Optimal Under-Frequency Load Shedding Setting at Altai-Uliastai Regional Power System, Mongolia

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.

Event-Based Under-Frequency Load Shedding Scheme in a Standalone Power System

“…ρ max and ρ min are set at 40% and 5% of the total system load, respectively. Generally, ρ max is set between 25% and 55% of the total system load [14,15,30]; the mean (40%) of 25% and 55% is adopted herein. ρ min is approximately set as the percentage of the largest single feeder load among all feeders.…”

“…Response-driven UFLS schemes use wide area measurement systems (WAMS) [2][3][4][5][6] or local real-time measurements [7][8][9][10][11][12][13][14][15][16][17][18][19] to activate a special protection system. Specifically, the prediction of the frequency nadir [2,3], the estimation of the rate of change of frequency (RoCoF) [4,5], and the optimization [6] were explored in WAMS-based UFLS schemes.…”

“…Regarding UFLS schemes in a bulk power system using local measurements, minimization of shed load and maximum of frequency nadir in [7], the inertia time constant and generation deficiency in [8], and the dynamics of governors and load damping in [9] were implemented. Flexible random and fixed load priorities in [10], wind and photovoltaic (PV) measurements in [11], a closed-form-based shed load solution in [12], uncertainty of generation loss in [13], minimization the total amount of disconnected load using harmonic search in [14], and usage of a linear function for the determination of each individual load shed in [15] were investigated. In relation to response-driven UFLS schemes that have been developed for standalone/isolated power systems, a fuzzy rule base [16], the measured frequency deviation [17], an estimated/updated droop coefficient [18] and time-continuous load flow [19] were used to estimate the deficit power generation to prioritize the shed loads.…”

An adaptive under-frequency optimal control strategy for power system combined pumped storage and under-frequency load shedding

“…The UFLS is a traditional frequency emergency control method for power systems. It removes a certain load to reduce the active power shortage, so as to keep the frequency of the system within the non-accident range of values, and to ensure the power supply reliability of important loads [ 26 ]. It is also known as the third line of defense of the power system [ 27 ].…”

System Parameter Identification of Thermal Generation Unit in the Mongolian Electrical Grid: Real-Life Frequency Response Test

“…In this case, the parameter estimation technique helps to test and validate the power components' dynamic models accurately. The main focus of this paper is performing the parameter estimation of one of the essential generation units in the MPG, Generator 1 (G1) of Thermal Power Plant-4 (TPP-4) [8]. The steam turbine governor of the G1 of the TPP-4 was subject to a massive improvement in 2019; a proportional-integral-derivative (PID) controller replaced a proportional controller.…”