SIMULATION OF A LCC RESONANT CIRCUIT ECE562: Power ...ECE 562 LCC Resonant Circuit (NL5 Simulation)...

ECE 562 LCC Resonant Circuit (NL5 Simulation)

SIMULATION OF A LCC RESONANT CIRCUIT ECE562: Power Electronics I

COLORADO STATE UNIVERSITY

Modified in Fall 2011


PURPOSE: The purpose of this lab is to simulate the LCC resonant circuit using MATLAB and NL5 to better familiarize the student with some of its operating characteristics. This lab will explore some of the following aspects of the parallel resonant circuit:

• Input impedance • Output impedance • Zero frequency • Output power • Output current • Output voltage • Zero poles • Phase of transfer function • Stable circuit • Unstable circuit

NOTE: The simulations that follow are intended to be completed with NL5. It is assumed that the student has a fundamental understanding of the operation of NL5. Build the schematic shown in Figure A.

• Vm is an AC voltage source. Set the type to ‘Sin,’ and the magnitude to 1 V. • L1 is an ideal inductor. Set to 25 μH. • R1 is an ideal resistor. Set to 25 Ω. • Cs is an ideal capacitor. Set to 200 nF. • Cp is an ideal capacitor. Set to 66 nF.

Figure A – Initial schematic.


Under the ‘AC Settings’ tab, specify I1 as the source, a frequency range of 100 Hz to 10 MHz, 1000 points, and a logarithmic scale.

Add a trace for the input impedance by selecting AC / Data / Traces from the menu. Click on ‘Function’ in the ‘Add new trace’ section. Add the function V(V1)/I(V1).


Run the simulation by selecting ‘AC’ and then ‘Start’ from the drop down menus. Referring to Figure B, what is the input impedance value of the circuit?

Figure B – Magnitude and phase of the input impedance.


Next, we want to measure the output voltage of the circuit. For this example, take the output voltage as the voltage across the resistor. Right click on the resistor and select Add trace / Voltage. Run the simulation and adjust the data display to show this voltage.

Figure C – Output voltage.

The current through the inductor is also of interest. Add a current trace and run the simulation. What can be said about the magnitude and phase of the inductor current with respect to frequency? Comment on the zero crossing point of the inductor current phase.


Figure D – Inductor current.

Add current traces to Cp and the load resistor. Run the simulation.

Figure E – Currents for inductor, parallel capacitor, and output resistor.


Note the different zero crossing points of phase for the three different currents. Comment on this phenomenon. Next, we want to simulate the output voltage of the parallel resonant circuit with a varying resistor. Use the same circuit as above, but change the resistor values to 10, 20, 40, 100, 200, and 400 Ω. This type of parametric sweep is accomplished in NL5 with a script. Go to Tools / Script and click on the Sweep tab. Select List instead of Loop. Enter R1 as the Name, enter the parametric values in the box, and select AC sweep. Click on the blue arrow to start the script.

Figure F – Output voltage as a function of load resistance.


What can be said about the output voltage magnitude and phase as the load resistance varies? Use the scripting to find an inductor value which changes the resonant frequency to approximately 500 kHz.

Figure G – Operating frequency shifted to 500 kHz.

What inductor value is required? What are the implications of this change on output voltage and current?


Figure H – Output voltage with alternate inductor.

Figure I – Output current with alternate inductor.


Change the circuit back to the 25 μH inductor. What is the output power of the circuit?

Figure J – Output power.


What happens to the output power when the load value changes?

Figure K – Output power as a function of varying load.

For Homework: You need to re-solve the LCC resonant circuit with Capacitor ESR included. Comment on the effects on the magnitude and phase plots. For example choose the ratio of the Cs and Cp ESR to the load resistance to be in the ratio range from 0.01 to 1.

Simulation of LCC Resonant Circuit Using MATLAB

NOTE: The simulations that follow are intended to be completed with MATLAB®

.

It is assumed that the student has a fundamental understanding of the operation

of MATLAB®

. MATLAB®

provides tutorials for users that are not experienced with

its functions.

PROCEDURE:

Part 1: write an m file shown in Figure 1.

Vm is a variable voltage. Set to 1 volts

L is a variable inductor. Set to 25µH.

R is a variable ideal resistor. Set to 25Ω.

Cp is a variable ideal capacitor. Change the value to 66nF.

Cs is a variable ideal capacitor. Change the value to 200nF.

Once the above m file is captured, the simulations can be run. First, go to your

directory. Find your m file and then run your file. If there is a red message on

your MATLAB window, then you need to correct your error. Otherwise, you will

see the solution as show in figure 1.

Figure 1. The output of Zinput_LCC m file.

Next, plot the output voltage of the LCC circuit by adding the output voltage

equation to the LCC m file. Then rerun the LCC m file.

Figure 2. The output voltage of LCC tank circuit

Now plot the inductor current of the LCC circuit by adding the inductor current

equations to the LCC m file. Then rerun the LCC m file.

Figure 3. Inductor current of LCC tank circuit

Now find the zero crossing of phase of inductor current. First define the input

impedance as a vector. Write a loop function to do the zero crossing of the

phase. Then rerun the simulation. If there is any error message on your MATLAB

windows, then correct your error and then rerun the simulation. Otherwise, you

will see the result as show below

Now calculate and plot the output of capacitor current by adding the capacitor

current equations to the LCC m file. Then rerun the LCC m file. Then rerun the

simulation. If there is any error message on your MATLAB windows, then correct

your error and then rerun the simulation. Otherwise, you will see the results as

show below

Now calculate and plot the output power of LCC circuit by adding the output

power equations to the LCC m file. But the output power is a vector function. First

define the input impedance as a vector. Write a loop function to do the zero

crossing of the phase. Then rerun the LCC m file. If there is any error message

on your MATLAB windows, then correct your error and then rerun the simulation.

Otherwise, you will see the results as show below

ans = 0.1769

SIMULATION OF A LCC RESONANT CIRCUIT ECE562: Power ...ECE 562 LCC Resonant Circuit (NL5 Simulation)...

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