Ramona Vatu

Analysis of power quality improvement in smart grids

Electrical distribution system is designed to operate in sinusoidal mode, but the voltage and current waveforms shows distortion compared to the sinusoidal mode. Current technology development, which results in an increasing adoption of the local generation and storage capacities, is pushing towards the adoption of smart grid paradigm. An effective technical solution for enforce limitation of various types of power quality (PQ) disturbance is based on power electronics in order to increase energy transmission capacity, improve voltage stability and dynamic behavior, control power flow and ensure a better power quality at distribution inside accepted boundaries. The objectives of this paper is to assess the harmonic disturbances present into a real smart grid, and to suggest a solution to maintain the operation of the distribution system with photovoltaic (PV) plant and electrical cars within PQ limits imposed by standards. A general analysis was addressed, in order to identify the current state-of-the art of smart grid and harmonic filters and their influence on power quality. An example was designed using ETAP software, starting from a real electric distribution system in order to build a general image of corresponding PQ issues. The solutions found for this technical issues are presented with their influence on electrical current and voltage and harmonic specter.

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 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.

Smart grids reliability indices assessment using sequential Monte Carlo method

This work is aimed at making a comprehensive evaluation of the probability density functions (PDFs) of a set of reliability indices applied to electricity distribution systems - including frequency and duration of interruptions, power and energy not supplied. By considering the number of occurrences and duration of the interruptions as random variables (RVs), the indices become RVs and are evaluated through analytical expressions for computing their expected values and variances and with the Monte Carlo method in order to obtain the PDFs.

Analysis of SVC influence on the power quality for grid-connected PV plants

The smart grid paradigm for the electric power systems is encompassing an increasingly adoption of distributed generation all over the world. This trend requires the input from flexible alternative current transmission systems (FACTS) devices, which 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 influence, by assessing the static VAR compensator (SVC) operation mode on the grid-connected PV plants in order to assess the power quality limitations imposed by PV plants operation on sensible loads. 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 to which a generic SVC device was added, in order to create a general image of issues and solutions.

Microgrids operation improvement using storage technologies

The advancements in technology and services are fundamentally transforming the traditional electrical power system operation. It is undergoing a full changeover into a collection of microgrids, which contains consumers that become prosumers. Energy storage is a vital component of the microgrids competitive operation. In this framework, current paper is addressing the issues of batteries capacity, prices and reliability. In the first section, a general analysis was performed, aimed at accurately identifying the current state-of-the art of storage systems. An example was designed, starting from a real electric distribution system, in order to identify the optimal solution from an array of possible technical issues and solutions which will be further discussed.

Analysis of ancillary services within smart grid framework

As a result of the changes that occur in the electrical distribution networks, there is guidance tendency toward users, not only to power systems. This is a feature of the smart grid that will ensure safety operational and power quality, and also facilitates network connection of renewable source. Smart grid can intelligently integrate the behavior of all users connected to this network - electricity producers, users and prosumers, in order to ensure efficient delivery, sustainable, economically and with security conditions of electricity. The power balance and ancillary services provided by the storage systems in distribution network represent two aspects of one problem that must be treated properly, with in an appropriate manner, taking into account the parameters of typical distribution network. Current limits of energy storage force production to correspond to the energy used in any moment. Using storage systems is a necessity for the power system, considering the current tendency to grow of renewable sources penetration, the requirements for reliability and power quality improvement and also the implementation of smart grid. Storage systems have an important role in increasing the system efficiency and ensuring stable operation of the system by contributing to secondary and fast tertiary control. In the first section, a general analysis was performed, in order to identify the current state-of-art of energy storage systems. An example was designed, starting from a real electric distribution system, in order to create an arrangement of possible issues and solutions for electricity storage systems which provide ancillary services.

Evolution of smart buildings. A Romanian case

The constant evolution of electricity grids towards smart grids is changing the paradigm. The intelligent layer which is added over the physical one is bringing a change in the mode in which the electricity is provided. Hence, the electricity providers are shifting their business from product-centered to service-centered ones, change that ensure a better use of their resources and a much wider acceptance from their customers. The wave of changes has reached the construction domain, and therefore the buildings have evolved into smart buildings, concept which offers a greater elasticity for both energy providers and end-users. Current paper deals with the Romanian framework for smart buildings, presenting comprehensively the drivers of change, as well as a very useful set of real-data simulations and smart solutions deployment, which will help complete the image of nowadays technological trends and future technical expectations for smart buildings.

Power quality issues produced by embedded storage technologies in smart grid environment

The advancement of new storage technologies is a powerful driver for a wide smart grids adoption by both electricity utilities and customers. However, the relative novelty of these technologies is posing a threat to their adequacy for electric distribution systems operation. In spite of the clear advantages brought by storage devices, such as fast response, reserve, resilience, fault ride-through capability and great help for electric system dispatchers, storage technology bears some disadvantages regarding early stage for deployment and power quality-related inadequacies. This paper addressed the issue of simulation studies for safe deployment of cutting-edge electricity storage technologies within electric distribution systems. The simulation results were assessed according with electric power quality standards, in order to build a comprehensive picture of the storage systems adequacy within smart grids.

Analysis of electromagnetic disturbances with or without SVC device

Considering that the electrical power system is designed to operate in sinusoidal mode, the waveforms of voltage and current shows distortion compared to sinusoidal wave. For allowing limitation of all kinds of disturbance an effective technical solution is based on power electronics. The smart grid paradigm is encompassing an increasingly adoption of distributed generation all over the world. The flexible alternative current transmission systems (FACTS) devices, can be used to increase transmission capacity, improving stability and dynamic behavior, and ensure a better power quality at distribution level by controlling several key-parameters. The purpose of this paper is to deal with issue of power quality alteration, by assessing the power electronics equipment behavior on a real-network example, in order to create a general image of issues and solutions. The first section identifies the current state-of-the art of FACTS technologies and their influence on power quality. An example was designed in ETAP software, starting from a real electric distribution system using PV generation in order to create a general image of issues and solutions. After the SVC device connection to the system, an analysis over voltage variation was performed and interesting conclusions have been drawn.