Integration Of Renewable Sources Research Articles

THE DESIGN OF A SMART ENERGY MANAGEMENT SYSTEM FOR MICROGRIDS

The increase in the use of renewable energy systems in recent years has led to an increase in the importance of work on micro-grids. In micro-grids, energy is consumed where it is produced. This leads to a reduction in transmission and power losses in the lines. At the same time, the negative effects of the industrial plants that disrupt the quality of power are eliminated by the micro-grid model and more efficient and reliable grids can be established. Technological developments that impact each field have also affected the electricity distribution grids. Problems such as inefficient energy transmission systems caused by high power losses, problems in the integration of renewable sources into the grid, inflexible demand, and wage problems make it difficult to meet the increasing demand with the traditional structure. In this study, a smart grid system was set up in the sample micro structure. The system consist from a photovoltaic system with a consumer and a grid system that feeds this consumer. There are a photovoltaic system and also a battery group in the applied micro grid. The power of the photovoltaic system in the micro-grid is continuously monitored by a microcontroller. The energy level information of PV panel system, the battery, and grid are supplied by voltage divider circuits to microcontroller. The information transmitted by the voltage dividers to the microcontroller is evaluated by the control algorithm. Considering account possible possibilities, the receiver is primarily fed by the photovoltaic system, in other cases fed from the grid or the battery system, thanks to the semiconductor switches used in the microcontroller control. In addition, excess energy generated by the microcontroller is transferred to the main grid. As a result of this application, the level of use of the renewable energy system has been increased and the energy cost has been reduced.

Battery Storage Systems as Grid-Balancing Measure in Low-Voltage Distribution Grids with Distributed Generation

Due to the promoted integration of renewable sources, a further growth of strongly transient, distributed generation is expected. Thus, the existing electrical grid may reach its physical limits. To counteract this, and to fully exploit the viable potential of renewables, grid-balancing measures are crucial. In this work, battery storage systems are embedded in a grid simulation to evaluate their potential for grid balancing. The overall setup is based on a real, low-voltage distribution grid topology, real smart meter household load profiles, and real photovoltaics load data. An autonomous optimization routine, driven by a one-way communicated incentive, determines the prospective battery operation mode. Different battery positions and incentives are compared to evaluate their impact. The configurations incorporate a baseline simulation without storage, a single, central battery storage or multiple, distributed battery storages which together have the same power and capacity. The incentives address either market conditions, grid balancing, optimal photovoltaic utilization, load shifting, or self-consumption. Simulations show that grid-balancing incentives result in lowest peak-to-average power ratios, while maintaining negligible voltage changes in comparison to a reference case. Incentives reflecting market conditions for electricity generation, such as real-time pricing, negatively influence the power quality, especially with respect to the peak-to-average power ratio. A central, feed-in-tied storage performs better in terms of minimizing the voltage drop/rise and shows lower distribution losses, while distributed storages attached at nodes with electricity generation by photovoltaics achieve lower peak-to-average power ratios.

Renewable sources integration through the optimization of the load for residential applications.

This work presents the implementation of two different control strategies for the control of Microgrids a Model Predictive Control (MPC) technique coupled with a Mixed-Integer Linear Program (MILP) structure and a Rule Based Control (RBC) strategy both applied to a residential MicroGrid. The validation of the models has been performed with an experimental setup laid out in the laboratory of University of Rome - Tor Vergata. Results obtained show that MicroGrids connected to the main network have enough potential to support grid balancing actions, thus allowing for a greater penetration of renewable sources into the mix, and giving economic benefits for both end users and providers. In particular, using a MPC strategy major benefits can be obtained in terms of reduction of the unbalanced energy exchange with the main grid and a more efficient use of the micro-grid components.

Optimal integration of renewable based processes for fuels and power production: Spain case study

In this work we propose a data independent framework for the optimal integration of renewable sources of energy to produce fuels and power. A network is formulated using surrogate models for various technologies that use solar energy (photovoltaic, concentrated solar power or algae to produce oil), wind, biomass (to obtain ethanol, methanol, FT-liquids and thermal energy), hydroelectric, and waste (to produce power plant via biogas production). The optimization model is formulated as a mixed-integer linear programming model that evaluates the use of renewable resources and technologies and their integration to meet power and fuels demand; sustainability and CO2 emissions are also considered. The network can be applied to evaluate process integration at different scales, county to country level, including uncertainty availability of resources. Spain and particular regions are used as a case study. The framework suggests that larger integration uses the resources more efficiently, while considering uncertainty in resource availability shows larger cost to ensure meeting the demand. For the particular case considered, hydropower is widely used while biofuels are produced close to large populated regions when larger areas are evaluated; otherwise a more distributed solution is proposed. Reaching large fuel substitution is difficult at current biomass yields and technology state of development.

Intelligent Early Warning of Power System Dynamic Insecurity Risk: Toward Optimal Accuracy-Earliness Tradeoff

Dynamic insecurity risk of a power system has been increasingly concerned due to the integration of stochastic renewable power sources (such as wind and solar power) and complicated demand response. In this paper, an intelligent early-warning system to achieve reliable online detection of risky operating conditions is proposed. The proposed intelligent system (IS) consists of an ensemble learning model based on extreme learning machine (ELM) and a decision-making process under a multiobjective programming framework. Taking an ensemble form, the randomness existing in individual ELM training is generalized and reliable classification results can be obtained. The decision making is designed for ELM ensemble whose parameters are optimized to search for the optimal tradeoff between the warning accuracy and the warning earliness of the proposed IS. The compromise solution turns out to significantly speed up the overall computation with an acceptable sacrifice in the accuracy (e.g., from 100% to 99.9%). More importantly, the proposed IS can provide multiple and switchable performances to the operators in order to satisfy different local dynamic security assessment requirements.

Pole-mounted battery energy storage for reliability enhancement of local distribution companies

Power systems currently experience paradigm changes due to the integration of renewable sources, penetration of electric vehicles, and advancements in smart grid technology. Energy storage elements are accordingly sought to rectify some drawbacks of the new system components. Energy storage technologies and their power grid applications are, therefore, developing in fast pace.This paper presents the design, development, and testing of a pole-mounted energy storage system (PMESS) based on lithium-ion batteries. The PMESS aims at enhancing the reliability of a local distribution company (LDC) at the residential level. The system provides load curve smoothing and peak shaving services to a pole-top distribution transformer feeding residential customers. An intelligent control algorithm is developed for optimal scheduling of the battery pack. The algorithm employs communication, load forecasting, and optimization software modules. A prototype unit of the PMESS is installed and tested on a Canadian LDC where the results show positive impact on the performance of the distribution transformer. Findings of this research are anticipated to attract the attention of those interested in distribution system operation, planning, and asset management.

A high-voltage-gain dc-dc converter based on modified dickson charge pump voltage multiplier

A high-voltage-gain dc–dc converter is introduced in this paper. The proposed converter resembles a two-phase interleaved boost converter on its input side while having a Dickson-charge-pump-based voltage multiplier (VM) on its output side. This converter offers continuous input current, which makes it more appealing for the integration of renewable sources like solar panels to a 400-V dc bus. Also, the proposed converter is capable of drawing power from either a single source or two independent sources. Furthermore, the VM used offers low voltage ratings for capacitors that potentially leads to size reduction. The converter design and component selection have been discussed in detail with supporting simulation results. A hardware prototype of the proposed converter with ${V}_{\rm{in}}= \rm{ 20}$ and ${V}_{\rm{out}}= \rm{ 400}$ V has been developed to validate the analytical results.

Unit Cell Model of a Regenerative Hydrogen-Vanadium Fuel Cell

All-Vanadium Redox Flow Batteries (VFBs) have been considered a promising system for the integration of renewable energy-based sources in electricity grids, but also have faced challenges related to cost, scale-up and optimization1–3. Cost dependency with regarding to vanadium price can be mitigated through utilization of new redox systems that employ only half of the vanadium1. Recently, a Regenerative Hydrogen-Vanadium Fuel Cell (RHVFC) based on an aqueous vanadium electrolyte V(V)/V(IV) and hydrogen has been introduced4. Hydrogen evolution, which is an adverse reaction in VFBs, is the main anodic process in this cell. During discharging V(V) is reduced to V(IV) and hydrogen is oxidized, while the reverse process occurs in charging mode and hydrogen is stored. The RHVFC could offer a better energy storage solution because of its fast hydrogen kinetics and absence of cross-mixing, even when the crossover of catholyte is possible, this could be collected at the anode side and pumped back to the catholyte tank4,5. Nonetheless, in order to assess key factors that limit the performance of the system a model is required that take into consideration various physical phenomena yet is capable to converge to a meaningful solution relatively fast. In this work, a simplified unit cell model of a RHVFC is presented, which is based on mathematical phenomenological descriptions reported for VFBs6 and Polymer-Electrolyte-Membrane (PEM) Fuel Cells7. The proposed model was developed by coupling mass transport phenomena along with electrochemical processes, and is capable of predicting cell potential under different operating conditions. Comparison of simulations against experimental data was performed by means of a 25 cm2 lab scale prototype operated at galvanostatic mode with moderates values of current density, 5-10 mA cm-2, and catholyte and hydrogen flow rates of 100 mL/min. Validation of the model was performed against experimental data of the Open Circuit Potential (OCP) using a complete Nernst equation, and cell potential data considering the ohmic loss and activation overpotential. Correct estimation of the catholyte proton concentration was shown to be important in accurately determining the OCP. A good OCP fit was obtained by assuming the complete dissociation of sulphuric acid to bisulphate during the first step and further dissociation controlled by a dissociation rate constant and an overall activity coefficient term. The modelled cell potential showed a good agreement with the experimental data, and it was observed that the overpotential contribution of the cathode was more important than the anode at the tested operating conditions. This first model approximation allows simulation of the system with good accuracy, and provides a foundation to further development of RHVFC physical-based models. Future work will include testing under wider range of operating conditions and the corresponding model validation with mass transport limitations associated with diffusion in the porous media, vanadium crossover into the anode side and anode flooding. The contribution of these effects will be significant under high current densities operation.

A feasibility study on the potential expansion of the district heating network of Turin

Reduction in energy consumptions and CO2 emissions and increase in the use of renewable energy sources can be reached through large scale implementation of energy efficiency measures. In urban contexts, district heating (DH) systems are expected to allow integration of waste heat and thermal renewable sources. In this work we propose a GIS-based model for the technical feasibility analysis of possible expansions of existing DH networks. The application to the City of Turin is presented as a case study.

Large-Scale Integration of Renewable Power Sources into the Vietnamese Power System

The Vietnamese Power system is expected to expand considerably in upcoming decades. However, pathways towards higher shares of renewables ought to be investigated. In this work, we investigate a highly renewable Vietnamese power system by jointly optimising the expansion of renewable generation facilities and the transmission grid. We show that in the cost-optimal case, highest amounts of wind capacities are installed in southern Vietnam and solar photovoltaics (PV) in central Vietnam. In addition, we show that transmission has the potential to reduce levelised cost of electricity by approximately 10%.

Nodal prices determination with wind integration for radial distribution system

With competitive electricity market operation, open access to the transmission and distribution network is essential for transparent and efficient market operation. Like transmission pricing, distribution network pricing must also be transparent and must include tile variations based on the change in the operating state of the system, integration of renewable sources and must be real time. In this paper, a distribution system nodal pricing scheme is proposed for radial distribution system with integration of wind power in the system. The main objective of the paper is: (i) an optimal power flow based approach for determination of nodal prices for distribution system, (ii) impact of wind generation on nodal prices. The results have been obtained for IEEE 33 bus test system.Keywords: Distribution system, electricity market; nodal prices, wind power integration

Adequacy assessment of a 2 area system with renewable integration

AbstractIn this paper, impacts of renewable sources on the adequacy of a 2 area system are presented. Integration of popular renewable sources like photovoltaic (PV) and wind is forcing the operational planner to operate differently. Here, an effort has been made to propose some planning scenarios for 2 area system on the basis of renewable sources integration, and reliability is evaluated corresponding to each scenario. Loss of load expectation is popular method for adequacy assessment following 2 state principle (available or unavailable) of conventional sources. Photovoltaic and wind system never follow 2 state principle unlike conventional. Existing PV module configuration determine the unavailability rate of PV plant considering component failure. Random wind speed is simulated using time series auto regressive moving average model. Wind turbine characteristics and simulated wind speed create multistate wind energy conversion system and reduced by apportioning method to predict unavailability rate. A simple 2 area system is considered to validate the efficacy of proposed theme.

The use of Model Predictive Control (MPC) in the optimal distribution of electrical energy in a microgrid located in southeastern of Spain: A case study simulation

The microgrids allow the integration of renewable sources of energy such as solar and wind and distributed energy resources such as combined heat and power, energy storage, and demand response. In addition, the use of local sources of energy to serve local loads helps reduce energy losses in transmission and distribution, further increasing efficiency of the electric delivery system. In this paper, the optimization problem of the energy in a microgrid (MG) located in southeastern of Spain, with Energy Storage System (ESS), which exchanges energy with the utility grid is developed using Model Predictive Control techniques. System modelling use the methodology of the Energy Hubs. The MPC techniques allow maximizing the economic benefit of the microgrid and to minimize the degradation of storage system.

CO2 content of electricity losses

Countries are implementing policies to develop greener energy markets worldwide. In Europe, the ¨2030 Energy and Climate Package¨ asks for further reductions of green house gases, renewable sources integration, and energy efficiency targets. But the polluting intensity of electricity may be different in average than when considering market inefficiencies, in particular losses, and therefore the implemented policy must take those differences into account. Precisely, herein we study the importance in terms of CO2 emissions the extra amount of energy necessary to cover losses. With this purpose we use Spanish market and system data with hourly frequency from 2011 to 2013. Our results show that indeed electricity losses significantly explain CO2 emissions, with a higher CO2 emissions rate when covering losses than the average rate of the system. Additionally, we find that the market closing technologies used to cover losses have a positive and significant impact on CO2 emissions: when polluting technologies (coal or combined cycle) close the market, the impact of losses on CO2 emissions is high compared to the rest of technologies (combined heat and power, renewables or hydropower). To the light of these results we make some policy recommendations to reduce the impact of losses on CO2 emissions.

Power Quality Enhancement of Smart Households Using a Multilevel-THSeAF With a PR Controller

In this paper a multilevel transformerless hybrid series active filter is proposed to enhance the power quality of a single-phase residential household. The proposed topology reflects new trends of consumers toward electronic polluting loads and integration of renewable sources which in fact may lead to the scope of a reliable and sustainable supply. This paper contributes to improvement of power quality for a modern single-phase system and emphasis integration of a compensator with energy storage capacity to ensure a sustainable supply. A proportional resonant (P+R) regulator is implemented in the controller to prevent current harmonic distortions of various non-linear loads to flow into the utility. The main significant features of the proposed topology include the great capability to correct the power factor as well as cleaning the grid simultaneously, while protecting consumers from voltage disturbances, sags, and swells during a grid perturbation. It investigates aspects of harmonic compensation and assesses the influence of the controller’s choice and time delay during a real-time implementation. Combinations of analysis and experimental results performed on a laboratory setup are presented for validation.

Energy Audit and Renewable Integration for Historic Buildings: The Case of Craiglockhart Primary School

Energy Audit and Planning for both existing and new-to-build buildings has been of increasing interest during the last years due to growing environmental concerns. Especially historic buildings, such Craiglockhart Primary School, which are of great importance because of their special architectural characteristics, are energy-demanding structures of incomplete and outdated technology. Improving the energy efficiency of such buildings would mean environmental and financial benefits as well as retaining of the historical heritage of Edinburgh. Additionally, integration of renewable sources in such buildings would result in a further gain from renewable heat incentives and in greener building as well. Firstly, this paper summarizes a study of possible actions for improving the energy efficiency of such buildings. Secondly, assuming that the proposed measures have been applied, possibility of renewables’ integration is assessed. Heat pumps and biomass integration is investigated and a hybrid system is finally proposed. This paper evaluates level of improvement and cost for all scenarios explored after considering possible constraints.

Review on Microgrid and its Protection Strategies

Microgrids are indispensable at the distribution level network and is capable of operating in both grid connected and islanded modes. Integration of renewable sources in a microgrid is a viable solution to provide continuity of supply to customers. Due to bidirectional power flow, conventional protection strategies are not applicable to microgrids. Also the change in topology of the network poses a key challenge to protection engineers. This paper reviews the advent of microgrid and also the protection strategies that are incorporated in the system integrated with renewable energy systems (RES).

Modeling power networks using dynamic phasors in the dq0 reference frame

The dynamic behavior of large power systems has been traditionally studied by means of time-varying phasors, under the assumption that the system is quasi-static. However, with increasing integration of fast renewable and distributed sources into power grids, this assumption is becoming increasingly inaccurate. In this paper, we present a dynamic model of general transmission and distribution networks that uses dynamic phasors in the dq0 reference frame. The model is formulated in the frequency domain, and is based on the network frequency dependent admittance matrix. We also present a simplified version of this model that is obtained by a first-order Taylor approximation of the dynamic equations. The proposed models extend the quasi-static model to higher frequencies, while employing dq0 signals that are static at steady-state, and therefore combine the advantages of high bandwidth and a well-defined operating point. The models are verified numerically using the 9-, 30-, and 118-bus test-case networks. Simulations show that frequency responses of all models coincide at low frequencies and diverge at high frequencies. In addition, responses of the dq0 model in the time domain and in the abc reference frame are very close to those of the transient model.

Nonlinear model-based control for minimum-time start of hydraulic turbines

Fast start of hydraulic turbines is mandatory for a successful integration of renewable sources of energy. Successful handling of this issue needs to operate close to the boundary of the admissible domain while fully exploiting the knowledge of the system dynamics. This paper introduces a simplified model of hydraulic turbines including the hydraulic nonlinear hill-chart and a first order model of the penstock. Based on the resulting reduced model, a graphical representation of the vector fields of the resulting controlled system is first obtained under the assumption of a band unlimited actuator. This ideal 2D-graphical representation enables an exact evaluation of the lower bound on the minimum achievable start-time as well as the time structure of the control profile. Based on this analysis, a real-life MPC scheme is proposed that takes into account realistic limitations on the actuator leading to feasible, almost time-optimal control design.

Design of a Sustainable and Efficient Transportation Station (SETS) Based on Renewable Sources and Efficient Electric Drives

The need for reduction in power consumption for public facilities has increased after the occurrences of multiple blackout events. In an effort to enable the development of green and smart social infrastructure, this paper introduces a design for a sustainable and efficient transportation system (SETS). For this design, renewable power sources and efficient electric drives are considered to be crucial technologies. Considering the subway station as an illustrative example, a power system design that uses wind and solar energy as major power sources is studied. The adjustable speed electric drive system that uses synchronous reluctance machines for ventilation systems contributes to increasing the overall power consumption efficiency. The effectiveness of the proposed SETS system is verified through a set of various field measurement data and simulation results. While the verification results demonstrate that operation of SETS is enabled by effective integration of renewable sources and efficient ventilation systems, future research directions have also been identified.