새로운 DFT 비교기를 이용한 자동 다전원 동기절체 스위치에 관한 연구

곽아림,박성미,손경종,박성준,김종철 한국산업융합학회 2022 한국산업융합학회 논문집 Vol.25 No.3

The UPS(Uninterruptible Power Supply) system operates in the battery charging mode when the grid is normal, and in the UPS mode, which is the battery discharge mode when a grid error occurs. Since the UPS must supply the same voltage as the grid to the load within 4 [ms] in case of a grid error, the switching time and power recovery time should be short when controlling the output voltage and current of the UPS, and the power failure detection time is also important. The power outage detection algorithm using DFT(Discrete Fourier Transform) proposed in this paper compares the grid voltage waveform with the voltage waveform including the 9th harmonic generated through DFT using Schmitt trigger to detect power outage faster than the existing power outage monitoring algorithm. There are advantages. Therefore, it is possible to supply instant and stable power when switching modes in the UPS system. The multi-power-applied UPS system proposed in this paper uses DFT, which is faster than the conventional blackout monitoring algorithm in detecting power failure, to provide stable power to the load in a shorter time than the existing power outage monitoring algorithm when a system error occurs. The detection method was applied. The changeover time of mode switching was set to less than 4 [ms], which is 1/4 of the system cycle, in accordance with KSC 4310 regulation, which was established by the Industrial Standards Council on the regulation of uninterruptible power supply. A 10 [kW] UPS system in which commercial voltage, vehicle generator, and auxiliary diesel generator can be connected to each of the proposed transfer devices was constructed and the feasibility was verified by conducting an experiment.

병렬 제어기법을 이용한 UPS 출력 전압의 개선

成炳模,姜弼淳,朴星濬,金喆禹 전력전자학회 2002 전력전자학회 논문지 Vol.7 No.2

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. 본 논문은 기존의 1차 예측 기법과 반복 제어기법을 이용하여 LC 필터와 정류 부하 등의 비선형 부하를 가지는 UPS 인버터의 출력전압 파형의 개선에 관한 연구이다. 기존의 1차 예측 기법은 정류부하에 대하여 우수한 특성을 가지므로 출력전류의 예측에 적합하나 정류 부하와 같은 비선형적인 부하의 정상 상태 오차를 보상하기에는 충분하지 못한 단점을 가진다. 따라서, 정상상태 오차를 최소화 할 수 있는 반복제어 기법을 적용하여 UPS 출력전압을 개선시키고자 한다. 제안된 제어기법에 대한 타당성을 시뮬레이션으로 검증하고, 이를 바탕으로 LC 필터를 가지는 3 kVA, 60 Hz UPS 시스템을 제작하여 실험으로 검증한다.

고효율 운전이 가능한 지능형 무정전 전원장치에 관한 연구

엄태욱(Tae-Wook Eom) 한국조명·전기설비학회 2013 조명·전기설비학회논문지 Vol.27 No.5

In this paper, a control scheme with the capability of high efficiency, which is realized by predicting the conditions of a load power and an input power, is proposed for the uninterruptible power supply (UPS). Generally, on-line UPS system supplies a constant voltage and a constant frequency (CVCF). However, the efficiency of the On-line UPS system can be reduced due to the switching losses of semiconductor devices during the power conversion. The these losses are improved by the proposed smart UPS with the high efficiency drive system, which is realized by analysing and predicting the conditions of a load power and an input power.

Zigbee 무선통신을 이용한 UPS DC링크 커패시터의 고장 모니터링 시스템 개발

김동준(Dong-Jun Kim),손진근(Jin-Geun Shon),전희종(Hee-Jong Jeon) 대한전기학회 2012 전기학회논문지 P Vol.61 No.1

Electrolytic power capacitors have been widely used in power conversion system such as inverter or UPS because of characteristics of large capacitance, high-voltage and low-cost. The electrolytic capacitor, which is most of the time affected by the aging effect, plays a very important role for the power-electronics system quality and reliability. Therefore it is important to diagnosis monitoring the condition of an electrolytic capacitor in real-time to predict the failure. In this paper, the on-line remote diagnosis monitoring system for UPS DC link electrolytic capacitors using low-cost single-chip zigbee communication modules is developed. To estimate the health status of the capacitor, the equivalent series resistor(ESR) of the component has to be determined. The capacitor ESR is estimated by using RMS computation using BPF modeling of DC link ripple voltage/current. Zigbee-based hardware experimental results show that the proposed remote capacitor diagnosis monitoring system can be applied to UPS successfully.

UPS Flux Compensation Techniques for Transformer Inrush Reduction

Ming-Yang Yeh,Yu-Hsing Chen,Po-Tai Cheng,Steven Liao,Charles Tsai 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5

This paper presents two flux compensation designs for the uninterruptible power supply system. The objective of the flux compensation is to reduce the potential inrush current of the uninterruptible power supply-fed load transformer in the event of grid disturbances and load transformer engagement. The proposed methods utilize the existing voltage and current sensors, and voltage and current control loops of the uninterruptible power supply system for easy implementation. The application scenario is explained, and details of the flux compensation techniques are presented. Laboratory test results are provided for validation.

위상변환장치를 이용한 새로운 배전변압기 무정전 교체벙법

신동열(Dong-Yeol Shin),김숙철(Suk-Cheol Kim),윤기갑(Gi-Gab Yoon),차한주(Han-Ju Cha) 한국조명·전기설비학회 2007 조명·전기설비학회논문지 Vol.21 No.10

전력 소비자들에 의한 전기품질 요구 수준이 날로 높아지고 있어 배전변압기 교체시 발생되는 정전에 의한 소비자들의 블편을 줄이기 위한 선진국형 무정전 배전변압기 교체방법이 요구되고 있다. 현재 시행되고 있는 주상변압기 무정전 교체공법은 변압기 이용률과 현장여건에 따라 1-2차를 고압 바이패스하는 방법이므로 작업공정이 불편하고, 편법작업에 의한 고장발생과 이에 따른 작업자 안전사고가 발생하는 문제점이 있어 새로운 무정전 교체방법이 절실히 요구되고 있다. 따라서 본 논문에서는 새로운 위상변환장치를 이용한 무정전 공법을 제안한다. 제안된 무정전 공법은 기존의 고압 바이패스 작업방법에 비해 작업공정을 줄이면서 안전하고 저렴한 방법으로 변압기 교체를 할 수 있다. 그러므로 본 논문에서 제시한 공법은 배전공사 원가 절감에 따른 전기요금 하락과 무정전 전력공급으로 국민생활에 편리함을 더하고 국가 경제 발전에 기여할 것으로 기대된다. Nowadays, the power quality issue becomes very important in the electric distribution system Especially, when a distribution transformer is replaced, the customers who are supplied electricity from the transformer feel inconvenience due to electric outage. Therefore, an advanced method for the distribution transformer replacement without outage is strongly required. The conventional method is the primary-secondary high voltage bypass method according to the transformer utilization factor and the field condition. But it is inconvenient and has some problems such as breakdown and security troubles of the workers according to the unauthorized and temporary work. Therefore, the new scheme for the replacement with uninterruptable power supply is demanded. This paper proposes the new replacement method using the phase converter. The proposed method can reduces the process of replacement work and also ensures worker's safty. Therefore, the method is reasonable in comparison with the conventional method. The proposed method is able to contribute the national economy growth and elevate the convenience of national life by uninterruptable power supply.

AC 라인 리액터와 병렬 및 직렬 능동필터를 가지는 새로운 3상 Line-Interactive UPS 시스템의 전압제어 방식

池俊根(Jun-Keun Ji),金長煥(Jang-Hwan Kim),薛承基(Seung-Ki Sul) 대한전기학회 2007 전기학회논문지 Vol.56 No.3

A new 3-phase line-interactive UPS(Uninterruptible Power Supply) system with parallel-series active power-line conditioning capability using AC line reactor and two four-leg PWM VSCs(Voltage Source Converters) was introduced recently. In this paper, the strategy of voltage control in suggested UPS system is explained. The objective of proposed voltage controllers in parallel(shunt) and series PWM VSC is to guarantee satisfactory characteristics in steady state and transient state. Therefore the experimental results to prototype UPS system having power rating of 60kVA is shown to prove the verification of voltage control strategy.

비상전원 기능을 갖는 3kW급 하이브리드 ESS 개발

양석현(Seok-Hyun Yang),김민재(Min-Jae Kim),최세완(Se-Wan Choi),조준석(Jun-Seok Cho) 전력전자학회 2015 전력전자학회 논문지 Vol.20 No.1

This paper proposes a high-efficiency 3-kW hybrid ESS with emergency power supply. The proposed system enables efficient use of power from photovoltaic (PV) cells and energy storage system (ESS). The proposed system can operate as an uninterruptible power supply (UPS) when grid fault occurs, providing seamless transfer from grid-connected mode to stand-alone mode. The LLC converter for PV achieves ZVS turn-on of switches and ZCS turn-off of diodes, and the isolated bidirectional DC-DC converter for ESS achieves ZCS turn-off regardless of load condition, resulting in high efficiency. The efficiency and performance of the proposed hybrid ESS has been verified by a 3-kW prototype.

A Nonlinear Droop Control for Supercapacitor-Hybrid Uninterruptible Power Supplies in DC Microgrids

Seung-Hyun Choi,Jae-Sang Kim,Jongyoon Chae,Juyeon Sim,Gun-Woo Moon 전력전자학회 2023 ICPE(ISPE)논문집 Vol.2023 No.-

Fuel cell-supercapacitor and battery-supercapacitor hybrid energy storage systems (HESS) are widely used in uninterruptible power supplies. Integral droop control is employed for managing supercapacitors, while linear droop control methods have been utilized for controlling fuel cells and batteries. However, linear droop control has excessive energy use of supercapacitors and low load-sharing performances. To address these issues, nonlinear droop control can be implemented. Nevertheless, selecting the appropriate nonlinear droop gain is crucial, as it can impact the system stability and dynamic performance of the HESS. Therefore, this conference paper proposes a nonlinear droop gain design method. By utilizing the proper nonlinear droop gain, the proposed method enhances load-sharing performance while maintaining high stability and dynamic performance. The paper demonstrates the effectiveness of the nonlinear control strategy through theoretical analysis and experimental validation.

An Observer-Based Optimal Voltage Control Scheme for Three-Phase UPS Systems

Eun-Kyung Kim,Mwasilu, Francis,Han Ho Choi,Jin-Woo Jung Institute of Electrical and Electronics Engineers 2015 IEEE transactions on industrial electronics Vol. No.

<P>This paper proposes a simple optimal voltage control method for three-phase uninterruptible-power-supply systems. The proposed voltage controller is composed of a feedback control term and a compensating control term. The former term is designed to make the system errors converge to zero, whereas the latter term is applied to compensate for the system uncertainties. Moreover, the optimal load current observer is used to optimize system cost and reliability. Particularly, the closed-loop stability of an observer-based optimal voltage control law is mathematically proven by showing that the whole states of the augmented observer-based control system errors exponentially converge to zero. Unlike previous algorithms, the proposed method can make a tradeoff between control input magnitude and tracking error by simply choosing proper performance indexes. The effectiveness of the proposed controller is validated through simulations on MATLAB/Simulink and experiments on a prototype 600-VA testbed with a TMS320LF28335 DSP. Finally, the comparative results for the proposed scheme and the conventional feedback linearization control scheme are presented to demonstrate that the proposed algorithm achieves an excellent performance such as fast transient response, small steady-state error, and low total harmonic distortion under load step change, unbalanced load, and nonlinear load with the parameter variations.</P>