Design of a Test Bench for 1.5kV Solid State Circuit Breaker for Transport Electrification

This paper deals with the detailed design and laboratory testing methodology for a 1.5kV/70A Solid State Circuit Breaker (SSCB) for Medium Voltage Direct Current (MVDC) applications. The paper reviews the parameters and characteristics of wide bandgap semiconductors suitable for the protection of MVDC circuits. This consisting of detailed design process for the selection of the main MOSFET, transient voltage suppressors (TVS) to achieve the allowable voltage transient, current sensor, gate driver, and current limiting inductor for the selected di/dt limit. The laboratory testing methodology uses fast-acting IGBTs which allows for the application of short circuit faults in a controlled environment. The stiff DC grid is created by using an appropriately sized capacitor that holds energy of which only 1% is used for testing. The whole test bench has to be kept in an enclosure that is only opened once the capacitor voltage reaches a safe level. This is first of kind effort to achieve the short circuit fault clearing time of less than 2μs for an MVDC application.

I. Introduction

T he increased electrification of transport has pushed the wider adoption of power converters that favour the power delivery of by Low Voltage Direct Current (LVDC) or Medium Voltage Direct Current (MVDC) grid systems. The main benefits often mentioned in literature are the improved efficiency, reduced parts usage, improved reliability, controllability and decreased cost of the system. LVDC is well-defined in European Union (EU) LV directive (2014/35/EU) & comprises volts of 75 to 1.5 kV DC [1]–[2]. The CIGRE Working Group SC6.31 established in 2015, aimed to conduct comprehensive feasibility study on MVDC grids. This group comprised of 35 domain experts from 14 different countries representing a diverse array of stakeholders including electrical transmission and distribution companies, academia, research institutes and manufacturers. The working group focused on the MVDC distribution system that fall within the voltage range of 1. to . This voltage range addresses the gap between HVDC systems and LVDC systems under the IEC SyC LVDC [3].