JP6740934B2 - Control device - Google Patents

Description

The present invention relates to a control device, and more particularly to a control device that controls a boost converter and a buck-boost converter.

Conventionally, as this type of control device, a control device that controls an inverter including a plurality of gate turn-off thyristors (GTO) and a plurality of diodes has been proposed (see, for example, Patent Document 1). The plurality of diodes are connected in anti-parallel to the corresponding GTO. In this device, when the gate of the GTO is turned on, the gate-cathode voltage of the GTO is used to determine whether or not a short circuit has occurred in the diode.

JP, 2003-88094, A

By the way, in a control device for controlling a step-up converter in which the upper arm is composed of a diode and the lower arm is composed of a semiconductor switching element, the upper arm does not have a switching element that can be turned on and off. Cannot be determined. As a method of determining that a short circuit has occurred in the diode, there is a method of detecting the voltage between the anode and the cathode of the diode. However, this method makes it difficult to determine a short circuit when the voltage applied to the diode changes or when the voltage changes due to various noises, for example, when the boost converter is mounted in an electric vehicle. In particular, when the boost converter is connected to the fuel cell, if the voltage higher than the cell voltage of the fuel cell is supplied from the load with the diode forming the upper arm short-circuited, the fuel cell may deteriorate. is there.

The control device of the present invention is mainly intended to properly determine a short circuit of a diode forming an upper arm of a boost converter and suppress deterioration of a fuel cell.

The control device of the present invention employs the following means in order to achieve the above-mentioned main object.

The control device of the present invention is
Two diodes forming an upper arm and connected in parallel to each other, at least one semiconductor switching element forming a lower arm, and a reactor having one end connected to a connection point between the upper arm and the lower arm are provided. And a boost converter connected to the first power line to which the load is connected and the second power line to which the fuel cell is connected,
A buck-boost converter connected to the first power line and a third power line connected to the battery;
A control device for controlling
Switching control of the semiconductor switching element of the boost converter and control of the buck-boost converter so that the voltage of the first power line becomes a target voltage,
In the case where the semiconductor switching element is turned off, when the ratio of the current of one of the two diodes to the current of the reactor is less than a predetermined ratio, the off continuation of continuing the turning off of the semiconductor switching element Controlling the buck-boost converter so that the voltage of the first power line becomes the target voltage.
In the case where the off continuation control is executed, when the current starts flowing from the other diode of the two diodes to the fuel cell, the voltage of the first power line becomes equal to the voltage of the second power line. To control the buck-boost converter,
That is the summary.

In the controller of the present invention, the semiconductor switching element of the boost converter is switching-controlled and the buck-boost converter is controlled so that the voltage of the first power line becomes the target voltage. In the case where the semiconductor switching element is off, when the ratio of the current of one of the two diodes to the current of the reactor is less than the predetermined ratio, the off continuation control for continuing the off of the semiconductor switching element is executed. At the same time, the buck-boost converter is controlled so that the voltage of the first power line becomes the target voltage. The "predetermined ratio" is a ratio predetermined as a ratio of the current flowing through one of the diodes to the current flowing through the reactor when the two diodes are not short-circuited. When a short circuit occurs in the other diode, current concentrates in the short-circuited diode, and the ratio of the current flowing in one diode to the current of the reactor becomes less than a predetermined ratio. Further, during operation of the boost converter, the current of the reactor and the current flowing through the two diodes change. Therefore, one of the two diodes corresponding to the current of the reactor is caused by a factor other than the short circuit of the other diode. There is a case where the ratio of the current is less than the predetermined ratio. Therefore, when the semiconductor switching element is off, if the ratio of the current of one diode to the current of the reactor is less than the predetermined ratio, it may be determined that the other diode may be short-circuited. it can. Then, in this case, by performing the off continuation control for continuing to turn off the semiconductor switching element and controlling the step-up/down converter so that the voltage of the first power line becomes the target voltage, the current from the reactor is gradually increased. It decreases to the value 0, and the current of the other diode gradually decreases to the value 0. When the other diode is short-circuited, current starts flowing from the other diode to the fuel cell. Therefore, when the current starts flowing from the other diode to the fuel cell, it is determined that the other diode is short-circuited, and the buck-boost converter is operated so that the voltage of the first power line becomes the voltage of the second power line. Control. Accordingly, it is possible to prevent a current from flowing from the first power line toward the fuel cell through the other short-circuited diode and preventing the voltage of the second power line from becoming equal to or higher than the voltage between the terminals of the fuel cell. Therefore, deterioration of the fuel cell can be suppressed. As a result, it is possible to properly determine the short circuit of the diode forming the upper arm of the boost converter and suppress the deterioration of the fuel cell.

In such a control device of the present invention, the boost converter is connected to the first power line via a relay, and when the off continuation control is executed, a current flows from the other diode to the fuel cell. Start to flow, the buck-boost converter is controlled so that the voltage of the first power line becomes the voltage of the second power line, and the voltage of the first power line becomes the voltage of the second power line. In case of, the relay may be turned off. In this case, the control device is mounted on a vehicle together with the load, the boost converter, and the step-up/down converter, and the load is connected to the motor for outputting power for traveling and the first power line. And an inverter for driving the inverter. When the relay is turned off, the inverter may be controlled so that the motor is driven by electric power from the battery. With this, the vehicle can be driven even when the diode of the boost converter is short-circuited.

It is a block diagram which shows the outline of a structure of the fuel cell vehicle 20 as one Example of this invention. 6 is a flowchart showing an example of a control routine executed by an ECU 70 of the embodiment. It is explanatory drawing which shows an example of the time change of the voltage difference dVfc which subtracted voltage VLfc from gate voltage Vg of switching elements S1 and S2, current ID2, forward voltage VD2 of diode D2, current ID1, IL, and voltage VHfc.

Next, modes for carrying out the present invention will be described using examples.

FIG. 1 is a configuration diagram showing an outline of the configuration of a fuel cell vehicle 20 as one embodiment of the present invention. As illustrated, the fuel cell vehicle 20 of the embodiment includes a motor 32, an inverter 34, a fuel cell (FC) 40, an FC boost converter 42, a battery 50, a buck-boost converter 52, and an electronic control unit ( Hereinafter, referred to as “ECU”) 70.

The motor 32 is configured as, for example, a synchronous generator motor, and is connected to a drive shaft 26 that is connected to the drive wheels 22a and 22b via a differential gear 24. The motor 32 is rotationally driven by the ECU 70 performing switching control of a switching element (not shown) of the inverter 34.

The fuel cell 40 includes hydrogen as fuel gas supplied from a high-pressure hydrogen tank and circulated by a fuel pump (circulation pump), and oxygen in the air supplied by an oxygen pump (air compressor) and humidified by a humidifier. The fuel cell is configured to generate electricity by the electrochemical reaction of. The operation of the fuel cell 40 is controlled by the ECU 70.

The FC boost converter 42 is connected to an inverter side power line 60 to which the inverter 34 is connected and a fuel cell side power line 61 to which the fuel cell 40 is connected. The FC boost converter 42 is connected to the inverter-side power line 60 via a relay 63. The FC boost converter 42 includes a booster 43, a capacitor 44, and a capacitor 45. The booster 43 includes two diodes D1 and D2 that form an upper arm, two switching elements S1 and S2 that form a lower arm, and two diodes that are antiparallel-connected to the switching elements S1 and S2, and a reactor L. With. The two switching elements S1 and S2 are formed as a metal oxide field effect transistor (MOSFET) made of a semiconductor (for example, silicon). The capacitor 44 is attached to the inverter-side power line 60 side of the booster 43. The capacitor 45 is attached to the fuel cell side power line 61 side of the booster 43. The FC boost converter 42 boosts the power of the fuel cell side power line 61 and supplies it to the inverter side power line 60 by the switching control of the two switching elements S1 and S2 by the ECU 70.

The battery 50 is configured as, for example, a lithium ion secondary battery or a nickel hydrogen secondary battery. The battery 50 is managed by the ECU 70.

The step-up/down converter 52 is connected to the inverter side power line 60 and the battery side power line 62 to which the battery 50 is connected. The step-up/step-down converter 52 includes a step-up/step-down unit 53, a capacitor 54, and a capacitor 55. The step-up/down unit 53 has two switching elements, two diodes, and a reactor. The capacitor 54 is attached to the inverter-side power line 60 side of the step-up/down unit 53, and the capacitor 55 is attached to the battery-side power line 62 side of the step-up/down unit 53. The buck-boost converter 52 boosts the power of the battery-side power line 62 and supplies the boosted power to the inverter-side power line 60 or the power of the inverter-side power line 60 by switching control of two switching elements by the ECU 70. The voltage is reduced and supplied to the battery side power line 62.

Although not shown, the ECU 70 is configured as a microprocessor centered on a CPU, and includes, in addition to the CPU, a ROM for storing a processing program, a RAM for temporarily storing data, an input/output port, and a communication port.

Signals from various sensors are input to the ECU 70 via input ports. The input signal may be, for example, a rotational position θm from a rotational position detection sensor that detects the rotational position of the rotor of the motor 32 or a current sensor that detects a phase current flowing in each phase of the three-phase coil of the motor 32. Phase currents Iu, Iv, Iw, tank pressure Pt from a pressure sensor that detects the pressure in the high-pressure hydrogen tank, voltage Vfc from a voltage sensor mounted between the output terminals of the fuel cell 40, output terminal of the fuel cell 40 The current Ifc from the current sensor attached to the, the current IL from the current sensor 43a that detects the current flowing in the reactor L, the current ID1 from the current sensor 43b that detects the current flowing in the diode D1, and the connection between the terminals of the capacitor 44. The voltage VHfc of the capacitor 44 from the attached voltage sensor, the voltage VLfc of the capacitor 45 from the voltage sensor 45a attached between the terminals of the capacitor 45, and the voltage VH of the capacitor 54 from the voltage sensor attached between the terminals of the capacitor 54. , The voltage VL of the capacitor 55 from the voltage sensor mounted between the terminals of the capacitor 55, the battery current Ib from the current sensor mounted to the output terminal of the battery 50, the battery temperature Tb from the temperature sensor mounted to the battery 50 And so on. Further, a shift position SP from a shift position sensor 82 for detecting an ignition signal from the ignition switch 80 and an operation position of the shift lever 81, an accelerator opening Acc from an accelerator pedal position sensor 84 for detecting a depression amount of an accelerator pedal 83, The brake pedal position BP from the brake pedal position sensor 86 that detects the depression amount of the brake pedal 85, the vehicle speed V from the vehicle speed sensor 88, and the like can be mentioned.

Various control signals and the like are output from the ECU 70 via the output port. As various control signals, a switching control signal to a switching element of the inverter 34, an operation control signal to an auxiliary device for operating the fuel cell 40 (such as a circulation pump and an air compressor), and switching elements S1 and S2 of the FC boost converter 42. To the buck-boost converter 52, on/off control signal of the relay 63, and the like.

In the fuel cell vehicle 20 of the embodiment thus configured, the ECU 70 sets the required torque Tr* based on the accelerator opening Acc and the vehicle speed V when traveling, and the required torque Tr* is applied to the drive shaft 26. The fuel cell 40, the FC boost converter 42, the step-up/down converter 52, and the motor 32 (inverter 34) are controlled so as to be output. Regarding the FC boost converter 42 and the buck-boost converter 52, the target voltages VHfc* and VH* of the capacitors 44 and 54 are set to the basic value VHb, and the voltages VHfc and VH of the capacitors 44 and 54 are set to the target voltages VHfc* and VH*. Thus, the switching elements S1 and S2 of the booster 43 of the FC boost converter 42 and the switching elements of the buck-boost portion 53 of the buck-boost converter 52 are controlled.

Next, the operation of the fuel cell vehicle 20 of the embodiment thus configured, particularly the operation when the diodes D1 and D2 are short-circuited will be described. FIG. 2 is a flowchart showing an example of a control routine executed by the ECU 70 of the embodiment. This routine is executed when the switching elements S1 and S2 of the booster 43 of the FC boost converter 42 are turned off during traveling. When the execution of this routine is started, in the step-up/step-down converter 52, the switching element of the step-up/step-down converter 53 of the step-up/step-down converter 52 is adjusted so that the voltage VH of the capacitor 54 becomes the target voltage VH* (basic value VHb). To control.

When this routine is executed, the ECU 70 starts the measurement of the off time Toff (step S100) and executes the process of inputting the currents IL, ID1 and the voltage VLfc (step S110). The currents IL and ID1 are those detected by the current sensors 43a and 43b. The voltage detected by the voltage sensor 45a is input as the voltage VLfc.

Then, it is determined whether the ratio Ri of the current ID1 to the current IL is less than the predetermined ratio Rref (step S120). Here, the predetermined ratio Rref is a predetermined ratio as the ratio of the current ID1 to the current IL when both the diodes D1 and D2 are not short-circuited, and is, for example, 40%, 50%, 60%. When a short circuit occurs in the diode D2, more current flows to the diode D2 than in the case where no short circuit occurs, and the current flowing in the diode D1 decreases. Therefore, the ratio Ri of the current ID1 to the current IL is less than the predetermined ratio Rref. become. Further, during traveling, the currents IL and ID1 change even when the diode D2 is not short-circuited, so that the ratio Ri may temporarily become less than the predetermined ratio Rref. Therefore, the process of step S120 is a process of determining whether or not a short circuit may occur in the diode D2.

When it is determined in the process of step S120 that the ratio Ri is equal to or greater than the predetermined ratio Rref, it is determined that the diode D2 may not be short-circuited, and the short-circuit flag F is set to the value 0 (step S130). .. The short-circuit flag F is a flag that is set to a value 0 when there is no possibility that the diode D2 is short-circuited and is set to a value 1 when there is a possibility that the diode D2 is short-circuited.

Then, it is determined whether the off time Toff exceeds the predetermined time Tref (step S160). Here, the predetermined time Tref is a time for turning off the switching elements S1 and S2 of the FC boost converter 42, and is a duty ratio when switching control of the FC boost converter 42 (of a gate signal for controlling the switching elements S1 and S2). It is a value determined from the ratio of the time for which the switching elements S1 and S2 are turned on to the cycle). Therefore, the process of step S160 is a process of determining whether the time during which the switching elements S1 and S2 are turned off exceeds the time corresponding to the duty ratio when the FC boost converter 42 is switching-controlled.

When the off time Toff does not exceed the predetermined time Tref, the process returns to step S110, and when the off time Toff exceeds the predetermined time Tref, it is checked whether or not the short-circuit flag F is 0 (step S170). .. When the short-circuit flag F has a value of 1, it is determined that the diode D2 may have a short circuit, and the process returns to step S110. When the short-circuit flag F has a value of 0, the diode D2 has a short circuit. When it is determined that there is no possibility, the gates of the switching elements S1 and S2 are turned on (step S180), and this routine ends. Now, considering that the short-circuit flag has a value of 0, the gates of the switching elements S1 and S2 are turned on. By such processing, when there is no possibility that the diode D2 is short-circuited, the gates of the switching elements S1 and S2 are turned on when the off time Toff exceeds the predetermined time Tref. That is, since the switching elements S1 and S2 are turned off for a time corresponding to the duty ratio when the FC boost converter 42 is switching-controlled, it is possible to prevent the switching element S1 and S2 from being unnecessarily turned off for a long time. be able to.

When it is determined that the ratio Ri is less than the predetermined ratio Rref in the process of step S120, it is determined that the diode D2 may be short-circuited, and the short-circuit flag F is set to the value 1 (step S140). Then, it is determined whether the current IL is less than 0 (step S150). FIG. 3 is an explanatory diagram showing an example of a change over time of the voltage difference dVfc obtained by subtracting the voltage VLfc from the gate voltage Vg of the switching elements S1 and S2, the current ID2, the forward voltage VD2 of the diode D2, the currents ID1 and IL, and the voltage VHfc. Is. Now, the buck-boost converter 52 is controlled so that the voltage VH of the capacitor 54 becomes the target voltage VH* (basic value VHb), so the voltage VH of the capacitor 54 is maintained at the target voltage VH* (basic value VHb). It Therefore, the voltage VHfc of the capacitor 44 is also maintained at the target voltage VH* (basic value VHb), and the voltage difference dV is maintained at a constant value. When a short circuit occurs in the diode D2 with the switching elements S1 and S2 turned off (time t1), the Schottky barrier of the diode D2 disappears and the forward voltage VD2 drops. The current IL of the reactor L decreases with a gradient (=VHfc-VLfc/L1) obtained by dividing the value obtained by subtracting the voltage VLfc from the voltage VHfc by the inductance L1 of the reactor L (time t2). Further, if such a state continues, a current starts to flow from the inverter side power line 60 in the direction of the reactor L. Therefore, by determining whether or not the current IL is less than 0, the diode D2 is short-circuited. Can be determined. Therefore, the process of step S140 is a process of determining (determining) whether or not a short circuit has occurred in the diode D2.

When it is determined in step S150 that the current IL is equal to or greater than 0, it is determined that the diode D2 may be short-circuited but cannot be confirmed, and the process proceeds to step S160 to set the off time Toff to a predetermined value. It is determined whether the time Tref is exceeded (step S160). When the off time Toff does not exceed the predetermined time Tref, the process returns to step S110, and the off control of the switching elements S1 and S2 is continued. When the off time Toff exceeds the predetermined time Tref, it is determined whether or not the short-circuit flag F is 0 (step S170). Since it is now considered that the short-circuit flag F has the value 1, the process returns to step S110 to continue the OFF control of the switching elements S1 and S2.

When it is determined in step S150 that the current IL is less than 0 while the OFF control of the switching elements S1 and S2 is continued, it is determined that the diode D2 is short-circuited and the voltage VH is The step-up/down converter 52 is controlled so that the voltage becomes VLfc (step S190). When the current IL is less than 0, that is, when the current continues to flow from the inverter-side power line 60 toward the fuel cell 40, a voltage exceeding the voltage VLfc is applied to the fuel cell 40, and the electricity of the fuel cell 40 is reduced. It may decompose and deteriorate. However, in the process of step S190, by controlling the step-up/down converter 52 so that the voltage VH becomes the voltage VLfc, the voltage of the inverter-side power line 60 and the voltage VHfc of the capacitor 44 are the same as or different from the voltage VLfc of the capacitor 55. It is possible to set the voltage near the voltage VLfc and set the current IL of the reactor L to a value 0 or a small current value near the value 0. Thereby, deterioration of the fuel cell 40 can be suppressed.

After controlling the step-up/down converter 52 so that the voltage VH becomes the voltage VLfc, the relay 63 is turned off (step S200). By controlling the step-up/down converter 52 so that the voltage VH becomes the voltage VLfc and turning off the relay 63 in a state where the voltage difference between the voltage of the inverter side power line 60 and the voltage VHfc of the capacitor 44 is set to 0 or small. It is possible to prevent the contacts of the relay 63 from being welded.

When the relay 63 is turned off in this way, battery EV traveling (retracting traveling) in which electric power from the battery 50 is supplied to the inverter 34 to drive the motor 32 to travel (step S210), and this routine ends. By such processing, even when the diode D2 of the FC boost converter 42 is short-circuited, the motor 32 can be driven and the fuel cell vehicle 20 can be driven.

According to the fuel cell vehicle 20 of the embodiment described above, the FC boost converter 42 is controlled so that the voltages VHfc and VH (voltages of the inverter side power line 60) of the capacitors 44 and 54 become the target voltage VH* (VHfc*). When the switching elements S1 and S2 are switched off and the switching elements of the step-up/down converter 52 are controlled to turn off the switching elements S1 and S2, when the ratio Ri is less than the predetermined ratio Rref, the switching element S1, While continuing to turn off S2, the buck-boost converter 52 is controlled so that the voltage VH of the capacitor 54 (voltage of the inverter side power line 60) becomes the target voltage VH*, and the switching elements S1 and S2 are continuously turned off. In this case, when the current starts to flow from the diode D2 to the fuel cell 40, the voltage VH of the capacitor 54 (voltage of the inverter side power line 60) rises and falls so as to become the voltage VLfc of the capacitor 45 (voltage of the fuel cell 40). By controlling the pressure converter 52, it is possible to properly determine the short circuit of the diode D2 and suppress the deterioration of the fuel cell 40.

In the fuel cell vehicle 20 of the embodiment, the processes of steps S200 and S210 are executed after the process of step S190, but the processes of steps S200 and S210 may not be executed.

In the fuel cell vehicle 20 of the embodiment, when it is determined that the current IL is less than 0 in the process of step S150, the process immediately proceeds to step S190 and the step-up/down converter 52 is operated so that the voltage VH becomes the voltage VLfc. Although controlled, the process proceeds to step S190 after a lapse of a time within a range in which the degree of deterioration of the fuel cell 40 is small after the current IL is determined to be less than 0 in the process of step S150. , The voltage step-up/down converter 52 may be controlled so that the voltage VH becomes the voltage VLfc.

In the fuel cell vehicle 20 of the embodiment, the FC boost converter 42 includes the switching elements S1 and S2 in the lower arm of the booster 43, but at least one semiconductor switching element may be provided in the lower arm. One semiconductor switching element may be provided, or three or more semiconductor switching elements may be provided.

Although the fuel cell vehicle 20 of the embodiment includes the relay 63 between the inverter 34 and the FC boost converter 42, the relay 63 may not be provided.

In the embodiment, the present invention is applied to the fuel cell vehicle 20 in which the motor 32 is connected to the drive shaft 26 connected to the drive wheels 22a and 22b through the differential gear 24. However, the present invention is not limited to this, and may be applied to other devices including the motor 32. Further, the FC boost converter 42 and the buck-boost converter 52 are not limited to being connected to the inverter 34 for driving the motor 32, and the FC boost converter 42 and the buck-boost converter 52 are connected to another device. It may have been done.

Correspondence between the main elements of the embodiment and the main elements of the invention described in the column of means for solving the problem will be described. In the embodiment, the FC boost converter 42 corresponds to the “boost converter”, the motor 32 and the inverter 34 correspond to the “load”, the buck-boost converter 52 corresponds to the “boost converter”, and the ECU 70 is the “control device”. Equivalent to.

The correspondence between the main elements of the embodiment and the main elements of the invention described in the column of means for solving the problem is that the embodiment implements the invention described in the section of means for solving the problem. This is an example for specifically explaining the mode for carrying out the invention, and does not limit the elements of the invention described in the column of means for solving the problem. That is, the interpretation of the invention described in the column of means for solving the problem should be made based on the description in that column, and the embodiment is the invention of the invention described in the column of means for solving the problem. This is just a specific example.

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

INDUSTRIAL APPLICABILITY The present invention can be used in the control device manufacturing industry and the like.

20 fuel cell vehicle, 22a, 22b drive wheels, 24 differential gear, 26 drive shaft, 32 motor, 34 inverter, 40 fuel cell, 42 FC boost converter, 43 booster section, 43a, 43b current sensor, 44, 45 capacitor, 45a Voltage sensor, 50 battery, 52 step-up/down converter, 53 step-up/down unit, 54, 55 capacitor, 60 inverter side power line, 61 fuel cell side power line, 62 battery side power line, 63 relay, 70 ECU, 80 ignition switch, 81 shift lever, 82 shift position sensor, 83 accelerator pedal, 84 accelerator pedal position sensor, 85 brake pedal, 86 brake pedal position sensor, 88 vehicle speed sensor, D1, D2 diode, S1, S2 switching element, L reactor.

Claims (1)

Two diodes forming an upper arm and connected in parallel to each other, at least one semiconductor switching element forming a lower arm, and a reactor having one end connected to a connection point between the upper arm and the lower arm are provided. And a boost converter connected to the first power line to which the load is connected and the second power line to which the fuel cell is connected,
A buck-boost converter connected to the first power line and a third power line connected to the battery;
A control device for controlling
Switching control of the semiconductor switching element of the boost converter and control of the buck-boost converter so that the voltage of the first power line becomes a target voltage,
In the case where the semiconductor switching element is turned off, when the ratio of the current of one of the two diodes to the current of the reactor is less than a predetermined ratio, the off continuation of continuing the turning off of the semiconductor switching element Controlling the buck-boost converter so that the voltage of the first power line becomes the target voltage.
In the case where the off continuation control is executed, when the current starts flowing from the other diode of the two diodes to the fuel cell, the voltage of the first power line becomes equal to the voltage of the second power line. To control the buck-boost converter,
Control device.

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