Parallel RLC Branch (Power System Blockset)

Implement a parallel RLC branch

Library

Description

The Parallel RLC Branch block implements a single resistor, inductor and capacitor or a parallel 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 infinity, infinity, and zero. 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 an eleventh-harmonic filter tuned at 660 Hz connected on a 60Hz power system is shown in the following figure. This example is available in the psbparalbranch.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 (Is) and one output (Vs) system. If you own the Control System Toolbox, you can get the transfer function Z(s) from the state-space matrices.

[A,B,C,D] = power2sys('psbparalbranch');
freq = logspace(1,4,500); 
w = 2*pi*freq;
[Z,phaseZ] = bode(A,B,C,D,1,w);
subplot(2,1,1) 
loglog(freq,Z)
grid
title('11th harmonic filter') 
xlabel('Frequency, Hz')
ylabel('Impedance Z') 
subplot(2,1,2) 
semilogx(freq,phaseZ) 
xlabel('Frequency, Hz') 
ylabel('phase Z') 
grid

Frequency response of the filter: