ОБРАТИМЫЙ ПРЕОБРАЗОВАТЕЛЬ ЭНЕРГИИ С МАХОВИЧНЫМ НАКОПИТЕЛЕМ В СИСТЕМАХ ЭЛЕКТРОСНАБЖЕНИЯ

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

In accordance with the randomness and intermittent characteristics of wind power, the static synchronous compensator (STATCOM) is more competent and competitive for reactive power compensation in large scale wind farm. An average state model for the VSC-STATCOM is derived, according to the wind farm reactive power compensation characteristics, a novel decoupling control strategy of active power and reactive power is proposed. The model and controller are suitable for the reactive power compensation and converter operation state control. A PSCAD/EMTDC simulation model is built and the simulated results are presented. The simulated results show that the proposed STATCOM control strategy provides high performances in both steady state and dynamics.

Owing to the characteristics of nonlinearity, asymmetry and stochastic volatility, electrified railway traction loads have arose some hazardous effects to security and stability, reactive power compensation and voltage control, power supply quality of power system. It has practical significance to research on the influence of traction loads to power system for ensuring security and stability of power system. By using Power System Analysis Software Package/User Program Interface (PSASP/UPI) function, the electrified railway traction measurement-based load model (traction load model, TLM) for transient stability simulation are established, and then the TLM is applied to Hunan Electrical Power Network. The dynamic characteristics of TLM and the difference characteristics between TLM and the traditional load model are analyzed through setting different faults. The paper provides a convenient reference for further research on the relay protection setting calculation of power system and safety controlling strategies of traction power supply system.

To reduce CO2 emissions, an oil and gas company has electrified two platforms in the Norwegian North Sea. The two platforms had several large gas turbines (GT's) driving 50MW of compression and 60MVA of power generation. The project has connected electric power from shore and discontinued the GT's. A subsea power cable delivers 150MW of power from the 50Hz Norwegian grid (powered by hydro electricity) to the two platforms; a static frequency converter (SFC) is required to feed the existing offshore platform 60Hz loads. This SFC will operate in grid forming mode to provide all the power, protection, and fault clearing functionality for the 60Hz grid. The SFC is 4 quadrant, and the active front end (AFE) will provide grid support for the power from shore cable to improve voltage and frequency disturbance events. The AFE will also export VARs to correct the power factor of the cable feeding power from shore. The compression load to be driven by AFE Variable Speed Drive (VFD)s and will also support the grid with disturbance ride through and power factor correction. Simulation results of the disturbance events will be presented as well as the CO2 reduction calculation. The system was successfully started in 2024 without any shutdown of the platform, a "hot" switch over was achieved.

Among the existing power quality problems, the reactive power compensation plays a key role once it helps to maintain the system stability and increases the efficiency. Currently, there are many solutions for reactive power compensation, which unfortunately present a wide variety of problems as large inrush currents, non-continuous compensation and harmonics injection in the system. The application of devices like static VAr compensator, static synchronous compensator or unified power flow controller has demonstrated to be an effective solution for reactive power compensation. However, it is important to note that these options are rarely used in distribution systems by companies that prefer to assimilate the drawbacks of switched capacitor banks instead of investing in more expensive, sophisticated and complex solutions. Despite the large number of proposed devices in distribution systems, there is a lack of solutions with emphasis on cost reduction. Therefore, this paper presents a new topology for reactive power compensation and voltage control in distribution systems. The proposed topology has several interesting features as reduced switching losses, small capacitors and simple control scheme. In addition, the proposed solution uses already existing capacitor banks which makes possible its usage in distribution companies with minimum modifications. Experimental results have been obtained on a 6-kVA prototype to demonstrate the feasibility of the proposed solution.

In this paper, a novel intelligent controller for grid connection of DC microgrids is presented. The proposed controller allows the bi-directional AC/DC converter, linking the DC microgrid to the main utility grid, to provide the main functionalities of an inverter. Such functions include bi-directional power flow control and independent control of both active power (P) and reactive power (Q). In addition, the developed controller acts as an intelligent active power filter (APF) to the main grid. This is because it autonomously detects any power quality problems, filters out load-created harmonics and compensates unbalances and/or DC offsets resulting from the local AC load connected at the point of common coupling (PCC). The objective of the controller is to force the AC grid currents at the PCC to be balanced three-phase currents with minor harmonics while maintaining its controllability of power flow regardless of the characteristics of the local AC load. The performance of the developed controller was examined under several extreme cases including: non-linear loads, distorted load currents, unbalanced and offset conditions. The results show that the developed controller succeeds to maintain bi-directional P/Q flow controllability, allows the inverter to provide ancillary services such as reactive power compensation or voltage control to the grid while simultaneously acting as an active power filter to assure improved power quality at the PCC under various loading conditions.

A combined reactive power compensation method of a static VAr compensator (SVC) and a series active filter is described for unbalanced three-phase four-wire distribution feeders with harmonic distortion. The SVC which consists of Δ-connected thyristor-controlled reactors, Y-connected thyristor-controlled reactors and passive filters, acts as a classic reactive power compensator for load balancing and power factor correction. The small rating active filter is used to improve the filtering characteristics of the passive filter in the SVC and suppress possible resonance between the system impedance and the passive filter. Simulation results performed by the electromagnetic transients program show that the proposed reactive power compensation configurations can effectively balance currents, correct power factor and eliminate harmonic currents.

The goal of this project is to model and control a novel unidirectional cascaded multilevel bridgeless rectifier as an active front end in medium and high voltage applications. This topology has many advantages over a conventional cascaded H-bridge rectifier, such as lower implementation cost, higher reliability, and greater flexibility with similar power quality.The steady-state mathematical model is used to develop a method for the voltage balancing of dc cells. Power factor analysis is discussed to achieve unity power factor using fully controlled hbridge cells. Power loss, efficiency, and cost comparison studies between the traditional cascaded H-Bridge converter and the proposed bridgeless converter demonstrate the advantages. A novel control strategy is proposed to achieve dc voltage balancing, fast and robust grid synchronization and power factor correction under unbalanced load conditions. Simulation and experimental results validate the models and control method.

This paper presents a control scheme for load balancing and power factor correction in three-phase four-wire systems using a three-phase four-leg active power filter. It is assumed that the active power filter is connected to a load that can be unbalanced and may also draw harmonic currents. The four-leg active power filter is used for harmonic compensation, reactive power compensation, load balancing and neutral current compensation as well as improving the supply side power factor. The proposed control strategy is more effective and flexible and also has lower cost and higher efficiency. The topology and operation principle of the proposed control method is discussed in detail, finally the feasibility of such a scheme is demonstrated through simulation studies.

This paper addresses the issue of functional possibilities of reversible electric drive based on active front end rectifier and voltage source inverter from the point of view of energy saving. This paper will review all theoretical capabilities of reactive power compensation in the supply mains by the active front end rectifiers. The reactive power consumption or generation can be created out by using of active front end converters which connect the electric drive with supply mains. Active front end rectifiers can be actively used in operation of supply mains of enterprise as they are able to provide controlled power factor and bidirectional power flow. The studies by mathematical modeling in the Matlab/Simulink program were carried out. It was established that the controlling of power factor of active front end rectifier can be used for reactive power compensation in supply mains. The huge prospects of energy-saving reversible electric drive integration to the Smart Grid have been determined as it is able to provide high power and capabilities of the controlling reactive power flow by means of active front end rectifier. It can reduce a share of the consumption reactive power from a substation and to improve the power quality.

Static compensators (or DSTATCOMs) are commonly used in the integration of renewable energy sources (RES) into the grid to provide a variety of functions such as reactive power compensation, harmonic elimination, zero voltage regulation (ZVR), power factor correction (PFC), grid current balancing, etc. Considering the recent trends on integration of the RES to the grid, an enhanced control structure is needed. In this paper, a hyperbolic tangent function based adaptive filter (HTFAF) is applied for effective operation of the static compensator. This adaptive filter’s (HTFAF) update rule is based on a cosine function and follows the stochastic gradient descent principle. The HTFAF is used to estimate the peak values of the active and reactive segments of load current. These peak values are used to precisely determine reference grid currents. The control structure for the DSTATCOM is designed to provide harmonics-free, sinusoidal, balanced grid currents under both linear and non-linear, as well as balanced and unbalanced loads. Furthermore, the system has the ability of operate in either PFC or ZVR modes. The proposed control structure is also compared with existing control structure LMF and LMS and found to be superior. The MATLAB/Simulink environment is used for the design of a grid-connected DSTATCOM and its control logic. The performance of the system is also validated using the OPAL-RT real-time simulator.

On-board chargers (OBCs) with conventional two-stage architecture, consisting of an active front-end (AFE) converter and an isolated dc-dc stage, require bulky line filters and dc-link capacitors, resulting in low volumetric efficiency. Active third-harmonic injection and current unfolding methods offer significant improvement in terms of efficiency and power density in power factor correction (PFC) applications. However, existing unfolding-based topologies require two isolated dc-dc converters capable of handling the rated power for PFC and output voltage regulation. This article presents a three-phase ac-dc converter with a third-harmonic current injection circuit that processes a fraction of the total power and a single isolated dc-dc converter for galvanic isolation. Line frequency switching in the rectifier produces varying dc-link voltages, eliminating the requirement of bulky electrolytic capacitors. The article discusses detailed operation and design procedures along with an elaborate comparative analysis between the proposed topology and the conventional two-stage and Swiss rectifier-based isolated topologies. A 6.6 kW prototype is developed and tested for experimental validation of the system in both balanced and unbalanced grid conditions. The experimental results demonstrate unity power factor (upf) operation throughout the operating range, achieving a peak efficiency above 97%.

The article deals with the problem of active power loss and voltage in the 220 kV electric network in the Northern part of the electric system of the Republic of Tajikistan. This problem is caused by the lack of reactive power com pentation in the nodes of the distribution network with a voltage of 10 kV and the transfer of the necessary reactive power to consumers via the electric network with a voltage of 220 kV or lower. In the nodes of the 10 kV distribution network, the maximum values of active and reactive power obtained by calculation are given. To solve the problem of reducing active power and voltage losses, it is proposed to decentralize reactive power compensation by placing reactive power compensation facilities on the 10 kV side. In order to justify the effectiveness of decentralization of reactive power compensation with the installation of reactive power compensation facilities on the 10 kV side, calculations were performed for all high-voltage substations of the Northern electric power system of the Republic of Tajikistan, as well as on the basis of the real existing 220 kV electric network for one node consisting of two transformer substations (TS Sughd - 500 and TS Hadzhent substations), using the Matlab software package, Power Systems built a computer model for optimizing the 220 kV power grid by reactive power.

Due to relatively low cost and flexible performance, Dynamic Capacitor (D-CAP) is often designed to implement dynamic reactive power compensation, whose output current might distort under the effects of background harmonic voltage from the grid or non-ideal PWM mode caused by non-linear switch characteristics. This paper presents a reactive power compensation control strategy with waveform quality amelioration of output capacitive current for single-phase Buck-type D-CAP. Through establishing basic control equations, reactive power compensation principle and equivalent model of single-phase Buck-type D-CAP are analyzed. In order to suppress output harmonic current, duty ratio of Buck-type D-CAP is generated by means of introducing Even Harmonic Modulation (EHM). Then a selective current control strategy in multiple synchronous reference frames is adopted to track reactive power compensation current reference with nearly zero steady-state error and alleviate output current distortion with demanded harmonic components. Finally, a series of experimental results from single-phase Buck-type D-CAP laboratory prototype are provided to verify the validity of dynamic reactive power compensation and almost sinusoidal output current waveform optimizing method.

Reactive power compensation in grid connected AC-systems contributes to improve grid stability and reliability. Given that Active Front-End (AFE) rectifiers have the same power circuit topology of static VAR generators, they can ensure reactive power ancillary service besides their basic functions. In this context, this paper presents steady-state analysis and optimal DC-link voltage control for an AFE rectifier with reactive power ancillary service. Firstly, the minimum required level of DC-link voltage for optimal operation of the AFE rectifier with reactive power ancillary service has been investigated. Secondly, an optimal design of the DC-link voltage PI controller has been carried out to ensure the following control objectives: i) minimization of the transient DC-link voltage fluctuations in response to rough changes of the consumed active power ii) mitigation of the third harmonic component of the grid current under steady-state condition to comply with standards. A genetic algorithm based on multi-objective optimization has been proposed to determine the gains of the PI controller used in the DC-link voltage control loop. Simulation results demonstrated that the obtained control performances comply with the analytical study.