Control method of power conversion device and control apparatus

Abstract

To provide a control method of a power conversion device, capable of suppressing the generation of a shutdown of a power conversion device.SOLUTION: In a control method of a power conversion device, connected to a rotator machine and a battery, the power conversion device comprises a power element, and a power between the rotator machine and the battery is controlled by performing an on / off control of the power element. In the case where a DC voltage of the power conversion device exceeds a predetermined value, the generation of a voltage abnormality is detected, and a first protection function performing a first protection processing for protecting the power conversion device against a voltage abnormality, and a second protection function performing a second protection processing for controlling the power element to the off by stopping the on / off control of the power element in the case where an abnormality that is different from a voltage abnormality is detected in the power conversion device are provided. In the case where the power element is controlled so as to be off by the second protection function, the first protection function increases the predetermined value for a predetermined period when the power element is turned off or does not execute the first protection processing.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a control method and a control device for a power conversion device. [Background technology]

[0002] In inverter circuits (power conversion devices) used in electric vehicles, hybrid vehicles, and the like, which convert power between a motor (rotating electric machine) and a battery, attempts are being made to miniaturize the devices by reducing the capacity of smoothing capacitors.

[0003] Patent Document 1 discloses a configuration in which the DC bus current of the inverter circuit is detected before the motor drive is stopped, and the motor is stopped when the current is equal to or lower than a predetermined value. In this way, the motor is stopped when the energy stored in the motor is small, thereby suppressing the voltage rise due to regeneration. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-059085 A Summary of the Invention

[0005] In the conventional technology, the motor is stopped at a timing when the energy during regeneration is small. Therefore, if the power element is controlled to be turned off at an unintended timing, a large amount of energy is input from the motor side to the power conversion device, which activates the protection function and may cause the operation of the power conversion device to be stopped (shut down) unnecessarily. One way to prevent this is to increase the capacity of the smoothing capacitor, but in that case, it is not possible to reduce the size of the device.

[0006] The present invention has been made in consideration of such problems, and aims to provide a control method and control device for a power conversion device that can suppress the occurrence of shutdown of the power conversion device even when a power element is turned off.

[0007] One embodiment of the present invention is applied to a method for controlling a power conversion device connected to a rotating electric machine and a battery. The power conversion device includes a power element, and the power between the rotating electric machine and the battery is controlled by controlling the power element to be on and off. The power conversion device has a first protection function that detects the occurrence of a voltage abnormality when the DC voltage of the power conversion device exceeds a predetermined value and performs a first protection process to protect the power conversion device against the voltage abnormality, and a second protection function that performs a second protection process to stop the on and off control of the power element and control the power element to be off when an abnormality other than the voltage abnormality in the power conversion device is detected. When the power element is controlled to be off by the second protection function, the first protection function increases a predetermined value or does not perform the first protection process for a predetermined period after the power element is turned off.

[0008] According to the present invention, when the power element is controlled to be turned off by the second protection function, the first protection function controls to increase the voltage threshold or not to execute the first protection process. As a result, even if the DC voltage value of the power conversion device temporarily rises due to the regenerative power of the motor, this is not detected as a voltage abnormality. As a result, the power conversion device does not perform the unnecessary first protection process, and the occurrence of a shutdown or the like in the power conversion device can be suppressed. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is an explanatory diagram of a drive device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a functional block diagram of the control device. [Diagram 3] FIG. 3 is a flowchart of the control of the first protection function. [Figure 4] FIG. 4 is a flow chart of the control of the second protection function. [Diagram 5] FIG. 5 is a time chart of the first protection function and the second protection function. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0011] FIG. 1 is an explanatory diagram of a drive device 1 according to the present embodiment.

[0012] The drive device 1 includes a motor 10 as a rotating electric machine, an inverter device (power conversion device) 20 that supplies power to the motor 10, a battery 30, and a control device 50. The drive device 1 is mounted on, for example, a vehicle, and drives the vehicle by rotating drive wheels with the rotation of the motor 10. Note that the drive device 1 may also be used as a drive power source for devices other than a vehicle, for example, various electric devices or industrial machines.

[0013] The power conversion device 20 is connected between the motor 10 and the battery 30. The power conversion device 20 includes six power elements 21, and by switching the on / off states of these power elements 21, converts the DC power of the battery 30 into three-phase AC power suitable for driving the motor 10 and supplies it to the motor 10. During regeneration of the motor 10, the power conversion device 20 converts the AC power supplied from the motor 10 into DC power suitable for charging the battery 30 and supplies it to the battery 30.

[0014] The power conversion device 20 also includes a smoothing capacitor 22 that smoothes the DC power, a voltage detection unit 25 that detects the voltage of the DC power, and a current detection unit 26 that detects the current values ​​(U phase, V phase, W phase) between the power conversion device 20 and the motor 10.

[0015] A main switch 40 is interposed between the power conversion device 20 and the battery 30 to electrically connect and disconnect them.

[0016] The control device 50 transmits a gate signal to each power element 21 of the power conversion device 20 to control the on / off of each power element 21.

[0017] As described below, the control device 50 has protection functions (first protection function and second protection function) for the power conversion device 20. The control device 50 has, for example, a processor and a memory, and these functions are realized by the processor executing a program stored in the memory.

[0018] The protection function executed by the control device 50 will be described with reference to Fig. 2. Fig. 2 is a functional block diagram illustrating the protection function of the control device 50.

[0019] The first protection function 61 determines whether or not a voltage abnormality has occurred based on the DC voltage value acquired from the voltage detection unit 25 of the power conversion device 20, by comparing the DC voltage value with a predetermined voltage threshold value.

[0020] If the acquired DC voltage value exceeds the voltage threshold, it is determined that there is a voltage abnormality (overvoltage state) in the power conversion device 20, and a first protection process is executed. Specifically, the first protection function 61 cuts off (turns off) the main switch 40 and stops (shuts down) the operation of the power conversion device 20 in order to protect the power conversion device 20 from an overvoltage.

[0021] The voltage threshold for determining whether or not an overvoltage state exists is set to a value that can be determined to be sufficiently abnormal with respect to voltage fluctuations in a state in which the battery 30 is normally used, and is set to a value that takes into consideration a margin of about 20% with respect to the rated voltage, for example. More specifically, when the rated voltage of the battery 30 is 400V, the voltage threshold is set to 470V.

[0022] The second protection function 62 detects an abnormality different from the voltage abnormality detected by the first protection function 61. Specifically, the second protection function 62 determines whether the AC current value acquired from the current detection unit 26 of the power conversion device 20 is normal by comparing it with a predetermined current threshold. If the acquired AC current value exceeds the range of the current threshold, it determines that there is an abnormality (overcurrent state or short-circuit state) in the power conversion device 20, and executes the second protection process. Specifically, the second protection function 62 controls all the power elements 21 of the power conversion device 20 to be turned off in order to protect the power elements 21 from the overcurrent state or short-circuit state.

[0023] Further, the second protection function 62 determines whether the element temperature value acquired from the power elements 21 of the power conversion device 20 is normal by comparing the element temperature value with a predetermined temperature threshold. If the acquired element temperature value exceeds the temperature threshold, it determines that the power conversion device 20 is abnormal (overheated), and similarly executes the second protection process. The second protection function 62 controls all the power elements 21 of the power conversion device 20 to be turned off in order to protect the power elements 21 from an overheated state.

[0024] In addition, due to the circuit configuration of the power conversion device 20 and the control device 50, the signal line transmitting the signal from the current detection unit 26 is adjacent to the signal line transmitting the high-frequency high-voltage voltage to the motor 10, and the signal line detecting the element temperature is adjacent to the signal line transmitting the gate signal of the power element 21, so that the configuration is prone to instantaneous signal changes due to the influence of spike noise, etc.

[0025] In the control device 50 configured in this way, the following problems may occur.

[0026] When the second protection function 62 determines that an overcurrent state, a short circuit state, or an overheat state has occurred and controls the power element 21 of the power conversion device 20 to be turned off, and regenerative control of the motor 10 is executed, the regenerative power of the motor 10 is supplied to the DC side of the power conversion device 20 via the diode of the power element 21.

[0027] At this time, if the regenerative power causes the DC voltage value of the power conversion device 20 to rise above the voltage threshold, the first protection function 61 executes the first protection process, and the main switch 40 is turned off and the power conversion device 20 may be shut down.

[0028] In particular, even if there is an instantaneous signal change in the current value or temperature value (including spike noise, etc.), the second protection function 62 controls the power element 21 of the power conversion device 20 to be turned off. At this time, if the first protection function 61 executes the first protection process due to a voltage abnormality due to regenerative power, the power conversion device 20 is protected (shut down). In particular, if the capacity of the smoothing capacitor 22 is reduced in order to reduce the size of the drive device 1 and the power conversion device 20, the change in the DC voltage value becomes large, and the frequency of occurrence of protection of the power conversion device 20 may increase.

[0029] Even if the second protection function 62 performs a protection operation (turning off the power element 21) due to an instantaneous signal change in the current value or temperature value, the normal state can be restored immediately. Therefore, even if a temporary rise in the DC voltage value occurs due to regenerative power, the operation of the power conversion device 20 is unlikely to be affected. On the other hand, if the first protection function 61 turns off the main switch 40 or shuts down the power conversion device 20, it generally takes a certain amount of time to recover from this state. Therefore, there is little need to protect the power conversion device 20 from a temporary change in the DC voltage value caused by the second protection function 62 turning off the power element 21, and it is desirable to continue control of the motor 10 by suppressing the occurrence of such a shutdown.

[0030] Therefore, in this embodiment, the following control is executed. Fig. 3 is a flowchart of the operation of the first protection function 61. This flowchart is executed by the control device 50 at predetermined intervals (for example, 10 ms).

[0031] In step S110, the first protection function 61 determines whether or not the second protection function 62 has detected an abnormality and all the power elements 21 have been turned off, that is, whether or not the second protection process is being executed. Whether or not the second protection process is being executed is determined by the control of the second protection function 62 (step S220), which will be described later with reference to FIG.

[0032] When the second protection process is executed and it is determined that the power element 21 is turned off, the process proceeds to step S120, where the first protection function 61 largely changes the value of the voltage threshold used to determine whether or not there is an overvoltage state, and relaxes the determination of whether or not there is an overvoltage state. For example, the voltage threshold is set to a value that is increased by about 10% from the set voltage threshold. More specifically, when the voltage threshold is set to 470V, the voltage threshold is changed to 500V.

[0033] In addition, in step S120, instead of changing the voltage threshold, it is also possible to perform control so that a determination as to whether or not there is a voltage abnormality is not made, or so that even if it is determined that there is a voltage abnormality, the protection process is not executed (the first protection process is disabled).

[0034] On the other hand, if it is determined in step S110 that the state is normal (normal state) in which the second protection process is not being performed, the process proceeds to step S121, and the first protection function 61 restores the voltage threshold value changed in step S120, or enables the first protection process that was disabled, thereby returning to the normal state (normal state).

[0035] Next, in step S130, the first protection function 61 determines whether or not the DC voltage value acquired from the voltage detection unit 25 exceeds the voltage threshold. If it is determined that the DC voltage value does not exceed the voltage threshold, the process according to this flowchart is temporarily terminated.

[0036] If it is determined that the DC voltage value exceeds the voltage threshold and is an abnormal voltage, the process proceeds to step S140, and the first protection function 61 executes the first protection process. The first protection function 61 turns off the main switch 40 and stops the operation of the power conversion device 20 to shut down the power conversion device 20. Thereafter, the process according to this flowchart is temporarily terminated, and the process proceeds to another process. Note that if the first protection process is set to be disabled in step S120, the first protection function 61 does not execute the process of step S140.

[0037] 3, the first protection function 61 relaxes the determination of a voltage abnormality when the second protection function 62 executes the second protection process and the power element 21 of the power conversion device 20 is turned off. As a result, even if the DC voltage value temporarily rises due to regenerative power while the second protection process is being executed due to an instantaneous signal change, this is not regarded as a voltage abnormality, and it is possible to avoid detecting a voltage abnormality. As a result, it is possible to suppress the occurrence of unnecessary protection processes such as shutdown in the power conversion device 20.

[0038] 4 is a flowchart of the operation of the second protection function 62. This flowchart is executed by the control device 50 at predetermined intervals (for example, 10 ms).

[0039] In step S210, the second protection function 62 determines whether or not the AC current value acquired from the current detection unit 26 exceeds the current threshold range, or whether or not the element temperature acquired from the power element 21 exceeds the temperature range value.

[0040] If it is determined that the AC current value exceeds the current threshold range or the element temperature exceeds the temperature range, it is determined that there is an overcurrent state, a short circuit state, or an overheat state, and the process proceeds to step S220. If not, the process proceeds to step S230.

[0041] In step S220, the second protection function 62 executes the second protection process, that is, controls all the power elements 21 of the power conversion device 20 to be turned off.

[0042] Next, the process proceeds to step S230, where it is determined whether a predetermined period of time has elapsed since the second protection process was executed in step S220, and whether the overcurrent state, short circuit state, or overheat state has already been resolved. If it is determined that the predetermined period of time has elapsed, the process proceeds to step S240. If the predetermined period of time has not elapsed, the process according to this flowchart is temporarily terminated.

[0043] The predetermined period in step S230 is set to a period (e.g., several hundreds of microseconds) sufficient for the change to be eliminated when the current value or temperature value is an instantaneous signal change. Note that in step S230, the second protection function 62 may proceed to step S240 when the overcurrent state, short circuit state, or overheat state is eliminated after the second protection process is executed, without waiting for the predetermined period to elapse.

[0044] In step S240, the second protection process is ended. That is, the power element 21 is turned on and off by the gate signal of the control device 50 to resume the operation of the power conversion device 20. Thereafter, the process according to this flowchart is temporarily ended.

[0045] As shown in the flowchart of Figure 4, when the second protection function 62 determines that there is a current abnormality or temperature abnormality based on the AC current value or the element temperature, it controls the power element 21 of the power conversion device 20 to be turned off to protect the power conversion device 20 from such abnormality.

[0046] Fig. 5 is a time chart showing the first protection process and the second protection process executed according to the flowcharts of Fig. 3 and Fig. 4. The time chart shown in Fig. 5 shows an example in which an overcurrent state is detected in the power conversion device 20.

[0047] In FIG. 5, the AC current value acquired by the current detection unit 26 is shown on the upper side, and the DC voltage value detected by the voltage detection unit 25 is shown on the lower side, both on the time axis.

[0048] If the AC current value increases at timing T0 and exceeds the current threshold at timing T1, resulting in an overcurrent state, the second protection function 62 controls the power element 21 of the power conversion device 20 to be turned off by the second protection process in step S220 of Figure 4 described above.

[0049] When the second protection process is executed, the first protection function 61 changes the voltage threshold to a more relaxed value by the process of step S120 in FIG.

[0050] At this time, when regenerative control of the motor 10 is executed, the regenerative power may temporarily increase the DC voltage value of the power conversion device 20. At this time, since the voltage threshold is relaxed, such a temporary voltage increase is not detected as a voltage abnormality, and the first protection process is not executed.

[0051] Thereafter, when the overcurrent state is resolved and a predetermined period of time has elapsed (timing T2), the second protection function 62 ends the second protection process, the first protection function 61 returns the voltage threshold to the original value, and the power conversion device 20 returns to the normal state.

[0052] In this way, by controlling the first protection function 61, even if the DC voltage value of the power conversion device 20 temporarily increases due to the execution of the second protection process due to, for example, a momentary signal change, this is not detected as a voltage abnormality, thereby preventing the occurrence of unnecessary protection processes such as shutdown in the power conversion device 20.

[0053] 5 shows an example in which the first protection function 61 sets the voltage threshold to a large value when the second protection process is being executed, but if the value of the voltage threshold is not changed and the time (indicated by S in FIG. 5) during which the DC voltage value exceeds the voltage threshold is less than a predetermined time (e.g., less than 100 μsec), this may not be detected as a voltage abnormality and the first protection process may not be executed. Even if the value of the voltage threshold is changed to a large value, if the time during which the DC voltage value exceeds the voltage threshold is similarly less than a predetermined time, this may not be detected as a voltage abnormality.

[0054] As described above, this embodiment relates to a control device 50 for a power conversion device 20 connected to a motor (rotating electric machine) 10 and a battery 30. The power conversion device 20 includes a power element 21, and the power element 21 is controlled to be turned on and off to control the power between the motor 10 and the battery 30. The control device 50 has a first protection function 61 that detects the occurrence of a voltage abnormality when the DC voltage value of the power conversion device 20 exceeds a voltage threshold that is a predetermined value and performs a first protection process to protect the power conversion device 20 against the voltage abnormality, and a second protection function 62 that performs a second protection process to stop the on / off control of the power element 21 and control the power element 21 to be turned off when an abnormality other than the voltage abnormality in the power conversion device 20 is detected. When the power element 21 is controlled to be turned off by the second protection function 62, the first protection function 61 increases the voltage threshold or does not perform the first protection process for a predetermined period after the power element 21 is turned off.

[0055] In this configuration, when the power element 21 is controlled to be turned off by the second protection function 62, the first protection function 61 controls to increase the voltage threshold value or not to execute the first protection process. As a result, even if a situation occurs in which the DC voltage value of the power conversion device 20 temporarily rises due to the regenerative power of the motor 10 while the second protection process is being executed, this is not regarded as a voltage abnormality, making it difficult to detect the voltage abnormality. As a result, even if the capacity of the smoothing capacitor 22 is reduced, unnecessary protection processes do not occur in the power conversion device 20, and the occurrence of shutdowns and the like in the power conversion device 20 can be suppressed.

[0056] In addition, in this embodiment, when the power element 21 is controlled to be turned off by the second protection function 62, the first protection function 61 does not execute the first protection process by the first protection function 61 if the time during which the DC voltage value in the power conversion device 20 exceeds the voltage threshold is less than a predetermined time.

[0057] In this configuration, when the power element 21 is controlled to be turned off by the second protection function 62, if a rise in the DC voltage value in the power conversion device 20 is temporary, this is not detected as an abnormality, or even if it is detected as an abnormality, protection processing is not executed, thereby preventing the occurrence of a shutdown of the power conversion device 20, etc.

[0058] In this embodiment, after the second protection function 62 controls the power element 21 to be turned off, the second protection process is terminated after a predetermined period of time has elapsed, and the on / off control of the power element 21 is resumed.

[0059] In this configuration, even if the second protection process is executed due to an instantaneous signal change, the normal state can be quickly restored, thereby preventing the control of the motor 10 by the power conversion device 20 from being interrupted.

[0060] In addition, in this embodiment, the second protection function 62 detects a current abnormality or a temperature abnormality as an abnormality different from a voltage abnormality when the AC current value in the power element 21 falls outside the range of the current threshold value, or when the element temperature of the power element 21 becomes equal to or higher than the temperature range value.

[0061] In this configuration, the second protection process is executed for the AC current value or element temperature, which are prone to instantaneous signal changes including spike noise due to the circuit configuration of the power conversion device 20 and the control device 50. This makes it possible to more reliably suppress the frequency of occurrence of shutdowns and the like in the power conversion device 20 due to voltage abnormalities.

[0062] The above-described embodiments of the present invention, the above-described embodiments, and the modified examples are merely examples of application of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above-described embodiments.

[0063] The above-mentioned second protection function 62 is configured to detect an abnormality in the AC current value or the element temperature, but it may be configured to detect only one of them, and detect only one abnormality. [Explanation of symbols]

[0064] 1: drive device, 10: motor, 20: power conversion device, 21: power element, 22: smoothing capacitor, 25: voltage detection section, 26: current detection section, 30: battery, 40: main switch, 50: control device, 61: first protection function, 62: second protection function

Claims

1. A method for controlling a power conversion device connected to a rotating electric machine and a battery, comprising: the power conversion device includes a power element, and the power element is on / off controlled to control the power between the rotating electric machine and the battery; a first protection function that detects occurrence of a voltage abnormality when a DC voltage of the power conversion device exceeds a predetermined value and performs a first protection process to protect the power conversion device against the voltage abnormality; A second protection function that performs a second protection process of stopping the on / off control of the power element and controlling the power element to be off when an abnormality other than the voltage abnormality is detected in the power conversion device, When the power element is controlled to be turned off by the second protection function, the first protection function increases the predetermined value or does not execute the first protection process for a predetermined period after the power element is turned off. A method for controlling a power conversion device.

2. A method for controlling a power conversion device according to claim 1, When the power element is controlled to be turned off by the second protection function, the first protection function does not execute the first protection process when a time during which the voltage in the power conversion device exceeds the predetermined value is less than a predetermined time. A method for controlling a power conversion device.

3. A method for controlling a power conversion device according to claim 1, After the power element is controlled to be turned off by the second protection function, the second protection process is terminated after the predetermined period has elapsed, and the on / off control of the power element is resumed. A method for controlling a power conversion device.

4. A method for controlling a power conversion device according to claim 1, The second protection function detects an abnormality other than the voltage abnormality when a current in the power element is outside a range of a predetermined current threshold or when the power element is equal to or higher than a predetermined temperature threshold. A method for controlling a power conversion device.

5. A control device for a power conversion device connected to a rotating electric machine and a battery, The control device includes: a power conversion device that controls the power between the rotating electric machine and the battery by controlling the power element to be turned on and off; a first protection function that detects occurrence of a voltage abnormality when a DC voltage of the power conversion device exceeds a predetermined value and performs a first protection process to protect the power conversion device against the voltage abnormality; A second protection function that performs a second protection process of stopping the on / off control of the power element and controlling the power element to be off when an abnormality other than the voltage abnormality is detected in the power conversion device, When the power element is controlled to be turned off by the second protection function, the predetermined value in the first protection function is increased or the first protection process is not executed for a predetermined period after the power element is turned off. A control device for a power conversion device.

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