maximum efficiency drives of interior permanent magnet synchronous motor considering iron loss and cross-magnetic saturation

1、 Maximum Efficiency Drives of Interior Permanent Magnet Synchronous Motor Considering Iron Loss and Cross-Magnetic SaturationAbstract-- This paper covers the proposed method to maximize the driving efficiency for int

2、erior permanent magnet synchronous motors considering iron loss and cross- magnetic saturation effects. Using a simple repetition calculation method, the proposed method automatically determines the optimum current co

3、mmand in real-time. This method not only maximizes the driving efficiency but also realizes high-precision torque control performance. The validity of this method is verified from experimental results. Index Term -- I

4、ron loss, magnetic saturation, maximum efficiency drive, optimum current command, torque control performance. I. INTRODUCTION Energy conservation is the primary goal and general objective of our latest research devel

5、opment in the field of electrical machines and system. From the perspective view of effective and efficient utilization of electrical energy, an essential technological issue to consider is to drive the machine at it

6、s maximum efficiency. Permanent Magnet Synchronous Motors (PMSM) are widely used in hybrid electronic vehicles, robotics, servo system, and other high-performance industry applications. Maximum efficiency drives of

7、 PMSM can be realized by the loss minimization control strategies. Loss minimization controllers of IPMSMs are roughly divided into search controllers and loss-model based controllers. The former is the search contro

8、l algorithm method [1]-[3] where the current command vector is generated so that input power is minimized. In this method, motor constants are unnecessary but the pulsation is superimposed to the d- and q-axis

9、currents during steady- state conditions. On the other hand, the latter which is the loss-model control method [4]-[9] utilizes motor constants in the generation of the current command vector. This method is superior

10、with regard to control stability and current pulsation reduction that’s why it is more often used in industrial drive systems. The latter method is generally classified into the off- line and the on-line methods. In t

11、he off-line method, the current reference signal corresponding to each speed and torque that minimizes loss is calculated beforehand, and stored in the memory table of the Digital Signal Processor (DSP) to be used fo

12、r vector control. In the on- line method, the current command vector that achieves minimum loss is automatically calculated in real time in the DSP while it carries out control operations. The off-line method has the

13、 advantage of being able to use a concise algorithm, however preparation of the table data is somewhat a time-consuming effort. The on-line method’s control algorithm is more complex but does not have the above-menti

14、oned weak points of the off-line method. In the on-line method, an often employed technique for generating the current command vector is to use the minimum loss conditional expression derived from partial differentia

15、tion of the motor electrical loss equation with respect to the d-axis current [4]-[6]. However in some IPMSMs, the inductance change caused by cross magnetization must be considered because it is necessary to accurat

16、ely evaluate motor characteristics including the efficiency. In this case, a direct derivation of the conditional expression that considers minimum loss is extremely difficult because this expression is complicated.

17、In other approach, a method that generates d- and q-axis current commands using a search algorithm employing the bisection method is described in [9]. However, magnetic saturation and iron loss are not considered, an

18、d linearity of torque control is not achieved. Thus, this paper presents a new loss-minimization vector-control method which can be applied to IPMSM having cross-magnetic saturation effect, and improves previous met

19、hods [10]-[12] to achieve real-time optimum current reference signal generation considering both iron loss and cross-magnetic saturation. The proposed method generates optimum d- and q-axis current commands by employ

20、ing a real-time current lead angle calculation algorithm utilizing a simple repetition calculation method. The proposed method can not only maximize the driving efficiency but also realize the high-precision and ac

21、curate torque control performance that considers both iron loss and cross-magnetic saturation. Experimental results of maximum-efficiency control on a 0.4kW-4P- 1800(r/min) IPMSM with concentrated windings demonst

22、rate the validity of the proposed method. II. D- AND Q-AXIS INDUCTANCES OF THE TESTED MACHINE The tested machine in this study is a concentrated- winding IPMSM (0.4-kW, 1800-min-1, 4-poles, 6-slots). John B. Adawey, Shu

23、 Yamamoto, Takashi Kano, and Takahiro Ara Department of Electrical Engineering, Polytechnic University, Sagamihara, Kanagawa, Japan most IPMSMs, 0 tan ) ( 4 > ? ? ? T L L p q d β , ....................................

24、.... (5) and T L L p K p pK q d e e ? ? ? 0 and imq must be positive, (4) can be rewritten as, ββtan ) ( 2tan ) ( 4 2 2q dq d e e mq L L pT L L p K p pK i ? ?? ? ? + ? =........... (7) B. Generation of the Optimum Curr

25、ent Command Vector In this research, the authors propose a maximum- efficiency vector control that minimizes electrical loss by utilizing (8). Fig. 5 is the PMSM vector-control system diagram with the proposed optim

26、um current command vector generator block. The output of this generator block is the calculated optimum current command id *and iq * taking iron loss and magnetic saturation into account. PIωre * T*PIiq *id * PI3αβ dq

27、αβ3αβ dqαβωreLqiq (+)(－)ωre(Ldid+Ke) (+)(+)idiq(+)(－)(+)(－)(+)(－)Compensator of ACRLqLdiwiuvu *vv *vw *θreωreOptimum current command vector generator blockLd_TBL(id,iq) Lq_TBL(id,iq)ωre *Fig. 5. Diagram of vector cont

28、rol system of PMSM showing the proposed controller block. Fig. 6 shows the internal structure of the optimum current command vector generator block. In this figure, the authors use the repetition expression, ) ( tan

29、)) ( ) ( ( 2) ( ) ( tan )) () ( ( 4) 1 ( ) ( ) ( ) (* ) ( ) () ( 2 2) (n n L n L pn T n n Ln L p K p pKn i m m q m dm m qm d e em mq ββ? ? ?? ?? ? + ?= + , ... (8) derived from (7). Where n expresses the number of sampl

30、e point of torque command T* in every new cycle. Using (8), the values of ) (m md i satisfying the prescribed β(m) for the same torque command T* are solved by repetition calculation. That is, from the minimum value ?

31、β(βmin) up to the maximum value (βmax), the imq values with respect to the values of β are respectively calculated in each new torque command T*. Using the measurement results of Ld(id, iq) and Lq(id, iq) [13], the ) (

32、 ) ( n L m dand ) ( ) ( n L m qin (8) are calculated from a two-dimensional function table (Ld_TBL(id,iq) and Lq_TBL(id,iq)) with linear interpolation as follows. ( ) ) ( ), ( ) ( ) ( ) ( _ ) ( n i n i L n L m mq m md

33、 TBL d m d =................................ (9) ( ) ) ( ), ( ) ( ) ( ) ( _ ) ( n i n i L n L m mq m mq TBL q m q =.............................. (10) The order of the calculation operation of the proposed generation bl

34、ock is shown in Fig. 7 where in imd, id, iq and Wloss in each β(m) are respectively calculated. The equations are as follows. ) ( tan ) ( ) ( ) ( ) ( ) ( n n i n i m m mq m md β ? ? =..................................

35、(11) ( ) ) ( ) ( ) ( ) ( / m mq c m q re m md m d i R L i i ω ? = , .................................. (12) ( ) c e re m md c m d re m mq m q R K i R L i i / / ) ( ) ( ) ( ) ( ω ω + + =.................. (13) Calculating

36、 the power loss ) (m loss W , we have, ( ) ( ) 2 ) ( ) ( 2 ) ( ) ( 2 ) ( 2 ) ( ) ( ) ( ) ( ) ( ) ( m mq m q m md m d c m q m d a m loss i i i i R i i R W ? + ? + + =.......................................................

37、........................ (14) β(m)imqEq. (8)T* imdWlossEq. (11)Eq. (12)Eq. (13)ωre *id *(m)(m)(m)iq *Eq. (12)imd *imq *Eq. (13) β(1)1/(p(Ld-Lq)imd *+pKe)i md 0W lossi md* Eq. (14)Fig. 6. Internal structure of the propos

38、ed optimum current command vector generator block. In here, the current controller period is 0.1ms and the speed controller period is 1ms. In the controller, the number of partitions m is set to 9 where β is assigned t

39、o each m. In other words, nine values for current lead angle β(1), β(2), β(3)…,β(9) were respectively assigned the values of 1, 10, 20, … , 80 electrical degrees to nine partition of m. Since the number of current co

40、ntrol interruptions generated in one speed control period (1ms) is 10, ) 1 ( md i , ) 2 ( md i , … ,) 9 ( md iare respectively calculated using (8) for the 1st to 9th current control interruption. Finally、at the 10th

41、current control interruption id * is renewed based on (15). Fig. 8 shows the curve of Wloss in the vicinity of three points of m (m1=mmin - 1, m2=mmin, and m3=mmin + 1, where Wloss is a minimal at m=mmin,) is express