Josif J. Tomic

Frequency Estimation of Three-Phase Power System Using Weighted-Least-Square Algorithm and Adaptive FIR Filtering

A new technique for estimation of the instantaneous frequency based on simultaneous sampling of three-phase voltage signals is presented. The structure consists of two decoupled modules: the first is for adaptive filtering of input signals, and the second is for frequency estimation. A suitable and robust algorithm for frequency estimation is obtained. This technique provides better performance, compared with the technique based on a single-phase signal in relation to waveforms with noise. The technique is particularly important when asymmetric sags generate zero voltage in one of the three phases. In addition, it allows the measurement of the instantaneous frequency value of real signals for single- or three-phase systems. To demonstrate the performance of the developed algorithm, computer-simulated data records and calibrator-generated signals are processed. The proposed algorithm has been put to test with distorted three-phase voltage signals.

A New Power System Digital Harmonic Analyzer

In this paper, new digital instruments measuring power-quality indicators and harmonic analyzers are developed. A new technique for simultaneous local system frequency and amplitudes of the fundamental and higher harmonics estimation from either a voltage or current signal is presented. The structure consists of three decoupled modules: the first one for an adaptive filter of input signal, the second one for frequency estimation, and the third one for harmonic amplitude estimation. A very suitable algorithm for frequency and harmonic amplitude estimation is obtained. This technique provides accurate frequency estimates with error in the range of 0.002 Hz and amplitude estimates with error in the range of 0.03% for SNR = 60 dB in about 25 ms. The theoretical basis and practical implementation of the technique are described. To demonstrate the performance of the developed algorithm, computer simulated data records are processed. Data of the distribution power system voltage signals are also collected in the laboratory environment and are processed in a newly developed digital PC-based harmonic analyzer. It has been found that the proposed method really meets the need of offline applications. Even more, by using the parallel computation algorithms, this method should meet the need of online applications and should be more practical

An Adaptive Resonator-Based Method for Power Measurements According to the IEEE Trial-Use Standard 1459–2000

This paper proposes an accurate and computationally efficient implementation of the IEEE Standard 1459-2000 for power measurements. The algorithm has two stages. In the first algorithm stage, the voltage and current signals are processed in parallel, and their spectrums are estimated independently of each other. Signal harmonics are estimated in a wide range of frequency using an efficient algorithm with reduced complexity. The algorithm is based on a recently introduced common structure for recursive discrete transforms and consists of digital resonators embedded in a common negative feedback loop. In the second algorithm stage, the unknown power components and other power quality indices are calculated according to definitions in the IEEE Standard 1459-2000. To demonstrate the efficiency of the proposed algorithm, the results of computer simulations and laboratory testing are presented. The laboratory results show accurate input power component estimates for a nonlinear load with rapid input current amplitude changes. In addition, a simple LabView implementation, based on the point-by-point processing feature, demonstrates the techniques modest computation requirements and confirms that the proposed algorithm is suitable for real-time applications.

Multiple-Resonator-Based Power System Taylor-Fourier Harmonic Analysis

In this paper, a new approach to the harmonic estimation based on the linear transformation named Taylor-Fourier transform has been proposed. A multiple-resonator-based observer structure has been used. The output taps of the multiple resonators may fix not only the complex harmonic values but also, according to the actual resonator multiplicity, their first, second, third, fourth, and so on, derivatives at the corresponding frequency. The algorithm is recursive, which allows its implementation in embedded environment with limited memory. The estimation technique is suitable for application in a wide range of frequency changes, transient conditions, and interharmonics presence, with benefits in a reduced complexity and computational effort. To demonstrate the performance of the developed algorithm, computer simulated data records are processed.

Realization of Measurement Station for Remote Environmental Monitoring

The greenhouse effect is a naturally occurring process that heats the Earths surface and atmosphere. It is a result of the fact that certain atmospheric gases, such as carbon dioxide, water vapor, and methane, are able to change the energy balance of the planet by absorbing long wave radiation emitted from the Earths surface. Number of gases are involved in the human caused enhancement of the greenhouse effect. Carbon dioxide is the most important gas of these gases, which contributes about 55% of the change in the intensity of the Earths greenhouse effect. The global monitoring of the greenhouse gases is necessary for handling the global warming issue. This paper presents a practical implementation of a measurement station for environmental monitoring using Internet technology and large sensor networks. The application of the sensor networks in the environmental monitoring requires the development specific solutions. This paper presents a solution that relies on existing technology, but offers hardware and software upgrade due to the advantages of using the concept of virtual instrumentation. The application uses temperature sensors, air relative humidity sensors, gas sensors and others. The measurement station collects the data from the sensors and sends them to the users using the UDP protocol via the Internet and GPRS modem. The measurement station was implemented in LabVIEW programming package.

Power Components Estimation According to IEEE Standard 1459–2010 Under Wide-Range Frequency Deviations

This paper proposes an accurate and computationally efficient time-domain implementation of the IEEE Standard 1459-2010 for power measurements. The most important parts are adaptive low- and bandpass finite-impulse-response (FIR) filters that extract dc and fundamental components, respectively. In addition, coefficient sensitivity problems of the large-order FIR comb cascade structure are overridden by using a multirate (decimation) digital signal processing technique. Even more, by using decimation antialiasing filters, the parameter estimation accuracy is improved. The symmetrical components are estimated through adaptive transformation matrix of phase shifters. The algorithm convergence provided a fast response and adaptability. The effectiveness of the proposed technique is demonstrated by simulation results. The algorithm shows a very high level of robustness and high measurement accuracy over a wide range of frequency changes.

Maximally Flat-Frequency-Response Multiple-Resonator-Based Harmonic Analysis

This paper presents an improved approach to the recently proposed multiple-resonator-based method for the harmonic analysis that has been provided in the previous papers. Previously, two inherent particular cases have been considered. In these cases, reference points in which estimation is performed are located either in the middle or at the end of the observation interval. The first case exhibits a good noises and unwanted harmonics attenuation but possesses a large delay time. In the second case, the filters are able to form a zero-flat phase response about the operation frequency and hence able to provide instantaneous estimates, but with large overshoots caused by resonant frequencies at the edges of the passband, and the high level of the sidelobes, that also makes it susceptible to interharmonics and noise interference. The aim of this paper is to propose a compromised solution provided by the tradeoff between those opposite requirements by shifting this point along the observation interval. This way the frequency responses of the estimator are reshaped. A maximally flatness of the frequency response in the operation harmonic frequency is kept in all cases, but only locating the reference point in a fraction around the center of the observation interval provides flat-top frequency responses. The effectiveness of the proposed estimation technique is shown through simulations.

Group-Delay-Controlled Multiple-Resonator-Based Harmonic Analysis

In this paper, a modified and improved approach to the recently proposed multiple-resonator-based observer structure for harmonic estimation has been proposed. In the previous papers, two inherent particular cases have been considered. In the first case, estimation is performed in the point located in the middle of the observation interval, and exhibits good noises and unwanted harmonics attenuation but possesses a large response delay. In the second case, the estimation point is at the end of the observation window. In this case, the filters are able to form a zero-flat phase response about the operation frequency and hence able to provide instantaneous estimates, but with large overshoots caused by resonant frequencies at the edges of the pass band, and the high level of the sidelobs. In this paper, the estimation point is shifted along the observation interval reshaping frequency responses to tradeoff between those opposite requirements. The effectiveness of the proposed algorithm is shown through simulations.

Methods of environmental monitoring parameters based on smart measurement systems

As the effects of global warming are spreading globally, the world population encounters one of the most important social and scientific phenomena-changing the parameters of the environment due to pollution. Any conducted action requires precise and accurate measuring of the environmental parameters at several dozens of thousands points deployed around the world. Since financially, as well as practically, it is impossible to create such a large number of measuring stations which would network all over the planet, it is obvious that some alternative solutions must be found. A new measuring system is developed and measuring methods for remote measurement of environmental parameters are implemented. This system can be implemented as a stationary or mobile measuring station. The working hypothesis is based on the use of statistical analysis of measurement data. It leads to the possibility of reducing the number of sensors at measure station, as based on the monitoring of one value-gas concentration (the concentration of carbon monoxide) can be estimated values of other gas (the concentration of nitrogen — dioxide) in the case that they originate from the same source. Using prediction and regression models — interpolation and extrapolation have shown the possibility to reduce the number of measuring stations. Also, based on a mathematical model (ARMA) estimation of concentrations of gases based on previous measurements is shown.