JP2019126184A - Polyphase converter - Google Patents

Abstract

To provide a polyphase converter which can distribute load in the polyphase converter in which a plurality of converter circuits are connected in parallel.SOLUTION: In an electric vehicle 100, a polyphase converter 2 has a plurality of converter circuits 10a-10d connected in parallel and converting input power to be outputted, and a controller 17. The controller increases the number of driven converter circuits as input current Ifdc becomes larger. When a load index value set based on at least one of a temperature of the converter circuit and current flowing through the converter circuit deviates from a predetermined load allowable range and during a predetermined period after a high load period determination index value becomes lower than a predetermined end determination threshold value, the controller drives more converter circuits than the number of driven converter circuits corresponding to the input current Ifdc at the time when the load index value does not exceed the load allowable range.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 multiphase 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, it is possible to distribute the load and to use the converter circuits within a range of high efficiency. In general, a converter circuit has a high efficiency input current range, and uses the converter circuit in a high efficiency input current range by reducing the number of converter circuits to be driven when the input current to the multiphase converter is small. This is because the frequency can be increased.

JP, 2017-153244, A

  The multiphase converter of Patent Document 1 can prevent overheating of the converter circuit by distributing the load to a plurality of converter circuits. However, for example, if a plurality of converter circuits operate in response to a large input current and then the input current decreases and only one converter circuit continues to operate, the temperature of one converter circuit It will be higher than the temperature of the converter circuit. In particular, if the temperature of each converter circuit rises correspondingly to a large input current and only one continues to operate, the temperature of that one converter exceeds the upper temperature limit for preventing overheat. There is a risk of There is room for improvement in the mechanism for distributing the load in the multiphase converter.

  The multiphase converter disclosed in the present specification includes a plurality of converter circuits connected in parallel and converting and outputting input power, and a controller. The controller increases the number of converter circuits to drive as the input power increases. In this controller, the load index value set based on at least one of the temperature of the converter circuit and the current flowing in the converter circuit is out of the predetermined load allowable range, and the high load period judgment index value is the predetermined end judgment threshold During a predetermined period after the load index value does not exceed the load allowable range, driving a greater number of converter circuits than the number of drives corresponding to the input power (however, the load When the number of drives is within the allowable range of load is the maximum number of drives, maintain the maximum number of drives). The multi-phase converter disclosed in the present specification continues to distribute the load by driving a larger number of converter circuits than usual even when the load is lowered after the load of each converter circuit is high. Such a process prevents the particular converter circuit from overheating.

  The details and further improvement of the technology disclosed in the present specification will be described in the following "Forms for Carrying Out the Invention".

It is a block diagram of the electric power system of the electric vehicle of an example. It is a transition diagram of the drive mode of a multiphase converter. It is a time chart which shows an example of a drive number change of a multiphase converter.

  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 motor 32 for traveling, a fuel cell 21 and a battery 34 as DC power supplies, 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 it 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 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 excess power not used for driving the motor 32 among the power output from the fuel cell 21 and store it in the battery 34.

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

  The four converter circuits 10a to 10d are connected in parallel between the common input ends 12a and 12b and the common output ends 13a and 13b. The four converter circuits 10a to 10d all 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 to 10d, and capacitor 24 smoothes the current output from converter circuits 10a to 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 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. Alternatively, temperature sensors may be provided in both the switching element and the reactor.

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

  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 circuits 10b-10d is the same as that of converter circuit 10a.

  The switching elements 3a to 3d of the converter circuits 10a to 10d are transistors, and are, for example, a MOSFET (Metal Oxide Field Effect Transistor) or an IGBT (Insulated Gate Bipolar Transistor). The switching elements 3a to 3d are controlled by the controller 17. In FIG. 1, illustration of signal lines from the controller 17 to the switching elements 3 a to 3 d is omitted. 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 and 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, the converter circuit 10a (10b-10d) boosts the input voltage by the switching element 3a (3b-3d) for power conversion controlled by the duty ratio.

  Converter circuits 10a-10d have the same structure. The controller 17 supplies drive signals of the same 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-10d performing the same operation, the four converter circuits 10a-10d operate as if they were one converter circuit. Multiphase converter 2 measures current sensor 23 for measuring the current (input current Ifdc to multiphase converter 2) supplied from fuel cell 21 and measures the voltage after boosting (output voltage VH of 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 upper controller 40 described later. Although described later in detail, the controller 17 adjusts the number of converter circuits to be driven according to the magnitude of the input current Ifdc.

  An accelerator pedal 42 and a brake pedal 43 are connected to the upper controller 40, and various types of information are 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 main switch (ignition switch) of the vehicle. Further, the host controller 40 controls not only the multiphase converter 2 but also the fuel cell 21 and the power converter 35. 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 operation amount 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. Control of multi-phase converter 2 will be described with reference to FIG. FIG. 2 is a transition diagram of drive modes of multiphase converter 2. Below, converter circuits 10a-10d may be expressed as a "phase." Further, each of the converter circuits 10a to 10d may be referred to as a first converter circuit 10a, a second converter circuit 10b, a third converter circuit 10c, and a fourth converter circuit 10d.

  The driving modes of multiphase converter 2 include first to third modes shown in FIG. 2 and a special mode described later. 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 out of the converter circuits 10a to 10d, and drives them in the phase of 180 degrees in order. 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). Drive signals of the same duty ratio are supplied to the first converter circuit 10a and the second converter circuit 10b.

  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 drive 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 out of 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). Drive signals having the same duty ratio are supplied to the first converter circuit 10a, the second converter circuit 10b, and the third converter circuit 10c. When one control cycle has elapsed, the first converter circuit 10a is driven again in order.

  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 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 of the same duty ratio are supplied to converter circuits 10a-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 the range where the input is appropriate 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 in a range that is as efficient as possible, and the load on the converter circuits 10a to 10d is prevented from being excessive.

  The plurality of phases are sequentially driven with a phase shift so that the on / off timings of the switching elements of the respective converter circuits do not overlap. When the on / off timings of the switching elements overlap, current ripple, voltage surge, and ringing are superimposed to increase the loss.

  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 three-phase driving in the third mode. The controller 17 changes the drive mode from the second mode to the first mode when the input current Ifdc is lower than the fourth current threshold while performing two-phase driving in the second mode. Here, the relationship between the magnitudes of the current threshold values is I2> I3> I1> I4. The threshold (first current threshold I1) of the input current Ifdc when switching from the first mode to the second mode is different from the threshold (fourth current threshold) of the input current Ifdc when switching from the second mode to the first mode The reason is to prevent hunting in mode switching. The threshold (second current threshold I2) of the input current Ifdc when switching from the second mode to the third mode is different from the threshold (third current threshold) of the input current Ifdc when switching from the third mode to the second mode The reason is to prevent hunting in mode switching.

  The controller 17 further performs control by the following logic to suppress the load of the four converter circuits 10a to 10d, that is, to equalize the temperatures of the four converter circuits 10a to 10d. The controller 17 is configured such that the load index value set based on at least one of the temperature of converter circuits 10a-10d and the current flowing in converter circuits 10a-10d (i.e., input current Ifdc) is out of a predetermined load tolerance range, During a predetermined period after the high load period judgment index value falls below the termination judgment threshold value, drive converter circuits whose number is greater than the number of driving corresponding to the input current Ifdc when the load index value is within the load allowable range. Do. For example, even if the magnitude of the input current Ifdc is a value that normally drives three phases in the second mode, the controller 17 determines that the above condition is satisfied (ie, the high load state is After that, it will drive four phases even if the load drops. Such control mode is hereinafter referred to as a special mode. In the predetermined period after the high load period determination index value falls below the termination determination threshold, when the number of drives when the load index value is within the load allowable range is the maximum number of operations, the maximum number of operations is performed over the entire predetermined period. Maintain.

  For the load index value, for example, the highest temperature Tk is selected among the temperatures measured by the temperature sensors 7a to 7d (that is, the temperatures of the converter circuits 10a to 10d). In this case, the allowable load range is set to Tk <Tmax. Temperature Tmax is the upper limit value of the temperature range allowed for converter circuits 10a-10d. For example, the change rate of the input current Ifdc is selected as the high load period determination index value. As the end determination threshold value, the change rate of the input current Ifdc = zero is selected. The controller 17 determines that the high load period has ended when the change rate of the input current Ifdc falls below zero, that is, when the time change of the input current Ifdc changes from a positive value to a negative value. The end time of the predetermined period is determined, for example, when the output torque of the motor 32 falls below a predetermined torque threshold Ath.

  In this case, when the highest temperature Tk of the converter circuits 10a to 10d exceeds the upper limit temperature Tmax, the controller 17 determines that it is in the high load period. In the high load period, the controller 17 determines that the high load period has ended when the slope of the input current Ifdc switches from a positive value to a negative value. After the end of the high load period, until the output torque of the motor 32 falls below the torque threshold Ath, the controller 17 may be in the first mode (two-phase drive) or the second mode (three-phase drive). , Drive a four-phase converter circuit. That is, the controller 17 drives the multiphase converter 2 in the special mode.

  A specific example of control of the controller 17 will be described with reference to FIG. FIG. 3 is a time chart showing an example of the change in the number of driving of multiphase converter 2 having four converter circuits 10a-10d. (1) shows the change of the input current Ifdc. (2) shows the output current of the first phase (first converter circuit 10a) and the second phase (second converter circuit 10b). The first phase (first converter circuit 10a) and the second phase (second converter circuit 10b) are always driven at the same time, as shown in the mode transition diagram of FIG. (3) shows the output current of the third phase (third converter circuit 10c), and (4) shows the output current of the fourth phase (fourth converter circuit 10d). While the output current is zero, it means that it is not driven. (5) shows the change of the output torque of the motor 32. In FIG. 3, in order to aid understanding, the first current threshold (the threshold when switching from the first mode to the second mode) and the fourth current threshold (the threshold when switching from the second mode to the first mode) Is assumed to be the first current threshold I1.

  Since the input current Ifdc is lower than the first current threshold I1 until time t1, the controller 17 drives the first mode, that is, the two converter circuits 10a and 10b. At time t1, the input current Ifdc exceeds the first current threshold I1, the controller 17 shifts to the second mode. That is, the controller 17 drives the three converter circuits 10a to 10c after time t1. Since the input current Ifdc falls below the first current threshold I1 at time t2, the controller 17 shifts from the second mode to the first mode. That is, after time t2, the controller 17 stops the third converter circuit 10c and drives the two converter circuits 10a and 10b.

  At time t3, the input current Ifdc again exceeds the first current threshold I1. Therefore, after time t3, the controller 17 shifts to the third mode to drive the three converter circuits 10a to 10c. Up to this point, it is assumed that the highest temperature Tk among the temperatures of the four converter circuits 10a to 10d does not exceed the upper limit temperature Tmax.

  It is assumed that the temperature Tk exceeds the upper limit temperature Tmax at time t4. That is, at time t4, the load index value (temperature Tk) deviates from the allowable load range (Tk <upper limit temperature Tmax). At time t5, the slope of the input current Ifdc changes from a positive value to a negative value (see point P1 in FIG. 3). As described above, the change rate of the input current Ifdc is selected as the high load period determination index value. Then, the change rate of the input current Ifdc = zero is selected as the end determination threshold value. That is, at time t5, the high load period determination index value (slope of the input current Ifdc) falls below the end determination threshold (slope = zero). Therefore, from time t5 to time t6, the controller 17 drives all the four converter circuits 10a to 10d where the second mode (three-phase drive) should normally be selected. In addition, since the input current Ifdc falls below the first current threshold I1 at time t6, the controller 17 continues to select the first mode (two-phase drive) normally after time t6. The converter circuits 10a-10d are driven. That is, the controller 17 controls the plurality of converter circuits 10a to 10d in the special mode after time t5. Even in the special mode, drive signals having the same duty ratio are supplied to the plurality of converter circuits to be driven.

  At time t7, the output torque of the motor 32 falls below the torque threshold Ath. At time t7, the controller 17 ends the special mode for driving a larger number of converter circuits than usual. After time t7, since the input current Ifdc is lower than the first current threshold I1, the controller 17 drives the first mode, that is, the two converters 10a and 10b.

  In the above example, the fourth converter circuit 10d is normally not driven from time t5 to time t7, but the load index value (temperature Tk) is within the allowable load range (Tk) at time t4 before that. Because of <Tmax), the controller 17 drives more converter circuits than usual. By driving more converter circuits than normal and distributing the load, the temperature of the converter circuits will drop more quickly than in normal mode.

  In the normal drive mode (first to third modes), the number of drives is determined by giving priority to the efficiency of the converter circuit, but in the case of the above-mentioned special mode, the temperature of the converter circuit is lowered than the efficiency. Drive many converter circuits.

  Points to note regarding the technology described in the embodiment will be described. The load index value is not limited to the highest temperature Tk among the plurality of converter circuits. For example, the load index value may be the temperature of the converter circuit (third converter circuit 10c) driven in the second mode and the third mode, and the converter circuit driven in the third mode but not driven in the second mode (fourth It may be an integral value of the difference (temperature difference) with the temperature of the converter circuit 10d). The small integral value means that the third mode ends in a short time, and the first mode and the fourth mode are frequently used. That is, the fact that the integral value is small means that the amount of operation of the accelerator pedal 42 changes frequently and frequently. In such a case, since the load is high, the special mode may be selected even when the high load period ends thereafter (that is, after the high load period determination index falls below the end determination threshold). The integral value may be reset when the opening degree (operation amount) of the accelerator pedal 42 becomes a positive value.

  Alternatively, the load index value may be an integral value of the difference between the temperature of the first converter circuit 10a which is always driven simultaneously and the temperature of the second converter circuit 10b. If both converter circuits 10a and 10b are normal, the temperature difference should be small. In the case where the temperature difference is large, there is a high possibility that a problem occurs in one of the converter circuits 10a and 10b and the load is high. In such cases, more converter circuits may be driven to distribute the load. Even in this case, the integral value may be reset when the opening degree (operation amount) of the accelerator pedal 42 becomes a positive value.

  Alternatively, the load index value may be an integral value of the input current Ifdc. The range of integration may be from the current time to a predetermined time before the past. In this case, the controller 17 determines that the load is high when the integral value of the input current Ifdc within the latest predetermined time is large.

  The special mode executed by the controller 17 of the embodiment can also be expressed as follows. When the load index value set based on at least one of the temperature of the converter circuit and the current flowing in the converter circuit is out of the predetermined load allowable range, the controller 17 changes the time change of the input current Ifdc from positive value to negative value During the predetermined period after switching to the current value, regardless of the magnitude of the input current, the number of drives when switching from the positive value to the negative value is maintained, or more than the number of drives when switching. Drive a large number of converter circuits.

  When switching from the third mode to the second mode or switching from the second mode to the first mode, the controller 17 may select the converter circuits to be driven in the order of low temperature. By doing so, the temperatures of the plurality of converter circuits can be further leveled. When switching from the first mode to the second mode, the controller 17 may select and drive the lower temperature converter circuit out of the two converter circuits not being driven. That is, when switching the drive mode, the controller 17 may select the converter circuits to be driven in ascending order of temperature.

  The technology disclosed herein is not limited to a multiphase converter having four converter circuits. The techniques disclosed herein can be applied to a multiphase converter having two or more converter circuits. The techniques disclosed herein can also be applied to multiple step-down converters or multi-phase converters in which multiple bidirectional DC-DC converters are connected in parallel.

  The technology disclosed in the present specification can also be applied to a hybrid vehicle equipped with 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 techniques exemplified in the present specification or the drawings can simultaneously achieve a plurality of purposes, and achieving one of the purposes itself has technical utility.

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 plurality of converter circuits connected in parallel for converting and outputting input power;
A controller which increases the number of converter circuits to be driven as the input power increases;
Equipped with
The controller determines that the load index value set based on at least one of the temperature of the converter circuit and the current flowing in the converter circuit is out of a predetermined load allowable range and that the high load period determination index value has a predetermined end A multiphase converter which drives a number of converter circuits whose number is larger than a driving number corresponding to the input power when the load index value is within the load allowable range for a predetermined period after falling below a threshold.

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