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This article presents the comparison of 3D and 2D finite element models of a power transformer designed for reactive power compensation stations. There is a lack of studies in the literature on internal electromagnetic phenomena in the active part of a transformer operated in these conditions. The results of numerical 2D and 3D calculations of no-load current and losses in the transformer core were obtained by using various methods and models. The impact of considering the hysteresis loop phenomenon on the calculation of core losses was investigated by using the Jiles–Atherton core losses model. The results obtained in the paper show that the model of the core must contain the areas representing the influence of overlappings on the no-load current and also on the flux density field in the core. The capacitive load of the transformer increases the flux density in the core limbs by several percent, so the power losses there must also increase accordingly. As a summary of the research, differences in the values of losses in each core element between the capacitive load and no-load conditions are presented. The results presented in this paper indicate that considering nonlinearity related to the magnetic hysteresis loop has a significant impact on the calculation of the core losses of power transformers. [ABSTRACT FROM AUTHOR]

This paper introduces a new partitioned ant lion optimizer (PALO) strategy to improve the solution accuracy and quality of the optimal power flow (OPF) considering multi Static VAR Compensator (SVC) and Thyristor Controlled Series Controller (TCSC)-based FACTS devices. An interactive partitioning structure-based ALO is proposed to improve the solution of OPF by creating an interactive equilibrium between diversification and intensification during the search process. The decision variables such as active power, voltage magnitudes of generating units, tap transformers; reactive power of Static VAR Compensator (SVC), and the reactance of TCSC devices are optimized using a flexible partitioned process. Three objective functions, such as total fuel cost, total power loss, and total voltage deviation have been optimized considering load growth. The robustness of the proposed PALO has been validated on three test systems, the IEEE 30-bus, and two large test systems, the 300-bus and 2736 ps bus of the Polish power system. Results compared to many recent techniques prove the particularity and competitiveness of the proposed optimization strategy-based PALO. [ABSTRACT FROM AUTHOR]

This study investigates the mitigation of transient overvoltages (TOVs) in a microgrid supplied by renewable distributed generation resources, which include photovoltaic (PV) generators, hydro generation unit, and wind power generators. ATP/EMTP is used in this study as electromagnetic transient software. Accurate simulation models are needed to carry out the study. Therefore, a three‐phase PV system model based on the equivalent Newton–Raphson circuit is used, and the efficiency of the PV system components is studied. Then, the use of the PV generation system model for switching studies is investigated using two different electrical systems. The use of different mitigation methods for TOVs at the microgrid is investigated. Three different mitigation methods are considered. First, a device to compensate reactive power such as static var compensator (SVC) is represented as a TOVs mitigation method. Then, adding a supercapacitor as TOVs mitigation method is evaluated. After that, a combination of active and reactive power simultaneously to mitigate TOV, by the addition of SVC to a supercapacitor, is investigated. The grid‐connected mode and isolated mode of the microgrid are considered. The results show that the usage of SVC with supercapacitor has the ability to mitigate the transient overvoltage and the waveforms are more regular. [ABSTRACT FROM AUTHOR]

This article presents a novel nonlinear coordinate damping controller (NCDC) for high‐voltage direct current (HVDC) and static var compensator (SVC) based on synergetic control theory, which can improve the stability of interarea power system and multi‐infeed HVDC system by quickly changing the transmission power of HVDC and reactive power of SVC. The traditional control design of HVDC and SVC can improve the stability, but there may be a negative interaction between the controllers of HVDC and HVDC or HVDC and SVC. Furthermore, the power system is a strong nonlinear system, and the controller designed by a linearized model may reduce its performance. To solve these problems, this article first constructs a unified macro variable and manifold, which contains the model of HVDC and SVC. The manifold sets the deviation value of the center of inertia (COI) frequency of the two systems connected by HVDC to zero. Then, a nonlinear HVDC and SVC coordinated controller is derived based on the synergetic control theory. The global stability of the controller is proven by the Lyapunov theorem. Finally, the simulation results in a two‐area power system and a multi‐infeed system using the power systems computer aided design (PSCAD) show the effectiveness and superiority of the proposed controller. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

In this study main reactive power calculation methods are evaluated and compared. Furthermore, a novel simple method that can be used for calculation of reactive power in electric arc furnace (EAF) plants is proposed. The focus here is on their application in the control system of static VAr compensators (SVCs). SVC can compensate only the fundamental harmonic component. So the reactive power signal used in the control system should be sensitive only to the main harmonic component. In addition, the reactive power calculation should be fast enough that SVC can follow the quick changes of the load to mitigate the flicker efficiently. To compare various reactive power calculation methods and to evaluate the proposed method, the simulated known loads are used beside huge amount of practical data recorded in Mobarakeh Steel Company in Isfahan/Iran. Results show the proposed method has the best performance for SVC control system. [ABSTRACT FROM AUTHOR]

In electrical arc furnaces (EAFs), an unstable arc leads to unfavorable operation of the EAF, which can be rectified by using series reactors. Installation of the series inductor affects some electrical parameters of the EAF, such as arc stability, power factor, arc length, and the EAF efficiency. Furthermore, it reduces the effective transferred power to the EAF. To achieve desired transferred power after installation of the series reactors, the secondary voltage of the EAF transformer should be increased. However, after any tap changing of the EAF transformer, arc stability and other relevant parameters are affected. So the impact on the EAF electrical magnitudes caused by changes in the series reactor and in the EAF transformer tap should be simultaneously studied. This research deals with a new method for optimal setting of the series reactor and EAF transformer tap to achieve the EAF best performance. Using a nonlinear model for the EAF, its electrical characteristics, at nominal transformer current and for all of the possible transformer and reactor taps, are calculated and the results are tabulated. Using these tables, the optimal setpoint for transformer and series reactor taps is determined in different conditions. Finally, the method is investigated from an economic point of view. [ABSTRACT FROM AUTHOR]

Electric train system is a very large load for the power network. This load consumes a large amount of reactive power. In addition, it causes a massive unbalance to the network, which results in many problems such as voltage drops, high transmission losses, reduction in the transformer output ability, negative sequence current, mal-operation of protective relays, etc. In this paper, a novel real-time optimization approach is presented to adjust the static VAR compensator (SVC) for the traction system to realize two objectives; current unbalance reduction and reactive power compensation. A multi-objective optimization technique entitled non-dominated sorting genetic algorithm (NSGA-II) is used to fulfill the regarded objectives simultaneously. A comprehensive simulator has been designed for electric train network modeling that is able to adjust the parameters of SVC in an optimum manner at any time and under any circumstances. The results illustrate that the provided method can efficiently reduce the unbalancing in current as well as supply the demanded reactive power with acceptable precision. [ABSTRACT FROM AUTHOR]

Voltage stability is a common issue in developing power system. It is mainly affected by reactive power balance in the system. If reactive power is not well planned and managed, there is possibility of occurrence of voltage instability in the system. One solution to prevent voltage instability in the system is by VAR compensation. In this work, new technique to determine the placement of different types of shunt VAR compensators based on sensitivity method is presented. Simultaneous planning of SVC and STATCOM placement is also conducted. Improvement in system stability is achieved using the method. [ABSTRACT FROM AUTHOR]