Global Optimal Stabilization of MT-HVDC Systems: Inverse Optimal Control Approach

Abstract

The stabilization problem of multi-terminal high-voltage direct current (MT-HVDC) systems feeding constant power loads is addressed in this paper using an inverse optimal control (IOC). A hierarchical control structure using a convex optimization model in the secondary control stage and the IOC in the primary control stage is proposed to determine the set of references that allows the stabilization of the network under load variations. The main advantage of the IOC is that this control method ensures the closed-loop stability of the whole MT-HVDC system using a control Lyapunov function to determine the optimal control law. Numerical results in a reduced version of the CIGRE MT-HVDC system show the effectiveness of the IOC to stabilize the system under large disturbance scenarios, such as short-circuit events and topology changes. All the simulations are carried out in the MATLAB/Simulink environment.

Hierarchical Control for DC Microgrids Using an Exact Feedback Controller with Integral Action

“…Numerical results in a multi-terminal high-voltage DC (i.e., MT-HVDC) grid confirm the effectiveness of including the integral action with respect to the pure proportional approach stated in [11]. Authors of [13] proposed the application of the inverse optimal control (IOC) design to stabilize MT-HVDC networks. The main contribution of these authors, as in [15], was the inclusion of an integral gain, thus maintaining the asymptotic stability properties of the studied controller.…”

“…The recent advancements in DC networks and their high-efficiency levels (compared with AC microgrids) served as our source of motivation to further research in this area and to contribute to the topic of employing the hierarchical control design to microgrid applications, where multiple constant power terminals are interconnected through a DC distribution grid [13]. Hierarchical controllers are complex systems that are entrusted with the safe operation of an electrical system where different dynamics interact; essentially, a hierarchical controller can be considered as the brain of an electrical network, since it takes decisions based on optimization concepts and sends these decisions to each controllable device to execute these orders in the physical layer of the grid [14].…”

Power Sharing Control Trends, Challenges, and Solutions in Multi-Terminal HVDC Systems: A Comprehensive Survey

“…This layer plays a crucial role in regulating power distribution. When renewable energy sources are used, it is able to effectively distribute energy by modifying the reference points for various components [39], [40]. Tertiary control acts as a mediator and translator between the primary and secondary levels of control.…”

An IDA-PBC Design with Integral Action for Output Voltage Regulation in an Interleaved Boost Converter for DC Microgrid Applications

“…Remark 1. The main characteristic of the dynamical model (2) is that it is possible to obtain a nonlinear feedback controller via passivity-based control that ensures the closed-loop stability in the sense of Lyapunov. This can be made by selecting an adequate desired dynamics to sustain its pH properties as presented in [29].…”

“…Recent advances in power electronics from high-to low-power voltages for direct current (DC) applications make owning DC distribution networks in medium and low voltage levels with high levels of efficiency possible [1,2]. Since DC distribution does not require reactive power and frequency concepts to operate, energy losses are inferior in these systems when compared with its traditional alternating current (AC) counterparts [3].…”