4,290 research outputs found
Optimal Net-Load Balancing in Smart Grids with High PV Penetration
Mitigating Supply-Demand mismatch is critical for smooth power grid
operation. Traditionally, load curtailment techniques such as Demand Response
(DR) have been used for this purpose. However, these cannot be the only
component of a net-load balancing framework for Smart Grids with high PV
penetration. These grids can sometimes exhibit supply surplus causing
over-voltages. Supply curtailment techniques such as Volt-Var Optimizations are
complex and computationally expensive. This increases the complexity of
net-load balancing systems used by the grid operator and limits their
scalability. Recently new technologies have been developed that enable the
rapid and selective connection of PV modules of an installation to the grid.
Taking advantage of these advancements, we develop a unified optimal net-load
balancing framework which performs both load and solar curtailment. We show
that when the available curtailment values are discrete, this problem is
NP-hard and develop bounded approximation algorithms for minimizing the
curtailment cost. Our algorithms produce fast solutions, given the tight timing
constraints required for grid operation. We also incorporate the notion of
fairness to ensure that curtailment is evenly distributed among all the nodes.
Finally, we develop an online algorithm which performs net-load balancing using
only data available for the current interval. Using both theoretical analysis
and practical evaluations, we show that our net-load balancing algorithms
provide solutions which are close to optimal in a small amount of time.Comment: 11 pages. To be published in the 4th ACM International Conference on
Systems for Energy-Efficient Built Environments (BuildSys 17) Changes from
previous version: Fixed a bug in Algorithm 1 which was causing some min cost
solutions to be misse
Local Control of Reactive Power by Distributed Photovoltaic Generators
High penetration levels of distributed photovoltaic (PV) generation on an
electrical distribution circuit may severely degrade power quality due to
voltage sags and swells caused by rapidly varying PV generation during cloud
transients coupled with the slow response of existing utility compensation and
regulation equipment. Although not permitted under current standards for
interconnection of distributed generation, fast-reacting, VAR-capable PV
inverters may provide the necessary reactive power injection or consumption to
maintain voltage regulation under difficult transient conditions. As side
benefit, the control of reactive power injection at each PV inverter provides
an opportunity and a new tool for distribution utilities to optimize the
performance of distribution circuits, e.g. by minimizing thermal losses. We
suggest a local control scheme that dispatches reactive power from each PV
inverter based on local instantaneous measurements of the real and reactive
components of the consumed power and the real power generated by the PVs. Using
one adjustable parameter per circuit, we balance the requirements on power
quality and desire to minimize thermal losses. Numerical analysis of two
exemplary systems, with comparable total PV generation albeit a different
spatial distribution, show how to adjust the optimization parameter depending
on the goal. Overall, this local scheme shows excellent performance; it's
capable of guaranteeing acceptable power quality and achieving significant
saving in thermal losses in various situations even when the renewable
generation in excess of the circuit own load, i.e. feeding power back to the
higher-level system.Comment: 6 pages, 5 figures, submitted to IEEE SmartGridComm 201
Mitigating unbalance using distributed network reconfiguration techniques in distributed power generation grids with services for electric vehicles: A review
© 2019 Elsevier Ltd With rapid movement to combat climate change by reducing greenhouse gases, there is an increasing trend to use more electric vehicles (EVs) and renewable energy sources (RES). With more EVs integration into electricity grid, this raises many challenges for the distribution service operators (DSOs) to integrate such RES-based, distributed generation (DG) and EV-like distributed loads into distribution grids. Effective management of distribution network imbalance is one of the challenges. The distribution network reconfiguration (DNR) techniques are promising to address the issue of imbalance along with other techniques such as the optimal distributed generation placement and allocation (OPDGA) method. This paper presents a systematic and thorough review of DNR techniques for mitigating unbalance of distribution networks, based on papers published in peer-reviewed journals in the last three decades. It puts more focus on how the DNR techniques have been used to manage network imbalance due to distributed loads and DG units. To the best of our knowledge, this is the first attempt to review the research works in the field using DNR techniques to mitigate unbalanced distribution networks. Therefore, this paper will serve as a prime source of the guidance for mitigating network imbalance using the DNR techniques to the new researchers in this field
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Challenges to the Integration of Renewable Resources at High System Penetration
Successfully integrating renewable resources into the electric grid at penetration levels to meet a 33 percent Renewables Portfolio Standard for California presents diverse technical and organizational challenges. This report characterizes these challenges by coordinating problems in time and space, balancing electric power on a range of scales from microseconds to decades and from individual homes to hundreds of miles. Crucial research needs were identified related to grid operation, standards and procedures, system design and analysis, and incentives, and public engagement in each scale of analysis. Performing this coordination on more refined scales of time and space independent of any particular technology, is defined as a “smart grid.” “Smart” coordination of the grid should mitigate technical difficulties associated with intermittent and distributed generation, support grid stability and reliability, and maximize benefits to California ratepayers by using the most economic technologies, design and operating approaches
Improving the Performance of Low Voltage Networks by an Optimized Unbalance Operation of Three-Phase Distributed Generators
This work focuses on using the full potential of PV inverters in order to improve the efficiency of low voltage networks. More specifically, the independent per-phase control capability of PV three-phase four-wire inverters, which are able to inject different active and reactive powers in each phase, in order to reduce the system phase unbalance is considered. This new operational procedure is analyzed by raising an optimization problem which uses a very accurate modelling of European low voltage networks. The paper includes a comprehensive quantitative comparison of the proposed strategy with two state-of-the-art methodologies to highlight the obtained benefits. The achieved results evidence that the proposed independent per-phase control of three-phase PV inverters improves considerably the network performance contributing to increase the penetration of renewable energy sources.Ministerio de EconomĂa y Competitividad ENE2017-84813-R, ENE2014-54115-
Regulatory strategies for selected Member States (Denmark, Germany, Netherlands, Spain, the UK):IMPROGRES project
Research Project supported by the European Commission, Directorate-General for Energy and Transport, under the Energy Intelligent Europe (EIE) programmeThis Work Package 6 report of the IMPROGRES project provides an overview of regulatory strategies and incentives, conducive to (i) network integration of increasing levels of distributed generation including notably intermittent renewable technology such as wind power and solar photovoltaics (PV) as well as (ii) options for reducing impacts on surging network integration costs. Similar to the IMPROGRES project in general, this report focuses on European distribution networks. It includes specific country studies of Denmark, Germany, the Netherlands, Spain and the UK. This summary presents the main findings of this report
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