C3-6
Parameter Identification of IPM Motor
Focusing on Current NormJi Xiang, Toshihiko Noguchi (Shizuoka University)
1. Introduction

Table 1. Parameters of IPMSM.

Number of poles
Winding resistance
Rated output power
Rated rotation speed
Damping coefficient
q-axis inductanceRange of q-axis inductanced-axis inductance
Setup d-axis inductanceField flux linkage
Setup field flux linkage
Rotation speed

This paper proposes a new approach to identify the q-axis
inductance Lq of an interior permanent magnet synchronous motor(IPMSM) focusing on the current norm characteristic. The current
norm depends on the mismatch of Lq, and the minimum or themaximum value of the current norm is obtained when the parameteris properly tuned. Using a simple method to search the minimum
point of the current norm, it is possible to achieve the off-line
parameter identification. This paper describes an improved
technique to identify Lq of the motor, which introduces a P
controller and a PI controller to the current loop of the field-orientedcontroller. The current norm characteristic is examined through1sLd + Rid∗

computer simulations and experimental tests.

2. Identification System
Fig.1 presents the proposed Lq identification technique. This^

identification system tunes Lq in the decoupling controller. The Pcontroller with a small gain is employed in the d-axis loop to get the^current variation caused by the mismatch between Lq and Lq. On theωL̂q

ωLq

ωL̂d

ωLdωψ̂

ψ

^

1.635

response:
Lq

(1)
(2)

Setting id* = 0 , id , iq andthe current norm can be obtained asfollows:i q* K q (1 + sτ q )ω ( Lq − Lˆ q )(3)( K q + R)( K d + R )τ q s

1.620

Speed unstable

1.615
0.020

0.025

0.030

0.035

0.040

Lq (mH)(4)( K q + R )( K d + R )τ q s

i n = i d2 + i q2 =

1.625

0.015

i q* K q (1 + sτ q )( R + K d )i q* K q (1 + τ q s )1.630
in (A)

R
K q = ω cq L q

iq =

ω

Theoretical result
Experimental result

following time constant and loop gain to obtain the optimum

id =iqFig. 1. Proposed Lq identification technique.

interference by the unidentified Ld and Ψ. The PI controller has theτq =id

1sLq + Riq∗

other hand, the PI control is used in the q-axis loop to reduce^

60.48 Ω
1.5 kW
3000 r/min
0.00019 Ns/rad
24.5 mH
22.5mH~36.0mH
13.0 mH
10.0 mH
0.06737 Wb
0.0 Wb320 r/minω ( Lq − Lˆ q ) + ( R + K d )222(5)( K q + R)( K d + R )τ q s

From (5), it is found that the current norm is varied by the^mismatch between L q and Lq. The current norm has a convex^

parabola characteristic and has the minimum value when Lq=Lq.

3. Simulation and Experimental Results

Fig. 2. Current norm characteristics with respect to Lq mismatch.

4. Conclusion
The current norm characteristic with respect to Lq mismatch has
been confirmed. The experimental and simulation results show thatthe identification of Lq can be achieved by using the current norm
characteristic.
References

The proposed technique is tested through computer simulations(1) Ji Xiang and T. Noguchi, “Off-Line Parameter Identification of Permanent Magnet

using PSIM software and experimental tests with a real IPMSM

Synchronous Motor Based on Current Norm,” IEEJ IAS Conference Proceedings No.

shown in the Table1. It can be seen in Fig. 2 that when the speed is

3,70, pp. 315-318, Aug. 2012(in Japanese).

stable and L q is equal to a real value of Lq, the current norm(2) Ji Xiang and T. Noguchi, “Offline Identification of q-axis Inductance in Interior^^

becomes the minimum. While the mismatch between Lq and Lq isobserved, the current norm is greater than the minimum value.

Permanent Magnet Synchronous Motor Based on Relationship between Its Parameter
Mismatch and Current Norm,” IEEJ Conference Proceedings No. 4,129, pp. 225-226,
Mar. 2013(in Japanese).

平成25年度 電気関係学会東海支部連合大会（2013年9月24日325日 於静岡大学 浜松キャンパス）