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.

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.

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 Robust LFC Strategy for Wind Integrated Time-Delay Power System Using EID Compensation

Energies ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 3223 ◽  
Author(s):  
Liu ◽  
Zhang ◽  
Zou
Keyword(s):  
Time Delay ◽  
Power System ◽  
Closed Loop ◽  
Frequency Control ◽  
Loop System ◽  
Load Frequency Control ◽  
System Stability ◽  
Linear Matrix ◽  
Closed Loop System ◽  
The Stability

This paper presents an active disturbance rejection control (ADRC) technique for load frequency control of a wind integrated power system when communication delays are considered. To improve the stability of frequency control, equivalent input disturbances (EID) compensation is used to eliminate the influence of the load variation. In wind integrated power systems, two area controllers are designed to guarantee the stability of the overall closed-loop system. First, a simplified frequency response model of the wind integrated time-delay power system was established. Then the state-space model of the closed-loop system was built by employing state observers. The system stability conditions and controller parameters can be solved by some linear matrix inequalities (LMIs) forms. Finally, the case studies were tested using MATLAB/SIMULINK software and the simulation results show its robustness and effectiveness to maintain power-system stability.

scholarly journals Design of PI controller for Liquid Level System using Siemens Distributed Control System

2019 ◽  
Vol 8 (3) ◽  
pp. 2783-2789
Keyword(s):  
Time Delay ◽  
Stability Region ◽  
Dead Time ◽  
Pi Controller ◽  
Liquid Level ◽  
Order System ◽  
System Response ◽  
Level System ◽  
Geometric Center ◽  
The Stability

The PI controller design for a liquid level system using the weighted geometric center method is discussed. Every real-time process have dead time. This dead time leads to the generation of oscillation in the system response. The oscillation generated due to dead time introduces instability in system performance. This paper presents a tuning method based on calculating a geometric center in the stability region for a higher order system. In this, the stability region calculated by plotting (Kp , Ki )-plane based on boundary locus stability technique. Further centre point computed in the stability locus by a geometric center method. This center point will provide Kp , Ki value for tuning the PI controller. The First Order Plus Dead Time (FOPDT) process considered to elaborate the method for computing the tuning parameters. A nonlinear time-delay system and a plant having time-delay response are controlled in simulation. The performance of the newly obtained PI controller based on weighted geometric center method is compared with the existing results to show the usefulness of the control scheme. Moreover, disturbance rejection ability of the newly obtained PI controller based on weighted geometric center method is demonstrated by applying disturbances. In addition, the designed controller implemented using Siemens DCS PCS7 V8.1 platform.

Lyapunov–Krasovskii based FPID controller for LFC in a time-delayed micro-grid system with fuel cell power units

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Kamel Sabahi ◽  
Amin Hajizadeh ◽  
Mehdi Tavan
Keyword(s):  
Fuel Cell ◽  
Time Delay ◽  
Frequency Control ◽  
Implementation Process ◽  
Load Frequency Control ◽  
Content Type ◽  
Nonlinear Input ◽  
Micro Grid ◽  
Mathematical Analyses ◽  
The Stability

Purpose In this paper, a novel Lyapunov–Krasovskii stable fuzzy proportional-integral-derivative (PID) (FPID) controller is introduced for load frequency control of a time-delayed micro-grid (MG) system that benefits from a fuel cell unit, wind turbine generator and plug-in electric vehicles. Design/methodology/approach Using the Lyapunov–Krasovskii theorem, the adaptation laws for the consequent parameters and output scaling factors of the FPID controller are developed in such a way that an upper limit (the maximum permissible value) for time delay is introduced for the stability of the closed-loop MG system. In this way, there is a stable FPID controller, the adaptive parameters of which are bounded. In the obtained adaptation laws and the way of stability analyses, there is no need to approximate the nonlinear model of the controlled system, which makes the implementation process of the proposed adaptive FPID controller much simpler. Findings It has been shown that for a different amount of time delay and intermittent resources/loads, the proposed adaptive FPID controller is able to enforce the frequency deviations to zero with better performance and a less amount of energy. In the proposed FPID controller, the increase in the amount of time delay leads to a small increase in the amount of overshoot/undershoot and settling time values, which indicate that the proposed controller is robust to the time delay changes. Originality/value Although the designed FPID controllers in the literature are very efficient in being applied to the uncertain and nonlinear systems, they suffer from stability problems. In this paper, the stability of the FPID controller has been examined in applying to the frequency control of a nonlinear input-delayed MG system. Based on the Lyapunov–Krasovskii theorem and using rigorous mathematical analyses, the stability conditions and the adaptation laws for the parameters of the FPID controller have been obtained in the presence of input delay and nonlinearities of the MG system.

Sign in / Sign up

Export Citation Format

Share Document