JP2010028984A - Power conversion apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power conversion apparatus capable of specifying in either which of a drive part or a current detection part a short circuit failure occurs in a multi-phase rotary machine. <P>SOLUTION: The current flowing into each phase of a motor 10 is detected with shunt resistors 31 to 33, operation amplifiers 34 to 36 and an arithmetic unit 60, and the current flowing into a power supply interruption device 40 is detected with the arithmetic unit 60. Thereby, when the current flowing into the motor 10 becomes excessive and when the current flowing into the power supply interruption device 40 is not excessive, the current detection part is decided to be defective, the current detection part being constituted of the shunt resistors 31 to 33, the operation amplifiers 34 to 36 and the arithmetic unit 60. At the same time, when the current flowing into the motor 10 is excessive and when the current flowing into the power supply interruption device 40 is also excessive, the drive part is decided to be defective, the drive part being constituted of FETs 21 to 26, a U-phase coil 11, a V-phase coil 12 and a W-phase coil 13. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power converter that drives and controls a multiphase rotating machine.

2. Description of the Related Art Conventionally, as an electric power steering apparatus, an apparatus that detects a steering torque of a steering with a torque sensor and performs assist control of the steering with a motor as necessary is known.
Here, as the motor, a multi-phase motor is generally used. At this time, the motor is driven and controlled by the power converter. Specifically, the drive control is performed by switching the switching element pair according to the number of phases of the motor according to the PWM signal.

  In such an electric power steering apparatus, it is desired to continue the assist control by the motor as much as possible. This is because if the assist control is stopped, the steering operation may become extremely difficult, for example. Thus, a control device that switches feedback control to open loop control when a failure occurs has been proposed (see, for example, Patent Document 1).

  By the way, as a premise for performing such control, motor failure detection is indispensable. Therefore, a device is disclosed in which a shunt resistor is arranged in each switching element pair of a multi-phase motor to detect a failure of each phase of the motor and a failure of a “drive unit” composed of the switching element pair (for example, a patent) Reference 2).

JP 2005-88877 A JP 2005-210871 A

However, in the device described in Patent Document 2, when the “current detection unit” configured by a shunt resistor or the like fails, it is specified whether the failure point is the “drive unit” or the “current detection unit”. I can't. Further, once the “current detection unit” fails, it is not possible to detect the failure of the “drive unit” in the subsequent control.
The present invention has been made to solve such a problem, and its purpose is to estimate whether a short-circuit fault has occurred in the “drive unit” or the “current detection unit” in the multiphase rotating machine. It is to provide a possible power converter.

  The power converter of the present invention is used for a multiphase rotating machine composed of a plurality of phases of three or more phases. The current supply control means supplies the drive current to the multiphase rotating machine. The current supply control means supplies the drive current by controlling the switching element of the switching means to be in a conductive state or a non-conductive state. The switching means is composed of a pair of switching elements corresponding to each phase of the multiphase rotating machine. The conduction state refers to an ON state in which the switching element conducts the drive current, and the non-conduction state refers to an OFF state in which the switching element interrupts the drive current.

  At this time, the current flowing through each phase of the multiphase rotating machine can be detected by the first current detection means. Further, the power supply and the switching means are interposed between the power supply and the switching means, and the power supply and the switching means can be electrically cut off. The second current detection means uses the resistance value of the cut-off means to The current flowing through the blocking means can be detected. Here, “current can be detected” in any current detection means is intended to include a configuration capable of detecting current as a result, for example, a configuration for detecting only a voltage value.

  In the present invention, the current flowing through each phase of the multi-phase rotating machine is detected by the first current detecting means, and the current flowing through the interrupting means is detected by the second current detecting means. Accordingly, when an overcurrent is detected only by the first current detection unit and no overcurrent is detected by the second current detection unit, it can be estimated that a failure has occurred in the current detection unit. On the other hand, when an overcurrent is detected by both the first current detection means and the second current detection means, it can be estimated that a failure has occurred in the drive unit of the multiphase rotating machine. As a result, it is possible to estimate in which of the “drive unit” and “current detection unit” the short-circuit failure in the multiphase rotating machine has occurred.

  Moreover, in the present invention, the second current detection means detects the current using the resistance value of the interruption means. That is, since the current is detected using the resistance of the blocking means itself, the number of parts is reduced as compared with a configuration in which a shunt resistor is separately provided.

  The first current detection unit is exemplified by a shunt resistor. In the case of a three-phase rotating machine, for example, a shunt resistor is provided corresponding to each phase. In addition, for example, a shunt resistor may be provided only in two phases, and the current that flows in the remaining one phase may be calculated from the current that flows in the other two phases. Since the first current detection means may be configured with two shunt resistors as in the latter, when the shunt resistance is provided corresponding to each of the three phases, any of the first current detection means may be damaged. Even if the current of one phase cannot be detected normally, the control is not hindered. In any case, in the present invention, even if the control of the multi-phase rotating machine is continued after the failure of the “current detection unit”, the failure of each phase of the multi-phase rotating machine (“driving unit”) Can be determined from the current detected by the second current detecting means.

  By the way, when an overcurrent is detected by both the first current detection means and the second current detection means, the switching element is brought into a non-conductive state. If an overcurrent is detected by both current detection means, it is presumed that a short-circuit fault has occurred in the “drive unit”. For example, power is supplied to a specific phase of a multiphase rotating machine in which a short-circuit fault has occurred. That is to avoid it. Or it is good also as a structure which controls an interruption | blocking means and interrupts | blocks a power supply and a switching element electrically.

  Even when disconnecting from the power supply by the shut-off means in this way, there is a possibility that current flows in the bridge-connected switching means due to the power running regeneration of the multiphase rotating machine, especially when the electric power steering device is taken into consideration There is a concern that the steering operation becomes extremely difficult.

  Therefore, the multi-phase rotating machine is configured to include a rotating machine shut-off means that can be electrically shut off from the switching means, and the current supply control means controls the rotating machine shut-off means together with the power shut-off by the shut-off means, and multi-phase rotation It is preferable that the apparatus and the switching means be shut off. In this way, since the multiphase rotating machine is disconnected from the switching means, there is a high possibility that a temporary steering operation can be performed.

  By the way, it is conceivable that the blocking means, which is a feature of the present invention, is constituted by a mechanical relay. Further, it is conceivable to use a semiconductor relay. Considering that the drive current becomes large, it is desirable that the latter is constituted by a semiconductor relay. When configured with a semiconductor relay, a plurality of relays may be provided corresponding to the power running regeneration of the multiphase rotating machine. For example, when a MOSFET (metal-oxide-semiconductor field-effect transistor) is used as a relay, a current flows in one direction by the diode even when it is in an OFF state. Therefore, it is exemplified that the two MOSFETs are arranged so that the directions of the diodes are alternate (specifically, the current passing directions are mutually outward).

  The present invention is characterized in that the current flowing through the blocking means is detected by using the resistance value of the blocking means, but it is conceivable that the resistance value of the blocking means changes depending on the temperature of the blocking means. . In this case, there is a possibility that an accurate current cannot be detected.

  Therefore, the second current detection unit may include a resistance value estimation unit, and the resistance value estimation unit may estimate the resistance value of the blocking unit that varies depending on the temperature. In this way, since the resistance value of the blocking means is estimated, the current can be detected more accurately.

  Specifically, it is exemplified that the resistance value of the blocking means is estimated on the assumption that the input power multiplied by the efficiency is equal to the output power. In addition, the temperature is estimated based on the current flowing through the blocking means, and the resistance value of the blocking means is estimated based on the temperature. Furthermore, it is exemplified that the resistance value of the shut-off means is estimated based on the current that flows when two paired switching elements are simultaneously turned on. Further, on the assumption that the above-described current supply control means creates a voltage command signal corresponding to each phase of the multiphase rotating machine and controls the switching means based on the voltage command signal and the PWM signal. In the specific state, assuming that the current detected by the first current detection means is equal to the current detected by the second current detection means, the resistance value of the cutoff means is estimated. Furthermore, the voltage command signal is offset on the assumption that the current supply control means creates a voltage command signal corresponding to each phase of the multiphase rotating machine and controls the switching means based on the voltage command signal and the PWM signal. A specific state of the switching means is created at a predetermined timing, and at this timing, the current detected by the first current detection means and the current detected by the second current detection means are equal to each other. The estimation of the resistance value is exemplified. The offset of the voltage command signal is exemplified such that the maximum duty ratio is 100%. Further, the offset is exemplified so that the minimum duty ratio becomes 0%. Regardless of which configuration is employed, the current flowing through the blocking means can be detected more accurately by employing these configurations.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
A power converter 1 according to this embodiment shown in FIG. 1 controls driving of a motor 10. And especially the power converter 1 is employ | adopted for the electric power steering apparatus for assisting steering operation of a vehicle with the motor 10. FIG.

  The motor 10 to be controlled by the power converter 1 is a three-phase brushless motor, and has a rotor and a stator (both not shown). The rotor is a disk-shaped member, and a permanent magnet is affixed to the surface thereof and has a magnetic pole. It is the stator that houses such a rotor and rotatably supports it. This stator has protrusions that protrude inwardly at predetermined angles, and the U-phase coil 11, V-phase coil 12, and W-phase coil 13 shown in FIG. 1 are wound around the protrusions. It is star-connected.

  The power converter 1 includes an inverter 20 in which switching elements are bridge-connected, three shunt resistors 31, 32, 33, three operational amplifiers 34, 35, 36, a power breaker 40, a motor-side breaker 50, and a calculation A device 60 is provided.

  The inverter 20 includes six MOSFETs (metal-oxide-semiconductor field-effect transistors) 21, 22, 23, 24, 25, and 26 that are a kind of field effect transistors. These MOSFETs 21 to 26 function as switching elements, and the drain-source is turned on (conductive) or turned off (cut off) depending on the potential of the gate. Hereinafter, the MOSFETs 21 to 26 are simply referred to as FETs 21 to 26. Further, when it is necessary to distinguish the six FETs 21 to 26, the symbols in FIG. 1 are used, and FET (Su +) 21, FET (Sv +) 22, FET (Sw +) 23, FET (Su−) 24, FET (Sv−) 25 and FET (Sw−) 26 are described.

Here, the connection of these FETs 21 to 26 will be described.
The drains of the three FETs 21 to 23 are connected to an external power source 70 via the power circuit breaker 40. The power source 70 is a so-called battery.

  The sources of the FETs 21 to 23 are connected to the drains of the remaining three FETs 24 to 26, respectively. Furthermore, the sources of the FETs 24 to 26 are grounded via the shunt resistors 31 to 33, respectively.

  A connection point between the paired FET (Su +) 21 and FET (Su−) 24 is connected to one end of the U-phase coil 11 via the motor-side circuit breaker 50. A connection point between the paired FET (Sv +) 22 and FET (Sv−) 25 is connected to one end of the V-phase coil 12 via the motor-side circuit breaker 50. Furthermore, the connection point between the FET (Sw +) 23 and the FET (Sw−) 26 is connected to one end of the W-phase coil 13 via the motor-side circuit breaker 50. Therefore, the current flowing through each phase of the motor 10 can be taken out as a potential difference between both ends of the shunt resistors 31 to 33.

  As described above, the shunt resistors 31 to 33 are connected to the sources of the FETs 24 to 26, respectively. The operational amplifiers 34 to 36 receive the voltages across the shunt resistors 31 to 33. Output terminals of the operational amplifiers 34 to 36 are connected to the arithmetic device 60. As a result, the operational amplifiers 34 to 36 amplify the potential difference between both ends of the shunt resistors 31 to 33 and input them to the arithmetic device 60.

  A power supply breaker 40 interposed between the inverter 20 and the power supply 70 is composed of two MOSFETs 41 and 42 similar to those constituting the inverter 20. These MOSFETs 41 and 42 function as switching elements, and the drain-source is turned on (conducted) or turned off (cut off) depending on the potential of the gate. Hereinafter, the MOSFETs 41 and 42 are simply referred to as FETs 41 and 42. Further, the FET 41 on the power supply 70 side is described as “A-FET 41”, and the FET 42 on the inverter 20 side is described as “B-FET 42”, and they are appropriately distinguished. In the present embodiment, both ends of the B-FET 42 are connected to the arithmetic device 60. Thereby, the voltages V 1 and V 2 across the B-FET 42 are input to the arithmetic device 60. Further, the A-FET 41 is arranged so that the current passing direction of the diode 41a faces the power supply 70 side. The B-FET 42 is arranged so that the current passing direction of the diode 42a faces the inverter 20 side. That is, the two FETs 41 and 42 are arranged so that the respective diodes 41a and 42a are staggered.

  On the other hand, the motor-side circuit breaker 50 interposed between the inverter 20 and the motor 10 is composed of a mechanical relay. The motor-side circuit breaker 50 can electrically disconnect the motor 10 from the inverter 20.

  The arithmetic device 60 controls the power converter 1 as a whole. Although a control line is not particularly illustrated in order to avoid complication, the arithmetic device 60 is configured such that the potential of the gates of the six FETs 21 to 26 of the inverter 20, the potential of the gates of the two FETs 41 and 42 of the power supply breaker 40, And the motor side circuit breaker 50 is controlled.

Next, drive control of the motor 10 by the arithmetic unit 60 will be described.
The inverter 20 is driven by so-called PWM control. That is, a triangular wave for PWM control is sent from a circuit not shown. The arithmetic device 60 creates a voltage command signal corresponding to each phase. Then, the FETs 21 to 26 of the inverter 20 are turned ON / OFF according to the magnitude relationship between the voltage command signal corresponding to each phase and the triangular wave. This will be specifically described.

  FIG. 2A shows a triangular wave T and voltage command signals U, V, and W in PWM control. The voltage command signal U indicates a U-phase voltage command signal and is a solid line in the figure. Similarly, the voltage command signal V indicates a V-phase voltage command signal, which is a broken line in the figure. Further, the voltage command signal W indicates a W-phase voltage command signal, which is indicated by a one-dot chain line in the drawing. Moreover, FIG.2 (b) is an enlarged schematic diagram of the part shown by the symbol T1 in Fig.2 (a).

  FIG. 2B shows the correspondence between the voltage command signal (Duty) of each phase indicated by a straight line and the triangular wave T, the ON / OFF states of the FETs 21 to 23, and the voltage vector pattern. As can be seen from FIG. 2B, in a period in which the triangular wave T is located above the voltage command signal, the corresponding FETs 21 to 23 are turned off, and in a period in which the triangular wave T is located below the voltage command signal, Corresponding FETs 21 to 23 are turned ON. The reverse is true for the FETs 24 to 26 paired with the FETs 21 to 23. For example, when the FET (Su +) 21 is ON, the FET (Su−) 24 is OFF.

  Specifically, for example, in the period K1, the triangular wave T is located below the voltage command signal U and is located above the voltage command signals V and W. Accordingly, at this time, the FET (Su +) 21 is turned on, the FET (Sv +) 22 is turned off, and the FET (Sw +) 23 is turned off. Then, the paired FET (Su−) 24 is turned off, the FET (Sv−) 25 is turned on, and the FET (Sw−) 26 is turned on. Similarly, for example, in the period K2, the FETs 21 to 26 are OFF, OFF, OFF, ON, ON, and ON, respectively.

  The voltage vector pattern shown in FIG. 2 (b) is a pattern indicating which three of the six FETs 21 to 26 are ON. As shown in FIG. 3, eight voltage vector patterns V0, V1, It can be divided into V2, V3, V4, V5, V6 and V7. Here, in the voltage vector pattern V0, the FETs 24 to 26 positioned on the lower side of the inverter 20 are all turned on, and in the voltage vector pattern V7, the FETs 21 to 23 positioned on the upper side of the inverter 20 are all turned on (see FIG. 1). ). Therefore, effective voltage vector patterns for driving the motor 10 are V1 to V6. Hereinafter, these voltage vector patterns V1 to V6 are referred to as “effective patterns”. In the example described above, the period K1 in FIG. 2B is a voltage vector pattern V1 which is an effective pattern, and the period K2 is a voltage vector pattern V0.

  In the present embodiment, the driving control of the motor 10 is performed by the arithmetic device 60 in this way, but the arithmetic device 60 is characterized in that current detection is performed at a certain timing. Next, current detection by the arithmetic device 60 will be described.

  The arithmetic device 60 performs current detection at time t1 in FIG. That is, current detection is performed at the peak of the triangular wave T where the voltage vector pattern is V0. Specifically, at this timing, the outputs from the operational amplifiers 34, 35, and 36 are taken in, and the current flowing through each phase (each shunt resistor 31 to 33) of the motor 10 is detected, and the power breaker 40 (of the B-FET 42) is detected. The voltages V1 and V2 at both ends) are taken in and the current flowing through the power breaker 40 is detected. Since the voltage vector pattern is V0 at this timing, the current flowing through each phase of the motor 10 can be detected in parallel.

Then, the arithmetic device 60 performs the following control based on the current detected here.
(1) When at least one of the currents flowing through the shunt resistors 31 to 33 is excessive and the current flowing through the power breaker 40 is not excessive, the shunt resistors 31 to 33, the operational amplifiers 34 to 36, and Then, it is determined that the current detection unit configured by the arithmetic device 60 is faulty. In this case, the drive control of the motor 10 is continued as it is. In this case, in the continuing control, the current flowing through the power breaker 40 is monitored, and when this current becomes excessive, stop processing as described later is performed. Further, when an overcurrent is detected in one of the three shunt resistors 31 to 33, the current can be estimated and calculated from the remaining two thereafter.

  (2) When at least one of the currents flowing through the shunt resistors 31 to 33 is excessive and when the current flowing through the power breaker 40 is excessive, the FETs 21 to 26, the U-phase coil 11, and the V-phase It is determined that the drive unit composed of the coil 12 and the W-phase coil 13 has failed. In this case, the inverter 20 is disconnected from the power source 70 by the power interrupter 40. Specifically, the two FETs 41 and 42 are both turned off. At the same time, the motor 10 is disconnected from the inverter 20 by the motor-side circuit breaker 50. In this case, the inverter 20 is disconnected from the power source 70 by the power breaker 40. However, instead of such control, the U-phase coil 11, the V-phase coil 12, and the W-phase coil 13 are switched to the failed phase. The corresponding FETs 21 to 26 may be turned off.

  Here, the short-circuit failure is judged and the control is continued or stopped accordingly. For example, when one of the currents flowing through the shunt resistors 31 to 33 becomes “0”, the disconnection occurs. It is good also as a structure judged to be a failure. At this time, if it can be determined that any one of the U-phase coil 11, the V-phase coil 12, and the W-phase coil 13 is disconnected, the drive control of the motor 10 can be continued with the remaining two. is there.

  The motor 10 in this embodiment constitutes a “multi-phase rotating machine”, the inverter 20 constitutes “switching means”, the FETs 21 to 26 constitute “switching elements”, and the arithmetic device 60 “current supply” "Control means". Further, the shunt resistors 31 to 33, the operational amplifiers 34 to 36, and the arithmetic device 60 constitute “first current detection means”, the power breaker 40 constitutes “interruption means”, and the arithmetic device 60 constitutes “second current detection means”. Means ". Furthermore, the motor side circuit breaker 50 constitutes “rotary machine blocking means”.

  As described above in detail, in this embodiment, the current flowing through each phase of the motor 10 is detected by the shunt resistors 31 to 33, the operational amplifiers 34 to 36, and the arithmetic device 60, and the current flowing through the power breaker 40 is detected. It is detected by the arithmetic device 60. Accordingly, when the current flowing through the motor 10 is excessive and when the current flowing through the power supply breaker 40 is not excessive, the shunt resistors 31 to 33, the operational amplifiers 34 to 36, and the arithmetic device 60 are configured. It is determined that the current detector is malfunctioning. On the other hand, when the current flowing through the motor 10 is excessive and when the current flowing through the power supply breaker 40 is excessive, the FETs 21 to 26, the U-phase coil 11, the V-phase coil 12, and the W-phase coil 13 is determined to be a failure of the drive unit. As a result, it can be estimated whether the short circuit fault in the power converter 1 occurs in the “drive unit” or the “current detection unit”.

  Moreover, in the present invention, the current flowing through the power breaker 40 is detected based on the potential difference between both ends of the B-FET 42. That is, since the current is detected using the resistance value of the B-FET 42 constituting the power breaker 40, the number of parts is reduced as compared with a configuration in which a shunt resistor is separately provided.

  In the present embodiment, when the current flowing through the motor 10 is excessive and when the current flowing through the power breaker 40 is excessive, the inverter 20 is disconnected from the power supply 70 by the power breaker 40. Therefore, no overcurrent continues to flow. At the same time, since the motor 10 is disconnected from the inverter 20 by the motor-side breaker 50, the steering operation can be performed temporarily without being affected by the power running regeneration of the motor 10.

  Furthermore, in this embodiment, the power shut-off device 40 is composed of FETs 41 and 42. This is advantageous in that it can withstand a large current. The power shut-off device 40 is composed of two FETs 41 and 42, and the FETs 41 and 42 are arranged so that the diodes 41a and 42a are staggered. Thereby, it can respond to the power running regeneration of the motor 10. FIG.

It should be noted that by configuring the power breaker 40 with the two FETs 41 and 42, it is possible to determine whether the power breaker 40 is abnormal.
Specifically, on the premise that a power source (not shown) is connected between the inverter 20 and the B-FET 42, the A-FET 41 is turned off and the B-FET 42 is turned on / off to turn the B-FET 42 on. Check the operation. Next, the operation of the A-FET 41 is confirmed by turning off the B-FET 42 and turning the A-FET 41 on and off. In this way, it is possible to determine in advance whether or not the power shut-off device 40 is normal when controlling the drive of the motor 10. Such an operation check is performed, for example, by detecting the voltage between the B-FET 42 and the power source 70 and between the B-FET 42 and the A-FET 41. The voltage detection for detecting the current flowing through the machine 40 can be shared.

  By the way, in this embodiment, the electric current which flows through the power supply circuit breaker 40 is detected based on the voltage of both ends of B-FET42 among FET41,42 which comprises the power supply circuit breaker40. However, the resistance value of the B-FET 42 usually has temperature characteristics.

  Therefore, a configuration in which the arithmetic device 60 estimates the resistance value of the B-FET 42 may be employed. Specifically, the following configurations (A) to (D) are exemplified.

(A) The resistance value of the B-FET 42 is estimated on the assumption that the output power of the power converter 1 is equal to the input power of the power converter 1 multiplied by the efficiency of the power converter 1.
It has already been described that the arithmetic device 60 performs current detection at the peak of the triangular wave T where the voltage vector pattern is V0 (see FIG. 2).

As shown in FIG. 4, when the resistance value of the B-FET 42 is Rr, the current value Ir flowing through the B-FET 42 is expressed by the following formula 1.

Ir = (V1-V2) / Rr Formula 1

On the other hand, if the voltage of the power source 70 is Vp, the voltages at the connection points of the paired FETs 21 to 26 are Vu, Vv, Vw, and the efficiency of the voltage converter 1 is η, the current Ir ′ flowing through the circuit is It is represented by the following formula 2.

Ir ′ = {(Iu × Vu + Iv × Vv + Iw × Vw) × η} / Vp Equation 2

Here, since Ir = Ir ′, the resistance value Rr of the B-FET 42 is expressed by the following expression 3 from the above expression 1.

Rr = (V1-V2) / Ir '... Formula 3

(B) The resistance value of the FET 42 is estimated by estimating the temperature from the current (or power value) flowing through the B-FET 42.
in this case,

(B-1) First, a current is detected from the potential difference obtained from the voltages V1 and V2 across the B-FET 42 and the resistance value Rr of the FET 42.
(B-2) Subsequently, the temperature is estimated from the detected current.
(B-3) Next, the resistance value Rr of the B-FET 42 is estimated (corrected) based on the estimated temperature.

  (C) Of the FETs 21 to 26 of the inverter 20, the paired FETs are simultaneously turned on at predetermined time intervals, and the resistance value Rr of the B-FET 42 is estimated based on the current flowing at this time. For example, the FETs 22 and 25 corresponding to the V phase are simultaneously turned on. Specifically, this is as follows.

(C-1) The FETs 22 and 25 corresponding to the V phase are simultaneously turned on, the remaining FETs 21, 23, 24 and 26 are turned off, and the current values Iv and Ir are detected.
(C-2) Rr is estimated from Iv = Ir. Rr is represented by the following formula 4.

Rr = (V1-V2) / Iv Equation 4

(D) A current is detected with an effective pattern, and the resistance value Rr of the B-FET 42 is estimated.
In this case, an effective pattern is created by offsetting the voltage command signal corresponding to each phase.
For example, as shown in FIG. 5A, the voltage command signal is offset upward so that the maximum duty ratio becomes 100%. At this time, the effective pattern appears at the peak of the triangular wave T in the PWM control. That is, at t2 in FIGS. 5A and 5B, the triangular wave T is located below the U-phase voltage command value. Here, as can be seen from FIG. 5B, the FET (Su +) 21 is ON, the FET (Sv +) 22 is OFF, and the FET (Sw +) 23 is OFF. At this time, the paired FET (Su−) 24 is OFF, the FET (Sv−) 25 is ON, and the FET (Sw−) is ON. This means that the voltage vector pattern becomes an effective pattern of V1.

Therefore, as can be seen from FIG. 6, since Ir = Iv + Iw, the following Expression 5 is satisfied.

(V1-V2) / Rr = Iv + Iw Formula 5

From this equation 5, Rr is expressed by the following equation 6.

Rr = (V1-V2) / (Iv + Iw) (6)

For example, the offset of the voltage command signal may be as shown in FIG.

  Further, for example, as shown in FIG. 8A, the voltage command signal may be offset downward so that the minimum duty ratio becomes 0 percent. In this case, the effective pattern appears in the trough of the triangular wave in the PWM control. That is, at time t4 in FIG. 8A, the triangular wave T is positioned above the W-phase voltage command value. Here, as can be seen from FIG. 8B, the FET (Su +) 21 is ON, the FET (Sv +) 22 is ON, and the FET (Sw +) 23 is OFF. At this time, the paired FET (Su−) 24 is OFF, the FET (Sv−) 25 is OFF, and the FET (Sw−) 26 is ON. This means that the voltage vector pattern becomes an effective pattern of V2.

Therefore, as can be seen from FIG. 9, since Ir = Iw, the following Expression 7 is established.

(V1-V2) / Rr = Iw Equation 7

From this equation 7, Rr is expressed by the following equation 8.

Rr = (V1-V2) / Iw Equation 8

The offset of the voltage command signal may be as shown in FIG. 10A or FIG. 10B, for example.

  With such configurations (A) to (D), if the resistance value Rr of the B-FET 42 constituting the power breaker 40 is estimated, it is advantageous in that current detection can be performed more accurately. In the configurations (A) to (D) described above, the arithmetic device 60 constitutes “resistance value estimating means”.

  As mentioned above, this invention is not limited to the said embodiment at all, In the range which does not deviate from the meaning of invention, it can implement with a various form.

  (A) In addition to the configuration of the above-described embodiment, as shown in FIG. 11, an operational amplifier 37 that amplifies the difference between the voltages V1 and V2 at both ends of the B-FET 42 may be provided. In this way, even if the potential difference (V1-V2) is small, appropriate detection is possible, contributing to detection of the current flowing through the power breaker 40. In this case, the operational amplifier 37 and the arithmetic device 60 constitute “second current detection means”.

(B) In the above embodiment, the power supply breaker 40 is configured by the two FETs 41 and 42.
On the other hand, you may make it comprise with the mechanical relay 43 as shown in FIG. At this time, as shown in FIG. 13, an operational amplifier 38 that amplifies the difference between the voltages V1 and V2 at both ends of the mechanical relay 43 may be provided. In this way, even if the potential difference (V1-V2) is small, appropriate detection is possible, contributing to current detection. In the configuration in which the operational amplifier 38 is provided, the operational amplifier 38 and the arithmetic device 60 constitute “second current detection means”.

(C) In the above embodiment, the configuration includes the three shunt resistors 31 to 33 corresponding to the respective phases of the motor 10.
On the other hand, it may be configured by two shunt resistors. For example, as shown in FIG. 14, two shunt resistors 32 and 33 corresponding to the V phase and the W phase and operational amplifiers 35 and 36 corresponding thereto are configured. In this case, it is conceivable to calculate the U-phase current value Iu from the V-phase and W-phase current values Iv and Iw. In this case, the shunt resistors 32 and 33, the operational amplifiers 35 and 36, and the arithmetic device 60 constitute “first current detection means”.

It is a schematic block diagram which shows the electric constitution of the power converter of embodiment of this invention. (A) is explanatory drawing which shows the relationship between the triangular wave in PWM control, and the voltage command signal corresponding to each phase, (b) is an enlarged schematic diagram of (a). It is explanatory drawing which shows the voltage vector pattern produced by control of FET. It is explanatory drawing for demonstrating electric current detection. (A) is explanatory drawing which shows a mode that the voltage command signal corresponding to each phase was offset upwards with respect to the triangular wave in PWM control, (b) is an enlarged schematic diagram of (a). It is explanatory drawing which shows the flow of the electric current in a predetermined voltage vector pattern. It is explanatory drawing which shows a mode that the voltage command signal corresponding to each phase was offset with respect to the triangular wave in PWM control. (A) is explanatory drawing which shows a mode that the voltage command signal corresponding to each phase was offset below with respect to the triangular wave in PWM control, (b) is an enlarged schematic diagram of (a). It is explanatory drawing which shows the flow of the electric current in a predetermined voltage vector pattern. It is explanatory drawing which shows a mode that the voltage command signal corresponding to each phase was offset with respect to the triangular wave in PWM control. It is a schematic block diagram which shows the electric constitution of the power converter of another embodiment of this invention. It is a schematic block diagram which shows the electric constitution of the power converter of another embodiment of this invention. It is a schematic block diagram which shows the electric constitution of the power converter of another embodiment of this invention. It is a schematic block diagram which shows the electric constitution of the power converter of another embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Voltage converter (power converter), 10 ... Motor (multi-phase rotating machine), 11 ... U-phase coil, 12 ... V-phase coil, 13 ... W-phase coil, 20 ... Inverter (switching means), 31-33 ... shunt resistor, 34 to 38 ... operational amplifier, 40 ... power supply breaker (breaker), 41a, 41b ... diode, 43 ... mechanical relay (breaker), 50 ... motor side breaker (rotating machine breaker), 60 ... Calculation device (current supply control means), 70 ... Power supply (power supply)

Claims (11)

A power converter used in a multi-phase rotating machine composed of a plurality of phases of three or more phases,
Switching means configured to include a pair of switching elements corresponding to each phase of the multiphase rotating machine, and for supplying a driving current to the multiphase rotating machine from a power source;
Current supply control means for controlling a switching element of the switching means to a conductive state or a non-conductive state and supplying a drive current to the multi-phase rotating machine;
First current detection means capable of detecting a current flowing in each phase of the multiphase rotating machine;
A blocking means interposed between the power supply and the switching means, and capable of electrically blocking the power supply and the switching element;
A second current detection means capable of detecting a current flowing through the cutoff means using a resistance value of the cutoff means;
A power converter comprising: The power converter according to claim 1, wherein
The current supply control means makes the switching element non-conductive or controls the interruption means when an overcurrent is detected by both the first current detection means and the second current detection means. A power converter characterized in that the power supply and the switching element are electrically cut off. The power converter according to claim 2, wherein
Rotating machine shut-off means capable of electrically shutting off the multi-phase rotating machine from the switching means,
The current supply control means controls the rotating machine shut-off means and shuts off the multi-phase rotating machine and the switching means together with shut-off of the power source by the shut-off means. In the power converter as described in any one of Claims 1-3,
The power shut-off means is constituted by a semiconductor relay. The power converter according to claim 4, wherein
A plurality of the semiconductor relays are provided corresponding to the power running regeneration of the multiphase rotating machine. In the power converter according to any one of claims 1 to 5,
The power converter, wherein the second current detection means includes resistance value estimation means for estimating a resistance value of the blocking means that varies with temperature. The power converter according to claim 6, wherein
The power converter according to claim 1, wherein the resistance value estimating means estimates the resistance value of the blocking means on the assumption that the output power is equal to the input power multiplied by the efficiency. The power converter according to claim 6, wherein
The resistance value estimating unit estimates a temperature based on a current flowing through the blocking unit, and estimates a resistance value of the blocking unit based on the temperature. The power converter according to claim 6, wherein
The power converter is characterized in that the resistance value estimating means estimates a resistance value of the blocking means based on a current that flows when two paired switching elements are simultaneously turned on. The power converter according to claim 6, wherein
The current supply control unit is configured to create a voltage command signal corresponding to each phase of the multiphase rotating machine, and to control the switching unit based on the voltage command signal and the PWM signal.
The resistance value estimation means assumes that the current detected by the first current detection means and the current detected by the second current detection means are equal in the specific state of the switching means, and the resistance value of the interruption means A power converter characterized by estimating. The power converter according to claim 6, wherein
The current supply control unit is configured to create a voltage command signal corresponding to each phase of the multiphase rotating machine, and to control the switching unit based on the voltage command signal and the PWM signal.
The resistance value estimation means creates a specific state of the switching means at a predetermined timing by offsetting the voltage command signal, and at this timing, the current detected by the first current detection means and the second current detection A power converter characterized by estimating a resistance value of the shut-off means on the assumption that the current detected by the means is equal.

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