Active gate drive based hybrid MVDC circuit breaker with a modular architecture for flexible voltage and current ratings

Abstract

MVDC networks present an effective means for integrating renewable-based Distributed Generators into the power network. Protection of Medium Voltage Direct Current (MVDC) networks presents significant challenges, including the absence of natural zero crossings, rapid fault current rise, and a lack of MVDC-compatible protection devices, standards, guidelines, and practical experience. Solid-state DC Circuit Breakers (DCCBs) have emerged as an attractive protection solution for DC networks, offering fast and reliable fault isolation. Seamless integration of DCCBs into MVDC networks is challenging due to the diverse voltage and power levels and varying network architectures. Furthermore, the limited current and voltage capability of semiconductor devices limits the full integration of solid-state DCCBs for MVDC applications. Series and parallel-connected IGBT arrays can be employed to match the required current and voltage levels. However, with passive gate drives, devices may fail due to non-homogeneous current and voltage distribution across IGBTs. Closed-loop Active Gate Drives (AGDs) offer a solution to overcome these challenges. This research aims to develop an AGD scheme that drives IGBTs with status feedback, allowing them to follow a set current/voltage trajectory during IGBT switching. Hybrid Circuit Breaker (HCB) architecture, based on standardized Active Switch Modules (ASMs), is proposed as a flexible protection solution for MVDC networks. Steady-state current imbalances in parallel-connected IGBTs can lead to thermal runaway conditions and degrade the IGBTs. Conventional steady-state current balancing methods rely on device matching and passive gate drive concepts, which are inadequate for modern MVDC applications. The proposed Active Current Balancing (ACB) scheme actively regulates the gate-drive voltage of each device based on measured current deviations, enabling precise control of the static operating point. The integrated operation of ACB-AGD schemes within a unified framework provides a practical and scalable solution for voltage and current management in MVDC-DCCB applications. Experimental validation on a unidirectional DCCB prototype confirms that the integrated ACB-AGD system maintains stable switching behavior while effectively correcting steady-state current imbalance. Collectively, the proposed ACB, AGD, and modular HCB architecture establish a scalable protection framework capable of delivering enhanced dynamic switching performance, steady-state current sharing, and secure fault-interruption capability for next generation MVDC networks.