A new differential current-based fast fault detection and accurate fault distance calculation is proposed for photovoltaic (PV)-based DC microgrid. A multiterminal direct current (MTDC) distribution network is studied as an adequate solution for present low-voltage utility grid scenario, where local distributed generators (DGs) are incorporated primarily by power electronics based DC-DC converters, DC-AC voltage-source converters (VSCs). PV and diesel generator (as auxiliary source) are considered for cascaded common DC bus, and AC utility bus integration is achieved by VSC unit for the proposed MTDC network. DC microgrid protection is quite significant research focus due to the absence of well-defined standards. Poleto-pole, pole-to-ground, PV-side DC series and ground arc faults are basically considered as DC distribution network hazards. A discrete model differential current solution is considered to detect, classify and locate the faults by modified cumulative sum average approach. A comprehensive case study is presented with different DC loadings, to deliberate effectiveness of the proposed protection scheme in terms of percentage error and trip time (Ts). The result verification is conducted in MATLAB environment as well as TMS320C6713 digital signal processor-based test bench with the proposed multiple DGs based DC microgrid.
Using a new improved harmony search-based hybrid firefly algorithm (IHBFA), a comprehensive controller gain parameter estimation of all distributed resources-based microgrid is proposed. To ensure a fast convergence and to endeavour less randomisation to conventional firefly algorithm (FA), diversity of population is increased by an improved harmony search (HS) algorithm. To decrease local optima searching delay, a linear incremental pitch adjustment rate and exponential decaying bandwidth is considered for proposed HS-based hybrid FA. Photovoltaic (PV), an auxiliary battery energy storage system (BESS) with the second-order phase-locked loop control, is considered as a primary DG (DG1) for the proposed microgrid. Padѐ approximation delay-based governor control is used for the diesel generator unit, considered as a secondary DG (DG2). The overall gain optimisation improves the dynamic stability limits by minimising low-frequency network behaviour. The effectiveness of proposed IHBFA in terms of power oscillation damping and improved stability limits is clearly demonstrated for microgrid applications.
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