A New Flicker Contribution Tracing Method Based on Individual Reactive Current Components of Multiple EAFs at PCC

In this paper, a new flicker contribution tracing method has been proposed to determine the individual flicker contributions of multiple electric arc furnace (EAF) loads to the flicker measured at the point of common coupling (PCC). The proposed method decouples the flicker contribution of the interconnected electricity system from the individual contributions of the loads connected to the measured PCC, using the individual current variations of the loads, and the estimated short-circuit system impedance. It has been shown that individual flicker contributions of the loads are mainly caused by the variation of their reactive current components. Since the computational complexity of the proposed method is low, it is appropriate for on-line applications. The algorithm can easily be embedded on a power quality analyzer, which can be employed as a flicker-contribution-meter. Field data collected at a PCC supplying multi-EAF plants have been used to verify the validity of the proposed method in a successful manner

All SiC PWM rectifier-based off-board ultrafast charger for heavy electric vehicles

This study deals with the design, implementation and experimental performance of all silicon carbide pulse width modulation (SiC PWM) rectifier-based off-board ultrafast chargers (UFCs) for lithium titanate batteries of heavy electric vehicles. Different UFC configurations are proposed, depending upon the nominal battery voltage (400-1000 V DC) and charge capacity. Operating principles and control of UFC at unity and leading power factors are assessed and corresponding operating modes of PWM rectifier are discussed. The combined effect of reverse conduction characteristic of SiC power metal oxide semiconductor field effect transistor (MOSFET) and built-in SiC Schottky diode is taken into account in all the analyses carried out. The operating performance of the developed UFC, such as the switching characteristics of SiC power MOSFET modules, efficiency, input current total demand distortion (ITDD), and thermal limitations of the SiC PWM rectifier have been assessed for various charge voltages and charge capacities, both by computer simulations and laboratory tests. Power circuit layout considerations of the proposed system are also given in this study. Excellent performance results for 10 kHz switching frequency are obtained from the developed 200 kW UFC, with operating efficiencies higher than 98.5% for all charging rates up to five times the battery capacity, and ITDDs <2.2% for the whole operating range

Identification of Harmonic Current Contributions of Iron and Steel Plants Based on Time-Synchronized Field Measurements - Part I: at PCC

This is the first of a two-paper series, in which a field-data-based analytical method is proposed to determine the harmonic current contributions of each Iron and Steel (I&S) Plant supplied from the Point of Common Coupling (PCC) and the upstream loads at the utility side. The non-linear characteristics of the plants and the utility are modeled as harmonic current sources, whereas the linear parts of the proposed model consist of passive circuit elements. In the proposed method, the harmonic current contributions of loads are decoupled from the upstream effects and they are determined through the harmonic Norton's equivalent circuit model of the system constructed on the basis of the sample by sample, time-synchronized field measurements of load current and PCC voltage signals. This method can be applied to circuit schemes with any number of plants supplied from a given PCC. The results have shown that the proposed method can be used as a successful estimation tool to determine the harmonic current contributions of all I&S Plants connected to the PCC

Correlation Between Multiple Electric Arc Furnace Operations and Unscheduled Power Flows in the Interconnection Lines at the Eastern Cross Border of ENTSO-E

In this paper, the correlation between unscheduled power flows in the interconnection lines at the eastern cross border of the European Network of Transmission System Operators for Electricity (ENTSO-E) and multiple electric arc furnace (EAF) operations in Turkey has been assessed. Turkey is interconnected to ENTSO-E at the eastern cross border via Greece and Bulgaria, with a 400-MW export and a 550-MW import agreement. In order to determine the degree of the relationship between the unscheduled power exchange between Turkey and Europe, and the multiple high-power EAF operations, Pearson correlation method has been employed. For this purpose, time-synchronized data of active power consumption have been collected from 17 major EAF plants during 1 week with a time resolution of 3 s, by using custom-design, synchronized power-quality (PQ) analyzers. A total peak-power consumption of nearly 1.5 GW of multiple EAF loads has been recorded. The results obtained have been evaluated by the use of the National Power Quality Monitoring System of Turkey, which continuously monitors the power flows in the interconnection lines of the ENTSO-E by PQ analyzers. The rate of change in total EAF power consumptions higher than 200 MW in less than 15 s against the rate of change in area control error (ACE) index is found to be closely correlated to each other, with a Pearson correlation coefficient (CC) of 0.8. Since the response of the frequency restoration reserve of power plants is much slower, such rapid fluctuations in the power consumption of multiple EAFs collectively result in uncontrollable power flows in the interconnection lines at the eastern cross border of ENTSO-E

Data Mining Framework for Power Quality Event Characterization of Iron and Steel Plants

In this paper, a power quality (PQ) knowledge discovery and modeling framework has been developed for both temporal and spatial PQ event data collected from transformer substations supplying iron and steel (I&S) plants. PQ event characteristics of various I&S plants have been obtained based on clustering and rule discovery techniques. The data are collected by the PQ analyzers, which detect the voltage sags, swells, and interruptions according to the IEC Standard 61000-4-30. The constructed clustering strategy ensures feasible system monitoring by reducing unmanageable number of PQ events collected by the distributed PQ measurement systems into event clusters count. An abstraction for event representation has been developed, through which representative feature bags are constructed for each event to be used in the similarity decisions. The developed model has been applied satisfactorily to PQ event data obtained from 15 major transformer substations supplying heavy industry zones of the transmission system up to a five-year time period and from two additional transformer substations supplying some other industrial zones, for comparison purposes. The developed PQ data mining framework, which is used to identify PQ event distributions based on the event descriptions given in the IEEE Std. 1159, provides a useful analysis and evaluation infrastructure for taking countermeasures against the most probable event occurrences, specific to those feeders of I&S plant transformer substations

A New Field-Data-Based EAF Model for Power Quality Studies

new electric arc furnace (EAF)-specific model based on field measurements of instantaneous furnace voltages and currents has been proposed. This model presents the dynamic behavior of the EAF system, including all parts, i.e., the EAF transformer, the secondary circuit, the electrode movements, and the arc. It consists of a cascade connected variable-resistance and -inductance combination to represent the time variation at the fundamental frequency and a current source in parallel with it to inject the harmonics and interharmonics of the EAF current. The model takes into account several typical tap-to-tap periods of the specific EAF operation. This model is particularly advantageous for power quality (PQ) analysis and development of flexible alternating current transmission system solutions for PQ problem mitigation of a given busbar supplying single- or multi-EAF installations. The validity of the proposed model has been verified by comparing EMTDC/Power Systems Computer-Aided Design simulations of the model with the field measurements. The results obtained have shown quite satisfactory correlation between the proposed model and the actual EAF operation

Enhanced Nationwide Wind-Electric Power Monitoring and Forecast System

This paper describes an enhanced monitoring and forecast system for the electrical power generated from wind in Turkey. Wind power plant (WPP) owners, transmission system operator, distribution system operators, and renewable energy experts are the shareholders of this system. The developed monitoring and forecast system is composed of wind electricity analyzers and reference wind masts, one for each WPP, a Wind-Electric Power Monitoring and Forecast Center (WPMFC) equipped with database, data processing, and application servers, and the associated monitoring and forecast software. All shareholders can communicate with the developed WPMFC in order to retrieve preprocessed wind-electric power forecast data and power quality data, through the IP network according to their authorization level. The electrical and meteorological raw data can also be retrieved for postprocessing. The developed system is based on global positioning system (GPS) synchronized, real-time field measurements taken from each WPP, in addition to the use of mesoscale numerical weather prediction models. Instantaneous electrical and meteorological quantities of each WPP can be monitored continuously through the WPMFC. The forecast system employs physical, statistical, and hybrid models combining both approaches. Some sample monitoring and forecast results are given in the paper to illustrate the benefits and abilities of the developed system

Operating principles and practical design aspects of all SiC DC/AC/DC converter for MPPT in grid-connected PV supplies

A 20 kW, 20 kHz high frequency (HF) link maximum power point tracking (MPPT) converter for a grid-connected PV supply, based on all silicon carbide (SiC) power semiconductors, is presented. In the developed converter, SiC power MOSFETs are used in the low-voltage PV panel side and SiC Schottky diodes on the high-voltage DC output, in order to maximize the power conversion efficiency and the power density. Operating principles of the resulting dual H-bridge MPPT converter and the practical aspects of the converter design and its circuit layout, are described in detail. The implemented converter performance is compared with that of a classical Si-IGBT and hybrid-IGBT based MPPT converter in terms of efficiency. This configuration can compete with the non-isolated MPPT converter topologies, such as the boost converter commonly used in grid-connected PV systems, since it allows the possibility of using a conventional two-level, three-phase grid-connected inverter. This is due to the enhanced common-mode EMI performance as compared to non-isolated MPPT topologies, resulting in a competitive high efficiency PV converter design with galvanic isolation. It has been shown that the converter size can be shrinked up to a power density of 1.6 kW/lt, with a DC-DC converter full-load efficiency of 98%. The resulting compact and highly efficient SiC power MOSFET based HF link MPPT converter is suggested to be a part of grid-connected, multi-string PV supplies with simple inverter topologies in the future

Multi-DSP and -FPGA-Based Fully Digital Control System for Cascaded Multilevel Converters Used in FACTS Applications

In this paper, a fully digital controller based on multiple digital signal processor (DSP) and field-programmable gate array (FPGA) boards has been proposed for parallel-operated cascaded multilevel converters (CMC) used in flexible AC transmission system (FACTS) applications. The proposed system is composed of a DSP-based master controller in combination with a multiple number of slave DSP boards, FPGA boards, microcontrollers, a programmable logic controller (PLC), an industrial computer, and their peripherals in interaction. Inter-communication of these digital controllers is achieved mainly through fiber-optic links, via synchronous serial data link wherever a high-speed, full duplex communication is needed, and via asynchronous serial communication interface wherever relatively slow communication speed is required. The proposed fully-digital control system has been implemented on a sample 11-level CMC-based 154-kV, +/-50-MVAr transmission type static synchronous compensator (T-STATCOM). Field test results have shown that the proposed fully digital control system provides good transient response and steady-state characteristics for the oveall system including protection and monitoring functions

Multipurpose Platform for Power System Monitoring and Analysis With Sample Grid Applications

This paper is devoted to the design and implementation of a multipurpose platform (MPP) for power system monitoring and analysis. This MPP is a novel device, which combines the abilities of a power quality (PQ) analyzer, an event logger, a synchronized phasor measurement unit, and an interarea oscillation identifier, all in one device. The multiple functions of the proposed MPP can serve the needs of the power system operators (SOs) as a wide-area monitoring system to observe the states and stability of the power system, and as a PQ analyzer to monitor the PQ events and parameters, permanently. Furthermore, the algorithms of flicker and harmonic current contributions at a point of common coupling can be embedded on this MPP, to determine the individual contributions of different loads supplied from the same bus. The operational features of the developed MPP have been tested on the Turkish electricity transmission system and its interfaces with the distribution system by installing 450 MPPs and integrating them with a monitoring and control center. The proposed all-in-one MPP can therefore meet the multiple requirements of the power SOs to serve the needs of modern electricity markets and convert an ordinary electricity system to a smart grid