• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.2
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• pp.158-164
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• 2002

This paper presents a proper parallel control method using a conventional control and a repetitive control for improving the output voltage waveform of uninterruptable power supply. Although first-order prediction control method shows a good characteristics to rectifier load, it is not sufficient to reduce steady state errors generated in nonlinear loads such as rectifier loads and phase controled loads. So we also employed a repetitive control method. A repetitive control method can eliminate steady state errors in the distorted output voltage caused by cyclic loads. The presented control scheme is verified through simulation and experiment. Experimental results Implemented on a single phase PWM inverter equipped with a LC output filter with 3 kVA, 60 Hz are shown.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2000.04a
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• pp.135-138
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• 2000

This paper is intended to propose what manufacturing configuration (manufacturing planning and shop floor control) is suitable for the tire industry. Basically tire-manufacturing process is mixed-products, parallel-disconnected-flow-shop. Both throughput time and cycle tine are very short, the variety of tires is very high, the setup time is long, shop floor data reporting requirements is high, and there are many equipments and people working. And with no exception, tire industry also now confronts increasing requirements of delivery conformance with the above peculiar characteristics of tire manufacturing and changing market environments, this paper suggests, weekly master scheduling with no MRP is desirable and traditional kanban is right selection for shop floor control/scheduling. This paper describes why this configuration should be, using the manufacturing engineering principles and some new insights like four primitives of parallel flow shop. Generally known that shop with high parallel-product-mix and long setup time isn't good candidate for kanban. The four primitives of parallel flow shop explain why kanban is also useful scheduling technique in that environment.

• Journal of Power Electronics
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• v.17 no.6
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• pp.1553-1562
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• 2017

For the purpose of enhancing the performance of the shunt active power filter (APF), this paper presents a novel Fast Weighted Compound Control (FWCC) strategy based on the synchronous frame. In this control strategy, the proposed new repetitive controller can work faster and more stably by reducing the internal model cycle and introducing a damping coefficient. In addition, the harmonic detector can be removed to simplify the structure of the APF owing to the improvements. Furthermore, a proportional-integral (PI) controller is added to work in parallel with the repetitive controller by using a weighted ratio. Then, a convergence speed analysis and design algorithm are given in detail. Simulation and experimental results show that the harmonic distortion is reduced from 2.91% to 1.89%. In addition, the content for each of the characteristic harmonic orders has decreased by more than three times.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2008.10a
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• pp.90-93
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• 2008

In natural language, it is common that repetitive constituents in an expression are to be left out and it is necessary to figure out the constituents omitted at analyzing the meaning of the sentence. This paper is on recognition of boundaries of parallel noun phrases by figuring out constituents omitted. Recognition of parallel noun phrases can greatly reduce complexity at the phase of sentence parsing. Moreover, in natural language information retrieval, recognition of noun with modifiers can play an important role in making indexes. We propose an unsupervised probabilistic model that identifies parallel cores as well as boundaries of parallel noun phrases conjoined by a conjunctive particle. It is based on the idea of swapping constituents, utilizing symmetry (two or more identical constituents are repeated) and reversibility (the order of constituents is changeable) in parallel structure. Semantic features of the modifiers around parallel noun phrase, are also used the probabilistic swapping model. The model is language-independent and in this paper presented on parallel noun phrases in Korean language. Experiment shows that our probabilistic model outperforms symmetry-based model and supervised machine learning based approaches.

• Journal of KIISE
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• v.44 no.8
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• pp.760-766
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• 2017

Repetitive strings have been studied in diverse fields such as data compression, bioinformatics and so on. Recently, two problems of approximate periods of strings over integer alphabets were introduced, finding minimum ${\delta}-approximate$ periods and finding minimum ${\gamma}-approximate$ periods. Both problems can be solved in $O(n^2)$ time when n is the length of the string. In this paper, we present two parallel algorithms for solving the above two problems in O(n) time using $O(n^2)$ threads, respectively. The experimental results show that our parallel algorithms for finding minimum ${\delta}-approximate$ (resp. ${\gamma}-approximate$) periods run approximately 19.7 (resp. 40.08) times faster than the sequential algorithms when n = 10,000.

• Journal of IKEEE
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• v.15 no.4
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• pp.305-312
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• 2011

A primary interest of this work is to develop an efficient and powerful repetitive pulser system for the application of ultra wide band generation. The important component of the pulser system is a small-sized coaxial type spark gap with planar electrodes filled with SF6 gas. A repetitive switching action by the coaxial spark gap generates two consecutive pulses in less than a microsecond with rise times of a few hundred picoseconds (ps). A set of several parameters for the repetitive switching of the spark gap is required to be optimized in charging and discharging systems of the pulser. The parameters in the charging system include a circuit scheme, circuit elements, the applied voltage and current ratings from power supplies. The parameters in the discharging system include the spark gap geometry, electrode gap distance, gas type, gas pressure and the load. The characteristics of the spark gap discharge, such as breakdown voltage, output current pulse and recovery rate are too dynamic to control by switching continuously at a high pulse repetition rate (PRR). This leads to a low charging efficiency of the spark gap system. The breakthrough of the low charging efficiency is achieved by a parallel operation of two spark gaps system. The operational behavior of the two spark gaps system is presented in this paper. The work has focused on improvement of the charging efficiency by scaling the PRR of each spark gap in the two spark gaps system.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.86-89
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• 1991

In recent years, Vacuum Circuit Breaker(VCB) has been widely used to enhance the confidence and at the same time to ease maintenance of waterworks requipment as the power supply breaker of high voltage motor. When making and breaking the sources as VCB the powerful surge voltage, repetitive reignition phenomenon resulted from exceeding inter-pole endurance voltage of CB, has occured. It has transmitted to the winding of motor stator through the cable, and this surge voltage is repeated over and over again before finishing making and breaking action of CB according to cumulation of repetitive reignition surge, motor has become burned in the end. This paper describes surge voltage occuring in making and breaking of VCB as circuit parameters by transient phenonenon and examines closely the variance of peak values, wavefront-length, wavetail-length, when changing inductance and capacitance of a cable. Finally we will expect to protect motor winding breakdown from surge voltage through parallel connection of suitable-size in the motor.

• Proceedings of the KIPE Conference
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• 2007.11a
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• pp.11-14
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• 2007

In recent years, installation of the new and renewable energy system is rapidly increasing. Because the new and renewable energy system is a practical distributed generation system to save energy resources and to keep environments clean. Conventional single-phase utility interactive inverter controls output current by using PI current controller. However, this method is insufficient to suppress harmonic current resulted from nonlinear loads in grid line. In this paper, in order to suppress periodic waveform distortion and improve THD(Total Harmonic Distortion), new type current controller added a parallel repetitive controller is proposed and then performance of the proposed controller was verified with computer simulation.

• JSTS:Journal of Semiconductor Technology and Science
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• v.12 no.2
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• pp.150-161
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• 2012

Eye detection is widely used in applications, such as face recognition, driver behavior analysis, and human-computer interaction. However, it is difficult to achieve real-time performance with software-based eye detection in an embedded environment. In this paper, we propose a parallel hardware architecture for real-time eye detection. We use the AdaBoost algorithm with modified census transform(MCT) to detect eyes on a face image. We parallelize part of the algorithm to speed up processing. Several downscaled pyramid images of the eye candidate region are generated in parallel using the input face image. We can detect the left and the right eye simultaneously using these downscaled images. The sequential data processing bottleneck caused by repetitive operation is removed by employing a pipelined parallel architecture. The proposed architecture is designed using Verilog HDL and implemented on a Virtex-5 FPGA for prototyping and evaluation. The proposed system can detect eyes within 0.15 ms in a VGA image.

• Journal of Power Electronics
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• v.18 no.2
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• pp.502-510
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• 2018

A circulating current is a major problem caused by directly connecting voltage-source inverters (VSIs) in parallel. This circulating current occurs as a zero-sequence current between the inverters by specific switch states. Several studies have presented alternatives using hardware and software methods. When coupled inductors (CIs) are employed for the high-frequency circulating current, a controller is required to prevent the low-frequency circulating current from saturating the CIs. In this study, the zero-sequence circulating current and its alternatives are investigated using hardware and mathematical description. A high-performance circulating current controller is proposed by applying a repetitive controller to the zero-sequence current control loop. The proposed controller can effectively minimize the low-frequency circulating current without any data sharing between the inverters in unfavorable conditions. It can also be applicable to the modular configuration of parallel three-phase VSIs. Experimental results verify the performance of the proposed controller.