Torque Control Part 7 pptx

Torque Control 110 Fig. 26. Adaptive stator fluxes estimator Fig. 27. 45(KW) motor behavior with the adaptive stator flux estimator Induction Motor Vector and Direct Torque Control Improvement during the Flux Weakening Phase 111 It is possible to combine the two previous estimators. The first one can be used for high speed, while the second estimator can be used for low speed range. In this case, there is no need to program the adaptive estimator of the stator fluxes, since it will not work during the flux weakening phase. 7. Conclusion This chapter has presented a full study of the magnetic state variation of the induction motor. Using a finite elements calculation program, it was possible to establish a two-phase model that takes into account the variation of the saturation level. A very simple resolution method of this new model was presented. The dynamic response of the new model was validated by comparing it to the dynamic response of the induction motor given by the finite element calculation program. After establishing the new model it was possible to review the advanced control laws like the FOC and the DTC laws. A new saturated FOC law was developed in order to enhance the dynamic behavior of the motor during the flux weakening phase, because of the difference between the motor cyclic inductances values and the values of the cyclic inductances introduced in the controllers. Concerning the DTC law, it was shown that a small error in the stator resistor value will highly influence the stator flux estimation, which is done using the stator electric equation. A new stator fluxes estimator was developed using rotor electric equations. This estimator is less sensitive to the motor temperature variation, but it is more sensitive to the variation of the saturation level. An adaptive solution was proposed to tune the estimator parameters according to the saturation level of the motor. Nevertheless the adaptive part added to the DTC algorithm, its computation time remains very small comparing to the FOC algorithm that takes into account the variation of the saturation level. It is important to mention that it is possible to combine the classical estimator and the new estimator according to the speed range. The classical estimator can be used at high speed, but at low speed, it is better to use the new stator flux estimator. 8. References Grotstollen, H. & Wiesing, J. (1995). Torque capability and control of saturated induction motor over a wide range of flux weakening, Transaction on Industrial Electronics, Vol. 42, No. 4, (August 1990) page numbers (374-381). Vas, P. & Alakula, M. (1990). Field oriented control of saturated induction motors, IEEE Transaction on Energy Conversion , Vol. 5, No. 1, (March 1990) page numbers (218- 224), ISSN 0885-8969. Kasmieh, T. & Lefevre, Y. (1998). Establishment of two-phase non-linear simulation model of the dynamic operation of the induction motor, EPJ European Physical Journal, Vol. 1, No. 1, (January 1998) page numbers (57-66). Vas, P. (1981). Generalized transient analysis of saturated a.c motors, Archiv fur Elektrotechnik , Vol. 64, No. 1-2, (June 1981) page numbers (57-62). Kasmieh, T. (2008). Adaptive stator flux estimator for the induction motor Direct Torque Control, Proceedings of SPEEDAM 2008, pp. 1239-1241, Ischia, June 2008, Italy. Torque Control 112 Blaschke, F. (1972). The principal of field orientation as applied to the new trans-vector closed-loop control system for rotating field machines, Siemens Review, (May (1972). Kasmieh, T.( 2002), Presentation of a powerful opened simulator for the saturated induction motor traction system, Proceedings of SPEEDAM 2002, (June 2002), pp. A1 24-A1 37, Ravello, June 2002, Italy. Noguchi, T. & Takahashi, I. (1984). Quick torque response control of an induction motor based on a new concept, IEEE Tech, Vol. RM84-76, (September 1984) page numbers (61-70). Depenbrock, M. & Steimel A.(1990). High power traction drives and convertors. Proc. of Elect. Drives Symp.’90 , pp. 1–9, Capri,1990, Italy. C.A, Martins.; T.A, Meynard.; X, Roboam. & A.S, Carvalho2. (1999). A predictive sampling scale model for direct torque control of the induction machine fed by multilevel voltage-source inverters. European Physical Journal-Applied Physics, AP. 5, (1999) page numbers (51-61). 5 Control of a Double Feed and Double Star Induction Machine Using Direct Torque Control Leila Benalia Department of electrical Engineering Batna University, Rue Chahid Med El Hadi boukhlouf Algeria 1. Introduction DTC is an excellent solution for general-purpose induction drives in very wide range The short sampling time required by the TC schemes makes them suited to a very fast torque and flux controlled drives as well the simplicity of the control algorithm. DTC is inherently a motion sensor less control method. 2. Objective of the work This chapter describes the control of doubly fed induction machine (DFIM) and the control of doubly star asynchronous machine (DSAM), using direct torque control (DTC). 3. Principe du control direct du couple Direct torque control is based on the flux orientation, using the instantaneous values of voltage vector. An inverter provides eight voltage vectors, among which two are zeros (Roys & Courtine, 1995), (Carlos et al., 2005). This vector are chosen from a switching table according to the flux and torque errors as well as the stator flux vector position. In this technique, we don’t need the rotor position in order to choose the voltage vector. This particularity defines the DTC as an adapted control technique of ac machines and is inherently a motion sensor less control method (Casdei et al., 2001), (Kouang-kyun et al., 2000). 4. Double feed induction machine (DFIM) In the training of high power as the rolling mill, there is a new and original solution using a double feed induction motor (DFIM). The stator is feed by a fixed network while the rotor by a variable supply which can be either a voltage or current source. The three phase induction motor with wound rotor is doubly fed when, as well as the stator windings being supplied with three phase power at an angular frequency s ω , the rotor windings are also fed with three phase power at a frequency rr ω . Torque Control 114 Under synchronous operating conditions, as shown in (Prescott & Alii., 1958), (Petersson., 2003) , the shaft turns at an angular velocity r ω , such that: rsrr ω ωω = + The sign on the right hand side is (+) when the phase sequences of the three phase supplies to the stator and rotor are in opposition and (-) when these supplies have the same phase sequence. The rotational velocity of the shaft, r ω , is expressed in electric radians per second, to normalize the number of poles. 4.1 Double feed induction machine modelling Using the frequently adopted assumptions, like sinusoid ally distributed air-gap flux density distribution and linear magnetic conditions and considering the stator voltages ( , ss vv α β ) and rotor voltages ( , rr vv α β ) as control inputs, the stator flux ( s , s α β ΦΦ), and the rotor current ( r , r ii α β ) as state variables. In the referential axis fixed in relation to the stator, the following electrical equations are deduced: 0 0 sss s sss s VI R d VI R dt α αα β ββ Φ ⎡ ⎤⎡⎤⎡⎤ ⎡⎤ =+ ⎢ ⎥⎢⎥⎢⎥ ⎢⎥ Φ ⎣⎦ ⎣ ⎦⎣⎦⎣⎦ (1) 00 00 rrrr r rrrr r VI R d VI R dt α αα α β ββ β ω ω ΦΦ ⎡ ⎤⎡⎤⎡⎤⎡⎤ ⎡⎤ ⎡⎤ =++ ⎢ ⎥⎢⎥⎢⎥⎢⎥ ⎢⎥ ⎢⎥ ΦΦ − ⎣⎦ ⎣⎦ ⎣ ⎦⎣⎦⎣⎦⎣⎦ (2) Expressions of fluxes are given by: sss r sss r rrr s rrr s lI MI lI MI lI MI lI MI α αα β ββ α αα β ββ Φ= + ⎧ ⎪ Φ= + ⎪ ⎨ Φ= + ⎪ ⎪ Φ= + ⎩ (3) The mathematical model is written as a set of equations of state, both for the electrical and mechanical parts: dX XAXBU dt • == + (4) Where: ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ Φ Φ = β α β α s s r r I I X and ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ = β α β α r r s s V V V V U (5) The matrices A and B are given by: Control of a Double Feed and Double Star Induction Machine Using Direct Torque Control 115 ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ − − −− − − − −−− = ss ss s r s r r s r s TT M TT M MTMT MMTT A 1 00 0 1 0 111 111 ' ' δ δ ω δ δ δ ω ω δ δ δ δ ω δ (6) B= ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ − − − − 0010 0001 1 0 1 0 0 1 0 1 δδ δ δδ δ r r LM LM (7) J d dt Ω =C em -C r -K f Ω. (8) Where J is the moment of inertia of the revolving parts, K f is the coefficient of viscous friction, arising from the bearings and the air flowing over the motor, and C r is the load couple. The equation of the electromagnetic torque is: 3 () 2 esrsr s pM CII L α ββα =Φ−Φ (9) The block diagram for the direct torque and flux control applied to the double feed induction motor is shown in figure 1.The stator flux Ψ ref and the torque C emref magnitudes are compared with respective estimated values and errors are processed through hysteresis- band controllers. Stator flux controller imposes the time duration of the active voltage vectors, which move the stator flux along the reference trajectory, and torque controller determinates the time duration of the zero voltage vectors, which keep the motor torque in the defined-by hysteresis tolerance band (Kouang-kyun et al.,2000), ( Xu & Cheng.,1995). Finally, in every sampling time the voltage vector selection block chooses the inverter switching state, which reduces the instantaneous flux and torque errors (Presada et al., 1998). 5. Simulation results machine Figure 2 refer in order, to the variation in magnitude of the following quantities, speed, flux and electromagnetic torque obtained while starting up the induction motor initially under no load then connecting the nominal load. During the starting up with no load the speed reaches rapidly its reference value without overtaking, however when the nominal load is applied a little overtaking is noticed and the command reject the disturbance. The excellent dynamic performance of torque and flux control is evident. Torque Control 116 DFIM PARK Transformation Estimated Stator flux Estimated electromagnetic Tor q ue ref φ 1 0 Switching Table c fl x ccpl _ + - S c S a S b U c i sa i sb βs i αs i αs V βs V βs i αs i β φ s α φ s sest φ emest C C emref 1 -1 0 Network 1 2 3 4 5 6 Load N Fig. 1. DTC applied to double feed induction machine 6. Robust control of the IP regulator a) Speed variation Figure 3 shows the simulation results obtained for a speed variation for the values: (Ω ref = 157, 100 and 157 rad/s), with the load of 3 N.m applied at t =0.8s. This results show that the variation lead to the variation in flux and the torque. The response of the system is positive, the speed follow its reference value while the torque return to its reference value with a little error. b) Speed reversal of rated value The excellent dynamic performance of torque control is evident in figure 4, which shows torque reversal for speed reversal of (157, -157 rad/s), with a load of 5N.m applied at t=1 s. The speed and torque response follow perfectly their reference values with the same response time. The reversal speed leads to a delay in the speed response, to a peak oscillation the current as well as a fall in the flux magnitude which stabilise at its reference value. Control of a Double Feed and Double Star Induction Machine Using Direct Torque Control 117 Angular speed (rad/s) Electromagnetic torque (N.m) Time (s)Time (s) Time (s) Stator flux( Wb) Fig. 2. Simulation results obtained with an IP regulator Angular speed (rad/s) Time (s) Electromagnetic torque (N.m) Time (s) Time (s) Stator flux( Wb) Fig. 3. Robust control for a speed variation Torque Control 118 Angular speed (rad/s) Time (s) Electromagnetic torque (N.m) Time (s) Time (s) Stator flux( Wb) Fig. 4. Robust control under reversal speed c) Robust control for load variation The simulation results obtained for a load variation (C r = 3 N.m, 6 N.m) in figure 5, show that the speed, the torque and the flux are inflated with this variation. Indeed the torque and the speed follow their reference values. Angular speed (rad/s) Time (s) Electromagnetic torque (N.m) Time (s) Time (s) Stator flux( Wb) Fig. 5. Robust control under load variation [...]... values We can see that the control is robust from the point of view load variation 124 Angular speed (rad/s) Electromagnetic torque (N.m) Torque Control Time (s) Stator flux( Wb) Time (s) Time (s) Angular speed (rad/s) Electromagnetic torque (N.m) Fig 10 Robust control for a speed variation Time (s) Stator flux( Wb) Time (s) Time (s) Fig 11 Robust control under load variation Control of a Double Feed... s α Estimated electromagnetic Torque Cemref Fig 8 DTC applied to double star induction machine Load Control of a Double Feed and Double Star Induction Machine Using Direct Torque Control 123 9 Simulation results Angular speed (rad/s) Electromagnetic torque (N.m) Figure 9 refer in order, to the variation in magnitude of the following quantities, speed, electromagnetic torque, current and flux obtained... 1 57 rad/s and a resistant torque of 5 N.m is applied at t= 1s Figure 6 shows the in order the torque response, the current, the stator flux and the speed The results indicate that the regulator is very sensitive to the resistance change which results in the influence on the torque and the stator flux Time (s) Stator flux( Wb) Time (s) Time (s) Fig 6 Robust control under stator resistance variation 7. .. direct control torque (DTC) using a PI regulator The simulation results show that the DTC is an excellent solution for general-purpose induction drives in a wide range of power The main features of DTC compared to the classical flux oriented control FOC can be summarized as follows: • DTC has a simple and a robust control structure • DTC operates with closed torque and flux loops but without current controllers... flux and the torque The response of the system is positive, the speed follow its reference value while the torque return to its reference value with a little error b) Robust control for load variation Figure.11 shows the simulation results obtained for a load variation (Cr = 5 N.m, 2.5 N.m) As can be seen the speed, the torque, the flux and current are influenced by this variation The torque and the... which must be 120 Torque Control strictly observed, leads to generate decoupled control with an optimal torque (Petersson., 2003) This is a maintenance free machine The machine studied is represented with two stars windings: As1Bs1Cs1 et As2Bs2Cs2 which are displaced by α = 30° and thee rotorical phases: Ar Br Cr B s2 B s1 A rRotor θ A s2 Br Star N°2 α Star N°1 A s1 C s1 C Cr Fig 7 Double star winding... Machine Using Direct Torque Control 125 c) Robust control of the regulator under star resistance variation Angular speed (rad/s) Electromagnetic torque (N.m) In order to verified the robustess of the regulator under motor parameters variations we carried out a test for a variation of 50% in the value of star resistance at time t= 1.5s The speed is fixed at 314 rad/s and a resistant torque of 5N.m is applied.. .Control of a Double Feed and Double Star Induction Machine Using Direct Torque Control 119 d) Robust control of the regulator under stator resistance variation Angular speed (rad/s) Electromagnetic torque (N.m) In order to verified the robustess of the regulator under motor parameters variations we... torque estimation and, therefore, is not sensitive to rotor parameters • DTC is inherently a motion sensor less control method The simulation results show that the DTC is an excellent solution for general-purpose induction drives in a very wide power range The short sampling time required by the DTC scheme makes it suited to very fast torque and flux controlled drives beside the simplicity of the control. .. (2005) Novel direct torque control for induction motors using schort voltage vectors of matrix converters IEEE Trans.ind.Appl, pp 1353- 1358, 2005 Casdei.D, Serra.G, Tani.A,.( 2001) The use of matrix converters in direct torque control of induction machines IEEE Trans.on Industrial Electronics, Vol 48,N 6, Hadiouche D, H.Razik, A.Rezzoug.(2000) Stady and simulation of space vector PWM control of Double-Star . performance of torque control is evident in figure 4, which shows torque reversal for speed reversal of (1 57, -1 57 rad/s), with a load of 5N.m applied at t=1 s. The speed and torque response. for the induction motor Direct Torque Control, Proceedings of SPEEDAM 2008, pp. 1239-1241, Ischia, June 2008, Italy. Torque Control 112 Blaschke, F. (1 972 ). The principal of field orientation. chapter describes the control of doubly fed induction machine (DFIM) and the control of doubly star asynchronous machine (DSAM), using direct torque control (DTC). 3. Principe du control direct du