Dynamic Modeling and Robust Controllers Design for Doubly Fed Induction Generator-Based Wind Turbines under Unbalanced Grid Fault Conditions

Abstract

High penetration of large capacity wind turbines into power grid has led to serious concern about its influence on the dynamic behaviors of the power system. Unbalanced grid voltage causing DC-voltage fluctuations and DC-link capacitor large harmonic current which results in degrading reliability and lifespan of capacitor used in voltage source converter. Furthermore, due to magnetic saturation in the generator and non-linear loads distorted active and reactive power delivered to the grid, violating grid code. This paper provides a detailed investigation of dynamic behavior and transient characteristics of Doubly Fed Induction Generator (DFIG) during grid faults and voltage sags. It also presents novel grid side controllers, Adaptive Proportional Integral Controller (API) and Proportional Resonant with Resonant Harmonic Compensator (PR+RHC) which eliminate the negative impact of unbalanced grid voltage on the DC-capacitor as well as achieving harmonic filtering by compensating harmonics which improve power quality. Proposed algorithm focuses on mitigation of harmonic currents and voltage fluctuation in DC-capacitor making capacitor more reliable under transient grid conditions as well as distorted active and reactive power delivered to the electric grid. MATLAB/Simulink simulation of 2 MW DFIG model with 1150 V DC-linked voltage has been considered for validating the effectiveness of proposed control algorithms. The proposed controllers performance authenticates robust, ripples free, and fault-tolerant capability. In addition, performance indices and Total Harmonic Distortions (THD) are also calculated to verify the robustness of the designed controller.

Design of Fuzzy-PI and Fuzzy-Sliding Mode Controllers for Single-Phase Two-Stages Grid-Connected Transformerless Photovoltaic Inverter

“…When sudden disturbances or parameter uncertainties occurs in the system, the performance of the PI controllers detunes and degrades. Therefore, the adaptive PI controller is required that adjusts its parameters according to the error function [52]. In this controller, fuzzy rules are employed in the PI controller presented in Table 2 and listed as:…”

Control of Transformerless Inverter-Based Two-Stage Grid-Connected Photovoltaic System Using Adaptive-PI and Adaptive Sliding Mode Controllers

“…A RHC-based PR controller is employed in the current-controlled loop. The PR controller with RHC mitigates the grid distortions, i.e., third, fifth, and seventh [32]. The magnitude, phase, and frequency information of the grid voltage are provided by SOGI-based PLL, which has harmonic immunity, fast-tracking accuracy, and a rapid-dynamic response.…”

Dynamic Modeling and Control of BDFRG under Unbalanced Grid Conditions

“…Under unbalanced conditions, negative-sequence components are present in the grid voltage, causing problems for wind generators such as unbalanced primary currents, current harmonics at the secondary side, unequal heating, or hot spots in the windings [30] which degrade the insulation and reduce the life expectancy of the windings, as well as producing power pulsations [31,32]. Unbalanced currents also create a pulsating torque, which may cause extra mechanical stress on the drive train and gearbox [33][34][35][36] and increase acoustic noise, too. Therefore, studying wind generators under unbalanced grid voltage conditions and designing a convenient control strategy are very important.…”