Controller and control method of power conversion device

Abstract

To determine an abnormal status of a power conversion device without adding a dedicated circuit.SOLUTION: A power conversion device includes: an inverter part for converting DC power of a DC power supply into AC power; a motor connected to an AC output side of the inverter part; a DC voltage detection part for detecting DC voltage of the DC power supply; and a current sensor for detecting output current of the inverter part. A maximum value, a minimum value or a maximum average value and a minimum average value of a current response when pulse voltage generated based on detected DC voltage is applied to a semiconductor switching element of the inverter part at normal time are stored, and the current response when pulse voltage is applied in a state in which a motor is stopped by a brake is detected at starting time of the power conversion device (steps S1 and S2), and when the current response exceeds the stored maximum value or falls below the minimum value, it is determined that abnormality occurs (steps S3 and S4).SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a power conversion device for motor control.

Background Art

[0002] Conventionally, regarding a power conversion device for motor control, it has been proposed in, for example, Patent Document 1 to detect the occurrence of overcurrent and determine whether restart of the power conversion device is necessary based on the characteristics of the detected overcurrent waveform.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the method for determining whether restart is necessary described in Patent Document 1, a dedicated circuit is required for overcurrent detection and overcurrent level determination. Therefore, for the current power conversion device, it is necessary to newly add a dedicated circuit, which has the problem of increasing cost and device volume.

[0005] The present invention solves the above problems, and an object thereof is to provide a control device for a power conversion device that can determine an abnormal status of the power conversion device without adding a dedicated circuit.

[0006] Specifically, when a normal output cannot be obtained due to an abnormality in the main circuit such as an output short circuit in a power conversion device for motor control, it is not possible to determine whether normal operation can be resumed in the stopped status. Therefore, the purpose is to determine the status inexpensively and safely by temporarily starting the inverter and using an existing current sensor.

Means for Solving the Problems

[0007] The control device of the power conversion device according to claim 1 for solving the above problems is In a power conversion device including a DC power supply, an inverter unit configured by bridge-connecting semiconductor switching elements to convert DC power of the DC power supply into AC power, a motor connected to an AC output side of the inverter unit, a DC voltage detection unit that detects a DC voltage of the DC power supply, and a current sensor that detects an output current of the inverter unit, A pulse signal application unit that applies, to each semiconductor switching element of the inverter unit, a pulse voltage command signal set to an arbitrary pulse period and pulse voltage width, or a pulse current command signal set to an arbitrary pulse period and pulse current width, generated based on the DC voltage detected by the DC voltage detection unit, to each position of the electrical angle obtained by dividing 360° of the UVW coordinate system by the set number of application times; An abnormality determination unit that determines the occurrence of an abnormality based on a response waveform of a pulse current detected by the current sensor when a pulse signal is applied to each semiconductor switching element of the inverter unit; characterized by comprising.

[0008] The control device of the power conversion device according to claim 2 is, in claim 1, The pulse signal application unit sequentially applies the pulse voltage command signal or the pulse current command signal to each position of the electrical angle obtained by dividing 360° of the UVW coordinate system by the set number of application times, in an order set so that no rotational torque is generated, starting from the set reference angle.

[0009] The control device of the power conversion device according to claim 3 is, in claim 1 or 2, The abnormality determination unit stores the maximum value, minimum value, or maximum average value, minimum average value of the current response when the pulse signal application unit applies a pulse command signal during normal operation, and when starting the power conversion device, when the current response when applying a pulse command signal to the semiconductor switching element with the motor stopped by a brake exceeds the stored maximum value, or is lower than the stored minimum value, it determines that an abnormality has occurred.

[0010] The control device of the power conversion device according to claim 4, in claim 1 or 2, the motor is a PM (Permanent Magnet) motor, the abnormality determination unit stores, during normal operation, the maximum value, minimum value, or maximum average value, minimum average value of the current response when the magnetic pole position of the PM motor is estimated by applying a pulse voltage or a pulse current, and after the power conversion device is started, when the current response when a pulse voltage or a pulse current is applied by magnetic pole position estimation exceeds the stored maximum value, or is lower than the stored minimum value, it is determined that an abnormality has occurred.

[0011] The control method of the power conversion device according to claim 5, a DC power supply, an inverter unit configured by bridge-connecting semiconductor switching elements to convert the DC power of the DC power supply into AC power, a motor connected to the AC output side of the inverter unit, a DC voltage detection unit for detecting the DC voltage of the DC power supply, a current sensor for detecting the output current of the inverter unit, a pulse voltage command signal set to an arbitrary pulse period and pulse voltage width, or a pulse current command signal set to an arbitrary pulse period and pulse current width, generated based on the DC voltage detected by the DC voltage detection unit, and applied to each semiconductor switching element of the inverter unit at each position of the electrical angle obtained by dividing 360° of the UVW coordinate system by the set number of application times, a pulse signal application unit, and an abnormality determination unit for determining the occurrence of an abnormality based on the response waveform of the pulse current detected by the current sensor when a pulse signal is applied to each semiconductor switching element of the inverter unit. a step in which the abnormality determination unit stores the maximum value, minimum value, or maximum average value, minimum average value of the current response when the pulse signal application unit applies a pulse command signal during normal operation, When the abnormality determination unit applies a pulse command signal to the semiconductor switching element while the motor is stopped by a brake at the time of starting the power conversion device, if the current response exceeds the stored maximum value or is lower than the stored minimum value, it is determined that an abnormality has occurred.

[0012] The control method of the power conversion device according to claim 6 is A DC power supply, an inverter unit configured by bridge-connecting semiconductor switching elements to convert the DC power of the DC power supply into AC power, a motor connected to the AC output side of the inverter unit, a DC voltage detection unit for detecting the DC voltage of the DC power supply, a current sensor for detecting the output current of the inverter unit, a pulse voltage command signal set to an arbitrary pulse period and pulse voltage width, or a pulse current command signal set to an arbitrary pulse period and pulse current width generated based on the DC voltage detected by the DC voltage detection unit, and applied to each semiconductor switching element of the inverter unit at each position of the electrical angle obtained by dividing 360° of the UVW coordinate system by the set application number, a pulse signal application unit, and an abnormality determination unit for determining the occurrence of an abnormality based on the response waveform of the pulse current detected by the current sensor when a pulse signal is applied to each semiconductor switching element of the inverter unit. The motor is a PM (Permanent Magnet) motor. The step of the abnormality determination unit storing the maximum value, minimum value, maximum average value, or minimum average value of the current response when the magnetic pole position of the PM motor is estimated by applying a pulse voltage or a pulse current during normal operation. The step of the abnormality determination unit determining that an abnormality has occurred when the current response when a pulse voltage or a pulse current is applied by magnetic pole position estimation after the power conversion device is started exceeds the stored maximum value or is lower than the stored minimum value.

Advantages of the Invention

[0013] According to the invention described in claims 1 to 6, the configuration of the existing power conversion device enables the grasping of the status during the stop of the power conversion device, and the determination is made using a dedicated response waveform corresponding to the pulse command signal. Therefore, the cost and the volume of the device can be reduced without mounting a dedicated circuit. Further, since the determination is made with the brake closed, even if the motor is in an unstable state, it can be stopped in a safe state after the abnormality is detected.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

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Figure 6

Figure 7

Figure 8

Modes for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiment examples. FIG. 1 is a configuration example of a power conversion device to which the present invention is applied. The power conversion device is for general motor drive, and 1 is a rectifying section configured by connecting diodes in a three-phase bridge connection to rectify alternating current.

[0016] C is a capacitor connected between the positive and negative output terminals of the rectifier section 1. Between both ends of the capacitor C, a semiconductor switching element 2 such as an IGBT U ,2 V ,2 W ,2 X ,2 Y ,2 Z is connected in a three-phase bridge configuration to form an inverter section 2 that converts DC power into AC power.

[0017] A motor M is connected to the AC output side of the inverter section 2, and a current sensor 3 for detecting the AC output current is provided.

[0018] 4 is a control section that controls the inverter section 2 based on the current data from the current sensor 3 and the voltage data from a DC voltage detection circuit (DC detection section) 5 that detects the DC voltage (voltage across both ends of the capacitor C) of the power conversion device.

[0019] 6 is a motor brake that physically stops the motor M and can be operated from the power conversion device.

[0020] In FIG. 1, the inverter section 2 has a three-phase configuration, but this is applicable to any polyphase motor and polyphase power conversion device. For the current sensor 3, a minimum necessary configuration (two phases if the inverter section 2 is three-phase) is sufficient. Also, a secondary battery may be used for the rectifier section 1. The power conversion device can detect statuses such as short circuits and overcurrents based on the gate terminals of the power semiconductors (semiconductor switching elements), the voltage of VCE, and the current values detected by the current sensor 3 during operation.

[0021] The control modes of the power conversion device are

[0022] (1) Overcurrent abnormal determination mode, and

[0023] (2) Motor normal operation mode and has two types.

Example

[0024] During the power conversion device stop in the first embodiment, the status determination is performed by applying a pulse voltage generated by an arbitrary voltage command to the semiconductor switching elements 2 of the inverter unit 2 U ,2 V ,2 W ,2 X ,2 Y ,2 Z and detecting and determining the current response at that time with the current sensor 3 (control mode of the above (1)).

[0025] As the current response when the pulse voltage is applied, the waveform shown in FIG. 2 is obtained by the inductance of the motor M. The maximum value or average value of the current response within the pulse period is used for status determination. The pulse voltage can be changed to an arbitrary pulse period and pulse voltage width. The voltage command is generated by a pulse signal application unit (not shown) in the control unit 4 based on the DC voltage of the main circuit of the power conversion device detected by the DC voltage detection circuit 5 in FIG. 1.

[0026] As a method of applying the pulse voltage of the pulse signal application unit, the pulse voltage is applied an arbitrarily set number of times. The application position is 360° divided by the arbitrarily set number a in the (UVW coordinate system), resulting in the electrical angle (α) shown in FIG. 3. When applying pulses in the order of α1, α2, α3, α4..., α1 = 360° / a, α2 = 360° / a + 180°, α3 = 360° / a * 2, α4 = 360° / a * 2 + 180°..., and the position is such that no rotational torque is generated. The reference 0° position is automatically set by the power conversion device.

[0027] FIG. 3 shows an example of applying pulses 12 times with the U axis as the reference (0°). Table 1 shows the switching states of the semiconductor switching elements of the inverter unit 2 when each pulse is applied.

Table 1

[0028] The arbitrary value at this time is set as a ratio to the motor rated current. An example of a normal value when applying a pulse voltage is shown in FIG. 4.

[0029] The status determination flow is divided into when the power conversion device is started and when an abnormality is detected during motor operation. The flowchart at startup will be described together with FIG. 6. Since it is impossible to determine whether it is in an abnormal state at startup, after startup, with the motor brake 6 of the motor M operating, status determination is performed by applying a pulse voltage in step S1.

[0030] Then, the current response is detected in step S2, and it is determined in step S3 whether it is within the determination value. If no current deviating from the determination value is detected (the determination result in step S3 is yes), it switches to the control mode in (2) above and starts the normal operation of the motor. Otherwise (when the determination result in step S3 is no), a determination is made again in step S4, and when it deviates from the determination value continuously for an arbitrarily set number of times (when the determination result in step S4 is yes), it is set as a permanent trip.

[0031] If the determination result in step S4 is no, the process returns to the process of step S1. When the normal operation can be started, as long as the motor is not stopped in a state where the power conversion device has detected an abnormality such as an overcurrent, no further status detection is performed. When making a determination due to an abnormality, the difference from the flow at startup is only the difference in whether the starting point is at startup or after the abnormality is detected, and since the subsequent flow is the same, the description is omitted.

[0032] In Patent Document 1 of the prior art, the overcurrent waveforms generated during normal operation are memorized and compared with their accumulated results to determine permanent trips and the like. In the present invention, however, a pulse voltage is output from a power conversion device, and an abnormality determination is made by comparing the generated pulse current waveform with the normal pulse current waveform.

[0033] Therefore, it is possible to determine permanent trips and the like based on the degree of deviation from the normal waveform. The current generated by the pulse voltage is set to be about 5 to 10% of the motor rating. Even when a short circuit occurs between the upper and lower arms or an output short circuit occurs in the inverter unit 2, only an abnormal current flows in an extremely short time, and a permanent trip occurs immediately. Also, the current detected by the current sensor is large in the case of an output short circuit and small in the case of an arm short circuit. However, since determination values are provided for both the upper limit and the lower limit, it is possible to handle both cases.

Embodiment

[0034] The status determination during the stop of the power conversion device in the second embodiment is performed by applying a pulse current according to an arbitrary current command and detecting and determining the current response at that time. In the case of a current command pulse, the value detected by the current sensor is fed back and controlled so that the current response follows the current command pulse. The waveform of the current response at this time becomes as shown in FIG. 5 depending on the inductance of the motor. The average value of the current response within the pulse period is used for the status determination. The method of applying the pulse current is the same as the method of applying the pulse voltage in the first embodiment.

[0035] That is, a pulse current command signal set to an arbitrary pulse period and pulse current width, which is generated based on the DC voltage detected by the DC voltage detection circuit 5, is applied by a pulse signal application unit (not shown) in the control unit 4 in FIG. 1.

[0036] As a determination method, an abnormality determination unit (not shown) in the control unit 4 stores the maximum average value and the minimum average value during normal pulse current application. If any value exceeds the maximum average value even once, or falls below the minimum average value, it is determined that an abnormality has occurred. The arbitrary value at this time is set as a ratio to the motor rated current. An example of the normal value when applying a pulse current is shown in FIG. 7.

[0037] Regarding the status determination flow in the second embodiment, a pulse current is applied instead of the pulse voltage application in step S1 of FIG. 6 in the first embodiment, and the rest is the same as the processing flow in FIG. 6.

[0038] As described above, according to the first and second embodiments, it is possible to grasp the status during the stop of the power conversion device according to the configuration of the existing power conversion device, and since the determination is made using a dedicated response waveform corresponding to the pulse command signal, the cost and the volume of the device can be reduced without mounting a dedicated circuit. Further, since the determination is made with the brake closed, even if the motor is in an unstable state, it can be stopped in a safe state after detecting an abnormality.

Embodiment

[0039] In a PM motor, pole position estimation for estimating the pole position by applying a pulse voltage or a pulse current is performed. In the third embodiment, in the pole position estimation of the PM motor, since the current response generated by the pulse voltage according to the voltage command as in the first embodiment is often used, the data at this time is used for status determination (when the pole position estimation of the PM motor is performed using the current response generated by applying a pulse current according to a current command, the data at that time is used for status determination).

[0040] In the normal pole position estimation, similar to the first embodiment, the maximum value, the minimum value, or the maximum average value and the minimum average value of the current response are stored. If any value (determination value) exceeds the maximum value even once, or falls below the minimum value, it is determined that an abnormality has occurred. The arbitrary value at this time is set as a ratio to the motor rated current.

[0041] The status determination flow is almost the same as that in the first and second embodiments, except that the determination is made during the magnetic pole position estimation as shown in FIG. 8.

[0042] In FIG. 8, it is premised that the magnetic pole position of the PM motor is estimated by applying a pulse current. The abnormality determination unit (not shown) in the control unit 4 in FIG. 1 stores the maximum value, minimum value, or maximum average value, minimum average value of the current response during the normal magnetic pole position estimation.

[0043] In step S11, the status determination based on the magnetic pole position estimation is started, and a pulse current is applied.

[0044] In step S12, the current response is detected in the same manner as step S2 in FIG. 6, and in step S13, it is determined whether or not the detected current is within the determination value in the same manner as step S3 in FIG. 6.

[0045] If the determination result in step S13 is yes, the magnetic pole position estimation is completed, and the normal operation of the motor is started.

[0046] If the determination result in step S13 is no, a re-determination is performed in step S14, and a permanent trip is made when the determination value is exceeded continuously for an arbitrarily set number of times (when the determination result in step S14 is yes). If the determination result in step S14 is no, the process returns to step S11.

[0047] As described above, according to the third embodiment, the same effects as those in the first and second embodiments can be obtained, and the status determination can be performed in parallel with the magnetic pole position estimation process of the PM motor.

Explanation of Signs

[0048] 1... Rectifier section 2... Inverter section 3... Current sensor 4... Control unit 5... DC voltage detection circuit 6... Motor brake

Claims

1. In a power conversion device comprising a DC power supply, an inverter section configured by bridge-connecting semiconductor switching elements to convert the DC power of the DC power supply into AC power, a motor connected to the AC output side of the inverter section, a DC voltage detection section for detecting the DC voltage of the DC power supply, and a current sensor for detecting the output current of the inverter section, a pulse signal application section that applies, to each semiconductor switching element of the inverter section, a pulse voltage command signal set to an arbitrary pulse period and pulse voltage width, or a pulse current command signal set to an arbitrary pulse period and pulse current width, generated based on the DC voltage detected by the DC voltage detection section, to each position of the electrical angle obtained by dividing 360° of the UVW coordinate system by the set number of application times; an abnormality determination section that determines the occurrence of an abnormality based on the response waveform of the pulse current detected by the current sensor when a pulse signal is applied to each semiconductor switching element of the inverter section; A control device for a power conversion device, characterized by comprising the above.

2. The control device for a power conversion device according to claim 1, wherein the pulse signal application section sequentially applies the pulse voltage command signal or the pulse current command signal in an order set so that no rotational torque is generated to each position of the electrical angle obtained by dividing 360° of the UVW coordinate system by the set number of application times, starting from the set reference angle.

3. The control device for a power conversion device according to claim 1 or 2, wherein the abnormality determination section stores the maximum value, minimum value, or maximum average value, minimum average value of the current response when the pulse signal application section applies a pulse command signal during normal operation, and determines that an abnormality has occurred when the current response when a pulse command signal is applied to the semiconductor switching element with the motor stopped by a brake at the start of the power conversion device exceeds the stored maximum value or is lower than the stored minimum value.

4. The motor is a PM (Permanent Magnet) motor, The abnormality determination unit stores, during normal operation, the maximum value, minimum value, or maximum average value and minimum average value of the current response when the magnetic pole position of the PM motor is estimated by applying a pulse voltage or a pulse current. After the power conversion device is started, when the current response when a pulse voltage or a pulse current is applied by magnetic pole position estimation exceeds the stored maximum value or falls below the stored minimum value, it is determined that an abnormality has occurred. The control device for a power conversion device according to claim 1 or 2, characterized in that.

5. A DC power supply, an inverter unit configured by bridge-connecting semiconductor switching elements to convert the DC power of the DC power supply into AC power, a motor connected to the AC output side of the inverter unit, a DC voltage detection unit for detecting the DC voltage of the DC power supply, a current sensor for detecting the output current of the inverter unit, a pulse voltage command signal set to an arbitrary pulse period and pulse voltage width, or a pulse current command signal set to an arbitrary pulse period and pulse current width, generated based on the DC voltage detected by the DC voltage detection unit, and applied to each semiconductor switching element of the inverter unit at each position of the electrical angle obtained by dividing 360° of the UVW coordinate system by the set number of application times. A pulse signal application unit, and an abnormality determination unit that determines the occurrence of an abnormality based on the response waveform of the pulse current detected by the current sensor when a pulse signal is applied to each semiconductor switching element of the inverter unit. A control method for a power conversion device, comprising: The step of the abnormality determination unit storing the maximum value, minimum value, or maximum average value and minimum average value of the current response when the pulse signal application unit applies a pulse command signal during normal operation; The step of the abnormality determination unit determining that an abnormality has occurred when the current response when a pulse command signal is applied to the semiconductor switching element with the motor stopped by a brake at the start of the power conversion device exceeds the stored maximum value or falls below the stored minimum value. A control method for a power conversion device, characterized by comprising.

6. A DC power supply, an inverter section configured by bridge-connecting semiconductor switching elements to convert the DC power of the DC power supply into AC power, a motor connected to the AC output side of the inverter section, a DC voltage detection section for detecting the DC voltage of the DC power supply, a current sensor for detecting the output current of the inverter section, a pulse voltage command signal set to an arbitrary pulse period and pulse voltage width, or a pulse current command signal set to an arbitrary pulse period and pulse current width, generated based on the DC voltage detected by the DC voltage detection section, and a pulse signal application section that applies the signal to each position of the electrical angle obtained by dividing 360° of the UVW coordinate system by the number of set application times to each semiconductor switching element of the inverter section, and an abnormality determination section that determines the occurrence of an abnormality based on the response waveform of the pulse current detected by the current sensor when the pulse signal is applied to each semiconductor switching element of the inverter section. A control method for a power conversion device, comprising: The motor is a PM (Permanent Magnet) motor. A step in which the abnormality determination section stores the maximum value, minimum value, or maximum average value, minimum average value of the current response when the magnetic pole position estimation for estimating the magnetic pole position of the PM motor is performed by applying a pulse voltage or a pulse current during normal operation. A step in which the abnormality determination section determines that an abnormality has occurred when the current response when a pulse voltage or a pulse current is applied by magnetic pole position estimation after the start of the power conversion device exceeds the stored maximum value or is lower than the stored minimum value. A control method for a power conversion device, characterized by comprising the above.

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