KR20240008642A - Apparatus and method for detecting arc - Google Patents

Abstract

This embodiment relates to an arc detection device and method, and more specifically, to a technology that can detect an arc in a power conversion device of a solar power generation system without separately installing an arc detection device in the solar power generation system. .

Description

Arc detection device and method {APPARATUS AND METHOD FOR DETECTING ARC}

This embodiment relates to an arc detection device and method.

Recently, energy systems have increasingly relied on renewable energy such as photovoltaics (PV) and wind power to achieve carbon neutrality.

As the number of renewable energy power generation systems that produce electricity using renewable energy increases, it is essential to improve the reliability and safety of these systems.

Among renewable energy power generation systems, the solar power generation system is essentially a DC (Direct Current) source, so arcs may occur in the electric power line of the solar power generation system, and arcs may cause fire in the solar power generation system. You can. Here, the arc occurring in the line of the solar power generation system may be a DC series arc.

Previously, an arc detection device (AFDD: Arc Fault Detection Device), a device that detects arcs, was installed in solar power generation systems to detect arcs in solar power generation systems.

Here, as the system complexity of the solar power generation system increases, the number of installed arc detection devices also increases, which reduces the cost-effectiveness of the overall system.

Meanwhile, in existing solar power generation systems, a DC optimizer, a power conversion device that can improve the power generation efficiency of photovoltaic (PV) panels, is installed on a solar panel basis. In addition, another power conversion device, a grid-connected inverter, is installed in the existing solar power generation system. Here, the grid-connected inverter can convert the DC power converted by the DC optimizer into AC power and supply it to the power system.

Against this background, the purpose of this embodiment is, in one aspect, to provide a technology that can detect an arc in a power conversion device without separately installing an arc detection device in the solar power generation system.

In order to achieve the above-mentioned object, in one aspect, the present embodiment is a method of detecting an arc in a power conversion device of a solar power generation system, in which the voltage of the first power input through the line of the solar power generation system is provided. detecting a drop in the first voltage; In order to determine the cause of the drop in the first voltage, gradually reducing the second voltage, which is the voltage of the second power output through power conversion for the first power; confirming a change in the first voltage; and determining that an arc has occurred in the line when the first voltage drops to a preset reference value in the checking step.

In the detecting step, the power conversion device may calculate an average value and an instantaneous value of the first voltage for a preset time period, and detect a drop in the first voltage using the instantaneous value and the average value.

The power conversion device may detect that the input voltage has dropped when the value obtained by subtracting the instantaneous value from the average value is greater than the first threshold and the instantaneous value is less than the second threshold.

The arc detection method may further include stopping power conversion for the first power after the determining step.

The first power and the second power may be direct current power, and the power conversion device may be a DC optimizer that performs DC (Direct Current)-DC power conversion.

The first power is direct current power, the second power is alternating current power, and the power conversion device may be a grid-connected inverter that performs DC-AC (Alternating Current) power conversion.

The arc detection method may further include a step of gradually increasing the second voltage by determining that an arc has not occurred when the first voltage increases in the checking step.

In another aspect, this embodiment provides a method for detecting an arc in a power conversion device of a solar power generation system, comprising: checking the average value and instantaneous value of the line current flowing through the line of the solar power generation system; detecting a decrease in the line current using the average value and the received value; In order to determine the cause of the decrease in the line current, gradually reducing the second voltage, which is the voltage of the second power output through power conversion for the first power input through the line; Checking a change in a first voltage, which is the voltage of the first power; and if the first voltage drops to a preset reference value in the checking step, determining that the cause of the decrease in the line current is an arc occurring in the line.

In the detecting step, the power conversion device may detect that the line current decreases if the value obtained by subtracting the instantaneous value from the average value is greater than the first threshold and the instantaneous value is less than the second threshold. there is.

The arc detection method may further include a step of gradually increasing the second voltage by determining that an arc has not occurred if the first voltage rises while the second voltage decreases in the checking step.

In another aspect, this embodiment includes a power conversion unit that converts first power input through a line connected to a solar panel (PV, Photovoltaics) into second power; And when the first voltage, which is the voltage of the first power, is monitored and a drop in the first voltage is detected, the power conversion unit is controlled to gradually reduce the second voltage, which is the voltage of the second power output from the power conversion unit. and an arc detection unit that detects whether an arc has occurred in the line by checking a change in the first voltage when the second voltage decreases.

The arc detector determines that an arc has occurred in the line if the first voltage drops to a preset reference value when the second voltage decreases, and if the first voltage increases when the second voltage decreases, It can be determined that no arc has occurred in the line.

The arc detection unit may control the power conversion unit to reduce the second voltage from a normal value to a minimum value and then maintain the second voltage at the minimum value for a certain period of time.

The arc detector calculates an average value and an instantaneous value of the first voltage for a preset time period, compares a value obtained by subtracting the instantaneous value from the average value with a previously stored first threshold value, and compares the instantaneous value with the previously stored first threshold value. A drop in the first voltage can be detected by comparing a second threshold value.

The arc detector may detect that the first voltage has dropped when a value obtained by subtracting the instantaneous value from the average value is greater than the first threshold and the instantaneous value is less than the second threshold.

As described above, according to this embodiment, the power conversion device that converts the direct current power generated from the solar panel can detect the arc occurring in the line of the solar power generation system, so a separate arc detection device is installed in the solar power generation system. It does not need to be installed in the system, which can improve the cost-effectiveness of the solar power system.

1 is a configuration diagram of a solar power generation system according to an embodiment.
Figures 2 and 3 are diagrams illustrating an equivalent circuit for an arc occurring in a first line in one embodiment.
Figure 4 is a diagram briefly showing the configuration of another power conversion device according to an embodiment.
Figure 5 is a flowchart showing a process in which a power conversion device detects an arc using a first voltage and a second voltage according to an embodiment.
Figure 6 is a flowchart showing a process in which a power conversion device detects an arc using a line current and a second voltage according to an embodiment.
Figure 7 is a diagram illustrating the duty ratio of the first direct current voltage and DC-DC power conversion when no arc occurs in the solar power generation system according to one embodiment.
FIG. 8 is a diagram illustrating a second direct current voltage when no arc occurs in a solar power generation system according to an embodiment.
FIG. 9 is a diagram illustrating the duty ratio of the first direct current voltage and DC-DC power conversion when an arc occurs in a solar power generation system according to an embodiment.
FIG. 10 is a diagram illustrating a second direct current voltage when an arc occurs in a solar power generation system according to an embodiment.

Hereinafter, some embodiments of the present invention will be described in detail through illustrative drawings. When adding reference numerals to components in each drawing, it should be noted that identical components are given the same reference numerals as much as possible even if they are shown in different drawings. Additionally, in describing the present invention, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present invention, the detailed description will be omitted.

Additionally, when describing the components of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are only used to distinguish the component from other components, and the nature, sequence, or order of the component is not limited by the term. When a component is described as being “connected,” “coupled,” or “connected” to another component, that component may be directly connected or connected to that other component, but there is another component between each component. It will be understood that elements may be “connected,” “combined,” or “connected.”

1 is a configuration diagram of a solar power generation system according to an embodiment.

Referring to FIG. 1, the solar power generation system 100 includes a solar panel (PV, Photovoltaics, 110), a first line 120, a DC optimizer 130, a second line 140, and a grid-connected inverter. It may include (150). Here, the solar power generation system 100 may include a plurality of solar panels 110. Additionally, the first line 120, DC optimizer 130, and second line 140 may be included as many as the number of solar panels 110. The operation method of the DC optimizer 130 arranged for each solar panel 110 may be the same.

The solar panel 110 can convert solar light energy into electrical energy and produce direct current (DC) power.

In general, when the amount of solar radiation reaching the solar panel 110 decreases, the amount of power produced by the solar panel 110 may also decrease.

Additionally, if the surface temperature of the solar panel 110 increases, the power generation efficiency of the solar panel 110 may decrease.

For example, the power generation efficiency of the solar panel 110 may be highest when the surface temperature of the solar panel 110 is 25°C, and the efficiency decreases by 0.1% every time the surface temperature increases by 1°C from 25°C. can do. And when the surface temperature of the solar panel 110 is 60°C, the efficiency may decrease by an average of 17.5% compared to when the surface temperature is 25°C.

If the surface temperature of the solar panel 110 increases due to abundant solar radiation and a high temperature environment and the power generation efficiency of the solar panel 110 decreases, the amount of power produced by the solar panel 110 may decrease.

As described above, the amount of power produced by the solar panel 110 may vary depending on external factors such as solar radiation and surface temperature.

The first line 120 electrically connects the solar panel 110 and the DC optimizer 130. In other words, the first line 120 transmits the first direct current power, which is the direct current power produced by the solar panel 110, to the DC optimizer 130.

Here, the first line 120 may have an inductance component (L _l ) and a resistance component (R _l ) as shown in FIG. 2 or 3 .

The first line 120 may include one or more power cables and multiple connectors. Here, multiple connectors may be used to electrically connect the solar panel 110 and the power cable, and to electrically connect the power cable and the DC optimizer 130. When the first line 120 includes two or more power cables, a plurality of connectors may also be used to electrically connect the two or more power cables.

Meanwhile, an arc may occur in the first line 120 due to causes such as poor connector contact, damage to the power cable, or cracks in the solder joint. This arc can be modeled as an arc resistance (R _arc ), which is a resistance component, as shown in FIG. 2 or FIG. 3 . Here, the arc occurring in the first line 120 may be a DC series arc.

When an arc occurs in the first line 120, arc resistance (R _arc ) increases. When the arc resistance (R _arc ) increases, the first direct current voltage (V _IN in FIG. 2), which is the voltage of the first direct current power input to the DC optimizer 130 through the first line 120, drops as shown in the equation below. It can be.

Here, V _IN is the first direct current voltage, V _pv is the voltage applied to both ends of the solar panel 110, I _pv is the first line current, which is the current flowing in the first line 120, and R _l is the first line ( The resistance component of 120), L _l , is the inductance component of the first line 120.

If the arc resistance (R _arc ) increases due to the occurrence of an arc in the first line 120, the first line current (I _pv in FIG. 3 ) may also decrease as shown in the equation below.

Here, Z _g means the arc spacing.

If an arc occurs in the first line 120 as above, the first direct current voltage (V _IN ) and the first line current (I _pv ) may decrease.

In addition, even if the amount of solar radiation reaching the solar panel 110 decreases or the surface temperature of the solar panel 110 increases, the first direct current voltage (V _IN ) and the first line current (I _pv ) may decrease.

The DC optimizer 130 is a type of power converter and can perform Maximum Power Point Tracking (MPPT) control to maximize the power generation efficiency of the solar panel 110.

The input of the DC optimizer 130 may be connected to the first line 120, and the output of the DC optimizer 130 may be connected to the second line 140.

Through this, the DC optimizer 130 can receive the first direct current power produced by the solar panel 110 through the first line 120. And the DC optimizer 130 can convert the first direct current power to DC-DC power and output the second direct current power. In other words, the DC optimizer 130 steps down or boosts the first direct current voltage (V _IN ), which is the voltage of the first direct current power, to produce second direct current power having the second direct current voltage (V _out in FIG. 8 or 10 ). can be output.

Here, the solar power generation system 100 may include a plurality of DC optimizers 130. And a plurality of DC optimizers 130 may be connected in series. The link voltage (V _link ) corresponding to the sum of the second direct current voltages (V _out,1 , V _out,2 ,...V _out,n ) output from the plurality of DC optimizers 130, respectively, is connected to the second line. It can be input to the grid-connected inverter 150 through (140).

In one embodiment, the DC optimizer 130 uses the first direct current voltage (V _IN ) and the second direct current voltage (V _out ), or the first line current (I _pv ) and the second direct current voltage (V _out ). Using this, the arc occurring in the first line 120 can be detected.

First, we will describe in detail the configuration in which the DC optimizer 130 detects an arc occurring in the first line 120 using the first direct current voltage (V _IN ) and the second direct current voltage (V _out ).

The DC optimizer 130 monitors the first direct current voltage (V _IN ) and can confirm that the first direct current voltage (V _IN ) maintains the voltage level when the solar panel 110 is operating in a normal state. there is.

In this state, the DC optimizer 130 can repeatedly detect whether the first direct current voltage (V _IN ) drops. Here, the DC optimizer 130 can calculate the average value and instantaneous value of the first direct current voltage (V _IN ) for a preset time period. And the DC optimizer 130 can detect whether the first direct current voltage (V _IN ) drops using the instantaneous value and the average value. For example, the DC optimizer 130 calculates the average value and instantaneous value of the first direct current voltage (V _IN ) for the time period from t ₀ to t ₁ as shown in FIG. 7 or FIG. 9, and from t ₀ to t ₁ It is possible to detect whether the first direct current voltage (V _IN ) drops using the average value and instantaneous value for the time period up to.

Specifically, the DC optimizer 130 determines that the value obtained by subtracting the instantaneous value (V IN (t)) from the average value (V _{IN ,a} ) is greater than the first threshold (V _th1 ), as shown in Equation 3 below, and As shown in Equation 4, if the instantaneous value (V _IN (t)) is less than the second threshold value (V _th2 ), it can be detected that the first direct current voltage (V _IN ) has dropped. The first threshold in Equation 3 and the second threshold in Equation 4 may be voltage thresholds.

The value obtained by subtracting the instantaneous value (V _IN (t)) from the average value (V _IN,a ) is less than the first threshold (V _th1 ), or the instantaneous value (V _IN (t)) is the second threshold (V If it is greater than _th2 ), the DC optimizer 130 may detect that the first direct current voltage (V _IN ) has not dropped and monitor the first direct current voltage (V _IN ) again.

Meanwhile, the DC optimizer 130 detects a drop in the first direct current voltage (V _IN ), that is, the value obtained by subtracting the instantaneous value (V _IN (t)) from the average value (V _IN,a ) is the first threshold ( If it is greater than V _th1 ) and the instantaneous value (V _IN (t)) is less than the second threshold (V _th2 ), the DC optimizer 130 determines the cause of the drop in the first DC voltage (V _IN ). In order to determine whether an arc has occurred in the first line 120, the second direct current voltage (V _out in FIG. 8 or 10) output through DC-DC power conversion of the first direct current voltage (V _IN ) is gradually reduced. You can. In other words, the DC optimizer 130 can linearly reduce the second direct current voltage (V _out ) so that the second direct current voltage (V _out ) goes from the normal value to the minimum value.

Here, the fact that the DC optimizer 130 linearly reduces the second direct current voltage (V _out ) so that the second direct current voltage (V _out ) becomes the minimum value from the normal value means that the duty cycle for DC-DC power conversion Cycle), it may mean linearly reducing any one of the operating frequencies from the normal value to the minimum value.

For example, the DC optimizer 130 linearly reduces the duty cycle of the normal value during the time period from t ₁ to t ₂ as shown in FIG. 7 or 9, thereby reducing the duty cycle from t ₁ to t in FIG. 8 or 10. The second direct current voltage (V _out ) may gradually decrease during _{the 2-} hour period.

Meanwhile, the DC optimizer 130 may reduce the duty cycle to the minimum value and then maintain the duty cycle at the minimum value for a certain period of time (for example, the time period t ₂ to t ₃ in FIG. 7 or FIG. 9 ).

When gradually decreasing the second direct current voltage (V _out ), the DC optimizer 130 can determine whether the first direct current voltage (V _IN ) increases by checking the change in the first direct current voltage (V _IN ). Here, the DC optimizer 130 starts reducing the size and duty cycle of the first direct current voltage (V _IN ) at the point when the duty cycle reaches the minimum value (for example, time t ₂ in FIG. 7 or FIG. 9). It is possible to determine whether the first direct current voltage (V _IN ) increases by comparing the magnitude of the first direct current voltage (V _IN ) at a time (for example, time t ₁ in FIG. 7 or FIG. 9 ).

In addition, the DC optimizer 130 determines whether the first direct current voltage (V IN ) rises or _falls when the second direct current voltage (V _out ) decreases (time period t ₁ to t ₂ in FIG. 7 or FIG. 9 ). It is also possible to determine whether the first direct current voltage (V _IN ) increases by checking .

When the second direct current voltage (V _out ) decreases, the first direct current voltage (V _IN ) rises as shown in FIG. 7, or the first direct current voltage (V IN) at the point when the duty cycle reaches the minimum value (at time t ₂ in FIG. 7) If V _IN ) is greater than the first direct current voltage (V _IN ) at the time when the duty cycle begins to decrease (time t ₁ in FIG. 7), the DC optimizer 130 determines that there is no arc in the first line 120. If it is determined that this has occurred, the second direct current voltage (V _out ) can be gradually increased as shown in FIG.

In this case, the drop in the first direct current voltage (V _IN ) detected by the DC optimizer 130 is due to external factors such as a decrease in solar radiation reaching the solar panel 110 and an increase in the surface temperature of the solar panel 110. This may be the cause.

If the cause of the drop in the first direct current voltage (V _IN ) is an external factor, the first direct current voltage (V _IN ) at the point when the duty cycle reaches the minimum value (at time t ₂ in FIG. 7) rises to the voltage level during the light load time. can do. The voltage level during the light load time, which is a time when there is little demand for the power produced by the solar power generation system 100, may be greater than the level of the first direct current voltage when the solar panel 110 is operating in a normal state.

In one embodiment, the DC optimizer 130 gradually increases the second direct current voltage (V _out ) by starting to linearly increase the duty cycle maintained at the minimum value (for example, at time _t3 in FIG. 7). This may mean returning the duty cycle to normal values. When the DC optimizer 130 returns the duty cycle to the normal value, the magnitude of the first direct current voltage (V _IN ) may become smaller than the voltage magnitude during the light load time.

The DC optimizer 130 may repeatedly perform the above operations until the solar power generation system 100 is turned off.

Meanwhile, when the second direct current voltage (V _out ) decreases (time period t ₁ to t ₂ in FIG. 9), if the first direct current voltage (V _IN ) drops to a preset reference value, the DC optimizer 130 It can be determined that an arc has occurred in the first line 120. Here, the reference value may be 0V (Volt), and the time when the first direct current voltage (V _IN ) reaches the reference value may coincide with the time when the duty cycle reaches the minimum value (time t ₂ in FIG. 7). And when the first direct current voltage (V _IN ) drops to the reference value, the arc voltage (V _arc ) may rise. The arc voltage (V _arc ) may refer to the voltage applied to the portion where the arc occurs in the first line 120.

When an arc occurs in the first line 120, the DC optimizer 130 can stop DC-DC power conversion by limiting the duty cycle as shown in FIG. 9. The DC optimizer 130 may stop DC-DC power conversion by limiting the operating frequency.

Additionally, the DC optimizer 130 may output an alarm sound or flash a warning light in response to arc occurrence.

From now on, we will describe in detail the configuration in which the DC optimizer 130 detects an arc occurring in the first line 120 using the first line current (I _pv ) and the second direct current voltage (V _out ).

The DC optimizer 130 monitors the first line current (I _pv in FIG. 3), which is the current flowing in the first line 120, so that the first line current (I _pv ) is in the normal state of the solar panel 110. It can be confirmed that the current value during operation is maintained. Here, a current sensor 310 that senses the first line current (I _pv ) may be installed in the first line 120. And the DC optimizer 130 can receive the current value of the first line current (I _pv ) from the current sensor 310 and monitor the first line current (I _pv ).

In a state where the first line current (I _pv ) maintains the current value during steady-state operation of the solar panel 110, the DC optimizer 130 determines whether the first line current (I _pv ) decreases. Can be detected repeatedly. Here, the DC optimizer 130 can calculate the average value and instantaneous value of the first line current (I _pv ) for a preset time period. And the DC optimizer 130 can detect whether the first line current (I _pv ) decreases using the instantaneous value and the average value.

Specifically, the DC optimizer 130 determines that the value obtained by subtracting the instantaneous value (I _pv (t)) from the average value (I _pv,a ) is greater than the first threshold (I _th1 ), as shown in Equation 5 below, and As shown in Equation 6, if the instantaneous value (I _pv (t)) is less than the second threshold (I _th2 ), it can be detected that the first line current (I _pv ) has decreased. The first threshold in Equation 5 and the second threshold in Equation 6 may be a current threshold.

The value obtained by subtracting the instantaneous value (I _pv (t)) from the average value (I _pv,a ) is less than the first threshold (I _th1 ), or the instantaneous value (I _pv (t)) is less than the second threshold (I If it is greater than _th2 ), the DC optimizer 130 may detect that the first line current (I _pv ) has not decreased and monitor the first line current (I _pv ) again.

Meanwhile, the DC optimizer 130 detects a decrease in the first line current (I _pv ), that is, the value obtained by subtracting the instantaneous value (I _pv (t)) from the average value (I _pv,a ) is the first threshold ( If the instantaneous value (I _pv ( _t )) is greater than I th1 ) and less than the second threshold (I _th2 ), the DC optimizer 130 determines that the cause of the decrease in the first line current (I _pv ) is the first In order to determine whether an arc has occurred in the line 120, the second direct current voltage (V _out in FIG. 8 or FIG. 10) can be gradually decreased. In other words, the DC optimizer 130 can linearly reduce the second direct current voltage (V _out ) so that the second direct current voltage (V _out ) goes from the normal value to the minimum value.

When gradually decreasing the second direct current voltage (V _out ), the DC optimizer 130 can determine whether the first direct current voltage (V _IN ) increases by checking the change in the first direct current voltage (V _IN ). Here, the DC optimizer 130 compares the size of the first direct current voltage (V _IN ) at the point when the duty cycle reaches the minimum value and the size of the first direct current voltage (V _IN ) at the point when the duty cycle begins to decrease, 1You can determine whether the direct current voltage (V _IN ) is rising.

In addition, the DC optimizer 130 determines whether the first DC voltage (V IN ) increases by checking whether the first DC voltage (V _IN ) increases or _decreases when the second DC voltage (V _out ) decreases. You may.

When the second direct current voltage (V _out ) decreases, the first direct current voltage (V _IN ) rises, or when the duty cycle reaches the minimum value, the first direct current voltage (V _IN ) begins to decrease the duty cycle. If it is greater than the first direct current voltage (V _IN ), the DC optimizer 130 determines that an arc has not occurred in the first line 120 and gradually increases the second direct current voltage (V _out ) as shown in FIG. You can.

In this case, the decrease in the first line current (I _pv ) detected by the DC optimizer 130 is due to external factors such as a decrease in solar radiation reaching the solar panel 110 and an increase in the surface temperature of the solar panel 110. This may be the cause.

If the cause of the drop in the first direct current voltage (V _IN ) is an external factor, the first direct current voltage (V _IN ) at the point when the duty cycle reaches the minimum value may rise to the voltage level during the light load time. The voltage level during light load time, which is a time when there is little demand for power produced by the solar power generation system 100, is greater than the size of the first direct current voltage (V _IN ) when the solar panel 110 is in normal state operation. You can.

In one embodiment, the DC optimizer 130 gradually increasing the second direct current voltage (V _out ) may mean starting to linearly increase the duty cycle maintained at a minimum value and returning the duty cycle to a normal value. there is. When the DC optimizer 130 returns the duty cycle to the normal value, the magnitude of the first direct current voltage (V _IN ) may become smaller than the voltage magnitude during the light load time.

The DC optimizer 130 may repeatedly perform the above operations until the solar power generation system 100 is turned off.

Meanwhile, when the second direct current voltage (V _out ) decreases (time period t ₁ to t ₂ in FIG. 9), if the first direct current voltage (V _IN ) drops to a preset reference value, the DC optimizer 130 It can be determined that an arc has occurred in the first line 120.

Here, the reference value may be 0V (Volt), and the time when the first direct current voltage (V _IN ) reaches the reference value may coincide with the time when the duty cycle reaches the minimum value. And when the first direct current voltage (V _IN ) drops to the reference value, the arc voltage (V _arc ) may rise.

If an arc occurs in the first line 120, the DC optimizer 130 may stop DC-DC power conversion by limiting the duty cycle or operating frequency. Additionally, the DC optimizer 130 may output an alarm sound or flash a warning light in response to arc occurrence.

The grid-connected inverter 150 is a power conversion device that converts direct current power into alternating current power, and can receive link voltage (V _link ) input through the second line 140. Here, the link voltage (V _link ) is a voltage corresponding to the sum of the second direct current voltages (V _out,1 , V _out,2 ,...V _out,n ) output from each of the plurality of DC optimizers 130. It can be.

In other words, the inverter input power, which is DC power corresponding to the sum of the second DC power output from each of the plurality of DC optimizers 130, can be input to the grid-connected inverter 150 through the second line 140. there is.

In addition, the grid-connected inverter 150 can convert the inverter input power into AC power through DC-AC (Alternating Current) power conversion and then supply the AC power to the power system 10. Here, the input of the grid-connected inverter 150 may be connected to the second line 140, and the output of the grid-connected inverter 150 may be connected to the power system 10.

In one embodiment, the grid-connected inverter 150 uses a link voltage (V _link in FIG. 1), which is the voltage of the inverter input power, and an AC voltage (V _ac in FIG. 1), which is the voltage of AC power, or a second line current. The arc occurring in the second line 140 can be detected using (I _dc in FIG. 1) and alternating current voltage (V _ac ).

The configuration in which the grid-connected inverter 150 detects an arc occurring in the second line 140 using the link voltage (V _link ) and the alternating current voltage (V _ac ) is that the DC optimizer 130 detects the first direct current voltage. It can correspond to a configuration that detects an arc occurring in the first line 120 using (V _IN ) and the second direct current voltage (V _out ).

And the configuration in which the grid-connected inverter 150 detects the arc occurring in the second line 140 using the second line current (I _dc ) and the alternating voltage (V _ac ) is provided by the DC optimizer 130. It may correspond to a configuration that detects an arc occurring in the first line 120 using the first line current (I _pv ) and the second direct current voltage (V _out ).

Here, the first direct current voltage (V _IN ) may correspond to the link voltage (V _link ), and the second direct current voltage (V _out ) may correspond to the alternating current voltage (V _ac ). And the first line current (I _pv ) may correspond to the second line current (I _dc ).

As above, the configuration in which the grid-connected inverter 150 detects the arc occurring in the second line 140 corresponds to the configuration in which the DC optimizer 130 detects the arc occurring in the first line 120. , a detailed description of the configuration in which the grid-connected inverter 150 detects the arc occurring in the second line 140 will be omitted.

As described above, in one embodiment, a power conversion device including one or more of the DC optimizer 130 and the grid-connected inverter 150 can detect an arc occurring in the line of the solar power generation system 100. Since there is no need to install a separate arc detection device in the solar power generation system 100, the cost efficiency of the solar power generation system 100 can be improved.

From now on, the power conversion device including one or more of the DC optimizer 130 and the grid-connected inverter 150 will be described in detail.

Figure 4 is a diagram briefly showing the configuration of a power conversion device according to an embodiment.

Referring to FIG. 4, the power conversion device 400 may include a power conversion unit 410 and an arc detection unit 420. Here, the power conversion device 400 may be a DC optimizer 130 or a grid-connected inverter 150.

The power conversion unit 410 may receive first power input through the line of the solar power generation system 100 and convert it into second power.

Here, when the power conversion device 400 is the DC optimizer 130, the power conversion unit 410 may be a DC-DC converter, and the line of the solar power generation system 100 is the first line 120. You can. And the first power may be first direct current power, and the second power may be second direct current power.

If the power conversion device 400 is a grid-connected inverter 150, the power conversion unit 410 may be a DC-AC inverter, and the line of the solar power generation system 100 may be the second line 140. there is. And the first power may be inverter input power, which is direct current power, and the second power may be alternating current power.

The arc detection unit 420 may have the following configuration to detect an arc occurring in the line of the solar power generation system 100.

First, the arc detection unit 420 can monitor the first voltage, which is the voltage of the first power, and detect whether the first voltage drops. Here, when the power conversion device 400 is the DC optimizer 130, the first voltage may be the first direct current voltage (V _IN ). When the power conversion device 400 is a grid-connected inverter 150, the first voltage may be a link voltage (V _link ).

Meanwhile, in order to detect whether the first voltage drops, the arc detection unit 420 may calculate the average value and instantaneous value of the first voltage for a preset time period. In addition, the arc detection unit 420 compares the value obtained by subtracting the instantaneous value from the average value with a previously stored first threshold value, and compares the instantaneous value with the previously stored second threshold value to detect whether the first voltage drops. there is.

Here, if the value obtained by subtracting the instantaneous value from the average value is less than the first threshold or the instantaneous value is greater than the second threshold, the arc detection unit 420 may detect that the first voltage has not dropped.

If the value obtained by subtracting the instantaneous value from the average value is greater than the first threshold and the instantaneous value is less than the second threshold, the arc detection unit 420 may detect that the first voltage has dropped. Here, the first threshold and the second threshold may be voltage thresholds.

Meanwhile, the arc detection unit 420 may monitor the line current, which is the current flowing in the line of the solar power generation system 100, and detect whether the line current decreases.

Specifically, the arc detection unit 420 can calculate the average value and instantaneous value of the line current for a preset time period. And the arc detection unit 420 can detect whether the line current decreases using the instantaneous value and the average value.

Here, if the value obtained by subtracting the instantaneous value from the average value is less than the first threshold or the instantaneous value is greater than the second threshold, the arc detection unit 420 may detect that the line current has not decreased.

If the value obtained by subtracting the instantaneous value from the average value is greater than the first threshold and the instantaneous value is less than the second threshold, the arc detection unit 420 may detect that the line current has decreased. Here, the first threshold and the second threshold may be current thresholds.

In one embodiment, when the power conversion device 400 is the DC optimizer 130, the line current may be the first line current (I _pv ) flowing in the first line 120. When the power conversion device 400 is a grid-connected inverter 150, the line current may be a second line current (I _dc ) flowing in the second line 140.

When the arc detection unit 420 detects a drop in the first voltage or a decrease in the line current, the arc detection unit 420 controls the power conversion unit 410 to output the second voltage from the power conversion unit 410. The voltage can be gradually reduced. Specifically, the arc detection unit 420 may control the power conversion unit 410 to reduce the second voltage from the normal value to the minimum value. And the arc detection unit 420 can control the power conversion unit 410 to maintain the second voltage at a minimum value for a certain period of time.

Here, the arc detection unit 420 gradually reduces the second voltage output from the power conversion unit 410 by reducing one of the duty cycle and operating frequency for power conversion of the power conversion unit 410 from the normal value to the minimum value. You can do it.

In one embodiment, when the power conversion device 400 is a DC optimizer 130, the second voltage may be a second direct current voltage (V _out ). When the power conversion device 400 is a grid-connected inverter 150, the second voltage may be an alternating current voltage (V _ac ).

Meanwhile, when the second voltage decreases, the arc detection unit 420 can detect whether an arc has occurred in the line of the solar power generation system 100 by checking the change in the first voltage.

Specifically, the arc detection unit 420 determines that an arc has occurred in the line of the solar power generation system 100 when the first voltage drops to a preset reference value when the second voltage decreases, and the second voltage decreases. When the first voltage rises, it can be determined that no arc has occurred in the line of the solar power generation system 100. Here, the line of the solar power generation system 100 is the first line 120 or the second line 140, and the arc occurring in the first line 120 or the second line 140 may be a DC series arc. there is.

The arc detection unit 420, which determines that an arc has occurred in the line of the solar power generation system 100, may control the power conversion unit 410 to stop power conversion. Additionally, the arc detection unit 420 may output an alarm sound or flash a warning light in response to arc occurrence.

Below, the process in which the power conversion device 400 detects an arc using the first voltage and the second voltage, and the process in which the arc is detected using the line current and the second voltage will be described, respectively.

Figure 5 is a flowchart showing a process in which a power conversion device detects an arc using a first voltage and a second voltage according to an embodiment.

Referring to FIG. 5, the power conversion device 400 can monitor the first voltage and confirm that the first voltage is maintained at the voltage when the solar panel 110 is operating in a normal state (S510).

In this state, the power conversion device 400 can repeatedly detect whether the first voltage drops (S520). In step S520, the power conversion device 400 may calculate the average value and instantaneous value of the first voltage for a preset time period. And, if the value obtained by subtracting the instantaneous value from the average value is greater than the first threshold and the instantaneous value is less than the second threshold, the power conversion device 400 may detect that the first voltage has dropped. The first threshold and the second threshold may be voltage thresholds.

If the value obtained by subtracting the instantaneous value from the average value is less than the first threshold or the instantaneous value is greater than the second threshold, the power conversion device 400 detects that the first voltage has not dropped and returns to step S510. The first voltage can be monitored.

When the power conversion device 400 detects a drop in the first voltage in step S520, the power conversion device 400 will gradually reduce the second voltage to confirm whether the cause of the drop in the first voltage is the occurrence of arc. (S530).

In step S530, the power conversion device 400 may linearly reduce the second voltage so that the second voltage goes from a normal value to a minimum value.

In step S530, the power conversion device 400 may reduce the second voltage to the minimum value and then maintain the second voltage at the minimum value for a certain period of time.

Meanwhile, when the second voltage is gradually reduced in step S530, the power conversion device 400 can determine whether the first voltage increases by checking the change in the first voltage (S540). Here, the power conversion device 400 determines whether the first voltage increases by comparing the magnitude of the first voltage at the time the second voltage reaches the minimum value and the first voltage at the time the second voltage begins to decrease. You can.

Additionally, the power conversion device 400 may determine whether the first voltage increases by checking whether the first voltage increases or decreases when the second voltage decreases.

If the first voltage rises when the second voltage decreases in step S540, or the first voltage at the time the second voltage reaches the minimum value is greater than the first voltage at the time the second voltage begins to decrease, the power The converter 400 determines that no arc has occurred in the line of the solar power generation system 100 and may gradually increase the second voltage (S550).

In this case, the drop in the first voltage detected by the power conversion device 400 in step S520 is caused by external factors such as a decrease in solar radiation reaching the solar panel 110 and an increase in the surface temperature of the solar panel 110. It can be.

In step S550, the first voltage at the point when the second voltage reaches the minimum value may rise to the voltage level during light load times when there is little demand for power produced by the solar power generation system 100. The voltage level during the light load time may be greater than the level of the first voltage when the solar panel 110 is operating in a normal state in step S510.

In step S550, the power conversion device 400 begins to linearly increase the second voltage maintained at a minimum value, thereby returning the second voltage to a normal value. When the power conversion device 400 returns the second voltage to the normal value, the level of the first voltage may become smaller than the voltage level during the light load time.

The power conversion device 400 may repeatedly perform steps S510 to S550 until the solar power generation system 100 is turned off (S560).

Meanwhile, if the first voltage drops to a preset reference value when the second voltage decreases in step S540, the power conversion device 400 may determine that an arc has occurred in the line of the solar power generation system 100 ( S570). In step S570, the reference value may be 0V (Volt), and the time when the first voltage reaches the reference value may coincide with the time when the second voltage reaches the minimum value. And when the first voltage drops to the reference value, the arc voltage may rise. Here, the arc voltage may refer to the voltage applied to the portion where the arc occurs in the line of the solar power generation system 100.

After step S570, the power conversion device 400 may stop power conversion for the first power by limiting the duty cycle or operating frequency. And the power conversion device 400 can output an alarm sound or flash a warning light in response to arc occurrence.

Figure 6 is a flowchart showing a process in which a power conversion device detects an arc using a first line current and a second voltage according to an embodiment.

Referring to FIG. 6, the power conversion device 400 can monitor the line current and confirm that the line current maintains the current value when the solar panel 110 is operating in a normal state (S610). Here, the power conversion device 400 can monitor the line current by receiving the current value of the line current from a current sensor that senses the line current on the line to the solar power generation system 100.

While the line current maintains the current value during normal operation of the solar panel 110, the power conversion device 400 can repeatedly detect whether the line current decreases (S620). In step S620, the power conversion device 400 can calculate the average value and instantaneous value of the line current for a preset time period. And, if the value obtained by subtracting the instantaneous value from the average value is greater than the first threshold and the instantaneous value is less than the second threshold, the power conversion device 400 may detect that the line current has decreased. The first threshold and the second threshold may be current thresholds.

If the value obtained by subtracting the instantaneous value from the average value is less than the first threshold or the instantaneous value is greater than the second threshold, the power conversion device 400 detects that the line current has not decreased and returns to step S610 to determine the line current. Current can be monitored.

When the power conversion device 400 detects a decrease in line current in step S620, the power conversion device 400 may gradually reduce the second voltage to confirm whether the decrease in line current is due to arc generation. (S630).

In step S630, the power conversion device 400 may linearly reduce the second voltage so that the second voltage goes from a normal value to a minimum value.

In step S630, the power conversion device 400 may reduce the second voltage to the minimum value and then maintain the second voltage at the minimum value for a certain period of time.

Meanwhile, when the second voltage is gradually reduced in step S630, the power conversion device 400 can determine whether the first voltage increases by checking the change in the first voltage (S640). Here, the power conversion device 400 determines whether the first voltage increases by comparing the magnitude of the first voltage at the time the second voltage reaches the minimum value and the first voltage at the time the second voltage begins to decrease. You can.

Additionally, the power conversion device 400 may determine whether the first voltage increases by checking whether the first voltage increases or decreases when the second voltage decreases.

If the first voltage rises when the second voltage decreases in step S640, or the first voltage at the time the second voltage reaches the minimum value is greater than the first voltage at the time the second voltage begins to decrease, the power The converter 400 may determine that no arc has occurred in the line of the solar power generation system 100 and gradually increase the second voltage (S650).

In this case, the drop in the first voltage detected by the power conversion device 400 in step S620 is caused by external factors such as a decrease in solar radiation reaching the solar panel 110 and an increase in the surface temperature of the solar panel 110. It can be.

At the point when the second voltage reaches the minimum value in step S650, the first voltage may increase to the voltage level during light load times when there is little demand for power produced by the solar power generation system 100. The voltage level during the light load time may be greater than the level of the first voltage when the solar panel 110 is operating in a normal state in step S610.

In step S650, the power conversion device 400 begins to linearly increase the second voltage maintained at a minimum value, thereby returning the second voltage to a normal value. When the power conversion device 400 returns the second voltage to the normal value, the level of the first voltage may become smaller than the voltage level during the light load time.

The power conversion device 400 may repeatedly perform steps S610 to S650 until the solar power generation system 100 is turned off (S660).

Meanwhile, if the first voltage drops to a preset reference value when the second voltage decreases in step S640, the power conversion device 400 may determine that an arc has occurred in the line of the solar power generation system 100 ( S670). In step S670, the reference value may be 0V (Volt), and the time when the first voltage reaches the reference value may coincide with the time when the second voltage reaches the minimum value. And when the first voltage drops to the reference value, the arc voltage may rise. Here, the arc voltage may refer to the voltage applied to the portion where the arc occurs in the line of the solar power generation system 100.

After step S670, the power conversion device 400 may stop power conversion to the first power by limiting the duty cycle or operating frequency. And the power conversion device 400 can output an alarm sound or flash a warning light in response to arc occurrence.

Terms such as “include,” “comprise,” or “have,” as used above, mean that the corresponding component may be included, unless specifically stated to the contrary, and do not exclude other components. It should be interpreted that it may further include other components. All terms, including technical or scientific terms, unless otherwise defined, have the same meaning as generally understood by a person of ordinary skill in the technical field to which the present invention pertains. Commonly used terms, such as terms defined in a dictionary, should be interpreted as consistent with the meaning in the context of the related technology, and should not be interpreted in an idealized or overly formal sense unless explicitly defined in the present invention.

The above description is merely an illustrative explanation of the technical idea of the present invention, and various modifications and variations will be possible to those skilled in the art without departing from the essential characteristics of the present invention. Accordingly, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention, but are for illustrative purposes, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be interpreted in accordance with the claims below, and all technical ideas within the equivalent scope should be construed as being included in the scope of rights of the present invention.

Claims (15)

In a method for detecting an arc in a power conversion device of a solar power generation system,
detecting a drop in a first voltage, which is the voltage of first power input through a line of the solar power generation system;
In order to determine the cause of the drop in the first voltage, gradually reducing the second voltage, which is the voltage of the second power output through power conversion for the first power;
confirming a change in the first voltage; and
If the first voltage drops to a preset reference value in the checking step, determining that an arc has occurred in the line
An arc detection method comprising: The method of claim 1, wherein in the detecting step
An arc detection method in which the power conversion device calculates an average value and an instantaneous value of the first voltage for a preset time period, and detects a drop in the first voltage using the instantaneous value and the average value. According to claim 2,
The power conversion device detects that the input voltage has dropped when a value obtained by subtracting the instantaneous value from the average value is greater than a first threshold value and the instantaneous value is less than a second threshold value. The method of claim 1, wherein after the determining step,
Stopping power conversion for the first power
An arc detection method further comprising: According to claim 1,
The first power and the second power are direct current power, and the power conversion device is a DC optimizer that performs DC (Direct Current)-DC power conversion. According to claim 1,
The first power is direct current power, the second power is alternating current power, and the power conversion device is a grid-connected inverter that performs DC-AC (Alternating Current) power conversion. According to claim 1,
If the first voltage rises in the checking step, determining that an arc has not occurred and gradually increasing the second voltage
An arc detection method further comprising: In a method for detecting an arc in a power conversion device of a solar power generation system,
Checking the average value and instantaneous value of the line current flowing through the line of the solar power generation system;
detecting a decrease in the line current using the average value and the received value;
In order to determine the cause of the decrease in the line current, gradually reducing the second voltage, which is the voltage of the second power output through power conversion for the first power input through the line;
Checking a change in a first voltage, which is the voltage of the first power; and
If the first voltage drops to a preset reference value in the checking step, determining that the cause of the decrease in the line current is an arc occurring in the line.
An arc detection method comprising: The method of claim 8, wherein in the detecting step
The power conversion device detects that the line current decreases when a value obtained by subtracting the instantaneous value from the average value is greater than a first threshold value and the instantaneous value is less than a second threshold value. According to claim 8,
If the first voltage rises while the second voltage decreases in the checking step, determining that an arc has not occurred and gradually increasing the second voltage
An arc detection method further comprising: A power conversion unit that converts first power input through a line connected to a solar panel (PV, Photovoltaics) into second power; and
When the first voltage, which is the voltage of the first power, is monitored and a drop in the first voltage is detected, the power conversion unit is controlled to gradually reduce the second voltage, which is the voltage of the second power output from the power conversion unit. , an arc detection unit that detects whether an arc has occurred in the line by checking the change in the first voltage when the second voltage decreases.
An arc detection device comprising: According to claim 11,
The arc detector determines that an arc has occurred in the line if the first voltage drops to a preset reference value when the second voltage decreases, and if the first voltage increases when the second voltage decreases, An arc detection device that determines that an arc has not occurred in the line. According to claim 11,
The arc detection unit controls the power conversion unit to reduce the second voltage from a normal value to a minimum value and then maintain the second voltage at the minimum value for a certain period of time. According to claim 11,
The arc detector calculates an average value and an instantaneous value of the first voltage for a preset time period, compares a value obtained by subtracting the instantaneous value from the average value with a previously stored first threshold value, and compares the instantaneous value with the previously stored first threshold value. An arc detection device that detects a drop in the first voltage by comparing it to a second threshold. According to claim 14,
The arc detection unit detects that the first voltage has dropped when a value obtained by subtracting the instantaneous value from the average value is greater than the first threshold value and the instantaneous value is less than the second threshold value.

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