Brushless Doubly-fed Reluctance Generator Research Articles

Optimum active power tracking based control of brushless doubly-fed reluctance generator tied to renewable microgrid

Among all the existing wind energy generators (WEG), a brushless doubly-fed reluctance generator (BDFRG) is the better option in terms of maintenance cost and constructional simplicity. For more adaptability, the efficiency of the BDFRG can be improved through proper control mechanisms. Therefore, this paper presents an optimum active power tracking-based control technique for BDFRG for minimum losses. Copper loss of the machine is considered to be the objective function for the proposed optimization technique. However, one issue found to be the major in all the existing controllers is the accuracy of sensor less control of the BDFRG. Therefore, this paper proposes an accurate model reference adaptive system (MRAS) based sensor less mechanism for computation of BDFRG secondary winding flux position. The no sensitivity of the proposed technique to the machine parameter variation and hence the accuracy, catch-on-fly, and non-inclusion of integrator and differentiators and hence less burden on the processor makes the proposed scheme robust. The control scheme is practically implemented with a 2.5 kW BDFRG using MATLAB/Simulink platform.

Passive Control for Brushless Doubly-Fed Reluctance Generator under Unbalanced Grid Voltages

Passive Control for Brushless Doubly-Fed Reluctance Generator under Unbalanced Grid Voltages

Direct Power Control and Space Vector Modulation‐Based Direct Power Control for Brushless Doubly‐Fed Reluctance Generator

This paper deduces the quantitative relationship between the flux vectors and the power of power winding (PW) in brushless doubly‐fed reluctance generator (BDFRG). On this basis, the direct power control (DPC) theory of BDFRG is established, which makes up the deficiency that the DPC theory of BDFRG is only based on qualitative analysis in the existing literature. The power derivative expression is derived for accurately analyzing the effect of voltage vector of control winding (CW) on the power of PW, concluding that the control effect of DPC is related to the operation point of a BDFRG. The number of basic voltage vectors of CW connected with two‐level converter is limited, resulting that under some operation conditions, a BDFRG controlled by DPC could present a time interval where the power cannot be controlled satisfactorily. Therefore, the space vector modulation‐based direct power control (SVM‐DPC) strategy of BDFRG is proposed, which can solve the above problem and fix the switching frequency. Experimental results prove the correctness of the elaboration and the proposed method. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

A Dual Observer for Parameter-Free Encoderless Control of Doubly-Fed Reluctance Generators

A novel, cascaded model reference adaptive system (MRAS) observer design for speed and reactive power ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathbf{Q}$</tex-math></inline-formula> ) control of the emerging brushless doubly-fed reluctance generator (BDFRG) without a shaft position sensor, and no machine parameter knowledge, is proposed. The main advantages of the underlying estimation technique over the existing ones reported in the open literature are the intrinsic versatility, robustness, and accuracy, offering entirely decoupled torque (power) and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathbf{Q}$</tex-math></inline-formula> responses. The reference model of the rotor angular velocity and position MRAS observer is purely based on the current measurements of the converter-fed (secondary) winding, and its adaptive counterpart on the measured grid voltages and currents at line frequency. The latter requires the inductance ratio for calculations, the online estimates of which being generated by the supplementary MRAS observer working in parallel. Doing so, a complete machine parameter independence and stability of the scheme have been achieved, and its viability fully experimentally validated under variable loading conditions of the small-scale BDFRG wind turbine emulated in a laboratory environment.

Super-twisting sliding mode control for brushless doubly fed reluctance generator based on wind energy conversion system

Introduction. Recently, wind power generation has grown at an alarming rate in the past decade and will continue to do so as power electronic technology continues to advance. Purpose. Super-twisting sliding mode control for brushless doubly-fed reluctance generator based on wind energy conversion system. Methods. This paper deals with the robust power control of a grid-connected brushless doubly-fed reluctance generator driven by the variable speed wind turbine using a variable structure control theory called sliding mode control. The traditional sliding mode approach produces an unpleasant chattering phenomenon that could harm the system. To eliminate chattering, it is necessary to employ a high-order sliding mode controller. The super-twisting algorithm is one type of nonlinear control presented in order to ensure the effectiveness of the control structure we tested these controllers in two different ways reference tracking, and robustness. Results. Simulation results using MATLAB/Simulink have demonstrated the effectiveness and robustness of the super-twisting sliding mode controller.

Research on Control Strategy of Grid-connected Brushless Doubly-fed Wind Power System Based on Virtual Synchronous Generator Control

The brushless doubly-fed wind power system based on conventional power control strategies lacks ‘inertia’ and the ability to support grid, which leads to the decline of grid stability. Therefore, a control strategy of brushless doubly-fed reluctance generator (BDFRG) based on virtual synchronous generator (VSG) control is proposed to solve the problem in this paper. The output characteristics of BDFRG based on VSG are similar to a synchronous generator (SG), which can support the grid frequency and increase the system ‘inertia’. According to the mathematical model of BDFRG, the inner loop voltage source control of BDFRG is derived. In addition, the specific structure and parameter selection principle of outer loop VSG control are expounded. The voltage source control inner loop of BDFRG is combined with the VSG control outer loop to establish the overall architecture of BDFRG-VSG control strategy. Finally, the effectiveness and feasibility of the proposed strategy are verified in the simulation.

High-Performance Sensorless Operation of Motor-Generator Set With an Improved Torque-Ripple Minimization Strategy

This paper aims at minimizing the torque ripples using variable switching frequency technique of PWM (VSFPWM) of the surface-mounted permanent magnet synchronous motor (SPMSM) for a high-performance operation of a motor-generator set. The proposed system was employed to drive the promising brushless doubly-fed reluctance generator (BDFRG) with a sensorless vector-control topology. Validity of the rotor-position/speed estimation critically affects most of the sensorless control strategies. Therefore, a simple estimation method is proposed for the positioning of rotor of the generator. The presented control strategies are confirmed with some of the obtained results to assure its controllability.

A Proposed Controllable Crowbar for a Brushless Doubly-Fed Reluctance Generator, a Grid-Integrated Wind Turbine

Brushless doubly fed reluctance generators (BDFRGs) are hopeful generators for using inside variable speed wind turbines (VSWTs), as these generators introduce a promising economical value because of their lower manufacturing and maintenance costs besides their higher reliability. For integrating WT generators, global networks codes require enabling these generators to stay connected under grid disturbances. The behavior of the BDFRG is strongly affected by grid disturbances, due to the small rating of the used partial power converters, as these converters cannot withstand high faults currents which leads to quick tripping of BDFRG. VSWTs can be safeguarded against faults using the crowbar. Usually, the conventual crowbar is shunt connected across the converter to protect it, but this configuration leads to absorbing reactive power with huge amounts from the grid, leading for more voltage decaying and more power system stability deterioration. This study proposes a simpler self-controllable crowbar to enhance the ability of the BDFRG to remain in service under faults. The operation technique of the proposed crowbar is compared to other crowbar operation techniques, the effectiveness of the proposed system would be analyzed. Through the simulation results and behavior analysis, the proposed crowbar technique demonstrates a decent improvement in the conduct of the studied system under faults.

Comparative study between sliding mode control and the vector control of a brushless doubly fed reluctance generator based on wind energy conversion systems

Introduction. Nowadays, global investment in renewable energy sources has been growing intensely. In particular, we mention here that wind source of energy has grown recently. Purpose. Comparative study between sliding mode control and vector control of a brushless doubly fed reluctance generator based on wind energy conversion systems. Methods. This paper deals with conceptual analysis and comparative study of two control techniques of a promising low-cost brushless doubly-fed reluctance generator for variable-speed wind turbine considering maximum power point tracking. This machine's growing interest because of the partially rated power electronics and the high reliability of the brushless design while offering performance competitive to its famous spring counterpart, the doubly-fed induction generator. We are particularly interested in comparing two kinds of control methods. We indicate here the direct vector control based on Proportional-Integral controller and sliding mode controller. Results. Simulation results show the optimized performances of the vector control strategy based on a sliding mode controller. We observe high performances in terms of response time and reference tracking without overshoots through the response characteristics. The decoupling, the stability, and the convergence towards the equilibrium are assured.

Real Time Simulation of Brushless Doubly Fed Reluctance Generator Driven Wind Turbine Considering Iron Saturation

Brushless doubly fed reluctance generator (BDFRG) provides a good substitute for the doubly fed induction generator for the wind energy applications due to the nonexistence of the slip rings. Real time modelling of the BDFRG is a challenge due to the high leakage inductance of the stator windings. While the magnetic saturation of the iron parts affects the inductances values, therefore studying the effect of magnetic saturation on the BDFRG performance is important. In this paper, a BDFRG model including iron saturation is built. The finite element (FE) analysis using FEMM software is used to generate the relationship between the generator currents and the inductances, the generated data are recorded in a lookup table. A Simulink model of the BDFRG driven wind turbine, with two cases of constant and variable inductances, are developed and verified with FE analyses at range of wind speeds above and below the synchronous speed. The lookup table proposes is verified using finite element analysis at different modes of operation of wind speed and compared with the constant inductance model to show the importance of saturation inclusion in the generator model for accurate generator modelling representation.

Parameter independent control of doubly-fed reluctance wind generators without a rotor position sensor

A novel model reference adaptive system (MRAS) based estimation technique for sensorless operation of a brushless doubly fed reluctance generator (BDFRG) with maximum power point tracking (MPPT) is proposed. The main advantage of this development is the truly machine parameter independent rotor angular velocity MRAS observer complemented by an original position error compensation scheme for higher accuracy, making it clearly superior to the existing designs. The simulation and experimental results have demonstrated the excellent performance prospects for typical wind turbines emulated in a laboratory environment.

Dynamic Modeling and Control of BDFRG under Unbalanced Grid Conditions

The Brushless Doubly-Fed Reluctance Generator (BDFRG) is a potential alternative to the Doubly Fed Induction Generator (DFIG) in wind power applications owing to its reasonable cost, competitive performance, and high reliability. In comparison with the Brushless Doubly-Fed Induction Generator (BDFIG), the BDFRG is more efficient and easier to control owing to the cage-less rotor. One of the most preferable advantages of BDFRG over DFIG is the inherently better performance under unbalanced grid conditions. The study conducted in this paper showed that conventional vector control of the BDFRG results in excessive oscillations of the primary active/reactive power, electromagnetic torque, and primary/secondary currents in this case. In order to address such limitations, this paper presented a new control strategy for the unbalanced operation of BDFRG-based wind generation systems. A modified vector control scheme was proposed with the capability to control the positive and the negative sequences of the secondary currents independently, thus greatly reducing the adverse implications of the unbalanced supply. The controller performance has been validated by simulations using a 1.5 MW BDFRG dynamical model built upon the positive and negative sequence equations. The main benefits of the new control strategy are quantified in comparison with conventional PI current control design.

Fault‐tolerant control strategy of open‐winding brushless doubly fed wind power generator based on direct power control

This study presents a study of fault-tolerant operation for a brushless doubly fed reluctance generator (BDFRG) system under a converter switch fault. The topology of the dual converter fed open-winding BDFRG is adopted to improve post-fault operation capacity. For post-fault operation, the appropriate voltage vectors of control winding are selected to directly adjust the active and reactive power of power winding based on the direct power control theory. Switching tables are formulated under different switch faults. The simulation and experimental results demonstrate the feasibility of the proposed strategy.

Fault-tolerant control of an open-winding brushless doubly-fed wind power generator system with dual three-level converter

To improve the fault redundancy capability for the high reliability requirement of a brushless doubly-fed generation system applied to large offshore wind farms, the control winding of a brushless doubly-fed reluctance generator is designed as an open-winding structure. Consequently, the two ends of the control winding are connected via dual three-phase converters for the emerging open-winding structure. Therefore, a novel fault-tolerant control strategy based on the direct power control scheme is brought to focus in this paper. Based on the direct power control (DPC) strategy, the post-fault voltage vector selection method is explained in detail according to the fault types of the dual converters. The fault-tolerant control strategy proposed enables the open-winding brushless doubly-fed reluctance generator (BDFRG) system to operate normally in one, two, or three switches fault of the converter, simultaneously achieving power tracking control. The presented results verify the feasibility and validity of the scheme proposed.

Mathematical proof of BDFRG model under unbalanced grid voltage condition

Abstract Brushless doubly fed reluctance generator (BDFRG) can be an appropriate choice for wind power application because of its brushless structure. Usually, wind power plants are located in remote areas which unbalanced voltage of the grid is a common problem. So, modeling of the BDFRG under unbalanced grid voltage condition (UGVC) is one of the major steps in the operation analysis. This paper provides mathematical proof of the BDFRG model under UGVC. Time domain equations of the BDFRG are used to derive the space vector and dq models under UGVC based on symmetrical component theory in the relative positive and negative sequence reference frames. In addition, electrical torque expression of the BDFRG in time domain is used to develop the electrical torque expression under UGVC. Furthermore, the mathematically derived model has been simulated in MATLAB/Simulink software to demonstrate operation of the BDFRG under UGVC.

Sensorless Speed Estimation of Brushless Doubly-Fed Reluctance Generator Using Active Power Based Mras by Pi and Anfis Controller

Sensorless Speed Estimation of Brushless Doubly-Fed Reluctance Generator Using Active Power Based Mras by Pi and Anfis Controller

Performance analysis of grid-integrated brushless doubly fed reluctance generator-based wind turbine: modelling, control and simulation

Due to the absence of the rotor windings, the brushless doubly fed reluctance generator (BDFRG) presented a much better efficiency with less complicated control and modelling than that introduced by the brushless doubly fed induction generator. As a result, the BDFRG gained more preference than that of the doubly fed induction generator. Moreover, this result led to the emerging of the (BDFRG) as one of the most promising generators in the new modern wind turbines. This paper introduces modelling as well as control strategy for the grid-connected BDFRG-based wind turbine systems. This study was carried out using MATLAB/Simulink environment.

Design and Modeling of Brushless Doubly-Fed Reluctance Generator for Wind Mills

For the wind energy systems the wind generators the most significant device for achieving better energy efficiencies. So in the case of wind generators, different generators are used for different conditions. In this paper we proposed to analyze the performance analysis of the Brushless Doubly-Fed Reluctance Generator (BDFRG). The BDFRG methods simulated in MATLAB/Simulink software. The proposed model is analyzed with different parameters like THD, ISE, IE, and ITE. The results of the parameters are combined with the other conventional generators like DFIG and BDFIG for result validation. The BDFRG achieved better results in all the parameters than the other conventional generators.

Sensorless Speed Estimation of Brushless Doubly-Fed Reluctance Generator Using Active Power Based MRAS

This paper proposes an active power based model reference adaptive system for sensorless speed estimation of primary field oriented brushless doubly-fed reluctance generator (BDFRG). In this regard, the active power associated with secondary winding of BDFRG is used for the process of speed estimation. BDFRG is more reliable and requires less maintenance. Its structural advantages demonstrate higher working efficiency and lower losses as compared to equivalent doubly-fed induction machines. Moreover, active power of BDFRG can be controlled by suitable speed regulation, which in turn can be achieved by a low rating bidirectional converter connected to the stator secondary (i.e., control) winding. These inherent features make BDFRG as a prospective candidate in the applications like wind and tidal power generation. The efficacy of the proposed control technique is established by a 1.6 kW BDFRG in Matlab /Simulink. A dSPACE-1103 based laboratory prototype is used for the hardware validation.

Sensorless DTC of BDFRG using LMS algorithm for wind energy conversion systems

This paper presents a new sensorless speed and secondary winding resistance estimation technique for brushless doubly fed reluctance generator (BDFRG) using least mean square (LMS) algorithm. Detailed mathematical derivation of the algorithm is explained and simulation results in MATLAB Simulink are shown for sensorless direct torque control (DTC) of BDFRG using LMS algorithm. A comparison to traditional speed estimation technique for BDFRG using primary winding flux linkage formula in stationary frame is then held to show the advantages of this proposed technique over the traditional method of speed estimation. Power electronics of the drive system is also simulated to consider effect of harmonics injected by electronic switches on both algorithms.