Accurate Fault Analysis and Proposed Protection Scheme for Battery Energy Storage System Integrated with DC Microgrids

The paper introduces non-unit protection scheme for the battery energy storage system (BESS). BESS is considered a vital source for microgrid operation. The most important challenge faced by the DC microgrid is the growth of fault current and consequently the rising rate. Because of the BESS has larger fault current contribution, fast detecting and isolating for the faults at BESS are required. The developed protection scheme is based on local measurements without the need for communication channel. Consequently, the relay operation is enhanced from avoiding the delay and any failure can be occurred in the communication media. For an accurate and fast protection scheme, the current derivative at BESS is analytically derived. During high impedance faults, the current derivative can fail in fault detection. So, the relay sensitivity is improved by taking the voltage derivative as a complementary feature for fault detection and discrimination in such critical cases. The fault analysis was carried out by selecting proper threshold values for the voltage and current derivative. Validation of the protection scheme is presented for several cases including internal and external faults and the relay operation showed satisfied results in DC microgrid protection.