Inverter simulation in Simulink - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define the inverter output frequency.

Simulink

output_frequency = [1];

Drag options to blanks, or click blank then click option'

A50

B60

C100

D120

Attempts:

3 left

💡 Hint

Common Mistakes

Using 50 Hz which is common in Europe but not in this simulation.

Using 100 or 120 which are too high for standard inverter output.

The standard inverter output frequency is set to 60 Hz for this simulation.

2fill in blank

medium

Complete the code to set the inverter DC input voltage.

Simulink

dc_voltage = [1];

Drag options to blanks, or click blank then click option'

A600

B400

C800

D220

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 220 or 400 which are lower than typical DC bus voltage.

Choosing 800 which is higher than the designed voltage.

The inverter DC input voltage is set to 600 volts for this simulation.

3fill in blank

hard

Fix the error in the PWM carrier frequency assignment.

Simulink

pwm_carrier_frequency = [1];

Drag options to blanks, or click blank then click option'

A5e3

B10e3

C15e3

D20e3

Attempts:

3 left

💡 Hint

Common Mistakes

Using 5 kHz or 10 kHz which may cause audible noise.

Using 15 kHz which is less common than 20 kHz for this simulation.

The PWM carrier frequency should be 20 kHz for proper inverter switching.

4fill in blank

hard

Fill both blanks to create a dictionary mapping phase names to their voltages.

Simulink

phase_voltages = dict('A', [1], 'B', [2] );

Drag options to blanks, or click blank then click option'

A230

B220

C240

D210

Attempts:

3 left

💡 Hint

Common Mistakes

Using voltages that are too low or too high for typical phase voltages.

Assigning the same voltage to both phases which is less realistic.

Phase A voltage is 230 V and phase B voltage is 240 V in this inverter simulation.

5fill in blank

hard

Fill all three blanks to create a dictionary with phase names and their frequencies.

Simulink

phase_frequencies = dict('A', [1], 'B', [2], 'C', [3] );

Drag options to blanks, or click blank then click option'

A60

B59.9

C60.1

D61

Attempts:

3 left

💡 Hint

Common Mistakes

Using identical frequencies for all phases which is less realistic.

Using frequencies too far from 60 Hz causing simulation errors.

Phase A frequency is 61 Hz, phase B is 59.9 Hz, and phase C is 60.1 Hz to simulate slight frequency variations.

Practice

1. What is the main purpose of an inverter simulation in Simulink?

easy

A. To convert DC voltage to AC voltage

B. To measure temperature changes

C. To analyze sound waves

D. To simulate water flow

Solution

1. Step 1: Understand inverter function

   An inverter changes direct current (DC) into alternating current (AC).

2. Step 2: Relate to simulation purpose

   Simulink inverter simulation models this DC to AC conversion process.

3. Final Answer:

   To convert DC voltage to AC voltage -> Option A

4. Quick Check:

   Inverter = DC to AC converter [OK]

Hint: Inverter always changes DC to AC [OK]

Common Mistakes:

• Confusing inverter with sensor functions
• Thinking inverter measures physical quantities
• Mixing inverter with unrelated simulations

2. Which Simulink block is commonly used to generate switching signals for an inverter?

easy

A. Gain

B. Integrator

C. Scope

D. Pulse Generator

Solution

1. Step 1: Identify switching signal source

   Switching signals control inverter switches and are periodic pulses.

2. Step 2: Match block function

   Pulse Generator creates periodic pulses suitable for switching control.

3. Final Answer:

   Pulse Generator -> Option D

4. Quick Check:

   Switching signal = Pulse Generator output [OK]

Hint: Switching needs pulses, so use Pulse Generator [OK]

Common Mistakes:

• Choosing Scope which only displays signals
• Selecting Integrator which accumulates signals
• Picking Gain which scales signals but doesn't generate pulses

3. Given this Simulink model snippet for inverter output voltage:

PulseGen = Pulse Generator with amplitude 1 and frequency 50 Hz
OutputVoltage = PulseGen * DCVoltage (100 V)

What is the peak AC output voltage amplitude?

medium

A. 50 V

B. 150 V

C. 100 V

D. 0 V

Solution

1. Step 1: Understand pulse amplitude effect

   The Pulse Generator outputs pulses with amplitude 1, switching DC voltage on/off.

2. Step 2: Calculate output voltage amplitude

   OutputVoltage = PulseGen amplitude (1) * DCVoltage (100 V) = 100 V peak.

3. Final Answer:

   100 V -> Option C

4. Quick Check:

   Pulse amplitude 1 * 100 V = 100 V [OK]

Hint: Multiply pulse amplitude by DC voltage for peak [OK]

Common Mistakes:

• Confusing frequency with amplitude
• Adding values instead of multiplying
• Ignoring pulse amplitude value

4. In a Simulink inverter model, the Scope shows a flat line instead of an AC waveform. What is the most likely cause?

medium

A. DC voltage set to zero

B. Pulse Generator frequency set to zero

C. Scope block disconnected

D. Integrator block missing

Solution

1. Step 1: Analyze flat line cause

   A flat line means no voltage variation, likely zero output voltage.

2. Step 2: Check DC voltage effect

   If DC voltage is zero, output voltage is zero regardless of switching pulses.

3. Final Answer:

   DC voltage set to zero -> Option A

4. Quick Check:

   Zero DC voltage = flat output [OK]

Hint: Zero DC voltage means no output waveform [OK]

Common Mistakes:

• Assuming frequency zero causes flat line (it causes no switching)
• Thinking Scope disconnection shows flat line (it shows no signal)
• Confusing missing Integrator with output shape

5. You want to simulate a three-phase inverter in Simulink producing balanced AC outputs. Which approach is best?

hard

A. Use one Pulse Generator connected to all three legs

B. Use three Pulse Generators with 120° phase shifts controlling three inverter legs

C. Use three Integrator blocks to create phase shifts

D. Use Scope blocks to generate phase-shifted signals

Solution

1. Step 1: Understand three-phase inverter needs

   Three-phase AC requires three signals shifted by 120° to balance phases.

2. Step 2: Identify correct signal generation method

   Three Pulse Generators with 120° phase shifts produce correct switching signals for each leg.

3. Step 3: Evaluate other options

   One Pulse Generator cannot create phase shifts; Integrators and Scopes do not generate pulses.

4. Final Answer:

   Use three Pulse Generators with 120° phase shifts controlling three inverter legs -> Option B

5. Quick Check:

   Three pulses, 120° apart = balanced three-phase [OK]

Hint: Three pulses with 120° shift create balanced three-phase [OK]

Common Mistakes:

• Using one pulse for all phases
• Confusing Integrator with pulse generation
• Trying to generate signals with Scope blocks