Excitation Control System Design of High Response Excitation Type Superconducting Generator for Improving Power System Dynamics

Abstract

MemberSuperconducting generator (SCG) with superconducting field winding has many advantages such as small size, light weight, high generation efficiency. A prominent advantage is to improve power system stability owing to lower synchronous reactance compared with the conventional generator. High response excitation type SCG has a rotor with thermal radiation shield without damping effect; it can enable very rapid change in field current and the magnetic flux due to the change of the field current can reach the armature winding quickly. The excitation power is large and has a rapid change enough to affect the conditions of power system in self-excited operation of the generator. This effect is equivalent to the effect of a superconducting magnetic energy storage (SMES), then so-called "SMES effect", and it is expected to contribuite to transient stabilty improvement. In this paper, excitation control system design for high response excitation type SCG in consideration of SMES effect is proposed for improving power system dynamics by employing eigenvalue sensitivity. The SMES effect is considered to couple with the power system as a nonlinear load. The control performance of the proposed excitation control system is examined in IEEJ East 10-machine and West 10-machine systems. It is made clear that the SMES effect of SCG is utilized effectively and results in both transient and dynamic stability improvement. However, the performance depends on the locations of SCGs and fault contingencies.Keywords: superconducting generator, high response excitation, excitation power, SMES, power system stabilizer, excitation system InroductionSuperconducting generator (SCG) with superconducting field winding offers various advantages, such as high efficiency, small size, light weight, and so forth. A prominent advantage is to improve power system stability owing to the lower synchronous reactance compared with the conventional generator (1) . High response excitation type SCG has a rotor with thermal radiation shield without damping effect for screening time-varying magnetic flux to enter the field winding part. It can enables very rapid change in field current and the magnetic flux due to the change of the field current can reach the armature winding quickly. The excitation power by the quick change of field current is large and has a rapid change enough to affect the conditions of power system in self-excited operation of the generator (2) . Since the field winding is made of superconducting wire and is connected to the generator terminal through AC-DC converter, the field winding coupling with the converter can be considered as superconducting magnetic energy storage (SMES); hence, the effect of the exciter coupling with the AC-DC converter is called "SMES effect". It is expected that high response excitation type SCG using appropriate excitation control system can improve power system dynamics by effectively utilizing the SMES effect.In single machine to infinite bus system, influence of SCG

Investigation of power system stability enhancement by Superconducting Generator with high response excitation considering its detailed excitation system

“…Since there is not special requirements of the field winding to generate extreme high field rapidly for SCG with low response excitation, this type of SCG is relatively low cost, and instead, the damping effect is scarified. On the other hand, SCG with high response excitation enables rapid change of field current by utilizing special field winding materials that can generate extremely high field with reasonable speed and lower loss, and may therefore has a potential to enhance power system stability [9] [13] . And, it is notable that in order to reflect the change of magnetic field to the stator effectively, the cold damper must be not equipped for this type of SCG.…”

Installation Schemes of Superconducting Generators in Power Systems

“…It should be noted here that we can design and manufacture a SCG with synchronous reactance at a specified value within the possible range. In order to take advantages of the above properties of SCGs in power system where the stability may become worse, in particular, in the deregulated environment, a lot of research works have so far been done on SCG design and manufacturing (2) (4) (5) , excitation control systems of SCGs (6)- (9) , power system stability improvement by SCG (10) . Installation of SCGs in the power systems becomes one of the topics that should be considered.…”