Motor control device and cable disconnection detection method
阅读说明:本技术 电动机的控制装置及电缆断线检测方法 (Motor control device and cable disconnection detection method ) 是由 正田智久 渡边益崇 西岛良雅 于 2018-02-08 设计创作,主要内容包括:本发明所涉及的电动机的控制装置包括:控制器,该控制器根据转矩指令对进行功率转换的逆变器进行开关控制,由此来控制提供给电动机的交流电;以及电流传感器,该电流传感器检测流过将电动机与逆变器相连接的AC电缆的相电流,控制器具有断线检测部,该断线检测部将电流传感器所检测出的相电流作为相电流检测值来获取,基于转矩指令计算给电动机的相电流指令值,并根据各个相中的相电流指令值与相电流检测值之间的差分值的转变结果,按每个相判定AC电缆有无断线。(The control device for an electric motor according to the present invention includes: a controller that controls switching of an inverter that performs power conversion in accordance with a torque command, thereby controlling alternating current supplied to the motor; and a current sensor that detects a phase current flowing through an AC cable connecting the motor and the inverter, wherein the controller includes a disconnection detecting section that acquires the phase current detected by the current sensor as a phase current detection value, calculates a phase current command value to the motor based on the torque command, and determines whether or not the AC cable is disconnected for each phase based on a result of transition of a difference value between the phase current command value and the phase current detection value in each phase.)
1. A control device of an electric motor, comprising:
a controller that controls the ac power supplied to the motor by switching-controlling switching elements provided in an inverter that converts dc power supplied from a dc power supply into ac power in accordance with a torque command supplied from the outside; and
a current sensor that detects a phase current flowing through an AC cable connecting the motor and the inverter, the control device of the motor being characterized in that,
the controller has a disconnection detecting section for executing a disconnection detecting process,
in the disconnection detection processing, the phase current detected by the current sensor is acquired as a phase current detection value, a command current to the motor is calculated as a phase current command value based on the torque command, and whether or not the AC cable is disconnected is determined for each phase based on a result of transition of a difference value between the phase current command value and the phase current detection value in each phase.
2. The control device of an electric motor according to claim 1,
the disconnection detecting unit calculates a difference value between the phase current detection value and the phase current command value for each calculation cycle, and detects whether the AC cable is disconnected based on an integrated value of the difference values calculated over a plurality of calculation cycles.
3. The control device of an electric motor according to claim 2,
further comprises a rotation angle sensor for detecting a rotation angle of the motor,
the controller further has a rotation angle processing section that calculates an electrical angle and a rotation speed of the motor based on a rotation angle of the motor,
the disconnection detecting unit calculates the integrated value in a plurality of calculation cycles included in a period from the calculation start point to the calculation end point, with a period when the phase current command value crosses 0A as a calculation start point of each phase, and a period when the phase current command value of a phase starting to be calculated after the electrical angle 1 cycle or after 1/2 cycles crosses 0A as a calculation end point.
4. The control device of an electric motor according to claim 3,
the wire breakage detection unit initializes a calculation result calculated by the wire breakage detection process without executing the wire breakage detection process when the absolute value of the rotation speed calculated by the rotation angle processing unit is equal to or less than a preset rotation speed determination value.
5. The control device of an electric motor according to claim 3 or 4,
the disconnection detecting unit repeatedly calculates the integrated value in a plurality of operation cycles included in a period from the operation start point to the operation end point, calculates a ratio of a last value to a present value of the integrated value, and determines that the AC cable is disconnected by a predetermined number of times of disconnection determination in a state where the ratio is higher than a predetermined determination threshold.
6. The control device of an electric motor according to any one of claims 1 to 5,
the wire breakage detection unit initializes a calculation result calculated by the wire breakage detection process without executing the wire breakage detection process when an absolute value of the torque command is equal to or less than a preset torque command determination value.
7. The control device of an electric motor according to any one of claims 1 to 6,
the controller performs switching control to stop driving of the switching element when the disconnection detecting unit detects disconnection of the AC cable.
8. A cable disconnection detecting method performed by a controller of a motor including the controller and a current sensor, wherein,
the controller controls the alternating current supplied to the motor by switching-controlling switching elements provided in an inverter that converts direct current supplied from a direct current power supply into alternating current in accordance with a torque command supplied from the outside,
the current sensor detects a phase current flowing through an AC cable connecting the motor with the inverter, the cable disconnection detecting method is characterized in that,
the controller comprises the following steps:
a storage step of causing a storage unit to store in advance a determination threshold value and a number of times of disconnection determination used for determining whether or not the AC cable is disconnected;
a detection value acquisition step of acquiring the phase current detected by the current sensor as a phase current detection value;
a command value calculating step of calculating a command current to the motor as a phase current command value based on the torque command;
an integration step of repeatedly calculating an integrated value corresponding to a period included from a start point to an end point of the operation by integrating the differential values calculated in a plurality of operation periods in each phase, the operation period being a period from the start point to the end point; and
and a disconnection determination step of calculating a ratio of a last value to a present value of the integrated value, and determining that the AC cable is disconnected when a state in which the ratio is higher than the determination threshold value stored in the storage unit continues for the number of times of disconnection determination stored in the storage unit.
Technical Field
The present invention relates to a motor control device and a cable disconnection detection method for detecting disconnection of a power connection line connecting a motor and a power conversion device.
Background
In recent years, vehicles equipped with an internal combustion engine and an electric motor, so-called hybrid vehicles, or electric vehicles that run with only an electric motor, have become popular for the purpose of reducing carbon dioxide emissions or improving fuel efficiency. The electrically powered vehicle equipped with the electric motor is equipped with, in addition to the electric motor, a power storage device that outputs a direct current and a power conversion device that converts the direct current from the power storage device into an alternating current and supplies the alternating current to the electric motor.
In the electric vehicle, when a power connection line connecting the electric motor and the power conversion device is broken or short-circuited, the electric motor may not operate normally, and an excessive current may flow through the power conversion device and the electric motor. As a result, there is a possibility that the motor and the power conversion device may malfunction. In addition, since the motor cannot operate normally, there is a possibility that unintended vehicle vibration occurs, which may cause discomfort to the driver and passengers.
In order to solve the above problem, there is a conventional technique of detecting a disconnection of a power connection line connecting a motor and a power conversion device (for example, see patent document 1).
Disclosure of Invention
Technical problem to be solved by the invention
However, the following problems exist in the prior art. In patent document 1, in order to determine a wire break, a phase current flowing through a motor is compared with a determination value. Therefore, for example, in the case of a low current or the like, it may be difficult to detect disconnection of the power connection line depending on the setting of the determination value.
In patent document 1, the disconnection of the power connection line is detected based on the determination of the phase current and the determination of the change rate of the phase current. However, in the case of an ac motor, if the motor is stopped at a specific rotation angle, there is a phase in which no current flows. Therefore, even if the phase to which the current does not flow is not broken, since the phase current and the rate of change of the phase current are both zero, there is a possibility that a false determination is made for the broken detection.
The present invention has been made in view of the above problems, and an object thereof is to provide a motor control device and a cable disconnection detection method capable of detecting disconnection of a power connection line connecting a motor and a power conversion device with high accuracy.
Technical scheme for solving technical problem
The control device for an electric motor according to the present invention includes: a controller that controls an alternating current supplied to the motor by switching-controlling a switching element provided in an inverter that converts a direct current supplied from a direct current power supply into an alternating current, in accordance with a torque command supplied from the outside; and a current sensor that detects a phase current flowing through an AC cable connecting the motor and the inverter, wherein the controller includes a disconnection detection unit that performs a disconnection detection process in which a phase current detected by the current sensor is acquired as a phase current detection value, a command current to the motor is calculated as a phase current command value based on a torque command, and whether or not the AC cable is disconnected is determined for each phase based on a result of transition of a difference value between the phase current command value and the phase current detection value in each phase.
A cable disconnection detecting method according to the present invention is a cable disconnection detecting method executed by a controller in a control device for a motor including the controller and a current sensor, the controller controlling an alternating current supplied to the motor by switching-controlling switching elements provided in an inverter that converts a direct current supplied from a direct current power supply into an alternating current in accordance with a torque command supplied from an outside, the current sensor detecting a phase current flowing through an AC cable connecting the motor and the inverter, the controller including: a storage step of causing a storage unit to store in advance a determination threshold value and a number of times of disconnection determination used for determining whether or not an AC cable is disconnected; a detection value acquisition step of acquiring a phase current detected by a current sensor as a phase current detection value; a command value calculating step of calculating a command current to the motor as a phase current command value based on the torque command; an integration step of calculating a difference value between the phase current detection value and the phase current command value for each phase for each calculation cycle, and integrating absolute values of the respective difference values calculated in a plurality of calculation cycles included in a period from the calculation start point to the calculation end point to repeatedly calculate an integration value corresponding to the period; and a disconnection determination step of calculating a ratio of a last value to a present value of the integrated value, and determining that the AC cable is disconnected when the ratio is higher than a determination threshold value stored in the storage unit and continues for the number of times of disconnection determination stored in the storage unit.
Effects of the invention
According to the present invention, the structure is as follows: disconnection detection of the power connection line is performed based on a result of transition of a differential value between a current command value and a current detection value of the motor. As a result, it is possible to obtain a motor control device and a cable disconnection detection method that can detect disconnection of a power connection line connecting a motor and a power conversion device with high accuracy.
Drawings
Fig. 1 is a general configuration diagram illustrating a control device of a motor including a power conversion device according to embodiment 1 of the present invention.
Fig. 2 is a functional block diagram of an MCU applied to a motor control device according to embodiment 1 of the present invention.
Fig. 3 is a flowchart showing a main flow of the AC cable disconnection detection process executed by the disconnection detecting unit in embodiment 1 of the present invention.
Fig. 4 is a flowchart showing a flow of AC cable disconnection detection calculation processing executed by the disconnection detecting unit in embodiment 1 of the present invention.
Fig. 5 is a flowchart showing a flow of the detected current calculation process executed by the disconnection detecting unit in embodiment 1 of the present invention.
Fig. 6 is a flowchart showing a flow of the disconnection determination calculation process executed by the disconnection detecting unit in embodiment 1 of the present invention.
Fig. 7 is a timing chart showing an operation of AC cable disconnection detection in embodiment 1 of the present invention.
Detailed Description
Hereinafter, preferred embodiments according to a motor control device and a cable disconnection detection method according to the present invention will be described with reference to the drawings.
Fig. 1 is a general configuration diagram illustrating a control device of a motor including a power conversion device according to embodiment 1 of the present invention. The motor control device shown in fig. 1 includes a motor control unit 1, a battery 2, a motor 4, a rotation angle sensor 5, and a
The motor control unit 1 is a controller that executes arithmetic processing relating to drive control of the power conversion unit, and is hereinafter referred to as an "MCU". The battery 2 is a power supply that supplies direct current. The
The motor 4 is driven to rotate by generating a driving force by the ac power supplied from the
The
Further, a U-phase upper diode element 3D1, a U-phase lower diode element 3D2, a V-phase upper diode element 3D3, a V-phase lower diode element 3D4, a W-phase upper diode element 3D5, and a W-phase lower diode element 3D6 are connected in reverse parallel to each switching element.
The
In the motor 4, one end of 3 coils of U-phase, V-phase, and W-phase is connected to a neutral point. On the other hand, the other ends of the 3 coils of the U-phase, V-phase, and W-phase are connected to intermediate points of the switching elements of the respective phases. Further, a U-phase
Fig. 2 is a functional block diagram of the MCU1 applied to the motor control device according to embodiment 1 of the present invention. The MCU1 shown in fig. 2 has a function of generating a switching signal to control the
A
The command
The rotation angle processing unit 12 calculates the rotation speed Nm and the electrical angle θ of the motor 4 based on the rotation angle signal output from the rotation angle sensor 5 provided in the motor 4. The rotation speed Nm calculated by the rotation angle processing unit 12 is input to the command
The detected current three-phase/two-phase conversion unit 13 receives detected currents obtained by current sensors (a U-phase
The command
The command voltage two-phase/three-
Switching
The switching signal generated by the switching
The
Then, based on the received signal, the
Fig. 3 is a flowchart showing a main flow of the AC cable disconnection detection process executed by the
First, in step S101, the
In embodiment 1, the disconnection detection process is performed based on the value of the current flowing through the motor 4. Therefore, even when any one of the
If it is determined as yes in step S101, that is, if there is no failure in the
When the process proceeds to step S102, the
If it is determined as yes in step S101, that is, if no failure has occurred in the rotation angle sensor 5, the process proceeds to step S103. On the other hand, if the determination is "no", the AC cable is not detected to be disconnected, and the series of processes is terminated.
When the process proceeds to step S103, the
If yes is determined in step S103, that is, if disconnection of the AC cable is not detected, the process proceeds to step S104. On the other hand, in the case of the "no" determination, that is, in the case where the disconnection of the AC cable has been detected, the disconnection detection of the AC cable is not performed, and the series of processes is ended.
When the process proceeds to step S104, the
When the AC cable disconnection detection operation is completed in step S104, the process proceeds to step S105, and the
When the AC cable is detected to be disconnected and the process proceeds to step S106, the
When receiving the disconnection detection signal from the
Next, a flowchart of the AC cable disconnection detection operation shown in fig. 4 will be described. Fig. 4 is a flowchart showing a flow of AC cable disconnection detection calculation processing executed by the
In step S201, the
Therefore, by determining the rotation speed in step S201, it is possible to avoid a false detection of a disconnection when there is a phase in which no current flows.
Specifically, in step S201, the
If yes is determined in step S201, that is, if the relationship | Nm | > Nm _ ts holds, the process proceeds to step S202. On the other hand, if the determination is "no", that is, if the relationship of | Nm | > Nm _ ts is not established, the process proceeds to step S206.
When the process proceeds to step S202, the
Specifically, in step S202, the
If yes is determined in step S202, that is, if the relationship of | Ttar | > Ttar _ ts is established, the process proceeds to step S203. On the other hand, if the determination is "no", that is, if | Ttar | > Ttar _ ts does not hold, the process proceeds to step S206.
When the process proceeds to step S203, the
When the current calculation is completed in step S203, the process proceeds to step S204, and the
When the process proceeds to step S205, the
When the process proceeds to step S201 or steps S202 to S206, the
Next, a flowchart of the detected current calculation shown in fig. 5 will be described. Fig. 5 is a flowchart showing the flow of the detected current calculation process executed by the
In step S301, the
More specifically, for each phase, the
Itar _ x (n-1) < 0, and
Itar_x(n)≥0(x:U、V、W)
if it is determined in step S301 that instruction current Itar _ x (x: U, V, W) has crossed 0A in the present cycle,
In the case of proceeding to step S320, the
Icad_x(n)=Icad_x(n-1)+Idiff_x(n)
When proceeding from step S301 to step S302, the
In step S302, when the "yes" determination is made, that is, when the three-phase step-0 counter F _ stc is 0, the condition that the current flowing through the motor 4 steps over 0A is first satisfied after the AC cable disconnection detection operation in fig. 4 is started. Therefore, if yes is determined in step S302, the process proceeds to step S303, and the
On the other hand, in step S302, if no is determined, that is, if the three-phase step 0 counter F _ stc is other than 0, the process proceeds to step S304, and the
In step S304, if the determination is yes, that is, if the three-phase cross 0 counter F _ stc is 1, the process proceeds to step S305, and the
On the other hand, in step S304, if the determination is no, that is, if the three-phase step 0 counter F _ stc is not 1, the process proceeds to step S306, and the
In step S306, if yes, that is, if the three-phase step-0 counter F _ stc is 2, the process proceeds to step S307, and the
On the other hand, in the case of the no determination in step S306, since the step 0 detection is completed for all the three phases, which corresponds to the case where the three-phase step 0 counter F _ stc is 3, the process proceeds to step S303, and the
When the process proceeds to step S308, the
If yes is determined in step S308, the process proceeds to step S309, and the
Icad_x1=Idiff_x(n)(x:U、V、W)
On the other hand, if the determination in step S308 is no, the process proceeds to step S311, and the
Icad_x2=Idiff_x(n)(x:U、V、W)
On the other hand, in the case of no determination in step S311, the process proceeds to step S309, and the
When the routine proceeds to step S314, the
If the determination in step S314 is yes, that is, if the condition of the above expression is satisfied and the calculation of the current difference accumulation storage values Icad _ x1 and Icad _ x2 (x: U, V, W) of the respective phases is completed, the process proceeds to step S315. Then, in step S315, the
On the other hand, if the determination in step S314 is no, that is, if the condition of the above expression is not satisfied and the operation of the current difference accumulation storage values Icad _ x1 and Icad _ x2 (x: U, V, W) of the respective phases is not completed, the process proceeds to step S316. Then, in step S316, the
In step S317, the
Then. In step S319, the
Next, a flowchart of the disconnection determination operation shown in fig. 6 will be described. Fig. 6 is a flowchart showing the flow of the disconnection determination calculation process executed by the
In step S401, the
In step S402, the
ΔIcad_x=|Icad_x2|/|Icad_x1|(x:U、V、W)
On the other hand, in step S402, if no is determined, the process proceeds to step S404. Then, in step S404, the
ΔIcad_x=|Icad_x1|/|Icad_x2|(x:U、V、W)
When the routine proceeds to step S406, the
When the AC cable connecting
The command current Itar _ x (x: U, V, W) is an ideal value, and the detection current Iact _ x (x: U, V, W) is an actual current flowing by PWM control or the like. Therefore, even in the case where the AC cable is not disconnected, a difference to some extent is generated between the command current and the detection current. Therefore, in order to avoid erroneous determination of AC cable disconnection, the determination of step S406 is provided.
The determination value α of the current difference integration ratio used in step S406 is set to a value that will not cause the
If the determination in step S406 is yes, that is, if the current difference integrated ratio Δ Icad _ x (x: U, V, W) of each phase is greater than the determination value α, the process proceeds to step S407, and the
The cumulative percentage abnormality counter ccad (n) is a total value of the determinations of the current difference cumulative percentage Δ Icad _ x (x: U, V, W) of each phase in step S406. When the operation of the accumulation ratio abnormality counter ccad (n) in step S407 is completed, the process proceeds to step S409.
When the routine proceeds to step S409, the
In step S409, if the integrated ratio abnormality counter ccad (n) is equal to or greater than the determination value β, yes determination is made, and the process proceeds to step S410. Then, in step S410, the
If the determination in step S406 is no, that is, if the current difference integrated ratio Δ Icad _ x (x: U, V, W) of each phase is equal to or less than the determination value α, the process proceeds to step S408. Then, in step S408, the
Then, in the case of proceeding to step S408 or steps S409 to S411, the
In addition, in the case of the no determination in the previous step S404, the series of processing of fig. 6 is ended without performing the disconnection determination operation.
Next, the disconnection detection processing in the motor control device according to embodiment 1 will be described with reference to a timing chart. Fig. 7 is a timing chart showing an operation of AC cable disconnection detection in embodiment 1 of the present invention. In fig. 7, the horizontal axis represents time, and the vertical axis represents the following values in order from the top. In addition, x represents U, V, W.
(A) Absolute value of command torque Ttar
(B) Absolute value of rotation speed Nm
(C) Electrical angle theta
(D) Instruction current Itar _ x
(E) Detecting the current Iact _ x
(F) Current differential value Idiff _ x
(G) Current difference integrated value Icad _ x
(H) Three-phase 0-crossing counter F _ stc
(I) Cross-0 info F _ sta _ x
(J) Current differential accumulation storage value Icad _ x1
(K) Current differential accumulation storage value Icad _ x2
(L) Current Difference accumulation ratio Δ Icad _ x
(M) cumulative ratio anomaly counter Ccad
(N) disconnection determination permission flag det _ jdg
(O) disconnection detection information F _ discon
First, at time T1, the absolute value (a) of the command torque Ttar changes to be greater than the command torque determination value Ttar _ ts, and thereafter, the absolute value (B) of the rotation speed Nm becomes greater than the rotation speed determination value Nm _ ts. Thereby, the detected current calculation routine explained with reference to fig. 5 is started.
Next, at time T2, V-phase command current Itar _ V (d) crosses 0A, and thereby three-phase cross-0 counter F _ stc (h) counts up 1, and V-phase cross-0 information F _ sta _ V (i) also counts up 1, and the operation of V-phase current difference value Idiff _ V (F) starts.
The V-phase current difference value Idiff _ V (f) is obtained by subtracting the V-phase command current Itar _ V (d) from the V-phase detection current Iact _ V (e), and is extremely small when the AC cable is not disconnected. When the V-phase current difference value Idiff _ V (f) is calculated, the V-phase current difference integrated value Icad _ V (g) is calculated next.
Thereafter, when W-phase command current Itar _ W crosses 0A, three-phase cross-0 counter F _ stc (h) counts up 1(F _ stc (h) ═ 2), and when U-phase command current Itar _ U also crosses 0A, three-phase cross-0 counter F _ stc (h) counts up 1(F _ stc (h) ═ 3). As a result, the same current calculation as V is started for the W phase.
The three-phase 0-crossing counter F _ stc (h) changes every time the determination of 0 crossing of each phase is established in step S301 of fig. 5. The three-phase cross-0 counter F _ stc (h) changes to the number of phases of the motor 4, and returns to 1 after becoming the number of phases. When the rotation speed is determined as "no" in step S201 in fig. 4 or when the command torque is determined as "no" in step S202 in fig. 4, the three-phase 0-crossing counter F _ stc (h) is initialized to 0.
In addition, if the command current Itar _ x (d) of each phase crosses 0A, the cross-0 information F _ sta _ x (i) also changes. Wherein, the 0 crossing information F _ sta _ x (i) crosses 0A by the x-phase command current Itar _ x to take the value of 1 or 2. Note that, when the rotation speed is determined as "no" in step S201 in fig. 4, or when the command torque is determined as "no" in step S202 in fig. 4, the 0-range information F _ sta _ x (i) is initialized to 0.
At time T3, V-phase command current Itar _ V (d) again crosses 0A, and in step S301 in fig. 5, a command current 0 crossing determination is established. At time T3, the other phases (W-phase and U-phase) also cross 0A once, and the command current cross 0 determination is established in step S301 in fig. 5. Therefore, the three-phase cross 0 counter F _ stc (h) is 3, and thus at time T3, the three-phase cross 0 counter changes from 3 to 1.
At time T3, the cross-0 information F _ sta _ V (i) of the V phase changes from 1 to 2. Then, the V-phase current difference integrated value Icad _ V (g) calculated from time T2 is stored as the current difference integrated storage value Icad _ V2(K), and is initialized to 0.
Next, until time T4, when V-phase command current Itar _ V (d) again crosses 0A and when the command current 0 crossing determination is established in step S301 of fig. 5, three-phase 0 crossing counter F _ stc (h) changes from 3 to 1 as in time T3.
The value of the current difference accumulation value Icad _ V (g) is stored as the current difference accumulation storage value Icad _ V1(K) while the cross-0 information F _ sta _ V (i) of the V phase changes from 2 to 1, and is then initialized to 0. The same operation as that for V-phase is performed for the W-phase and U-phase, which are other phases.
At time T4, when the U-phase AC cable is disconnected, three-phase detected current Iact _ U (e) becomes 0A, but command current Itar _ U (d) does not become 0A. Therefore, the current difference value Idiff _ u (f) changes rapidly, and the increase amount of the current difference integrated value Icad _ u (g) also increases. Further, the amount of change in the detected currents iac _ V and iac _ W (e) of the other phases, i.e., the V-phase and the W-phase, increases due to the influence of the U-phase, and the increase amounts of the current difference integrated values Icad _ V and Icad _ W (g) increase.
At time T5 when the 2 nd integration of the U-phase current is completed, the integration of all phases (U, V, W) can be performed 2 or more times. Therefore, at time T5, the disconnection determination permission flag det _ jdg (n) is set, the disconnection determination calculation routine explained with reference to fig. 6 is started, and the current difference accumulation ratio Δ Icad _ x (l) is calculated based on the cross-0 information F _ sta _ x (x: U, V, W).
In fig. 7, the time at time T5 when the disconnection determination permission flag det _ jdg (n) is satisfied corresponds to the timing at which the 0-crossing information F _ sta _ U (i) of the U-phase changes. Therefore, the operation information of the U phase is used for the operation of the current difference accumulation ratio Δ Icad _ x (l).
At time T5, the cross-0 information F _ sta _ U (i) of the U phase changes from 2 to 1. Therefore, the current difference accumulation ratio Δ Icad _ u (l) is calculated using the mathematical expression described in step S405. Then, since the value of the calculated current difference integrated ratio Δ Icad _ u (l) is equal to or greater than the determination value α, the integrated ratio abnormality counter ccad (m) counts up by 1.
Then, at time T6, when V-phase command current Itar _ V (d) crosses 0A, 0 crossing information F _ sta _ V (i) of the V-phase changes from 1 to 2. Therefore, the current difference integration ratio Δ Icad _ v (l) is calculated using the equation described in step S403, and is compared with the determination value α. The current difference accumulation ratio Δ Icad _ V (l) of the V phase is also larger than the determination value α, and therefore, the accumulation ratio abnormality counter ccad (m) counts up by 1.
Then, W-phase command current Itar _ W (d) crosses 0A, and W-phase cross-0 information F _ sta _ W (i) changes from 1 to 2. Therefore, similarly to the above-described V-phase operation, the current difference integration ratio Δ Icad _ w (l) is calculated using the equation described in step S403, and compared with the determination value α. The current difference accumulation ratio Δ Icad _ W (l) of the W phase is also larger than the determination value α, and therefore, the accumulation ratio abnormality counter ccad (m) counts up by 1.
Thus, after the disconnection determination permission flag det _ jdg (n) is asserted, the 0 crossing information F _ sta _ x (x: U, V, W) (I) of each phase changes every time the command current Itar _ x (x: U, V, W) (D) of each phase crosses 0A. Then, based on the change in the cross-0 information F _ sta _ x (x: U, V, W) (I) of each phase, the current difference integrated ratio Δ Icad _ x (x: U, V, W) (L) is sequentially calculated using the formula described in step S403 or the formula described in step S405, compared with the determination value α, and the integrated ratio abnormality counter ccad (m) counts up.
Then, at time T7, W-phase command current Itar _ W (d) crosses 0A, and current difference accumulation ratio Δ Icad _ W (l) is calculated. The calculated current difference accumulation ratio Δ Icad _ w (l) is larger than the determination value α, and the accumulation ratio abnormality counter ccad (m) counts up. The cumulative rate abnormality counter ccad (m) is equal to or greater than the determination value β, and the disconnection detection information F _ discon (o) is established and set to 1.
As described above, according to embodiment 1, the following structure is provided: disconnection detection of an AC cable is performed based on a result of transition of a differential value between a current command value and a current detection value of a motor. With the above configuration, even when the AC cable connecting the inverter and the motor is disconnected, the disconnection can be detected quickly.
Further, when the disconnection is detected, the driving of the switching elements constituting the inverter can be immediately stopped, and a state in which the abnormal operation of the motor continues can be prevented. Further, by preventing the motor mounted on the vehicle from continuing to perform an abnormal operation, it is possible to suppress occurrence of a vehicle shock, and there is no fear of annoyance to the driver and the passenger.
The disconnection detecting unit according to the present invention has the following functions: a difference value between the phase current detection value and the phase current command value is calculated for each calculation cycle, and the presence or absence of a disconnection of the AC cable is detected based on an integrated value of the difference values calculated over a plurality of calculation cycles.
The disconnection detecting unit according to the present invention has the following functions: the integrated value is calculated by taking the time when the phase current command value crosses 0A as the calculation starting point of each phase, and the time when the phase current command value of the phase which starts to be calculated after 1 period of the electrical angle or after 1/2 periods crosses 0A as the calculation ending point.
The disconnection detecting unit according to the present invention has the following functions: when the rotation speed is equal to or less than a preset rotation speed determination value, or when the torque command is equal to or less than a preset torque command determination value, the disconnection detection processing is not executed.
By providing the above-described function, it is not necessary to set a judgment value of the phase current for detecting the disconnection, and the disconnection detection process can be executed quickly based on the calculation result of the integrated value during 1 cycle or 1/2 cycles. Further, it is possible to avoid disconnection detection processing in a state where erroneous determination of disconnection detection is caused, such as when the rotation of the motor is stopped, and to reliably perform disconnection detection of the AC cable.
In addition, in the present embodiment, the following case is explained: the disconnection detection of the current flowing in each phase of the motor is performed in the electrical angle 1 cycle. However, the present invention is not limited to the disconnection detection as described above. As shown in fig. 7, the current flowing in each phase may cross 0A every 1/2 cycles of electrical angle. Therefore, the disconnection detection of the AC cable can be performed also in 1/2 cycles.
In embodiment 1, the following case is explained: a determination value for detecting disconnection of the AC cable is set to a fixed value based on phase currents flowing in the respective phases of the motor. However, the present invention is not limited to the case where a fixed determination value is used. The determination value can be variably set according to the rotation speed of the motor.
In embodiment 1, the following case is explained: for the disconnection determination of the AC cable, the current difference integrated value of each phase is used. However, the present invention may perform the disconnection determination using the theorem of the sum of three-phase currents in which the U-phase current + V-phase current + W-phase current is 0.
Description of the reference symbols
1 MCU (motor control unit),
2, a battery is arranged in the container,
4, a motor is arranged in the middle of the frame,
5 a rotation angle sensor is provided for detecting the rotation angle,
11 a command current calculating section for calculating a command current,
12 a rotation angle processing part for rotating the rotary shaft,
13 a current three-phase/two-phase converting section,
14 a command voltage calculating unit for calculating a command voltage,
15 a two-phase/three-phase conversion section of the command voltage,
16 a switching signal generating section for generating a switching signal,
17 a wire-break detection section for detecting a broken wire,
30 an inverter (power conversion device),
a 33U-phase current sensor is provided,
a 34V phase current sensor is arranged on the shell,
35W phase current sensor.