Design of State Feedback Current Controller for Fast Synchronization of DFIG in Wind Power Generation Systems

Abstract

Doubly-fed induction generators (DFIGs) are widely used in wind energy conversion systems. The dynamic features of DFIGs make it important to focus on designing high-performance control schemes. However, the dynamic characteristics of such generators depend on nonlinear parameters, such as stator flux, stator current, and rotor current, which increase the overall system complexity. In addition, the DFIG Wind Energy Conversion Systems (WECSs) size is growing beyond 7 MW, which increases stress on both the mechanical drive train and the power circuits during connection to the grid. Such stress and dynamic features cannot be neglected. Therefore, robust controllers must be implemented which have the ability to support the dynamic frequencies of wind energy to ensure system stability in grid connection mode and during subsequent use. Conventional vector control configurations that use proportional-integral controllers have various drawbacks, such as parameter tuning difficulties, mediocre dynamic performance, and reduced robustness. In this study, we focused on improving DFIG synchronization to the grid by applying state feedback current controllers with a feedforward component to smooth the connection to the grid, as well as to improve the steady-state and transient characteristics of the controller. State feedback controllers are proposed to replace the proportional-integral controllers on both the rotor and grid sides. The proposed controller is designed using a multivariable system and feedforward control for input reference and incorporating disturbances into the control equations for fast synchronization and transient responses. To demonstrate the advantages of this controller, experimental studies are presented for both the transient and steady states.

Design and Analysis of Planar Transformers in Modern Switching Mode Power Supply

“…The inductance of the leakage is a parasitic element in the transformer and energy stored in the inductance of the leakage may produce voltage spikes [29,[40][41][42][43][44][45]. Spikes increase the switching losses and decrease the efficiency of the transformer.…”

“…Spikes increase the switching losses and decrease the efficiency of the transformer. The leakage inductance of the planar transformer can be calculated by [30] [45]:…”

LMI-Based State Feedback Control Structure for Resolving Grid Connectivity Issues in DFIG-Based WT Systems

“…Stator voltage-oriented control and stator flux-oriented control (SFOC) are two prominent types of FOC, and they exhibit the same dynamic performance. However, few published studies explain the startup and synchronization process of a DFIG-based WECS with the grid [7,8,10,[15][16][17][18][19][20][21]. The authors of [7] presented an efficient control scheme for the grid synchronization of a DFIG.…”

“…Grid synchronization is significant for aligning highly stable system operations with wind-driven doubly-fed induction generators (DFIGs). It involves the voltage amplitude, phase angle, and frequency between the wind-turbine-generator terminal voltage and the grid voltage, with minimal deviations before establishing a connection [7][8][9]. The advantages of soft and fast grid synchronization are twofold: (1) It permits the grid connection of a DFIG with the least impact on the power system, and (2) it enables the fast reclosing of DFIGs immediately after grid faults, which is favorable in terms of providing voltage support to the grid and improving the fault ride-through capability of wind-energy conversion systems (WECSs).…”

A Sensorless Wind Speed and Rotor Position Control of PMSG in Wind Power Generation Systems

“…The dual formulation of the SVR problem provides an alternative to modeling in a high dimensional space. Additionally, it is possible to perform a non-linear mapping of temporal input data to higher spaces, in which linear regression becomes possible, provided that SVR approaches based on non-linear kernel functions are used, which are denoted, generically, by K(x i , x) [38].…”