Alexander Domijan

Directions of research on electric power quality

Several important research areas in electric power quality are described. Aspects of electric power quality are categorized as fundamental concepts, modeling and analysis, measurement and instrumentation, sources, solutions, effects, and educational issues. The goals are to identify the high-priority research areas in electric power quality and to stimulate interest in this topic. >

Investigation of Microgrids With Both Inverter Interfaced and Direct AC-Connected Distributed Energy Resources

With the increasing use of renewable energy resources and energy storage devices, inverter-based distributed energy resources (DERs) become the important components in microgrids. As diesel generators with direct ac connections are the current most cost effective and reliable power sources, the stability investigation of microgrids should include both types of DERs. In this paper, dynamics of diesel generation will be included and the interaction of the diesel generators and the inverter-based DERs will be investigated using eigenvalue analysis and time-domain simulations. The significant contributions of this paper include: 1) identification of the stability problem in microgrids with inverter-based DERs and conventional generators and 2) investigation of the interaction problem of inverter-based DERs and conventional generators in islanded microgrids.

On power quality indices and real time measurement

Power quality (PQ) indices are used to quantify the quality of the power supply and serve as the basis for comparing the negative impacts of different disturbances on power networks. To overcome the limitations and deficiencies of the practical applications of some power quality indices in common use, a set of three new indices, namely the fundamental frequency deviation ratio (FDR), waveform distortion ratio (WDR), and symmetrical components deviation ratio (SDR) are proposed in this paper to summarize different types of power disturbances in a comprehensive manner. As instantaneous quantities, these novel indices can reveal the time varying characteristics of power disturbances in real time. Hence, the new PQ indices can well accommodate practical waveform distortions in power networks, which may be caused by multiple types of time varying power disturbances. They can therefore be further used to evaluate both the effectiveness and dynamic responses of PQ mitigation equipment in practical applications. To fully realize the advantages of the new PQ indices, a novel Atom (transform kernel) based time frequency transform and its recursive algorithm are also proposed as the supporting measurement technique. The new Atom approach can continuously measure the instantaneous frequencies and amplitudes of signal components in a nonstationary disturbance waveform with high accuracy, and then update the new PQ indices at each sample. The effectiveness of the new PQ indices and the supporting measurement technique were ascertained using various PQ events, both simulated events and those recorded at an industrial site.

Recursive algorithm for real-time measurement of electrical variables in power systems

In this paper, a novel complex bandpass filter is presented which overcomes the pitfalls of the techniques in common use. This complex bandpass filter can correctly extract the phasor of the fundamental component and symmetrical components in voltage or current waveforms and then accurately estimate their instantaneous amplitude, phase angle, and frequency, even encountering various power disturbances. Further, a recursive algorithm is also developed for the complex bandpass filtering that updates current filtering output only using several previous sample values and filtering outputs. This attribute greatly reduces the computational complexity of complex bandpass filtering, which is the weakness of the continuous wavelet transform based on the well-known Morlet Wavelet. Thus, this recursive algorithm is highly desirable for real-time applications. The performance of the proposed technique is ascertained by using both simulated and practical power disturbance waveforms.

Simulation study of the world's first distributed premium power quality park

This paper describes the performance of the worlds first premium power park (PPP) located at the Delaware Industrial Park in Delaware, Ohio. Issues such as the need for a supervisor system to coordinate the responses of the different power quality devices and the study of the combined operation or interaction of a dynamic voltage restorer (DVR), a static var compensator (SVC), and a transfer switch in close electrical proximity are discussed in this paper. The system response to different power disturbances is simulated in EMTP-ATPdraw and compared to field measurements. The PPP presented here is just an approach to a premium power system, which is considered the next step in the evolution of power quality.

Custom power devices: an interaction study

This paper presents a simulation study about the coordination and interaction of advanced power electronic devices working in close electrical proximity. In particular, three major power quality devices (PQDs)-an advanced static VAR compensator, a dynamic voltage restorer, and a high-speed transfer switch as well as their combined performance-are modeled and studied in detail using ATP-EMTP. The paper addresses potential problems related to the PQDs combined operation, in addition to coordination issues. Comparison between simulation results and field measurements of individual PQDs are also presented.

A review of wireless and PLC propagation channel characteristics for smart grid environments

Wireless, power line communication (PLC), fiber optic, Ethernet, and so forth are among the communication technologies on which smart grid communication infrastructure is envisioned to be built. Among these, wireless and PLC-based solutions are attractive considering the cost of initial deployment. Wireless communication deployment in smart grid covers a variety of environments such as indoor, outdoor, and electric-power-system facilities. Similar diversity is expected in PLC deployment as well covering low voltage (LV), medium voltage (MV), and high voltage (HV) segments of the grid. In spite of being attractive, wireless and PLC channels are very harsh posing great challenges to performance of communication systems. In proposing solutions to smart grid communication needs, two approaches are likely to be followed. One is based on the use of existing wireless and PLC technologies with some modifications, and the other relies upon developing novel communication protocols particularly addressing the smart grid needs. Both of these approaches require an in-depth knowledge of communication channel characteristics. The aim of this study is to reveal the wireless and PLC channel characteristics of smart grid environments in terms of several parameters such as path loss and attenuation, time dispersion, time selectivity, amplitude statistics, and noise characteristics.

A summary and evaluation of recent development on harmonic mitigation techniques useful to adjustable speed drives

The authors examine harmonics in three main power areas: the harmonic source, the harmonic effects on power components, and the mitigation techniques used to reduce the amplitude of such harmonics. They cover briefly background information on the first two areas by focusing on electronic motor drives, specifically adjustable speed drives since there are an estimated 400000 units online in the United States, which translates into a large harmonic penetration level. Further summarized are some of the harmonic effects on power system components. A summary and evaluation of developments on harmonic mitigation techniques (HMTs) that have been introduced in the past four years are presented. A classification for all of these HMTs is provided, along with several other facts related to this topic. >

Watthour meter accuracy under controlled unbalanced harmonic voltage and current conditions

This work presents the results of phase I of the project on the accuracy of watthour meters when subjected to closely-duplicated real-world unbalanced harmonic voltage and current conditions. Such real-world conditions involved differences in voltage and current magnitudes as well as differences in the voltage and current total harmonic distortion levels of each phase. Tests were performed on a selected sample of nine three-phase and three single-phase watthour meters. Some results showed that under a particular set of unbalanced waveforms with harmonic conditions of I/sub THD/>80% and V/sub THD/>2%, the percentage errors exhibited by these meters ranged from -10.09% to +0.52%.

A novel electric power laboratory for power quality and energy studies: training aspects

The laboratory described can examine issues in power quality (PQ) with regard to both stand-alone devices and their behavior in the power system. A project justification which identifies PQ problem areas is presented. Historical backgrounds of both PQ and laboratories in general are provided, to give a brief educational tutorial in the area, and to set the stage for bringing into creation a lab which addresses correctly the needs of industry and students. Development aspects of the lab are presented. This is followed by a description of the testing capabilities of the laboratory that are needed to address the PQ problem areas, along with the laboratorys presentation of results and training/educational capabilities. Aspects of how the laboratory is used cooperating with other facilities are examined so that broader PQ problems can be studied. >