JP5708283B2 - vehicle - Google Patents

Description

  The present invention relates to a vehicle, and more particularly, to a vehicle provided with a drive circuit for driving a motor using electric power from a DC power source.

  2. Description of the Related Art Conventionally, there is known a motor drive circuit that includes a converter that has a reactor and a switching element and boosts a DC voltage from a DC power supply, and an inverter that converts an output voltage of the converter into an AC voltage and supplies the AC voltage to a motor. Yes.

  The main control methods of the inverter include a pulse width modulation (hereinafter also referred to as “PWM”) control method and a rectangular wave voltage control (hereinafter also simply referred to as “rectangular control”) method. The rectangular control method is inferior to the PWM control method in control accuracy (control responsiveness), but the voltage conversion modulation rate (value corresponding to the ratio of the output voltage to the input voltage) is large, and the motor output can be increased. It is. Therefore, in general, a PWM control method is used in a motor operation region (low rotation region) where the rotation speed is lower than a predetermined value, and a rectangular control method is used in a motor operation region (high rotation region) where the rotation speed is higher than a predetermined value. Is used.

  However, converters often have smoothing capacitors on each of the DC power supply side and inverter side of the converter, and these smoothing capacitors and the reactor of the converter constitute a resonance circuit, and the motor operating area has a predetermined resonance. When included in the generation region, resonance of voltage or current may occur in the motor drive circuit.

  In consideration of such points, in Japanese Patent Application Laid-Open No. 2009-225633 (Patent Document 1), in a vehicle having the above-described motor drive circuit, when the motor operation region is included in the resonance generation region, the converter is in a boost state. And controlling the inverter by the PWM control method to compensate for the motor output decrease in the PWM control by boosting the converter while avoiding resonance.

JP 2009-225633 A JP 2008-72868 A

  However, there may be a case where the converter cannot be controlled to a boosted state due to a failure of a voltage sensor that detects a voltage on the DC power source side or the inverter side of the converter. In such a case, the technique of Patent Document 1 that presupposes that the converter is controlled to be in a boosted state cannot be handled. Also, if the inverter control method is switched to the rectangular control method in response to the inability to control the converter to the boost state, resonance will occur and the temperature of the DC power supply may rise due to the effect. There is sex.

  The present invention has been made to solve the above-described problems, and an object thereof is to resonate a drive circuit in a vehicle including a drive circuit for driving a motor using power from a DC power supply. This is to appropriately suppress the overheating of the direct current power source.

  A vehicle according to the present invention includes a DC power supply, a motor, a converter having a resonance circuit that resonates in a predetermined resonance frequency band, a converter that converts the voltage of the DC power supply, and an inverter that performs power conversion between the converter and the motor. And a control device for controlling the drive circuit. When the motor rotation speed is included in the band where resonance occurs in the drive circuit during non-voltage conversion of the converter, the control device depends on the motor rotation speed when the amount of heat generated by the DC power supply is greater than or equal to the threshold value. Execution of the first control that operates the inverter in a cycle is limited.

  Preferably, the first control is a rectangular control that generates a rectangular wave voltage at a cycle according to the rotation speed of the motor.

  Preferably, when the calorific value of the DC power source is equal to or greater than the threshold value, the control device does not allow the rectangular control to be performed and performs the second control for operating the inverter at a control cycle that does not depend on the rotation speed of the motor. Is allowed to execute.

  Preferably, the second control is pulse width modulation control that generates a pulse width modulation voltage that does not depend on the rotational speed of the motor.

  Preferably, the control device allows execution of rectangular control when the amount of heat generated by the DC power supply is less than a threshold value.

  Preferably, the control device monitors the amount of heat generated by the DC power supply using the square value of the current of the DC power supply.

  Preferably, the resonance circuit includes a reactor and a capacitor.

  ADVANTAGE OF THE INVENTION According to this invention, in the vehicle provided with the drive circuit for driving a motor using the electric power from DC power supply, the overheating of DC power supply resulting from resonance of a drive circuit can be suppressed appropriately.

It is a figure which shows the structure of a vehicle. It is a figure explaining the control mode (control system) of an inverter. It is the figure which plotted the motor operating point in which a resonance phenomenon generate | occur | produces. It is a figure which shows an example of the time change of the motor rotational speed N and the battery current Ib during upper arm ON control and rectangular control. It is a functional block diagram of a control device. It is a flowchart which shows the process sequence of a control apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  FIG. 1 is a diagram showing a structure of a vehicle 1 according to an embodiment of the present invention. The vehicle 1 includes a DC power source B, a converter 12, a smoothing capacitor C0, an inverter 14, a motor M1, and a control device 100.

  The motor M1 generates torque for driving the drive wheels of the vehicle 1. Or this motor M1 may be comprised so that it may have the function of the generator driven with an engine, and may be comprised so that it may have the function of an electric motor and a generator together. Furthermore, the motor M1 may operate as an electric motor for the engine, and may be incorporated in a hybrid vehicle so that the engine can be started, for example.

  DC power supply B includes a secondary battery such as nickel metal hydride or lithium ion.

  Converter 12 is connected to DC power supply B via positive electrode line 6 and negative electrode line 5. Converter 12 includes a smoothing capacitor C1, a reactor L1, switching elements Q1, Q2 formed of a power semiconductor, and diodes D1, D2.

  Smoothing capacitor C <b> 1 is connected between positive electrode line 6 and negative electrode line 5, and smoothes voltage fluctuations between positive electrode line 6 and negative electrode line 5.

  Switching elements Q 1 and Q 2 are connected in series between positive line 7 and negative line 5. As the switching element, an IGBT (Insulated Gate Bipolar Transistor), a power MOS (Metal Oxide Semiconductor) transistor, a power bipolar transistor, or the like can be used. Diodes D1 and D2 are arranged for switching elements Q1 and Q2, respectively.

  Reactor L1 is connected between a connection node of switching elements Q1 and Q2 and positive electrode line 6.

  Converter 12 performs voltage conversion between DC power source B and inverter 14 by controlling switching of switching elements Q1 and Q2 in accordance with control signals S1 and S2 from control device 100. During the boosting operation of converter 12, DC voltage Vb supplied from DC power supply B is boosted by converter 12 and supplied to inverter 14. During the step-down operation of the converter 12, the voltage supplied from the inverter 14 is stepped down by the converter 12 and supplied to the DC power source B. During such voltage conversion of the converter 12 (during step-up operation or step-down operation), the opening / closing of the switching element Q1 and the opening / closing of the switching element Q2 are complementarily repeated.

  On the other hand, at the time of non-voltage conversion of converter 12, switching element Q1 (upper arm) is maintained in the closed state and switching element Q2 (lower arm) is maintained in the open state. At the time of non-voltage conversion of the converter 12, the DC voltage Vb supplied from the DC power supply B is supplied to the inverter 14 as it is without being converted. Hereinafter, controlling the converter 12 in such a non-voltage conversion state is referred to as “upper arm on control”.

  The smoothing capacitor C0 is connected between the positive electrode line 7 and the negative electrode line 5, and smoothes voltage fluctuation between the positive electrode line 7 and the negative electrode line 5.

  Inverter 14 is connected to converter 12 via positive line 7 and negative line 5. Inverter 14 includes a U-phase arm 15, a V-phase arm 16, and a W-phase arm 17 provided in parallel between positive electrode line 7 and negative electrode line 5. Each phase arm includes a switching element connected in series between positive electrode line 7 and negative electrode line 5. That is, U-phase arm 15 includes switching elements Q3 and Q4. V-phase arm 16 includes switching elements Q5 and Q6. W-phase arm 17 includes switching elements Q7 and Q8. Diodes D3 to D8 are connected to switching elements Q3 to Q8, respectively.

  An intermediate point of each phase arm is connected to each phase end of each phase coil of motor M1. Typically, the motor M1 is a three-phase permanent magnet motor, and is configured by commonly connecting one end of three coils of U, V, and W phases to a neutral point. Furthermore, the other end of each phase coil is connected to the midpoint of the switching elements of each phase arm 15-17.

  Inverter 14 performs power conversion between converter 12 and motor M <b> 1 by controlling opening and closing of switching elements Q <b> 3 to Q <b> 8 according to control signals S <b> 3 to S <b> 8 from control device 100. When the motor M1 functions as an electric motor, the inverter 14 converts the DC power from the converter 12 into AC power and supplies the AC power to the motor M1. During regenerative braking of the vehicle 1 (when the motor M1 functions as a generator), the inverter 14 converts the regenerative power generated by the motor M1 into DC power and supplies it to the converter 12.

  Further, the vehicle 1 includes voltage sensors 20 to 22, current sensors 23 and 24, and a resolver 25. The voltage sensor 20 detects the DC voltage Vb output from the DC power source B. The voltage sensor 21 detects a voltage across the smoothing capacitor C1 (hereinafter also referred to as “voltage VL”). The voltage sensor 22 detects the voltage across the smoothing capacitor C0 (hereinafter also referred to as “voltage VH”). The current sensor 23 detects a current Ib flowing through the DC power source B. The current sensor 24 detects a current flowing through the motor M1. Since the sum of instantaneous values of the three-phase currents iu, iv, and iw is zero, the current sensor 24 has a motor current for two phases (for example, a V-phase current iv and a W-phase current iw) as shown in FIG. It is sufficient to arrange it so as to detect. The resolver 25 detects the rotor rotation angle θ and the rotation speed N of the motor M1. These sensors output the detection result to the control device 100.

  The control device 100 includes a CPU (Central Processing Unit) (not shown) and an electronic control unit (ECU: Electronic Control Unit) with a built-in memory, and performs predetermined arithmetic processing based on a map and a program stored in the memory. Configured to run.

  As described above, control device 100 opens and closes voltage VL and voltage VH by complementarily opening and closing switching element Q1 (upper arm) and switching element Q2 (lower arm) of converter 12 in accordance with a user request. Voltage conversion (step-up or step-down) is performed. On the other hand, when a state in which voltage conversion of converter 12 cannot be performed normally (hereinafter referred to as “voltage conversion abnormality”) occurs due to failure of voltage sensors 21 and 22 that detect voltages VL and VH, respectively, control device 100. Performs the above-described “upper arm on control” to control the converter 12 to the non-voltage conversion state.

  In addition, the control device 100 switches and uses three control modes for voltage conversion in the inverter 14. The three control modes are sine wave PWM control, overmodulation PWM control, and rectangular control.

  FIG. 2 is a diagram for explaining the control mode (control method) of the inverter 14. Note that the numerical value of the modulation factor described in FIG. 2 is merely an example, and the present invention is not limited to this.

  As described above, the control mode of the inverter 14 has three control modes: sine wave PWM control, overmodulation PWM control, and rectangular control.

  The sine wave PWM control is used as a general PWM control method, and controls the opening and closing of the switching element in each phase arm according to a voltage comparison between a sine wave voltage command value and a carrier wave (carrier signal). As a result, the fundamental wave component of the inverter output voltage becomes a pseudo sine wave within a certain period. As is well known, in sine wave PWM control, this fundamental wave component amplitude can only be increased up to 0.61 times the inverter input voltage (modulation rate can only be increased up to 0.61).

  The overmodulation PWM control performs PWM control similar to the sine wave PWM control after distorting the carrier wave to reduce the amplitude. As a result, the modulation rate can be increased to a range of 0.61 to 0.78. In the present embodiment, both sine wave PWM control and overmodulation PWM control are combined and classified as “PWM control”. In PWM control, the control cycle (switching cycle) of the inverter 14 usually depends on the frequency of the carrier wave (carrier frequency) and does not depend on the motor rotation speed N.

  In the rectangular control, a rectangular wave voltage for one pulse is applied to the motor M1 by a switching operation once in one output cycle (one electrical cycle) of the motor rotation angle θ. That is, in the rectangular control, the inverter 14 operates at a control cycle that depends on the motor rotation speed N. Thereby, rectangular control is inferior to PWM control in control accuracy (control responsiveness), while the modulation rate can be increased to 0.78 and the motor output can be increased.

  In consideration of the difference in the characteristics of these control methods, during normal operation, the control device 100 determines a motor determined by the motor torque T and the motor rotation speed N (both of which may be a target value or an actual value). When the operating point belongs to the side lower than the predetermined inverter control boundary line (low torque low rotation side), the PWM control method is selected, and the motor operating point is higher than the inverter control boundary line (high torque high rotation side). If it belongs to the above, the rectangular control method is selected.

  Furthermore, control device 100 changes the above-described inverter control boundary line according to the control mode of converter 12. Since the motor torque T can be increased by boosting during the boosting operation of the converter 12, the control device 100 increases the inverter control boundary line to expand the PWM control region (region with good control accuracy). On the other hand, when the converter 12 is not boosted, the motor torque T cannot be increased by boosting. Therefore, the inverter control boundary line is lowered to form a rectangular control region (a region where the motor output can be increased by increasing the modulation factor). Enlarge. Therefore, when the upper arm of the converter 12 is on (non-voltage conversion), the rectangular control tends to be easily entered.

  In the vehicle 1 having the above-described configuration, the converter 12 constituting a part of the drive circuit of the motor M1 includes a reactor L1 having an inductance component (L component) and a smoothing capacitor C1 having a capacitance component (C component). And are included. Therefore, during the upper arm on control of converter 12, resonant circuit LC (see FIG. 1) is formed between reactor L1 and smoothing capacitor C1. In other words, the drive circuit of the motor M1 has a resonance frequency band determined by the L component and the C component.

  On the other hand, in the “rectangular control” that is one of the control methods of the inverter 14, the inverter 14 operates in a control cycle that depends on the motor rotation speed N as described above. As a result, when the rectangular control of the inverter 14 is executed during the upper arm on control of the converter 12, a resonance phenomenon may occur in the drive circuit of the motor M1 depending on the value of the motor rotation speed N.

  FIG. 3 is a diagram in which the motor operating point at which the resonance phenomenon occurs during the upper arm on control of the converter 12 and the rectangular control of the inverter 14 is obtained by experimentation and plotted.

  During upper arm-on control and rectangular control, the motor torque T is included in the predetermined torque T1 to the predetermined torque T2 and the motor rotation speed N is included in the predetermined speed N1 to the predetermined speed N2 (hereinafter referred to as “resonance operation area”). ")" Includes a motor operating point, the control frequency of the inverter 14 and the resonance frequency of the drive circuit are in an integral multiple relationship, and a resonance phenomenon is likely to occur as shown in FIG. Hereinafter, the region of the predetermined speed N1 to the predetermined speed N2 is referred to as “resonance rotational speed region”.

  FIG. 4 is a diagram illustrating an example of temporal changes in the motor rotation speed N and the current Ib during the upper arm on control and the rectangular control.

  As can be seen from FIG. 4, after the time t1 when the state in which the motor rotation speed N is included in the resonance rotation speed region (N1 to N2 region) continues, the fluctuation width of the current Ib due to the effect of the resonance phenomenon. Becomes very large. If the current Ib fluctuates, heat is generated inside the DC power supply B, and if the amount of generated heat exceeds an allowable value, the DC power supply B may be deteriorated.

  Therefore, the control device 100 according to the present embodiment monitors the heat generation amount of the DC power supply B when the motor rotation speed N is included in the resonance rotation speed region during the upper arm on control, and the heat generation amount is greater than or equal to the allowable amount. In that case, overheating of the DC power supply B is prevented by restricting (prohibiting) the execution of the rectangular control. This is the most characteristic point of the present embodiment.

  FIG. 5 is a functional block diagram of the control device 100. Each functional block shown in FIG. 5 may be realized by hardware or software.

  The control device 100 includes a first determination unit 110, a second determination unit 120, a third determination unit 130, and an inverter control unit 140.

  The first determination unit 110 determines whether or not the upper arm on control of the converter 12 is being performed based on the states of the control signals S1 and S2 of the converter 12. It should be noted that when the failure of the voltage sensors 21 and 22 that detect the voltages VL and VH has occurred (when the voltage conversion is abnormal), it may be determined that the upper arm on control is being performed.

  The second determination unit 120 determines whether or not the motor rotation speed N is included in the resonance rotation speed region.

The third determination unit 130 determines whether or not the amount of heat generated by the DC power source B is greater than or equal to an allowable amount. In the present embodiment, the third determination unit 130 monitors the square value (= Ib ² ) of the current Ib as a value corresponding to the heat generation amount of the DC power supply B, and the square value of the current Ib is allowable. When the value is equal to or greater than the value, it is determined that the heat generation amount of the DC power source B is equal to or greater than the allowable amount. The integrated value of the square value of the current Ib may be the amount of heat generated by the DC power supply B.

  When the motor rotation speed N is included in the resonance rotation speed region during the upper arm ON control, the inverter control unit 140 performs rectangular control of the inverter 14 according to whether or not the heat generation amount of the DC power supply B is greater than or equal to the allowable amount. Decide whether to allow execution.

  When the heat generation amount of the DC power source B is less than the allowable amount, the inverter control unit 140 executes the rectangular control even when the motor rotation speed N is included in the resonance rotation speed region during the upper arm on control. Allow. As described above, when the heat generation amount of the DC power supply B is less than the allowable amount (when the DC power supply B is predicted not to be in an overheated state), the rectangular control having a higher modulation rate than the PWM control is permitted. Thus, the torque output requested by the user can be realized.

  On the other hand, when the heat generation amount of the DC power supply B is equal to or greater than the allowable amount, the inverter control unit 140 prohibits execution of the rectangular control. Thereby, since the control method of the inverter 14 is switched to PWM control with higher control accuracy than the rectangular control, the resonance phenomenon is avoided and the fluctuation of the current Ib (that is, overheating of the DC power supply B) is also prevented.

  FIG. 6 is a flowchart showing a processing procedure of the control device 100 for realizing the above-described function. This flowchart is repeatedly executed at a predetermined cycle.

  In S10, control device 100 determines whether or not the upper arm on control is being performed. When the upper arm on control is being performed (YES in S10), control device 100 determines in S11 whether motor rotation speed N is included in the resonance rotation speed region.

  If motor rotation speed N is included in the resonance rotation speed region (YES in S11), control device 100 determines in S12 whether the square value of current Ib is greater than or equal to an allowable value.

  When the square value of current Ib is equal to or greater than the allowable value (YES in S12), control device 100 prohibits the execution of the rectangular control in S13 (allows the execution of the PWM control).

  On the other hand, when the upper arm on control is not being performed (NO at S10), when the motor rotation speed N is not included in the resonance rotation speed region (NO at S11), when the square value of the current Ib is less than the allowable value ( In at least one of cases of NO in S12, control device 100 allows execution of rectangular control in S14.

  As described above, according to the present embodiment, when motor rotation speed N is included in the resonance rotation speed region during upper arm on control of converter 12, the amount of heat generated by DC power supply B (the square value of current Ib) is calculated. Monitoring is performed, and when the amount of generated heat is equal to or greater than the allowable amount, execution of the rectangular control is prohibited. For this reason, it is possible to appropriately suppress overheating of the DC power supply B due to resonance of the drive circuit.

In addition, this Embodiment can also be changed as follows, for example.
In the present embodiment, “whether or not the motor rotation speed N is included in the resonance rotation speed region” is determined in the process of S11 of FIG. You may make it determine whether it is contained "(refer FIG. 3).

  Further, in the present embodiment, “rectangular control” of the inverter 14 is cited as control for prohibiting execution in the process of S13 of FIG. 6, but it depends on the motor rotation speed N instead of or in addition to “rectangular control”. When there is a control for operating the motor drive circuit (inverter 14) in the control cycle, the execution of the control may be prohibited.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Vehicle, 5 Negative electrode line, 6, 7 Positive electrode line, 12 Converter, 14 Inverter, 20-22 Voltage sensor, 23, 24 Current sensor, 25 Resolver, 100 Control apparatus, 110 1st determination part, 120 2nd determination part, 130 3rd determination part, 140 inverter control part, B DC power supply, L1 reactor, M1 motor.

Claims (6)

DC power supply,
A motor,
A drive circuit including a converter having a resonance circuit that resonates in a predetermined resonance frequency band and converting the voltage of the DC power supply; and an inverter that performs power conversion between the converter and the motor;
A control device for controlling the drive circuit,
When the rotational speed of the motor is included in a band where resonance occurs in the drive circuit at the time of non-voltage conversion of the converter, when the amount of heat generated by the DC power source is equal to or greater than a threshold value, the control device Limiting the execution of the first control to operate the inverter in a control cycle that depends on the rotational speed ;
The vehicle in which the first control is a rectangular wave control that generates a rectangular wave voltage at a cycle according to a rotation speed of the motor . When the amount of heat generated by the DC power supply is equal to or greater than the threshold value, the control device does not allow the execution of the rectangular wave control and operates the inverter at a control cycle that does not depend on the rotation speed of the motor. allowing execution of the second control to the vehicle according to claim 1. The vehicle according to claim 2 , wherein the second control is pulse width modulation control that generates a pulse width modulation voltage that does not depend on a rotation speed of the motor. The vehicle according to claim 1 , wherein the control device permits execution of the rectangular wave control when a calorific value of the DC power supply is less than the threshold value.   The vehicle according to claim 1, wherein the control device monitors the amount of heat generated by the DC power supply using a square value of the current of the DC power supply.   The vehicle according to claim 1, wherein the resonance circuit includes a reactor and a capacitor.

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