Position sensorless drive for permanent magnet synchronous motors
View Patent ↗A sensorless motor control algorithm that single-handedly permits operation over the entire speed range from low speed to high speed. This “fusion” algorithm seamlessly fuses the position data generated respectively by high speed and low speed sensorless algorithms. The resulting sensorless drive permits effective position sensorless operation over the entire speed range of a PM motor.
1. A position sensorless drive for PM synchronous motors, comprising:
drive circuits operable for driving a PM synchronous motor; and
a control module which receives voltage and current information from said PM synchronous motor, determines a rotor position of said PM motor, and generates control signals which control said drive circuits on the basis of said rotor position at zero, low and high motor speeds,
wherein for relatively low speeds, said control module derives said rotor position on the basis of rotor inductance variations, and
wherein said inductance variations are determined according to:
V
d
r
=
R
i
d
r
+
L
ⅆ
ⅆ
t
i
d
r
-
L
ω
m
i
q
r
(
1
)
V
q
r
=
R
i
q
r
+
L
ⅆ
ⅆ
t
i
q
r
-
Δ
L
r
ⅆ
ⅆ
t
i
q
r
+
L
ω
m
i
d
r
+
λ
r
ω
m
(
2
)
Where:
V d r and V q r are the direct and quadrature voltages,
i d r and i q r are the direct and quadrature currents,
ω m is the mechanical velocity of the rotor,
λ r is the equivalent magnet flux,
L is the average stator winding inductance,
R is the stator resistance,
ΔL r is the constant difference between the d-axis and q-axis inductances, due to saliency.
2. The drive of claim 1 , wherein said control module further controls injection of a high frequency excitation voltage into the stator of the motor for amplifying said inductance variations.
3. The drive of claim 2 , wherein said excitation voltage is reduced as motor speed increases.
4. The drive of claim 3 , wherein said excitation voltage is controlled according to:
V
h
=
max
{
0
V
h
max
+
K
scale
ⅆ
ⅆ
θ
_
e
e
(
θ
_
e
)
|
θ
_
e
=
θ
e
.
(
12
)
5. The drive of claim 2 , wherein a current feedback due to said excitation voltage is demodulated by a demodulation module.
6. The drive of claim 5 , wherein said demodulation module comprises a filter, a reference frame transformation, and a PLL.
7. The drive of claim 1 , wherein at zero and low speeds said control module determines the polarity of said rotor position.
8. The drive of claim 1 , wherein for relatively high motor speeds the control module derives said rotor position on the basis of back-EMF.
9. A position sensorless drive for PM synchronous motors, comprising:
drive circuits operable for driving a PM synchronous motor; and
a control module which receives voltage and current information from said PM synchronous motor, determines a rotor position of said PM motor, and generates control signals which control said drive circuits on the basis of said rotor position at zero, low and high motor speeds,
wherein for relatively high motor speeds the control module derives said rotor position on the basis of back-EMF,
comprising a back-EMF observer module,
wherein estimated back-EMF values are expressed by:
E
α
β
s
_
≈
[
λ
r
ω
m
sin
(
θ
e
)
-
λ
r
ω
m
cos
(
θ
e
)
]
.
(
9
)
10. The drive of claim 9 , wherein said rotor position is expressed by:
θ
_
e
=
arctan
[
λ
r
ω
m
sin
(
θ
e
)
λ
r
ω
m
cos
(
θ
e
)
]
.
(
10
)
11. A position sensorless drive for PM synchronous motors, comprising:
drive circuits operable for driving a PM synchronous motor; and
a control module which receives voltage and current information from said PM synchronous motor, determines a rotor position of said PM motor, and generates control signals which control said drive circuits on the basis of said rotor position at zero, low and high motor speeds,
wherein for relatively high motor speeds the control module derives said rotor position on the basis of back-EMF,
comprising a back-EMF observer module,
wherein a PLL extracts rotor position from the output of said back-EMF observer module.
12. A position sensorless drive for PM synchronous motors, comprising:
drive circuits operable for driving a PM synchronous motor; and
a control module which receives voltage and current information from said PM synchronous motor, determines a rotor position of said PM motor, and generates control signals which control said drive circuits on the basis of said rotor position at zero, low and high motor speeds,
wherein said control module comprises
a first module which extracts and processes inductance variations and supplies position information at relatively low or zero speeds; and
a second module which extracts and processes back-EMF variations and supplies position information at relatively high speeds,
wherein said rotor position is related to said inductance and back-EMF variations as follows:
V
α
s
=
R
i
α
s
+
L
ⅆ
ⅆ
t
i
α
s
+
Δ
L
r
sin
(
2
θ
e
)
ⅆ
ⅆ
t
i
α
s
-
L
ω
m
i
β
s
-
λ
r
ω
m
sin
(
θ
e
)
(
3
)
V
β
s
=
R
i
β
s
+
L
ⅆ
ⅆ
t
i
β
s
-
Δ
L
r
cos
(
2
θ
e
)
ⅆ
ⅆ
t
i
β
r
+
L
ω
m
i
α
r
+
λ
r
ω
m
cos
(
θ
e
)
(
4
)
wherein θ e is the rotor electrical position.
13. A position sensorless drive for PM synchronous motors, comprising:
drive circuits operable for driving a PM synchronous motor; and
a control module which receives voltage and current information from said PM synchronous motor, determines a rotor position of said PM motor, and generates control signals which control said drive circuits on the basis of said rotor position at zero, low and high motor speeds,
wherein said control module comprises
a first module which extracts and processes inductance variations and supplies position information at relatively low or zero speeds;
a second module which extracts and processes back-EMF variations and supplies position information at relatively high speeds, and
a combining module which combines position data output by said first and second modules at all of said zero, low and high speeds and delivers position data for all of said zero, low and high speeds.
14. The drive of claim 13 , wherein said combining module comprises respective PLL's for said first and second modules.
15. A method of providing position sensorless drive for PM synchronous motors, comprising the steps of:
providing drive circuits operable for driving a PM synchronous motor; and
controlling said drive circuits by the steps of receiving voltage and current information from said PM synchronous motor, determining a rotor position of said PM motor, and generating control signals which control said drive circuits on the basis of said rotor position at zero, low and high motor speeds,
wherein for relatively low speeds, said controlling step derives said rotor position on the basis of rotor inductance variations,
wherein said inductance variations are determined according to:
V
d
r
=
R
i
d
r
+
L
ⅆ
ⅆ
t
i
d
r
-
L
ω
m
i
q
r
(
1
)
V
q
r
=
R
i
q
r
+
L
ⅆ
ⅆ
t
i
q
r
-
Δ
L
r
ⅆ
ⅆ
t
i
q
r
+
L
ω
m
i
d
r
+
λ
r
ω
m
(
2
)
Where:
V d r and V d r are the direct and quadrature voltages.
i d r and i q r are the direct and quadrature currents.
ω m is the mechanical velocity of the rotor.
λ r is the equivalent magnet flux.
L is the average stator winding inductance.
R is the stator resistance.
ΔL r is the constant difference between the d-axis and q-axis inductances, due to saliency.
16. The method of claim 15 , wherein said controlling step further controls injection of a high frequency excitation voltage into the stator of the motor for amplifying said inductance variations.
17. The method of claim 16 , wherein said excitation voltage is reduced as motor speed increases.
18. The method of claim 17 , wherein said excitation voltage is controlled according to:
V
h
=
max
{
0
V
h
max
+
K
scale
ⅆ
ⅆ
θ
_
e
e
(
θ
_
e
)
|
θ
_
e
=
θ
e
.
(
12
)
19. The method of claim 16 , further comprising a step of demodulating a current feedback due to said excitation voltage.
20. The method of claim 19 , wherein said demodulation step includes the steps of filtering, a reference frame transformation, and extraction by a PLL.
21. The method of claim 15 , wherein at zero and low speeds said controlling step determines the polarity of said rotor position.
22. The method of claim 15 , wherein for relatively high motor speeds the controlling step derives said rotor position on the basis of back-EMF.
23. The method of claim 22 , wherein a PLL extracts rotor position from the output of a back-EMF observer module.
24. A method of providing position sensorless drive for PM synchronous motors, comprising the steps of:
providing drive circuits operable for driving a PM synchronous motor; and
controlling said drive circuits by the steps of receiving voltage and current information from said PM synchronous motor, determining a rotor position of said PM motor, and generating control signals which control said drive circuits on the basis of said rotor position at zero, low and high motor speeds,
wherein for relatively high motor speeds the controlling step derives said rotor position on the basis of back-EMF,
wherein estimated back-EMF values are expressed by:
E
α
β
s
_
≈
[
λ
r
ω
m
sin
(
θ
e
)
-
λ
r
ω
m
cos
(
θ
e
)
]
.
(
9
)
25. The method of claim 24 , wherein said rotor position is expressed by:
θ
_
e
=
arctan
[
λ
r
ω
m
sin
(
θ
e
)
λ
r
ω
m
cos
(
θ
e
)
]
.
(
10
)
26. A method of providing position sensorless drive for PM synchronous motors, comprising the steps of:
providing drive circuits operable for driving a PM synchronous motor; and
controlling said drive circuits by the steps of receiving voltage and current information from said PM synchronous motor, determining a rotor position of said PM motor, and generating control signals which control said drive circuits on the basis of said rotor position at zero, low and high motor speeds,
wherein said controlling step includes:
a first step of extracting and processing inductance variations and supplying position information at relatively low or zero speeds based thereon; and
a second step of extracting and processing back-EMF variations and supplying position information at relatively high speeds based thereon,
wherein said rotor position is related to said inductance and back-EMF variations as follows:
V
α
s
=
R
i
α
s
+
L
ⅆ
ⅆ
t
i
α
s
+
Δ
L
r
sin
(
2
θ
e
)
ⅆ
ⅆ
t
i
α
s
-
L
ω
m
i
β
s
-
λ
r
ω
m
sin
(
θ
e
)
(
3
)
V
β
s
=
R
i
β
s
+
L
ⅆ
ⅆ
t
i
β
s
-
Δ
L
r
cos
(
2
θ
e
)
ⅆ
ⅆ
t
i
β
r
+
L
ω
m
i
α
r
+
λ
r
ω
m
cos
(
θ
e
)
(
4
)
wherein θ e is the rotor electrical position.
27. A method of providing position sensorless drive for PM synchronous motors, comprising the steps of:
providing drive circuits operable for driving a PM synchronous motor; and
controlling said drive circuits by the steps of receiving voltage and current information from said PM synchronous motor, determining a rotor position of said PM motor, and generating control signals which control said drive circuits on the basis of said rotor position at zero, low and high motor speeds,
wherein said controlling step includes:
a first step of extracting and processing inductance variations and supplying position information at relatively low or zero speeds based thereon;
a second step of extracting and processing back-EMF variations and supplying position information at relatively high speeds based thereon, and
the steps of combining position data output by said first and second steps at all of said zero, low and high speeds and delivering position data for all of said zero, low and high speeds.
28. The method of claim 27 , wherein said combining step utilizes respective PLL's for said first and second steps.