Abstract
The Altai-Uliastai regional power system (AURPS) is a regional power system radially interconnected to the power system of Mongolia. The 110 kV interconnection is exceptionally long and susceptible to frequent trips because of weather conditions. The load-rich and low-inertia AURPS must be islanded during interconnection outages, and the under-frequency load shedding (UFLS) scheme must act to ensure secure operation. Traditional UFLS over-sheds local demand, negatively affecting the local population, especially during the cold Mongolian winter season. This research paper proposes a novel methodology to optimally calculate the settings of the UFLS scheme, where each parameter of the scheme is individually adjusted to minimise the total amount of disconnected load. This paper presents a computationally efficient methodology that is illustrated in a specially created co-simulation environment (DIgSILENT® PowerFactoryTM + Python). The results demonstrate an outstanding performance of the proposed approach when compared with the traditional one.
Highlights
The power system continuously deals with power imbalances coming from fluctuations caused by imbalances between generation and demand
The optimal settings of under-frequency relays (UFRs) produced a minimum load shedding of PLS = 3.144 MW, which was reached in improvisation 303
The optimal settings of UFRs produced a minimum load shedding of PLS(xFC) = 3.144 MW, which was reached in improvisation 303
Summary
The power system continuously deals with power imbalances coming from fluctuations caused by imbalances between generation and demand. This fact can produce an over-frequency condition Another drawback of several methodologies, such as [14,18,19,21,22], is that they simplify the optimisation problem by considering only the block size of LS as a control variable and keep the number of load shedding stages, frequency threshold and time delay as fixed values. The main objective of this research paper was to overcome the disadvantages of existing methodologies by introducing a novel method to optimally calculate the settings of the UFLS scheme In this new approach, the principal parameters of the UFRs (number of load shedding stages, block size of load shedding, frequency threshold and the time delay for each stage) are considered in order to minimise the total amount of disconnected load.
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