KR100706181B1 - Single-Phase Active Power Filter Using Rotating Reference Frame - Google Patents

Abstract

In the present invention, a single phase active power filter can create a virtual phase in addition to the original single phase current to make a coordinate system such as that used in three phases to facilitate forward clock calculation even in a single phase, and the virtual phase has passed through a low pass filter. The present invention relates to a single-phase active power filter using a rotational coordinate system capable of reducing harmonics by simply generating a virtual phase and generating a harmonic compensation reference voltage by using a delayed phase as a virtual phase.

The single phase active power filter includes a power detector for detecting a distorted signal generated by a nonlinear load, a signal input through the power detector, generating an arbitrary virtual phase, and then powering it through a predetermined control algorithm. A harmonic detector which detects harmonics using the normal and reverse phase components of a rotating coordinate system synchronized with frequency and obtains a compensation reference voltage of the harmonics, and a compensation reference signal output from the harmonic detector and a predetermined triangular reference signal. And a PWM generator for outputting a pulse width modulated signal after comparing with each other, and an inverter driving means for receiving the PWM signal and driving a gate of the inverter.

Description

Single-Phase Active Power Filter Using Rotating Reference Frame}

1 is a block diagram showing a single-phase active power filter according to the present invention.

2 is a conceptual diagram illustrating a harmonic detection algorithm of the harmonic detector of FIG. 1 according to the present invention.

3 is a diagram showing a current vector on α- β and dq coordinates according to the present invention.

4 is a block diagram showing a single-phase active power filter according to an embodiment of the present invention.

5 to 9 are waveform diagrams showing the results of experiments using the single-phase active power filter of FIG. 4, FIG. 5 is an experimental waveform before compensation, FIG. 6 is a waveform shown when compensating with a parallel passive power filter, and FIG. 8 shows the experimental waveforms in the transient state, and FIG. 9 shows the waveforms of the power current and voltage in the non-compensation, the compensation with the passive filter, and the compensation with the hybrid active power filter. A diagram showing current and load voltage waveforms.

* Explanation of symbols for the main parts of the drawings

10: diode rectifier 20: LC filter

30: load 50: inverter

100: single-phase active power filter 110: power detector

130: Harmonic Detector (DSP) 131, 133, 135: Low Pass Filter (LPF)

132,134: coordinate conversion means 136,137,139: mixer

138: inverse conversion means 139: amplification means

150: PWM generating unit 170: inverter driving means

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single phase active power filter, and in particular, generates a virtual phase through a harmonic detector by detecting voltage and current generated in a nonlinear load, and then uses a normal and reverse phase component of a rotational coordinate system to determine fundamental wave components. The present invention relates to a single-phase active power filter using a rotational coordinate system which extracts and subtracts the fundamental wave component from an actual current to obtain a harmonic component, and obtains a harmonic compensation reference voltage by taking k times the harmonic component.

As the demand for power increases, the optimum interface between the power system and the load is very important to make full use of power transmission capacity and to suppress power voltage fluctuations as much as possible. Increasingly, research on the interface between the power supply and the power electronic device is urgently required.

Therefore, the present invention has been developed for a single-phase hybrid active power filter having a harmonic reduction function to suppress the harmonics generated from the load side to improve the quality of power at the power source side.

Most power conversion systems such as variable speed systems, SMPS, UPS, HVDC transmission, etc., are connected to the power supply by diodes or thyristor rectifiers. Due to the large DC-Link filter and switching elements of the rectifiers The waveform is distorted, which includes many lower harmonic components.

Harmonics of the input current generated in this way result in increased VA capacity of the power system devices, causing excessive heat generation and abnormal vibration of the apparatus, motor failure, transient of neutral current, and inaccurate power measurement.

In addition, it may cause EMI of sensitive electronic and communication devices, which may cause not only power loss but also communication failure.

As nonlinear loads such as power conversion systems that use diodes or thyristor rectifiers are increasing, the problem of harmonic currents on the power supply side has led to the introduction of harmonic currents such as IEEE-519 and IEC6100-3-2. These guidelines apply to electronic equipment imported from 1998 in Europe and other countries.

At first, passive filters were used to remove harmonics. Although passive filters are inexpensive, they can selectively compensate only for harmonics of a certain order, which makes it difficult to achieve satisfactory performance when a wide range of harmonics occur at the power stage. There is always the possibility of power supply impedance and series resonance.

As a solution of the disadvantage of the passive filter, a three-phase active power filter has been developed.

The three-phase active power filter has been studied as a standard solution to the problem of nonlinear loads, and many topologies and control methods, such as parallel, series, hybrid, and parallel, have been proposed.

In general, when a three-phase active power filter is installed at a point of common coupling (PCC) where mechanical equipment is installed, voltage distortion occurs due to converter switching. In addition, current harmonics and reactive power circulate in the installed device, and interference occurs between loads in each phase.

However, the single-phase active power filter compensates for each of the loads, thereby reducing the possibility of interference between the loads by eliminating current harmonics and compensating reactive power. In addition, even if a single-phase active power filter fails, the input current is not so distorted.

However, research and development of single phase active power filter is considerably smaller than three phase active power filter. Depending on the type of inverter, it can be divided into single-phase half-bridge, single-phase full-bridge, current source inverter, voltage source inverter, etc. The most commonly used are parallel and series active power filters using full-bridge voltage source inverters.

In Korea, research on harmonics and reactive power compensation as a series active power filter is limited to the study of three-phase active power filter. In the case of single phase, there was research and development on parallel active power filter, but it is inadequate. Recently, with the increase in the spread of industrial equipment or home appliances that applied a voltage inverter, harmonics generated by a capacitor-type diode rectifier have been a problem. In this regard, we present the results of a single-phase series active power filter to reduce harmonics.

Accordingly, an object of the present invention is to provide a single-phase active power filter using a rotational coordinate system capable of reducing harmonics after detecting a harmonic generated from a nonlinear load using a diode rectifier to obtain a compensation command value.

Another object of the present invention is that the conventional method requires a minimum half-cycle time to detect harmonics, making it difficult to perform real-time calculations, while in the present invention, a virtual system can be used to create a coordinate system as used in three phases. It is to provide a single-phase active power filter using a rotational coordinate system that can facilitate forward time calculation.

It is another object of the present invention to generate a second phase by giving a time delay to the load current, and then to make a complex calculation by forming a system having a single phase system. It is to provide a single-phase active power filter using a rotational coordinate system that can easily create a virtual phase by using the delayed phase after passing through the filter as a second phase.

Another object of the present invention, without applying the conventional instantaneous reactive power theory using a fixed coordinate system in order to obtain a normal component, using a rotational coordinate system synchronized with the power frequency to calculate the forward time and calculate the compensation current and then the converter It is to provide a single-phase active power filter using a rotational coordinate system to reduce the harmonics by multiplying the gain to obtain the compensation voltage command value.

A technical means of the present invention for achieving the above object is a single-phase active power filter for compensating harmonic components generated by a nonlinear load, comprising: a power detector for detecting a distorted signal generated by the nonlinear load; Generate a virtual phase by receiving a signal input through the power detector and detect harmonics using the normal and reverse phase components of the rotational coordinate system synchronized with the power frequency through a predetermined control algorithm. A harmonic detector for obtaining a compensation reference voltage; A PWM generator which receives a compensation reference signal output from the harmonic detector and a predetermined triangular wave reference signal, compares each other, and outputs a pulse width modulation signal; And an inverter driving means for receiving the PWM signal and driving the gate of the inverter.

The harmonic detector includes: an A / D converter for converting an analog signal output from the power detector into a digital signal; A digital signal processor for converting a signal input from the A / D converter into an actual voltage and current value and calculating a compensation reference voltage by a control algorithm; And a D / A converter for converting the signal output from the digital signal processor into an analog signal. Characterized in that consisting of.

Specifically, the control algorithm of the harmonic detector separates the DC component and the AC component through the coordinate transformation of the actual current component, extracts only the DC component, and obtains the fundamental wave component of the actual current through the coordinate inverse transformation. It is configured to obtain a harmonic component by mixing the entire current, and characterized in that configured to obtain a compensation reference voltage by taking k times the harmonic component.

The harmonic detector may further include: a first LPF configured to provide an actual current component to pass a low current and to delay a predetermined time to create a virtual phase; First coordinate conversion means for converting αβ coordinates into d coordinates by receiving angular frequencies of signals output from the first LPF and normal components synchronized with actual current components and power supply voltages; A second LPF which receives a steady current component outputted from the first coordinate converting means and passes a low pass and separates the DC component into an AC component; Second coordinate conversion means for converting αβ coordinates into d coordinates by receiving angular frequencies of signals output from the first LPF, and reverse phase components synchronized with actual current components and power supply voltages; A third LPF configured to receive a reverse phase current component output from the second coordinate converting means and to pass a low pass and separate the DC component into an AC component; A first mixer receiving and mixing the AC component output from the second LPF and the AC component output from the third LPF, and outputting a DC component; A second mixer configured to receive a DC component output from the second LPF and a DC component output from the third LPF, mix and output the DC component; Inverse conversion means for receiving the signals output from the first mixer and the second mixer and the angular frequencies of the normal components, respectively, and inversely converting the d coordinates into the α β coordinates to obtain fundamental wave components of the actual current; A third mixer configured to obtain harmonic current components after receiving and mixing the fundamental wave components and the total current of the actual current output from the inverse conversion means; And amplifying means for amplifying the harmonic current components obtained by the third mixer to obtain a compensation reference voltage.

The first mixer is configured to subtract the AC component output from the third LPF from the AC signal output from the second LPF, and the second mixer outputs the DC signal output from the second LPF and the third LPF. The third mixer is configured to subtract the fundamental wave component of the actual current output from the inverse conversion means from the total current.

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

1 is a block diagram illustrating a series single-phase active power filter according to the present invention, and FIG. 2 is a conceptual diagram illustrating a harmonic detection algorithm of the harmonic detector of FIG. 1 according to the present invention. ) Is composed of a power detector 110, a harmonic detector 130, a PWM generator 150 and the inverter driving means (170).

First, in Fig. 1, the load of the system is composed of a diode rectifier 10 serving as a load of a current source and an RL load 30.

)을 생성한 후 소정의 제어알고리즘을 통해 전원주파수에 동기하는 회전좌표계의 정상 및 역상 성분을 이용하여 고조파 성분(

)을 검출함과 아울러 상기 고조파의 보상 기준전압(

)을 획득하여 출력하도록 구성되어 있고, PWM발생부(150)는 상기 고조파검출기(130)에서 출력된 보상 기준신호(

)와 소정의 삼각파 기준신호(Tri-wave)를 제공받아 상호 비교한 후 펄스폭 변조신호를 출력하도록 구성되어 있고, 인버터구동수단(170)은 상기 PWM발생부(150)로부터 출력되는 신호를 제공받아 인버터(50)의 게이트단을 전원전압으로 풀업시키거나 또는 접지전압으로 풀다운시켜 게이트를 온/오프시키도록 구성되어 있다.The power detector 110 is configured to detect a distorted signal generated by the nonlinear load 30, such as the diode rectifier 10, and the harmonic detector 130 is a signal input through the power detector 110. Is supplied to any virtual image (

) And harmonic components using the normal and reverse phase components of the rotating coordinate system synchronized with the power frequency through a predetermined control algorithm.

) And the compensation reference voltage of the harmonic

) Is obtained and outputted, and the PWM generator 150 is a compensation reference signal (outputted from the harmonic detector 130)

) And a predetermined triangular wave reference signal (Tri-wave) are compared to each other and configured to output a pulse width modulated signal, the inverter driving means 170 provides a signal output from the PWM generator 150 And the gate terminal of the inverter 50 is pulled up to the power supply voltage or pulled down to the ground voltage to turn the gate on and off.

)의 좌표변환을 통해 직류성분과 교류성분을 분리하여 직류성분만을 추출한 후 좌표 역변환을 통해 실제 전류의 기본파 성분(

)을 얻고, 상기 기본파 성분(

)에서 전체전류(

)를 믹싱하여 고조파 성분(

)을 구하도록 구성되어 있고, 상기에서 산출한 고조파 성분(

)에 k배를 취하여 보상 기준전압(

)을 얻도록 구성되어 있다.The control algorithm of the harmonic detector 130, the actual current component (

Separate DC and AC components through the coordinate transformation of) and extract only the DC components.

) And the fundamental wave component (

) At full current (

) By mixing the harmonic content (

), And the harmonic components (

) K times the compensation reference voltage (

Is configured to obtain

)을 제공받아 로우패스시킴과 아울러 소정의 시간만큼 지연시켜 임의의 가상의 상(

)을 만드는 제 1 LPF(131)와, 상기 제 1 LPF(131)로부터 출력되는 신호 (

)와 실제 전류성분(

) 및 전원전압에 동기하는 정상성분의 각주파수(ω)를 제공받아 αβ좌표를 ｄｑ좌표로 변환하는 제 1 좌표변환수단(132)과, 상기 제 1 좌표변환수단(132)으로부터 출력되는 정상전류 성분(

,

)을 제공받아 로우패스시킨 후 직류성분(

)과 교류성분(

)으로 분리하는 제 2 LPF(133)와, 상기 제 1 LPF(131)로부터 출력되는 신호(

)와 실제 전류성분(

) 및 전원전압에 동기하는 역상성분의 각주파수(-ω)를 제공받아 αβ좌표를 ｄｑ좌표로 변환하는 제 2 좌표변환수단(134)과, 상기 제 2 좌표변환수단(134)으로부터 출력되는 역상전류 성분(

,

)을 제공받아 로우패스시킨 후 직류성분(

)과 교류성분(

)으로 분리하는 제 3 LPF(135)와, 상기 제 2 LPF(133)에서 출력되는 교류성분(

)과 제 3 LPF(135)에서 출력되는 교류성분(

)을 제공받아 믹싱한 후 직류성분(

)을 출력하는 제 1 믹서(136)와, 상기 제 2 LPF(133)에서 출력되는 직류성분(

)과 제 3 LPF(135)에서 출력되는 직류성분(

)을 제공받아 믹싱한 후 직류성분(

)을 출력하는 제 2 믹서(137)와, 상기 제 1 믹서(136)와 제 2 믹서(137)의 출력신호(

,

) 및 정상 성분의 각주파수(ω)를 각각 제공받아 ｄｑ좌표를 αβ좌표로 역변환하여 실제 전류의 기본파 성분(

)을 구하는 역변환수단 (138)과, 상기 역변환수단(138)의 출력되는 실제 전류의 기본파 성분(

)과 전체 전류(

)를 각각 제공받아 믹싱한 후 고조파 전류성분(

)을 구하는 제 3 믹서(139), 및 상기 제 3 믹서(139)에서 구한 고조파 전류성분(

)을 증폭(k배)하여 보상 기준전압(

)을 구하는 증폭수단(140)을 포함하고 있다. That is, the algorithm of the harmonic detector 130 as shown in FIG.

) And low pass as well as delay for a certain amount of time

) A first LPF 131 to produce a signal, and a signal output from the first LPF 131 (

) And the actual current component (

First coordinate conversion means 132 for converting αβ coordinates into d coordinates, and a steady current output from the first coordinate conversion means 132. ingredient(

,

) And pass low current

) And AC component (

The second LPF 133 to be separated into a) and the signal (output from the first LPF 131 (

) And the actual current component (

Second coordinate conversion means 134 for converting αβ coordinates into d coordinates and receiving the angular frequency (−ω) of the inverse phase component synchronized with the power supply voltage; and the reversed phase output from the second coordinate conversion means 134. Current component

,

) And pass low current

) And AC component (

The third LPF 135 to be separated into a) and the AC component output from the second LPF (133)

) And the AC component output from the third LPF 135

) And mix the DC component (

) Is a first mixer 136 and a DC component output from the second LPF 133 (

) And a DC component output from the third LPF 135

) And mix the DC component (

) Outputs a second mixer 137 and output signals of the first mixer 136 and the second mixer 137.

,

) And the angular frequency (ω) of the normal component, respectively, and inversely converts the d coordinates to the α β coordinates,

) And the fundamental wave component of the actual current outputted by the inverse transform means (138).

) And total current (

) And mix harmonic current components ()

) And a harmonic current component obtained by the third mixer 139

) By amplifying (k times)

Amplification means 140 is obtained.

)에서 제 3 LPF(135)에서 출력되는 교류성분(

)을 감산하도록 구성되어 있고, 상기 제 2 믹서(137)는 상기 제 2 LPF(133)에서 출력되는 직류신호(

)와 제 3 LPF(135)에서 출력되는 직류성분(

)을 가산하도록 구성되어 있으며, 상기 제 3 믹서(139)는 상기 역변환수단(138)의 출력되는 실제 전류의 기본파 성분(

)을 전체 전류(

)에서 감산하도록 구성되어 있다.In addition, the first mixer 136 is an AC signal (output from the second LPF 133)

AC component output from the third LPF (135)

), And the second mixer 137 is a DC signal output from the second LPF 133.

) And a DC component output from the third LPF 135

), And the third mixer 139 is a fundamental wave component of the actual current output of the inverse converting means 138 (

) The total current (

Is subtracted from).

)을 보상해줌으로서, 안정적인 전원을 부하로 공급할 수 있도록 하는 데, 상기 다이오드정류기(10)를 사용하는 비선형 부하(30)에 의해 생성된 왜곡된 전류를 고조파검출기(130)에 입력시키고, 고조파검출기(130)를 통해 얻은 고조파 성분(

)에 k배를 취한 출력신호를 보상지령치(

; 보상 기준전압)로 사용하게 된다.Accordingly, the single phase active power filter has a harmonic content generated by the nonlinear load 30 (

) To supply a stable power supply to the load, inputting the distorted current generated by the nonlinear load 30 using the diode rectifier 10 to the harmonic detector 130, the harmonic detector Harmonic component obtained through (130)

The output signal multiplied by k times to the compensation command value (

; Compensation reference voltage).

That is, the algorithm proposed in the present invention can make a coordinate system as used in the three phases using the virtual phase, and instantaneous calculation that is difficult to perform on a single phase is performed.

Existing methods using fixed coordinates require software or hardware configuration to delay the phase of the current by T / 4. The proposed method has the advantage of simply generating a second phase by simply using LPF. have.

If the two axes do not have exactly the phase difference of T / 4, interference occurs between the two axes, and the exact fundamental wave component cannot be extracted. This problem is solved by using the normal and reverse phase components of the rotational coordinate system. After detecting the wave component, the harmonic component is obtained by subtracting the fundamental wave component of the current from the actual current, and the compensation command value can be obtained by taking k times the harmonic component.

In the harmonic detection method based on instantaneous reactive power theory in three phases (a-b-c), the instantaneous power is always calculated after the three-phase two-phase conversion (a-b-c to α-β).

In the single-phase circuit as shown in FIG. 3, the above-described method merely makes a virtual phase by giving a time delay to the actual phase, and makes it possible to simply create fixed coordinate systems (α-β co-ordinates).

By converting a single-phase system to two-phase in this way, instantaneous power can be calculated by applying a Cartesian coordinate system as used in three-phase.

It uses the delay characteristics of the low pass filter (LPF) unlike the conventional method of creating a virtual phase of the same type by giving the actual single phase current a time delay of T / 4 (T: period of the fundamental wave). Induced virtual phase current.

The proposed method has the advantage that it is possible to detect the exact current setpoint even if the two axes have 90 ° phase difference and do not have the same size.

로 놓고, 저역통과필터(LPF)를 통과한 후의 만큼 지연되고 크기가 감소한 전류신호는

라고 하고 각각 수학식 1, 2로 정의한다.Then, as shown in Figure 2 the actual component of the current

After passing through the low pass filter (LPF) Delayed and reduced in magnitude

And are defined by Equations 1 and 2, respectively.

는 α축 전류로,

는 β축 전류로 각각 정의한다.remind

Is the α-axis current,

Are each defined by the β-axis current.

Using two components of Equation 3, a coordinate system having two axes in a single phase may be obtained.

는 ω의 속도로 회전하는 전류의 성분을,

은 -ω의 속도로 회전하는 전류의 성분을 나타내고, 각각 전류의 정상 성분과 역상 성분으로 명명한다.

Is the component of the current that rotates at the rate of ω,

Denotes a component of a current rotating at a rate of -ω, and is named as the normal component and the reverse phase component of the current, respectively.

■ α-β, d-ｑ coordinate transformation for the normal component

The method proposed in the present invention is to obtain the fundamental wave component of the actual current by separating the DC component and the AC component through coordinate transformation and extracting only the DC component to perform the inverse transformation.

의 기본파 성분(

)에 대해서만 수식을 전개하였다.Since the harmonic components except the fundamental components appear as AC components after the coordinate transformation, they are blocked by the low pass filter. For this reason, the equation that is developed next includes the DC component after the coordinate transformation.

Fundamental wave component of

) Is developed only for

ｄｑ 좌표변환을 수식으로 나타내면 아래 수학식 4로 표현할 수 있다.αβ

If the kD coordinate transformation is expressed by an equation, it can be expressed by Equation 4 below.

에 대하여 계산하면,remind

Calculating for

It can be represented as.

와

는 각각

의 DC성분과 AC성분을 나타낸다.In Equation 5

Wow

Are each

DC component and AC component are shown.

를

와

로 나눈 것처럼

을 DC성분과 AC성분으로 분리시킬 수 있다.remind

To

Wow

As divided by

It can be separated into DC component and AC component.

와

는 다음의 수학식 9, 10으로 나타낸다.In equation (8)

Wow

Is represented by the following equations (9) and (10).

■ αβ, δｑ coordinate transformation for inverse phase component

As in the method obtained from the normal component, the reverse phase component of the current may be divided into DC and AC components, respectively.

ｄｑ 좌표변환을 수식으로 나타내면,Αβ for reversed phase rotation

If the coordinate transformation is represented by an equation,

to be. The d-axis current of the negative sequence is represented by Equation 12.

및

는 아래 수학식 13, 14와 같다.here,

And

Is as shown in Equations 13 and 14 below.

The q-axis current of the negative sequence is represented by the following equation (15).

및

는 아래 수학식 16 및 17과 같다.here,

And

Is as shown in Equations 16 and 17 below.

,

는 Negative sequence의 DC 성분을,

,

는 AC 성분을 각각 나타낸다.From above

,

Is the DC component of the negative sequence,

,

Represents an AC component, respectively.

■ Settlement Setpoint

를 구하기 위하여 새로운 상을 이용하여 2상 시스템을 구축하였다. 실제전류의 성분인 α축의 기본파 성분(

)을 구한 후, 전체전류(

) 에서 그 값을 빼줌으로서 구하고자 하는 고조파 성분을 얻을 수 있다. 이 고조파 성분에 k배함으로서 보상전압을 산출하였다.Harmonic Current Components

In order to obtain a new phase, a two-phase system was constructed. Fundamental wave component of α-axis which is a component of actual current

), Then the total current (

We can get the harmonic component to get by subtracting the value from. The compensation voltage was calculated by k times this harmonic component.

를 수학식 18과 같이 구한다.Using the equations (6) and (13), the DC component of the d-axis current

Is obtained as shown in Equation 18.

는 수학식 9와 16의 합에 의해 수학식 19와 같이 구해진다.And the DC component of the q-axis current

Is obtained as in Equation 19 by the sum of Equations 9 and 16.

αβ 역변환 매트릭스이다.Equation 20 is

αβ inverse transformation matrix.

와

는 좌표변환 후의 α축과 β축의 기본파 성분이다.here,

Wow

Is the fundamental wave component of the α and β axes after the coordinate transformation.

Only the α-axis component, which is the actual current, is used to find the harmonic components, and the β-axis component is not used.

는 다음 수학식 21과 같다.The fundamental wave component of the actual current

Is as shown in Equation 21 below.

는 다음 수학식 22와 같다.Harmonic component

Is as shown in Equation 22 below.

)는 수학식 23과 같이 전류 고조파 성분에 k배를 함으로써 구할 수 있다.Then, the voltage setpoint (

) Can be obtained by multiplying the current harmonic component by k times, as shown in Equation (23).

는 실제 전류를 나타내고, ω는 전원전압에 동기하는 각주파수이고, ｄｑ

αβ변환과, ｄｑ

αβ 역변환은 다음 수학식 24와 같이 주어진다.The overall operation of such a single phase hybrid type active power filter is shown in FIG.

Is the actual current, ω is the angular frequency synchronized with the power supply voltage,

αβ conversion and dｑ

αβ inverse transform is given by the following equation (24).

)을 만들었다.That is, in order to perform complex calculation by forming a coordinate system in a single phase, a current component different from a conventional single phase current is required, and the algorithm proposed in the present invention can be easily simulated using an LPF having a delay characteristic.

)

Experimental Example

4 is a system diagram showing an active power filter according to an embodiment of the present invention. The harmonic detector includes an A / D converter 129 for converting an analog signal output from the power detector 110 into a digital signal. A digital signal processor 130 (DSP) that converts a signal input from the A / D converter 129 into an actual voltage and current value and then calculates a compensation reference voltage by a control algorithm, and outputs it from the digital signal processor 130. The D / A converter 141 converts the converted signal into an analog signal.

In FIG. 4, an input voltage source of the inverter 50 was used by attaching an electrolytic capacitor of 450 [V] and 4700 [kV] to smooth the DC-link stage of the inverter 50, and used the switching element of the inverter 50. IGBT module was used.

As the load of the system, a single phase diode rectifier 10 and an RL load 30 serving as a current source load are used as shown in FIG.

The voltage and current converted to the voltage value of ± 10 [V] through the power detectors 110 (PT and CT) are converted into digital values of predetermined bits (16 bits) through the A / D converter 129 of the harmonic detector 130. The signal is converted and input to the digital signal processor 130.

The digital signal processor 130 calculates the compensation reference voltage by a predetermined control algorithm after converting it to the actual voltage and current values.

The calculated compensation reference voltage is converted into an analog signal again through the D / A converter 141 and transferred to the PWM generator 150, and the output signal of the D / A converter 141 is output from the PWM generator 150. The inverter control signal is output by comparing predetermined triangular waves with each other, and the inverter control signal is configured to drive the inverter 50 via the inverter driving means 170.

The inverter driving means 170 uses a gate driver capable of driving up to 40 [kHz] and uses a capacitor and a resistor to prevent a dark short of the switching element of the inverter 50. Dead time).

In order to simplify the hardware, most algorithms except for the inverter 50 are composed of software, and the digital signal processor 130 is used to perform a high-speed and high-precision operation in order to apply the software.

In the present invention, the digital signal processor used as a microprocessor uses a 32-bit digital signal processor 130 capable of high-speed and high-precision operation and capable of floating-point processing.

The performance and state quantity of the proposed algorithm are calculated through the digital signal processor 130 and the signal converted into an analog value through the D / A converter 141 can be confirmed through an external oscilloscope.

Table 1 below shows the constant of the circuit used in the experiment, and Table 2 shows the circuit parameters of the parallel passive filter.

3th

)Inductor (

) 5.2 [mH] Capacitor

) 150 [μF] 5th Inductor (

) 2 [mH] Capacitor

) 140 [μF]

Supply Voltage Voltage frequency 110 [Vrms] 60 [Hz] Sampling Frequency 25 [kHz] Cut-off Frequency (1) Cut-off Frequency (2) 70 [Hz] 20 [Hz]

)DC-Link Capacitance

) 4700 [㎌] Load Inductance

) 35 [mH] Load Resistance

) 15 [Ω] LC Filter Inductance

) 4 [mH] LC Filter Capacitance

) 0.5 [㎌]

As the non-linear load 30 used in the experiment, a single-phase full-wave rectifier circuit connected to the RL series load was used, and the power supply voltages were 110 [V] and 60 [Hz] which are commonly used. The cutoff frequency of LPF used to make single-phase system into vector system was 70 [Hz].

)와 15[Ω]의 저항(

)을 사용하였고, LC필터(20)의 인덕턴스(

)는 4[mH]를 사용하였고, 커패시턴스(

)는 0.5[μF]를 사용하였다. The DC-Link capacitor of the inverter 50 is 4700 [μF], and the load 30 of the output terminal of the diode rectifier 10 is 35 [mH].

) And 15 [Ω] resistance (

), And the inductance of the LC filter 20

) Used 4 [mH] and the capacitance (

) Used 0.5 [μF].

In the harmonic detection algorithm of FIG. 2, 20 [Hz] was used as the cutoff frequency of the LPF used to separate the DC components.

Looking at the experimental results in the state configured as described above are as follows.

In this experimental example, the experimental results applying the control algorithm of the single-phase hybrid active power filter using the normal, reversed-phase component rotational coordinate system are presented.

5 to 7 show waveforms compensated by a hybrid type active power filter that compensates with a passive filter and a passive filter and an active power filter before compensation.

좌표 상에서의 전류 벡터 궤적이다. That is, FIG. 5 is an experimental waveform before compensation, 5a is a real current and a delayed imaginary current, 5b is a current spectrum (THD: 22.9%), 5c is a dq current component on a rotational coordinate, and 5d is

Current vector trajectory on the coordinates.

좌표 상에서의 전류 벡터 궤적이다.6 is a waveform shown when compensating with a parallel passive power filter, 6a is a real current and a delayed imaginary current, 6b is a current spectrum (THD: 5.8%), 6c is a dq current component on a rotational coordinate, and 6d is

Current vector trajectory on the coordinates.

좌표 상에서의 전류 벡터 궤적이다.7 is a waveform shown when the hybrid system is compensated, 7a is a real current and a delayed imaginary current, 7b is a current spectrum (THD: 3.8%), 7c is a dq current component of a rotational coordinate, and 7d is

Current vector trajectory on the coordinates.

좌표 상에서 회전하는 벡터의 궤적을 나타내고 있다. That is, the waveforms of each of (a) of FIGS. 5 to 7 represent waveforms of the input current and the delayed current through filtering, and the waveforms of each of (b) of FIGS. 5 to 7 represent the harmonic spectrum of the supply-side current. 5 to 7 show the components of each axis after dq coordinate conversion of the input current, and the waveform of each (d) of FIGS.

The trajectory of the vector rotating on the coordinates is shown.

In case of non-compensation, the THD of power supply current is about 22.9%, about 5.8% when passive filter compensation, and about 3.8% when compensating with hybrid active power filter, and the remaining components compensated by passive filter are in series. By compensating the active power filter, it can be seen that the active power filter can be reduced in capacity.

It can be seen that the waveform of the rotation vector is expressed in the form of an ellipse as the sine wave gets closer.

FIG. 8 is an experimental waveform of a transient state, and shows a transient state when an active power filter is inserted in FIG. 8, and shows a quick response and a transition of a current phase.

8a is the actual current and the delayed imaginary current, and 8b is the load stage voltage and the compensation voltage.

9 shows waveforms of power current and voltage at the time of non-compensation, compensation with the passive filter, and compensation with the hybrid active power filter, and current and load terminal voltage of the passive filter.

9a is the power current and voltage at non-compensation, 9b is the power current and voltage at compensation with passive filter, 9c is the power current and voltage at compensation with hybrid active power filter, 9d is filter at compensation with hybrid active power filter Current and load-stage current.

At this time, the power current is changed from 5.9 [A] to 13.9 [A] and 13.8 [A], and the power factor is changed from 0.93 above ground to 0.46, and the power factor is controlled to 0.99 above ground when compensating with a hybrid active power filter. have.

These results show that the power factor is also improved by compensating harmonics.

In addition, the passive filter has a large current flowing in the reactive power component and harmonic components, causing a burden in the form of voltage drop on the power supply side when the passive filter is used.

Therefore, in the present invention, a control method is proposed for a single phase hybrid type active power filter, which is a method of reducing harmonics generated by the single phase nonlinear load 30. However, the conventional method requires a minimum half-cycle time to detect harmonics. Real time computation is difficult.

The proposed control method enables real-time control using DSP and drives inverter 50 through PWM control. Simulation and experiment were performed on the RL load 30 and the results were presented.

THD was about 5.8% when operated with passive filter alone, but THD was about 3.8% and 2% of harmonics were removed when compensating with hybrid active power filter. It can be seen that the proposed method satisfies the IEEE's harmonic regulation of less than 5%.

In addition, such single-phase active power filter is used to supply high-quality power to loads distributed in small capacity in large buildings or large apartments as well as industrial equipment, or apply single-phase small capacity active power filter to home appliances that cause EMI. Can be used.

While specific embodiments of the present invention have been described and illustrated above, it will be apparent that the present invention may be embodied in various modifications by those skilled in the art. Such modified embodiments should not be understood individually from the technical spirit or the prospect of the present invention, but should fall within the claims appended to the present invention.

Therefore, the present invention improves the quality of power at the power supply side and suppresses reactive power and harmonics generated at the load side with the increase in the spread of industrial equipment or home appliances to which voltage voltage inverters are applied. And there is an advantage that can compensate for the instantaneous active power.

By using single-phase active power filter in each load group in the system using several types of loads, the compensation characteristics are improved compared to the three-phase active power filter, and various problems caused by harmonic current are overcome. It has the advantage of extending the life and eliminating noise from the electric equipment.

In addition, it is possible to achieve high efficiency and high quality of electric energy by improving power factor, and compensating for unbalanced load is more effective because single phase active power filter is compensated for load group of each phase. It can solve the problem of deterioration of the product due to the fluctuation, and can improve the quality level of the power system which is being unmanned and automated recently with stable power supply.

Finally, single-phase active power filters have smaller capacities and lower costs than conventional three-phase active power filters, making manufacturing costs considerably more economical. Compensating the harmonics and power factor of large single-phase loads such as electric railways and electric furnaces There is an advantage to improve quality.

Claims (8)

In a single-phase active power filter to compensate for harmonics caused by nonlinear loads: A power detector for detecting a distorted signal generated by the nonlinear load; Generate a virtual phase by receiving a signal input through the power detector and detect harmonics using the normal and reverse phase components of the rotational coordinate system synchronized with the power frequency through a predetermined control algorithm. A harmonic detector for obtaining a compensation reference voltage; A PWM generator which receives a compensation reference signal output from the harmonic detector and a predetermined triangular wave reference signal, compares each other, and outputs a pulse width modulation signal; And Single-phase active power filter using a rotational coordinate system, characterized in that consisting of; inverter drive means for receiving the PWM signal to drive the gate of the inverter. The method according to claim 1, The harmonic detector includes: an A / D converter for converting an analog signal output from the power detector into a digital signal; A digital signal processor for converting a signal input from the A / D converter into an actual voltage and current value and calculating a compensation reference voltage by a control algorithm; And a D / A converter for converting the signal output from the digital signal processor into an analog signal. Single phase active power filter using a rotational coordinate system, characterized in that consisting of. The method according to claim 1 or 2, The control algorithm of the harmonic detector extracts the direct current component by separating the direct current component and the alternating current component through the coordinate transformation of the actual current component, and then obtains the fundamental wave component of the actual current through the coordinate inverse transformation, and the total current in the fundamental wave component. Single phase active power filter using a rotational coordinate system, characterized in that to obtain a harmonic component by mixing, and to obtain a compensation reference voltage by amplifying the harmonic component. delete The method according to claim 1 or 2, The control algorithm of the harmonic detector includes: a first LPF which receives an actual current component to pass a low current and delays a predetermined time to create a virtual phase; First coordinate conversion means for converting αβ coordinates into d coordinates by receiving respective signals of the signal output from the first LPF and the normal components synchronized with actual current components and power supply voltages; A second LPF which receives a steady current component outputted from the first coordinate converting means and passes a low pass and separates the DC component into an AC component; Second coordinate conversion means for converting αβ coordinates into d coordinates by receiving angular frequencies of signals output from the first LPF, and reverse phase components synchronized with actual current components and power supply voltages; A third LPF configured to receive a reverse phase current component output from the second coordinate converting means and to pass a low pass and separate the DC component into an AC component; A first mixer receiving and mixing the AC component output from the second LPF and the AC component output from the third LPF, and outputting a DC component; A second mixer configured to receive a DC component output from the second LPF and a DC component output from the third LPF, mix and output the DC component; Inverse conversion means for receiving the signals output from the first mixer and the second mixer and the angular frequencies of the normal components, respectively, and inversely converting the d coordinates into the α β coordinates to obtain fundamental wave components of the actual current; A third mixer configured to obtain harmonic current components after receiving and mixing the fundamental wave components and the total current of the actual current output from the inverse conversion means; And amplifying means for amplifying a harmonic current component obtained by the third mixer to obtain a compensation reference voltage. The method according to claim 5, And the first mixer is configured to subtract an AC component output from the third LPF from an AC signal output from the second LPF. The method according to claim 5, The second mixer is a single-phase active power filter using a rotational coordinate system, characterized in that for adding the DC signal output from the second LPF and the DC component output from the third LPF. The method according to claim 5, The third mixer is a single-phase active power filter using a rotational coordinate system, characterized in that configured to subtract the fundamental wave component of the actual current output from the inverse conversion means from the total current.

Images