JP6671853B2 - Power conversion device and industrial machine using the same - Google Patents

Description

  The present invention relates to a power converter.

  Power conversion devices are used for industrial machines such as cranes and hybrid shovels. FIG. 1 is a block diagram illustrating an electric 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 and rotates the motor 206 during the power running operation. During the regenerative operation of the motor 206, the inverter 204 rectifies the current from the motor 206 and supplies the rectified current to the power converter 100R. The power 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.

  Power conversion device 100R is provided between power storage device 200, generator 202, and inverter 204, and appropriately converts a 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 C1 is connected to the DC link bus 102. The step-down side terminal of engine converter 120 is connected to generator 202, and the step-up side terminal is connected to DC link bus 102. Engine converter 120 boosts the DC voltage from generator 202 and stabilizes the voltage of DC link bus 102 (DC link voltage) to a predetermined level.

The step-down side terminal of the battery converter 104 is connected to the power storage device 200, and the step-up side terminal is connected to the DC link bus 102. Battery converter 104 operates as a boost converter during power running 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

In some applications, the DC link voltage _VDC is very high (eg, several hundred volts or more). Therefore, when the power conversion device 100R is not operating, if the charge of the smoothing capacitor C1 remains, it is dangerous because the high DC link voltage _VDC is maintained.

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

On the other hand, discharge resistor R1 always forms a discharge path of smoothing capacitor C1 even during operation of power conversion device 100R. Therefore, useless 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 An advantage of some aspects of the invention is to provide a power conversion device for industrial machines with reduced power consumption.

  One embodiment of the present invention relates to a power conversion device used for an industrial machine including a motor, an inverter, and a power storage device. The power converter includes a DC link bus, a smoothing capacitor connected to the DC link bus, a step-up terminal connected to the DC link bus, a step-down terminal connected to the power storage device, and a reactor and a switching element. A first step-up / down converter, a discharge resistor and a discharge switch provided in series on a path parallel to the smoothing capacitor, and an internal control power supply for receiving a DC link voltage generated on a DC link bus and generating a first power supply voltage. A discharge controller supplied with a first power supply voltage from an internal control power supply and controlling a discharge switch.

  According to this aspect, the discharge path can be cut off by turning off the discharge switch during normal operation, so that useless power consumption can be reduced. Further, since the power supply of the discharge controller for controlling the discharge switch is generated based on the DC link voltage, the discharge controller is reliably operated during the period when the discharge switch is to be turned on, that is, in a state where the DC link voltage is somewhat high. be able to. As a result, the DC link voltage can be reliably reduced to the safe voltage or less.

The power converter may further include an external control power supply that is externally supplied with power and generates the 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 converter may further include a second step-up / step-down converter having a step-up side terminal connected to the DC link bus and a step-down side terminal connected to a generator using the engine as a power source.

The discharge controller may turn on the discharge switch when the motor performs the regenerative operation in the stop state of the first buck-boost converter.
This can prevent the DC link voltage from becoming overvoltage.

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

  It should be noted that any combination of the above-described components, and any replacement of the components and expressions of the present invention between methods, apparatuses, systems, and the like are also effective as embodiments of the present invention.

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

FIG. 2 is a block diagram illustrating an electric system of an industrial machine. It is a block diagram of a power converter concerning an embodiment. FIG. 3 is an operation waveform diagram of the power converter of FIG. 2.

  Hereinafter, the present invention will be described based on preferred embodiments with reference to the drawings. The same or equivalent components, members, and processes shown in each drawing are denoted by the same reference numerals, and the repeated description will be omitted as appropriate. In addition, 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 physically directly connected, and that the member A and the member B It does not substantially affect the actual connection state, or does not impair the function or effect exerted by the combination thereof, and also includes the case where the connection is made indirectly via another member.
Similarly, “the state in which the member C is provided between the member A and the member B” means that the member A and the member C or the member B and the member C are directly connected, It does not substantially affect the actual connection state, or does not impair the function or effect exerted by the combination thereof, and also includes the case where the connection is made indirectly via another member.

  FIG. 2 is a block diagram of the power converter 100 according to the embodiment. The power conversion device 100 uses an electric system similar to that shown in FIG. 1 for an industrial machine. As described later, a crane or a hybrid shovel is preferable as the industrial machine. The power conversion device 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, connected to the tertiary side) connected to the DC link bus 102. ) Can be transmitted and received.

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

  The power conversion device 100 includes a DC link bus 102, a smoothing capacitor C1, a battery converter 104 as a first buck-boost 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 buck-boost converter.

A smoothing capacitor C1 is connected to the DC link bus 102, to smooth and stabilize 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 M1 and M2 of engine converter 120 are controlled by converter controller 122.

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

Converter controller 106 controls switching elements M1 and M2 of battery converter 104. Converter controller 106 operates upon receiving power supply voltage _VDD3 generated by control power supply 108.

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

The discharge resistor R1 and the discharge switch SW1 are provided in series on a path parallel to the smoothing capacitor C1, in other words, between the DC link bus 102 and the ground line 103. The internal control power supply 110 is provided separately from the control power supply 108, receives the DC link voltage _VDC , and generates the first power supply voltage _VDD1 .

The discharge controller 112 receives the first power supply voltage _VDD1 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 device 100 is stopped. The discharge controller 112 turns on the discharge switch SW1 even when the power converter 100 is operating, when the power supply from the inverter or the engine converter 120 (not shown) to the DC link bus 102 is excessive, so that the discharge switch SW1 is turned on. Overshoot of 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. Therefore, the discharge controller 112 turns on the discharge switch SW1 when the motor performs the regenerative operation while the battery converter 104 is stopped. The discharge controller 112 may control the discharge switch SW1 in response to an external control command, or may monitor and monitor the states of the generator 202, the battery converter 104, the engine converter 120, the inverter, the motor, and the like. The discharge switch SW1 may be adaptively controlled based on the result.

The external control power supply 114 receives a supply of the power supply voltage _VEXT from the outside, and generates a 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.

The discharge controller 112, in addition to the first power supply voltage _{V DD1,} the second power supply voltage _{V DD2} may be capable of providing. 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 using one of the higher voltage levels as a power supply.

The above is the configuration of the power conversion device 100. Subsequently, the operation will be described.
FIG. 3 is an operation waveform diagram of the power converter 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.

Before time t0, power conversion device 100 is in the operating state, and DC link voltage _VDC is stabilized at predetermined voltage V _REF . During this time, the first power supply voltage _VDD1 generated by the internal control power supply 110 is supplied to the discharge controller 112, and the discharge switch SW1 can be controlled. Before time t0, the discharge controller 112 has turned off the discharge switch SW1, so that the discharge path 130 is shut off, and wasteful power consumption is suppressed.

At time t0, the generator 202 stops, and the power conversion device 100 also stops. When the power conversion device 100 is stopped, both the engine converter 120 and the battery converter 104 stop. In response to this, the discharge controller 112 turns on the discharge switch SW1. As a result, the charge of the smoothing capacitor C1 is discharged via 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 _VDC 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 cannot control the discharge switch SW1, and the on / off state of the discharge switch SW1 is undefined. The DC link voltage _VDC becomes unstable in a range lower than the safe voltage V _SAFE , and gradually decreases due to a leak current.

The above is the operation of the power conversion device 100. Subsequently, the effect will be described.
First, according to the power converter 100, the discharge path 130 can be cut off by turning off the discharge switch SW1 during a normal operation, so that wasteful power consumption can be reduced.

Second, the power supply of the discharge controller 112 that controls the discharge switch SW1 is generated based on the DC link voltage _VDC . Here, the safe 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.}

Therefore, during a period in which the discharge switch SW1 is to be turned on, that is, in a state where the DC link voltage _VDC is higher than the safe voltage V _SAFE , the discharge controller 112 can be reliably operated. Thus, the DC link voltage _VDC can be reliably reduced to the safe voltage V _SAFE or less.

  The second advantage is clarified by comparison with the comparative technique. As a comparative technique, a configuration in which a voltage originating from the generator 202 is supplied as a power supply voltage of the discharge controller 112 will be considered. In this configuration, when the generator 202 is stopped, that is, when the power converter 100 is stopped, the power supply voltage is not supplied to the discharge controller 112, so that the discharge switch SW1 cannot be turned on.

  As another comparative technique, a configuration in which a voltage derived from a commercial AC voltage is supplied as a power supply voltage of the discharge controller 112 will be considered. In this configuration, when no commercial AC voltage is supplied, the power supply voltage is not supplied to the discharge controller 112, so that the discharge switch SW1 cannot be turned on.

In contrast to these comparative techniques, according to the power converter 100 according to the embodiment, the first power supply voltage _VDD1 originating from the DC link voltage _VDC is supplied to the discharge controller 112, so The discharge switch SW1 can be turned on.

(Application)
Next, applications of the power conversion device 100 will be described. The power conversion device 100 is used for a crane that is one of the industrial machines. The crane has the electric 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, and at this time, the engine converter 120 and the battery converter 104 perform a boost operation to supply power to the inverter. On the other hand, when the crane is lowered, the motor 206 performs 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 collected in the power storage device 200.

  During the operation of the power converter 100, the power consumption is reduced by turning off the discharge switch SW1. However, even in the operation of the power converter 100, if the battery converter 104 breaks down or stops under control during the lowering operation, the discharge switch SW1 is turned on. This can prevent an excessive voltage from being generated on the DC link bus 102 and protect circuit components such as the smoothing capacitor C1.

  In another embodiment, the power conversion device 100 is used in a hybrid shovel that is one of industrial machines. The hybrid shovel 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, and at this time, the engine converter 120 and the battery converter 104 perform a boost operation to supply power to the inverter. On the other hand, at the time of turning braking, motor 206 performs regenerative operation. At this time, engine converter 120 stops, battery converter 104 performs a step-down operation, and recovers regenerative energy to power storage device 200.

  Also in the shovel, during the operation of the power converter 100, the power consumption is reduced by turning off the discharge switch SW1. However, even in the operation of the power converter 100, if the battery converter 104 breaks down during turning deceleration, or if the battery converter 104 is intentionally stopped to protect the circuit, the discharge switch SW1 is turned on. . This can prevent an excessive voltage from being generated on the DC link bus 102 and protect circuit components such as the smoothing capacitor C1.

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

  The present invention has been described based on the embodiments. It is understood by those skilled in the art that the present invention is not limited to the above embodiment, and that various design changes are possible, various modifications are possible, and such modifications are also 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. Thus, 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 replacing the cable. Further, the external control power supply 114 may be omitted.

(Second Modification)
The converter controller 106 operates the battery converter 104 as a boost converter having the DC link bus 102 side as an output and the power storage device 200 side as an input, boosting the battery voltage V _BAT , and supplying power to the DC link bus 102. The DC link voltage _VDC may be increased. Further, instead of engine converter 120, an inverter that drives a motor or the like or recovers a regenerative current from the motor to smoothing capacitor C1 may be provided.

  Although the present invention has been described using specific words and phrases based on the embodiments, the embodiments are merely illustrative of the principles and applications of the present invention, and the embodiments are defined in the appended claims. Many modifications and changes in arrangement may be made without departing from the spirit of the present invention.

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, Reference numeral 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 generator,
A converter for converting the output of the generator into a DC voltage,
A DC link connected to the converter;
A smoothing capacitor connected to the DC link;
A discharge resistor and a discharge switch connected in series, connectable to the DC link;
A step-up / step-down converter having a step-up side terminal connected to the DC link and a step-down side terminal connected to the power storage device;
A controller that controls the discharge switch with the voltage of the DC link as a power supply voltage, provided that at least one of the generator, the converter, and the buck-boost converter is stopped;
An industrial machine comprising: And wherein the converter, both of the buck-boost converter stops, said converter, said electric power to said DC link from the buck-boost converter for controlling the discharge switch a voltage of the DC link state is not supplied as a power supply voltage The industrial machine according to claim 1, wherein: A power conversion device used for an industrial machine including a motor, an inverter, and a power storage device,
A DC link bus;
A smoothing capacitor connected to the DC link bus;
A first step-up / down converter including 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 on a path parallel to the smoothing capacitor;
An internal control power supply that receives a DC link voltage generated on the DC link bus and generates a first power supply voltage;
A discharge controller supplied with the first power supply voltage from the internal control power supply and controlling the discharge switch;
A power conversion device comprising: An external control power supply that is externally supplied with power and generates a second power supply voltage;
The power converter according to claim 3, wherein the discharge controller is operable by receiving one of the first power supply voltage and the second power supply voltage.   5. The power converter according to claim 3, wherein the discharge controller turns on the discharge switch when the motor performs a regenerative operation while the first buck-boost converter is stopped. 6.

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