Abstract
In this paper, we present a nonlinear coordinated excitation and static var compensator (SVC) control for regulating the output voltage and improving the transient stability of a synchronous generator infinite bus (SGIB) power system. In the first stage, advanced nonlinear methods are applied to regulate the SVC susceptance in a manner that can potentially improve the overall transient performance and stability. However, as distant from the generator measurements are needed, time delays are expected in the control loop. This fact substantially complicates the whole design. Therefore, a novel design is proposed that uses backstepping methodologies and feedback linearization techniques suitably modified to take into account the delayed measurement feedback laws in order to implement both the excitation voltage and the SVC compensator input. A detailed and rigorous Lyapunov stability analysis reveals that if the time delays do not exceed some specific limits, then all closed-loop signals remain bounded and the frequency deviations are effectively regulated to approach zero. Applying this control scheme, output voltage changes occur after the large power angle deviations have been eliminated. The scheme is thus completed, in a second stage, by a soft-switching mechanism employed on a classical proportional integral (PI) PI voltage controller acting on the excitation loop when the frequency deviations tend to zero in order to smoothly recover the output voltage level at its nominal value. Detailed simulation studies verify the effectiveness of the proposed design approach.
Highlights
Power systems are nonlinear, large-scale, widely dispersed systems with many different interconnected components
A a coordinated control strategy can be used in the static var compensator (SVC), which ensures that, initially, the power coordinated control strategy can be used in the SVC, which ensures that, initially, the power angle angle generator oscillations are rapidly damped, and the SVC bus voltage is regulated towards its generator oscillations are rapidly damped, and the SVC bus voltage is regulated towards its nominal value
The nonlinear excitation controller parameters are chosen as c1 = 4, c2 = 4, c3 = 50, and the gain in the nonlinear SVC controller is taken as cB = 5
Summary
Large-scale, widely dispersed systems with many different interconnected components. A feedback linearization approach is used, resulting in a linear dynamic system representation with two controlled inputs, the generator excitation input and the input of the SVC regulator Both inputs are used in conjunction to formulate a faster and effective feedback loop that can substantially improve the overall system transient response and stability. The excitation input initially employs the proposed nonlinear control, while in the sequel, after the large frequency deviations are mitigated, it switches in a smooth way to a classical automatic voltage regulator and power system stabilizer (AVR/PSS). This work is the first to consider the use of SVC control laws with delayed measurements from the generator in order to improve the overall transient stability and performance. The soft switching coordination approach of [22], which improves global transient stability and voltage regulation, is extended to the SVC control case.
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