Wind powered DC bus

Wind power is one of the most promising renewable energy sources. The reasons for this are for example high efficiency also for the present wind power technologies and the fact that wind power turbines can be located both onshore and off-shore [53] and in both cases produce high power also for rather small installations. This means that the ecological footprint can be kept at acceptable levels. Another benefit is that the rotating mass constitutes an energy storage, which means that small wind variations might not disturb the power transfer extensively. in this chapter it is investigated if a DC distribution system can be operated only with wind powered generators. The investigation focuses on a load case where three wind power generators are fed by a wind speed corresponding to rated power and delivers power approximately equal to half the rated to a DC grid with two converters delivering power to loads. The excess power fed to the wind turbines is removed by pitch angle control. The problem in this case is that the turbine speed might increase beyond the rated, which might result in severe mechanical stress. Another problem is that the increased speed results in an increased back-emf of the generators. In a worst-case scenario, the back-emf might be so high that the controlled voltage source converter looses controllability of the current and instead operates as diode rectifiers due to the freewheeling diodes. Most modern wind power turbines are speed controlled by means of pitch angle control. However, pitch angle control has a rather low bandwidth, with time constants in the range of seconds.

The chapter starts with pitch angle control and then droop offset control follows. The added features of converter control in the case of wind power generators, i.e. speed estimation and field weakening, are discussed. Three different dynamic load conditions are investigated.

Renewable Energy Eco Friendly

Renewable Energy Eco Friendly

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable.

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