Kharitonov Theorem Based Robust Stability Analysis of a Wind Turbine Pitch Control System

Abstract

Wind energy has recently become one of the most prominent technologies among electrical energy generation systems. As a result, wind-based renewable energy generation systems are incessantly growing, and wind turbines of different characteristics are being installed in many locations around the world. One drawback associated with different characteristics of the wind turbines is that controllers have to be designed individually for each of them. Additionally, stable performance of the wind turbines needs to be ensured in the whole range of their operating conditions. Nowadays, there are many causes for uncertainties in the actual performance of a horizontal axis wind turbine, such as variations in the characteristics of the wind turbine, fabrication tolerances of its elements or non-linearities related to different operating-points. Hence, in order to respond to these uncertainties and ensure the stability of the wind turbine, robust control and stability theories have been gaining importance during recent years. Nevertheless, the use of robust stability analyses with complex wind turbine models still needs to be faced and remarkably improved. In this paper, a stability analysis of the pitch system control of a horizontal axis wind turbine based on the Kharitonov robust stability method is proposed. The objective was to assess the robust stability of a pitch controller in response to uncertainties arising from varying operating conditions of the National Renewable Energies Laboratory (NREL) 5 MW class IIA wind turbine. According to the results, the proposed method could satisfactorily respond to limited variations in the characteristics of the model, but could lack accuracy in cases of bigger variations or employment of high order complex mathematical models.

Grid Frequency and Amplitude Control Using DFIG Wind Turbines in a Smart Grid

“…Figure 8 also includes droop control, inertial energy, and the pitch controller. The pitch controller will act when the active power surpasses the maximum deloaded power, the peak mechanical power or when the wind turbine speed is greater than the higher limit [39]. The control command ∆P supervisor is applied by the network supervisor for other control strategies such as automatic control of generation and energy flow or to limit the energy level to a specified level [20,40].…”

Design of FOPID controller for higher order continuous interval system using improved approximation ensuring stability

“…The entries in top two rows of Table 1 are taken from (23), while the entries in the successive rows are completed using (24).…”

“…For this problem, (16) and (18) are identified as Gain cross-over frequency gc = 3.1 rad/sec and phase margin pm = 80 are the given design specifications of the system. For these criteria, (23) and (24) The FOPID controller for the specified design criteria is obtained as…”

“…The controller design methodology based on twodegrees-of-freedom criterion for interval processes is also appeared in [19]. The pre-filter guarantees the robust performance and the stability is ensured using Hurwitz theorem [19] through making use of Kharitonov theorem [7,24,26]. Yeroglu and Tan [28] designed FOPID controller by combining the Bode envelopes with design criteria for the interval plants.…”

Wind Power Extraction Optimization by Dynamic Gain Scheduling Approximation Based on Non-Linear Functions for a WECS Based on a PMSG

“…One of the significant problems related to wind power generation is that the wind is continuously varying its velocity and direction [13]. Because of this, diverse and advanced technologies have been developed in order to obtain the highest wind power efficiency and to ensure the most profitable wind energy technologies [14][15][16][17]. Some studies, for example, are specialized in methods, techniques, and technologies to guarantee a proper connection between wind power generation and the electrical grid [18,19].…”