Power System Blockset | ![]() ![]() |
Implement a series RLC branch.
Library
Description
The Series RLC Branch block implements a single resistor, inductor or capacitor, or a series combination of these. To eliminate either the resistance, inductance, or capacitance of the branch, the R, L, and C values must be set respectively to zero, zero, and infinity. Only existing elements will be displayed in the block icon.
Negative values are allowed for resistance inductance and capacitance.
Dialog Box and Parameters
Example
Obtain the frequency response of a fifth-harmonic filter (tuned frequency = 300 Hz) connected on a 60 Hz power system. This example is available in the psbseriesbranch.mdl
file.
The network impedance in Laplace domain is:
To obtain the frequency response of the impedance you have to get the state-space model (A B C D matrices) of the system.
This system is a one input (Vsource) and one output (Current Measurement block) system. If you own the Control System Toolbox, you can get the transfer function Z(s) from the state-space matrices and the bode function as follows:
[A,B,C,D] = power2sys('psbseriesbranch');
freq = logspace(1,4,500);
w = 2*pi*freq;
[Ymag,Yphase ] = bode(A,B,C,D,1,w);
% invert Y(s) to get Z(s)
Zmag = 1./Ymag;
Zphase = -Yphase;
subplot(2,1,1)
loglog(freq,Zphase)
grid
title('5th harmonic filter')
xlabel('Frequency, Hz')
ylabel('Impedance Zmag')
subplot(2,1,2)
semilogx(freq,Zphase)
xlabel('Frequency, Hz')
ylabel('phase Z')
grid
You can also use the Impedance Measurement block and the Powergui block to plot the impedance as function of frequency. In order to measure the impedance you must disconnect the voltage source.
See Also
Series RLC Load, Parallel RLC Branch, Parallel RLC Load
![]() | Saturable Transformer | Series RLC Load | ![]() |