JP5928442B2 - Vehicle power supply - Google Patents

Description

  The present invention relates to a power supply device for a vehicle.

  2. Description of the Related Art In a vehicle capable of driving drive wheels with a motor, a configuration is known in which the voltage of a battery is boosted and supplied to an inverter that drives the motor.

  In JP 2010-172139 A (Patent Document 1), when the battery temperature is lower than a predetermined value, the boost voltage target value of the boost converter is set as compared with the case where the battery temperature is higher than the predetermined value. It is stated that the limit is low. By controlling in this way, it is possible to prevent an overvoltage from being applied to the smoothing capacitor that smoothes the boosted voltage when the battery is cold.

JP 2010-172139 A JP 2007-290478 A

  By the way, when current consumption in the motor generator is small, it is conceivable to execute intermittent boost control for reducing power loss due to switching of the boost converter by intermittently operating and stopping the boost converter. When this control is performed, the current passing through the boost converter and the current flowing into and out of the battery are switched at high speed between when the current flows and when the current does not flow.

  By the way, depending on the configuration of an ECU (Electric Control Unit) that performs vehicle control, there may be a case in which the current change cannot be observed with high accuracy because the cycle of measuring current data used for control is slow. In this case, the controllability of current may be reduced.

  Further, since the internal resistance generally increases when the battery temperature is low, the battery voltage fluctuation with respect to the current fluctuation also increases. Therefore, when the battery voltage is low and the intermittent boost control is performed in a state where the current controllability is reduced, the battery voltage greatly fluctuates while the controllability is reduced. For this reason, there is a possibility that the battery voltage exceeds the limit voltage value without being able to control the battery voltage to be within the limit voltage range. As a result, battery performance may be reduced.

  The objective of this invention is providing the power supply device of the vehicle which can prevent that battery performance falls, utilizing the power loss reduction effect by intermittent pressure | voltage rise control.

  In summary, the present invention provides a power supply device for a vehicle, the power storage device, a boost converter that boosts the voltage of the power storage device and supplies the boosted voltage to an electric load of the vehicle, and a continuous boost mode that continuously operates the boost converter. And a control device for controlling the boost converter in an intermittent boost mode in which the boost converter is operated intermittently. The control device prohibits the operation of the boost converter in the intermittent boost mode when the temperature of the power storage device is equal to or lower than a predetermined value.

  When the temperature is low, the internal resistance of the power storage device increases, so that the influence of the current fluctuation on the voltage fluctuation of the power storage device increases. Therefore, if possible, control the boost converter in the intermittent boost mode to reduce power loss and prohibit the operation of the boost converter in the intermittent boost mode at low temperatures when the internal resistance of the power storage device increases. Thus, the limit voltage value determined from the viewpoint of protection of the power storage device can be reliably protected.

  Preferably, the predetermined value is the value of the power storage device in which the voltage of the power storage device becomes the upper limit voltage or the lower limit voltage of the power storage device when the absolute value of the passing current of the boost converter shows the maximum value when the boost converter operates in the intermittent boost mode. Determined based on temperature.

  By defining the temperature threshold in this way, the intermittent voltage boost mode is permitted in an appropriate temperature range.

  ADVANTAGE OF THE INVENTION According to this invention, it can prevent that a battery performance falls, utilizing an electric power loss reduction effect by intermittent pressure | voltage rise control in an electric vehicle.

It is a block diagram for explaining a configuration example of a hybrid vehicle shown as a representative example of an electric vehicle according to an embodiment of the present invention. It is a circuit diagram explaining the structural example of the electric system of the hybrid vehicle shown in FIG. 3 is a flowchart showing a procedure for boost control by converter 200. It is a flowchart which shows the detail of step ST25 of the flowchart of FIG. It is a wave form diagram for demonstrating operation | movement of a continuous boost mode and an intermittent boost mode. It is a wave form diagram for demonstrating the battery current IB when the converter 200 is controlled by intermittent boosting mode.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  FIG. 1 is a block diagram for explaining a configuration example of a hybrid vehicle shown as a representative example of an electric vehicle according to an embodiment of the present invention.

  Referring to FIG. 1, the hybrid vehicle includes an engine 100 corresponding to an “internal combustion engine”, a first MG (Motor Generator) 110, a second MG 120, a power split mechanism 130, a speed reducer 140, a battery 150, Drive wheel 160 and control device 500 are provided. The control device 500 includes a PM (Power Management) -ECU (Electronic Control Unit) 170 and an MG (Motor Generator) -ECU 172.

  The hybrid vehicle travels by driving force from at least one of engine 100 and second MG 120. Engine 100, first MG 110, and second MG 120 are connected via power split mechanism 130.

  The power split mechanism 130 is typically configured as a planetary gear mechanism. The power split mechanism 130 includes an external gear sun gear 131, an internal gear ring gear 132 disposed concentrically with the sun gear 131, a plurality of pinion gears 133 that mesh with the sun gear 131 and mesh with the ring gear 132, and a carrier 134. The carrier 134 is configured to hold a plurality of pinion gears 133 so as to rotate and revolve freely.

  The power split mechanism 130 splits the power generated by the engine 100 into two paths. One is a path for driving the drive wheels 160 via the speed reducer 140. The other is a path for driving the first MG 110 to generate power.

  The first MG 110 and the second MG 120 are typically three-phase AC rotating electric machines configured by permanent magnet motors.

  First MG 110 mainly operates as a “generator” and can generate electric power by the driving force from engine 100 divided by power split device 130. The electric power generated by first MG 110 is selectively used according to the running state of the vehicle and the state of charge (SOC) of battery 150. Thereafter, the electric power is adjusted in voltage by a converter described later and stored in the battery 150. First MG 110 can also operate as an electric motor as a result of torque control, for example, when motoring engine 100 at the time of engine start.

  Second MG 120 mainly operates as a “motor” and is driven using at least one of the electric power stored in battery 150 and the electric power generated by first MG 110. The power generated by the second MG 120 is transmitted to the drive shaft 135 and further transmitted to the drive wheel 160 via the speed reducer 140. Thereby, second MG 120 assists engine 100 or causes the vehicle to travel by the driving force from second MG 120.

  During regenerative braking of the hybrid vehicle, second MG 120 is driven by drive wheels 160 via reduction gear 140. In this case, the second MG 120 operates as a generator. Thus, second MG 120 functions as a regenerative brake that converts braking energy into electric power. The electric power generated by second MG 120 is stored in battery 150.

  The battery 150 is an assembled battery configured by connecting a plurality of battery modules in which a plurality of battery cells are integrated in series. The voltage of the battery 150 is about 200V, for example. Battery 150 can be charged with the electric power generated by first MG 110 or second MG 120. The temperature, voltage, and current of the battery 150 are detected by the battery sensor 152. The battery sensor 152 comprehensively indicates a temperature sensor, a voltage sensor, and a current sensor.

  PM-ECU 170 and MG-ECU 172 are configured to include a CPU (Central Processing Unit) and a memory (not shown), and perform a calculation process based on a detection value by each sensor by a software process according to a map and a program stored in the memory. Configured to run. Alternatively, at least a part of the PM-ECU 170 and the MG-ECU 172 may be configured to execute predetermined numerical operation processing and / or logical operation processing by hardware processing using a dedicated electronic circuit or the like.

  Engine 100 is controlled in accordance with an operation command value from PM-ECU 170. First MG 110, second MG 120, converter 200, and inverters 210 and 220 are controlled by MG-ECU 172. PM-ECU 170 and MG-ECU 172 are connected so that they can communicate in both directions.

  In this embodiment, PM-ECU 170 and MG-ECU 172 are configured by separate ECUs, but a single ECU that includes both functions may be provided.

  FIG. 2 is a circuit diagram illustrating a configuration example of the electric system of the hybrid vehicle illustrated in FIG.

  Referring to FIG. 2, the electric system of the hybrid vehicle includes a converter 200, an inverter 210 corresponding to the first MG 110, an inverter 220 corresponding to the second MG 120, an SMR (System Main Relay) 230, and capacitors C1, C2. And are provided.

  Converter 200 includes two power semiconductor switching elements Q1 and Q2 (hereinafter also simply referred to as “switching elements”) connected in series, and diodes D1 and D2 provided corresponding to the switching elements Q1 and Q2, respectively. , Including reactor L.

  Switching elements Q1, Q2 are connected in series between positive electrode line PL2 and ground line GL connected to the negative electrode of battery 150. Switching element Q1 has a collector connected to positive line PL2, and switching element Q2 has an emitter connected to ground line GL. Diodes D1 and D2 are connected in antiparallel to switching elements Q1 and Q2, respectively. Switching element Q1 and diode D1 constitute the upper arm of converter 200, and switching element Q2 and diode D2 constitute the lower arm of converter 200.

  As the power semiconductor switching elements Q1 and Q2, an IGBT (Insulated Gate Bipolar Transistor), a power MOS (Metal Oxide Semiconductor) transistor, a power bipolar transistor, or the like can be appropriately employed. On / off of each switching element Q1, Q2 is controlled by a switching control signal from MG-ECU 172.

  Reactor L has one end connected to positive line PL1 connected to the positive electrode of battery 150, and the other end connected to a connection node of switching elements Q1, Q2, that is, an emitter of switching element Q1 and a collector of switching element Q2. Connected to the connection point.

  Capacitor C2 is connected between positive electrode line PL2 and ground line GL. Capacitor C2 smoothes the AC component of the voltage fluctuation between positive line PL2 and ground line GL. Capacitor C1 is connected between positive electrode line PL1 and ground line GL. Capacitor C1 smoothes the AC component of voltage fluctuation between positive line PL1 and ground line GL.

A current (hereinafter referred to as a reactor current) IL flowing through the reactor L is detected by a current sensor SEIL. Voltage sensor 180 detects the voltage across capacitor C2, which is the output voltage of converter 200, that is, voltage VH (system voltage) between positive line PL2 and ground line GL, and outputs the detected value to MG-ECU 172. Converter 200, inverter 210 and inverter 220 are electrically connected to each other through positive line PL2 and ground line GL.

  Converter 200 boosts DC voltage VB (voltage across capacitor C1) supplied from battery 150 and supplies boosted system voltage VH to inverters 210 and 220 during the boosting operation. More specifically, in response to a switching control signal from MG-ECU 172, an ON period of switching element Q1 and an ON period of Q2 are alternately provided, and the step-up ratio corresponds to the ratio of these ON periods. It becomes.

  During the step-down operation, converter 200 steps down system voltage VH supplied from inverters 210 and 220 via capacitor C2 and charges battery 150. More specifically, in response to the switching control signal from MG-ECU 172, a period in which only switching element Q1 is turned on and a period in which both switching elements Q1, Q2 are turned off are alternately provided, and the step-down ratio is This is in accordance with the duty ratio of the ON period.

  When the converter 200 stops the step-up / step-down operation, the switching element Q1 is set to be on and the switching element Q2 is set to be off.

  Inverter 210 is formed of a general three-phase inverter, and includes U-phase arm 15, V-phase arm 16, and W-phase arm 17. Arms 15-17 include switching elements Q3-Q8 and antiparallel diodes D3-D8.

  Inverter 210 operates when first MG 110 operates according to an operation command value (typically torque command value) set to generate a driving force (vehicle driving torque, power generation torque, etc.) required for vehicle traveling. As described above, the current or voltage of each phase coil of the first MG 110 is controlled. That is, inverter 210 performs bidirectional DC / AC power conversion between positive electrode line PL2 and first MG 110.

  Inverter 220 is formed of a general three-phase inverter, similarly to inverter 210. When the vehicle is traveling, the inverter 220 sets the second MG 120 according to an operation command value (typically a torque command value) set to generate a driving force (vehicle driving torque, regenerative braking torque, etc.) required for vehicle traveling. The current or voltage of each phase coil of the second MG 120 is controlled so as to operate. In other words, inverter 220 performs bidirectional DC / AC power conversion between positive line PL2 and second MG 120.

  PM-ECU 170 calculates torque command value TR1 of first MG 110 and torque command value TR2 of second MG 120 based on accelerator opening Acc and vehicle speed V of the hybrid vehicle.

  Based on torque command value TR1 of first MG 110, torque command value TR2 of second MG 120, motor rotational speed MRN1 of first MG 110, and motor rotational speed MRN2 of second MG 120, MG-ECU 172 The optimum value (target value) of the output voltage (system voltage) VH, that is, the command voltage VH * is calculated. MG-ECU 172 calculates a duty ratio to control output voltage VH to command voltage VH * based on output voltage VH of converter 200 detected by voltage sensor 180 and command voltage VH *, and Control.

  MG-ECU 172 sets and controls converter 200 in either a continuous boost mode or an intermittent boost mode. The continuous boost mode is a mode in which the converter 200 executes without stopping the boost operation. The intermittent boost mode is a mode in which converter 200 intermittently repeats the boost operation and the stop of the boost operation. When converter 200 performs the boosting operation, switching elements Q1, Q2 are switched on / off. When converter 200 stops the boosting operation, switching element Q1 is set to be on and switching element Q2 is set to be off.

  The case where converter 200 does not boost in the continuous boost mode and the case where converter 200 stops boosting in intermittent boost mode are different in the following points.

  Continuous boost mode is a mode in which operation is performed without stopping converter 200. When converter 200 is in operation, the voltage of battery 150 is supplied to inverters 210 and 220 via converter 200. For example, a case where the duty ratio is 1 and the voltage of battery 150 is supplied as it is to inverters 210 and 220 without boosting converter 200 is also included in the operation of the continuous boosting mode.

  On the other hand, when converter 200 stops boosting in the intermittent boost mode, the voltage of battery 150 is not supplied to inverters 210 and 220 via converter 200.

  FIG. 3 is a flowchart showing the procedure of boost control by converter 200. FIG. 5 is a waveform diagram for explaining operations in the continuous boost mode and the intermittent boost mode.

  FIG. 5A shows output voltage (system voltage) VH of converter 200 in the continuous boost mode and the intermittent boost mode. FIG. 5B shows reactor current IL in the continuous boost mode and the intermittent boost mode. Reactor current IL actually fluctuates due to switching of converter 200, but FIG. 5B shows a smoothed fluctuation component due to switching. FIG. 5C is a diagram showing the boost loss power LP due to switching in the continuous boost mode and the intermittent boost mode.

  2 and 3, in step ST10, control device 500 sets converter 200 in the continuous boost mode. Converter 200 performs the boosting operation without stopping the boosting operation.

  Thereafter, in step ST20, control device 500 causes the process to proceed to step ST25 when average value ILM of reactor current IL in the past predetermined period becomes less than threshold value TH1. In step ST25, control device 500 checks the battery condition in order to determine whether or not to set the intermittent boost mode.

  FIG. 4 is a flowchart showing details of step ST25 in the flowchart of FIG. 2 and 4, when the process of step ST25 is started, in step ST100, control device 500 acquires battery temperature TB from battery sensor 152, and battery temperature TB is lower than the threshold value. Determine whether or not.

  In step ST100, when battery temperature TB is lower than the threshold value, control device 500 proceeds to step ST110 to determine that the intermittent boost mode is prohibited, and step ST10 in the flowchart of FIG. Return processing to. In this case, converter 200 is set to the continuous boost mode and operates.

  In step ST100, when battery temperature TB is equal to or higher than the threshold value, control device 500 advances the process to step ST120, determines that the intermittent boost mode is permitted, and performs step ST30 in the flowchart of FIG. Proceed with the process. In this case, converter 200 is set to the intermittent boost mode and operates.

  In step ST30, control device 500 sets converter 200 in the intermittent boost mode. When the intermittent boost mode is set, control device 500 first stops the boost operation by converter 200 (see, for example, time point (1) in FIG. 5).

  When the boosting operation of converter 200 is stopped, no current is output from battery 150, reactor current IL becomes zero, and boosting loss energy LP becomes zero. When the boosting operation of converter 200 is stopped, first MG 110 and / or second MG 120 is driven by the electric power stored in capacitor C2. As the electric charge is discharged from the capacitor C2, the system voltage VH is decreased.

  Thereafter, in step ST40, control device 500 causes the process to proceed to step ST50 when the amount of deviation | VH * −VH | between system voltage VH and command voltage VH * is equal to or greater than limit value ΔVH. In step ST50, control device 500 restarts the boosting operation by converter 200 (see, for example, the time point (2) in FIG. 5).

  When the boosting operation of converter 200 is resumed, current (recovery current) necessary for driving first MG 110 and / or second MG 120 while charging capacitor C2 is supplied from battery 150, and thus reactor current IL increases. The step-up loss power LP increases.

  Thereafter, in step ST60, when system voltage VH becomes equal to command voltage VH *, control device 500 causes the process to proceed to step ST70. In step ST70, control device 500 stops the boosting operation by converter 200 (see, for example, the time point (3) in FIG. 5). After step ST70, the processes after step ST40 are executed again.

  On the other hand, in step ST80, when average value ILM of reactor current IL in the past predetermined period exceeds threshold value TH2, control device 500 proceeds to step ST90 to set converter 200 in the continuous boost mode. . Converter 200 performs the boosting operation without stopping (see, for example, the time point (4) in FIG. 5). It is shown that the command voltage VH * increases and the reactor current IL increases at the time point (4) in FIG. After step ST90 is executed, the process of this flowchart ends.

  FIG. 5C shows how much the boost loss power LP is reduced when one boost stop period and the subsequent boost period in the intermittent boost mode are set as one set. The area P3 of the region between the line representing the boost loss power LP above the reference loss power BS and the line representing the reference loss power BS is equal to the boost loss power LP increased compared to the operation in the continuous boost mode. Represents the total. The area P0 of the region between the line representing the step-up loss power LP below the reference loss power BS and the line representing the reference loss power BS is smaller than that in the continuous step-up mode. Represents the total. A value P1 obtained by subtracting P2 (= P3) from P0 has a reduced boosting loss energy amount in one set of boost stop periods and subsequent boost periods, compared to operating in the continuous boost mode by operating in the intermittent boost mode. It is the sum.

  As shown in FIG. 5C, by setting the intermittent boost mode, the boost loss power can be reduced. In addition, the longer the boost stop period, the greater the loss reduction effect.

  As described above, when the average value ILM of the current IL is larger than the threshold value TH2, the intermittent boost mode is changed to the continuous boost mode, and when the average value ILM of the current IL is smaller than the threshold value TH1, The continuous boost mode is changed to the intermittent boost mode. In order to suppress frequent mode changes, it is preferable that TH1> TH2.

  Here, in step ST25, it is determined whether or not to shift to the intermittent boost mode by judging the battery condition when the converter 200 is controlled in the intermittent boost mode when the battery temperature is low. This is because the fluctuation may exceed the allowable value. Therefore, when the battery temperature TB is lower than the threshold value, it is determined that the intermittent boost mode should not be executed, and the transition to the intermittent boost mode is prohibited. Thus, when possible, the converter 200 is controlled in the intermittent boost mode to improve fuel efficiency, and when the battery temperature is low, the battery can be reliably protected.

  Next, a determination threshold value determination method used in step S100 of FIG. 4 will be described below.

  FIG. 6 is a waveform diagram for explaining battery current IB when converter 200 is controlled in the intermittent boost mode. Referring to FIG. 6, a pulse-like current peak corresponding to the return current between time points (2) to (3) shown in FIG. 5 is generated in battery current IB. From the viewpoint of battery protection, it is important that the battery voltage VB does not exceed the upper limit value and does not fall below the lower limit value when the peak current IBmax flows.

The battery voltage VB is expressed by the following formula.
VB = OCV− (IB × R)
Here, OCV indicates the open circuit voltage, IB indicates the battery current, and R indicates the internal resistance of the battery. Note that IB takes a positive value during discharging, and takes a negative value during charging. When the battery temperature is low, the internal resistance R increases. As can be seen from the above equation, when the battery temperature is low and the internal resistance R is large, the variation in the battery voltage VB also increases with respect to the variation in the battery current IB.

  In addition, when intermittent boost control is performed, battery current IB fluctuates at high speed. When the absolute value of the battery current IB increases, intermittent control can be performed by limiting the motor. However, if the time interval for observing the current is not sufficiently small compared to the current fluctuation interval, it is accurate. Cannot observe the current. However, if the time interval for observing the current is reduced, a high-speed CPU must be used or the communication frequency must be increased, which causes an increase in cost.

  In the present embodiment, when the battery temperature TB is lower than the threshold value, control is performed so as not to shift to the intermittent boost mode. The threshold value at this time is such that when the absolute value of the return current at the time points (2) to (3) shown in FIG. 5 is maximum, the battery voltage exceeds the upper limit voltage determined from the viewpoint of battery protection. The battery temperature or the battery temperature below the lower limit voltage is set as the threshold value.

  The current IBmax in FIG. 6 can be estimated by adding the expected auxiliary machine current consumption or air conditioner current to the return current IL maximum value. The battery resistance R at which the battery voltage VB is equal to the upper limit value or the lower limit value can be calculated from the estimated IBmax and OCV.

  The battery temperature at which the battery resistance R is obtained can be used as a threshold value for determining whether or not the intermittent boost mode is permitted.

  The OCV and IBmax may vary depending on the state of charge SOC of the battery and the current consumption of the load. For example, the values in the case of the strictest conditions for the battery voltage upper limit value and the battery voltage lower limit value should be used. Can do. Further, a map having SOC and load current consumption as variables may be experimentally obtained in advance and prepared.

  Finally, this embodiment will be summarized with reference to FIG. 2 again. The power supply device of the vehicle includes a power storage device (battery 150), a boost converter 200 that boosts the voltage of the battery 150 and supplies the boosted voltage to an electric load of the vehicle, a continuous boost mode that continuously operates the boost converter 200, and a boost converter And a control device 500 that controls the boost converter 200 in an intermittent boost mode in which 200 is intermittently operated. As shown in FIG. 4, control device 500 prohibits operation of boost converter 200 in the intermittent boost mode when the temperature of battery 150 is equal to or lower than a predetermined value.

  Preferably, the predetermined value is the upper limit voltage or the lower limit voltage of battery 150 when the absolute value of the passing current of boost converter 200 shows the maximum value when boost converter 200 operates in the intermittent boost mode. It is determined based on temperature TB of battery 150.

  In the embodiment of the present invention, the continuous voltage step-up mode and the intermittent voltage step-up mode are provided, but a continuous voltage step-down mode and an intermittent voltage step-down mode may be provided. That is, MG-ECU 172 sets converter 200 in either the continuous voltage step-down mode or the intermittent voltage step-down mode. The continuous step-down mode is a mode in which converter 200 executes the step-down operation without stopping. The intermittent step-down mode is a mode in which converter 200 intermittently repeats the step-down operation and the stop of the step-down operation. When converter 200 performs the step-down operation, a period in which only switching element Q1 is turned on and a period in which both switching elements Q1, Q2 are turned off are alternately switched. When converter 200 stops the step-down operation, switching element Q1 is set to fixed on and switching element Q2 is set to fixed off.

  Even in such an intermittent voltage step-down mode, if the battery temperature is low, there is a possibility that the battery voltage may exceed the upper limit value or lower than the lower limit value. Therefore, when the battery temperature is lower than the threshold value, the battery can be well protected by prohibiting the operation in the intermittent step-down mode.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  100 Engine, 110 1st MG, 120 2nd MG, 112, 122 Neutral point, 130 Power split mechanism, 131 Sun gear, 132 Ring gear, 133 Pinion gear, 134 Carrier, 135 Ring gear shaft (drive shaft), 140 Reducer, 150 Battery, 152 battery sensor, 160 driving wheel, 170 PM-ECU, 172 MG-ECU, 180 voltage sensor, 200 converter, 210, 220 inverter, 230 SMR, 500 control device, PL1, PL2 positive line, GL ground line, Q1-Q8 Switching element, D1-D8 diode, C1, C2 capacitor, L reactor.

Claims (2)

A power storage device;
A boost converter that boosts the voltage of the power storage device and supplies the boosted voltage to an electric load of the vehicle;
A controller for controlling the boost converter in a continuous boost mode for continuously operating the boost converter and an intermittent boost mode for intermittently operating the boost converter;
The control device prohibits the operation of the boost converter in the intermittent boost mode and operates the boost converter in the continuous boost mode when the temperature of the power storage device is equal to or lower than a predetermined value. .   The predetermined value is such that the voltage of the power storage device becomes the upper limit voltage or the lower limit voltage of the power storage device when the absolute value of the passing current of the boost converter shows a maximum value when the boost converter operates in the intermittent boost mode. The power supply device for a vehicle according to claim 1, which is determined based on a temperature of the power storage device.

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