Abstract
Frequency security is vital to the safety of power systems and has been scrutinized for many years. The conventional frequency security analysis only checks whether the frequency after anticipated initial failures can remain in the normal range based on some aggregated models, but the influence of potential cascading failures has not been considered yet. This is not enough, especially when the modern power system suffers the increasing threat of cascading failures. Therefore, this paper proposes a novel frequency simulation model considering the influence of cascading failure to reveal the security level of power systems comprehensively. The proposed model is based on a platform on which the frequency dynamics and the power flow distributions can be calculated jointly. Moreover, simulation models of protection devices and some supervisory operation-control schemes are also taken into account. Case studies validate the effectiveness of the proposed model on the IEEE 39-bus system. Moreover, the results of some further probabilistic simulations under different operation parameters are obtained, which show the great significance of improving the frequency regulation performance to cope with challenges of blackouts.
Highlights
Frequency security has been the focus of power system operation for a long time
In order to further reveal the impact of frequency insecurity, exhaustive screening for all N-2 initial branch outages is made to obtain the samples
The frequency insecurity becomes a more dominant factor when load loss of the power blackout increases. These results demonstrate the threat of frequency insecurity to the power system
Summary
Frequency security has been the focus of power system operation for a long time. As an effective reflection of active power balance, frequency should be maintained within a specific range to ensure the uninterrupted working of electrical elements. For those free-connected power grids that do not have apparent hierarchical or zoned structures, the spreading of cascading failures is highly likely to result in unexpected splitting of the grid This dynamic process may not be examined when planning the operation conditions or setting the parameters of frequency-related protection devices. Some full-time transient simulation-embedded models were proposed by [13,14,15] They can simulate the detailed dynamics of the cascading process, but their computations are relatively slow, and some important supervisory control measures are not considered, for example, frequency-related generator tripping and emergency dispatch (ED) scheme.
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