Hybrid Residual Current Device and Solid State Circuit Breaker for Residential DC Microgrids

DC microgrids need fast and dependable methods for detecting residual current and protecting against overload and overcurrent. DC microgrids, often having hich capacitance and low inductance, are unsuitable for conventional fuses and electrothermal circuit breakers. Solid-state circuit breakers offer a solution that uses MOSFETs as the switching element. However, they also need reliable means of residual DC current measurement. Only a few established technologies for monitoring residual current can be directly applied in DC grids. A fluxgate, Hall effect sensor, or other active sensor technology is required to measure the tiny leakage currents in DC grids. The Hall effect sensors utilize low power consumption and small physical dimensions. However, the fluxgate-based current sensors have superior linearity and accuracy. Hence, it is proposed to design a hybrid DC protection device that functions as a solid-state circuit breaker and residual current detector. In order to evaluate the proposed hybrid device, different residual current measurement methods were analyzed, the power circuit topology was chosen, and a compact prototype was constructed and tested in the laboratory. Conducted tests have proven its usability in residential 350 V DC microgrids and its ability to protect users from electric shock.