JP2018078768A - Working machine and power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power converter capable of achieving suppression of operations under an unstable state when an abnormality occurs in a voltage on low-tension side.SOLUTION: A power converter, installed on a working machine such as a crane, converts electric power input from a power supply and supplies electric power to an electric actuator. A detection part, upon detection of an input of an overvoltage into the power converter from a power supply, executes processing to be taken upon detection of an overvoltage.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a work machine and a power conversion device.

  Commercial power sources, generators driven by engines, power storage devices, and the like are used as power sources for driving crane hoisting motors, traverse motors, travel motors, and the like. When the driving power supply is alternating current, alternating current power is converted into direct current power by an AC-DC converter or a power conversion device that combines a rectifier and a DC-DC converter. When the driving power supply is a direct current, the power supply voltage is boosted by the DC-DC converter. After the DC power converted from AC to DC or the boosted DC power is converted into three-phase AC power by an inverter, a winding motor or the like is driven by the three-phase AC power.

  A power supply device that suppresses the occurrence of a voltage drop or overvoltage on the high-voltage side that can occur during sudden changes in power input / output by electric equipment connected to the high-voltage side of a power conversion device such as an AC-DC converter or a DC-DC converter. It is disclosed in Document 1.

  The power supply device disclosed in Patent Document 1 includes a diode connected in a forward direction with respect to an electrical device as viewed from the positive electrode of the low-voltage DC power supply. When the voltage on the high-voltage side decreases and becomes less than the voltage on the low-voltage side, power is supplied from the low-voltage side to the high-voltage side through this diode. For this reason, it is suppressed that the voltage of the high voltage side falls below the voltage of the low voltage side.

Japanese Patent No. 4747933

  If an abnormality occurs in the voltage on the low voltage side of the power conversion device, the operation of the power conversion device may become unstable, or the operation of the electrical equipment connected to the high voltage side may become unstable.

  The objective of this invention is providing the working machine which can suppress generation | occurrence | production of the malfunction resulting from the operation | movement of a power converter device becoming unstable when an overvoltage is input. Another object of the present invention is to provide a power conversion device that can suppress operation in an unstable state when an abnormality occurs in the low-voltage side voltage.

According to one aspect of the invention,
An operating part;
An electric actuator for driving the operating unit;
A power conversion device that converts power input from a power source and supplies power to the electric actuator;
When it is detected that an overvoltage is input from the power source to the power converter, a work machine is provided that includes a detection unit that executes a process when an overvoltage is detected.

According to another aspect of the invention,
A chopper circuit that boosts the voltage of the low-voltage side terminal and outputs power to the high-voltage side terminal;
When the overvoltage higher than the voltage of the high-voltage side terminal is applied to the low-voltage side terminal, the blocking means detects the state where the overvoltage is applied and blocks the abnormal current flowing from the low-voltage side terminal to the high-voltage side terminal Is provided.

  By detecting that the overvoltage has been input and executing the process at the time of detecting the overvoltage, it is possible to suppress the occurrence of a problem. By interrupting the abnormal current when the overvoltage occurs, it is possible to avoid the operation of the power conversion device in an unstable state.

1A and 1B are a schematic front view and a schematic side view, respectively, of a crane system using a power conversion device according to an embodiment. FIG. 2A is a power system diagram of a crane system using the power converter according to the embodiment, and FIG. 2B is a schematic diagram of an AC power source and the power converter. FIG. 3 is an equivalent circuit diagram of the DC-DC converter of the power conversion device according to the embodiment shown in FIGS. 2A to 2B. FIG. 4 is a graph showing an example of an abnormal current that flows through the upper protection diode when an overvoltage is applied to the low-voltage side terminal. FIG. 5 is an equivalent circuit diagram of a DC-DC converter of a power converter according to another embodiment. FIG. 6 is a graph showing an example of a current measurement value by a current sensor of a DC-DC converter used in the power conversion apparatus according to the embodiment shown in FIG. FIG. 7 is an equivalent circuit diagram of a DC-DC converter used in a power conversion device according to still another embodiment. FIG. 8 is a graph showing the change over time in the voltage measurement value VL by the low voltage sensor of the DC-DC converter used in the power converter according to the embodiment shown in FIG. 7 and the voltage measurement value VH by the high voltage sensor. It is a graph which shows an example. FIG. 9A is an equivalent circuit diagram of the AC-DC converter according to the present embodiment, and FIG. 9B is an equivalent circuit diagram of the relay circuit. FIG. 10A is a side view of an excavator using a power conversion device according to still another embodiment, and FIG. 10B is a block diagram of a hydraulic drive system and an electric drive system of the shovel.

  With reference to FIG. 1A-FIG. 4, the crane system using the power converter device by an Example is demonstrated.

  1A and 1B are a schematic front view and a schematic side view, respectively, of a crane system according to an embodiment. A plurality of pillars 13 support the beam 14. The pillar 13 and the girder 14 constitute a portal frame. A wheel 17 is attached to the lower end of the pillar 13, and the portal frame runs along the rail 18. The direction perpendicular to the paper surface of FIG. 1A and the left-right direction of FIG. 1B correspond to the traveling direction. A trolley 15 is mounted on the beam 14. A winder 16 is mounted on the trolley 15.

  A plurality of electric actuators drive each operating part. For example, the traveling motor 67 mounted on the portal frame drives the wheels 17. A traverse motor 66 mounted on the trolley 15 moves the trolley 15 in the traverse direction. The horizontal direction in FIG. 1A and the direction perpendicular to the paper surface in FIG. 1B correspond to the transverse direction. A winding motor 65 mounted on the winding machine 16 winds and feeds a wire having a hanging tool 16A such as a hook attached to the tip. Thus, the electric actuators such as the hoisting motor 65, the traversing motor 66, and the traveling motor 67 drive the operating parts such as the hanging tool 16A, the trolley 15, and the wheels 17, respectively.

  An AC power supply 10, a power conversion device 20, a power storage device 30, and a DC-DC converter 32 are mounted on the portal frame. AC power supply 10 includes an engine 11 and a generator 12. The AC power supply 10 supplies driving power to the winding motor 65, the traversing motor 66, and the traveling motor 67. Further, the power storage device 30 is charged with the electric power supplied from the AC power supply 10.

  FIG. 2A is a power system diagram of the crane system. AC power supply 10 is connected to DC bus 50 via power converter 20. The power conversion device 20 converts the AC power supplied from the AC power supply 10 into DC power having a target voltage and supplies it to the DC bus 50. A smoothing capacitor 52 is connected between the positive bus 50P and the negative bus 50N of the DC bus 50.

  The power storage device 30 is connected to the DC bus 50 via the DC-DC converter 32. The DC-DC converter 32 controls charging / discharging of the power storage device 30. When discharging power storage device 30, DC-DC converter 32 boosts the output voltage of power storage device 30 and supplies DC power from power storage device 30 to DC bus 50. When charging the power storage device 30, the DC-DC converter 32 steps down the voltage of the DC bus 50 and supplies DC power from the DC bus 50 to the power storage device 30.

  When the crane system shown in FIG. 2A is a gantry crane system, a hoisting motor 65, a traversing motor 66, and a traveling motor 67 are connected to the DC bus 50 via inverters 61, 62, and 63, respectively. The winding motor 65 lifts the object to be conveyed and moves it in the vertical direction. The traversing motor 66 and the traveling motor 67 function as moving motors that move the object to be conveyed in the horizontal direction intersecting the vertical direction. When the crane system shown in FIG. 2A is a swing type crane system, a boom hoisting motor and a swing motor are used as the moving motor.

  The controller 70 controls the power conversion device 20, the DC-DC converter 32, and the inverters 61, 62, 63 to supply power to the hoisting motor 65, the traversing motor 66, and the traveling motor 67 from the DC bus 50. . The controller 70 controls the power converter 20 and the DC-DC converter 32 so as to maintain the voltage of the DC bus 50 at a preset target value. When the hoisting motor 65 performs the lowering operation, the controller 70 controls the inverter 61 to supply the regenerative power generated by the hoisting motor 65 to the DC bus 50. The power storage device 30 can be charged with the regenerative power.

  FIG. 2B is a schematic diagram of the AC power supply 10 and the power conversion device 20. The AC power supply 10 includes an engine 11 such as an internal combustion engine and a generator 12. AC power generated by the engine 11 driving the generator 12 is supplied to the power converter 20.

  The power conversion device 20 includes a three-phase full-wave rectifier 21 and a DC-DC converter 22. The three-phase full-wave rectifier 21 converts the three-phase AC power generated by the generator 12 into DC power and supplies it to the DC-DC converter 22. The DC-DC converter 22 boosts the input DC power and supplies it to the DC bus 50. A commercial power source may be used instead of the engine 11 and the generator 12.

  FIG. 3 is an equivalent circuit diagram of the DC-DC converter 22. Since the configuration of the DC-DC converter 32 (FIG. 2A) is the same as the configuration of the DC-DC converter 22 shown in FIG. 3, the description of the configuration of the DC-DC converter 32 is omitted.

  The negative terminal 222 of the primary terminal pair connected to the three-phase full-wave rectifier 21 (FIG. 2B) and the negative terminal 224 of the secondary terminal pair connected to the DC bus 50 are both grounded. The positive terminal of the primary terminal pair is referred to as a low voltage terminal 221, and the positive terminal of the secondary terminal pair is referred to as a high voltage terminal 223. The power storage device 30 (FIG. 2A) is connected to the primary terminal pair of the DC-DC converter 32 (FIG. 2A).

  The low voltage side terminal 221 is connected to the chopper circuit 230 via the relay 225. A series circuit of another relay 226 and a charging resistor 227 is connected in parallel to the relay 225. The chopper circuit 230 has a function of boosting the voltage of the low-voltage side terminal 221 and outputting power to the high-voltage side terminal 223. The chopper circuit 230 includes a reactor 231, an upper switching element 232, and a lower switching element 233.

  One terminal of the reactor 231 is connected to the low voltage side terminal 221 through the relay 225. The other terminal of the reactor 231 is connected to the high voltage side terminal 223 via the upper switching element 232 and grounded via the lower switching element 233. For example, an insulated gate bipolar transistor (IGBT) is used for the upper switching element 232 and the lower switching element 233. A freewheel diode 234 is connected to the upper switching element 232, and a freewheel diode 235 is connected to the lower switching element 233.

  Between the connection point between the relay 225 and the chopper circuit 230 and the high voltage side terminal 223, the upper protection diode 241 has a polarity in which the direction from the connection point between the relay 225 and the chopper circuit 230 toward the high voltage side terminal 223 is a forward direction. It is connected. The upper protection diode 241 constitutes a detour that flows current from the low voltage side terminal 221 to the high voltage side terminal 223 by bypassing the chopper circuit 230. A lower protection diode 242 is connected between the connection point between the relay 225 and the chopper circuit 230 and the ground with a polarity in which the direction from the ground toward the connection point between the relay 225 and the chopper circuit 230 is a forward direction.

  The current sensor 250 measures the current flowing through the detour of the chopper circuit 230 configured by the upper protection diode 241. A measured value of current from the current sensor 250 is input to the controller 70. The controller 70 performs on / off control of the relay 225 and the relay 226 and on / off control of the upper switching element 232 and the lower switching element 233.

  Next, the operation of the DC-DC converter 22 shown in FIG. 3 will be described. In an initial state where a DC power supply voltage is applied to the low-voltage side terminal 221 and energy is not accumulated in the smoothing capacitor 52, the controller 70 turns on the relay 226. A current flows from the low voltage side terminal 221 to the DC bus 50 via the charging resistor 227 and the upper protection diode 241, and the smoothing capacitor 52 is charged. Charging resistor 227 suppresses the occurrence of inrush current when relay 226 is turned on. When the smoothing capacitor 52 is charged, the voltage of the high-voltage side terminal 223 rises, and when the voltage approaches the voltage of the low-voltage side terminal 221, the controller 70 turns on the relay 225 and turns off the relay 226. As a result, it is possible to obtain a state in which a current can flow from the low voltage side terminal 221 to the high voltage side terminal 223 without going through the charging resistor 227.

  Next, the boosting operation will be described. During the step-up operation, the controller 70 inputs the pulse width modulation signal to the lower switching element 233, thereby periodically turning the lower switching element 233 on and off. When the lower switching element 233 is switched off, the voltage of the low-voltage side terminal 221 is boosted by a voltage corresponding to the induced electromotive force generated in the reactor 231, and power is supplied to the high-voltage side terminal 223 via the freewheel diode 234. Is output.

  Next, the step-down operation will be described. During the step-down operation, the controller 70 inputs the pulse width modulation signal to the upper switching element 232, thereby periodically turning the upper switching element 232 on and off. The voltage is stepped down from the voltage at the high-voltage side terminal 223 by a voltage depending on the ratio (duty ratio) at which the upper switching element 232 is turned on, and power is output to the low-voltage side terminal 221. When the upper switching element 232 is switched off, a current flows from the ground to the low voltage side terminal 221 through the free wheel diode 235 due to the induced electromotive force generated in the reactor 231.

  Next, the function of the upper protection diode 241 will be described. During the step-down operation, a current flowing through the reactor 231 toward the low-voltage side terminal 221 flows. When relay 225 is interrupted for some reason, an induced electromotive force generated in reactor 231 causes a current to flow in a closed current path including reactor 231, upper protection diode 241, smoothing capacitor 52, and freewheel diode 235. With this current, energy remaining in the reactor 231 is released. As described above, the upper protection diode 241 has a function of flowing a current for discharging the residual energy of the reactor 231 when the relay 225 is interrupted for some reason during the step-down operation.

  Next, the function of the lower protection diode 242 will be described. During the step-up operation, a current in a direction flowing into the reactor 231 from the low-voltage side terminal 221 flows through the reactor 231. When relay 225 is interrupted for some reason, an induced electromotive force generated in reactor 231 causes a current to flow through a closed current path including reactor 231, free wheel diode 234, smoothing capacitor 52, and lower protection diode 242. With this current, energy remaining in the reactor 231 is released. Thus, the lower protection diode 242 has a function of flowing a current for discharging the residual energy of the reactor 231 when the relay 225 is interrupted for some reason during the boosting operation.

  Next, an operation when an overvoltage higher than the voltage of the high voltage side terminal 223 is applied to the low voltage side terminal 221 will be described. In this embodiment, the generator 12 (FIG. 2B) is connected to the low-voltage side terminal 221 of the DC-DC converter 22 via the three-phase full-wave rectifier 21. In some cases, the voltage applied to the low-voltage terminal 221 becomes unstable due to fluctuations in the rotational speed of the engine 11 that drives the generator 12, and an overvoltage may be applied. Even when the low-voltage side terminal 221 of the DC-DC converter 22 is connected to the commercial power supply via the three-phase full-wave rectifier 21 (FIG. 2B), an overvoltage may be applied due to an abnormality of the commercial power supply. is there.

  When an overvoltage is applied to the low voltage side terminal 221, an abnormal current flows from the low voltage side terminal 221 to the high voltage side terminal 223 via the upper protection diode 241.

  FIG. 4 is a graph showing an example of an abnormal current that flows through the upper protection diode 241 when an overvoltage is applied to the low-voltage terminal 221. The horizontal axis represents the elapsed time, and the vertical axis represents the magnitude of the current flowing through the upper protection diode 241.

  When the DC-DC converter 22 is operating normally, no current flows through the detour where the current sensor 250 is inserted. Here, “normal operation” means a step-up / step-down operation in a state where the voltage of the low-voltage side terminal 221 is lower than the voltage of the high-voltage side terminal 223.

  When an overvoltage is applied to the low voltage side terminal 221 (FIG. 3) and the voltage of the low voltage side terminal 221 exceeds the voltage of the high voltage side terminal 223, an abnormal current starts to flow through the upper protection diode 241 (time t1). At this time, the voltage of the DC bus 50 may not be maintained at the target value. The controller 70 (FIG. 3) compares the measured current value by the current sensor 250 (FIG. 3) with the allowable upper limit value I0. When the measured value of the current exceeds the allowable upper limit value I0, the controller 70 cuts off the abnormal current by turning off the relay 225. Further, the operation of the chopper circuit 230 (FIG. 3) is stopped. The current sensor 250 and the controller 70 have a function as a detection unit that detects that an overvoltage is input to the power conversion device.

  At this time, the controller 70 also stops the operation of the DC-DC converter 32. The controller 70 may continue the operation of the DC-DC converter 32 and cause the power storage device 30 to discharge. At this time, it is preferable to continue supplying power from the power storage device 30 to at least an auxiliary machine such as an air conditioner or lighting equipment in the cabin for the operator.

Next, the excellent effect of the present embodiment will be described.
In this embodiment, the current sensor 250, the controller 70, and the relay 225 (FIG. 3) detect a state in which an overvoltage is applied to the low-voltage side terminal 221 (FIG. 3), and the low-voltage side terminal 221 changes to the high-voltage side terminal 223. It has a function as a blocking means for blocking the flowing abnormal current. When an overvoltage is applied to the low-voltage terminal 221 and an abnormal current flows, a part of a path through which the abnormal current flows or a part to which the overvoltage is applied may break down. In this embodiment, an abnormal current due to an overvoltage is detected at an early stage and the relay 225 is turned off, so that it is possible to prevent a component failure due to the overvoltage or the abnormal current. Further, by turning off the relay 225 and stopping the operation of the chopper circuit 230, it is possible to prevent the DC-DC converter 22 from continuing operation in an unstable state.

  If the operation of the DC-DC converter 22 is not stopped when the operation of the DC-DC converter 22 is stopped, the hoisting motor 65 and the like can be continuously operated by the electric power of the power storage device 30.

  Since an abnormal current is detected by a detour that does not flow current during normal operation of the DC-DC converter 22, it is not affected by fluctuations in the current flowing from the low-voltage side terminal 221 toward the high-voltage side terminal 223 during normal operation. An abnormal current can be detected. For this reason, it is possible to detect an abnormal current with high accuracy and at an early stage.

  For example, when determining whether or not an overvoltage is applied based on various physical quantities measured by a plurality of sensors, in order to eliminate erroneous detection in consideration of variations in measurement accuracy of each of the plurality of sensors. It is preferable to provide a certain margin for the determination level. In this embodiment, since the abnormal current is measured by only one current sensor 250, it is not necessary to consider variation in measurement accuracy of a plurality of sensors. For this reason, it is possible to reduce the margin of the determination level as to whether or not the overvoltage state exists. Thereby, an overvoltage state can be detected early and with high accuracy.

  Next, another embodiment will be described with reference to FIGS. Hereinafter, description of the configuration common to the embodiment shown in FIGS. 2A to 4 will be omitted.

  FIG. 5 is an equivalent circuit diagram of the DC-DC converter 22 used in the power conversion apparatus according to this embodiment. In this embodiment, instead of the current sensor 250 (FIG. 3), a current sensor 251 is inserted at a location where current flows even during normal operation of the DC-DC converter 22. For example, a current sensor 251 is connected between the relay 225 and the chopper circuit 230. The current sensor 251 measures the total value of the current that flows during normal operation of the DC-DC converter 22 and the abnormal current caused by overvoltage.

  A measured value of current from the current sensor 251 is input to the controller 70. The controller 70 determines whether or not an overvoltage is applied based on the measured current value. If it is determined that an overvoltage is applied, the abnormal current is interrupted by turning off the relay 225. Further, the operation of the chopper circuit 230 is stopped.

  FIG. 6 is a graph showing an example of a current measured value by the current sensor 251 (FIG. 5). The horizontal axis represents elapsed time, and the vertical axis represents the magnitude of current. When the DC-DC converter 22 is operating normally, the current sensor 251 measures the current In that flows during normal operation. When the abnormal current Ia due to the overvoltage starts to flow from the time t1, the measured value of the current by the current sensor 251 becomes equal to the sum of the current In and the abnormal current Ia during normal operation.

  The controller 70 compares the measured current value by the current sensor 251 with the allowable upper limit value I1, and shuts off the relay 225 when the measured current value exceeds the allowable upper limit value I1. The current In that flows during the normal operation of the DC-DC converter 22 includes ripples due to switching of the upper switching element 232 and the lower switching element 233. Furthermore, the current In during normal operation varies depending on the on-off control frequency and duty ratio of the upper switching element 232 and the lower switching element 233. The controller 70 (FIG. 5) determines the allowable upper limit value I1 of the current according to the control conditions of the upper switching element 232 and the lower switching element 233.

Next, the excellent effect of the embodiment shown in FIGS. 5 and 6 will be described.
In this embodiment, the current sensor 251, the controller 70, and the relay 225 (FIG. 5) detect a state in which an overvoltage is applied to the low voltage side terminal 221, and an abnormal current flowing from the low voltage side terminal 221 to the high voltage side terminal 223 is detected. It functions as a blocking means for blocking. Also in this embodiment, by detecting an abnormal current caused by an overvoltage and shutting off the relay 225, it is possible to prevent a component failure due to the overvoltage or the abnormal current. In this embodiment, the current sensor 251 for detecting the overvoltage can also be used as a current sensor for measuring the current flowing during the normal operation of the DC-DC converter 22.

  Next, still another embodiment will be described with reference to FIGS. Hereinafter, description of the configuration common to the embodiment shown in FIGS. 2A to 4 will be omitted.

  FIG. 7 is an equivalent circuit diagram of the DC-DC converter 22 used in the power conversion apparatus according to this embodiment. In this embodiment, a low voltage side voltage sensor 252 and a high voltage side voltage sensor 253 are used instead of the current sensor 250 (FIG. 3). The low voltage side voltage sensor 252 measures the voltage between the ground and the low voltage side terminal 221, and the high voltage side voltage sensor 253 measures the voltage between the ground and the high voltage side terminal 223.

  The controller 70 detects the occurrence of overvoltage based on the measured voltage values measured by the low-voltage side voltage sensor 252 and the high-voltage side voltage sensor 253, and turns off the relay 225 when determining that the overvoltage has occurred. To do.

  FIG. 8 is a graph showing an example of a time change between the measured voltage value VL of the low voltage side voltage sensor 252 (FIG. 7) and the measured voltage value VH of the high voltage side voltage sensor 253 (FIG. 7). The horizontal axis represents elapsed time, and the vertical axis represents voltage magnitude.

  During normal operation of the DC-DC converter 22, the voltage measurement value VL by the low voltage sensor 252 is lower than the voltage measurement value VH by the high voltage sensor 253. When an overvoltage is applied to the low voltage side terminal 221 (FIG. 7) (time t1), the voltage measurement value VL by the low voltage side voltage sensor 252 starts to rise and exceeds the voltage measurement value VH by the high voltage side voltage sensor 253.

  As a result of comparing the measured voltage values VL and VH, the controller 70 turns off the relay 225 (FIG. 7) when determining that an overvoltage is applied to the low-voltage side terminal 221. For example, the difference or ratio between the measured values VL and VH is calculated, and when the calculation result is out of the allowable value, it may be determined that an overvoltage is applied to the low-voltage side terminal 221.

  For example, when the measured value VL exceeds the value obtained by subtracting the margin VM from the measured value VH, the controller 70 determines that an overvoltage is applied to the low-voltage side terminal 221. The margin VM is provided to avoid an overvoltage detection delay due to variations in measurement errors between the low voltage side voltage sensor 252 and the high voltage side voltage sensor 253.

Next, the excellent effect of the embodiment shown in FIGS. 7 and 8 will be described.
In this embodiment, the low voltage side voltage sensor 252, the high voltage side voltage sensor 253, the controller 70, and the relay 225 detect a state in which an overvoltage is applied to the low voltage side terminal 221, and the low voltage side terminal 221 changes to the high voltage side terminal 223. It has a function as a blocking means for blocking the flowing abnormal current. Also in this embodiment, by detecting an abnormal current caused by an overvoltage and shutting off the relay 225, it is possible to prevent a component failure due to the overvoltage or the abnormal current. In this embodiment, the low voltage side voltage sensor 252 and the high voltage side voltage sensor 253 for detecting overvoltage are also used as the voltage sensor for measuring the voltage of the low voltage side terminal 221 and the voltage sensor for measuring the voltage of the high voltage side terminal 223, respectively. can do.

  Next, a power converter according to another embodiment will be described with reference to FIGS. 9A and 9B. Hereinafter, description of the configuration common to the embodiment shown in FIGS. 2A to 4 will be omitted. In the embodiment shown in FIGS. 2A to 4, the power conversion device 20 is configured by the three-phase full-wave rectifier 21 and the DC-DC converter 22 (FIG. 2B), but in this embodiment, as the power conversion device 20. An AC-DC converter is used.

  FIG. 9A is an equivalent circuit diagram of the AC-DC converter according to the present embodiment. The primary terminal group of the AC-DC converter includes low voltage side terminals 221U, 221V, and 221W, and the secondary terminal pair includes a high voltage side terminal 223 and a negative side terminal 224. The low voltage side terminals 221U, 221V, and 221W are connected to the U phase, V phase, and W phase of the AC power supply, respectively. The high voltage side terminal 223 and the negative side terminal 224 are connected to the positive side bus 50P and the negative side bus 50N of the DC bus 50, respectively.

  The chopper circuit 90 includes a U-phase reactor 91U, an upper switching element 92U, and a lower switching element 93U. Freewheel diodes 94U and 95U are connected to the upper switching element 92U and the lower switching element 93U, respectively. The connection configuration of the reactor 91U, the upper switching element 92U, the lower switching element 93U, and the free wheel diodes 94U and 95U includes the reactor 231 of the DC-DC converter 22 (FIG. 3), the upper switching element 232, the lower switching element 233, The connection configuration of the freewheel diodes 234 and 235 is the same. Similarly, a reactor, an upper switching element, a lower switching element, and a free wheel diode are provided for the V phase and the W phase.

  A U-phase low-voltage side terminal 221U is connected to a U-phase reactor 91U via a U-phase relay circuit 80U. The upper side for the U phase with a polarity in which the direction from the connection point between the relay circuit 80U and the reactor 91U to the high voltage side terminal 223 is the forward direction between the connection point between the relay circuit 80U and the reactor 91U and the high voltage side terminal 223 A protective diode 81U is connected. Between the connection point between the relay circuit 80U and the reactor 91U and the negative side terminal 224, the direction from the negative terminal 224 to the connection point between the relay circuit 80U and the reactor 91U is a forward polarity and the bottom for the U phase A side protection diode 82U is connected. The upper protection diode 81U and the lower protection diode 82U correspond to the upper protection diode 241 and the lower protection diode 242 of the DC-DC converter 22 (FIG. 3), respectively. Similarly, a relay circuit, an upper protection diode, and a lower protection diode are provided for the V phase and the W phase.

  FIG. 9B is an equivalent circuit diagram of the relay circuit 80U. Relay circuit 80U includes relays 84U and 85U and a charging resistor 86U. The connection configuration of the relays 84U and 85U and the charging resistor 86U is the same as the connection configuration of the relays 225 and 226 and the charging resistor 227 of the embodiment supported in FIG. The V-phase and W-phase relay circuits have the same configuration as the U-phase relay circuit 80U.

  The U-phase upper protection diode 81U, the V-phase upper protection diode, and the W-phase upper protection diode bypass the chopper circuit 90 from the low-voltage side terminals 221U, 221V, and 221W to the high-voltage side terminal 223, respectively. It constitutes a detour that allows current to flow. The current sensor 83 measures the current flowing through the location where the U-phase, V-phase, and W-phase detours merge. The controller 70 determines whether or not an overvoltage is applied to any of the low-voltage side terminals 221U, 221V, and 221W based on the measured current value by the current sensor 83. When it is determined that the overvoltage is applied, the U-phase relay circuit 80U and the V-phase and W-phase relay circuits are shut off.

  Next, the excellent effect of the embodiment shown in FIGS. 9A and 9B will be described. In this embodiment, the current sensor 83, the controller 70, the U-phase relay circuit 80U, the V-phase and W-phase relay circuits detect a state in which an overvoltage is applied to the low-voltage side terminals 221U, 221V, and 221W. And has a function as a blocking means for blocking abnormal current flowing from the low voltage side terminals 221U, 221V, 221W to the high voltage side terminal 223. Also in this embodiment, by detecting an abnormal current caused by an overvoltage and cutting off the relay circuit 80U and the like, it is possible to prevent a failure of the component due to the overvoltage or the abnormal current.

Although the example which applied the power converter device by an Example to the crane was shown in FIGS. 1-8, the power converter device by an Example can also be applied to another working machine, for example, an excavator.
Next, with reference to FIG. 10A and 10B, the shovel using the power converter device by another Example is demonstrated.

  FIG. 10A is a side view of an excavator using the power conversion device according to the present embodiment. An upper turning body 101 is mounted so as to be turnable with respect to the lower traveling body 100. An attachment 110 is attached to the upper swing body 101. The attachment 110 includes a boom 112 attached to the upper swing body 101, an arm 113 attached to the tip of the boom 112, and a bucket 114 attached to the tip of the arm 113. The boom cylinder 115 raises and lowers the boom 112. The arm cylinder 116 opens and closes the arm 113. A bucket cylinder 117 opens and closes the bucket.

  FIG. 10B is a block diagram of a hydraulic drive system and an electric drive system of the excavator. The engine 120, the motor generator 122, and the hydraulic pump 123 are connected to each other via the torque converter 121. Power is supplied from the hydraulic pump 123 to the hydraulic load 124. The hydraulic load 124 includes, for example, a boom cylinder 115, an arm cylinder 116, a bucket cylinder 117 (FIG. 10A), a hydraulic motor that drives a crawler of the lower traveling body 100, and the like.

  The electric power generated by the motor generator 122 is supplied to the DC bus 131 via the power converter 130. A smoothing capacitor 132 is connected to the DC bus 131. As the power converter 130, for example, a bidirectional inverter such as a power converter according to the embodiment shown in FIG. 9 is used.

  A power storage device 135 is connected to the DC bus 131 via a DC-DC converter 136. Further, a swing motor 140 is connected to the DC bus 131 via an inverter 141. The configuration of the DC-DC converter 136 is the same as the configuration of the DC-DC converter 32 of the embodiment shown in FIG. 2A.

  The motor generator 122 can perform both the assist operation and the power generation operation. When the motor generator 122 is in a power generation operation, power is transmitted from the engine 120 to the motor generator 122 via the torque converter 121. When the motor generator 122 is assisted, electric power is supplied from the power storage device 135 to the motor generator 122 via the DC-DC converter 136, the DC bus 131, and the power converter 130. It is predicted that the motor generator 122 will generate power, and assists the engine 120.

  The inverter 141 supplies electric power from the DC bus 131 to the turning motor 140 to drive the turning motor 140. When the swing motor 140 performs a regenerative operation, the regenerative power generated by the swing motor 140 is supplied to the DC bus 131.

  Each of the above embodiments is an exemplification, and needless to say, partial replacement or combination of the configurations shown in the different embodiments is possible. About the same effect by the same composition of a plurality of examples, it does not refer to every example one by one. Furthermore, the present invention is not limited to the embodiments described above. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

DESCRIPTION OF SYMBOLS 10 AC power supply 11 Engine 12 Generator 13 Pillar 14 Digit 15 Trolley 16 Hoisting machine 16A Hanging tool 17 Wheel 18 Rail 20 Power converter 21 Three-phase full wave rectifier 22 DC-DC converter 30 Power storage device 32 DC-DC converter 50 DC Bus 50P Positive side bus 50N Negative side bus 52 Smoothing capacitors 61, 62, 63 Inverter 65 Hoisting motor 66 Traverse motor 67 Traveling motor 70 Controller 80U U phase relay circuit 81U U phase upper protection diode 82U U phase Lower protection diode 83 Current sensor 84U, 85U Relay 86U Charging resistor 90 Chopper circuit 91U U-phase reactor 92U U-phase upper switching element 93U U-phase lower switching element 94U, 95U Freewheel diode 100 Body 101 Upper swing body 110 Attachment 112 Boom 113 Arm 114 Bucket 115 Boom cylinder 116 Arm cylinder 117 Bucket cylinder 120 Engine 121 Torque converter 122 Motor generator 123 Hydraulic pump 124 Hydraulic load 130 Power converter 131 DC bus 132 Smoothing capacitor 135 Power storage device 136 DC-DC converter 140 Swivel motor 141 Inverter 221 Low voltage side terminal 221U Low voltage side terminal 221V for U phase Low voltage side terminal 221W for V phase Low voltage side terminal 222 for W phase Negative side terminal 223 High side terminal 224 Negative side terminal 225, 226 Relay 227 Charging resistor 230 Chopper circuit 231 Reactor 232 Upper switching element 233 Lower switching element 234, 235 Freewheel diode 2 1 upper protective diodes 242 lower protective diodes 250, 251 current sensor 252 low-side voltage sensor 253 high side voltage sensor

Claims (10)

An operating part;
An electric actuator for driving the operating unit;
A power conversion device that converts power input from a power source and supplies power to the electric actuator;
A work machine comprising: a detection unit that executes processing when an overvoltage is detected when it is detected that an overvoltage is input from the power source to the power conversion device.   The work machine according to claim 1, wherein the process at the time of detecting the overvoltage is a process of cutting off a current input to the power converter. And a power storage device that supplies power to the electric actuator,
The work machine according to claim 2, wherein the detection unit cuts off a current input to the power conversion device and executes a process of supplying power from the power storage device to the electric actuator. The power converter includes a chopper circuit that boosts the voltage of the low-voltage side terminal and outputs power to the high-voltage side terminal,
The detection unit detects that an overvoltage is applied to the low voltage side terminal when an overvoltage higher than the voltage of the high voltage side terminal is applied,
The work machine according to any one of claims 1 to 3, wherein the process at the time of detecting the overvoltage is a process of cutting off an abnormal current flowing from the low voltage side terminal to the high voltage side terminal. The power converter further includes a diode connected to be able to flow current from the low-voltage side terminal to the high-voltage side terminal by bypassing the chopper circuit,
The work machine according to claim 4, wherein the detection unit detects the abnormal current that flows from the low voltage side terminal through the diode to the high voltage side terminal when the overvoltage is applied to the low voltage side terminal. further,
An internal combustion engine;
A generator driven by the internal combustion engine to generate electricity;
The work machine according to claim 1, further comprising: a rectifier that rectifies AC power generated by the generator and supplies the AC power to the power converter. A chopper circuit that boosts the voltage of the low-voltage side terminal and outputs power to the high-voltage side terminal;
When the overvoltage higher than the voltage of the high-voltage side terminal is applied to the low-voltage side terminal, the blocking means detects the state where the overvoltage is applied and blocks the abnormal current flowing from the low-voltage side terminal to the high-voltage side terminal And a power conversion device. And a diode connected to allow the current to flow around the chopper circuit from the low voltage side terminal to the high voltage side terminal,
The blocking means detects the abnormal current flowing from the low voltage side terminal through the diode to the high voltage side terminal when the overvoltage is applied to the low voltage side terminal, and when the abnormal current is detected, the abnormal current is detected. The power conversion device according to claim 7 which cuts off. The blocking means is
Current sensor does not flow during normal operation of the chopper circuit, a current sensor inserted at a location where the abnormal current flows when the overvoltage is applied to the low-voltage side terminal,
A relay that cuts off a path through which the abnormal current flows;
The power conversion device according to claim 8, further comprising: a controller that turns off the relay based on a measured value of current by the current sensor. The chopper circuit is
A reactor in which a first terminal as one terminal is connected to the low-voltage side terminal;
An upper switching element connected between a second terminal which is the other terminal of the reactor and the high-voltage side terminal;
A lower switching element connected between the second terminal of the reactor and ground,
The diode is connected between the first terminal of the reactor and the high-voltage side terminal so that a direction from the first terminal toward the high-voltage side terminal is a forward direction. 9. The power conversion device according to 9.

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