• East Asian mathematical journal
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• v.29 no.3
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• pp.259-268
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• 2013

There are a lot of unsolved problems or issues regarding Kronecker products, vec-operator and Commutation matrices. We derived further properties and results of Kronecker products, vec-operator and Commutation Matrices.

• Journal of Electrical Engineering and Technology
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• v.12 no.5
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• pp.1925-1933
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• 2017

The brushless DC motor's commutation torque ripple is caused by inconsistency in the rate of phase current change. Thus, a method that considers armature resistance is proposed to modulate phase current. The three-phase control strategy, which involves the "open-phase conduction, off-phase pulse width modulation, and maintained non-commutation phase" technique, is applied during commutation at full-speed segments of the motor. Changes in each phase current are analyzed theoretically by establishing mathematical model based on phase current to determine the relative difference among shutdown phase, duty, and motor operating parameters. The turn-on and turn-off phase current change rates are made to be consistent to ensure less non-commutation phase current ripple, then the torque ripple is inhibited. The simulation results show that the phase commutation current and torque ripple coefficient of the proposed method are reduced from 56.9% and 55.5% to 6.8% and 6.1%, respectively. In the experiment system, the pulsation coefficient of the motor phase current is reduced from 40.0% to 16.7% at low speed and 50.0% to 18.8% at high speed. The simulation and experimental results show that the proposed control method significantly inhibits commutation current and torque in the full section.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.1
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• pp.1-8
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• 2000

Switched reluctance motor(SRM) has simple magnetic structure, and requires simple power electronic driving circuit. It is very useful for wide range adjustable speed drive system. But, SRM drive generates large vibration and acoustic noise because it is commutated individually by step pulse m.m.f of each phase pole. In the vibration and acoustic noise characteristics. The considerable vibration and noise is induced by radial deforming of stator, so the frequency of dominant vibration and noise is coincident with the frequency of natural mode frequency of mechanical structure. This radial vibration force is generated in the phase commutation region. This paper suggests the new electromagnetic structure of SRM with auxiliary commutation winding which is excited by direct current. This phase and commutation winding are coupled magnetically between one phase winding and the other. Therefore, the switch-off phase current is absorbed by the another phase winding. By this interaction of phase and commutation winding in commutation mechanism, vibration and noise is reduced. And this reduction effect is examined by the test of prototype machine. As a result, SRM with DC exciting commutation winding is very useful to reduce vibration and acoustic noise.

• Journal of Electrical Engineering and Technology
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• v.13 no.4
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• pp.1450-1458
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• 2018

Commutation failures can deteriorate the availability of high-voltage direct current (HVDC) links and may lead to outage of the HVDC system. Most commutation failures are caused by voltage reduction due to ac system faults on inverter side. The commutation failure process can be divided into two stages. The first stage, from the occurrence to the clearing of faults, is called 'Deterioration Stage'. The second stage, from the faults clearing to restoring the power system stability, is called 'Recovery Stage'. Based on the analysis of the commutation failure process, this paper proposes a direct-current fuzzy controller including prevention and recovery controller. The prevention controller reduces the direct current to prevent Commutation failures in the 'Deterioration Stage' according to the variation of ac voltage. The recovery controller magnifies the direct current to speed up the recovery of power system in the 'Recovery Stage', based on the recovery of direct voltage. The validity of this proposed fuzzy controller is further proved by simulation with CIGRE HVDC benchmark model in PSCAD/EMTDC. The results show the commutation failures can be mitigated by the proposed direct-current fuzzy controller.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1216-1217
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• 2011

본 논문에서는 제주 스마트그리드 실증단지 계통에 연계될 전류형 HVDC 상세 모델을 이용하여 계통에 외란이 발생할 경우에 일어날 수 있는 Commutation Failure를 고려한 HVDC 고장영향을 분석한 내용에 대해 기술하고 있다. 전류형 HVDC 시스템의 Commutation Failure 기본원리를 정리하고, 계통의 3상 지락고장을 가정하여 이론적인 전압감소 시점에 대해 설명하였고, 이를 통해 3상 지락고장시 리액턴스(계통 임피던스 + HVDC 부가설비 리액턴스) 값 변동에 따른 Commutation Failure 지속시간을 Multiple Transient Simulation 방법을 통해 확인하였다. 도출된 결과를 통해 리액턴스 값이 작을수록 Commutation Failure 진행 시간을 줄일 수 있음을 보여주였다.

• Journal of Power Electronics
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• v.18 no.4
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• pp.1086-1098
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• 2018

This study presents a new sensorless commutation method for brushless direct current motors to replace Hall sensor signals with virtual Hall signals. The importance of the proposed method lies in the simultaneous elimination of the phase shifter and the low-pass filters, which makes the method simple and cost-effective. The method removes high ripple switching noises from motor terminals, thereby decreasing motor losses. The proposed method utilizes unfiltered line voltages with notches caused by current commutation. Hence, specific sign signals are defined to compensate for the effects of commutation noise. The proposed method is free from phase delay that originates from low-pass filters. The method directly produces virtual Hall signals, and thus, it can be interfaced with low-cost commercial commutation integrated circuits based on Hall sensors. Simulation and experimental results show the effectiveness and validity of the proposed method.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.117-120
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• 1988

A new current source inverter (CSl) with dc-side commutation and load-side energy recovery circuit is proposed with analysis and explanation of the circuit operation. Proposed inverter overcomes the most drawbacks of the conventional CSI's - high device voltage stress, low operating frequency range, large commutation capacitance, etc. - by employing simultaneous recovery and commutation concept. The new CSI employs only one commutation capacitor and it can be built with considerably low cost. The commutation energies are temporarily stored into a large dc capacitor and recovered to the load side, thus the device voltage stress is low and the efficiency is high in the proposed inverter. Computer simulation results are given at the steady state, and a guideline determining the commutation circuit is given.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.55-57
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• 1999

SRM Drives generate large vibration and acoustic noise because it is rotated by step pulse mmf and switching commutation mechanism. The main vibration source of SRM Drive is generated by rapidly variation of radial force when phase winding current is extinguished for commutation action. So the rapidly variation of radial force is repressed firstly to reduce vibrating force of SRM Drive. This paper suggests the vibration reduction method that SRM Drive with unidirect-short compensation winding is excited by a two stage commutation method at commutation period. This reduction effect of vibration is verified with the result obtained in the test of prototype machine.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.1
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• pp.57-62
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• 2013

Because of high torque and easiness of speed control, Direct Current(DC) motors have been used for a long time. But, its applications are limited in circumstance and performance, since they contained brush and commutator. The commutation characteristic gives effect to life and performance of the DC motor. Naturally, the commutation characteristic analysis is strongly required. In this paper, With the result of finite element analysis, The inductance is calculated each rotor position and applied to the voltage equations coupled with commutation equation. Also, contact resistances of brush/commutator assembly are considered using contact area and brush width converted with commutator segments. The time derivative term in the differential equation is solved in time difference method. This algorithm was applied to 2-pole shunt DC motor. We considered commutation characteristic by changing contact resistance between brush and commutator segment.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.2B no.4
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• pp.183-190
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• 2002

This paper presents an improved Zero Voltage/Zero Current Switching (ZVZCS) commutation cell with minimum additional components, which provides soft switching at both turn-on and turn-off of main and auxiliary switches as well as diodes in a PWM DC/DC converter. The proposed soft-switching technique is suitable for not only minority, but also majority carrier semiconductor devices. The auxiliary switch of the proposed ZVZCS commutation cell is in parallel with the main switch, and therefore, the main switch and the diode are free of currentstress. The operation principles of the proposed ZVZCS commutation cell are theoretically analyzed using the PWM boost converter topology as an example. The validity of the PWM boost converter topology with the proposed ZVZCS commutation cell is verified through theoretical analysis, simulation and experimental results.