Method for controlling voltage of DC link for electric vehicle
View Patent ↗Disclosed is a method for controlling a voltage of a DC link for an electric vehicle, which can reduce a capacitance of the DC link interposed between an inverter and a DC/DC converter. The method for controlling the voltage of the DC link in a power system of a vehicle including a battery, a DC/DC converter, the DC link, an inverter, a motor, and a control part controlling the DC/DC converter and the inverter includes the steps of installing a compensator in a control loop of the control part such that a DC link current of the DC/DC converter follows a DC link current of the inverter, calculating a predetermined compensation term based on information of the motor inputted into the compensator, and applying the compensation term to a voltage node in the control loop of the control part in the compensator.
1. A method for controlling a voltage of a DC link in a power system of a vehicle including a battery, a DC/DC converter, the DC link, an inverter, a motor, and a control part controlling the DC/DC converter and the inverter, the method comprising:
installing a compensator in a control loop of the control part such that a DC link current of the DC/DC converter follows a DC link current of the inverter;
calculating a compensation term based on information of the motor inputted into the compensator; and
applying the compensation term to a voltage node in the control loop of the control part.
2. The method as claimed in claim 1 , wherein the information about the motor includes a current, a voltage, and a speed of the motor.
3. The method as claimed in claim 1 , wherein the compensation term is determined through an equation,
sLi
B
=
sL
v
DC
i
inv
v
B
,
wherein s, L, i B , v B , v DC , and i inv denote a Laplacian differential operator, an inductance of a coil installed the DC/DC converter, a battery current, a battery voltage, a voltage of the DC link, and an average of the inverter current.
4. The method as claimed in claim 3 , wherein the average i inv of the inverter current is obtained through a voltage equation, a phase current equation, and a phase voltage equation of the motor.
5. The method as claimed in claim 3 , wherein, when the motor is a permanent magnetic synchronization motor, the equation,
sLi
B
=
sL
v
DC
i
inv
v
B
,
is identical to an equation,
L
v
DC
v
B
si
inv
=
3
L
2
v
B
[
L
d
L
q
ω
r
v
ds
r
(
kT
s
)
+
1
T
s
{
v
qs
r
(
kT
s
)
-
v
qs
r
(
(
k
-
1
)
T
s
)
}
-
R
s
L
q
v
qs
r
(
kT
s
)
]
i
qs
r
(
kT
s
)
+
3
L
2
v
B
[
v
ds
r
(
kT
s
)
2
L
d
+
v
qs
r
(
kT
s
)
2
L
q
ω
r
ϕ
m
L
q
v
qs
r
(
kT
s
)
]
,
wherein the L d , L q , R s w r and φ m denote a d-phase inductance, a q-phase inductance, a stator resistance, a rotator speed, and a rotator magnetic flux of the motor, respectively, and the T s and the K denote a PWM period (or, a sampling period) and an integer, respectively.
6. The method as claimed in claim 3 , wherein the compensation term
(
sLi
B
=
sL
v
DC
i
inv
v
B
)
is subtracted at the voltage node in the control loop of the control part, so that the average of the inverter current i inv is compensated.
7. A power system for a vehicle, comprising:
a battery;
a DC/DC converter coupled to the battery;
a motor;
an inverter coupled to the motor;
a DC link interposed between the DC/DC converter and the inverter; and
a control part for controlling a voltage of the DC link, the control part including a control loop that includes a compensator to generate a compensation term such that a DC link current of the DC/DC converter follows a DC link current of the inverter,
wherein the compensator receives motor information as an input and determines the compensation term based on the motor information, and
wherein the motor information includes a current, a voltage, and a speed of the motor.
8. The system of claim 7 , wherein the compensation term is supplied to a voltage node in the control loop of the control part instead of being supplied to a current node in the control loop.
9. A power system for a vehicle, comprising:
a battery;
a DC/DC converter coupled to the battery;
a motor;
an inverter coupled to the motor;
a DC link interposed between the DC/DC converter and the inverter; and
a control part for controlling a voltage of the DC link, the control part including a control loop that includes a compensator to generate a compensation term such that a DC link current of the DC/DC converter follows a DC link current of the inverter,
wherein the compensation term is determined through an equation,
sLi
B
=
sL
v
DC
i
inv
v
B
,
wherein s, L, i B , v B , v DC , and i inv denote a Laplacian differential operator, an inductance of a coil installed the DC/DC converter, a battery current, a battery voltage, a voltage of the DC link, and an inverter current.
10. The system of claim 9 , wherein the inverter current is obtained through a voltage equation, a phase current equation, and a phase voltage equation of the motor.
11. The system of claim 9 , wherein, when the motor is a permanent magnetic synchronization motor, the equation,
sLi
B
=
sL
v
DC
i
inv
v
B
,
is identical to an equation,
L
v
DC
v
B
si
inv
=
3
L
2
v
B
[
L
d
L
q
ω
r
v
ds
r
(
kT
s
)
+
1
T
s
{
v
qs
r
(
kT
S
)
-
v
qs
r
(
(
k
-
1
)
T
s
)
}
-
R
s
L
q
v
qs
r
(
kT
s
)
]
i
qs
r
(
kT
s
)
+
3
L
2
v
B
[
v
ds
r
(
kT
s
)
2
L
d
+
v
qs
r
(
kT
s
)
2
L
q
ω
r
ϕ
m
L
q
v
qs
r
(
kT
s
)
]
,
wherein the L d , L q , R s w r and φ m denote a d-phase inductance, a q-phase inductance, a stator resistance, a rotator speed, and a rotator magnetic flux of the motor, respectively, and the T s and the K denote a PWM period and an integer, respectively.
12. The system of claim 9 , wherein the compensation term is supplied to a voltage node in the control loop of the control part instead of being supplied to a current node in the control loop.