This paper proposes a one-terminal traveling wave (TW)-based transmission line earth fault distance protection function. It only needs the detection of the first incident modal earth fault-induced TWs, so that, the challenging detection of wavefronts reflected from the fault point is not required. Both the sampling frequency effect and inaccuracies on the wave propagation velocity are considered in order to define the distance protection zone. Simulated fault records were played back in an actual relay, allowing the comparison between a commercially existing time-domain distance protection element and the proposed one. The proposed function is more accurate and significantly reduces transmission line distance protection tripping times without dependability losses.

A microgrid consists of a grid capable of operating in connection to the main interconnected power system or in island mode. This paper deals with a microgrid containing a small hydroelectric power plant (HPP), a battery energy storage system (BESS), a wind energy conversion system (WECS), and a photovoltaic array (PV). The WECS and PV systems are connected to the grid through one full-power voltage source converter (VSC). In order to provide frequency and voltage supports to the microgrid, the VSC is controlled by a virtual synchronous generator (VSG) technique of synchronverter. The considered scenario was divided into three parts: first, the microgrid operates connected to the main system and then it starts operating in island mode; posteriorly, frequency and voltage variations occur due to load variations in the microgrid; finally, the microgrid returns to operate connected to the interconected system. Simulation results have shown that the synchronverter is an alternative to provide efficient frequency and voltage control to a microgrid for both connected and island modes, considering a hybrid generation unit.

High voltage direct current (HVDC) systems are an alternative for transmission of energy with higher efficiency and lower electrical losses over long distances. HVDC systems have become more common with the evolution of power electronics, promoting the interest of research in power flow control techniques. The main objective of this paper is to perform evaluations of the power flow in a meshed multiterminal HVDC (MT-HVDC) system based on the multilevel modular converter (MMC). Two different control strategies were considered; The margin voltage; and the voltage droop strategies. Two assessment scenarios were considered: when an active power reference takes place in the system; and when a DC transmission line is open-circuit due to a failure in the DC grid. For both of these test cases, the system with the margin voltage control obtained a new balance of power flow with less oscillations in power andvoltage than the one with the voltage droop control.

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