KR0136411B1 - Phase tracking control system having a high precision slew rate - Google Patents

Abstract

The present invention relates to a phase tracking control system having a high precision slew rate that enables phase tracking with a high precision slew rate.

The present invention is a three-phase / two-phase conversion of a three-phase power supply to an orthogonal DQ coordinate axis in view of the fact that the conventional phase tracking control system cannot set the slew rate and the uncertainty problem of zero crossing at the time of asynchronous control and noise inflow. Phase error control of the converter and the three-phase and two-phase converters by comparing the values calculated by the first, first multiplier, the first and second multipliers to multiply the sine and cosine values finally obtained A comparator for generating a signal; a PI controller for controlling in a direction of reducing an error output from the comparator; a limiter for limiting an output after the PI control by the PI controller within a slew rate range; and based on the output of the limiter An adder that adds the difference compared to the frequency and a frequency limiter that limits the output of the adder within a frequency range to be tracked, Implement the phase tracking control system with an integrator that changes the frequency limited by the frequency limiter into a phase component and a sine / cosine converter that converts the value integrated by the integrator into sine and cosine values to enable instant phase tracking control. In addition, it is resistant to noise and controls the slew rate by the calculation by the orthogonal coordinate axis, the comparison addition and subtraction by the reference frequency, and the limiting of the tracking frequency through the limiter.

Description

Phase Tracking Control System with High Precision Slew Rate

1 is a block diagram of a conventional phase tracking control system

2 (a) to (d) are waveform diagrams for explaining phase tracking control according to FIG.

3 is a block diagram of a phase tracking control system having a high precision slew rate according to the present invention.

* Description of the symbols for the main parts of the drawings *

11: 3-phase / two-phase converter 12a, 12b: multiplier

13 comparator 14 PI controller

15: limiter 16: adder

17: frequency limiter 18: integrator

19: sine / cosine converter

The present invention relates to a phase tracking system for tracking a phase of a three-phase waveform, and more particularly, to a phase tracking control system having a high precision slew rate for tracking a phase with a high precision slew rate. .

1 is a block diagram of a conventional phase tracking control system, and includes a zero crossing detector 1 that detects zero crossings and generates zero crossing pulses, and zero crossings of the zero crossing detector 1. A state comparator (2) for generating a new frequency by comparing the pulse output with the output from the reset overflow moder (6), which will be described later, to generate a new frequency, and the value output from the state comparator (2) is constant. A limiter (3) that limits the range, that is, the limit of the frequency that can be traced, and an adder (4) that adds the difference by comparing the value limited by the limiter (3) with the reference frequency (ω). A counter 5 that integrates the phase component with the adjusted frequency component through the adder 4 and a reset overflow that resets the overflow (360 degree point in phase) at the output of the counter 5. Mode group consists of 6, a sine / cosine converter 7 that converts the waveform of the frequency to control the output from the reset overflow mode group (6).

The conventional phase tracking control system configured as described above is represented by a waveform as shown in FIG.

When the waveform passes through the zero grossing detector 1, it becomes as shown in FIG. 2B, and if the zero crossing pulse is output as shown in FIG. 2B, it is increased by the counter 5 before. And the value at the time when the zero crossing pulse, which is the zero crossing time point, is compared to determine the integration constant of the next counter 5 in the state comparator 2.

For example, if the output value of the counter 5 during the first half period does not reach the overflow as shown in FIG. 2C, and the zero crossing pulse is generated in the zero crossing detector 1, the overflow at that time When the counter 5 is operated by comparing the difference with the value, the slope is increased by the difference, and the value is adjusted to reach the overflow faster.

Integrating at the counter 5 in this manner will approach a value close to zero crossing in the next waveform.

And since the value thus reached can be expressed as a phase value corresponding to 180 degrees, determining the slope from the output value of the counter 5 is equivalent to changing the frequency.

The frequency variation at this time is limited by the limiter 3 to the frequency within the tracking range because there is a limit of the frequency to be tracked.

On the contrary, if overflow occurs even before the zero crossing pulse is generated as shown in FIG. 2 (d), the counting value at the time when the zero crossing pulse occurs is compared and the inclination of the counter 5 is reduced by the difference of the value. It will be adjusted in the thin direction, which allows tracking of the phase of subsequent power waveforms.

However, in the conventional phase tracking control system as described above, instantaneous phase tracking control is difficult because the feedback of the phase is made only after a half cycle in which the zero crossing is performed as the zero crossing detector.

In addition, if the noise is introduced, it is difficult to detect zero crossing. If the noise is removed by using a filter during the zero crossing detection to correct this, the phase delay according to the filter also varies in phase with frequency variation, so that an accurate phase delay can be calculated. There is a problem that can not limit the frequency range to be tracked, but can not set the slew rate.

SUMMARY OF THE INVENTION The present invention has been made to solve this problem, and an object of the present invention is to perform phase tracking control at every interrupt by direct operation by a coordinate axis orthogonal to a three-phase waveform, so that instantaneous phase tracking control is possible, The present invention provides a phase tracking control system having a high precision slew rate capable of tracking a phase with a strong and high precision slew rate.

A characteristic of the present invention for achieving this object is a three-phase / two-phase converter for converting a three-phase power source to an orthogonal coordinate axis, and the sine finally derived by performing phase tracking control of the value from the three-phase / two-phase converter A first and second multipliers multiplied by a cosine value, a comparator for generating an error by comparing a value calculated by the first and second multipliers, and a PI controller for controlling in a direction of reducing an error output from the comparator And a limiter for limiting the output after being PI controlled by the PI controller to within a slew rate range, an adder for comparing the output of the limiter with a reference frequency and adding the difference by the difference, and tracking the output of the adder. A frequency limiter for limiting within the frequency range, an integrator for converting a frequency limited by the frequency limiter into a phase component, and In the phase tracking control system has a high precision slew rate consisting of a sine / cosine converter for converting the integral value from the sine, cosine.

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

3 is a block diagram of a phase tracking control system having a high precision slew rate according to the present invention, wherein the three-phase / two-phase converter 11 converts a three-phase power supply into an orthogonal DQ coordinate axis, and the three-phase / Phase tracking control is performed on the values from the two-phase converter 11 to compare the values calculated by the multipliers 12a and 12b and the multipliers 12a and 12b. By a comparator 13 for generating a signal, a proportional integral controller 14 for controlling in a direction of reducing an error output from the comparator 13, and a PI controller 14 A limiter 15 that limits the PI-controlled output within the slew rate range, an adder 16 that adds the difference by comparing the output of the limiter 15 with a reference frequency ω, and the adder ( 16) Frequency range to track output Integrator 18 converts the frequency limited by the frequency limiter 17 into a phase component, and the value obtained by integrating the integrator 18 into sine and cosine values. It consists of a sine / cosine converter 19 to convert.

In the present invention configured as described above, first, three-phase voltage is defined as Vsu, Vsv, and Vsw, and the voltage at this time

Vsu = V * SINωt

Vsv = V * SIN (ωt-2π / 3)

Vsw = V * SIN (ωt + 2π / 3) ....... (1)

When the three-phase voltage is converted by the three-phase / two-phase converter 11, it is derived as follows.

Vsd = 2 Vsu / 3-Vsv / 3-Vsw / 3

Vdq = -Vsv / √3 + Vsw / √3 ....... (2)

In this case, the converted voltages Vsd and Vsq may be expressed differently as follows.

Vsd = V * SINωt

Vsq = -V * Cosωt ....... (3)

When the value derived by Equation (3) is multiplied by Sinθ and Cosθ output after tracking control, the following equation is derived.

Verror = V * SINωt * Cosθ-V * Cosωt * Sinθ = V * Sin (ωt-θ) ... (4)

Here, if ωt − θ = Δθ and Δθ is expressed as a sufficiently small value, it can be expressed as Sin (ωt−θ) = Δθ in Equation (4).

When control is performed in the direction of reducing the error by the PI controller 14 with Δθ thus obtained, the output value of the PI controller 14 is expressed as an angular velocity component.

Since the angular velocity ω = 2πf is proportional to the frequency, the value from the PI controller 14 can be expressed in frequency.

With this value, the limiter 15 limits the frequency within the slew rate range.

Here, if the slew rate is expressed as 5 Hz / sec, this means that the frequency changes with a rate of change of 5 Hz per second. Therefore, if the system has an interrupt of 1 msec and corresponds to a value of 5000 as a digital value per 5 Hz, the value limited by the limiter 15 may be represented by 5. FIG.

That is, the actual frequency value corresponding to 5 as the digital value is 0.05 Hz, and if it is changed to the value of 0.05 Hz for each interrupt, the rate of change is 5 Hz after 1 second.

When the value corresponding to the reference frequency 60 Hz and the addition and subtraction are performed by the adder 16 with the limited value within the slew rate range, the newly controlled frequency is set and this frequency is to be tracked by the frequency limiter 17. Finally limited within frequency range.

At this time, the limited frequency is fed back and the reference frequency (ω *) is again set and repeated operation is performed.

The phase component can be obtained by passing through the integrator 18 with the limited frequency value via the frequency limiter 17. The phase component is converted into Sinθ and Cosθ values by the sine / cosine converter 19 and the next interrupt is obtained. When recomputation is performed again, the phase of the three-phase power supply having the slew rate can be tracked.

In this way, the phase difference between the phase of the actual phase tracking controller and the reference waveform is controlled by the phase tracking controller, the limit is then compared with the reference angular velocity, and again controlled by the integrator (18). To have it.

As described above, the present invention enables instantaneous phase tracking control by performing phase tracking control at every interrupt by a direct operation based on a coordinate axis orthogonal to a three-phase power supply, and compares the operation based on an orthogonal coordinate axis and a reference frequency. Addition and subtraction and limiting of the tracking frequency through the limiter are strong against noise, and the slew rate can be adjusted.

Claims (2)

Three-phase / two-phase converter for converting three-phase power source to the orthogonal coordinate axis First and second multipliers for multiplying the values from the three-phase and two-phase converters with the sine and cosine values finally obtained by performing phase tracking control; A comparator for generating an error by comparing the values calculated by the first and second multipliers, a PI controller for controlling in a direction of reducing an error output from the comparator, and an output after being PI controlled by the PI controller A limiter that limits the to within the slew rate range, An adder for comparing the output of the limiter with a reference frequency and adding the difference by the difference, a frequency limiter for limiting the output of the adder within a frequency range to be tracked; A phase tracking control system having a high precision slew rate comprising an integrator for converting a frequency limited by the frequency limiter into a phase component and a sine / cosine converter for converting the values integrated by the integrator into sine and cosine values. . The method of claim 1, And outputting the output of the frequency limiter as a reference frequency of the adder to track the phase in a constant slew rate range.