Detection of Grid Voltage Anomalies via Broadband Subspace Decomposition

Due to the increase of sensitive loads on the mains power grid, measurement and monitoring of the power quality (PQ) have become an important factor for both consumers and operators. As is well-known, PQ problems occur in a very short time period with specific characteristics. In transmission or distribution systems, power quality data are collected from monitoring devices such as digital fault recorders, power quality and dynamic system monitors, etc. The recorded data has to be analysed in order to understand system anomalies. These anomalies may be due to sources of broadband noise. In this study, we employ broadband subspace decomposition, using polynomial eigenvalue decomposition, to detect these anomalies. Results demonstrate that this method may be considered as a new and effective tool for measurement and monitoring of PQ problems

Relevance of polynomial matrix decompositions to broadband blind signal separation

The polynomial matrix EVD (PEVD) is an extension of the conventional eigenvalue decomposition (EVD) to polynomial matrices. The purpose of this article is to provide a review of the theoretical foundations of the PEVD and to highlight practical applications in the area of broadband blind source separation (BSS). Based on basic definitions of polynomial matrix terminology such as parahermitian and paraunitary matrices, strong decorrelation and spectral majorization, the PEVD and its theoretical foundations will be briefly outlined. The paper then focuses on the applicability of the PEVD and broadband subspace techniques — enabled by the diagonalization and spectral majorization capabilities of PEVD algorithms—to define broadband BSS solutions that generalise well-known narrowband techniques based on the EVD. This is achieved through the analysis of new results from three exemplar broadband BSS applications — underwater acoustics, radar clutter suppression, and domain-weighted broadband beamforming — and their comparison with classical broadband methods

Design of FIR paraunitary filter banks for subband coding using a polynomial eigenvalue decomposition

The problem of paraunitary filter bank design for subband coding has received considerable attention in recent years, not least because of the energy preserving property of this class of filter banks. In this paper, we consider the design of signal-adapted, finite impulse response (FIR), paraunitary filter banks using polynomial matrix EVD (PEVD) techniques. Modifications are proposed to an iterative, time-domain PEVD method, known as the sequential best rotation (SBR2) algorithm, which enables its effective application to the problem of FIR orthonormal filter bank design for efficient subband coding. By choosing an optimisation scheme that maximises the coding gain at each stage of the algorithm, it is shown that the resulting filter bank behaves more and more like the infiniteorder principle component filter bank (PCFB). The proposed method is compared to state-of-the-art techniques, namely the iterative greedy algorithm (IGA), the approximate EVD (AEVD), standard SBR2 and a fast algorithm for FIR compaction filter design, called the window method (WM). We demonstrate that for the calculation of the subband coder, the WM approach offers a low-cost alternative at lower coding gains, while at moderate to high complexity, the proposed approach outperforms the benchmarkers. In terms of run-time complexity, AEVD performs well at low orders, while the proposed algorithm offers a better coding gain than the benchmarkers at moderate to high filter order for a number of simulation scenarios

Voltage Distortion Mitigation in a Distributed Generation-integrated Weak Utility Network Via a Self-tuning Filter-based Dynamic Voltage Restorer

The dynamic voltage restorer (DVR) is mainly used in a utility grid to protect sensitive loads from power quality problems, such as voltage sags and swells. However, the effectiveness of the DVR can wane under unbalanced grid voltage conditions. Recently, DVR control algorithms have been developed that enable the elimination of voltage harmonics in weak and distorted utility networks. This paper presents a modified control method for the DVR, which can (1) compensate the voltage swell and (2) eliminate the voltage harmonics in a combined utility condition consisting of voltage unbalance and harmonic distortion. A self-tuning filter (STF) is used along with the pq controlmethod to increase the control performance of the DVR. One of the advantages of STF is that it eliminates the need to have multiple filters as part of the control method, and thus reduces the controller complexity. Analysis of the fault ride-through capability of the new DVR revealed an improvement in the voltage stability offered to distributed generation-integrated weak utility networks. The proposed DVR control method is modeled in MATLAB/Simulink and tested in both off-line and real-time environments using theOPALRT real-time platform. Results are then presented as a verification of the proposed system

Control of the Shunt Active Power Filter under Non-ideal Grid Voltage and Unbalanced Load Conditions

In this study a new method is proposed in order to improve the harmonic suppression efficiency of Active Power Filter for the problems caused by the distorted and unbalanced voltages with unbalanced load currents in control strategy. The proposed control method gives an adequate compensating current reference even for non ideal voltage and unbalanced current conditions. The results of simulation study are presented to verify the effectiveness of the proposed control technique in this study

New hybrid active power filter for harmonic current suppression and reactive power compensation

In the case of undistorted and balanced grid voltages, low ratio shunt Active Power Filters (APFs) can give unity power factors and achieve current harmonic cancellation. However, this is not possible when source voltages are distorted and unbalanced. In this study, the cost-effective hybrid active power filter (HAPF) topology for satisfying the requirements of harmonic-current suppression and non-active power compensation for industry is presented. An effective strategy is developed to observe the effect of the placement of power capacitors and LC filters with the shunt active power filter. A new method for alleviating the negative effects of a non-ideal grid voltage is proposed that uses a self-tuning filter algorithm with instantaneous reactive power theory. The real-time control of the studied system was achieved with a field programmable gate array (FPGA) architecture, which was developed using the OPAL-RT system. The performance results of the proposed HAPF system is tested and presented under non-ideal supply voltage conditions

Improved harmonic suppression efficiency of single-phase APFs in distorted distribution systems

In this study, a control method is proposed to improve the harmonic suppression efficiency of the single phase active power filter in a distorted power system to suppress current harmonics and reactive power. The proposed method uses the self-tuning filter (STF) algorithm to process single phase grid voltage in order to provide a uniform reference grid current, which increases the efficiency of the system. The results of the simulation study are presented to verify the effectiveness of the proposed control technique in this study

Investigation of a polynomial matrix generalised EVD for multi-channel Wiener filtering

State of the art narrowband noise cancellation techniques utilise the generalised eigenvalue decomposition (GEVD) for multichannel Wiener filtering which can be applied to independent frequency bins in order to achieve broadband processing. Here we investigate the extension of the GEVD to broadband, polynomial matrices, akin to strategies that have already been developed by McWhirter et. al on the polynomial matrix eigenvalue decomposition (PEVD)

Analysis of broadband GEVD-based blind source separation

One approach to blind source separation of instantaneously mixed, non-stationary sources involves using the generalized eigenvalue decomposition of two estimated covariance matrices. The assumption is that the source statistics change with time whilst the mixing matrix does not. A recent generalisation of this approach to convolutive mixtures was achieved by extending the generalized eigenvalue decomposition to polynomial matrices. In this paper, we present a further investigation into this broadband BSS technique. We derive some expressions for the conditions under which source separation is possible. The validity of our analysis is illustrated through some computer simulations

Control of the shunt Active Power Filter under non-ideal grid voltage and unbalanced load conditions

In this study a new method is proposed in order to improve the harmonic suppression efficiency of Active Power Filter for the problems caused by the distorted and unbalanced voltages with unbalanced load currents in control strategy. The proposed control method gives an adequate compensating current reference even for non ideal voltage and unbalanced current conditions. The results of simulation study are presented to verify the effectiveness of the proposed control technique in this study