JP5362392B2 - DC / DC converter device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a DC/DC converter which improves controllability of a DC/DC converter, in synchronized switching control. <P>SOLUTION: The operator part 120 of the DC/DC converter 50 sets a correction duty DUTcor for correcting the influence of dead time setting treatment, using a peak value I1pk, bottom value I1btm, and average value I1ave of a primary current I1, and a positive current threshold THmax and a negative current threshold THmin. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a DC / DC converter device including a step-down switching element and a step-up switching element. More specifically, the present invention relates to a DC / DC converter device that alternately outputs a drive signal to a step-down switching element and a step-up switching element with a dead time between switching periods.

  So-called synchronous switching control is known in which drive signals are alternately output to a step-down switching element and a step-up switching element for each switching period (for example, Patent Document 1). In the synchronous switching control of Patent Document 1, a dead time is sandwiched between drive signals in order to prevent the step-down switching element and the step-up switching element from flowing simultaneously and short-circuiting (for example, FIG. 9 of Patent Document 1). (See (a)).

International Publication No. 02/093730 Pamphlet

  In Patent Document 1, there is a description of a dead time generation method (for example, FIGS. 9 (a) and 9 (b) and page 11, line 5 to the last line of Patent Document 1). No consideration has been given to the controllability of the DC / DC converter device considered.

  The present invention has been made in consideration of such problems, and an object thereof is to provide a DC / DC converter device capable of improving the controllability of the DC / DC converter device in synchronous switching control.

  The DC / DC converter device according to the present invention alternately includes a step-down switching element, a step-up switching element, a reactor, and the step-down switching element and the step-up switching element with a dead time between switching periods. A chopper type DC / DC converter device comprising: a control unit that outputs a drive signal to a current sensor; and a current sensor that measures a primary current on which the reactor is disposed, wherein the control unit includes the step-down switching A calculation unit for calculating a drive duty of at least one of an element and the step-up switching element, and an output period of the drive signal for the step-down switching element and the step-up switching element determined based on the drive duty, respectively. Dead time setting process to subtract dead time An output unit that outputs the drive signal to the step-down switching element and the step-up switching element in an output period after the dead time setting process, and the calculation unit further includes the step-down switching element, Prior to the dead time setting process, a target drive duty corresponding to a period in which at least one of the boost switching elements is actually driven and a correction duty for correcting the influence of the dead time setting process are calculated. The drive duty to be output to the output unit is calculated by correcting the target drive duty with the correction duty, and when the bottom value of the primary current in one switching cycle is equal to or greater than a positive threshold value, Output period of the drive signal to the boosting switching element due to the dead time The correction duty is set so as to compensate for the decrease, and when the peak value of the primary-side current in one switching cycle is equal to or less than a negative threshold, the drive signal for the step-down switching element due to the dead time is reduced. When the correction duty is set to compensate for a decrease in the output period, the peak value is between the negative threshold and the positive threshold, and the bottom value is less than the negative threshold, Based on the bottom value when the correction duty is set based on the peak value, the bottom value is between the negative threshold and the positive threshold, and the peak value exceeds the positive threshold The correction duty is set, and when the peak value and the bottom value are between the negative threshold value and the positive threshold value, The correction duty is set based on an average value of current.

  According to the present invention, in so-called synchronous switching control in which a drive signal is alternately output to a step-down switching element and a step-up switching element with a dead time between switching periods, switching between a step-up state and a step-down state is performed. Voltage fluctuation can be suppressed. As a result, the controllability of the DC / DC converter device can be improved.

  In addition, the calculation unit may perform a filtering process that restricts a change in at least one of the peak value, the bottom value, and the average value.

  Furthermore, the calculation unit may perform a filter process for limiting a change in the correction duty.

  A power storage device may be connected to the primary side, and a power generation device and a motor may be connected to the secondary side.

  The power generation device may be a fuel cell.

  According to the present invention, in so-called synchronous switching control in which a drive signal is alternately output to a step-down switching element and a step-up switching element with a dead time between switching periods, switching between a step-up state and a step-down state is performed. Voltage fluctuation can be suppressed. As a result, the controllability of the DC / DC converter device can be improved.

1 is a schematic overall configuration diagram of a fuel cell vehicle equipped with a DC / DC converter device according to an embodiment of the present invention. It is a circuit diagram which shows the detailed structure of the DC / DC converter which concerns on the said embodiment. It is a circuit diagram which shows the detailed structure of the converter control part which concerns on the said embodiment. It is a time chart used for description of the synchronous switching control in the said embodiment. It is explanatory drawing which shows the relationship between a primary current and correction | amendment duty. FIG. 6A is an explanatory diagram showing the relationship between the peak value of the primary current and the correction duty. FIG. 6B is an explanatory diagram showing the relationship between the average value of the primary current and the correction duty. FIG. 6C is an explanatory diagram illustrating the relationship between the bottom value of the primary current and the correction duty. FIG. 7A is an explanatory diagram when the correction duty is set using the relationship of FIG. 6A. FIG. 7B is an explanatory diagram when the correction duty is set using the relationship of FIG. 6B. FIG. 7C is an explanatory diagram when the correction duty is set using the relationship of FIG. 6C. 5 is a flowchart for setting a correction duty in the embodiment. It is a circuit diagram which shows the structure of the modification of a converter control part. FIG. 10A is an explanatory diagram illustrating a first modification of the relationship between the peak value of the primary current and the correction duty. FIG. 10B is an explanatory diagram illustrating a first modification of the relationship between the average value of the primary current and the correction duty. FIG. 10C is an explanatory diagram illustrating a first modification of the relationship between the bottom value of the primary current and the correction duty. FIG. 11A is an explanatory diagram illustrating a second modification of the relationship between the peak value of the primary current and the correction duty. FIG. 11B is an explanatory diagram illustrating a second modification of the relationship between the average value of the primary current and the correction duty. FIG. 11C is an explanatory diagram illustrating a second modification of the relationship between the bottom value of the primary current and the correction duty.

1. Explanation of overall configuration [Overall configuration]
FIG. 1 shows a schematic overall configuration diagram of a fuel cell vehicle 10 equipped with a DC / DC converter device 50 according to an embodiment of the present invention.

  The fuel cell vehicle 10 basically includes a battery 12 as a first DC power supply device that generates a primary voltage V1 on the primary side 1S and a second DC power supply that generates a secondary voltage V2 on the secondary side 2S. A hybrid DC power supply device including a fuel cell 14 as a device, and a traveling motor 16 that is a load supplied with power from the hybrid DC power supply device.

[Fuel cell and its system]
The fuel cell 14 has, for example, a stack structure in which cells formed by sandwiching a solid polymer electrolyte membrane between an anode electrode and a cathode electrode from both sides are stacked. A reaction gas supply unit 18 is connected to the fuel cell 14 through a pipe. The reactive gas supply unit 18 includes a hydrogen tank that stores hydrogen (fuel gas) that is one reactive gas, and a compressor that compresses air (oxidant gas) that is the other reactive gas. The generated current generated by the electrochemical reaction in the fuel cell 14 of hydrogen and air supplied from the reaction gas supply unit 18 to the fuel cell 14 is supplied to the motor 16 and the battery 12 via the diode 13.

  The fuel cell system 11 includes a fuel cell 14 and a reaction gas supply unit 18 and a fuel cell control unit (FC control unit) 44 that controls them.

[DC / DC converter]
The DC / DC converter 20 is a chopper type voltage converter in which one side is connected to the battery 12 and the other side is connected to the secondary side 2S that is a connection point between the fuel cell 14 and the motor 16.

  The DC / DC converter 20 converts the primary voltage V1 into a secondary voltage V2 (V1 ≦ V2) (boost conversion), and also converts the secondary voltage V2 into a primary voltage V1 (step-down conversion). This is a voltage conversion device.

[Inverter, motor and drive system]
The inverter 22 has a three-phase full-bridge configuration, performs DC / AC conversion, converts DC to three-phase AC, and supplies it to the motor 16, while DC after AC / DC conversion accompanying the regenerative operation. Is supplied from the secondary side 2S to the primary side 1S through the DC / DC converter 20, and the battery 12 is charged.

  The motor 16 rotates the wheels 26 through the transmission 24. In practice, the inverter 22 and the motor 16 are collectively referred to as a load 23.

[High voltage battery]
A high voltage battery 12 connected to the primary side 1S is a power storage device (energy storage), and for example, a lithium ion secondary battery or a capacitor can be used. In this embodiment, a lithium ion secondary battery is used.

[Various sensors, main switches and communication lines]
A main switch (power switch) 34 and various sensors 36 are connected to the overall control unit 40. The main switch 34 has a function as an ignition switch that turns on (starts or starts) and turns off (stops) the fuel cell vehicle 10 and the fuel cell system 11. Various sensors 36 detect state information, such as a vehicle state and an environmental state. As the communication line 38, a CAN (Controller Area Network) that is an in-vehicle LAN is used.

[Control unit]
The overall control unit 40, the FC control unit 44, the motor control unit 46, the converter control unit 48, and the battery control unit 52 are connected to the communication line 38. A DC / DC converter device 50 is formed by the DC / DC converter 20 and the converter control unit 48 that controls the DC / DC converter 20.

  Each control unit 40, 44, 46, 48, 52 includes a microcomputer, detects state information of various switches such as the main switch 34 and various sensors 36, and also controls each of the control units 40, 44, 46, 48, 52. Each CPU implements various functions by inputting status information from these switches and sensors and information (commands, etc.) from other controllers, and executing programs stored in memory (ROM). It operates as a function realization unit (function realization means). The control units 40, 44, 46, 48, and 52 have an input / output interface such as a timer, an A / D converter, and a D / A converter, as necessary, in addition to a CPU and a memory.

2. Detailed configuration description [DC / DC converter device]
FIG. 2 shows a detailed configuration of the DC / DC converter 20. The DC / DC converter 20 includes a phase arm UA disposed between the primary side 1S and the secondary side 2S, and a reactor 90.

  The phase arm UA includes an upper arm element (upper arm switching element 81 and diode 83) and a lower arm element (lower arm switching element 82 and diode 84).

  As the upper arm switching element 81 and the lower arm switching element 82, for example, a MOSFET or an IGBT is employed.

  Reactor 90 is inserted between the midpoint (common connection point) of phase arm UA and the positive electrode of battery 12, and converts voltage between primary voltage V1 and secondary voltage V2 by DC / DC converter 20. In particular, it has the function of releasing and storing energy.

  The upper arm switching element 81 is turned on by the high level of the gate drive signal (drive voltage) UH output from the converter control unit 48, and the lower arm switching element 82 is turned on by the high level of the gate drive signal (drive voltage) UL. Turned on by. The converter control unit 48 detects the primary voltage V1 by the voltage sensor 91 provided in parallel with the smoothing capacitor 94 on the primary side, detects the primary current I1 by the current sensor 101, and smoothes the secondary side. The secondary voltage V2 is detected by the voltage sensor 92 provided in parallel with the capacitor 96, and the secondary current I2 is detected by the current sensor 102.

  FIG. 3 is a functional block diagram illustrating a flow in which the converter control unit 48 generates the drive signals UH and UL in the present embodiment.

  Converter control unit 48 includes a calculation unit 120 and an output unit 122. The calculation unit 120 and the output unit 122 may be configured as either hardware or software.

  The converter control unit 48 uses so-called synchronous switching control. The synchronous switching control is a control for outputting drive signals UH and UL to the upper arm switching element 81 and the lower arm switching element 82 in each switching cycle Tsw [s] (see FIG. 4). A dead time dt [s] is set between the outputs of the drive signals UH and UL to prevent a short circuit. The processing for setting the dead time dt in this way is hereinafter referred to as “dead time setting processing”.

  The calculation unit 120 calculates a drive duty DUT [%] that defines an output period [s] of the drive signals UH and UL in one switching cycle Tsw.

  The calculation unit 120 includes a subtractor 130, a feedback term calculation unit 132 (hereinafter also referred to as “FB term calculation unit 132”), and a feedforward term calculation unit 134 (hereinafter also referred to as “FF term calculation unit 134”). , A correction duty calculation unit 136, a first adder 138, and a second adder 140.

  The subtractor 130 is a difference ΔV2 (= V2com−V2) between the command value (secondary voltage command value V2com) [V] of the secondary voltage V2 from the overall control unit 40 and the secondary voltage V2 from the voltage sensor 92. [V] is calculated and output to the FB term calculation unit 132.

  The FB term computing unit 132 computes a feedback term (hereinafter also referred to as “FB term”) by PID control (proportional / integral / derivative control) using the difference ΔV <b> 2 from the subtractor 130.

  The FF term calculation unit 134 is a feedforward term (hereinafter also referred to as “FF term”) that is a quotient V1 / V2com of the primary voltage V1 from the voltage sensor 91 and the secondary voltage command value V2com from the overall control unit 40. ) Is calculated.

  The correction duty calculator 136 calculates a correction duty DUTcor [%] based on the primary current I1 from the current sensor 101. The correction duty DUTcor is a correction amount for reducing a deviation between the drive duty DUT and the output period of the drive signals UH and UL due to the influence of the dead time dt.

  The first adder 138 adds the FB term from the FB term computing unit 132 and the FF term from the FF term computing unit 134, and outputs the sum as the target drive duty DUTtar. The target drive duty DUTtar is directly calculated as a value for the calculation unit 120 to set a period during which the drive signal UH is output to the upper arm switching element 81 (upper arm target drive period Tud_tar) [s]. It is a thing.

  The second adder 140 adds the target drive duty DUTtar (the sum of the FB term and the FF term) from the first adder 138 and the correction duty DUTcor from the correction duty calculator 136, and outputs it as a drive duty DUT. It outputs to 122.

  The drive duty DUT in this embodiment is the drive duty of the upper arm switching element 81, that is, the ratio of the period during which the drive signal UH is output to the upper arm switching element 81 in one switching cycle Tsw [s] (drive signal UH The ratio of the period during which is at a high level) [%]. The ratio of the period during which the drive signal UL is output to the lower arm switching element 82 in one switching cycle Tsw (the ratio of the period during which the drive signal UL is at a high level) ranges from 100% to the ratio of the upper arm switching element 81. It is assumed that it was subtracted.

  The output unit 122 outputs drive signals UH and UL based on the drive duty DUT from the calculation unit 120. Specifically, as shown in FIG. 4, a period (upper arm driving period Tud) obtained by subtracting the dead time dt from a period (upper arm target driving period Tud_tar) [s] corresponding to the driving duty DUT in one switching period Tsw. [S], the drive signal UH is output to the upper arm switching element 81. Further, the output unit 122 calculates a period (lower arm target drive period Tld_tar) [s] obtained by subtracting the upper arm target drive period Tud_tar from one switching cycle Tsw, and further calculates a dead time dt from the lower arm target drive period Tld_tar. During the subtracted period (lower arm driving period Tld) [s], the driving signal UL is output to the lower arm switching element 82.

[Operation of DC / DC converter device]
(Synchronous switching control)
The time chart of FIG. 4 is an explanatory diagram of the synchronous switching control of the DC / DC converter device 50.

  In the step-down chopper control related to the step-down operation (regeneration operation), the secondary current I2 flowing out from the load 23 and the fuel cell 14 passes through the DC / DC converter 20 and charges the battery 12 as the primary current I1. In the step-up chopper control related to the step-up operation (assist operation), the primary current I1 flowing out from the battery 12 passes through the DC / DC converter 20 and the load 23 including the motor 16 is driven as the secondary current I2.

  In the waveforms of the drive signals UH and UL, during the hatched period, the arm switching element to which the drive signals UH and UL are supplied (for example, the upper arm switching element 81 is the arm switching element corresponding to the drive signal UH). The period during which current is flowing (current is flowing) is shown.

  In both the step-down chopper control and the step-up chopper control of the DC / DC converter 20, high level drive signals UH and UL are applied to the upper arm switching element 81 and the lower arm switching element 82 for each switching period Tsw. Output. In the step-down chopper control, the upper arm switching element 81 is allowed to flow, and in the step-up chopper control, the lower arm switching element 82 is allowed to flow.

  In this case, in order to prevent the secondary voltage V2 from being short-circuited through the upper and lower arm switching elements 81 and 82 at the same time, the drive signals UH and UL are set to the high level with the dead time dt interposed therebetween. I have to. That is, synchronous switching is performed with the dead time dt interposed therebetween.

  In the step-down chopper control, first, during the period in which only the upper arm switching element 81 is passed by the drive signal UH, the secondary current I2 flows as the primary current I1 to the reactor 90 through the upper arm switching element 81 and flows to the reactor 90. Energy is stored and the battery 12 is charged.

  Next, during the period when only the drive signal UL is at a high level, the lower arm switching element 82 does not flow, the diode 84 is turned on, and the energy stored in the reactor 90 is released, and the battery 12 is discharged. Charged.

  In the step-up chopper control, first, energy is accumulated in the reactor 90 by the primary current I1 from the battery 12 during a period in which only the drive signal UL is at a high level (a period indicated by hatching). At this time, a current is supplied from the smoothing capacitor 96 on the secondary side to the load 23.

  Next, during the period when only the drive signal UH is at the high level, the upper arm switching element 81 does not flow, the diode 83 is turned on, and the energy accumulated in the reactor 90 is released, and the reactor 90 releases the energy. The primary current I1 passes through the DC / DC converter 20, charges the secondary-side smoothing capacitor 96 as the secondary current I2, and is supplied to the load 23.

[Calculation of drive duty DUT]
As described above, in the present embodiment, the drive duty DUT is calculated by the calculation unit 120 and the drive duty DUT is output to the output unit 122. The output unit 122 outputs the drive signals UH and UL after equally allocating the dead time dt to the upper arm target drive time Tud_tar and the lower arm target drive time Tld_tar based on the drive duty DUT. In other words, the output of the drive signals UH and UL is stopped for the dead time dt from the start of the upper arm target drive time Tud_tar and the lower arm target drive time Tld_tar.

  The fuel cell vehicle 10 as a whole is required to have the secondary voltage command value V2com determined by the overall control unit 40 equal to the secondary voltage V2. The target drive duty DUTtar (the sum of the FF term and the FB term) calculated by the calculation unit 120 directly corresponds to the secondary voltage command value V2com.

  However, the output unit 122 outputs the drive signals UH and UL by subtracting the dead time dt from the upper arm target drive time Tud_tar and the lower arm target drive time Tld_tar. For this reason, if the target drive duty DUTtar is transmitted to the output unit 122 as it is, a deviation corresponding to the dead time dt occurs between the secondary voltage command value V2com and the secondary voltage V2, and the controllability of the DC / DC converter 20 is increased. May be affected.

  In order to reduce the influence of such a dead time dt, in this embodiment, the target drive duty DUTtar is corrected by the correction duty DUTcor, and the output time of the drive signals UH and UL accompanying the allocation of the dead time dt in the output unit 122 is corrected. Compensate for the decrease in advance. In other words, considering that the dead time dt is subtracted from the upper arm target drive time Tud_tar and the lower arm target drive time Tld_tar, one of the upper arm target drive time Tud_tar and the lower arm target drive time Tld_tar is equal to the dead time dt. The drive duty DUT is calculated so as to be longer. Which of the upper arm target drive time Tud_tar and the lower arm target drive time Tld_tar is to be increased is determined according to the polarity of the primary current I1 in each switching cycle Tsw.

  That is, when the polarity of the primary current I1 is negative, it is in a step-down (regenerative) state, the step-down upper arm switching element 81 is turned on (current flow), and the step-up lower arm switching element 82 is turned on (passage). Do not flow. Therefore, the upper arm target drive period Tud_tar is set in advance longer by the dead time dt. As a result, the upper arm drive period Tud obtained by subtracting the dead time dt from the upper arm target drive time Tud_tar in the output unit 122 becomes equal to the period directly corresponding to the target drive duty DUTtar.

  On the other hand, when the polarity of the primary current I1 is positive, it is in a boosting (assist) state, the boosting lower arm switching element 82 is turned on (flowing), and the stepping down upper arm switching element 81 is turned on (passing). Do not flow. Therefore, the lower arm target drive period Tld_tar is set longer by the dead time dt in advance. As a result, the lower arm drive period Tld obtained by subtracting the dead time dt from the lower arm target drive time Tld_tar in the output unit 122 becomes equal to the period directly corresponding to the target drive duty DUTtar.

  Furthermore, in the present embodiment, when the primary current I1 is in the vicinity of zero ampere (when in a state of crossing zero ampere), the correction duty DUTcor is changed (details will be described later).

  In order to perform the above processing, in the present embodiment, the bottom value I1btm [A] and the peak value I1pk [A] of the primary current I1, the positive current threshold THmax [A], and the negative current threshold THmin [A]. And are used. The positive current threshold value THmax and the negative current threshold value THmin are set to values that can determine the operating state of the DC / DC converter 20 (step-down (regeneration), step-up (assist), or crossing zero amps).

  FIG. 5 shows the relationship between the primary current I1 and the correction duty DUTcor. 6A, 6B, and 6C show the correction duty DUTcor when the primary current I1 is across zero amperes. 7A, 7B, and 7C are explanatory diagrams when the correction duty DUTcor is set for the primary current I1.

  Like the primary current I1a in FIG. 5, when both the peak value I1pk and the bottom value I1btm are less than the negative current threshold THmin (I1btm, I1pk <THmin), that is, the primary current I1 over the entire switching period Tsw. Is negative, the correction duty DUTcor is set to “(dt / Tsw) × 100”.

  When the peak value I1pk is between the positive current threshold value THmax and the negative current threshold value THmin and the bottom value I1btm is less than the negative current threshold value THmin (I1btm <THmin ≦ I1pk) as in the primary current I1b of FIG. ≦ THmax), the correction duty DUTcor is set using the peak value I1pk and the characteristic Cpk of the table TBLpk shown in FIG. 6A (see FIG. 7A). In the characteristic Cpk, the correction duty DUTcor is decreased from “(dt / Tsw) × 100” [%] to zero [%] as the peak value I1pk increases.

  When the peak value I1pk exceeds the positive current threshold THmax (I1pk> THmax) and the bottom value I1btm is less than the negative current threshold THmin (I1btm <THmin) as in the primary current I1c of FIG. Set DUTcor to zero [%].

  When the peak value I1pk and the bottom value I1btm are between the positive current threshold THmax and the negative current threshold THmin (THmin ≦ I1btm, I1pk ≦ THmax) as in the primary current I1d of FIG. 5, the primary current I1 The correction duty DUTcor is set using the average value (here, the average value I1ave [A] of the peak value I1pk and the bottom I1btm) and the characteristic Cave of the table TBAVE shown in FIG. 6B (see FIG. 7B). In the characteristic Cave, the correction duty DUTcor is decreased from “(dt / Tsw) × 100” [%] to “(−dt / Tsw) × 100” as the average value I1ave increases.

  When the bottom value I1btm is between the positive current threshold value THmax and the negative current threshold value THmin and the peak value I1pk exceeds the positive current threshold value THmax (THmin ≦ I1btm ≦ THmax <) as in the primary current I1e of FIG. I1pk), the bottom value I1btm, and the characteristic Cbtm of the table TBLbtm in FIG. 6C are used to set the correction duty DUTcor (see FIG. 7C). In the characteristic Cbtm, the correction duty DUTcor is decreased from zero [%] to “(−dt / Tsw) × 100” [%] as the bottom value I1btm increases.

  When both the peak value I1pk and the bottom value I1btm exceed the positive current threshold THmax (I1btm, I1pk> THmax) as in the primary current I1f of FIG. 6, the correction duty DUTcor is “(−dt / Tsw) × 100 To "".

  FIG. 8 is a flowchart for setting the correction duty DUTcor. In step S1, the correction duty calculation unit 136 of the calculation unit 120 determines whether or not the peak value I1pk of the primary current I1 is less than the negative current threshold THmin (I1pk <THmin). When the peak value I1pk is less than the negative current threshold THmin (S1: YES), the DC / DC converter 20 is in a step-down (regenerative) state. Therefore, in step S2, the correction duty calculation unit 136 sets the correction duty DUTcor to “(dt / Tsw) × 100”. When the peak value I1pk is equal to or greater than the negative current threshold THmin (S1: NO), the process proceeds to step S3.

  In step S3, correction duty calculation unit 136 determines whether bottom value I1btm exceeds positive current threshold value THmax (I1btm> THmax). When bottom value I1btm exceeds positive current threshold value THmax (S3: YES), DC / DC converter 20 is in a boost (assist) state. Therefore, in step S4, the correction duty calculation unit 136 sets the correction duty DUTcor to “(−dt / Tsw) × 100”. When the bottom value I1btm is equal to or less than the positive current threshold THmax (S3: NO), the process proceeds to step S5.

  In step S5, the correction duty calculator 136 determines whether the bottom value I1btm is less than the negative current threshold THmin (I1btm <THmin) and the peak value I1pk exceeds the positive current threshold THmax (I1pk> THmax). To do. When the bottom value I1btm is less than the negative current threshold THmin and the peak value I1pk exceeds the positive current threshold THmax (S5: YES), in step S6, the correction duty calculator 136 sets the correction duty DUTcor to zero. Set. When the bottom value I1btm is greater than or equal to the negative current threshold THmin, or when the peak value I1pk is less than or equal to the positive current threshold THmax (S5: NO), the process proceeds to step S7.

  In step S7, the correction duty calculation unit 136 determines whether or not the bottom value I1btm is less than the negative current threshold THmin (I1btm <THmin) and the peak value I1pk is not less than the negative current threshold THmin and not more than the positive current threshold THmax ( THmin ≦ I1pk ≦ THmax) is determined. When the bottom value I1btm is less than the negative current threshold THmin and the peak value I1pk is not less than the negative current threshold THmin and not more than the positive current threshold THmax (S7: YES), in step S8, the correction duty calculating unit 136 The correction duty DUTcor is set using the value I1pk and the characteristic Cpk of the table TBLpk (FIG. 6A). When the bottom value I1btm is greater than or equal to the negative current threshold THmin, or when the peak value I1pk is less than the negative current threshold THmin or exceeds the positive current threshold THmax (S7: NO), the process proceeds to step S9.

  In step S9, the correction duty calculation unit 136 determines whether the bottom value I1btm is greater than or equal to the negative current threshold THmin and less than or equal to the positive current threshold THmax (THmin ≦ I1btm ≦ THmax), and the peak value I1pk exceeds the positive current threshold THmax. (I1pk> THmax) is determined. When the bottom value I1btm is greater than or equal to the negative current threshold value THmin and less than or equal to the positive current threshold value THmax and the peak value I1pk exceeds the positive current threshold value THmax (S9: YES), in step S10, the correction duty calculation unit 136 The correction duty DUTcor is set using the bottom value I1btm and the characteristic Cbtm (FIG. 6C) of the table TBLbtm. When the bottom value I1btm is less than the negative current threshold THmin or exceeds the positive current threshold THmax, or the peak value I1pk is equal to or less than the positive current threshold THmax (S9: NO), in step S11, the corrected duty calculator 136 Sets the correction duty DUTcor using the average value I1ave of the peak value I1pk, the bottom value I1btm, and the characteristic Cave (FIG. 6B) of the table TBLove.

[Effect of this embodiment]
As described above, according to the present embodiment, the operating state of the DC / DC converter device 50 is changed using the peak value I1pk, the bottom value I1btm, the positive current threshold THmax, and the negative current threshold THmin of the primary current I1. The correction duty DUTcor is set using the determined operation state, the peak value I1pk, the bottom value I1btm, and the average value I1ave. As a result, at least one of the output period of the drive signal UH and the drive signal UL (upper arm drive time Tud and lower arm drive time Tld) is reduced by the dead time dt in accordance with the operating state of the DC / DC converter device 50. Can be compensated. Therefore, voltage fluctuation due to switching between the step-up state and the step-down state can be suppressed in the synchronous switching control. As a result, the controllability of the DC / DC converter device 50 can be improved.

  In the above embodiment, the battery 12 is connected to the primary side 1S of the DC / DC converter device 50, and the fuel cell 14 and the motor 16 are connected to the secondary side 2S. According to this configuration, it is possible to suppress the deterioration of the stack of the fuel cells 14 and to improve the efficiency of the fuel cell vehicle 10 that uses the fuel cells 14 as a power generator.

  That is, in the current-voltage characteristics of a general fuel cell, the voltage increases as the current decreases (in contrast, the current increases as the voltage decreases). Further, when a fuel cell is used as a power generation device, it is necessary to supply an amount of reaction gas corresponding to the required output of the power generation device to the fuel cell. However, when the amount of the reaction gas supplied to the fuel cell is less than the amount corresponding to the required output (for example, when the voltage of the fuel cell is lower than the target value), in addition to the current generated by the reaction of the reaction gas, Current is drawn from the fuel cell stack itself, which degrades the stack. If the DC / DC converter device 50 according to the present embodiment is used, it is possible to suppress voltage fluctuations associated with switching between the step-up state and the step-down state. For this reason, even when switching between the step-up state and the step-down state occurs, it is possible to prevent the voltage of the fuel cell 14 from becoming lower than the target value and to suppress the deterioration of the stack.

  In addition, in order to suppress the deterioration of the stack as described above, in the case of supplying an amount of reaction gas in which an amount of reaction gas actually required is added with a margin, in the DC / DC converter device 50, the step-up state and the step-down state Since voltage fluctuations associated with switching are suppressed, the margin can be set low. As a result, the efficiency of the fuel cell vehicle 10 that uses the fuel cell 14 as a power generation device can be improved.

3. Modifications It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that various configurations can be adopted based on the contents described in this specification. For example, the following configuration can be adopted.

[Target]
In the above embodiment, the DC / DC converter device 50 is mounted on the fuel cell vehicle 10, but is not limited thereto, and may be mounted on another target. For example, the DC / DC converter device 50 can be used for a moving body such as a ship or an aircraft. Alternatively, the DC / DC converter device 50 may be applied to a household power system.

[DC / DC converter]
In the above embodiment, the number of the upper arm switching elements 81 and the number of the lower arm switching elements 82 is one. However, the number is not limited to this, and may be two or more.

[Calculator]
In the above embodiment, the correction duty DUTcor is added by the second adder 140, but the present invention is not limited to this. For example, it is possible to add to the FF term calculated by the FF term calculation unit 134.

  FIG. 9 shows a configuration of a converter control unit 48a having a calculation unit 120a as a modification of the calculation unit 120. In the calculation unit 120a, the FF term calculated by the FF term calculation unit 134 and the correction duty DUTcor calculated by the correction duty calculation unit 136 are added by the first adder 142, and the sum (FF term + correction duty DUTcor) is added. ) And the FB term calculated by the FB term calculation unit 132 are added by the second adder 144 to calculate the drive duty DUT.

[Driving duty]
In the above embodiment, the drive duty DUT directly defines the upper arm target drive period Tud_tar (the target period for driving the upper arm switching element 81 in one switching cycle Tsw), but the lower arm target drive period. A configuration in which Tld_tar (a target period for driving the lower arm switching element 82 in one switching period Tsw) is directly defined is also possible. In this case, for example, when the polarity of the primary current I1 is only positive in one switching cycle Tsw, the calculation unit 120 calculates the drive duty DUT using “(dt / Tsw) × 100” as the correction duty DUTcor, When the polarity of the primary current I1 is only negative in the switching cycle Tsw, the drive duty DUT is calculated using “(−dt / Tsw) × 100” as the correction duty DUTcor, and the primary current I1 is zero in one switching cycle Tsw. When straddling amperes, the drive duty DUT can be calculated by changing the correction duty DUTcor.

[Correction duty]
In the above embodiment, the correction duty DUTcor is set using the peak value I1pk, the bottom value I1btm, and the average value I1ave of the primary current I1 as they are, but the present invention is not limited to this.

  10A, 10B, and 10C are explanatory diagrams of a first modified example of the relationship between the primary current I1 and the correction duty DUTcor. The first modification is basically the same as that of the above embodiment, but the correction duty is applied to the peak value I1pk, the bottom value I1btm, and the average value I1ave after performing filter processing for limiting the change in the value. The difference is in determining the DUTcor. Examples of filter processing include first-order lag processing and averaging processing. According to the first modification, it is possible to limit the change in the correction duty DUTcor and suppress the primary current I1 from fluctuating excessively.

  11A, 11B, and 11C are explanatory diagrams of a second modification of the relationship between the primary current I1 and the correction duty DUTcor. The second modified example is basically the same as the above-described embodiment, except that a filter process for limiting the change in the value of the correction duty DUTcor determined from the peak value I1pk, the bottom value I1btm, or the average value I1ave is performed. The difference is that the correction duty DUTcor2 after filtering is determined. Examples of filter processing include first-order lag processing and averaging processing. According to the second modification, it is possible to limit the change in the correction duty DUTcor and suppress the primary current I1 from fluctuating excessively.

  In the first embodiment, the first modification example of FIGS. 10A to 10C and the second modification example of FIGS. 11A to 11C, the correction duty DUTcor is determined using the peak value I1pk, the bottom value I1btm, and the average value I1ave. Not limited to. For example, as the peak value I1pk and the bottom value I1btm, respective moving average values may be used. Further, instead of the average value I1ave of the peak value I1pk and the bottom value I1btm, an average value (average value of all values) of the primary current I1 in each switching cycle Tsw may be used.

DESCRIPTION OF SYMBOLS 12 ... Battery (electric storage apparatus) 14 ... Fuel cell 16 ... Motor 48, 48a ... Converter control part (control part)
DESCRIPTION OF SYMBOLS 50 ... DC / DC converter apparatus 81 ... Upper arm switching element 82 ... Lower arm switching element 90 ... Reactor 101,102 ... Current sensor 120, 120a ... Calculation part 122 ... Output part dt ... Dead time DUT ... Drive duty DUTcor ... Correction duty DUTtar: Target drive duty I1, I1a to I1f ... Primary current I1ave ... Average value of primary current I1btm ... Bottom value of primary current I1pk ... Peak value of primary current THmax ... Positive current threshold THmin ... Negative current threshold Tld: Lower arm drive period Tld_tar ... Lower arm target drive period Tsw ... Switching cycle Tud ... Upper arm drive period Tud_tar ... Upper arm target drive periods UH, UL ... Drive signal 1S ... Primary side 2S ... Secondary side

Claims (5)

A step-down switching element;
A step-up switching element;
Reactor,
A controller that alternately outputs a drive signal to the step-down switching element and the step-up switching element across a dead time for each switching period;
A chopper-type DC / DC converter device comprising: a current sensor that measures a primary current on which the reactor is disposed;
The controller is
A calculation unit for calculating a drive duty of at least one of the step-down switching element and the step-up switching element;
A dead time setting process for subtracting the dead time from an output period of the drive signal for the step-down switching element and the step-up switching element determined based on the drive duty is performed, and an output period after the dead time setting process And an output section for outputting the drive signal to the step-down switching element and the step-up switching element.
The calculation unit further includes:
Calculating a target drive duty corresponding to a period in which at least one of the step-down switching element and the step-up switching element is actually driven and a correction duty for correcting the influence of the dead time setting process;
Prior to the dead time setting process, by correcting the target drive duty with the correction duty, the drive duty to be output to the output unit is calculated,
When the bottom value of the primary current in one switching cycle is equal to or greater than a positive threshold, the correction duty is set so as to compensate for a decrease in the output period of the drive signal to the boosting switching element due to the dead time. Set,
When the peak value of the primary-side current in one switching cycle is equal to or less than a negative threshold, the correction duty is set so as to compensate for a decrease in the output period of the drive signal to the step-down switching element due to the dead time. Set,
When the peak value is between the negative threshold value and the positive threshold value, and the bottom value is less than the negative threshold value, the correction duty is set based on the peak value;
When the bottom value is between the negative threshold and the positive threshold, and the peak value exceeds the positive threshold, the correction duty is set based on the bottom value,
When the peak value and the bottom value are between the negative threshold value and the positive threshold value, the correction duty is set based on an average value of the primary-side current in the switching period. DC / DC converter device. The DC / DC converter device according to claim 1, wherein
The DC / DC converter device, wherein the arithmetic unit performs a filtering process for limiting a change in at least one of the peak value, the bottom value, and the average value. The DC / DC converter device according to claim 1 or 2,
The DC / DC converter device, wherein the arithmetic unit performs a filter process for limiting a change in the correction duty. In the DC / DC converter device according to any one of claims 1 to 3,
A DC / DC converter device, wherein a power storage device is connected to the primary side, and a power generation device and a motor are connected to the secondary side. The DC / DC converter device according to claim 4,
The power generation device is a fuel cell.

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