JP7657704B2 - Inverter control system and inverter control method - Google Patents

Description

The present invention relates to an inverter control system and an inverter control method.

Elevators and other elevators use AC motors as their power source. To control the operating state of AC motors, an inverter is used to convert the voltage and frequency of the power source. For example, in the case of an elevator installed in a building, the three-phase AC power source supplied by the power company is converted in voltage and frequency by an inverter before being supplied to the AC motor that constitutes the hoist.
When converting the voltage and frequency of a three-phase AC power supply using an inverter, specifically, the three-phase AC power supply is converted into DC power supply using a converter, and the converted DC power supply is converted into AC power supply of the desired voltage and frequency using an inverter. Here, the converter and the inverter can have the same basic configuration, in which case, the only difference is that the operating direction is reversed. In the following explanation, when the word "inverter" is used, it also includes the converter, unless a special distinction is made.

When using inverters to control the power supply of elevators and other lifting machines, multiple inverters are connected in parallel depending on the required power supply capacity, and the multiple inverters perform processing simultaneously. That is, inverters are made up of semiconductor switches such as IGBTs (Insulated Gate Bipolar Transistors), and since there is a limit to the current and voltage that can pass through a single semiconductor switch, multiple inverters are connected in parallel to ensure the required power supply capacity. For example, when configuring an inverter with an output of 200 kW, four inverters, each with an output of 50 kW, are connected in parallel to ensure 200 kW.

Patent document 1 describes an example of an inverter as a power conversion device. It describes a technology that makes uniform the current flowing through multiple capacitors connected to wiring in a power module that serves as an inverter, thereby preventing the inverter from generating heat and preventing variations in its lifespan.

JP 2015-198554 A

As described in Patent Document 1, the inverter generates heat depending on the state of use, and depending on the state of heat generation, there is a problem that the life of the inverter may be shortened.
Conventionally, in inverters connected in multiple stages, sufficient consideration has not been given to equalizing or extending the life span of each inverter.

In the technology described in Patent Document 1, the current flowing through multiple capacitors is made uniform by modifying the wiring of the capacitors connected to the main circuit, but there is a limit to how much heat can be prevented by dealing with the capacitors, so a more effective solution was desired.

The present invention aims to provide an inverter control system and an inverter control method that can appropriately equalize and extend the life spans of inverters connected in parallel.

In order to solve the above problems, for example, the configurations described in the claims are adopted.
The present application includes a number of means for solving the above problems. One example of such an inverter control system is an inverter control system for controlling each of N inverters (N being an integer of 2 or more) connected in parallel to supply power to a motor that drives an elevator, the inverter control system including a load detection unit that detects the load on the elevator, a maximum load current calculation unit that calculates a maximum load current required in accordance with the load detected by the load detection unit and the speed of the elevator, a gate command unit that limits the number of inverters to be operated to supply power to the motor to less than N among the N inverters connected in parallel in accordance with the maximum load current calculated by the maximum load current calculation unit, and a gate command unit that controls each of the inverters connected in parallel to supply power to the motor. The system includes a memory unit that stores the drive time and temperature stress of each inverter, and a life calculation unit that estimates the life of each inverter connected in parallel based on the drive time and temperature stress stored in the memory unit, and when the number of inverters operated to supply power to the motor is limited to less than N, if the maximum load current calculated by the maximum load current calculation unit is a current that allows the motor to be driven with one or more inverters stopped, the gate command unit stops one or more inverters in accordance with the calculated maximum load current, and when the gate command unit stops one or more inverters, the inverters are stopped in order of the shortest life calculated by the life calculation unit.

According to the present invention, a process is performed to limit the inverters that are operated to supply power to the motor among a plurality of inverters connected in parallel according to the maximum load current. Therefore, since not all inverters are operated all the time, the life of the inverters can be extended. In addition, by appropriately selecting the inverters to be limited, the life of the inverters can be equalized.
Problems, configurations and effects other than those described above will become apparent from the following description of the embodiments.

1 is a diagram showing a schematic configuration of an inverter device circuit and an elevator controlled by an inverter control system according to an embodiment of the present invention; 2 is a plan view showing an example of the arrangement of the inverter device shown in FIG. 1; 1 is a perspective view showing the shape of one unit of an inverter device controlled by an inverter control system according to an embodiment of the present invention; 1 is a block diagram showing an example of the configuration of an inverter control system according to an embodiment of the present invention; 4 is a flowchart showing an example of a control process of the inverter control system according to the embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An inverter control system according to an embodiment of the present invention (hereinafter referred to as "this embodiment") will be described below with reference to the accompanying drawings.
The inverter control system of this embodiment is a system for an inverter device that supplies power to a hoist of an elevator, which is a lifting machine.

[Configuration of inverter device]
Fig. 1 shows a circuit configuration of an inverter device 100. Fig. 1 also shows a schematic configuration of an elevator to which power is supplied by the inverter device 100.
The inverter device 100 includes a first parallel inverter 110, a second parallel inverter 120, . . . , an Nth parallel inverter 190 (N is an integer of 2 or more).

Two inverter units are connected in series to each of the parallel inverters 110 to 190. For example, the first parallel inverter 110 has two inverter units 111 and 112 connected in parallel. The inverter unit 111 operates as a converter that converts the three-phase AC power supply 11 into DC, and has six semiconductor switches in total, two for each of the U phase, V phase, and W phase: 111-U1, 111-U2, 111-V1, 111-V2, 111-W1, and 111-W2.
In addition, a capacitor 111-C is connected to the inverter unit 111 to smooth the power supply after it has been converted into a direct current.
A power supply filter unit 12 is connected between the three-phase AC power supply 11 and the inverter unit 111 .

Inverter unit 112 converts the DC obtained by inverter unit 111 into a three-phase AC power supply, and has six semiconductor switches in total: 112-U1, 112-U2, 112-V1, 112-V2, 112-W1, and 112-W2, two for each of the U, V, and W phases. A capacitor 112-C is also connected to the DC side of inverter unit 112.

Similarly, the second parallel inverter 120 to the Nth parallel inverter 190 each include two inverter units 121, 122 to 191, 192. For example, the inverter unit 121 of the second parallel inverter 120 includes six semiconductor switches 121-U1, 121-U2, 121-V1, 121-V2, 121-W1, and 121-W2, and converts a three-phase AC power supply into a DC power supply. The inverter unit 122 of the second parallel inverter 120 includes six semiconductor switches 122-U1, 122-U2, 122-V1, 122-V2, 122-W1, and 122-W2, and converts a DC power supply into a three-phase AC power supply.

Furthermore, the inverter unit 191 of the Nth parallel inverter 190 has six semiconductor switches 191-U1, 191-U2, 191-V1, 191-V2, 191-W1, and 191-W2, and operates to convert three-phase AC power to DC power. Also, the inverter unit 192 has six semiconductor switches 192-U1, 192-U2, 192-V1, 192-V2, 192-W1, and 192-W2, and operates to convert DC power to three-phase AC power.

Capacitors 121-C, 122-C to 191-C, 192-C are also connected to the two inverter units 121, 122 to 191, 192 of the second parallel inverter 120 to the Nth parallel inverter 190.

The semiconductor switches (121-U1, etc.) arranged in each of the inverter units 111, 112-191, 192 are composed of semiconductor elements such as IGBTs, and are controlled to be turned on and off by the inverter control unit 200 (Figure 4), which will be described later. In this case, the voltage and frequency for driving the elevator are set by controlling the on and off of the inverter units 112-192, which obtain the three-phase AC power supply for each of the parallel inverters 110-190.

The three-phase AC power obtained by the inverter units 112-192 of each parallel inverter 110-190 is supplied via a reactor 13 to a motor (e.g., a three-phase synchronous motor) 14 that serves as the elevator hoist.

To briefly explain the elevator configuration, a main rope 16 is wound around a net wheel 15 that rotates in conjunction with the rotation of a motor 14. A car 17 is connected to one end of the main rope 16, and a counterweight 19 is connected to the other end, so that the car 17 rises and falls with the rotation of the motor 14. A load sensor 18 is installed on the car 17 as a load detection unit that detects the load on the car 17.
The inverter device 100 is installed, for example, in a machine room of an elevator.

[Example of inverter device placement]
FIG. 2 shows an example of the layout of the inverter device 100 of this embodiment.
The inverter device 100 in the example of FIG. 2 has a four-parallel configuration including a first parallel inverter 110 to a fourth parallel inverter 140 .
Each of the parallel inverters 110 to 140 includes two inverter units, so that there are eight inverter units 111 to 141 and 112 to 142 in total.

As shown in FIG. 2, the inverter device 100 of this example has eight inverter units 111-141 and 112-142 stacked vertically on the control panel 109. That is, in the example of FIG. 2, the inverter units are arranged in the following order from the top: 111, 121, 131, 141, 112, 122, 132, 142. However, the arrangement of the units shown in FIG. 2 is just one example, and other arrangement orders may also be used.

Each of the inverter units 111, 112, 121, 122, 131, 132, 141, and 142 includes six semiconductor switches (not shown in FIG. 2), and each unit is provided with three cooling fans.
For example, cooling fans 111-F1, 111-F2, and 111-F3 are attached to the inverter unit 111. Similarly, cooling fans indicated by adding "F1, F2, and F3" to the end of the reference numerals of the inverter units 121 to 141 and 112 to 142 are attached to the inverter units 121 to 141 and 112 to 142. Handles 101 are attached to the left and right ends of each of the inverter units 111 to 142.

The four inverter units 111, 121, 131, and 141 that operate as converters are connected in parallel to the three terminals 102U, 102V, and 102W of the terminal section 102. The three terminals 102U, 102V, and 102W of the terminal section 102 are connected to the three-phase AC power source 11 side shown in FIG. 1.

Further, the four inverter units 112, 122, 132, and 142 operating as inverters are connected in parallel to the three terminals 103U, 103V, and 103W of the terminal section 103. The three terminals 103U, 103V, and 103W of the terminal section 103 are connected to the motor 14 side shown in FIG.
The parallel inverters 110 to 140 are set to have the same maximum output current.

[Configuration of inverter unit]
FIG. 3 is a perspective view showing the configuration of one inverter unit 111. As shown in FIG.
The other inverter units 112 to 142 have the same configuration as the inverter unit 111 .
The inverter unit 111 has three cooling fans 111-F1, 111-F2, and 111-F3 attached to the front side of the frame 107, which also serves as a heat sink. The inverter unit 111 has six semiconductor switches 111-U1, 111-U2, 111-V1, 111-V2, 111-W1, and 111-W2. In this example, the inverter unit is configured using a 2-in-1 type IGBT module, but a 1-in-1 or 6-in-1 type may also be used. A capacitor 111-C and the like are also disposed in the inverter unit 111. Handles 101 are attached to the left and right ends of the front side of the frame 107.

Three-phase AC side terminals 104-U, 104-V, 104-W are arranged on the upper front side of frame 107, and DC side terminals 105-P, 105-N are arranged on the upper rear side of frame 107.
In the case of the inverter unit 111 operating as a converter, the three-phase AC side terminals 104-U, 104-V, and 104-W are connected to the three-phase AC power source 11 (FIG. 1). In the case of the inverter unit 121 operating as an inverter, the three-phase AC side terminals 104-U, 104-V, and 104-W are connected to the motor 14 side.
The DC side terminals 105 -P, 105 -N are connected to DC side terminals (not shown) of the inverter units 112 of the same parallel inverter 110 .

[Configuration of inverter control unit and elevator control unit]
4 shows the configuration of the inverter control unit 200 that controls the inverter device 100 of this example, and the elevator control unit 300. Here, as shown in FIG. 4, the inverter device 100 is configured to include four parallel inverters 110 to 140.

Each semiconductor switch 111-U1, 111-V1, ... of the inverter device 100 is turned on and off under the control of a gate command unit 201 of the inverter control unit 200. The gate command unit 201 controls the three-phase AC power source 11 by turning on and off each semiconductor switch 111-U1, 111-V1, ... so as to convert the voltage and frequency for driving the corresponding motor 14 based on the load and speed command of the car 17 supplied from the elevator control unit 300.

In this example, the gate command unit 201 performs a process of selecting an inverter to be operated from the four parallel inverters 110 to 140 based on the maximum load current corresponding to the load of the car 17 detected by the load sensor 18. Details of the process of selecting the inverter to be operated will be described later with reference to FIG. 5.

The inverter control unit 200 also includes an inverter drive time/temperature stress storage unit 202. The inverter drive time/temperature stress storage unit 202 stores the operating drive time and the temperature stress state of each of the four parallel inverters 110-140. The temperature stress is calculated from the operating state of the four parallel inverters 110-140, or is obtained by a temperature sensor (not shown) arranged in each parallel inverter 110-140.

The inverter control unit 200 further includes a life calculation unit 203. The life calculation unit 203 calculates the life of each of the parallel inverters 110 to 140 individually based on the inverter drive time and temperature stress stored in the inverter drive time/temperature stress storage unit 202. When calculating the life, the life calculation unit 203 preferably refers to both the inverter drive time and the temperature stress, but it may refer to only one of them.

Information on the life span of each of the parallel inverters 110 to 140 calculated by the life span calculation unit 203 is supplied to the gate command unit 201 .
When selecting the parallel inverters 110 to 140 to be operated, the gate command unit 201 selects the inverter to be operated based on information about the life span of each of the parallel inverters 110 to 140 .

The elevator control unit 300 includes a load detection unit 301 and a maximum load current calculation unit 302.
The load detection unit 301 detects the load of the car 17 from the detection data of the load sensor 18. That is, the load detection unit 301 performs a load detection process for the car 17.
The maximum load current calculation unit 302 calculates the maximum load current according to the lifting speed of the car 17 and the load amount (loading rate) detected by the load detection unit 301. That is, the maximum load current calculation unit 302 performs a maximum load current calculation process. Information on the calculated maximum load current is supplied to the inverter control unit 200.

[Control process by inverter control unit]
FIG. 5 is a flowchart showing a process for selecting the parallel inverters 110 to 140 to be operated when the inverter control unit 200 controls the inverter device 100 to be on and off.
It should be noted that INV1 shown in the flowchart of FIG. 5 is the parallel inverter having the shortest remaining life calculated by the life calculation unit 203 among the four parallel inverters 110 to 140.
Similarly, INV2, INV3, and INV4 are parallel inverters having the second, third, and fourth shortest remaining lives, respectively, among the four parallel inverters 110 to 140, as calculated by the life calculation unit 203. Furthermore, I_load is the maximum load current calculated by the maximum load current calculation unit 302, and I_max is the maximum current that can be output by each of the parallel inverters 110 to 140 per unit.

First, the gate command unit 201 of the inverter control unit 200 compares the required maximum load current I_load transmitted from the maximum load current calculation unit 302 with the maximum current I_max that can be output by one of the parallel inverters 110 to 140. Specifically, the gate command unit 201 determines whether the condition [maximum outputtable current I_max < required maximum load current I_load/4] is satisfied (step S11).

In step S11, when the current of one inverter, which is one-fourth the required maximum load current I_load, exceeds the maximum current I_max that one parallel inverter can output (Yes in step S11), the inverter control unit 200 detects an overcurrent (step S12). When this overcurrent is detected, the inverter control unit 200 notifies the elevator control unit 300 of the overcurrent.

The elevator control unit 300, which has received the overcurrent, issues an announcement to the passengers in the car 17 urging them to get off the car because the car is over capacity, and restricts the drive of the car 17 until the overcurrent state is resolved (step S13). After restricting the drive of the car 17, the gate command unit 201 returns to the judgment in step S11.
In step S13, the inverter control unit 200 only performs the process of stopping the operation of the inverter device 100, and the process of making an announcement encouraging passengers to disembark may be performed independently by the elevator control unit 300 by detecting the load amount (load rate).

In step S11, if the current of one inverter, which is one-fourth the required maximum load current I_load, does not exceed the maximum current I_max that one parallel inverter can output (No in step S11), the gate command unit 201 performs the process of step S14. That is, the gate command unit 201 determines whether the maximum outputtable current I_max satisfies the condition [required maximum load current I_load/4≦maximum outputtable current I_max<required maximum load current I_load/3] (step S14).

In step S14, when the maximum outputtable current I_max is equal to or less than one load current equal to one-fourth the maximum load current I_load and exceeds one load current equal to one-third the maximum load current I_load (Yes in step S14), the gate command unit 201 performs the process of step S15. That is, the gate command unit 201 selects the four parallel inverters 110, 120, 130, 140 to be all operated, controls the four parallel inverters 110, 120, 130, 140 to be turned on and off, and supplies driving power to the motor 14 (step S15). This control in step S15 performs the driving process until the motor 14 stops.

In addition, in step S14, when the maximum possible output current I_max does not exceed one load current obtained by dividing the maximum load current I_load by one third (No in step S14), the gate command unit 201 performs the judgment in step S16. That is, the gate command unit 201 judges whether the maximum possible output current I_max satisfies the condition [maximum possible output current I_load/3≦maximum possible output current I_max<maximum possible output current I_load/2] (step S16).

In step S16, when the maximum outputtable current I_max is equal to or less than one load current obtained by dividing the maximum load current I_load by one third and exceeds one load current obtained by dividing the maximum load current I_load by half (Yes in step S16), the gate command unit 201 performs the process of step S17. That is, the gate command unit 201 controls the on/off of three parallel inverters INV2, INV3, and INV4 out of the four parallel inverters 110, 120, 130, and 140 to supply driving power to the motor 14 (step S17). The parallel inverters INV2, INV3, and INV4 are the three parallel inverters with the second, third, and fourth shortest remaining lifespans in terms of driving time and temperature stress. The driving process is performed by the control in step S17 until the motor 14 stops.

In addition, in step S16, when the maximum possible output current I_max does not exceed one load current obtained by dividing the maximum load current I_load by half (No in step S16), the gate command unit 201 performs the judgment in step S18. That is, the gate command unit 201 judges whether the maximum possible output current I_max satisfies the condition [required maximum load current I_load/2≦maximum possible output current I_max<required maximum load current I_load] (step S18).

In step S18, when the maximum possible output current I_max is equal to or less than one load current that is half the maximum load current I_load and exceeds the maximum load current I_load (Yes in step S18), the gate command unit 201 performs the process of step S19. That is, the gate command unit 201 controls the on/off of two parallel inverters INV3 and INV4 among the four parallel inverters 110, 120, 130, and 140 to supply driving power to the motor 14 (step S17).
The parallel inverters INV3 and INV4 are the two parallel inverters with the third and fourth shortest remaining lives in terms of drive time and temperature stress. By the control in step S19, drive processing is performed until the motor 14 stops.

Furthermore, in step S18, when the maximum outputtable current I_max is equal to or less than the load current of one inverter (No in step S18), the gate command unit 201 performs the process of step S20. That is, the gate command unit 201 controls the on/off of one parallel inverter INV4 among the four parallel inverters 110, 120, 130, and 140 to supply driving power to the motor 14 (step S20). The parallel inverter INV4 is the parallel inverter with the fourth shortest remaining life (i.e., the longest remaining life) in terms of driving time and temperature stress. The control in step S20 performs the driving process until the motor 14 stops.

[Effect of performing control by the inverter control unit]
The inverter control unit 200 of this example performs the control process shown in FIG. 5, and the inverter device 100 performs a process of limiting the inverters that are operated to supply power to the motor among the parallel-connected inverters, based on the maximum load current corresponding to the load amount and speed during driving.

For example, when the load is at its lightest, only the parallel inverter INV4 operates. As a result, the remaining three parallel inverters INV1 to INV3 are stopped, which extends the lifespan of the inverters. As the load increases and the maximum load current increases, the number of inverters that are stopped decreases, and when the load is at its heaviest, operation is performed using all of the parallel inverters INV1 to INV4.

Furthermore, the inverter to be stopped is selected by giving priority to the inverter with the shortest remaining life based on the driving time and temperature stress of each parallel inverter at that time, so that the lives of the inverters can be equalized.
Furthermore, by giving priority to selecting an inverter that is subject to less temperature stress, an inverter with high conversion efficiency can be selected, and the conversion efficiency of the driving power supply by the inverter device 100 can be improved.

[Modification]
It should be noted that the embodiment examples described so far have been described in detail in order to explain the present invention in an easily understandable manner, and are not necessarily limited to those having all of the configurations described.
For example, the flowchart in FIG. 5 describes the process for a case in which four parallel inverters 110 to 140 are provided, but the present invention can be applied to a process for selecting an inverter to be operated in a similar manner when N parallel inverters (N is an integer of 2 or more) are provided.
Further, the arrangement of the inverter units 111 to 142 shown in FIG. 2 is also one example, and other configurations may be used.

In the above-described embodiment, the invention is applied to the control of an inverter device that supplies power to an elevator motor, but it may also be applied to motors in elevators other than elevators. For example, it may be applied to the control of an inverter device that supplies power to a motor in an elevator such as an escalator. In addition, when applied to the control of an inverter device that supplies power to a motor with large load fluctuations other than an elevator, it has the effect of extending the life of the inverter device.

In addition, the configuration diagram shown in Figure 4 shows only the control lines and information lines that are considered necessary for explanation, and does not necessarily show all control lines and information lines in the product. In reality, it can be assumed that almost all components are interconnected.

11: Three-phase AC power supply, 12: Power supply filter section, 13: Reactor, 14: Motor, 15: Net pulley, 16: Main rope, 18: Load sensor, 19: Counterweight, 100: Inverter device, 101: Handle, 102, 103: Terminal section, 102U, 102V, 102W: Terminal, 103: Terminal section, 103U: Terminal, 104-U, 104-V, 104-W, 105-P, 105-N: Terminal, 107: Frame, 109: Control panel, 110 to 190: Parallel inverter, 111, 112, 121, 122, 131, 132, 141, 142... inverter units 111-C, 112-U1... capacitor, 111-F1, 111-F2, 111-F3... cooling fan, 111-U1, 111-U2, 111-V1, 111-V2, 111-W1, 111-W2... semiconductor switch, 200... inverter control unit, 201... gate command unit, 202... inverter drive time/temperature stress storage unit, 203... life calculation unit, 300... elevator control unit, 301... load detection unit, 302... maximum load current calculation unit

Claims (3)

An inverter control system in which N inverters (N is an integer of 2 or more) connected in parallel supply power to a motor that drives an elevator and control each of the parallel-connected inverters,
A load detection unit that detects a load amount of the elevator;
a maximum load current calculation unit that calculates a required maximum load current according to the load detected by the load detection unit and the speed of the elevator;
a gate command unit that limits the number of inverters to be operated to supply power to the motor, among the N inverters connected in parallel, to less than N in accordance with the maximum load current obtained by the maximum load current calculation unit;
A storage unit that stores a driving time and a temperature stress of each of the inverters connected in parallel;
a life calculation unit that estimates a life of each of the inverters connected in parallel based on the drive time and the temperature stress stored in the storage unit,
when limiting the number of the inverters operated to supply power to the motor to less than N, if the maximum load current calculated by the maximum load current calculation unit is a current capable of driving the motor by stopping one or more of the inverters, the gate command unit stops one or more of the inverters in accordance with the calculated maximum load current;
When the gate command unit stops one or more of the inverters, the gate command unit stops the inverters in order of the shortest lifespan calculated by the lifespan calculation unit.
Inverter control system. The inverter control system according to claim 1 , further comprising: a limiting unit that limits the elevator when the maximum load current calculated by the maximum load current calculation unit exceeds a maximum load current when all of the N inverters connected in parallel are used. An inverter control method for controlling each of N inverters (N being an integer of 2 or more) connected in parallel to supply power to a motor that drives an elevator, the method comprising:
A load detection process for detecting a load of the elevator;
a maximum load current calculation process for calculating a required maximum load current according to the load amount detected by the load detection process and the speed of the elevator;
a gate command process for limiting the number of inverters to be operated to supply power to the motor, among the N inverters connected in parallel, to less than N, in accordance with the maximum load current calculated by the maximum load current calculation process;
A storage process for storing the driving time and the temperature stress of each of the inverters connected in parallel;
A life calculation process of estimating a life of each of the inverters connected in parallel based on the drive time and the temperature stress stored by the storage process,
when limiting the number of the inverters operated to supply power to the motor to less than N, if the maximum load current calculated in the maximum load current calculation process is a current that allows the motor to be driven by stopping one or more of the inverters, the gate command process stops one or more of the inverters in accordance with the calculated maximum load current;
When one or more of the inverters are stopped in the gate command process, the inverters are stopped in order of the shortest life calculated in the life calculation process.
Inverter control method.

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