Control and Limit Enforcements for VSC Multi-Terminal HVDC in Newton Power Flow

This paper proposes a novel method to automatically enforce controls and limits for Voltage Source Converter (VSC) based multi-terminal HVDC in the Newton power flow iteration process. A general VSC MT-HVDC model with primary PQ or PV control and secondary voltage control is formulated. Both the dependent and independent variables are included in the propose formulation so that the algebraic variables of the VSC MT-HVDC are adjusted simultaneously. The proposed method also maintains the number of equations and the dimension of the Jacobian matrix unchanged so that, when a limit is reached and a control is released, the Jacobian needs no re-factorization. Simulations on the IEEE 14-bus and Polish 9241-bus systems are performed to demonstrate the effectiveness of the method.Comment: IEEE PES General Meeting 201

A Study on Wide-area Measurement-based Approaches for Power System Voltage Stability

With the development of wide-area monitoring system (WAMS) enabled by the synchrophasor technology, measurement-based approaches for power system voltage stability and control have been widely discussed in recent years. Based on high-frequency synchronized measurement signals collected from phasor measurement units (PMUs), these approaches have great potentials to significantly improve the situational awareness and to effectively guide the controls of interconnected modern power systems. If compared with conventional model-based voltage stability assessment (VSA) and control methods, the measurement-based methods are relatively new. Although their simplicity and independence of system models make them suitable for online deployment, the applications of these measurement-based methods are not as well explored as their model-based counterparts, which have been improved and matured over several decades. Therefore, the motivation of this dissertation is to explore new applications of measurement-based voltage stability assessment and control. In this dissertation, first, a comparative study on existing measurement-based approaches is provided; second, a hybrid VSA approach for N-1 contingency is proposed; third, measurement-based wide-area loading margin sensitivity suitable for voltage stability control is presented with a sample control study; fourth, mitigation approaches for overestimation of voltage stability margin when using coupled single-port circuit are proposed; and fifth, voltage dependent load model is integrated into measurement-based voltage stability analysis to provide a practical and accurate assessment of voltage stability margin

二酸化炭素を原料とする有機カルバメート合成に関する研究

筑波大学 (University of Tsukuba)201

Response of "Glacier-Runoff" system in a typical monsoonal temperate glacier region, Hailuogou Basin in Mt. Gongga of China, to global warming

International audienceThe method of correlation analysis and trend analysis were used in this research in order to confirm the response of "glacier-runoff" system to global warming. Hailuogou glacier had retreated by 1871.8 m over the past 76 years, Hailuogou No. 2 glacier had also retreated by 1100 m. Glaciers retreats are contrary to the climatic warming trend in China and the Northern Hemisphere. Glaciers in Hailuogou basin were in the loss with a fluctuating manner since 1950s, and accumulative value of mass balance is ?10 825.5 mm water equivalent with an annual mean value of ?240.6 mm. The inverse correlation is highly significant between mass balance variation and climatic fluctuation of China and the Northern Hemisphere after 1950s. Glacier ablation is intensive with a ratio of 7.86 m yr?1. A steady rise tendency toward glaciers runoff has been observed since 1980s, and the runoff rise is mainly responsible for melt water in Hailuogou basin. It is noticeable that climatic warming not only strengthened ablation extent and enlarged ablation area, but also prolonged ablation period. Global warming is the main cause of glacier retreat, mass loss and runoff rise in Hailuogou basin