Robustness analysis and controller design for static var compensators in power systems

Yu, Xuechun
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In the North American electric power interconnection, control systems play a prominent role in the stabilization and reliable operation of the system. With the advent of competition and deregulation, systems are being operated closer than ever to the limits. This setting necessitates a systematic procedure to analyze and design controls in power systems which demonstrate good performance for a range of operating conditions;The current industry practice for the analysis and design of controls consists of conventional linear analysis tools coupled with detailed nonlinear simulation of the designed controls. This approach is time consuming and does not guarantee robustness;In this dissertation, we analyze the robustness of the static var compensator's (SVC's) control setting and design a supplementary damping controller for the SVC based on the structured singular value (SSV or mu), which allows computation of an effective measure for robustness in the presence of real parametric uncertainties. The robustness problem in the SSV framework is set up for the multimachine power system. In this formulation the effect of the parameter variations is captured in terms of the varying elements of the linearized system matrix. The uncertainty bounds on the varying elements are determined by running a series of power flow calculations and performing a polynomial fit. The system robustness in terms of the SSV or mu is examined using both the frequency sweep test and the state space mu test. The results on test systems show that the analysis procedure accurately predicts the range of stable operating conditions which are verified by repeated eigenvalue analysis;Some of the issues that arise in the design of a suitable supplementary controller for the SVC include the choice of the location and voltage level of the SVC, and the choice of the control signals for the supplementary controller. These issues are carefully investigated and incorporated into the design procedure. The effect of the supplementary controller on improving system dynamic performance and stability limits is also examined;The technique is applied to two test systems which are the four-machine test system and the IEEE 50-generator test system. Both the analysis and synthesis results clearly demonstrate the efficacy of the mu-based technique in analyzing and designing controls to meet robust performance and stability requirement.

Electrical and computer engineering, Electrical engineering (Electric power), Electric power