M. H. Hocaoglu

Optimal placement and sizing of distributed generation on radial feeder with different static load models

Due to the increasing interest on renewable sources in recent times, the studies on integration of distributed generation to the power grid have rapidly increased. In order to minimize line losses of power systems, it is crucially important to define the size and location of local generation to be placed. There have been studies, to define the optimum location of distributed generation. Additional to the current studies in the literature, in this study, the optimum size and location of distributed generation that is placed in the radial system is defined by an analytical method so as to minimize total power loss for the uniformly, centrally and increasingly distributed system profile. Additionally the analytical approach is also evaluated against classical grid search algorithm for different load models

Distribution Systems Forward/Backward Sweep-based Power Flow Algorithms: A Review and Comparison Study

Abstract Because of different characteristic features of distribution networks, such as radial structure and high R/X ratio, distribution system load flow analysis differs significantly from transmission systems. Accordingly, a number of methods that are specially designed for the solution of the power flow problem in radial distribution systems are found in the literature. Most of the developed methods are based on the forward/backward sweep processes for the solution of the ladder networks. In this article, various distribution system load flow algorithms, based on the forward/backward sweeps, are reviewed, and their convergence ability is quantitatively evaluated for different loading conditions, R/X ratios, and sub-station voltage levels. Moreover, the effects of static load modeling on the convergence characteristics of algorithms are also investigated.

A tool for voltage stability and optimization (VS&OP) in radial distribution systems using matlab graphical user interface (GUI)

Abstract This paper describes a software package whose purpose is to provide a tool to be used for identifying the closeness of the each bus and the critical bus which is the most sensitive to the voltage collapse in radial distribution networks. The package also facilitates two optimization algorithms to be used for the optimal placement of DG and shunt capacitors with their optimal size in distribution networks for power system studies. It uses the graphical user interface (GUI) capabilities of Matlab and is called voltage stability and optimization (VS&OP) Package. It is available at http://www.gyte.edu.tr/Dosya/102/power/ and can freely be downloaded.

A voltage stability index for radial distribution networks

This paper presents a voltage stability index for identifying the most sensitive bus to the voltage collapse in the radial distribution networks. The developed index is based on the transferred active and reactive power of the distribution line. The performance of the index is tested on different loading conditions for different load models and different substation voltage levels. Results suggest that the proposed index is reliable and can easily be applied to the radial distribution networks.

Effects of Source Voltage Harmonic Distortion on Power Factor Compensation in Triac Controlled AC Chopper Circuits

In recent years, detailed modeling of power electronic devices and their behavior on different system conditions are a great concern of the power industries and customers. One of the widely proliferated such devices is the triac controlled ac choppers. Although these types of devices have important application areas, their poor power factor performance is the main obstacle for the large scale implementation in power systems. This paper presents an analysis on the behaviour of a single phase load composed with triac controlled ac chopper during reactive power compensation under nonsinusoidal voltage. The results of these analysis shows that for high conduction angle distortion on the source voltage improve the power factor which is contradicting with the previous findings. In addition, it is observed that, performance of power factor compensation systems are heavily affected by source voltage harmonics phase angles which are ignored in existing literature.

DSPFAP: Distribution systems power flow analysis package using Matlab graphical user interface (GUI)

This paper describes a software package whose purpose is to provide a tool to be used for load flow analysis in Power System Analysis courses. The software package which is called Distribution Systems Power Flow Analysis Package (DSPFAP) uses the graphical user interface (GUI) capabilities of Matlab. The main advantage of the developed package is that the load flow analysis can be achieved in both transmission and distribution levels. The package facilitates different forward/backward sweep‐based algorithms to be used for the distribution systems and conventional Newton–Raphson, Gauss–Seidel algorithms for the transmission system load flow analysis. In addition to that, effect of voltage dependent load models and effects of DGs on the distribution systems load flow solution can be investigated using the program. It is also possible to use conventional algorithms for distribution system load flow analysis in the package. The package can freely be downloaded from the website: http://www.gyte.edu.tr/Dosya/102/power/.

Experimental verification of harmonic load models

Present day power systems invariably have nonlinear loads, which inject harmonics into the system and give rise to nonsinusoidal voltages and currents. Power quality issues are a prime concern of the power industries as well as of customers. Thus under these conditions, it becomes imperative to study these nonlinear loads; their characteristics and effects. Accordingly, the harmonic analyses have become a regularly used tool in predicting the effects of harmonic producing loads on power systems. State of power system can be obtained in respect to the results of these analyses. The accuracy of these results depends on the modeling of harmonic producing loads. There are a large number of harmonic analysis methods that are in widespread use. In these analyses, the harmonic producing loads are widely modeled by various techniques namely; constant current sources, Norton and crossed frequency admittance matrix. In this paper, the sensitivities of these models are evaluated for the system, which covers some of the harmonic producing loads, under the various waveform cases of supply voltages.

Comparison of power definitions for reactive power compensation in nonsinusoidal conditions

Since the beginning of the power systems, harmonic distortion have been existed due to nonlinear equipments such as; generators, transformers motors etc. Moreover, harmonic pollution on power systems has dramatically increased in parallel with large proliferation of power electronic devices. Consequently, the reactive power compensation in nonsinusoidal conditions became one of the most important problems in power systems. This paper presents a comparison on widely accepted power definitions in a simple single phase circuits with nonsinusoidal waveforms of voltage and/or currents by giving particular emphasis to the reactive power compensation.

A robust power flow algorithm for radial distribution systems

In this paper, a new algorithm is presented to solve the power flow problem in radial distribution systems. The proposed method takes into account the voltage dependency of static loads, and line charging capacitance. The method is based on the forward and backward voltage calculation by using polynomial voltage equation and KirchofPs Law for each branch. Convergence speed and reliability of the method is compared with the standard Newton-Raphson, PFLOW and Ratio-Flow method which is based on classical forward-backward ladder method. The convergence ability is also tested for different loading conditions and different R/X ratios under wide range of the exponents of the loads. Results show that the proposed algorithm is reliable, simple and has fast convergence ability. Furthermore, it is observed that the method is less sensitive to the systems parameters such as R/X ratio and loading levels.

An analysis into the effect of voltage harmonics on the maximum loading capability of transformers

In this paper, some exemplary cases are presented to show the effect of voltage total harmonic distortion (THDV) and its spectrum on the harmonic loss factors (FHL and FHL-STR) of the six-pulse rectifiers accompanied with a constant power dc load and a battery. Accordingly, the winding losses and maximum loading capability of a transformer supplying both non-linear load types are investigated for sinusoidal and non-sinusoidal bus voltage conditions. The obtained numerical results clearly shows that the current harmonics of the considered non-linear load types are highly dependent on the THDV level and spectrum of the supply voltage, thus, the voltage harmonic profile should be considered in the design stage of the transformers, which are under influence of particular to supply them.