KR101059355B1 - Output wave quality monitoring system for solar power inverter and method therefor - Google Patents

Abstract

PURPOSE: An output quality monitoring device of a solar light power generation inverter and a method thereof are provided to monitor instantaneous voltage rise, voltage noise, voltage drop, and instantaneous power failure of an output voltage and an output current, thereby preventing performance lowering and failure of a solar light power generation system. CONSTITUTION: An A/D converter(400) converts an output voltage and an output current into digital data by each phase of grid output. A controller(410) receives voltage and current data which are provided from the A/D converter and stores the voltage and current data in a work memory(430). A clock timer(420) supplies a clock signal to the A/D converter by a conversion start control signal which is supplied from the controller. A display device(450) displays a processing result from the controller and generates an alarm.

Description

Output wave quality monitoring system for solar power inverter and method therefor}

The present invention relates to an apparatus and method for monitoring output quality of a photovoltaic inverter, and more particularly, power supplied from a solar cell string is connected to an inverter input terminal, and the power is switched by a bridge circuit of an inverter driver. An apparatus and method for monitoring output quality of a photovoltaic inverter configured to be supplied to an output transformer as a sinusoidal power waveform through a harmonic filter and to be transformer-transformed and supplied to a power grid as a grid output.

A solar system that processes the voltage and current waveforms for each phase in integral multiples of cycles to determine and display steady state, voltage rise, voltage noise, voltage drop, and momentary power outage, and alarms for ongoing abnormal conditions. An apparatus and method for monitoring output quality of a photovoltaic inverter are provided.

Conventional photovoltaic power generation system is provided with a non-return diode connected in series to a plurality of solar cell array and each string output stage, and integrates the power from the plurality of solar cell array through the non-return diode to supply to the input terminal of the inverter. . The input and output terminals of the inverter are configured to connect an input VI sensor and an output VI sensor to monitor input voltage and current and measure current voltages of the input and output by measuring means. However, since the conventional voltage and current measuring means is configured to convert the waveform of AC into an RMS value or take an average value for a predetermined time, it is impossible to identify an instantaneous change or abnormality.

The instantaneous voltage rise, voltage noise, voltage drop and instantaneous power outage of the output voltage current generated in the photovoltaic system result in degradation and failure of the photovoltaic system. The present invention provides an apparatus and method for monitoring output quality of a photovoltaic inverter having a function of detecting and displaying a steady state, a voltage rise, a voltage noise, a voltage drop, and a power failure with respect to a voltage current waveform of a photovoltaic system. To provide a task to solve.

The present invention to solve the above problems,

The power supplied from the solar cell string is connected to the inverter input stage, the power is switched by the bridge circuit of the inverter driver, the phase-specific output of the inverter driver is supplied to the output transformer as a sinusoidal power waveform through a harmonic filter and the current flow- A device for monitoring the output quality of a photovoltaic inverter configured to be transformed and supplied to a power grid as a grid output,

An A / D converter converting output voltage and current of each phase of the grid output into digital data; and

A controller which receives voltage and current data provided from the A / D converter and stores the received data in a working memory;

A clock timer for supplying and driving a clock signal to the A / D converter according to a conversion start control signal supplied from the controller;

An output quality monitoring device for a photovoltaic inverter, comprising a display and an alarm for displaying a result of processing from the controller and generating an alarm, as a means for solving the problem.

In addition, the present invention,

The power supplied from the solar cell string is connected to the inverter input stage, the power is switched by the bridge circuit of the inverter driver, the phase-specific output of the inverter driver is supplied to the output transformer as a sinusoidal power waveform through a harmonic filter and the current flow- A method for monitoring the output quality of a photovoltaic inverter configured to be transformed and supplied to a power grid as a grid output,

A start step, a count initialization step, and an initial value setting step; A / D conversion step; A storage step; Sample can be checked step; Absolute value calculating step; Sorting step; Difference value calculating step;

Difference value determining step; Accumulation step; Sample number comparison step; Cumulative value comparison step; Normal / abnormal judgment step; An abnormal state processing step; provides an output quality monitoring method of a photovoltaic inverter as a solution to the problem.

The present invention provides an apparatus and method for monitoring output quality of a photovoltaic inverter having a function of detecting and displaying a steady state, a voltage rise, a voltage noise, a voltage drop and a momentary power failure with respect to a voltage current waveform of a photovoltaic system. By monitoring the instantaneous voltage rise, voltage noise, voltage drop and instantaneous power outage of the output voltage current generated by the photovoltaic system, thereby reducing the performance and failure of the photovoltaic system. have.

1 is a general configuration of a multi-string solar power system
2 is an example of a circuit configuration and each sub waveform of a three-phase inverter of a multi-string solar power system;
3 is a block diagram of a multi-string solar power system three-phase inverter circuit
4 shows anomaly waveforms that can be generated instantaneously in a solar power system.
Figure 5 is an embodiment of the output quality monitoring apparatus of the solar power inverter of the present invention
Figure 6 is another embodiment of the output quality monitoring device of the solar power inverter of the present invention
7 is a summary of data analysis in the output quality monitoring apparatus of the solar power inverter of the present invention
8 is a criterion for determining the presence or absence of abnormality by comparing the waveform data of the present invention with a calculated value
9 is a flowchart (1/2) for performing a method for monitoring output quality of a photovoltaic inverter of the present invention.
10 is a flowchart (2/2) for performing a method for monitoring output quality of a photovoltaic inverter of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

1 shows a general configuration of a multi-string solar power system. In the conventional photovoltaic system, a backflow prevention diode is connected in series to a plurality of solar cell arrays 100 and each string output terminal, and integrates power from the plurality of solar cell arrays 100 through the backflow prevention diode. Supply to the input terminal of the inverter 200. An input VI sensor and an output VI sensor are connected to the input terminal and the output terminal of the inverter 200 to monitor input voltage and current, and the current voltages of the input and output are measured by measuring means.

FIG. 2 shows an example of a circuit configuration and each sub waveform of a three-phase inverter of a general multi-string solar power generation system. Power supplied from the solar cell string is connected to the inverter input. This power is supplied across the smoothing capacitor of the inverter driver 210 and the smoothed power is switched by the three-phase bridge circuit of the inverter driver 210. The bridge circuit typically uses a pulse width modulation (PWM) scheme and consists of a set of switching elements for each phase. At this time, the output voltage of the bridge circuit is output in the form of a pulse train by switching, as shown in (b) of FIG. 2, and the current is provided in the form of a sine wave including switching noise by a reactance of a later stage. . The output of the three-phase bridge circuit of the inverter driver 210 is supplied to the output transformer 230 as a sinusoidal power waveform in which noise is removed through the harmonic filter 220. In this case, the harmonic filter 220 is configured to remove switching noise mixed in the output of the inverter driver 210 as an LC filter provided for each phase and to resonate with a sine wave of 50/60 Hz. The LC filter is configured by connecting one end of three inductors to three outputs of the inverter driver 210 and connecting capacitors between two inductors at the other ends of the three inductors. The three outputs of the harmonic filter 220 are current-transformed through an output transformer 230 consisting of a three-phase transformer of Δ-Y connection and supplied to the power grid as a grid output. The three outputs of the harmonic filter 220 are connected to each end of the primary side Δ connection of the output transformer 230, and supply three-phase power to the power grid from the Y connection end of the secondary side. FIG. 2A illustrates a voltage from the solar cell string supplied to the inverter input terminal, and FIG. 2B illustrates an output voltage and a current waveform of the inverter driver 210. The output voltage of the inverter driver 210 is a pulse train switched to PWM. The current value is an integral value of the pulse train voltage by the inductor of the harmonic filter 220 connected thereto, and is provided as a waveform shown in FIG. The output voltage of the harmonic filter 220 is the sinusoidal wave Figure 2 (c) of the noise is removed, the grid output is provided to the transformed voltage Figure 2 (d).

3 shows a block diagram of a typical multi-string solar power system three phase inverter circuit of FIG. 2. Power supplied from the solar cell string is connected to the inverter input terminal 301, which is switched by the three-phase bridge circuit of the inverter driver 210. The phase-specific outputs of the three-phase bridge circuit of the inverter driver 210 are output to the output transformer 230 in a sine wave power waveform through the harmonic filter 220. The three outputs of the harmonic filter 220 are current-transformed through the output transformer 230 and supplied to the power grid as the grid output 300. In the bridge circuit, a pulse width modulation (PWM) method is typically used, and the inverter driver 240 which feeds back the grid output 300 for each phase of φ1, φ2, and φ3 to generate pulse width modulation (PWM) switching pulses for each bridge switching element. Switching control is achieved by

As described above with reference to FIG. 1, the inverter of the solar power generation system monitors the voltage and current of the inverter input terminal 301 and the grid output 300 and adds a function of detecting an abnormality to the grid according to the load variation. It is configured to keep the output 300 constant and to supply stable power. However, since the conventional voltage and current measuring means is configured to convert the waveform of AC into an RMS value or take an average value for a predetermined time, it is impossible to identify an instantaneous change or abnormality.

FIG. 4 illustrates anomalies occurring at the inverter to grid output 300 of the photovoltaic system, in particular anomalies that may occur instantaneously. 4 (a) shows the instantaneous voltage drop waveform. This phenomenon occurs when the load connected to the grid stage consumes instantaneous large power or an accident such as an instantaneous short circuit, or when the supply power of the solar cell array 100 becomes insufficient for a moment compared to the consumption of the grid. . (B) of FIG. 4 illustrates a case in which the output voltage rises instantaneously according to the transient response speed of the inverter 200 of the photovoltaic system when the load of the grid is sharply reduced. . (C) of the figure shows a momentary power failure. This phenomenon may be caused by abnormal power consumption or instantaneous short-circuit in the grid as in the case of a specific switching element of the inverter or a diagram (a), or when the power supply of the solar cell array 100 It occurs when the case is extremely short compared to the consumption amount and if this case is repeated, the inverter 200 may be seriously damaged. FIG. 4D shows a case where miserability appears in a waveform supplied to a grid. Such noise may be caused by switching noise of a grid stage load or activation of a large inductive load, and in extreme cases, may cause unnecessary oscillation in the inverter driver 240 that provides a switching signal to the inverter 200 of the photovoltaic system. . Such abnormalities may occur in the form of current as well as voltage, and accurate and instantaneous waveform monitoring is required for the protection of the photovoltaic system against repeated occurrences.

The abnormalities illustrated in FIG. 4 are not detectable by means of measuring a conventional voltage or current, and cause failures and accidents of the entire photovoltaic system when an early response due to repetitive occurrence is not possible.

Figure 5 shows an embodiment of the output quality monitoring apparatus of the solar power inverter of the present invention. Power supplied from the solar cell string is connected to the inverter input terminal 301, and the power is switched by the three-phase bridge circuit of the inverter driver 210, and φ1 and φ2 of the three-phase bridge circuit of the inverter driver 210. , φ3 phase-specific output is supplied to the output transformer 230 as a sinusoidal power waveform through the harmonic filter 220. The three outputs of the harmonic filter 220 are current-transformed through the output transformer 230 and supplied to the power grid as the grid output 300. In the bridge circuit, a pulse width modulation (PWM) method is typically used, and the inverter driver 240 which feeds back the grid output 300 for each phase of φ1, φ2, and φ3 to generate pulse width modulation (PWM) switching pulses for each bridge switching element. Switching control is achieved by For the photovoltaic power generation system as described above, the present invention provides an A / D converter 400 for converting output voltage and current for each phase of the grid output 300 into digital data; A controller 410 which receives the voltage and current data provided from the A / D converter 400 and stores the data in the working memory 430; A clock timer 420 for supplying and driving a clock signal to the A / D converter 400 according to the conversion start control signal supplied from the controller 410; And a display 450 and an alarm 440 for displaying a result of the processing from the controller 410 and generating an alarm.

6 shows another embodiment of the output quality monitoring apparatus of the solar power inverter of the present invention. Power supplied from the solar cell string is connected to the inverter input terminal 301, and the power is switched by the three-phase bridge circuit of the inverter driver 210, and φ1 and φ2 of the three-phase bridge circuit of the inverter driver 210. , φ3 phase-specific output is supplied to the output transformer 230 as a sinusoidal power waveform through the harmonic filter 220. The three outputs of the harmonic filter 220 are current-transformed through the output transformer 230 and supplied to the power grid as the grid output 300. In the bridge circuit, a pulse width modulation (PWM) method is typically used, and the inverter driver 240 which feeds back the grid output 300 for each phase of φ1, φ2, and φ3 to generate pulse width modulation (PWM) switching pulses for each bridge switching element. Switching control is achieved by For the solar power generation system as described above, the present invention provides an A / D converter 400 for converting voltage and current for each phase connecting the harmonic filter 220 and the output transformer 230 into digital data. Wow; A controller 410 which receives the voltage and current data provided from the A / D converter 400 and stores the data in the working memory 430; A clock timer 420 for supplying and driving a clock signal to the A / D converter 400 according to the conversion start control signal supplied from the controller 410; And a display 450 and an alarm 440 for displaying a result of the processing from the controller 410 and generating an alarm.

5 and 6, the A / D converter 400 for converting voltage and current for each phase into digital data has a built-in means for sensing instantaneous values of voltage and current. As a means for sensing the instantaneous value of voltage, the voltage for each phase is divided and supplied to the A / D converter 400, and as a means for detecting the instantaneous value of the current, a hall sensor or a current pickup transformer Etc. can also be used.

In addition, the instantaneous value of the voltage and current of the present invention is one wavelength of the voltage and current of each phase (phase) connecting the grid output 300 waveform to each phase to the harmonic filter 220 and the output transformer 230 for each phase. The A / D converter 400 converts data over an integer multiple of wavelengths into digital data according to the control of the controller 410. As a reason for such a process, in an abnormal waveform as described in FIG. 4 above, there is a concern that incorrect waveform information may be detected when a process such as zero crossing is performed to convert an integer multiple of one cycle into data. This is because the wavelength is not detected in the case of a momentary power failure.

In order to overcome this problem, the clock timer 420 of the present invention may control the phase of the grid output 300 waveform to the harmonic filter 220 and the output transformer 230 under the control of the controller 410. The A / D converter 400 is configured to convert the output voltage and current into digital data by an integer multiple of the phase-specific voltage and current frequency. Table 1 below shows the sampling frequency and grid output 300 waveform of the clock timer 420, and the voltage and current frequency of each phase connecting the harmonic filter 220 and the output transformer 230. The relationship is illustrated.

Example of the relationship between sampling frequency and output frequency 10 sample / cyc 20
sample / cyc 40
sample / cyc 80
sample / cyc 100
sample / cyc 200 sample / cyc 400
sample / cyc 50 Hz 500 Hz 1KHz 2KHz 4KHz 5KHz 10KHz 20KHz 60 Hz 600 Hz 1.2KHz 2.4KHz 4.8KHz 6KHz 12KHz 24KHz

The specific meaning of Table 1 will be described by taking the voltage and current frequency of each phase connecting the grid output 300 waveform of 60 Hz to the harmonic filter 220 and the output transformer 230 as an example. The clock timer to drive the A / D converter 400 with 600 A / D conversions per second, i.e., a sampling frequency of 6KHz, when A / D conversion is performed for 100 waveforms on a waveform having a frequency of 60 Hz. In this case, the controller 410 reads 100 samples from the A / D converter 400, and the samples are output from the waveform of the grid output 300 to the harmonic filter 220. Data corresponding to one period of the voltage and current waveforms for each phase connecting the output transformer 230 become data. Therefore, in this case, the controller 410 can take as much data as the period of the desired waveform in units of 100 samples. In the example of Table 1, the voltage for each phase connecting the grid output 300 waveform to the harmonic filter 220 and the output transformer 230 when the grid output 300 frequency is 50/60 Hz. And when processing 10 ~ 400 smaple data per cycle of the current waveform, the sampling frequency is presented, it is also possible to set a higher sampling frequency as needed. From the above configuration, the output quality monitoring apparatus of the solar power inverter of the present invention connects the grid output 300 waveform to the harmonic filter 220 and the output transformer 230 at a sampling frequency set for the frequency of voltage and current. It is characterized in that the voltage and current waveforms for each phase can be processed in cycles of integer multiples.

7 shows an overview of data analysis in the output quality monitoring apparatus of the solar power inverter of the present invention. The analysis example of FIG. 7 will be described based on a period of a voltage and current waveform for each phase connecting the grid output 300 waveform to the harmonic filter 220 and the output transformer 230. FIG. 7A illustrates a voltage and current for each phase connecting the grid output 300 waveform to the harmonic filter 220 and the output transformer 230 in the above-described configuration of FIGS. 5 and 6. As a period data of a waveform, the controller 410 is received from the A / D converter 400 and stored in the working memory 430 as a waveform. The waveform data of one cycle stored in the working memory 430 is converted into an absolute value by the controller 410 as shown in (b) of the figure, and the absolute value data is sorted by the controller 410. As a result, it is rearranged in size order in the working memory 430 as shown in (c) of the drawing. Then, the controller 410 compares the waveform data of one cycle rearranged in the order of magnitude in the working memory 430 with the calculated value stored in the working memory 430 in advance as shown in (d) of FIG. Judgments are displayed on the display 450, and an abnormal state is reported by activating the alarm 440 by performing judgment according to the abnormal state.

At this time, the calculated value stored in the working memory 430 in advance is n as the number of samples in one cycle as described in Table 1 by the setting of the clock timer 420, and the value of the steady state voltage or current A / D converted to the maximum value Sm;

        Ci = Sm sin [(ωt / n) * i] (i = 0, 1, 2, 3…, n-1)

It is calculated as and sorted by the value provided. If the voltage and current waveform data for each phase connecting the grid output 300 waveform to the harmonic filter 220 and the output transformer 230 are set to a plurality of periods m, the Ci data is m. What is necessary is just to provide more than one each.

FIG. 8 illustrates, as a voltage, a criterion for determining whether there is an abnormality by comparing the waveform data of one cycle rearranged in size order in the above-described working memory 430 with the calculated value stored in the working memory 430. When the waveform data (solid line) rearranged in the order of magnitude in the working memory 430 is compared with the calculated value stored in the working memory 430 shown by a dotted line in the drawing, the waveform data are all smaller than the calculated value as shown in (a). Is determined by the voltage drop. Comparing the waveform data (solid line) to the calculated value, if all the waveform data are larger than the calculated value as shown in (b), it is judged to be a voltage rise.If the waveform data is all close to 0 or too small than the calculated value, the power failure It can be judged by (c). If the waveform data (solid line) is compared with the calculated value and the large and small values are calculated at the same time, it is determined that there is noise in the voltage waveform.

9 and 10 show a flowchart for performing a method for monitoring the output quality of the solar power inverter of the present invention.

The output quality monitoring method of the photovoltaic inverter of the present invention is a count in which c1, c2, c3, and c4, which are variables for counting the number of times of voltage rise, voltage noise, voltage drop, and instantaneous power failure after start, are counted as 0. Initialization step (S100); Then, d1 and d2, which are variables that accumulate the negative difference and the positive difference, respectively, of the above-described waveform data and the calculated value are set to 0, and the negative difference between the above-described waveform data and the calculated value ( Tolerance values tr1, tr2, tr3 of negative difference and positive difference, and threshold accumulation values of voltage rise, voltage noise, voltage drop and the number of instantaneous power failures for alarm operation, and m1, m2, m3, m4 values. Variables are set by the controller 410 as an initial value setting step S110 of setting.

Then, according to the control of the clock timer 420 according to the setting of the controller 410, the voltage and current for each phase connecting the grid output 300 waveform to the harmonic filter 220 and the output transformer 230. An A / D conversion step (S120) of converting data of the waveform into the A / D conversion unit 400 on a periodic basis; a storage step of storing the data in the working memory 430 by the controller 410 (S130); Then, in the sample number checking step (S140) for checking whether the sample number satisfies the period unit, the A / D conversion step (S120) is repeated until the sample number becomes n samples. When the number of samples becomes n samples in the sample number checking step (S140), the controller 410 may calculate an absolute value of the samples of the working memory 430 (S150); The sorting step (S160) of relocating the controller 410 may be performed to rearrange the data in the working memory 430.

The controller 410 performs a difference value calculating step (S170) for calculating a difference between the i-th data ri rearranged in the working memory 430 and the calculated value si; and determines a difference value sign for determining the sign of the difference value. In step S180; when the value of ri-si is smaller than 0, that is, when the data value is small for the calculated value, a negative difference accumulating step (S190) accumulating the absolute value of the difference value in d1; Alternatively, when the value of ri-si is greater than 0, that is, when the data value is large with respect to the calculated value, the difference accumulating amount accumulates in d2 (S200).

The accumulation step (S190) (S200) is performed to repeat the accumulation of the difference between the total number of rearranged data and the calculated value in the sample number comparison step (S210), through which the difference between the total data and the total calculated value is respectively The result is the cumulative result of d2. Then, the controller 410 compares a cumulative value comparing step of comparing the allowable values tr1, tr2, and tr3 of the negative difference and the positive difference between the waveform data and the calculated value with respect to the accumulated d1 and d2 ( S220 ~ S240); In this step, the negative difference accumulated value accumulated in d1 and the negative difference allowable values tr1 and tr3, and the positive difference accumulated value accumulated in d2 and the positive difference allowed value tr2 are compared and classified into five categories. Subsequently, the controller 410 performs a normal / abnormal determination step S250 according to the result of the cumulative value comparison step S220 to S240. In the normal / abnormal determination step (S250), the controller 410 determines normal if d1 and d2 are within tr1 and tr2, respectively, and displays the result, and returns to the initial value setting step (S110) to start performing again. If d1 is a value within tr1 and d2 is larger than tr2, it is determined that the voltage rises and is displayed. The value of the voltage rise counter c1 is increased by one. In addition, if d1 is larger than tr1 and d2 is larger than tr2, it is judged and displayed as noise voltage and the value of noise voltage counter c2 is increased by one. When d1 is larger than tr1 and d2 is smaller than tr2 and d2 is larger than tr3 in the accumulated value comparison step (S220 to S240), it is determined that the voltage drop is displayed and the value of the voltage drop counter c3 is increased by one. If d1 is larger than tr1 and d2 is smaller than tr2 and tr2 is larger than tr1 and d2 is larger than tr3, the data value is very different from the above calculated value. Increment the value of counter c4 by 1.

When the voltage rise, the voltage noise, the voltage drop, and the momentary power failure are determined in the normal / abnormal determination step (S250), the controller 410 performs an abnormal state processing step (S260) for determining an alarm operation according to the abnormal state. The controller 410 increases the value of the voltage rising counter c1, the value of the noise voltage counter c2, the value of the voltage drop counter c3, and the value of the instantaneous blackout counter c4 at the normal / abnormal determination step S250, respectively. , Compare with the accumulated value m1, m2, m3, m4 of the voltage drop and the number of instantaneous blackouts.If any one of c1, c2, c3, c4 becomes the boundary accumulated value, the alarm is driven and the corresponding counter value is zero. After setting, the process returns to the initial value setting step (S110) and starts again. In this case, the alarm may be distinguished by different driving according to a voltage increase, a voltage noise, a voltage drop, and a momentary power failure. The alarm 440 shown in FIGS. In addition, each of the voltage drop and the instantaneous power failure may be provided separately for driving.

The output quality monitoring apparatus and method of the solar power inverter of the present invention as described above can monitor instantaneous transients that cannot be detected by conventional voltage and current measuring means, and thus stable driving of the system is achieved. Possible features

In addition, although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited thereto and will be described below by the person skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of the claims.

100: solar cell array 200: inverter
210: inverter drive unit 220: harmonic filter
230: output transformer 240: inverter driver
300: grid output 301: inverter input terminal
400: A / D converter 410: controller
420: clock timer 430: working memory
440: alarm 450: display

Claims (8)

The power supplied from the solar cell string is connected to the inverter input stage, the power is switched by the bridge circuit of the inverter driver, the phase-specific output of the inverter driver is supplied to the output transformer as a sinusoidal power waveform through a harmonic filter and the current flow- An apparatus for monitoring the output quality of a photovoltaic inverter configured to be transformed and supplied to a power grid as a grid output,


An A / D converter converting output voltage and current of each phase of the grid output into digital data; and
A controller for receiving voltage and current data provided from the A / D converter and storing the received data in a working memory; and
A clock timer for supplying and driving a clock signal to the A / D converter according to a conversion start control signal supplied from the controller; and
A display for displaying a processing result from the controller and generating an alarm;
And an alarm;


The A / D converter has a built-in means for detecting the instantaneous value of the voltage and current, and as a means for detecting the instantaneous value of the voltage, divides the voltage for each phase and supplies it to the A / D converter. Means for sensing the instantaneous value of the current includes a hall sensor or a current pickup transformer, and is operated by the clock timer under the control of the controller, and one wavelength of voltage and current for each phase. The A / D converter converts data over an integer multiple of wavelengths based on the controller into digital data under control of the controller.


The controller receives data of each phase of the voltage and current waveforms for each phase from the A / D converter and stores the data in the working memory.


The waveform data stored in the work memory is converted into an absolute value by the controller, and the absolute value data is rearranged in the order of size in the work memory through a sorting process by the controller, and the calculated value stored in the work memory. Compared with, it determines whether there is an abnormality and displays it on the display, and performs an alarm according to the abnormal state to report an abnormal state by operating an alarm.
The calculated value stored in the working memory is n for the number of samples of one cycle of steady state voltage or current, and Sm is a value obtained by A / D conversion of the maximum value of steady state voltage or current.
Ci = Sm sin [(ωt / n) * i] (i = 0, 1, 2, 3…, n-1)
When the voltage and current waveform data is set to a plurality of periods m, the Ci data is composed of a plurality of m pieces each.


The controller,
Compare the recalculated waveform data with the calculated value in order of magnitude,
If the waveform data are all smaller than the calculated value, it is judged as a voltage drop.
If all of the waveform data for the calculated value is larger than the calculated value, it is determined as a voltage rise.
If the waveform data are all close to zero or too small than the calculated value, it is determined as a momentary power failure (c).
Output quality monitoring device of a photovoltaic inverter characterized in that it is configured to determine that there is noise in the voltage waveform when large and small values are simultaneously calculated as a result of comparing the waveform data with respect to the calculated value. The method of claim 1,
The A / D conversion unit output quality monitoring device of the solar power inverter, characterized in that for converting the voltage and current for each phase connecting the harmonic filter and the output transformer into digital data. The power supplied from the solar cell string is connected to the inverter input stage, the power is switched by the bridge circuit of the inverter driver, the phase-specific output of the inverter driver is supplied to the output transformer as a sinusoidal power waveform through a harmonic filter and the current flow- A method for monitoring the output quality of a photovoltaic inverter configured to be transformed and supplied to a power grid as a grid output,
A count initialization step (S100) in which variables c1, c2, c3, and c4, which are variables for counting the number of voltage rises, voltage noises, voltage drops, and momentary power failures, are set to 0 after the start step (start);
An initial value setting step (S110) of setting initial values of variables following the count initialization step (S100);
An A / D conversion step (S120) of converting data of voltage and current waveforms into A / D conversion units 400 on a periodic basis after the initial value setting step (S110);
A storage step (S130) of storing the A / D converted data in the working memory (430) by the controller (410) following the A / D conversion step (S120);
A sample number checking step (S140) of checking whether the sample number satisfies a period unit following the storing step (S130);
Following the sample number checking step (S140), when the number of samples becomes n samples, an absolute value calculating step (S150) of which the controller takes the absolute values of the samples in the working memory;
Following the absolute value calculating step (S150), the controller sorts the data in the working memory in order of size (S160);
A difference value calculating step (S170) of calculating a difference between the i-th data ri rearranged in the working memory and the calculated value si after the sorting step (S160);
A difference value sign determining step (S180) of determining a sign of the difference value after the difference value calculating step (S170);
In the difference sign determining step (S180), when the value of ri-si is smaller than 0, that is, when the data value is small for the calculated value, a negative difference accumulating step of accumulating the absolute value of the difference value in d1 (S190). ;;
If the value of ri-si is greater than 0 in the difference value sign determination step (S180), that is, if the data value is large with respect to the calculated value, accumulating a positive difference value (S200) accumulating the difference value in d2; ,

A sample number comparison step (S210) for repeating the accumulation step (S190) (S200) with respect to the total rearranged data and the calculated value;
A cumulative value comparison step of comparing the d1 and d2 with an allowable value by the controller (S220 to S240);
A normal / abnormal determination step (S250) of performing determinations classified into five categories according to the results of the cumulative value comparison step (S220 to S240);
An abnormal state processing step (S260) of determining, by the controller, an alarm operation according to an abnormal state following the normal / abnormal determination step (S250);
Return to the initial value setting step (S110) and the output quality monitoring method of the solar power inverter, characterized in that configured to start again The method of claim 3,
In the initial value setting step (S110), the variables d1 and d2, which accumulate negative and positive differences between the waveform data and the calculated value, respectively, are 0,
Allowable value tr1 of negative difference accumulating value accumulated in d1, Allowable value of positive difference accumulating value accumulated in d2, Instantaneous power failure value tr3 of negative difference accumulating value accumulated in d1 and voltage rise for alarm operation Monitoring output quality of the photovoltaic inverter, wherein the boundary accumulation value m1 of the number of times, the boundary accumulation value m2 of the number of voltage noises, the boundary accumulation value m3 of the number of voltage drops, and the boundary accumulation value m4 of the number of instantaneous power failures are monitored. Way The method of claim 3,
The sample number checking step (S140) may be repeated from the A / D conversion step (S120) until the number of samples becomes n samples. The method of claim 3,
The cumulative value comparison step (S220 to S240) is normal by comparing the negative difference accumulated value accumulated in d1 and the negative difference allowed value tr1 and tr3 and d2, and the positive difference accumulated value and positive difference allowed value tr2. It is classified into five categories: status, voltage rise, voltage noise, voltage drop, and power failure.
In the normal / abnormal determination step (S250), the controller determines that the controller is normal when d1 and d2 are within tr1 and tr2, respectively, and displays the result, returns to the initial value setting step (S110), and starts again. If this value is within tr1 and d2 is larger than tr2, it is judged to be the voltage increase and displayed.
If d1 is larger than tr1 and d2 is also larger than tr2, it is judged as noise voltage and displayed and increases the value of noise voltage counter c2 by 1.
When d1 is larger than tr1 and d2 is smaller than tr2, and d2 is larger than tr3, it is determined that the voltage drop is displayed and the value of the voltage drop counter c3 is increased by one,
When d1 is larger than tr1 and d2 is smaller than tr2 and tr2 is larger than tr1, d2 is larger than tr3, the data value is very different from the calculated value. Output quality monitoring method of a solar power inverter, characterized in that configured to increase the value by 1
Output quality monitoring method of the solar power inverter, characterized in that delete The method of claim 3,
In the abnormal state processing step S260, the controller may determine the value of the voltage rise counter c1, the noise voltage counter c2, the voltage drop counter c3, and the value of the instantaneous blackout counter c4 that are increased in the normal / abnormal determination step S250. Compared to the boundary accumulation values m1, m2, m3, and m4 of voltage rise, voltage noise, voltage drop, and the number of instantaneous power failures, respectively, and when any one of c1, c2, c3, and c4 reaches the boundary accumulation value, an alarm is driven and The output quality monitoring method of the solar power inverter, characterized in that configured to set the counter value to 0 and return to the initial value setting step (S110) to start again.

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