Power conversion system

Abstract

Provided is a power conversion system comprising a power conversion device and equipment. The power conversion device includes: an inverter that converts power into AC power and outputs the AC power; and a filter circuit in which a circuit component provided on the AC output side of the inverter and having a damping resistor and / or a filter reactor, and an AC capacitor that is disconnected from the circuit in the event of a fault, are connected in series. The equipment includes: a voltage recognition unit that recognizes the voltage value of a voltage generated by the circuit component; a voltage calculation unit that calculates a prescribed voltage calculation value on the basis of the voltage value of the voltages generated by the circuit component and recognized by the voltage recognition unit; a fault determination unit that compares the magnitude of the voltage calculation value calculated by the voltage calculation unit with a predetermined threshold value, and determines that there is a fault in the AC capacitor when the voltage calculation value is smaller than the predetermined threshold value; and an operation control unit that stops the power conversion device when the fault determination unit has determined that there is a fault in the AC capacitor while the power conversion device is running.

Description

Power Conversion Systems

[0001] The present invention relates to a power conversion system.

[0002] Conventionally, there has been known a power conversion device in which a voltage matching operation is performed before grid-connected operation is performed (before an AC switch is turned on), and then the AC switch is turned on to start the grid-connected operation. The voltage matching operation is performed by matching the amplitude and phase of the AC output voltage of the power conversion device to the amplitude and phase of the grid voltage before grid-connected operation is performed (before the AC switch is turned on) (for example, see Patent Document 1).

[0003] Japanese Patent Publication No. 2017-212838

[0004] Some AC capacitors used as filters for the AC output of power conversion devices have a fuse mechanism that disconnects the capacitor element from the circuit in the event of abnormal overheating, for example. When the fuse mechanism is activated, the AC capacitor experiences an open circuit fault. In such a case, a conventional power conversion device may detect the fault as a synchronization error during voltage matching operation.

[0005] However, in conventional power conversion devices, even if an AC capacitor has an open circuit fault, the fault may not be detected during voltage matching operation. In this case, the AC switch of the power conversion device is turned on after voltage matching operation to start grid-connected operation, and operation may continue without detecting the fault. If operation is started with an AC capacitor having an open circuit fault, the power conversion device may leak large harmonics into the grid. In addition, since voltage application is concentrated on the normal AC capacitor, there is a risk that the fault may spread to the normal AC capacitor.

[0006] Therefore, the present disclosure aims to prevent harmonics from leaking into the grid and the spread of the failure to normal AC capacitors by detecting a failure in an AC capacitor during grid-connected operation of a power conversion device and issuing a specified operational instruction.

[0007] A power conversion system according to one embodiment includes a power conversion device having an inverter that converts electric power and outputs AC power, and a filter circuit that is provided on the AC output side of the inverter and has circuit components having at least one of a damping resistor and a filter reactor, and an AC capacitor that is disconnected from the circuit in the event of a fault, connected in series; a voltage recognition unit that recognizes a voltage value of a voltage generated by the circuit components, a voltage calculation unit that calculates a predetermined voltage calculation value based on the voltage value of the voltage generated by the circuit components recognized by the voltage recognition unit, a failure determination unit that compares the voltage calculation value calculated by the voltage calculation unit with a predetermined threshold value and determines that the AC capacitor has failed when the voltage calculation value is smaller than the predetermined threshold value, and an operation control unit that stops the power conversion device when the failure determination unit determines that the AC capacitor has failed during operation of the power conversion device.

[0008] According to another aspect, a power conversion system includes a power conversion device having an inverter that converts electric power and outputs AC power, and a filter circuit that is provided on the AC output side of the inverter and has circuit components having at least one of a damping resistor and a filter reactor, and an AC capacitor that is disconnected from the circuit in the event of a fault, connected in series; a voltage recognition unit that recognizes a voltage value of a voltage generated by the circuit components, a voltage calculation unit that calculates a predetermined voltage calculation value based on the voltage value of the voltage generated by the circuit components recognized by the voltage recognition unit, a failure determination unit that compares the calculated voltage value calculated by the voltage calculation unit with a predetermined threshold value and determines that the AC capacitor has failed when the calculated voltage value is smaller than the predetermined threshold value, and a warning issuance unit that issues a warning that the AC capacitor has failed when the failure determination unit determines that the AC capacitor has failed during operation of the power conversion device.

[0009] According to the present disclosure, by detecting a fault in an AC capacitor during grid-connected operation of a power conversion device and issuing a predetermined operational instruction, it is possible to prevent harmonics from leaking into the grid and prevent the fault from spreading to normal AC capacitors.

[0010] 12 is a diagram showing an example of the configuration of a power conversion system according to the first embodiment. FIG. 13 is a diagram showing an example of the control configuration of a control device in the power conversion system shown in FIG. 1. FIG. 14 is a diagram showing an example of the configuration of a power conversion system according to a first modified example of the first embodiment. FIG. 15 is a diagram showing an example of the control configuration of a control device in the power conversion system shown in FIG. 3. FIG. 16 is a diagram showing an example of the configuration of a power conversion system according to a second modified example of the first embodiment. FIG. 17 is a diagram showing an example of the control configuration of a control device in the power conversion system shown in FIG. 5. FIG. 18 is a diagram showing an example of the configuration of a power conversion system according to a third modified example of the first embodiment. FIG. 19 is a diagram showing an example of the control configuration of a control device in the power conversion system shown in FIG. 7. FIG. 19 is a diagram showing an example of the control configuration of a control device in the power conversion system according to the second embodiment. FIG. 19 is a diagram showing an example of the control configuration of a control device in the power conversion system according to the third embodiment. FIG. 19 is a diagram showing an example of the control configuration of a control device in the power conversion system according to the fourth embodiment. A conceptual diagram showing an example of the hardware configuration of a processing circuit included in the control device in the embodiments shown in FIGS. 1 to 11. FIG. 19 is a diagram showing an example of a combination of each configuration of the present disclosure.

[0011] Hereinafter, an embodiment of a power conversion system according to the present disclosure will be described with reference to the drawings.

[0012] First Embodiment FIG. 1 is a diagram showing an example of the configuration of a power conversion system 1 according to a first embodiment.

[0013] As shown in FIG. 1 , the power conversion system 1 includes a solar cell 10 , an AC power system 20 , a power conversion device 30 , and a control device 60 .

[0014] A power conversion system (PCS: Power Conditioning System) 1 converts, for example, DC power supplied from a solar cell 10 into AC power via a power conversion device 30, and outputs the converted AC power to an AC power grid 20. Note that the power conversion system 1 (power conversion device 30) is not limited to converting DC power into AC power, but may also convert AC power into AC power. Hereinafter, in this specification, the power conversion system 1 (power conversion device 30) will be described as converting DC power into AC power.

[0015] The solar cell (PV: Photovoltaics) 10 is connected to one end (input side) of the power conversion device 30 and supplies DC power to the power conversion device 30 via this one end. The solar cell 10 is an example of a "DC power source," and the DC power source may be a storage battery (ESS: Energy Storage System), a DC power source system including a wind power generator and an AC-DC converter, etc. Note that the power source connected to one end (input side) of the power conversion device 30 is not limited to a DC power source, and may be an AC power source if the power conversion system 1 (power conversion device 30) converts AC power to AC power.

[0016] The AC power system 20 is connected to the other end (output side) of the power conversion device 30 and is a system that integrates power generation, power transformation, power transmission, and power distribution in order to supply AC power output from the power conversion device 30 to power receiving equipment of consumers, and is connected to, for example, an unspecified load. Note that the AC power system 20 is not limited to a power system and may also be a load. Hereinafter, in this specification, the AC power system 20 is also referred to as "system 20."

[0017] The power conversion device 30 includes a DC bus 31, a DC capacitor 32, an inverter circuit 33, an AC circuit 34, an AC reactor 35, an AC switch 36, and a filter circuit 37. The filter circuit 37 includes, for example, a damping resistor 41, a filter reactor 42, and a filter capacitor 43. In this embodiment, a first voltage sensor 51 is disposed in the filter circuit 37, and a second voltage sensor 52 is disposed on the grid 20 side of the AC switch 36 in the AC circuit 34.

[0018] 1 , the AC circuit 34, the AC reactor 35, the AC switch 36, the filter circuit 37, the damping resistor 41, the filter reactor 42, and the filter capacitor 43 are provided or arranged in each of the three phases (U phase, V phase, and W phase). Similarly, the first voltage sensor 51 and the second voltage sensor 52 are also arranged in each of the three phases. For this reason, hereinafter in this specification, when these components in each of the three phases are to be distinguished, the suffix "U," "V," or "W" is added to the reference numeral, and when these components in each of the three phases are not to be distinguished, the suffix "U," "V," or "W" is not added.

[0019] For example, when the U-phase, V-phase, and W-phase filter capacitors 43 are to be distinguished from one another, they are referred to as "filter capacitor 43U," "filter capacitor 43V," and "filter capacitor 43U," respectively. On the other hand, when the U-phase, V-phase, and W-phase filter capacitors 43 are not to be distinguished from one another, they are simply referred to as "filter capacitors 43."

[0020] The power conversion device 30 is connected to the solar cell 10 via a DC bus 31 at one end (input side) on the left side in Fig. 1, and is connected to the grid 20 via an AC circuit 34 at the other end (output side) on the right side in Fig. 1. Furthermore, each part of the power conversion device 30 is connected to a control device 60 via signal lines etc. (not shown), and the operation of the power conversion device 30 is controlled by the control device 60.

[0021] The power conversion device 30 performs voltage matching operation (synchronization control) under the control of the control device 60 before the AC switch 36 is turned on, and then the AC switch 36 is turned on to start grid-connected operation. Note that the voltage matching operation is performed, for example, by an AC automatic voltage regulator (AC-AV ｒ When grid-connected operation starts, the power conversion device 30, under the control of the control device 60, converts the DC power supplied from the solar cell 10 into AC power and outputs it to the grid 20.

[0022] The DC bus 31 has a DC switch (not shown), one end of which is connected to the solar cell 10, and the other end of which is connected to a DC end of the inverter circuit 33. The DC bus 31 has a positive DC bus and a negative DC bus, and supplies DC power supplied from the solar cell 10 to the inverter circuit 33. Note that if the power conversion device 30 converts AC power into AC power, the reference numeral 31 may be an AC circuit.

[0023] The DC capacitor 32 is a smoothing capacitor that is provided in the DC bus 31, for example, between the positive DC bus and the negative DC bus, and smoothes the DC voltage output from the solar cell 10. Hereinafter in this specification, the DC capacitor 32 is also referred to as a "DC (Direct Current) capacitor 32."

[0024] One end of the inverter circuit 33, which is a DC end, is connected to the DC bus 31, and the other end, which is an AC end, is connected to the AC circuit 34. The inverter circuit 33 is configured with a plurality of switching elements such as IGBTs (Insulated Gate Bipolar Transistors). The inverter circuit 33 is controlled by, for example, a pulse width modulation (PWM) signal, which is a gate drive signal (gate signal) for the switching elements, generated by an inverter control unit (not shown).

[0025] The inverter circuit 33 acquires DC power supplied from the solar cell 10 from one end, converts the acquired DC power into AC power under control of a pulse width modulation signal (gate signal), and outputs the converted AC power from the other end, which is the output end, to the AC circuit 34. Note that if the power conversion device 30 converts AC power to AC power, the inverter circuit 33 may also convert AC power to AC power. Hereinafter, in this specification, the inverter circuit 33 is also simply referred to as the "inverter 33." Also, in this specification, the pulse width modulation signal is also referred to as the "PWM signal."

[0026] One end of the AC circuit 34 is connected to the output terminal of the inverter 33, and the other end is connected to the grid 20. The AC circuit 34 is, for example, a three-phase, three-wire three-phase AC circuit that supplies three-phase AC power by combining three systems of single-phase AC with mutually shifted phases of current or voltage using three electric wires, cables, conductors, etc. The AC circuit 34 supplies the AC power converted by the inverter 33 to the grid 20 side.

[0027] The AC reactor 35 is connected in series with the AC circuit 34 on the output side of the inverter 33 and is a smoothing element that has the effect of reducing noise and suppressing surge voltage, for example. The AC reactor 35, together with a filter capacitor 43 connected in an L-shape with the AC circuit 34 via a branch point 34a, reduces ripples (vibrations) that occur when the switching elements of the inverter 33 switch. Hereinafter, in this specification, the AC reactor 35 is also referred to as an "AC (alternating-current) reactor 35."

[0028] The AC switch (AC switchgear) 36 is provided in series in the AC circuit 34, for example, closer to the grid 20 than the branch point 34a. The AC switch 36 makes (connects) or opens (disconnects) the AC circuit 34 and the grid 20 in accordance with an on / off instruction from the control device 60, a monitoring device (not shown) described below, or an operator (not shown). When the AC switch 36 is opened, AC power supplied from the inverter 33 is blocked from flowing out to the grid 20. When the power conversion device 30 is started (activated), the AC switch 36 is opened when the power conversion device 30 is performing voltage matching operation (synchronization control) with the grid 20, and is closed when grid-connected operation starts. Hereinafter, in this specification, the AC switch 36 is also referred to as an "AC switch 36."

[0029] The filter circuit 37 is a circuit branched from the AC circuit 34 on the AC output side of the inverter 33 via a branch point 34a between the AC reactor 35 and the AC switch 36, and one end is connected to the branch point 34a. In the filter circuit 37, for example, a damping resistor 41, a filter reactor 42, and a filter capacitor 43 are connected in series. Note that the damping resistor 41, the filter reactor 42, and the filter capacitor 43 only need to be connected in series, and the order of connection is not limited to this order. In the present embodiment, both the damping resistor 41 and the filter reactor 42 are connected to the filter circuit 37, but this is not a limitation, and it is sufficient that at least one of them is connected.

[0030] The damping resistor 41 is an electrical resistor for attenuating noise by, for example, suppressing the sharpness of the resonance of the LC resonant circuit, and is connected in series with the filter reactor 42 and the filter capacitor 43 in the filter circuit 37. The damping resistor 41 is an example of a "circuit component."

[0031] The filter reactor 42, for example, constitutes an LC resonant circuit with the filter capacitor 43, which cancels out the potentials of the other at a specific resonant frequency, and is connected in series with the damping resistor 41 and the filter capacitor 43 in the filter circuit 37. The filter reactor 42 is an example of a "circuit component."

[0032] The filter capacitor 43 is, for example, an electronic component that stores or releases electricity (charge), and is connected in series with the damping resistor 41 and the filter reactor 42 in the filter circuit 37. The filter capacitor 43, together with the AC reactor 35 connected in an L-shape, reduces ripples (vibrations) that occur when a switching element (not shown) of the inverter 33 switches on and off. The filter capacitor 43, together with the AC reactor 35, suppresses harmonics (harmonic currents) from flowing out to the grid 20.

[0033] The filter capacitor 43 may be at least one AC capacitor that is disconnected from the circuit in the event of a malfunction, and may have a fuse mechanism (not shown) that disconnects the capacitor element from the circuit in the event of abnormal overheating, etc. The filter capacitor 43 is an example of an "AC capacitor."

[0034] The first voltage sensors 51 (51U, 51V, 51W) are, for example, known AC voltmeters or AC voltage sensors, and detect the capacitor voltage V ｃｕ , V ｃｖ , V ｃｗ The first voltage sensor 51 is disposed at a position where it can detect the three-phase capacitor voltage V ｃｕ , V ｃｖ , V ｃｗ The position where the first voltage sensor 51 is disposed is not limited to the position shown in FIG. ｃｕ , V ｃｖ , V ｃｗ The capacitor voltage V detected by the first voltage sensor 51 may be any position where the capacitor voltage V ｃｕ , V ｃｖ , V ｃｗ is acquired by the control device 60. Hereinafter, in this specification, the capacitor voltage V ｃｕ , V ｃｖ , V ｃｗ is the three-phase capacitor voltage V ｃｕ , V ｃｖ , V ｃｗ When the voltages are not distinguished, the suffixes "u", "v" and "w" are not added, and these are collectively referred to as "capacitor voltage V ｃ "It is also called ".

[0035] The second voltage sensors 52 (52U, 52V, 52W) are, for example, known AC voltmeters or AC voltage sensors, and are arranged between the AC switch 36 and the grid 20. The second voltage sensors 52 detect a three-phase grid voltage V ｓｕ , V ｓｖ , V ｓｗThe position where the second voltage sensor 52 is disposed is not limited to the position shown in FIG. ｓｕ , V ｓｖ , V ｓｗ The system voltage V detected by the second voltage sensor 52 may be any position where the system voltage V ｓｕ , V ｓｖ , V ｓｗ is acquired by the control device 60.

[0036] Hereinafter, in this specification, for example, the system voltage V ｓｕ , V ｓｖ , V ｓｗ For each configuration with "u", "v" or "w" added at the end, if the three-phase configuration is not distinguished, the "u", "v" or "w" added at the end is omitted. For example, for a system voltage V ｓｕ , V ｓｖ , V ｓｗ In the three-phase configuration (three-phase system voltage V ｓｕ , V ｓｖ , V ｓｗ ) are not distinguished, the suffix "u", "v" or "w" is not added, and they are collectively referred to as "system voltage V ｓ "It is also called ".

[0037] The control device 60 is provided, for example, inside or outside the power conversion device 30, and although wiring and the like are omitted in the drawing, it is electrically connected, by wire or wirelessly, to each element of the power conversion device 30, including the inverter 33, and each sensor, including the first voltage sensor 51. The control device 60 has the configuration or function of an inverter control unit (not shown) that controls the operation of the inverter 33 of the power conversion device 30 using a PWM signal.

[0038] The control device 60 has a processor 91 (see FIG. 12 ) such as a CPU (Central Processing Unit) that operates by executing a program, which will be described later. The control device 60 has a storage unit 73 (see FIG. 2 ) or a memory 92 (see FIG. 12 ), which will be described later, and for example, executes a predetermined program stored in the storage unit 73 or the memory 92 to operate the processor 91, thereby comprehensively controlling the operation of the power conversion device 30. Note that the control device 60 may operate in accordance with instructions from a monitoring device or a higher-level device (not shown), or instructions received from an operator (not shown) via an operation unit (not shown). The control device 60 receives the capacitor voltage V detected by the first voltage sensor 51 (51U, 51V, 51W), and outputs the capacitor voltage V ｃｕ , V ｃｖ , V ｃｗ and the system voltage V detected by the second voltage sensor 52 (52U, 52V, 52W). ｓｕ , V ｓｖ , V ｓｗ and get.

[0039] In this embodiment, the control device 60 is not limited to one having the configuration or function of an inverter control unit (not shown), but may be, for example, a monitoring device (not shown) that controls, monitors, detects faults, issues fault alerts, etc., of the power conversion device 30 other than the control of the inverter 33. In this case, the monitoring device (not shown) may be provided in the power conversion device 30 as a separate configuration from the control device 60 that has the configuration or function of an inverter control unit (not shown) and controls the inverter 33.

[0040] In this case, the monitoring device (not shown) may, for example, directly acquire values ​​detected by the first voltage sensor 51, the second voltage sensor 52, etc. from the first voltage sensor 51, the second voltage sensor 52, etc., or may acquire the values ​​from the control device 60 after they have been acquired by the control device 60. In this case, the monitoring device (not shown) may, for example, acquire the values ​​(raw values) detected by the first voltage sensor 51, the second voltage sensor 52, etc. as they are from the control device 60, or may acquire values ​​from the control device 60 after a predetermined calculation has been performed by the control device 60.

[0041] The monitoring device (not shown) may be, for example, a higher-level device (not shown) that is connected to the plurality of power electronics devices 30 by wire or wirelessly and comprehensively controls or monitors the plurality of connected power electronics devices 30. The control device 60 and the monitoring device (not shown) are examples of "devices."

[0042] FIG. 2 is a diagram showing an example of the control configuration of the control device 60 in the power conversion system 1 shown in FIG.

[0043] As shown in FIG. 2, the control device 60 includes a U-phase determination unit 61U, a V-phase determination unit 61V, a W-phase determination unit 61W, a fault detection unit 71, an operation control unit 72, and a storage unit 73.

[0044] The U-phase determination unit 61U detects the U-phase capacitor voltage V ｃｕ and obtains the U-phase system voltage V from the second voltage sensor 52U. ｓｕ and obtains the U-phase fault determination level V from the storage unit 73. ｔｈｕ Then, the U-phase determination unit 61U acquires the acquired U-phase capacitor voltage V ｃｕ and the U-phase system voltage V ｓｕ and the fault determination level V of the U-phase filter capacitor 43U. ｔｈｕ Based on this, it is determined whether or not the U-phase filter capacitor 43U has failed.

[0045] The V-phase determination unit 61V detects the V-phase capacitor voltage V from the first voltage sensor 51V. ｃｖ and obtains the V-phase system voltage V from the second voltage sensor 52V. ｓｖ and obtains the V-phase fault determination level V from the storage unit 73. ｔｈｖ Then, the V-phase determination unit 61V obtains the obtained V-phase capacitor voltage V ｃｖ and the V-phase system voltage V ｓｖ and the fault determination level V of the V-phase filter capacitor 43V. ｔｈｖ Based on this, it is determined whether or not the V-phase filter capacitor 43V has failed.

[0046] The W-phase determination unit 61W detects the W-phase capacitor voltage V ｃｗ and obtains the W-phase system voltage V from the second voltage sensor 52W. ｓｗand obtains the W-phase fault determination level V from the storage unit 73. ｔｈｗ Then, the W-phase determination unit 61W acquires the acquired W-phase capacitor voltage V ｃｗ and the W-phase system voltage V ｓｗ and the fault determination level V of the W-phase filter capacitor 43W. ｔｈｗ Based on this, it is determined whether or not the W-phase filter capacitor 43W has failed.

[0047] In the following, in this specification, when the configurations of the U-phase determination unit 61U, the V-phase determination unit 61V, and the W-phase determination unit 61W are not to be distinguished, the suffix "U," "V," or "W" is omitted, and these are also simply referred to as "determination unit 61."

[0048] Since the U-phase determination unit 61U, the V-phase determination unit 61V, and the W-phase determination unit 61W have the same configuration or function, the following explanation will use the U-phase determination unit 61U as an example, and explanations of the V-phase determination unit 61V and the W-phase determination unit 61W will be omitted.

[0049] The U-phase determination unit 61U has the configurations or functions of a subtraction unit 62U, an effective value calculation unit 63U, and a failure determination unit 64U.

[0050] The subtraction unit 62U calculates the U-phase system voltage V from the U-phase second voltage sensor 52U. ｓｕ and the U-phase capacitor voltage V is obtained from the first voltage sensor 51U of the U-phase. ｃｕ The subtraction unit 62U obtains the obtained system voltage V ｓｕ to the capacitor voltage V ｃｕ Subtract the system voltage V ｓｕ and the capacitor voltage V ｃｕ Calculate the differential voltage between

[0051] System voltage V ｓｕ and the capacitor voltage V ｃｕ The differential voltage, which is the difference between the system voltage V and the damping resistor 41U, is a voltage generated by at least one of the damping resistor 41U and the filter reactor 42U in the U-phase filter circuit 37U. ｓｕ and the capacitor voltage V ｃｕBy calculating the differential voltage between the damping resistor 41U and the filter reactor 42U, the circuit component voltage V Ａｕ The subtraction unit 62U recognizes the recognized circuit component voltage V Ａｕ to the effective value calculation unit 63U. The subtraction unit 62U is an example of a "voltage recognition unit."

[0052] The effective value calculation unit 63U calculates the circuit component voltage V Ａｕ The obtained circuit component voltage V Ａｕ A predetermined calculation is performed to obtain the circuit component voltage V Ａｕ The effective value V ＡＲＭＳｕ The effective value calculation unit 63U calculates the calculated circuit component voltage V Ａｕ The effective value V ＡＲＭＳｕ The effective value calculation unit 63U is an example of a "voltage calculation unit" and outputs the circuit component voltage V Ａｕ The effective value V ＡＲＭＳｕ is an example of a "predetermined voltage calculation value."

[0053] The effective value calculation unit 63U has the configuration or functions of a multiplication unit 63aU, a low-pass filter (LPF) 63bU, and a square root calculation unit 63cU. Note that, hereinafter in this specification, the low-pass filter 63bU is also referred to as "LPF 63bU."

[0054] The multiplication unit 63aU receives the circuit component voltage V Ａｕ The obtained circuit component voltage V Ａｕ The circuit component voltage V is the squared value of Ａｕ The squared value of V Ａｕ ２ The multiplication unit 63aU calculates the calculated circuit component voltage V Ａｕ The squared value of V Ａｕ ２ is output to the LPF 63bU.

[0055] The low-pass filter (LPF) 63bU receives the circuit component voltage V Ａｕ The squared value of V Ａｕ ２ and obtain the squared value V Ａｕ２ By filtering the circuit component voltage V Ａｕ The squared value of V Ａｕ ２ Average value of <V Ａｕ ２ The LPF 63bU calculates the average value <V Ａｕ ２ > to the square root calculation unit 63cU. In this specification, angle brackets (<>) may be used as symbols to indicate an average value.

[0056] The square root calculation unit 63cU receives the circuit component voltage V Ａｕ The squared value of V Ａｕ ２ Average value of <V Ａｕ ２ > and the obtained average value <V Ａｕ ２ > Square root √<V Ａｕ ２ >, the circuit component voltage V Ａｕ The effective value V ＡＲＭＳｕ The square root calculation unit 63cU calculates the calculated circuit component voltage V Ａｕ The root mean square of (√<V Ａｕ ２ >) circuit component voltage V Ａｕ The effective value V ＡＲＭＳｕ is output to the failure determination unit 64. Note that the circuit component voltage V Ａｕ The effective value V ＡＲＭＳｕ The method for determining is not limited to the root mean square (RMS) method described above, but may be any other well-known method.

[0057] The fault determination unit 64U receives the circuit component voltage V Ａｕ The effective value V ＡＲＭＳｕ and the fault determination level V of the U-phase filter capacitor 43U is acquired from the storage unit 73 via a system bus or the like (not shown). ｔｈｕ The failure determination unit 64U acquires the circuit component voltage V Ａｕ The effective value V ＡＲＭＳｕ and the U-phase fault determination level V ｔｈｕ and the effective value V ＡＲＭＳｕ than the fault determination level Vｔｈｕ It is determined whether or not is greater.

[0058] That is, for example, when the U-phase filter capacitor 43U has an open circuit fault, the circuit component voltage V Ａｕ The effective value V ＡＲＭＳｕ Therefore, the failure determination unit 64U determines whether the circuit component voltage V Ａｕ The effective value V ＡＲＭＳｕ and fault determination level V ｔｈｕ By comparing the magnitudes of the voltages V and V, it is determined whether or not the U-phase filter capacitor 43U is faulty. ｔｈｕ is, for example, the circuit component voltage V generated by the circuit component when the filter capacitor 43U is normal. Ａｕ The effective value V ＡＲＭＳｕ The effective value V generated when an open fault occurs is smaller than ＡＲＭＳｕ is set to a value greater than

[0059] In addition, the filter capacitor 43U is set to the effective value V ＡＲＭＳｕ The effective value V generated by a circuit component when an open fault occurs ＡＲＭＳｕ may be obtained by actual measurement, or may be obtained by theoretical calculation, simulation, etc. ｔｈｕ may be obtained by actual measurement, or may be obtained by theoretical calculation, simulation, etc. Also, the circuit component voltage V generated by the circuit component of each phase Ａ The effective value V ＡＲＭＳｕ and fault determination level V ｔｈ The fault determination level V may be the same for each phase or may be different for each phase. ｔｈｕ is an example of a "predetermined threshold value."

[0060] The fault determination unit 64U determines the effective value V ＡＲＭＳｕ than the fault determination level V ｔｈｕ is larger, it is determined that the U-phase filter capacitor 43U is faulty. In this case, the fault determination unit 64U outputs “1” to the fault detection unit 71, which indicates that the U-phase filter capacitor 43U is faulty.

[0061] On the other hand, the failure determination unit 64U determines the effective value V ＡＲＭＳｕ than the fault determination level V ｔｈｕ is smaller, the failure determination unit 64U determines that the U-phase filter capacitor 43U is not faulty. In this case, the failure determination unit 64U outputs "0" to the failure detection unit 71, which indicates that the U-phase filter capacitor 43U is not faulty. In this case, the failure determination unit 64U determines that the U-phase filter capacitor 43U is not faulty. ＡＲＭＳｕ than the fault determination level V ｔｈｕ becomes larger and it is determined that the U-phase filter capacitor 43U is faulty. Alternatively, in this case, the fault determination unit 64U may continue to output "0". ＡＲＭＳｕ than the fault determination level V ｔｈｕ becomes larger and it is determined that the U-phase filter capacitor 43U has a fault, there is no need to output anything to the fault detection unit 71.

[0062] As mentioned above, the U-phase determination unit 61U, the V-phase determination unit 61V, and the W-phase determination unit 61W have the same configuration and function, so explanations of the configuration and operation of the V-phase determination unit 61V and the W-phase determination unit 61W will be omitted.

[0063] Fault detection unit 71 acquires the outputs from fault determination unit 64U, fault determination unit 64V, and fault determination unit 64W, and acquires information on whether or not filter capacitor 43 (any of 43U, 43V, and 43W) has failed. Fault detection unit 71 then determines whether or not "1," indicating that filter capacitor 43 (any of 43U, 43V, and 43W) has failed, has been acquired from the output of any of fault determination units 64U, 64V, and 64W.

[0064] When the fault detection unit 71 determines that it has obtained a "1" from the output of any of the fault judgment units 64U, 64V, 64W, indicating that the filter capacitor 43 is faulty, it outputs a "1" to the operation control unit 72, indicating that a fault in the filter capacitor 43 has been detected.

[0065] On the other hand, when the fault detection unit 71 determines that it has not received a "1" from the output of any of the fault determination units 64U, 64V, and 64W, it outputs a "0" to the operation control unit 72, indicating that no fault has been detected in the filter capacitor 43. In this case, the fault detection unit 71 may continue to output a "0" to the operation control unit 72 until it determines that it has received a "1" from any of the fault determination units 64U, 64V, and 64W, indicating that a fault in the filter capacitor 43 has been detected. Alternatively, in this case, the fault detection unit 71 may not output anything to the operation control unit 72 until it determines that it has received a "1" from any of the fault determination units 64U, 64V, and 64W, indicating that a fault in the filter capacitor 43 has been detected.

[0066] The failure determination units 64U, 64V, 64W, and failure detection unit 71 are examples of a "failure determination unit."

[0067] The operation control unit 72 acquires information on whether or not a failure has been detected in the filter capacitor 43 from the failure detection unit 71. For example, when the failure detection unit 71 detects a failure in the filter capacitor 43, the operation control unit 72 acquires from the failure detection unit 71 a "1" indicating that a failure has been detected. On the other hand, for example, when the failure detection unit 71 has not detected a failure in the filter capacitor 43, the operation control unit 72 acquires from the failure detection unit 71 a "0" indicating that no failure has been detected. Note that in this case, the operation control unit 72 does not need to acquire anything in particular from the failure detection unit 71 until it acquires from the failure detection unit 71 a "1" indicating that a failure in the filter capacitor 43 has been detected.

[0068] Furthermore, the operation control unit 72 acquires information on whether the power conversion device 30 is in operation (in grid-connected operation), for example, from an inverter control unit (not shown) or the like. For example, when the power conversion device 30 is in operation, the operation control unit 72 acquires "1" indicating that the power conversion device 30 is in operation from, for example, an inverter control unit (not shown) or the like, and when the power conversion device 30 is not in operation, the operation control unit 72 acquires "0" indicating that the power conversion device 30 is not in operation. Note that in this case, the operation control unit 72 does not need to acquire anything in particular from, for example, the inverter control unit (not shown) or the like until it acquires "1" indicating that the power conversion device 30 is in operation.

[0069] Then, when the operation control unit 72 receives, for example, a "1" from an inverter control unit (not shown) or the like, which indicates that the power conversion device 30 is in operation, it determines whether or not it receives a "1" from the fault detection unit 71, which indicates that a fault in the filter capacitor 43 has been detected.

[0070] When the operation control unit 72 acquires "1" indicating that the power conversion device 30 is in operation, and acquires "1" indicating that a failure of the filter capacitor 43 has been detected, it issues a warning or alarm (failure information) to indicate that the filter capacitor 43 has failed.

[0071] In this case, the operation control unit 72 issues a warning or alarm (fault information) by, for example, outputting a fault display, alarm, lamp, or the like on a display screen or operation panel (not shown) of the power conversion device 30, or by outputting a signal indicating a fault to, for example, a monitoring device or a higher-level device (not shown). The operation control unit 72 is an example of a "warning issuing unit."

[0072] In addition, when the operation control unit 72 acquires "1" indicating that the power conversion device 30 is in operation, and acquires "1" indicating that a failure of the filter capacitor 43 has been detected, it issues an operation instruction to each part of the power conversion device 30 to stop the power conversion device 30.

[0073] In this case, the operation control unit 72 issues an operation instruction to an inverter control unit (not shown) to protectively stop (gate block) the switching operation of the semiconductor switching elements of the inverter 33, turning off all gate signals. As a result, the operation control unit 72 stops the inverter 33 and stops the power conversion device 30. Alternatively, the operation control unit 72 issues an operation instruction to perform a protective operation, such as opening the AC switch 36, thereby opening the AC switch 36 and stopping the power conversion device 30. Alternatively, the operation control unit 72 issues an operation instruction to stop the inverter 33, thereby stopping the inverter 33, and an operation instruction to open the AC switch 36, thereby opening the AC switch 36 and stopping the power conversion device 30.

[0074] The operation control unit 72 (control device 60) may issue a warning or alarm (failure information) indicating that the filter capacitor 43 has failed, and may also issue an operation instruction to each unit of the power conversion device 30 to stop the power conversion device 30. Alternatively, the operation control unit 72 (control device 60) may have either the function of issuing a warning or alarm (failure information) indicating that the filter capacitor 43 has failed, or the function of issuing an operation instruction to each unit of the power conversion device 30 to stop the power conversion device 30.

[0075] Either or both of these functions may be provided by a monitoring device (not shown), a higher-level device, etc. Furthermore, for example, the operation control unit 72 (control device 60) may issue a warning or the like that indicates that the filter capacitor 43 has failed, and may issue an operation instruction to stop the power conversion device 30 when receiving an operation instruction from a monitoring device (not shown), a higher-level device, an operator, etc. that has acquired the warning.

[0076] In addition, when either the information indicating whether the power conversion device 30 is in operation or not and the information indicating whether a fault has been detected in the filter capacitor 43 is "0", the operation control unit 72 does not issue a warning or alarm (fault information) or issue any operation instructions.

[0077] The storage unit 73 is a volatile or non-volatile storage medium such as, for example, a hard disk drive (HDD), a solid state drive (SSD), a dynamic random access memory (DRAM), or other semiconductor memory. The storage unit 73 stores, for example, programs required for the operation of each unit of the control device 60, and various pieces of information are written to and read from the storage unit 73 by each unit of the control device 60. The storage unit 73 stores, for example, values ​​acquired by each sensor such as the first voltage sensor 51 and the second voltage sensor 52, values ​​used for various calculations, and a fault determination level V used by the fault determination unit 64, etc. ｔｈ The values ​​etc. are stored.

[0078] The storage unit 73 is connected to each unit of the control device 60 via, for example, a bus (system bus) not shown. The storage unit 73 may be provided outside the control device 60 and connected to the control device 60 by wire or wirelessly, and may be an external storage medium such as a memory card or a DVD (Digital Versatile Disc), or may be online storage. The storage unit 73 may also be a memory 92 (see FIG. 12 ) described later.

[0079] <Operation and Effect of First Embodiment> As described above, according to the first embodiment shown in FIGS. 1 and 2, the determination unit 61 of each phase determines the capacitor voltage V ｃ and the system voltage V of each phase ｓ Based on this, the circuit component voltage V of each phase Ａ Then, the determination unit 61 for each phase recognizes the recognized circuit component voltage V Ａ Based on this, the circuit component voltage V of each phase Ａ The effective value V ＡＲＭＳ Then, the determination unit 61 for each phase calculates the circuit component voltage V Ａ The effective value V ＡＲＭＳ and a predetermined fault determination level V ｔｈ 1 and 2, the circuit component voltage V of the circuit component of the filter circuit 37 (AC filter) is compared to determine whether or not the filter capacitor 43 of each phase has failed. Ａ and calculate the circuit component voltage V ＡA fault in the filter capacitor 43 is detected by comparing a quantity that is approximately proportional to the magnitude of the circuit component voltage V Ａ The "quantity approximately proportional to the magnitude of" is, for example, an effective value or an absolute value. For example, normally, current flows through the filter circuit 37, and therefore a voltage is generated in each circuit component. However, when the filter capacitor 43 has an open circuit fault and no current flows, no voltage is generated in each circuit component. When no voltage is generated in a circuit component, the circuit component voltage V Ａ Since the amount approximately proportional to the magnitude of the circuit component voltage V Ａ 1 and 2, a fault in the filter capacitor 43 can be detected by comparing a quantity (effective value) that is approximately proportional to the magnitude of the voltage V Ａ Based on this, a failure in the filter capacitor 43 can be detected.

[0080] Furthermore, when the fault detection unit 71 determines that any of the filter capacitors 43 of the three phases (U phase, V phase, W phase) has a fault, it outputs information indicating that the filter capacitor 43 has a fault to the operation control unit 72. Then, when the operation control unit 72 acquires information indicating that the filter capacitor 43 has a fault while the power conversion device 30 is operating, it issues a predetermined operation instruction to the power conversion device 30. As a result, according to the first embodiment shown in Figures 1 and 2, it is possible to suppress the leakage of harmonics to the grid 20 side and the spread of the fault to normal filter capacitors 43.

[0081] <First Modification of First Embodiment> Fig. 3 is a diagram showing a configuration example of a power conversion system 1A according to a first modification of Embodiment 1. In the first modification of the first embodiment, the same or similar components as those in the embodiment shown in Figs. 1 and 2 are denoted by the same reference numerals, and detailed description thereof will be omitted or simplified.

[0082] The configuration of the power conversion system 1A (power conversion device 30A) shown in Fig. 3 is substantially the same as that of the power conversion system 1 (power conversion device 30) shown in Fig. 1, but some configuration has been changed. In the power conversion system 1A (power conversion device 30A), the second voltage sensor 52 is removed and a third voltage sensor 53 is provided.

[0083] The third voltage sensors 53 (53U, 53V, 53W) are, for example, known AC voltmeters or AC voltage sensors, and are arranged between the inverter 33 and the AC switch 36 in the AC circuit 34. The third voltage sensors 53 detect three-phase inverter voltage V ｓ２ｕ , V ｓ２ｖ , V ｓ２ｗ are detected respectively.

[0084] The position where the third voltage sensor 53 is disposed is not limited to the position shown in FIG. 3, and the inverter voltage V ｓ２ｕ , V ｓ２ｖ , V ｓ２ｗ The inverter voltage V detected by the third voltage sensor 53 may be detected at any position. ｓ２ｕ , V ｓ２ｖ , V ｓ２ｗ is acquired by the control device 60A.

[0085] Fig. 4 is a diagram showing an example of the control configuration of the control device 60A in the power conversion system 1A shown in Fig. 3. The configuration of the control device 60A shown in Fig. 4 is substantially the same as that of the control device 60 shown in Fig. 2, but each determination unit 61A has the configuration or function of a subtraction unit 62A instead of the subtraction unit 62. The subtraction unit 62AU of the U-phase determination unit 61AU will be described below. Note that the control device 60A is an example of a "device" and may be a monitoring device (not shown) or the like, similar to the control device 60 shown in Fig. 2.

[0086] The subtraction unit 62AU calculates the U-phase inverter voltage V from the U-phase third voltage sensor 53U. ｓ２ｕ and the U-phase capacitor voltage V is obtained from the first voltage sensor 51U of the U-phase. ｃｕ The subtraction unit 62AU obtains the obtained inverter voltage V ｓ２ｕ to the capacitor voltage Vｃｕ is subtracted, and the inverter voltage V ｓ２ｕ and the capacitor voltage V ｃｕ Calculate the differential voltage between

[0087] As a result, the subtraction unit 62AU calculates the inverter voltage V ｓ２ｕ and the capacitor voltage V ｃｕ By calculating the differential voltage between the filter circuit 37U and the circuit component voltage V Ａｕ The subtraction unit 62AU recognizes the recognized circuit component voltage V Ａｕ to the effective value calculation unit 63U. The subtraction unit 62AU is an example of a "voltage recognition unit."

[0088] As described above, in the first modification of the first embodiment shown in FIGS. 3 and 4, the subtraction unit 62AU calculates the inverter voltage V ｓ２ｕ and the capacitor voltage V ｃｕ By calculating the differential voltage between Ａｕ As a result, according to the first modification of the first embodiment shown in Figures 3 and 4, it is possible to achieve the same effects as those of the embodiment shown in Figures 1 and 2.

[0089] <Second Modification of First Embodiment> Fig. 5 is a diagram showing a configuration example of a power conversion system 1B according to a second modification of the first embodiment. Note that in the second modification of the first embodiment, the same reference numerals are used for the same or similar configurations as those in the embodiment shown in Figs. 1 to 4, and detailed descriptions thereof will be omitted or simplified.

[0090] The configuration of the power conversion system 1B (power conversion device 30B) shown in Fig. 5 is substantially the same as that of the power conversion system 1 (power conversion device 30) shown in Fig. 1, but some configuration changes have been made. In the power conversion system 1B (power conversion device 30B), the first voltage sensor 51 and the second voltage sensor 52 are removed, and a fourth voltage sensor 54 is provided.

[0091] The fourth voltage sensor 54 (54U, 54V, 54W) is, for example, a known AC voltmeter or AC voltage sensor, and detects the voltage V across the damping resistor 41 in the filter circuit 37. ｒThe fourth voltage sensor 54 is disposed at a position where it can detect the voltage V across the damping resistor 41 in the filter circuit 37. ｒｕ , V ｒｖ , V ｒｗ are detected respectively.

[0092] The position of the fourth voltage sensor 54 is not limited to the position shown in FIG. 5, and the voltage V ｒｕ , V ｒｖ , V ｒｗ The voltage V across the damping resistor 41 detected by the fourth voltage sensor 54 may be detected at any position. ｒｕ , V ｒｖ , V ｒｗ is acquired by the control device 60B. The fourth voltage sensor 54 may detect the voltages across the damping resistor 41 and the filter reactor 42.

[0093] Fig. 6 is a diagram showing an example of the control configuration of a control device 60B in the power conversion system 1B shown in Fig. 5. The configuration of the control device 60B shown in Fig. 6 is substantially the same as that of the control device 60 shown in Fig. 2, but each determination unit 61B has the configuration or function of a voltage recognition unit 62B instead of the subtraction unit 62. The voltage recognition unit 62BU of the U-phase determination unit 61BU will be described below. Note that the control device 60B is an example of a "device" and may be a monitoring device (not shown) or the like, similar to the control device 60 shown in Fig. 2.

[0094] The voltage recognition unit 62BU detects the voltage V across the U-phase damping resistor 41 from the U-phase fourth voltage sensor 54U. ｒｕ The voltage recognition unit 62BU acquires the acquired voltage V across the damping resistor 41U. ｒｕ Based on this, the circuit component voltage V Ａｕ Recognize.

[0095] For example, when only the damping resistor 41U is arranged as a circuit component of the filter circuit 37U, the voltage recognition unit 62BU recognizes the acquired voltage V across the damping resistor 41U. ｒｕ the circuit component voltage V ＡｕIn addition, for example, when circuit components other than the damping resistor 41U are arranged as circuit components of the filter circuit 37U, the voltage recognition unit 62BU may recognize the acquired voltage V across the damping resistor 41U as ｒｕ By performing a predetermined calculation on the circuit component voltage V Ａｕ The voltage recognition unit 62BU may recognize the recognized circuit component voltage V Ａｕ to the effective value calculation unit 63U. The voltage recognition unit 62BU is an example of a "voltage recognition unit."

[0096] As described above, in the second modification of the first embodiment shown in FIGS. 5 and 6, the voltage recognition unit 62BU detects the voltage V across the damping resistor 41U. ｒｕ Based on this, the circuit component voltage V Ａｕ As a result, according to the second modification of the first embodiment shown in Figures 5 and 6, it is possible to achieve the same effects as those of the embodiment shown in Figures 1 to 4.

[0097] <Third Modification of First Embodiment> Fig. 7 is a diagram showing a configuration example of a power conversion system 1C according to a third modification of Embodiment 1. In the third modification of the first embodiment, the same or similar components as those in the embodiment shown in Figs. 1 to 6 are denoted by the same reference numerals, and detailed description thereof will be omitted or simplified.

[0098] The configuration of the power conversion system 1C (power conversion device 30C) shown in Fig. 7 is substantially the same as that of the power conversion system 1 (power conversion device 30) shown in Fig. 1, but some configuration changes have been made. In the power conversion system 1C (power conversion device 30C), the first voltage sensor 51 and the second voltage sensor 52 are removed, and a fifth voltage sensor 55 is provided.

[0099] The fifth voltage sensor 55 (55U, 55V, 55W) is, for example, a known AC voltmeter or AC voltage sensor, and detects the voltage V across the filter reactor 42 in the filter circuit 37. ｒ The fifth voltage sensor 55 is disposed at a position where it can detect the voltage V across the filter reactor 42 in the filter circuit 37. ｌｕ , V ｌｖ , V ｌｗ are detected respectively.

[0100] The position where the fifth voltage sensor 55 is disposed is not limited to the position shown in FIG. 7, and the voltage V ｌｕ , V ｌｖ , V ｌｗ The voltage V across the filter reactor 42 detected by the fifth voltage sensor 55 may be detected at any position. ｌｕ , V ｌｖ , V ｌｗ is acquired by the control device 60C. The fifth voltage sensor 55 may detect the voltages across the damping resistor 41 and the filter reactor 42.

[0101] Fig. 8 is a diagram showing an example of the control configuration of a control device 60C in the power conversion system 1C shown in Fig. 7. The configuration of the control device 60C shown in Fig. 8 is substantially the same as that of the control device 60 shown in Fig. 2, but each determination unit 61C has the configuration or function of a voltage recognition unit 62C instead of the subtraction unit 62. The voltage recognition unit 62CU of the U-phase determination unit 61CU will be described below. Note that the control device 60C is an example of a "device" and may be a monitoring device (not shown) or the like, similar to the control device 60 shown in Fig. 2.

[0102] The voltage recognition unit 62CU detects the voltage V across the U-phase filter reactor 42U from the U-phase fifth voltage sensor 55U. ｌｕ The voltage recognition unit 62CU acquires the acquired voltage V across the filter reactor 42U. ｌｕ Based on this, the circuit component voltage V Ａｕ Recognize.

[0103] For example, when only the filter reactor 42U is arranged as a circuit component of the filter circuit 37U, the voltage recognition unit 62CU recognizes the acquired voltage V across the filter reactor 42U. ｌｕ the circuit component voltage V Ａｕ In addition, for example, when circuit components other than the filter reactor 42U are arranged as circuit components of the filter circuit 37U, the voltage recognition unit 62CU may recognize the voltage V across the filter reactor 42U as ｌｕBy performing a predetermined calculation on the circuit component voltage V Ａｕ The voltage recognition unit 62CU may recognize the recognized circuit component voltage V Ａｕ to the effective value calculation unit 63U. The voltage recognition unit 62CU is an example of a "voltage recognition unit."

[0104] As described above, in the third modification of the first embodiment shown in FIGS. 7 and 8, the voltage recognition unit 62CU recognizes the voltage V ｌｕ Based on this, the circuit component voltage V Ａｕ As a result, according to the third modification of the first embodiment shown in Figures 7 and 8, it is possible to achieve the same effects as those of the embodiment shown in Figures 1 to 6.

[0105] 9 is a diagram showing an example of a control configuration of a control device 60D in a power conversion system 1D according to a second embodiment. Note that in the second embodiment, the same or similar components as those in the embodiment shown in FIGS. 1 to 8 are denoted by the same reference numerals, and detailed descriptions thereof will be omitted or simplified.

[0106] Here, the overall configuration of the power conversion system 1D (power conversion device 30D) in the second embodiment is the same as or similar to the overall configuration of the power conversion system 1 (power conversion device 30) in the first embodiment shown in Fig. 1, so illustration and description of the overall configuration will be omitted. Below, an example of the control configuration of the control device 60D in the power conversion system 1D (power conversion device 30D) according to the second embodiment will be described with reference to Fig. 9.

[0107] The control configuration of the control device 60D shown in FIG. 9 is substantially the same as that of the control device 60 shown in FIG. 2 , but each determination unit 61D has the configuration or function of an absolute value calculation unit 65D instead of the effective value calculation unit 63. Furthermore, each determination unit 61D has the configuration or function of a second fault determination unit 66D inserted between the fault determination unit 64 and the fault detection unit 71. Accordingly, the fault determination unit 64 and the fault detection unit 71 are replaced with a fault determination unit 64D and a fault detection unit 71D. The control device 60D is an example of a "device" and may be a monitoring device (not shown) or the like, similar to the control device 60 shown in FIG. 2 .

[0108] As in the first embodiment, the U-phase determination unit 61DU, the V-phase determination unit 61DV, and the W-phase determination unit 61DW in the second embodiment have the same configurations and functions. Therefore, the following description of the U-phase determination unit 61DU shown in Figure 9 will focus on the differences from the U-phase determination unit 61U shown in Figure 2, and descriptions of the V-phase determination unit 61DV and the W-phase determination unit 61DW will be omitted.

[0109] The absolute value calculation unit 65DU calculates the circuit component voltage V Ａｕ The obtained circuit component voltage V Ａｕ A predetermined known calculation is performed to obtain the circuit component voltage V Ａｕ The absolute value of V ＡＡＢＳｕ The absolute value calculation unit 65DU calculates the calculated circuit component voltage V Ａｕ The absolute value of V ＡＡＢＳｕ The absolute value calculation unit 65DU is an example of a "voltage calculation unit" and outputs the circuit component voltage V Ａｕ The absolute value of V ＡＡＢＳｕ is an example of a "predetermined voltage calculation value."

[0110] The fault determination unit 64DU receives the circuit component voltage V Ａｕ The absolute value of V ＡＡＢＳｕ and the fault determination level V of the U-phase filter capacitor 43U is acquired from the storage unit 73 via a system bus or the like (not shown). ｔｈｕ The failure determination unit 64DU acquires the circuit component voltage V Ａｕ The absolute value of V ＡＡＢＳｕ and the U-phase fault determination level V ｔｈｕ and are compared to determine the absolute value V ＡＡＢＳｕ than the fault determination level V ｔｈｕ It is determined whether or not is greater.

[0111] The fault determination unit 64DU determines the absolute value V ＡＡＢＳｕ than the fault determination level V ｔｈｕ is larger, it is determined that the U-phase filter capacitor 43U has failed. In this case, the failure determination unit 64DU outputs "1" to the second failure determination unit 66DU, indicating that the U-phase filter capacitor 43U has failed.

[0112] On the other hand, the fault determination unit 64DU determines the absolute value VＡＡＢＳｕ than the fault determination level V ｔｈｕ is smaller, it is determined that the U-phase filter capacitor 43U is not faulty. In this case, the fault determination unit 64DU outputs "0" to the second fault determination unit 66DU, indicating that the U-phase filter capacitor 43U is not faulty. Note that other functions and operations of the fault determination unit 64DU are the same as or similar to those of the fault determination unit 64U, and therefore will not be described here.

[0113] The second failure determination unit 66DU acquires the output from the failure determination unit 64DU and determines whether the output of the failure determination unit 64DU has continuously acquired "1," which indicates that the filter capacitor 43U is faulty, for a predetermined time. Note that the "predetermined time" here is preferably longer than one cycle of the system voltage, such as one second.

[0114] When the second failure determination unit 66DU determines that the filter capacitor 43U has failed when it determines that the output of the failure determination unit 64DU has continuously acquired "1" indicating that the filter capacitor 43U has failed for a predetermined period of time, the second failure determination unit 66DU outputs "1" indicating that the filter capacitor 43U has failed to the failure detection unit 71D.

[0115] On the other hand, the second failure determination unit 66DU determines that the filter capacitor 43U is not faulty in any other cases. That is, when the second failure determination unit 66DU determines that the filter capacitor 43U is faulty, it determines that the filter capacitor 43U is faulty when it determines that it has not continuously acquired "1" indicating that the filter capacitor 43U is faulty from the output of the failure determination unit 64DU for a predetermined time. In this case, the second failure determination unit 66DU outputs "0" indicating that the filter capacitor 43U is not faulty to the failure detection unit 71D. In this case, the second failure determination unit 66DU may continue to output "0" indicating that the filter capacitor 43U is not faulty to the failure detection unit 71D until it determines that it has continuously acquired "1" from the output of the failure determination unit 64DU for a predetermined time. Alternatively, in this case, the second failure determination unit 66DU does not need to output anything to the failure detection unit 71D until it determines that it has continuously obtained "1" from the output of the failure determination unit 64DU for a predetermined period of time.

[0116] The fault detection unit 71D acquires the outputs from the second fault determination units 66DU, 66DV, and 66DW, respectively, and acquires information as to whether or not the filter capacitor 43 (any of 43U, 43V, or 43W) has failed. Then, the fault detection unit 71D determines whether or not the output of any of the second fault determination units 66DU, 66DV, or 66DW has acquired "1," which indicates that the filter capacitor 43 (any of 43U, 43V, or 43W) has failed.

[0117] When the fault detection unit 71D determines that it has obtained a "1" from any of the second fault judgment units 66DU, 66DV, 66DW, indicating that the filter capacitor 43 is faulty, it outputs a "1" to the operation control unit 72, indicating that a fault in the filter capacitor 43 has been detected.

[0118] On the other hand, when the fault detection unit 71D determines that it has not obtained "1" from the output of any of the second fault determination units 66DU, 66DV, 66DW, it outputs "0" to the operation control unit 72, indicating that it has not detected a fault in the filter capacitor 43. Note that other functions and operations of the fault detection unit 71D are the same as or similar to those of the fault detection unit 71, and therefore will not be described here.

[0119] <Operations and Effects of Second Embodiment> As described above, the second embodiment shown in FIG. 9 provides the same operations and effects as the first embodiment shown in FIGS.

[0120] 9, the second failure determination unit 66D does not output "1" indicating that the filter capacitor 43 is faulty to the failure detection unit 71D until it determines that it has continuously obtained "1" from the output of the failure determination unit 64D for a predetermined period of time. As a result, according to the second embodiment shown in FIG. 9, fluctuations in the determination result and erroneous determinations of the failure of the filter capacitor 43 can be suppressed.

[0121] Note that, in the second embodiment shown in Fig. 9, for example, modifications similar to the first to third modifications of the first embodiment shown in Fig. 3 to Fig. 8 can be applied to the position of the voltage sensor, the configuration of the voltage recognition unit (subtraction unit), etc. When these modifications are applied to the second embodiment shown in Fig. 9, the second embodiment shown in Fig. 9 also achieves the same effects as those of these modifications.

[0122] 10 is a diagram showing an example of a control configuration of a control device 60E in a power conversion system 1E according to a third embodiment. In the third embodiment, the same or similar components as those in the embodiments shown in FIGS. 1 to 9 are denoted by the same reference numerals, and detailed descriptions thereof will be omitted or simplified.

[0123] Here, the overall configuration of the power conversion system 1E (power conversion device 30E) in the third embodiment is the same as or similar to the overall configuration of the power conversion system 1 (power conversion device 30) in the first embodiment shown in Fig. 1, so illustration and description of the overall configuration will be omitted. Below, an example of the control configuration of the control device 60E in the power conversion system 1E (power conversion device 30E) according to the third embodiment will be described with reference to Fig. 10.

[0124] The control configuration of the control device 60E shown in FIG. 10 is substantially the same as that of the control device 60 shown in FIG. 2 , but each determination unit 61E has the configuration or function of an absolute value calculation unit 65E instead of the effective value calculation unit 63. Furthermore, each determination unit 61E has the configuration or function of a low-pass filter (LPF) 67E inserted between the absolute value calculation unit 65E and the fault determination unit 64. Accordingly, the fault determination unit 64 is replaced with a fault determination unit 64E. The control device 60E is an example of a "device" and may be a monitoring device (not shown) or the like, similar to the control device 60 shown in FIG. 2 .

[0125] As in the first embodiment, the U-phase determination unit 61EU, the V-phase determination unit 61EV, and the W-phase determination unit 61EW of the third embodiment have the same configurations and functions. Therefore, the following description of the U-phase determination unit 61EU shown in Figure 10 will focus on differences from the U-phase determination unit 61 shown in Figure 2, and descriptions of the V-phase determination unit 61EV and the W-phase determination unit 61EW will be omitted.

[0126] The absolute value calculation unit 65EU, like the absolute value calculation unit 65DU of the second embodiment, receives the circuit component voltage V Ａｕ The obtained circuit component voltage V Ａｕ A predetermined known calculation is performed to obtain the circuit component voltage V Ａｕ The absolute value of V ＡＡＢＳｕ The absolute value calculation unit 65EU calculates the calculated circuit component voltage V Ａｕ The absolute value of V ＡＡＢＳｕ The absolute value calculation unit 65EU is an example of a "voltage calculation unit" and outputs the circuit component voltage V Ａｕ The absolute value of V ＡＡＢＳｕ is an example of a "predetermined voltage calculation value."

[0127] The low-pass filter (LPF) 67EU receives the circuit component voltage V Ａｕ The absolute value of V ＡＡＢＳｕ and obtain the absolute value V ＡＡＢＳｕ By performing filtering by the LPF 67EU, for example, the circuit component voltage V Ａｕ The absolute value of V ＡＡＢＳｕ From the above, the predetermined filtering value V required for the determination ＡＡＢＳｆｕ The LPF 67EU extracts only the extracted filtered value V ＡＡＢＳｆｕ is output to the failure determination unit 64EU.

[0128] The failure determination unit 64EU receives the filtered value V extracted by the LPF 67EU from the LPF 67EU. ＡＡＢＳｆｕ and the fault determination level V of the U-phase filter capacitor 43U is acquired from the storage unit 73 via a system bus or the like (not shown). ｔｈｕ The failure determination unit 64EU obtains the obtained filtered value V ＡＡＢＳｆｕ and the U-phase fault determination level V ｔｈｕ and the filtered value V ＡＡＢＳｆｕ than the fault determination level V ｔｈｕ It is determined whether or not is greater.

[0129] The failure determination unit 64EU determines the filtered value V ＡＡＢＳｆｕ than the fault determination level V ｔｈｕ is larger, it is determined that the U-phase filter capacitor 43U is faulty. In this case, the fault determination unit 64EU outputs "1" to the fault detection unit 71, which indicates that the U-phase filter capacitor 43U is faulty.

[0130] On the other hand, the failure determination unit 64EU determines the filtered value V ＡＡＢＳｆｕ than the fault determination level V ｔｈｕ is smaller, it is determined that the U-phase filter capacitor 43U is not faulty. In this case, the fault determination unit 64EU outputs "0" to the fault detection unit 71, which indicates that the U-phase filter capacitor 43U is not faulty. The LPF 67EU is an example of a "voltage calculation unit" and calculates the filtered value V ＡＡＢＳｆｕis an example of a "predetermined voltage calculation value." Note that other functions and operations of the failure determination unit 64EU are the same as or similar to those of the failure determination unit 64U, and therefore description thereof will be omitted.

[0131] <Operations and Effects of Third Embodiment> As described above, the third embodiment shown in FIG. 10 provides the same operations and effects as the first embodiment shown in FIGS.

[0132] According to the third embodiment shown in FIG. 10, the filtering process is performed by the LPF 67EU, so that, for example, the circuit component voltage V Ａｕ The absolute value of V ＡＡＢＳｕ From the above, the predetermined filtering value V required for the determination ＡＡＢＳｆｕ Then, the fault determination unit 64EU extracts only the filtered value V ＡＡＢＳｆｕ and the U-phase fault determination level V ｔｈｕ and the magnitude of the filter capacitor 43 are compared to determine whether or not there is a failure in the filter capacitor 43. As a result, according to the third embodiment shown in Fig. 10, it is possible to suppress fluctuations in the determination result of the failure determination of the filter capacitor 43, erroneous determination, etc.

[0133] Note that, in the third embodiment shown in Fig. 10 as well, modifications similar to the first to third modifications of the first embodiment shown in Fig. 3 to Fig. 8 can be applied, for example, to the position of the voltage sensor, the configuration of the voltage recognition unit (subtraction unit), etc. When these modifications are applied to the third embodiment shown in Fig. 10, the third embodiment shown in Fig. 10 also achieves the same effects as those of these modifications.

[0134] 11 is a diagram showing an example of a control configuration of a control device 60F in a power conversion system 1F according to a fourth embodiment. In the fourth embodiment, the same or similar components as those in the embodiments shown in FIGS. 1 to 10 are denoted by the same reference numerals, and detailed descriptions thereof will be omitted or simplified.

[0135] Here, the overall configuration of the power conversion system 1F (power conversion device 30F) in the fourth embodiment is the same as or similar to the overall configuration of the power conversion system 1 (power conversion device 30) in the first embodiment shown in Fig. 1, so illustration and description of the overall configuration will be omitted. Below, an example of the control configuration of the control device 60F in the power conversion system 1F (power conversion device 30F) according to the fourth embodiment will be described with reference to Fig. 11.

[0136] The control configuration of the control device 60F shown in Fig. 11 is substantially the same as that of the control device 60 shown in Fig. 2, except that the U-phase determination unit 61U, the V-phase determination unit 61V, and the W-phase determination unit 61W are replaced with a d-axis determination unit 61Fd and a q-axis determination unit 61Fq. The control device 60F also has the configuration or function of a three-phase to two-phase conversion unit 74F. The control device 60F is an example of a "device" and may be a monitoring device (not shown) or the like, similar to the control device 60 shown in Fig. 2.

[0137] The three-phase to two-phase conversion unit (dq conversion unit) 74F is connected to the three-phase first voltage sensors 51U, 51V, 51W via signal lines (not shown) or the like. The three-phase to two-phase conversion unit 74F converts the three-phase capacitor voltages V ｃｕ , V ｃｖ , V ｃｗ Then, the three-phase to two-phase conversion unit 74F obtains the obtained capacitor voltage V ｃｕ , V ｃｖ , V ｃｗ is converted into a three-phase to two-phase (dq conversion) to obtain the d-axis capacitor voltage V ｃｄ and the q-axis capacitor voltage V ｃｑ and asks for.

[0138] The three-phase to two-phase conversion (dq conversion) may be performed by a known method. For example, the three-phase to two-phase conversion unit 74F converts the capacitor voltage V ｃ , the system voltage V ｓ The d-axis capacitor voltage V on the dq coordinate is calculated by dq transformation using a phase angle θ that is synchronized with the frequency of ｃｄ and the q-axis capacitor voltage V ｃｑ Then, the three-phase to two-phase conversion unit 74F calculates the calculated d-axis capacitor voltage V ｃｄ is output to the d-axis determination unit 61Fd, and the calculated q-axis capacitor voltage Vｃｑ is output to the q-axis determination unit 61Fq.

[0139] The three-phase to two-phase converter 74F is also connected to the three-phase second voltage sensors 52U, 52V, and 52W via signal lines (not shown). The three-phase to two-phase converter 74F converts the three-phase system voltage V ｓｕ , V ｓｖ , V ｓｗ Then, the three-phase to two-phase conversion unit 74F obtains the obtained system voltage V ｓｕ , V ｓｖ , V ｓｗ is converted into a three-phase to two-phase voltage (dq conversion), and the d-axis system voltage V ｓｄ and q-axis system voltage V ｓｑ and asks for.

[0140] The three-phase to two-phase conversion (dq conversion) may be performed by a known method. For example, the three-phase to two-phase conversion unit 74F converts the system voltage V ｓ , the system voltage V ｓ The d-axis system voltage V on the dq coordinate is calculated by dq transformation using a phase angle θ that is synchronized with the frequency of ｓｄ and q-axis system voltage V ｓｑ Then, the three-phase to two-phase conversion unit 74F calculates the obtained d-axis system voltage V ｓｄ is output to the d-axis determination unit 61Fd, and the obtained q-axis system voltage V ｓｑ is output to the q-axis determination unit 61Fq.

[0141] The d-axis determination unit 61Fd has the configuration or functions of a subtraction unit 62Fd, an effective value calculation unit 63Fd, and a failure determination unit 64Fd.

[0142] The subtraction unit 62Fd receives the d-axis system voltage V ｓｄ and the d-axis capacitor voltage V ｃｄ The subtraction unit 62Fd obtains the obtained d-axis system voltage V ｓｄ to the d-axis capacitor voltage V ｃｄ is subtracted, and the d-axis system voltage V ｓｄ and the d-axis capacitor voltage V ｃｄ Calculate the differential voltage between

[0143] d-axis system voltage V ｓｄ and the d-axis capacitor voltage Vｃｄ The differential voltage, which is the difference between the d-axis system voltage V and the damping resistor 41U and the filter reactor 42U, is the d-axis voltage generated by at least one of the circuit components in the U-phase filter circuit 37U. ｓｄ and the d-axis capacitor voltage V ｃｄ By calculating the differential voltage between the d-axis voltage value of the voltage generated by the circuit components in the filter circuit 37U and the Ａｄ The subtraction unit 62Fd recognizes the recognized circuit component voltage V Ａｄ to the effective value calculation unit 63Fd. The subtraction unit 62Fd is an example of a "voltage recognition unit."

[0144] The effective value calculation unit 63Fd calculates the circuit component voltage V Ａｄ The obtained circuit component voltage V Ａｄ A predetermined calculation is performed to obtain the circuit component voltage V Ａｄ The effective value V ＡＲＭＳｄ The effective value calculation unit 63Fd calculates the calculated circuit component voltage V Ａｄ The effective value V ＡＲＭＳｄ The effective value calculation unit 63Fd is an example of a "voltage calculation unit" and outputs the circuit component voltage V Ａｄ The effective value V ＡＲＭＳｄ is an example of a "predetermined voltage calculation value."

[0145] The effective value calculation unit 63Fd has the configurations or functions of a multiplication unit 63Fad, a low-pass filter (LPF) 63Fbd, and a square root calculation unit 63Fcd. Note that the functions and operations of the multiplication unit 63Fad, the LPF 63Fbd, and the square root calculation unit 63Fcd in the fourth embodiment are the same as or similar to the multiplication unit 63aU, the LPF 63bU, and the square root calculation unit 63cU in the first embodiment, and therefore will not be described here.

[0146] The fault determination unit 64Fd receives the circuit component voltage V from the effective value calculation unit 63Fd (square root calculation unit 63Fcd). Ａｄ The effective value V ＡＲＭＳｄ and transmits the fault determination level V of the U-phase filter capacitor 43U from the storage unit 73 via a system bus or the like (not shown). ｔｈｄThe failure determination unit 64Fd acquires the circuit component voltage V Ａｄ The effective value V ＡＲＭＳｄ and the d-axis fault determination level V ｔｈｄ and the effective value V ＡＲＭＳｄ than the fault determination level V ｔｈｄ It is determined whether or not is greater.

[0147] The failure determination unit 64Fd determines the effective value V ＡＲＭＳｄ than the fault determination level V ｔｈｄ is larger, it is determined that one of the filter capacitors 43 of the three phases has failed. In this case, the failure determination unit 64Fd outputs "1" to the failure detection unit 71, indicating that the filter capacitor 43 has failed.

[0148] On the other hand, the failure determination unit 64Fd determines the effective value V ＡＲＭＳｄ than the fault determination level V ｔｈｄ is smaller, it is determined that none of the three-phase filter capacitors 43U is faulty. In this case, the fault determination unit 64Fd outputs "0" to the fault detection unit 71, indicating that none of the filter capacitors 43U is faulty. Note that other functions and operations of the fault determination unit 64Fd are the same as or similar to those of the fault determination unit 64, and therefore will not be described here.

[0149] In addition, since the d-axis determination unit 61Fd and the q-axis determination unit 61Fq of the fourth embodiment have the same configuration or function, a description of the q-axis determination unit 61Fq will be omitted.

[0150] The fault detection unit 71F acquires the outputs from the fault determination unit 64Fd and the fault determination unit 64Fq, and acquires information on whether or not the filter capacitor 43 (43U, 43V, or 43W) has failed. The fault detection unit 71F then determines whether or not the output of either the fault determination unit 64Fd or the fault determination unit 64Fq has acquired "1," which indicates that the filter capacitor 43 (43U, 43V, or 43W) has failed.

[0151] When the fault detection unit 71F determines that it has obtained a "1" from the output of either the fault judgment unit 64Fd or 64Fq, indicating that the filter capacitor 43 is faulty, it outputs a "1" to the operation control unit 72, indicating that a fault in the filter capacitor 43 has been detected.

[0152] On the other hand, when the fault detection unit 71F determines that it has not obtained "1" from the output of either of the fault determination units 64Fd, 64Fq, it outputs "0" to the operation control unit 72, indicating that it has not detected a fault in the filter capacitor 43. Note that other functions and operations of the fault detection unit 71F are the same as or similar to those of the fault detection unit 71, and therefore will not be described here.

[0153] The failure determination unit 64Fd, the failure determination unit 64Fq, and the failure detection unit 71F are examples of a "failure determination unit."

[0154] <Operations and Effects of Fourth Embodiment> As described above, the fourth embodiment shown in FIG. 11 provides the same operations and effects as the first embodiment shown in FIGS.

[0155] Furthermore, according to the fourth embodiment shown in FIG. 11, a failure in the filter capacitor 43 can be detected based on the dq coordinate system, not the stationary coordinate system.

[0156] Note that, in the fourth embodiment shown in Fig. 11 as well, modifications similar to the first to third modifications of the first embodiment shown in Fig. 3 to Fig. 8 can be applied, for example, to the position of the voltage sensor, the configuration of the voltage recognition unit (subtraction unit), etc. When these modifications are applied to the fourth embodiment shown in Fig. 11, the fourth embodiment shown in Fig. 11 also achieves the same effects as those of these modifications.

[0157] <Hardware Configuration Example> Fig. 12 is a conceptual diagram showing an example of the hardware configuration of a processing circuit 90 included in the control devices 60, 60A, 60B, 60C, 60D, 60E, and 60F (hereinafter referred to as "control devices 60, etc.") in the embodiment shown in Figs. 1 to 11. Each of the functions described above is realized by the processing circuit 90. In one aspect, the processing circuit 90 includes at least one processor 91 and at least one memory 92. In another aspect, the processing circuit 90 includes at least one dedicated hardware 93.

[0158] When the processing circuit 90 includes a processor 91 and a memory 92, each function is realized by software, firmware, or a combination of software and firmware. At least one of the software and firmware is written as a program. At least one of the software and firmware is stored in the memory 92. The processor 91 realizes each function by reading and executing the program stored in the memory 92.

[0159] When the processing circuitry 90 includes dedicated hardware 93, the processing circuitry 90 may be, for example, a single circuit, multiple circuits, a programmed processor, or a combination thereof. Each function is implemented by the processing circuitry 90.

[0160] Each function of the control device 60 etc. may be partially or entirely configured by hardware, or may be configured as a program executed by a processor. That is, the control device 60 etc. can also be realized by a computer and a program, and the program can be stored in a storage medium or provided via a network.

[0161] <Supplementary Notes on the Embodiments> As described above, the embodiments shown in Figures 1 to 12 are divided into the first embodiment and its modified example shown in Figures 1 to 8, the second embodiment shown in Figure 9, the third embodiment shown in Figure 10, and the fourth embodiment shown in Figure 11, but are not limited to this. A plurality of these embodiments may be combined in series or in parallel. Even the combined embodiments can achieve the same effects as the respective embodiments before being combined.

[0162] It should be noted that the combinations of the various configurations disclosed herein are not limited to the combinations shown in the embodiments illustrated in FIGS.

[0163] Fig. 13 is a diagram showing an example of a combination of the components of the present disclosure. The combination of the components of the present disclosure is not limited to the combinations shown in the embodiments of Figs. 1 to 11, and may be any combination of the components shown in Fig. 13.

[0164] For example, the entity that performs the fault detection and the action that is taken after the fault detection may be a control device that issues a fault report or stops the power conversion device, or a monitoring device that issues a fault report.

[0165] The voltage for fault detection may be a measurement of the capacitor voltage and the voltage on the system side of the AC switch, or a measurement of the capacitor voltage and the voltage on the inverter side of the AC switch, or a measurement of the voltage across a damping resistor or a measurement of the voltage across a filter reactor.

[0166] The number of phases of the AC output of the power conversion device may be single-phase or three-phase.

[0167] Furthermore, the voltage (calculated voltage value) compared with the predetermined threshold value may be a raw voltage value, a voltage value that has been subjected to a low-pass filter, an effective value, or an amplitude value of the fundamental wave component.

[0168] Furthermore, the coordinate system for calculating the voltage (calculated voltage value) to be compared with the predetermined threshold value may be either a stationary coordinate system or a dq coordinate system.

[0169] Furthermore, the coordinate system used for comparison with the predetermined threshold value may be a stationary coordinate system or a dq coordinate system.

[0170] Furthermore, what is connected to the AC side of the power conversion device may be a power system or a load.

[0171] As described above, any combination of the configurations shown in FIG. 13 can achieve the same effects as those achieved by the embodiments shown in FIGS.

[0172] 1 to 12, the power conversion systems 1 to 1F (power conversion devices 30 to 30F) and the control devices 60 to 60F included therein have been described as examples of one aspect of the present disclosure, but the present disclosure is not limited thereto. The present disclosure can also be realized as a fault detection method for a filter capacitor 43 in which processing steps are performed in each part of the control device 60, etc.

[0173] The present disclosure can also be realized as a fault detection program for the filter capacitor 43 that causes a computer to execute processing steps in each part of the control device 60 and the like.

[0174] The present disclosure can also be realized as a storage medium (non-transitory computer-readable storage medium) storing a fault detection program for the filter capacitor 43. The fault detection program for the filter capacitor 43 can be stored and distributed on removable media such as a CD (Compact Disc), a DVD (Digital Versatile Disc), or a USB (Universal Serial Bus) memory. The fault detection program for the filter capacitor 43 may be uploaded to a network via a network interface (not shown) included in the control device 60 or the like, or may be downloaded from the network and stored in the storage unit 73 or the like.

[0175] The features and advantages of the embodiments will be apparent from the above detailed description. It is intended that the claims encompass the features and advantages of the above-described embodiments without departing from the spirit and scope of the claims. Furthermore, any improvements and modifications will be readily apparent to those skilled in the art. Therefore, it is not intended that the scope of the inventive embodiments be limited to the above-described embodiments, and appropriate improvements and equivalents within the scope of the disclosed embodiments may be utilized.

[0176] 1, 1A, 1B, 1C, 1D, 1E, 1F... Power conversion system (PCS: Power Conditioning System); 10... Solar cell (PV: Photovoltaics); 20... AC power system (system, load); 30, 30A, 30B, 30C, 30D, 30E, 30F,... Power conversion device; 31... DC bus; 32... DC capacitor (DC capacitor); 33... Inverter circuit (inverter); 34... AC circuit; 34a... Branch point; 35... AC reactor (AC reactor); 36... AC switch (AC switch); 37, 37U, 37V, 37W... Filter circuit; 41, 41U, 41V, 41W... Damping resistor; 42, 4 2U, 42V, 42W... Filter reactor; 43, 43U, 43V, 43W... Filter capacitor; 51, 51U, 51V, 51W... First voltage sensor; 52, 52U, 52V, 52W... Second voltage sensor; 53, 53U, 53V, 53W... Third voltage sensor; 54, 54U, 54V, 54W... Fourth voltage sensor; 55, 55U, 55V, 55W... Fifth voltage sensor; 60, 60A, 60B, 60C, 60D, 60E, 60F... Control device (monitoring device, device); 61, 61A, 61B, 61C, 61D, 61E, 61F... Determination unit; 6 1U, 61AU, 61BU, 61CU, 61DU, 61EU...U-phase determination unit; 61V, 61AV, 61BV, 61CV, 61DV, 61EV...V-phase determination unit; 61W, 61AW, 61BW, 61CW, 61DW, 61EW...W-phase determination unit; 61Fd...d-axis determination unit; 61Fq...q-axis determination unit; 62, 62U, 62V, 62W...subtraction unit (voltage recognition unit); 62A, 62AU, 62AV, 62AW...subtraction unit (voltage recognition unit); 62B, 62BU, 62BV, 62BW...voltage recognition unit; 62C, 62CU, 62CV, 62CW...voltage recognition unit; 62F, 62Fd, 62Fq... subtraction unit (voltage recognition unit); 63, 63U, 63V, 63W... effective value calculation unit (voltage calculation unit); 63F, 63Fd, 63Fq... effective value calculation unit (voltage calculation unit); 63a, 63aU, 63aV, 63aW... multiplication unit; 63b, 63bU, 63bV, 63bW... low-pass filter (LPF); 63c, 63cU, 63cV, 63cW... square root calculation unit; 63Fa, 63Fad, 63Faq... multiplication unit; 63Fb, 63Fbd, 63Fbq... low-pass filter (LPF); 63Fc, 63Fcd, 63Fcq... square root calculation unit;64, 64U, 64V, 64W...Fault determination unit; 64D, 64DU, 64DV, 64DW...Fault determination unit; 64E, 64EU, 64EV, 64EW...Fault determination unit; 64F, 64Fd, 64Fq...Fault determination unit; 65D, 65DU, 65DV, 65DW...Absolute value calculation unit (voltage calculation unit); 65E, 65EU, 65EV, 65EW...Absolute value calculation unit (voltage calculation unit); 66D, 66DU, 66DV, 66DW...Second fault determination unit (fault determination unit); 71, 71D, 71F...Fault detection unit (fault determination unit); 72...Operation control unit; 73...Storage unit; 74F...Three-phase to two-phase conversion unit (dq conversion unit); 90...Processing circuit; 91...Processor; 92...Memory; 93...Hardware; V; Ａ , V Ａｕ , V Ａｖ , V Ａｗ , V Ａｄ , V Ａｑ ...circuit component voltage; V ＡＡＢＳｆ , V ＡＡＢＳｆｕ , V ＡＡＢＳｆｖ , V ＡＡＢＳｆｗ ...filtered value (predetermined voltage calculation value); V ＡＡＢＳ , V ＡＡＢＳｕ , V ＡＡＢＳｖ , V ＡＡＢＳｗ ...absolute value (predetermined voltage calculation value); V ＡＲＭＳ , V ＡＲＭＳｕ , V ＡＲＭＳｖ , V ＡＲＭＳｗ , V ＡＲＭＳｄ , V ＡＲＭＳｑ ...effective value (predetermined voltage calculation value); V ｃ , V ｃｕ , V ｃｖ , V ｃｗ ...capacitor voltage; V ｃｄ ...d-axis capacitor voltage; V ｃｑ ...q-axis capacitor voltage; V ｌ , V ｌｕ , V ｌｖ , V ｌｗ ...Voltage across both ends; V ｒ , V ｒｕ , V ｒｖ , V ｒｗ ...Voltage across both ends; V ｓ , V ｓｕ , V ｓｖ , V ｓｗ ...System voltage; V ｓｄ ...d-axis system voltage; V ｓｑ ...q-axis system voltage; Vｓ２ , V ｓ２ｕ , V ｓ２ｖ , V ｓ２ｗ ... inverter voltage; V ｔｈ , V ｔｈｕ , V ｔｈｖ , V ｔｈｗ , V ｔｈｄ , V ｔｈｑ …fault determination level (predetermined threshold value); θ…phase angle

Claims

1. A power conversion system comprising: a power conversion device having: an inverter that converts electric power and outputs AC power; and a filter circuit that is provided on the AC output side of the inverter and has in series connected thereto a circuit component having at least one of a damping resistor and a filter reactor, and an AC capacitor that is disconnected from the circuit in the event of a fault; and a voltage recognition unit that recognizes a voltage value of a voltage generated by the circuit component; a voltage calculation unit that calculates a predetermined voltage calculation value based on the voltage value of the voltage generated by the circuit component recognized by the voltage recognition unit; a failure determination unit that compares the voltage calculation value calculated by the voltage calculation unit with a predetermined threshold value and determines that the AC capacitor has failed when the voltage calculation value is smaller than the predetermined threshold; and an operation control unit that stops the power conversion device when it is determined by the failure determination unit that the AC capacitor has failed during operation of the power conversion device.

2. A power conversion system comprising: a power conversion device having: an inverter that converts electric power and outputs AC power; and a filter circuit that is provided on the AC output side of the inverter and has in series connected thereto a circuit component having at least one of a damping resistor and a filter reactor, and an AC capacitor that is disconnected from the circuit in the event of a fault; and a device having: a voltage recognition unit that recognizes a voltage value of a voltage generated by the circuit component; a voltage calculation unit that calculates a predetermined voltage calculation value based on the voltage value of the voltage generated by the circuit component recognized by the voltage recognition unit; a failure determination unit that compares the voltage calculation value calculated by the voltage calculation unit with a predetermined threshold value and determines that the AC capacitor has failed when the voltage calculation value is smaller than the predetermined threshold; and a warning issuance unit that issues a warning to the effect that the AC capacitor has failed when the failure determination unit determines that the AC capacitor has failed during operation of the power conversion device.

3. A power conversion system according to claim 1 or 2, wherein the voltage recognition unit acquires a capacitor voltage value, which is the voltage value of the AC capacitor, and a system voltage value, which is the voltage value on the system side of an AC switch arranged on the AC output side, and calculates the difference between the capacitor voltage value and the system voltage value, thereby recognizing the voltage value of the voltage generated by the circuit component.

4. A power conversion system according to claim 1 or 2, wherein the voltage recognition unit acquires a capacitor voltage value, which is the voltage value of the AC capacitor, and an inverter voltage value, which is the voltage value on the inverter side of an AC switch arranged on the AC output side, and calculates the difference between the capacitor voltage value and the inverter voltage value, thereby recognizing the voltage value of the voltage generated by the circuit component.

5. A power conversion system according to claim 1 or 2, wherein the circuit components include at least the damping resistor, and the voltage recognition unit recognizes the voltage value of the voltage generated by the circuit components by acquiring the voltage across the damping resistor.

6. A power conversion system according to claim 1 or 2, wherein the circuit components include at least the filter reactor, and the voltage recognition unit recognizes the voltage value of the voltage generated by the circuit components by acquiring the voltage across the filter reactor.