Сучасні підходи до компенсації реактивної потужності в системах тягового електропостачання змінного струму

El aumento de la demanda en los distintos sistemas eléctricos de potencia (SEP) tiene un impacto negativo en la estabilidad de la tensión, la confiabilidad y la calidad del suministro eléctrico. El perfil de tensión disminuye cuando las unidades de generación no son capaces de suministrar potencia reactiva al sistema eléctrico en los momentos que se requiere. Con el desarrollo de la electrónica de potencia y los complejos sistemas de control, se han podido introducir dispositivos de sistemas flexibles de transmisión de corriente alterna (FACTS, del inglés Flexible Alternating Current Transmission System). En este artículo se analiza en detalle el impacto que genera la introducción de un tipo de FACTS que permite la compensación de potencia reactiva en el SEP. Además, se analizará una metodología para decidir la capacidad del compensador síncrono estático (STATCOM, del inglés Static Synchronous Compensator) y su ubicación óptima con la ejecución de flujos de potencia continuos (FPC). Finalmente, se estudiará el impacto positivo de la instalación de un control estabilizador de potencia (PSS, del inglés Power System Stabilizer) para asegurar la estabilidad de tensión en el SEP. Este artículo se desarrolla utilizando el sistema base IEEE de 14 barras bajo dos modelos matemáticos para el cálculo del flujo de potencia desarrollados en el software Matlab, que son: i) utilizando las ecuaciones de balance de potencia y ii) Newton Raphson con el toolbox de MATLAB (PSAT, del inglés Power System Analysis Toolbox).

The main problems of stray current and the low availability of the regenerative braking energy widely exist in DC traction power supply system which is currently widely used in China. The AC traction power supply system for Urban Rail Transit based on negative sequence current compensator is proposed as a kind of novel power supply scheme to solve these problems in DC system. And the construction of the AC traction power supply system is designed in detail. In the meantime, the system of negative sequence compensator based on three - phase three - level rectifier parallel is designed to compensate for the negative sequence generated by the proposed system in the paper. The negative sequence current compensation algorithm of the AC traction power supply system and the control method of the negative sequence current compensator are deeply analyzed and designed, and the proposed system is feasible to connect with three-phase power grid. Meanwhile, the equalization of the AC traction power supply system was also achieved. Finally, the performance of the power electronic compensator to eliminate the negative sequence current was verified by simulations and experiments.

In power grid modernisation, optimal network use is essential to preserving acceptable voltage profiles, boosting voltage stability, reducing power losses, and strengthening system security and dependability. This can be accomplished by strategically placing reactive power compensation devices within transmission and distribution networks, such as capacitor banks, synchronous condensers, flexible alternating current transmission system (FACTS) devices and custom power devices. The optimal location and size of these devices are essential for effective investment, but previous research has mostly concentrated on a variety of methods for this goal, using different indices to evaluate power loss, voltage stability, voltage profile and line loadability. Despite these initiatives, there is still a lack of a thorough analysis of how current indices and methodologies are applied to all varieties of reactive power compensation devices. This paper offers a detailed literature review on the ideal placement and sizing of these devices, encompassing analytical, conventional and hybrid-based techniques. It discusses key objectives such as power loss reduction, voltage deviation (VD) mitigation, voltage stability enhancement and improvements in system reliability and security. Additionally, the paper examines the relevance of reactive power for stakeholders, including transmission system operators (TSOs), distribution system operators (DSOs) and power generating companies, and explores the mathematical modelling of optimal reactive power dispatch (ORPD), considering the impact of renewable energy sources (RESs) and the role of FACTS devices.

With the daily expansion of global energy consumption, developing the power grids is of uttermost importance. However, building a new transmission line is costly and time-consuming, so utilizing the same lines with possible higher transmission capacity is very cost-effective. In this regard, to increase the capacity of the transmission lines, the flexible alternating current transmission system (FACTS) has been widely used in power grids in recent years by industrialized countries. One of the essential topics in electrical power systems is the reactive power compensation, and the FACTS plays a significant role in controlling the reactive power current in the power grid and the system voltage oscillations and stability. When a static synchronous compensator (STATCOM) is embedded in a power system to increase the bus voltage, a supplementary damping controller can be designed to enhance the system oscillation damping. Given the expansion of the grids in the power system, the complexity of their optimization and the extraordinary ability of the imperialist competitive algorithm (ICA) for solving such problems, in this paper, the ICA has been used to determine the optimal position and size of the FACTS devices.

The necessity to deliver cost effective energy in the power market has become a major concern in this emerging technology era. Therefore, establishing a desired power condition at the given points are best achieved using power controllers such as the well known High Voltage Direct Current (HVDC) and Flexible Alternating Current Transmission System (FACTS) devices. High Voltage Direct Current (HVDC) is used to transmit large amounts of power over long distances. The factors to be considered are Cost, Technical Performance and Reliability. A Flexible Alternating Current Transmission System (FACTS) is a system composed of static equipment used for the AC transmission of electrical energy. It is meant to enhance controllability and increase power transfer capability of the network. It is generally a power electronics-based system. A Unified Power Flow Controller (or UPFC) is a FACTS device for providing fast-acting reactive power compensation on high-voltage electricity transmission networks. The UPFC is a versatile controller which can be used to control active and reactive power flows in a transmission line. The focus of this paper is to identify the improved Power Transmission Capability through control scheme and comprehensive analysis for a Unified Power Flow Controller (UPFC) on the basis of theory, computer simulation. The conventional control scheme cannot attenuate the power fluctuation, and so the time constant of damping is independent of active- and reactive-power feedback gains integrated in its control circuit. The model was analyzed for different types of faults at different locations, keeping the location of UPFC fixed at the receiving end of the line, With the addition of UPFC, the magnitude of fault current and oscillations of excitation voltage reduces. Series and Shunt parts of UPFC provide series and shunt injected voltage at certain different angles.

Voltage instability results from a lack of reactive power support in a power system. One effective solution for supplying reactive power to a power system is utilization of flexible alternating-current transmission system (FACTS) facilities. Currently, two FACTS facilities are operated for stable operation of the power system on Jeju Island in South Korea. Both FACTS respond to disturbances to stabilize voltage fluctuations in the island power system, however there is potential for mutual interference between them because they are operated using measured voltage without a coherent system operation strategy; cooperative control between the two would result in more effective system operation. Here, a multiple FACTS control algorithm is developed for effective operation of the island power system. The algorithm is based on two methods: calculation of the effective reactive power (Q) reserve (EQR) to obtain an accurate reactive power for the system, and GV analysis to account for the two HVDC interconnections between Jeju Island and the Korean Peninsula.

This paper deals with the design and implementation of cascaded H-bridge multilevel voltage source converter-based static synchronous compensator (STATCOM) for simultaneous active and reactive power compensation, voltage stability and damping of power oscillations. The main objective is to provide active power support and maintain the voltage stability by compensating the reactive power in the power system. In this paper, the multi pulse inverter-based STATCOM has been replaced by multilevel inverter-based STATCOM to overcome the drawbacks of the former. Cascaded H-bridge (CHB) MLI for implementation of STATCOM has been used as CHB MLI is considered the best for STATCOM applications due to its modular structure and requirement of lesser number of components. MLI-based STATCOM is used to provide simultaneous reactive power and active power compensation established by using super-capacitor. The super-capacitors are connected with each DC link capacitor of CHB MLI by using the DC-DC buck boost converter. The STATCOM is also used to provide voltage stability during the power quality problems such as voltage sag and voltage swell, it is established by injecting or absorbing reactive power. The STATCOM is also used for damping the power oscillations by controlled injection of reactive power hence enhancing transient stability. Nine-level cascaded H-bridge MLI-based STATCOM is designed for simultaneous reactive power and active power compensation, voltage stability and damping the power oscillations. Exhaustive simulations have been carried out using MATLAB/Simulink and SimPowerSystems software. The simulation results are presented to prove the effectiveness of MLI-based STATCOM for simultaneous active and reactive power compensation, voltage stability and damping of power oscillation.

Abstract— The concept of Var compensation embraces a wide and diverse field of both system and customer problems, especially related with power quality issues, since most power quality problems can be attenuated or solved with an adequate control of reactive power. In general, the problem of reactive power compensation is viewed from two aspects: load compensation and voltage support. Static voltage instability is mainly associated with reactive power imbalance. Thus, the load ability of a bus in a system depends on the reactive power support that the bus can receive from the system. As the system approaches the maximum loading point or voltage collapse point, both real and reactive power losses increase rapidly, therefore the reactive power supports have to be locally adequate. With static voltage stability, slowly developing changes in the power system occur that eventually lead to a shortage of reactive power and declining voltage. The Flexible AC Transmission System (FACTS) technology is a promising technology to achieve complete deregulation of power system based on power electronic devices, used to enhance the existing transmission capabilities in order to make the system flexible and independent in operation then the system will be kept within limits without affecting the stability. Increased transmission demand is met where possible by increasing the existing transmission capacity. When trying to improve the transmission capacity, a key assumption is made that if the overall system reliability is not improved, at least the existing system reliability is maintained. The research work in this work is focused on FACT’S Controllers. Keywords: Flexible AC Transmission System, variable-speed wind turbine, rotor-side converter, grid-side converter, doubly fed induction generator, Static Synchronous Compensator, phase-locked loop.

The reactive power compensation problem prevalent in modern power systems makes the power distribution performance not fully utilized and the load power consumption of the equipment increases. According to the operation of the Yulin substation line and the load, the theoretical calculation of the reactive power compensation scheme is developed. The installation capacity, installation position, control scheme of the intelligent magnetic control reactive power compensation system are researched. Through the coordinated control at the beginning and the end of the line, the real-time regulation of the reactive power in the substation and the transmission line can achieve the effect of stabilizing the whole area voltage, improving the power supply radius and power quality. The system finally implemented the stability of the substation voltage and reduced the line loss, made the voltage of the power system stable within the utility required range.

The development of the shipbuilding industry involves increasing the competitiveness of manufactured products, replacing obsolete electrical equipment, and increasing the efficiency of power supply systems. The introduction of the latest technologies reduces the weight and size of equipment, expands their functionality, but these technologies are based on nonlinear and asymmetrical power consumers, which causes a negative impact on the power grid. The power supply system of the Baltic Shipyard "Yantar" is characterized by a significant share of nonlinear, asymmetrical loads, often single-phase. An integrated approach to the analysis of the plant's power supply system included experimental studies of nonlinear power consumers, during which a high level of higher current harmonics (3rd, 5th and 7th orders) was established. One of the effective methods for reducing zero-sequence voltage asymmetry is to replace a transformer with a Y/Y0 winding connection diagram with a Δ/Y0 diagram. Circuit and technological solutions (separation of nonlinear loads to a separate bus system; increasing the phase of semiconductor converters; connecting a nonlinear load to a system with greater short-circuit power) and filtering devices (narrow-band filters, filter-balancing devices and active filters) are used to increase the efficiency of the power supply system when it operates under conditions of increasing distorting loads.

Increased freight turnover on railway transport inevitably leads to increased traction current in DC and AC traction power supply systems. The increase in traction current is already causing problems related to the normal operation of the 25 kV AC traction power supply systems. One of the adverse consequences of the increased traction currents is the increased rail-to-ground potential. This has already caused a number of accidents and related traffic interruptions on the Far Eastern Railway of Russia and other railway sections powered with alternating current. The study considers the problem of increased rail-to-ground potentials and provides basic formulae for calculating the wave parameters of the rail network and rail-to-ground potentials. Various methods are given for calculating rail-to-ground potentials for a 25 kV AC traction power supply system. Since in an alternating current system, expressions for calculating the potential are functions of a complex variable, the calculation of such expressions requires the use of special programs. Adaptation of existing methods to modern software and computing systems allows you to optimize and significantly speed up the process of calculating the “rail-to-ground” potentials, either considering the use of certain potential-reducing measures or not. A calculation method includes an algorithm developed for calculating the rail-to-ground potentials in the 25 kV AC traction power supply system for an inter-substation zone of any length with any number of electric locomotives within the zone.

Large renewable power plants connected to the high-voltage network have the potential to make an important contribution to the grid's reactive power management. This is especially true when rather than using a predetermined Q characteristic, the system operator can control the power plant's reactive power output via a direct interface. However, the intermittent nature of the primary resources and today's reactive power requirements inhibit the permanent availability of reactive power from wind and photovoltaic (PV) power plants. This study shows that a synchronized, so-called symbiotic control of PV and wind power plants can vastly increase their capability of fulfilling reactive power demands. This is demonstrated by simulating the properties of a real PV and wind farm located in Germany. Furthermore, generating units coupled to the grid via power electronics have an even larger potential of providing reactive power when their P-Q characteristics are adapted. On the downside, this can lead to an undesired coupling of reactive and active power control in the grid. A symbiosis of wind farms and PV parks can once again improve this situation when smart power allocation methods are employed. An appropriate algorithm has been developed for this study and is tested on the above-mentioned simulation model.

Flexible Alternating Current Transmission Systems (FACTS) got in the recent years a well known term for higher controllability in power systems by means of power electronic devices. FACTS devices can effectively control the load flow distribution, improve the usage of existing system installations by increasing transmission capability, compensate reactive power, improve power quality, and improve stabilities of the power network. However, the location and settings of these devices in the system plays a significant role to achieve such benefits. This work presents the application of Real Coded Genetic Algorithm (RGA) and Particle Swarm Optimisation (PSO) for finding out the optimal locations, and the optimal parameter settings of multi type FACTS devices to achieve maximum system loadability (MSL) in the power system. The FACTS devices used are Thyristor Controlled Series Capacitor (TCSC) and Unified Power Flow Controller (UPFC). The reactance model of TCSC and the decoupled model of UPFC are considered in this work. The thermal limits of the line and voltage limits of the buses are taken as constraints during the optimization. Simulated Binary Crossover (SBX) and Non-uniform polynomial mutation are employed to improve the performance of the Genetic Algorithm used. Simulations are performed on IEEE 6 bus and 30 bus power systems. The obtained results are encouraging and show the effectiveness of RGA over PSO algorithm

The study aimed to quantitatively assess the effectiveness of neural network-based control of dynamic reactive power compensation in the traction network of Ukrzaliznytsia. The methodology involved high-frequency monitoring of 118 substations (≈16 trillion measurements), aggregation of 52 million Supervisory Control and Data Acquisition records, Theil-Sen trend estimation, Seasonal-Trend decomposition using Loess, the Brown Forsythe test, and a deep neural network with 64-32-16 layers optimised through a Tree-structured Parzen Estimator, validated in 120 Monte Carlo scenarios in Simscape. The results demonstrated that the average daily Q increased from 309.8 to 367.2 Mvar (18.5%) with a trend of 0.95 Mvar/month (95% CI 0.82-1.08; p < 0.001). Winter peaks reached 520 Mvar, while variance after February 2022 increased 1.5-fold (F = 34.9; p < 0.001). The neural network achieved Mean Squared Error = 184 Mvar² and R² = 0.982; in testing, R² = 0.975, Mean Absolute Error = 11.2 Mvar, and the median error of winter peaks did not exceed 3%. In simulations, the algorithm maintained cos φ between 0.985 and 0.991 for loads ranging from 0.3 to 1.2 p.u., reduced daily losses by 6.1-9.4% (≈1.2 MWh/day), and decreased the number of Static Var Compensator switchings by 38%. Under failure of 20% of Insulated-Gate Bipolar Transistor modules, the duration of cos φ < 0.98 was 0.7%, compared with 19% for the Proportional Integral-Derivative controller. Quantitative comparison of compensation strategies confirmed that the simulated STATCOM-DL system achieved the lowest average cos φ deviations (0.015 vs. 0.030-0.048 for competitors) and minimal annual losses (≈ 430 MWh), outperforming all alternative approaches. The findings confirmed that the combination of deep learning and statistical validation enhances network stability and improves energy efficiency. The practical significance lies in the fact that the resulting algorithms may be employed by railway dispatch centres and energy integrators for real-time optimisation

When designing oil and gas industry facilities and petrochemical facilities, the issue of the organization of their power supply system does not lose its relevance. At the stage of the feasibility study, the options based on the use of renewable energy sources, as well as energy storage systems are not often considered due to the high cost of solutions. The absence of standard solutions for the use of renewable energy sources and energy storage systems, the incompleteness of the regulatory framework force designers to refuse to consider them when designing power supply systems. This article analyzes the theoretical aspects and practical examples of the use of additional non-traditional sources of power supply, contributing to the improvement of energy efficiency of power supply systems as a whole.