JP6879194B2 - Inverter control device - Google Patents

Description

The present invention relates to the technical field of an inverter control device.

Known systems of this type implement output limits to protect the inverter from overheating. For example, Patent Document 1 discloses a technique of limiting a load factor of a motor when the temperature of a switching element exceeds a predetermined threshold value. The threshold value for executing the output limitation is changed according to the parameters affecting the heat generation or cooling of the inverter.

International Publication No. 2012/124073

In Patent Document 1 described above, since the threshold value is changed based only on the parameters of the inverter, there is a possibility that the inverter cannot be properly protected. Specifically, since the output of the inverter is limited even at low rotation speed of the motor, the output torque from the motor cannot be increased, and the technical problem that the performance of the inverter cannot be fully exhibited. A point arises.

The present invention has been made in view of the above problems, for example, and an object of the present invention is to provide an inverter control device capable of realizing a sufficient output while appropriately protecting the inverter.

One aspect of the inverter control device according to the present invention is an inverter control device that supplies electric power to a motor, and when the temperature of the switching element of the inverter is equal to or higher than a predetermined temperature threshold, the output of the inverter is limited. When the rotation speed of the motor is equal to or less than the first threshold value and the amount of change in the rotation speed of the motor is equal to or less than the second threshold value, the rotation speed of the motor is the first threshold value or less. It is provided with a changing means for changing the temperature threshold to be larger than that of the case where the change amount of the rotation speed of the motor is larger than or larger than the second threshold value.

It is a block diagram which shows the structure of the control device of the inverter which concerns on this embodiment. It is a flowchart which shows the flow of the output limitation operation by the control device of the inverter which concerns on this embodiment. It is a flowchart which shows the flow of the threshold value change operation by the control device of the inverter which concerns on this embodiment. It is a graph which shows the relationship between the element temperature and the output of an inverter. It is a graph which shows the relationship between the element temperature of an inverter and a temperature threshold value. It is a graph which shows the torque expansion effect by the control device of the inverter which concerns on this embodiment. It is a graph which shows the effect at the time of high water temperature by the control device of the inverter which concerns on this embodiment.

Hereinafter, embodiments of the inverter control device will be described with reference to the drawings.

<Device configuration>
First, the configuration of the inverter control device according to the present embodiment will be described with reference to FIG. FIG. 1 is a block diagram showing a configuration of an inverter control device according to the present embodiment.

As shown in FIG. 1, the inverter control device according to the present embodiment is configured as an ECU (Electric Control Unit) 100 capable of controlling the operation of the inverter 30 of the vehicle.

The inverter 30 is configured to be able to convert the electric power supplied from the power source 10 and output it to the motor 20. The inverter 30 includes a U-phase arm including a p-side switching element Cup and an n-side switching element Qun, a V-phase arm including a p-side switching element Qbp and an n-side switching element Qvn, and a p-side switching element Qwp and an n-side switching element Qwn. It is equipped with a W-phase arm including. Each arm included in the inverter 30 is connected in parallel between the positive electrode line and the negative electrode line. Rectifying diodes Dup, Dvp, and Dwp are connected to the p-side switching elements Up, Qvp, and Qwp, respectively. Similarly, for the n-side switching elements Qun, Qvn and Qwn, the rectifying diodes Dun, Dvn and Dwn are connected, respectively. Switching on / off of each of the switching elements Cup to Qwn of the inverter 30 is controlled by PWM (Pulse Width Modulation) control.

The p-side switching elements Cup, Qvp and Qwp in the inverter 30, and the n-side switching elements Qun, Qvn and Qwn include element temperature sensors Sup, Sbp and Swp for detecting the temperature of each switching element, and Sun, Svn and Swn is provided. The temperature of each switching element Cup to Qwn detected by each of the element temperature sensors Up to Swn is output to the ECU 100.

The intermediate points between the upper arm (that is, each p-side switching element) and the lower arm (that is, each n-side switching element) of each phase arm in the inverter 30 are connected to each phase coil of the motor 20. Therefore, the electric power output from the inverter 30 (specifically, the three-phase AC voltage) is supplied to the motor 20.

The motor 20 generates a driving force (that is, torque) necessary for the vehicle to travel. The torque generated by the motor 20 is transmitted to the drive wheels of the vehicle via a drive shaft mechanically connected to the rotation shaft of the motor 20. The motor 20 may be a motor generator having a function of regenerating electric power (that is, generating electric power).

The motor 20 is provided with a rotation speed sensor 25 that detects the rotation speed (or angle) of the motor. The rotation speed of the motor 20 detected by the rotation speed sensor 25 is output to the ECU 100.

The ECU 100 includes an element temperature acquisition unit 110, an element control unit 120, a rotation speed acquisition unit 130, and a condition determination unit 140 as processing blocks for realizing the function.

The element temperature acquisition unit 110 acquires the temperature of each switching element Cup to Qwn (hereinafter, appropriately referred to as “element temperature”) detected by each of the element temperature sensors Up to Swn. The element temperature acquired by the element temperature acquisition unit 110 is output to the element control unit 120.

The element control unit 120 controls the operation of each switching element Cup to Qwn in the inverter 30. In particular, the element control unit 120 according to the present embodiment is configured to be capable of executing control that limits the output of the inverter 30. Specifically, the element control unit 120 executes control to limit the output of the inverter 30 depending on whether or not the element temperature is equal to or higher than a predetermined temperature threshold value. The element control unit 120 is a specific example of the “restriction means” in the appendix described later.

The rotation speed acquisition unit 130 acquires the rotation speed (or angle) of the motor 20. The rotation speed acquired by the rotation speed acquisition unit 130 is output to the condition determination unit 140.

The condition determination unit 140 determines whether or not the rotation speed of the motor 20 and the amount of change in the rotation speed satisfy a predetermined condition. The specific content of this determination process will be described in detail later. The condition determination unit 140 is configured to be able to change the temperature threshold value used by the element control unit 120 according to the determination result. The condition determination unit 140 is a specific example of the "changing means" in the appendix described later.

<Output limit operation>
Next, the output limiting operation (that is, the operation for limiting the output of the inverter) executed by the ECU 100 will be described with reference to FIG. FIG. 2 is a flowchart showing a flow of output limiting operation by the inverter control device according to the present embodiment.

As shown in FIG. 2, during the output limiting operation, the element temperature acquisition unit 110 first acquires the element temperatures of the switching elements Cup to Qwn of the inverter 30 (step S11). The element temperature acquired by the element temperature acquisition unit 110 is output to the element control unit 120.

Subsequently, the element control unit 120 determines whether or not the element temperature is equal to or higher than a predetermined temperature threshold value T (step S12). The element temperature used here is, for example, the highest temperature among the element temperatures of the switching elements Cup to Qwn. Alternatively, the average value of the element temperatures of the switching elements Cup to Qwn may be used. The temperature threshold value T is a threshold value set to protect the switching elements Cup to Qwn of the inverter 30 from overheating. As will be described later, the temperature threshold value T is changed depending on the situation.

When the element temperature is equal to or higher than the temperature threshold value T (step S12: YES), the element control unit 120 executes control for limiting the output of the inverter 30 (step 13). That is, control is performed so that the output of the inverter 30 is reduced. By limiting the output of the inverter 30 in this way, the rise in the element temperature of the switching elements Cup to Qwn is suppressed, and as a result, the switching elements Cup to Qwn can be protected from overheating. When the element temperature is not equal to or higher than the temperature threshold value T (step S12: NO), the above-mentioned process of limiting the output of the inverter 20 is omitted (that is, it is not executed).

<Threshold change operation>
Next, the threshold value changing operation (that is, the operation for changing the temperature threshold value used by the element control unit 120) executed by the ECU 100 will be described with reference to FIGS. 3 to 5. FIG. 3 is a flowchart showing the flow of the threshold value changing operation by the inverter control device according to the present embodiment. FIG. 4 is a graph showing the relationship between the element temperature of the inverter and the output. FIG. 5 is a graph showing the relationship between the element temperature of the inverter and the temperature threshold value.

As shown in FIG. 3, at the time of the threshold value change operation, the rotation speed acquisition unit 130 first acquires the rotation speed of the motor 20 (step S21). The rotation speed of the motor 20 acquired by the rotation speed acquisition unit 130 is output to the condition determination unit 140.

Subsequently, the condition determination unit 140 determines whether or not the rotation speed of the motor 20 is equal to or less than the threshold value Nth (step S22). The threshold value Nth is a specific example of the "first threshold value" in the appendix described later, and is for determining whether or not the rotation speed of the motor 20 is small enough to sufficiently reduce the transient heat generation in the switching elements Cup to Qwn. It is a threshold.

When it is determined that the rotation speed of the motor 20 is equal to or less than the threshold value Nth (step S22: YES), the condition determination unit 140 further determines whether or not the amount of change in the rotation speed of the motor 20 is equal to or less than the threshold value R. (Step S23). The threshold value R is a specific example of the “second threshold value” in the appendix described later, and whether or not the amount of change in the rotation speed of the motor 20 is small enough to sufficiently reduce the transient heat generation in the switching elements Cup to Qwn (more). Specifically, it is a threshold value for determining (whether or not slip has occurred).

When it is determined that the amount of change in the rotation speed of the motor 20 is equal to or less than the threshold value R (step S23: YES), the condition determination unit 140 sets the temperature threshold value T used by the element control unit 120 from the normal values T1 to T1. Change to a larger T2. That is, the condition determination unit 140 is changed so that the temperature threshold value becomes high.

On the other hand, when it is determined that the rotation speed of the motor 20 is not equal to or less than the threshold value Nth (step S22: NO), or when it is determined that the amount of change in the rotation speed of the motor 20 is not equal to or less than the threshold value R (step S23: NO). ), The condition determination unit 140 maintains the temperature threshold value T used by the element control unit 120 at the normal value T1.

As shown in FIG. 4, when the temperature threshold value is changed from T1 to T2, the execution timing of the process for limiting the output of the inverter 30 changes. Specifically, even when the element temperature is relatively high, the output of the inverter 30 is less likely to be limited.

As shown in FIG. 5, the temperature threshold value T1 is switched during normal control (in other words, when the rotation speed of the motor 20 is not equal to or less than the threshold value Nth and the amount of change in the rotation speed of the motor 20 is not equal to or less than the threshold value R). The element temperature of the elements Cup to Qwn is set as a value that does not exceed the element heat resistant temperature. On the other hand, the temperature threshold T2 is set when the motor speed is low (that is, when the rotation speed of the motor 20 is equal to or less than the threshold Nth) and when there is no slip determination (that is, the amount of change in the rotation speed of the motor 20 is equal to or less than the threshold R). In the case of), the element temperature of the switching elements Cup to Qwn is set as a value that does not exceed the element heat resistant temperature. Therefore, even when the temperature threshold value T is changed, the switching elements Cup to Qwn are appropriately protected.

The "water temperature" in the figure is the water temperature of the cooling water for cooling the switching elements Cup to Qwn. Further, the "steady heat generation" in the figure is heat generation generated in the switching elements Cup to Qwn depending on the output (that is, voltage, current) of the inverter 30, and the "transient heat generation" is a load when slip occurs or the like. Is the heat generated by the switching elements Cup to Qwn when

<Technical effect>
Next, the technical effects obtained by the operation of the inverter control device (that is, the ECU 100) according to the present embodiment will be described with reference to FIGS. 6 and 7. FIG. 6 is a graph showing the torque expansion effect of the inverter control device according to the present embodiment. FIG. 7 is a graph showing the effect of the inverter control device according to the present embodiment at high water temperature.

As shown in FIG. 6, when the temperature threshold is changed from T1 to T2, the output torque of the motor 20 is increased. Specifically, the torque that can be output increases when the motor 20 rotates at a low speed (that is, when the rotation speed of the motor 20 is equal to or less than the threshold value Nth). Therefore, for example, it is possible to output a high torque even when the vehicle starts.

As shown in FIG. 7, at normal water temperature (that is, when the water temperature is relatively low), the element temperature does not exceed the temperature threshold T1 even when the element heat generation is taken into consideration. In other words, the process of limiting the output of the inverter 30 is not executed. However, when the water temperature is high (that is, when the water temperature is relatively high), the element temperature exceeds the temperature threshold value T1 in consideration of the element heat generation. That is, if the temperature threshold value T1 is used, the process of limiting the output of the inverter 30 is executed.

However, in the present embodiment, the temperature threshold value T2 is used when the motor 20 rotates at a low speed and there is no slip determination. In this case, the element temperature does not exceed the temperature threshold value T2 even when the water temperature is high. That is, the process of limiting the output of the inverter 30 is not executed. In this way, if the temperature threshold value T is changed according to the situation, it becomes difficult to execute the process of limiting the output of the inverter 30 even when the water temperature is high. Therefore, the chance that the output torque is limited can be reduced.

As described above, according to the inverter control device according to the present embodiment, the temperature threshold value T is changed according to the rotation speed of the motor 20 and the amount of change in the rotation speed. Thereby, it is possible to realize a sufficient output while appropriately protecting the switching elements Cup to Qwn of the inverter 30.

<Additional notes>
Various aspects of the invention derived from the embodiments described above will be described below.

(Appendix 1)
The inverter control device according to Appendix 1 is an inverter control device that supplies electric power to a motor, and executes output limitation of the inverter when the temperature of the switching element of the inverter is equal to or higher than a predetermined temperature threshold. When the rotation speed of the motor is equal to or less than the first threshold value and the amount of change in the rotation speed of the motor is equal to or less than the second threshold value, the rotation speed of the motor is larger than the first threshold value. Or, it is provided with a changing means for changing the temperature threshold so that the change amount of the rotation speed of the motor is larger than the second threshold value.

According to the inverter control device described in Appendix 1, the output limit of the inverter is set when the rotation speed of the motor is equal to or less than the first threshold value and the amount of change in the rotation speed of the front motor is equal to or less than the second threshold value. The temperature threshold for execution is changed to be higher. Therefore, it is possible to prevent the output of the inverter from being limited in a situation where excessive heat generation in the switching element does not occur or is small. Therefore, the performance of the inverter can be fully exhibited, and as a result, the output torque of the motor can be increased.

The present invention is not limited to the above-described embodiment, and can be appropriately modified within the scope of claims and within a range not contrary to the gist or idea of the invention that can be read from the entire specification, and an inverter control device accompanied by such a modification. Is also included in the technical scope of the present invention.

10 Power supply 20 Motor 25 Rotation speed sensor 30 Inverter 100 ECU
110 Element temperature acquisition unit 120 Element control unit 130 Rotation speed acquisition unit 140 Condition judgment unit Cup to Qw Switching element Dup to Dw Rectifier diode Sup to Swn Element temperature sensor T, T1, T2 Temperature threshold Nth Rotation speed threshold R Rotation speed change Threshold

Claims (1)

It is an inverter control device that supplies electric power to the motor.
When the temperature of the switching element of the inverter is equal to or higher than a predetermined temperature threshold value, the limiting means for executing the output limiting of the inverter and the limiting means.
When the rotation speed of the motor is equal to or less than the first threshold value and the amount of change in the rotation speed of the motor is equal to or less than the second threshold value, the rotation speed of the motor is larger than the first threshold value or the motor. A control device for an inverter, comprising: a changing means for changing the temperature threshold value so that the temperature threshold value becomes higher than that in the case where the change amount of the rotation speed is larger than the second threshold value.

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