I have plotted a signal in Simulink and now i want to write a code to integrate that signal over the limits? can anyone help me with this please

clc;

clear all;

open('tranmissionfault.slx');

sim('tranmissionfault.slx');

syms t

P=int(Phasecurrent,t,0,0.008)

Answer 1

[madhan ravi]

Use Integrated Limited block specifying the upper limit as 0.008 and lower as 0.

edit: Thanks @Paul, i overlooked it, yes the same goal can be achieved in Simulink using a switch block, but not going in detail into it, since the OP's intention is to use MATLAB code

[A Lumbini]

But i want to do integration by coding it in matlab not using Simulink

[madhan ravi]

cumtrapz(phasecurrent.Data(phasecurrent.Time < 0.008))

Assuming phasecurrent is logged as timeseries through To workspace block. Use trapz() if you want the answer to be a scalar.

[A Lumbini]

What if i want to specify upper and lower limits

[madhan ravi]

cumtrapz(phasecurrent.Data((phasecurrent.Time >= lower_limit) & (phasecurrent.Time <= upper_limit)))

[A Lumbini]

Thank you so much for your time sir, i have been working on it for a long time as part of my semester project and i don't know much about matlab.

Your inputs were very helpful

[madhan ravi]

But I would suggest you to do it in Simulink directly.

[A Lumbini]

I have to implement DFT algorithm under fault conditions with selective intervals and i have to write a code for it

[A Lumbini]

I used your code which lead to another question

if we integrate sine wave by taking its timeperiod as an inteval we need to get 0.But, i am getting a value

[Paul]

@madhan ravi

Based on the code in the question, it appears that the OP wants to integrate the signal over the interval 0 < t < 0.008. The "Integrator Limited" doesn't do that. Rather it integrates the input signal over the whole simulation, but limits the integral itself to the specified limits.

I haven't tried it .... does cumtrapz really accept a timeseries as an input?

[madhan ravi]

@A Lumbini

ix = (out.sinewave.Time >= 0) & (out.sinewave.Time <= 4); % lower limit 0 and upper limit 4
Int = cumtrapz(out.sinewave.Data(ix))
vpa(Int(end)) % very close to zero 

Int =

         0
    0.1545
    0.6029
    1.3013
    2.1813
    3.1569
    4.1324
    5.0124
    5.7108
    6.1592
    6.3138
    6.1592
    5.7108
    5.0124
    4.1324
    3.1569
    2.1813
    1.3013
    0.6029
    0.1545
   -0.0000

 
ans =
 
-0.0000000000000016375

[Paul]

@madhan ravi

My mistake. For some reason I didn't see you were dot indexing into PhaseCurrent, i.e., PhaseCurrent.Data.

However, shouldn't the cumtrapz use the two argument form?

ix = (out.sinewave.Time >= 0) & (out.sinewave.Time <= 4); % lower limit 0 and upper limit 4
Int = cumtrapz(out.sinewave.Time(ix),out.sinewave.Data(ix))

[madhan ravi]

the form you have used is also correct, as we do the indexing directly into the data itself, i just use the first snytax mentioned in the docu

[Paul]

Except the first syntax assumes that the independent variable has unit spacing, which is not likely to be the case for the time vector of logged signal from a simulink model. The time spacing of the logged signal might not even be uniform if the solver is variable step.

[madhan ravi]

Yes, i just noticed that specialzed power system's powergui uses Continuos method. I always work with Discrete models hence didn't notice it. Thanks for noticing it.

[A Lumbini]

Thank you sir, got the answer

clc;

clear all;

open('tranmissionfault.slx');

sim('tranmissionfault.slx');

ix = (Phasecurrent.Time >= 0.012) & (Phasecurrent.Time <= 0.032016);

Int = cumtrapz(Phasecurrent.Data(ix))

vpa(Int(end))

Int =

1.0e+04 *

0

-0.0146

-0.0599

-0.1199

-0.1939

-0.2938

-0.4152

-0.5528

-0.7004

-0.8513

-1.0025

-1.1506

-1.2893

-1.4123

-1.5146

-1.6055

-1.6826

-1.7309

-1.7481

-1.7335

-1.6882

-1.6282

-1.5542

-1.4543

-1.3328

-1.1953

-1.0477

-0.8968

-0.7456

-0.5974

-0.4588

-0.3358

-0.2335

-0.1426

-0.0654

-0.0172

0.0000

ans =

0.15362797623171786653983872383833

[A Lumbini]

Sir, i got 0.15 approximately when i integrate the sine wave

But,then i tried the same after the fault and i am getting huge value

F=0.05

ix = (Phasecurrent.Time >= F) & (Phasecurrent.Time <=F+0.020047);

Int = cumtrapz(Phasecurrent.Data(ix))

vpa(Int(end))

ans =

137031976.93982961773872375488281

[madhan ravi]

To be continued here:

https://in.mathworks.com/matlabcentral/answers/2067336-i-integrated-fault-current-which-is-sine-wave-with-its-time-period-as-an-interval-but-i-am-getting