• Journal of the Korean Society for Precision Engineering
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• v.29 no.10
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• pp.1096-1100
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• 2012

In the phase-shift measurement method, the distance light travels can be obtained based on the phase difference between the reference signal and the measured signal. When the object having various colors is measured, the intensity of the measured signal much varies even at the same distance, and it causes different phase delay due to wide dynamic range input to a signal processing circuit. In this work, an measured intensity control method is proposed to solve this phase delay problem.

• Journal of Power Electronics
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• v.15 no.3
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• pp.796-805
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• 2015

New direct and indirect current control methods for a fault-tolerant active power filter topology are presented in this paper. Since a three-phase four-switch topology has a phase bridge current which cannot be directly controlled, a hysteresis control method in the α-β plane which controls the three-phase current in the two-phase stationary coordinate system is proposed. The improved SVPWM algorithm is able to eliminate the operation of the trigonometric functions in the traditional algorithm by rotating the α-β coordinates and alternating the sequence of the output vectors, which in turn simplifies the algorithm and reduces the switching frequency. The selection of the DC-side reference voltage and DC-side capacitor equalization strategy are also discussed. Simulation and experiments demonstrate that the proposed control method is correct and feasible.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.2
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• pp.144-149
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• 2016

This paper presents a power control method of high-speed single-phase BLDC motor. Most electric appliances require a power factor corrector (PFC) to mitigate grid current harmonics. However, the reactive components and power semiconductors in the PFC increase system cost and dimension. In this paper, a new motor drive system for a high-speed single-phase BLDC motor is proposed, which can decrease grid current harmonics without PFC by directly manipulating motor power and eliminating bulky electrolytic dc-link capacitor. Given that the proposed motor power control method does not require motor current controller, no current sensor is necessary. Moreover, the proposed algorithms can be easily implemented using a low-cost micro-controller. The effectiveness of the proposed power control method is verified by experiments.

• Proceedings of the KIPE Conference
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• 2012.11a
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• pp.52-53
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• 2012

This paper presents a new control scheme for a three-phase split DC-link capacitor inverter as an AC power supplies. The proposed control method can maintain the balanced sinusoidal output voltage under unbalanced and nonlinear load conditions. The validity of the control method has been verified by simulation results.

• Journal of Power Electronics
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• v.16 no.6
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• pp.2231-2242
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• 2016

A simplified model predictive control method is presented in this paper. This method is based on a future reference voltage vector for a three-phase four-leg voltage source inverter (VSI). Compared with the three-leg VSIs, the four-leg VSI increases the possible switching states from 8 to 16 owing to a fourth leg. Among the possible states, this should be considered in the model predictive control method for selecting an optimal state. The increased number of candidate switching states and the corresponding voltage vectors increase the calculation burden. The proposed technique can preselect 5 among the 16 possible voltage vectors produced by the three-phase four-leg voltage source inverters, based on the position of the future reference voltage vector. The discrete-time model of the future reference voltage vector is built to predict the future movement of the load currents, and its position is used to choose five preselected vectors at every sampling period. As a result, the proposed method can reduce calculation load by decreasing the candidate voltage vectors used in the cost function for the four-leg VSIs, while exhibiting the same performance as the conventional method. The effectiveness of the proposed method is demonstrated with simulation and experiment results.

• Proceedings of the KIEE Conference
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• 2001.11c
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• pp.22-25
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• 2001

In this paper, a fuzzy advance angle control method is described to drive an industrial low voltage SRM (Switched Reluctance Motor) for 10kW forklift truck. SRM has a highly non-linear characteristic that is due to change the rotor and stator. And low voltage SRM is designed that its phase resistance and phase inductance is very low to inject high current into the phase windings. In this reason, the proper current control is necessary to drive the low voltage SRM efficiently. SRM has positive torque at increasing inductance region and negative torque at decreasing inductance region. Due to this reason, the current has to be built up in the increasing phase inductance part as soon as possible. Therefore, the phase switch must be turned on before the phase inductance increases, and this angle is called as the advance angle. Also, the phase current has to be dropped before the phase inductance decreases. Fuzzy logic is a flexible and general-purposed method of implementing non-linear functions and as such it is useful in control applications. Consequently, we designed a fuzzy advance angle controller to control the phase current appropriately.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.4
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• pp.88-96
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• 1997

This paper suggests a new non-linear friction compensation for digital control systems. This control adopts a hysteresis nonlinear element which can introduce the phase lead of the control system to compensate the phase delay comes from the inherent time delay of a digital control. A proper Lyapunov function is selected and the Lyapunov direct method is used to prove the asymptotic stability of the suggested control.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.987-993
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• 1996

This report suggests a new non-linear friction compensation for digital control systems. This control adopts a hysteric nonlinear clement which can introduce the phase lead of the control system to compensate the phase delay comes from the inherent time delay of a digital control. The Lyapunov direct method is used to prove the asymtotic stability of the suggested control, and the stability and the effectiveness are verified analytically and experimentally on a single axis servo driving system.

• Proceedings of the KIEE Conference
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• 2000.11a
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• pp.139-141
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• 2000

High voltage direct current(HVDC) transmission system uses the phase controlled rectifier triggered by means of IPC(individual phase control) or EPC(equidistant pulse control). Most HVDC system has adopted EPC method that can solve the harmonic instability problem of IPC method in weak power system. But EPC has inherent indirect synchronizing problem requiring the closed loop control. This paper presents the new gate pulse generating method for 12-pulse HVDC converter, which combines IPC with EPC. Simulation and test results are presented. The basic concept is that it generates the gating pulse for 12-pulse converter by synthesizing the internal phase reference using the frequency and phase information of a sin91e phase voltage. To ensure the reliability of the external phase input, Potential transformer that detects the phase voltage has redundancy. Using fault detecting algorithm the healthy input is always guaranteed. And the frequency compensation function was reinforced.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.8
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• pp.902-913
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• 1992

There have been several control schemes for the single input systems with unmeasurable state variables using variable structure control(VSC) theory. In the previous VSC, the systems must be represented in phase canonical form and the complete measurements for each state variable must be assumed. In order to eliminate these restrictions several VSC methods were proposed. And especially for the systems in phase canonical form with unmeasurable state variables, the reduced order switching function algorithm was proposed. But this method has many drawbacks and can not be used in the case of general form (not phase canonical form) dynamic system. Therefore this paper propose new construction method of switching fuction for the systems in phase canonical form, which reduce the restriction of reduced order switching function algorithm. And this algorithm can be realized for any state representation and adopted in the systems where not all states are available for switching function synthesis or control.