Index in position 1 exceeds array bounds (must not exceed 28).

Hello guys, I am trying to run the backward-forward sweep program for power flow and I keep getting the error: Index in position 1 exceeds array bounds (must not exceed 28). Error in Test4 (line 131 [c e]=find(ldata(:,2:3)==NLD(i,3)); Can anyone help me with this?

Here is the code:

clear
clc

%branch no sending reciving  R(PU)       X(pu)
linedata=[  1    1   2  0.057525912  0.029324489
            2    2   3  0.307595167  0.156667640
            3    3   4  0.228356656  0.116299674
            4    4   5  0.237777928  0.121103899
            5    5   6  0.510994811  0.441115179
            6    6   7  0.116798814  0.386084969
            7	 7	 8	0.443860450	 0.146684835
            8	 8	 9	0.642643047	 0.461704714
            9	 9	10	0.651378001	 0.461704714
            10	10	11	0.122663712	 0.040555144
            11	11	12	0.233597628	 0.077241951
            12	12	13	0.915922324	 0.720633708
            13	13	14	0.337917936	 0.444796338
            14	14	15	0.368739846	 0.328184702
            15	15	16	0.465635443	 0.340039282
            16	16	17	0.804239697	 1.073775422
            17	17	18	0.456713311	 0.358133116
            18	 2	19	0.102323747	 0.097644308
            19	19	20	0.938508419	 0.845668336
            20	20	21	0.255497406	 0.298485858
            21	21	22	0.442300637	 0.584805173
            22	 3	23	0.281515090	 0.192356167
            23	23	24	0.560284909	 0.442425422
            24	24	25	0.559037059	 0.437434020
            25	 6	26	0.126656834	 0.064513875
            26	26	27	0.177319567	 0.090281989
            27	27	28	0.660736881	 0.582559042
            28	28	29	0.501760717	 0.437122057
            29	29	30	0.316642084	 0.161284687
            30	30	31	0.607952801	 0.600840053
            31	31	32	0.193728802	 0.225798562
            32	32	33	0.212758523	 0.330805188];
        

tielines = [33  8 21 2.00000000  2.00000000
           34  9 15 2.00000000  2.00000000
           35 12 22 2.00000000  2.00000000
           36 18 33 0.50000000  0.50000000
           37 25 29 0.50000000  0.50000000];
       

        
 

% bus no     activepower   reactivepower
  busdata = [1	0	    0
             2	0.001	0.0006
             3	0.0009	0.0004
             4	0.0012	0.0008
             5	0.0006	0.0003
             6	0.0006	0.0002
             7	0.002	0.001
             8	0.002	0.001
             9	0.0006	0.0002
            10	0.0006	0.0002
            11	0.00045	0.0003
            12	0.0006	0.00035
            13	0.0006	0.00035
            14  0.0012	0.0008
            15	0.0006	0.0001
            16	0.0006	0.0002
            17	0.0006	0.0002
            18	0.0009	0.0004
            19	0.0009	0.0004
            20	0.0009	0.0004
            21	0.0009	0.0004
            22	0.0009	0.0004
            23	0.0009	0.0005
            24	0.0042	0.002
            25	0.0042	0.002
            26	0.0006	0.00025
            27	0.0006	0.00025
            28	0.0006	0.0002
            29	0.0012	0.0007
            30	0.002	0.006
            31	0.0015	0.0007
            32	0.0021	0.001
            33	0.0006	0.0004] ; 
        
        rand('state',0);    %temporary (demo purpose)
        %Loop 1
        %backup data first
        linedata2 = linedata;
        
        %copy original data
        linedata = linedata2;
        x=randperm(32, 5);
        
        
        linedata(x,:) = [];
   
        
%          ori+tielines
        linedata = [linedata;tielines];
         
nbus  = 33; 
bdata = busdata;
ldata = linedata;
Pl = bdata(:,2);                 % PLi..
Ql = bdata(:,3);                 % QLi.

Branch=ldata(:,2:3);
M=max(ldata(:,2:3));
Totalbus=max(M);
f=[1:Totalbus]';
for i=1:Totalbus
    g=find(Branch(:,:)==i);
    h(i)=length(g);
end
k(:,1)=f;
k(:,2)=h';
%   cent=input('central bus');
cent = 1;
% this section of the code is to adjust line data to the standard 
  NLD=zeros(Totalbus,size(ldata,2));
c=find(ldata(:,2:3)==cent);
NLD=ldata(c,:);
ldata(c,:)=[];
t=find(k(:,1)==cent);
k(t,2)=k(t,2)-size(c,1);
j=size(c,1);
i=1;
while sum(k(:,2))>0
    c=[];
    b=[];
    t=[];
    [c, e]=find(ldata(:,2:3)==NLD(i,3));
    if size(c,2)~=0
        b=ldata(c,:);
        ldata(c,:)=[];
        t=find(k(:,1)==NLD(i,3));
        k(t,2)=k(t,2)-(size(c,1)+1);
        d=find(b(:,3)==NLD(i,3));
        b(d,2:3)=[b(d,3),b(d,2)];
        NLD(j+1:j+size(c,1),:)=b;
        j=j+size(c,1);
    end
    i=i+1;
end

Answer 1

[Cris LaPierre]

I suspect the error is here: NLD(i,3)

Position 1 is indexed by i. Since you are using a while loop, check what the value of i is. I suspect it is 29. The error message says it can't be greater than 28. What is the size of NLD? It likely only has 28 rows.

The fix is likely to improve the criteria used on your while loop.

while sum(k(:,2))>0

[Desmond Loh Hou Yin]

NLD is affected by the ldata and is supposed to stay at 33 however it kept dropping below 33. Is there any way to fix this?

[Cris LaPierre]

Perhaps. Follow your code backwards. How do you create NLD? You actually do it three ways. The second way replaces the first way. The third adds to it.

NLD=zeros(Totalbus,size(ldata,2));
NLD=ldata(c,:);
NLD(j+1:j+size(c,1),:)=b;

You also define c three times.

c=find(ldata(:,2:3)==cent);
c=[];
[c, e]=find(ldata(:,2:3)==NLD(i,3));

Ultimately, it is j that is larger than you expect. I suggest cleaning up your code. Avoid reusing the same varilable names over and over. It will make the code much easier to follow. Perhaps in the process, you'll discover how NLD goes from 28x5 to 1x5 to 29x5.