Maximum power extraction and DC-Bus voltage regulation in grid-connected PV/BES system using modified incremental...

Area of Science:

• Electrical Engineering
• Renewable Energy Systems
• Power Electronics

Background:

• Single-phase Photovoltaic/Battery Energy Storage (PV/BES) grid-connected systems face challenges with DC-Bus voltage ripples, leading to harmonics distortion, instability, and reduced power factor.
• Traditional use of electrolytic capacitors for ripple reduction results in short inverter lifetimes.
• Replacing electrolytic capacitors with film capacitors extends system lifetime but introduces output current oscillations and voltage drops due to low capacitance.

Purpose of the Study:

• To eliminate output current ripples and voltage fluctuations in PV/BES systems utilizing film capacitors.
• To enhance the dynamic performance and stability of grid-connected PV/BES systems.
• To enable the use of smaller, longer-lasting film capacitors in DC-Bus applications.

Main Methods:

• A modified incremental conductance (MIC) technique was developed to control the DC-DC boost converter for maximum power point tracking.
• A novel d-q current regulation technique, using flowchart decision logic, was implemented for DC-Bus control of both PV power and Battery Energy Storage (BES) state of charge (SOC).
• The Battery Energy Storage (BES) was integrated to improve dynamic performance and ensure stable energy harvest from PV modules under varying loads.

Main Results:

• The proposed MIC technique effectively reduced DC-Bus voltage overshoot to 1 V and undershoot to 2.5 V.
• Total Harmonic Distortion (THD) of the output current was maintained below 5%.
• The MIC technique demonstrated a superior average time response of 1.403 s for tracking the global peak under rising radiation, compared to traditional methods.

Conclusions:

• The developed d-q current control and MIC technique successfully eliminate voltage distortion and fluctuations in PV/BES systems.
• The integration of BES significantly improves the dynamic performance and reliability of the overall system.
• The proposed methods enable the use of small, cost-effective 10-µF bus capacitors, extending system lifetime and maintaining high power quality.