4-032

平成 27 年電気学会全国大会

Online q-axis Inductance Identification of IPM Synchronous Motor
Based on Relationship between Its Parameter Mismatch and Current NormJi Xiang*, Toshihiko Noguchi (Shizuoka University)
This paper proposes a new approach to achieve on-line identification of the q-axis inductance of the interior permanent
magnet synchronous motor (IPMSM) based on the relationship between the mismatch of Lq and the d-axis feedback current.
The value of the d-axis feedback current depends on the mismatch of Lq, and the consecutive samplings of the d-axis feedback
current make it possible to calculate the true value of Lq. The proposed identification technique is examined through somecomputer simulations.

The simulation result demonstrates the fast convergence of the identified value to the true one with asmall error.
Keywords：interior permanent magnet synchronous motor, online, parameter, identification, P control, PI control

1. Introduction
In recent years, interior permanent magnet (IPM) motors arewidely used in a variety of industry, home appliance andid∗

automotive applications, owing to their high-efficiency andhigh-power-density features.

1sLd + R

The IPM motor is usuallycontrolled by means of a field-orientation technique (vectorω L̂ qωLqcontrol), and requires a current controller on the synchronous

ωL̂d

ωLd

rotating

referenceframe(dq-reference-frame)

instantaneous torque and the magnetic flux control.

forthe1sLq + R

ω*The current

idcontrol on the dq-reference-frame mainly consists of theiqψω

coordinate transformation, the PI regulation, and the decoupling
compensation, which is based on the mathematical model of theωFig. 1. Field-oriented control system of IPM motor.

motor. Figure 1 shows the field-oriented control system of theIPM motor. As can be seen in the figure, it is indispensable forid∗+P

the controller not only to detect the magnetic-pole-position and+-1sLd + R++

the motor currents, but also to know the motor parameters

ω L̂q

ωLq

accurately because the controller has an inverse model of theωL̂dωLdmotor.

Identification of the motor parameters is significantlyω*

important to control the motor properly in starting up of the++PIPI-control as well as the running operation, and the on-line+++--id

1sLq + Riqψωω

parameter identification is particularly required during therunning condition.

This paper proposes a novel technique to(a) Proposed Lq identification system.

achieve the on-line identification of the IPM motor parameters,
which requires only the d-axis feedback current information ofthe motor.

1sLd + Rid∗

The proposed technique employs a P regulator

ωLˆqinstead of the PI regulator in the d-axis current control loop.

idωLq

Using this technique Lq can be estimated by checking the d-axis
feedback current when the motor is working in the steady state.

ω*Some computer simulations have been conducted to check the1sLq + Riqψωω

identification performance of the proposed technique in thepaper.

(b) Simplified Lq identification system.

Fig. 2. Online Lq identification system.

2015/3/24～26 東京-47( 第 4 分冊 )1／2

©2015 IEE Japan

4-032

平成 27 年電気学会全国大会

Table 1. Parameters of test IPMSM.
4
Number of poles
Winding resistance
4.3 Ω
Gain of d-axis P regulator
1 V/Aq-axis inductance
67 mHd-axis inductance
27 mH
Setup d-axis inductance
1.0 mH
Field flux linkage
0.544 Wb
Setup field flux linkage
1.0 WbRotation speed
6000 r/min

Id

P1

Id1
P2

Id2

0

Lq1

Lq2

LqL̂q

Fig. 3. Lq identification description.

2. Proposed Identification Technique

Id1

Id2

Figure 2(a) shows the proposed Lq identification system. In thesystem, the PI regulator used in the d-axis current control loop isreplaced with a P regulator. Because the P regulator is unable toLq1

Lq2

Lqeliminate the steady-state error, the mismatch of Lq affects thed-axis feedback current. Figure 2(b) shows the simplified Lq

I q*

Iq

identification system. From Fig. 2(b), the rotation speed is equal
to its command, and the q-axis current is stable when the motor isoperated in the steady state because both of the controllers consist

ω*of the PI regulators. By setting the d-axis current command at

ωzero, the d-axis feedback current can be expressed asId =ωI q
K pd + R( Lq − Lˆ q ) .

Fig. 4. Simulation result of Lq identification.

(1)

From (1), it is found that the mismatch of Lq has a linear

shows the test motor parameters which are used in therelationship with the d-axis feedback current Id when thesimulations.

command of the d-axis current is set at zero. Based on this linear

One of the simulation results is shown in Fig. 4. The rotation

characteristic, it is possible to estimate the true value of Lq. As

speed and the q-axis current are controlled to be equal to theirshown in Fig. 3. The basic mathematic knowledge tells that if twocommands. As L̂q of the controller changes from Lq1 to Lq2 andpoints on the line is known the whole equation of the line isknown.

so on, the d-axis feedback current also accordingly changes. The

By setting two different values of Lq to the system, which may

final identification result is 66.48 mH, where the true value is 67

have the parameter mismatch, two corresponding d-axis feedback

mH. The identification error is 0.78%, and the convergence timecurrent values are recorded in the memory. Assuming that thefor the identification is only 0.08 s.

following consecutive sampling actions are performed:

4. Conclusion

Id = Id1 when Lˆ q = Lq1 , andThe online parameter identification technique of the IPM
motor has been proposed in this paper. The most unique features

Id = Id2 when Lˆ q = Lq 2 ,of the technique are capability to identify Lq by using only thethe true value of Lq can be calculated by the following equation:

Lq =I d 1 Lq 2 − I d 2 Lq1
I d1 − I d 2

motor d-axis feedback current information, and robustness to thewinding resistance variation as well as the control variables.

.

(2)

According to the simulation result, the proposed technique canestimate Lq within the identification error of 0.78%.

Equation (2) implies that the true value of Lq can be calculated
regardless of any parameters and any variables used in (1).

Reference

Therefore, the proposed identification technique requires only the(1)d-axis feedback current information to estimate Lq.

3. Simulation Result
Some computer simulations have been conducted to verify theXiang Ji・Toshihiko Noguchi：「Off-line Parameter Identification ofInterior Permanent Magnet Motor by Searching Minimum Pointof Current Norm Characteristics 」 International Symposium on
Power Electronics, Electrical Drivers, Automation and Motion pp.
282-287(2014)

identification performance of the proposed technique. Table 1

2015/3/24～26 東京-48( 第 4 分冊 )2／2

©2015 IEE Japan