Inverter simulation in Simulink - Step-by-Step Execution

Concept Flow - Inverter simulation

Start Simulation

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Input DC Voltage

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Generate PWM Signals

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Switching Devices ON/OFF

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Output AC Voltage

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Measure Output Waveforms

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End Simulation

The inverter simulation starts with DC input, generates PWM signals to control switches, produces AC output, and measures waveforms.

Execution Sample

Simulink

1. Set DC input voltage = 100V
2. Generate PWM with 50Hz frequency
3. Switch devices ON/OFF based on PWM
4. Output AC voltage waveform
5. Measure voltage and current

This code simulates an inverter converting DC to AC using PWM control and measures output waveforms.

Execution Table

Step	Action	Input Voltage (V)	PWM Signal	Switch State	Output Voltage (V)	Measurement
1	Initialize DC input	100	N/A	All OFF	0	No output
2	Generate PWM signal	100	PWM ON	Switch ON	Approx 100 (pulsed)	Start waveform capture
3	Switching ON/OFF	100	PWM OFF	Switch OFF	0	Waveform low
4	Repeat PWM cycle	100	PWM ON	Switch ON	Approx 100 (pulsed)	Waveform high
5	Output AC waveform formed	100	PWM varying	Switch toggling	Sine-like AC voltage	Voltage and current measured
6	End simulation	100	N/A	All OFF	0	Final waveform data saved

💡 Simulation ends after completing PWM cycles and capturing output waveforms.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	After Step 5	Final
Input Voltage	0	100	100	100	100	100
PWM Signal	N/A	ON	OFF	ON	Varying	N/A
Switch State	All OFF	ON	OFF	ON	Toggling	All OFF
Output Voltage	0	Approx 100	0	Approx 100	Sine-like AC	0
Measurement	None	Start capture	Low waveform	High waveform	Final waveform	Saved data

Key Moments - 3 Insights

Why does the output voltage switch between approx 100V and 0V during PWM?

Because the PWM signal turns the switches ON and OFF rapidly, creating pulses of voltage that approximate AC output (see execution_table steps 2-4).

How does the inverter create a sine-like AC voltage from a DC input?

By varying the PWM duty cycle over time, the output voltage pulses form a waveform that resembles a sine wave (see execution_table step 5).

Why is the switch state 'All OFF' at the start and end of simulation?

The simulation initializes and ends with switches off to represent no output and safe conditions (see execution_table steps 1 and 6).

Visual Quiz - 3 Questions

Look at the execution table, what is the switch state at step 3?

A Toggling

B Switch ON

C Switch OFF

D All OFF

💡 Hint

Check the 'Switch State' column at step 3 in the execution_table.

At which step does the output voltage first approximate 100V?

A Step 2

B Step 3

C Step 1

D Step 6

💡 Hint

Look at the 'Output Voltage' column in the execution_table for when voltage changes from 0.

If the PWM signal stayed OFF all the time, what would the output voltage be?

A Approx 100V pulsed

B 0V

C Sine-like AC voltage

D Constant DC voltage

💡 Hint

Refer to the 'PWM Signal' and 'Output Voltage' columns in the execution_table steps where PWM is OFF.

Concept Snapshot

Inverter simulation converts DC to AC using PWM.
PWM controls switches ON/OFF rapidly.
Output voltage pulses form AC waveform.
Measure voltage and current waveforms.
Simulation starts and ends with switches OFF.

Full Transcript

This inverter simulation starts by setting a DC input voltage. Then it generates PWM signals to control switching devices ON and OFF. These switches create pulsed output voltage approximating AC. The simulation measures output voltage and current waveforms. The switches start OFF, toggle during PWM cycles, and return OFF at the end. The output voltage changes from 0 to pulses near input voltage, forming a sine-like AC waveform. This process is repeated until the simulation ends and waveform data is saved.

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