Function Of Flux Linkage Research Articles

A Synchronous Machine Transient Model Based upon an Algebraic Loop Accounting for Nonlinearity and Cross-Magnetization

The purpose of this paper is to carry out an alternative to the present transient models for field wound synchronous machines, which is able to take into account the nonlinearity of the magnetic materials as well as the cross-magnetization. After presenting the principal model structures according to the state variables, a model based on two lookup tables for the magnetizing flux linkages is introduced and built step by step. The resulting signal flowchart shows an algebraic loop within the model, where the main flux linkage rapidly converges to its instantaneous value by simple iteration. The proof of this convergence is given for both saturated and unsaturated machine. Even though the proposed model uses the total linkage flux as state variable, as many alternative models do, it does not require the inversion of the current to flux linkage function (i.e., of lookup tables). This can spare a heavy computational task, especially with very large lookup tables. In the proposed model, the computational effort in the worst case scenario is reduced to few iterations (<10). Finally, the nonlinear behavior of the model is verified in four different transient scenarios by comparing its outcomes with those of a linear model for the same test machine.

A Position Sensorless Control Strategy for the BLDCM Based on a Flux-Linkage Function

A novel sensorless control strategy for the brushless dc motor (BLDCM) is proposed in this paper. The proposed strategy is realized by employing new flux-linkage functions and can be applied to drive the sensorless BLDCM in the high-speed and low-speed ranges with highly accurate and reliable commutation. Another attractive feature is that the jumping edges of the flux-linkage functions are utilized to determine the commutation points, so there is no threshold needed as compared with other sensorless control methods. In addition, the three-phase current control method is adopted, and terminal voltages in flux-linkage function expressions can be easily obtained by calculation. By this way, the sample delay and the influence of the floating phase voltage can be eliminated, which can improve the accuracy and reliability of the sensorless control strategy. The effectiveness of the proposed strategy is verified by experimental results.

Adaptive Commutation Error Compensation Strategy Based on a Flux Linkage Function for Sensorless Brushless DC Motor Drives in a Wide Speed Range

This paper presents a novel adaptive commutation error compensation strategy for the sensorless brushless DC (BLDC) motor based on the flux linkage function. It addresses the two key challenge problems on the sensorless control of the BLDC motor. The one is presenting a novel detection method for the BLDC motor rotor position signal to filter out the interference and the noise by the high frequency. The other one is proposing a commutation error compensation strategy to improve the system efficiency. In traditional sensorless control strategy, a deep low-pass filter is usually used to obtain the BLDC motor rotor position signal from the high-frequency interference. However, the delayed angle caused by the low-pass filter may be more than 90 electrical degrees in the high speed range. Therefore, a novel sensorless control strategy based on the speed-independent flux linkage function was proposed in this paper. The interference of the diode freewheeling was filtered by the software filter, and a closed-loop compensation algorithm based on the deviation of line-to-line voltages was illustrated to correct the commutation error in the high speed range. The stability and accuracy of the method was confirmed by a series of experiments.

Sensorless Control Strategy of a 315 kW High-Speed BLDC Motor Based on a Speed-Independent Flux Linkage Function

A sensorless control strategy of a high-speed 315 kW brushless dc (BLDC) motor based on a speed-independent flux linkage function is proposed in this paper. It addresses the two key challenges on the sensorless control of high-speed BLDC motor: proposing a speed-independent flux linkage function to ensure reliable operation in the low-speed range, and presenting correction strategy to provide accurate commutation points in the high-speed range. First, the sensorless detection circuit model of a 315 kW BLDC motor is discussed. The analysis shows that the speed-independent flux linkage function is really suitable for BLDC motor sensorless control strategy in the low-speed range. Then, an improved closed-loop system based on the change of current in the full speed range is proposed. The experimental results show that the proposed control strategy can provide a highly accurate and robust sensorless operation from near zero to 20 000 r/min.

Impact of equalizing currents on losses and torque ripples in electrical machines with fractional slot concentrated windings

The implementation of parallel branches is a commonly used manufacturing method of the realizing of fractional slot concentrated windings in electrical machines. If the rotor eccentricity is enabled in a machine with parallel branches, the equalizing currents can arise. The simulation approach of the equalizing currents in parallel branches of an electrical machine winding based on magnetic field calculation by using Finite Elements Method is discussed in the paper. The high accuracy of the model is provided by the dynamic improvement of the inductances in the differential equation system describing a machine. The pre-computed table flux linkage functions are used for that. The functions are the dependences of the flux linkage of parallel branches on the branches currents and rotor position angle. The functions permit to calculate self-inductances and mutual inductances by partial derivative. The calculated results obtained for the electric machine specimen are presented.The results received show that the adverse combination of design solutions and the rotor eccentricity leads to a high value of the equalizing currents and windings heating. Additional torque ripples also arise. The additional ripples harmonic content is not similar to the cogging torque or ripples caused by the rotor eccentricity.

An Efficient Design Optimization Framework for Nonlinear Switched Reluctance Machines

A new computationally efficient paradigm for the design and analysis of switched reluctance machines is proposed. At the heart of the rapid analysis and design methodology is the reduced-order computational method based on a flux-tube model, which has been refined and extended. It is demonstrated how the improved model enables consistent and accurate analysis and design optimization. Instead of an analytical derivation, an automatic generation of cubic splines is introduced to model the magnetic flux. The flux-linkage functions obtained from the improved flux-tube method indicate that the method offers good accuracy compared with the finite-element-based analysis, but with significantly improved computational efficiency. The approach is applicable to translating and rotating switched reluctance machines of various topologies, and therefore, enables rapid design search and optimization of novel topologies.

Implementation of Control Variables to Exploit Output Power for Switched Reluctance Generators in Single Pulse Mode Operation

A B S T R A C T This paper presents an analytical modeling method of optimal control variables to maximize output power for switched reluctance generators (SRGs) in single pulse mode operation. This method extends the basic theory of the Stiebler model and utilizes the flux linkage function to express the inductance model of SRG. In this paper, the optimal phase current shape of SRG for maximum output power is investigated to determine optimal control variables based on phase current model. The expression of phase current in this paper that is in terms of control variables is solved using the basic equation of phase voltage based on inductance model, and then the characteristics of phase current and the energy conversion relations are analyzed to determine optimal shape of phase current. Furthermore, the expressions of phase flux linkage, rms phase current, and phase torque based on the proposed phase current model are presented in this paper to know the trend of main electrical losses. Results from analysis show that the switched reluctance generator with the optimal control variables can produce maximum output power and the shape of phase current in this case is flat top. Simulation and experimental results are presented to verify the proposed method. doi: 10.5829/idosi.ije.2016.29.04a.09

Sensor less Control of PMBLDC Motor Based on Speed Independent Position Function

This paper presents the methodology and implementation of a novel sensor less control technique for the permanent magnet brushless dc (PMBLDC) motor. In this new sensor less control technique, a novel flux linkage function is defined, which is speed independent. A physically insightful speed-independent function of flux linkage along with the combination of two differential equations governing the stator phase windings have been used for this purpose. The proposed new sensor less method solves the problem of sensor less PMBLDC motor at low speeds.

IPM Traction Machine With Single Layer Non-Overlapping Concentrated Windings

In this paper, an interior permanent-magnet traction drive machine with single layer non-overlapping concentrated stator winding is analyzed. In the single layer winding design, the number of stator slots and a winding factor are specifically considered. Moreover, the effect of varying the coil pitch on the winding factor and torque pulsations is investigated. A new calculation method is proposed, whereby the constant torque and field-weakening speed characteristics of the machine drive can be predicted using torque and flux linkage functions. The measured and predicted field-weakening performance of a 150-kW direct traction drive machine is presented.

Sensorless Control of the BLDC Motors From Near-Zero to High Speeds

This work presents the theory and implementation of a novel sensorless control technique for the brushless DC (BLDC) motor. The proposed new sensorless drive method solves the problem of the sensorless BLDC motor drives at very low speeds. It provides a highly accurate and robust sensorless operation from near zero to high speeds. For this purpose, an approach, a new flux linkage function is defined, that is speed-independent. The validity of the proposed method is verified through both simulation and experimental results and discussion.

Nonlinear modelling of switched reluctance motors using artificial intelligence techniques

This paper develops and compares different techniques for the modelling of a switched reluctance motor (SRM) in view of its nonlinear magnetisation characteristics due to the doubly salient structure. A complete range of models based on fuzzy logic, neuro-fuzzy and neural network approach is developed. All models are separately simulated and applied for nonlinear modelling, especially for finding the rotor angle positions at different currents, from a suitable measured data set for an associated SRM. The data comprised flux linkage, current and rotor position. All models are constructed to allow them to be modelled as a function of flux linkage against current with rotor position as an undetermined parameter. The models' evaluation results are compared with the measured values, and the error analyses are given to determine the performance of the developed models. The error analyses have shown great accuracy and successful modelling of SRMs using artificial intelligence techniques.

An analytical model of switched reluctance machines

An analytical model is introduced to describe switched reluctance machines (SRM). The nonlinear function of flux linkage depending on the winding current and rotor position is considered to be composed by three components: aligned and unaligned flux linkages, and an angular function, where the two flux linkages are only determined by phase current, and the angular function depends only on the rotor position. Examples of the application of this model in simulating the phase current, calculating the instantaneous torque and estimating the rotor position are presented. The results are compared with measurements.