D. J. Morrow

Wavelets for the analysis and compression of power system disturbances

Wavelets introduce new classes of basis functions for time-frequency signal analysis and have properties particularly suited to the transient components and discontinuities evident in power system disturbances. Wavelet analysis involves representing signals in terms of simpler, fixed building blocks at different scales and positions. This paper examines the analysis and subsequent compression properties of the discrete wavelet and wavelet packet transforms and evaluates both transforms using an actual power system disturbance from a digital fault recorder. The paper presents comparative compression results using the wavelet and discrete cosine transforms and examines the application of wavelet compression in power monitoring to mitigate against data communications overheads.

The OpenPMU Platform for Open-Source Phasor Measurements

OpenPMU is an open platform for the development of phasor measurement unit (PMU) technology. A need has been identified for an open-source alternative to commercial PMU devices tailored to the needs of the university researcher and for enabling the development of new synchrophasor instruments from this foundation. OpenPMU achieves this through open-source hardware design specifications and software source code, allowing duplicates of the OpenPMU to be fabricated under open-source licenses. This paper presents the OpenPMU device based on the Labview development environment. The device is performance tested according to the IEEE C37.118.1 standard. Compatibility with the IEEE C37.118.2 messaging format is achieved through middleware which is readily adaptable to other PMU projects or applications. Improvements have been made to the original design to increase its flexibility. A new modularized architecture for the OpenPMU is presented using an open messaging format which the authors propose is adopted as a platform for PMU research.

Synchronous Islanded Operation of a Diesel Generator

The amount of distributed generation connected to the distribution network is increasing. To use this resource more effectively, splitting of the distribution network, or islanding the system, for prevention of power outages is being considered by some utilities. In this paper an islanding method that avoids out-of-synchronism re-closure is proposed. The island is kept in synchronism with the rest of the utility while it is not electrically connected. This is referred to as synchronous islanded operation. A phase difference control algorithm, developed by the authors, was tested in a single set scenario on a 50-kVA diesel generator using two different governors. These are the ldquostandard productrdquo variable gain governor of the diesel generator and a governor developed by the authors, which utilizes supplementary inputs in addition to engine speed. The results show that phase difference can be controlled within acceptable limits, both in steady state and after load disturbances are applied. The advantages of employing supplementary governor inputs are fully evaluated.

Online Tracking of Thévenin Equivalent Parameters Using PMU Measurements

This paper presents a new method for tracking Thévenin equivalent parameters for a power system at a node using local phasor measurement unit (PMU) measurements. Three consecutive phasor measurements for voltage and current, recorded at one location, are used. The phase drifts caused by the measurement slip frequency are first determined and phase angles of the measured phasors are corrected so that the corrected phasors are synchronized to the same reference. The synchronized phasors are then used to determine the equivalent Thévenin parameters of the system.

Noninvasive detection of brushless exciter rotating diode failure

A noninvasive method for detecting failure of brushless exciter rotating diodes is presented in this paper. Diodes can fail in one of two ways: either open circuit or short circuit. It is shown by actual test, on a 31.5-kVA alternator, that the exciter field current waveform changes distinctly when a diode fails. Harmonic analysis of the exciter field current waveform is performed. The results of this analysis form the basis of a method for real-time detection of diode failure on a microprocessor-based platform.

Synchronous machine parameter determination using the sudden short-circuit axis currents

Small salient-pole alternators are being embedded in power systems in growing numbers and parameter sets which accurately reflect the transient response of such machines are in demand. High levels of local saturation and rapidly changing flux densities result in transient currents that are far from the pure exponentials of classical theory so that estimation by curve fitting is difficult. A new approach, which encourages designer intervention, is described and this is seen to be reliable and repeatable, with a good quality of fit, even in the sub-transient region.

Integrated governor control for a diesel-generating set

This paper is concerned with the detailed implementation of real-time fuzzy logic speed control for a standby diesel-generating set. The implementation platform is that of the Mathworks xPC Target. This rapid prototyping scheme permits the automatic cross-compiling of the nonreal-time Simulink control system model into real-time C code, which is executable on the xPC target PC. The digital governor xPC target hardware consists of a desktop PC with a National Instrument Input/Ouput card and a Softing Controller Area Network Card. The paper details the fuzzy control model and the methods with which to communicate with the engine control module. Tests were conducted on a 50-kVA diesel-generating set. The results show that the fuzzy controller is superior to the variable gain PID-type governor used by the conventional engine control module.

Techniques for Multiple-Set Synchronous Islanding Control

Power system islanding can improve the continuity of power supply. Synchronous islanded operation enables the islanded system to remain in phase with the main power system while not electrically connected, so avoiding out-of-synchronism re-closure. Specific consideration is required for the multiple-set scenario. In this paper a suitable island management system is proposed, with the emphasis being on maximum island flexibility by allowing passive islanding transitions to occur, facilitated by intelligent control. These transitions include: island detection, identification, fragmentation, merging and return-to-mains. It can be challenging to detect these transitions while maintaining synchronous islanded operation. The performance of this control system in the presence of a variable wind power in-feed is also examined. A Mathworks SimPowerSystems simulation is used to investigate the performance of the island management system. The benefit and requirements for energy storage, communications and distribution system protection for this application are considered.

A digital PID speed controller for a diesel generating set

With rise in the number of commercial and industrial companies using diesel generating sets to maintain the continuity or reduce the cost of their electricity supply, a more sophisticated control of the generator is sought. Traditionally analogue technology has been employed to provide generator speed and excitation control however by employing digital technology, much improved generator control can be achieved. This paper is concerned with the implementation of a digital PID governor. The results show that with even a simple digital PID control algorithm and the tuning there off, the ease of tuning can be improved via computer simulation and that the controller itself can match and out perform its analogue counterpart. The ultimate goal of the work is the integration of the governor and automatic voltage regulator. By using modern control techniques such as fuzzy logic, full integration of the two controllers is sought and hence a more intelligent generator control system.

Principal Component Analysis of Wide-Area Phasor Measurements for Islanding Detection—A Geometric View

This paper presents a new technique for the detection of islanding conditions in electrical power systems. This problem is especially prevalent in systems with significant penetrations of distributed renewable generation. The proposed technique is based on the application of principal component analysis (PCA) to data sets of wide-area frequency measurements, recorded by phasor measurement units. The PCA approach was able to detect islanding accurately and quickly when compared with conventional RoCoF techniques, as well as with the frequency difference and change-of-angle difference methods recently proposed in the literature. The reliability and accuracy of the proposed PCA approach is demonstrated by using a number of test cases, which consider islanding and nonislanding events. The test cases are based on real data, recorded from several phasor measurement units located in the U.K. power system.