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In this paper, a new approach is proposed to increase the flexibility of the reference current generation for active compensators. Although compensating all useless components of the current is ideal, it is sometimes desirable to target a subset of the possible components of the current due to power electronic converter power, switching speed limitations, etc. Furthermore, power quality objectives may vary over time. The proposed strategy utilizes a novel reference signal generator to provide online flexibility with respect to the compensation objectives. The reference signal generator utilizes a computationally efficient moving-window discrete Fourier transform along with an orthogonal decomposition of the current instead of the filters typically used to extract the desired components of the current. Each orthogonal component of the current can be adjusted independently in any percentage, thus providing the selective current compensation. The proposed reference signal generator also allows for easy extrapolation of the measured current, effectively canceling the delay inherent in the digital current control loop. Cancellation of the delay allows for the elimination of the spikes that typically occur due to poor tracking of fast slope transitions of the current reference. The advantages of the proposed control architecture have been verified by an experimental prototype. Index Terms--Active compensators, active power filter, harmonics, predictive control, recursive discrete Fourier transform (RDFT), selective current compensation.

Electric Power Research Institute's Control Center Application Programming Interface proposed the Common Information Model (CIM) as the common information exchange model, which provides an excellent platform for representing the components of a power system. This paper discusses using CIM for data modeling for ship power system analysis. Features include using the CIM to accommodate shipboard power systems. Detailed data models for a pulsed load and an active filter are presented and validated through simulation in Matlab. The general process to extend CIM for shipboard power system is briefly outlined. Further efforts are underway to develop a CIM-based shipboard baseline test case to standardize modeling terminology. Index Terms--Active filter, Common Information Model (CIM), data model, pulsed loads, shipboard power system.

Shunt active power filters (APF) are commonly used for the reduction of current harmonics and improvement of the power factor in power systems with nonlinear loads, such as diode rectifiers. A pulsewidth modulation (PWM) power converter constitutes the main component of the APF. The low-order harmonics of the line current are attenuated, but the switch-mode operation of the converter results in electromagnetic interference (EMI) spreading to the grid. Specifically, clusters of harmonics appear in the frequency spectra of voltages and currents of the converter at multiples of the switching frequency. In this paper, transferring the discrete spectral power of those harmonics to the continuous spectral power density is proposed as means for mitigation of the EMI. It is accomplished by randomization of the switching periods using a novel random PWM method (RPWM II). In contrast to the existing random PWM methods, in RPWM II the sampling frequency of the digital modulator is constant and equal to the average switching frequency. Computer simulations and experimental investigation of an APF designed for shipboard power systems are described, and the results are presented. They demonstrate significant reduction of the EMI, a feat achieved at practically no expense. Index Terms--Active power filters (APFs), electromagnetic interference (EMI) mitigation, random pulsewidth modulation (RPWM).

Resonant harmonic filters (RHFs) are effective devices for reducing supply current harmonics when only those load generated harmonics for which they are tuned are present. Other current harmonics as well as supply voltage harmonics may reduce the effectiveness of RHFs in harmonic suppression. To counter such reductions in effectiveness, an optimization based method for selection of filter branch parameters is developed for the conventional RHF. It takes into consideration the interaction of the filter with the distribution system and provides filter parameters that give the maximum effectiveness with respect to harmonic suppression. To accomplish this, a cost function is developed, its behavior examined, and appropriate constraint functions are developed. The results for optimized filters, applied in a test case, are given. Index Terms--Harmonic distortion, harmonic filter design, passive harmonic filters, shunt tuned harmonic filters.

Distribution voltage harmonics and load current harmonics other than harmonics to which a resonant harmonic filter (RHF) is tuned, deteriorate the filter efficiency in reducing harmonic distortion. The paper presents results of a study on dependence of this deterioration on the method of the filter design. The study was confined to four-branch RHFs of the 5th, 7th, 11th, and 13th order harmonics, installed on buses that predominantly supply six-pulse ac/dc converters or rectifiers. The filters under investigation were designed according to two different approaches: a traditional approach and an approach based on an optimization procedure. In the traditional approach, the reactive power allocated to particular branches of the filter and their tuning frequencies are selected at the designer's discretion, according to recommended practices. In the optimization based approach, the reactive power allocated to particular branches and tuning frequencies are resultants of an optimization procedure that minimizes the bus voltage and the supply current THD in the system with the filter under design. Index Terms--Harmonic distortion, harmonic filter design, non-sinusoidal systems, resonant harmonic filters.

The effectiveness of resonant harmonic filters (RHFs) in harmonic suppression is the resultant of two different types of resonance that affect the filters' effectiveness in an opposite manner. They are the resonance of the filter branches and the resonance of the entire filter with the distribution system inductance. Damping these resonances by reduction of the filter Q-factor affects the filter performance in a complex way. There are suggestions in the literature on RHFs that such a damping would improve the filter effectiveness. Unfortunately, no quantitative information to support such a suggestion is available. This paper presents the results from a study of the effect of the Q-factor on the filter effectiveness and on the loss of active power in the filter. Index Terms--Harmonics, resonant harmonic filters.