KR0138573B1 - A current control method for thyistor rectifier and cycloconverter - Google Patents

Abstract

The present invention relates to a current control method of a thyristors rectifier and a micro-converter, in particular, the current error zero or maximum that is the intersection point of the command current and the actual current to be suitable for high-precision current control, such as speed control of the motor. Current tracking performance in transient state can be achieved by applying the firing signal by the current error code and the logic of the actual current at the minimum firing phase firing angle, so that the actual current follows the command current as quickly as possible without a separate current control compensator. The present invention relates to a current control method of a die Lister rectifier and a microconverter which is economical and has high reliability in circuit operation since it is simple to implement hardware and can be implemented as a general-purpose microprocessor.

Description

Current control method of thyristors rectifier and cycloconverter

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a current control method for various types of thyristor rectifiers and microconverters that perform natural currents, such as single-phase and three-phase rectifiers, 6-pulse cycloconverters, and 12-pulse cycloconverters. The present invention relates to a current control method which is not only excellent in current tracking capability but also easy and easy to implement, and improves reliability of operation.

The current control method of the conventional thyristor rectifier and the cycloconverter indirectly controlled the current of the load by controlling the output voltage through the phase angle control of the die thyristor rectifier and the dichroverter.

Referring to the current control block diagram of the conventional thyristor rectifier and the microconverter shown in FIG. 1, the error between the command current and the actual current fed back from the diistor rectifier or the microconverter is input to the current control compensator, and the output of the compensator is output. The phase angle of the thyristor is determined accordingly, so that the output voltage of the converter is controlled, and the output voltage is applied to the load to control the current of the load.

In order to determine the phase angle of the thyristors in the prior art as described above, the rectifier generates a sawtooth wave or cosine wave synchronized with the power supply and compares it with the output of the current control compensator. Since a fairly complex voltage control method called wave control method has to be carried out, not only complicated control circuits are required for its implementation, but also the current control of the load depends on the output voltage control of the thyristor rectifier or the microconverter through the current control compensator. In a transient state such as a sudden change in the command current or a sudden change in the load state, a delay in the control response occurs. Particularly, in the case of a micro-converter, the current error is caused by a phase error caused by a change in the output frequency. There are technical difficulties in designing Also there is a problem, such as a high level of skill and complicated method is required to.

Disclosure of the Invention An object of the present invention for solving the above problems is to use a dyster rectifier and a cycle that allows the actual current to follow the command current as quickly as possible directly without using an additional current control compensator, regardless of the state of the power supply or load. It is to provide a current control method of the converter.

1 is a block diagram of current control of a conventional thyristor rectifier and a cycloconverter.

2 is a block diagram of a current controller for implementing the present invention.

Figure 3 is a flow chart showing a current control method of the present invention

4A to 4C are waveform diagrams for explaining the basic operating principle of the present invention.

5a and 5b is a computer simulation result in accordance with the present invention

6 is a speed control block diagram of an electric motor to which the present invention is applied.

7a and 7b is a result of the current control experiment according to the present invention

* Explanation of symbols for main parts of the drawings

10; A power synchronizer 20; Maximum / minimum voltage phase firing angle generator

30; Sequential mode generator 40; Control device judging unit

50; A current error code and current error zero determination unit 60; Current polarity discrimination unit

70; Current controller 80; Speed control compensator

In order to achieve the above object, the present invention provides a firing signal to the thyristor by the sign logic of the current error code and the actual current at the current error zero point or the maximum / minimum voltage generated phase firing angle which is the intersection point of the command current and the actual current. It is characterized in that the current tracking performance of the transient state is improved by allowing the actual current to follow the command current directly as quickly as possible without applying a separate current control compensator.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram of a current controller 70 for implementing the current control method of the thyristors rectifier and the micro-converter of the present invention, detecting a phase of a specific voltage selected as a reference among a plurality of power supply line voltages. Maximum and minimum voltage generation phase firing phase firings The power supply synchronization unit 10 used to synchronize the generator 20 and the firing point for generating the maximum / minimum voltage to the firing element determination unit 40 are provided. / Sequential mode generation section for determining the mode according to the voltage present in the current output terminal of the plurality of power supply line voltage between the phase firing angle generator 20 and outputs the information to the firing device determination unit 40 ( 30), and compares the actual current and the command current output from the thyristors rectifier or the micro-converter to determine the sign of the current error and the current error zero point and output the current to the firing element determination unit 40. A differential sign and current error zero point determination unit 50, a current polarity discrimination unit 60 for determining the polarity of the output current of the thyristors rectifier or the micro-converter, and the maximum / minimum voltage generation phase firing angle generator ( 20), a mode in which the thyristor element to which the firing signal is to be applied is determined according to the logic of the current error code and the current error zero determination unit 50 and the current polarity determination unit 60 and provided by the sequential mode generation unit 30. And a firing element determination section 40 for applying a firing signal.

The current polarity determining unit 60 is necessary only when it is necessary to flow negative and positive currents, such as a micro-converter or a quadrant rectifier, and this current polarity when only a positive current flows to the load, such as a two-quadrant rectifier. The determination unit 60 is omitted.

The current control process of the thyristor rectifier and the micro-converter according to the method of the present invention using the current controller 70 having such a configuration will be described with reference to FIG. 3.

In the current control of the thyristors rectifier and the micro-converter according to the present invention, comparing the actual current and the command current (S10) to determine the magnitude of the current error, and if the current error is 0, the present time (current error zero point). Generating a firing signal at step S13; and if the current error is greater than 0, determining whether the firing point is at the maximum voltage generation (S11). The method returns to step S10 of determining the magnitude of the error, and if the current error is less than zero as a result of the determination in step S10, it is determined whether it is the minimum voltage occurrence firing point (S12). Generation (S13) or the process returns to step S10 to determine the magnitude of the current error again.

In detail, the current error code and the current error zero determination unit 50 determine the magnitude of the current error by comparing the command current with respect to the output current and the actual output currents of the thyristors rectifier and the micro-converter and determine the information of the firing device. Outputting to the judging section 40, the maximum / minimum voltage generating phase firing angle generating section 20 outputs information on the maximum / minimum voltage generating firing point to the firing element determining section 40, and the current polarity determining section ( 60 determines the output current polarity of the thyristors rectifier and the micro-converter and outputs them to the firing element determination unit 40.

Then, the firing element determining unit 40 determines the current (from the information of the maximum / minimum voltage generating phase firing angle generating unit 20, the sequential mode generating unit 30, and the above-described current error code and current error zero determining unit 50). The actual output current follows the command current by determining the mode to perform the flow, the starting point of the firing, and the thyristor element to which the firing signal is to be applied, and applying the firing signal to the die Lister rectifier or the cycloconverter.

In addition, after the firing element determining unit 40 performs a current, when the control signal is output to the sequential mode generating unit 30, the sequential mode generating unit 30 changes to a mode in which current is to be performed.

Here, when it is necessary to flow a negative or positive current, such as a micro-converter or a four-quadrant rectifier, the thyristor element to which a firing signal should be applied by referring also to the information on the current polarity input from the current polarity discrimination unit 60. Determine.

FIG. 4A shows the current error code and the current error zero determination unit 50 comparing the command current and the actual current to determine the magnitude of the current error because there is no sudden change of the command current or a sudden change in the load. is 0, as if the current error zero point occurs, the firing device determining section 40 is the intersection of the sequential mode, generating unit 30 the command current i _r and an actual current i by using the mode information of the g _1, g _2, g ₃ shows that the actual current directly follows the command current by conducting current at.

At this time, in the case of a normal two-quadrant rectifier, no negative current is generated. Here, since the thyristor rectifier and the micro-converter modulate a plurality of line voltages of the input power to configure the output voltage, the waveform of the actual current pulsates as shown in the drawing of the conventional inductive load. Using this pulsating property of the real current, it generates a firing signal at the point where the command current equals the real current, that is, the current error zero point g ₂ , to control the output currents of the thyristors rectifier and the cycloconverter.

However, as shown in FIG. 4B, in a transient state such as a sudden change in the command current or a severe fluctuation in the load, since the actual current is smaller than the command current, the current error code and the current error zero determination unit 50 Since the current error comparing the actual current is greater than zero, there may be a case where the current error zero point g ₂ does not occur.

At this time, the firing element determination unit 40 generates a current at the maximum voltage generating phase firing angle g _max inputted from the mode information input from the sequential mode generating unit 30 and the maximum / minimum voltage generating phase firing angle generating unit 20. The flow is performed so that the actual current approaches the command current as soon as possible.

As shown in FIG. 4C, when the actual current is larger than the command current and the current error is less than zero, the firing element determination unit 40 generates mode information and maximum / minimum voltage input from the sequential mode generation unit 30. Current is performed at the minimum voltage generation phase firing angle g _min inputted from the phase firing angle generating unit 20 so as to control the actual current to approach the command current as soon as possible.

As described above, when current is performed at the maximum / minimum voltage generation phase firing angle, the synchronization between the power supply voltage and the maximum / minimum voltage generation phase firing angle generation unit 20 is performed by using the output signal of the power supply synchronization unit 10. Will be corrected.

5A and 5B show an example of a result of applying the current controller 70 shown in FIG. 2 to a six-pulse cycloconverter. FIG. 5A shows a computer that commands a current of 10 Hz and 40 A with a RL manual load of 5 Ω / 20 mH. Simulation results show that the application of the present invention is well achieved.

5B is a result of harmonic analysis of the actual current i shown in FIG. 5A, but the overall harmonic content was found to be insignificant, but the analysis of up to 100 harmonics indicates that the fundamental current is 41.88A for the command current 40A. The magnitude of the actual current was somewhat larger than the magnitude of the command current. This is a natural result in the characteristic of the steady state operation of the present invention as shown in Fig. 4a.

However, in the practical application, considering the case of the motor speed control as shown in Fig. 6, there is no problem because the speed control compensator 80 inserted in the speed control loop automatically compensates the magnitude of the actual current for the current command. Does not occur.

7A and 7B show a current control experiment of a 2-pulse cycloconverter using an LC resonant circuit according to the present invention. FIG. 6A shows that the actual current i almost completely follows the magnitude and frequency change of the command current i _r . 7b shows that the speed of the three-phase induction motor is rapidly accelerated and decelerated by the waveform of the speed command ωr and the actual speed ω at the variable speed operation of the three-phase induction motor and the phase current i of the three-phase induction motor at this time. It proves the usefulness of this invention.

As described above, the current control method of the thyristor rectifier and the micro-converter of the present invention does not need a separate compensator for current control by controlling the output current of the converter itself, and is a current error that is simply the intersection point of the command current and the actual current. It is possible to control the actual current to follow the command current as quickly as possible by generating the firing signal by the current error code at the zero or maximum / minimum voltage phase phase firing angle. Compared with the control performance is very good.

In addition, since the current controller implementing the present invention is composed of simple size comparison and logic determination elements, the circuit can be simplified, and moreover, the linear circuit is mainly used to implement the conventional technology, but the present invention mainly uses digital circuits. It can increase reliability and can be easily implemented by using a general-purpose microprocessor instead of dedicated hardware.

Therefore, the present invention can easily and quickly perform a reliable control of the output current of the thyristors rectifier and the micro-converter is very suitable for high-performance current control such as DC motors and AC motors that require rapid acceleration and deceleration operation.

Claims (1)

Determining the magnitude of the current error by comparing the actual current and the command current in controlling the output currents of the thyristors rectifier and the micro-converter; Generating a firing signal at the current point (current error zero point) if the current error is 0; Determining that the current error is greater than zero when the current error is greater than zero, and generating a firing signal when the maximum voltage is occurring; otherwise, returning to determining the magnitude of the current error; Judging whether the current error is less than zero, and determining whether it is the minimum voltage generation firing point; and if the minimum voltage generation firing point is generated, generating a firing signal or returning to determining the magnitude of the current error. The current control method of the thyristor rectifier and the micro-converter, characterized in that made.