Abstract
This paper proposes a novel application for the optimal Linear Quadratic Gaussian (LQG) servo controller to enable a proper coordination of the AC/HVDC interconnected system with Virtual Synchronous Power (VSP) based inertia emulation. Particularly, the proposed control design takes the process disturbances and measurement noise of the studied VSP-HVDC system into account, while few studies have focused on this perspective. The proposed LQG controller with modifications is designed by means of a combination of Kalman Filter (state estimator) and an added Linear Quadratic Integrator (LQI) to observe the system model’s states and track the reference commands while rejecting the effects of system noise. Besides, we utilize a swarm-based optimization algorithm to operate as the search process for the tuning of the elements in the weighting matrices involved in the controller design. The role of the proposed optimal LQG controller is to stabilize such AC/DC interconnected system with VSP-based inertia emulator while minimizing the associated performance index. According to the obtained simulation results, in addition to the advancement from the VSP-based approach for damping frequency oscillations excited by faults, application of the proposed LQG servo controller can achieve the targets on both estimating the state variables and tracking the reference signals with satisfactory performance, comparing with the conventional LQG regulator.
Highlights
Frequency control considering different approaches for enhancing its dynamic performance is the key to stability of modern power systems with low inertia [1,2,3]
This paper proposes a novel application for the optimal Linear Quadratic Gaussian (LQG) servo controller to enable a proper coordination of the AC/HVDC interconnected system with Virtual Synchronous Power (VSP) based inertia emulation
According to the obtained simulation results, in addition to the advancement from the VSP-based approach for damping frequency oscillations excited by faults, application of the proposed LQG servo controller can achieve the targets on both estimating the state variables and tracking the reference signals with satisfactory performance, comparing with the conventional LQG regulator
Summary
Frequency control considering different approaches for enhancing its dynamic performance is the key to stability of modern power systems with low inertia [1,2,3]. The main objectives for modeling and controlling of this type of system are: (i) rejecting possible disturbances and noise which could appear in the practice of the VSP-HVDC system and affect system stability, while few studies have focused on this perspective; (ii) defining a suitable model with a global feedback law to enable a proper coordination between the VSP station and the rest of the AC/DC system for a stabilization and dynamic improvement of system dynamics To achieve these targets, the design of an optimal regulator for a novel application on the AC/DC interconnected system with VSP-based inertia emulation will be proposed. Such noise might still lead to instability problems in the task of frequency control enabled by VSP for inertia emulation To resolve this tracking issue, in this paper, a modification of the aforementioned LQG servo controller has been performed by incorporating the Kalman Filter (state estimator) with a Linear Quadratic Integrator (LQI). The VSP approach for inertia emulation through the converter stations of the HVDC links in a multi-area AC/DC inter connected system will be presented
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