Fed Induction Machine Research Articles

Intelligent vector control for a novel mechatronic modeling of a 1.5MW variable speed WECS using the bicausality concept under a real wind flow: A Bond Graph Approach

Enhancing the dynamic behaviors of Wind Energy conversion Systems (WECS) based on a doubly fed induction machine (DFIG) is one of the most attractive challenging in the field of maximizing renewable energy's output power, improving its quality and ensuring its efficient grid integration. For this purpose, a novel mechatronic modelling of a 1.5 MW variable-speed WECS based on a doubly fed induction machine using the Bond graph Approach is proposed, and three robust control strategies are displayed to regulate: the DFIG's active and reactive powers for the networks side converter (NSC), maximizing the extracted power and controlling the pitch angle for the load area. The flux oriented vector control laws presented in this contribution are based upon the independent control of magnetic flux and the electromagnetic torque inside the DFIG machine. They are derived from the integrated model's Inverse Bond Graph (IBG). This robust control strategy based on the bicausality concept enabled us to elaborate the Vector Control model that relies on a Radial Basis Function RBF-VC to be trained online with an optimal dataset under some real wind profiles. The robustness and effectiveness of the proposed model and RBF-VC controller are verified. The simulation results were conducted to confirm the validity of the proposed technique. Hands-on experience is carried out by means of the 20-sim software package.

Quantifying power regulation characteristics in pump mode of variable‐speed pumped storage unit with DFIM

AbstractPumped storage plants (PSPs) play an important role in renewable energy consumption in power systems. Variable‐speed technology is a new and critical direction for the development of PSPs. In pump mode, variable‐speed pumped storage units (VSPSUs) have wider power regulation ranges and more flexible power responses than fixed‐speed pumped storage units (FSPSUs); however, the corresponding quantification study of VSPSUs is rare. Therefore, this study aims to quantify the static and dynamic power regulation characteristics of VSPSU in pump mode. First, the modeling of the fast speed control strategy of VSPSU in pump mode is improved. Then, the power regulation range of the VSPSU is explored. The factors (i.e., power command, governor, and converter) affecting the power response rapidity are quantified through the engineering case of a variable‐speed PSP adopting the doubly fed induction machine. Accordingly, suggestions on the settings of the parameters are provided. Quantification results show that parameter tuning based on this study effectively solves the problem of low regulation rate caused by great power fluctuations under typical power regulation cases in pump mode. This VSPSU has the fastest regulation rate of 13.75%/s when adjusting 40% power. This study could provide technical support to the practical operation of VSPSU.

Control strategies for grid-connected hybrid renewable energy systems: Integrating modified direct torque control based doubly fed induction generator and ANFIS based maximum power point tracking for solar PV generation

This research article introduces advanced control strategies for grid-connected hybrid renewable energy systems, focusing on a doubly fed induction machine (DFIM) based wind power plant and a photovoltaic based solar power plant. The proposed approach integrates Direct Torque Control (DTC) with modified filters and a fractional Proportional-Integral (PI) controller for the DFIM wind power plant. The modified DTC utilizes estimated torque and flux, employing a modified filter to minimize deviations, and a fractional PI controller for improved vector selection. This results in an enhanced duty cycle for the rotor side converter, optimizing power output to the grid. Additionally, an Adaptive Neuro-Fuzzy Inference System (ANFIS)-based Maximum Power Point Tracking (MPPT) algorithm is implemented for the solar power plant, dynamically adjusting the duty cycle for increased power output compared to conventional MPPT methods. Simulation results in MATLAB and experimental verification demonstrates the stability and feasibility of the proposed controllers, showcasing superior performance compared to conventional counterparts under various operating conditions.

Comparative study between sliding mode and DTC of doubly fed induction machine

Although the great advance in term of AC machine construction, control strategies are also necessary to be developed and improved continuously satisfying output torque/power. Hence the Doubly fed induction motor (DFIM)is widely used in industry, since it can operates in wide range of speed variation around the synchronous speed and the control of flux and torque is independent. In this paper, control of doubly fed induction motor (DFIM) has been investigated, which two control strategies have been studied and compared: the first strategy uses a sliding mode control (SMC); the second employs Direct Torque Control (DTC). Modeling of DFIM and details of both control strategies have been presented. the mathematical description of different basic dynamic models of the DFIM have been carried out The performances in terms of torque tracking, accuracy and robustness of both control techniques under normal and various speed and load conditions have been demonstrated and compared.

Rotor–stator interaction investigations in variable speed reversible pump-turbine at higher head

Efficiency and grid stability can be improved by variable speed operation using doubly fed induction machine technology for pumped storage plants experiencing significant head variations. With the higher penetration of intermittent and variable renewable energy sources, viz., solar and wind, the grid may be stabilized by operating the reversible pump-turbines (RPTs) in off-design conditions. In a turbine mode, the RPT is more susceptible to fatigue and vibrations when operating at a higher head as a result of hydraulic instability generated by rotor–stator interaction (RSI); therefore, its performance becomes even more critical. The powerhouse structural components, including floors and columns, could experience intense vibrations because of this instability. Therefore, it is essential to investigate the RSI in the variable speed RPTs at the higher head. These investigations present the results of a numerical analysis of RSI and its associated pressure fluctuations in the variable speed RPTs at the higher head. The high-head scaled model of variable speed RPT was used, and the numerical simulations were executed by utilizing the shear stress transport k-ω turbulence model. The numerical analysis was performed at the best efficiency point and high-head operating conditions having optimized rotational speed. The results show that the main source of pressure fluctuations in the variable speed RPT at all operating conditions is RSI, where the dominant frequencies are blade passing frequency (9fn) and its harmonics. It is also found that the variable speed operation lowers the pressure fluctuations in the RPT.

Advanced Doubly Fed Induction Machine Rotor Fault Diagnosis Based on Wavelet Analysis in Closed-Loop Operation Under Time–varying Condition

This paper introduces a new diagnostic technique for the detection of incipient electrical rotor faults in doubly fed induction Machine (DFIM) for wind power systems. In the considered application, the rotor is supplied by a static converter for the control of active and reactive power flows from the generator to the electrical grid. A new diagnostic method based on the rotor modulating signals pre-processing by Frequency Sliding (FS) and Discrete Wavelet Transform (DWT) thereby is here proposed to detect rotor faults dynamically over time. Experimental and simulation results demonstrate the effectiveness of the proposed approach under time-varying conditions.

Maximum Torque per Ampere Operation of Brushless Doubly Fed Induction Machines

In this paper, an analytical method for increasing the steady state torque per ampere capability for BDFMs, using equivalent circuit is presented. In this approach, uni-current proposition proposed to define a unique current value for optimization, and find the current angel corresponding to maximum torque. The accuracy of the proposition is verified by simulation. The effect of pole pair number selection of power and control windings on maximum torque is explained by dividing torque expression into synchronous and asynchronous terms. Finally, the optimal current values and optimal torque are achieved. Based on the optimal value of torque, or MTPA index, analytical optimization of machine design is suggested, which can be performed by manipulation of components of the MTPA index

Hysteresis loss in Brushless Doubly Fed Induction Machines

Brushless doubly fed machine (BDFM) is a potential for future wind energy generation, due to its lower maintenance costs and higher reliability than conventional doubly fed systems. While efficiency and design optimization of the machine has become critical issues recently, no analytical core loss model is investigated in the literature. Furthermore, core loss modeling is different from conventional induction machines, because of double frequency excitation of the machine. In this paper, a dynamical system is used for modeling of hysteretic behavior of iron core, and hysteresis losses of BDFM are analyzed and modeled mathematically. The flux waveforms of BDFM are assumed pure double sine, as in wound rotor BDFM lower harmonic values than nested loop design exist.

A Ground Fault Detection Method for Double Fed Induction Machines via DC Grounding Resistor Voltage Evaluation

A Ground Fault Detection Method for Double Fed Induction Machines via DC Grounding Resistor Voltage Evaluation

Performance Analysis of 9, 11, 13, and 15 – Level Back-to-Back Connected Modular Multilevel Converters fed Doubly Fed Induction Machine

In this paper, back-to-back Modular Multilevel Converters are used to feed the Doubly Fed Induction Machine. The MMC with 9, 11, 13, and 15 – Level output voltages are generated and fed to the DFIM and the performance of the DFIM is analyzed, when the machine is working as Doubly Fed Induction Generator (DFIG) and when the machine is working as Doubly Fed Induction Motor. The performance of the DFIG is analyzed in terms of power factor at Grid Side Converter (GSC) for different levels of operation of MMC. The results show that the power factor is maintained near to unity power factor at grid side. The performance of the Doubly Fed Induction Motor is analyzed in terms of variation of the load torque being applied to motor. The results show that there is clear variation of the speed for two different load conditions. The work is carried out by using Typhoon HIL Real-Time Simulation platform, i.e., both Software and Hardware.

Improved start-up strategy for a doubly fed induction machine fed large rated variable speed pumped storage unit in pumping mode operation

Improved start-up strategy for a doubly fed induction machine fed large rated variable speed pumped storage unit in pumping mode operation

Estimation of Stator Vibration in DFIM Under Various Types of Rotor Excitation

Variable speed power generation using Doubly Fed Induction Machine requires an adjustable frequency supply at the rotor terminals which can be achieved using power converters. Ideally, a variable frequency sinusoidal voltage should be applied, but it is not possible without the help of power converters. For a typical 250 MW DFIM with a speed variation of -10.73% to +8.33%, excitation power of 25 MW at 3.3kV and 11600 Amps is required. With this much high rotor current at low fundamental rotor frequency (3.75 Hz) electromagnetic forces in the air gap contain harmonic force components. Also, any time harmonic of radial force density in the rotor will be induced in the stator as a distinct time harmonic, modified by the influence of space harmonics in DFIM with regular three phase integral slot winding on both stator and rotor and vice versa. So, if the frequency and order of electromagnetic force components conflicts with mode shape and natural frequencies of the machine stator strong magnification in vibration will occur or more severely develops mechanical resonance. The stator vibration of electrical machine is generated by the electromagnetic forces acting on the surface of the stator tooths. This paper analyzes stator vibration for 250 MW DFIM in multiphysics simulation with its rotor winding excited through pure sinusoidal excitation at fundamental rotor frequency of 3.75 Hz and with two-Level voltage source converter at 3.75 Hz fundamental rotor frequency. Hardware results with supported multiphysics simulation on a laboratory prototype of 2.2 kW rating DFIM.

Direct power control using space vector modulation strategy control for wind energy conversion system using three-phase matrix converter

Introduction. Wind energy conversion system is getting a lot of attention since, they are provide several advantages, such as cost competitive, environmentally clean, and safe renewable power source as compared with the fossil fuel and nuclear power generation. A special type of induction generator, called a doubly fed induction generator is used extensively for high-power wind energy conversion system. They are used more and more in wind turbine applications due to the advantages of variable speed operation range and its four quadrants active and reactive power capabilities, high energy efficiency, and the improved power quality. Wind energy conversion systems require a good choice of power electronic converters for the improvement of the quality of the electrical energy produced at the generator terminals. There are several power electronics converters that are the most popular such as the two stage back-back converter. Because of the disadvantage of these converters to produce large harmonics distortions, we will choose using of three-phase matrix converter. Purpose. Work presents a direct power control using space vector modulation for a doubly fed induction generator based wind turbine. The main strategy control is to control the active and reactive powers and reduce the harmonic distortion of stator currents for variable wind speed. The novelty of the work is to use a doubly fed induction machine and a three pulses matrix converter to reduce the low cost, volume and the elimination of the grid side converter controller are very attractive aspects of the proposed topology compared to the conventional methods such as back-to-back converters. Simulation results are carried out on a 1.5 MW of wind energy conversion system connected to the grid. The efficiency of the proposed system has been simulated and high results performances are evaluated to show the validity of the proposed control strategy to decouple and control the active and reactive power for different values of wind speed.

Time‐harmonic field‐circuit model for brushless doubly fed induction machine

AbstractA computationally efficient time‐harmonic finite element model for the steady‐state analysis of a brushless doubly fed induction machine (BDFIM) is proposed. In the model, the electromagnetic couplings of the BDFIM are described by means of the sum of two complex magnetic vector potentials that represent the two fundamental harmonic time components of the magnetic flux density distribution in the rotor frame of reference. As in an ordinary induction motor, the non‐linearity of the magnetisation characteristic is accounted for using an effective magnetic permeability. For the BDFIM, this is derived by considering the features of modulated magnetic flux density waveform. The accuracy of the approach has been validated by comparing the characteristics of a D270 machine operating in the double‐feed mode with ones obtained from the experimentally verified time‐stepping model at various operating conditions. High accuracy of the results coming from the proposed model is demonstrated even under deep saturation conditions within the magnetic circuit.

Analysis and Damping of Sub-Synchronous Oscillations in a 250 MW DFIM Hydro Unit Connected to Series Compensated 765 kV Transmission Lines

Increasing energy consumption has required a greater need for connections between the grid and nonconventional energy sources. Recently, doubly fed induction machine (DFIM) fed hydro power units are increasingly connected to the power system due to the requirement of large energy storage option and cost-effective converter solution in the variable speed units. On the other hand, stability related issues are raised in the power system due to the sub synchronous control interaction (SSCI) that occurs between radially connected DFIM, and series compensated transmission line. This article focuses on analysis of resonance stability in a doubly fed induction machine (DFIM) based hydropower system. The controller of the rotor side converter is tuned using a dampness optimization approach. Additionally, optimized SSCI damping controller in the grid side converter is designed to attenuate the sub-synchronous oscillation (SSO) of the DFIM. Time domain simulation analysis is conducted for this research to validate the SSCI mitigation in the DFIM-based hydro units. In MATLAB/Simulink environment, the efficacy of the proposed system with 250 MW DFIM and a series compensated 765 kV extra high voltage transmission line is tested. To scale down the model and check SSO in the 2.2 kW DFIM system, a practical demonstration is carried out in the Lab.

Reactive Power Circulation Based Fault Tolerance Schemes for Multi-Megawatt 3L-NPC Paralleled Converters in Variable Speed Hydro Applications

Parallel connected multi-MW three-level neutral point clamped power converters (3L-NPC) are widely preferred in large-rated variable speed pumped storage unit as it improves operating efficiency and reliability. During open circuit fault conditions/gate drive malfunction, the entire unit must be shut down to ensure the safety of other healthier components. This article proposes reactive power circulation-based fault tolerance control strategies for grid side converter (GSC) during inner and outer switch fault conditions. In case of an open-circuit fault in outer switches, the normal sinusoidal currents are achieved in GSC by circulating reactive power among the healthy to faulty power converters. In case of an open-circuit fault in inner switches, the reactive power is circulated between healthy converters and a doubly fed induction machine (DFIM). In addition, neutral-point (NP) voltage oscillations are suppressed by injecting a zero-sequence signal into the reference voltage. The feasibility study and performance analysis of the proposed fault tolerance control strategies are carried out in the MATLAB/Simulink 2014a environment for the 250 MW DFIM unit. Furthermore, experimental validation is carried out in 3HP DFIM scale-down laboratory prototype with three parallel connected converters.

Dynamic modeling and favorable speed command of variable-speed pumped-storage unit during power regulation

Variable-speed pumped-storage unit (VSPSU) has advantages in flexibility, efficiency, and reliability. It has become a state-of-the-art technology in pumped-storage industry. However, there is little research about the transient process of VSPSU working at a favorable speed command during power regulation. To study the issue, a refined model considering hydraulic–mechanical and electrical subsystems is built in this work. All submodels are created by the authors as individual modules on Simulink platform, and these modules can be easily combined to model different VSPSUs. For the VSPSU that uses a doubly fed induction machine and adopts the fast power control strategy, there are several speed constraints. To satisfy the speed constraints during transient process, the speed command is adjusted to avoid exceeding the allowable speed variation range and eliminate the oscillation caused by the S-shaped region, while being guided by the optimal speed to achieve higher efficiency. The faster the speed command changes, the more rapid the power regulation could be. But fast-changing speed command also leads to larger pressure fluctuations in penstocks. Hence, different schemes of the speed command are compared, and suitable schemes are proposed by comprehensively considering the balance between rapidity and safety. The dynamic model and analysis of favorable speed command can provide support and advice for engineering practice.

Doubly Fed Induction Machine-Based DC Voltage Generator with Reduced Oscillations of Torque and Output Voltage

The doubly fed induction machine (DFIM)-based DC voltage generator is equipped with a stator-connected diode rectifier. The six-pulse diode rectifier as a nonlinear circuit introduces harmonics in the stator and rotor current and distorts the machine stator voltage, as well as the stator flux. This causes electromagnetic torque oscillations and instantaneous power components oscillations. The torque oscillations adversely impact the mechanical parts of the drive-train and oscillations of the p component of instantaneous power influence DC-bus voltage oscillations. The oscillations can be somewhat cancelled by control methods. However, cancellation of electromagnetic torque is not strictly coupled with cancellation of oscillations of the p component of instantaneous power. The paper presents an analysis of influence of the control methods aimed at a reduction of torque oscillations on the output voltage oscillations level in the stand-alone DFIM-based DC voltage generator. Field-oriented control FOC with current controllers and space vector modulation-based direct torque control DTC-SVM with flux module regulation have been compared with control in which electromagnetic torque is one of the commanded variables, whereas the second variable is the dot product of stator flux and rotor current space vectors. The contributions of this paper are the introduction of a new variable in the second control path in the DTC-SVM method instead of flux vector length and the proof that it can reduce torque and DC-bus voltage oscillations in the DFIG-DC system. Additionally, this paper reveals that for proper stator-to-rotor-turns ratio of a doubly fed machine necessary for reduction of the rotor converter power, lower DC-bus voltage can be obtained than is required for full realization rotor side voltage requested by rotor current controllers. This is the reason why, regardless of the control method, torque oscillations cannot be always fully cancelled, and a comparative study of the methods at these conditions has been conducted in simulation and in laboratory tests.

An Analytical Prediction Model of Balanced and Unbalanced Faults in Doubly Fed Induction Machines

In this article, we present the exact transient solution to the unbalanced and balanced faults in the doubly fed induction machine (DFIM). Stator currents, rotor currents, and stator fluxes have been validated using simulation and experiment. The work is meant to strengthen and fasten the predictability of large DFIMs in the design stage to comply with mechanical constraints or grid fault issues. Moreover, the analytical approach reduces the computational costs of large-scale stability studies and is especially suited to the initial phase, where plethora design computations must be carried out for the DFIM before it is checked for its transient interaction with the power system. The possibility to dynamically estimate the DFIM performance is simplified by original equations derived from first principles. First, case studies of two large <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$265 \,{\rm MVA}$</tex-math></inline-formula> DFIMs are used to verify the analytical approach, and to justify the proposed “large machine approximation” using simulation with an exact match. Finally, laboratory measurements were conducted on a 10.96 and a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$1.94 \,{\rm kVA}$</tex-math></inline-formula> DFIM to validate the transient current peaks predicted in the proposed analytic expressions for two-phase and three-phase faults, respectively.

Speed estimation of a Doubly Fed Induction Machine controlled by a Field Oriented Control Strategy

This paper studies the estimation problem of speed in a Doubly Fed Induction Machine (DFIM) controlled by a Field Oriented Control (FOC) Strategy. The DFIM is the most responsive in variable speed. The chosen configuration uses two voltage inverters connected to the stator and rotor windings, to adopt the power distribution between them through the pulses distribution of the stator and the rotor in motor operating mode. It is necessary to model the DFIM in three-phase equations and then in two-phase equations faithfully representing the characteristics of the machine. From this model, we can design and simulate the control. The control by oriented rotor flux can be realized by using the speed provided by sensors or estimators. In this paper, we have used the Extended Kalman Filter (EKF) in order to avoid problems caused by the motor speed sensor and improve the robustness of the control and its performance without using any speed sensor.