JP2012125083A - Ac motor driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively use energy accumulated in a power storage device without providing an excessive additional circuit, and to prevent a temperature rise of the power storage device by discharging the accumulated energy with a low loss.SOLUTION: An AC motor driving device comprises: an inverter 3 connected to a DC bus 2 to which DC power is supplied from a DC supply 1 and driving an AC motor 4; and a power storage device 5 connected to the DC bus 2 in parallel. The power storage device 5 includes: a power storage element 21 for accumulating energy; a two-way type DC/DC converter 22 capable of charging to the power storage element 21 through the DC bus 2 and discharging from the power storage element 21 to the DC bus 2 side; and controlling means 23 for controlling the DC/DC converter 22. When discharging the energy accumulated in the power storage element 21, the DC/DC converter 22 is controlled to carry out power supply regeneration at a constant current.

Description

  The present invention relates to an AC motor drive device including a power storage device for converting DC power from a DC power source into AC power by an inverter and supplying the AC power to the AC motor and controlling the DC power. The present invention relates to an AC motor drive device that performs power regeneration when discharging a power storage element.

  In the AC motor drive device, a large drive current flows for acceleration when the AC motor is powered, while a regenerative current is generated when the AC motor is decelerated. At this time, it is particularly undesirable to simply consume the regenerative current of the motor with a resistor and release it as heat because the energy utilization efficiency is low.

  For this reason, in the prior art, a power storage device having a large-capacity electrolytic capacitor, electric double layer capacitor, or the like as a power storage element is interposed between the converter for DC conversion and the inverter for AC conversion. When the motor is powered, the power stored in the power storage device is supplied to the AC motor via the inverter, while during motor regeneration, the regenerative power is stored in the power storage device via the inverter. There has been proposed a system that achieves leveling and uses the regenerative power effectively (see, for example, Patent Document 1).

  By the way, when the operation of the AC motor is stopped, for example, when the operation of the day is finished, it is desirable to positively discharge the energy stored in the power storage device. That is, if power is stored in the power storage device, power storage elements such as electrolytic capacitors and electric double layer capacitors remain charged in a high voltage state, and the characteristic deterioration becomes significant. Life is shortened. Further, when performing maintenance and inspection of the power storage device, if the power storage device remains charged in a high voltage state, the safety of the worker is significantly impaired. Furthermore, if the power storage device is charged in a high voltage state, there is a disadvantage that a current flows naturally through the balance resistor connected to maintain the voltage balance of the power storage element, resulting in useless loss.

  Therefore, when the AC motor stops operating, if the energy stored in the power storage device is actively regenerated to the power supply side and the output voltage of the power storage device is lowered to a sufficiently low level, the long life of the power storage element In addition to ensuring safety and ensuring safety, it is possible to increase the overall energy utilization efficiency.

  Therefore, in the prior art, a relay circuit is provided on the input side of the DC converter with respect to a motor power supply path in which a DC converter, a power storage device, and an AC inverter are sequentially connected. A boost DC / DC converter that boosts the voltage of the power storage device and an AC inverter that converts the boosted power to AC are provided, and the relay circuit is turned off in accordance with the motor stoppage to switch the power storage device to AC. There has been proposed an apparatus in which the voltage of the power storage device is once boosted by a DC / DC converter and then AC is converted by an AC inverter to regenerate energy to an AC power supply while being disconnected from the power supply side (for example, Patent Document 2). reference).

JP-A-4-75485 JP 2006-101600 A

  However, in the conventional AC motor driving device described in Patent Document 2, the relay circuit, the boost type, and the like are used to regenerate the energy stored in the power storage device to the AC power source side as described above. Since a dedicated additional circuit for power regeneration such as a DC / DC converter and an inverter is required, an extra cost is generated.

  Moreover, conventionally, when the energy of the power storage device is regenerated to the AC power supply side via the step-up DC / DC converter, the magnitude of the discharge current at the time of regeneration has not yet been sufficiently considered. Therefore, especially when the discharge current from a large-capacity power storage device is large, the energy loss due to the internal resistance of the power storage element that constitutes the power storage device becomes large, which is insufficient to increase the energy efficiency. In addition, there is a problem that the energy storage element rises in temperature due to the energy loss, leading to a decrease in life.

  The present invention has been made in order to solve the above-described problems. When the energy stored in the power storage device is regenerated to the power supply side in response to the stoppage of the operation of the AC motor, the present invention is dedicated to the conventional one. An object of the present invention is to provide an AC motor driving apparatus that does not require an additional circuit. Also, an AC motor drive device that can reduce energy loss of the power storage element due to the discharge of the power storage device as much as possible, has high energy efficiency, and can contribute to the extension of the life of the power storage element is also provided. The purpose is to do.

  The present invention relates to an AC motor driving device comprising: an inverter connected to a DC bus to which DC power is supplied from a DC power source to drive an AC motor; and an electric power storage device connected in parallel to the DC bus. The storage device is a bidirectional type capable of both the power storage element for storing energy and the charging to the power storage element via the DC bus and the discharge from the power storage element toward the DC bus. A DC / DC converter, and a control circuit that performs power regeneration at a constant current by the DC / DC converter when the energy stored in the power storage element is discharged.

  According to the present invention, when the energy stored in the power storage device is discharged, the power is regenerated with a constant current via the DC / DC converter, so that the energy can be effectively used without providing an additional circuit as in the prior art. Moreover, energy loss due to the internal resistance of the power storage element constituting the power storage device can be reduced. For this reason, it becomes possible to complete | finish discharge in a short time, suppressing the temperature rise of an electric power storage element and contributing to lifetime extension.

It is a block diagram which shows the whole AC motor drive device in Embodiment 1 of this invention. It is a circuit diagram which shows the detail of the direct-current power supply part of the same AC motor drive device. It is a block diagram which shows the detail of the electric power storage apparatus of the same AC motor drive device. It is a block diagram which shows the detail of the electric power storage element which comprises the electric power storage apparatus of FIG. It is a circuit diagram which shows the detail of the DC / DC converter which comprises the electric power storage apparatus of FIG. It is a circuit diagram which shows the detail of the other type of DC / DC converter which comprises the electric power storage apparatus of FIG. It is a wave form diagram at the time of discharging the electric power storage element shown in FIG. 4 with a constant current. It is a wave form diagram at the time of making it discharge naturally by connecting a discharge resistance to the electric power storage element of the structure shown in FIG. It is a block diagram which shows an example of a specific structure of the gate signal production | generation part with which the control means of the same AC motor drive device is provided. It is a block diagram which shows an example of a specific structure of the gate signal generation part with which the control means in the alternating current motor drive device of Embodiment 2 of this invention is provided. It is a wave form diagram at the time of discharging an electric power storage element with a constant current by control of the DC / DC converter based on the gate signal produced | generated by the gate signal production | generation part shown in FIG. It is a block diagram which shows the electric power storage apparatus of the alternating current motor drive device in Embodiment 3 of this invention. It is a block diagram which shows an example of a specific structure of the gate signal production | generation part with which the control means of the same AC motor drive device is provided. FIG. 14 is a characteristic diagram showing a relationship between the case where the discharge signal command value is determined based on the temperature detection value in the gate signal generation unit shown in FIG. 13. It is a characteristic view which shows the relationship between both in the case of determining a discharge current command value based on a temperature detection value in the gate signal generation part which comprises the control means of the alternating current motor drive device which concerns on Embodiment 4 of this invention. It is a block diagram which shows an example of the discharge current command value production | generation part of the alternating current motor drive device in Embodiment 5 of this invention. It is a block diagram which shows the modification of the discharge current command value production | generation part.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram showing the entire AC motor driving apparatus according to Embodiment 1 of the present invention.

  The AC motor driving apparatus according to the first embodiment includes a plurality of inverters 3, 3,... Connected to a DC bus 2 to which DC power is supplied from a DC power supply 1, and one DC connected in parallel to the DC bus 2. Are provided with an electric power storage device 5, and AC motors 4, 4,.

  The DC power output from the DC power source 1 is supplied to the inverters 3, 3,... Via the DC bus 2, and a desired AC voltage is generated by the inverters 3, 3,. Drive 4 ... Here, a plurality of sets of inverters 3, 3... And AC motors 4, 4,... Are provided for the DC bus 2, but only one set may be connected.

  For example, as shown in FIG. 2, the DC power source 1 includes a reactor 13, a rectifier 14 for full-wave rectification that can regenerate power, and a smoothing capacitor 15. Then, AC power from the AC power supply 11 is input to the rectifier 14 via the transformer 12 and the reactor 13 and rectified, and then smoothed by the smoothing capacitor 15 to obtain DC power.

  As shown in FIG. 3, the power storage device 5 includes a power storage element 21 that stores energy, a charge to the power storage element 21 through the DC bus 2, and a discharge from the power storage element 21 to the DC bus 2 side. And a control unit 23 such as a microcomputer for controlling the operation of the DC / DC converter 22. Note that the control means 23 may be further connected to a higher-level control means (not shown). In particular, in the first embodiment, as will be described in detail later, when the AC motor is stopped, the control means 23 actively discharges the energy accumulated in the power storage element 21 and regenerates it to the power source side. Is configured to perform power regeneration with a constant current by the DC / DC converter 22.

  The power storage element 21 is configured as shown in FIG. 4, for example. That is, the power storage element 21 connects a plurality of EDLC cells 31, 31,... Composed of electric double layer capacitors (EDLC) in series, and reduces the voltage variation between the EDLC cells 31, 31,. The EDLC modules 32, 32,... Are formed by individually connecting the voltage balance resistors 33, 33,. The power storage element 21 is configured as an EDLC unit by connecting m × n (m, n is a number of 1 or more) of these EDLC modules 32, 32,.

  The power storage element 21 configured as described above has a large capacitance of, for example, about 1F, and the capacitance of one EDLC cell 31 normally exceeds 100F, but the maximum voltage is about 3V. It is as follows. Moreover, since the voltage of the DC bus 2 is usually 300 V or 600 V, the voltage of the power storage element 21 is practically 150 V or more. The power storage element 25 may include a fuse, a breaker, or the like, but is omitted here. Further, the voltage balance resistor 33 can be omitted or another method can be adopted.

  On the other hand, as shown in FIG. 5, the DC / DC converter 22 is generally capable of both charging the power storage element 21 via the DC bus 2 and discharging from the power storage element 21 to the DC bus 2. In the bidirectional chopper circuit, the high voltage side is connected to the DC bus 2 and the low voltage side is connected to the power storage element 21.

  As a specific configuration of the DC / DC converter 22, self-extinguishing semiconductor switching elements 41a and 41b such as IGBTs are connected in series, and the free-wheeling diodes 42a are connected in antiparallel to the IGBTs 41a and 41b, respectively. , 42b are connected. One end of a DC reactor 43 is connected to the connection point between the IGBT 41a and the freewheeling diode 42b. The collector of the IGBT 41a and the emitter of the IGBT 41b are connected to the DC bus 2 and one smoothing capacitor 44a, respectively. The end and the emitter of the IGBT 41b are connected to the power storage element 21 and the other smoothing capacitor 44b, respectively. The smoothing capacitors 44a and 44b may be omitted.

  Further, the DC / DC converter 22 is not limited to the one shown in FIG. 5, and for example, a DC / DC converter having a configuration shown in each of FIGS. 6A to 6C can be applied.

  The DC / DC converter shown in FIG. 6A is a three-way bidirectional chopper. In this case, a current sensor is installed for each DC reactor. When the phases are multiplexed and the carrier phase is shifted, the ripple of the input / output current can be reduced, and further, the current capacity of the semiconductor element and the DC reactor can be reduced. Further, the DC / DC converter of FIG. 6B is a step-up / step-down bidirectional chopper, and the DC / DC converter of FIG. 6C is a triple multiple step-up / step-down bidirectional chopper. Note that the step-up / step-down bidirectional chopper can control the discharge current from the power storage element 21 to be constant while the power storage element 21 is at a higher voltage than the DC bus 2.

  For example, in the configuration of FIG. 5, the control unit 23 is configured to control the IGBTs 41 a and IGBTs 41 b of the DC / DC converter 22 based on the detection values of the voltage sensors 45 a and 45 b and the current sensors 46 a and 46 b provided in the DC / DC converter 22. A gate signal for performing switching control is output. The detection value input to the control unit 23 is an example, and other detection values may be input. In some cases, signals are exchanged with a host controller (not shown).

  In the AC motor driving apparatus having the above-described configuration, for example, when the operation of the AC motor 4 is stopped after the operation of the day is finished, as described above, the life of the power storage element 21 is increased, the safety is ensured, the energy is increased. In order to increase the overall utilization efficiency, the DC / DC converter 22 is controlled by the control means 23 to discharge the energy stored in the power storage element 21.

At that time, the internal resistance of the power storage element 21 and the magnitude of the discharge current affect the magnitude of the energy loss, which causes the temperature of the power storage element 21 to rise. Therefore, when the discharge current flowing through the power storage element 21 is I and the value of the internal resistance is R, the power loss P is P = I ² · R. If the energy stored in the power storage element 21 is constant, the energy loss W (= ∫ (I ² · R) dt), which is an integrated value of the power loss P caused by the internal resistance R generated during discharge, is Since it works by the square of the discharge current I flowing through the power storage element 21, the energy loss W can be reduced by discharging the power storage element 21 with a constant current.

  An illustration of this is shown in FIGS. Here, the electrostatic capacity of the power storage element 21 is 2 F, the internal resistance is 90 mΩ, and it is charged to 300 V, and the amount of energy accumulated at this time is 90 kJ.

  FIG. 7 shows measurement results of the discharge voltage V, the discharge current I (discharge is positive), the power loss P, and the energy loss W when the power storage element 21 is discharged at a constant current of 30A. FIG. 8 shows an example of each result of discharge voltage V, discharge current I (discharge positive), power loss P, and energy loss W when a 3Ω discharge resistor is connected to the power storage element 21 for spontaneous discharge. Is shown.

  As can be seen by comparing FIG. 7 and FIG. 8, it can be confirmed that the voltage V is slightly smaller when the constant current discharge is slightly performed after the simultaneous discharge is completed. Further, in the case of the constant current discharge of FIG. 7, the energy loss W is only about 60% compared to the resistance discharge of FIG. 8, and the energy loss W due to the internal resistance of the power storage element 21 is small. The temperature rise of the element 21 is suppressed. Further, in the case of the resistance discharge of FIG. 8, since the discharge voltage V of the power storage element 21 is high at the start of discharge, a large current flows as the discharge current I, and thereafter, the discharge rate decreases rapidly.

  Therefore, for example, when a discharge command for discharging the energy stored in the power storage element 21 and regenerating the power source is given in order to stop the operation of the AC motor 4 after the operation of the day is finished, The control means 23 controls the on-time of the IGBTs 41a and 41b so that the average current flowing through the reactor 43 (see FIG. 5) of the DC / DC converter 22 is constant, so that the power storage element 21 to the DC bus 2 is controlled. Discharge. The discharge control by the control means 23 stops when the voltage of the power storage element 21 reaches substantially zero or a voltage that is low enough to cause an electric shock or can be discharged by the voltage balance resistor 33.

  FIG. 9 shows a specific configuration of the gate signal generation unit 24 provided in the control means 23 in order to control the DC / DC converter 22 and perform power regeneration with constant current for the energy stored in the power storage element 21. It is a block diagram which shows an example.

  In the gate signal generation unit 24, the discharge current command value IL * and the DC reactor current detection value IL detected by the current detector 46b are input to the subtractor 51. The output is input to the PI controller 52, and the proportional-integral calculation is performed and output. The output of the PI controller 52 corresponds to the discharge voltage command value V *. Next, the limiter 53 limits the discharge voltage command value V * to a value between the maximum voltage and the minimum voltage, for example.

  On the other hand, the limiter 54 limits the bus voltage detection value Vload, which is the voltage of the DC bus 2 detected by the voltage detector 45a, to a value larger than zero. Divider 55 divides discharge voltage command value V * by bus voltage detection value Vload to obtain a PWM command value. By comparing the PWM command value and the carrier (in this case, a triangular wave in the range of 0 to 1) by the comparator 56, the gate signal IGBTp of the IGBT 41a is inverted by the inverter 57, and the gate signal IGBTn of the IGBT 41b is inverted by the inverter 57. Are created. As a result, the output voltage of the power storage element 21 is boosted by the DC / DC converter 22 and the energy stored in the power storage element 21 is discharged at a constant current toward the DC bus 2 side. Then, when the power storage element 21 reaches a sufficiently low voltage, the discharge control by the control means 23 is stopped.

  In practice, a short-circuit prevention period is provided between the gate signals IGBTp and IGBTn. Further, at the time of discharging, one gate signal IGBTp may be always set to L, that is, turned off. At this time, it is not necessary to provide a short-circuit prevention period.

  In this way, when the energy stored in the power storage element 21 is discharged by the constant current, the voltage of the DC bus 2 rises, and the AC via the rectifier 14 of FIG. Electric power is regenerated toward the power source 11. At that time, although some loss due to the DC / DC converter 22 is generated, as shown in FIG. 8, in the resistive discharge, all the power is consumed by the resistance component, whereas as shown in FIG. In the current discharge, the energy loss W due to the internal resistance of the power storage element 21 is reduced, so that the energy saving effect is great. Furthermore, there is an effect that it is not necessary to select a discharge resistance suitable for the allowable discharge time.

  As described above, in the first embodiment, the energy stored in the power storage element 21 is discharged at a constant current via the DC / DC converter 22 to perform power regeneration, so that a conventional dedicated discharge is added. Energy can be effectively used without providing a circuit. Moreover, energy loss due to the internal resistance of the power storage element 21 can be reduced. For this reason, discharge time can be shortened, suppressing the temperature rise of the electric power storage element 21 and contributing to long life.

Embodiment 2. FIG.
FIG. 10 is a block diagram showing an example of a specific configuration of the gate signal generation unit provided in the control means in the AC motor driving apparatus according to the second embodiment of the present invention, corresponding to the first embodiment shown in FIG. Corresponding components are denoted by the same reference numerals.

  The feature of the second embodiment is that, when the discharge power from the power storage element 21 is equal to or greater than a preset specified value, the control means 23 controls the discharge current until the discharge power becomes equal to the preset specified value. That is, it is configured to perform control to be reduced.

  That is, in the second embodiment, for example, in order to stop the operation of the AC motor 4 after the operation of the day is finished, a discharge command for discharging the energy accumulated in the power storage element 21 and regenerating the power is given. In response to this, in the gate signal generator 24 shown in FIG. 10, the discharge current command value IL * for constant current discharge and the voltage detection that is the output voltage of the power storage element 21 detected by the voltage detector 45b. The value Vedlc is input to the multiplier 58 to obtain the discharge power command PL *. Then, the discharge power command PL * is limited by the limiter 59 at the next stage. In this case, the specified value for limiting the discharge power command PL * by the limiter 59 is set in advance in consideration of the power rating of the DC / DC converter 22, the capacity of the rectifier 14, the AC reactor 13, and the transformer 12. Is done. The discharge voltage command PL * thus limited is divided by the detected voltage value Vedlc by the next divider 61 to obtain a discharge current command value with power limitation. The limiter 60 is provided so that the divider 61 does not divide the discharge voltage command PL * by zero.

  Since the configuration and processing contents of the signal processing until the generation of each gate signal IGBTp, IGBTn after the discharge current command value with power limitation is obtained in this way are the same as those shown in FIG. Is omitted.

FIG. 11 shows the discharge voltage V, discharge current I (positive discharge), power loss P, energy loss W when discharging with a constant current of 30 A with the discharge power of the power storage element 21 limited to 7.5 kW. Each measurement result is shown. As can be seen from FIG. 11, since the discharge power is limited to 7.5 kW from the start of discharge to time t ₀ , the discharge current I is small.

  During constant current discharge, the discharge power is large when the discharge voltage V is high, and the discharge power is small when the discharge voltage V is low. Therefore, in the second embodiment, when the discharge voltage V is high, the regenerative power is limited according to the capacity of the DC / DC converter 22, the regenerative rectifier 14, and further the AC reactor 13 and the transformer 12. Outside the range, constant current discharge can be performed.

  As described above, in the second embodiment, when the discharge power from the power storage element 21 is equal to or higher than a predetermined value, the control unit 23 reduces the discharge current until the discharge power becomes equal to the predetermined value. Therefore, the discharge power can be limited in a region where the voltage of the power storage element 21 is high. For this reason, the power rating of the DC / DC converter 22 is not exceeded, and a device failure can be prevented. Furthermore, since the current command value of the discharge current can be determined without being limited by the power limitation, as in the first embodiment, energy loss due to the internal resistance of the power storage element 21 is reduced to suppress the temperature rise. The discharge time can be shortened while contributing to the long life.

Embodiment 3 FIG.
FIG. 12 is a configuration diagram showing an electric power storage device of an AC motor driving device according to Embodiment 3 of the present invention, and FIG. 13 shows an example of a specific configuration of a gate signal generation unit provided in the control means of the AC motor driving device. FIG. 10 is a block diagram, and components corresponding to or corresponding to those of the first embodiment shown in FIGS. 3 and 9 are denoted by the same reference numerals.

  In the third embodiment, a temperature sensor 25 is attached to, for example, a storage case of the power storage element 24, the ambient temperature is detected by the temperature sensor 25, and the temperature detection value T is input to the control means 23. . The gate signal generation unit 24 of the control unit 23 includes a table 62 in which the temperature detection value T and the discharge current command value IL * are associated in advance, and refers to the table 62 based on the temperature detection value T. The discharge current command value IL * corresponding to this is output. In this case, as shown in FIG. 14, the table 62 is set so that the discharge current command value IL * is switched between large and small at the reference value Ta as a boundary. The reference value Ta corresponds to the first reference value in the claims.

  Therefore, a constant discharge current command value IL * is output from the table 62 when the temperature detection value T is less than the preset reference value Ta, but when the temperature detection value T is greater than or equal to the reference value Ta, the discharge current command value is output. IL * is reduced. Since the configuration and processing contents of the signal processing from when the discharge current command value IL * is obtained until the gate signals IGBTp and IGBTn are generated are the same as those shown in FIG. 9, the description thereof is omitted here. To do.

  As described above, in the third embodiment, since the discharge current command value IL * can be determined in consideration of the temperature of the power storage element 21, the temperature detection value T exceeds the preset reference value Ta. Reduces the discharge power I by reducing the discharge current I of the power storage element 21, reduces the energy loss W due to the internal resistance of the power storage element 21, suppresses temperature rise, and prevents deterioration. When the temperature detection value T is less than the preset reference value Ta and the temperature of the power storage element 21 is not high, the discharge time can be shortened.

  Here, the temperature sensor 25 is attached to the storage case of the power storage element 24 to detect the ambient temperature. However, the present invention is not limited to this, and the temperature sensor 25 may be provided inside the storage case. There are no particular restrictions on the location or number of detections. Here, as shown in FIG. 14, the discharge current command value IL * is switched between large and small at the reference value Ta as a boundary. However, the present invention is not limited to this, and the temperature detection value T exceeds the reference value Ta. In this case, the discharge current command value IL * may be gradually decreased as the temperature increases. Further, in addition to the configuration of the third embodiment, a limiter 59 may be provided as in the second embodiment to limit the discharge power.

Embodiment 4 FIG.
The basic configuration of the gate signal generation unit 24 of the fourth embodiment is the same as that of the third embodiment shown in FIG. 13 except that a table 62 provided in the gate signal generation unit 24 is different from that shown in FIG. As shown in FIG. 15, when the temperature detection value T is equal to or higher than the first reference value Ta, the discharge current command value IL * is lowered as in the case of the third embodiment, while the temperature detection value T is the second reference value Ta. When the value is less than the reference value Tb (<Ta), the discharge current command value IL * is set to be increased. The rest of the configuration is the same as that of the third embodiment, and a detailed description thereof is omitted here.

  Since the internal resistance of the power storage element 21 generally increases at a low temperature and it becomes difficult for a discharge current to flow, it is desirable to discharge after increasing the internal resistance to a temperature at which the internal resistance decreases. Therefore, in the fourth embodiment, when the temperature of the power storage element 21 is detected by the temperature sensor 25, if the detected temperature detection value T is less than the second reference value Tb, the discharge current command value IL * is positively set. Increase. Thereby, the total of the energy loss resulting from the internal resistance of the power storage element 21 can be reduced while shortening the discharge time as a whole. Other functions and effects are the same as those of the third embodiment.

Embodiment 5 FIG.
FIG. 16 is a configuration diagram illustrating an example of a discharge current command value generation unit of the AC motor drive device according to Embodiment 5 of the present invention.

  When discharging the energy stored in the power storage element 21 to regenerate the power source, if the discharge current of the power storage element 21 is large, the required discharge time is shortened, and the energy loss due to the internal resistance is correspondingly increased. The amount becomes smaller. On the other hand, when the discharge current is small, the energy loss due to the internal resistance is correspondingly small, so that the required discharge time is lengthened, but the regenerative power amount is large. As described above, since there are merits and demerits depending on the method of power regeneration, the operator can select a discharge method that gives priority to the amount of regenerative power or the time required for discharge depending on the situation during power regeneration. Is desirable.

  Therefore, in the fifth embodiment, in addition to any one of the configurations of the first to fourth embodiments, as shown in FIG. 16, a discharge current command that becomes a control target value when the power storage element 21 is discharged at a constant current. When the operator selects a discharge method when a discharge current command value generation unit 26 for creating a value is provided and the operation of the AC motor 4 is stopped after one day of operation is finished, a discharge current command value suitable for the method is selected. IL * is obtained.

  That is, the discharge current command value generation unit 26 according to the fifth embodiment calculates a combination of a plurality of regenerative electric energy and required discharge time in response to a discharge command for the energy stored in the power storage element 21. From the electric energy / time calculating means 71, a display 72 for displaying the calculation results of the plurality of combinations calculated by the electric energy / time calculating means 71, and a plurality of combinations displayed on the display 72. When a combination of a single regenerative electric energy and a required discharge time is selected, a current command value generating means 73 that generates a discharge current command value IL * suitable for the selected combination (regenerative electric energy and required discharge time). And.

  In the above configuration, for example, when a discharge command for discharging the energy stored in the power storage element 21 and regenerating the power source is given to stop the operation of the AC motor 4 after the operation of the day is finished, Accordingly, the power amount / time calculation means 71 takes in the discharge voltage V and the temperature detection value T of the power storage element 21 detected by the voltage sensor 45b and the temperature sensor 25, and stores power stored in advance in the inside. Based on the specification data regarding the device 5, a plurality of approximate values of the regenerative electric energy and the required discharge time are calculated, and the calculation results are displayed on the display device 72. At that time, the electric energy / time calculating means 71 roughly calculates the regenerative electric energy and the required discharge time, and also displays a plurality of discharge current command values IL * corresponding to them on the display 72.

  Here, the worker considers whether the regenerative power amount priority or the discharge required time priority from among the plurality of displayed combinations (regenerative power amount and required discharge time), and one regenerative power amount and the required discharge time. Select a combination. Then, when a combination is selected and input from an operation means such as a keyboard (not shown), the current command value creation means 73 responds accordingly to a discharge current that matches the selected combination (regenerative power amount and discharge given time). A command value IL * is created, and this discharge current command value IL * is output to the gate signal generator 24 as shown in FIG. 9, for example. As a result, the energy utilization efficiency is increased, and the operator can select the discharge method from the viewpoint of the required discharge time, so that the work efficiency is improved.

  In addition, it can replace with the structure of the discharge current command value production | generation part 26 shown in FIG. 16, and can also have a structure as shown in FIG.

  That is, the discharge current command value generation unit 26 having the configuration shown in FIG. 17 includes an electric energy / time table 75. The electric energy / time table 75 includes various types such as priority on regenerative electric energy or priority on required discharge time. For each discharge condition, approximate values of a plurality of regenerative electric energy and the required discharge time that satisfy these discharge conditions are registered in advance in a table format.

  Then, when the operator selects one discharge condition according to the discharge situation such as at the end of daily operation or maintenance, the regenerative electric energy suitable for the selected one discharge condition is selected from the electric energy / time table 75. An approximate value of the required discharge time is read out and displayed on the display 72, and is also given to the current command value creating means 73. Therefore, unless the operator changes the discharge conditions, the power / time table 75 continuously outputs the approximate values of the regenerative electric energy and the required discharge time suitable for the selected discharge condition.

  When an operator gives a discharge command for discharging the energy stored in the power storage element 21 to regenerate the power source, the worker displays the contents of the approximate values (regenerative power amount and required discharge time) displayed on the display 72. If there is no change in the contents, a discharge condition determination command is given to the current command value creation means 73 from an operation means such as a keyboard (not shown). In response to this, the current command value creating means 73 takes in the discharge voltage V and the temperature detection value T of the power storage element 21 detected by the voltage sensor 45 b and the temperature sensor 25 and gives them from the power amount / time table 75. A discharge current command value IL * that meets these conditions is created based on the estimated value and the specification data relating to the power storage device 5 registered in advance in the interior, and this discharge current command value IL * is, for example, shown in FIG. To the gate signal generator 24 as shown in FIG.

  In this method, unless the discharge condition is changed, the operator does not need to select and input an approximate value (regenerative electric energy and required discharge time) that suits the discharge condition each time. Since a preferred discharge method can be automatically selected according to the discharge situation such as at the end of daily operation or maintenance, work efficiency is improved.

  As described above, in the fifth embodiment, when a preferable discharge method is selected in consideration of a discharge situation such as the end of daily operation or maintenance, a discharge current command value IL * suitable for the discharge method is automatically set. Alternatively, since it is determined semi-automatically, not only can the stored energy of the power storage element 21 be used effectively, but also energy loss due to its internal resistance can be reduced to prevent deterioration.

Embodiment 6 FIG.
In each of the above-described first to fifth embodiments, the case where an electric double layer capacitor (EDLC) is used as the power storage element 21 has been described. However, the present invention is not limited to this, and for example, an electrolytic capacitor or a lithium ion secondary It may be composed of a battery such as a battery.

  In particular, in the case of a lithium ion secondary battery, for example, 20% is recommended as the state of charge (SOC) when storing the lithium ion secondary battery. A high SOC not only promotes deterioration, but also increases the risk of short-circuiting because of the large stored energy. For this reason, it is desirable to lower the SOC during maintenance or during a fixed period of time. Further, as with EDLC, energy loss due to internal resistance cannot be ignored. Furthermore, it should be avoided that the temperature is high, and the internal resistance increases at low temperatures. Therefore, even when a lithium ion secondary battery is used as the power storage element 21, it is effective to discharge to a predetermined SOC by the method described in the first to fifth embodiments.

1 DC power supply, 2 DC bus, 3 inverter, 4 AC motor, 5 power storage device, 21 power storage element, 22 DC / DC converter, 23 control means,
24 gate signal generation unit, 25 temperature sensor, 26 discharge current command value generation unit,
71 electric energy / time calculating means, 72 indicator, 73 current command value creating means,
75 Electricity / time table.

Claims (6)

In an AC motor drive device comprising an inverter connected to a DC bus to which DC power is supplied from a DC power source and driving an AC motor, and a power storage device connected in parallel to the DC bus,
The power storage device includes a power storage element that stores energy and bidirectional operation capable of both charging to the power storage element via the DC bus and discharging to the DC bus from the power storage element. AC motor drive apparatus comprising: a DC / DC converter of a type; and control means for performing power regeneration at a constant current by the DC / DC converter when discharging the energy stored in the power storage element. The control means performs control to reduce the discharge current until the discharge power becomes equal to the specified value when the discharged power from the power storage element is equal to or greater than a predetermined specified value. 1. The AC motor drive device according to 1. A temperature sensor for detecting the temperature of the power storage element; and the control means determines the discharge current when the temperature detection value of the temperature sensor is equal to or higher than a preset first reference value. The AC motor drive device according to claim 1 or 2, wherein the control is performed so that the discharge current is lower than the discharge current in the case of less than 1. A temperature sensor for detecting the temperature of the power storage element, and the control means determines the discharge current as the second reference when the temperature detection value of the temperature sensor is less than a preset second reference value. The AC motor drive device according to any one of claims 1 to 3, wherein the control is performed to increase the discharge current when the value is greater than or equal to the value. A discharge current command value generation unit that generates a discharge current command value that is a control target value when the power storage element is discharged at a constant current, and the discharge current command value generation unit receives a discharge command for the power storage element; A power amount / time calculation means for calculating a combination of a plurality of regenerative electric energy and a required discharge time according to a given value, and a display for displaying a calculation result of the combination calculated by the power amount / time calculation means; When a combination of one regenerative electric energy and a required discharge time is selected from the plurality of combinations displayed on the display, a current command for creating a discharge current command value suitable for the selected combination The AC motor drive device according to any one of claims 1 to 4, further comprising a value creating unit. A discharge current command value generation unit for generating a discharge current command value that is a control target value when the power storage element is discharged at a constant current, and the discharge current command value generation unit is configured for each discharge condition for each discharge condition; A power / time table in which approximate values of a plurality of regenerative electric energy satisfying the conditions and the required discharge time are registered in advance, and if one discharge condition is selected, the power / time table is selected from the above A display that displays an approximate value corresponding to one discharge condition, and when one discharge condition is determined and a discharge command is given to the power storage element, the power amount / time is 5. An alternating current according to claim 1, further comprising: a current command value creating unit that creates a discharge current command value suitable for an approximate value satisfying one discharge condition read from the table. Motor drive Location.

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