Automatic Generation Control of Three Area Hydro-Thermal Power Systems considering Electric and Mechanical Governor with conventional controller and Ant Colony Optimization technique

© 2014 AENSI Publisher All rights reserved. To Cite This Article: K.Jagatheesan, Dr.B.Anand ., Automatic Generation Control of Three Area Hydro-Thermal Power Systems considering Electric and Mechanical Governor with conventional controller and Ant Colony Optimization technique. Adv. in Nat. Appl. Sci., 8(20): 2533, 2014 INTRODUCTION Nowadays electrical device has become the basic need of human day to day life. But going on to the technical way due to this need there is a huge variation in the load as the number of users will vary from time to time. In order to fulfill these variations in load, n number of power systems (generally hydropower systems or thermal power systems) are connected to each other through tie lines (Report, I.C, (1973); Nagrath and Kothari (1994); Elgerd (1970)). Interconnecting the control areas are useful because, 1. It makes the system more reliable by delivering the power to the system. Even if there is any damage to any of the area. 2. It makes small frequency deviations during change in load by exchanging the load among the areas through tie lines. During the variations in load, these n number of areas distribute the load among themselves. When load to a system varies, the speed of the turbine starts varying which effects the generation of desired amount of power. Thus there arises fluctuations and disturbance in the frequency. These fluctuations depend on the maximum or minimum overshoot and settling time. The main aim of this paper is to decrease the maximum or minimum overshoot and reduce the settling time near to zero. This paper deals with three area power plant in which two are thermal plant and one is hydro power plant. 1% of load is applied to any one of the power plant and the variation in frequency of the areas and tie lines are observed. ACO optimized PID controller is introduced in the system to modify the error signal and to produce a control signal so as to control the variations and fluctuations in frequency. Optimized value of gain is calculated using ITAE optimization technique so as to get better system performance (Jagatheesan and Anand (2012)). 26 K. Jagatheesan and Dr.B.Anand, 2014 Advances in Natural and Applied Sciences, 8(20) Special 2014, Pages: 25-33 Two control loops, which are used to maintain the voltage and frequency variations are Automatic Voltage Regulator (AVR) and Automatic Load Frequency Control loop (ALFC)( Nagrath and Kothari (1994);Kundur (1994); Elgerd (1970)). The primary objective of load frequency control is to regulate the frequency to a specified nominal value and to maintain the interchange power between control areas. System Investigated: The investigated system consists of three generating areas. Area1, area2 and area3 are thermal, thermal and hydro power system respectively. Fig.1 shows the simulink AGC model of three area hydro-thermal power system(Jagatheesan and Anand (2012); Nanda and Mishra (2010)). In practical, there exists a maximum and minimum limit on the rate of change in the generating power. A GRC of the order of 0.0017puMW-1 for thermal power system and 4.5% sec-1 for rising generation and 6% sec-1 for lowering generation is considered for this present work (Nanda and Mishra (2010); Anand and Ebenezer Jeyakumar (2009a)). Fig. 1: Block diagram for AGC of Three area Hydro-Thermal power systems with Reheater, Mechanical, Electric Governor and Generation Rate Constraint The thermal and hydro plants are equipped with single stage reheat turbine and either mechanical or electric governor respectively. The advantage of replacing mechanical governor with electric governor is that the electronic components are used to perform low power with speed sensing and droop compensation. Electronic components deliver greater flexible and improved performance in the presence of dead band and dead time. So the selection of suitable electric governor parameter is very important(Nanda et al. (2006); Anand and Ebenezer Jeyakumar (2009b)) . Otherwise improper selection of these parameters yields instability in system response. The interconnected power system parameters are given in the appendix of (Anand and Ebenezer Jeyakumar (2009a) ; Anand and Ebenezer Jeyakumar (2009b)). In figures 2 and 3, the frequency deviations of area1 and the tie-line power deviation for a 1% step load perturbation in thermal area 1 are shown, respectively. In the figures, the results shows the open loop comparisons of mechanical and electric governor without considering GRC non-linearity. 27 K. Jagatheesan and Dr.B.Anand, 2014 Advances in Natural and Applied Sciences, 8(20) Special 2014, Pages: 25-33 -0.04 -0.03 -0.02 -0.01 0 0.01 0 10 20 30 40 50 60 Time (s) d el F 1 ( H z) Electric Governor Mechanical Goveror ` Fig. 2: Open loop response comparisons without GRC ( ) f  -0.012 -0.008 -0.004 0 0.004 0 10 20 30 40 50 60 Time (s) d el P ti e1 3 ( p u M W ) Electric Governor Mechanical Goveror ` Fig. 3: Open loop response comparisons without GRC ( ) tie P  The figures 4 and 5, show the open loop frequency deviation in area1 and tie-line power deviation in area 1 respectively. These responses clearly indicate that the electric governor always yields minimum damping oscillations with better settling and less steady state error compared to the mechanical governor with and without considering Generation Rate Constraint (Anand and Ebenezer Jeyakumar (2009b)). -0.06 -0.04 -0.02 0 0.02 0 10 20 30 40 50 60 Time (s) d el F 1 ( H z) Electric Governor Mechanical Goveror ` Fig. 4: Open loop response comparisons with GRC ( ) f  -0.016 -0.012 -0.008 -0.004 0 0.004 0 10 20 30 40 50 60 Time (s) d el P ti e1 3 ( p u M W )