JP4927655B2 - Buck-boost converter - Google Patents

Description

  The present invention relates to a step-up / step-down converter that includes a step-up switching element and a step-down switching element and performs control of power supply to a load and control of supply of regenerative power obtained from the load to a storage element.

Conventionally, a general buck-boost converter has been provided with a switch for cutting off power supply to a power source (see, for example, Patent Document 1). Such a switch is used not only to cut off the power supply from the buck-boost converter to the power source when a current exceeding a certain level flows, but also to disconnect (or remove) the power source from the buck-boost converter. It is done.
JP 2005-176567 A

  By the way, when opening the switch of such a step-up / step-down converter, arc discharge may occur due to the release of energy remaining in the reactor.

  Such arc discharge is particularly problematic when the power handled is particularly large. For example, the power control part of a so-called heavy machine such as a construction machine is much larger than that of a general application. In a buck-boost converter that requires a high voltage, problems such as damage to equipment due to arc discharge may become apparent.

  Then, an object of this invention is to provide the buck-boost converter which can isolate | separate a power supply safely.

  The buck-boost converter according to one aspect of the present invention is connected to a first terminal for transferring power to and from a motor that performs both power running operation and regenerative operation, and a power source that stores power supplied to the motor. A second terminal; a step-up switching element for controlling supply of electric power to the electric motor; a step-down switching element for controlling supply of regenerative electric power obtained from the electric motor to the power source; and a first terminal A reactor connected to a connection point of the step-up switching element and the step-down switching element, a switch provided between the second end of the reactor and the second terminal, and when the switch is opened, Current induction means for guiding a current discharged from the reactor to a DC bus connected to the first terminal.

  The current induction means is connected between the second end of the reactor and the negative terminal of the first terminal, and first rectification that rectifies current in a direction from the negative terminal to the second end of the reactor. An element and a second rectifying element that is disposed between the second end of the reactor and the DC bus and rectifies current in a direction from the second end of the reactor to the DC bus may be included.

  According to the present invention, it is possible to provide a specific effect that a buck-boost converter capable of safely disconnecting a power source even when a large amount of power is handled can be provided.

  Embodiments to which the buck-boost converter of the present invention is applied will be described below.

  FIG. 1 is a diagram schematically showing a circuit configuration of the buck-boost converter according to the present embodiment. This step-up / down converter receives power from a reactor 1, a step-up IGBT (Insulated Gate Bipolar Transistor) 2, a step-down IGBT 3, a power supply connection terminal 5 for connecting a capacitor 4 used as a power supply, and a motor 6. Output terminal 7, a smoothing capacitor 8 inserted in parallel with the pair of output terminals 7, a relay 9, a controller 11, and a protection circuit 12.

  1 shows a capacitor 4 as a power storage element used as a power source, the power storage element only needs to be a chargeable / dischargeable secondary battery. Further, the motor 6 connected to the output terminal 7 may be an electric motor capable of power running operation and regenerative operation.

  Reactor 1 has one end connected between boosting IGBT 2 and step-down IGBT 3 and the other end connected to power supply connection terminal 5. The smoothing capacitor 8 is inserted between the positive terminal and the negative terminal of the output terminal 7 to smooth the output voltage.

  The relay 9 is opened when the capacitor 4 as a power source is removed from the power source connection terminal 5. This relay 9 is driven by a controller 11.

  A DC bus 10 is provided between the positive terminal of the output terminal 7 and the motor 6.

  The protection circuit 12 includes two diodes 12 a and 12 b that are rectifying elements, and is a circuit for guiding a current discharged from the reactor 1 to the output terminal 7 when the relay 9 is opened. One end of the diode 12 a is connected to the negative terminal of the power supply connection terminal 5, and the other end is connected between the reactor 1 and the relay 9. The rectification direction is a direction that flows from one end to the other end.

  The diode 12b has one end connected between the reactor 1 and the relay 9, and the other end connected to the source terminal of the step-down IGBT 3 (and the positive terminal of the output terminal 7). The rectification direction is a direction that flows from one end to the other end.

  The buck-boost converter according to the present embodiment can be applied to, for example, a power supply control unit of a hybrid construction machine. As a specific example, a configuration in which the angle operation of the arm of the construction machine is driven and controlled by an electric motor, a mode in which a bucket link is electrically driven or a lifting magnet is electrified, or a driving device for an endless track for traveling Can be used for a power supply control unit in a form of electrification or hybridization.

  In these applications, for example, the voltage value of the capacitor 4 is about 100 to 300 V, the rated output voltage at the output terminal 7 is about 360 V, the rated output is about 20 kW, the instantaneous maximum output power is ± 60 kW, the rated current is ± 55 A, the instantaneous The maximum current is about ± 170A.

  Therefore, the reactor 1, the step-up IGBT 2, the step-down IGBT 3, the power connection terminal 5, the output terminal 7, the capacitor 8, and the relay 9 in the present embodiment are such as one step-up / down converter shown in FIG. It must be able to withstand the application.

  In addition, when the buck-boost converter according to the present embodiment is used in the power control unit of the hybrid construction machine as described above, the capacitor 4 is removed from the power connection terminal 5, for example, by the operator There are emergency cases in which the capacitor 4 is disconnected in order to avoid this failure, and cases in which the construction machine is brought to an emergency stop.

  The step-up IGBT 2 and the step-down IGBT 3 are PWM (Pulse Width Modulation) driven by a drive control unit (not shown). That is, a driving pulse voltage is applied to the gate terminals of the IGBTs 2 and 3 from the drive control unit. Such a control unit can be realized by either an electronic circuit or an arithmetic processing unit.

  In such a step-up / step-down converter, when a boosting operation is performed, the drive control unit applies a pulse voltage to the gate terminal of the boosting IGBT 2 and performs PWM driving, thereby boosting the voltage value of the capacitor 4 and reducing the voltage. Electric power is supplied to the motor 6 through a diode connected in parallel to the IGBT 3 for use.

  Further, when performing the step-down operation, the drive controller applies a pulse voltage to the gate terminal of the step-down IGBT 3 and performs PWM driving, thereby charging the capacitor 4 with regenerative energy obtained from the motor 6.

  The step-up / step-down operation is realized as described above.

  In the conventional step-up / down converter, in order to cut off the connection between the reactor 1 and the capacitor 4 that is a power source, a common one is provided with a magnet conductor or a relay, but like the step-up / down converter of the present embodiment. When handling high power, problems such as damage to equipment may occur due to arc discharge caused by energy remaining in the reactor.

  The buck-boost converter according to the present embodiment includes a protection circuit 12 including a pair of diodes 12a and 12b. Therefore, when the relay 9 is opened, current is passed from the reactor 1 to the negative terminal of the power connection terminal 5 by the diode 12a. The flow is suppressed, and a current flows from the reactor 1 to the positive terminal of the output terminal 7 through the diode 12 b and the DC bus 10. Thereby, the energy remaining in the reactor 1 is discharged from the output terminal 7 to the motor 6.

  As described above, since the energy remaining in the reactor 1 is released from the output terminal 7 to the motor 6, generation of arc discharge due to the relay 9 being turned off is suppressed.

  As described above, it is possible to provide a step-up / step-down converter with improved safety when the capacitor 4 as a power source is disconnected.

[Modification]
FIG. 2 is a diagram schematically showing a circuit configuration of a buck-boost converter according to a modified example of the present embodiment. This step-up / down converter differs from the step-up / down converter shown in FIG. 1 in that it includes reactors 1a, 1b, 1c, boosting IGBTs 2a, 2b, 2c, and step-down IGBTs 3a, 3b, 3c.

  Here, an element including one reactor, one step-up IGBT, and one step-down IGBT is treated as a “step-up / step-down element”. That is, in the circuit configuration shown in FIG. 2, three elements for step-up / step-down are connected in parallel. Here, an element in which the elements for step-up / step-down are connected in parallel as described above is referred to as a parallel type step-up / step-down element.

  As shown here, the reactor 1a is disposed between the step-up IGBT 2a and step-down IGBT 3a and the power supply connection terminal 5, and the capacitor 8 includes the step-up IGBT 2a and step-down IGBT 3a and the output terminal 7. Inserted between. This connection relationship is the same for the reactor 1b, the step-up IGBT 2b, and the step-down IGBT 3b, and the reactor 1c, the step-up IGBT 2c, and the step-down IGBT 3c.

  The step-up IGBTs 2a to 2c and the step-down IGBTs 3a to 3c shown in FIG. 2 are PWM-driven by a drive control unit (not shown). That is, a driving pulse voltage is applied to the gate terminals of these IGBTs (2a to 2c, 3a to 3c) from the drive control unit. Such a control unit can be realized by either an electronic circuit or an arithmetic processing unit.

  The buck-boost converter according to the modification of the present embodiment includes the protection circuit 12 including the pair of diodes 12a and 12b. Therefore, when the relay 9 is opened, the diode 12a causes the negative terminal of the power connection terminal 5 from the reactor 1. Current from the boosting IGBT 2 is suppressed, and current flows from the reactor 1 to the output terminal 7 through the diode 12b. Thereby, the energy remaining in the reactor 1 is released. At this time, a current flows from the reactor 1 to the output terminal 7 also through a path through a diode connected in parallel to the step-down IGBT 3. This is the same as the circuit configuration shown in FIG.

  Thus, even in a step-up / down converter having a circuit configuration in which a plurality of boosting elements are connected in parallel, arc discharge when the relay 9 is opened can be suppressed. In particular, in a buck-boost converter that handles high power like a construction machine, the current value flowing through each buck-boost element can be kept low by connecting multiple buck-boost elements in parallel. A pressure element can be used. Even in such a step-up / step-down converter having a modular parallel step-up / step-down element, since the current value flowing through the relay 9 is large, the arc discharge can be suppressed, so that the safety at the time of disconnection of the capacitor 4 as the power source can be achieved. It is possible to provide a step-up / step-down converter with improved characteristics.

  Here, the embodiment in which the parallel number N of the step-up / step-down elements is 3 has been described, but the parallel number N may be set to an optimal value according to the current value or voltage value applied to the reactor or the IGBT.

  In the above description, the DC drive motor 6 is directly connected to the output terminal 7. However, instead of this, an AC drive motor may be connected to the output terminal 7 via an inverter.

  The step-up / step-down converter according to the exemplary embodiment of the present invention has been described above, but the present invention is not limited to the specifically disclosed embodiment and does not depart from the scope of the claims. Various modifications and changes are possible.

It is a figure which shows roughly the circuit structure of the buck-boost converter of this Embodiment. It is a figure which shows schematically the circuit structure of the buck-boost converter by the modification of this Embodiment.

Explanation of symbols

1, 1a, 1b, 1c reactor 2, 2a, 2b, 2c Boost IGBT
3, 3a, 3b, 3c IGBT for step-down
4 capacitors,
5 Power connection terminal 6 Motor 7 Output terminal 8 Capacitor 9 Relay 10 DC bus 11 Controller 12 Protection circuit 12a, 12b Diode

Claims (2)

A first terminal for transferring power to and from an electric motor that performs both power running operation and regenerative operation; and a second terminal to which a power source that stores power supplied to the electric motor is connected;
A step-up switching element for controlling the supply of electric power to the electric motor;
A step-down switching element for controlling supply of regenerative power obtained from the electric motor to the power source;
A reactor having a first end connected to a connection point of the step-up switching element and the step-down switching element;
A switch provided between the second end of the reactor and the second terminal;
A step-up / down converter comprising: current induction means for guiding a current discharged from the reactor to a DC bus connected to the first terminal when the switch is opened.   The current induction means is connected between a second end of the reactor and a negative terminal of the first terminal, and a first rectifying element that rectifies current in a direction from the negative terminal to the second end of the reactor; And a second rectifying element disposed between the second end of the reactor and the DC bus and rectifying current in a direction from the second end of the reactor to the DC bus. Buck-boost converter.

Images