2,816 research outputs found

    pandapower - an Open Source Python Tool for Convenient Modeling, Analysis and Optimization of Electric Power Systems

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    pandapower is a Python based, BSD-licensed power system analysis tool aimed at automation of static and quasi-static analysis and optimization of balanced power systems. It provides power flow, optimal power flow, state estimation, topological graph searches and short circuit calculations according to IEC 60909. pandapower includes a Newton-Raphson power flow solver formerly based on PYPOWER, which has been accelerated with just-in-time compilation. Additional enhancements to the solver include the capability to model constant current loads, grids with multiple reference nodes and a connectivity check. The pandapower network model is based on electric elements, such as lines, two and three-winding transformers or ideal switches. All elements can be defined with nameplate parameters and are internally processed with equivalent circuit models, which have been validated against industry standard software tools. The tabular data structure used to define networks is based on the Python library pandas, which allows comfortable handling of input and output parameters. The implementation in Python makes pandapower easy to use and allows comfortable extension with third-party libraries. pandapower has been successfully applied in several grid studies as well as for educational purposes. A comprehensive, publicly available case-study demonstrates a possible application of pandapower in an automated time series calculation

    Efficient and Risk-Aware Control of Electricity Distribution Grids

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    This article presents an economic model predictive control (EMPC) algorithm for reducing losses and increasing the resilience of medium-voltage electricity distribution grids characterized by high penetration of renewable energy sources and possibly subject to natural or malicious adverse events. The proposed control system optimizes grid operations through network reconfiguration, control of distributed energy storage systems (ESSs), and on-load tap changers. The core of the EMPC algorithm is a nonconvex optimization problem integrating the ESSs dynamics, the topological and power technical constraints of the grid, and the modeling of the cascading effects of potential adverse events. An equivalent (i.e., having the same optimal solution) proxy of the nonconvex problem is proposed to make the solution more tractable. Simulations performed on a 16-bus test distribution network validate the proposed control strategy

    An open-source tool for reliability analysis in radial distribution grids

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    We present an open-source software implementation of an approximate contingency enumeration approach for calculating reliability in distribution grids based on RELRAD. The tool is coded using the efficient programming language Julia, to ensure fast and scaleable calculations. The network topology is mapped as a graph. This allows us to efficiently determine load points affected by contingencies by using standard graph algorithms. The tool is demonstrated on a simple synthetic test system and an actual Norway distribution grid.acceptedVersio

    Operating principle of Soft Open Points for electrical distribution network operation

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    Soft Open Points (SOPs) are power electronic devices installed in place of normally-open points in electrical power distribution networks. They are able to provide active power flow control, reactive power compensation and voltage regulation under normal network operating conditions, as well as fast fault isolation and supply restoration under abnormal conditions. Two control modes were developed for the operation of an SOP, using back-to-back voltage-source converters (VSCs). A power flow control mode with current control provides independent control of real and reactive power. A supply restoration mode with a voltage controller enables power supply to isolated loads due to network faults. The operating principle of the back-to-back VSCs based SOP was investigated under both normal and abnormal network operating conditions. Studies on a two-feeder medium-voltage distribution network showed the performance of the SOP under different network-operating conditions: normal, during a fault and post-fault supply restoration. During the change of network operating conditions, a mode switch method based on the phase locked loop controller was used to achieve the transitions between the two control modes. Hard transitions by a direct mode switching were noticed unfavourable, but seamless transitions were obtained by deploying a soft cold load pickup and voltage synchronization process

    Risk-based assessment for distribution network via an efficient Monte Carlo simulation model

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    Given the fact that Smart Grid technologies are implemented mainly in distribution networks, it is essential to build a risk-based assessment tool which can model the operational characteristics of distribution networks operation. This thesis presented a distribution network model which captures the features of distribution network restoration, based on approximations of real-time switching actions. It enables the evaluation of complex distribution network reliability with active network control. The development of an explicit switching model which better reflects actual network switching actions allows for deliberate accuracy and efficiency trade-offs. Combined with importance sampling approach, a significant improvement in computational efficiency has been achieved with both simplified and detailed network switching models. The assessment model also provides flexibility for users to analyse system reliability with various levels of complexity and efficiency. With the proposed assessment tool, different network improvement technologies were investigated for their values of substituting traditional network constructions and impacts on network reliability performances. It has been found that a combination of different technologies, according to specific network requirements, provide the best solution to network investments. Models of customer interruption cost were analysed and compared. The study shows that using different cost models will result in large differences in results and lead to different investment decisions. A single value of lost load is not appropriate to achieve an accurate interruption cost quantification. A chronological simulation model was also built for evaluating the implications of High Impact Low Probability events on distribution network planning. This model provides the insights for the cost of such events and helps network planners justify the cost-effectiveness of post-fault corrections and preventive solutions. Finally, the overall security of supply for GB system was assessed to investigate the impacts of a recent demand reduction at grid supply points (for transmission networks) resulting from the fast growing of generation capacity in distribution networks. It has been found that the current security standard may not be able to guarantee an acceptable reliability performance with the increasing penetration of distributed generation, if further balancing service investment is not available.Open Acces

    Intelligent distribution network design

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    Distribution networks (medium voltage and low voltage) are subject to changes caused by re-regulation of the energy supply, economical and environmental constraints more sensitive equipment, power quality requirements and the increasing penetration of distributed generation. The latter is seen as one of the main challenges for today’s and future network operation and design. In this thesis it is investigated in what way these developments enforce intelligent distribution network design and new engineering tools. Furthermore it should be investigated how a new design and control strategy can contribute to meet the power quality and performance requirements in distribution networks in future. This thesis focuses on network structures that, typical for the Netherlands, are based on relatively short underground cables.Managing current and voltage in such networks both during normal and disturbed operation, requires a good network design and an adequate earthing concept. The limited size of Dutch distribution networks has a positive effect on power quality aspects and reliability. The use of impedance earthing for medium voltage (MV) cable networks reduces the risk of multi-phase faults that cause large fault currents and deep dips. It also reduces the risk on transient overvoltages due to re-striking of cable faults. A TN earthing system for the low voltage (LV) network reduces the risk of damaged apparatus and it maintains safety for people. However, care must be taken for the earthing of devices of other service providers, which requires a co-operative solution. The fast developments of computation techniques and IT equipment in the network opened the possibility to perform many calculations in short time based on both actual and historical data. Examples are the on-line distribution loadflow and the short-circuit calculation for protection coordination and intelligent fault location. In LV and MV network calculations the accuracy of the models and the availability of data are the main obstacles. Because of the unsymmetrical nature of load and generation in LV networks a multiple conductor model is needed. For safety calculations also the earth impedances have to be modelled as well as the neutral and protective earth impedances and their mutual interactions. The protection philosophy in MV networks must take into account the changing requirements regarding safety and power quality. An overall philosophy concerning both network and generator protection is necessary. New developments in substation automation benefit future upgrade and refurbishment of substation control and protection. As a result, also cheap,accurate and fast fault location becomes feasible, reducing the outage time of the customers. Next the influence of distributed generation on the above subjects is investigated. The increasing magnitude of short-circuit currents and the increasing voltage variations in the network are seen as a major challenge for the network planners. Conventional measures for reducing voltage problems may introduce problems with the short-circuit current level and vice versa. In networks which contain a large amount of both load and distributed generation, adverse voltage problems may occur, especially when the generation is located in the LV network. In order to reduce this, specific control strategies need to be developed. The last part of the thesis is related to these control strategies as a solution for operating future distribution networks. By introducing storage and power electronics, networks can be transformed into autonomously controlled networks. These networks remain an inseparable part of the electricity network but may behave in a fairly autonomous manner, both internally and externally, with respect to the rest of the network. The focus in this thesis is on maintaining an optimal voltage for all customers during all combinations of load and generation. Because of the autonomous behaviour of the control systems, their operation must be based on local measurements. A suggested approach is to replace the normal open point between MV feeders by a so called "intelligent node". This node is able to control the power flow in several feeders by means of power electronics and, if provided, by electricity storage. The voltage profile can be improved further, by introducing an intelligent voltage control on the HV/MV transformer feeding the distribution network. The simulation studies in this research have been performed on a realistic model of a typical Dutch MV/LV distribution system. Based on the results the following conclusions are drawn: • The HV/MV transformer control must be based on line drop compensation. This compensation must use the load situation instead of the measured exchange signal. The compensation factor must differ between cases of high load and of high generation. • The optimal control of the intelligent node is a voltage control, based on a linear dependence of the voltage at the node and the power flow towards that node. This method can be improved when the voltage of the MV bus bar in the substation is taken into account. • Methods to obtain a perfect voltage profile will lead to a storage device that is not available for this voltage level yet. • A voltage control based on a fixed value at both terminals of the intelligent node and at the MV bus bar of the HV/MV substation does not result in the optimal voltage profile, although guarantee a good voltage quality and might therefore be a good alternativ

    Distribution automation applications of fiber optics

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    Motivations for interest and research in distribution automation are discussed. The communication requirements of distribution automation are examined and shown to exceed the capabilities of power line carrier, radio, and telephone systems. A fiber optic based communication system is described that is co-located with the distribution system and that could satisfy the data rate and reliability requirements. A cost comparison shows that it could be constructed at a cost that is similar to that of a power line carrier system. The requirements for fiber optic sensors for distribution automation are discussed. The design of a data link suitable for optically-powered electronic sensing is presented. Empirical results are given. A modeling technique that was used to understand the reflections of guided light from a variety of surfaces is described. An optical position-indicator design is discussed. Systems aspects of distribution automation are discussed, in particular, the lack of interface, communications, and data standards. The economics of distribution automation are examined

    The Galaxy Evolution Explorer

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    The Galaxy Evolution Explorer (GALEX), a NASA Small Explorer Mission planned for launch in Fall 2002, will perform the first Space Ultraviolet sky survey. Five imaging surveys in each of two bands (1350-1750Å and 1750-2800Å) will range from an all-sky survey (limit m_(AB)~20-21) to an ultra-deep survey of 4 square degrees (limit m_(AB)~26). Three spectroscopic grism surveys (R=100-300) will be performed with various depths (m_(AB)~20-25) and sky coverage (100 to 2 square degrees) over the 1350-2800Å band. The instrument includes a 50 cm modified Ritchey-Chrétien telescope, a dichroic beam splitter and astigmatism corrector, two large sealed tube microchannel plate detectors to simultaneously cover the two bands and the 1.2 degree field of view. A rotating wheel provides either imaging or grism spectroscopy with transmitting optics. We will use the measured UV properties of local galaxies, along with corollary observations, to calibrate the UV-global star formation rate relationship in galaxies. We will apply this calibration to distant galaxies discovered in the deep imaging and spectroscopic surveys to map the history of star formation in the universe over the red shift range zero to two. The GALEX mission will include an Associate Investigator program for additional observations and supporting data analysis. This will support a wide variety of investigations made possible by the first UV sky survey
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