KR101678965B1 - Power factor computation system in harmonics distorted environment - Google Patents

Abstract

A power factor measuring system in a harmonic distortion environment according to the present invention includes a voltage current measuring unit for measuring a voltage and a current from a power line and a harmonics component included in a voltage and a current measured by the voltage and current measuring unit And a power factor measuring unit for measuring a power factor using a voltage and a current having a fundamental frequency of 60 Hz. The voltage current measuring unit measures a voltage of the high voltage output from the power line to measure a high voltage output from the power line, A current transformer for measuring the high current output from the power line, a current transformer for converting the high-current electricity output from the power line into a low-current electricity proportional to the high-current electricity, Output from a meter transformer or an instrument current transformer An A / D converter for converting an analog signal output from the amplifying unit into digital data, and a voltage calculating unit for calculating a voltage and a current output from the power line using the digital data output from the A / D converter, And a current measurement control unit.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power factor computation system in a harmonic distortion environment,

The present invention relates to a power factor measurement system in a harmonic distortion environment, and more particularly, to a power factor measurement system in a harmonic distortion environment that can accurately measure fundamental power factor irrespective of harmonic distortion.

Generally, the power factor means the ratio of the power supplied to the customer to the actual power used.

Most of the customers have a loss of power due to the low power factor of the load. In particular, the actual power factor is around 70% at the manufacturing site using the ground load such as the motor, and the energy loss due to the power factor reduction is serious.

As demand for electricity continues to increase and construction of new power plants is becoming difficult, energy efficiency improvement technologies such as power factor improvement are being recognized as an alternative to energy policy.

Improvement in power factor The power generation side of the power generation business can secure transmission capacity and reduction of power generation. On the customer side, it is possible to reduce line loss and increase load capacity.

Therefore, the Ministry of Land, Infrastructure and Transport is stipulating the 'Building Energy Efficiency Rating Certification System', recommending the improvement of power factor through installation of automatic power factor control device, and KEPCO has been implementing power factor management .

In the power factor plan, the base rate is reduced or added based on the 90% power factor.

In response to such a power factor, the consumer is also aware of the need for power factor compensation and has installed an automatic power factor control system.

The automatic power factor control device is operated in such a manner that a capacitor for compensating reactive power generated on the customer side is connected to the line and it is essential to accurately calculate the power factor in order to determine the capacity of the reactive power compensating capacitor.

However, in the case of the conventional power factor measurement method, when the voltage and current distortion due to harmonics occur, an error occurs in the fundamental power factor measurement required for the automatic power factor control device.

Since the harmonic distortion increases due to the spread of nonlinear load such as switching power supply, it leads to a power factor correction error, which lowers energy efficiency.

Meanwhile, a power triangle method and a time delay method are used as a conventional power factor measurement method.

The characteristics of the conventional two power factor calculation methods and harmonic generation environment are as follows.

First, the power triangle method can calculate the grid voltage and the grid current in the situation where harmonic distortion occurs.

이고, Grid voltage

ego,

이다.Grid current

to be.

과

은 고조파 차수별 실효값,

은 고조파 차수별 전압과 전류의 위상차를 나타낸다.Where n is the harmonic order,

and

Is the rms value of harmonic order,

Represents the phase difference between voltage and current for each harmonic order.

The rms value of the voltage and the current in the grid voltage and the grid current can be obtained as follows.

이고,Voltage effective value

ego,

이다. Current effective value

to be.

At this time, the average effective power can be obtained as follows.

이다.Average Active Power

to be.

In addition, the power factor can be obtained as follows.

이다.Power factor

to be.

At this time, the power factor includes harmonics information of voltage and current, such as voltage rms value, current rms value, and average effective power, so that power factor of basic wave can not be calculated separately.

Therefore, the power triangle method has a problem in that an error is generated depending on whether a voltage or current is distorted by a harmonic wave.

On the other hand, the time delay method is a method of calculating the reactive power directly from the measured values of voltage and current.

The current that delayed the grid current by a quarter cycle time can be expressed as follows.

The one-period average of the system voltage and the system current multiplied by the current delayed by 1/4 cycle time can be expressed as follows.

On the other hand, assuming that no harmonic distortion occurs in the grid voltage, it can be expressed as follows.

를 이용하여 상기 한 주기 평균을 정리하면, 하기와 같이, 기본파의 무효 전력으로 나타낼 수 있다.remind

The above periodic averages can be summarized as the reactive power of the fundamental wave as follows.

Next, using the reactive power of the fundamental wave, the power factor of the fundamental wave can be obtained as follows.

In the time delay method, the reactive power is calculated using the reactive power of the fundamental wave, and then the power factor of the fundamental wave is calculated. At this time, it is necessary to assume that the voltage does not become harmonic distortion.

That is, if the voltage is not distorted by using the time delay method, it is possible to measure the power factor without any error regardless of whether the current is distorted. However, if the voltage is distorted, an error occurs in the power factor measurement.

On the other hand, the prior art of the present invention is an automatic power factor adjusting device and method thereof, which is filed and registered by the present applicant in Patent Registration No. "10-1190515" An automatic power factor adjusting apparatus for automatically controlling a power factor through a measured current and a voltage, comprising: a main breaker connected in parallel to a load for inputting one or three phase commercial power; A power capacitor connected to an output side of the voltage regulator and to which an operating voltage is applied, a voltage and current detecting unit for detecting the voltages and currents of the respective phases, and comparing the power states through the detected voltages and currents And outputs a step-up / step-down level signal for controlling the target power factor, detects the temperature inside and outside the system, And a control circuit breaker connected in parallel with the main circuit breaker and supplying / cutting the driving power to the automatic power factor control unit, wherein the voltage regulator is slidacs, The position of the tap provided on one side of the proportional voltage winding is changed so that the operation voltage output to the capacitor is variable within a range of 0 to 100% of the rated voltage drawn through the main breaker, thereby adjusting the step- And a stepping motor.

Korean Patent Publication No. 1995-0004833 (May 13, 1995) Korean Patent Registration No. 10-0578491 (2006.05.10) Korea Patent Registration No. 10-1190515 (October 16, 2012) Korea Patent Registration No. 10-1567714 (Nov.

In order to solve the above problem, the present invention uses a method of calculating a power factor by converting a measured voltage and a current into a DQ rotational coordinate system, and thereby, in a harmonic distortion environment in which an accurate fundamental wave power factor can be measured regardless of harmonic distortion The present invention provides a power factor measuring system of the present invention.

According to an aspect of the present invention, there is provided a system for measuring a power factor in a harmonic distortion environment, comprising: a voltage / current measurement unit for measuring a voltage and a current from a power line; Harmonics), and a power factor measuring unit for measuring a power factor using a voltage and a current having a fundamental frequency of 60 Hz, and the voltage / current measuring unit outputs the voltage signal from the power line to measure a high voltage output from the power line A meter transformer for converting high-voltage electricity into low-voltage electricity proportional to high-voltage electricity; and a low-voltage electricity transformer for measuring high-current output from the power line and high-current electricity output from the power line to a high- Current transformers for meters, transformer or instrument for meters An A / D converter for converting an analog signal output from the amplifying unit into digital data; and an A / D converter for converting a voltage output from the power line using digital data output from the A / D converter, And a voltage / current measurement controller for calculating a current.

The power factor measuring system in the harmonic distortion environment according to the present invention having such a configuration can accurately measure the fundamental power factor regardless of harmonic distortion by using a method of calculating the power factor by converting the measured voltage and current into the DQ rotational coordinate system .

Therefore, when the power factor measuring system in the harmonic distortion environment according to the present invention is applied to the automatic power factor control device, the power factor compensation performance can be maximized in a harmonic distortion environment.

As a result, it is expected that electric power consumption will be reduced through improvement of power factor, reduction of line loss, and load capacity increase.

In particular, the power generation business side has an advantage of securing transmission capacity and reducing power generation by improving power factor compensation performance.

,

의 고조파 차수에 따른 특성을 도시한 표,
도면 7은 현재 역률을 목표 역률에 맞추기 위한 역률 보상기 제어부와 연속 가변형 역률 보상부 및 부가 장치를 설명하기 위한 제어 블록도,
도면 8은 연속 가변형 역률 보상부를 도시한 도면,
도면 9는 전압과 전류에 고조파 왜곡이 없는 제1 실험 조건을 도시한 표,
도면 10은 고조파 왜곡이 없는 상태에서 전압과 전류의 파형을 도시한 도면,
도면 11은 고조파 왜곡이 없는 실험에서 DQ 회전 좌표계의 전압과 평균 전압을 도시한 도면,
도면 12는 고조파 왜곡이 없는 실험에서 DQ 회전 좌표계의 전류와 평균 전류를 도시한 도면,
도면 13은 고조파 왜곡이 없는 조건에서 역률 계측 결과를 도시한 도면,
도면 14는 전류만 고조파 왜곡된 제2 실험 조건을 도시한 도면,
도면 15는 전류에만 고조파 왜곡이 발생한 상태에서 전압과 전류의 파형을 도시한 도면,
도면 16은 전류만 왜곡된 상태에서 DQ 회전 좌표계의 전압과 평균 전압을 도시한 도면,
도면 17은 전류만 왜곡된 상태에서 DQ 회전 좌표계의 전류와 평균 전류를 도시한 도면,
도면 18은 전류에만 고조파 왜곡이 된 조건에서 역률 계측 결과를 도시한 도면,
도면 19는 전압과 전류에 고조파 왜곡된 제3 실험 조건을 도시한 도면,
도면 20은 전압과 전류에 고조파 왜곡이 발생한 상태에서 전압과 전류의 파형을 도시한 도면,
도면 21은 전압과 전류가 왜곡된 상태에서 DQ 회전 좌표계의 전압과 평균 전압을 도시한 도면,
도면 22는 전압과 전류가 왜곡된 상태에서 DQ 회전 좌표계의 전류와 평균 전류를 도시한 도면,
도면 23은 전압과 전류 모두 왜곡이 된 조건에서 역률 계측 결과를 도시한 도면.1 is a control block diagram of the present invention,
2 is a control block diagram of the voltage / current measuring unit,
3 is a control block diagram of the power factor measuring unit,
4 is a diagram showing voltage vectors in the DQ stationary coordinate system and the DQ rotational coordinate system,
5 shows voltage vectors and current vectors in the DQ rotational coordinate system,
6,

,

Table 1 shows the characteristics according to the order of harmonics,
7 is a control block diagram for explaining a power factor compensator controller, a continuous variable power factor compensator, and an adder for adjusting a current power factor to a target power factor,
8 is a view showing a continuous variable power factor compensator,
9 is a table showing first experimental conditions in which no voltage and current are harmonic distortion,
10 shows waveforms of voltage and current in the absence of harmonic distortion,
11 shows the voltage and average voltage of the DQ rotational coordinate system in experiments without harmonic distortion,
12 shows the current and average current of the DQ rotational coordinate system in an experiment without harmonic distortion,
13 is a graph showing the result of the power factor measurement under the condition of no harmonic distortion,
14 shows a second experimental condition in which only current is harmonic distorted,
15 is a diagram showing waveforms of voltage and current in a state where harmonic distortion only occurs in a current,
16 is a diagram showing a voltage and an average voltage in the DQ rotation coordinate system in a state where only a current is distorted,
17 is a diagram showing a current and an average current in a DQ rotational coordinate system in a state where only a current is distorted,
18 is a graph showing the result of the power factor measurement under the condition that only harmonic distortion occurs in the current,
19 shows a third experimental condition in which harmonics are distorted by voltage and current,
20 is a diagram showing waveforms of voltage and current in a state where harmonic distortion occurs in voltage and current,
21 is a diagram showing a voltage and an average voltage of the DQ rotational coordinate system in a state where voltage and current are distorted,
22 is a diagram showing a current and an average current in a DQ rotational coordinate system in a state where a voltage and a current are distorted,
FIG. 23 shows the result of the power factor measurement under the condition that both voltage and current are distorted. FIG.

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

As shown in FIGS. 1 to 2, the power factor measuring system in a harmonic distortion environment according to the present invention includes a voltage current measuring unit 3 for measuring voltage and current from a power line 1, And a power factor measuring unit 5 for measuring a power factor using a voltage and a current having a pure fundamental frequency of 60 Hz, except for the harmonics included in the voltage and current measured by the current measuring unit 3.

As shown in FIG. 2, the voltage and current measuring unit 3 measures the high voltage output from the power line 1 in order to measure the high voltage output from the power line 1 by using a low-voltage electric furnace A transformer 7 for transforming the electric power supplied from the power line 1 to a transformer 7 for measuring a high current output from the power line 1 and a current transformer for converting the high current output from the power line 1 into a low current electricity proportional to the high- 9 for converting an analog signal output from the amplifier 11 into digital data, an A / D converter 9 for converting an analog signal output from the amplifier 11 into digital data, an amplifier 11 for amplifying a signal output from the meter transformer 7 or the instrumental current transformer 9, Converter 13 and a voltage / current measurement controller 15 for calculating the voltage and current output from the power line 1 using the digital data output from the A / D converter 13.

As shown in FIG. 3, the power factor measuring unit 5 includes a DQ stationary coordinate system voltage-current vector deriving unit 5 for obtaining a voltage vector and a current vector on the DQ stationary coordinate system using the voltage and current measured from the voltage / current measuring unit 3, A DQ rotational coordinate system voltage current vector deriving unit 18 for converting the voltage vector and the current vector on the DQ stationary coordinate system into a voltage vector and a current vector on the DQ rotational coordinate system using a rotation matrix, A harmonic component cancellation unit 25 for obtaining a one-period average of the D-axis current and the Q-axis current of the current vector on the DQ rotational coordinate system and the D-axis voltage and the Q-axis voltage of the voltage vector to cancel the harmonic component, The D-axis voltage of the vector, the Q-axis voltage, the D-axis current of the current vector on the DQ rotation coordinate system, and the one-period average value of the Q- (27) derives the reactive power using the D-axis voltage of the voltage vector on the DQ rotation coordinate system, the Q-axis voltage, the D-axis current of the current vector on the DQ rotation coordinate system, And a power factor deriving unit 31 for deriving a power factor using the reactive power and the reactive power derived by the reactive power deriving unit 27 and the reactive power deriving unit 29 do.

를 구하는 DQ 정지 좌표계 전압 벡터 도출부(17)와, 전압 전류 측정부(3)로부터 측정된 전압과 전류로부터 도출된 DQ 정지 좌표계 상의 전류 벡터

를 구하는 DQ 정지 좌표계 전류 벡터 도출부(20), 및 상기 DQ 정지 좌표계 상에서 Q축 전압

를 1/4주기 시간 지연한 값을

라고 했을 때,

,

식으로 변환하는 DQ 정지 좌표계 전압 변환부(19)를 포함한다.As shown in FIGS. 3 and 4, the DQ stationary coordinate system voltage / current vector derivation unit 16 derives the voltage vector on the DQ stationary coordinate system derived from the voltage and current measured from the voltage / current measurement unit 3,

A current vector on the DQ stationary coordinate system derived from the voltage and current measured from the voltage and current measuring unit 3;

A DQ stationary coordinate system current vector deriving unit 20 for obtaining a Q-axis voltage on the DQ stationary coordinate system,

The value obtained by delaying the 1/4 cycle time

When you say,

,

And a DQ stationary coordinate system voltage converter 19 for converting the DQ stationary coordinate system voltage into an equation.

)과 Q축 전압(

)에 회전 행렬

을 적용하여 DQ 회전 좌표계상의 전압 벡터

로 변환하고,As shown in FIGS. 3 and 4, the DQ rotational coordinate system voltage / current vector derivation unit 18 calculates a D-axis voltage (DQ) on the DQ stationary coordinate system

) And the Q-axis voltage

) Rotation matrix

And the voltage vector on the DQ rotational coordinate system

≪ / RTI >

,

,

을 얻는 DQ 회전 좌표계 전압 변환부(21)와,

A DQ rotating coordinate system voltage converting unit 21 for obtaining a rotating coordinate system voltage,

에서 D축 전류값

과 Q축 전류값

을 회전 행렬을 이용하여 DQ 회전 좌표계상의 전류값으로 변환하여 DQ 회전 좌표계상의 D축 전류값The current vector on the DQ stationary coordinate system

The D axis current value

And Q-axis current value

Is converted into a current value on the DQ rotation coordinate system by using a rotation matrix, and the D-axis current value on the DQ rotation coordinate system

과,

and,

DQ Q-axis current value on the rotating coordinate system

을 도출하는 DQ 회전 좌표계 전류 변환부(23)를 포함한다.

And a DQ rotational coordinate system current converting unit 23 for deriving the DQ rotational coordinate system current.

As shown in FIG. 5, the harmonic component canceling unit 25 divides the voltage and current on the DQ rotational coordinate system derived by the DQ rotational coordinate system voltage converting unit 21 and the DQ rotational coordinate system current converting unit 23

,

,

,

,

,

에 적용하여 60Hz 기본파의 한 주기동안 평균값을 구함으로써 고조파 성분은 상쇄하고 60Hz 기본파 성분으로만 구성된 DQ 회전 좌표계 상의 전압과 전류값을 도출한다.

,

To calculate the average value for one cycle of the 60 Hz fundamental wave, thereby deriving the voltage and current values on the DQ rotational coordinate system consisting of only the 60 Hz fundamental component, canceling the harmonic components.

와,

,

,

를 As shown in FIG. 3 and FIG. 5, the active power derivation unit 27 calculates the average value of the voltage currents for one period on the DQ rotation coordinate system derived by the harmonic component canceling unit 25

Wow,

,

,

To

에 적용하여 유효 전력을 도출한다.

To derive the effective power.

와,

,

,

를 The reactive power deriving unit 29 receives the average value of the voltage currents for one period on the DQ rotational coordinate system derived by the harmonic component canceling unit 25

Wow,

,

,

To

에 적용하여 무효 전력을 도출한다.

To derive the reactive power.

와 상기 무효 전력 도출부(29)에 의해 도출된 무효 전력

값을 역률

에 적용하여 역률을 구한다.The power factor deriving unit 31 calculates the power factor Deriving Unit 31 based on the active power derived by the active power deriving unit 27

And the reactive power derived by the reactive power deriving part (29)

The power factor

To obtain the power factor.

와,

,

, 및

는 측정 전압과 전류 값을 DQ 회전 좌표계로 변환한 신호이고, 도면 6에 도시한 바와 같이, 고조파 차수 n에 따라 신호의 특성을 분석할 수 있다.remind

Wow,

,

, And

Is a signal obtained by converting the measured voltage and the current value into the DQ rotational coordinate system. As shown in FIG. 6, the characteristic of the signal can be analyzed according to the harmonic order n.

로 회전하는 DQ 회전 좌표계에서

와

의 주파수를 가지는 신호로 표현된다.If harmonic distortion occurs in the grid voltage and current in Fig. 6, the nth order harmonic component is

In the DQ rotary coordinate system

Wow

Of the frequency.

는 DQ 정지 좌표계에서 D축 상의 전압 벡터의 전압값이고, 상기

는 DQ 정지 좌표계에서 Q축 상의 전압 벡터의 전압값, 상기

는 DQ 정지 좌표계에서 D축 상의 전류 벡터의 전류값, 상기

는 DQ 정지 좌표계에서 Q축 상의 전류 벡터의 전류값, 상기

는 DQ 회전 좌표계에서 D축 상의 전압 벡터의 전압값이고, 상기

는 DQ 회전 좌표계에서 Q축 상의 전압 벡터의 전압값, 상기

는 DQ 회전 좌표계에서 D축 상의 전류 벡터의 전류값, 상기

는 DQ 회전 좌표계에서 Q축 상의 전류 벡터의 전류값, 상기 t는 시간, T는 주기,

는

, n은 고조파 차수,

은 고조파 차수별 실효값,

은 고조파 차수별 실효값,

은 고조파 차수별 전압과 전류의 위상차, DQ 회전 좌표계의 변위각

이고,

는 회전 좌표계의 초기값, 상기

는 DQ 회전 좌표계에서 전압 벡터의 D축 상의 전압 값을 60Hz 기본파의 한 주기동안 평균 낸 값, 상기

는 DQ 회전 좌표계에서 전압 벡터의 Q축 상의 전압 값을 60Hz 기본파의 한 주기동안 평균 낸 값, 상기

는 DQ 회전 좌표계에서 전류 벡터의 D축 상의 전류 값을 60Hz 기본파의 한 주기동안 평균 낸 값, 상기

는 DQ 회전 좌표계에서 전류 벡터의 Q축 상의 전류 값을 60Hz 기본파의 한 주기동안 평균 낸 값,

는 DQ 회전 좌표계에서 전압 벡터의 위상각,

는 DQ 회전 좌표계에서 전류 벡터의 위상각이다.For reference, the parameters are summarized in the above equation,

Is the voltage value of the voltage vector on the D axis in the DQ stationary coordinate system,

The voltage value of the voltage vector on the Q axis in the DQ stationary coordinate system,

The current value of the current vector on the D axis in the DQ stationary coordinate system,

The current value of the current vector on the Q axis in the DQ stationary coordinate system,

Is the voltage value of the voltage vector on the D axis in the DQ rotation coordinate system,

The voltage value of the voltage vector on the Q axis in the DQ rotational coordinate system,

The current value of the current vector on the D axis in the DQ rotation coordinate system,

Is the current value of the current vector on the Q-axis in the DQ rotation coordinate system, t is the time, T is the period,

The

, n is a harmonic order,

Is the rms value of harmonic order,

Is the rms value of harmonic order,

Is the phase difference between voltage and current for each harmonic order, the displacement angle of the DQ rotational coordinate system

ego,

Is an initial value of the rotation coordinate system,

Is a value obtained by averaging the voltage value on the D axis of the voltage vector in the DQ rotation coordinate system over one period of a 60 Hz fundamental wave,

Is a value obtained by averaging the voltage value on the Q axis of the voltage vector in the DQ rotational coordinate system during one period of the fundamental wave of 60 Hz,

Is a value obtained by averaging the current value on the D axis of the current vector in the DQ rotation coordinate system during one period of a 60 Hz fundamental wave,

Is a value obtained by averaging the current value on the Q-axis of the current vector in the DQ rotation coordinate system during one period of a 60 Hz fundamental wave,

The phase angle of the voltage vector in the DQ rotation coordinate system,

Is the phase angle of the current vector in the DQ rotational coordinate system.

Further, the present invention compares the current power factor measured by the power factor measuring unit 5 with a target power factor to be changed, and adjusts the output voltage of the slider duck 33 to compensate for the difference between the target power factor and the current power factor A power factor compensator control section 35 for transmitting a control signal for adjusting the rotation direction or the rotation amount of the motor to the motor, (37) connected to any one of the power capacitors (1). If the current power factor is lower than the target power factor, the voltage output from the slider dancer (33) is increased through the motor rotation to increase the capacity of the power capacitor If the current power factor is higher than the target power factor while increasing the current power factor, the voltage output from the slider shaft 33 is lowered through the motor rotation to increase the capacity of the power capacitor 37 And a continuous variable power factor compensator 39 for lowering the current power factor by lowering the current power factor.

As a result, the continuous variable power factor compensator 39 can adjust the current power factor to the target power factor by continuously adjusting the voltage input to the power capacitor 37. [

The motor increases or decreases the voltage output from the slider dancer 33 by changing the position of the tab provided on one side of the proportional voltage winding in the slider dancer 33.

In addition, the present invention can be operated on a PC or a web through a protocol for transmitting and receiving an external signal, and can control the voltage, current, and power situation of each phase through the voltage and current detected by the voltage / And a monitoring unit 41 for monitoring the power factor detected by the power factor measuring unit 5 and setting the target power factor.

The monitoring unit 41 further includes operation keys including an LCD for displaying the voltage of each phase, a current, a power, a power factor, and a power status and a key necessary for user setting including a target power factor.

At this time, the operation keys may be a touch input such as a touch screen or a touch pen.

In addition, the present invention further includes an over-temperature prevention unit 43 for detecting an internal temperature and an external temperature of the system, and operating the ventilation fan primarily to discharge the internal temperature of the system when the sensed temperature is higher than the set temperature.

When the inside / outside temperature of the sensed system is higher than a set temperature after the ventilation fan is operated and a predetermined time has elapsed, the over-temperature prevention unit 43 secondarily lowers the voltage supplied to the power capacitor 37, The power factor is lowered by reducing the capacity of the condenser 37. [

In addition, the present invention is characterized in that, when replacing the power capacitor (37), the power is cut off when the button is depressed and the rush current and harmonics flowing into the power system when the power capacitor (37) And a stop button 45.

Further, the present invention further includes an overvoltage prevention unit 47 for preventing an overvoltage from being output from the power line 1. [

In order to verify the validity of the power factor measurement of the power factor measuring system in the harmonic distortion environment according to the present invention, the simulation was performed using MATLAB.

Experiments were conducted assuming that harmonic distortion occurs in both current and voltage when there is no harmonic distortion.

First, experiments were conducted in the absence of harmonic distortion.

Experimental conditions are shown in Fig. 9, and voltage and current waveforms without harmonic distortion are shown in Fig.

Since the voltage and current have a phase difference of 60 degrees, the power factor is 50%.

Figures 11 and 12 show the voltage and current waveforms on the DQ rotary coordinate system.

In this case, only the 60Hz fundamental wave exists, so that the voltage and the current have a DC value in the DQ rotation coordinate system.

The results of the power factor measurement by the present invention are shown in FIG.

In Figure 13, the power triangle method calculates the power factor using the rms value of the voltage and current and the average effective power. The time delay method calculates the reactive power directly using the value of the current delayed by 1/4 cycle. The invention converts a voltage and a current into a DQ rotational coordinate system, and then calculates a power factor using a one-period average value.

13, accurate power factor can be measured in both the conventional method and the power factor measurement result using the present invention under the condition of no harmonic distortion.

Second, we experimented in an environment where harmonic distortion occurs only in the current.

The experimental conditions are shown in FIG. 14, and the voltage and current waveforms in FIG. 15 show only current distortion.

16 and 17 show voltage and current waveforms on the DQ rotation coordinate system.

In FIG. 16, it can be seen that the distortion-free voltage appears as a DC value.

In FIG. 17, it can be seen that the current generated by the third-order and fifth-order harmonic distortion appears as a signal corresponding to the fourth harmonic, as shown in FIG.

In FIG. 17, it can be seen that the current waveform changing to 240 Hz, which corresponds to the fourth harmonic, appears as a DC value when averaged over one period of the 60 Hz fundamental wave.

In this case, as shown in FIG. 18, the Power triangle method has an error, but the time delay method and the present invention can calculate a correct basic power factor of 50%.

Finally, both voltage and current were tested in an environment with harmonic distortion.

In FIG. 19, experimental conditions are shown, and in FIG. 19, both harmonics and voltages are observed.

Figure 20 shows the voltage and current on the DQ rotational coordinate system.

In Figure 21 and Figure 22, both the voltage and the current are distorted by the third and fifth harmonic components. Therefore, it can be seen that the waveform corresponding to the fourth harmonic frequency is observed in the DQ rotation coordinate system. You can see that it appears as a DC value.

In the power factor measurement results shown in FIG. 23, both the power triangle method and the time delay method generate an error, but the present invention calculates an accurate fundamental power factor of 50%.

The power factor measuring system in the harmonic distortion environment according to the present invention having such a configuration can accurately measure the fundamental power factor regardless of harmonic distortion by using a method of calculating the power factor by converting the measured voltage and current into the DQ rotational coordinate system .

Therefore, when the power factor measuring system in the harmonic distortion environment according to the present invention is applied to the automatic power factor control device, the power factor compensation performance can be maximized in a harmonic distortion environment.

As a result, it is expected that electric power consumption will be reduced through improvement of power factor, reduction of line loss, and load capacity increase.

In particular, the power generation business side has an advantage of securing transmission capacity and reducing power generation by improving power factor compensation performance.

1. Power line 3. Voltage and current measuring unit
5. Power factor meter 7. Instrument transformer
9. Current transformer 11. Amplifier
13. A / D converter 15. Voltage and current measurement control unit
17. DQ stationary coordinate system voltage vector derivation unit 19. DQ stationary coordinate system voltage conversion unit
21. DQ rotation coordinate system voltage conversion unit 23. DQ rotation coordinate system current conversion unit
25. Harmonic component canceling part 27. Active power deriving part
29. Reactive power deriving part 31. Power factor deriving part
33. Slidax 35. Power factor compensator control unit
37. Power capacitor 39. Continuous variable power factor compensator
41. Monitoring section 43. Overheat prevention section
45. Soft stop button 47. Overvoltage protection

Claims (4)

A voltage / current measuring unit 3 for measuring voltage and current from the power line 1,
A power factor measuring unit for measuring a power factor using voltages and currents having a fundamental frequency of 60 Hz excluding the harmonic components included in the voltage and current measured by the voltage and current measuring unit 3 5)
The voltage / current measuring unit 3 includes a meter transformer 7 for converting high-voltage electricity output from the power line 1 into low-voltage electricity proportional to high-voltage electricity for measuring a high voltage output from the power line 1, Wow,
A meter current transformer 9 for measuring the high current output from the power line 1 and for converting the high-current electricity output from the power line 1 into a low-current electricity proportional to the high-current electricity,
An amplifier (11) for amplifying a signal output from the meter transformer (7) or the meter current transformer (9)
An A / D converter 13 for converting an analog signal output from the amplifier 11 into digital data,
And a voltage and current measurement control unit (15) for calculating voltage and current output from the power line (1) using digital data output from the A / D converter (13)
The power factor measuring unit 5 includes a DQ stationary coordinate system voltage current vector deriving unit 16 for obtaining a voltage vector and a current vector on the DQ stationary coordinate system using the voltage and current measured from the voltage and current measuring unit 3,
A DQ rotational coordinate system voltage current vector deriving unit 18 for converting a voltage vector and a current vector on the DQ stationary coordinate system into a voltage vector and a current vector on the DQ rotational coordinate system using a rotation matrix,
A harmonic component canceling unit 25 for obtaining a one-period average of the D-axis current and the Q-axis current of the current vector on the DQ rotational coordinate system and the D-axis voltage and the Q-axis voltage of the voltage vector on the DQ rotational coordinate system to cancel the harmonic component,
A D-axis voltage of the voltage vector on the DQ rotation coordinate system, a D-axis current of a current vector on the DQ rotation coordinate system, and a Q-axis average value of the Q- (27),
A reactive power deriving unit for deriving the reactive power using the D-axis voltage of the voltage vector on the DQ rotation coordinate system, the Q-axis voltage, the D-axis current of the current vector on the DQ rotation coordinate system, (29),
And a power factor deriving unit (31) for deriving a power factor using the reactive power and the reactive power derived by the reactive power deriving unit (27) and the reactive power deriving unit (29)
The DQ stationary coordinate system voltage / current vector derivation unit 16 derives the voltage vector on the DQ stationary coordinate system derived from the voltage and current measured from the voltage / current measurement unit 3,

A DQ stationary coordinate system voltage vector deriving unit 17 for obtaining a DQ stationary coordinate system voltage vector,
The current vector on the DQ stationary coordinate system derived from the voltage and current measured from the voltage / current measuring unit 3

A DQ stationary coordinate system current vector deriving unit 20 for deriving a DQ stationary coordinate system current vector,
And the Q-axis voltage on the DQ stationary coordinate system

The value obtained by delaying the 1/4 cycle time

When you say,

,

And a DQ stationary coordinate system voltage converting unit (19)
The DQ rotational coordinate system voltage current derivation unit 18 outputs the D-axis voltage (

) And the Q-axis voltage

) Rotation matrix

And the voltage vector on the DQ rotational coordinate system

≪ / RTI >

,

A DQ rotating coordinate system voltage converting unit 21 for obtaining a rotating coordinate system voltage,
The current vector on the DQ stationary coordinate system

The D axis current value

And Q-axis current value

Is converted into a current value on the DQ rotation coordinate system by using a rotation matrix, and the D-axis current value on the DQ rotation coordinate system

and,
DQ Q-axis current value on the rotating coordinate system

And a DQ rotational coordinate system current converter (23) for deriving a DQ rotational coordinate system current converter (23).

Here,

Is the voltage value of the voltage vector on the D axis in the DQ stationary coordinate system,
remind

Is the voltage value of the voltage vector on the Q axis in the DQ stationary coordinate system,
remind

Represents the current value of the current vector on the D axis in the DQ stationary coordinate system,
remind

Is the current value of the current vector on the Q axis in the DQ stationary coordinate system,
remind

The voltage value of the voltage vector on the D axis in the DQ rotation coordinate system,
remind

Represents the voltage value of the voltage vector on the Q axis in the DQ rotation coordinate system,
remind

Represents the current value of the current vector on the D axis in the DQ rotation coordinate system,
remind

Represents the current value of the current vector on the Q axis in the DQ rotation coordinate system,
T is the time, T is the period,

The

, n is a harmonic order,

Is the rms value of harmonic order,

Is the rms value of harmonic order,

Is the phase difference between voltage and current for each harmonic order, the displacement angle of the DQ rotational coordinate system

ego,

Is the initial value of the rotation coordinate system.
delete delete The method according to claim 1,
The harmonic component canceling unit 25 receives the voltage and current on the DQ rotational coordinate system derived by the DQ rotational coordinate system voltage converting unit 21 and the DQ rotational coordinate system current converting unit 23,

,

,

,

To obtain an average value for one cycle of a 60 Hz fundamental wave to derive the voltage and current values on the DQ rotational coordinate system consisting of only the 60 Hz fundamental wave component and canceling the harmonic component.

Here,

Is a value obtained by averaging the voltage value on the D axis of the voltage vector in the DQ rotation coordinate system during one cycle of the 60 Hz fundamental wave,
remind

Is a value obtained by averaging the voltage value on the Q axis of the voltage vector in the DQ rotation coordinate system over one period of the fundamental wave of 60 Hz,
remind

Is a value obtained by averaging the current value on the D axis of the current vector in the DQ rotation coordinate system during one cycle of a 60 Hz fundamental wave,
remind

Is a value obtained by averaging the current value on the Q-axis of the current vector in the DQ rotation coordinate system during one period of a 60 Hz fundamental wave,

The phase angle of the voltage vector in the DQ rotation coordinate system,

Is the phase angle of the current vector in the DQ rotational coordinate system.

Images