Automatic load frequency control of multi-area power system using ANN controller and Genetic algorithm

In this paper work we analyze and design Automatic load frequency control of two areas power system using Genetic Algorithm and also for four area power system using artificial neural network (ANN), generation control is becoming increasingly important in view of increased load demand & reducing generating resources. The increasing load demands are posing serious threats to reliable operation of power systems. As we all that Maintaining power system frequency at constant value is very important for the health of the power generating equipment and the utilization equipment at the customer end. The job of automatic frequency regulation is achieved by governing systems of individual turbinegenerators and Automatic Generation Control (AGC) or Load frequency control ( LFC) system of the power system. The healthy and undamaged operation of generator needs the control of the following parameters: (a) Frequency to be maintained constant i.e. at 50 Hz (b) the tie line power to be maintained between specified limits. If the above parameters are maintained with in desired limits the generation control is said to be most effective. There are so Many techniques for automatic load frequency control like integral controller, PID controller. The main objective of automatic generation control is to maintain the balance between the generation and demand of a particular power system. Keyword: Load Frequency Control (LFC), Automatic Generation Control (AGC), Four and Two area power system, ANN Controller, Genetic algorithm. INTRODUCTION For large scale power systems which consists of inter-connected control areas, then it is important to keep the frequency and inter area tie power near to the scheduled values. The input mechanical power is used to control the frequency of the generators and the change in the frequency and tie-line power are sensed, which is a measure of the change in rotor angle. A well designed power system should be able to provide the acceptable levels of power quality by keeping the frequency and voltage magnitude within tolerable limits Changes in the power system load affects mainly the system frequency, while the reactive power is less sensitive to changes in frequency and is mainly dependent on fluctuations of voltage magnitude. So the control of the real and reactive power in the power system is dealt separately. The load frequency control mainly deals with the control of the system frequency and real power whereas the automatic Voltage regulator loop regulates the changes in the International Journal of Engineering Trends and Technology (IJETT) – Volume 4 Issue 9Sep 2013 ISSN: 2231-5381 http://www.ijettjournal.org Page 3778 reactive power and voltage magnitude. Load frequency control is the basis of many advanced concepts of the large scale control of the power system. Automatic generation control (AGC) is very important issue in power system operation and control to ensure the supply of sufficient and reliable electric power with good quality. Owing to the continuous growth of electrical power system in size and complexity with increasing interconnections, the problem of power and frequency oscillations due to unpredictable load changes, has become increasingly serious. These random load changes result in power generation-consumption mismatch, which in turn, affects the quality and reliability of electric power. These mismatches have to be corrected because generation and distribution of sufficient. One of the important issues in the operation of power system is Automatic Generation Control (AGC). It helps in supplying adequate and consistent electric power with good quality. It is the secondary control in LFC which re-establishes the frequency to its nominal value (50 Hz) and sustains the interchange of power between areas (in case of more than one control area). For this the load demand in the generator prime mover set is increased or decreased in the form of kinetic energy, resulting in change of frequency. The transient in primary, secondary and tertiary control is of the order of seconds and minutes respectively Automatic generation control is to provide control signals to regulate the real power output of various electric generators within a prescribed area in response to changes in system frequency and tie-line loading so as to maintain the scheduled system frequency and established interchange with other areas. In other words the design of automatic generation controller depends upon various energy source dynamics involved in the AGC of the area. Automatic Generation Control If the load on the system is increased suddenly then the turbine speed drops before the governor can adjust the input of the steam to the new load. As the change in the value of speed diminishes the error signal becomes smaller and the positions of the governor and not of the fly balls get closer to the point required to maintain the constant speed. One way to restore the speed or frequency to its nominal value is to add an integrator on the way. The integrator will unit shall monitor the the average error over a period of time and will overcome the offset. Thus as the load of the system changes continuously the generation is adjusted automatically to restore the frequency to the nominal value. This scheme is known as automatic generation control. In an interconnected system consisting of several pools, the role of the AGC is to divide the load among the system, stations and generators so as to achieve maximum economy and reasonably uniform frequency MATHEMATICAL MODELING OF SYSTEM 1. Mathematical modeling for Generator Applying the swing equation of a synchronous machine to small perturbation, we have: ∆ = ∆ ∆ ................ (1) Or in terms of small deviation in speed ∆ = (∆ − ∆ )................... (2) Taking Laplace Transform, we obtain ∆Ω( ) = [∆ (s) -∆ (s)... (3) International Journal of Engineering Trends and Technology (IJETT) – Volume 4 Issue 9Sep 2013 ISSN: 2231-5381 http://www.ijettjournal.org Page 3779 Fig.1 Represent the Block diagram of Generator 2. Mathematical Modeling of Load The load on the power system consists of a verity of electrical drives. The equipments used for lighting purposes are basically resistive in nature and the rotating devices are basically a composite of the resistive and inductive components. The speed-load characteristic of the composite load is given by