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Photovoltaic generators installed in Unterfarrnbach The voltage and current controller is currently tested in distribution networks (LV and MV) in the south of Germany. Both grid are characterized by a high share of PV plants, that actually cause problems due to voltage increase. Figure 3 shows a mashed LV distribution grid which is composed of two transformers connected in a ring-network. There are 137 households with about 500kW installed photovoltaic generators. As it can be observed in the magnified part of Figure 4 if uncontrolled, the voltage constraints will be violated in the case of full sunshine. One of the challenges in implementing the central control in the Area Administrator is the computation complexity generated for large networks. Still, for the sequential quadratic programming algorithm the gradients of the cost function and the constraints can be analytically derived, which accelerates substantially the computation. Even for a large network, the optimization could be performed in less than one second.
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The increasing share of renewable energy resources like wind or solar power opens up interesting options for a paradigmatic change of network operation strategies. On the one hand volatile generation principally endanger robust network operation. On the other hand there is an political and ecological pressure to maximize the in-feed of renewable en...
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... 3. Photovoltaic generators installed in Unterfarrnbach The voltage and current controller is currently tested in distribution networks (LV and MV) in the south of Germany. Both grid are characterized by a high share of PV plants, that actually cause problems due to voltage increase. Figure 3 shows a mashed LV distribution grid which is composed of two transformers connected in a ring-network. There are 137 households with about 500kW installed photovoltaic generators. As it can be observed in the magnified part of Figure 4 if uncontrolled, the voltage constraints will be violated in the case of full sunshine. One of the challenges in implementing the central control in the Area Administrator is the computation complexity generated for large networks. Still, for the sequential quadratic programming algorithm the gradients of the cost function and the constraints can be analytically derived, which accelerates substantially the computation. Even for a large network, the optimization could be performed in less than one second.
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Citations
... Becoming a prosumer [21] with lowest energy costs and maximal self-consumption is nowadays an intensely studied aspect with benefits both for the end-user and the local electrical energy distributor [22]. Different types of prosumers are analysed in literature, with different production, storage and consumption technologies, which depend on the consumer type and on the installation location. ...
Romania introduced in 2018 an amendment to the national law 220/2008 by including the Prosumer concept that allows investors in grid-connected photovoltaic systems with a capacity up to 27 kWp to receive a feed in tariff for the electricity delivered to the grid representing approximatively one third of the price paid when the electricity is consumed from the grid. Thus, the challenge is to use as much as possible the photovoltaic power when it is produced. A methodology is developed to evaluate how much of the electrical energy output of a grid-connected photovoltaic platform is used by a geothermal heat pump for space heating in a building. A numerical simulation is performed in Trnsys17 based on locally measured meteorological parameters over a period of one entire year. A case study is presented for which the characteristics of the building, of the heat pump system and of the photovoltaic system are described and integrated into the transient simulation environment. The numerical results are comparatively presented and discussed along with experimental data for sunny days in cold season. For the analysed case study, the self-consumption is 16%, significantly lower than the yearly coverage degree of 70%. Further research can be done to increase the self-consumption.
... To deal with these challenges, concepts for decentralized management of the decentral energy resources are discussed [3,29]. But different to the situation in the early years of power technology, a cellular system architecture will still be connected with the outside world on the electrical and information side. ...
The increasing integration of renewable power generation in power systems poses new challenges to power system control. In this article, we describe a multi-layer power system control architecture that addresses these challenges and comprises economic planning, supervisory power control, as well as voltage and frequency control as main layers. Several parts of this architecture have already been developed and tested on diverse components including building energy management, micro grid management and wind park control. We provide an overview of these applications and indicate white spots in this control architecture that require further research.
i. The UK energy landscape is partially orienting towards renewable electricity generation. Recently, this has begun to include solar PV (photovoltaic) technologies.
ii. Solar PV technologies exist at a distributed scale (e.g. roof mounted solar panels) and at utility scale (i.e. solar farms) in the UK.
iii. Utility scale solar PV developments are likely to have a greater ecological impact than distributed scale developments due to their larger size and the requirement for new infrastructure. As such, this review will focus on utility scale solar PV developments.
iv. Birds and bats have been identified by Natural England as the taxa most urgently requiring an evidence base for potential impacts relating to solar PV developments. The focus of this review will be on these taxa, however general ecological impacts will also be considered.
v. Around 420 scientific documents with potential relevance to this review were identified using tailored search strings and subsequently screened for evidence relating to the ecological impacts of solar farms. The majority of these documents were of no relevance, and were returned by the literature search due to irresolvable linguistic and conceptual ambiguities. These documents were not considered further.
vi. Grey literature from a total of 37 non-governmental and governmental organisations was examined for evidence of the potential ecological impacts of solar farms.
vii. Twelve rejected planning applications for solar PV developments with generating capacity of > 1 MW in the north west of England were examined to determine whether these rejections were made on an ecological basis.
viii. No peer reviewed experimental scientific evidence exists relating solely to the ecological impacts of solar PV developments.
ix. Some scientific and grey literature data, based upon carcass searches around solar PV developments suggests that bird collision risk from solar panels is very low. There is likely to be more of a collision risk to birds presented by infrastructure associated with solar PV developments, such as overhead power lines.
x. Evidence from both the grey literature and the peer-reviewed scientific literature suggests that protected areas should be avoided when considering site selection of solar PV developments, with some sources suggesting that locations close to protected areas should be avoided also. This recommendation is not quantified in any of the reviewed literature.
xi. Indirect evidence of bird presence is often presented in the engineering literature, where designs for solar panel cleaning devices often cite bird droppings as a contaminant.
xii. Solar panels have the capacity to reflect polarised light which can attract polarotactic insects, which has the potential to impact their reproductive biology. The polarising effect of solar panels may also induce drinking behaviour in some bird taxa, where the birds mistake the panels for water.
xiii. Birds and bats should be assessed by taxon or guild, with different behavioural traits and habitat requirements taken into consideration. The potential for solar developments to attract or repel birds or bats should be considered, alongside the potential for negative interactions to occurs between these taxa and solar farms.
xiv. Future research should focus on examining the potential of solar PV developments to support biodiversity. The grey literature often refers to mitigation/enhancement practices such as wildflower meadow planting, hedgerow laying and tree planting with some grey literature studies attempting to quantify diversity on solar PV sites. These studies should be formalised and replicated within a scientific framework.
xv. Governmental and non-governmental organisations that provide advice and guidance that may have ecological implications have a duty to contribute to evidence towards their guidance, especially where evidence is lacking. In the case of solar farms, there is almost no evidence and research into their ecological impacts is urgently needed.
We present a novel algorithm for economic dispatch in electric power grids. The method is inspired by statistical inference methods. Using discretized optimization variables, our algorithm finds the globally optimal, single time-step dispatch assignment for radial grids in linear time with respect to the number of network nodes. For such problems, the algorithm outperforms state-of-the-art mixed-integer scheduling, both in run-time and in the allowed complexity of component and line models. Moreover, the necessary computations can be performed in a distributed fashion, facilitating both practical implementation as well as information privacy. Our algorithm is thus optimally suited for the very large dispatch problems that will arise in future smart distribution grids with hosts of small, decentralized, and flexibly controllable prosumers, i.e., entities able to consume and produce electricity.
The focus of the German federal government’s energy agenda is an environmental friendly, reliable and affordable energy supply with the emphasis on renewable energy sources. The projected increase in renewable energy production requires new concepts for suitable grid and energy market integration. The installation of an ever increasing capacity of renewable energy sources goes in hand with increasingly stringent system requirements on the distribution grid. These challenges require novel operational strategies to hold the gird state within a permissible region, ensuring the supply security of the end customer. One possible solution-approach in this context pose managed micro-grids. Micro-grids have the property that on the one hand they are able to form electrical islands for a limited amount of time (e.g. in case of failure) and on the other hand they can deliver grid services to the (connected) overlaying electricity grid – a functionality that we denote ‘topological power plant’. In the context of IREN2 (Sustainable Grids for the Integration of Renewable Energy Systems) we will evaluate the technological and economical aspects of real-world micro grid operation. IREN2 builds on the insights gained from IRENE (project term 2011 – 2013) which was concerned with the integration of renewable energy sources as well as electric mobility.
Since July 2014, the project partners are in the process of realizing an island grid capable micro-grid in the center of Wildpoldsried. Key components are tab changing transformers, a battery storage system, a number of (controllable) PV-systems, load/PV emulators, diesel generators with vegetable oil as well as an elaborate measurement and communication infrastructure.
AÜW GmbH is responsible for all grid-related tasks within IREN2 and will be supported by their subsidiary egrid applications & consulting GmbH offers consulting services in respect to smart grid expansion.
The wide spread of distributed generation from renewable power sources may cause severe degradation of electricity quality due to its hardly predictable nature. In order to maintain the desired electricity quality, new actuators and advanced control techniques needs to be developed and integrated in the grid. The reactive power injection of photovoltaic (PV) inverters provides an effective mean for the control of voltage levels and their fluctuation. This paper describes a combined central and local control scheme for the reactive power. The use of local controllers based only on local measurements enables a fast reaction of the controllers on changes in generated and consumed powers, while the central optimization of their parameters ensures an optimal use of the resources and minimization of losses. MATLAB simulations prove the concept for a realistic distribution grid.
