JP2010136581A - Controller for electric motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller for an electric motor capable of preventing improper control of the electric motor. <P>SOLUTION: The controller 10 of the electric motor includes: an abnormality detecting section 26 for determining that a DC side current sensor 31 is normal when all the transistors of a bridge circuit 13a are off and the number of rotations of the motor 11 is zero and when a DC side current detected by the DC side current sensor 31 is zero, and determining that the DC side current sensor 31 is abnormal when the DC side current is not zero. When the DC side current detected by the DC side current sensor 31 at a time when a command voltage vector is a zero vector of a basic voltage vector is not zero when the motor 11 is driven, the abnormality detecting section 26 detects that either a high transistor or a low transistor configuring the bridge circuit 13a is abnormal in accordance with a conduction pattern of the bridge circuit 13a corresponding to the zero voltage vector. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control device for an electric motor.

Conventionally, for example, when converting a direct current output from a single direct current sensor into a three-phase alternating current, two different states of each carrier period are generated in the process of changing six different gate states by three pairs of transistors. There is known a device that detects two current values having different phases in a section and calculates a current value of another phase from these two current values on the assumption that the sum of three-phase currents is always equal to zero. (For example, refer to Patent Document 1).
Japanese Patent No. 2563226

By the way, in the device according to the above prior art, when abnormality occurs in the three pairs of transistors or the DC current sensor, it becomes impossible to properly estimate the phase current, and it becomes difficult to appropriately control the motor. It is desired to determine whether there is an abnormality in the apparatus.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a motor control device capable of preventing the motor control from becoming inappropriate.

  In order to solve the above problems and achieve the object, the motor control device according to the first aspect of the present invention sequentially energizes the motor (for example, the motor 11 in the embodiment) by the pulse width modulation signal. A bridge circuit for commutation (for example, the bridge circuit 13a in the embodiment) and pulse width modulation signal generation means for generating the pulse width modulation signal from a carrier wave signal (for example, the PWM signal generation unit 25 in the embodiment) A DC-side current sensor (for example, a DC-side current sensor 31 in the embodiment) that detects a DC-side current of the bridge circuit and outputs a detection result signal, and a command voltage vector is basically used when the electric motor is driven. Judgment to determine whether or not the DC side current is zero based on the signal output from the DC side current sensor at the timing when the voltage vector becomes the zero voltage vector And the bridge circuit corresponding to the zero voltage vector when the DC-side current is not zero in the determination result by the determination unit (for example, the abnormality detection unit 26, step S06, step S09 in the embodiment) In accordance with the energization pattern, abnormality determination means for determining that either the high-side transistor or the low-side transistor constituting the bridge circuit is abnormal (for example, the abnormality detection unit 26 in the embodiment, step S07, step S10).

  Furthermore, the electric motor control device according to the second aspect of the present invention is configured such that the high-side transistor and the low-side transistor of the bridge circuit are off and the rotational speed of the electric motor is zero. Based on the signal output from the current sensor, it is determined that the DC side current sensor is normal when the DC side current is zero, and the DC side current sensor is abnormal when the DC side current is not zero. Sensor abnormality determination means (for example, abnormality detection unit 26 in the embodiment, step S02) is determined, and the determination means determines that the DC-side current sensor is normal by the sensor abnormality determination means. If so, the determination process is executed.

  According to the motor control device of the first aspect of the present invention, the DC side current is zero at the timing when the command voltage vector becomes the zero voltage vector, taking into account the offset value included in the output of the DC side current sensor, for example. Therefore, it is possible to determine the abnormality of the high-side transistor and the abnormality of the low-side transistor that constitute the bridge circuit, and that the control of the motor becomes inappropriate according to the determination result. Can be prevented.

  Furthermore, according to the motor control device of the second aspect of the present invention, for example, at the time of starting the motor, the high-side transistor and the low-side transistor of the bridge circuit are turned off in advance, and the rotational speed of the motor is By determining whether or not the DC side current is zero when it is zero, it is possible to determine the abnormality of the DC side current sensor, and that the control of the motor becomes inappropriate according to the determination result. Can be prevented.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of an electric motor control device of the present invention will be described with reference to the accompanying drawings.
The motor control device 10 according to this embodiment controls, for example, a three-phase AC brushless DC motor 11 (hereinafter simply referred to as the motor 11), and the motor 11 is a permanent magnet used for a field. And a stator (not shown) that generates a rotating magnetic field for rotating the rotor.
As shown in FIG. 1, for example, the motor control device 10 includes an inverter 13 using a battery 12 as a DC power source and a motor control device 14.

The three-phase (for example, U-phase, V-phase, and W-phase) AC motor 11 is driven by the inverter 13 in response to a control command output from the motor control device 14.
The inverter 13 includes a bridge circuit 13a formed by bridge connection using a plurality of switching elements (for example, MOSFETs: Metal Oxide Semi-conductor Field Effect Transistors) and a smoothing capacitor C, and the bridge circuit 13a performs pulse width modulation ( It is driven by the PWM signal.

  In this bridge circuit 13a, for example, a high-side and low-side U-phase transistor UH, UL paired for each phase, a high-side and low-side V-phase transistor VH, VL, a high-side and low-side W-phase transistor WH, WL is bridge-connected. Each transistor UH, VH, WH has a drain connected to the positive terminal of the battery 12 to form a high side arm, and each transistor UL, VL, WL has a source connected to the grounded negative terminal of the battery 12. It constitutes the low side arm. For each phase, the sources of the high-side arm transistors UH, VH, WH are connected to the drains of the low-side arm transistors UL, VL, WL, and the transistors UH, UL, VH, VL, WH, WL. Each of the diodes DUH, DUL, DVH, DVL, DWH, DWL is connected between the drain and the source so as to be in the forward direction from the source to the drain.

  The inverter 13 is, for example, a gate signal (that is, a PWM signal) that is a switching command that is output from the motor control device 14 when driving the motor 11 and is input to the gates of the transistors UH, VH, WH, UL, VL, WL. ), The DC power supplied from the battery 12 is converted into the three-phase AC power by switching the on / off (cut-off) state of each pair of transistors for each phase. By sequentially commutating energization to the windings, AC U-phase current Iu, V-phase current Iv and W-phase current Iw are passed through the stator windings of each phase.

  The motor control device 14 performs current feedback control (vector control) on the dq coordinates forming the rotation orthogonal coordinates, calculates the target d-axis current Idc and the target q-axis current Iqc, and calculates the target d-axis current Idc and Each phase voltage command Vu, Vv, Vw is calculated based on the target q-axis current Iqc, and a PWM signal that is a gate signal for the inverter 13 is output according to each phase voltage command Vu, Vv, Vw. The d-axis current Ids and q-axis current Iqs obtained by converting the phase currents Iu, Iv, and Iw supplied from the motor 13 to the motor 11 on the dq coordinate, and the target d-axis current Idc and the target q-axis current Iqc. Control is performed so that each deviation becomes zero.

The motor control device 14 includes, for example, a current sensor I / F (interface) 21, an overcurrent protection device 22, a phase current estimation unit 23, a control device 24, a PWM signal generation unit 25, and an abnormality detection unit 26. Configured.
The current sensor I / F (interface) 21 is connected to a DC side current sensor 31 that detects a DC side current Idc of the bridge circuit 13a of the inverter 13 between the bridge circuit 13a of the inverter 13 and the negative terminal of the battery 12. The detection signal output from the DC side current sensor 31 is output to the overcurrent protection device 22, the phase current estimation unit 23, and the abnormality detection unit 26.
The direct current sensor 31 may be disposed between the bridge circuit 13a of the inverter 13 and the positive terminal of the battery 12.
Further, it is output from the angle sensor 32 that detects the rotation angle of the rotor of the motor 11 (that is, the rotation angle of the rotor magnetic pole from the predetermined reference rotation position and the rotation position of the rotation shaft of the motor 11). The detection signal is input to the control device 24.
Note that the angle sensor 32 may be omitted, and a device for estimating the magnetic pole position of the rotor may be provided instead.

The overcurrent protection device 22 performs a predetermined overcurrent protection operation according to the DC side current Idc detected by the DC side current sensor 31.
The phase current estimation unit 23 actually uses the inverter 13 based on the DC side current Idc detected by the DC side current sensor 31 at the detection timing according to the gate signal (that is, PWM signal) output from the PWM signal generation unit 25. The phase currents Iu, Iv, and Iw supplied to the motor 11 are estimated. Details of the operation of the phase current estimation unit 23 will be described later.

  The control device 24 converts the phase currents Iu, Iv, Iw output from the phase current estimation unit 23 into dq coordinates according to the rotation angle of the motor 11 output from the angle sensor 32, and the d-axis obtained. Current feedback control (vector control) is performed so that each deviation between the current Ids and the q-axis current Iqs and the target d-axis current Idc and the target q-axis current Iqc becomes zero, and each phase voltage command Vu, Vv, Vw Is output.

  The PWM signal generation unit 25 compares each phase voltage command Vu, Vv, Vw with a carrier signal such as a triangular wave in order to pass a sinusoidal current to the three-phase stator winding, and A gate signal (that is, a PWM signal) for driving the transistors UH, VH, WH, UL, VL, WL on / off is generated. Then, the inverter 13 converts the DC power supplied from the battery 12 into three-phase AC power by switching the on (conductive) / off (cut-off) state of each transistor that forms a pair for each of the three phases. By sequentially commutating energization to each stator winding of the three-phase motor 11, AC U-phase current Iu, V-phase current Iv, and W-phase current Iw are energized to each stator winding.

The gate signal input from the PWM signal generation unit 25 to the inverter 13 is, for example, according to the combination of the on / off states of the transistors UH, UL and VH, VL and WH, WL that are paired for each phase. 1 and FIGS. 2A to 2H, the PWM (pulse width) corresponding to each of the eight switching states S1 to S8 (that is, the states of the basic voltage vectors V0 to V7 having different phases by 60 degrees). Modulation) signal. In Table 1 below, the transistors that are turned on among the high-side (High) and low-side (Low) transistors are shown, and the transistors that are turned on in FIGS. Is shaded.
Then, phase currents Iu, Iv, Iw are intermittently generated on the DC side of the bridge circuit 13a of the inverter 13 according to the switching states S1 to S8, and the DC side current Idc detected by the DC side current sensor 31. Is one of the phase currents Iu, Iv, Iw, or one of the phase currents Iu, Iv, Iw inverted, or zero.

  The phase current estimation unit 23, for example, in each of the switching states S2 to S7 (that is, the states of the basic voltage vectors V1 to V6 having different phases by 60 degrees) in one period of a carrier signal such as a triangular wave. The two-phase phase currents of the three-phase phase currents are acquired from the DC-side current Idc detected by the DC-side current sensor 31 in two predetermined sets of states. Based on these two-phase phase currents, the other one-phase phase current among the three-phase phase currents is estimated. Then, each estimated value of the three-phase current obtained by estimating from the DC-side current Idc detected by the DC-side current sensor 31 is output to the control device 24.

For example, as shown in FIG. 3, in the case of three-phase modulation using a triangular carrier signal, the carrier signal with a voltage pattern symmetrical to the peak (carrier vertex) on the valley side of the triangular carrier signal is obtained. In the period of one cycle Ts, the detected value of each phase current for two phases can be acquired twice.
In other words, the phase current estimation unit 23 is symmetric with respect to the carrier vertex at times tu1 and tu2 (that is, at the time tp of the carrier vertex on the valley side) in the state of the two basic voltage vectors V1 symmetrical with respect to the carrier vertex. On the other hand, the first U-phase current Iu1 and the second U-phase current Iu2 are obtained from the DC-side current Idc detected by the DC-side current sensor 31 at the time having the same time interval T1 and at the DC-side current detection timing). To do. Further, in the state of the two times basic voltage vector V3 symmetric with respect to the carrier vertex, times tw1 and tw2 that are symmetric with respect to the carrier vertex (that is, the same time interval with respect to the time tp of the carrier vertex on the valley side) The first W-phase current Iw1 and the second W-phase current Iw2 are obtained from the DC-side current Idc detected by the DC-side current sensor 31 at the time having T2 and at the DC-side current detection timing).

Then, for example, the phase current estimation unit 23 calculates an average value for each phase based on the phase currents Iu1, Iu2 and Iw1, Iw2, and calculates the average value at the time tp of the carrier peak on the valley side (ie, estimation Current value at phase current synchronization timing). Thereby, the timing of the current value of the two-phase phase current (that is, the U-phase current and the W-phase current) is changed from the DC-side current detection timing (that is, each time tu1, tu2, tw1, tw2) to the carrier peak on the valley side. At time tp (estimated phase current synchronization timing).
Then, the phase current estimation unit 23 uses the fact that the sum of the current values of the respective phase currents at the same timing is zero, so that the current values of the two-phase currents (for example, the U-phase current and the W-phase current) ( That is, the current value of the other one-phase phase current (for example, V-phase current) is calculated from the current value at the time tp at the carrier apex on the valley side. Thereby, the timing of the current value of the three-phase phase current is synchronized with the time tp of the carrier peak on the valley side.
The phase current estimation unit 23 calculates the average value based on the phase currents Iu1, Iu2 and Iw1, Iw2, and estimates the phase current of the other one phase from the two-phase phase current. However, the present invention is not limited to this. Instead, each phase current may be estimated by another estimation method.

The abnormality detection unit 26 first detects the DC-side current sensor when all the transistors of the bridge circuit 13a are off and the number of revolutions of the motor 11 is zero, for example, when the motor control device 10 is started. On the basis of the signal output from 31, the DC side current sensor 31 is determined to be normal when the DC side current Idc is zero, and the DC side current sensor 31 is abnormal when the DC side current Idc is not zero. Judge that there is. When the signal output from the DC side current sensor 31 has an appropriate offset value, it is determined whether or not the DC side current Idc is zero after the offset value is corrected.
And if it determines with the DC side current sensor 31 being normal, Furthermore, based on the signal output from the DC side current sensor 31 at the timing when the command voltage vector becomes the zero voltage vector of the basic voltage vector when the motor 11 is driven, It is determined whether or not the DC side current Idc is zero. If the DC-side current Idc is not zero in this determination result, either the high-side transistor or the low-side transistor constituting the bridge circuit 13a is abnormal depending on the energization pattern of the bridge circuit 13a corresponding to the zero voltage vector. It is determined that

The motor control device 10 according to the present embodiment has the above-described configuration. Next, the operation of the motor control device 10, in particular, the process for determining whether or not the DC-side current sensor 31 and the bridge circuit 13 a are abnormal. explain.
First, in step S01 shown in FIG. 4, for example, at the time of starting the motor control device 10, all the transistors of the bridge circuit 13a are turned off, and the rotation speed of the motor 11 is set to zero.
In step S02, based on the signal output from the DC-side current sensor 31 at this time, whether or not the DC-side current Idc is zero, that is, the signal output from the DC-side current sensor 31 is an appropriate offset. If it has a value, it is determined whether or not the output of the DC side current sensor 31 is an offset value.
If this determination is “NO”, the flow proceeds to step S 03, in which it is determined that the DC-side current sensor 31 is abnormal, and the process ends.
On the other hand, if this determination is “YES”, the flow proceeds to step S 04.

In step S04, the energization of the motor 11 is sequentially commutated by the PWM signal, and the driving of the motor 11 is started.
In step S05, it is determined whether or not the command voltage vector is the zero voltage vector V7 of the basic voltage vector, that is, the timing when the high-side arm transistor of the bridge circuit 13a is turned on.
If this determination is “NO”, the flow proceeds to step S 08 described later.
On the other hand, if this determination is “YES”, the flow proceeds to step S 06.
In step S06, based on the signal output from the DC side current sensor 31 at this time, whether or not the DC side current Idc is zero, that is, the signal output from the DC side current sensor 31 is appropriately offset. If it has a value, it is determined whether or not the output of the DC side current sensor 31 is an offset value.
If the determination result is “NO”, the process proceeds to step S07. In step S07, it is determined that the transistor of the low-side arm of the bridge circuit 13a is abnormal, and the process ends.
On the other hand, if the determination is “YES”, the flow proceeds to step S08.

In step S08, it is determined whether or not the command voltage vector is the zero voltage vector V0 of the basic voltage vector, that is, the timing when the transistor of the low side arm of the bridge circuit 13a is turned on.
If this determination is “NO”, the flow returns to step S 05 described above.
On the other hand, if this determination is “YES”, the flow proceeds to step S 09.
In step S09, based on the signal output from the DC-side current sensor 31 at this time, whether or not the DC-side current Idc is zero, that is, the signal output from the DC-side current sensor 31 is an appropriate offset. If it has a value, it is determined whether or not the output of the DC side current sensor 31 is an offset value.
If this determination is “NO”, the flow proceeds to step S 10, in which it is determined that the high-side arm transistor of the bridge circuit 13 a is abnormal, and the processing is ended.
On the other hand, if this determination is “YES”, the flow returns to step S 05 described above.

As described above, according to the motor control device 10 of the present embodiment, for example, when the motor 11 is started, the high-side transistor and the low-side transistor of the bridge circuit 13a are turned off in advance, and the motor 11 By determining whether or not the DC-side current Idc is zero when the rotational speed is zero, it is possible to determine whether or not the DC-side current sensor 31 is abnormal. Depending on this determination result, the motor 11 Inappropriate control can be prevented.
Further, when the motor 11 is driven, it is determined whether or not the DC side current Idc is zero at the timing when the command voltage vector becomes the zero voltage vector, so that an abnormality of the high side transistor constituting the bridge circuit 13a is detected. The presence / absence and the presence / absence of abnormality of the low-side transistor can be determined, and the control of the motor 11 can be prevented from becoming inappropriate according to the determination result. Moreover, by determining whether or not the DC side current Idc is zero, for example, a short circuit current generated due to an abnormality of the high side transistor or the low side transistor is very small, or the inductance of the current path of the short circuit current Even when the time for which the short-circuit current flows is short due to components or the like, it is possible to accurately determine whether there is an abnormality.

  In the above-described embodiment, with respect to the three-phase modulation using a triangular carrier signal, the detected values of the phase currents for two phases are acquired twice in the period of one cycle Ts of the carrier signal, The average value is calculated. However, the present invention is not limited to this. For example, the transistors UH and UL with respect to the carrier apex at the time of 1/2 period in the two-phase modulation or at one cycle Ts of an appropriate carrier signal. In addition, when the on / off patterns of VH, VL and WH, WL are symmetric, the detected value of each phase current for two phases may be acquired twice to calculate the average value.

  In the above-described embodiment, the three-phase phase current is estimated from the DC-side current Idc detected by the DC-side current sensor 31. However, the present invention is not limited to this, and the phase current estimation unit 23 is omitted. A phase current sensor that directly detects each phase current may be provided.

It is a block diagram of the control apparatus of the electric motor which concerns on embodiment of this invention. It is a figure which shows each switching state S1-S8 of the inverter shown in FIG. It is a figure which shows the example of the detection timing of the on-off pattern and each phase current of the carrier wave and each transistor UH, UL and VH, VL and WH, WL which concern on embodiment of this invention. It is a flowchart which shows the operation | movement of the control apparatus of the electric motor which concerns on embodiment of this invention, especially the process which determines the presence or absence of abnormality of a DC side current sensor and a bridge circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Electric motor control apparatus 11 Motor (electric motor)
13 Inverter 13a Bridge circuit 23 Phase current estimator 25 PWM signal generator (pulse width modulation signal generator)
26 Abnormality detection unit (determination means, abnormality determination means, sensor abnormality determination means)
31 DC side current sensor Step S02 Sensor abnormality determination means Step S06, Step S09 Determination means Step S07, Step S10 Abnormality determination means

Claims (2)

A bridge circuit that sequentially commutates the energization of the electric motor with a pulse width modulation signal; and a pulse width modulation signal generation means that generates the pulse width modulation signal with a carrier wave signal;
A DC-side current sensor that detects a DC-side current of the bridge circuit and outputs a detection result signal;
Determining means for determining whether or not the DC side current is zero based on a signal output from the DC side current sensor at a timing when a command voltage vector becomes a zero voltage vector of a basic voltage vector when the electric motor is driven; ,
When the DC-side current is not zero in the determination result by the determination means, either the high-side transistor or the low-side transistor that constitutes the bridge circuit according to the energization pattern of the bridge circuit corresponding to the zero voltage vector. An electric motor control device comprising: an abnormality determination unit that determines that the abnormality is abnormal. Based on a signal output from the DC-side current sensor when the high-side transistor and the low-side transistor of the bridge circuit are OFF and the rotation speed of the electric motor is zero, the DC-side current is zero. Sensor abnormality determining means for determining that the DC side current sensor is normal when the DC side current sensor is not zero, and determining that the DC side current sensor is abnormal when the DC side current is not zero,
The motor control device according to claim 1, wherein the determination unit executes a determination process when the sensor abnormality determination unit determines that the DC-side current sensor is normal.

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