Boost converter control device and control method for boost converter control device

Abstract

To provide a step-up converter control device capable of increasing a heat release value of a secondary battery by increasing a ripple current by a plurality of step-up converters in the case where a warm air of the secondary battery is required.SOLUTION: A step-up converter control device 1 comprises: a plurality of step-up converters (30 and 40) connected in parallel with each other to a secondary battery 10; and an ECU 200 (a control part) that controls each of the plurality of step-up converters (30 and 40). The ECU 200 performs a first control that performs adjustment so that phases of the plurality of step-up converters (30 and 40) become the same phase each other in accordance with a fact that an increase in current value flowing through the secondary battery 10 than a predetermined threshold value in the case where a warm air of the secondary battery 10 is required, and performs a second control that stops a partial part operation of the plurality of step-up converters (30 and 40) in accordance with a fact that the current value flowing though the secondary battery 10 is the predetermined threshold value or less.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present disclosure relates to a boost converter control device and a control method for a boost converter control device. [Background technology]

[0002] Japanese Patent Application Laid-Open No. 2020-137391 (Patent Document 1) discloses a system in which two boost converters are connected in parallel to a battery of an electric vehicle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-137391 Summary of the Invention [Problem to be solved by the invention]

[0004] In the system disclosed in Patent Document 1, there are cases where it is necessary to warm up the battery. In such cases, it is desirable to increase the amount of heat generated by the battery by increasing the ripple current generated by the multiple boost converters.

[0005] The present disclosure has been made to solve the above-mentioned problems, and its purpose is to provide a boost converter control device and a control method for a boost converter control device that can increase the amount of heat generated by a secondary battery by increasing the ripple current generated by multiple boost converters when warming up the secondary battery is required. [Means for solving the problem]

[0006] A boost converter control device according to a first aspect of the present disclosure is a boost converter control device for driving a traction motor of an electric vehicle, and includes: a plurality of boost converters connected in parallel to a secondary battery that supplies power to the traction motor and boosting the voltage of the secondary battery; and a control unit that controls each of the plurality of boost converters. Each of the plurality of boost converters includes a reactor and a switching element. When warming up of the secondary battery is required, the control unit performs a first control to adjust at least two of the plurality of boost converters to be in phase in response to a current value flowing through the secondary battery exceeding a predetermined threshold, and a second control to stop operation of some of the plurality of boost converters in response to a current value flowing through the secondary battery falling below the predetermined threshold. Note that the plurality of boost converters being in phase means that the on (off) timings of the switching elements in the plurality of boost converters are synchronized.

[0007] In the boost converter control device according to the first aspect of the present disclosure, as described above, when the secondary battery needs to be warmed up, a first control is performed in response to the current value flowing through the secondary battery becoming greater than a predetermined threshold, adjusting at least two phases of the multiple boost converters to be in phase. This allows the timing of ripple current generation based on the operation of each of the multiple boost converters to be synchronized, thereby increasing the amount of heat generated by the secondary battery based on the magnitude (total value) of the ripple current. Furthermore, in the boost converter control device described above, a second control is performed in response to the current value flowing through the secondary battery becoming equal to or less than a predetermined threshold, stopping the operation of some of the multiple boost converters. This allows the current value flowing through the surviving boost converters to be larger than when all the boost converters are operating. Here, the inductance of the reactor decreases as the current value flowing increases. Furthermore, the ripple current increases as the inductance of the reactor decreases. Therefore, the amount of heat generated by the secondary battery based on the ripple current can be increased. As described above, increasing the ripple current generated by the multiple boost converters increases the amount of heat generated by the secondary battery.

[0008] In the boost converter control device according to the first aspect, the predetermined threshold is preferably half the maximum allowable value of the current flowing through the secondary battery. This configuration can prevent the current value flowing through the boost converter (reactor) from decreasing during the second control compared to when the predetermined threshold is smaller than half the maximum allowable value. As a result, it is possible to easily prevent the ripple current during the second control from decreasing.

[0009] The boost converter control device according to the first aspect preferably further includes a temperature sensor that detects the temperature of the secondary battery. The control unit determines that the secondary battery requires warming when the detected value of the temperature sensor is within a predetermined range below freezing. With this configuration, the first control and the second control that increase the ripple current are performed under temperature conditions below freezing. As a result, deterioration of electrical devices other than the secondary battery due to an increase in ripple current (increase in heat generation) can be suppressed by the low temperature.

[0010] In the boost converter control device according to the first aspect, the plurality of boost converters preferably include a first boost converter and a second boost converter. The control unit performs third control to adjust the phases of the first boost converter and the second boost converter to be opposite to each other when warm-up of the secondary battery is not required. The first control includes control to adjust the phases of the first boost converter and the second boost converter to be in phase with each other. The second control includes control to stop the other of the first boost converter and the second boost converter while operating one of the first boost converter and the second boost converter. With this configuration, when warm-up of the secondary battery is not required, the timing at which a ripple current is generated by operation of the first boost converter and the timing at which a ripple current is generated by operation of the second boost converter can be shifted from each other. As a result, an increase in the amount of heat generated by the secondary battery due to the ripple current can be suppressed. Furthermore, when warm-up of the secondary battery is required, the amount of heat generated by the secondary battery can be increased by increasing the ripple current generated by the first boost converter and the second boost converter.

[0011] A control method for a boost converter control device according to a second aspect of the present disclosure is a control method for a boost converter control device that drives a traction motor. A plurality of boost converters are connected in parallel to a secondary battery that supplies power to the traction motor, and each of the boost converters that boost the voltage of the secondary battery includes a reactor and a switching element. The control method includes: a first control step of adjusting at least two of the plurality of boost converters to be in phase in response to a current value flowing through the secondary battery exceeding a predetermined threshold when warming up of the secondary battery is required; and a second control step of stopping some of the plurality of boost converters in response to a current value flowing through the secondary battery falling below the predetermined threshold when warming up of the secondary battery is required.

[0012] In a control method for a boost converter control device according to a second aspect of the present disclosure, as described above, when warming up of the secondary battery is required, a first control is performed to adjust at least two phases of the multiple boost converters to be in phase in response to the value of current flowing through the secondary battery becoming greater than a predetermined threshold. Also, in the above control method, when warming up of the secondary battery is required, a second control is performed to stop operation of some of the multiple boost converters in response to the value of current flowing through the secondary battery becoming equal to or less than a predetermined threshold. This makes it possible to provide a control method for a boost converter control device that can increase the amount of heat generated by the secondary battery by increasing the ripple current through the multiple boost converters. [Effects of the Invention]

[0013] According to the present disclosure, when the secondary battery needs to be warmed up, the amount of heat generated by the secondary battery can be increased by increasing the ripple current generated by the multiple boost converters. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram illustrating a configuration of a boost converter control device according to an embodiment; [Figure 2] FIG. 4 is a diagram illustrating a first control (in-phase control) of the boost converter control device according to one embodiment. [Figure 3] FIG. 10 is a diagram showing a current value of a reactor during first control. [Figure 4] FIG. 4 is a diagram illustrating a second control (one-sided control) of the boost converter control device according to one embodiment. [Figure 5] FIG. 10 is a diagram showing a current value of a reactor during second control. [Figure 6] FIG. 10 is a diagram showing the relationship between the current value and inductance of a reactor. [Figure 7] FIG. 4 is a diagram illustrating a third control (normal operation) of the boost converter control device according to one embodiment. [Figure 8] FIG. 10 is a diagram showing a current value of a reactor during third control. [Figure 9]FIG. 3 is a flow chart illustrating a control method for a boost converter controller according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0016] 1 is a diagram showing the configuration of a boost converter control device 1 according to this embodiment. The boost converter control device 1 drives a traction motor 310 of an electric vehicle 300. The boost converter control device 1 includes a boost circuit 100 and an electronic control unit (ECU) 200. The ECU 200 is an example of a "control unit" in the present disclosure.

[0017] The boost circuit 100 includes a secondary battery 10, a film capacitor 20, a first boost converter 30, a second boost converter 40, an inverter 50, a temperature sensor 60, and a current sensor 70. Each of the first boost converter 30 and the second boost converter 40 is an example of a "boost converter" of the present disclosure.

[0018] The secondary battery 10 supplies power to the traction motor 310. In addition, regenerated energy from the traction motor 310 is supplied to the secondary battery 10. The film capacitor 20 is connected in parallel to the secondary battery 10.

[0019] The first boost converter 30 has an upper arm switching element 31, a lower arm switching element 32, and a reactor 33. The reactor 33 is connected to a node 34 connecting the switching elements 31 and 32.

[0020] The second boost converter 40 has an upper arm switching element 41, a lower arm switching element 42, and a reactor 43. The reactor 43 is connected to a node 44 that connects the switching elements 41 and 42.

[0021] The first boost converter 30 and the second boost converter 40 are connected in parallel to each other with respect to the secondary battery 10. That is, the first boost converter 30 and the second boost converter 40 each receive current from the common secondary battery 10. Furthermore, each of the first boost converter 30 and the second boost converter 40 boosts the voltage provided to the inverter 50 to a voltage equal to or higher than the voltage of the secondary battery 10.

[0022] The temperature sensor 60 measures the temperature of the secondary battery 10. The measurement result of the temperature sensor 60 is transmitted to the ECU 200.

[0023] The current sensor 70 measures the value of the current Ib flowing through the secondary battery 10. The current sensor 70 is provided between the secondary battery 10 and each of the reactor 33 and the reactor 43.

[0024] The ECU 200 controls each of the first boost converter 30 and the second boost converter 40. The ECU 200 includes a processor 201, a memory 202, a storage 203, and an interface 204.

[0025] The processor 201 is, for example, a central processing unit (CPU) or a micro-processing unit (MPU). The memory 202 is, for example, a random access memory (RAM). The storage 203 is a rewritable non-volatile memory such as a hard disk drive (HDD), a solid state drive (SSD), or a flash memory. The interface 204 controls communication between the ECU 200 and the components of the boost circuit 100.

[0026] The ECU 500 generates a control command based on sensor values acquired from various sensors (60, 70) included in the boost circuit 100, and outputs the generated control command to the boost circuit 100. The ECU 200 may be divided into multiple ECUs for each function. Also, while FIG. 1 shows an example in which the ECU 200 includes one processor 201, the ECU 200 may include multiple processors. The same applies to the memory 202 and the storage 203.

[0027] In conventional systems, there are cases where the secondary battery needs to be warmed up. In such cases, it is desirable to increase the ripple current generated by the multiple boost converters to increase the amount of heat generated by the secondary battery.

[0028] Therefore, in this embodiment, when the secondary battery 10 needs to be warmed up, the ECU 200 performs a first control (same-phase control) to adjust the phases of the first boost converter 30 and the second boost converter 40 to be in phase with each other in response to the value of the current Ib flowing through the secondary battery 10 becoming larger than a predetermined threshold. Specifically, as shown in FIG. 2 , in the first control, the timing at which the switching element 31 (CTP1) is turned on (off) is aligned with the timing at which the switching element 41 (CTP2) is turned on (off). The switching element 32 (CTN1) is turned on and off in the opposite phase to the switching element 31. The switching element 42 (CTN2) is turned on and off in the opposite phase to the switching element 41.

[0029] As a result, as shown in FIG. 3, the ripple current in the reactor 33 caused by the operation of the first boost converter 30 and the ripple current in the reactor 43 caused by the operation of the second boost converter 40 occur at the same timing.

[0030] The predetermined threshold value is half the maximum allowable value of the current Ib flowing through the secondary battery 10. The threshold value of half the maximum allowable value is stored in advance in the memory 202 of the ECU 200. The maximum allowable value of the current Ib is the maximum current value determined by the capacity of the secondary battery 10. The secondary battery 10 is designed to be able to operate within a range equal to or less than the maximum allowable value.

[0031] Furthermore, in this embodiment, when the secondary battery 10 needs to be warmed up, the ECU 200 performs second control (one-sided control) in which one of the first boost converter 30 and the second boost converter 40 is stopped while the other is operating in response to the value of the current Ib flowing through the secondary battery 10 becoming equal to or less than the predetermined threshold. For example, as shown in FIG. 4 , it is assumed that the second boost converter 40 is stopped while the first boost converter 30 is operating. In this case, the value of the current flowing through the reactor 33 of the first boost converter 30 is doubled compared to the values during normal operation and the first control. Therefore, as shown in FIG. 5 , the ripple current value of the reactor 33 during the second control is larger than the ripple current value of the reactor 33 during normal operation and the first control.

[0032] The ripple current value (Ir) of the reactor is determined based on the following formula (1). In the following formula (1), Vin means the voltage value of the reactor. Duty means the duty ratio of the boost converter. L means the inductance of the reactor. fs means the control period of the boost converter.

[0033] Ir=Vin×Duty / (L×fs) ···(1) Furthermore, as shown in Figure 6, the inductance (vertical axis of Figure 6) of the reactor decreases as the current value (horizontal axis of Figure 6) flowing through the reactor increases. Therefore, in the second control, the inductance of the reactor decreases due to the increase in the current flowing through the reactor. As a result, the ripple current of the reactor increases based on the above equation (1).

[0034] Furthermore, when warming up of the secondary battery 10 is not required, the ECU 200 performs a third control (normal operation) that adjusts the phases of the first boost converter 30 and the second boost converter 40 to be opposite to each other. Specifically, as shown in Fig. 7, in the third control, the switching element 41 (CTP2) is turned off at the timing when the switching element 31 (CTP1) is turned on. Furthermore, the switching element 41 (CTP2) is turned on at the timing when the switching element 31 (CTP1) is turned off.

[0035] As a result, as shown in FIG. 8, the ripple current in the reactor 33 caused by the operation of the first boost converter 30 and the ripple current in the reactor 43 caused by the operation of the second boost converter 40 occur at different times.

[0036] Furthermore, when the detected value of the temperature sensor 60 that measures the temperature of the secondary battery 10 is within a predetermined range below freezing, the ECU 200 determines that the secondary battery 10 needs to be warmed up. The predetermined range is, for example, a range of -40°C to 0°C.

[0037] (Control method for boost converter control device) Next, a control method of the boost converter control device 1 will be described with reference to Fig. 9. The processing flow of steps S1 to S8 is executed every predetermined control period (for example, every 10 minutes).

[0038] In step S1, the ECU 200 determines whether or not warming up of the secondary battery 10 is necessary. Specifically, the ECU 200 determines that warming up of the secondary battery 10 is necessary when the detected value of the temperature sensor 60 is within a predetermined range below freezing (-40°C to 0°C). If warming up of the secondary battery 10 is necessary (Yes in S1), the process proceeds to step S2. If warming up of the secondary battery 10 is not necessary (No in S1), the process proceeds to step S7.

[0039] In step S2, ECU 200 sets the carrier frequency (control frequency) for driving (turning on / off the switching elements of) boost converters (30, 40) to a predetermined low value. The predetermined low value is, for example, the lowest value among the settable carrier frequencies.

[0040] In step S3, ECU 200 determines whether the value of current Ib flowing through secondary battery 10 (the value detected by current sensor 70) is greater than half the maximum allowable value of current Ib. If the value of current Ib is greater than half the maximum allowable value (Yes in S3), the process proceeds to step S4. If the value of current Ib is equal to or less than half the maximum allowable value (No in S3), the process proceeds to step S5.

[0041] In step S4, ECU 200 starts a first control (same phase control) for making the phases of first boost converter 30 and second boost converter 40 the same phase.

[0042] In step S5, the ECU 200 starts a second control (one-sided control) for stopping the other of the first boost converter 30 and the second boost converter 40 while operating one of the first boost converter 30 and the second boost converter 40. It should be noted that which of the first boost converter 30 and the second boost converter 40 is stopped may be set in advance.

[0043] In step S6, the ECU 200 warms up the secondary battery 10 by the first control (same phase control) or the second control (one-sided control).

[0044] On the other hand, in step S7, ECU 200 determines whether the first control or the second control is being executed. If the first control or the second control is being executed (Yes in S7), the process proceeds to step S8. If the first control or the second control is not being executed and normal operation is being performed (No in S7), the process ends.

[0045] In step S8, ECU 200 performs a process of returning the operations of first boost converter 30 and second boost converter 40 to the third control (normal operation).

[0046] As described above, in the above embodiment, when the secondary battery 10 needs to be warmed up, the ECU 200 performs first control to adjust the phases of the first boost converter 30 and the second boost converter 40 to be in phase with each other in response to the value of the current flowing through the secondary battery 10 becoming greater than a predetermined threshold (half the maximum allowable value of the current Ib). Furthermore, when the secondary battery 10 needs to be warmed up, the ECU 200 performs second control to stop one of the first boost converter 30 and the second boost converter 40 while keeping the other in operation in response to the value of the current flowing through the secondary battery 10 becoming equal to or less than the predetermined threshold. This allows the ripple current generated by the first boost converter 30 and the ripple current generated by the second boost converter 40 to be superimposed on each other through the first control. Furthermore, the second control allows the current Ib flowing through the secondary battery 10 to be concentrated in either the first boost converter 30 or the second boost converter 40. As a result, the ripple current generated in the reactor can be increased in each of the first control and the second control, and as a result, the secondary battery 10 can be warmed up.

[0047] In the above embodiment, the ripple current is increased by combining the reduction in the carrier frequency of the boost converter with the first control and the second control, which makes it possible to increase the ripple current more than when only the carrier frequency is reduced.

[0048] In the above embodiment, an example was shown in which the threshold value for determining whether the first control or the second control is executed is 1 / 2 of the maximum allowable value of the current Ib flowing through the secondary battery 10, but the present disclosure is not limited to this. The threshold value may be a value other than 1 / 2 of the maximum allowable value (for example, 1 / 3 of the maximum allowable value).

[0049] In the above embodiment, an example was shown in which the temperature range of the secondary battery 10 in which it is determined that warming up of the secondary battery 10 is necessary is below freezing, but the present disclosure is not limited to this. At least the upper limit value of the temperature range may be higher than 0°C.

[0050] In the above embodiment, an example has been shown in which two boost converters are provided in parallel with the secondary battery 10, but the present disclosure is not limited to this. Three or more boost converters may be provided in parallel with the secondary battery 10. In this case, the threshold for determining whether the first control or the second control is executed may be a value obtained by dividing the maximum allowable value of the current Ib flowing through the secondary battery 10 by the number of boost converters.

[0051] In the above embodiment, an example has been described in which control is executed to set the carrier frequency to a predetermined low value, but the present disclosure is not limited to this.

[0052] In the above embodiment, an example has been described in which one current sensor 70 is provided for the two reactors (33, 43), but the present disclosure is not limited to this. Two current sensors may be provided so as to correspond to the two reactors, respectively.

[0053] In the above embodiment, an example was shown in which normal operation was performed when warming up of the secondary battery 10 was not required, but the present disclosure is not limited to this. When warming up of the secondary battery 10 is not required, the first control (same-phase control) or the second control (one-sided control) may be performed.

[0054] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0055] 1 Boost converter control device, 10 Secondary battery, 30 First boost converter (boost converter), 31, 32, 41, 42 Switching element, 33, 43 Reactor, 40 Second boost converter (boost converter), 60 Temperature sensor, 200 ECU (control unit), 300 Electric vehicle, 310 Driving motor, Ib Current (current flowing through the secondary battery).

Claims

1. A boost converter control device that drives a traction motor of an electric vehicle, a plurality of boost converters connected in parallel to a secondary battery that supplies power to the traction motor, and that boost the voltage of the secondary battery; a control unit that controls each of the plurality of boost converters, each of the plurality of boost converters includes a reactor and a switching element; The control unit When the secondary battery needs to be warmed up, performing a first control to adjust at least two phases of the plurality of boost converters to be in phase in response to a current value flowing through the secondary battery becoming larger than a predetermined threshold; The boost converter control device performs second control to stop operation of some of the plurality of boost converters in response to a current value flowing through the secondary battery becoming equal to or less than the predetermined threshold.

2. 2. The boost converter control device according to claim 1, wherein the predetermined threshold value is half of a maximum allowable value of the current flowing through the secondary battery.

3. further comprising a temperature sensor that detects the temperature of the secondary battery; 3. The boost converter control device according to claim 1, wherein the control unit determines that the secondary battery needs to be warmed up when the detected value of the temperature sensor is within a predetermined range below freezing.

4. the plurality of boost converters include a first boost converter and a second boost converter; The control unit When warming up of the secondary battery is not required, a third control is performed to adjust the phases of the first boost converter and the second boost converter to be opposite phases to each other; the first control includes control for adjusting the phases of the first boost converter and the second boost converter to be in phase with each other; 3. The boost converter control device according to claim 1, wherein the second control includes control for stopping one of the first boost converter and the second boost converter while keeping the other of the first boost converter and the second boost converter operating.

5. A control method for a boost converter control device that drives a traction motor, comprising: a plurality of boost converters connected in parallel to a secondary battery that supplies power to the traction motor and that boost a voltage of the secondary battery, each of the boost converters including a reactor and a switching element; performing a first control to adjust at least two phases of the plurality of boost converters to be in phase in response to a current value flowing through the secondary battery becoming larger than a predetermined threshold when warming up of the secondary battery is required; and performing a second control to stop some of the plurality of boost converters in response to a current value flowing through the secondary battery becoming equal to or less than the predetermined threshold when warming up of the secondary battery is required.

Images