Power conversion apparatus and temperature control method

Abstract

To provide a power conversion apparatus capable of reducing thermal cycle fatigue of the power conversion apparatus, and a temperature control method.SOLUTION: A power conversion apparatus comprises an arithmetic section, a temperature adjustment device, and a temperature control section. The arithmetic section operates a heat generation amount prediction value of a semiconductor switching element with power conversion. The temperature adjustment device includes at least a heat generation source capable of adjusting a temperature in a periphery of the semiconductor switching element. The temperature control section controls the temperature adjustment device, through control using the heat generation amount prediction value, in such a manner that a temperature of the semiconductor switching element becomes a target temperature.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] FIELD An embodiment of the present invention relates to a power conversion device and a temperature control method. [Background technology]

[0002] When a semiconductor switching element of a power conversion device is switched, loss occurs and the semiconductor switching element generates heat. During operation of the power conversion device, a heat cycle occurs in which the operating environment changes from low to high temperatures, and there has been concern that this may cause heat cycle fatigue in the semiconductor switching element or in the solder joints of the semiconductor switching element. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-083135 A Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a power conversion device and a temperature control method capable of reducing thermal cycle fatigue of the power conversion device. [Means for solving the problem]

[0005] According to one embodiment, a power conversion device includes a calculation unit, a temperature adjustment device, and a temperature control unit. The calculation unit calculates a predicted value of heat generation of a semiconductor switching element due to power conversion. The temperature adjustment device has at least a heat source capable of adjusting a temperature around the semiconductor switching element. The temperature control unit controls the temperature adjustment device using the predicted value of heat generation so that the temperature of the semiconductor switching element becomes a target temperature. [Brief description of the drawings]

[0006] [Figure 1]FIG. 1 is a configuration diagram of a power conversion device according to an embodiment. [Diagram 2] FIG. 4 is a configuration diagram of a temperature control unit according to the embodiment. [Diagram 3] FIG. 4 is a diagram for explaining an arrangement of a temperature sensor according to the embodiment. [Figure 4A] FIG. 11 is a plan view illustrating a second example of an arrangement of temperature sensors in the embodiment. [Figure 4B] FIG. 11 is an elevation view illustrating a second example of an arrangement of temperature sensors according to the embodiment. [Diagram 5] 5 is a diagram for explaining the relationship between output capacitance and temperature according to the embodiment. FIG. [Figure 6] 4 is a flowchart showing a procedure for identifying a state of a power conversion device according to an embodiment. [Figure 7] 5A and 5B are diagrams for explaining transient thermal impedance of the heat sink according to the embodiment. [Figure 8] 4 is a flowchart of an element temperature estimation process according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Hereinafter, a power conversion device and a temperature control method according to an embodiment will be described with reference to the drawings. In the following description, components having the same or similar functions are given the same reference numerals. Duplicate descriptions of those components may be omitted. Electrical connection may simply be referred to as "connected." In the following description, "equal in size" includes substantially equal sizes.

[0008] FIG. 1 is a configuration diagram of a power conversion device 1 according to an embodiment. In FIG. 1, a power conversion device 1, a three-phase AC power source 2 connected to the power conversion device 1, and an AC motor 3 are shown. The three-phase AC power source 2 supplies, for example, three-phase AC power. For example, the three-phase AC power source 2 includes a power grid of a power company, a generator, etc. The three-phase AC power source 2 supplies the three-phase AC power to the DC conversion unit 4 of the power conversion device 1. The AC motor 3 is, for example, a three-phase AC motor. AC power is supplied to the AC motor 3 from the power conversion device 1.

[0009] In FIG. 1, power conversion device 1 includes a DC conversion unit 4, a smoothing capacitor 5, a power conversion unit 6, a current detector 7, temperature sensors 8A and 8B, a temperature adjustment device 9, and a control device 10.

[0010] The DC converter 4 is, for example, a rectifier constituted by diodes or the like, or a DC converter circuit including a semiconductor switching element. The semiconductor switching element may be an IGBT, a MOSFET, or the like. This semiconductor switching element may be provided with a flywheel diode. The DC converter 4 converts AC power input from the three-phase AC power source 2 into DC power and outputs it. FIG. 1 shows the DC converter 4 constituted by diodes as an example. The DC converter 4 may be provided with a heat sink for dissipating heat generated by losses in the diodes and the like.

[0011] Smoothing capacitor 5 stores the power supplied from DC converter 4 and smoothes the voltage output by DC converter 4.

[0012] The power conversion unit 6 is an AC conversion circuit including a semiconductor switching element 6SW. An IGBT, a MOSFET, or the like can be used as the semiconductor switching element 6SW. A flywheel diode may be provided in the semiconductor switching element 6SW. The power conversion unit 6 converts DC power into three-phase AC power and outputs it. FIG. 1 shows an example of a configuration in which an IGBT and a flywheel diode are combined. The number of semiconductor switching elements 6SW, etc. in the power conversion unit 6 is not limited to that shown in the figure, and may be multiple. The power conversion unit 6 is provided with a heat sink 6HS for dissipating heat generated by loss in the semiconductor switching element 6SW. The heat sink 6HS dissipates heat caused by loss in the semiconductor switching element 6SW.

[0013] The current detector 7 is an example of a current transformer including a Hall CT or a shunt resistor. The current detector 7 detects the current output to the AC motor 3, and outputs the current value of the detection result to the current detection unit 101. The location where the current detector 7 is provided is not limited to the AC buses of two or more of the three phases, and may be a location where the current waveform of the current flowing through the power conversion unit 6 can be reproduced, for example, inside the power conversion unit 6 or between the DC conversion unit 4 and the power conversion unit 6.

[0014] The temperature sensors 8A and 8B include, for example, a thermistor, a resistance temperature detector, etc. The temperature sensors 8A and 8B detect the temperature at the positions where they are placed and generate a signal that changes according to the temperature. For example, the temperature sensor 8A is placed at a point in the power conversion device 1, such as the power conversion unit 6, where the temperature is relatively high. The temperature sensor 8B is placed at a point in the panel of the power conversion device 1 that is relatively close to the outside air temperature. The positions of the temperature sensors 8A and 8B are not limited to the positions shown in FIG. 1. For example, the position of the temperature sensor 8A may be any place where a temperature rise due to the output power of the power conversion device 1 can be detected.

[0015] The temperature adjustment device 9 includes, for example, a cooling device 9F and a heater 9H. The cooling device 9F cools, for example, the heat sink 6HS of the power conversion unit 6. For example, the cooling device 9F includes a fan for air-cooling the heat sink 6HS, a heat exchange system for water-cooling the heat sink 6HS, etc. The cooling device 9F lowers the temperature inside the power conversion device 1 by its operation. The heater 9H heats, for example, air taken in from outside the power conversion device 1. For example, the heater 9H is provided near an outside air intake in the housing of the power conversion device 1, and heats the outside air taken into the housing by operating the heater 9H. The heater 9H increases the temperature inside the power conversion device 1 by operating the heater 9H. As described above, the temperature adjustment device 9 has at least a heat source capable of adjusting the temperature around the semiconductor switching element 6SW. The heater 9H is one example of the heat source.

[0016] The control device 10 includes an arithmetic unit such as an MCU or an FPGA, and its peripheral circuits. The arithmetic unit of the control device 10 includes a processor that executes processing by software (program), or a hardware arithmetic circuit.

[0017] For example, the control device 10 includes a current detection unit 101, a current calculation unit 102, a heat sink temperature detection unit 103, a heat sink temperature calculation unit 104, an element temperature estimation unit 105, an internal temperature detection unit 106, an internal temperature calculation unit 107, an external command receiving unit 108, a memory unit 110, a control unit 120, a PWM output unit 130, a temperature control unit 140, and a relay board 150.

[0018] The current detection unit 101 includes a conversion unit such as an AD converter, receives the signal output by the current detector 7 as input, converts the signal into current data for calculation, and outputs it to the current calculation unit 102 .

[0019] The current calculation section 102 receives the current data output by the current detection section 101 , calculates, for example, an effective value of the current based on the current data, and outputs the calculated value to the control section 120 and the temperature control section 140 .

[0020] The heat sink temperature detection unit 103 is a conversion unit such as an AD converter, and receives the signal output by the temperature sensor 8 , converts it into temperature data for calculation, and outputs it to the heat sink temperature calculation unit 104 .

[0021] The heat sink temperature calculation unit 104 receives the temperature data output by the heat sink temperature detection unit 103 , calculates, for example, a temperature in degrees Celsius based on the temperature data, and outputs the calculated temperature to the element temperature estimation unit 105 .

[0022] The element temperature estimation unit 105 receives the temperature data from the heat sink temperature calculation unit 104 and the predicted heat generation value, calculates the junction temperature of the semiconductor switching element 6SW based on the temperature data, etc., and outputs an estimated value of the junction temperature of the semiconductor switching element 6SW to the temperature control unit 140. For example, the element temperature estimation unit 105 derives an estimate (first estimate) of the temperature of the semiconductor switching element 6SW by using a detected temperature value at a predetermined position within a predetermined range from the position of the semiconductor switching element 6SW. Note that the element temperature estimation unit 105 may calculate a value obtained by standardizing the estimate of the temperature of the semiconductor switching element 6SW based on a reference temperature (e.g., a target element temperature) of the temperature of the semiconductor switching element 6SW, and output the normalized value.

[0023] The internal temperature detection unit 106 is a conversion unit such as an AD converter, and receives the signal output by the temperature sensor 8B, converts it into temperature data for calculation, and outputs it to the internal temperature calculation unit 107.

[0024] The internal temperature calculation unit 107 receives the temperature data output by the internal temperature detection unit 106, calculates, for example, the temperature in degrees Celsius based on the temperature data, and outputs the detected value of the internal temperature (referred to as the internal temperature Ta) to the temperature control unit 140. The internal temperature calculation unit 107 may also calculate a value by standardizing the detected value of the internal temperature based on a reference temperature for the internal temperature, and output this. The above-mentioned current calculation unit 102, heat sink temperature detection unit 103, heat sink temperature calculation unit 104, element temperature estimation unit 105, internal temperature detection unit 106, and internal temperature calculation unit 107 are examples of a calculation unit. For example, the element temperature estimation unit 105 in the calculation unit may calculate a predicted value of the heat generation amount of the semiconductor switching element 6SW due to power conversion in the process of calculating an estimated value of the junction temperature of the semiconductor switching element 6SW.

[0025] The external command receiving unit 108 receives an external command value used for controlling the AC motor 3 from, for example, a higher-level device, and outputs the received command value to the control unit 120.

[0026] The storage unit 110 includes a storage medium such as a semiconductor memory or a magnetic storage device. New data is written to the storage unit 110 by a write process from the control unit 120 or the temperature control unit 140, and the storage unit 110 holds this data. The storage unit 110 outputs the held data by a read process from the control unit 120 or the temperature control unit 140. Each piece of data may be written to the storage unit 110 by a dedicated controller instead of by the control unit 120 or the temperature control unit 140.

[0027] The control unit 120 performs various processes related to collection and management of various data, identification of the state of the power conversion device 1, etc. For example, the control unit 120 performs the following processes related to the control of the power conversion unit 6. Using various data stored in the memory unit 110 or collected data, the control unit 120 calculates a control amount (e.g., a voltage reference) for PWM control of the AC motor 3 for each control period and outputs the control amount to the PWM output unit 130.

[0028] The PWM output unit 130 generates a PWM signal based on the control amount (voltage reference) supplied from the control unit 120, and outputs the PWM signal to the power conversion unit 6.

[0029] The temperature control unit 140 adjusts the temperature inside the control device 10. For example, the temperature control unit 140 may be provided separately from the control unit 120, and may be configured as a part of the control unit 120.

[0030] For example, the temperature control unit 140 performs the following processes in relation to adjusting the temperature inside the control device 10. The temperature control unit 140 acquires element temperature data calculated by the element temperature estimation unit 105, internal temperature data calculated by the internal temperature calculation unit 107, and current data calculated by the current calculation unit 102. The temperature control unit 140 monitors the various acquired data. The temperature control unit 140 writes and stores the monitoring results and the above various data in the memory unit 110 as time history data.

[0031] The temperature control unit 140 controls the temperature adjustment device 9 using the predicted heat generation amount value described above so that the temperature of the semiconductor switching element 6SW becomes the target temperature. The temperature control unit 140 controls the temperature adjustment device 9 so as to increase the cooling capacity of the temperature adjustment device 9 when the predicted heat generation value is high, and to increase the heating capacity of the temperature adjustment device 9 when the predicted heat generation value is low.

[0032] The relay board 150 has a switch (relay) capable of cutting off the power supply to the temperature adjustment device 9. The relay board 150 controls the power supply to the temperature adjustment device 9 under the control of the temperature control unit 140.

[0033] FIG. 2 is a configuration diagram of the temperature control unit 140 according to the embodiment. The temperature control unit 140 acquires the current detection value which is the calculation result of the current calculation unit 102 , the temperature detection value which is the calculation result of the internal temperature calculation unit 107 , and the temperature estimation value which is the calculation result of the element temperature estimation unit 105 . The temperature control unit 140 controls the temperature adjustment device 9 using the above-mentioned current detection value, temperature detection value, and temperature estimation value. For example, the element target temperature setting unit 141 includes subtractors 142 , 144 , and 145 , calculation units 143 and 146 , a comparator 147 , a normalization calculation unit 148 , and an average heat generation calculation unit 149 .

[0034] When the element target temperature is set to a predetermined value (fixed value), the element target temperature setting unit 141 holds the element target temperature. The element target temperature setting unit 141 outputs the value of the element target temperature at a predetermined magnitude. The subtractors 142, 144, and 145 are two-input subtractors. The calculation units 143 and 146 perform linear calculations such as PI, PID, etc. The calculations by the calculation units 143 and 146 may output continuous values ​​or quantized discrete values ​​as output values.

[0035] The comparator 147 compares the input value with a predetermined threshold value. The comparator 147 may be configured to have a hysteresis characteristic in which the result of the determination is switched between a threshold value TH1 and a threshold value TH2. For example, the threshold value TH1 is smaller than the threshold value TH2.

[0036] The normalization calculation section 148 normalizes the effective value of the current obtained from the current calculation section 102 based on the rated value of the current.

[0037] The average heat generation calculation unit 149 calculates the average heat generation based on the effective value of the current obtained from the current calculation unit 102 .

[0038] The above-mentioned parts are related to each other, for example, as follows.

[0039] The output of the element target temperature setting unit 141 is connected to a first input of a subtractor 142 . The output of the element temperature estimation unit 105 is connected to a second input of the subtractor 142. The subtractor 142 subtracts the estimated value of the element temperature Tj supplied from the element target temperature setting unit 141 from the first estimated value of the temperature of the semiconductor switching element 6SW supplied from the element temperature estimation unit 105, and outputs a temperature deviation ε which is the difference.

[0040] The input of the calculation unit 143 is connected to the output of the subtractor 142. The calculation unit 143 obtains the temperature deviation ε as the calculation result of the subtractor 142, performs a predetermined calculation, and generates a state quantity α such that the temperature deviation ε becomes zero.

[0041] A first input of the subtractor 144 is connected to the output of the calculation unit 143. A second input of the subtractor 144 is connected to the output of the internal temperature calculation unit 107. The subtractor 144 subtracts the internal temperature Ta supplied from the internal temperature calculation unit 107 from the state quantity α supplied from the calculation unit 143, and outputs a state quantity β which is the difference.

[0042] A first input of the subtractor 145 is connected to the output of the subtractor 144. A second input of the subtractor 145 is connected to the output of the normalization calculation unit 148. The subtractor 145 subtracts the current value ifbk supplied from the normalization calculation unit 148 from the state quantity β supplied from the subtractor 144, and outputs a state quantity γ which is the difference.

[0043] The input of the calculation unit 146 is connected to the output of the subtractor 145. The calculation unit 146 acquires the state quantity γ which is the calculation result of the subtractor 145, performs a predetermined calculation, and generates a state quantity δ such that the state quantity γ becomes zero.

[0044] The input of the comparator 147 is connected to the output of the calculation unit 146. The comparator 147 acquires a state quantity δ that is a calculation result of the calculation unit 146, and judges this state quantity δ using the threshold value TH1 and the threshold value TH2. The comparator 147 controls the relay board 150 to control the temperature adjustment device 9 as follows.

[0045] For example, when the state quantity δ is smaller than the threshold value TH1, the comparator 147 energizes the heater 9H and does not energize the cooling device 9F. Moreover, when the state quantity δ is greater than the threshold value TH1 and smaller than the threshold value TH2, the comparator 147 does not energize both the heater 9H and the cooling device 9F. Moreover, when the state quantity δ is greater than the threshold value TH2, the comparator 147 does not energize the heater 9H but energizes the cooling device 9F.

[0046] As a result, when the state quantity δ is smaller than the threshold value TH1, it can be estimated that the temperature of the surrounding environment is relatively low and a thermal cycle is occurring. In such a case, the heat generated by the heater 9H can be used to prevent the temperature from becoming excessively low.

[0047] An example of a method for estimating the junction temperature (referred to as element temperature Tj) of semiconductor switching element 6SW from the temperature measured by temperature sensor 8 will be described.

[0048] In the configuration example shown here, a temperature sensor 8A is placed on the heat sink HS.

[0049] The relationship between the element temperature Tj of the semiconductor switching element 6SW and the temperature measured by the temperature sensor 8A is determined in advance, and a table or a relational expression is prepared to estimate the element temperature Tj based on the temperature measured by the temperature sensor 8A.

[0050] First example: For example, a measurement system is used that correlates and measures the element temperature Tj of a semiconductor switching element module 6MA (hereinafter simply referred to as module 6MA) that incorporates a semiconductor switching element 6SW with the temperature of the heat sink HS, and the power converter is operated in the state of the measurement system. The relationship between the element temperature Tj according to the observation results of this measurement system and the temperature of the heat sink HS is compiled into a table. The element temperature Tj is estimated by referring to this table using the temperature of the heat sink HS as a key.

[0051] Second example: For example, the element temperature Tj of the semiconductor switching element 6SW in the module 6MA incorporating the semiconductor switching element 6SW, and the thermal resistance Rth(h) between the temperature measurement point determined between the semiconductor switching element 6SW and the heat sink HS and the heat sink temperature measurement point are determined based on the results of a preliminary test. For example, the relationship is organized into formula (1) using the thermal resistance Rth(jc) from the semiconductor switching element 6SW to the heat sink temperature measurement point.

[0052] Element temperature Tj = Sensor measurement temperature + (Rth(h) + Rth(jc)) × Average heat generation [W] (1)

[0053] The average heat generation [W] in the above equation (1) is the average heat generation of the IGBT module estimated from the average output.

[0054] FIG. 3 is a diagram for explaining the arrangement of the temperature sensor 8A according to the embodiment.

[0055] 3, a DC converter 4, a smoothing capacitor 5, a power converter 6, a temperature regulator 9, etc. are arranged on the panel (housing) of the power converter 1. Furthermore, a temperature sensor 8B, etc. are arranged inside the panel (housing) of the power converter 1.

[0056] The cooling device 9F shown in Fig. 3 includes a fan unit for air cooling. In this case, the cooling device 9F may be configured as follows. A case where the cooling device 9F includes an exhaust type fan unit will be described. In this case, the cooling device 9F is arranged to match the opening on the top surface of the panel (housing) of the power conversion device 1 (FIG. 3). An air intake is provided on the door or the like of the panel (housing) of the power conversion device 1, and the air intake is provided with a filter for removing dust and preventing insects. The cool air taken in from the air intake absorbs heat while passing through the panel (inside the housing) and is exhausted outside the panel via the fan unit of the cooling device 9F.

[0057] Alternatively, the cooling device 9F may include a blower-type fan unit, in which case the cooling device 9F may be disposed upstream of the heat sink HS so as to blow cool air around the heat sink HS. The cooling device 9F may include a heat exchanger for water cooling. In this case, the cooling device 9F may be arranged so that the heat exchanger is thermally coupled to the heat sink HS. As noted above, the cooling device 9F can take a variety of forms. Regardless of the above cases, the temperature sensor 8A may be disposed in the panel (housing) of the power conversion device 1 near its air intake or on a path through which the cool air taken in from the air intake passes.

[0058] A second example of the arrangement of the temperature sensor 8A according to the embodiment will be described with reference to FIGS. 4A and 4B. FIG. 4A is a plan view for explaining a second example of the arrangement of the temperature sensor 8A according to the embodiment. FIG. 4B is an elevation view for explaining a second example of the arrangement of the temperature sensor 8A according to the embodiment.

[0059] The module 6MA is disposed on the heat sink 6HS.

[0060] The module 6MA includes, for example, a substrate 6BS, a semiconductor switching element 6SW, and a temperature sensor 8A. The substrate 6BS includes an insulating core material such as ceramic, glass fiber resin, or the like. The semiconductor switching element 6SW of the module 6MA is disposed on a first surface 6F1 of the substrate 6BS. The temperature sensor 8A is disposed in the module 6MA. For example, the temperature sensor 8A may be disposed within the module 6MA. The inside of the module 6MA is filled with air, resin, or the like.

[0061] The second surface 6F2 of the substrate 6BS of the module 6MA is arranged so as to be thermally coupled to the heat sink 6HS. For example, a curtain (e.g., a curtain made of silicon, mylar, etc.) that enhances thermal conductivity may be provided between the second surface 6F2 of the substrate 6BS of the module 6MA and the heat sink 6HS, or oil may be applied. A general method may be selected as the thermal coupling method.

[0062] As shown in FIG. 5, a temperature sensor 8A is provided on the module 6MA itself. In this case, the thermal resistance Rth between the installation location of the temperature sensor 8A and the representative position of the semiconductor switching element 6SW is set in advance. For example, the control unit 120 uses the thermal resistance Rth to calculate the element temperature Tj of the semiconductor switching element 6SW from the measured temperature of the temperature sensor 8A (referred to as the sensor measured temperature). This calculation may be performed using the following formula (2).

[0063] Element temperature Tj = sensor measurement temperature + thermal resistance Rth × average heat generation [W] (2)

[0064] In addition, the "average heat generation [W]" in formula (2) may be the average heat generation amount of the module 6MA estimated from the average (moving average) of the output current of the module 6MA.

[0065] The relationship between the output capacity and the estimated temperature in this embodiment will be described with reference to FIG. Fig. 5 is a diagram for explaining the relationship between the output capacitance and temperature in the embodiment. The graph shown in Fig. 5 shows the relationship between the output capacitance (horizontal axis) and the temperature measured by the temperature sensor 8A (vertical axis) and the estimated temperature of the semiconductor switching element 6SW (vertical axis). The output capacity range shown in this graph is from 0 to 150%, with the rated output being 100%. Over the entire range of output capacity shown in Figure 5, the temperature measured by temperature sensor 8A (vertical axis) and the estimated temperature of semiconductor switching element 6SW increase monotonically in an upward sloping manner. Comparing the temperature measured by temperature sensor 8A (vertical axis) and the estimated temperature of semiconductor switching element 6SW, the estimated temperature of semiconductor switching element 6SW is higher, as shown in equation (1) above.

[0066] FIG. 6 is a flowchart showing a procedure for identifying the state of the power conversion device 1 of the embodiment.

[0067] The control device 10 performs an estimation process (element temperature estimation) of the element temperature Tj (SA11) using the element temperature estimation unit 105 etc. For example, the element temperature estimation unit 105 estimates the junction temperature of the semiconductor switching element 6SW based on the temperature data output by the heat sink temperature detection unit 103. The details of the estimation process of the element temperature Tj will be described later.

[0068] In addition, the internal temperature calculation unit 107 may also perform an estimation process (internal temperature estimation) of the internal temperature Ta to generate the internal temperature (internal temperature data) and update the internal temperature Ta as the latest estimated value. For ease of explanation, the internal temperature Ta may be assumed to be constant. In fact, when an environment is provided in which the internal temperature Ta can be assumed to be constant, this estimation process of the internal temperature Ta may be omitted.

[0069] The temperature control unit 140 calculates an estimate of the element temperature rise (Tj-Ta) based on the temperature difference between the element temperature Tj and the internal temperature Ta (SA12). The element temperature rise (Tj-Ta) is set to, for example, the temperature rise of the element temperature Tj from the reference internal temperature Ta.

[0070] The temperature control unit 140 determines whether the element temperature rise (Tj-Ta) is smaller than a predetermined judgment value (SA13).

[0071] If the element temperature rise (Tj-Ta) is equal to or greater than a predetermined judgment value, the temperature control unit 140 issues a temperature abnormality alarm (temperature abnormality alarm) indicating a decrease in cooling capacity (SA14), controls the device to a protection operation mode (SA15), and then ends the series of processes.

[0072] If the element temperature rise (Tj-Ta) is smaller than a predetermined judgment value (e.g., threshold value TH2), the temperature control unit 140 identifies whether the element temperature rise (Tj-Ta) is smaller than a judgment value (e.g., threshold value TH2) that is the value of the initial data plus a predetermined value α (SA16). If the element temperature rise (Tj-Ta) is smaller than a judgment value (e.g., threshold value TH1) obtained by adding a predetermined value α to the initial data value, the temperature control unit 140 performs a temperature compensation process (SA18) and operates the heater 9H to prevent an excessive drop in temperature. After this, the series of processes is terminated. The above temperature compensation process may include a temperature adjustment process by the temperature adjustment device 9. For example, the comparator 147 of the temperature control unit 140 compares a predetermined threshold value with an input value. The comparator 147 may be configured to have a hysteresis characteristic in which the result of the determination is switched between a threshold value TH1 and a threshold value TH2. For example, the threshold value TH1 may be set smaller than the threshold value TH2.

[0073] For example, when the state quantity δ is smaller than the threshold value TH1, the comparator 147 energizes the heater 9H and does not energize the cooling device 9F. Moreover, when the state quantity δ is greater than the threshold value TH1 and smaller than the threshold value TH2, the comparator 147 does not energize both the heater 9H and the cooling device 9F. Moreover, when the state quantity δ is greater than the threshold value TH2, the comparator 147 does not energize the heater 9H but energizes the cooling device 9F. By controlling the temperature adjustment device 9 as described above, it is possible to prevent an extreme drop in temperature.

[0074] If the element temperature rise (Tj-Ta) is not smaller than the judgment value obtained by adding a predetermined value α to the initial data value, the temperature control unit 140 issues an alarm (a cooling capacity decrease alarm) indicating that the cooling capacity has decreased (SA17) and ends the series of processes.

[0075] Through the above process, the state of the power conversion device 1 can be identified. The threshold temperature used for the above-mentioned identification may be associated with initial data obtained by operating the semiconductor switching element 6SW in the power conversion device 1. In this case, the temperature control unit 140 may identify that an abnormality has occurred in the state of the cooling device 9F based on the initial data and an estimated value of the temperature of the semiconductor switching element 6SW.

[0076] First, the transient thermal impedance will be described. 7 is a diagram for explaining the transient thermal impedance of the heat sink of the embodiment. The characteristics of the transient thermal impedance of the heat sink shown in FIG. 7 are modeled for ease of explanation. 7 shows an example of the relationship between the averaging time (LOG scale) and the transient thermal impedance (LOG scale). The averaging time is the width of the time window that defines the target period for which the averaging process is applied. If the averaging time is in the range of 1 second or more, the transient thermal impedance will be a constant value (for example, 1). If the averaging time is shorter than 1 second, the value of the transient thermal impedance will decrease as the time becomes shorter. The averaging time may be a fixed value. When changing the averaging time, it is advisable to include the effect of this transient thermal impedance in the calculation conditions. If this effect is not included, the error in the estimated value may become large. Furthermore, because real devices and detection systems take time to dissipate the heat they receive, it can be difficult to accurately reproduce time ranges of 1 second or more.

[0077] Thus, when considering the average heat generation in the embodiment, it is advisable to use an averaging time longer than, for example, one second.

[0078] The element temperature estimation process according to the embodiment will be described with reference to FIG. FIG. 8 is a flowchart of the element temperature estimation process according to the embodiment.

[0079] The heat sink temperature detection unit 103 and the heat sink temperature calculation unit 104 detect the temperature of the heat sink 6HS by having the temperature sensor 8A detect the temperature (SC11).

[0080] The element temperature estimation unit 105 acquires temperature data of the temperature Th corresponding to the measurement result. The element temperature estimation unit 105 estimates the output capacitance for the temperature Th and the element temperature Tj for the output capacitance using the temperature Th and information in the table showing the characteristics of the graph shown in Fig. 7 (SC12).

[0081] The temperature control unit 140 obtains an estimate of the element temperature Tj through the above processing.

[0082] In this manner, the element temperature estimator 105 derives an estimate of the element temperature Tj of the semiconductor switching element 6SW using the detected temperature values ​​at predetermined positions within a predetermined range from the position of the semiconductor switching element 6SW.

[0083] According to the above embodiment, the power conversion device 1 includes a calculation unit, a temperature adjustment device 9, and a temperature control unit 140. The heat sink temperature calculation unit 104 and the element temperature estimation unit 105 (calculation unit) calculate a predicted value of the amount of heat generated by the semiconductor switching element 6SW due to power conversion. The temperature adjustment device 9 has at least a heater 9H (heat source) capable of adjusting the temperature around the semiconductor switching element 6SW. The temperature control unit 140 controls the temperature adjustment device 9 using the predicted value of the amount of heat generated so that the element temperature Tj of the semiconductor switching element 6SW becomes a target temperature. This makes it possible to reduce thermal cycle fatigue of the power conversion device 1.

[0084] For example, the heat sink temperature calculation unit 104 and the element temperature estimation unit 105 (calculation unit) estimate the temperature (estimated temperature) of the semiconductor switching element using the external temperature (heat sink temperature) of the semiconductor switching element and the magnitude of the output (output current) of the power converter. The temperature control unit 140 generates a control command so that the estimated temperature (element temperature Tj) of the semiconductor switching element 6SW becomes the element target temperature. The temperature control unit 140 corrects the control command based on the internal temperature of the power converter (power conversion unit 6) or the magnitude of the output current, and controls the temperature adjustment device based on the correction result.

[0085] The external temperature of the semiconductor switching element 6SW is preferably the temperature of a heat sink 6HS thermally coupled to the semiconductor switching element 6SW. The magnitude of the output of the power converter (power conversion unit 6) may be an index value based on the magnitude of the current flowing between the output of the power converter (power conversion unit 6) and the load. The element temperature estimation unit 105 (calculation unit) may use the average heat generation amount based on the magnitude of the current flowing between the output of the power converter (power conversion unit 6) and the load (AC motor 3) as the magnitude of the output of the power converter (power conversion unit 6). The temperature control unit 140 may control the temperature adjustment device 9 to increase the cooling capacity of the temperature adjustment device 9 when the predicted heat generation value is high, and to increase the heating capacity of the temperature adjustment device 9 when the predicted heat generation value is low.

[0086] For example, the above-mentioned control device 10 includes a temperature sensor 8A (second sensor) arranged within a predetermined range (on the surface or near the surface) based on the surface of the heat sink 6HS, and a temperature sensor 8B (third sensor) arranged at a predetermined position within the panel of the power conversion device 1. The element temperature estimation unit 105 derives a first estimate of the temperature of the semiconductor switching element 6SW using the value detected by the temperature sensor 8A. The temperature control unit 140 can identify an abnormal state of a cooling mechanism such as the cooling device 9F when the temperature difference between the estimated value of the temperature of the semiconductor switching element 6SW based on the detection value by the temperature sensor 8A and the temperature at a specified position within the panel of the power conversion device 1 based on the detection result by the temperature sensor 8B exceeds a predetermined threshold temperature.

[0087] According to at least one of the embodiments described above, the power conversion device includes a calculation unit, a temperature adjustment device, and a temperature control unit. The calculation unit calculates a predicted value of heat generation of a semiconductor switching element due to power conversion. The temperature adjustment device has at least a heat source capable of adjusting a temperature around the semiconductor switching element. The temperature control unit controls the temperature adjustment device using the predicted value of heat generation so that the temperature of the semiconductor switching element becomes a target temperature, thereby reducing thermal cycle fatigue of the power conversion device.

[0088] A part or all of the functional units of the control device 10 in the power conversion device 1 of the embodiment described above may have software functional units that are realized by, for example, executing a program (computer program, software component) stored in a storage unit (memory, etc.) of a computer by a processor (hardware processor) of the computer. Note that a part or all of the functional units of the control device 10 may be realized by hardware such as, for example, an LSI (Large Scale Integration), an ASIC (Application Specific Integrated Circuit), or an FPGA (Field-Programmable Gate Array), or may be realized by a combination of the software functional units and hardware.

[0089] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. For example, the configurations of each embodiment may be implemented in combination with each other, and can be applied to components whose descriptions are omitted. These embodiments and their modifications are included in the scope of the invention and its equivalents described in the claims, as well as in the scope and spirit of the invention. [Explanation of symbols]

[0090] 1...Power conversion device 3…AC motor (load) 6...Power converter (power conversion section) 6HS…Heat sink 6SW…Semiconductor switching element 8A, 8B...Temperature sensor 9…Temperature adjustment device 9F…Cooling device 9H…Heater 10...Control device 105...Element temperature estimation unit 110...Storage section 120...Control unit 140...Temperature control unit

Claims

1. a calculation unit that calculates a predicted value of heat generation amount of a semiconductor switching element due to power conversion; a temperature adjusting device that adjusts the temperature around the semiconductor switching element using a heat source; a temperature control unit that controls the temperature adjustment device by using the predicted heat generation value so that the temperature of the semiconductor switching element becomes a target temperature; A power conversion device comprising:

2. The heat source is a heater. The power conversion device according to claim 1 .

3. The calculation unit is estimating a temperature of the semiconductor switching element using an external temperature of the semiconductor switching element and a magnitude of an output of the power converter; The temperature control unit is A control command is generated so that the estimated temperature of the semiconductor switching element becomes a target element temperature, and the control command is corrected based on the temperature inside the panel of the power converter or the magnitude of the output current, and a temperature adjustment device is controlled based on the result of the correction. The power conversion device according to claim 1 .

4. The external temperature of the semiconductor switching element is the temperature of a heat sink thermally coupled to the semiconductor switching element. The power conversion device according to claim 3 .

5. The magnitude of the output of the power converter is an index value based on the magnitude of the current flowing between the output of the power converter and a load. The power conversion device according to claim 3 .

6. The calculation unit is The average heat generation amount based on the magnitude of the current flowing between the output of the power converter and the load is used as the magnitude of the output of the power converter. The power conversion device according to claim 3 .

7. The temperature control unit is Controlling the temperature adjustment device so as to increase the cooling capacity of the temperature adjustment device when the predicted heat generation value is high, and to increase the heating capacity of the temperature adjustment device when the predicted heat generation value is low The power conversion device according to claim 1 .

8. A predicted value of heat generation of a semiconductor switching element due to power conversion is calculated; adjusting the temperature around the semiconductor switching element using a heat source of a temperature adjustment device; Controlling the temperature adjustment device using the predicted heat generation value so that the temperature of the semiconductor switching element becomes a target temperature. A temperature control method comprising:

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