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Exercices Part 2 - Buck-Boost Converter With Inductive Load
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In the panel, choose from the menu Pre-Selected: Inductive Load and set the inductive load (R= 12.5 ohms, L= 20mH) as load value for exercises 7 to 10.
Figure 21: Buck-Boost Panel with an Inductive Load with R=12.5 ohms and L =20 mH
Default Parameters
- Source Voltage: V_{DC}= 100 V
- L= 100 mH
- C= 400 µF
- Switching Frequency: 1500 Hz
- Duty Cycle: 0.5
Exercise 7: Varying Duty Ratio
Set V_{DC} to 50 V, the switching frequency to 1500 Hz, and vary the duty cycle from 10% to 75%.
Observe the effects of change in output voltage and measure the average DC load voltage for the corresponding values of duty ratio, and complete the following table with the theoretical average output voltage.
Duty Cycle (%) | 10 | 15 | 20 | 25 | 35 | 45 | 55 | 65 | 75 |
---|---|---|---|---|---|---|---|---|---|
Measured average load voltage (V) | |||||||||
Calculated average load voltage (V) |
Table 34: Outcome of Varying Duty Cycle (inductive load scenario)
What effect will a duty ratio at the boost converter have on the voltage output?
Explain.- For duty cycle = 0.65, what are the values for:
- Average inductor current
- Maximum value of inductor current
- Minimum value of inductor current
- Compare the observed values with the calculated ones
Exercise 8: Varying Switching frequency
Set V_{DC} to 100 V, duty cycle to 0.6 and vary the switching frequency from 1500 Hz to 3600 Hz.
Observe simulation results and complete the following table.
Switching Frequency (Hz) | 1500 | 1620 | 1800 | 2400 | 3000 | 3600 |
---|---|---|---|---|---|---|
Measured maximum value of inductor current (A) | ||||||
Calculated maximum value of inductor current (A) | ||||||
Measured average load voltage (V) | ||||||
Measured average load current (A) |
Table 35: Outcome of Varying Switching Frequency (inductive load scenario)
- What is the effect of frequency change on the output voltage and inductor current?
Exercise 9: Varying DC Source Voltage
Set the switching frequency to 1500 Hz, duty cycle to 55%, and complete the following table for different values of the input voltage.
DC source voltage (V) | 80 | 100 | 120 | 140 | 180 | 200 |
---|---|---|---|---|---|---|
Measured average load voltage (V) | ||||||
Calculated average load voltage (V) | ||||||
Measured average load current (A) | ||||||
Calculated average load current (A) |
Table 36: Outcome of Varying DC source Voltage (inductive load scenario)
- What is the effect of varying DC source voltage on the inductor’s current waveform?
- Set the V_{DC} voltage to 120 V, calculate the theoretical values of input and output powers and compare them with the observed ones.
What do you conclude?
Exercise 10: Changing Value of L
From the panel, change the inductance L from 100 mH to 50 mH.
Set V_{DC} to 100 V, duty cycle to 60%, and C=400 µF.
Vary the switching frequency from 1500 Hz to 3600 Hz, observe the simulation results and complete the following table.
Switching Frequency (Hz) | 1500 | 1800 | 2400 | 3000 | 3600 |
---|---|---|---|---|---|
Measured average load voltage (V) | |||||
Measured average load current (A) |
Table 37: Outcome of Changing the Buck-Boost Inductance (inductive load scenario)
- What is the effect of decreasing the value of L?
Hint: Compare to results obtained in exercise 8.
Exercise 11: Changing Value of R
From the panel, select the inductive load with R= 8.5 ohms and L= 20 mH, which is equivalent to changing the resistance value of the load.
Set V_{DC }to 100 V, switching frequency to 1500 Hz, duty cycle to 0.60, L= 100 mH and the capacitance as C =400 µF.
- What is the effect of decreasing the resistive load value on the load current, inductor current, load voltage, and output power?
Explain your observations.
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