Effective current derivative protection scheme for LVDC grids based on discrete wavelet transform

DC grids offer unique advantages compared to conventional AC grids. However, these grids face protection challenges that impede their widespread. To fully leverage the potential of DC grids, this paper presents an effective signal processing-based protection scheme for these grids. The proposed protection scheme is tailored for complex LVDC grid topologies, particularly those with meshed topologies. It utilizes the discrete wavelet transformation of the first derivative of the current. The scheme utilizes the mean value of the level-one detail coefficients as the fault detection signal, offering a computationally efficient alternative to more complex metrics which are commonly used in existing schemes. Unlike other approaches, the proposed method does not require any additional hardware components. It relies solely on local current measurements avoiding communications that may introduce latency. The proposed scheme achieves ultra-fast fault detection in terms of microseconds, ensuring timely protection of sensitive power electronic components. The threshold settings are independent of the grid operation mode, either grid-connected or island mode highlighting its resilience to different operating conditions. In addition, the faulty cable can be identified through the selectivity of the proposed scheme. The scheme's robust performance across various grid configurations highlights its reliability and adaptability to diverse operating conditions.