Distributed Secondary Control for Average Voltage Recovery and Current Sharing of DC MGs via a Fully Actuated Error...

Area of Science:

• Electrical Engineering
• Control Systems
• Renewable Energy Systems

Background:

• Converter-based multibus DC microgrids (MGs) face challenges in balancing voltage regulation and current sharing due to line impedance.
• Existing models for DC MGs often lack a balance between accuracy and simplicity, hindering model-based secondary control research.
• Voltage stability and power quality are crucial for MGs, while effective current sharing extends the lifespan of generation units.

Purpose of the Study:

• To develop a simplified yet accurate error model for DC MGs that incorporates circuit and inner control loop dynamics.
• To propose a distributed optimal control strategy to address the conflict between voltage regulation and current balancing.
• To validate the proposed model and control method through theoretical analysis and experimental implementation.

Main Methods:

• Development of a DC MG error model using the FA system theory, capturing power characteristics and control loop dynamics.
• Design of a distributed optimal control based on the unified regulation error for voltage recovery and current allocation.
• Stability analysis of the closed-loop MG system, including consensus analysis for current sharing and tracking analysis for average voltages.

Main Results:

• The proposed error model offers a novel approach by unifying voltage and current regulation objectives into a single error term.
• The distributed optimal control demonstrates effective voltage recovery and precise current allocation, resolving the inherent conflict.
• Theoretical analyses confirm the stability of the closed-loop system and the effectiveness of current sharing and voltage tracking.

Conclusions:

• The developed error model and distributed optimal control provide a robust and efficient solution for managing converter-based DC MGs.
• The unified approach simplifies control design while improving performance in terms of voltage stability and current sharing.
• Experimental validation on a laboratory-scale MG prototype confirms the practical applicability and effectiveness of the proposed method.