Power Flow Analysis of MMC-HVDC System with Margin Voltage and Voltage Droop Control Strategies

Abstract

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.