Implementation of Protection Features for a Modular Bidirectional Solid-State Battery Disconnector

The growing adoption of batteries with high voltages (HV), ranging from 400V to 800V, in Electric Vehicles (EV), coupled with the high load demand, necessitates enhanced circuit protection against over-current events and short-circuit faults. This is crucial to prevent damage to the connected wiring harness, battery, and loads. Conventional approaches like thermal fuses, DC contactors, and pyro-fuses are constrained by factors such as slow response times, degradation with fault occurrences, and the need for regular maintenance and replacement, respectively. In response to these limitations, this paper proposes the introduction of a compact, resettable, and bi-directional solid-state DC disconnector (SSD) as a solution to overcome these challenges. The proposed disconnector is based on an anti-series connection of Silicon Carbide (SiC) switches, which offer fast response times and operate under a wide voltage range. It can differentiate between over-current events and short-circuit faults and can be configured for different trip current threshold values. In addition to a Current-ADC-based sampling method for over-current detection, analog hardware path-based short circuit detection has been implemented for faster fault interruption. A variable inverse time-current characteristic trip curve, based on the I²t profile, has been implemented to prevent unintentional tripping during transient inrush current events. The paper also proposes a modular solid-state DC disconnector (SSD) to enhance reliability and scalability for high-current operation using low-power-rated devices and low-current-rated sensors in each module. The performance of the proposed SSD, with each module designed for a system rating of 800V/30 A, has been experimentally validated using both single and two-module operations for protection against over-current, short-circuit faults, and under-voltage protection.