JP2006238519A - Load driving unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a load driving unit which can efficiently perform the drive of a load by the power accumulated in a capacitor and the recovery of regenerative power from the load by properly controlling the quantity of power to be accumulated in the capacitor. <P>SOLUTION: This load driving unit possesses an AC/DC converter 2 which charges the capacitor 3 with power given from an external power source 1 and regenerates the accumulated power of the capacitor into an external power source, and an inverter 5 which drives the load, using the power accummulted in the capacitor 3, and also accumulates the regenerative power obtained from the load into the capacitor 3. A controller, which controls the operation of the AC/DC converter 2, makes it perform the power supply operation from the external power source 1 while limiting the current when the detected value of DC voltage is between the upper limit value of DC voltage and the lower limit value of the DC voltage, and makes it perform the power regenerative operation to the external power source 1 by lifting the limitation on the current when the detected value of the DC voltage is over the upper limit value of the DC voltage, and makes it perform the power supply operation from the external power source by lifting the limitation on the current when the detected value of the DC voltage is under the lower limit value of the DC voltage. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a load driving device suitable for driving an elevator such as a crane.

  Load drive devices that drive cranes and other elevators generally convert a DC / AC converter that converts AC power into DC power, and the DC power output from this DC / AC converter is converted to AC with controlled voltage and frequency. And an inverter for driving the electric motor. Further, the DC power output from the DC / AC converter is stored in a capacitor (capacitor), and the inverter is power-driven using the power stored in the capacitor, and the regenerative power obtained via the motor is supplied to the capacitor. It is also proposed to accumulate the data in the inverter and reuse it for driving the inverter (see, for example, Patent Document 1).

Recently, attention has been focused on a small-sized and large-capacity electric double layer capacitor, and it is considered to use an electric double layer capacitor as a power storage capacitor in the load driving device described above.
Japanese Patent Laid-Open No. 10-267076

  By the way, driving the electric motor in the elevator such as the crane described above requires a large amount of electric power (powering energy), and the regenerative electric power (regenerative energy) obtained from the electric motor is large. Therefore, how to efficiently input / output the electric power (power energy) to / from the electric double layer capacitor becomes a problem. Moreover, in order to effectively use the energy stored in the electric double layer capacitor and to recover and reuse the regenerative power obtained from the motor without waste, it was stored in the electric double layer capacitor according to the operating conditions of the motor. It is necessary to keep the amount of power appropriate.

  Specifically, when a power running operation of the electric motor is assumed, it is necessary to store power energy required for the power running drive in advance in an electric double layer capacitor. Conversely, when regenerative operation of the motor is expected, the amount of power stored in the electric double layer capacitor can be kept low so that the regenerative power can be reliably stored in the electric double layer capacitor, and the electric charge can be charged. It is necessary to provide a sufficient capacity.

  The present invention has been made in view of such circumstances, and its purpose is to appropriately control the amount of power stored in the capacitor in accordance with the operating condition of the load, and thereby the load through the capacitor. It is an object of the present invention to provide a load driving device that can efficiently perform the driving of the motor and accumulation of regenerative power recovered from the load.

In order to achieve the above-described object, a load driving device according to the present invention has a function of converting AC power supplied from an external power source into DC power, and a function of converting DC power into AC power and regenerating the external power source. AC / DC converter, a capacitor for storing DC power output from the AC / DC converter, DC power stored in the capacitor and / or DC power output from the AC / DC converter, An inverter that converts the frequency-converted AC power to drive the load and collects the regenerative power generated in the load and stores it in the capacitor;
In the controller that controls the operation of the AC / DC converter,
<a> When the DC voltage detection value on the DC side of the AC / DC converter is between a preset DC voltage upper limit value and a DC voltage lower limit value, the external power source is within a predetermined current value limit value range. Power supply operation from
<b> When the DC voltage detection value is larger than the DC voltage upper limit value, the current value restriction is canceled and the power regeneration operation to the external power source is performed.
<c> Further, when the detected DC voltage value is smaller than the lower limit value of the DC voltage, the current value restriction is canceled and the power supply operation from the external power source is performed.

  Preferably, the current value limit value is set in advance as a value less than the maximum allowable current of the AC / DC converter as described in claim 2, and the DC voltage upper limit value is set as described in claim 3. The voltage value that defines the maximum charge capacity of the capacitor that guarantees the operating characteristics of the AC / DC converter, and the DC voltage lower limit value that specifies the minimum charge capacity of the capacitor that guarantees the operating characteristics of the AC / DC converter It is desirable to set it as a voltage value.

  Incidentally, the capacitor is a small and large-capacity electric double layer capacitor as described in claim 4, and the load is an electric motor for driving an elevator.

  According to the load driving apparatus configured as described above, the controller for controlling the operation of the AC / DC converter is the DC voltage detection value on the DC side of the AC / DC converter, that is, the charging voltage (terminal voltage) of the capacitor. Is between a preset DC voltage upper limit value and a DC voltage lower limit value, and the operation of the AC / DC converter is controlled according to the determination result. When the charging voltage of the capacitor is between the DC voltage upper limit value and the DC voltage lower limit value, a power supply operation is performed to supply power to the capacitor from an external power source to the AC / DC converter under a predetermined current value limit. Make it. When the charging voltage of the capacitor exceeds the DC voltage upper limit value, it is determined that the power energy (capacity of the capacitor) on the DC side is excessive due to recovery of regenerative power from the load, Under the current limit, the AC / DC converter is caused to perform a power regeneration operation for returning the power stored in the capacitor to an external power source. Further, when the charging voltage of the capacitor is less than the lower limit value of the DC voltage, it is determined that the charging amount of the capacitor is significantly insufficient, and the power supply for supplying power to the capacitor from the external power source to the AC / DC converter Let's drive.

  Therefore, the charge amount of the capacitor can be appropriately controlled under the control of the DC voltage upper limit value and the DC voltage lower limit value. In addition, unless the charge amount of the capacitor is significantly insufficient, the above-described power supply operation and power regeneration operation are executed within the preset current limit value range, which places an excessive burden on the capacitor. Without charge, the charge amount can be optimized.

Hereinafter, a load driving device according to an embodiment of the present invention will be described with reference to the drawings.
This load driving device is supplied from an external power source, for example, with a driving induction motor (motor) in a crane that lifts and lowers an article (luggage) and a lifter that moves an elevating stage for placing the article up and down. The electric motor is driven using AC power (for example, 200V power system three-phase AC power). In particular, the load driving device basically generates DC power from AC power using an AC / DC converter, and further generates AC power whose voltage and frequency are controlled from this DC power using an inverter. Load).

  That is, the load driving device according to the present invention includes an AC / DC converter 2 that converts AC power supplied from an external power source 1 into DC power, as shown in FIG. 2 includes a capacitor 3 for accumulating the DC power output from 2. The capacitor 3 is composed of, for example, an electric double layer capacitor that is small and has a large charge capacity. Further, the load driving device generates AC power having a controlled voltage and frequency from DC power stored in the capacitor 3 and / or DC power output from the AC / DC converter 1, and loads the load (motor) 4. An inverter 5 for driving is provided. The inverter 5 has a function of converting the regenerative power into DC power, collecting it and storing it in the capacitor 3 when regenerative power is obtained from the load (electric motor) 4.

  The operation of the inverter 5 is controlled by a load controller 6 according to the driving state of the load 4. In particular, when the power required for driving the load 4 is positive (+), the load controller 6 controls the load 4 using the power stored in the capacitor 3 and / or the power obtained from the AC / DC converter 2. When power driving is performed and the power required for driving the load 4 is negative (−) and power is regenerated through the load 4, the regenerative power is recovered and the capacitor 3 is charged. ing.

  The operation of the AC / DC converter 2 is controlled by the power supply controller 7 according to the DC side voltage, specifically, the charging voltage (terminal voltage) of the capacitor 3. In particular, the power supply controller 7 compares the charging voltage Vsenc of the capacitor 3 detected in the DC system with a DC voltage upper limit value Vmax and a DC voltage lower limit value Vmin that can be output controlled by the AC / DC converter 2, respectively. The charge amount of the capacitor 3 is controlled by causing the AC / DC converter 2 to perform a power supply operation or a power regeneration operation according to the comparison result.

Specifically, the charge amount U of the capacitor 3 is expressed as [U = (1/2) CV ² ] when its capacity is C, and is proportional to the square of the charge voltage V as shown in FIG. Change. In other words, when the voltage (applied voltage) applied to the capacitor 3 is higher than the terminal voltage, there is a margin in the electric capacity (electric energy amount) that can be stored in the capacitor 3, so that the terminal voltage reaches the applied voltage. Until the capacitor 3 is charged. On the other hand, when the voltage (applied voltage) applied to the capacitor 3 is lower than the terminal voltage, since the electric capacity (electric energy amount) stored in the capacitor 3 is excessive, the terminal voltage reaches the applied voltage. Until the capacitor 3 is discharged.

  The power supply controller 7 pays attention to the fact that the amount of charge in the capacitor 3 changes in proportion to the square of the DC voltage applied to the capacitor 3 as described above, and the aforementioned DC voltage upper limit value Vmax and DC voltage lower limit value Vmin. In this range, the charge amount of the capacitor 3 is appropriately controlled. In particular, the charging voltage (DC voltage detection value) Vsenc of the capacitor 3 detected in the DC system is compared with the DC voltage upper limit value Vmax (first determination function 7a), and the DC voltage detection value Vsenc is better. If it is high, it is determined that the DC voltage is excessively accumulated in the capacitor 3, and the AC / DC converter 2 is in a power regeneration operation (power regeneration operation function 7b). By this power regeneration operation of the AC / DC converter 2, excess DC power accumulated in the capacitor 3 is converted into AC power and regenerated (returned) to the external power source 1.

  Further, when the charging voltage (DC voltage detection value) Vsenc of the capacitor 3 is lower than the DC voltage upper limit value Vmax, the power supply controller 7 determines the charging voltage (DC voltage detection value) Vsenc and the DC voltage lower limit value described above. Vmin is compared (second determination function 7c). When the DC voltage detection value Vsenc is less than the DC voltage lower limit value Vmin, it is determined that the charge amount of the capacitor 3 is significantly insufficient, and the AC / DC converter 2 is operated to supply power. (Power supply operation function 7d). By this power supply operation, power is supplied from the external power source 1 to the capacitor 3, and the voltage of the capacitor 3 is prevented from dropping to a voltage that the AC / DC converter 2 cannot control.

  When the charging voltage (DC voltage detection value) Vsenc of the capacitor 3 is within the range of the DC voltage upper limit value Vmax and the DC voltage lower limit value Vmin described above (determination functions 7a and 7c), the power supply controller 7 In order to compensate for the amount of power consumed by the drive, the AC / DC converter 2 is operated to supply power under a predetermined current limit (power supply operation function 7e). In this power supply operation with current limitation, the DC voltage detection value Vsenc is set to, for example, a preset DC voltage in order to store the power corresponding to the amount of power (required power) required for driving the load 4 in the capacitor 3. The process is executed until the set value Vfix is reached. The DC voltage set value Vfix can be set as the above-described DC voltage upper limit value Vmax in anticipation of an amount of power necessary and sufficient for driving the load 4.

  Specifically, the power supply control unit 7 first determines whether or not the operating condition is satisfied as shown in a schematic control procedure in FIG. 3 (step S1). If the operating condition is satisfied, as the initial setting process, the DC / DC converter 2 takes in a preset DC voltage set value Vfix to be output and is detected by a sensor (voltmeter) (not shown). The detected DC voltage (charge voltage of the capacitor 3) is taken in the DC voltage detection value Vsenc <step S2>. At this time, the current limit value Isup at the time of power supply in the AC / DC converter 2 and the current limit value Ireg at the time of power regeneration are taken in, respectively, and the output voltage range that guarantees the operating characteristics of the AC / DC converter 2 is further obtained. A DC voltage upper limit value Vmax and a DC voltage lower limit value Vmin shown in FIG.

  The current limit values Isup and Ireg at the time of power supply and power regeneration may be arbitrarily set within the allowable maximum current range determined by the specifications of the AC / DC converter 2. Further, the DC voltage set value Vfix can be fixedly set to the DC voltage upper limit value Vmax so as to store the maximum amount of electric power in the capacitor 3 within a range in which the operating characteristics of the AC / DC converter 2 are guaranteed. Further, as will be described later, it can be variably set according to the driving condition of the load 4.

  Thereafter, the power supply controller 7 first compares the DC voltage setting value Vfix and the DC voltage detection value Vsenc to determine whether or not the required amount of power is stored in the capacitor 3 <Step S3>. . When it is confirmed that the DC voltage detection value Vsenc is equal to the DC voltage setting value Vfix and the required amount of power is stored in the capacitor 3, the control on the AC / DC converter 2 is stopped and Return <Step S4>.

  On the other hand, if the DC voltage setting value Vfix and the DC voltage detection value Vsenc are different, it is determined whether or not the DC voltage detection value Vsenc is higher than the DC voltage setting value Vfix <step S5>. When the DC voltage detection value Vsenc is higher than the DC voltage setting value Vfix, it is determined that the capacitor 3 stores more power than the desired amount of power, so that the AC / DC converter 2 is powered. Regenerative operation. At this time, it is determined whether or not the DC voltage detection value Vsenc exceeds the DC voltage upper limit value Vmax <step S6>. If the DC voltage detection value Vsenc is high, the power stored excessively in the capacitor 3 is determined. In order to quickly recover the energy to the external power source 1, the AC / DC converter 2 is released from the above-described current limitation and the power regeneration operation is performed (step S7). However, when the DC voltage detection value Vsenc is low, the AC / DC converter 2 is set to a constant current under the current limit value Ireg described above in order to gradually recover the charging power of the capacitor 3 to the external power source 1. The power regeneration operation is performed at <Step S8>.

  On the other hand, when the DC voltage detection value Vsenc is lower than the DC voltage setting value Vfix, it is determined that the desired amount of electric power is not stored in the capacitor 3, so the AC / DC converter 2 Power supply operation. At this time, it is determined whether or not the DC voltage detection value Vsenc is less than the DC voltage lower limit value Vmin <step S9>. If the DC voltage detection value Vsenc is less than the DC voltage lower limit value Vmin, the capacitor 3 In order to quickly charge the amount of charge to the range in which the operating characteristics of the AC / DC converter 2 are guaranteed, the AC / DC converter 2 is released from the above-described current restriction and is operated for power supply (step S10). However, when the DC voltage detection value Vsenc exceeds the DC voltage lower limit value Vmin, the AC / DC converter 2 is set to the current limit value Isup described above in order to gradually charge the capacitor 3 to a desired charge amount. A power supply operation is performed at a constant current under the current limit (step S11).

  That is, the DC voltage detection value Vsenc in the DC system that is the charging voltage of the capacitor 3 is within the range of the DC voltage upper limit value Vmax and the DC voltage lower limit value Vmin that can control the charge amount of the capacitor 3 by the AC / DC converter 2. In some cases, according to the voltage relationship with the DC voltage setting value Vfix that controls the charge amount of the capacitor 3, the AC / DC converter 2 is operated to supply power or regenerate under the above-mentioned current limiting conditions, and the capacitor 3 The charge amount is controlled to be constant. However, when the DC voltage detection value Vsenc exceeds the DC voltage upper limit value Vmax and the charge amount of the capacitor 3 is excessive, the AC / DC converter 2 is forcibly regenerated and the excess power energy is supplied to the external power source 1. When the DC voltage detection value Vsenc is less than the DC voltage lower limit value Vmin, the voltage (charge amount) of the capacitor 3 is reduced to a voltage that the AC / DC converter 2 cannot control. In order to prevent this, the AC / DC converter 2 is forcibly supplied with power.

  Thus, according to the operation control of the AC / DC converter 2 as described above, the DC voltage detection value Vsenc in the DC system exceeds the DC voltage upper limit value Vmax, and the amount of power to be stored in the capacitor 3 is changed to the AC / DC converter. Since the AC / DC converter 2 is regeneratively operated so that 2 does not exceed the charge amount of the controllable capacitor 3, surplus power in the DC system can be effectively returned to the external power source 1 to recover the power. . Further, when the DC voltage detection value Vsenc in the DC system is less than the DC voltage lower limit value Vmin, the capacitor 3 is charged with the electric power from the external power source 1 by operating the AC / DC converter 2 to supply power. The charging amount (accumulated electric power amount) of the capacitor 3 can be quickly charged to a range in which the operating characteristics of the AC / DC converter 2 are guaranteed.

  In addition, the capacitor 3 is charged with a constant current or a constant amount of power by the power supply operation with the current limitation of the AC / DC converter 2 within the range of the DC voltage upper limit value Vmax and the DC voltage lower limit value Vmin described above. Therefore, it is possible to power-run and regenerate the load 4 while steadily supplementing the capacitor 3 with the power consumption associated with the driving of the load 4.

  Furthermore, it is possible to stably control the amount of power stored in the capacitor 3 in consideration of the amount of power required to drive the load 4 and the amount of regenerative power obtained from the load 4. Then, the power consumed by driving the load 4 by the load driving device is supplied with constant current or constant power to optimize the charging flow of the capacitor 3, and the surplus power stored in the capacitor 3 is efficiently supplied to the external power source 1. Can be regenerated. Therefore, effects such as the ability to effectively reduce the power consumption as the load driving device can be achieved.

  The present invention is not limited to the embodiment described above. For example, the DC voltage set value Vfix described above may be variably set according to the operating state of the load 4. Specifically, when a load is moved (lifted) to a high place using a crane, it is necessary to power-run (wind up) the electric motor as the load 4. Accordingly, the amount of electric power required for the power running drive is predicted, and the DC voltage set value Vfix is set higher in the range of the DC voltage upper limit value Vmax and the DC voltage lower limit value Vmin so as to secure the electric energy in the capacitor 3 in advance. Set.

  In addition, when unloading a load from a high place using the crane, the regenerative electric power can be obtained from the load (electric) 4 because the vehicle is lowered (rewinded) while being braked by an electric motor against the weight of the load. . Therefore, the DC voltage set value Vfix is previously set to the DC voltage upper limit value Vmax and the DC voltage lower limit value Vmin so that the electric energy obtained by the regenerative operation can be predicted and the regenerative power can be reliably stored in the capacitor 3. The power amount stored in the capacitor 3 is regenerated to the external power source 1. Then, it is sufficient that the capacitor 3 has a surplus power that can accumulate the electric power regenerated from the load 4.

  In addition, for overhead cranes installed in factories, etc., the basic operation is to lift the load, move it to another location, and then drop the load to that location. The amount of regenerative electric power obtained at the time of the lowering operation is predicted, and the amount of power to be stored in the capacitor 3 is determined in consideration of the power running power amount and the regenerative power amount input to and output from the load 4. The DC voltage set value Vfix may be set.

  Moreover, although driving | operation of elevators, such as a crane and a lifter, was demonstrated here as an example, if regenerative electric power is obtained from the load 4, it can apply similarly. Specifically, the load 4 can be accelerated and decelerated, powering energy can be consumed during acceleration, and the drive can be similarly used for driving a load that can recover regenerative energy during deceleration. Specific examples of elevators include container transfer (transport) cranes in port facilities, jib climbing cranes used in building construction, stacker cranes in automatic warehouses, and lifters in mechanical multilevel parking lots. . In addition, the present invention can be variously modified and implemented without departing from the scope of the invention.

The block diagram which shows the principal part schematic structure of the load drive device which concerns on one Embodiment of this invention. The figure which shows the processing concept of the electric power supply to the capacitor | condenser for demonstrating one Embodiment of this invention, and the electric power regeneration from the said capacitor | condenser. The figure which shows the example of the operation control procedure of the alternating current and direct current | flow inverter in the load drive device which concerns on one Embodiment of this invention.

Explanation of symbols

1 External power supply 2 AC / DC converter 3 Capacitor (electric double layer capacitor)
4 Load (motor)
5 Inverter 6 Load controller 7 Power supply controller 7a First determination function 7b Power regeneration operation function 7c Second determination function 7d Power supply operation function 7e Power supply operation function (with current limit)

Claims (4)

An AC / DC converter having a function of converting AC power supplied from an external power source into DC power, and a function of converting DC power into AC power and regenerating the external power source;
A capacitor for storing the DC power output from the AC / DC converter;
The DC power stored in the capacitor and / or the DC power output from the AC / DC converter is converted to AC power with a controlled voltage and frequency to drive the load, and the regenerative power generated in the load An inverter that collects and accumulates in the capacitor,
The controller for controlling the operation of the AC / DC converter is:
When the DC voltage detection value on the DC side of the AC / DC converter is between a preset DC voltage upper limit value and a DC voltage lower limit value, the power from the external power source is within a predetermined current value limit value range. Let the supply run,
When the DC voltage detection value is greater than the DC voltage upper limit value, cancel the current value limit and perform power regeneration operation to the external power source,
When the DC voltage detection value is smaller than the DC voltage lower limit value, the load value driving device is configured to cancel the current value limitation and perform the power supply operation from the external power source.   The load driving device according to claim 1, wherein the current value limit value is set in advance as a value equal to or less than a maximum allowable current of the AC / DC converter.   The DC voltage upper limit value is a voltage value that defines the maximum charge capacity of the capacitor that guarantees the operating characteristics of the AC / DC converter, and the DC voltage lower limit value guarantees the operating characteristics of the AC / DC converter. The load driving device according to claim 1, wherein the load driving device has a voltage value defining a minimum charging capacity of the capacitor.   The load driving device according to claim 1, wherein the capacitor is an electric double layer capacitor, and the load is an electric motor that drives an elevator.

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