JP2005057974A - Inverter device for driving ac motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inverter device for driving an AC motor that can drive and control the AC motor in a desired state, even if there are delay time, a voltage drop of a switching element and the like between the command of a control circuit and the operation of the switching element. <P>SOLUTION: The inverter device 20, arranged between a DC power supply 10 and the AC motor 15, has an inverter circuit 50 that includes a first phase switching element pair 24, a second phase switching element pair 41, and a third phase switching element pair 45. Furthermore, the inverter device 20 includes a phase-voltage detecting means 60 that detects the phase voltage of an output wiring 65 extended from the connection point 64b of the paired first, second, or third switching element, and a control circuit 57 that controls the pulse width modulation of the paired first, second, and third switching element based on the detection result of the phase voltage detecting means. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an inverter device that controls an AC motor.

  The inverter device is controlled by a control circuit, converts the direct current of a direct current power source into alternating current, and is used to drive an alternating current motor in home appliances (home appliances) and electric vehicles. Here, there are different circumstances between home appliances and electric vehicles. First, there is a problem with the stability of the voltage of the DC power supply. In home appliances, the DC power supply voltage is almost constant. On the other hand, in an electric vehicle or the like, for example, the voltage of the DC power supply varies between acceleration and deceleration.

  Another problem is fluctuations in the operating environment temperature of the inverter. In home appliances installed indoors, the temperature difference between day and night and season is small, and the fluctuation of the operating temperature of the inverter device is small. On the other hand, in an electric vehicle or the like that travels outdoors or is left outdoors throughout the day and night, the operating environment temperature of the inverter device varies greatly.

  In consideration of these, for example, a conventional control drive device for an electric compressor for automobiles (see Patent Document 1) includes a DC power source (battery) or a generator that is a power source of the vehicle driving motor 100 as shown in FIG. 102, a DC / AC converting means (inverter) 104, a DC voltage detecting means 106 for detecting a DC voltage, a pulse width changing means 108, and an electric compressor 110.

The DC voltage detecting means 106 detects the voltage of the DC power supply 102 and outputs the result to the pulse width changing means 108. The pulse width changing unit 108 changes the basic pulse width read from the ROM with the information from the DC voltage detecting unit 106, and then outputs it to the switching element control signal generating unit 112. Based on the signal from the control signal generator 112, the DC / AC changing means 106 converts the DC voltage from the DC power source 102 for turning on and off the switching element 105 into a three-phase pseudo AC voltage in the form of a rectangular pulse train and applies it to the electric compressor 110. To do.
Japanese Patent No. 3084866

  In the above conventional example, the pulse width changing unit 108 changes the pulse width based on a signal from the DC voltage detecting unit 106 disposed between the DC power source 102 and the DC / AC converting unit 104. However, there is a delay time between the command signal from the pulse width changing unit 108 and the operation of the switching element 105 of the DC / AC switching unit 106. Even if the switching element 105 receives an ON command from the pulse width changing means 108, a voltage drop occurs at both ends thereof.

  As a result, an error occurs between the applied voltage recognized by the pulse width changing unit 108 and the applied voltage actually applied from the DC / AC switching unit 104 to the electric compressor 110. (In addition, this error is generally easily affected by the operating environment temperature of the inverter.) It is difficult to say that accurate pulse width control can be performed.

  The present invention has been made in view of the above circumstances, and suitable PWM control can be performed even if there is a delay time between the command of the pulse width changing means and the operation of the switching element and / or a voltage drop of the switching element, An object of the present invention is to provide an inverter device that can drive and control an AC motor in a desired state.

  The inventor of the present application detects the phase voltage of the three-phase AC between the inverter device and the AC motor, and corrects the output from the control circuit to the inverter circuit by the input from the phase voltage detection means to the microcomputer of the control circuit. With this in mind, the present invention has been completed.

  The inverter device for an AC motor according to the present invention includes a DC power source, first, second and third positive-side semiconductor switching elements connected to the positive electrode side of the DC power source, and a negative electrode side. First, second, and third negative-side semiconductor switching elements connected in series to the first, second, and third positive-side semiconductor switching elements, respectively, and first, second, and third positive-side semiconductor switching elements And first, second, and third output wirings extending from the first, second, and third connection points of the first, second, and third negative-side semiconductor switching elements to the AC motor, respectively, The AC motor is driven by a three-phase AC voltage generated by pulse-width modulating the voltage of the first, second and third semiconductor switching element pairs.

  In this inverter device, the phase voltage detection means is connected to at least one of the first, second and third output wirings and detects at least one phase voltage of the AC motor. The control circuit controls the pulse width modulation of the first, second and third semiconductor switching element pairs based on the input from the phase voltage detecting means.

  According to a second aspect of the present invention, in the first aspect, the control circuit corrects the modulation width ratio of the pulse width modulation voltage applied to the switching element based on the operation delay time of the switching element calculated from the change timing of the phase voltage. First correction means.

  According to a third aspect of the present invention, there is provided the inverter device according to the first or second aspect, wherein the control circuit detects the amplitude of the phase voltage obtained by subtracting the voltage drop of the switching element from the power supply voltage, and the pulse width modulation voltage of the switching element is based on the detected value. Second modulation means for correcting the modulation width ratio. According to a fourth aspect of the present invention, in any one of the first to third aspects, the DC power source is an in-vehicle battery and the AC motor is an in-vehicle motor.

  According to the inverter apparatus for driving an AC motor of the present invention, the control circuit detects a voltage drop at the switching element based on the command to the switching element of the inverter circuit and the amplitude and timing of the phase voltage input from the phase voltage detecting means. The delay time is calculated to control the PWM. Therefore, it is possible to cope with an error caused by a voltage drop and a delay time in the switching element without being affected by a change in voltage of the DC power supply.

  According to the inverter device of the second aspect, the error due to the delay time between the command to the inverter circuit and the operation of the switching element can be dealt with by correcting the PWM duty ratio by the first correcting means of the control circuit. According to the inverter device of the third aspect, the error due to the voltage drop in the switching element can be dealt with by correcting the duty ratio of PWM by the second correcting means of the control circuit. According to the inverter device of the fourth aspect, the PWM duty ratio can be corrected in an electric vehicle or the like in which the voltage of the DC power source is likely to fluctuate and the use environment temperature of the inverter device is likely to fluctuate.

<AC motor>
The AC motor includes a synchronous motor in which a permanent magnet is inserted into a rotor, and an induction motor in which a coil is loaded in the rotor. In either case, the stator is loaded with a coil. The application of the AC motor is not limited and can be applied to various electric vehicles and various home appliances. However, when used in an electric vehicle in which the fluctuation of the DC power supply voltage is large and the operating temperature of the inverter device tends to fluctuate, a particularly remarkable effect is obtained.
<Inverter device>
(1) The inverter device includes three pairs of switching elements constituting a voltage-controlled inverter circuit, a control circuit that drives and controls the switching element pair, a phase voltage detection circuit that detects a three-phase AC phase voltage of the output wiring, and the like. . Each pair of switching elements includes a positive side switching element and a negative side switching element connected in series thereto, and an output wiring extends from the connection point to the AC motor.
(2) The phase voltage detection means detects at least one phase voltage of three-phase AC flowing through the output wiring between the inverter circuit and the AC motor. Changes in the phase voltages of the U phase, the V phase, and the W phase usually show similar tendencies, so it is sufficient to detect at least one phase voltage. However, when showing a different tendency, it is desirable to detect the phase voltage of each phase.
(3) The control circuit can include a driver and a microcomputer. The driver drives each switching element and includes a terminal corresponding to the switching element.

  The microcomputer controls the inverter circuit through a driver and corrects the PWM duty ratio based on the input from the phase voltage detecting means. Specifically, the operation delay time of the switching element is detected from the detection result (change timing) in the phase voltage detection means, and the modulation width ratio (duty ratio) of the pulse width modulation voltage to the switching element is corrected based on the detection result. To do. For example, when the operation delay time is long, the duty ratio is reduced.

  The microcomputer also detects the amplitude of the phase voltage, which is a value obtained by subtracting the voltage drop of the switching element from the power supply voltage from the detection result of the phase voltage detection means, and corrects the modulation width ratio based on the detection result. For example, when the amplitude is large, the duty ratio is decreased. Although it is possible to calculate only the operation delay time of the switching element or the amplitude of the phase voltage by one correction means, it is desirable to calculate both the operation delay time and the amplitude by one or two correction means.

  The “duty ratio” is the ratio of the on time to the sum of the on time and off time of the rectangular pulse.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
(Constitution)
FIG. 1 shows a circuit diagram of an inverter device according to the embodiment. An inverter device 20 is arranged between a DC power source (battery) 10 having a voltage Vb and a three-phase AC motor (AC motor) 15. The AC motor 15 is a permanent magnet synchronous motor, and a plurality of coils are loaded on the stator, and a plurality of permanent magnets are inserted in the rotor.

  The inverter device 20 includes a smoothing capacitor 22, an inverter circuit 50 including three sets of switching elements 41, a microcomputer 57, a driver 55, and phase voltage detection means 60.

  The U-phase switching element 24 of the inverter circuit 50 includes an upper element 25 and a lower element 29. A switching transistor 26 and a diode 27 reversely connected thereto constitute an upper element 25. The transistor 31 and the diode 32 arranged in parallel form a lower element 29. The upper element 25 and the lower element 29 are arranged in series between the upper line 34 and the lower line 35.

  Similarly, the V-phase switching element 41 includes an upper element 42 and a lower element 43, and the W-phase switching element 45 includes an upper element 46 and a lower element 47. The three sets of switching elements 24, 41 and 45 constitute an inverter circuit 50.

  Each element 25, 29, etc. is driven by a driver 55. The driver 55 includes six terminals 56a to 56f, and command signals HIN1, LIN1, HIN2, LIN2, HIN3, and LIN3 are input to the terminals. The command signal HIN1 is output to the U-phase upper element 25, and the command signal HIN2 is output to the lower element 29. Command signals LIN1 and LIN2 are output to the upper element 42 and the lower element 43 of the V phase, respectively. Command signals HIN3 and LIN3 are output to the upper element 46 and the lower element 47 of the W phase, respectively.

  The microcomputer 57 controls the drive timing of the inverter circuit 50, particularly the switching elements 25, 29, etc. via the driver 55. The driver 55 and the microcomputer 57 constitute a control circuit.

  A U-phase wire 65 extends to the AC motor 15 from a connection point 64 b on the connecting wire 64 a that connects the U-phase upper element 25 and the lower element 29. Similarly, a V-phase line 67 extends to the AC motor 15 from a connection point 66b on the connection line 66a that connects the upper element 42 and the lower element 43 of the V phase. A W-phase wire 69 extends to the AC motor 15 from a connection point 68 b on the connection wiring 68 a that connects the upper element 46 and the lower element 47 of the W-phase.

A phase voltage detection means 60 is disposed between the U-phase line 65 and the lower line 35, and measures the rise and fall timing and amplitude of the applied voltage in the U-phase line 65.
(Function)
The operation in this embodiment (when the current Iu flowing through the U-phase line 65 is positive) will be described with reference to FIG. As shown in FIGS. 2A, 2B, and 2C, the U-phase upper element 25 is turned off after being turned on for a predetermined time in response to a command from the microcomputer 57, and the applied voltage Vu drops accordingly, and then the lower element is turned on. 29 turns on. The lower element 29 is turned off after being turned on for a predetermined time, and then the upper element 25 is turned on. Along with this, the applied voltage Vu increases.

  The microcomputer 57 determines the timing when the command signals HIN1 and LIN1 output from the terminals 56a and 56b of the driver 55 last time to the inverter circuit 50 are changed, and the amplitude and timing of the applied voltage Vu of the U-phase line 65 detected by the phase voltage detecting means 60. Based on the above, the voltage drop and delay time in the upper element 25 and the lower element 29 are calculated, and the next PWM output is controlled.

  Specifically, as shown in FIG. 2 (a), the command signal HIN1 from the microcomputer 57 to the terminal 56a is turned off at time t1, and after a predetermined time td has elapsed, the command signal LIN1 is timed as shown in FIG. 2 (b). Turns on at t3. A time td between the times t1 and 3 is a dead time in which both the command signals HIN1 and LIN1 are off. As shown in FIG. 2C, the applied voltage Vu drops at time t2 during the dead time td.

  The microcomputer 57 calculates the amplitude of the applied voltage obtained by subtracting the voltage drop of the upper element 25 and the voltage drop of the lower element 29 based on the amplitude of the applied voltage (phase voltage) Vu detected by the phase voltage detecting means 60. For example, when the voltage of the battery 10 is Vb and the voltage drop of the upper element 25 is Vhs at the timing when the upper element 25 is turned on, the applied voltage detected by the phase voltage detecting means 60 is (Vb−Vhs). . If the voltage drop of the lower element 29 is Vls at the timing when the lower element 29 is turned on, the applied voltage detected by the phase voltage detection means 60 is Vls.

  From this detection result, the microcomputer 57 detects the amplitude of the applied voltage output from the inverter circuit 50 and corrects the modulation width ratio (duty ratio) based on the detection result. When the amplitude of the applied voltage is larger than a predetermined value, the duty ratio is decreased. Conversely, when the amplitude of the applied voltage is small, the duty ratio is increased.

  The microcomputer 57 also calculates the delay time (operation delay time) of the upper element 25 and the lower element 29 based on the change timing of the applied voltage (phase voltage) Vu. It is understood that the delay time tdoffh is (t2−t1), where t2 is the timing when the upper element 25 is turned off, that is, the applied voltage Vu is turned off, with respect to the timing t1 when the command HIN1 to the terminal 56a of the driver 55 is turned on. .

  From this detection result, the microcomputer 57 detects the off delay time of the upper element 25 and corrects the modulation width ratio (duty ratio) of the pulse width modulation voltage output to the inverter circuit 50 via the driver 55 based on the detection result. . For example, when the delay time is longer than a predetermined value, the duty ratio is decreased. Conversely, when the delay time is short, the duty ratio is increased.

  When the command signal LIN1 is turned off at time t4, the command signal HIN1 is turned on at time t6 after the dead time td has elapsed, and the applied voltage Vu is turned on thereafter, the on-delay time tdonh of the upper element 25 similarly. Is detected and the PWM output is corrected.

  FIGS. 3A, 3B and 3C show the operation when the current value of the U-phase phase current Iu is negative. There is a dead time td between the turn-off of the command signal HIN1 to the terminals 56a and 56b of the driver 55 and the turn-on of the LIN1, and there is a delay time tdonl between the turn-on of the command signal LIN1 and the turn-off of the phase voltage Vu. To do. In addition, there is a delay time tdoffl between the turn-off of the command signal LIN1 and the turn-on of the phase voltage Vu.

Also in this case, the PWM output output from the microcomputer 57 to the inverter circuit 50 via the driver 55 is corrected based on the phase voltage change timing measured by the phase voltage detection means 60.
(effect)
According to this embodiment, first, the phase voltage does not fluctuate even if the power supply voltage fluctuates depending on the driving state of the automobile. The second correction means of the microcomputer 57 outputs the PWM to the switching elements 24, 41 and 45 according to the output related to the amplitude from the microcomputer 57 to the driver 55 and the input related to the amplitude from the phase voltage detection means 60 to the microcomputer 57. This is because the duty ratio is corrected.

  Second, it is possible to cope with an error due to a delay time between the command to the driver 55 and the operation of the switching elements 24, 41 and 45 of the inverter circuit 50. The first correction means of the microcomputer 57 provided between the driver 55 and the phase voltage detection means 60 responds to the output related to the timing from the microcomputer 57 to the driver 55 and the input related to the timing from the phase voltage detection means 60 to the microcomputer 57. This is because the duty ratio of the PWM output to the switching elements 24, 41 and 45 is corrected.

  Third, it is possible to cope with an error caused by a voltage drop of the switching elements 24, 41 and 45 of the inverter circuit 50. The second correction means of the microcomputer 57 outputs the PWM to the switching elements 24, 41 and 45 according to the output related to the amplitude from the microcomputer 57 to the driver 55 and the input related to the amplitude from the phase voltage detection means 60 to the microcomputer 57. This is because the duty ratio is corrected.

  The following effects can also be obtained. First, the PWM output is corrected based on the phase voltage drop timing and amplitude that fluctuate due to fluctuations in the operating environment temperature of the inverter device 20, so that even if there is a temperature fluctuation, the delay time and the voltage drop error will occur. I can deal with it. Furthermore, since the determination is made only with the phase voltage of the U phase, the phase voltage detection means 60 and the microcomputer 57 are simplified.

It is circuit explanatory drawing which shows the Example of this invention. (A) (b) And (c) is an operation explanatory view of the above-mentioned embodiment. (A) (b) And (c) is an operation explanatory view of the above-mentioned embodiment. It is circuit explanatory drawing of a prior art example.

Explanation of symbols

10: DC power supply 15: AC motor 20: Inverter device 24, 41, 45: Switching element 50: Inverter circuit 55: Driver 57: Microcomputer 55, 57: Control circuit 60: Phase voltage detection circuit

Claims (4)

First, second and third positive-side semiconductor switching elements disposed between a direct-current power supply and an alternating-current motor and connected to the positive-electrode side of the direct-current power source, and the first, second and second connected to the negative-electrode side First, second and third negative electrode-side semiconductor elements connected in series to three positive electrode-side semiconductor switching elements, respectively, the first, second and third positive electrode-side semiconductor switching elements and the first, second The first, second and third output wirings extend from the first, second and third connection points between the first negative electrode side semiconductor switching element and the third negative electrode side semiconductor switching element to the AC motor, respectively. An inverter device that drives the AC motor by a three-phase AC voltage generated by pulse width modulation with a pair of second and third semiconductor switching elements,
Phase voltage detection means for detecting a phase voltage connected to at least one of the first, second and third output wirings and detecting at least one phase voltage of the AC motor;
A control circuit for controlling pulse width modulation of the first, second and third semiconductor switching element pairs based on an input from the phase voltage detection means;
An inverter device for an AC motor, comprising:   The control circuit determines a pulse width of the first, second, and third semiconductor switching element pairs based on an operation delay time of the first, second, or third semiconductor switching element pair calculated from the change timing of the phase voltage. The inverter device according to claim 1, wherein the modulation width ratio of the modulation voltage is corrected.   2. The control circuit according to claim 1, further comprising: a second correction unit configured to correct a modulation width ratio of the pulse width modulation voltage of the first, second, and third semiconductor switching element pairs based on the amplitude of the phase voltage. 2. The inverter device according to 2.   The inverter device according to any one of claims 1 to 3, wherein the DC power source is a vehicle-mounted battery, and the AC motor is a vehicle-mounted AC motor.

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