Nonlinear generator excitation and superconducting magnetic energy storage control for transient stability enhancement via immersion and invariance

This paper focuses on the design of nonlinear coordinated generator excitation and superconducting magnetic energy storage (SMES) control to enhance the transient stability of an electrical power system. An immersion and invariance (I&I) nonlinear control design technique is used to achieve power angle stability and frequency and voltage regulation, and to ensure that the closed-loop system is asymptotically stable. The main contributions of this paper are: (1) use of a generator excitation and SMES combination to improve transient stability, (2) demonstrating the applicability of nonlinear control theory (particularly the I&I methodology) for the design of a stabilizing (state) feedback controller in a single machine infinite bus system to enhance transient system performance and (3) developing a methodology that can employ the additional degree of freedom in power systems that include the combined excitation and SMES and advanced nonlinear control in a way that can further improve the dynamic transient performance of the system. In order to show the effectiveness of the proposed controller design, numerical simulation results are provided to illustrate the performance in maintaining stability and simultaneously achieving improvements in voltage regulation during small and large disturbances, and to show that our proposed nonlinear controller has more advantages by comparing it with the control performance of two existing nonlinear controllers and a conventional linear controller, in particular, feedback linearizing and coordinated passivation controllers, and a power system stabilizer (PSS), respectively.