KR100440388B1 - A power factor correction digital controller with a variable gain - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a power factor correction digital controller having a variable gain that compensates the total open loop gain by discontinuously or continuously varying the gain of the current loop in response to the magnitude of the input voltage. Signal processing means for detecting the voltage / current of the AC / DC converter and converting the digital value into a digital value and inputting the digital value to the digital controller; And calculating a gain in a time domain that is continuously or discontinuously changed based on the value of the voltage or current input to the digital controller, and providing the calculated gain to the signal processing means as a variable gain of the current control loop. With variable gain providing means, the gain of the controller is continuously or discontinuously changed in a system in which the gain of the open loop is changed, so that it has an improved power factor correction characteristic even in a portion where the input voltage is low and in a high portion.

Description

A power factor correction digital controller with a variable gain

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power factor correction digital controller having a variable gain, and more particularly, to a power factor improvement digital controller that provides a gain that is continuously or discontinuously varied according to the magnitude of an input voltage.

An AC / DC converter is a power conversion circuit widely used in the industry. In particular, various applications have been applied to the front end of rectifiers and inverters for communication and various DC power supplies.

In general, the trend in accordance with international regulatory regulations for power circuits sets the maximum allowable current limit for high frequencies corresponding to each frequency of the input current. Recently, international standards such as IEC555-2 and IEEE 519 have established standards for harmonics, and interest in harmonics reduction technology and high power factor correction circuits on the input side has increased.

Therefore, the application of power factor correction in AC / DC converters is becoming more common, and for this reason, many industrial sites have dedicated devices for input power factor correction (Microlinear ML4812). It is a general trend to configure the controller using Unitrode UC3854, Motorola MC34261, etc.).

AC / DC converters have various applications, and many kinds of controllers are applied to the AC / DC converters. The importance of the power factor (PF) of AC / DC converters is being emphasized in the situation where various harmonics and power quality are emphasized.

The most widely used controller is a single chip type controller, which is frequently used in industrial fields due to its cost and convenience of application.

The most common single-chip controller is described as follows.

The single chip type controller has two control loops. The outer control loop is the voltage control loop and the inner loop is the current control loop. Here, the current control loop directly affects the PF.

The gain of the current control loop gives a proportional gain with a constant gain at all frequencies in a typical controller. In particular, the current control loop has an AC reference value. In this current control loop, time delay causes a very direct adverse effect on the performance of the controller.

The AC reference value of the current control loop is generated from the input voltage, and this value is multiplied by the error signal of the voltage loop controller and generates a current error signal by a difference from the feedback current signal.

The voltage control loop generally does not directly affect power factor correction (PFC) because the controller's dynamic characteristics of the part consisting of proportional gain and integral gain are slow.

As a feature of the single chip type controller described above, the system open loop gain is changed according to the input voltage, and it is difficult to sufficiently secure the gain at the peak of the voltage peak and at the low input voltage. As a result, not tuning the gain precisely will result in distortion of the current in the zero-crossing portion, resulting in poor PF and difficult tuning.

In particular, when a digital controller is configured in an application in which a request to be configured and integrated with communication is applied, a problem arises that the stability of the controller becomes worse due to a time delay factor due to sampling. This makes controller design and tuning more difficult than single-chip controllers in the form of analog controllers. In addition, the high gain of the digital controller is not set sufficiently, which degrades the performance of the controller.

In addition, the digital controller also has problems in the single-chip analog controller described above, making the controller design much more difficult than the analog controller.

Since the input voltage, which is a problem of the analog controller described above, is AC, the overall system gain changes according to the input voltage, which makes it difficult to select the gain of the entire system and worsens the control characteristics according to the load variation.

In particular, the current controller directly controls the current. The performance of the controller determines the characteristics of the PFC and directly determines the characteristics of the entire system. Since the reference value of the current controller is AC, general PI (Propagation and Integration) controllers cannot be used, so the controller is configured with a controller having only P (Propagation) gain. As a result, there is a problem of controller configuration and tuning having high performance.

As described above, when the power factor improvement controller is digitally configured, the above-described problems are exacerbated, and the controller design becomes more difficult.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and provides a power factor improving digital controller for compensating the total open loop gain by discontinuously or continuously varying the gain of the current loop according to the change of the input voltage. There is a purpose.

1 is a schematic diagram of an AC / DC converter employing a power factor improving digital controller having a variable gain according to an embodiment of the present invention;

2A is a waveform diagram of input voltage and current employed in the description of FIG. 1;

2B is a harmonic analysis waveform diagram of an input current employed in the description of FIG. 1;

3 is a configuration diagram of an AC / DC converter when the input voltage source in FIG. 1 is used as a single phase AC voltage source;

4 is a configuration diagram of an AC / DC converter when the input voltage source in FIG. 1 is a three-phase AC voltage source;

5A through 5C are internal configuration examples of the variable gain providing unit of FIGS. 1, 3, and 4.

※ Explanation of code for main part of drawing

5 input voltage sensor stage 6 input current sensor stage

7: output voltage sensor stage 10: load

12: 1st A / D converter 14: 1st gain providing unit

16: first operator 18: proportional integral controller

20: input voltage source 22: second A / D converter

24: first filter 26: second filter

28: second gain providing unit 30: second operator

32: third A / D converter 34: third gain providing unit

36: third operator 38: variable gain providing unit

40: fourth operation 42: pulse width modulation generator

44: gate driver 46: switching unit

In order to achieve the above object, a power factor improving digital controller having a variable gain in accordance with a preferred embodiment of the present invention, in a digital controller of a single-phase, three-phase AC / DC converter,

Signal processing means for detecting the voltage / current of the AC / DC converter and converting the voltage / current into a digital value and inputting the digital value to the digital controller; And calculating a gain in a time domain that is continuously or discontinuously changed based on the value of the voltage or current input to the digital controller, and providing the calculated gain to the signal processing means as a variable gain of the current control loop. A variable gain providing means is provided.

Hereinafter, a power factor improving digital controller having a variable gain according to an embodiment of the present invention will be described with reference to the accompanying drawings.

1 is a schematic diagram of an AC / DC converter using a power factor improving digital controller having a variable gain according to an exemplary embodiment of the present invention, in which an output voltage of an analog component applied to a load 10 of an output terminal through a switching unit 46 A first A / D converter 12 for digitizing the output voltage of the input analog component as sensed and provided by the output voltage sensor stage 7; A first gain providing unit (14) for outputting a value of a predetermined DC voltage (Vdc) by providing a predetermined first gain to the output value of the first A / D converter (12) and normalizing it; A first operator 16 which receives an input value of the normalized reference DC voltage Vdc_ref and a value of the DC voltage Vdc from the first gain providing unit 14 and processes the input value; A proportional integration controller 18 that performs proportional integration on the DC voltage input from the first operator 16 and outputs a predetermined DC voltage error signal Vdc_error; A second A / D converter 22 for digitally converting the input voltage of the input analog component as the voltage of the analog component from the three-phase or single-phase input voltage source 20 is sensed and provided at the input voltage sensor stage 5; A first filter (24) for removing a distortion present in the magnitude of the voltage of the digital component input from the second A / D converter (22) to produce a complete sine wave; A second filter 26 for compensating for the phase delay occurring in the first filter 24; A second gain providing unit (28) for providing a predetermined second gain to the output value of the second filter (26) to normalize and outputting a predetermined input voltage (Vin); A second operator for receiving and calculating a signal Vdc_error output from the proportional integration controller 18 and an input voltage Vin output from the second gain providing unit 28 to output a predetermined reference current value Iref. 30; A third A / D converter 32 for digitally converting the input current of the input analog component as the analog current from the inductor Lin which changes the input voltage to the current source is sensed and provided at the input current sensor stage 6; A third gain providing unit 34 for supplying a predetermined third gain to the output value of the third A / D converter 32 to normalize it and outputting a predetermined input current Iin; A third outputting a predetermined current error signal Ierror by receiving and calculating a signal Iref output from the second operator 30 and an input current Iin output from the third gain providing unit 34. Arithmetic unit 36; The variable gain agent outputs a variable gain (Ierror *) that changes in a time domain that is continuously and discontinuously by performing arithmetic processing based on the values of the input voltage Vin, the input current Iin, and the current error signal Ierror. Study 38; A fourth operator for receiving and calculating a current error signal Ierror output from the third operator 36 and a variable gain Ierror * output from the variable gain providing unit 38 and outputting the resultant value ( 40); A pulse width modulation generator 42 for receiving a signal from the fourth operator 40 and outputting the pulse width modulation; And a gate driver 44 for driving the switching unit 46 based on the signal output from the pulse width modulation generator 42.

The first filter 24 is a filter used to generate the reference current value required by the digital controller of the present invention, and the first filter 24 in the phase delay compensation operation performed by the second filter 26. The magnitude of the input voltage passed through) does not change.

Since the signal output from the first A / D converter 12, the signal output from the second A / D converter 22, and the signal output from the third A / D converter 32 are not all in the same range. Since normalization is only available in the power factor improving digital controller of the present invention, it is normalized using the first gain, the second gain, and the third gain.

The proportional integral controller 18 is a controller configured digitally in consideration of the response speed and the error with respect to the voltage output from the first operator 16.

The pulse width modulation generator 42 generates a pulse using a digital counter and adjusts the width of the pulse to the final control value (i.e., Ierror *) from the fourth operator 40 so that the gate driver 44 To send. The signal output from the pulse width modulation generator 42 is a logic level signal.

The gate driver 44 drives the switching unit 46 by changing the output signal (logic level signal) of the pulse width modulation generator 42 into a signal suitable for a power circuit.

1, the first to third gain providing units 14, 28, and 34, the first to fourth operators 16, 30, 36, and 40, the proportional integral controller 18, and the pulse width modulation generator Reference numeral 42 can be referred to as a conventional digital controller. In FIG. 1, the first to third A / D converters 12, 22, and 32 and the first to second filters 24 and 26 detect voltage / current of an AC / DC converter and convert them into digital values. It can be said that the signal processing means input to the digital controller.

FIG. 2A is a waveform diagram of input voltage and current employed in the description of FIG. 1. The waveform of the input voltage Vin input to the second operator 30 and the current error signal input to the fourth operator 40 are shown in FIG. The waveform of Ierror, the waveform of the DC voltage Vdc input to the first operator 16, and the waveform of the input current Iin input to the third operator 36 are respectively shown, and have good characteristics. It can be seen.

FIG. 2B is a harmonic analysis waveform diagram of the input current employed in the description of FIG. 1, which is an experimental waveform confirming harmonics of the input current Iin, and has confirmed good operating characteristics of less than 3%.

FIG. 3 is a configuration diagram of the AC / DC converter in the case where the input voltage source in FIG. 1 is a single-phase AC voltage source, and there is no difference from the configuration of FIG. 1 described above, and only the configuration of the switching unit 46 is detailed. The difference is that it is shown.

That is, the switching unit 46 in FIG. 3 includes the transistors Q1 and Q2 interconnected with one end of the inductor Lin interposed therebetween, and one end of the input voltage source 20 (that is, the inductor Lin). Diodes D1 and D2 interconnected with each other). The transistors Q1 and Q2 are driven by a drive signal from the gate driver 44. The collector of the transistor Q1 and the cathode of the diode D1 are interconnected, and the emitter of the transistor Q2 and the anode of the diode D2 are interconnected.

In Fig. 3, the capacitor on the input voltage side is connected to both ends of the input voltage source 20 to remove switching noise generated when switching the power circuit elements, and the diodes D1 and D2 are fast recovery (FRD). It can be configured using a general rectifier diode, not a diode.

FIG. 4 is a configuration diagram of the AC / DC converter in the case where the input voltage source in FIG. 1 is a three-phase AC voltage source, and there is no difference from the configuration of FIG. 1 described above, and only the configuration of the switching unit 46 is detailed. The difference is that it is shown. In other words, the switching section 46 in Fig. 4 has a configuration in which a plurality of transistors are interconnected.

5A through 5C are internal configuration examples of the variable gain providing unit of FIGS. 1, 3, and 4.

The variable gain providing unit 38 of FIG. 5A includes a first gain generating unit 50 for generating a constant first gain Kp1 with respect to a predetermined current error signal Ierror output from the third operator 36; A second output of dividing the constant second gain Kp2 by a predetermined multiple of the absolute value of the input voltage Vin (that is, abs (Vin)) (that is, abs (Vin) ⁿ , n; positive rational number) A gain generator 52; An arithmetic processing unit (54) which receives arithmetic output signals from the first and second gain generating units (50, 52); And a third gain generator 56 which provides the fourth operator 40 with a value Ierror * generated by generating a constant third gain Kp3 with respect to the signal output from the operation processor 54. Equipped.

The variable gain providing unit 38 of FIG. 5B includes a first gain generating unit 50 for generating a constant first gain Kp1 with respect to a predetermined current error signal Ierror output from the third operator 36; A second gain generator 58 for dividing and outputting a constant second gain Kp2 by a predetermined multiple of the input voltage Vin value (that is, Vin ⁿ , n; positive rational numbers); An arithmetic processing unit (54) which receives arithmetic output signals from the first and second gain generating units (50, 58); And a third gain generator 56 which provides the fourth operator 40 with a value Ierror * generated by generating a constant third gain Kp3 with respect to the signal output from the operation processor 54. Equipped.

The variable gain providing unit 38 of FIG. 5C includes a first gain generation unit 50 for generating a constant first gain Kp1 with respect to a predetermined current error signal Ierror output from the third operator 36; A second gain generator 60 for obtaining and outputting a gain in the time domain based on the input voltage value Vin and the current value Iin; An arithmetic processing unit (54) for receiving and arithmetic processing output signals from the first and second gain generating units (50, 60); And a third gain generator 56 which provides a value Ierror * generated by generating a constant third gain 56 with respect to the signal output from the operation processor 54 to the fourth operator 40. Equipped.

Next, an operation of the digital controller for providing a variable gain according to an exemplary embodiment of the present invention will be described with reference to the drawings of FIG. 3. Since the same operation is performed in the configuration of FIGS. 1 and 4, the description will be given with reference to the drawings of FIG. 3.

The input voltage Vin sensed by the input voltage sensor stage 5 is digitally converted through the second A / D converter 22. The digitally converted value becomes a sine wave completely through the first filter 24. The sinusoidal signal output from the first filter 24 becomes an elaborate voltage waveform without distortion in which phase delay is compensated through the second filter 26. The fine voltage waveform becomes the reference value (i.e., input voltage Vin) at the current controller side by passing through the second gain providing unit 28. The input voltage Vin is an input side voltage sensed to generate a reference current value Iref.

At this time, the output voltage sensed by the output voltage sensor stage 7 is converted into a digital value through the first A / D converter 12 and then is converted into a predetermined DC voltage Vdc through the first gain providing unit 14. It is input to one operator 16.

Since the DC voltage Vdc_ref to be normalized is also input in the first operator 16, the result of calculating the two DC voltages Vdc_ref and Vdc inputted are transmitted to the proportional integral controller 18. The proportional integral controller 18 performs proportional integration on the input value, but may determine the gain value in consideration of the response speed and the steady state.

The signal Vdc_error output from the proportional integral controller 18 is input to one input terminal of the second operator 30, and the other input terminal of the second operator 30 is input from the second gain providing unit 28. The output signal Vin is input.

Accordingly, the reference current value Iref calculated and output by the second operator 30 is input to one input terminal of the third operator 36. The input current Iin, which is a feedback value of the current controller, is input to the other input terminal of the third operator 36, and the input current Iin is the input current sensed at the input current sensor terminal 6 by the third A / D. It is the current formed as it passes through the third gain providing unit 34 after being digitally converted by the converter 32. The reason why the digitally converted current value is directly transmitted to the third gain providing unit 34 without passing through the digital filter is because the third A / D converter 32 is the most important value in terms of time delay element or system dynamics. .

The current error signal Ierror calculated and output by the third operator 36 is input to one input terminal of the fourth operator 40, and the variable gain providing unit 38 is input to the other input terminal of the fourth operator 40. Variable gain (Ierror *) is inputted. The variable gain providing unit 38 performs arithmetic processing based on the values of the input voltage Vin, the input current Iin, and the current error signal Ierror to continuously and discontinuously the current error signal Ierror. It provides varying gain (Ierror *) in the varying time domain.

Accordingly, the fourth operator 40 calculates the input current error signal Ierror and the variable gain Ierror * and sends the power control signal to the pulse width modulation generator 42.

As a result, the pulse width modulation generator 42 adjusts the width of the internally generated pulse based on the input power control signal, and transmits it to the gate driver 44, and the gate driver 44 transmits the pulse width. The signal from the modulation generator 42 (ie, the logic level signal) is converted into a signal suitable for the power circuit to drive the switching section 46.

In other words, the above-described configuration of FIG. 3 minimizes response characteristics or steady state errors by using a PI controller which is generally used as an outer loop to control an output DC voltage. After passing the error of the output voltage through the PI controller, the reference value Iref of the current control loop (inner loop) is generated by multiplying with the input voltage Vin, and the controller of the current control loop has a variable gain providing unit ( 38) has a variable gain (Ierror *).

As described in detail above, according to the present invention, the system in which the gain of the open loop is changed continuously or discontinuously, thus having a good PFC characteristic even in a portion of low and high input voltage.

On the other hand, the present invention is not limited only to the above-described embodiments and can be carried out by modifications and variations within the scope not departing from the gist of the present invention, the technical idea that such modifications and variations are also within the scope of the claims Must see

Claims (4)

A digital controller for improving the power factor of a single phase or three phase AC / DC converter, First sensing means for detecting and converting an output voltage applied to an output load of the AC / DC converter to a digital value; Second sensing means for detecting and digitally converting an input voltage from a single-phase or three-phase input voltage source, and filtering for distortion component removal and phase delay compensation; Third sensing means for detecting an input current from an inductor for converting a voltage input to the AC / DC converter into a current and converting the input current into a digital value; Outputs a current error signal by calculating an output voltage from the first sensing means, an input voltage from the second sensing means, and an input current from the third sensing means, and outputs a current error signal to obtain a variable gain for the current error signal. Calculation means for inputting according to a control loop scheme and calculating with the current error signal to provide a driving signal of the AC / DC inverter; And Calculating a variable gain in a time domain that changes continuously or discontinuously by calculating processing based on an input voltage from the second sensing means, an input current from the third sensing means, and a current error signal from the computing means, And a variable gain providing means for providing the calculated variable gain to the calculating means in accordance with a current control loop method. The method of claim 1, The variable gain providing means may include: a first gain generating unit generating a constant first gain with respect to the current error signal from the calculating means; A second gain generating unit for dividing and outputting a predetermined second gain by a predetermined multiple of an absolute value of an input voltage value from the second sensing means; An arithmetic processing unit which receives arithmetic output signals from the first and second gain generating units; And a third gain generator for generating a predetermined third gain for the signal output from the calculation processor and providing the generated value to the calculation means. The method of claim 1, The variable gain providing means may include: a first gain generating unit generating a constant first gain with respect to the current error signal from the calculating means; A second gain generator for dividing and outputting a predetermined second gain by a predetermined multiple of a value of an input voltage from the second sensing means; An arithmetic processing unit which receives arithmetic output signals from the first and second gain generating units; And a third gain generator for generating a predetermined third gain for the signal output from the calculation processor and providing the generated value to the calculation means. The method of claim 1, The variable gain providing means may include: a first gain generating unit generating a constant first gain with respect to the current error signal from the calculating means; A second gain generator for obtaining and outputting a gain in a time domain based on an input voltage value of the second sensing means and an input current value of the third sensing means; An arithmetic processing unit which receives arithmetic output signals from the first and second gain generating units; And a third gain generator for generating a predetermined third gain for the signal output from the calculation processor and providing the generated value to the calculation means.