The multi-terminal High voltage Direct Current (HVDC) using voltage source converters (VSC) is proposed for interconnecting the renewable energy source such as offshore wind farms because it can facilitate the transnational exchange with high-cost efficiency. This paper analyses a model of three terminals VSC-HVDC system with a Voltage Margin control strategy using PSCAD/EMTDC simulation software. First, the paper begins with an overview of the development of Multi-terminal direct current system. The second part presents a review of the methodology that controls MTDC grids named Voltage Margin control. The simulation is performed to confirm the proposed Voltage margin control strategy.

This paper investigates the steady-state and transient performance of high-voltage DC (HVDC) transmission systems connected to passive network. The VSC HVDC tie employing PWM may well represent the ultimate FACTS device. In addition to the control of the active power flow, it can supply reactive power and provide independent dynamic control at its two terminals. The control systems for rectifier and inverter are discussed in DC (HVDC) transmission systems based on three-level voltage source converters. The study involves analysis of active-reactive power capabilities (P-Q envelope) including active power flow and provision of voltage support to AC networks. The transient performance is explored by examining the VSC_HVDC response to external AC faults. Finally, the models and results are presented and tested by simulations using Matlab Simulink and its toolbox SimPowerSystems.

The rising power demand has forced power systems all over the world to operate very close to their stability limits. When power systems are overloaded, faulty, or in lack of reactive power, voltage collapses would ensue. The capacity of a power system to keep the voltage of every bus constant under disturbances is called voltage stability. This dynamic phenomenon hinges on the load features. It is commonly known that flexible AC transmission systems (FACTS) can improve voltage stability. This paper puts forward a load flow model with the unified power flow controller (UPFC), and relies on the model to investigate the voltage stability of a power system through continuation power flow (CPF) method. The validity of the model was verified through a simulation, using the power system analysis toolbox (PSAT) in MATLAB/Simulink environment.

The development of renewable energies and in particular offshore wind energy as well as the multiplication of High Voltage Direct Current (HVDC) links leads us to consider the building of a multi-terminal HVDC based on Voltage Source Converter (VSC). In this paper, a four terminals HVDC network with droop control are investigated using PSCAD/ EMTDC simulation software. This strategy is applied for MTDC network under the change of the active power, then transient operation conditions. First, the paper begins with a review of the methodology that controls MTDC grids the so-called DC voltage Droop control. The second parte describes the configuration and parameters of four terminals HVDC. Finally, a simulation case study is presented to verify the proposed control strategy.

The VSC HVDC back-to-back arrangement is used when two asynchronous AC systems need to be interconnected for bulk power transmission or for AC system stabilization reasons. Besides controlling the through power flow, it can supply reactive power and provide independent dynamic control at its two terminals. This paper investigates the steady-state and transient performance of high-voltage DC (HVDC) back-to-back transmission systems based on three-level voltage source converters. The study involves analysis of active-reactive power capabilities (P-Q envelope) including active power reversal and provision of voltage support to AC networks. The transient performance is explored by examining the VSC_HVDC response to external AC faults. Finally, the models and results are presented and tested by simulations using Matlab Simulink and its toolbox SimPowerSystems.