KR101967734B1 - Harmonic control apparautus using phase based frequency of adaptive repetitive controller - Google Patents

Abstract

Disclosed in the present technique is a harmonic control device using a phase-based frequency-adaptive repetitive controller. According to a specific example of the present technique, the sampling number and an array period are derived by using frequency components of an object to be controlled, and the number of memories in a repetitive controller is adjusted based on the derived sampling number and array period, thereby stably compensating for the harmonics of a load. A memory controller deriving the sampling number and the array period according to changes in the frequency of the object to be controlled is additionally disposed in a conventional repetitive controller, thereby stably compensating for the harmonics without changing a high-frequency controller. Therefore, the quality of voltage and current can be stably improved. The memory controller can be easily provided, thereby further improving economic efficiency. Thus, the harmonic performance can be stably ensured even according to the changes in the frequency of the load in various energy storage device application fields.

Description

[0001] HARMONIC CONTROL APPARATUS USING PHASE BASED FREQUENCY OF ADAPTIVE REPETITION CONTROLLER [0002]

The present invention relates to a harmonic control apparatus using a phase-based frequency adaptive repetitive controller, and more particularly, to a technique capable of stable harmonic control by setting a sampling time of a repetitive controller according to a frequency variation of a load.

Power converters are widely used in systems such as Uninterruptible Power Supplies (UPS), Energy Storage Systems (ESS), or distributed power systems. One of the research trends of such power conversion devices is to achieve excellent voltage, current quality and stable power supply.

However, proportional-integral controller or proportional-resonance controller, which is a controller of power conversion devices generally used throughout the industry, is limited in terms of harmonic components due to limitation of physical bandwidth, so that distortion of voltage and current is compensated There is a disadvantage that it can not.

There are two conventional control techniques for improving this.

First, there is a control method in which a resonance controller is added in parallel according to a harmonic order to synthesize a proportional resonance controller. The second is a repetitive controller that compensates harmonic components by using a model of periodic error. It can secure improved performance compared with the control methods described above.

 However, recently uninterruptible power supplies require I / O frequency control for the frequency range of ± 10% (± 6 Hz) due to compatibility with diesel generators. In the case of grid-connected energy storage devices, maximum ± 5% ± 3 Hz).

However, in the case of a method in which the first-mentioned resonance controller is constructed in parallel according to the harmonic order to be synthesized, since the control variable of the resonance controller must be calculated according to the frequency change in real time, a high-performance microprocessor is required, There is a disadvantage in that there is a limitation on the harmonic order to be synthesized due to the time limitation.

In order for the second-mentioned repetitive controller to perform harmonic compensation according to the frequency change, the sampling time of the microprocessor must be changed in real time or the number of memory must be changed.

However, the change of the sampling time and the number of memory can cause problems in implementation complexity and stability of system control, and there is also a disadvantage that an expensive microprocessor is required. In order to solve this problem, a control scheme for coping with a frequency change through interpolation of a sampling time based on a fixed sampling time and a memory number has been proposed, but has a disadvantage in that the allowable frequency variation range is very small.

 For this reason, in the conventional control schemes, the harmonics compensation region is limited or impossible depending on the frequency, and the improvement of the voltage and current of the power converter can not be expected.

An object of the present invention is to provide a harmonic control apparatus using a phase-based frequency adaptive repetitive controller capable of stably performing harmonic compensation of a load as the sampling time varies according to a frequency of a load.

Further, according to the present invention, a memory controller which changes the sampling time according to the frequency of the load is arranged in the existing repeater controller, so that the harmonics can be stably compensated without changing the existing high frequency control device. And a phase-based frequency adaptive repetitive controller that can improve the phase-based frequency adaptive repetitive controller.

The present invention relates to a harmonics control method using a phase-based frequency adaptive repetitive controller capable of ensuring harmonic performance stably even in a frequency variation of a load in a variety of energy storage device applications, And to provide a device.

The objects of the present invention are not limited to the above-mentioned objects, and other objects and advantages of the present invention which are not mentioned can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. It will also be readily apparent that the objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

An embodiment of the present invention includes a harmonic control apparatus using a phase-based frequency adaptive repetitive controller. The apparatus comprises: a voltage controller for performing voltage control on an error between a reference command value and a load voltage; And a repetitive controller for performing harmonic control on the error between the reference command value and the load voltage, wherein the number of samplings set according to the frequency variation of the object to be controlled is set, and the number of memories of the repetitive controller is controlled based on the set sampling number And a memory controller for transferring the sampling number to the repetition controller.

Preferably, the object to be controlled is one of a load voltage and a load current.

Preferably, the memory controller includes: a phase angle converter for converting a phase angle in units of degrees of the object to be controlled in a radial form; A normalizer for converting a maximum value and a minimum value of the phase angle in degrees into a maximum value and a minimum value of the sampling number; And a quantizer for converting the output value of the normalizer into an integer value to derive a sampling number and an array period (trigger period), and to transmit the derived sampling number to the iterative controller.

Preferably, the arrangement period may be set to be in inverse proportion to the product of the frequency of the object to be controlled and the number of samples.

According to the present invention having the above-described configuration, the sampling number reflecting the frequency of the object to be controlled is derived, and the derived sampling number is reflected in the memory number of the repetitive controller, so that the harmonic compensation of the object to be controlled is stably performed And a memory controller for changing the frequency of the load voltage of the object to be controlled is additionally disposed in the existing repetitive controller so that harmonic compensation can be stably performed without changing the high frequency control device and thus the voltage, The effect of improving the quality of the substrate can be obtained.

According to the present invention, the memory controller can be easily implemented, thereby further improving the economical efficiency. Hence, it is possible to secure the harmonic performance stably even in the frequency variation of the load in various energy storage device applications.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention and, together with the description of the invention given below, serve to further understand the technical idea of the invention. And should not be construed as limiting.
1 is a configuration diagram of an uninterruptible power supply system to which the present embodiment is applied.
2 is a detailed configuration diagram of the inverter control unit of the present embodiment.
3 is a detailed configuration diagram of the repetitive controller of this embodiment.
4 is a detailed configuration diagram of the memory controller of this embodiment.
5 and 6 are output waveform diagrams of the memory controller of this embodiment.
7 is an output waveform diagram for each of the systematic frequencies in this embodiment.
Fig. 8 is an output waveform diagram for each of the system frequency fluctuations in this embodiment.
9 is a comparative diagram showing the total harmonic distortion (THD) before and after the application of this embodiment.

It is noted that the technical terms used herein are used only to describe specific embodiments and are not intended to limit the invention. It is also to be understood that the technical terms used herein are to be interpreted in a sense generally understood by a person skilled in the art to which the present invention belongs, Should not be construed to mean, or be interpreted in an excessively reduced sense. It is also to be understood that the technical terms used herein may be mistaken for technical terms that do not accurately represent the spirit of the present invention, and should be understood to be replaced by technical terms that are well understood by those skilled in the art. In addition, the general terms used in the present invention should be interpreted according to a predefined or prior context, and should not be construed as being excessively reduced.

Also, the singular forms "as used herein include plural referents unless the context clearly dictates otherwise. In the present application, the term "comprising" or "comprising" or the like should not be construed as necessarily including the various elements or steps described in the specification, Or may be further comprised of additional components or steps.

Furthermore, terms including ordinals such as first, second, etc. used in this specification can be used to describe various elements, but the elements should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.

When an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, but other elements may be present in between. On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, wherein like reference numerals refer to like or similar elements throughout the several views, and redundant description thereof will be omitted. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. It is to be noted that the accompanying drawings are only for the understanding of the present invention and should not be construed as limiting the scope of the present invention. The spirit of the present invention should be construed as extending to all modifications, equivalents, and alternatives in addition to the appended drawings.

The present invention is a technique for deriving a sampling number and an array period by using a frequency component of an object to be controlled and adjusting the number of repeater controllers in accordance with the derived sampling number and array period. In the embodiment of the present invention, the object to be controlled is a load voltage, but the present invention is not limited thereto.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a diagram showing a configuration of an uninterruptible power supply (UPS) to which an embodiment of the present invention is applied, FIG. 2 is a diagram showing a detailed configuration of the inverter control unit shown in FIG. 1, FIG. 4 is a diagram illustrating a detailed configuration of the memory controller 130 shown in FIG. 2. Referring to FIG.

1 to 4, an uninterruptible power supply system (hereinafter abbreviated as UPS) 1 according to an embodiment of the present invention converts a DC voltage output from a smoothing capacitor into a commercial frequency through a pulse width modulation An invertor switch unit 30 for outputting pulses in the form of three-phase alternating current (U, V, W), and an inductor and capacitor including a constant amount of reactance for filtering the PWM waveform output from the inverter switch unit 30 An LC filter unit 50 and an inverter control unit 10 for controlling the operation of the inverter switch unit 30. [

Here, the inverter switch unit 30 is connected to a single-phase or three-phase half bridge and a full bridge having two-level or three-level switching devices IGBT and FRD, And converts the direct current voltage into a single-phase or three-phase alternating current, and outputs this single-phase or three-phase alternating current.

2, the inverter control unit 10 may include a subtracter 11, a voltage controller 110, a repetitive controller 120, a memory controller 130, and an adder 13.

The voltage controller 110 is provided as a general proportional integral or proportional resonant controller and is provided to ensure the dynamic characteristics of the UPS S and generates a reference voltage command r and a load voltage y derived from the subtracter 11, (E) of the voltage controller 110, and performs a proportional control and an integral control on the derived first control value to perform correction on the error of the load voltage, Since the technique is a known technique, a more detailed description will be omitted.

On the other hand, the repetition controller 120 amplifies the periodic disturbance to compensate for the periodic disturbance due to the nonlinear load with respect to the load voltage (y), and performs the function of removing harmonic components that can not be compensated. That is, the repetitive controller 120 is configured to receive the reference voltage command r and the error e of the load voltage y to output a second control value, and the input of the repetitive controller 120 is a reference voltage command and the output of the repetitive controller 120 is a value obtained by subtracting the load voltage y from the first control value of the voltage controller 110 by the adder 13 Added.

The structure of the repetitive controller 120 applied to the embodiment of the present invention is as shown in FIG. Here, N is a fixed number of memories, M is a predetermined integer value for compensating for delay in sampling and processing, and z ^{-N + M} performs a delay function so that the control operation is performed at a pre-cycle value. That is, in order to maintain the fixed number of memories (N) despite the fluctuation of the frequency of the load voltage to be controlled, the sampling number and the array period are derived using the frequency of the load voltage, The number of memories N of the repeater controller 120 is adjusted and the number of memories N of the repeater controller 120 is maintained.

Here, in order to stably perform the harmonic compensation in the repetition controller 120, the sampling number N _r must be changed in real time according to the frequency variation. Thus, the setting of the sampling number N _r in accordance with the frequency variation is performed in the memory controller 130. The sampling number Nr derived based on the frequency variation of the load voltage to be controlled by the memory controller 130 is provided to the repetition controller 120. [ In the embodiment of the present invention, the object to be controlled is described as a load voltage, but may be a load current, but is not limited thereto.

Referring to FIG. 4, the memory controller 130 may include a phase angle transformer 131, a normalizer 132, and a quantizer 133.

The phase angle converter 131 calculates a phase angle ( _deg ) in units of degrees based on a predetermined relational expression with respect to the frequency of the load voltage y in the radian unit ( _rad ) The angle ( _deg ) satisfies the following equation (1).

.. 식 1

.. Equation 1

The phase angle _{deg in degrees} is provided to the normalizer 132. The normalizer 132 samples the maximum and minimum values of the phase angle _{deg in} degree units based on a predetermined relational expression, (N) and the output value (q _N ) of the normalizer 132 is derived from the following equation (2).

.. 식 2

.. Equation 2

Then, the output value q _N of the rectifier 132 is transmitted to the quantizer 133

)는 다음 식 3으로 나타낸다.The quantizer 133 applies the output value q _N of the normalizer 132 to a predetermined relational expression and converts the output value q _N to an integer value and outputs the sampled number of the quantizer 133

) Is expressed by the following equation (3).

.. 식 3

.. Equation 3

)는 반복 제어기(120)로 전달된다.The number of samplings of the quantizer 133 (

Is transmitted to the iterative controller 120. [

)를 제공받은 반복 제어기(120)는 주파수 변동에 따라 설정된 샘플링 개수가 반영된 메모리 수로 주기적인 외란을 증폭시킨 후 보상이 불가능한 고조파 성분을 제거한다.The number of samplings of the quantizer 133 (

The repetition controller 120 amplifies the periodic disturbance by the number of memories in which the sampling number set in accordance with the frequency variation is reflected, and then removes harmonic components that can not be compensated.

The repetitive controller 120 may include a low-pass filter q (z) without phase delay. Therefore, the transfer function G _rp (z) of the repetitive controller 120 is represented by an error and a constant L of the reference voltage instruction r and the load voltage y, and the transfer function G _rp (z) The following Equation 4 can be satisfied.

.. 식 4G _rp (z) =

.. Equation 4

는 반복 제어기(120)의 비례 제어를 수행하기 위한 제어값이고, q(z)는 위상 지연이 없는 저역통과필터(제로위상 지연 로우패스필터) 로 반복 제어기(120)의 안정성 및 필터의 차단 특성을 제어하는 기능이 수행된다. 여기서, L은 샘플링 데이터들을 기본 위상각 대비 진상시키기 위한 정수이다.here,

Is a control value for performing proportional control of the repetitive controller 120 and q (z) is a low-pass filter (zero phase delay low-pass filter) free of phase delay, Is performed. Here, L is an integer for advancing the sampling data with respect to the basic phase angle.

와 샘플링 개수(N_r)의 곱에 반비례하며 이에 배열 주기는 다음 식 5로 나타낸다. In addition, the arrangement period in which the repetitive control is performed in units of the sampling number Nr set in accordance with the frequency fluctuation may be a voltage or current frequency

And the number of samples (N _r ), and the arrangement period is represented by the following equation (5).

.. 식 5Array period =

.. Equation 5

는 제어 하고자 하는 대상의 주파수 대역이다.here

Is the frequency band of the object to be controlled.

A value obtained by adding the first control value of the voltage controller 110 and the second control value of the repetitive controller 120 is used as a control value for controlling the operation of the inverter switching unit 30, The output of the inverter switching unit 30 is filtered by the LC filter unit 50 and then supplied to the load 70. [

As the number of memories for iterative control changes based on the sampling number and the array period derived according to the frequency variation of the object to be controlled, the periodic disturbance is stably removed with respect to the non-linear load voltage, And the current quality can be improved. Since the structure of the memory controller is simple and the memory controller can be applied to the conventional repetitive controller, the stability of the conventional repetitive control is maintained while the design is easy to implement, .

5 is an output waveform diagram of the normalizer 132 shown in FIG. 4. Referring to FIG. 5, it is confirmed that the maximum value and the minimum value of the phase of the load voltage in units of degrees are normalized based on the predetermined relational expression have.

FIG. 6 is an output waveform diagram of the quantizer 133 shown in FIG. 4. Referring to FIG. 6, the minimum value and the maximum value of the digitized number N of memories to the normalizer 132 are given by a predetermined rounding function Can be converted to an integer value.

FIG. 7 is a waveform diagram showing the input / output frequency of the uninterruptible power supply system USP. Referring to FIG. 7, the screen period setting of the oscilloscope is 30 ms / div, the size per screen is 4 A / div and 5 A / If the target frequency is 50Hz and 52Hz, it can be confirmed that the output waveform of the repetitive controller is stable without regard to each frequency.

FIG. 8 is a waveform diagram showing the input / output frequency of the uninterruptible power supply system (UPS). Referring to FIG. 8, when the screen period setting of the oscilloscope is 30 ms / div and the size per screen is 4 A / , It can be seen that the load current error is reduced to zero without a large transient interval even if the power frequency is changed from 50 Hz to 52 Hz. Thus, it can be confirmed that the repetitive controller operates stably regardless of the frequency variation.

FIG. 9 is a diagram showing input / output voltage waveforms of an uninterruptible power supply system (UPS). Referring to FIG. 9, when the repetitive control is performed by changing the sampling time, the total harmonic distortion (THD) It can be confirmed that the output current of the load current is reduced from 12.8% to 3.7%, and the output quality of the load current is improved with respect to the nonlinear load.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. It can be understood that it is possible.

10: inverter controller 110: voltage controller
120: Repetition controller 130: Memory controller
131: phase angle converter 132: normalizer
133: Quantizer

Claims (4)

A voltage controller for performing a voltage control on an error between a reference command value and a load voltage; And an iterative controller for performing harmonic control on an error between a reference command value and a load voltage,
Further comprising a memory controller for setting a sampling number of the repetition controller according to a frequency variation of an object to be controlled, deriving a memory number from the set sampling number, and transmitting the number of memories to the repetition controller,
The memory controller comprising:
A phase angle converter for converting the frequency of the load voltage in units of radians into a phase angle in degrees;
A normalizer for converting a maximum value and a minimum value of the phase angle in degrees into a maximum value and a minimum value of the sampling number; And
And a quantizer for converting the output value of the normalizer into an integer value to derive a sampling number and an array period (trigger period), and adjusting the number of memories of the iterative controller according to the derived sampling number and array period. Harmonic control system using frequency - based adaptive iterative controller. The apparatus according to claim 1,
A load voltage, and a load current. The harmonic control apparatus of claim 1, wherein the phase-based frequency adaptive repetitive controller comprises: delete The method according to claim 1,
Wherein the frequency of the load voltage is set to be inversely proportional to the product of the frequency of the load voltage and the number of sampling times.

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