JP2005094873A - Controller for three-phase ac motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To offer a controller for a three-phase AC motor which can generate torque by continuing vector control even in a region where a faulty switching element is used, in case that the switching element of an inverter for drive goes wrong. <P>SOLUTION: At trouble of an upper switching element, this controller for a three-phase AC motor fixes the phase angle of a composite voltage vector to a specified value when the operation value of a voltage command value of a faulty phase becomes larger than zero, and inverts the phase angle by 180° when a q-axis current becomes zero, and fixes the inverted phase angle until the operation value of the voltage command value of the faulty phase comes to zero or under. At a trouble of a lower switching element, this fixes the phase angle of the composite voltage vector to a specified value when the operation value of the voltage command value of the faulty phase comes to zero or under, and inverts the phase angle when the q-axis current becomes zero by 180°, and fixes the phase angle of the inverted composite voltage vector until the operation value of the voltage command value of the faulty phase becomes larger than zero. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a control device for a three-phase AC motor, and more particularly to a fail-safe control technique at the time of failure.

As a conventional control device, there is one described in Patent Document 1 below. In the above prior art, when the switching element of the inverter that drives the motor has an open failure (failure that remains off), control is performed to stop the combination of PWM drive signals that turn on the failed switching element. doing. That is, when the switching element has an open failure, the voltage (or current) applied to the phase in which the switching element has failed is simply stopped, and the generation of the vector using the failed switching element is stopped. No control is possible in the area where no error occurs.
For example, in the voltage vector diagram shown in FIG. 3, when the U-phase lower switching element has an open failure, a negative voltage cannot be applied to the U phase, and no negative current flows in the U phase. When a positive voltage is applied to the V-phase and the W-phase (positive current is passed) as in the lower half of FIG. 5, it is impossible to set V-phase current + W-phase current + U-phase current = 0. Therefore, the torque on the lower half of FIG. 3 (when the U-phase voltage becomes negative) cannot be obtained. That is, in the three-phase AC motor, the sum of the three-phase currents is 0, but if the U-phase voltage Vu = 0, a positive current cannot be passed to the other phases.

JP-A-8-196984

As described above, in the conventional control device for a three-phase AC motor, when the switching element of the drive inverter fails, the vector control cannot be continued and a region where torque cannot be generated occurs. There was a problem.
The present invention has been made in order to solve the above-described problems. A control device for a three-phase AC motor that can continue vector control and generate torque even in a region where a failed switching element is used. The purpose is to provide.

  In the present invention, when an open failure of the upper switching element is detected in any one of the three phases, the failure obtained by the voltage command value calculation means from the d-axis q-axis voltage command value for failure is detected. When the calculated value of the phase voltage command value becomes larger than 0, the phase angle of the combined voltage vector, which is the combined vector of the three-phase voltage command values, is fixed to a predetermined value (for example, as shown in FIG. A voltage command value is output to a value that fixes the vector Va at a phase angle of 90 °. When the q-axis current becomes 0, the phase angle of the three-phase composite voltage vector is inverted by 180 ° from the predetermined value (for example, FIG. As shown in FIG. 7, the voltage command value for causing the combined voltage vector Va to have a phase angle of 90 + 180 = 270 ° is output, and the calculated value of the voltage command value of the phase in which the phase angle of the inverted combined voltage vector has failed is 0 or less. Until it is When an open failure of the lower switching element is detected in any one of the three phases, when the operation value of the voltage command value of the failed phase becomes 0 or less, the voltage command value of the three phases A voltage command value having a value that fixes the phase angle of the composite voltage vector, which is a composite vector, to a predetermined value is output, and when the q-axis current becomes 0, the phase angle of the three-phase composite voltage vector is 180 ° from the predetermined value. A voltage command value to be inverted is output, and control is performed so that the phase angle of the inverted combined voltage vector is fixed until the calculated value of the voltage command value of the failed phase is greater than zero.

  In the present invention, when an inverter switching element has an open failure, it is configured to generate torque by continuing vector control with a fixed composite voltage vector even in an area where the failed switching element is normally used. Yes. Therefore, it is possible to generate some torque in almost all regions, and the effect that the vehicle can travel in the fail-safe mode is obtained.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing an embodiment of a current feedback control block for performing vector control of a three-phase AC synchronous motor to which the present invention is applied. In addition, although a present Example demonstrates as what applied a three-phase alternating current synchronous motor to the drive motor of an electric vehicle, it is not restricted to this.
In an electric vehicle, an accelerator opening is detected and output using an accelerator opening sensor (not shown). A torque command value calculation unit (not shown) calculates a torque command value T ^* from the accelerator opening detected by the accelerator opening sensor, and outputs the torque command value as a digital signal.

The current command calculation unit 1 outputs a d-axis current command value Id * and a q-axis current command value Iq * corresponding to the torque command value T *. These current command values are input to the current PI control unit 2.
The current PI control unit 2 performs a proportional-integral calculation based on a deviation between the d-axis current command value Id * and the d-axis current current value Id, and outputs a d-axis voltage command value Vd *. Similarly, the q-axis current command value A q-axis voltage command value Vq * is output based on the deviation between Iq * and the q-axis current value Iq.

  The d-axis voltage command value Vd * and the q-axis voltage command value Vq * (hereinafter referred to as “d-axis q-axis voltage command value” when both are combined) are subjected to non-interference calculation processing as necessary. The two-phase / three-phase converter 3 converts the voltage into the three-phase voltage command values Vu *, Vv *, and Vw *. In addition, special control is performed at the time of an open failure in which the switching element of the inverter remains off (details will be described later).

The above three-phase voltage command values Vu *, Vv *, Vw * are given to the PWM converter 4 and converted into PWM signals.
The inverter 5 converts the power of a DC power source (battery or the like) (not shown) into three-phase AC power in response to the PWM signal, and drives a three-phase motor 6 (hereinafter, the motor is abbreviated as a motor).
The three-phase currents iu, iv and iw flowing at this time are detected by current sensors 7-1, 7-2 and 7-3, respectively, and the current values Iu, Iv, Convert to Iw. Then, the current is converted into the d-axis current value Id and the q-axis current value Iq by the three-phase / two-phase converter 10 and fed back to the current PI controller 2.

The rotation angle detector 8 detects the rotation angle θ (rotor: rotation angle of the rotor) of the three-phase motor 6. This rotation angle θ is used for the coordinate conversion calculation in the two-phase three-phase converter 3 and the three-phase two-phase converter 10 and the calculation in the current command calculation unit 1.
The above processing is repeated to perform vector control by current feedback of the three-phase motor 6.
The failure detection unit 11 detects an open failure in which the switching element of the inverter shown in FIG. 2 remains off, and sends a failure detection signal S ₀ to the failure control unit 12 when a failure occurs. The failure-time control unit 12 controls the voltage command value of the two-phase / three-phase converter 3 to perform fail-safe control at the time of an open failure (details will be described later for 11 and 12).

FIG. 2 is a circuit diagram of the inverter 5.
As shown in FIG. 2, the inverter 5 includes a three-phase series circuit in which two switching elements (transistors) are connected in series, and the three-phase winding of the three-phase motor 6 from the connection point of the two switching elements. The switching elements 21, 23, 25 connected to the positive side of the power source 20 are connected to the respective phases of the line, the upper switching element, and the switching element 22, connected to the negative side of the power source 20, 24 and 26 are referred to as lower switching elements.

The drive signals on the upper side and the lower side of each series circuit are in opposite phases to each other, and the two switching elements in one series circuit are controlled so as not to be turned on simultaneously. For example, as shown by a broken line in FIG. 2, when a current is passed from the U phase to the V phase of the three-phase motor 6, the upper drive signal A and the lower drive signal D are “Hi”, and the lower drive signal. B and the upper drive signal C become “Lo”, the switching elements 21 and 24 are turned on, and the switching elements 22 and 23 are turned off. On the other hand, when the current flows from the V phase to the U phase, the upper drive signal C and the lower drive signal B are “Hi”, and the lower drive signal D and the upper drive signal A are “Lo”. Elements 22 and 23 are turned on, and switching elements 21 and 24 are turned off.
Therefore, if the direction of current flowing from the positive terminal of the power source toward the neutral point in each phase winding is the forward direction and the direction of current flowing from the neutral point toward the negative terminal of the power source is the reverse direction, When a current flows in the V phase, a forward current flows in the U-phase winding and in a reverse direction in the V-phase winding. When a current flows from the V phase to the U phase, Vice versa.

  FIG. 3 shows a voltage vector diagram. The combined vector Va is a combined vector of the voltage vectors Vu, Vv, and Vw. For example, when the U-phase lower switching element 22 cannot be turned on due to an open failure as in the above example, the voltage vector that comes to the lower half of FIG. In the three-phase current waveform at the constant rotation and constant output shown in FIG. 4, among the current waveforms that are sine waves shifted by 120 ° in each of the three phases, the current in the broken line portion cannot be output. V phase and W phase cannot be controlled. That is, when the U-phase lower switching element 22 in FIG. 2 is open-failed, the path of “power source + terminal → V phase winding → neutral point → U phase winding → power source −terminal” and “power source + terminal” The path “W-phase winding → neutral point → U-phase winding → power source −terminal” becomes non-conductive.

  In the conventional example (Patent Document 1), it is shown that the vector output is stopped on the lower half surface of FIG. 3 and the control is performed only on the upper half surface. However, in the present invention, any one-phase switching element is provided. 3 shows a fail-safe control method that enables torque to be generated even in the lower half of FIG. 3 by fail-safe control even when an open failure occurs.

The direction of the voltage vector to be output first will be described.
For example, when the switching element 22 on the lower side of the U-phase has an open failure and the voltage vector on the lower half of FIG. 3 cannot be output, the d-axis q-axis for failure (for fail-safe) is used on the upper half. When the U-phase voltage command value Vu ^{* obtained} by converting the voltage command value (details will be described later) into two-phase and three-phase becomes 0 or less (greater than 0 in the case of an upper fault), as shown in FIG. Fix the position (phase). This is performed by sending a voltage command value for fixing from the two-phase / three-phase converter 3 to the PWM converter 4.
In the following drawings, a portion indicated by a thick black line and attached with an NS polarity code is a motor rotor 13 (rotor).

As shown in FIG. 6, when the angle formed between the combined current vector Ia as the current vector corresponding to the combined voltage vector Va and the q axis is the current phase angle ζ (rad), the motor angle θ ₁ (currently read) rad / sec) and motor angle θ ₀ (rad / sec) read in the previous control cycle, the motor advance angle α (rad / control cycle) during one control cycle is calculated, and the rotor further rotates, The sum of the current phase angle ζ and the motor advance angle α is ζ + α> π (rad)
Is satisfied, the output voltage vector direction (phase) is switched to the vector shown in FIG. 7 assuming that the q-axis current has become zero. That is, it is reversed 180 ° from the state of FIG.
In FIG. 6, Γ indicates the magnitude of the voltage vector for fail safe.

Further, when the rotor rotates and the U-phase voltage command value obtained by converting the d-axis q-axis voltage command value for fail-safe two-phase / three-phase conversion becomes larger than 0 (0 or less in case of an upper failure) (FIG. 8). The state returns to the normal voltage vector output.
The above control is repeated without using the switching element 22 on the lower side of the U-phase that has an open failure. By controlling in this way and continuously outputting a vector in a certain direction (FIGS. 5 and 7) in the lower half surface region, the torque shaft current Iq can be obtained regardless of the position of the rotor as shown in FIGS. And torque can be generated. The fail-safe control at the time of the open failure as described above is performed by the failure-time control unit 12 in FIG. 1 controlling the voltage command value of the two-phase / three-phase conversion unit 3. Note that the fail safe time (failure time) d-axis q-axis voltage command value may be supplied from the current PI control unit 2 or from the failure time control unit 12.

Next, the magnitude Γ of the voltage vector for fail-safe and the d-axis q-axis voltage command value for fail-safe will be described.
In the voltage vector fixed control region according to the present invention, as shown in FIG. 10, there is a region in which a positive current is generated in the d-axis that allows a negative current to flow as a weak field current and the induced voltage is increased. Therefore, attention must be paid to the magnitude Γ of the voltage vector (hereinafter simply referred to as magnitude Γ) when the voltage vector Va is fixed. Specifically, since the induced voltage value changes depending on the motor speed and the allowable value of the magnitude Γ when the voltage vector Va is fixed changes (that is, the difference between the induced voltage and the power supply voltage becomes too small), each rotational speed. The magnitude Γ of the voltage vector Va for fail-safe running at is stored. The allowable value of the magnitude Γ of the voltage vector Va is the most severe condition when the rotor further rotates from the state of FIG. 6 and the d axis coincides with the Ia axis when the voltage vector is fixed. Therefore, the amount of d-axis current that can flow at each rotation speed is obtained from experiments, and the magnitude of the voltage vector Va corresponding to the obtained d-axis current is set as the magnitude Γ of the voltage vector Va for fail-safe. This value is stored for each rotation speed, and is read and used as necessary.

Further, in other states, that is, in a region where the normal voltage vector Va output on the upper half of FIG. 3 is possible (that is, a region in which the failed switching element is not originally used), the d-axis voltage command value = 0 during fail-safe traveling. The q-axis voltage command value = Γ (= the magnitude when the voltage vector Va is fixed), and the three-phase voltage command values Vu ^* and Vv are obtained by converting the d-axis voltage command value and the q-axis voltage command value into two-phase three-phase conversion. Control is performed as ^* and Vw ^* .

In the present embodiment, the q-axis voltage command value on the upper half surface of FIG. 3 at the time of fail-safe driving = the magnitude Γ of the voltage vector Va. For example, the d-axis voltage command value and the q-axis on the upper half surface of FIG. The voltage command values are the d-axis current command value Vd ^* and the q-axis current command value Vq ^* as in the normal control, and in the lower half of FIG. 3 (that is, the area where the failed switching element was supposed to be used) May be d-axis voltage command value = 0, q-axis voltage command value = magnitude Γ of voltage vector Va.

Next, the control in the present invention will be described in detail using the flowcharts of FIGS.
FIG. 13 is a flowchart showing a current control calculation that is normally controlled at a cycle of about 100 μs.
In FIG. 13, first, in step S1, the detection values Iu, Iv, Iw of the current sensors 7-1, 7-2, 7-3 and the detection value θ of the angle detector 8 are read, and the three phases shown by the following equations are read. Two-phase conversion is performed to calculate two-phase current values Id and Iq.
Id = {√ (3/2) Iu cos θ + [√ (1/2) Iu + √ (2) Iv] sin θ}
Iq = {− √ (3/2) Iu sinθ + [√ (1/2) Iu + √ (2) Iv] cosθ}
Next, in step S2, the presence or absence of an open failure of the switching element is detected. If there is a failure, the process proceeds to “switching element fail-safe control” in FIG. 14, and if there is no failure, the process proceeds to step S3. If an open failure is detected even once, it will not be restored again.

In step S2, whether or not there is an open failure is determined by, for example, accumulating current for each phase. If the value during one rotation of the motor is positive (greater than 0), failure of the upper switching element, negative (from 0) Small), it is determined that the lower switching element is faulty, and 0 is normal. In consideration of the detection error of the current sensor, it may be determined that the upper switching element has failed when the integrated value is greater than or equal to a predetermined positive threshold value, and that the lower switching element has failed when the integrated value is less than or equal to a negative predetermined threshold value. Good.
The failure detection unit 11 in FIG. 1 performs the above determination to detect the presence or absence of an open failure and whether the failed phase is on the upper side or the lower side (see the flowchart in FIG. 14).

Next, in step S3, voltage command values Vd ^* and Vq ^* for the d-axis and q-axis are calculated by well-known proportional-integral control (PI control), and the process proceeds to step S4. That is, the d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* are controlled by PI control according to the deviation between the d-axis and q-axis current command values Id ^* and Iq ^* and the d-axis and q-axis actual current values. calculate.

In step S4, the three-phase voltage command values Vu ^* , Vv ^* , Vw ^* are calculated from the d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* calculated in step S3 by the two-phase three-phase conversion shown in the following formula ^. And the process proceeds to step S5.
Vu ^* = √ (2/3) × (Vd ^* × cosθ′−Vq ^* × sinθ ′)
Vv ^* = √ (1/2) × (Vd ^* × sin θ ′ + Vq ^* × cos θ ′) − Vu ^* / 2
Vw ^* = ^{-Vu *} -Vv ^*
However, θ ': Estimated value of motor angle at output (estimated value of rotor rotation angle)
The estimated motor angle θ ′ at the time of output changes from the calculation of the three-phase voltage command value to the rotation angle θ ₁ (see FIG. 6) detected by the angle detector 8 so that the actual voltage changes corresponding to the voltage command value. This is calculated by adding the advance angle α of the motor until it is done (for one control period).
Next, in step S5, the three-phase voltage command values Vu ^* , Vv ^* , Vw ^* are converted into PWM signals and output. The above is the current control process at the normal time.

Next, FIG. 14 is a flowchart showing “switching element fail-safe control” after detecting an open failure of the switching element in step S2.
In step S6, the d-axis and q-axis voltage command values at the time of switching element open failure (for fail-safe control) according to the motor rotational speed and the magnitude Γ of the voltage vector Va at the time of fixation are read, and the process proceeds to step S7. Hereinafter, the “fixed voltage vector” is abbreviated as “fixed voltage vector”.
In step S7, the position of the switching element in which the open failure has occurred is specified. If the U-phase is on the upper side, the process proceeds to “U-phase upper switching element fail-safe control” in FIG.
In step S8, the position of the switching element that has failed in the open state is specified. If the U-phase is on the lower side, the process proceeds to “U-phase lower-side switching element fail-safe control”; otherwise, the process proceeds to step S9.
Even in step S9, the position of the switching element that has an open failure is specified. If the V-phase is upper, the process proceeds to “V-phase upper switching element fail-safe control”; otherwise, the process proceeds to step S10.
Also in step S10, the position of the switching element that has failed open is specified. If the V-phase is lower, the process proceeds to “V-phase lower switching element fail-safe control” in FIG. 16, and otherwise the process proceeds to step 11.
Even in step S11, the position of the switching element that has failed open is specified. If the W phase is on the upper side, the process proceeds to "W phase upper switching element fail safe control"; otherwise, the process proceeds to "W phase lower switching element fail safe control". Transition.

Thus, although it transfers to the fail safe control according to the position of the switching element which carried out an open failure, the fail safe control when a U-phase upper side switching element carries out an open failure as an example is demonstrated with the flowchart of FIG.
15, in step S12, the d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* at the time of switching element open failure (for fail-safe control) read in step S6 of FIG. Phase conversion is performed, and three-phase voltage command values Vu ^* , Vv ^* , Vw ^* are calculated.
Vu ^* = √ (2/3) × (Vd ^* × cosθ′−Vq ^* × sinθ ′)
Vv ^* = √ (1/2) × (Vd ^* × sin θ ′ + Vq ^* × cos θ ′) − Vu ^* / 2
Vw ^* = ^{-Vu *} -Vv ^*
However, θ ′: Estimated motor angle at output (calculated in the same way as above)
Next, in step S13, if the value of the U-phase voltage command value Vu ^* calculated in step S12 is greater than 0, the process proceeds to step S15, and if it is less, the process proceeds to step S14.

If Vu ^* is 0 or less, it is not the ON region of the failed U-phase upper switching element. Therefore, in step S14, the three-phase voltage command values Vu ^* , Vv ^* , Vw ^* calculated in step S13 are converted to PWM. And return to step S12.
On the other hand, if Vu ^* > 0, since the faulty U-phase upper switching element is in the ON region, control is performed to fix the voltage vector. That is, in step S15, the current phase angle ζ (rad) in FIG. 17 is calculated from the d-axis and q-axis current values Id and Iq read in step S1 in FIG. 13, and the process proceeds to step S16.
Where ζ = tan ⁻¹ (Id / Iq)
Next, in step S16, the motor advance angle α (rad / control cycle: same as α) for one control period calculated in step S1 of FIG. 13 is read, and the process proceeds to step S17.

In step 17, it is determined whether or not a value (ζ + α) obtained by adding the current phase angle ζ (rad) and the motor advance angle α (rad / control cycle) between control cycles exceeds 2π (= 0). If so, the process proceeds to step S19, and if below, the process proceeds to step S18.
That is, step 17 is a step of determining when the q-axis current becomes 0. When ζ + α = 2π, it is determined that the q-axis current is 0. When ζ + α <2π, in step S18, the fixed voltage vector A having the magnitude of Γ read in step S6 in FIG. 14 is output in the direction of A in FIG. Therefore, the voltage command values Vu ^* , Vv ^* , Vw ^* of each phase are set to Vu ^* = 0.
Vv ^* = − [Γ × 4 / (√3)]
Vw ^* = [Γ × 4 / (√3)]
Then, the PWM signal is converted and output, and the process returns to step S12. By this processing, the voltage vector is fixed to the fixed voltage vector A.

When ζ + α> 2π in step 17, the voltage vector is set to B obtained by inverting 180 ° from A. Therefore, in step S19, the magnitude of Γ read in step S6 in FIG. 14 in the direction of the fixed voltage vector B in FIG. The fixed voltage vector B is output. for that reason,
Vu ^* = 0
Vv ^* = [Γ × 4 / (√3)]
Vw ^* = − [Γ × 4 / (√3)]
It is converted into a PWM signal and output, and the process returns to step S12. By this processing, the voltage vector is fixed to the fixed voltage vector B.
Since steps S18 and S19 perform RETURN to step S12, it is determined again in step S13 whether or not Vu ^* > 0. When Vu ^* becomes 0 or less, the voltage vector is unfixed.

As described above, fail-safe control for switching element open failure is executed. That is, when an open failure of the upper switching element is detected, the voltage command value of the failed phase obtained by the two-phase / three-phase conversion unit 3 from the d-axis q-axis voltage command value for fail-safe (for failure) When the calculated value Vu ^* is greater than 0, the voltage command value Vu is a value that fixes the phase angle of the combined voltage vector, which is a combined vector of the three-phase voltage command values, to a predetermined value (90 ° in the above example). ^* , Vv ^* , Vw ^* are output, and when the q-axis current determined in Step 17 becomes 0, the phase angle of the three-phase composite voltage vector is inverted by 180 ° from the predetermined value (90 + 180 = 270 °) The voltage command value to be output is output, and control is performed to fix the phase angle of the inverted composite voltage vector until the calculated value Vu ^* of the voltage command value of the failed phase is 0 or less.

As another example, fail safe control in the case where an open failure occurs on the lower side of the V phase will be described with reference to the flowchart of FIG.
As in the case of FIG. 15, in step S20, two-phase three-phase is obtained using the following formula from the d-axis and q-axis voltage command values for fail-safe control read in step S6 of FIG. The three-phase voltage command values Vu ^* , Vv ^* , Vw ^* are calculated and the process proceeds to step S21.
Vu ^* = √ (2/3) × (Vd ^* × cosθ′−Vq ^* × sinθ ′)
Vv ^* = √ (1/2) × (Vd ^* × sin θ ′ + Vq ^* × cos θ ′) − Vu ^* / 2
Vw ^* = − Vu ^* −Vv
However, θ ′: Estimated motor angle at output (calculated in the same way as above)
In step S21, if the value of the V-phase voltage command value Vv ^* calculated in step S20 is smaller than 0, the process proceeds to step S23.

When the value of Vv ^* is equal to or greater than 0, it is not the ON region of the V-phase lower switching element, so in step S22, the three-phase voltage command values Vu ^* , Vv ^* , Vw ^* calculated in step S21 are converted to PWM. And return to step S20.
When Vv ^* <0, since the V-phase lower switching element is in the ON region, control for fixing the voltage vector is performed. That is, in step S23, the current phase angle ζ (rad) in FIG. 17 is calculated from the d-axis and q-axis current values read in step S1 in FIG. 13, and the process proceeds to step S24.
Where ζ = tan ⁻¹ (Id / Iq)
In step S24, the motor advance angle α (rad / control period) between the control periods calculated in step S1 of FIG. 13 is read, and the process proceeds to step S25.

  Step S25 is a step of determining when the q-axis current becomes 0, and the value obtained by adding the current phase angle ζ (rad) and the motor advance angle α (rad / control cycle) between the control cycles is π + 120 ° (= 300 °), the process proceeds to step S27 if π + 120 ° (= 300 °) or more, and to step S26 if less. In addition, since said angle is an angle on the basis of the U phase, π + 120 ° of the V phase corresponds to 2π of the U phase.

In step S26, in order to output the fixed voltage vector C having the magnitude of Γ read in step S6 in FIG. 14 in the direction of C in FIG. 19, voltage command values Vu ^* and Vv ^* for the U, V, and W phases ^. , Vw ^* is Vu ^* = − [Γ × 4 / (√3)]
Vv ^* = 0
Vw ^* = [Γ × 4 / (√3)]
It is converted into a PWM signal and output, and the process returns to step S20. The voltage vector is fixed to the fixed voltage vector C by the above processing.

In step S27, in order to output the fixed voltage vector D having the magnitude of Γ read in step S6 in FIG. 14 in the direction of the fixed voltage vector D in FIG. 19, the voltage command values Vu ^* , U, V, W for each phase. Vv ^* and Vw ^* are Vu ^* = [Γ × 4 / (√3)]
Vv ^* = 0
Vw ^* = − [Γ × 4 / (√3)]
It is converted into a PWM signal and output, and the process returns to step S20. The voltage vector is fixed to the fixed voltage vector D by the above processing.

  In the above description, FIG. 15 is shown as an example when the upper switching element has an open failure, and FIG. 16 is shown as an example when the lower switching element has failed. However, depending on the failing phase, step S13, The determination values of S17, S21, and S25 change.

FIG. 20 is a flowchart showing general control in accordance with the position of the switching element in which an open failure occurs. The switching element is substituted by substituting the values in FIG. 21 into L in step S29, M in step S34, and N in step S35. Perform fail-safe control in case of an open failure. FIG. 22 is a diagram showing the fixed voltage vectors A to F in FIG.
Note that θth in step S33 in FIG. 20 is changed as shown in FIG. 23 according to the phase in which the open failure occurs and whether the switching element is on the upper side or the lower side.

  Further, as can be seen from the above description and FIG. 21, when the phase angle of the composite voltage vector is fixed, and when the phase angle is inverted by 180 °, by fixing the positive / negative and magnitude of the voltage command value, By fixing the phase angle of the combined voltage vector and inverting only the positive / negative voltage command value, the phase angle of the combined voltage vector can be inverted by 180 °.

  In the description so far, the rotation angle at the time of inversion of the composite voltage vector is as shown in FIG. 23 because the angle is based on the U phase, but the composite voltage depends on the reference phase. The rotation angle when the vector is reversed is different. For example, when the V phase is used as a reference, the rotation angles when the U phase is reversed are 240 ° and 60 °.

1 is a diagram showing an embodiment of a current feedback control block that performs vector control of a three-phase AC synchronous motor to which the present invention is applied. The circuit diagram of the inverter 5. FIG. Voltage vector illustration. The three-phase current waveform diagram at the time of constant rotation and constant output. Voltage vector illustration. Voltage vector illustration. Voltage vector illustration. Voltage vector illustration. Voltage vector illustration. Voltage vector illustration. Voltage vector illustration. Voltage vector illustration. The flowchart which shows an electric current control calculation. The flowchart which shows switching element fail safe control. The flowchart which shows the fail safe control when a U-phase upper side switching element carries out an open failure. The flowchart which shows the fail safe control when a V-phase lower side switching element carries out an open failure. The vector diagram which shows electric current phase angle (zeta). Voltage vector illustration. Voltage vector illustration. The flowchart which shows the general control according to the position of the switching element in which the open failure occurred. The chart which shows the value in L of step S29 of FIG. 20, M of step S34, and N of step S35. The voltage vector figure which shows each fixed voltage vector AF in FIG. FIG. 21 is a chart showing the value of θth in step S33 of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Current command calculating part 2 ... Current PI control part 3 ... Two-phase three-phase converter 4 ... PWM conversion part 5 ... Inverter 6 ... Three-phase motor 7-1, 7-2, 7-3 ... Current sensor 8 ... Rotation Angle detector 9 ... A / D converter 10 ... 3-phase 2-phase converter 11 ... failure detector 12 ... failure control unit 13 ... motor rotor 20 ... power supply 21, 23, 25 ... upper switching elements 22,24, 26. Lower switching element

Claims (8)

Current command value calculating means for calculating a current command value based on the torque command value;
An actual current detecting means for detecting an actual current that is a current flowing through each winding of the three-phase AC motor;
Rotation angle detection means for detecting the rotation angle of the rotor of the three-phase AC motor;
A d-axis q-axis voltage command value calculator that calculates a d-axis q-axis voltage command value based on the current command value, the actual current value, and the rotation angle;
Voltage command value calculation means for calculating the voltage command value of each phase of the three-phase AC motor by performing two-phase three-phase conversion on the d-axis q-axis voltage command value;
A PWM converter for calculating a PWM signal for driving the inverter based on the voltage command value;
A series circuit of an upper switching element and a lower switching element is provided for three phases, the upper side of each series circuit is connected to the positive side of the power source, the lower side is connected to the negative side of the power source, and the 3 The inverter connected to each phase winding of the phase AC motor, and a motor control device comprising:
Failure detection means for detecting an open failure in which the switching element of the inverter continues to be turned off;
When the failure detection means detects an open failure of the upper switching element in any one of the three phases, the voltage command value calculation means is obtained from the d-axis q-axis voltage command value for failure. When the calculated value of the voltage command value of the faulty phase is greater than 0, a voltage command value is output that fixes the phase angle of the combined voltage vector, which is a combined vector of the three-phase voltage command values, to a predetermined value. When the q-axis current becomes 0, a voltage command value for inverting the phase angle of the three-phase composite voltage vector by 180 ° from the predetermined value is output, and the phase angle of the inverted composite voltage vector is failed. When the operation value of the voltage command value of the phase is fixed to 0 or less, and when the failure detection means detects an open failure of the lower switching element in any one of the three phases, Faulty phase voltage When the calculated value of the command value becomes 0 or less, a voltage command value of a value that fixes the phase angle of the combined voltage vector, which is a combined vector of the three-phase voltage command values, to a predetermined value is output, and the q-axis current is When it becomes 0, a voltage command value for inverting the phase angle of the three-phase composite voltage vector by 180 ° from the predetermined value is output, and the phase angle of the inverted composite voltage vector is set to the voltage command value of the failed phase. Control means for controlling the calculation value to be fixed until it becomes greater than 0;
A control device for a three-phase AC motor, comprising:   The d-axis and q-axis voltage command values for failure are d-axis voltage command value = 0 and q-axis voltage command value = Γ (where Γ = the magnitude of the voltage vector Va when fixed). The control device for a three-phase AC motor according to claim 1. The d-axis q-axis voltage command value for failure is set to the same d-axis current command value Vd ^* and q-axis current command value Vq ^* as in normal control in a region where the failed switching element is not originally used. The region where the switching element should have been originally used is d-axis voltage command value = 0 and q-axis voltage command value = Γ (however, the magnitude of the voltage vector Va when fixed). The control device for the three-phase AC motor according to claim 1.   The control means fixes the phase angle of the composite voltage vector by fixing the positive and negative and magnitude of the voltage command value, and inverts only the positive and negative of the voltage command value, thereby changing the phase angle of the composite voltage vector by 180 °. The three-phase AC electric motor control device according to any one of claims 1 to 3, wherein the control device is reversed. The control means includes a d-axis phase angle θ ₁ , a current phase angle ζ that is a phase difference between the combined current vector and the q-axis as a current vector corresponding to the combined voltage vector, and the actual voltage from the time when the voltage command value is output. The time point at which the q-axis current becomes 0 is determined based on the total value of the advance angle α which is the rotation angle until the current value changes corresponding to the voltage command value. Item 5. The control device for the three-phase AC electric period according to any one of Items 4 to 5. When the U-phase upper switching element has an open failure, the d-axis phase angle θ ₁ , the current phase angle ζ, and the lead angle α with respect to the voltage axis of the phase in which the switching element has an open failure If the q-axis current is determined to be 0 when the total value of 0 is 0 and the U-phase lower switching element has an open failure, the voltage axis of the phase in which the switching element has an open failure The q-axis current is determined to be 0 when the total value of the d-axis phase angle θ ₁ , the current phase angle ζ, and the advance angle α is 180 ° with reference to. Item 6. The control device for the three-phase AC electric motor cycle according to Item 5. When the V-phase upper switching element has an open failure, the d-axis phase angle θ ₁ , the current phase angle ζ, and the lead angle α with respect to the voltage axis of the phase in which the switching element has an open failure When the q-axis current is determined to be 0 when the total value of 120 ° is reached and the U-phase lower switching element has an open failure, the voltage axis of the phase in which the switching element has an open failure The q-axis current is determined to be zero when the sum of the d-axis phase angle θ ₁ , the current phase angle ζ, and the advance angle α is 300 ° with reference to Item 6. The control device for the three-phase AC electric motor cycle according to Item 5. When the W-phase upper switching element has an open failure, the d-axis phase angle θ ₁ , the current phase angle ζ, and the lead angle α with respect to the voltage axis of the phase in which the switching element has an open failure When the q-axis current is determined to be 0 when the total value of λ becomes 240 ° and the U-phase lower switching element has an open failure, the voltage axis of the phase in which the switching element has an open failure The q-axis current is determined to be 0 when the total value of the d-axis phase angle θ ₁ , the current phase angle ζ, and the advance angle α is 60 °. Item 6. The control device for the three-phase AC electric motor cycle according to Item 5.

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