U.S. patent application number 17/027596 was filed with the patent office on 2021-01-14 for control system and method for permanent magnet synchronous traction and transmission system.
The applicant listed for this patent is CRRC QINGDAO SIFANG ROLLING STOCK RESEARCH INSTITUTE CO., LTD.. Invention is credited to Jingbin BI, Hu CAO, Meng XIA, Fanfei ZENG.
Application Number | 20210013821 17/027596 |
Document ID | / |
Family ID | 1000005160705 |
Filed Date | 2021-01-14 |
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United States Patent
Application |
20210013821 |
Kind Code |
A1 |
BI; Jingbin ; et
al. |
January 14, 2021 |
CONTROL SYSTEM AND METHOD FOR PERMANENT MAGNET SYNCHRONOUS TRACTION
AND TRANSMISSION SYSTEM
Abstract
The present application provides a control system and method for
a permanent magnet synchronous traction and transmission system. A
The control system comprises a sampling unit and a controller; the
sampling unit collecting an operation excitation current and an
operation torque current, a input capacitor voltage and a rotor
frequency; the controller acquires a target torque instruction
issued to the traction and transmission system, calculates a target
excitation current value and a target torque current value, and
generates an excitation current regulation value and a torque
current regulation value; a regulation unit is configured to
generate a torque current regulation value according to the target
torque current value and an operation torque current value and
generate a target modulation ratio and a modulation frequency
according to the excitation current regulation value and the torque
current regulation value output from the regulation unit and
finally output a PWM modulation wave control signal.
Inventors: |
BI; Jingbin; (Qingdao,
CN) ; XIA; Meng; (Qingdao, CN) ; CAO; Hu;
(Qingdao, CN) ; ZENG; Fanfei; (Qingdao,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CRRC QINGDAO SIFANG ROLLING STOCK RESEARCH INSTITUTE CO.,
LTD. |
Qingdao |
|
CN |
|
|
Family ID: |
1000005160705 |
Appl. No.: |
17/027596 |
Filed: |
September 21, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/CN2018/115118 |
Nov 13, 2018 |
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17027596 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02P 27/14 20130101;
H02P 25/024 20160201; H02P 27/12 20130101; H02P 2207/05 20130101;
H02P 21/22 20160201 |
International
Class: |
H02P 25/024 20060101
H02P025/024; H02P 27/14 20060101 H02P027/14; H02P 21/22 20060101
H02P021/22; H02P 27/12 20060101 H02P027/12 |
Foreign Application Data
Date |
Code |
Application Number |
May 30, 2018 |
CN |
201810537327.0 |
Claims
1. A control system for a permanent magnet synchronous traction and
transmission system, for controlling of the permanent magnet
synchronous traction and transmission system, wherein the control
system comprises a sampling unit and a controller; the sampling
unit is connected to a permanent magnet synchronous motor, and
comprises: a current sensor for collecting an operation excitation
current and an operation torque current of the permanent magnet
synchronous motor, a voltage sensor for collecting a input
capacitor voltage of the permanent magnet synchronous motor, and a
resolver for collecting an initial rotor position and a rotor
frequency of the permanent magnet synchronous motor; the controller
comprises: an instruction acquisition unit, configured to acquire a
target torque instruction issued to the traction and transmission
system; a Maximum Torque Per Ampere (MTPA) calculation unit,
configured to calculate a target excitation current value and a
target torque current value according to the target torque
instruction; a regulation unit, comprising: an excitation
regulation unit and a torque regulation unit; the excitation
regulation unit configured to generate an excitation current
regulation value according to the target excitation current value
and an operation excitation current value; and the torque
regulation unit configured to generate a torque current regulation
value according to the target torque current value and an operation
torque current value; a decoupling control unit, configured to
generate a target modulation ratio and a modulation frequency
according to the excitation current regulation value and the torque
current regulation value output from the regulation unit; a method
for generating the target modulation ratio M is as follows: U s = U
d + U q M = 3 * ( U s + PID I d o u t ) F c ##EQU00012## wherein Fc
is the input capacitor voltage, and PID.I.sub.dout is an excitation
current regulation value; U.sub.d is a control voltage component of
a shaft d , and U.sub.q is a control voltage component of a shaft
q; a method for generating the modulation frequency Fs_out is as
follows: Fs_out=(1+PID.I.sub.qout)*Fs wherein PID.I.sub.qout is a
torque current regulation value, and Fs is a rotor frequency; a
segment synchronous modulation unit, configured to output a Pulse
Width Modulation (PWM) modulation wave control signal for the
permanent magnet synchronous motor, according to the target
modulation ratio and the modulation frequency generated by the
decoupling control unit; and the segment synchronous modulation
unit receives the information of M and Fs_out and generates a
three-phase (u, v, w) pulse by determining a sector where a voltage
vector is located.
2. The control system according to claim 1, wherein the controller
further comprises a flux-weakening compensation unit configured to
generate compensation signals for the target excitation current
value and the target torque current value to compensate for
both.
3. The control system according to claim 2, wherein the controller
further comprises an current accurate calculation unit configured
to convert the target excitation current value and the target
torque current value into an accurate excitation current value and
an accurate torque current value; the excitation regulation unit
generates the excitation current regulation value by regulation
according to the accurate excitation current value, and the torque
regulation unit generates the torque current regulation value by
regulation according to the accurate torque current value.
4. The control system according to claim 3, wherein the controller
further comprises a voltage feedforward unit configured to acquire
output data of the current accurate calculation unit and generates
a compensation data for target torque.
5. A control method for a permanent magnet synchronous traction and
transmission system, comprising following steps of: converting a
target torque instruction of the traction and transmission system
into a target excitation current value and a target torque current
value; regulating and calculating the target excitation current
value and the target torque current value; decoupling the target
excitation current value and the target torque current value,
generating a target modulation ratio according to the target
excitation current value, and generating a modulation frequency
according to the target torque current value; and using the target
modulation ratio and the modulation frequency to control a
permanent magnet synchronous traction motor; a method for
converting the target torque instruction of the traction and
transmission system into the target excitation current value and
the target torque current value of the permanent magnet synchronous
motor is as follows: according to: T e = 3 2 P n .psi. .fwdarw. f
.times. i .fwdarw. s = 3 2 P n [ .psi. f i s sin .phi. + 1 2 ( L q
- L d ) i s 2 sin 2 .phi. ] = 3 2 P n [ .psi. f i q + 1 2 ( L q - L
d ) i d i q ] 1 ) i d = .psi. f 2 ( L q - L d ) .+-. .psi. f 2 4 (
L q - L d ) 2 + i q 2 2 ) ##EQU00013## the above two equations are
combined to calculate the target excitation current value and the
target torque current value; wherein T.sub.e is a target torque,
L.sub.q is an equivalent inductance of a shaft q, L.sub.d is an
equivalent inductance of a shaft d, i.sub.d is the target
excitation current value, i.sub.q is the target torque current
value, i.sub.s is a target phase current, .psi..sub.f is a motor
flux linkage, P.sub.n is a number of pole pairs of the motor, and
.phi. is a voltage-current angle difference of the motor.
6. The control method according to claim 5, wherein further
comprises a step of: converting a converted input capacitor voltage
according to a set target modulation ratio; after a comparison with
a input capacitor voltage acquired by sampling, generating a torque
current compensation amount i.sub.q_crr and an excitation current
compensation amount i.sub.d_crr by regulation, and synthesizing the
torque current compensation amount and the excitation current
compensation amount with the target torque current value and the
target excitation current value, respectively, for a subsequent
calculation.
7. The control method according to claim 6, wherein further
comprises a step of: performing an accurate calculation for the
target excitation current value and the target torque current value
to obtain an accurate excitation current value i.sub.dt arg et and
an accurate torque current value i.sub.qt arg et of the motor: i
dtarget = .psi. f + .psi. f 2 + 4 ( L q - L d - .differential. L q
.differential. L d ) i qtarget 2 2 ( L q - L d - .differential. L q
.differential. L d i qtarget ) 3 ) i dtarget = i d + i d - c c r 4
) ##EQU00014## using the obtained accurate excitation current value
i.sub.dt arg et and accurate torque current value i.sub.qt arg et
for the regulating and calculating.
8. The control method according to claim 6, wherein further
comprises a step of: calculating a voltage compensation value using
the accurate excitation current value i.sub.dt arg et and the
accurate torque current value i.sub.qt arg et, so as to perform a
compensation calculating for the target modulation ratio: { U d = R
s i dtarget + L d d i dtarget d t - .omega. r L q i qtarget U q = R
s i qtarget + L q d i qtarget d t + .omega. r ( L d i dtarget +
.psi. f ) 5 ) ##EQU00015## R.sub.s is a rotor resistance,
.omega..sub.r is an angular velocity, U.sub.d is a control voltage
component of a shaft d, and U.sub.q is a control voltage component
of a shaft q, .psi..sub.f is a motor flux linkage.
9. The control method according to claim 8, wherein a method for
generating the target modulation ratio M is as follows: U s = U d +
U q 6 ) M = 3 * ( U s + P I D I d o u t ) F c 7 ) ##EQU00016##
wherein Fc is the input capacitor voltage, and PID.I.sub.dout is an
excitation current regulation value; a method for generating the
modulation frequency Fs_out is as follows:
Fs_out=(1+PID.I.sub.qout)*Fs 8) wherein PID.I.sub.qout is a torque
current regulation value, and Fs is a rotor frequency.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of PCT/CN2018/115118
filed on Nov. 13, 2018, which claims the priority benefit of
Chinese patent application No. 201810537327.0 filed on May 30,
2018. The entirety of the above-mentioned patent applications is
hereby incorporated by reference herein and made a part of this
specification.
TECHNICAL FIELD
[0002] The present application relates to the field of traction and
transmission control, and particularly to a control system and a
control method suitable for a permanent magnet synchronous traction
and transmission system.
BACKGROUND ART
[0003] The traction and transmission system is a power system of a
train, and mainly composed of a converter and a motor. The motor
completes a conversion from electrical energy to mechanical energy
and drives the train to operate.
[0004] The permanent magnet synchronous traction and transmission
system adopts a permanent magnet synchronous motor. Compared with
an asynchronous motor, the permanent magnet synchronous motor has
the characteristics of high power factor, low heat generation, low
noise and high reliability. The application of the urban-rail
permanent magnet synchronous motor in the rail traffic traction and
transmission system is at an initial stage. The control of the
permanent magnet synchronous traction and transmission system has
many technical problems which need to be further researched.
Although there are similarities between the control of the traction
motor and the traction converter and the control of the
asynchronous traction and transmission system, the permanent magnet
synchronous motor also has many practical problems unique
thereto.
[0005] At present, the existing urban-rail permanent magnet
synchronous motor control algorithms mostly adopt the asynchronous
Space Vector Pulse Width Modulation (SVPWM) for operation. Under a
condition of a high rotation speed, in order to meet the harmonic
requirement of the output current, the switching frequency of the
Insulated Gate Bipolar Transistor (IGBT) is greatly increased, the
output loss rises, and the hardware cost is also increased to meet
the heat dissipation requirement.
[0006] Because the permanent magnet synchronous motor is excited by
a permanent magnet, the flux-weakening range is narrow and the
flux-weakening is difficult. A better flux-weakening control
technology can greatly improve the system performance without
changing a capacity of inverter. At present, many flux-weakening
schemes have complex algorithms, while the flux-weakening
efficiencies are low and the effects are poor.
SUMMARY
[0007] In view of the problems of complex algorithms and low
control precision existing in the control of the permanent magnet
synchronous motor in the prior art, the present application
proposes a novel control system and method for a permanent magnet
synchronous traction and transmission system. The specific
technical solutions are as follows:
[0008] A control system for a permanent magnet synchronous traction
and transmission system, for controlling the permanent magnet
synchronous traction and transmission system, the control system
comprising a sampling unit and a controller;
[0009] the sampling unit is connected to a permanent magnet
synchronous motor, and comprises: a current sensor for collecting
an operation excitation current and an operation torque current of
the permanent magnet synchronous motor, a voltage sensor for
collecting a input capacitor voltage of the permanent magnet
synchronous motor, and a resolver for collecting an initial rotor
position and a rotor frequency of the permanent magnet synchronous
motor;
[0010] the controller comprises:
[0011] an instruction acquisition unit, configured to acquire a
target torque instruction issued to the traction and transmission
system;
[0012] a Maximum Torque Per Ampere (MTPA) calculation unit,
configured to calculate a target excitation current value and a
target torque current value according to the target torque
instruction;
[0013] a regulation unit, comprising: an excitation regulation unit
and a torque regulation unit; the excitation regulation unit
configured to generate an excitation current regulation value
according to the target excitation current value and an operation
excitation current value; and the torque regulation unit configured
to generate a torque current regulation value according to the
target torque current value and an operation torque current
value;
[0014] a decoupling control unit, configured to generate a target
modulation ratio and a modulation frequency according to the
excitation current regulation value and the torque current
regulation value output from the regulation unit; and
[0015] a segment synchronous modulation unit, configured to output
a PWM modulation wave control signal for the permanent magnet
synchronous motor, according to the target modulation ratio and the
modulation frequency generated by the decoupling control unit.
[0016] Preferably, the controller further comprises a
flux-weakening compensation unit configured to generate
compensation signals for the target excitation current value and
the target torque current value to compensate for both.
[0017] Preferably, the controller further comprises an current
accurate calculation unit configured to convert the target
excitation current value and the target torque current value into
an accurate excitation current value and an accurate torque current
value; the excitation regulation unit generates the excitation
current regulation value by regulation according to the accurate
excitation current value, and the torque regulation unit generates
the torque current regulation value by regulation according to the
accurate torque current value.
[0018] Preferably, the controller further comprises a voltage
feedforward unit configured to acquire output data of the current
accurate calculation unit and generates a compensation data for
target torque.
[0019] The present application further provides a control method
for a permanent magnet synchronous traction and transmission
system, comprising following steps of:
[0020] converting a target torque instruction of a traction and
transmission system converted into a target excitation current
value and a target torque current value;
[0021] regulating and calculating the target excitation current
value and the target torque current value;
[0022] decoupling the target excitation current value and the
target torque current value, generating a target modulation ratio
according to the target excitation current value, and generating a
modulation frequency according to the target torque current value;
and
[0023] using the target modulation ratio and the modulation
frequency to control a permanent magnet synchronous traction
motor.
[0024] Preferably, a method for converting the target torque
instruction of the traction and transmission system into the target
excitation current value and the target torque current value of the
permanent magnet synchronous motor is as follows:
[0025] according to:
T e = 3 2 P n .psi. .fwdarw. f .times. i s .fwdarw. = 3 2 P n [
.psi. f i s sin .phi. + 1 2 ( L q - L d ) i s 2 sin 2 .phi. ] = 3 2
P n [ .psi. f i q + 1 2 ( L q - L d ) i d i q ] ( 1 ) i d = .psi. f
2 ( L q - L d ) .+-. .psi. f 2 4 ( L q - L d ) 2 + i q 2 ( 2 )
##EQU00001##
[0026] the above two equations are combined to calculate the target
excitation current value and the target torque current value;
[0027] wherein T.sub.e is a target torque, L.sub.q is an equivalent
inductance of a shaft q, L.sub.d is an equivalent inductance of a
shaft d, i.sub.q is the target torque current value, i.sub.d is the
target excitation current value, i.sub.s is a target phase current,
.psi..sub.f is a motor flux linkage, P.sub.n is a number of pole
pairs of the motor, and .phi. is a voltage-current angle difference
of the motor.
[0028] Preferably, the method further comprises a step of:
converting a converted input capacitor voltage according to a set
target modulation ratio; after a comparison with a input capacitor
voltage acquired by sampling, generating a torque current
compensation amount i.sub.q_crr and an excitation current
compensation amount i.sub.d_crr by regulation, and synthesizing the
torque current compensation amount and the excitation current
compensation amount with the target torque current value and the
target excitation current value, respectively, for a subsequent
calculation.
[0029] Preferably, the method further comprises a step of:
performing an accurate calculation for the target excitation
current value and the target torque current value to obtain an
accurate excitation current value i.sub.dt arg et and an accurate
torque current value i.sub.qt arg et of the motor:
i dtarget = .psi. f + .psi. f 2 + 4 ( L q - L d - .differential. L
q .differential. L d ) i qtarget 2 2 ( L q - L d - .differential. L
q .differential. L d i qtarget ) 3 ) i dtarget = i d + i d - c c r
4 ) ##EQU00002##
[0030] using the obtained accurate excitation current value
i.sub.dt arg et and accurate torque current value i.sub.qt arg et
for the regulating and calculating.
[0031] Preferably, the method further comprises a step of:
calculating a voltage compensation value using the accurate
excitation current value i.sub.dt arg et and the accurate torque
current value i.sub.qt arg et so as to perform a compensation
calculation for the target modulation ratio:
{ U d = R s i dtarget + L d d i d t a r g e t d t - .omega. r L q i
qtarget U q = R s i qtarget + L q d i q t a r g e t d t + .omega. r
( L d i dtarget + .psi. j ) 5 ) ##EQU00003##
[0032] wherein R.sub.s is a rotor resistance, .omega..sub.r is an
angular velocity, U.sub.d is a control voltage component of a shaft
d, and U.sub.q is a control voltage component of a shaft q.
[0033] Preferably, a method for generating the target modulation
ratio M is:
U s = U d + U q 6 ) M = 3 * ( U s + PID I dout ) F c 7 )
##EQU00004##
[0034] wherein Fc is the input capacitor voltage, and
PID.I.sub.dout is an excitation current regulation value;
[0035] a method for generating the modulation frequency Fs_out is
as follows:
Fs_out=(1+PID.I.sub.qout)*Fs 8)
[0036] wherein PID.I.sub.qout is a torque current regulation value,
and Fs is a rotor frequency.
[0037] Compared with the prior art, the present application has the
advantages and positive effects as follows:
[0038] 1) In the control method for the permanent magnet
synchronous traction and transmission system provided by the
present application, through further researches on output
characteristics and counter electromotive force of the permanent
magnet synchronous motor, a novel SVPWM pulse control method is
adopted to further decrease switching frequency, reduce switching
loss of the converter, improve the system efficiency and realize a
stable operation of the system at a low switching frequency.
[0039] 2) In the present application, a new flux-weakening control
algorithm is proposed for the control algorithm. By fitting the
output voltage and comparing it with the input voltage, the system
can operate stably in the flux-weakening region while the
flux-weakening efficiency can be improved.
[0040] 3) The present application proposes an accurate current
calculation method, which can improve the control accuracy of the
flux-weakening through a cooperation between the accurate current
calculation unit and the flux-weakening compensation unit, and
improve the system performance without changing the inverter
capacity.
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] FIG. 1 is a schematic structural diagram of a permanent
magnet synchronous traction and transmission system;
[0042] FIG. 2 is a simplified structural diagram of a control
system in the present application;
[0043] FIG. 3 is a schematic structural diagram of a control system
according to an embodiment of the present application;
[0044] FIG. 4 is a schematic structural diagram of a control system
according to another embodiment of the present application;
[0045] FIG. 5 is a principle diagram of a flux-weakening control in
the present application;
[0046] FIG. 6 is a principle diagram of a decoupling control in the
present application;
[0047] FIG. 7 is a principle diagram of an asynchronous SVPWM
modulation;
[0048] FIG. 8 is a distribution diagram of switching angles of
11-frequency-division synchronous SVPWM in the present
application.
[0049] In which,
[0050] 1--sampling unit; 101--current sensor; 102--voltage sensor;
103--resolver; 2--controller; 21--instruction acquisition unit;
22--MTPA calculation unit; 23--regulation unit; 231--excitation
regulation unit; 232--torque regulation unit; 24--decoupling
control unit; 25--segment synchronous modulation unit; 26--current
accurate calculation unit; 27--flux-weakening compensation unit;
28--voltage feedforward unit; 3--permanent magnet synchronous
motor; 4--traction converter; 41--IGBT converter module;
42--chopper module; 43--precharge module; 5--three-phase
controllable contactor.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0051] Hereinafter, specific embodiments of the present application
will be further described with reference to the drawings.
[0052] A control system for a permanent magnet synchronous traction
and transmission system provided by the present application can be
applied into a train traction system powered by a permanent magnet
synchronous motor, i.e., applied into a permanent magnet
synchronous traction and transmission system (hereinafter referred
to as a traction and transmission system).
[0053] A main topology of the permanent magnet synchronous traction
and transmission system is illustrated in FIG. 1, comprising a
traction converter 4 and a Permanent Magnet Synchronous Motor 3
(PMSM), wherein an internal circuit of the traction converter 4
comprises an IGBT converter module 41, a chopper module 42 and a
precharge module 43; and an output end of the traction converter 4
is connected to the permanent magnet synchronous motor 3 via a
three-phase controllable contactor 5.
[0054] The control system comprises a sampling unit 1 and a
controller 2. FIG. 2 is a simplified structural diagram of the
control system. In FIG. 2, the traction converter 4 is simplified
as a symbol. By controlling a switching pulse of the IGBT converter
module 41 in the traction converter 4, the permanent magnet
synchronous traction and transmission system is controlled by the
control system.
[0055] As illustrated in FIG. 2, the sampling unit 1 is connected
to the permanent magnet synchronous motor 3, and comprises: a
current sensor 101 for collecting operation excitation current
i.sub.d_fed and operation torque current i.sub.q_fed of the
permanent magnet synchronous motor 3, a voltage sensor 102 for
collecting a input capacitor voltage Fc of the permanent magnet
synchronous motor 3, and a resolver 103 for collecting an initial
rotor position Theta and a rotor frequency Fs of the permanent
magnet synchronous motor 3, wherein the above data collected by the
sampling unit will be transmitted to the controller 2.
[0056] The current sensor 101, the voltage sensor 102 and the
resolver 103 are all connected to the controller 2.
[0057] The data collected by the sampling unit 1 may be stored
therein, and when any other unit needs to make a calculation,
corresponding data will be extracted from the sampling unit 1. It
should be noted that for convenience of illustration, only a data
reading process between the sampling unit 1 and one of the units is
illustrated in FIGS. 3 and 4. However, it can be understood that
when any other unit needs to make a calculation, corresponding data
may also be extracted from the sampling unit 1.
[0058] FIG. 3 is a schematic structural diagram of the control
system, and it illustrates a structural composition of the
controller 2. The controller 2 comprises:
[0059] an instruction acquisition unit 21 configured to acquire a
target torque instruction issued to the traction and transmission
system; the target torque instruction is an operation instruction
for the whole traction and transmission system, and a control goal
of the control system is to enable the traction and transmission
system to operate stably according to the target torque
instruction;
[0060] a Maximum Torque Per Ampere (MTPA) calculation unit 22
configured to calculate a target excitation current value i.sub.d
and a target torque current value i.sub.q according to the target
torque instruction; the MTPA calculation unit converts the target
torque instruction into current signals i.sub.d and i.sub.q that
can be used by the control system, and the control system performs
a control according to target currents (i.sub.d, i.sub.q) and
feedback currents (i.sub.d_fed, i.sub.q_fed) collected by the
sampling unit;
[0061] a regulation unit 23, comprising: an excitation regulation
unit 231 and a torque regulation unit 232, the excitation
regulation unit 231 configured to generate an excitation current
regulation value according to the target excitation current value
i.sub.d and an operation excitation current value i.sub.d_fed; and
the torque regulation unit 232 configured to generate a torque
current regulation value according to the target torque current
value i.sub.q and an operation torque current value
i.sub.q_fed;
[0062] a decoupling control unit 24 configured to generate a target
modulation ratio M and a modulation frequency Fs_out according to
the excitation current regulation value and the torque current
regulation value output from the regulation unit 23; and
[0063] a segment synchronous modulation unit 25 configured to
output a Pulse Width Modulation
[0064] (PWM) modulation wave control signal for the permanent
magnet synchronous motor 3, according to the target modulation
ratio M and the modulation frequency Fs_out generated by the
decoupling control unit 24.
[0065] Based on the above structure, the control system can
complete a tracking control of the permanent magnet synchronous
motor 3 according to the torque instruction.
[0066] As a further optimization of the structure of the control
system, referring to FIG. 4, the controller 2 further comprises an
current accurate calculation unit 26 configured to convert the
target excitation current value i.sub.d and the target torque
current value i.sub.q calculated by the MTPA calculation unit 22
into an accurate excitation current value and an accurate torque
current value, and the current is calibrated through accurate
current calculation, so that a control accuracy can be further
improved. At this time, the excitation regulation unit 231
generates the excitation current regulation value by regulation
according to the accurate excitation current value, and the torque
regulation unit 232 generates the torque current regulation value
by regulation according to the accurate torque current value.
[0067] As a further optimization of the control system, referring
to FIG. 4, the controller 2 further comprises a flux-weakening
compensation unit 27 configured to generate compensation signals
for the target excitation current value i.sub.d and the target
torque current value i.sub.q to compensate for both. The
flux-weakening compensation unit 27 receives a signal output from
the decoupling control unit 24 and a signal of the input capacitor
voltage Fc , and generates current compensation values which are
transmitted to an output end of the MTPA calculation unit 22. The
current accurate calculation unit 26 performs an accurate current
calculation according to a combination of output values of the MTPA
calculation unit 22 and the compensation values fed back by the
flux-weakening compensation unit 27.
[0068] It can be understood that the current accurate calculation
unit 26 and the flux-weakening compensation unit 27 cooperate with
each other to realize the accurate current calculation. That is,
the flux-weakening compensation unit 27 receives signals output
from the decoupling control unit 24 and the input capacitor voltage
Fc collected by the sampling unit 1, and generates the compensation
values for the target excitation current value i.sub.d and the
target torque current value i.sub.q, respectively. Further, the
compensation values are transmitted to the current accurate
calculation unit 26, which performs the accurate current
calculation according to i.sub.d and i.sub.q output from the MTPA
calculation unit 22 and the compensation values output from the
flux-weakening compensation unit 27.
[0069] As a further optimization of the control system, the
controller further comprises a voltage feedforward unit 28
configured to acquire output data of the current accurate
calculation unit 26 and generates a compensation data for target
torque. The compensation data will be fed back to the decoupling
control unit 24 for calculating the modulation ratio.
[0070] The present application further provides a control method
for the permanent magnet synchronous traction and transmission
system, and the control method is classified into the following two
embodiments according to the fact whether the accurate current
calculation is performed.
Embodiment 1
[0071] A control method for the permanent magnet synchronous
traction and transmission system provided by this embodiment
comprises the following steps:
[0072] 1) Converting a Control Target Parameter
[0073] A target torque instruction of the traction and transmission
system is converted into a target excitation current value i.sub.d
and a target torque current value i.sub.q.
[0074] An instruction acquired by the traction and transmission
system is the target torque instruction, which is converted into
the target excitation current value i.sub.d and the target torque
current value i.sub.q of the permanent magnet synchronous motor 3
by the MTPA calculation unit 22. A specific conversion method
is:
[0075] according to:
T e = 3 2 P n .psi. .fwdarw. f .times. i .fwdarw. s = 3 2 P n [
.psi. f i s sin .phi. + 1 2 ( L q - L d ) i s 2 sin 2 .phi. ] = 3 2
P n [ .psi. f i q + 1 2 ( L q - L d ) i d i q ] 1 ) i d = .psi. f 2
( L q - L d ) .+-. .psi. f 2 4 ( L q - L d ) 2 + i q 2 2 )
##EQU00005##
[0076] the above two equations are combined to calculate the target
excitation current value i.sub.d and the target torque current
value i.sub.q;
[0077] wherein T.sub.e is a target torque, L.sub.q is an equivalent
inductance of a shaft q, L.sub.d is an equivalent inductance of a
shaft d, i.sub.d is the target excitation current value, i.sub.q is
the target torque current value, i.sub.s is a target phase current,
.psi..sub.f is a motor flux linkage, P.sub.n is a number of pole
pairs of the motor, and .phi. is a voltage-current angle difference
of the motor.
[0078] 2) Regulating and Calculating the Target Excitation Current
Value and the Target Torque Current Value
[0079] The target excitation current value i.sub.d and the target
torque current value i.sub.q calculated by the MTPA calculation
unit 22 are transmitted to the regulation unit 23 for current
regulation and calculation. An excitation current regulation value
PID.I.sub.outis generated by the excitation regulation unit 231
according to the target excitation current value i .sub.d and an
operation excitation current value i.sub.d_fed; A torque current
regulation value PID.I.sub.qout is generated by the torque
regulation unit according to the target torque current value
i.sub.q and an operation torque current value i.sub.q_fed. The
excitation current regulation value and the torque current
regulation value will be used for decoupling control to generate a
target modulation ratio and a modulation frequency.
[0080] In this embodiment, a Proportion Integration Differentiation
(PID) regulating and calculating method is adopted by the
regulation unit 23, which is a well-known calculating method, and
will not be described in detail here.
[0081] 3) Decoupling the target excitation current value and the
target torque current value, generating the target modulation ratio
according to the target excitation current value, and generating
the modulation frequency according to the target torque current
value.
[0082] 3.1) Calculating a Voltage Compensation Value
[0083] The target excitation current value i.sub.d and the target
torque current value i.sub.q are transmitted to the voltage
feedforward unit 28 to calculate the voltage compensation value,
i.e., the compensation data for target torque as aforementioned. A
specific calculation method is as follows:
{ U d = R s i d + L d d i d d t - .omega. r L q i q U q = R s i q +
L q d i q d t - .omega. r ( L d i d + .psi. j ) 5 - 1 )
##EQU00006##
[0084] wherein R.sub.s is a rotor resistance, .omega..sub.r is an
angular velocity, U.sub.d is a control voltage component of a shaft
d , and U.sub.q is a control voltage component of a shaft q.
[0085] 3.2) Generating the Target Modulation Ratio and the
Modulation Frequency
[0086] Referring to FIG. 6, the U.sub.d and U.sub.q are output to
the decoupling control unit 24 by the voltage feedforward unit 28,
the excitation current regulation value PID.I.sub.dout and the
torque current regulation value PID.I.sub.quot are generated and
output to the decoupling control unit 24 by the regulation unit 23,
and the target modulation ratio M and the modulation frequency
Fs_out are generated by the decoupling control unit 24.
[0087] A method for generating the target modulation ratio M is as
follows:
U s = U d + U q 6 ) M = 3 * ( U s + PID I dout ) F c 7 )
##EQU00007##
[0088] wherein Fc is a input capacitor voltage, and PID.I.sub.dout
is the excitation current regulation value generated and outputted
by the torque regulation unit 232.
[0089] A method for generating the modulation frequency Fs_out is
as follows:
Fs_out=(1+PID.sub.qout)*Fs 8)
[0090] wherein PID.I.sub.qout is the torque current regulation
value generated and outputted by the excitation regulation unit
231, and Fs is a rotor frequency collected by the sampling unit
1.
[0091] A synthesis of the target modulation ratio M and the
modulation frequency F.sub.s_out is finally completed by the
decoupling control unit 24.
[0092] 4) Segment Synchronous Modulating
[0093] According to the target modulation ratio M and the
modulation frequency Fs_out, a PWM modulation wave is generated by
the segment synchronous modulation unit for the control of the
permanent magnet synchronous traction motor 3.
[0094] An asynchronous SVPWM modulation program receives the
information of M and Fs_out, and generates a three-phase (u, v, w)
pulse by determining a sector where a voltage vector is
located.
[0095] Referring to FIG. 7, the target modulation ratio adopted in
this embodiment is 0.906, and a modulation of a segment modulation
module of the synchronous 11-frequency-division SVPWM modulation
(Basic Boundary Clamping Strategy) is switched in such a way that
when a modulation degree is greater than 0.906 and enters an
overmodulation region, 4 of 11 pulses disappear symmetrically and 7
pulses remain; the modulation degree further increases, 2 pulses
disappear symmetrically and 5 pulses remain; and when the
modulation degree is greater than 1, only a square wave single
pulse remains.
[0096] As illustrated in FIG. 7, within 30 Hz to 40 Hz is
11-frequency-division synchronous modulation I, and each modulation
period has 30 interruptions; from above 40 Hz until the square wave
is 11-frequency-division synchronous modulation II, and each
modulation period has 15 interruptions; after entering the
overmodulation region, the number of pulses decreases symmetrically
with a increase of the modulation degree, and only a square wave
single pulse remains when the modulation degree is greater than
1.
[0097] As illustrated in FIG. 8, by using an A-phase pulse of
11-frequency-division synchronous SVPWM with 30 interruptions, it
is possible to derive five switching angles .alpha.2, .alpha.2,
.alpha.3, 60 4, and .alpha.5 within 1/4 period according to a
comparison value corresponding to each sector.
[0098] According to characteristics of the synchronous SVPWM (1/2
period symmetry, 1/4 period anti-symmetry), it is possible to
derive a pulse width within the whole period, and then control On
and OFF of the IGBT converter module. An angle calculation formula
is as follows:
{ .alpha. 1 = 57.2958 * ( 0.20944 - 0.219864 * M ) * pi / 180.0
.alpha. 2 = ( 12.0 + 12.9427 * M ) * pi / 18 0 . 0 .alpha. 3 = ( 2
4 . 0 + 28.6479 * ( 0.20944 - 0.23094 * M ) ) * pi / 18 0 . 0
.alpha. 4 = ( 60.0 + 57.2958 * ( 0.20944 - 0.024139 8 * M ) ) * pi
/ 18 0 . 0 .alpha. 5 = ( 7 2 . 0 + 4 . 0 8888 * M ) * pi / 18 0 . 0
##EQU00008##
Embodiment 2
[0099] A control method for the permanent magnet synchronous
traction and transmission system provided by this embodiment
comprises an accurate current calculation, and specifically
comprises the following steps:
[0100] 1) Converting of a control target parameter, which is the
same as step 1) in Embodiment 1.
[0101] 2) Performing an accurate current calculation
[0102] Further, a converted input capacitor voltage F.sub.c1 is
obtained according to a set target modulation ratio Mt; after a
comparison with the input capacitor voltage Fc acquired by
sampling, a torque current compensation amount i.sub.q_crr and an
excitation current compensation amount i.sub.d_crr are generated by
regulation, and respectively added with the target torque current
value i.sub.q and the target excitation current value i.sub.d for
synthesis, so as to perform the accurate current calculation.
[0103] A principle of the flux-weakening control of the
flux-weakening compensation unit 27 is illustrated in FIG. 5. The
flux-weakening compensation unit 27 uses an accurate voltage
compensation amount, and takes the modulation ratio as a final
control target to generate the compensation amounts of i.sub.d and
i.sub.q;
[0104] wherein Mt is the set target modulation ratio for the
flux-weakening control (it can be construed as a modulation ratio
expected by the system to be output to the segment synchronous
modulation unit 25, and the flux-weakening compensation unit 27 is
for the purpose that a final output of the decoupling control unit
24 is M=Mt), with a value range of 0 to 1, and an empirical value
range of 0.88 to 0.91. A calculation formula of the feedback amount
F.sub.c1 is as follows:
F c 1 = 3 * ( U s + PID I d o u t ) M t 9 ) ##EQU00009##
[0105] wherein U.sub.q and U.sub.d are output results of the
voltage feedforward unit, and PID.Idout is a PID regulation output
result of a shaft d, i.e., an output result of the torque
modulation unit 232. F.sub.c1 is calculated using the set target
modulation ratio Mt.
[0106] A method for the accurate current calculation is:
[0107] performing an accurate calculation for the target excitation
current value i.sub.d and the target torque current value i.sub.q
to obtain an accurate excitation current value i.sub.dt arg et and
an accurate torque current value i.sub.qt arg et of the motor:
i dtarget = .psi. f + .psi. f 2 + 4 ( L q - L d - .differential. L
q .differential. L d ) i qtarget 2 2 ( L q - L d - .differential. L
q .differential. L d i qtarget ) 3 ) i dtarget = i d + i d - c c r
4 ) ##EQU00010##
[0108] For the above process, it can be understood that the Us and
PID.Idout is generated and output to the flux-weakening
compensation control unit 27 by the decoupling control unit 24, and
the converted input capacitor voltage F.sub.c1 is obtained by the
flux-weakening compensation control unit 27 according to the set
target modulation ratio Mt; after a comparison with the input
capacitor voltage Fc acquired by sampling, the torque current
compensation amount i.sub.q_crr and the excitation current
compensation amount i.sub.d_crr are generated by regulation, and
outputted to the current accurate calculation unit 26 and added
with the target torque current value i.sub.q and the target
excitation current value i.sub.d calculated by the MTPA calculation
unit 22 for synthesis, so as to perform the accurate current
calculation.
[0109] In which, the regulating and calculating method of the
torque current compensation amount i.sub.q_crr and the excitation
current compensation amount i.sub.d_crr may be the PID regulating
and calculating method, which will not be described in detail
here.
[0110] 3) Regulating and calculating the accurate excitation
current value and the accurate torque current value.
[0111] The acquired accurate excitation current value i.sub.dt arg
et and the accurate torque current value i.sub.qt arg et the motor
are used for the regulation and calculation. In this embodiment,
the PID regulating method is adopted.
[0112] An excitation current regulation value PID.I.sub.dout is
generated by the excitation regulation unit 231 according to the
accurate excitation current value i.sub.dt arg et and an operation
excitation current value i.sub.d_fed; a torque current regulation
value PID.I.sub.qout is generated by the torque regulation unit 232
according to the accurate torque current value i.sub.qt arg et and
an operation torque current value i.sub.q_fed; the excitation
current regulation value PID.I.sub.dout and the torque current
regulation value PID.I.sub.qout are used for the decoupling control
to generate a target modulation ratio and a modulation
frequency.
[0113] 4) Generating the Target Modulation Ratio and the Modulation
Frequency.
[0114] Referring to FIG. 6, the target excitation current value and
the target torque current value are decoupled, the target
modulation ratio is generated according to the target excitation
current value, and the modulation frequency is generated according
to the target torque current value.
[0115] In order to further improve a calculation accuracy of the
modulation ratio, in this embodiment, a voltage compensation value
is calculated by using the accurate excitation current value
i.sub.dt arg et and the accurate torque current value i.sub.qt arg
et so as to perform a compensation calculating for the target
modulation ratio:
{ U d = R s i dtarget + L d d i dtarget d t - .omega. r L q i
qtarget U q = R s i qtarget + L q d i qtarget d t + .omega. r ( L d
i dtarget + .psi. j ) 5 ) ##EQU00011##
[0116] wherein R.sub.s is a rotor resistance, .omega..sub.r is an
angular velocity, U.sub.d is a control voltage component of a shaft
d, and U.sub.q is a control voltage component of a shaft q.
[0117] The method for generating the target modulation ratio and
the modulation frequency is the same as the step 3.2) in Embodiment
1, and will not be repeated here.
[0118] 5) Segment synchronous modulation, which is the same as step
4) in embodiment 1 and will not be repeated here.
[0119] It should be noted that the accurate current calculation is
adopted by this embodiment. At an initial time, i.e., a start time,
each data is substantially 0. After the start, an initial target
excitation current value i.sub.d and an initial target torque
current value i.sub.q are acquired by calculating the torque
instruction. Since there is no operation data at this time and the
accurate calculation cannot be performed, the target excitation
current value i.sub.d and the target torque current value i.sub.q
are decoupled by the regulation unit, and then a PWM signal is
output to start the traction and transmission system; next, the
sampling unit 1 collects corresponding operation data, and the
entire control system starts to operate normally to achieve the
accurate control.
[0120] The method described in the present application is used for
the control of the permanent magnet traction and transmission
system, which can reduce switching frequency, increase efficiency,
and improve dynamic response speed and stability of the system.
[0121] Those described above are only preferred embodiments of the
present application, rather than limitations to the present
application in other forms. Any person skilled in the art can
change or modify the technical content disclosed above into
equivalent embodiments to be applied in other fields. However, any
simple amendment, equivalent change or modification made to the
above embodiments according to the technical essence of the present
application without departing from the technical solutions of the
present application still fall within the protection scope of the
present application.
* * * * *