JP2024109503A - MOTOR CONTROL DEVICE AND METHOD FOR DETECTING DETECTION PHASE DEFLECTION FOR MOTOR CONTROL DEVICE - Google Patents

Abstract

To avoid dangerous events caused by unintended application of torque by detecting the deviation between the detected phase and the actual phase of a motor in a motor control device.SOLUTION: A pulse voltage generator 1 outputs, from among voltage vectors V1 to V12, the one closest to the motor rotor phase γ as a voltage vector command V+* for a pulse voltage application time. A current detector 4 detects three-phase output currents Iu, Iv, and Iw of the power converter 2 when the first to sixth switching elements of the power converter 2 are turned on and off on the basis of the voltage vector command V+*. A detected phase shift determiner 6 determines whether a detected phase shift of the rotor has occurred on the basis of the current calculated on the basis of the output current after the pulse voltage application time has elapsed.SELECTED DRAWING: Figure 1

Description

The present invention relates to determining the detection phase shift of a motor control device.

When controlling PM motors that use inverters, a method of controlling the inverter based on the detected phase of the PM motor's rotor is widely used. If a detected phase shift (a deviation between the actual phase and the detected phase) occurs due to a malfunction of the rotor position sensor, etc., the inverter cannot pass motor current to the correct phase, which may lead to the generation of unintended torque.

To solve this problem, Patent Document 1 discloses a technology for determining abnormalities in the rotor phase detector.

Meanwhile, Patent Document 2 discloses a technology for diagnosing demagnetization of the permanent magnets in the motor rotor in an inverter that controls a PM motor.

Japanese Patent Application Publication No. 5-83977 JP 2021-93894 A

Patent Document 1 requires a sensor to detect active power, which results in high costs and large size of the device.

As described above, the challenge for motor control devices is to avoid dangerous events caused by unintended application of torque by detecting the deviation between the motor's detected phase and actual phase while avoiding high costs and large size of the device.

The present invention was devised in view of the above-mentioned problems in the prior art, and one aspect of the present invention is a power converter including first and second switching elements connected in series in sequence between one end and the other end of a DC power source, third and fourth switching elements connected in series in sequence between one end and the other end of the DC power source, and fifth and sixth switching elements connected in series in sequence between one end and the other end of the DC power source, a first winding connected to a connection point of the first and second switching elements, a second winding connected to a connection point of the third and fourth switching elements, and a third winding connected to a connection point of the fifth and sixth switching elements, The system is characterized by comprising a motor having the above-mentioned, a pulse voltage generator that outputs, as a voltage vector command, the voltage vector V1 to V12 shown in Table 1 below that is closest to the rotor phase of the motor for a pulse voltage application time, a current detector that detects the three-phase output current of the power converter when the first to sixth switching elements of the power converter are turned on and off according to Table 1 based on the voltage vector command, and a detection phase shift determiner that determines whether or not a detection phase shift of the rotor has occurred based on the current calculated based on the output current after the pulse voltage application time has elapsed.

In one embodiment, the detected phase shift determiner sets a phase shift determination threshold based on the normal current value when the phase shift is zero, and determines that a detected phase shift of the rotor has occurred when the current after the pulse voltage application time has elapsed is equal to or less than the phase shift determination threshold.

In one aspect, the detected phase shift determiner determines that a detected phase shift of the rotor has occurred when the current after the pulse voltage application time has elapsed is greater than the phase shift determination threshold and the d-axis current of the output current is less than zero.

In one embodiment, the normal current value is calculated based on the following formula (5):

ΔI1: Current fluctuation value with respect to pulse voltage application time (normal current value)
ΔId: d-axis current fluctuation value with respect to pulse voltage application time ΔIq: q-axis current fluctuation value with respect to pulse voltage application time Δt: pulse voltage application time VDC: power converter input DC voltage Ld: d-axis component of motor inductance Lq: q-axis component of motor inductance θ: difference between rotor phase γ and the phase of the voltage vector command.

The present invention makes it possible to prevent dangerous events caused by unintended torque application by detecting the deviation between the detected phase and the actual phase of the motor in a motor control device while avoiding high costs and large size of the device.

FIG. 4 is a block diagram showing detection phase shift diagnosis of the motor control device in the first embodiment. A diagram showing voltage vectors. FIG. 2 is a diagram showing an inverter and a motor. FIG. 13 is a diagram showing the relationship between a phase shift Δθ and a current I1. FIG. 13 is a diagram showing the relationship between the phase shift Δθ and the current I1 and the d-axis current Id. FIG. 11 is a block diagram showing detection phase deviation diagnosis of a motor control device according to a second embodiment.

The present invention applies the technology of Patent Document 2 to the determination of abnormalities in the detected phase of the rotor. Below, the first and second embodiments of the motor control device of the present invention will be described in detail with reference to Figures 1 to 6.

[Embodiment 1]
Fig. 1 shows a block diagram of detection phase shift diagnosis of a motor control device in the present embodiment 1. Detection phase shift diagnosis in the present embodiment 1 is performed while the PM motor is stopped. Normal rotation operation of the PM motor is performed by a control block different from that shown in Fig. 1. Explanation of the normal rotation operation of the PM motor is omitted because it is not directly related to the present invention.

The detection phase shift diagnosis of the motor control device of this embodiment 1 will be explained based on FIG. 1. The pulse voltage generator 1 inputs the rotor phase γ of the PM motor 3. The rotor phase γ is the phase difference between the axis of the N pole of the rotor (d-axis) and the U-phase winding axis. Based on the rotor phase γ, the pulse voltage generator 1 selects the voltage vector closest to the d-axis from the 12 types of voltage vectors V1 to V12 shown in FIG. 2, and outputs it as the voltage vector command V+* for a predetermined time Ton. For example, when -15°<γ<+15°, V1 is selected as the voltage vector command V+*. The predetermined time Ton is the pulse voltage application time Δt described below.

The inverter (power converter) 2 turns on and off switching elements according to the voltage vector of the input voltage vector command V+*, and applies a pulsed output voltage to the PM motor 3.

Here, the configuration of the inverter 2 and PM motor 3 to which the detection phase shift diagnosis of the motor control device in this embodiment 1 is applied will be described with reference to FIG.

The inverter 2 has first and second switching elements U+, U- connected in series between one end and the other end of the DC power source DC, third and fourth switching elements V+, V- connected in series between one end and the other end of the DC power source DC, and fifth and sixth switching elements W+, W- connected in series between one end and the other end of the DC power source DC.

The PM motor 3 includes a U-phase winding (first winding) 3U connected to the connection point of the first and second switching elements U+, U-, a V-phase winding (second winding) 3V connected to the connection point of the third and fourth switching elements V+, V-, and a W-phase winding (third winding) 3W connected to the connection point of the fifth and sixth switching elements W+, W-. The U-phase winding 3U, V-phase winding 3V, and W-phase winding 3W are connected in a star connection.

The following Table 1 shows the relationship between the voltage vector and the on/off commands for each switching element U+, U-, V+, V-, W+, and W-. Based on the voltage vector command V+*, the inverter 2 turns on and off the first to sixth switching elements U+, U-, V+, V-, W+, and W- as shown in Table 1.

The current detector 4 detects the winding currents Iu, Iv, and Iw of the UVW phases of the PM motor 3 (the three-phase output currents of the inverter 2) when the first to sixth switching elements U+ to W- of the inverter 2 are turned on and off based on the voltage vector command V+*.

Note that, since the U-phase winding 3U, the V-phase winding 3V, and the W-phase winding 3W are connected in a star connection, the output current of the three phases is Iu + Iv + Iw = 0. Therefore, a current detector may be used for each of the three phases to detect the output current of each phase, or a two-phase current detector may be used to detect the output current of two phases, and the output current of the remaining phase may be detected by calculation using the above formula. The latter has the advantage of requiring fewer current detectors.

The three-phase/two-phase converter 5 converts the three-phase output currents Iu, Iv, Iw (iu, iv, iw) and the rotor phase γ into two-phase output currents, d-axis current id and q-axis current iq, using the following formulas (1) and (2). Based on the d-axis current id and q-axis current iq, the current i1 (I1) after the pulse voltage application time Δt (Ton) has elapsed is calculated using formula (3).

The detected phase deviation determiner 6 determines the normal current value based on the input rotor phase γ and voltage vector command V+*, as described below. Furthermore, based on the normal current value and the current I1 output by the three-phase/two-phase converter 5, it diagnoses whether or not an abnormality (deviation between the actual phase and the detected phase) has occurred in the rotor position sensor.

Next, we will explain the operating principle when the position sensor is normal.

The voltage vector closest to the d-axis is selected for the voltage vector command V+*, so the q-axis current Iq ≒ 0. As a result, almost no torque is generated by the winding current, and the rotor remains stopped.

The approximate equations for the d-axis current fluctuation value ΔId and the q-axis current fluctuation value ΔIq versus pulse voltage application time are given by the following equation (4).

From equation (4), the current fluctuation value ΔI1 with respect to the pulse voltage application time is given by the following equation (5).

The ratio of Ld and Lq determines the amount of change in current I1 with θ. In equations (4) and (5), Vd and Vq are the d-axis and q-axis components of the inverter output voltage. Ld and Lq are the d-axis and q-axis components of the motor inductance, and are known fixed values. Δt corresponds to the predetermined time (pulse voltage application time) Ton for outputting the voltage vector command described above. VDC is the inverter input DC voltage (DC voltage of the DC power supply DC). θ is the difference between the rotor phase γ and the phase of the voltage vector command. This θ corresponds to Δθ in equation (6) of Patent Document 2, and details are described in Patent Document 2.

This concludes the explanation of the operating principle when the position sensor is normal.

Figure 4 shows the relationship between the phase shift Δθ and the current I1 when the d-axis and q-axis components Ld and Lq of the motor inductance are fixed values (for example, Ld/Lq = 0.3, 0.4).

In the detection phase shift diagnosis of this embodiment 1, the pulse voltage application is started in a state where no current is flowing, so the current I1 is the same as the current fluctuation value ΔI1 with respect to the pulse voltage application time in equation (5). Therefore, ΔI1 in equation (5) is the normal value of the current I1 when the phase shift Δθ = 0 (hereinafter referred to as the normal current value). Also, in FIG. 4, the normal current value when the phase shift Δθ = 0 is normalized as I1 = 1.

As shown in FIG. 4, if Ld/Lq ≠ 1, and the phase shift Δθ is not ≒ 0, a difference occurs between the value of current I1 (output value of three-phase/two-phase converter 5) and the normal current value (value when Δθ = 0 in FIG. 4) when the same pulse voltage is applied. Therefore, the detection phase shift judger 6 can diagnose that the rotor phase γ has deviated from its normal value when current I1 falls below the phase shift judgement threshold. The normal current value is calculated in advance for each θ and VDC using equation (5) in a table. Alternatively, it may be calculated using equation (5) immediately before the pulse voltage is applied. The phase shift judgement threshold is set appropriately by the designer based on the normal current value, and specific numerical values are omitted here.

As described above, according to the first embodiment, if there is an abnormality in the rotor detection phase, a difference occurs between the inverter current I1 when the pulse voltage is applied and the normal current value, making it possible to detect the rotor detection phase shift of the inverter.

In addition, compared to Patent Document 1, since active power detection is not required, it is easier to reduce the size and cost of the device.

[Embodiment 2]
As can be seen from Fig. 4, when the phase shift Δθ of the rotor phase γ is around 180°, the method of the first embodiment alone has a problem in that the current I1 becomes close to the value in the normal state (phase shift Δθ = 0°), and the phase shift cannot be detected. This problem is solved by the second embodiment.

Figure 5 shows the relationship between the phase shift Δθ and the current I1 and the d-axis current Id when the d-axis and q-axis components Ld and Lq of the motor inductance are fixed (for example, Ld/Lq = 0.4).

Current I1 alone cannot detect the difference between when the phase shift Δθ of rotor phase γ is near 0° and when it is near 180°, but as shown in Figure 5, the sign of the d-axis current Id reverses when the phase shift Δθ of rotor phase γ is near 0° and when it is near 180°.

Therefore, in this embodiment 2, when the current I1 becomes equal to or greater than the phase shift determination threshold, the sign of the d-axis current Id of the output current calculated by equation (2) is checked. If the current I1 is greater than the phase shift determination threshold and Id<0, it is diagnosed that a rotor phase γ shift has occurred.

Figure 6 is a block diagram showing the detection phase shift diagnosis of the motor control device in this embodiment 2. As shown in Figure 6, the detection phase shift determiner 6 inputs the d-axis current Id in addition to the current I1, the voltage vector command V+*, and the rotor phase γ. The rest is the same as in embodiment 1.

As described above, according to the second embodiment, the same action and effect as the first embodiment is achieved. In addition, in the second embodiment, the detection value of the d-axis current Id is used to determine the phase shift, so that it is possible to detect the rotor detection phase shift even in cases where the phase shift is close to Δθ = 180°, which was difficult to detect in the first embodiment. This makes it possible to improve the reliability of the device.

Although the present invention has been described in detail above only with respect to the specific examples, it will be clear to those skilled in the art that various modifications and alterations are possible within the scope of the technical concept of the present invention, and it goes without saying that such modifications and alterations fall within the scope of the claims.

1...Pulse voltage generator 2...Inverter (power converter)
3...PM motor (motor)
3U, 3V, 3W...U-phase winding, V-phase winding, W-phase winding (first winding, second winding, third winding)
4...Current detector 5...Three-phase/two-phase converter 6...Detection phase shift determiner

Claims (5)

a power converter including: first and second switching elements sequentially connected in series between one end and the other end of a DC power source; third and fourth switching elements sequentially connected in series between one end and the other end of the DC power source; and fifth and sixth switching elements sequentially connected in series between the one end and the other end of the DC power source;
a motor having a first winding connected to a connection point between the first and second switching elements, a second winding connected to a connection point between the third and fourth switching elements, and a third winding connected to a connection point between the fifth and sixth switching elements;
a pulse voltage generator that outputs, as a voltage vector command, a voltage vector V1 to V12 shown in Table 1 below that is closest to a rotor phase of the motor for a pulse voltage application time;
a current detector that detects three-phase output currents of the power converter when the first to sixth switching elements of the power converter are turned on and off in accordance with Table 1 based on the voltage vector command;
a detection phase shift determiner that determines whether or not a detection phase shift of a rotor occurs based on a current after a lapse of the pulse voltage application time calculated based on the output current;
A motor control device comprising:

The detection phase shift determiner includes:
2. The motor control device according to claim 1, wherein a phase shift determination threshold is set based on a normal current value when the phase shift is zero, and it is determined that a detected phase shift of the rotor has occurred when the current after the pulse voltage application time has elapsed becomes equal to or less than the phase shift determination threshold. The detection phase shift determiner includes:
3. The motor control device according to claim 2, further comprising: a motor control circuit for controlling a rotor according to claim 2, wherein the motor control circuit determines that a detected phase shift of the rotor has occurred when the current after the pulse voltage application time has elapsed is greater than the phase shift determination threshold value and the d-axis current of the output current is smaller than 0. 3. The motor control device according to claim 2, wherein the normal current value is calculated based on the following equation (5).

ΔI1: Current fluctuation value with respect to pulse voltage application time (normal current value)
ΔId: d-axis current fluctuation value with respect to pulse voltage application time ΔIq: q-axis current fluctuation value with respect to pulse voltage application time Δt: pulse voltage application time VDC: power converter input DC voltage Ld: d-axis component of motor inductance Lq: q-axis component of motor inductance θ: difference between rotor phase γ and voltage vector command phase a power converter including: first and second switching elements sequentially connected in series between one end and the other end of a DC power source; third and fourth switching elements sequentially connected in series between one end and the other end of the DC power source; and fifth and sixth switching elements sequentially connected in series between the one end and the other end of the DC power source;
a motor having a first winding connected to a connection point between the first and second switching elements, a second winding connected to a connection point between the third and fourth switching elements, and a third winding connected to a connection point between the fifth and sixth switching elements;
A method for determining a detected phase shift in a motor control device comprising:
A pulse voltage generator outputs, as a voltage vector command, a voltage vector V1 to V12 shown in Table 1 below that is closest to the rotor phase of the motor, for a pulse voltage application time.
a current detector detects three-phase output currents of the power converter when the first to sixth switching elements of the power converter are turned on and off in accordance with Table 1 based on the voltage vector command;
A method for determining a detected phase shift in a motor control device, characterized in that a detected phase shift determiner determines whether or not a detected phase shift has occurred in the rotor based on the current calculated based on the output current after the pulse voltage application time has elapsed.

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