CN112217410B - Fault-tolerant control method and system for open-circuit fault of three-level inverter - Google Patents

Fault-tolerant control method and system for open-circuit fault of three-level inverter Download PDF

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CN112217410B
CN112217410B CN202011285212.0A CN202011285212A CN112217410B CN 112217410 B CN112217410 B CN 112217410B CN 202011285212 A CN202011285212 A CN 202011285212A CN 112217410 B CN112217410 B CN 112217410B
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open
circuit fault
inverter
output voltage
control
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CN112217410A (en
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彭涛
陶宏伟
徐琰淞
廖菁
杨超
樊欣宇
阳春华
陈志文
桂卫华
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Central South University
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/505—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means
    • H02M7/515—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only
    • H02M7/521—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only in a bridge configuration
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
    • H02P21/0085—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation specially adapted for high speeds, e.g. above nominal speed
    • H02P21/0089—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation specially adapted for high speeds, e.g. above nominal speed using field weakening
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
    • H02P21/14—Estimation or adaptation of machine parameters, e.g. flux, current or voltage
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
    • H02P21/24—Vector control not involving the use of rotor position or rotor speed sensors
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P27/00—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage
    • H02P27/04—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage
    • H02P27/06—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters
    • H02P27/08—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters with pulse width modulation
    • H02P27/085—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters with pulse width modulation wherein the PWM mode is adapted on the running conditions of the motor, e.g. the switching frequency
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H02M1/325—Means for protecting converters other than automatic disconnection with means for allowing continuous operation despite a fault, i.e. fault tolerant converters

Abstract

The invention relates to the field of circuit fault tolerance control, and discloses a three-level inverter open-circuit fault tolerance control method and system, which improve the reliability and safety of the system. The method comprises the following steps: s1: establishing a relation between inverter switching signals and an evaluation function, establishing the evaluation function based on finite set model predictive control, determining an optional inverter output voltage vector set under the normal operation condition, and realizing the three-level inverter finite set model predictive control under the normal operation condition; s2: respectively analyzing the influence of various open-circuit faults on the output voltage vector of the inverter, and determining the influenced and available output voltage vector of the inverter after the open-circuit fault; s3: when an open-circuit fault occurs, the affected voltage vector is removed, the selectable inverter output voltage vector set is updated, the finite set model is used for predictive control, the pulse control signal corresponding to the value which enables the evaluation function to be minimum is selected, and fault-tolerant control is achieved.

Description

Fault-tolerant control method and system for open-circuit fault of three-level inverter
Technical Field
The invention relates to the field of circuit fault tolerance control, in particular to a three-level inverter open-circuit fault tolerance control method and system.
Background
The three-level inverter is a common power conversion device, can convert direct current into three-phase alternating current, is often used for a traction drive control system and a renewable energy conversion system, and needs the inverter to have high reliability and safety in application scenes, but power devices and diodes in the inverter run uninterruptedly for a long time under the conditions of high voltage, high frequency and large current, so that faults are easy to occur, statistics shows that the power devices which are most easy to fail of the power conversion device account for about 50% of the total number of system faults in many application occasions. The power device faults mainly comprise open circuit faults and short circuit faults, for the short circuit faults, a fast fuse is added in a system for protection, and when the short circuit faults occur, the fuse can be fused at a very high speed, so that the situation of the open circuit faults is changed; when an open-circuit fault occurs, if the open-circuit fault cannot be processed in time, the adjacent power devices can bear larger voltage and current, secondary fault is easily caused, and the operation reliability and safety of the converter and even the power conversion system are seriously influenced. Therefore, a fault-tolerant control method is urgently needed, and fault-tolerant control is performed when an open-circuit fault occurs in a converter, so that the reliability and the safety of the whole system are improved.
Disclosure of Invention
The invention mainly aims to disclose a three-level inverter open-circuit fault-tolerant control method and a three-level inverter open-circuit fault-tolerant control system, which are used for improving the reliability and safety of the system.
In order to achieve the purpose, the open-circuit fault-tolerant control method of the three-level inverter comprises the following steps:
s1: establishing a relation between inverter switching signals and an evaluation function, establishing the evaluation function based on finite set model predictive control, determining an optional inverter output voltage vector set under the normal operation condition, and realizing the three-level inverter finite set model predictive control under the normal operation condition;
s2: respectively analyzing the influence of various open-circuit faults on the output voltage vector of the inverter, and determining the influenced and available output voltage vector of the inverter after the open-circuit fault;
s3: when an open-circuit fault occurs, the affected voltage vector is removed, the selectable inverter output voltage vector set is updated, the finite set model is used for predictive control, the pulse control signal corresponding to the value which enables the evaluation function to be minimum is selected, and fault-tolerant control is achieved.
Optionally, the open-circuit fault includes at least one of a clamping diode open-circuit fault, a power device open-circuit fault outside the converter bridge arm, and a power device open-circuit fault inside the converter bridge arm.
Preferably, for an open-circuit fault of a power device outside a converter bridge arm, the step S3 further includes: and the fault-tolerant control is realized by combining the finite set model predictive control and the weak magnetic control. For an open-circuit fault of a power device inside a converter bridge arm, the step S3 further includes: before the affected voltage vector is removed, the power device with the open-circuit fault is short-circuited by using the thyristor, and after the pulse control signal corresponding to the value which enables the evaluation function to be minimum is selected, the fault-tolerant control is realized by combining the finite set model predictive control and the weak magnetic control.
The invention has the following beneficial effects:
the adopted finite set model predictive control concept is visual, easy to model, free from accurate model and complex control parameter design, has good effect on overcoming the problems of nonlinearity, uncertainty and the like in the industrial control process, is easy to increase constraint, and has quick dynamic response and strong robustness. The fault-tolerant control can be performed on various open-circuit faults and the like of the inverter based on the finite set model predictive control, and the fault-tolerant control can be further performed by combining the weak magnetic control when the power device is in the open-circuit fault, so that the reliability and the safety of the system are improved.
The present invention will be described in further detail below with reference to the accompanying drawings.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 is a flow chart of a method for fault-tolerant control of open-circuit faults of a three-level inverter according to a preferred embodiment of the present invention;
FIG. 2 is a diagram of a three-level inverter main circuit topology in accordance with a preferred embodiment of the present invention;
FIG. 3 is D of a preferred embodiment of the present invention1uOpen-circuit fault-tolerant control stator three-phase current oscillogram;
FIG. 4 is D of a preferred embodiment of the present invention1uOpen-circuit fault-tolerant control train speed oscillogram;
FIG. 5 is T of a preferred embodiment of the present inventionu1Open-circuit fault-tolerant control stator three-phase current oscillogram;
FIG. 6 is T of the preferred embodiment of the present inventionu1Open-circuit fault-tolerant control train speed oscillogram;
FIG. 7 is T of a preferred embodiment of the present inventionu2Open-circuit fault-tolerant control stator three-phase current oscillogram;
FIG. 8 is T of a preferred embodiment of the present inventionu2Open-circuit fault-tolerant control train speed oscillogram.
Detailed Description
The embodiments of the invention will be described in detail below with reference to the drawings, but the invention can be implemented in many different ways as defined and covered by the claims.
Example 1
The embodiment provides an open-circuit fault-tolerant control method for a three-level inverter.
Specifically, the present embodiment is described by taking as an example a three-level inverter in a traction drive control system, the main circuit schematic diagram of which is shown in fig. 1, and the dc-side voltage u1、u21500V, a DC side capacitor C1、C2At 16mF, the traction motor parameters used are shown in Table 1 below:
TABLE 1 traction Motor parameters
Parameter(s) Numerical value
Stator resistance Rs 0.15Ω
Stator self-inductance Ls 34.3mH
Rotor resistance Rr 0.16Ω
Rotor self-inductance Lr 34.1mH
Stator/rotor mutual inductance Lm 32.8mH
Rated voltage Urate 2000V
Rated frequency frate 140Hz
Rated speed nrate 4140r/min
Rated output power Prate 300kW
Rated slip srate 1.4％
Number of pole pairs n p 2
Sampling time ts 40us
As shown in fig. 2, the three-level open-circuit fault modeling method based on the single-bridge-arm model includes the following steps.
The method comprises the steps of firstly, establishing a relation between inverter switching signals and an evaluation function, establishing the evaluation function based on finite set model predictive control, determining an optional inverter output voltage vector set under the normal operation condition, and realizing the three-level inverter finite set model predictive control under the normal operation condition.
Step 11: establishing a relation between the output voltage of the inverter and the switching signal of the inverter, wherein the formula is as follows:
Figure BDA0002782148270000031
wherein u is1Is an upper side voltage source voltage u2Is a lower side voltage source voltage, SU、SV、SWRespectively equivalent switching signals u of three converter arms of the inverter U, V, WαIs the component u of the converter output voltage on the alpha axis of the stationary frameβIs the component of the converter output voltage on the axis of the stationary frame beta.
Step 12: establishing a relation between the rotating coordinate current and the stator three-phase current, wherein the formula is as follows:
Figure BDA0002782148270000041
wherein isdIs the d-axis current component of the rotation coordinate, isqIs the current component of the q-axis of the rotation coordinate, iu、iv、iwIs the stator three phase current.
Step 13: establishing a discrete current prediction model of the traction motor, wherein the formula is as follows:
Figure BDA0002782148270000042
wherein psisd(k)、ψsq(k) The flux linkages of the d axis and the q axis at the moment k can be obtained by a flux linkage observer, isd(k)、isq(k) D-axis and q-axis current components at time k, Rs、RrRespectively stator and rotor resistances, LsAnd LrRespectively the self-inductance of two equivalent windings of the stator and the self-inductance of two equivalent windings of the rotor under the dq coordinate system, omegar(k) Is the angular velocity of the rotor of the motor at time k, omegasl(k) Is the slip at time k, sigma is the leakage coefficient of the motor, TrIs the rotor electromagnetic time constant, tsIs the sampling time. The inverters have a total of R output voltage vectors,
Figure BDA0002782148270000043
Figure BDA0002782148270000044
respectively outputting voltage vectors of a delta d axis and a q axis at the moment of k + 1;
Figure BDA0002782148270000045
the δ -th d-axis and q-axis current components at the time k +1, respectively.
Step 14: constructing a finite set model predictive control evaluation function, wherein the formula is as follows:
Figure BDA0002782148270000046
wherein the content of the first and second substances,
Figure BDA0002782148270000047
respectively d-axis and q-axis current reference values (which can also be understood as target current values for realizing subsequent target speed control and the like), g at the time kδ(k) Is the evaluation function value g under the action of the delta-th output voltage vectorδ(k) The smaller the representative value, the better the system control performance.
The three-level inverter has R output voltage vectors, and the selectable output voltage vector set is determined to be
Figure BDA0002782148270000048
By comparing the evaluation function g corresponding to the delta-th output voltage vector in the set one by oneδ(k) Calculating the value of gδ(k) The pulse control signal (output voltage vector) corresponding to the minimum value is subjected to predictive control by using a finite set model, so that the three-level inverter control is realized.
Under normal conditions, the output voltage of each current-converting bridge arm is three, and the output voltage is u1、0、-u2If P, O, and N are respectively substituted, there are 27 output voltage vectors of the three-level inverter, which are PPP, PPO, PPN, POP, POO, PON, PNP, PNO, PNN, OPP, OPO, OPN, OOP, OOO, OON, ONP, ONO, ONN, NPP, NPO, NPN, NOP, NOO, NON, NNP, NNO, and NNN, and the set of selectable voltage vectors is determined to be { PPP, PPO, PPN, POP, POO, PON, PNP, PNO, PNN, OPP, OPO, OPN, oopp, OOO, OON, ONP, ONO, ONN, NPP, NPO, NPN, NOP, NOO, NON, NNP, NNO, NNN }; by comparing the evaluation function g corresponding to the delta-th voltage vector in the set one by oneδ(k) Calculating the value of gδ(k) The pulse control signal (output voltage vector) corresponding to the minimum value is subjected to predictive control by using a finite set model, so that the three-level inverter control is realized.
And secondly, analyzing the influence of the open-circuit fault of the clamping diode and the power device on the output voltage vector of the inverter respectively, and determining the influenced and available output voltage vector of the inverter after the open-circuit fault.
Step 21: d on bridge arm with U-phase current change1uFor example, the influence of open-circuit fault of a clamping diode on the output voltage of the inverter is analyzed, and under the normal condition, the three-level inverter can output 27 voltage vectors D1uAfter an open circuit fault occurs, the affected voltage vector is No. 10-18 voltage vector: OPP, OPO, OPN, OOP, OOO, OON, ONP, ONO, ONN, 9 kinds in total; the available output voltage vectors of the three-level inverter are No. 1-9 and No. 19-27 voltage vectors, and the number is reduced to 18.
Step 22: t on U-phase current-changing bridge armu1For example, the influence of the power device outside the converter arm on the output voltage of the inverter, T, is analyzedu1After an open circuit fault occurs, the affected voltage vector is No. 1-9 voltage vector: PPP, PPO, PPN, POP, POO, PON, PNP, PNO, PNN, 9 kinds in total; the available output voltage vector of the three-level inverter is No. 10-27 voltage vectors, and the number of the available output voltage vectors is reduced to 18.
Step 23: t on U-phase current-changing bridge armu2For example, the influence of the power device inside the converter arm on the output voltage of the inverter, T, is analyzedu2After an open circuit fault occurs, the No. 1 to No. 18 voltage vectors can be influenced: PPP, PPO, PPN, POP, POO, PON, PNP, PNO, PNN, OPP, OPO, OPN, OOP, OOO, OON, ONP, ONO, ONN, 18 kinds in total; the available output voltage vector of the three-level inverter is 19-27 voltage vectors, and the number of the available output voltage vectors is reduced to 9.
Thirdly, removing the affected voltage vector aiming at the open-circuit fault of the clamping diode, updating the selectable inverter output voltage vector set, and realizing fault-tolerant control by using a finite set model for predictive control; aiming at the open-circuit fault of a power device outside a converter bridge arm, removing an affected voltage vector, updating an optional inverter output voltage vector set, and realizing fault-tolerant control by combining finite set model predictive control and flux weakening control; aiming at the open-circuit fault of a power device at the inner side of a converter bridge arm, a thyristor is used for short-circuiting the power device with the open-circuit fault, then the affected voltage vector is removed, the optional inverter output voltage vector set is updated, and the fault-tolerant control is realized by combining the finite set model predictive control and the flux weakening control.
Step 31: aiming at open-circuit faults of the clamping diodes, after the open-circuit faults of the clamping diodes occur, the set of selectable voltage vectors is updated to be { PPP, PPO, PPN, POP, POO, PON, PNP, PNO, PNN, NPP, NPO, NPN, NOP, NOO, NON, NNP, NNO and NNN }, and evaluation functions g corresponding to 18 voltage vectors in the set are compared one by oneδ(k) Calculating the value of gδ(k) The pulse control signal (output voltage vector) corresponding to the minimum value is predicted and controlled by using a finite set model to realize the open-circuit fault tolerance control of the clamping diode, and the figure 3 is D1uOpen-circuit fault-tolerant control stator three-phase current waveform diagram, FIG. 4D1uThe fault-tolerant control train speed oscillogram of open circuit fault, the open circuit fault occurs in 2s, and the fault-tolerant control is carried out in 2.02 s.
S32: the common methods for improving the speed of the traction motor include two methods, one is to improve the input voltage of the traction motor, the other is to reduce the magnetic flux of a rotor of the traction motor, when a power device on a converter bridge arm has an open-circuit fault, the output voltage vector of an inverter is reduced, so that the input voltage of the traction motor is reduced, in order to ensure that the speed of the motor does not obviously reduce, when the power device has the open-circuit fault, weak magnetic control is used to stabilize the speed of the traction motor, and the weak magnetic control formula is considered as follows:
Figure BDA0002782148270000061
wherein psirIn order to determine the flux of the rotor before failure,
Figure BDA0002782148270000062
is the flux of the rotor after the flux weakening control, and lambda is the flux weakening coefficient.
Aiming at the open-circuit fault of the power device at the outer side of the converter bridge arm, updating the selectable voltage vector set into a selectable voltage vector set after the open-circuit fault of the power device at the outer side occurs; { OPP, OPO, OPN, OOP, OOO, OON, ONP, ONO, ONN, NPP, NPO, NPN, NOP, NOO, NON, NNP, NNO, NNN }, by comparing the evaluation functions g corresponding to the 18 voltage vectors in the set one by oneδ(k) Calculating the value of gδ(k) The minimum value corresponds to a pulse control signal (output voltage vector) and modifies the rotor flux to
Figure BDA0002782148270000063
The fault-tolerant control of the open-circuit fault of the power device outside the converter bridge arm is completed by combining the finite set model predictive control and the flux weakening control, and the T is shown in figure 5u1Open-circuit fault-tolerant control stator three-phase current oscillogram, FIG. 6 is Tu1The fault-tolerant control train speed oscillogram of open circuit fault, the open circuit fault occurs in 2s, and the fault-tolerant control is carried out in 2.02 s.
Step 33: aiming at the open-circuit fault of the power device at the inner side of the converter bridge arm, after the open-circuit fault of the power device at the inner side occurs, the available output voltage vector of the three-level inverter is 9 voltage vectors with 19-27 numbers; the power device with the open-circuit fault is in short circuit by using a thyristor, at the moment, the affected No. 19-27 voltage vectors are removed, the selectable voltage vector set is updated to be { PPP, PPO, PPN, POP, POO, PON, PNP, PNO, PNN, OPP, OPO, OPN, OOP, OOO, OON, ONP, ONO and ONN }, and evaluation functions g corresponding to 18 voltage vectors in the set are compared one by oneδ(k) Calculating the value of gδ(k) The minimum value corresponds to a pulse control signal (output voltage vector) and modifies the rotor flux to
Figure BDA0002782148270000064
The open-circuit fault-tolerant control of the power device inside the converter bridge arm is completed by combining the finite set model predictive control and the flux weakening control, and FIG. 7 is Tu2Open-circuit fault-tolerant control stator three-phase current oscillogram, FIG. 8 is Tu2The fault-tolerant control train speed oscillogram of open circuit fault, the open circuit fault occurs in 2s, and the fault-tolerant control is carried out in 2.02 s.
In the above steps 32 and 33, unlike the slow and continuous speed increasing method of flux weakening control in the conventional traction drive control system, the fault-tolerant flux weakening of the present embodiment is usually performed to reduce the input voltage, and in order to achieve the fault-tolerant control effect quickly, the present embodiment is mostly performed in a manner of instantaneously reducing the magnetic flux.
In summary, the embodiment can perform fault-tolerant control on open-circuit faults of power devices and clamp diodes of the inverter, construct a finite set model predictive control evaluation function, and provide a hardware fault-tolerant topology structure.
Example 2
The embodiment discloses a three-level inverter open-circuit fault tolerance control system, which comprises a memory, a processor and a computer program which is stored on the memory and can run on the processor, wherein the steps of the method corresponding to the embodiment are realized when the processor executes the computer program.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (6)

1. The open-circuit fault-tolerant control method of the three-level inverter is characterized by comprising the following steps of:
s1: establishing a relation between inverter switching signals and an evaluation function, establishing the evaluation function based on finite set model predictive control, determining an optional inverter output voltage vector set under the normal operation condition, and realizing the three-level inverter finite set model predictive control under the normal operation condition;
s2: respectively analyzing the influence of various open-circuit faults on the output voltage vector of the inverter, and determining the influenced and available output voltage vector of the inverter after the open-circuit fault; the open-circuit fault comprises at least one of a clamping diode open-circuit fault, a power device open-circuit fault at the outer side of the converter bridge arm and a power device open-circuit fault at the inner side of the converter bridge arm;
s3: when an open-circuit fault occurs, removing the affected voltage vector, updating the selectable inverter output voltage vector set, using the finite set model for predictive control, and selecting the pulse control signal corresponding to the value which enables the evaluation function to be minimum to realize fault-tolerant control; the method comprises the following steps: aiming at the open-circuit fault of the power device at the outer side of the converter bridge arm: the method combines the finite set model predictive control and the weak magnetic control to realize the fault-tolerant control; and/or aiming at the open-circuit fault of the power device inside the converter bridge arm: before the affected voltage vector is removed, the power device with the open-circuit fault is short-circuited by using the thyristor, and after the pulse control signal corresponding to the value which enables the evaluation function to be minimum is selected, the fault-tolerant control is realized by combining the finite set model predictive control and the weak magnetic control.
2. The three-level inverter open-circuit fault-tolerant control method according to claim 1, wherein the S1 specifically includes:
s11: establishing a relation between the output voltage of the inverter and the switching signal of the inverter, wherein the formula is as follows:
Figure FDA0003342601600000011
wherein u is1Is an upper side voltage source voltage u2Is a lower side voltage source voltage, SU、SV、SWRespectively equivalent switching signals u of three converter arms of the inverter U, V, WαIs the component u of the converter output voltage on the alpha axis of the stationary frameβIs the component of the converter output voltage on the beta axis of the static coordinate system;
s12: establishing a relation between the rotating coordinate current and the stator three-phase current, wherein the formula is as follows:
Figure FDA0003342601600000012
wherein isdIs the d-axis current component of the rotation coordinate, isqIs the current component of the q-axis of the rotation coordinate, iu、iv、iwIs the stator three phase current;
s13, establishing a discrete current prediction model of the traction motor, wherein the formula is as follows:
Figure FDA0003342601600000021
wherein psisd(k)、ψsq(k) The flux linkages of the d axis and the q axis at the moment k can be obtained by a flux linkage observer, isd(k)、isq(k) D-axis and q-axis current components at time k, Rs、RrRespectively stator and rotor resistances, LsAnd LrRespectively the self-inductance of two equivalent windings of the stator and the self-inductance of two equivalent windings of the rotor under the dq coordinate system, omegar(k) Is the angular velocity of the rotor of the motor at time k, omegasl(k) Is the slip at time k, sigma is the leakage coefficient of the motor, TrIs the rotor electromagnetic time constant, tsIs the sampling time; the inverters share R output voltage vectors, delta is 1,2,3 … R,
Figure FDA0003342601600000022
respectively outputting voltage vectors of a delta d axis and a q axis at the moment of k + 1;
Figure FDA0003342601600000023
d-axis and q-axis current components at the k +1 moment respectively;
s14: constructing a finite set model predictive control evaluation function, wherein the formula is as follows:
Figure FDA0003342601600000024
wherein the content of the first and second substances,
Figure FDA0003342601600000025
d-axis and q-axis current reference values at the time of k, gδ(k) Is the evaluation function value g under the action of the delta-th output voltage vectorδ(k) The smaller the representative system control performance is;
the three-level inverter has R output voltage vectors, and the selectable output voltage vector set is determined to be
Figure FDA0003342601600000026
By comparing the evaluation function g corresponding to the delta-th output voltage vector in the set one by oneδ(k) Calculating the value of gδ(k) And the pulse control signal corresponding to the minimum value is subjected to predictive control by using a finite set model, so that the three-level inverter control is realized.
3. The three-level inverter open-circuit fault-tolerant control method according to claim 2, wherein the S2 specifically includes:
s21: analyzing the influence of open-circuit faults of the clamping diodes on the output voltage of the inverter, wherein the influenced voltage vector is as follows:
Figure FDA0003342601600000027
{a,b,…,R′1belongs to {1,2, …, R }, and is total R'1Seed growing; the vector of the available output voltage of the three-level inverter is reduced to R under the condition that the open-circuit fault occurs to the clamping diode1Seed growing;
correspondingly, the S3 specifically includes:
s31: aiming at the open-circuit fault of the clamping diode, updating the vector set of the output voltage of the selectable inverter to be
Figure FDA0003342601600000028
By comparing R in the set one by one1Evaluation function g corresponding to seed voltage vectorδ(k) Calculating the value of gδ(k) And the pulse control signal corresponding to the minimum value is subjected to predictive control by using a finite set model, so that the fault-tolerant control of the three-level inverter under the open-circuit fault of the clamping diode is realized.
4. The three-level inverter open-circuit fault-tolerant control method according to claim 2, wherein the S2 specifically includes:
s22: analyzing the influence of a power device outside a converter bridge arm on the output voltage of the inverter, wherein the influenced voltage vector is as follows:
Figure FDA0003342601600000031
{i,j,…,R′2belongs to {1,2, …, R }, and is total R'2Seed growing; the vector of the available output voltage of the three-level inverter is reduced to R under the condition that the open-circuit fault occurs in the outer power device2Seed growing;
correspondingly, the S3 specifically includes:
s32: when a power device on a converter bridge arm has an open-circuit fault, the output voltage vector of an inverter is reduced, so that the input voltage of a traction motor is reduced, and in order to ensure that the speed of the motor does not obviously decrease, when the power device has the open-circuit fault, the speed of the traction motor is stabilized by using weak magnetic control, wherein the weak magnetic control formula is as follows:
Figure FDA0003342601600000032
wherein psirIn order to determine the flux of the rotor before failure,
Figure FDA0003342601600000033
is the flux of the rotor after the flux weakening control, and lambda is the flux weakening coefficient;
aiming at the open-circuit fault of the power device at the outer side of the converter bridge arm, and updating the vector set of the output voltage of the selectable inverter to be
Figure FDA0003342601600000034
By comparing R in the set one by one2Evaluation function g corresponding to seed voltage vectorδ(k) Calculating the value of gδ(k) A pulse control signal corresponding to the minimum value and changing the rotor flux to
Figure FDA0003342601600000035
Predictive control with combined use of finite set modelsAnd the system and the field weakening control realize the fault-tolerant control of the three-level inverter under the open-circuit fault of the power device outside the converter bridge arm.
5. The three-level inverter open-circuit fault-tolerant control method according to claim 2, wherein the S2 specifically includes:
s23: analyzing the influence of a power device inside a converter bridge arm on the output voltage of the inverter, wherein the influenced voltage vector is as follows:
Figure FDA0003342601600000036
{l,m,…,R′3belongs to {1,2, …, R }, and is total R'3Seed growing; the vector of the available output voltage of the three-level inverter is reduced to R under the condition that the inner side power device has open circuit fault3Seed growing;
correspondingly, the S3 specifically includes:
s33: aiming at the open-circuit fault of the power device at the inner side of the converter bridge arm, after the open-circuit fault of the power device at the inner side occurs, the output voltage vector of the inverter is R3Seed growing; the power device with open-circuit fault is short-circuited by using a thyristor, and at the moment, the influenced voltage vector is as follows:
Figure FDA0003342601600000037
{p,q,...,R′4r' is the same as {1, 2.4In one embodiment, the available output voltage vector of the three-level inverter is reduced to R4Seed growing; updating a set of selectable inverter output voltage vectors to
Figure FDA0003342601600000038
By comparing R in the set one by one4Evaluation function g corresponding to seed voltage vectorδ(k) Calculating the value of gδ(k) A pulse control signal corresponding to the minimum value and changing the rotor flux to
Figure FDA0003342601600000041
The method combines the prediction control of a finite set model and the weak magnetic control to realize the power of the inner side of the converter bridge armAnd carrying out fault-tolerant control on the three-level inverter under the condition of open-circuit fault of the device.
6. A three-level inverter open-circuit fault-tolerant control system comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor implements the steps of the method of any of the preceding claims 1 to 5 when executing the computer program.
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