Power converter

Abstract

To provide an optical signal transceiver and power converter that can transmit and receive multiple signals of different frequencies with a simpler configuration. [Solution] An optical signal transmitting and receiving device is provided, comprising: an optical transmitting unit that transmits an optical signal; an optical receiving unit connected to the optical transmitting unit via an optical transmission path, which receives an optical signal and outputs a received electrical signal by converting it into an electrical signal of a magnitude corresponding to the amount of light emitted by the optical signal; a light emission control unit that receives a first input signal having a predetermined frequency and a second input signal having a lower frequency than the first input signal, generates a superimposed signal by superimposing the second input signal on the first input signal, and inputs the superimposed signal to the optical transmitting unit, thereby causing the optical transmitting unit to transmit an optical signal corresponding to the superimposed signal; and a light receiving control unit that generates a first restored signal corresponding to the first input signal and a second restored signal corresponding to the second input signal based on the received signal output from the optical receiving unit.

Description

Technical Field

[0001] Embodiments of the present invention relate to an optical signal transceiver and a power conversion device.

Background Art

[0002] There is an optical signal transceiver including an optical transmitter that transmits an optical signal, an optical receiver that receives the optical signal, and an optical transmission line that connects the optical transmitter and the optical receiver. The optical signal transceiver is used, for example, in a power conversion device or the like. In the power conversion device, for example, an optical signal is used for signal transmission and reception for insulation.

[0003] In such an optical signal transceiver, there may be a case where a plurality of signals having different frequencies are transmitted and received. At this time, if each part of the optical transmitter, the optical receiver, and the optical transmission line is provided for each of the plurality of signals, there is a concern that the number of parts will increase, leading to an increase in the size and cost of the device. For this reason, in an optical signal transceiver and a power conversion device using the same, it is desired to be able to transmit and receive a plurality of signals having different frequencies with a simpler configuration.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Embodiments of the present invention provide an optical signal transceiver and a power conversion device that can transmit and receive a plurality of signals having different frequencies with a simpler configuration.

Means for Solving the Problems

[0006] According to an embodiment of the present invention, an optical signal transmitting and receiving device is provided, comprising: an optical transmitting unit that transmits an optical signal; an optical transmission path connected to the optical transmitting unit; an optical receiving unit connected to the optical transmitting unit via the optical transmission path, which receives the optical signal and outputs a received electrical signal by converting it into an electrical signal of a magnitude corresponding to the amount of light emitted by the optical signal; a light emission control unit that receives a first input signal having a predetermined frequency and a second input signal having a lower frequency than the first input signal, generates a superimposed signal by superimposing the second input signal on the first input signal, and inputs the superimposed signal to the optical transmitting unit, thereby causing the optical transmitting unit to transmit the optical signal corresponding to the superimposed signal; and a light receiving control unit that, based on the received signal output from the optical receiving unit, restores the first input signal and the second input signal, thereby generating a first restored signal corresponding to the first input signal and a second restored signal corresponding to the second input signal. [Effects of the Invention]

[0007] An optical signal transceiver and power converter are provided that can transmit and receive multiple signals of different frequencies with a simpler configuration. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic block diagram showing an optical signal transceiver according to the first embodiment. [Figure 2] This is a timing chart schematically illustrating an example of the operation of the optical signal transceiver according to the first embodiment. [Figure 3] This is a schematic block diagram showing a power conversion device according to the second embodiment. [Figure 4] This is a schematic block diagram showing a power conversion device according to the third embodiment. [Figure 5] This is a block diagram schematically representing the converter.

[0009] Each embodiment will be described below with reference to the drawings. Please note that the drawings are schematic or conceptual, and the relationships between the thickness and width of each part, as well as the ratios of the sizes of the parts, are not necessarily identical to those of reality. Furthermore, even when representing the same part, the dimensions and ratios may differ between drawings. In this specification and in each figure, elements similar to those described above are denoted by the same reference numerals, and detailed explanations are omitted as appropriate.

[0010] (First embodiment) Figure 1 is a schematic block diagram showing an optical signal transceiver according to the first embodiment. As shown in Figure 1, the optical signal transceiver 10 comprises an optical transmission unit 11, an optical transmission line 12, an optical reception unit 13, an optical emission control unit 14, and an optical light receiving control unit 15.

[0011] The optical transmitting unit 11 transmits an optical signal. The optical transmitting unit 11 has, for example, an optical light-emitting element such as a light-emitting diode or a laser diode, and transmits an optical signal by turning the optical light-emitting element on and off. The optical signal has, for example, an illumination period and an extinction period. The illumination period is, for example, the period during which the optical light-emitting element is on, and the extinction period is, for example, the period during which the optical light-emitting element is off. The extinction period is not limited to a state in which the optical light-emitting element is off, but may also be, for example, a state in which the amount of light emitted from the optical light-emitting element is sufficiently reduced. In other words, the illumination period is a state in which the amount of light emitted from the optical light-emitting element is above a threshold, and the extinction period is a state in which the amount of light emitted from the optical light-emitting element is below a threshold.

[0012] One end of the optical transmission path 12 is connected to the optical transmitter 11. The other end of the optical transmission path 12 is connected to the optical receiver 13. In other words, the optical transmission path 12 connects the optical transmitter 11 and the optical receiver 13. The optical transmission path 12 is, for example, an optical fiber. The optical transmission path 12 enables the transmission of optical signals transmitted from the optical transmitter 11 to the optical receiver 13. The optical transmission path 12 may include, for example, an optical repeater or an optical distributor. The configuration of the optical transmission path 12 can be any configuration that enables the transmission of optical signals transmitted from the optical transmitter 11 to the optical receiver 13.

[0013] The optical receiving unit 13 is connected to the optical transmitting unit 11 via the optical transmission path 12, receives an optical signal, and outputs a received electrical signal by converting it into an electrical signal of a magnitude corresponding to the amount of light emitted by the optical signal. The optical receiving unit 13 has a light-receiving element such as a photodiode, and the light-receiving element converts the optical signal into a received electrical signal.

[0014] The light emission control unit 14 receives inputs of a first input signal having a predetermined frequency and a second input signal having a lower frequency than the first input signal. The first input signal is, for example, a high-frequency signal, and the second input signal is, for example, a low-frequency signal. The frequency of the first input signal is, for example, 1 kHz or higher. The frequency of the second input signal is, for example, less than 1 kHz. The first input signal is, for example, a signal having a frequency of 1 kHz or higher, and the second input signal is, for example, a signal having a frequency of less than 1 kHz. However, the frequencies of the first input signal and the second input signal are not limited to the above and may be any frequencies. The frequency of the first input signal may be any frequency higher than the frequency of the second input signal. The frequency of the second input signal may be any frequency lower than the frequency of the first input signal.

[0015] The light emission control unit 14 generates a superimposed signal by superimposing the second input signal onto the first input signal, and inputs the superimposed signal to the optical transmission unit 11, causing the optical transmission unit 11 to transmit an optical signal corresponding to the superimposed signal.

[0016] The light receiving control unit 15 reconstructs the first input signal and the second input signal based on the received signal output from the light receiving unit 13, thereby generating a first reconstructed signal corresponding to the first input signal and a second reconstructed signal corresponding to the second input signal. The light receiving control unit 15 outputs the generated first reconstructed signal and second reconstructed signal to the outside.

[0017] Figure 2 is a timing chart schematically illustrating an example of the operation of the optical signal transceiver according to the first embodiment. Figure 2 schematically shows examples of the first input signal, second input signal, superimposed signal, first restored signal, and second restored signal.

[0018] As shown in FIG. 2, the first input signal and the second input signal are digital signals having, for example, a low voltage state and a high voltage state. The low voltage state (Lo) corresponds to, for example, the digital value "0", and the high voltage state (Hi) corresponds to, for example, the digital value "1".

[0019] Based on the input first input signal and second input signal, the light emission control unit 14 generates a superimposed signal of the digital signals and inputs the generated superimposed signal to the optical transmission unit 11. For example, the optical transmission unit 11 uses the low voltage state of the input superimposed signal as the extinction period of the optical signal and the high voltage state of the input superimposed signal as the light emission period of the optical signal, thereby transmitting an optical signal corresponding to the digital signal. The extinction period corresponds to, for example, the digital value "0", and the light emission period corresponds to, for example, the digital value "1". The optical reception unit 13 outputs a reception signal of the digital signal by converting the optical signal into an electrical signal.

[0020] In this way, the optical signal transceiver 10 converts a digital signal into an optical signal and transmits it, and restores the optical signal to a digital signal. In other words, the optical signal transceiver 10 is a device for performing digital communication using an optical signal, for example.

[0021] The light emission control unit 14 has, for example, an exclusive OR circuit (XOR circuit) 20. The exclusive OR circuit 20 generates a superimposed signal of the digital signals from the first input signal and the second input signal by calculating the exclusive OR of the first input signal and the second input signal of the input digital signal.

[0022] In an exclusive OR operation, the digital value of the output signal changes in accordance with the change in the digital value of either the first input signal or the second input signal. This makes it possible to generate a superimposed signal by superimposing the second input signal onto the first input signal. However, the method of generating the superimposed signal is not limited to the method using the exclusive OR circuit 20, but can be any method that can appropriately generate a superimposed signal by superimposing the second input signal onto the first input signal. The configuration of the light emission control unit 14 can be any configuration that generates a superimposed signal from the first input signal and the second input signal, and inputs the superimposed signal to the optical transmission unit 11, thereby causing the optical transmission unit 11 to transmit an optical signal corresponding to the superimposed signal.

[0023] The light receiving control unit 15 includes, for example, a one-shot circuit 30 and a filter circuit 32. The light receiving control unit 15 inputs the received signal output from the light receiving unit 13 to the one-shot circuit 30 and the filter circuit 32, respectively.

[0024] The one-shot circuit 30 is a circuit that outputs a pulse of a predetermined width in response to a change in the received signal. For example, the one-shot circuit 30 outputs a pulse of a predetermined width in response to the rising edge and falling edge of the received signal, which is a digital signal. In other words, the one-shot circuit 30 sets the output signal to a high voltage state for a predetermined time in response to the rising edge and falling edge of the received signal, which is a digital signal.

[0025] If the one-shot circuit 30 detects the next change in the received signal before a predetermined time corresponding to the pulse width has elapsed after outputting a pulse, it outputs the next pulse at that point to maintain a high voltage state of the output signal. On the other hand, if the one-shot circuit 30 does not detect the next change in the received signal within the predetermined time corresponding to the pulse width after outputting a pulse, it switches the output signal from a high voltage state to a low voltage state in accordance with the elapsed time.

[0026] In other words, the one-shot circuit 30 is a first restoration circuit that restores the first input signal from the received signal and generates a first restored signal. The light receiving control unit 15 outputs the output of the one-shot circuit 30 as a first restored signal corresponding to the first input signal.

[0027] The filter circuit 32 attenuates the frequency components of the first input signal contained in the received signal and allows the frequency components of the second input signal to pass through. In other words, the filter circuit 32 restores the second input signal by outputting only the frequency components of the second input signal contained in the received signal. The filter circuit 32 is, for example, a low-pass filter. In other words, the filter circuit 32 is a second restoration circuit that restores the second input signal from the received signal and generates a second restored signal. The light receiving control unit 15 outputs the output of the filter circuit 32 as a second restored signal corresponding to the second input signal.

[0028] As shown in Figure 2, the first input signal is, for example, a signal that alternates between a high voltage state and a low voltage state at a predetermined period T1. In other words, the first input signal is a pulsed signal that oscillates at a predetermined period T1. The first input signal is, for example, a signal that allows the receiving device to detect an abnormality in the transmitting device. The first input signal is, for example, a heartbeat signal. The receiving device detects an abnormality in the transmitting device when, for example, the oscillation of the signal stops or the interval between the oscillations of the signal changes from the predetermined period T1.

[0029] The second input signal is a control signal used to control the system by, for example, alternating between a high voltage state and a low voltage state at a predetermined period T2, and by changing the ratio of the high voltage state to the low voltage state. The second input signal is, for example, a control signal for PWM control. The period T2 of the second input signal is longer than the period T1 of the first input signal. For example, the period T2 of the second input signal is 10 times or more the period T1 of the first input signal.

[0030] The one-shot circuit 30 outputs a pulse with width T3 in response to changes in the received signal. The width T3 of the pulse output by the one-shot circuit 30 is set to be, for example, longer than the period T1 of the first input signal and less than or equal to half the period T2 of the second input signal. As a result, if the first input signal is output normally with a predetermined period T1, the timing of the next period T1 will arrive before the time of width T3 has elapsed, so the first restoration signal, which is the output signal of the one-shot circuit 30, will remain at a high voltage. The first restoration signal will then become low in voltage when the oscillation of the first input signal stops or when the period of the first input signal becomes longer than period T1.

[0031] Therefore, the receiving device determines that the transmitting device is functioning normally when the first restoration signal has a high voltage, and detects an abnormality in the transmitting device when the first restoration signal has a low voltage. As a result, the one-shot circuit 30 can restore the first input signal and generate a first restoration signal corresponding to the first input signal.

[0032] Thus, the light receiving control unit 15 does not necessarily have to be configured to restore the first input signal and the second input signal in their original form. The first restored signal may be any signal having at least the same function as the first input signal. The second restored signal may be any signal having at least the same function as the second input signal.

[0033] The configuration of the light receiving control unit 15 is not limited to the above. The light receiving control unit 15 may, for example, use a high-pass filter as the first restoration circuit to reconstruct the first input signal from the received signal by outputting only the frequency component signal of the first input signal included in the received signal, thereby generating a first restored signal. The first and second restoration circuits may be set appropriately according to the contents of the first and second input signals, the contents of the superimposed signal, etc. The configuration of the light receiving control unit 15 may be any configuration that can generate a first restored signal corresponding to the first input signal and a second restored signal corresponding to the second input signal by reconstructing the first and second input signals based on the received signal output from the optical receiving unit 13. The configuration of the light receiving control unit 15 may be any configuration that can generate a first restored signal having at least the same function as the first input signal, and a second restored signal having the same function as the second input signal.

[0034] As described above, in the optical signal transceiver 10 according to this embodiment, the light emission control unit 14 generates a superimposed signal by superimposing the second input signal on the first input signal, and inputs the superimposed signal to the optical transmission unit 11, causing the optical transmission unit 11 to transmit an optical signal corresponding to the superimposed signal. The light receiving control unit 15 then reconstructs the first input signal and the second input signal based on the received signal output from the optical receiving unit 13, thereby generating a first reconstructed signal corresponding to the first input signal and a second reconstructed signal corresponding to the second input signal.

[0035] As a result, the optical signal transceiver 10 can transmit two signals, a first input signal and a second input signal, using a single optical transmission path 12. Therefore, the optical signal transceiver 10 can transmit and receive multiple signals of different frequencies with a simpler configuration compared to, for example, a case where two optical transmitting units 11, two optical transmission paths 12, and two optical receiving units 13 are provided, each corresponding to one of the two signals.

[0036] The number of signals superimposed on the superimposed signal is not necessarily limited to two. The light emission control unit 14 may, for example, generate a superimposed signal with three or more signals superimposed on it. The light receiving control unit 15 may restore each of the three or more signals. The number of signals superimposed on the superimposed signal is not limited to two; it may be three or more, as long as the light receiving control unit 15 can restore them appropriately. For example, three or more signals with different frequencies may be superimposed, and each signal may be restored by multiple bandpass filters corresponding to the frequency of each signal. The light emission control unit 14 only needs to be configured to generate a superimposed signal with at least two signals superimposed on it. The light receiving control unit 15 only needs to be configured to restore at least two signals corresponding to the number of signals superimposed on the superimposed signal.

[0037] (Second embodiment) Figure 3 is a schematic block diagram showing a power conversion device according to the second embodiment. As shown in Figure 3, the power conversion device 100 comprises a main circuit unit 101, a control device 102, and an optical signal transceiver 104.

[0038] The main circuit unit 101 has a converter 101a, and power conversion is performed 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 transceiver 104 communicates between the main circuit unit 101 and the control device 102.

[0039] The converter 101a includes six three-phase bridge-connected switching elements 111-116, six rectifier elements 121-126 connected in antiparallel 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 six drive circuits 131-136 that switch each of the six switching elements 111-116 on and off.

[0040] In converter 101a, both ends of each switching element 111 to 116 become a pair of DC terminals 106a and 106b, and the connection points between switching element 111 and switching element 112, the connection point between switching element 113 and switching element 114, and the connection point between switching element 115 and switching element 116 become three AC terminals 108a to 108c, respectively. Converter 101a is a so-called three-phase two-level inverter.

[0041] The converter 101a is connected to an AC power system via AC terminals 108a to 108c. Each AC terminal 108a to 108c is connected to the AC power system via, for example, a circuit breaker or transformer (not shown in the diagram). The converter 101a is also connected to a DC power source or 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 the following: DC to AC conversion and AC to DC conversion, for example, by switching the switching elements 111 to 116 of the converter 101a.

[0042] The optical signal transceiver 104, like the optical signal transceiver 10 of the first embodiment, includes an optical transmission unit 11, an optical transmission line 12, an optical reception unit 13, an emission control unit 14, and a light receiving control unit 15. The configurations of the optical transmission unit 11, the optical transmission line 12, the optical reception unit 13, the emission control unit 14, and the light receiving control unit 15 are substantially the same as those described with respect to the first embodiment, so a detailed explanation is omitted.

[0043] The light emission control unit 14 is connected to the main circuit unit 101. The light receiving control unit 15 is connected to the control device 102. This enables the optical signal transceiver 104 to transmit signals from the main circuit unit 101 to the control device 102. The optical signal transceiver 104 also has other optical transmitting units, optical transmission lines, and optical receiving units (not shown), which enable the transmission of signals from the control device 102 to the main circuit unit 101. The optical signal transceiver 104 electrically isolates the main circuit unit 101 and the control device 102 while enabling bidirectional communication between them. However, the optical signal transceiver 104 does not necessarily have to enable bidirectional communication. The optical signal transceiver 104 may be configured to only perform communication in one direction, either from the main circuit unit 101 to the control device 102, or from the control device 102 to the main circuit unit 101. For example, the transmission of signals from the control device 102 to the main circuit unit 101 may be performed by an optical signal transceiver separate from the optical signal transceiver 104.

[0044] The control device 102 transmits control signals to the drive circuits 131-136 via the optical signal transceiver 104. The control signals are, for example, control signals for switching each switching element 111-116 by repeating a high voltage state and a low voltage state at a predetermined period and changing the ratio of the high voltage state to the low voltage state. The control signals are, for example, control signals for PWM control. The control signals are, for example, digital signals. The control signals are sometimes called, for example, gate signals or gate commands.

[0045] The drive circuits 131-136 switch the on and off states of each switching element 111-116 based on control signals input from the control device 102. Each switching element 111-116 has, for example, a pair of main terminals and a control terminal. Each switching element 111-116 also has an on state and an off state. The on state is a state in which current flows between the pair of main terminals. The off state is a state in which the flow of current between the pair of main terminals is interrupted. Each switching element 111-116 switches between the on state and the off state according to the voltage between the pair of main terminals and the voltage of the control terminal. Note that the off state is not limited to a state in which no current flows at all between the pair of main terminals, but may also be a state in which a weak current flows between the pair of main terminals within a range that does not affect the operation of the main circuit section 101. Each switching element 111-116 is, for example, a self-oscillating semiconductor element such as an IGBT or a MOSFET. However, each switching element 111 to 116 is not limited to these, and may be any element capable of arbitrarily switching between an on state and an off state.

[0046] The control device 102 transmits control signals to each drive circuit 131-136 via the optical signal transceiver 104, and controls the switching of each switching element 111-116, thereby controlling the power conversion by the main circuit 101.

[0047] Each drive circuit 131 to 136 switches the on and off states of each switching element 111 to 116 by changing the magnitude of the voltage at the control terminals of each switching element 111 to 116 in accordance with the control signal input from the control device 102. For example, each drive circuit 131 to 136 turns each switching element 111 to 116 off by lowering the voltage at the control terminals of each switching element 111 to 116 when the voltage of the control signal is low, and turns each switching element 111 to 116 on by raising the voltage at the control terminals of each switching element 111 to 116 when the voltage of the control signal is high.

[0048] Thus, the magnitude of the voltage at the control terminals of each switching element 111 to 116 changes according to the control signal. However, the magnitude of the control signal voltage, the magnitude of the voltage at the control terminals of each switching element 111 to 116, and the on / off relationship of each switching element 111 to 116 are not limited to those described above. The magnitude of the control signal voltage, the magnitude of the voltage at the control terminals of each switching element 111 to 116, and the on / off relationship of each switching element 111 to 116 should be set appropriately according to the characteristics of each switching element 111 to 116.

[0049] The optical signal transceiver 104 includes, for example, a plurality of optical transmitting units 11, a plurality of optical transmission lines 12, a plurality of optical receiving units 13, a plurality of light emission control units 14, and a plurality of light receiving control units 15, each corresponding to a drive circuit 131 to 136. Signals output from each of the drive circuits 131 to 136 are input to the control device 102 via the optical signal transceiver 104.

[0050] Each drive circuit 131-136 repeatedly cycles between a high voltage state and a low voltage state at a predetermined interval, and inputs a heartbeat signal as a first input signal to each light emission control unit 14 so that the control device 102 can detect any abnormality in each drive circuit 131-136. The heartbeat signal is, for example, a digital signal.

[0051] Furthermore, each drive circuit 131-136 measures the voltage at the control terminal of each switching element 111-116, and inputs a feedback signal corresponding to the measurement result of the control terminal voltage to each light emission control unit 14 as a second input signal. The voltage at the control terminal is sometimes called, for example, the gate voltage. As described above, the voltage at the control terminal of each switching element 111-116 changes according to the control signal. For example, when each switching element 111-116 and each drive circuit 131-136 are functioning normally, the feedback signal is a signal that changes in the same way as the control signal. The feedback signal is, for example, a signal that alternates between a high voltage state and a low voltage state at a predetermined period, and also changes the ratio of the high voltage state to the low voltage state. The feedback signal is, for example, a PWM signal. The feedback signal is, for example, a digital signal. In other words, the feedback signal is a signal that allows the control device 102 to confirm whether or not the control signal has been properly input to the control terminal of each switching element 111-116.

[0052] In other words, the main circuit unit 101 repeatedly switches between a high voltage state and a low voltage state at a predetermined interval, and inputs a heartbeat signal as the first input signal to the light emission control unit 14 so that the control device 102 can detect any abnormality in the main circuit unit 101. The main circuit unit 101 then measures the voltage at the control terminals of each switching element 111 to 116 and inputs a feedback signal corresponding to the measurement result of the voltage at the control terminals as the second input signal to the light emission control unit 14. As explained with respect to Figure 2 of the first embodiment above, the period of the feedback signal (control signal) is longer than the period of the heartbeat signal. In other words, the period T2 of the second input signal is longer than the period T1 of the first input signal.

[0053] As a result, the power converter 100 according to this embodiment can transmit two signals, a first input signal and a second input signal, using a single optical transmission line 12. Therefore, the power converter 100 can transmit and receive multiple signals of different frequencies with a simpler configuration compared to, for example, a case where two optical transmitting units 11, two optical transmission lines 12, and two optical receiving units 13 are provided, each corresponding to one of the two signals.

[0054] Furthermore, the power converter 100 is provided with, for example, multiple optical transmitting units 11, multiple optical transmission lines 12, multiple optical receiving units 13, multiple light emission control units 14, and multiple light receiving control units 15, each corresponding to one of the multiple drive circuits 131 to 136. In this case, by enabling the transmission of two signals, a first input signal and a second input signal, through a single optical transmission line 12, the number of optical transmission lines 12 can be further reduced, and the increase in the number of components of the power converter 100 can be further suppressed.

[0055] In this example, the optical signal transceiver 104 is provided separately from the main circuit unit 101 and the control device 102. However, the optical signal transceiver 104 is not limited to this configuration and may be incorporated into the main circuit unit 101 or the control device 102. In other words, the optical signal transceiver 104 may be provided integrally with the main circuit unit 101 or integrally with the control device 102. Furthermore, the optical signal transceiver 104 may be divided and provided in the main circuit unit 101 and the control device 102, for example, by providing the optical transmission unit 11 and the light emission control unit 14 in the main circuit unit 101 and the optical reception unit 13 and the light receiving control unit 15 in the control device 102. In other words, the optical signal transceiver 104 may be provided in part in the main circuit unit 101 (for example, in each drive circuit 131 to 136) and in another part in the control device 102. The configuration of the optical signal transceiver 104 is not limited to the above, and may be any configuration that enables proper communication between the main circuit unit 101 and the control device 102.

[0056] (Third embodiment) Figure 4 is a schematic block diagram showing a power conversion device according to the third embodiment. As shown in Figure 4, the power converter 200 comprises a main circuit section 212, a control device 214, and an optical signal transceiver 216. The power converter 200 is used, for example, in a DC power transmission system. In the DC power transmission system, the power converter 200 is connected to an AC power system 202 and a pair of DC transmission lines 203 and 204.

[0057] The DC power transmission system includes, for example, a transformer 206. The main circuit section 212 of the power converter 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 section 212. The transformer 206 changes the effective value of each phase of the three-phase AC power to match the main circuit section 212. The transformer 206 is a three-phase transformer. The transformer 206 is provided as needed and is optional. The main circuit section 212 may also be directly supplied with the three-phase AC power of the AC power system 202.

[0058] The power converter 200 converts three-phase AC power supplied from the AC power system 202 into DC power and supplies the converted DC power to DC transmission lines 203 and 204. The power converter 200 also converts DC power supplied from 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 converter 200 performs AC-DC conversion and AC-DC conversion.

[0059] For example, DC transmission line 203 is a high-voltage transmission line for DC power, and DC transmission line 204 is a low-voltage transmission line for DC power. The power converter 200 outputs the converted DC power to DC transmission lines 203 and 204 such that the DC transmission line 203 side is high voltage and the DC transmission line 204 side is low voltage.

[0060] The main circuit section 212 is installed between the AC power system 202 and the DC transmission lines 203 and 204. The main circuit section 212 performs conversion from three-phase AC power to DC power and from DC power to three-phase AC power. The main circuit section 212 is, for example, a multilevel power converter having multiple converters connected in series. The main circuit section 212 is, for example, an MMC (Modular Multilevel Converter) type power converter. The MMC type main circuit section 212 has multiple converters connected in series. Each converter has multiple switching elements connected in half-bridge or full-bridge configuration, and a charge storage element connected in parallel to each switching element. The main circuit section 212 performs power conversion by the operation of the multiple converters. The main circuit section 212 performs AC / DC conversion by, for example, switching each switching element of the multiple converters.

[0061] The control device 214 controls the operation of the main circuit unit 212. The optical signal transceiver 216 communicates with the main circuit unit 212 and the control device 214. The control device 214 communicates with the main circuit unit 212 via the optical signal transceiver 216 and controls the on / off state 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 unit 212.

[0062] The main circuit section 212 includes a first and second pair of DC terminals 220a and 220b, three AC terminals 221a to 221c (1st to 3rd), and six arm sections 222a to 222f (1st to 6th).

[0063] The first DC terminal 220a is connected to the high-voltage DC transmission line 203. The second DC terminal 220b is connected to the low-voltage DC transmission line 204. As a result, the DC power converted by the main circuit unit 212 is supplied to the DC transmission lines 203 and 204, and the DC power supplied from the DC transmission lines 203 and 204 is input to the main circuit unit 212.

[0064] The first arm section 222a is connected to the first DC terminal 220a. The second arm section 222b is connected between the first arm section 222a and the second DC terminal 220b. The first arm section 222a and the second arm section 222b are connected in series between the respective DC terminals 220a and 220b.

[0065] The third arm section 222c is connected to the first DC terminal 220a. The fourth arm section 222d is connected between the third arm section 222c and the second DC terminal 220b. The third arm section 222c and the fourth arm section 222d are connected in parallel to the first arm section 222a and the second arm section 222b.

[0066] The fifth arm section 222e is connected to the first DC terminal 220a. The sixth arm section 222f is connected between the fifth arm section 222e and the second DC terminal 220b. That is, the fifth arm section 222e and the sixth arm section 222f are connected in parallel to the first arm section 222a and the second arm section 222b, and also in parallel to the third arm section 222c and the fourth arm section 222d.

[0067] In the main circuit section 212, the first leg LG1 is formed by the first arm section 222a and the second arm section 222b, the second leg LG2 is formed by the third arm section 222c and the fourth arm section 222d, and the third leg LG3 is formed by the fifth arm section 222e and the sixth arm section 222f. In other words, in this example, the main circuit section 212 is a three-phase inverter with three legs and six arms. The first arm section 222a, the third arm section 222c, and the fifth arm section 222e are upper arms. The second arm section 222b, the fourth arm section 222d, and the sixth arm section 222f are lower arms. Thus, the main circuit section 212 has multiple arm sections and multiple legs, each composed of multiple switching elements. The main circuit section 212 may also be, for example, a single-phase inverter with two legs and four arms. The number of arms and legs is not limited to those mentioned above and may be any number.

[0068] 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.

[0069] However, in the following, when referring to each converter UP1, UP2...UPM1, UN1, UN2...UNM2, VP1, VP2...VPM3, VN1, VN2...VNM4, WP1, WP2...WPM5, WN1, WN2...WNM6 collectively, they will be referred to as "Converter CEL".

[0070] In each arm section 222a to 222f, M1, M2, M3, M4, M5, and M6 represent the number of series-connected converter CELs. In each arm section 222a to 222f, the number of series-connected converter CELs is, for example, around 100 to 120 units. However, the number of series-connected converter CELs is not limited to this and can be any number.

[0071] The number of converter CELs provided in each arm section 222a to 222f is substantially the same. For example, when a large number of converter CELs are connected, the number of converter CELs provided in each arm section 222a to 222f may differ to the extent that it does not affect the operation of the main circuit section 212. For example, when 100 converter CELs are connected in series to one arm section, the number of converter CELs provided in other arm sections may differ by 1 to 2.

[0072] Each of the arm sections 222a to 222f further comprises buffer reactors 223a to 223f and a plurality of current detectors 224a to 224f. The power converter 200 also further comprises a voltage detection unit 225.

[0073] Each buffer reactor 223a to 223f is connected in series to each converter CEL in each of the arm sections 222a to 222f. The buffer reactor 223a of the first arm section 222a is provided between the connection point between the first arm section 222a and the second arm section 222b and the converter UP1. The buffer reactor 223b of the second arm section 222b is provided between the connection point between the first arm section 222a and the second arm section 222b and the converter UN1. The buffer reactor 223c of the third arm section 222c is provided between the connection point between the third arm section 222c and the fourth arm section 222d and the converter VP1. The buffer reactor 223d of the fourth arm section 222d is provided between the connection point between the third arm section 222c and the fourth arm section 222d and the converter VN1. The buffer reactor 223e of the fifth arm section 222e is provided between the connection point between the fifth arm section 222e and the sixth arm section 222f and the converter WP1. The buffer reactor 223f of the sixth arm section 222f is provided between the connection point between the fifth arm section 222e and the sixth arm section 222f and the converter WN1.

[0074] The current detector 224a is installed on the first arm portion 222a and detects the current flowing through the first arm portion 222a. That is, the current detector 224a detects the arm current of the first arm portion 222a. The current detector 224a is connected to the control device 214 via wiring, etc., which is not shown in the figure. The current detector 224a inputs the detected current value of the first arm portion 222a to the control device 214. As a result, the control device 214 receives the current value of the first arm portion 222a.

[0075] Similarly, current detector 224b detects the current flowing through the second arm section 222b and inputs the detected current value to the control device 214. Current detector 224c detects the current flowing through the third arm section 222c and inputs the detected current value to the control device 214. Current detector 224d detects the current flowing through the fourth arm section 222d and inputs the detected current value to the control device 214. Current detector 224e detects the current flowing through the fifth arm section 222e and inputs the detected current value to the control device 214. Current detector 224f detects the current flowing through the sixth arm section 222f and inputs the detected current value to the control device 214.

[0076] 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.

[0077] In the main circuit section 212, the connection points between the first arm section 222a and the second arm section 222b, the connection points between the third arm section 222c and the fourth arm section 222d, and the connection points between the fifth arm section 222e and the sixth arm section 222f each serve as AC output points.

[0078] The first AC terminal 221a is connected to the connection point between the first arm section 222a and the second arm section 222b. The second AC terminal 221b is connected to the connection point between the third arm section 222c and the fourth arm section 222d. The third AC terminal 221c is connected to the connection point between the fifth arm section 222e and the sixth arm section 222f. Each of the AC terminals 221a to 221c is connected to, for example, the transformer 206.

[0079] Each converter CEL communicates with the control device 214, for example, via the optical signal transceiver 216. The control device 214 controls the operation of the converter CEL by inputting control signals to the converter CEL via the optical signal transceiver 216. The converter CEL also inputs control signals and protection signals related to the control and operation protection of the converter CEL to the control device 214 via the optical signal transceiver 216. The communication method between the control device 214 and each converter CEL is not limited to the above. For example, multiple converter CELs 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 connection 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 allows for appropriate communication between the control device 214 and each converter CEL.

[0080] Figure 5 is a block diagram schematically representing the converter. As shown in Figure 5, the converter CEL includes a plurality of switching elements 241, 242, a plurality of rectifier elements 251, 252, a plurality of drive circuits 261, 262, a pair of connection terminals 271, 272, a charge storage element 274, a power supply circuit 276, a voltage detection circuit 278, and a control circuit 280.

[0081] Each switching element 241, 242 can be the same as the switching elements 111 to 116 in the second embodiment described above. Therefore, a detailed explanation of the element configuration of each switching element 241, 242 will be omitted.

[0082] The pair of main terminals of switching element 242 are connected in series with the pair of main terminals of switching element 241. In this example, the converter CEL has two switching elements 241 and 242 connected in series. In this example, the converter CEL is a half-bridge converter.

[0083] The rectifier element 251 is connected in antiparallel to the 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 antiparallel to the pair of main terminals of the switching element 242. The rectifier elements 251 and 252 are so-called freewheeling diodes.

[0084] The connection terminal 271 is connected between the switching element 241 and the switching element 242. The connection terminal 272 is connected to the main terminal of the switching element 241 on the opposite side of the main terminal connected to the switching element 242.

[0085] Multiple converters CEL within the same arm are connected in series via a pair of connection terminals 271 and 272. Power is supplied to the converters CEL via each connection terminal 271 and 272. Switching element 241 is a so-called low-side switch, and switching element 242 is a so-called high-side switch.

[0086] The control circuit 280 communicates with the control device 214 via the optical signal transceiver 216. The control device 214 transmits control signals to the control circuit 280 via the optical signal transceiver 216 to control the on / off state of each switching element 241, 242. Based on the input control signals, the control circuit 280 inputs drive signals to the drive circuits 261, 262 to switch the on / off state of each switching element 241, 242.

[0087] The drive circuit 261 is connected to the control terminal of the switching element 241. The drive circuit 262 is connected to the control terminal of the switching element 242. The drive circuits 261 and 262 switch the on and off of each switching element 241 and 242 based on the drive signal input from the control circuit 280. In this way, the on and off of each switching element 241 and 242 is controlled according to the control signal from the control device 214. The control device 214 generates a control signal for each converter CEL and controls the on and off of each switching element 241 and 242 of each converter CEL. In this way, the control device 214 controls the power conversion by the main circuit 212.

[0088] The configurations of the drive circuits 261 and 262 and the control circuit 280 are not limited to those described above, and may be any configuration capable of controlling the on / off state of each switching element 241 and 242. For example, control signals from the control device 214 may be directly input to the drive circuits 261 and 262. In this case, the control circuit 280 can be omitted.

[0089] The charge storage element 274 is connected in parallel with the switching elements 241 and 242. The charge storage element 274 is, for example, a capacitor.

[0090] When switching element 241 is in the off state and switching element 242 is in the on state, the voltage of the charge storage element 274 appears between the connection terminals 271 and 272. When switching element 241 is in the on state and switching element 242 is in the off state, the connection terminals 271 and 272 conduct, and the voltage between the connection terminals 271 and 272 becomes virtually zero.

[0091] In this way, the converter CEL switches between an output state in which the voltage of the charge storage element 274 is output between the connection terminals 271 and 272, a bypass state in which the connection terminals 271 and 272 are conductive, and a stopped state in which the switching elements 241 and 242 are turned off, by switching the switching elements 241 and 242 based on the control signal from the control device 214.

[0092] In each arm section 222a to 222f, the sum of the voltages of the converters CEL in the output state becomes the voltage of each 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.

[0093] When both switching elements 241 and 242 are in the off state (when the converter CEL is stopped), the voltage between each connection terminal 271 and 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, the rectifier element 251 turns on, and the voltage between each connection terminal 271 and 272 becomes virtually zero. Conversely, when the arm current flows from connection terminal 271 to connection terminal 272, the rectifier element 252 turns on, the charge storage element 274 is charged, and the voltage of the charge storage element 274 appears between each connection terminal 271 and 272.

[0094] The power supply circuit 276 is connected in parallel to the charge storage element 274. Based on the charge stored in the charge storage element 274, the power supply circuit 276 generates a power supply for the drive circuits 261, 262 and the control circuit 280, and supplies the generated power supply 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 power supply from the power supply circuit 276.

[0095] The power supply method 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 power supply method to the drive circuits 261, 262 and the control circuit 280 can be any method that can appropriately supply power to the drive circuits 261, 262 and the control circuit 280.

[0096] 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 detected voltage value of the DC voltage of the charge storage element 274 to the control circuit 280.

[0097] The optical signal transceiver 216, like the optical signal transceiver 10 of the first embodiment, includes an optical transmission unit 11, an optical transmission line 12, an optical reception unit 13, an emission control unit 14, and a light receiving control unit 15. The configurations of the optical transmission unit 11, the optical transmission line 12, the optical reception unit 13, the emission control unit 14, and the light receiving control unit 15 are substantially the same as those described with respect to the first embodiment, so a detailed explanation is omitted.

[0098] The light emission control unit 14 is connected to the main circuit unit 212. The light receiving control unit 15 is connected to the control device 214. This enables the optical signal transceiver 216 to transmit signals from the main circuit unit 212 to the control device 214. The optical signal transceiver 216 also has other optical transmitting units, optical transmission lines, and optical receiving units (not shown), which enable the transmission of signals from the control device 214 to the main circuit unit 212. The optical signal transceiver 216 electrically isolates the main circuit unit 212 and the control device 214 while enabling bidirectional communication between them, for example. However, the optical signal transceiver 216 does not necessarily have to enable bidirectional communication.

[0099] The control device 214 transmits control signals to each converter CEL of the main circuit unit 212 via the optical signal transceiver 216. The control signals are, for example, control signals for switching the switching of each switching element 241, 242 by repeating a high voltage state and a low voltage state at a predetermined period and changing the ratio of the high voltage state to the low voltage state. The control signals are, for example, control signals for PWM control. The control signals are, for example, digital signals.

[0100] The control circuit 280 of each converter CEL switches the switching elements 241 and 242 on and off based on the control signal input from the control device 214. The control device 214 transmits control signals to the control circuit 280 of each converter CEL via the optical signal transceiver 216, and controls the power conversion by the main circuit 212 by controlling the switching of each switching element 241 and 242.

[0101] The control circuit 280 of each converter CEL switches the on and off states of each switching element 241 and 242 by changing the magnitude of the voltage at the control terminals of each switching element 241 and 242 in response to the control signal input from the control device 214. The magnitude of the control signal voltage, the magnitude of the voltage at the control terminals of each switching element 241 and 242, and the on / off relationship of each switching element 241 and 242 can be the same as described in the second embodiment above.

[0102] The optical signal transceiver 216 includes, for example, a plurality of optical transmitting units 11, a plurality of optical transmission lines 12, a plurality of optical receiving units 13, a plurality of light emission control units 14, and a plurality of light receiving control units 15, each corresponding to each of the converters CEL. The plurality of light emission control units 14 are connected, for example, to the respective control circuits 280 of each converter CEL. The signals output from the respective control circuits 280 of each converter CEL are input to the control device 214 via the optical signal transceiver 216.

[0103] The control circuit 280 of each converter CEL repeatedly switches between a high voltage state and a low voltage state at a predetermined period, and inputs a heartbeat signal as the first input signal to each light emission control unit 14 so that the control device 214 can detect abnormalities in each converter CEL. The heartbeat signal is, for example, a digital signal.

[0104] Furthermore, the control circuit 280 of each converter CEL measures, for example, the voltage at the control terminals of each switching element 241, 242, and inputs a feedback signal corresponding to the measurement result of the voltage at the control terminals as a second input signal to each light emission control unit 14. The feedback signal is, for example, a signal that alternates between a high voltage state and a low voltage state at a predetermined period, and changes the ratio of the high voltage state to the low voltage state. The feedback signal is, for example, a PWM signal. The feedback signal is, for example, a digital signal. In other words, the feedback signal is a signal that allows the control device 214 to confirm whether or not the control signal has been properly input to the control terminals of each switching element 241, 242.

[0105] In other words, the main circuit unit 212 repeatedly switches between a high voltage state and a low voltage state at a predetermined period, and inputs a heartbeat signal as a first input signal to the light emission control unit 14 so that the control device 214 can detect any abnormality in the main circuit unit 212. The main circuit unit 212 then measures the voltage at the control terminals of each switching element 241, 242, and inputs a feedback signal corresponding to the measurement result of the voltage at the control terminals as a second input signal to the light emission control unit 14. As explained with respect to Figure 2 of the first embodiment above, the period of the feedback signal (control signal) is longer than the period of the heartbeat signal. In other words, the period T2 of the second input signal is longer than the period T1 of the first input signal.

[0106] As a result, the power converter 200 according to this embodiment can transmit two signals, a first input signal and a second input signal, using a single optical transmission line 12. Therefore, the power converter 200 can transmit and receive multiple signals of different frequencies with a simpler configuration compared to, for example, a case where two optical transmitting units 11, two optical transmission lines 12, and two optical receiving units 13 are provided, each corresponding to one of the two signals.

[0107] Furthermore, the power converter 200 is provided with, for example, multiple optical transmitting units 11, multiple optical transmission lines 12, multiple optical receiving units 13, multiple light emission control units 14, and multiple light receiving control units 15, each corresponding to one of the multiple converters CEL. In this case, by enabling the transmission of two signals, a first input signal and a second input signal, through one optical transmission line 12, the number of optical transmission lines 12 can be further reduced, and the increase in the number of components in the power converter 200 can be further suppressed. In a power converter 200 in which many converters CEL are connected in series, the number of optical components such as optical transmitting units 11, optical transmission lines 12, and optical receiving units 13 also becomes large. Therefore, in such a power converter 200, by enabling the transmission of two signals, a first input signal and a second input signal, through one optical transmission line 12 as described above, the increase in the number of components can be significantly suppressed. For example, the increase in cost associated with the increase in optical components can be significantly suppressed.

[0108] Similar to the second embodiment described above, the optical signal transceiver 216 may be incorporated into the main circuit unit 212 or the control device 214. In other words, the optical signal transceiver 216 may be integrally provided in the main circuit unit 212 or integrally provided in the control device 214. Alternatively, the optical signal transceiver 216 may be divided and provided in the main circuit unit 212 and the control device 214, for example, by providing the optical transmission unit 11 and the light emission control unit 14 in the main circuit unit 212 and the optical reception unit 13 and the light receiving control unit 15 in the control device 214. In other words, the optical signal transceiver 216 may be partially provided in the main circuit unit 212 (for example, each converter CEL) and another part in the control device 214. The configuration of the optical signal transceiver 216 is not limited to the above, and any configuration that allows for appropriate communication between the main circuit unit 212 and the control device 214 is acceptable.

[0109] Furthermore, in the MMC-type main circuit section 212, the configuration of the converter CEL is not limited to a half-bridge circuit configuration, but may also be a full-bridge circuit configuration having four switching elements connected in a full-bridge configuration.

[0110] In the third embodiment described above, an MMC-type power converter is used in the main circuit section 212. The main circuit section 212 is not limited to the MMC type; for example, it may be a power converter of another type in which multiple converters CEL are connected in series.

[0111] The power converter 200 is not limited to DC power transmission systems, but may be applied to any other system requiring AC to DC conversion and DC to AC conversion. The AC to DC conversion by the main circuit 212 is not limited to both AC to DC and DC to AC, but may be AC ​​to DC or DC to AC only. Furthermore, the main circuit 212 may be, for example, an AC to AC direct conversion circuit.

[0112] The main circuit section 212 may be configured in a way that connects multiple arm sections in a star, delta, or matrix configuration. The main circuit section 212 may also be a modular matrix converter, for example. The main circuit section 212 does not necessarily have to have multiple legs. The main circuit section 212 only needs to have at least multiple arm sections. The main circuit section 212 may be configured in any way that allows for power conversion. The power conversion device may be a frequency converter, a DC power transmission device, a reactive power compensation device, or a power flow control device, for example.

[0113] Thus, the configuration of the main circuit is not limited to the three-phase two-level inverter configuration shown in the second embodiment above, but may also be a configuration in which multiple converters CEL are connected in series. The configuration of the main circuit is not limited to a three-phase two-level inverter, but may also 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 is not limited to the configurations shown in each of the embodiments above, but may be any configuration that has a converter and performs power conversion by the operation of the converter.

[0114] The above embodiment shows an example in which an optical signal transceiver is applied to a power converter. The optical signal transceiver is not limited to a power converter and may be used in any other device.

[0115] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0116] 10…Optical signal transceiver, 11…Optical transmitter, 12…Optical transmission line, 13…Optical receiver, 14…Light emission control unit, 15…Light receiving control unit, 20…Exclusive OR circuit, 30…One-shot circuit, 32…Filter circuit, 100…Power converter, 101…Main circuit section, 101a…Converter, 102…Control device, 104…Optical signal transceiver, 111~116…Switching elements, 121~126…Rectifier elements, 130…Charge storage element, 131~136…Drive circuit, 200…Power converter, 202…AC power system, 203, 204…DC transmission line, 206…Transformer, 212…Main circuit section, 214…Control device, 216…Optical signal transceiver, 220a…First DC terminal, 220b...Second DC terminal, 221a...First AC terminal, 221b...Second AC terminal, 221c...Third AC terminal, 222a...First arm section, 222b...Second arm section, 222c...Third arm section, 222d...Fourth arm section, 222e...Fifth arm section, 222f...Sixth arm section, 223a~223f...Buffer reactor, 224a~224f...Current detector, 225...Voltage detection section, 241, 242...Switching elements, 251, 252...Rectifier elements, 261, 262...Drive circuit, 271, 272...Connection terminals, 274...Charge storage element, 276...Power supply circuit, 278...Voltage detection circuit, 280...Control circuit, CEL...Converter, LG1... Leg 1, LG2... Leg 2, LG3... Leg 3

Claims

1. A main circuit section having a plurality of switching elements for converting power, and a plurality of drive units for driving the plurality of switching elements, A control device that controls the operation of the main circuit section and has a first signal processing circuit and a second signal processing circuit, Equipped with, Each of the aforementioned plurality of drive units is A first signal is generated that changes between two values ​​at a period corresponding to the state of one switching element to be driven, and a second signal is generated that changes between two values ​​at a predetermined period shorter than the change of the first signal, for detecting whether an abnormality has occurred in itself. A superimposed signal is generated by superimposing the first signal and the second signal generated above. The generated superimposed signal is transmitted to the control device. The control device inputs the superimposed signals received from each of the plurality of drive units to the first signal processing circuit and the second signal processing circuit, The first signal processing circuit generates a restored signal of the first signal by passing the frequency components of the first signal through the superimposed signal. The second signal processing circuit outputs a first value indicating that the drive unit is functioning normally for a predetermined time after the superimposed signal changes from one value to the other, and outputs a second value indicating that the drive unit is malfunctioning if the signal does not change from one value to the other within the predetermined time. The control device is a power converter that, upon receiving the second value, detects that an abnormality has occurred in the drive unit that transmitted the superimposed signal.

2. The power conversion device according to claim 1, wherein the state of the switching element is the gate terminal voltage of the switching element.

3. The power conversion device according to claim 1, wherein the control device determines whether the main circuit is functioning normally based on the restoration signal of the first signal and the control signal input to the drive unit.

4. The power conversion device according to claim 1, wherein the predetermined time is longer than the period during which the second signal changes between the two values, and is less than or equal to half the period during which the first signal changes between the two values.

5. The power conversion device according to claim 1, wherein the superimposed signal is obtained by the exclusive OR of the first signal and the second signal.

Images