Power Quality Performance Analysis for Nonlinear Loads
Introduction
Non-linear loads, such as rectifiers and variable speed drives, can significantly distort the current waveform in power systems, leading to poor power quality. This distortion is quantified using THD, which measures the presence of harmonics in a signal. In this tutorial, we will create a Simulink model to simulate a power system with a non-linear load and analyze its impact on power quality.
1. Set Up the Working Directory
Create Folder: Create a folder named PowerQualityAnalysis in your documents directory.
Set Directory in MATLAB: Open MATLAB, change the current directory to this new folder.
2. Create and Save a Simulink Model
Open Simulink: Click on the Simulink button in MATLAB.
Create Blank Model: Click "Blank Model."
Save Model: Save as PowerQualityNonLinearLoads.
3. Add Components to the Model
Three-Phase Source:
Go to Simscape > Power Systems > Specialized Technology > Fundamental Blocks > Electrical Sources.
Drag Three-Phase Source into the model.
Measurement Blocks:
Go to Measurements and drag Current Measurement and Voltage Measurement blocks.
Universal Bridge:
Go to Power Electronics and drag Universal Bridge.
Diode and Load:
Add Diode and Series RLC Branch blocks.
Configure the Series RLC Branch as a resistor (1000 ohms).
4. Connect Components
Connect the three-phase source to the Universal Bridge.
Connect the bridge output to the R load.
Insert voltage and current measurement blocks.
5. Configure Scope
Add Scope Block:
Go to Simulink > Sinks and drag a Scope block.
Configure Scope:
Set to 2 input ports and enable logging to the workspace (Structure with time).
6. Add Power GUI Block
Go to Simscape > Power Systems > Specialized Technology > Fundamental Blocks and add PowerGUI.
7. Run Simulation
Set Simulation Time: Set to 0.4 seconds.
Run Simulation: Click the Run button.
8. Analyze Results
View Scope: Check the voltage and current waveforms.
FFT Analysis:
In PowerGUI, select FFT Analysis.
Use logged data and configure for 50 Hz.
Evaluate THD:
Display results to check THD of the source current.
Ensure THD is within acceptable limits (typically < 5%).
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