Unit Commitment Using Priority List Scheme Objectives: •
Methods to solve the U.C problem
•
To understand Priority List Scheme
•
To solve Unit Commitment Problem (UCP) using Priority List Scheme
Theory: The different methods to solve the U.C problem are:1. LR me method 2. Prio Priori rity ty lis listt meth method od 3. Dynam Dynamic ic prog progra ramm mming ing met method hod The P.L method is also also called the merit order method. method. In this method, the number of combinations are reduced. Important features of this method are that first Full Load Average Cost is calculated generators are then loaded on the bases of FLA cost is loaded & generator with minimum cost is loaded first and so on.
SYSTEM 2
H 1 ( P 1 ) = 510 + 72 P 1 + 0.00142 P 1 H 2 ( P 2 ) =
310 + 7.85 P 2
+ 0.00194 P 2
H 3 ( P 3 ) =
78 + 7.97 P 3 + 0.00482 P 3
LIMITS
150 ≤ P 1 ≤ 600 100 ≤ P 2 50 ≤ P 3
≤
≤
400
200
COSTS C 1 = 1.1 $ / h C 2 = 1.0 $ / h C 3 = 1.2 $ / h Power Demand =
550 MW
2
2
Code: function [p,cost]=Pri_list(h,C,plower,pupper,pd) %h=[510 72 0.00142;310 7.85 0.00194;78 7.97 0.00482]; %C=[1.1 1.0 1.2]; %plower=[150 100 50]; %pupper=[600 400 200]; %pd=550; n=length(plower); disp('F(p)=') for i=1:n cost(i,:)=h(i,:)*C(1,i); disp(cost(i,:)); end for i=1:n a(i,1)=cost(i,1); b(i,1)=cost(i,2); y(i,1)=cost(i,3); end disp('full load average cost=') for i=1:n fla(i,1)=(a(i,1)+b(i,1)*pupper(1,i)+y(i,1)*pupper(1,i)^2)/pupper(1,i); disp(fla(i,1)) end p=fla; p(:,2)=plower'; p(:,3)=pupper'; p=sortrows(p); p(1,4)=p(1,2); p(1,5)=p(1,3); for i=1:n-1 p(i+1,4)=p(i+1,2)+p(i,4); p(i+1,5)=p(i+1,3)+p(i,5); end for i=1:n if pd>=p(i,5) p(i,6)=p(i,3); end if pd
g=0; for j=1:i-1 g=g+p(j,3); end p(i,6)=pd-g; end end for i=1:n if p(i,6)<0 p(i,6)=0; end end c=p(:,6); cost=sum( [sum(a) sum(b.*c) sum(y.*c.*c)]); end Result: F(p)= 561.0000 79.2000
0.0016
310.0000
7.8500
0.0019
93.6000
9.5640
0.0058
full load average cost= 9.7922 9.4010 11.1888
p = 1.0e+003 * 0.0094 0.0112 0.0811
0.1000 0.0500 0.1500
cost = 3.4116e+004
0.4000 0.2000 0.6000
0.1000 0.1500 0.3000
0.4000 0.6000 1.2000
0.4000 0.1500 0
Conclusion: Unit Commitment Problem is a problem on broad basis i.e. to select units from a no. of available stations to meet forecasted load on the system during certain period. Economic Dispatch Problem is a step within UCP which is performed for all possible combinations. Also EDP is performed later when UC has already been done to minimize the cost.
