JP6642296B2 - Converter error determination method - Google Patents

Description

  The present invention relates to a converter abnormality determination method.

  BACKGROUND ART In recent years, fuel cell vehicles equipped with a power supply system using a fuel cell and a secondary battery as a power source have attracted attention. Electric power from the power supply is supplied to an electric load including a traveling motor and auxiliary equipment (for example, a radiator fan, a cooling water pump, an electric light, and the like). Such an electric vehicle such as a fuel cell vehicle is equipped with a traveling motor capable of generating a driving force for traveling and generating electricity by regeneration. In addition, an inverter is mounted for controlling the traveling motor.

  In order to stably supply power to the inverter, a boost converter is provided between the fuel cell or the secondary battery and the inverter. The converter is provided with a sensor for detecting each of a pre-boost voltage, a post-boost voltage, and a reactor current, and the operation of the converter is controlled based on a detection result by the sensor.

  Patent Literature 1 discloses a converter including a plurality of booster circuits connected in parallel and each provided with a reactor. The converter is provided with a plurality of sensors for measuring the current of each reactor, the pre-boost voltage, and the post-boost voltage.

JP-A-2005-194448

  Since the operation of the converter is controlled based on the output of the sensor, in order for the converter to output a stable output, a technology is required that specifies whether each of the multiple sensors is operating normally. I have.

  The present invention has been made in view of the above. An object of the present invention is to provide a technique for detecting an abnormality of a sensor provided in a converter.

  An abnormality determination method according to the present invention provides at least a two-phase transformer including a first transformer having a first reactor and a second transformer having a second reactor provided in parallel with the first transformer. An abnormality determination method performed in a converter including a circuit and a current sensor that measures a current flowing through each of the first reactor and the second reactor, wherein the voltage is fixed, The voltage before boosting by the first transformer circuit and the voltage before boosting by the second transformer circuit are fixed, or the voltage after boosting by the first transformer circuit and the voltage after boosting by the second transformer circuit are constant. And the rate of change of the current measured by the current sensor and the inductance of the reactor, before boosting by the first transformer circuit or Calculating the fixed voltage after the pressure and the fixed voltage before or after the voltage boosting by the second transformer circuit; and calculating the calculated voltage before the boosting by the first transformer circuit. When the voltage is different from the voltage before boosting by the second transformer, or when the calculated voltage after boosting by the first transformer is different from the voltage after boosting by the second transformer, the current sensor Judging as abnormal.

  According to the present invention, when there is an abnormality in a current sensor in a state where the voltage (VL) before boosting or the voltage (VH) after boosting of the boost converter is constant, each boosting circuit is obtained from the current sensor. Since the voltage (VL) before boosting or the voltage (VH) after boosting calculated (estimated) using the obtained current value indicates a different value, abnormality of the current sensor can be determined.

FIG. 1 is a diagram illustrating a schematic configuration of a power supply system according to an embodiment. 4 is a graph showing control in the power supply system according to one embodiment. It is a figure showing the schematic structure of the electric power supply system concerning other embodiments. It is a flow chart which shows a flow of control processing in a power supply system concerning other embodiments.

Embodiment 1
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the scope of the invention is not limited to these.

[Configuration of power supply system]
An example of a schematic configuration of a power supply system according to the present embodiment will be described with reference to FIG. The power supply system 1 shown in FIG. 1 is a system that can be mounted on a vehicle such as a fuel cell vehicle. The power supply system 1 includes a boost converter 10, a fuel cell 21, a load 22, a voltage sensor 23, a voltage sensor 24, and a control unit 25 as main components. FIG. 1 shows only a main configuration included in the power supply system 1, and the power supply system 1 can include another configuration included in a general power supply system mounted on a vehicle. . Hereinafter, each configuration shown in the figure will be described.

The fuel cell 21 is configured to include a solid polymer electrolyte type cell stack in which a plurality of cells (a single cell (power generator) including an anode, a cathode, and an electrolyte) are stacked in series. In the operation during normal power generation by the fuel cell 21, the oxidation reaction of the formula (1) occurs at the anode, and the reduction reaction of the formula (2) occurs at the cathode. The fuel cell 21 as a whole generates electric power when the electromotive reaction of the formula (3) occurs.
_{^{H 2 → 2H + + 2e -}} (1)
(1/2) O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O (2)
H ₂ + (１ ／) O ₂ → H ₂ O (3)

  The load 22 is an electric load such as an inverter or a traveling motor connected to the boost converter 10 via the inverter. The load 22 operates using the power supplied from the boost converter 10 as driving power.

  Voltage sensor 23 is a sensor that measures the input voltage to boost converter 10 (that is, the voltage before boosting). Voltage sensor 24 is a sensor that measures output power from boost converter 10 (that is, boosted voltage).

  The boost converter 10 is a DC voltage boost converter provided between the fuel cell 21 and the load 22. The boost converter 10 boosts the DC voltage of the power supplied from the fuel cell 21 and outputs the boosted DC voltage to the load 22.

  The boost converter 10 includes a current sensor 11, a reactor 12, a diode 13, a switching element 14, and a capacitor 15. The current sensor 11 is a sensor that measures a reactor current that is a current flowing through the reactor 12. Reactor 12 is a reactor connected to power supply line PL from fuel cell 21 and configured to store energy based on electric power from fuel cell 21. The diode 13 is a rectifier provided between the output side of the reactor 12 and the load 22. Switching element 14 is connected between the output side of reactor 12 and ground line NL. The capacitor 15 is connected between the output side of the diode 13 and the ground line NL, smoothes the DC voltage from the diode 13, and supplies the smoothed DC voltage to the load 22.

  The control unit 25 is configured by a computer including a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The control unit 25 controls the processing and operation of each component included in the power supply system 1 based on a signal input from another component, a program stored in a storage unit such as a RAM, and the like. Performs various calculations required for

  The control unit 25 controls turn-on and turn-off of the switching element 14 at a preset duty ratio by, for example, outputting a control signal. When the switching element 14 is turned on, a current starts to flow from the fuel cell 21 to the switching element 14 via the reactor 12, and magnetic energy is accumulated in the reactor 12. When the switching element 14 is turned off, the magnetic energy stored in the reactor 12 during the turned-on time is output to the load 22 via the diode 13.

  With reference to FIG. 2, an example of a timing chart showing ON and OFF timings of the switching element 14 and an example of a graph showing a change in a measured value of the current flowing through the reactor 12 according to the state of the switching element 14 will be described.

In the example shown in FIG. 2, when a control signal for turning off is output from control unit 25 (that is, state CS of switching element 14 is OFF), current LI flowing through reactor 12 continues to decrease. In addition, while the control unit 25 outputs the turn-on control signal (that is, the state CS of the switching element 14 is ON), the current LI flowing through the reactor 12 continues to increase. In the figure, at time T ₀ (when the state CS of the switching element 14 switches from OFF to ON), the value of the current LI is I ₀ . Thereafter, at time T ₁ of the after period Ton, switches to the OFF state CS of the switching element 14 from ON, the value of the current LI at this time is I _1. Thereafter, at time T ₂ of the post-period Toff has elapsed, switches to the ON state CS from OFF of the switching element 14, the value of the current LI at this time is I _2.

  Here, the induced voltage generated by the magnetic energy stored in the reactor 12 when the state of the switching element 14 is OFF is superimposed on the output voltage of the fuel cell 21. Therefore, the output voltage of the diode 13 becomes higher than the output voltage of the fuel cell 21. That is, in the present embodiment, a transformer circuit is configured by elements including the reactor 12, the diode 13, and the switching element 14.

  Returning to the description of the control unit 25 in FIG. The control unit 25 can further calculate an estimated value of the voltage before boosting or the voltage after boosting by the above-described transformer circuit based on the rate of change of the current measured by the current sensor 11 and the inductance of the reactor 12. . The calculation of the estimated value can be performed, for example, as follows.

First, in the example shown in FIG. 2, when the voltage before boosting by the transformer circuit is VL and the inductance of reactor 12 is L, the rising gradient of the reactor current is VL / L. Further, the rising slope of the reactor current that can be calculated from the value measured by the current sensor 11 is (I ₁ −I ₀ ) / Ton. Therefore, the following equation holds.
VL / L = (I ₁ −I ₀ ) / Ton (1)

From Expression (1), the pre-boost voltage VL can be expressed by the following expression.
VL = L (I ₁ −I ₀ ) / Ton (2)

That is, an estimated value of the pre-boost voltage VL can be calculated using the current change rate obtained from I ₁ , I ₀ and Ton, which are values measurable by the current sensor 11, and the inductance L of the reactor 12. .

In the example shown in FIG. 2, when the voltage after boosting by the transformer circuit is VH, the falling slope of the reactor current is-(VH-VL) / L. The falling slope of the reactor current that can be calculated from the value measured by the current sensor 11 is (I ₂ −I ₁ ) / Toff. Therefore, the following equation holds.
− (VH−VL) / L = (I ₂ −I ₁ ) / Toff (3)

From Expressions (1) and (3), the voltage VH after boosting by the transformer circuit can be expressed by the following two expressions.
VH = VL (1− (Ton / Toff) · (I ₂ −I ₁ ) / (I ₁ −I ₀ )) (4)
VH = L ((I ₁ −I ₀ ) / Ton− (I ₂ −I ₁ ) / Toff) (5)

That is, after boosting using the change rate of the current obtained from I ₀ , I ₁ , I ₂ and Ton, Toff, which are values measurable by the current sensor 11, and the inductance L of the reactor 12 according to the equation (5). An estimated value of the voltage VH can be calculated.

From the equations (1), (2), and (3), the inductance L and the pre-boost voltage VL can be expressed by the following equations.
L = VL · Ton / (I ₁ −I ₀ ) (6)
L = VH / ((I ₁ −I ₀ ) / Ton− (I ₂ −I ₁ ) / Toff)) (7)
VL = (VH (I ₁ −I ₀ ) / Ton) / ((I ₁ −I ₀ ) / Ton− (I ₂ −I ₁ ) / Toff) (8)

  That is, if any one of the inductance L, the pre-boost voltage VL, and the post-boost voltage VH is known, the other two values can be calculated using the value measured by the current sensor 11.

Embodiment 2
In the present embodiment, a method for detecting a sensor abnormality using the formula described in the first embodiment will be described.

[Configuration of power supply system]
An example of a schematic configuration of the power supply system according to the second embodiment will be described with reference to FIG. The power supply system 3 shown in FIG. 1 is a system that can be mounted on a vehicle such as a fuel cell vehicle. The power supply system 3 includes a boost converter 30, a fuel cell 21, a load 22, a voltage sensor 23, a voltage sensor 24, and a control unit 31 as main components. 3, the same components as those of the power supply system 1 shown in FIG. 1 are denoted by the same reference numerals. Here, the present embodiment will be described focusing on parts different from the first embodiment.

  Boost converter 30 includes a current sensor 16, a reactor 17, a diode 18, and a switching element 19 in addition to the components included in boost converter 10 shown in FIG. 1. The current sensor 16 is a sensor that measures a reactor current that is a current flowing through the reactor 17. Reactor 17 is a reactor connected in parallel with reactor 12 to power supply line PL from fuel cell 21 and configured to store energy based on electric power from fuel cell 21. The diode 18 is a rectifying element provided between the output side of the reactor 17 and the load 22 in parallel with the diode 13. Switching element 19 is connected between the output side of reactor 17 and ground line NL.

  Here, in boost converter 30, a first transformer circuit is configured by elements including reactor 12 (first reactor), diode 13, and switching element 14. Further, a configuration including the reactor 17 (second reactor), the diode 18 and the switching element 19 constitutes a second transformer circuit. Further, as shown in FIG. 3, in the boost converter 30, the first transformer circuit and the second transformer circuit are provided in parallel.

  The control unit 31 is configured by a computer including a CPU, a ROM, and a RAM. The control unit 31 controls processing and operation of each component included in the power supply system 3 based on a signal input from another component, a program stored in a storage unit such as a RAM, and the like. Performs various calculations required for The control unit 31 performs the same control as the control unit 25 of the first embodiment, and also controls the current sensors 11 and 16 to detect an abnormality.

[Control flow by control unit]
With reference to FIG. 4, a description will be given of a flow of a control process in which the control unit 31 detects an abnormality of the current sensors 11 and 16. This processing is performed when the control unit 31 makes the voltage before boosting by the first transformer circuit and the voltage before boosting by the second transformer circuit constant, or the voltage after boosting by the first transformer circuit and the voltage by the second transformer circuit. It starts when the voltage after boosting is made constant.

  First, in step S11, the control unit 31 compares the measured value of the reactor current of the reactor 12 in the first transformer circuit with the current sensor 11 and the measured value of the reactor current of the reactor 17 in the second transformer circuit with the current sensor 16. To get. For example, the control unit 31 determines the values measured by the current sensors 11 and 16 at the timing when the switching elements 14 and 19 switch from OFF to ON, the timing when the switching elements 14 and 19 subsequently switch from ON to OFF, and the timing thereafter when the switching elements 14 and 19 switch from OFF to ON. Timing information is obtained from the current sensors 11 and 16. Further, control unit 31 acquires the measured value of the reactor current when voltage VL before boosting is constant.

  Next, in step S12, the control unit 31 determines the above equation (2) based on the measured value of the reactor current acquired in step S11, information on the measurement timing, and the known inductances of the reactors 12 and 17. Alternatively, the above-mentioned fixed voltage before or after boosting by the first transformer circuit and the above-mentioned constant voltage before or after boosting by the second transformer circuit are calculated by equation (5). I do. That is, the control unit 31 determines the voltage before or after the boosting by the first and second transformer circuits based on the rate of change of the current measured by the current sensors 11 and 16 and the inductance of the reactors 12 and 17. An estimate can be calculated.

  Next, in step S13, the control unit 31 compares the calculation results in step S12 with each other. That is, when the pre-boost voltage is calculated in step S12, the control unit 31 compares the pre-boost voltage by the first transformer circuit with the pre-boost voltage by the second transformer circuit. When the boosted voltage is calculated in step S12, the control unit 31 compares the boosted voltage by the first transformer circuit with the boosted voltage by the second transformer circuit.

  Next, in step S14, the control unit 31 determines whether or not the current sensors 11, 16 are abnormal based on the comparison result in step S13. That is, the voltage before boosting by the first transformer circuit, the voltage before boosting by the second transformer circuit (or the voltage after boosting by the first transformer circuit, and the voltage after boosting by the second transformer circuit) match. (Or when the difference is less than a threshold set so that it can be determined that the difference is a sufficiently small value), it is determined to be normal. When the voltage is different (or when the voltage is equal to or more than the threshold), it is determined that at least one of the current sensor 11 and the current sensor 16 has an abnormality (that is, the abnormality is detected).

  As described above, according to the present embodiment, it is possible to detect an abnormality of the current sensors 11 and 16 provided in the boost converter 30.

[Modification]
The following modifications can be applied to the second embodiment. That is, in the second embodiment, boost converter 30 has two phases of the voltage transformer circuit, and determines whether or not current sensors 11 and 16 are abnormal by comparing the voltages in the two-phase voltage transformer circuit. As a modified example, the boost converter 30 can be configured to include a three-phase transformer circuit, and can specify which current sensor has an abnormality. For example, when the measured current values of the reactors of the two-phase transformer circuit in the three-phase transformer circuit match each other and only the measured current values of the reactors in the other one-phase transformer circuit do not match, the control unit 31 determines that the measured value is It can be determined that there is an abnormality in the current sensors that do not match. By configuring boost converter 30 to include a four-phase or higher voltage transformation circuit, a current sensor having an abnormality can be specified by the same method. That is, for example, when the measured current values of the reactors of the three-phase transformer circuit in the four-phase transformer circuit match each other and only the measured current values of the reactors in the other one-phase transformer circuit do not match, the control unit 31 performs the measurement. It can be determined that there is an abnormality in the current sensors whose values do not match.

1,3 Power supply system 10,30 Boost converter 11,16 Current sensor 12,17 Reactor 13,18 Diode 14,19 Switching element 15 Capacitor 21 Fuel cell 22 Load 23 Voltage sensor 24 Voltage sensor 25,31 Control unit

Claims (1)

At least a two-phase transformer circuit including a first transformer circuit having a first reactor and a second transformer circuit provided in parallel with the first transformer circuit and having a second reactor; An abnormality determination method implemented in a converter including a current sensor that measures a current flowing through each of the second reactors,
Making the voltage constant, the voltage before boosting by the first transformer circuit and the voltage before boosting by the second transformer circuit being constant, or the voltage after boosting by the first transformer circuit and the (2) keeping the voltage after boosting by the transformer circuit of (2) constant;
Based on the rate of change of the current measured by the current sensor and the inductance of the reactor, the constant voltage before or after boosting by the first transformer circuit, and the constant voltage by the second transformer circuit. Calculating the fixed voltage before or after boosting,
If the calculated pre-boost voltage by the first transformer circuit is different from the pre-boost voltage by the second transformer circuit, or if the calculated post-boost voltage by the first transformer circuit is the second transformer Judging that the current sensor is abnormal when the voltage is different from the voltage after boosting by the circuit.

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