Abstract
The demand for a low voltage direct current (LVDC) microgrid is increasing by the increase of DC-based digital loads and renewable resources and the rapid development of power electronics technology. For the stable operation of an LVDC microgrid, it is necessary to develop a protection method. In this paper, the new protection scheme considering the fault section is proposed using wavelet transform (WT) in an LVDC microgrid. The fault sections are classified into DC side of the alternating current (AC)/DC converter, DC/DC converter connected to photovoltaic (PV) system, DC line, and DC bus. The characteristics of fault current at each fault section are analyzed. Based on these analyses, the new protection scheme including the fault section estimation is proposed using WT. The proposed scheme estimates the fault section using the detail component after performing WT and sends the trip signal to each circuit breaker according to the fault section. The proposed protection scheme is verified through various simulations according to the fault region and fault current using electromagnetic transient program (EMTP)/ATPDraw and MATLAB. The simulation results show that the fault section is accurately determined, and the corresponding circuit breaker (CB) operations are performed.
Highlights
Energies 2022, 15, 283. https://The demand for the development of a low voltage direct current (LVDC) distribution technology is increasing with expectations for the rapid development of power conversion technology, the increase in direct current (DC)-based digital loads, and the expansion of DC-based renewable energy, energy storage devices, and electric vehicles
We have focused on the protection technology to judge electrical faults, to isolate the fault sections, and to maintain the normal power supply to non-faulted sections
In CB3, the fault current flows in the opposite direction to the steady state owing to the discharge of the capacitor of the DC/DC converter connected to the load
Summary
The demand for the development of a low voltage direct current (LVDC) distribution technology is increasing with expectations for the rapid development of power conversion technology, the increase in direct current (DC)-based digital loads, and the expansion of DC-based renewable energy, energy storage devices, and electric vehicles. In [7], a method to detect and locate DC faults was proposed using several intelligent relays based on the DC current direction and combined with controllable solid-state circuit breakers. In [15], a protection method in a ring-bus LVDC microgrid with intelligent electronic equipment and a solid-state circuit breaker was proposed. In [18], a new protection method was proposed combining the change in voltage (dv/dt) and the change in current (di/dt). These previous studies have suggested fault detection methods, but have not proposed an adaptive protection method in connection with the fault section determination.
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