JP2733724B2 - Current control device for multi-winding AC motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC variable speed drive system in which a multi-phase AC motor is variable-speed driven by a plurality of inverters, and more particularly to a current control device for a multi-winding AC motor using a multiplexed inverter.

[0002]

2. Description of the Related Art To realize a large-capacity AC variable-speed drive system, there is a multiplexing technique for increasing the capacity by combining a plurality of unit power converters. As a multiplexing method, a method of connecting unit power converters in series or in parallel is generally known. However, in the case of a series connection, the voltage sharing of each unit power converter is not averaged, and in the case of a parallel connection, the current sharing of each unit power converter is not averaged, and all of these are applied to the load. There is a problem that it becomes a factor to reduce the power that can be supplied. As a method of improving current sharing, for example, a method of connecting two power converters in parallel to an output terminal via a reactor is known, but requires ancillary equipment such as a reactor, There is a problem that the cost of the apparatus is increased. Here, taking a case where a three-phase output voltage type inverter device is used as a unit power converter as an example, a case where a plurality of inverter devices are connected in parallel and multiplexed will be specifically described. As an example of multiplexing multiple units in parallel,
There is a method as described in JP-A-305792. FIG. 2 shows a main circuit configuration of the publication, showing an example in which two voltage source inverter devices are connected in parallel to a multi-winding motor divided into two winding groups and multiplexed. 1 is a DC power supply, 2A and 2B are voltage type inverter devices, and 3 is a 6-terminal U
_1, is _{V 1, W 1, U 2} , V 2, W 2 3 -phase AC motor having a. Incidentally, Iu1, iU2 denotes a current flowing through the terminal U _1, U _2. Now, the two inverter devices 2A and 2B are operated to output the same voltage according to one voltage command (not shown). However, there are variations in the operation of the gate circuit, the operation of the switching elements, and the like in the inverter, and an imbalance occurs in the output voltage between the inverters, and an imbalance occurs in each winding current of the multi-winding motor 3. Therefore, it is necessary to increase the capacity of each inverter. Further, due to the current imbalance, torque ripple is generated in the output torque of the multi-winding motor 3, and there is a problem that high response and high precision variable speed control cannot be performed. As a method for eliminating the current imbalance, a method in which each inverter has an individual current control circuit can be considered. However, according to this method,
Although the magnitude of each inverter output current is matched, the current phase between the windings of the polyphase AC machine becomes unbalanced. Therefore, torque ripple occurs in the output torque of the motor, and high-response current control cannot be performed. The problem remains. The prior art described above does not consider the problem that the current phases between the windings of the multi-winding motor become unbalanced, thereby causing torque ripple in the output torque, and there is a problem that the torque ripple cannot be reduced.

[0003]

SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to provide a multi-winding AC motor which eliminates imbalance between the magnitude and phase of the current between windings, and provides low torque ripple and high response current control. It is an object of the present invention to provide a current control device for a multi-winding AC motor suitable for realizing a high-response, high-accuracy large-capacity AC variable speed.

[0004]

The object of the present invention is to convert each winding current of a multi-winding AC motor into a two-axis component current (hereinafter referred to as a dq-axis component current Id, an excitation component current and a torque component current orthogonal thereto). Note that the difference signal of each component current means the phase difference of the AC current of each winding, and the difference signal of Id and Iq of each winding becomes zero. By providing a current unbalance compensation circuit that corrects the voltage command signal of each inverter and an average current detection circuit that calculates the average value of the dq-axis component currents of each winding,
Achieved.

[0005]

[Function] The magnitude and phase of each winding current of a multi-winding AC motor are detected, and when a difference occurs between the magnitude and phase of each winding current, the current imbalance compensation circuit and the average current detection circuit determine the magnitude and phase of the AC current. It works to eliminate phase errors. For this reason, current imbalance between the windings is eliminated, and low torque ripple, high response, and high precision current control are realized.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 3 is a vector diagram for explaining a current control method according to the present invention. In FIG. 1, the main circuit configuration is the same as that of the conventional main circuit configuration of FIG.
This is an example in which A and 2B are connected in parallel to a multi-winding motor 3 divided into two winding groups and multiplexed. Each inverter 2A, 2
Current detectors 4A and 4B for detecting the output current of each inverter are provided on the output side of B. Although not shown, each of the current detectors 4A and 4B has three detectors for detecting a three-phase current. Each inverter 2
A and 2B are PWM (Pulse Width Modul) corresponding to the respective AC voltage command signals Va * and vb *.
ation) PWM pulse generating circuit 5 for outputting a pulse
A, 5B, the AC voltage command signals Va *, vb
A voltage corresponding to * is output to supply power to the multi-winding motor 3. The current control system converts the current magnitude and phase commands into an excitation component current command Id * and a torque component current command Iq.
* AC frequency command signals va * and vb * required for each winding of the motor are calculated and output by the multiplex current control circuit 6 described below.
Current control ia, ib is supplied to the multi-winding motor 3 via the M pulse generation circuits 5A, 5B and the inverters 2A, 2B, and current control is performed using the detection values ia, ib from the current detectors 4A, 4B as feedback values. Make up the system. The multiplex current control circuit 6 receives a primary frequency command ω1 * as input and outputs a two-phase sine wave reference (phase) signal, a d-q axis component voltage command Vda *, Vq
a *, Vdb *, Vqb *, voltage command coordinate converters 8A, 8B for coordinate conversion into three-phase AC voltage command signals va *, vb * in the stator coordinate system, and d-
Current component detection coordinate converters 9A and 9B for performing coordinate conversion into q-axis component currents Ida, Iqa, Idb and Iqb, and d of each winding
-Average current detection circuit 1 for calculating the average value of the q-axis component current
0, each component current command Id *, Iq * as a command, and the average current I {d, I} which is the output of the average current detection circuit 10
The average current control circuit 11, which receives the deviation from q as an input, corrects the imbalance between the winding currents by inputting the deviation between the average currents I￣d, I￣q and the dq-axis component currents of each winding. Current imbalance compensation circuits 12A and 12B, adder 13
A, 13B.

Assuming that there is no imbalance in the output voltage between the inverters, equal alternating currents ia and ib flow through the windings, and the dq axis component currents of the windings become equal. That is,
The outputs of the current component detection coordinate converters 9A and 9B become equal, and the outputs of the current imbalance compensation circuits 12A and 12B become zero. In this state, the dq axis component voltage command output from the average current control circuit 11 is input to the voltage command coordinate converters 8A and 8B of the respective windings, and the AC voltage is equal to the voltage command coordinate converters 8A and 8B. Command signal va
*, Vb * are output, and the output voltages between the inverters become equal. Next, the operation when the output voltages between the inverters are unbalanced will be described below. If the output voltage of the inverter is unbalanced as described above, an unbalance occurs in each winding current. First, when the magnitudes of the respective winding currents ia and ib are unbalanced, dq-axis component current detection values of the respective windings (outputs of the current component detection coordinate converters 9A and 9B) Id
Differences occur between a, Iqa, Idb, and Iqb. The d-axis component current detection value Id of each winding in the average current detection circuit 10
The average value I￣d of a and Idb and the average value I￣q of the q-axis component current detection values Iqa and Iqb of each winding are obtained, and these average values are input to the current imbalance compensation circuits 12A and 12B. The deviation of the dq-axis component current detection value of each winding from the average value of. Each of the current imbalance compensation circuits 12A and 12B determines the dq of each winding based on the deviation so that the difference between the dq axis component currents of each winding becomes zero.
A signal for correcting the axis component voltage command is output. These signals are added in adders 13A and 13B, and AC voltage command signals va * and vb * are output from voltage command coordinate converters 8A and 8B.
Is output, and the inverter operates so as to compensate for the voltage imbalance in the inverter, so that the magnitudes of the alternating currents between the windings match. Next, each winding current ia, ib
FIG. 3A shows an example of the current waveform at this time when there is an imbalance due to the current phase of FIG. In the state where the AC currents ia and ib having the waveforms of the A-system and the B-system shown in FIG.
When the current phases of the windings are different from each other, such as the current phase θb of the AC current ib of the a and B systems, the dq-axis component current detection value of each winding (the output of the current component detection coordinate converters 9A and 9B). 3) Ida, Iqa, Idb, Iqb are shown in FIG.
Detection is performed as shown in the vector diagram of FIG. That is, for the reference commands Id * and Iq *, A system Ida is small, Iqa is large, and B system Idb is large.
Iqb is detected small. Therefore, the current command i *
In contrast, if there is a phase difference between the AC currents ia and ib of the respective windings, a difference occurs in the dq-axis component current detection values of the respective windings. This difference detects the phase difference of the AC current. Is equivalent to Then, when a difference occurs between the dq-axis component current detection values of the windings, the dq-axis component current detection values of the windings are input to the current imbalance compensation circuits 12A and 12B, respectively.
As described above, the deviation between the average value I￣d of the d-axis component current of each winding of the average current detection circuit 10 and the average value I￣q of the q-axis component current of each winding is calculated. Each current imbalance compensation circuit 1
2A and 12B are dq of each winding based on this deviation.
A signal for correcting the dq axis component voltage command of each winding is output so that the difference between the axis component currents becomes zero, and the adders 13A, 13A
The AC voltage command signals va *, vb * are output via B, and the inverter operates to compensate for the voltage imbalance in the inverter, so that the phases of the AC currents between the windings match. In each case, each winding current ia, i
Although the case where there is an imbalance due to the magnitude of b or the current phase has been described, the present embodiment also functions similarly when imbalance occurs due to the magnitude and current phase of each winding current ia, ib. Needless to say.

The embodiment of FIG. 1 described above is a system in which an in-phase current flows through each winding of a multi-winding motor. As another embodiment, for example, the current phase between the windings is set to 30 °. There is a six-phase AC motor system in which a current flows through a phase difference. An embodiment in this case is shown in FIG. FIG. 4 shows a current control configuration diagram for a six-phase AC motor. 4 differs from FIG. 1 in that a phase addition circuit 14 is added, and the other circuits operate in the same manner, and therefore description thereof is omitted.
In the case of a six-phase AC motor, the reference sine wave signal of each winding has a phase difference of 30 ° by the phase adding circuit 14. Thus, the AC voltage command signals va * and vb * of each winding and the reference phase which is the input of the dq-axis component current detectors 9A and 9B of each winding have a phase difference of 30 °. For this reason,
Alternating currents having different phases can be detected as dq-axis component currents with respect to the reference phase, and the same operation as in the embodiment of FIG. 1 can be performed.

As another embodiment of the present invention, there is a nine-phase or nine-terminal motor system. Also in this case, the concept of providing an average current detection circuit that calculates the average value of the dq axis component currents of each winding and a current unbalance compensation circuit that corrects the current imbalance of each winding is the same, and the present invention is the same. With a multiplex current control circuit, the control circuit can be easily expanded from six phases to nine phases, and the capacity can be easily increased.

[0010]

According to the present invention, an average current detecting circuit and a current imbalance compensating circuit are provided without using any additional equipment for performing multiplexing. Since current imbalance can be eliminated, a low-cost multiplex inverter device can be provided, low-torque ripple, high-response current control can be realized, and high-response, high-accuracy, large-capacity AC variable speed There are advantages that can be provided with the device.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a configuration diagram showing an example of a duplex configuration of a conventional voltage source inverter.

FIG. 3 is a vector diagram for explaining current control according to the present invention.

FIG. 4 is a configuration diagram showing another embodiment of the present invention.

[Explanation of symbols]

 2A, 2B Voltage source inverter device 3 Multi-winding AC motor 4A, 4B Current detector 9A, 9B Current component detection coordinate converter 10 Average current detection circuit 11 Average current control circuit 12A, 12B Current unbalance compensation circuit 13A, 13B Addition vessel

Continuation of front page (72) Inventor Masami Onodera 5-2-1 Omika-cho, Hitachi City, Ibaraki Pref. Hitachi, Ltd. Omika Plant (56) References JP-A-4-3255893 (JP, A) JP-A-3 −253293 (JP, A)

Claims (4)

(57) [Claims] 1. An AC variable speed control device comprising: a plurality of power converters for converting a voltage of a DC power supply into a variable voltage / variable frequency AC; and a multi-winding AC motor driven by the plurality of power converters. A voltage command coordinate conversion means for issuing an AC voltage command signal to each power converter; an excitation current and an excitation current of each winding current of the multi-winding motor; Average current detection means for calculating an average current value from an output signal of the current detection means,
An average current control unit that outputs each component voltage command based on a deviation between each component current command of an excitation component current and a torque component current and an output signal of the average current detection unit; an output signal of the average current detection unit; A winding current unbalance compensating unit that outputs an unbalance compensation voltage for each component based on a deviation from an output signal of each component current detecting unit; A current control device for a multi-winding AC motor, wherein the current control device corrects the voltage command signal. 2. The method according to claim 1, wherein each component current detecting means converts the AC current of each winding into an excitation component current and a torque component current, and when the current phases of the windings are different,
A current control device for a multi-winding AC motor, wherein a difference between an excitation component current detection value and a torque component current detection value of each winding with respect to a reference command is obtained, and the difference is equivalent to a phase difference of an AC current. 3. The method according to claim 1, further comprising a phase adding means for giving a predetermined phase difference between a reference phase of the voltage command coordinate converting means of each winding and a reference phase of each of the component current detecting means. Control device for multi-winding AC motors. 4. The current control device for a multi-winding AC motor according to claim 1, wherein the multi-winding AC motor is a 9-phase or 9-terminal motor.