How we can operate hydro and thermal power plants optimizely and combinely

1. HYDROTHERMAL
SCHEDULING
PRESENTED BY:
ASHIRBAD BARIK
SIC NO:EE145210
REGD:1401209153
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GUIDED BY:
PROF. L.N PATHY

2. CONTENTS
 Introduction
 What is hydrothermal scheduling?
 Types of Hydrothermal scheduling
 What is Power system Optimization?
 Some terms related to Hydrothermal Scheduling
 Conclusion
 References
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3. INTRODUCTION
 Modern Power system consists of a large number of thermal and hydel
plants connected at various load centre through a transmission
network.
 Our important objective is generate and transmit power to meet the
load demand at minimum cost by optimal mix of different types of
plants.
 Therefore the study of the optimal scheduling for power generation at
different plants in a power system is of high importance.
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4. COMPARISION BETWEEN THERMAL AND
HYDEL POWER PLANTS
Thermal Power Plant
 It is non-renewable source
of energy
 Initial cost is low
 But operational cost is high
 It produces air pollution
Hydel Power Plant
 It is renewable source of
energy
 Initial cost is high
 But operational cost is low
 It is a clean source of
energy
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5. HYDROTHERMAL SCHEDULING
 The operating cost of thermal plant is very high , though their initial
cost is low.
 On the other hand the operating cost is low in case of hydroelectric
generation
 Due the low operating cost in case of hydel plants so we can operate
it in conjuction with thermal plants which will lead to save fuel
 So Hydrothermal scheduling is a power system optimization problem
which gives us idea how to manage the hydel and thermal plant
combinely.
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6. CLASSIFICATION OF HYDROTHERMAL
SCHEDULING
Hydrothermal scheduling is classified into two parts , that are
 a)Long range Problem : This type of scheduling having the
scheduling interval of a month or a year.
 b)Short range Problem : This type of scheduling having the
scheduling interval of a day or a week.
According to this different mathematical formulations are made
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7. POWER SYSTEM OPTIMIZATION
 Generally optimization is a technique in which we try to maximize our
profit or gain and to minimize loss or expenditure under some pratical
conditions known as constraints.
 In load flow analysis we know that every bus associated with four
operational variables like P,Q,|V| and δ.Out of these four,two are
specified variable and other two are not given.
 According to these two specified variables we have three types bus
that are PQ bus(Load bus),PV bus(Generator Bus),Slack bus.
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8.  If the specified variables are varied within their constraints that cause
an infinite number of load flow solution.
 Each value of load flow solution related to one set of specified
variables.
 The optimal choice is that values of specified variable for which gives
best load flow solution.
 Optimal and economical system operation it predominantly depends
on best or optimal load flow solution.
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9. OPTIMAL UNIT COMMITMENT
 Unit commitment is the process to determine the units of a plant that should
operate for a particular load.
 As it is not economical to run all the units available all the time.
 So it is an optimal approach in which the most efficient unit is loaded first
and then followed by least efficient unit when load increases.
 It is very difficult to find economical combination of units to meet a particular
load demand as it is highly time consuming.
 To determine the combination which has the least operating cost we use
different computational method like dynamic programming method.
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10. ECONOMIC LOAD DISPATCH
 The main objective of economic load dispatch to minimise the cost of
generation.
 The other objective is to maintain total power generation is the
summation of total load demand plus loss.
 Under the incremental loading condition,the load flow will give
several solutions but one solution is best in respect of economy.
 So the analysis made for obtaining this solution known as Economic
load dispatch.
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11. INCREMENTAL PRODUCTION COST(IPC)
 The fuel cost in hydel units is practically zero.So it is considered to be
for thermal units only.
 IPC can be modelled under two considerations that are with
transmission losses and without transmission losses.
 With losses:
Let us consider a system consisting of ‘n’ number of generators.
So total fuel cost CT=C1+C2+C3+…………+Cn= 𝑖=1
𝑛
𝐶𝑖
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12.  PG=P1+P2+…..+Pn= 𝑖=1
𝑛
𝑃𝑖 =PD+PL
Where PG=Total generating power
PD=Load Demand
PL=Transmission loss
By using Langrange optimization technique we find the expression for IPC as
𝑑𝐶𝑖
𝑑𝑃𝑖
+ λ
𝜕𝑃𝑖
𝜕𝑃𝑖
=λ
where λ is Langrangian multiplier and the equation known as coordination
equation and without losses it is given as
𝑑𝐶𝑖
𝑑𝑃𝑖
=λ,so for economical operation IPC of all generating units must be same
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13. OPTIMAL SCHEDULING OF HYDROTHERMAL
SYSTEM
 Operation of the system having both hydro and thermal power plants
is a complex method.
 We perform static optimization when the plant is thermal power plant
 But hydro thermal scheduling is a dynamic optimization due to the
water constraint i.e. water availability.
 There are basically three types of hydroelectric plant but we use
storage type because optimization possible in storage tank
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14.  For easy analysis we consider one hydro and one thermal power
plant supplying power to load and it is called as fundamental system
given as below
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15. MATHEMATICAL FORMULATION
 In this we consider time interval ‘T’(which can be One year,month,day or
hours)
 We have to determine the water discharge rate i.e. q(t) as to minimize the
cost of thermal generation Under the following constraints
1)Meeting the load demand:
PGT(t)+PGH(t)-PL(t)-PD(t)=0,t ϵ [0,T]
PGT(t)=Thermal power generation
PGH(t)=Hydro power generation
PL(t)=Total loss in line
PD(t)=Total load demand
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16. 2)Water availability:
X’(T)- X’(T)- 0
𝑇
𝐽 𝑡 𝑑𝑡 + 0
𝑇
𝑞 𝑡 𝑑𝑡=0
where X’(T) and X’(0) are the water level at the end and beginning , J(t) is the
water inflow.
3)Hydro generation PGH(t)=f(X’(t),q(t))
here we discrtitize time interval T into M intervals for our calculations
Using these constraints and Langrangian optimization technique,we find the
most optimal equation for hydrothermal scheduling.
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17. CONCLUSION
 Hydrothermal scheduling is very beneficial as it helps us to minimise
the cost and less use of fossil fuel for the power generation but due
to the uncertainty of inflows of water makes it a very complex
problem
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18. REFERENCES
 www.nptel.ac.in/courses
 Power System Engineering D P Kothari, I J Nagrath
 ieeexplore.ieee.org
 www.wikipedia.org
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19. THANK YOU
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