Effects of fractional-order PI controller on delay margin in single-area delayed load frequency control systems

Vedat Çelik,Mahmut Temel Özdemir,Kwang Y Lee

doi:10.1007/s40565-018-0458-5

Vedat Çelik, Mahmut Temel Özdemir + Show 1 more

Open Access

https://doi.org/10.1007/s40565-018-0458-5

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Abstract

This study aims to determine the improvement effect on the delay margin if fractional-order proportional integral (PI) controller is used in the control of a single-area delayed load frequency control (LFC) system. The delay margin of the system with fractional-order PI control has been obtained for various fractional integral orders and the effect of them has been shown on the delay margin as a third controller parameter. Furthermore, the stability of the system that is either under or over the delay margin is examined by generalized modified Mikhailov criterion. The stability results obtained have been confirmed numerically in time domain. It is demonstrated that the proposed controller for delayed LFC system provides more flexibility on delay margin according to integer-order PI controller.

Highlights

The voltage and frequency of the power systems vary depending on the demand of consumers
The fractional-order proportional integral (PI) controller has been proposed for controlling a single-area delayed Load frequency control (LFC) system
We aim to present the effects of the fractional integral order on the delay margins for controller gains, and they have been computed by using the direct method

Summary

Introduction

The voltage and frequency of the power systems vary depending on the demand of consumers. Load frequency control (LFC) of conventional power systems is performed with three different control loops [2, 3], which loops are primary, secondary and tertiary control loops. The tertiary control loop is the central loop that regulates the system frequency error and includes measures performed by verbal instructions in case primary and secondary loops are insufficient. The time delay may reduce the damping performance of the control system and even cause the instability if it exceeds the delay margin [7,8,9]. The time delay must be considered for both analysis and design of a power system For this purpose, linear models including time delay have been proposed [3,4,5]

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