JP2013059158A - Electric vehicle - Google Patents

Abstract

An electric vehicle capable of increasing a maximum voltage that can be supplied to a motor at a high altitude is provided.
An electric vehicle includes a main battery MB that supplies electric power to a wheel driving motor MG, a sub-battery SB that supplies electric power to auxiliary devices, a voltage converter 40, and Y capacitors YC1 and YC2. . The output voltage of the sub battery SB is lower than the output voltage of the main battery MB, and the voltage converter 40 steps down the output voltage of the main battery MB or the regenerative power voltage of the motor MG to a voltage suitable for charging the sub battery SB. The Y capacitors YC1 and YC2 are connected to the input side or the output side of the voltage converter 40. The electric vehicle 100 reduces the capacity of the Y capacitor when the altitude at which the vehicle is located exceeds the altitude threshold.
[Selection] Figure 1

Description

  The present invention relates to an electric vehicle provided with an electric motor for driving wheels (hereinafter simply referred to as a motor). The electric vehicle in this specification includes a hybrid vehicle having a wheel driving motor and an engine. Electric vehicles also include fuel cell vehicles.

  An electric vehicle often includes a main battery that supplies electric power to a wheel driving motor and a sub-battery that supplies electric power to auxiliary machines. Here, “auxiliary equipment” refers to devices that do not require as much electric power as motors for driving wheels, such as electronic devices such as car audio and engine controllers, room lamps, and instrument panel lighting. In other words, the “auxiliary machinery” corresponds to a device that is a battery supply target of a conventional engine vehicle that does not have a main battery.

  In an electric vehicle, the auxiliary battery is charged using the power of the main battery or the regenerative power of the motor. The voltage of the auxiliary battery is at most about 50V, such as 12V, 24V, or 42V. On the other hand, the output voltage of the main battery and the voltage of the regenerative power of the motor are higher than the voltage of the auxiliary battery, and are usually 100V or more. Therefore, the electric vehicle includes a voltage converter (DCDC converter) that steps down the output voltage of the main battery and the voltage of the regenerative power of the motor to a voltage suitable for charging the auxiliary battery. The switching operation of the switching element provided in this voltage converter generates noise (noise electromagnetic wave). The noise generated by the voltage converter is called radio noise because it affects radio reception of radio broadcasts. For example, Patent Literature 1 discloses a technique for reducing radio noise. A typical measure to reduce radio noise is to insert a capacitor in the circuit. The technique of Patent Document 1 also reduces radio noise by inserting a capacitor.

JP 2002-223560 A

  In order to reduce radio noise, the capacitance of the capacitor may be increased. In general, noise generated by a circuit is classified into two types: normal mode noise (or differential mode noise) and common mode noise. A capacitor for removing normal mode noise is called an X capacitor (or across the line capacitor), and a capacitor for removing common mode noise is called a Y capacitor (or line bypass capacitor). The common mode noise is caused by signal fluctuation (high frequency component) with respect to the ground line (earth line). The Y capacitor is inserted between the signal line and the ground line (earth line).

  On the other hand, an induction motor is generally used as a wheel driving motor, and a surge voltage is generated in the induction motor (hereinafter simply referred to as a motor). One factor that determines the maximum voltage (maximum voltage) that can be supplied to the motor is the magnitude of the surge voltage. That is, the maximum voltage supplied to the motor is determined by the magnitude of the surge voltage that the motor can withstand. Strictly speaking, the “maximum voltage” is the maximum value of the voltage that can be supplied to the motor in the design for avoiding the breakdown due to the surge voltage.

  According to the inventors' investigation, it has been found that the Y capacitor affects the surge voltage generated in the induction motor. It is presumed that the charge accumulated in the Y capacitor flows to the motor and the surge voltage increases. Therefore, the suppression of radio noise and the maximum motor voltage are in a trade-off relationship. This specification makes use of this trade-off relationship to provide a technique for increasing the maximum voltage that can be supplied to a motor at a high altitude.

  The electric vehicle provided by the present specification includes a main battery that supplies electric power to a wheel driving motor, a sub-battery that supplies electric power to auxiliary devices, a voltage converter, and a Y capacitor. As described above, the output voltage of the sub battery is lower than the output voltage of the main battery, and the voltage converter steps down the output voltage of the main battery or the voltage of the regenerative power of the motor to a voltage suitable for sub battery charging. The Y capacitor is connected to the input side or output side (high voltage side or low voltage side) of the voltage converter. The feature of the technology disclosed in this specification is that the capacitance of the Y capacitor is reduced when the altitude at which the vehicle is located exceeds the altitude threshold. As an example of “reducing the capacitance of the Y capacitor”, a plurality of capacitors may be connected in parallel as the Y capacitor, and a switch (semiconductor switch) may be provided for each capacitor, and the switch may be controlled in accordance with the altitude. The number of capacitors to be connected may be reduced as the altitude increases.

  The relationship between the altitude, the maximum motor voltage, and the Y capacitor capacity will be described below. When the altitude rises to some extent, radio waves also weaken, so the motivation for the vehicle occupant to listen to the radio decreases. Therefore, in places with high altitude (hereinafter referred to as “high places”), even if radio noise is allowed by reducing the Y capacitor, the influence is small. On the other hand, the withstand voltage (or insulation resistance) of the circuit decreases as the atmospheric pressure decreases (typically as the altitude increases). In other words, the maximum voltage of the motor must be reduced at high places. This is because discharge becomes easier as the atmospheric pressure becomes lower. Therefore, the maximum voltage of the motor at a high place can be increased by reducing the surge voltage by decreasing the capacity of the Y capacitor as the altitude increases.

It is a circuit diagram of the electric power system in an electric vehicle. It is a figure which shows an example of a structure of Y capacitor | condenser. It is a graph which shows the relationship between an altitude and a Y capacitor capacity. It is an example of the circuit diagram of a full bridge voltage converter and a common mode filter.

  FIG. 1 shows a circuit diagram of a power system of an electric vehicle. The electric vehicle 100 includes a wheel driving motor MG, a main battery MB for supplying electric power to the motor MG, a sub-battery SB for supplying electric power to an auxiliary machine, a power controller 20, and a car navigation system 10. Prepare. The output voltage of the main battery MB is 200V, and the output voltage of the sub battery SB is 12V. Note that FIG. 1 shows some of the components of the electric vehicle 100. For example, in FIG. 1, illustration of an auxiliary machine (for example, a room lamp, audio, etc.) that receives power supply from the sub battery SB is omitted.

  The power controller 20 boosts the voltage of the main battery MB to a voltage suitable for driving the motor (for example, 600V), and then converts DC power into AC current and supplies it to the motor MG. The power controller 20 also steps down the output of the main battery MB or the regenerative power of the motor MG to a voltage suitable for charging the sub battery SB. The power controller 20 includes the first voltage converter 23 that boosts the voltage of the main battery MB to a voltage suitable for driving the motor, the inverter 21, the output of the main battery MB, or the regenerative power of the motor MG for charging the sub battery SB. A second voltage converter 40 that steps down to a suitable voltage, other circuits, and a control module 25 that controls these modules are included. The control module 25 in the power controller 20 is connected to the car navigation 10 and acquires altitude data from the car navigation. Specifically, since the car navigation 10 has map information including altitude data and a GPS system, the position of the vehicle is specified by the GPS system, and the altitude at the current position is specified by collating with the map. .

  The internal configuration of the power controller 20 will be described in more detail. The main battery MB is connected to the first voltage converter 23 via the system main relay SMR. The system main relay SMR is a so-called main switch of the drive system, and is controlled by a signal SC from the control module 25. A smoothing capacitor C1 is inserted between the terminals of the first voltage converter 23 on the main battery MB side.

  The first voltage converter 23 includes a reactor L1, two transistors Tr7 and Tr8, and diodes D7 and D8 connected in parallel to the respective transistors. The circuit configuration of the first voltage converter 23 shown in FIG. 1 is a step-up / step-down converter that boosts the voltage of the main battery MB and outputs it to the inverter side, and steps down the inverter-side voltage and outputs it to the main battery side. can do. The inverter side of the first voltage converter may be referred to as a high voltage side, and the main battery side may be referred to as a low voltage side. The regenerative power generated by the motor MG is converted from AC power to DC power by tracing back the inverter 21 and then stepped down by the first voltage converter 23 and output from the main battery side (low voltage side). The circuit configuration of the first voltage converter 23 shown in FIG. 1 is well known and will not be described in detail.

  A smoothing capacitor C2 is connected between the inverter side (high voltage side) terminals of the first voltage converter 23. The smoothing capacitor C <b> 2 suppresses pulsation of the inverter side output current of the first voltage converter 23. A voltage sensor Vd is connected between terminals on the inverter side of the first voltage converter 23. The measured value (inverter input voltage VH) of the voltage sensor Vd is sent to the control module 25.

  The inverter 21 includes six switching circuits each composed of a transistor Tr and a freewheeling diode D, and generates and outputs three-phase AC power composed of a U phase, a V phase, and a W phase by the switching circuits. . Since the circuit configuration of the inverter 21 is also well known, detailed description thereof will be omitted.

  The control module 25 generates and outputs a PWM command (PWMB) for switching the transistors (Tr1 to Tr6) of the inverter 21 and a PWM command (PWMA) for switching the transistors (Tr7, Tr8) of the first voltage converter 23. To do.

  A terminal on the main battery side (low voltage side) of the first voltage converter 23 is connected to a terminal on the high voltage side of the second voltage converter 40 via the common mode filter 30. A sub battery SB is connected to the low voltage side of the second voltage converter 40. The second voltage converter 40 outputs the output of the main battery MB or the regenerative power generated by the motor MG (more accurately, the regenerative power converted to DC power having the same voltage as the main battery MB by tracing the inverter 21 in the reverse direction). The voltage is stepped down to a voltage (12 V) suitable for charging the sub battery SB. A specific example of the circuit configuration of the second voltage converter 40 will be described later.

  The common mode filter 30 connected between the main battery side of the first voltage converter 23 and the high voltage side of the second voltage converter 40 is composed of two Y capacitors YC1 and YC2. The two Y capacitors are inserted between each of the two signal lines (power lines) and the ground. A “common mode filter” is a filter that suppresses fluctuations in the voltage of a signal line (power line) with respect to a ground potential, and typically includes a capacitor inserted between the ground line and the signal line as a main component. . This capacitor is called a Y capacitor or a line pass capacitor. The common mode filter 30 connected between the main battery side of the first voltage converter 23 and the high voltage side of the second voltage converter 40 reduces common mode noise caused by the operation of the switching circuit in the second voltage converter 40. To do. This common mode noise in an electric vehicle affects the radio wave reception of a car radio or a television, and thus contributes to radio noise. The common mode filter 30 is provided mainly for the purpose of reducing radio noise.

  The common mode filter 30 in FIG. 1 is the simplest filter including a Y capacitor YC1 (YC2) inserted between a signal line (power line) and a ground line.

  In FIG. 1, the Y capacitors YC1 and YC2 are depicted as one capacitor, but in detail, as shown in FIG. 2, three capacitors Ca, Cb and Cc are connected in parallel via the semiconductor switch 132. Circuit configuration. The semiconductor switch 132 connects or disconnects the three capacitors Ca, Cb, and Cc from the circuit. The switching is controlled by a command signal CMD from the control module 25. The total capacity when all three capacitors are connected to the circuit is YC_a, and the total capacity when one capacitor is disconnected and two capacitors are connected is YC_b. When Y is disconnected and only one capacitor is connected, the total capacity is YC_c. The relative capacity relationship is YC_a> YC_b> YC_c.

  The electric vehicle 100 changes the capacities of the Y capacitors YC1 and YC2 according to the altitude at which the vehicle is located. Specifically, as shown in FIG. 3, when the altitude is below AL1, all three capacitors Ca, Cb, Cc are connected, and the capacitances of the Y capacitors YC1, YC2 are set to YC_a. When the altitude is higher than AL1 and lower than AL2, one capacitor is disconnected and the capacitances of Y capacitors YC1 and YC2 are set to YC_b. When the altitude is higher than AL2, the two capacitors are disconnected, and the capacities of the Y capacitors YC1 and YC2 are set to YC_c. That is, as the altitude increases, the capacitance of the Y capacitor is reduced. In other words, the electric vehicle 100 reduces the capacity of the Y capacitor when the altitude at which the vehicle is located exceeds a predetermined altitude threshold (for example, altitudes AL1 and AL2 in FIG. 3). Switching of the capacity of the Y capacitor is performed by the control module 25 based on the altitude data at the current position sent from the car navigation system 10. Specifically, the control module 25 controls the semiconductor switch 132 shown in FIG. 2 by the command signal CMD. The altitude threshold values (for example, altitudes AL1 and AL2 in FIG. 3) are determined in advance and stored in the control module 25.

  The advantage of changing the capacity of the Y capacitor according to the altitude will be described. In electric vehicle 100, a surge voltage is generated in motor MG, and the magnitude thereof increases as the capacitance of the Y capacitor increases. Moreover, the maximum value (maximum voltage) of the power supplied to the motor MG must be reduced as the surge voltage is increased. This is because the motor MG is damaged when the sum of the voltage supplied from the inverter 21 to the motor MG and the surge voltage exceeds the withstand voltage of the motor MG. If the capacity of the Y capacitor is reduced, the surge voltage is reduced, and the maximum voltage that can be supplied by the inverter 21 can be increased accordingly. Note that the higher the altitude, the lower the atmospheric pressure and the easier the discharge, so the withstand voltage of the motor decreases. On the other hand, Y capacitors YC1 and YC2 are provided to reduce radio noise. If the altitude is higher, the radio and television radio waves will be weaker, and the possibility of passengers of electric vehicles using the radio and television will be reduced. Therefore, as the altitude is increased (when the altitude threshold is exceeded), there is little trouble even if the capacitance of the Y capacitor is reduced. In places where the altitude is high enough that radio / TV radio waves do not reach, there is almost no problem even if the capacitance of the Y capacitor is made extremely small. Therefore, in the electric vehicle 100 according to the embodiment, the capacity of the Y capacitor is reduced as the altitude increases. By doing so, the highest voltage at high altitude can be increased. That is, traveling performance at high altitudes can be improved.

  FIG. 4 shows an example of the circuit configuration of the second voltage converter 40 and an example of another common mode filter 130. 4 corresponds to a part of the circuit diagram of FIG. 1 (second voltage converter 40 and common mode filter 30). It connects with the battery side terminal of the voltage converter 23.

  In the second voltage converter 40, diodes D41, D42, a reactor L41, and a capacitor C41 are connected as shown in the figure with a transformer 45 at the center, and four transistors Tr41, Tr42, Tr43, Tr44 are connected to the high voltage side. The capacitor XC has a circuit configuration connected as shown in the figure. In the second voltage converter 40, the low voltage side and the high voltage side are insulated via a transformer 45. The circuit configuration of the second voltage converter 40 shown in FIG. 4 is a well-known circuit called a full bridge type, and detailed description thereof is omitted.

  In the common mode filter 130, coils YL1 and YL2 are fitted and inserted into respective signal lines (power lines), and Y capacitors YC1, YC2, YC3, and YC3 are connected to ground lines on both sides of the coil. Yes. The circuit configuration of the common mode filter 130 in FIG. 4 is also well known, and detailed description thereof is omitted. In detail, the Y capacitors YC1 to YC4 of the common mode filter are also composed of three capacitors connected in parallel as shown in FIG. 2, and their capacities are changed according to the altitude difference. The capacitance changing algorithm is the same as that of the common mode filter 30 described above, and is switched according to the map of FIG.

  Points to be noted regarding the embodiment will be described. In the embodiment, the Y capacitor is connected to the high voltage side (main battery side) of the second voltage converter 40. The Y capacitor may be connected to the low voltage side (sub battery side) of the second voltage converter 40.

  A sensor that acquires the altitude of the vehicle may use an atmospheric pressure sensor instead of the car navigation 10. This is because the altitude and the atmospheric pressure are in a substantially proportional relationship, and the altitude can be estimated from the atmospheric pressure.

  In the embodiment, each Y capacitor is constituted by a parallel circuit of three capacitors. The number of capacitors connected in parallel is not limited to three.

  The electric vehicle 100 of an Example is a vehicle provided with one motor. The technology disclosed in this specification can also be applied to an electric vehicle including a plurality of wheel driving motors and a hybrid vehicle including a motor and an engine. It can also be applied to a fuel cell vehicle.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

10: car navigation 20: power controller 21: inverter 23: first voltage converter 25: control module 30, 130: common mode filter 40: first voltage converter 45: transformer 100: electric vehicle 132: semiconductor switches C1, C2: smoothing Filter C41, Ca, Cb, Cc, XC: capacitor D: freewheeling diode L: reactor MB: main battery MG: motor SB: sub-battery Tr: transistor XC capacitors YC1, YC2, YC3, YC4: Y capacitors YL1, YL2: coil

Claims (1)

A main battery for supplying power to the wheel drive motor;
A battery that supplies power to the auxiliary equipment and has a lower output voltage than the main battery,
A voltage converter that steps down the output voltage of the main battery or the voltage of the regenerative power of the motor to a voltage suitable for charging the sub-battery;
A Y capacitor connected to the voltage converter;
With
An electric vehicle characterized in that the capacity of a Y capacitor is reduced when the altitude at which the vehicle is located exceeds a predetermined altitude threshold.

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