Communication system and communication method

Abstract

To provide a communication system and a communication method capable of suppressing a communication load without monitoring the communication load.SOLUTION: A communication system (electric power system F1) includes a first device (centralized management device A) and a second device (control device B), in which the first device acquires information from the second device via communication. The first device includes a communication part 11. The second device includes a communication part 21 that communicates with communication part 11, and a storage part 23 that stores various information. The storage part 23 stores recorded information 232 and change notification information 235 indicating whether the recorded information 232 has changed. The communication part 11 reads the change notification information 235 and reads the recorded information 232 only when the change notification information 235 indicates a change.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a communication system including a plurality of devices that communicate with each other, and a communication method. [Background technology]

[0002] In a device equipped with a communication function, if communication processing becomes overloaded, other functions may be delayed or unable to operate. To prevent this, a method has been proposed in which the communication load is monitored and, if an overload occurs, the communication speed is reduced to suppress the communication load. For example, Patent Document 1 discloses a communication device that determines the communication load state from the transmission status of communication data addressed to itself and reduces the communication function according to the communication load state. This reduces the possibility that functions other than the communication function will be unable to provide their intended functions when the communication load becomes overloaded. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-352402 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the conventional method, in order to suppress the communication load, a function for monitoring the communication load is required, and also a function for suppressing the communication function or communication speed according to the monitoring result is required.

[0005] The present invention has been devised in light of the above circumstances, and has an object to provide a communication system and a communication method that can suppress a communication load without monitoring the communication load. [Means for solving the problem]

[0006] A communication system provided by a first aspect of the present invention comprises a first device and a second device, and the first device acquires information from the second device through communication, wherein the first device comprises a first communication unit, and the second device comprises a second communication unit that communicates with the first communication unit, and a memory unit that stores various information, and the memory unit stores recorded information and change notification information that indicates whether or not there has been a change in the recorded information, and the first communication unit reads the change notification information and reads the recorded information only if the change notification information indicates that there has been a change.

[0007] In a preferred embodiment of the present invention, when the state in which the recorded information has changed continues for a first time or more, the second device changes the change notification information to information indicating that there has been a change.

[0008] In a preferred embodiment of the present invention, the first communication unit reads out the change notification information every second time period, and the first time period is at least twice the second time period.

[0009] In a preferred embodiment of the present invention, the memory unit further stores read notification information which is information indicating whether the first communication unit has read the recorded information, and when the first communication unit has read the recorded information, the first communication unit changes the read notification information to information indicating that reading has occurred, and when the read notification information indicates that reading has occurred, the second device changes the change notification information to information indicating that there is no change.

[0010] In a preferred embodiment of the present invention, the memory unit further stores a communication log, and the second device refers to the communication log and, when it detects that the first communication unit has read the recorded information, changes the change notification information to information indicating no change.

[0011] In a preferred embodiment of the present invention, the second device starts timing when the change notification information is changed to information indicating that there has been a change, and when the timed time has exceeded a third period, the second device changes the change notification information to information indicating that there has been no change.

[0012] A communication method provided by a second aspect of the present invention is a communication method in a communication system comprising a first device having a first communication unit, a second communication unit that communicates with the first communication unit, and a second device having a memory unit that stores various information, in which the first device acquires information from the second device through communication, wherein the memory unit stores recorded information and change notification information that is information indicating whether or not there has been a change in the recorded information, and the method comprises a first step in which the first communication unit reads out the change notification information, a second step in which the first communication unit determines whether or not the change notification information indicates a change, and a third step in which the first communication unit reads out the recorded information only if it determines that there is a change. [Effects of the Invention]

[0013] According to the present invention, the first communication unit reads the recorded information only when the change notification information indicates that the recorded information has changed. Since the first communication unit does not read the recorded information if there has been no change, unnecessary communication can be reduced. This allows the first device to reduce the communication load compared to when the recorded information is read every time. Furthermore, the first device does not require a function to monitor the communication load. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram for explaining a power system according to a first embodiment, and is a block diagram showing the overall configuration of the power system. FIG. [Figure 2] 10 is an example of a flowchart illustrating a read process performed by a centralized management device. [Figure 3] 4 is an example of a flowchart illustrating a control process performed by a control device. [Figure 4] 10 is a timing chart for explaining a load reduction communication process. [Figure 5] 10 is a timing chart for explaining a load reduction communication process. [Figure 6] 10 is a timing chart for explaining a load reduction communication process. [Figure 7] 10A and 10B are diagrams for explaining a power system according to a second embodiment, in which FIG. 10A is a block diagram showing the internal configuration of a control device, and FIG. 10B is an example of a flowchart showing control processing performed by the control device. [Figure 8] 10A and 10B are diagrams for explaining a power system according to a third embodiment, in which FIG. 10A is a block diagram showing the internal configuration of a control device, and FIG. 10B is an example of a flowchart showing control processing performed by the control device. DETAILED DESCRIPTION OF THE INVENTION

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, taking an electric power system as an example.

[0016] FIG. 1 is a diagram for explaining a power system F1 according to a first embodiment. FIG. 1 is a block diagram showing the overall configuration of the power system F1. The power system F1 is connected to a power system G and can transmit and receive power from the power system G. The power system F1 includes a centralized management device A, a control device B, multiple control devices C, multiple control devices D, and a load E. The power system F1 controls the output power of each of the control devices B, C, and D so that the power at the connection point between the power system F1 and the power system G (hereinafter referred to as "connection point power") becomes a target power.

[0017] The centralized control device A manages the entire power system F1. The centralized control device A collects information from each control device B, C, and D, sets a target value for the output power of each control device B, C, and D, and transmits it to each device. Each control device B, C, and D controls its own output power to match the received target value. The centralized control device A may also calculate a guidance index for controlling the connection point power to the target power and transmit the calculated guidance index to each control device B, C, and D. In this case, each control device B, C, and D calculates a target value for its own output power based on the received common guidance index and controls its own output power to match the calculated target value.

[0018] The control device B is connected to a storage battery 29. The control device B is equipped with a power conditioner (not shown). The power conditioner converts DC power discharged from the storage battery 29 into AC power and outputs it, and converts AC power into DC power to charge the storage battery 29. In other words, the control device B controls the output power of its own device (power output by the power conditioner to the power system G side), thereby controlling the charging and discharging of the storage battery 29.

[0019] Each control device C is connected to a solar cell 39. The control device C is equipped with a power conditioner (not shown). The power conditioner converts DC power generated by the solar cell 39 into AC power and outputs it. The control device C controls the power output of the solar cell 39 by controlling the output power of the control device itself.

[0020] Each control device D is a device that charges and discharges the connected electric vehicle 5, and is a so-called EV charger / discharger. The control device D is equipped with a power conditioner (not shown). The power conditioner charges and discharges the storage battery 51 mounted on the electric vehicle 5 connected via a charging cable 52. In other words, the control device D controls the charging and discharging of the electric vehicle 5 by controlling the output power of its own device.

[0021] The centralized control device A acquires information from each of the control devices B, C, and D through communication, and also transmits commands to each of the control devices B, C, and D. In this embodiment, the centralized control device A communicates with each of the control devices B, C, and D using the Modbus (registered trademark) protocol. Note that the communication protocol is not limited to Modbus. Furthermore, the communication method is not limited, and may be wired communication or wireless communication.

[0022] The control device B includes a communication unit 21 and a storage unit 23. The communication unit 21 communicates with the centralized control device A (the communication unit 11 described later). In response to a command from the centralized control device A, the communication unit 21 executes a corresponding function or returns a response. When the communication unit 21 receives a command to read information from the centralized control device A, it transmits the corresponding information to the centralized control device A. When the communication unit 21 receives a command to write information from the centralized control device A, it stores the corresponding information in the storage unit 23.

[0023] The storage unit 23 stores various types of information, including power information 231, recording information 232, change notification information 235, and read notification information 236.

[0024] The power information 231 is information about the output power of the control device B. The control device B periodically detects its own output power using a power sensor (not shown) and stores it in the storage unit 23 as power information 231. Therefore, the power information 231 is periodically changed. The centralized management device A periodically reads out the power information 231 stored in the storage unit 23 of the control device B using a conventional communication method.

[0025] The recorded information 232 includes setting information, fault information, and the like. The setting information is information on set values ​​such as a set voltage and a set current that are set in the control device B. The setting information is changed when each set value is changed. The fault information is information on faults and malfunctions of the control device B and the storage battery 29. The fault information is changed when a fault or malfunction is detected. In other words, the recorded information 232 is changed at irregular intervals.

[0026] In a conventional communication method, the centralized control device A periodically reads out all of the recorded information 232 stored in the memory unit 23 of the control device B. The centralized control device A also reads out information from each of the control devices C and D. Therefore, the centralized control device A frequently receives large amounts of information, which makes it prone to communication overload. In a communication method according to this embodiment, the centralized control device A reads out the recorded information 232 only when any of the recorded information 232 has been changed. If none of the recorded information 232 has been changed, the centralized control device A does not read out the recorded information 232. Compared to when the centralized control device A periodically reads out all of the recorded information 232, the amount of information communicated is reduced, which makes it possible to prevent the communication load from becoming overloaded.

[0027] The change notification information 235 is information indicating whether or not there has been a change in the recorded information 232, and is information stored at a predetermined address in the storage area of ​​the storage unit 23. If there has been no change in the recorded information 232, the control device B sets the change notification information 235 to "0," indicating no change. On the other hand, if there has been a change in the recorded information 232, the control device B sets the change notification information 235 to "1," indicating a change. The storage unit 23 stores past recorded information 232 as past information, separate from the current recorded information 232. The control device B compares the recorded information 232 with the past information, and when a difference continues for a first time T1 or more, the control device B determines that there has been a change in the recorded information 232 and changes the change notification information 235 from "0" to "1" (changed). In this embodiment, the first time T1 is set to be at least twice the second time T2, which is the communication cycle of the centralized management device A. Note that the first time T1 is not limited to this. The reason why the condition for determining whether a change has occurred is that the change must continue for at least the first time T1 is to prevent a case in which the recorded information 232 changes instantaneously and then immediately returns to its original state from being erroneously detected as a change. Furthermore, the reason why the first time T1 is set to at least twice the second time T2 is to prevent a change in the recorded information 232 from being overlooked. Prevention of overlooked detection of a change in the recorded information 232 will be described in detail later.

[0028] The read notification information 236 is information indicating whether the recorded information 232 has been read by the centralized control device A, and is information stored at a predetermined address in the storage area of ​​the storage unit 23. When the centralized control device A reads the recorded information 232, the read notification information 236 is set to "1" indicating that the information has been read, and is later changed to "0" indicating that the information has not been read. Specifically, when the centralized control device A reads the recorded information 232, it transmits a command to the control device B at the next communication timing to change the read notification information 236 to "1" (read). Upon receiving this command, the control device B changes the read notification information 236 to "1." When the read notification information 236 becomes "1," the control device B changes the change notification information 235 from "1" to "0" (no change) and copies the current recorded information 232 to the past information. At the next communication timing, the centralized management device A sends a command to the control device B to change the read notification information 236 from "1" to "0" (no read). When the control device B receives the command, it changes the read notification information 236 to "0." Note that changing the read notification information 236 from "1" to "0" is not limited to being an instruction from the centralized management device A to the control device B, and may be performed by the control device B.

[0029] Although not shown, each of the control devices C and D is also provided with a communication unit 21 and a storage unit 23, similar to the control device B.

[0030] The centralized control device A includes a communication unit 11 and a storage unit 13. The communication unit 11 communicates with each of the control devices B, C, and D (communication units 21). The communication unit 11 transmits commands to each of the control devices B, C, and D (communication units 21).

[0031] The communication unit 11 periodically transmits a command to the control device B (communication unit 21) to read out the power information 231. When the control device B (communication unit 21) receives the command, it reads out the power information 231 from the memory unit 23 and transmits it to the centralized control device A (communication unit 11). The centralized control device A stores the received power information 231 in the memory unit 13 and uses it for calculations for control. Similarly, the communication unit 11 also periodically transmits a command to each of the control devices C and D (communication units 21) to read out the power information 231, and receives the power information 231 from each of the control devices.

[0032] Furthermore, in order to read the recorded information 232, the communication unit 11 first transmits a command to the control device B (communication unit 21) to read the change notification information 235 at every second time T2, which is a communication cycle. The second time T2 is not limited to, but may be, for example, one second. When the control device B (communication unit 21) receives the command, it reads the change notification information 235 from the storage unit 23 and transmits it to the centralized management device A (communication unit 11). If the received change notification information 235 is "0" (no change), the centralized management device A does not read the recorded information 232. On the other hand, if the received change notification information 235 is "1" (change), the centralized management device A reads the recorded information 232. Specifically, the centralized management device A (communication unit 11) transmits a command to the control device B (communication unit 21) to read the recorded information 232. When the control device B (communication unit 21) receives the command, it reads out the recorded information 232 from the memory unit 23 and transmits it to the centralized control device A (communication unit 11). When the centralized control device A (communication unit 11) receives the recorded information 232, it transmits a command to the control device B to change the read notification information 236 to "1" (reading enabled). The centralized control device A stores the received recorded information 232 in the memory unit 13 and uses it for calculations for control. The method by which the communication unit 11 reads out the recorded information 232 of each of the control devices C and D (communication units 21) is also similar.

[0033] Next, the load reduction communication process that is performed when the central control device A reads out the recorded information 232 from each of the control devices B, C, and D will be described with reference to a flowchart.

[0034] 2 is an example of a flowchart showing the readout process performed by the centralized control device A. The readout process is executed every second time T2.

[0035] First, it is determined whether the previously read change notification information 235 is "1" or not (S1). If it is "1", the read notification information 236 is changed to "1" (read) (S2). Specifically, the communication unit 11 sends a command to the communication unit 21 to write "1" to the read notification information 236. On the other hand, if it is not "1", the read notification information 236 is changed to "0" (no reading) (S3). Specifically, the communication unit 11 sends a command to the communication unit 21 to write "0" to the read notification information 236.

[0036] Next, change notification information 235 is read (S4). Specifically, communication unit 11 transmits a command to communication unit 21 to read change notification information 235. Next, it is determined whether change notification information 235 has been received (S5). Specifically, it is determined whether communication unit 11 has received change notification information 235 from communication unit 21. If change notification information 235 has not been received (S5: NO), the process returns to step S5, and the determination of step S5 is repeated. In other words, communication unit 11 waits to receive change notification information 235. Note that if change notification information 235 has not been received for a predetermined time or longer, the process may return to step S4, and read change notification information 235 again.

[0037] If change notification information 235 is received (S5: YES), it is determined whether or not change notification information 235 is "1" (changed) (S6). That is, communication unit 11 determines whether or not the received change notification information 235 is "1." If change notification information 235 is not "1" (S6: NO), that is, if it is "0," the read process ends. That is, if recorded information 232 has not changed, communication unit 11 does not read recorded information 232.

[0038] On the other hand, if the change notification information 235 is "1" (S6: YES), the recorded information 232 is read (S7). Specifically, the communication unit 11 sends a command to the communication unit 21 to read the recorded information 232. Next, it is determined whether the recorded information 232 has been received (S8). Specifically, it is determined whether the communication unit 11 has received all of the recorded information 232 from the communication unit 21. If all of the recorded information 232 has not been received (S8: NO), the process returns to step S8, and the determination of step S8 is repeated. In other words, the communication unit 11 waits until all of the recorded information 232 has been received. Note that if the recorded information 232 has not been received for a predetermined time or longer, the process may return to step S7, and the recorded information 232 may be read again.

[0039] If all of the recording information 232 has been received (S8: YES), the received recording information 232 is stored (S9), and the read process ends. Specifically, the communication unit 11 stores the received recording information 232 in the storage unit 13.

[0040] 3 is an example of a flowchart showing the control process performed by the control device B. This control process is executed at a predetermined cycle. The control processes performed by the control devices C and D are similar.

[0041] First, it is determined whether or not a read command has been issued (S11). Specifically, communication unit 21 determines whether or not a read command has been received from communication unit 11. If there has been no read command (S11: NO), the process proceeds to step S13. On the other hand, if there has been a read command (S11: YES), corresponding information is transmitted (S12), and the process proceeds to step S13. Specifically, when communication unit 21 receives a read command from communication unit 11, it reads the corresponding information from storage unit 23 and transmits it to communication unit 11. When communication unit 21 receives a read command for power information 231, it reads and transmits power information 231, and when communication unit 21 receives a read command for recorded information 232, it reads and transmits recorded information 232. When communication unit 21 receives a read command for change notification information 235, it reads and transmits change notification information 235.

[0042] Next, in step S13, it is determined whether or not there has been a change in the recorded information 232 (S13). Specifically, the control device B determines whether or not a state in which there is a difference between the recorded information 232 and the past information has continued for a first time T1 or more. If there has been no change in the recorded information 232 (S13: NO), that is, if the recorded information 232 and the past information match or the state in which there is a difference has not continued for a first time T1 or more, the process proceeds to step S15. On the other hand, if there has been a change (S13: YES), the change notification information 235 is changed to "1" (S14), and the process proceeds to step S15. Specifically, the control device B changes the change notification information 235 to "1" (changed).

[0043] Next, in step S15, it is determined whether the read notification information 236 is "1" (read) or not (S15). Specifically, the control device B determines whether the read notification information 236 stored in the storage unit 23 is "1". If the read notification information 236 is not "1" (S15: NO), that is, if it is "0", the control process ends. On the other hand, if the read notification information 236 is "1" (S15: YES), the change notification information 235 is changed to "0" (S16). Specifically, the control device B changes the change notification information 235 to "0". Next, the past information is updated (S17), the read notification information 236 is changed to "0" (S18), and the control process ends. Specifically, the control device B copies the current recorded information 232 to the past information.

[0044] 2 and 3 are merely examples, and the processes performed by the centralized management device A and the control device B are not limited to those described above. For example, instead of the centralized management device A changing the read notification information 236 to "0" in step S3 in Fig. 2, a process in which the control device B changes the read notification information 236 to "0" may be added after step S17 in Fig. 3.

[0045] 4 to 6 are timing charts for explaining the load reduction communication process. In each diagram, (a) shows the state in which a fault X occurs, and (b) shows the state in which a fault Y occurs. Faults X and Y are examples of fault information recorded in the recording information 232, where "0" indicates that the fault has not occurred and "1" indicates that the fault has occurred and has been recorded in the fault information. Note that other information recorded in the recording information 232 remains unchanged. (c) of each diagram shows the state of the change notification information 235, and (d) of each diagram shows the state of the read notification information 236. Also, (e) of each diagram shows the communication timing. As shown in each diagram, the communication timing occurs at times t1, t2, ..., t10 every second time T2 from a certain time t0.

[0046] Figure 4 shows a case where the first time T1, which is the time from when a failure occurs and is recorded in the failure information (i.e., from when the recorded information 232 changes) until the change notification information 235 becomes "1", is set to be shorter than the second time T2, which is the communication period.

[0047] As shown in Fig. 4, shortly before time t3, failure X occurs and is recorded in the failure information. A first time T1 later (shorter than time t3), change notification information 235 is changed to "1". At the next communication timing, time t4, change notification information 235 is "1", so recorded information 232 is read. Then, at the next communication timing, time t5, read notification information 236 is changed to "1", and change notification information 235 is changed to "0". Therefore, recorded information 232 is not read from time t5 onwards.

[0048] On the other hand, shortly after time t4, failure Y occurs and is recorded in the failure information. A first time T1 later (shorter than time t5), the change notification information 235 still remains at "1." At time t4, the recorded information 232 before failure Y was recorded is read out, and at time t5, the change notification information 235 is changed to "0." Therefore, the recorded information 232 in which failure Y is recorded is not read out. This results in a failure to detect the change in the recorded information 232. If failure Y occurs after time t4 and the first time T1 after the occurrence of failure Y is before the read notification information 236 becomes "0," similarly, the recorded information 232 in which failure Y is recorded is not read out. To prevent such a failure to detect the change in the recorded information 232, in this embodiment, the first time T1 is set to be at least twice the second time T2, which is the communication cycle of the centralized management device A.

[0049] FIG. 5 shows a case where the first time T1 is set to twice the second time T2, and a failure Y occurs immediately after the recorded information 232 corresponding to a failure X is read.

[0050] As shown in Fig. 5, shortly before time t3, failure X occurs and is recorded in the failure information. A first time T1 later (shortly before time t5), change notification information 235 is changed to "1". At the next communication timing, time t5, change notification information 235 is "1", so recorded information 232 is read out. Then, at the next communication timing, time t6, read notification information 236 is changed to "1" and change notification information 235 is changed to "0", and at time t7 read notification information 236 is changed to "0".

[0051] Meanwhile, shortly after time t5 when recorded information 232 is read, failure Y occurs and is recorded in the failure information. A first time T1 later (shortly after time t7), change notification information 235 is changed to "1." At the next communication timing, time t8, change notification information 235 is "1," so recorded information 232 is read. Then, at the next communication timing, time t9, read notification information 236 is changed to "1," and change notification information 235 is changed to "0." In other words, recorded information 232 in which failure X is recorded is read at time t5, and recorded information 232 in which failure Y is recorded is read at time t8.

[0052] FIG. 6 shows a case where the first time T1 is set to twice the second time T2, as in FIG. 5, and a fault Y occurs immediately after the occurrence of a fault X.

[0053] As shown in Fig. 6, shortly before time t3, failure X occurs and is recorded in the failure information. A first time T1 later (shortly before time t5), change notification information 235 is changed to "1". At the next communication timing, time t5, change notification information 235 is "1", so recorded information 232 is read out. Then, at the next communication timing, time t6, read notification information 236 is changed to "1" and change notification information 235 is changed to "0", and at time t7 read notification information 236 is changed to "0".

[0054] Meanwhile, shortly after time t3, failure Y occurs and is recorded in the failure information. A first time T1 later (shortly after time t5), change notification information 235 still remains at "1". However, because failure Y was recorded in the failure information before time t5, recorded information 232 in which failure Y is also recorded is read out at time t5. In this way, in this embodiment, by setting first time T1 to at least twice the second time T2, it is possible to prevent a change in recorded information 232 from being overlooked.

[0055] Next, the operation and effects of the power system F1 according to this embodiment will be described.

[0056] According to this embodiment, the communication unit 11 of the centralized management device A periodically reads the change notification information 235 of the control device B. The communication unit 11 reads the recorded information 232 only when the change notification information 235 is "1" (changed). The communication unit 11 does not read the recorded information 232 when the change notification information 235 is "0" (no change). Therefore, the centralized management device A can reduce unnecessary communications compared to when the recorded information 232 is periodically read, thereby suppressing the communication load. Furthermore, the centralized management device A does not require a function to monitor the communication load.

[0057] Furthermore, according to this embodiment, the control device B determines that a change has occurred in the recorded information 232 when the state in which the recorded information 232 differs from the past information continues for a first time T1 or more. Therefore, a case in which the recorded information 232 changes instantaneously and then immediately returns to its original state is prevented from being erroneously detected as a change. This makes it possible to prevent the recorded information 232 from being read due to an erroneous detection of a change, thereby enabling the centralized control device A to further reduce the communication load.

[0058] Furthermore, according to this embodiment, the first time T1 is at least twice the second time T2, which is the communication cycle of the centralized management device A. This prevents a change in the recorded information 232 from being overlooked due to the shortness of the first time T1.

[0059] Furthermore, according to this embodiment, when the communication unit 11 of the centralized management device A reads out the recorded information 232, it changes the read notification information 236 to "1" (read). This allows the control device B to recognize that the recorded information 232 has been read out by the centralized management device A. Furthermore, when the read notification information 236 becomes "1", the control device B changes the change notification information 235 from "1" to "0" (no change). This prevents the centralized management device A from re-reading the recorded information 232 that it has already read out.

[0060] In this embodiment, the case where the storage unit 23 of the control device B stores change notification information 235 indicating whether or not a change has occurred in the recorded information 232 has been described, but the present invention is not limited to this. Instead of change notification information 235, the storage unit 23 may store first change notification information indicating whether or not a change has occurred in the setting information of the recorded information 232, and second change notification information indicating whether or not a change has occurred in the malfunction information. In this case, for example, when there is a change in the setting information but no change in the malfunction information, the communication unit 11 of the centralized control device A can read only the changed setting information (and not read the unchanged malfunction information) rather than reading the entire recorded information 232. This allows the centralized control device A to further reduce the communication load.

[0061] FIG. 7 is a diagram for explaining a power system F2 according to a second embodiment. FIG. 7(a) is a block diagram showing the internal configuration of a control device B of the power system F2 according to the second embodiment. The configuration of the power system F2 according to the second embodiment, other than the control device B, is the same as that of the power system F1. In FIG. 7(a), elements that are the same as or similar to those of the power system F1 according to the first embodiment are given the same reference numerals, and redundant description will be omitted. FIG. 7(b) is an example of a flowchart showing the control processing performed by the control device B in the load suppression communication processing according to the second embodiment. The flowchart showing the read processing performed by the centralized management device A is the flowchart of FIG. 2 with step S7 deleted, and therefore will not be shown or described here. The power system F2 according to this embodiment differs from the power system F1 according to the first embodiment in the method for confirming that the recorded information 232 has been read.

[0062] 7(a), in the control device B according to the second embodiment, the memory unit 23 stores a communication log 237 instead of read notification information 236. The communication log 237 records information relating to communication between the communication unit 21 of the control device B and the communication unit 11 of the centralized management device A. When the communication unit 21 communicates with the communication unit 11, the control device B automatically stores information relating to the communication as the communication log 237 in the memory unit 23.

[0063] The control device B refers to the communication log 237 and detects that the communication unit 11 has read the recorded information 232, specifically, that the communication unit 21 has transmitted the recorded information 232 to the communication unit 11. When the control device B detects this, it changes the change notification information 235 from "1" to "0" (no change) and copies the current recorded information 232 to the past information.

[0064] As shown in FIG. 7(b), in the control processing performed by the control device B in the load reduction communication processing according to the second embodiment, the processing from steps S11 to S14 is the same as that in the flowchart of FIG. 3. Next, instead of the determination in step S15, it is determined whether or not the recorded information 232 has been read (S21). Specifically, the control device B refers to the communication log 237 and determines whether or not it has detected that the communication unit 21 has transmitted the recorded information 232 to the communication unit 11. If this detection has not been made (S21: NO), the control processing ends. On the other hand, if this detection has been made (S21: YES), the change notification information 235 is changed to "0" (S16), the past information is updated (S17), and the control processing ends.

[0065] In this embodiment, the communication unit 11 of the centralized management device A also periodically reads the change notification information 235 of the control device B. The communication unit 11 reads the record information 232 only when the change notification information 235 is “1” (changed), and does not read the record information 232 when the change notification information 235 is “0” (no change). Therefore, the centralized management device A can reduce unnecessary communications, thereby suppressing the communication load. Furthermore, the centralized management device A does not require a function to monitor the communication load. This embodiment also achieves the same effects as the first embodiment by using a configuration common to the first embodiment. Furthermore, according to this embodiment, the control device B can detect that the record information 232 has been read by referring to the communication log 237. Furthermore, when the control device B detects this, it changes the change notification information 235 from “1” to “0” (no change). This prevents the centralized management device A from re-reading the record information 232 that it has already read.

[0066] FIG. 8 is a diagram illustrating a power system F3 according to a third embodiment. FIG. 8(a) is a block diagram illustrating the internal configuration of a control device B of the power system F3 according to the third embodiment. The configuration of the power system F3 according to the third embodiment, other than the control device B, is the same as that of the power system F1. In FIG. 8(a), elements that are the same as or similar to those of the power system F1 according to the first embodiment are designated by the same reference numerals, and redundant description will be omitted. FIG. 8(b) is an example of a flowchart illustrating the control processing performed by the control device B in the load suppression communication processing according to the third embodiment. The flowchart illustrating the read processing performed by the centralized management device A is the same as that of FIG. 2, except that step S7 has been deleted, and therefore will not be illustrated or described here. The power system F3 according to this embodiment differs from the power system F1 according to the first embodiment in that it does not confirm that the recorded information 232 has been read.

[0067] As shown in FIG. 8(a), in the control device B according to the third embodiment, the storage unit 23 does not store the read notification information 236.

[0068] Control device B starts timing when it changes change notification information 235 from "0" to "1" (changed). Then, when the measured time has passed a third time T3, control device B changes change notification information 235 from "1" to "0" (no change) and copies current recorded information 232 to past information. The third time T3 is not limited, but is equal to or longer than the second time T2, which is the communication cycle of centralized management device A.

[0069] As shown in FIG. 8(b), in the control processing performed by the control device B in the load reduction communication processing according to the third embodiment, steps S11 to S14 are the same as those in the flowchart of FIG. 3. In the control processing according to the third embodiment, after step S14, timing is started (S31). Next, instead of the determination in step S15, it is determined whether or not a third time T3 has elapsed (S32). If it has not elapsed (S32: NO), the control processing ends. On the other hand, if it has elapsed (S32: YES), the change notification information 235 is changed to "0" (S16), the past information is updated (S17), and the control processing ends.

[0070] In this embodiment, the communication unit 11 of the centralized management device A also periodically reads the change notification information 235 of the control device B. The communication unit 11 reads the recorded information 232 only when the change notification information 235 is “1” (changed), and does not read the recorded information 232 when the change notification information 235 is “0” (no change). Therefore, the centralized management device A can reduce unnecessary communications, thereby suppressing the communication load. Furthermore, the centralized management device A does not require a function for monitoring the communication load. This embodiment also achieves the same effects as the first embodiment by using a configuration common to the first embodiment. Furthermore, according to this embodiment, the control device B starts clocking when the change notification information 235 changes from “0” to “1” (changed), and changes the change notification information 235 from “1” to “0” (no change) when the clocked time has elapsed a third time T3. If the third time T3 is set to be equal to or greater than the second time T2, the recorded information 232 has been read when the third time T3 has elapsed. Therefore, the control device B can change the change notification information 235 to “0” (no change) after reading the recorded information 232. This prevents the centralized control device A from re-reading the recorded information 232 that it has already read.

[0071] In the above first to third embodiments, a power system has been described as an example of a communication system according to the present invention, but the present invention is not limited to this. The present invention can be applied to any system in which a first device and a second device communicate with each other. For example, the present invention can be applied to a welding system in which a welding power supply and a monitoring device that monitors the welding power supply communicate with each other.

[0072] In the first to third embodiments, the power information 231 of the information stored in the storage unit 23 is periodically read out, and the recorded information 232 is read out only when there is a change, but this is not limiting. If the information stored in the storage unit 23 is irregularly changed, all of the information may be read out when any of the information is changed.

[0073] The communication system and communication method according to the present invention are not limited to the above-described embodiments. The specific configuration of each part of the communication system according to the present invention and the specific processing of each step of the communication method can be freely designed and modified in various ways. [Explanation of symbols]

[0074] F1, F2, F3: power system, A: centralized control device, 11: communication unit, B: control device, 21: communication unit, 23: memory unit, 232: recorded information, 235: change notification information, 236: read notification information, 237: communication log

Claims

1. A communication system comprising a first device and a second device, wherein the first device acquires information from the second device through communication, the first device includes a first communication unit; the second device includes a second communication unit that communicates with the first communication unit and a storage unit that stores various information; the storage unit stores record information and change notification information that is information indicating whether or not there has been a change in the record information; the first communication unit reads the change notification information, and reads the recorded information only when the change notification information indicates that there is a change; Communication system.

2. the second device changes the change notification information to information indicating that the recorded information has changed when the state in which the recorded information has changed continues for a first time or more; The communication system of claim 1 .

3. the first communication unit reads out the change notification information every second time; The first time period is at least twice the second time period. The communication system according to claim 2 .

4. the storage unit further stores read notification information that is information indicating whether the first communication unit has read the recorded information; When the first communication unit has read the recorded information, the first communication unit changes the read notification information to information indicating that the recorded information has been read, When the read notification information indicates that a read has been performed, the second device changes the change notification information to information indicating that no change has been performed.

4. A communication system according to claim 1.

5. The storage unit further stores a communication log, the second device refers to the communication log, and when detecting that the first communication unit has read the recorded information, changes the change notification information to information indicating no change.

4. A communication system according to claim 1.

6. the second device starts timing when the change notification information is changed to information indicating that there is a change, and when the timed time has elapsed, changes the change notification information to information indicating that there is no change.

4. A communication system according to claim 1.

7. A communication method in a communication system including a first device having a first communication unit, a second device having a second communication unit that communicates with the first communication unit, and a storage unit that stores various information, wherein the first device acquires information from the second device through communication, the storage unit stores record information and change notification information that is information indicating whether or not there has been a change in the record information; a first step in which the first communication unit reads out the change notification information; a second step in which the first communication unit determines whether the change notification information indicates that there is a change; a third step of reading the recorded information only when the first communication unit determines that there is a change; Equipped with Communication method.

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