Showing papers by "Michele Pastorelli published in 2015"

Current control loop design and analysis based on resonant regulators for microgrid applications

Abstract: Voltage and current control loops play an important role in the performance of microgrids employing power electronics voltage source inverters. Correct design of feedback loops is essential for the proper operation of these systems. This paper analyzes the influence of state feedback cross-coupling in the design of resonant regulators for inner current loops in power converters operating in standalone microgrids. It is also demonstrated that the effect of state feedback cross-coupling degrades the performance of the control loops by increasing the steady-state error. Different resonant regulators structures are analyzed and compared, performing experimental tests to validate the results of the theoretical analysis.

Advanced control of inverter-interfaced generation behaving as a virtual synchronous generator

Abstract: The amount of inverter-interfaced distributed generation in the electrical networks is continuously increasing. However, the presence of a large amount of local generation is raising a number of issues referring to the power system stability. In particular, high sensitivity in the response to frequency variations after disturbances is emerging, because of the low inertia of the local generators. Recent studies indicate the possibility of introducing some forms of short-term energy storage and operating on the control of the inverter to introduce a virtual inertia in the system, emulating the typical behavior of synchronous generators. This paper starts from the concept of virtual synchronous generator introduced in the literature and presents an extended model of the control system for a voltage source inverter embedding the typical functions of a synchronous generator, including virtual inertia, active and reactive power capability limits, and appropriate protections to enable fault ride-through capability. Simulations are presented by using the data of a real inverter in order to show the effectiveness of the proposed controls and the effects of introducing a dynamically variable virtual inertia.

Urban morphology and energy consumption in Italian residential buildings

Abstract: The reduction of greenhouse gas emissions is a key issue to mitigate the climate change and the global warming. The European Union (EU) has defined important goals to 2020 and is promoting a low carbon Roadmap to 2050. The EU is pushing for the reduction of CO2,eq emissions by increasing buildings' efficiency and the use of renewable energy. In 2012, in Europe, the energy consumption was 1.1 GTOE and almost one third was spent in the residential sector. Between the European countries, Italy is in the sixth position for energy demand in the residential sector. Nowadays, most of the policies are related to the retrofit of the existing stock and to the diffusion of new high performing buildings (f.i. nZEB, Passivhaus, etc.). Anyway, especially in the areas with high urbanization rates, investigating how the urban form can affect the energy consumption of a city is extremely important for planning the expansion of new city districts.

A model for the evaluation of thermal and electric energy consumptions in residential buildings: The case study in Torino (Italy)

Abstract: This work analyzes the thermal and electrical consumptions of residential buildings located in the town of Turin (northwest Italy). The aim is to create mathematical models to evaluate monthly behavior of energy consumption as a function of two predictable variables. In the evaluation of the different variables, two climatic data were chosen: the monthly average temperature and the monthly average daily solar irradiation. Two multiple linear regression models have been determined, one using standardized variables to evaluate how climatic data influence thermal and electric energy consumptions in residential buildings. The fields of application of these models can be: the evaluation of monthly energy-use data knowing the annual value with the construction of seasonal trends, the prediction of monthly energy-use data knowing the weather forecast, the management of the buildings' energy consumptions to optimize the heating or electric networks for more future expansion in urban contests. After an initial state of the art review, the case study of Torino is presented, with more than 2700 users for the electric consumptions and 130 residential condominiums. A selection of the users was made to consider an homogeneous set of users and finally the models were developed with about 1200 electric users and 100 condominiums. The results show good correlations between energy consumption and climatic data, especially with the air temperature. For electrical consumption the monthly variation is limited compared with thermal energy-use, for both the seasonal patterns obtained have a deviation of less than 5% between calculated and real consumptions.

Choice of the most suitable wind turbine in the installation site: A case study

Abstract: This paper deals with a case study regarding the most suitable wind turbine for the energy production in an installation site in the South of Italy. Starting from the anemometer data of the installation site, in which the terrain is flat and without obstacles, at regular speed and low turbulence, five types of wind turbines with different sizes and technologies are considered in order to calculate, as accurately as possible, the energy production. These energy productions are properly normalized and presented by conventional parameters. Remarkable deviations are found among the different wind turbines proving the importance of this analysis before the installation of a wind farm. In this way, the best wind turbine can be selected.

Inner current loop analysis and design based on resonant regulators for isolated microgrids

Abstract: Inner current and voltage loops are fundamental in achieving good performance of microgrids based on power electronics voltage source inverters. The analysis and design of these loops are essential for the adequate operation of these systems. This paper investigates the effect of state feedback coupling in the design of proportional resonant controllers for these inner loops in voltage source inverters operating in islanded microgrids. It is also shown that the state feedback coupling has an important effect in the performance of the control loops by increasing the steady-state error. A comparison between different types of proportional+resonant controllers is done. Experimental results verify the theoretical assumptions done.

Smart energy users: ICT instruments for the consumer awareness

Abstract: The European Commission is supporting many projects in the field of energy saving, with the aim to improve user behavior and to help Europe to meet emission targets. In October 2012, the European Union adopted the Energy Efficiency Directive with the aim to reduce the primary energy consumption by 20% by 2020. One key point in the reduction of energy consumption energy is the awareness of final users about their usage of energy. At the same time, policies aimed at improving the efficiency of energy use, are a keystone in the strategies of leading Distribution System Operators (DSOs) and energy retail companies that started to offer, in addition to the energy supply, services and suggestions concerning the energy management in the daily family life. The first step toward a better use of energy is the awareness and the monitoring of the consumption. Since not all the final users have a professional education concerning energy, the figure of energy consumption are not enough to transfer the information. In order to support the final users to improve their energy behavior, additional information, comments, comparison (with similar users and with past consumption) have to be supplied with proper channel. The smart meters at the final users must be able to communicate with the users themselves or have to be connected to a storage and computation unit, in order to give a feedback, useful to evaluate and improved the final users' behaviors. In the paper are illustrated the activities carried out in the frame of the Empowering project the methods adopted for the evaluation of energy savings along with the ICT tools adopted in the Torino (Italy) pilot site.

Sea-wave power converter modeling for fault conditions analysis

Abstract: This paper investigates the contribution of a three-phase inverter used for the grid connection of a wave energy generation to the short-circuit currents when a grid fault occurs. By considering a real MV distribution network, the voltage ride-through capability of the power converter is verified both in case of a three-phase and a two-phase fault. The steady-state and transient evolutions of the short-circuit current are obtained from a tool developed for power flow analysis and calculation and from time domain simulations.

Clustering-based performance assessment of thermal energy management in buildings

Abstract: In recent years a growing attention is being paid towards energy efficiency in civil and industrial applications. In order to achieve better efficiency and enhance the energy management strategies, better knowledge is needed on the characterization of energy consumers. Categorization of electrical consumers through clustering procedures has been widely addressed in the literature. However, the categorization of the thermal users has been considered to a lower extent, also because of the difficulty of gathering a sufficient and reliable amount of data. This paper analyzes the behavior of several final users on the thermal side. At first, the energy behavior of the buildings from a thermal point is defined by its energy signature, represented as a straight line derived from measurements gathered in the heating period. Then, the parameters of the energy signature are used within a clustering procedure to create consistent groups of buildings. The results enable the operators to identify salient features of the groups of buildings under analysis, and to monitor the changes carried out in the buildings, leading to possible changes of the group during time.

Embedding final users in energy saving programs

Abstract: Several programs for energy savings are running in the world and most of them are related to the civil and small business environment. The results of energy saving programs depend on technical improvements but are also heavily affected by final users behaviors. The best way to obtain durable energy saving is involving the final users in the program in order to change their habits. Energy consumptions in an assigned environment are affected by several constrains (i. e. weather condition and social habits), in order to evaluate the savings related to a specific program, the energy saving, due to the program only, have to be identified and isolated. Since a large number of factors that can affect the energy consumption, it is difficult to define reliable models that allows the computation or the prediction of energy consumption from the environment input values. In order to evaluate the savings an approach based on the different behaviors of a selected: — experimental group: users that receive all the information related to energy saving program and are involved in the activities of the program itself; — control group: users located in the same environment of the experimental group, but not involved in the in the activities of the energy saving program; is usually adopted. With reference to the EU-IEE program Empowering the procedures for the selection of the experimental and control groups are presented. Some example of additional information to increase the final users' energy awareness is also presented.