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Study on voltage regulation method in the power distribution system
Kenichiro Yamaguchi,Kyungsoo Lee,Kosuke Kurokawa 전력전자학회 2007 ICPE(ISPE)논문집 Vol.- No.-
This paper focuses on distribution voltage control when over-voltage or under-voltage occurs in the low-voltage (LV) distribution line. The distribution voltage control is performed by transformer and ac-ac converter. Transformer supports a part of settled voltage and ac-ac converter controls voltage disturbance. Bi-directional ac-ac converter employs digital control using Field Programmable Gate Array (FPGA). This method enables simple and fast the distribution voltage control. In this paper, voltage control concept is explained. Scaled-down experimental result is shown, when load condition is changed.
Case study of distrubution-unified power flow controller (D-UPFC) in the clustered PV system
Kyungsoo Lee,Kenichiro Yamaguchi,Kosuke Kurokawa 전력전자학회 2007 ICPE(ISPE)논문집 Vol.- No.-
This paper shows the case study of D-UPFC in the clustered PV system. D-UPFC mainly controls distribution voltage and thus, it is installed in the low-voltage distribution system connects with clustered PV system. Proposed D-UPFC topology is shown and compared with existing topology. The proposed topology can decrease the transformer capacity compared with existing topology. In the case study, voltage control and dynamic characteristic of D-UPFC are analyzed. Forward power flow, reverse power flow, and load power factor change conditions are simulated using ATP-EMTP tool.
Proposed Distribution Voltage Control Method for Connected Cluster PV Systems
Lee, Kyung-Soo,Yamaguchi, Kenichiro,Kurokawa, Kosuke The Korean Institute of Power Electronics 2007 JOURNAL OF POWER ELECTRONICS Vol.7 No.4
This paper proposes a distribution voltage control method when a voltage increase condition occurs due to reverse power flow from the clustered photovoltaic (PV) system. This proposed distribution voltage control is performed a by distribution-unified power flow controller (D-UPFC). D-UPFC consists of a hi-directional ac-ac converter and transformer. It does not use any energy storage component or rectifier circuit, but it directly converts ac to ac. The distribution model and D-UPFC voltage control using the ATP-EMTP program were simulated and the results show the voltage increase control in the distribution system.
Proposed Distribution Voltage Control Method for Connected Cluster PV Systems
Kyung-soo Lee,Kenichiro Yamaguchi,Kosuke Kurokawa 전력전자학회 2007 JOURNAL OF POWER ELECTRONICS Vol.7 No.4
This paper proposes a distribution voltage control method when a voltage increase condition occurs due to reverse power flow from the clustered photovoltaic (PV) system. This proposed distribution voltage control is performed a by distribution-unified power flow controller (D-UPFC). D-UPFC consists of a bi-directional ac-ac converter and transformer. It does not use any energy storage component or rectifier circuit, but it directly converts ac to ac. The distribution model and D-UPFC voltage control using the ATP-EMTP program were simulated and the results show the voltage increase control in the distribution system.
Naotaka Ogasawara,Mari Mizuno,Ryuta Masui,Yoshihiro Kondo,Yoshiharu Yamaguchi,Kenichiro Yanamoto,Hisatsugu Noda,Noriko Okaniwa,Makoto Sasaki,Kunio Kasugai 대한소화기내시경학회 2014 Clinical Endoscopy Vol.47 No.2
Background/Aims: Despite improvements in endoscopic hemostasis and pharmacological therapies, upper gastrointestinal (UGI) ulcersrepeatedly bleed in 10% to 20% of patients, and those without early endoscopic reintervention or definitive surgery might be at ahigh risk for mortality. This study aimed to identify the risk factors for intractability to initial endoscopic hemostasis. Methods: We analyzed intractability among 428 patients who underwent emergency endoscopy for bleeding UGI ulcers within 24hours of arrival at the hospital. Results: Durable hemostasis was achieved in 354 patients by using initial endoscopic procedures. Sixty-nine patients with Forrest typesIa, Ib, IIa, and IIb at the second-look endoscopy were considered intractable to the initial endoscopic hemostasis. Multivariate analysisindicated that age ≥70 years (odds ratio [OR], 2.06; 95% confidence interval [CI], 1.07 to 4.03), shock on admission (OR, 5.26; 95% CI,2.43 to 11.6), hemoglobin <8.0 mg/dL (OR, 2.80; 95% CI, 1.39 to 5.91), serum albumin <3.3 g/dL (OR, 2.23; 95% CI, 1.07 to 4.89), exposedvessels with a diameter of ≥2 mm on the bottom of ulcers (OR, 4.38; 95% CI, 1.25 to 7.01), and Forrest type Ia and Ib (OR, 2.21;95% CI, 1.33 to 3.00) predicted intractable endoscopic hemostasis. Conclusions: Various factors contribute to intractable endoscopic hemostasis. Careful observation after endoscopic hemostasis is importantfor patients at a high risk for incomplete hemostasis.