No abstract

No abstract

Most of power quality problems for grid connected doubly fed induction generators (DFIGs) with wind turbine include flicker, variations of voltage RMS profile, and injected harmonics due to switching in DFIG converters. Flicker phenomenon is the most important problem in wind power systems. This paper described an effective method for mitigating flicker emission and power quality improvement for a fairly weak grid connected to a wind farm with DFIGs. The method was applied in the rotor side converter (RSC) of the DFIG to control the output reactive power. q axis reference current was directly derived according to the mathematical relation between rotor q axis current and DFIG output reactive power without using PI controller. To extract the reference reactive power, the stator voltage control loop with the droop coefficient was proposed to regulate the grid voltage level in each operational condition. The DFIG output active power was separately controlled in d axis considering the stator voltage orientation control (SVOC). Different simulations were carried out on the test system and the flicker short term severity index ðP st Þ was calculated for each case study using the discrete flickermeter model according to IEC 61400 standard. The obtained results validated flicker mitigation and power quality enhancement for the grid. Ó 2015 Faculty of Engineering, Ain Shams University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

No abstract

This paper deals with the performance improvement of synchronous generator Type 4 driven by the wind turbine at high wind speed operation in a microgrid connected to a weak utility grid. The importance of applying the pitch angle control loop at high wind speeds in wind turbine generators is undeniable to prevent overloading and other destructive effects on the generator parameters caused by the wind speed increase. Thus, a robust control scheme in the pitch angle loop would certainly improve the performance of the wind turbine generator. In this study, the principle of the proposed method is based on the design and applying the different fractional order controllers including the Fractional Order Proportional Integral (FOPI) and FO[PI] types in the pitch compensation loop, instead of the conventional Proportional Integral (PI) controller to extract the proper values for the pitch angle reference profile. An analytical method is extended to the pitch servo control for designing the PI and fraction order PI controllers to ensure the frequency domain specifications. To verify the efficacy of the FOPI and FO[PI] controllers in comparison with the PI one, various simulation results in the high wind speed operation mode of 18 m/s considering 10% turbulence intensity are obtained using MATLAB/SIMULINK software. The performance enhancement is surveyed by monitoring the generator parameters including the mechanical torque, the active/reactive power, and the DC link voltage profiles. The results validated the effectiveness of the proposed controllers.