Power converter overheat protection control device

Abstract

To obtain a power converter overheat protection control device capable of suppressing excessive protection of a power converter, and suppressing reduction of the operation efficiency of the power converter.SOLUTION: A DC power command unit 78 controls power of an inverter 20 on the basis of a heat quantity equivalent value calculated by a heat quantity calculation unit 75. When the heat quantity equivalent value calculated by the heat quantity calculation unit 75 becomes equal to or greater than a first determination heat quantity equivalent value, the DC power command unit 78 reduces a DC power limit value. When the heat quantity equivalent value calculated by the heat quantity calculation unit 75 becomes equal to or less than a second determination heat quantity equivalent value, the DC power command unit 78 increases the DC power limit value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an overheat protection control device for a power converter. [Background technology]

[0002] In a conventional power conversion device, when the AC motor is operating under overload, the control unit electronically adds a weighted value corresponding to the current detected by the current detector to the integrated value of the built-in electronic counter. When the AC motor is not operating under overload, the control unit subtracts a weighted value corresponding to the squared time product of the current detected by the current detector during overload from the integrated value of the electronic counter.

[0003] Furthermore, when the integrated value of the electronic counter reaches a set value on the thermal time limit characteristic, the control unit sends an inverter stop signal to the drive circuit to stop the AC motor (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5520639 Summary of the Invention [Problem to be solved by the invention]

[0005] In the conventional power conversion device as described above, the operation of the inverter is stopped during overheat protection, so that the output to the inverter is limited due to overprotection, which may result in a decrease in the operating efficiency of the inverter.

[0006] The present disclosure has been made to solve the above-mentioned problems, and aims to provide an overheat protection control device for a power converter that can suppress excessive protection of the power converter and suppress a decrease in the operating efficiency of the power converter. [Means for solving the problem]

[0007] The overheat protection control device for a power converter according to the present disclosure includes a power calculation unit that calculates the power in a power converter provided between a DC power source and an AC rotating electric machine, a heat quantity calculation unit that calculates a heat quantity equivalent value based on the power calculated by the power calculation unit and a first determination output value that is a power threshold value, and a power command unit that controls the power in the power converter based on the heat quantity equivalent value calculated by the heat quantity calculation unit, and when the power is equal to or greater than the first determination output value, the heat quantity calculation unit calculates a current squared time product value, which is a value obtained by multiplying the square of the current flowing between the DC power source and the power converter by time, as a current squared time product value. The power command unit adds the calculated heat quantity equivalent value to the first determined heat quantity equivalent value, and if the power is less than the first determined output value, subtracts the subtraction value from the previous heat quantity equivalent value. When the heat quantity equivalent value calculated by the heat quantity calculation unit becomes equal to or greater than the first determined heat quantity equivalent value, the power command unit limits the power in the power converter. When the heat quantity equivalent value calculated by the heat quantity calculation unit becomes equal to or less than a second determined heat quantity equivalent value that is smaller than the first determined heat quantity equivalent value, the power command unit releases the limit on the power in the power converter. The second determined heat quantity equivalent value is fixed from when the heat quantity equivalent value becomes equal to or greater than the first determined heat quantity equivalent value until the heat quantity equivalent value becomes equal to or less than the second determined heat quantity equivalent value. [Effects of the Invention]

[0008] According to the overheat protection control device for a power converter of the present disclosure, excessive protection of the power converter can be suppressed, and a decrease in the operating efficiency of the power converter can be suppressed. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a configuration diagram showing a vehicle drive system according to a first embodiment. [Figure 2] 2 is a graph showing an input signal to a first determination heat quantity equivalent value setting unit and an output signal from the first determination heat quantity equivalent value setting unit when the first low-pass filter and the second low-pass filter of FIG. 1 are not used. [Figure 3] 2 is a graph showing input signals to the first low-pass filter and the second low-pass filter of FIG. 1 and an output signal from a first determination heat quantity equivalent value setting unit. [Figure 4] 10 is a graph showing an example of the relationship between a heat quantity equivalent value and temperature. [Figure 5] 10 is a graph showing a change in the DC power limit value when the DC power command unit in FIG. 1 switches the DC power limit value, comparing a case where a gradual increase process is performed with a case where a gradual increase process is not performed. [Figure 6] 10 is a graph showing a change in the DC power limit value when the DC power command unit in FIG. 1 switches the DC power limit value, comparing a case where a gradual decrease process is performed with a case where a gradual decrease process is not performed. [Figure 7] 2 is a block diagram showing a main part of the overheat protection control device of FIG. 1. FIG. [Figure 8] 8 is a block diagram showing an example of a detailed configuration of a maximum current adjusting section in FIG. 7. FIG. [Figure 9] 8 is a graph showing a first example of the relationship between input and output in the maximum current adjusting unit of FIG. 7; [Figure 10] 8 is a graph showing a second example of the relationship between input and output in the maximum current adjusting unit of FIG. 7. [Figure 11] 8 is a table showing an example of a method for determining an upper limit value of the allowable torque in the allowable torque calculation unit of FIG. 7. [Figure 12] 8 is a table showing an example of a method for determining a lower limit value of the allowable torque in the allowable torque calculation unit of FIG. 7. [Figure 13] 2 is a flowchart showing the first half of the operation of the overheat protection control device of FIG. 1. [Figure 14] 2 is a flowchart showing the second half of the operation of the overheat protection control device of FIG. 1. [Figure 15] 10 is a table showing an example of the relationship between water temperature, DC power, and a first determination heat quantity equivalent value. [Figure 16] 16 is a graph showing the relationship between water temperature, DC power, and a first determination heat quantity equivalent value corresponding to FIG. 15. [Figure 17] 10 is a table showing an example of the relationship between water temperature, DC power, and subtraction value. [Figure 18] 18 is a graph showing the relationship between water temperature, DC power, and subtraction value corresponding to FIG. 17. [Figure 19]2 is a graph showing the results of measuring the change over time in temperature of a conductor connected to the inverter of FIG. 1 at high water temperature and at low water temperature. [Figure 20] 10 is a table showing an example of the relationship between water temperature and a DC power limit value during limiting. [Figure 21] 21 is a graph showing the relationship between the water temperature and the DC power limit value during limiting, corresponding to FIG. 20. [Figure 22] 4 is a timing chart showing an overheat protection operation according to the first embodiment. [Figure 23] FIG. 10 is a block diagram showing a main part of an overheat protection control device according to a second embodiment. [Figure 24] 1 is a graph showing an example of the relationship between the rotation speed and AC current. [Figure 25] 10 is a graph showing an example of the relationship between the rotation speed and a first judgment heat quantity equivalent value. [Figure 26] FIG. 11 is a block diagram showing a main part of an overheat protection control device according to a third embodiment. [Figure 27] 1 is a graph showing an example of the relationship between AC current and DC current. [Figure 28] 10 is a graph showing an example of the relationship between AC current and a first judgment heat quantity equivalent value. [Figure 29] FIG. 10 is a block diagram showing elements of an overheat protection control device according to a fourth embodiment. [Figure 30] FIG. 10 is a block diagram showing elements of an overheat protection control device according to a fifth embodiment. [Figure 31] FIG. 13 is a block diagram showing elements of an overheat protection control device according to a sixth embodiment. [Figure 32] FIG. 13 is a block diagram showing elements of an overheat protection control device according to a seventh embodiment. [Figure 33] 10 is a table showing an example of the relationship between water temperature, DC power, and a second determination heat quantity equivalent value. [Figure 34] 34 is a graph showing the relationship between water temperature, DC power, and a second determination heat quantity equivalent value corresponding to FIG. 33. [Figure 35] FIG. 13 is a block diagram showing a main part of an overheat protection control device according to an eighth embodiment. [Figure 36] 10 is a graph showing an example of the relationship between the rotation speed and the first and second determination heat quantity equivalent values. [Figure 37] FIG. 13 is a block diagram showing the main parts of an overheat protection control device according to a ninth embodiment. [Figure 38] 10 is a graph showing an example of the relationship between AC current and a first determination heat quantity equivalent value and a second determination heat quantity equivalent value. [Figure 39] 1 is a configuration diagram showing a first example of a processing circuit that realizes each function of the inverter control device and the overheat protection control device according to the first to ninth embodiments. [Figure 40] FIG. 10 is a configuration diagram showing a second example of a processing circuit that realizes each function of the inverter control device and the overheat protection control device according to the first to ninth embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments will be described with reference to the drawings. Embodiment 1 <Vehicle drive system> 1 is a configuration diagram showing a vehicle drive system according to embodiment 1. In the figure, the vehicle drive system includes a DC power supply 10, a voltage detector 11, a current detector 12, a smoothing capacitor 13, an inverter 20 as a power converter, an AC rotating electric machine 30, a magnetic pole position detector 31, a first current sensor 33a, a second current sensor 33b, a third current sensor 33c, an inverter control device 40, an electrical angular velocity calculation unit 50, an overheat protection control device 70, and a water temperature detector 80.

[0011] The DC power supply 10 is a chargeable and dischargeable power supply. The DC power supply 10 exchanges power with an AC rotating electric machine 30 via an inverter 20. The DC power supply 10 has a high-voltage side node P and a low-voltage side node N.

[0012] Smoothing capacitor 13 is connected between high-voltage side node P and low-voltage side node N at high-voltage side node Pcap and low-voltage side node Ncap. A boost converter (not shown) may be provided between high-voltage side node P and inverter 20. In this case, the DC voltage supplied from DC power supply 10 is boosted by DC / DC conversion.

[0013] The voltage detector 11 detects the DC voltage Vdc of the DC power supply 10. Specifically, the voltage detector 11 outputs the inter-terminal voltage between a high-voltage side node P and a low-voltage side node N as the DC voltage Vdc. Note that the voltage detector 11 may also output the voltage between a high-voltage side connection point Pcap and a low-voltage side connection point Ncap as the DC voltage Vdc.

[0014] Current detector 12 detects DC current Idc flowing between DC power supply 10 and inverter 20. Specifically, current detector 12 outputs the current between high-voltage side node P and multiple terminals Pu, Pv, and Pw as DC current Idc. Alternatively, current detector 12 outputs the current between low-voltage side node N and multiple terminals Nu, Nv, and Nw as DC current Idc.

[0015] Note that, assuming that the DC power (Vdc×Idc) and the AC power (Vac×Iac) are equal, the DC current Idc may be estimated by the following equation.

[0016] Idc=(Vac×Iac) / Vdc (1)

[0017] In this case, the AC current Iac may be estimated from the d-axis current id and the q-axis current iq using the following equation:

[0018]

number

[0019] For example, if the AC voltage Vac is the line voltage between U and V, it can be calculated by Vu - Vv. If the AC voltage Vac is the line voltage between V and W, it can be calculated by Vv - Vw. If the AC voltage Vac is the line voltage between W and U, it can be calculated by Vw - Vu. The AC voltage Vac may also be calculated as the average of multiple line voltages.

[0020] The water temperature detector 80 detects the temperature of the cooling water for the inverter 20, that is, the water temperature.

[0021] <Inverter> The inverter 20 has a plurality of switching elements. The inverter 20 performs DC / AC conversion of the DC voltage from the DC power supply 10 by the switching operation of the plurality of switching elements. The AC voltage obtained by the DC / AC conversion is applied to the AC rotating electric machine 30.

[0022] The multiple switching elements include multiple switching elements on the upper arm side and multiple switching elements on the lower arm side. The multiple switching elements on the upper arm side include a first upper arm switching element 21a, a second upper arm switching element 21b, and a third upper arm switching element 21c. The switching elements on the lower arm side include a first lower arm switching element 22a, a second lower arm switching element 22b, and a third lower arm switching element 22c.

[0023] <AC rotating electric machine> The AC rotating electric machine 30 controls the driving force and braking force of the vehicle by applying an AC voltage from the inverter 20. The vehicle is an electrically powered vehicle such as an electric vehicle or a hybrid vehicle. The AC rotating electric machine 30 is, for example, a permanent magnet synchronous motor. In the first embodiment, an AC rotating electric machine having a three-phase armature winding is used as the AC rotating electric machine 30. However, the number of phases of the AC rotating electric machine 30 is not limited to three, and any number of phases may be used.

[0024] The magnetic pole position detector 31 detects the magnetic pole position of the AC rotating electric machine 30. The magnetic pole position detector 31 includes, for example, a Hall element, a resolver, or an encoder. The magnetic pole position detector 31 detects the rotation angle of the magnetic pole with respect to a reference rotation position of the rotor of the AC rotating electric machine 30, and outputs a signal indicating the detected value of the rotation angle as the magnetic pole position θ. The magnetic pole position θ indicates the rotation angle of the q axis. The reference rotation position of the rotor is preset to an arbitrary position.

[0025] The electrical angular velocity calculation unit 50 calculates the electrical angular velocity ω using the magnetic pole position θ output from the magnetic pole position detector 31. Note that the electrical angular velocity calculation unit 50 may directly detect the electrical angular velocity ω of the AC rotating electric machine 30 using a Hall element, an encoder, or the like.

[0026] The first current sensor 33a detects the amount of current iU flowing through the U-phase of the AC rotary electric machine 30. The second current sensor 33b detects the amount of current iV flowing through the V-phase of the AC rotary electric machine 30. The third current sensor 33c detects the amount of current iW flowing through the W-phase of the AC rotary electric machine 30.

[0027] The number of current sensors may be two. In this case, only the current amounts of two phases are detected, and the current amount of the remaining phase is calculated from the detected current amounts of the two phases.

[0028] <Inverter control device> The inverter control device 40 controls the switching operations of a plurality of switching elements included in the inverter 20. As a result, the inverter control device 40 adjusts the potentials Vu, Vv, and Vw of the connection nodes between the inverter 20 and the AC rotating electric machine 30, and controls the amount of current flowing through the AC rotating electric machine 30.

[0029] The inverter control device 40 has, as functional blocks, a current command calculation unit 41, a d-axis current controller 42, a q-axis current controller 43, a two-phase to three-phase voltage conversion unit 44, a PWM (Pulse Width Modulation) circuit 45, a gate driver 46, and a three-phase to two-phase current conversion unit 47. The inverter control device 40 also controls the inverter 20 by dq vector control, thereby controlling the rotation of the AC rotating electric machine 30.

[0030] The current command calculation unit 41 receives a torque command from the overheat protection control device 70. The torque command is a command related to the torque to be generated by the AC rotating electric machine 30. The current command calculation unit 41 calculates a d-axis current command value Cid and a q-axis current command value Ciq based on the torque command. The current command calculation unit 41 outputs the d-axis current command value Cid to the d-axis current controller 42. The current command calculation unit 41 outputs the q-axis current command value Ciq to the q-axis current controller 43.

[0031] The current amounts iU, iV, and iW are input to the three-phase to two-phase current converter 47 from the first current sensor 33a, the second current sensor 33b, and the third current sensor 33c, respectively. Based on the magnetic pole position θ from the magnetic pole position detector 31, the three-phase to two-phase current converter 47 converts the three-phase current amounts iU, iV, and iW into two-phase current amounts, i.e., a d-axis current id and a q-axis current iq.

[0032] Furthermore, the three-phase to two-phase current converter 47 outputs the d-axis current id to the d-axis current controller 42 and outputs the q-axis current iq to the q-axis current controller 43 .

[0033] The d-axis current controller 42 calculates a DC d-axis voltage command value Cvd so that the deviation between the d-axis current command value Cid from the current command calculation unit 41 and the d-axis current id from the three-phase-to-two-phase current conversion unit 47 becomes "0", and outputs the calculated value to the two-phase-to-three-phase voltage conversion unit 44.

[0034] The q-axis current controller 43 calculates a DC q-axis voltage command value Cvq so that the deviation between the q-axis current command value Ciq from the current command calculation unit 41 and the q-axis current iq from the three-phase-to-two-phase current conversion unit 47 becomes "0", and outputs the calculated value to the two-phase-to-three-phase voltage conversion unit 44.

[0035] The two-phase to three-phase voltage converter 44 converts the two-phase DC d-axis voltage command value Cvd and the q-axis voltage command value Cvq into three-phase AC voltage command values ​​Cvu, Cvv, and Cvw based on the magnetic pole position θ from the magnetic pole position detector 31, and outputs them to the PWM circuit 45.

[0036] The PWM circuit 45 outputs a plurality of switch control signals to the gate driver 46. Each switch control signal is a signal that controls a corresponding one of a plurality of switching elements included in the inverter 20.

[0037] Based on each switch control signal from the PWM circuit 45, the gate driver 46 causes the corresponding switching element to perform a switching operation.

[0038] <Overheat protection control device> The overheat protection control device 70 has, as functional blocks, a DC power calculation unit 71, a first judgment output value setting unit 72, a heat quantity calculation unit 75, a first judgment heat quantity equivalent value setting unit 76, a second judgment heat quantity equivalent value setting unit 77, a DC power command unit 78, a maximum current adjustment unit 81, an allowable torque calculation unit 82, a torque command calculation unit 83, a heat dissipation amount setting unit 84, a first low-pass filter 85, and a second low-pass filter 86.

[0039] The overheat protection controller 70 also protects the monitored components from overheating. That is, the overheat protection controller 70 protects the monitored components from overheating. The monitored components are components between the high-voltage side node P and the low-voltage side node N, components between the high-voltage side connection point Pcap and the low-voltage side connection point Ncap, or components surrounding these. The overheat protection controller 70 also outputs a torque command to the current command calculation unit 41.

[0040] The DC power calculation unit 71 calculates the power in the inverter 20. Specifically, the DC power calculation unit 71 calculates the DC power supplied to the inverter 20 based on the DC voltage Vdc and the DC current Idc. The DC power is a value obtained by performing absolute value processing on the product of the DC voltage Vdc and the DC current Idc. Because the DC power has been subjected to absolute value processing, it is a value that can be used in both powering operation and regenerative operation.

[0041] The DC power calculation unit 71 outputs DC power to the heat quantity calculation unit 75, the first determination heat quantity equivalent value setting unit 76, and the maximum current adjustment unit 81.

[0042] The DC power may be calculated by other calculation methods, not limited to the calculation method of absolute value processing of the product of the DC voltage and the DC current. For example, in the powering operation of the AC rotating electric machine 30, the DC power may be calculated by a calculation method of absolute value processing of the product of the torque and the rotation speed divided by the motor efficiency and the inverter efficiency, or may be calculated from the value obtained by dividing the AC power by the inverter efficiency. In the regenerative operation of the AC rotating electric machine 30, the DC power may be calculated by a calculation method of absolute value processing of the product of the torque, the rotation speed, the motor efficiency, and the inverter efficiency, or may be calculated from the product of the AC power and the inverter efficiency. These calculation methods can be used for both the powering operation and the regenerative operation.

[0043] The first judgment output value setting unit 72 stores a first judgment output value. The first judgment output value is a preset threshold value for DC power. The first judgment output value is set to a minimum value at which, if output continuously, the temperature of the monitored component exceeds a limit temperature, causing damage to the monitored component. The limit temperature is a temperature specific to the monitored component. The first judgment output value from the first judgment output value setting unit 72 is input to the heat quantity calculation unit 75.

[0044] The heat quantity calculation unit 75 receives as input the DC power calculated by the DC power calculation unit 71, the first determination output value from the first determination output value setting unit 72, and the water temperature detected by the water temperature detector 80. The heat quantity calculation unit 75 also has a current squared time product calculation unit 73 and a subtraction value acquisition unit 74.

[0045] The current squared time product calculation unit 73 calculates a current squared time product value. The current squared time product value is a value obtained by multiplying the square of the DC current Idc flowing between the DC power supply 10 and the inverter 20 by time. The subtraction value acquisition unit 74 acquires a subtraction value. The subtraction value is a value that is set based on the DC power and the water temperature detected by the water temperature detector 80. Furthermore, when setting the subtraction value, the DC power and the water temperature may each be values ​​that have been subjected to low-pass filtering.

[0046] The heat quantity calculation unit 75 compares the DC power calculated by the DC power calculation unit 71 with the first determination output value from the first determination output value setting unit 72, and calculates a heat quantity equivalent value based on the comparison result.

[0047] If the value of the DC power is equal to or greater than the first judgment output value, the heat quantity calculation unit 75 calculates the current heat quantity equivalent value by adding the current squared time product value calculated by the current squared time product calculation unit 73 to the previous heat quantity equivalent value.

[0048] If the value of the DC power is less than the first determination output value, the heat quantity calculation unit 75 calculates the current heat quantity equivalent value by subtracting the subtraction value acquired by the subtraction value acquisition unit 74 from the previous heat quantity equivalent value.

[0049] Heat quantity calculation unit 75 outputs the heat quantity equivalent value to DC power command unit 78 and second judgment heat quantity equivalent value setting unit 77. At this time, the minimum value of the heat quantity equivalent value calculated by heat quantity calculation unit 75 is set to 0. When the heat quantity equivalent value falls to a negative value, the current squared time product value added until the heat quantity equivalent value reaches the overheat protection temperature increases, and the temperature becomes equal to or higher than the set overheat protection temperature.

[0050] A heat dissipation amount setting value is preset in the heat dissipation amount setting unit 84. The heat dissipation amount setting value is a value equivalent to the heat dissipation amount of the monitored component. By subtracting the heat dissipation amount setting value from the heat amount equivalent value calculated by the heat amount calculation unit 75, the monitored component becomes equal to or lower than the overheat protection temperature.

[0051] The output from the DC power calculation unit 71 is input to the first determination heat quantity equivalent value setting unit 76 via a first low-pass filter 85. The output from the water temperature detector 80 is input to the first determination heat quantity equivalent value setting unit 76 via a second low-pass filter 86. A gain is set in each of the first low-pass filter 85 and the second low-pass filter 86 to reduce the signal amplitude in a frequency band equal to or higher than a preset frequency fc.

[0052] Fig. 2 is a graph showing an input signal to the first determination heat quantity equivalent value setting unit 76 and an output signal from the first determination heat quantity equivalent value setting unit 76 when the first low-pass filter 85 and the second low-pass filter 86 of Fig. 1 are not used. Fig. 3 is a graph showing an input signal to the first low-pass filter 85 and the second low-pass filter 86 of Fig. 1 and an output signal from the first determination heat quantity equivalent value setting unit 76. In Figs. 2 and 3, the horizontal axis represents time.

[0053] 2, when the first low-pass filter 85 and the second low-pass filter 86 are not used, i.e., when low-pass filtering is not performed, the input signal to the first determination heat quantity equivalent value setting unit 76 contains noise components, resulting in a large amplitude of the input signal. As a result, an output signal corresponding to the input signal containing the noise components is output from the first determination heat quantity equivalent value setting unit 76.

[0054] In contrast to this, when the first low-pass filter 85 and the second low-pass filter 86 are used, the input signal that has been subjected to low-pass filtering is input to the first determination heat quantity equivalent value setting unit 76. As a result, an output signal corresponding to the input signal with suppressed noise components is output from the first determination heat quantity equivalent value setting unit 76, as shown in FIG.

[0055] Figure 4 is a graph showing an example of the relationship between the heat equivalent value and temperature. The heat equivalent value, or the amount of heat generated, is expressed as the square of the DC current Idc multiplied by time. Naturally, the greater the amount of heat generated, the higher the temperature of the monitored component.

[0056] Returning to FIG. 1 , the first determination heat quantity equivalent value setting unit 76 sets a first determination heat quantity equivalent value. The first determination heat quantity equivalent value is a heat quantity equivalent value that changes depending on a value obtained by performing low-pass filtering on one or more of the water temperature, DC power, rotation speed, and AC current. In the first embodiment, low-pass filtering is performed on the water temperature and DC power. Furthermore, the first determination heat quantity equivalent value is a heat quantity equivalent value at which the monitored component reaches an overheat protection temperature. The first determination heat quantity equivalent value from the first determination heat quantity equivalent value setting unit 76 is input to the DC power command unit 78. A method for setting the first determination heat quantity equivalent value will be described later.

[0057] The second determination heat quantity equivalent value setting unit 77 sets a second determination heat quantity equivalent value. The second determination heat quantity equivalent value is a heat quantity equivalent value obtained by subtracting a heat radiation quantity setting value acquired in advance from the heat quantity equivalent value when the heat quantity equivalent value calculated by the heat quantity calculation unit 75 becomes equal to or greater than the first determination heat quantity equivalent value. The second determination heat quantity equivalent value is also a heat quantity equivalent value at which the monitored component becomes equal to or lower than the overheat protection temperature.

[0058] Furthermore, the second determination heat quantity equivalent value is fixed from when the heat quantity equivalent value calculated by the heat quantity calculation unit 75 becomes equal to or greater than the first determination heat quantity equivalent value until the heat quantity equivalent value calculated by the heat quantity calculation unit 75 becomes equal to or less than the second determination heat quantity equivalent value. The second determination heat quantity equivalent value from the second determination heat quantity equivalent value setting unit 77 is input to the DC power command unit 78. The second determination heat quantity equivalent value is a value smaller than the first determination heat quantity equivalent value. A specific method for setting the second determination heat quantity equivalent value will be described later.

[0059] The DC power command unit 78 controls the power of the inverter 20 based on the heat quantity equivalent value calculated by the heat quantity calculation unit 75. More specifically, the DC power command unit 78 compares the heat quantity equivalent value calculated by the heat quantity calculation unit 75 with the first determined heat quantity equivalent value and the second determined heat quantity equivalent value, respectively, and sets the DC power limit value based on the comparison results.

[0060] When the heat quantity equivalent value calculated by the heat quantity calculation unit 75 becomes equal to or greater than the first judgment heat quantity equivalent value, the DC power command unit 78 lowers the DC power limit value. As a result, the DC power in the inverter 20 is limited to the DC power limit value, and the monitored components are protected from overheating.

[0061] When the heat quantity equivalent value calculated by the heat quantity calculation unit 75 becomes equal to or less than the second judgment heat quantity equivalent value, the DC power command unit 78 increases the DC power limit value. As a result, the limit on the DC power in the inverter 20 is lifted, the DC power limit value becomes equal to or greater than the DC power, and protection of the monitored components is released.

[0062] When switching the DC power limit value, the DC power command unit 78 gradually decreases or increases the DC power limit value at a preset gradient.

[0063] Fig. 5 is a graph showing a comparison of changes in the DC power limit value when the DC power command unit 78 in Fig. 1 switches the DC power limit value between cases where gradual increase processing is performed and cases where it is not performed. The horizontal axis of Fig. 5 represents time. The vertical axis of Fig. 5 represents the DC power limit value.

[0064] The upper part of Fig. 5 shows the state of the DC power limit value when the gradual increase process is not performed, for example, the DC power limit value changes from Pa to Pb at time ta. The lower part of Fig. 5 shows the state of the DC power limit value when the gradual increase process is performed, for example, when the gradual increase slope is (Pb-Pa) / (tb-ta), when the DC power limit value is switched from Pa to Pb, the DC power limit value changes from Pa to Pb over time (tb-ta).

[0065] Fig. 6 is a graph showing a comparison of changes in the DC power limit value when the DC power command unit 78 in Fig. 1 switches the DC power limit value between cases where gradual reduction processing is performed and cases where it is not performed. The horizontal axis of Fig. 6 represents time. The vertical axis of Fig. 6 represents the DC power limit value.

[0066] The upper part of Fig. 6 shows the state of the DC power limit value when the gradual decrease process is not performed, for example, at time ta the DC power limit value changes from Pb to Pa. The lower part of Fig. 6 shows the state of the DC power limit value when the gradual decrease process is performed, for example, when the gradual decrease slope is (Pa-Pb) / (tb-ta), when the DC power limit value is switched from Pb to Pa, the DC power limit value changes from Pb to Pa over time (tb-ta).

[0067] Returning to FIG. 1, the maximum current adjusting unit 81 adjusts the maximum current of the AC rotary electric machine 30, and outputs the adjusted maximum current Imax_adj to the allowable torque calculating unit .

[0068] The maximum current adjusting unit 81 limits the maximum current of the AC rotating electric machine 30 so that the DC power obtained by the DC power calculating unit 71 does not exceed the DC power limit value set by the DC power commanding unit 78. This prevents the temperature of the monitored components from exceeding the preset limit temperature, preventing damage to the monitored components due to overheating.

[0069] The specific configuration and operation of maximum current adjuster 81 will be described later. The adjuster that performs the control does not have to be a current adjuster as long as it is a parameter adjuster that can suppress the temperature.

[0070] The allowable torque calculation unit 82 calculates the allowable torque Ctrq_alw based on the adjusted maximum current Imax_adj output from the maximum current adjustment unit 81. A specific method for calculating the allowable torque Ctrq_alw will be described later.

[0071] The torque command calculation unit 83 calculates the torque command value Ctrq so that it falls within the range of the allowable torque Ctrq_alw output from the allowable torque calculation unit 82 , and outputs the calculated value to the current command calculation unit 41 .

[0072] <Maximum current adjustment section> Fig. 7 is a block diagram showing the main components of the overheat protection control device 70 shown in Fig. 1. A maximum current adjuster 81 adjusts the maximum current Imax based on the DC power and the power deviation ΔPdc of the DC power limit value set by the DC power commander 78, and outputs the adjusted maximum current Imax_adj. The adjusted maximum current Imax_adj is the maximum allowable current value.

[0073] Furthermore, the maximum current adjusting unit 81 adjusts the value of the maximum current Imax so that the DC power limit value set by the DC power command unit 78 does not exceed the preset temperature of the monitored component. This prevents the temperature of the monitored component from exceeding the preset limit temperature, preventing damage to the monitored component due to overheating.

[0074] Fig. 8 is a block diagram showing an example of a detailed configuration of the maximum current adjustment unit 81 in Fig. 7. In the example in Fig. 8, the maximum current adjustment unit 81 has a proportional regulator 60, an integral regulator 61, and an upper and lower limit limiting unit 62.

[0075] The maximum current adjustment unit 81 receives as input a power deviation ΔPdc between the DC power and the DC power limit value set by the DC power command unit 78. The power deviation ΔPdc is a value obtained by subtracting the DC power from the DC power limit value set by the DC power command unit 78. Therefore, if the value of the DC power exceeds the DC power limit value, the DC power deviation ΔPdc becomes a negative value. In this case, the greater the value of the DC power, the smaller the value of the DC power deviation ΔPdc becomes.

[0076] The proportional regulator 60 outputs a value obtained by multiplying the input deviation by the proportional gain Kpa. In this example, the proportional gain Kpa in the proportional regulator 60 is assumed to be a positive value.

[0077] The integral regulator 61 integrates the output of the proportional regulator 60, using the "upper limit of the maximum current Imax" as its initial value. The "upper limit of the maximum current Imax" is the value obtained when the "phase current absolute value" shown by the above equation (2) is calculated using the maximum d-axis current and the maximum q-axis current in the design.

[0078] That is, under any conditions, a current having a "phase current absolute value" greater than the "upper limit value of the maximum current Imax" is not intentionally caused to flow. On the other hand, the maximum current Imax is a variable value, and is adjusted between "zero" and the "upper limit value of the maximum current Imax."

[0079] When the value of the DC power becomes greater than the DC power limit value set by the DC power command unit 78, the output of the proportional regulator 60 becomes a negative value, and accordingly the output of the integral regulator 61 decreases.

[0080] Proportional regulator 60 outputs a value obtained by multiplying the deviation by proportional gain Kpa. Therefore, when the DC power deviation ΔPdc is a negative value, the output of proportional regulator 60 becomes a negative value. In this case, integral regulator 61 integrates the negative value, so the output of integral regulator 61 gradually decreases from the initial value.

[0081] On the other hand, when the DC power is equal to or less than the DC power limit value set by DC power command unit 78, the output of proportional regulator 60 becomes a positive value, and accordingly, the output of integral regulator 61 increases.

[0082] In this way, proportional adjustment and integral adjustment of the DC power deviation ΔPdc are performed by proportional regulator 60 and integral regulator 61. The outputs of proportional regulator 60 and integral regulator 61 are input to an adder. The adder adds the outputs of proportional regulator 60 and integral regulator 61 and outputs the sum as the output value after proportional adjustment and integral adjustment.

[0083] The upper and lower limit limiting unit 62 imposes upper and lower limits on the output value from the adder. In the upper and lower limit limiting unit 62, the upper limit value is the "upper limit value of the maximum current Imax" and the lower limit value is "0".

[0084] The upper and lower limit limiting unit 62 calculates the adjusted maximum current Imax_adj by performing upper and lower limit limits using the upper and lower limit values.

[0085] Specifically, when the output value from the adder is equal to or less than the upper limit value and equal to or greater than the lower limit value, the upper / lower limit limiting unit 62 outputs the output value from the adder as is as the adjusted maximum current Imax_adj.

[0086] On the other hand, if the output value from the adder is greater than the upper limit, the upper / lower limit limiting unit 62 outputs the upper limit as the adjusted maximum current Imax_adj. If the output value from the adder is less than the lower limit, the upper / lower limit limiting unit 62 outputs the lower limit as the adjusted maximum current Imax_adj.

[0087] FIG. 9 is a graph showing a first example of the relationship between input and output in maximum current adjustment unit 81 of FIG. 7, with the upper part of FIG. 9 showing the input state and the lower part of FIG. 9 showing the output state. FIG. 9 also shows a case where DC power deviation ΔPdc is positive. FIG. 10 is a graph showing a second example of the relationship between input and output in maximum current adjustment unit 81 of FIG. 7, with the upper part of FIG. 10 showing the input state and the lower part of FIG. 10 showing the output state. FIG. 10 also shows a case where DC power deviation ΔPdc is negative.

[0088] The initial value of the maximum current Imax_adj, which is the output, is the upper limit of the maximum current Imax, and is, for example, 1000A.

[0089] First, consider the case where the DC power deviation ΔPdc shown in Fig. 9 is positive. Because the DC power value is smaller than the DC power limit value, the output of proportional regulator 60 is positive, the output of integral regulator 61 is also positive, and the output of upper / lower limiter 62 increases. As a result, the adjusted maximum current Imax_adj continues to be added, and upper / lower limiter 62 outputs the upper limit value of 1000 A as the adjusted maximum current Imax_adj.

[0090] Next, consider the case where the DC power deviation ΔPdc shown in Fig. 10 is negative. Because the DC power value is greater than the DC power limit value, the output of proportional regulator 60 becomes negative, the output of integral regulator 61 also becomes negative, and the output of upper / lower limit limiter 62 decreases. As a result, the adjusted maximum current Imax_adj continues to be subtracted, and the output of upper / lower limit limiter 62 becomes a value reduced from the upper limit value of 1000 A.

[0091] In this case, if the current when the DC power value reaches the DC power limit value is 500 A, the value input to the upper / lower limiting unit 62 decreases until the maximum current Imax reaches 500 A. When the current settles at 500 A, the DC power value and the DC power limit value are balanced, and the DC power deviation ΔPdc becomes 0. As a result, the adjusted maximum current Imax_adj continues to be feedback-controlled to become the current of the DC power limit value, and 500 A is output from the upper / lower limiting unit 62 as the adjusted maximum current Imax_adj.

[0092] In the example of Fig. 8, the upper limit value is set to the "upper limit value of the maximum current Imax," so the adjusted maximum current Imax_adj will not exceed the "upper limit value of the maximum current Imax." In addition, the lower limit value is set to "0," so the adjusted maximum current Imax_adj is prevented from becoming a negative value.

[0093] The configuration of the maximum current adjusting unit 81 is not limited to the example shown in FIG. 8, and the maximum current Imax flowing through the AC rotary electric machine 30 may be adjusted by other methods.

[0094] <Allowable torque calculation section> Next, the allowable torque calculation unit 82 in Fig. 7 will be described. The allowable torque calculation unit 82 first calculates the maximum voltage Vmax using the DC voltage Vdc detected by the voltage detector 11 and a preset maximum modulation factor MFmax according to the following calculation formula.

[0095]

number

[0096] Next, the allowable torque calculation unit 82 calculates the maximum interlinkage magnetic flux FLmax using the maximum voltage Vmax and the electrical angular velocity ω detected by the electrical angular velocity calculation unit 50 according to the following calculation formula.

[0097] FLmax=Vmax÷ω

[0098] Furthermore, the allowable torque calculation unit 82 calculates the upper limit Ctrq_alw_upper and lower limit Ctrq_alw_lower of the allowable torque Ctrq_alw based on the maximum flux linkage FLmax and the adjusted maximum current Imax_adj input from the maximum current adjustment unit 81.

[0099] Fig. 11 is a table showing an example of a method for calculating the upper limit value Ctrq_alw_upper of the allowable torque in the allowable torque calculation unit 82 in Fig. 7. Fig. 12 is a table showing an example of a method for calculating the lower limit value Ctrq_alw_lower of the allowable torque in the allowable torque calculation unit 82 in Fig. 7.

[0100] 11 and 12, the horizontal axis represents the maximum flux linkage FLmax, and the vertical axis represents the adjusted maximum current Imax_adj. The allowable torque calculation unit 82 determines the upper limit Ctrq_alw_upper and lower limit Ctrq_alw_lower of the allowable torque, for example, using the tables shown in FIGS.

[0101] The upper limit value Ctrq_alw_upper and lower limit value Ctrq_alw_lower of the allowable torque calculated by the allowable torque calculation unit 82 are input to the torque command calculation unit 83, which then sets the torque command value Ctrq.

[0102] <Torque command calculation unit> The torque command calculation unit 83 sets the value of the adjusted torque command value Ctrq as shown in the following (1) to (3).

[0103] (1) When the torque command value is greater than the upper limit of the allowable torque: →Ctrq=Ctrq_alw_upper (2) When the upper limit of the allowable torque is greater than or equal to the torque command value and the lower limit of the allowable torque is greater than or equal to the torque command value: →Ctrq=Ctrq (3) When the torque command value is less than the lower limit of the allowable torque: →Ctrq=Ctrq_alw_lower

[0104] In this way, the adjusted torque command value Ctrq is set by the torque command calculation unit 83. Thereafter, the adjusted torque command value Ctrq is passed from the torque command calculation unit 83 to the current command calculation unit 41 of the inverter control device 40.

[0105] <Operation of the overheat protection control device> Next, the flow of operation in the overheat protection controller 70 will be described with reference to Fig. 13 and Fig. 14. Fig. 13 is a flowchart showing the first half of the operation of the overheat protection controller 70 in Fig. 1. Fig. 14 is a flowchart showing the second half of the operation of the overheat protection controller 70 in Fig. 1.

[0106] The operation of FIG. 13 is called at regular intervals in step S100. When the operation of FIG. 13 starts, the overheat protection controller 70 acquires the first determination output value Pdc_1 set in the first determination output value setting unit 72 in step S101. Next, the overheat protection controller 70 acquires the non-limit DC power limit value Pdc_N_Re in step S102. The non-limit DC power limit value Pdc_N_Re is the maximum DC power allowable in the inverter 20. Furthermore, the overheat protection controller 70 acquires water temperature information from the water temperature detector 80 in step S103.

[0107] Thereafter, in step S104, the overheat protection controller 70 acquires the restricted DC power limit value Pdc_Re based on the acquired water temperature information. Next, in step S105, the overheat protection controller 70 acquires the DC current Idc. Furthermore, in step S106, the overheat protection controller 70 acquires the DC voltage Vdc.

[0108] Thereafter, in step S107, the overheat protection controller 70 calculates the DC power Pdc. Then, in step S108, the overheat protection controller 70 performs low-pass filtering on the acquired water temperature information and the calculated DC power Pdc. Furthermore, in step S109, the overheat protection controller 70 calculates a first determination heat quantity equivalent value N_1.

[0109] Next, in step S110, the overheat protection controller 70 compares the DC power Pdc obtained in the process of step S107 with the first determination output value Pdc_1 obtained in the process of step S101.

[0110] If the DC power Pdc is equal to or greater than the first determination output value Pdc_1, in step S111, the overheat protection controller 70 calculates a current-squared-time product value N. The current-squared-time product value N is a value obtained by multiplying the square of the DC current Idc acquired in the process of step S105 by time.

[0111] After calculating the current squared time product value N, the overheat protection controller 70 adds the current squared time product value N calculated in the process of step S111 to the previous heat quantity equivalent value in step S112.

[0112] On the other hand, if the DC power Pdc is less than the first judgment output value Pdc_1, in step S113, the overheat protection control device 70 calculates the subtraction value N_dec based on the water temperature obtained by the processing of step S103 and the DC power Pdc calculated by the processing of step S107.

[0113] After calculating the subtraction value N_dec, the overheat protection controller 70 subtracts the subtraction value N_dec calculated in the process of step S113 from the previous heat quantity equivalent value in step S114.

[0114] Next, in step S115, the overheat protection controller 70 acquires the heat dissipation amount set value. Furthermore, in step S116, the overheat protection controller 70 subtracts the heat dissipation amount set value acquired in the process of step S115 from the heat amount equivalent value acquired in the process of step S112 or the process of step S114 to calculate a second judgment heat amount equivalent value N_2. Thereafter, the overheat protection controller 70 proceeds to the process of step S117 in FIG. 14.

[0115] Next, in step S117 of FIG. 14, the overheat protection controller 70 compares the heat quantity equivalent value calculated in the process of step S112 or the process of step S114 with the first judgment heat quantity equivalent value N_1 acquired in the process of step S109.

[0116] If the heat quantity equivalent value is equal to or greater than the first determination heat quantity equivalent value N_1, the overheat protection controller 70 determines in step S118 whether the protection flag is 1. If the protection flag is 1, the overheat protection controller 70 proceeds to the processing of step S125.

[0117] If the protection flag is "0", the overheat protection controller 70 sets the protection flag to "1" in step S119. Furthermore, the overheat protection controller 70 fixes the second judgment heat quantity equivalent value N_2 in step S120, and proceeds to the processing of step S125.

[0118] On the other hand, if the heat quantity equivalent value is smaller than the first judgment heat quantity equivalent value N_1, in step S121, the overheating protection control device 70 compares the heat quantity equivalent value calculated by the processing of step S112 or the processing of step S114 with the second judgment heat quantity equivalent value N_2 obtained by the processing of step S116.

[0119] If the heat quantity equivalent value is equal to or less than the second judgment heat quantity equivalent value N_2, the overheat protection controller 70 sets the protection flag to 0 in step S122. Furthermore, in step S123, the overheat protection controller 70 releases the second judgment heat quantity equivalent value N_2 from being fixed, and proceeds to the processing of step S125.

[0120] On the other hand, if the heat quantity equivalent value is greater than the second judgment heat quantity equivalent value N_2, the overheat protection controller 70 holds the previous protection flag in step S124, and proceeds to the processing of step S125.

[0121] Next, in step S125, the overheat protection controller 70 determines whether the protection flag is "1".

[0122] If the protection flag is "1", in step S126 the overheat protection controller 70 sets the DC power limit value to the limiting DC power limit value Pdc_Re acquired in the process of step S104, and limits the output.

[0123] If the protection flag is "0", in step S127, the overheat protection controller 70 sets the DC power limit value to the non-limit DC power limit value Pdc_N_Re acquired in the process of step S102, and does not limit the output.

[0124] Thereafter, in step S128, the overheat protection controller 70 substitutes the current equivalent heat value for the previous equivalent heat value, and updates the equivalent heat value information to the latest value.

[0125] Through such operations, the inverter 20 is controlled to have an overheat protection function for the monitored components. The processes in Figures 13 and 14 are repeatedly executed every fixed time Δt. Δt may be, for example, the processing cycle of a microcomputer. The shorter the processing cycle Δt, the more frequently the heat equivalent value is updated, allowing for more accurate temperature estimation.

[0126] Next, a data acquisition method in the overheat protection control device 70 will be described.

[0127] <Current squared time product value N> The current squared time product value N corresponds to the amount of heat generated, and a value proportional to the square of the DC current Idc is calculated for each time Δt during current detection. Similar to the commonly known concept of Joule heat, the amount of heat generated naturally increases as the current increases and the longer the current flows. In addition, the amount of heat generated decreases as the current decreases and the shorter the current flows.

[0128] <First judgment heat quantity equivalent value N_1> The first determination heat quantity equivalent value N_1 corresponds to the temperature at which overheat protection is performed, and is a value determined based on a value obtained by performing low-pass filtering on one or more of the water temperature, DC power, rotation speed, and AC current.

[0129] Fig. 15 is a table showing an example of the relationship between water temperature, DC power, and the first determination heat quantity equivalent value N_1. Fig. 16 is a graph showing the relationship between water temperature, DC power, and the first determination heat quantity equivalent value N_1 corresponding to Fig. 15.

[0130] 15 and 16 are values ​​determined based on data acquired in advance, and will vary depending on the product, usage environment, etc. In other words, the first judgment heat quantity equivalent value N_1 is not limited to the values ​​shown in FIGS.

[0131] First, consider the case where the water temperature changes. For example, if the water temperature is 25°C and the DC power is 15kW, the first determination heat quantity equivalent value N_1 is 15,000,000. If the water temperature is 65°C and the DC power is 15kW, the first determination heat quantity equivalent value N_1 is 4,000,000. If the water temperature is 85°C and the DC power is 15kW, the first determination heat quantity equivalent value N_1 is 0.

[0132] In this way, the higher the water temperature, the smaller the first judgment heat quantity equivalent value N_1 is set. Since the higher the water temperature, the higher the temperature of the monitored component will be even with the same heat generation amount, by reducing the first judgment heat quantity equivalent value N_1, the overheat protection temperature can be adjusted to a constant value. Also, if the first judgment heat quantity equivalent value N_1 is 0, output above the first judgment output value is limited.

[0133] If the water temperature is other than a preset temperature, the first determined heat quantity equivalent value N_1 is calculated by linear interpolation between two preset water temperatures. For example, if the water temperature is 75°C and the DC power is 15kW, the value at a water temperature of 65°C and DC power of 15kW and the value at a water temperature of 85°C and DC power of 15kW are linearly interpolated to obtain the first determined heat quantity equivalent value N_1 of 2,000,000.

[0134] Next, consider the case where the DC power changes. For example, when the water temperature is 25°C and the DC power is 15kW, the first determined heat quantity equivalent value N_1 is 15,000,000. When the water temperature is 25°C and the DC power is 19kW, the first determined heat quantity equivalent value N_1 is 7,500,000. When the water temperature is 25°C and the DC power is 20kW, the first determined heat quantity equivalent value N_1 is 6,100,000.

[0135] In this way, the higher the DC power, the smaller the first judgment heat quantity equivalent value N_1 is set to. Since the higher the DC power, the higher the temperature of the monitored components will be even at the same water temperature, by reducing the first judgment heat quantity equivalent value N_1, the overheat protection temperature can be adjusted to a constant value.

[0136] If the DC power value is other than a preset value, linear interpolation is performed between two preset DC power points to calculate the first determined heat quantity equivalent value N_1. For example, if the water temperature is 25°C and the DC power is 19.5kW, linear interpolation is performed between the value at a water temperature of 25°C and DC power of 19kW and the value at a water temperature of 25°C and DC power of 20kW, and the first determined heat quantity equivalent value N_1 is calculated as 6,800,000.

[0137] <Second judgment heat quantity equivalent value N_2> The second judgment heat quantity equivalent value N_2 corresponds to the temperature at which overheat protection is released, and is a heat quantity equivalent value obtained by subtracting the heat quantity setting value obtained in advance from the heat quantity equivalent value calculated by the heat quantity calculation unit 75 when the heat quantity equivalent value becomes equal to or greater than the first judgment heat quantity equivalent value N_1.

[0138] The second judgment heat quantity equivalent value N_2 is fixed from the time when the heat quantity equivalent value calculated by the heat quantity calculation unit 75 becomes equal to or greater than the first judgment heat quantity equivalent value N_1 until the heat quantity equivalent value calculated by the heat quantity calculation unit 75 becomes equal to or less than the second judgment heat quantity equivalent value N_2.

[0139] The heat radiation amount setting value, that is, the heat radiation amount equivalent value, is subtracted from the heat amount equivalent value calculated by the heat amount calculation unit 75, thereby suppressing the temperature of the monitored component to a temperature equal to or lower than the overheat protection temperature.

[0140] <Subtraction value N_dec> The subtraction value N_dec corresponds to the temperature decrease and is a value determined by the water temperature and the DC power. Each of the water temperature and the DC power may be a value that has been subjected to low-pass filtering.

[0141] Fig. 17 is a table showing an example of the relationship between water temperature, DC power, and subtraction value N_dec. Fig. 18 is a graph showing the relationship between water temperature, DC power, and subtraction value N_dec corresponding to Fig. 17.

[0142] 17 and 18 are values ​​determined based on data acquired in advance, and will vary depending on the product, usage environment, etc. In other words, the subtraction value N_dec is not limited to the values ​​shown in FIGS.

[0143] 17 and 18 is a value assuming that processing is performed every 10 ms, for example. In this case, if the actual processing period is 1 ms, the subtraction value N_dec used is one-tenth of the value shown in FIGS. 17 and 18.

[0144] When obtaining the data shown in Figures 17 and 18, the time it takes for the temperature to drop from a first temperature to a second temperature that is lower than the first temperature is measured, and the first temperature and the second temperature are converted into equivalent heat values ​​to calculate the subtraction value N_dec per hour.

[0145] FIG. 19 is a graph showing the results of measuring the change over time in temperature of the conductor connected to inverter 20 in FIG. 1 at high water temperature and at low water temperature.

[0146] When the water temperature is low, the time required for the conductor temperature to rise from the first temperature TA to the second temperature TB is tB - tA. On the other hand, when the water temperature is high, the temperature does not drop as easily, so the time required for the conductor temperature to rise from the first temperature TA to the second temperature TB is tC - tA, which is longer than when the water temperature is low.

[0147] The subtraction value N_dec per unit time can be calculated by converting the temperature into a value equivalent to the amount of heat from the relationship shown in Figure 4. The calculated subtraction value N_dec will be smaller when the water temperature is high than when the water temperature is low.

[0148] First, consider the case where the water temperature changes. For example, if the water temperature is 25°C and the DC power is 0kW, the subtraction value N_dec is 120. If the water temperature is 65°C and the DC power is 0kW, the subtraction value N_dec is 75. If the water temperature is 85°C or higher and the DC power is 0kW, the subtraction value N_dec is 0.

[0149] In this way, the higher the water temperature, the smaller the subtraction value N_dec. The higher the water temperature, the more difficult it is for the temperature of the monitored component to decrease even with the same amount of heat generated, so by making the subtraction value N_dec smaller, it is possible to simulate temperature transitions that correspond to changes over time. Conversely, the lower the water temperature, the more likely it is for the temperature of the monitored component to decrease even with the same amount of heat generated, so by making the subtraction value N_dec larger, it is possible to simulate temperature transitions that correspond to changes over time.

[0150] If the water temperature is other than a preset temperature, the subtraction value N_dec is calculated by linear interpolation between two water temperatures. For example, if the water temperature is 75°C and the DC power is 0kW, the subtraction value N_dec is calculated as 37.5 by linearly interpolating the value at a water temperature of 65°C and DC power of 0kW and the value at a water temperature of 85°C and DC power of 0kW.

[0151] Next, consider the case where the DC power changes. For example, if the water temperature is 25°C and the DC power is 0kW, the subtraction value N_dec is 120. If the water temperature is 25°C and the DC power is 10kW, the subtraction value N_dec is 70. If the water temperature is 25°C and the DC power is 13kW, the subtraction value N_dec is 0.

[0152] In this way, the higher the DC power, the smaller the subtraction value N_dec is set. The higher the DC power, the greater the amount of heat generated and the more difficult it is for the temperature of the monitored components to decrease; therefore, by setting the subtraction value to a smaller value, it is possible to simulate temperature transitions that correspond to changes over time. Conversely, the lower the DC power, the smaller the amount of heat generated and the more easily the temperature of the monitored components decreases; therefore, by setting the subtraction value to a larger value, it is possible to simulate temperature transitions that correspond to changes over time.

[0153] If the DC power value is other than a preset value, the subtraction value N_dec is calculated by linear interpolation between the DC power at two preset points. For example, if the water temperature is 25°C and the DC power is 11.5kW, the subtraction value N_dec is calculated as 35 by linear interpolation between the value at a water temperature of 25°C and a DC power of 10kW and the value at a water temperature of 25°C and a DC power of 13kW.

[0154] <DC power limit value during limit Pdc_Re> The restricted DC power limit value Pdc_Re corresponds to the maximum output and is a value determined by the water temperature.

[0155] Fig. 20 is a table showing an example of the relationship between the water temperature and the limiting DC power limit value Pdc_Re. Fig. 21 is a graph showing the relationship between the water temperature and the limiting DC power limit value Pdc_Re corresponding to Fig. 20.

[0156] 20 and 21 are values ​​determined based on data acquired in advance, and will vary depending on the product, usage environment, etc. In other words, the DC power limit value Pdc_Re during limiting is not limited to the values ​​shown in FIGS.

[0157] For example, when the water temperature is 25°C, the DC power limit value Pdc_Re during limiting is 12 kW. When the water temperature is 65°C, the DC power limit value Pdc_Re during limiting is 8 kW. When the water temperature is 85°C, the DC power limit value Pdc_Re during limiting is 0 kW.

[0158] In this way, the higher the water temperature, the smaller the DC power limit value during limit Pdc_Re is set. The higher the water temperature, the higher the temperature of the monitored components will be even with the same amount of heat generation. Therefore, by reducing the DC power limit value during limit Pdc_Re, the temperature of the monitored components can be kept within the overheat protection temperature. Also, when the DC power limit value during limit Pdc_Re is 0 kW, the amount of heat generation cannot be increased any further, so output is limited to 0 kW.

[0159] If the water temperature is not a preset temperature, the limiting DC power limit value Pdc_Re is calculated by linear interpolation between two preset water temperatures. For example, if the water temperature is 75°C, the limiting DC power limit value Pdc_Re is calculated as 4 kW by linearly interpolating the value at a water temperature of 65°C and the value at a water temperature of 85°C.

[0160] <Timing chart> 22 is a timing chart showing the overheat protection operation according to embodiment 1. The overheat protection operation and the overheat protection cancellation operation will be described below with reference to FIG.

[0161] In Fig. 22(a), the horizontal axis represents time and the vertical axis represents the DC power command value. In Fig. 22(a), the first determination output value Pdc_1 and the DC power limit value during limiting Pdc_Re are also shown.

[0162] In Fig. 22(b), the horizontal axis represents time and the vertical axis represents DC power. In Fig. 22(b), the first judgment output value Pdc_1 and the DC power limit value during limiting Pdc_Re are also plotted.

[0163] In Fig. 22(c), the horizontal axis represents time and the vertical axis represents DC current. Fig. 22(c) also shows the current Pdc_1 / Vdc at the first determination output value Pdc_1 and the current Pdc_Re / Vdc at the limit-time DC power limit value Pdc_Re when the DC voltage is Vdc.

[0164] In Fig. 22(d), the horizontal axis represents time, and the vertical axis represents the heat quantity equivalent value. Fig. 22(d) also shows the heat quantity equivalent value, the first determination heat quantity equivalent value N_1, and the second determination heat quantity equivalent value N_2.

[0165] In Fig. 22(e), the horizontal axis represents time and the vertical axis represents the DC power limit value. Fig. 22(e) also shows the non-limit DC power limit value Pdc_N_Re and the limit DC power limit value Pdc_Re.

[0166] In FIG. 22(f), the horizontal axis indicates time, and the vertical axis indicates the overheat protection flag.

[0167] For example, if the initial heat quantity equivalent value is 0, the DC power is equal to or less than the first determination output value Pdc_1 in the section t0 to t1, so no heat quantity equivalent value is added and the heat quantity equivalent value at time t1 is 0.

[0168] In the section t1 to t2, the DC power is equal to or greater than the first judgment output value Pdc_1, so a value equivalent to the amount of heat is added. The current squared time product value N, which is the added value at this time, is expressed as N=Idc 2 t2-t1 × (t2-t1), and the heat equivalent value at time t2 is Idc 2 t2-t1 ×(t2-t1).

[0169] In the section t2 to t3, the DC power is equal to or less than the first determination output value Pdc_1, so the value equivalent to the amount of heat is subtracted. At this time, the subtraction value is N_dec t2-t3 And the heat equivalent value at time t3 is Idc 2 t2-t1 ×(t2-t1)-N_dec t2-t3×(t3-t2).

[0170] In the section t3 to t4, the DC power is equal to or greater than the first judgment output value Pdc_1, so a value equivalent to the amount of heat is added. The current squared time product value N, which is the added value at this time, is expressed as N=Idc 2 t4-t3 × (t4-t3). The heat equivalent value at time t4 is Idc 2 t2-t1 ×(t2-t1)-N_dec t2-t3 ×(t3-t2)+Idc 2 t4-t3 ×(t4-t3).

[0171] As the condition for adding the heat quantity equivalent value continues, the heat quantity equivalent value at time t4 reaches the first determination heat quantity equivalent value N_1, and the overheat protection flag switches from "0" to "1." In addition, the second determination heat quantity equivalent value N_2 is fixed at the timing when the overheat protection flag switches to "1." When the overheat protection flag becomes "1," the DC power command unit 78 restricts the DC power limit value from the non-restricted DC power limit value Pdc_N_Re to the restricted DC power limit value Pdc_Re.

[0172] At this time, the restricted DC power limit value Pdc_Re is set with reference to Fig. 20. However, the DC power limit value is gradually reduced over a fixed time from the non-restricted DC power limit value Pdc_N_Re to the restricted DC power limit value Pdc_Re, as shown in Fig. 6. As a result, the DC power command value and DC power also gradually decrease along with the DC power limit value.

[0173] However, even after the output is limited, in the section t4 to t5, the DC power is equal to or greater than the first judgment output value Pdc_1, so the heat quantity equivalent value is added. At this time, the DC power is changing, and when the DC voltage Vdc is constant, Idc t5-t4 changes.

[0174] For the sake of simplicity, let us take the average value of the DC current between t4 and t5 as Idc t5-t4 Then, the added value is N=Idc 2 t5-t4× (t5-t4). The heat equivalent value at time t5 is Idc 2 t2-t1 ×(t2-t1)-N_dec t2-t3 ×(t3-t2)+Idc 2 t4-t3 ×(t4-t3)+Idc 2 t5-t4 ×(t5-t4).

[0175] In the section t5 to t6, the output is limited, and the DC power continues to gradually decrease according to the DC power limit value until it becomes equal to or less than the first determination output value Pdc_1. Therefore, the heat quantity equivalent value is subtracted. At this time, the subtraction value N_dec is N_dec with reference to FIG. t5-t6 This becomes:

[0176] In the section t6 to t7, the DC power is limited to the DC power limit value Pdc_Re during limiting, and is equal to or less than the first judgment output value Pdc_1. Therefore, the heat quantity equivalent value is subtracted. The subtraction value N_dec at this time is N_dec with reference to FIG. t6-t7 And the heat equivalent value at time t7 is Idc 2 t2-t1 ×(t2-t1)-N_dec t2-t3 ×(t3-t2)+Idc 2 t4-t3 ×(t4-t3)+Idc 2 t5-t4 ×(t5-t4)-N_dec t5-t6 ×(t6-t5)-N_dec t6-t7 ×(t7-t6).

[0177] In the section t7 to t8, the DC power command value is smaller than the DC power limit value Pdc_Re during limiting, and the value of the DC power is also smaller than the DC power limit value Pdc_Re during limiting. Since the DC power is equal to or smaller than the first judgment output value Pdc_1, a value equivalent to the amount of heat is subtracted. The subtraction value N_dec at this time is N_dec with reference to FIG. 17. t7-t8 In the section t7 to t8, the DC power is smaller than in the section t6 to t7, and therefore the subtraction value is smaller.

[0178] And the heat equivalent value at time t8 is Idc 2 t2-t1 ×(t2-t1)-N_dec t2-t3 ×(t3-t2)+Idc 2 t4-t3 ×(t4-t3)+Idc 2 t5-t4 ×(t5-t4)-N_dec t5-t6 ×(t6-t5)-N_dec t6-t7 ×(t7-t6)-N_dec t7-t8 ×(t8-t7).

[0179] As the condition for subtracting the heat quantity equivalent value continues, the heat quantity equivalent value at time t8 reaches the second determination heat quantity equivalent value N_2, and the overheat protection flag switches from "1" to "0." Also, the second determination heat quantity equivalent value N_2 is released from its fixed state at the timing when the overheat protection flag switches to "0." When the overheat protection flag becomes "0," the DC power command unit 78 releases the DC power limit value from the limited DC power limit value Pdc_Re to the non-limited DC power limit value Pdc_N_Re.

[0180] At this time, the DC power limit value is the non-limiting DC power limit value Pdc_N_Re t8 By switching the DC power limit value, the DC power limit value becomes the non-limit DC power limit value Pdc_N_Re t8 5, the DC power command value and the DC power are gradually increased in accordance with the DC power limit value.

[0181] In the section t8 to t9, the output limitation is released, and the DC power gradually increases according to the DC power limit value, but since it is equal to or less than the first determination output value Pdc_1, the value equivalent to the amount of heat is subtracted. The subtraction value N_dec at this time is N_dec with reference to FIG. t8-t9 This becomes:

[0182] And the heat equivalent value at time t9 is Idc 2 t2-t1 ×(t2-t1)-N_dec t2-t3 ×(t3-t2)+Idc2 t4-t3 ×(t4-t3)+Idc 2 t5-t4 ×(t5-t4)-N_dec t5-t6 ×(t6-t5)-N_dec t6-t7 ×(t7-t6)-N_dec t7-t8 ×(t8-t7)-N_dec t8-t9 ×(t9-t8).

[0183] In the section t9 to t10, the DC power again becomes equal to or greater than the first judgment output value Pdc_1, and the heat quantity equivalent value is added. The current squared time product value N, which is the added value at this time, is calculated by averaging the DC current in the section t9 to t10. t10-t9 Then, N=Idc 2 t10-t9 ×(t10-t9).

[0184] And the heat equivalent value at time t10 is Idc 2 t2-t1 ×(t2-t1)-N_dec t2-t3 ×(t3-t2)+Idc 2 t4-t3 ×(t4-t3)+Idc 2 t5-t4 ×(t5-t4)-N_dec t5-t6 ×(t6-t5)-N_dec t6-t7 ×(t7-t6)-N_dec t7-t8 ×(t8-t7)-N_dec t8-t9 ×(t9-t8)+Idc 2 t10-t9 ×(t10-t9).

[0185] In the overheat protection control device 70, when the value of the DC power is equal to or greater than the first determination output value Pdc_1, the heat quantity calculation unit 75 adds the current squared time product value N calculated by the current squared time product calculation unit 73 to the previous heat quantity equivalent value. When the value of the DC power is less than the first determination output value Pdc_1, the heat quantity calculation unit 75 calculates the current heat quantity equivalent value by subtracting the subtraction value N_dec acquired by the subtraction value acquisition unit 74 from the previous heat quantity equivalent value.

[0186] Furthermore, when the heat quantity equivalent value calculated by the heat quantity calculation unit 75 becomes equal to or greater than the first judgment heat quantity equivalent value N_1, the DC power command unit 78 limits the DC power in the inverter 20. Furthermore, when the heat quantity equivalent value calculated by the heat quantity calculation unit 75 becomes equal to or less than the second judgment heat quantity equivalent value N_2, the DC power command unit 78 releases the limit on the DC power in the inverter 20.

[0187] Therefore, even when overheat protection is performed on the monitored components, the operation of the inverter 20 is not stopped. This makes it possible to prevent excessive protection of the inverter 20 and to prevent a decrease in the operating efficiency of the inverter 20.

[0188] The second determination heat quantity equivalent value N_2 is a heat quantity equivalent value obtained by subtracting the heat radiation amount setting value from the heat quantity equivalent value at the start of power limiting. The second determination heat quantity equivalent value N_2 is fixed from the time when the heat quantity equivalent value calculated by the heat quantity calculation unit 75 becomes equal to or greater than the first determination heat quantity equivalent value N_1 until the heat quantity equivalent value calculated by the heat quantity calculation unit 75 becomes equal to or less than the second determination heat quantity equivalent value N_2. In other words, the second determination heat quantity equivalent value N_2 is fixed from the time when power limiting starts until the limiting is lifted.

[0189] Therefore, even if power drops due to the start of power limiting, the power limiting can be released at the expected timing, and the limiting will be maintained until the monitored components drop below the overheat protection temperature, more reliably preventing failure of the monitored components.

[0190] The first heat quantity equivalent value N_1 is a heat quantity equivalent value that changes depending on the values ​​obtained by applying low-pass filtering to the water temperature and DC power, respectively. Therefore, even if the water temperature and DC power contain noise components, the temperature of the monitored components is limited to the overheat protection temperature, thereby more reliably preventing failure of the monitored components.

[0191] The second heat quantity equivalent value N_2 is set to the value obtained by subtracting the heat dissipation setting value from the heat quantity equivalent value at the start of power limitation. This makes it possible to more reliably keep the temperature of the monitored component below the overheat protection temperature.

[0192] Embodiment 2 Next, Fig. 23 is a block diagram showing the main parts of an overheat protection control device 70 according to embodiment 2. In embodiment 2, the method of setting the first determination heat quantity equivalent value N_1 by the first determination heat quantity equivalent value setting unit 76 is changed from embodiment 1. Since the rest is the same as embodiment 1, only the parts that are different from embodiment 1 will be described.

[0193] The first judgment heat quantity equivalent value N_1 in the second embodiment is a heat quantity equivalent value that changes in accordance with values ​​obtained by performing low-pass filtering on the water temperature and DC power, respectively, and the rotation speed of the AC rotary electric machine 30.

[0194] 23, in the second embodiment, the rotation speed ω is input to the first determination heat quantity equivalent value setting unit 76. A value that has been subjected to low-pass filtering may be used as the rotation speed ω.

[0195] Fig. 24 is a graph showing an example of the relationship between the rotation speed and the AC current. Fig. 25 is a graph showing an example of the relationship between the rotation speed and the first judgment heat quantity equivalent value N_1.

[0196] For example, at a rotation speed up to the shoulder of the TN characteristic, if the DC power, DC voltage, DC current, and water temperature are all constant, the AC current decreases as the rotation speed increases. When the AC current decreases, the amount of heat generated on the AC side decreases. If the heat generated on the AC side affects the DC side, an increase in the rotation speed will lower the temperature on the DC side. Therefore, the higher the rotation speed, the lower the temperature of the monitored components will be even with the same water temperature and power. Therefore, by increasing the first judgment heat equivalent value N_1, the overheat protection temperature can be adjusted to a constant value.

[0197] In this way, even when the first judgment heat quantity equivalent value N_1 is a heat quantity equivalent value that changes depending on the rotation speed ω, the same effects as those of the first embodiment can be obtained.

[0198] Embodiment 3 Next, Fig. 26 is a block diagram showing the main parts of an overheat protection control device 70 according to embodiment 3. In embodiment 3, the method of setting the first determination heat quantity equivalent value N_1 by the first determination heat quantity equivalent value setting unit 76 is changed from embodiment 1. Since the rest is the same as embodiment 1, only the parts that are different from embodiment 1 will be described.

[0199] The first determination heat quantity equivalent value N_1 in the third embodiment is a heat quantity equivalent value that changes in accordance with values ​​obtained by performing low-pass filtering on the water temperature and DC power, and the AC current.

[0200] 26, in the third embodiment, an AC current, i.e., a phase current effective value, is input to the first determination heat quantity equivalent value setting unit 76 in the first embodiment. A value that has been subjected to low-pass filtering may be used as the phase current effective value.

[0201] Fig. 27 is a graph showing an example of the relationship between AC current and DC current, and Fig. 28 is a graph showing an example of the relationship between AC current and the first judgment heat quantity equivalent value N_1.

[0202] When the DC voltage, water temperature, and rotation speed are constant, an increase in AC current also increases the DC current, and the amount of heat generated increases. Therefore, the higher the AC current, the higher the temperature of the monitored component will be, even at the same water temperature and rotation speed. Therefore, by reducing the first heat quantity equivalent value N_1, the overheat protection temperature can be adjusted to a constant value.

[0203] In this way, even when the first judgment heat quantity equivalent value N_1 is a heat quantity equivalent value that changes depending on the AC current, the same effects as those of the first embodiment can be obtained.

[0204] Embodiment 4 Next, Fig. 29 is a block diagram showing elements of an overheat protection control device 70 according to embodiment 4. In embodiment 4, the method of setting the second determination heat quantity equivalent value N_2 by the second determination heat quantity equivalent value setting unit 77 is changed from embodiment 1. Since the rest is the same as embodiment 1, only the parts that are different from embodiment 1 will be described.

[0205] In the fourth embodiment, a case will be described in which the second judgment heat quantity equivalent value N_2 is calculated using the first judgment heat quantity equivalent value N_1.

[0206] As shown in FIG. 29, in the fourth embodiment, the first judgment heat quantity equivalent value N_1 is input to the second judgment heat quantity equivalent value setting unit 77 in the first embodiment.

[0207] The second determination heat quantity equivalent value N_2 is set to a heat quantity equivalent value obtained by subtracting the heat radiation quantity set value from the first determination heat quantity equivalent value N_1 when the heat quantity equivalent value calculated by the heat quantity calculation unit 75 becomes equal to or greater than the first determination heat quantity equivalent value N_1. That is, the second determination heat quantity equivalent value N_2 is set to a heat quantity equivalent value obtained by subtracting the heat radiation quantity set value from the first determination heat quantity equivalent value N_1 at the start of limiting the current.

[0208] The second judgment heat quantity equivalent value N_2 is fixed from the time when the heat quantity equivalent value calculated by the heat quantity calculation unit 75 becomes equal to or greater than the first judgment heat quantity equivalent value N_1 until the heat quantity equivalent value calculated by the heat quantity calculation unit 75 becomes equal to or less than the second judgment heat quantity equivalent value N_2.

[0209] In this way, even when the second judgment heat quantity equivalent value N_2 is calculated using the first judgment heat quantity equivalent value N_1, the same effects as those of the first embodiment can be obtained.

[0210] Embodiment 5. Next, Fig. 30 is a block diagram showing elements of an overheat protection control device 70 according to embodiment 5. In embodiment 5, the method of setting the first determination heat quantity equivalent value N_1 by the first determination heat quantity equivalent value setting unit 76 is changed from embodiment 4. Since the rest is the same as embodiment 4, only the parts that are different from embodiment 4 will be described.

[0211] In the fifth embodiment, a case will be described in which the first judgment heat quantity equivalent value N_1 changes depending on the rotation speed ω of the AC rotary electric machine 30.

[0212] 30, in the fifth embodiment, the rotation speed ω is input to the first determination heat quantity equivalent value setting unit 76 in the fourth embodiment. A value that has been subjected to low-pass filtering may be used as the rotation speed ω.

[0213] As in the second embodiment, at a rotation speed up to the shoulder of the TN characteristic, if the DC power, DC voltage, DC current, and water temperature are all constant, the AC current decreases as the rotation speed increases. If the AC current decreases, the amount of heat generated on the AC side decreases. If the amount of heat generated on the AC side affects the DC side, an increase in the rotation speed will lower the temperature on the DC side. Therefore, the higher the rotation speed, the lower the temperature of the monitored component will be even at the same water temperature and power. Therefore, by increasing the first judgment heat quantity equivalent value N_1, the overheat protection temperature can be adjusted to a constant value.

[0214] Embodiment 6 Next, Fig. 31 is a block diagram showing the main parts of an overheat protection control device 70 according to embodiment 6. In embodiment 6, the method of setting the first determination heat quantity equivalent value N_1 by the first determination heat quantity equivalent value setting unit 76 is changed from embodiment 4. Since the rest is the same as embodiment 4, only the parts that are different from embodiment 4 will be described.

[0215] In the sixth embodiment, a case will be described in which the first judgment heat quantity equivalent value N_1 changes depending on the AC current.

[0216] 31, in the sixth embodiment, an AC current, i.e., a phase current effective value, is input to the first determination heat quantity equivalent value setting unit 76 in the fourth embodiment. A value that has been subjected to low-pass filtering may be used as the phase current effective value.

[0217] As in the third embodiment, when the DC voltage, water temperature, and rotation speed are constant, an increase in the AC current also increases the DC current, and the amount of heat generated increases. Therefore, the higher the AC current, the higher the temperature of the monitored component becomes even at the same water temperature and rotation speed. Therefore, by reducing the first judgment heat quantity equivalent value N_1, the overheat protection temperature can be adjusted to a constant value.

[0218] Embodiment 7 Next, Fig. 32 is a block diagram showing elements of an overheat protection control device 70 according to embodiment 7. In embodiment 7, the method of setting the second determination heat quantity equivalent value N_2 by the second determination heat quantity equivalent value setting unit 77 is changed from embodiment 1. Since the rest is the same as embodiment 1, only the parts that are different from embodiment 1 will be described.

[0219] The second determination heat quantity equivalent value N_2 in the seventh embodiment is set to a heat quantity equivalent value that changes depending on one or more of the water temperature, DC power, rotation speed, and AC current. Values ​​that have been subjected to low-pass filtering may be used as the water temperature, DC power, rotation speed, and AC current.

[0220] 32, in the seventh embodiment, the water temperature and DC power are input to the second determination heat quantity equivalent value setting unit 77 in the first embodiment. The second determination heat quantity equivalent value N_2 is fixed from the time when the heat quantity equivalent value calculated by the heat quantity calculation unit 75 becomes equal to or greater than the first determination heat quantity equivalent value N_1 until the heat quantity equivalent value calculated by the heat quantity calculation unit 75 becomes equal to or less than the second determination heat quantity equivalent value N_2.

[0221] Fig. 33 is a table showing an example of the relationship between water temperature, DC power, and the second determination heat quantity equivalent value N_2. Fig. 34 is a graph showing the relationship between water temperature, DC power, and the second determination heat quantity equivalent value N_2 corresponding to Fig. 33.

[0222] The values ​​shown in Figures 33 and 34 are determined based on data acquired in advance, and will vary depending on the product, usage environment, etc. In other words, the second judgment heat quantity equivalent value N_2 is not limited to the values ​​shown in Figures 33 and 34.

[0223] First, consider the case where the water temperature changes. For example, when the water temperature is 25°C and the DC power is 15kW, the second determination heat quantity equivalent value N_2 is 13,300,000. When the water temperature is 65°C and the DC power is 15kW, the second determination heat quantity equivalent value N_2 is 2,300,000. When the water temperature is 85°C and the DC power is 15kW, the second determination heat quantity equivalent value N_2 is 0.

[0224] In this way, the higher the water temperature, the smaller the second judgment heat quantity equivalent value N_2 is set. Since the higher the water temperature, the higher the temperature of the monitored component will be even if the heat generation amount is the same, by reducing the second judgment heat quantity equivalent value N_2, the temperature at which overheat protection is released can be adjusted to a constant value. Note that the temperature at which overheat protection is released can also be adjusted depending on the usage conditions.

[0225] If the water temperature is other than a preset temperature, the second determined heat quantity equivalent value N_2 is calculated by linear interpolation between two preset water temperatures. For example, if the water temperature is 75°C and the DC power is 15kW, the value at a water temperature of 65°C and DC power of 15kW and the value at a water temperature of 85°C and DC power of 15kW are linearly interpolated to obtain the second determined heat quantity equivalent value N_2 of 1,150,000.

[0226] Next, consider the case where the DC power changes. For example, when the water temperature is 25°C and the DC power is 15kW, the second determination heat quantity equivalent value N_2 is 13,300,000. When the water temperature is 25°C and the output is 19kW, the second determination heat quantity equivalent value N_2 is 5,800,000. When the water temperature is 25°C and the output is 20kW, the second determination heat quantity equivalent value N_2 is 4,400,000.

[0227] In this way, the higher the DC power, the smaller the second judgment heat quantity equivalent value N_2 is set to. Since the higher the DC power, the higher the temperature of the monitored components will be even at the same water temperature, by reducing the second judgment heat quantity equivalent value N_2, the temperature at which overheat protection is released can be adjusted to a constant value.

[0228] If the DC power value is other than a preset value, the second determined heat quantity equivalent value N_2 is calculated by linear interpolation between the DC power values ​​at two preset points. For example, if the water temperature is 25°C and the DC power is 19.5kW, the value at a water temperature of 25°C and DC power of 19kW and the value at a water temperature of 25°C and DC power of 20kW are linearly interpolated to obtain the second determined heat quantity equivalent value N_2 of 5,100,000.

[0229] In this way, even when the second judgment heat quantity equivalent value N_2 is set to a heat quantity equivalent value that changes depending on one or more of the water temperature, DC power, rotation speed, and AC current, the same effect as in embodiment 1 can be obtained.

[0230] Furthermore, if the second judgment heat quantity equivalent value N_2 is calculated based on a value obtained by applying low-pass filtering to one or more of the water temperature, DC power, rotation speed, and AC current, noise components can be removed, and overheat protection can be released at a more appropriate timing.

[0231] Embodiment 8 Next, Fig. 35 is a block diagram showing the main parts of an overheat protection control device 70 according to embodiment 8. In embodiment 8, the method of setting the first determination heat quantity equivalent value N_1 by the first determination heat quantity equivalent value setting unit 76 and the method of setting the second determination heat quantity equivalent value N_2 by the second determination heat quantity equivalent value setting unit 77 are changed compared to embodiment 7. As the rest is the same as embodiment 7, only the parts that differ from embodiment 7 will be described.

[0232] In the eighth embodiment, the first determination heat quantity equivalent value N_1 and the second determination heat quantity equivalent value N_2 change depending on the rotation speed ω of the AC rotating electric machine 30. A value that has been subjected to low-pass filtering may be used as the rotation speed ω.

[0233] As shown in FIG. 35, in the eighth embodiment, the rotation speed ω is input to a first determination heat quantity equivalent value setting unit 76 and a second determination heat quantity equivalent value setting unit 77, respectively.

[0234] FIG. 36 is a graph showing an example of the relationship between the rotation speed and the first determination heat quantity equivalent value N_1 and the second determination heat quantity equivalent value N_2.

[0235] As in the second embodiment, at a rotation speed up to the shoulder of the TN characteristic, if the DC power, DC voltage, DC current, and water temperature are all constant, the AC current decreases as the rotation speed increases. If the AC current decreases, the amount of heat generated on the AC side decreases. If the amount of heat generated on the AC side affects the DC side, an increase in the rotation speed will lower the temperature on the DC side. Therefore, the higher the rotation speed, the lower the temperature of the monitored component will be even at the same water temperature and power. Therefore, by increasing the first judgment heat quantity equivalent value N_1, the overheat protection temperature can be adjusted to a constant value.

[0236] The same can be said for the second judgment heat quantity equivalent value N_2. The higher the rotation speed, the lower the temperature of the monitored components will be, even with the same water temperature and power. Therefore, by increasing the second judgment heat quantity equivalent value N_2, the temperature at which overheat protection is released can be adjusted to a constant value. Note that it is also possible to adjust the temperature at which overheat protection is released depending on the usage conditions.

[0237] Embodiment 9 Next, Fig. 37 is a block diagram showing the main parts of an overheat protection control device 70 according to embodiment 9. In embodiment 9, the method of setting the first determination heat quantity equivalent value N_1 by the first determination heat quantity equivalent value setting unit 76 and the method of setting the second determination heat quantity equivalent value N_2 by the second determination heat quantity equivalent value setting unit 77 are changed compared to embodiment 7. As the rest is the same as embodiment 7, only the parts that differ from embodiment 7 will be described.

[0238] In the ninth embodiment, a case will be described in which the first determination heat quantity equivalent value N_1 and the second determination heat quantity equivalent value N_2 change depending on the AC current.

[0239] 37, in the ninth embodiment, an AC current, i.e., a phase current effective value, is input to the first determination heat quantity equivalent value setting unit 76 and the second determination heat quantity equivalent value setting unit 77 in the seventh embodiment. A value that has been subjected to low-pass filtering may be used as the phase current effective value.

[0240] FIG. 38 is a graph showing an example of the relationship between the AC current and the first and second determination heat quantity equivalent values ​​N_1 and N_2.

[0241] As in the third embodiment, when the DC voltage, water temperature, and rotation speed are constant, an increase in the AC current also increases the DC current, and the amount of heat generated increases. Therefore, the higher the AC current, the higher the temperature of the monitored component becomes even at the same water temperature and rotation speed. Therefore, by reducing the first judgment heat quantity equivalent value N_1, the overheat protection temperature can be adjusted to a constant value.

[0242] The same can be said for the second judgment heat quantity equivalent value N_2. The higher the AC current, the higher the temperature of the monitored components will be, even at the same water temperature and rotation speed. Therefore, by reducing the second judgment heat quantity equivalent value N_2, the temperature at which overheat protection is released can be adjusted to a constant value. Note that it is also possible to adjust the temperature at which overheat protection is released depending on the usage conditions.

[0243] In the first to ninth embodiments, the components to be monitored are those on the DC power supply 10 side of the inverter 20, that is, those on the DC side. However, the components to be monitored may also be those on the AC side.

[0244] Furthermore, the functions of the inverter control device 40 and the overheat protection control device 70 according to the first to ninth embodiments are realized by a processing circuit. Fig. 39 is a configuration diagram showing a first example of a processing circuit that realizes the functions of the inverter control device 40 and the overheat protection control device 70 according to the first to ninth embodiments. The processing circuit 100 of the first example is dedicated hardware.

[0245] The processing circuit 100 may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof. The functions of the inverter control device 40 and the overheat protection control device 70 may be realized by individual processing circuits 100, or the functions may be realized collectively by the processing circuit 100.

[0246] 40 is a configuration diagram showing a second example of a processing circuit that realizes each function of the inverter control device 40 and the overheat protection control device 70 according to the first to ninth embodiments. The processing circuit 200 of the second example includes a processor 201 and a memory 202.

[0247] In the processing circuit 200, each function of the inverter control device 40 and the overheat protection control device 70 is realized by software, firmware, or a combination of software and firmware. The software and firmware are written as programs and stored in the memory 202. The processor 201 realizes each function by reading and executing the programs stored in the memory 202.

[0248] It can also be said that the programs stored in memory 202 cause the computer to execute the procedures or methods of the above-mentioned sections. Here, memory 202 refers to non-volatile or volatile semiconductor memory, such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), and EEPROM (Electrically Erasable and Programmable Read Only Memory). Magnetic disks, flexible disks, optical disks, compact disks, minidisks, DVDs, and the like also fall under memory 202.

[0249] It should be noted that some of the functions of the above-described units may be realized by dedicated hardware, and other parts may be realized by software or firmware.

[0250] In this way, the processing circuit can realize the functions of each of the above-mentioned units by hardware, software, firmware, or a combination of these. [Explanation of symbols]

[0251] 10 DC power supply, 20 inverter (power converter), 30 AC rotating electric machine, 70 overheat protection control device, 71 DC power calculation unit, 75 heat quantity calculation unit, 77 second judgment heat quantity equivalent value setting unit, 78 DC power command unit.

Claims

1. a power calculation unit that calculates power in a power converter that is provided between the DC power supply and the AC rotating electric machine; a heat quantity calculation unit that calculates a heat quantity equivalent value based on the power calculated by the power calculation unit and a first determination output value that is a threshold value of the power; and a power command unit that controls the power in the power converter based on the heat quantity equivalent value calculated by the heat quantity calculation unit; Equipped with The heat quantity calculation unit If the power is equal to or greater than the first determination output value, a current squared time product value, which is a value obtained by multiplying the square of the current flowing between the DC power supply and the power converter by time, is added to the previous heat quantity equivalent value; If the electric power is less than the first determination output value, a subtraction value is subtracted from the previous heat quantity equivalent value; The power command unit limiting the power in the power converter when the heat quantity equivalent value calculated by the heat quantity calculation unit becomes equal to or greater than a first judgment heat quantity equivalent value; When the heat quantity equivalent value calculated by the heat quantity calculation unit becomes equal to or less than a second determination heat quantity equivalent value which is smaller than the first determination heat quantity equivalent value, the power limit in the power converter is lifted; The second determination heat quantity equivalent value is fixed from when the heat quantity equivalent value becomes equal to or greater than the first determination heat quantity equivalent value until the heat quantity equivalent value becomes equal to or less than the second determination heat quantity equivalent value. Overheat protection control device for power converters.

2. 2. The overheat protection control device for a power converter according to claim 1, wherein the first judgment heat quantity equivalent value is a heat quantity equivalent value that changes depending on a value obtained by performing low-pass filtering on one or more of the following: the water temperature of the cooling water of the power converter; the electric power calculated by the power calculation unit; the rotation speed of the AC rotating electric machine; and the AC current.

3. 2. The overheat protection control device for a power converter according to claim 1, wherein the second judgment heat quantity equivalent value is set to a value obtained by subtracting a heat quantity setting value, which is a value equivalent to the heat quantity of the monitored component, from the heat quantity equivalent value at the start of the power restriction.

4. 2. An overheat protection control device for a power converter as described in claim 1, wherein the second judgment heat quantity equivalent value is set to a value obtained by subtracting a heat dissipation setting value, which is a value equivalent to the heat dissipation amount of the monitored component, from the first judgment heat quantity equivalent value at the start of the power restriction.

5. 2. The overheat protection control device for a power converter according to claim 1, wherein the second judgment heat quantity equivalent value is calculated based on one or more of the temperature of the cooling water of the power converter, the power calculated by the power calculation unit, the rotation speed of the AC rotating electric machine, and the AC current at the start of the power restriction.

6. 6. The overheat protection control device for a power converter according to claim 5, wherein the second judgment heat quantity equivalent value is calculated based on a value obtained by performing low-pass filtering on one or more of the water temperature, the electric power, the rotation speed, and the AC current.

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