JP2019129606A - Multi-phase converter - Google Patents

Abstract

To provide a temperature management technology of a multi-phase converter in which a plurality of converter circuits are connected in parallel to each other.SOLUTION: A controller 17 of a multi-phase converter 2 increases the number of converter circuits 10a-10d to be driven as an input current Ifdc becomes larger. The controller 17, when increasing the drive number from a state where the drive number is equal to or less than n-2, stops at least one converter circuit driven up to that time and drives two converter circuits not driven up to that time. The controller 17, when decreasing the drive number from a state where the drive number is equal to or more than three and equal to or less than n-1, stops the converter circuit driven the longest up to that time, and in a case where a temperature difference between two converter circuits that have simultaneously started to be driven in advance is larger than a predetermined temperature difference threshold, stops one with higher temperature of the two converter circuits, and drives the converter circuit not driven up to that time instead of the stopped converter circuit.SELECTED DRAWING: Figure 1

Description

  The technology disclosed herein relates to a multiphase converter in which a plurality of converter circuits are connected in parallel.

  A multi-phase converter in which a plurality of converter circuits are connected in parallel is known. The multiphase converter of Patent Document 1 increases the number of converter circuits to be driven as the input current increases. By adjusting the number of converter circuits to be driven according to the magnitude of the input current, the load can be distributed and the converter circuit can be used in an efficient range. In general, the converter circuit has an input current range with high efficiency, and uses the converter circuit in the input current range with high efficiency by reducing the number of converter circuits to drive when the input current to the polyphase converter is small. This is because the frequency can be increased.

JP, 2017-153244, A

  If the converter circuit to be driven is fixed when the input current is small, the temperature difference between the converter circuit and the other converter circuits becomes large. A method of stopping the converter circuit whose temperature exceeds the temperature threshold and driving another converter circuit is conceivable, but the converter circuit once exceeding the temperature threshold cannot be used until the temperature drops. The present specification provides a temperature management technique for a multiphase converter in which a plurality of converter circuits are connected in parallel.

  The multiphase converter disclosed herein comprises n converter circuits and a controller connected in parallel. The controller increases the number of converter circuits to drive as the input current to the polyphase converter increases. The controller executes the following processing as temperature management of a plurality of converter circuits. (1) When the controller increases the number of drives from n-2 or less, the controller stops at least one converter circuit that has been driven and the two converters that have not been driven. Drive the circuit. (2) When the drive number is reduced from a state where the drive number is 3 or more and n-1 or less, the controller stops the converter circuit that has been driven the longest so far, and at the same time as in (1) above If the temperature difference between the two converter circuits that have started to drive exceeds the predetermined temperature difference threshold, the higher one of the two converter circuits that has started to drive at the same time is stopped, and instead, Drive the converter circuit that was not driving.

  By the process (1), the temperature rise of the converter circuit that has been driven for the longest time can be suppressed. In addition, even if the process (2) starts to drive simultaneously, if the temperature difference is large, there is a possibility that the converter circuit having a large temperature may have a problem, and such converter circuit is stopped. Control the temperature rise further. The polyphase converters disclosed herein can be rested before the temperature of the respective converter circuit rises. Details and further improvements of the technology disclosed in this specification will be described in the following “DETAILED DESCRIPTION”.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram of the electric power system of an electric vehicle containing the multiphase converter of an Example. It is a transition diagram of the number of drives. It is a flowchart at the time of changing from two-phase drive to three-phase drive. It is a flowchart at the time of changing to three-phase drive from three-phase drive.

  The multiphase converter of the embodiment will be described with reference to the drawings. The multiphase converter of the embodiment is mounted on an electric vehicle. FIG. 1 shows a block diagram of a power system of an electric vehicle 100 equipped with the multiphase converter 2. Arrows and broken lines in FIG. 1 mean signal lines.

  The electric vehicle 100 includes a traveling motor 32, a fuel cell 21 and a battery 34 as a DC power source, a multiphase converter 2, an inverter 31, and a power converter 35. The multiphase converter 2 boosts the output voltage of the fuel cell 21 to the drive voltage of the motor 32 and supplies the boosted voltage to the inverter 31. The power converter 35 boosts the output power of the battery 34 to the drive voltage of the motor 32 and supplies it to the inverter 31. The inverter 31 converts the DC power output from the multiphase converter 2 and the power converter 35 into AC power and supplies the AC power to the motor 32.

  The inverter 31 also has a function of converting AC power generated by the motor 32 into DC power. The power converter 35 also has a function of stepping down the DC power converted by the inverter 31 and supplying it to the battery 34. The power converter 35 is a so-called bidirectional DC-DC converter. The power reduced by the power converter 35 is stored in the battery 34. The power converter 35 may step down the excess power that has not been used for driving the motor 32 out of the power output from the fuel cell 21 and store it in the battery 34.

  The multiphase converter 2 includes four boost converter circuits 10a to 10d, capacitors 22, 24, a current sensor 23, a voltage sensor 25, and a controller 17. Hereinafter, for convenience of description, boost converter circuits 10a-10d are simply referred to as converter circuits 10a-10d.

  The four converter circuits 10a to 10d are connected in parallel between the common input terminals 12a and 12b and the common output terminals 13a and 13b. All of the four converter circuits 10a to 10d have a function of boosting and outputting the voltage of the input power. That is, converter circuits 10 a-10 d respectively boost the output voltage of fuel cell 21 to the drive voltage of motor 32. Converter circuits 10a-10d all have the same structure.

  A capacitor 22 is connected between the common input terminals 12a and 12b, and a capacitor 24 is connected between the common output terminals 13a and 13b. Capacitor 22 smoothes the current input to converter circuits 10a-10d, and capacitor 24 smoothes the current output from converter circuits 10a-10d.

  The converter circuit 10a will be described. The converter circuit 10a includes a switching element 3a, diodes 4a and 6a, a reactor 5a, and a temperature sensor 7a. One end of the reactor 5a is connected to the input terminal positive electrode 12a, and the other end is connected to the anode of the diode 6a. The cathode of the diode 6a is connected to the output terminal positive electrode 13a.

  The input terminal negative electrode 12b and the output terminal negative electrode 13b of the converter circuit 10a are directly connected. The switching element 3a is connected between the intermediate point of the reactor 5a and the diode 6a and the input end negative electrode 12b (output end negative electrode 13b). The diode 4a is connected in antiparallel to the switching element 3a.

  The temperature sensor 7a measures the temperature of the switching element 3a. The temperature sensor 7a may be disposed at the highest temperature in the converter circuit 10a. The temperature sensor 7a is provided, for example, in the chip of the switching element 3a. When the temperature of the reactor 5a is more important in the converter circuit 10a, the temperature sensor 7a may be disposed in the reactor 5a. Or the temperature sensor may be provided in both the switching element and the reactor.

  The converter circuit 10b includes a switching element 3b, diodes 4b and 6b, a reactor 5b, and a temperature sensor 7b. The converter circuit 10c includes a switching element 3c, diodes 4c and 6c, a reactor 5c, and a temperature sensor 7c. The converter circuit 10d includes a switching element 3d, diodes 4d and 6d, a reactor 5d, and a temperature sensor 7d. The structure of converter circuit 10b-10d is the same as that of converter circuit 10a.

  Switching elements 3a-3d of converter circuits 10a-10d are transistors, for example, MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) and IGBTs (Insulated Gate Bipolar Transistors). The switching elements 3a to 3d are controlled by the controller 17. The controller 17 supplies a drive signal of a predetermined duty ratio to the switching elements 3a to 3d. When each of the switching elements 3a to 3d is turned on / off at the duty ratio of the drive signal, the voltage of the power of the fuel cell 21 applied to the input terminals 12a and 12b is boosted and output from the output terminals 13a and 13b. In other words, converter circuit 10a (10b, 10c, 10d) boosts the input voltage by power conversion switching element 3a (3b, 3c, 3d) controlled by the duty ratio.

  Converter circuits 10a-10d have the same structure. The controller 17 supplies a drive signal having a predetermined duty ratio to each of the switching elements 3a to 3d. However, the controller 17 supplies drive signals to the respective switching elements 3a to 3d at different timings. Converter circuits 10a-10d operate in the same manner, but at different timings. By the four converter circuits 10a to 10d performing the same operation, the parallel connection circuit of the four converter circuits 10a to 10d operates as if it were one converter circuit.

  The multiphase converter 2 measures a current sensor 23 that measures a current supplied from the fuel cell 21 (input current Ifdc to the multiphase converter 2) and a voltage after boosting (the output voltage VH of the multiphase converter 2). A voltage sensor 25 is provided, and the measured value of each sensor is sent to the controller 17. The controller 17 controls the converter circuits 10a to 10d based on data from the sensor and information sent from the host controller 40 described later.

  An accelerator pedal 42 and a brake pedal 43 are connected to the host controller 40, and various information is sent to the controller 17 of the multiphase converter 2 based on signals from these devices. In addition to the devices described above, the host controller 40 is also connected to a vehicle main switch (ignition switch) and the like. The host controller 40 also controls the fuel cell 21 and the power converter 35 as well as the multiphase converter 2. The host controller 40 can control the output of the fuel cell 21. In particular, the host controller 40 increases the output of the fuel cell 21 when the amount of operation of the accelerator pedal 42 is large.

  The description will return to the description of the multiphase converter 2. The controller 17 of the multiphase converter 2 adjusts the number of converter circuits to be driven according to the magnitude of the input current Ifdc (the output current of the fuel cell 21). Specifically, as the input current Ifdc increases, the number of converter circuits to be driven is increased. The drive mode of multiphase converter 2 includes first to third modes shown in FIG. When the vehicle main switch (IG: also called an ignition switch) is turned on, the controller 17 first selects the first mode (M1). The first mode is a drive mode for driving two phases of the four-phase converter circuits 10a to 10d. In the first mode, the controller 17 selects two phases from the converter circuits 10a to 10d and drives them sequentially in a phase of 180 degrees. That is, the drive signal is supplied to the first converter circuit 10a at the start of the control cycle, and the drive signal is supplied to the second converter circuit 10b at the timing of the half control cycle (phase 180 degrees). A drive signal having the same duty ratio is supplied to the two converter circuits.

  As described above, the fuel cell 21 is controlled by the host controller 40. Therefore, the magnitude of the output current of the fuel cell 21 changes. The controller 17 of the multiphase converter 2 monitors the input current Ifdc supplied from the fuel cell 21 by the current sensor 23. The controller 17 adjusts the number of phases to be driven according to the magnitude of the input current Ifdc.

  When the input current Ifdc exceeds the first current threshold I1, the controller 17 switches the driving mode of the multiphase converter 2 from the first mode (M1) to the second mode (M2). In the second mode, the controller 17 drives three phases of the four-phase converter circuits 10a to 10d. The controller 17 selects three phases from the converter circuits 10a to 10d and sequentially drives them at a phase of 120 degrees. That is, the drive signal is supplied to the first converter circuit 10a at the start of the control cycle, and the drive signal is supplied to the second converter circuit 10b at the timing of 1/3 control cycle (phase 120 degrees). Furthermore, the drive signal is supplied to the third converter circuit 10c at a timing of 2/3 control cycle (phase 240 degrees). The three converter circuits are supplied with drive signals having the same duty ratio. When one control cycle elapses, the three converter circuits are sequentially driven again. The multiphase converter 2 of the embodiment is characterized by a converter circuit selection algorithm when the number of converter circuits to be driven is increased. The selection algorithm will be described later.

  When the input current Ifdc exceeds the second current threshold I2 (> I1), the controller 17 switches the drive mode of the multiphase converter 2 from the second mode (M2) to the third mode (M3). In the third mode (M3), the controller 17 drives all of the four-phase converter circuits 10a to 10d. The controller 17 sequentially drives the converter circuits 10a to 10d with a phase of 90 degrees. That is, the drive signal is supplied to the first converter circuit 10a at the start of the control cycle, and the drive signal is supplied to the second converter circuit 10b at the timing of the 1/4 control cycle (phase 90 degrees). Furthermore, the drive signal is supplied to the third converter circuit 10c at the timing of 1/2 control cycle (phase 180 degrees), and the drive signal is supplied to the fourth converter circuit 10d at the timing of 3/4 control cycle (phase 270 degrees). Do. Drive signals having the same duty ratio are supplied to the converter circuits 10a to 10d. When one control cycle has elapsed, the controller 17 drives again in order from the first converter circuit 10a.

  Each of the converter circuits 10a to 10d is more efficient in an appropriate input range than when the input is too small. The controller 17 increases the number of phases to be driven as the input current Ifdc increases. By doing so, the converter circuits 10a to 10d are used as efficiently as possible, and the load on the converter circuits 10a to 10d is prevented from becoming excessive.

  The reason why the plurality of phases are driven with the phases shifted is to prevent the ON / OFF timings of the switching elements of the respective converter circuits from overlapping. When the on / off timings of the switching elements overlap, ripples overlap and the loss increases.

  The controller 17 changes the drive mode from the third mode to the second mode when the input current Ifdc falls below the third current threshold I3 during the four-phase drive in the third mode. The controller 17 changes the drive mode from the second mode to the first mode when the input current Ifdc falls below the fourth current threshold I4 during the three-phase drive in the second mode. Here, the relationship between the magnitudes of the current threshold values is I2> I3> I1> I4. The threshold value of the input current Ifdc when switching from the first mode to the second mode (first current threshold value I1) is different from the threshold value of the input current Ifdc when switching from the second mode to the first mode (fourth current threshold value). The reason is to prevent hunting in mode switching. The threshold value of the input current Ifdc when switching from the second mode to the third mode (second current threshold value I2) is different from the threshold value of the input current Ifdc when switching from the third mode to the second mode (third current threshold value). The reason is to prevent hunting in mode switching.

  The multiphase converter 2 of the embodiment is also characterized in the selection algorithm of the converter circuit when reducing the number of converter circuits to be driven. Next, as an example, a converter circuit selection algorithm when increasing from two phases to three phases and a selection algorithm when decreasing from three to two will be described.

  FIG. 3 is a flowchart when transitioning from the two-phase drive (first mode) to the three-phase drive (second mode). The symbols “No1,” “No2,” “No3,” and “No4” in FIG. 3 mean the first converter circuit 10a, the second converter circuit 10b, the third converter circuit 10c, and the fourth converter circuit 10d, respectively. Moreover, in FIG. 3 (and FIG. 4 mentioned later), a "circuit" means a converter circuit.

  Now, it is assumed that the first converter circuit 10a and the second converter circuit 10b are driven in the first mode. Here, since the input current Ifdc has exceeded the first current threshold I1, the controller 17 switches the drive mode from the first mode (M1) to the second mode (M2). At that time, the controller 17 selects a converter circuit to be driven according to the flowchart of FIG. First, the controller 17 acquires the temperatures of the first and second converter circuits 10a and 10b that are currently driven (step S2). Then, the controller 17 compares the temperature T1 of the first converter circuit 10a with the temperature T2 of the second converter circuit 10b. Now, it is assumed that the temperature T1 of the first converter circuit 10a is higher than the temperature T2 of the second converter circuit 10b. The controller 17 stops the converter circuit 10a having the higher temperature (step S3). At this time, the controller 17 stores the number “No2” of the second converter circuit 10b to be continuously driven in the “longest drive” which is a variable on the software (step S3).

  Next, the controller 17 drives the third converter circuit 10c (No3) and the fourth converter circuit 10d (No4) that have been stopped (step S4). At this point, transition is made from two-phase drive to three-phase drive. Finally, the controller 17 stores the number (No. 3, No. 4) of the converter circuit which has started driving at the same time in step S4 in "simultaneous driving start" which is a variable on software (step S5).

  In this example, in the multiphase converter 2, the second, third, and fourth converter circuits 10b, 10c, and 10d operate from the first mode in which the first and second converter circuits 10a and 10b operate. Transition to mode

  In the transition from the two-phase drive mode (first mode) to the three-phase drive mode (second mode), the converter circuit to be driven is not simply increased by one, but the temperature of the converter circuit that has been driven so far is the highest. Stop the high circuit. By doing so, the high temperature converter circuit can be rested.

  Next, processing of the controller 17 when transitioning from the three-phase drive (second mode) to the two-phase drive (first mode) will be described. FIG. 4 is a flowchart when transitioning from three-phase drive (second mode) to two-phase drive (first mode). Here, after shifting from the first mode by the first and second converter circuits 10a and 10b described above to the second mode by the second to fourth converter circuits 10b to 10d, the input current Ifdc is changed to the fourth current threshold value. Since it is less than I4, the case where it transfers to the 1st mode from the 2nd mode is assumed. In the second mode, the second to fourth converter circuits 10b to 10d are in operation. The variable “longest drive” stores “No2” indicating the second converter circuit 10b, and the variable “start simultaneous drive” stores “No3,” indicating the third and fourth converter circuits 10c and 10d. "No 4" is stored.

  The controller 17 stops the converter circuit (second converter circuit 10b) of the number (No. 2) stored in the variable “longest drive” (step S12). Next, the controller 17 obtains the temperatures T3 and T4 of the converter circuits (third and fourth converter circuits 10c and 10d) of the numbers stored in the variable "simultaneous drive start" (step S13). Then, the temperature difference (| T3−T4 |) between the acquired temperatures T3 and T4 is compared with a predetermined temperature difference threshold value (step S14). When the temperature difference (| T3-T4 |) is below the temperature difference threshold (step S14: NO), the controller 17 ends the process as it is. In this case, from the second mode (three-phase drive mode) in which the second to fourth converter circuits 10b to 10d are operating, the first mode (two-phase drive in which the third and fourth converter circuits 10c and 10d operate) Mode).

  On the other hand, when the temperature difference (| T3-T4 |) exceeds the temperature difference threshold (step S14: YES), the controller 17 stops the higher temperature converter circuit (step S15). Here, for example, it is assumed that the temperature T3 of the third converter circuit 10c is higher than the temperature T4 of the fourth converter circuit 10d. The controller 17 stops the third converter circuit 10c having a temperature higher than that of the fourth converter circuit. Then, instead of the stopped third converter circuit 10c, the controller 17 starts driving another converter circuit (here, the first converter circuit 10a) that has been stopped (step S15). In this case, from the second mode (three-phase drive mode) in which the second to fourth converter circuits 10b-10d are operating, the first mode (two-phase drive in which the first and fourth converter circuits 10a and 10d are operated Mode).

  If the determination in step S14 is YES, it means that one of the two converter circuits that started driving at the same time has become higher in temperature than the other for some reason. The following factors are assumed, for example, that the temperature difference between the two converter circuits that have started driving simultaneously is increased. First, while using multi-phase converter 2, in a particular converter circuit, the power between the power module sealing the switching element and the cooler is removed, and the power module of the other converter circuit is removed. The temperature is likely to be higher than that. The other is a case where the solder joining the switching element and the terminal in a specific power module deteriorates and the resistance increases. There are other possible causes for the temperature difference to increase. In the multiphase converter 2 of the embodiment, when the number of drives is reduced, if the temperature difference between the two converter circuits that have started the simultaneous driving previously exceeds a predetermined temperature difference threshold, the converter circuit with the higher temperature Stop and drive the alternate converter circuit. By doing so, the high temperature converter circuit can be rested.

  The process of the controller 17 (the process of FIG. 3) when increasing the number of converter circuits to be driven can be expressed as follows when generalized. It is assumed that the multiphase converter has a parallel connection of n converter circuits. (1) When the controller 17 increases the drive number from the state where the drive number is n-2 or less, the controller 17 stops at least one converter circuit that has been driven so far, and the two that have not been driven so far Drive the converter circuit. Further, the process of the controller 17 (the process of FIG. 4) when reducing the number of converter circuits to be driven can be expressed as follows. (2) When the controller 17 reduces the drive number from the state where the drive number is 3 or more and n−1 or less, the controller 17 stops the converter circuit that has been driven for the longest time and If the temperature difference between the two converter circuits that have started to drive at the same time exceeds the predetermined temperature difference threshold, the higher one of the two converter circuits is shut down, and instead, it is driven until that time. Drive the converter circuit that was not present.

  The above process allows multiphase converter 2 to rest the high temperature converter circuit every time the number of driving is changed, so the temperature of a particular converter circuit is significantly higher than that of other converter circuits. It can prevent that it becomes high.

  Points to note regarding the technology described in the embodiment will be described. The technology disclosed in this specification can be applied to a polyphase converter in which three or more converter circuits are connected in parallel. In addition to the multiphase converter in which a plurality of step-up converter circuits are connected in parallel, the technique disclosed in this specification is also preferably applied to a multiphase converter in which a plurality of step-down converter circuits are connected in parallel is there.

  In the multi-phase converter 2 of the embodiment, in the mode transition diagram shown in FIG. 2, when a vehicle main switch (IG: also called an ignition switch) is turned on, the controller 17 first starts the first mode for driving two phases. Select (M1). Each time the main switch is turned on, the controller 17 switches the first and second converter circuits 10a and 10b and the third and fourth converter circuits 10c and 10d as two converter circuits to be driven first. Alternatively, they may be selected.

  The technology disclosed in this specification can also be applied to a hybrid vehicle including an engine together with a motor for traveling.

  As mentioned above, although the specific example of this invention was described in detail, these are only an illustration and do not limit a claim. The art set forth in the claims includes various variations and modifications of the specific examples illustrated above. The technical elements described in the present specification or the drawings exhibit technical usefulness singly or in various combinations, and are not limited to the combinations described in the claims at the time of application. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

2: Multi-phase converter 3a-3d: switching element 4a-4d, 6a-6d: diode 5a-5d: reactor 7a-7d: temperature sensor 10a-10d: boost converter circuit (converter circuit)
17: controller 21: fuel cell 22, 24: capacitor 23: current sensor 25: voltage sensor 31: inverter 32: motor 34: battery 35: power converter 40: host controller 42: accelerator pedal 43: brake pedal 100: electric car

Claims (1)

A multiphase converter,
N converter circuits connected in parallel,
A controller that increases the number of converter circuits to be driven as the input current to the multiphase converter increases;
Equipped with
The controller
(1) When increasing the number of driving from a state where the number of driving is n-2 or less, stop at least one converter circuit that has been driven and two converter circuits that have not been driven so far Drive,
(2) When reducing the number of driving from the state where the number of driving is 3 or more and n-1 or less, the converter circuit that has been driven the longest until then is stopped, and at the same time as (1), it starts driving simultaneously. If the temperature difference between the two converter circuits exceeds a predetermined temperature difference threshold, one of the two converter circuits which has a higher temperature is stopped, and instead, the converter which has not been driven until that time. Driving circuit,
Multiphase converter.

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