JP2012171369A - Hybrid vehicle and control method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To conduct random carrier control to appropriately control the level of electromagnetic noise according to the state of a vehicle, in a hybrid vehicle where an engine and a motor are mounted.SOLUTION: The turning-on/off of a semiconductor switching element for the electric power of a power converter for driving the motor is controlled by pulse width modulation control. The frequency of a carrier signal used for the pulse width modulation control is randomly changed within a frequency range having a control width Δf to a predetermined central frequency by random carrier control. The control width Δf is set to be relatively small during the stoppage of the engine when the vehicle tries to positively output noise to the outside of the vehicle (Δf=f1). Meanwhile, the control width Δf is set to be relatively large during the start of the engine when the vehicle tries to suppress the noise detected in the vehicle (Δf=f3).

Description

  The present invention relates to a hybrid vehicle and a control method thereof, and more specifically to control of a carrier frequency used for controlling an electric motor mounted on the hybrid vehicle.

  Conventionally, pulse width modulation control (PWM control) has been applied to power converters (inverters and converters) used for motor control.

  For example, Japanese Patent Laid-Open No. 2004-048844 (Patent Document 1) describes that the carrier frequency of an inverter that controls an electric motor mounted on a hybrid vehicle is controlled according to the engine speed and the vehicle speed. Specifically, it is described that the carrier frequency of the inverter is increased when the engine speed is low, while the carrier frequency is decreased when the engine speed is high. Further, it is described that the carrier frequency is increased when the vehicle speed is low, while the carrier frequency is decreased when the vehicle speed is high.

  Japanese Patent Laid-Open No. 2002-171606 (Patent Document 2) discloses that in a hybrid vehicle inverter system, the PWM control frequency (carrier frequency) of an inverter circuit is changed randomly within a predetermined frequency range, thereby It is described that noise is reduced. Furthermore, it is described that the frequency range for modulating the carrier frequency is narrowed as the speed of the electric motor increases.

  Similarly to Japanese Patent Application Laid-Open No. 2010-130850 (Patent Document 3) and Japanese Patent Application Laid-Open No. 2007-020320 (Patent Document 4), similarly to Patent Document 2, a carrier frequency used for PWM control of a converter or an inverter is predetermined. In the frequency range (hereinafter also referred to as “random carrier control”).

JP 2004-048844 A JP 2002-171606 A JP 2010-130850 A JP 2007-020320 A

  In power converters such as inverters and converters, when the carrier frequency in PWM control is low, the harmonic component (ripple component) included in the output current (voltage) increases. Thereby, in the motor control, since the eddy current generated in the stator becomes large, there is a concern about an increase in loss due to an increase in iron loss. Further, the current error may increase due to the influence of the ripple current. Moreover, in a permanent magnet motor, there is a concern that demagnetization may occur due to an increase in magnet temperature. On the other hand, when the carrier frequency is high, there is a concern that the power loss in the power converter increases due to an increase in the number of switching times per unit time.

  In the carrier frequency control described in Patent Document 1, since the carrier frequency is fixedly decreased or increased, there is a concern about the above-described problem caused by the increase in ripple current when the carrier frequency is fixedly decreased.

  In the random carrier control described in Patent Documents 2 to 4, the generation level of electromagnetic noise can be suppressed by changing the carrier frequency within a predetermined frequency range. However, in the electric motor control of the hybrid vehicle, there is a concern that the ripple current increases when the carrier frequency instantaneously decreases depending on the frequency change width in the random carrier control. In particular, the current control error increases during the period when the carrier frequency is low, and thus there is a concern that the running performance may deteriorate due to the fluctuation of the vehicle driving torque.

  Further, it has been pointed out that in a hybrid vehicle, when the engine is stopped and the vehicle is driven only by an electric motor, the generated sound of the vehicle is small, so that it is difficult for pedestrians around the vehicle to recognize the approach of the vehicle. Therefore, when random carrier control is applied in such a scene, there is a possibility that the notification of the approach of the vehicle to the surroundings of the vehicle is further deteriorated.

  The present invention has been made to solve such problems, and an object of the present invention is to appropriately set the level of electromagnetic noise in a hybrid vehicle equipped with an engine and an electric motor according to the state of the vehicle. Random carrier control is performed to control.

  In one aspect of the present invention, a hybrid vehicle equipped with an internal combustion engine and an electric motor includes a power converter and a control device for controlling the power converter. The power converter is arranged between the power storage device and the electric motor and configured to include at least one switching element. The control device includes a carrier generation unit for generating a carrier signal used for on / off control of the switching element, a carrier frequency control unit for controlling the frequency of the carrier signal generated by the carrier generation unit, a pulse width modulation unit, including. The pulse width modulation unit controls on / off of the switching element based on a comparison between a control command for the power converter and a carrier signal from the carrier generation unit. The carrier frequency control unit varies the frequency of the carrier signal within a first frequency range centered on a predetermined frequency when the internal combustion engine is started, while the second frequency range including the predetermined frequency when the internal combustion engine is stopped. The carrier generator is controlled so as to vary the frequency of the carrier signal. The second frequency range is narrower than the first frequency range.

  Preferably, the carrier frequency control unit fixes the frequency of the carrier signal when the internal combustion engine is stopped and the vehicle speed of the hybrid vehicle is lower than a predetermined speed.

  Preferably, the carrier frequency control unit controls the carrier generation unit so as to change the frequency of the carrier signal within a third frequency range centered on the predetermined frequency after the internal combustion engine is started, The frequency range is set to be narrower as the rotational speed of the internal combustion engine is higher.

  Alternatively, preferably, when the internal combustion engine is stopped and the vehicle speed of the hybrid vehicle is higher than a predetermined speed, the carrier frequency control unit sets the second frequency range to be narrower as the vehicle speed is higher.

  In another aspect of the present invention, there is provided a method for controlling a hybrid vehicle, wherein the hybrid vehicle is disposed between an internal combustion engine, an electric motor, a power storage device, the power storage device and the motor, and includes at least one switching element. It is equipped with a power converter configured in the above. The control method includes a step of controlling a frequency of a carrier signal used for on / off control of the switching element, a step of generating a carrier signal according to the frequency of the carrier signal determined by the controlling step, a control command of the power converter, Generating a signal for controlling on / off of the switching element based on the comparison with the carrier signal. The controlling step includes a step of changing the frequency of the carrier signal within a first frequency range centered on a predetermined frequency when the internal combustion engine is started, and a second frequency range including the predetermined frequency when the internal combustion engine is stopped. And fluctuating the frequency of the carrier signal. The second frequency range is narrower than the first frequency range.

  Preferably, the controlling step includes the step of comparing the vehicle speed of the hybrid vehicle with a predetermined speed when the internal combustion engine is stopped, and the step of fixing the frequency of the carrier signal when the vehicle speed is lower than the predetermined speed when the internal combustion engine is stopped. And further including.

  Also preferably, the controlling step further includes a step of changing the frequency of the carrier signal within a third frequency range centered on a predetermined frequency after the internal combustion engine is started. This third frequency range is set to become narrower as the rotational speed of the internal combustion engine is higher.

  Alternatively, preferably, the controlling step includes the step of comparing the vehicle speed of the hybrid vehicle with a predetermined speed when the internal combustion engine is stopped, and the vehicle speed when the internal combustion engine is stopped and the vehicle speed is higher than the predetermined speed. A step of setting the second frequency range to be narrower as the value is higher.

  According to this invention, in a hybrid vehicle equipped with an engine and an electric motor, random carrier control can be executed so as to appropriately control the level of electromagnetic noise in accordance with the state of the vehicle.

1 is a block diagram illustrating an overall configuration of a hybrid vehicle according to an embodiment of the present invention. FIG. 2 is a collinear diagram showing a rotational speed relationship between an engine and a motor generator in the hybrid vehicle of FIG. 1. It is a circuit diagram which shows the structure of the electric system for driving the motor generator shown in FIG. It is a functional block diagram for demonstrating the motor control in the hybrid vehicle by embodiment of this invention. FIG. 5 is a conceptual waveform diagram for explaining PWM control by a pulse width modulation unit shown in FIG. 4. It is a conceptual waveform diagram for explaining the relationship between the carrier frequency and the ripple current. It is a conceptual diagram explaining control of the carrier frequency in each inverter. It is a conceptual diagram which shows the sound pressure level distribution of the electromagnetic noise in the random carrier control shown in FIG. It is a flowchart for demonstrating the process sequence of the motor control in the hybrid vehicle by embodiment of this invention. It is a flowchart explaining the 1st example of the process sequence of random carrier control. It is a flowchart explaining the 2nd example of the process sequence of random carrier control. FIG. 4 is a conceptual waveform diagram for explaining PWM control applied to the converter shown in FIG. 3.

  Embodiments of the present invention will be described below in detail with reference to the drawings. In the following, the same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated in principle.

  FIG. 1 is a block diagram illustrating the overall configuration of a hybrid vehicle according to an embodiment of the present invention.

  Referring to FIG. 1, a hybrid vehicle includes an engine 100, a first motor generator 110 (hereinafter also simply referred to as “MG1”), a second motor generator 120 (hereinafter also simply referred to as “MG2”), and power. The division mechanism 130, the reduction gear 140, the battery 150, and ECU (Electronic Control Unit) 170 are provided. Each of MG1 and MG2 corresponds to a “motor” that is an object of motor control according to the embodiment of the present invention.

  The hybrid vehicle shown in FIG. 1 travels by driving force from at least one of engine 100 and MG2. Engine 100, MG1 and MG2 are connected via power split device 130. The power generated by the engine 100 is divided into two paths by the power split mechanism 130. One is a path for driving the drive wheels 190 via the speed reducer 140. The other is a path for driving MG1 to generate power.

  The engine 100 is an “internal combustion engine” that outputs power using a hydrocarbon-based fuel such as gasoline or light oil. Engine 100 is stopped or started in accordance with a command from ECU 170. After the engine is started, engine control such as fuel injection control, ignition control, and intake air amount control is executed so that the engine 100 operates at an operating point (torque / rotational speed) determined by the ECU 170. The engine 100 is provided with various sensors for detecting the operating state of the engine 100 such as a crank angle of a crankshaft and an engine speed (not shown). These sensor outputs are transmitted to ECU 170 as necessary.

  Each of MG1 and MG2 is typically a three-phase AC rotating electric machine. MG1 generates power using the power of engine 100 divided by power split device 130. The electric power generated by MG1 is selectively used according to the running state of the vehicle and the SOC (State Of Charge) of battery 150. For example, during normal travel, the electric power generated by MG1 becomes the electric power for driving MG2 as it is. On the other hand, when the SOC of battery 150 is lower than a predetermined value, the electric power generated by MG1 is converted from AC to DC by an inverter described later. Thereafter, the voltage is adjusted by a converter described later and stored in the battery 150.

  When MG1 is acting as a generator, MG1 generates a negative torque. Here, the negative torque means a torque that becomes a load on engine 100. When MG1 receives power supply and acts as an electric motor, MG1 generates a positive torque. Here, the positive torque means a torque that does not become a load on the engine 100, that is, a torque that assists the rotation of the engine 100. The same applies to MG2. Typically, when engine 100 is started, MG1 outputs a positive torque for motoring engine 100.

  MG2 generates torque using at least one of the electric power stored in battery 150 and the electric power generated by MG1. The torque of MG2 is transmitted to the drive wheels 190 via the speed reducer 140. Thereby, MG2 assists engine 100 or causes the vehicle to travel by the driving force from MG2.

  At the time of regenerative braking of the hybrid vehicle, MG2 is driven by the drive wheel 190 via the speed reducer 140, and MG2 operates as a generator. Thus, MG2 operates as a regenerative brake that converts braking energy into electric power. The electric power generated by MG2 is stored in battery 150.

  Power split device 130 includes a planetary gear including a sun gear, a pinion gear, a carrier, and a ring gear. The pinion gear engages with the sun gear and the ring gear. The carrier supports the pinion gear so that it can rotate. The sun gear is connected to the rotation shaft of MG1. The carrier is connected to the crankshaft of engine 100. The ring gear is connected to the rotation shaft of MG 2 and the speed reducer 140.

  Engine 100, MG1 and MG2 are connected via power split mechanism 130 formed of planetary gears, so that the rotational speeds of engine 100, MG1 and MG2 are connected in a straight line in the collinear diagram as shown in FIG. It becomes a relationship.

  The hybrid vehicle shown in FIG. 1 basically travels only by the driving force of MG2 while the engine 100 is stopped in an operation region where the efficiency of the engine 100 is poor, such as at the time of starting or at a low vehicle speed. During normal traveling, engine 100 is operated in a highly efficient region, and power of engine 100 is divided into two paths by power split mechanism 130. The power transmitted to one path drives the drive wheels 190. The power transmitted to the other path drives MG1 to generate power. At this time, MG2 assists driving of driving wheel 190 by outputting torque using the generated power of MG1. Further, when driving at high speed, driving power is added to the driving wheels 190 by further increasing the torque of MG2 by supplying electric power from battery 150 to MG2.

  On the other hand, at the time of deceleration, MG2 driven by drive wheel 190 functions as a generator to generate power by regenerative braking. Electric power collected by regenerative power generation is charged in the battery 150. In addition, regenerative braking here means regenerative power generation by braking with regenerative power generation when a driver operating a hybrid vehicle has a foot brake operation or by turning off the accelerator pedal while driving without operating the foot brake. Including decelerating the vehicle (or stopping acceleration) while

  The battery 150 is an assembled battery composed of a plurality of secondary battery cells (not shown). The voltage of the battery 150 is about 200V, for example. Battery 150 may be charged by electric power supplied from an external power source of the vehicle in addition to electric power generated by MG1 and MG2.

  Engine 100, MG1 and MG2 are controlled by ECU 170. ECU 170 may be divided into a plurality of ECUs. ECU 170 is composed of a CPU (Central Processing Unit) (not shown) and an electronic control unit having a built-in memory, and performs arithmetic processing using detection values from each sensor based on a map and a program stored in the memory. Composed. Alternatively, at least a part of the ECU may be configured to execute predetermined numerical / logical operation processing by hardware such as an electronic circuit.

  FIG. 3 shows a configuration of an electric system for driving MG1 and MG2 shown in FIG.

  Referring to FIG. 3, the hybrid vehicle is provided with a converter 200, a first inverter 210 corresponding to MG1, a second inverter 220 corresponding to MG2, and an SMR (System Main Relay) 250.

  SMR 250 is provided between battery 150 and converter 200. When SMR 250 is opened, battery 150 is disconnected from the electrical system. On the other hand, when SMR 250 is closed, battery 150 is connected to the electrical system. Thereby, DC voltage VL corresponding to the output voltage of battery 150 is supplied to converter 200. The DC voltage VL is detected by the voltage sensor 182. The detection result of voltage sensor 182 is transmitted to ECU 170.

  The state of SMR 250 is controlled by ECU 170. For example, SMR 250 is closed in response to an on operation of a power-on switch (not shown) that instructs system activation of the hybrid vehicle, while SMR 250 is opened in response to an off operation of the power-on switch. The

  Converter 200 includes a reactor, two power semiconductor switching elements connected in series (hereinafter, also simply referred to as “switching elements”) Q1 and Q2, antiparallel diodes provided corresponding to the switching elements, Including reactors. As the power semiconductor switching element, an IGBT (Insulated Gate Bipolar Transistor), a power MOS (Metal Oxide Semiconductor) transistor, a power bipolar transistor, or the like can be appropriately employed.

  Reactor has one end connected to the positive electrode side of battery 150 and the other end connected to the connection point of switching elements Q1, Q2. On / off of each switching element Q1, Q2 is controlled by ECU 170. Hereinafter, the switching element Q1 is also referred to as an upper arm element, and the switching element Q2 is also referred to as a lower arm element.

  DC voltage VH (hereinafter also referred to as system voltage VH) between converter 200 and first inverter 210 and second inverter 220 is detected by voltage sensor 180. The detection result of voltage sensor 180 is transmitted to ECU 170.

  Converter 200 is configured to perform bidirectional DC voltage conversion between DC voltages VL and VH by on / off control of switching elements Q1 and / or Q2. Voltage conversion ratio (VH / VL) by converter 200 is controlled according to the duty ratio of switching elements Q1, Q2. Basically, the switching elements Q1 and Q2 are controlled to be turned on and off in a complementary manner and alternately in each switching period. In this way, DC voltage VH can be controlled in accordance with both charging and discharging of battery 150 without particularly switching the control operation of converter 200.

  When there is no need to boost DC voltage VH from DC voltage VL, switching elements Q1 and Q2 are fixed to ON and OFF, respectively, so that VH = VL (voltage conversion ratio = 1.0). You can also.

  First inverter 210 is formed of a general three-phase inverter and includes a U-phase arm, a V-phase arm, and a W-phase arm connected in parallel. Each of the U-phase arm, the V-phase arm, and the W-phase arm has two switching elements (upper arm element and lower arm element) connected in series. An antiparallel diode is connected to each switching element.

  MG1 has a star-connected U-phase coil, V-phase coil, and W-phase coil as stator windings. One end of each phase coil is connected to each other at a neutral point 112. The other end of each phase coil is connected to the connection point of the switching element of each phase arm of first inverter 210.

  When the vehicle travels, the first inverter 210 operates MG1 according to an operation command value (typically a torque command value) set to generate an output (vehicle drive torque, power generation torque, etc.) required for vehicle travel. In this manner, the current or voltage of each phase coil of MG1 is controlled. First inverter 210 converts bidirectionally DC power supplied from battery 150 into AC power and supplies it to MG1 and bidirectional power conversion operation that converts AC power generated by MG1 into DC power. Power conversion can be performed.

  Similar to the first inverter 210, the second inverter 220 is configured by a general three-phase inverter. Similar to MG1, MG2 has a star-connected U-phase coil, V-phase coil, and W-phase coil as stator windings. One end of each phase coil is connected to each other at a neutral point 122. The other end of each phase coil is connected to the connection point of the switching element of each phase arm of second inverter 220. Each of MG1 and MG2 is provided with a rotation angle sensor (typically a resolver) (not shown) for detecting the rotation position (angle) of a rotor (not shown). Based on the output of the rotation angle sensor, the rotation speeds of MG1 and MG2 can be detected.

  When the vehicle travels, the second inverter 220 has MG2 set according to an operation command value (typically a torque command value) set to generate an output (vehicle drive torque, regenerative braking torque, etc.) required for vehicle travel. The current or voltage of each phase coil of MG2 is controlled to operate. For the second inverter 220 as well, both a power conversion operation for converting DC power supplied from the battery 150 into AC power and supplying it to MG2, and a power conversion operation for converting AC power generated by MG2 into DC power. Direction power conversion is possible.

  FIG. 4 is a functional block diagram for explaining motor control in the hybrid vehicle according to the embodiment of the present invention. For each functional block shown in FIG. 4, a circuit (hardware) having a function corresponding to the block may be configured in the ECU 170, or realized by the ECU executing software processing according to a preset program. May be.

  Referring to FIG. 4, ECU 170 includes electric motor command calculation units 300 and 305, pulse width modulation units 310 and 315, a carrier frequency control unit 350, and carrier generation units 360 and 365.

  Electric motor command calculation unit 300 calculates a control command for first inverter 210 by feedback control of MG1. Here, the control command is a command value of voltage or current supplied to MG1 and MG2, which is controlled by each inverter 210 and 220. In the following, voltage commands Vu, Vv, Vw of each phase of MG1, MG2 will be exemplified as control commands. For example, electric motor command calculation unit 300 controls the output torque of MG1 by feedback of current Imt (1) of each phase of MG1. Specifically, electric motor command calculation unit 300 sets a current command value corresponding to torque command value Tqcom (1) of MG1, and also determines a voltage command according to the deviation between the current command value and current Imt (1). Vu, Vv, and Vw are generated. At this time, it is common to use a control calculation involving coordinate transformation (typically, dq axis transformation) using the rotation angle θ (1) of MG1.

  Similarly to the motor command calculation unit 300, the motor command calculation unit 305 generates a control command for the second inverter 220, specifically, the phase voltage commands Vu, Vv, and Vw for MG2 by feedback control of MG2. That is, voltage commands Vu, Vv, Vw are generated based on current mt (2) of MG2, rotation angle θ (2), and torque command value Tqcom (2).

  Based on the carrier signal 160 (1) from the carrier generator 360 and the voltage commands Vu, Vv, Vw from the electric motor command calculator 300, the pulse width modulator 310 controls the switching element control signal of the first inverter 210. S11 to S16 are generated. The control signals S11 to S16 control the on / off of the six switching elements that constitute the upper, lower, and lower arms of the first inverter 210.

  Similarly, the pulse width modulation unit 315 is configured to switch the switching element of the second inverter 220 based on the carrier signal 160 (2) from the carrier generation unit 365 and the voltage commands Vu, Vv, and Vw from the electric motor command calculation unit 305. Control signals S21 to S26 are generated. By the control signals S21 to S26, on / off of the six switching elements constituting the U-phase, V-phase, and W-phase upper and lower arms of the second inverter 220 is controlled.

  In the pulse width modulation units 310 and 315, PWM control is performed for comparing the carrier signal 160 (which generically refers to 160 (1) and 160 (2)) and the voltage commands Vu, Vv, and Vw.

FIG. 5 is a waveform diagram for explaining PWM control by the pulse width modulators 310 and 315.
Referring to FIG. 5, in PWM control, on / off of switching elements of each phase of the inverter is controlled based on voltage comparison between carrier signal 160 and voltage command 270 (a collective term for voltage commands Vu, Vv, and Vw). Is done. As a result, a pulse width modulation voltage 280 as a pseudo sine wave voltage is applied to each phase coil winding of MG1 and MG2. The carrier signal 160 can be composed of a periodic triangular wave or a sawtooth wave.

  Referring to FIG. 4 again, carrier frequency control unit 350 controls carrier frequency f1 used for PWM control in first inverter 210 and carrier frequency f2 used for PWM control of second inverter 220. Information regarding the state of engine 100 and the vehicle speed of the hybrid vehicle is input to carrier frequency control unit 350. The vehicle speed can be detected by an output signal of a vehicle speed sensor (not shown). Further, the state of the engine 100 includes information that can detect whether the engine 100 is in a stopped state / starting state / operating state (after the starting state), and the engine speed.

  Carrier generating section 360 generates carrier signal 160 (1) according to carrier frequency f 1 set by carrier frequency control section 350. Carrier generation unit 365 generates carrier signal 160 (2) according to carrier frequency f 2 set by carrier frequency control unit 350.

  That is, the frequencies of carrier signals 160 (1) and 160 (2) change according to carrier frequencies f 1 and f 2 set by carrier frequency control unit 350. As a result, the carrier frequency control unit 350 controls the switching frequency by PWM control in the first inverter 210 and the second inverter 220.

  In inverters 210 and 220, the switching elements shown in FIG. 3 are turned on and off according to the carrier frequency. For this reason, a harmonic current (ripple current) according to the switching frequency is superimposed on the current supplied from the inverters 210 and 220 to the MG1 and MG2.

  FIG. 6 is a conceptual waveform diagram for explaining the relationship between the carrier frequency and the ripple current.

Referring to FIG. 6, on / off of the switching element is controlled according to the carrier frequency so as to generate AC current 285 according to the control command value. Therefore, current 290 supplied to motor generators MG1 and MG2 has a waveform in which ripple current according to the switching frequency is superimposed on AC current 285. The magnitude ΔIrp of the ripple current is determined by the inductance of the current path and the switching period (reciprocal of the switching frequency). Therefore, it is understood that ΔIrp increases as the switching frequency decreases.
As ΔIrp increases, the current control error also increases. For this reason, when the carrier frequency is instantaneously lowered by random carrier control, there is a possibility that the controllability of the vehicle driving torque may be reduced due to an increase in current error.

  Due to the ripple current shown in FIG. 6, the electromagnetic force acting on MG1 and MG2 fluctuates at a cycle according to the switching frequency. On the other hand, a plurality of mechanical vibration systems based on a combination of mass elements and spring elements are formed by devices mounted on hybrid vehicles including MG1 and MG2. For example, in MG1 and MG2, there are a mechanical vibration system including a rotor as a mass element and a support bearing as a spring element, and a mechanical vibration system including a stator and a case. A mechanical vibration system is also configured by a transmission case or the like (not shown). These mechanical vibration systems vibrate by the action of external force and vibrations transmitted, and generate sound by vibrating air.

  In MG1 and MG2, the electromagnetic force acting between the stator and the rotor periodically varies according to the carrier frequency due to the ripple current, thereby generating vibrations in the mechanical vibration system of the rotor and the stator. Since this vibration is further transmitted to other mechanical vibration systems, sound (so-called electromagnetic noise) is generated by the vibrations of these mechanical vibration systems. Electromagnetic noise propagates outside the vehicle as an operating sound of the electric vehicle and also propagates into the passenger compartment.

  FIG. 7 is a conceptual diagram illustrating carrier frequency control (random carrier control) in each inverter 210, 220 in the hybrid vehicle according to the embodiment of the present invention. FIG. 7 illustrates control of the carrier frequency f1 of the inverter 210.

  Referring to FIG. 7, carrier frequency control unit 350 changes carrier frequency f <b> 1 within a predetermined frequency range 420 at a constant cycle or a random cycle as time elapses. The center value of the frequency range 420 is fa (center frequency), and the frequency control width is Δf. As a result, the upper limit value f1max of the carrier frequency is fa + Δf, and the lower limit value f1min is fa−Δf.

  The carrier frequency f1 is changed every time the change period Tr elapses within the frequency range of the upper limit value f1max to the lower limit value f1min. When Tr is a fixed value, the carrier frequency varies at a constant period. On the other hand, it is also possible to change the carrier frequency in a random cycle by changing Tr.

  FIG. 8 is a conceptual diagram showing a sound pressure level distribution of electromagnetic noise in the random carrier control shown in FIG.

  Referring to FIG. 8, reference numeral 400 indicates a frequency distribution of the sound pressure level when the carrier frequency f1 = fa is fixed. In this case, since the sound pressure level of the fixed frequency corresponding to the frequency fa becomes high, noise at the frequency is easily detected in the passenger compartment.

  On the other hand, reference numeral 410 denotes a frequency distribution of the sound pressure level when the carrier frequency f1 is varied in the frequency range from the lower limit value f1min to the upper limit value f1max as shown in FIG. If the level of electromagnetic noise generated at each carrier frequency is constant, by shortening the cycle of changing the carrier frequency (for example, about Tr = 2 to 10 [ms]), the frequency range for human hearing It is recognized as a sound with uniform intensity. As a result, as indicated by reference numeral 410, the sound pressure level can be dispersed within the frequency region, so that the sound pressure level of noise can be reduced.

  As described above, generally, the electromagnetic noise generated by the motor control by the inverter can be reduced by the random carrier control. When the random carrier control is executed, the frequency variation pattern is set in advance so that the average value of the carrier frequencies becomes the center frequency fa.

  As understood from FIG. 8, the sound pressure level of the electromagnetic noise decreases as the control width Δf is set wider, so that the electromagnetic noise is suppressed. On the other hand, since the lower limit value of the carrier frequency is also lowered, there is a concern that the current controllability (torque controllability) is lowered due to the carrier frequency reduction.

  On the other hand, as the control width Δf is set narrower, the sound pressure level of the electromagnetic noise becomes higher, so that the electromagnetic noise becomes relatively larger. On the other hand, a decrease in controllability associated with a decrease in carrier frequency is suppressed.

  FIG. 9 is a flowchart for illustrating a procedure of electric motor control in the hybrid vehicle according to the embodiment of the present invention. The control process shown in FIG. 9 is executed by the ECU 170 at a predetermined cycle. That is, each step described in each flowchart including FIG. 9 is realized by software processing and / or hardware processing by the ECU 170.

  Referring to FIG. 9, ECU 170 performs random carrier control for determining carrier frequencies in inverters 210 and 220 in step S100. The processing in step S100 corresponds to the function of the carrier frequency control unit 350 in FIG.

  FIG. 10 is a flowchart for explaining a first example of the processing procedure of step S100 (random carrier control) in FIG.

  Referring to FIG. 10, ECU 170 determines in step S110 whether engine 100 is stopped. Then, when the engine is stopped (when YES is determined in S110), ECU 170 proceeds to step S150 and sets the control width Δf = f1 of random carrier control.

  On the other hand, when the engine is not stopped (NO determination in S110), ECU 170 determines whether engine 100 is being started in step S120. During engine startup (when YES is determined in S120), ECU 170 sets control width Δf = f3 in step S160.

  On the other hand, after starting the engine, that is, during engine operation (when NO is determined in S120), ECU 170 proceeds to step S170 and sets the control width Δf = f2.

  A relationship of f1 <f2 <f3 is established between the control widths f1 to f3. That is, the control width Δf of random carrier control is set to be the narrowest while the engine is stopped. Note that, with f1 = 0, the random carrier control may be stopped and the carrier frequency may be fixed at the center frequency fa while the engine is stopped.

  While the engine is generating a small amount of vehicle noise, the electromagnetic noise is relatively increased by relatively narrowing the control width Δf. As a result, it is possible to improve the notification of approaching the vehicle to the surroundings of the vehicle. In the present invention, setting the frequency change range when the engine is stopped to be relatively narrow means that the random carrier control is executed when the engine is stopped, while the random carrier control is stopped while the engine is stopped (carrier frequency). The point that is a concept that includes fixing) is confirmed.

  Furthermore, when the engine is stopped, the vehicle travels only with the output of the motor generator MG2, but since the decrease in the carrier frequency due to the random carrier control is suppressed, the current controllability, that is, the decrease in the controllability of the vehicle driving torque is suppressed. can do.

  On the other hand, the control width Δf of the random carrier control is set to the widest during engine startup. During engine operation, the control width Δf of random carrier control is set to an intermediate width between when the engine is starting and when the engine is stopped.

  Since it is not necessary to increase the sound generated outside the vehicle except when the engine is stopped, the control range of the random carrier control is relatively widened to reduce the sound pressure level of electromagnetic noise in order to suppress in-vehicle noise. . In particular, when the engine is started at a low engine speed, the control width Δf of the random carrier control becomes the widest (Δf = f3). During engine operation, the control width Δf is an intermediate value between when the engine is stopped and when the engine is started (Δf = f2).

  FIG. 11 shows a second example of the processing procedure of step S100 (random carrier control) in FIG.

  Referring to FIG. 11, ECU 170 determines “whether the engine is stopped” and “whether the engine is starting” by steps S110 and S120 similar to FIG. Then, ECU 170 determines whether or not the vehicle speed of the hybrid vehicle is lower than a predetermined threshold value V1 in step S130 while the engine is stopped (YES in S110). This threshold value V1 is set in advance so that a low vehicle speed region where it is necessary to notify the approach of the vehicle to pedestrians and the like around the vehicle can be distinguished.

  ECU 170 sets Δf = f1 in step S155 when the vehicle speed is lower than V1 (when YES is determined in S120). Preferably, by setting f1 = 0 and stopping the random carrier control, the electromagnetic noise output to the outside of the vehicle can be increased at the low vehicle speed when the engine 100 is stopped.

  On the other hand, when vehicle speed> V1 (NO in S120), ECU 170 sets Δf according to the vehicle speed in step S152. Specifically, as the vehicle speed increases, the increase in road noise makes it difficult for electromagnetic noise to be detected in the vehicle interior, so Δf is set narrower. In step S152, the control width Δf is set in a range higher than f1 set in step S155.

  On the other hand, when the engine is not stopped (NO in S100) and the engine is running (YES in S120), ECU 170 executes step S160 similar to FIG. Δf = f3 is set. As in the case of FIG. 10, f3> f1.

  In contrast, ECU 170 proceeds to step S170 # after engine startup is completed, that is, during engine operation (when NO is determined in S120), and sets control width Δf in accordance with the engine speed. . Specifically, as the engine speed increases, electromagnetic noise is less likely to be detected in the passenger compartment due to an increase in operating noise, so Δf is set narrower. Control width Δf set in step S170 # is narrower than f3 set in step S160.

  As described above, through FIG. 10 and FIG. 11, the control width Δf in the random carrier control is variably set according to the state of the engine 100. Preferably, as shown in FIG. 11, the control width Δf is variably set to further reflect the vehicle speed of the hybrid vehicle.

  10 and 11, the frequency range determined by the control width set in step S160 during engine startup corresponds to the “first frequency range”. Similarly, the frequency range determined by the control width set in steps S150 to S155 while the engine is stopped corresponds to the “second frequency range”. Further, the frequency range determined by the control width set in steps S170 and S170 # during engine operation (after startup) corresponds to the “third frequency range”. The center frequency fa is preferably common between these first to third frequency ranges, but the center frequency in the first to third frequency ranges is changed according to conditions such as the state of the engine. Also good.

  Referring to FIG. 9 again, in step S200, ECU 170 generates carrier signals 160 (1) and 160 (2) according to carrier frequencies f1 and f2 determined in step S100. That is, the processing in step S200 corresponds to the functions of the carrier generation units 360 and 365 in FIG.

  In step S300, ECU 170 calculates control commands for first inverter 210 and second inverter 220. Typically, voltage commands Vu, Vv, Vw for each phase of the inverter are calculated as control commands. That is, the calculation in step S300 can be executed in the same manner as the motor command calculation units 300 and 305 in FIG.

  In step S400, ECU 170 generates an on / off control signal for the switching element of first inverter 210 by PWM control that compares the control command for first inverter 210 with carrier signal 160 (1). In step S400, an ON / OFF control signal for the switching element of the second inverter 220 is further generated by PWM control that compares the control command for the second inverter 220 with the carrier signal 160 (2). That is, the processing in step S400 can be executed in the same manner as the pulse width modulation units 310 and 315 in FIG.

  The first inverter 210 and the second inverter 220 that control MG1 and MG2 using the carrier frequency according to the random carrier control described in FIG. 10 or FIG. 11 by repeating the processes of steps S100 to S400 at a predetermined cycle. PWM control can be executed.

  As described above, in the hybrid vehicle according to the present embodiment, the carrier frequency change range (Δf) in the random carrier control is set according to the state of the engine. As a result, it is possible to discriminate between a vehicle state in which sound is positively output to the outside of the vehicle and a vehicle state in which noise detected in the vehicle interior is to be suppressed, and to appropriately execute random carrier control.

  Furthermore, by reducing the carrier frequency change range so that the noise is less likely to be detected in the passenger compartment depending on the vehicle speed, electromagnetic noise can be reduced while minimizing the disadvantages associated with the decrease in carrier frequency. Random carrier control can be appropriately performed so as to suppress sensing in the room.

  In the above embodiment, the random carrier control in the PWM control in inverters 210 and 220 has been described, but the same random carrier control can also be applied to converter 200.

  FIG. 12 is a conceptual waveform diagram for explaining the PWM control applied to the converter shown in FIG.

  Referring to FIG. 12, on / off of switching elements Q1, Q2 of converter 200 is controlled based on a comparison between carrier signal 165 and control voltage command value Vcnt. Control voltage command value Vcnt corresponds to a “control command” in converter control.

  The control voltage command value Vcnt is a value calculated by feedforward control and / or feedback control for making the system voltage VH coincide with the voltage command value. For example, feedforward control is executed based on a voltage ratio between the command value of DC voltage VH and DC voltage VL. Further, feedback control can be executed based on the deviation between the command value of the DC voltage VH and the detected value.

  In a section where the carrier signal 165 is higher in voltage than the control voltage command value Vcnt, the upper arm element Q1 is turned on (the lower arm element Q2 is off), while the control voltage command value Vcnt is more than the carrier signal 165. In the high voltage section, the lower arm element Q2 is turned on (the upper arm element Q1 is turned off).

  When control voltage command value Vcnt increases, the period during which lower arm element Q2 is turned on becomes longer, so that the boost ratio of converter 200 increases. That is, the system voltage VH increases. On the contrary, when the control voltage command value Vcnt is lowered, the period during which the upper arm element Q1 is turned on becomes longer, so that the boost ratio of the converter 200 is lowered. That is, the system voltage VH decreases. Thus, converter 200 can control system voltage VH by PWM control.

  In converter 200, a ripple current according to the frequency of carrier signal 165 passes through the reactor (FIG. 3). For this reason, the electromagnetic noise according to a carrier frequency may generate | occur | produce by the fluctuation | variation of the magnetic field which acts on a reactor resulting from a ripple current. On the other hand, carrier signal 165 used for control of converter 200 can be easily configured to arbitrarily control the carrier frequency, similarly to carrier signal 160 used for inverter control.

  Therefore, the random carrier control described in the present embodiment can also be applied to the PWM control of converter 200. That is, the frequency of the carrier signal 165 can be set similarly in accordance with the control process shown in FIG.

  Thus, with the configuration of the present embodiment (FIGS. 1 and 3), the above-described random carrier control can be applied to each of converter 200, inverter 210, and inverter 220. Random carrier control may be applied to only a part of converter 200, inverter 210, and inverter 220.

  In the present embodiment, the configurations of FIGS. 1 and 3 are exemplified as hybrid vehicles to which the random carrier control according to the present invention is applied, but the application of the present invention is not limited to such examples. That is, if the hybrid vehicle is equipped with an electric motor driven by a power converter (inverter and / or inverter) controlled by PWM control using a carrier signal and an engine, the configuration of the driving system different from that shown in FIG. The present invention can also be applied to a hybrid vehicle having the same. That is, the number of motors (motor generators) is not particularly limited, and it is confirmed that the present invention can be applied to a hybrid vehicle in which one or three or more motors are mounted. Describe.

  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.

  The present invention can be applied to a hybrid vehicle equipped with an electric motor driven by a power converter controlled by PWM control and an engine.

  100 Engine, 110 First motor generator (MG1), 112, 122 Neutral point, 120 Second motor generator (MG2), 130 Power split mechanism, 140 Reducer, 150 Battery, 160 (1), 160 (2), 165 carrier signal, 180 voltage sensor, 190 driving wheel, 200 converter, 210, 220 inverter, 270 voltage command, 280 pulse width modulation voltage, 285 AC current, 290 ripple current, 300, 305 motor command calculation unit, 310, 315 pulse Width modulation unit, 350 carrier frequency control unit, 360, 365 carrier generation unit, 420 frequency range (random carrier control), Q1 power semiconductor switching element (upper arm element), Q2 power semiconductor switching element (lower arm element), S11 ~ S16, S21 ~ S26 Control signal, Imt (1), Imt (2) Current (MG1, MG2), Tqcom (1), Tqcom (2) Torque command value, Tr change cycle (random carrier control), VH DC voltage (System voltage), VL DC voltage, Vcnt control voltage command value, Vu, Vv, Vw phase voltage command, Δf, f1-f3 control width, f1max carrier frequency upper limit value, f1min carrier frequency lower limit value, f1, f2 carrier frequency , Fa Center frequency.

Claims (8)

A hybrid vehicle equipped with an internal combustion engine and an electric motor,
A power converter configured to include at least one switching element disposed between a power storage device and the electric motor;
A control device for controlling the power converter,
The controller is
A carrier generating unit for generating a carrier signal used for on / off control of the switching element;
A carrier frequency control unit for controlling the frequency of the carrier signal generated by the carrier generation unit;
A pulse width modulation unit for controlling on / off of the switching element based on a comparison between the control command of the power converter and the carrier signal from the carrier generation unit;
The carrier frequency control unit varies the frequency of the carrier signal within a first frequency range centered on a predetermined frequency when the internal combustion engine is started, and includes the predetermined frequency when the internal combustion engine is stopped. Controlling the carrier generator to vary the frequency of the carrier signal within a second frequency range;
The hybrid vehicle, wherein the second frequency range is narrower than the first frequency range.   The hybrid vehicle according to claim 1, wherein the carrier frequency control unit fixes the frequency of the carrier signal when the internal combustion engine is stopped and the vehicle speed of the hybrid vehicle is lower than a predetermined speed. The carrier frequency control unit controls the carrier generation unit so as to vary the frequency of the carrier signal within a third frequency range centered on the predetermined frequency after the internal combustion engine is started.
3. The hybrid vehicle according to claim 1, wherein the third frequency range is set to become narrower as the rotational speed of the internal combustion engine is higher.   The carrier frequency control unit is configured to set the second frequency range to be narrower as the vehicle speed is higher when the internal combustion engine is stopped and the vehicle speed of the hybrid vehicle is higher than a predetermined speed. 1. The hybrid vehicle according to 1. A control method for a hybrid vehicle including an internal combustion engine, an electric motor, a power storage device, and a power converter disposed between the power storage device and the motor and configured to include at least one switching element. ,
Controlling the frequency of a carrier signal used for on / off control of the switching element;
Generating the carrier signal according to the frequency of the carrier signal determined by the controlling step;
Generating a signal for controlling on / off of the switching element based on a comparison between the control command of the power converter and the carrier signal;
The controlling step includes
Varying the frequency of the carrier signal within a first frequency range centered on a predetermined frequency when the internal combustion engine is started; and
Varying the frequency of the carrier signal within a second frequency range including the predetermined frequency when the internal combustion engine is stopped,
The method for controlling a hybrid vehicle, wherein the second frequency range is narrower than the first frequency range. The controlling step includes
Comparing the vehicle speed of the hybrid vehicle with a predetermined speed when the internal combustion engine is stopped;
The hybrid vehicle control method according to claim 5, further comprising: fixing the frequency of the carrier signal when the vehicle speed is lower than the predetermined speed when the internal combustion engine is stopped. The controlling step includes
After starting the internal combustion engine, further comprising the step of changing the frequency of the carrier signal within a third frequency range centered on the predetermined frequency;
The method for controlling a hybrid vehicle according to claim 5 or 6, wherein the third frequency range is set to become narrower as the rotational speed of the internal combustion engine is higher. The controlling step includes
Comparing the vehicle speed of the hybrid vehicle with a predetermined speed when the internal combustion engine is stopped;
6. The hybrid according to claim 5, further comprising a step of setting the second frequency range to be narrower as the vehicle speed is higher when the internal combustion engine is stopped and the vehicle speed is higher than a predetermined speed. Vehicle control method.

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