In 2021, the world's total installed capacity of generation units based on renewable energy sources (not including hydropower) amounted to about 1674 GW: over 825 GW and 849 GW of wind and solar ...power plants were installed respectively. The growing of the installed capacity of these distributed generators is a response to the increasing the power consumption, global environmental issues and has also become possible due to the development of technology in field of power semiconductor devices. However, on the way of large-scale implementation of distributed generators based on renewable energy sources, traditional electric power system meets new challenges to ensure the reliability and sustainability of new electric power systems with renewable energy sources. In particular, distributed generators change processes in the electric power system, impact to the parameters and power balance, change the magnitude and direction of power flow and short-circuit current, which determines the need to update the settings of the relay protection and automation systems of traditional electric power system and to coordinate their operation with automatic control systems of installed distributed generators. The above-mentioned tasks form a number of scientific research directions, one of which is a task of determining optimal size and location of distributed generators. The main purpose of this optimization task is to reduce power losses, operating and total electricity cost, improve the voltage profile, etc. In addition, the correct and reasonable placement of distributed generators defines an effective planning of the operating modes of electric power system and power plants (especially based on renewable energy sources, the operating modes of which depend on weather conditions and can be sharply variable).
The paper highlighted the impacts of distributed generators on power losses, the voltage level, maintaining the power balance and the possibility of participating in the frequency regulation, and short-circuit current in power system. The optimization criteria, the main limiting conditions, as well as methods for solving this optimization problem are considered. This review will help the System operators and investing companies, especially in Russia, to form the main aim, objective function and constraints that will aid to meet their load demand at minimum cost and to choose from the options available for optimization of location and capacity of distributed generators.
The growing share of generation from wind farms is becoming one of the challenges in maintaining the sustainability of electric power systems. System operators approve requirements for the ...participation of such plants in frequency and power regulation, but they do not contain requirements for specific technologies in the control of wind turbines. There are several methods of frequency and power control, which are implemented by additional control systems, the implementation of underload mode, extraction of hidden inertia, the use of energy storage devices, etc. Each of these methods has both advantages and disadvantages. In this paper we consider the combined coordinated control of type 3 wind turbines using kinetic energy and energy from hydrogen storage to provide the best frequency response in order to minimize the negative factors. A digital-analog-physical model of type 3 wind turbine is used as a model, which allows to reproduce the whole range of transients most accurately and avoid the limitations of strictly numerical simulation.
Nowadays, the development of the electric power system is associated with the penetration of power generation units based on renewable energy sources and operated with energy storage systems. ...However, the operation of such generation units changes and complicates the processes in the electric power system, which determines the need for a number of studies and analyses. This paper presents the results of assessing the impact of the operation of photovoltaic plants on the static stability of the electric power system. To achieve the goal, the EUROSTAG software was used. The results of studies of normal and post-emergency modes of electric power system with the different penetration level of generation units are presented, power system stability coefficients of active power and voltage are determined, damping properties of electric power system based on the calculation of the transient damping coefficient of the damping process are estimated.
One of the global energy trends is the introduction of distributed generating facilities (distributed generation, DG). Therefore, the ongoing transformation of electric power systems (EPS) ...significantly changes the properties of power systems. Problems arise with ensuring sustainability, which is generally the main condition for validity and survivability of energy districts with DG facilities and EPS. Moreover, ensuring sustainability under remarkable perturbation remains one of the main tasks. This problem is mainly solved via mathematical modeling. However, the necessary EPS mathematical model of real dimension contains a rigid nonlinear system of differential equations of an extremely high order. Simplifications and restrictions, which reduce the completeness and significance of the obtained simulation results, are inevitably applied to improve the conditionality of the EPS mathematical model in numerical integration. Such an application requires verification. This article proposes a direction of verification alternative to the existing ones based on the use of a model standard instead of full-scale data. Such verification reveals the influence of the applied simplifications and limitations in numerical modeling on the quality of solving the sustainability estimation problems of an EPS with a DG under remarkable perturbation. The studies presented in this article are conducted using the example of an energy district with DG facilities included in EPS with real dimensions. The findings of these studies demonstrate the resulting errors of stability calculations under remarkable perturbation, the nature of their change and the causes of occurrence, as well as the influencing factors.
Nowadays, renewable energy sources are integral to programs for the development of electric power systems. It is established that modern renewable generation units and energy storage systems utilize ...power electronic-based interfaces, such as voltage source converters, to convert power. On the one hand, the utilization of a voltage source converter provides certain advantages, such as the absence of a direct link to the network, the ability to operate on all quadrants of the PQ diagram, and the possibility of connecting renewable generation units to a weak network. On the other hand, the widespread use of renewable generation units utilizing voltage source converters reduces the overall inertia of the electric power system. However, excessive use of power electronic converters in the network leads to a significant increase in harmonic pollution, thereby introducing fresh challenges to ensuring safe and stable operation of the electric power system. To ensure the dependable operation of an electric power system with renewable energy sources units and energy storage systems based on the voltage source converter, it is essential to update the control system of the voltage source converter to meet the requirements for traditional generation as part of the electric power system. This paper presents the outcome of the power oscillation damping controller application implemented in the voltage source converter, which enhances the electric power system's stability.
The widespread introduction of renewable energy sources (RES) into modern electric power systems (EPS) significantly changes their dynamic properties. EPS stability issues arise due to the properties ...of non-synchronous generating units (GU) based on RES with power converters (PC), which are fundamentally different from conventional synchronous generation. Mathematical modeling of EPS stability issues is currently performed by purely numerical calculation of electromechanical transients in which various simplifications and limitations are applied based on the development and modification “generic” mathematical models of EPS-based GUs with PCs. In the present study, stability calculations of EPS with GU based on RES with PC reveal the impact of the applied simplifications and constraints in the purely numerical calculation of electromechanical transients on the quality of the solution of problems of stability evaluation of EPS with RES. Areas of application of the modified GU model based on RES with PC as part of the EPS model of real dimensionality are identified at which the largest and smallest errors occur, along with their causes. Such “all-mode” verification becomes feasible due to the alternative approach proposed in the article, which is based on the use of a model benchmark instead of field data.
In the article an experimental power system consisting of Russian equipment, as well as 220 kV power line distance protection, are simulated in the RTDS Simulator. The settings were calculated and ...the polygonal characteristics of distance protection were constructed. A sequential installation of wind turbines into various nodes of the power system was carried out and the correct operation of the protection was verified. As a result of the study, the impact of wind turbines on the distance protection when they are connected between the protection installation site and the point of the short circuit is revealed. The analysis of this impact is made. Possible ways to solve the identified problems are proposed, such as the use of adaptive distance protection, as well as numerous studies of the behaviour of wind turbines in various operating modes for further analysis and possible adjustment of guidelines for relay protection using new algorithms for calculating and configuring of distance protection. The results of this work can be used to improve and clarify the recommendations for tuning, produced by manufacturers of relay protection devices, which currently do not take into account the impact of wind power generation.
In this article the research results of steady-state and dynamic performance of asynchronous back-to-back HVDC link in Tomsk electric power system are presented. It is proposed to use the ...back-to-back HVDC link to provide an asynchronous link for parallel operation of the North and South parts of Tomsk electric power system. The steady-state stability limit and maximum allowed power flow were defined. Based on this the more effective location and power of back-to-back HVDC link were determined. Therefore, it is shown the application of back-to-back HVDC link decreases the level of short-circuit current, power fluctuations and increases the stability of load operation, especially of motor load at substation.
After discharge from the Intensive Care Unit (ICU), more than 50 % of patients experience pathological symptoms that are not related to the primary emergency but reduce the quality of life and ...require rehabilitation. Post Intensive Care Syndrome (PIСS) include only those conditions that do not have a direct causal relationship with the emergency condition that gave rise to hospitalization in the ICU. The pathophysiological basis of the PICS is the phenomenon of “learned non-use”: a state of artificial limitation of the patient’s motor and cognitive activity as a result of the use of analgosedation, bed rest and immobilization. The clinical picture of PICS is determined by the severity of its individual components, detailed using a package of clinimetric scales. Based on the results of dynamic testing, the PICS severity index is calculated. The sum of the scores in the range from 0 to 10 reflects the severity and effectiveness of rehabilitation measures. For the prevention of PICS, the Union of Rehabilitologists of Russia together with the Federation of Anesthesiologists and Resuscitators of Russia has developed the rehabilitation complex “ReabICU”. In the English-language literature, such a complex is called “Awakening and Breathing Coordination, Delirium monitoring/management, and Early exercise/mobility” bundle. ReabICU is a complex of technologically therapeutic and diagnostic modules “positioning and mobilization”, “prevention of dysphagia and nutritional deficiency”, “prevention of emotional and cognitive impairment and delirium”, “prevention of loss of self-care skills”. The basis of the multidisciplinary rehabilitation team, which includes a doctor for medical rehabilitation, 2 specialists in physical rehabilitation, a specialist in occupation therapy, a medical psychologist, a medical speech therapist, a nurse for medical rehabilitation. The activity of multidisciplinary rehabilitation team is evaluated on the basis of quality criteria and the achievement of the main goal of ReabICU — the preservation of the premorbid status of the patient’s socialization.
This study is aimed at improving the efficiency of photovoltaic plants operated in the electric networks of various densities by adjusting the synthetic inertia algorithm and automatic frequency ...control circuits. To this end, the automatic control system of a photovoltaic plant was investigated using hybrid modelling methods in an all-mode online simulation complex of electric power systems. It was shown that the stability of photovoltaic power plants could be improved through the use of synthetic inertia. According to the conducted research, effective operation of this algorithm can be ensured by a correct determination of the bandwidth of automatic frequency control. Operation of this automatic frequency control circuit can lead to the oscillations of various frequencies during the installation of photovoltaic power plants in low-current electrical networks (electrical networks with the short circuit coefficient of less than 10 a.u.) and, subsequently, negatively affect the operability of the synthetic inertia algorithm. In addition, in high-current networks with an increased bandwidth of the automatic frequency control unit, the value of the network frequency reduction decreases (optimal bandwidth of 50 Hz). Conversely, in low-current networks, the automatic frequency control unit, under an increase in the bandwidth, decreases the response rate of the synthetic inertia algorithm, which leads to an increase in the frequency reduction value (optimal bandwidth of 0.3 Hz). Thus, the conducted investigations showed that the automatic frequency control circuit in the control system of a photovoltaic power plant can be used to alter the operation of the synthetic inertia algorithm. However, the nature of this effect depends on the electrical network density and can be both positive and negative. The effect observed in the tested power system was confirmed for a real-dimension power system.
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