Radu Porumb

Electrical Load Pattern Grouping Based on Centroid Model With Ant Colony Clustering

Load pattern clustering based on the shape of the electricity consumption is a key tool to provide enhanced knowledge on the nature of the consumption and assist meaningful customer partitioning. This paper presents new developments to group the load patterns using an initial set of centroids specified according to a user-defined centroid model. The original Electrical Pattern Ant Colony Clustering (EPACC) algorithm is illustrated, highlighting its characteristics and parameters, with centroids evolution during the iterative process until stabilization. The EPACC results are compared with those obtained from the classical k-means algorithm to group the representative load patterns taken from a set of non-residential customers in typical weekdays.

New nested evolutionary programming approach for voltage control optimization with distributed generation

This paper addresses the optimization of voltage control in distribution systems in the presence of distributed generation. The objective is minimizing the voltage deviations at the load nodes with respect to specified reference values. The optimization is solved by means of a new approach based on nested evolutionary programming. Results are shown on a test system including controls at the HV/MV and MV/LV substations, and voltage-controlled local generation sources.

Experimental Evaluation of Unbalance and Distortion Indicators in Three-Phase Systems with Neutral

The characterization of three-phase systems with neutral under unbalanced operation in the presence of waveform distortion is a key aspect in the power quality studies. This paper presents the application to a number of real cases of a unified framework providing a set of synthetic indicators capable to explain the individual effects of unbalance and harmonic distortion. The use of specific indicators extending the notion of total harmonic distortion to the case of unbalanced systems, and the notion of unbalance to the systems with distorted waveforms is illustrated and discussed on various sets of data gathered from real-time measurements on office and laboratory feeders and on a photovoltaic system.

Experimental Indicators of Current Unbalance in Building-Integrated Photovoltaic Systems

Unbalance of the three-phase currents in photovoltaic (PV) systems may depend on structural aspects of the installation, the effect of partial shading, or both. In this paper, a number of unbalance indicators are calculated starting from data that are measured during experimental analyses on a real building-integrated PV system that represents different types of unbalance. Detailed information is obtained from indices that identify the balance and unbalance components that are also in the presence of waveform distortion. These indices extend the current definitions of unbalance given in the power quality standards. The results show that the unbalance cannot be considered negligible, even with no single-phase inverters and is more significant if nonlinear loads add a contribution to both harmonic distortion and unbalance seen from the distribution transformer.

Formation of load pattern clusters exploiting ant colony clustering principles

Electrical load pattern clustering provides useful information on how to partition the customers on the basis of the shape of their actual consumption. The results of the clustering procedure are then used to group the customers into classes by identifying a suitable set of attributes describing each class in a non-overlapping way. Starting from an initial set of centroids, it is possible to construct a clustering algorithm to upgrade the clustering results by refining the initial centroids. The Electrical Pattern Ant Colony Clustering (EPACC) method recently introduced by the authors, based on ant colony clustering principles, has been shown to outperform the classical k-means for electrical load pattern clustering based on an initial centroid model. This paper illustrates the genesis of the EPACC algorithm by providing additional information on how the method parameters have been chosen and set up. Examples are taken from a case study application with actual load patterns.

Wind generation assessment proposal by experimental harmonic and distortion factor analysis

The ever-increasing presence of the wind generation in Romania power system triggers a vast array of challenges ranging from reliability, fault-ride-through capabilities, green certificates incentives, etc. The impact on power quality of a wind farm located in south-east of Romania composed of 45 wind turbines is investigated. The paper deals with power quality case studies conducted on existing renewable sources based systems. Harmonics determined by a wind farm up to 200 MW are analyzed. The measurements are carried out in different points of the power system supplying the wind farm. The correlation between the generated power and the main harmonic indices is highlighted.

Analysis of the grid-connected PV plants behavior with FACTS influence

Within the EU Directive 20-20-20, which imposed a decisive action towards renewable energy adoption within electric power systems, this change brought a series of issues for the electric power systems, like losses increase, reliability alteration and power quality depreciation. The power generation of grid-connected PV plants is increasing continuously all over the world reaching values of hundreds of megawatts, thus making these plants a crucial part of the future electric energy system and Smart Grids. FACTS devices can be used to increase transmission capacity, improving stability and dynamic behavior, and ensure a better quality of energy by controlling several parameters. Current paper deals with the issue of power quality alteration, by assessing the influence which FACTS devices might have on the grid-connected PV plants both on normal and restricted conditions operation. In the first section, a general analysis was performed, aimed at identifying the current state-of-the art of FACTS technologies and their influence on power quality. An example was designed, starting from a real electric distribution system, in order to create an array of possible issues and solutions which will be further scrutinized.

Analysis of power quality issues raised by PV generation and e-parking storage capacities in UPB smart grid environment

This paper concentrated on identifying the main issues raised by the adoption of new PV generation and e-cars storage technologies, and their influence on power quality parameters. The main difficulty of this paper was to create a simulation tool which replicates the actual consumption behavior of UPB electric network, and to project scenarios for PV generation and e-cars capacities. A main point in the analysis performed in this work is the characterization of the electric loads present in the upcoming smart grid. An intimate view of a PV system implemented into UPB electric distribution system was delivered, along with its operation mode and its influence on power quality. The full picture was achieved by proposing a reactive energy compensator, which proved to have significant influence in increasing the harmonic distortion indexes and increasing the possible damage hazard for the sensible electronic devices.

Integration of Dispersed Power Generation

Current paper deals with three main issues, regarding the operation of the electric power systems in the presence of distributed generation. The first issue regards the assessment of the main continuity of supply parameters, such as frequency of interruptions, duration of interruption, power not served and energy no served. This issues are the base guidelines for the network system operators’ decision of building new distributed generation capacities which might be able to mitigate the electric network loss of operation. The second issue addressed was the consume variability of the various low-voltage consumers. This particularity, in conjunction with the sheer number of consumers leads to the creation of serious unbalance for the daily curve. This means that if the network system operator cannot contain the load variability, it must buy energy from intraday energy market, with a price decisively higher than the one of the reserved capacity. This issue leads to a two-fold necessity: implementing a better know-how system in order to better contain the customers load fluctuation and the necessity of distributed generation implementation, in order to help load shedding. The third issue regards general technical aspects with respect to the electrical distribution systems operation in the presence of distributed generation.

Analysis of electromagnetic disturbances for grid-connected PV plants

The expansion of the electricity grid connected photovoltaic sources requires the development of solutions for solving problems caused by disturbances in the electrical network due to their strong variable character of energy sources. The power generation of grid-connected photovoltaic plants is increasing all over the world and these plants a crucial part of the future electric energy system. To restrict the level of electromagnetic disturbance, currently effective technical solutions are based on power electronics. This paper deals with the issue of power quality alteration, by assessing the power electronics equipment operation mode on the grid-connected PV plants both on normal and restricted conditions operation. A general analysis was performed in the first section, to identifying the current state-of-the art of photovoltaic plants and their influence on power quality and an example was designed, starting from a real electric distribution system in order to create a general image of issues and solutions.