JP7613345B2 - Power supply control device - Google Patents

Description

The present invention relates to a control device for a power supply device, and more specifically, to a control device for a power supply device that is installed in a power supply device that includes a DC power supply, an electric circuit, a relay, a power supply circuit, and a capacitor.

Conventionally, as a control device for this type of power supply device, a device mounted on a power supply device (power supply system) including a DC power supply (battery), an electric circuit (DC/DC converter), a relay (two contactors on the positive and negative sides), a power supply circuit (precharge contactor and resistor section), and a capacitor has been proposed (see, for example, Patent Document 1). The electric circuit receives power from the DC power supply. The relay connects and disconnects a first power line from the DC power supply and a second power line (positive and negative current supply paths) from the electric circuit. The power supply circuit can supply power to the second power line when the relay is off. The capacitor is connected to the positive line (positive current supply path) and negative line (negative current supply path) of the second power line. When the control device of this power supply device switches the relay from off to on, it executes a precharge that controls the relay and the power supply circuit so that the voltage of the second power line becomes the terminal voltage of the DC power supply while the relay is off, and turns on the relay after executing the precharge. In the precharge, it is determined that the precharge is completed when a set time has elapsed since the voltage difference between the terminal voltage of the DC power supply and the voltage of the second power line becomes equal to or less than a set voltage. The set voltage is set using a maximum error based on the maximum value of the detection error of the terminal voltage of the DC power supply and the voltage of the second power line. The set time is set based on the time constant with which the power supply circuit charges the capacitor, the maximum error of the voltage difference, and the withstand voltage of the relay. This makes it possible to perform the precharge so that the voltage difference does not exceed the withstand voltage of the relay.

JP 2020-137334 A

However, in the above-mentioned power supply control device, even if it is determined that precharging is complete, due to detection errors of the terminal voltage of the DC power supply and the capacitor voltage, the voltage difference may not actually be 0, and a current may be generated when the relay is connected, causing stress that roughens the contacts. Such stress may cause the relay to weld in the future. Therefore, it is desirable to be able to determine the signs of relay welding.

The main purpose of the power supply control device of the present invention is to detect signs of relay welding.

The power supply control device of the present invention employs the following means to achieve the above-mentioned main objective.

The control device for a power supply device of the present invention comprises:
A DC power source;
an electric circuit that receives power from the DC power source;
a relay for connecting and disconnecting a first power line from the DC power source and a second power line from the electric circuit;
a power supply circuit capable of supplying power to the second power line when the relay is in an off state;
a capacitor attached to a positive line and a negative line of the second power line;
The power supply device includes:
a control device for a power supply device, which executes a precharge to control the relay and the power supply circuit when the relay is switched from off to on so that a voltage of the second power line becomes a voltage between terminals of the DC power supply while the relay is in an off state, and controls the relay to be on after the precharge is completed,
The gist of the present invention is to determine a sign of welding of the relay based on a histogram in which a voltage difference, which is the difference between the voltage of the second power line after the precharge is completed and before the relay is turned on, and the voltage of the second power line after the relay is turned on, is classified.

In the power supply control device of the present invention, signs of relay welding are judged based on a histogram in which the voltage difference, which is the difference between the voltage of the second power line after precharging is completed and before the relay is turned on, and the voltage of the second power line after the relay is turned on, is classified. The inventors have found that the shape of the histogram in which the voltage difference is classified changes depending on the state of stress on the relay. Therefore, the state of stress on the relay can be judged based on the histogram in which the voltage difference is classified. As a result, signs of relay welding can be judged.

In the power supply control device of the present invention, when the kurtosis when the first histogram is considered as a normal distribution is a negative value, it may be determined that there is a sign of welding of the relay, or when the ratio of the number of occurrences in which the voltage difference is included in a class in which the voltage difference is less than a predetermined voltage to the number of occurrences in which the voltage difference is included in a class in which the voltage difference is equal to or greater than a predetermined voltage in the first histogram is equal to or greater than a predetermined value. In this way, it is possible to more accurately determine the sign of welding of the relay.

In the power supply control device of the present invention, the power supply circuit may have an auxiliary power source different from the DC power source, and a voltage conversion circuit that converts the voltage of the power from the auxiliary power source and supplies it to the second power line, or may be a circuit in which a charging relay is connected via a resistor between the negative electrode line of the first power line and the negative electrode line of the second power line, or between the positive electrode line of the first power line and the positive electrode line of the second power line.

1 is a diagram showing an outline of the configuration of an electric vehicle 20 equipped with a control device for a power supply device as an embodiment of the present invention; 4 is a flowchart showing an example of a determination routine executed by an ECU 70. FIG. 11 is an explanatory diagram showing an example of a frequency distribution of a voltage difference ΔVL. FIG. 11 is an explanatory diagram illustrating an example of a second histogram. 13 is an explanatory diagram showing an example of a histogram (third histogram) in a case where there is a large deviation between the voltage VL detected by the voltage sensor 39a and the actual voltage of the capacitor 39 (the voltage of the low-voltage side power line 38b). FIG.

Next, we will explain how to implement the present invention using examples.

Figure 1 is a schematic diagram showing the configuration of an electric vehicle 20 equipped with a power supply control device as one embodiment of the present invention. As shown in the figure, the electric vehicle 20 equipped with the power supply device of the embodiment includes a motor 32, an inverter 34, a battery 36 as a DC power source, a system main relay SMR, an auxiliary battery 40 and a DC/DC converter 48 as a power supply circuit, a step-up/step-down converter 50, and an electronic control unit (hereinafter referred to as "ECU") 70. The ECU 70 mainly serves as the control device for the power supply device of the embodiment.

The motor 32 is configured as a synchronous generator motor, and includes a rotor with a permanent magnet embedded in the rotor core, and a stator with a three-phase coil wound around the stator core. The rotor of the motor 32 is connected to a drive shaft 26 that is connected to the drive wheels 22a, 22b via a differential gear 24. The inverter 34 is connected to the motor 32 and to a high-voltage power line 38a. The inverter 34 is configured as a well-known inverter circuit having six transistors and six diodes. The motor 32 is driven to rotate by switching control of multiple switching elements (not shown) of the inverter 34. The inverter 34 is connected to the ECU 70 via a communication line (e.g., a communication line for CAN communication).

The step-up/step-down converter 50 is connected to the high-voltage power line 38a and the low-voltage power line (second power line) 38b, and is configured as a well-known step-up/step-down converter circuit having two transistors and two diodes that constitute the upper and lower arms, and a reactor. The step-up/step-down converter 50 boosts the power of the low-voltage power line 38b and supplies it to the high-voltage power line 38a, or reduces the voltage of the high-voltage power line 38a and supplies it to the low-voltage power line 38b, by adjusting the ratio of the on-time of the two transistors that constitute the upper and lower arms by the ECU 70. Although not shown, smoothing capacitors are attached to the positive and negative lines of the high-voltage power line 38a. A smoothing capacitor 39 is attached to the positive and negative lines of the low-voltage power line 38b.

The battery 36 is configured as, for example, a lithium ion secondary battery or a nickel-metal hydride secondary battery with a rated voltage of several hundred volts.

The system main relay (relay) SMR is connected to the battery side power line (first power line) 37 from the battery 36 and the low voltage side power line 38b. This system main relay SMR has a positive side relay SMRB provided on the positive line of the battery side power line 37 and the positive line of the low voltage side power line 38b, and a negative side relay SMRG provided on the negative line of the battery side power line 37 and the negative line of the low voltage side power line 38b. The system main relay SMR connects and disconnects the battery side power line 37 and the low voltage side power line 38b by turning it on and off. The system main relay SMR is connected to the ECU 70 via a communication line (e.g., a communication line for CAN communication).

The auxiliary battery 40 is configured as, for example, a lithium-ion secondary battery, a nickel-hydrogen secondary battery, or a lead-acid battery with a rated voltage of about 10 V, and is connected to the auxiliary power line 42 together with the auxiliary equipment, DC/DC converter 48, and ECU 70 (not shown).

The DC/DC converter 48 is connected to the low-voltage power line 38b and the auxiliary power line 42. This DC/DC converter 48 steps down the power of the low-voltage power line 38b and supplies it to the auxiliary power line 42, or steps up the power of the auxiliary power line 42 and supplies it to the low-voltage power line 38b. The DC/DC converter 48 is connected to the ECU 70 and the like via a communication line (e.g., a communication line for CAN communication).

Although not shown, the ECU 70 is configured as a microprocessor centered on a CPU, and in addition to the CPU, it is equipped with a ROM for storing processing programs, a RAM for temporarily storing data, a flash memory for storing and holding data, an input/output port, and a communication port. The ECU 70 is connected to the inverter 34, the system main relay SMR, the DC/DC converter 48, and the step-up/step-down converter 50 via communication lines (e.g., communication lines for CAN communication).

Signals from various sensors are input to the ECU 70 via input ports. Examples of signals input to the ECU 70 include the rotational position θm from the rotational position detection sensor (e.g., resolver) 32a that detects the rotational position of the rotor of the motor 32, the voltage (terminal voltage of the battery 36) 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. Also included is the voltage VL of the capacitor 39 (low-voltage side power line 38b) from the voltage sensor 39a attached between the terminals of the capacitor 39. Examples of the signals include an ignition signal from the ignition switch 80, a shift position SP from a shift position sensor 82 that detects the operating position of the shift lever 81, an accelerator opening Acc from an accelerator pedal position sensor 84 that detects the amount of depression of the accelerator pedal 83, a brake pedal position BP from a brake pedal position sensor 86 that detects the amount of depression of the brake pedal 85, and a vehicle speed V from a vehicle speed sensor 87. The operating positions of the shift lever 81 (shift position SP detected by the shift position sensor 82) include a parking position (P position), a reverse position (R position), a neutral position (N position), and a forward position (D position).

Various control signals are output from the ECU 70 via the output port. Examples of signals output from the ECU 70 include a control signal to the transistors of the inverter 34, a control signal to the system main relay SMR, a control signal to the DC/DC converter 48, and a control signal to the step-up/step-down converter 50.

In the electric vehicle 20 of the embodiment thus configured, when the system main relay SMR is turned on from off, for example, when the ignition signal from the ignition switch 80 is turned on from off, a precharge is executed to control the system main relay SMR and the DC/DC converter 48 so that the voltage VL of the capacitor 39 detected by the voltage sensor 39a becomes the voltage Vb of the battery 36 detected by the voltage sensor 36a while the system main relay SMR is off. Then, when the voltage VL of the capacitor 39 detected by the voltage sensor 39a becomes the voltage Vb of the battery 36 detected by the voltage sensor 36a, that is, when a predetermined time tref has elapsed after the completion of the precharge, the system main relay SMR is turned on and the DC/DC converter 48 is controlled so that the auxiliary battery 40 is charged. The time tref may be 0, and in this case, the system main relay SMR is turned on immediately after the completion of the precharge.

Next, the operation of the electric vehicle 20 of the embodiment thus configured, in particular the operation when determining whether there is a sign of welding of the system main relay SMR, will be described. FIG. 2 is a flowchart showing an example of a determination routine executed by the ECU 70. This routine is executed when the above-mentioned pre-charging is started.

When this routine is executed, the CPU of the ECU 70 determines whether precharging is complete (step S100). If precharging is not complete, the CPU waits until precharging is complete.

When the precharge is completed in step S100, the voltage VL of the capacitor 39 is input (step S110), and the input voltage VL is set to the pre-on voltage Vbefore (step S120). The voltage VL is the value detected by the voltage sensor 39a.

Next, it is determined whether the system main relay SMR is on or not (step S130). If the system main relay SMR is off, the process returns to step S110, and steps S110 to S130 are repeated until the system main relay SMR is on. Therefore, the before-on voltage Vbefore is set to the voltage VL after the precharge is completed and before the system main relay SMR is turned on.

When the system main relay SMR is turned on, the voltage VL of the capacitor 39 is input (step S140) in the same process as in step S110, and the input voltage VL is set as the after-on voltage Vafter (step S150). Then, the voltage difference ΔVL is calculated by subtracting the before-on voltage Vbefore set in step S110 from the set after-on voltage Vafter (step S160).

After the voltage difference ΔVL is calculated, the frequency distribution of the voltage difference ΔVL is updated (if a frequency distribution has not yet been created, a frequency distribution is created) (step S170). FIG. 3 is an explanatory diagram showing an example of a frequency distribution of the voltage difference ΔVL. As shown in the figure, the frequency distribution is updated (created) by dividing the voltage difference into multiple intervals for each predetermined voltage width (in this embodiment, 10 V, for example) and increasing the number of times of the class to which the calculated voltage difference ΔVL belongs by a value of 1. In the frequency distribution, the interval where the voltage difference ΔVL includes the value 0 (in this embodiment, the interval where the voltage difference ΔVL is greater than -5 V and less than or equal to 5 V) is placed in the center.

After updating the frequency distribution in this way, it is determined whether the number of data N, which is the total number of data included in the frequency distribution, is equal to or greater than a predetermined number Nref (step S180). The predetermined number Nref is a threshold value for determining whether the number of data N has reached a number sufficient to reduce statistical error, and is set to, for example, 100, 200, 300, etc. When the number of data N is less than the predetermined number Nref, this routine is terminated.

When the number of data N is equal to or greater than the predetermined number Nref, a first histogram is created from the frequency distribution (step S190), and a welding sign determination is performed to determine whether there are signs of welding in the system main relay SMR based on the first histogram (step S200), and this routine ends. The welding sign determination is performed by examining the shape of the first histogram.

4 is an explanatory diagram showing an example of the second histogram. The second histogram is a histogram determined in advance by experiments, analysis, etc., as a histogram in which the voltage difference of the capacitor 39 voltage before and after the system main relay SMR is turned on after the precharge is completed when the detection error of the voltage sensor 36a or the voltage sensor 39a is small is classified. When the detection error of the voltage sensor 36a or the voltage sensor 39a is small, the deviation between the voltage Vb of the battery 36 detected by the voltage sensor 36a and the actual voltage of the battery 36, and the deviation between the voltage VL detected by the voltage sensor 39a and the actual voltage of the capacitor 39 (the voltage of the low-voltage side power line 38b) are small. Therefore, the difference between the voltage of the battery 36 and the voltage of the capacitor 39 (the voltage of the low-voltage power line 38b) before and after the system main relay SMR is turned on after the precharging is completed is small, and as shown in the figure, if the class in which the voltage difference ΔVL has a value of 0 is placed in the center of the second histogram, the data will be concentrated near the center and the distribution will have a heavy tail. If the second histogram is considered to be a normal distribution, the kurtosis will be large and the value will be positive. In this case, it can be determined that the current generated when the system main relay SMR is connected is small, the stress on the system main relay SMR that roughens the contacts is small, and there are no signs of the system main relay SMR welding.

5 is an explanatory diagram showing an example of the third histogram. The third histogram is a histogram determined in advance by experiments, analysis, etc. as a histogram in which the voltage difference between the voltage of the capacitor 39 before and after the system main relay SMR is turned on after the precharge is completed when the detection error of the voltage sensor 36a or the voltage sensor 39a is large is a class. When the detection error of the voltage sensor 36a or the voltage sensor 39a is large, the deviation between the voltage VL detected by the voltage sensor 39a and the actual voltage of the capacitor 39 (the voltage of the low-voltage side power line 38b) becomes large. Therefore, the number of times that the difference between the voltage of the battery 36 before and after the system main relay SMR is turned on after the precharge is completed and the voltage of the capacitor 39 (the voltage of the low-voltage side power line 38b) becomes large increases, and in the third histogram, as shown in the figure, if the class including the voltage difference ΔVL value 0 is placed in the center, the data will vary as a whole and the tail of the distribution will be light. If the third histogram is considered to be a normal distribution, the kurtosis will be small and negative. In this case, the current generated when the system main relay SMR is connected is large, and the stress on the system main relay SMR that roughens the contacts is large, so it can be determined that there are signs that the system main relay SMR may weld.

In this way, by examining the shape of the histogram in which the voltage difference between the voltages of the capacitor 39 before and after the system main relay SMR is turned on after the precharging is completed, it is possible to determine whether the system main relay SMR is under a large amount of stress, i.e., whether there are signs that the system main relay SMR will melt. For this reason, in the embodiment, the shape (kurtosis) of the first histogram is examined to determine whether there are signs that the system main relay SMR will melt.

In the welding indication determination in step S200, when the kurtosis K1 of the first histogram is equal to or greater than 0, it is determined that the shape of the first histogram is close to the shape of the second histogram, and it is determined that there is no indication that the system main relay SMR will weld. When the kurtosis K1 of the first histogram is less than 0, it is determined that the shape of the first histogram is close to the shape of the third histogram, and it is determined that there is an indication that the system main relay SMR will weld. In this way, by examining the shape (kurtosis Sp1) of the first histogram, it is possible to determine whether there is an indication that the system main relay SMR will weld.

According to the electric vehicle 20 equipped with the control device for the power supply device of the embodiment described above, the signs of welding of the system main relay SMR can be determined by determining the signs of welding of the system main relay SMR based on the first histogram that classifies the voltage difference ΔVL, which is the difference between the pre-on voltage Vbefore and the post-on voltage Vafter.

In an electric vehicle 20 equipped with the power supply control device of the embodiment, in step S200, the kurtosis Sp1 of the first histogram is examined to determine whether there is a sign of welding. However, instead of examining the kurtosis Sp1 of the first histogram, the ratio of the number of times (frequency) of the interval in which the voltage difference ΔVL of the first histogram includes a value of 0 (in the embodiment, the interval in which the voltage difference ΔVL is greater than -5 V and less than or equal to 5 V) to the total number of times of other intervals may be calculated, and if this ratio is large, it may be determined that there is a sign of welding of the system main relay SMR.

In the electric vehicle 20 equipped with the control device of the power supply device of the embodiment, in pre-charge, the system main relay SMR and the DC/DC converter 48 are controlled so that the voltage VL of the capacitor 39 becomes the voltage Vb of the battery 36 when the system main relay SMR is off. However, a charging relay may be connected between the negative line of the battery side power line 37 and the negative line of the low-voltage side power line 38b or between the positive line of the battery side power line 37 and the positive line of the low-voltage side power line 38b via a resistor, and in pre-charge, the relay that is not connected to the charging relay among the positive side relay SMRB and the negative side relay SMRG may be turned on and the relay that is connected to the charging relay may be turned off, and the charging relay may be turned on to supply power from the battery 36 to the capacitor 39, and the voltage VL of the capacitor 39 may become the voltage Vb of the battery 36.

In the embodiment, the power supply control device of the present invention is applied to an electric vehicle 20. However, the power supply control device of the present invention may be applied to any vehicle equipped with a power supply device including a DC power supply, an electric circuit that receives power from the DC power supply, a relay that connects and disconnects a first power line from the DC power supply and a second power line from the electric circuit, a power supply circuit that can supply power to the second power line when the relay is off, capacitors attached to the positive and negative lines of the second power line, and a voltage sensor that detects the voltage of the second power line.

The following explains the relationship between the main elements of the embodiment and the main elements of the invention described in the section on means for solving the problem. In the embodiment, the ECU 70 corresponds to the "power supply device control device."

The correspondence between the main elements of the Examples and the main elements of the invention described in the Means for Solving the Problem column does not limit the elements of the invention described in the Means for Solving the Problem column, since the Examples are examples for specifically explaining the form for implementing the invention described in the Means for Solving the Problem column. In other words, the interpretation of the invention described in the Means for Solving the Problem column should be based on the description in that column, and the Examples are merely a specific example of the invention described in the Means for Solving the Problem column.

The above describes the form for carrying out the present invention using examples, but the present invention is not limited to these examples in any way, and it goes without saying that the present invention can be carried out in various forms without departing from the scope of the invention.

The present invention can be used in the power supply control device manufacturing industry, etc.

20 Electric vehicle, 22a, 22b Drive wheels, 24 Differential gear, 26 Drive shaft, 32 Motor, 34 Inverter, 36 Battery, 36a Voltage sensor, 36b Current sensor, 37 Battery side power line, 38a High voltage side power line, 38b Low voltage side power line, 39 Capacitor, 39a Voltage sensor, 40 Auxiliary battery, 42 Auxiliary side power line, 48 DC/DC converter, 50 Step-up/step-down converter, 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, 87 Vehicle speed sensor, SMR System main relay, SMRB Positive side relay, SMRG Negative side relay.

Claims (1)

A DC power source;
an electric circuit that receives power from the DC power source;
a relay for connecting and disconnecting a first power line from the DC power source and a second power line from the electric circuit;
a power supply circuit capable of supplying power to the second power line when the relay is in an off state;
a capacitor attached to a positive line and a negative line of the second power line;
The power supply device includes:
a control device for a power supply device, which executes a precharge to control the relay and the power supply circuit when the relay is switched from off to on so that a voltage of the second power line becomes a voltage between terminals of the DC power supply while the relay is in an off state, and controls the relay to be on after the precharge is completed,
A control device for a power supply device that determines a sign of welding of the relay based on a histogram that classes a voltage difference as a difference between the voltage of the second power line after the precharge is completed and before the relay is turned on, and the voltage of the second power line after the relay is turned on.

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