JP2018085803A - Power supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To acquire accurate current value even when an inexpensive ammeter is used in a power supply system which acquires a current value between a battery pack and vehicular load on the basis of an output signal of an ammeter installed between the battery pack and the vehicular load.SOLUTION: On the basis of an output signal of an ammeter 3a when a main contactor 2b, a sub contactor 2c, and a precharge contactor 2e2 are in off states and an output signal of the ammeter 3a when the main contactor 2b is in an off state and the sub contactor 2c and the precharge contactor 2e2 are in on states, gain characteristic and an offset error of the ammeter 3a are obtained. On the basis of the gain characteristic and the off-set error, a current value is obtained.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power supply system.

  As is well known, a battery or a motor is mounted on a vehicle such as an automobile. For example, as shown in Patent Document 1, a current flowing between a battery and a vehicle load such as a motor is measured by an ammeter, and an output signal indicating the current value is output from the ammeter. An output signal from such an ammeter is input to a battery ECU mounted on the vehicle. In the battery ECU, the current value is acquired by replacing the voltage value indicated by the output signal of the input ammeter with a current value flowing between the battery and a vehicle load such as a motor.

  However, the voltage value of the output signal with respect to the current value between the battery and the vehicle load may deviate from the original value due to individual differences of the ammeter. In such a case, since an output signal having a voltage value that does not indicate the original current value is output from the ammeter, the battery ECU cannot obtain an accurate current value. Therefore, in Patent Document 1, an offset error detection circuit is provided, and a more accurate current value can be acquired by performing correction based on the offset error detected by the offset error detection circuit.

JP 2005-91185 A

  However, when an inexpensive ammeter is used, not only the offset error but also the gain error is large, and an accurate current value cannot be obtained only by correction based on the offset error.

  The present invention has been made in view of the above-described problems, and the current value between the DC power supply and the vehicle load is calculated based on the output signal of an ammeter installed between the DC power supply and the vehicle load. It is an object of the present invention to make it possible to acquire an accurate current value even when an inexpensive ammeter is used in an acquired power supply system.

  As means for solving the above-mentioned problems, the present invention provides a first switch provided between one output end of a DC power source and a vehicle load, the other output end of the DC power source, and the vehicle load. A second switch provided between the first switch and the vehicle load, and one end connected between the second switch and the vehicle load. And a precharge circuit that bypasses the first switch and has a resistor and a third switch connected in series, and is installed between the DC power source and the vehicle load. A power supply system comprising an ammeter and a current detection unit for obtaining a current value flowing between the DC power source and the vehicle load based on an output signal of the ammeter, wherein the current detection unit is the first 1 switch, the second switch, and the third switch A first output signal that is an output signal of the ammeter in an off state is acquired, the second switch is in an off state, and the ammeter in the state in which the second switch and the third switch are on A second output signal that is an output signal is acquired, a gain characteristic and an offset error of the ammeter are obtained based on the first output signal and the second output signal, and the gain characteristic and the offset error are calculated based on the gain characteristic and the offset error. A configuration in which the current value is obtained is adopted.

  According to the present invention, the output signal (first output signal) of the ammeter when the first switch, the second switch, and the third switch are off, the first switch is off, and the second switch Based on the output signal (second output signal) of the ammeter when the switch and the third switch are on, the gain characteristic and the offset error of the ammeter are obtained, and the current value is calculated based on the gain characteristic and the offset error. Ask. That is, according to the present invention, the current value is obtained in consideration of not only the offset error but also the gain characteristic of the ammeter. For this reason, according to the present invention, in a power supply system that acquires a current value between a DC power supply and a vehicle load based on an output signal of an ammeter installed between the DC power supply and the vehicle load, Even when an ammeter is used, an accurate current value can be obtained.

It is a block diagram which shows the function structure of the power supply system in one Embodiment of this invention.

  Hereinafter, an embodiment of a power supply system according to the present invention will be described with reference to the drawings. In the following drawings, the scale of each member is appropriately changed in order to make each member a recognizable size.

  FIG. 1 is a block diagram showing a functional configuration of the power supply system 1 of the present embodiment. As shown in this figure, the power supply system 1 of this embodiment includes a power supply device 2 and a power supply control device 3. The power supply device 2 is mounted on a vehicle such as a hybrid car, a fuel cell vehicle, and an electric vehicle, and uses a DC power source such as a lithium ion battery or a nickel metal hydride battery as a power source. As shown in FIG. 1, the power supply device 2 includes an assembled battery 2a (DC power supply), a main contactor 2b (first switch), a sub contactor 2c (second switch), a smoothing capacitor 2d, and a precharge circuit 2e. And supplies electric power to a vehicle load L including an inverter and a travel motor.

  The assembled battery 2a includes a plurality of battery cells b1 to bn connected in series, and includes a pair of output terminals, that is, a plus terminal P1 and a minus terminal P2. The assembled battery 2a supplies DC power to the vehicle load L via a main contactor 2b connected to the plus terminal P1 (one output end) and a sub contactor 2c connected to the minus terminal P2 (the other output end). Supply.

  Each of the battery cells b1 to bn includes a non-illustrated interrupting element called CID (Current Interrupt Device), and when the internal pressure becomes abnormally high, the output terminals (plus end and minus end) of the battery cells b1 to bn One is opened mechanically. When such a CID is activated and one of the output ends of the battery cells b1 to bn is opened, the assembled battery 2a cannot supply DC power to the outside, and the output voltage is within a predetermined normal voltage range. Overvoltage.

  The main contactor 2b is a switch that opens and closes by energizing a drive current to the exciting coil. The main contactor 2b has a pair of contacts connected to each other by displacing the movable piece by the action of a magnetic force generated by an exciting coil based on a drive current input from a contactor drive unit 3b2 described later of the power supply control device 3. It is to be in a disconnected state. In such a main contactor 2b, one contact is connected to the plus terminal P1 of the assembled battery 2a, and the other contact is connected to the first input terminal of the vehicle load L.

  The sub-contactor 2c has a configuration similar to that of the main contactor 2b, and is a switch that opens and closes when a drive current is supplied to the exciting coil. This sub-contactor 2c is also operated based on a drive current supplied to the exciting coil from a contactor drive unit 3b2 (to be described later) of the power supply control device 3, and one contact is connected to the negative terminal P2 of the assembled battery 2a. The other contact is connected to the second input end of the vehicle load L.

  The main contactor 2b and the sub contactor 2c are power supply switches that turn on / off the power supply from the assembled battery 2a to the vehicle load L. The smoothing capacitor 2d is provided between the other contact of the main contactor 2b and the other contact of the sub contactor 2c. One end of the smoothing capacitor 2d is connected between the main contactor 2b and the vehicle load L, and the other end is connected between the sub contactor 2c and the vehicle load L. The smoothing capacitor 2d is for stabilizing the voltage of the DC power supplied from the assembled battery 2a to the vehicle load L via the main contactor 2b and the sub contactor 2c.

  The precharge circuit 2e is a circuit having a precharge resistor 2e1 (resistor) and a precharge contactor 2e2 (third switch) connected in series, and precharges before the main contactor 2b when the power supply system 1 is started. When the contactor 2e2 is turned on, the smoothing capacitor 2d is charged in advance. The precharge circuit 2e has one end connected between the main contactor 2b and the assembled battery 2a and the other end connected between the main contactor 2b and the vehicle load L so as to bypass the main contactor 2b. ing. The precharge resistor 2e1 defines the amount of current flowing through the precharge circuit 2e.

  The precharge contactor 2e2 is a switch that opens and closes when a drive current is supplied to the exciting coil. The precharge contactor 2e2 is connected to a pair of contacts by displacing the movable piece by the action of magnetic force generated by the exciting coil based on a driving current input from a contactor driving unit 3b2 described later of the power supply control device 3. Alternatively, a non-connected state is set. In such a precharge contactor 2e2, one contact is connected to the plus terminal P1 of the assembled battery 2a, and the other contact is connected to the first input terminal of the vehicle load L.

  The power supply control device 3 controls the power supply device 2 as described above, and controls the power supply device 2 to supply DC power to the inverter of the vehicle load L. Such a power supply control device 3 includes an ammeter 3a and a battery ECU 3b.

  The ammeter 3a is provided between the plus terminal P1 of the assembled battery 2a and one contact point of the main contactor 2b. The ammeter 3a detects a current value flowing from the assembled battery 2a to the main contactor 2b, and a voltage indicating this current value. The signal (output signal) is output.

  The battery ECU 3b is connected to the main contactor 2b and the sub contactor 2c based on a predetermined control program, the voltage at the output terminal input from each of the battery cells b1 to bn, the output signal of the ammeter 3a, the control command input from the outside, and the like. And a control device for controlling the precharge contactor 2e2. The battery ECU 3b includes, as hardware, a storage unit that stores the control program, a calculation unit that executes the control program, an interface unit that exchanges signals with interconnected external elements, and the like.

  In the present embodiment, the battery ECU 3b includes a main control unit 3b1, a contactor driving unit 3b2, a gain calculation unit 3b3, an offset error calculation unit 3b4, and a current value calculation unit that are embodied by the hardware and the control program. 3b5.

  The main control unit 3b1 is connected to the main contactor 2b, the sub-contact, based on the voltage at the output terminal input from each of the battery cells b1 to bn, the control command input from the outside, and the current value input from the current value calculation unit 3b5. The ON / OFF state of the contactor 2c and the precharge contactor 2e2 is determined, and a command signal indicating the determination result is input to the contactor drive unit 3b2. Further, in the present embodiment, the main control unit 3b1 performs a correction formula calculation process when the ignition switch is turned on and the power supply system 1 is activated. As will be described in detail later, this correction formula calculation process is a process for obtaining a correction formula for obtaining an accurate current value by removing an error from the output signal of the ammeter 3a including an error.

  The contactor drive unit 3b2 opens and closes the main contactor 2b, the sub contactor 2c, and the precharge contactor 2e2 based on a command signal input from the main control unit 3b1. The gain calculation unit 3b3 obtains the gain characteristic of the ammeter 3a from the output signal of the ammeter 3a in the correction formula calculation step. The offset error calculation unit 3b4 obtains an offset error of the ammeter 3a from the output signal of the ammeter 3a in the correction formula calculation step. In the correction formula calculation step, the current value calculation unit 3b5 calculates the above correction formula based on the gain characteristics obtained by the gain calculation unit 3b3 and the offset error obtained by the offset error calculation unit 3b4. Further, after the correction formula calculation step, the current value calculation unit 3b5 corrects the current value indicated by the output signal of the ammeter 3a based on the correction formula, and inputs the corrected current value to the main control unit 3b1.

  In the power supply system 1 of the present embodiment having such a configuration, when activated by turning on the ignition switch, a correction formula calculation step is performed under the control of the main control unit 3b1. In this correction formula calculation step, the main control unit 3b1 first causes the contactor driving unit 3b2 to turn off the main contactor 2b, the sub-contactor 2c, and the precharge contactor 2e2. The main control unit 3b1 stores the voltage (hereinafter referred to as a first detection value) of the output signal (first output signal) of the ammeter 3a at this time in the gain calculation unit 3b3.

  Next, the main control unit 3b1 causes the contactor driving unit 3b2 to turn off the main contactor 2b and turn on the sub-contactor 2c and the precharge contactor 2e2. Then, the main control unit 3b1 stores the voltage (hereinafter referred to as a second detection value) of the output signal (second output signal) of the ammeter 3a at this time in the gain calculation unit 3b3 and the offset error calculation unit 3b4.

  When calculating the gain characteristic, the gain calculation unit 3b3 first calculates the peak current at the installation position of the ammeter 3a at the time of startup. When the main contactor 2b, the sub-contactor 2c, and the precharge contactor 2e2 are turned off after the power supply system 1 is started, the main contactor 2b is turned off, and the sub-contactor 2c and the precharge contactor 2e2 are turned on. Since no electric charge is charged in the smoothing capacitor 2d, a current flows through the installation position of the ammeter 3a for a certain period of time until the smoothing capacitor 2d stores the electric charge sufficiently. Since this current becomes the largest when the smoothing capacitor 2d is 0V, the gain calculation unit 3b3 obtains the current value that flows when the smoothing capacitor 2d is 0V as the peak current.

The gain calculation unit 3b3 acquires the total voltage of the battery cells b1 to bn from the main control unit 3b1, and based on the pre-stored resistance value of the precharge resistor 2e1 of the precharge circuit 2e, for example, the peak current is calculated by the following equation: Is calculated.
([Total voltage]-[Smoothing capacitor voltage]) / "Resistance value" = "Peak current"

  For example, when the total voltage of the battery cells b1 to bn is 480 (V) and the resistance value of the precharge resistor 2e1 is 40 (Ω), the smoothing capacitor voltage when the peak current flows is 0 (V). Therefore, the peak current is calculated to be 12 (A).

Subsequently, the gain calculation unit 3b3 calculates the gain characteristic using, for example, the following equation based on the above-described peak current, the first detection value, and the second detection value.
([Peak current]-[current when all contactors are off]) / ([second detection value]-[first detection value]) = gain characteristics

  For example, when the first detection value is 2.7 (V) and the second detection value is 3.7 (V), the current when all contactors are off is naturally 0 (A). The characteristic is 12 (A / V).

The offset error calculation unit 3b4 calculates an offset error using, for example, the following expression based on the gain characteristic obtained by the gain calculation unit 3b3 and the first detection value.
[Current when all contactors are off]-[Gain characteristics] x [First detection value] = [Offset error]

  For example, when the first detection value is 2.7 (V) and the gain characteristic is 12 (A / V), the current when all contactors are off is naturally 0 (A). The offset error is -32.4 (A).

The current value calculation unit 3b5 creates and stores a correction formula such as the following formula based on the gain characteristic calculated by the gain calculation unit 3b3 and the offset error calculated by the offset error calculation unit 3b4.
[Gain characteristics] x [Output voltage of ammeter]-[Offset error] = [Current value]

  After the correction formula is obtained in the correction formula calculation step and charging to the smoothing capacitor 2d is completed, the main control unit 3b1 turns on the main contactor 2b and the sub contactor 2c to the contactor drive unit 3b2 based on the control command. State, the precharge contactor 2e2 is turned off. At this time, the output signal of the ammeter 3a (the output voltage of the ammeter 3a) is input to the current value calculator 3b5. The current value calculation unit 3b5 calculates an accurate current value by applying the correction formula obtained as described above and inputs it to the main control unit 3b1. The main controller 3b1 performs various controls based on the input current value.

  For example, when the gain characteristic is 12 (A / V), the offset error is −32.4 (A), and the output voltage of the ammeter 3a is 2.7 (V), the current value is 0. (A). On the other hand, when the gain characteristic is 12 (A / V), the offset error is -32.4 (A), and the output voltage of the ammeter 3a is 3.7 (V), the current value is 12 (A).

  According to the power supply system 1 of the present embodiment, the battery ECU 3b functions as a current detection unit of the present invention to obtain an accurate current value. More specifically, in the power supply system 1 of the present embodiment, the output signal (first output signal) of the ammeter 3a when the main contactor 2b, the sub-contactor 2c, and the precharge contactor 2e2 are off, and the main contactor 2b are off. The gain characteristic and the offset error of the ammeter 3a are obtained based on the output signal (second output signal) of the ammeter 3a when the sub contactor 2c and the precharge contactor 2e2 are in the on state. A current value is obtained based on the error. That is, according to the power supply system 1 of the present embodiment, the current value is obtained in consideration of not only the offset error but also the gain characteristic of the ammeter 3a. For this reason, according to the power supply system 1 of the present embodiment, an accurate current value can be acquired even when an inexpensive ammeter is used.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the said embodiment. Various shapes, combinations, and the like of the constituent members shown in the above-described embodiments are examples, and various modifications can be made based on design requirements and the like without departing from the spirit of the present invention.

  For example, in the above embodiment, a configuration in which the precharge circuit 2e is provided so as to bypass the main contactor 2b is employed. However, the present invention is not limited to this, and the precharge circuit 2e may be provided so as to bypass the sub contactor 2c.

  DESCRIPTION OF SYMBOLS 1 ... Power supply system, 2 ... Power supply device, 2a ... Battery assembly (DC power supply), 2b ... Main contactor (first switch), 2c ... Sub-contactor (second switch), 2d ... Smooth Capacitor, 2e ...... Precharge circuit, 2e1 ... Precharge resistor (resistor), 2e2 ... Precharge contactor (third switch), 3 ... Power supply control device, 3a ... Ammeter, 3b1 ... Main Control unit, 3b2 ... contactor drive unit, 3b3 ... gain calculation unit, 3b4 ... offset error calculation unit, 3b5 ... current value calculation unit, L ... vehicle load

Claims (1)

A first switch provided between one output end of the DC power supply and the vehicle load;
A second switch provided between the other output terminal of the DC power supply and the vehicle load;
A smoothing capacitor having one end connected between the first switch and the vehicle load and the other end connected between the second switch and the vehicle load;
A precharge circuit that bypasses the first switch and includes a resistor and a third switch connected in series;
An ammeter installed between the DC power source and the vehicle load;
A power detection system comprising: a current detection unit that obtains a current value flowing between the DC power source and the vehicle load based on an output signal of the ammeter;
The current detector is
Obtaining a first output signal which is an output signal of the ammeter when the first switch, the second switch and the third switch are in an off state;
Obtaining a second output signal that is an output signal of an ammeter when the first switch is in an off state and the second switch and the third switch are in an on state;
Obtaining a gain characteristic and an offset error of the ammeter based on the first output signal and the second output signal;
The power supply system, wherein the current value is obtained based on the gain characteristic and the offset error.

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