Andrzej Bien

Improvement of Accuracy of Power System Spectral Analysis by Coherent Resampling

The coherent resampling (CR) algorithm, which improves the accuracy of discrete Fourier transform (DFT)-based power system frequency analysis, is described in the paper. The algorithm uses extended Kalman filter for instantaneous frequency tracking and fractional B-spline resampler for signal approximation. The CR algorithm is a software counterpart of synchronous sampling, i.e., sampling, synchronized with fundamental frequency of the signal. CR may either be applied to previously noncoherently sampled signals or to work in realtime. Frequency estimation, amplitude spectrum estimation and THD factor estimation results obtained by presented algorithm are compared to those obtained by other methods. Both simulated and real signals were used for tests. Brief summary of realtime DSP implementation of CR algorithm is also given.

New method for noninvasive measurement of utility harmonic impedance

The new, noninvasive method of measurement for power system harmonic impedance is presented in the paper. The method is based on the observation of variations of voltage and current harmonics caused by natural load variability. The novelty of the method lays in a way the method rejects segments of data containing insufficient or false information about the identified power system. Segment selection/rejection uses logical conditions applied to RMS values of measured voltage and current. Harmonic impedance of the power grid is then calculated using modified power spectral method. The method was validated in a field test conducted at 30 kV feeder bus of HV/MV substation. Details of the experiment and the results are discussed the paper. Obtained results confirm that the method copes with temporal, band-limited excitation as well as with deep, sudden changes of utility background voltage.

Estimation of power system parameters based on load variance observations - laboratory studies

The paper concerns important problem: estimation of power system equivalent parameters. Knowledge of these parameters is needed to determine disturbances propagation ability through power grid. Authors present new techniques, which may significantly improve accuracy of noninvasive power system identification. These are: voltage and current coherent resampling algorithm, which ensures that sampling frequency match actual fundamental frequency of power system, so the DFT analysis is almost leakage-free; envelope detection algorithm which allows to estimate equivalent impedance of the load and its variability for fundamental frequency; the method of load change detection ensuring that only fragments having sufficient amount of information for power system identification will be used in parameters estimation. The proposed methods were tested using laboratory power system model of known parameters. Presented results of laboratory experiments confirmed correctness of the described methods.

Contactless Measurement of Substation Busbars Voltages and Waveforms Reconstruction Using Electric Field Sensors and Artificial Neural Network

This paper presents a method for contactless measurement of instantaneous voltage and waveform reconstruction for use in a medium voltage (MV) indoor substation. Voltage waveforms are reconstructed by artificial neural network (ANN) using the signals originating from electric field sensors located under MV bus. The method is validated by the experiment in a typical indoor MV substation. Depending on the selection of ANN architecture and data used for training the root mean squared error of waveforms, reconstruction as low as 0.3% to 2.1% can be achieved in a steady state. The practical advice on the application of the proposed measurement method in a production environment is also given.

Design, optimization, and deployment of a waterworks pumping station control system

This article presents a summary of the development and realization of a custom control and monitoring system for a water supply facility consisting of fixed-capacity intake pumps, a reservoir tank, and variable-speed outtake pumps. Project realization included the design and building of control hardware, as well as the design and deployment of the intake pump switching algorithm. Details of the control system design with an emphasis on the pump switching algorithm are given. The stages of the system development, including process modeling, design goal formulation, optimization of control algorithm using genetic algorithms, simulation, and implementation, are presented. Finally, deployment and real-life results are shown.

New Measures of Power-Grid Voltage Variation

This paper describes a new method of power-grid signal variation measurement, consisting of a demodulation algorithm and a set of measures (indices). The measures that will be presented are the abstract functionals, operating on the complex envelope of a signal. This paper presents a demodulation algorithm, definitions of proposed functionals, results of simulations, as well as laboratory experiments.

The hilbert transform adaptation for measuring amplitude and phase low-frequency disturbances in power system voltage

Phase disturbances in electric power signals are neglected and only amplitude (envelope) distortions are discussed in a literature. Amplitude disturbances are interpreted as amplitude modulation (AM) of main 50 Hz frequency. Detailed analysis of all disturbances and their sources are presented in the paper. It is shown that AM and narrow band PM (phase modulation) take place in power network simultaneously and those two modulations interact with each other. Voltage variation is proposed as disturbances measurement. Theoretical results are verified by field experiments and their results are presented.