الفهرس 
Title : A Novel Control Technique for MPPT and LVRT Capability Investigation of Wind Driven Dual Excited Synchronous Generator
SummaryOnly 14 pages are availabe for public view
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Abstract
Over the last decades, the global demand for electrical energy has greatly increased due to
the huge industrial development and population growth. As a result, traditional fossil fuel
consumption has been excessively raised. Consequently, this results in many significant
problems, such as pollution, global warming, and the shortage of traditional fossil energy
resources. To overcome these problems, there is a great interest in various areas of renewable
energy resources like solar, wind, and hydropower around the world. At present, wind energy
has become one of the most rapidly growing renewable resources of electrical energy due to
its many advantages. As a result of wind energy attention, the overall capacity of wind energy
installed worldwide by the end of 2021 reached 817 GW with an additional 74 GW of new
wind power capacity compared to 2020.
Because of the importance of wind energy, there is a lot of interest in improving the
existing generating systems or establishing new ones. According to the grid code
requirements (GCRs), the wind farm should be controlled to generate the maximum available
power in the wind during healthy conditions. On the other hand, during grid faults, the wind
farm must remain connected and provide suitable reactive power to support the grid voltage.
This thesis presents the dual excited synchronous generator (DESG) as a new and suitable
alternative generation system in wind energy conversion systems. In addition, a novel control
strategy has been proposed for the DESG wind turbine system during various operating
conditions.
To verify the main objectives of the thesis, a complete mathematical model of the DESG
wind turbine system was derived in the rotor reference frame. Based on the mathematical
model, a direct relationship between the electromechanical torque and the armature reactive
power in terms of the field current space phasor magnitude and the field voltage space phasor
angle is provided.
In the proposed control technique, the magnitude of the field current space phasor has
been used to control the electromechanical torque as well as the generated active power,
while the phase angle of the field voltage space phasor has been used to control the injected
reactive power to the grid.
With the proposed control technique, the DESG can achieve the GCRs efficiently in both
healthy and faulty conditions without using extra protection circuits or using any additional
control techniques during grid fault conditions. During healthy operating conditions, the
DESG proved its ability to operate as a constant-speed constant-frequency (CSCF) generation
system with the benefit of adjusting the reactive power or as a variable-speed constantfrequency
(VSCF) generation system with the benefit of maximizing the captured mechanical
power. With the same proposed control strategy, the DESG can generate extra reactive power
to support the grid voltage recovery under grid faults and hence improve the low-voltage
ride-through (LVRT) capability.
Simulation results based on MATLAB/SIMULINK for a 1.1 kW DESG wind turbine
system have been executed to verify the introduced control technique under various operating
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conditions. Also, experimental studies have been carried out to validate the simulation results
using the proposed control algorithm. The obtained results reveal a good correlation between
the experimental and simulation results. Consequently, using the proposed control strategy,
the DESG wind turbine can capture the maximum mechanical power during the variations of
wind speed while simultaneously controlling the injected reactive power and supporting the
grid voltage during the fault period.
Finally, it can be deduced that the DESG is capable to achieve the GCRs efficiently in
both healthy and faulty operating states when the DESG field parameters are controlled using
the proposed control strategy without the need for any additional protection circuits or
additional control strategies during fault conditions. Hence, according to the obtained results,it can conclude that the DESG has the capability to use as a new and suitable alternative generator for WECS.