Frequency and voltage regulation in hybrid AC/DC networks
For power system engineers, this work addresses frequency and voltage regulation in hybrid AC/DC networks, offering improved control over existing methods.
This paper proposes decentralized primary and distributed secondary control schemes for interlinking converters in hybrid AC/DC networks, proving stability and demonstrating improved power-sharing compared to dual droop control, with simulations verifying convergence of AC frequencies and DC voltages to nominal values.
Hybrid AC/DC networks are a key technology for future electrical power systems, due to the increasing number of converter-based loads and distributed energy resources. In this paper, we consider the design of control schemes for hybrid AC/DC networks, focusing especially on the control of the interlinking converters (ILC(s)). We present two control schemes: firstly for decentralized primary control, and secondly, a distributed secondary controller. In the primary case, the stability of the controlled system is proven in a general hybrid AC/DC network which may include asynchronous AC subsystems. Furthermore, it is demonstrated that power-sharing across the AC/DC network is significantly improved compared to previously proposed dual droop control. The proposed scheme for secondary control guarantees the convergence of the AC system frequencies and the average DC voltage of each DC subsystem to their nominal values respectively. An optimal power allocation is also achieved at steady-state. The applicability and effectiveness of the proposed algorithms are verified by simulation on a test hybrid AC/DC network in MATLAB / Simscape Power Systems.