Control of an autonomous wind energy conversion system based on doubly fed induction generator supplying a non-linear load

This paper presents a variable speed constant frequency (VSCF) system for aircraft applications. More accurately, it focuses on the design of an output filter to reduce the influence of non-linear loads. The VSCF system consists in a doubly fed induction generator (DFIG) supplying a stand-alone aircraft grid through its stator windings. It uses back-to-back PWM converters connected to the rotor for sub and super synchronous speed operation. A permanent magnet synchronous machine (PMSM) connected to a variable speed prime mover supplies these converters. An efficient control strategy of the system was presented in a previous paper for linear loads. However, non-linear loads such as 6-pulse diode rectifiers, that can represent up to 50% of the total load introduce undesirable current harmonic components. A LC output filter is thus designed to eliminate them. Simulation results demonstrate the feasibility of the proposed system.

In this paper, an electrical generation system with variable speed and constant frequency (VSCF) to supply isolated loads is presented. This system is composed of a doubly fed induction generator (DFIG), providing energy to an autonomous grid. It is driven in the rotor by a static converter with operation in hypo and hyper synchronism. A permanent magnet synchronous machine (PMSM) connected to a wind turbine feeds this converter. This paper presents the general control system applied for linear loads. The DFIG is controlled by an internal control loop of rotor flux and an external control loop of output stator voltage. We present also the control of the PMSM and the DC bus of the converter. A power maximization algorithm determines the speed of the turbine that achieves maximum generated power.

The main objective of this paper is to analyse Low Voltage Ride through capability (LVRT) of Doubly Fed Induction Generator (DFIG) and Permanent Magnet Synchronous Machine (PMSM) in Real Time Simulation. DFIG and PMSM wind turbines consists of power electronics circuits which are modeled in detail in RSCAD software of Real Time Digital Simulator (RTDS) for analysis. A Sample 33kV system is considered and LVRT capability of DFIG and PMSM for different Short circuit ratios is analyzed.

Recently, scientists and academics are discovering progressive improvements in the arena of wind power technology economically and reliably, allowing them to produce electricity focusing on renewable energy resources. Wind turbines (WT) using the Doubly Fed Induction Generators (DFIGs) have attracted particular attention because of their advantages such as variable speed constant frequency (VSCF) operation, independent control capabilities for maximum power point tracking (MPPT), active and reactive power controls, and voltage control strategy at the point of common coupling (PCC). When such resources have to be integrated into the existing power system, the operation becomes more challenging, particularly in terms of stability, security, and reliability. A DFIG system with its control strategies is simulated on MATLAB software. This entails the rapid control prototype testing of grid-connected, variable speed DFIG wind turbines to investigate the WT’s steady-state and dynamic behavior under normal and disturbed wind conditions. To augment the transient stability of DFIG, the simulation results for the active and reactive power of conventional controllers are compared with the adaptive tracking, self-tuned feed-forward PI controller model for optimum performance. Conclusive outcomes manifest the superior robustness of the feed-forward PI controller in terms of rising time, settling time, and overshoot value.

Amid the rising challenges arising from environmental issues and fossil fuel depletion due to the growing concerns of the world. Sustainable energy is the most appropriate solution to rising energy demand. Because of global interest to reduce Greenhouse Gas (GHG) emissions and provide sustainable energy, efforts are being made to supplement the use of fossil fuels with renewable energy sources. In this context, wind energy has been identified as one of the promising environmentally friendly, social, and economically beneficial, as a renewable energy option. Wind turbines using the Doubly Fed Induction Generators (DFIGs) have attracted particular attention because of their advantages such as variable speed, constant frequency (VSCF) operation, reduced voltage flicker, and independent control capabilities for maximum power point tracking (MPPT), active and reactive power controls, and voltage control strategy at the point of common coupling (PCC). When such resources have to be integrated into the existing power system, the operation becomes more challengeable particularly in terms of stability, security, and reliability. This paper presents the study that was used to develop and implement a model to investigate the impacts of the integration of wind energy into the distribution network. This entails the rapid control prototype testing of a grid-connected, variable speed DFIG wind turbines to investigate the steady state and dynamic behavior of each grid integrated wind turbine under normal and disturbance conditions. This model was implemented in the MATLAB / Simulink environment. The control strategy was experimentally validated in a laboratory designed wind turbine (EWT) driven by the CO3208-3A controller, integrated to grid-connected DFIG.

This paper demonstrates validation of modified control algorithm for MPPT (Maximum Power Point Tracking) for Doubly Fed Induction Generator (DFIG) based WECS (Wind Energy Conversion System). The main objective is maximizing the wind energy by optimizing the losses. MPPT algorithm implementation is done by performing control of duty cycle of DC to DC boost converter. This method establishes effective system for wind energy utilization and reduces rating for control. The implementation of the MPPT algorithm is done with the use of instantaneous values of input-side electrical parameters. The complete idea is verified by simulation in the simulation environment of MATLAB—Simulink. Keywords: MPPT, duty cycle, DFIG, WECS Cite this Article Komal Bagai, Sidharth Talia, Sandeep Banerjee, Himanshu Sharma, Nikunj Kumar Agarwal. Operation of isolated DFIG with Modified PO 7(1): 29–33p.

This paper presents the design and control of a distributed generation system using wind and solar PV (Photovoltaic) energy sources feeding to a 3-phase 4-wire network. The wind energy conversion system consists of a wind turbine coupled to DFIG (Double Fed Induction Generator) equipped with MPPT (Maximum Power Point Tracking). The MPPT demands speed control which is realized using vector control of the rotor side converter. The voltage and frequency control is achieved through load side converter connected to the common DC bus. Solar PV power is fed to the same DC bus using DC-DC boost converter which is also equipped with MPPT algorithm to extract maximum energy from the incident solar energy. The system is modeled in Sim-Power System tool of MATLAB and its performance under all the practical conditions e.g. varying wind speed and radiation; unbalanced and nonlinear load is presented. Under all these conditions; the stator currents flowing through DFIG are balanced and sinusoidal. The harmonics in load voltage under all conditions are within requirement of IEEE 519 standard. The scheme doesn't envisage measurement of any mechanical quantities e.g. wind speed or rotor position. Finally the effectiveness of the system is demonstrated experimentally using a 3.7 kW DFIG and a 5 kW solar array simulator.

This paper presents the design and control of wind diesel hybrid system feeding 3-phase 4-wire distribution network. The grid is energized by conventional diesel generators. Wind energy block consists of a wind turbine coupled to DFIG (Double Fed Induction Generator) equipped with MPPT (Maximum Power Point Tracking). The MPPT demands regulation of the turbine speed which is realized with the help of rotor side converter. The DFIG control consists of two voltage source converters connected back to back at DC bus with a battery bank. The control system is designed such that the loading of diesel generator(s) remains in optimum loading condition keeping currents of wind generator as well as diesel generators balanced. Any surplus or deficient energy is circulated through a battery bank connected to the DC side of both converters. The complete system is modeled using Simpowersystem tool box of MATLAB 7.10 and its results are presented for conditions such as synchronisation of wind generator, load variation, nonlinear load and unbalanced load, varying wind speed etc. Under all the above conditions, the currents flowing through DFIG and diesel generators are balanced.

This paper deals with the modeling and control of a three phase four wire autonomous Wind Energy Conversion System (AWECS) using Doubly Fed Induction Generator (DFIG) feeding local loads. It presents a procedure for design and selection of the components and a vector control algorithm for AWECS. The proposed control algorithm for AWECS is realized using back to back connected Pulse Width Modulated (PWM) Insulated Gate Bipolar Transistors (IGBTs) based voltage source converters (VSCs) with a battery energy storage system (BESS) at their dc link. The main objectives of the control algorithm are maximum power tracking (MPT) through rotor speed control, and voltage and frequency control (VFC) at the stator terminals of the DFIG under dynamic electrical and mechanical conditions. A zigzag transformer is used between stator side converter and the stator for harmonic elimination, optimum selection of the voltage of dc link and providing the neutral terminal for the three phase four wire system. The proposed electro-mechanical system is modeled and simulated in MATLAB using Simulink and Sim Power System (SPS) set toolboxes. The performance of the proposed AWECS is presented to demonstrate its capability of MPT, VFC at stator terminals, harmonic elimination, load balancing and load leveling.

To improve wind energy utilization and power generation efficiency, the variable speed constant frequency (VSCF) wind generation system is an efficient way. Tracing the maximum wind power can be realized through the active and reactive power decoupled control. Based on the mathematical model of doubly-fed induction generator(DFIG), the strategy of using stator field oriented vector control technology was made. The output active power of DFIG can be controlled to realize the maximum power point tracking(MPPT). Detailed simulation on Matlab/Simulink verifies the correctness and feasibility of the proposed control strategy.

This paper deals with a control algorithm for two parallel-operated doubly fed induction generators (DFIGs) driven by wind turbines in a three-phase four-wire autonomous system feeding local loads. The proposed autonomous wind energy conversion system (AWECS) is using back-to-back-connected pulsewidth-modulated insulated-gate-bipolar-transistor-based voltage source converters with a battery energy storage system at their dc link. The system utilizes separate rotor-side converters for each DFIG for maximum power tracking (MPT) through its rotor speed control. However, a common dc bus and a battery bank and stator-side converter are used for voltage and frequency control at the stator terminals of the DFIGs. A delta–star transformer is connected between the stator-side converter and the stator terminals of DFIGs for optimizing the voltage of dc bus, and the load-side neutral is connected to the neutral of the star side of the transformer. The proposed electromechanical system is modeled and simulated in MATLAB using Simulink and Sim Power Systems set toolboxes. The performance of the proposed AWECS is presented to demonstrate its capability of MPT, stator voltage and frequency control, harmonic elimination, load balancing, and load leveling.

Nowadays, the electricity demand in remote areas is increasing. Among a variety kinds of renewable energy sources, wind energy is very used. This type of energy presents a realistic alternative for power production. Therefore, to ensure optimal use of this energy, different control strategies are well studied in the literature. In this work, an autonomous wind energy conversion system based on a double fed induction generator (DFIG) is studied and modeled. The main goal of this work is to maintain the stator voltage and frequency to their reference values (220V, 50Hz) under variable mechanical speed and load variations. To achieve this purpose, two types of controllers are studied and compared: The vector control (PI) and the sliding mode controllers. Simulation results demonstrate the high precision and the robustness of the sliding mode controller compared with the vector controller (PI) mainly in case of wind speed variations and load demand changes.

This paper deals with a control algorithm for two parallel operated Doubly Fed Induction Generators (DFIGs) driven by wind turbines in a three phase four wire autonomous system feeding local loads. The proposed Autonomous Wind Energy Conversion System (AWECS) is using back to back connected Pulse Width Modulated (PWM) Insulated Gate Bipolar Transistors (IGBTs) based voltage source converters (VSCs) with a battery energy storage system (BESS) at their dc link. The system utilizes separate rotor side converters for each DFIG for maximum power tracking (MPT) through its rotor speed control. However a common dc bus and battery bank, and stator side converter are used for voltage and frequency control (VFC) at the stator terminals of the DFIGs. A delta star transformer is connected between the stator side converter and the stator terminals of DFIGs for optimizing the voltage of dc bus, and the load side neutral is connected to the neutral of the star side of the transformer. The proposed electro-mechanical system is modeled and simulated in MATLAB using Simulink and Sim Power Systems (SPS) set toolboxes. The performance of the proposed AWECS is presented to demonstrate its capability of maximum power tracking, stator voltage and frequency control, harmonic elimination, load balancing and load leveling.

Recently, the advanced developments in the field of wind energy technology have had a direct impact on the increased power production globally. Presented in this paper is the developed experimental model of a wind turbine control system, used to investigate the integration of a wind farm into the distribution network, which is a complicated engineering process requiring good engineering practices. This experiment was conducted at the High Voltage and Direct Current (HVDC) laboratory situated at the University of KwaZulu-Natal, Westville Campus. This wind turbine system uses the Doubly Fed Induction Generator (DFIG) which is advantageous due to: the variable speed constant frequency (VSCF) operation, the reduced voltage flicker and independent control capabilities for maximum power point tracking (MPPT), and active and reactive power controls at the point of common coupling (PCC). The aim of this experiment is to analyze the impact of the connected variable speed DFIG wind turbine on the distribution network at normal wind conditions and disturbance wind conditions. The large-scale integration of wind energy sources in to the power grid creates technical challenges due to the intermittent nature of wind. Thus, there is a need to investigate the impact of the specified challenges on voltage quality and power system stability. From this experimental study, it was revealed that the influence of these technical challenges increases with the increase in the integration of wind energy into the power grid.

In this paper, a control strategy is proposed to enhance the capability in terms of active filtering, of a Wind Energy Conversion System (WECS) based on a Doubly Fed Induction Generator (DFIG). The stator of the DFIG is directly connected to the grid and the rotor is connected to the grid through a back to back AC-DC-AC PWM converter. The proposed algorithm is applied to the Rotor Side Converter (RSC) to achieve simultaneously the Maximum Power Point Tracking (MPPT) and the power quality improvement at the Point of Common Coupling (PCC). This enables the grid to supply only sinusoidal currents at Unity Power Factor (UPF). Depending on the nominal RSC power, reactive power of linear loads and harmonic currents due to the nonlinear loads can be compensated. The proposed RSC control strategy manages the WECS function's priorities between active power production, reactive power compensation and active filtering without any system over-rating. To enhance the capability of the RSC, in terms of active filtering, it is proposed to eliminate instantaneously the whole of the 5th and the 7th predominant harmonic components if possible, otherwise, the filtering operation is omitted. The Grid Side Converter (GSC) is controlled in such a way to guarantee a smooth DC voltage. The presented simulation results demonstrate the performance and the effectiveness of the proposed control strategy.