Series RLC Branch (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

Example

Obtain the frequency response of a fifth-harmonic filter (tuned frequency = 300 Hz) connected on a 60Hz power system. This example is available in psbseriesbranch.mdl.

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) system. If you own the Control System Toolbox, you can get the transfer function Z(s) from the state-space matrices as follows:

[A,B,C,D] = power2sys('psbseriesbranch');
freq = logspace(1,4,500); 
w = 2*pi*freq;
[Y,phaseY] = bode(A,B,C,D,1,w);
% invert Y(s) to get Z(s)
Z = 1./Y;
phaseZ = -phaseY;
subplot(2,1,1) 
loglog(freq,Z)
grid
title('5th harmonic filter')
xlabel('Frequency, Hz')
ylabel('Impedance Z') 
subplot(2,1,2) 
semilogx(freq,phaseZ) 
xlabel('Frequency, Hz') 
ylabel('phase Z') 
grid