JP2020150612A - Inverter system and inverter control method - Google Patents

Abstract

To provide a technique capable of contributing to simplification of a configuration and energy saving measures of an inverter system.SOLUTION: In a power failure state during regeneration operation in which a power system 2 is determined to be a power failure state by a power failure determining function unit 11 of a control unit 1 while a motor M performs regeneration operation, when a DC link capacitor voltage Vdc is determined to be equal to or larger than a first threshold voltage Vth1, by a threshold voltage determining unit 12, a rectifier control function unit 15 switches off a switching element of a rectifier 3 and stops rectification operation. Further, a first circuit control function unit 16 switches off one of switching elements S11 to S13 on a first upper arm side of a first inverter circuit 4 and switching elements S14 to S16 on a first lower arm side, and switches on the other. Furthermore, a second circuit control function unit 17 controls switching of switching elements S21 to S26 of a second inverter circuit 61, and regenerates regenerative power of regenerative operation to a charging/discharging unit 62.SELECTED DRAWING: Figure 1

Description

The present invention relates to the technology of an inverter system and an inverter control method, and relates to, for example, drive control of an electric motor capable of power running operation and regenerative operation.

In an inverter system that controls the power running operation and regenerative operation of an electric motor that uses the power of the power system as a drive source, for example, between the power system and the inverter circuit (the first inverter circuit 4 in FIG. 1 described later), the power system side. A rectifier that converts the AC voltage from the inverter into a DC voltage is provided, and a DC link capacitor having a buffer function is provided. Further, for example, an active filter is provided between the inverter circuit and the electric motor via a transformer (see, for example, FIG. 12 of Non-Patent Document 1).

The active filter has an inverter circuit (second inverter circuit 61 in FIG. 1 described later), a capacitor connected to the DC side of the inverter circuit, and the like, and a harmonic component (AC voltage) is controlled by switching control of the inverter circuit. A configuration in which a desired compensation voltage is output so as to suppress the influence of the harmonic component caused by the source operation can be mentioned.

The regenerative power generated by the regenerative operation of the electric motor can be stored in a DC link capacitor, or the regenerative power can be regenerated to the power system side to take energy saving measures. Further, in the event of a power failure on the power system side, the electric motor can be driven by power operation by applying the DC link capacitor as an emergency power supply.

However, for example, when the DC link capacitor voltage exceeds the rated voltage or the like and the power system side is in a power failure state, the regenerated power cannot be regenerated to the power system side. In such a case, it is conceivable that the regenerative operation may be hindered (regeneration expired, etc.) or the DC link capacitor may be overvoltage damaged.

As a configuration for suppressing such a situation, for example, a device such as a resistor for power consumption or a changeover switch (hereinafter, simply referred to as a power consumption device) is provided between the DC link capacitor and the inverter to regenerate the power. A configuration is known in which electric power can be appropriately consumed (for example, thermally consumed by a resistor) (see, for example, FIGS. 1 and 2 of Patent Document 1).

Tadashi Pengkata, Masakazu Kohata, Yasufumi Akagi, "Examination of Compensation Characteristics of Parallel Active Filters and Series Active Filters", Institute of Electrical Engineers of Japan D, Vol. 113, No. 1, 1993, pp33-40.

Japanese Unexamined Patent Publication No. 2005-145678

When the above-mentioned power consumption device is provided, for example, the configuration of the inverter system may be increased in size and cost. In addition, since the consumption of regenerative power can be a mere power loss, energy saving measures may be insufficient.

The present invention has been made in view of such technical problems, and an object of the present invention is to provide a technique capable of contributing to simplification of configuration and energy saving measures.

One aspect of the present invention is a rectifier that converts an AC voltage of a power system into a DC voltage, a first inverter circuit connected between the rectifier DC side and an electric motor, and a rectifier DC side and a first inverter circuit DC side. The DC link capacitor connected between the two inverter circuits, the second inverter circuit connected between the AC side of the first inverter circuit and the electric motor via a transformer, and the DC side of the second inverter circuit. It includes a series-type active filter having a charge / discharge unit, and a control unit that controls a rectifier, a first inverter circuit, and a second inverter circuit, respectively.

The control unit is set based on the power failure determination function unit that detects the power system status and determines the presence or absence of a power failure in the power system, and the DC link capacitor voltage that is detected and the allowable voltage of the DC link capacitor. The threshold voltage determination function unit that determines by comparing with the first threshold voltage or by comparing with the second threshold voltage set smaller than the first threshold voltage and the operating state of the electric motor are detected, and the electric motor is driven by force. It is set based on the operation judgment function unit that determines whether it is in the state, regenerative operation state, or rotation stop state, and the charge / discharge unit that detects the charge / discharge unit voltage during the compensation operation of the active filter. Connected to the upper arm of the first inverter circuit, the specified voltage determination function unit that determines by comparing with the specified voltage, the rectifier control function unit that controls the switching element of the rectifier by switching, and controls the rectification operation of the rectifier. The first circuit control function unit that controls the power running operation and regenerative operation of the electric motor by switching control of the first upper arm side switching element and the first lower arm side switching element connected to the lower arm, and the second It includes a second circuit control function unit that controls switching of the switching element of the inverter circuit to control the voltage output due to the discharge of the stored energy of the charge / discharge unit and the regeneration of the regenerated power to the charge / discharge unit.

Then, in the power failure state during the regenerative operation in which the power system is determined to have a power failure while the electric motor is in the regenerative operation by the power failure determination function unit, the DC link capacitor voltage is set to the first threshold by the threshold voltage determination function unit. When it is determined that the voltage is equal to or higher than the voltage, the rectifier control function unit switches off the switching element of the rectifier to stop the rectification operation, and the first circuit control function unit is on the first upper arm side of the first inverter circuit. One of the switching element and the switching element on the first lower arm side is switched off and the other is switched on, and the second circuit control function unit switches and controls the switching element of the second inverter circuit to regenerate the regenerative power of the regenerative operation. Is characterized in that it is regenerated in the charge / discharge part.

Further, in the power recovery state during regenerative operation in which the power system is determined to be restored from the power failure state during regenerative operation by the power failure determination function unit, the DC link capacitor voltage is set to the first threshold voltage by the threshold voltage determination function unit. When it is determined that the above is the case, the rectifier control function unit switches and controls the switching element of the rectifier to perform rectification operation until the DC link capacitor voltage reaches the second threshold voltage or less, and the stored energy of the DC link capacitor is stored. Is discharged to the power system side, and when the threshold voltage determination function unit determines that the DC link capacitor voltage has reached the second threshold voltage or less due to the discharge of the stored energy of the DC link capacitor to the power system side. , The first circuit control function unit switches and controls the first inverter circuit to regenerate the regenerated power of the regenerative operation to the power system side, and the specified voltage determination function unit determines that the charge / discharge unit voltage is larger than the specified voltage. If this is the case, the second circuit control function unit switches and controls the second inverter circuit until the charge / discharge unit voltage reaches the specified voltage or less, and discharges the stored energy of the charge / discharge unit to the power system side. It may be characterized by doing.

In addition, the threshold voltage determination function unit is in the rotation-stopped power recovery state in which it is determined by the power failure determination function unit that the regenerative operation is stopped from the power failure state during the regeneration operation and the power system is being restored while the motor is stopped rotating. When the DC link capacitor voltage is determined to be equal to or higher than the first threshold voltage and the specified voltage determination function unit determines that the charge / discharge unit voltage is larger than the specified voltage, the first circuit control function unit determines. One of the first upper arm side switching element and the first lower arm side switching element of the first inverter circuit is switched off and the other is switched on, and the charge / discharge unit voltage of the second circuit control function unit is equal to or less than the specified voltage. The second inverter circuit is switched and controlled to discharge the stored energy of the charging / discharging section to control the power running operation of the electric motor, and the specified voltage determination function section charges the stored energy of the charging / discharging section. When it is determined that the discharge unit voltage has reached the specified voltage or less, the rectifier control function unit switches off the switching element of the rectifier until the DC link capacitor voltage reaches the second threshold voltage or less, and stops the rectification operation. Then, the first circuit control function unit switches and controls the first inverter circuit until the DC link capacitor voltage reaches the second threshold voltage or less, discharges the stored energy of the DC link capacitor to the electric motor side, and causes the electric motor. It may be characterized in that the power running operation is controlled and the second circuit control function unit switches and controls the second inverter circuit to control the voltage output due to the discharge of the stored energy of the charge / discharge unit.

In another aspect, a rectifier that converts the AC voltage of the power system into a DC voltage, a first inverter circuit connected between the rectifier DC side and the electric motor, and a rectifier DC side and the first inverter circuit DC side. A DC link capacitor connected between them, a second inverter circuit connected between the AC side of the first inverter circuit and the electric motor via a transformer, and charging / discharging connected to the DC side of the second inverter circuit. A method of controlling an inverter system including a series-type active filter having a unit by a control unit, characterized in that the inverter system is realized by the same control configuration as the control device according to the above aspect. Is.

As shown above, according to the present invention, it is possible to contribute to simplification of the configuration and energy saving measures.

The schematic block diagram for demonstrating the inverter system 10A which is an example of this embodiment. The schematic block diagram for demonstrating the inverter system 10B which is an example of this embodiment. The schematic block diagram for demonstrating an example of control unit 1. The voltage change characteristic diagram with respect to time change in Example 1. FIG. A circuit configuration diagram between the active filter 6 and the electric motor M when the first inverter circuit 4 is in a short-circuited state (when a capacitor is applied to the charging / discharging section 62). The voltage change characteristic diagram with respect to time change in Example 2. FIG. The voltage change characteristic diagram with respect to time change in Example 3. FIG. A circuit configuration diagram between the active filter 6 and the electric motor M when the first inverter circuit 4 is in a short-circuited state (when a storage battery is applied to the charge / discharge unit 62). The voltage change characteristic diagram with respect to time change in Example 4. FIG.

As shown in Non-Patent Document 1, Patent Document 1, etc., the inverter system and the inverter control method according to the embodiment of the present invention have a control configuration in which a compensation voltage is simply output in an active filter or a power consumption device is provided. (Hereinafter, simply referred to as a conventional control configuration as appropriate) is completely different.

That is, in the present embodiment, the rectifier that converts the AC voltage of the power system into the DC voltage, the first inverter circuit connected between the rectifier DC side and the electric motor, the rectifier DC side and the first inverter circuit DC side. A series type active having a DC link capacitor connected between the two inverter circuits, a second inverter circuit connected between the AC side of the first inverter circuit and the electric motor via a transformer, and a charge / discharge unit. It relates to an inverter system equipped with a filter. Then, depending on the state of the power system, the electric motor, the DC link capacitor, etc. (for example, the presence or absence of a power failure in the power system, the operating state of the electric motor, the voltage state of the DC link capacitor, etc.), the rectifier, the first inverter circuit, and the active filter are individually installed. The configuration is controlled as appropriate.

In the control configuration according to this embodiment, the DC link capacitor voltage (voltage Vdc described later) is set in a state where the power system is interrupted during the regenerative operation of the electric motor (hereinafter, appropriately referred to as a power failure state during the regenerative operation). If it is larger than the threshold voltage (first threshold voltage Vth1 described later) set based on the allowable voltage of the DC link capacitor, the rectifying operation of the rectifier is stopped by the switching control of the rectifier.

Further, by the switching control of the first inverter circuit, one of the first upper arm side switching element and the first lower arm side switching element connected to the upper and lower arms of the first inverter circuit is switched off and the other. To switch on. Further, the regenerative power of the regenerative operation is regenerated to the charge / discharge unit by the switching control of the second inverter circuit.

According to the control configuration of this embodiment, it is possible to suppress a situation (regeneration expiration, etc.) in which the regenerative operation is hindered in a power failure state during the regenerative operation even if the device for power consumption is not provided, and the regenerative power is effective. It can also be used. For example, even if the power system is in a power failure state, the power running operation of the electric motor can be performed by appropriately discharging the stored energy of the charging / discharging unit. In addition, overvoltage damage of the DC link capacitor can be suppressed.

That is, according to the control configuration of the present embodiment, it is possible to contribute to simplification of the configuration, energy saving measures, power failure countermeasures, and the like as compared with the conventional control configuration. It also makes it possible to contribute to the improvement of safety and reliability.

As described above, the inverter system and the control method of the present embodiment are various as long as the rectifier, the first inverter circuit, and the active filter can be appropriately controlled according to the states of the power system, the electric motor, and the DC link capacitor. It is possible to design by appropriately applying the common technical knowledge of the fields (for example, power system technology, inverter technology, rectifier technology, active filter technology, electric motor technology, etc.), and the following are examples.

<< Configuration example of the inverter system according to this embodiment >>
The inverter system 10A shown in FIG. 1 shows an example of a control configuration according to the present embodiment, and is interposed between the power system 2 and the electric motor M so that the power running operation and the regenerative operation of the electric motor M can be controlled. It is configured in.

The inverter system 10A includes a rectifier 3 that converts an AC voltage from the power system 2 into a DC voltage, a first inverter circuit 4 connected between the rectifier 3 DC side and the electric motor M, and a rectifier 3 DC side. The DC link capacitor 5 connected between the first inverter circuit 4 DC side and the series type active filter 6 connected between the first inverter circuit 4 AC side and the electric motor M via a transformer 60. And have. The rectifier 3, the first inverter circuit 4, and the active filter 6 (mainly the second inverter circuit 61 described later) can be controlled by the control unit 1, respectively.

The rectifier 3 has a plurality of semiconductor switching elements (detailed illustration is omitted; hereinafter, simply referred to as a rectifier switch), and the rectifier switch is controlled by the control unit 1 (for example, a gate signal or the like on the rectifier switch). It is configured so that a desired rectifying operation can be performed by outputting the control signal of (switching control).

The first inverter circuit 4 has a plurality of semiconductor switching elements (hereinafter, simply referred to as first switches) S11 to S16, and the first switches S11 to S16 are switched controlled by the control unit 1 (for example, the first switch). It is configured so that a control signal such as a gate signal can be output to 1 switch S11 to S16 for switching control).

In the case of the first inverter circuit 4 in FIG. 1, the first switches S11 to S13 are connected to the upper arm of the first inverter circuit, and the first switches S14 to S16 are the lower arms of the first inverter circuit. It is connected to the.

The DC link capacitor 5 is connected in parallel to the rectifier 3 and the first inverter circuit 4, and is configured to have a buffer function. Such a DC link capacitor 5 is charged by, for example, a DC voltage output from the rectifier 3 during the power running operation of the electric motor M, or a DC voltage output from the first inverter circuit 4 during the regenerative operation of the electric motor M. , Smooth the DC voltage.

The series-type active filter 6 is connected to the second inverter circuit 61, which is connected in series between the AC side of the first inverter circuit 4 and the electric motor M via a transformer 60, and the DC side of the second inverter circuit 61. It has a structure including a charging / discharging unit 62.

The second inverter circuit 61 has a plurality of semiconductor switching elements (hereinafter, simply appropriately referred to as second switches) S21 to S26, and the second switches S21 to S26 are switched controlled by the control unit 1 (for example, the first switch). It is configured so that a control signal such as a gate signal can be output to the two switches S21 to S26 for switching control).

In the case of the second inverter circuit 61 in FIG. 1, the second switches S21 to S23 are connected to the upper arm of the second inverter circuit 61, and the second switches S24 to S26 are the second inverter circuit 61. It is connected to the lower arm.

As shown in FIG. 3 described later, the control unit 1 has various determination function units and control function units, and detects the states of the power system 2, the electric motor M, the DC link capacitor 5, etc. with a detector or the like (not shown). It is configured so that the rectifier 3, the first inverter circuit 4, and the active filter 6 can be appropriately controlled according to the determination result.

In the inverter system 10A shown above, it is possible to appropriately change the mode according to the purpose. For example, as shown in FIG. 1, reactors L1 to L3 may be provided between the transformer 60 and the second inverter circuit 61 for the purpose of improving the power factor and suppressing harmonic components.

Further, in the rectifying switch, the first switches S11 to S16, and the second switches S21 to S26, various semiconductor switching elements and the like can be appropriately applied, and the present invention is not particularly limited. A specific example is the application of a self-extinguishing semiconductor switching element such as an IGBT.

As long as the charging / discharging unit 62 can be charged / discharged according to the switching control of the second inverter circuit 61 and can store energy, various modes can be applied. Typical examples are capacitors and storage batteries. The inverter system 10A of FIG. 1 has a configuration in which a capacitor is applied to the DC side of the second inverter circuit 61, but a storage battery may be applied as in the inverter system 10B of FIG. 2, for example. In FIG. 2, the same reference numerals as those shown in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

In a situation where the motor M is operated at a relatively low rotation speed (hereinafter, simply referred to as low-speed operation), the energy ripple flowing in and out of the active filter 6 tends to be large, and the active filter 6 tends to be large. A phenomenon may occur in which the charging / discharging section 62 of the above becomes a supply source of the energy ripple.

Even when such a phenomenon during low-speed operation occurs, the active filter is required to exhibit various functions required for the active filter 6 (compensation function for suppressing the influence of harmonic components, etc.) as desired. It is conceivable to apply the charge / discharge unit 62 having a relatively large capacity in No. 6 to sufficiently suppress the voltage ripple. As an example thereof, it is possible to apply a charge / discharge unit 62 having a storage capacity of several times to several tens of times that of the storage capacity of the DC link capacitor 5. In particular, in many storage batteries, the energy that can be stored is larger than that of capacitors.

In the state of the power system 2, the electric motor M, the DC link capacitor 5, etc. detected by the control unit 1, it may be appropriately detected according to the purpose. For example, the voltage Vdc of the DC link capacitor 5 and the voltage of the charging / discharging unit 62 (voltage Vc of the capacitor described later and voltage Vbat of the storage battery) are detected via a voltage sensor or the like (not shown), and in the operating state of the electric motor M. Can be detected via a rotation speed sensor or the like (not shown). Further, the state of the power system 2, for example, the presence or absence of a power failure, may be detected by a power failure detection device or the like including a system voltage sensor or the like.

<< Configuration example of control unit 1 >>
FIG. 3 shows a configuration example of the control unit 1, which includes a power failure determination function unit 11, a threshold voltage determination function unit 12, an operation determination function unit 13, a specified voltage determination function unit 14, a rectifier control function unit 15, and a first circuit. It mainly includes a control function unit 16 and a second circuit control function unit 17. The same components as those shown in FIGS. 1 and 2 are designated by the same reference numerals, and detailed description thereof will be omitted.

The power failure determination function unit 11 determines the presence or absence of a power failure in the power system 2 by detecting the state of the power system 2 with a power failure detection device or the like (not shown) (power failure determination process).

The threshold voltage determination function unit 12 detects the voltage Vdc of the DC link capacitor 5 by a voltage sensor or the like, and compares the voltage Vdc with the first threshold voltage Vth1 set according to the performance of the DC link capacitor 5. Alternatively, the state of the DC link capacitor 5 is determined by comparing with the second threshold voltage Vth2, which is set smaller than the first threshold voltage Vth1 (threshold voltage determination process).

The first and second threshold voltages Vth1 and Vth2 can be appropriately set according to the performance of the DC link capacitor 5 as described above. For example, the storage capacity, allowable voltage, and rated voltage of the DC link capacitor 5 can be set appropriately. Considering (a voltage that is lower than the allowable voltage and can operate safely), it is possible to set the voltage within a voltage range in which overvoltage damage can be suppressed. In Examples 1 to 4 described later, the allowable voltage of the DC link capacitor 5 is set to the first threshold voltage Vth1, and a voltage smaller than the allowable voltage is set to the second threshold voltage Vth2.

The operation determination function unit 13 detects the operating state of the electric motor M by an electric motor power detector, a rotation speed sensor, or the like (not shown), and the electric motor M is in a power running state, a regenerative operation state, or a rotation stop according to the detection result. It determines which of the states is (operation determination process).

The specified voltage determination function unit 14 detects the voltage of the charge / discharge unit 62 (the voltage Vc of the capacitor in FIG. 1 and the voltage Vbat of the storage battery in FIG. 2), and sets the detected voltage based on the performance of the active filter 6. The state of the charge / discharge unit 62 is determined by comparing with the specified voltage Vr (specified voltage determination process).

This specified voltage Vr can be appropriately set according to the performance of the charge / discharge unit 62. For example, the storage capacity, allowable voltage, and rated voltage of the charge / discharge unit 62 (lower than the allowable voltage and can operate safely). The voltage) and the characteristics of the charge / discharge unit 62 during the compensation operation of the active filter 6 may be taken into consideration, and the setting may be made within a voltage range in which the compensation function can be exhibited in the active filter 6.

The rectifier control function unit 15 appropriately switches and controls the rectifier switch according to the determination results of the determination function units 11 to 14 to operate the rectifier (rectifier control process). In this rectification operation, the AC voltage from the power system 2 is converted into a DC voltage and input to the first inverter circuit 4, or the DC voltage from the first inverter circuit 4 or the DC link capacitor 5 (for example, generated by the electric motor M). The regenerated power) is converted back into an AC voltage and supplied to the power system 2 side. Another example is to switch off all the rectifying switches to stop the rectifying operation.

The first circuit control function unit 16 appropriately switches and controls the first switches S11 to S16 according to the determination results of the determination function units 11 to 14 (first circuit control process).

In the switching control by the first circuit control function unit 16, for example, the DC voltage from the rectifier 3 is converted into a three-phase AC voltage and output to the electric motor M to control the desired power running operation in the electric motor M. .. When the electric motor M regenerates, the switching control of the first switches S11 to S16 reversely converts the regenerative power generated by the regenerative operation into a DC voltage, and regenerates the power system 2 side and the DC link capacitor 5 side. To do.

The second circuit control function unit 17 appropriately switches and controls the second switches S21 to S26 according to the determination results of the determination function units 11 to 14, and appropriately charges and discharges the stored energy (charge) of the charge / discharge unit 62. (Second circuit control process).

In the switching control by the second circuit control function unit 17, when the charging / discharging unit 62 is discharged, a desired AC voltage is output from the second inverter circuit 61 between the AC side of the first inverter circuit 4 and the electric motor M. Will be done. In this way, the AC voltage output from the second inverter circuit 61 is output so as to be in opposite phase to the harmonic components caused by the operation of the AC voltage source of the power system 2, etc., so that the desired compensation voltage ( For example, a voltage that is 180 degrees out of phase with respect to the fundamental wave component of the output voltage of the first inverter circuit 4) can be output.

When the electric motor M is in regenerative operation, the second circuit control function unit 17 appropriately switches and controls the regenerative power generated by the regenerative operation to a DC voltage in the second inverter circuit 61. Regeneration to the charging / discharging unit 62 can be mentioned. As a result, the charging / discharging unit 62 is charged.

As shown above, in the control unit 1, it is possible to appropriately function each of the control function units 15 to 17 based on the determination results of the determination function units 11 to 14. Specifically, it may be made to function as in Examples 1 to 4 shown below.

It should be noted that detailed description thereof will be omitted as appropriate by applying the same reference numerals to the same ones shown in FIGS. 1 to 3. Further, it is assumed that the storage capacity of the charge / discharge unit 62 of FIGS. 1 and 2 is about several times to several tens of times the storage capacity of the DC link capacitor 5, respectively.

<Example 1>
The voltage change characteristic diagram with respect to the time change shown in FIG. 4 illustrates Example 1 in the case of being controlled by the control unit 1 in the inverter system 10A. The charging / discharging section 62 has a configuration in which a capacitor is applied as shown in FIG.

In FIG. 4, the period t10 is a case where the power system 2 is in a normal state, the rectifier control function unit 15 rectifies the rectifier 3, and the first circuit control function unit 16 V / f the first inverter circuit 4. This is a state in which the electric motor M is in a regenerative operation by operating an AC voltage source such as control. Further, the second circuit control function unit 17 is in a state in which the active filter 6 is compensated and operated to output a compensated voltage, and the harmonic component caused by the AC voltage source operation is suppressed. The regenerative power generated by the regenerative operation is regenerated to the power system 2 and the DC link capacitor 5.

The period t11 is a state in which the power failure determination function unit 11 determines that the power system 2 has a power failure while the electric motor M is in the regenerative operation (that is, a power failure state during the regenerative operation), and the threshold voltage determination function unit 12 indicates that the voltage Vdc is smaller than the first threshold voltage Vth1.

During this period t11, the rectifier control function unit 15 switches off the rectifier switch of the rectifier 3 to stop the rectification operation. The first circuit control function unit 16 and the second circuit control function unit 17 continue the same operation as the period t10, respectively. As a result, the regenerative power is regenerated only in the DC link capacitor 5, and the voltage Vdc of the DC link capacitor 5 gradually increases.

In this period t11 (and the periods t21, t31, t41 described later), when the power failure determination function unit 11 determines that the power system 2 is quickly recovering power, that is, the power failure period is a minute time (instantaneous voltage). In the case of a decrease, etc.), it is possible to restart the same operation as in the period t10. Specifically, the rectifier control function unit 15 restarts the rectification operation of the rectifier 3, and the first and second circuit control function units 16 and 17 continue the same operation as the period t10.

The period t12 is a state in which the threshold voltage determination function unit 12 determines that the voltage Vdc is equal to or higher than the first threshold voltage Vth1 in the state of the period t11.

During this period t12, the rectifier control function unit 15 continues to stop the rectifying operation as in the period t11. In the first circuit control function unit 16, one of the first switches S11 to S13 on the upper arm side and the first switches S14 to S16 on the lower arm side of the first inverter circuit 4 is switched off. Switching control (hereinafter, simply referred to as vertical arm control) is performed so that the other is switched on.

Due to the vertical arm control of the first circuit control function unit 16, the first inverter circuit 4 is short-circuited at points a to c in FIG. 1, and the active filter 6 and the electric motor M are as shown in FIG. The circuit will be configured.

That is, the active filter 6 is in a state of being connected to the electric motor M on a one-to-one basis via a transformer 60. As a result, the second circuit control function unit 17 can appropriately switch and control the second inverter circuit 61 to operate the AC voltage source in the same manner as the first inverter circuit 4 in the period t11. Then, the AC voltage source operation of the second inverter circuit 61 causes the regenerative power generated by the regenerative operation to be regenerated in the charge / discharge unit 62.

When the regenerative power is regenerated in the charge / discharge unit 62 in this way, the voltage Vc of the charge / discharge unit 62 gradually increases, but since the storage capacity is sufficiently larger than that of the DC link capacitor 5, the overvoltage The grace period until damage occurs is sufficiently secured.

As a result, even if the power failure state during the regenerative operation continues for a long period of time such as the periods t11 and t12, the regenerative power can be regenerated (charging the charging / discharging unit 62) in response to the power failure state during the regenerative operation. It will be possible to continue.

Further, in the short-circuited state, the electric motor M and the DC link capacitor 5 are electrically cut off, and the increase in the voltage Vdc is suppressed in the DC link capacitor 5.

The period t13 is a state in which the power failure determination function unit 11 determines that the power system 2 is recovering power in the state of the period t12 (hereinafter, simply referred to as a power recovery state during regenerative operation), and the threshold voltage determination is made. This is a state in which the functional unit 12 determines that the voltage Vdc is equal to or higher than the first threshold voltage Vth1.

In this period t13, the rectifier control function unit 15 restarts the rectifying operation of the rectifier 3, and the stored energy (charge) of the DC link capacitor 5 is transferred to the power system 2 side until the voltage Vdc reaches the second threshold voltage Vth2 or less. Discharge. As a result, in the DC link capacitor 5, the voltage Vdc gradually decreases. The first and second circuit control function units 16 and 17 continue the same operation as in the period t12.

In the period t14, the threshold voltage determination function unit 12 determines that the voltage Vdc is equal to or less than the second threshold voltage Vth2 in the state of the period t13, and the specified voltage determination function unit 14 determines that the voltage Vc is larger than the specified voltage Vr. It is in the state of being judged.

During this period t14, the rectifier control function unit 15 continues the same rectifying operation as during the period t13. The first circuit control function unit 16 restarts the AC voltage source operation of the first inverter circuit 4 by switching control, whereby the regenerative power from the electric motor M is regenerated to the power system 2 side.

Further, in the second circuit control function unit 17, the stored energy of the charge / discharge unit 62 is discharged to the power system 2 side by the switching control of the second inverter circuit 61 until the voltage Vc reaches the specified voltage Vr or less. As a result, the voltage Vc gradually drops in the charging / discharging section 62.

The period t15 is a state in which the specified voltage determination function unit 14 determines that the voltage Vc is equal to or less than the specified voltage Vr in the state of the period t14.

During this period t15, the rectifier control function unit 15 and the first circuit control function unit 16 continue to operate in the same manner as in the period t14, respectively. In the second circuit control function unit 17, the compensation operation of the second inverter circuit 61 is restarted by switching control to output the compensation voltage, and the harmonic component caused by the AC voltage source operation is suppressed. That is, in the period t15, the same operation as in the period t10 can be resumed.

As described above, according to the control unit 1 that operates as in the first embodiment, even if the power consumption device as in the conventional control configuration is not provided, the situation where the regenerative operation is hindered in the power failure state during the regenerative operation is suppressed. Therefore, the regenerative power generated by the regenerative operation can be regenerated to the charging / discharging section 62 and the like for effective use. It also makes it possible to contribute to the improvement of safety and reliability.

Further, since a power consumption device is not required, it is possible to contribute to the miniaturization of the inverter system 10A.

<Example 2>
The voltage change characteristic diagram with respect to time change shown in FIG. 6 illustrates Example 2 in the case of being controlled by the control unit 1 in the inverter system 10A. A detailed description thereof will be omitted by applying the same reference numerals to the same ones shown in Example 1.

In FIG. 6, the periods t20 to t22 are in the same state as the periods t10 to t12 of the first embodiment, and the rectifier control function unit 15, the first circuit control function unit 16, and the second circuit control function unit 17 are in the same period t10. The operation is the same as that of ~ t12.

The period t23 is a state in which the operation determination function unit 13 determines that the regenerative operation of the electric motor M is stopped in the state of the period t22.

During this period t23, the motor M has stopped rotating and no regenerative power is generated. In the rectifier control function unit 15, the first circuit control function unit 16, and the second circuit control function unit 17, the rectifier switch, The first switches S11 to S16 and the second switches S21 to S26 are switched off, respectively.

The period t24 is a state in which the operation determination function unit 13 determines that the power system is recovering power in the state of the period t23 (hereinafter, appropriately referred to as a power recovery state while the rotation is stopped), and the threshold voltage determination The function unit 12 determines that the voltage Vdc is equal to or higher than the first threshold voltage Vth1, and the specified voltage determination function unit 14 determines that the voltage Vc is larger than the specified voltage Vr.

In this period t24, the rectifier control function unit 15 is in the same state as in the period t23. In the first circuit control function unit 16, switching control is restarted, the first inverter circuit 4 is controlled by the upper and lower arms, and a circuit as shown in FIG. 5 is formed between the active filter 6 and the electric motor M. To.

In the second circuit control function unit 17, switching control is restarted, and the second inverter circuit 61 is operated as an AC voltage source until the voltage Vc reaches the specified voltage Vr or less to discharge the stored energy of the charge / discharge unit 62. The power running operation of the electric motor M is started. As a result, the voltage Vc gradually drops in the charging / discharging section 62.

The period t25 is a state in which the specified voltage determination function unit 14 determines that the charge / discharge voltage Vc of the charge / discharge unit 62 is equal to or less than the specified voltage Vr in the state of the period t24.

In this period t25, the rectifier control function unit 15 is in the same state as in the period t24. In the first circuit control function unit 16, the AC voltage source operation of the first inverter circuit 4 is restarted by switching control, and the stored energy (charge) of the DC link capacitor 5 is discharged to the motor M side, whereby the motor M Control power driving. As a result, in the DC link capacitor 5, the voltage Vdc gradually decreases.

In the second circuit control function unit 17, the compensation operation of the second inverter circuit 61 is restarted by switching control to output the compensation voltage, and the harmonic component caused by the AC voltage source operation is suppressed.

The period t26 is a state in which the threshold voltage determination function unit 12 determines that the voltage Vdc is equal to or lower than the second threshold voltage Vth2 in the state of the period t25.

During this period t26, the rectifier control function unit 15 restarts the rectifying operation of the rectifier 3. The first and second circuit control function units 16 and 17 continue the same operation as in the period t25, respectively. As a result, in the electric motor M, the electric power of the electric power system 2 is used as a drive source for power running operation.

As described above, according to the control unit 1 that operates as in the second embodiment, in addition to exhibiting the same action and effect as in the first embodiment, the following can be said. That is, it can be seen that even if the power system 2 is in a power failure state, the electric motor M can be power-operated by appropriately discharging the stored energy of the charging / discharging unit 62.

<Example 3>
The voltage change characteristic diagram with respect to time change shown in FIG. 7 describes Example 3 in the case of being controlled by the control unit 1 in the inverter system 10B. It should be noted that detailed description thereof will be omitted by applying the same reference numerals to the same ones shown in Examples 1 and 2. Further, the charge / discharge unit 62 has a configuration in which a storage battery is applied as shown in FIG. 2, and has a larger storage capacity as compared with the cases of Examples 1 and 2.

In FIG. 7, the periods t30 to t33 are in the same state as the periods t10 to t13 of the first embodiment, and the rectifier control function unit 15, the first circuit control function unit 16, and the second circuit control function unit 17 are in the same period t10. The operation is the same as that of ~ t13.

During the periods t32 and t33, the upper and lower arm control of the first circuit control function unit 16 causes the first inverter circuit 4 to be short-circuited at points a to c in FIG. 2, between the active filter 6 and the electric motor M. The circuit as shown in FIG. 8 is configured.

Further, the AC voltage source operation of the second circuit control function unit 17 causes the regenerative power generated by the regenerative operation of the electric motor M to be regenerated to the charge / discharge unit 62, but the storage capacity of the storage battery of the charge / discharge unit 62 is relatively large. Since it is large, the voltage Vbat can be suppressed so as not to rise as shown in FIG. 7, as compared with the case where a capacitor is applied to the charging / discharging section 62 as in Example 1.

In this case, the specified voltage determination function unit 14 determines, for example, that the voltage Vbat is equal to or less than the specified voltage Vr. That is, it is not necessary to discharge the stored energy of the charging / discharging unit 62 to the power system 2 side as in the period t14 of the first embodiment (the operation of the period t14 can be omitted).

As a result, for example, when the power is restored during the regenerative operation from the power failure state during the regenerative operation, the active filter 6 can resume the normal compensation operation at an early stage.

The period t34 is in the same state as the period t15 of the first embodiment, and the threshold voltage determination function unit 12 determines that the voltage Vdc is equal to or less than the second threshold voltage Vth2, and the specified voltage determination function unit 14 determines. It is a state in which it is determined that the voltage Vbat is equal to or less than the specified voltage Vr.

During this period t34, the rectifier control function unit 15 operates in the same manner as during the period t15. In the first circuit control function unit 16, the first inverter circuit 4 is operated as an AC voltage source by switching control, and the regenerative power from the electric motor M is regenerated to the power system 2 side. In the second circuit control function unit 17, the second inverter circuit 61 is compensated and operated by switching control to output the compensated voltage, and the harmonic component caused by the AC voltage source operation is suppressed. That is, in the period t34, the same operation as in the period t30 can be resumed.

As described above, according to the control unit 1 that operates as in the third embodiment, in addition to exhibiting the same action and effect as in the first embodiment, the following can be said. That is, since the storage capacity of the charge / discharge unit 62 is larger than that of the first embodiment, it is possible to store a large amount of regenerative power in a power failure state during the regenerative operation, for example, from the power failure state during the regenerative operation. When the power is restored during the regenerative operation, the active filter 6 can resume the normal compensation operation at an early stage. Moreover, not only the active power but also the active power can be controlled. In addition, it becomes easy to contribute to the improvement of safety and reliability.

<Example 4>
The voltage change characteristic diagram with respect to time change shown in FIG. 9 describes Example 4 in the case of being controlled by the control unit 1 in the inverter system 10B. It should be noted that detailed description thereof will be omitted by applying the same reference numerals to the same ones shown in Examples 1 to 3.

In FIG. 9, the periods t40 to t44 are in the same state as the periods t20 to t23 and t25 of the second embodiment, and the rectifier control function unit 15, the first circuit control function unit 16, and the second circuit control function unit 17 are the same. The operation is the same as that of the periods t20 to t23.

In the period t42, the AC voltage source operation of the second circuit control function unit 17 causes the regenerative power generated by the regenerative operation of the electric motor M to be regenerated in the charge / discharge unit 62, as compared with the case of the second embodiment. Since the storage capacity of the charge / discharge unit 62 is large, the voltage Vbat can be suppressed so as not to increase as shown in FIG.

In this case, the specified voltage determination function unit 14 determines, for example, that the voltage Vbat is equal to or less than the specified voltage Vr. That is, for example, when the power is restored while the rotation is stopped, it is no longer necessary to discharge the stored energy of the charge / discharge unit 62 to the motor M side as in the period t24 of the second embodiment (the operation in the period t24 can be omitted). , The active filter 6 can resume the normal compensation operation at an early stage.

The period t45 is in the same state as the period t26 of the second embodiment, respectively, and the threshold voltage determination function unit 12 determines that the voltage Vdc of the DC link capacitor 5 is equal to or less than the second threshold voltage Vth2, and determines the specified voltage. The determination function unit 14 determines that the voltage Vbat is equal to or less than the specified voltage Vr.

During this period t45, the rectifier control function unit 15 operates in the same manner as during the period t26. In the first circuit control function unit 16, the first inverter circuit 4 is operated as an AC voltage source by switching control, and the power running operation of the electric motor M is controlled by using the electric power of the power system 2 as a drive source. In the second circuit control function unit 17, the second inverter circuit 61 is compensated and operated by switching control to output the compensated voltage, and the harmonic component caused by the AC voltage source operation is suppressed. That is, in the period t45, the same operation as in the period t40 can be resumed.

As described above, according to the control unit 1 that operates as in the fourth embodiment, in addition to exhibiting the same action and effect as in the second embodiment, the following can be said. That is, since the storage capacity of the charge / discharge unit 62 is larger than that of the second embodiment, it is possible to store a large amount of regenerative power in a power failure state during the regenerative operation, for example, from the power failure state during the regenerative operation. When the power is restored during the regenerative operation, the active filter 6 can resume the normal compensation operation at an early stage. Moreover, not only the active power but also the active power can be controlled. In addition, it becomes easy to contribute to the improvement of safety and reliability.

Although the above description has been made in detail only for the specific examples described in the present invention, it is clear to those skilled in the art that various changes and the like can be made within the scope of the technical idea of the present invention. It goes without saying that such changes belong to the scope of claims.

10A, 10B ... Inverter system 1 ... Control unit 11 ... Power failure judgment function unit, 12 ... Threshold voltage judgment function unit, 13 ... Operation judgment function unit, 14 ... Specified voltage judgment function unit 15 ... Rectifier control function unit, 16 ... First Circuit control function unit, 17 ... 2nd circuit control function unit 2 ... Power system 3 ... Rectifier 4 ... 1st inverter circuit 4
5 ... DC link capacitor 60 ... Transformer 6 ... Active filter 61 ... Second inverter circuit 62 ... Charging / discharging part M ... Electric motor

Claims (4)

A rectifier that converts the AC voltage of the power system into a DC voltage,
The first inverter circuit connected between the DC side of the rectifier and the electric motor,
The DC link capacitor connected between the DC side of the rectifier and the DC side of the first inverter circuit,
First inverter circuit A series-type active filter having a second inverter circuit connected between the AC side and the electric motor via a transformer, and a charge / discharge unit connected to the DC side of the second inverter circuit. When,
A control unit that controls the rectifier, the first inverter circuit, and the second inverter circuit, respectively.
With
The control unit
A power failure determination function unit that detects the power system status and determines whether or not there is a power failure in the power system.
The DC link capacitor voltage is detected and compared with the first threshold voltage set based on the allowable voltage of the DC link capacitor, or compared with the second threshold voltage set smaller than the first threshold voltage. Judgment threshold voltage judgment function unit and
An operation determination function unit that detects the operating state of the electric motor and determines whether the electric motor is in a power running state, a regenerative operation state, or a rotation stop state.
A specified voltage determination function unit that detects the charge / discharge unit voltage and compares it with the specified voltage set based on the charge / discharge unit during the compensation operation of the active filter.
A rectifier control function unit that controls the switching element of the rectifier to control the rectification operation of the rectifier.
The power running operation and regenerative operation of the electric motor are controlled by switching control of the first upper arm side switching element connected to the upper arm of the first inverter circuit and the first lower arm side switching element connected to the lower arm. 1st circuit control function unit
A second circuit control function unit that controls switching of the switching element of the second inverter circuit to control the voltage output due to the discharge of the stored energy in the charge / discharge unit and the regeneration of the regenerative power to the charge / discharge unit.
With
In a power failure state during regenerative operation, it is determined by the power failure determination function unit that the power system is out of power while the motor is in regenerative operation.
When the threshold voltage determination function unit determines that the DC link capacitor voltage is equal to or higher than the first threshold voltage,
The rectifier control function unit switches off the switching element of the rectifier to stop the rectification operation.
The first circuit control function unit switches off one of the first upper arm side switching element and the first lower arm side switching element of the first inverter circuit and switches on the other.
The second circuit control function unit switches and controls the switching element of the second inverter circuit to regenerate the regenerative power of the regenerative operation to the charge / discharge unit.
Inverter system featuring that. In the power recovery state during regenerative operation, it is determined by the power failure judgment function unit that the power system is recovering from the power failure state during regenerative operation.
When the threshold voltage determination function unit determines that the DC link capacitor voltage is equal to or higher than the first threshold voltage,
The rectifier control function unit switches and controls the switching element of the rectifier to perform rectification operation until the DC link capacitor voltage falls below the second threshold voltage, and discharges the stored energy of the DC link capacitor to the power system side.
When the threshold voltage determination function unit determines that the DC link capacitor voltage has reached the second threshold voltage or less due to the discharge of the stored energy of the DC link capacitor to the power system side.
The first circuit control function unit switches and controls the first inverter circuit to regenerate the regenerative power of the regenerative operation to the power system side.
When the charge / discharge unit voltage is determined by the specified voltage determination function unit to be larger than the specified voltage,
The second circuit control function unit switches and controls the second inverter circuit until the charge / discharge unit voltage reaches the specified voltage or less, and discharges the stored energy of the charge / discharge unit to the power system side.
The inverter system according to claim 1, wherein the inverter system is characterized in that. In the power recovery state during rotation stop, it is determined by the power failure determination function unit that the power system is being restored while the power system is stopping the rotation of the motor after the regeneration operation is stopped from the power failure state during the regeneration operation.
When the threshold voltage determination function unit determines that the DC link capacitor voltage is equal to or higher than the first threshold voltage, and the specified voltage determination function unit determines that the charge / discharge unit voltage is larger than the specified voltage.
The first circuit control function unit switches off one of the first upper arm side switching element and the first lower arm side switching element of the first inverter circuit and switches on the other.
The second circuit control function unit switches and controls the second inverter circuit until the charge / discharge unit voltage falls below the specified voltage, discharges the stored energy of the charge / discharge unit, and controls the power running operation of the electric motor.
When the specified voltage determination function unit determines that the charge / discharge unit voltage has reached the specified voltage or less due to the discharge of the stored energy of the charge / discharge unit,
The rectifier control function unit switches off the switching element of the rectifier and stops the rectification operation until the DC link capacitor voltage falls below the second threshold voltage.
The first circuit control function unit switches and controls the first inverter circuit until the DC link capacitor voltage falls below the second threshold voltage, discharges the stored energy of the DC link capacitor to the motor side, and drives the motor. Control and
The second circuit control function unit switches and controls the second inverter circuit to control the voltage output due to the discharge of the stored energy of the charge / discharge unit.
The inverter system according to claim 1, wherein the inverter system is characterized in that. A rectifier that converts the AC voltage of the power system into a DC voltage,
The first inverter circuit connected between the DC side of the rectifier and the electric motor,
The DC link capacitor connected between the DC side of the rectifier and the DC side of the first inverter circuit,
First inverter circuit A series-type active filter having a second inverter circuit connected between the AC side and the electric motor via a transformer, and a charge / discharge unit connected to the DC side of the second inverter circuit. When,
It is a method of controlling an inverter system equipped with a control unit by a control unit.
By the control unit
A power failure determination process that detects the power system status and determines whether or not there is a power failure in the power system.
Detects the DC link capacitor voltage and compares it with the first threshold voltage set based on the allowable voltage of the DC link capacitor, or compares it with the second threshold voltage set smaller than the first threshold voltage. Threshold voltage determination process and
An operation determination process that detects the operating state of an electric motor and determines whether the electric motor is in a power running state, a regenerative operation state, or a rotation stop state.
A specified voltage determination process that detects the charge / discharge unit voltage and compares it with the specified voltage set based on the charge / discharge unit during the compensation operation of the active filter.
A rectifier control process that controls the switching element of a rectifier to control the rectifying operation of the rectifier,
The power running operation and regenerative operation of the electric motor are controlled by switching control of the first upper arm side switching element connected to the upper arm of the first inverter circuit and the first lower arm side switching element connected to the lower arm. 1st circuit control process and
A second circuit control process that controls the switching element of the second inverter circuit to control the voltage output due to the discharge of the stored energy in the charge / discharge section and the regeneration of the regenerative power to the charge / discharge section.
Have,
In a power failure state during regenerative operation, it is determined that the power system is out of power while the motor is in regenerative operation by the power failure determination process.
When it is determined by the threshold voltage determination process that the DC link capacitor voltage is equal to or higher than the first threshold voltage,
In the rectifier control process, the switching element of the rectifier is switched off to stop the rectification operation.
In the first circuit control process, one of the first upper arm side switching element and the first lower arm side switching element of the first inverter circuit is switched off and the other is switched on.
In the second circuit control process, the switching element of the second inverter circuit is switched and controlled to regenerate the regenerative power of the regenerative operation to the charge / discharge unit.
An inverter control method characterized by this.

Images