JP2020137153A - Power conversion device - Google Patents

Abstract

To sufficiently control a temperature and output currents of a power conversion circuit over a range from low currents to large currents.SOLUTION: A power conversion device 10 includes: a power conversion unit 20 including a power conversion circuit 210 configured of a semiconductor for power; a cooling unit 510 for cooling the power conversion circuit by circulating coolant; a coolant temperature sensor 570 for detecting a temperature of the coolant; and a control unit 40 for controlling an operation of the power conversion unit. The control unit changes a control temperature upper limit value Tul allowed as a temperature of the semiconductor for power configuring the power conversion circuit and an upper limit value Idul of output currents Id of the power conversion circuit by a detected value of the coolant temperature sensor under control of an operation of the power conversion unit.SELECTED DRAWING: Figure 3

Description

The present disclosure relates to a power converter.

Patent Document 1 discloses a power conversion device that controls an upper limit value of an output current of an inverter that converts DC power generated by a solar cell into AC power based on the ambient temperature of the inverter or the solar cell. The upper limit value ILIM of the output current is obtained from the formula “ILIM = ILIM0 + K1 × (T0-TF)”. ILIM0 is the upper limit of the output current when the ambient temperature of the inverter is T0, K1 is a proportionality constant, T0 is the design maximum value of the ambient temperature of the inverter, and TF is the ambient temperature of the inverter or the solar cell.

Japanese Unexamined Patent Publication No. 9-205775

Here, the power conversion device is an automobile that travels using electricity as an energy source and an electric motor as a power source, for example, an electric vehicle such as a secondary battery type electric vehicle or a fuel cell vehicle, or an automobile that uses electric power such as a hybrid vehicle. It is also used in. The power conversion device mounted on such an automobile is used up to a region having a larger current than the power conversion device of the prior art.

For example, a circuit that actually performs power conversion (hereinafter, also referred to as a “power conversion circuit”) such as the above inverter generally refers to a power semiconductor element (hereinafter, also referred to as a “power semiconductor” or a “power semiconductor element”). Constructed using. Power semiconductors generally have the property that the temperature rises as the current increases. Therefore, in the power conversion device mounted on the vehicle, the power conversion circuit is forcibly cooled by the refrigerant in order to enable use in a large current region.

The temperature sensitivity of the power semiconductor to the current in the large current region, that is, the temperature gradient, increases as the current increases. Further, it is considered that the tendency of the temperature gradient is the same even if the forced cooling is performed by the refrigerant. Therefore, in the large current region, even if forced cooling is performed by the refrigerant, the temperature of the power semiconductor rises sharply even with a slight increase in current, and the upper limit temperature allowed for the power semiconductor is reached in a short time. There is a risk of failure of the power conversion circuit.

From the above, simply controlling the upper limit of the output current based on the temperature of the power conversion circuit using the prior art is enough to control the power conversion circuit used up to the large current region by forced cooling of the refrigerant. It is insufficient in terms of the margin for semiconductor failure. Further, in the low current region where the temperature gradient becomes small, the margin for failure of the power semiconductor due to the temperature rise tends to be excessive. Therefore, as the control of the power conversion circuit in the low current region, the available high temperature region cannot be fully utilized and is insufficient. Therefore, there is a demand for a technique for sufficiently controlling the temperature and output current of the power conversion circuit in the region from low current to large current.

The present disclosure can be realized in the following forms.

The power conversion device (10, 10B, 10C) according to one embodiment of the present disclosure is a power conversion unit (20) including a power conversion circuit (210) composed of a power semiconductor, and the power conversion by circulating a refrigerant. A cooling unit (510) for cooling the circuit, a refrigerant temperature sensor (570) for detecting the temperature of the refrigerant, and a control unit (40, 40B, 40C) for controlling the operation of the power conversion unit are provided. During control of the operation of the power conversion unit, the control unit has a control temperature upper limit value (Tul) allowed as the temperature of the power semiconductor constituting the power conversion circuit based on the detection value of the refrigerant temperature sensor, and the power. The upper limit value (Idul) of the output current (Id) of the conversion circuit is changed.
According to this form, for example, in a large current region where the temperature sensitivity to the current flowing through the power semiconductor, that is, the temperature gradient indicating the temperature change with respect to the current change suddenly increases, the margin for the temperature causing a failure due to heat It is possible to set the upper limit of the output current of the power conversion circuit so as to increase the temperature. As a result, it is possible to improve the margin for failure of the power semiconductor due to the temperature rise. Further, for example, in a low current region where the temperature gradient sharply decreases, the upper limit of the output current of the power conversion circuit can be increased by increasing the upper limit of the control temperature. This can improve the utilization of available hot regions. Therefore, it is possible to sufficiently control the temperature and output current of the power conversion circuit over the region from low current to large current.
It should be noted that the present disclosure can be realized in various forms, for example, in the form of a control method of the power conversion device in addition to the power conversion device.

The explanatory view which shows typically the structure of the power conversion apparatus of 1st Embodiment. The flowchart which shows the setting process of the control temperature upper limit value and the output current upper limit value. Explanatory drawing which shows the set control temperature upper limit value and the current upper limit value. The explanatory view which shows typically the structure of the power conversion apparatus of 2nd Embodiment. The flowchart which shows the setting process of the control temperature upper limit value and the output current upper limit value. Explanatory drawing which shows the set control temperature upper limit value and the current upper limit value. Explanatory drawing which shows typically the structure of the power conversion apparatus of 3rd Embodiment. The flowchart which shows the correction process of the temperature characteristic and the control temperature upper limit value. Explanatory drawing which shows the temperature characteristic to be corrected and the control temperature upper limit value.

A. First Embodiment:
Hereinafter, a case where the electric power conversion device 10 shown in FIG. 1 is applied as a drive device for supplying electric power to an electric motor (hereinafter, also referred to as “motor”) as a power source of a vehicle (not shown) will be described as an example. Further, the motor is an example of a three-phase AC motor.

The power conversion device 10 includes a power conversion unit 20 that converts the DC power output from the secondary battery 30 into three-phase AC power supplied to the motor, a control unit 40 that controls the operation of the power conversion unit 20. To be equipped.

The power conversion unit 20 includes a power conversion circuit 210 that actually performs power conversion, and a drive circuit 220 that drives the power conversion circuit 210. The power conversion circuit 210 includes a three-phase inverter composed of a plurality of power semiconductors Se as switching elements. The drive circuit 220 generates a switching signal to be supplied to the power semiconductor Se included in each of the three-phase inverters under the control of the control unit 40.

A temperature sensor 230 for detecting the temperature of the power semiconductor constituting the power conversion circuit 210 is provided on the surface or inside of a package (not shown) of the power conversion circuit 210. The temperature detected by the temperature sensor 230 is the temperature of the power conversion circuit 210 at the position where the temperature sensor 230 is arranged. When the temperature sensor 230 is provided inside the power semiconductor Se, the detected value of the temperature sensor 230 corresponds to the temperature of the power semiconductor Se. When arranged on the package surface of the power conversion circuit 210, the detected value of the temperature sensor 230 is the surface temperature thereof. In this case, the temperature of the power semiconductor Se is obtained by adding the temperature rise obtained from the known thermal resistance and current between the package surface of the power conversion circuit 210 and the inside of the power semiconductor Se. Therefore, in the following description, the temperature detected by the temperature sensor 230 will be described as "the temperature of the power semiconductor Se" regardless of whether it is direct or indirect. Further, a cooling unit 510 through which the refrigerant flows is provided on the package surface of the power conversion circuit 210. A refrigerant temperature sensor 570 that detects the temperature of the circulating refrigerant is provided in the flow path of the refrigerant of the cooling unit 510.

The detected value of the temperature sensor 230 indicating the temperature of the power semiconductor Se is supplied to the control unit 40 via the drive circuit 220. However, the temperature of the power conversion circuit 210 may be supplied from the temperature sensor 230 to the control unit 40 without going through the drive circuit 220. Further, the detection value of the refrigerant temperature sensor 570 indicating the temperature of the refrigerant is also supplied to the control unit 40. Hereinafter, this detected value is also referred to as “refrigerant temperature”.

Of the two-phase wiring that supplies AC power from the power conversion circuit 210 to the motor, current sensors 242 and 243 are provided in any two-phase wiring. The current sensors 242 and 243 acquire the output current Id flowing through each wiring. The acquired two-phase output current Id is supplied to the control unit 40. The remaining one-phase current is obtained from the acquired two-phase current.

The cooling unit 510 cools the power conversion circuit 210 by dissipating the heat generated by the power conversion circuit 210 to the refrigerant in the process of circulating the refrigerant supplied from the refrigerant circulation supply unit 50. The refrigerant circulation supply unit 50 includes a radiator 540, a supply pipe 520 on the refrigerant supply side and a discharge pipe 530 on the refrigerant discharge side connecting the radiator 540 and the cooling unit 510, and a circulation pump 550 and a flow sensor provided in the supply pipe 520. 560 and. The radiator 540 and the circulation pump 550 operate according to the instructions from the control unit 40. The flow rate of the refrigerant detected by the flow rate sensor 560 is supplied to the control unit 40. The refrigerant circulation supply unit 50 is controlled by the control unit 40 so that the temperature of the refrigerant detected by the refrigerant temperature sensor 570 becomes a temperature at which the equilibrium state is maintained.

The control unit 40 is composed of, for example, a microcomputer, and is a drive that sets the drive conditions of the drive unit 410 that controls the drive circuit 220, the cooling drive unit 420 that controls the refrigerant circulation supply unit 50, and the power conversion circuit 210. It functions as a condition setting unit 430 and the like. The drive unit 410 controls the drive circuit 220 of the power conversion unit 20 so that the acquired three-phase output current Id becomes the required output current to the motor, and operates the power conversion circuit 210. Control. Further, the drive unit 410 controls the drive circuit 220 to control the operation of the power conversion circuit 210 so as not to exceed the control temperature upper limit value and the output current upper limit value described later.

The rewritable non-volatile memory (not shown) of the control unit 40 is provided with an upper limit value storage unit 440, a temperature characteristic storage unit 450, and a setting condition storage unit 460. The upper limit value storage unit 440 stores the control temperature upper limit value of the power conversion circuit 210 corresponding to each of the plurality of refrigerant temperatures as a map. The temperature characteristic storage unit 450 stores temperature characteristic data indicating a temperature change with respect to a current change in the refrigerant temperature under steady conditions for the power semiconductor constituting the power conversion circuit 210. The drive condition setting unit 430 stores the drive condition data set by the drive condition setting unit 430. In the following, the refrigerant temperature under steady-state conditions is also referred to as a "standard refrigerant temperature" set by design. Further, the temperature characteristic at the standard refrigerant temperature is also referred to as "standard temperature characteristic".

During the execution of the power conversion operation by the power conversion unit 20, the drive condition setting unit 430 performs the processing shown in FIG. 2 periodically, for example, at intervals of several tens of seconds, to control the temperature. The upper limit value Tul is obtained and the upper limit value Idul of the output current Id (hereinafter, also referred to as the output current upper limit value Idul) is set.

The drive condition setting unit 430 acquires the refrigerant temperature Tc from the refrigerant temperature sensor 570 (step S110), and acquires the control temperature upper limit value Tul corresponding to the acquired refrigerant temperature Tc from the map stored in the upper limit value storage unit 440. (Step S120).

Here, the map stored in the upper limit value storage unit 440 is required to be described below.

As shown in FIG. 3, the temperature Te of the power semiconductor Se with respect to the output current Id of the power semiconductor Se constituting the power conversion circuit 210 has a temperature characteristic that the slope increases as the output current Id increases. Therefore, the lower the output current, the sharper the gradient of the temperature change, and the larger the output current, the sharper the gradient of the temperature change. However, in this temperature characteristic, the position (so-called offset) of the temperature Te of the power semiconductor Se changes in the vertical direction depending on the refrigerant temperature Tc, but the characteristic of the change itself can be found at any refrigerant temperature Tc. The same is true. In addition, in FIG. 3, representative of a plurality of refrigerant temperatures Tc included in the map, the case where the refrigerant temperature Tc is the standard refrigerant temperature Tc0, the case where the refrigerant temperature Tc1 is lower than the standard refrigerant temperature Tc0, and the case where the standard refrigerant is Three temperature characteristics are shown for a refrigerant temperature Tc2 higher than the temperature Tc0.

The control temperature upper limit value Tul is allowed in the operation of the power conversion circuit 210 in order to operate the power conversion circuit 210 so that the temperature Te of the power semiconductor Se constituting the power conversion circuit 210 does not exceed the upper limit temperature Tbd. This is the upper limit of temperature. The temperature Te of the power semiconductor Se means the "junction temperature" or the "channel temperature" of the power semiconductor Se. Further, the upper limit temperature Tbd is a temperature defined as a temperature at which a so-called junction or channel of the power semiconductor Se fails.

First, as a comparative example, a constant value Turr obtained by subtracting various variations such as temperature characteristic variations and temperature measurement variations from the upper limit temperature Tbd and a margin in consideration of the margin for the upper limit temperature Tbd is defined as the control temperature upper limit value. This case will be described. In this case, the output current upper limit value Idul at each refrigerant temperature Tc is limited to the value of the output current Id at the intersection of the temperature characteristic of each refrigerant temperature Tc and the constant control temperature upper limit value Turr. In the example of FIG. 3, the output current upper limit value Idul at each refrigerant temperature Tc value Tc0, Tc1, Tc2 is the intersection (symbol "Tul0") of each temperature characteristic and a constant control temperature upper limit value Turr (= Tul0). The output current Id values (shown by ●) are limited to Id0, Id1r, and Id2r. In FIG. 3, the symbol “○” containing the symbol “●” is not a single symbol, but the symbol “●” indicating the intersection of the temperature characteristic of the standard refrigerant temperature Tc0 and the control temperature upper limit value Tull. A state in which the symbol “◯” at the intersection of the temperature characteristic of the standard refrigerant temperature Tc0 and the control temperature upper limit value Tul, which will be described later, overlaps with each other.

As shown in FIG. 3, as the refrigerant temperature Tc becomes lower than the standard refrigerant temperature Tc0, the temperature gradient at the intersection of the temperature characteristic and the control temperature upper limit value Tull increases sharply. For example, when the refrigerant temperature Tc is a value Tc1 lower than the standard refrigerant temperature Tc0, the temperature gradient Kt1r at the intersection is larger than the temperature gradient Kt0 at the standard refrigerant temperature Tc0. Therefore, the lower the refrigerant temperature Tc, the greater the influence of various variations such as variations in temperature characteristics and variations in temperature measurement. Considering the margin with respect to the upper limit temperature Tbd, a slight fluctuation in the output current Id easily causes a rapid rise in the temperature Te of the power semiconductor Se, which increases the risk of failure of the power conversion circuit 210.

Further, as the refrigerant temperature Tc becomes higher than the standard refrigerant temperature Tc0, the temperature gradient at the intersection of the temperature characteristic and the control temperature upper limit value Tull becomes sharply smaller. For example, when the refrigerant temperature Tc is a value Tc2 higher than the standard refrigerant temperature Tc0, the temperature gradient Kt2r at the intersection is smaller than the temperature gradient Kt0 of the standard refrigerant temperature Tc0. Therefore, the higher the refrigerant temperature Tc, the smaller the influence of various variations. Considering the margin with respect to the upper limit temperature Tbd, even if the output current upper limit value Idul is raised with the control temperature upper limit value raised to a temperature higher than the control temperature upper limit value Tull in the comparative example, failure is prevented and power is supplied. It is considered possible to operate the conversion circuit 210.

Therefore, in consideration of the above points, the map stored in the upper limit value storage unit 440 (see FIG. 1) is obtained as follows.

When the refrigerant temperature Tc is the standard refrigerant temperature Tc0 (see FIG. 3), the same value Tul0 as the control temperature upper limit Tull of the comparative example is set as the control temperature upper limit Tul. As the value Tul0 of the control temperature upper limit value Tul0, the value of the temperature Te of the power semiconductor Se at a point having a predetermined temperature gradient Kt0 in the temperature characteristic of the standard refrigerant temperature Tc0 is used. The temperature gradient Kt0 is set to a value that satisfies a margin considering various variations such as temperature characteristic variation and temperature measurement variation, and a margin with respect to the upper limit temperature Tbd. In this case, the output current upper limit value Idul is limited to the value Id0 at the intersection (indicated by the symbol “◯”) of the temperature characteristic and the value Tul0 of the control temperature upper limit value Tul.

When the refrigerant temperature Tc is lower than the standard refrigerant temperature Tc0 (see FIG. 3), the control temperature upper limit value Tul is lower than the control temperature upper limit Tul0 of the standard refrigerant temperature Tc0 as the refrigerant temperature Tc becomes lower. Is set to. For example, as shown in FIG. 3, when the refrigerant temperature Tc is the value Tc1, the control temperature upper limit value Tul is set to the value Tul1 (<Tul0). In this case, the output current upper limit value Idul is limited to the output current value Id1 at the intersection (indicated by the symbol “◯”) of the temperature characteristic and the value Tul1 of the control temperature upper limit value Tul1. This output current value Id1 is smaller than the upper limit value Id1r of the output current Id in the case of the control temperature upper limit value Tull of the comparative example. As the value Tul1 of the control temperature upper limit value Tul, the temperature Te of the power semiconductor Se at a point having a predetermined temperature gradient Kt1 in the temperature characteristics when the refrigerant temperature Tc is the value Tc1 is used. The temperature gradient Kt1 is a value having a temperature gradient Kt0 or more and less than the temperature gradient Kt1r, and satisfies a margin considering various variations such as temperature characteristic variation and temperature measurement variation, and a margin for the upper limit temperature Tbd. Is set to the value to be set. The same applies to other refrigerant temperatures Tc lower than the standard refrigerant temperature Tc0, and the control temperature upper limit value Tul is set to a value lower than the control temperature upper limit Tul0 of the standard refrigerant temperature Tc0 as the refrigerant temperature Tc becomes lower. To.

When the refrigerant temperature Tc is higher than the standard refrigerant temperature Tc0 (see FIG. 3), the control temperature upper limit value Tul is higher than the control temperature upper limit Tul0 of the standard refrigerant temperature Tc0 as the refrigerant temperature Tc increases. Is set to. For example, as shown in FIG. 3, when the refrigerant temperature Tc is the value Tc2, the control temperature upper limit value Tul is set to the value Tul2 (> Tul0). In this case, in this case, the output current upper limit value Idul is limited to the output current value Id2 at the intersection (indicated by the symbol “◯”) between the temperature characteristic and the value Tul2 of the control temperature upper limit value Tul. This output current value Id2 is larger than the upper limit value Id2r of the output current Id in the case of the control temperature upper limit value Tull of the comparative example. As the value Tul2 of the control temperature upper limit value Tul, the temperature Te of the power semiconductor Se having a temperature gradient Kt2 determined in advance in the temperature characteristics when the refrigerant temperature Tc is the value Tc2 is used. The temperature gradient Kt2 is a value larger than the temperature gradient Kt2r at a temperature gradient Kt0 or less, and has a margin considering various variations such as temperature characteristic variation and temperature measurement variation, and a margin for the upper limit temperature Tbd. Set to a satisfactory value. The same applies to other refrigerant temperatures Tc higher than the standard refrigerant temperature Tc0, and the control temperature upper limit value Tul is set to a value higher than the control temperature upper limit value Tul0 of the standard refrigerant temperature Tc0 as the refrigerant temperature Tc increases. To.

As described above, the control temperature upper limit value Tul corresponding to each refrigerant temperature Tc can be obtained from the temperature characteristics of the plurality of refrigerant temperatures Tc obtained from the standard temperature characteristics at the standard refrigerant temperature Tc0. Then, the control temperature upper limit value Tul corresponding to each of the obtained plurality of refrigerant temperature Tc can be stored in the upper limit value storage unit 440 as a map.

The control temperature upper limit value Tul corresponding to the refrigerant temperature Tc not stored in the upper limit value storage unit 440 sandwiches this temperature above and below, and the control temperature corresponding to the refrigerant temperature Tc stored in the upper limit value storage unit 440. It is obtained by performing an interpolation calculation using the upper limit value Tul.

Next, as shown in FIG. 2, the drive condition setting unit 430 stores the output current Id of the power conversion circuit 210 corresponding to the acquired control temperature upper limit value Tul in the temperature characteristic storage unit 450 as a standard temperature characteristic. (Step S130), the obtained output current Id is set as the output current upper limit value Idul (step S140), and the process ends. The acquired refrigerant temperature Tc, control temperature upper limit value Tul, and output current upper limit value Idul are stored in the setting condition storage unit 460 and used for the control of the power conversion unit 20 by the drive unit 410.

Here, in step S130, the calculation of the output current Id of the power conversion circuit 210 corresponding to the control temperature upper limit value Tul is executed, for example, as follows. By offsetting the standard temperature characteristic data stored in the temperature characteristic storage unit 450 by the temperature difference between the refrigerant temperature Tc acquired in step S110 and the standard refrigerant temperature Tc0, the temperature corresponding to the acquired refrigerant temperature Tc. Obtain characteristic data (see FIG. 3). Then, from the obtained temperature characteristic data, the output current Id corresponding to the control temperature upper limit value Tul acquired in step S120 can be obtained. As a result, the output current Id of the power conversion circuit 210 corresponding to the acquired control temperature upper limit value Tul can be obtained in advance and set as the output current upper limit value Idul. As a result, in the control of the power conversion unit 20 by the drive unit 410, it is possible to limit the operation not only by the control temperature upper limit value Tul but also by the output current upper limit value Idul.

As described above, in the power conversion device 10 of the first embodiment, control is performed in a large current region in which the temperature sensitivity to the current flowing through the power semiconductor Se, that is, the temperature gradient indicating the temperature change with respect to the current change suddenly increases. The temperature upper limit value Tul is limited to a low value so as to increase the margin for the upper limit temperature Tbd that causes a failure due to heat. As a result, the upper limit of the output current of the power conversion circuit 210 can be lowered, and the margin for failure of the power semiconductor Se due to the temperature rise can be improved. Further, in the low current region where the temperature gradient sharply decreases, it is possible to increase the output current upper limit value Idul of the power conversion circuit 210 by increasing the control temperature upper limit value Tul. This can improve the utilization of available hot regions. Therefore, it is possible to sufficiently control the temperature and output current of the power conversion circuit over the region from low current to large current.

B. Second embodiment:
The power conversion device 10B of the second embodiment shown in FIG. 4 is a control in which the drive condition setting unit 430 of the control unit 40 of the power conversion device 10 (see FIG. 1) of the first embodiment is replaced with the drive condition setting unit 430B. It is the same except that it is a part 40B.

During the execution of the power conversion operation by the power conversion unit 20, the drive condition setting unit 430B periodically, for example, at intervals of several minutes, performs the process shown in FIG. 5 to perform the process shown in FIG. The value Tul is obtained and the output current upper limit value Idul is set.

The drive condition setting unit 430B controls the increase in the refrigerant flow rate (step S104). The refrigerant flow rate increase control is executed by increasing the drive amount of the circulation pump 550 (see FIG. 4) by the cooling drive unit 420. The circulation pump 550 corresponds to the "variable flow rate unit".

Next, the drive condition setting unit 430B acquires the refrigerant flow rate Vc from the flow rate sensor 560 (step S106) and acquires the refrigerant temperature Tc from the refrigerant temperature sensor 570. (Step S110). Then, the drive condition setting unit 430B acquires the control temperature upper limit value Tul corresponding to the acquired refrigerant flow rate Vc and the refrigerant temperature Tc from the map stored in the upper limit value storage unit 440 (step S120B).

Here, as shown in FIG. 6, when the refrigerant temperature Tc is the standard refrigerant temperature Tc0, the refrigerant flow rate Vc is the standard refrigerant flow rate with respect to the temperature characteristics at the standard refrigerant flow rate Vc0 in which the refrigerant flow rate Vc is set by design. The temperature characteristic at a value Vc1 larger than Vc0 is a characteristic that the temperature gradient decreases according to the degree of increase in the flow rate. Therefore, the control temperature upper limit value Tul0 (Vc1) at the increased refrigerant flow rate Vc value Vc1 with respect to the output current upper limit value Id0 (Vc0) corresponding to the control temperature upper limit value Tul0 (Vc0) at the standard refrigerant flow rate Vc0. The value Id0 (Vc1) of the output current upper limit value Idul corresponding to is large. In other words, by increasing the refrigerant flow rate Vc, the output current upper limit value Idul can be increased and set on the larger current side. In the above description, the standard refrigerant temperature characteristic when the refrigerant temperature Tc is the standard refrigerant temperature Tc0 has been described as an example, but the same applies to other refrigerant temperatures Tc. Therefore, as shown in FIG. 6, the position of the control temperature upper limit value Tul corresponding to each refrigerant temperature Tc moves to the large current side as the refrigerant flow rate Vc increases.

From the above, the upper limit value storage unit 440 stores a map of the control temperature upper limit value corresponding to each of the plurality of refrigerant temperatures for each of the plurality of refrigerant flow rates. Further, the upper limit value storage unit 440 may store the refrigerant temperature and the refrigerant flow rate as parameters and the control temperature upper limit values corresponding to them as a map.

Next, as shown in FIG. 5, the drive condition setting unit 430B stores the acquired refrigerant flow rate Vc and the output current Id of the power conversion circuit 210 corresponding to the control temperature upper limit value Tul in the temperature characteristic storage unit 450. Obtained using the standard temperature characteristics (step S130B), the obtained output current Id is set as the output current upper limit value Idul (step S140), and the process ends. The acquired refrigerant flow rate Vc, refrigerant temperature Tc, control temperature upper limit value Tul, and output current upper limit value Idul are stored in the setting condition storage unit 460 and used for the control of the power conversion unit 20 by the drive unit 410. ..

Here, in step S130B, the calculation of the output current Id of the power conversion circuit 210 corresponding to the refrigerant flow rate Vc and the control temperature upper limit value Tul is executed, for example, as follows. Similar to step S130 of FIG. 2, the standard temperature characteristic data stored in the temperature characteristic storage unit 450 is offset by the temperature difference between the refrigerant temperature Tc and the standard refrigerant temperature Tc0 acquired in step S110. Obtain the temperature characteristic data corresponding to the acquired refrigerant temperature Tc (see FIG. 3). Then, by multiplying the obtained temperature characteristic data by the relaxation coefficient Kvc (<1) corresponding to the refrigerant flow rate Vc, the temperature characteristic data corresponding to the refrigerant flow rate Vc and the refrigerant temperature Tc can be obtained. The relaxation coefficient Kvc corresponding to the refrigerant flow rate Vc is stored in advance in, for example, the upper limit value storage unit 440 together with the refrigerant flow rate Vc and the control temperature upper limit value Tul corresponding to the refrigerant temperature Tc. Alternatively, it may be stored as a map of the relaxation coefficient Kvc corresponding to the refrigerant flow rate Vc in another storage unit.

As described above, also in the power conversion device 10B of the second embodiment, similarly to the power conversion device 10 of the first embodiment, the margin for failure of the power semiconductor due to the temperature rise is improved in the large current region. be able to. Further, in the low current region, the utilization of the available high temperature region can be improved. As a result, it is possible to sufficiently control the temperature and output current of the power conversion circuit over the region from low current to large current. Further, in the power conversion device 10B of the second embodiment, the upper limit value of the output current can be increased and set by increasing the flow rate of the refrigerant. As a result, it is possible to increase the upper limit of the output current while improving the margin for failure of the power semiconductor Se due to the temperature rise. Therefore, for example, by controlling the refrigerant flow rate Vc, it is possible to use the power conversion device on the large current side as compared with the case where the refrigerant flow rate Vc is not controlled.

C. Third Embodiment:
The power conversion device 10C of the third embodiment shown in FIG. 7 is a control unit 40C in which a correction unit 435C is added to the control unit 40 of the power conversion device 10 (see FIG. 1) of the first embodiment. It is the same except.

FIG. 8C is in a state where the motor is disconnected from the axle at a timing when the motor can be disconnected from the axle, such as when the vehicle is stopped, when a period during which aging deterioration can be detected has elapsed. Perform the processing shown in. The correction unit 435C resets the standard temperature characteristic stored in the temperature characteristic storage unit 450 and the limit temperature upper limit value stored in the upper limit value storage unit 440 by performing the process shown in FIG.

The correction unit 435C acquires the refrigerant temperature Tc (step S210). Next, the correction unit 435C controls the drive unit 410 to start constant current output from the power conversion circuit 210 to the motor (step S220), and the output current Id of the power conversion circuit 210 and the temperature Te of the power semiconductor Se The measurement is started (step S230). Then, the correction unit 435C increases the output current Id until the temperature Te of the power semiconductor Se reaches the control temperature upper limit value Tul corresponding to the acquired refrigerant temperature Tc, and the output current Id and the temperature Te of the power semiconductor Se are increased. Is measured (step S240). The measurement of the output current Id is acquired by the current sensors 242 and 243 as described in the first embodiment. Further, the temperature Te of the power semiconductor Se is directly or indirectly obtained by the detected value of the temperature sensor 230 as described in the first embodiment.

Here, the output current Id at a temperature equal to or higher than the control temperature upper limit value Tul, that is, the output current Id equal to or higher than the output current upper limit value Idul corresponding to the control temperature upper limit value Tul, limits the operation of the power conversion circuit 210. Cannot measure. Therefore, the correction unit 435C estimates the output current Id of the control temperature upper limit value Tul or more and the temperature Te of the power semiconductor Se from the change in the temperature gradient in the temperature characteristic data measured so far (step S250).

Then, the correction unit 435C obtains the standard temperature characteristic at the standard refrigerant temperature Tc0 from the measurement result (step S240) and the estimation result (step S250) at the acquired refrigerant temperature Tc (step S210), and the temperature characteristic storage unit 450. (Step S260). Further, the correction unit 435C obtains the control temperature upper limit value Tul at each of the plurality of refrigerant temperature Tc by using the newly stored standard temperature characteristic, and stores it in the upper limit value storage unit 440 as a map (step S270). Then, the correction unit 435C instructs the drive condition setting unit 430 to execute the control temperature upper limit value setting process (step S280), and ends the process. In the drive condition setting unit 430 instructed to execute, the control temperature upper limit setting process (see FIG. 2) is performed on the map of the control temperature upper limit newly stored in the upper limit storage unit 440 and the temperature characteristic storage unit 450. It is executed based on the temperature characteristics, and the control temperature upper limit value Tul and the output current upper limit value Idul are set.

When the power semiconductor Se of the power conversion circuit 210 deteriorates over time, its temperature characteristics usually change so that the temperature gradient becomes high. For example, as shown in FIG. 9, it is assumed that the temperature characteristic before measurement shown by the alternate long and short dash line changes as shown by the broken line. In this state, if the control temperature upper limit value Tul remains the value Tul0 (b) before the measurement, the output current Id value Id0 (b) corresponding to the point where the temperature gradient becomes higher becomes the output current upper limit value Idul. Therefore, the margin with respect to the upper limit temperature Tbd deteriorates. On the other hand, the value Tul0 (a) of the control temperature upper limit value Tul newly set based on the temperature characteristics after measurement is set for the temperature characteristics according to the aging deterioration, so that the upper limit is set. The value Id0 (a) of the output current Id with respect to the temperature Tbd is set as the output current upper limit value Idul, and the margin with respect to the upper limit temperature Tbd can be corrected from the deteriorated state to the improved state.

As described above, in the power conversion device 10C of the third embodiment, it is possible to correct the change in the temperature characteristics due to aged deterioration, and it is possible to improve the decrease in the margin for failure of the power semiconductor Se due to the temperature rise. ..

In the above description, the power conversion device 10 including the control unit 40C in which the correction unit 435C is added to the control unit 40 of the power conversion device 10 of the first embodiment has been described as an example, but the power conversion of the second embodiment has been described. The same effect can be obtained in a power conversion device including a control unit in which a correction unit 435C is added to the control unit 40B of the device 10B.

D. Other embodiments:
(1) In the above embodiment, an inverter is described as an example of the power conversion circuit 210, but it may be a converter, and may be a power conversion device having various power conversion circuits configured by using a power semiconductor Se. Applicable.

(2) In the above embodiment, the control temperature upper limit value corresponding to the acquired refrigerant temperature is acquired from the map of the control temperature upper limit value corresponding to each of the plurality of refrigerant temperatures stored in the upper limit value storage unit 440. On the other hand, the control temperature upper limit value corresponding to the acquired refrigerant temperature may be acquired from a functional expression that approximates the relationship between the control temperature upper limit values corresponding to each of the plurality of refrigerant temperatures. According to the map and the function formula stored in the upper limit value storage unit 440, the control temperature upper limit value corresponding to the acquired refrigerant temperature can be easily acquired.

(3) In the above embodiment, during control of the operation of the power conversion unit 20, the control temperature upper limit value Tul becomes larger as the refrigerant temperature Tc becomes higher than the standard refrigerant temperature Tc0 and becomes smaller as the refrigerant temperature Tc becomes lower than the standard refrigerant temperature Tc0. The upper limit value Idul of the output current Id of the power conversion circuit 210 is changed so as to be. However, the present invention is not limited to this, and the upper limit of the control temperature and the upper limit of the output current of the power conversion circuit are determined by the detection value of the refrigerant temperature sensor according to the control conditions required in advance for the operation of the power conversion circuit. It would be nice if the value and could be changed.

The present disclosure is not limited to the above-described embodiment, and can be realized by various configurations within a range not deviating from the gist thereof. For example, the technical features of the embodiments corresponding to the technical features in each embodiment described in the column of the outline of the invention are for solving a part or all of the above-mentioned problems, or a part of the above-mentioned effects. Or, in order to achieve all of them, it is possible to replace or combine them as appropriate. Further, if the technical feature is not described as essential in the present specification, it can be appropriately deleted.

10, 10B, 10C ... Power conversion device, 20 ... Power conversion unit, 40, 40B, 40C ... Control unit, 210 ... Power conversion circuit, 220 ... Drive circuit, 440 ... Upper limit value storage unit, 450 ... Temperature characteristic storage unit, 510 ... Cooling unit, 570 ... Refrigerator temperature sensor, Id ... Output current, Idul ... Output current upper limit value, Tc ... Refrigerator temperature, Tc0 ... Standard refrigerant temperature, Tul ... Control temperature upper limit value

Claims (5)

It is a power converter (10, 10B, 10C) and
A power conversion unit (20) including a power conversion circuit (210) composed of a power semiconductor, and a power conversion unit (20).
A cooling unit (510) that cools the power conversion circuit by circulating a refrigerant, and
A refrigerant temperature sensor (570) that detects the temperature of the refrigerant and
Control units (40, 40B, 40C) that control the operation of the power conversion unit, and
With
The control unit
During control of the operation of the power conversion unit, the control temperature upper limit value (Tul) allowed as the temperature of the power semiconductor constituting the power conversion circuit and the output of the power conversion circuit are determined by the detection value of the refrigerant temperature sensor. A power conversion device characterized by changing an upper limit value (Idul) of an electric current (Id). The power conversion device according to claim 1.
The control unit
It has an upper limit value storage unit for storing the control temperature upper limit value corresponding to each of the temperatures of the plurality of the refrigerants.
A power conversion device characterized in that the control temperature upper limit value corresponding to the temperature of the refrigerant acquired by the refrigerant temperature sensor is acquired from the upper limit value storage unit. The power conversion device according to claim 1 or 2.
The control unit
It has a temperature characteristic storage unit that stores as a standard temperature characteristic a temperature characteristic indicating a change in the temperature of the power semiconductor constituting the power conversion circuit with respect to the output current of the power conversion circuit at a standard refrigerant temperature.
The temperature characteristic at the temperature of the refrigerant acquired by the refrigerant temperature sensor obtained from the standard temperature characteristic stored in the temperature characteristic storage unit, and the temperature of the refrigerant acquired by the refrigerant temperature sensor. A power conversion device characterized in that the upper limit value of the output current at the temperature of the refrigerant acquired by the refrigerant temperature sensor is obtained from the control temperature upper limit value. The power conversion device according to any one of claims 1 to 3, and further.
A flow rate variable unit (550) that changes the flow rate of the refrigerant, and
A flow rate sensor (560) that detects the flow rate of the refrigerant and
With
The control unit
As the flow rate (Vc) of the refrigerant acquired by the flow rate sensor becomes larger than the standard refrigerant flow rate (Vc0), the upper limit of the output current becomes larger, and the flow rate of the obtained refrigerant becomes smaller than the standard refrigerant flow rate. A power conversion device characterized in that the control temperature upper limit value is changed so that the upper limit value of the output current becomes smaller. The power conversion device according to claim 3 or claim 4, which is subordinate to claim 3, and further.
A temperature sensor (230) for detecting the temperature of the power semiconductor and
A current sensor (242,243) that detects the output current and
With
The control unit
The temperature sensor and the current sensor measure the temperature change of the power conversion circuit with respect to the change of the output current, and the process of correcting the standard temperature characteristic of the temperature characteristic storage unit is repeatedly executed using the measurement result. Characterized power conversion device.

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