JP7258920B2 - power converter - Google Patents

Description

The present invention relates to a power conversion device used for driving a motor, and more particularly to a power conversion device for use in controlling a motor by digitally converting a rotation angle with a rotation angle sensor.

2. Description of the Related Art A power conversion device used to drive an electric motor sometimes uses a rotation angle sensor such as a resolver or an absolute encoder for controlling the electric motor. When the rotation angle sensor outputs an analog quantity, the power conversion device digitally converts the rotation angle in synchronization with the control cycle of the power conversion device and uses it for motor control, thereby detecting the rotation angle. Delay can be reduced.

Japanese Patent Laid-Open No. 7-218290

When using a rotation angle sensor that performs digital conversion in the rotation angle sensor instead of analog output as described above and transmits the digital amount to the power conversion device by serial communication etc., the communication cycle does not necessarily correspond to that of the power conversion device. Not synchronized with the control cycle. If a rotation angle that is asynchronous with the control period of the power conversion device is used for controlling the power conversion device, there is a concern that the control performance may be lowered due to an increase in speed ripple or torque ripple, which poses a problem.

If it is possible to match the communication cycle and the control cycle, the above problem will be solved. However, since the specifications required for the communication cycle and the control cycle are different, it is generally difficult to match the two.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. A power conversion device capable of obtaining a rotation angle with high accuracy and stably driving an electric motor even when the communication cycle between the power conversion devices and the control cycle are different.

A power conversion device according to the present invention includes a main circuit unit including an inverter that supplies AC power to an electric motor , a rotation angle sensor that detects a rotation angle of the electric motor, an inverter control unit that controls the inverter , and the rotation angle. and a control unit having a rotation angle reception unit that receives a digital rotation angle obtained by digitizing the rotation angle value of the electric motor by a sensor , wherein the rotation angle reception unit receives the digital rotation angle through communication. A restoring unit for calculating a rotation angle signal at a calculation timing that is temporally independent of a communication cycle consisting of a communication timing of , the rotation speed is calculated based on the amount of change in the digitized received value of the rotation angle and the value calculated with the received value related to the communication cycle, and the integrator calculates the rotation speed at the communication timing n When ω(n), the time t(n) at which the communication timing is completed, and the rotation angle θ(n) received by the communication unit at the communication timing n,
A continuous rotation angle signal θ (t), and the control section generates a gate signal for the inverter from the continuous rotation angle signal θ(t) output from the restoration section.

According to the present invention, even when the communication cycle between the rotation angle sensor and the power conversion device is different from the control cycle of the power conversion device, it is possible to obtain the rotation angle with high accuracy and to stably drive the electric motor. It is possible to provide a power converter.

BRIEF DESCRIPTION OF THE DRAWINGS The whole block diagram of the power converter device which concerns on the 1st Embodiment of this invention. FIG. 3 is a block diagram of a rotation angle restoring unit according to the first embodiment of the present invention; FIG. 10 is an example waveform of the operation of the rotation angle restoration unit according to the first embodiment of the present invention; FIG. The whole block diagram of the power converter device which concerns on the 2nd Embodiment of this invention. FIG. 5 is a block diagram of a rotation angle restoring unit according to a second embodiment of the present invention;

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

(First embodiment)
A power converter according to a first embodiment of the present invention will be described below with reference to FIGS. 1 to 3. FIG. FIG. 1 is a block diagram of a power converter and drive system according to a first embodiment of the present invention. The power conversion device according to the first embodiment is a power conversion device that frequency-converts AC power from a commercial three-phase AC power supply 1 by a power converter 2 and supplies it to an electric motor 3 .

The power converter 2 is composed of a main circuit section 20 and a control section 25 . The main circuit section 20 is composed of a converter 21, an inverter 22, a current detector 23, and the like. The AC power input to the power converter 2 is converted into DC power by the converter 21 . The DC power output from the converter 21 is converted into AC power by the inverter 22 and output from the power converter 2 to the electric motor 3 . The electric motor 3 is variable-speed driven by AC power output from the power converter 3 . The electric motor 3 is, for example, a synchronous motor.

The main circuit section 20 is controlled by a control section 25 . The inverter 22 of the power converter 2 is a PWM converter. A power device (not shown) forming the inverter 22 is on/off controlled by a gate signal provided from the control section 25 . A rotation angle sensor 100 is attached to the electric motor 3 and its output is given to the control section 25 . A current detector (inverter output current detector) 23 is provided on the output side of the inverter 22 , and its output is also given to the control section 25 .

The control unit 25 is composed of an inverter control unit 50, a rotation angle receiving unit 60, and the like. A rotation angle sensor 100 attached to the electric motor 3 detects the rotation angle of the electric motor 3 and transmits the detected rotation angle to the rotation angle reception unit 60 by communication.

A speed reference is given to the control unit 25 from the outside. An externally applied speed reference is input to the first input of subtractor 51 . A second input of the subtractor 51 receives the speed feedback ωF obtained by the speed calculator 56 . The subtractor 51 calculates the difference between the first input and the second input, and provides it to the current reference circuit 52 . The current reference circuit 52 is, for example, a PI controller, and outputs a torque current reference so that a speed feedback ωF, which will be described later, follows the speed reference.

The velocity feedback .omega.F is the output of the velocity calculator 56, and can be obtained by performing computation such as differentiation on the rotation angle .theta.(m), which will be described later. Here, the suffix (m) represents timing of control described later. The rotation angle θ (m) represents the rotation angle that the inverter control section 50 uses for control at the control timing m. The inverter control unit 50 is composed of a digital circuit, and its control timing cycle is the control cycle.

The torque current reference is input to voltage reference circuit 53 . The output of current detector 23 is also input to voltage reference circuit 53 . The voltage reference circuit 53 generates a three-phase voltage command so that the torque current component of the output current of the inverter 22 follows the torque current reference based on the rotation angle θ (m). is provided to PWM controller 54 . The PWM controller 54 supplies a PWM-modulated gate signal to each power device of the inverter 22 so that the output voltage of each phase of the inverter 22 becomes a given three-phase voltage command. The inverter 22 is controlled in this way.

The rotation angle sensor 100 will be explained. The rotation angle sensor 100 includes an angle detection section 101, an A/D conversion section 102, a communication section 103, and the like. The angle detection unit 101 detects the rotation angle of the rotating shaft of the electric motor 3 . The rotation angle θ(t0) calculated by the angle detection unit 101 is digitized by the A/D conversion unit 102 and sent to the communication unit 103 . Here, the notations of suffix (t) and suffix (t0) represent temporally continuous values. The digitized rotation angle is transmitted to the control unit 25 of the power converter 2 via the communication unit 103 . The communication unit 103 is not particularly limited as long as it can transmit digital signals.

The rotation angle reception unit 60 includes a communication unit 111, a latch circuit 112, a restoration unit 113, and the like. The rotation angle signal transmitted from the communication unit 103 is received by the communication unit 111 in the rotation angle reception unit 60 . The rotation angle θ(n) is held in the latch circuit 112 by the communication completion signal S1(n) from the communication unit 111 . Here, the notation of suffix (n) indicates that the value is updated in the communication cycle. That is, the rotation angle θ(n) is updated for each communication cycle of the communication unit 103, is used as the rotation angle by the rotation angle reception unit 60 in the communication cycle n, and is maintained at a constant value within the communication cycle. . Based on the rotation angle θ(n) output from the latch circuit 112 and the communication completion signal S1(n), the restoration unit 113 restores the temporally continuous rotation angle signal θ(t).

The rotation angle value of the continuous rotation angle signal θ(t) is held in the control cycle of the inverter control unit 50 by the motor control synchronization signal S2(m) in the latch circuit 55 in the inverter control unit 50, and the inverter control unit 50 used within. Here, the notation of the suffix (m) indicates that the value is updated in the control period of the inverter control unit 50. FIG.

Here, the continuous rotation angle signal .theta.(t) can be regarded as a continuous value by making the calculation period of the rotation angle receiving section 60 shorter than the calculation period of the inverter control section. In particular, the continuous rotation angle signal .theta.(t) can be regarded as a continuous value by performing the calculation of the integrator 202 at high speed. That is, obtaining a continuous rotation angle or a continuous rotation angle means that a rotation angle can be obtained at arbitrary calculation timing independent of the communication cycle.

In this way, the continuous rotation angle signal θ(t) is restored from the rotation angle θ(n) of the communication cycle, and the latch circuit 55 generates the rotation angle θ(m). can be used for motor control.

FIG. 2 is a block diagram of the restoration unit 113 according to the first embodiment of this invention. First, the speed calculator 201 calculates the rotation speed ω(n) from the rotation angle θ(n) and the communication period. The rotation speed ω(n) may be calculated, for example, simply from the amount of change in the rotation angle θ(n) and the time associated with the communication cycle, or may be calculated based on the delay caused by the communication means and the A/ A value corrected in consideration of the conversion delay of the D conversion unit 102 and a value related to the acceleration of the rotational speed may be used.

For example, the rotation speed ω(n) at communication timing n may be calculated by the following procedure.

Let t(n) be the time when communication timing n is completed. At this time, the rotation angle received by the communication unit 111 at the communication timing n is the rotation angle θ(n).

Also, let t103(n) be the time when the communication unit 103 transmits the data of the rotation angle θ(n) received by the communication unit 111 at the communication timing n. Let t(n-1) be the time when the previous communication timing n-1 was completed. At this time, the rotation angle received by the communication unit 111 at the communication timing n−1 is the rotation angle θ(n−1).

Also, let t103(n-1) be the time when the communication unit 103 transmits the data of the rotation angle θ(n−1) received by the communication unit 111 at the communication timing n−1.

Also, let Td be the delay time from the actual rotation angle detection to the communication unit 103 after AD conversion. The communication unit 103 transmits the rotation angle and the time transmitted as communication data, and the communication unit 111 receives the rotation angle and the time transmitted by the communication unit 103 as communication data.

In this case, the rotational speed ω(n) may be calculated, for example, by the following formula (1).

Here, for example, the first term corresponds to a value calculated from the amount of change in the rotation angle and the time related to the communication cycle, and the second term corresponds to a value related to the acceleration of the rotating shaft and the delay time of detection and communication. If a dedicated line or the like is used between the communication unit 103 and the communication unit 111, and the communication cycle can be regarded as fixed, t103(n)-t103(n-1) or t(n)-(t103(n)-Td) may be a fixed value.

Next, a rotation angle compensation speed ω1(n), which will be described later, is added to the rotation speed ω(n) by an adder 205, and then integrated by an integrator 202 to generate a continuous rotation angle signal θ(t). The rotation angle compensation speed ω1(n) is intended to eliminate the difference between the continuous rotation angle signal θ(t) and the rotation angle θ(n) received from the rotation angle sensor 100, and is particularly useful for reducing detection errors when the rotation angle changes rapidly. effective.

The rotation angle compensating speed ω1(n) is the output of the rotation angle compensator 203. The rotation angle compensator 203 outputs the rotation angle θ(n) and the continuous rotation angle signal θ(t) to the latch circuit 204 (see claim). holding circuit) outputs a rotation angle compensation speed ω1(n) according to the difference in the rotation angle θ1(n) latched by the communication completion signal S1(n). For example, the rotation angle compensation speed ω1(n) can be calculated by multiplying the difference between the rotation angle θ(n) and the rotation angle θ1(n) by a predetermined gain K. That is, for example, the rotation compensation angular velocity ω1(n) can be calculated by the following equation (2).
ω1(n)=K・[θ(n)−θ1(n)] (2)

FIG. 3 shows the operation of the rotation angle compensator 203, where the horizontal axis represents time (t). In the figure, the white circles represent the rotation angle θ(n), the black circles represent the rotation angle θ(m), and the solid line represents the continuous rotation angle θ(t). In FIG. 3, the communication cycle timing of the communication unit 103 at time T1 is denoted as nT1.

FIG. 3 shows a case where the rotation angle θ(n) suddenly changes at time T1 to the values of rotation angle θ(nT1) and rotation speed ω(nT1). and the rotation angle θ1 (nT1) which is the latched value of the continuous rotation angle signal θ(t). n) and the continuous rotation angle signal θ(t) can be quickly reduced.

Incidentally, the second term of the equation (1) may be omitted by appropriately selecting the gain of the rotation angle compensator 203 . Note that the conversion from the mechanical rotation angle (not shown) to the electrical rotation angle is performed in consideration of the number of poles of the electric motor 3 . The conversion from the mechanical rotation angle to the electrical rotation angle may be performed, for example, by the inverter control unit 50, or may be performed by another part.

As described above, according to the present embodiment, even when the communication cycle between the rotation angle sensor and the power conversion device and the control cycle of the power conversion device are different, it is possible to obtain the rotation angle with high accuracy, thereby stabilizing the electric motor. Therefore, it is possible to provide a power conversion device capable of being driven in a stable manner.

(Second embodiment)
A second embodiment of the present invention will be described with reference to FIGS. 4 and 5. FIG. FIG. 4 is a block diagram of a power converter and drive system according to a second embodiment of the present invention. FIG. 5 is a block diagram of the restorer 413 according to the second embodiment of the present invention. In this figure, the same reference numerals are assigned to elements that are common to those of the first embodiment. In the following description, the configuration already described in the first embodiment will be omitted, and the configuration specific to the second embodiment will be described.

A rotation angle sensor 400 is provided instead of the rotation angle sensor 100 in the second embodiment. Furthermore, a rotation angle receiver 70 is provided instead of the rotation angle receiver 60 .

The rotation angle sensor 400 will be explained. The rotation angle sensor 400 includes an angle detection section 401, an A/D conversion section 402, a communication section 403, a speed calculator 404, and the like. The angle detection unit 401 detects the rotation angle of the rotating shaft of the electric motor 3 . The rotation angle θ(t0) calculated by the angle detection unit 401 is digitized by the A/D conversion unit 402 and used as the rotation angle θ(u). Here, the notation of suffix (u) indicates that it is a value updated in the detection period of A/D conversion section 402 .

Rotation angle θ(u) is sent to communication unit 403 and speed calculator 404 . At the same time, the speed calculator 404 calculates the rotation speed ω(u) from the rotation angle θ(u) and the detection period of the A/D converter 402 . The digitized rotation angle θ(u) and rotation speed ω(u) are transmitted to the control unit 25 of the power converter 2 by the communication unit 403 . The communication unit 403 is not particularly limited as long as it can transmit digital signals.

The operation of the speed calculator 404 is the same as that of the speed calculator 201, and is calculated by, for example, the following formula (3).

Let t(u) be the time when the A/D conversion timing u is completed. At this time, the rotation angle received by the speed calculator 404 at the A/D conversion timing u is assumed to be the rotation angle θ(u). Also, let t(u-1) be the time when the previous AD conversion timing n-1 was completed. At this time, the rotation angle received by the speed calculator 404 at the A/D conversion timing u-1 is assumed to be the rotation angle θ(u-1). Let Tad be the AD conversion cycle of the A/D converter 402, and Td2 be the delay between the phase detector and the A/D converter. Here, for example, the first term corresponds to a value calculated by the amount of change in the rotation angle and the time related to the communication cycle, and the second term is a value related to the acceleration of the rotation angle and the delay time of detection.

The rotation angle reception unit 70 includes a communication unit 411, a latch circuit 412, a restoration unit 413, and the like. The signals (rotational angle θ(n) and rotational speed ω(n)) transmitted by communication from the communication unit 403 are received by the communication unit 411 in the rotation angle reception unit 70, and the communication completion signal S3 from the communication unit 411 is received. (n) are held in the latch circuit 412 as the rotation angle .theta.(n) and the rotation speed .omega.(n). Here, the notation of suffix (n) indicates that the value is updated in the communication cycle.

Rotation angle θ(n) and rotation speed ω(n), which are outputs of latch circuit 412, are reconstructed into continuous rotation angle signal θ(t), which is continuous in terms of time, by reconstruction unit 413 according to communication completion signal S3(n). do. The operation after generating the continuous rotation angle signal θ(t) is the same as in the first embodiment.

FIG. 5 is a block diagram of the restoration unit 413 according to the second embodiment of this invention. The rotation speed ω3(n) is a value received from the rotation angle sensor 400 via the communication unit 411 and the latch circuit 412 without the speed calculator 201, unlike the restoring unit 113 of the first embodiment. 305 is the same as the first embodiment except for the above.

5 corresponds to the integrator 202 in FIG. 2, the rotation angle compensator 303 in FIG. 5 corresponds to the rotation angle compensator 203 in FIG. 2, and the latch circuit 304 in FIG. holding circuit) corresponds to the latch circuit 204 in FIG. 2, and the adder 305 in FIG. 5 corresponds to the adder 205 in FIG. Furthermore, ω3(n) in FIG. 5 corresponds to ω(n) in FIG. 2, ω4(n) in FIG. 5 corresponds to ω1(n) in FIG. 2, and θ3(n) in FIG. 5 corresponds to θ(n), S3(n) in FIG. 5 corresponds to S1(n) in FIG. 2, and θ4(n) in FIG. 5 corresponds to θ1(n) in FIG.

As described above, according to the present embodiment, even when the communication cycle between the rotation angle sensor and the power conversion device and the control cycle of the power conversion device are different, it is possible to obtain the rotation angle with high accuracy, thereby stabilizing the electric motor. It is possible to provide a power conversion device that can be driven in a stable manner.

In the above description, the electric motor 3 is assumed to be a synchronous motor, but it is clear that the present invention can be applied to a system for driving an induction motor by providing a slip calculation section or the like in the inverter control section 50.

Reference Signs List 1 AC power supply 2 Power converter 3 Electric motor 20 Main circuit 21 Converter 22 Inverter 23 Current detector 25 Control unit 50 Inverter control unit 51 Subtractor 52 Current reference circuit 53 Voltage reference Circuit 54 PWM controller 55 Latch circuit 56 Speed calculator 60 Rotation angle receiver 70 Rotation angle receiver 100 Rotation angle sensor 101 Angle detector 102 A/D converter 103 Communication unit 111 Communication unit 112 Latch circuit 113 Restoration unit 201 Speed calculator 202 Integrator 203 Rotational angle compensator 203
204 Latch circuit 205 Adder 302 Integrator 303 Rotation angle compensator 304 Latch circuit 305 Adder 400 Rotation angle sensor 401 Angle detection unit 402 A/D conversion unit 403 Communication unit 404 Speed Arithmetic unit 411...Communication unit 412...Latch circuit 413...Restoration unit

Claims (4)

a main circuit unit having an inverter that supplies AC power to the electric motor ;
a rotation angle sensor that detects the rotation angle of the electric motor;
A power conversion device comprising: an inverter control unit that controls the inverter ; and a control unit that has a rotation angle reception unit that receives, through communication, a digital rotation angle obtained by digitizing the rotation angle value of the electric motor from the rotation angle sensor. There is
The rotation angle receiving unit is
A restoring unit that calculates a rotation angle signal at a calculation timing that is temporally independent of a communication cycle that is the communication timing of the communication,
The restoration unit
a speed calculator;
and an integrator,
The speed calculator is
an amount of change in the digitized received value of the rotation angle;
a value calculated with a time related to the received communication cycle;
Calculate the rotation speed based on
The integrator is
Assuming that the rotation speed ω(n) at communication timing n, the time t(n) at which communication timing is completed, and the rotation angle θ(n) received by the communication unit at communication timing n,
A continuous rotation angle signal θ restore (t),
The control unit
A power converter, wherein a gate signal for the inverter is generated from the continuous rotation angle signal θ(t) output from the restoring section. The restorer also
a speed calculator;
and an integrator,
The speed calculator is
an amount of change in the digitized received value of the rotation angle;
a value calculated by the time related to the received communication cycle;
delay time and
a value related to acceleration;
2. The power conversion device according to claim 1, wherein the rotational speed ω(n) is calculated based on . The restoration unit further
further comprising a holding circuit that holds the output of the integrator for each reception cycle of the rotation angle;
The integrator is
2. The power conversion apparatus according to claim 1 , wherein calculation is performed using a value based on a value obtained by adding the output of said holding circuit as a correction value to the output of said speed calculator. The rotation angle receiving unit is
further receiving the rotation speed of the electric motor through communication;
The restoration unit
further comprising an adder, an integrator and a holding circuit,
the adder adds the digitized rotation speed input from the rotation angle receiving unit and the output value of the holding circuit;
the holding circuit holds the output of the integrator for each reception cycle of the rotation angle;
2. The power conversion apparatus according to claim 1, wherein said integrator performs calculation using a value based on the output of said adder.

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