JP3566797B2 - Harmonic current analyzer - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a harmonic current analyzer, and more particularly, to a harmonic current analyzer that performs harmonic analysis in a fluctuation measurement mode conforming to, for example, the IEC standard.
[0002]
[Prior art]
In recent years, failures due to harmonics have been increasing, and as a countermeasure, suppression of generation of harmonic currents in electronic devices has become a major issue in the field of electric and electronic devices. In other words, the current waveform of the commercial power supplied from the power plant is originally a clean sine wave, but flows through a switching power supply used in televisions and personal computers, air conditioners employing inverters, fluorescent lamps, and the like. The current is not a sine wave but a pulse-shaped current waveform, for example.
[0003]
With the spread of this type of electronic equipment, if the total amount of harmonic current increases, the impedance of the power supply transmission line is not zero, so the voltage drop due to the harmonic current causes the distortion of the voltage waveform of the commercial power supply to increase, For example, problems such as abnormal heating, burning, and abnormal noise of a power capacitor or a transformer due to an overcurrent caused by harmonics occur. In addition, malfunctions such as breakers, earth leakage breakers, and control devices due to voltage waveform distortion caused by harmonics, and malfunctions such as malfunctions of electronic circuits and noise generation due to induction faults caused by harmonics are problematic.
[0004]
Against this background, the IEC (International Electrotechnical Commission) has proposed a power supply harmonic standard (IEC 555-2, revised as of now) for electronic equipment connected to a general low-voltage power supply and having an input current of 16 A or less. draft) has been issued, in 2.5 minutes variance measurement mode one of among them is defined.
[0005]
This measurement mode is intended to capture the transient state of the harmonic current. The measurement window width must include 4 to 30 cycles of the input waveform, and this is defined as one window, and FFT (Fast Fourier Transform) is used. arithmetic processing is performed a measurement with continuous 2.5 minutes. For example, assuming that the power supply frequency is 50 Hz and one window includes 16 cycles, the window becomes 469 windows in 2.5 minutes.
[0006]
[Problems to be solved by the invention]
As a result, measurement data for all orders is obtained over 2.5 minutes, and the limit value and the like are set by the calculation unit (CPU). FIG. The state displayed as a graph is shown.
[0007]
Various information can be extracted from this screen by operating a mouse or the like. For example, if it is desired to know the peak value, move the cursor to a bar graph position of a desired order (for example, 11th order), When the instruction is clicked, in this example, a child screen is opened in a predetermined display area of the display, and the limit value (0.030A) is displayed together with the eleventh peak value (0.040A).
[0008]
In this way, the peak value can be known, but in the conventional apparatus, it is not known when the peak value occurs in time, that is, in what window. In particular, in the continuous fluctuation measurement in which the above-described 2.5 minute fluctuation measurement mode is repeatedly and continuously performed, not only the peak value but also the occurrence time (occurrence window number) is an important analysis factor in analyzing the data. is there.
[0009]
The present invention has been made in view of such a conventional situation, and has as its object to provide a harmonic current analysis apparatus which displays time information on the occurrence time of each peak value together with the peak value. Is to do.
[0010]
[Means for Solving the Problems]
To achieve the above object, according to the first aspect of the present invention, an input unit including an A / D converter for converting a current input waveform of an AC power supply supplied to a load into a digital signal, and a waveform output from the input unit A first memory for storing data, a signal processing unit for performing fast Fourier transform (FFT) of the waveform data to obtain measurement data of harmonic components up to a predetermined order, and a second memory for storing the measurement data; Control means for calculating a limit value for each order based on the measurement data, comparing the limit value with the measurement data and performing waveform determination, and various displays based on instructions from the control means. the includes an operation portion that gives instructions on the operation to the display and the control means performs, when the fluctuation measurement mode to 1 unit of measurement for a predetermined time is carried out continuously repeated A waveform corresponding to m periods of the input waveform is defined as one window, and measurement is performed for each order in each of n windows (m and n are both positive integers and m <n) corresponding to the one measurement unit time. In the harmonic current analyzer for calculating data and storing the data in the second memory, when displaying the peak value of each order on the display, the peak value occurs during the fluctuation measurement mode currently being measured. If the peak value is generated, the window number at which the peak value is generated is also displayed . If the peak value is generated before the fluctuation measurement mode currently being measured, the peak value has a specific identification means. It is characterized by:
[0011]
In a preferable embodiment inventions of claim 2, which is contained in the invention described in claim 1, in the case where variation graph of a predetermined order according to the fluctuation measuring mode on the display is being displayed, the control means the operating unit The cursor is moved to the peak position on the fluctuation graph based on the peak value instruction signal from the controller.
[0012]
Also, as aspects of the inventions preferred alternative included in the invention of the claims 1 to 3, when the bar graph orders belonging to a predetermined window number on the display is being displayed, said control means the operation The peak value of the specific order and the generation window number thereof are displayed in a predetermined display area of the display based on a peak value instruction signal for the specific order from the unit.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings for better understanding of the technical concept of the present invention.
[0014]
FIG. 1 is a schematic block diagram of the harmonic current analyzing apparatus. According to this, the apparatus includes an input unit 10 to which a current from an AC power supply line supplied to a load (not shown) is input. I have. The input unit 10 includes an A / D conversion unit for converting the input current into a digital signal, the four input portions 10 so as to correspond are prepared to a three-phase four-wire in this example.
[0015]
The harmonic current analyzer also includes a signal processing unit 11 that performs fast Fourier transform (FFT) on digitally converted waveform data at the input unit 10 to obtain, for example, harmonic data up to the 40th order. A trigger control unit 12 for generating a trigger, a PLL control unit 13 for synchronously controlling sampling and the like of each input unit 10, a storage memory 14 for storing waveform data from the input unit 10, a CPU 15 as a central control unit, A ROM 16 in which a control program of the CPU 15 is written, a memory 17 including a RAM for storing harmonic measurement data calculated by the signal processing unit 11, and a clock unit 18 used for time management of measurement time A floppy disk device 19 as external storage means; a display 20 as display means; And it includes an operation unit 21 including a mouse giving various operation instructions, a GP-IB interface 22 for connecting to an external computer, and a printer 23 as printing means.
[0016]
According to the IEC standard, the measurement window width must include 4 to 30 cycles of the fundamental frequency. Therefore, in this example, as shown in FIG. Cycle). Therefore, when the fundamental frequency is 50 Hz, the total number of windows in the 2.5-minute fluctuation measurement mode is 469, and when the fundamental frequency is 60 Hz, the total number of windows is 563.
[0017]
The FFT operation in the signal processing unit 11 is performed for each window, and the first to 40th measurement data obtained by the operation is written to the memory 17 together with the window number, but the storage capacity of the memory 17 is limited. Therefore, in this embodiment, the so-called FI-FO (which holds only the measurement data for 2.5 minutes currently being measured, and discards the previous measurement data (except for the peak value) sequentially from the oldest one, is called a FI-FO ( (First-in-first-out) method.
[0018]
FIG. 3 shows the lapse of time in the case of continuous fluctuation measurement in which the fluctuation measurement mode is repeatedly and continuously performed for 2.5 minutes. The CPU 15 monitors the peak value of each order, and finally, performs all measurement. The peak value over time is stored in a predetermined area of the memory 17, for example.
[0019]
For example, if the peak value generated during the current measurement is B, and the peak value generated during the previous measurement period is A, B is held as the peak value when A ≦ B, and when A> B A is held as a peak value as it is. It should be noted that the peak value A generated before and during the current measurement is not held until the generation window number and is in an indeterminate state. In addition, the CPU 15 calculates an average value, an effective value, and the like for each order, and sets a limit value as a comparison determination reference.
[0020]
After the measurement in the fluctuation measurement mode for 2.5 minutes is completed, by selecting the peak button on the operation unit 21, a list screen of the peak value display as shown in FIG. Although only the data from the basic order to the twelfth order are shown in the figure for the sake of drawing, data of all orders (up to the 40th order in this example) is actually displayed.
[0021]
According to this, the window number where the peak value occurred is displayed after the order number, the peak value, and the limit value. For example, focusing on the third order, it can be seen that the peak value is 16.783 A, the limit value is 3.960 A, and the peak occurrence window number is 241st.
[0022]
Looking at the seventh-order data, the window number is "---". This means that the peak value (7.194A) was generated before the measurement mode for 2.5 minutes at the end of the measurement, and in order to more clearly indicate this, in this example, the seventh line is used. Is displayed in a different color from the other lines. For example, yellow is displayed while other display colors are green. Alternatively, the data may be distinguished from other order data by attaching an underline, a symbol, or the like to the data.
[0023]
As described above, according to this display screen, it is easy to know in which window the peak value occurred. The number of objects exceeding 1.5 times and the number of objects exceeding 1.5 times are displayed together so as to be useful for judgment.
[0024]
FIG. 5A shows an example in which the list screen of FIG. 4 is switched to a change graph display screen. FIG. 2B is a child screen originally opened in a predetermined display area in the fluctuation graph display screen (parent screen), but is separately shown for convenience of drawing. In this example, up to five arbitrary orders can be designated by the operation unit 21, whereby the waveforms of the respective harmonic currents are displayed in a color-coded manner on the fluctuation graph display screen. In addition, in order to avoid complication, only two waveforms are shown in the drawing.
[0025]
In this case, in the child screen, the displayed order number and cursor reading value, and a measurement value selection button and a peak selection button are displayed. Here, the desired order (for example, the third order) is displayed by a mouse. Is clicked, the cursor C is instantaneously moved to the position indicating the peak value in the fluctuation waveform of that order, and the read value (5.418A) is displayed on the sub-screen and the parent screen is displayed. Window No. The generation window number is displayed in the column as (165/469).
[0026]
Since the vertical axis of the fluctuation graph display screen is a logarithmic scale, when determining the peak value on the graph, if the difference is small, there is a delicate problem as to which is the maximum value. Is automatically skipped to the peak value location, so that the determination can be made easily and the generation window number is also displayed, which is very convenient for analyzing the waveform.
[0027]
FIG. 6A shows a state where the display screen of the display 20 is a bar graph display screen, and FIG. 6B shows a state where the display screen is originally opened in a predetermined display area in the bar graph display screen (parent screen). Although it is a child screen, it is shown as a separate screen for the same reason as described above. In this bar graph display, a bar graph of all orders (1 to 40 orders) is displayed for each window, and a bar graph of each order belonging to the first window is displayed on the parent screen of FIG. It is shown.
[0028]
According to the present invention, the peak value of the desired order and the window number of its occurrence can be known from the bar graph display screen. That is, the user operates the mouse of the operation unit 21 to position the cursor (in this case, indicated by an inverted triangle) on, for example, a tertiary bar graph, clicks the cursor, and selects the peak display button with the cursor. Then, the CPU 15 searches for a tertiary peak value over, for example, all windows. In some cases, a tertiary peak value can be picked up from the list data of FIG. 4 described above.
[0029]
Then, as shown in FIG. 6 (b), the measured value (5.416A) and its limit value (3.416A) of the first window of the order (third order) currently displayed in the child screen are displayed. with .960A), displays 3rd order peak value and (5.4 22 a), also the peak occurs window number (165) is displayed next to it.
[0030]
【The invention's effect】
As described above, according to the invention of claim 1, for example, in the case where fluctuation measuring mode 2.5 minutes is continuously performed by repeating, in order to display the peak value for each order on a display, said peak If the value is generated during the fluctuation measurement mode currently being measured, the window number at which the peak value has occurred is also displayed, so that the peak value can be analyzed from more angles. In addition, when the peak value is generated before the fluctuation measurement mode currently being measured, the peak value is provided with a specific identification means, so that whether the peak value is within the storage range can be easily determined. Can be determined.
[0031]
Further, when the variation graph of a predetermined order due to the variation measurement mode is shown on the display, based on the peak value instruction signal from the operation unit, according to claim 2 which is adapted to move the cursor to the peak position on the variation graph According to the invention, when the peak value is determined on the fluctuation graph, the determination can be easily performed, and the generation window number is also displayed, which is very convenient in analyzing the waveform.
[0032]
Further, when a bar graph of an order belonging to a predetermined window number is displayed on the display, the specific order of the specific order is displayed in a predetermined display area of the display based on a peak value instruction signal for the specific order from the operation unit. According to the invention of claim 3 , wherein the peak value and the generation window number are displayed, the peak value of the desired order and the generation window number can be known without particularly switching the bar graph screen.
[Brief description of the drawings]
FIG. 1 is a schematic block diagram according to an embodiment of a harmonic current analysis device according to the present invention.
FIG. 2 is a waveform diagram illustrating waveforms included in one window.
FIG. 3 is a time lapse diagram illustrating the relationship between the fluctuation measurement mode per unit time and the total measurement time during continuous fluctuation measurement.
FIG. 4 is a screen diagram of a display showing a peak value display list screen according to the present invention.
FIG. 5 is a screen diagram of a display showing a parent screen and a child screen of a fluctuation graph display screen according to the present invention.
FIG. 6 is a screen diagram of a display showing a parent screen and a child screen of a bar graph display screen according to the present invention.
FIG. 7 is a screen view of a display showing a bar graph display screen by a conventional device.
[Explanation of symbols]
10 input unit 11 FFT signal processing unit 14 storage memory 15 CPU
17 Memory (RAM)
20 display 21 operation unit (mouse)

Claims (3)

An input section including an A / D converter for converting a current input waveform of an AC power supply supplied to a load into a digital signal; a first memory for storing waveform data output from the input section; A signal processing unit for performing fast Fourier transform (FFT) to obtain measurement data of harmonic components up to a predetermined order, a second memory for storing the measurement data, and calculating a limit value for each order based on the measurement data Control means for comparing the limit value with the measurement data to determine a waveform, etc .; and a display for performing various displays based on instructions from the control means, and providing operational instructions to the control means. Including an operation unit,
In a case where the fluctuation measurement mode in which the predetermined time is set as one measurement unit is repeatedly and continuously performed, a waveform corresponding to m cycles of the input waveform is set as one window, and an n window (m) corresponding to the one measurement unit time is set. , N are both positive integers, and for each m <n), a harmonic current analyzer that calculates measurement data for each order and stores the measurement data in the second memory,
When displaying the peak value for each order on the display, if the peak value is generated during the fluctuation measurement mode currently being measured, the window number at which the peak value is generated is also displayed , When the peak value is generated before the fluctuation measurement mode currently being measured, the peak value is provided with specific identification means . When a fluctuation graph of a predetermined order in the fluctuation measurement mode is displayed on the display, the control means moves a cursor to a peak position on the fluctuation graph based on a peak value instruction signal from the operation unit. The harmonic current analysis device according to claim 1, wherein: In the case where a bar graph of an order belonging to a predetermined window number is displayed on the display, the control unit controls a predetermined display area in the display based on a peak value instruction signal for a specific order from the operation unit . 2. The harmonic current analyzer according to claim 1, wherein the peak value of the specific order and the generation window number are displayed .

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