JP2010178556A - Motor drive system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor drive system capable of detecting an inverter one-phase open fault. <P>SOLUTION: A controller compares the detecting value of the DC current of a DC power supply by a current sensor and the estimate of the DC current arithmetically operated on the basis of the power incomings and outgoings of the whole motor drive system (steps S01 to S03). The controller detects the fluctuation of the DC current when a deviation between both the detecting value and the estimate exceeds a threshold (a YES decision time at the step S04). The controller decides whether the fluctuating frequency of the arithmetically operated DC current is synchronized with the rotational speed of a motor generator (the steps S06 to S08) when the fluctuating frequency of the DC current is operated arithmetically (the step S05). When the fluctuating frequency of the DC current is synchronized with the rotational speed of the motor generator in this case, the controller detects the generation of the one-phase open fault in an inverter (the steps S09 and S10). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a motor drive system, and more particularly to a technique for detecting occurrence of an inverter failure in a motor drive system that drives an AC motor.

  In recent years, an increasing number of vehicles use electric motors to drive electric vehicles such as electric vehicles and hybrid vehicles. In general, an inverter is used to drive such a motor.

  Japanese Patent Laying-Open No. 2005-143242 (Patent Document 1) discloses that a power semiconductor bridge of a power semiconductor power converter connected between a DC power supply and a multiphase AC power supply is turned on / off by itself in the reverse bridge. A configuration using a power semiconductor switch capable of performing the above and using a thyristor for the forward bridge is disclosed. In such a configuration, the load short circuit or the element abnormality is determined by the abnormal current determination unit from the measured value of the direct current of the direct current power supply and the measured value of the alternating current of the multiphase alternating current power supply.

JP 2005-143242 A JP 2007-89240 A JP 2005-160190 A

  Here, in the hybrid vehicle, a first rotating electric machine that mainly functions as a generator and a second rotating electric machine that mainly operates as a motor that drives wheels are mounted, and the engine speed is efficiently improved by a power split mechanism. There is also a system that controls the vehicle speed by controlling the first and second rotating electric machines while operating in a good rotational range.

  In an inverter for a vehicle having such a complicated configuration, when one of the two inverters has an open failure that is always in an off state in one of the inverters (hereinafter, inverter one-phase open) It was difficult to detect. Therefore, it has been difficult to realize a failure detection device that can detect when such an inverter single-phase open failure occurs.

  An object of the present invention is to provide a motor drive system capable of detecting an inverter one-phase open failure.

  The present invention is a motor drive system for driving an AC motor, and includes a DC power source, an inverter that receives power from the DC power source and drives the AC motor, and a current that detects a DC current input to and output from the DC power source. A sensor, a speed sensor for detecting the rotational speed of the AC motor, and a failure detection device for detecting occurrence of a failure in the inverter are provided. The inverter includes a plurality of arms each corresponding to each phase of the AC motor, and each of the plurality of arms includes two switching elements connected in series. The failure detection device includes a fluctuation frequency calculating means for calculating the fluctuation frequency of the direct current based on the detection value output from the current sensor, and the calculated fluctuation frequency of the direct current is converted into the rotational speed detected by the speed sensor. In the case of synchronization, open failure detecting means for detecting occurrence of an open failure in which one switching element included in any one of the plurality of arms is always in an OFF state is included.

  According to the present invention, it is possible to detect an inverter one-phase open failure that could not be detected in a conventional vehicle.

1 is an overall block diagram of a hybrid vehicle shown as an example of an electric vehicle on which a motor drive system according to an embodiment of the present invention is mounted. It is a wave form diagram for demonstrating the change of the voltage and electric current when the inverter is operating normally. It is a figure for demonstrating the inverter 1 phase open failure detected in this Embodiment. It is a wave form diagram for demonstrating the change of the voltage and electric current when an inverter 1 phase open failure generate | occur | produces. It is the flowchart which showed the detail of the abnormality detection process which the control apparatus of FIG. 1 performs. It is the flowchart which showed the detail of the driving | operation process at the time of abnormality which the control apparatus of FIG. 1 performs.

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

  FIG. 1 is an overall block diagram of a hybrid vehicle 100 shown as an example of an electric vehicle on which a motor drive system according to an embodiment of the present invention is mounted.

  Referring to FIG. 1, hybrid vehicle 100 includes an engine 4, motor generators MG <b> 1 and MG <b> 2, power split mechanism 3, and wheels 2. Hybrid vehicle 100 also includes DC power supply B, system relays SR1 and SR2, buck-boost converter 12, inverters 14 and 31, control device 30, capacitors C0 and C1, power lines PL1 and PL2, and ground line. SL, voltage sensors 10, 13, and 18, current sensors 11, 20, and 22 and rotation angle sensors (resolvers) 24 and 26 are further provided.

  This hybrid vehicle 100 runs using engine 4 and motor generator MG2 as power sources. Power split device 3 is coupled to engine 4 and motor generators MG1 and MG2 to distribute power between them. For example, as the power split mechanism 3, a planetary gear mechanism having three rotation shafts of a sun gear, a planetary carrier, and a ring gear can be used. These three rotary shafts are connected to the rotary shafts of engine 4 and motor generators MG1, MG2, respectively. For example, engine 4 and motor generators MG1 and MG2 can be mechanically connected to power split mechanism 3 by making the rotor of motor generator MG1 hollow and passing the crankshaft of engine 4 through its center. The rotation shaft of motor generator MG2 is coupled to wheel 2 by a reduction gear (not shown).

  Motor generator MG1 operates as a generator driven by engine 4 and is incorporated in hybrid vehicle 100 as an electric motor that can start engine 4, and motor generator MG2 drives wheels 2. As an electric motor, the hybrid vehicle 100 is incorporated.

  The DC power supply B is a chargeable / dischargeable power storage device, and is typically constituted by a secondary battery such as nickel hydride or lithium ion, an electric double layer capacitor, or the like. The DC voltage VB output from the DC power source B and the input / output DC current IB are detected by the voltage sensor 10 and the current sensor 11, respectively.

  System relay SR1 is connected between the positive terminal of DC power supply B and power line PL1, and system relay SR2 is connected between the negative terminal of DC power supply B and ground line SL. System relays SR1 and SR2 are turned on / off by signal SE from control device 30.

  Capacitor C1 smoothes voltage fluctuation between power line PL1 and ground line SL. Voltage sensor 13 is connected between power line PL1 and ground line SL, and detects the voltage at both ends of capacitor C1 (this DC voltage corresponding to the input voltage to buck-boost converter 12 is hereinafter also referred to as “input voltage”). Then, the detected input voltage VL is output to the control device 30.

  Buck-boost converter 12 includes a reactor L1, power semiconductor switching elements Q1, Q2, and diodes D1, D2. Power semiconductor switching elements Q1 and Q2 are connected in series between power line PL2 and ground line SL. On / off of power semiconductor switching elements Q1 and Q2 is controlled by switching control signal PWC from control device 30.

  In the embodiment of the present invention, an IGBT (Insulated Gate Bipolar Transistor), a power MOS (Metal Oxide Semiconductor) transistor, or a power bipolar transistor is used as a power semiconductor switching element (hereinafter simply referred to as “switching element”). Etc. can be used. Anti-parallel diodes D1, D2 are arranged for switching elements Q1, Q2. Reactor L1 is connected between a connection node of switching elements Q1 and Q2 and power line PL1. Smoothing capacitor C0 is connected between power line PL2 and ground line SL.

  Inverter 14 includes a U-phase arm 15, a V-phase arm 16, and a W-phase arm 17 provided in parallel between power line PL 2 and ground line SL. Each phase arm includes a switching element connected in series between power line PL2 and ground line SL. For example, U-phase arm 15 includes switching elements Q13 and Q14. V-phase arm 16 includes switching elements Q15 and Q16. W-phase arm 17 includes switching elements Q17 and Q18. Antiparallel diodes D13 to D18 are connected to switching elements Q13 to Q18, respectively. Switching elements Q13 to Q18 are turned on / off by a switching control signal PWM1 from control device 30.

  An intermediate point of each phase arm is connected to each phase end of each phase coil of motor generator MG1. Alternatively, motor generator MG1 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 31 includes a U-phase arm 25, a V-phase arm 26 and a W-phase arm 27. The configurations of inverter 31 and motor generator MG2 are the same as inverter 14 and motor generator MG1, respectively. Switching elements Q23 to Q28 are turned on / off by a switching control signal PWM2 from control device 30.

  In the step-up / down converter 12, the DC voltage VH obtained by boosting the DC voltage VB supplied from the DC power supply B (this DC voltage corresponding to the input voltage to the inverters 14, 31 is also referred to as “system voltage” hereinafter). ) To the power line PL2. Specifically, based on the switching control signal PWC from the control device 30, the DC voltage from the DC power source B is boosted by accumulating the current flowing according to the switching operation of the switching element Q2 as magnetic field energy in the reactor L1. . Then, the step-up / down converter 12 outputs the boosted boosted voltage to the power line PL2 via the anti-parallel diode D1 in synchronization with the timing when the switching element Q2 is turned off. Further, the step-up / step-down converter 12 charges the DC power supply B by stepping down the DC voltage supplied from the power line PL <b> 2 based on the switching control signal PWC from the control device 30.

  Smoothing capacitor C0 smoothes voltage fluctuation between power line PL2 and ground line SL. The voltage sensor 18 detects the voltage across the smoothing capacitor C 0, that is, the system voltage VH, and outputs the detected value to the control device 30.

  Inverter 14 converts a DC voltage received from power line PL2 into a three-phase AC voltage based on switching control signal PWM1 from control device 30, and outputs the converted three-phase AC voltage to motor generator MG1. Inverter 14 converts the three-phase AC voltage generated by motor generator MG1 using the output from engine 4 into a DC voltage based on switching control signal PWM1 from control device 30, and converts the converted DC voltage to a power line. Output to PL2.

  Inverter 31 converts a DC voltage received from power line PL2 into a three-phase AC voltage based on switching control signal PWM2 from control device 30, and outputs the converted three-phase AC voltage to motor generator MG2. In addition, during regenerative braking of hybrid vehicle 100, inverter 31 uses a three-phase AC voltage generated by motor generator MG <b> 1 using the output from engine 4 as the rotational force from wheel 2 as switching control signal PWM <b> 1 from control device 30. Based on this, the voltage is converted to a DC voltage, and the converted DC voltage is output to power line PL2.

  Each of motor generators MG1 and MG2 is a three-phase AC motor, for example, an IPM (Interior Permanent Magnet) type three-phase AC synchronous motor. Motor generator MG <b> 1 is connected to engine 4 by power split mechanism 3, generates a three-phase AC voltage using the output from engine 4, and outputs the generated three-phase AC voltage to inverter 14. Motor generator MG <b> 1 generates driving force by the three-phase AC voltage received from inverter 14 and starts engine 4. Motor generator MG <b> 2 is connected to wheel 2 and generates a driving torque of the vehicle by a three-phase AC voltage received from inverter 31. Motor generator MG2 generates a three-phase AC voltage and outputs it to inverter 31 during regenerative braking of the vehicle.

  Current sensor 20 detects motor current MCRT1 flowing through motor generator MG1 and outputs the detected value to control device 30. Current sensor 22 detects motor current MCRT2 flowing through motor generator MG2, and outputs the detected value to control device 30. Since the sum of instantaneous values of the three-phase currents iu, iv and iw is zero, the current sensors 20 and 22 have two-phase motor currents (for example, V-phase current iv and W-phase current as shown in FIG. 1). It is sufficient to arrange so that iw) is detected.

  The rotation angle sensor (resolver) 24 detects the rotor rotation angle θ1 of the motor generator MG1, and sends the detected rotation angle θ1 to the control device 30. The rotation angle sensor 26 detects the rotor rotation angle θ2 of the motor generator MG2, and sends the detected rotation angle θ2 to the control device 30. Control device 30 can calculate rotational speeds (rotational speeds) MRN1, MRN2 and angular speeds ω1, ω2 (rad / s) of motor generators MG1, MG2 based on rotational angles θ1, θ2. The rotation angle sensors 24 and 26 may be omitted by directly calculating the rotation angles θ1 and θ2 from the motor voltage and current by the control device 30.

  The control device 30 is configured by an electronic control unit (ECU), and is driven by a motor by software processing by executing a program stored in advance by a CPU (not shown) and / or hardware processing by a dedicated electronic circuit. Control system operation.

  As a representative function, control device 30 is based on torque command values TR1 and TR2 of motor generators MG1 and MG2, motor rotational speeds MRN1 and MRN2, input voltage VL from voltage sensor 13, and system voltage VH from voltage sensor 18. Then, a signal PWC for driving the step-up / down converter 12 is generated, and the generated signal PWC is output to the step-up / down converter 12.

  Control device 30 generates signal PWM1 for driving motor generator MG1 based on system voltage VH, torque command value TR1, motor current MCRT1 from current sensor 20, and rotor rotation angle θ1 of motor generator MG1. The generated signal PWM1 is output to the inverter 14. Further, control device 30 generates signal PWM2 for driving motor generator MG2 based on system voltage VH, torque command value TR2, motor current MCRT2 from current sensor 22, and rotor rotation angle θ2 of motor generator MG2. The generated signal PWM2 is output to the inverter 31.

  Further, control device 30 executes “abnormality detection processing” for detecting the occurrence of a one-phase open failure in inverters 14 and 31 by the method described later during execution of drive control of motor generators MG1 and MG2 described above. To do. When a one-phase open failure is detected in either one of the inverters 14 and 31 in this abnormality detection process, the control device 30 operates in an abnormality using the motor generator corresponding to the other inverter (evacuation operation). ). Thereby, the movement distance by evacuation operation can be extended.

  FIG. 2 is a waveform diagram for explaining changes in voltage and current when the inverter 14 is operating normally. Although illustration is omitted, even when the inverter 31 is operating normally, changes in voltage and current as shown in FIG. 2 can be obtained.

  Referring to FIG. 2, in inverter 14 driving motor generator MG1, when all six switching elements Q11-Q16 are normal, three-phase current (V-phase current MG1_V, W-phase) constituting motor current MCRT1 Current MG1_W and U-phase current MG1_U) indicate AC waveforms having a constant amplitude. V phase current MG1_V and W phase current MG1_W each have a phase difference of + 120 ° or −120 ° with respect to U phase current MG1_U.

  At this time, the input voltage VL and the system voltage VH are maintained at substantially constant values. As a result, the DC current IB is also maintained at a substantially constant value.

  FIG. 3 is a diagram for explaining an inverter one-phase open failure detected in the present embodiment.

  Referring to FIG. 3, in inverter 14 driving motor generator MG1, a failure in which any of six switching elements Q11 to Q16 is broken and fixed in an off state is referred to as an inverter one-phase open failure. . FIG. 3 illustrates a case where the switching element Q13 of the V-phase arm 16 is broken. In addition, one of the six phases of the inverter 14 may not move due to a drive IC failure, a photocoupler failure, a broken connection, or the like.

  FIG. 4 is a waveform diagram for explaining changes in voltage and current when an inverter one-phase open failure occurs.

  Referring to FIG. 4, when an open failure occurs in the V phase, a state in which the V phase current MG1_V does not swing in the + direction is shown. As a result, the power fluctuation of motor generator MG1 increases, so that the boost control of buck-boost converter 12 cannot follow, and the amplitudes of system voltage VH and input voltage VL increase. As a result, the amplitude of the direct current IB also increases. That is, when a one-phase open failure occurs, one phase of the motor generator current becomes a half wave. Thereby, since the voltage VH oscillates, the amplitude of the direct current IB increases.

  FIG. 5 is a flowchart showing details of the abnormality detection process executed by the control device 30 of FIG. The flowchart shown in FIG. 5 is executed as a series of control processes programmed in the control device 30 shown in FIG.

  Referring to FIG. 5, when the process is started, control device 30 obtains a detected value of DC current IB by current sensor 11 (step S01), and changes in DC current IB based on the obtained detected value. The presence or absence of is determined.

  Specifically, first, the control device 30 calculates a power balance P of the entire motor drive system (FIG. 1), and calculates an estimated value IB (E) of the direct current based on the calculated power balance P. (Step S02).

Here, in hybrid vehicle 100, input / output power of motor generator MG1 that basically operates as a generator (hereinafter also referred to as MG1 power) and motor generator that basically operates as a motor for generating vehicle driving force. The power balance is such that the excess or deficiency of power in the whole motor generators MG1 and MG2 shown by the sum of the input / output power of MG2 (hereinafter also referred to as MG2 power) is covered by the input / output power of DC power supply B Composed. Therefore, in this power balance control, the input / output power PB of the DC power source B can be calculated according to the following equation (1).
PB = Pm1 + Pm2 + Ploss (1)
In the equation (1), Pm1 is MG1 power, Pm2 is MG2 power, and Ploss is a loss generated in inverters 14 and 31 and motor generators MG1 and MG2. MG1 electric power Pm1 can be estimated based on the operating state (torque command value TR1 and rotational speed MRN1) of motor generator MG1, and MG2 electric power Pm2 can be estimated based on the operating state (torque command value TR2 and rotational speed) of motor generator MG2. It can be estimated on the basis of the speed MRN2). The power balance control is executed so that the input / output power PB in the above equation (1) is within the range of the input / output possible powers Win and Wout of the DC power supply B.

When the input / output power PB of the DC power supply B is calculated, the control device 30 estimates the DC current IB according to the following equation (2) based on the input voltage VL detected by the voltage sensor 13.
PB = VL × IB (2)
When estimated value IB (E) is calculated in this way, control device 30 compares the detected value of DC current IB with estimated value IB (E) (step S03). Then, it is determined whether or not the deviation ΔIB (= | IB−IB (E) |) obtained by this comparison is greater than or equal to a threshold (step S04). If the deviation ΔIB is smaller than the threshold (NO in step S04). At the time of determination), control device 30 determines that fluctuation in DC current IB has not occurred, and ends a series of abnormality detection processing.

  On the other hand, when deviation ΔIB is equal to or larger than the threshold value (when YES is determined in step S04), control device 30 detects the fluctuation of DC current IB and calculates the fluctuation frequency fc of DC current IB (step S05). .

  As one method for calculating the fluctuation frequency fc, the control device 30 compares the detected value of the direct current IB and the estimated value IB (E) during a predetermined period, and generates a signal indicating the comparison result. To do. This comparison result signal indicates an H (logic high) level during a period in which the detected value of the direct current IB is equal to or greater than the estimated value IB (E), and L (in a period during which the detected value is less than the estimated value IB (E). Generated to indicate a logic low) level. Then, control device 30 refers to the generated comparison result signal and calculates fluctuation frequency fc of DC current IB based on the time between the timings when the signal rises from the L level that is temporally adjacent to the H level.

  Next, when control device 30 obtains rotational speed MRN1 of motor generator MG1 and rotational speed MRN2 of motor generator MG2 (step S06), fluctuation frequency fc of DC current IB calculated in step S05 is the rotational speed of motor generator MG1. It is determined whether or not it is synchronized with the speed MRN1 (step S07). When fluctuation frequency fc of DC current IB is synchronized with rotation speed MRN1 of motor generator MG1 (when YES is determined in step S07), control device 30 detects the occurrence of a one-phase open failure in inverter 14. (Step S09).

  On the other hand, when fluctuation frequency fc of DC current IB calculated in step S05 is not synchronized with rotation speed MRN1 of motor generator MG1 (when NO is determined in step S07), control device 30 further It is determined whether or not fluctuation frequency fc of DC current IB is synchronized with rotation speed MRN2 of motor generator MG2 (step S08). When fluctuation frequency fc of DC current IB is synchronized with rotation speed MRN2 of motor generator MG2 (when YES is determined in step S08), control device 30 detects the occurrence of a one-phase open failure in inverter 31. Then, the control process related to abnormality detection is terminated (step S10).

  As described above, it is possible to detect the inverter one-phase open failure by detecting the fluctuation of the direct current IB. When an inverter one-phase open failure is detected, the operation of the corresponding motor generator is stopped, and an abnormal operation (retreat operation) is performed using the motor generator corresponding to the other inverter. Thereby, the movement distance by evacuation operation can be extended.

  FIG. 6 is a flowchart showing details of the abnormal operation process executed by the control device 30 of FIG. The flowchart shown in FIG. 6 is executed as a series of control processes subsequent to the abnormality detection process shown in FIG.

  Referring to FIG. 6, when the process is started, control device 30 determines whether or not a one-phase open failure has been detected in inverter 14 (step S11). When a one-phase open failure is detected in inverter 14 (YES in step S11), control device 30 issues a gate cutoff instruction for each of switching elements Q11 to Q16 constituting inverter 14 (step S13). Thereby, each of Q11-Q16 of inverter 14 stops switching operation (OFF state). Then, control device 30 instructs operation at the time of abnormality (retreat operation) by motor generator MG2 (step S14).

  On the other hand, when the one-phase open failure is not detected in the inverter 14 (when NO is determined in step S11), the control device 30 determines whether or not the one-phase open failure is detected in the inverter 31. (Step S12). When a one-phase open failure is detected in inverter 31 (when YES is determined in step S12), control device 30 issues a gate cutoff instruction for each of switching elements Q21 to Q26 constituting inverter 31 (step S15). ), The switching operation of each of Q21 to Q26 of the inverter 31 is stopped (OFF state). And the control apparatus 30 instruct | indicates the evacuation driving | operation using the motive power by the engine 4 (step S16).

  On the other hand, when the one-phase open failure is not detected in inverter 31 (when NO is determined in step S12), control device 30 ends the control process related to the evacuation operation without instructing the evacuation operation.

  As described above, in the embodiment of the present invention, when an inverter one-phase open failure occurs, the system voltage VH causes hunting, so that the DC current IB input to and output from the DC power source B varies. Therefore, when the fluctuation of the direct current IB is detected and the fluctuation frequency is synchronized with the rotation speed of the motor generator, an inverter one-phase open failure is issued. By doing so, it is possible to minimize the influence on the motor generator (such as demagnetization of the permanent magnet) by detecting the inverter one-phase open failure at an early stage.

  Further, when an inverter one-phase open failure is detected, an abnormal operation (evacuation operation) using a motor generator corresponding to the other inverter becomes possible. Thereby, the movement distance by evacuation operation can be extended.

  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.

  2 wheel, 3 power split mechanism, 4 engine, 10, 13, 18 voltage sensor, 11, 20, 22 current sensor, 12 buck-boost converter, 14, 31 inverter, 15, 25 U-phase arm, 16, 26 V-phase arm , 17, 27 W phase arm, 24, 26 rotation angle sensor, 30 control device, 100 hybrid vehicle, B DC power supply, C0, C1 capacitor, D1, D2, D11-D16, D21-D26 anti-parallel diode, MG1, MG2 Motor generator, PL1, PL2 power line, Q1, Q2, Q11 to Q16, Q21 to Q26 Power semiconductor switching element, SL ground line, SR1, SR2 System relay.

Claims (1)

A motor drive system for driving an AC motor,
DC power supply,
An inverter that receives power from the DC power supply and drives the AC motor;
A current sensor for detecting a direct current input to and output from the direct current power source;
A speed sensor for detecting the rotational speed of the AC motor;
A failure detection device for detecting a failure occurrence in the inverter;
The inverter includes a plurality of arms each corresponding to each phase of the AC motor, and each of the plurality of arms includes two switching elements connected in series,
The failure detection device is:
Based on a detection value output from the current sensor, a fluctuation frequency calculating means for calculating a fluctuation frequency of the direct current;
When the calculated fluctuation frequency of the direct current is synchronized with the rotation speed detected by the speed sensor, one switching element included in any one of the plurality of arms A motor drive system including open failure detection means for detecting occurrence of an open failure that is always in an off state;

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