Hans-Peter Beck

Virtual synchronous machine

Demands in the area of electrical energy generation and distribution, as a result of energy policies, are leading to far reaching changes in the structure of the energy supply, which is characterised, on the one hand, by the substitution of conventional power stations by renewable energy generation, a decision which has already been made, and, on the other hand, by the changeover from centralised to decentralised energy generation. From an electrical engineering point of view, a new situation will arise for consumers concerning security of supply and power quality, which calls for further technical measures by the grid operators to ensure that the increasingly stringent supply criteria can be met. This article describes a new power electronics based approach which allows a grid compatible integration of predominantly renewable electricity generators even in weak grids making them appear to be electromechanical synchronous machines. As a consequence, all the proven properties of this type of machine which have so far defined the grid continue to do so, even when integrating photovoltaic or wind energy. These properties include, for instance, interaction between grid and generator as in a remote power dispatch, reaction to transients as well as the full electrical effects of a rotating mass. In addition, this new development can be operated in such a way that it provides primary reserve allowing, from a grid point of view, electricity generators such as wind and PV to be regarded as conventional power stations.

Commissioning of a state-controlled high-powered electrical drive using evolutionary algorithms

The subject of this research is the automated startup procedure of a PI state-controlled rolling-mill motor by using evolutionary algorithms. Compared to the conventional PI speed control, applying the method of deliberate pole placement to the state controller design succeeds in improving the transient response of setpoint and disturbance changes. To put the PI state-controlled drive with observer into operation to obtain a controller with a high robustness and dynamics, the precise knowledge of this physical parameter is necessary. An evolution-based system is used to solve the estimation problem. A high degree of reliability respecting multimodal characteristics and robustness against random noise is expected from the identification method. Evulotionary algorithms fulfill this requirement. With genetic operators like mutation, crossover, and selection, evolutionary algorithms mimic the principles of organic evolution in order to solve the optimization problem.

Investigation of the Virtual Synchronous Machine in the island mode

In this paper the investigation results of the Virtual Synchronous Machine (VISMA) in the island mode are presented. The increasing integration of the distributed generation units leads to continual growing of the amount of the inverter interface in the electrical grid. Therefore, the characteristics of inverters will more and more significantly influence the grid operation. The VISMA is a novel control method for the inverter to make it possible that an inverter-interfaced decentralized generation unit can be operated as a real electromechanical synchronous machine, which up to now as the main generation unit in the electrical grid has many advantages in consideration of the grid stability. These advantages can be implemented in the VISMA and are proved experimentally in the grid-connected operation mode. The island-mode is another important operation mode that will be necessary for a stand-alone grid without connecting of the main grid or when the main grid fails due to a disturbance. Therefore this operation mode of the VISMA is focused in this paper.

Variable motor operating point by integration of power electronic device into rotor

The main issue of this work is to analyze and to test how the characteristic curve of the induction machine can be adjusted by the power electronic devices, when these are integrated into rotor circuits. In order to technically analyze the characteristic performances of the induction machine by switching between cages, the simulator softwares MATLAB and NETASIM have been used. The simulated current- and torque-waveforms are compared with the experimental values from the test bench. To practical validation of the results, a main feed induction machine with working-cage controller has been designed and tested at the Institute of Electrical Power Engineering in Clausthal, Germany.

A New Approach to the Analysis of Network Observability in Medium and Low Voltage Electrical Grids

Medium and low voltage electrical power grids are typically sparsely instrumented, and thus, not observable in a systems’ theory sense. However, this is a requirement to carry out state estimation methods. To this end, many approaches for optimal sensor placement are proposed in the literature. Such methods are typically motivated from a mathematical perspective, not taking the physical properties of the network into account. As a consequence, the dimensionality of the mathematical problem is typically quite large resulting in significant numerical complexity. Therefore, a new approach is proposed here which is based on analyzing the characteristic observable and unobservable nodes by using singular value decomposition (SVD) and the breadth-first search method. The aim of the method is to identify all possibilities for the placement of measuring equipment to achieve observability. The proposed method does render the network observable with a minimal number of sensors. In this way, this reduces the dimensionality for conventional optimal sensor placement algorithms substantially.

Auswirkungen der Anreizsysteme für private PV-Anlagenbetreiber auf das lokale Verteilnetz

Erneuerbare Energien werden in Deutschland zu einem grosen Teil in Verteilnetzen bereitgestellt. Hierdurch andern sich die Anforderungen an die Verteilnetze, da der Leistungsfluss weniger gut prognostizierbar wird und dieser zunehmend durch Einspeisungen in den unteren Netzebenen und der damit einhergehenden Umkehrung des Lastflusses hin zur Ruckspeisung gepragt ist. In der Vergangenheit wurden von verschiedenen Institutionen die Potenziale verschiedener Technologien zur Entlastung der Verteilnetze und des Gesamtsystems ermittelt, hierunter auch die Moglichkeiten des systemdienlichen Erzeugungsmanagements. Wie gut dieses Potential genutzt werden kann, hangt masgeblich davon ab, ob es sich unter den aktuellen rechtliche-regulatorischen Rahmenbedingungen fur den einzelnen Akteur betriebswirtschaftlich lohnt, seine Anlage netzdienlich zu betreiben. Dieses Paper untersucht innerhalb einer zweistufigen – wirtschaftlichen und technischen – Modellierung und Simulation, wie private PV-Anlagenbetreiber, welche ihre Einspeisung durch die zusatzliche Installation eines Speichers flexibilisieren, unter den aktuellen Anreizmechanismen des Rechts- und Forderrahmens handeln. Es ermittelt, welche Effekte dies auf die resultierende Austauschleistung eines lokalen Verteilnetzes hat. Die Arbeiten sind innerhalb des vom Bundesministerium fur Bildung und Forschung geforderten Projekts „Effiziente Nutzung erneuerbarer Energien durch regionale ressourcenoptimierte ‚intelligente‘ Versorgungs- und Verbrauchsnetze (Smart Microgrids)“ (FKZ: 03EK3524 B, C und D) entstanden.