JP2005269818A - Control unit of polyphase ac current - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow the actual current value of each phase of polyphase AC current having the number of phases exceeding three phases follow the current instruction value of respective phase without phase delay. <P>SOLUTION: In order to PWM-control a 5-phase motor 2, for example, through an inverter 1, there are provided a coordinate converter 7 which converts, for coordinate transformation, phase currents i1-i5 to the current component on an orthogonal rotation coordinate and calculates at least two current components id and iq being AC current in a normal state, current controllers 8 and 9 to feedback-control the acquired current components, and a current controller 13 for direct feedback controlling of the current of respective phase. The inverter 1 is controlled using a synthetic value of the voltage command from the current controllers 8 and 9 and that from the current controller 13. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a control device that controls a multiphase alternating current exceeding three phases by using a power converter.

In vector control of an AC motor, it is known that high-performance torque control characteristics and speed control characteristics equivalent to those of a DC motor can be obtained. However, in order to realize this, it is necessary that the three-phase alternating current of the motor is controlled in a three-phase balanced manner with no phase delay with respect to the target value. For this reason, generally, the following current control system is configured to cope with this.
FIG. 3 shows a conventional example in which the speed control of a permanent magnet synchronous motor is performed using an inverter.

FIG. 3 will be described below.
The inverter 1 converts power from a DC power source to a three-phase AC power source. The output is connected to the electric motor 2 through two sets of current detectors 3, and the position detector 4 is connected to the electric motor 2. The speed ω of the motor is obtained by differentiating the rotor position θ detected by the position detector 4 with the speed calculator 5. The speed regulator 6 amplifies the deviation between the speed command value ω ^* and the speed ω.

It is known that the current of a permanent magnet synchronous motor can be decomposed into a current component that produces a magnetic flux in the same direction as the magnetic flux produced by the permanent magnet, and a current component that contributes to torque generation orthogonal to the current component. The former current component is called a direct-axis current or d-axis current, and the latter current component is called a horizontal-axis current or q-axis current. If the output of the speed regulator 6 is a q-axis current command iq ^* and the d-axis current command is id ^* , id ^* is set to zero, for example. The d-axis current id and the q-axis current iq are calculated from the two-phase currents ia and ib of the motor detected by the current detector 3 in the coordinate converter 7 as shown in the following equation (1). It is calculated by doing.

The deviation between the q-axis current command iq ^* and the q-axis current iq is amplified by the current regulator 8 to obtain the q-axis voltage command vq ^* . Similarly, the deviation between the d-axis current command id ^* and the d-axis current id is amplified by the current regulator 9, and the d-axis voltage command vd ^* is obtained. The coordinate converter 10 calculates the three-phase voltage commands va ^* , vb ^* , and vc ^* from vd ^* and vq ^* and the rotor position θ by performing an operation as shown in the following equation (2). Ask. A PWM (pulse width modulation) circuit 11 generates a PWM signal from the obtained three-phase voltage command, and the inverter 1 is controlled by the PWM signal.

  What is characteristic of the above control is that the three-phase alternating current is not directly controlled, but is once transformed into d-axis current and q-axis current, and both currents are controlled to the target current. Is Rukoto. If the alternating current is directly controlled, the actual current value is not less than a phase delay with respect to the current command value, and the effective current value also causes an error with respect to the command value. That is, a steady current deviation occurs. However, when the three-phase alternating current is coordinate-converted into the dq axis coordinate system, which is an orthogonal rotation coordinate system, the coordinate-converted d-axis current and q-axis current are continually DC, so the d-axis current and q By controlling the shaft current, the current can be controlled without a steady deviation. As a result, high-performance current control can be achieved, and high-performance speed control of the motor can be performed.

Japanese Examined Patent Publication No. 59-049797 (pages 2, 6 and 2, 10)

  In general industrial motors, a three-phase motor is usually used. However, for various purposes, a multi-phase motor exceeding three phases may be used. For example, a large-capacity multi-phase motor may be driven using a plurality of small and medium capacity power converters that are easy to manufacture. In addition, harmonic current flows in an electric motor driven by a power conversion device such as an inverter, and torque ripple caused by this harmonic current may be a problem, but in multi-phase motors, torque ripple caused by multi-phase harmonic current may occur. Therefore, a multiphase motor exceeding three phases may be applied for the purpose of reducing torque ripple.

  By the way, when controlling a multiphase current, it is necessary to pay attention to the number of independent variables (or degrees of freedom) of the current. In the example of FIG. 3 as the conventional example, when the current values of the two phases are determined, the current values of the remaining phases are also determined, and therefore the number of independent variables of the current is two. On the other hand, the current after coordinate conversion is also a d-axis current and a q-axis current, and the number of independent variables is two. As described above, when the number of independent variables is the same before and after coordinate conversion, the current of each phase is controlled to the target value indirectly by controlling the d-axis current and the q-axis current to the target command values. Can do.

  However, in the case of a multiphase motor having more than three phases, the above relationship does not occur. For example, consider the case of a five-phase motor driven by five sets of single-phase inverters. In this case, the independent variable of the current is 5, but the independent variable of the current is 2 when the coordinates are converted into the d-axis current and the q-axis current. This indicates that even if the d-axis current and the q-axis current are controlled to the target values, the current of each phase does not always become the target current.

For example, the specific phase current becomes excessive due to the imbalance of the impedance and induced voltage of each winding, and conversely, the current of the specific phase becomes abnormally small. In this case, the utilization rate of the inverter and the electric motor may be deteriorated, and a target output may not be obtained, or in the worst case, an accident may be caused to damage the device.
Therefore, an object of the present invention is to be able to control the current of each phase of a multiphase load exceeding three phases without phase delay.

In order to solve such problems, in the invention of claim 1, in a control device that controls a multiphase alternating current having a number of phases exceeding three phases using a power converter,
Coordinate conversion means for converting multiphase AC current into current components on orthogonal rotation coordinates and calculating at least two current components that are DC current in a steady state, and each current component obtained from the coordinate conversion means A plurality of first current adjusting means for feedback control and a plurality of second current adjusting means for directly feedback controlling the current of each phase are provided, and a voltage command obtained from the first current adjusting means and the second The power converter is controlled based on a combined value with a voltage command obtained from a current adjusting means.

  In the first aspect of the present invention, the first current adjusting means can have at least an integration element (invention of the second aspect), or the first current adjusting means is an integrator, and the second current is adjusted. The adjusting means may be a proportional amplifier (invention of claim 3).

According to the present invention, current control without phase delay can be achieved by the first current adjusting means, and current of each phase can be balanced and controlled by the second current adjusting means. Control can be performed.
Further, by providing the d-axis current and q-axis current regulators with integral elements, the steady-state deviation can be theoretically made zero.
Furthermore, the configuration of the control system can be simplified by using the d-axis current and q-axis current regulator as an integrator and the second current adjustment means as a proportional amplifier.

FIG. 1 is a block diagram showing an embodiment of the present invention.
The description of the same part as the conventional example is omitted, and different points will be mainly described.
The illustrated inverter includes, for example, five sets of single-phase inverters, and the output thereof is connected to the five-phase motor 2 via five current detectors 3. A position detector 4 is connected to the five-phase motor 2. The seat converter 7 performs an operation such as the following expression (3) from the rotor position θ detected by the position detector 4 and the five-phase currents i1 to i5, The d-axis current id and the q-axis current iq are calculated.

The deviation between the q-axis current command iq ^* and the q-axis current iq is amplified by the current regulator 8 to obtain the q-axis voltage command vq1 ^* . Similarly, the deviation between the d-axis current command id ^* and the d-axis current id is amplified by the current regulator 9 to obtain the d-axis voltage command vd1 ^* . The coordinate converter 10 calculates the five-phase voltage commands v10 ^{* to} v50 ^* from vd1 ^* and vq1 ^* and the rotor position θ by performing an operation as shown in the following equation (4).

On the other hand, the coordinate converter 12 performs an operation such as the following equation (5) from the d-axis current command id ^* , the q-axis current command iq ^* and the rotor position θ, thereby calculating each phase. The current commands i1 ^{* to} i5 ^* are obtained.

The deviations of the current commands i1 ^{* to} i5 ^* of each phase and the phase currents i1 to i5 are amplified by five sets of alternating current regulators 13, and the outputs of the alternating current regulators 13 are The voltage commands v1 ^{* to} v5 ^* for each phase are obtained by adding v10 ^{* to} v50 ^* . From this voltage command, a PWM (pulse width modulation) circuit 11 generates a PWM signal, and the inverter 1 is controlled by the PWM signal.

Although the example of the multiphase motor has been described above, the present invention can also be applied to a case where a multiphase AC current is supplied to a plurality of reactors, for example. FIG. 2 shows an example in which a multiphase AC current is supplied to more than three sets of multiphase reactors.
Here, the current command is given separately as the current magnitude and the frequency, the current magnitude is set as the d-axis current command id ^* and the q-axis current command iq ^* , and the frequency command is set in the transmitter 4A. . That is, the electric motor 2 in FIG. 1 is replaced with the reactor 2A and the position detector 4 is replaced with the transmitter 4A, but the other parts relating to current control are the same as in FIG. Therefore, detailed description thereof is omitted.

The coordinate converter 7 calculates the d-axis current and the q-axis current, but further adds a calculation such as a zero-phase current and adds a function for controlling the zero-phase current to a desired value. Also good.
1 and 2, the current regulator 8 that controls the q-axis current and the current regulator 9 that controls the d-axis current are regulators having at least an integral element, thereby reducing the steady-state deviation. It can theoretically be zero.
1 and 2, the current regulator 8 that controls the q-axis current and the current regulator 9 that controls the d-axis current are integrators, and the AC current regulator 13 that controls the current of each phase is By using a proportional amplifier, the configuration of the control system can be simplified.

Block diagram showing an embodiment of the present invention The block diagram which shows the modification of FIG. Block diagram showing a conventional example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Inverter, 2 ... Electric motor, 2A ... Reactor, 3 ... Current detector, 4 ... Position detector, 4A ... Transmitter (OSC), 5 ... Speed calculator, 6 ... Speed regulator, 7, 10, 12 ... Coordinate converter, 8, 9 ... current regulator, 11 ... PWM (pulse width modulation) circuit.

Claims (3)

In a control device that controls a multiphase alternating current having a number of phases exceeding three phases using a power conversion device,
Coordinate conversion means for converting multiphase AC current into current components on orthogonal rotation coordinates and calculating at least two current components that are DC current in a steady state, and each current component obtained from the coordinate conversion means A plurality of first current adjusting means for feedback control and a plurality of second current adjusting means for directly feedback controlling the current of each phase are provided, and a voltage command obtained from the first current adjusting means and the second A control apparatus for a multiphase alternating current, wherein the power converter is controlled based on a combined value with a voltage command obtained from a current adjusting means.   The control apparatus for a multiphase alternating current according to claim 1, wherein the first current adjusting means includes at least an integration element. 2. The control apparatus for a multiphase alternating current according to claim 1, wherein the first current adjusting means is an integrator, and the second current adjusting means is a proportional amplifier.

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