Adaptive observer-based nonlinear control of grid-tied PV-fed multicell inverter with harmonic mitigation capability

Area of Science:

• Electrical Engineering
• Power Electronics
• Control Systems

Background:

• Grid-connected photovoltaic (PV) systems require robust control for stable power injection.
• Harmonic currents in distorted electrical grids degrade power quality and system efficiency.
• Single-stage PV systems offer simplicity but face challenges in power quality management.

Purpose of the Study:

• To develop an adaptive nonlinear control strategy for single-stage grid-connected PV systems.
• To mitigate harmonic currents in highly distorted electrical grids.
• To improve power quality, maximize power extraction, reduce voltage stress, and achieve power factor correction.

Main Methods:

• Utilized a multilevel inverter topology for enhanced power quality.
• Implemented a dual-loop control structure for system objectives.
• Incorporated an adaptive observer for real-time grid voltage and impedance estimation.
• Employed Lyapunov stability theory for controller design and analysis.

Main Results:

• The adaptive observer effectively estimated grid voltage and impedance under dynamic conditions.
• The dual-loop controller successfully achieved maximum power extraction from PV arrays.
• Harmonic current mitigation was demonstrated, improving overall power quality.
• Reduced voltage stress on switching devices was observed.
• Power factor correction was achieved.

Conclusions:

• The proposed adaptive nonlinear control is effective for single-stage PV systems in distorted grids.
• The system enhances power quality, efficiency, and reliability.
• Simulation and Processor-In-the-Loop (PIL) results validate the controller's performance.