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Steel production worldwide continues to grow and, consequently, also the energy consumption of the steel sector. With the applications of the electric arc furnace route in the steelmaking process, the concern with aspects of power quality and overload of the transmission grid lines increases. This work presents the zero harmonic distortion (ZHD) converter static synchronous compensator (STATCOM), which makes it possible to increase the displacement power factor of an electric arc furnace (EAF) application from 0.88 to 0.98 with total demand distortion in the grid around 1.44% with the ZHD prototype operation, this being accomplished without using high-order sinusoidal filters and with consolidated components in the industry. [ABSTRACT FROM AUTHOR]

This article proposes a modified grey wolf optimization (MGWO) which has improved rate of convergence and avoids local optima stagnation. This is achieved by improving the exploration–exploitation balance in conventional grey wolf optimization (GWO). Moreover, the use of weighted-distance strategy allows quick identification of the global optima in the proposed MGWO. This optimization is then applied for the control of a three-phase, 11-level hybrid cascaded multilevel inverter (HC-MLI). Selective harmonic elimination pulsewidth modulation technique is implemented through MGWO which generates optimal switching angles for the HC-MLI so as to eliminate lower order harmonics such as 5th, 7th, 11th, and 13th from the output voltage. In MGWO optimized HC-MLI, balancing of capacitor voltage is made possible at higher modulation index by making use of the available redundant switching states. The performance of the proposed work is validated through simulation and experimentation on a 1.5 kW prototype. The results obtained through simulation show that the MGWO algorithm is more efficient and accurate than other reported algorithms such as GWO, genetic algorithm, and particle swarm optimization in terms of performance, harmonic reduction, and convergence rate. [ABSTRACT FROM AUTHOR]

A 12-pulse converter has been commonly used for a large-scale power generating system. The arrangement of a delta–delta (Δ–Δ) and a delta–wye (Δ–Y) phase-shift transformer pair in series with the voltage source eliminates undesirable harmonics from nonlinear loads. Recently, a novel front-end for a multi-generator power system was proposed, which utilizes a single Y–Δ transformer to shunt between the two 30° phase-shifted generator outputs and results in the comparable harmonic elimination performance to the conventional 12-pulse rectifier. The shunt-type Y–Δ transformer front-end achieves more than 75% transformer size reduction, making it extremely attractive to large-scale industrial and shipboard applications. However, the exact 30° phase shift between the two rotating generators can drift in a practical system, especially under dynamic conditions. The harmonic performance under the non-ideal 30° phase-shift condition can deteriorate with the Y–Δ shunt-type front-end. To understand the impact of non-ideal phase-shifted generator sources, this paper derives the mathematical models through the use of an equivalent circuit, a square-wave analysis, and the phasor representation to show the harmonic cancellation principle and verifies the results with the computer simulation. [ABSTRACT FROM AUTHOR]

In this paper, an electronic phase-shifting strategy has been optimized for a multiparallel configuration of line-commutated rectifiers with a common dc-bus voltage used in motor drive application. This feature makes the performance of the system independent of the load profile and maximizes its harmonic reduction ability. In order to further reduce the generated low-order harmonics, a dc-link current modulation scheme and its phase-shift values of multidrive systems have been optimized. Analysis, simulations, and experiments have been carried out to verify the proposed method. [ABSTRACT FROM PUBLISHER]

This work approximates the selective harmonic elimination problem using artificial neural networks (ANNs) to generate the switching angles in an 11-level full-bridge cascade inverter powered by five varying dc input sources. Each of the five full bridges of the cascade inverter was connected to a separate 195-W solar panel. The angles were chosen such that the fundamental was kept constant and the low-order harmonics were minimized or eliminated. A nondeterministic method is used to solve the system for the angles and to obtain the data set for the ANN training. The method also provides a set of acceptable solutions in the space where solutions do not exist by analytical methods. The trained ANN is a suitable tool that brings a small generalization effect on the angles' precision and is able to perform in real time (50-/60-Hz time window). [ABSTRACT FROM AUTHOR]

This paper presents the control of distribution static synchronous compensator (DSTATCOM) for reactive power, harmonics and unbalanced load current compensation of a diesel generator set for an isolated system. The control of DSTATCOM is achieved using least mean square-based adaptive linear element (Adaline). An Adaline is used to extract balanced positive-sequence real fundamental frequency component of the load current and a proportional–integral (PI) controller is used to maintain a constant voltage at the dc-bus of a voltage-source converter (VSC) working as a DSTATCOM. Switching of VSC is achieved by controlling source currents to follow reference currents using hysteresis-based PWM control. This scheme is simulated under MATLAB environment using Simulink and PSB block-set toolboxes for feeding linear and nonlinear loads. The modeling is performed for a three-phase, three-wire star-connected synchronous generator coupled to a diesel engine, along with the three-leg VSC working as a DSTATCOM. Results are presented to verify the effectiveness of the control of DSTATCOM for the load compensation and an optimal operation of the DG set. [ABSTRACT FROM AUTHOR]

This paper deals with the development and implementation of a current-source-converter-based static synchronous compensator (CSC-STATCOM) applied to the volt-ampere- reactive (VAR) compensation problem of coal mining excavators. It is composed of a ±750-kVAR full-bridge CSC with selective harmonic elimination, a low-pass input filter tuned to 200 Hz, and a Δ/Y-connected coupling transformer for connection to medium-voltage load bus. Each power semiconductor switch is composed of an asymmetrical integrated gate commutated thyristor (IGCT) connected in series with a reverse-blocking diode and switched at 500 Hz to eliminate 5th, 7th, 11th, and 13th current harmonics produced by the CSC. Operating principles, power stage, design of dc link, and input filter are also described in this paper. It has been verified by field tests that the developed STATCOM follows rapid fluctuations in nearly symmetrical lagging and leading VAR consumption of electric excavators, resulting in nearly unity power factor on monthly basis, and the harmonic current spectra in the lines of CSC-STATCOM at the point of common coupling comply with the IEEE Std. 519-1992. [ABSTRACT FROM AUTHOR]