Inverter simulation in Simulink - Mini Project: Build & Apply

Inverter simulation

📖 Scenario: You are working on a simple simulation of an electrical inverter. An inverter converts DC voltage to AC voltage by switching the output on and off in a pattern. We will simulate the inverter output over time using Python.

🎯 Goal: Build a Python program that simulates the inverter output voltage over a series of time steps. You will create the data, set a threshold, apply the switching logic, and then display the output voltage pattern.

📋 What You'll Learn

Create a list of DC input voltages over 10 time steps

Create a threshold voltage variable

Use a list comprehension to simulate the inverter output voltage: output voltage is the DC voltage if above threshold, else zero

Print the inverter output voltage list

💡 Why This Matters

🌍 Real World

Inverters are used in solar power systems and uninterruptible power supplies to convert DC to AC power.

💼 Career

Understanding inverter simulation helps in roles like electrical engineering, renewable energy system design, and embedded systems programming.

1

Create the DC input voltage list

Create a list called dc_voltages with these exact values: [0, 2, 5, 7, 10, 7, 5, 2, 0, 0] representing DC voltage at 10 time steps.

Simulink

# Create the dc_voltages list with the given values
# Your code here

Hint

Use square brackets to create a list and separate values with commas.

2

Set the threshold voltage

Create a variable called threshold and set it to 5. This will be the voltage level that decides if the inverter output is on or off.

Simulink

dc_voltages = [0, 2, 5, 7, 10, 7, 5, 2, 0, 0]
# Create the threshold variable and set it to 5
# Your code here

Hint

Use a simple assignment statement to create the threshold variable.

3

Simulate inverter output using list comprehension

Create a list called inverter_output using a list comprehension. For each voltage v in dc_voltages, output v if it is greater than or equal to threshold, otherwise output 0.

Simulink

dc_voltages = [0, 2, 5, 7, 10, 7, 5, 2, 0, 0]
threshold = 5
# Create inverter_output list using list comprehension
# Your code here

Hint

Use the syntax: [expression for item in list]. Use a conditional expression inside.

4

Display the inverter output voltage

Print the inverter_output list to show the simulated inverter voltage over time.

Simulink

dc_voltages = [0, 2, 5, 7, 10, 7, 5, 2, 0, 0]
threshold = 5
inverter_output = [v if v >= threshold else 0 for v in dc_voltages]
# Print the inverter_output list
# Your code here

Hint

Use the print() function to display the list.

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