Parallel RLC Branch (Power System Blockset)

Implement a parallel RLC branch.

Library

Elements

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 and Parameters

Resistance R

The branch resistance, in ohms (

Inductance L

The branch inductance, in henries (H).

Capacitance C

The branch capacitance, in farads (F).

Measurements

Select Branch voltage to measure the voltage across the Parallel RLC Branch block terminals.

Select Branch current to measure the total current (sum of R, L, C currents) flowing through the Parallel RLC Branch block.

Select Branch voltage and current to measure the voltage and the current of the Parallel RLC Branch block.

Place a Multimeter block in your model to display the selected measurements during the simulation. In the Available Measurement listbox of the Multimeter block, the measurement will be identified by a label followed by the block name.


Measurement	Label
Branch voltage	`ub:`
Branch current	`ib:`

Example

Obtain the frequency response of an eleventh-harmonic filter turned at 660 Hz connected on the 60 Hz power system 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 and the bode function.

[A,B,C,D] = power2sys('psbparalbranch');
freq = logspace(1,4,500); 
w = 2*pi*freq;
[Zmag,Zphase] = bode(A,B,C,D,1,w);
subplot(2,1,1) 
loglog(freq,Zmag)
grid
title('11th harmonic filter') 
xlabel('Frequency, Hz')
ylabel('Impedance Z') 
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 to plot the impedance as function of frequency.

Neutral Parallel RLC Load