Control device, power conversion device

Abstract

A control device is a control device of a power conversion device, characterized by comprising: a conversion value calculation section that obtains a current value of a current flowing through an alternating current capacitor connected to a capacitor circuit in an output circuit on an alternating current side of an inverter circuit, and converts the current value to calculate a prescribed conversion value; and a fault detection section that compares the conversion value calculated by the conversion value calculation section with a prescribed determination value used in fault detection, and detects a fault of the alternating current capacitor.

Description

Technical Field

[0001] This invention relates to a fault detection method for control devices, power conversion devices, and AC capacitors. Background Technology

[0002] Conventionally, to obtain capacitor capacitance, it is known to have a structure in which multiple capacitors are connected in parallel (for example, see Patent Document 1). Furthermore, in power conversion devices that perform DC-to-three-phase AC conversion, multiple AC capacitors are also connected in parallel to the filter circuits (capacitor circuits) of each phase of the three-phase AC circuit in order to obtain capacitor capacitance.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2013-042072 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] In such power conversion devices, when a portion of the multiple AC capacitors connected in parallel experiences an open-circuit fault, although the voltage waveform is distorted, it has historically been unable to be detected as a fault during operation, and the power conversion device continues to operate. Furthermore, when all of the multiple AC capacitors connected in parallel experience an open-circuit fault, the voltage waveform is even more distorted than when only a portion is open-circuited; however, even in such cases, it has historically been unable to be detected as a fault during operation, and sometimes the power conversion device continues to operate.

[0008] However, if a partial open-circuit fault occurs in an AC capacitor and the fault cannot be detected during operation, the voltage applied will be concentrated on the normal AC capacitors, potentially causing the fault to spread to them. Furthermore, if the fault continues to be undetectable during operation even when all AC capacitors are open-circuited, significant harmonics may flow to the grid side.

[0009] Therefore, the purpose of this invention is to detect AC capacitor faults earlier in the event of an open-circuit fault in the AC capacitor during the operation of a power conversion device, and to suppress the spread of the fault to normal AC capacitors and the outflow of harmonics to the power grid side.

[0010] Methods used to solve problems

[0011] One control device related to the present invention is a control device for a power conversion device, characterized in that it comprises: a conversion value calculation unit that obtains the current value of the current flowing through an AC capacitor connected to a capacitor circuit in the output circuit on the AC side of the inverter circuit, and converts the current value to obtain a predetermined conversion value; and a fault detection unit that compares the conversion value obtained by the conversion value calculation unit with a predetermined judgment value used in fault detection to detect a fault in the AC capacitor.

[0012] Alternatively, in the control device of a certain technical solution, there may also be a determination value calculation unit, which obtains the voltage value of the output voltage of the inverter circuit and calculates the determination value used in fault detection based on the voltage value; the fault detection unit compares the transformation value calculated by the transformation value calculation unit with the determination value calculated by the determination value calculation unit to detect the fault of the AC capacitor.

[0013] Furthermore, in the control device of a certain technical solution, the output circuit on the AC side may be a three-phase AC circuit; the transformation value is the first q-axis current value, which is the value of the current component of the axis that is offset by 90 degrees from the capacitor voltage, obtained by the transformation value calculation unit by performing dq transformation on the current values ​​of each current flowing through each phase in multiple AC capacitors connected in parallel in each phase of the three-phase AC circuit.

[0014] Furthermore, in the control device of a certain technical solution, the determination value may be the second q-axis current value, which is the current component of the axis that is offset by 90 degrees from the capacitor voltage, calculated by the determination value calculation unit using the voltage value of the output voltage of the inverter circuit and the rated conductance value of the AC capacitor.

[0015] Furthermore, in the control device of a certain technical solution, the judgment value may be a value with an allowable error based on the value obtained by multiplying by a specified abnormality detection level.

[0016] In addition, in the control device of a certain technical solution, the fault detection unit may compare the magnitude of the change value and the judgment value, and detect the fault of the AC capacitor when the change value is smaller than the judgment value.

[0017] Furthermore, in the control device of a certain technical solution, a fault information reporting unit may also be provided, which reports the fault information to a designated upper device when the fault detection unit detects a fault in the AC capacitor.

[0018] Furthermore, in the control device of the relevant technical solution, there may also be an action control unit. When the fault detection unit detects a fault in the AC capacitor, the action control unit gives an action instruction to perform at least one of the actions of stopping the power conversion device or disconnecting the AC switch in the output circuit on the AC side.

[0019] The power conversion device of one aspect of the present invention is characterized by comprising: an inverter circuit for converting DC power to AC power; an AC capacitor connected to the capacitor circuit of each phase of the three-phase AC circuit on the AC side of the inverter circuit; a current sensor for acquiring the current value of the current flowing into the AC capacitor of each phase; a voltage sensor for acquiring the voltage value of the output voltage of the inverter circuit; and a control device as described in any one of technical solutions 1 to 7; a conversion value calculation unit for acquiring the current value acquired by the current sensor and calculating the conversion value; and a determination value calculation unit for acquiring the voltage value acquired by the voltage sensor and calculating the determination value.

[0020] Alternatively, in a power conversion device of a certain technical solution, the current sensor may be located in a capacitor circuit branching from the three-phase AC circuit.

[0021] In addition, in a power conversion device of a certain technical solution, the current sensor may be located before and after the branch point from the three-phase AC circuit to the capacitor circuit in the three-phase AC circuit.

[0022] Furthermore, in a power conversion device of a certain technical solution, AC capacitors may be connected in parallel with multiple packages that are connected by star or delta connections.

[0023] A fault detection method for an AC capacitor according to a technical solution of the present invention is a method for detecting faults in an AC capacitor in a power conversion device. The power conversion device comprises: an inverter circuit for converting DC power to AC power; an AC capacitor connected to the capacitor circuits of each phase of the three-phase AC circuit on the AC side of the inverter circuit; a current sensor for acquiring the current value flowing into the AC capacitors of each phase; and a voltage sensor for acquiring the voltage value of the output voltage of the inverter circuit. The fault detection method for the AC capacitor comprises: a transformation value calculation step for transforming the current value acquired by the current sensor to obtain a predetermined transformation value; and a fault detection step for comparing the transformation value obtained in the transformation value calculation step with a predetermined judgment value used in fault detection to detect a fault in the AC capacitor.

[0024] Invention Effects

[0025] According to the present invention, in the event of an open-circuit fault in an AC capacitor during the operation of a power conversion device, the fault in the AC capacitor can be detected earlier, and the fault can be prevented from spreading to normal AC capacitors and harmonics from flowing out to the power grid side. Attached Figure Description

[0026] Figure 1 This is a diagram illustrating one embodiment of a fault detection method for a control device, a power conversion device, and an AC capacitor.

[0027] Figure 2 It means in Figure 1 A diagram showing an example of another connection method for AC capacitors in a power conversion device.

[0028] Figure 3 It means Figure 1 and Figure 2 A diagram showing an example of the internal structure of a power conversion device.

[0029] Figure 4 It means Figure 3 The diagram shows an example of the structure of the inverter control unit.

[0030] Figure 5 It means Figures 1 to 4 The diagram shows an example of a fault detection action of the control device.

[0031] Figure 6 This is an explanation Figure 5 The diagram shows the fault detection logic.

[0032] Figure 7 It means Figures 1 to 6 The diagram shows an example of the operation of the power conversion device according to the relevant implementation.

[0033] Figure 8 It means Figures 1 to 7 The diagram shows other operational examples of the power conversion device according to the relevant embodiments.

[0034] Figure 9 This is a diagram illustrating an example of the operation of a power conversion device for a comparative example. Detailed Implementation

[0035] Hereinafter, embodiments of the control device, power conversion device, and AC capacitor fault detection method of the present invention will be described with reference to the accompanying drawings.

[0036] <One Implementation Method>

[0037] Figure 1 This is a diagram illustrating one embodiment of a fault detection method for a control device, a power conversion device, and an AC capacitor.

[0038] exist Figure 1 In the middle, the power conversion device 1 is in Figure 1 The DC terminal on the left side is connected to DC power supply 2. Figure 1 The AC terminal on the right side is connected to AC power system 3 (hereinafter also referred to as "grid 3").

[0039] The power conversion device 1 converts the DC power supplied from the DC power source 2 via the DC bus into AC power, and outputs the converted AC power to the power grid 3. The power conversion device 1 is also referred to as a power converter, inverter unit, power conditioner, or power conditioning subsystem (PCS).

[0040] The DC power supply 2 can be, for example, a solar cell consisting of a solar panel, solar cell module, or solar cell array, or a battery consisting of various secondary batteries or fuel cells, or both. Furthermore, the DC power supply 2 can be a DC power system consisting of a wind turbine and an AC-DC converter, or various renewable energy generation devices. The DC power supply 2 supplies DC power to the power conversion device 1.

[0041] The AC power system 3 (grid 3) is used to supply AC power output from the power conversion device 1 to the receiving equipment of the demanding user. It is an integrated system of power generation, transformation, transmission and distribution, and is connected to unspecified loads.

[0042] In addition, Figure 1 In the power conversion device 1, there are an inverter circuit 10, a three-phase AC circuit 20, an AC reactor 30, an AC switch 40, a capacitor circuit 50, an AC capacitor 60, a current sensor 70, and a control device 80.

[0043] The power conversion device 1 has a three-phase AC circuit 20 as an output circuit at the AC terminal (AC side) of the inverter circuit 10. The three-phase AC circuit 20 includes an AC reactor 30 and an AC switch 40. The three-phase AC circuit 20 is branched into a capacitor circuit 50 between the AC reactor 30 and the AC switch 40. The capacitor circuit 50 is connected to an AC capacitor 60 via a current sensor 70. The control device 80 is omitted from the diagram in its wiring, but it is electrically connected to all components of the power conversion device 1.

[0044] Inverter circuit 10, also known as power conversion circuit or simply inverter, is constructed from multiple switching elements such as IGBT (Insulated Gate Bipolar Transistor). Inverter circuit 10 has an inverter control circuit (not shown) that generates pulse-width modulated signals as gate drive signals for the switching elements. Inverter circuit 10 is connected to DC power supply 2 at the DC terminal via a DC bus, and to AC reactor 30 at the AC terminal via AC circuit 20. Inverter circuit 10 receives DC power from DC power supply 2 at the DC terminal via the DC bus, converts it into AC power, and outputs it at the AC terminal.

[0045] One end of the AC circuit 20 is connected to the AC terminal of the inverter circuit 10, and the other end is connected to the AC power system 3. The AC circuit 20 in this embodiment is a three-phase, three-wire AC circuit that supplies three-phase AC power from three systems of single-phase AC that combine current or voltage phases that are offset from each other using three wires / cables. Hereinafter, the AC circuit 20 will also be referred to as "three-phase AC circuit 20".

[0046] The AC reactor 30, also known as an AC (alternating current) reactor, is connected in series with each phase of the three-phase AC circuit 20 on the output side of the inverter circuit 10. The AC reactor 30 on the output side of the inverter circuit 10 reduces noise and suppresses surge voltage. The AC reactor 30 and the AC capacitor 60 (described later) constitute an L-type connected LC filter circuit (filter circuit).

[0047] An AC switch (AC on / off switch) 40 is connected in series in each phase of the three-phase AC circuit 20 between the aforementioned LC filter circuit and the AC power system 3, and connects or disconnects the AC circuit 20 according to the on / off instructions from the control device 80 (described later) or the operator. If the AC switch 40 is disconnected, the flow of AC power supplied from the inverter circuit 10 to the AC power system 3 is cut off.

[0048] The capacitor circuit 50 is a circuit with one end branching from each phase of the three-phase AC circuit 20 between the AC reactor 30 and the AC switch 40, and the other end connected to the AC capacitor 60. Additionally, the capacitor circuit 50 is an example of an LC filter circuit (filter circuit).

[0049] The AC capacitor 60 is an electronic component that stores or releases electrical charge, and is also called an AC (alternating-current) capacitor, AC capacitor (alternating-current capacitor), or filter capacitor. Hereinafter, the AC capacitor 60 will also be referred to as "AC capacitor 60". The AC capacitor 60 acts as a filter to remove fluctuations (vibrations) when the switching elements (not shown) of the inverter circuit 10 are switched on and off, suppressing harmonics (harmonic currents) from flowing out to the power grid 3 side.

[0050] To obtain electrostatic capacitance or to meet rated current, the capacitor circuits 50 of each phase (u-phase, v-phase, w-phase) of the three-phase AC circuit 20 are branched into multiple branches and connected in parallel. In this embodiment, each phase of the capacitor circuit 50 is branched into 3 branches, and each phase of the AC capacitor 60 is connected in parallel with 3 branches, but the number of branches and parallel connections is not limited to this. For example, each phase of the capacitor circuit 50 may be branched into 5 branches, and each phase of the AC capacitor 60 may be connected in parallel with 5 branches. The AC capacitor 60 may also be packaged in three phases, with one AC capacitor package 61 connected in parallel. Furthermore, in each AC capacitor package 61, the AC capacitor 60 is delta connected (Δ connection), but it may also be star connected (Y connection), or other connection methods. In addition, AC capacitors 60 or AC capacitor packages 61 with different connection methods may be mixed and connected in parallel.

[0051] Each AC capacitor 60 has a protection mechanism 62. The protection mechanism 62 functions like a fuse to disconnect the AC capacitor 60 from the circuit when an abnormality occurs in the AC capacitor 60, such as a rise in the internal voltage of the AC capacitor 60. The protection mechanism 62 can be a mechanism that disconnects the AC capacitor 60 from the circuit individually, or it can disconnect the AC capacitor 60 from the circuit for each AC capacitor package 61. Furthermore, the protection mechanism 62 is not limited to... Figure 1 It can be configured as shown with each AC capacitor 60, or it can be configured with each AC capacitor package 61.

[0052] Figure 2 It means in Figure 1 A diagram showing an example of another connection method for the AC capacitor 60 in the power conversion device 1. Figure 2 In China, for the sake of Figure 1 The same structure is given to Figure 1 The same designation is used; detailed descriptions are omitted. For example, an AC capacitor of 60 can be... Figure 2 The connection shown can also be Figure 2 The AC capacitor 61 is shown in a specific configuration. That is, the parallel connection method of the AC capacitors 60 is not particularly limited. Furthermore, in... Figure 2Nakaya and Figure 1 Similarly, the location of the protection mechanism 62 is not limited to... Figure 2 The location shown.

[0053] Back Figure 1 The current sensor 70, such as a Hall effect sensor or a current transformer (CT) sensor, is configured in each of the three-phase capacitor circuits 50 to measure the current flowing into each of the three-phase AC capacitors 60. Furthermore, the location of the current sensor 70 is not limited to... Figure 1 The location shown can, for example, be set in the branch destination circuit of each of the three-phase capacitor circuits 50.

[0054] In addition, as will be discussed later Figure 8 As shown, the current sensor 70 can also be positioned before and after the branch point where the three-phase AC circuit 20 branches off to the capacitor circuit 50. This is because, as will be explained later... Figure 8 As shown, theoretically, the current value I measured by the current sensor 70... 70 Equal to the current value I measured by the current sensor 70X X Subtract the current value I measured by current sensor 70Y Y The obtained value. That is, theoretically, the current value I. 70 = Current value I X - Current value I Y This is true. Therefore, as long as the current value I is known... X The value and current value I Y Theoretically, the current value I can be calculated from the value of . 70 The value. Therefore, even if the current sensor 70 is not configured in each of the three-phase capacitor circuits 50, as long as the current sensor 70 is not configured in each of the three-phase capacitor circuits 50, the current sensor 70 can still be used. Figure 8 The current sensors 70X and 70Y shown are configured in the three-phase AC circuit 20, which can obtain the current values ​​of the current flowing into each AC capacitor 60 of the three phases.

[0055] The control device 80, for example, is a processor such as a CPU (Central Processing Unit) or GPU (Graphics Processing Unit) that operates by executing programs, and performs overall control of the operation of the power conversion device 1 according to a predetermined program. The control device 80 is located inside or outside the power conversion device 1; wiring is omitted in the figure, but it is electrically connected to the various components of the power conversion device 1 via wired or wireless means. The control device 80, for example, can acquire the measured value of the current sensor 70 or control the operation of the inverter circuit 10 and the AC switch 40.

[0056] The control device 80 has the functions of a voltage conversion unit 81, a current conversion unit 82, a phase synchronization circuit 83, a power control unit 84, and an inverter control unit 85 (see reference). Figure 3 Additionally, some or all of these functions may also be provided by an inverter control circuit (not shown) of the inverter circuit 10. Further details regarding the aforementioned functions of the control device 80 will be described later.

[0057] Figure 3 It means Figure 1 and Figure 2 A diagram showing an example of the internal structure of the power conversion device 1. Figure 3 In China, for the sake of Figure 1 and Figure 2 The same structure is given to Figure 1 and Figure 2 For the same numbering, detailed explanations will be omitted. Additionally, in Figure 3 In reality, as shown in the text. Figure 1 and Figure 2 As shown, a three-phase AC circuit 20 is connected to the output side of the inverter circuit 10, and is equipped with a three-phase AC reactor 30, an AC switch 40, and an AC capacitor 60. Furthermore, the AC capacitor 60 is actually... Figure 1 and Figure 2 As shown, multiple elements are connected in parallel on each phase, but for the sake of simplicity, these elements are simplified.

[0058] exist Figure 3 In the inverter circuit 1, the power conversion device 1 has a voltage sensor 21 and a current sensor 22 in the AC circuit 20 between the AC switch 40 and the power grid 3. The voltage sensor 21 measures the voltage value V of the output voltage of the inverter circuit 10. The current sensor 22 measures the current value I of the current output from the inverter circuit 10.

[0059] As described above, the control device 80 has the functions of a voltage conversion unit 81, a current conversion unit 82, a phase synchronization circuit 83, a power control unit 84, and an inverter control unit 85.

[0060] The voltage conversion unit 81 obtains the voltage value V from the voltage sensor 21 and the phase command value θ from the phase synchronization circuit 83. * The voltage conversion unit 81 converts the acquired voltage value V based on the acquired phase command value θ. * Convert the signal to a dq signal (dq transformation) and calculate the d-axis voltage value V. d and q-axis voltage value V q The voltage is output to the power control unit 84. Furthermore, the voltage conversion unit 81 converts the voltage value V measured by the voltage sensor 21 or the d-axis voltage value V after dq conversion by the voltage conversion unit 81. d and q-axis voltage value V qOutput is sent to phase synchronization circuit 83. Furthermore, the dq transformation is a 3-phase to 2-phase transformation, i.e., a coordinate transformation from 3-phase to 2-phase, used to represent three-phase AC using two axes. Here, in this embodiment, the d-axis is the same as the capacitor voltage, and the q-axis is an axis offset by 90 degrees from the capacitor voltage.

[0061] The current conversion unit 82 obtains the current value I from the current sensor 22 and the phase command value θ from the phase synchronization circuit 83. * The current conversion unit 82 converts the acquired current value I based on the acquired phase command value θ. * Perform a dq transformation to obtain the d-axis current value I. d and q-axis current value I q The current is output to the power control unit 84. Furthermore, as described above, in this embodiment, the d-axis is the same axis as the capacitor voltage, and the q-axis is an axis offset by 90 degrees from the capacitor voltage. Therefore, the q-axis current value I... q It is the value of the current component relative to an axis that is 90 degrees out of phase with respect to the capacitor voltage.

[0062] The phase synchronization circuit 83 constitutes a frequency negative feedback circuit. The phase synchronization circuit 83 is an electronic circuit that uses feedback control based on an input periodic signal to output a phase-synchronized signal from other oscillators. The phase synchronization circuit 83 obtains the voltage value V or the d-axis voltage value V from the voltage conversion unit 81. d and q-axis voltage value V q The phase synchronization circuit 83 performs PLL (Phase Locked Loop) control based on the phase θ of the acquired voltage value to ensure that the q-axis voltage value V... q If the value becomes 0, calculate the phase command value θ. * The phase synchronization circuit 83 calculates the phase command value θ. * Output to voltage conversion unit 81 and current conversion unit 82.

[0063] The power control unit 84 obtains the d-axis voltage value V from the voltage conversion unit 81. d and q-axis voltage value V q The d-axis current value I is obtained from the current conversion unit 82. d and q-axis current value I q The power control unit 84 is connected to the inverter circuit 10 and uses these voltage values ​​V. d V q and current value I d I q The inverter circuit 10 (power conversion device 1) is controlled as a whole. The power control unit 84 is also connected to the inverter control unit 85 and outputs these voltage values ​​V to the inverter control unit 85. d V qand current value I d I q Furthermore, the structure of the inverter control unit 85 will be described later.

[0064] Figure 4 It means Figure 3 The diagram shows an example of the structure of the inverter control unit 85. Additionally, Figure 3 The structure of the power control unit 84 and the inverter control unit 85 is one example. Alternatively, the power control unit 84 may have the functions of the inverter control unit 85, or the inverter control unit 85 may have the functions of the power control unit 84. Furthermore, other elements within the control device 80 may also have these functions.

[0065] The inverter control unit 85 has the functions of a conversion value calculation unit 91, a judgment value calculation unit 92, a storage unit 93, a fault detection unit 94, a fault information reporting unit 95, and an operation control unit 96. The conversion value calculation unit 91, the judgment value calculation unit 92, the fault detection unit 94, the fault information reporting unit 95, and the operation control unit 96 execute, for example, a program stored in the storage unit 93 to perform the following processing.

[0066] The transformation value calculation unit 91 obtains the measured current values ​​Iu, Iv, and Iw from the current sensor 70, which are the currents flowing into the three-phase (u-phase, v-phase, w-phase) AC capacitor 60. The transformation value calculation unit 91 performs a dq transformation on the current values ​​Iu, Iv, and Iw using a prescribed calculation program to calculate the transformation value, i.e., the d-axis current value I. d1 and q-axis current value I q1 Additionally, the q-axis current value I q1 This is an example of the "transformation value" and "1st q-axis current value" in the technical solution.

[0067] The determination value calculation unit 92 obtains the d-axis voltage value V, which is a measured value of the output voltage of the inverter circuit 10, from the power control unit 84. d The determination value calculation unit 92 obtains the rated conductance value of the AC capacitor 60 stored in the storage unit 93. The rated conductance value of the AC capacitor 60 is, for example, the total value of all the AC capacitors 60 connected in parallel under normal conditions, and is a constant value. The determination value calculation unit 92, for example, uses the obtained d-axis voltage value V... d Multiply the value of the rated conductance of the obtained AC capacitor 60 to obtain the q-axis current value I'. q Additionally, the calculated q-axis current value I' q This is the theoretical value of the q-axis current when all 60A of the AC capacitors are functioning normally.

[0068] The judgment value calculation unit 92 obtains the anomaly detection level value stored in the storage unit 93. Alternatively, the anomaly detection level value can be pre-loaded into the program executed by the judgment value calculation unit 92. The judgment value calculation unit 92 then calculates the theoretical q-axis current value I'. q Multiply the value of the obtained or programmed anomaly detection level by the value of the q-axis current I', which serves as the decision value. q2 Here, the anomaly detection level value in this embodiment is, for example, a value smaller than 1, such as 0.8. Additionally, the q-axis current value I' q Or q-axis current value I' q2 The (judgment value) can also be a predetermined value (a specified judgment value used in fault detection). In this case, the judgment value calculation unit 92 can be omitted. Additionally, the q-axis current value I' q 2 is an example of the "judgment value" and "second q-axis current value" in the technical solution.

[0069] The storage unit 93 is, for example, a volatile or non-volatile storage medium such as DRAM (Dynamic Random Access Memory), HDD (Hard Disk Drive), or SSD (Solid State Drive). The storage unit 93 stores programs executed by each part of the control device 80, and various information is written and read by each part of the control device 80. The storage unit 93 also stores programs and information executed by the inverter control unit 85, such as the rated conductance value of the AC capacitor 60 used by the judgment value calculation unit 92 and the abnormality detection level value. Alternatively, the storage unit 93 can be located externally to the control device 80 and connected to the control device 80 via a wired or wireless network.

[0070] The fault detection unit 94 calculates the q-axis current value I obtained by the transformation value calculation unit 91. q1 The q-axis current value I' calculated by the determination value calculation unit 92 q2 The fault detection unit 94 compares the AC capacitor 60 to the q-axis current value I. q1 and q-axis current value I' q2 Perform a magnitude comparison when the q-axis current value I q1 Comparison of q-axis current value I' q2 After a certain period of time, it is determined that AC capacitor 60 has malfunctioned, and the fault in AC capacitor 60 is detected. When the fault detection unit 94 detects a fault in AC capacitor 60, it outputs fault information to at least one of the fault information reporting unit 95 and the action control unit 96. Alternatively, the fault detection unit 94 may also use the q-axis current value I calculated by the transformation value calculation unit 91. q1The AC capacitor 60 is fault-detected by comparing it with a predetermined judgment value (a specified judgment value used in fault detection). In this case, the judgment value calculation unit 92 can also be omitted.

[0071] When the fault detection unit 94 detects a fault in the AC capacitor 60, the fault information reporting unit 95 obtains the fault information of the AC capacitor 60 from the fault detection unit 94, and reports the fault information to a host device (not shown) or the like. That is, the fault information reporting unit 95 may report an alarm or warning to a host device (not shown) or the operation panel of the power conversion device 1, for example.

[0072] When the fault detection unit 94 detects a fault in the AC capacitor 60, the operation control unit 96 obtains fault information about the AC capacitor 60 from the fault detection unit 94. Then, in order to perform at least one of the actions of stopping the power conversion device 1 or disconnecting the AC switch 40, the operation control unit 96 issues operation instructions to them.

[0073] <Action of Implementation Method 1>

[0074] Figure 5 It means Figures 1 to 4 The diagram shows an example of the fault detection operation of the control device 80. Additionally, Figure 5 This is an example of a fault detection operation of the inverter control unit 85 during the operation of the power conversion device 1. Here, in this embodiment, as described above, the d-axis is the same as the capacitor voltage, and the q-axis is an axis offset by 90 degrees from the capacitor voltage.

[0075] In step S1, the transformation value calculation unit 91 obtains the current values ​​Iu, Iv, and Iw from the current sensor 70 as measured values ​​of the current flowing into the three-phase (u-phase, v-phase, w-phase) AC capacitor 60. Additionally, the current sensor 70 measures the constant current values ​​Iu, Iv, and Iw, and the transformation value calculation unit 91 obtains these constant current values.

[0076] In step S2, the transformation value calculation unit 91 performs dq transformation on the current values ​​Iu, Iv, and Iw using a prescribed calculation program to calculate the d-axis current value I. d1 and q-axis current value I q1 .

[0077] In step S3, the transformation value calculation unit 91 calculates the q-axis current value I. q1 Output to fault detection unit 94. Furthermore, when performing a dq transformation to make the q-axis voltage zero, i.e., only the d-axis voltage is visible, even if the capacitance of AC capacitor 60 is reduced, the d-axis current value I... d1 It does not change, so the d-axis current value I d1This will not affect the fault detection of the AC capacitor 60. Therefore, the transformation value calculation unit 91 will calculate the q-axis current value I. q1 Output to fault detection unit 94.

[0078] In step S4, the determination value calculation unit 92 obtains the d-axis voltage value V, which is a measured value of the output voltage of the inverter circuit 10, from the power control unit 84. d .

[0079] In step S5, the determination value calculation unit 92 obtains the rated conductance value (a certain value) of the AC capacitor 60 stored in the storage unit 93.

[0080] In step S6, the determination value calculation unit 92 calculates the obtained d-axis voltage value V d Multiply by the obtained rated conductance of AC capacitor 60 to obtain the theoretical q-axis current value I'. q .

[0081] In step S7, the determination value calculation unit 92 obtains the anomaly detection level value stored in the storage unit 93. Furthermore, in this embodiment, it is assumed that the anomaly detection level value is 0.8.

[0082] In step S8, the determination value calculation unit 92 determines the q-axis current value I' as the theoretical value. q Multiply by 0.8, which is the anomaly detection level, to obtain the q-axis current value I', which serves as the judgment value. q2 .

[0083] In step S9, the fault detection unit 94 calculates the q-axis current value I from the transformation value calculation unit 91. q1 The q-axis current value I' is calculated by the determination value calculation unit 92. q2 A size comparison is performed. Furthermore, the fault detection unit 94 checks the q-axis current value I. q1 Comparison of q-axis current value I' q2 If the fault occurs within a certain time frame, it is determined that AC capacitor 60 has malfunctioned, and the fault in AC capacitor 60 is detected. Additionally, the fault detection unit 94 can also process the q-axis current value I calculated by the transformation value calculation unit 91. q1 The fault is detected by comparing the value with a predetermined judgment value (a specified judgment value used in fault detection). Furthermore, when the fault detection unit 94 detects a fault in the AC capacitor 60, it outputs fault information to at least one of the fault information reporting unit 95 and the action control unit 96.

[0084] Figure 6 This is an explanation Figure 5 The diagram shows the fault detection logic. Figure 6 In (a), the central comparator represents the fault detection unit 94. The upper left I...q1 The q-axis current value I obtained in step S3 q1 The I' in the center left q The q-axis current value I' is the theoretical value obtained in step S6. q The 0.8 in the lower left corner is the anomaly detection level value obtained in step S7. Furthermore, in Figure 6 In (a), the q-axis current value I is represented. q1 and the q-axis current value I' which will be used as the theoretical value q The q-axis current value I' is obtained by multiplying it by 0.8, which is the value used for anomaly detection. q2 The status output to the fault detection unit 94.

[0085] Here, as mentioned above, the anomaly detection level is a value less than 1; for example, it is 0.8 in this embodiment. Typically, when the AC capacitor 60 is functioning normally, the q-axis current value I is calculated based on the measured value of the current flowing into the AC capacitor 60. q1 And the q-axis current value I' calculated based on the output voltage value (measured value) of inverter circuit 10. q The values ​​should be the same. However, since there is also some error, in order to allow for some error, the determination value calculation unit 92 sets the q-axis current value I', which is the theoretical value, to be the same. q Multiply by the anomaly detection level, which is less than 1 (0.8), to obtain the q-axis current value I'. q2 Therefore, even with some error, under normal conditions with an AC capacitor of 60, the q-axis current value I should still be [value missing]. q1 The q-axis current value I' multiplied by 0.8 q2 big.

[0086] Despite this, the q-axis current value I q1 The q-axis current value I' multiplied by 0.8 q2 The fact that the current value was measured within hours suggests that some abnormality has occurred in the AC capacitor 60. Therefore, the fault detection unit 94 checks the q-axis current value I. q1 and q-axis current value I' q2 Perform a magnitude comparison when the q-axis current value I q1 Comparison of q-axis current value I' q2 After one hour, it was determined that AC capacitor 60 had malfunctioned, and the fault in AC capacitor 60 was detected.

[0087] If explained using numerical formulas, it would be as follows. Let's take the case of an AC capacitor 60 open-circuit failure as an example. First, the theoretical q-axis current value I' is calculated using the following equation (1). q .

[0088] [Formula 1]

[0089] I' q =2πf′CV d ·····(1)

[0090] Next, for example, if three AC capacitors 60 are connected in parallel, and all AC capacitors 60 are in normal condition, the q-axis current value I is... q1 It can be obtained from the following equation (2).

[0091] [Formula 2]

[0092] I q1 =2πfCV d ·····(2)

[0093] That is, in V d Under the same conditions, the q-axis current value I' obtained from equation (1) q and the q-axis current value I obtained from equation (2) q1 The values ​​are the same. Therefore, even with some error, under the condition that the AC capacitor is 60° and the current is normal, the q-axis current value I obtained from equation (2) is the same. q1 Also compare the q-axis current value I' obtained from equation (1) q The q-axis current value I' obtained by multiplying by 0.8 q2 big.

[0094] Next, for example, in the case where there are 3 AC capacitors connected in parallel (60), and one of the 3 capacitors experiences an open-circuit fault, the q-axis current value I... q1 It can be obtained from the following equation (3).

[0095] [Formula 3]

[0096]

[0097] According to equation (3), the q-axis current value I of AC capacitor 60 under normal conditions is... q1 Multiply by (2 / 3) ≒ 0.67. Therefore, the q-axis current value I obtained from equation (3) is... q1 Compare the q-axis current value I' obtained from equation (1) q The q-axis current value I' obtained by multiplying by 0.8 q2 Small. Therefore, the fault detection unit 94 detects the q-axis current value I. q1 Comparison of q-axis current value I' q2 After one hour, the fault was determined to be AC ​​capacitor 60, and the fault of AC capacitor 60 was detected.

[0098] Here, taking the case of an open-circuit fault in AC capacitor 60 as an example, we will explain why the q-axis current value I changes when an abnormality occurs in AC capacitor 60. q1 It becomes more than the q-axis current value I'q2 Small. Typically, the current flowing through AC capacitor 60 is represented by a complex number and is calculated using equation (4) below. Additionally, Figure 6 (b) will represent equation (4) graphically.

[0099] [Formula 4]

[0100]

[0101] According to equation (4), since the capacitance C of the AC capacitor decreases when the AC capacitor is open-circuited (60°), the current value I also decreases proportionally. Thus, the q-axis current value I... q1 It also decreases. Therefore, if the AC capacitor 60 has an open circuit fault, the q-axis current value I... q1 It becomes more than the q-axis current value I' q (q-axis current value I') q2 Small. In addition, according to equation (4), it represents the current flowing through AC capacitor 60 with a phase relative to the voltage and a magnitude of ωC phase advanced by 90 degrees.

[0102] Therefore, the fault detection unit 94 measures the q-axis current value I. q1 and q-axis current value I' q2 Perform a magnitude comparison when the q-axis current value I q1 Comparison of q-axis current value I' q2 If the voltage drops below a certain level, the AC capacitor 60 is determined to be faulty, and the fault is detected. This is because when the capacitance C of the AC capacitor 60 decreases, the current also decreases, and the fault detection unit 94 utilizes this property to detect the fault in the AC capacitor 60. Furthermore, the fault detection unit 94 also detects the fault in the AC capacitor 60 based on the magnitude of the current component that is 90 degrees phase ahead of the voltage phase.

[0103] Back Figure 5 In step S10, when the fault detection unit 94 detects a fault in the AC capacitor 60, the fault information reporting unit 95 obtains the fault information of the AC capacitor 60 from the fault detection unit 94. Furthermore, the fault information reporting unit 95 reports fault information such as alarms or warnings to, for example, a host device (not shown) or the operation panel of the power conversion device 1.

[0104] Therefore, the power conversion device 1 can be stopped or the AC switch 40 can be disconnected, either manually, by a host device (not shown), or by software. By doing so, the propagation of faults to the normal AC capacitor 60 or the outflow of harmonics to the power grid 3 can be suppressed. Alternatively, the stopping of the power conversion device 1 can be prioritized over the disconnection of the AC switch 40.

[0105] In addition, a host device (not shown) monitors and controls multiple power conversion devices 1 as a whole, and is connected to each power conversion device 1 via wired or wireless means.

[0106] In step S11, when the fault detection unit 94 detects a fault in the AC capacitor 60, the operation control unit 96 obtains fault information of the AC capacitor 60 from the fault detection unit 94. Furthermore, the operation control unit 96 provides operation instructions to either stop the power conversion device 1 or disconnect the AC switch 40.

[0107] Therefore, by stopping the power conversion device 1 or opening the AC switch 40, or both, the spread of the fault to the normal AC capacitor 60 or the outflow of harmonics to the power grid 3 can be suppressed. Alternatively, similar to step S9 described above, stopping the power conversion device 1 or opening the AC switch 40 can be prioritized.

[0108] Figure 7 It means Figures 1 to 6 The diagram shows an example of the operation of the power conversion device 1 according to the relevant embodiment. Figure 7 (a) is a diagram showing the operating state of the power conversion device 1. Figure 7 (b) is a diagram showing the state when an open-circuit fault occurs in AC capacitor 60 during the operation of power conversion device 1.

[0109] In addition, Figure 7 In reality, as shown in the text. Figure 1 and Figure 2 As shown, a three-phase AC circuit 20 is connected to the output side of the inverter circuit 10, and is equipped with a three-phase AC reactor 30, an AC switch 40, and an AC capacitor 60. Furthermore, the AC capacitor 60 is actually... Figure 1 and Figure 2 As shown, multiple connections are linked in parallel across each phase. However, with... Figure 3 Similarly, these elements are simplified for the sake of simplicity in the illustration.

[0110] exist Figure 7 In (a), during the operation of the power conversion device 1, the AC switch 40 is turned on. As a result, AC power output from the inverter circuit 10 flows to the grid 3 side. In the power conversion device 1, a current sensor 70 is provided in the capacitor circuit 50, which constantly detects the current values ​​Iu, Iv, and Iw of the multiple AC capacitors connected in parallel for each phase. Furthermore, the control device 80 constantly performs... Figure 5 The actions shown are from step S1 to step S9.

[0111] exist Figure 7In (b), if an open-circuit fault occurs in a portion of the AC capacitor 60 during the operation of the power conversion device 1, the q-axis current value I is calculated based on the current values ​​Iu, Iv, and Iw of the multiple AC capacitors 60 connected in parallel for each phase. q1 It becomes smaller than normal. Therefore, the control device 80 in Figure 5 In step S9, the situation is detected as an open-circuit fault in AC capacitor 60. When the control device 80 detects an open-circuit fault in AC capacitor 60, it reports the fault information in step S10 and stops the power conversion device 1 in step S11, disconnecting the AC switch 40 and stopping the voltage application to AC capacitor 60. This prevents the fault from spreading to the normal AC capacitor 60 and suppresses harmonic outflow to the power grid 3 side.

[0112] <Effects of the first implementation method>

[0113] The above, in Figures 1 to 7 In the illustrated embodiment, multiple current sensors 70 are provided to measure the current values ​​flowing into multiple AC capacitors 60, which are connected in parallel in the capacitor circuits 50 of each phase of the AC circuit 20. Therefore, the control device 80 can detect changes in the current values ​​flowing into the AC capacitors 60 during the operation of the power conversion device 1, and thus can detect open-circuit faults in the AC capacitors 60 during the operation of the power conversion device 1.

[0114] In addition, Figures 1 to 7 In the embodiment shown, in step S8, the determination value calculation unit 92 calculates the q-axis current value I', which is the theoretical value, obtained in step S6. q Multiply by the value of the anomaly detection level obtained in step S7. Therefore, even if there are some errors in the current values ​​compared by the fault detection unit 94, some error can be tolerated.

[0115] In addition, Figures 1 to 7 In the illustrated embodiment, in step S10, when the fault information reporting unit 95 obtains fault information about the AC capacitor 60, it reports the obtained fault information to a host device (not shown). This allows for, for example, manual operation, operation of the power conversion device 1, or disconnection of the AC switch 40 via a host device (not shown), or software. In this way, the propagation of the fault to the normal AC capacitor 60 and the outflow of harmonics to the power grid 3 can be suppressed.

[0116] In addition, Figures 1 to 7In the illustrated embodiment, in step S11, when the operation control unit 96 obtains fault information about the AC capacitor 60, it provides operation instructions for at least one of the following actions: stopping the power conversion device 1 or disconnecting the AC switch 40. Thus, by stopping the power conversion device 1 or disconnecting the AC switch 40, or both, the spread of the fault to the normal AC capacitor 60 and the outflow of harmonics to the power grid 3 side can be suppressed.

[0117] <Variation Example>

[0118] Figure 8 It means as Figures 1 to 7 A diagram illustrating an operational example of a modified embodiment of the power conversion device 1'. Figure 8 In China, for the sake of Figures 1 to 7 The same structures shown in the embodiments are given the same reference numerals, and detailed descriptions are omitted. Additionally, in Figure 8 In, also with Figure 7 same, Figure 8 (a) indicates that the power conversion device 1' is in operation. Figure 8 (b) indicates the state when an open-circuit fault occurs in AC capacitor 60 during the operation of power conversion device 1'. Furthermore, in Figure 8 Nakaya and Figure 7 Similarly, the elements are simplified for the sake of simplicity in the diagram.

[0119] exist Figure 8 In this circuit, the power conversion device 1' replaces the current sensor 70 in the capacitor circuit 50, and current sensors 70X and 70Y are provided in the three-phase AC circuit 20. In the three-phase AC circuit 20, current sensor 70X is located before the branch point from the three-phase AC circuit 20 to the capacitor circuit 50, and current sensor 70Y is located after the branch point from the three-phase AC circuit 20 to the capacitor circuit 50.

[0120] Theoretically, the current value I measured by the current sensor 70 70 Equal to the current value I measured by the current sensor 70X X Subtract the current value I measured by current sensor 70Y Y The obtained value. That is, theoretically, the current value I. 70 = Current value I X - Current value I Y This is true. Therefore, as long as the current value I is known... X The value and current value I Y Theoretically, the current value I can be calculated from the value of . 70 The value. Therefore, even if the current sensor 70 is not configured in each of the three-phase capacitor circuits 50, as long as in Figure 8With current sensors 70X and 70Y positioned as shown, the control device 80 can obtain the current values ​​flowing into each of the three-phase AC capacitors 60.

[0121] Based on the above, through Figure 8 The power conversion device 1' shown, and the control device 80, can also theoretically calculate and obtain the current value I measured by the current sensor 70. 70 Therefore, it plays the role of Figures 1 to 7 The implementation shown achieves the same effect.

[0122] <Comparative Example>

[0123] Figure 9 This is a diagram illustrating an example of the operation of the power conversion device 100 in relation to a comparative example. Figure 9 (a) is a diagram showing the state when an open-circuit fault occurs in a portion of the AC capacitor 60 of the power conversion device 100. Figure 9 (b) is a diagram showing the state when an open-circuit fault occurs in all of the AC capacitors 60. Additionally, in Figure 9 In China, for the sake of Figures 1 to 7 The same structures shown in the embodiments are assigned the same reference numerals, and detailed descriptions are omitted.

[0124] In addition, Figure 9 In fact, as Figure 1 and Figure 2 As shown, a three-phase AC circuit 20 is connected to the output side of the inverter circuit 10, and is equipped with a three-phase AC reactor 30, an AC switch 40, and an AC capacitor 60. Furthermore, the AC capacitor 60 is actually... Figure 1 and Figure 2 As shown, multiple connections are linked in parallel across each phase. However, with... Figure 3 and Figure 7 Similarly, for the sake of simplicity, these elements are simplified and represented.

[0125] exist Figure 9 In the comparative examples shown, with Figures 1 to 7 The implementation shown differs in that a current sensor 70 is not provided in the capacitor circuit 50. Therefore, the control device 80 cannot detect the current flowing into the AC capacitor 60.

[0126] exist Figure 9In (a), when an open-circuit fault occurs in a portion of the AC capacitor 60 during operation of the power conversion device 100 in the comparative example, the control device 80 can only detect voltage waveform distortion. However, since no current sensor 70 is provided in the capacitor circuit 50, the control device 80 cannot detect it as a fault in the AC capacitor 60, and therefore continues to operate. Thus, in the power conversion device 100 of the comparative example, the load may be concentrated on the normal AC capacitor 60, and the normal AC capacitor 60 may also fail like dominoes. Furthermore, in the power conversion device 100 of the comparative example, if the load is too concentrated on a single AC capacitor 60, the protection mechanism 62 may not be able to keep up, and the AC capacitor 60 (AC capacitor package 61) may also be damaged.

[0127] In addition, Figure 9 In (a), when the power conversion device 100 of the comparative example is stopped, the control device 80 starts the power conversion device 100 by synchronizing the inverter output voltage of the AC circuit 20 with the voltage of the power grid 3 and then turning on the AC switch 40. However, in the power conversion device 100 of the comparative example, the control device 80 cannot detect the fault of the AC capacitor 60, so even if an open circuit fault occurs in a part of the AC capacitor 60, the power conversion device 100 can still be started. Therefore, in the power conversion device 100 of the comparative example, there is a possibility that the fault may spread to the normal AC capacitor 60, just as it does during operation.

[0128] On the other hand, Figures 1 to 7 In the illustrated embodiment, a current sensor 70 is provided in the capacitor circuit 50. Therefore, the control device 80 can immediately detect an open-circuit fault in the AC capacitor 60 during or after the operation of the power conversion device 1, and can suppress the fault from spreading to the normal AC capacitor 60 or the harmonics from flowing out to the power grid 3. Furthermore, in Figure 8 In the variant examples shown, it also plays a role similar to Figures 1 to 7 The implementation shown achieves the same effect.

[0129] exist Figure 9 In (b), when an open-circuit fault occurs in all of the AC capacitors 60 during operation of the power conversion device 100 in the comparative example, the control device 80 can detect the voltage waveform distortion due to further distortion. However, since no current sensor 70 is provided in the capacitor circuit 50, the control device 80 cannot detect it as a fault in the AC capacitors 60, and operation continues. Therefore, in the power conversion device 100 of the comparative example, it is possible for harmonic current to flow out to the grid 3 side.

[0130] In addition, Figure 9 In (b), when the power conversion device 100 in the comparative example is stopped, the control device 80 synchronizes the inverter output voltage of the AC circuit 20 with the voltage of the power grid 3, and then turns on the AC switch 40 to start the power conversion device 100. Figure 9 In the case shown in (b), where all AC capacitors 60 fail, the synchronization control between the inverter output voltage and the grid voltage 3 no longer operates correctly, and the control device 80 detects a fault in the power conversion device 1 as a "synchronization mismatch". This is because the control device 80 calculates the inverter output voltage by taking into account the capacitance of the AC capacitors 60 in its software, so if all AC capacitors 60 fail, the calculation will no longer be a match.

[0131] That is, since the control device 80 performs power control of the power conversion device 1, it only needs to know the capacitance of the AC capacitor 60 to determine how much current should flow to match the inverter output voltage with the grid voltage 3. However, if the AC capacitor 60 fails, more current will flow, resulting in a larger inverter output voltage. Therefore, the control device 80 will not match the inverter output voltage with the grid voltage 3, and will detect a fault in the power conversion device 1 as a "synchronization mismatch".

[0132] Thus, in the power conversion device 100 of the comparative example, the fault of AC capacitor 60 cannot be detected during operation, but can be detected by measuring voltage during synchronization matching at startup. As a result, in the power conversion device 100 of the comparative example, the fault may amplify to the normal AC capacitor 60 during operation, or harmonics may flow to the power grid 3 side.

[0133] On the other hand, Figures 1 to 7 In the illustrated embodiment, a current sensor 70 is provided in the capacitor circuit 50. Therefore, the control device 80 can detect the open-circuit fault of the AC capacitor 60 not only during the startup of the power conversion device 1, but also immediately during the operation of the power conversion device 1. Therefore, according to... Figures 1 to 7 The power conversion device 1 shown in the relevant embodiment can suppress the propagation of faults to the normal AC capacitor 60 and the outflow of harmonics to the power grid 3. Furthermore, in Figure 8 In the variant examples shown, it also plays a role similar to Figures 1 to 7 The implementation shown achieves the same effect.

[0134] <Supplementary Notes on Implementation Methods>

[0135] exist Figures 1 to 7 In the embodiments shown, in Figure 5 In step S8 shown, the q-axis current value I' is... qMultiply by the anomaly detection level value (0.8). However, the q-axis current value I' can also be left unchecked. q Multiply by the anomaly detection level value. That is, it can also be the q-axis current value I. q1 and q-axis current value I' q A comparison of magnitudes is performed. In this case, the "second q-axis current value" in the technical solution is the theoretical q-axis current value I'. q Additionally, in Figure 8 The same applies to the variant examples shown.

[0136] In addition, Figures 1 to 7 In the embodiments shown, in Figure 5 In step S9, the fault detection unit 94 detects a fault in AC capacitor 60 once a portion of it becomes open-circuited. However, the fault detection unit 94 may also fail to detect a fault in AC capacitor 60 if only one fault occurs, but detect a fault in AC capacitor 60 if two or more faults occur. This method is effective, for example, when the impact on the power conversion device 1 is minimal due to only one fault in AC capacitor 60. Furthermore, the fault detection unit 94 may also detect a fault in AC capacitor 60 if three or more faults occur, depending on the actual situation. Figure 8 The same applies to the variant examples shown.

[0137] also, Figures 1 to 7 The processing steps of each part in the illustrated embodiment can be implemented as either a fault detection method or a fault detection program executed by a computer. Furthermore, the fault detection program can also be implemented as a storage medium storing the fault detection program. That is, the fault detection program can be distributed, for example, by recording it onto a removable disc such as a CD (Compact Disc), DVD (Digital Versatile Disc), or USB (Universal Serial Bus) memory. Alternatively, the fault detection program can also be downloaded from a network and saved to the storage unit 93 via the network interface included in the power conversion device 1. Additionally, in Figure 8 The same applies to the variant examples shown.

[0138] Through the detailed description above, the features and advantages of the embodiments should become clear. This means that the claims relate 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 limited to the above description, but can be explored with appropriate modifications and equivalents included within the scope disclosed in the embodiments.

[0139] Label Explanation

[0140] 1, 1', 100… Power conversion device; 2… DC power supply; 3… AC power system (grid); 10… Inverter circuit; 20… AC circuit (three-phase AC circuit); 21… Voltage sensor; 22… Current sensor; 30… AC reactor; 40… AC switch; 50… Capacitor circuit; 60… AC capacitor; 61… AC capacitor package; 62… Protection mechanism; 70, 70X, 70Y… Current sensor; 80… Control device; 81… Voltage conversion unit; 82… Current conversion unit; 83… Phase synchronization circuit; 84… Power control unit; 85… Inverter control unit; 91… Conversion value calculation unit; 92… Judgment value calculation unit; 93… Storage unit; 94… Fault detection unit; 95… Fault information reporting unit; 96… Action control unit; I, I 70 I X I Y …current value; I d I d1 …d-axis current value; I q I q1 、I' q 、I' q2 …q-axis current value; V…voltage value; V d …d-axis voltage value; V q …q-axis voltage value; θ…phase; θ * …phase command value.

Claims

1. A control device, which is a control device for a power conversion device, characterized in that, have: The transformation value calculation unit obtains the current value of the current flowing through the AC capacitor connected to the capacitor circuit in the output circuit on the AC side of the inverter circuit, and transforms the above current value to obtain the specified transformation value. The fault detection unit compares the transformation value calculated by the transformation value calculation unit with the predetermined judgment value used in fault detection to detect the fault of the AC capacitor. as well as The judgment value calculation unit obtains the voltage value of the output voltage of the inverter circuit mentioned above, and calculates the judgment value used in fault detection based on the voltage value mentioned above. The fault detection unit compares the transformation value calculated by the transformation value calculation unit with the judgment value calculated by the judgment value calculation unit to detect the fault of the AC capacitor.

2. The control device as described in claim 1, characterized in that, The aforementioned determination value is the 2q-axis current value, which is the current component of the axis that is offset by 90 degrees relative to the capacitor voltage, calculated by the determination value calculation unit using the voltage value of the output voltage of the inverter circuit and the rated conductance value of the AC capacitor.

3. A control device, which is a control device for a power conversion device, characterized in that, have: The transformation value calculation unit obtains the current value of the current flowing through the AC capacitor connected to the capacitor circuit in the output circuit on the AC side of the inverter circuit, and transforms the above current value to obtain the specified transformation value. The fault detection unit compares the transformation value calculated by the transformation value calculation unit with the predetermined judgment value used in fault detection to detect faults in the AC capacitor. The output circuit on the AC side described above is a three-phase AC circuit; The aforementioned transformation value is the first q-axis current value, which is the value of the current component of the axis that is offset by 90 degrees relative to the capacitor voltage. This value is obtained by the transformation value calculation unit by performing a dq transformation on the current values ​​of each current flowing through one or more AC capacitors in the capacitor circuit of each phase of the three-phase AC circuit.

4. The control device as described in claim 1 or 3, characterized in that, The above judgment value is a permissible error value based on the value obtained by multiplying by the specified anomaly detection level.

5. The control device as described in claim 1 or 3, characterized in that, The fault detection unit compares the change value and the judgment value. When the change value is smaller than the judgment value, a fault is detected in the AC capacitor.

6. The control device as described in claim 1 or 3, characterized in that, It also has a fault information reporting unit, which reports the fault information to the designated upper-level device when the fault detection unit detects a fault in the AC capacitor.

7. The control device as described in claim 1 or 3, characterized in that, It also includes an action control unit, which, when the fault detection unit detects a fault in the AC capacitor, gives an action instruction to perform at least one of the actions of stopping the power conversion device or disconnecting the AC switch in the AC side output circuit.

8. A power conversion device, characterized in that, have: An inverter circuit converts DC power into AC power. An AC capacitor is connected to the capacitor circuit of each phase of the three-phase AC circuit on the AC side of the inverter circuit described above. A current sensor acquires the current value of the current flowing into the AC capacitors of the aforementioned phases. A voltage sensor is used to obtain the voltage value of the output voltage of the inverter circuit described above. as well as The control device according to claim 1 or 3; The aforementioned transformation value calculation unit obtains the current value obtained by the aforementioned current sensor and calculates the aforementioned transformation value; The determination value calculation unit obtains the voltage value obtained by the voltage sensor and calculates the determination value.

9. The power conversion device as described in claim 8, characterized in that, The aforementioned current sensor is located in a capacitor circuit that branches off from the aforementioned three-phase AC circuit.

10. The power conversion device as described in claim 8, characterized in that, The aforementioned current sensor is located before and after the branch point from the three-phase AC circuit to the capacitor circuit in the aforementioned three-phase AC circuit.

11. The power conversion device as described in claim 8, characterized in that, The aforementioned AC capacitors are connected in parallel to multiple packages that are connected by star or delta connections.

Images