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이중 변환 UPS의 병렬 운전 시 외란 저감 성능 향상을 위한 정지 좌표계 상의 전향 보상 기법
류효준,윤영두,모재성,최승철,우태겸 전력전자학회 2022 전력전자학회 논문지 Vol.27 No.5
Generally, a proportional-resonant controller is used to eliminate steady-state errors during the voltage– current control of a double-conversion uninterruptible power supply (UPS) in a stationary reference frame. Additionally, the feed-forward control compensating for the load current, which can be considered a disturbance of the voltage controller, can be used to improve the disturbance rejection performance. However, during the parallel operation of UPSs, circulating current can occur between UPS modules when performing both feed-forward control and droop control because feed-forward control reduces the circulating current impedance. This study proposes a feed-forward compensation technique that considers the impedance of circulating current. An additional feed-forward compensation technique is developed to enhance the disturbance rejection performance. The validity of the proposed feed-forward compensation technique is verified by the experiment results of the parallel operation of a 500 W double-conversion UPS module.
이중 변환 UPS의 병렬 운전 시 외란 저감 성능 향상을 위한 정지 좌표계 상의 전향 보상 기법
류효준(Hyo-Jun Ryu),모재성(Jaesung Mo),최승철(Seung-Cheol Choi),이승은(Seung-Eun Lee),윤영두(Young-Doo Yoon) 전력전자학회 2021 전력전자학술대회 논문집 Vol.2021 No.11
정지 좌표계 상에서 이중 변환 UPS의 출력단 전압-전류 제어시, 정상 상태 오차를 제거하기 위해 비례-공진 제어기를 사용한다. 그리고 UPS의 외란 저감 성능을 향상시키기 위해, 전압 제어기의 외란인 부하 전류를 전향 보상하는 기법을 사용할 수 있다. UPS 병렬 운전 시 부하 분담을 하기 위한 Droop 제어를 수행하면서 부하 전류 전향 보상을 수행할 경우, UPS 모듈간의 순환 전류가 발생한다. 이는 비례-공진 제어기를 사용한 전압-전류 제어기에서 부하 전류 전향 보상이 순환 전류 임피던스를 감소시키기 때문이다. 본 논문에서는 순환 전류 임피던스 감소를 고려하여, 부하 전류의 일부분을 전향 보상한다. 또한, 기존보다 줄어든 부하 전류 전향 보상으로 인해 감소한 외란 저감 성능을 개선하는 새로운 전향 보상 기법을 제안하고, 이를 실험을 통해 유효성을 검증하였다.
이중 변환 UPS 병렬 운전의 제어 동특성 향상을 위한 동기 좌표계 전압 제어기 구조
모재성,윤영두,류효준,이민성,최승철,김성민,김석민,강호현,김희중 전력전자학회 2022 전력전자학회 논문지 Vol.27 No.4
This study proposes a voltage control scheme in a synchronous reference frame to improve the dynamic characteristics of double-conversion UPSs. UPSs need to control positive and negative sequence voltage, so that positive and negative sequence extractors are generally used to obtain each sequence of the voltage and current. Voltage and current controllers for each sequence are implemented. However, the extractor causes considerable delay, and the delay restricts the control performance, especially for the current controller. To improve the dynamics of the current controller, the proposed scheme adopts a unified current controller without separating positive and negative sequences. By using discrete-time current controller, the control bandwidth can be extended significantly so that negative sequence current can be controlled. To enhance the performance, an additional feed-forward technique for output voltage regulation is proposed. The validity of the proposed controller is verified by experiments.
지중온도 경사를 이용한 효율적 지중에너지 이용 방안에 관한 연구
류형규(Hyungkyou Ryu),정민호(Minho Chung),이병석(Byungseok Lee),류효준(Hyojun Rhew),최현준(Hyunjun Choi),최항석(Hangseok Choi) 대한설비공학회 2014 설비공학 논문집 Vol.26 No.9
This paper proposes an optimum operation method for open type ground heat exchangers. A series of TRTs and artificial heating/cooling operations were carried out while monitoring temperature in the hole of SCW. The ground temperature naturally increases with depth, but a switch between the cooling/heating mode results in a change in the distribution of ground temperature. The effect of the mode change was evaluated by performing LMTD and COMSOL multiphysics analysis for a reduced model with the depth of 150 m. As a result, in the cooling mode, the upstream operation is more efficient than the downstream operation and reduces EWT by 2.26℃. On the other hand, in the heating mode, the downstream operation is advantageous over the upstream operation and increases EWT by 3.19℃. The merit of the optimum operation will be enhanced for the typical dimension of SCW with a depth of 400~500 m. In the future, an open type ground heat exchanger system adopting the optimum operation with variation in the ground temperature will be used in practice.