Control device and power conversion device

Abstract

A control device of a power conversion device having at least one AC capacitor arranged in a capacitor circuit branched from an AC circuit on an output side of an inverter, which is cut off from the circuit at the time of a fault, and a current sensor arranged in the capacitor circuit, which respectively acquires current values of AC currents flowing into respective phases of the AC capacitor, includes an amplitude calculation section that respectively acquires the current values of the AC currents flowing into the respective phases of the AC capacitor from the current sensor, and calculates values of amplitudes of fundamental components of the AC currents of the respective phases based on the acquired current values of the AC currents of the respective phases, and a fault determination section that respectively compares the values of the amplitudes of the fundamental components of the AC currents of the respective phases calculated by the amplitude calculation section with a prescribed determination value, and determines a fault of the AC capacitor when at least an amplitude value of a certain one of the values of the amplitudes of the fundamental components of the AC currents of the respective phases is smaller than the prescribed determination value.

Description

Technical Field

[0001] This invention relates to control devices and power conversion devices. Background Technology

[0002] Previously, there were known power conversion devices that performed voltage matching operation before starting grid-connected operation (before the AC switch was turned on) and then started grid-connected operation (when the AC switch was turned on) (for example, see Patent Document 1).

[0003] Voltage matching operation is a control mechanism that synchronizes the output voltage of a power conversion device with the system voltage before grid-connected operation begins. This is achieved, for example, by matching the amplitude and phase of the AC output voltage of the power conversion device with the amplitude and phase of the system voltage. Voltage matching operation is performed, for example, by an alternating current-automatic voltage regulator (AC-AVR). Hereinafter, in this specification, voltage matching operation will also be referred to as "synchronization control".

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2017-212838 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] Furthermore, capacitors used as filters in the AC output of power conversion devices have structures with fuses that disconnect the capacitor elements from the circuit in case of abnormal overheating. When this fuse operates, the AC capacitor becomes open-circuit faulty. In such cases, the fault is typically detected as a synchronization mismatch during voltage matching operation in the power conversion device.

[0009] However, in conventional power conversion systems, there have been instances where an open-circuit fault occurred in the AC capacitor, but the fault was not detected during voltage matching operation. In such cases, the power conversion system would sometimes start grid-connected operation after voltage matching, and then continue operation without further fault detection. Operating with an open-circuit fault in the AC capacitor can cause significant harmonic flows to the system side. Furthermore, because the voltage application is concentrated on the normal AC capacitor, the fault could potentially spread to the normal AC capacitor.

[0010] Therefore, the purpose of this disclosure is to detect faults based on the current components flowing into each phase of the AC capacitor, report fault information and stop the power conversion device, suppress the outflow of harmonics to the system side and the spread of faults to normal AC capacitors.

[0011] Methods used to solve problems

[0012] A control device for a power conversion device includes: at least one AC capacitor disposed in a capacitor circuit branching from the AC circuit on the output side of an inverter, which is disconnected from the circuit in case of a fault; and a current sensor disposed in the capacitor circuit, which acquires the current value of the AC current flowing into each phase of the AC capacitor; characterized in that the control device includes: an amplitude calculation unit that acquires the current value of the AC current flowing into each phase of the AC capacitor from the current sensor, and calculates the amplitude value of the fundamental component of the AC current of each phase based on the acquired current value of the AC current of each phase; and a fault determination unit that compares the amplitude value of the fundamental component of the AC current of each phase calculated by the amplitude calculation unit with a predetermined determination value, and determines that the AC capacitor is faulty when the amplitude value of at least one phase of the fundamental component of the AC current of each phase is smaller than the predetermined determination value.

[0013] In addition, in the control device of a certain technical solution, the amplitude calculation unit can also calculate the amplitude value of the fundamental component of the AC current of each phase based on the predetermined current component of the AC current of each phase, which is calculated by multiplying the current value of the AC current of each phase by the phase angle value after adjusting the system voltage on the system side.

[0014] Furthermore, in the control device of a certain technical solution, the amplitude calculation unit can also calculate the amplitude value of the fundamental component of the alternating current of each phase based on the DC component extracted from the specified current component of the alternating current of each phase using a specified low-pass filter.

[0015] Furthermore, in the control device of the relevant technical solution, there may also be an operation control unit. When the inverter is connected to the system side and the AC switch is turned on, the operation control unit outputs an operation instruction to stop the power conversion device and disconnect the AC switch when the fault determination unit determines that the AC capacitor is faulty.

[0016] Furthermore, in the control device of the relevant technical solution, there may also be an operation control unit. When the AC switch on the system side is disconnected and the power conversion device is started, the operation control unit performs synchronization control to synchronize the output voltage of the inverter with the system voltage on the system side. When the fault determination unit determines that the AC capacitor is faulty, it outputs an operation instruction to stop the power conversion device.

[0017] A power conversion device according to a technical solution is characterized by comprising: an inverter for converting power to output AC power; at least one AC capacitor provided in a capacitor circuit branching from the AC circuit on the output side of the inverter, which is disconnected from the circuit in case of a fault; a current sensor provided in the capacitor circuit for acquiring the current value of the AC current flowing into each phase of the AC capacitor; an AC switch provided in the AC circuit closer to the system side than the branch point of the capacitor circuit, capable of cutting off the AC current flowing toward the system side; and a control device as described in any one of the above.

[0018] Another control device related to the technical solution is a control device for a power conversion device, which includes: at least one AC capacitor disposed in a capacitor circuit branching from the AC circuit on the output side of the inverter, and disconnected from the circuit in case of a fault; and a current sensor disposed in series with an AC reactor in the AC circuit on the output side of the inverter between the inverter and the branch point to the capacitor circuit, respectively acquiring the current value of the AC current flowing into each phase of the AC circuit; characterized in that the control device includes: an amplitude calculation unit, which calculates the output voltage of the inverter and the system voltage on the system side when the AC switch on the system side is open during the start-up of the power conversion device. During synchronous control, the current values ​​of the AC current flowing into the AC capacitor for each phase are obtained from the current sensor. Based on the obtained current values ​​of the AC current for each phase, the amplitude of the fundamental component of the AC current for each phase is calculated. The fault determination unit compares the amplitude values ​​of the fundamental component of the AC current for each phase calculated by the amplitude calculation unit with a predetermined determination value. If the amplitude value of at least one phase is smaller than the predetermined determination value, the AC capacitor is determined to be faulty. The fault information reporting unit reports the AC capacitor fault information when the fault determination unit determines that the AC capacitor is faulty during synchronous control.

[0019] In another technical solution, the amplitude calculation unit can calculate the amplitude value of the fundamental component of the alternating current of each phase based on the predetermined current component of the alternating current of each phase, which is calculated by multiplying the current value of the alternating current of each phase by the phase angle value adjusted according to the system voltage on the system side.

[0020] Furthermore, in a control device for another technical solution, the amplitude calculation unit calculates the amplitude value of the fundamental component of the alternating current of each phase based on the DC component extracted from the specified current component of the alternating current of each phase using a specified low-pass filter.

[0021] In addition, in the control device of another technical solution, there may also be an action control unit, which outputs an action instruction to stop the power conversion device when the fault information reporting unit reports a fault in the AC capacitor during the above-mentioned synchronous control.

[0022] Another power conversion device is characterized by comprising: an inverter that converts power to output AC power; at least one AC capacitor provided in a capacitor circuit branching off from the AC circuit on the output side of the inverter, which is disconnected from the circuit in case of a fault; a current sensor disposed in series with an AC reactor in the AC circuit on the output side of the inverter between the inverter and the branch point to the capacitor circuit, which respectively obtains the current value of the AC current flowing into each phase of the AC circuit; an AC switch disposed in the AC circuit closer to the system side than the branch point, which is capable of cutting off the AC current flowing toward the system side; and a control device as described in any one of the above.

[0023] Invention Effects

[0024] According to this disclosure, by detecting faults based on the current components flowing into each phase of the AC capacitor, it is possible to report fault information and stop the power conversion device, suppress the outflow of harmonics to the system side and the spread of faults to normal AC capacitors. Attached Figure Description

[0025] Figure 1 This is a diagram illustrating an example of the structure of the control device and power conversion device according to the first embodiment.

[0026] Figure 2 Is Figure 1 The diagram shows an example of the actual connection configuration of an AC capacitor in a power conversion device.

[0027] Figure 3 It means Figure 1 and Figure 2 A diagram showing an example of the structure of the control device in a power conversion device.

[0028] Figure 4 It means Figures 1 to 3 The diagram shows an example of a fault detection action of the control device.

[0029] Figure 5 It is a schematic representation of... Figure 1 and Figure 2The diagram shows the state of an open-circuit fault in the AC capacitor between U and V in the Δ-type connection.

[0030] Figure 6 It means Figure 5 The diagram shows the simulated waveforms of the capacitor current in each phase under the given conditions.

[0031] Figure 7 It means Figures 1 to 6 The diagram shows an example of the operation of a power conversion device after the start command is input.

[0032] Figure 8 It means Figures 1 to 6 The diagram shows an example of the operation of the inverter in a power conversion device during grid-connected operation.

[0033] Figure 9 This is a diagram illustrating an example of the structure of the control device and power conversion device according to the second embodiment.

[0034] Figure 10 It means Figure 9 A diagram showing an example of the structure of the control device in a power conversion device.

[0035] Figure 11 It means Figure 9 and Figure 10 The diagram shows an example of a fault detection action of the control device.

[0036] Figure 12 It means Figures 9 to 11 The diagram shows an example of the operation of a power conversion device in voltage matching (synchronous control) mode.

[0037] Figure 13 It means Figures 1 to 12 The diagram shows a conceptual example of the hardware structure of the processing circuit of the control device in the embodiment shown. Detailed Implementation

[0038] Hereinafter, embodiments of the control device and power conversion device of this disclosure will be described with reference to the accompanying drawings.

[0039] <Structure of the First Embodiment>

[0040] Figure 1 This is a diagram illustrating an example of the structure of the control device 30 and the power conversion device 1 according to the first embodiment. (See diagram for example.) Figure 1 As shown, power conversion device 1 in Figure 1 One end on the left side is connected to DC power supply 2. Figure 1 The other end (output side) on the right side is connected to AC power system 3 (hereinafter also referred to as "system 3").

[0041] The power conversion device (PCS) 1, for example, converts the DC power supplied from the DC power source 2 into AC power, and outputs the converted AC power to the system 3. However, the power conversion device 1 is not limited to a device that converts DC power to AC power; it can also be a device that converts AC power to AC power. Furthermore, the power conversion device 1 can also be a power conversion device (PV-PCS: Photovoltaics-Power Conditioning System) for solar power generation (PV). Additionally, the power conversion device 1 can also be a power conversion device (ESS-PCS: Energy Storage System-Power Conditioning System) for a battery (ESS). Hereinafter, the power conversion device 1 will also be referred to as "PCS1".

[0042] DC power supply 2 is connected to one end of power conversion device 1, supplying DC power to power conversion device 1 via that end. DC power supply 2 can be, for example, a solar power generation device (PV) with solar panels or an energy storage battery (ESS), or a DC power system consisting of a wind turbine and an AC-DC converter. Furthermore, the connection to one end of power conversion device 1 is not limited to DC power supply 2; if power conversion device 1 is a device that converts AC power to AC power, it can also be an AC power source.

[0043] The AC power system (system) 3 is connected to the output terminal of the other end of the power conversion device 1. It is a system that integrates power generation, power transformation, power transmission and power distribution, and is used to supply AC power output from the power conversion device 1 to the power receiving equipment of the demand side. For example, it is connected to an unspecified load.

[0044] In addition, Figure 1 In this device, the power conversion unit 1 includes an inverter circuit 11, a three-phase AC circuit 12, an AC reactor 13, an AC switch 14, a capacitor circuit 15, and an AC capacitor 16. Furthermore, the power conversion unit 1 includes a current sensor 21, a first voltage sensor 22, a second voltage sensor 23, and a control device 30.

[0045] The power conversion device 1 has a three-phase AC circuit 12 as an output circuit on the output side of the inverter 11. An AC reactor 13 and an AC switch 14 are provided in the three-phase AC circuit 12. The three-phase AC circuit 12 branches to a capacitor circuit 15 via a branch point 12a between the AC reactor 13 and the AC switch 14. The capacitor circuit 15 is connected to an AC capacitor 16. Furthermore, a current sensor 21 is arranged in the capacitor circuit 15 between the branch point 12a and the AC capacitor 16. Additionally, a first voltage sensor 22 is arranged in the AC circuit 12 between the AC reactor 13 and the branch point 12a, and a second voltage sensor 23 is arranged on the system 3 side of the AC switch 14. The control device 30, although its wiring is omitted in the figure, is electrically connected to the various components of the power conversion device 1.

[0046] The inverter circuit 11 is constructed, for example, from multiple switching elements such as an IGBT (Insulated Gate Bipolar Transistor). One end of the inverter circuit 11 is connected to the DC power supply 2, and the other end, serving as the output side, is connected to the AC reactor 13. The inverter 11 is controlled, for example, by the inverter control unit 32A (see below). Figure 10 , Figure 11 The inverter 11 is controlled by a pulse width modulation (PWM) signal, which serves as the gate drive signal (gate signal) for switching elements. The inverter 11 receives DC power from the DC power supply 2 at one end and, under control based on the pulse width modulation signal (gate signal), converts the received DC power into AC power, outputting it from the other end (the output terminal) to supply the three-phase AC circuit 12. Hereinafter, the inverter circuit 11 will be simply referred to as "inverter 11". Furthermore, the pulse width modulation signal will be referred to as "PWM signal" in this specification.

[0047] The three-phase AC circuit 12 has one end connected to the output terminal of the inverter 11 and the other end connected to the system 3. The three-phase AC circuit 12 is, for example, a three-phase, three-wire three-phase AC circuit that uses three wires / cables to supply three-phase AC power to a combination of three single-phase AC systems with phases of current or voltage that are staggered. Hereinafter, in this specification, the three-phase AC circuit 12 will also be referred to simply as "AC circuit 12".

[0048] The alternating current reactor 13, also referred to as the AC (alternating-current) reactor, is connected in series with the AC circuit 12 on the output side of the inverter 11. Hereinafter, the alternating current reactor 13 will also be referred to as "AC reactor 13". The AC reactor 13 is, for example, a smoothing element that reduces noise and suppresses surge voltage. The AC reactor 13, together with the AC capacitor 16 connected in an L-shape via branch point 12a, forms an LC filter circuit (filter circuit) that reduces the ripple (vibration) that occurs when the switching elements (not shown) of the inverter 11 are switched.

[0049] The AC switch (AC switch-off device) 14, also referred to as the AC switch, is connected in series in the AC circuit 12, closer to the system 3 side than the branch point 12a of the LC filter circuit described above. Hereinafter, the AC switch 14 or AC switch-off device 14 will also be referred to as "AC switch 14". The AC switch 14 connects (connects) the AC circuit 12 to the system 3 according to the on / off instructions from the control device 30, a higher-level device (not shown), or the operator. The AC switch 14 can interrupt the AC current flowing towards the system 3 side; if the AC switch 14 is disconnected, the flow of AC power supplied from the inverter 11 to the system 3 is interrupted. The AC switch 14 is disconnected when the power conversion device 1 is started (start-up), when the power conversion device 1 performs voltage matching operation (synchronization control) with the system 3 side, and is connected when grid-connected operation is started.

[0050] The capacitor circuit 15 is a branch circuit that branches off from the AC reactor 13 and AC switch 14 in the AC circuit 12 at a branch point 12a. One end of the circuit is connected to the branch point 12a, and the other end is connected to the AC capacitor 16. In addition, a current sensor 21 is disposed between the branch point 12a and the AC capacitor 16 in the capacitor circuit 15.

[0051] The AC capacitor 16, also known as an AC (alternating-current) capacitor, AC capacitor (alternating-current capacitor), or filter capacitor, is an electronic component that stores or discharges electrical charge. Hereinafter, in this specification, the AC capacitor 16 will also be referred to as "AC capacitor 16". The AC capacitor 16, together with, for example, an AC reactor 13 connected in an L-shape, constitutes an LC filter circuit (filter circuit) that reduces ripple (vibration) generated when the switching element (not shown) of the inverter 11 is switched. By forming a filter circuit together with the AC reactor 13, the AC capacitor 16 suppresses harmonic currents from flowing to the system 3 side. The AC capacitor 16 can be any at least one AC capacitor that is disconnected from the circuit in case of a fault.

[0052] For example, to obtain electrostatic capacitance or to meet the rated current, the capacitor circuit 15 is branched into multiple branches, and multiple AC capacitors 16a are connected in parallel to form a configuration.

[0053] Each of the multiple AC capacitors 16a has a safety mechanism 16b. Furthermore, in this embodiment, it is not necessary to connect multiple AC capacitors 16 in parallel; at least one AC capacitor 16 having both an AC capacitor 16a and a safety mechanism 16b is sufficient.

[0054] Safety mechanism 16b, such as a fuse or switch, has the function of disconnecting AC capacitor 16a from the circuit when AC capacitor 16a fails or when an abnormality occurs in AC capacitor 16a causing an increase in its internal voltage. Furthermore, safety mechanism 16b is not limited to fuses or switches that are separate from AC capacitor 16a; it can also be a function inherent in AC capacitor 16a itself, allowing it to be disconnected from the circuit in case of a fault.

[0055] Furthermore, the safety mechanism 16b can be a mechanism that individually disconnects the AC capacitor 16a from the circuit, or it can be a mechanism that disconnects the AC capacitor 16 from the circuit according to each specified package of the AC capacitor 16 having multiple AC capacitors 16a. That is, for example, in the case where multiple AC capacitors 16 having multiple AC capacitors 16a are connected in parallel according to a specified package, the safety mechanism 16b can also be configured according to each specified package of the AC capacitor 16.

[0056] A current sensor 21 is disposed between branch point 12a in capacitor circuit 15 and AC capacitor 16. The current sensor 21 is, for example, a known AC ammeter or AC current sensor. By distributing the current sensor 21 in capacitor circuit 15, the current sensor 21 can measure the current flowing into AC capacitor 16 during voltage-matched operation (synchronous control) when AC switch 14 is open. Furthermore, the current sensor 21 can also measure the current flowing into AC capacitor 16 during grid-connected operation when AC switch 14 is closed.

[0057] Figure 2 Is Figure 1 The diagram shows an example of the actual connection configuration of the AC capacitor 16 in the power conversion device 1. Figure 2 In China, for the sake of Figure 1 The same or identical structures are assigned the same labels, and detailed descriptions are omitted or simplified.

[0058] like Figure 2As shown, the AC circuit 12 is actually, for example, a three-phase three-wire AC circuit, and the constituent components, represented by the AC capacitor 16, are actually disposed in the three-phase AC circuit 12. Furthermore, in Figure 1 In the accompanying drawings, for the sake of simplicity, the constituent elements represented by these AC circuits 12 and AC capacitors 16 are simplified.

[0059] exist Figure 2 In the process, AC capacitor 16 is branched into multiple three-phase AC circuits 12, each consisting of a phase (U phase, V phase, W phase), for obtaining electrostatic capacitance or to meet rated current requirements. Multiple such circuits are connected in parallel. Furthermore, in... Figure 2 In this configuration, capacitor circuit 15 is branched into three in each phase, and AC capacitor 16 is connected in parallel in each phase, but the number of branches and parallel connections is not limited to this. For example, capacitor circuit 15 can also be branched into five in each phase, and AC capacitor 16 can be connected in parallel in each phase, totaling five. Furthermore, AC capacitor 16 can also be packaged as a single unit across three phases, with one AC capacitor package connected in parallel.

[0060] In addition, Figure 2 In each AC capacitor package, the AC capacitor 16 is connected in a delta configuration (Δ connection), but it can also be connected in a star configuration (Y connection), or other connection methods. Furthermore, AC capacitors 16 or AC capacitor packages with different connection methods can be mixed and connected in parallel. That is, the parallel connection method of the AC capacitors 16 is not particularly limited. Furthermore, in Figure 2 In this configuration, the safety mechanism 16b is arranged for each AC capacitor 16a, but it can also be arranged for each AC capacitor package as described above. Furthermore, the location of the safety mechanism 16b is not limited to... Figure 2 The location shown can be anywhere that allows AC capacitors 16 or 16a to be disconnected from the circuit in case of a fault.

[0061] In addition, such as Figure 2 As shown, the current sensor 21 is configured to detect the current value I of the three-phase alternating current in the capacitor circuit 15. U I V I W Furthermore, the location of the current sensor 21 is not limited to... Figure 2 The position shown can also be configured to detect the current value I of the three-phase AC current flowing into each AC capacitor package separately. U I V I W The location. That is, the current sensor 21 can also be configured, for example, per AC capacitor package. The current value I of the three-phase AC current detected by the current sensor 21.U I V I W Acquired by the controlled device 30.

[0062] Back Figure 1 The first voltage sensor 22 is, for example, configured in the AC circuit 12 on the output side of the inverter 11 between the inverter 11 and the branch point 12a of the capacitor circuit 15. The first voltage sensor 22 is, for example, a known AC voltmeter or AC voltage sensor, and detects the voltage value V of the output voltage of the inverter 11. i The first voltage sensor 22 detects the voltage value V of the output voltage of the inverter 11, for example, during voltage matching operation (synchronous control). i The voltage value V of the output voltage detected by the first voltage sensor 22. i The voltage is acquired by the controlled device 30. Furthermore, the first voltage sensor 22 is positioned where the voltage value V of the inverter 11 can be measured. i The location can be anywhere, it is not limited to. Figure 1 The location shown.

[0063] The second voltage sensor 23 is, for example, configured between the AC switch 14 in the AC circuit 12 on the output side of the inverter 11 and the system 3. The second voltage sensor 23 is, for example, a known AC voltmeter or AC voltage sensor, which detects the voltage value V of the three-phase system voltage. U V V V W The voltage value V detected by the second voltage sensor 23 U V V V W The voltage is acquired by the controlled device 30. Furthermore, the second voltage sensor 23 is positioned where it can measure the voltage value V of the three-phase system voltage on the three sides of the system. U V V V W The location can be anywhere, it is not limited to. Figure 1 The location shown.

[0064] The control device 30 may be located inside or outside the power conversion device 1, for example. Wiring is omitted in the figure, but it is electrically connected to the various components of the power conversion device 1, represented by the inverter 11, via wired or wireless means. Alternatively, the control device 30 may also function as an inverter control circuit (not shown).

[0065] The control device 30 includes, for example, a processor 91 (described later) that operates by executing programs, such as a CPU (Central Processing Unit), MPU (Micro Processing Unit), or GPU (Graphics Processing Unit). Figure 13 The control device 30 has a storage unit 40 (described later, etc.). Figure 3 ), memory 92 (reference) Figure 13 The control device 30, for example, operates by executing a predetermined program stored in the storage unit 40 or the memory 92, thereby comprehensively controlling the operation of the power conversion device 1. Additionally, the control device 30 may also operate according to instructions from a host device (not shown) or from an operator (not shown) via an operation unit (not shown). The control device 30 is based on the current value I of the three-phase alternating current detected by the current sensor 21. U I V I W The current value of at least one phase (e.g., the current value I of phase U). U The detection logic described later is used to detect faults in AC capacitor 16 (see reference). Figures 4-6 (etc.). In addition, a higher-level device, not shown, may monitor and control multiple power conversion devices 1 in a general manner, and be connected to each power conversion device 1 via wired or wireless connection.

[0066] Figure 3 It means Figure 1 and Figure 2 A diagram showing an example of the structure of the control device 30 in the power conversion device 1.

[0067] The control device 30 has a storage unit 40, for example, by executing the memory 92 stored in the storage unit 40 or described later (see reference). Figure 13 The control device 30 functions as the phase angle adjustment unit 31, amplitude calculation unit 33, fault determination unit 35, and motion control unit 37, according to the procedures specified in the document. Furthermore, each of the above functions can also be achieved through the processing circuit 90 (described later) of the control device 30. Figure 13 The processor 91 described later in the text (see reference) Figure 13 The program executed by ) can also be implemented through hardware 93 described later (see reference). Figure 13 The phase angle adjustment unit 31, amplitude calculation unit 33, fault determination unit 35, and motion control unit 37 execute the prescribed program and perform the following processing.

[0068] Phase angle adjustment unit 31 obtains the measured voltage value V, which is the system voltage of the three phases (U phase, V phase, W phase) on the three sides of the system, from the second voltage sensor 23.U V V V W The phase angle adjustment unit 31, for example, adjusts the voltage value V of the acquired system voltage based on an arbitrary phase angle θ. U V V V W Perform a three-phase to two-phase transformation (dq transformation) to determine the d-axis voltage V. d and q-axis voltage V q The phase angle adjustment unit 31 adjusts the calculated d-axis voltage V. d and q-axis voltage V q PLL (Phase Locked Loop) control is performed to adjust the rate of change of the phase angle θ so that the q-axis voltage V... q Relative to d-axis voltage V d It is reduced sufficiently (becomes 0). As a result, the frequency and phase of the phase angle θ are consistent with the frequency and phase of the system voltage, and the direction of the system voltage vector is consistent with the d-axis direction on the dq coordinate system.

[0069] The phase angle adjustment unit 31 adjusts the three-phase voltage values ​​V of the system voltage based on the adjusted phase angle θ. U V V V W A three-phase two-phase conversion (dq conversion) is performed, outputting d-axis and q-axis components. Thus, on the dq coordinate axis, the q-axis is positioned with its phase 90 degrees ahead of the d-axis. The phase angle adjustment unit 31 adjusts the system voltage value V based on the adjusted phase angle θ. U V V V W Perform a three-phase to two-phase transformation (dq transformation) to determine the d-axis voltage V. d and q-axis voltage V q The phase angle adjustment unit 31 outputs the adjusted phase angle θ to the amplitude calculation unit 33.

[0070] The amplitude calculation unit 33 obtains the current value I from the current sensor 21 as a measurement of the alternating current of each of the three phases (U phase, V phase, W phase) flowing into the AC capacitor 16. U I V I W Additionally, the amplitude calculation unit 33 can also obtain the current value I from the current sensor 21 as the measured value of the alternating current of each of the three phases (U phase, V phase, W phase). U I V I W The amplitude calculation unit 33 calculates the current value of at least one phase. Furthermore, the amplitude calculation unit 33 calculates the current value I of each phase. U I V I WThe specified current component of each phase is calculated by multiplying the values ​​of sinθ and cosθ, which are based on the phase angle adjustment unit 31 adjusted by the phase angle adjustment unit 31. Furthermore, the amplitude calculation unit 33 extracts the DC component of each phase from the calculated specified current components of each phase without passing through a specified low-pass filter (LPF). Based on the extracted DC components of each phase, the amplitude calculation unit 33 calculates the amplitude value of the frequency component (fundamental component) of the AC current of each phase. The amplitude calculation unit 33 outputs the calculated amplitude values ​​of the frequency component (fundamental component) of the AC current of each phase to the fault determination unit 35. Details regarding the calculation method for the amplitude values ​​of the fundamental component of the AC current of each phase will be described later (see [reference]). Figures 4-6 wait).

[0071] The fault determination unit (comparator) 35 compares the amplitude values ​​of the frequency components (fundamental components) of the alternating current in each phase calculated by the amplitude calculation unit 33 with a predetermined determination value obtained from the storage unit 40. Furthermore, if at least one of the amplitude values ​​of the alternating current in each phase calculated by the amplitude calculation unit 33 is smaller than the predetermined determination value obtained from the storage unit 40, the fault determination unit 35 determines that the AC capacitor 16 is faulty. That is, for example, if at least one of the multiple AC capacitors 16 is open-circuited, the amplitude value of at least one phase connected to the faulty AC capacitor 16 is smaller than normal. Therefore, the fault determination unit 35 detects this situation and determines a fault by comparing the amplitude values ​​of each phase calculated by the amplitude calculation unit 33 with the predetermined determination value. When the fault determination unit 35 determines that the AC capacitor 16 is faulty, it outputs a "1" as a fault determination result to the operation control unit 37. In addition, the fault determination unit 35 may output a "1" as a fault determination result to a host device (not shown), or output an alarm or alarm signal to a display or operation unit (not shown) of the power conversion device 1.

[0072] When the operation control unit 37 receives a "1" result from the fault determination unit 35 indicating that the AC capacitor 16 has failed, and if it is a synchronous control before the AC switch 14 is turned on, it issues an operation instruction to each part of the power conversion device 1 to stop the power conversion device 1. On the other hand, in the above-mentioned case, under grid-connected operation or other similar conditions, if the AC switch 14 is turned on, the operation control unit 37 issues an operation instruction to each part of the power conversion device 1 to stop the power conversion device 1 and issues an operation instruction to turn off the AC switch 14.

[0073] The storage unit 40 is, for example, a volatile or non-volatile storage medium such as an HDD (Hard Disk Drive), SSD (Solid State Drive), DRAM (Dynamic Random Access Memory), or other semiconductor memory. The storage unit 40 stores programs required for the operation of each part of the control device 30, and various information is written to or read from each part of the control device 30. Furthermore, the storage unit 40 stores, for example, values ​​obtained by sensors such as the current sensor 21, various formulas or coefficients used in calculations performed by the amplitude calculation unit 33, and predetermined judgment values ​​used in magnitude comparisons performed by the fault determination unit 35.

[0074] The storage unit 40 is connected to various parts of the control device 30 via, for example, a bus (system bus) not shown, to enable various information inputs and outputs. Alternatively, the storage unit 40 may be located externally to the control device 30 and connected to it via wired or wireless means. It may also be an external storage medium such as a memory card or DVD (Digital Versatile Disc), or an online storage device. Furthermore, the storage unit 40 may also be connected to the memory 92 described later (see reference). Figure 13 () is for shared use.

[0075] <Operation of the first embodiment>

[0076] Figure 4 It means Figures 1 to 3 A diagram showing an example of the fault detection operation of the control device 30. Figure 4 The operation shown is initiated during voltage matching operation (synchronization control) when the power conversion unit 1 is started (start command received) or during grid-connected operation of the power conversion unit 1. That is, it begins whether the power conversion unit 1 is started during voltage matching operation (synchronization control) when the AC switch 14 on the system 3 side is open, or during grid-connected operation of the power conversion unit 1 when the AC switch 14 on the system 3 side is closed. Figure 4 The actions shown. Additionally... Figure 4 The actions shown can be performed continuously or at predetermined intervals, for example, following instructions from control device 30, a higher-level device (not shown), or an operator (not shown).

[0077] In step S11, the phase angle adjustment unit 31 of the control device 30 obtains the voltage value V, which is the measured value of the system voltage of the three phases (U phase, V phase, W phase) on the three sides of the system, from the second voltage sensor 23. U V V V WThis allows the processing to proceed to step S12.

[0078] In step S12, the phase angle adjustment unit 31 adjusts the voltage value V of the acquired system voltage. U V V V W For example, a three-phase two-phase transformation (dq transformation) can be performed based on an arbitrary phase angle θ to obtain the d-axis voltage V. d and q-axis voltage V q This allows the processing to proceed to step S13.

[0079] In step S13, the phase angle adjustment unit 31 obtains the calculated d-axis voltage V. d and q-axis voltage V q This allows the processing to proceed to step S14.

[0080] In step S14, the d-axis voltage V obtained by the phase angle adjustment unit at 31 degrees is... d and q-axis voltage V q PLL (Phase Locked Loop) control is performed. Furthermore, the phase angle adjustment unit 31 adjusts the rate of change of the phase angle θ to adjust the q-axis voltage V. q Relative to d-axis voltage V d The phase angle θ is reduced sufficiently (becomes 0). Therefore, the frequency and phase of the phase angle θ are consistent with the frequency and phase of the system voltage, and the direction of the system voltage vector is consistent with the d-axis direction on the dq coordinate system. The phase angle adjustment unit 31 outputs the adjusted phase angle θ, transferring the processing to step S15. Furthermore, the phase angle adjustment unit 31 also outputs the adjusted phase angle θ to the amplitude calculation unit 33.

[0081] In step S15, the phase angle adjustment unit 31 adjusts the voltage value V of the three-phase system voltage based on the adjusted phase angle θ. U V V V W Perform a three-phase two-phase transformation (dq transformation) to determine the d-axis component (d-axis voltage V). d ) and q-axis component (q-axis voltage V) q Therefore, on the dq coordinate axis, the q-axis is positioned with its phase 90 degrees ahead of the d-axis. Furthermore, the phase angle adjustment unit 31 transfers the processing to step S13, and the processing from steps S13 to S15 is repeated during the operation of the power conversion device 1.

[0082] In step S31, the amplitude calculation unit 33 of the control device 30 obtains the current value I from the current sensor 21 as the measured value of the alternating current flowing into the AC capacitor 16 for each phase (U phase, V phase, W phase). U I V I WThis allows the process to proceed to step S32. Additionally, the current sensor 21 continuously or at predetermined intervals measures the current value I. U I V I W The amplitude calculation unit 33 obtains the current value I at regular intervals or at specified intervals. U I V I W .

[0083] In addition, Figure 4 In the example shown, the current value I is represented as an example. U The processing flow is as follows. Therefore, the following uses the current value I... U This will be used as an example for explanation, but regarding other current values ​​I... V I W They also performed the same actions.

[0084] In step S32, the amplitude calculation unit 33 obtains the current value I, which is a measured value of the alternating current flowing into each phase of the AC capacitor 16. U I V I W The value of the phase angle θ, adjusted by the PLL control in step S14, is used. Furthermore, the amplitude calculation unit 33 calculates the current value I, which is the measured value of the alternating current flowing into the AC capacitor 16 for each phase. U I V I W The specified current component is calculated by multiplying it by the value of the phase angle θ adjusted by the PLL control in step S14. Specifically, if the current value I... U Taking this as an example, the amplitude calculation unit 33 will calculate the current value I. U Multiplying it by sinθ, which is a value based on the phase angle θ, we calculate I as a specified current component. U sinθ. Furthermore, the amplitude calculation unit 33 calculates the current value I. U Multiplying it by cosθ, which is a value based on the phase angle θ, I is calculated as a specified current component. U cosθ. Furthermore, the amplitude calculation unit 33 transfers the processing to step S33.

[0085] Additionally, in step S14, the phase angle adjustment unit 31 adjusts the phase angle θ to adjust the q-axis voltage V. q Relative to d-axis voltage V d The value is reduced sufficiently (becomes 0). Therefore, the result of the PLL control in step S14 is that the frequency and phase of θ are consistent with the frequency and phase of the system voltage, and the direction of the system voltage vector is consistent with the d-axis direction on the dq coordinate.

[0086] In step S33, the amplitude calculation unit 33 uses a predetermined low-pass filter (LPF) to extract the DC component, and extracts the I value, which is a predetermined current component, from the value obtained in step S32. U The DC component is extracted from sinθ. Therefore, the current value I is extracted. U The component in phase with sinθ. Furthermore, the amplitude calculation unit 33 uses a predetermined low-pass filter (LPF) to extract the DC component, and extracts the I component, which is a predetermined current component, from step S32. U The DC component is extracted from cosθ. Therefore, the current value I is extracted. U The component in phase with cosθ. Furthermore, the amplitude calculation unit 33 transfers the processing to step S34.

[0087] In step S34, the amplitude calculation unit 33 calculates the amplitude of the amplitude extracted in step S33. U The DC component (current value I) contained in sinθ U The value of the squared component (in phase with sinθ) is calculated. Furthermore, the amplitude calculation unit 33 calculates the value of the squared component (in phase with sinθ) extracted in step S33. U The DC component (current value I) contained in cosθ U The amplitude calculation unit 33 then squares the component in phase with cosθ. The process is then transferred to step S35.

[0088] In step S35, the amplitude calculation unit 33 calculates the amplitude of the wave calculated in step S34. U The square of the DC component of sinθ and the value of I U The squared values ​​of the DC components of cosθ are summed, and the process is transferred to step S36.

[0089] In step S36, the amplitude calculation unit 33 calculates the capacitor current I, which is the square root of the sum of squares of the extracted components obtained in step S35. Uabs The processing is then transferred to step S37. The amplitude calculation unit 33 executes the processes from steps S31 to S36, and calculates the current value I by calculating the square root of the sum of the squares of the extracted components. U The amplitude value of the frequency component (fundamental component) with phase angle θ. Furthermore, the amplitude calculation unit 33 performs steps S31 to S36, calculating the square root of the sum of squares of each extracted component, for example, even if the current value I... U Even a negative value can cause the capacitor current I to... Uabs It becomes a positive value.

[0090] In step S37, the amplitude calculation unit 33 obtains the capacitor current I calculated in step S36. UabsThe amplitude of the fundamental component is output to the fault determination unit (comparator) 35. Alternatively, the amplitude calculation unit 33 may also output the capacitor current (the sum of values ​​obtained in step S35) before taking the square root in step S36 to the fault determination unit (comparator) 35.

[0091] In step S41, the control device 30, for example, acquires a predetermined determination value I stored in the storage unit 40. Ut The output is sent to the fault determination unit (comparator) 35. Additionally, the specified determination value I... Ut Based on various experiments, simulations, various conditions, and prescribed calculation methods, the settings are stored in the storage unit 40.

[0092] In addition, the specified judgment value I Ut It can also be based on instructions from control device 30, a higher-level device (not shown), or an operator. Furthermore, it can be based on a predetermined judgment value I. Ut Multiply by, for example, a value less than 1, a specified fault detection level (e.g., 0.8), so that even if the capacitor current I... Uabs A certain level of error is acceptable, and a fault in AC capacitor 16 can be detected. Furthermore, when outputting the capacitor current (summed value) before taking the square root in step S37, a predetermined judgment value I is used. Ut It needs to be set to a value that takes into account the square calculation.

[0093] In step S51, the fault determination unit (comparator) 35 obtains the capacitor current I calculated by the amplitude calculation unit 33. Uabs (fundamental frequency component amplitude) and the predetermined judgment value I stored in the storage unit 40 Ut Furthermore, the fault determination unit (comparator) 35 compares their magnitudes to determine whether the AC capacitor 16 is faulty. Additionally, the fault determination unit 35 determines whether the capacitor current I... Uabs (Fundamental component amplitude) ratio judgment value I Ut After a period of time, the AC capacitor 16 is determined to be faulty. That is, the fault determination unit 35 determines that, for example, in the case that at least one of the multiple AC capacitors 16 is open-circuited, due to the capacitor current I... Uabs The amplitude of the fundamental frequency component is smaller than normal, so this situation is detected and determined to be a fault. When the fault determination unit 35 determines that the AC capacitor 16 is faulty, the process is transferred to step S52.

[0094] In step S52, when the fault determination unit 35 determines that the AC capacitor 16 is faulty, it outputs a "1" as a fault determination result to the motion control unit 37. Alternatively, when the fault determination unit 35 determines that the AC capacitor 16 is not faulty, it may output a "0" as a fault-free determination result to the motion control unit 37, or it may output nothing until a fault is determined.

[0095] Alternatively, the fault determination unit 35 can also use the "1" as the fault determination result to report the fault information to the fault information reporting unit 36A (see below). Figure 10 , Figure 11 (etc.) output. In this case, the fault information reporting unit 36A (see below) will be used. Figure 10 , Figure 11 (e.g.,) For example, fault information can also be reported by reporting (outputting) fault information to a host device (not shown) or by reporting alarms or alarm messages to a display screen or control panel (not shown) of the power conversion device 1.

[0096] Figure 5 It is a schematic representation of... Figure 1 and Figure 2 The diagram shows the state of an open-circuit fault in AC capacitor 16a between U and V in the Δ-type connection of AC capacitor 16.

[0097] exist Figure 5 In the capacitor circuit 15, three-phase alternating current flows through it, and the current value I of each phase is obtained by the current sensor 21. U I V I W Furthermore, in Figure 5 An open-circuit fault occurred in AC capacitor 16a between phase U and phase V of AC capacitor 16 with a delta connection (between U and V).

[0098] Figure 6 It means Figure 5 The diagram shows the simulated waveforms of the capacitor currents in each phase under the given conditions. Figure 6 In the diagram, the vertical axis represents current (A: amperes), and the horizontal axis represents time (s: seconds). Additionally, the solid line represents the capacitor current I of phase U. Uabs The dashed line represents the capacitor current I of phase V. Vabs The dashed line represents the capacitor current I of phase W. Wabs That is, in Figure 6 The diagram shown illustrates the relationship between... Figure 5 The current values ​​I of each phase obtained by current sensor 21 are shown. U I V I W Execution by Figure 4The value represents the result of processing steps S31 to S37.

[0099] exist Figure 6 In the middle, at a point where time has advanced by 0.5 seconds, at... Figure 5 An open-circuit fault occurred in the AC capacitor 16a between phase U and phase V (U-V). Therefore, as shown... Figure 6 As shown, in the normal state before time advances by 0.5 (s), the three-phase capacitor current I... Uabs I Vabs I Wabs They all shifted around a roughly constant value near 0.65(A).

[0100] On the other hand, when the open-circuit fault occurs at a time advance of 0.5 (s), the capacitor current I of phase U, represented by the solid line, is... Uabs and the capacitor current I of phase V, represented by the dashed line. Vabs It dropped below 0.4 (A). Additionally, as... Figure 6 As shown, even after an open-circuit fault occurs at a time 0.5 seconds ahead, the capacitor current I of phase W, represented by the dashed line, remains unchanged. Wabs It also shifts to a roughly constant value around 0.65(A).

[0101] Therefore, for example, if a judgment value I is set between 0.4 (A) and 0.6 (A)... Ut I Vt I Wt The capacitor current I of the three phases Uabs I Vabs I Wabs By comparing the magnitudes, it can be determined whether AC capacitor 16 is faulty. Therefore, in this embodiment, the fault determination unit 35 determines whether the capacitor current I is faulty. Uabs I Vabs I Wabs and judgment value I Ut I Vt I Wt Perform a size comparison to determine whether AC capacitor 16 (one of AC capacitor 16a) is faulty.

[0102] Additionally, when the capacitor current (summed value) before taking the square root is output in step S37, it is worth considering... Figure 6 The graph shown is stretched along the vertical axis. Therefore, in this case, the judgment value I... Ut I Vt I Wt It also needs to be set to a value that takes into account the square (the value that is stretched in the vertical direction).

[0103] Furthermore, although the configurations differ in the case of a Δ-connection and a Y-connection, in the case of a Y-connection, since the current value of a certain phase can be considered to have decreased, it is possible to determine whether the AC capacitor 16 is faulty using the method shown in this embodiment.

[0104] Back Figure 4 In step S71, when the operation control unit 37 of the control device 30 obtains a "1" result indicating that the AC capacitor 16 has failed from the fault determination unit 35, it issues operation instructions to each part of the power conversion device 1 to stop the power conversion device 1. Furthermore, in grid-connected operation or other situations, if the operation control unit 37 obtains a "1" result indicating that the AC capacitor 16 has failed while the AC switch 14 is on, it issues an operation instruction to disconnect the AC switch 14. Thus, the operation control unit 37 can stop the power conversion device 1, suppressing the spread of the fault to the normal AC capacitor 16a and the outflow of harmonics to the system 3 side.

[0105] In addition, when the motion control unit 37 receives an action instruction from a host device (not shown) or an operator (not shown) via the operation unit, it can also issue an action instruction to stop the power conversion device 1 (and disconnect the AC switch 14). Furthermore, during synchronization control, if the motion control unit 37 obtains synchronization determination OK information but does not obtain a fault determination result from the fault determination unit 35, it can also issue an action instruction to turn on the AC switch 14 to start grid-connected operation.

[0106] Based on the above, control device 30 ends. Figure 4 The fault detection actions shown are as follows. Additionally... Figure 4 The fault detection action shown can be performed continuously as described above, or at predetermined intervals, for example, following instructions from control device 30, a host device not shown, or an operator not shown.

[0107] Figure 7 It means Figures 1 to 6 The diagram shows an example of the operation of the power conversion device 1 after the start command is input. Figure 7 (a) is a diagram showing the state of the power conversion device 1 under normal conditions after the start command is input, in voltage matching operation (synchronous control). Figure 7 (b) is a diagram showing the state of voltage matching operation (synchronous control) of the power conversion device 1 after the start command is input in the case of a partial open circuit fault of AC capacitor 16.

[0108] In addition, Figure 7 In fact, as Figure 2As shown, a three-phase AC circuit 12 is connected to the output side of the inverter 11, and is equipped with a three-phase AC reactor 13, an AC switch 14, an AC capacitor 16, etc. Furthermore, the AC capacitor 16 is actually... Figure 2 As shown, there are multiple components connected in parallel in each phase. However, for the sake of simplicity, these components are omitted or simplified in the diagram.

[0109] exist Figure 7 In (a), when AC capacitor 16 is functioning normally, after receiving the start command from the stop state, power conversion device 1 drives inverter 11 (inverter circuit 11) to perform voltage matching operation (synchronization control), synchronizing the voltages before and after AC switch 14. At this time, since AC switch 14 is open, the AC power output from inverter circuit 11 does not flow to system 3, but current flows through AC capacitor 16.

[0110] In this case, the current value I of the capacitor current flowing into the AC capacitor 16 of each phase is constantly detected by the current sensor 21 configured in the capacitor circuit 15. U I V I W Furthermore, the control device 30 operates continuously at this time. Figure 4 The actions shown are steps S11 to S51. In this case, a current value I typically flows through the AC capacitor 16. U I V I W The current. In this case, as described above, the three-phase capacitor current I... Uabs I Vabs I Wabs It shifts at roughly a certain value.

[0111] exist Figure 7 In (b), if a portion of the AC capacitor 16 fails to open, the power conversion device 1 also performs a corresponding operation. Figure 7 (a) The same action. In this case, if a portion of AC capacitor 16 fails to open, then as described above, the three-phase capacitor current I... Uabs I Vabs I Wabs At least one of them decreases, so the control device 30 detects a fault in the AC capacitor 16.

[0112] That is, the control device 30 determines that the AC capacitor 16 is faulty (S51) and outputs a "1" as the determination result of the AC capacitor 16 being faulty to the operation control unit 37 (S52). In this case, the operation control unit 37 obtains a "1" as the determination result of the AC capacitor 16 being faulty during the voltage matching operation of the power conversion device 1. In this case, the operation control unit 37 stops the power conversion device 1 (S71), thereby stopping the application of voltage to the AC capacitor 16.

[0113] Therefore, if a fault is detected during voltage matching operation (synchronous control), the power conversion device 1 can be stopped (preventing starting) before grid-connected operation. This can suppress the amplification of the fault to the normal AC capacitor 16a and the outflow of harmonics to the system 3 side.

[0114] Figure 8 It means Figures 1 to 6 A diagram showing an example of the operation of the inverter in grid-connected power conversion device 1. Figure 8 (a) is a diagram showing the state of the inverter of the power conversion device 1 in grid-connected operation (grid-connected operation) when the AC capacitor 16 is in normal condition. Figure 8 (b) is a diagram showing the state of the inverter of the power conversion device 1 during grid-connected operation (grid-connected operation) under the condition of a partial open-circuit fault in the AC capacitor 16. Additionally, in Figure 8 Nakaya and Figure 7 Similarly, for the sake of simplicity in the diagram, the components are omitted or simplified.

[0115] like Figure 8 As shown in (a), the current sensor 21 is configured in the capacitor circuit 15, so that the current value I of the capacitor current can be detected even when the AC switch 14 of the power conversion device 1 is turned on and the inverter circuit 11 is being driven. U I V I W .

[0116] In this situation, when the AC switch 14 of the power conversion device 1 is turned on and the inverter circuit 11 is being driven, the current value I of the capacitor current flowing into the AC capacitor 16 of each phase is also constantly detected by the current sensor 21 of each phase. U I V I W In this case, it is also related to Figure 7 Similarly, control device 30 is constantly in operation. Figure 4 The actions shown are steps S11 to S51. In this case, with... Figure 7 Similarly, a current value I typically flows through AC capacitor 16. U I VI W The current, the three-phase capacitor current I Uabs I Vabs I Wabs It shifts at roughly a certain value.

[0117] exist Figure 8 In (b), if a portion of the AC capacitor 16 fails to open, the power conversion device 1 also performs a corresponding operation. Figure 8 (a) The same action. In this case, with Figure 7 Similarly, if a portion of AC capacitor 16 fails to open, then as described above, the three-phase capacitor current I... Uabs I Vabs I Wabs At least one of them decreases, so the control device 30 detects a fault in the AC capacitor 16.

[0118] That is, with Figure 7 Similarly, the control device 30 determines that the AC capacitor 16 is faulty (S51) and outputs a "1" as the determination result of the AC capacitor 16 being faulty to the operation control unit 37 (S52). In this case, the operation control unit 37 obtains a "1" as the determination result of the AC capacitor 16 being faulty during the inverter grid-connected operation of the power conversion device 1. In this case, the operation control unit 37 disconnects the AC switch 14 of the AC circuit 12 and stops the power conversion device 1 (S71), thereby stopping the voltage applied to the AC capacitor 16. In addition, the stopping method at this time is not limited to the operation control unit 37; the operation of the power conversion device 1 can also be stopped by the specified software, or the AC switch 14 can be manually disconnected by an operator (not shown).

[0119] Therefore, even if a fault is detected during grid-connected operation of the inverter, the propagation of the fault to the normal AC capacitor 16a and the outflow of harmonics to the system 3 side can be suppressed.

[0120] <Effects of the first implementation method>

[0121] Based on the above, Figures 1 to 8 In the first embodiment shown, the fault determination unit 35 determines the capacitor current I obtained by the amplitude calculation unit 33. Uabs I Vabs I Wabs (Fundamental frequency component amplitude) and judgment value I Ut I Vt I Wt A size comparison is performed. Furthermore, the fault determination unit 35 determines the fault when the capacitor current I... Uabs I Vabs I Wabs(Fundamental component amplitude) ratio judgment value I Ut I Vt I Wt After one hour, it was determined that AC capacitor 16 was faulty, and the judgment result (S51, S52) was output. That is, in Figures 1 to 8 In the first embodiment shown, faults in AC capacitor 16 are detected based on the current components flowing into each phase of AC capacitor 16. This allows for the reporting of fault information in AC capacitor 16 and the shutdown of power conversion device 1, suppressing the outflow of harmonics to system 3 and the propagation of faults to normal AC capacitor 16a.

[0122] In addition, according to Figures 1 to 8 In the first embodiment shown, the current sensor 21 is disposed in the capacitor circuit 15. Therefore, whether in voltage matching operation of the power conversion device 1 (when the AC switch 14 is open) or grid-connected operation (when the AC switch 14 is closed), the current value I of the current flowing into the AC capacitor 16 (capacitor current) can be distinguished and measured. U I V I W Therefore, in Figures 1 to 8 In the first embodiment shown, whether the power conversion device 1 is in voltage matching operation (when AC switch 14 is open) or in grid-connected operation (when AC switch 14 is closed), it is possible to determine whether there is a fault in AC capacitor 16. Furthermore, this allows the propagation of the fault to the normal AC capacitor 16a and the outflow of harmonics to the system 3 side to be suppressed, whether the power conversion device 1 is in voltage matching operation (when AC switch 14 is open) or in grid-connected operation (when AC switch 14 is closed).

[0123] In addition, according to Figures 1 to 8 In the first embodiment shown, the current sensor 21 disposed in the capacitor circuit 15 can use a component with a smaller rated current because it only detects a small current flowing into the AC capacitor 16 (capacitor circuit 15). Therefore, compared to a current sensor with a larger rated current such as that disposed in the AC circuit 12, the current sensor 21 with a smaller rated current can measure the capacitor current, which is a smaller current, with better accuracy. Furthermore, compared to a current sensor with a larger rated current such as that disposed in the AC circuit 12, the current sensor 21 with a smaller rated current can use smaller and cheaper components.

[0124] In addition, according to Figures 1 to 8In the first embodiment shown, the current sensor 21 is disposed in the capacitor circuit 15. Therefore, even if, by specification, the current sensor is disposed only on the AC circuit 12 closer to the system 3 side than the AC switch 14, fault detection of the AC capacitor 16 and shutdown of the power conversion device 1 are still possible. Thus, in such a case, the outflow of harmonics to the system 3 side and the propagation of harmonics to the normal AC capacitor 16a can also be suppressed.

[0125] <Structure of the Second Embodiment>

[0126] Figure 9 This is a diagram illustrating an example of the structure of the control device 30A and the power conversion device 1A according to the second embodiment. Additionally, in Figure 9 In China, for the sake of Figures 1 to 8 The same structures shown in the embodiments are given the same reference numerals, and detailed descriptions are omitted or simplified. Additionally, Figure 9 The structure shown is Figure 2 Similarly, AC circuit 12 is actually a three-phase, three-wire AC circuit, and the constituent components, represented by AC capacitor 16, are actually disposed separately in the three-phase AC circuit 12. However, in Figure 9 Nakaya and Figure 1 Similarly, for the sake of simplicity, the components are simplified in representation.

[0127] exist Figure 9 In the embodiments shown, with Figures 1 to 8 The implementation shown differs; current sensor 21 is not configured in capacitor circuit 15, and current sensor 21A is configured in AC circuit 12. Figure 9 In the embodiment shown, the current value I of the current flowing into the AC capacitor 16 (capacitor current) can be measured by the current sensor 21A only when the AC switch 14 is disconnected during voltage matching operation (synchronous control). U I V I W .

[0128] A current sensor 21A is configured in series with an AC reactor 13 in the AC circuit 12 on the output side of the inverter 11, between the inverter 11 and the branch point 12a of the capacitor circuit 15. The current sensor 21A is, for example, a known AC ammeter or AC current sensor, and detects the current value I of the three-phase output current in the power conversion device 1A. U I V I W The current value I detected by current sensor 21A U I V I W Acquired by the controlled device 30A.

[0129] Furthermore, the current sensor 21A can be connected in series with the AC reactor 13 in the AC circuit 12, and the connection order is not restricted. However, the current sensor 21A needs to be positioned between the inverter 11 and the branch point 12a in the AC circuit 12. By positioning the current sensor 21A at this location, the current value I flowing into the AC capacitor 16 can be measured when the AC switch 14 is disconnected and the voltage is matched for operation (during synchronous control). U I V I W Furthermore, since the current sensor 21A is already standardly installed in the aforementioned location in many power conversion devices 1A, the existing current sensor 21A can be used in this embodiment.

[0130] Control device 30A is capable of operating only when voltage is matched (in synchronous control) based on the current value I measured by current sensor 21A. U I V I W To detect faults in AC capacitor 16. Furthermore, details regarding the structure, function, and operation of control device 30A will be described later (see [reference]). Figure 10 , Figure 11 wait).

[0131] Figure 10 It means Figure 9 The diagram shows an example of the structure of the control device 30A in the power conversion device 1A shown. Additionally, in Figure 10 In, also for with Figures 1 to 8 The same structures shown in the embodiments are given the same reference numerals, and detailed descriptions are omitted or simplified.

[0132] The control device 30A has a storage unit 40, for example, by executing the memory 92 stored in the storage unit 40 or described later (see reference). Figure 13 The control device 30A functions as the phase angle adjustment unit 31A, inverter control unit 32A, amplitude calculation unit 33, fault determination unit 35A, fault information reporting unit 36A, and motion control unit 37A, according to the prescribed procedures. The phase angle adjustment unit 31A, inverter control unit 32A, amplitude calculation unit 33, fault determination unit 35A, fault information reporting unit 36A, and motion control unit 37A execute the prescribed procedures and perform the following processing.

[0133] The phase angle adjustment unit 31A adjusts the calculated d-axis voltage V. d and q-axis voltage V q Output to inverter control unit 32A. Other structures or functions of phase angle adjustment unit 31A are the same as... Figures 1 to 8The phase angle adjustment unit 31 in the illustrated embodiment is the same.

[0134] Inverter control unit 32A obtains the d-axis voltage V based on the phase angle θ adjusted by phase angle adjustment unit 31A. d and q-axis voltage V q The inverter control unit 32A measures the acquired d-axis voltage V. d and q-axis voltage V q The inverter output voltage command value V is obtained by performing a two-phase to three-phase conversion (inverse conversion) through a specified filter. U * V V * V W * The inverter control unit 32A processes the calculated inverter output voltage command value V. U * V V * V W * PWM (Pulse Width Modulation) control is performed to generate a gate signal.

[0135] The inverter control unit 32A controls the switching elements (not shown) of the inverter 11 using the generated gate signal to perform voltage matching operation (synchronization control) of the power conversion device 1A. Furthermore, information regarding whether the power conversion device 1A is operating under voltage matching operation (synchronization control) is appropriately obtained from the inverter control unit 32A by the fault information reporting unit 36A.

[0136] When the fault determination unit (comparator) 35A determines that the AC capacitor 16 is faulty, it outputs a "1" as the fault determination result to the fault information reporting unit 36A. Other structures or functions of the fault determination unit 35A are similar to those of the AC capacitor 166A. Figures 1 to 8 The fault determination unit 35 in the embodiment shown is the same.

[0137] The fault information reporting unit 36A appropriately obtains information from the inverter control unit 32A regarding whether the power conversion device 1A is operating under voltage matching (synchronization control). When the fault determination unit 35A determines that the AC capacitor is faulty, the fault information reporting unit 36A obtains a "1" as the determination result of the fault. When the fault information reporting unit 36A obtains information that the power conversion device 1A is operating under voltage matching (synchronization control), and when it obtains a "1" as the determination result of the AC capacitor 16 being faulty from the fault determination unit 35A, it reports the fault information. The fault information reporting unit 36A reports the fault information, for example, by outputting the fault information to a higher-level device (not shown), or by reporting alarm or warning information to a display or operation unit (not shown) of the power conversion device 1A. Furthermore, the fault information reporting unit 36A also reports the fault information to the operation control unit 37A.

[0138] When the operation control unit 37A receives a fault report from the fault information reporting unit 36A regarding the AC capacitor 16, it issues an operation instruction to each part of the power conversion device 1A to stop the power conversion device 1A, thus stopping the power conversion device 1A before the AC switch 14 is turned on. Alternatively, when the operation control unit 37A receives synchronization determination OK information from the inverter control unit 32A, and even if no fault report for the AC capacitor 16 is received from the fault information reporting unit 36A, it can also issue an operation instruction to turn on the AC switch 14, initiating grid-connected operation.

[0139] <Operations of the Second Embodiment>

[0140] Figure 11 It means Figure 9 and Figure 10 A diagram showing an example of the fault detection operation of the control device 30A. Additionally, in Figure 11 In, also for with Figures 1 to 8 The same actions (processes) shown in the embodiments are assigned the same labels (processing step numbers), and detailed descriptions are omitted or simplified.

[0141] Figure 11 The operation shown begins simultaneously with the activation (start command received) of the power conversion device 1A. That is, Figure 11 The operation shown begins during voltage matching operation (synchronous control) when the power conversion device 1A is started (start-up) after the AC switch 14 on system 3 is disconnected. Additionally, Figure 11 The actions shown can be performed either during voltage matching operation (synchronous control) or at specified intervals, for example, following instructions from control device 30A, a host device not shown, or an operator not shown.

[0142] In steps S12A and S15A, the phase angle adjustment unit 31A adjusts the calculated d-axis voltage V. d and q-axis voltage V q It also outputs to the inverter control unit 32A. Other processing in steps S12A and S15A is similar. Figures 1 to 8 Steps S12 and S15 in the illustrated embodiment are the same.

[0143] In step S21A, the inverter control unit 32A of the control device 30A first obtains the d-axis voltage V output in step S12A. d and q-axis voltage V q Then obtain the d-axis voltage V output in step S15A. d and q-axis voltage V q The inverter control unit 32A processes the acquired d-axis voltage V. d and q-axis voltage V q For example, a prescribed filtering process can be performed to transfer the processing to step S22A. Alternatively, this prescribed filtering process is not mandatory and can be omitted.

[0144] In step S22A, the inverter control unit 32A measures the acquired d-axis voltage V. d and q-axis voltage V q Perform a two-phase to three-phase conversion (inverse conversion) to determine the inverter output voltage command value V. U * V V * V W * This transfers the processing to step S23A. Additionally, regarding the system voltage value V... U V V V W The reason for performing a three-phase two-phase conversion (dq conversion) first, followed by a two-phase three-phase conversion (inverse conversion), is that the voltage values ​​V of the three phases are related. U V V V W In comparison, the d-axis voltage V of the two axes d and q-axis voltage V q Its filtering process is easier.

[0145] In step S23A, the inverter control unit 32A processes the calculated inverter output voltage command value V. U * V V * V W *PWM control is performed to generate a gate signal. The inverter control unit 32A uses the generated gate signal to control the switching elements (not shown) of the inverter 11, performing voltage matching operation (synchronization control) of the power conversion device 1A, thus transferring the processing to step S24A. Furthermore, as a result of the above control, during voltage matching operation (synchronization control), the phase and amplitude of the inverter 11's output voltage are approximately synchronized with the phase and amplitude of the system voltage. Therefore, the d-axis current I... d For components in phase with the output voltage of inverter 11, the q-axis current I q This is a component whose phase leads the output voltage of inverter 11 by 90 degrees.

[0146] In step S24A, the inverter control unit 32A outputs information indicating whether the power conversion device 1A is operating under voltage matching (synchronization control). This information is appropriately obtained by the fault information reporting unit 36A.

[0147] Figure 12 It means Figures 9 to 11 The diagram shows an example of the operation of the voltage matching (synchronous control) of the power conversion device 1A. Figure 12 (a) is a diagram showing the state from the start-up of the power conversion device 1A to the voltage matching operation (synchronization control) synchronized with the system 3 side. Figure 12 (b) is a diagram showing the state when the power conversion device 1A achieves synchronization with the system 3 side as a result of voltage matching operation (synchronization control). Figure 12 (c) is a diagram showing the state when AC switch 14 is turned on because the power conversion device 1A is synchronized with the system 3 side through voltage matching operation (synchronization control).

[0148] exist Figure 12 In the middle, the left side indicates the circuit status. Figure 12 The left side indicates that Figure 9 The diagram shows a portion of the structure of the power conversion device 1A, omitted from the original drawing. Figure 12 On the left side, the output voltage of the inverter 11 is applied to the left side of the AC switch 14, and the system voltage from the system 3 side is applied to the right side of the AC switch 14. Furthermore, in Figure 12 On the left, the arrow indicates the current path from inverter 11. Figure 12 The right side represents the voltage waveform. Figure 12 On the right side, the solid line represents the waveform of the system voltage, and the dashed line represents the waveform of the output voltage of inverter 11. Additionally, the output voltage value V of inverter 11... i The voltage value V of the three-phase system voltage is detected by the first voltage sensor 22. U V VV W The second voltage sensor 23 detects the voltage, and the detection results are obtained by the control device 30A (see reference). Figure 9 wait).

[0149] exist Figure 12 In (a), if the power conversion device 1A is started (if a start command is received), the inverter 11 is controlled by the gate signal output from the inverter control unit 32A and begins voltage matching operation (synchronous control). During startup, since the inverter 11 is controlled by the gate signal based on an arbitrary phase angle θ, the voltage waveforms of the output voltage of the inverter 11 and the system voltage are initially disordered (S12A, S21A to S23A).

[0150] exist Figure 12 In (b), the result of voltage matching operation (synchronization control) is that synchronization is determined to be OK. That is, the phase angle adjustment unit 31A adjusts the three-phase voltage values ​​V obtained from the system voltage. U V V V W PLL control is performed to adjust the phase angle θ (S14). Furthermore, if the inverter 11 is controlled by a gate signal based on the adjusted phase angle θ, the phase and amplitude of the output voltage of the inverter 11 are made to be approximately consistent with the phase and amplitude of the system voltage (S15A, S21A to S23A).

[0151] exist Figure 12 In (c), when the synchronization is determined to be OK, since the voltage waveform of the output voltage of the inverter 11 is roughly the same as the voltage waveform of the system voltage, the AC switch 14 is turned on by the operation indication of the operation control unit 37A, for example, and grid-connected operation begins.

[0152] Back Figure 11 In step S52A, when the fault determination unit 35A of the control device 30A determines that the AC capacitor 16 is faulty, it outputs a "1" as a fault determination result to the fault information reporting unit 36A. Alternatively, when the fault determination unit 35A determines that the AC capacitor 16 is not faulty, it may output a "0" as a fault-free determination result to the fault information reporting unit 36A, or it may output nothing until a fault is determined.

[0153] In step S61A, the fault information reporting unit 36A of the control device 30A appropriately obtains information from the inverter control unit 32A regarding whether the power conversion device 1A is in voltage matching operation (synchronous control) (see S24A). Furthermore, when the fault determination unit 35A determines that the AC capacitor is faulty, the fault information reporting unit 36A obtains a "1" as a fault determination result from the fault determination unit 35A (see S52A). Moreover, when the fault information reporting unit 36A obtains information that the power conversion device 1A is in voltage matching operation (synchronous control), and obtains a "1" as a fault determination result for the AC capacitor 16 from the fault determination unit 35A, the processing is transferred to step S62A.

[0154] In step S62A, when the fault information reporting unit 36A obtains information that the power conversion device 1A is in voltage matching operation (synchronous control), and obtains a "1" indicating that the AC capacitor 16 has failed, it reports fault information. The fault information reporting unit 36A reports fault information, for example, by reporting (outputting) fault information to a host device (not shown), or by reporting alarm or warning information to a display screen or control panel (not shown) of the power conversion device 1A. Furthermore, the fault information reporting unit 36A also reports (outputs) fault information to the motion control unit 37A.

[0155] In step S71A, when the operation control unit 37A of the control device 30A receives a report of fault information of AC capacitor 16 from the fault information reporting unit 36A, it issues operation instructions to each part of the power conversion device 1A to stop the power conversion device 1A. Thus, the operation control unit 37A stops the power conversion device 1A before grid-connected operation begins (before the AC switch 14 is turned on). This suppresses the propagation of the fault to the normal AC capacitor 16a and the outflow of harmonics to the system 3 side.

[0156] Additionally, the operation control unit 37A can also stop the power conversion device 1A upon receiving an operation instruction from an unshown upper-level device or an unshown operator via the operation unit, which has received a report of fault information from the fault information reporting unit 36A. Furthermore, for example, when the operation control unit 37A receives synchronization determination OK information from the inverter control unit 32A, and no fault information report is received from the fault information reporting unit 36A, it can also issue a switch-on operation instruction to the AC switch 14 to start grid-connected operation.

[0157] In addition, Figures 1 to 8 In the first embodiment shown, Figure 7 The operation of the power conversion device 1 after the start command is input can also be controlled. Figures 9-12 The operation of the power conversion device 1A according to the second embodiment shown is applied after the start command is input. When the power conversion device 1A of the second embodiment is shown... Figure 7 The actions shown are for Figures 9-12 In the case of the power conversion device 1A of the second embodiment shown, the current value I of the capacitor current flowing into the three-phase AC capacitor 16 is detected by the current sensor 21A, not the current sensor 21. U I V I W .

[0158] Furthermore, the control device 30A determines that the AC capacitor 16 is faulty (S51) and outputs a "1" as the determination result of the AC capacitor 16 being faulty to the fault information reporting unit 36A (S52A). In this case, the fault information reporting unit 36A has obtained a "1" as the determination result of the AC capacitor 16 being faulty during the voltage matching operation of the power conversion device 1A (S61A), and therefore reports the fault information (S62A). In this case, the operation control unit 37A stops the power conversion device 1A (S71), thereby stopping the application of voltage to the AC capacitor 16.

[0159] Therefore, in Figures 9-12 In the second embodiment shown, if a fault is detected during voltage matching operation (synchronous control), the power conversion device 1A can be stopped (start-preventing) before grid-connected operation. This suppresses the propagation of the fault to the normal AC capacitor 16a and the outflow of harmonics to the system 3 side.

[0160] <Effects of the second implementation method>

[0161] Based on the above, Figures 9-12 The second embodiment shown serves the same purpose as... Figures 1 to 8 The same effect is achieved in the first embodiment shown.

[0162] In addition, Figures 9-12 In the second embodiment shown, the current sensor 21A is configured in series with the AC reactor 13 between the inverter 11 and the branch point 12a of the capacitor circuit 15 in the AC circuit 12 on the output side of the inverter 11. Therefore, the current sensor 21A can measure the current flowing into the AC capacitor 16 during voltage-matched operation (synchronous control) when the AC switch 14 is open. Thus, according to... Figures 9-12 In the second embodiment shown, the control device 30A can monitor the open-circuit fault of the AC capacitor 16 during voltage matching operation (synchronous control).

[0163] In addition, Figures 9-12In the second embodiment shown, the current sensor 21A is disposed at the aforementioned location. In this case, the current sensor 21A is confused with the current flowing to the system 3 side during grid-connected operation when the AC switch 14 is turned on (cannot be distinguished), so it cannot extract only the current flowing to the AC capacitor 16. However, in existing power conversion devices 1A, the current sensor 21A is often already disposed at the aforementioned location as per specifications. Therefore, according to... Figures 9-12 The second embodiment shown allows the use of existing current sensors 21A that have already been configured in a number of existing power conversion devices 1A.

[0164] In addition, Figures 9-12 In the second embodiment shown, when the control device 30A detects a fault in the AC capacitor 16 during voltage matching operation (synchronous control), it reports fault information (S62A) before grid-connected operation begins (before the AC switch 14 is turned on). Furthermore, in Figures 9-12 In the second embodiment shown, when the control device 30A is operating under voltage matching conditions (synchronous control), if a fault is detected in the AC capacitor 16, it stops the power conversion device 1A before grid-connected operation begins (before the AC switch 14 is turned on) (S71A). This suppresses the propagation of the fault to the normal AC capacitor 16a and the outflow of harmonics to the system 3 side.

[0165] <Hardware Structure Example>

[0166] Figure 13 It means Figures 1 to 12 The diagram shows a conceptual example of the hardware structure of the processing circuit 90 in the control devices 30 and 30A of the illustrated embodiments. The aforementioned functions are implemented by the processing circuit 90. In one embodiment, the processing circuit 90 includes at least one processor 91 and at least one memory 92. In another embodiment, the processing circuit 90 includes at least one dedicated hardware 93.

[0167] When the processing circuit 90 includes a processor 91 and a memory 92, each function is implemented by software, firmware, or a combination of software and firmware. At least one of the software and firmware is described as a program. At least one of the software and firmware is stored in the memory 92. The processor 91 implements each function by reading and executing the program stored in the memory 92.

[0168] When the processing circuit 90 has dedicated hardware 93, the processing circuit 90 may be, for example, a single circuit, a composite circuit, a programmed processor, or a combination thereof. Each function is implemented by the processing circuit 90.

[0169] The functions of control devices 30 and 30A can be partially or entirely constituted by hardware, or they can be constituted as programs executed by a processor. That is, control devices 30 and 30A can also be implemented by a computer and a program, which can be stored in a storage medium or provided via a network.

[0170] <Supplementary Notes on Implementation Methods>

[0171] Based on the above, Figures 1 to 13 The implementation methods shown are divided into Figures 1 to 8 The first embodiment shown and Figures 9-12 The second embodiment is shown, but these embodiments can also be combined. That is, the power conversion device 1 or 1A may include both current sensor 21 and current sensor 21A. Furthermore, the current flowing into the AC capacitor 16 (capacitor circuit 15) can be measured by one or both current sensors. Even in the combined embodiments, the same effects can be achieved as in the embodiments before the combination.

[0172] In addition, Figures 1 to 13 In the embodiments shown, once Figure 4 and Figure 11 In step S51 shown, if a portion of AC capacitor 16a experiences an open-circuit fault, the fault determination unit 35 or 35A determines that AC capacitor 16 is faulty. However, for example, the fault determination unit 35 or 35A may not determine that AC capacitor 16 is faulty if only one AC capacitor 16a is faulty, but may determine that AC capacitor 16 is faulty if two or more are faulty. Such a method is effective, for example, when the impact on the power conversion device 1 or 1A is minimal due to only one AC capacitor 16a fault. Furthermore, the fault determination unit 35 or 35A may also detect a fault in AC capacitor 16 when three or more AC capacitors 16a are faulty, depending on the actual situation.

[0173] In addition, Figures 1 to 13 The illustrated embodiment describes an example of applying three-phase alternating current in a three-phase alternating circuit 12, but is not limited thereto. This disclosure can also be applied, for example, to single-phase alternating circuits (single-phase alternating current) or other multi-phase alternating circuits (multi-phase alternating current).

[0174] In addition, according to Figures 1 to 13 The embodiments shown are examples of power conversion devices 1 and 1A and their control devices 30 and 30A, but are not limited thereto. This disclosure can also be implemented as a method for detecting faults in AC capacitors that perform processing steps in each part of the control devices 30 and 30A.

[0175] Furthermore, this disclosure can also be implemented as a fault detection program for AC capacitors that enables the computer to execute the processing steps of each part of the control devices 30, 30A.

[0176] Furthermore, this disclosure can also be implemented as a storage medium (non-transitory computer-readable medium) storing a fault detection program for an AC capacitor. The AC capacitor fault detection program can be stored and distributed on removable media such as CDs (CompactDiscs), DVDs (Digital Versatile Discs), or USB (Universal Serial Bus) memory. Alternatively, the AC capacitor fault detection program can be uploaded to a network via a network interface (not shown) provided with the control devices 30 and 30A, or downloaded from the network and saved to the storage unit 40.

[0177] Through the detailed description above, the features and advantages of the embodiments should become clear. This means that the scope of the claims relates to the features and advantages of the embodiments described above without departing from their spirit and scope. Furthermore, those skilled in the art should be able to readily conceive of all modifications and variations. Therefore, the scope of the inventive embodiments is not intended to be limited to the above-described scope, but can be based on suitable modifications and equivalents included within the scope disclosed in the embodiments.

[0178] Label Explanation

[0179] 1. 1A…Power conversion device (PCS); 2…DC power supply; 3…AC power system; 11…Inverter circuit (inverter); 12…Three-phase AC circuit (AC circuit); 12a…Branch point; 13…AC reactor; 14…AC switch (AC switch); 15…Capacitor circuit; 16…AC capacitor; 16a…AC capacitor; 16b…Safety mechanism ; 21, 21A… Current sensor; 22… First voltage sensor; 23… Second voltage sensor; 30, 30A… Control device; 31, 31A… Phase angle adjustment unit; 32A… Inverter control unit; 33… Amplitude calculation unit; 35, 35A… Fault determination unit (comparator); 36A… Fault information reporting unit; 37, 37A… Action control unit; 40… Storage unit; 90… Processing circuit; 91… Processor; 92… Memory; 93… Hardware; I d …d-axis current; I q …q-axis current; I U …current value; I Uabs …capacitor current; IUt …judgment value; I V …current value; I Vabs …capacitor current; I Vt …judgment value; I W …current value; I Wabs …capacitor current; I Wt …judgment value; V d …d-axis voltage; V i …voltage value; V q …q-axis voltage; V U * …Inverter output voltage command value; V U …voltage value; V V * …Inverter output voltage command value; V V …voltage value; V W * …Inverter output voltage command value; V W …voltage value; θ…phase angle.

Claims

1. A control device for a power conversion device, the power conversion device comprising: at least one AC capacitor disposed in a capacitor circuit branched from the AC circuit of an inverter output side, which is disconnected from the circuit in case of a fault; and a current sensor disposed in the capacitor circuit, which acquires the current value of the AC current flowing into each phase of the AC capacitor. Its features are, The control device has the following features: The amplitude calculation unit obtains the current value of the AC current flowing into the AC capacitor of each phase from the current sensor, and calculates the amplitude value of the fundamental component of the AC current of each phase based on the obtained current value of the AC current of each phase. as well as The fault determination unit compares the amplitude values ​​of the fundamental component of the AC current in each phase, calculated by the amplitude calculation unit, with a predetermined determination value. If the amplitude value of at least one phase of the fundamental component of the AC current in each phase is smaller than the predetermined determination value, the AC capacitor is determined to be faulty. The amplitude calculation unit calculates the amplitude value of the fundamental component of the AC current of each phase based on the specified current components of the AC current of each phase. The specified current components of the AC current of each phase are calculated by multiplying the current value of the AC current of each phase by the phase angle value adjusted based on the system voltage on the system side.

2. The control device as described in claim 1, characterized in that, The amplitude calculation unit calculates the amplitude value of the fundamental component of the alternating current of each phase based on the DC component extracted from the specified current component of the alternating current of each phase using a specified low-pass filter.

3. The control device as described in claim 1, characterized in that, It also includes an operation control unit. If the AC switch on the system side is turned on, and the fault determination unit determines that the AC capacitor is faulty, the operation control unit outputs an operation instruction to stop the power conversion device and disconnect the AC switch.

4. The control device as described in claim 1, characterized in that, It also includes an operation control unit. When the AC switch on the system side is turned off and the power conversion device is started, the operation control unit performs synchronization control to synchronize the output voltage of the inverter with the system voltage on the system side. When the fault determination unit determines that the AC capacitor is faulty, it outputs an operation instruction to stop the power conversion device.

5. A power conversion device, characterized in that, have: An inverter converts electrical energy into AC power. At least one AC capacitor is provided in the capacitor circuit branched from the AC circuit on the output side of the inverter, and is disconnected from the circuit in case of a fault. A current sensor is configured in the capacitor circuit to obtain the current value of the AC current flowing into each phase of the AC capacitor. An AC switch, configured in the AC circuit further on the system side than the branch point leading to the capacitor circuit, is capable of cutting off the AC current flowing to the system side; and The control device according to any one of claims 1 to 4.

6. A control device for a power conversion device, the power conversion device comprising: at least one AC capacitor disposed in a capacitor circuit branching from the AC circuit on the output side of an inverter, which is disconnected from the circuit in case of a fault; and a current sensor disposed in series with an AC reactor in the AC circuit on the output side of the inverter between the inverter and the branch point branching to the capacitor circuit, respectively acquiring the current value of the AC current flowing into each phase of the AC circuit; Its features are, The control device has the following features: The amplitude calculation unit, when performing synchronization control to synchronize the output voltage of the inverter with the system voltage on the system side during the startup of the power conversion device with the AC switch on the system side disconnected, obtains the current value of the AC current flowing into the AC capacitor from the current sensor, and calculates the amplitude value of the fundamental component of the AC current of each phase based on the obtained current value of the AC current of each phase. The fault determination unit compares the amplitude values ​​of the fundamental component of the AC current of each phase calculated by the amplitude calculation unit with a predetermined determination value. When the amplitude value of at least one phase of the fundamental component of the AC current of each phase is smaller than the predetermined determination value, the AC capacitor is determined to be faulty. as well as During the aforementioned synchronization control, when the fault determination unit determines that the AC capacitor is faulty, the fault information reporting unit reports the fault information of the AC capacitor. The amplitude calculation unit calculates the amplitude value of the fundamental component of the alternating current of each phase based on the specified current components of the alternating current of each phase. The specified current components of the alternating current of each phase are calculated by multiplying the current value of the alternating current of each phase by the phase angle value adjusted according to the system voltage on the system side.

7. The control device as described in claim 6, characterized in that, The amplitude calculation unit calculates the amplitude value of the fundamental component of the alternating current of each phase based on the DC component extracted from the specified current component of the alternating current of each phase using a specified low-pass filter.

8. The control device as described in claim 6, characterized in that, It also includes an action control unit, which, during the aforementioned synchronous control, outputs an action instruction to stop the aforementioned power conversion device when the fault information reporting unit reports a fault in the aforementioned AC capacitor.

9. A power conversion device, characterized in that, have: An inverter converts electrical energy into AC power. At least one AC capacitor is provided in the capacitor circuit branching off from the AC circuit on the output side of the inverter, and is disconnected from the circuit in case of a fault. A current sensor is configured in series with an AC reactor in the AC circuit on the output side of the inverter, between the inverter and the branch point leading to the capacitor circuit, to obtain the current value of the AC current flowing into each phase of the AC circuit. An AC switch, configured in the AC circuit closer to the system side than the branch point, is capable of cutting off the AC current flowing to the system side; and The control device according to any one of claims 6 to 8.

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