JP2001231291A - Pwm inverter system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress electromagnetic noise and vibration which are caused by a waveform distortion generated when a plurality of single-phase windings are influenced by a change in current of other phases since the electromagnetic coupling force among the single-phase windings is large. SOLUTION: A PWM inverter system comprises a plurality of inverters 3-1 to 3-8, current command determining means 4-1 to 4-8, and characteristic improvement signal calculation means 6-1 to 6-8. The inverters 3-1 to 3-8 are installed respectively for a plurality of the single-phase windings of an AC motor. The inverters 3-1 to 3-8 conduct a PMW control and supply a current to the corresponding single-phase windings according to a current command. The current command determining means 4-1 to 4-8 are installed respectively for the inverters 3-1 to 3-8. Based on a common current reference and AC motor rotor position detection signal, the current command determining means produce a plurality of current commands which have such a phase difference that a rotating magnetic field may be produced by each single-phase winding and then supply the produced current commands to the corresponding converters. Based on the common current reference and AC motor rotor position detection signal, the characteristic improvement signal calculation means 6-1 to 6-8 produce such characteristic improvement signals as to prevent the decrease of the output which is caused by strong electromagnetic coupling among the single-phase windings by which the single-phase windings are influenced by a change of current of other phase and a current is not caused to flow smoothly. The characteristic improvement signal calculation means supply the produced signals to the corresponding inverters.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-phase AC motor (hereinafter simply referred to as a "phase motor") that generates a rotating magnetic field by a multi-phase winding formed by arranging a plurality of independent single-phase windings with a predetermined phase difference. PWM that drives an AC motor)
(Pulse width modulation) The present invention relates to an inverter device, and more particularly to a PWM inverter capable of suppressing electromagnetic noise and vibration due to waveform distortion when the electromagnetic coupling force between a plurality of single-phase windings is strong and is affected by a current change in another phase. It concerns the device.

[0002]

2. Description of the Related Art Conventionally, as an inverter device, an AC motor that generates a rotating magnetic field by a multi-phase winding configured by arranging a plurality of independent single-phase windings with a predetermined phase difference has been proposed. A PWM inverter device that supplies a three-phase AC current by PWM control to drive an AC motor has been generally widely used.

FIG. 7 is a block diagram showing a configuration example of a conventional general PWM inverter device of this kind.

In FIG. 7, a PWM inverter 51 includes:
Speed controller 52, current controller 53, PWM controller 5
4 and an inverter unit 55.

[0005] The speed control unit 52 receives a given speed reference N
The three-phase current reference Ir is generated based on the difference between r and the actual speed N of the AC motor 50, that is, the speed deviation.

The current control unit 53 compares the three-phase current reference Ir from the speed control unit 52 with the three-phase current detection values I detected via the current detector 56 for each phase. A three-phase current control signal Sc that reduces the deviation is generated.

The PWM control unit 54 receives a PWM signal Sp based on the three-phase current control signal Sc from the current control unit 53.
Generate

The inverter unit 55 controls the AC motor 50 based on the PWM signal Sp from the PWM control unit 54.

Thus, the inverter 55 operates to supply the AC motor 50 with an AC current corresponding to the three-phase current reference Sc.

Generally, a sine wave is used as the alternating current supplied by the PWM inverter in order to obtain a smooth rotating magnetic field.

In the case where the induced voltage waveform of the single-phase winding is a square wave like a permanent magnet motor or the like, when the induced voltage of the AC motor 50 approaches the DC power supply voltage, the inverter unit 55 outputs Since the peak value of the AC voltage is limited to the DC power supply voltage, the voltage for flowing the peak current may be insufficient and the capacity may be insufficient.

For this reason, there is known a method of improving the utilization factor of the power supply voltage and securing the output capacity by using a square wave or the like instead of a sine wave for the AC waveform.

[0013]

However, in the case of an AC motor composed of a large number of single-phase windings wound in such a structure that the coupling force between the single-phase windings is strong, the other phase has Since the current change appears as a current change or a voltage change in the winding of the self-phase, the voltage of the self-phase is controlled so as to counter the voltage change due to the influence of the other phase so that the current matches the current command value. Then, the stronger the electromagnetic coupling between the single-phase windings and the greater the number of phases of the single-phase windings, the greater the effect.

Therefore, in order to control according to the current command value, a response speed corresponding to the change amount is required, and the control gain becomes extremely large, which may cause an unstable state.

When it is difficult to increase the response speed, the current waveform cannot be kept up with the current change or the voltage change, so that the current waveform is distorted, and torque pulsation occurs to generate vibration.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for driving an AC motor by PWM control, in which the electromagnetic coupling force between a plurality of single-phase windings is strong, and the electromagnetic noise or waveform noise due to waveform distortion is affected by the change in the current of the other phase. An object of the present invention is to provide a PWM inverter device capable of suppressing vibration.

[0017]

To achieve the above object, according to the first aspect of the present invention, a multi-phase winding is constituted by arranging a plurality of independent single-phase windings with a predetermined phase difference. In a PWM inverter device that drives an AC motor that generates a rotating magnetic field by a wire, a single-phase winding corresponding to a current according to a current command is provided for each of a plurality of single-phase windings, and performs PWM control. And a plurality of single-phase windings, based on a common current reference and a rotor position detection signal of the AC motor, provided in correspondence with the plurality of inverters. Current command determining means for generating a plurality of current commands having a phase difference with each other and applying the generated current commands to the corresponding inverters, based on a common current reference and a rotor position detection signal of the AC motor Generates a characteristic improvement signal that suppresses a decrease in output due to a strong electromagnetic coupling force between a plurality of single-phase windings and a current change due to the influence of a current change in another phase, and gives it to a corresponding inverter. And a characteristic improvement signal calculation means.

According to a second aspect of the present invention, in the PWM inverter device according to the first aspect, the plurality of single-phase windings are insulated from each other so as to generate a rotating magnetic field having a plurality of poles. The plurality of inverters are arranged to synchronize the phase of each output current with the phase of the induced voltage generated in the single-phase winding by the rotation of the AC motor based on the current command, thereby inducing the phase sequence of each output current. The current is supplied so as to generate the rotating magnetic field in accordance with the phase sequence of the voltage.

Therefore, in the PWM inverter according to the first and second aspects of the present invention, by providing the above-described means, the alternating current supplied to each single-phase winding of the AC motor is controlled by the alternating current. Synchronize with the phase of the induced voltage generated in the single-phase winding when the motor rotates, so that the phase order of each AC current generates a rotating magnetic field in accordance with the phase order of the induced voltage of each single-phase winding. Supplied. Accordingly, when the electromagnetic coupling force between the single-phase windings of the AC motor is strong and the interaction due to the current change of the other phase is large, even when the response speed of the current control unit of the individual inverter cannot be increased, the individual The amplitude of the electromagnetic sound generated from the single-phase winding of the AC motor due to the ripple current of the AC current supplied from the inverter can be reduced. In addition, since it is effective for increasing the interaction when the number of phases of the single-phase winding increases, in the case of a large-capacity AC motor, the number of single-phase windings is increased to several hundreds and the corresponding It is also possible to configure so that current is supplied from one inverter. As a result, the capacity per AC single-phase winding of the AC motor can be reduced, and the induced voltage can be reduced with respect to the power supply voltage. Therefore, the influence of current waveform distortion due to insufficient capacity can be reduced. As described above, when an AC motor is driven by PWM control, it is possible to suppress electromagnetic noise and vibration due to waveform distortion when the electromagnetic coupling force between a plurality of single-phase windings is strong and is affected by a current change in another phase. It becomes possible. Further, by increasing the number of single-phase windings, even if some of the inverters fail, the operation of the entire device can be continued without any trouble by disconnecting the failed inverter.

Further, according to a third aspect of the present invention, in the PWM inverter device according to the first or second aspect, the current command determining means is configured to detect the rotor position detection signal based on a common current reference. Means for generating a current command using the obtained phase signal, wherein each of the plurality of inverters has a current control signal for reducing the difference between the current command given from the corresponding current command determination means and the detected value of the output current. , A current control signal generated by the current control unit, and a characteristic improvement signal generated by the characteristic improvement signal calculating means.
A PWM control unit that generates a signal and an inverter unit that is driven by the PWM signal generated by the PWM control unit, converts DC to AC, and outputs a single-phase AC current.

Therefore, in the PWM inverter device according to the third aspect of the present invention, by providing the above means, each phase of the current command given from the current command determining means to the inverter is such that the AC motor rotates. Sometimes, each inverter is synchronized with the phase of the induced voltage generated in the connected single-phase winding, and the phase order of each current command is such that a rotating magnetic field is generated according to the arrangement order of each single-phase winding. , And the current command of each inverter is generated individually. Thereby, the operation of the inventions according to the first and second aspects can be more effectively achieved.

According to a fourth aspect of the present invention, in the PWM inverter device according to the third aspect of the present invention, the characteristic improvement signal operation means includes a simulation operation section for simulating the drive characteristics of the AC motor, a current instruction and the current command, An ideal current control signal operation unit that generates an ideal current control signal by applying a phase signal obtained from the rotor position detection signal to the simulation operation unit.

Therefore, in the PWM inverter device according to the fourth aspect of the present invention, by providing the above-mentioned means, the ideal current control signal can reduce the deviation between the current command and the actual current. Since the current control section is almost equal to the control signal, the current control section only needs to generate the error between the ideal current control signal and the current control signal to be actually output, so that the current command follows the current command even when the current changes sharply. Can be done.

According to a fifth aspect of the present invention, in the PWM inverter device according to the third aspect of the present invention, the characteristic improvement signal calculation section inputs a phase signal obtained from a rotor position detection signal of the AC motor. A basic improvement signal output unit that outputs a basic improvement signal that is a basis for generating a characteristic improvement signal, and a current command and the phase signal,
An auxiliary improvement signal calculation unit that adds a signal corresponding to the current command to the basic improvement signal.

Therefore, in the PWM inverter device according to the fifth aspect of the present invention, by providing the above means, the output should be in accordance with the basic improvement signal generated by the basic improvement signal output section and the current command. The auxiliary improvement signal, which is a difference from the current control signal, is a potential difference between an output voltage of the inverter necessary for flowing a current according to the current command and a voltage induced by a terminal voltage of each single-phase winding of the AC motor. Since the current command and the phase signal can be approximated, it is possible to calculate the approximate expression in advance, and incorporate the approximate expression into the auxiliary improvement signal calculation unit, thereby simplifying the internal configuration and reducing the calculation time. Can be shortened.

According to a sixth aspect of the present invention, in the PWM inverter device according to the third aspect of the present invention, the detected value of the DC power supply voltage of the inverter section is given to the characteristic improvement signal calculating means, and The characteristic improvement signal is changed according to a change in the detected value.

Therefore, in the PWM inverter device according to the sixth aspect of the present invention, by providing the above means, the detection signal of the DC power supply voltage input to the inverter is given to the auxiliary improvement signal to improve the characteristic. Since the signal changes, even when the power supply voltage changes, a characteristic improvement signal corresponding to the change can be output.

Further, in the invention according to claim 7, in the PWM inverter device according to the invention according to claim 1, a current reference for reducing the speed deviation based on the speed deviation of the AC motor is generated, and Speed control means is provided for giving a current reference to each of the current command determination means together with the rotor position detection signal.

Therefore, in the PWM inverter device according to the seventh aspect of the present invention, by providing the above means, a current reference for eliminating the speed deviation of the AC motor is generated, and this is used for detecting the rotor position. Since the signal is given to each current command determining means together with the signal, the operation of the invention according to claim 1 and claim 2 can be further effectively achieved.

[0030]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(First Embodiment: Corresponding to Claims 1, 2 and 7) FIG. 1 is a block diagram showing a basic configuration example of a PWM inverter device according to this embodiment.

In FIG. 1, AC motor 1 is provided with a plurality of independent (eight in this embodiment) single-phase windings.

The plurality of single-phase windings are all configured as independent (insulated) single-phase windings, and a plurality of poles are formed by an alternating magnetic field generated by each single-phase winding to generate a rotating magnetic field. Are arranged at positions shifted sequentially by a predetermined angular position.

On the other hand, the PWM inverter device includes a position detector 2, inverters 3-1 to 3-8, current command determination units 4-1 to 4-8, a speed control unit 5, and a characteristic improvement signal calculation unit. 6-1 to 6-8.

The position detector 2 detects the rotor position of the AC motor 1.

The inverters 3-1 to 3-8 are individually provided for a plurality of single-phase windings of the AC motor 1, respectively.
PWM control is performed to supply a current according to the current command to the corresponding single-phase winding.

The current command determining units 4-1 to 4-8 are provided corresponding to the plurality of inverters 3-1 to 3-8, respectively, and rotate the AC motor 1 from the common current reference and position detector 2. Based on the slave position detection signal, a plurality of current commands having a phase difference with each other such that a rotating magnetic field is generated by a plurality of single-phase windings are generated, and the corresponding inverter 3-1 is generated.
~ 3-8.

The characteristic improvement signal calculation units 6-1 to 6-8 perform an electromagnetic control between a plurality of single-phase windings based on a common current reference and a rotor position detection signal of the AC motor 1 from the position detector 2. A characteristic improvement signal is generated which suppresses a current from becoming difficult to flow due to a strong coupling force and being affected by a current change in another phase, thereby suppressing a decrease in output.
Give to.

The speed controller 5 generates a current reference for reducing the speed deviation based on the speed deviation of the AC motor 1, and uses the current reference to detect the rotor position of the AC motor 1 from the position detector 2. Current command determination unit 4-1 together with the signal
To 4-8.

As described above, a plurality of inverters 3-1 to 3-3
-8 synchronizes the phase of each output current with the phase of the induced voltage generated in the single-phase winding by the rotation of the AC motor 1 based on the current command, and sets the phase sequence of each output current to the phase of the induced voltage. Current is supplied so as to generate a rotating magnetic field in accordance with the order.

Next, the operation of the PWM inverter according to the present embodiment configured as described above will be described.

In FIG. 1, the position of the rotor of the AC motor 1 is detected by the position detector 2, and the position detection signal R
p is input to the speed control unit 5.

Each of the plurality of single-phase windings of the AC motor 1 has a unique single-phase inverter 3 provided for each single-phase winding.
Single phase AC currents I1 to I8 having predetermined phase differences and waveforms are supplied from -1 to 3-8.

Each of the inverters 3-1 to 3-8 is provided with a unique current command determination unit 4-1 to 4-8, and each of the inverters 3-1 to 3-8 is adapted to determine a corresponding current command determination unit. Currents I1 to I8 according to current commands Ir1 to Ir8 output from the section are supplied to corresponding single-phase windings of AC motor 1.

In the speed control section 5, the difference between the actual speed N of the AC motor 1 detected based on the speed reference Nr supplied from the outside and the position detection signal Rp of the AC motor 1 from the position detector 2, that is, A current reference Ir that eliminates the speed deviation is generated and sent to the current command determination units 411 to 4-8 together with the position detection signal Rp.

In order to generate a rotating magnetic field in AC motor 1, each of current command determining units 4-1 to 4-8 has an inverter (ie, a single-phase winding) having a predetermined phase difference corresponding to polyphase AC. Are generated, the current commands Ir1 to Ir8 taking into account the waveform (that is, the instantaneous value) are generated.

Inverters 3-1 to 3-8 individually perform PWM control independently of each other, and apply single-phase AC currents 11 to 18 corresponding to current commands Ir1 to Ir8 to AC motor 1 respectively. To generate a rotating magnetic field to rotate the AC motor 1.

In the characteristic improvement signal operation units 6-1 to 6-8,
A signal that suppresses the interaction of the current changes of the other phases generated by the rotation of the AC motor 1 is added to the current control signals generated inside the inverters 3-1 to 3-8.

As described above, the AC current supplied to each single-phase winding of the AC motor 1 is synchronized with the phase of the induced voltage generated in the single-phase winding when the AC motor 1 rotates, and In order to generate a rotating magnetic field in accordance with the phase sequence of the induced voltage of each single-phase winding.

As described above, in the PWM inverter device of the present embodiment, when the electromagnetic coupling force between the windings of the AC motor 1 is strong and the interaction due to the current change of the other phase is large,
Even when the response speed of the current control units of the individual inverters 3-1 to 3-8 cannot be increased, the individual inverters 3
It is possible to reduce the amplitude of the electromagnetic sound generated from the winding of the AC motor 1 due to the ripple current of the AC current supplied from -1 to 3-8.

Further, since it is effective for increasing the interaction when the number of phases of the single-phase winding is increased, in the case of a large-capacity AC motor 1, the number of single-phase windings is increased to several hundreds, and It can also be configured to supply current from several hundreds of corresponding inverters. As a result, the capacity per AC single-phase winding of the AC motor can be reduced, and the induced voltage can be reduced with respect to the power supply voltage. Therefore, it is possible to reduce the influence of current waveform distortion due to insufficient capacity. .

Furthermore, by increasing the number of single-phase windings, even if some of the inverters fail, the failed inverter can be disconnected to continue the operation of the entire apparatus substantially without hindrance. It becomes possible.

(Second Embodiment: Corresponding to Claim 3) FIG. 2 is a block diagram showing a configuration example of a main part of a PWM inverter device according to this embodiment.

Here, a plurality of inverters 3-1 are used.
To 3-8, and a plurality of current command determination units 4-1 to 4-8
Of the internal configuration of FIG.

As shown in FIG. 2, the current command determining section 4-1
4 to 8 includes a phase calculation unit 41 and a current command calculation unit 42.

The phase calculation section 41 calculates the phase to be supplied to the self-phase single-phase winding based on the position detection signal of the AC motor 1 from the position detector 2.

The current command calculator 42 generates a current command for the self-phase based on the current reference and the phase calculated by the phase calculator 41.

That is, the current command determining units 4-1 to 4-8
Generates a current command using a phase signal obtained from a rotor position detection signal of the AC motor 1 from the position detector 2 based on a common current reference.

On the other hand, inverters 3-1 to 3-8 are provided with a current control unit 31, a PWM control unit 32, and an inverter unit 33.
And a current detector 34.

The current control unit 31 generates a current control signal for reducing the difference between the current command given from the corresponding current command determination units 4-1 to 4-8 and the detected value of the output current.

The PWM control unit 32 generates a PWM signal by combining the current control signal generated by the current control unit 31 and the characteristic improvement signals generated by the characteristic improvement signal calculation units 6-1 to 6-8. .

The inverter unit 33 is driven by the PWM signal generated by the PWM control unit 32, converts DC to AC, and outputs a single-phase AC current.

The current detector 34 detects a single-phase alternating current output from the inverter 33.

Next, the operation of the PWM inverter according to the present embodiment configured as described above will be described.

In FIG. 2, current command determination units 4-1 to 4-4
Based on the position detection signal Rp of the AC motor 1 from the position detector 2, the phase calculation unit 41 of −8 calculates the phase to be energized to the self-phase single-phase winding.

Then, the current command calculation section 42 generates self-phase current commands Ir1 to Ir8 based on the current reference Ir and the phase calculated by the phase calculation section 41.

On the other hand, in the current control units 31 of the inverters 3-1 to 3-8, the current commands Ir1 to Ir8 given from the current command determination units 4-1 to 4-8 and the single currents detected by the current detector 34 are used. The PWM control unit 32, which compares the AC current detection values I1 to I8 of the phase and outputs a current control signal Sc formed from the deviation, outputs a pulse based on the current control signal Sc from the current control unit 31. A PWM signal Sp for width modulation control is output.

In the inverter unit 33, the PWM control unit 32
Is converted into an alternating current based on the PWM signal Sp from the AC motor 1, and single-phase alternating currents I1 to I8 are supplied to the corresponding single-phase windings of the AC motor 1.

In the characteristic improvement signal calculation units 6-1 to 6-8,
A current command and a phase signal are provided from the current command determination units 4-1 to 4-8, and the characteristic improvement signals Sc'1 to Sc'1 corresponding to the current command and the phase signal are provided.
Sc′8 is generated and added to the current control signal Sc from the current control unit 31.

That is, when the current commands Ir1 to Ir8 are input to the inverters 3-1 to 3-8, the current control unit 31
Output the current control signal Sc so as to reduce the difference between the detected AC currents I1 to I8, that is, the current deviation.

When a current command and a phase signal are input to the characteristic improvement signal calculation units 611 to 6-8, a characteristic improvement signal in consideration of the interaction of other phases is generated and output from the current control unit 31. To the current control signal Sc. In response to this, the PWM control unit 32 outputs the PWM signal Sp.

Thus, the current commands Ir1 to Ir1 are supplied from the inverter 33 to the corresponding single-phase windings of the AC motor 1.
Single-phase alternating currents I1 to I8 corresponding to Ir8 are supplied.

In this case, current commands Ir1 to Ir given from current command calculation section 42 to inverters 3-1 to 3-8
8 is synchronized with the phase of the induced voltage generated in the single-phase winding to which each of the inverters 3-1 to 3-8 is connected when the AC motor 1 rotates, and the respective current commands Ir1 to Ir
8 are supplied in such a phase order as to generate a rotating magnetic field in accordance with the arrangement order of the single-phase windings, and the current commands Ir1 to Ir8 of the inverters 3-1 to 3-8 are individually provided. Generated.

As described above, in the PWM inverter device of the present embodiment, the effects of the above-described first embodiment can be more effectively exerted.

(Third Embodiment: Corresponding to Claim 4) FIG. 3 is a block diagram showing a configuration example of a main part of a PWM inverter device according to this embodiment.

Here, the characteristic improvement signal calculation unit 6-
1 to 6-8 specifically show internal configuration examples;
Inverters 3-1 to 3-8 and current command determination unit 4-
About 1-4-8, since it is the same as that of FIG.
Here, illustration and description thereof are omitted.

As shown in FIG. 3, the characteristic improvement signal operation unit 6
Each of -1 to 6-8 includes an ideal current control signal operation unit 61 and a simulation operation unit 62.

The ideal current control signal calculation section 61 gives a phase signal obtained from the current command and the rotor position detection signal of the AC motor 1 from the position detector 2 to the simulation calculation section 62 to provide the inverters 3-1 to 3-1. An ideal current control signal 3-8 is a voltage to be output.

The simulation calculation section 62 simulates the driving characteristics of the AC motor 1.

Next, the operation of the PWM inverter according to the present embodiment configured as described above will be described.

In FIG. 3, the ideal current control signal calculating section 6
1, the current command I from the current command determination units 4-1 to 4-8
When r1 to Ir8 and the phase signals Rp1 to Rp8 are input, a current according to a current command is caused to flow through the single-phase winding of the AC motor 1 based on the calculation result of the driving state of the AC motor 1 by the simulation calculation unit 62. An ideal current control signal, that is, a voltage command to be output by the inverters 3-1 to 3-8 is generated.

The simulation operation section 62 incorporates an operation means for generating a winding terminal voltage for flowing an arbitrary current in consideration of the winding structure of the AC motor 1 and the like.

Therefore, the ideal current control signal is substantially equal to the current control signal for reducing the deviation between the current command and the actual current. Since only the error from the control signal needs to be generated, the current command can be followed even when the current changes sharply.

As described above, in the PWM inverter according to the present embodiment, the ideal current control signal is substantially equal to the current control signal for reducing the deviation between the current command and the actual current. At 31, only the error between the ideal current control signal and the current control signal to be actually output need be generated, so that the current command can be followed even when the current changes sharply.

(Fourth Embodiment: Corresponding to Claim 5) FIG. 4 is a block diagram showing a configuration example of a main part of a PWM inverter device according to this embodiment.

Here, the characteristic improvement signal calculation unit 6-
1 to 6-8 specifically show internal configuration examples;
Inverters 3-1 to 3-8 and current command determination unit 4-
About 1-4-8, since it is the same as that of FIG.
Here, illustration and description thereof are omitted.

As shown in FIG. 4, the characteristic improvement signal operation unit 6
Each of -1 to 6-8 includes a basic improvement signal output unit 63, a waveform data storage unit 64, and an auxiliary improvement signal calculation unit 65.

The basic improvement signal output section 63 supplies a phase signal obtained from the position detection signal of the AC motor 1 from the position detector 2 to generate a basic improvement signal which is a basis for generating the characteristic improvement signal. Output.

The waveform data storage section 64 stores the waveform data which is the basis of the characteristic improvement signal.

The auxiliary improvement signal calculation section 65 receives the current command and the phase signal, and adds a signal corresponding to the current command to the basic improvement signal from the basic improvement signal output section 63.

Next, the operation of the PWM inverter according to the present embodiment configured as described above will be described.

In FIG. 4, the basic improvement signal output unit 63 outputs the phase signal Rp1 from the current command determination units 4-1 to 4-8.
When Rp8 is input, a series of waveform data is cyclically read out from the waveform data storage unit 64 in synchronization with the phase signal, and a characteristic improvement signal which is a basis of the characteristic improvement signal is generated based on this signal. .

The waveform data storage section 64 stores waveform data as a basis of the characteristic improvement signal, for example, voltage waveform data induced between the terminals of each single-phase winding when the AC motor 1 is rotated with no load. Have been.

When the current commands Ir1 to Ir8 and the phase signals Rp1 to Rp8 are input from the current command determination sections 4-1 to 4-8, the auxiliary improvement signal calculation section 65 controls the current to be output according to the current commands. An auxiliary improvement signal, which is a difference between the signal and the basic improvement signal, is output.

The auxiliary improvement signal is induced by the output voltages of inverters 3-1 to 3-8 and the terminal voltages of the single-phase windings of AC motor 1, which are necessary to supply a current according to the current command. It can be considered as a potential difference from the voltage, and can be approximately obtained with respect to the current command and the phase signal.

As an example, a case of an AC motor 1 having eight single-phase windings as shown in FIG. 1 will be described.

The voltage equation of the AC motor 1 can be written as: v = Rl + dLl / dt + E (1)

However,

[0099]

(Equation 1)

Here, v, i, e, R, L, and l represent the voltage, current, back electromotive force, resistance, self-inductance, and leakage inductance of each phase, respectively.

FIG. 5 illustrates a method of obtaining an approximate expression of the voltage VE, which is an auxiliary improvement signal when the current command 10, that is, the current I in the above equation (1) is a trapezoidal wave as shown in FIG. FIG.

In FIG. 5, the calculation region is divided into eight for a half cycle, focusing on the portion where the current of each phase changes.

Hereinafter, the first phase voltage v1 will be described.

From the above equation (1),

[0105]

(Equation 2)

Here,

(Equation 3)

Is obtained.

In the area (a) of FIG. 5, since i'3 = i'4 = i'5 = i'6 = i'7 = i'8 = 0,

[0109]

(Equation 4)

In the area (b) of FIG. 5, since i'1 = i'4 = i'5 = i'6 = 1'7 = i'8 = 0,

[0111]

(Equation 5)

Hereinafter, similarly, (c) v1 = R · Ir + 12 · L · Ir · f (d) v1 = R · Ir + 4 · L · Ir · f (e) v1 = R · Ir−4 · L · Ir.f (f) v1 = R.Ir-12.L.Ir.f (g) v1 = R.Ir-20.L.Ir.f (h) v1 = R.i1- (28L + 16l) .Ir. f These results are summarized in a waveform v1 shown in FIG.

The other phases have waveforms shifted by the phase difference from the first phase. This waveform is represented by the dashed line 12
A signal approximated as shown in FIG. Then, by combining the basic improvement signal 11 and the auxiliary improvement signal 12, a characteristic improvement signal 13 is generated.

In FIG. 5, two straight lines are approximated, but depending on the waveform, more straight lines may be used.
Alternatively, approximation by an arbitrary function is also possible.

Further, by further increasing the number of windings of the AC motor 1, the error of the approximate expression is reduced.

By calculating this approximate expression in advance and incorporating it into the auxiliary improvement signal calculation unit 65, the internal configuration is simplified and the calculation time can be shortened.

As described above, in the PWM inverter device of the present embodiment, the auxiliary improvement which is the difference between the basic improvement signal generated by the basic improvement signal output unit 63 and the current control signal to be output according to the current command. The signal is considered to be a potential difference between the output voltage of the inverters 3-1 to 3-8 necessary for flowing the current according to the current command and the voltage induced at the terminal voltage of each single-phase winding of the AC motor 1. Since the current command and the phase signal can be approximately obtained, the approximate expression is calculated in advance, and the auxiliary improvement signal operation unit 65 is calculated.
, The internal configuration is simplified, and the calculation time can be shortened.

(Fifth Embodiment: Corresponding to Claim 6) FIG. 6 is a block diagram showing a configuration example of a main part of a PWM inverter device according to this embodiment.

Here, the characteristic improvement signal calculation section 6-
1 to 6-8 specifically show internal configuration examples;
Inverters 3-1 to 3-8 and current command determination unit 4-
About 1-4-8, since it is the same as that of FIG.
Here, illustration and description thereof are omitted.

As shown in FIG. 6, the characteristic improvement signal operation unit 6
Each of -1 to 6-8 has a configuration in which a gain setting unit 66 and a multiplication unit 67 are added to the characteristic improvement signal calculation units 6-1 to 6-8 in FIG.

The gain setting section 66 is provided with the inverter 3-
A detected value of the DC power supply voltage of 1 to 3-8 is input, a gain corresponding to the change is set, and a setting signal is output.

The multiplication section 67 multiplies the setting signal from the gain setting section 66 by the auxiliary improvement signal from the auxiliary improvement signal calculation section 65.

That is, the detected values of the DC power supply voltages of the inverters 3-1 to 3-8 are converted into the characteristic improvement signal calculations 6-1 to 6-8.
And the characteristic improvement signal is changed in accordance with a change in the detected value of the DC power supply voltage.

Next, the operation of the PWM inverter according to the present embodiment configured as described above will be described.

In FIG. 6, inverters 3-1 to 3-8
The detection signal of the DC power supply voltage Ed, which is input to the auxiliary improvement signal calculation unit 6 through the gain setting unit 66 and the multiplication unit 67.
5 is multiplied by the auxiliary improvement signal.

Therefore, even when the power supply voltage fluctuates, a characteristic improvement signal according to the fluctuation can be output.

The operation of the other parts is the same as in the case of FIG.

As described above, in the PWM inverter device of the present embodiment, the detection signal of the DC power supply voltage input to inverters 3-1 to 3-8 is given to the auxiliary improvement signal, and the characteristic improvement signal changes. Therefore, even when the power supply voltage fluctuates, it is possible to output a characteristic improvement signal corresponding to the fluctuation.

(Other Embodiments) In each of the above embodiments, a current reference for reducing the speed deviation is generated based on the speed deviation of the AC motor 1, and this current reference is output from the position detector 2. The case has been described in which the speed control unit 5 is provided to each of the current command determination units 4-1 to 4-8 together with the rotor position detection signal of the AC motor 1, but this is not indispensable. Just prepare.

[0130]

As described above, according to the PWM inverter apparatus of the present invention, when driving an AC motor by PWM control, a plurality of single-phase AC currents are supplied from a plurality of inverters to drive the AC motor. Since it can be driven, it is possible to suppress electromagnetic noise and vibration due to waveform distortion when the electromagnetic coupling force between a plurality of single-phase windings is strong and is affected by current changes in other phases.

Further, even when some of the inverters have failed, by disconnecting the failed inverters, the operation of the entire apparatus can be continued without any hindrance.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a PWM inverter device according to the present invention.

FIG. 2 is a block diagram showing a second embodiment of the PWM inverter device according to the present invention.

FIG. 3 is a block diagram showing a third embodiment of the PWM inverter device according to the present invention.

FIG. 4 is a block diagram showing a fourth embodiment of the PWM inverter device according to the present invention.

FIG. 5 is a waveform chart for explaining the operation of the PWM inverter device according to the fourth embodiment.

FIG. 6 is a block diagram showing a fifth embodiment of the PWM inverter device according to the present invention.

FIG. 7 is a block diagram showing a configuration example of a conventional general PWM inverter device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... AC motor 2 ... Position detector 3-1-3-8 ... Inverter 4-1-4-8 ... Current command determination part 5 ... Speed control part 6-1-6-8 ... Characteristic improvement signal calculation part 10 ... Current command 11 Basic improvement signal 12 Auxiliary improvement signal 13 Characteristic improvement signal 31 Current controller 32 PWM controller 33 Inverter 41 Phase calculator 42 Current command calculator 61 Ideal current control signal calculator Reference numeral 62: simulation operation unit 63: basic improvement signal output unit 64: waveform data storage unit 65: auxiliary improvement signal operation unit 66: gain setting unit 67: multiplication unit.

Claims (7)

[Claims] 1. A PWM inverter device for driving an AC motor that generates a rotating magnetic field by a multi-phase winding configured by arranging a plurality of independent single-phase windings with a predetermined phase difference, Provided separately for each phase winding,
A plurality of inverters for performing a PWM control to supply a current according to a current command to the corresponding single-phase winding; a common current reference and a rotor of the AC motor provided for each of the plurality of inverters; Current command determining means for generating a plurality of current commands having a phase difference with respect to each other to generate a rotating magnetic field by the plurality of single-phase windings based on a position detection signal and providing the current commands to the corresponding inverters; Based on a reference and a rotor position detection signal of the AC motor, the electromagnetic coupling force between the plurality of single-phase windings is strongly affected by a change in the current of the other phase. And a characteristic improvement signal calculating means for generating a characteristic improvement signal for suppressing the above and providing the characteristic improvement signal to the corresponding inverter. 2. The PWM inverter device according to claim 1, wherein the plurality of single-phase windings are arranged so as to be insulated from each other so as to generate a rotating magnetic field having a plurality of poles. Based on the current command, the phase of each output current is synchronized with the phase of the induced voltage generated in the single-phase winding by the rotation of the AC motor,
A PWM inverter device which supplies currents so as to generate the rotating magnetic field by adjusting the phase order of each output current to the phase order of the induced voltage. 3. The P according to claim 1 or 2, wherein
In the WM inverter device, the current command determination unit includes a unit that generates a current command using a phase signal obtained from the rotor position detection signal based on the common current reference. A current control unit that generates a current control signal that reduces a difference between a current command given from the corresponding current command determination unit and a detected value of an output current; a current control signal generated by the current control unit; A PWM control unit that generates a PWM signal by combining the characteristic improvement signal generated by the characteristic improvement signal calculation unit; and a single-phase converter that is driven by the PWM signal generated by the PWM control unit, converts DC to AC, and And an inverter for outputting an AC current
M inverter device. 4. The PWM inverter device according to claim 3, wherein the characteristic improvement signal calculation means includes: a simulation calculation unit that simulates a driving characteristic of the AC motor; A PWM inverter device comprising: an ideal current control signal operation unit that supplies an obtained phase signal to the simulation operation unit to generate an ideal current control signal. 5. The PWM inverter according to claim 3, wherein the characteristic improvement signal calculation unit receives the phase signal obtained from the rotor position detection signal of the AC motor and generates the characteristic improvement signal. A basic improvement signal output unit that outputs a basic improvement signal that is a basis for performing the operation, an auxiliary improvement signal calculation that inputs the current command and the phase signal, and adds a signal corresponding to the current command to the basic improvement signal. And a PWM inverter device. 6. The PWM inverter according to claim 3, wherein a detected value of the DC power supply voltage of the inverter unit is provided to the characteristic improvement signal calculating means, and the detected value of the DC power supply voltage is changed according to the change of the detected value of the DC power supply voltage. A PWM inverter device that changes a characteristic improvement signal. 7. The PWM inverter device according to claim 1, wherein a current reference for reducing the speed deviation is generated based on a speed deviation of the AC motor, and the current reference is generated together with the rotor position detection signal. PW comprising a speed control means for giving to each of said current command determination means.
M inverter device.