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This paper analyzes and proposes technical considerations for the selection and design of passive filter schemes rated at several mega VARs to compensate reactive power and current harmonics in mining power distribution systems. The paper includes technical information and analysis required to select the most adequate passive filter topology, to select the tuning frequency for each unit, to calculate filter parameters, and to distribute reactive power between passive filters. Passive filter schemes analyzed in this paper are used to compensate mining power distribution systems, especially when high-power grinding mill drives energized from 12-pulse cycloconverters are used in conjunction with several other nonlinear loads. This paper also analyzes technical limitations that passive filters present in the attenuation of low-frequency current harmonics. Finally, two power distribution systems with different passive filters schemes are evaluated, and the limitations in the attenuation of low-frequency current harmonics generated by cycloconverters are demonstrated with measured results. [ABSTRACT FROM AUTHOR]

A single-objective predictive control method that deals with four main control objectives applied to a multivariable single-phase three-level neutral-point-clamped converter operating as an active power filter is proposed in this paper. The four control objectives are to self-support the dc-bus voltage under load variations, to compensate the reactive power and the current harmonics, and to balance the dc capacitor voltages by using a predefined combination of the redundant switching states of the converter. The main contribution of the proposed method is that these objectives are accomplished without using weighting factors in the cost function, which eliminates problems such as multiobjective optimization or additional empirical procedures for determination of these factors. As a result, the method is easy to implement and rapidly selects the optimal voltage to improve the dynamic-state performance. Experimental results from a 2-kVA prototype are presented to prove that the method is valid for single-phase compensation. The well-known effect of model parameter errors' issue, which is inherent in predictive control methods, is also tested to confirm that the harmonic distortion in the grid current is below 5% even when the predictive model has a 25% error between actual and theoretically estimated grid impedance values. [ABSTRACT FROM PUBLISHER]

This paper presents a method for predicting the flicker level that is generated by the high-power load in a distribution system. Through the development of the Flickermeter that met the International Electrotechnical Commission requirements, a reference curve is obtained based on the variation of voltage and the amount of changes per minute of the load. The purpose of this prediction is to determine if the load operation will produce flicker before being connected to the electrical system. This analysis cannot be developed by power system software due to the Flickermeter complexity and the amount of data that is required for processing. [ABSTRACT FROM PUBLISHER]

A discrete-time linear control strategy for a multilevel three-phase unified power quality conditioner (UPQC) based on single-phase power cells is presented. The multi-variable, nonlinear, and coupled features of these topologies make the control strategy design a difficult task. Controlling this kind of system with single-variable linear controllers—as proposed in this work—presents significant advantages compared with other approaches as simplicity in the design steps due to the large amount of tools developed for this kind of schemes. Particularly, a classic design method based on the root locus approach is used to choose the controllers parameters in order to achieve a given dynamical behavior. Compensation of reactive power and fundamental frequency disturbances is presented in this paper as part of a general control strategy for multilevel active power filters. The proposed control strategy is implemented on the TMS320C6713 DSP-based system for a low-power laboratory prototype, and thus the controllers design is carried out on the discrete-time and -frequency domain. Also, due to the inherent asymmetries among the power cells in a modular topology, a dedicated local control strategy is proposed to ensure a symmetrical distribution of the power among the power cells. This feature allows the semiconductor devices of each module to operate under the same voltage and current ratings. Simulated and experimental results showing stationary and transient conditions demonstrate the feasibility of the control scheme. [ABSTRACT FROM PUBLISHER]