Fachbereich Ingenieurwissenschaften und Kommunikation
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The need for innovation around the control functions of inverters is great. PV inverters were initially expected to be passive followers of the grid and to disconnect as soon as abnormal conditions happened. Since future power systems will be dominated by generation and storage resources interfaced through inverters these converters must move from following to forming and sustaining the grid. As “digital natives” PV inverters can also play an important role in the digitalisation of distribution networks. In this short review we identified a large potential to make the PV inverter the smart local hub in a distributed energy system. At the micro level, costs and coordination can be improved with bidirectional inverters between the AC grid and PV production, stationary storage, car chargers and DC loads. At the macro level the distributed nature of PV generation means that the same devices will support both to the local distribution network and to the global stability of the grid. Much success has been obtained in the former. The later remains a challenge, in particular in terms of scaling. Yet there is some urgency in researching and demonstrating such solutions. And while digitalisation offers promise in all control aspects it also raises significant cybersecurity concerns.
In this paper, modeling of piston and generic type gas compressors for a globally convergent algorithm for solving stationary gas transport problems is carried out. A theoretical analysis of the simulation stability, its practical implementation and verification of convergence on a realistic gas network have been carried out. The relevance of the paper for the topics of the conference is defined by a significance of gas transport networks as an advanced application of simulation and modeling, including the development of novel mathematical and numerical algorithms and methods.
Solving transport network problems can be complicated by non-linear effects. In the particular case of gas transport networks, the most complex non-linear elements are compressors and their drives. They are described by a system of equations, composed of a piecewise linear ‘free’ model for the control logic and a non-linear ‘advanced’ model for calibrated characteristics of the compressor. For all element equations, certain stability criteria must be fulfilled, providing the absence of folds in associated system mapping. In this paper, we consider a transformation (warping) of a system from the space of calibration parameters to the space of transport variables, satisfying these criteria. The algorithm drastically improves stability of the network solver. Numerous tests on realistic networks show that nearly 100% convergence rate of the solver is achieved with this approach.
In this paper, an analysis of the error ellipsoid in the space of solutions of stationary gas transport problems is carried out. For this purpose, a Principal Component Analysis of the solution set has been performed. The presence of unstable directions is shown associated with the marginal fulfillment of the resistivity conditions for the equations of compressors and other control elements in gas networks. Practically, the instabilities occur when multiple compressors or regulators try to control pressures or flows in the same part of the network. Such problems can occur, in particular, when the compressors or regulators reach their working limits. Possible ways of resolving instabilities are considered.
The paper presents the topological reduction method applied to gas transport networks, using contraction of series, parallel and tree-like subgraphs. The contraction operations are implemented for pipe elements, described by quadratic friction law. This allows significant reduction of the graphs and acceleration of solution procedure for stationary network problems. The algorithm has been tested on several realistic network examples. The possible extensions of the method to different friction laws and other elements are discussed.
Kinetic Inductance Detectors with Integrated Antennas for Ground and Space-Based Sub-mm Astronomy
(2009)
Very large arrays of Microwave Kinetic Inductance Detectors (MKIDs) have the potential to revolutionize ground and space based astronomy. They can offer in excess of 10.000 pixels with large dynamic range and very high sensitivity in combination with very efficient frequency division multiplexing at GHz frequencies. In this paper we present the development of a 400 pixel MKID demonstration array, including optical coupling, sensitivity measurements, beam pattern measurements and readout. The design presented can be scaled to any frequency between 80 GHz and >5 THz because there is no need for superconducting structures that become lossy at frequencies above the gap frequency of the materials used. The latter would limit the frequency coverage to below 1 THz for relatively high gap materials such as NbTiN. An individual pixels of the array consist of a distributed Aluminium CPW MKID with an integrated twin slot antenna at its end. The antenna is placed in the in the second focus of an elliptical high purity Si lens. The lens-antenna coupling design allows room for the MKID resonator outside of the focal point of the lens. The best dark noise equivalent power of these devices is measured to be NEP = 7×10-19 W/[square root]Hz and the optical coupling efficiency is around 30%, in which no antireflection coating was used on the Si lens. For the readout we use a commercial arbitrary waveform generator and a 1.5 GHz FFTS. We show that using this concept it is possible to read out in excess of 400 pixels with 1 board and 1 pair of coaxial cables.
Für die Entwicklung steuerungstechnischer Sicherheitsfunktionen muss ab 2012 die Normen EN ISO 13849-1 oder EN 62061 befolgt werden, die sowohl Anforderungen an die Hardware als auch Anforderungen an die Software beschreibt. Die Anforderungen an die Software spielten bis vor einigen Jahren kaum eine Rolle, da Sicherheitsfunktionen vorzugsweise in Hardware realisiert wurden. Heutzutage ist es jedoch sehr häufig üblich, Sicherheitsfunktionen mit einer dafür geeigneten programmierbaren SPS zu realisieren. Die neuen Normen bzgl. der sicheren Steuerung von Maschinen verlangen neben der Quantifizierung der Hardware-Ausfallraten von Sicherheitsfunktionen noch ein Management der Sicherheitsfunktionen. Dazu gehört auch ein Management der Softwareentwicklung für Sicherheitsfunktionen, um systematische Fehler zu minimieren. Dieses Management der Softwareentwicklung wird im Wesentlichen durch das V-Modell repräsentiert. Für die Maschinebauindustrie darf dieser Managementprozess nicht zu aufwendig sein, ansonsten wird dieser in der Praxis nur schwer angenommen. Eine Möglichkeit der Abarbeitung des V-Modells wird vorgestellt. Wahrscheinlich ist diese aufgezeigte Möglichkeit für die Industrie noch zu aufwendig.