JP6881280B2 - Converter device - Google Patents

Description

The present invention relates to a converter device, and more particularly to a converter device including a buck-boost converter having two switching elements, an upper arm and a lower arm, and a reactor.

Conventionally, as this type of converter device, in a converter device including a buck-boost converter having two switching elements of an upper arm and a lower arm and a reactor, a switching element constituting the lower arm when the duty ratio D is 0%. Has been proposed (see, for example, Patent Document 1). In this device, the responsiveness of the boosted current is improved by fixing the switching element constituting the lower arm on.

Japanese Unexamined Patent Publication No. 2014-082814

However, in the above-mentioned converter device, an overcurrent may occur depending on the timing of releasing the on-fixing of the switching element constituting the lower arm. Since the switching control of the switching element of the buck-boost converter is performed in a fixed cycle (control cycle), the timing of releasing the on-fixing of the switching element constituting the lower arm can be performed only at the timing of the control cycle. Therefore, even if an attempt is made to release the on-fixing of the switching element constituting the lower arm at the timing immediately before the boost current reaches the upper limit current, the boost current may exceed the upper limit current depending on the timing of the control cycle.

The main object of the converter device of the present invention is to improve the responsiveness of the boosted current without causing an overcurrent.

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

The converter device of the present invention
A buck-boost converter that has two switching elements, an upper arm and a lower arm, and a reactor, and exchanges power between the low-voltage side power line and the high-voltage side power line with a change in voltage.
When the duty command is less than the threshold value, the lower limit of duty is limited to control the buck-boost converter, and
It is a converter device equipped with
In the control device, when the duty command is less than the threshold value, the boosted current value estimated after two cycles in the switching control cycle of the two switching elements is set in a state where the switching elements constituting the lower arm are fixed on. When it is less than the upper limit current value, the lower limit of duty is released and the switching element constituting the lower arm is allowed to be fixed on.
It is characterized by that.

In the converter device of the present invention, when the duty command is equal to or less than the threshold value, the lower limit of duty is limited to control the buck-boost converter. When the duty command is below the threshold, the duty is when the boosted current value estimated after two cycles in the switching control cycle of the two switching elements is less than or equal to the upper limit current value with the switching elements constituting the lower arm fixed on. The lower limit is released and the switching elements that make up the lower arm are allowed to be fixed on. Since the switching control cycle requires time to calculate the switching pattern for one cycle of the two switching elements based on the duty command from the start of the cycle, the calculation time has elapsed from the start of the cycle for the switching pattern for one cycle. It is one cycle from the timing. For example, it is one cycle from the timing half a cycle after the start of the cycle. Therefore, when the switching elements constituting the lower arm are fixed on, the on-fixing cannot be released from the start of the next switching control cycle to the timing when the calculation time has elapsed. Therefore, even if the boosted current value estimated after one cycle in the switching control cycle is equal to or less than the upper limit current value with the switching element constituting the lower arm fixed on, the boosted current value exceeds the upper limit current value. Occurs. In the present invention, the switching element constituting the lower arm is allowed to be fixed on when the boosted current value estimated after two cycles in the switching control cycle is equal to or less than the upper limit current value in the state where the switching element constituting the lower arm is fixed on. Therefore, if the on-fixing permission is canceled when the boosted current value estimated after two cycles in the switching control cycle exceeds the upper limit current value, the on-fixing is turned on within two cycles from the start of the switching control cycle in which the on-fixing is permitted. The fixed permission can be released, and it is possible to prevent the boosted current value from exceeding the upper limit current value. As a result, the responsiveness of the boosted current can be improved without causing an overcurrent.

It is a block diagram which shows the outline of the structure of the electric vehicle 20 which mounts the converter device as one Example of this invention. It is a flowchart which shows an example of the responsiveness promotion processing routine executed by the electronic control unit 50 of an Example. It is explanatory drawing which shows an example of the state of the switching pattern of the carrier and the lower arm of a boost converter 40 in the duty control of a boost converter 40, and the time change of a boost current IL.

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 the configuration of an electric vehicle 20 equipped with a converter device 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 boost converter 40, a high voltage side capacitor 46, a low voltage side capacitor 48, a system main relay SMR, and the like. It includes an electronic control unit 50. Here, in the embodiment, the boost converter 40 and the electronic control unit 50 correspond to the “converter device”.

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 also to the high voltage side 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 side 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 paired with 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. Hereinafter, the transistors T11 to T13 may be referred to as an “upper arm”, and the transistors T14 to T16 may be referred to as a “lower arm”.

The battery 36 is configured as, for example, a lithium ion secondary battery or a nickel hydrogen secondary battery, and is connected to the low voltage side power line 44.

The boost converter 40 is connected to the high voltage side power line 42 and the low voltage side power line 44. 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 side power line 42. The transistor T32 is connected to the transistor T31 and the negative electrode bus of the high voltage side power line 42 and the low voltage side 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 side power line 44. In the boost converter 40, the electronic control unit 50 adjusts the ratio of the on-time of the transistors T31 and T32 by the duty command, so that the power of the low voltage side power line 44 is boosted by the voltage of the high voltage side power line. It supplies power to 42, or supplies power from the high-voltage side power line 42 to the low-voltage side power line 44 with a voltage step-down.

The high-voltage side capacitor 46 is connected to the positive electrode bus and the negative electrode bus of the high-voltage side power line 42. The low-voltage side capacitor 48 is attached to the positive electrode bus and the negative electrode bus of the low-voltage side power line 44. The system main relay SMR is provided on the battery 36 side of the low voltage side capacitor 48 in the low voltage side power line 44. The system main relay SMR connects and disconnects the battery 36 from the boost converter 40 and the low voltage side capacitor 48 by being controlled on and off by the electronic control unit 50.

The electronic control unit 50 is configured as a microprocessor centered on a 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. As signals input to the electronic control unit 50, for example, the rotation position θm from the rotation position detection sensor (for example, resolver) 32a that detects the rotation position of the rotor of the motor 32, and the current flowing in each phase of the motor 32 are detected. The phase currents Iu and Iv from the current sensors 32u and 32v can be mentioned. Further, the voltage VB from the voltage sensor 36a attached between the terminals of the battery 36 and the current IB from the current sensor 36b attached to the output terminal of the battery 36 can also be mentioned. Further, the voltage VH of the high voltage side capacitor 46 (high voltage side power line 42) from the voltage sensor 46a attached between the terminals of the high voltage side capacitor 46, and the voltage sensor attached between the terminals of the low voltage side capacitor 48. The voltage VL of the low voltage side capacitor 48 (low voltage side power line 44) from 48a and the reactor current IL from the current sensor 40a attached to the reactor L of the boost converter 40 can also be mentioned. Further, the ignition signal from the ignition switch 60, the shift position SP from the shift position sensor 62 that detects the operation position of the shift lever 61, the accelerator opening Acc from the accelerator pedal position sensor 64 that detects the amount of depression 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 VS from the vehicle speed sensor 68 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, the angular velocity ωm, 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.

In the electric vehicle 20 of the embodiment configured in this way, the electronic control unit 50 performs the following traveling control. In the traveling control, the required torque Td * required for the drive shaft 26 is set based on the accelerator opening Acc and the vehicle speed VS, the set required torque Td * is set as the torque command Tm * of the motor 32, and the motor 32. Is driven by the torque command Tm *, and the switching control of the transistors T11 to T16 of the inverter 34 is performed. Further, the target voltage VH * of the high voltage side power line 42 is set so that the motor 32 can be driven by the torque command Tm *, and the boost converter 40 is set so that the voltage VH of the high voltage side power line 42 becomes the target voltage VH *. Duty control is performed for the switching of the transistors T31 and T32.

Next, the operation of the electric vehicle 20 of the embodiment configured in this way, particularly the operation of improving the responsiveness of the current (boosting current) IL flowing through the reactor L of the boost converter 40 to the target current IL * will be described. To do. FIG. 2 is a flowchart showing an example of a responsiveness promotion processing routine executed by the electronic control unit 50 of the embodiment. This routine is repeatedly executed every control cycle of the switching control of the transistors T31 and T32 of the boost converter 40.

When the responsiveness promotion processing routine is executed, the electronic control unit 50 first determines whether or not the duty command D * is less than the threshold value Dreff (step S100). Here, as the threshold value Dr, a duty ratio corresponding to, for example, a dead time can be used. When it is determined that the duty command D * is not less than the threshold value Dref, the duty control for limiting the lower limit of the duty is executed (step S150), and this routine is terminated.

When it is determined in step S100 that the duty command D * is less than the threshold value Dreff, the boosted current ILest after two control cycles is predicted with the transistor T32 constituting the lower arm fixed on (step S110). This prediction can be made by adding the amount of current increase in which the current value increases during the two control cycles with the transistor T32 constituting the lower arm fixed on to the boosted current IL at that time. The amount of current increase can be obtained in advance by, for example, an experiment. Then, the boosted current Irest after the predicted two control cycles is compared with the upper limit current value Illim (step S120), and when it is determined that the boosted current Irest after the two control cycles is equal to or less than the upper limit current value Illim, the lower limit of duty is set. It is released (step S130), the transistor T32 constituting the lower arm is allowed to be fixed on (step S140), and this routine is terminated. On the other hand, when it is determined that the boosted current ILest after the two control cycles is larger than the upper limit current value Illim, the duty control for limiting the lower limit of the normal duty is executed (step S150), and this routine is terminated.

FIG. 3 is an explanatory diagram showing an example of a switch pattern of the transistor T32 constituting the carrier and the lower arm and a time change of the boosted current IL. In the figure, the alternate long and short dash line in the carrier indicates the lower limit of duty. The alternate long and short dash line in the boosted current IL indicates the estimated boosted current IL when the transistor T32 constituting the lower arm is fixed on. The broken line in the boosted current IL indicates the boosted current when the lower limit of duty is limited. In FIG. 3, for the sake of simplicity, the control cycle of the switching control is one cycle of the carrier as a triangular wave in the duty control, and the start timing of the calculation of the control cycle is the timing of the valley of the carrier. Based on this, it takes less than 1/2 cycle to calculate the switching pattern for one cycle of the two transistors T31 and T32, and the execution start timing according to the calculated switching pattern is 1/2 from the start timing of the calculation of the control cycle. The timing is the peak of the carrier after the cycle has passed.

It is determined that the duty command D * is less than the threshold value Dref at the time T1 of the carrier valley timing at the start of the control cycle, and after two control cycles (time T5) with the transistor T32 constituting the lower arm fixed on. ) Predict the step-up current Irest. Since the predicted boosted current ILest is less than or equal to the current upper limit value Illim, the duty lower limit limit is released, the transistor T32 constituting the lower arm is allowed to be fixed on, and the carrier peak after 1/2 cycle is allowed with this permission. The transistor T32 constituting the lower arm is fixed on at the time T2 of the timing of. Similarly, at the time T3 and T5 of the carrier valley timing at the start of the control cycle, the boosted current ILest after two control cycles (time T7 and T9) is predicted. Since the predicted boosted current ILest is equal to or less than the current upper limit value Illim, the transistor T32 constituting the lower arm is continuously fixed on. Similarly, at the time T7 of the carrier valley timing at the start of the control cycle, the boosted current ILest after 2 control cycles (time T11) is predicted. The predicted boost current ILest is larger than the current upper limit Illim. Therefore, the duty control is performed with the normal lower limit of the duty, and the normal control is performed from the time T8 after 1/2 cycle. Therefore, the lower limit of duty is applied at time T9, and the transistor T32 is turned off for a time corresponding to the lower limit of duty constituting the lower arm.

As a comparative example, consider a case where the boosted current Irest after one control cycle is predicted and the transistor T32 constituting the lower arm is allowed to be fixed on. The boosted current Irest after one control cycle (time T11) is predicted at time T9, and since the predicted boosted current Irest is larger than the current upper limit value Illim, the time T10 after 1/2 cycle is accompanied by the normal lower limit of duty. Duty control will be performed. In this case, the boosted current IL may exceed the upper limit current value Illim before reaching the time T11. In the embodiment, by predicting the boosted current ILest after two control cycles and allowing the transistor T32 constituting the lower arm to be fixed on, it is possible to prevent the boosted current IL from exceeding the upper limit current value Illim.

Further, as a comparative example, consider a case where the transistor T32 constituting the lower arm is not fixed on. As shown by the broken line in FIG. 3, the degree of increase in the boosting current IL is slower than in the case of the embodiment in which the transistor T32 constituting the lower arm is fixed on. Therefore, in the examples, the responsiveness of the boosted current IL to the target current IL * can be improved as compared with the comparative example.

In the converter device mounted on the electric vehicle 20 of the above-described embodiment, when the duty command D * is less than the threshold value Dref, the boosted current Irest after two control cycles with the transistor T32 constituting the lower arm fixed on. When the predicted boost current ILest is equal to or less than the current upper limit value Illim, the duty lower limit limit is released and the transistor T32 constituting the lower arm is allowed to be fixed on. As a result, the responsiveness of the boosted current IL can be improved without causing an overcurrent.

In the embodiment, the control cycle of the switching control is one cycle of the carrier as a triangular wave in the duty control, the start timing of the operation of the control cycle is the timing of the valley of the carrier, and the two transistors T31 are based on the duty command D *. , It takes less than 1/2 cycle to calculate the switching pattern for one cycle of T32, and the execution start timing by the calculated switching pattern is the peak of carriers that have passed 1/2 cycle from the start timing of the calculation of the control cycle. It was the timing of. However, the control cycle of the switching control may be two cycles of the carrier as a triangular wave in the duty control, the start timing of the calculation of the control cycle may be the timing of the peak of the carrier, or the execution start timing according to the calculated switching pattern. May be the timing when one cycle has elapsed from the start timing of the calculation of the control cycle.

In the embodiment, the converter device is mounted on the electric vehicle 20, but it may be mounted on a hybrid vehicle, it may be mounted on a moving body such as a vehicle other than a vehicle, or it may be constructed. It may be incorporated into equipment such as equipment.

The correspondence between the main elements of the examples and the main elements of the invention described in the column of means for solving the problem will be described. In the embodiment, the transistor T31 and the transistor T32 correspond to "two switching elements of the upper arm and the lower arm", the reactor L corresponds to the "reactor", the boost converter 40 corresponds to the "boost converter", and the electrons. The control unit 50 corresponds to a "control device".

Regarding the correspondence between the main elements of the examples and the main elements of the invention described in the column of means for solving the problem, the invention described in the column of means for solving the problem in the examples is carried out. Since it is an example for specifically explaining the form for solving the problem, the elements of the invention described in the column of means for solving the problem are not limited. That is, the interpretation of the invention described in the column of means for solving the problem should be performed based on the description in the column, and the examples are the inventions described in the column of means for solving the problem. It is just a concrete example.

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 converter devices 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 side power line, 44 low voltage side power line, 46 high voltage side capacitor, 48 low voltage side capacitor, 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, 69 acceleration sensor, D11 to D16, D31, D32 diode, L reactor, SMR system main relay, T11-T16, T31, T32 transistors.

Claims (1)

A buck-boost converter that has two switching elements, an upper arm and a lower arm, and a reactor, and exchanges power between the low-voltage side power line and the high-voltage side power line with a change in voltage.
When the duty command is less than the threshold value, the lower limit of duty is limited to control the buck-boost converter, and
It is a converter device equipped with
In the control device, when the duty command is less than the threshold value, the boosted current value estimated after two cycles in the switching control cycle of the two switching elements is set in a state where the switching elements constituting the lower arm are fixed on. When the current value is less than the upper limit, the switching elements that make up the lower arm are allowed to be fixed on.
A converter device characterized by that.

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