Design and implementation of a virtual capacitor based DC current suppression method for grid-connected inverters.

Area of Science:

• Electrical Engineering
• Power Systems
• Renewable Energy Integration

Background:

• Grid-connected inverters, essential for renewable energy (RE) integration, can inject undesirable DC components into the power grid.
• This DC injection degrades power quality and violates international grid certification standards.

Purpose of the Study:

• To propose and validate a novel virtual-capacitor-based control technique for DC current suppression in grid-connected inverters.
• To address the limitations of existing methods, such as complex algorithms, power losses, and high costs.

Main Methods:

• Implementation of a virtual-capacitor control strategy within a 3-phase inverter interfaced with an LCL filter.
• Integration of active damping and grid voltage feedforward strategies for enhanced control.
• Detailed analysis of inverter controller parameter design and allowable regions.

Main Results:

• The proposed virtual-capacitor technique demonstrates fast implementation and effective DC component suppression.
• Simulation and experimental results confirm successful mitigation of DC current injection.
• The system meets International Grid Certification standards for DC component limits.

Conclusions:

• The virtual-capacitor based DC current suppression control is a viable and efficient solution for grid-connected inverters.
• This technique offers a practical approach to improving power quality in renewable energy systems.
• The method provides a cost-effective and high-performance alternative to existing DC suppression techniques.