Harmonic Reduction in Grid-Connected PV System with Double Tuned Filter in MATLAB
- lms editor
- Aug 16, 2025
- 2 min read
In modern renewable energy systems, power quality plays a vital role in ensuring stable and efficient grid operation. One of the major issues in grid-connected PV (photovoltaic) systems is the presence of harmonics, especially when nonlinear loads are involved. High Total Harmonic Distortion (THD) can lead to overheating, reduced efficiency, and failure of electrical equipment. In this article, we explore how double-tuned filters can effectively mitigate harmonics in a MATLAB/Simulink-based PV system.
📌 Introduction to the System
The simulated model consists of:
PV Panel with MPPT control using the Perturb and Observe (P&O) algorithm.
Boost Converter designed to step up PV output voltage from ~319 V to 600 V.
Voltage Source Inverter (VSI) with dual-loop control (voltage loop and current loop).
Grid Connection with a nonlinear load.
Double-Tuned Filter targeting specific harmonic orders.
The point of common coupling (PCC) serves as the connection between the inverter, load, and grid.
🔋 Maximum Power Point Tracking (MPPT) Control
The boost converter’s duty cycle is dynamically adjusted based on:
PV voltage (VPVV_{PV}VPV)
PV current (IPVI_{PV}IPV)
Change in power (ΔP)
Change in voltage (ΔV)
This ensures the PV array operates at its maximum power point, yielding ~3.048 MW under standard conditions (1000 W/m²).
⚡ Inverter Control Strategy
The inverter uses DQ-axis control:
Voltage Control Loop – Regulates DC link voltage at 600 V to generate the reference D-axis current (ID∗I_D^*ID∗).
Current Control Loop – Compares actual DQ currents to references, processes through a PI controller, and generates sinusoidal PWM switching pulses.
Park & Inverse Park Transformation – Converts between ABC and DQ reference frames for effective control.
📉 Harmonic Distortion Without Filtering
Three simulation cases were analyzed:
Without Nonlinear Load & Filter –Grid current THD ≈ 4.65% (acceptable as per IEEE-519 standard).
With Nonlinear Load & No Filter –Grid current THD rises to ≈ 7.87%, exceeding the 5% limit.
🎯 Double-Tuned Filter for Harmonic Reduction
Analysis revealed that 5th and 7th harmonics had the highest magnitude.A double-tuned passive filter was designed with:
Grid voltage: 400 V
Frequency: 50 Hz
Tuned to: 5th and 7th harmonics
Capacitance and inductance values derived from grid parameters.
After implementing the filter:
Grid current became almost sinusoidal.
THD reduced to 4.57%, bringing it back within IEEE-519 limits.
✅ Key Takeaways
Nonlinear loads in PV systems significantly degrade grid current quality.
Double-tuned filters are effective for targeted harmonic suppression.
MATLAB/Simulink is a powerful tool for system design, control, and validation.
Maintaining THD < 5% ensures compliance with international standards and enhances system reliability.
📌 Final Thoughts
As the integration of renewable energy into power grids continues to grow, harmonic mitigation techniques will play a crucial role in maintaining power quality. Double-tuned filters provide a cost-effective and targeted solution for harmonic reduction, especially in PV-grid systems with nonlinear loads.
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