scholarly journals A New Method for Computing the Delay Margin for the Stability of Load Frequency Control Systems

2018 ◽  
Author(s):  
Ashraf Khalil ◽  
Ang Swee Ping
Keyword(s):  
Time Delay ◽  
Control Systems ◽  
Frequency Control ◽  
Pi Controller ◽  
Load Frequency Control ◽  
New Method ◽  
Open Communication ◽  
Load Frequency ◽  
The Stability ◽  
Delay Margin

The open communication is an exigent need for future power system where the time delay is unavoidable. In order to secure the stability of the grid, the frequency must remain within its limited range which is achieved through the load frequency control. The load frequency control signals are transmitted through communication networks which induces time delay that could destabilize the power systems. So, in order to guarantee the stability the delay margin should be computed. In this paper, we present a new method for calculating the delay margin in load frequency control systems. The transcendental time delay characteristics equation is transformed to frequency dependant equation. The spectral radius is used to find the frequencies at which the roots crosses the imaginary axis. The crossing frequencies are determined through the sweeping test and the binary iteration algorithm. A one-area load frequency control system is chosen as case study. The effectiveness of the proposed method has been proved through comparing with the most recent published methods. The method shows its merit with less conservativeness and less computations. The PI controller gains are preferable to be chosen large to reduce the damping, however, the delay margin decreases with increasing the PI controller gains.

scholarly journals A New Method for Computing the Delay Margin for the Stability of Load Frequency Control Systems

Energies ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 3460 ◽  
Author(s):  
Ashraf Khalil ◽  
Ang Swee Peng
Keyword(s):  
Time Delay ◽  
Power Systems ◽  
Control Systems ◽  
Frequency Control ◽  
Pi Controller ◽  
Load Frequency Control ◽  
New Method ◽  
Load Frequency ◽  
The Stability ◽  
Delay Margin

Open communication is an exigent need for future power systems, where time delay is unavoidable. In order to secure the stability of the grid, the frequency must remain within its limited range which is achieved through the load frequency control. Load frequency control signals are transmitted through communication networks which induce time delays that could destabilize power systems. So, in order to guarantee stability, the delay margin should be computed. In this paper, we present a new method for calculating the delay margin in load frequency control systems. The transcendental time delay characteristics equation is transformed into a frequency dependent equation. The spectral radius was used to find the frequencies at which the root crosses the imaginary axis. The crossing frequencies were determined through the sweeping test and the binary iteration algorithm. A one-area load frequency control system was chosen as a case study. The effectiveness of the proposed method was proven through comparison with the most recent published methods. The method shows its merit with less conservativeness and less computations. The impact of the proportional integral (PI) controller gains on the delay margin was investigated. It was found that increasing the PI controller gains reduces the delay margin.

The effects on stability region of the fractional-order PI controller for one-area time-delayed load–frequency control systems

2016 ◽  
Vol 39 (10) ◽  
pp. 1509-1521 ◽  
Author(s):  
Vedat Çelik ◽  
Mahmut Temel Özdemir ◽  
Gökay Bayrak
Keyword(s):  
Time Delay ◽  
Control Systems ◽  
Fractional Order ◽  
Stability Region ◽  
Fractional Integral ◽  
Frequency Control ◽  
Pi Controller ◽  
Load Frequency Control ◽  
Fractional Order Pi Controller ◽  
The Stability

One of the controllers used in load–frequency control systems is the PI controller, taking account of time delay originating from measurement and communication. In control systems, along with the use of the fractional-order controller, computing parameter space exhibited stable behaviour on the controller parameters and analysing its efficiency have become a significant issue. This study focuses on computing the effects of the fractional integral order ( α) on the stable parameter space for the control of a one-area delayed load–frequency control system in the case of a fractional-order PI controller. The effect of time delay on the stable parameter space is also investigated at different fractional integral orders ( α) in the time-delayed system with fractional-order PI controller. For this purpose, a characteristic equation of the delayed system with the fractional-order PI controller is obtained, and the stable parameter spaces of the controller are computed according to the fractional integral order ( α) and time delay ( τ) values using the stability boundary locus method, which is graphics based. Moreover, the generalized modified Mikhailov criterion is used for testing the stability region on the Kp − Ki plane. The obtained results verified that the stability region on the Kp − Ki plane change depending on the α and τ.

Gain and phase margins-based delay margin computation of load frequency control systems using Rekasius substitution

2019 ◽  
Vol 41 (12) ◽  
pp. 3385-3395 ◽  
Author(s):  
Şahin Sönmez ◽  
Saffet Ayasun
Keyword(s):  
Time Delay ◽  
Frequency Control ◽  
Dynamic Performance ◽  
Stability Margin ◽  
Load Frequency Control ◽  
Hurwitz Stability ◽  
Load Frequency ◽  
Complex Roots ◽  
Wide Range ◽  
Delay Margin

This paper investigates the effect of gain and phase margins (GPMs) on stability delay margin of a two-area load frequency control (LFC) system with constant communication delay. A gain-phase margin tester (GPMT) is introduced to the LFC system as to take into GPMs in delay margin computation. A frequency domain exact method, Rekasius substitution, is proposed to compute the GPMs-based stability delay margins. The method aims to calculate all possible purely complex roots of the characteristic equation for a finite positive time delay. The approach first transforms the characteristic polynomial of the LFC system with transcendental terms into a regular polynomial. Routh-Hurwitz stability criterion is then implemented to compute the purely imaginary roots with the crossing frequency and stability delay margin. For a wide range of proportional–integral controller gains and GPMs, time delay values at which LFC system is both stable and has desired stability margin measured by GPMs are computed. The accuracy of complex roots and delay margins are verified by using an independent algorithm, the quasi-polynomial mapping-based root finder and time-domain simulations. Simulation studies indicate that delay margins must be determined considering GPMs to have a better dynamic performance in term of fast damping of oscillations, less overshoot and settling time.

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