CN109450315B - Phase failure fault-tolerant control method for surface-mounted permanent magnet synchronous motor - Google Patents

Abstract

The invention relates to a fault-tolerant control method for an open-phase fault of a surface-mounted permanent magnet synchronous motor. Under the condition of phase failure, by designing a novel reference coordinate conversion matrix, time-varying sine type non-fault phase reference current and neutral current under a three-phase static coordinate system can be converted into two direct current quantities under a novel synchronous rotating coordinate system in a reference mode, and the two direct current quantities are equal to a current given value of a motor system. Based on novel coordinate transformation, a motor control system does not need to redesign a complex current controller after the phase failure of the motor, and can directly apply a current PI controller before the failure to carry out motor control, thereby realizing the fault-tolerant control of the surface-mounted permanent magnet synchronous motor under the phase failure.

Description

Phase failure fault-tolerant control method for surface-mounted permanent magnet synchronous motor

Technical Field

The invention relates to a phase failure fault-tolerant control method for a surface-mounted permanent magnet synchronous motor, which is used for realizing high-performance safe and stable operation of a motor driving system after the phase failure of the surface-mounted permanent magnet synchronous motor.

Background

The permanent magnet synchronous motor has the advantages of wide speed regulation range, good dynamic response, strong controllability, high power factor and the like, and is widely applied to the fields of industry, military, aerospace and the like. Open-phase faults are a common fault in permanent magnet synchronous machines that can degrade machine performance and increase losses due to phase current imbalance. In order to avoid the adverse factors, the open-phase fault-tolerant driving technology is applied to the open-phase motor, so that the current of a non-fault phase winding after the motor is open-phase can be reduced, the torque pulsation is restrained, and the high-performance safe and stable operation of a motor driving system is ensured. Researches show that the permanent magnet synchronous motor mainly comprises a surface-mounted type and a built-in type according to the rotor structure. The surface-mounted permanent magnet synchronous motor has excellent performance and mainly adopts i_d Control method 0. i.e. i_dThe control method 0 can simplify the analysis and modeling of the four-leg inverter-based motor. Considering i_d0 control method is widely applied to surface-mounted permanent magnet synchronous motorThe study on the open-phase fault-tolerant control method is of great significance.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: aiming at the problem of phase failure of a surface-mounted permanent magnet synchronous motor based on four-bridge arm topology, a novel reference coordinate transformation matrix is provided, the transformation matrix can convert time-varying sinusoidal non-fault phase reference current and neutral current reference quantity in a three-phase static coordinate system into two direct current quantities in a novel synchronous rotating coordinate system, and the two direct current quantities are equal to a given current value of a motor system. Based on novel coordinate transformation, the current PI controller before the fault can be directly applied after the phase failure of the motor system, and the high-performance fault-tolerant control of the surface-mounted permanent magnet synchronous motor under the phase failure can be realized without redesigning a complex current controller.

The technical scheme adopted by the invention for solving the technical problems is as follows: a surface-mounted permanent magnet synchronous motor open-phase fault-tolerant control method comprises the following steps:

step one, establishing an open-phase fault-tolerant control system. The system comprises seven modules: the system comprises a PI controller module 1, a coordinate inverse transformation module 2, a PWM wave generation module 3, a four-bridge inverter module 4, a permanent magnet synchronous motor module 5, a fault diagnosis module 6 and a coordinate transformation module 7, wherein the 7 modules are used for realizing high-performance control on the motor before and after phase failure. The fault diagnosis module 6 is responsible for detecting three-phase currents of the permanent magnet synchronous motor module 5, judging the health condition of the permanent magnet synchronous motor module 5 according to the three-phase currents and further controlling the system operation mode; the coordinate inverse transformation module 7 is responsible for converting the three-phase current into a current feedback value under a synchronous rotating coordinate system; the PI control module 1 is responsible for converting a current error value (namely the difference between a current reference value and a current feedback value) in a synchronous rotation coordinate system into a voltage reference value; the coordinate inverse transformation module 2 is responsible for converting the voltage reference value under the synchronous rotating coordinate system into a voltage reference value under a three-phase static coordinate system; the PWM wave generation module 3 generates 8 paths of PWM waves according to the three-phase voltage reference value and is used for controlling a switching tube in the four-bridge arm inverter module 4, so that the driving control of the permanent magnet synchronous motor module 5 is realized;

step two, the control system switches the operation mode according to the motor health condition output by the fault diagnosis module 6:

when the fault diagnosis module judges that the motor has no fault, the system operates in a conventional mode, namely the coordinate transformation module 7 adopts a transformation matrix P (namely an a-b-c coordinate system → a d-q-0 coordinate system transformation matrix), and the coordinate inverse transformation module 2 adopts the matrix P^-1(i.e., d-q-0 coordinate system → a-b-c coordinate system transformation matrix), and the PWM wave generating module 3 adopts a conventional carrier-based PWM modulation method, i is normally the case_nThe three-phase current i fed back by the motor can be ignored when the value is 0_a,i_b,i_cThe direct current feedback current i under the synchronous rotating coordinate system is converted through a coordinate transformation matrix P of a coordinate transformation module 7_d,i_qFeedback current i_d、i_qWith given value of current i_d ^*、i_q ^*Comparing, and inputting the difference value into the current PI controller module 1; the current PI controller calculates and outputs a reference voltage u according to the error value_d ^*、u_q ^*；u_d ^*、u_q ^*As input to the inverse coordinate transformation module 2, by inverse coordinate transformation (P)^-1) Converted into three-phase reference voltage u_an ^*,u_bn ^*,u_cn ^*(ii) a Three-phase reference voltage is input into the PWM wave generation module 3 and is used as the input of the PWM wave generator, and the PWM wave generator firstly adopts a PWM modulation mode based on carrier waves to generate 4 paths of PWM switching signals S_a、S_b、S_cAnd S_nGenerating 4 paths of inverting switch signals through logical negation operation; the 8 paths of PWM switching signals generated by the PWM generating module are input into the four-bridge arm inverter module 4 and control 8 switching tubes of the four-bridge arm inverter; the inverter drives the motor by correspondingly connecting the four bridge arms with a phase line and a neutral line of the motor;

once the fault diagnosis module 6 detects that the phase failure of the motor occurs, the output signal F of the fault diagnosis module is used for repeating three modules of the coordinate inverse transformation module 2, the PWM wave generation module 3 and the coordinate transformation module 7 in the control systemThe system is switched to a fault mode of operation, i.e. the coordinate transformation module uses the transformation matrix (ST) (i.e. the transformation matrix of the b-c-n coordinate system → the transformation matrix of the d-q-0 coordinate system), and the inverse coordinate transformation module uses the transformation matrix (ST)^-1(i.e., d-q-0 coordinate system → b-c-n coordinate system transformation matrix), and the PWM wave generation module adopts a carrier-based PWM modulation scheme (setting A-phase voltage reference u) in an open-phase fault mode_an ^*Setting the switching signal corresponding to the phase failure to be zero); in the fault state, the current of the faulted phase is zero, i.e. i_aOther feedback currents i of the motor, 0_b,i_c,i_nThe current is converted into a feedback current i under a synchronous rotating coordinate system through a coordinate transformation matrix (ST) of a coordinate transformation module 7_r,i_kFeedback current i_r、i_kWith given value of current i_d ^*、i_q ^*Comparing, and inputting the difference value to a PI controller in the PI controller module 1; the PI controller calculates and outputs a reference voltage u_d ^*、u_q ^*；u_d ^*、u_q ^*Inputting into the coordinate inverse transformation module 2, passing through the coordinate inverse transformation matrix (ST) of the coordinate inverse transformation module 2^-1Obtain a two-phase reference voltage u_bn ^*,u_cn ^*Two-phase reference voltage is input into the PWM wave generation module 3 as the input of the PWM wave generator, and the PWM wave generator sets u first in the fault mode_an ^*When the signal is equal to 0, the 4 paths of PWM switching signals S are directly generated by using a PWM modulation mode based on a carrier wave method_b,S_c,S_nThe 4 switching signals are converted into 4 inverting switching signals through logical negation, and the switching signal S corresponding to the break fault in the 8 switching signals_aAnd

the three-phase inverter is set to zero to realize the isolation of the fault phase, finally generated 8-path switching signals are input into the four-leg inverter module 4 through signal lines to control 8 switching tubes in the four-leg inverter, and four legs of the inverter are respectively and correspondingly connected with a phase line and a middle line of the motor (the fault phase is cut off), thereby realizing the fault stateThe drive control of the motor is performed.

The new coordinate transformation (x-y-n coordinate system → r-k coordinate system) is:

wherein i_rk＝[i_r i_k]^TThe current in the synchronous rotating coordinate system at the time of phase failure is the current i in the synchronous rotating coordinate system of the motor before the failure_d、i_qEqual; i.e. i_xyn＝[i_x i_y i_n]^TAnd the feedback currents of the healthy phase and the neutral line of the motor in fault are shown, subscripts x and y represent non-fault phases, and k is a phase adjustment coefficient: when A is out of phase, x is b, y is c, and k is 0; when B phase is out of phase, x is c, y is a, and k is 2; when C is out of phase, x is a, y is b, and k is 1.θ represents the rotor angular position; k is a radical of₁、k₂、k₃Is constant, with a value of:

the new inverse coordinate transformation (r-k coordinate system → x-y-n coordinate system) is:

wherein u is_xyn ^*＝[u_x ^* u_y ^* u_n ^*]^TThe voltage commands corresponding to the healthy phase and the neutral line; u. of_rk ^*＝[u_r ^* u_k ^*]^TThe voltage command is a voltage command in an r-k coordinate system, and the values of the voltage command are respectively equal to a voltage reference u in a synchronous rotating coordinate system of the motor before the fault_d ^*、u_q ^*Are equal.

The principle of the invention is as follows: under the condition of phase failure, three-phase static coordinates can be converted by designing a novel reference coordinate conversion matrixUnder-system time-varying sine type non-fault phase reference current and neutral current reference are converted into two direct current quantities i under novel synchronous rotating coordinate system_r ^*、i_k ^*So that the two direct current quantities are respectively equal to the given current value i of the motor system_d ^*、i_q ^*Equal (i)_d ^*、i_q ^*May be calculated from the torque command). Based on novel coordinate transformation, the current PI controller before the fault can be directly applied after the phase failure of the motor system, and the high-performance fault-tolerant control of the surface-mounted permanent magnet synchronous motor under the phase failure can be realized without redesigning a complex current controller.

The method comprises the following implementation steps:

in the first step, the three-phase reference current and the neutral reference current at the time of the fault are calculated.

The transformation formula of the permanent magnet synchronous motor from a d-q-0 coordinate system to an a-b-c coordinate system under the normal condition is as follows:

in the formula i_a、i_b、i_cRepresenting three-phase current i in a-b-c coordinate system_d、i_q、i₀Represents armature current in a d-q-0 coordinate system and theta represents rotor angular position.

If the phase A is in phase failure, the phase A current is constantly 0 after the failure and is not controlled by the system. If the calculation method of the reference current is not changed, the actual current on the d-q axis is difficult to track the current command, and the performance of the control system is greatly reduced. To reduce the impact of phase interruption on system control performance, the phase current command for the a-phase winding may be set to 0 (i.e., i)_a ^*0) and substituting the phase current transformation formula from the d-q-0 coordinate system to the a-b-c coordinate system to obtain the reference current of the non-fault phase winding and the neutral line when the phase A fails, wherein the reference current of the non-fault phase winding and the neutral line should satisfy the following formula:

in the formula, the neutral reference current i_n ^*＝3·i₀ ^*＝-(i_a+i_b+i_c)，i_b ^*And i_c ^*Reference currents of phase B and phase C, i_d ^*、i_q ^*And i₀ ^*D-axis, q-axis and zero-axis reference currents, respectively.

Similarly, the reference current corresponding to the non-fault phase winding and the neutral line when the phase B is open is as follows:

and the reference current corresponding to the non-fault phase winding and the neutral line when the phase C is open is as follows:

it can be known from the expression of the reference current after the phase failure of A, B, C phases, that in order to ensure the equal torque values of the motor before and after the phase failure, the phase current amplitudes of the two remaining non-failure phases must be increased to the original amplitudes

Multiple and 60 deg. out of phase with each other, while the neutral current amplitude has to be increased by a factor of 3. The reference current of k after the phase failure of the motor can be written as follows:

in the formula, subscripts x and y denote non-failed phases, subscript z denotes failed phase, i_x ^*、i_y ^*Phase current reference for non-faulted phases of the machine, i_z ^*For phase current reference of a failed phase of the motor, k is a phase adjustment coefficient and has: when the phase A is out of phase, x is b, y is c,k is 0; when the phase B fails, x is c, y is a, and k is 2; when the phase C fails, x is a, y is b, and k is 1.

For surface-mounted permanent magnet synchronous motors, i is usually adopted_dControl method of 0, set i_d ^*0 can simplify the above formula:

and secondly, designing novel current coordinate transformation.

From the above equation, it can be seen that the non-fault phase reference current and the neutral reference current are both synchronized with the rotor flux linkage. If the reference current is converted into the same current reference value (the reference value is a direct current quantity) as the system before the fault through novel coordinate transformation, the design of the controller can be simplified, and the performance of the system after the fault is improved.

First, a stationary x-y-n reference frame can be converted into a stationary s-t orthogonal frame, as shown in FIG. 3. The coordinate transformation is similar to the transformation of a-b-c coordinate system → alpha-beta coordinate system, and the transformation formula can be obtained by utilizing the projection relation:

in the formula, the matrix T is:

secondly, the motor reference current is converted from a stationary s-t orthogonal coordinate system to a synchronous rotating r-k coordinate system. However, since the expression of the sine term of the non-fault reference current in the fault state is different from the expression of the reference value of the three-phase current in the normal state, the current reference cannot be converted to the synchronous rotating coordinate system through the transformation matrix of the conventional alpha-beta coordinate system → d-q coordinate system.

The transformation matrix of the α - β coordinate system → the d-q coordinate system when phase A is open can be obtained first. It is assumed that the time-varying sinusoidal non-fault phase reference current can be converted to a corresponding synchronous rotational variable (i.e., the b-c-n coordinate system → the r-k coordinate system) by the following changes:

wherein S ═ a · cos θ b · sin θ; c sin thetad cos theta]，i_r ^*、i_k ^*Is converted into a DC current reference value under a novel r-k coordinate system through novel coordinate transformation (a b-c-n coordinate system → a r-k coordinate system). Substituting the phase reference current and the neutral reference current expressions into the above expression, which can be expressed as:

to simplify the design of the controller, set i_r ^*、i_k ^*The value is respectively compared with the current reference i of the motor system before the fault_d ^*、i_q ^*Are equal, i_r ^*＝i_d ^*And i_k ^*＝i_q ^*And setting a to 1, the following formula can be obtained:

therefore, a novel coordinate transformation of the b-c-n coordinate system → r-k coordinate system is available:

when B, C are respectively out of phase, the reference current vector i of the motor under the x-y-n coordinate system can be known by observing the reference current obtained in the first step_x ^*、i_y ^*、i_n ^*The phase difference between the corresponding reference current vectors when the phase is disconnected from the phase A is 4 pi/3 and 2 pi/3, and the phase difference is the same as that of the corresponding reference current vectors when the phase A is disconnected from the phase AReference current vector i under step rotation coordinate system_r ^*、i_k ^*Then the same is i before the failure_d ^*、i_q ^*The spatial orientation and transformation relationship of each current vector are shown in fig. 3. Therefore, the coordinate transformation relation of the x-y-n coordinate system → the r-k coordinate system when the phases of B, C are respectively disconnected can be obtained through the Euler rotation matrix. A. B, C the coordinate transformation relationship of x-y-n coordinate system → r-k coordinate system when phase is open is as follows:

in the formula, subscripts x and y denote non-failed phases, subscript z denotes failed phase, i_x、i_yPhase current of non-faulted phase of motor, i_zThe phase current of the motor fault phase, k is a phase adjustment coefficient and has: when the phase A fails, x is b, y is c, and k is 0; when the phase B fails, x is c, y is a, and k is 2; when the phase C fails, x is a, y is b, and k is 1. k is a radical of₁、k₂、k₃Is constant, with a value of:

and thirdly, designing coordinate transformation of the voltage command. Because the three-bridge-arm inverter does not have the fault-tolerant capability of the open-phase fault, the four-bridge-arm inverter is adopted to carry out fault-tolerant control of the open-phase fault. Inverters are classified into a voltage-type inverter and a current-type inverter, and the voltage-type inverter is widely used for reasons such as high cost performance of a permanent magnet synchronous motor control system. In order to control the four-leg voltage inverter, the system needs to give voltage reference values of three-phase windings and a neutral line. However, the motor control system only carries out PI closed-loop control on the d-q axis current, and the output of the PI current controller is a d-q axis voltage reference value (u)_d ^*,u_q ^*). In order to obtain the voltage reference value of the three-phase winding and the neutral wire, the system needs to give a voltage instruction u_d ^*,u_q ^*The transformation is performed (r-k coordinate system → x-y-n coordinate system).

When the phase failure occurs to the z phase, an inverse transformation matrix of the r-k coordinate system → the x-y-n coordinate system is derived according to the current coordinate transformation relation of the x-y-n coordinate system → the r-k coordinate system and is as follows:

wherein u is_xyn ^*＝[u_x ^* u_y ^* u_n ^*]^TThe voltage commands corresponding to the healthy phase and the neutral line; u. of_rk ^*＝[u_r ^* u_k ^*]^TThe voltage command is a voltage command in an r-k coordinate system, and the values of the voltage command are respectively equal to a voltage reference u in a synchronous rotating coordinate system of the motor before the fault_d ^*、u_q ^*Are equal.

And fourthly, generating the PWM wave. The motor control system adopts a PWM (pulse-width modulation) method based on a carrier wave to obtain a four-bridge arm inverter switching signal. Under normal conditions, the carrier-based PWM method calculates a neutral voltage reference value (taking the midpoint of a direct-current bus capacitor as a reference zero potential) by adopting the following formula:

the reference voltage at the phase end of A, B, C can be expressed as:

wherein u is_as ^*、u_bs ^*、u_cs ^*And u_n ^*The neutral point voltage reference and the neutral point voltage reference are from the motor end to the bus voltage. When the z-phase is open-phase, the z-phase voltage instruction cannot be obtained through the coordinate inverse transformation module. Calculating to know when setting u_an ^*When equal to 0The PWM generation according to the above method can maximize the voltage modulation range (consistent with the voltage modulation range before the fault), so that in the fault mode, the PWM generation module sets the voltage command of the z-phase to zero (i.e. makes u command to be u command) first_zn ^*0), and then the terminal voltage command u is calculated by the method_as ^*、u_bs ^*、u_cs ^*And u_n ^*。

The PWM generation module directly generates a four-way switching signal S by comparing the terminal voltage command with the triangular carrier wave_a,S_b,S_c,S_nAnd 4 corresponding inverting switch signals are obtained through logical negation operation to drive the lower bridge arm switch tube. In the normal mode, the 8 switching signals are directly input to the four-leg inverter module. In the fault mode, in order to isolate the fault, 2 paths of switching signals corresponding to the fault are input into the four-bridge arm inverter after being set to zero.

Compared with the prior art, the invention has the advantages that:

1. compared with an open-phase fault-tolerant control strategy based on a three-phase converter topology, the method has higher voltage utilization rate. In a three-phase converter based topology, the motor neutral is connected to the bus capacitor midpoint. The voltage utilization based on the three-phase converter topology was analyzed as v 3/4, while the voltage utilization based on the four-leg converter topology was v 3/2. The voltage utilization rate of the four-bridge-arm converter is the same as that in a normal state. Therefore, the open-phase fault-tolerant method based on the four-bridge-arm topology has high voltage utilization rate.

2. Compared with an open-phase fault-tolerant control strategy based on a four-bridge-arm converter topology, the method is simple in design, a current controller does not need to be redesigned, and high control performance can be achieved by adopting PI current controllers with the same control parameters before and after a fault. The method converts the non-fault phase current into direct current by designing novel coordinate transformation, thereby simplifying the design of the open-phase fault motor controller. Through novel coordinate transformation, the transfer function of the motor system is basically kept unchanged before and after a fault, so that the motor control system can directly apply a current PI controller before the fault after the phase failure, and a complex current controller does not need to be redesigned. The method has simple structure and is easy to realize.

Drawings

FIG. 1 is a flow chart of the algorithm of the present invention;

FIG. 2 is a system architecture of the present invention, wherein 1 represents a PI controller module; 2 represents a coordinate inverse transformation module; 3 represents a PWM generation module; 4 represents a four-leg inverter module; 5 represents a permanent magnet synchronous motor module; 6 represents a fault diagnosis module; 7 represents a coordinate transformation module;

fig. 3 is a schematic diagram of a reference current coordinate transformation relation according to the present invention. Wherein, fig. 3(a), 3(b), and 3(c) are schematic diagrams of reference current vectors in the x-y-n coordinate system and the conventional a-b-c coordinate system corresponding to A, B, C phases with single phase loss, respectively; and 3(d), 3(e) and 3(f) are schematic diagrams of reference current vectors under an x-y-n coordinate system, an s-t coordinate system and an r-k coordinate system when A, B, C phases are independently open respectively.

Detailed Description

The invention is further described with reference to the following figures and detailed description.

Fig. 2 is a phase failure fault-tolerant control system of a surface-mounted permanent magnet synchronous motor designed by the invention, which mainly comprises seven modules: the system comprises a PI controller module 1, a coordinate inverse transformation module 2, a PWM wave generation module 3, a four-bridge arm inverter module 4, a permanent magnet synchronous motor module 5, a fault diagnosis module 6 and a coordinate transformation module 7.

In the motor control system, a coordinate transformation module 7 carries out coordinate transformation on the measured values (from a current sensor) of three-phase current and neutral current to convert the measured values into current measured values of d-q axes, and is used as a feedback quantity to be compared (differenced) with a given value of the d-q axis current, the compared result (error value) is input into the current PI controller module 1, the controller converts the error value of the d-q axis current into a voltage command of the d-q axis according to a corresponding control rule, the voltage command is converted into a three-phase voltage command through a coordinate inverse conversion module 2, the three-phase voltage command is transmitted to a PWM wave generation module 3 through a signal line, the module generates PWM signals by adopting a PWM (pulse-width modulation) mode based on a carrier, and the generated PWM signals are sent to the four-arm inverter module 4 to control 8 switching tubes of the four arms of the inverter. Because the four bridge arms are connected with the 4 ports of the motor module 5, the control of the voltage and the phase current of each end of the motor is realized, and finally the control of the stator flux linkage and the electromagnetic torque of the motor is realized, namely the control of the motor is realized. And a fault diagnosis module 6 in the motor control system is responsible for carrying out fault detection on the motor, and controlling algorithms of 3 modules, namely a coordinate transformation module, a coordinate inverse transformation module and a PWM wave generation module, in the system according to a detection result, wherein if the system is detected to be in a normal state, the three modules use a conventional algorithm, and when a fault is detected, the three modules use a fault algorithm. The specific algorithm of each module is described in detail below.

The coordinate transformation module 7: the module uses a coordinate transformation matrix (P or ST) to convert the detected three-phase winding and neutral currents (i)_abcOr i_xyn) Conversion into current feedback (i) under synchronous rotating coordinate system_dqOr i_rk). The algorithm of the module will change with the system state. The normal case algorithm (conventional algorithm) is:

the algorithm in case of failure is as follows:

wherein i_rk＝[i_r i_k]^TThe current in the synchronous rotating coordinate system at the time of phase failure is the current i in the synchronous rotating coordinate system of the motor before the failure_d、i_qEqual; i.e. i_xyn＝[i_x i_y i_n]^TAnd the feedback currents of the healthy phase and the neutral line of the motor in fault are shown, subscripts x and y represent non-fault phases, and k is a phase adjustment coefficient: when A is out of phase, x is b, y is c, and k is 0; when B phase is out of phase, x is c, y is a, and k is 2; when C is out of phase, x is a, y is b, and k is 1.θ represents the rotor angular position; k is a radical of₁、k₂、k₃Is constant, with a value of:

current PI controller module 1: the module converts the current error value into a voltage expected value by using a PI control rule, and the algorithm before and after the fault is not changed, wherein the specific algorithm can be expressed as follows:

in the algorithm K_pd、K_IdAnd K_pq、K_IqThe control parameters of the current PI controllers on the d axis and the q axis are determined by motor parameters, and in practical application, the control parameters can be set by a trial and error method according to the step response of the system under the normal running state of the motor. The parameter before the fault is used after the fault, and the value of the parameter is not required to be additionally set.

And the coordinate inverse transformation module 2: the module utilizes an inverse coordinate transformation matrix P^-1/(ST)^-1And converting the d-q axis voltage command into an a-b-c three-phase voltage command. The algorithm used by the module is determined by the system state. The normal case algorithm (conventional algorithm) is:

in the fault state, the algorithm is changed as follows:

wherein u is_xyn ^*＝[u_x ^* u_y ^* u_n ^*]^TThe voltage commands corresponding to the healthy phase and the neutral line; u. of_rk ^*＝[u_r ^* u_k ^*]^TIs a voltage command in an r-k coordinate system, and has a valueVoltage reference u under synchronous rotating coordinate system with motor before fault_d ^*、u_q ^*Are equal.

PWM wave generation module 3: the module algorithm can be divided into four parts of phase voltage instruction zero setting, terminal voltage instruction calculation, 4 paths of PWM wave generation and PWM wave logic operation according to the flow sequence. The phase voltage command zero setting operation refers to performing command preprocessing on the phase voltage command obtained from the coordinate inverse transformation module, namely setting the phase voltage command of a fault phase to be zero (if the z phase is in fault, setting u phase_zn ^*0) while the terminal voltage command of the non-failed phase remains unchanged. The terminal voltage instruction calculating part calculates the terminal voltage instruction according to the following formula from the preprocessed phase voltage instruction:

the PWM wave generation operation is to compare the obtained terminal voltage command with the isosceles triangular carrier wave and determine the positive and negative of the comparison value, thereby obtaining four PWM waves. The amplitude of the triangular carrier wave is the direct current bus voltage, the average value is 0, the frequency can be selected according to the compromise on the aspects of performance requirements and the like of the system, and the frequency can be generally 10 kHz. The logical operation of the PWM waves means that 4 paths of PWM waves obtained in the previous step are subjected to a logical negation operation to obtain 4 paths of PWM inversion signals for driving the lower bridge arm switching tube. The inverted signal is added with the original 4 paths of PWM signals to form 8 paths of PWM signals. After 8 paths of PWM signals are obtained, according to the state of the motor, the two paths of PWM signals corresponding to the fault are subjected to zero setting operation, namely, the two paths of PWM signals are subjected to logical AND operation with logical '0'). And the PWM wave corresponding to the non-fault is logically and ' ed with logic ' 1 ').

The module completes the generation of 8 paths of PWM signals through the four operations.

Four-leg inverter module 4 and permanent magnet synchronous motor module 5: the two modules are strong electric systems, are analog circuit modules and are execution modules of a control system. The four-bridge arm inverter is a driving circuit of the motor, four bridge arms of the four-bridge arm inverter are respectively connected to four ends of the motor, and the control of the voltage, the phase voltage and the phase current of the motor can be realized through the on-off of 8 switching tubes, so that the control of the motor is realized.

The fault diagnosis module 6: the module carries out fault detection in real time and transmits the detection result to the coordinate transformation module, the coordinate inverse transformation module and the PWM wave generation module, and the algorithms of the three modules are controlled, so that the switching of the state of the whole system is realized. When the fault detection algorithm detects an open-phase fault, the module sets 1 to the corresponding fault flag variable, but sets zero to the fault flag variable of the non-fault phase. If phase A fails, set F_a＝1，F_b＝F_cAnd (5) the module outputs the three fault flag variables, so that the state switching of the system is controlled.

The algorithm flow chart of the whole control system is shown in figure 1.

The whole system flow is in time sequence, and the signal flow direction is as follows: current measurement (three-phase winding and neutral wire) → fault diagnosis → mode selection (algorithm reconstruction) → coordinate transformation → PI control → coordinate inverse transformation → PWM generation → inverter switching tube action → motor operation, and the whole process is operated circularly.

The invention has not been described in detail and is within the skill of the art.

Claims (2)

1. A surface-mounted permanent magnet synchronous motor open-phase fault-tolerant control method is characterized by comprising the following steps: by adopting a new coordinate transformation method, the control performance of the system before and after the fault is almost kept unchanged on the premise of not changing a current controller; the method comprises the following steps:

step one, building an open-phase fault-tolerant control system, wherein the system comprises seven modules: the system comprises a PI controller module (1), a coordinate inverse transformation module (2), a PWM wave generation module (3), a four-leg inverter module (4), a permanent magnet synchronous motor module (5), a fault diagnosis module (6) and a coordinate transformation module (7), wherein the 7 modules are used for realizing high-performance control on the motor before and after an open-phase fault, wherein the fault diagnosis module (6) is responsible for detecting three-phase current of the permanent magnet synchronous motor module (5), judging the health condition of the motor (5) according to the three-phase current and further controlling the system operation mode; the coordinate transformation module (7) is responsible for converting the three-phase current into a current feedback value under a synchronous rotating coordinate system; the PI controller module (1) is responsible for converting a current error value, namely the difference between a current reference value and a current feedback value, in a synchronous rotating coordinate system into a voltage reference value; the coordinate inverse transformation module (2) is responsible for converting the voltage reference value under the synchronous rotating coordinate system into the voltage reference value under the three-phase static coordinate system; the PWM wave generation module (3) generates 8 paths of PWM waves according to the three-phase voltage reference value and is used for controlling a switching tube in the four-bridge arm inverter (4), so that the driving control of the permanent magnet synchronous motor module (5) is realized;

step two, the control system switches the operation mode according to the motor health condition output by the fault diagnosis module (6):

when the fault diagnosis module judges that the motor has no fault, the system operates in a conventional mode, namely the coordinate transformation module (7) adopts a coordinate transformation matrix P, namely an a-b-c coordinate system → d-q-0 coordinate system transformation matrix, and the coordinate inverse transformation module (2) adopts an inverse coordinate transformation matrix P^-1Namely a d-q-0 coordinate system → a-b-c coordinate system transformation matrix, and the PWM wave generation module (3) adopts a conventional carrier-based PWM modulation mode, and under the normal condition, i_nThe three-phase current i fed back by the motor can be ignored when the value is 0_a,i_b,i_cThe direct current feedback current i under the synchronous rotating coordinate system is converted through a coordinate transformation matrix P of a coordinate transformation module (7)_d,i_qFeedback current i_d、i_qWith given value of current i_d ^*、i_q ^*Comparing, and inputting the difference value into a current PI controller module (1); the current PI controller calculates and outputs a reference voltage u according to the error value_d ^*、u_q ^*；u_d ^*、u_q ^*As input to the inverse coordinate transformation module (2), by means of an inverse coordinate transformation matrix P^-1Converted into three-phase reference voltage u_an ^*,u_bn ^*,u_cn ^*(ii) a Three-phase reference voltage is input into a PWM wave generation module (3) and is used as the input of a PWM wave generator, and the PWM wave generator firstly adopts a PWM modulation mode based on carrier waves to generate 4 paths of PWM switchesOff signal S_a、S_b、S_cAnd S_nGenerating 4 paths of inverting switch signals through logical negation operation; 8 paths of PWM switching signals generated by the PWM generating module are input into a four-bridge arm inverter module (4) and control 8 switching tubes of the four-bridge arm inverter; the inverter drives the motor by correspondingly connecting the four bridge arms with a phase line and a neutral line of the motor;

once the fault diagnosis module (6) detects that the phase failure of the motor occurs, the output signal F of the fault diagnosis module controls the reconstruction of three modules, namely a coordinate inverse transformation module (2), a PWM wave generation module (3) and a coordinate transformation module (7) in the system, so that the system is switched to a fault operation mode, namely the coordinate transformation module adopts a transformation matrix ST: x-y-n coordinate system → d-q-0 coordinate system transformation matrix, x, y and z are three phases of motor A, B, C, wherein x and y represent non-fault phases, z represents fault phase, and when A phase is fault, x ═ b, y ═ c, z ═ a; when the phase B fails, x is c, y is a, and z is B; when the C phase fails, x is a, y is b, z is C, and the coordinate inverse transformation module adopts a matrix (ST)^-1Namely a d-q-0 coordinate system → an x-y-n coordinate system transformation matrix, and the PWM wave generation module adopts a carrier-based PWM modulation mode in an open-phase fault mode to set a voltage reference u of a fault phase_zn ^*Setting the switching signal corresponding to the phase failure to be zero when the phase failure is equal to 0; in the fault state, the current of the faulted phase is zero, i.e. i_zOther feedback currents i of the motor, 0_x,i_y,i_nThe current is converted into a feedback current i under a synchronous rotating coordinate system through a coordinate transformation matrix ST of a coordinate transformation module (7)_r,i_kFeedback current i_r、i_kWith given value of current i_d ^*、i_q ^*Comparing, and inputting the difference value to a PI controller in a PI controller module (1); the PI controller calculates and outputs a reference voltage u_d ^*、u_q ^*；u_d ^*、u_q ^*Inputting into the coordinate inverse transformation module (2), passing through the coordinate inverse transformation matrix (ST) of the coordinate inverse transformation module (2)^-1Obtain a two-phase reference voltage u_xn ^*,u_yn ^*Two phase reference voltageThe input is input into a PWM wave generation module (3) as the input of a PWM wave generator which is firstly set with u_zn ^*When the signal is equal to 0, the 4 paths of PWM switching signals S are directly generated by using a PWM modulation mode based on a carrier wave method_a,S_b,S_c,S_nThe 4 switching signals are regenerated into 4 inverting switching signals through logical negation, and the switching signal S corresponding to the phase failure in the 8 switching signals_zAnd

the three-phase inverter is set to zero to realize the isolation of a fault phase, finally generated 8 paths of switching signals are input into a four-leg inverter module (4) through signal lines to control 8 switching tubes in the four-leg inverter, four legs of the inverter are respectively and correspondingly connected with a phase line and a central line of the motor, and the fault phase is cut off, so that the driving control of the motor in a fault state is realized.

2. The phase failure fault-tolerant control method of the surface-mounted permanent magnet synchronous motor according to claim 1, characterized in that: the new coordinate transformation x-y-n coordinate system → r-k coordinate system:

wherein i_rk＝[i_r i_k]^TThe current in the synchronous rotating coordinate system at the time of phase failure is the current i in the synchronous rotating coordinate system of the motor before the failure_d、i_qEqual; i.e. i_xyn＝[i_x i_y i_n]^TAnd the feedback currents of the healthy phase and the neutral line of the motor in fault are shown, subscripts x and y represent non-fault phases, and k is a phase adjustment coefficient: when A is out of phase, x is b, y is c, and k is 0; when B phase is out of phase, x is c, y is a, and k is 2; when phase C is out of phase, x ═ a, y ═ b, k ═ 1, and θ denotes the rotor angular position; k is a radical of₁、k₂、k₃Is constant, with a value of:

the new coordinates are back-transformed to:

wherein u is_xyn ^*＝[u_x ^* u_y ^* u_n ^*]^TThe voltage commands corresponding to the healthy phase and the neutral line; u. of_rk ^*＝[u_r ^* u_k ^*]^TThe voltage command is a voltage command in an r-k coordinate system, and the values of the voltage command are respectively equal to a voltage reference u in a synchronous rotating coordinate system of the motor before the fault_d ^*、u_q ^*Are equal.

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