JP7127584B2 - Inverter system and inverter control method - Google Patents

Description

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

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

The active filter has an inverter circuit (a second inverter circuit 61 in FIG. 1 to be described later), a capacitor connected to the DC side of the inverter circuit, and the like. In FIG. 1, there is a configuration for outputting a desired compensation voltage so as to suppress the influence of harmonic components caused by the operation of the AC voltage source of the first inverter circuit 4 .

Energy saving measures can be taken by, for example, storing the regenerated power generated by the regenerative operation of the motor in a DC link capacitor or regenerating the regenerated power to the power system side. In addition, in the event of a power failure on the power system side, by applying the DC link capacitor as an emergency power supply, it is possible to power the motor.

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 regenerative operation may be hindered (regeneration invalidation, etc.), or that overvoltage damage to the DC link capacitor may occur.

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

Fangzheng Peng, Masakazu Kohata, and Yasufumi Akagi, "Study of Compensation Characteristics of Parallel Active Filters and Series Active Filters", Theory of Electrical Engineering, Vol. 113, No. 1, 1993, pp.33-40.

JP 2005-145687 A

If a power consuming device as described above is provided, there is a risk that the size and cost of the configuration of the inverter system will increase, for example. In addition, since the consumption of regenerative power can simply result in power loss, there is a risk that energy saving measures will be inadequate.

The present invention has been made in view of such technical problems, and aims to provide a technique that can contribute to simplification of configuration and energy saving measures.

One aspect of the present invention includes a rectifier that converts an AC voltage of a power system to a DC voltage, a first inverter circuit that is connected between the rectifier DC side and the motor, and a rectifier DC side and the first inverter circuit DC side. and a second inverter circuit and a charge/discharge unit connected to the second inverter circuit DC side, wherein the configuration is the first inverter circuit AC side and the electric motor via a transformer, and a series type active filter capable of compensating operation to output a compensating voltage for suppressing harmonic components caused by the AC voltage source operation of the first inverter circuit; , a control unit for controlling the rectifier, the first inverter circuit, and the second inverter circuit, respectively.

The control unit detects the state of the power system and determines whether or not there is a power failure in the power system, and a power failure determination function unit that detects the DC link capacitor voltage and is set based on the allowable voltage of the DC link capacitor. A threshold voltage determination function unit for determination by comparison with a first threshold voltage or by comparison with a second threshold voltage set lower than the first threshold voltage; state, regenerative operation state, or rotation stop state, and the charge/discharge unit voltage is detected and set based on the characteristics of the charge/discharge unit during the compensation operation of the active filter. a stipulated voltage determination function unit that performs switching control of the switching elements of the rectifier to control the rectification operation of the rectifier; and the upper arm of the first inverter circuit. a first circuit control function unit that switches and controls the connected first upper arm side switching element and the first lower arm side switching element connected to the lower arm to control the power running operation and the regenerative operation of the electric motor; and a second circuit control function unit that controls switching of the switching element of the second inverter circuit to control the output of the compensation voltage due to the discharge of the stored energy in the charging/discharging unit and the regeneration of the regenerative power to the charging/discharging unit. .

Then, in a power failure state during regenerative operation in which the power failure determination function unit determines that the electric power system is out of power while the motor is regenerating, the threshold voltage determination function unit determines that the DC link capacitor voltage is the first threshold. 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 switches the voltage to the first upper arm side of the first inverter circuit. One of the switching element and the first lower arm side switching element 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 generate regenerative power for regenerative operation. is regenerated to the charging/discharging part.

Further, in the power recovery state during regenerative operation in which the power failure determination function unit determines that the power system has recovered from the power failure state during regeneration operation, the threshold voltage determination function unit determines that the DC link capacitor voltage is the first threshold voltage. If it is determined that the above is the case, the rectifier control function unit performs switching control of the switching element of the rectifier to perform rectification operation until the DC link capacitor voltage reaches the second threshold voltage or less, thereby storing energy in the DC link capacitor. is discharged to the power system side, and 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 performs switching control of 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 higher than the specified voltage. the second circuit control function unit performs switching control of the second inverter circuit until the voltage of the charge/discharge unit drops below a specified voltage, and discharges the energy stored in the charge/discharge unit to the power system side. It may be characterized by:

In addition, the threshold voltage determination function unit judges that the electric power system is restored while the regenerative operation is stopped from the power failure state during regenerative operation and the electric power system is restored while the rotation of the motor is stopped by the power failure determination function unit. When it is determined 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 greater than the specified voltage, the first circuit control function unit 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 second circuit control function section controls the charging/discharging section voltage to be equal to or less than a specified voltage. until the second inverter circuit is controlled to discharge the stored energy of the charging/discharging unit to control the power running of the motor, and the specified voltage determination function unit charges by discharging the stored energy of the charging/discharging unit 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 to stop the rectification operation until the DC link capacitor voltage reaches the second threshold voltage or less. Then, the first circuit control function unit performs switching control of the first inverter circuit until the DC link capacitor voltage reaches the second threshold voltage or less, and discharges the stored energy of the DC link capacitor to the motor side, thereby The power running operation may be controlled, and the second circuit control function unit may perform switching control of the second inverter circuit to control the voltage output due to the discharge of the stored energy in the charging/discharging unit.

Another aspect is a rectifier that converts the AC voltage of the power system to a DC voltage, a first inverter circuit connected between the rectifier DC side and the motor, and a rectifier DC side and the first inverter circuit DC side. A configuration having a DC link capacitor connected between, a second inverter circuit, and a charging/discharging section connected to the second inverter circuit DC side, the configuration including the first inverter circuit AC side and the motor and a series type active filter capable of compensating operation for outputting a compensating voltage for suppressing harmonic components caused by the AC voltage source operation of the first inverter circuit, connected via a transformer between A method of controlling the provided inverter system by a control unit, characterized by being realized by a control configuration similar to that of the control device according to the above aspect.

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

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

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

That is, the present embodiment includes a rectifier that converts the AC voltage of the electric power system into a DC voltage, a first inverter circuit that is connected between the rectifier DC side and the motor, the rectifier DC side and the first inverter circuit DC side. and a second inverter circuit and a charge/discharge unit connected to the second inverter circuit DC side, wherein the configuration is the first inverter circuit AC side and the electric motor via a transformer, and a series type active filter capable of compensating operation to output a compensating voltage for suppressing harmonic components caused by the AC voltage source operation of the first inverter circuit; , and relates to an inverter system. Then, the rectifier, the first inverter circuit, and the active filter are switched according to the state of the power system, the motor, the DC link capacitor, etc. It is the structure which controls suitably.

In the control configuration according to this embodiment, in a state in which the electric power system fails while the motor is in regenerative operation (hereinafter simply referred to as a power failure state during regenerative operation), the DC link capacitor voltage (voltage Vdc described later) is When it is higher than a threshold voltage (first threshold voltage Vth1 described later) set based on the allowable voltage of the DC link capacitor, the rectifier stops its rectifying operation by switching control of the rectifier.

Further, by 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 is switched off. switch on. Also, the regenerative electric power of the regenerative operation is regenerated to the charging/discharging section by the switching control of the second inverter circuit.

According to the control configuration of this embodiment, for example, even without a device for consuming power, it is possible to suppress a situation in which regenerative operation is hindered in a power failure state during regenerative operation (regeneration invalidation, etc.). can also be used. For example, even if the electric power system is in a blackout state, the electric motor can be powered by appropriately discharging the stored energy in the charging/discharging unit. Also, overvoltage damage and the like to the DC link capacitor can be suppressed.

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

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

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

This inverter system 10A includes a rectifier 3 that converts an AC voltage from a power system 2 to a DC voltage, a first inverter circuit 4 connected between the DC side of the rectifier 3 and a motor M, and a DC side of the rectifier 3. A DC link capacitor 5 connected between the DC side of the first inverter circuit 4 and a series type active filter 6 connected between the AC side of the first inverter circuit 4 and the 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, which will be described later) can be controlled by the controller 1, respectively.

The rectifier 3 has a plurality of semiconductor switching elements (detailed illustration is omitted; hereinafter simply referred to as rectifier switches), and the rectifier switches are controlled by the control unit 1 (for example, gate signals to the rectifier switches, etc.). is controlled by outputting a control signal for switching, a desired rectifying operation can be performed.

The first inverter circuit 4 has a plurality of semiconductor switching elements (hereinafter simply referred to as first switches) S11 to S16. 1 Switches S11 to S16 are configured to output a control signal such as a gate signal to perform 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 connected to the lower arm of the first inverter circuit. It is connected to the.

The DC link capacitor 5 is connected in parallel with 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 power running operation of the motor M or a DC voltage output from the first inverter circuit 4 during regenerative operation of the motor M and the like. , to smooth the DC voltage.

The serial type active filter 6 has a configuration including a second inverter circuit 61 and a charging/discharging section 62 connected to the DC side of the second inverter circuit 61 . Specifically, in the case of FIG. 1, a second inverter circuit 61 is connected in series via a transformer 60 between the AC side of the first inverter circuit 4 and the motor M, and the second inverter circuit 61 is connected to the DC side. and a charging/discharging section 62.

The second inverter circuit 61 has a plurality of semiconductor switching elements (hereinafter simply referred to as second switches) S21 to S26. A control signal such as a gate signal is output to the two switches S21 to S26 to perform 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 connected to the Connected to the lower arm.

The control unit 1 has various determination function units and control function units as shown in FIG. 3 which will be described later. 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 aspect 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 suppressing harmonic components.

Various semiconductor switching elements can be appropriately applied to the rectifying switches, the first switches S11 to S16, and the second switches S21 to S26, and are not particularly limited. A specific example is the application of a self arc-extinguishing semiconductor switching element such as an IGBT.

The charge/discharge unit 62 can be charged/discharged in accordance with the switching control of the second inverter circuit 61, and various aspects can be applied as long as it can store energy. Typical examples are capacitors and storage batteries. Although 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, it may have a configuration in which a storage battery is applied, as in the inverter system 10B of FIG. 2, for example. In FIG. 2, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

When the electric motor M is operated at a relatively low speed (hereinafter simply referred to as low-speed operation), the energy ripple flowing into and out of the active filter 6 tends to increase. A phenomenon may occur in which the charging/discharging portion 62 of the battery becomes an energy ripple supply source.

In order to exhibit various functions required of the active filter 6 (compensation function for suppressing the influence of harmonic components, etc.) as desired even when such a phenomenon occurs during low-speed operation, the active filter 6, a relatively large-capacity charge/discharge unit 62 may be used to sufficiently suppress voltage ripple. One example is to apply the charging/discharging section 62 having a storage capacity several times to several tens of times the storage capacity of the DC link capacitor 5 . In particular, many storage batteries have a large amount of energy that can be stored compared to capacitors.

The states of the electric power system 2, the motor M, the DC link capacitor 5, etc. detected by the control unit 1 may be appropriately detected according to the purpose. For example, the voltage Vdc of the DC link capacitor 5 and the voltage of the charge/discharge unit 62 (the voltage Vc of the capacitor and the voltage Vbat of the storage battery to be described later) are detected via a voltage sensor (not shown) or the like, and can be detected through a rotational speed sensor (not shown) or the like. Further, the state of the electric 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 comprising a system voltage sensor or the like.

<<Configuration example of the 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 . 1 and 2 are denoted by the same reference numerals, and detailed description thereof will be omitted.

The power failure determination function unit 11 determines whether or not there is a power failure in the power system 2 by detecting the state of the power system 2 with a power failure detection device (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, compares the voltage Vdc with a 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 it with a second threshold voltage Vth2 set lower 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. (a voltage that is lower than the allowable voltage and allows safe operation), etc., and is set within a voltage range that can suppress overvoltage damage and the like. 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 lower 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 means of a motor power detector (not shown), a rotation speed sensor, etc., and depending on the detection result, the electric motor M is in a power running state, a regenerative operating state, or stops rotating. It is to determine which of the states it is (driving determination process).

The specified voltage determination function unit 14 detects the voltage of the charging/discharging unit 62 (capacitor voltage Vc in FIG. 1, storage battery voltage Vbat 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 charging/discharging unit 62. For example, the storage capacity of the charging/discharging unit 62, the allowable voltage, the rated voltage (lower than the allowable voltage and safe to operate) voltage), the characteristics of the charge/discharge unit 62 during the compensation operation of the active filter 6, and the like, and are set within a voltage range in which the active filter 6 can perform the compensation function.

The rectifier control function unit 15 appropriately performs switching control of the rectifier switches according to the determination results of the determination function units 11 to 14 to perform rectification operation (rectifier control process). In this rectification operation, the AC voltage from the electric 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 motor M) regenerated power) is reverse-converted to AC voltage and supplied to the power system 2 side. Alternatively, all rectifying switches may be switched off to stop the rectifying operation.

The first circuit control function unit 16 controls the switching of the first switches S11 to S16 as appropriate 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, and the desired power running operation of the electric motor M is controlled. . Further, when the electric motor M performs regenerative operation, the switching control of the first switches S11 to S16 reversely converts the regenerated electric power generated by the regenerative operation into a DC voltage, and regenerates it to the electric power system 2 side or the DC link capacitor 5 side. to do.

The second circuit control function unit 17 appropriately controls the switching of 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 charge/discharge 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. It will be done. In this manner, the AC voltage output from the second inverter circuit 61 is output so as to have an opposite phase to the harmonic component caused by the operation of the AC voltage source of the electric power system 2 or the like, thereby obtaining a desired compensation voltage ( For example, a voltage 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.

Further, when the electric motor M is in regenerative operation, the second circuit control function unit 17 appropriately performs switching control so that the regenerated electric power generated by the regenerative operation is reversely converted into a DC voltage by the second inverter circuit 61. Regeneration in the charge/discharge unit 62 can be mentioned. As a result, the charging/discharging section 62 is charged.
The charging/discharging of the charging/discharging unit 62 by the switching control of the second circuit control function unit 17 can be appropriately generated even in operations other than the compensation operation of the active filter 6 . Examples of charging and discharging of the charging/discharging unit 62 by operations other than the compensating operation include charging during regenerative operation during a period t11 described later, discharging during regenerative operation during a period t14 described later (discharging to the power system 2 side), Discharge during power running in period t24, which will be described later, and the like can be mentioned.

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

1 to 3 are denoted by the same reference numerals, and detailed description thereof will be omitted as appropriate. 1 and 2, it is assumed that the storage capacity of the charging/discharging section 62 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 time change shown in FIG. 4 explains Example 1 in the case of control by the control unit 1 in the inverter system 10A. Note that the charging/discharging section 62 has a configuration in which a capacitor is applied as shown in FIG.

In FIG. 4 , period t10 is when the power system 2 is in the normal state, the rectifier control function unit 15 causes the rectifier 3 to perform rectification, and the first circuit control function unit 16 changes the first inverter circuit 4 to V/f This is a state in which the electric motor M is in regenerative operation by operating the AC voltage source for control and the like. Further, in the second circuit control function unit 17, the active filter 6 is made to perform a compensating operation to output a compensating voltage, thereby suppressing harmonic components caused by the operation of the AC voltage source. The regenerated power generated by the regenerative operation is regenerated to the electric power system 2 and the DC link capacitor 5 .

A period t11 is a state in which the power failure determination function unit 11 determines that the electric power system 2 is in a power failure while the electric motor M is performing regenerative operation (that is, a power failure state during regenerative operation). 12, the voltage Vdc is determined to be lower 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 to operate in the same manner as during period t10. As a result, the regenerated electric 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 periods t21, t31, and t41, which will be described later), if the power failure determination function unit 11 determines that the power system 2 is quickly restored, that is, the power failure period is a minute time (instantaneous voltage decrease, etc.), it is possible to restart the same operation as in the period t10. Specifically, the rectifier control function unit 15 resumes the rectification operation of the rectifier 3, and the first and second circuit control function units 16 and 17 continue the same operations as in period t10.

A 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 rectification operation in the same manner as during period t11. In the first circuit control function unit 16, one of the first switches S11 to S13 on the upper arm side of the first inverter circuit 4 and the first switches S14 to S16 on the lower arm side is switched off. Switching control (hereinafter simply referred to as upper/lower arm control as appropriate) is performed so that the other is switched on.

Due to the upper and lower 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. A circuit is constructed.

That is, the active filter 6 is connected to the motor M one-to-one via the transformer 60 . As a result, the second circuit control function unit 17 can appropriately perform switching control of the second inverter circuit 61 to operate the AC voltage source in the same manner as the first inverter circuit 4 during the period t11. Then, the regenerated electric power by the regenerative operation is regenerated to the charging/discharging section 62 by the operation of the AC voltage source of the second inverter circuit 61 .

When the regenerative electric power is regenerated in the charge/discharge unit 62 in this way, the voltage Vc of the charge/discharge unit 62 gradually increases. The grace period until damage, etc. occurs is sufficiently secured.

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

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

Period t13 is a state in which the power failure determination function unit 11 determines that power has been restored in the power system 2 in the state of period t12 (hereinafter simply referred to as a power recovery state during regenerative operation), and the threshold voltage is determined. This is a state in which the function unit 12 has determined 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 rectification operation of the rectifier 3, and transfers the stored energy (charge) of the DC link capacitor 5 to the power system 2 side until the voltage Vdc reaches the second threshold voltage Vth2 or less. Discharge. As a result, the voltage Vdc in the DC link capacitor 5 gradually drops. The first and second circuit control function units 16 and 17 continue to operate in the same manner as during period t12.

During period t14, 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 period t13, and the specified voltage determination function unit 14 determines that the voltage Vc is greater than the specified voltage Vr. It is in a state of being judged as

During this period t14, the rectifier control function unit 15 continues the rectification operation similar to that during 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 regenerated power from the electric motor M is regenerated to the power system 2 side.

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

A 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 each continue the same operation as during period t14. In the second circuit control function unit 17, the compensation operation of the second inverter circuit 61 is resumed by switching control to output the compensation voltage, thereby suppressing the harmonic component caused by the AC voltage source operation. That is, in period t15, the same operation as in period t10 can be resumed.

As described above, according to the control unit 1 that operates as in the first embodiment, even if it does not have a power consumption device such as the conventional control configuration, it suppresses the situation where the regenerative operation is hindered in the power failure state during the regenerative operation. The regenerated electric power generated by the regenerative operation can be regenerated to the charging/discharging unit 62 and the like and effectively used. It is also possible to contribute to the improvement of safety and reliability.

In addition, since no power consumption device is required, it is possible to contribute to miniaturization of the inverter system 10A.

<Example 2>
The voltage change characteristic diagram with respect to time change shown in FIG. 6 explains Example 2 in the case of control by the control unit 1 in the inverter system 10A. It should be noted that the same reference numerals are applied to the same components as those shown in the first embodiment, and detailed description thereof will be omitted.

In FIG. 6, the period t20 to t22 is the same state as the period 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 ∼ t12 performs the same operation.

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 period t22.

During this period t23, the electric motor M stops rotating and no regenerative electric power is generated. The first switches S11 to S16 and the second switches S21 to S26 are switched off.

Period t24 is a state in which it is determined by the operation determination function unit 13 that the electric power system is restored in the state of period t23 (hereinafter simply referred to as a power restoration state during rotation stop), and threshold voltage determination is performed. This is a state in which the function unit 12 has determined that the voltage Vdc is equal to or higher than the first threshold voltage Vth1, and the specified voltage determination function unit 14 has determined that the voltage Vc is greater than the specified voltage Vr.

During period t24, the rectifier control function unit 15 is in the same state as during period t23. In the first circuit control function unit 16, switching control is resumed and the first inverter circuit 4 is controlled by the upper and lower arms so that the circuit shown in FIG. to

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

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 period t24.

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

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

A 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.

In this period t26, the rectifier control function unit 15 resumes the rectification operation of the rectifier 3. The first and second circuit control function units 16 and 17 continue the same operation as during period t25. As a result, the electric motor M is powered using the electric power of the electric power system 2 as a drive source.

As described above, according to the control unit 1 that operates as in the second embodiment, in addition to the same effects as in the first embodiment, the following can be said. That is, even if the electric power system 2 is in a power outage state, the electric motor M can be power-running by appropriately discharging the stored energy of the charge/discharge unit 62 .

<Example 3>
The voltage change characteristic diagram with respect to time change shown in FIG. 7 explains Example 3 in the case of control by the control unit 1 in the inverter system 10B. It should be noted that the same reference numerals are applied to the same components as those shown in the first and second embodiments, and detailed description thereof will be omitted. Moreover, as shown in FIG. 2, the charging/discharging unit 62 is configured to apply a storage battery, and has a large power storage capacity as compared with the case of the first and second embodiments.

In FIG. 7, the period t30 to t33 is the same state as the period 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 ∼ t13 performs the same operation.

In periods t32 and t33, the first inverter circuit 4 is short-circuited at points a to c in FIG. , a circuit as shown in FIG. 8 is constructed.

In addition, due to the operation of the AC voltage source of the second circuit control function unit 17, the regenerated electric power generated by the regenerative operation of the electric motor M is regenerated to the charging/discharging unit 62, but the storage capacity of the storage battery of the charging/discharging unit 62 is relatively Since it is large, the voltage Vbat can be suppressed so that it hardly rises as shown in FIG.

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

As a result, for example, when a power failure state during regenerative operation changes to a power recovery state during regenerative operation, the active filter 6 can quickly resume the normal compensation operation.

The period t34 is the same state as the period t15 of the first embodiment. This is a state in which it is determined that the voltage Vbat is equal to or lower than the specified voltage Vr.

During period t34, the rectifier control function unit 15 operates in the same manner as during period t15. The first circuit control function unit 16 causes the first inverter circuit 4 to operate as an AC voltage source by switching control, and regenerates the regenerated power from the electric motor M to the power system 2 side. In the second circuit control function unit 17, the second inverter circuit 61 performs a compensating operation by switching control, outputs a compensating voltage, and suppresses harmonic components caused by the AC voltage source operation. That is, in period t34, the same operation as in period t30 can be resumed.

As described above, according to the control unit 1 that operates as in the third embodiment, in addition to the same effects as in the first embodiment, the following can be said. That is, since the charging/discharging unit 62 has a larger power storage capacity than in the first embodiment, it is possible to store a large amount of regenerative electric power in a power failure state during regenerative operation, for example. When power is restored during regenerative operation, the active filter 6 can quickly resume the normal compensation operation. Also, it becomes possible to control not only reactive power but also active power. Moreover, 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 explains Example 4 in the case of control by the control unit 1 in the inverter system 10B. It should be noted that the same reference numerals are applied to the same components as those shown in Examples 1 to 3, and detailed description thereof will be omitted.

In FIG. 9, periods t40 to t44 are the same states 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 The same operation as in the period t20-t23 is performed.

In period t42, the AC voltage source operation of the second circuit control function unit 17 causes the regenerated electric power generated by the regenerative operation of the electric motor M to be regenerated in the charge/discharge unit 62. However, compared with the case of the second embodiment, Since the charging/discharging unit 62 has a large storage capacity, 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 that the voltage Vbat is equal to or lower than the specified voltage Vr, for example. That is, for example, when power is restored while rotation is stopped, there is no need to discharge the energy stored in the charge/discharge unit 62 to the electric motor M side as in the period t24 of the second embodiment (the operation in the period t24 can be omitted). , the normal compensation operation in the active filter 6 can be resumed early.

Period t45 is the same state as period t26 in the second embodiment, and the threshold voltage determination function unit 12 determines that the voltage Vdc of the DC link capacitor 5 is equal to or lower than the second threshold voltage Vth2. This is a state in which the determination function unit 14 has determined that the voltage Vbat is equal to or lower than the specified voltage Vr.

During period t45, the rectifier control function unit 15 operates in the same manner as during period t26. The first circuit control function unit 16 causes the first inverter circuit 4 to operate as an AC voltage source by switching control, and controls the power running of the electric motor M using the electric power of the electric power system 2 as a drive source. In the second circuit control function unit 17, the second inverter circuit 61 performs a compensating operation by switching control, outputs a compensating voltage, and suppresses harmonic components caused by the AC voltage source operation. That is, in period t45, the same operation as in period t40 can be resumed.

As described above, according to the control unit 1 that operates as in the fourth embodiment, in addition to the same effects as in the second embodiment, the following can be said. That is, since the power storage capacity of the charge/discharge unit 62 is larger than that in the second embodiment, a large amount of regenerated electric power can be stored in a power failure state during regenerative operation, for example. When power is restored during regenerative operation, the active filter 6 can quickly resume the normal compensation operation. Also, it becomes possible to control not only reactive power but also active power. Moreover, it becomes easy to contribute to the improvement of safety and reliability.

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

DESCRIPTION OF SYMBOLS 10A, 10B... Inverter system 1... Control part 11... Power failure determination function part 12... Threshold voltage determination function part 13... Operation determination function part 14... Stipulated voltage determination function part 15... Rectifier control function part 16... 1st Circuit control function unit 17 Second circuit control function unit 2 Power system 3 Rectifier 4 First inverter circuit 4
5 DC link capacitor 60 transformer 6 active filter 61 second inverter circuit 62 charge/discharge unit M motor

Claims (4)

a rectifier that converts the AC voltage of the power system to a DC voltage;
a first inverter circuit connected between the rectifier DC side and the electric motor;
a DC link capacitor connected between the rectifier DC side and the first inverter circuit DC side;
A configuration having a second inverter circuit and a charging/discharging section connected to the DC side of the second inverter circuit, wherein the configuration is connected between the AC side of the first inverter circuit and the motor via a transformer. a series type active filter capable of compensating operation for outputting a compensating voltage for suppressing harmonic components caused by the AC voltage source operation of the first inverter circuit ;
a control unit that controls the rectifier, the first inverter circuit, and the second inverter circuit;
with
The control unit
A power failure determination function unit that detects the state of the power system and determines whether there is a power failure in the power system;
The DC link capacitor voltage is detected and compared with a first threshold voltage set based on the allowable voltage of the DC link capacitor, or compared with a second threshold voltage set lower than the first threshold voltage. a threshold voltage determination function unit for determining;
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 operating state, or a rotation stop state;
a specified voltage determination function unit that detects the charge/discharge unit voltage and compares it with a specified voltage that is set based on the characteristics of the charge/discharge unit during the compensation operation of the active filter ;
a rectifier control function unit that controls switching of a switching element of a rectifier to control a rectifying operation of the rectifier;
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 are switching-controlled to control power running and regenerative operation of the electric motor. a first circuit control function unit to
a second circuit control function unit that controls switching of the switching element of the second inverter circuit to control the output of the compensation voltage due to the discharge of the stored energy in the charging/discharging unit and the regeneration of the regenerative electric power to the charging/discharging unit;
with
In a power failure state during regenerative operation in which the power failure determination function unit determines that the power system has a power failure 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 elements of the rectifier to stop the rectification operation,
the first circuit control function unit switching off one of the first upper arm switching element and the first lower arm switching element of the first inverter circuit and switching on the other;
The second circuit control function unit controls switching of the switching element of the second inverter circuit to regenerate the regenerated power of the regenerative operation to the charging/discharging unit.
An inverter system characterized by: In the power recovery state during regenerative operation when it is determined that the power system has recovered from the power failure state during regenerative operation by the power failure determination function unit,
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 elements of the rectifier to perform rectifying operation until the DC link capacitor voltage reaches the second threshold voltage or less, 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 switching-controls the first inverter circuit to regenerate the regenerated electric power of the regenerative operation to the electric power system side;
When the specified voltage determination function unit determines that the charging/discharging unit voltage is higher than the specified voltage,
The second circuit control function unit controls switching of the second inverter circuit until the charge/discharge unit voltage reaches a specified voltage or less, and discharges the stored energy of the charge/discharge unit to the power system side.
2. The inverter system according to claim 1, characterized in that: In the power recovery state during rotation stop when it is determined by the power failure determination function unit that the power system is restored while the regenerative operation is stopped from the power failure state during regeneration operation and the rotation of the motor is stopped,
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 greater than the specified voltage,
the first circuit control function unit switching off one of the first upper arm switching element and the first lower arm switching element of the first inverter circuit and switching on the other;
The second circuit control function unit performs switching control of the second inverter circuit until the charge/discharge unit voltage reaches a specified voltage or less, discharges the stored energy of the charge/discharge unit, and controls power running of the electric motor,
When the specified voltage determination function unit determines that the charge/discharge unit voltage has reached a specified voltage or less due to the discharge of the stored energy in the charge/discharge unit,
The rectifier control function unit switches off the switching element of the rectifier to stop the rectification operation until the DC link capacitor voltage reaches the second threshold voltage or less,
The first circuit control function unit performs switching control of 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 motor side, and powers the motor. to control the
The second circuit control function unit controls switching of the second inverter circuit to control the voltage output by discharging the stored energy of the charging/discharging unit.
2. The inverter system according to claim 1, characterized in that: a rectifier that converts the AC voltage of the power system to a DC voltage;
a first inverter circuit connected between the rectifier DC side and the electric motor;
a DC link capacitor connected between the rectifier DC side and the first inverter circuit DC side;
A configuration having a second inverter circuit and a charging/discharging section connected to the DC side of the second inverter circuit, wherein the configuration is connected between the AC side of the first inverter circuit and the motor via a transformer. a series type active filter capable of compensating operation for outputting a compensating voltage for suppressing harmonic components caused by the AC voltage source operation of the first inverter circuit ;
A method for controlling an inverter system with a control unit,
By the control unit,
A power failure determination process for detecting the state of the power system and determining whether or not there is a power failure in the power system;
Detects the DC link capacitor voltage and compares it with a first threshold voltage set based on the allowable voltage of the DC link capacitor, or compares it with a second threshold voltage set to be smaller than the first threshold voltage. a threshold voltage determination process for
an operation determination process for detecting the operating state of the electric motor and determining whether the electric motor is in a power running state, a regenerative operating state, or a rotation stop state;
a specified voltage determination process of detecting the charging/discharging unit voltage and comparing it with a specified voltage set based on the characteristics of the charging/discharging unit during the compensation operation of the active filter ;
a rectifier control process for controlling the rectifying operation of the rectifier by switching-controlling the switching elements of the rectifier;
The power running operation and regenerative operation of the electric motor are controlled by controlling the switching 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. a first circuit control process to
a second circuit control step of switching-controlling the switching element of the second inverter circuit to control the output of the compensation voltage due to the discharge of the stored energy in the charging/discharging unit and the regeneration of the regenerative power to the charging/discharging unit;
has
In a power failure state during regenerative operation in which it is determined by the power failure determination process that the power system is out of power while the motor is in regenerative operation,
When it is determined that the DC link capacitor voltage is equal to or higher than the first threshold voltage by the threshold voltage determination process,
In the rectifier control process, switching off the switching elements of the rectifier 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, switching control is performed on the switching element of the second inverter circuit to regenerate the regenerated electric power of the regenerative operation to the charge/discharge unit.
An inverter control method characterized by:

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