Simulation of Cascading Outages Using a Power-Flow Model Considering Frequency

Abstract

Many steady-state power-flow-based models for cascading outage simulation have not considered frequency, which, however, is an important indicator of generation-load imbalance. This paper proposes a novel steady-state approach for simulating cascading outages. The approach employs a power-flow-based model that considers static power-frequency characteristics of both generators and loads. Thus, the frequency deviation due to active power imbalance can be calculated under cascading outages. Furthermore, a new ac optimal power-flow model considering frequency deviation is proposed to simulate the remedial control when system collapse happens as indicated by the divergence of power flows. Case studies first benchmark the steady-state frequency calculated by the power-flow-based model with time-domain simulation results on a two-area power system, and then test the proposed approach for simulation of cascading outages on the IEEE 39-bus system and an NPCC 48-machine 140-bus power system. The test results are compared with a traditional frequency-independent approach using the conventional power flow and ac optimal power-flow models, and verify that by capturing frequency variations under cascading outages, the proposed approach can more accurately simulate the mechanism of outage propagation.

Keywords

• Cascading outages
• cascading failures
• dynamic load flow
• ac optimal power flow considering frequency deviation
• frequency
• under-frequency load shedding