JP6751497B2 - Boost system - Google Patents

Description

The present invention relates to a boosting system, and more particularly to a boosting system including a boosting circuit having two switching elements, two diodes and one reactor.

Conventionally, as a booster system of this type, a system including a booster circuit having two switching elements, two diodes, and one reactor has been proposed (see, for example, Patent Document 1). In this system, the smaller the atmospheric pressure, the smaller the insulation resistance between the phases of the motor. Therefore, from the viewpoint of protecting the motor, the smaller the atmospheric pressure is, the smaller the voltage of the high voltage system voltage line is controlled.

Japanese Unexamined Patent Publication No. 2008-199769

In the above-mentioned boosting system, the upper limit voltage of the high-voltage power line is set, and the ratio of turning the two switching elements on and off alternately is controlled by using the dead time for turning off the two switching elements at the same time. The voltage of the voltage system power line is also controlled within the set upper limit voltage range. In this system, when the power of the high voltage system power line is supplied to the low voltage system power line, the voltage of the capacitor attached to the low voltage system voltage line may become high. In this case, since the voltage of the high-voltage power line is controlled using the dead time, a dead time dead zone is generated, and the voltage of the low voltage power line can be lowered only to a voltage higher by the dead time. Therefore, the upper limit voltage of the high voltage system power line must be set within the range where the voltage is the lower limit value.

The main purpose of the booster system of the present invention is to lower the lower limit of the upper limit voltage of the high voltage system power line when the power of the high voltage system power line is supplied to the low voltage system power line.

The booster system of the present invention has adopted the following means in order to achieve the above-mentioned main object.

The booster system of the present invention
A reactor in which one terminal is connected to the positive electrode line of the low-voltage power line, and a first switching element in which one terminal is connected to the other terminal of the reactor and another terminal is connected to the positive voltage line of the high-voltage power line. A second switching in which one terminal is connected to the low voltage system power line and the negative voltage line of the high voltage system power line, and another terminal is connected to the other terminal of the reactor and one terminal of the first switching element. A booster circuit including an element, a first diode connected in parallel to the first switching element in the opposite direction, and a second diode connected in parallel to the second switching element in the opposite direction. ,
A capacitor in which one terminal and another terminal are connected to the positive electrode line and the negative electrode line of the low-voltage power line, and
The high-voltage system power is obtained by manipulating the ratio of alternately turning on and off the first switching element and the second switching element by using a dead time for turning off the first switching element and the second switching element at the same time. A control device that controls the voltage of the line and
It is a booster system equipped with
The control device turns off the second switching element when the voltage of the capacitor is equal to or higher than a predetermined voltage while the power of the high voltage system power line is stepped down and supplied to the low voltage system power line. The voltage of the high voltage system power line is controlled by manipulating the ratio of turning on and off the first switching element in the above state.
It is characterized by that.

In the booster system of the present invention, the ratio of alternately turning the first switching element and the second switching element on and off is controlled by using a dead time for turning off the first switching element and the second switching element of the booster circuit at the same time. By controlling the voltage of the high voltage system power line. The second switching element is turned off when the voltage of the capacitor attached to the low-voltage power line is equal to or higher than the specified voltage while the power of the high-voltage power line is stepped down and supplied to the low-voltage power line. The voltage of the high-voltage power line is controlled by manipulating the ratio of turning the first switching element on and off in this state. By controlling in this way, the dead time can be reduced to a value of 0, so that the dead time zone can be reduced to a value of 0. As a result, the lower limit of the upper limit voltage of the high voltage system power line can be lowered.

In this case, the dead time setting time may be shortened as the reactor current increases to the negative side. In this way, it is possible to suppress a sudden change in the duty ratio due to a sudden change in the dead time setting time, resulting in an overcurrent or an overvoltage.

It is a block diagram which shows the outline of the structure of the electric vehicle 20 which mounts the boosting system as one Example of this invention. It is a flowchart which shows an example of the boost control routine executed by an electronic control unit 50. It is explanatory drawing which shows an example of the map for setting a dead time. It is explanatory drawing which shows an example of the command value in the normal control of a step-up converter 40, and the on / off state of the actual transistors T31, 32. It is explanatory drawing which shows an example of the relationship between the use range of the low voltage system voltage VL of the Example and the comparative example, and the lower limit value VHlim of the upper limit voltage VHigh of the high voltage system voltage VH.

Next, a mode for carrying out the present invention will be described with reference to examples.

FIG. 1 is a configuration diagram showing an outline of a configuration of an electric vehicle 20 equipped with a boosting system as an embodiment of the present invention. As shown in the figure, the electric vehicle 20 of the embodiment includes a motor 32, an inverter 34, a battery 36, a step-up converter 40, and an electronic control unit 50.

The motor 32 is configured as a synchronous generator motor, and includes a rotor in which a permanent magnet is embedded and a stator in which a three-phase coil is wound. The rotor of the motor 32 is connected to a drive shaft 26 connected to the drive wheels 22a and 22b via a differential gear 24.

The inverter 34 is connected to the motor 32 and is connected to the boost converter 40 via the high voltage system power line 42. The inverter 34 has six transistors T11 to T16 and six diodes D11 to D16. Two transistors T11 to T16 are arranged in pairs so as to be on the source side and the sink side with respect to the positive electrode bus and the negative electrode bus of the high voltage system power line 42, respectively. The six diodes D11 to D16 are connected in parallel to the transistors T11 to T16 in opposite directions, respectively. Each of the three-phase coils (U-phase, V-phase, W-phase) of the motor 32 is connected to each of the connection points between the transistors that are a pair of the transistors T11 to T16. Therefore, when a voltage is applied to the inverter 34, the electronic control unit 50 adjusts the ratio of the on-time of the paired transistors T11 to T16, so that a rotating magnetic field is formed in the three-phase coil and the motor. 32 is rotationally driven. A smoothing capacitor 46 is attached to the positive electrode bus and the negative electrode bus of the high-voltage power line 42.

The battery 36 is configured as, for example, a lithium ion secondary battery or a nickel hydrogen secondary battery, and is connected to the step-up converter 40 via a low-voltage power line 44. A smoothing capacitor 48 is attached to the positive electrode bus and the negative electrode bus of the low-voltage power line 44.

The boost converter 40 is connected to a high-voltage power line 42 to which the inverter 34 is connected and a low-voltage power line 44 to which the battery 36 is connected. The boost converter 40 has two transistors T31 and T32, two diodes D31 and D32, and a reactor L. The transistor T31 is connected to the positive electrode bus of the high voltage system power line 42. The transistor T32 is connected to the transistor T31 and the negative electrode bus of the high voltage system power line 42 and the low voltage system power line 44. The two diodes D31 and D32 are connected in parallel to the transistors T31 and T32 in opposite directions, respectively. The reactor L is connected to a connection point between the transistors T31 and T32 and a positive electrode bus of the low-voltage power line 44. The boost converter 40 is basically a state in which the transistor T31 is turned on and the transistor T32 is turned off and the transistor T31 is turned off by the electronic control unit 50 with a dead time for turning off both the transistors T31 and T32. By adjusting the ratio with the state in which the transistor T32 is turned on, the power of the low-voltage power line 44 can be boosted and supplied to the high-voltage power line 42, or the power of the high-voltage power line 42 can be increased. Is stepped down and supplied to the low-voltage power line 44.

The electronic control unit 50 is configured as a microprocessor centered on the CPU 52, and includes a ROM 54 for storing a processing program, a RAM 56 for temporarily storing data, and an input / output port in addition to the CPU 52. Signals from various sensors are input to the electronic control unit 50 via input ports. The signals input to the electronic control unit 50 include, for example, the rotation position θm of the rotor of the motor 32 from the rotation position detection sensor (for example, resolver) 32a that detects the rotation position of the rotor of the motor 32, and the rotation position θm of the motor 32. Examples include the phase currents Iu and Iv flowing through the motor 32 from the current sensors 32u and 32v that detect the current flowing through each phase. Further, from the voltage Vb of the voltage sensor 36a attached between the terminals of the battery 36, the battery current Ib from the current sensor 36b attached to the output terminal of the battery 36, and the current sensor 40a connected in series with the reactor L. The reactor current IL of is also mentioned. Further, the voltage VH of the capacitor 46 (high voltage system power line 42) from the voltage sensor 46a attached between the terminals of the capacitor 46 and the capacitor 48 (low voltage) from the voltage sensor 48a attached between the terminals of the capacitor 48. The voltage VL of the system power line 44) can also be mentioned. In addition, the ignition signal from the ignition switch 60 and the shift position SP from the shift position sensor 62 that detects the operation position of the shift lever 61 can also be mentioned. Further, the accelerator opening Acc from the accelerator pedal position sensor 64 that detects the depression amount of the accelerator pedal 63, the brake pedal position BP from the brake pedal position sensor 66 that detects the depression amount of the brake pedal 65, and the vehicle speed sensor 68. The vehicle speed V can also be mentioned. Various control signals are output from the electronic control unit 50 via the output port. Examples of the signal output from the electronic control unit 50 include a switching control signal for the transistors T11 to T16 of the inverter 34 and a switching control signal for the transistors T31 and T32 of the boost converter 40. The electronic control unit 50 calculates the electric angle θe and the rotation speed Nm of the motor 32 based on the rotation position θm of the rotor of the motor 32 from the rotation position detection sensor 32a. Further, the electronic control unit 50 calculates the storage ratio SOC of the battery 36 based on the integrated value of the current Ib of the battery 36 from the current sensor 36b. Here, the storage ratio SOC is the ratio of the capacity of electric power that can be discharged from the battery 36 to the total capacity of the battery 36.

The boost converter 40, the capacitor 46, the voltage sensor 46a, the capacitor 48, the voltage sensor 48a, and the electronic control unit 50 correspond to the boost system of the embodiment.

In the boosting system of the embodiment configured in this way, the upper limit voltage VHigh of the voltage VH of the high voltage system power line 42 is set and the target voltage VH * is set within the range of the upper limit voltage VHigh according to the running state and the like. Basically, as normal control, the transistor T31 is turned on with a dead time that turns off both the transistors T31 and T32 so that the voltage VH of the high voltage system power line 42 becomes the target voltage VH *. At the same time, feedback control is performed to adjust the ratio between the state in which the transistor T32 is turned off and the state in which the transistor T31 is turned off and the transistor T32 is turned on.

Next, the operation of the boosting system of the embodiment, particularly the operation when the power of the high voltage system power line 42 is stepped down and supplied to the low voltage system power line 44 by the regeneration control of the motor 32 will be described. .. FIG. 2 is a flowchart showing an example of a boost control routine executed by the electronic control unit 50. This routine is repeatedly executed at predetermined time intervals (for example, every several tens of ms).

When the boost control routine is executed, the electronic control unit 50 first performs a process of inputting data necessary for boost control such as the reactor current IL from the current sensor 40a and the low voltage system voltage VL from the voltage sensor 48a. Execute (step S100). Subsequently, it is determined whether or not the reactor current IL is less than the threshold value ILref and whether or not the low voltage system voltage VL is equal to or more than the threshold value VLref (step S110). Here, the threshold ILref is a current value (negative value) when the power of the high voltage system power line 42 is stepped down and supplied to the low voltage system power line 44, and is a negative value predetermined by the boosting system. A value larger than the lower limit of the usage range on the side and smaller than the median value can be used. As the threshold value VLref, a value smaller than the upper limit value of the predetermined use range and larger than the median value can be used as the voltage of the low voltage system power line 44.

When it is determined in step S110 that the reactor current IL is equal to or higher than the threshold value ILref or the low voltage system voltage VL is determined to be less than the threshold value VLref, the above-mentioned normal control is performed (step S120), and the transistors T31 and T32 are executed. A default value dtset (for example, several μsec) is set in the dead time dt that turns off both of the above (step S130), and this routine ends.

On the other hand, when it is determined in step S110 that the reactor current IL is less than the threshold value ILref and the low voltage system voltage VL is equal to or higher than the threshold value VLref, one-element control is performed instead of the normal control (step S140), and the dead time is set. The dt is set based on the reactor current IL (step S150), and this routine ends. In single element control, the transistor T32, which is the lower arm of the boost converter 40, is turned off, and the transistor T31, which is the upper arm, is turned on and off so that the voltage VH of the high voltage system power line 42 becomes the target voltage VH *. It is a control that adjusts the ratio. In the one-element control, the transistor T32 of the lower arm is always off, so that the dead time dt is unnecessary. In the embodiment, the dead time dt is set by predetermining the relationship between the reactor current IL and the dead time dt and storing it as a dead time setting map, and when the reactor current IL is given, the corresponding dead time dt is set from the map. It was decided to do it by deriving. FIG. 3 shows an example of a map for setting a dead time. As shown in the figure, in the embodiment, it is defined that the dead time dt becomes smaller as the reactor current IL becomes smaller than the threshold value ILref (as it becomes larger as a negative value). The reason for setting the dead time dt in this way is to prevent an overcurrent or an overvoltage from occurring in the system. In the one-element control, the dead time dt is unnecessary and may be set to 0. However, in this case, the dead time dt suddenly changes when switching between the normal control and the one-element control. Therefore, the actual duty changes suddenly, and an overcurrent or an overvoltage occurs in the system. In order to suppress this, the dead time dt is set so as to smoothly change between the default value dtset and the value 0.

The reason why the one-element control is performed when it is determined that the reactor current IL is less than the threshold value ILref and the low voltage system voltage VL is equal to or more than the threshold value VLref will be described. FIG. 4 is an explanatory diagram showing an example of an on / off state of the transistors T31 and 32 at the time of the command duty and the actual duty in the normal control of the step-up converter 40. In the figure, the "upper arm" is the transistor T31, and the "lower arm" is the transistor T32. The command duty indicates an on / off state when the duty of the upper arm is 99%, and the actual duty indicates an on / off state when the duty of the lower arm is 1%. Since the command duty does not consider the dead time dt, 99% of the duty of the upper arm agrees with the duty of 1% of the lower arm. On the other hand, the duty of the upper arm of the lower arm 1% of the actual duty is "99-2 dt / SWt"% when 1/100 of the switching cycle is SWt. Assuming that the upper arm is also 1% or more of the lower arm as the controllable duty, the maximum duty of the controllable upper arm is "99-2 dt / SWt"% in consideration of the dead time dt. Therefore, the high voltage system voltage VH can be controlled only to a voltage slightly higher than the low voltage system voltage VL. As described above, in the normal control, the upper limit voltage VHigh of the high voltage system voltage VH is set according to the running state and the like. Therefore, the low voltage system voltage VL is used as the lower limit value VHlim that can be set as the upper limit voltage VHigh. The voltage will be slightly higher than the maximum voltage in the range. FIG. 5 shows the relationship between the range of use of the low voltage system voltage VL of Examples and Comparative Examples and the lower limit value VHlim of the upper limit voltage VHigh of the high voltage system voltage VH. In FIG. 5, the solid line shows the minimum controllable voltage of the high voltage system voltage VH of the example, the broken line shows the minimum controllable voltage of the high voltage system voltage VH of the comparative example, and the hatched region is dead. A region (dead zone) in which the high voltage system voltage VH cannot be controlled by considering the time dt is shown. In the comparative example, normal control is performed regardless of the reactor current IL and the low voltage system voltage VL. The upper limit value VHlim of the high voltage system voltage VH is the minimum value of the controllable voltage of the high voltage system voltage VH in the usage range of the low voltage system voltage VL, considering that the low voltage system voltage VL changes. It becomes the maximum value of. In the comparative example, the voltage VH1, which is the maximum value of the hatched region, is the lower limit value VHlim. In the embodiment, when the low voltage system voltage VL is equal to or higher than the threshold value VLref, single element control is executed, so that the dead time dt becomes unnecessary, and the minimum controllable voltage of the high voltage system voltage VH is set to the low voltage system voltage VL. Match. Therefore, in the usage range of the low voltage system voltage VL, the maximum value among the minimum values of the controllable voltage of the high voltage system voltage VH is the voltage VH2 as the maximum value of the usage range of the low voltage system voltage VL. Therefore, in the embodiment, the lower limit value VHlim of the upper limit voltage VHigh of the high voltage system voltage VH is the voltage VH2, which can be made lower than that of the comparative example.

In the boosting system of the embodiment described above, the reactor current IL of the boosting converter 40 is less than the threshold ILref while the power of the high voltage system power line 42 is stepped down and supplied to the low voltage system power line 44. Moreover, when the low voltage system voltage VL is equal to or higher than the threshold value VLref, one-element control is performed instead of the normal control. Since the dead time dt is unnecessary in the one-element control, the maximum value in the usage range of the low voltage system voltage VL can be set as the lower limit value VHlim of the upper limit voltage VHigh of the high voltage system voltage VH. Therefore, the lower limit value VHlim of the upper limit voltage VHigh of the high voltage system voltage VH can be lowered as compared with the normal control requiring the dead time dt, and the component protection when the atmospheric pressure is low can be performed more appropriately. it can.

Further, in the boosting system of the embodiment, when the one-element control is performed instead of the normal control, the dead time dt is set so that the smaller the reactor current IL becomes smaller than the threshold value ILref (the larger the negative value), the smaller the dead time dt. As a result, it is possible to prevent an overcurrent, an overvoltage, or the like from occurring in the system due to a sudden change in the actual duty due to a sudden change in the dead time dt when switching between the normal control and the one-element control.

In the embodiment, the boosting system is mounted on the electric vehicle 20, but such a boosting system may be mounted on the hybrid vehicle, or the boosting system may be mounted on a drive device other than the vehicle.

Although the embodiments for carrying out the present invention have been described above with reference to examples, the present invention is not limited to these examples, and various embodiments are used without departing from the gist of the present invention. Of course, it can be done.

The present invention can be used in the manufacturing industry of boosting systems and the like.

20 electric vehicle, 22a, 22b drive wheel, 24 differential gear, 26 drive shaft, 32 motor, 32a rotation position detection sensor, 32u, 32v, 36b current sensor, 34 inverter, 36 battery, 36a, 46a, 48a voltage sensor, 40 Boost converter, 40a current sensor, 42 high voltage power line, 44 low voltage power line, 46,48 capacitors, 50 electronic control unit, 52 CPU, 54 ROM, 56 RAM, 60 ignition switch, 61 shift lever, 62 shift Position sensor, 63 accelerator pedal, 64 accelerator pedal position sensor, 65 brake pedal, 66 brake pedal position sensor, 68 vehicle speed sensor, D11 to D16, D31, D32 diode, L reactor, T11 to T16, T31, T32 transistor.

Claims (1)

A reactor in which one terminal is connected to the positive electrode line of the low-voltage power line, and a first switching element in which one terminal is connected to the other terminal of the reactor and another terminal is connected to the positive voltage line of the high-voltage power line. A second switching in which one terminal is connected to the low voltage system power line and the negative voltage line of the high voltage system power line, and another terminal is connected to the other terminal of the reactor and one terminal of the first switching element. A booster circuit including an element, a first diode connected in parallel to the first switching element in the opposite direction, and a second diode connected in parallel to the second switching element in the opposite direction. ,
A capacitor in which one terminal and another terminal are connected to the positive electrode line and the negative electrode line of the low-voltage power line, and
The high-voltage system power is obtained by manipulating the ratio of alternately turning on and off the first switching element and the second switching element by using a dead time for turning off the first switching element and the second switching element at the same time. A control device that controls the voltage of the line and
It is a booster system equipped with
The control device turns off the second switching element when the voltage of the capacitor is equal to or higher than a predetermined voltage while the power of the high voltage system power line is stepped down and supplied to the low voltage system power line. The voltage of the high voltage system power line is controlled by manipulating the ratio of turning on and off the first switching element in the above state.
A boosting system characterized by that.

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