JP2023077482A - power control system - Google Patents

Abstract

To provide a technology capable of suppressing over-voltage.SOLUTION: A power control system includes: a secondary battery; a first converter that boosts an output voltage of the secondary battery; a relay circuit that electrically connects/disconnects the secondary battery to/from the first converter; a first sensor that measures a first voltage which is an output voltage of the secondary battery; a second sensor that measures a second voltage which is a voltage to be inputted to the first converter; a third sensor that measures a third voltage which is a voltage outputted from the first converter; and a control unit that can perform first control of controlling the first converter by using the second voltage, and perform second control of controlling the first converter by using the first voltage or controlling refraining from boosting the voltage. When the power control system has been started and the connection processing by the relay circuit is not completed, the control unit performs the second control if a disconnection probability condition is satisfied.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to power control systems.

A fuel cell system including a secondary battery is known. Patent Document 1 discloses that when the boost converter of the secondary battery cannot boost due to an abnormality, the ratio of the output voltage to the input voltage of the boost converter of the fuel cell is the minimum within the range in which the boost operation of the boost converter of the fuel cell is guaranteed. A fuel cell system is described that controls the voltage of the fuel cell to satisfy a minimum step-up ratio of . By performing such control, even if the boost converter of the secondary battery fails, the voltage output by the boost converter of the fuel cell becomes higher than the voltage on the output side of the boost converter of the secondary battery. You can limit your chances.

JP 2018-181834 A

However, in the fuel cell system described in Patent Document 1, since disconnection of the sensor that measures the pre-boosted voltage of the boost converter of the secondary battery cannot be detected, if the sensor disconnects before starting the fuel cell system, The fuel cell system may perform control using an erroneous pre-boost voltage value of the boost converter of the secondary battery. In this case, the boosted voltage of the boost converter of the secondary battery becomes an overvoltage, and there is a risk that the fuel cell system cannot be started. Therefore, there is a demand for a technique that can suppress overvoltage even when a sensor for measuring the pre-boost voltage of a boost converter for a secondary battery is disconnected.

The present disclosure has been made to solve the above problems, and can be implemented as the following modes.

According to one aspect of the present disclosure, a power control system is provided. This power control system includes a secondary battery, a first converter that boosts the output voltage of the secondary battery, a relay circuit that electrically connects or disconnects the secondary battery and the first converter, and A first sensor that measures a first voltage that is an output voltage of a secondary battery, a second sensor that measures a second voltage that is a voltage input to the first converter, and a voltage output from the first converter. a third sensor that measures a third voltage, a first control that uses the second voltage to control the first converter, and a voltage that controls the first converter using the first voltage, or boosts a second control that controls the first converter so as not to perform; After the power control system is activated, the control unit controls the difference between the first voltage and the second voltage to be a predetermined first threshold value when the connection processing of the relay circuit is not completed. and the disconnection possibility condition is satisfied that the time during which the difference between the second voltage and the third voltage is equal to or greater than a predetermined second threshold continues for a predetermined threshold time or longer. , to perform the second control.
According to the power control system of this aspect, the control unit uses the first voltage, the second voltage, and the third voltage to determine the possibility of disconnection of the second sensor when the disconnection possibility condition is satisfied. It is determined that the value of 1 voltage is used to control the first converter. That is, when there is a possibility that a disconnection has occurred in the second sensor, the first converter is controlled using a second voltage value that may differ from the voltage value actually input to the first converter. As a result, it is possible to suppress the third voltage from becoming an overvoltage. Therefore, even if the second sensor that measures the pre-boosted voltage of the first converter is disconnected, it is possible to prevent the third voltage from becoming an overvoltage.

Note that the present disclosure can be implemented in various forms, for example, it can be implemented in a mode such as a method for determining disconnection of a sensor that measures the pre-boosted voltage of a secondary battery converter. be.

1 is a schematic diagram showing a schematic configuration of a power control system; FIG. 4 is a flowchart showing an overview of boost control processing of the power control system; 9 is a flowchart of boost control processing in the second embodiment; FIG. 11 is an explanatory diagram of a power control system according to a fourth embodiment;

A. First embodiment:
FIG. 1 is a schematic diagram showing a schematic configuration of a power control system 100 according to an embodiment of the present disclosure. The power control system 100 includes a secondary battery 10, a relay circuit 20, a first converter 30, an inverter 40, a first sensor 11, a second sensor 12, a third sensor 13, a control unit 50, Prepare.

The secondary battery 10 is, for example, a lithium ion battery. Relay circuit 20 is a circuit that electrically connects or disconnects secondary battery 10 and first converter 30 .

The first converter 30 is a non-isolated bidirectional DC/DC converter. First converter 30 incorporates switches S1 and S2, reactor L1, and capacitor C1. First converter 30 is arranged between secondary battery 10 and inverter 40 and performs step-up operation and step-down operation according to the control of control unit 50 . Switch S1 is connected to power line W1 that connects secondary battery 10 and inverter 40 . Switch S2 is connected to ground line W2 that connects secondary battery 10 and inverter 40 . One end of reactor L1 is connected in series to switch S1, and the other end of reactor L1 is connected to power line W1. One end of the capacitor C1 is connected to the power line W1, and the other end of the capacitor C1 is connected to the ground line W2. More specifically, when first converter 30 performs a step-down operation, control unit 50 turns on/off switch S1 on the upper arm side while keeping switch S2 on the lower arm side off. Further, when the first converter 30 performs the boosting operation, the control unit 50 turns on/off the switch S2 on the lower arm side while the switch S1 on the upper arm side is turned off. The first converter 30 is also called a battery converter.

Inverter 40 converts DC power supplied from secondary battery 10 into AC power, and supplies power to load 200 including components such as a three-phase AC motor driven at high voltage. The DC power supplied from the first converter is converted into AC power and supplied to the load.

The first sensor 11 measures a first voltage, which is the output voltage of the secondary battery 10 . The second sensor 12 measures a second voltage, which is the voltage input to the first converter 30 . An abnormality in the relay circuit 20 can be detected by detecting a difference between the first voltage and the second voltage. Third sensor 13 measures a third voltage, which is the voltage output from first converter 30 . The first sensor 11 , the second sensor 12 , and the third sensor 13 each transmit the measured voltage values to the control unit 50 .

The control unit 50 is configured as a computer including a CPU, a memory, and an interface circuit to which the components described above are connected. The CPU executes a control program stored in the memory to implement boost control processing, which will be described later. Control unit 50 performs first control for controlling first converter 30 using the second voltage, and controls first converter 30 using the first voltage instead of the second voltage.

FIG. 2 is a flow chart showing an outline of boost control processing of power control system 100 in the present embodiment. The boost control process is a process in which the controller 50 switches between the first control and the second control depending on the possibility that the second sensor 12 is disconnected. This process is a process performed after the power control system 100 is activated.

In step S100, the control unit 50 determines whether or not the connection processing of the relay circuit 20 has been completed. More specifically, it is determined whether the status of the relay circuit 20 is completed. By completing the connection processing of the relay circuit 20, the operating state of the power control system 100 is stabilized, and the components such as the load 200 connected by the relay circuit 20 can be stably driven. If the connection process of the relay circuit 20 has not been completed, the process proceeds to step S110. On the other hand, when the connection process of the relay circuit 20 is completed, the process proceeds to step S125 to perform the first control.

In step S110, the control unit 50 determines whether or not the disconnection possibility condition is satisfied. The disconnection possibility condition is a condition indicating that the second sensor 12 may be disconnected. More specifically, the controller 50 determines that the difference between the first voltage and the second voltage is equal to or greater than a predetermined first threshold, and the difference between the second voltage and the third voltage is a predetermined threshold. A determination is made as to whether or not the time of two or more thresholds has continued for a predetermined first threshold time or longer. The first threshold and the second threshold can be obtained experimentally or empirically from the relationship between the voltage value at which the third voltage becomes an overvoltage and the step-up ratio. The first threshold may be the same value as the second threshold. Also, the first threshold time is the time until connection processing of the relay circuit 20 is completed, and is, for example, 100 milliseconds. Note that the control unit 50 determines that the time during which the difference between the first voltage and the second voltage is equal to or greater than the first threshold and the difference between the second voltage and the third voltage is equal to or greater than the second threshold is less than the first threshold time. If it continues only, it is not determined that there is a possibility that the second sensor 12 is disconnected. If the connection processing of the relay circuit 20 is not completed, the first voltage, the second voltage, and the third voltage are not stable. may be greater than or equal to the first threshold for a period of less than the first threshold time. Therefore, the control unit 50 determines that the time during which the difference between the first voltage and the second voltage is equal to or greater than the first threshold and the difference between the second voltage and the third voltage is equal to or greater than the second threshold is equal to or longer than the first threshold time. Since it is set as the disconnection possibility condition, it is possible to suppress an erroneous determination that there is a possibility that the second sensor 12 is disconnected.

If the disconnection possibility condition is satisfied, that is, if there is a possibility that the second sensor 12 is disconnected, the control unit 50 proceeds to the process of step S120 and performs the second control. On the other hand, if the disconnection possibility condition is not satisfied, that is, if there is no possibility that the second sensor 12 is disconnected, the control unit 50 proceeds to the process of step S125 and performs the first control.

In step S<b>130 , the control unit 50 determines whether or not there is a request to terminate the power control system 100 . If there is a request to end the power control system 100, the boost limiting process ends. On the other hand, if there is no request to terminate power control system 100, that is, if power control system 100 continues to be driven, the process returns to step S100.

According to the power control system 100 of the present embodiment described above, the control unit 50 uses the first voltage, the second voltage, and the third voltage, and when the disconnection possibility condition is satisfied, the first voltage The value is used to control the first converter 30 . That is, when there is a possibility that a disconnection has occurred in the second sensor 12, the first converter 30 is controlled using a second voltage value different from the voltage value actually input to the first converter 30. Therefore, it is possible to suppress the third voltage from becoming an overvoltage. Therefore, even if the second sensor 12 that measures the pre-boosted voltage of the first converter 30 is disconnected, it is possible to prevent the third voltage from becoming an overvoltage.

Further, if the time period during which the difference between the first voltage and the second voltage is equal to or greater than the first threshold and the difference between the second voltage and the third voltage is equal to or greater than the second threshold continues for the first threshold time or longer, the disconnection occurs. Since the possibility condition is set, the control unit 50 can accurately identify the situation in which there is a possibility of disconnection of the second sensor 12 .

B. Second embodiment:
FIG. 3 is a flow chart of boost control processing in the second embodiment. The step-up control process in the second embodiment differs from that in the first embodiment in that when the connection process of the relay circuit 20 is completed in step S100, the process proceeds to step S115 and the process after step S115. The configuration of the power control system 100 in the second embodiment is the same as in the first embodiment.

In step S115, the control unit 50 determines whether or not the first sensor 11 or the second sensor 12 is abnormal. In the present embodiment, the control unit 50 determines whether or not the time during which the difference between the first voltage and the second voltage is equal to or greater than a predetermined third threshold continues for a predetermined second threshold or longer. do. The third threshold is less than the first threshold. Also, the second threshold time is longer than the first threshold time. The second threshold time is, for example, 5 seconds. If no abnormality is detected in the first sensor 11 and the second sensor 12, the process proceeds to step S125. On the other hand, if an abnormality is detected in the first sensor 11 or the second sensor 12, the process proceeds to step S127.

In step S125, the control unit 50 performs first control. That is, if the second control has been executed until then, more specifically, the control unit 50 executes the second control in step S120, and in the process of step S130, the request to end the power control system 100 is received. When it is determined that there is not, the process returns to step S100, and the connection process of the relay circuit 20 is completed, the second control shifts to the first control.

In step S127, the control unit 50 performs predetermined abnormality control. Abnormal control is control performed when there is a possibility that the first sensor 11 or the second sensor 12 is out of order. For example, the first converter 30 is controlled so as not to boost the voltage.

Since the second control uses the first voltage instead of the second voltage to control the first converter 30, the control content is more complicated than the first control. According to the power control system 100 of the present embodiment described above, even after the control unit 50 determines to perform the second control, the abnormality of the first sensor 11 and the second sensor 12 is not detected. In this case, since the second control is shifted to the first control, it is possible to prevent the control from becoming complicated.

C. Third embodiment:

The third embodiment differs from the first embodiment in that the second control controls the first converter 30 so as not to boost the voltage. The configuration of the power control system 100 in the second embodiment is the same as in the first embodiment.

As the second control, the control unit 50 turns on the switch S1 on the upper arm side. As a result, the first converter 30 does not boost the voltage.

According to the power control system 100 of the present embodiment described above, when there is a possibility that disconnection has occurred in the second sensor 12, the control unit 50 does not boost the third voltage. can be further suppressed from becoming overvoltage.

D. Fourth embodiment:
FIG. 4 is an explanatory diagram of the power control system 100B in the fourth embodiment. A power control system 100B according to the fourth embodiment differs from the power control system 100 according to the second embodiment in that it includes a fuel cell 60, a first converter 30, and a fourth sensor 61. Other configurations are the same as those of the second embodiment. are the same. The power control system 100B of this embodiment is mounted on, for example, a fuel cell vehicle.

The fuel cell 60 is a polymer electrolyte fuel cell that generates electricity by receiving supply of hydrogen gas (anode gas) and air (cathode gas) as reaction gases. The fuel cell 60 is constructed by stacking a plurality of cells (not shown). Each cell has a membrane electrode assembly in which electrodes are arranged on both sides of an electrolyte membrane, and a set of separators sandwiching the membrane electrode assembly. Electric power generated by fuel cell 60 is stored in secondary battery 10 via second converter 70 and first converter 30 .

The second converter 70 is a non-isolated DC/DC converter. The second converter 70 is connected to the fuel cell 60 and boosts the output voltage of the fuel cell 60 under the control of the controller 50 . The second converter 70 is also called a fuel cell converter. The voltage boosted by second converter 70 is supplied to load 200 via inverter 40 . In this embodiment, the load 200 is, for example, a traction motor (not shown) for driving wheels (not shown) or an air compressor (not shown).

A fourth sensor 61 measures a fourth voltage, which is the voltage of the fuel cell 60 . In the boost control process, the controller 50 controls the first converter 30 so as not to boost the voltage when the fourth voltage is lower than the first voltage.

According to the power control system 100B of the present embodiment described above, when the fourth voltage is lower than the first voltage, the control unit 50 does not boost the third voltage so that the third voltage becomes an overvoltage. can be more suppressed.

E. Other embodiments:
(E1) In the above-described embodiment, the control unit 50 performs the first control when the disconnection possibility condition is not satisfied in step S110. Not limited to this, the control unit 50 may further perform the first control when other conditions are satisfied.

(E2) In the second embodiment described above, the third threshold is smaller than the first threshold. The third threshold is not limited to this, and may be equal to or higher than the first threshold. When the connection processing of the relay circuit 20 is completed, the first voltage and the second voltage are more stable than when the connection processing of the relay circuit 20 is not completed. 12, the first voltage and the second voltage do not deviate greatly. That is, even if the third threshold value is set to a small value, the possibility of erroneously determining that the first sensor 11 and the second sensor 12 are abnormal is low. Therefore, the third threshold is preferably smaller than the first threshold.

(E3) In the second embodiment described above, the second threshold time is longer than the first threshold time. The second threshold time is not limited to this, and the second threshold time may be less than or equal to the first threshold time. The first threshold time is equal to or less than the time until the connection processing of the relay circuit 20 is completed, but the second threshold time can be set longer than the time until the connection processing of the relay circuit 20 is completed. When the second time is long, it is possible to more reliably determine the possibility that the first sensor 11 and the second sensor 12 are out of order than when the second time is short. Therefore, the second threshold time is preferably longer than the first threshold time. Moreover, when the second threshold time is sufficiently long, it is possible to reliably determine that the first sensor 11 and the second sensor 12 are abnormal even if the third threshold is set to a small value.

The present disclosure is not limited to the embodiments described above, and can be implemented in various configurations without departing from the scope of the present disclosure. For example, the technical features in the embodiments corresponding to the technical features in each form described in the outline of the invention are In addition, it is possible to perform replacement and combination as appropriate. Moreover, if the technical feature is not described as essential in this specification, it can be deleted as appropriate.

DESCRIPTION OF SYMBOLS 10... Secondary battery 11... 1st sensor 12... 2nd sensor 13... 3rd sensor 20... Relay circuit 30... 1st converter 40... Inverter 50... Control part 60... Fuel cell 61 Fourth sensor 70 Second converter 100, 100B Power control system 200 Load C1 Capacitor L1 Reactor S1, S2 Switch W1 Power line W2 Ground line

Claims (4)

A power control system,
a secondary battery;
a first converter that boosts the output voltage of the secondary battery;
a relay circuit that electrically connects or disconnects the secondary battery and the first converter;
a first sensor that measures a first voltage that is the output voltage of the secondary battery;
a second sensor that measures a second voltage that is the voltage input to the first converter;
a third sensor that measures a third voltage that is the voltage output from the first converter;
A first control that controls the first converter using the second voltage, and a second control that controls the first converter using the first voltage or controls the first converter so as not to boost the voltage. a control unit capable of executing a control,
After starting the power control system, the control unit
When the connection process of the relay circuit is not completed, the difference between the first voltage and the second voltage is equal to or greater than a predetermined first threshold, and the difference between the second voltage and the third voltage is A power control system that performs the second control when a disconnection possibility condition is satisfied that a time period in which the difference is equal to or greater than a predetermined second threshold continues for a predetermined threshold time or longer. A power control system according to claim 1,
When the control unit is executing the second control and when the connection process is completed, if an abnormality between the first sensor and the second sensor is not detected, the A power control system that transitions from a second control to the first control. A power control system according to claim 1 or claim 2,
The power control system, wherein the second control controls the first converter to prevent boosting. 3. A power control system according to claim 1 or claim 2, further comprising:
a fuel cell;
a second converter that boosts the voltage of the fuel cell;
a fourth sensor that measures a fourth voltage that is the voltage of the fuel cell;
The power control system, wherein the control unit controls the first converter to perform the second control so as not to boost the voltage when the fourth voltage is lower than the first voltage.

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