Power conversion device and control method

Abstract

To provide a power conversion device and a control method capable of suppressing variations in accumulated operation time of each of a plurality of fans and reducing capacity of a memory used for storing the accumulated operation time.SOLUTION: A power conversion device includes: a plurality of fans; a housing for housing the plurality of fans; a control unit for controlling an operation state of each of the plurality of fans; and a memory for storing an accumulation value of the operation time of the plurality of fans. The control unit determines an operating number indicating the number of fans to be operated among the plurality of fans based on at least one variable value of temperature inside the housing, power during power conversion operation by the power conversion device, and a current during power conversion operation, determines the fans to be operated based on a predetermined plurality of phases and the operating number, switches the phase in accordance with a predetermined switching order, and determines timing of switching the phase based on the accumulation value after being calculated by a calculation unit so that the accumulation value does not exceed a first predetermined value.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a power conversion device and a control method.

Background Art

[0002] There is known a power storage system that is connected to a commercial power system, performs self - operation during a power outage of the power system, and supplies the power stored in a storage battery to a specific load via a power conversion device. There is also known a power storage system that is connected to a photovoltaic power generation system and stores the generated power (i.e., surplus power) exceeding the power supplied to the load in a storage battery. The power storage system connected to the photovoltaic power generation system can be interconnected with the power system, for example, by supplying the generated power to the commercial power system via a power conversion device according to the power generation state of the photovoltaic power generation system.

[0003] The power conversion function of the power conversion device is realized by a converter (for example, a DC / DC converter and a DC / AC converter) composed of switching elements. The power conversion device includes a fan to suppress the temperature rise inside the power conversion device due to heat generation caused by the operation of the switching elements. When a plurality of fans are provided, the number of operating fans is changed according to the operating state of the power conversion device, etc. For example, Patent Document 1 discloses a fan control method for a cooling device for an indoor installation transformer that detects either the temperature or the load current and controls the number of operating fans among a plurality of fans. This control method counts the cumulative operation time of each fan. When increasing the number of operating fans, the fans are operated in ascending order of the cumulative operation time, and when decreasing the number of operating fans, the fans are stopped in descending order of the cumulative operation time. Also, it is disclosed that the fan number control is reset at regular intervals so that a large deviation does not occur in the operation time even when there is a long period during which the number of operating fans does not change. At that time, the cumulative operation time of each fan is maintained.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Japanese Patent Publication No. 2006-19349 [Overview of the project] [Problems that the invention aims to solve]

[0005] In the configuration disclosed in Patent Document 1, it is necessary to maintain the cumulative operating time of each fan in order to equalize the operating time of multiple fans. When storing the cumulative operating time in memory, a larger memory capacity is required to prevent overflow and to avoid exceeding the upper limit of the data type. The cumulative operating time also needs to be retained when the device itself is shut down for maintenance, etc., and for this purpose, non-volatile memory (e.g., flash memory) is used. Non-volatile memory has a limit on the number of times data can be written and is prone to failure. To address this, it is conceivable to periodically change the write address, i.e., the write location, to the non-volatile memory, but this requires securing a memory capacity larger than the size of the data to be stored. It is also possible to store the cumulative operating time in volatile memory such as RAM (Random Access Memory) and periodically write the cumulative operating time to non-volatile memory, but if the device is shut down in an emergency, there is a problem that the latest cumulative operating time of the fan (i.e., the accurate cumulative operating time) will be lost. It is possible to use the cumulative operating time held in non-volatile memory, but if the number of emergency shutdowns increases, the bias in the cumulative operating time may become larger.

[0006] Furthermore, in power conversion devices used in energy storage systems and solar power generation systems, a large amount of non-volatile memory is used to adjust output power according to the load, control grid connection, and store information related to system operation. If the operating time of individual components such as fans is stored, the memory capacity becomes excessive.

[0007] Therefore, the present disclosure aims to provide a power conversion device and control method that can suppress variations in the cumulative operating time of each of multiple fans and reduce the capacity of the memory used to store the cumulative operating time. [Means for solving the problem]

[0008] A power converter according to one aspect of the present disclosure includes a plurality of fans, a housing for housing the plurality of fans, a control unit for controlling the operating state of each of the plurality of fans, and a memory for storing the cumulative operating time of the plurality of fans. The control unit determines the number of fans to be operated from the plurality of fans based on at least one variable value among the temperature inside the housing, the power during the power conversion operation by the power converter, and the current during the power conversion operation. The control unit determines which fans to operate from the plurality of fans based on one of a predetermined number of phases and the number of operating fans. The phases are switched according to a predetermined switching order. For each of the phases, a combination of fans to be operated from the plurality of fans is specified for each number of operating fans. The cumulative value includes the cumulative value obtained by accumulating at least one of the operating time of each of the plurality of fans and the operating time for each phase. The control unit includes a calculation unit that calculates the cumulative value so that the cumulative value does not exceed a first predetermined value. The control unit determines the timing for switching phases based on the cumulative value calculated by the calculation unit.

[0009] A control method relating to another aspect of the present disclosure is a control method for a power converter including a plurality of fans and a housing housing the plurality of fans, comprising: a control step for controlling the operating state of each of the plurality of fans; and a storage step for storing a cumulative value of the operating time of the plurality of fans, wherein the control step includes: determining the number of operating fans, which represents the number of fans to be operated from the plurality of fans, based on at least one variable value among the temperature inside the housing, the power during the power conversion operation by the power converter, and the current during the power conversion operation; determining which fans to operate from the plurality of fans based on one of a predetermined phase and the number of operating fans; and switching steps for switching phases according to a predetermined switching order, wherein for each of the plurality of phases, a combination of fans to be operated from the plurality of fans is specified for each number of operating fans, and the cumulative value includes the cumulative value of at least one of the operating time of each of the plurality of fans and the operating time for each phase, wherein the switching step includes: a calculation step for calculating the cumulative value such that the cumulative value does not exceed a first predetermined value; and a step for determining the timing to switch phases based on the cumulative value calculated by the calculation step. [Effects of the Invention]

[0010] According to this disclosure, it is possible to provide a power conversion device and control method that can suppress variations in the cumulative operating time of each of multiple fans and reduce the capacity of the memory used to store the cumulative operating time. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a block diagram showing the configuration of a power converter according to an embodiment of this disclosure. [Figure 2] Figure 2 is a flowchart showing the operation of the power converter shown in Figure 1. [Figure 3] Figure 3 is a flowchart showing the process for identifying the operating fan as shown in Figure 2. [Figure 4] Figure 4 is a table showing the changes in the counters of each fan when only one of the three fans is running. [Figure 5] Figure 5 is a timing chart showing the changes in the counters for each fan shown in Figure 4. [Figure 6] Figure 6 is a table showing the changes in the counters of each fan when two of the three fans are in operation. [Figure 7] Figure 7 is a timing chart showing the changes in the counters for each fan shown in Figure 6. [Figure 8] Figure 8 is a table showing the changes in the counters of each fan when the number of operating fans changes. [Figure 9] Figure 9 is a timing chart showing the changes in the counters for each fan shown in Figure 8. [Figure 10] Figure 10 shows an example of a fan control method that switches phases based on phase operating time. [Figure 11] Figure 11 is a flowchart showing temperature protection control. [Figure 12] Figure 12 is a flowchart showing the process of sequentially starting up multiple fans. [Modes for carrying out the invention]

[0012] [Description of Embodiments in this Disclosure] First, the embodiments of this disclosure will be listed and explained. At least some of the embodiments described below may be combined in any way.

[0013] (1) The power conversion device according to the first aspect of the present disclosure includes a plurality of fans, a housing that houses the plurality of fans, a control unit that controls the operating state of each of the plurality of fans, and a memory that stores the cumulative value of the operating time of the plurality of fans. The control unit determines the number of operating fans, which represents the number of fans to be operated among the plurality of fans, based on at least one variable value of the temperature inside the housing, the power during the power conversion operation by the power conversion device, and the current during the power conversion operation. The control unit determines the fans to be operated among the plurality of fans based on one of a plurality of predetermined phases and the number of operating fans, switches the phases according to a predetermined switching order, and for each of the plurality of phases, the combination of the fans to be operated among the plurality of fans is specified for each number of operating fans. The cumulative value includes a value obtained by accumulating at least one of the operating time of each of the plurality of fans and the operating time for each phase. The control unit includes an arithmetic unit that calculates the cumulative value so that the cumulative value does not exceed a first predetermined value, and determines the timing for switching the phase based on the cumulative value calculated by the arithmetic unit. Thereby, the capacity of the memory used for storing the cumulative operating time can be reduced, and the variation in the cumulative operating time of each of the plurality of fans can be suppressed.

[0014] (2) In the above (1), the number of phases can be equal to or greater than the number of the plurality of fans, and the cumulative value can include a value obtained by accumulating the operating time of each of the plurality of fans. Thereby, the variation in the cumulative operating time of each of the plurality of fans can be further suppressed. Therefore, it is possible to avoid the situation where only a specific fan operates for a long time and fails.

[0015] (3) In the above (1) or (2), the plurality of phases may be defined such that each of the plurality of fans operates the same number of times in the combination determined corresponding to the same number of operating fans. Thereby, the variation in the cumulative operating time of each of the plurality of fans can be further suppressed.

[0016] (4) In any one of (1) to (3) above, the control unit may switch the phase upon receiving that the cumulative value after being calculated by the calculation unit becomes equal to or greater than a first threshold value smaller than the first predetermined value. Thereby, since the operating fan can be changed, variations in the cumulative operating time of each of the plurality of fans can be suppressed.

[0017] (5) In (4) above, the calculation unit may store the number of times the calculation has been executed in a memory. Thereby, the approximate cumulative operating time of the fan can be grasped as the product of the number of times the calculation has been executed and the first threshold value (for example, 60 minutes) for switching the phase. When a fan fails, it can be determined whether it is due to the lifespan of the fan or the fan being a defective product, and it can be utilized for failure analysis.

[0018] (6) In any one of (1) to (5) above, the cumulative value may include, as a count value, a value obtained by accumulating the operating time of each of the plurality of fans, and the calculation unit may calculate the cumulative value by subtracting a second predetermined value from each of all the count values to obtain a new count value upon receiving that all the count values of each of the plurality of fans have become equal to or greater than the first threshold value, and the control unit may further switch the phase according to the switching order upon receiving that the count value of the fan corresponding to the phase being executed among the operating fans has become equal to or greater than the first threshold value. Thereby, the capacity of the memory used for storing the cumulative operating time can be reduced, and variations in the cumulative operating time of each of the plurality of fans can be suppressed.

[0019] (7) In any one of (1) to (6) above, the control unit may operate the fans of the operating number after a predetermined time has elapsed upon receiving that the operating number determined based on the variable value is different from the number of operating fans. Thereby, it is possible to suppress frequent switching between the operation and stop of the fans within a short period of time, and suppress the failure of the fans.

[0020] (8) In any one of (1) to (7) above, the control unit may increase the number of operating fans when the variable value changes from less than the second threshold to the second threshold or greater, and decrease the number of operating fans when the variable value changes from a state greater than the third threshold (less than the second threshold) to the third threshold or less. This can suppress frequent switching between fan operation and stopping in a short period of time, and can suppress fan failure.

[0021] (9) In any one of (1) to (8) above, if the control unit receives that the number of operating fans determined based on the variable value is 2 or more greater than the number of fans currently in operation, it may start the stopped fans one by one until the number of operating fans reaches the determined number. This avoids the generation of a large inrush current when starting two or more fans from a stopped state.

[0022] (10) In any one of (1) to (9) above, the power converter may further include a temperature detection unit for detecting the temperature inside the enclosure and a determination unit for determining whether the temperature detected by the temperature detection unit is greater than a fourth threshold, and the control unit may increase the number of operating fans in response to the determination unit determining that the temperature is greater than the fourth threshold. This makes it possible to protect the temperature of the power converter.

[0023] (11) A control method relating to a second aspect of the present disclosure is a control method for a power converter including a plurality of fans and a housing housing the plurality of fans, comprising: a control step for controlling the operating state of each of the plurality of fans; and a storage step for storing a cumulative value of the operating time of the plurality of fans, wherein the control step includes: determining the number of fans to be operated from the plurality of fans based on at least one variable value among the temperature inside the housing, the power during power conversion operation by the power converter, and the current during power conversion operation; determining which fans to be operated from the plurality of fans based on one of a predetermined plurality of phases and the number of operating fans; and switching steps for switching phases according to a predetermined switching order, wherein for each of the plurality of phases, a combination of fans to be operated from the plurality of fans is specified for each number of operating fans, and the cumulative value includes the cumulative value of at least one of the operating time of each of the plurality of fans and the operating time for each phase, and the switching step includes: a calculation step for calculating the cumulative value such that the cumulative value does not exceed a first predetermined value; and a step for determining the timing to switch phases based on the cumulative value calculated by the calculation step. This reduces the amount of memory used to store cumulative operating time, and suppresses variations in the cumulative operating time of each of the multiple fans.

[0024] [Details of the embodiments of this disclosure] In the following embodiments, identical parts are assigned the same reference numeral. Their names and functions are also identical. Therefore, detailed descriptions of them will not be repeated.

[0025] Referring to Figure 1, the power converter 100 according to the first embodiment of this disclosure includes a first DC / DC converter 102, a second DC / DC converter 104, a DC / AC converter 106, a control unit 108, a memory 110, a first fan 112, a second fan 114, a third fan 116, and a temperature sensor 118. These components are housed in a casing (not shown). The power converter 100 is connected to a PV (photovoltaic) panel 200 and a battery 202, and together with the PV panel 200 and the battery 202, constitutes a power supply system. The power converter 100 is also connected to a load 204 and a grid 206. The PV panel 200 is a photovoltaic panel in which a plurality of series-connected solar cells are arranged on a plane and sealed using tempered glass or the like. The battery 202 is a rechargeable battery such as a lithium-ion secondary battery. The power converter 100 supplies power to the load 204 and the grid 206 connected to the power converter 100 as appropriate. Load 204 is, for example, electrical equipment (e.g., household appliances). System 206 is the commercial power grid.

[0026] The first DC / DC converter 102, under the control of the control unit 108, boosts the DC voltage output from the PV panel 200 and outputs it to the DC / AC converter 106. The second DC / DC converter 104, under the control of the control unit 108, boosts the DC voltage output from the battery 202 and outputs it to the DC / AC converter 106. The outputs of the first DC / DC converter 102 and the second DC / DC converter 104 are connected in parallel. The second DC / DC converter 104 is capable of bidirectional power conversion and converts the surplus power output from the first DC / DC converter 102 to charge the battery 202. The first DC / DC converter 102 and the second DC / DC converter 104 are implemented, for example, by a bridge circuit using semiconductor switching elements (FETs (Field Effect Transistors) etc.).

[0027] The DC / AC converter 106, under the control of the control unit 108, converts the DC voltage output from the first DC / DC converter 102 and the second DC / DC converter 104 into an AC voltage and outputs it. The output power of the DC / AC converter 106 is supplied to the load 204 and the power system 206 as appropriate. The DC / AC converter 106 is implemented, for example, by a bridge circuit using semiconductor switching elements.

[0028] Each of the first fan 112, second fan 114, and third fan 116 includes an intake port and an exhaust port, the exhaust port being located in an opening formed in the wall of the power converter 100 (i.e., the housing). The first fan 112, second fan 114, and third fan 116 are for cooling the inside of the power converter 100 (i.e., the inside of the housing). The first fan 112, second fan 114, and third fan 116 operate under the control of the control unit 108, and discharge the hot air inside the power converter 100 to the outside of the power converter 100 through the opening. The temperature sensor 118 detects the temperature. The temperature detected by the temperature sensor 118 (specifically, the electrical signal corresponding to the temperature) is input to the control unit 108.

[0029] The control unit 108 controls the power conversion function of each DC / DC converter, i.e., the input and output voltages and currents, by outputting control signals (e.g., gate signals) for the switching elements (e.g., FETs) that constitute each of the first DC / DC converter 102, the second DC / DC converter 104, and the DC / AC converter 106. The power converter 100 has sensors (not shown) that measure the voltage and current of each part, and the control unit 108 controls the first DC / DC converter 102, the second DC / DC converter 104, and the DC / AC converter 106 based on the current and voltage detected by the sensors. In addition, the control unit 108 controls the operating state (specifically, the number of fans to operate) of the first fan 112, the second fan 114, and the third fan 116 according to the temperature detected by the temperature sensor 118 and the power of the power converter 100.

[0030] The control unit 108 is, for example, a CPU (Central Processing Unit). The memory 110 stores the program and parameters that the control unit 108 executes. The memory 110 is, for example, non-volatile memory (e.g., flash memory). The functions of the control unit 108 are realized by executing the program stored in the memory 110. For example, if the temperature inside the enclosure becomes high (e.g., above a predetermined value), the number of fans to be operated is increased. That is, the control unit 108 operates the fans that are currently stopped among the first fan 112, the second fan 114, and the third fan 116. If the temperature inside the enclosure becomes low (e.g., below a predetermined value), the number of fans to be operated is decreased. That is, the control unit 108 stops the fans that are currently running among the first fan 112, the second fan 114, and the third fan 116. This allows for efficient cooling of the inside of the power converter 100 (i.e., inside the enclosure) while suppressing unnecessary power consumption caused by continuously operating all fans.

[0031] (Fan control operation) Referring to Figures 2 and 3, the control operation of the first fan 112, second fan 114, and third fan 116 by the control unit 108 will be explained. Here, the control unit 108 controls the number of fans to operate, for example, as shown in Table 1. The memory 110 is assumed to store a table corresponding to Table 1. In Table 1, Power P represents the operating power of the power converter 100, Temperature T represents the temperature inside the power converter 100, and Quantity represents the number of fans to operate. The memory 110 is also provided with an area (hereinafter referred to as a counter) for storing the cumulative operating time of the first fan 112, second fan 114, and third fan 116, as will be described later. The value stored in the counter (hereinafter referred to as the count value) represents the cumulative operating time of the fans. The count value is stored, for example, in minutes.

[0032] [Table 1]

[0033] In step 300, the control unit 108 acquires the temperature T inside the housing of the power conversion device 100 and the operating power P of the power conversion device 100 from the temperature sensor 118. Thereafter, the control proceeds to step 302. The control unit 108 acquires the temperature T by the temperature sensor 118. The control unit 108 calculates the power of, for example, the first DC / DC converter 102, the second DC / DC converter 104, and the DC / AC converter 106 from current sensors and voltage sensors arranged inside the power conversion device 100, and sets the maximum value among the calculated powers as the operating power P. Note that the sum of the calculated powers may be set as the operating power P.

[0034] In step 302, the control unit 108 determines whether or not the power P acquired in step 300 is equal to or greater than P1 and less than P3. If it is determined that P1 ≤ P < P3, the control proceeds to step 310. Otherwise, the control proceeds to step 304.

[0035] In step 304, the control unit 108 determines whether or not the power P acquired in step 300 is less than P1. If it is determined that P < P1, the control proceeds to step 308. Otherwise, the control proceeds to step 306.

[0036] In step 306, the control unit 108 operates all of the first fan 112, the second fan 114, and the third fan 116. Thereafter, the control proceeds to step 312. When the fans operate, the corresponding counters provided in a predetermined area of the memory 110 are incremented as time elapses.

[0037] In step 308, the control unit 108 stops all of the first fan 112, the second fan 114, and the third fan 116. Thereafter, the control proceeds to step 322. If all of the first fan 112, the second fan 114, and the third fan 116 are stopped, that state is maintained. Note that if the fans are stopped, the corresponding counters provided in a predetermined area of the memory 110 are not incremented even as time elapses, and the count values are maintained.

[0038] In step 310, the control unit 108 executes a process of identifying the fan to be operated (hereinafter referred to as the operating fan identification process). Step 306 is executed when P1 ≤ P < P3. As shown in Table 1, the number of fans to be operated is determined according to the temperature T and the power P, and further the phase is determined. Specifically, the control unit 108 executes the flowchart shown in FIG. 4.

[0039] Referring to FIG. 4, in step 330, the control unit 108 uses the temperature T and the power P acquired in step 300 to determine the number of fans to be operated by referring to Table 1 stored in the memory 110. Then, the control proceeds to step 332. Specifically, if T < T1 and P1 ≤ P < P2, the number of fans to be operated is determined to be 1. If T < T1 and P2 ≤ P < P3, or if T ≥ T1 and P1 ≤ P < P2, the number of fans to be operated is determined to be 2. If T ≥ T1 and P2 ≤ P < P3, the number of fans to be operated is determined to be 3.

[0040] In step 332, the control unit 108 determines whether the number determined in step 330 has been changed from the number determined when step 330 was executed last time. Specifically, the control unit 108 determines whether the number determined in step 330 is different from the number of fans to be operated stored in the memory 110. In the memory 110, 0 is set as the initial value of the number of fans to be operated. If it is determined that there is a change, the control unit 108 stores the number determined in step 330 in the memory 110, and the control proceeds to step 334. Otherwise, the control proceeds to step 342.

[0041] In step 334, the control unit 108 determines whether to decrease the number of operating fans. That is, it determines whether the change determined in step 332 is a decrease in the number. If it is determined that there is a decrease, the control proceeds to step 338. Otherwise, the control proceeds to step 336.

[0042] In step 336, the control unit 108 increases the number of operating fans. That is, the control unit 108 sets the number of operating fans to the number determined in step 330. After that, the control proceeds to step 342.

[0043] In step 338, the control unit 108 determines whether the power P is less than or equal to Pi-Pd. Here, Pi refers to the lower boundary values ​​P1, P2, or P3 of the range to which the current power P belongs, as shown in Table 1. Pd is a predetermined value. That is, the control unit 108 determines whether the current power P is less than or equal to a value slightly smaller than the lower boundary value Pi (Pi-Pd). If it is determined that P ≤ Pi-Pd, the control proceeds to step 340. Otherwise, the control unit 108 does not change (specifically, does not decrease) the number of fans to operate, and the control proceeds to step 342. Step 338 is intended to introduce hysteresis to the increase or decrease in the number of fans to operate, so that the operating state tends to be maintained. This suppresses repeated fan shutdowns in short periods of time and suppresses fan failure.

[0044] In step 340, the control unit 108 reduces the number of operating fans. That is, it sets the number of operating fans to the number determined in step 330. After that, the control proceeds to step 342.

[0045] In step 342, the control unit 108 identifies the phase and controls the first fan 112, the second fan 114, and the third fan 116. The control of each fan is determined, for example, by Table 2, which is stored in memory 110. In Table 2, ON and OFF represent the operation and shutdown of the first fan 112, the second fan 114, and the third fan 116, respectively. Table 2 is used to identify the operation or shutdown of each fan for each combination of the number of fans in operation (i.e., the number of fans to be operated) and the phase.

[0046] [Table 2]

[0047] Specifically, the control unit 108 uses the current phase and the current number of fans, or the number of fans changed in step 336 or step 340, to refer to Table 2 stored in memory 110 and determine which fans to operate and which to stop. As will be described later, the current phase is stored in memory 110, and the control unit 108 obtains the current phase by referring to memory 110. It is assumed that memory 110 stores data representing the first phase Ph1 as the initial value of the current phase. Therefore, when step 342 is executed for the first time, the control unit 108 obtains the first phase Ph1. The control unit 108 operates the determined fans. After that, the control returns to the flowchart in Figure 2 and proceeds to step 312. When a fan is operating, the corresponding counter in a predetermined area of ​​memory 110 is incremented over time. When a fan is stopped, the corresponding counter in the predetermined area of ​​memory 110 is not incremented even after time has passed, and the count value is maintained.

[0048] In step 312, the control unit 108 determines whether the count value of the fan corresponding to the current phase is greater than or equal to the threshold Th. If it is determined that the count value ≥ the threshold Th, the control proceeds to step 314. Otherwise, the control proceeds to step 316. The fan corresponding to the phase is the first fan 112 if the first phase Ph1 is being executed, the second fan 114 if the second phase Ph2 is being executed, and the third fan 116 if the third phase Ph3 is being executed. The threshold is, for example, 60 (in minutes).

[0049] In step 314, the control unit 108 switches phases. Then, the control proceeds to step 316. Specifically, the control unit 108 reads the current phase from memory 110, identifies the next phase, and overwrites the current phase in memory 110 with the next phase. The phases are switched cyclically in the order of the first phase Ph1, the second phase Ph2, and the third phase Ph3 as shown in Table 2. That is, if it is currently the third phase Ph3, it will switch to the first phase Ph1.

[0050] In step 316, the control unit 108 determines whether the count value of all fans is greater than or equal to the threshold Th. If it is determined that the count value ≥ the threshold Th for all count values, the control proceeds to step 318. Otherwise, the control proceeds to step 320.

[0051] In step 318, the control unit 108 decreases the count values ​​of the first fan 112, the second fan 114, and the third fan 116. Then, the control proceeds to step 320. Specifically, the control unit 108 subtracts a predetermined value from the count value of each fan stored in memory 110. The predetermined value is, for example, 60 (in minutes).

[0052] In step 320, the control unit 108, similar to step 312, determines whether the count value of the fan corresponding to the current phase is greater than or equal to the threshold Th. If it is determined that the count value ≥ the threshold Th, control returns to step 314 and the phase is switched again. Otherwise, control proceeds to step 322. By executing step 320, which is the same as step 312, even after the phase has been switched or after the count value has been decreased, if the count value of the fan used to determine whether or not to switch phases is greater than the threshold Th, the phase will be switched again. This prevents fans with count values ​​exceeding the threshold from operating continuously.

[0053] In step 322, the control unit 108 determines whether or not a termination instruction has been received. For example, if the power converter 100 is turned off, the control unit 108 determines that a termination instruction has been received. If a termination instruction has been received, the program terminates. Otherwise, control returns to step 300, and the above process is repeated.

[0054] As described above, the control unit 108 can identify which fans to operate and which to stop based on the number of operating fans determined according to the temperature T and power P, and the phase. At this time, by sequentially switching between multiple phases, the fans to operate (i.e., the fans to stop) are changed, so variations in the cumulative operating time of multiple fans can be suppressed. In addition, when the count value of each fan exceeds a predetermined value, the count value is reduced, thereby preventing the count value from exceeding the memory capacity allocated to the counter. Therefore, the memory capacity required to store the cumulative operating time of the fans can be reduced.

[0055] (Control operation of one fan) The process shown in Figures 2 and 3 will be used to specifically explain how the first fan 112, second fan 114, and third fan 116 are controlled in the power converter 100. Referring to Figures 4 and 5, the case where only one of the first fan 112, second fan 114, and third fan 116 is operating will be explained.

[0056] Figure 4 shows a state where, for example in Table 1, T < T1 and P1 ≤ P < P2 are maintained. In Figure 4, the single-step notation using an arrow indicates that as the phase shown above it is maintained for the time shown below that phase, the count value changes from the left value to the right value. The same applies to the lower notation in the two-step notation using an arrow. In the two-step notation using an arrow, the upper notation indicates that the count value is subtracted before the count value changes or is maintained as in the lower notation. A numerical value without an arrow indicates that the count value is not incremented and the numerical value is maintained while the phase shown above it is maintained for the time shown below that phase. The threshold Th is set to 60 (in minutes), and at time t0, it is assumed that the first fan 112 first operates in the first phase Ph1.

[0057] Figure 5 shows the time changes of the first count value CNT1 of the first fan 112, the second count value CNT2 of the second fan 114, and the third count value CNT3 of the third fan 116. Referring to Figure 5, when the first fan 112 starts operating from time t0, the first count value CNT1 increases. After 60 minutes have elapsed, at time t1, the first count value CNT1 reaches the threshold Th (i.e., 60) (see point A). Therefore, the determination result in step 312 of Figure 2 becomes YES, and in step 314, the switching is made from the first phase Ph1 to the second phase Ph2. Note that the determination result in step 320 is NO. As a result, the second fan 114 starts operating. Since the operating first fan 112 stops, the first count value CNT1 is maintained at 60.

[0058] At time t1, 60 minutes after the second fan 114 started operating, at time t2, the second count value CNT2 reaches the threshold Th (see point B). Therefore, the result of the determination in step 312 in Figure 2 is YES, and step 314 switches from the second phase Ph2 to the third phase Ph3. The result of the determination in step 320 is NO. As a result, the third fan 116 starts operating. The operating second fan 114 stops, so the second count value CNT2 is maintained at 60.

[0059] At time t2, 60 minutes after the third fan 116 starts operating, at time t3, the third count value CNT3 reaches the threshold Th (see point C). Therefore, the result of the judgment in step 312 in Figure 2 is YES, and step 314 switches from the third phase Ph3 to the first phase Ph1. At this time, the first count value CNT1, the second count value CNT2, and the third count value CNT3 are all above the threshold Th, so the result of the judgment in step 316 in Figure 2 is YES, and step 318 subtracts 60 from each count value. Subsequently, step 320 is executed, but regarding the first phase Ph1, which is the phase after the switch, the first count value CNT1 of the first fan 112 is below the threshold, so the first phase Ph1 is maintained and the first fan 112 starts operating. The operating third fan 116 is stopped, and the second count value CNT2 and the third count value CNT3 are maintained at 0, which is the value after subtraction.

[0060] Subsequently, the same process as described above is repeated, and the phase is switched every 60 minutes, changing the operating fan. Therefore, variations in the cumulative operating time of the first fan 112, the second fan 114, and the third fan 116 can be suppressed. If the count value of all fans exceeds the threshold, each count value is subtracted. Therefore, the memory capacity required to store the count values ​​can be reduced. In Figure 5, the upper limit of each count value is equal to the threshold Th.

[0061] (Control operation of two fans) Referring to FIGS. 6 and 7, the case where two of the first fan 112, the second fan 114, and the third fan 116 are operating (i.e., only one is stopped) will be described. FIG. 6 represents a state where, for example, in Table 1, T < T1 and P2 ≤ P < P3 are maintained. The notation in FIG. 6 is the same as that in FIG. 4. However, in FIG. 6, two-stage notation is not adopted, and the subtraction of the count value is individually noted. This is to clearly show that the phase is changed again without the execution of the changed phase, as will be described later. Also, FIG. 7 represents the time change of the first count value CNT1 of the first fan 112, the second count value CNT2 of the second fan 114, and the third count value CNT3 of the third fan 116, similar to FIG. 5. The threshold Th is set to 60 (in minutes), and at time t0, it is assumed that first the first fan 112 and the second fan 114 start operating in the first phase Ph1.

[0062] Referring to FIG. 7, when the first fan 112 and the second fan 114 start operating from time t0, the first count value CNT1 and the second count value CNT2 increase. After 60 minutes have elapsed, at time t1, the first count value CNT1 reaches the threshold Th (i.e., 60) (see point A1). Therefore, the determination result in step 312 of FIG. 2 becomes YES, and in step 314, the switch is made from the first phase Ph1 to the second phase Ph2. At this time, since the second count value CNT2 of the second fan 114, which determines the switching of the second phase Ph2, has reached the threshold Th (see point B1), the determination result in step 320 becomes YES, and step 314 is executed again to switch the phase to the third phase Ph3. That is, as shown in FIG. 6, the period of the second phase Ph2 is 0 minutes. As a result, the second fan 114 stops, and the third fan 116 starts operating. The first fan 112 that was operating maintains its operation. The second count value CNT2 is maintained at 60.

[0063] 60 minutes have elapsed from time t1, and at time t2, the third count value CNT3 reaches the threshold Th (see point C1). Therefore, the result of the determination in step 312 in Figure 2 is YES, and step 314 switches from the third phase Ph3 to the first phase Ph1. At this time, the first count value CNT1, the second count value CNT2, and the third count value CNT3 are all above the threshold Th, so the result of the determination in step 316 in Figure 2 is YES, and step 318 subtracts 60 from each count value. As a result, the first count value CNT1, the second count value CNT2, and the third count value CNT3 become 60, 0, and 0, respectively. After that, step 320 is executed. The first count value CNT1 of the first fan 112, which determines the switch to the first phase Ph1, has reached the threshold Th (see point A2), so the result of the determination in step 320 is YES, and step 314 is executed again to switch the phase to the second phase Ph2. That is, as shown in Figure 6, the duration of the first phase Ph1 after the count value is subtracted is 0 minutes. As a result, the first fan 112 stops and the second fan 114 starts operating. The third fan 116, which was operating, continues to operate. The first count value CNT1 is maintained at 60.

[0064] 60 minutes have passed since time t2, and at time t3, the second count value CNT2 reaches the threshold Th (see point B2). Therefore, the result of the determination in step 312 in Figure 2 is YES, and step 314 switches from the second phase Ph2 to the third phase Ph3. At this time, the first count value CNT1, the second count value CNT2, and the third count value CNT3 are all above the threshold Th, so the result of the determination in step 316 in Figure 2 is YES, and step 318 subtracts 60 from each count value. As a result, the first count value CNT1, the second count value CNT2, and the third count value CNT3 all become 0. The third phase Ph3 is executed, so the second fan 114 stops and the first fan 112 starts operating. The third fan 116, which was operating, continues to operate. The second count value CNT2 is maintained at 0.

[0065] Subsequently, the same process as described above is repeated, and as shown in Figures 6 and 7, at time t4, the phase switches to the second phase Ph2 (the first phase Ph is 0 minutes), and at time t5, after the count value is subtracted, the phase switches to the first phase Ph1. Therefore, variations in the cumulative operating time of the first fan 112, the second fan 114, and the third fan 116 can be suppressed. In addition, if the count value of all fans exceeds the threshold, each count value is subtracted, so the memory capacity required to store the count values ​​can be reduced. In Figure 7, the upper limit of each count value is twice the threshold Th.

[0066] (When the number of operating fans changes) Referring to Figures 8 and 9, we will now explain the case where the number of operating fans 112, 214, and 316 changes. Here, we assume that the number of operating fans changes as shown in (a) to (e). The times indicated in parentheses are the times shown in Figure 9. (a) Only the first fan 112 starts operating due to the first phase Ph1 (time t0). (b) After 30 minutes have elapsed (time t1), the number of operating fans will be 2. (c) After 70 minutes have passed since the number of operating fans became 2 (time t4), the number of operating fans will become 3. (d) After 60 minutes have passed since the number of operating fans reached 3 (time t7), the number of operating fans will decrease to 2. (e) After 30 minutes have passed since the number of operating fans decreased to 2 (time t9), the number of operating fans decreases to 1.

[0067] As a result, the operating states of the first fan 112, the second fan 114, and the third fan 116 change as shown in Figures 8 and 9. Figure 8 is written in the same way as Figures 4 and 6, except that Figure 8 shows the number of operating fans. Figure 9, like Figures 5 and 7, shows the time changes of the first count value CNT1 of the first fan 112, the second count value CNT2 of the second fan 114, and the third count value CNT3 of the third fan 116. The threshold Th is set to 60 (in minutes), and at time t0, the first fan 112 is assumed to be operating first in the first phase Ph1 as described above.

[0068] Referring to Figure 9, the first count value CNT1 increases as the first fan 112 starts operating in the first phase from time t0. At time t1, 30 minutes after time t0, the number of operating fans becomes 2, as described above. At this time, the phase is the first phase Ph1, so the second fan 114 starts operating (see Table 2).

[0069] After 30 minutes have elapsed from time t1, the first count value CNT1 reaches the threshold Th (i.e., 60). Therefore, the result of the determination in step 312 in Figure 2 is YES, and step 314 switches from the first phase Ph1 to the second phase Ph2. The result of the determination in step 320 is NO. As a result, the third fan 116 starts operating. The second fan 114 continues to operate. Since the operating first fan 112 stops, the first count value CNT1 is maintained at 60.

[0070] At time t2, 30 minutes after the third fan 116 started operating, at time t3, the second count value CNT2 reaches the threshold Th. Therefore, the result of the determination in step 312 in Figure 2 is YES, and step 314 switches from the second phase Ph2 to the third phase Ph3. The result of the determination in step 320 is NO. As a result, the first fan 112 starts operating. The third fan 116 continues to operate. The second fan 114, which was operating, stops, so the second count value CNT2 is maintained at 60.

[0071] Subsequently, after 10 minutes have elapsed, as described above, at time t4, the number of operating fans becomes 3. As a result, the second fan 114, which had been stopped, starts operating. The phase is maintained in the third phase, Ph3. At time t5, 20 minutes after time t4 (i.e., 60 minutes after time t2), the third count value CNT3 reaches the threshold Th. Therefore, the judgment result of step 312 in Figure 2 is YES, and step 314 switches from the third phase, Ph3 to the first phase, Ph1. At this time, since the first count value CNT1, the second count value CNT2, and the third count value CNT3 are all above the threshold Th, the judgment result of step 316 in Figure 2 is YES, and step 318 subtracts 60 from each count value. As a result, the first count value CNT1, the second count value CNT2, and the third count value CNT3 become 30, 20, and 0, respectively (see Figure 8).

[0072] After 30 minutes, at time t6, the first count value CNT1 reaches the threshold Th (i.e., 60). Therefore, the system switches from the first phase Ph1 to the second phase Ph2. Only the phase changes; the first fan 112, the second fan 114, and the third fan 116 remain operational.

[0073] Subsequently, at time t7, 10 minutes later, the second count value CNT2 reaches the threshold Th (i.e., 60). Therefore, the system switches from the second phase Ph2 to the third phase Ph3. Also, at time t7, as described above, the number of operating fans becomes 2, so the second fan 114 stops (see Table 2). The second count value CNT2 is maintained at 60. The first fan 112 and the third fan 116 continue to operate.

[0074] Subsequently, at time t8, 20 minutes later, the third count value CNT3 reaches the threshold Th (i.e., 60). Therefore, the system switches from the third phase Ph3 to the first phase Ph1, with the first fan 112 remaining operational, the third fan 116 stopping, and the second fan 114 starting to operate. At this point, since the first count value CNT1, the second count value CNT2, and the third count value CNT3 are all above the threshold Th, 60 is subtracted from each count value. As a result, the first count value CNT1, the second count value CNT2, and the third count value CNT3 become 30, 0, and 0, respectively (see Figure 8). From this state, as described above, the first fan 112 and the second fan 114 start operating, and the first count value CNT1 and the second count value CNT2 are counted up. The third count value CNT3 is maintained at 0.

[0075] Subsequently, at time t9, 10 minutes after time t8 (i.e., 30 minutes after time t7), the number of operating fans becomes 1 as described above. Since the phase at this time is Phase 1 (Ph1), the first fan 112 remains operational, and the second fan 114 stops. The third fan 116 remains stopped.

[0076] Subsequently, at time t10, 20 minutes after time t9 (30 minutes after time t8), the first count value CNT1 reaches the threshold Th (i.e., 60). Therefore, the system switches from the first phase Ph1 to the second phase Ph2, the first fan 112 stops, and the second fan 114 starts operating. The third fan 116 remains stopped.

[0077] Therefore, variations in the cumulative operating time of the first fan 112, the second fan 114, and the third fan 116 can be suppressed. Also, if the count value of all fans exceeds the threshold, each count value is subtracted, so the memory capacity required to store the count values ​​can be reduced. In Figure 9, the upper limit of the count value is 1.5 times the threshold Th.

[0078] As described above, the threshold Th for determining the phase switch is smaller than the maximum count value of each fan. For example, in Figure 7, the maximum count value is twice the threshold Th. Also, in Figure 9, the maximum count value is 1.5 times the threshold. When the count value exceeds the threshold Th, the phase is switched. This allows the operating fan to be changed, thus suppressing variations in the cumulative operating time of each of the multiple fans.

[0079] In the above, the change in the count value was shown in minutes, but the timing of incrementing the counter is not limited to minutes; it can be arbitrary. For example, the counter could be incremented in seconds.

[0080] The number of times the count value has been subtracted may be stored. For example, a memory 110 may be provided with an area to store the number of subtractions with an initial value of 0, and the control unit 108 may add 1 to the number of subtractions in memory 110 each time it executes step 318 shown in Figure 2. This makes it possible to determine the approximate cumulative operating time of the fan from the product of the value to be subtracted from the count value (for example, 60 minutes) and the number of subtractions. Therefore, when a fan fails, it is possible to determine whether the failure is due to the end of the fan's lifespan or because the fan was defective, and this can be used for failure analysis.

[0081] The above describes the case where the number of operating fans and the combination of operating fans for each phase are specified, as shown in Table 2, but it is not limited to this. For example, the number of operating fans and the combination of operating fans for each phase may also be specified, as shown in Table 3. In Table 3, the ON / OFF settings for 2 operating fans are different from those in Table 2. In Table 3, the other settings are the same as in Table 2. Even when using Table 3, the nth fan operates in the nth phase (n=1, 2, 3), so to determine whether or not to switch the nth phase, one should compare the nth count value CNTn with the threshold value Th.

[0082] [Table 3]

[0083] The above explanation describes the case where there are 3 fans, but it is not limited to this. Two fans or four or more fans may be used. When using four fans, for example, as shown in Table 4, the number of operating fans and the combination of operating fans for each phase can be specified. Even when using Table 4, the nth fan operates in the nth phase (n=1, 2, 3, 4), so to determine whether or not to switch the nth phase, the nth count value CNTn should be compared with the threshold value Th.

[0084] [Table 4]

[0085] As shown in Tables 2, 3, and 4, the multiple phases are designed so that each of the multiple fans operates the same number of times in combinations of fans that are operated corresponding to the same number of operating fans. For example, in Table 4, if there are two operating fans, each fan operates twice (i.e., in two phases). That is, the first fan operates in the first and fourth phases. The second fan operates in the first and second phases. The third fan operates in the second and third phases. The fourth fan operates in the third and fourth phases. This further reduces the variation in the cumulative operating time of each of the multiple fans.

[0086] The above describes the case where the subtraction process for each count value is performed when all count values ​​exceed the threshold Th, but it is not limited to this. For example, the subtraction process for each count value may be performed when the last phase (for example, the third phase in Tables 2 and 3, or the fourth phase in Table 4) is completed. For example, if the total number of fans is 3 and the number of operating fans changes as described in (a) to (e) above, by performing the subtraction process for each count value when the third phase is completed, the changes in each count value will be as shown in Figure 9. In Figure 9, the subtraction process is performed at times t5 and t8 when the third phase Ph3 is completed. As a result, in the flowchart of Figure 2, step 316 (i.e., the process of determining whether all count values ​​are above the threshold) which is always performed after step 312 is executed, becomes unnecessary, and the load on the control unit 108 can be reduced. The control unit 108 only needs to determine whether the phase after switching is the last phase when step 314, which switches phases, is executed, and if it is the last phase, it should perform the subtraction process for the counter value. It is possible that all count values ​​may exceed the threshold Th before the last phase is selected, making it impossible to select any phase. In that case, the system should be forced to select the last phase.

[0087] (modified version) The above describes a case where phases are switched based on a count value corresponding to the cumulative operating time of each fan, but it is not limited to this. Phases may also be switched based on the time each phase is maintained (i.e., the operating time for each phase). That is, in the power converter 100 shown in Figure 1, the control unit 108 may switch phases based on the operating time for each phase.

[0088] The control unit 108, similarly to the above, determines the number of operating fans from the temperature T and power P based on Table 1, and determines the combination of operating fans corresponding to the phase based on Table 2. The control unit 108 switches phases when the time each phase has been maintained reaches a threshold Th. The memory 110 stores the operating times of the first phase Ph1, the second phase Ph2, and the third phase Ph3. That is, when the control unit 108 is controlling three fans in the first phase Ph1, it switches from the first phase Ph1 to the second phase Ph2 when the operating time of the first phase Ph1 reaches a threshold Th. When the control unit 108 is controlling three fans in the second phase Ph2, it switches from the second phase Ph2 to the third phase Ph3 when the operating time of the second phase Ph2 reaches a threshold Th. When the control unit 108 is controlling three fans in the third phase Ph3, if the operating time of the third phase Ph3 reaches a threshold Th, it switches from the third phase Ph3 to the first phase Ph1. Thereafter, it switches cyclically in the same manner.

[0089] Let's explain this in detail with reference to Figure 10. The threshold Th is set to 60 (in minutes). Figure 10 shows the state changes when the first fan 112 is initially operating in the first phase Ph1, the number of operating fans becomes 2 after 30 minutes, and then the number of operating fans becomes 3 after another 100 minutes.

[0090] For 30 minutes after the first fan 112 starts operating, the first phase operating time of memory 110 is counted up. When the number of operating fans reaches 2, the second fan 114 starts operating while the first fan 112 remains operational. Until the first phase operating time reaches the threshold Th (i.e., 60), only the first phase operating time of memory 110 is counted up, while the second phase operating time and third phase operating time are maintained at their respective values.

[0091] When the operating time of the first phase reaches the threshold Th (i.e., 60), the system switches to the second phase, Ph2. The first fan 112 stops, the second fan 114 continues to operate, and the third fan 116 starts operating. The counting up of the first phase operating time stops, and the counting up of the second phase operating time begins.

[0092] When the operating time for the second phase reaches the threshold Th, the system switches to the third phase Ph3. The second fan 114 stops, the third fan 116 continues to operate, and the first fan 112 starts operating. The count-up for the second phase operating time stops, and the count-up for the third phase operating time begins.

[0093] Ten minutes after the start of Phase 3 (Ph3), the number of operating fans becomes 3, as described above. Therefore, while Phase 3 (Ph3) is maintained, the previously stopped second fan 114 starts operating. After 50 minutes, the Phase 3 operating time reaches the threshold Th, and the system switches to Phase 1 (Ph1). At this point, the Phase 1, Phase 2, and Phase 3 operating times have all reached the threshold Th and are therefore reset. That is, the Phase 1, Phase 2, and Phase 3 operating times all become 0, the Phase 1 operating time count-up begins, and the Phase 2 and Phase 3 operating times remain at 0.

[0094] Therefore, by switching phases, the combination of fans operating among the first fan 112, second fan 114, and third fan 116 changes, thus suppressing variations in the cumulative operating time of those fans. In addition, the memory capacity required to suppress variations in cumulative operating time can be reduced. That is, as shown in Figure 10, the upper limit of the operating time for each phase is the same as the threshold Th.

[0095] (temperature protection) In addition, in the power conversion device of the power storage system, its internal temperature is measured, and a protection operation is performed if the internal temperature becomes high. That is, when the internal temperature exceeds a predetermined temperature, it has a temperature protection stop function for stopping operation or a temperature protection control operation function for limiting the power to be less than the rated power. Thereby, it is possible to prevent components inside the power conversion device from becoming high temperature and being damaged. In the power conversion device 100 shown in FIG. 1, a protection operation may also be executed. For example, the control unit 108 of the power conversion device 100 performs the control shown in FIG. 11.

[0096] The process shown in FIG. 11 is realized by the control unit 108 reading and executing a predetermined program from the power conversion device 100. In parallel with the program for executing the process shown in FIG. 11, a program for executing the processes shown in FIGS. 2 and 3 is executed.

[0097] In step 400, the control unit 108 detects the internal temperature T of the housing of the power conversion device 100. Specifically, the control unit 108 acquires the temperature T from the temperature sensor 118. Thereafter, the control proceeds to step 402.

[0098] In step 402, the control unit 108 determines whether the temperature T acquired in step 400 is greater than a predetermined value T3. If it is determined that T>T3, the control proceeds to step 404. Otherwise, the control proceeds to step 406. The predetermined value T3 represents the temperature at which it is necessary to execute temperature protection control.

[0099] In step 404, the control unit 108 executes temperature protection control. Specifically, if there is a fan that is stopped among the first fan 112, the second fan 114, and the third fan 116, the control unit 108 operates that fan. That is, 108 increases the number of fans to be operated. For example, in the processes shown in FIGS. 2 and 3 that are being executed in parallel, the control unit 108 controls the number of fans to be operated using Table 5 instead of Table 1. In Table 5, even if the range of the power P is the same as in Table 1 (for example, P<P1 and P1≦P<P2), the number of operating fans is increased.

[0100]

Table 5

[0101] If all the fans are already operating, the control unit 108 stops the operation of the power conversion device 100 or reduces the operating power. Thereafter, the control proceeds to step 406.

[0102] In step 406, the control unit 108 determines whether the temperature T acquired in step 400 is less than a predetermined value T4. If it is determined that T < T4, the control proceeds to step 408. Otherwise, the control proceeds to step 410. The predetermined value T4 represents a temperature at which temperature protection control is not necessary. Values are set for the predetermined value T3 and the predetermined value T4 such that T3 > T4.

[0103] In step 408, the control unit 108 releases the temperature protection control. Specifically, in the processes shown in FIGS. 2 and 3 that are being executed in parallel, the control unit 108 controls the number of fans to be operated using Table 1 instead of Table 5. If the temperature protection control executed in step 404 is the stop of the operation of the power conversion device 100, the control unit 108 resumes the operation of the power conversion device 100. If the temperature protection control executed in step 404 is the reduction of the operating power of the power conversion device 100, the operating state of the power conversion device 100 is returned to the state before the temperature protection control was executed. Thereafter, the control proceeds to step 410.

[0104] In step 410, the control unit 108 determines whether an end instruction has been given. For example, when the power conversion device 100 is turned off, the control unit 108 determines that an end instruction has been received. If it is determined that an end instruction has been received, this program ends. Otherwise, the control returns to step 400 and the above-described processing is repeated.

[0105] This allows for temperature protection of the power converter 100 while suppressing variations in the cumulative operating time of the multiple fans in the power converter 100. Therefore, it is possible to prevent internal components of the power converter 100 from overheating and being damaged.

[0106] (Fans start up sequentially) When a fan is started, a large current (i.e., inrush current) flows in a short time. Therefore, when operating multiple fans, it is preferable to start the fans one by one to reduce the burden on the power supply that provides the power for the fans to operate. For example, as shown in Figure 12, the fans can be started sequentially. For example, if the control unit 108 starts multiple fans in step 306 of Figure 2 or step 342 of Figure 3, it executes the process shown in Figure 12.

[0107] Referring to Figure 12, in step 430, the control unit 108 selects one of the multiple fans to be started and starts it, and resets the standby counter CNT. For example, the value of the counter CNT stored in memory 110 becomes 0, and the counter CNT starts counting up. After that, the control proceeds to step 432.

[0108] In step 432, the control unit 108 determines whether all the fans that should be started have started. If it is determined that all have started, the program terminates. Otherwise, control proceeds to step 434.

[0109] In step 434, the control unit 108 determines whether the value of the standby counter CNT is greater than a predetermined value ΔT. If it is determined that CNT > ΔT, control returns to step 430, and the control unit 108 starts one of the fans that is currently stopped among those to be started. Otherwise (i.e., CNT ≤ ΔT), step 434 is repeated.

[0110] As a result, when starting multiple fans in step 306 of Figure 2 or step 342 of Figure 3, it is possible to prevent multiple fans from starting simultaneously. Therefore, the burden on the power supply that provides power to operate the fans can be reduced.

[0111] Furthermore, when changing the number of operating fans, a period of time during which the change is prohibited may be set. That is, the number of fans may be changed after the predetermined time has elapsed. This can prevent fans from frequently switching between operating and stopping in a short period of time, thereby reducing the risk of fan failure.

[0112] The above describes the case where the number of fans and the number of phases are the same, but it is not limited to this. The number of phases may be greater than the number of fans. For example, when controlling four fans, there are fan combinations other than those shown in Table 4 when operating two fans. Therefore, a different phase (e.g., a fifth phase) can be assigned to that combination. In this case as well, by controlling in the same manner as described above, the variation in the cumulative operating time of multiple fans can be further suppressed.

[0113] The above describes a case where the number of fans to be operated is determined based on the power P during operation of the power converter and the temperature T inside the enclosure, but it is not limited to this. The number of fans to be operated may be determined based on either the power P during operation of the power converter or the temperature T inside the enclosure. The current value during operation of the power converter is also related to the temperature inside the enclosure. Therefore, the number of fans to be operated may be determined based on the current value during operation of the power converter. Alternatively, the number of fans to be operated may be determined based on at least one of the power P during operation of the power converter, the temperature T inside the enclosure, and the current value.

[0114] The present invention has been described above by describing embodiments, but the embodiments described above are illustrative, and the present invention is not limited to the embodiments described above. The scope of the present invention is given with reference to the description in the detailed description of the invention, and includes all modifications within the meaning and scope equivalent to the wording contained herein. [Explanation of symbols]

[0115] 100 Power converter 102 First DC / DC Converter 104 Second DC / DC Converter 106 DC / AC Converter 108 Control Unit 110 memory 112 First Fan 114 Second Fan 116 Third Fan 118 Temperature Sensor 200 PV panels 202 Battery 204 load 206 strains 300, 302, 304, 306, 308, 310, 312, 314, 316, 318, 320, 322, 330, 332, 334, 336, 338, 340, 342, 400, 402, 404, 406, 408, 410, 430, 432, 434 step A, A1, A2, B, B1, B2, C, C1, C2 points CNT1 1st count value CNT2 2nd count value CNT3 3rd Count Value Phase 1 Phase 2 Phase 3 Th threshold t0, t1, t2, t3, t4, t5, t6, t7, t8, t9, t10 time

Claims

1. With multiple fans, A housing for the aforementioned multiple fans, A control unit that controls the operating state of each of the aforementioned multiple fans, A power conversion device including a memory for storing the cumulative operating time of the plurality of fans, The control unit, Based on the internal temperature of the enclosure, the power during the power conversion operation by the power converter, and the current during the power conversion operation, the number of fans to be operated among the plurality of fans is determined. Based on one of the predetermined phases and the number of operating fans, the fan to be operated from among the multiple fans is determined. The phases are switched according to a predetermined switching sequence. In each of the aforementioned multiple phases, for each number of operating units, the combination of fans to be operated from among the multiple fans is identified. The cumulative value includes, as a count value, the cumulative value of at least one of the operating time of each of the multiple fans and the operating time for each phase. The control unit, The system includes a calculation unit that calculates the cumulative value by subtracting a second predetermined value from each of the count values ​​to obtain a new count value, in response to all of the count values ​​becoming equal to or greater than a first threshold value which is smaller than a first predetermined value, so that the cumulative value does not exceed the first predetermined value. A power converter that determines the timing for switching the phase based on the cumulative value calculated by the calculation unit.

2. The second predetermined value is a value that, when subtracted from the count value, makes the count value zero. The power conversion device according to claim 1, wherein the calculation unit calculates the cumulative value by resetting each of the count values ​​by subtracting the second predetermined value corresponding to each of the count values ​​from each of the count values.

3. The number of the aforementioned phases is greater than or equal to the number of the aforementioned multiple fans. The power conversion device according to claim 1 or claim 2, wherein the cumulative value includes the cumulative value of the operating time of each of the plurality of fans.

4. The power conversion device according to claim 1 or claim 2, wherein in the combination of the multiple phases determined to correspond to the same number of operating units, each of the multiple fans is configured to operate the same number of times.

5. The power conversion device according to claim 1 or 2, wherein the control unit switches the phase when the cumulative value calculated by the calculation unit becomes equal to or greater than the first threshold value.

6. The power conversion device according to claim 5, wherein the calculation unit stores the number of times the calculation has been performed in the memory.

7. The cumulative value includes the cumulative value obtained by accumulating the operating time of each of the multiple fans as the count value. The power conversion device according to claim 6, further comprising: the control unit, upon receiving that the count value of the fan corresponding to the currently running phase among the number of operating fans has reached or exceeds a first threshold value, switches the phase according to the switching order.

8. The power conversion device according to claim 1 or 2, wherein the control unit, upon receiving that the number of operating units determined based on the variable value differs from the number of fans currently in operation, operates the number of operating fans after a predetermined time has elapsed.

9. The control unit, In response to the variable value changing from below the second threshold to above the second threshold, the number of operating units is increased. The power conversion device according to claim 1 or 2, wherein the number of operating units is reduced in response to the variable value changing from a state where it is greater than a third threshold less than the second threshold to a state where it is less than or equal to the third threshold.

10. The power conversion device according to claim 1 or 2, wherein the control unit, upon receiving that the number of operating units determined based on the variable value is two or more greater than the number of operating fans, operates the stopped fans one by one until the number of operating fans reaches the determined number of operating units.

11. A temperature detection unit for detecting the temperature inside the housing, The system further includes a determination unit that determines whether the temperature detected by the temperature detection unit is greater than a fourth threshold, The power conversion device according to claim 1 or 2, wherein the control unit, upon receiving a determination from the determination unit that the temperature is greater than the fourth threshold, increases the number of the multiple fans that are in operation.

12. A control method for a power conversion device including a plurality of fans and a housing that accommodates the plurality of fans, A control step that controls the operating state of each of the aforementioned multiple fans, The process includes a storage step of storing the cumulative operating time of the plurality of fans, The control step is, A step of determining the number of fans to be operated from among the plurality of fans, based on the temperature inside the enclosure, the power during the power conversion operation by the power converter, and the current during the power conversion operation. A step of determining which of the multiple fans to operate based on one of the predetermined phases and the number of operating fans, This includes a switching step that switches the phases according to a predetermined switching sequence, In each of the aforementioned multiple phases, for each number of operating units, the combination of fans to be operated from among the multiple fans is identified. The cumulative value includes, as a count value, the cumulative value of at least one of the operating time of each of the multiple fans and the operating time for each phase. The previous switching step is, The calculation step involves calculating the cumulative value by subtracting a second predetermined value from each of the count values ​​to obtain a new count value, in response to all of the count values ​​becoming greater than or equal to a first threshold value which is smaller than a first predetermined value, so that the cumulative value does not exceed the first predetermined value. A control method comprising the step of determining the timing for switching the phase based on the cumulative value calculated in the calculation step.

Images