Thomas Hartkopf

STATIC AND DYNAMIC MEASUREMENTS OF A PERMANENT MAGNET INDUCTION GENERATOR: TEST RESULTS OF A NEW WIND GENERATOR CONCEPT

The Permanent Magnet Induction Machine, a new wind generator concept, is considered to be a highly efficient, low maintenance solution for offshore wind turbines. Static and dynamic measurements have been performed with a test machine. Due to the inherent soft behavior of that machine type compared to normal synchronous machines, no dynamic excitation is found during operation that might endanger the stability of the system. Results of static measurements show high efficiency and little reactive power consumption.

Smarter Micro Grid for energy solution to rural Ethiopia

Use of modern energy, like electricity, is a key factor to economic development, poverty reduction, improved health and cleaner environment for a society. Moreover, if the electricity is generated with Renewable Energy (RE) resources the benefit will be profound. Unlike the developed countries though, developing countries have little access to electricity. The African continent for example covers 15% of the world land and has a population of about 13.4% of the total world population and is rapidly growing. But it has only 2% of the worlds industrial capacity. This fact is closely tied to a limited access to modern energy, like electricity. When it comes to Ethiopia, the population who has access to electricity is less than 10% and of this figure 1% of it accounts for the rural areas where the majority of its population live. Hence it is critical to devise a method that can increase access to electricity especially in rural areas where the national grid does not reach. Therefore, in this paper, we propose a method of Distributed Generation (DG) of electrical power units operated entirely by RE sources and a typical micro grid structure for a local village network. The DG and Local Micro Grid (LMG) layout allows reaching out for remote locations and efficient distribution in island mode. In effect, the electricity would be made available locally instead of being transported such a long distance with inevitable loss and huge capital investment. Then different villages LMGs are interconnected in ring and form a Micro Grid (MG) to increase the reliability and efficiency of electric power delivery. This MG network will be capable of interconnecting to the national grid as well as work in the ring system or autonomously at the local distribution level with a concept of Smarter Micro Grid Controller (SMGC). The longer term benefit of this system also supports the main national grid with a power network in distributed villages in order to lessen the peak hour demand surge. This essential set of investment will change the current distribution problem of electrical energy in Ethiopia and permit access to electricity more efficiently, reliably and affordably to by all sectors of the society.

Novel wind turbine reliability model-implementation to estimate wind farms capacity credit

The expanded integration of wind energy imposes technical challenges to maintain system reliability. In order to tackle these challenges, comprehensive reliability models for wind turbines and related factors are essential. Proposed algorithm classifies Wind Turbine Generator (WTG) components based on their impact on WTG output. There upon, the WTG has a composite three-state reliability model which aggregates WTG foremost components. The chronological operation conditions of each component is obtained using state duration sampling method. Precise Wind Farms (WFs) reliability assessment requires accurate Wind Speed (WS) forecasting methods which acknowledge WSs propagation through WFs terrains. Thus, WS variations are developed based on Weibull distribution. Offered algorithms are integrated to estimate the capacity factor of some WFs using Monte Carlo simulation method. The implied WS data are recorded in certain locations in Egypt which are candidates to host WFs. The utilized simulation environments are MATLAB and Simulink.

Grid services with PV-converters in distribution systems

The most affected parts of the electrical power system in Germany are the distribution grids due to the rapid expansion of renewable energies. Most of these micro power plants e.g. photovoltaic systems feed into the low (LV) and medium (MV) voltage level. The voltage stability in these levels is thus much more complex and is partially violated in moments of strong feed-in. To reduce this negative impact the directive VDE-AR-N 4105 was specified that PV-inverters must provide reactive power instead of pure active power. This directive should however only be the beginning. In a smart grid, the asset inverter should be used much more intensively. In this paper it is demonstrated by power flow simulations with the data of a real distribution grid including PV-system feed-in that there are more possibilities but providing the reactive power for the distribution and voltage stability. It is illustrated that the use of the complete apparent power of the inverter is a more appropriate way to obtain the stationary stability of distribution grids. With this strategy in addition, the power loss can be influenced in LV- and MV-level and the power factor of the feed-in of the HV/MV-supplying transformer can be adjusted.

A reliable and efficient new generator system for offshore wind farms with DC farm grid

This paper discusses a new patent pending rectifier system for direct-drive permanent-magnet wind generators. The basic idea is to use a generator with two sets of three-phase windings. One will be connected to a diode bridge rectifier and the other to an active rectifier (e.g. IGBT). The purpose of this new concept is to achieve maximum generator torque, which allows compact and cost-effective permanent-magnet generators, with a reliable and cheap rectifier.