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Intelligent power regulation is a prominent feature of smart railway systems; to enhance the grid-connected performance of railway loads while economically determining the size of power regulating units, this paper proposes a novel computation-efficient power programming strategy for railway power flow controller (RPFC) to implement power regulation in a.c. railway systems. Two key methods are developed: 1) determining two-phase loads’ PF-P & PF-PF combination model by accurately partitioning two-phase loads’ occurrence region with high probability, and 2) dynamically adjusting the exploring region of two-phase PFs for every load point in 1); in those methods, the intrinsic two-phase PF-PF and PF-P distribution properties of real train loads are fully considered (Note: “P” and “PF” stated above present active power and power factor respectively). In addition, the insight of the compensation principle and the advanced design capacity visualization scheme of RPFC are discussed with emphasis. Finally, a comprehensive performance investigation is carried out to validate the correctness of the proposed method. In this process, an exquisite power regulation unit in digital sense is created, contributing to the system-level application of smart railway systems. [ABSTRACT FROM AUTHOR]

In this article, a new harmonic mitigation system using double balanced impedance filtering power transformer (DBI-FPT) is proposed for improving the power quality (PQ). Designed for multistage distribution network with severe harmonic pollution, the proposed system enhances multiport filtering performance, mitigates resonance along with reduction of construction and maintenance costs compared to other alternative system. The simplified model of the proposed system is established by combining the short-circuit impedance calculation method and the characteristics of dual-balanced winding. By analyzing the influence of manufacturing errors on the dual-balanced winding in detail, the optimization method for filtering performance is given, which in turn guides the practical application of DBI-FPT effectively. After that, through comprehensively comparative analysis, the multiport harmonic mitigation characteristics, resonance avoidance, and amplification weaken mechanism of the proposed method are revealed. The experimental results validate that the proposed system is suitable for multiterminal PQ improvement and industrial application in multistage regional distribution network. [ABSTRACT FROM AUTHOR]

This paper proposes a transformer integrated filtering system (TIFS) for harmonic suppression in the industrial dc supply system. Designed for the electric environment with large current and severe harmonic contamination and the installation space with restricted planning area, the proposed TIFS has the merits of lower transformer loss, stronger ability in harmonic elimination, and higher integration of the electric equipment in the high-power industrial applications. The winding arrangement of the inductive filtering transformer with integrated reactor is introduced. Considering the influence of the residual weak coupling, the electromagnetic decoupling model of TIFS is established. Then, the interaction between the zero-impedance designed filtering winding and the decoupled winding is analyzed to determine the restricted range of the design parameter. The control strategy together with the transformer design method is further illuminated. At last, the prototype of TIFS is established in the laboratory. The experimental results verify the feasibility and effectiveness of the proposed filtering method. [ABSTRACT FROM AUTHOR]

This paper presents a new solution of power quality management for the photovoltaic (PV) power plant with the transformer integrated filtering method. The innovation of the PV power plant is that it contains two-stage filtering station, which consists of a box-type transformer with integrated filter and a 110 kV grid-connected transformer based on inductive filtering method. The filtering reactor can be integrated into the box-type transformer as a decoupled winding, so that the modular design of the box-type transformer and the passive filter is realized. Inductive filtering method applied in the grid-connected transformer not only improves the power quality at the point of common coupling, but dampens the harmonic resonance between the passive filter and grid. The hierarchical structure of the PV power plant is introduced firstly. Then, the equivalent circuit model and the mathematical model of the primary and secondary filtering stations are established, respectively. Moreover, the influence of the weak coupling of integrated reactor on the filtering performance is analyzed. The antijamming capabilities of the inductive filtering method and the traditional filtering method are compared under the condition of parameter disturbance. At last, the site tests of the PV power plant with transformer integrated filtering method are made, which show that the PV grid-connected system comprised of the two-stage filtering station has the characteristics of low harmonic emission, high power factor, and stable operation. [ABSTRACT FROM AUTHOR]

In this study, magnetic potential balance based active power filter integrated with distribution transformer (DT‐APF) is proposed for harmonic reduction in distribution systems. Instead of using a step‐down transformer for voltage matching, the active power filter is connected to the taps from the secondary windings of the distribution transformer. The filtering system's integration, operating efficiency as well as reliability are significantly enhanced. The topology of the proposed DT‐APF is introduced; the compensation principle, mathematical model as well as the corresponding detection method are described in detail. A non‐linear controller based on passivity‐based control (PBC) that ensures global asymptotic stability is proposed to obtain an excellent compensation performance. To verify the feasibility and effectiveness of the presented DT‐APF and PBC in harmonic suppression, results from MATLAB simulations and experiments of a down‐scaled prototype system at laboratory are demonstrated. [ABSTRACT FROM AUTHOR]

In this paper, a system with series hybrid converter and shunt active converter (SHC&SAC) for compensation in cophase high-speed electric railways is proposed. Unlike the general power flow conditioners, the dc-links of the two converters are separated, and therefore, the two converters can operate independently. Just by taking the advantage of the reactive power generation ability and novel connection of SHC&SAC, the grid-side power factor can be improved and negative-sequence current can be suppressed, especially on the cases of high-speed trains. Besides, because of the capacitor in SHC, the active capacity of SHC is significantly lower than that of SAC. To obtain a good current tracking performance, the passive control method, which is based on the dissipation characteristic of resistor, is adopted for controlling converters. And finally, the effectiveness of the system is verified by simulation and experimental results. [ABSTRACT FROM AUTHOR]

This paper presents a new system for reactive power compensation and suppression of negative-sequence current for power quality improvement in electrical railways and the feeding three-phase utility grid, based on YNvd-connected balance transformer. Different from the conventional railway static power conditioner based compensation systems, this system integrates multiplex back-to-back converters (MBTBC) into phase-β side flexible taps through a cascade connection instead of into phase-β side feeder via a coupling transformer, thus the installation space and initial costs are reduced significantly. In addition, a new power distribution strategy with simple implementation is adopted in this paper, by which the compensation capacity of MBTBC can be decreased by 25%, compared with the commonly used full compensation scheme. As the first part of this topic, this paper focuses on the theoretical analysis, including the system topology, basic and partial compensation principles and its implementation method. While, the controller design on converter-level, stability analysis, and simulation and experimental verification are the main tasks of the second part of this topic. [ABSTRACT FROM PUBLISHER]

This part mainly focuses on the implementation and verification of the reactive power compensation and negative-sequence current suppression system with YNvd-connected balance transformer, by means of simulation and experiment. The system model is presented, and a current control method, which explores the dissipation characteristic of the proposed system under two-phase rotating frame, is analyzed. Then, a stability analysis of this control is made, considering the deviations of system parameters and the time delay caused by the low-pass filter. Besides, dc-link overall control and balance control are investigated, and the self-balance ability of multiple dc links is briefly discussed. Both the simulation and experimental results verify the effectiveness of the proposed system topology, compensation strategy, and control method. [ABSTRACT FROM AUTHOR]

This paper proposes a controllably inductive power filtering (CIPF) method to improve the power quality of a shipboard power system (SPS). The main circuit topology for implementing the CIPF method in the SPS is presented, which contains a rectifier transformer integrated with linear filtering reactors, fully tuned branches, and a voltage-source inverter. The characteristic parameters of the rectifier transformer integrated with linear filtering reactors are investigated in detail by theoretical analysis. Furthermore, a mathematical model and an equivalent model are established to reveal the mechanism of harmonic suppression and the advantage of damping harmonic resonance of SPS. Moreover, a coordinated control strategy is designed based on the theoretical analysis. Finally, a detailed case study validates the proposed CIPF method and indicates that this method is suitable for SPS, because it can decrease the installed space and effectively prevent harmonic components from flowing into the generator side (power source), thus resulting in suppressing the vibration and noise pollution of the rectifier transformer. Besides, this method can effectively dampen harmonic resonance caused by the varied short-circuit capacity or the harmonic voltage in SPS. [ABSTRACT FROM AUTHOR]

In conventional HVDC systems where the harmonic filters and shunt capacitors are installed at the ac grid side, the converter transformers inevitably suffer the detrimental impacts caused by harmonic penetration. In this paper, combined with an inductive filtering method, a parallel delta-connected filtering-winding scheme for 12-pulse converter transformer units is proposed to reduce the harmonic currents flowing through the transformers and, thus, to attenuate the harmonic effects on them. This paper describes the presented transformer configuration in terms of the wiring scheme of the 12-pulse converter transformer unit and corresponding flowing paths of different harmonic currents with the orders of 3,6n\pm 1\left(\mathrmn=1,3,5,\ldots \right), 11 and 13 in the filtering winding circuit. Then, the mechanism of the proposed scheme on harmonic suppression to the converter transformers is explained theoretically. In an attempt to validate the theoretical analysis, simulations based on PSCAD/EMTDC and experiments in a laboratory prototype system are performed to evaluate the harmonic eliminating performance of the proposed scheme. [ABSTRACT FROM PUBLISHER]

In this letter, a virtual impedance comprehensive control (VICC) strategy is proposed for the controllably inductive power filtering (CIPF) system with a new filtering mechanism. This control strategy aims to satisfy the zero-impedance design precondition of the inductive power filtering system, and can dampen the harmonic resonance at the grid side. By the proposed zero-impedance control, the quality factor of the passive power device can be adjustable, and the single-tuned filter can be multituned. First, the main circuit topology for implementing the VICC-based CIPF is presented. Then, on the basis of the multipurpose control, the VICC strategy is designed. Furthermore, by means of the established equivalent circuit model and the corresponding mathematical model, the principles of the harmonic damping and the zero-impedance realization are revealed. Finally, the experimental results verify that the proposed control strategy can weaken the harmonic amplification effectively, and improve the filtering performance significantly. [ABSTRACT FROM PUBLISHER]

In this paper, a new industrial direct-current (dc) power supply system with the four-winding inductively filtered rectifier transformer (FW-IFRT) is proposed based on an inductive filtering (IF) method, which can effectively solve the power quality problems generally existing in the high-power rectifier system, such as high energy consumption, serious harmonic pollution, low power factor, and so on. The single-phase equivalent circuit model of such a new system is established based on the multiwinding transformer theory, and then its operating characteristics are investigated in detail. The harmonic suppression factor is proposed, and the influences of system and transformer impedances on the harmonic suppression characteristic are revealed. Finally, the simulation and experimental case studies are used to verify the effectiveness of the proposed system on the comprehensive improvement of power quality and operating efficiency. [ABSTRACT FROM PUBLISHER]

There are ever-increasing harmonic concerns caused by nonlinear loads in today’s low-voltage distribution systems. Therefore, a passive-filter-based transformer equipped in the box-type distribution substations is conceived for power quality improvement. Attempting to address the problem that physical size is strictly confined in these prefabricated substations, a distribution transformer with integrated filtering inductors is proposed in this paper. The configuration, electromagnetic decoupling circuit, and design procedures of this transformer are described. To verify the theoretical analysis, finite-element simulations and experiments of an integrated distribution transformer prototype are performed, by which the essential electromagnetic performances of the proposed transformer, such as electromagnetic decoupling and inductance linearity of the integrated inductors, are validated. [ABSTRACT FROM AUTHOR]

This paper presents an integrated hybrid railway power quality control system (HRPQC) to deal with the power quality problems in the electrical railway supply system. The prominent advantage of HRPQC is that, in the premise of adopting a hybrid compensating scheme for better performance, it can integrate the active system with the main transformer without other expensive low-frequency high-power auxiliary transformers. HRPQC's mathematical model, control idea, and transforming relationship in harmonic frequency are first presented. Second, the harmonic-suppressing mechanism and the resonance characteristics are analyzed in detail. Finally, simulation and experimental results verify the effectiveness of the proposed compensating system. [ABSTRACT FROM PUBLISHER]

A field-circuit coupling computation method is proposed in this paper to reveal the special electromagnetic characteristic of a novel inductive filtering (IF) method applied in high-voltage direct current (HVDC) converter station. The new converter transformer is modeled by using 3-D finite-element method, and the surrounding fully tuned branches, for creating precondition of implementing the IF method, are modeled by using the coupled circuits. The harmonic characteristic of the load-side current is modeled by using mixed harmonic current sources. The parameter design of the coupled circuit is also performed for the coupling model. Following this, based on the established coupling model, the multiphysical characteristics (e.g., electric field, magnetic field, excitation characteristic, and core losses) are analyzed in detail. The system simulation and the experimental results validate the modeling method. All of the research results indicate that the IF method can greatly reduce the harmonic currents in the grid winding, can improve the excitation performance, can improve the electromagnetic environment, and can reduce the harmonic losses of the HVDC converter transformer. [ABSTRACT FROM PUBLISHER]

This paper proposes a new direct current (dc) power supply system based on an inductive filtering method for one industrial dc load. The operating mechanism of the new inductive filtering method is analyzed, and then, the harmonic model and the equivalent model are established. Moreover, the impedance conditions for the implementation of the inductive filtering method are presented, and the influence of the filtering loop's impedance on the filtering performance is clarified. Both the simulation and the experimental study on one practical inductive-filtering-based industrial dc supply system for chemical electrolysis are used to validate the theoretical analysis. The research results show that the inductive filtering method not only greatly reduces the harmonic magnetic flux in the rectifier transformer but also prevents harmonic currents from flowing into the primary (grid) winding of the rectifier transformer. It presents good filtering and reactive power compensating performances to public networks and also increases the operating efficiency of the industrial dc power supply system itself. [ABSTRACT FROM PUBLISHER]

Different from the main circuit topology of the traditional current source converter (CSC)-based HVdc transmission system, this paper proposes a new CSC-HVdc transmission system based on a new inductive filtering method. Such new HVdc system characters as a new main circuit topology and mainly contains a new converter transformer and related full-tuned (FT) branches. With regard to the implementation conditions of the new inductive filtering method, the basic main circuit parameter design for the new converter transformer, the related FT branches, and the HVdc control system are presented, respectively. Based on these designed main circuit parameters and control system, the new CSC-HVdc system is modeled in the PSCAD/EMTDC environment, and correspondingly, through comparative study with the International Council on Large Electric Systems (CIGRE) HVdc benchmark model, the steady- and the transient-state operating characteristics of the new CSC-HVdc system are studied in detail. The research results show that the new CSC-HVdc system can widen the stable operating range, increase the dc transmission capacity, and meanwhile, improve the commutating performance of the CSC-HVdc converter. Moreover, it maintains the stable operating performance and represents the good fault-recovery ability when suffering the typical faults (e.g., single-phase or three-phase faults at the rectifier and the inverter side of the HVdc transmission system). [ABSTRACT FROM AUTHOR]

Harmonic magnetic fluxes in transformer's core and harmonic currents in grid‐side winding can be restrained via the inductive filtering technology. Vibration and abating noise of the core caused by the harmonic magnetic fluxes are controlled at the source, and has a good effect in reducing vibration and abating noise of the grid‐side winding. Vibration and noise characteristics of the inductive filtering converter transformer are tested under load. The experimental results verify this theory. [ABSTRACT FROM AUTHOR]