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Models and methods for power system online dynamic contingency monitoring and control

University of British Columbia

Motivated by environmental concerns, DERs are progressively replacing conventional fossil fuel-based generators in modern power systems. This transition towards renewable generation lowers the overall system inertia and introduces variability and uncertainty that are unprecedented in conventional power systems. As a result, future power systems will have reshaped dynamics and increased risk of instability. To mitigate these challenges, we develop operational monitoring and control schemes that ensure reliable and efficient operation of power systems. These schemes enable real-time detection and identification of disturbances, offer tractable computational efficiency for fast dynamic contingency analysis, and utilize DERs and existing resources through optimal control strategies. Using a reduced-order system dynamic model, we develop an optimization-based method to detect, identify the location, and estimate the magnitude of load disturbances in the network. The proposed method requires measurements of only synchronous generator rotor speed variations which is enabled by leveraging the sparsity structure of load-change disturbances. Furthermore, a convex relaxation of the problem ensures that it can be solved online in a computationally efficient manner. Rapid variations in renewable generation are likely to cause large excursions away from the nominal operating point and frequent operational limit violations. To address this, we leverage a transfer-function representation of a reduced-order aggregate system model to derive analytical closed-form expressions that estimate bus frequencies and predict them under what-if contingency scenarios. Furthermore, we derive a dynamic version of distribution factors to predict dynamic line flows throughout the post-contingency transient period following a disturbance. These expressions offer advancement in dynamic contingency analysis by eliminating the need for repeated time-domain simulations. The widespread integration of DERs offers tremendous potential to provide ancillary services required to operate the bulk power system reliably. To this extent, we develop optimal controllers that aim to maximize the utilization of inverter-interfaced DERs and controllable loads. First, we propose a decentralized optimal controller to regulate line active-power flows while maintaining the nominal system frequency. Next, we propose an optimal controller to track feeder-head active- and reactive-power flows in distribution networks. The proposed control schemes offer intuitive tuning of design parameters and are susceptible to disturbances and measurement noise.

Text

2022-04-30

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/77824

Electrical and Computer Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/