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SHORT TERM HYDRO-THERMAL COORDINATION Presented By napati Roll no-26243 Regd. No.-0701105115 22 nd MAR 2011

Short term hydro thermal scheduling

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Short term hydro thermal scheduling, unit commitment

Text of Short term hydro thermal scheduling

Presented By Rajendra Narayan Senapati Roll no-26243 Regd. No.-070110511522nd MAR 2011

Outline1) 2) 3) 4) 5) 6) 7) Introduction Need of Hydrothermal Scheduling Classification of Hydro Plants Classification of Hydrothermal Scheduling Problem Solution for Short-term Scheduling Problem Conclusion References

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Introductiono o o o Hydro-plants can be easily started and assigned load in very short time. Slow response of thermal power due to boiler, super heater, and turbine system. Thermal plant base load plant Hydro plant peak load plant

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Need of Hydrothermal SchedulingThe optimal scheduling problem in a hydro-thermal system stated as to minimize the fuel cost of thermal plants under the constraint of water availability for hydro-generation over a given period of operation To maintain an optimal balance between fuel cost and water storage level to maintain reliable and uninterrupted operation. To test these techniques on different problems.

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Classification of Hydro PlantsClassification 1. Pumped storage plants 2. Conventional plants Classification on the basis of location 1. Hydro plants on different streams 2. Hydro plants on the same stream 3. Multi-chain hydro plants Classification on the basis of Quantity of Water Available 1. Run-off- River Plants without Pondage 2. Run-off River Plants with Pondage22nd MAR 2011

Classification of Hydrothermal Scheduling ProblemLong range problem long-range scheduling is validity ranges from 1 week to 1 year or several years. Long-term hydrothermal scheduling is used for breaking down the long-term problem into a number of midterm (e.g., monthly) problems. Short range problem Involves the hour-by-hour scheduling of all generation on a system to achieve minimum production cost for the given time period. The load, hydraulic inflows, and unit availabilities are assumed known. 22 MAR 2011 Reservoir levels is givennd

Scheduling ProblemsScheduling problem consists of Problem characteristics. Problem formulation. Solution approach

Two-unit hydrothermal systems

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For any time period j

However, the energy available from the hydro plant is insufficient to meet the load

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Use here the entire amount of energy from the hydro plant in such a way that the cost of running the steam plant is minimized. The steam-plant energy required is

i.e. (Load energy) - (Hydro energy) = (Steam energy) It does not require the steam unit to run for the entire interval of Tmax hours. Therefore

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Where = run period for steam plant Then

The scheduling problem becomes

Subject to

And the Lagrange function is22nd MAR 2011


The total cost over the interval is


Let the steam plant cost be expressed as Then22nd MAR 2011


Where Then And

= Optimum value of stem generated power= /

Now we can establish the value of Ps* by minimizing FT:


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Which means the unit should be operated at its maximum efficiency point long enough to supply the energy needed, E. If Where fc is the fuel cost Now the heat rate is

And the heat rate has a minimum when

Giving best efficiency at

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Solution for Short-term Scheduling ProblemFixed head hydro thermal scheduling Variable head hydro thermal scheduling

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Problem Characteristics

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Problem FormulationThermal Model operating cost

fuel cost

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Hydro Model rate of discharge


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Classical Method

Hydrothermal system with hydraulic constraints

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Subject to


= length

of jth interval

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The loads are constant in each interval. Other constraints could be imposed, such as:

The Lagrange function is:

for a specific interval j =k,

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Suppose we add the network losses to the problem. Then at each hour

And the Lagrange function becomes

With resulting coordination equations (hour k):

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Flow Chart for Classical Method

ConclusionHydro-thermal scheduling is done when power demand is less than the maximum capacity of power generation by the hydro and thermal plants. The benefit of this scheduling is to save the cost of generation, in addition to meeting the agricultural and irrigational requirements. The operating cost of thermal plant is very high, though their capital cost is low. On the other hand the operating cost of hydroelectric plant is low, though their capital cost is high. So it has become economical as well convenient to have both thermal and hydro plants in the same grid.

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ReferrencesKothari D.P., Dhillon J.S., Power System Optimization , Prentice Hall of India Private Limited, New Delhi, 2004. Elgerd O.I, Electric Energy Systems theory, An Introduction , Tata McGraw Hill Limited, New York, 1983. Grainger J.J., Stevenson W.D., Power System Analysis , Tata McGraw Hill Limited, New York,2003. Fabrcio Y. K. Takigawa, Erlon C. Finardi, Edson L. da Silva, A Decomposition Strategy to Solve the Short-Term Hydrothermal Scheduling Based on Lagrangian Relaxation ,2005. Hota P.K., Barisal A.K., Chakrabarti R., An improved PSO technique for shortterm optimal hydrothermal scheduling ,2009. Ramos L.M., Lora A.T., Santos J.R., Short-term Hydro-thermal Coordination Based on Interior Point Nonlinear Programming and Genetic Algorithms ,2001.

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