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This paper presents a practical approach for supplementary control of high voltage direct current (HVDC) system to damp subsynchronous oscillation (SSO) involving HVDC converters and turbine-generator shaft systems. A novel eigenvalue analysis (NEA) program, HVDC system modeling to consider steady-state and dynamic conditions in a combined ac/dc system, and an appropriate control scheme have been utilized. The design method proposed facilitates the design of a subsynchronous oscillation damping controller (SODC) to provide positive damping torque for the dominant torsional mode in combined ac/dc systems. The suggested SODC design method has been applied to an ac/dc system to verify its practicality using the EMTDC simulation program. Index Terms--Damping controller, eigenvalue analysis, high voltage direct current (HVDC) system, subsynchronous oscillation, time domain simulation.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2005.04.007 Byline: Sung-Jun Park (a), Feel-Soon Kang (b), Su Eog Cho (c), Chae-Joo Moon (d), Hae-Kon Nam (a), Toshifumi Ise (e) Keywords: Dc-to-dc converter; Parallel driving; Peak current control mode; Photovoltaic system Abstract: This paper proposes a modified converter for use in photovoltaic system. In the modified converter, the voltage ratio of output to input is equal to that of the general boost converter. The difference between the two converters is the configuration of output terminal. Therefore, the working voltage of an output capacitor and the value of its capacitance can be lower than those of the general boost converter. This paper also presents an efficient parallel driving scheme to increase output power and to reduce the output voltage ripple. The parallel driving method using the modified converter and current mode control gives a good solution for alleviating the current sharing unbalance problem. It reduces the output voltage ripple by increasing the equivalent switching frequency of the modified converter. The performance of the proposed converter system is verified through computer-aided simulations and experimental results. Author Affiliation: (a) Department of Electrical Engineering, Chonnam National University, 300 Yongbong-dong, Puk-gu, Gwangju 500-757, Republic of Korea (b) Department of Control and Instrumentation Engineering, Hanbat National University, San 16-1, Duckmyong, Yuseong, Daejeon 305-719, Republic of Korea (c) Department of Electrical Engineering, Pusan National University, Changjurn, Gumjung, Busan 609-735, Republic of Korea (d) Department of Electrical Engineering, Mokpo National University, 61 Dorim-ri, Cheonggye-myeon, Muan-gun, Jeonnam 534-729, Republic of Korea (e) Department of Electrical Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita 565-0871, Japan Article History: Received 26 April 2004; Revised 31 March 2005; Accepted 11 April 2005 Article Note: (miscellaneous) Communicated by: Associate Editor Arturo Morales-Acevedo

In this paper, a new second-order eigen-sensitivity and perturbation theory of the augmented matrix is developed using of only dominant eigenvalues and their left and right-eigenvectors. Eigen-sensitivities on various system and control parameters are computed for analysis of small signal and voltage stability of the New England system. It is also shown that the sensitivity analysis may be used as an invaluable tool for analysis, planning, and operation of power systems: identification of the cause of the stability problems and weak lines; optimal tuning of control parameters; determining locations of compensating devices for stability enhancement such as capacitor compensation and FACTS devices. Index Terms--Augmented matrix, dominant eigenvalue, eigen-sensitivity, eigenvalue perturbation, eigenvector, power system stability.