Abstract
The application of the phasor measurement units and the wide expansion of the wide area measurement units make the time delay inevitable in power systems. The time delay could result in poor system performance or at worst lead to system instability. Therefore, it is important to determine the maximum time delay margin required for the system stability. In this paper, we present a new method for determining the delay margin in the power system. The method is based on the analysis in the s-domain. The transcendental time delay characteristics equation is transformed to a frequency dependent equation. The spectral radius is used to find the frequencies at which the roots cross the imaginary axis. The crossing frequencies are determined through the sweeping test and the binary iteration algorithm. A single machine infinite bus system equipped with automatic voltage regulator and power system stabilizer is chosen as a case study. The delay margin is calculated for different values of the power system stabilizer (PSS) gain, and it is found that increasing the PSS gain decreases the delay margin. The effectiveness of the proposed method has been proved through comparing it with the most recent published methods. The method shows its merit with less conservativeness and fewer computations.
Highlights
A time delay exists inherently in many dynamical systems
We proposed a method for computing the delay margin in a power system with
We proposed a method for computing the delay margin a power system with the resultant delay system
Summary
A time delay exists inherently in many dynamical systems. Time delays could arise in power systems for different reasons and their magnitudes depend on the type of the communication link, for example, telephone lines, fiber-optics, power lines, and satellites [2]. The time delay for the feedback signals is in the order of 100 ms [3]. The time delays in the communication links induced into the power systems are within the range of a few milliseconds to one hundred milliseconds depending on the communication network type used, the transmission protocol, network load, and other factors [3,4]. The time delay is in the order of a few seconds in the load frequency control systems [5,6]. The presence of the time delay could lead to poor system performance, or at worst, system instability
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