MATLAB Simulink for Power Electronics

§ 01

Introduction

This experiment introduces Power Electronics circuit simulation using MATLAB Simulink. A half-wave diode rectifier is simulated and the results are verified experimentally. The laboratory bridges theoretical knowledge with practical measurement techniques using industry-standard tools.

§ 02

Learning Outcomes

1Simulink Simulation

Build and simulate power electronic circuits using the Simscape Specialized Power Systems library.

2Powergui Analysis

Extract DC average, RMS values, harmonic content, and THD using the Powergui FFT Analysis tool.

3Hardware Verification

Implement the circuit in hardware using the Power Module kit and compare with DSO measurements.

§ 03

Familiarization with MATLAB / Simulink

Launch MATLAB and click New → Simulink Model. Save the new .slx file.
Open the Simulink Library Browser from the toolbar.
Navigate to Simscape → Electrical → Specialized Power Systems → Fundamental Blocks → Power Electronics.
Drag and connect components. Use Voltage/Current Measurement blocks and a Scope.
Add a Powergui block (required). Configure scope logging: enable Log data to workspace (Structure with time).

Fig. 1 — MATLAB launch screen. Click New or Simulink to begin.

Simulink blank model — Fig. 2 — Click Blank Model and save the `.slx` file.

Simscape library path — Fig. 4 — Simscape → Electrical → Specialized Power Systems.

Fig. 5 — Fundamental Blocks → Power Electronics.

Power Electronics blocks — Fig. 6 — Diode, Thyristor, IGBT, MOSFET blocks.

Sources and measurements — Fig. 7 — AC Voltage Source and Measurement blocks.

§ 04

Problem 1 — Half-Wave Rectifier with R Load

Problem Statement

Implement a 1-phase half-wave diode rectifier with R = 100 Ω. Input: \(V_{peak} = 50\text{ V}\) (35.35 V RMS), 50 Hz. Observe waveforms and perform FFT analysis.

Key formulas:

\(V_{dc} = V_m/\pi\)
\(V_{rms} = V_m/2\)
Form Factor \(= V_{rms}/V_{dc} = \pi/2 \approx 1.571\)

Simulink procedure:

Run simulation for 0.5 s
Observe waveforms in Scope
Use Powergui FFT for harmonic analysis

Half-wave rectifier circuit — Fig. 8 — Half-wave diode rectifier circuit diagram.

Simulink model — Fig. 9 — Simulink implementation with measurement blocks.

Scope logging configuration — Fig. 10 — Scope: enable Log data to workspace for FFT.

Simulated waveforms — Fig. 11 — Sample waveforms: input voltage, output voltage, diode current.

§ 05

FFT Analysis using Powergui

Double-click Powergui → select FFT Analysis.
Select the workspace variable and the signal to analyse.
Set Fundamental frequency = 50 Hz; choose Bar or List display.
Record V_fundamental, THD, 2nd and 3rd harmonic values.

Tip: Uncheck "Limit data points to last" in scope settings so the full waveform is available for accurate FFT analysis.

Powergui FFT bar chart — Fig. 12 — Powergui FFT window: harmonic bar chart.

Fig. 13 — FFT list view showing harmonic amplitudes.

Performance Metrics

\[\text{FF} = \frac{V_{rms}}{V_{dc}},\quad \text{RF} = \sqrt{\text{FF}^2 - 1},\quad \text{THD} = \sqrt{\frac{V_{AC,rms}^2 - V_{1,rms}^2}{V_{1,rms}^2}}\times 100\%\]

where \(V_{AC,rms} = \sqrt{V_{rms}^2 - V_{avg}^2}\).

§ 06

Problem 2 — Half-Wave Rectifier with RL Load

Problem Statement

Repeat with R = 100 Ω, L = 6 mH. Observe the effect of inductance: extended conduction angle and smoother current waveform.

Key Observation: Inductance extends diode conduction beyond the zero-crossing of source voltage. The output current becomes smoother, reducing the ripple factor.

§ 07

Hardware Implementation

🔌 Power Supply Module

Variable AC supply with push-button voltage adjustment. Set to 35.35 V RMS. MCB must be ON before voltage adjustments show on display.

⚡ SCR–Diode Power Module

Houses all power semiconductor devices: MCB, firing signal I/O, thyristors, and diodes. Connected via banana-plug terminals.

Power supply module — Fig. 14 — Power Supply Module with ± push buttons for fine voltage adjustment.

SCR-Diode Power Module — Fig. 15 — SCR–Diode Power Module housing all power semiconductors.

Hardware circuit R load — Fig. 16 — Hardware circuit: half-wave rectifier with R load (100 Ω).

Hardware circuit RL load — Fig. 17 — Hardware circuit: half-wave rectifier with RL load (100 Ω, 6 mH).

Procedure (R Load)

Connect circuit as in Fig. 16 (R = 100 Ω). Switch ON the 3φ supply MCB.
Switch ON POWER MODULE MCB, then SCR–Diode Power Module MCB.
Slowly increase voltage to 35.35 V RMS using + push button.
Connect CRO probes across R load. Observe waveforms and FFT in DSO; save to USB.

Procedure (RL Load)

Replace R load with RL load: R = 100 Ω, L = 6 mH (Fig. 17).
Repeat steps 2–4 above. Note the difference in waveform due to inductance.

§ 08

Results

Attach waveforms: (a) Output Voltage (b) Output Current (c) Diode Voltage (d) Diode Current (e) Input Voltage — in Simulink and experimentally.

Performance Parameters — R & RL Load (Simulink)

Parameter	R Load — Theory	R Load — Simulation	R Load — Hardware	RL Load — Theory	RL Load — Simulation
V_RMS (V)
I_RMS (A)
V_AVG (V)
I_AVG (A)
Form Factor
Ripple Factor
PIV (V)

FFT Analysis

Parameter	R Load — Sim	R Load — HW	RL Load — Sim
V_fundamental (RMS)
V_THD (%)
V 2nd Harmonic
V 3rd Harmonic
I_fundamental (RMS)
I_THD (%)
I 2nd Harmonic
I 3rd Harmonic