Load frequency control (LFC) or Automatic generation control (AGC) is an emerging issue in electric power systems. The objective is to maintain the system frequency and the power exchange between the areas within specified limits, irrespective of sudden change in load. The prime mover governing system provides a means of controlling power and frequency; and this function commonly called Load Frequency Control or Automatic Generation Control. The automatic load frequency control (ALFC) loop regulates the megawatt output and the frequency variations when a power plant is subjected to a unit step load disturbance. The automatic frequency loop consists of 2 loops. The primary loop responds to a frequency signal which is a indirect measure of megawatt balance. By tending to maintain a megawatt balance, the primary loop performs indirectly a frequency control depending upon 2 to 3% of droop setting of the generator. Secondary loop control is done by a PID controller, as it accounts 2% frequency drop. It is the role of secondary controller to eliminate the frequency deviation and the tie line power variation when subjected to unit step load disturbances. There are several methods for tuning a PID controller. The most effective methods generally involves the development of some form of process model, and then choosing P,I and D based on dynamic model parameters. Classical Ziegler Nichols method, Pessen’s Ziegler Nichols method, Integral Squared Error (ISE) method, Integral Time Squared Error (ISTE) method, software tools or even manual tuning can be used for the design of PID controller. Load frequency controllers implemented in real time power plants are usually proportional, integral and derivative controller (PID) type, and they have many drawbacks, such as long settling time and relatively large overshoots with sustained oscillations And proportional and integral gain of PID type beyond a value leads to sluggish behavior in the system performance.
1.2 LITERATURE SURVEY
The objective of load frequency control or automatic generation control (AGC) is to maintain the system frequency and the power exchange between areas within the specified limits, irrespective of sudden change in the load. Exhaustive bibliography on the AGC of power systems is mentioned. The automatic frequency loop consists of two. The primary loop responds to the frequency signal which is an indirect measure megawatt balance. By tending to maintain a megawatt balance, the primary loop performs indirectly a frequency control depending upon 2 to 3% droop setting of the generator. During 1990’s, different method for tuning the PID controllers were studied.PID controller is used in AGC for the fine adjustment of frequency and megawatt interchange between the two areas. Early 2000 different optimization techniques in LFC subject to control on derivatives of the control input was used for energy saving in the power system. Tuning methods like Integral of time squared error (ITSE) gives an overdamped response with no overshoot when applied to a PID controller. Other methods like Zeigler Nichol’s (ZN) method and partial model matching helped to produce the desired results. It is seen that optimization based on Integral of squared error (ISE) gives a poorly damped response. It was stated that although PID controller is used in many wide applications due to its simplicity and robustness, it may not be sufficient for the processes with more than one oscillatory made. Therefore, the project was focused on using the PID controller, whose gains are tuned with ZN method. The optimal value of PID was determined In the recent papers, secondary controller in AGC adopts intelligent techniques like Fuzzy logic, Genetic algorithm and Artificial neural networks which helps in achieving even better system response reducing transient and steady state errors. They are used to optimize Kp, Ki and Kd values.
MODELLING OF HYDRO...