Power conversion device and control device

Abstract

This power conversion device is provided with an inverter device and a control device, and the inverter device has: a DC input unit having a positive electrode terminal and a negative electrode terminal; an inverter circuit that converts power on the basis of the switching operation of the switching element; and a DC capacitor that absorbs and smoothes a ripple current between the positive electrode terminal and the negative electrode terminal, said ripple current being generated by the switching operation of the inverter circuit. A discharge resistor for discharging the charge of the DC capacitor; and a DC voltage sensor that detects a DC voltage value of the DC capacitor, the control device comprising: a monitoring unit that monitors the DC voltage value detected by the DC voltage sensor; a timing unit for timing the elapsed time from when the inverter device is stopped; a determination unit that determines that the DC capacitor is abnormal when the DC voltage value monitored by the monitoring unit is lower than a predetermined threshold value, which is a value smaller than a normal value, by a predetermined range or more when a predetermined time has elapsed since the inverter device is stopped by the timer unit; and a reporting unit that reports an abnormality of the DC capacitor when the determination unit determines that the DC capacitor is abnormal.

Description

Technical Field

[0001] The present invention relates to a power conversion device and a control device. Background Art

[0002] For example, in a power conversion device that converts power between DC power and AC power, a DC capacitor is provided in the DC input section for absorbing (smoothing) ripple current. The DC capacitor may have abnormalities such as reduced capacitance due to, for example, aging, malfunction, etc. However, it is difficult to properly detect abnormalities in the DC capacitor.

[0003] Therefore, conventionally, a method has been proposed for detecting abnormalities such as a decrease in the capacitance of a DC capacitor in an inverter based on the magnitude of the resistance current and the magnitude of the voltage between the capacitor terminals when a predetermined reference time has elapsed from the start of energization (for example, see Patent Document 1).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2008-228370 Summary of the invention

[0007] Problems to be solved by the invention

[0008] Generally, when the capacitance of the DC capacitor decreases, the magnitude of the voltage of the DC capacitor becomes different from that in normal times when the DC capacitor is charged when the device is started and when the DC capacitor is discharged when the device is stopped.

[0009] However, in the conventional method, although an abnormality of the DC capacitor can be detected based on the charging voltage of the DC capacitor when the device is started, an abnormality of the DC capacitor cannot be detected based on the discharging voltage of the DC capacitor when the device is stopped.

[0010] Therefore, an object of the present invention is to provide a means for detecting an abnormality of a DC capacitor connected to a DC input side of a power conversion device based on the discharge voltage of the DC voltage when the device is stopped by monitoring the discharge speed of the DC voltage when the device is stopped.

[0011] Means for solving problems

[0012] A power conversion device of one embodiment includes an inverter device and a control device, wherein the inverter device includes: a DC input unit having a positive terminal and a negative terminal; an inverter circuit that converts power based on the switching action of a switching element; and a DC capacitor that absorbs and smoothes the ripple current generated by the switching action of the inverter circuit between the positive terminal and the negative terminal; a discharge resistor that discharges the charge of the DC capacitor; and a DC voltage sensor that detects the DC voltage value of the DC capacitor, wherein the control device includes: a monitoring unit that monitors the DC voltage value detected by the DC voltage sensor; a timing unit that counts the time elapsed from the time when the inverter device stops; a determination unit that determines that the DC capacitor is abnormal when the timing unit counts that a specified time has elapsed from the time when the inverter device stops, and when the DC voltage value monitored by the monitoring unit is lower than a value less than a normal value, that is, a specified threshold value, by more than a specified range; and a reporting unit that reports the DC capacitor abnormality when the determination unit determines that the DC capacitor is abnormal.

[0013] A power conversion device according to another embodiment includes an inverter device and a control device, wherein the inverter device includes: a DC input unit having a positive terminal and a negative terminal; an inverter circuit that converts power based on a switching operation of a switching element; a plurality of DC capacitors that are connected in series between the positive terminal and the negative terminal via a DC neutral point and absorb and smooth a ripple current generated by the switching operation of the inverter circuit; a discharge resistor that discharges the charges of the plurality of DC capacitors; and a DC voltage sensor that detects the DC voltage values ​​of the plurality of DC capacitors, respectively. The control device includes: a monitoring unit that monitors the DC voltage values ​​detected by the DC voltage sensor, respectively. The invention relates to a method for manufacturing a plurality of DC capacitors comprising: providing a DC voltage value of a plurality of DC capacitors; a timing unit for timing the time elapsed from the time when the inverter device is stopped; a determination unit for comparing the DC voltage values ​​of the plurality of DC capacitors monitored by the monitoring unit when the timing unit measures the time elapsed from the time when the inverter device is stopped, and determining that one of the plurality of DC capacitors being compared is abnormal when the DC voltage values ​​of the plurality of DC capacitors being compared differ from each other by more than a predetermined threshold value; and a reporting unit for reporting that one of the plurality of DC capacitors is abnormal when the determination unit determines that one of the plurality of DC capacitors is abnormal.

[0014] In a control device according to one embodiment, the control device is a control device of a power conversion device, the power conversion device includes an inverter device, the inverter device includes: a DC input unit having a positive terminal and a negative terminal; an inverter circuit that converts power based on the switching action of a switching element; a DC capacitor that absorbs and smoothes a ripple current generated by the switching action of the inverter circuit between the positive terminal and the negative terminal; a discharge resistor that discharges the charge of the DC capacitor; and a DC voltage sensor that detects a DC voltage value of the DC capacitor, the control device includes: a monitoring unit that monitors the DC voltage value detected by the DC voltage sensor; a timing unit that counts the time elapsed from when the inverter device stops; a determination unit that determines that the DC capacitor is abnormal when the timing unit counts that a predetermined time has elapsed from when the inverter device stops, and when the DC voltage value monitored by the monitoring unit is lower than a value that is smaller than a normal value, that is, a predetermined threshold value, by more than a predetermined range; and a reporting unit that reports the DC capacitor abnormality when the determination unit determines that the DC capacitor is abnormal.

[0015] Effects of the Invention

[0016] According to the present disclosure, it is possible to provide a means for detecting an abnormality of a DC capacitor connected to a DC input side of a power conversion device based on the discharge voltage of the DC voltage when the device is stopped by monitoring the discharge speed of the DC voltage when the device is stopped. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a diagram showing a configuration example of the power conversion device according to the first embodiment.

[0018] Figure 2 Yes means Figure 1 A diagram showing an example of the configuration of a control device in a power conversion device shown.

[0019] Figure 3 Yes means Figure 1 and Figure 2 A flowchart showing an example of the operation of the control device in the power conversion device shown.

[0020] Figure 4 This is a diagram showing an example of a discharge curve when the DC capacitor is discharged after the inverter device stops.

[0021] Figure 5 Yes means Figure 4 FIG. 4 is a diagram showing an example of a normal discharge curve of a DC capacitor and a discharge curve as a predetermined threshold value.

[0022] Figure 6This is a diagram showing an example of a discharge curve of a normal DC capacitor, a discharge curve as a predetermined threshold value, and a discharge curve as a second predetermined threshold value according to a modification of the first embodiment.

[0023] Figure 7 It is a diagram showing a configuration example of a power conversion device according to a second embodiment.

[0024] Figure 8 express Figure 7 An example of the configuration of a control device in the power conversion device shown.

[0025] Fig. 9 Yes means Figure 7 and Figure 8 A flowchart showing an example of the operation of the control device in the power conversion device shown.

[0026] Fig.10 Yes means Figures 1 to 9 A conceptual diagram of an example of a hardware configuration of a processing circuit included in a control device according to the illustrated embodiment. DETAILED DESCRIPTION

[0027] Hereinafter, embodiments of a power conversion device and a control device according to the present disclosure will be described using the drawings.

[0028] <Configuration of First Embodiment>

[0029] Figure 1 It is a diagram showing a configuration example of the power conversion device 1 according to the first embodiment.

[0030] like Figure 1 As shown, the power conversion device 1 includes an inverter device 10 and a control device 30 .

[0031] The inverter device 10 includes a DC input unit 11, a DC capacitor 12, a discharge resistor 13, an inverter circuit 14, and an AC output unit 15. The inverter device 10 converts DC power supplied from the DC input unit 11 into AC power via the inverter circuit 14, and outputs the converted AC power to the AC output unit 15.

[0032] The inverter device 10 is, for example, a DC-AC inverter that converts DC power into AC power, the DC input unit 11 is connected to DC power such as a solar panel (solar cell), a storage battery, and the like, and the AC output unit 15 is connected to an AC power system, a motor, and other loads. In the following embodiments, the inverter device 10 is described by taking a DC-AC inverter that converts DC power into AC power as an example. However, this is not limited to the above, and the inverter device 10 of the present disclosure can be established as long as it has a DC capacitor 12, a discharge resistor 13, and a unit for detecting the DC voltage Vdc of the DC capacitor 12 described later.

[0033] That is, the inverter device 10 only needs to have a DC capacitor 12, a discharge resistor 13, and a unit for detecting the DC voltage Vdc of the DC capacitor 12 described later, and may be, for example, a converter that converts AC to DC. Alternatively, the inverter device 10 may be, for example, a reactive power compensation device that generates a DC voltage by the operation of an inverter circuit 14, controls the DC voltage to be constant, and exchanges reactive power between the DC capacitor and the system, thereby achieving voltage stabilization. Alternatively, the inverter device 10 may be a DC-DC conversion device such as a DC chopper. In addition, hereinafter, in this specification, the inverter device 10 is also referred to as a "device" or "device 10" for short.

[0034] The DC input unit 11 has a positive terminal 11P and a negative terminal 11N. The positive terminal 11P and the negative terminal 11N of the DC input unit 11 are Figure 1 One end on the left side of the middle portion is connected to a DC power source (not shown) such as a solar cell. Figure 1 The other end on the right side is connected to the inverter device 10. When the inverter device 10 is a reactive power compensation device, for example, the positive terminal 11P and the negative terminal 11N of the DC input unit 11 may not be connected to any component.

[0035] The DC capacitor 12 is disposed, for example, between the positive terminal 11P and the negative terminal 11N, and absorbs and smoothes the ripple current generated by the switching operation of the switching element of the inverter circuit 14. The DC capacitor 12 is basically required in the voltage source inverter, and is charged when the inverter device 10 is started (when power is supplied), and is discharged when the inverter device 10 is stopped.

[0036] When the capacitance of the DC capacitor 12 decreases due to aging, abnormality (failure), etc., the voltage becomes different from that in normal times during charging when the inverter device 10 is started and discharging when the inverter device 10 is stopped. In addition, in this case, the charging curve representing the charging speed during charging and the discharge curve representing the discharge speed during discharging of the DC capacitor 12 become different from those in normal times.

[0037] The discharge resistor 13 is, for example, disposed between the positive terminal 11P and the negative terminal 11N, and is a resistor for discharging the charge of the DC capacitor 12 after the inverter device 10 stops. The discharge resistor 13 may be always connected, or may be turned on and connected after the inverter device 10 stops. For example, the discharge resistor 13 may be always connected in an inverter device 10 having a DC capacitor 12 with a small or medium capacitance, and may be turned on and connected by a switch or the like (not shown) after the inverter device 10 stops in an inverter device 10 having a DC capacitor 12 with a large capacitance.

[0038] The inverter circuit 14 is constructed by, for example, a plurality of semiconductor switching elements Q such as IGBT (Insulated Gate Bipolar Transistor) and a plurality of return diodes D. In addition, the semiconductor switching element Q is not limited to IGBT, and may be a MOSFET (metal-oxide-semiconductor field-effect transistor) or the like. The inverter circuit 14 is connected to a DC power (not shown) or the like via a DC input unit 11 at one end as an input side, and is connected to an AC power system (not shown) or the like via an AC output unit at the other end as an output side.

[0039] The inverter circuit 14 is controlled to operate by a gate drive signal (gate signal) of the semiconductor switch element Q, that is, a pulse width modulation (PWM) signal generated by the control device 30. The inverter circuit 14 obtains DC power supplied from the DC input unit 11, for example, converts the obtained DC power into AC power according to control based on the PWM signal (gate signal), and outputs the converted AC power from the AC output unit 15.

[0040] The inverter circuit 14 has, for example, a circuit in which three branches (U-phase branch, V-phase branch, and W-phase branch) are connected in parallel. Each branch is formed by, for example, connecting in series two arms in which a semiconductor switch element Q and a return diode D are connected in anti-parallel. Each branch is, for example, connected in parallel between a positive terminal 11P and a negative terminal 11N, and the midpoint of each branch is connected to a U-phase terminal 15U, a V-phase terminal 15V, and a W-phase terminal 15W of an AC output unit 15 described later. In addition, the inverter circuit 14 is not limited to a three-phase inverter, and may be a single-phase inverter or other inverters.

[0041] The AC output unit 15 has a U-phase terminal 15U, a V-phase terminal 15V, and a W-phase terminal 15W. Figure 1 The left end of the inverter is connected to the inverter device 10. Figure 1The other end side on the right side is connected to a power system or load not shown in the figure. The AC output unit 15 is, for example, a three-phase three-wire type three-phase AC circuit that uses three wires, cables, and conductors to supply three-phase AC power composed of three systems of single-phase AC with phases of current or voltage mutually offset. In addition, the AC output unit 15 is not limited to a three-phase AC circuit, and can be a single-phase AC circuit or other AC circuits. The AC output unit 15 outputs the AC power converted by the inverter circuit 14 to the power system or load not shown in the figure.

[0042] In addition, the inverter device 10 includes a DC current sensor 21 , a DC voltage sensor 22 , an AC current sensor 23 , and an AC voltage sensor 24 .

[0043] The DC current sensor 21 is, for example, a known DC ammeter or DC current sensor, and detects the value of the DC current Idc flowing through the positive terminal 11P and the negative terminal 11N of the DC input unit 11. The position of the DC current sensor 21 is not limited to Figure 1 The position shown may be any position as long as the value of the DC current Idc can be detected. Hereinafter, in this specification, etc., the value of the DC current Idc is also simply referred to as “DC current Idc”. The DC current Idc detected by the DC current sensor 21 is monitored by the control device 30 .

[0044] The DC voltage sensor 22 is, for example, a known DC voltmeter or DC voltage sensor, and detects the value of the DC voltage Vdc of the DC capacitor 12 of the DC input unit 11. The position where the DC voltage sensor 22 is arranged is not limited to Figure 1 The position shown may be any position as long as the value of the DC voltage Vdc of the DC capacitor 12 can be detected. Hereinafter, in this specification, the value of the DC voltage Vdc is also simply referred to as “DC voltage Vdc”. The DC voltage Vdc detected by the DC voltage sensor 22 is monitored by the control device 30.

[0045] The AC current sensor 23 is, for example, a known AC ammeter or AC current sensor, and detects the output current of the inverter circuit 14, that is, the value of the AC current Iac of the AC output unit 15. The position of the AC current sensor 23 is not limited to Figure 1 The position shown may be any position as long as the value of the AC current Iac can be detected. Hereinafter, in this specification, the value of the AC current Iac is also simply referred to as “AC current Iac”. The AC current Iac detected by the AC current sensor 23 is monitored and controlled by the control device 30 .

[0046] The AC voltage sensor 24 is, for example, a known AC voltmeter or AC voltage sensor, and detects the output voltage of the inverter circuit 14, that is, the value of the AC voltage Vac of the AC output unit 15. The position of the AC voltage sensor 24 is not limited to Figure 1 The position shown may be any position as long as the value of the AC voltage Vac of the AC voltage sensor 24 can be detected. Hereinafter, in this specification, the value of the AC voltage Vac is also simply referred to as "AC voltage Vac". The AC voltage Vac detected by the AC voltage sensor 24 is monitored and controlled by the control device 30.

[0047] The control device 30 is, for example, provided inside or outside the power conversion device 1, and wiring etc. are omitted in the figure, but the control device 30 is electrically connected to each component of the inverter device 10 headed by the inverter circuit 14 by wire or wireless. In addition, the control device 30 can also be realized as a function of an inverter control circuit not shown.

[0048] The control device 30 includes, for example, a processor 91 (see FIG. 1 ) described later, such as a CPU (Central Processing Unit) that operates by executing a program. Fig.10 The control device 30 includes a storage unit 40 (see Figure 2 )、Memory 92 (refer to Fig.10 ), etc., for example, by executing a predetermined program stored in the storage unit 40 or the memory 92 to operate the processor 91, thereby controlling the overall operation of the inverter device 10. In addition, the control device 30 may also control the operation of the inverter device 10 according to instructions received from an unillustrated upper device, instructions received from an unillustrated operator via an unillustrated operating unit, etc.

[0049] Control device 30 detects failure, abnormality, capacitance reduction, etc. of DC capacitor 12 based on DC voltage Vdc detected by DC voltage sensor 22. When detecting abnormality, etc. of DC capacitor 12, control device 30 reports that abnormality, etc. of DC capacitor 12 has been detected.

[0050] Figure 2 Yes means Figure 1 FIG. 2 is a diagram showing a configuration example of the control device 30 in the power conversion device 1 shown.

[0051] The control device 30 includes a storage unit 40, and executes, for example, a program stored in the storage unit 40 or a memory 92 (see Fig.10 ) according to the prescribed program, and functions as the following units. That is, the control device 30 functions as the monitoring unit 31, the timing unit 32, the determination unit 33, the reporting unit 34, and the PWM control unit 35 by executing the prescribed program. In addition, the above functions can be performed by the processor 91 (see Fig.10 ) can be implemented by a program executed by hardware 93 (refer to Fig.10 The above-mentioned units execute the prescribed procedures and perform the following processing.

[0052] The monitoring unit 31 is connected to the DC voltage sensor 22, and always obtains and monitors the information of the DC voltage Vdc of the DC capacitor 12 detected by the DC voltage sensor 22. In addition, the monitoring unit 31 can obtain the information of the DC voltage Vdc of the DC capacitor 12 for monitoring at predetermined time intervals, or obtain the information of the DC voltage Vdc of the DC capacitor 12 for monitoring according to instructions received from an operator or the like via an unillustrated upper device or an unillustrated operating unit. In addition, the monitoring unit 31 can also obtain the information of the DC voltage Vdc of the DC capacitor 12 and monitor it when the inverter device 10 stops. In addition, the monitoring unit 31 can also be connected to the DC current sensor 21, the AC current sensor 23, and the AC voltage sensor 24, and obtain and monitor the information of the DC current Idc, the AC current Iac, and the AC voltage Vac detected by them.

[0053] When the inverter device 10 stops, the timing unit 32 counts the time that has passed since the inverter device 10 stopped. The time that has passed by the timing unit 32 is acquired by the determination unit 33. In addition, the timing unit 32 may count whether a predetermined time t1 has passed since the inverter device 10 stopped. In this case, when the predetermined time t1 has passed since the inverter device 10 stopped, the timing unit 32 outputs information indicating that the predetermined time t1 has passed since the inverter device 10 stopped to the determination unit 33.

[0054] The determination unit 33 obtains information on the DC voltage Vdc monitored by the monitoring unit 31 when the timing unit 32 measures the elapse of a predetermined time t1 from when the inverter device 10 is stopped. The determination unit 33 compares the DC voltage Vdc monitored by the monitoring unit 31 with a predetermined threshold value V th Make a comparison.

[0055] In addition, the determination unit 33 may always obtain information on the DC voltage Vdc monitored by the monitoring unit 31. Furthermore, the determination unit 33 may always continuously compare the DC voltage Vdc monitored by the monitoring unit 31 with a predetermined threshold value V th .

[0056] The determination unit 33 determines that the DC voltage Vdc monitored by the monitoring unit 31 is lower than a predetermined threshold value V thWhen the DC capacitor 12 is abnormal, the DC capacitor 12 is determined to be abnormal. This is because when the DC capacitor 12 is abnormal, the capacitance of the DC capacitor 12 decreases. Then, when the DC capacitor 12 is determined to be abnormal, the determination unit 33 outputs information indicating that the DC capacitor 12 is abnormal to the reporting unit 34. In addition, when the DC capacitor 12 is determined to be abnormal, the determination unit 33 may output information indicating that the DC capacitor 12 is abnormal to an external device such as a higher-level device (not shown).

[0057] In addition, the threshold V th For example, it may be changed according to the operating status of the inverter device 10, or it may be determined in advance through experiments, simulations, etc. and stored in the storage unit 40. th For example, the determination may be made according to an instruction received from a higher-level device (not shown), an instruction received from an operator (not shown) via an operation unit (not shown), or the like.

[0058] Here, the threshold value V th The predetermined threshold value V is a value (voltage value) smaller than the normal DC voltage Vdc (normal value) detected by the normal DC capacitor 12 when a predetermined time t1 has passed since the inverter device 10 was stopped. th The determination unit 33 may have a bandwidth or margin within a predetermined range (predetermined voltage value) (upward or downward). That is, the determination unit 33 may not determine the DC voltage Vdc when it is lower than the predetermined threshold value V th When the DC capacitor 12 is abnormal, it is immediately determined that the DC capacitor 12 is abnormal, but when the DC voltage Vdc is lower than the predetermined threshold value V th When the value is lower than or equal to the predetermined range, it is determined that the DC capacitor 12 is abnormal. In addition, the bandwidth or margin of the predetermined range may be changed according to the assumed life of the DC capacitor 12 and the like.

[0059] Thus, for example, the determination unit 33 does not detect an abnormality of the DC capacitor 12 due to a temporary or accidental change in the DC voltage Vdc. th Compared with a case where the bandwidth or margin does not have a predetermined range, it is possible to suppress erroneous detection of an abnormality by the determination unit 33 , and the determination unit 33 can detect an abnormality of the DC capacitor 12 more accurately.

[0060] In addition, as described above, the determination unit 33 may also determine the DC voltage Vdc to be lower than the predetermined threshold value V th If the DC voltage Vdc is lower than a predetermined range (predetermined voltage value) or more, it is determined that the DC capacitor 12 is abnormal. However, the present invention is not limited to this, and the determination unit 33 may also determine that the DC capacitor 12 is abnormal when the DC voltage Vdc is lower than a predetermined threshold value Vdc for a predetermined time or more. th Alternatively, the determination unit 33 may determine that the DC capacitor 12 is abnormal when the DC voltage Vdc is lower than the predetermined threshold value Vdc for a predetermined number of times or more.th , it is determined that the DC capacitor 12 is abnormal.

[0061] Furthermore, the determination unit 33 may also determine the value of the threshold value V th The DC capacitor 12 is determined to be abnormal by any combination of the bandwidth or margin of the specified range, time, and number of times. For example, the determination unit 33 may determine that the DC capacitor 12 is abnormal when the DC voltage Vdc is lower than the specified threshold value V for more than a specified time and more than a specified number of times. th , it is determined that the DC capacitor 12 is abnormal.

[0062] For example, the determination unit 33 may determine that the DC voltage Vdc exceeds a predetermined threshold value Vdc for a predetermined period of time or longer. th When the DC voltage Vdc is lower than a predetermined range (predetermined voltage value) or more, it is determined that the DC capacitor 12 is abnormal. In addition, for example, the determination unit 33 may also determine that the DC capacitor 12 is abnormal when the DC voltage Vdc exceeds a predetermined threshold value Vdc for a predetermined number of times or more. th When the DC voltage Vdc is lower than a predetermined range (predetermined voltage value) or more, the DC capacitor 12 is determined to be abnormal. Alternatively, for example, the determination unit 33 may determine that the DC capacitor 12 is abnormal when the DC voltage Vdc is lower than a predetermined threshold value Vdc for a predetermined time or more and a predetermined number of times or more. th When the voltage is lower than a predetermined range (predetermined voltage value) or more, it is determined that the DC capacitor 12 is abnormal.

[0063] Therefore, the threshold V th The bandwidth or margin in the predetermined range can suppress erroneous detection of abnormality by the determination unit 33 compared to the case where the time and the number of times are combined, and the determination unit 33 can detect abnormality of the DC capacitor 12 more accurately.

[0064] When the reporting unit 34 obtains information indicating that the DC capacitor 12 is abnormal from the determination unit 33, it reports that the DC capacitor 12 is abnormal. The reporting unit 34 reports that the DC capacitor 12 is abnormal by, for example, outputting fault information to a higher-level device (not shown) or outputting a display such as an alarm or a bell, or voice, etc. to a display unit or an operation unit (not shown) of the power conversion device 1. In addition, the reporting unit 34 may also stop the discharge of the DC capacitor 12. In addition, the function of the reporting unit 34 may also be provided by an external device such as a higher-level device (not shown).

[0065] The PWM control unit 35 performs PWM control based on, for example, a predetermined output voltage command signal and a predetermined triangular wave carrier signal, and generates a gate signal for turning on and off the semiconductor switch element Q of the inverter circuit 14. The PWM control unit 35 outputs the generated gate signal to the inverter circuit 14 of the inverter device 10 to control the operation of the inverter circuit 14. The PWM control unit 35 may also output information indicating that the inverter device 10 has stopped to the timing unit when the inverter device 10 stops outputting the gate signal.

[0066] The storage unit 40 is, for example, a volatile or non-volatile storage medium such as a HDD (Hard Disk Drive), an SSD (Solid State Drive), a DRAM (Dynamic Random Access Memory), or other semiconductor memory. The storage unit 40 stores, for example, programs required for the operation of each unit of the control device 30, and writes and reads various information through each unit of the control device 30. The storage unit 40 stores, for example, information on the values ​​of the DC current Idc, DC voltage Vdc, AC current Iac, and AC voltage Vac monitored by the monitoring unit 31. In addition, the storage unit 40 stores, for example, a predetermined time t1, a predetermined threshold value V th etc., various calculation expressions and various threshold values ​​used in the determination of the determination unit 33, etc.

[0067] The storage unit 40 is connected to each part of the control device 30, for example, through a bus (not shown) in such a manner that various information can be input and output by each part of the control device 30. In addition, the storage unit 40 can be provided outside the control device 30 and connected to the control device 30 by wire or wireless, or can be an external storage medium such as a memory card or DVD (Digital Versatile Disc), or can be an online storage, etc. In addition, the storage unit 40 can also be connected to the memory 92 (see Fig.10 )Shared.

[0068] <Operation of the First Embodiment>

[0069] Figure 3 Yes means Figure 1 and Figure 2 1 is a flowchart showing an example of the operation of the control device 30 in the power conversion device 1 shown. Figure 3 The flowchart shown starts when the inverter device 10 is stopped.

[0070] In step S1 , the timing unit 32 of the control device 30 obtains information indicating that the inverter device 10 is stopped, and starts counting the elapsed time from when the inverter device 10 is stopped.

[0071] In step S2, the determination unit 33 of the control device 30 obtains the time counted by the timer unit 32 from the timer unit 32, and determines whether the timer unit 32 has counted the time t1 that has passed since the inverter device 10 stopped. When the determination unit 33 determines that the timer unit 32 has counted the time t1 that has passed since the inverter device 10 stopped ("Yes" side), the processing is transferred to step S3. On the other hand, when the determination unit 33 determines that the timer unit 32 has not counted the time t1 that has passed since the inverter device 10 stopped ("No" side), the processing of step S2 is repeated until it is determined that the timer unit 32 has counted the time t1 that has passed.

[0072] In step S3, the determination unit 33 obtains information on the DC voltage Vdc of the DC capacitor 12 at a time point after a predetermined time t1 has passed from the monitoring unit 31. In addition, the determination unit 33 obtains a predetermined threshold value Vdc at a time point after a predetermined time t1 has passed from the storage unit 40. th information.

[0073] In step S4, the determination unit 33 determines whether the DC voltage Vdc is lower than the predetermined threshold value V at the time point when the predetermined time t1 has passed. th Whether it converges within the specified range.

[0074] Then, the determination unit 33 determines that the DC voltage Vdc is lower than the predetermined threshold value Vdc at a time point when the predetermined time t1 has passed. th When it is within the predetermined range ("Yes" side), the process is transferred to step S5.

[0075] On the other hand, the determination unit 33 determines that the DC voltage Vdc is lower than the predetermined threshold value Vdc at a time point when the predetermined time t1 has passed. th If it does not converge within the prescribed range ("No" side), the process is transferred to step S6. That is, when the timing unit 32 counts that the prescribed time t1 has passed since the inverter device 10 was stopped, the determination unit 33 determines that the DC voltage Vdc is lower than the prescribed threshold value V th If the value is lower than the predetermined range ("No" side), the process is transferred to step S6. th It can also be determined based on the discharge curve.

[0076] Figure 4 1 is a diagram showing an example of a discharge curve when the DC capacitor 12 is discharged after the inverter device 10 stops. Figure 4 The diagram shows a discharge curve indicating the transition of the DC voltage value when the DC capacitor 12 is discharged after the inverter device 10 is stopped.

[0077] exist Figure 4In the figure, the vertical axis is voltage (V) and the horizontal axis is time (t). Figure 4 In FIG. 1 , the DC voltage Vdc represents the value of the DC voltage when the inverter device 10 is operating (stopped). Figure 4 In the embodiment, the DC voltage value from the operation of the inverter device 10 to the stop of the inverter device 10 (time t0) is maintained at the DC voltage Vdc. At time t0, when the inverter device 10 stops, the charge of the DC capacitor 12 is discharged to the discharge resistor 13. Figure 4 2 shows a discharge curve (v(t)) showing the change in the DC voltage value when the DC capacitor 12 is discharged after the inverter device 10 stops at time t0. The discharge curve (v(t)) is obtained by the following formula (1).

[0078] [Number 1]

[0079]

[0080] In formula (1), C represents the design value of the capacitance of the DC capacitor 12, R represents the design value of the resistance of the discharge resistor 13, Vdc represents the DC voltage value of the DC capacitor 12 when the inverter device 10 stops, and t represents the time elapsed from the time when the inverter device 10 stops.

[0081] In formula (1), a discharge curve (v(t)) is shown that represents the natural decay of the DC voltage value when the DC capacitor 12 is discharged after the inverter device 10 stops. If t0 is set to the time when the inverter device 10 stops (=0), and t1 is set to the time when a predetermined time has passed since the inverter device 10 stopped, the DC voltage value of the DC capacitor 12 at the time when the predetermined time (t1) has passed since the inverter device 10 stopped (t0) becomes v(t1).

[0082] In addition, in most cases, the design value (C) of the capacitance of the DC capacitor 12 is, for example, a value of the order of uF or mF. In addition, in most cases, the design value (R) of the resistance value of the discharge resistor 13 is, for example, a value of the order of kΩ. In addition, if the inverter device 10 is a large-capacitance inverter device 10, there is almost no single DC capacitor 12, and therefore, the design value (C) of the capacitance of the DC capacitor 12 is its combined value (composite capacitance) when the DC capacitors 12 are connected in parallel.

[0083] Figure 5 Yes means Figure 4 The normal discharge curve of the DC capacitor 12 and the threshold value V th A diagram showing an example of a discharge curve of .

[0084] exist Figure 5 In the figure, the vertical axis, horizontal axis and symbols represent the same Figure 4 The same. That is, Figure 5 In FIG. 1 , the DC voltage Vdc represents the value of the DC voltage when the inverter device 10 is operating (or stopped). Figure 5 In the figure, the solid line L1 and Figure 4 The discharge curve shown is the same as that of the normal DC capacitor 12. On the other hand, the dashed line L2 represents the predetermined threshold value V th The discharge curve.

[0085] like Figure 5 As shown, if the DC capacitor 12 decreases in capacitance due to abnormality, degradation, etc., the charge decreases, and thus it is rapidly discharged relative to the same discharge resistor 13, and the voltage decreases faster. For example, when an abnormality such as a disconnection occurs in one of the combined capacitances of the plurality of DC capacitors 12 connected in parallel, since the charge of one amount decreases, it is rapidly discharged relative to the same discharge resistor 13, and the voltage decreases faster.

[0086] Therefore, the discharge curve of the DC capacitor 12 with reduced capacitor capacitance has a smaller voltage value than the discharge curve of the normal DC capacitor 12, and thus becomes a lower line. Figure 5 As shown, it is indicated as the prescribed threshold value V th The dotted line L2 of the discharge curve is lower than the solid line L1 representing the discharge curve of the normal DC capacitor 12 .

[0087] In addition, the predetermined threshold value V th The dotted line L2 of the discharge curve may also have a bandwidth or margin (width) of a predetermined range (predetermined voltage value) as described above. Therefore, the determination unit 33 may also determine that the DC voltage value monitored by the monitoring unit 31 is greater than the predetermined threshold value V when the predetermined time t1 has elapsed. th When the voltage is lower than or equal to the predetermined range, it is determined that the DC capacitor 12 is abnormal.

[0088] In addition, the prescribed time t1 is not limited to one time, but may be counted multiple times, or may have a prescribed time length. th It is also possible to judge not by one sampling point but by multiple sampling points, or to judge based on the entire discharge curve or a specified part of the discharge curve.

[0089] Here, the threshold value V th The threshold voltage V may be obtained (or determined) from a discharge curve obtained based on actual measured values ​​of the DC voltage value after the inverter device 10 is stopped during the factory delivery test of the power conversion device 1. thThe dashed line L2 may be a discharge curve obtained based on actual measured values ​​during the factory delivery test of the power conversion device 1, and may be a value (discharge curve) obtained based on experiments, simulations, etc. and stored in the storage unit 40. th = L2) can also be obtained based on the time constant (τ) obtained based on the actual measured values ​​of the capacitance (C) of the DC capacitor 12 and the resistance value (R) of the discharge resistor during the factory shipment test. In addition, the above-mentioned predetermined threshold value (V) obtained based on the discharge curve or time constant (τ) obtained based on the actual measured values ​​during the factory shipment test th =L2) can also be obtained in advance and stored in the storage unit 40 in advance.

[0090] In this case, when the timing unit 32 counts that a predetermined time (t1) has passed since the inverter device 10 was stopped (t0), the determination unit 33 compares the actual measurement value of the DC voltage value monitored by the monitoring unit with the determined predetermined threshold value (V th =L2) for comparison.

[0091] When the actual measured value of the DC voltage monitored by the monitoring unit is greater than a predetermined threshold value (V th =L2) is lower than a predetermined range or more, the determination unit 33 determines that the DC capacitor 12 is abnormal.

[0092] In this way, the threshold V th The threshold value V that meets the requirements of the actual device can be determined by obtaining the actual measured value during the factory delivery test of the power conversion device 1. th , compared with the case that does not conform to the actual machine, the abnormality of the DC capacitor 12 can be accurately discovered.

[0093] In addition, the threshold V th It can also be obtained (or determined) based on the value calculated by the above formula (1) according to the design value (C) of the capacitance of the DC capacitor and the design value (R) of the resistance of the discharge resistor. th The dashed line L2 may be a discharge curve (v(t)) obtained based on the value calculated by the above formula (1) and a value obtained based on experiments, simulations, etc. For example, the predetermined threshold value V th It may be a value obtained based on experiments, simulations, etc., by substituting a predetermined diagnosis timing (predetermined time (t1)) into the above-mentioned formula (1).

[0094] In this case, when the timing unit 32 counts that the predetermined time (t1) has passed since the inverter device 10 stopped (t0), the determination unit 33 obtains the voltage value (v(t1)) when the predetermined time (t1) is substituted into the above-mentioned formula (1). In addition, the voltage value (v(t1)) when the predetermined time (t1) is substituted into the above-mentioned formula (1) may be obtained in advance and stored in the storage unit 40 in advance.

[0095] Then, when the timing unit 32 counts that a predetermined time (t1) has passed since the inverter device 10 was stopped (t0), the determination unit 33 compares the measured value of the DC voltage value monitored by the monitoring unit 31 with the obtained voltage value (v(t1)). Then, when the measured value of the DC voltage value monitored by the monitoring unit 31 is lower than the obtained voltage value (v(t1)) by more than a predetermined range, the determination unit 33 determines that the DC capacitor 12 is abnormal.

[0096] In this way, the threshold V th By finding the design value (C) of the capacitance of the DC capacitor and the design value (R) of the resistance of the discharge resistor, it is possible to accurately find an abnormality in the DC capacitor 12 based on the design values.

[0097] return Figure 3 In step S5, the reporting unit 34 does not obtain information from the determining unit 33 indicating that the DC capacitor 12 is abnormal, so the control device 30 continues the discharge of the DC capacitor 12. Figure 3 The processing of the flowchart is completed.

[0098] In step S6, the reporting unit 34 obtains information indicating that the DC capacitor 12 is determined to be abnormal from the determination unit 33, and reports that the DC capacitor 12 is abnormal. Then, the control device 30 ends Figure 3 Flowchart of the process.

[0099] <Effects of the First Embodiment>

[0100] Above, in Figures 1 to 5 In the first embodiment shown in the figure, when a predetermined time t1 has passed since the inverter device 10 was stopped, the DC voltage value Vdc becomes greater than a predetermined threshold value V th When the voltage Vdc is lower than the predetermined range, it is determined that the DC capacitor 12 is abnormal. Thus, according to the present embodiment, by monitoring the discharge speed of the DC voltage Vdc when the inverter device 10 is stopped, the abnormality of the DC capacitor 12 can be found from the discharge voltage of the DC voltage Vdc when the inverter device 10 is stopped.

[0101] In addition, according to Figures 1 to 5 In the first embodiment shown, the threshold value V thIt is also possible to have a bandwidth or margin within a predetermined range (predetermined voltage value). th Compared with a case where the bandwidth or margin does not have a predetermined range, erroneous detection of an abnormality by the determination unit 33 can be suppressed, and the determination unit 33 can detect an abnormality of the DC capacitor 12 more accurately.

[0102] In addition, according to Figures 1 to 5 In the first embodiment shown, the threshold value V th It can also be obtained from a discharge curve obtained based on the actual measured value of the change in the DC voltage value after the inverter device 10 is stopped during the factory shipment test of the power conversion device 1. Thus, according to this embodiment, it is possible to determine the threshold value V that meets the requirements of the actual device. th , compared with the case that does not conform to the actual machine, the abnormality of the DC capacitor 12 can be accurately discovered.

[0103] In addition, according to Figures 1 to 5 In the first embodiment shown, the threshold value V th It can also be obtained based on the value calculated by the above formula (1) from the design value (C) of the capacitance of the DC capacitor and the design value (R) of the resistance of the discharge resistor. Thus, according to this embodiment, an abnormality of the DC capacitor 12 can be accurately found based on the design value.

[0104] <Modification of First Embodiment>

[0105] Figure 6 1 is a curve showing a normal discharge of the DC capacitor 12 according to a modification of the first embodiment, and a predetermined threshold value V th The discharge curve and the second threshold value V th2 FIG. 1 is a diagram showing an example of a discharge curve of FIG.

[0106] In a modification of the first embodiment, Figures 1 to 5 The same or similar components as those in the first embodiment are denoted by the same reference numerals, and detailed descriptions thereof are omitted or simplified. Figures 1 to 5 The first embodiment shown is the same or similar, so the illustration is omitted. Figures 1 to 5 The predetermined threshold value V of the first embodiment shown in FIG. th In addition, a second predetermined threshold value V th2 .

[0107] exist Figure 6 In the figure, the vertical axis, horizontal axis and symbols represent the same Figure 4 and Figure 5 The same. That is, Figure 6In the figure, the solid line L1 and Figure 5 The solid line L1 of the discharge curve shown is the same, and represents an example of a discharge curve of a normal DC capacitor 12. For example, the solid line L1 represents an example of a discharge curve as a reference value obtained based on an actual measured value during a factory shipment test of the power conversion device 1, or a reference value obtained based on a design value of the capacitance of the DC capacitor and a design value of the resistance value of the discharge resistor.

[0108] In addition, Figure 6 In the figure, the dotted line L2 is Figure 5 The dashed line L2 of the discharge curve shown in FIG. 1 is the same, and represents a predetermined threshold value V for detecting (determining) an abnormality of the DC capacitor 12. th An example of a discharge curve.

[0109] And, in Figure 6 In the figure, a dashed line L3 is shown. The dashed line L3 represents a second predetermined threshold value V for detecting whether the DC capacitor 12 should be replaced (determining the replacement time). th2 An example of a discharge curve of . The second predetermined threshold value V th2 The dashed line L3 is smaller than the solid line L1 indicating the reference value and smaller than the predetermined threshold value V indicating the abnormality of the DC capacitor 12. th The dotted line L2 is larger.

[0110] When the DC capacitor 12 is abnormal, such as when the DC capacitor 12 fails or the DC capacitor 12 lacks a certain amount of capacitance, the capacitance of the DC capacitor 12 decreases significantly compared to when the DC capacitor 12 deteriorates over time. On the other hand, when the capacitance of the DC capacitor 12 decreases due to deterioration over time or life, the capacitance decreases more slowly (the capacitance does not decrease much) than when the capacitance of the DC capacitor 12 decreases due to capacitance deficiency or abnormality. Therefore, the second predetermined threshold value V th2 The dashed line L3 shows a predetermined threshold value V for detecting an abnormality of the DC capacitor 12. th The dotted line L2 is larger.

[0111] In the modified example of the first embodiment, when the DC voltage Vdc monitored by the monitoring unit 31 is lower than the second predetermined threshold value V th2 and is higher than the specified threshold V th When the determination unit 33 determines that the DC capacitor 12 has reached the replacement time, the notification unit 34 notifies that the DC capacitor 12 has reached the replacement time when the determination unit 33 determines that the DC capacitor 12 has reached the replacement time.

[0112] In addition, in a modification of the first embodiment, Figures 1 to 5Similarly to the first embodiment shown in the figure, when the DC voltage Vdc monitored by the monitoring unit 31 is lower than the predetermined threshold value V th When the determination unit 33 determines that the DC capacitor 12 is abnormal, the notification unit 34 notifies that the DC capacitor 12 is abnormal when the determination unit 33 determines that the DC capacitor 12 is abnormal.

[0113] In addition, in a modified example of the first embodiment, the second predetermined threshold value V th2 It can also be specified with the threshold V th Similarly, the determination unit 33 may have a bandwidth or margin within a predetermined range (predetermined voltage value) (upward or downward). th2 When the DC capacitor 12 is immediately determined to be replaced, the DC voltage Vdc is lower than the second predetermined threshold value V th2 When the voltage is lower than the predetermined range, it is determined that the DC capacitor 12 is due for replacement.

[0114] In addition, at the second predetermined threshold V th2 Also, with the specified threshold V th Similarly, the bandwidth or margin of the predetermined range may also be changed according to the assumed life of the DC capacitor 12, etc. th The dashed line L2 represents the second prescribed threshold value V th2 The single-dot chain line L3 may also be determined through experiments, calculations, simulations, etc. and stored in the storage unit 40 .

[0115] In addition, the predetermined threshold value V th The dashed line L2 represents the second prescribed threshold value V th2 The single-dot chain line L3 can also be expressed by making the bandwidth or margin different with respect to a threshold value (discharge curve). That is, in a threshold value (discharge curve), the first bandwidth can also be set to a predetermined threshold value V th , a second bandwidth smaller than the first bandwidth is set as a second predetermined threshold value V th2 .

[0116] In addition, the predetermined threshold value V th The dashed line L2 represents the second prescribed threshold value V th2 The single-dot chain line L3 can also be expressed by making the slope of the discharge curve different. That is, the discharge curve with the first slope can be set as the predetermined threshold value V th , a discharge curve having a second slope which is gentler than the first slope is set as a second predetermined threshold value V th2 .

[0117] In addition, regarding the other second predetermined threshold value V th2The processing of the determination unit 33 and the determination operation of the determination unit 33 are Figures 1 to 5 The predetermined threshold value V in the first embodiment shown in FIG. th The processing of the determination unit 33 and the determination operation of the determination unit 33 are the same or similar. Therefore, detailed description and illustration are omitted.

[0118] <Effects of Modification Example of First Embodiment>

[0119] Above, in Figure 6 In the modified example of the first embodiment shown in FIG. Figures 1 to 5 The same functions and effects as those of the first embodiment shown.

[0120] And, in Figure 6 In the modified example of the first embodiment shown in FIG. 1 , a second predetermined threshold value (V th2 = L3). Thus, according to the present embodiment, not only the abnormality of the DC capacitor 12 but also the replacement timing of the DC capacitor 12 can be grasped based on the discharge voltage of the DC voltage Vdc when the inverter device 10 is stopped.

[0121] <Second Embodiment>

[0122] Figure 7 It is a diagram showing a configuration example of a power conversion device 1A according to the second embodiment.

[0123] In the second embodiment, Figures 1 to 6 The same or similar components of the first embodiment and its modified examples are denoted by the same reference numerals, and detailed description thereof will be omitted or simplified.

[0124] In the second embodiment, the inverter device 10A of the power conversion device 1A is a multi-level power converter in which two DC capacitors 12P and 12N are connected in series via a DC neutral point C. Figure 7 In the embodiment, as an example of the inverter device 10A, a three-level multi-level power converter in which two DC capacitors 12P and 12N are connected in series via a DC neutral point C is described, but the number of the DC capacitors 12P and 12N may be more than two. In addition, the number of the discharge resistor 13 may also be more than one depending on the number of the DC capacitors 12P and 12N.

[0125] like Figure 7 As shown, in the inverter device 10A, two (plural) DC capacitors 12P and 12N are connected in series via a DC neutral point C, and at the DC neutral point C, two semiconductor switching elements (neutral point elements) Q are connected in anti-series for the three phases. Figure 7In the example shown, the semiconductor switching elements (neutral point elements) Q are connected in anti-series with the collector side of the IGBTs being shared, but may be connected in anti-series with the emitter side being shared.

[0126] Figure 8 Yes means Figure 7 FIG. 1 is a diagram showing an example of a configuration of a control device 30A in a power conversion device 1A. Figure 8 As shown, the control device 30A in the second embodiment replaces Figures 1 to 6 The monitoring unit 31 in the first embodiment and its modified example shown above is replaced by a monitoring unit 31A, and a determination unit 33A is replaced by the determination unit 33 .

[0127] The monitoring unit 31A always obtains and monitors the information of the DC voltage Vdcp of the DC capacitor 12P and the DC voltage Vdcn of the DC capacitor 12N detected by the DC voltage sensor 22. In addition, the monitoring unit 31A may obtain the information of the DC voltage Vdcp of the DC capacitor 12P and the DC voltage Vdcn of the DC capacitor 12N at predetermined time intervals for monitoring. In addition, the monitoring unit 31A may obtain the information of the DC voltage Vdcp of the DC capacitor 12P and the DC voltage Vdcn of the DC capacitor 12N and monitor them according to instructions received from an operator or the like via a higher-level device (not shown) or an operating unit (not shown). In addition, the monitoring unit 31A may obtain the information of the DC voltage Vdcp of the DC capacitor 12P and the DC voltage Vdcn of the DC capacitor 12N and monitor them when the inverter device 10A stops.

[0128] The determination unit 33A obtains information on the DC voltage Vdcp of the DC capacitor 12P and the DC voltage Vdcn of the DC capacitor 12N monitored by the monitoring unit 31A when the timing unit 32 counts that a predetermined time t1 has passed since the inverter device 10A stopped. Then, when the timing unit 32 counts that a predetermined time t1 has passed since the inverter device 10 stopped, the determination unit 33A compares the DC voltage Vdcp of the DC capacitor 12P with the DC voltage Vdcn of the DC capacitor 12N. In other words, the determination unit 33A compares the DC voltage values ​​of the plurality of DC capacitors 12P and 12N.

[0129] Furthermore, the determination unit 33A may always obtain information on the DC voltage Vdcp of the DC capacitor 12P and the DC voltage Vdcn of the DC capacitor 12N monitored by the monitoring unit 31A. Furthermore, the determination unit 33A may always continuously compare the DC voltage Vdcp of the DC capacitor 12P with the DC voltage Vdcn of the DC capacitor 12N.

[0130] The determination unit 33A determines that the DC voltage Vdcp of the DC capacitor 12P and the DC voltage Vdcn of the DC capacitor 12N to be compared differ by a predetermined threshold value V th3 When the above is true, it is determined that there is an abnormality in the DC capacitor 12P or 12N. Then, when determining that there is an abnormality in the DC capacitor 12P or 12N, the determination unit 33A outputs information indicating that there is an abnormality in the DC capacitor 12P or 12N to the reporting unit 34. In addition, when determining that there is an abnormality in the DC capacitor 12, the determination unit 33A may output information indicating that there is an abnormality in the DC capacitor 12P or 12N to an external device such as a higher-level device (not shown).

[0131] That is, when an abnormality occurs in either DC capacitor 12P or 12N, the capacitance of the DC capacitor decreases. Therefore, when an abnormality occurs in either DC capacitor 12P or 12N, if the DC voltage Vdcp of DC capacitor 12P is compared with the DC voltage Vdcn of DC capacitor 12N, the voltage values ​​of the two will differ by a predetermined threshold value Vdcp. th3 On the other hand, when both the DC capacitors 12P and 12N are normal, when the DC voltage Vdcp of the DC capacitor 12P is compared with the DC voltage Vdcn of the DC capacitor 12N, the voltage values ​​of the two will not differ by a predetermined threshold value V th3 In the second embodiment, based on such a principle, an abnormality in either the DC capacitor 12P or 12N is detected.

[0132] In addition, the threshold V th3 For example, the threshold V may be changed according to the operating status of the inverter device 10A, or may be determined in advance through experiments, simulations, etc. and stored in the storage unit 40. th3 For example, the determination may be made according to an instruction received from a higher-level device (not shown), an instruction received from an operator (not shown) via an operation unit (not shown), or the like.

[0133] In the second embodiment, the predetermined threshold value V th3 It can also be specified with the threshold V th Similarly, the determination unit 33A may have a bandwidth or margin within a predetermined range (predetermined voltage value) (upward or downward). th3 In the above case, it is not immediately determined that one of the DC capacitors 12P or 12N is abnormal, but when the phase difference is greater than the predetermined threshold value V th3 If the value exceeds the specified range, it is determined that a certain DC capacitor is abnormal. th3 Also, with the specified threshold V thLikewise, the bandwidth or margin of the predetermined range may be changed according to the assumed life of the DC capacitor 12P or 12N, etc.

[0134] In the second embodiment, it is also possible to Figure 6 Similarly to the modification of the first embodiment shown in FIG. 1 , the second predetermined threshold value V is used to detect the replacement time (determination replacement time) of whether one of the DC capacitors 12P or 12N should be replaced. th4 In this case, the determination unit 33A compares the DC voltage Vdcp of the DC capacitor 12P with the DC voltage Vdcn of the DC capacitor 12N, and determines whether the difference between them is greater than the second predetermined threshold value V th4 If the value is above 1, it is determined that one of the DC capacitors 12P or 12N is due for replacement. th4 becomes greater than the prescribed threshold value V th3 Small value.

[0135] In addition, at the second predetermined threshold V th4 It can also be specified with the threshold V th3 Similarly, (up or down) there is a bandwidth or margin within a specified range (specified voltage value). In addition, at the second specified threshold V th4 Also, with the specified threshold V th Likewise, the bandwidth or margin of the predetermined range may be changed according to the assumed life of the DC capacitor 12 and the like.

[0136] Fig. 9 Yes means Figure 7 and Figure 8 1A is a flowchart showing an example of the operation of the control device 30A in the power conversion device 1A shown. Fig. 9 The flowchart shown has steps S3A and S4A instead of Figure 3 Steps S3 and S4 of the flowchart shown.

[0137] In step S3A, the determination unit 33A obtains information on the DC voltage Vdcp of the DC capacitor 12P and the DC voltage Vdcn of the DC capacitor 12N at a time point after a predetermined time t1 has passed from the monitoring unit 31A.

[0138] In step S4A, the determination unit 33A compares the DC voltage Vdcp of the DC capacitor 12P with the DC voltage Vdcn of the DC capacitor 12N at a time point after a predetermined time t1 has passed. Then, the determination unit 33A determines whether the difference between the compared DC voltage Vdcp of the DC capacitor 12P and the DC voltage Vdcn of the DC capacitor 12N converges to a predetermined threshold value V th3 Within the range (relative to the specified threshold V th3within the prescribed range).

[0139] Then, the determination unit 33A determines that the difference between the DC voltage Vdcp of the DC capacitor 12P and the DC voltage Vdcn of the DC capacitor 12N to be compared has converged to a predetermined threshold value V th3 When it is within the range (“Yes” side), the processing is transferred to step S5.

[0140] On the other hand, the determination unit 33A determines that the difference between the DC voltage Vdcp of the DC capacitor 12P and the DC voltage Vdcn of the DC capacitor 12N to be compared has not converged to the predetermined threshold value V th3 When it is within the range (“No” side), the processing is transferred to step S6.

[0141] In addition, regarding other configurations and operations of the second embodiment, Figures 1 to 6 The configuration and operation of the first embodiment and its modified examples are the same or the same, and therefore, detailed description and illustration are omitted.

[0142] <Effects of the Second Embodiment>

[0143] Above, in Figures 7 to 9 In the second embodiment shown, Figures 1 to 6 The same functions and effects as those of the first embodiment and its modified examples are shown.

[0144] And, in Figures 7 to 9 In the second embodiment shown in FIG. 1 , by comparing the DC voltage Vdcp of the DC capacitor 12P with the DC voltage Vdcn of the DC capacitor 12N, it is possible to understand the abnormality and replacement time of either the DC capacitor 12P or 12N. As a result, in the multilevel power converter, a predetermined threshold value Vdcp obtained based on a discharge curve or the like at the time of factory shipment test or based on a design value is not used. th or the second prescribed threshold V th2 , it is possible to grasp the abnormality or replacement time of either DC capacitor 12P or 12N. Thus, according to this embodiment, it is possible to know the abnormality or replacement time of either DC capacitor 12P or 12N in a simple way.

[0145] <Hardware Configuration Example>

[0146] Fig.10 Yes means Figures 1 to 9 A conceptual diagram of an example of a hardware configuration of a processing circuit 90 included in the control device 30 or 30A in the embodiment shown. The above-mentioned 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.

[0147] 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.

[0148] When the processing circuit 90 includes dedicated hardware 93 , the processing circuit 90 is, for example, a single circuit, a complex circuit, a programmed processor, or a circuit formed by combining them. Each function is implemented by the processing circuit 90 .

[0149] Each function of the control device 30 or 30A may be partially or entirely constituted by hardware, or may be constituted as a program executed by a processor. That is, the control device 30 or 30A may also be implemented by a computer and a program, and the program may be stored in a storage medium or provided via a network.

[0150] <Supplementary matters regarding implementation>

[0151] Above, according to Figures 1 to 10 The embodiment shown is divided into Figure 1 to Figure 6 The first embodiment and its modified examples shown are Figure 7 to Figure 9 The second embodiment shown. However, any or all of these embodiments may be combined in series or in parallel. The combined embodiment can also achieve the same effects as the effects achieved by the embodiments before the combination.

[0152] In addition, according to Figures 1 to 10 The embodiment shown is an example of the power converter 1 and 1A and the control device 30 and 30A included therein as one mode of the present disclosure, but the present disclosure is not limited thereto. The present disclosure can also be implemented as a control method for executing the processing steps in each unit of the control device 30 or 30A.

[0153] Furthermore, the present disclosure may be implemented as a control program that causes a computer to execute processing steps in each unit of the control devices 30 and 30A.

[0154] In addition, the present disclosure may be implemented as a storage medium (non-temporary computer-readable storage medium) storing a control program. The control program may be stored in a removable medium such as a CD (Compact Disc), a DVD (Digital Versatile Disc), or a USB (Universal Serial Bus) memory and released. In addition, the control program may be uploaded to a network via a network interface (not shown) of the control device 30 or 30A, or may be downloaded from a network and stored in the storage unit 40, the memory 92, or the like.

[0155] Through the above detailed description, the features and advantages of the embodiments will become clear. It is intended that the claims relate to the features and advantages of the embodiments described above without departing from their spirit and scope of rights. In addition, if it is a person with ordinary knowledge in the technical field, all improvements and changes should be easily conceived. Therefore, it is not intended to limit the scope of the inventive embodiments to the above scope, and appropriate improvements and equivalents can also be included in the scope disclosed in the embodiments.

[0156] Description of Reference Numerals

[0157] 1, 1A…power conversion device; 10, 10A…inverter device (device); 11…DC input section; 11N…negative terminal; 11P…positive terminal; 12, 12P, 12N…DC capacitor; 13…discharge resistor; 14…inverter circuit; 15…AC output section; 15U…U phase terminal; 15V…V phase terminal; 15W…W phase terminal; 21…DC current sensor; 22…DC voltage sensor; 23…AC current sensor; 24…AC voltage sensor; 30, 30A…control device; 31, 31A… Monitoring unit; 32…timing unit; 33, 33A…judgment unit; 34…reporting unit; 35…PWM control unit; 40…storage unit; 90…processing circuit; 91…processor; 92…memory; 93…hardware; C…DC neutral point; D…return diode; Iac…AC current; Idc…DC current; L1…solid line; L2…dashed line; L3…single-point chain line; Q…semiconductor switch element; t0, t1…time; Vac…AC voltage (AC voltage value); Vdc, Vdcn, Vdcp…DC voltage (DC voltage value); V th …the specified threshold; V th2 ...the second specified threshold; V th3 …the specified threshold; V th4 …the second prescribed threshold.

Claims

1. A power conversion device, characterized in that: Equipped with inverter device and control device, The inverter device comprises: A DC input portion having a positive terminal and a negative terminal; an inverter circuit that converts electric power based on a switching action of a switching element; and a DC capacitor between the positive terminal and the negative terminal for absorbing and smoothing a ripple current generated by the switching operation of the inverter circuit; A discharge resistor for discharging the charge of the DC capacitor; as well as A DC voltage sensor detects the DC voltage value of the DC capacitor, The control device has: a monitoring unit that monitors the DC voltage value detected by the DC voltage sensor; a timing unit for timing an elapsed time from when the inverter device is stopped; a determination unit that determines that the DC capacitor is abnormal when the DC voltage value monitored by the monitoring unit is lower than a predetermined threshold value, which is a value smaller than a normal value, by more than a predetermined range when the predetermined time has elapsed since the inverter device was stopped as measured by the timing unit; as well as The reporting unit reports the abnormality of the DC capacitor when the determination unit determines that the DC capacitor is abnormal.

2. The power conversion device according to claim 1, characterized in that: The predetermined threshold value is determined based on a discharge curve indicating a change in the DC voltage value when the DC capacitor is discharged after the inverter device is stopped. The discharge curve is obtained based on an actually measured value of a change in the DC voltage value after the inverter device is stopped during a factory shipment test of the power conversion device. The determination unit determines that the DC capacitor is abnormal when the predetermined time has passed since the inverter device was stopped and the DC voltage value monitored by the monitoring unit is lower than the predetermined threshold value determined based on the discharge curve by more than a predetermined range.

3. The power conversion device according to claim 1, characterized in that: The predetermined threshold value is determined based on a discharge curve (v(t)) indicating a change in the DC voltage value when the DC capacitor is discharged after the inverter device is stopped. The discharge curve (v(t)) is obtained by substituting the design value (C) of the capacitance of the DC capacitor, the design value (R) of the resistance of the discharge resistor, the DC voltage value (Vdc) when the inverter device is stopped, and the time (t) elapsed from the stop of the inverter device into the following formula (1). [Number 1] When the timing unit measures the elapse of the prescribed time (t1) from the time when the inverter device is stopped, the determination unit calculates a DC voltage value (v(t1)) when the prescribed time (t1) is substituted into the formula (1); when the timing unit measures the elapse of the prescribed time (t1) from the time when the inverter device is stopped, and when the DC voltage value monitored by the monitoring unit is lower than the prescribed threshold value determined based on the calculated DC voltage value (v(t1)) by more than a prescribed range, the DC capacitor is determined to be abnormal.

4. The power conversion device according to claim 1, characterized in that: The determination unit determines that it is time to replace the DC capacitor when the DC voltage value monitored by the monitoring unit is lower than a second predetermined threshold value that is smaller than the normal value and larger than the predetermined threshold value by more than a predetermined range and is higher than the predetermined threshold value when the predetermined time has elapsed since the inverter device was stopped by the timing unit, and when the DC voltage value monitored by the monitoring unit is lower than a second predetermined threshold value that is smaller than the normal value and larger than the predetermined threshold value by more than a predetermined range and is higher than the predetermined threshold value, When the determination unit determines that the DC capacitor has reached the time for replacement, a notification is given to the effect that the DC capacitor has reached the time for replacement.

5. A power conversion device, characterized in that: Equipped with inverter device and control device, The inverter device comprises: A DC input portion having a positive terminal and a negative terminal; An inverter circuit converts electric power based on the switching action of a switching element; a plurality of DC capacitors connected in series between the positive terminal and the negative terminal via a DC neutral point, absorbing and smoothing a ripple current generated by the switching operation of the inverter circuit; a discharge resistor for discharging the charges of the plurality of DC capacitors respectively; and a DC voltage sensor, for respectively detecting the DC voltage values ​​of the plurality of DC capacitors; The control device has: a monitoring unit that monitors the DC voltage values ​​of the plurality of DC capacitors detected by the DC voltage sensor, respectively; a timing unit for timing an elapsed time from when the inverter device is stopped; a determination unit that compares the DC voltage values ​​of the plurality of DC capacitors monitored by the monitoring unit when the timing unit measures a predetermined time that has passed since the inverter device was stopped, and determines that one of the plurality of DC capacitors being compared is abnormal when the DC voltage values ​​of the plurality of DC capacitors being compared differ from each other by more than a predetermined threshold value; as well as The reporting unit reports that one of the plurality of DC capacitors is abnormal, when the determining unit determines that one of the plurality of DC capacitors is abnormal.

6. A control device, which is a control device for a power conversion device, characterized in that: The power conversion device includes an inverter device, and the inverter device has: A DC input portion having a positive terminal and a negative terminal; An inverter circuit converts electric power based on the switching action of a switching element; a DC capacitor between the positive terminal and the negative terminal for absorbing and smoothing a ripple current generated by the switching operation of the inverter circuit; A discharge resistor for discharging the charge of the DC capacitor; as well as A DC voltage sensor detects the DC voltage value of the DC capacitor, The control device has: a monitoring unit that monitors the DC voltage value detected by the DC voltage sensor; a timing unit for timing an elapsed time from when the inverter device is stopped; a determination unit that determines that the DC capacitor is abnormal when the DC voltage value monitored by the monitoring unit is lower than a predetermined threshold value, which is a value smaller than a normal value, by more than a predetermined range when the predetermined time has elapsed since the inverter device was stopped as measured by the timing unit; as well as The reporting unit reports the abnormality of the DC capacitor when the determination unit determines that the DC capacitor is abnormal.

Images