Coordinated Frequency Control through MTDC Transmission Systems

TL;DR

This paper introduces a distributed control method for multi-terminal HVDC systems that ensures frequency stability, optimizes power generation costs, and maintains voltage levels across asynchronous AC grids.

Contribution

It presents a novel distributed dynamic controller that guarantees stability, optimal reserve sharing, and voltage regulation in MTDC-connected asynchronous AC systems.

Findings

Controller guarantees frequency convergence to nominal values.

Optimal distribution of generation reserves achieved.

Voltage deviations are minimized asymptotically.

Abstract

In this paper we propose a distributed dynamic controller for sharing frequency control reserves of asynchronous AC systems connected through a multi-terminal HVDC (MTDC) grid. We derive sufficient stability conditions, which guarantee that the frequencies of the AC systems converge to the nominal frequency. Simultaneously, the global quadratic cost of power generation is minimized, resulting in an optimal distribution of generation control reserves. The proposed controller also regulates the voltages of the MTDC grid, asymptotically minimizing a quadratic cost function of the deviations from the nominal voltages. The proposed controller is tested on a high-order dynamic model of a power system consisting of asynchronous AC grids, modelled as IEEE 14 bus networks, connected through a six-terminal HVDC grid. The performance of the controller is successfully evaluated through simulation.