JP2014121172A - Failure detection device for power conversion system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly detect a failure of an inverter while preventing damage of a booster due to an overcurrent.SOLUTION: If an overcurrent of a booster 7 occurs, all switching elements 13 in an inverter 5 are temporarily controlled to be an off state in a forced stop period. Failure determination means 51b determines failure occurrence by: measuring a cumulative time period during which an amount of a current deviation between a detected current value and a target value for a motor 2 is maintained at or above the amount of the threshold value for determination, before and after occurrence of an overcurrent state except a forced stop period, in the case that the overcurrent state occurs while measuring a time period in which the amount of the current deviation between the detected current value and the target value for the motor 2 is maintained at or above the amount of the threshold value for determination; and by determining that the measured cumulative time period is at or above a reference time.

Description

  The present invention relates to an apparatus for detecting a failure in a power conversion system for operating a rotating electrical machine.

  When controlling the operation of a rotating electrical machine such as an electric motor, the inverter having a switching element on the upper arm and the lower arm performs DC / AC power conversion while energizing the rotating electrical machine (the power between the rotating electrical machine and the DC power source). A system that performs transmission) has been generally used.

  In this type of system, as described in Patent Document 1, for example, a method of detecting a failure of an inverter based on a deviation between a detected value of a phase current of a rotating electrical machine and a target value is known.

Japanese Patent No. 3291390

  By the way, in order to operate the rotating electrical machine in a wide range of rotation speed, a booster (DC / DC converter) is connected to the DC power input / output terminal of the inverter, and the DC voltage input / output to the DC power input / output terminal of the inverter is variable. In some cases.

  Thus, in a system including a booster, for example, when the load of the rotating electrical machine is suddenly reduced (for example, when an idling slip of a wheel driven by the rotating electrical machine), the current flowing through the booster may be excessive.

  In this case, since the booster may be damaged, when the current flowing through the booster is detected and the current becomes excessive, all the switching elements of the inverter are quickly turned off. It is desirable to keep the off-state temporarily (temporarily cut off energization of the rotating electrical machine) so that an excessive current does not continue to flow through the booster.

  On the other hand, it has been clarified through various experiments and examinations by the inventor of the present application that the phenomenon that an excessive current flows through the booster occurs not only when the load of the rotating electrical machine suddenly decreases but also when the inverter fails. For example, in a situation in which any switching element of the inverter cannot be turned on (turned on) from the off state due to disconnection of the control signal line of the inverter, the switching element is turned off (from the on state). There is a case where an excessive current instantaneously flows to the booster at a timing when the power is turned off.

  Since such a situation is a situation in which an inverter failure has occurred, unlike the case of a sudden decrease in the load on the rotating electrical machine, measures such as stopping or restricting the operation of the rotating electrical machine are detected by detecting the failure. Is desirable.

  In this case, it is conceivable to detect a failure of the inverter by a technique similar to the technique found in Patent Document 1.

  However, in the situation where the current flowing through the booster is excessive, there is a possibility that the following inconvenience may occur if an attempt is made to detect the failure of the inverter in the same manner as the situation where the current flowing through the booster does not become excessive.

  In other words, the situation where the current flowing through the booster is excessive is not necessarily the situation where the inverter has failed, so quickly turn off all switching elements of the inverter to prevent the booster from being damaged. It is desirable to be in a state.

  However, the situation where all the switching elements of the inverter are turned off is a situation where the target value of the energization current of the rotating electrical machine becomes zero and the detected value of the current becomes very small. It is difficult to detect the deviation between the target value of the current and the detected value with high reliability due to the influence of a noise component included in the value. As a result, there has been a risk of erroneously detecting an inverter failure.

  The present invention has been made in view of such a background, and provides a failure detection device for a power conversion system that can appropriately detect a failure of an inverter while preventing a booster from being damaged by an excessive current. The purpose is to do.

In order to achieve this object, the failure detection apparatus for a power conversion system according to the present invention is connected to an inverter configured to have switching elements in an upper arm and a lower arm, and a DC power input / output terminal of the inverter. A booster; a rotating electrical machine connected to an AC power input / output terminal of the inverter; a first current sensor that detects a rotating electrical machine side current that is a current flowing between the inverter and the rotating electrical machine; and the booster A failure detection device for detecting a failure in a power conversion system including a second current sensor that detects a booster side current that is a current flowing through
In the inverter, when an overcurrent state occurs in which the magnitude of the detected value of the booster side current indicated by the output of the second current sensor is equal to or greater than a predetermined overcurrent determination value, all of the inverters Inverter control means configured to temporarily control the switching element in an off state is connected,
The deviation between the detected value of the rotating electrical machine side current and the target value of the rotating electrical machine side current indicated by the output of the first current sensor is inputted with the output of the 1 current sensor and the target value of the rotating electrical machine side current. Failure determination means for measuring the time during which the magnitude of the inverter is maintained above a predetermined failure determination threshold and determining that the inverter has failed when the measured value of the time exceeds a predetermined reference time With
When the overcurrent state occurs when the failure determination unit is measuring the time during which the magnitude of the deviation is maintained to be equal to or greater than the failure determination threshold, the inverter control unit performs the Except for the inverter operation forced stop period during which all switching elements of the inverter are controlled to be in the OFF state, the magnitude of the deviation before or after the inverter operation forced stop period is greater than or equal to the failure determination threshold value. It is configured to accumulate and measure the maintained time (first invention).

  According to the first invention, when the overcurrent state occurs, all the switching elements of the inverter are temporarily set by the inverter control means regardless of whether or not the inverter is operating normally. Is controlled to be turned off automatically. As a result, excessive current continues to flow through the booster, and the booster is prevented from being damaged.

  On the other hand, when the magnitude of the deviation becomes greater than or equal to the failure determination threshold, the failure determination means starts measuring the time during which the magnitude of the deviation is maintained at or greater than the failure determination threshold.

  In this case, when the inverter is operating normally, the situation in which the magnitude of the deviation is greater than or equal to the threshold value for failure determination is temporarily shorter than the reference time.

  On the other hand, when the inverter has failed, if the control of each switching element of the inverter is continued in the same form as when the inverter is normal, the magnitude of the deviation is basically determined by the failure determination. It will be continuously maintained at a size equal to or greater than the threshold for use.

  However, when the overcurrent state occurs, as described above, all the switching elements of the inverter are controlled to be temporarily turned off by the inverter control means.

  And, in such a state that all the switching elements of the inverter are controlled to be temporarily turned off, the target value of the rotating electrical machine side current is set to zero. Even if it is operating normally, a situation in which the magnitude of the deviation is greater than or equal to the failure determination threshold is likely to occur due to the influence of a noise component or the like mixed in the rotating electrical machine side current detected by the first current sensor. Become.

  For this reason, the deviation in the period in which all the switching elements of the inverter are controlled to be temporarily turned off, that is, the inverter operation forced stop period, is used as data for determining the presence or absence of an inverter failure. Is unreliable.

  Therefore, it is not preferable to use the deviation in the inverter operation forced stop period as data for determining whether or not the inverter has failed.

  Here, it is assumed that the overcurrent state occurs while measuring the time during which the magnitude of the deviation is maintained to be equal to or greater than the failure determination threshold. In this case, in the situation where the overcurrent state occurs due to the failure of the inverter, the overcurrent state due to the failure of the inverter may occur again after the inverter operation forced stop period ends. High nature.

  For this reason, when the overcurrent state occurs while measuring the time during which the magnitude of the deviation is maintained to be equal to or greater than the failure determination threshold, the inverter operation forced stop period In order not to use the deviation as data for determining whether or not there is a failure in the inverter, the measurement of the time is temporarily stopped and the measurement value is reset (in other words, the deviation after the suspension is determined). When the time is started again after the failure determination threshold value is greater than or equal to the failure determination threshold value, the overcurrent state has occurred due to the failure of the inverter. In such a situation, each time the overcurrent state occurs, the measured value of the time is reset, and the measured value may not reach the reference time. As a result, there is a possibility that the occurrence of the failure of the inverter cannot be detected.

  Therefore, in the first invention, when the overcurrent state occurs when the failure determination means is measuring a time during which the magnitude of the deviation is maintained to be equal to or greater than the failure determination threshold value. Except for the inverter operation forced stop period, and cumulatively measure the time during which the magnitude of the deviation is maintained at or above the failure determination threshold before and after the inverter operation forced stop period.

  Therefore, when the overcurrent state occurs in the state where the time is being measured, the failure determination unit is configured to reduce the time during the inverter operation stop period during which the deviation is likely to be affected by a noise component or the like. The measurement of the time is interrupted while the measurement value is held at the value until the start of the inverter operation stop period, and the inverter operation is performed without resetting the measurement value of the time after the end of the inverter operation stop period. The measurement of the time is continued from the measurement value before the stop period as a starting point.

  Here, when the inverter is in failure, the magnitude of the deviation is maintained to be equal to or greater than the failure determination threshold before and after the inverter operation stop period (a period other than the inverter operation stop period). Therefore, by measuring the time as described above, the measured value of the time finally reaches the reference time. As a result, the failure determination means determines that the inverter has failed.

  In addition, when the inverter has not failed, the magnitude of the deviation is basically determined after the end of the inverter operation stop period and before the measured value of the time reaches the reference time. It becomes smaller than the threshold for determination. As a result, it will not be determined that the inverter has failed.

  Therefore, according to the first aspect of the invention, it is possible to appropriately detect a failure of the inverter while preventing the booster from being damaged by an excessive current.

  In the first aspect of the invention, the failure determination means needs that the target value of the output torque of the rotating electrical machine or the target value of the amplitude of the rotating electrical machine side current corresponding to the target value is not less than a predetermined value. The condition is configured to measure the time, and during the time measurement, the overcurrent state does not occur, and the output torque target value of the rotating electrical machine or the target value corresponding to the target value. When the target value of the amplitude of the rotating electrical machine side current becomes smaller than the predetermined value, it is preferable to stop the measurement of the time and reset the measurement value of the time (second invention). .

  That is, in the case where the target value of the output torque of the rotating electrical machine or the target value of the amplitude of the rotating electrical machine side current corresponding to the target value is sufficiently small, similarly to the inverter operation forced stop period. Even when the inverter is operating normally, there is a situation in which the deviation is greater than or equal to the failure determination threshold value due to the influence of noise components mixed in the rotating electrical machine side current detected by the first current sensor. It becomes easy.

  Therefore, in the second aspect of the invention, the failure determination means determines that the target value of the output torque of the rotating electrical machine or the target value of the amplitude of the rotating electrical machine side current corresponding to the target value is greater than or equal to a predetermined value. As a necessary condition, the time is measured.

  For this reason, a situation where the target value of the output torque of the rotating electrical machine or the target value of the amplitude of the rotating electrical machine side current corresponding to the target value is smaller than the predetermined value, that is, the deviation is a noise component or the like. In a situation that is easily affected, even if the deviation is greater than or equal to the failure determination threshold, the failure determination means does not start measuring the time.

  In addition, the failure determination means may be configured such that a target value of the output torque of the rotating electrical machine or a target of the amplitude of the rotating electrical machine side current corresponding to the target value without the occurrence of the overcurrent state during the measurement of the time. When the magnitude of the value becomes smaller than the predetermined value, the time measurement is stopped and the time measurement value is reset.

  Therefore, according to the second aspect of the present invention, in a situation where an overcurrent state does not occur, the target value of the output torque of the rotating electrical machine or the target value of the amplitude of the rotating electrical machine side current corresponding to the target value is the predetermined value. When the value is continuously maintained over the value (at least continuously over the reference time), that is, the situation in which the deviation is highly reliable as data according to the presence or absence of the failure of the inverter is continuous. When the operation is continued, the time measurement is continuously performed.

  For this reason, according to the second aspect of the invention, in addition to being able to properly detect the failure of the inverter in a situation where an overcurrent state occurs, the failure of the inverter is highly reliable even in a situation where no overcurrent state occurs. Can be detected appropriately by sex.

  In the first invention or the second invention, the failure determination means performs a first failure determination according to a target value of the output torque of the rotating electrical machine or a target value of the amplitude of the rotating electrical machine side current corresponding to the target value. Means for variably determining a threshold value for use, and means for determining a second threshold value for failure determination by applying a low-pass characteristic filtering process to the first failure determination threshold value. The second failure determination threshold is used as a failure determination threshold to be compared with the magnitude of the deviation after the inverter operation forcible stop period ends for a predetermined period after the occurrence of the non-predetermined period. In the period, it is preferable that the first failure determination threshold is used as a failure determination threshold to be compared with the magnitude of the deviation (third invention).

  That is, basically, the greater the target value of the output torque of the rotating electrical machine or the target value of the amplitude of the rotating electrical machine side current corresponding to the target value, the more the inverter Even when operating normally, the magnitude of the deviation tends to increase. Therefore, the failure determination threshold value can basically be variably set according to the target value of the output torque of the rotating electrical machine or the target value of the amplitude of the rotating electrical machine side current corresponding to the target value. preferable.

  However, when the overcurrent state occurs, all the switching elements of the inverter are controlled to be temporarily turned off, so that the overcurrent state is caused by a failure of the inverter or the like. In a situation that occurs frequently, the target value of the output torque of the rotating electrical machine or the target value of the amplitude of the rotating electrical machine-side current corresponding to the target value frequently fluctuates and is set according to the target value. The failure determination threshold value fluctuates frequently. As a result, the reliability of the comparison result between the failure determination threshold value and the magnitude of the deviation may be impaired.

  Therefore, in the third invention, the failure determination means uses the first threshold as a failure determination threshold value to be compared with the magnitude of the deviation after the end of the inverter operation forced stop period for a predetermined period after the occurrence of the overcurrent state. 2 is low-passed to the first failure determination threshold value determined according to the target value of the output torque of the rotating electrical machine or the target value of the amplitude of the rotating electrical machine side current corresponding to the target value. The value obtained by performing the characteristic filtering process is used.

  Further, the failure determination means uses the first failure determination threshold as a failure determination threshold to be compared with the magnitude of the deviation in a period other than the predetermined period in which the second failure determination threshold is used.

  Thus, in a situation where the overcurrent state does not occur, an appropriate failure determination threshold value corresponding to the target value of the output torque of the rotating electrical machine or the target value of the amplitude of the rotating electrical machine side current corresponding to the target value (First failure determination threshold value) can be used to determine whether or not an inverter failure has occurred.

  Further, in a situation where the overcurrent state frequently occurs, the stability of the failure determination threshold (second failure determination threshold) is increased, and as a result, the stability of the comparison result with the deviation is increased. Can do. As a result, it is possible to improve the reliability of the determination result of the presence or absence of the failure of the inverter in a situation where the overcurrent state frequently occurs.

The figure which shows the structure of the power conversion system of one Embodiment of this invention. The block diagram which shows the process of the failure detection part shown in FIG. The graph which shows the example of a waveform for demonstrating the process of the failure detection part shown in FIG. The graph which shows the example of a waveform for demonstrating the process of the failure detection part shown in FIG.

  An embodiment of the present invention will be described below with reference to FIGS.

  As shown in FIG. 1, a power conversion system 1 according to the present embodiment generates a traction motor 2 (hereinafter simply referred to as a motor 2) as a rotating electrical machine for generating a driving force (powering torque) and generates electric power. This is a system for operating the generator 3 as a rotating electric machine.

  This power conversion system 1 is mounted on, for example, an electric vehicle. In this case, the motor 2 is used as a power source for running the vehicle. In order to transmit the torque generated by the motor 2 to the drive wheels of the vehicle, the rotor of the motor 2 is connected to the drive wheels of the vehicle via an appropriate power transmission mechanism (not shown).

  The generator 3 is used as a source for generating power to be supplied to the motor 2 or a source for generating power for charging the battery 4 that stores the power to be supplied to the motor 2. Then, the rotor of the generator 3 is fixed to the output shaft of the engine so that the rotor of the generator 3 is rotated by an engine (not shown), or the rotor is connected to the output shaft of the engine via an appropriate power transmission mechanism. .

  In the present embodiment, the motor 2 and the generator 3 are configured by, for example, a three-phase (U phase, V phase, W phase) synchronous machine. Moreover, the said capacitor | condenser 4 is comprised by batteries (secondary battery), such as a lithium ion battery, for example.

  The power conversion system 1 includes an inverter 5 (hereinafter referred to as a motor inverter 5) as a drive circuit for the motor 2, an inverter 6 (hereinafter referred to as a generator inverter 6) as a drive circuit for the generator 3, and a direct current input thereto. And a booster (DC / DC converter) 7 capable of boosting and outputting electric power.

  The motor inverter 5 includes an arm composed of an upper arm 11 and a lower arm 12 connected in series for three phases (three) of U phase, V phase, and W phase. The arm is configured to be connected in parallel between a pair of DC power input / output terminals 5p and 5m. Of the DC power input / output terminals 5p and 5m, the terminal 5p is a positive terminal and the terminal 5m is a negative terminal.

  In FIG. 1, for convenience of illustration, reference numerals are typically assigned to the arms corresponding to the U phase, and reference numerals are omitted for the arms corresponding to the V phase and the W phase.

  Each of the upper arm 11 and the lower arm 12 in each phase arm has a switching element 13 and a diode 14 connected in parallel to the switching element 13 in the opposite direction. The switching element 13 is configured by a semiconductor switching element, for example, an IGBT (insulated gate bipolar transistor).

  The arm of the three-phase armature windings 2u, 2v, and 2w of the motor 2 is connected to the AC power input / output terminal 15 that conducts to the midpoint between the upper arm 11 and the lower arm 12 in each phase arm. The armature winding of the phase corresponding to is connected.

  The motor inverter 5 controls the on / off of each switching element 13 during the operation of the motor 2 (powering operation) by the PWM method or the like, so that the direct current input to the direct current power input / output terminals 5p and 5m is performed. The power is converted into AC power (three-phase AC power), and the AC power is output from the AC power input / output terminal 15 to the armature windings 2u, 2v, 2w of the motor 2.

  The motor inverter 5 can also cause the motor 2 to perform a regenerative operation. That is, by controlling on / off of each switching element 13 of the motor inverter 5 in a state where the rotor of the motor 2 is rotationally driven by an external force, power generated by the regenerative operation of the motor 2 (three-phase AC power) ) Can be converted into DC power, and the DC power can be output from DC power input / output terminals 5p and 5m.

  The generator inverter 6 has the same circuit configuration as the motor inverter 5. That is, the generator inverter 6 includes three arms (three) of U phase, V phase, and W phase, which are composed of an upper arm 21 and a lower arm 22 connected in series. The minute arm is connected in parallel between the pair of DC power input / output terminals 6p and 6m. Of the DC power input / output terminals 6p and 6m, the terminal 6p is a positive terminal and the terminal 6m is a negative terminal.

  Each of the upper arm 21 and the lower arm 22 in each phase arm has a switching element 23 formed of an IGBT as a semiconductor switching element, and a diode 24 connected in parallel to the switching element 23 in the opposite direction.

  The arm of the three-phase armature windings 3u, 3v, 3w of the generator 3 is connected to the AC power input / output terminal 25 that is electrically connected to the midpoint between the upper arm 21 and the lower arm 22 in each phase arm. The armature winding of the phase corresponding to is connected.

  The generator inverter 6 controls each switching element 23 on and off by a PWM method or the like when the generator 3 whose rotor is driven to rotate by the engine (power generation operation) is controlled from the generator 3 to each phase. The generated power (three-phase AC power) input through the AC power input / output terminal 25 is converted into DC power, and the DC power is output from the DC power input / output terminals 6p and 6m.

  The generator inverter 6 can also cause the generator 3 to perform a power running operation. That is, the DC power input / output terminals 6p and 6m of the generator inverter 6 are input to the DC power input / output terminals 6p and 6m by controlling on / off of each switching element 23 in a state where the DC power is input to the generator inverter 6. It is also possible to convert DC power into AC power (three-phase AC power), and output the AC power from the AC power input / output terminal 25 to the armature windings 3u, 3v, 3w of the generator 3.

  The booster 7 includes a switching operation part 31 as a main body part and a reactor 32. The capacitor 4 and the smoothing capacitor 41 are connected in parallel between a pair of low-voltage side terminals 33p and 33m as input terminals for low voltage DC power of the booster 7. Of the low-voltage side terminals 33p and 33m, the terminal 33p is a positive terminal, and the terminal 33m is a negative terminal.

  Further, between the pair of high-voltage side terminals 34p and 34m serving as output terminals for the high voltage DC power of the booster 7, a smoothing capacitor 42, a resistance element 43, a motor inverter 5 and a generator inverter 6 are connected in parallel. It is connected.

  In this case, of the high-voltage side terminals 34p and 34m, the terminal 34p is a positive terminal and the terminal 34m is a negative terminal. The negative terminal 34m is electrically connected to the negative terminal 33m of the low voltage terminals 33p and 33m of the booster 7.

  The DC power input / output terminal 5p on the positive side of the motor inverter 5 and the DC power input / output terminal 6p on the positive side of the generator inverter 6 are electrically connected to the high-voltage side terminal 34p on the positive side of the booster 7. . The DC power input / output terminal 5m on the negative side of the motor inverter 5 and the DC power input / output terminal 6m on the negative side of the generator inverter 6 are electrically connected to the high-voltage side terminal 34m on the negative side of the booster 7. .

  The switching operation unit 31 of the booster 7 has a circuit configuration similar to that of each phase arm of the motor inverter 5 (or the generator inverter 6). That is, the switching operation unit 31 includes two sets of parallel circuits including a switching element 35 and a diode 36 connected in parallel to the switching element 35. The parallel circuits are connected to the high voltage side of the booster 7. The terminals 34p and 34m are connected in series. Each switching element 35 is comprised by IGBT as a semiconductor switch element, for example.

  A reactor 32 is connected between the midpoint between the two sets of parallel circuits of the switching operation unit 31 and the positive terminal 33p of the low voltage terminals 33p and 33m of the booster 7. .

  The booster 7 configured as described above is configured so that the two switching elements 35 and 35 of the switching operation unit 31 are alternately turned on (in other words, alternately turned off). By causing each of 35 to be turned on and off at regular intervals, the DC power input from the battery 4 is boosted and output.

  In this case, the step-up rate (the input side of the booster 7) is changed by changing the duty of the on-time in one cycle of turning on and off of the switching elements 35, 35 (the ratio of the time in the on state to the time of one cycle) The ratio of the voltage on the output side with respect to the voltage of) changes.

  The booster 7 can transmit DC power bidirectionally between the input side (low voltage side) and the output side (high voltage side). When DC power is transmitted from the output side of the booster 7 to the input side, the DC power applied to the output side is stepped down at a ratio of the reciprocal of the step-up rate and transmitted to the input side. As a result, the battery 4 can be charged from the output side of the booster 7 via the booster 7.

  In addition to the configuration described above, the power conversion system 1 includes a motor ECU 51 that is a control unit for operation control of the motor 2, a generator ECU 52 that is a control unit for operation control of the generator 3, and operation control of the booster 7. And a booster ECU 53 that is a control unit.

  Further, as sensors for obtaining detection data for control processing of these ECUs 51, 52, 53, three (three-phase components) for detecting each phase current flowing between the traction motor 2 and the motor inverter 5 respectively. 3) (three phases of) generator current sensors 55, 55, 55 for detecting the currents of the respective phases flowing between the generator current sensor 54, 54, 54 and the generator 3 and the generator inverter 6. And a booster current sensor 56 for detecting a current flowing through the booster 7.

  In this case, each motor current sensor 54 is provided in a current-carrying line for each phase between the AC power input / output terminal 15 for each phase of the motor inverter 5 and the traction motor 2. Similarly, each generator current sensor 55 is provided in a current-carrying line for each phase between the AC power input / output terminal 25 for each phase of the generator inverter 6 and the generator 3.

  Further, the booster current sensor 56 is a current that flows to the input side (low voltage side) of the booster 7 (specifically, a current that flows through the low voltage side terminal 33p or 33m of the booster 7 (= current that flows to the reactor 32)). Is provided in the energization line between the low-voltage side terminal 33m on the negative side of the booster 7 and the capacitor 4 and the smoothing capacitor 41.

  Note that the booster current sensor 56 may be provided in a current-carrying line between the low-voltage side terminal 33 p on the positive electrode side of the booster 7 and the capacitor 4 and the smoothing capacitor 41.

  Supplementally, the motor current sensor 54 and the generator current sensor 55 correspond to the first current sensor in the present invention, and the currents detected by the current sensors 54 and 55 correspond to the rotating electrical machine side current in the present invention. Is. The booster current sensor 56 corresponds to the second current sensor in the present invention, and the current detected by the current sensor 56 corresponds to the booster-side current in the present invention.

  The motor ECU 51, the generator ECU 52, and the booster ECU 53 are each configured by an electronic circuit unit including a CPU, a RAM, a ROM, and the like.

  The motor ECU 51 controls on / off of each switching element 13 of the motor inverter 5 as a function realized by executing a mounted program (a function realized by software) or a function realized by hardware. Thus, the inverter control unit 51a that controls the operation of the traction motor 2 and the failure detection unit 51b that detects a failure of the motor inverter 5 are provided.

  The inverter control unit 51a of the motor ECU 51 outputs an electric current corresponding to the target torque (target value of output torque) of the traction motor 2 during the operation of the traction motor 2 (powering operation). On / off of each switching element 13 of the motor inverter 5 is controlled by a known PWM method or the like so that the windings 2u, 2v, 2w are energized.

  In this case, in the present embodiment, the target torque during operation of the traction motor 2 is basically determined according to the accelerator depression amount of the vehicle on which the power conversion system 1 is mounted (hereinafter referred to as the accelerator operation amount). Is done.

  However, in the present embodiment, the motor ECU 51 monitors the magnitude of the current (hereinafter referred to as booster side current) indicated by the output of the booster current sensor 56. And when the magnitude | size of this booster side electric current becomes more than the overcurrent determination value which is a predetermined predetermined value (hereinafter, this situation is referred to as an overcurrent state of the booster side current), In order to prevent the switching element 35 of the booster 7 from being damaged by the overcurrent, the motor ECU 51 detects the occurrence of the overcurrent state of the booster side current and then performs an inverter operation for a predetermined period of time. The target torque of the traction motor 2 is forcibly set to zero only for the forced stop period.

  In this case, setting the target torque of the traction motor 2 to zero cuts off the energization of the armature windings 2u, 2v, 2w of the traction motor 2, so that the inverter control unit 51a is connected to the motor inverter 5 A control signal is output to each switching element 13 such that all the switching elements 13 are temporarily turned off during the inverter operation forced stop period.

  The failure detection unit 51b of the motor ECU 51 is configured such that the energization line between the motor inverter 5 and the traction motor 2 is disconnected or the signal line that applies a control signal (gate signal) to each switching element 13 is disconnected. A state in which the motor inverter 5 cannot operate normally is detected as a failure of the motor inverter 5. This failure detection process is performed as described later using detected values of actual currents of the armature windings 2u, 2v, 2w of each phase of the traction motor 2 indicated by the output of the motor current sensor 54.

  The generator ECU 52 controls on / off of each switching element 23 of the generator inverter 6 as a function realized by executing a program to be implemented (a function realized by software) or a function realized by hardware. Thus, the inverter control unit 52a that controls the operation of the generator 3 and the failure detection unit 52b that detects a failure of the generator inverter 6 are provided.

  The inverter control unit 52a of the generator ECU 52 responds to the target power generation output of the generator 3 (or the target torque defined according to the target power generation output and the rotational speed of the rotor of the generator 3) during the power generation operation of the generator 3. On / off of each switching element 23 of the generator inverter 6 is controlled by a known PWM method or the like so that current is supplied to the armature windings 3u, 3v, 3w of the generator 3.

  In this case, the target power generation output of the generator 3 (or the target torque corresponding to the target power generation output) basically corresponds to the required power corresponding to the target torque of the traction motor 2 (corresponding to the target torque). Thus, the electric power to be supplied to the traction motor 2) or the charged amount (remaining capacity) of the battery 4 is determined.

  However, in the present embodiment, as in the case of the motor ECU 51, the generator ECU 52 causes the booster-side current indicated by the output of the booster current sensor 56 to exceed the predetermined predetermined value (overcurrent determination value). When the state is detected, the target power generation output (or target torque) of the generator 3 is forcibly set to zero temporarily only during the inverter operation forced stop period which is a predetermined predetermined time period.

  In this case, as in the case of the traction motor 2, setting the target power generation output (or target torque) of the generator 3 to zero cuts off the energization of the armature windings 3u, 3v, 3w of the generator 3. Therefore, the inverter control unit 52a outputs a control signal to each switching element 23 so that all the switching elements 23 of the generator inverter 6 are temporarily turned off during the inverter operation forced stop period.

  The failure detection unit 52b of the generator ECU 52 is connected to the generator line by disconnection of the energization line between the generator inverter 6 and the generator 3 or disconnection of a signal line for applying a control signal (gate signal) to each switching element 23. A state in which the inverter 6 cannot operate normally is detected as a failure of the generator inverter 6. This failure detection process is performed by the failure detection unit 51b of the motor ECU 51 using the detected values of the actual currents of the armature windings 3u, 3v, 3w of each phase of the generator 3 indicated by the output of the generator current sensor 55. This is performed in the same manner as the failure detection process.

  The booster ECU 53 turns on and off the switching elements 35 and 35 of the booster 7 as a function realized by executing a mounted program (a function realized by software) or a function realized by hardware. By controlling, the boosting rate of the booster 7 is controlled to the target boosting rate.

  In this case, the target boosting rate of the booster 7 is such that the DC voltage applied from the booster 7 to the DC power input / output terminals 5p and 5m of the motor inverter 5 supplies power to the traction motor 2 from the motor inverter 5. The DC voltage applied to the DC power input / output terminals 6p and 6m of the generator inverter 6 from the booster 7 is changed so that the generated power of the generator 3 is transferred from the generator inverter 6 to the motor inverter 5 or the capacitor. 4 is determined in accordance with the operating state of the traction motor 2 and the generator 3 so as to ensure a voltage that can be supplied to the traction motor 2.

  Supplementally, each of the motor ECU 51 and the generator ECU 52 corresponds to a failure detection device according to the present invention. The inverter control unit 51a of the motor ECU 51 and the inverter control unit 52a of the generator ECU 52 respectively correspond to inverter control means in the present invention. Further, the failure detection unit 51b of the motor ECU 51 and the failure detection unit 52b of the generator ECU 52 respectively correspond to failure determination means in the present invention.

  Next, processing of the failure detection unit 51b of the motor ECU 51 and the failure detection unit 52b of the generator ECU 52 will be described in detail. Since the processes of these failure detection units 51b and 52b are the same, hereinafter, the process of the failure detection unit 51b of the motor ECU 51 will be representatively described.

  With reference to FIG. 2, the failure detection unit 51 b sequentially executes the processes of the current deviation calculation unit 61, the MAX selection unit 62, and the filtering processing unit 63 at a predetermined control processing period when the motor 2 is operated. The reference data to be monitored in order to detect a failure of the inverter 5 is sequentially calculated.

  More specifically, the actual current of each phase of the motor 2 indicated by the target current (U-phase target current, V-phase target current, W-phase target current) of each phase of the motor 2 and the output of the current sensor 54 for the motor. The detected values of current (U-phase actual current, V-phase actual current, and W-phase actual current) are sequentially input to the current deviation calculation unit 61.

  The target current of each phase of the motor 2 depends on the target torque of the motor 2, the detected value of the rotational speed of the rotor of the motor 2, and the detected value of the phase angle (rotational angle position) of the rotor of the motor 2. It is to be decided. In this case, the rotational speed and phase angle of the rotor of the motor 2 are detected using a sensor such as a resolver (not shown).

  Then, the current deviation calculation unit 61 calculates the current deviation (U-phase current deviation, V-phase current deviation, W-phase current deviation) of each phase of the motor 2 from the above input value. The current deviation calculated here is the magnitude (absolute value) of the difference between the actual current of each phase and the target current.

  Since the sum of the U-phase actual current, V-phase actual current, and W-phase actual current is zero, the actual current of any one phase can be calculated from the detected values of the actual currents of the other two phases. Good. Then, the current deviation of the one phase may be calculated using the calculated value.

  The current deviation of each phase calculated as described above is input to the MAX selection unit 62. In the MAX selection unit 62, the maximum value (maximum current deviation) of the current deviation of each phase is sequentially selected as a representative value of the current deviation of each phase.

  This maximum current deviation is input to the filtering processing unit 63. In the filtering processing unit 63, a filtering process with a low-pass characteristic is performed on the maximum current deviation. As a result, a current deviation filter value IXPHERR_FLT, which is a filtering value of the maximum current deviation, is calculated as reference data to be monitored in order to detect a failure of the motor inverter 5. In the present embodiment, the current deviation filter value IXPHERR_FLT corresponds to the deviation in the present invention.

  Here, when the motor inverter 5 is operating normally, the magnitude of the current deviation of each phase is basically zero or sufficiently small. As a result, the current deviation filter value IXPHERR_FLT is also maintained at zero or a sufficiently small value.

  On the other hand, when a failure of the motor inverter 5 occurs, the magnitude of the current deviation of any phase becomes periodically large. For example, when a signal line for applying a control signal (gate signal) to the switching element 13 of the upper arm 11 (or lower arm 12) of the U phase is disconnected, and the switching element 13 cannot be turned on. The magnitude of the U-phase current deviation is periodically large. As a result, the current deviation filter value IXPHERR_FLT increases to a relatively large value.

  The fault detection unit 51b includes a current amplitude calculation unit 64, a coefficient determination unit 65, a multiplication unit 66, a filtering processing unit 67, in parallel with the processes of the current deviation calculation unit 61, the MAX selection unit 62, and the filtering processing unit 63 described above. Then, by executing the processing of the threshold value switching selection unit 68, a failure determination threshold value to be compared with the current deviation filter value IXPHERR_FLT is determined in order to determine whether or not the motor inverter 5 has failed.

  More specifically, a target current in the d-axis direction (d-axis target current) and a target current in the q-axis direction (q-axis target current) of the motor 2 are sequentially input to the current amplitude calculation unit 64. The d-axis and q-axis are dq coordinate systems that are generally used as a rotational coordinate system (coordinate system that rotates at the same electrical angular velocity as the rotor) for expressing the electrical behavior of the motor 2 in vector control of the motor 2 and the like. The two axes. The d-axis target current and the q-axis target current are determined according to the target torque of the motor 2 and the detected value of the rotational speed of the rotor of the motor 2.

  Note that the set of the current component in the d-axis direction and the current component in the q-axis direction and the set of the U-phase current, the V-phase current, and the W-phase current of the motor 2 are matrices determined according to the phase angle of the rotor of the motor 2. One-to-one correspondence by the linear mapping by

  Accordingly, the d-axis target current and the q-axis target current can be calculated from the U-phase target current, the V-phase target current, and the W-phase target current that are input to the current deviation calculation unit 61. Conversely, after determining the d-axis target current and the q-axis target current according to the target torque of the motor 2, the U-phase target current, the V-phase target current, and the W-phase target are determined from the d-axis target current and the q-axis target current. The current may be calculated.

  The current amplitude calculator 64 calculates the target current amplitude (target current amplitude) of the motor 2 from the input d-axis target current and q-axis target current. Specifically, the target current amplitude is calculated by multiplying the square root of the sum of the square values of the d-axis target current and the q-axis target current by a predetermined constant value. The target current amplitude is substantially proportional to the target torque of the motor 2.

  Further, the rotation speed (detection value) of the rotor of the motor 2 is sequentially input to the coefficient determination unit 65. The coefficient determination unit 65 determines a coefficient K_calib (<1) to be multiplied by the target current amplitude according to the input rotational speed using a predetermined data table or an arithmetic expression. In this case, the coefficient K_calib is determined so as to increase as the rotational speed of the motor 2 increases.

  The target current amplitude calculated by the current amplitude calculation unit 64 and the coefficient K_calib determined by the coefficient determination unit 65 are input to the multiplication unit 66. Then, the multiplication unit 66 multiplies the target current amplitude by the coefficient K_calib to calculate the failure determination first threshold value I1THSH of the motor inverter 5.

  Here, in the present embodiment, the failure determination threshold value compared with the current deviation filter value IXPHERR_FLT to determine whether or not the motor inverter 5 has failed is a situation in which an overcurrent state of the booster side current does not occur ( There are two types: a threshold value used in a normal situation) and a threshold value used when the overcurrent state occurs. The failure determination first threshold value I1THSH is a threshold value used in a situation where the overcurrent state of the booster side current does not occur (normal situation).

  The failure determination first threshold value I1THSH is input to the filtering processing unit 67 in order to determine a failure determination threshold value used when an overcurrent state of the booster side current occurs. In the filtering processing unit 67, a low-pass characteristic filtering process is performed on the failure determination first threshold value I1THSH. Thereby, the filtering value of the failure determination first threshold value I1THSH is calculated as the failure determination second threshold value I1THSH_FLT.

  In the present embodiment, the first threshold value for failure determination I1THSH and the second threshold value for failure determination I1THSH_FLT correspond to the first threshold value for failure determination and the second threshold value for failure determination in the present invention, respectively.

  Here, when an overcurrent state of the booster-side current occurs, as described above, the target torque of the motor 2 is forcibly temporarily only during the inverter operation forcible stop period which is a predetermined predetermined time period. To zero. For this reason, in the situation where the overcurrent state of the booster side current frequently occurs intermittently, the rapid fluctuation of the failure determination first threshold value I1THSH frequently occurs. However, since the failure determination second threshold I1THSH_FLT is obtained by performing low-pass characteristic filtering on the failure determination first threshold I1THSH, the failure determination second threshold I1THSH_FLT is an overcurrent of the booster side current. Even in a situation where the state frequently occurs intermittently, it can be obtained as a highly stable threshold.

  The failure determination first threshold value I1THSH and the failure determination second threshold value I1THSH_FLT calculated as described above are input to the threshold value switching selection unit 68. The threshold switching selector 68 is provided with an overcurrent detection flag indicating whether or not an overcurrent state of the booster side current has occurred. This overcurrent detection flag is set according to whether or not the detected value of the booster-side current indicated by the output of the booster current sensor 56 is an excessive value equal to or greater than an overcurrent determination value that is a predetermined predetermined value. Flag to be

  In the following description, for convenience, the value of the overcurrent detection flag when the detected value of the booster side current is an excessive value equal to or greater than the overcurrent determination value is set to “1”, and the detected value of the booster side current is the overcurrent. When the value is smaller than the determination value, the value of the overcurrent detection flag is set to “0”.

  In a situation where the value of the overcurrent detection flag is “0” (a value indicating that an overcurrent state of the booster side current has not occurred), the threshold value switching selection unit 68 is the first threshold for failure determination. I1THSH is output as a threshold value that is actually used to determine whether or not the motor inverter 5 has failed.

  Further, when the value of the overcurrent detection flag changes from “0” to “1” (a value indicating that the overcurrent state of the booster side current has occurred), the threshold switching selection unit 68 After the change, the period in which the value of the overcurrent detection flag is maintained at “1” and the period of the predetermined predetermined time immediately after the value of the overcurrent detection flag returns from “1” to “0” The failure determination second threshold value I1THSH_FLT is output as a threshold value that is actually used to determine whether or not the motor inverter 5 has failed.

  FIG. 3D shows an example of temporal changes of the current deviation filter value IXPHERR_FLT, the failure determination first threshold value I1THSH, and the failure determination second threshold value I1THSH_FLT calculated as described above. This illustrated example is an example under a situation in which any one of the switching elements 13 of the motor inverter 5 (for example, one switching element 13 of the U-phase arm) cannot be controlled to be in an ON state.

  Note that FIG. 3A is a graph that binaryly illustrates whether or not the inverter operation is forcibly stopped according to the occurrence of an overcurrent state of the booster side current using “OFF_YES” and “OFF_NO”, respectively. FIG. 3B is a graph illustrating the change over time of the U-phase actual current, and FIG. 3C is a graph illustrating the change over time of the target current amplitude of the motor 2 (which is approximately proportional to the target torque). .

  As described above, after performing the calculation process of the current deviation filter value IXPHERR_FLT and the determination process of the failure determination threshold value, the failure detection unit 51b next executes the process of the failure determination unit 69.

  The failure determination unit 69 receives the current deviation filter value IXPHERR_FLT and the failure determination threshold (the failure determination first threshold I1THSH or the failure determination second threshold I1THSH_FLT), and the value of the overcurrent detection flag, A predetermined time for determination determination is input.

  Then, the failure determination unit 69 sets the current deviation filter value IXPHERR_FLT under the condition that the target torque (or the target current amplitude) of the motor 2 is greater than or equal to a predetermined value (not a minute value near zero). Based on the comparison with the failure determination threshold value, the presence or absence of failure of the motor inverter 5 is determined.

  Here, in the situation where the magnitude of the target torque of the motor 2 is small (the situation where the magnitude of the target torque (or target current amplitude) is a value close to zero), noise mixed in the actual current of each phase of the motor 2 Due to the influence of components and the like, it is difficult to obtain a highly reliable current deviation filter value IXPHERR_FLT in determining whether or not the motor inverter 5 has failed.

  For this reason, the failure determination unit 69 calculates the current deviation under the condition that the magnitude of the target torque (or the target current amplitude) of the motor 2 is equal to or greater than a predetermined value (hereinafter, this condition is referred to as a necessary determination condition). Using the filter value IXPHERR_FLT and the failure determination threshold (the failure determination first threshold I1THSH or the failure determination second threshold I1THSH_FLT), it is determined whether or not the motor inverter 5 has failed. In the example shown in FIG. 3, the situation where the determination necessary condition is satisfied is, for example, a situation where the target current amplitude rises within the period B in FIG. 3C, and in the period A in FIG. The situation is a situation where the determination necessary condition is not satisfied.

  When an overcurrent state of the booster side current occurs, the target torque of the motor 2 is temporarily set to zero only during the inverter operation forcible stop period as described above, and thus the above determination necessary condition is satisfied. Will not. Therefore, even in this inverter operation forced stop period (for example, the period in which the graph of FIG. 3A is “OFF_YES”), whether or not the motor inverter 5 has failed is not determined.

  The determination of the failure of the motor inverter 5 when the determination necessary condition is satisfied is specifically performed as follows. That is, the failure determination unit 69 sequentially compares the current deviation filter value IXPHERR_FLT and the failure determination threshold value in a situation where the determination necessary condition is satisfied. In this case, in a situation where the motor inverter 5 is operating normally, the current deviation filter value IXPHERR_FLT is zero or a value close thereto, so IXPHERR_FLT <failure determination threshold.

  On the other hand, when a failure occurs in the motor inverter 5 such as disconnection of a signal line for applying a control signal to any switching element 13 of the motor inverter 5 or disconnection of an energization line between the motor inverter 5 and the motor 2. The current deviation filter value IXPHERR_FLT is a large value that is greater than or equal to the failure determination threshold value.

  However, the current deviation filter value IXPHERR_FLT may instantaneously exceed the failure determination threshold value due to the influence of noise components included in the current of each phase of the motor 2.

  Therefore, when the current deviation filter value IXPHERR_FLT becomes a value greater than or equal to the failure judgment threshold value, the failure judgment unit 69 measures the time during which this state is continuously maintained (hereinafter referred to as excessive current deviation continuation time). Start the timer. Then, when this excessive current deviation continuation time reaches a predetermined determination confirmation time, the failure determination unit 69 determines (determines) that a failure of the motor inverter 5 has occurred, and indicates data (for example, failure determination) Flag).

  The determination determination time corresponds to the reference time in the present invention.

  In the present embodiment, for example, a countdown timer is used as the timer. In this case, with the current deviation filter value IXPHERR_FLT being smaller than the failure determination threshold value, the count value of the countdown timer is initialized to a value corresponding to the determination determination time. Then, when the current deviation filter value IXPHERR_FLT becomes equal to or greater than the failure determination threshold, the countdown timer starts to count down using that as a trigger. The count value of this countdown timer is determined when the current deviation filter value IXPHERR_FLT is kept above the failure judgment threshold while the necessary judgment condition is satisfied, and the current deviation excess duration time reaches the decision confirmation time. It becomes zero. In response to this, the failure determination unit 69 determines (confirms) that a failure of the motor inverter 5 has occurred.

  On the other hand, if the current deviation filter value IXPHERR_FLT returns to a value smaller than the failure determination threshold without causing an overcurrent state of the booster side current while the determination necessary condition is satisfied while the countdown timer is counting In this case, the countdown timer is stopped and the count value is reset (initialized). In addition, when the target torque (or target current amplitude) of the motor 2 is reduced and the determination necessary condition is not satisfied without counting the booster side current during the countdown timer. However, the countdown timer is stopped and the count value is reset (initialized).

  By the way, an overcurrent state of the booster side current may occur while the countdown timer is counting (during the measurement of the current deviation excess duration).

  This overcurrent state can occur both when the motor inverter 5 is operating normally and when the motor inverter 5 fails. For example, when the driving wheel of the vehicle on which the power conversion system 1 is mounted (the driving wheel that is rotationally driven by the motor 2) slips and slides on a low mu road such as a snowy road surface, the current on the booster side is excessive. Current conditions may occur.

  Further, the switching element 13 cannot be turned on due to disconnection of a signal line for applying a control signal to any switching element 13 of the motor inverter 5 (the switching element 13 is kept in the off state). Even when such a failure occurs, an overcurrent state of the booster side current may occur.

  On the other hand, in the present embodiment, when the overcurrent state of the booster side current occurs, as described above, the switching element 35 of the booster 7 is prevented from being damaged by the overcurrent (as a result, the booster 7), the target torque of the motor 2 is forcibly made zero for the inverter operation forced stop period, which is a predetermined period of time. Therefore, in the inverter operation forced stop period, the determination necessary condition is not satisfied, and the current deviation excessive continuation time by the countdown timer cannot be measured.

  As described above, when the overcurrent state of the booster side current occurs while the countdown timer is counting (during the measurement of the excessive current deviation duration), the target torque of the motor 2 is supposed to be zero. If the countdown timer is stopped and the count value is reset, especially in situations where the overcurrent state of the booster current occurs frequently, even if a motor inverter failure occurs Before the count value of the countdown timer is counted down to zero (before the measured value of the current deviation excess continuation time reaches the determination confirmation time), the countdown timer may be reset whenever the overcurrent state occurs. . As a result, there is a possibility that it is not determined that the motor inverter has failed.

  Then, the switching element 13 cannot be turned on by disconnection of a signal line that gives a control signal to any switching element 13 of the motor inverter 5 (the switching element 13 is kept in the off state). When such a failure occurs, an overcurrent state of the booster side current is likely to occur every time the inverter operation forced stop period corresponding to the occurrence of the overcurrent state of the booster side current ends.

  For example, the switching element 13 cannot be turned on due to disconnection of a signal line that gives a control signal to any switching element 13 of the motor inverter 5 (the switching element 13 is kept in the off state). ), The current deviation filter value IXPHERR_FLT, the failure determination first threshold value I1THSH, and the failure determination second threshold value I1THSH_FLT calculated by the failure detection unit 51b change as shown in FIG. 4B, for example.

  FIG. 4A shows a change with time of the accelerator operation amount (accelerator depression amount) of the vehicle that defines the target torque of the motor 2.

  Times t1, t2, and t5 are timings when the overcurrent state of the booster side current has occurred, and at each timing, the target torque of the motor 2 is made zero (and the target current amplitude is made zero). In response, the failure determination first threshold value I1THSH becomes zero.

  In the illustrated example, an overcurrent state of the booster-side current continuously occurs every control processing cycle between times t2 and t3.

  In this case, when the overcurrent state of the booster side current occurs during counting of the countdown timer (during measurement of the current deviation excess duration), the target torque of the motor 2 becomes zero as described above. Accordingly, when the countdown timer is stopped and the count value is reset, the overcurrent state of the booster side current is changed to the countdown timer count value as shown by a two-dot chain line in FIG. , The booster side current is reset at the timing (time t2, t5) when the overcurrent state occurs. For this reason, even if a failure of the motor inverter 5 occurs, the count value of the countdown timer does not reach zero, and therefore, it is not determined that the failure of the motor inverter 5 has occurred.

  Therefore, in this embodiment, the failure determination unit 69, when the overcurrent state of the booster side current occurs during counting of the countdown timer (during measurement of the current deviation excess duration), In the inverter operation forced stop period in which the target torque of the motor 2 is maintained at zero, the count value of the countdown timer is held at the value at the start of the period.

  Then, after the end of the inverter operation forced stop period (after restarting the on / off control of each switching element 13 of the motor inverter 5), the failure determination unit 69 causes the current deviation filter value IXPHERR_FLT to be greater than or equal to the failure determination threshold value. If it is, the countdown timer resumes downcounting.

  In this case, the second threshold value for failure determination I1THSH_FLT is used as the failure determination threshold value for a predetermined time period immediately after the end of the inverter operation forced stop period.

  As a result, if the motor inverter 5 has failed, the count value of the countdown timer will eventually become zero even if the booster-side current overcurrent condition frequently occurs, and the motor inverter 5 will fail. Is determined to have occurred. That is, a failure of the motor inverter 5 can be detected without any trouble.

  For example, when the current deviation filter value IXPHERR_FLT, the failure determination first threshold value I1THSH, and the failure determination second threshold value I1THSH_FLT calculated by the failure detection unit 51b change as shown in FIG. Even if an overcurrent state of the booster side current occurs at time t2 during counting, the count value of the countdown timer is held at the value at the time of occurrence of the overcurrent state as shown in FIG. .

  Then, when the inverter operation forced stop period ends (time t3), the target torque is forcibly set to zero (and thus all the switching elements 13 of the motor inverter 5 are controlled to be in the OFF state). Timer countdown (measurement of excessive current deviation duration) is resumed. Finally (at the time t4 in the example shown in FIG. 4C), the count value of the countdown timer becomes zero. That is, the measured value of the current deviation excessive continuation time reaches the determination confirmation time.

  Therefore, failure determination unit 69 determines that a failure has occurred in motor inverter 5 at time t4.

  In the situation where the overcurrent state of the booster side current frequently occurs as in the illustrated example, the failure determination second threshold value I1THSH_FLT is basically used as the failure determination threshold value. For this reason, the failure determination unit 69 can compare the current deviation filter value IXPHERR_FLT with a failure determination threshold value (= failure determination second threshold value I1THSH_FLT) having high stability (that is unlikely to cause a rapid change). As a result, the reliability of the determination result of the failure determination unit 69 can be ensured.

  The above is the details of the processing of the failure detection unit 51b of the motor ECU 51. The process of the failure detection unit 52b of the generator ECU 52 is the same as the process of the failure detection unit 51b of the motor ECU 51 shown in the block diagram of FIG. Thereby, when a failure of the generator inverter 6 occurs, the failure is detected by the failure detection unit 52b of the generator ECU 52 in the same manner as the processing of the failure detection unit 51b of the motor ECU 51.

  As described above, according to the power conversion system 1 of the present embodiment, when the overcurrent state of the booster-side current occurs, the booster 7 is prevented from being damaged, and the motor inverter 5 or the generator A failure of the inverter 6 can be detected appropriately.

  In particular, a failure in which the switching element 13 cannot be turned on due to a disconnection of a signal line for applying a control signal to any switching element 13 of the motor inverter 5 causes an excessive current on the booster side. Even in a situation where the current state frequently occurs, the occurrence of the failure of the motor inverter 5 can be appropriately detected.

  Similarly, a failure that prevents the switching element 23 from being turned on due to disconnection of a signal line that applies a control signal to any switching element 23 of the generator inverter 6 causes the booster-side current Even in a situation where an overcurrent state frequently occurs, it is possible to appropriately detect the occurrence of the failure of the generator inverter 6.

  Further, in any of the processes of the failure detection unit 51b of the motor ECU 51 and the failure detection unit 52b of the generator ECU 52, in a situation where an overcurrent state of the booster side current frequently occurs, As the determination threshold, the failure determination second threshold I1THSH_FLT, which is the filtering value of the failure determination first threshold I1THSH, is used, so that the reliability of the determination result of the failure determination unit 69 is ensured stably (with high robustness). can do.

  In the process of the failure detection unit 51b of the motor ECU 51, when the overcurrent state of the booster side current does not occur, the count value of the countdown timer (measured value of the excessive current deviation continuation time) is the target torque of the motor 2. When the magnitude of (or target current deviation) becomes a minute value of a predetermined value or less, it is reset. For this reason, the reliability of the determination result of the failure determination part 69 in the said situation can be improved. The same applies to the processing of the failure detection unit 52b of the generator ECU 52.

  In addition, although the power conversion system 1 of the actual form demonstrated above is a system provided with two inverters, the inverter 5 for motors, and the inverter 6 for generators, the system provided with either one inverter may be sufficient.

  Further, the motor 2 and the generator 3 as the rotating electric machine in the embodiment are synchronous machines, but may be induction machines, for example.

  DESCRIPTION OF SYMBOLS 1 ... Power conversion system, 2 ... Motor (rotating electrical machine), 3 ... Generator (rotating electrical machine), 5, 6 ... Inverter, 7 ... Booster, 11, 21 ... Upper arm, 12, 22 ... Lower arm, 13, 23 ... Switching element, 54 ... Current sensor for motor (first current sensor), 55 ... Current sensor for generator (first current sensor 9, 56 ... Current sensor for booster (second current sensor)), 51 ... Motor ECU (failure detection) Device), 52... Generator ECU (failure detection device), 51 a, 52 a... Inverter control unit (inverter control means), 51 b, 52 b .. failure detection unit (failure determination means).

Claims (3)

An inverter configured to have switching elements in the upper arm and the lower arm, a booster connected to the DC power input / output terminal of the inverter, a rotating electrical machine connected to the AC power input / output terminal of the inverter, A first current sensor for detecting a rotating electrical machine side current that is a current flowing between the inverter and the rotating electrical machine; and a second current sensor for detecting a booster side current that is a current flowing through the booster. A failure detection device for detecting a failure in a power conversion system,
In the inverter, when an overcurrent state occurs in which the magnitude of the detected value of the booster side current indicated by the output of the second current sensor is equal to or greater than a predetermined overcurrent determination value, all of the inverters Inverter control means configured to temporarily control the switching element in an off state is connected,
The deviation between the detected value of the rotating electrical machine side current and the target value of the rotating electrical machine side current indicated by the output of the first current sensor is inputted with the output of the 1 current sensor and the target value of the rotating electrical machine side current. Failure determination means for measuring the time during which the magnitude of the inverter is maintained above a predetermined failure determination threshold and determining that the inverter has failed when the measured value of the time exceeds a predetermined reference time With
When the overcurrent state occurs when the failure determination unit is measuring the time during which the magnitude of the deviation is maintained to be equal to or greater than the failure determination threshold, the inverter control unit performs the Except for the inverter operation forced stop period during which all switching elements of the inverter are controlled to be in the OFF state, the magnitude of the deviation before or after the inverter operation forced stop period is greater than or equal to the failure determination threshold value. A failure detection apparatus for a power conversion system, configured to accumulate and measure the maintained time. In the failure detection apparatus of the power conversion system according to claim 1,
The failure determination means has a condition that the target value of the output torque of the rotating electrical machine or the target value of the amplitude of the current of the rotating electrical machine corresponding to the target value is a predetermined value or more as a necessary condition. It is configured to perform measurement, and during the time measurement, the output current target value of the rotating electrical machine or the amplitude of the rotating electrical machine side current corresponding to the target value without the occurrence of the overcurrent state. A failure detection apparatus for a power conversion system, wherein the time measurement is stopped and the time measurement value is reset when the magnitude of the target value is smaller than the predetermined value. In the failure detection apparatus of the power conversion system according to claim 1 or 2,
The failure determination means variably determines a first failure determination threshold value according to a target value of the output torque of the rotating electrical machine or a target value of the amplitude of the rotating electrical machine side current corresponding to the target value; And a means for determining a second failure determination threshold value by applying a low-pass characteristic filtering process to the first failure determination threshold value, and a predetermined period after the occurrence of the overcurrent state, The second failure determination threshold is used as a failure determination threshold to be compared with the deviation after completion of the inverter operation forced stop period, and is compared with the deviation in a period other than the predetermined period. A failure detection apparatus for a power conversion system, characterized in that the first failure determination threshold is used as a failure determination threshold.

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