Optical signal transmitting / receiving device and power conversion device

Abstract

To provide an optical signal transmitting / receiving device and power conversion equipment enabling optical components thereof to be inspected more easily.SOLUTION: An optical signal transmitting / receiving device is provided, comprising: an optical transmission unit which transmitting an optical signal having a light emission period and a light extinction period, can set a normal light quantity period and a low-light quantity period having a lower light quantity than the normal light quantity period, in the light emission period; an optical reception unit receiving an optical signal and outputting a reception signal converted to an electric signal according to light emission amount of the optical signal; a light emission control unit controlling changeover of the light emission period and the light extinction period of the light signal and controlling the setting of the normal light quantity period and the low-light quantity period in the light emission period; and a light reception control unit determining degradation of at least the optical transmission unit or the light reception unit from a difference between a reception signal in a case that the low-light quantity period is determined as the light emission period and a reception signal in a case that the low-light quantity period is determined as the light extinction period.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to an optical signal transmitting / receiving device and a power conversion device. [Background technology]

[0002] There is an optical signal transmitting and receiving device that includes an optical transmitting unit that transmits an optical signal and an optical receiving unit that receives the optical signal. The optical signal transmitting and receiving device is used, for example, in a power conversion device. In the power conversion device, for example, an optical signal is used to transmit and receive a signal for insulation purposes.

[0003] Optical components such as optical transmitters and optical receivers deteriorate with use. For example, the amount of light emitted by an optical transmitter decreases, and the amount of light received by an optical receiver decreases with use. In order to prevent such deterioration of optical components from affecting the operation of optical signal transmitting and receiving devices and power conversion devices, optical components are inspected periodically.

[0004] Inspection of optical components is performed, for example, by an operator measuring the amount of light emitted by the optical transmitter and the amount of light received by the optical receiver. However, this method is laborious, and the inspection of optical components takes time and costs money. For this reason, it is desirable to make it easier to inspect optical components in optical signal transmitting and receiving devices and power conversion devices. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5657292 Summary of the Invention [Problem to be solved by the invention]

[0006] The embodiments of the present invention provide an optical signal transmitting / receiving device and a power conversion device that allow inspection of optical components to be performed more easily. [Means for solving the problem]

[0007] According to an embodiment of the present invention, there is provided an optical transmitting unit that transmits an optical signal having an emission period and an extinction period, and is capable of setting, during the emission period, a normal light amount period with a predetermined emission amount and a low light amount period with an emission amount lower than the emission amount of the normal light amount period; an optical receiving unit that receives the optical signal, converts it into an electrical signal having a magnitude according to the emission amount of the optical signal, and outputs a received signal of the electrical signal; an emission control unit that controls switching between the emission period and the extinction period of the optical signal transmitted from the optical transmitting unit, and controls setting of the normal light amount period and the low light amount period in the emission period; and a period corresponding to the emission period of the received signal and a period corresponding to the extinction period of the received signal based on the magnitude of the electrical signal, Based on the change in the discrimination result of the period corresponding to the light emission period and the period corresponding to the extinction period, a light receiving control unit that determines deterioration of at least one of the optical transmitting unit and the optical receiving unit; The light emission control unit sets a certain period after the transition from the light-extinguishing period to the light-emitting period as the low light amount period. An optical signal transmitting and receiving device is provided. Effect of the Invention

[0008] An optical signal transmitting / receiving device and a power conversion device are provided that allow for easier inspection of optical components. [Brief description of the drawings]

[0009] [Figure 1] 1 is a block diagram illustrating an optical signal transmitting and receiving device according to a first embodiment. [Diagram 2] 2(a) and 2(b) are timing charts illustrating an example of the operation of the optical signal transmitting and receiving device according to the first embodiment. [Diagram 3] 3(a) and 3(b) are timing charts illustrating a modified example of the operation of the optical signal transmitting and receiving device according to the first embodiment. [Figure 4] 4(a) and 4(b) are timing charts illustrating a modified example of the operation of the optical signal transmitting and receiving device according to the first embodiment. [Diagram 5]5(a) and 5(b) are timing charts illustrating a modified example of the operation of the optical signal transmitting and receiving device according to the first embodiment. [Figure 6] 6(a) and 6(b) are timing charts illustrating a modified example of the operation of the optical signal transmitting and receiving device according to the first embodiment. [Figure 7] FIG. 11 is a block diagram illustrating an optical signal transmitting and receiving device according to a second embodiment. [Figure 8] 8(a) and 8(b) are timing charts illustrating an example of the operation of the optical signal transmitting and receiving device according to the second embodiment. [Figure 9] FIG. 11 is a block diagram illustrating an optical signal transmitting and receiving device according to a third embodiment. [Figure 10] 10(a) and 10(b) are timing charts illustrating an example of the operation of the optical signal transmitting and receiving device according to the third embodiment. [Figure 11] FIG. 11 is a block diagram illustrating a power conversion device according to a fourth embodiment. [Figure 12] 12(a) and 12(b) are timing charts illustrating an example of the operation of the power conversion device according to the fourth embodiment. [Figure 13] 13(a) and 13(b) are timing charts that typically illustrate a modified example of the operation of the power conversion device according to the fourth embodiment. [Figure 14] 14(a) and 14(b) are timing charts that typically illustrate a modified example of the operation of the power conversion device according to the fourth embodiment. [Figure 15] 13 is a flowchart illustrating an example of an operation of a control device for a power converter according to the fourth embodiment. [Figure 16] FIG. 13 is a block diagram illustrating a power conversion device according to a fifth embodiment. [Figure 17] FIG. 2 is a block diagram illustrating a converter.

[0010] Each embodiment will be described below with reference to the drawings. The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between parts, etc. are not necessarily the same as in reality. Even when the same part is shown, the dimensions and ratios of each part may be different depending on the drawing. In this specification and each drawing, elements similar to those described above with reference to the previous drawings are given the same reference numerals and detailed descriptions thereof will be omitted as appropriate.

[0011] (First embodiment) FIG. 1 is a block diagram illustrating an optical signal transmitting and receiving device according to the first embodiment. As shown in FIG. 1, the optical signal transmitting and receiving device 10 includes an optical transmitting section 12, an optical receiving section 14, an emission control section 16, and a light reception control section 18.

[0012] The optical transmitter 12 transmits an optical signal having an emission period and an extinction period. The optical transmitter 12 has a light source such as a light emitting diode or a laser diode, and switches between the emission period and the extinction period of the optical signal by turning on and off the light source. The emission period is, for example, a period during which the light source is turned on, and the extinction period is, for example, a period during which the light source is turned off. The extinction period is not limited to a state in which the light source is turned off, and may be, for example, a state in which the amount of light emitted from the light source is sufficiently small.

[0013] The optical transmitter 12 can set a normal light amount period with a predetermined light amount and a low light amount period with a light amount lower than the normal light amount period during the light emission period. The optical transmitter 12, for example, adjusts the magnitude of the current supplied to the light source. The optical transmitter 12 sets the low light amount period by, for example, supplying a current to the light source that is smaller than the current supplied to the light source during the normal light amount period. However, the method of setting the normal light amount period and the low light amount period is not limited to the above. For example, the normal light amount period and the low light amount period may be set by using two light sources with different light amounts, or the normal light amount period and the low light amount period may be set by using a filter that can adjust the light amount. The method of setting the normal light amount period and the low light amount period may be any method.

[0014] The optical receiving unit 14 receives an optical signal. The optical receiving unit 14 receives an optical signal transmitted from the optical transmitting unit 12. The optical receiving unit 14 is connected to the optical transmitting unit 12 via an optical transmission path such as an optical fiber, and receives the optical signal transmitted from the optical transmitting unit 12. However, the optical receiving unit 14 is not limited to a configuration in which it directly receives the optical signal transmitted from the optical transmitting unit 12, and may be configured to receive the optical signal via, for example, an optical repeater or an optical distributor.

[0015] The optical receiving unit 14 converts the optical signal into an electrical signal having a magnitude corresponding to the amount of light emitted, and outputs the received electrical signal. The optical receiving unit 14 uses a light receiving element such as a photodiode. The optical receiving unit 14 increases the magnitude of the received signal during the emission period of the optical signal, and decreases the magnitude of the received signal during the extinction period of the optical signal.

[0016] The light emission control unit 16 controls switching between the light emission period and the extinction period of the optical signal transmitted from the optical transmitting unit 12, and also controls the setting of the normal light intensity period and the low light intensity period in the light emission period.

[0017] The light-reception control unit 18 distinguishes between a period corresponding to the light emission period of the received signal and a period corresponding to the extinction period of the received signal based on the magnitude of the electrical signal of the received signal output from the optical receiving unit 14. The light-reception control unit 18 sets a predetermined threshold value for the received signal, for example. When the magnitude of the electrical signal of the received signal is equal to or greater than the threshold value, the light-reception control unit 18 distinguishes the period as corresponding to the light emission period, and when the magnitude of the electrical signal of the received signal is less than the threshold value, the light-reception control unit 18 distinguishes the period as corresponding to the extinction period.

[0018] 2(a) and 2(b) are timing charts illustrating an example of the operation of the optical signal transmitting and receiving device according to the first embodiment. 2(a) and 2(b) are schematic diagrams showing an example of an optical signal transmitted from the optical transmitter 12 and an example of a discrimination result of a received signal by the light receiving controller 18. For convenience, the discrimination result is shown as a signal that is low when a light-extinguishing period is discriminated and is high when a light-emitting period is discriminated. However, the method of expressing the discrimination result is not limited to this.

[0019] 2(a) and 2(b), the light emission control unit 16 sets, for example, a certain period after a transition from the extinction period to the light emission period as a low light intensity period. For example, the light emission control unit 16 sets the amount of light emission in the low light intensity period to a predetermined amount of light emission lower than the amount of light emission in the normal light intensity period.

[0020] However, the position where the low light period is set is not limited to this. For example, contrary to the above, a certain period before the transition from the light emission period to the extinction period may be set as the low light period. Alternatively, the low light period may be set in the middle of the light emission period. The position where the low light period is set may be any position in the light emission period.

[0021] Fig. 2(a) shows an example of an optical signal and a determination result when both the optical transmitting unit 12 and the optical receiving unit 14 are normal. As shown in Fig. 2(a), when both the optical transmitting unit 12 and the optical receiving unit 14 are normal, the light reception control unit 18 determines that a low light amount period is an emission period.

[0022] For example, when both the optical transmitting unit 12 and the optical receiving unit 14 are normal, the light emission amount of the low light amount period of the optical signal transmitted from the optical transmitting unit 12 is set so that the magnitude of the electrical signal of the received signal is equal to or greater than the threshold value of the light-reception control unit 18. This allows the light-reception control unit 18 to distinguish the low light amount period as a light emission period when both the optical transmitting unit 12 and the optical receiving unit 14 are normal, as described above.

[0023] Fig. 2(b) shows an example of an optical signal and a determination result when at least one of the optical transmitting unit 12 and the optical receiving unit 14 is deteriorated. As shown in Fig. 2(b), when at least one of the optical transmitting unit 12 and the optical receiving unit 14 is deteriorated, the light receiving control unit 18 determines that the low light amount period is an extinction period.

[0024] For example, when the light emission amount of the optical transmitting unit 12 during a low light period is set as described above, deterioration of the optical transmitting unit 12 may reduce the light emission amount of the optical signal, or deterioration of the optical receiving unit 14 may reduce the received light amount of the optical signal, causing the magnitude of the electrical signal of the received signal to fall below the threshold of the light receiving control unit 18, allowing the light receiving control unit 18 to distinguish the low light period as an extinction period.

[0025] In this way, the determination result of the light-reception control unit 18 varies depending on whether the low-light period is determined to be a light-emitting period or a light-extinction period. Therefore, the light-reception control unit 18 determines the deterioration of at least one of the optical transmitting unit 12 and the optical receiving unit 14 from the difference between the received signal when the low-light period is determined to be a light-emitting period and the received signal when the low-light period is determined to be a light-extinction period.

[0026] The light reception control unit 18 determines that at least one of the optical transmitting unit 12 and the optical receiving unit 14 has deteriorated, for example, when a period corresponding to the light emission period of the received signal becomes shorter than a predetermined time.

[0027] For example, the ratio between the light emission period and the extinction period may change depending on the content of the signal transmitted from the optical transmitting unit 12. In this case, for example, the above-mentioned predetermined time is set shorter than the shortest light emission period during normal operation. As a result, even if the ratio between the light emission period and the extinction period changes, the period corresponding to the light emission period of the received signal becomes shorter than the predetermined time, so that deterioration of at least one of the optical transmitting unit 12 and the optical receiving unit 14 can be appropriately determined.

[0028] When determining that at least one of the optical transmitting unit 12 and the optical receiving unit 14 has deteriorated, the light-receiving control unit 18, for example, notifies the deterioration determination. This makes it possible to notify, for example, a user of the optical signal transmitting / receiving device 10 of deterioration of at least one of the optical transmitting unit 12 and the optical receiving unit 14. For example, it is possible to urge the user of the optical signal transmitting / receiving device 10 to replace at least one of the optical transmitting unit 12 and the optical receiving unit 14.

[0029] The light receiving control unit 18 has, for example, a display unit (not shown) and notifies of deterioration of at least one of the optical transmitting unit 12 and the optical receiving unit 14 by displaying on the display unit. For example, the detection of deterioration may be notified by transmitting information on the detection of deterioration to a portable terminal of a user or the like and displaying the information on a display unit of the portable terminal. In this manner, the detection of deterioration may be notified by outputting information to an external terminal or the like. The detection of deterioration may be notified by outputting sound or light or the like. The mode of notifying of the detection of deterioration may be any mode that can appropriately notify the user of the optical signal transmitting / receiving device 10 of the deterioration of at least one of the optical transmitting unit 12 and the optical receiving unit 14.

[0030] As described above, in the optical signal transmitting and receiving device 10 according to this embodiment, the light emission control unit 16 controls the setting of the normal light intensity period and the low light intensity period during the light emission period, and the light reception control unit 18 determines the deterioration of at least one of the optical transmitting unit 12 and the optical receiving unit 14 from the difference between the received signal when the low light intensity period is determined to be the light emission period and the received signal when the low light intensity period is determined to be the extinction period.

[0031] As a result, in the optical signal transmitting / receiving device 10 according to this embodiment, the inspection of the optical components, the optical transmitting unit 12 and the optical receiving unit 14, can be more easily performed. For example, workers need to inspect the optical transmitting unit 12 and the optical receiving unit 14 only when the light-receiving control unit 18 determines that they have deteriorated, which can reduce the effort of having to inspect the optical transmitting unit 12 and the optical receiving unit 14 periodically. Therefore, the number of inspections of the optical components, the optical transmitting unit 12 and the optical receiving unit 14, can be reduced, and the time and cost required for inspecting the optical components can be reduced.

[0032] 3(a) and 3(b) are timing charts illustrating a modified example of the operation of the optical signal transmitting and receiving device according to the first embodiment. As shown in Figures 3(a) and 3(b), in this example, the light emission control unit 16 gradually increases the amount of light emitted during the low light period. For example, when a certain period after the transition from the extinction period to the light emission period is set as the low light period, the light emission control unit 16 continuously increases the amount of light emitted from the timing of the transition from the extinction period to the light emission period to the normal light period. In other words, the light emission control unit 16 increases the amount of light emitted linearly (straight line) during the low light period. However, the increase in the amount of light emitted during the low light period is not limited to this, and may be increased curvilinearly or in stages (stepwise).

[0033] The light reception control unit 18 determines the degree of deterioration of at least one of the optical transmitting unit 12 and the optical receiving unit 14 according to the duration of a period corresponding to the light emission period of the received signal.

[0034] For example, as described above, when the amount of light emission is gradually increased during a low light period, the length of the period corresponding to the light emission period of the received signal becomes shorter as the degree of deterioration of at least one of the optical transmitting unit 12 and the optical receiving unit 14 increases. Therefore, in this case, the light-receiving control unit 18 determines that the degree of deterioration of at least one of the optical transmitting unit 12 and the optical receiving unit 14 is increasing as the length of the period corresponding to the light emission period of the received signal becomes shorter.

[0035] In this way, the light emission control unit 16 gradually increases the amount of light emission during the low light period, and the light reception control unit 18 determines the degree of deterioration of at least one of the optical transmitting unit 12 and the optical receiving unit 14 according to the time period corresponding to the light emission period of the received signal. This allows, for example, a user of the optical signal transmitting and receiving device 10 to more accurately know when to inspect or replace the optical transmitting unit 12 and the optical receiving unit 14.

[0036] 4(a) and 4(b) are timing charts illustrating a modified example of the operation of the optical signal transmitting and receiving device according to the first embodiment. As shown in Figures 4(a) and 4(b), in this example, the light emission control unit 16 switches between a light emission period and a light-off period at a predetermined cycle, and transmits a pulse signal in which the light emission period is a pulse as an optical signal.

[0037] When the number of consecutive pulses of the pulse signal is N, the light emission control unit 16 sets pulses in the range of 1 in N to N-1 times as the low light intensity period. In Fig. 4(a) and Fig. 4(b), N=2, and an example is shown in which a pulse is set as the low light intensity period at a rate of 1 in 2 times. In other words, Fig. 4(a) and Fig. 4(b) show an example in which a normal light intensity period and a low light intensity period are set alternately in each pulse. The rate at which the low light intensity period is set is not limited to the above, and may be any rate in the range of 1 in N to N-1 times.

[0038] When the light emission control unit 16 transmits a pulse signal as an optical signal, as shown in FIG. 4(a), if the light reception control unit 18 determines that a low light period is an emission period, the period between the emission period and the extinction period also becomes a predetermined period corresponding to the pulse signal (optical signal) in the determination result of the light reception control unit 18.

[0039] On the other hand, as shown in FIG. 4(b), when the light receiving control unit 18 determines that the low light intensity period is an extinction period, the period between the light emission period and the extinction period in the determination result of the light receiving control unit 18 becomes longer than the specified period of the pulse signal.

[0040] Therefore, when the light emission control unit 16 transmits a pulse signal as an optical signal, the light reception control unit 18 determines that at least one of the optical transmitting unit 12 and the optical receiving unit 14 has deteriorated when the period between the period corresponding to the light emission period of the received signal and the period corresponding to the extinction period of the received signal becomes longer than a specified period of the pulse signal.

[0041] In this way, the optical signal transmitted from the optical transmitting unit 12 may be a pulse signal. In this case as well, a pulse in the range of 1 in N to N-1 times is set as a low light intensity period, and when the period corresponding to the light emission period of the received signal and the period corresponding to the extinction period of the received signal become longer than a predetermined period of the pulse signal, deterioration of at least one of the optical transmitting unit 12 and the optical receiving unit 14 is determined, so that inspection of the optical components, the optical transmitting unit 12 and the optical receiving unit 14, can be more easily performed, as in the above example.

[0042] 5(a) and 5(b) are timing charts illustrating a modified example of the operation of the optical signal transmitting and receiving device according to the first embodiment. As shown in Figures 5(a) and 5(b), in this example, the light emission control unit 16 sets multiple consecutive pulses as a low light period, and sequentially increases the light amount of the multiple consecutive pulses that make up the low light period in the order in which the pulses are transmitted.

[0043] 5(a) and 5(b) show an example in which N=4 and three consecutive pulses out of four pulses are set as the low light period. However, the number of pulses set in the low light period is not limited to three and may be any number of two or more. Also, in FIG. 5(a) and 5(b), the number of pulses set in the normal light period is one, but the number of pulses set in the normal light period is not limited to one and may be two or more.

[0044] In this way, when the light amount of consecutive multiple pulses that are to be the low light amount period is increased in sequence in the order of transmission of the pulses, the number of pulses determined to be in the light emission period decreases as the degree of deterioration of at least one of the optical transmitting unit 12 and the optical receiving unit 14 increases. More specifically, as the degree of deterioration of at least one of the optical transmitting unit 12 and the optical receiving unit 14 increases, the pulses that are determined to be in the extinction period will start from the pulse with the smallest light amount.

[0045] Therefore, the light reception control unit 18 determines the degree of deterioration of at least one of the optical transmitting unit 12 and the optical receiving unit 14 according to the number of periods equivalent to the light emitting period determined within the period of N pulses in the received signal. This allows, for example, a user of the optical signal transmitting and receiving device 10 to more accurately know when to inspect or replace the optical transmitting unit 12 and the optical receiving unit 14.

[0046] 6(a) and 6(b) are timing charts illustrating a modified example of the operation of the optical signal transmitting and receiving device according to the first embodiment. As shown in Figures 6(a) and 6(b), the light emission control unit 16 may set multiple consecutive pulses as a low light period and sequentially reduce the light amount of the multiple consecutive pulses that make up the low light period in the order in which the pulses are transmitted. In this case, the same effect as that of the example shown in Figures 5(a) and 5(b) can be obtained. For example, the user of the optical signal transmitting and receiving device 10 can more accurately know when to inspect or replace the optical transmitting unit 12 and the optical receiving unit 14.

[0047] Second Embodiment FIG. 7 is a block diagram illustrating an optical signal transmitting and receiving device according to the second embodiment. 7, the optical signal transmitting and receiving device 20 includes a first optical signal transmitting and receiving unit 21 and a second optical signal transmitting and receiving unit 22. The first optical signal transmitting and receiving unit 21 includes a first optical transmitting unit 30, a first optical receiving unit 32, an emission control unit 34, and a light reception control unit 36. The second optical signal transmitting and receiving unit 22 includes a second optical transmitting unit 40 and a second optical receiving unit 42.

[0048] The first optical transmitter 30 transmits a first optical signal having an emission period and an extinction period to the second optical signal transmitter / receiver 22, and can set, in the emission period, a normal light amount period with a predetermined emission amount and a low light amount period with an emission amount lower than the emission amount of the normal light amount period. The configuration of the first optical transmitter 30 is, for example, similar to the configuration of the optical transmitter 12 of the first embodiment.

[0049] The light emission control unit 34 controls switching between the light emission period and the extinction period of the first optical signal transmitted from the first optical transmitting unit 30, and controls the setting of the normal light intensity period and the low light intensity period in the light emission period.

[0050] The second optical receiving section 42 receives the first optical signal, converts it into an electrical signal having a magnitude corresponding to the amount of light emitted from the first optical signal, and outputs a received electrical signal.

[0051] The second optical transmitting unit 40 transmits to the first optical signal transmitting / receiving unit 21 a second optical signal that switches between an emission period and an extinction period based on a predetermined signal that changes according to the signal received by the second optical receiving unit 42. The predetermined signal may be any signal that changes according to the signal received by the second optical receiving unit 42.

[0052] The first optical receiving unit 32 receives the second optical signal, converts it into an electrical signal having a magnitude corresponding to the amount of light emitted by the second optical signal, and outputs a received electrical signal.

[0053] 8(a) and 8(b) are timing charts illustrating an example of the operation of the optical signal transmitting and receiving device according to the second embodiment. Figures 8(a) and 8(b) show schematic diagrams of an example of a first optical signal transmitted from the first optical transmitting unit 30, an example of a specified signal that changes depending on the received signal of the second optical receiving unit 42, an example of a second optical signal transmitted from the second optical transmitting unit 40, and an example of a received signal of the first optical receiving unit 32.

[0054] 8(a) and 8(b), the light emission control unit 34 sets, for example, a certain period after the transition from the extinction period to the light emission period as the low light intensity period. For example, the light emission control unit 34 sets the amount of light emission in the low light intensity period to a predetermined amount of light emission lower than the amount of light emission in the normal light intensity period.

[0055] When there is a predetermined signal that changes in response to the received signal of the second optical receiving unit 42, and the second optical signal is transmitted to the first optical signal transmitting / receiving unit 21 based on this predetermined signal, the time until the received signal of the first optical receiving unit 32 changes in response to a change in the first optical signal changes depending on whether the low light period is determined to be an emission period or an extinction period when the predetermined signal changes in response to the received signal of the second optical receiving unit 42.

[0056] For example, in the examples shown in Figures 8(a) and 8(b), after the first optical signal changes from the extinction period to the emission period, the time until the received signal of the first optical receiving unit 32 changes from the period corresponding to the extinction period to the period corresponding to the emission period varies depending on whether the low light period is determined to be the emission period or the low light period is determined to be the extinction period.

[0057] Therefore, the light receiving control unit 36 ​​determines that at least one of the first optical signal transmitting / receiving unit 21 and the second optical signal transmitting / receiving unit 22 has deteriorated when the delay time between the change in the received signal of the first optical receiving unit 32 and the change in the first optical signal becomes longer than a certain time.

[0058] As a result, in the optical signal transmission / reception device 20 according to this embodiment, inspection of the first optical signal transmission / reception unit 21 and the second optical signal transmission / reception unit 22 can be more easily performed. For example, a worker or the like only needs to inspect the first optical signal transmission / reception unit 21 and the second optical signal transmission / reception unit 22 when deterioration is determined by the light-receiving control unit 36, and this can reduce the effort of having to inspect the first optical signal transmission / reception unit 21 and the second optical signal transmission / reception unit 22 periodically. This can reduce the number of inspections of the first optical signal transmission / reception unit 21 and the second optical signal transmission / reception unit 22, thereby reducing the time and cost required for inspecting optical components.

[0059] 3, the light emission control unit 34 may gradually increase the amount of light emitted during a low light period. The light reception control unit 36 ​​may determine the degree of deterioration of at least one of the first optical signal transceiver 21 and the second optical signal transceiver 22 according to the duration of the light emission period of the received signal of the first optical receiver 32. In other words, the light reception control unit 36 ​​may determine the degree of deterioration of at least one of the first optical signal transceiver 21 and the second optical signal transceiver 22 according to the length of delay time of a change in the received signal of the first optical receiver 32 relative to a change in the first optical signal.

[0060] Similar to the light-receiving control unit 18 of the first embodiment described above, the light-receiving control unit 36 ​​may notify the deterioration determination when it determines that at least one of the first optical signal transceiver unit 21 and the second optical signal transceiver unit 22 has deteriorated.

[0061] (Third embodiment) FIG. 9 is a block diagram illustrating an optical signal transmitting and receiving device according to the third embodiment. 9, the optical signal transmitting and receiving device 50 includes a first optical signal transmitting and receiving unit 51 and a second optical signal transmitting and receiving unit 52. The first optical signal transmitting and receiving unit 51 includes a first optical transmitting unit 60, a first optical receiving unit 62, and a light reception control unit 64. The second optical signal transmitting and receiving unit 52 includes a second optical transmitting unit 70, a second optical receiving unit 72, and a light emission control unit 74.

[0062] The first optical transmitter 60 transmits a first optical signal having an emission period and an extinction period to the second optical signal transmitter / receiver 52 .

[0063] The second optical receiving section 72 receives the first optical signal, converts it into an electrical signal having a magnitude corresponding to the amount of light emitted by the first optical signal, and outputs a received electrical signal.

[0064] The second optical transmitting unit 70 transmits a second optical signal having an emission period and an extinction period to the first optical signal transmitting and receiving unit 51, and can set, in the emission period, a normal light amount period with a predetermined emission amount and a low light amount period with an emission amount lower than the emission amount of the normal light amount period. The configuration of the second optical transmitting unit 70 is, for example, similar to the configuration of the optical transmitting unit 12 of the first embodiment.

[0065] The first optical receiving section 62 receives the second optical signal, converts it into an electrical signal having a magnitude corresponding to the amount of light emitted by the second optical signal, and outputs a received electrical signal.

[0066] 10(a) and 10(b) are timing charts illustrating an example of the operation of the optical signal transmitting and receiving device according to the third embodiment. Figures 10(a) and 10(b) show schematic diagrams of an example of a first optical signal transmitted from the first optical transmitting unit 60, an example of a predetermined signal that changes depending on the received signal of the second optical receiving unit 72, an example of a second optical signal transmitted from the second optical transmitting unit 70, and an example of the discrimination result of the received signal of the first optical receiving unit 62 by the light receiving control unit 64.

[0067] As shown in FIG. 10(a) and FIG. 10(b), the light emission control unit 74 controls switching between the light emission period and the extinction period of the second optical signal transmitted from the second optical transmitting unit 70 based on a predetermined signal that changes according to the received signal of the second optical receiving unit 72. The light emission control unit 74 sets the light emission period based on the predetermined signal to a normal light intensity period. The light emission control unit 74 then sets a low light intensity period to a portion of the extinction period based on the predetermined signal. The predetermined signal may be any signal that changes according to the received signal of the second optical receiving unit 72.

[0068] The light receiving control unit 64 distinguishes between a period corresponding to the light emission period of the received signal of the first optical receiving unit 62 and a period corresponding to the extinction period of the received signal of the first optical receiving unit 62 based on the magnitude of the electrical signal of the received signal of the first optical receiving unit 62, and determines deterioration of at least one of the first optical signal transmitting / receiving unit 51 and the second optical signal transmitting / receiving unit 52 from the difference between the received signal of the first optical receiving unit 62 when the low light period is distinguished as the light emission period and the received signal of the first optical receiving unit 62 when the low light period is distinguished as the extinction period.

[0069] As a result, in the optical signal transmission / reception device 50 according to this embodiment, it is possible to more easily inspect the first optical signal transmission / reception unit 51 and the second optical signal transmission / reception unit 52. The number of inspections of the first optical signal transmission / reception unit 51 and the second optical signal transmission / reception unit 52 can be reduced, and the time and cost required for inspecting optical components can be suppressed.

[0070] (Fourth embodiment) FIG. 11 is a block diagram illustrating a power conversion device according to the fourth embodiment. As shown in FIG. 11, the power conversion device 100 includes a main circuit unit 101, a control device 102, and an optical signal transmitting and receiving device 104.

[0071] The main circuit unit 101 has a converter 101a, and performs power conversion by the operation of the converter 101a. The control device 102 controls the operation of the main circuit unit 101. In other words, the control device 102 controls the operation of power conversion by the converter 101a. The optical signal transmitting and receiving device 104 performs communication between the main circuit unit 101 and the control device 102.

[0072] Converter 101a has six switching elements 111-116 connected in a three-phase bridge, six rectifier elements 121-126 connected in anti-parallel to each of the six switching elements 111-116, a charge storage element 130 connected in parallel to each of the six switching elements 111-116, and drive circuits 131-136 that switch each of the switching elements 111-116 on and off.

[0073] In the converter 101a, both ends of each of the switching elements 111 to 116 become a pair of DC terminals 106a, 106b, and the connection point between the switching elements 111 and 112, the connection point between the switching elements 113 and 114, and the connection point between the switching elements 115 and 116 become three AC terminals 108a to 108c, respectively. The converter 101a is a so-called three-phase two-level inverter.

[0074] The converter 101a is connected to an AC power system via each of the AC terminals 108a to 108c. Each of the AC terminals 108a to 108c is connected to the AC power system via, for example, a circuit breaker or a transformer (not shown). The converter 101a is also connected to a DC power source or a DC load via a pair of DC terminals 106a and 106b. As a result, the main circuit unit 101 performs power conversion by the operation of the converter 101a. The main circuit unit 101 performs at least one of DC to AC conversion and AC to DC conversion by, for example, switching of each of the switching elements 111 to 116 of the converter 101a.

[0075] The optical signal transmitting and receiving device 104 has a first optical signal transmitting and receiving unit 141 and a second optical signal transmitting and receiving unit 142. The configurations of the first optical signal transmitting and receiving unit 141 and the second optical signal transmitting and receiving unit 142 are substantially the same as the configurations of the first optical signal transmitting and receiving unit 21 and the second optical signal transmitting and receiving unit 22 described with reference to Fig. 7, for example. The first optical signal transmitting and receiving unit 141 has, for example, a first optical transmitting unit 30, a first optical receiving unit 32, a light emission control unit 34, and a light reception control unit 36. The second optical signal transmitting and receiving unit 142 has, for example, a second optical transmitting unit 40 and a second optical receiving unit 42.

[0076] The first optical signal transmitting / receiving unit 141 is connected to, for example, the control device 102. The second optical signal transmitting / receiving unit 142 is connected to, for example, the main circuit unit 101. In this way, the optical signal transmitting / receiving device 104 electrically insulates the main circuit unit 101 from the control device 102 while enabling communication between the main circuit unit 101 and the control device 102.

[0077] The control device 102 transmits a control signal to the drive circuits 131-136 via the optical signal transmission / reception device 104. The control signal may be called, for example, a gate signal or a gate command. The drive circuits 131-136 switch the switching elements 111-116 on and off based on the control signal input from the control device 102. The control device 102 transmits a control signal to the drive circuits 131-136 via the optical signal transmission / reception device 104 and controls the on and off of the switching elements 111-116, thereby controlling the power conversion by the main circuit unit 101.

[0078] The optical signal transmitting / receiving device 104 has, for example, a plurality of first optical signal transmitting / receiving units 141 and a plurality of second optical signal transmitting / receiving units 142 provided corresponding to the respective driving circuits 131 to 136. Each control signal output from the control device 102 is input to each of the driving circuits 131 to 136 via each of the first optical signal transmitting / receiving units 141 and each of the second optical signal transmitting / receiving units 142.

[0079] The driving circuits 131-136 measure, for example, the voltages at the control terminals of the switching elements 111-116, and transmit a feedback signal according to the measurement result of the control terminal voltage to the control device 102 via the optical signal transmitting / receiving device 104. The control terminal voltage may be called, for example, a gate voltage. In the following description, the control signal transmitted from the control device 102 to the driving circuits 131-136 is referred to as a gate command, and the voltages at the control terminals of the switching elements 111-116 are referred to as gate voltages.

[0080] 12(a) and 12(b) are timing charts illustrating an example of the operation of the power conversion device according to the fourth embodiment. 12(a) and 12(b) show an example of a gate command transmitted from the control device 102 to the switching element 111, and an example of a feedback signal transmitted from the drive circuit 131 to the control device 102. The gate command transmitted from the control device 102 to the switching elements 112-116, and the feedback signals transmitted from the drive circuits 132-136 to the control device 102 can be the same as those described above, except for the on / off timing, and so a detailed description thereof will be omitted.

[0081] As shown in Figures 12(a) and 12(b), the control device 102 transmits a gate command to the first optical signal transceiver 141 of the optical signal transceiver 104, in which a high voltage state (high state) corresponds to the on state of the switching element 111 and a low voltage state (low state) corresponds to the off state of the switching element 111.

[0082] The light-emission control unit 34 of the first optical signal transmitting / receiving unit 141 transmits the first optical signal from the first optical transmitting unit 30 to the second optical signal transmitting / receiving unit 142, with the high voltage state of the gate command as the light-emission period and the low voltage state of the gate command as the extinction period. At this time, the light-emission control unit 34 sets a certain period after the transition from the extinction period to the light-emission period as the low-light-amount period. For example, the light-emission control unit 34 sets the amount of light emission in the low-light-amount period to a predetermined amount of light emission lower than the amount of light emission in the normal-light-amount period.

[0083] The second optical receiving unit 42 of the second optical signal transmitting / receiving unit 142 receives the first optical signal and converts it into an electrical signal having a magnitude corresponding to the amount of light emitted by the first optical signal, thereby outputting the received electrical signal to the driving circuit 131.

[0084] The drive circuit 131 switches the on state and off state of the switching element 111 in response to the reception signal input from the second optical receiving unit 42. The drive circuit 131 switches the switching element 111 from an off state to an on state by setting the gate voltage to a high state in response to the reception signal switching from a low state (period corresponding to the extinction period) to a high state (period corresponding to the emission period), and switches the switching element 111 from an off state to an on state by setting the gate voltage to a low state in response to the reception signal switching from a high state to a low state.

[0085] The drive circuit 131 measures the gate voltage of the switching element 111, and transmits a feedback signal corresponding to the gate voltage to the second optical signal transmitting and receiving unit 142 of the optical signal transmitting and receiving device 104. The feedback signal is, for example, a signal that is in a high state when the gate voltage is less than a predetermined voltage, and is in a low state when the gate voltage is equal to or greater than the predetermined voltage. That is, in this example, the gate voltage or the feedback signal is a predetermined signal that changes according to the received signal of the second optical receiving unit 42.

[0086] The second optical transmitting unit 40 of the second optical signal transmitting / receiving unit 142 transmits a second optical signal corresponding to the feedback signal to the first optical signal transmitting / receiving unit 141. The second optical transmitting unit 40 transmits the second optical signal, for example, with the low state of the feedback signal as an extinction period and the high state of the feedback signal as an emission period.

[0087] The first optical receiving unit 32 of the first optical signal transmitting / receiving unit 141 receives the second optical signal and converts it into an electrical signal having a magnitude corresponding to the amount of light emitted by the second optical signal, thereby outputting the received electrical signal to the control device 102. This allows the control device 102 to grasp the on / off state of the switching element 111.

[0088] In this way, when the second optical signal is transmitted to the first optical signal transmitting / receiving unit 141 based on the feedback signal that changes according to the reception signal of the second optical receiving unit 42, the time until the reception signal of the first optical receiving unit 32 changes according to the change in the first optical signal changes depending on whether the drive circuit 131 determines the low light period as a light emission period or the low light period as a light extinction period. In other words, the time until the reception signal of the first optical receiving unit 32 changes according to the change in the first optical signal changes depending on the time until the drive circuit 131 switches the on and off states of the switching element 111 based on the first optical signal and the feedback signal changes.

[0089] The delay time of the change in the reception signal of the first optical receiving unit 32 relative to the change in the first optical signal is longer when the drive circuit 131 determines that the low light amount period is an extinction period than when the drive circuit 131 determines that the low light amount period is an emission period. Therefore, the light receiving control unit 36 ​​of the first optical signal transmitting and receiving unit 141 determines that at least one of the first optical signal transmitting and receiving unit 141 and the second optical signal transmitting and receiving unit 142 has deteriorated when the delay time of the change in the reception signal of the first optical receiving unit 32 relative to the change in the first optical signal becomes equal to or longer than a certain time.

[0090] As a result, in the power conversion device 100 according to this embodiment, the inspection of the first optical signal transceiver 141 and the second optical signal transceiver 142 can be more easily performed. For example, a worker or the like only needs to inspect the first optical signal transceiver 141 and the second optical signal transceiver 142 when the light-receiving control unit 36 ​​determines that the unit has deteriorated, and this can reduce the effort required to periodically inspect the first optical signal transceiver 141 and the second optical signal transceiver 142. This can reduce the number of inspections of the first optical signal transceiver 141 and the second optical signal transceiver 142, thereby reducing the time and cost required for inspecting optical components.

[0091] Similar to the light-receiving control unit 18 of the first embodiment described above, when the light-receiving control unit 36 ​​determines that at least one of the first optical signal transceiver unit 21 and the second optical signal transceiver unit 22 has deteriorated, it may notify the control device 102 or the like of the determination of the deterioration.

[0092] In this example, the light emission control unit 34 and the light reception control unit 36 ​​are provided in the first optical signal transmitting and receiving unit 141. The light emission control unit 34 and the light reception control unit 36 ​​may be provided in, for example, the control device 102. Also, for example, the first optical signal transmitting and receiving unit 141 may be provided in the control device 102. The second optical signal transmitting and receiving unit 142 may be provided in the main circuit unit 101. A portion of the configuration of the optical signal transmitting and receiving device 104 may be provided in the main circuit unit 101 or the control device 102.

[0093] 13(a) and 13(b) are timing charts that typically illustrate a modified example of the operation of the power conversion device according to the fourth embodiment. 13(a) and 13(b), the light emission control unit 34 of the first optical signal transmitting and receiving unit 141 may gradually increase the amount of light emitted during a low light amount period of the first optical signal. The light reception control unit 36 ​​of the first optical signal transmitting and receiving unit 141 may determine the degree of deterioration of at least one of the first optical signal transmitting and receiving unit 141 and the second optical signal transmitting and receiving unit 142 according to the length of delay time of a change in the received signal of the first optical receiving unit 32 relative to a change in the first optical signal.

[0094] In the power conversion device 100, the configurations of the first optical signal transceiver 141 and the second optical signal transceiver 142 of the optical signal transceiver 104 may be substantially the same as the configurations of the first optical signal transceiver 51 and the second optical signal transceiver 52 described with reference to Fig. 9. The first optical signal transceiver 141 may be configured to include, for example, a first optical transmitter 60, a first optical receiver 62, and a light reception control unit 64. The second optical signal transceiver 142 may be configured to include, for example, a second optical transmitter 70, a second optical receiver 72, and a light emission control unit 74.

[0095] 14(a) and 14(b) are timing charts that typically illustrate a modified example of the operation of the power conversion device according to the fourth embodiment. When the second optical signal transmitting / receiving unit 142 has an emission control unit 74, as shown in Figures 14(a) and 14(b), the emission control unit 74 can set a low light intensity period during a portion of the extinction period of the second optical signal based on the feedback signal.

[0096] The light receiving control unit 64 of the first optical signal transmitting / receiving unit 141 distinguishes between a period corresponding to the light emission period of the received signal of the first optical receiving unit 62 and a period corresponding to the extinction period of the received signal of the first optical receiving unit 62 based on the magnitude of the electrical signal of the received signal of the first optical receiving unit 62, and determines deterioration of at least one of the first optical signal transmitting / receiving unit 141 and the second optical signal transmitting / receiving unit 142 from the difference between the received signal of the first optical receiving unit 62 when the low light period is distinguished as the light emission period and the received signal of the first optical receiving unit 62 when the low light period is distinguished as the extinction period.

[0097] This makes it possible to more easily inspect the first optical signal transceiver unit 141 and the second optical signal transceiver unit 142, even when the configurations of the first optical signal transceiver unit 141 and the second optical signal transceiver unit 142 are substantially the same as the configurations of the first optical signal transceiver unit 51 and the second optical signal transceiver unit 52 described with reference to Fig. 9. This makes it possible to reduce the number of inspections of the first optical signal transceiver unit 141 and the second optical signal transceiver unit 142, and to suppress the time and cost required for inspecting optical components.

[0098] In addition, in the power conversion device 100, a pulse signal called a heartbeat signal may be periodically transmitted from the main circuit unit 101 to the control device 102 to notify the control device 102 that the main circuit unit 101 is operating normally.

[0099] When the second optical signal transceiver 142 on the main circuit unit 101 side has a light emission control unit 74, for example, as in the example described with reference to Figures 4(a) and 4(b), a predetermined number of pulses of the heartbeat signal may be set to a low light period, thereby making it possible to detect deterioration of the first optical signal transceiver 141 and the second optical signal transceiver 142.

[0100] For example, as described with reference to Figures 5 and 6, the light amount of multiple consecutive pulses that constitute a low light amount period may be increased or decreased sequentially in the order in which the pulses are transmitted, thereby making it possible to determine the degree of deterioration of at least one of the first optical signal transceiver 141 and the second optical signal transceiver 142.

[0101] The configuration of the optical signal transmitting / receiving device 104 provided in the power conversion device 100 is not limited to the above. For example, the first optical signal transmitting / receiving unit 141 and the second optical signal transmitting / receiving unit 142 may each be provided with a light emission control unit and a light reception control unit. In this case, the method shown in Figs. 2 to 6 may be used to detect deterioration of at least one of the optical transmitting unit and the optical receiving unit of each of the first optical signal transmitting / receiving unit 141 and the second optical signal transmitting / receiving unit 142. In addition, for example, when there is no need to transmit a feedback signal from the main circuit unit 101 to the control device 102, the optical transmitting unit and the light emission control unit may be provided only on the control device 102 side, and the optical receiving unit and the light reception control unit may be provided only on the main circuit unit 101 side. In this case, deterioration of at least one of the optical transmitting unit and the optical receiving unit can be detected by the method shown in Figs. 2 to 6.

[0102] FIG. 15 is a flowchart illustrating an example of the operation of the control device for the power conversion device according to the fourth embodiment. 15, the control device 102 has, for example, a normal operation mode in which the main circuit unit 101 controls the conversion of power, and a deterioration detection mode in which deterioration of the optical signal transmitting and receiving device 104 is detected. In the deterioration detection mode, the control device 102 causes the light emission control unit and the light reception control unit of the optical signal transmitting and receiving device 104 to detect deterioration. Any of the above-mentioned methods may be used as a method for detecting deterioration. In the normal operation mode, for example, when transmitting a gate command, a low light intensity period is not set, and the entire light emission period is set to a normal light intensity period.

[0103] 15, the control device 102 executes the degradation detection mode at a startup timing before starting the normal operation mode and at a stop timing after terminating the normal operation mode. For example, when degradation of at least one of the first optical signal transceiver 141 and the second optical signal transceiver 142 is detected in the degradation detection mode at the startup timing, the normal operation mode may not be started as shown in FIG.

[0104] The degradation detection mode does not necessarily have to be performed at both the start-up timing and the stop timing. The degradation detection mode may be performed only at the start-up timing or only at the stop timing. In other words, the degradation detection mode may be performed at least at either the start-up timing or the stop timing.

[0105] Also, as described above, without providing the degradation detection mode, degradation of optical components may be detected by setting a low light intensity period as part of the light emission period during normal operation mode operation. Furthermore, whether or not to perform the degradation detection mode may be arbitrarily switched based on, for example, the operation of the operator of the control device 102. The degradation detection mode may be executed at an arbitrary timing based on, for example, the operation of the operator of the control device 102.

[0106] Fifth embodiment FIG. 16 is a block diagram illustrating a power conversion device according to the fifth embodiment. 16, the power conversion device 200 includes a main circuit unit 212, a control device 214, and an optical signal transmission / reception device 216. The power conversion device 200 is used in, for example, a DC power transmission system. The power conversion device 200 is connected to an AC power system 202 and a pair of DC transmission lines 203 and 204 in the DC power transmission system.

[0107] The DC transmission system includes, for example, a transformer 206. The main circuit unit 212 of the power conversion device 200 is connected to the AC power system 202 via the transformer 206. The AC power of the AC power system 202 is three-phase AC power. More specifically, it is symmetrical three-phase AC power. The transformer 206 converts the three-phase AC power of the AC power system 202 into AC power corresponding to the main circuit unit 212. The transformer 206 changes the effective value of each phase of the three-phase AC power in accordance with the main circuit unit 212. The transformer 206 is a three-phase transformer. The transformer 206 is provided as necessary and can be omitted. The three-phase AC power of the AC power system 202 may be directly supplied to the main circuit unit 212.

[0108] The power conversion device 200 converts three-phase AC power supplied from an AC power system 202 into DC power, and supplies the converted DC power to DC transmission lines 203 and 204. The power conversion device 200 also converts DC power supplied from the DC transmission lines 203 and 204 into three-phase AC power, and supplies the converted three-phase AC power to the AC power system 202. In this way, the power conversion device 200 performs AC-to-DC conversion from AC to DC, and AC-to-DC conversion from DC to AC.

[0109] For example, DC transmission line 203 is a high-voltage side transmission line of DC power, and DC transmission line 204 is a low-voltage side transmission line of DC power. Power conversion device 200 outputs converted DC power to DC transmission lines 203 and 204 so that DC transmission line 203 side is high voltage and DC transmission line 204 side is low voltage.

[0110] The main circuit unit 212 is provided between the AC power system 202 and each of the DC transmission lines 203 and 204. The main circuit unit 212 converts three-phase AC power to DC power and converts DC power to three-phase AC power. The main circuit unit 212 is, for example, a multilevel power converter having a plurality of converters connected in series. The main circuit unit 212 is, for example, an MMC (Modular Multilevel Converter) type power converter. The MMC type main circuit unit 212 has a plurality of converters connected in series. Each converter has a plurality of switching elements connected in half-bridge connection or full-bridge connection, and a charge storage element connected in parallel to each switching element. The main circuit unit 212 converts power by the operation of the plurality of converters. The main circuit unit 212 converts AC to DC by, for example, switching each switching element of the plurality of converters.

[0111] The control device 214 controls the operation of the main circuit section 212. The optical signal transceiver 216 performs communication between the main circuit section 212 and the control device 214. The control device 214 communicates with the main circuit section 212 via the optical signal transceiver 216, and controls the on / off of each switching element, thereby controlling the conversion from three-phase AC power to DC power and the conversion from DC power to three-phase AC power by the main circuit section 212.

[0112] The main circuit portion 212 has a pair of first and second DC terminals 220a, 220b, three AC terminals (first to third) 221a to 221c, and six arm portions (first to sixth) 222a to 222f.

[0113] The first DC terminal 220a is connected to the high-voltage side DC transmission line 203. The second DC terminal 220b is connected to the low-voltage side DC transmission line 204. As a result, DC power converted by the main circuit unit 212 is supplied to the DC transmission lines 203, 204, and DC power supplied from the DC transmission lines 203, 204 is input to the main circuit unit 212.

[0114] The first arm portion 222a is connected to the first DC terminal 220a. The second arm portion 222b is connected between the first arm portion 222a and the second DC terminal 220b. The first arm portion 222a and the second arm portion 222b are connected in series between the DC terminals 220a, 220b.

[0115] The third arm portion 222c is connected to the first DC terminal 220a. The fourth arm portion 222d is connected between the third arm portion 222c and the second DC terminal 220b. The third arm portion 222c and the fourth arm portion 222d are connected in parallel to the first arm portion 222a and the second arm portion 222b.

[0116] The fifth arm portion 222e is connected to the first DC terminal 220a. The sixth arm portion 222f is connected between the fifth arm portion 222e and the second DC terminal 220b. That is, the fifth arm portion 222e and the sixth arm portion 222f are connected in parallel to the first arm portion 222a and the second arm portion 222b, and are connected in parallel to the third arm portion 222c and the fourth arm portion 222d.

[0117] In the main circuit unit 212, the first leg LG1 is configured by the first arm portion 222a and the second arm portion 222b, the second leg LG2 is configured by the third arm portion 222c and the fourth arm portion 222d, and the third leg LG3 is configured by the fifth arm portion 222e and the sixth arm portion 222f. That is, in this example, the main circuit unit 212 is a three-phase inverter with three legs and six arms. The first arm portion 222a, the third arm portion 222c, and the fifth arm portion 222e are upper arms. The second arm portion 222b, the fourth arm portion 222d, and the sixth arm portion 222f are lower arms. In this way, the main circuit unit 212 has a plurality of arms and a plurality of legs configured by a plurality of switching elements. The main circuit unit 212 may be, for example, a single-phase inverter with two legs and four arms. The number of arms and legs is not limited to the above, and may be any number.

[0118] The first arm section 222a has a plurality of converters UP1, UP2...UPM1 connected in series. The second arm section 222b has a plurality of converters UN1, UN2...UNM2 connected in series. The third arm section 222c has a plurality of converters VP1, VP2...VPM3 connected in series. The fourth arm section 222d has a plurality of converters VN1, VN2...VNM4 connected in series. The fifth arm section 222e has a plurality of converters WP1, WP2...WPM5 connected in series. The sixth arm section 222f has a plurality of converters WN1, WN2...WNM6 connected in series.

[0119] However, in the following, when the converters UP1, UP2...UPM1, UN1, UN2...UNM2, VP1, VP2...VPM3, VN1, VN2...VNM4, WP1, WP2...WPM5, WN1, WN2...WNM6 are referred to collectively as the "converter CEL."

[0120] In each of the arm sections 222a to 222f, M1, M2, M3, M4, M5, and M6 represent the number of converters CEL connected in series. In each of the arm sections 222a to 222f, the number of converters CEL connected in series is, for example, about 100 to 120. However, the number of converters CEL connected in series is not limited to this and may be any number.

[0121] The number of converters CEL provided in each of the arm sections 222a to 222f is substantially the same. For example, when a large number of converters CEL are connected, the number of converters CEL provided in each of the arm sections 222a to 222f may differ as long as it does not affect the operation of the main circuit section 212. For example, when 100 converters CEL are connected in series to one arm section, the number of converters CEL provided in another arm section may differ by one or two.

[0122] The arm sections 222a to 222f further include buffer reactors 223a to 223f and a plurality of current detectors 224a to 224f, respectively. The power conversion device 200 further includes a voltage detection section 225.

[0123] The buffer reactors 223a to 223f are connected in series to the converters CEL in the arm sections 222a to 222f, respectively. The buffer reactor 223a of the first arm section 222a is provided between the converter UP1 and a connection point between the AC terminal 221a and the first arm section 222a and the second arm section 222b. The buffer reactor 223b of the second arm section 222b is provided between the converter UN1 and a connection point between the AC terminal 221a and the first arm section 222a and the second arm section 222b. The buffer reactor 223c of the third arm section 222c is provided between the converter VP1 and a connection point between the AC terminal 221b and the third arm section 222c and the fourth arm section 222d. The buffer reactor 223d of the fourth arm portion 222d is provided between the converter VN1 and a connection point between the AC terminal 221b and the third arm portion 222c and the fourth arm portion 222d. The buffer reactor 223e of the fifth arm portion 222e is provided between the converter WP1 and a connection point between the AC terminal 221c and the fifth arm portion 222e and the sixth arm portion 222f. The buffer reactor 223f of the sixth arm portion 222f is provided between the converter WN1 and a connection point between the AC terminal 221c and the fifth arm portion 222e and the sixth arm portion 222f.

[0124] The current detector 224a is provided in the first arm portion 222a and detects a current flowing through the first arm portion 222a. That is, the current detector 224a detects an arm current of the first arm portion 222a. The current detector 224a is connected to the control device 214 via wiring or the like (not shown). The current detector 224a inputs the detected current value of the first arm portion 222a to the control device 214. As a result, the current value of the first arm portion 222a is input to the control device 214.

[0125] Similarly, current detector 224b detects the current flowing through the second arm portion 222b and inputs the detected current value to the control device 214. Current detector 224c detects the current flowing through the third arm portion 222c and inputs the detected current value to the control device 214. Current detector 224d detects the current flowing through the fourth arm portion 222d and inputs the detected current value to the control device 214. Current detector 224e detects the current flowing through the fifth arm portion 222e and inputs the detected current value to the control device 214. Current detector 224f detects the current flowing through the sixth arm portion 222f and inputs the detected current value to the control device 214.

[0126] The voltage detection unit 225 detects the AC voltage (phase voltage) of each phase of the AC power system 202, and inputs the detected value to the control device 214. The voltage detection unit 225 may be connected to the primary side or the secondary side of the transformer 206.

[0127] In the main circuit section 212, the connection point between the first arm section 222a and the second arm section 222b, the connection point between the third arm section 222c and the fourth arm section 222d, and the connection point between the fifth arm section 222e and the sixth arm section 222f are each an AC output point.

[0128] The first AC terminal 221a is connected to a connection point between the first arm portion 222a and the second arm portion 222b. The second AC terminal 221b is connected to a connection point between the third arm portion 222c and the fourth arm portion 222d. The third AC terminal 221c is connected to a connection point between the fifth arm portion 222e and the sixth arm portion 222f. Each of the AC terminals 221a to 221c is connected to a transformer 206, for example.

[0129] Each converter CEL communicates with the control device 214 via, for example, the optical signal transmitting / receiving device 216. The control device 214 controls the operation of the converter CEL by inputting a control signal to the converter CEL via the optical signal transmitting / receiving device 216. In addition, the converter CEL inputs, for example, a control signal and a protection signal related to the control and operation protection of the converter CEL to the control device 214 via the optical signal transmitting / receiving device 216. Note that the communication method between the control device 214 and each converter CEL is not limited to the above. For example, a plurality of converters CEL connected in series may be daisy-chained, and the control device 214 may communicate only with the converter CEL at one end of the daisy-chained converter and the converter CEL at the other end. The communication method between the control device 214 and each converter CEL may be any communication method that can appropriately communicate between the control device 214 and each converter CEL.

[0130] FIG. 17 is a block diagram that illustrates a schematic representation of a converter. As shown in FIG. 17, the converter CEL has a plurality of switching elements 241, 242, a plurality of rectifying elements 251, 252, a plurality of driving circuits 261, 262, a pair of connecting terminals 271, 272, a charge storage element 274, a power supply circuit 276, a voltage detection circuit 278, and a control circuit 280.

[0131] Each of the switching elements 241, 242 has a pair of main terminals and a control terminal. The control terminal controls a current flowing between the pair of main terminals. For each of the switching elements 241, 242, a self-extinguishing element such as an IGBT is used. The pair of main terminals is, for example, an emitter and a collector, and the control terminal is, for example, a gate.

[0132] Each of the switching elements 241, 242 switches between an on state that allows current to flow between a pair of main terminals and an off state that blocks the current flowing between the pair of main terminals. The off state is not limited to a state in which no current flows between the pair of main terminals, but may be, for example, a state in which a weak current that does not affect the operation of the converter CEL flows between the pair of main terminals. In other words, the off state is a state in which the current flowing between the pair of main terminals is sufficiently small.

[0133] For example, a normally-off type semiconductor element is used for each of the switching elements 241, 242. Each of the switching elements 241, 242 is in an on state when the voltage of the control terminal is high, and in an off state when the voltage of the control terminal is low. Each of the switching elements 241, 242 is in an off state when the voltage of the control terminal is lower than the on state. Each of the switching elements 241, 242 is in an on state when a positive voltage is applied to the control terminal, and in an off state when the voltage of the control terminal is set to 0 V or a negative voltage is applied to the control terminal.

[0134] A pair of main terminals of the switching element 242 are connected in series to a pair of main terminals of the switching element 241. In this example, the converter CEL has two switching elements 241, 242 connected in series. In this example, the converter CEL is a half-bridge configured converter.

[0135] The rectifier element 251 is connected in anti-parallel to a pair of main terminals of the switching element 241. The forward direction of the rectifier element 251 is opposite to the direction of the current flowing between the pair of main terminals of the switching element 241. Similarly, the rectifier element 252 is connected in anti-parallel to the pair of main terminals of the switching element 242. The rectifier elements 251 and 252 are so-called freewheel diodes.

[0136] The connection terminal 271 is connected between the switching element 241 and the switching element 242. The connection terminal 272 is connected to a main terminal of the switching element 241 opposite to the main terminal connected to the switching element 242.

[0137] The multiple converters CEL in the same arm portion are connected in series via a pair of connection terminals 271, 272. Power is supplied to the converters CEL via each of the connection terminals 271, 272. The switching element 241 is a so-called low-side switch, and the switching element 242 is a so-called high-side switch.

[0138] The control circuit 280 communicates with the control device 214 via the optical signal transmitting / receiving device 216. The control device 214 transmits a control signal for controlling the on / off of each of the switching elements 241, 242 to the control circuit 280 via the optical signal transmitting / receiving device 216. The control circuit 280 inputs a drive signal for switching the on / off of each of the switching elements 241, 242 to the drive circuits 261, 262 based on the input control signal.

[0139] The drive circuit 261 is connected to a control terminal of the switching element 241. The drive circuit 262 is connected to a control terminal of the switching element 242. The drive circuits 261, 262 switch the on / off of each of the switching elements 241, 242 based on a drive signal input from the control circuit 280. In this way, the on / off of each of the switching elements 241, 242 is controlled in response to a control signal from the control device 214. The control device 214 generates a control signal for each converter CEL and controls the on / off of each of the switching elements 241, 242 of each converter CEL. In this way, the control device 214 controls the power conversion by the main circuit unit 212.

[0140] The configurations of the drive circuits 261, 262 and the control circuit 280 are not limited to those described above, and may be any configuration capable of controlling the on / off of each of the switching elements 241, 242. For example, a control signal from the control device 214 may be directly input to the drive circuits 261, 262. In this case, the control circuit 280 can be omitted.

[0141] The charge storage element 274 is connected in parallel to the switching element 241 and the switching element 242. The charge storage element 274 is, for example, a capacitor.

[0142] When switching element 241 is in the off state and switching element 242 is in the on state, the voltage of charge storage element 274 appears between connection terminals 271, 272. When switching element 241 is in the on state and switching element 242 is in the off state, conduction occurs between connection terminals 271, 272, and the voltage between connection terminals 271, 272 becomes substantially zero.

[0143] In this way, the converter CEL switches between an output state in which the voltage of the charge storage element 274 is output between each of the connection terminals 271, 272, a bypass state in which conduction is established between each of the connection terminals 271, 272, and a stop state in which each of the switching elements 241, 242 is turned off, by switching each of the switching elements 241, 242 based on a control signal from the control device 214.

[0144] In each of the arm sections 222a to 222f, the total voltage of the converters CEL in the output state becomes the voltage of the arm section 222a to 222f. The main circuit section 212 and the control device 214 perform multi-level power conversion by controlling the number of converters CEL in the output state.

[0145] When both switching elements 241, 242 are in the off state (when converter CEL is in the stopped state), the voltage between each connection terminal 271, 272 is determined by the direction of the arm current. For example, when the arm current flows from connection terminal 272 to connection terminal 271, rectifier element 251 turns on, and the voltage between each connection terminal 271, 272 becomes substantially zero. Conversely, when the arm current flows from connection terminal 271 to connection terminal 272, rectifier element 252 turns on, charge storage element 274 is charged, and the voltage of charge storage element 274 appears between each connection terminal 271, 272.

[0146] The power supply circuit 276 is connected in parallel to the charge storage element 274. The power supply circuit 276 generates drive power for the drive circuits 261, 262 and the control circuit 280 based on the charge stored in the charge storage element 274, and supplies the generated drive power to the drive circuits 261, 262 and the control circuit 280. The drive circuits 261, 262 and the control circuit 280 operate in response to the supply of drive power from the power supply circuit 276.

[0147] The method of supplying power to the drive circuits 261, 262 and the control circuit 280 is not limited to the above. For example, power may be supplied to the drive circuits 261, 262 and the control circuit 280 from a power source separate from the charge storage element 274. The method of supplying power to the drive circuits 261, 262 and the control circuit 280 may be any method that can appropriately supply power to the drive circuits 261, 262 and the control circuit 280.

[0148] The voltage detection circuit 278 is connected in parallel to the charge storage element 274. The voltage detection circuit 278 is connected to the control circuit 280. The voltage detection circuit 278 detects the DC voltage of the charge storage element 274, and inputs the voltage detection value of the DC voltage of the charge storage element 274 to the control circuit 280.

[0149] The optical signal transmitting / receiving device 216 has a first optical signal transmitting / receiving unit 216a and a second optical signal transmitting / receiving unit 216b. The first optical signal transmitting / receiving unit 216a is connected to the control device 214. The second optical signal transmitting / receiving unit 216b is connected to the control circuit 280 of the converter CEL. In this way, the optical signal transmitting / receiving device 216 electrically insulates the control circuit 280 of the converter CEL from the control device 214 while enabling communication between the control circuit 280 of the converter CEL and the control device 214.

[0150] The optical signal transmitting / receiving device 216 has, for example, a plurality of first optical signal transmitting / receiving units 216a and a plurality of second optical signal transmitting / receiving units 216b provided corresponding to each of the plurality of converters CEL. Each control signal output from the control device 214 is input to each converter CEL via each of the first optical signal transmitting / receiving units 216a and each of the second optical signal transmitting / receiving units 216b. In this way, the optical signal transmitting / receiving device 216 performs communication between each of the plurality of converters CEL of the main circuit unit 212 and the control device 214.

[0151] The configurations of the first optical signal transceiver 216a and the second optical signal transceiver 216b of the optical signal transceiver 216 can be the same as those described in the optical signal transceiver 104 of the fourth embodiment. As a result, in the power conversion device 200 according to this embodiment as well, like the above embodiment, inspection of optical components such as the first optical signal transceiver 216a and the second optical signal transceiver 21b can be more easily performed. The time and cost required for inspection of optical components can be reduced.

[0152] Furthermore, in a power conversion device 200 in which many converters CEL are connected in series, the number of optical components such as the first optical signal transceiver 216a and the second optical signal transceiver 21b also becomes large. Therefore, in such a power conversion device 200, by detecting the deterioration of the first optical signal transceiver 216a and the second optical signal transceiver 21b as described above, the effort required for inspecting the optical components can be significantly reduced. For example, the time and cost required for inspecting the optical components can be significantly reduced.

[0153] In the MMC type main circuit section 212, the configuration of the converter CEL is not limited to the half-bridge circuit configuration, and may be a full-bridge circuit configuration having four switching elements in a full-bridge connection.

[0154] In the above-described fifth embodiment, an MMC type power converter is used for the main circuit unit 212. The main circuit unit 212 is not limited to the MMC type, and may be, for example, another type of power converter in which a plurality of converters CEL are connected in series.

[0155] The power conversion device 200 is not limited to a DC power transmission system, but may be applied to any other system that requires conversion from AC to DC and from DC to AC. The AC / DC conversion by the main circuit unit 212 is not limited to both AC to DC and DC to AC, but may be only AC to DC or DC to AC. The main circuit unit 212 may be, for example, an AC-AC direct conversion circuit.

[0156] The main circuit unit 212 may have a configuration in which a plurality of arms are star-connected, delta-connected, or matrix-connected, for example. The main circuit unit 212 may be, for example, a modular matrix converter. The main circuit unit 212 does not necessarily have to have a plurality of legs. The main circuit unit 212 only needs to have at least a plurality of arms. The main circuit unit 212 may have any configuration capable of converting power. The power conversion device may be, for example, a frequency conversion device, a direct current transmission device, a reactive power compensation device, or a power flow control device.

[0157] In this way, the configuration of the main circuit unit is not limited to the three-phase two-level inverter configuration shown in the fourth embodiment, and may be a configuration in which a plurality of converters CEL are connected in series. The configuration of the main circuit unit is not limited to the three-phase two-level inverter, and may be a single-phase two-level inverter, a single-phase three-level inverter, a three-phase three-level inverter, etc. The configuration of the main circuit unit is not limited to the configurations shown in each of the above embodiments, and may be any configuration that has a converter and converts power by the operation of the converter.

[0158] In the above embodiment, an example is shown in which the optical signal transmission and reception device is applied to a power conversion device. The optical signal transmission and reception device is not limited to being used in a power conversion device, and may be used in any other device.

[0159] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0160] 10...optical signal transmitting / receiving device, 12...optical transmitting section, 14...optical receiving section, 16...light emission control section, 18...light reception control section, 20...optical signal transmitting / receiving device, 21...first optical signal transmitting / receiving section, 22...second optical signal transmitting / receiving section, 30...first optical transmitting section, 32...first optical receiving section, 34...light emission control section, 36...light reception control section, 40...second optical transmitting section, 42...second optical receiving section, 50...optical signal transmitting / receiving device, 51...first optical signal transmitting / receiving section, 52...second optical signal transmitting / receiving section, 60...first optical transmitting section, 62...first optical receiving section, 64...light reception control section, 70...second optical transmitting section, 72...second optical receiving section, 74...light emission control section, 100...power conversion device, 101...main circuit section, 101a...converter, 102...control device, 104...optical signal transmitting / receiving device, 111-116...switching elements, 121-126...rectifying elements, 130...charge storage element, 131-136...drive circuit, 141...first optical signal transmitting / receiving unit, 142...second optical signal transmitting / receiving unit, 200...power conversion device, 202...AC power system, 203, 204...DC transmission line, 206...transformer, 212...main circuit unit, 214...control device, 216...optical signal transmitting / receiving device, 216a...first optical signal transmitting / receiving unit, 216b...second optical signal transmitting / receiving unit, 220a...first DC terminal, 220b...second DC terminal, 221a...first AC terminal, 221b...second AC terminal, 221c...third AC terminal, 222a...first arm unit, 222b...second arm portion, 222c...third arm portion, 222d...fourth arm portion, 222e...fifth arm portion, 222f...sixth arm portion, 223a to 223f...buffer reactor, 224a to 224f...current detector, 225...voltage detection portion, 241, 242...switching element, 251, 252...rectifier element, 261, 262...drive circuit, 271, 272...connection terminal, 274...charge storage element, 276...power supply circuit, 278...voltage detection circuit, 280...control circuit, CEL...converter, LG1...first leg, LG2...second leg, LG3...third leg

Claims

1. an optical transmitter that transmits an optical signal having an emission period and an extinction period, and is capable of setting, in the emission period, a normal light amount period in which a predetermined emission amount is achieved and a low light amount period in which an emission amount is lower than that of the normal light amount period; an optical receiving unit that receives the optical signal, converts the optical signal into an electrical signal having a magnitude corresponding to an amount of light emitted from the optical signal, and outputs a received signal of the electrical signal; a light emission control unit that controls switching between the light emission period and the extinction period of the optical signal transmitted from the optical transmission unit, and controls setting of the normal light amount period and the low light amount period in the light emission period; a light-receiving control unit that distinguishes between a period corresponding to the light-emitting period of the received signal and a period corresponding to the extinction period of the received signal based on the magnitude of the electrical signal, and that determines degradation of at least one of the optical transmitting unit and the optical receiving unit based on a change in a result of distinguishing between the period corresponding to the light-emitting period and the period corresponding to the extinction period; Equipped with The light emission control unit sets a certain period after a transition from the extinction period to the light emission period as the low light amount period.

2. 2. The optical signal transmitting and receiving device according to claim 1, wherein the light receiving control unit determines deterioration of at least one of the optical transmitting unit and the optical receiving unit when a period corresponding to the light emitting period of the received signal becomes shorter than a predetermined time.

3. 3. The optical signal transmitting and receiving device according to claim 1, wherein the light emission control unit gradually increases an amount of light emitted during the low light period.

4. 4. The optical signal transmitting and receiving device according to claim 3, wherein the light-receiving control section determines a degree of deterioration of at least one of the optical transmitting section and the optical receiving section depending on the duration of a period corresponding to the light-emitting period of the received signal.

5. An optical transmitter that transmits an optical signal having an emission period and an extinction period, and is capable of setting, in the emission period, a normal light amount period having a predetermined emission amount and a low light amount period having an emission amount lower than the emission amount of the normal light amount period; an optical receiving unit that receives the optical signal, converts the optical signal into an electrical signal having a magnitude corresponding to an amount of light emitted from the optical signal, and outputs a received signal of the electrical signal; a light emission control unit that controls switching between the light emission period and the extinction period of the optical signal transmitted from the optical transmission unit, and controls setting of the normal light amount period and the low light amount period in the light emission period; a light-receiving control unit that distinguishes between a period corresponding to the light-emitting period of the received signal and a period corresponding to the extinction period of the received signal based on the magnitude of the electrical signal, and that determines degradation of at least one of the optical transmitting unit and the optical receiving unit based on a change in a result of distinguishing between the period corresponding to the light-emitting period and the period corresponding to the extinction period; Equipped with The light emission control unit switches between the light emission period and the extinction period at a predetermined cycle, transmits a pulse signal having the light emission period as a pulse as the optical signal, and, when the number of the predetermined number of consecutive pulses of the pulse signal is N, sets the low light intensity period to a range of 1 in N to N-1 in N.

6. The optical signal transmitting and receiving device of claim 5, wherein the light receiving control unit determines deterioration of at least one of the optical transmitting unit and the optical receiving unit when a period corresponding to the light emission period of the received signal and a period corresponding to the extinction period of the received signal become longer than the specified period of the pulse signal.

7. 6. The optical signal transmitting and receiving device according to claim 5, wherein the light emission control unit sets a series of multiple pulses as the low light intensity period, and sequentially increases or decreases the light intensity of the series of multiple pulses that set the low light intensity period in the order in which the pulses are transmitted.

8. The optical signal transmitting and receiving device of claim 7, wherein the light receiving control unit determines the degree of deterioration of at least one of the optical transmitting unit and the optical receiving unit depending on the number of periods equivalent to the light emitting period determined within the period of the N pulses in the received signal.

9. a first optical signal transmitting / receiving unit including a first optical transmitting unit, a first optical receiving unit, a light emission control unit, and a light reception control unit; a second optical signal transmitting / receiving unit having a second optical transmitting unit and a second optical receiving unit; Equipped with the first optical transmitting unit transmits a first optical signal having an emission period and an extinction period to the second optical signal transmitting and receiving unit, and is capable of setting, in the emission period, a normal light amount period having a predetermined emission amount and a low light amount period having an emission amount lower than the emission amount of the normal light amount period; the light emission control unit controls switching between the light emission period and the extinction period of the first optical signal transmitted from the first optical transmission unit, and controls setting of the normal light amount period and the low light amount period in the light emission period; the second optical receiving unit receives the first optical signal and converts the first optical signal into an electrical signal having a magnitude corresponding to an amount of light emitted by the first optical signal, thereby outputting a received signal of the electrical signal; the second optical transmitting unit transmits to the first optical signal transmitting / receiving unit a second optical signal that switches between the light emission period and the extinction period based on a predetermined signal that changes in response to the reception signal of the second optical receiving unit; the first optical receiving unit receives the second optical signal and converts the second optical signal into an electrical signal having a magnitude corresponding to an amount of light emitted by the second optical signal, thereby outputting a received signal of the electrical signal; The optical signal transmitting / receiving control unit determines deterioration of at least one of the first optical signal transmitting / receiving unit and the second optical signal transmitting / receiving unit when the delay time of the change in the received signal of the first optical receiving unit relative to the change in the first optical signal becomes longer than a certain time.

10. a first optical signal transmitting / receiving unit having a first optical transmitting unit, a first optical receiving unit, and a light reception control unit; a second optical signal transmitting / receiving unit having a second optical transmitting unit, a second optical receiving unit, and a light emission control unit; Equipped with the first optical transmitter transmits a first optical signal having an emission period and an extinction period to the second optical signal transceiver; the second optical receiving unit receives the first optical signal and converts the first optical signal into an electrical signal having a magnitude corresponding to an amount of light emitted by the first optical signal, thereby outputting a received signal of the electrical signal; the second optical transmitting unit transmits a second optical signal having the light emission period and the extinction period to the first optical signal transmitting and receiving unit, and is capable of setting, in the light emission period, a normal light amount period having a predetermined light emission amount and a low light amount period having a light emission amount lower than the light emission amount of the normal light amount period; the light emission control unit controls switching between the light emission period and the extinction period of the second optical signal transmitted from the second optical transmitting unit based on a predetermined signal that changes in response to the reception signal of the second optical receiving unit, and sets the low light amount period to a part of the extinction period based on the predetermined signal; the first optical receiving unit receives the second optical signal and converts the second optical signal into an electrical signal having a magnitude corresponding to an amount of light emitted by the second optical signal, thereby outputting a received signal of the electrical signal; an optical signal transmitting / receiving control unit that, based on the magnitude of the electrical signal of the received signal at the first optical receiving unit, distinguishes between a period corresponding to the light emission period of the received signal at the first optical receiving unit and a period corresponding to the extinction period of the received signal at the first optical receiving unit, and, based on changes in the distinguished result of the period corresponding to the light emission period and the period corresponding to the extinction period, determines deterioration of at least one of the first optical signal transmitting / receiving unit and the second optical signal transmitting / receiving unit.

11. A main circuit unit having a converter and converting power by the operation of the converter; A control device for controlling the operation of the main circuit unit; An optical signal transmitting and receiving device according to any one of claims 1 to 10, which performs communication between the main circuit unit and the control device; A power conversion device comprising:

12. the main circuit unit has a plurality of the converters connected in series, Each of the plurality of converters comprises: A pair of connection terminals; A plurality of switching elements; a charge storage element connected in parallel to the plurality of switching elements; and the charge storage element is connected in series via the pair of connection terminals, and is capable of switching between an output state in which a voltage of the charge storage element is output between the pair of connection terminals, a bypass state in which the pair of connection terminals are electrically connected, and a stop state in which the plurality of switching elements are in an off state by switching the plurality of switching elements; The power conversion device according to claim 11 , wherein the optical signal transmitting / receiving device performs communication between each of the plurality of converters in the main circuit section and the control device.

13. The control device has a normal operation mode in which it controls the conversion of power by the main circuit unit, and a degradation detection mode in which it detects degradation of the optical signal transmitting and receiving device, and in the degradation detection mode it causes the light emission control unit and the light reception control unit of the optical signal transmitting and receiving device to detect degradation.

14. The power conversion device according to claim 13 , wherein the control device executes the degradation detection mode at least one of a start timing before starting the normal operation mode and a stop timing after terminating the normal operation mode.

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