Power System Stability
M. Nasiri; J. Milimonfared; S. H. Fathi
Abstract
This paper presents a new nonlinear backstepping controller for a direct-driven permanent magnet synchronous generator-based wind turbine, which is connected to the power system via back-to-back converters. The proposed controller deals with maximum power point tracking (MPPT) in normal condition and ...
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This paper presents a new nonlinear backstepping controller for a direct-driven permanent magnet synchronous generator-based wind turbine, which is connected to the power system via back-to-back converters. The proposed controller deals with maximum power point tracking (MPPT) in normal condition and enhances the low-voltage ride-through (LVRT) capability in fault conditions. In this method, to improve LVRT capability, machine-side converter controls dc-link voltage and MPPT is performed by grid side converter. Hence, PMSG output power is reduced very fast and dc-link voltage variation is reduced. Due to nonlinear relationship between dc-link voltage and controller input, nonlinear backstepping controller has good performances. By applying the proposed controller, dc-link overvoltage is significantly decreased. The proposed controller has good performance in comparison with Proportional-Integral (PI) controller and Sliding Mode Controller (SMC). In asymmetrical faults, to decrease grid side active power oscillations, the nonlinear backstepping dual-current controller is designed for positive- and negative- sequence components. The simulation results confirm that the proposed controller is efficient in different conditions.
Power System Stability
R. Ajabi-Farshbaf; M. R. Azizian; V. Yousefizad
Abstract
This paper presents a new algorithm based on Model Reference Adaptive System (MRAS) and its stability analysis for sensorless control of Doubly-Fed Induction Generators (DFIGs). The reference and adjustable models of the suggested observer are based on the active power of the machine. A hysteresis block ...
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This paper presents a new algorithm based on Model Reference Adaptive System (MRAS) and its stability analysis for sensorless control of Doubly-Fed Induction Generators (DFIGs). The reference and adjustable models of the suggested observer are based on the active power of the machine. A hysteresis block is used in the structure of the adaptation mechanism, and the stability analysis is performed based on sliding mode conditions. Simulation and practical results show appropriate operation and speed tracking of the observer with regard to obtained stability conditions.
Power System Stability
Ahmadreza Nafar; Gholam Reza Arab Markadeh; Amir Elahi; Reza pouraghababa
Volume 4, Issue 1 , June 2016, , Pages 16-28
Abstract
In the conventional structure of the wind turbines along with the doubly-fed induction generator (DFIG), the stator is directly connected to the power grid. Therefore, voltage changes in the grid result in severe transient conditions in the stator and rotor. In cases where the changes are severe, the ...
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In the conventional structure of the wind turbines along with the doubly-fed induction generator (DFIG), the stator is directly connected to the power grid. Therefore, voltage changes in the grid result in severe transient conditions in the stator and rotor. In cases where the changes are severe, the generator will be disconnected from the grid and consequently the grid stability will be attenuated. In this paper, a completely review of conventional methodes for DFIG control under fault conditions is done and then a series grid side converter (SGSC) with sliding mode control method is proposed to enhance the fault ride through capability and direct power control of machine. By applying this controlling strategy, the over current in the rotor and stator windings will totally be attenuated without using additional equipments like as crowbar resistance; Moreover, the DC link voltage oscillations will be attenuated to a great extent and the generator will continue operating without being disconnected from the grid. In addition, the proposed method is able to improve the direct power control of DFIG in harmonically grid voltage condition. To validate the performance of this method, the simulation results are presented under the symmetrical and asymmetrical faults and harmonically grid voltage conditions and compared with the other conventional methods.
