Modeling of Frequency Security Constraints and Quantification of Frequency Control Reserve Requirements for Unit Commitment

TL;DR

This paper proposes an adaptive method for optimizing frequency security constraints and reserve requirements in unit commitment, using copula theory and robust optimization to enhance system reliability and efficiency.

Contribution

It introduces a novel approach combining copula-based joint distribution modeling and distributionally robust optimization for frequency reserve quantification in unit commitment.

Findings

Optimal PFC droop gain improves economic efficiency.

Proposed reserve requirement is more accurate than historical data.

Method enhances operational flexibility and system security.

Abstract

The high penetration of converter-based renewable energy sources has brought challenges to the power system frequency control. It is essential to consider the frequency security constraints and frequency control reserve requirements in unit commitment (UC). Considering that the risk of frequency insecurity varies under the changeable operational condition, we propose to optimize the PFC droop gains and reserve capacities in the UC model to provide diverse control efforts in different risk levels adaptively. Copula theory is used to establish the joint distribution model among frequency control performance, secondary frequency control (SFC) reserve capacities, and power fluctuations. Then the distributionally robust optimization technique is utilized in the SFC reserve requirement determination to handle the possible error in the probability model. The UC simulation is conducted on IEEE 118-bus system to test the proposed optimal PFC droop gain strategy and SFC reserve requirement quantification method. Simulation results show that the proposed optimal PFC droop gain strategy is better than the traditional fixed PFC droop gain setting on economic efficiency and operational flexibility. Besides, the SFC reserve requirement calculated by the proposed method is more appropriate than the actual SFC reserve capacity in the historical operation.