Design and analysis of a cost-effective magnetless multi-phase flux-reversal DC field machine for wind power generation. Theoretical characterization of flux reversing machine in low speed servo drives - the pole PM configuration.
Introduction
It is found that the performance of the proposed predictive DTC strategy for DFIM is quite good compared to classical DTC strategy. This control technique is based on a prediction of the torque and flux development by the DFIM.
Contributions and novelty
Therefore, the new Predictive DTC (PDTC) strategy presented in this paper is based on the direct control of the electromagnetic torque and flux of the machine rotor. The control strategy even minimizes the switching losses of the converter and reduces electromagnetic torque and current ripple at low switching frequency even under variable speed operating conditions.
Modeling of DFIM
Section 4 explains the basic control principle of predictive DTC and also describes the implementation of DFIM's proposed predictive DTC strategy, along with the selection of rotor voltage vectors for constant switching frequency and reduction of switching power losses. The transient solution of the DFIM model is possible because of the transformation from abc to qd0 that converts the differential equations with time-varying inductances into differential equations with constant inductances.
Description of proposed predictive direct torque control strategy for torque and flux ripple minimization
- Effect of voltage vector on the DFIM
- Selection of first rotor voltage vector
- Selection of second and third vector rotor voltage vector
- Reduction of switching power losses
The first vector is selected depending on the errors in torque and flux and the sector where the rotor flux lies, the vector selection lookup table is shown in Table 1. These two active vectors along with zero vectors are useful for controlling torque and rotor flux.
Results and discussion
Transient and steady state analysis of DFIM
From the Figure 3(a), it is observed that there are no overcurrents in the stator, which indicates the effectiveness of the proposed control scheme even with sudden variation in torque demand. From the Figure 3(g), it is observed that there are no overflow currents in rotor, which indicates the effectiveness of the proposed control scheme, even with sudden variation in torque demand.
Performance analysis of DFIM during variable torque behavior
From Figure 4(c) and (d), it is observed that the change in torque command has no effect on the stator and rotor fluxes of the DFIM. From Figure 4(f), it is observed that there is a continuous increase and decrease in the amplitude of the rotor currents, similar to the stator currents as shown in Figure 4(a).
Performance of DFIM near synchronous speed
The predictive DTC strategy has good tracking and it is confirmed that torque and current ripple reduction is achieved as there is no absolute absence of overcurrents and reduced ripples in the rotor currents as shown in Figure 4(f). It can be seen from the figure that the stator current remains constant and is not affected by the change in rotor speed, and it is also sinusoidal in nature. The rotor flux response is shown in Figure 5(d), from the figure it can be seen that a sudden change in the rotor speed does not affect the rotor flux and the switching does not affect the rotor current either.
The rotor speed response is as shown in Figure 5(e), when the reference speed is varied from hypersynchronous value to subsynchronous value and the rotor speed response of DFIM is observed to follow the command speed.
Conclusions
Similar to stator currents as shown in Figure 5(a), there are not many transient peaks in rotor currents, as shown in Figure 5(f), that is, there is reduction in overcurrents in the rotor, which is the result of the proper selection of switching sequence of rotor voltage vectors. Similar to stator currents as shown in Figure 5(a), there are not many transient peaks in rotor currents, as shown in Figure 5(f), that is, there is reduction in overcurrents in the rotor, which is the result of the proper selection of switching sequence of rotor voltage vectors. Second, it is crucial to achieve the overall good performance of the DFIM, in terms of torque and current ripples, by reducing the ripples of both directly controlled variables instead of just one. a) Response of stator currents of DFIM with variation in rotor speed from 1580 to 1340 rpm.
Torque response of DFIM with rotor speed variation from 1580 to 1340 rpm (i) proposed strategy and (ii) classical DTC.
Summary
The simulation results showed the effectiveness of the proposed method for DFIM torque and flux control at a rather low constant switching frequency. Predictive direct power control of a doubly fed induction machine with reduced power ripple at low constant switching frequency. In this chapter, we studied the theoretical background of using a screw working body in front of a planer bucket and the execution of experiments in laboratory conditions with the proposed working body.
Keywords: screw working body productivity, planning unit translation speed, screw pitch, screw diameter, drawing prisms.
Literature review
Through world and domestic agricultural practices, it has been proven that planning or leveling the surface of the fields is the primary land reclamation measure. Experiments have established that under conditions of turbulent terrain, crop loss amounts to 40% of the potential crop. In the United States, much attention is paid to the planning of the surface of irrigated areas.
Annually, in this country, approximately more than half of the irrigated areas are subject to planning [3, 6, 7].
Research methods
Selection and justification of the main parameters of the screw
3 m/sec.; andКаis the coefficient that takes into account the inclination of the cutting edge of the screw,Кa= l1ш/dш= 0.7…1.0. The working speed of the soil movement with the auger should be equal to the speed of filling the planer bucket with soil. For our case, with some accuracy, we can takeϑгр=ϑков=ϑп, whereϑгр is the speed of the ground movement with the screw,ϑков.
0.4; andКβis the coefficient taking into account the angle of inclination of the propeller relative to the horizonβш,Кβ.
Results and discussion
Figure 5 below shows the location of the screws in the planer bucket. The variation of screw performance as a function (Ds) of screw diameter is shown in Figure 8. The increase in productivity of the screw working element due to the increase in screw pitch reduces screw metal consumption and.
Furthermore, further increase in the diameter of the screw causes problems in their layout in the bucket of the planner.
Types of induction motor
Advanced control techniques, such as terrain-oriented control and direct torque control, play a key role in today's high-performance AC drives. Later in the 1980s, Takahashi and Depenbrock [1, 2] proposed the direct torque control (DTC) method. Ben Salem and Derbel [3] proposed direct torque control of induction motors based on discrete space vector modulation using adaptive sliding mode control, the results show the efficiency and robustness of DTC-discrete adaptive sliding mode control of SVM induction motors.
The advantages of this direct torque control method are improved efficiency and fast response of torque in dynamic conditions [6, 7].
Classification of IM control strategies
Scalar control
The variations of induction motor parameters are shown by Ben Salem and Derbel in their next two publications, respectively Performance Analysis of DTC-SVM Sliding Mode Controllers-Based on Estimator of Electric Motor Speed Drive [4], and DTC-SVM Based Sliding Mode Controllers with Load Torque Estimators for Induction Motor Drives [5]. The general classification of IM control strategies [8, 9] that are based on the variable frequency control is shown in figure 4. It can adjust the speed of induction motor by controlling the amplitude and frequency of induction motor stator voltage, the ratio of stator voltage and frequency should be kept constant, so it is referred to as V/F control of induction motor drive.
Voltage/current/frequency sizing is based on the steady state equivalent circuit model, which ignores transient conditions.
Vector control methods
The vector diagram for IM is shown in Figure 5. From the motor voltage Eq. 5) for the omitted voltage drop on the stator resistance, the stator flux can be expressed. It can be seen from Eq. 7) that the stator flux directly depends on the inverter voltage Eq. The stator flux does not change when one of the zero vectors U0 or U7 is used.
The appropriate voltage vector from the switching table is selected by the digitized output variables dΨ, dM and the stator flux position sectorγssð Þ. The circuit breakers in the inverter are controlled by the pulses SN A, SB, SC generated from the switching table.
Modified DTC
- SVM-DTC
In the DTC-SVM methods, control algorithm calculations are based on average values, whereas the switching signals for the inverter are calculated by space vector modulator. Space Vector PWM (SVPWM) is a technique used to solve the switching losses in the power converter. The following figure 17 shows the structure of neural network (NN) which is used in the proposed ANN controller for DTC-SVM scheme for induction motor.
Torque ripple factor¼ðPeak to peak torqueÞ=Rated torque (16) FLC simulation results for DTC-SVM IM with HASVPWM are shown in Figures 18 and 19. ANN simulation results for DTC-SVM IM with.
Modern strategies of DTC 1 Fuzzy logic control (FLC)
Artificial neural network (ANN)
So by using FLC and ANN based controller for DTC or IM, the ripples are completely reduced. It includes both minimizing torque ripples and improving IM dynamic performance. The inverter switching state is a sharp value obtained as an output from the FLC [11].
For electric vehicle applications, the FLC and ANN based monitoring systems for the DTC controlled induction motor drive were implemented to detect a very small change in performance parameters [23].
Appendices
Appendix 1: parameters of 3 phase squirrel cage induction motor
Reduction of torque ripple in direct rotation control of induction motors by improving the shift table. Fast Dynamic Torque Control in DTC-Hysteresis Based Induction Motor Using New Optimized Switching Strategy. 15]RK.Behra, SP.Das Improved direct torque control of induction motor with dither injection, Sadhana; Vol.
Modern improvement techniques of direct torque control for induction motor drives - An overview, protection and control of modern power systems.
