Load Frequency Control For Distributed Grid Power System Single Area & Multi-area System

This project presents decentralized control scheme for Load-Frequency Control in Multi-area power System. In this era renewable energy is most promising solution to man’s ever increasing energy needs. But the power production by these resources cannot be controlled unlike in thermal plants. A number of optimal control techniques are adopted to implement a reliable stabilising controller. It is necessary to interconnect more distributed generation in power systems because of environmental concerns. Primary concern includes global environmental and energy depletion problem. A serious attempt has been undertaken aiming at investigating the load frequency control problem in a power system consisting of two power generation unit and multiple variable load units. The robustness and reliability of the various control schemes is examined through simulations. A system involving thermal plants and a hydro plant is modelled using MATLAB 2011b. Keywords— Load Frequency Control, Distributed control system, Thermal Plants, Hydro Plants. I.INTRODUCTION Load frequency control (LFC) in power system maintains frequency deviation & tie-line power flow deviation, which constantly vary according to load and disturbance with in preset values. In India majority of power production, around 65% is from thermal plants. Due to problem related to uncertainty, pricing and supply of fossil fuels renewable resources have been identified as best alternative [1]. The fitful nature of resources increases the frequency deviation which further adds to deviation caused by Load variation. This necessitates the grid connection of renewable resources [2]. For large scale power systems which consists of inter-connected control areas, load frequency then it is important to keep the frequency and inter area tie power near to the scheduled values. However one concern is that large, short term output fluctuations may influence system frequency because it is difficult to estimate renewable energy output. Frequency deviation is undesirable because most of AC motors are directly related to frequency. Also the generator turbines are designed to operate at precise speed. This is imperative to maintain constant frequency. This is done by implementing Load Frequency Control (LFC). There are many LFC methods developed for controlling frequency [3]. 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 reactive power and voltage magnitude. Load frequency control is the basis of many advanced concepts of the large scale control of the power system. II. MODELLING 1.Modelling of Generator :Applying the swing equation of synchronous machine to small perturbation we have, = ∆Pm-∆Pe (1) Taking Laplace transform we get, ∆Ω(s) = [∆Pm(s)-∆Pe(s)] (2) Fig 1. Block representation of Generator 2.Mathematical modelling of Load :The load on power system consists of variety of electrical drives. The speed-Load characteristic of composite load is given by:∆Pe= ∆PL D∆ω (3) Fig 2. Fig 1. Block representation of Load 3.Mathematical modelling of prime mover :The sources of power generation are commonly known as the prime mover.