JP2013055132A - Method of fault diagnosis of photovoltaic power generation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fault diagnosis method which does not require time or work without adding excess measuring means or communication means in a photovoltaic power generation system.SOLUTION: A fault diagnosis method calculates first working voltage and first working current (S102) of a solar cell array at normal temperature under a measured amount of solar radiation pb, calculates working temperature Tb of the solar cell array (S103) with the use of the first working voltage and measured second working voltage, calculates third working current (S104) at normal temperature with the use of measured second working current and the working temperature Tb, compares the first working current with the third working current (S106), and calculates the number of solar cell modules having a disconnected wire in the solar cell array based on the comparison result.

Description

  The present invention relates to a failure diagnosis method for a photovoltaic power generation system including a large number of solar cell modules.

  In recent years, large-scale photovoltaic power generation systems such as mega solar have attracted attention. In the mega solar system, several hundred to several tens of thousands of 100-200 W class solar cell modules are arranged at one power generation site.

  As a method for detecting a failure of a solar cell module, visual inspection, inspection of heat generation by a thermometer, and inspection of electrical characteristics by a tester are performed. Since these inspections are performed for each solar cell module, there is a problem that when the number of solar cell modules increases, labor and time required for the inspection increase.

  In order to quickly check the status of the solar cell module for this problem, a measurement means and a communication means are provided for each solar cell module, thereby controlling the measured characteristic value and a signal indicating the identifier of the solar cell module. A method of transmitting to an apparatus is described in Patent Document 1.

  Furthermore, in order to automatically determine whether or not a failure has occurred in the solar cell with respect to the result transmitted from the communication means, a method for determining a failure by comparing the transmitted result with a threshold is disclosed in Patent Literature It is written in 2.

JP 2004-221479 A JP 2010-123880 A

  However, although the problem of the labor of measuring each solar cell module is solved by using the technique of the above-mentioned prior art document, a new measure that a measuring means and a communication means must be provided for each solar cell module. Challenges arise.

  In view of the above circumstances, an object of the present invention is to provide a failure diagnosis method that does not require extra time and labor in a photovoltaic power generation system without adding extra measurement means and communication means.

  In order to solve the above problems, a failure diagnosis method for a photovoltaic power generation system according to one aspect of the present invention includes a module in which a plurality of solar cells are connected in series, and a protection diode is connected to electrodes at both ends of the series connection portion. As a unit of two solar cell modules, a solar cell string in which the modules are connected in series, a solar cell array in which the solar cell strings are connected in parallel, a voltage detection unit that detects an output voltage of the solar cell array, and In a failure diagnosis method for a solar power generation system having a current detection unit for detecting an output current of a solar cell array and a solar radiation measurement unit, the solar cell array at room temperature in an environment of the solar radiation amount pb measured by the solar radiation measurement unit Calculating a first operating voltage and a first operating current; and a second operating voltage detected by the voltage detector. Calculating the operating temperature Tb of the solar cell array using the first operating voltage, and calculating the third operating current at room temperature using the second operating current and the operating temperature Tb. Comparing the first operating current and the third operating current, and calculating the number of disconnected solar cell modules in the solar cell array based on the comparison result. Features.

  Further, a plurality of solar cells are connected in series, a module in which a protection diode is connected to electrodes at both ends of a series connection portion as a unit of one solar cell module, a solar cell string in which the modules are connected in series, A solar cell array in which solar cell strings are connected in parallel, a voltage detector that detects an output voltage of the solar cell array, a current detector that detects an output current of the solar cell array, solar radiation measuring means, and the solar In a failure diagnosis method for a photovoltaic power generation system having an operating temperature measuring means for measuring an operating temperature of a battery array, the solar radiation amount pb measured by the solar radiation measuring means and the operating temperature Tb measured by the operating temperature measuring means Calculating a maximum operating voltage of the solar cell array in the maximum operating voltage and the voltage detector Comparing the detected operating voltage have, characterized in that it comprises the steps of: calculating a number of solar cell modules disconnected within said solar cell array on the basis of the result of the comparison.

  According to the present invention, in a fault diagnosis method for a photovoltaic power generation system, there is no extra measurement means and communication means, and there is no time or labor, and it is present in a solar cell array using data that has been collected in the past. It becomes possible to know the number of failures of the solar cell module.

It is a figure which shows the structure of a solar cell array. It is a figure which shows the structure of a large-scale photovoltaic power generation system. It is a figure which shows the structure which monitors the characteristic of a solar cell using a part of structure of the power conditioner (PCS) in a solar energy power generation system, and the measuring device in PCS. It is a figure which shows the electric current path | route of a solar cell module, (a) shows a normal case, (b) shows a case where a solder peeling failure occurs, and (c) shows a case where a disconnection failure occurs. It is a figure which shows the change of the characteristic when a solar cell module fails. It is a figure which shows the method of the array calculation of a solar cell array, (a) is a case of a string analysis, (b) is a case of an array analysis. It is the solar energy power generation system which concerns on Example 1 of this invention, and is the figure which showed the structure for monitoring the characteristic of a solar cell array. It is a flowchart which shows the procedure of the failure diagnosis method which concerns on Example 1 of this invention, and is the figure which showed the algorithm for calculating how many solar cell modules which have a disconnection failure exist in a solar cell array. It is a flowchart which shows the procedure of the failure diagnosis method which concerns on Example 1 of this invention, and is the figure which showed the algorithm for calculating how many solar cell modules with which solder peeling failure existed in a solar cell array. It is a photovoltaic power generation system which concerns on Example 2 of this invention, and is the figure which showed the structure for monitoring the characteristic of a solar cell array. It is a flowchart which shows the procedure of the failure diagnostic method which concerns on Example 2 of this invention, and is the figure which showed the algorithm for calculating how many solar cell modules which have a disconnection failure exist in a solar cell array. It is the flowchart which shows the procedure of the failure diagnosis method which concerns on Example 2 of this invention, and is the figure which showed the algorithm for calculating how many solar cell modules with which the solder peeling failure existed in the solar cell array.

  Hereinafter, the embodiment will be described in detail.

  FIG. 1 is a configuration diagram of the photovoltaic power generation array 1. The solar cell array 1 is configured by arranging units called a solar cell string 3 in which a plurality of solar cell modules 2 are arranged in series in parallel. Each solar cell module 2 is provided with a bypass diode 4 for preventing a reverse current from flowing when a reverse bias is applied. In order to prevent a current from flowing in the reverse direction even in each string unit. The backflow prevention diode 5 is attached. It is also possible to select the current path of each string by selecting the switch 6. In addition, the same code | symbol shows the same component.

  FIG. 2 is a block diagram showing a functional configuration of the photovoltaic power generation system. The plurality of solar cell strings 3 are connected in parallel through the backflow prevention diode 5 and the switch 6 in the connection box 7. The solar cell arrays configured by the parallel connection are further connected in parallel by the current collecting rack 8 via the switch 9. The power conditioner 10 is connected to both end electrodes of a large-scale unit in which the plurality of solar cell arrays are connected in parallel. The power conditioner 10 includes a control unit 10a that controls DC power so that maximum power can be extracted from a plurality of parallel-connected solar cell arrays, and a DC / AC conversion unit that converts the DC power generated by the control into an AC signal and outputs the AC signal. 10b.

  FIG. 3 is a block diagram of the control unit 10a that controls the DC power of the power conditioner. Controlling DC power so that maximum power can be extracted from the solar cell array is called MPPT control (Maximum Power Point Tracking). This MPPT control is achieved by controlling the DC / DC converter circuit using the measured DC power in the ammeter 20 and the voltmeter 21 in the control unit 10a. In general, in a large-scale photovoltaic power generation system, a direct-current voltage and direct-current measured during MPPT control and an amount of solar radiation measured by the pyranometer 22 installed at the power generation site are transmitted to the monitor 10c. That is, with respect to the DC voltage and DC current, the power generation amount in power conditioner units is monitored.

  The failure of the solar cell module 2 proceeds by a mechanism as shown in FIGS. 4 (a), 4 (b), and 4 (c). The solar cell module 2 is configured by connecting a plurality of solar cells 11 in series. Connection between cells is performed by soldering. When the solder is peeled off, the resistance component 13 of the wiring increases. At this time, the normal state of FIG. 4A shifts to the state of FIG. 4B having the hot spot 12b. A hot spot is a phenomenon in which a solder peeling cell becomes hot compared to the surroundings, and failure diagnosis using a thermo camera or the like is used as a general technique.

  Further, when the solder is peeled off, the value of the wiring resistance is further increased, and the current driving capability of the solar cell module 2 having the hot spot 12b is significantly reduced. At this time, the bypass diode 4 operates. This state is shown in FIG. This phenomenon is generally diagnosed by observing heat generation in a junction box in which the bypass diode 4 is mounted. Reference numeral 12c indicates a broken cell. Further, 14a represents a current flowing through a normal string, 14b represents a current flowing through a string including a hot spot, and 14c represents a current flowing through a string including a disconnected cell.

Here, the relationship between wiring resistance and loss, which is the main cause of failure (solder peeling and disconnection), is quantified. Assuming that the wiring resistance is Rs and the loss is Ploss, Ploss can be expressed by a change (に 対 す る Ploss / ∂Rs) with respect to a certain loss value P0 and Rs, as shown in Expression (1).

Ploss = P0 + (∂Ploss / ∂Rs) ・ ΔRs… (1)

As shown in FIG. 4, when the wiring resistance Rs of the failed module increases, a current flows through the bypass diode 4 from a certain point in time. FIG. 5 shows changes in the solar cell characteristics at this time. The current-voltage characteristic of the solar cell changes from the characteristic 15a to 15b as the wiring resistance Rs increases, and it is assumed that m modules are disconnected from the solar cell string in which n modules are connected in series. As shown in FIG. 5, a characteristic 15c is obtained by shifting the voltage by a ratio of m / n while maintaining the current Ipmax with respect to the normal state. At this time, since the loss is m / n, this is set as P0.

The formula for a solar cell module composed of Ncells is: I: Output current [A] Is: Reverse saturation current [A] V: Output voltage [V] Isc: Short-circuit current [A] T: Solar cell element Absolute temperature [K] k: Boltzmann constant [J / K] Rs: Wiring resistance [Ω] q: Electron charge [C] Rsh: Parallel resistance [Ω] nf: Junction constant p: Solar radiation intensity [kW / m ² ] Can be expressed by equation (2).

I = Isc · p – Is · {exp (q · (V / (Ncell) + Rs · I) / (nf · k · T))}
− (V / (Ncell) + Rs · I) / Rsh (2)

Solar radiation intensity Ea (1 kW / m ² ), normal temperature (Ta = 298K) Ia: Output current [A] Va: Output voltage [V] Isca: Short-circuit current [A] and Rs: Wiring resistance [Ω], Short-circuit current Using the temperature coefficient α [A / ° C], the open circuit voltage coefficient β [V / ° C], and the curve correction factor K, Ib: output current [A] and Vb: output voltage at solar radiation intensity Eb and temperature Tb [ V] can be calculated using Equation (3) and Equation (4).

Ib = Ia + Isca ・ (Eb / Ea − 1) + α ・ (Tb − Ta) (3)

Vb = Va + β ・ (Tb − Ta) − Rs ・ (Ib − Ia) − K ・ Ib ・ (Tb − Ta) (4)

The normal Vpmax of a solar cell string in which n modules are connected in series is normal Rs is sufficiently small and the leakage resistance Rsh is sufficiently large and can be ignored. It can be expressed as equation (5). Therefore, Pmax can be expressed as an equation (5) obtained by multiplying Vpmax by Ipmax.

Vpmax = n · {Ncell · (nf · k · T) / q · ln ((Isc · p − Ipmax) / Is)} (5)

Pmax = n · {Ncell · (nf · k · T) / q · ln ((Isc · p − Ipmax) / Is)} · Ipmax (6)

On the other hand, regarding the voltage and power when the current I of the solar cell string in which m of the n modules are disconnected flows, the effect of increasing Rs appears, so express them as equations (7) and (8). Can do.

V = (n−m) ・ {Ncell ・ (nf ・ k ・ T) / q ・ ln ((Isc ・ p − I) / Is)}
-M · Ncell · Rs · I (7)

P = (n−m) ・ {Ncell ・ (nf ・ k ・ T) / q ・ ln ((Isc ・ p − I) / Is)} ・ I − m ・ Ncell
・ Rs ・ I ² (8)

Therefore, Ploss becomes Formula (9), and the change (∂Ploss / ∂Rs) with respect to Rs can be expressed as Formula (10).

Ploss = P / Pmax
＝ {(n−m) ・ {Ncell ・ (nf ・ k ・ T) / q ・ ln ((Isc ・ p − I) / Is)} ・ I − m ・ Ncell
・ Rs ・ I ² } / {n ・ {Ncell ・ (nf ・ k ・ T) / q ・ ln ((Isc ・ p − Ipmax) / Is)} ・ Ipmax}
... (9)

(∂Ploss) / ∂Rs
= (− M · I ² ) / {n · {(nf · k · T) / q · ln ((Isc · p − Ipmax) / Is)} · Ipmax}
... (10)

Here, when Rth is defined as in Expression (11) and substituted into Expression (10), it can be expressed as in Expression (12).

Rth = {(nf.k.T) /q.ln ((Isc.p-Ipmax) / Is)} / Ipmax (11)

(∂Ploss) / ∂Rs = (− (m / n)) ・ (I / Ipmax) ²・ (1 / Rth) (12)

Since one extra disconnection is used as a reference, if P0 = (m + 1) / n and ΔRs = (Rth-Rs) in equation (1), then Ploss is given by equation (13) Can be represented.

Ploss = ((m + 1) / n)-(m / n)-(I / Ipmax) ^2- (1-Rs / Rth) ... (13)

In equation (13), when Rs = Rth, P0 = (m + 1) / n. In other words, Rth is the wiring resistance threshold at which the bypass diode starts to turn on, and the loss of the panel connected in series is calculated by calculating the change in Rs based on the loss at the point where the bypass diode starts to operate. Can be easily quantified.

  From the above, it is possible to quantize Rs according to the loss by using the equations (11) and (13).

  Here, the calculation method of the solar cell array 1 is shown in FIG. This array calculation is called an array operation. Array operations are realized by a combination of string analysis and array analysis. When performing string analysis, since the currents flowing through a plurality of modules are common, as shown in FIG. 6A, the module voltage of each solar cell when a certain current I flows: V [1], V [2], V [3],... V [N−1] and V [N] are obtained from equation (2), and the sum Vstring is obtained. When the voltage is calculated from the equation (2), an inverse function is obtained, but it can be easily obtained by applying an iterative operation such as Newton's method. When the module is peeled off or disconnected, the voltage drops compared to the normal module voltage. When the module is disconnected, the bypass diode functions, so the module voltage is considered to be approximately zero. When performing an array analysis, the voltages applied to a plurality of strings are common, so as shown in FIG. 6 (b), the current extracted from each string when a certain voltage V is applied: I [1], I [2]... I [N] is obtained from equation (2), and the sum: Iarray is obtained. The array operation is an operation for obtaining the current-voltage characteristics of the solar cell array by a combination of string analysis and array analysis.

  As shown in FIG. 7, the information obtained for the diagnosis is the maximum operating voltage obtained from the voltmeter 21 and the ammeter 20 mounted on the controller 10a in the power conditioner 10 that controls the solar cell array 1. Vpmax_b and maximum operating current: log data of Ipmax_b and solar radiation intensity obtained from the pyranometer 22 installed in the power generation site: log data of pb, operating temperature obtained from the temperature sensor 16 of the solar cell array: log data of Tb is there. These data are transmitted to the monitor 10c.

The solar radiation intensity measured by the pyranometer 22: pb may be substituted into p: solar radiation intensity [kW / m ² ] in the equation (2).

  Regarding the operating temperature Tb measured by the temperature sensor 16, Tb indicating the operating temperature itself in the formula (2): Tb is substituted for the absolute temperature [K] of the solar cell element, and the change with respect to the temperature is large. Isc: Calculates the short-circuit current [A], Is: reverse saturation current [A].

Isc: short circuit current [A] at the operating temperature: Tb can be obtained by using Expression (14), which is a modification of Expression (3).

Isc = Isca + α ・ (Tb − Ta) (14)

Here, Isca is a short circuit current [A] at normal temperature (Ta = 298K), and α [A / ° C.] is a temperature coefficient of the short circuit current.

Is at operating temperature: Tb: Reverse saturation current [A] is calculated via the open-circuit voltage Voc and the open-circuit voltage temperature coefficient β [V / ° C.]. First, when the reverse saturation current [A] at normal temperature Ta is Isa and the open circuit voltage Voc_a at normal temperature Ta is obtained from equation (2), equation (15) is obtained.

Voc_a = n. {Ncell. (Nf.k.Ta) /q.ln ((Isca.p) / Isa)} (15)

Similarly, the open circuit voltage at the operating temperature Tb of the array is expressed by equations (16) and (17).

Voc = Voc_a + β ・ (Tb − Ta) (16)

Voc = n · {Ncell · (nf · k · Tb) / q · ln ((Isc · p) / Is)} (17)

By solving the equations (15) and (17), it is possible to calculate the reverse saturation current Is at Tb from each parameter value at normal temperature and the measured operating temperature Tb.

  By performing array calculation using the values of Isc: short-circuit current [A] and Is: reverse saturation current [A] at the operating temperature Tb, the exposure state of the solar cell array (irradiation amount: pb, operating temperature) : Ipmax and Vpmax in Tb) are calculated. Further, Ipmax is also used for calculating Rth defined by the equation (11). Once Rth is calculated, Rs can be quantized according to the failure using equation (13).

  It exists in the solar cell array by using the array calculation described above, the calculation of the parameters constituting the equation (2), the quantization of Rs, and the measured maximum operating voltage: Vpmax_b and maximum operating current: Ipmax_b. The number of module failures to be performed can be obtained. FIG. 8A and FIG. 8B show a calculation flow showing the procedure of the failure diagnosis method for the photovoltaic power generation system.

  Calculation of the number of module failures in the solar cell array is performed in the order of obtaining the number of modules in which disconnection has occurred, and then obtaining the number of modules in which solder peeling has occurred.

  As a first step, a method of obtaining the number of modules in which a disconnection has occurred will be described using the flow of FIG. First, the solar radiation amount: pb and the operating temperature: Tb of the measurement data are taken in, and the parameters under the exposure conditions are calculated (S801). Next, an array operation is performed to calculate the maximum operating voltage Vpmax under conditions where there is no failure (S802). Here, a value obtained by subtracting the measured maximum operating voltage Vpmax_b from the calculated Vpmax is set as ΔV (S803). Next, ΔV is compared with 0 (S804). If the calculated value Vpmax is larger (ΔV> 0), x indicating the number of disconnected modules is incremented (S805), and if it is equal to Vpmax (ΔV = 0) and x as they are (S806). If Vpmax is smaller (ΔV <0), x is decremented (S807), and the array operation is performed again. In the array operation, which module is to be disconnected is randomly selected using the Monte Carlo method or the like. The above operation is monitored by Count (S808), and the array calculation and the setting of the number of disconnections are repeated until Count is increased up to the number of modules constituting the solar cell array (S809).

  As a second stage, a method of obtaining the number of modules in which solder peeling has occurred will be described using the flow of FIG. First, as in FIG. 8A, the amount of solar radiation of measurement data: pb and the operating temperature: Tb are taken in, and parameters under exposure conditions are calculated (S811). Simultaneously with this calculation, the wiring resistance value Rs ′ at which the module loss is 10% is set using the equations (11) and (13). Next, the number of breaks x set in FIG. 8A is taken in and array calculation is performed (S812). As described above, the module to be disconnected is randomly extracted using the Monte Carlo method or the like. In the array calculation here, the maximum operating voltage Vpmax and the maximum operating current Ipmax of the solar cell array including the disconnection information are calculated, and the maximum power Pmax is calculated by multiplying them. A value obtained by subtracting the measured maximum power Pmax_b from the calculated Pmax is set as ΔP (S813). Next, this ΔP is compared with 0 (S814). If the calculated value Pmax is larger (ΔP> 0), y indicating the number of modules having the wiring resistance Rs ′ is incremented (S815), and it should be the same as Pmax. If (ΔP = 0), y remains unchanged (S816), and if Pmax is smaller (ΔP <0), y is decremented (S817), and the array operation is performed again. In the array calculation, Rs' is set as the wiring resistance of which module is randomly selected using the Monte Carlo method or the like. The above operation is monitored by Count (S818), and is repeated until Count is increased to the number of modules constituting the solar cell array (S819). In this embodiment, the module loss is 10%, but is not necessarily limited to 10%.

  From the above flow, it is possible to grasp the number of failures of the solar cell modules existing in the solar cell array without adding measuring means and communication means for each solar cell.

  When this flow is applied with all the selection switches 9 in FIG. 2 turned on and it is determined that the number of failures is large, the number of failures can be monitored by the selection switch 9 in units of the solar cell array 1. it can. Further, for the solar cell array 1 determined to have a large number of failures, the failure inspection can be performed in units of solar cell strings by switching the selection switch 6 in FIG.

  A second embodiment will be described with reference to FIG. 9, FIG. 10 (a), and FIG. 10 (b). Note that the matters described in the first embodiment but not described in the present embodiment can be applied to the present embodiment as long as there is no particular circumstance.

  FIG. 9 shows, as information obtained for diagnosis, the maximum operating voltage obtained from the voltmeter 21 and the ammeter 20 mounted on the control unit 10a in the power conditioner 10 that controls the solar cell array: Vpmax_b and the maximum operation. It shows the case of only log data of current: log data of Ipmax_b and solar radiation intensity obtained from the pyranometer 22 installed in the power generation site: log data of pb.

  Normally, a thermocouple or the like is used as the temperature sensor, but generally the measurement accuracy is low. Therefore, in this embodiment, the failure is calculated only from the log data of Vpmax_b, Ipmax_b, and pb.

First, from the temperature coefficient β [V / ° C.] of the open-circuit voltage, the open-circuit voltage: Voc can be expressed as in Expression (18), where the open-circuit voltage at room temperature: Ta is Voc_a.

Voc = Voc_a + β · (Tb − Ta) (18)

Next, the following relationship is obtained from the equations (2), (3), and (14). Room temperature: Under the condition of Ta,

Ipmax_a ≒ j · Isca (j: constant) (19)

Similarly, under the condition of the operating temperature: Tb,

Ipmax ≒ i ・ Isc (l: constant)… (20)

It is.

If Is is eliminated from the equations (5) and (17) and the operating temperature is Tb, it can be expressed by the equation (21).

(Vpmax−Voc) / Tb = n ・ {Ncell ・ (nf ・ k ・ Tb) / q} ・ ln {(Isc ・ p − Ipmax) / Isc}
... (21)

Normal temperature: If it asks similarly about Ta, formula (22) will be obtained.

(Vpmax_a−Voc_a) / Ta = n ・ {Ncell ・ (nf ・ k ・ Ta) / q} ・ ln {(Isca ・ p
− Ipmax_a) / Isca} (22)

Here, when the relationship between the equations (21) and (22) is obtained using the equations (19) and (20), Vpmax can be obtained as in the equation (23).

Vpmax = {ln (1−i)} / {ln (1−l)} ・ {(Vpmax_a−Voc_a) / Ta} ・ Tb + Voc
... (23)

For simplicity, assuming i = j, equation (24) is obtained.

Vpmax = {(Vpmax_a−Voc_a) / Ta} · Tb + Voc (24)

Substituting equation (18) into equation (24) with Vpmax as the measured value Vpmax_b,

Tb = (Vpmax_b−Voc_a + β · Ta) / {((Vpmax_a−Voc_a) / Ta) + β} (25)

The operating temperature of the solar cell array: Tb can be determined from the open voltage at room temperature (Ta = 298K): Voc_a, the temperature coefficient β [V / ° C] of the open voltage, the maximum operating voltage: Vpmax_a and the measured Vpmax_b. It becomes.

After obtaining Tb, the operating current Ipmax_a ′ at room temperature is obtained from the equation (4) obtained by modifying the equation (3). Isca is obtained from the temperature coefficient α of the short circuit current and the measured value: Ipmax_b.

Ipmax_a ′ = Ipmax_b − Isca · (pb − 1) + α · (Tb − Ta) (26)

The calculated value Tb of the operating temperature of the solar cell array and the calculated value Ipmax_a ′ of the operating current at room temperature are incorporated in the flow of the first embodiment. As a result, the maximum operating voltage obtained from the voltmeter and ammeter installed in the inverter and the maximum operating current: Vpmax_b and the maximum operating current: log data of Ipmax_b and the solar radiation intensity obtained from the pyranometer installed in the power generation site: pb The number of failures in the solar cell array can be calculated from only the log data. FIG. 10 (a) and FIG. 10 (b) show a calculation flow showing the procedure of the failure diagnosis method for the photovoltaic power generation system.

  The number of failed modules in the solar cell array is calculated in the same order as in the first embodiment, in which the number of modules in which disconnection has occurred is first obtained, and then the number of modules in which solder peeling has occurred is obtained.

  As a first stage, a method of obtaining the number of modules in which a disconnection has occurred will be described using the flow of FIG. First, the amount of solar radiation of measurement data: pb is taken in, and the parameters at the amount of solar radiation: pb and room temperature: Ta are calculated (S101). Next, array operation is performed to calculate the maximum operating voltage Vpmax_a and the maximum operating current Ipmax_a under the condition that there is no failure (S102). Here, using the calculated Vpmax_a and the measured maximum operating voltage Vpmax_b, the open-circuit voltage Voc_a at the normal temperature Ta calculated using the formula (2) and the array calculation, and the open-circuit voltage temperature coefficient β, the formula (25) And the operating temperature Tb of the solar cell array is calculated (S103). The calculated Tb and the measured maximum operating current Ipmax_b are substituted into equation (26) to calculate the operating current Ipmax_a ′ at room temperature (S104). Ipmax_a 'and Ipmax_a obtained by array calculation are both values calculated under the conditions of room temperature: Ta and solar radiation intensity pb kW / m2. In consideration, the value obtained from the measured value is equal to or smaller than the theoretical value, so that Ipmax_a ≧ Ipmax_a ′ holds. When ΔI = Ipmax_a−Ipmax_a ′ (S105), ΔI> 0 (S106) is satisfied and Ipmax_a≈Ipmax_a ′ (S108), the number of disconnections x is increased (S107), the operating temperature Tb is calculated, and Ipmax_a 'The calculation operation is repeated. When ΔI <0 (S106), x and Tb are returned to the state immediately before the repeated calculation (S109), and the repeated calculation is terminated, so that the condition of ΔI> 0 and Ipmax_a≈Ipmax_a ′ is satisfied. It is filled.

  Which cluster is to be disconnected is selected at random using a method such as the Monte Carlo method as in the first embodiment.

  Next, the second stage will be described with reference to the flow of FIG. This flow is merely the replacement of the measured operating temperature: Tb with the operating temperature: Tb calculated in the first stage with respect to the flow of FIG. 8B, and the calculation flow is the same as in the first embodiment. . That is, step S111 to step S119 shown in FIG. 10B correspond to step S811 to step S819 shown in FIG. 8B, respectively.

  From the above flow, it becomes possible to grasp the number of failures of the solar cell modules existing in the solar cell array without adding measuring means, communication means, and temperature measuring means for each solar cell.

  As in the first embodiment, this flow is applied with all the selection switches 9 in FIG. 2 turned on, and when it is determined that the number of failures is large, the number of failures in the unit of the solar cell array 1 is determined by the selection switch 9. Monitoring can be realized. Furthermore, about the solar cell array 1 judged that there are many faults, it can be narrowed down to which string contains many faults by switching the selection switch 6 of FIG.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of a certain embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of a certain embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  A failure diagnosis that does not require time and labor without adding measurement means and communication means is possible in the solar cell system.

DESCRIPTION OF SYMBOLS 1 ... Solar cell array, 2 ... Solar cell module, 3 ... Solar cell string, 4 ... Bypass diode, 5 ... Backflow prevention diode, 6 ... Switch, 7 ... Junction box, 8 ... Current collection rack, 9 ... Switch, 10 ... Power conditioner, 10a ... control unit, 10b ... DC / AC conversion unit, 10c ... monitoring monitor, 11 ... solar cell, 12b ... hot spot, 12c ... disconnected cell, 13 ... wiring resistance component, 14a ... flowing through normal string Current, 14b: Current flowing through a string including a hot spot, 14c: Current flowing through a string including a disconnected cell, 15a: Characteristic when normal, 15b: Characteristic when including a hot spot (solder peeling), 15c: Disconnected cell 16 ... temperature sensor, 20 ... ammeter, 21 ... voltmeter, 22 ... pyranometer.

Claims (12)

As a unit of one solar cell module, a plurality of solar cells are connected in series, and a module in which protective diodes are connected to electrodes at both ends of the series connection part,
A solar cell string in which the modules are connected in series;
A solar cell array in which the solar cell strings are connected in parallel;
A voltage detector for detecting the output voltage of the solar cell array;
A current detector for detecting an output current of the solar cell array;
In a failure diagnosis method for a solar power generation system having solar radiation measuring means,
Calculating a first operating voltage and a first operating current at normal temperature of the solar cell array under an environment of an amount of solar radiation pb measured by the solar radiation measuring means;
Calculating an operating temperature Tb of the solar cell array using the second operating voltage detected by the voltage detector and the first operating voltage;
Calculating a third operating current at room temperature using the second operating current and the operating temperature Tb;
Comparing the first operating current and the third operating current;
Calculating the number of disconnected solar cell modules in the solar cell array based on the comparison result, and a failure diagnosis method for a solar power generation system, comprising: Setting a wiring resistance Rs ′ for a predetermined loss of the solar cell module;
The first maximum power of the solar cell array, the second operating current, and the second operating voltage calculated under the conditions of the calculated number of disconnected solar cell modules, the amount of solar radiation pb, and the operating temperature Tb. Comparing the second maximum power calculated from the above while varying the number of solar cell modules having the wiring resistance Rs ′;
The failure diagnosis method for a photovoltaic system according to claim 1, further comprising: calculating a number of solar cell modules having the wiring resistance Rs ′ in the solar cell array according to the comparison result. . The solar power generation system further includes a plurality of the solar cell arrays connected in parallel, and a selection unit for selecting each of the solar cell arrays,
The solar power generation system according to claim 1, further comprising a step of calculating the number of disconnected solar cell modules existing in each solar cell array by switching the solar cell array using the selection unit. Fault diagnosis method. The solar power generation system further includes a plurality of the solar cell arrays connected in parallel, and a selection unit for selecting each of the solar cell arrays,
The method according to claim 2, further comprising: calculating the number of solar cell modules having the wiring resistance Rs ′ present in each solar cell array by switching the solar cell array using the selection unit. Fault diagnosis method for solar power generation system. The solar power generation system further includes selection means for selecting each of the solar cell strings,
2. The solar power generation system according to claim 1, further comprising: calculating the number of disconnected solar cell modules existing in each solar cell string by switching the solar cell strings using the selection unit. Fault diagnosis method. The solar power generation system further includes selection means for selecting each of the solar cell strings,
The method according to claim 2, further comprising: calculating the number of solar cell modules having the wiring resistance Rs ′ present in each solar cell string by switching the solar cell strings using the selection unit. Fault diagnosis method for solar power generation system. As a unit of one solar cell module, a plurality of solar cells are connected in series, and a module in which protective diodes are connected to electrodes at both ends of the series connection part,
A solar cell string in which the modules are connected in series;
A solar cell array in which the solar cell strings are connected in parallel;
A voltage detector for detecting the output voltage of the solar cell array;
A current detector for detecting an output current of the solar cell array;
Solar radiation measuring means;
In a fault diagnosis method for a photovoltaic power generation system having an operating temperature measuring means for measuring the operating temperature of the solar cell array,
Calculating the maximum operating voltage of the solar cell array in the environment of the solar radiation amount pb measured by the solar radiation measuring means and the operating temperature Tb measured by the operating temperature measuring means;
Comparing the maximum operating voltage with the operating voltage detected by the voltage detector;
Calculating the number of disconnected solar cell modules in the solar cell array based on the comparison result, and a failure diagnosis method for a solar power generation system, comprising: Setting a wiring resistance Rs ′ for a predetermined loss of the solar cell module;
The first maximum power of the solar cell array calculated from the calculated number of disconnected solar cell modules and the solar radiation amount pb, and the second maximum power calculated from the measured operating current and the operating voltage, A step of comparing while varying the number of solar cell modules having the wiring resistance Rs ′;
The failure diagnosis method for a photovoltaic system according to claim 7, further comprising: calculating the number of solar cell modules having the wiring resistance Rs ′ in the solar cell array based on the comparison result. . The solar power generation system further includes a plurality of the solar cell arrays connected in parallel, and a selection unit for selecting each of the solar cell arrays,
The solar power generation system according to claim 7, further comprising a step of calculating the number of disconnected solar cell modules existing in each solar cell array by switching the solar cell array using the selection unit. Fault diagnosis method. The solar power generation system further includes a plurality of the solar cell arrays connected in parallel, and a selection unit for selecting each of the solar cell arrays,
The method according to claim 8, further comprising: calculating the number of solar cell modules having the wiring resistance Rs ′ present in each solar cell array by switching the solar cell array using the selection unit. Fault diagnosis method for solar power generation system. The solar power generation system further includes selection means for selecting each of the solar cell strings,
The solar power generation system according to claim 7, further comprising: calculating the number of disconnected solar cell modules existing in each solar cell string by switching the solar cell strings using the selection unit. Fault diagnosis method. The solar power generation system further includes selection means for selecting each of the solar cell strings,
The solar cell according to claim 8, further comprising: calculating a number of solar cell modules having the wiring resistance Rs ′ present in each solar cell string by switching the solar cell string using the selection unit. Fault diagnosis method for photovoltaic system.

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