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Permanent Magnet Synchronous Machines (PMSMs) are popular due to their high efficiency and favorable dynamic properties. In practice, these machines often have a back-emf waveform which deviates from an theoretically ideal sinusoid or trapezoid. In the past, current waveform shaping techniques were developed for these machines to calculate non-conventional current waveforms to reduce the torque ripple...
During the development of a wave energy converter (WEC), a test device was laid out at sea. Due to the absence of a grid connection at the test location, an energy storage system (ESS) is designed and implemented as an islanding power supply to test the WEC requiring motoring actions during operation. The ESS comprises long-term battery power supply for the controllers, supercapacitors (SC) for motoring...
The increased deployment of Distributed Energy Resources (DER) and their connection to the existing distribution networks influences the feeder voltage profiles and challenges the voltage control in distribution networks. Traditionally, On-Load Tap Changing (OLTC) transformers are the most common voltage control devices. In this paper, the problem of voltage rise mitigation in distribution networks...
This paper applies a long term network observability analysis for investigating the potential contribution of photovoltaic (PV) inverters to the mitigation of voltage unbalance in low voltage (LV) feeders. For this purpose, a probabilistic offline state estimation algorithm is used, which simulates the time-varying action of local voltage (magnitude and unbalance) control schemes. The paper focuses...
Due to an increasing amount of wind turbines in the power system, which have a volatile power output, the need for flexibility increases. This flexibility can be obtained by ancillary services. Therefore, the provision of ancillary services with wind turbines is gaining interest. As they currently do not participate in the frequency control, this might compromise the proper functioning of the power...
In several countries, the wind power penetration increased tremendously in recent years. As the current wind turbines do not participate in inertial response nor primary control, this may compromise the proper functioning of the power system. This paper discusses the emulated inertial response with wind turbines. In literature, several strategies to provide inertial response with wind turbines are...
In several countries, the wind power penetration increased tremendously in the last years. As the current wind turbines do not participate in frequency control nor reserve provision, this may compromise the proper functioning of the primary control and the provision of power reserves. If no actions are taken, increasing levels of wind penetration may result in serious problems concerning the stable...
Grid-connected small and medium wind turbines are a promising technology to further increase the share of renewable energy sources. Although their impact on the environment is proven to be advantageous, the cost effectiveness still needs to increase. In this paper, the impact of the passive diode rectifier on the Joule losses in the generator is investigated. Passive diode rectifiers cause unwanted...
Installed photo voltaic energy grew exponentially during the last decade. One of the driving forces was the often generous governmental support. In Belgium (Flanders) for example, investors could acquire green power certificates worth €450/MWh during several years. However, due to the large boom of solar plants and hence rising subsidy cost, governments are dropping this support (eg. €450/MWh in 2009...
In the scope of a further increase in the production of renewable energy, grid-connected small wind turbines offer a promising new technology. To ensure a market breakthrough of small wind turbines, the cost effectiveness must be maximized. Therefore, the aerodynamic efficiency or power coefficient of the turbine blades is an important factor. This power coefficient is determined by the Tip Speed...
Smart microgrids are becoming an important concept to cope with the increasing demand of electricity and to integrate the large amounts of intermittent power sources in the electrical network. Microgrids are able to operate in grid-connected and islanded mode and present themselves to the utility network as controllable entities. For the primary control of the inverter-interfaced DG units, voltage-based...
Distributed renewable electricity generators, such as solar cells and wind turbines introduce bidirectional energy flows in the low-voltage power grid, possibly causing voltage violations and grid instabilities. The current solution to this problem comprises automatically switching off some of the local generators, resulting in a loss of green energy. In this paper we study the impact of different...
The increasing presence of single-phase distributed generators and unbalanced loads in the electric power system may lead to unbalance of the three phase voltages, resulting in increased losses and heating. To decrease this voltage unbalance problem three-phase four-wire inverter-connected distributed generation units may be used. In this paper, the influence of the control strategy of three-phase...
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