JP7008613B2 - Power converter - Google Patents

Description

Embodiments of the present invention relate to a power conversion device.

In the detection of a ground fault in a power converter, a ground resistor is connected to the DC circuit section between the converter and the inverter, and when a ground fault occurs in the power converter, the amount of current flowing through the ground resistor changes to the ground. A method of detecting the entanglement current is used.

By the way, in a power conversion device for controlling a plurality of electric motors, one converter may be branched by a direct current circuit and a plurality of inverters may be connected to the power conversion device. In the inverter ground fault detection device, in a power conversion device in which multiple inverters are connected, if a ground fault occurs between the connections between multiple inverters and the load of the inverter or somewhere in the load, a ground fault occurs. It takes time and effort to identify the branch of the inverter and the load (the branch where the ground fault is occurring). For example, when a ground fault occurs in a circuit configuration in which a converter, multiple inverters, and a motor are connected, a cable between the inverter and the motor is connected one by one in order to identify the branch where the ground fault is occurring. It is necessary to remove it and confirm the measurement. For this reason, it may be preferable to be able to improve the efficiency of identifying a branch in which a ground fault has occurred in a power conversion device to which a plurality of inverters are connected.

Japanese Unexamined Patent Publication No. 2017-175795

An object to be solved by the present invention is to provide a power conversion device capable of improving the efficiency of identifying a branch in which a ground fault has occurred in a power conversion device including a plurality of inverters.

The power conversion device of the embodiment includes a plurality of inverters, a plurality of inverter control units, a system control unit, a first electric component, a second electric component, a detector, and a detection circuit. .. The plurality of inverters are provided electrically in parallel with each other, are not directly grounded, and convert DC power supplied from a DC power source into AC power. The plurality of inverter control units control each of the plurality of inverters. The system control unit controls the plurality of inverter control units. The first electrical component is electrically connected to the positive electrode of the DC power supply. The second electrical component is electrically connected to the negative electrode of the DC power supply. In the detector, a connection point where a terminal not connected to the positive electrode of the first electrical component and a terminal not connected to the negative electrode of the second electrical component are electrically connected to each other is directly or In a structure grounded via a third electrical component, a value relating to the grounding current flowing between the connection point and the grounding point is detected. The detection circuit outputs a ground fault signal indicating that a ground fault occurs when the value detected by the detector is equal to or higher than a threshold value to the system control unit. The system control unit includes a division group generation unit, a determination target group selection unit, a bias signal output unit, and a ground fault determination unit. The division group generation unit divides the plurality of inverters into a plurality of groups based on deterioration-related information indicating the amount of deterioration of at least one of the inverter and the component electrically connected to the inverter. .. The determination target group selection unit selects a determination target group to be determined for a ground fault from the plurality of groups generated by the division group generation unit. The bias signal output unit outputs a bias signal for applying a bias to the output of the inverter included in the determination target group selected by the determination target group selection unit to the inverter control unit that controls the inverter. .. When the ground fault signal is output from the detection circuit in a state where the bias is applied to the output of the inverter based on the bias signal output by the bias signal output unit. In addition, it is determined that the inverter having a ground fault is included in the determination target group.

The figure which shows an example of the power conversion apparatus which concerns on embodiment. The figure which shows an example of the current detector and the detection circuit which concerns on embodiment. The figure which shows an example of the current detector and the detection circuit which concerns on the modification which concerns on embodiment. The figure which shows an example of the inverter control part which concerns on embodiment. The figure which shows an example of the structure of the system control part which concerns on embodiment. The flowchart which shows an example of the flow of the process which the system control part which concerns on embodiment starts the process at the time of the ground fault detection. The flowchart which shows an example of the flow of the ground fault detection processing flow which concerns on embodiment. The flowchart which shows an example of the flow of the ground fault inverter determination process which concerns on embodiment. The figure which shows an example of the confirmation number of times which concerns on embodiment.

(Embodiment)
Hereinafter, the power conversion device (power conversion system) of the embodiment will be described with reference to the drawings. In the following description, configurations having the same or similar functions are designated by the same reference numerals. Then, the duplicate description of those configurations may be omitted. As used herein, "based on XX" means "based on at least XX" and includes cases where it is based on another element in addition to XX. Further, "based on XX" is not limited to the case where XX is directly used, but also includes the case where it is based on a case where calculation or processing is performed on XX. "XX" is an arbitrary element (for example, arbitrary information).

FIG. 1 is a diagram showing an example of a power conversion device D according to the present embodiment. The power conversion device D includes a DC power supply 1, a high resistance 2A, a high resistance 2B, a plurality of inverters 3, a plurality of inverter control units 4, a current detector 6, a detection circuit 7, and a system control unit 8. And prepare. The high resistance 2A is an example of the first electrical component. The high resistance 2B is an example of a second electrical component. The current detector 6 is an example of a detector.

The DC power supply 1 supplies DC power to a plurality of inverters 3. The DC power supply 1 includes, for example, an AC power supply 11 and a converter 12. The AC power supply 11 supplies AC power to the converter 12. The converter 12 converts the AC power supplied by the AC power supply 11 into DC power.
The AC power supply 11 is not a part of the power conversion device D, but may be an external power supply provided in a factory or the like.

The plurality of inverters 3 include inverters 3-i (i = 1, 2, ..., N: n is the number of inverters) provided in parallel electrically with each other. Each of the plurality of inverters 3 converts the DC power supplied by the DC power source 1 into AC power and drives the plurality of loads 5. The plurality of inverter control units 4 control each of the plurality of inverters 3. The plurality of inverter control units 4 include an inverter control unit 4-i (i = 1, 2, ..., N: n is the number of inverters).

The plurality of loads 5 include a load 5-i (i = 1, 2, ..., N: n is the number of inverters). The load 5-i (i = 1, 2, ..., N: n is the number of inverters) is, for example, an electric motor. Here, the plurality of inverters 3 and the plurality of loads 5 are not directly grounded.

The high resistance 2A and the high resistance 2B ground the output end of the DC power supply 1 with high resistance. The high resistance 2A and the high resistance 2B are, for example, ground resistance. High resistance grounding is grounding through a grounding resistance. Here, the high resistance 2A and the high resistance 2B form a series circuit. The series circuit is connected in parallel with the DC power supply 1. Here, the high resistance 2A is electrically connected to the positive electrode of the DC power supply 1, and the high resistance 2B is electrically connected to the negative electrode of the DC power supply 1. The terminal not connected to the positive electrode of the DC power supply 1 having a high resistance of 2A and the terminal not connected to the negative electrode of the DC power supply 1 having a high resistance of 2B are electrically connected to each other at the connection point C. The connection point C is the midpoint of the series circuit, and the midpoint is grounded.
The current detector 6 detects the current flowing between the connection point C and the grounding point where the connection point C is grounded. The current flowing between the connection point C and the grounding point where the connection point C is grounded is the difference between the current flowing through the high resistance 2A and the current flowing through the high resistance 2B. That is, the current detector 6 detects the difference between the current flowing through the high resistance 2A and the current flowing through the high resistance 2B. The difference between the current flowing through the high resistance 2A and the current flowing through the high resistance 2B is the grounding current. The current detector 6 outputs a detection signal to the detection circuit 7. The detection signal is a signal indicating the magnitude of the ground current.

Based on the detection signal output by the current detector 6, the detection circuit 7 outputs the ground fault signal DS to the system control unit 8 when the magnitude of the current detected by the current detector 6 is equal to or greater than the threshold value. .. Here, the ground fault signal DS output by the detection circuit 7 includes a ground fault signal DS1 during operation and a ground fault signal DS2 during detection.

The operating ground fault signal DS1 is a signal indicating that the power conversion device D has a ground fault during normal operation. The ground fault signal DS2 at the time of detection is a signal indicating that there is a ground fault at the time of the detection operation. Here, in the detection operation, when a ground fault is detected during normal operation, the plurality of inverters 3 are stopped once and then operated in the low voltage region, and the load or load and the inverter are selected from among the plurality of inverters 3. This is an operation performed to identify the inverter connected to the branch where the connected wiring is ground fault. Hereinafter, the detection operation is also referred to as maintenance work. Hereinafter, the inverter connected to such a ground fault branch is referred to as a ground fault inverter A.

Further, the detection circuit 7 may perform a protection operation such as stopping the operation of the power conversion device D or an alarm operation such as an alarm transmission when the magnitude of the current detected by the current detector 6 is equal to or greater than the threshold value. .. When the system control unit 8 receives the ground fault signal DS1 during operation, the protection operation such as stopping the operation of the power conversion device D may be performed by the system control unit 8.

Here, the current detector 6 and the detection circuit 7 will be described with reference to FIGS. 2 and 3.
FIG. 2 is a diagram showing an example of the current detector 6 and the detection circuit 7 according to the present embodiment.
In the present embodiment, the current detector 6 detects the grounding current flowing between the connection point C and the grounding point in the structure in which the connection point C is directly grounded.

The detection circuit 7 includes an operation detection unit LD1 and a detection time detection unit LD2.
The operation detection unit LD1 sends the operation ground fault signal DS1 to the system control unit 8 when the magnitude of the current detected by the current detector 6 during the normal operation of the power conversion device D is equal to or larger than the first threshold value TH1. Output.
The detection unit LD2 outputs the detection ground fault signal DS2 to the system control unit 8 when the magnitude of the current detected by the current detector 6 during the detection operation is equal to or greater than the second threshold value TH2.

Here, the first threshold value TH1 may be set higher than the second threshold value TH2. Even if the power converter D is normal without a ground fault, a predetermined amount of ground current is affected by the parasitic capacitance of the inverter, load, or electrical components such as the connection line between the inverter and the load during normal operation. Is flowing. The first threshold value TH1 is set high enough that the detection circuit 7 does not erroneously detect the ground current flowing during normal operation even if it is normal.

FIG. 3 is a diagram showing an example of the detection circuit 7A according to the modified example of the present embodiment. In the example of FIG. 2, the current detector 6 directly grounds the connection point C, whereas in the example of FIG. 3, the connection point C is grounded via the high resistance 2C, and the detection circuit is replaced with the detection circuit 7. 7A is provided, and the detection circuit 7A detects the current flowing through the high resistance 2C equivalently by detecting the terminal voltage of the high resistance 2C. The high resistance 2C is an example of a third electrical component.

In FIGS. 2 and 3, the case where the electric component has high resistance 2A, high resistance 2B, and high resistance 2C has been described as an example, but the present invention is not limited to this. For example, in FIG. 2, a capacitor may be provided as an electric component instead of the high resistance 2A and the high resistance 2B.

Returning to FIG. 1, the description of the power conversion device D will be continued.
The system control unit 8 controls a plurality of inverter control units 4 based on the operation command DEB output from the host device M and the command speed reference ω *. The system control unit 8 can simultaneously output a bias signal BS for applying a bias to the outputs of the plurality of inverters 3, an operation command DEB, and a speed reference ωr * to the plurality of inverter control units 4. Here, the system control unit 8 may output the bias signal BS, the operation command DEB, and the speed reference ωr * by transmission or by a hard interface.
Here, the output by transmission is, for example, signal transmission via a communication line. The output by the hard interface is, for example, signal transmission using a contact such as a relay.

As will be described later, the system control unit 8 divides the plurality of inverters 3 into a plurality of groups, and determines the presence or absence of the ground fault inverter A, which is a ground fault inverter, for each group. The system control unit 8 outputs a bias signal BS to the inverter control unit 4 that controls the inverters included in the group to be determined for the ground fault among the plurality of inverter control units 4.

Here, with reference to FIG. 4, the internal configuration of one inverter control unit 4 will be described.
FIG. 4 is a diagram showing an example of the inverter control unit 4 according to the present embodiment. In FIG. 4, a plurality of inverter control units 4 are represented by the inverter control unit 4-i, and the inverter control unit 4-i is shown. Further, in FIG. 4, in response to the fact that the plurality of inverter control units 4 are represented by the inverter control unit 4-i, the inverter 3-i among the plurality of inverters 3 and the load 5- among the plurality of loads 5 It shows i and.

The rotation detector 10 detects the rotation position of the load 5-i, and outputs a value indicating the detected rotation position of the load 5-i to the inverter control unit 4-i. The load current detector 9 detects the input current for the load 5-i and outputs a value indicating the detected input current to the inverter control unit 4-i. The rotation position and the input current are output to the inverter control unit 4-i as a feedback amount.

The inverter control unit 4-i includes a differentiator 41, an electric controller 42, a voltage reference converter 43, an adder 44, a bias generator 45, and a PWM controller 46.
The differentiator 41 converts the phase angle indicating the rotation position detected by the rotation detector 10 into the rotation speed ωr.

The electric controller 42 compares and amplifies the rotation speed ωr converted by the differentiator 41 and the speed reference ωr * −i output from the system control unit 8 to generate a current reference. Here, the speed reference ωr * -i is a speed reference output to the inverter control unit 4-i among the speed reference ωr * output by the system control unit 8 to the plurality of inverter control units 4. The electric controller 42 compares and amplifies the generated current reference and the separately given magnetic flux reference with those obtained by converting the output of the load current detector 9 into two axes, respectively, thereby amplifying the d-axis voltage reference ED_R and the q-axis voltage reference. Generate EQ_R. Here, the electric controller 42 uses the phase reference θr based on the phase angle detected by the rotation detector 10 in the two-axis conversion.

In the present embodiment, the case where the electric controller 42 uses the speed reference ωr * -i output from the system control unit 8 as the speed reference to be compared with the rotation speed ωr will be described, but the present invention is not limited to this. The electric controller 42 holds in advance a speed reference during normal operation and a speed reference for detection operation, and when acquiring the bias signal BS-i output from the system control unit 8, the speed reference is set during normal operation. You may switch from the speed reference of the above to the speed reference for the detection operation.

The voltage reference converter 43 converts the d-axis voltage reference ED_R and the q-axis voltage reference EQ_R generated by the electric controller 42 into the three-phase basic voltage reference EU_R, EV_R and EW_R which are AC quantities using the phase reference θr. do.

The bias generator 45 outputs the bias Vbias to the adder 44 when acquiring the bias signal BS-i output from the system control unit 8. The bias generator 45 outputs the bias Vbias according to the rotation speed ωr converted by the differentiator 41 according to the method described in Patent Document 1.
The bias signal BS-i is a bias signal output to the inverter control unit 4-i among the bias signal BSs output by the system control unit 8 to the plurality of inverter control units 4.

The adder 44 adds the bias Vbias output by the bias generator 45 to each of the three-phase basic voltage reference EU_R, EV_R and EW_R converted by the voltage reference converter 43, and outputs the output voltage reference VU_REF, VV_REF and VW_REF. To generate.

The PWM controller 46 generates a gate signal for each switching element of the inverter 3-i by comparing the output voltage references VU_REF, VV_REF and VW_REF generated by the adder 44 with a predetermined PWM carrier. Here, the PWM controller 46 acquires the operation command DEB-i output from the system control unit 8, and generates the gate signal when the acquired operation command DEB-i is high. The operation command DEB-i is a gate deblock signal, and when it is high, the PWM controller 46 is permitted to output a gate signal, and when it is low, the PWM controller 46 is not permitted to output a gate signal. Is shown.
The operation command DEB-i is an operation command output to the inverter control unit 4-i among the operation command DEBs output to the plurality of inverter control units 4 by the system control unit 8.

In this embodiment, a case where a plurality of inverter control units 4 and a system control unit 8 are provided independently will be described, but the present invention is not limited to this. The plurality of inverter control units 4 may be provided in the system control unit 8.

Next, the configuration of the system control unit 8 will be described with reference to FIG.
FIG. 5 is a diagram showing an example of the configuration of the system control unit 8 according to the present embodiment. The system control unit 8 includes a division group generation unit 81, a determination target group selection unit 82, a bias signal output unit 83, a ground fault determination unit 84, an end determination unit 85, a storage unit 86, and an operation control unit 87. And the speed reference generation unit 88.

The division group generation unit 81 divides the plurality of inverters 3 into a plurality of groups G based on the deterioration-related information 861 stored in the storage unit 86. Here, the deterioration-related information 861 is information indicating an amount related to deterioration of at least one of the inverter 3-i and the component electrically connected to the inverter 3-i. The component electrically connected to the inverter 3-i is, for example, a cable connecting the inverter 3-i and the load 5-i.
In the deterioration-related information 861, each of the plurality of inverters 3 is associated with one or more deterioration-related amounts. The amount associated with deterioration is, for example, the cumulative operating time of each of the plurality of inverters 3 or the plurality of loads 5. That is, the deterioration-related information 861 includes the cumulative operating time of each of the plurality of inverters 3 and the plurality of loads 5.

The deterioration-related information 861 may include, as an amount related to deterioration, the lengths of a plurality of cables connecting the plurality of inverters 3 and the plurality of loads 5 driven by the plurality of inverters 3, respectively. The deterioration-related information 861 may include the installation environment of each of the plurality of inverters 3 or the plurality of loads 5 as the amount related to the deterioration. Here, the installation environment is, for example, temperature, humidity, or the like. The deterioration-related information 861 may include the maintenance frequency of each of the plurality of inverters 3 or the plurality of loads 5 as the amount related to the deterioration. The deterioration-related information 861 may include the elapsed time from the latest maintenance and inspection of each of the plurality of inverters 3 or the plurality of loads 5 as the amount related to the deterioration.

The determination target group selection unit 82 selects the determination target group TG to be the determination target of the ground fault from the plurality of group G generated by the division group generation unit 81.
The bias signal output unit 83 is included in the determination target group TG among the inverters 3-j (j is i = 1, 2, ..., N) included in the determination target group TG selected by the determination target group selection unit 82. It is a number indicating an inverter, where n is the number of inverters.) The bias signal BS-j for applying a bias to the output is output to the inverter control unit 4-j that controls the inverter 3-j. do.

The ground fault determination unit 84 determines whether or not the ground fault inverter A is included in the determination target group TG based on the ground fault signal DS2 at the time of detection.
The end determination unit 85 determines whether or not the determination of the ground fault inverter A is completed.
Deterioration-related information 861 is stored in the storage unit 86. The storage unit 86 may be provided as an external storage device independent of the system control unit 8.

The operation control unit 87 outputs the operation command DEB-j to the inverter control unit 4-j based on the operation command DEB output from the host device M.
The speed reference generation unit 88 outputs the speed reference ωr * −j to the inverter control unit 4-j based on the command speed reference ω * output from the host device M.

As described above, the system control unit 8 may perform a protective operation such as stopping the operation of the power conversion device D when the ground fault signal DS1 during operation is received from the detection circuit 7.

Here, with reference to FIG. 6, the process in which the system control unit 8 starts the ground fault detection processing according to whether or not the operating ground fault signal DS1 is high will be described.
FIG. 6 is a diagram showing an example of a processing flow in which the system control unit 8 according to the present embodiment starts the processing at the time of ground fault detection.

Step S100: The operation control unit 87 determines whether the operation ground fault signal DS1 output from the detection circuit 7 is high. When the operation control unit 87 determines that the ground fault signal DS1 during operation is high (step S100; YES), the operation control unit 87 executes the process of step S110. On the other hand, when it is determined that the ground fault signal DS1 during operation is not high (step S100; NO), the operation control unit 87 executes the process of step S130.

Step S110: The operation control unit 87 outputs a low operation command DEB-i to all the inverter control units 4-i of the plurality of inverter control units 4.
Step S120: The system control unit 8 executes a ground fault detection time process. The details of the ground fault detection processing will be described later with reference to FIG. 7.

Step S130: The system control unit 8 starts a process of outputting the operation command DEB-i, the bias signal BS-i, and the speed reference ωr * -i for each of the plurality of inverters 3.
Step S140: The operation control unit 87 determines whether or not the operation command DEB output from the host device M is high. When the operation control unit 87 determines that the operation command DEB is high (step S140; YES), the operation control unit 87 executes the process of step S150. On the other hand, when it is determined that the operation command DEB is not high (step S140; NO), the operation control unit 87 executes the process of step S160.

Step S150: The operation control unit 87 sets the operation command DEB-i to high and outputs the output to the inverter control unit 4-i. The speed reference generation unit 88 converts the value of the speed reference ωr * −i into the value of the command speed reference ω * and outputs the value to the inverter control unit 4-i. The bias signal output unit 83 does not output the bias signal BS-i to the inverter control unit 4-i.

Step S160: The operation control unit 87 sets the operation command DEB-i to low and outputs it to the inverter control unit 4-i. The speed reference generation unit 88 sets the value of the speed reference ωr * -i to zero and outputs the output to the inverter control unit 4-i. The bias signal output unit 83 does not output the bias signal BS-i to the inverter control unit 4-i.
Step S170: The system control unit 8 ends the process of outputting the operation command DEB-i, the bias signal BS-i, and the speed reference ωr * -i for each of the plurality of inverters 3.

Here, with reference to FIG. 7, a ground fault detection process, which is a process in which the system control unit 8 determines the ground fault inverter A, will be described.
FIG. 7 is a flowchart showing an example of the flow of the ground fault detection processing flow according to the present embodiment. The process shown in this flowchart corresponds to the process at the time of ground fault detection in step S120 of FIG. The process shown in this flowchart is executed when a signal indicating an instruction to execute the determination process of the ground fault inverter A is received when the maintenance work of the power conversion device D is performed. As described in steps S100 and S110 of FIG. 6, for example, after the system control unit 8 receives the ground fault signal DS1 during operation and the operation of the power conversion device D is stopped, a plurality of maintenance operations are performed. Each of the inverters 3 is operated in a low voltage region.

Step S200: The division group generation unit 81 divides the plurality of inverters 3 into a plurality of groups G based on the deterioration-related information 861 stored in the storage unit 86. Here, the division group generation unit 81 makes the plurality of inverters 3 relative to the first group including the plurality of inverters having a relatively large amount of deterioration related to the deterioration-related information 861. It may be at least divided into a second group containing a small number of inverters.

For example, the division group generation unit 81 relatives the plurality of inverters 3 to the first group including the plurality of inverters 3 or the first group including a plurality of inverters having a relatively long cumulative operating time among the plurality of loads 5. It is divided into two groups with a second group containing a plurality of short inverters. The division group generation unit 81 may divide the plurality of inverters 3 into three or more groups.

As another example, the division group generation unit 81 uses a plurality of inverters 3 and a plurality of inverters having a relatively long cable length for connecting the plurality of inverters 3 and the plurality of loads 5 among the plurality of inverters 3. It may be divided into two groups, a first group including the first group and a second group including a plurality of inverters having a relatively short cable length.

As another example, the division group generation unit 81 is installed with a plurality of inverters 3 as a first group including a plurality of inverters 3 having a relatively high temperature or humidity in the environment in which the inverters 3 are installed. It may be divided into two groups with a second group containing a plurality of inverters having relatively low environmental temperature or humidity.

As another example, the division group generation unit 81 includes a plurality of inverters 3 as a first group including a plurality of inverters 3 among the plurality of inverters 3 or a plurality of inverters having a relatively small number of maintenance times of the plurality of loads 5. , It may be divided into two groups, a second group including a plurality of inverters having a relatively large number of maintenances.
Here, it is considered that the more maintenance is performed, the less likely the inverter is to have a ground fault. Therefore, in the first group including a plurality of inverters having a relatively small number of maintenance and the second group including a plurality of inverters having a relatively large number of maintenance, the first group is more likely to cause a ground fault. Conceivable.

On the other hand, as the number of maintenances increases, it may be considered that the inverter is more likely to cause a ground fault and requires maintenance. When it is considered that the ground fault is more likely to occur as the number of maintenances increases, the division group generation unit 81 includes a plurality of inverters 3 and a plurality of inverters 3 having a relatively large number of maintenances. It may be divided into two groups, a group and a second group including a plurality of inverters having a relatively small number of maintenances.

As another example, the division group generation unit 81 uses a plurality of inverters 3 as a plurality of inverters having a relatively long elapsed time from the maintenance and inspection of the most recent plurality of inverters 3 or the plurality of loads 5 among the plurality of inverters 3. It may be divided into two groups, a first group including the above and a second group including a plurality of inverters having a relatively short elapsed time from the maintenance and inspection of the latest plurality of inverters 3 or the plurality of loads 5.

The division group generation unit 81 may divide the plurality of inverters 3 into a plurality of groups G by combining two or more of the amounts related to the deterioration indicated by the deterioration-related information 861. For example, the division group generation unit 81 may divide the plurality of inverters 3 into a plurality of groups G by combining the cumulative operating time and the number of maintenances.

Here, the division group generation unit 81 uses, for example, a plurality of inverters 3 having a relatively long cumulative operating time and a relatively large number of maintenances of the plurality of inverters 3 or the plurality of loads 5 among the plurality of inverters 3. The first group including the inverters of the above, the second group including a plurality of inverters having a relatively long cumulative operating time and a relatively small number of maintenances among the plurality of inverters 3, and the cumulative operating time of the plurality of inverters 3. Includes a third group that includes a plurality of inverters that are relatively short and have a relatively large number of maintenance, and a plurality of inverters 3 that have a relatively short cumulative operating time and a relatively small number of maintenance. It may be divided into four groups with the fourth group.

Step S210: The system control unit 8 starts a process of determining whether the ground fault inverter A is included in the determination target group TG for each determination target group TG.
Step S220: The determination target group selection unit 82 selects the determination target group TG from the plurality of groups G generated by the division group generation unit 81. Here, the determination target group selection unit 82 selects the first group as the determination target group TG before the second group among the plurality of groups G.

In step S200, when the plurality of inverters 3 are divided into three groups, that is, the first group, the second group, and the third group, in which the amount related to deterioration is relatively large in this order, the determination target is The group selection unit 82 selects the first group, the second group, and the third group among the plurality of groups G as the determination target group TG first in this order.

Step S230: The system control unit 8 executes a ground fault inverter determination process, which is a process for determining the ground fault inverter A.

Here, the ground fault inverter determination process will be described with reference to FIG.
FIG. 8 is a diagram showing an example of a ground fault inverter determination process according to the present embodiment. The ground fault inverter determination process shown in FIG. 8 corresponds to the process of step S230 of FIG.

Step S300: The ground fault determination unit 84 resets the timer.
Step S310: The operation control unit 87 issues a high operation command DEB-j to the inverter control unit 4-j that controls the inverter 3-j included in the determination target group TG selected by the determination target group selection unit 82. Output. The speed reference generation unit 88 outputs the speed reference ωr * whose value is the speed for ground fault detection to the inverter control unit 4-j. The bias signal output unit 83 outputs the bias signal BS-j for applying a bias to the output of the inverter 3-j to the inverter control unit 4-j.

The bias signal output unit 83 increases the ground fault detection speed from zero to a predetermined value over time while the ground fault inverter determination process of FIG. 8 is executed. After the ground fault detection speed reaches a predetermined value, the bias signal output unit 83 keeps the ground fault detection speed at the predetermined value. The bias signal output unit 83 may gradually reduce the value after the ground fault detection speed reaches a predetermined value.
The bias signal output unit 83 may set a different value as the ground fault detection speed for each of the inverter control units 4-j.

On the other hand, the operation control unit 87 issues a low operation command DEB-k to the inverter control unit 4-k that controls the inverter 3-k not included in the judgment target group TG selected by the judgment target group selection unit 82. Output. The speed reference generation unit 88 outputs the speed reference ωr * whose value is set to zero to the inverter control unit 4-k. The bias signal output unit 83 does not output the bias signal BS-k to the inverter control unit 4-k.

The size of the bias signal output unit 83 differs depending on at least one of the type of the inverter 3-j included in the determination target group TG and the type of the load 5-j driven by the inverter 3-j. The bias signal BS-j for applying a bias may be output to the inverter control unit 4-j.

For example, the bias signal output unit 83 outputs a bias signal BS-j for applying a low voltage to the inverter 3-j to which a load 5-j having a small inertia is connected to the inverter control unit 4-j. You may. The bias signal output unit 83 may output a bias signal BS-j for applying a high voltage to the inverter 3-j having a large inertia to the inverter control unit 4-j.
Further, for example, when the load 5-j is, for example, an electric motor, the bias signal output unit 83 outputs a bias signal BS-j having different bias positive / negative depending on the restriction of the rotation direction of the electric motor, for example, in the inverter control unit 4-. It may be output to j.

Step S320: The ground fault determination unit 84 determines whether or not the detection ground fault signal DS2 is output from the detection circuit 7. When it is determined that the ground fault signal DS2 at the time of detection is output (step S320; YES), the ground fault determination unit 84 executes the process of step S330. On the other hand, when the ground fault determination unit 84 determines that the ground fault signal DS2 at the time of detection is not output (step S320; NO), the ground fault determination unit 84 executes the process of step S340.

Step S330: The ground fault determination unit 84 determines that the ground fault inverter A is included in the determination target group TG. That is, in the ground fault determination unit 84, the ground fault signal DS2 at the time of detection is transmitted from the detection circuit 7 in a state where the output of the inverter is biased based on the bias signal BS—j output by the bias signal output unit 83. When it is output, it is determined that the ground fault inverter A is included in the determination target group TG. After that, the ground fault determination unit 84 ends the ground fault inverter determination process.
In addition, a plurality of ground fault inverters A may be included in the determination target group TG.

Step S340: The ground fault determination unit 84 counts the timer.
Step S350: The ground fault determination unit 84 determines whether or not the timer count is equal to or greater than a predetermined value. When the ground fault determination unit 84 determines that the timer count is equal to or greater than a predetermined value (step S350; YES), the ground fault determination unit 84 executes the process of step S360. On the other hand, when the ground fault determination unit 84 determines that the timer count is not equal to or greater than a predetermined value (step S350; NO), the system control unit 8 re-executes the process of step S310.

Step S360: The ground fault determination unit 84 determines that the ground fault inverter A is not included in the determination target group TG. After that, the ground fault determination unit 84 ends the ground fault inverter determination process.

Returning to FIG. 7, the description of the ground fault detection processing will be continued.
Step S240: The system control unit 8 ends the process of determining whether the ground fault inverter A is included in the determination target group TG.

Step S250: The end determination unit 85 determines whether or not the determination of the ground fault inverter A is completed. Here, the end determination unit 85 makes a determination based on the determination result in the ground fault inverter determination process of step SS230. The end determination unit 85 determines that there is no determination target group TG that is determined to include the ground fault inverter A in step S230, or that the determination target is determined to include the ground fault inverter A in step S230. When there is no determination target group TG including a plurality of inverters in the group TG, it is determined that the determination of the ground fault inverter A is completed.

On the other hand, the end determination unit 85 has one or more determination target group TGs determined to include the ground fault inverter A in step S230, and the determination target includes a plurality of inverters among the determination target group TGs. If there is a group TG, it is determined that the determination of the ground fault inverter A has not been completed.

When the end determination unit 85 determines that the determination of the ground fault inverter A is completed (step S250; YES), the system control unit 8 ends the process of determining the ground fault inverter A. On the other hand, when the end determination unit 85 determines that the determination of the ground fault inverter A has not been completed (step S250; NO), the system control unit 8 repeats the processes from step S200 to step S240.

Here, the division group generation unit 81 further divides the determination target group TG determined in step S230 to include the ground fault inverter A into a plurality of sub-division groups based on the deterioration-related information 861. That is, when it is determined that the ground fault inverter (ground fault inverter A) is included in the determination target group TG, the division group generation unit 81 further increases the number of the determination target group TGs based on the deterioration-related information 861. Subdivision group SG.

In the process of dividing the determination target group TG into a plurality of sub-division group SGs, the division group generation unit 81 uses one or more of the amounts indicating deterioration included in the deterioration-related information 861 as used in the previous step S200. It may be used again, or an amount of 1 or more different from the amount of 1 or more may be used.

For example, the division group generation unit 81 uses the cumulative operating time of each of the plurality of inverters 3 in the process of dividing the plurality of inverters 3 into the plurality of groups G in the first step S200, and is used in the second step S200. In the above, the cumulative operating time may be used again in the process of dividing the determination target group TG into a plurality of sub-division groups SG.

Further, for example, in the first step S200, the division group generation unit 81 uses the cumulative operating time of each of the plurality of inverters 3 for the process of dividing the plurality of inverters 3 into the plurality of groups G for the second time. In step S200, instead of the cumulative operating time, for example, the lengths of a plurality of cables connecting a plurality of inverters 3 and a plurality of loads 5 driven by the plurality of inverters 3 are determined by a plurality of determination target group TGs. It may be used for the process of dividing into the sub-division group SG of.

In the second and subsequent steps S220, the determination target group selection unit 82 further selects the determination target group TG from the plurality of subdivision group SGs generated by the division group generation unit 81.
In the second and subsequent steps S230, the system control unit 8 executes the ground fault inverter determination process. That is, in the second and subsequent steps S310, the bias signal output unit 83 biases the output of the inverter 3-j included in the subdivision group SG, which is the determination target group TG selected by the determination target group selection unit 82. The bias signal BS-j for this purpose is output to the inverter control unit 4-j that controls the inverter 3-j.
Further, in the second and subsequent steps S330, the ground fault determination unit 84 is in a state where the output of the inverter 3-j is biased based on the bias signal BS-j output by the bias signal output unit 83. When the detection circuit ground fault signal DS2 is output from the detection circuit 7, it is determined that the ground fault inverter (ground fault inverter A) is included in the subdivision group SG which is the determination target group TG.

In the present embodiment, the division group generation unit 81 further subdivides the determination target group TG determined to include the ground fault inverter A in the previous step S200 in the second and subsequent steps S200. The case of dividing into group SGs has been described, but the present invention is not limited to this. The division group generation unit 81 is included in all the determination target group TGs that are determined to include the ground fault inverter A in the previous step S200 among the plurality of inverters 3 in the second and subsequent steps S200. Inverters may be divided into multiple groups.

Here, the number of times the system control unit 8 repeats the processes from step S200 to step S250 differs depending on the number of division group generation units 81 that divide the plurality of inverters 3 into a plurality of groups. Here, the number of times the system control unit 8 outputs the bias signal BS to the plurality of inverter control units 4 is referred to as the confirmation number x.
The number of confirmations x is expressed using the equation (1).

Here, the number of inverters n indicates the number of a plurality of inverters 3 included in the power conversion device D. The number of groups y indicates the number of a plurality of groups in which the plurality of inverters 3 are divided.

Here, the number of confirmations x will be described with reference to FIG.
FIG. 9 is a diagram showing an example of the number of confirmations x according to the present embodiment. In the example shown in FIG. 9, the number of the plurality of inverters 3 is 3000. For comparison with the present embodiment, the number of confirmations x when the plurality of inverters 3 are not divided into a plurality of groups is shown. The number of confirmations x when not divided into a plurality of groups increases according to the number of the plurality of inverters 3.

The larger the number of groups y, the smaller the number of confirmations x. Here, the minimum value of the number of groups y changes according to the number of inverters n.
The division group generation unit 81 may select the number of divisions of the plurality of inverters 3 into a plurality of groups according to the number of the plurality of inverters 3. The division group generation unit 81 may select the number of divisions of the plurality of inverters 3 into a plurality of groups according to the number of the plurality of inverters 3 so that the number of confirmations x is minimized.

As described above, the power conversion device D according to the present embodiment includes a DC power supply 1, a plurality of inverters 3, a plurality of inverter control units 4, a system control unit 8, and a first electric component (this). In one example, it comprises a high resistance 2A), a second electrical component (high resistance 2B in this example), a detector (current detector 6 in this example), and a detection circuit 7.

The system control unit 8 includes a division group generation unit 81, a determination target group selection unit 82, a bias signal output unit 83, and a ground fault determination unit 84. The division group generation unit 81 uses a plurality of inverters 3 based on deterioration-related information 861 indicating an amount related to deterioration of at least one of the inverter 3-i and the component electrically connected to the inverter 3-i. Divide into groups of. The determination target group selection unit 82 selects the determination target group TG to be the determination target of the ground fault from the plurality of group G generated by the division group generation unit 81. The bias signal output unit 83 controls the inverter 3j to control the bias signal BS for applying a bias to the output of the inverter 3-j included in the determination target group TG selected by the determination target group selection unit 82. Output to section 4-j. When the ground fault signal DS is output from the detection circuit 7, the ground fault determination unit 84 is in a state where the output of the inverter is biased based on the bias signal BS output by the bias signal output unit 83. It is determined that the ground fault inverter (ground fault inverter A) is included in the determination target group TG.

With this configuration, in the power conversion device D according to the present embodiment, the number of confirmations x can be reduced as compared with the case where the plurality of inverters 3 are not divided into a plurality of groups. You can increase the efficiency of doing so.

Further, in the power conversion device D according to the present embodiment, the division group generation unit 81 includes a plurality of inverters 3 including a plurality of inverters having a relatively large amount of deterioration-related information based on the deterioration-related information 861. At least divide into a group and a second group containing a plurality of inverters with a relatively small amount associated with degradation. The determination target group selection unit 82 selects the first group as the determination target group TG before the second group.

With this configuration, in the power conversion device D according to the present embodiment, the ground fault can be determined first from the group including the inverter having a relatively high possibility of ground fault, so that the amount related to deterioration is relatively large. Compared with the case where the group including a large number of inverters is not selected as the determination target group TG first, the efficiency for identifying the branch where the ground fault has occurred can be improved.
Here, an inverter with a relatively large amount of deterioration is more likely to have a ground fault, and an inverter with a relatively small amount of deterioration is likely to have a ground fault. It is considered to be low. Rather than mixing inverters with a relatively large amount of deterioration and inverters with a relatively small amount of deterioration into one group, multiple inverters with a relatively large amount of deterioration are related. It is possible to reduce the number of confirmations x for determining a ground fault by dividing the group into a first group including the above and a second group including a plurality of inverters having a relatively small amount of deterioration.

Further, in the power conversion device D according to the present embodiment, when the division group generation unit 81 determines that the ground fault inverter (ground fault inverter A) is included in the determination target group TG, the determination target group The TG is further divided into a plurality of sub-division groups SG based on the deterioration-related information 861.
The determination target group selection unit 82 further selects the determination target group TG from the plurality of subdivision group SGs generated by the division group generation unit 81.
The bias signal output unit 83 uses the inverter 3 to provide a bias signal BS for biasing the output of the inverter 3-j included in the subdivision group SG, which is the determination target group TG selected by the determination target group selection unit 82. Output to the inverter control unit 4-j that controls -j.
The ground fault determination unit 84 outputs the ground fault signal DS from the detection circuit 7 in a state where the output of the inverter 3-j is biased based on the bias signal BS output by the bias signal output unit 83. In this case, it is determined that the ground fault inverter (ground fault inverter A) is included in the subdivision group SG which is the determination target group TG.

With this configuration, in the power conversion device D according to the present embodiment, the determination target group TG determined to include the ground fault inverter A is further divided into a plurality of subdivision group SGs, and the ground fault is divided into the subdivision group SGs. Since it can be repeatedly determined whether or not the inverter A is included, the ground fault inverter A can be determined. Here, in the power conversion device D according to the present embodiment, even if a plurality of ground fault inverters A are included in the plurality of inverters 3, any one of the plurality of inverters 3 is a plurality of ground fault inverters A. It can be determined whether or not there is.

Further, in the power conversion device D according to the present embodiment, the deterioration-related information 861 includes the cumulative operating time of each of the plurality of inverters 3.
With this configuration, the power conversion device D according to the present embodiment can be divided into a plurality of groups of the plurality of inverters 3 based on the cumulative operating time of each of the plurality of inverters 3, as compared with the case where the power conversion device D is not based on the cumulative operating time. It is possible to improve the efficiency for identifying the branch where the ground fault is occurring.
The result of identifying the branch in which the ground fault has occurred may be used for prediction and maintenance of aging deterioration due to the frequency of use of the plurality of inverters 3.

Further, in the power conversion device D according to the present embodiment, the deterioration-related information 861 includes the lengths of a plurality of cables connecting the plurality of inverters 3 and the plurality of loads 5 driven by the plurality of inverters 3, respectively.
With this configuration, the power conversion device D according to the present embodiment can be divided into a plurality of inverters 3 and a plurality of groups based on the lengths of the plurality of cables, as compared with the case where the power conversion device D is not based on the lengths of the plurality of cables. It is possible to increase the efficiency for identifying the branch where the ground fault is occurring.
The result of identifying the branch where the ground fault has occurred may be used for prediction and maintenance of aged deterioration of the material such as poor insulation of the cable.

Further, in the power conversion device D according to the present embodiment, the deterioration-related information 861 includes the installation environment of each of the plurality of inverters 3.
With this configuration, the power conversion device D according to the present embodiment can be divided into a plurality of inverters 3 and a plurality of groups based on the installation environment. The efficiency for identification can be increased.
The result of identifying the branch where the ground fault has occurred may be used for prediction and maintenance of aging deterioration due to environmental changes such as rainwater and dew condensation.

Further, in the power conversion device D according to the present embodiment, the deterioration-related information 861 includes the number of maintenance times of each of the plurality of inverters 3.
With this configuration, the power conversion device D according to the present embodiment can be divided into a plurality of inverters 3 and a plurality of groups based on the number of maintenances, so that a branch in which a ground fault occurs is generated as compared with the case where the number of maintenances is not used. The efficiency for identification can be increased.
The result of identifying the branch where the ground fault has occurred may be used for determining the priority of maintenance and inspection.

Further, in the power conversion device D according to the present embodiment, the deterioration-related information 861 includes the elapsed time from the latest maintenance and inspection of each of the plurality of inverters 3.
With this configuration, the power conversion device D according to the present embodiment can be divided into a plurality of inverters 3 into a plurality of groups based on the elapsed time from the latest maintenance and inspection, so that it is not based on the elapsed time from the latest maintenance and inspection. It is possible to improve the efficiency for identifying the branch where the ground fault is occurring.
The result of identifying the branch where the ground fault has occurred may be used for determining the timing of maintenance and inspection.

Further, in the power conversion device D according to the present embodiment, the bias signal output unit 83 has the type of the inverter 3-i included in the determination target group TG and the type of the load 5-i driven by the inverter 3-i. A bias signal BS for applying a bias having a different magnitude according to at least one of them is output to the inverter control unit 4-i.
With this configuration, in the power conversion device D according to the present embodiment, the size of the bias signal BS used for determining the ground fault is driven by the types of inverters 3-i and the inverters 3-i included in the determination target group TG. Since it can be made different according to at least one of the types of loads 5-i, it is possible to identify the branch where the ground fault is occurring without applying unnecessary stress to the plurality of inverters 3 and the plurality of loads 5. ..

A part of the system control unit 8 in the above-described embodiment, for example, the division group generation unit 81, the determination target group selection unit 82, the bias signal output unit 83, and the ground fault determination unit 84 is realized by a computer. May be good. In that case, the program for realizing this control function may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read by a computer system and executed. The "computer system" referred to here is a computer system built in the system control unit 8, and includes hardware such as an OS and peripheral devices. Further, the "computer-readable recording medium" refers to a portable medium such as a flexible disk, a magneto-optical disk, a ROM, or a CD-ROM, and a storage device such as a hard disk built in a computer system. Further, a "computer-readable recording medium" is a medium that dynamically holds a program for a short time, such as a communication line when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In that case, a program may be held for a certain period of time, such as a volatile memory inside a computer system serving as a server or a client. Further, the above-mentioned program may be for realizing a part of the above-mentioned functions, and may be further realized for realizing the above-mentioned functions in combination with a program already recorded in the computer system.
Further, a part or all of the system control unit 8 in the above-described embodiment may be realized as an integrated circuit such as an LSI (Large Scale Integration). Each functional block of the system control unit 8 may be individually made into a processor, or a part or all of them may be integrated into a processor. Further, the method of making an integrated circuit is not limited to the LSI, and may be realized by a dedicated circuit or a general-purpose processor. Further, when an integrated circuit technology that replaces an LSI appears due to advances in semiconductor technology, an integrated circuit based on this technology may be used.

Although one embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to the above, and various design changes and the like are made without departing from the gist of the present invention. It is possible to do.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and variations thereof are included in the scope of the invention described in the claims and the equivalent scope thereof, as are included in the scope and gist of the invention.

D ... Power converter, 1 ... DC power supply, 11 ... AC power supply, 12 ... Converter, 2A, 2B, 2C ... High resistance, 3 ... Multiple inverters, 3-i ... Inverter, 4 ... Multiple inverter control units, 4 -I ... Inverter control unit, 5 ... Multiple loads, 5-i ... Load, 6 ... Current detector, 7 ... Detection circuit, 8 ... System control unit, 9 ... Load current detector, 10 ... Rotation detector, 41 ... Differential, 42 ... Electric controller, 43 ... Voltage reference converter, 44 ... Adder, 45 ... Bias generator, 46 ... PWM controller, 81 ... Division group generator, 82 ... Judgment target group selection unit, 83 ... Bias signal output unit, 84 ... Ground fault determination unit, 85 ... End determination unit, 86 ... Storage unit, 861 ... Deterioration-related information, BS ... Bias signal, DS1 ... Operation ground fault signal, DS2 ... Detection time ground fault Signal, G ... Multiple groups, TG ... Judgment target group, A ... Ground fault inverter, SG ... Sub-division group

Claims (9)

Multiple inverters that are electrically parallel to each other, are not directly grounded, and convert DC power supplied from a DC power source to AC power.
A plurality of inverter control units that control each of the plurality of inverters,
A system control unit that controls the plurality of inverter control units,
The first electrical component electrically connected to the positive electrode of the DC power supply and
A second electrical component electrically connected to the negative electrode of the DC power supply,
The connection point where the terminal not connected to the positive electrode of the first electric component and the terminal not connected to the negative electrode of the second electric component are electrically connected to each other is a direct or third electrical component. A detector that detects a value related to the grounding current flowing between the connection point and the grounding point in a structure grounded via
A detection circuit that outputs a ground fault signal indicating that a ground fault occurs when the value detected by the detector is equal to or greater than a threshold value, and a detection circuit that outputs the ground fault signal to the system control unit.
Equipped with
The system control unit
A division group generation unit that divides the plurality of inverters into a plurality of groups based on deterioration-related information indicating the amount of deterioration of at least one of the inverter and the component electrically connected to the inverter.
A determination target group selection unit that selects a determination target group to be determined for a ground fault from the plurality of groups generated by the division group generation unit, and a determination target group selection unit.
A bias signal output unit that outputs a bias signal for applying a bias to the output of the inverter included in the determination target group selected by the determination target group selection unit to the inverter control unit that controls the inverter.
When the ground fault signal is output from the detection circuit in a state where the bias is applied to the output of the inverter based on the bias signal output by the bias signal output unit, the ground fault occurs. A power conversion device including a ground fault determination unit for determining that the inverter is included in the determination target group. The division group generation unit has the plurality of inverters relative to the first group including the plurality of inverters having a relatively large amount of deterioration related to the deterioration based on the deterioration-related information. At least divided into a second group containing a small number of inverters
The determination target group selection unit selects the first group as the determination target group before the second group.
The power conversion device according to claim 1. When it is determined that the inverter having a ground fault is included in the determination target group, the division group generation unit further divides the determination target group into a plurality of sub-division groups based on the deterioration-related information.
The determination target group selection unit further selects the determination target group from the plurality of subdivision groups generated by the division group generation unit.
The bias signal output unit controls the inverter with a bias signal for applying a bias to the output of the inverter included in the subdivision group which is the determination target group selected by the determination target group selection unit. Output to the inverter control unit
When the ground fault signal is output from the detection circuit in a state where the bias is applied to the output of the inverter based on the bias signal output by the bias signal output unit. In addition, it is determined that the inverter having a ground fault is included in the subdivision group which is the determination target group.
The power conversion device according to claim 1 or 2. The deterioration-related information includes the cumulative operating time of each of the plurality of inverters.
The power conversion device according to any one of claims 1 to 3. The deterioration-related information includes the lengths of a plurality of cables connecting the plurality of inverters and the plurality of loads driven by the plurality of inverters, respectively.
The power conversion device according to any one of claims 1 to 4. The deterioration-related information includes the installation environment of each of the plurality of inverters.
The power conversion device according to any one of claims 1 to 5. The deterioration-related information includes the number of maintenance times of each of the plurality of inverters.
The power conversion device according to any one of claims 1 to 6. The deterioration-related information includes the elapsed time from the latest maintenance and inspection of each of the plurality of inverters.
The power conversion device according to any one of claims 1 to 7. The bias signal output unit obtains the bias signal for applying a bias having a different magnitude depending on at least one of the type of the inverter included in the determination target group and the type of the load driven by the inverter. Output to the inverter control unit,
The power conversion device according to any one of claims 1 to 8.

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