JP7490976B2 - Power Converter - Google Patents

Description

The technology disclosed in this specification relates to a power converter. In particular, the technology relates to a power converter that includes a voltage converter that converts voltage between an on-board battery and an on-board storage battery, a current sensor, and a controller.

The power converter installed in an electric vehicle boosts the output voltage of the on-board battery using a voltage converter arranged between the on-board battery and the on-board storage battery, and transmits it to the electric vehicle's driving motor. In order to smooth the voltage transmitted to the driving motor, the voltage converter is connected to an on-board storage battery such as a capacitor and the driving motor. The power converter also uses the voltage converter to step down the power (regenerative power) generated by the driving motor and charge the on-board battery. The voltage converter converts and transforms electrical energy into magnetic energy by passing a current through a reactor. The power converter is equipped with a current sensor that detects the current flowing through the reactor, and the power converter's controller controls the switching element of the voltage converter based on the current value detected by the current sensor. In this specification, "electric vehicle" includes hybrid vehicles equipped with both a motor and an engine.

If an error occurs in the current sensor that detects the current flowing through the reactor, the switching element of the voltage converter cannot be controlled accurately. If an error occurs in the current sensor, the output of the current sensor will indicate something other than 0 A (zero amperes) even though no current is actually flowing. This phenomenon is known as a zero point (origin) shift.

A technology for correcting the zero point shift is disclosed in, for example, Patent Document 1. The amount by which the zero point of the current sensor shifts varies depending on the temperature of the current sensor. The power converter in Patent Document 1 (referred to as a boost converter device in Patent Document 1) reduces errors due to temperature characteristics by changing the amount of correction used to correct the zero point shift when the current sensor is within a specified temperature range.

JP 2019-106744 A

The current sensor of the power converter has a magnetic core. The current sensor measures the current value from the magnetic flux generated in the magnetic core due to the current to be measured. The reactor also has a magnetic core through which a coil is inserted. When a current flows in the same direction for a certain period of time through a current sensor or a reactor that has a magnetic core, the magnetic core of the current sensor or the reactor becomes magnetized. As a result, the measurement value of the current sensor contains a hysteresis error. The power converter of Patent Document 1 may correct the zero point of the current sensor based on a measurement value that contains a hysteresis error. If the zero point of the current sensor is corrected based on a measurement value that contains a hysteresis error, the zero point will shift by the amount of the hysteresis error. If the current value is measured based on the zero point that is shifted due to the hysteresis error, a shift will occur in the power balance. This specification provides a power converter that can reduce the hysteresis error when correcting the zero point.

The power converter disclosed in this specification includes a voltage converter that transforms the voltage between the vehicle battery and the vehicle storage battery, a current sensor, and a controller. The voltage converter includes an upper switching element, a lower switching element connected in series to the upper switching element, and a reactor with one end connected to the midpoint between the upper switching element and the lower switching element and the other end connected to the vehicle battery. The current sensor includes a magnetic core and measures the current value flowing through the reactor from the magnetic flux generated in the magnetic core due to the current flowing through the reactor. The controller selects a timing that satisfies the conditions that the vehicle is in a stopped state, the measurement value of the current sensor or its time derivative is smaller than a predetermined threshold value, and the voltage of the vehicle storage battery is higher than the battery voltage, and alternately turns on and off the upper switching element and the lower switching element for a predetermined time. The controller corrects the zero point of the current sensor based on the measurement value of the current sensor thereafter.

If the measurement value of the current sensor contains an error, the measurement value of the current sensor will not be 0 A even if no current is flowing through the reactor. The controller selects a timing that satisfies the condition that the measurement value of the current sensor or its time differential value is smaller than a predetermined threshold value and the voltage of the on-board storage battery is higher than the battery voltage, and alternately turns on and off the upper switching element and the lower switching element. The threshold value used here is a value that can be assumed to indicate that no current is flowing through the current sensor, and is a value larger than the possible error or its time differential value. When the upper switching element and the lower switching element are alternately turned on and off at a timing that satisfies the condition that the voltage of the on-board storage battery is higher than the battery voltage, the direction of the current flowing through the current sensor and the reactor alternates. In other words, when the upper switching element and the lower switching element are alternately turned on and off at a timing that satisfies the condition that the voltage of the on-board storage battery is higher than the battery voltage, an AC current having a waveform that crosses 0 A flows through the current sensor and the reactor. The AC current having a waveform that crosses 0 A reduces the hysteresis error. The controller of the above-mentioned power converter corrects the zero point based on the measurement value of the current sensor after the hysteresis error is reduced by the AC current. In other words, the power converter disclosed in this specification can reduce the hysteresis error when correcting the zero point.

Details and further improvements of the technology disclosed in this specification are explained in the "Description of Embodiments" below.

1 is a block diagram of an electric vehicle equipped with a power converter according to an embodiment of the present invention. 4 is a graph showing changes in the measurement value of a current sensor. 1 is a graph showing a hysteresis curve. 4 is a flowchart showing a process executed by a controller during zero point correction. 11 is a graph showing a measurement value of a current sensor during zero point correction.

The power converter of the embodiment will be described with reference to the drawings. FIG. 1 shows a block diagram of the power system of an electric vehicle 100 equipped with a power converter 5 of the embodiment. The electric vehicle 100 includes a main battery 2, a system main relay 4, a power converter 5, an on-board storage battery 7, an inverter 20, and a traction motor 8.

The main battery 2 is a battery mounted on the electric vehicle 100 to drive the motor 8. That is, the main battery 2 is an on-board battery. The output voltage of the main battery 2 exceeds 100 volts. The main battery 2 is, for example, a lithium-ion battery. The motor 8 is a three-phase AC motor. The power converter 5 is connected to the main battery 2 via the system main relay 4, and is connected to the motor 8 via the on-board storage battery 7 and the inverter 20. The power converter 5 boosts the voltage output by the main battery 2 to the drive voltage of the motor 8 and stores it in the on-board storage battery 7, or reduces the voltage of the on-board storage battery 7 to the voltage of the main battery 2 to charge the main battery 2.

The system main relay 4 is controlled by the controller 6. The system main relay 4 is a normally open type and is held in an open state while power is not being supplied. When the vehicle's main switch 31 is switched from off to on, the controller 6 closes the system main relay 4 and connects the main battery 2 to the power converter 5. When the vehicle's main switch 31 is switched from on to off, the controller 6 opens the system main relay 4 and disconnects the main battery 2 from the power converter 5. Although not shown in the figure, the electric vehicle 100 is equipped with a sub-battery. The sub-battery supplies power to low-power devices such as the controller 6 and the system main relay 4.

The dashed lines with arrows in the diagram indicate the flow of signals. As mentioned above, the controller 6 controls the system main relay 4. The controller 6 also calculates the target output value of the motor 8 based on sensor data from the vehicle speed sensor 32 and the accelerator opening sensor 33. The controller 6 controls the power converter 5 and the inverter 20 so that the target output value is realized. As will be described later, the power converter 5 has several switching elements, and the controller 6 controls the switching elements of the power converter 5 so that the output of the power converter 5 matches the target output value.

The power converter 5 includes a bidirectional voltage converter 10 and a controller 6. The low-voltage end 11 (low-voltage positive terminal 11a, low-voltage negative terminal 11b) of the bidirectional voltage converter 10 is connected to the main battery 2 via the system main relay 4. The high-voltage end 12 (high-voltage positive terminal 12a, high-voltage negative terminal 12b) is connected to the smoothing capacitor 7 and the inverter 20. The high-voltage end 12 is connected to the motor 8 via the smoothing capacitor 7 and the inverter 20.

The smoothing capacitor 7 is connected between the high-voltage positive terminal 12a and the high-voltage negative terminal 12b of the bidirectional voltage converter 10. The smoothing capacitor 7 is an on-board storage device mounted on the electric vehicle 100 to suppress pulsation of the voltage flowing between the bidirectional voltage converter 10 and the inverter 20. In addition, the filter capacitor 14 is connected between the low-voltage positive terminal 11a and the low-voltage negative terminal 11b.

The inverter 20 converts the DC power output by the bidirectional voltage converter 10 and smoothed by the smoothing capacitor 7 into AC power and supplies it to the motor 8. The motor 8 may generate power using the inertial energy of the vehicle. The power generated by the motor 8 is called regenerative power. The inverter 20 can also convert the regenerative power (AC power) of the motor 8 into DC power and supply it to the bidirectional voltage converter 10. The circuit configuration of the inverter 20 is well known, so illustrations and explanations are omitted.

The bidirectional voltage converter 10 has a boost function that boosts the voltage of the main battery 2 and supplies it to the smoothing capacitor 7 and the inverter 20, and a step-down function that steps down the voltage of the regenerative power (DC power) supplied from the smoothing capacitor 7 and the inverter 20 and supplies it to the main battery 2. Hereinafter, for ease of explanation, the bidirectional voltage converter 10 will be simply referred to as the voltage converter 10.

The circuit configuration of the voltage converter 10 will be described. The voltage converter 10 includes a filter capacitor 14, a reactor 15, switching elements 16a and 16b, and freewheel diodes 17a and 17b. The voltage converter 10 further includes a current sensor 18 and voltage sensors 13a and 13b. The two switching elements 16a and 16b are connected in series between the high voltage positive terminal 12a and the high voltage negative terminal 12b. In the following, the switching element 16a closer to the high voltage positive terminal 12a may be referred to as the upper switching element 16a, and the switching element 16b closer to the high voltage negative terminal 12b may be referred to as the lower switching element 16b. The switching elements 16a and 16b are n-type IGBTs (Insulated Gate Bipolar Transistors) or n-type MOSFETs (Metal Oxide Semiconductor Field Effect Transistors). When switching elements 16a and 16b are turned on, they pass current from the collector (drain) to the emitter (source).

The freewheel diode 17a is connected in anti-parallel to the upper switching element 16a, and the freewheel diode 17b is connected in anti-parallel to the lower switching element 16b. More specifically, the cathode of the freewheel diode 17a is connected to the collector (drain) of the upper switching element 16a, and the anode of the freewheel diode 17a is connected to the emitter (source). The connection relationship between the lower switching element 16b and the freewheel diode 17b is also similar.

The reactor 15 is connected between the midpoint of the series connection of the two switching elements 16a, 16b and the low-voltage positive pole terminal 11a. That is, one end of the reactor 15 is connected to the midpoint of the upper switching element 16a and the lower switching element 16b, and the other end is connected to the main battery 2 via the system main relay 4. Although not shown in the figure, the reactor 15 includes a coil and a dust core formed of a magnetic material. The coil is wound around the dust core. When a current flows through the coil of the reactor 15, a magnetic flux is generated in the core. The reactor 15 transforms the voltage by converting the electric energy of the current flowing through the coil into the magnetic energy of the dust core.

A current sensor 18 is connected between the midpoint of the upper switching element 16a and the lower switching element 16b and the reactor 15. The current sensor 18 measures the current flowing through the reactor 15. As shown in the enlarged view at the top of FIG. 1, the current sensor 18 includes a magnetic core 18a. The magnetic core 18a has a ring shape with a notch in one part, and a Hall element 18b is arranged in the notch of the magnetic core 18a. The magnetic core 18a passes a conductor (e.g., a bus bar) connected to the reactor 15. When the current flowing through the reactor 15 passes through the magnetic core 18a, the current generates a magnetic flux in the magnetic core 18a. The magnetic flux generated in the magnetic core 18a due to the current flowing through the reactor 15 is converted into an output voltage by the Hall element 18b. The magnetic flux generated in the magnetic core 18a changes depending on the magnitude of the current flowing through the reactor 15. When the current flowing through the reactor 15 increases, the output voltage of the Hall element 18b also increases. When the current flowing through the reactor 15 decreases, the output voltage of the Hall element 18b also decreases. In this way, the current sensor 18 measures the value of the current flowing through the reactor 15 from the magnetic flux generated in the magnetic core 18a.

The voltage sensor 13a measures the voltage between the low-voltage positive terminal 11a and the low-voltage negative terminal 11b. In other words, the voltage sensor 13a measures the voltage of the main battery 2. The voltage sensor 13b measures the voltage between the high-voltage positive terminal 12a and the high-voltage negative terminal 12b. In other words, the voltage sensor 13b measures the voltage of the smoothing capacitor 7.

The switching elements 16a and 16b are controlled by a controller 6. The controller 6 determines a target voltage ratio between the voltage on the battery side and the voltage on the inverter side of the voltage converter 10 based on sensor data from a vehicle speed sensor 32 and an accelerator opening sensor 33. The controller 6 controls the switching elements 16a and 16b based on sensor data from a current sensor 18 and voltage sensors 13a and 13b so that the actual voltage ratio matches the target voltage ratio.

The lower switching element 16b and the freewheel diode 17a are mainly involved in the boost function, while the upper switching element 16a and the freewheel diode 17b are mainly involved in the step-down function. The controller 6 generates drive signals (PWM signals) for each of the switching elements 16a and 16b so that the target voltage ratio is realized, and supplies them to each of the switching elements 16a and 16b.

Referring to Figure 2, changes in the measured value IL of the current flowing through the reactor 15 will be described. Figure 2 shows changes in the measured value of the current sensor 18 while the electric vehicle 100 (see Figure 1) is traveling. Sections (A1, A2) of Figure 2 show the measured value of the current sensor 18 while the electric vehicle 100 is stopped. Figure 2 (B) shows the measured value of the current sensor 18 while the electric vehicle 100 is accelerating. Figure 2 (C) shows the measured value of the current sensor 18 while the electric vehicle 100 is traveling at a constant speed. Figure 2 (D) shows the measured value of the current sensor 18 while the electric vehicle 100 is decelerating.

In addition, in FIG. 2, the current flowing through the current sensor 18 from the main battery 2 (see FIG. 1) toward the motor 8 is represented by a positive value (i.e., above 0 A). The current flowing through the current sensor 18 from the motor 8 toward the main battery 2 is represented by a negative value (i.e., below 0 A). In other words, in FIG. 2, the current flowing through the current sensor 18 when the voltage converter 10 is stepping up is represented by a positive value, and the current flowing through the current sensor 18 when the voltage converter 10 is stepping down is represented by a negative value.

As shown in FIG. 2 (A1), when the electric vehicle 100 (see FIG. 1) is stopped, the measurement value of the current sensor 18 is approximately 0 A. When the electric vehicle 100 subsequently accelerates, the voltage converter 10 boosts the voltage of the main battery 2. As a result, as shown in FIG. 2 (B), the measurement value of the current sensor 18 becomes a large positive value. When the electric vehicle 100 subsequently stops accelerating and travels at a constant speed, the voltage converter 10 neither boosts nor reduces the voltage. As a result, as shown in FIG. 2 (C), the measurement value of the current sensor 18 becomes approximately 0 A. Furthermore, when the electric vehicle 100 decelerates, the voltage converter 10 reduces the regenerative power generated by the motor 8 and supplies it to the main battery 2. As a result, as shown in FIG. 2 (D), the measurement value of the current sensor 18 becomes a large negative value. Thereafter, the electric vehicle 100 continues to decelerate, and when the electric vehicle 100 stops, the voltage converter 10 neither increases nor decreases the voltage, so that the measurement value of the current sensor 18 approaches 0 A, as shown in FIG. 2 (A2).

As mentioned above, the current sensor 18 includes a magnetic core 18a (see FIG. 1). When the electric vehicle 100 accelerates or decelerates, the upper switching element 16a and the lower switching element 16b are turned on and off. At that time, the upper switching element 16a and the lower switching element 16b generate heat. As a result, the temperature of the current sensor 18 becomes high. The zero point of the current sensor 18 may be shifted due to the influence of the temperature characteristics of the magnetic core 18a of the current sensor 18. When the zero point of the current sensor 18 is shifted, as shown in FIG. 2 (A2), even if no current flows through the current sensor 18, the measurement value of the current sensor 18 is not 0 A. The measurement value of the current sensor 18 has an error d1. For this reason, the power converter 5 of the embodiment performs zero point correction, which corrects the zero point of the current sensor 18 and measures the current value flowing through the reactor 15 based on the new zero point. By performing zero point correction, the power balance can be adjusted even if the zero point of the current sensor 18 is shifted.

Like the current sensor 18, the reactor 15 also has a dust core made of a magnetic material. When a current flows through a magnetic material in the same direction for a certain period of time, the magnetic material becomes magnetized. A magnetized magnetic material generates a magnetic flux regardless of whether a current is flowing or not. As described with reference to FIG. 1, the current sensor 18 converts the magnetic flux of the magnetic core 18a into an output voltage using the Hall element 18b to measure the current value. Therefore, when the magnetic core 18a of the current sensor 18 and the dust core of the reactor 15 are magnetized, the current sensor 18 converts the magnetized magnetic flux and measures it as a current value even when no current is flowing through the reactor 15. In other words, when the magnetic core 18a of the current sensor 18 and the dust core of the reactor 15 are magnetized, the zero point of the current sensor 18 becomes more shifted. If a zero point correction is performed using a zero point that is significantly shifted due to the influence of magnetization, the power balance will be shifted.

Here, the general characteristics of the magnetic core 18a of the current sensor 18 (see FIG. 1) will be described using FIG. 3. The horizontal axis Iin of the graph in FIG. 3 is the current (i.e., the measured current) flowing through the reactor 15 (see FIG. 1), and the vertical axis Vout is the measurement value of the current sensor 18 (i.e., the output voltage). FIG. 3 shows the hysteresis characteristics of the residual magnetic flux of the magnetic core 18a of the current sensor 18. When the current flowing through the reactor 15 increases, the measurement value of the current sensor 18 also increases, as shown by the arrow I1 in FIG. 3. After that, when the magnetic core 18a is magnetized, as shown by the arrow I2, even if the current flowing through the reactor 15 becomes 0 A (i.e., on the vertical axis Vout in FIG. 3), the output voltage of the current sensor 18 becomes a hysteresis error Hd. When a current flows through the reactor 15 for a certain period of time due to the hysteresis characteristics of the magnetic core 18a, the measurement value of the current sensor 18 includes a hysteresis error Hd. As described with reference to FIG. 2, in the section shown in FIG. 2(D), the electric vehicle 100 (see FIG. 1) decelerates for a certain time. That is, the power converter 5 (see FIG. 1) steps down for a certain time. As a result, a current flows from the motor 8 to the main battery 2 (both see FIG. 1) for a certain time in the current sensor 18. That is, the error d1 in FIG. 2 includes a hysteresis error Hd. Therefore, when the value of the error d1 is corrected to a new zero point, the zero point shifts by the amount of the hysteresis error Hd. In addition, a hysteresis error occurs in the dust core of the reactor 15 (see FIG. 1) as in the magnetic core 18a, and the measurement value of the current sensor 18 shifts due to the influence of the hysteresis error.

The hysteresis error Hd generated by magnetizing the magnetic core 18a can be reduced by passing an AC current that crosses 0 A through the magnetized magnetic core 18a. When a current that crosses 0 A between positive Ir and negative Ir flows through the magnetized magnetic core 18a, the hysteresis curve becomes smaller in a spiral shape, as shown by the dashed arrow in Figure 3.

Referring to FIG. 4, the process executed by the controller 6 included in the power converter 5 (see FIG. 1) of the embodiment when correcting the zero point will be described. First, the controller 6 determines whether the vehicle speed of the electric vehicle 100 is 0 Km/h or not (step S2). As described above, the controller 6 receives a signal from the vehicle speed sensor 32. Based on the signal from the vehicle speed sensor 32, the controller 6 determines whether the vehicle speed of the electric vehicle 100 is 0 Km/h or not. If the vehicle speed of the electric vehicle 100 is not 0 Km/h (step S2: NO), the electric vehicle 100 is running, and therefore current flows through the reactor 15 and the current sensor 18. Therefore, the controller 6 stops correcting the zero point.

When the vehicle speed of the electric vehicle 100 is 0 Km/h (step S2: YES), the electric vehicle 100 is in a stopped state, so there is a high possibility that no current is flowing through the reactor 15 and the current sensor 18 (see FIG. 1 for both). Therefore, the controller 6 determines whether the measurement value IL of the current sensor 18 is smaller than the threshold value Ith (step S4). Here, the threshold value Ith is a value that can be used to infer that no current is flowing through the reactor 15 and the current sensor 18. Furthermore, the threshold value Ith is a value smaller than the value of the current that may flow through the reactor 15 and the current sensor 18 when the vehicle is stopped, such as when the main battery 2 is charged by the engine (shown in the appendix) of the electric vehicle 100. Therefore, when the measurement value IL of the current sensor 18 is larger than the threshold value Ith (step S2: NO), the controller 6 determines that the main battery 2 is in a charged state and stops the correction of the zero point. The controller 6 may compare the time derivative of the measured value IL with a threshold value, and determine that the main battery 2 is in a charging state if the time derivative of the measured value IL is greater than the threshold value. By comparing the time derivative of the measured value IL with a threshold value instead of comparing the measured value IL with the threshold value Ith, it is possible to eliminate an abnormality in which the measured value IL of the current sensor 18 momentarily exceeds the threshold value Ith and then returns to below the threshold value Ith. In other words, it is possible to more accurately determine whether or not a current is flowing through the current sensor 18. The threshold value Ith is set to be greater than the maximum value that the error d1 can take, and step S4 will not result in NO due to an error.

If the measured value IL of the current sensor 18 is smaller than the threshold value Ith (step S4: YES), it can be determined that no current is flowing through the reactor 15 and the current sensor 18 (both see FIG. 1). In this case, the controller 6 compares the measured value Va of the voltage sensor 13a with the measured value Vb of the voltage sensor 13b (step S6). That is, the controller 6 compares the voltage of the smoothing capacitor 7 (see FIG. 1) with the voltage of the main battery 2 (see FIG. 1).

When the measured value Vb of the voltage sensor 13b (i.e., the voltage of the smoothing capacitor 7) is greater than the measured value Va of the voltage sensor 13a (i.e., the voltage of the main battery 2) (step S6: YES), the upper switching element 16a and the lower switching element 16b (both see FIG. 1) are alternately turned on and off (step S8) to allow an AC current that crosses 0 A to flow through the voltage converter 10. In order to allow an AC current that crosses 0 A to flow through the voltage converter 10, the timing at which step S6 becomes YES is selected, and step S8 is performed.

In step S8, the controller 6 continues to turn on and off the upper switching element 16a and the lower switching element 16b until a predetermined time has elapsed (until step S12 becomes YES). The predetermined time here is the time required to eliminate the hysteresis error that occurs in the dust core of the reactor 15 and the magnetic core 18a of the current sensor 18, and is determined by conditions such as the material and size of the magnetic cores of the reactor 15 and the current sensor 18, or the maximum current value flowing through the voltage converter 10.

After the upper switching element 16a and the lower switching element 16b are turned on and off for a predetermined time (step S12 is YES), the controller 6 turns off both the upper switching element 16a and the lower switching element 16b (step S14). This stops the AC current flowing through the reactor 15 and the current sensor 18, and the value of the current flowing through the reactor 15 and the current sensor 18 becomes constant. In addition, the AC current crossing 0 A reduces the hysteresis error Hd (see FIG. 3) of the current sensor 18. The controller 6 corrects the zero point of the current sensor 18 based on the measurement value of the current sensor 18 with the reduced hysteresis error Hd (step S16).

With reference to FIG. 5, the change in current when the zero point of the current sensor 18 (see FIG. 1) is corrected will be described. FIG. 5 is a graph showing an enlarged view of a part of FIG. 2 (D) and FIG. 2 (A2). As shown in FIG. 5, after the electric vehicle 100 finishes deceleration (FIG. 5 (D)), the measurement value IL of the current sensor 18 becomes an error d1. As described above, the error d1 includes a hysteresis error Hd (see FIG. 3). As described with reference to FIG. 4, when correcting the zero point of the current sensor 18, the controller 6 selects a timing when the voltage of the smoothing capacitor 7 is greater than the voltage of the main battery 2, and alternately turns on and off the upper switching element 16a and the lower switching element 16b. As a result, the AC current LI across the OA flows through the reactor 15 and the current sensor 18. The AC current LI flows through the magnetized magnetic core of the reactor 15 or the current sensor 18, reducing the hysteresis error Hd. It is preferable that the controller 6 sets the period during which the upper switching element 16a and the lower switching element 16b are turned on and off to be shorter than the period during which they are turned on and off during voltage step-up or voltage step-down. As a result, the value of the AC current LI becomes smaller than during voltage step-up or voltage step-down. This allows the hysteresis error Hd to be reduced in a short period of time.

The controller 6 passes the AC current LI through the reactor 15 and the current sensor 18 for a predetermined time, and then turns off both the upper switching element 16a and the lower switching element 16b. As a result, the AC current LI disappears, and the measured value IL has an error d2. The error d2, in which the hysteresis error Hd has been reduced, is smaller than the error d1. At timing t0, the controller 6 corrects the zero point of the current sensor 18 based on the error d2, in which the hysteresis error Hd has been reduced. As a result, the measured value IL of the current sensor 18 is corrected, and the measured value IL becomes 0 A.

In this way, when correcting the zero point of the current sensor 18, the power converter 5 of the embodiment intentionally passes an AC current LI that crosses 0 A through the reactor 15 and the current sensor 18, thereby reducing the hysteresis error of the reactor 15 and the magnetic core 18a of the current sensor 18. In other words, the power converter 5 can correct the zero point based on the measurement value of the current sensor 18 with the reduced hysteresis error.

Notes on the embodiment are as follows. The current sensor 18 in the embodiment is provided between the reactor 15 and the midpoint of the switching elements 16a, 16b, but is not limited to this. For example, the current sensor 18 may be provided between the reactor 15 and the filter capacitor 14. The current sensor 18 may also be configured separately from the voltage converter 10. Furthermore, the controller 6 in the embodiment determines the vehicle stopped state based on the vehicle speed of the electric vehicle 100, but is not limited to this. The controller 6 may determine that the vehicle is stopped, for example, when the shift lever is in the parking position. Furthermore, the AC current LI may be attenuated so as to gradually decrease.

Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. The technical elements described in this specification or drawings exert technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of those objectives is itself technically useful.

2: Main battery 4: System main relay 5: Power converter 6: Controller 7: Smoothing capacitor 8: Motor 10: Bidirectional voltage converter 11: Low voltage end 11a: Low voltage positive electrode end 11b: Low voltage negative electrode end 12: High voltage end 12a: High voltage positive electrode end 12b: High voltage negative electrode end 13a: Voltage sensor 13b: Voltage sensor 14: Filter capacitor 15: Reactor 16a: Upper switching element 16b: Lower switching elements 17a, 17b: Freewheel diode 18: Current sensor 18a: Magnetic core 18b: Hall element 20: Inverter 31: Main switch 32: Vehicle speed sensor 33: Accelerator opening sensor 100: Electric vehicle

Claims (1)

A power converter including a voltage converter that converts a voltage between an on-board battery and an on-board storage battery, a current sensor, and a controller,
The voltage converter includes:
An upper switching element;
A lower switching element connected in series to the upper switching element;
a reactor having one end connected to a midpoint between the upper switching element and the lower switching element and the other end connected to the vehicle-mounted battery,
the current sensor includes a magnetic core, and measures a value of a current flowing through the reactor from a magnetic flux generated in the magnetic core due to a current flowing through the reactor;
The controller:
The vehicle is stationary and
the measurement value of the current sensor or its time derivative value is smaller than a predetermined threshold value,
and selecting a timing that satisfies the condition that the voltage of the in-vehicle storage device is higher than the voltage of the in-vehicle battery;
The upper switching element and the lower switching element are alternately turned on and off for a predetermined time,
The power converter corrects the zero point of the current sensor based on a subsequent measurement value of the current sensor.

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