Direct locating method for calculating position of permanent magnet synchronous motor
A direct locating method for calculating a position of a permanent magnet synchronous motor is provided. The direct locating method performed by a processor includes: three-phase stator currents of the permanent magnet synchronous motor are converted by coordinate to obtain the stator currents in the αβ two-phase stationary coordinate system, and the initial position region is determined. The stator currents in dq two-phase synchronous rotating coordinate system are obtained by coordinate conversion. The stator current cost model is established. Then the d-axis stator current is inputted into the cost model and the position is outputted, and the final estimated position is determined to realize the direct locating of the permanent magnet synchronous motor's position.
1 . A direct locating method for calculating a position of a permanent magnet synchronous motor (PMSM), comprising the following steps performed by a processor:
step 1: converting three-phase stator currents of the PMSM sampled at each period to obtain the stator currents in αβ two-phase stationary coordinate system, and determining an initial position region of the PMSM according to the stator currents in the αβ two-phase stationary coordinate system;
step 2: converting the stator currents of the PMSM in the αβ two-phase stationary coordinate system to obtain the stator current of the PMSM in the dq two-phase synchronous rotation coordinate system;
step 3: establishing the stator current cost model of the permanent magnet synchronous motor, and inputting the d-axis stator current of the permanent magnet synchronous motor in the dq two-phase synchronous rotation coordinate system into the stator current cost model and then the position of the permanent magnet synchronous motor is outputted; at the same time, determining a final estimated position from the initial position region of the PMSM according to the stator currents of PMSM in the αβ two-phase stationary coordinate system and dq two-phase synchronous rotation coordinate system, and the direct locating of the PMSM position is realized,
wherein in step 3, the stator current cost model of the permanent magnet synchronous motor is established as follows:
min
g
op
(
k
)
=
❘
"\[LeftBracketingBar]"
i
dref
(
k
)
-
i
d
(
k
)
❘
"\[RightBracketingBar]"
i
d
(
k
)
=
A
sin
(
θ
+
φ
k
)
i
q
(
k
)
=
A
sin
(
θ
+
φ
k
+
π
/
2
)
where g op (k) is the d-axis stator current error of the permanent magnet synchronous motor at the kth sampling period in the dq two-phase synchronous rotation coordinate system;
i dref (k) is the d-axis stator current reference of the permanent magnet synchronous motor at the kth sampling period in the dq two-phase synchronous rotation coordinate system;
i d (k) and i q (k) are the d-axis stator current and q-axis stator current of a permanent magnet synchronous motor in dq two-phase synchronous rotation coordinate system at the kth sampling period, respectively;
θ is the position of the permanent magnet synchronous motor;
A is the stator current amplitude of the permanent magnet synchronous motor;
φ k is the Angle between the stator current of the permanent magnet synchronous motor and the αβ two-phase stationary coordinate system at the kth sampling period,
wherein an angle between the stator current of the permanent magnet synchronous motor and the αβ two-phase stationary coordinate system at the kth sampling period, φ k , is as follows:
φ
k
=
arc
tan
(
i
α
(
k
)
/
i
β
(
k
)
)
where i α (k) and i β (k) are the α-axis stator current and β-axis stator current of the permanent magnet synchronous motor in the αβ two-phase stationary coordinate system at the kth sampling period, respectively,
wherein in step 3, according to the stator currents of the permanent magnet synchronous motor in the αβ two-phase stationary coordinate system and dq two-phase synchronous rotating coordinate system, the final estimated position is determined in the initial position region of the permanent magnet synchronous motor, as follows:
Region
i α
i β
i q
θ o1
R1
+
+
+
2π-φ k
−
π-φ k
R2
−
+
+
2π-φ k
−
3π-φ k
R3
−
−
+
2π-φ k
−
3π-φ k
R4
+
−
+
2π-φ k
−
π-φ k
where θ o1 is the final estimated position of the permanent magnet synchronous motor in the initial rotor position region.
2 . The direct locating method according to claim 1 , wherein in step 1, the three-phase stator currents of the PMSM sampled at each period are converted by coordinate to obtain the stator currents of the PMSM in the αβ two-phase stationary coordinate system, wherein a A-phase stator current i a , a B-phase stator current i b and a C-phase stator current i c of the PMSM are converted to obtain the α-axis stator current i α and β-axis stator current i β in the αβ two-phase stationary coordinate system, respectively.
3 . The direct locating method according to claim 2 , wherein in step 1, the initial position region of the PMSM's position is determined according to the stator currents of the PMSM in the αβ two-phase stationary coordinate system,
wherein when i α (k)>0 and i β (k)>0, the initial position region is R1, [0, 0.5π];
when i α (k)<0 and i β (k)>0, the initial position region is R2, [0.5π, π];
\when i α (k)<0 and i β (k)<0, the initial position region is R3, [π, 1.5π];
when i α (k)>0 and i β (k)<0, the initial position region is R4, [1.5π, 2π];
wherein i α (k) and i β (k) are the α-axis stator current and β-axis stator current of a permanent magnet synchronous motor in the αβ two-phase stationary coordinate system at the kth sampling period, respectively.
4 . The direct locating method according to the claim 2 , wherein in step 2, the stator currents of the permanent magnet synchronous motor in the αβ two-phase stationary coordinate system are converted to obtain the stator currents of the permanent magnet synchronous motor in the dq two-phase synchronous rotating coordinate system, wherein the α-axis stator current i a and β-axis stator current i β in the αβ two-phase stationary coordinate system of the permanent magnet synchronous motor are converted by coordinate transformation to obtain the d-axis stator current i d and q-axis stator current i q in the dq two-phase synchronous rotation coordinate system.