Control device, control system, and control method

Abstract

To provide a control device, a control system and a control method which can appropriately cool a plurality of power converters.SOLUTION: In a control system 1, a control device 10 comprises a control part which controls each flow rate of coolants allocated to each power converter within a range in which each predetermined temperature of a plurality of power converters 20A to 20D included in each of power modules does not exceed each temperature management value.EFFECT: According to the control system and a control method, the plurality of power converters can be appropriately cooled.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a control device, a control system, and a control method. [Background technology]

[0002] Patent Document 1 discloses the following electronic component cooling device. Specifically, the electronic component cooling device disclosed in Patent Document 1 includes a cooler for cooling an electronic component, a coolant temperature acquisition unit for acquiring the temperature of the coolant, a coolant flow rate acquisition unit for acquiring the flow rate of the coolant, a heat loss estimation unit for estimating heat loss in the electronic component, a loss threshold calculation unit for calculating an appropriate upper threshold for heat loss in the electronic component based on the coolant temperature and the refrigerant flow rate, and a coolant flow rate control unit for controlling the flow rate of the coolant. Furthermore, the coolant flow rate control unit increases the flow rate of the coolant circulating through the cooler when the estimated heat loss exceeds the appropriate upper threshold. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-92263 Summary of the Invention [Problem to be solved by the invention]

[0004] However, Patent Document 1 does not show how to deal with the case where there are multiple objects to be cooled.

[0005] An object of the present disclosure is to provide a control device, a control system, and a control method that are capable of appropriately cooling multiple power converters. [Means for solving the problem]

[0006] In order to solve the above problem, the control device according to the present disclosure includes a control unit that controls the flow rate of refrigerant distributed to each of a plurality of power converters, each of which has a power module, within a range in which the respective predetermined temperatures of the power converters do not exceed the respective temperature control values.

[0007] The control method according to the present disclosure controls the flow rate of refrigerant distributed to each of a plurality of power converters, each of which has a power module, within a range in which the respective predetermined temperatures of the power converters do not exceed the respective temperature control values. [Effects of the Invention]

[0008] According to the control device, control system, and control method of the present disclosure, it is possible to appropriately cool a plurality of power converters. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating a configuration example of a control system according to an embodiment of the present disclosure. [Figure 2] 1 is a block diagram illustrating a configuration example of a power converter according to an embodiment of the present disclosure. [Figure 3] 1 is a perspective view illustrating a configuration example of a power converter according to an embodiment of the present disclosure. [Figure 4] 1 is a perspective view showing a configuration example of a power converter according to an embodiment of the present disclosure, with a cover removed; [Figure 5] 1 is a perspective view showing a configuration example of a power converter according to an embodiment of the present disclosure, viewed from below; [Figure 6] FIG. 2 is a block diagram illustrating an example functional configuration of a control device according to an embodiment of the present disclosure. [Figure 7] FIG. 2 is a schematic diagram for explaining an example of operation of a control system according to an embodiment of the present disclosure. [Figure 8] FIG. 2 is a schematic diagram for explaining an example of operation of a control system according to an embodiment of the present disclosure. [Figure 9] FIG. 2 is a schematic diagram for explaining an example of operation of a control system according to an embodiment of the present disclosure. [Figure 10]FIG. 10 is a schematic diagram for explaining an example of the operation of the control device according to the embodiment of the present disclosure. [Figure 11] 10 is a flowchart illustrating an example of the operation of a control device according to an embodiment of the present disclosure. [Figure 12] FIG. 1 is a schematic block diagram illustrating the configuration of a computer according to at least one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] First Embodiment (Control System) A control device, a control system, and a control method according to an embodiment of the present disclosure will be described below with reference to Figures 1 to 11. Note that the same or corresponding components in each figure are designated by the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0011] FIG. 1 is a diagram illustrating an example configuration of a control system according to an embodiment of the present disclosure. FIG. 2 is a block diagram illustrating an example configuration of a power converter according to an embodiment of the present disclosure. FIG. 3 is a perspective view illustrating an example configuration of a power converter according to an embodiment of the present disclosure. FIG. 4 is a perspective view illustrating an example configuration of a power converter according to an embodiment of the present disclosure, with a cover removed. FIG. 5 is a perspective view illustrating an example configuration of a power converter according to an embodiment of the present disclosure, viewed from below. FIG. 6 is a block diagram illustrating an example functional configuration of a control device according to an embodiment of the present disclosure. FIGS. 7 to 9 are schematic diagrams illustrating an example operation of a control system according to an embodiment of the present disclosure. FIG. 10 is a schematic diagram illustrating an example operation of a control device according to an embodiment of the present disclosure. FIG. 11 is a flowchart illustrating an example operation of a control device according to an embodiment of the present disclosure.

[0012] As shown in FIG. 1, a control system 1 according to an embodiment of the present disclosure includes a control device 10, four power converters 20A to 20D, a cooling device 30, a host control device 40, and a communication line 50. The control system 1 is a power system used, for example, in mobile objects such as automobiles and ships, smart grids, and the like. The control system 1 converts DC power supplied from, for example, a battery or a power generation device into DC power or AC power of a predetermined voltage and current, and outputs the converted power. The load in this case is, for example, an electrical appliance such as a motor, lighting equipment, or air conditioning equipment. The control system 1 also converts AC or DC power supplied from an external source into DC power of a predetermined voltage and current, and outputs the converted power. The load in this case is, for example, a battery. However, these are merely examples, and the use of the control system 1 is not limited to these.

[0013] (power converter) The power converters 20A-20D shown in FIG. 1 have conversion functions, such as converting input DC power to AC power and outputting it, converting AC power to DC power, increasing or decreasing the voltage of DC power, and converting AC power between AC and DC power. The power converters 20A-20D are cooled by a refrigerant supplied from a cooling device 30. The power converters 20A-20D may have different conversion functions, or some or all of them may have the same conversion function. Examples of use of the power converters 20A-20D include three-phase inverters for driving motors in electric vehicles, chargers for on-board batteries, three-phase inverters for driving small motors such as pumps and compressors, and DC-DC converters for other electrical equipment. In the example shown in FIG. 1, the power converters 20A-20D each control, for example, output power (and / or output voltage or output current) in response to an output command from a higher-level control device 40 (or control device 10). The power converters 20A to 20D may operate or not, or may have different loads, depending on, for example, the operation mode of the control system 1. The power converters 20A to 20D are collectively referred to as power converters 20. The number of power converters 20 is not limited to four, and may be any number.

[0014] Fig. 2 shows a configuration example of the power converter 20. In the example shown in Fig. 2, the power converter 20 includes a power module 21, a capacitor 22, a current sensor 23, a temperature sensor 24, a fan 25, and a power converter control device 26. Note that the power module 21, the capacitor 22, the current sensor 23, the temperature sensor 24, and the fan 25 may each be one, or some or all of them may be multiple, and some of the components, such as the temperature sensor 24 and the fan 25, may not be present.

[0015] The power module 21 includes a plurality of semiconductor elements 27. The semiconductor elements 27 are, for example, power semiconductor elements such as transistors and diodes. The transistors are, for example, power transistors such as insulated gate bipolar transistors (IGBTs) and metal oxide semiconductor field effect transistors (MOSFETs). However, there is no limitation. If the semiconductor elements 27 are transistors, they are controlled to be turned on and off at a predetermined switching frequency by the power converter control device 26, for example.

[0016] The capacitor 22 is a smoothing capacitor or a DC link capacitor, and smoothes, for example, a ripple voltage generated by the switching operation of the power module 21. The capacitor 22 also removes, for example, high-frequency components from the external power input to the power converter 20. An example of the capacitor 22 in this embodiment is a film capacitor. The power converter 20 of this embodiment includes, for example, a plurality of capacitors 22.

[0017] The current sensor 23 detects the DC or AC current input to or output from the power module 21, and outputs the detection result to the power converter control device 26. The temperature sensor 24 detects the temperature inside the housing of the power converter 20, and outputs the detection result to the power converter control device 26. The fan 25 circulates air inside the housing of the power converter 20. The wind speed of the fan 25 is controlled by the power converter control device 26, for example.

[0018] The power converter control device 26 transmits and receives predetermined information between the control device 10 and the upper control device 40 via communication line 50. The power converter control device 26 also receives the detection results of the current sensor 23, the detection results of the temperature sensor 24, the voltages of various components, etc., and controls the operation of the semiconductor element 27 of the power module 21 based on output commands received from the upper control device 40, etc. The power converter control device 26 also transmits the detection results of the current sensor 23 and the detection results of the temperature sensor 24 to the control device 10, etc. The power converter control device 26 also switches the switching frequency of the semiconductor element 27 of the power module 21 based on a switching frequency switching command received from the control device 10.

[0019] Next, a structural configuration example of the power converter 20 will be described with reference to Figures 3 to 5. The power module 13 shown in Figures 3 to 5 is a module in which a plurality of power semiconductor elements (semiconductor elements 27) such as surface-mount type power MOSFETs and IGBTs are mounted on a circuit board. Figures 3 to 5 show an example of a power module 21 capable of outputting three-phase power.

[0020] As shown in FIGS. 3 to 5, the power converter 20 of this embodiment includes a housing 201, a capacitor 22, a power module 21, a control board 206, a bus bar 204, and a current sensor 23.

[0021] Housing 201 is a box for accommodating capacitor 22, power module 21, control board 206, and current sensor 23. Housing 201 can be made of, for example, a metal or synthetic resin with high thermal conductivity. Housing 201 includes a capacitor accommodating section 202, a cover section 203, and a refrigerant flow path forming section 205.

[0022] Refrigerant flow path forming portion 205 forms a flow path through which the refrigerant flows. Refrigerant inlet 207 and refrigerant outlet 208 communicate the inside and outside of refrigerant flow path forming portion 205. That is, when refrigerant flows in through refrigerant inlet 207, it flows through the flow path within refrigerant flow path forming portion 205 and is then discharged from refrigerant outlet 208 to the outside of refrigerant flow path forming portion 205.

[0023] The condenser accommodating section 202 accommodates the condenser 22. The condenser accommodating section 202 is formed integrally with a portion of the refrigerant flow path forming section 205. The cover section 203, together with the remaining portion of the refrigerant flow path forming section 205 where the condenser accommodating section 202 is not formed, defines a power module accommodating space that accommodates at least the power module 21. Here, the remaining portion of the refrigerant flow path forming section 205 refers to the portion of the refrigerant flow path forming section 205 excluding the portion that is formed integrally with the condenser accommodating section 202. The cover section 203 is configured to be detachable from the refrigerant flow path forming section 205 and the condenser accommodating section 202. In the refrigerant flow path forming section 205 of this embodiment, the portion of the refrigerant flow path forming section 205 that is formed integrally with the condenser accommodating section 202 cools the condenser, and the remaining portion of the refrigerant flow path forming section 205 cools the power module 21.

[0024] The power module 21 is equipped with cooling fins (not shown) for cooling the power semiconductor elements. The cooling fins are fixed to the back surface of the circuit board, which faces away from the mounting surface on which the power semiconductor elements are mounted. The cooling fins are electrically insulated from the circuit board, allowing heat generated by the power semiconductor elements to be transferred. At least a portion of the cooling fins is located within the flow path of the refrigerant flow path forming portion 205. In other words, heat can be indirectly exchanged between the power semiconductor elements and the refrigerant via the cooling fins, the circuit board, etc.

[0025] (cooling device) The cooling device 30 shown in FIG. 1 includes pipes 301 to 310, a pump, a heat exchanger, multiple control valves, one or more refrigerant temperature sensors, multiple flow sensors, and the like (not shown). In FIG. 1, the flow of the refrigerant is indicated by open arrows. The cooling device 30 may or may not include a device for variably controlling the temperature of the refrigerant. The refrigerant that cools the power converter 20A flows in from pipe 301 through pipe 303 and flows out from pipe 304 to pipe 302. The refrigerant that cools the power converter 20B flows in from pipe 301 through pipe 305 and flows out from pipe 306 to pipe 302. The refrigerant that cools the power converter 20C flows in from pipe 301 through pipe 307 and flows out from pipe 308 to pipe 302. The refrigerant that cools the power converter 20D flows in from pipe 301 through pipe 309 and flows out from pipe 310 to pipe 302. For example, pipe 303 or pipe 304 is provided with a control valve (not shown) that controls the flow rate of the refrigerant and a flow sensor (not shown) that measures the flow rate of the refrigerant. For example, pipe 305 or pipe 306 is provided with a control valve (not shown) that controls the flow rate of the refrigerant and a flow sensor (not shown) that measures the flow rate of the refrigerant. For example, pipe 307 or pipe 308 is provided with a control valve (not shown) that controls the flow rate of the refrigerant and a flow sensor (not shown) that measures the flow rate of the refrigerant. For example, pipe 309 or pipe 310 is provided with a control valve (not shown) that controls the flow rate of the refrigerant and a flow sensor (not shown) that measures the flow rate of the refrigerant. For example, pipe 301 or pipe 302 is provided with a refrigerant temperature sensor (not shown) that measures the temperature of the refrigerant. These control valves are controlled by the control device 10. The detection results of the refrigerant temperature sensor are output to the control device 10. If the cooling device 30 is provided with a device that variably controls the temperature of the refrigerant, the cooling device 30 variably controls the temperature of the refrigerant in response to a control command from the control device 10. The device for variably controlling the temperature includes, for example, a compressor, a heat exchanger, and the like.

[0026] (Host control device) The upper control device 40 shown in FIG. 1 outputs an output command to each power converter 20, which is information indicating a required value of output power, for example, in accordance with the operation mode of each load of the power converter 20. For example, if the load of the power converter 20 is a motor, the output command is information including a value of power to be output to the motor. Note that the output command may not only indicate the output power (and / or output voltage or output current), but also indicate the conversion efficiency. For example, the output command may include an instruction to suppress output and prioritize efficiency in accordance with the remaining battery capacity when a motor or the like is driven by a battery. In this case, the output command may include, for example, an instruction to control the output power within a range from a first value to a second value (greater than the first value) and to control the efficiency as high as possible.

[0027] (Control device) The control device 10 can be configured using, for example, a computer such as a microcomputer, peripheral circuits and devices of the computer, etc. The control device 10 has a functional configuration formed by a combination of hardware such as a computer and software such as a program executed by the computer, and includes a control unit 11 and a communication unit 12 as shown in FIG.

[0028] The control unit 11 controls the flow rates of the refrigerant distributed to each of the power converters 20, each of which has a power module 21, within a range in which the predetermined temperatures of the power converters 20 do not exceed the respective temperature control values. The control unit 11 controls the flow rates, for example, in accordance with the output of each power converter 20. Alternatively, the control unit 11 controls the flow rates in accordance with the efficiency of each power converter 20. This flow rate control in accordance with efficiency will be described later. The predetermined temperatures are the temperatures of each part within the power converter 20, such as the junction temperature of the semiconductor element 27 of the power module 21, the temperature of the capacitor 22, and the temperature of the current sensor 23. The temperature control values ​​are values ​​that allow a predetermined margin above the maximum allowable temperature of each part.

[0029] 7 shows a state in which the flow rate of the refrigerant to each power converter 20 is uniformly controlled under the control of the control unit 11. In this case, the total flow rate of the refrigerant is 60 L / min, and the flow rate of the refrigerant to each power converter 20 is uniformly 15 L / min.

[0030] 8 shows an example in which the load on power converter 20A is relatively large, power converter 20B is stopped, the load on power converter 20C is relatively small, and power converter 20D is stopped. In this case, control unit 11 controls the above-mentioned control valves (not shown) so that the flow rate of refrigerant to power converter 20A is 35 L / min, the flow rate of refrigerant to power converter 20B is 5 L / min, the flow rate of refrigerant to power converter 20C is 15 L / min, and the flow rate of refrigerant to power converter 20D is 5 L / min. Note that control unit 11 may instruct each control valve to specify the flow rate value itself, or may instruct each control valve to specify the opening degree of the valve based on the flow rate value detected by a flow sensor.

[0031] FIG. 9 shows an example in which the control unit 11 controls the airflow speed of the fan 25 in addition to the refrigerant flow rate. In the power converter 20, the power module 21 is largely unaffected by the ambient temperature and is dominated by the cooling effect of the refrigerant. On the other hand, the capacitor 22 and the current sensor 23 are not so dominated by the cooling effect of the refrigerant, and the temperature inside the power converter 20 can be a thermal issue. Therefore, the control unit 11 controls the flow rate and the airflow speed of the fan 25 to lower the temperatures of the capacitor 22 and the current sensor 23. The load state of each power converter 20 is the same as in the example of FIG. 8. In the example shown in FIG. 9, the control unit 11 controls the airflow speed of the fan 25 of the power converter 20A to 3 m / s, the airflow speed of the fan 25 of the power converter 20B to 0 m / s, the airflow speed of the fan 25 of the power converter 20C to 1 m / s, and the airflow speed of the fan 25 of the power converter 20D to 0 m / s.

[0032] For example, if power converter 20 has current sensor 23, fan 25 which is an example of a forced air-cooling device, and temperature sensor 24 which detects the temperature inside the housing of power converter 20, the predetermined temperature includes the temperature of current sensor 23. Furthermore, control unit 11 can control the flow rate and the air speed of fan 25 based on the ambient temperature detected by temperature sensor 24 and the operating state of current sensor 23. The operating state of current sensor 23 is indicated by whether or not a current detected by current sensor 23 is flowing, and if so, by the magnitude of the current.

[0033] Furthermore, for example, if the power converter 20 has a capacitor 22, the predetermined temperature includes the temperature of the capacitor 22. Furthermore, the control unit 11 can control the flow rate based on the loss of the capacitor 22 and the temperature of the refrigerant, and can also control the wind speed of the fan 25 based on the ambient temperature.

[0034] 6 transmits and receives predetermined information to and from the upper control device 40, each power converter 20, and the cooling device 30. The communication unit 12 shown in FIG.

[0035] (Flow rate control according to efficiency) As described above, the control unit 11 controls the flow rates of the refrigerant distributed to each power converter 20 within a range in which the predetermined temperatures of the power converters 20 do not exceed the respective temperature control values. In this case, the control unit 11 controls the flow rates in accordance with the efficiency of each power converter 20, for example.

[0036] The following description will be given taking as an example a case where the predetermined temperature is the junction temperature of the semiconductor element 27 of the power module 21. The junction temperature Tj can be calculated by the following formula.

[0037] Tj=loss x thermal resistance+refrigerant temperature

[0038] The loss depends on the on-state voltage, current flow, switching frequency, etc. of the semiconductor element 27. Here, the on-state voltage corresponds to the voltage according to the on-state resistance or the saturation voltage. In other words, the on-state voltage corresponds to the drain-source voltage or collector-emitter voltage when current is flowing. The current flow is a value based on the output command and cannot be changed by the control unit 11. Furthermore, the minimum on-state voltage is a value according to the characteristics of the semiconductor element 27 when it is being driven appropriately. Therefore, the control unit 11 cannot further reduce the on-state voltage. However, the on-state voltage is temperature dependent.

[0039] FIG. 10 shows the temperature dependency of the voltage when the semiconductor element 27 is on. The horizontal axis represents the current flowing through it, and the vertical axis represents the voltage when the semiconductor element 27 is on. FIG. 10 compares the voltage when Tj is 150°C with the voltage when Tj is 25°C. As shown by the voltage difference in FIG. 10, there is a difference in voltage between the cases when Tj is 150°C and when Tj is 25°C, so the loss when Tj is 150°C is greater than the loss when Tj is 25°C. Therefore, when estimating the junction temperature Tj, the control unit 11 of this embodiment estimates the junction temperature Tj using the above calculation formula based on the refrigerant temperature, the thermal resistance of the power module 21, and the loss of the power module 21 taking into account the temperature dependency.

[0040] On the other hand, the switching frequency, which affects the loss, is a factor that can be changed by the control unit 11.

[0041] Next, thermal resistance is a value that indicates the difficulty of temperature transmission or the difficulty of heat flow in the heat transfer that occurs when heat is applied to an object, and is expressed in units of (K / W) or (°C / W). In the case of power module 21, thermal resistance varies depending on, for example, the material and structure of the members between the cooling fins and the junctions in semiconductor element 27, and the flow rate of the refrigerant. The material and structure cannot be controlled by control unit 11. However, control unit 11 can control the flow rate.

[0042] Furthermore, when the cooling device 30 is equipped with a device for variably controlling the temperature of the refrigerant, the control unit 11 can control the refrigerant temperature.

[0043] From the above, when controlling the junction temperature Tj of the power module 21 of the power converter 20 so that it does not exceed the temperature management value of the junction temperature Tj, the control unit 11 can control the switching frequency, the flow rate of the refrigerant, and the temperature of the refrigerant, among the factors that determine Tj. However, the temperature of the refrigerant is limited to the case where the cooling device 30 is equipped with a device that variably controls the temperature of the refrigerant.

[0044] Furthermore, since the loss is temperature dependent, the efficiency of the power module 21 can be improved by lowering the junction temperature Tj.

[0045] Therefore, the control unit 11 controls the flow rate of the refrigerant to each power converter 20 so as to satisfy the following two control conditions.

[0046] Control condition 1: Variable elements (switching frequency, flow rate, and refrigerant temperature) are changed so as not to exceed the temperature control value of the power module 21. The premise for controlling the flow rate, etc. is to control so as not to cause thermal destruction of the power module 21.

[0047] Control condition 2: As explained with reference to Fig. 10, by utilizing the fact that the loss of the power module 21 is temperature dependent, the flow rate to the power converter 20 that can reduce the overall loss by increasing the flow rate is increased, and the flow rate to the power converter 20 that cannot reduce the overall loss even by increasing the flow rate is decreased. Here, the overall loss means the sum of the losses of each power converter 20.

[0048] That is, control condition 2 is a condition for performing control that pursues high efficiency of the entire system. Note that control condition 2 may also be intended to reduce losses in some of the power converters 20, rather than to reduce losses overall.

[0049] For control condition 2, control unit 11 first calculates the loss of each of power converters 20A to 20D from the temperature estimation result to calculate the total system loss. Next, control unit 11 allocates the flow rate based on the current total loss and each loss, and calculates the efficiency of each power converter 20 so as to further improve efficiency. In the specific example described with reference to FIG. 7, the current total flow rate is set to 60 L / min, and the upper limit of the total remains unchanged, but flow rate control is performed for each power converter 20, with control to cool the flow rate focusing on power converters 20 whose efficiency will improve if cooled more.

[0050] Although the power module 21 has been described as an example, the same can be done for the capacitor 22 and the current sensor 23. Since wind speed control by the fan 25 is also added, the parameters of the ambient temperature and wind speed (flow velocity) are added. Overall, the first objective is to achieve control condition 1 so that the temperature falls within the temperature control value, and the second objective is to achieve high efficiency as a system.

[0051] (Example of operation of the control device 10) Next, an example of the operation of the control device 10 (control unit 11) will be described with reference to Fig. 11. The process shown in Fig. 11 is repeatedly executed at a predetermined cycle. When the process shown in Fig. 11 starts, the control unit 11 calculates the temperature and efficiency (loss) of each power converter when the flow rate is set to a uniform value based on the current operating conditions (step S11). Next, the control unit 11 calculates the loss ratio of each power converter 20 (step S12). Next, the control unit 11 calculates the flow rate ratio based on the loss ratio (step S13).

[0052] 7, in step S11, the flow rates of the four power converters 20A to 20D are set to a uniform 15 L / min for each power converter 20. If the loss ratio is A:B:C:D::4:3:2:1 in step S12, then in step S13, the flow rates are determined to be 24:18:12:6 when the total flow rate is 60 L / min. Note that A, B, C, and D represent the respective losses or flow rates of the power converters 20A to 20D.

[0053] Next, the control unit 11 calculates a plurality of flow rate increase / decrease patterns at predetermined flow rate increments using the calculated flow rate ratio as a base pattern (step S15). In step S15, for example, the flow rate increment of each power converter 20 is set to 0.5 L / min, and the flow rate calculation result obtained in step S13 is used as (1) base pattern (24:18:12:6), and the following six patterns are obtained. (2) When the flow rate of A is increased by 1.5 L / min and the flow rates of all other components are decreased by 0.5 L / min. (3) When the flow rate of A is increased by 3.0 L / min and the flow rates of all other components are decreased by 1.0 L / min. (4) When the flow rate of A is increased by 4.5 L / min and the flow rates of all other components are decreased by 1.5 L / min. (5) When the flow rate of A is decreased by 1.5 L / min and the flow rates of all other components are increased by 0.5 L / min. (6) When the flow rate of A is decreased by 3.0 L / min and the flow rates of all other components are increased by 1.0 L / min. (7) When the flow rate of A is decreased by 4.5 L / min and the flow rates of all other components are increased by 1.5 L / min.

[0054] Next, the control unit 11 calculates the temperature and efficiency (loss) for a plurality of patterns (step S16), and then selects the pattern that provides the highest efficiency for the entire system (step S17).

[0055] Next, the control unit 11 determines whether a predetermined switching condition is met (step S18). The switching condition is, for example, that an improvement in system efficiency of at least a predetermined value can be expected compared to a uniform flow rate, and that a predetermined temperature of each power converter 20 is within a temperature control value. The value of the improvement in system efficiency of at least the predetermined value can be, for example, 1 kW or more, but is not limited to this. The predetermined value is, for example, a value below which there is a possibility that the benefits of switching the flow rate do not outweigh the disadvantages of switching.

[0056] If a predetermined switching condition is met (step S18: YES), the control unit 11 executes control to switch the flow rate to the selected pattern (step S19). If the predetermined switching condition is not met (step S18: NO), the control unit 11 determines whether all patterns have been selected (step S20). If all patterns have not been selected (step S20: NO), the control unit 11 selects the pattern with the next highest efficiency (step S21) and executes the determination process of step S18. On the other hand, if all patterns have been selected (step S20: YES), the control unit 11 sets the flow rate uniformly (step S22) and ends the process shown in FIG. 11.

[0057] Through the above process, the control device 10 can perform flow rate control that satisfies the above-mentioned control condition 1 and can improve the efficiency of the entire system.

[0058] In step S14, the control unit 11 may additionally execute the following variable processing of the switching frequency. For example, the control unit 11 switches the frequency from 10 kHz to 5 kHz when the output of the power converter 20 is 75% or more, and switches it from 5 kHz to 10 kHz when the output of the power converter 20 is 65% or less. However, when the output is greater than 65% and less than 75%, hysteresis is provided, so that if the current frequency is 10 kHz, it is set to 10 kHz, and if the current frequency is 5 kHz, it is set to 5 kHz. Note that the value (%) of the ratio of output to rated output and the value (kHz) of the frequency are merely examples and can be any value.

[0059] Furthermore, in step S18, control unit 11 may additionally execute the following refrigerant temperature varying process. That is, control unit 11 may execute the refrigerant temperature reduction control when the system efficiency is expected to be improved by a predetermined value or more but the predetermined temperature of any of power converters 20 is not within the temperature control value.

[0060] As described above, according to this embodiment, when the predetermined temperature includes the junction temperature of the power module 21, the control unit 11 can estimate the junction temperature Tj based on the temperature of the refrigerant and the loss of the power module 21 taking into account the thermal resistance and temperature dependency of the power module 21. The control unit 11 can also control the switching frequency of at least one power module in accordance with the efficiency of each power converter 20. The control unit 11 can also control the flow rates of the refrigerant and the temperature of the refrigerant.

[0061] (Variation) The control unit 11 may be included in any of the power converters 20. In this case, the power converter 20 including the control unit 11 also functions as the control device 10 and can control the other power converters 20 as slaves as a master.

[0062] (Actions and Effects) According to the control device 10, the control system 1, and the control method of the present embodiment, the plurality of power converters 20 can be appropriately cooled.

[0063] (Other embodiments) Although the embodiments of the present disclosure have been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like are also included within the scope of the gist of the present disclosure. For example, the structure of the power converter 20 is not limited to that described with reference to Figures 3 to 5, and may be one that uses a housing conforming to standards such as a rack-mount type or a tower type.

[0064] <Computer Configuration> FIG. 12 is a schematic block diagram illustrating the configuration of a computer according to at least one embodiment. The computer 90 includes a processor 91 , a main memory 92 , a storage 93 , and an interface 94 . The above-described control device 10, power converter control device 26, etc. are implemented in a computer 90. The operations of the above-described processing units are stored in the form of a program in a storage 93. A processor 91 reads the program from the storage 93, loads it into a main memory 92, and executes the above-described processing in accordance with the program. The processor 91 also allocates storage areas in the main memory 92 corresponding to the above-described storage units in accordance with the program.

[0065] The program may be for realizing some of the functions to be performed by the computer 90. For example, the program may be combined with other programs already stored in storage or other programs implemented in other devices to perform the functions. In other embodiments, the computer may include a custom LSI (Large Scale Integrated Circuit) such as a PLD (Programmable Logic Device) in addition to or instead of the above configuration. Examples of PLDs include PAL (Programmable Array Logic), GAL (Generic Array Logic), CPLD (Complex Programmable Logic Device), and FPGA (Field Programmable Gate Array). In this case, some or all of the functions realized by the processor may be realized by the integrated circuit.

[0066] Examples of storage 93 include a hard disk drive (HDD), a solid state drive (SSD), a magnetic disk, a magneto-optical disk, a compact disc read-only memory (CD-ROM), a digital versatile disc read-only memory (DVD-ROM), and a semiconductor memory. Storage 93 may be an internal medium directly connected to the bus of computer 90, or an external medium connected to computer 90 via interface 94 or a communication line. Furthermore, when this program is distributed to computer 90 via a communication line, computer 90 that receives the program may load the program into main memory 92 and execute the above-described processing. In at least one embodiment, storage 93 is a non-transitory tangible storage medium.

[0067] <Additional Notes> The control device 10 described in each embodiment can be understood, for example, as follows.

[0068] (1) A control device 10 according to a first aspect includes a control unit 11 that controls the flow rate of refrigerant distributed to each of a plurality of power converters 20, each of which has a power module 21, so that the predetermined temperatures of the power converters 20 do not exceed the respective temperature control values. According to this aspect and the following aspects, the plurality of power converters 20 can be appropriately cooled.

[0069] (2) The control device 10 according to a first aspect is the control device 10 of (1), in which the control unit 11 controls the flow rates in accordance with the outputs of the power converters 20 .

[0070] (3) The control device 10 according to a third aspect is the control device 10 of (1), in which the control unit 11 controls the flow rates in accordance with the efficiencies of the power converters 20.

[0071] (4) The control device 10 according to a fourth aspect is the control device 10 of (1) to (3), wherein the predetermined temperature includes the junction temperature of the power module 21, and the control unit 11 estimates the junction temperature based on the temperature of the refrigerant and the thermal resistance and loss of the power module 21 taking into account temperature dependency of the power module 21.

[0072] (5) The control device 10 according to the fifth aspect is the control device 10 of (1) to (4), wherein the power converter 20 further has a current sensor 23, a forced air cooling device (fan 25), and a temperature sensor 24 that detects the temperature inside the power converter housing, the predetermined temperature includes the temperature of the current sensor 23, and the control unit 11 controls the flow rate and the wind speed of the forced air cooling device based on the ambient temperature detected by the temperature sensor 24 and the operating state of the current sensor 23.

[0073] (6) The control device 10 according to the sixth aspect is the control device 10 of (6), wherein the power converter 20 further has a capacitor 22, the predetermined temperature includes the temperature of the capacitor 22, and the control unit 11 controls the flow rate based on the loss of the capacitor 22 and the temperature of the refrigerant, and controls the wind speed of the forced air cooling device based on the ambient temperature.

[0074] (7) The control device 10 according to the seventh aspect is the control device 10 of (1) to (6), wherein the control unit 11 further controls the switching frequency of at least one of the power modules 21 in accordance with the efficiency of each of the power converters 20.

[0075] (8) The control device 10 according to an eighth aspect is the control device 10 of (1) to (7), wherein the control unit 11 controls the flow rates of the refrigerants and also controls the temperature of the refrigerants.

[0076] (9) The control device 10 according to a ninth aspect is the control device 10 according to any one of (1) to (8), in which the control unit 11 is included in one of the power converters 20 . [Explanation of symbols]

[0077] 1. Control system 10...Control device 11...Control unit 20, 20A, 20B, 20C, 20D... Power converters 21...Power module 22...Capacitor 23...Current sensor 24...Temperature sensor 25...Fan 26...Power converter control device 27...Semiconductor element

Claims

1. a control unit that controls the flow rate of a refrigerant distributed to each of a plurality of power converters, each of which has a power module, within a range in which each predetermined temperature of the power converters does not exceed each temperature control value; The control unit calculating a loss ratio of each power converter when the flow rate is uniform based on the current operating conditions; calculating a flow rate ratio of the refrigerant according to the loss ratio; calculating a plurality of flow rate increase / decrease patterns using the flow rate ratio as a base pattern; calculating a temperature and a loss of each of the power converters when the plurality of flow rate increase / decrease patterns are applied; selecting a flow rate increase / decrease pattern that provides the highest overall system efficiency; Execute Control device.

2. the predetermined temperature includes a junction temperature of the power module, The control unit estimates the junction temperature based on the temperature of the coolant and the loss of the power module taking into account the thermal resistance and temperature dependency of the power module. The control device according to claim 1 .

3. the power converter further includes a current sensor, a forced air cooling device, and a temperature sensor for detecting a temperature inside the power converter housing; the predetermined temperature includes the temperature of the current sensor; The control unit controls the flow rate and the air speed of the forced air cooling device based on the ambient temperature detected by the temperature sensor and the operating state of the current sensor. The control device according to claim 1 or 2.

4. the power converter further comprises a capacitor; the predetermined temperature includes a temperature of the capacitor; The control unit controls the flow rate based on the loss of the capacitor and the temperature of the refrigerant, and controls the air speed of the forced air cooling device based on the ambient temperature. The control device according to claim 3 .

5. The control unit further controls a switching frequency of at least one of the power modules in accordance with each efficiency of each of the power converters. The control device according to any one of claims 1 to 4.

6. The control unit controls the flow rates of the refrigerant and also controls the temperature of the refrigerant. The control device according to any one of claims 1 to 5.

7. Any of the power converters includes the control unit. The control device according to any one of claims 1 to 6.

8. a cooling device that supplies the refrigerant to each of the power converters; The control device according to any one of claims 1 to 7. A control system comprising:

9. a control unit that controls the flow rate of a refrigerant distributed to each of a plurality of power converters, each of which has a power module, within a range in which each predetermined temperature of the power converters does not exceed each temperature control value; calculating a loss ratio of each power converter when the flow rate is uniform based on the current operating conditions; calculating a flow rate ratio of the refrigerant according to the loss ratio; calculating a plurality of flow rate increase / decrease patterns using the flow rate ratio as a base pattern; calculating a temperature and a loss of each of the power converters when the plurality of flow rate increase / decrease patterns are applied; selecting a flow rate increase / decrease pattern that provides the highest overall system efficiency; Execute Control method.

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