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.