ABSTRACT
Owing to different stochastic characteristics of wind energy systems, there would commonly be uncertainties in the processes of wind energy conversion that may ultimately cause to severely degrade the quality of electric power production. These uncertainties include time-varying fluctuations of mechanical & electrical parameters that can be generated during both linear, and nonlinear operating behaviors of doubly fed induction generator-based wind energy conversion system (DFIG WECS). In order to handle a wind power quality problem, the previous studies largely focused on adjustment of mechanical parameters particularly based on blade pitch angle control by proposing different control strategies, and controller models. This work proposes a rarely studied electrical parameter control method that is particularly used to implement the regulation of rotor current components & electromagnetic torque in a DFIG WECS, based on Indirect Field Oriented Control (IFOC) strategy. Accordingly, a novel Proportional Integral controller model that employs a 2-Degree-of-Freedom [PI (2DOF)] is illustrated for an enhanced control of the rotor current components (quadrature & direct currents), electromagnetic torque under a 2MW DFIG WECS, which is operationally assumed to behave both linearly & nonlinearly. Herein, nonlinear operating behavior signifies a voltage dip that was assumed to be resulting when the system's normal (linear) voltage would suddenly drop by 90%. Furthermore, the overall model of the DFIG system was simulated in MATLAB-SIMULINK environment to evaluate the performances of PI controller (2DOF) under the system's stated operating behaviors. Based on the simulation signal statistics, the quadrature current distortion levels & DC mean values were mainly considered as the criteria for evaluating the controller performances. Finally, the proposed PI controller (2DOF) model has been tested to achieve an enhanced power quality in comparison with the traditional PI controller model.
ABSTRACT
Nowadays, engineers are toiling away to achieve the maximum possible wind energy harvesting with low costs through enhancing the performances of WECSs in efforts to realize the wind power future forecasts. In fact, achieving this is basically not an easy task due to the intricacies that partly stem from the stochastic nature of wind energy. Further, the efforts in this regard can also be impacted by the ongoing trends in various wind energy conversion-related technologies, and engineering approaches. Hence, the wind power optimization is determined depending on the types of WECS technologies, output power smoothing, and design development approaches that be employed. Currently, the variable speed operations-based WECS technologies are generally opted in wind farm applications. Meanwhile, power management system is the heart of a WECS, where smoothing output power with reducing costs could be implemented. On the other hand, the automated control strategies were reported in literatures to better optimize WECSs' performances particularly in terms of costs compared to ESS devices. On this basis, MBPC and hybrid control algorithms were commonly presented as the current state-of-the-art for systems modeling, whereas MBD was preferred to be an efficient and cost-saving approach for advanced development of automated control systems. This study aims to conduct comparative analyses on WECS technologies (with different generators, and PECs) based on their energy harvesting capability, cost-effectiveness, and advances in designs. Assessments of the approaches and strategies for smoothing power production are also presented. Finally, the study concludes that trends in PECs, automated control strategies and MBD are the most compelling.
