Marko Dimitrijevic

POWER FACTOR AND DISTORTION MEASURING FOR SMALL LOADS USING USB ACQUISITION MODULE

Power factor and distortion measuring usually require dedicated and expensive equipments. Computer-based acquisition modules and software provide for a possibility to create simple and nonexpensive methods and instruments for power factor measurement and distortion characterization of small loads and bring all advantages of virtual instrumentation. A new approach to power quality characterization by measuring power factor, distortion, and several other parameters of small electric loads (up to 0.5 kW) will be described in this paper. Besides low price maximum versatility and adaptability are provided without any loss in accuracy.

A small-signal model of a solar cell

Starting with the experience that the output voltage and the output current of a photovoltaic panel are not pure direct current constants due to the inevitable connection to a converter (or inverter) that is working as a switching system, we came to the conclusion that interest exists for the behavior of the solar cell at the frequencies of the harmonics of the converter’s switching frequency, which is subject to change according to the maximum power-point tracking. In other words, a need exists for frequency domain characterization of the solar cell, for which a linear small-signal model is necessary. To enable simulation for small signals, development of a linear reactive model was considered. Since a one-diode large-signal model already exists, it was used as a basis for the extraction of the parameters of the small-signal model. The new model was represented in the form of a parallel RC two-terminal circuit, the R and C being functions of the photocurrent (acting as a map of the illumination) and the diode voltage. Since the R and C of the model are quiescent-point dependent, their values as a function of the illumination and the diode voltages were approximated by artificial neural networks (ANNs). Separate ANNs were created for modeling R and C. To verify the model, two small-signal simulations were performed. The first one was done with the existing nonlinear model, while the second was done with the new linear model (running the ANNs). Excellent agreement was obtained.

Computer Security Vulnerability as Concerns the Electricity Distribution Grid

The usual way of creating a cyber attack is through implementation of malware via the Internet. Among many types of malware, of special interest are those that enable eavesdropping on the activities within the computer, making it possible to define the software on which the computer is running. An adversary can benefit from this information in a way that is convenient for him or her. Here, we expose a new, entirely different way of eavesdropping and of monitoring the activities within the computer. It is based on measurement of the supply current taken from the electricity distribution grid. Because the computer, as many other electronic loads, is a nonlinear one, abundance of harmonics can be found in that current. Our discovery is the fact that the harmonic content is dependent on the type of activity within the computer, so, by proper analysis of the current waveform, one may recognize what is going on in it. We propose an artificial neural network-based method that unambiguously recognizes which software is running. We also propose a proper measurement procedure based on the technology we described in our earlier articles.

ICT and power: Synergy and hostility

An attempt is made in this paper to summarize the state of the art in the interaction between the ICT (information communication technologies) that becomes ubiquitous and the electrical power production and distribution. Both are considered to have a difficult task to fulfill enormous rise of demand that is becoming above all expectations. In the same time they technologically interfere in the sense that they mutually help in the fulfillment of their main task while in the same time loading each other with problems inherent to the respective technology. In the paper we will try to merge our (LEDA laboratory of the University of Niš) own results with ones available in the literature in order to give as complete a picture of the subject as possible.

Compensation of harmonics in smart grid using photovoltaic energy source

In this proceeding we present basic steps for design a system for harmonic and reactive power compensation in smart grid, using photovoltaic (PV) system. First, methods for harmonic monitoring and measurement will be elaborated. Next, we will discuss harmonic reduction techniques that are usually used. The system for harmonic compensation based on photovoltaic energy generation that provides the functions of a power quality conditioner will be proposed. We will also address the issue of proper quantity for harmonic compensation contribution measurement at power grid.

Efficient nonintrusive distinguisher of small nonlinear electrical loads

The work contributes to the identification of small nonlinear appliances which are hardly distinguished by existing noninvasive load monitoring methods. It improves the steady load monitoring by introducing distortion power as an additional parameter to the widely used Harts algorithm based on measurement of active and reactive power. The results show that the method efficiently distinguishes the variety of nonlinear appliances whose usage is fast growing nowadays. Furthermore, this approach is advantageous in comparison with other approaches, which use three parameters to precisely identify the appliances, due to its simplicity. Namely, distortion power can be easily determined using only smart meters and thus no any additional measuring equipment is required.

USB HW/SW Co-Simulation Environment with Custom Test Tool Integration

This paper describes a new verification environment for USB 2.0 controller. New methodology is presented, where a co-simulation environment is used as one of the starting points for the embedded hardware/software development and as an accelerator of the overall design process. The verification environment is based on the device emulation/virtualization technique, using USB controllers real register transfer level (RTL) instead of models. This approach is functionally very close to the corresponding real-world devices and allows wider opportunities for hardware debugging. The new software utilities for USB host and device functionality testing are also presented. This tool allows generating custom tests by including various transfer types and modifying parameters such as data payload, interval, number of pipes, etc. It can be used for both hardware (HW) and software (SW) limitations characterization, as well as debugging.

MPPT controller design for a standalone PV system

Circuit for maximum power point tracking (MPPT) is one among several equally important subsystems of a standalone photovoltaic (PV) system. In this paper we will implement one algorithm for maximum power point tracking, based on the maximum simplicity criteria, into the whole PV system. SPICE circuit simulation of the complete standalone PV system will be performed in order to verify the proposed algorithm. Different working conditions will be examined.