Distributed Optimal Power Flow for VSC-MTDC Meshed AC/DC Grids Using ALADIN

Abstract

Coordination of transmission and distribution power systems is increasingly critical in the context of the ongoing energy transition. However, traditional centralized energy management faces challenges related to privacy and/or sovereignty concerns, leading to growing research interests in distributed approaches. Nevertheless, solving distributed AC optimal power flow (OPF) problems encounters difficulties due to their nonlinearity and nonconvexity, making it challenging for state-of-the-art distributed approaches. To solve this issue, the present paper focuses on investigating the distributed AC OPF problem of generic integrated transmission-distribution (ITD) systems, considering complex grid topology, by employing a new variant of Augmented Lagrangian based Alternating Direction Inexact Newton method (ALADIN). In contrast to the standard ALADIN, we introduce a second-order correction into ALADIN to enhance its numerical robustness and properly convexify distribution subproblems within the ALADIN framework for computing efficiency. Moreover, a rigorous proof shows that the locally quadratic convergence rate can be preserved for solving the resulting distributed nonconvex problems. Extensive numerical simulations with varying problem sizes and grid topologies demonstrate the effectiveness of the proposed algorithm, outperforming state-of-the-art approaches in terms of numerical robustness, convergence speed, and scalability.

Assessment and Mitigation of DC Breaker Impacts on VSC-MTDC Grid Equipped With Power Flow Controller

“…An MTDC grid consists of multiple VSCs linked through a network of transmission lines which continues to function under contingency. In Europe, a large-scale MTDC grid called "SuperGrid" is under implementation to interconnect the European countries [4]. However, the MTDC grid concept raises several technical challenges related to the grid's control, operation, and protection.…”

Controllability and Flexibility of HVDC Converters in Hybrid AC/DC Grids: A Stochastic Approach

“…As the installed capacity of renewables continues to increase, reaching over 3 TW globally [4] with significant growth seen in the wind and photovoltaic power plants, grid operators are facing new uncertainties due to the intermittent generation of renewable electricity and unpredictable demand, which must be taken into consideration in both planning and operation of power systems. Given the fact that most renewable energy sources are located away from consumption centers, the transmission of the generated energy will increasingly be carried out by using High Voltage Direct Current (HVDC) lines [5]. There are several advantages of using HVDC transmission as an alternative to classical AC transmission, such as granting better controllability and flexibility in active and reactive power flows, lower transmission losses, and asynchronous grid connection [6]- [9].…”

Controllability and Flexibility of HVDC Converters in Hybrid AC/DC Grids: A Stochastic Approach

“…As the installed capacity of renewables continues to increase, reaching over 3 TW globally [4] with significant growth seen in the wind and photovoltaic power plants, grid operators are facing new uncertainties due to the intermittent generation of renewable electricity and unpredictable demand, which must be taken into consideration in both planning and operation of power systems. Given the fact that most renewable energy sources are located away from consumption centers, the transmission of the generated energy will increasingly be carried out by using High Voltage Direct Current (HVDC) lines [5]. There are several advantages of using HVDC transmission as an alternative to classical AC transmission, such as granting better controllability and flexibility in active and reactive power flows, lower transmission losses, asynchronous grid connection, and submarine transmission [6]- [9].…”