Abstract— plants have capability to handle fast changing

 

Abstract— the objective of optimum
hydrothermal scheduling is to minimize fuel cost of thermal plants under
constraints of water availability for hydro plants over a given period of time.
In this paper, generation schedule, daily water used by hydro plant and daily
operating cost of the thermal plant is obtain using Kirchmayer’s method for
short term scheduling.

Keywords— hydro-thermal scheduling,
optimization and Kirchmayer’s method.

                                                                                                               
I.      Introduction to
hydro-thermal scheduling

The hydro plants requires less starting
time and takes load in very short
time as compared to thermal plants which takes several
time to make the boilers, superheater
and turbine system ready to take the load. Hydro
plants have capability to handle fast changing loads but thermal plants are
slow in response. Due to this, hydro plants are preferred to operate as peak
load plants and thermal plants as base load plant. In order to utilize energy
efficiently, cost must be as minimum as possible. So the main aim of operation
of power system is to generate and transmit power to meet the system load
demand at minimum fuel cost and minimum environmental pollution1. Hence, hydrothermal
scheduling is necessary.
The objective of optimum hydrothermal scheduling
is to minimize fuel cost of thermal plants under constraints of water
availability for hydro plants over a given period of time.

The hydrothermal scheduling is
classified into:-

1.Long term
Coordination is extended from one week to one year or several years. This is used for long term minimization of
cost of the whole system. The long term coordination problem becomes very
difficult to solve due to its size, time span (several
years) and randomness of water
inflows for long time2.

2.Short term Scheduling is required
for one day or one week.
In short
term problem, the head of water is assumed to be constant as there will not be any appreciable change in
the water level in the reservoirs.
So, this is quite easy to solve due to
its size, time span (one week).

                                                                                                           
II.    SHORT-TERM  HYDRO-THERMAL SCHEDULING

Short-term scheduling is required for
one day or one week involving the hour-by-hour scheduling of both hydro and
thermal plants to get minimum production cost for the given time. In this
scheduling problem, the load, the hydraulic inflows and unit availability are
assumed to be known3. In addition, the generating unit limits and the load demand over
the scheduling interval are known. In short term problem, the head of water is assumed to be constant as there will not be
any appreciable change in the water level in the reservoirs.  Several mathematical optimization techniques
have been used to solve short term hydrothermal scheduling problems4.

Load cycle, expected
water inflow, water head and generation in hydro plant, incremental fuel cost
of thermal plant and incremental transmission loss are the various factors on
which the economic operation of hydro-thermal scheduling depends.

The various methods used for
hydro-thermal scheduling are constant hydro generation method, constant thermal
generation method, maximum hydro-efficiency method and Kirchmayer’s method 5. A large number of researchers have
extensively investigated the short-term hydro scheduling problem. Main
computational techniques that have been employed are maximum principal 6, variational
calculus 7, dynamic programming 8 and nonlinear programming 9. In this paper, Kirchmayer’s method for short term scheduling is
presented. The proposed method is
one of the effective method for solving short term hydro-thermal scheduling problem.