Installation Schemes of Superconducting Generators in Power Systems

Abstract

Superconducting generator (SCG) with superconducting field winding offers various advantages, such as high efficiency, smallsize light weight, and so forth. A prominent one is to improve system stability and voltage stability owing to decreased synchronous reactance compared with conventional generators. Installation of SCGs in the power systems becomes one of the topics that should be considered. It concerns how and where SCGs should be installed and parameters setting of machines and controllers. Many conventional generators in power systems have been operated for many years and they have been nearly about to be reinstalled; replacement of conventional generators by SCGs in power systems might be a possible idea for the locations. It should be noted that it is not practical to replace all conventional generators by SCGs from economic and technical viewpoints; it is, however, necessary to determine appropriate locations and parameters such as synchronous reactance X d of as small as possible number of SCGs. In addition, control parameters such as gain values of AVRs and speed governors should also be selected appropriately.A method for determining optimal locations and synchronous reactance X d of SCG with low response excitation for stability enhancement in multi-machine power system has been proposed in Ref.(1). Eigenvalue sensitivity based parameter optimization technique has been employed to determine optimally synchronous reactance X d and used a specific rule that any generator which has a final synchronous reactance X d less than a threshold value is considered to be the SCG installing location and the determined synchronous reactance is used as the synchronous reactance X d of the SCG. In addition, gains of AVRs and speed governors of generators are also determined by the same parameter optimization technique. However, the method is found to have two main flaws. The first one is at the specific rule that the synchronous reactance of any generator which is not replaced by SCG is set back to the original values; that causes this method not to guarantee that the determined locations are optimal. The second one is that transient open-circuit time constant, which is comparatively very large because of near zero resistance of field winding has not been considered in optimization process. Such method should be modified or improved to obtain more reliable and systematic algorithm.In this paper, new methods for determining optimal locations and parameters of SCGs under multiple load flow conditions in multimachine power system for the purpose of dynamic stability improvement are proposed. Two new methods for installation schemes of SCG with low response excitation are proposed. The method type 1 uses the observation of global inter-area mode and approximated eigenvalue sensitivity to determine installation indices used to determine the SCG location. Synchronous reactance X d (X q ) and transient open-circuit time constant T do are determined later by eigenvalue sensitivity based parameter optimization technique....