLS with 100 $\Omega$ of quench impedance for a three-phase-fault in the 154 kV transmission system. The fault simulation at the phase angles 0$^{\circ}$ , 45$^{\circ}$ , and 90$^{\circ}$ showed that the resistive SFCL limited the fault current less than 16 kA without any DC component after one half cycle from the instant of the fault. On the other hand, the inductive SFCL suppressed the current below 11 kA, but with 3-4 kA of DC component which decreased to zero in 5 cycles. We concluded that the inductive SFCL had higher performance in current limiting but the resistive SFCL was better from the view point of DC components.

• Journal of Electrical Engineering and Technology
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• v.13 no.4
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• pp.1623-1630
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• 2018

Normally, various auxiliary loads are installed along with the main load in industrial applications. Usually, load transformers are used to convey such types of auxiliary loads. The transformers become energized when the loads are turned-on, consequently, high amplitude of inrush current appears at the output of the uninterrupted power supply (UPS) system. To mitigate these high current amplitudes, this manuscript suggests a three-phase line-interactive UPS system to counter the inrush current during the turning-on of the auxiliary load transformer while powering the main load by using a current controlled inverter. Experimental results of a laboratory-sized prototype are provided in the support of the proposed UPS system for validation.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.268-270
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• 1995

This paper proposes a novel PWM technique for a three phase current fad type converters. A minor loop compensation method is introduced to compensate leading current and to minimize input line current (Iu) distortion resulting from the resonance between AC filter capacitor and source inductance of power system. This PWM converter has excellent characterics as next. The control system is simply designed, and the operation with unity power factor can be easily obtained by automatic compensating the leading current of the filter circuit. Also. the three phase sinusoidal input current can be obtained.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.157-158
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• 2005

Superconducting fault currents(SFCLs) are expected to improve not only reliability but also stability of real power systems. The analysis on the single line-to-ground fault of the integrated three phase flux-lock type SFCL, which consists of three flux-lock reactor wound on an iron core in each single phase and three YBCO thin films, was investigated in current limiting operation characteristics. We compared 21turn numbers with 42turn numbers according to wound turn numbers each the coil 2 under the additive polarity winding operation between coil 1 and coil 2. The three phase flux-lock type SFCL using an iron core differently operates general three phase resistive SFCLs. When a single line-to-ground fault occurred, the SFCL's three units were quenched after fault onset. We confirmed effective current limiting operation characteristics with adjustable inductance level.