Mongolian power grid (MPG) is becoming more eco-friendly as the power system is continuously integrating renewable energy, which reached 20% of the total installed capacity of Mongolia in 2020. The daily operation and the safety of the MPG have become very challenging because of increased levels of energy in the system. Therefore, the dynamic behaviour of conventional power plants (CPPs) must be demonstrated to fulfil the requirements of integrating more renewable energy in the MPG, especially for frequency stability. This paper illustrates the results of the system parameter identification of an actual steam turbine and a governor system with PID controller by using a real-life test performed on Generator 1 (G1) of the biggest thermal power plant (TPP-4) in Mongolia on 6^th March 2020. The main contribution of this paper is to clear uncertainties about the PID controller's parameters installed in the steam turbine of G1 in early 2019, consequently giving the system operator an accurate dynamic model of the generation unit. The steam turbine and governor are modelled in DIgSILENT® PowerFactory, and the Particle Swarm Optimization (PSO) method is used for identifying the parameters of the PID controller of the G1 at TPP-4. Simulation results from the PowerFactory software matched firmly (error <0.3%) with the measured frequency from the Phasor Measurement Unit (PMU).@en

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^® PowerFactory^TM + Python). The results demonstrate an outstanding performance of the proposed approach when compared with the traditional one.

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Mongolia power system (MPS) is evolving quite fast, and the integration of renewable resources (mainly wind power and solar photovoltaic) reached 20% by 2019. The MPS is interconnected to Russia in order to cover local energy deficits, especially during freezing winters. However, the interconnection to Russia is a sensible element of the MPS, especially from the frequency control and stability point of view. This situation was evident during the sudden disconnection of the two interconnecting lines that provoked the major event of 29th June 2018, disconnecting 112 MW by the action of the Under-Frequency Load Shedding (UFLS) and making more than 1.5 million without electricity that day. This paper is dedicated to using numerical time-domain simulations to assess the existing UFLS schemes installed in the MPS. As the MPS is especially sensitive to disconnection from the Russian grid, this event is used to assess the suitability of the UFLS considering two scenarios: Summer and Winter. Results of this research paper have demonstrated that the actual UFLS scheme is not enough to avoid frequency collapse in real-life conditions during the Summer low-demand and low inertia scenario.

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The Mongolian power system (MPS) has been changing in recent years mainly by the integration of wind power and solar photovoltaic sources which until 2019 has been reached a 20% of the total generation sources. The interconnection with the Russian power system is crucial from the frequency control and stability point of view, especially during the winter, since it provides the necessary power to cover the local energy lack. The importance of this interconnection was evident during the disconnection of the two transmission lines that connect MPS to RPS producing the major frequency event on 29 th June 2018, disconnecting 112 MW by the action of the under-frequency load shedding (UFLS) and making more than 1.5 million without electricity that day. The objective of this paper is assessing the existing UFLS schemes installed in the MPS by using numerical time-domain simulations. The disconnection from the RPS is used to evaluate the suitability of the UFLS considering two scenarios: winter high-demand, high-inertia and summer low-demand, low-inertia. Results of this research paper have demonstrated that the actual UFLS scheme is not enough to avoid frequency collapse in real-life conditions during the summer low-demand, low-inertia scenario.@en

This research investigates the positive changes in the system frequency response indicators caused by the implementation of a set of optimal settings of an under-frequency load shedding (UFLS) scheme. The optimal under-frequency load shedding (UFLS) scheme is optimised by minimising the total amount of load shedding and taking into account the recovery process of the system frequency into its operational values after several losses of generation and satisfies the requirements of the under-frequency load shedding standard (PRC-006-SERC-02). The idea of implementing the optimal UFLS scheme is to identify how changes the minimum frequency, minimum time, rate of change of frequency and steady-state frequency when the amount of load shedding change. The optimal UFLS scheme formulation starts with identifying the variables to control with the optimisation and its respective bounds. Then, the objective function is formulated in terms of the total load shedding, and finally, the restrictions and requirements of the systems are written as inequality constraints. The optimal UFLS is evaluated in the IEEE 39-bus system. The simulations results demonstrate the suitability of the optimal UFLS to improve the frequency response indicators.

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This paper investigates the positive changes in the system frequency response indicators caused by the implementation of a set of optimal settings of an under-frequency load shedding (UFLS) scheme. The optimal UFLS scheme is optimised by minimising the total amount of load shedding and considering the recovery process of the system frequency into its operational values after several losses of generation and satisfies the requirements of the UFLS standard (PRC-006-SERC-02). The idea of implementing the optimal UFLS scheme is to identify how changes the minimum frequency, minimum time, rate of change of frequency and steady-state frequency when the amount of load shedding change. The optimal UFLS scheme formulation starts with identifying the variables to control with the optimisation and its respective bounds. Then, the objective function is formulated in terms of the total load shedding, and finally, the restrictions and requirements of the systems are written as inequality constraints. The optimal UFLS is evaluated in the IEEE 39-bus system. The simulations results demonstrate the suitability of the optimal UFLS to improve the frequency response indicators.@en