DC Power Flow Analysis matlab script not working. My problem seems to be not getting the correct dimensions for my matrices to get them to multiply.

Using MATPOWER data. trying to build a code that will work with an unlimited bus system. A IEEE 14 Bus system is going to do for now.

Here is my Code:

% DC Power Flow %

% Unlimited Bus %

% PL = D * A * delta %

% Load data from MATPOWER

mpc = loadcase('case14');

% Branch Column

N_Branch = size(mpc.branch);

% Bus column

N_bus = size(mpc.bus);

% Column 1 = From

% Column 2 = To

% Column 3 = X from the professors equation "" A (X,Y-1) where x=number of

% line and y=number of the bus

% A Matrix is a (K*n-1) incident matrix

A = zeros(N_Branch(1,1),N_Branch(1,1));

% Line Data

Line_Data = zeros(N_Branch(1,1),3);

for i = 1 : N_Branch(1,1)

% Injecting bus Number

Line_Data(i,1) = mpc.branch(i,1);

% Load bus Number

Line_Data(i,2) = mpc.branch(i,2);

% Reactance of TL

Line_Data(i,3) = mpc.branch(i,4);

end

for i = 1 : N_Branch(1,1)

% A matrix data

A(i,Line_Data(i,1)) = 1;

% A matrix data

A(i,Line_Data(i,2)) = -1;

end

%% A Matrix

A(:,1) = [];

%% Power Demand Bus

for i = 1 : N_bus

PD (i,1) = mpc.bus(i,3);

end

PD(1,:) = [];

%% B Bus, B' Matrix

Bprime = makeBdc(mpc);

% Eliminate rows and columns corresponding with the slack bus

Bprime(:,1) = [];

Bprime(1,:) = [];

%% D Matrix

% The number of rows need to match A and delta to be multiplied thourgh.

% Ds hould be multiplied by the identity matrix for the N_Branch cmd

D_identity = eye(N_Branch(1,1));

% D Matrix = (k*k) matrix w/ 0 on off-diagonal elements & Bk in diagonal elements, therefore

% changes need to be made to the syntax to work with the future equation for Power flow

for i = 1 : N_Branch(1,1)

D_diagonal(i,1) = 1/mpc.branch(i,4);

end

D = D_identity .* D_diagonal;

%% Delta = Inverse B prime matrix multiplied by the Power demand matrix.

delta = (Bprime)^(-1) * PD

%% Power Flow

% P = Bprime * delta

PL = D * A * delta

% Base MVA

Base = mpc.baseMVA;

% Bus Data

Bus_Data = mpc.bus;

% function [PF] = dcpflow(P,Line_Data)

for i = 1 : N_bus(1,1)

% Bus Number

Demand(:,1) = -mpc.bus(:,1); % Negative Value

% Bus Active Load

Demand(:,2) = -mpc.bus(:,3); % Negative Value

% Bus Number

Generation(i:1) = mpc.gen(i:1);

% Scheduled Active Power Generation

Generation(i:2) = mpc.gen(i:2);

end

% end

% Run DC Power Flow

% rundcpf;

I have commenter out a few things toward the end bc I am going to implement them later. disregard these for now.

Here is my error code:

delta =

10.7310

24.3753

20.0517

17.3170

27.4108

25.8280

25.8280

28.9350

29.4132

28.7715

29.3611

29.6657

31.5217

Error using *

Incorrect dimensions for matrix multiplication. Check that the number of

columns in the first matrix matches the number of rows in the second

matrix. To operate on each element of the matrix individually, use TIMES

(.*) for elementwise multiplication.

Error in FinalMatlabProject142 (line 88)

PL = D * A * delta

Answer 1

[Manikanta Aditya]

I feel you need to ensure that the dimensions of your matrix aligns for multiplication, You might need to transpose one of your matrices, or perhaps there's an issue with how the matrices and being constructed.

The error message you’re seeing is due to a mismatch in the dimensions of the matrices being multiplied. In your case, the error is occurring at the line PL = D * A * delta.

Looks like from the above line:

• D is a square matrix of size N_Branch(1,1) x N_Branch(1,1).
• A is a matrix of size N_Branch(1,1) x (N_Branch(1,1)-1), because you removed the first column.
• delta is a column vector of size N_bus x 1

The multiplication D * A is valid because the number of columns in D matches the number of rows in A. However, the result of D * A is a matrix of size N_Branch(1,1) x (N_Branch(1,1)-1), and this cannot be multiplied with delta because the number of columns in D * A does not match the number of rows in delta.