1. INTRODUCTIONPower Engineer has the responsibility to deliver economically, adequate andquality power to consumer. In order to achieve this, the power system must bemaintained at the desired operating level by suitable modern control strategies.Load frequency control (LFC) is a simple mechanism to maintain or restore thefrequency and tie line power flow among the interconnected power systemswithin the specified limit.For safe, secure, reliable and economic operation, it is found necessary tointerconnect neighboring powers, forming power pools. In power systemnetwork, power is exchanged between the utilities over the tie - lines by whichthey are connected. In an interconnected network a disturbance in one line leadsto effects on the neighboring systems change in tie-line power and frequencycausing serious problem of load frequency control (LFC). This change in tie-linepower and frequency is called an area control error.LFC is very important item in power system operation and control for sufficientand reliable electric power with good quality. Many control strategies have beenproposed to achieve improved performance. The Integral and Proportional plusIntegral control approach is one such strategy. In this thesis proportional andintegral controller technique is employed for the design of an efficient loadfrequency controller.
2. SCOPE AND OBJECTIVES1. Zero steady - state error of area control error.2. Ensure good transient response under disturbance.3. Closed loop stability of the system to be assured.4. Reliable operation and control of power system.5. Controller must be easy for implementation.
3. DESIGN OF LOAD FREQUENCY CONTROLLER FOR TWO AREAINTERCONNECTED HYDRO POWER SYSTEMSTransfer Function Model of an Interconnected Two Area Hydro PowerSystems (Closed Loop)
4. DESIGN OF DIGITAL CONTROLLERProportional Controller:Pout = Kp e(t)Two Area Hydro Electric Power System - P controller DesigntdtACEwJ02)(1
5. Integral Controller:t02J dtACEi ACEi = Fi + PtieiTwo Area Hydro Electric Power System - I controller design
6. PI Controller :PI out = Kp ACEi + Ki ACEi2 dtTwo Area Hydro Electric Power System - PI controller design
7. FLOW CHART
8. BLOCK DIAGRAM
9. Frequency Response for Area -1
10. Frequency Response for Area -2
11. Frequency Response for Area -1 and Area -2
12. PI APPLICATION TO POWER SYSTEMSPI were used in many of the power system application such asReactive power and voltage control, Economic dispatch problem,Power system reliability and security, Generation expansionproblem, State estimation, Load flow and optimal power flow,Power system identification and control.Other application to non-linear optimization problems are electricmachinery, capacitor and Facts placement , generator maintenanceand unit commitment scheduling, short term load forecasting,generator contribution to transmission system etc.
13. CONCLUSIONPI controller has been successfully applied to tune theparameters of load frequency control systems of theproportional plus integral type. A two area interconnectedHydro power system was assumed to demonstrate themethod. The Integral Square of the error (ISE) was used asobjective function.The Design of Load Frequency Controller for an Inter-Connected Two Area Hydro Power Systems was simulatedusing MATLAB Simulink and the results were observed. Theresponses of the power system with Proportional Integralcontroller gain were simulated and their Peak Over Shoot andSettling time were analyzed.
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