Optimization-Based Capacitor Balancing Method with Selective DC Current Ripple Reduction for CHB Converters

Area of Science:

• Electrical Engineering
• Power Electronics
• Renewable Energy Systems

Background:

• Cascaded H-Bridge (CHB) multilevel converters are widely used but require capacitor balancing due to floating DC-link capacitors.
• Existing balancing methods often use optimization or zero-sequence voltage injection, leveraging converter redundancies.

Purpose of the Study:

• To introduce an advanced optimization-based capacitor balancing method for CHB converters.
• To enhance converter adaptability for diverse applications like photovoltaic (PV) systems and energy storage.

Main Methods:

• Development of an optimization-based control strategy for capacitor voltage balancing.
• Implementation of features for independent DC-link voltage control and active power set-point management.
• Reduction of DC current ripple in specific modules to enhance component lifespan.

Main Results:

• The proposed method demonstrates superior speed, robustness, and current wave quality compared to state-of-the-art techniques.
• Achieved comparable or better performance with significantly fewer switching operations (approximately 1/3 less).
• Validated through real hardware testing, confirming its practical applicability and effectiveness.

Conclusions:

• The novel balancing method significantly improves CHB converter performance and adaptability.
• Enables advanced functionalities such as independent maximum power point tracking (MPPT) in PV applications and flexible power control for energy storage.
• Offers a robust and efficient solution for CHB converter capacitor balancing, extending component life and improving overall system efficiency.