JP2016187284A - Power conversion device and industrial machine using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conversion device capable of suppressing power consumption.SOLUTION: A smoothing capacitor is connected with a DC link bus 102. A battery converter 104 is connected with the DC link bus 102 and includes a reactor L1 and a switching element. A discharge switch SW1 and a discharge resistance R1 are provided in series to a path in parallel to the smoothing capacitor C1. An internal control power supply 110 receives a DC link voltage Vgenerated by the DC link bus 102 to generate a first power supply voltage V. A discharge controller 112 receives a first power supply voltage Vfrom the internal control power supply 110 to control the discharge switch SW1.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a power conversion device.

  Power conversion devices are used in industrial machines such as cranes and hybrid excavators. FIG. 1 is a block diagram showing an electrical system of the industrial machine 10. The industrial machine includes a power conversion device 100R, a power storage device 200, a generator 202, an inverter 204, and a motor 206.

  The inverter 204 supplies electric power to the motor 206 during the power running operation and rotates it. In addition, during the regenerative operation of the motor 206, the inverter 204 rectifies the current from the motor 206 and supplies it to the power conversion device 100R. The electricity storage device 200 is a secondary battery such as a lithium ion battery, or an electric double layer capacitor. The generator 202 generates electric power according to the rotation of the engine.

  The power conversion device 100R is provided between the power storage device 200, the generator 202, and the inverter 204, and appropriately converts the voltage level among them. The power conversion device 100R includes a DC link bus 102, a battery converter 104, an engine converter 120, a smoothing capacitor C1, and a discharge resistor R1.

  The smoothing capacitor C <b> 1 is connected to the DC link bus 102. The step-down terminal of engine converter 120 is connected to generator 202, and the step-up terminal is connected to DC link bus 102. The engine converter 120 boosts the direct current voltage from the generator 202 and stabilizes the voltage of the DC link bus 102 (DC link voltage) at a predetermined level.

The step-down terminal of battery converter 104 is connected to power storage device 200, and the step-up terminal is connected to DC link bus 102. Battery converter 104 operates as a boost converter during powering operation of motor 206 and boosts voltage V _BAT of power storage device 200. The battery converter 104 operates as a step-down converter during the regenerative operation of the motor 206, recovers energy from the DC link bus 102 to the power storage device 200, and stabilizes the DC link voltage _VDC .

JP 2008-254830 A

Depending on the application, the DC link voltage V _DC is very high (eg, several hundred volts or more). Therefore, when the electric power converter 100R is not operating, if the electric charge of the smoothing capacitor C1 remains, it is dangerous because the high voltage of the DC link voltage _VDC is maintained.

Therefore, a discharge resistor R1 is inserted in parallel with the smoothing capacitor C1. When the operation of the power conversion device 100R stops, the electric charge of the smoothing capacitor C1 is discharged through the discharge resistor R1, and the DC link voltage V _DC decreases to the safe voltage V _SAFE (for example, 60 V or less). Further, the discharge resistor R1 suppresses the smoothing capacitor C1 from exceeding the allowable voltage level when the battery converter 104 is in a regenerative operation and excessive power is supplied from the inverter 204.

On the other hand, the discharge resistor R1 always forms the discharge path of the smoothing capacitor C1 even during the operation of the power conversion device 100R. Therefore, wasteful power (P = R × I _DIS ² = V _DC ² / R) is always consumed by the discharge resistor R1, which is against the demand for energy saving.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and one of the exemplary objects of an aspect thereof is to provide a power conversion device for industrial machines with reduced power consumption.

  An aspect of the present invention relates to a power conversion device used in an industrial machine including a motor, an inverter, and an electricity storage device. The power conversion device includes a DC link bus, a smoothing capacitor connected to the DC link bus, a boost side terminal connected to the DC link bus, a step down side terminal connected to the power storage device, a reactor and a switching element. A first step-up / down converter including a discharge resistor and a discharge switch provided in series on a path parallel to the smoothing capacitor, and an internal control power supply that receives a DC link voltage generated in the DC link bus and generates a first power supply voltage. A discharge controller that is supplied with a first power supply voltage from the internal control power supply and controls the discharge switch.

  According to this aspect, since the discharge path can be cut off by turning off the discharge switch during normal operation, wasteful power consumption can be reduced. In addition, since the power source of the discharge controller that controls the discharge switch is generated based on the DC link voltage, the discharge controller is reliably operated in a period during which the discharge switch should be turned on, that is, in a state where the DC link voltage is high to some extent. be able to. As a result, the DC link voltage can be reliably reduced to a safe voltage or less.

The power conversion device may further include an external control power supply that is supplied with power from outside and generates a second power supply voltage. The discharge controller may be operable by receiving one of the first power supply voltage and the second power supply voltage.
By multiplexing the power supply to the discharge controller, the discharge switch can be controlled more reliably.

  The power conversion device may further include a second step-up / step-down converter whose boost side terminal is connected to the DC link bus and whose buck side terminal is connected to a generator that uses the engine as a power source.

The discharge controller may turn on the discharge switch when the motor performs a regenerative operation when the first step-up / down converter is stopped.
Thereby, it is possible to prevent the DC link voltage from becoming an overvoltage.

  Another aspect of the present invention relates to an industrial machine. The industrial machine includes a motor, an inverter, an electricity storage device, and any one of the above-described power conversion devices.

  Note that any combination of the above-described constituent elements and the constituent elements and expressions of the present invention replaced with each other among methods, apparatuses, systems, and the like are also effective as an aspect of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the power consumption of a power converter device can be reduced.

It is a block diagram which shows the electric system of an industrial machine. It is a block diagram of the power converter device concerning an embodiment. It is an operation | movement waveform diagram of the power converter device of FIG.

  The present invention will be described below based on preferred embodiments with reference to the drawings. The same or equivalent components, members, and processes shown in the drawings are denoted by the same reference numerals, and repeated descriptions are omitted as appropriate. The embodiments do not limit the invention but are exemplifications, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

In this specification, “the state in which the member A is connected to the member B” means that the member A and the member B are electrically connected to each other in addition to the case where the member A and the member B are physically directly connected. It includes cases where the connection is indirectly made through other members that do not substantially affect the general connection state, or that do not impair the functions and effects achieved by their combination.
Similarly, “the state in which the member C is provided between the member A and the member B” refers to the case where the member A and the member C or the member B and the member C are directly connected, as well as their electric It includes cases where the connection is indirectly made through other members that do not substantially affect the general connection state, or that do not impair the functions and effects achieved by their combination.

  FIG. 2 is a block diagram of the power conversion apparatus 100 according to the embodiment. In the power conversion apparatus 100, an electrical system similar to FIG. 1 is used for an industrial machine. As will be described later, cranes and hybrid excavators are suitable as industrial machines. The power conversion apparatus 100 includes a generator 202 connected to the primary side P, a power storage device 200 connected to the secondary side S, and an inverter and a motor (not shown, a tertiary side connected to the DC link bus 102). Energy).

  For example, a generator 202 driven by an engine and a rectifier circuit 203 that rectifies an AC voltage generated by the generator 202 are connected to the primary side P. Further, the secondary side S is connected to the power storage device 200. The electricity storage device 200 is, for example, a secondary battery such as lithium ion or a capacitor such as an electric double layer capacitor.

  The power conversion apparatus 100 includes a DC link bus 102, a smoothing capacitor C1, a battery converter 104 that is a first step-up / step-down converter, a converter controller 106, a control power supply 108, a discharge resistor R1, a discharge switch SW1, a discharge controller 112, and an internal control power supply. 110, an external control power supply 114, and an engine converter 120 as a second step-up / down converter.

The smoothing capacitor C1 is connected to the DC link bus 102, and smoothes and stabilizes the voltage (DC link voltage) V _DC of the DC link bus 102.

The engine converter 120 has a step-up terminal A connected to the DC link bus 102 and a step-down terminal B connected to the rectifier circuit 203. Engine converter 120 receives the DC voltage _{V P} of the rectifying circuit 203 boosts it, stabilizes the DC link voltage _{V DC} of the DC link bus 102 to a predetermined target voltage _{V REF.} Engine converter 120 includes a reactor L1, switching elements M1, M2, and a smoothing capacitor C2. Switching elements M 1 and M 2 of engine converter 120 are controlled by converter controller 122.

  The battery converter 104 has a step-up terminal A connected to the DC link bus 102 and a step-down terminal B connected to the power storage device 200. Battery converter 104 is configured in the same manner as engine converter 120. The smoothing capacitor C2 may be omitted.

Converter controller 106 controls switching elements M <b> 1 and M <b> 2 of battery converter 104. Converter controller 106 operates in response to power supply voltage V _DD3 generated by control power supply 108.

Converter controller 106 operates as a boost converter during powering operation of the motor, and boosts voltage V _BAT of power storage device 200 to stabilize DC link voltage V _DC . That is, the supply from the engine converter 120 to the inverter is assisted. On the contrary, the converter controller 106 operates as a step-down converter during the regenerative operation of the motor, recovers energy from the DC link bus 102 to the power storage device 200, and stabilizes the DC link voltage _VDC .

Discharge resistor R1 and discharge switch SW1 are provided in a path parallel to smoothing capacitor C1, in other words, in series between DC link bus 102 and ground line 103. The internal control power supply 110 is provided separately from the control power supply 108 and receives the DC link voltage V _DC and generates the first power supply voltage V _DD1 .

The discharge controller 112 receives the first power supply voltage V _DD1 from the internal control power supply 110 and controls the discharge switch SW1. Specifically, the discharge controller 112 turns on the discharge switch SW1 when the operation of the power conversion apparatus 100 is stopped. In addition, even when the power conversion apparatus 100 is in operation, the discharge controller 112 turns on the discharge switch SW1 when the power supply from the inverter (not shown) or the engine converter 120 to the DC link bus 102 is excessive, and the DC link The overshoot of the voltage _VDC may be suppressed. For example, when the motor performs a regenerative operation while the battery converter 104 is stopped, the power supply to the DC link bus 102 becomes excessive. Accordingly, the discharge controller 112 turns on the discharge switch SW1 when the motor performs a regenerative operation while the battery converter 104 is stopped. The discharge controller 112 may control the discharge switch SW1 according to a control command from the outside, or monitors the state of the generator 202, the battery converter 104, the engine converter 120, the inverter, the motor, and the like by itself. The discharge switch SW1 may be controlled adaptively based on the result.

The external control power supply 114 receives the supply of the power supply voltage _VEXT from the outside and generates the second power supply voltage _VDD2 . External supply voltage V _EXT may be a DC voltage V _P of the rectifying circuit 203 generates may be a commercial AC voltage supplied from the outside, its origin is not particularly limited.

In addition to the first power supply voltage V _DD1 , the second power supply voltage V _DD2 may be supplied to the discharge controller 112. For example, the discharge controller 112 may be supplied with two power supply voltages V _DD1 and V _DD2 via the diode OR circuit 116, and may operate with one of the higher voltage levels as a power source.

The above is the configuration of the power conversion apparatus 100. Next, the operation will be described.
FIG. 3 is an operation waveform diagram of the power conversion apparatus 100 of FIG. Here, the second power supply voltage V _DD2 from the external control power supply 114 is not supplied to the discharge controller 112, and the first power supply voltage V _DD1 is supplied to the discharge controller 112.

Prior to time t0, the power conversion apparatus 100 is in an operating state, and the DC link voltage V _DC is stabilized at the predetermined voltage V _REF . During this time, the first power supply voltage V _DD1 generated by the internal control power supply 110 is supplied to the discharge controller 112 so that the discharge switch SW1 can be controlled. Prior to time t0, the discharge controller 112 has turned off the discharge switch SW1, so that the discharge path 130 is cut off and wasteful power consumption is suppressed.

At time t0, the generator 202 is stopped and the power conversion apparatus 100 is also stopped. In the stop state of power conversion device 100, both engine converter 120 and battery converter 104 are stopped. In response to this, the discharge controller 112 turns on the discharge switch SW1. As a result, the electric charge of the smoothing capacitor C1 is discharged through the discharge path 130 including the discharge resistor R1 and the discharge switch SW1, and the DC link voltage _VDC decreases with time. Eventually, at time t1, the DC link voltage V _DC becomes equal to or lower than the safe voltage V _SAFE that does not cause harm even if the human body contacts the DC link bus 102.

When the DC link voltage V _DC further decreases, the first power supply voltage V _DD1 generated by the internal control power supply 110 starts to decrease, and at time t2, the first power supply voltage V _DD1 falls below the minimum operating voltage V _LOW of the discharge controller 112. . After time t2, the discharge controller 112 becomes unable to control the discharge switch SW1, and the on / off state of the discharge switch SW1 becomes indefinite. The DC link voltage V _DC becomes indefinite in a range lower than the safety voltage V _SAFE and gradually decreases due to a leakage current.

The above is the operation of the power conversion apparatus 100. Next, the effect will be described.
First, according to the power conversion device 100, since the discharge path 130 can be cut off by turning off the discharge switch SW <b> 1 during normal operation, wasteful power consumption can be reduced.

Second, the power source of the discharge controller 112 that controls the discharge switch SW1 is generated based on the DC link voltage _VDC . Here, the safety voltage V _SAFE is about 60 V, and the minimum operating voltage V _LOW of the discharge controller 112 is about several V to about 20 V at most. Thus, the internal control power supply 110, while after the DC link voltage _{V DC} is lower than the safety voltage _{V SAFE} can maintain the first power supply voltage _{V DD1} to range higher than the minimum operating voltage _{V LOW.}

Accordingly, the discharge controller 112 can be reliably operated in a period during which the discharge switch SW1 is to be turned on, that is, in a state where the DC link voltage V _DC is higher than the safety voltage V _SAFE . As a result, the DC link voltage V _DC can be surely lowered to the safety voltage V _SAFE or lower.

  The second advantage becomes clear by comparison with the comparative technique. As a comparative technique, consider a configuration in which a voltage originating from the generator 202 is supplied as the power supply voltage of the discharge controller 112. In this configuration, when the generator 202 is stopped, that is, when the power conversion apparatus 100 is stopped, the power supply voltage is not supplied to the discharge controller 112, and thus the discharge switch SW1 cannot be turned on.

  As another comparative technique, a configuration in which a voltage originating from a commercial AC voltage is supplied as the power supply voltage of the discharge controller 112 is considered. In this configuration, in a situation where the commercial AC voltage is not supplied, the power supply voltage is not supplied to the discharge controller 112, and thus the discharge switch SW1 cannot be turned on.

In contrast to these comparative techniques, according to the power conversion device 100 according to the embodiment, the first power supply voltage V _DD1 originating from the DC link voltage V _DC is supplied to the discharge controller 112, so that The discharge switch SW1 can be turned on.

(Use)
Then, the use of the power converter device 100 is demonstrated. The power conversion device 100 is used in a crane that is one of industrial machines. The crane has the electrical system shown in FIG. 1. For example, the motor 206 corresponds to a main winding motor for hoisting and lowering. When the crane is hoisted, the motor 206 performs a power running operation. At this time, the engine converter 120 and the battery converter 104 are boosted to supply electric power to the inverter. On the other hand, when the crane is lowered, the motor 206 is in a regenerative operation. At this time, the engine converter 120 is stopped, the battery converter 104 is stepped down, and the regenerative energy is recovered in the power storage device 200.

  During operation of the power conversion apparatus 100, the power consumption is reduced by turning off the discharge switch SW1. However, even in the operation of the power conversion device 100, when the battery converter 104 is broken down or stopped under control during the lowering operation, the discharge switch SW1 is turned on. As a result, it is possible to prevent an excessive voltage from being generated in the DC link bus 102 and to protect circuit components such as the smoothing capacitor C1.

  In another embodiment, the power conversion device 100 is used in a hybrid excavator that is one of industrial machines. The hybrid excavator also has the electric system shown in FIG. 1. For example, the motor 206 corresponds to a turning motor that rotates the upper turning body. At the time of turning, the motor 206 performs a power running operation. At this time, the engine converter 120 and the battery converter 104 are boosted to supply power to the inverter. On the other hand, at the time of turning braking, the motor 206 is in a regenerative operation. At this time, the engine converter 120 stops, the battery converter 104 performs a step-down operation, and the regenerative energy is recovered in the power storage device 200.

  Also in the shovel, power consumption is reduced by turning off the discharge switch SW1 during the operation of the power conversion apparatus 100. However, even in the operation of the power conversion device 100, if the battery converter 104 fails during turning deceleration or the battery converter 104 is intentionally stopped for circuit protection, the discharge switch SW1 is turned on. . As a result, it is possible to prevent an excessive voltage from being generated in the DC link bus 102 and to protect circuit components such as the smoothing capacitor C1.

  By mounting the power conversion device 100 according to the embodiment on such an industrial machine, energy efficiency can be improved and commercial value can be increased.

  In the above, this invention was demonstrated based on the Example. It will be understood by those skilled in the art that the present invention is not limited to the above-described embodiment, and various design changes are possible, various modifications are possible, and such modifications are within the scope of the present invention. By the way. Hereinafter, such modifications will be described.

(First modification)
The power conversion device 100 may include a switch or a selector instead of the diode OR circuit 116. Thereby, the power supply voltages V _DD1 and V _DD2 generated by the internal control power supply 110 and the external control power supply 114 may be selectively supplied to the discharge controller 112. Alternatively, the internal control power supply 110 and the external control power supply 114 may be selectable by cable replacement. Further, the external control power supply 114 may be omitted.

(Second modification)
The converter controller 106 operates the battery converter 104 as a step-up converter having the DC link bus 102 side as an output and the power storage device 200 side as an input, boosts the battery voltage V _BAT , supplies power to the DC link bus 102, The DC link voltage V _DC may be increased. Instead of engine converter 120, an inverter that drives an electric motor or the like or collects a regenerative current from the electric motor in smoothing capacitor C1 may be provided.

  Although the present invention has been described using specific terms based on the embodiments, the embodiments only illustrate the principles and applications of the present invention, and the embodiments are defined in the claims. Many variations and modifications of the arrangement are permitted without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 100 ... Power converter, 102 ... DC link bus, 104 ... Battery converter, 106 ... Converter controller, 108 ... Control power supply, 110 ... Internal control power supply, 112 ... Discharge controller, 114 ... External control power supply, 116 ... Diode OR circuit, DESCRIPTION OF SYMBOLS 120 ... Engine converter, 130 ... Discharge path, 200 ... Power storage device, 202 ... Generator, 203 ... Rectifier circuit, L1 ... Reactor, C1 ... Smoothing capacitor, M1, M2 ... Switching element, C2 ... Smoothing capacitor, R1 ... Discharge resistance , SW1 ... discharge switch, V _DD1 ... first power supply voltage, V _DD2 ... second power supply voltage.

Claims (5)

A power conversion device used in an industrial machine including a motor, an inverter, and a power storage device,
DC link bus,
A smoothing capacitor connected to the DC link bus;
A first step-up / step-down converter having a step-up side terminal connected to the DC link bus, a step-down side terminal connected to the power storage device, and including a reactor and a switching element;
A discharge resistor and a discharge switch provided in series in a path parallel to the smoothing capacitor;
An internal control power supply for receiving a DC link voltage generated in the DC link bus and generating a first power supply voltage;
A discharge controller that is supplied with the first power supply voltage from the internal control power supply and controls the discharge switch;
A power conversion device comprising: An external control power source that is externally powered and generates a second power supply voltage;
The power converter according to claim 1, wherein the discharge controller is operable by receiving one of the first power supply voltage and the second power supply voltage.   The boost-side terminal is connected to the DC link bus, and the step-down-side terminal is further provided with a second step-up / down converter connected to a generator using the engine as a power source. Power converter.   4. The power converter according to claim 1, wherein the discharge controller turns on the discharge switch when the motor performs a regenerative operation in a stopped state of the first step-up / down converter. 5. A motor, an inverter and an electricity storage device;
The power conversion device according to any one of claims 1 to 4,
An industrial machine characterized by comprising:

Images