A novel control strategy based on a look-up table for optimal operation of MTDC systems in post-contingency conditions

Abstract

Multi terminal VSC-HVDC systems are a promising solution to the problem of connecting offshore wind farms to AC grids. Optimal power sharing and appropriate control of DC-link voltages are essential and must be maintained during the operation of VSC-MTDC systems, particularly in post-contingency conditions. The traditional droop control methods cannot satisfy these requirements, and accordingly, this paper proposes a novel centralized control strategy based on a look-up table to ensure optimal power sharing and minimum DC voltage deviation immediately during post-contingency conditions by considering converter limits. It also reduces destructive effects (e.g., frequency deviation) on onshore AC grids and guarantees the stable operation of the entire MTDC system. The proposed look-up table is an array of data that relates operating conditions to optimal droop coefficients and is determined according to N-1 contingency analysis and a linearized system model. Stability constraints and contingencies such as wind power changes, converter outage, and DC line disconnection are considered in its formation procedure. Simulations performed on a 4-terminal VSC-MTDC system in the MATLAB-Simulink environment validate the effectiveness and superiority of the proposed control strategy.

Research on Adaptive Exponential Droop Control Strategy for VSC-MTDC System

“…At present, the control methods based on VSC-MTDC mainly include master-slave control [13,14], voltage droop control [15][16][17][18][19], voltage margin control [20], and combinations of these [21][22][23]. Different control strategies have different applications and scope.…”

Black Start and Voltage Establishment Strategy for PMSG-Based Wind Turbine

“…The power balance is achieved between two wind turbines with the power-sharing strategy and one common local load, but the power flow between the grid and generator of one single turbine needs to be balanced during the effect of the power-sharing strategy with two turbines. A novel centralized control strategy based on the look-up table to ensure optimal power sharing is proposed (Alavi and Ghazi, 2022), using the optimal results from the centralized controller and data in the look-up table to achieve the optimal active power-sharing between multiple turbines. Though the optimal control command is obtained from the available wind power, it can still be a good reference when it comes to power balance with loads.…”