Energy transition technology roadmap. Distinguishing hype from reality – 2020 strategic technological plan and business targets
Climate change and global warming in particular may be a controversial scientific theory, particularly in the US, but its growing impact on business is undeniable. The energy generation landscape, to begin with, is being disrupted by the growth of renewables; transport is witnessing the affirmation of the electric car, in its pure form or as a hybrid, and, most pervasive of all, the search for energy efficiency is creating new businesses – think for example smart metering or behind-the-meter distributed generation – and is modifying existing ones in a variety of ways. Our vision of the macrotrends shaping the energy transition is consistent with the narrative of Bloomberg New Energy Finance's New Energy Outlook, to which we make extensive reference in this overview.
Hybrid micro-grid experimental application in Tanzania
This paper is intended to introduce the project Energy4Growing that aims at studying and setting up a hybrid micro-grid to supply power to a school in rural Tanzania. It describes the results of the early project actions which concerned in: (i) analysing the actual school power supply system through locally metered data; (ii) developing the first step of a new electro-mechanical model which addresses the simulation of operation and dynamics within an off-grid power system; (iii) validating the new model. In particular the paper focuses on describing the development and the first step implementation of the new modelling approach which address: (i) voltage and frequency analyses over medium term period by means of simplified electromechanical models of power sources and power electronics, (ii) the analysis of different dispatch strategies and their consequence on voltage and frequency trends, (iii) the effects of dispatch strategies on the energy performances of particular components such as battery bank or dump loads. The new approach has also been applied in modelling the current school power supply system.
Technical Strategies for Voltage Power Regulation in LV Distribution Networks
We report the integration of a novel voltage regulation strategy in the inverter control algorithm for Dispersed Generation (DG) applications. The adoption of a decentralized voltage control based on local curves allows the voltage profile to be controlled at the Point of Common Coupling (PCC) of the generators and, therefore, the capacity of existing distribution networks to host more generation from renewables. The work is focused on a low voltage distribution network and both the reactive power modulation and the real power curtailment are considered in the proposed local strategy. Both numerical and experimental analysis are necessary in order to test and validate the proposed voltage control strategy. Firstly, the performances of the proposed control are tested by a numeral analysis and the impact on both the electrical system and the inverter apparatus is evaluated. Secondly, the benefit of the control strategy is analysed by experimental analysis in a test facility to verify the feasibility of voltage regulation in a real feeder.
Hybrid distributed generation system for a rural village in Africa
Nowadays the use of distributed generating systems, which use a renewable energy source, has experienced a fast development. Moreover, their intrinsic intermittent nature can be overcome using hybrid systems which combine more energy sources. This paper proposes the study and design of a hybrid generation system able to cover the energy needs of a school in a rural village in Africa (Tanzania), combining renewable and/or alternative sources and storage systems. The final results consist in the definition of an electric grid architecture suitable to interface renewable and energy needs in the most reliable way, exploiting advanced regulation and control techniques.
Dispersed generation to provide ancillary services: AlpStore project
In the future, electrical systems should be able to integrate all users at the same time and guarantee power quality, stability and safety over time. The integration of renewable energy sources leads to new issues involving the intermittence of this generation typology. A high penetration of intermittent power plants will reduce the capability of the system to overcome critical events (e.g. frequency oscillations and voltage profile perturbation). This work presents new regulation schemes/functions developed in the AlpStore project framework, devoted to managing dispersed generation in order to provide ancillary services to the main grid. The work developed can be split into two main items: reactive injection regulation and frequency control regulation. The first regulation is devoted to increasing the Hosting Capacity of the distribution grid (i.e. it results to be a local control), whereas the latter aims to guarantee the energy balance of the national electric grid (i.e. it could be classified as a grid control).
Control strategies and configurations of hybrid distributed generation systems
Nowadays the use of distributed generating systems, which use a renewable energy source, has experienced a fast development. Moreover, their intrinsic intermittent nature can be overcome using hybrid systems which combine more energy sources. This paper discusses the main topologies which can be adopted for a general hybrid generation system and it focuses on a particular hybrid system which combines two different energy sources, evidencing high level and local level power flow control strategies in both stand-alone and grid connected operation. A full experience in the realization of a hybrid plant which uses an internal combustion engine with cogeneration functionalities and solar source, installed in Delebio, Italy is then presented. System design aspects, with particular attention to the possible topologies and power flow control strategies, are analyzed. After the analysis of the design aspects, experimental results of the real plant are reported.
Design and analysis of a Medium Voltage DC wind farm with a transformer-less wind turbine generator
In recent years, the interest in offshore wind farms has been increased significantly. One of the reasons of this development is the less perceived environmental cost of an offshore wind farm with respect to an in-land one, especially for new installations where big turbines are preferred. However, they have also the advantage of an increased and more constant wind speed, leading to higher and more constant production of electrical power. For these kinds of wind farms a pure DC system could be an interesting and cost effective solution. This paper describes an innovative Medium Voltage Direct Current electrical grid system (MVDC) for wind farms, based on transformer-less wind turbines. An accurate analysis is presented and the proposed solution has been validated through a simulation and experimental phase performed on a low voltage prototype.
Reduction of motor overvoltage fed by PWM AC drives using a universal model
An induction motor model construction and the validation of the model response to a filtering technique is analyzed in this paper. The filter is connected to the rotating machine terminals in order to suppress overvoltages due to the long cables and high frequency pulses of the inverter. With the help of high frequency measurements made by the authors on a 1.1kW induction motor, an accurate simulation with Matlab Simulink™ based on differential mode analysis, is made. The simulation shows realistic results for the determination of the filter parameters among different values of rise time and cable length.
MVDC connection of offshore wind farms to the transmission system
This paper describes an innovative Medium Voltage Direct Current electrical grid system (MVDC) for wind farms, based on transformer-less wind turbines, equipped with modular, multilevel converter (M2LC). A comparison between this MVDC system and a traditional MVAC one has been done using EECC (Electrical Energy Conversion Cost) index in order to evaluate the competitiveness of this solution for an offshore wind farm in the Mediterranean Sea.
Hybrid PV-CHP distributed system: Design aspects and realization
The use of distributed generating systems, which use a renewable energy source, has experienced a fast development. Moreover, their intermittent nature can be overcome using hybrid systems which combine more energy sources. This paper discusses a full experience in the realization of a hybrid plant which uses an internal combustion engine with cogeneration/trigeneration functionalities and solar source, installed in Delebio, Italy. System design aspects, with particular attention to the possible topologies and power flow control strategies are analyzed. After the analysis of design aspects, some simulations are presented to validate the proposed solution and finally experimental results of the real plant are reported.