JPH0744831B2 - Reversible converter control method - Google Patents

Description

The present invention relates to a control method for a reversible conversion device such as a cycloconverter.

[Conventional technology]

FIG. 4 is a schematic configuration diagram of a direct frequency converter (hereinafter referred to as a cycloconverter) that supplies variable voltage and variable frequency AC power to a load, and FIG. 5 is a waveform diagram showing an example of waveforms of respective parts of FIG. is there.

C1 and C2 in FIG. 4 are control rectification circuits composed of thyristor bridges. The thyristor bridge C1 supplies a positive current to the load L, and the thyristor bridge C2 supplies a negative current. The selection of the bridge is made according to the polarity of the current command value i ^* as shown in FIG. 5 (a).
This is performed by issuing a thyristor selection signal as shown in FIG. The PC is a control device that compares the current command value i ^* with the actual current value i detected by the current detector CT to perform the phase control of the thyristor groups C1 and C2.

In recent years, with the development of computer technology, digitalization of a control device has come to be performed, and one in which a cycloconverter is controlled by a plurality of, for example, a micro computer has also appeared. FIG. 6 is a block diagram showing a control device previously proposed by the applicant (Japanese Patent Application No. 61-159841: hereinafter also simply referred to as a proposed device).

In FIG. 6, the microcomputer 1 is a speed adjusting unit.
12, a magnetic flux controller 11, a magnetic flux vector calculator 14, 15, 16 and a vector converter 17 for converting a current command value vector into a polar coordinate format represented by a size ₁ ^* and an angle θ _i1 ^* from the magnetic flux vector position. Then, each processing is performed. That is, the vector conversion unit 17 calculates the magnitude and the angle from the magnetizing current command vector (i _M ^* ) which is a biaxial amount current command value vector and the torque current command vector (i _T ^* ) which is orthogonal to this. . The components ₁ ^* , θ _i1 ^* of the current command value vector calculated by the microcomputer 1 are sent to the microcomputers 2A, 2B, 2C. The microcomputers 2A, 2B and 2C use the data and the information of the angle formed by the stator a-phase winding axis and the magnetic flux vector calculated by the magnetic flux position calculator 3 to determine the winding of each phase in the current command value calculator 21. Calculate the current command values i _a ^* , i _b ^* , i _c ^* . The current adjusting unit 22 performs current adjustment based on the current command value and the actual current values i _a , i _b , and i _c to perform phase control of the thyristor. Further, the thyristor group selection unit 23 selects the positive side or negative side thyristor group according to the polarity of each current command value.

An example of the configuration of the magnetic flux position calculator 3 of FIG. 6 is shown in FIG. This is a digital / analog (D / A) converter 30, integrator 3
1, adder 32 and analog / digital (A / D) converter
From 33, the position of the magnetic flux from the stator axis is calculated by the following equation.

= ∫ω _sl dt + θ (1) FIG. 8 shows an example of the current command value calculation unit 21 in FIG. This is the addition unit 21a, 21b, the cosine function unit 21C and the multiplication unit 21d.
And performs the arithmetic processing of the following equation.

Microcomputers 2A, 2B, 2C calculate the current command value,
The current is adjusted, the positive / negative converter is selected, and the like, all of which are performed in synchronization with the generation of the thyristor firing pulse. For example, if the power supply frequency is 50Hz, 3.3m on average
The calculation process is repeated at intervals of sec.

FIG. 9 shows a control flow chart of the positive / negative converter group switching determination processing in the control block diagram of FIG.

First, the component of the current command value displayed in polar coordinates (the vector size ₁ ^* and the phase angle θ _i1 ^* from the magnetic flux axis) is read out (see the processing in FIG. 9). Then, the angle formed by the reference axis and the magnetic flux vector is read (see the same process). An instantaneous value i ^* of the AC current command value is calculated by performing angle calculation (see the same process) and cosine function process (see the same process) using each input information ^.
(See the same process). The constant B in the processing is a constant for expressing the phase difference between the three phases. For example, when the value in the a phase is 0, the b phase is Phase c is Becomes Next, a converter group to be phase-controlled is selected according to the polarity of the obtained AC current command value i ^* (see the same process), and compared with the converter group currently being controlled. It is determined that there is no switching, and if the two are different, it is determined that they are switched (see the same process).

If the converter switching determination process as described above is performed in synchronization with the thyristor firing pulse, for example, with a 50Hz power supply, an average of 3.3ms
It will be done every time. However, when the output frequency of the cycloconverter becomes high, the selection of the positive / negative converter group is judged in synchronization with the generation of the thyristor firing pulse, so that there is a time delay in switching the converter (for example, 50 Hz).
In the power supply, the average delay is 3.3 ms), and converter switching may not be performed at a desired time, and the current command value and the actual current value may not match. For example, if the output frequency of the cycloconverter is 20Hz, the time delay of 3.3ms is about 24 °.
Corresponds to the phase shift of ^el . Therefore, it is necessary to calculate the current command value at a fast sampling cycle and detect the polarity reversal quickly.

[Problems to be solved by the invention]

However, as is apparent from the above description, the current command value calculation includes the multiplication process and the cosine function process, and it is impossible to increase the repetition speed of the current command value calculation from the processing time required for these processes. There are constraints,
As a result, in a region where the output frequency of the cycloconverter is high, the switching time of the converter group is delayed, and the control performance of the control device deteriorates.

Therefore, an object of the present invention is to make it possible to promptly detect the switching time point of each of the positive-side and negative-side converter groups forming the cycloconverter and prevent the control performance from deteriorating.

[Means for solving problems]

In order to achieve the above object, the present invention converts a magnetizing current command vector (i _M ^* ) that determines an output current of the reversible converter and a torque current command vector (i _T ^* ) orthogonal to the magnetizing current command vector into polar coordinates. Based on the angle (A) of the current command from the angle (θ _i1 ) of the current command value vector from the magnetic flux vector and the magnetic flux position information (φ) from the magnetic flux position calculator Switch.

[Action]

This invention focuses on the fact that the positive and negative polarities of the stator current command value of each phase are determined by the angle or phase formed by the stator winding axis of each phase and the current command value vector. It is intended to directly detect the polarity of the current command value.

Example of Invention

FIG. 1 is a schematic diagram for explaining an embodiment of the present invention.

In the figure, the configuration and processing function of each unit are the same as those of the proposed device (Fig. 6), except that the angle information θ _i1 ^* ,
The angle A of the current command value is obtained by addition processing 21a and 21b from the constant B and the constant B, and the converter group to be controlled is directly selected by the thyristor group selection unit 23 from the value, and it is determined whether or not to switch. is there.

FIG. 2 is an example of a control flow chart according to the present invention.
Same process number (~)
) Indicates the same processing content. Therefore, only the processing is different, but this is to select the positive / negative converter group to be controlled from the calculated size of the angle A, and FIG. 3 shows an example of the selection method.

In this example, as is clear from FIGS. 7A, 7C, and 7D, in the range of 0 ° ^el ≤ angle A <90 ° ^el , the positive side converter group, 90 ° ^el ≤ angle <270 ° ^It can be seen that the negative converter group is selected in the range of ^el , and the positive converter group is selected in the range of 270 ° ^el ≤ angle A <360 ° ^el .

In this way, by selecting the converter group to be controlled by the angle or phase information forming the AC current command value, the cosine function processing and the multiplication processing, which were conventionally required for the converter switching determination, are unnecessary, The switching determination processing time is shortened by that much, and the switching determination processing can be performed quickly and repeatedly. Note that the current command value i ^*
Is calculated by using the angle A calculated by the fast repeat processing, and the cosine function processing is performed in synchronization with the firing pulse generation as in the conventional case.
It is obtained by performing multiplication processing.

〔The invention's effect〕

According to the present invention, the method of selecting the converter group to be controlled is configured to be determined from the angle (phase) information forming the current command value, whereby the converter group selection processing time is shortened and the processing is repeated. The cycle can be shortened, and as a result, the detection delay time at the time of switching the converter group can be shortened, and the deterioration of control performance can be prevented.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining an embodiment of the present invention, and FIG. 2 is a flow chart for explaining its processing operation.
FIG. 3 is an operation waveform diagram showing an example of a positive side / negative side converter selection method, FIG. 4 is a schematic configuration diagram showing a general frequency converter, and FIG. 5 is a waveform diagram for explaining the operation. FIG. 6 is a block diagram showing a proposed device, FIG. 7 is a block diagram showing a concrete example of a magnetic flux position calculation circuit, FIG. 8 is a block diagram showing a concrete example of a current command value calculation unit, and FIG. 3 is a flow chart for explaining the converter switching operation of FIG. Reference code 1,2A, 2B, 2C …… Microcomputer, 3 …… Magnetic flux position calculator, 4 …… Cycloconverter, 5a to 5c, CT …… Current detector, 6 …… Motor, 7 …… Rotor position Detector, 8
...... Speed detector, 11 …… Magnetic flux controller, 12 …… Speed controller, 13,16 …… Division element, 14 …… First-order lag element, 15 ……
Proportional element, 17 ... Vector converter, 21 ... Current command value calculator, 21a, 21b ... Adder, 21c ... Cosine function calculator, 21
d …… Multiplying section, 22 …… Current adjusting section, 23 …… Thyristor group selecting section, 30 …… D / A converter, 31 …… Integrator, 32 …… Adder, 33 …… A / D converter , C1, C2 ... Converter, PC ... Control device.

Claims (1)

[Claims] 1. A positive side converter formed by connecting semiconductor switching elements in series with the same polarity and connecting three sets of the series circuits in parallel with each other, and a negative side formed with a polarity opposite to that of the positive side converter. The converter and the converter are connected in parallel to each other, the positive side current is supplied by the switch operation of the positive side converter, the negative current is supplied by the switch operation of the negative side converter, and the positive side converter and the negative side converter are mutually connected. In a method of controlling a reversible conversion device that supplies a variable voltage and a variable frequency AC power to a load by switching, a magnetizing current command vector (i _M ^* ) that determines an output current of the reversible conversion device and a torque current command that is orthogonal thereto The angle (θ _i1 ) from the magnetic flux vector of the current command value vector obtained by converting the vector (i _T ^* ) into polar coordinates and the magnetic flux position information (φ) from the magnetic flux position calculator (current angle) ( A) is obtained, and the current command Based on the angle, the control method of the reversible transform and wherein the switching the transducer to be controlled.