WO2023080149A1 - Operating voltage estimation device and operating voltage estimation method - Google Patents

Abstract

This operating voltage estimation device irradiates a multi-junction solar cell with color bias light, calculates an external quantum efficiency spectrum of each sub-cell under irradiation with the color bias light, irradiates the multi-junction solar cell, which is being operated by solar radiation, with micro-intensity monochromatic modulated light during estimation of the operating voltage of each sub-cell, and selects a wavelength of the monochromatic modulated light. During irradiation with the monochromatic modulated light, a phase detection unit receives, as an input, a reference signal indicating a phase of the monochromatic modulated light, and a signal indicating an output current of the multi-junction solar cell into which is mixed a component that is synchronous with the monochromatic modulated light in accordance with the operating voltage of each sub-cell of the multi-junction solar cell. The phase detection unit extracts and outputs the component that is synchronous with the monochromatic modulated light mixed into the output current of the multi-junction solar cell. A differential resistance corresponding to the operating voltage of each sub-cell is calculated on the basis of the output component that is synchronous with the monochromatic modulated light, and the operating voltage of each sub-cell is calculated on the basis of the calculated differential resistance.

Description

Operating voltage estimation device and operating voltage estimation method

The present invention relates to an operating voltage estimating device and an operating voltage estimating method.
This application claims priority based on Japanese Patent Application No. 2021-181765 filed in Japan on November 8, 2021, the contents of which are incorporated herein.

A multi-junction solar cell having a plurality of sub-cells is conventionally known (see Patent Document 1). For example, a multi-junction solar cell as described in FIG. 4 of Patent Document 1 is composed of stacked solar cells of different semiconductors, and absorbs sunlight over a wide wavelength range by dividing it by wavelength. Therefore, multi-junction solar cells can convert sunlight with high efficiency and are used for artificial satellites and the like because of their high performance.
The light absorbed by the solar cells in each layer is the light that the solar cells in the previous layer could not absorb. For example, in the multi-junction solar cell described in FIG. 4 of Patent Document 1, the light absorbed by the middle sub-cell is the light that could not be absorbed by the preceding top sub-cell. Assuming that the bandgap E _g1 (eV) of the semiconductor in the preceding layer and the bandgap E _g2 (eV) of the semiconductor in the layer of interest, the wavelength range of light absorbed by the solar cell of the layer of interest is 1240/E _g1 to It can be expressed as 1240/E _g2 (nm). If there is no preceding stage, the first term is the shortest wavelength of the incident light.
However, if the intensity of the incident light _is very strong or if the preceding layer is thin, light of 1240/E _g1 (nm) or less cannot be absorbed by the preceding layer. Even the layer of interest will be absorbed by the solar cell.
In order to satisfy the wavelength range of 1240/E _g1 to 1240/E _g2 (nm) shared by the solar cells of each layer, the wavelength dependence of the incident light intensity should be understood and then the light absorption layers of the solar cells of each layer should be are designed to absorb light in each wavelength range.

It is difficult to directly measure the cell voltage of each layer of a multi-junction solar cell, and it is usually evaluated only by the output voltage and current of the multi-junction solar cell. If we dare to measure, it is necessary to partially insert the metal electrodes between the constituent cells, so the multi-junction solar cell is evaluated approximately.
In designing a multi-junction solar cell, the output current of each cell is determined to be equal, assuming that the current is proportional to the cell film thickness, based on the IV characteristics of each layer in each cell. However, in reality, as described above, there is an influence of transmitted light that is not absorbed by the preceding cell, and thus only an inaccurate prediction can be made based on the evaluation result of each cell alone. A computer simulation can be used to accurately obtain the optical light absorption characteristics of the cells in each layer, but the current at a voltage of 0 V in each cell, that is, the short-circuit current, is only estimated. Furthermore, the performance of tunnel junctions between cells may deviate from the design, and it is extremely difficult to predict the electrical characteristics of the entire constituent cells.
Designing a multi-junction solar cell is thus difficult, and we had to empirically optimize it based on prototypes with various layer structures. In particular, there has been no means in the past to determine the actual operating voltage of each layer cell in a multi-junction solar cell during power generation with high accuracy, and it has not been easy to optimize the operating voltage of each layer cell.

Japanese Patent No. 5999887 Japanese Patent No. 6712816

The inventors of the present invention have made intensive research and found that by applying the technique of irradiating modulated laser light described in Patent Document 2, it is possible to estimate the operating voltage of each sub-cell of a multi-junction solar cell with high accuracy. be.
In other words, an object of the present invention is to provide an operating voltage estimating device and an operating voltage estimating method capable of estimating the operating voltage of each sub-cell of a multi-junction solar cell with high accuracy.

One aspect of the present invention is an operating voltage estimating device for estimating the operating voltage of each of a plurality of sub-cells of a multi-junction solar cell having a plurality of sub-cells, wherein the multi-junction solar cell is irradiated with color bias light. and an external quantum efficiency for calculating an external quantum efficiency spectrum of each of the plurality of sub-cells when the multi-junction solar cell is irradiated with the color bias light by the color bias light irradiation unit. a spectrum calculation unit, a modulated light irradiation unit that irradiates the multi-junction solar cell that is in operation by irradiation with sunlight with a monochromatic modulated light having a weak intensity when estimating the operating voltage of each of the plurality of sub-cells; a wavelength selection unit that selects the wavelength of the monochromatic modulated light irradiated by the modulated light irradiation unit; and a reference signal that indicates the phase of the monochromatic modulated light when the monochromatic modulated light is irradiated by the modulated light irradiation unit. , a signal indicating an output current of the multi-junction solar cell in which a synchronous component with the monochromatic modulated light is mixed according to the operating voltage of each of the plurality of sub-cells of the multi-junction solar cell; a phase detection unit that extracts and outputs a synchronous component with the monochromatic modulated light mixed in the output current of the junction-type solar cell; and the monochromatic modulated light that is output by the phase detection unit when the monochromatic modulated light is irradiated. a differential resistance calculator for calculating differential resistances corresponding to respective operating voltages of the plurality of sub-cells based on the synchronous component; and an operating voltage calculator for calculating each operating voltage.

In the operating voltage estimating device according to one aspect of the present invention, the number of wavelengths of the monochromatic modulated light selected by the wavelength selection unit is equal to the number of the plurality of sub-cells, and the wavelength selection unit selects the external quantum efficiency spectrum The wavelength of the monochromatic modulated light may be selected based on the external quantum efficiency spectrum of each of the plurality of sub-cells calculated by the calculator.

In the operating voltage estimating device according to one aspect of the present invention, the wavelength selection unit selects the plurality of sub-cells calculated by the external quantum efficiency spectrum calculation unit as the wavelength of the monochromatic modulated light irradiated by the modulated light irradiation unit. may be selected to correspond to the peak of the external quantum efficiency spectrum of each.

In the operating voltage estimating device according to one aspect of the present invention, the differential resistance calculator includes simultaneous equations of a number equal to the number of the differential resistances as unknowns, and the single color having the wavelength selected by the wavelength selector a synchronous component with the monochromatic modulated light extracted by the phase detection section when the modulated light is irradiated by the modulated light irradiation section; the differential resistance; and the wavelength selected by the wavelength selection section. The differential resistance may be calculated by solving a system of equations relating it to the external quantum efficiency spectrum.

In the operating voltage estimating device according to one aspect of the present invention, the wavelength selection section may select a number of wavelengths of the monochromatic modulated light that is greater than the number of the plurality of sub-cells.

In the operating voltage estimating device according to one aspect of the present invention, the differential resistance calculator includes a number of simultaneous equations equal to the number of wavelengths of the monochromatic modulated light selected by the wavelength selector, Selected by the synchronous component with the monochromatic modulated light extracted by the phase detection section when the monochromatic modulated light of the selected wavelength is irradiated by the modulated light irradiation section, the differential resistance, and the wavelength selection section Simultaneous equations showing the relationship between the external quantum efficiency spectrum corresponding to the wavelengths obtained using a matrix, a first vector showing the synchronous component with the monochromatic modulated light, and a second vector showing the differential resistance The differential resistance corresponding to the component of the second vector may be calculated by expressing with the first relational expression and using the method of least squares.

In the operating voltage estimating device according to one aspect of the present invention, the differential resistance calculator expresses the first relational expression using a normal equation, and calculates the second vector included in the normal equation using an inverse matrix. The differential resistance corresponding to the component of the second vector may be calculated by expressing it with a second relational expression and solving the second relational expression.

In the operating voltage estimating device according to one aspect of the present invention, when the inverse matrix does not exist or when the inverse matrix becomes unstable, the differential resistance calculator calculates the components of the second vector by ridge regression. The corresponding differential resistance may be calculated.

In the operating voltage estimating device according to one aspect of the present invention, the differential resistance calculator expresses the second vector by a third relational expression in which a unit matrix and a regularization constant are added, and the wavelength selector expresses the regular The constant may be selected as a set value that allows negligible effects of a measurement error of a measuring device and a numerical error of a calculator for calculating ridge regression in the wavelength of the monochromatic modulated light emitted by the modulated light irradiator.

In the operating voltage estimating device according to one aspect of the present invention, the wavelength selection section selects a number of wavelengths of the monochromatic modulated light equal to the number of the plurality of sub-cells, and the differential resistance calculation section causes the wavelength selection section to Simultaneous equations equal in number to the number of wavelengths of the selected monochromatic modulated light, wherein the phase detection is performed when the monochromatic modulated light of the wavelength selected by the wavelength selection section is irradiated by the modulated light irradiation section. Simultaneous equations showing the relationship between the synchronous component with the monochromatic modulated light extracted by the unit, the differential resistance, and the external quantum efficiency spectrum corresponding to the wavelength selected by the wavelength selection unit, the matrix and the A first relational expression using a first vector indicating a synchronous component with monochromatic modulated light and a second vector indicating the differential resistance, the first relational expression being expressed using a normal equation, and the normal equation The second vector contained in is represented by a second relational expression using an inverse matrix, and when the value of the determinant of the matrix is approximately zero, the derivative corresponding to the component of the second vector by ridge regression Resistance may be calculated.

One aspect of the present invention is an operating voltage estimation method for estimating an operating voltage of each of a plurality of sub-cells of a multi-junction solar cell having a plurality of sub-cells, wherein the multi-junction solar cell is irradiated with color bias light. and an external quantum efficiency for calculating an external quantum efficiency spectrum of each of the plurality of sub-cells when the multi-junction solar cell is irradiated with the color bias light in the color bias light irradiation step. a spectrum calculating step, a modulated light irradiation step of irradiating the multi-junction solar cell operating by irradiation with sunlight with a monochromatic modulated light having a weak intensity when estimating the operating voltage of each of the plurality of sub-cells; a wavelength selection step of selecting the wavelength of the monochromatic modulated light irradiated in the modulated light irradiation step; and a reference signal indicating the phase of the monochromatic modulated light when the monochromatic modulated light is irradiated in the modulated light irradiation step. , a signal indicating an output current of the multi-junction solar cell in which a synchronous component with the monochromatic modulated light is mixed according to the operating voltage of each of the plurality of sub-cells of the multi-junction solar cell; a phase detection step of extracting and outputting a synchronous component with the monochromatic modulated light mixed in the output current of the junction solar cell; and the monochromatic modulated light output in the phase detection step when the monochromatic modulated light is irradiated. a differential resistance calculation step of calculating a differential resistance corresponding to an operating voltage of each of the plurality of sub-cells based on the synchronous component; and an operating voltage calculating step of calculating each operating voltage.

According to the present invention, it is possible to provide an operating voltage estimating device and an operating voltage estimating method capable of estimating the operating voltage of each sub-cell of a multi-junction solar cell with high accuracy.

It is a figure which shows an example of the operating voltage estimation apparatus 1 of 1st Embodiment applied to the multi-junction-type solar cell M. FIG. An example of the external quantum efficiency spectrum Φj (j=1 to m) of each of m (m=3) subcells M1, . FIG. 4 is a diagram showing; An example of the external quantum efficiency spectrum Φj (j=1 to m) of each of m (m=2) subcells M1, . FIG. 4 is a diagram showing; 4 is a flowchart for explaining an example of processing executed by the operating voltage estimating device 1 of the first embodiment;

Embodiments of the operating voltage estimating device and operating voltage estimating method of the present invention will be described below.

[First embodiment]
FIG. 1 is a diagram showing an example of an operating voltage estimating device 1 according to a first embodiment applied to a multijunction solar cell M. FIG.
In the example shown in FIG. 1, the operating voltage estimating device 1 calculates the operating voltage of each subcell M1, . to estimate A multi-junction solar cell M is connected to a load resistor R. The operating voltage estimation device 1 includes a color bias light irradiation section 1A, an external quantum efficiency spectrum calculation section 1B, a modulated light irradiation section 1C, a wavelength selection section 1D, a phase detection section 1E, a differential resistance calculation section 1F, An operating voltage calculator 1G and a current clamp sensor 11 are provided.
The color bias light irradiation section 1A irradiates the multi-junction solar cell M with color bias light. The external quantum efficiency spectrum calculator 1B calculates the external quantum efficiency spectrum Φj of each of the m sub-cells M1, . (j=1 to m) is calculated. The external quantum efficiency spectrum calculator 1B also includes a variable-wavelength monochromatic light source corresponding to the measurement wavelength range for measuring the external quantum efficiency spectrum, a wavelength controller for the monochromatic light source, and the like.

The color bias light irradiation unit 1A and the external quantum efficiency spectrum calculation unit 1B irradiate the multi-junction solar cell M with color bias light, for example, by using a technique similar to the technique shown in the following URL, An external quantum efficiency spectrum Φj (j=1 to m) is calculated for each of the m sub-cells M1, .
http://www.bunkoukeiki.co.jp/spectralresponse-cep-2000.html
https://www.newport-japan.jp/pdf/65.pdf
https://www.san-eielectric.co.jp/qe-r.htm
https://www.japanlaser.co.jp/product/oriel_iqe-200/
http://www.techno-synergy.co.jp/pdt/2_Spectroscopy_Systems/pdf/BQE-100v2-1706s.pdf

2 and 3 are examples of external quantum efficiency spectra Φj (j=1 to m) of m subcells M1, . It is a figure which shows.
Specifically, FIG. 2A shows the external quantum efficiency spectra Φ1, Φ2, and Φ3 of the three sub-cells M1, M2, and M3 of the multi-junction solar cell M calculated by the external quantum efficiency spectrum calculator 1B. A first example is shown, and FIG. 2(B) shows external quantum efficiency spectra Φ1, A second example of Φ2 and Φ3 is shown, and FIG. 3 shows external quantum efficiency spectra Φ1 and Φ2 of two sub-cells M1 and M2 of the multi-junction solar cell M calculated by the external quantum efficiency spectrum calculator 1B. shows an example.
In FIGS. 2A, 2B and 3, the vertical axis indicates the external quantum efficiency (EQE) and the horizontal axis indicates the wavelength.
In the example shown in FIGS. 2A and 2B, the multijunction solar cell M has three subcells M1, M2, M3. The external quantum efficiency spectrum calculator 1B calculates an external quantum efficiency spectrum Φ1 of the subcell M1, an external quantum efficiency spectrum Φ2 of the subcell M2, and an external quantum efficiency spectrum Φ3 of the subcell M3.
In the example shown in FIG. 3, the multijunction solar cell M has two subcells M1 and M2. The external quantum efficiency spectrum calculator 1B calculates an external quantum efficiency spectrum Φ1 of the sub-cell M1 and an external quantum efficiency spectrum Φ2 of the sub-cell M2.

In the example shown in FIG. 1, the modulated light irradiator 1C emits a monochromatic modulated light beam with a weak intensity when estimating the operating voltage of each of the sub-cells M1, . . . to irradiate. The modulated light irradiation section 1C includes a laser light irradiation section 1C1 and a chopper control section 1C2. The laser beam irradiation unit 1C1 irradiates a laser beam such as a He—Ne laser.
In the example shown in FIG. 1, the modulated light irradiation unit 1C includes a laser light irradiation unit 1C1. A portion (not shown) may be provided.

In the example shown in FIG. 1, the chopper control unit 1C2 modulates the laser light emitted from the laser light irradiation unit 1C1 into monochromatic modulated light with a predetermined phase (frequency) and minute intensity. The chopper control unit 1C2 also outputs a reference signal indicating the phase (frequency) of the monochromatic modulated light with a weak intensity to the phase detection unit 1E.
The wavelength selection unit 1D selects a wavelength λi (i=1 to n (n is an integer equal to or greater than 2)) of the monochromatic modulated light of very low intensity irradiated by the modulated light irradiation unit 1C. Specifically, the wavelength selection unit 1D selects n different wavelengths λ1, .

In the example shown in FIG. 1 (that is, in the operating voltage estimating device 1 of the first embodiment), the number n of wavelengths λi (i=1 to n) of monochromatic modulated light with a weak intensity selected by the wavelength selection unit 1D and , and the number m of the plurality of subcells M1, . . . , Mm included in the multi-junction solar cell M.
For example, in the examples shown in FIGS. 1, 2A, and 2B, the number n of wavelengths λi (i=1 to n) of monochromatic modulated light with a weak intensity selected by the wavelength selection unit 1D and the number n The number m of the subcells M1, . . . , Mm included in the junction solar cell M is three.
In the examples shown in FIGS. 1 and 3, the number n of wavelengths λi (i=1 to n) of monochromatic modulated light with a weak intensity selected by the wavelength selection unit 1D, the subcell M1 of the multijunction solar cell M, , the number m of Mm is 2.

In the example shown in FIG. 1 (that is, the example where m=n), the wavelength selector 1D calculates the external quantum efficiency spectrum Φj(j = 1 to m), select the wavelength λi (i = 1 to n) of monochromatic modulated light with a weak intensity. Specifically, the wavelength selection unit 1D uses the wavelength λi (i=1 to n) of the monochromatic modulated light with a very low intensity irradiated by the modulated light irradiation unit 1C for each sub-cell calculated by the external quantum efficiency spectrum calculation unit 1B. Select the wavelengths λi (i=1 to n) corresponding to the peaks of the external quantum efficiency spectra Φj (j=1 to m) of M1, . . . , Mm.

For example, in the example shown in FIGS. 1 and 2A, the wavelength selection unit 1D uses the wavelength λ1 of the monochromatic modulated light with a very low intensity irradiated by the modulated light irradiation unit 1C, which is calculated by the external quantum efficiency spectrum calculation unit 1B. A wavelength (for example, 500 (nm)) corresponding to the peak of the external quantum efficiency spectrum Φ1 of the sub-cell M1 is selected, and the wavelength λ2 (>λ1) of the monochromatic modulated light of very low intensity irradiated by the modulated light irradiation unit 1C is A wavelength (for example, 750 (nm)) corresponding to the peak of the external quantum efficiency spectrum Φ2 of the sub-cell M2 calculated by the external quantum efficiency spectrum calculation unit 1B is selected, and the modulated light irradiation unit 1C irradiates a micro-intensity monochromatic modulation. As the wavelength λ3 (>λ2) of light, a wavelength (for example, 950 (nm)) corresponding to the peak of the external quantum efficiency spectrum Φ3 of the sub-cell M3 calculated by the external quantum efficiency spectrum calculator 1B is selected.
For example, in the example shown in FIG. 1 and FIG. 2B, the wavelength selection unit 1D is calculated by the external quantum efficiency spectrum calculation unit 1B as the wavelength λ1 of the monochromatic modulated light of very low intensity irradiated by the modulated light irradiation unit 1C. A wavelength (for example, 500 (nm)) corresponding to the peak of the external quantum efficiency spectrum Φ1 of the sub-cell M1 is selected, and the wavelength λ2 (>λ1) of the monochromatic modulated light of very low intensity irradiated by the modulated light irradiation unit 1C is A wavelength (for example, 650 (nm)) corresponding to the peak of the external quantum efficiency spectrum Φ2 of the sub-cell M2 calculated by the external quantum efficiency spectrum calculator 1B is selected, and the modulated light irradiator 1C irradiates a micro-intensity monochromatic modulation. As the light wavelength λ3 (>λ2), a wavelength (for example, 750 (nm)) corresponding to the peak of the external quantum efficiency spectrum Φ3 of the sub-cell M3 calculated by the external quantum efficiency spectrum calculator 1B is selected.
In the example shown in FIGS. 1 and 3, the wavelength selection unit 1D uses the wavelength λ1 of the monochromatic modulated light of very low intensity irradiated by the modulated light irradiation unit 1C as the wavelength λ1 of the subcell M1 calculated by the external quantum efficiency spectrum calculation unit 1B. A wavelength (e.g., 500 (nm)) corresponding to the peak of the external quantum efficiency spectrum Φ1 is selected, and the wavelength λ2 (>λ1) of the monochromatic modulated light of very low intensity irradiated by the modulated light irradiation unit 1C is defined as the external quantum efficiency spectrum. A wavelength (for example, 750 (nm)) corresponding to the peak of the external quantum efficiency spectrum Φ2 of the sub-cell M2 calculated by the calculator 1B is selected.

In the example shown in FIG. 1, the current clamp sensor 11 is electrically out of contact with the wiring connected to the multi-junction solar cell M. In the example shown in FIG. The current clamp sensor 11 detects the output current of the multi-junction solar cell M, and outputs a signal indicating the output current of the multi-junction solar cell M (indicated by "input signal" in FIG. 1) to the phase detector 1E. .
The phase detector 1E has a lock-in amplifier 1E1. While the modulated light irradiation unit 1C is irradiating the monochromatic modulated light with a weak intensity, the lock-in amplifier 1E1 receives a reference signal indicating the phase (frequency) of the monochromatic modulated light with a weak intensity and the multi-junction solar cell M. Fig. 2 shows the output current of a multi-junction solar cell M in which a synchronous component ΔIi (i = 1 to n) with monochromatic modulated light of very low intensity mixes according to the operating voltage of each of m subcells M1, ..., Mm. A signal (input signal) is input. When the modulated light irradiation unit 1C irradiates the monochromatic modulated light with a weak intensity, the lock-in amplifier 1E1 detects a synchronous component ΔIi ( i=1 to n) are extracted and output as an output signal.

For example, in the examples shown in FIGS. 1, 2A, and 2B, the modulated light irradiation unit 1C emits a weak monochromatic modulated light having a wavelength λ1 corresponding to the peak of the external quantum efficiency spectrum Φ1 of the subcell M1. During irradiation, the lock-in amplifier 1E1 supplies a reference signal indicating the phase of the weak monochromatic modulated light having the wavelength λ1 and a weak monochromatic signal in accordance with the operating voltage of the subcell M1 of the multijunction solar cell M. A signal (input signal) indicating the output current of the multi-junction solar cell M mixed with the synchronous component ΔI1 with the modulated light is input. The lock-in amplifier 1E1 extracts a synchronous component .DELTA.I1 with the minute intensity monochromatic modulated light mixed in the output current of the multi-junction solar cell M, and outputs it as an output signal.
When the modulated light irradiator 1C is irradiating the monochromatic modulated light with a weak intensity having a wavelength λ2 corresponding to the peak of the external quantum efficiency spectrum Φ2 of the subcell M2, the lock-in amplifier 1E1 emits a weak intensity light having a wavelength λ2. The output current of the multi-junction solar cell M, in which the reference signal indicating the phase of the monochromatic modulated light and the synchronous component ΔI2 with the monochromatic modulated light of very low intensity are mixed according to the operating voltage of the sub-cell M2 of the multi-junction solar cell M. A signal (input signal) indicating is input. The lock-in amplifier 1E1 extracts the synchronous component ΔI2 with the weak monochromatic modulated light mixed in the output current of the multi-junction solar cell M, and outputs it as an output signal.
When the modulated light irradiator 1C is irradiating the monochromatic modulated light with a weak intensity having a wavelength λ3 corresponding to the peak of the external quantum efficiency spectrum Φ3 of the sub-cell M3, the lock-in amplifier 1E1 emits a weak intensity light having a wavelength λ3. The output current of the multi-junction solar cell M, in which the reference signal indicating the phase of the monochromatic modulated light and the synchronous component ΔI3 with the monochromatic modulated light of very low intensity are mixed according to the operating voltage of the sub-cell M3 of the multi-junction solar cell M. A signal (input signal) indicating is input. The lock-in amplifier 1E1 extracts a synchronous component .DELTA.I3 with a weak monochromatic modulated light mixed in the output current of the multi-junction solar cell M and outputs it as an output signal.

In the example shown in FIGS. 1 and 3, when the modulated light irradiation unit 1C irradiates monochromatic modulated light with a weak intensity having a wavelength λ1 corresponding to the peak of the external quantum efficiency spectrum Φ1 of the subcell M1, the lock-in amplifier 1E1 contains a reference signal indicating the phase of the weak intensity monochromatic modulated light having a wavelength λ1 and a synchronization component ΔI1 of the weak intensity monochromatic modulated light according to the operating voltage of the sub-cell M1 of the multi-junction solar cell M. A signal (input signal) indicating the output current of the multi-junction solar cell M is input. The lock-in amplifier 1E1 extracts a synchronous component .DELTA.I1 with the minute intensity monochromatic modulated light mixed in the output current of the multi-junction solar cell M, and outputs it as an output signal. When the modulated light irradiator 1C is irradiating the monochromatic modulated light with a weak intensity having a wavelength λ2 corresponding to the peak of the external quantum efficiency spectrum Φ2 of the subcell M2, the lock-in amplifier 1E1 emits a weak intensity light having a wavelength λ2. The output current of the multi-junction solar cell M, in which the reference signal indicating the phase of the monochromatic modulated light and the synchronous component ΔI2 with the monochromatic modulated light of very low intensity are mixed according to the operating voltage of the sub-cell M2 of the multi-junction solar cell M. A signal (input signal) indicating is input. The lock-in amplifier 1E1 extracts the synchronous component ΔI2 with the weak monochromatic modulated light mixed in the output current of the multi-junction solar cell M, and outputs it as an output signal.

In the example shown in FIG. 1, the differential resistance calculation unit 1F calculates the micro-intensity monochromatic modulated light mixed in the output current of the multi-junction solar cell M output by the phase detection unit 1E when the micro-intensity monochromatic modulated light is irradiated. Based on the synchronous component ΔIi (i = 1 to n) of the multi-junction solar cell M, the differential resistance Rdj (j = 1 to m) corresponding to the operating voltage of each of the m subcells M1, ..., Mm Calculate
Specifically, the differential resistance calculation unit 1F calculates simultaneous equations of a number equal to the number m of differential resistances Rdj (j=1 to m) as unknowns, and the wavelength λi (i= 1 to n), the synchronous component ΔIi ( i=1 to n), the differential resistance Rdj (j=1 to m), and the external quantum efficiency spectrum Φj (λi) corresponding to the wavelength λi (i=1 to n) selected by the wavelength selection unit 1D The differential resistance Rdj (j=1 to m) is calculated by solving the simultaneous equations (specifically, the following equation (1)) showing the relationship.
In the equation (1), ΔI _phi indicates the light-generated current due to monochromatic modulated light of very low intensity, and C indicates a constant (=1/(ΣRdj+R)).

For example, in the example (m=n=3) shown in FIGS. Differential resistances Rd1, Rd2, and Rd3 are calculated by simultaneously solving the corresponding equation (1) and the equation (1) corresponding to i=3.
For example, in the example (m=n=2) shown in FIGS. 1 and 3, the differential resistance calculator 1F simultaneously formulates the equation (1) corresponding to i=1 and the equation (1) corresponding to i=2. and solving simultaneously, the differential resistances Rd1 and Rd2 are calculated.

In the example shown in FIG. 1, the operating voltage calculator 1G uses the technique described in Patent Document 2, based on the differential resistance Rdj (j=1 to m) calculated by the differential resistance calculator 1F, , Mm are calculated.

FIG. 4 is a flowchart for explaining an example of processing executed by the operating voltage estimating device 1 of the first embodiment.
In the example shown in FIG. 4, the color bias light irradiation unit 1A irradiates the multi-junction solar cell M with color bias light in step S11.
In step S12, the external quantum efficiency spectrum calculator 1B calculates the external quantum efficiency spectrum Φj of each of the m sub-cells M1, . (j=1 to m) is calculated.

Next, in step S13, the wavelength selection unit 1D selects a wavelength λi (i=1 to n) of monochromatic modulated light with a weak intensity.
Next, in step S14, the modulated light irradiation unit 1C is selected in step S13 when estimating the operating voltage of each subcell M1, . A very weak monochromatic modulated light having a wavelength λi (i=1 to n) is applied.
In step S15, the phase detection unit 1E detects the reference signal indicating the phase of the low intensity monochromatic modulated light input when the low intensity monochromatic modulated light is irradiated in step S14, and the m A signal indicating the output current of the multi-junction solar cell M in which the synchronous component ΔIi (i=1 to n) with the monochromatic modulated light of very low intensity is mixed according to the operating voltage of each of the subcells M1, . . . , Mm. , extracts and outputs a synchronous component ΔIi (i=1 to n) with a weak monochromatic modulated light mixed in the output current of the multijunction solar cell M. FIG.

Next, in step S16, the differential resistance calculator 1F calculates the synchronous component of the weak intensity monochromatic modulated light mixed in the output current of the multi-junction solar cell M output in step S15 when the weak intensity monochromatic modulated light is irradiated. Based on ΔIi (i=1 to n), differential resistance Rdj (j=1 to m) corresponding to the operating voltage of each of the m subcells M1, . . . , Mm of the multijunction solar cell M is calculated. .
Next, in step S17, the operating voltage calculator 1G calculates respective operating voltages of the m subcells M1, . .

As described above, according to the operating voltage estimating device 1 of the first embodiment, the operating voltage of each subcell M1, . . . , Mm of the multi-junction solar cell M can be estimated with high accuracy.

[Second embodiment]
A second embodiment of the operating voltage estimating device and operating voltage estimating method of the present invention will be described below.
The operating voltage estimating device 1 of the second embodiment is configured in the same manner as the operating voltage estimating device 1 of the first embodiment described above, except for the points described later. Therefore, according to the operating voltage estimating device 1 of the second embodiment, it is possible to obtain the same effects as the operating voltage estimating device 1 of the above-described first embodiment, except for the points described later.

The operating voltage estimating device 1 of the second embodiment is configured similarly to the operating voltage estimating device 1 of the first embodiment shown in FIG. Like the operating voltage estimating device 1 of the first embodiment, the operating voltage estimating device 1 of the second embodiment has m (m is an integer equal to or greater than 2) subcells M1, . . . , Mm. Estimate the operating voltage of each subcell M1, . . . , Mm of M.
In the operating voltage estimating device 1 of the second embodiment, similarly to the operating voltage estimating device 1 of the first embodiment, the color bias light irradiation unit 1A irradiates the multi-junction solar cell M with color bias light, The efficiency spectrum calculator 1B calculates external quantum efficiency spectra Φj(j = 1 to m).

As described above, in the operating voltage estimating device 1 of the first embodiment, the number n of wavelengths λi (i=1 to n) of the monochromatic modulated light of very low intensity selected by the wavelength selection unit 1D and the multijunction solar The number m of the plurality of sub-cells M1, . . . , Mm that the battery M has is equal (m=n).
On the other hand, in the operating voltage estimating device 1 of the second embodiment, the number n of wavelengths λi (i=1 to n) of the monochromatic modulated light of very low intensity selected by the wavelength selection unit 1D is The number of sub-cells M1, . That is, the wavelength selection unit 1D selects the wavelengths λi (i=1 to n) of monochromatic modulated light with weak intensity, the number n being larger than the number m of the plurality of sub-cells M1, . . . , Mm (m<n).
In the operating voltage estimating device 1 of the second embodiment, when estimating the operating voltage of each of the sub-cells M1, . A weak intensity monochromatic modulated light having a wavelength λi (i=1 to n) selected by the wavelength selection unit 1D is emitted. That is, the modulated light irradiator 1C irradiates monochromatic modulated light with a weak intensity having a wavelength λi (i=1 to n) in order to estimate the operating voltage of each of the m subcells M1, . . . , Mm ( That is, n (>m) times of irradiation with weak monochromatic modulated light having different wavelengths λi (i=1 to n).

In the operating voltage estimating device 1 of the second embodiment, the differential resistance calculator 1F has a number n equal to the number n of wavelengths λi (i=1 to n) of monochromatic modulated light with a weak intensity selected by the wavelength selector 1D. Simultaneous equations, the lock-in of the phase detection unit 1E when the modulated light irradiation unit 1C is irradiating the modulated light irradiation unit 1C with a weak intensity monochromatic modulated light having a wavelength λi (i = 1 to n) selected by the wavelength selection unit 1D Synchronous component ΔIi (i=1 to n) with the monochromatic modulated light of weak intensity extracted by amplifier 1E1, differential resistance Rdj (j=1 to m), and wavelength λi ( Simultaneous equations (specifically, the above equation (1)) showing the relationship with the external quantum efficiency spectrum Φj (λi) corresponding to i = 1 to n) are the matrix A and the monochromatic modulated light of very low intensity. A first relational expression (b=Ax) (details is expressed by the following equation (2), and the differential resistance Rdj (j=1 to m) corresponding to the component of the second vector x is calculated by using the method of least squares.
The method of least squares is described, for example, at the following URL.
https://www.osc-japan.com/wp-content/uploads/2013/04/ODN53.pdf

Specifically, in the operating voltage estimating device 1 of the second embodiment, the differential resistance calculator 1F converts the first relational expression (b=Ax) into a normal ^equation ( ^AT Ax= A ^T b) is used. Further, the differential resistance calculator 1F converts ^the second vector x included in the normal equation (A ^T Ax=A ^T b) into a second relational expression ( ^x =(A ^T A) ⁻¹ A ^T b). Further, the differential resistance calculator 1F solves the second relational expression (x=(A ^T A) ⁻¹ A ^T b) to obtain differential resistance Rdj (j=1 to m ) is calculated.
A method for solving the second relational expression (x=(A ^T A) ⁻¹ A ^T b) is described, for example, at the following URL.
http://manabukano.brilliant-future.net/lecture/dataanalysis/doc04_MRA.pdf

By the way, depending on the conditions, the above-mentioned inverse matrix (A ^T A) ⁻¹ does not exist (determinant |A ^T A|=0), or the inverse matrix (A ^T A) ⁻¹ may be unstable (determinant |A ^T A|≈0). According to the above URL description, such a case corresponds to the case where the column or row elements of the matrix A ^TA are linearly dependent, specifically, the column or row elements of the matrix A ^TA This corresponds to the case where there is a strong correlation between In other words, when the components of each other are very similar, (A ^T A) ⁻¹ A ^T b cannot be calculated or the accuracy of the calculation result is poor, so the differential resistance corresponding to the component of the second vector x Rdj (j=1 to m) cannot be calculated properly.

Therefore, in the operating voltage estimating device 1 of the second embodiment, when the inverse matrix (A ^T A) ⁻¹ does not exist (determinant |A ^T A |=0), When the inverse matrix (A ^T A) ⁻¹ becomes unstable due to the influence (determinant |A ^T A|≈0), the differential resistance calculator 1F performs differentiation corresponding to the component of the second vector x by ridge regression. A resistance Rdj (j=1 to m) is calculated.
Specifically, the differential resistance calculator 1F expresses the second vector x by a third relational expression (x=(A ^T A+ρI) ⁻¹ A ^T b) obtained by adding the unit matrix I and the regularization constant ρ. . The regularization constant ρ is determined in a numerical experiment on a computer so that, for example, the information criterion AIC is minimized.
The information amount criterion AIC is described, for example, at the following URL.
http://watanabe-www.math.dis.titech.ac.jp/users/swatanab/inf-crite.html

Furthermore, in the operating voltage estimation device 1 of the second embodiment, the wavelength selection unit 1D sets the regularization constant ρ to the wavelength λi (i=1 to n ) in which the influence of the measurement error of the measuring device and the numerical error of the calculator for calculating the ridge regression is negligible.
In the operating voltage estimating device 1 of the second embodiment, as in the operating voltage estimating device 1 of the first embodiment, the operating voltage calculator 1G uses the technique described in Patent Document 2 to calculate the differential resistance. Based on the differential resistance Rdj (j=1 to m) calculated by the unit 1F, the operating voltage of each of the m subcells M1, . . . , Mm is calculated.
Therefore, according to the operating voltage estimating device 1 of the second embodiment, the operating voltage of each subcell M1, . . . , Mm of the multi-junction solar cell M can be estimated with high accuracy.

[Third embodiment]
A third embodiment of the operating voltage estimating device and operating voltage estimating method of the present invention will be described below.
The operating voltage estimating device 1 of the third embodiment is configured in the same manner as the operating voltage estimating device 1 of the first embodiment described above, except for the points described later. Therefore, according to the operating voltage estimating device 1 of the third embodiment, it is possible to obtain the same effects as the operating voltage estimating device 1 of the above-described first embodiment, except for the points described later.

The operating voltage estimating device 1 of the third embodiment is configured similarly to the operating voltage estimating device 1 of the first embodiment shown in FIG. Like the operating voltage estimating device 1 of the first embodiment, the operating voltage estimating device 1 of the third embodiment has m (m is an integer equal to or greater than 2) subcells M1, . . . , Mm. Estimate the operating voltage of each subcell M1, . . . , Mm of M.
In the operating voltage estimating device 1 of the third embodiment, similarly to the operating voltage estimating device 1 of the first embodiment, the color bias light irradiation unit 1A irradiates the multi-junction solar cell M with color bias light, The efficiency spectrum calculator 1B calculates external quantum efficiency spectra Φj(j = 1 to m).

In the operating voltage estimating device 1 of the third embodiment, similarly to the operating voltage estimating device 1 of the first embodiment, the wavelength λi (i=1 to n) of the weak intensity monochromatic modulated light selected by the wavelength selection unit 1D is is equal to the number m of the plurality of sub-cells M1, . . . , Mm included in the multi-junction solar cell M (m=n).
That is, in the operating voltage estimating device 1 of the third embodiment, the modulated light irradiation unit 1C uses wavelengths λi (i=1 to n) to estimate the operating voltages of the m subcells M1, . . . , Mm. (that is, n (=m) irradiations of n (=m) times of n (=m) monochromatic modulated light beams with different wavelengths λi (i=1 to n) different from each other)).

By the way, even when m=n, the value of the determinant of matrix A may be approximately zero (|A|≈0).
Therefore, in the operating voltage estimating device 1 of the third embodiment, when the value of the determinant of the matrix A is approximately zero (|A|≈0), the differential resistance calculator 1F calculates the operating voltage Similar to the estimation device 1, the differential resistance Rdj (j=1 to m) corresponding to the component of the second vector x is calculated by ridge regression.
Specifically, the differential resistance calculation unit 1F provides a number of simultaneous equations equal to the number n of wavelengths λi (i=1 to n) of monochromatic modulated light of very low intensity selected by the wavelength selection unit 1D, The minute intensity extracted by the lock-in amplifier 1E1 of the phase detection unit 1E when the modulated light irradiation unit 1C is irradiating the monochromatic modulated light having the wavelength λi (i=1 to n) selected by the selection unit 1D. Synchronous component ΔIi (i=1 to n) with intensity monochromatic modulated light, differential resistance Rdj (j=1 to m), and wavelength λi (i=1 to n) selected by wavelength selector 1D Simultaneous equations (more specifically, equation (1)) showing the relationship with the corresponding external quantum efficiency spectrum Φj (λi) are expressed by the matrix A and the synchronous component ΔIi (i=1 to n) and the second vector x representing the differential resistance Rdj (j=1 to m), the first relational expression (b=Ax) (specifically, equation (2)) show.
Further, the differential resistance calculator 1F expresses the first relational expression (b=Ax) using a normal equation (A ^T Ax=A ^T b). Further, the differential resistance calculator 1F converts the ^second vector x included in the normal equation (A ^T Ax=A ^T b) ^into a second relational expression (x= (A ^T A) ⁻¹ A ^T b).
When the value of the determinant of the matrix A is approximately zero (|A|≈0), the differential resistance calculator 1F calculates the differential resistance Rdj (j=1 to m ) is calculated.

In the operating voltage estimating device 1 of the third embodiment, as in the operating voltage estimating device 1 of the first embodiment, the operating voltage calculator 1G uses the technique described in Patent Document 2 to calculate the differential resistance. Based on the differential resistance Rdj (j=1 to m) calculated by the unit 1F, the operating voltage of each of the m subcells M1, . . . , Mm is calculated.
Therefore, according to the operating voltage estimating device 1 of the third embodiment, the operating voltage of each subcell M1, . . . , Mm of the multi-junction solar cell M can be estimated with high accuracy.

<First embodiment>
In the first embodiment, the external quantum efficiency spectrum calculator 1B calculates the external quantum efficiency spectrum Φj (j=1 to m) of each of the m subcells M1, . An external quantum efficiency spectrum Φ1 of the sub-cell M1, an external quantum efficiency spectrum Φ2 of the sub-cell M2, and an external quantum efficiency spectrum Φ3 of the sub-cell M3 shown in 2(A) are calculated.
The definition of the external quantum efficiency spectrum Φj calculated by the external quantum efficiency spectrum calculator 1B is the number of photons of energy of a given wavelength λ externally irradiated onto the solar cell (incident photons) collected by the solar cell is the ratio of the number of charge carriers. The product qP(λ)・Φj of the external quantum efficiency spectrum Φj(λ) of each subcell and the current conversion value qP(λ) obtained by multiplying the photon number P(λ) for each wavelength of the standard light source by the elementary charge q Integrating (λ) over the wavelength λ corresponds to the short-circuit current at the operating voltage of 0 V of each subcell. Therefore, the external quantum efficiency spectrum Φj does not represent the operating voltage of each subcell.
The wavelength selection unit 1D selects about 500 (nm) (short wavelength) as the wavelength λ _short of the monochromatic modulated light of very low intensity irradiated by the modulated light irradiation unit 1C for estimating the operating voltage of the subcell M1. In order to estimate the operating voltage of M2, select about 750 (nm) (middle wavelength) _as the wavelength λ of the monochromatic modulated light of very low intensity irradiated by the modulated light irradiation unit 1C, and estimate the operating voltage of the subcell M3. For this purpose, approximately 1000 (nm) (long wavelength) is selected as the wavelength λ _length of the monochromatic modulated light of very low intensity irradiated by the modulated light irradiation section 1C.
The wavelength selector 1D selects a wavelength absorbed by only one subcell from the external quantum efficiency spectra Φ1, Φ2, Φ3 of each of the subcells M1, M2, M3. When wavelengths absorbed by two or more subcells must be selected, the wavelength selector 1D selects the wavelengths.
The modulated light irradiation unit 1C irradiates monochromatic modulated light of short wavelength and low intensity to estimate the operating voltage of the subcell M1, and emits monochromatic modulated light of medium wavelength and low intensity to estimate the operating voltage of the subcell M2. illuminate and emit long-wavelength, low-intensity, monochromatic modulated light to estimate the operating voltage of subcell M3. The short-wavelength, low-intensity monochromatic modulated light emitted by the modulated-light irradiation unit 1C is mainly absorbed by the sub-cell M1 in the first stage, and the medium-wavelength, low-intensity monochromatic modulated light emitted by the modulated-light irradiation unit 1C is absorbed. is mainly absorbed by the sub-cell M2 on the second stage, and the monochromatic modulated light of long wavelength and low intensity irradiated by the modulated light irradiation section 1C is mainly absorbed by the sub-cell M3 on the third stage.

When the modulated light irradiation unit 1C irradiates the monochromatic modulated light of short wavelength and low intensity, the lock-in amplifier 1E1 receives a reference signal indicating the phase of the monochromatic modulated light of short wavelength and low intensity, and a multijunction solar cell. 1 shows the output current of a multi-junction solar cell M in which a synchronous component ΔI with a monochromatic modulated light of short wavelength and _low intensity is mixed depending on the operating voltage of each of the three sub-cells M1, M2 and M3 of the cell M. A signal is input. Further, when the modulated light irradiator 1C irradiates the monochromatic modulated light of short wavelength and weak intensity, the lock-in amplifier 1E1 detects the monochromatic modulated light of short wavelength and weak intensity mixed in the output current of the multi-junction solar cell M. A _synchronous component ΔI with light is extracted and output.
When the modulated light irradiation unit 1C irradiates the monochromatic modulated light of medium wavelength and low intensity, the lock-in amplifier 1E1 receives a reference signal indicating the phase of the low intensity monochromatic modulated light of medium wavelength and a multijunction solar cell. The output current of the multi-junction solar cell M in which the synchronous component ΔI with the monochromatic modulated light of medium wavelength and low intensity is mixed is shown according to the operating voltage _of each of the three sub-cells M1, M2, and M3 of the cell M. A signal is input. Further, when the modulated light irradiator 1C irradiates the monochromatic modulated light of medium wavelength and weak intensity, the lock-in amplifier 1E1 detects the monochromatic modulated light of medium wavelength and weak intensity mixed in the output current of the multi-junction solar cell M. The synchronous component ΔI with light is _extracted and output.
When the modulated light irradiation unit 1C irradiates the monochromatic modulated light of long wavelength and weak intensity, the lock-in amplifier 1E1 receives a reference signal indicating the phase of the monochromatic modulated light of long wavelength and weak intensity and a multijunction solar cell. The output current of the multi-junction solar cell M in which the synchronous component ΔI _length with the monochromatic modulated light of long wavelength and low intensity is mixed according to the operating voltage of each of the three sub-cells M1, M2 and M3 of the cell M is shown. A signal is input. Further, when the modulated light irradiator 1C irradiates the monochromatic modulated light of long wavelength and low intensity, the lock-in amplifier 1E1 detects the monochromatic modulated light of long wavelength and low intensity mixed in the output current of the multi-junction solar cell M. The synchronous component ΔI _length with light is extracted and output.

The differential resistance calculation unit 1F calculates the minute intensity monochromatic modulation mixed in the output current of the multi-junction solar cell M output by the phase detection unit 1E when irradiated with minute intensity monochromatic modulated light of short, medium and long wavelengths. Differential _{resistance Rdj} (j ₌ 1 to 3) are calculated.
Specifically, the differential resistance calculator 1F calculates the number of simultaneous equations equal to the number 3 of differential resistances Rdj (j=1 to 3) as unknowns (specifically, the following equations (3-1), (3- 2) and (3-3)), the differential resistance Rdj (j=1 to 3) is calculated.
In equations (3-1), (3-2) and (3-3), ΔI _ph indicates the light-generated current due to monochromatic modulated light of very low intensity, and C is a constant (=1/(ΣRdj+R )).

In other words, when the multi-junction solar cell M, which is in operation under the irradiation of natural sunlight or pseudo-sunlight, is irradiated with a monochromatic modulated light (wavelength λ) of very low intensity, the modulated light synchronized with the lock-in amplifier output is slightly superimposed. The component can be represented by the sum of the components generated in each subcell (right side of equation (1)) from the theory of superposition.

The operating voltage calculator 1G uses the technique described in Patent Document 2 to calculate three subcells M1 and M2 based on the differential resistance Rdj (j=1 to 3) calculated by the differential resistance calculator 1F. , M3 are calculated.
As much as possible, the multi-junction solar cell M is arranged such that there is only one Φj(λ) where Φj(λ)>0 at one wavelength of the monochromatic modulated light, and other Φj(λ) are negligibly small. It is desirable to select the wavelength λi of the weak intensity monochromatic modulated light irradiated by the modulated light irradiation unit 1C based on the external quantum efficiency spectrum Φj (j=1 to m) of each subcell M1, . . . , Mm.

<Second embodiment>
In the second embodiment, as in the first embodiment, the external quantum efficiency spectrum calculator 1B calculates the external quantum efficiency spectrum Φj (j= 1 to m), the external quantum efficiency spectrum Φ1 of the subcell M1, the external quantum efficiency spectrum Φ2 of the subcell M2, and the external quantum efficiency spectrum Φ3 of the subcell M3 shown in FIG. 2A, for example, are calculated.
As in the first embodiment, the wavelength selector 1D _selects about 500 (nm) ( about 750 (nm) (medium wavelength) _as the wavelength λ of the weak intensity monochromatic modulated light irradiated by the modulated light irradiation unit 1C for estimating the operating voltage of the sub-cell M2, In order to estimate the operating voltage of the sub-cell M3, approximately 1000 (nm) (long wavelength) is selected as the wavelength λ _length of the monochromatic modulated light of very low intensity irradiated by the modulated light irradiation section 1C.
As in the first embodiment, the modulated light irradiation unit 1C irradiates monochromatic modulated light of short wavelength and low intensity for estimating the operating voltage of the subcell M1, and emits medium wavelength light for estimating the operating voltage of the subcell M2. to estimate the operating voltage of the sub-cell M3.
In the second embodiment, it is assumed that the monochromatic modulated light of short wavelength and weak intensity is mainly absorbed by the sub-cell M1 in the first stage and hardly absorbed by the sub-cells M2 and M3 in the latter stage. Further, it is assumed that the monochromatic modulated light of long wavelength and low intensity is mainly absorbed by the sub-cell M3 in the third stage and hardly absorbed by the sub-cells M1 and M2 in the preceding stage.

When the modulated light irradiation unit 1C irradiates the monochromatic modulated light of short wavelength and low intensity, the lock-in amplifier 1E1 receives a reference signal indicating the phase of the monochromatic modulated light of short wavelength and low intensity, and a multijunction solar cell. 1 shows the output current of a multi-junction solar cell M in which a synchronous component ΔI with a monochromatic modulated light of short wavelength and _low intensity is mixed depending on the operating voltage of each of the three sub-cells M1, M2 and M3 of the cell M. A signal is input. Further, when the modulated light irradiator 1C irradiates the monochromatic modulated light of short wavelength and weak intensity, the lock-in amplifier 1E1 detects the monochromatic modulated light of short wavelength and weak intensity mixed in the output current of the multi-junction solar cell M. A _synchronous component ΔI with light is extracted and output.
When the modulated light irradiation unit 1C irradiates the monochromatic modulated light of medium wavelength and low intensity, the lock-in amplifier 1E1 receives a reference signal indicating the phase of the low intensity monochromatic modulated light of medium wavelength and a multijunction solar cell. The output current of the multi-junction solar cell M in which the synchronous component ΔI with the monochromatic modulated light of medium wavelength and low intensity is mixed is shown according to the operating voltage _of each of the three sub-cells M1, M2, and M3 of the cell M. A signal is input. Further, when the modulated light irradiator 1C irradiates the monochromatic modulated light of medium wavelength and weak intensity, the lock-in amplifier 1E1 detects the monochromatic modulated light of medium wavelength and weak intensity mixed in the output current of the multi-junction solar cell M. The synchronous component ΔI with light is _extracted and output.
When the modulated light irradiation unit 1C irradiates the monochromatic modulated light of long wavelength and weak intensity, the lock-in amplifier 1E1 receives a reference signal indicating the phase of the monochromatic modulated light of long wavelength and weak intensity and a multijunction solar cell. The output current of the multi-junction solar cell M in which the synchronous component ΔI _length with the monochromatic modulated light of long wavelength and low intensity is mixed according to the operating voltage of each of the three sub-cells M1, M2 and M3 of the cell M is shown. A signal is input. Further, when the modulated light irradiator 1C irradiates the monochromatic modulated light of long wavelength and low intensity, the lock-in amplifier 1E1 detects the monochromatic modulated light of long wavelength and low intensity mixed in the output current of the multi-junction solar cell M. The synchronous component ΔI _length with light is extracted and output.

The differential resistance calculation unit 1F calculates the minute intensity monochromatic modulation mixed in the output current of the multi-junction solar cell M output by the phase detection unit 1E when irradiated with minute intensity monochromatic modulated light of short, medium and long wavelengths. Differential _{resistance Rdj} (j ₌ 1 to 3) are calculated.
Specifically, the differential resistance calculator 1F calculates the number of simultaneous equations equal to the number 3 of differential resistances Rdj (j=1 to 3) as unknowns (specifically, the following equations (4-1), (4- 2) and (4-3)), the differential resistance Rdj (j=1 to 3) is calculated.
In equations (4-1), (4-2) and (4-3), ΔI _ph indicates the light-generated current due to monochromatic modulated light of very low intensity, and C is a constant (=1/(ΣRdj+R )).

The operating voltage calculator 1G uses the technique described in Patent Document 2 to calculate three subcells M1 and M2 based on the differential resistance Rdj (j=1 to 3) calculated by the differential resistance calculator 1F. , M3 are calculated.

As described above, in the operating voltage estimating apparatus and operating voltage estimating method of the present invention, the wavelength of monochromatic modulated light with a weak intensity mainly absorbed by each of the sub-cells M1, . I need to estimate. The subcell of interest (for example, the subcell M2 corresponding to the external quantum efficiency spectrum Φ2 shown in FIG. 2B) mainly absorbs the wavelength of the monochromatic modulated light of low intensity and the adjacent subcell (for example, the external If the wavelength is close to the wavelength of the monochromatic modulated light of very low intensity mainly absorbed by the sub-cell M3) corresponding to the quantum efficiency spectrum Φ3, the first embodiment described above is required. On the other hand, the subcell of interest (for example, subcell M2 corresponding to external quantum efficiency spectrum Φ2 shown in FIG. If the wavelength of the subcell M1) corresponding to the external quantum efficiency spectrum Φ1 shown is not close to the wavelength of the monochromatic modulated light of low intensity that is mainly absorbed, the second embodiment described above is possible.

Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and modifications can be made as appropriate without departing from the scope of the present invention. . You may combine the structure as described in each embodiment and each example which were mentioned above.

All or part of the operating voltage estimating apparatus 1 in the above embodiment may be implemented by dedicated hardware, or may be implemented by a memory and a microprocessor.
All or part of the operating voltage estimating apparatus 1 is composed of a memory and a CPU (Central Processing Unit). It may be one that realizes a function.
A program for realizing all or part of the functions of the operating voltage estimating device 1 may be recorded in a computer-readable recording medium, and the program recorded in the recording medium may be read and executed by a computer system. Each part may be processed by . It should be noted that the "computer system" referred to here includes hardware such as an OS and peripheral devices. The "computer system" also includes the home page providing environment (or display environment) if the WWW system is used.
The term "computer-readable recording medium" refers to portable media such as flexible discs, magneto-optical discs, ROMs and CD-ROMs, and storage devices such as hard discs incorporated in computer systems. Furthermore, "computer-readable recording medium" means a medium that dynamically retains a program for a short period of time, like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. It also includes those that hold programs for a certain period of time, such as volatile memories inside computer systems that serve as servers and clients in that case. Further, the program may be for realizing part of the functions described above, or may be capable of realizing the functions described above in combination with a program already recorded in the computer system.

Reference Signs List 1 operating voltage estimating device 1A color bias light irradiation unit 1B external quantum efficiency spectrum calculation unit 1C modulated light irradiation unit 1C1 laser light irradiation unit 1C2 chopper control unit 1D wavelength selection unit 1E... phase detector, 1E1... lock-in amplifier, 1F... differential resistance calculator, 1G... operating voltage calculator, 11... current clamp sensor, M... multi-junction solar cell, M1... sub-cell, M2... sub-cell, M3... Subcell, R... Load resistance

Claims (11)

1. An operating voltage estimating device for estimating operating voltages of each of a plurality of sub-cells of a multi-junction solar cell having a plurality of sub-cells,
   a color bias light irradiation unit that irradiates the multijunction solar cell with color bias light;
   an external quantum efficiency spectrum calculating unit for calculating an external quantum efficiency spectrum of each of the plurality of sub-cells when the multi-junction solar cell is irradiated with the color bias light by the color bias light irradiation unit;
   a modulated light irradiator that irradiates the multi-junction solar cell, which is in operation under irradiation with sunlight, with a monochromatic modulated light of very low intensity when estimating the operating voltage of each of the plurality of sub-cells;
   a wavelength selection unit that selects a wavelength of the monochromatic modulated light irradiated by the modulated light irradiation unit;
   When the modulated light irradiation section irradiates the monochromatic modulated light, the monochromatic light according to a reference signal indicating the phase of the monochromatic modulated light and the operating voltage of each of the plurality of sub-cells of the multi-junction solar cell A signal indicating the output current of the multi-junction solar cell mixed with the synchronous component with the modulated light is input, and the synchronous component with the monochromatic modulated light mixed in the output current of the multi-junction solar cell is extracted. an output phase detector;
   a differential resistance calculation unit that calculates a differential resistance corresponding to the operating voltage of each of the plurality of sub-cells based on a synchronous component with the monochromatic modulated light output by the phase detection unit when the monochromatic modulated light is irradiated;
   an operating voltage calculator that calculates the operating voltage of each of the plurality of sub-cells based on the differential resistance calculated by the differential resistance calculator;
   Operating voltage estimator.
2. the number of wavelengths of the monochromatic modulated light selected by the wavelength selection unit is equal to the number of the plurality of sub-cells;
   The wavelength selection unit selects the wavelength of the monochromatic modulated light based on the external quantum efficiency spectrum of each of the plurality of sub-cells calculated by the external quantum efficiency spectrum calculation unit.
   The operating voltage estimating device according to claim 1.
3. The wavelength selection unit corresponds to the peak of the external quantum efficiency spectrum of each of the plurality of sub-cells calculated by the external quantum efficiency spectrum calculation unit as the wavelength of the monochromatic modulated light irradiated by the modulated light irradiation unit. select a wavelength,
   The operating voltage estimating device according to claim 2.
4. The differential resistance calculator,
   Simultaneous equations of a number equal to the number of the differential resistances as unknowns, wherein the phase detection unit detects when the monochromatic modulated light having the wavelength selected by the wavelength selection unit is irradiated by the modulated light irradiation unit. By solving simultaneous equations showing the relationship between the synchronous component with the extracted monochromatic modulated light, the differential resistance, and the external quantum efficiency spectrum corresponding to the wavelength selected by the wavelength selection unit, the differential resistance to calculate
   The operating voltage estimating device according to claim 2.
5. The wavelength selection unit selects wavelengths of the monochromatic modulated light that are greater in number than the number of the plurality of sub-cells.
   The operating voltage estimating device according to claim 1.
6. The differential resistance calculator,
   a number of simultaneous equations equal to the number of wavelengths of the monochromatic modulated light selected by the wavelength selection unit, wherein the monochromatic modulated light of the wavelengths selected by the wavelength selection unit is irradiated by the modulated light irradiation unit; Simultaneous equations showing the relationship between the synchronous component with the monochromatic modulated light extracted by the phase detection unit when the phase detector, the differential resistance, and the external quantum efficiency spectrum corresponding to the wavelength selected by the wavelength selection unit , a matrix, a first vector indicating the synchronous component with the monochromatic modulated light, and a second vector indicating the differential resistance, and using the least squares method, the second vector calculating the differential resistance corresponding to the component of
   The operating voltage estimating device according to claim 5.
7. The differential resistance calculator,
   The first relational expression is expressed using a normal equation,
   The second vector included in the normal equation is represented by a second relational expression using an inverse matrix,
   calculating the differential resistance corresponding to the component of the second vector by solving the second relational expression;
   The operating voltage estimating device according to claim 6.
8. The differential resistance calculator,
   If the inverse matrix does not exist, or if the inverse matrix becomes unstable,
   calculating the differential resistance corresponding to the component of the second vector by ridge regression;
   The operating voltage estimating device according to claim 7.
9. The differential resistance calculator,
   The second vector is represented by a third relational expression in which a unit matrix and a regularization constant are added,
   The wavelength selection unit sets the regularization constant so that the effects of the measurement error of a measuring device and the numerical error of a computer for calculating ridge regression in the wavelength of the monochromatic modulated light irradiated by the modulated light irradiation unit can be ignored. Select as value,
   The operating voltage estimating device according to claim 8.
10. The wavelength selection unit selects a number of wavelengths of the monochromatic modulated light equal to the number of the plurality of sub-cells,
    The differential resistance calculator,
    a number of simultaneous equations equal to the number of wavelengths of the monochromatic modulated light selected by the wavelength selection unit, wherein the monochromatic modulated light of the wavelengths selected by the wavelength selection unit is irradiated by the modulated light irradiation unit; Simultaneous equations showing the relationship between the synchronous component with the monochromatic modulated light extracted by the phase detection unit when the phase detector, the differential resistance, and the external quantum efficiency spectrum corresponding to the wavelength selected by the wavelength selection unit , a first relational expression using a matrix, a first vector indicating a synchronous component with the monochromatic modulated light, and a second vector indicating the differential resistance, and the first relational expression is expressed using a normal equation represent,
    The second vector included in the normal equation is represented by a second relational expression using an inverse matrix,
    if the value of the determinant of said matrix is approximately zero,
    calculating the differential resistance corresponding to the component of the second vector by ridge regression;
    The operating voltage estimating device according to claim 1.
11. An operating voltage estimation method for estimating the operating voltage of each of a plurality of sub-cells of a multi-junction solar cell having a plurality of sub-cells, comprising:
    a color bias light irradiation step of irradiating the multijunction solar cell with color bias light;
    an external quantum efficiency spectrum calculating step of calculating an external quantum efficiency spectrum of each of the plurality of sub-cells when the multi-junction solar cell is irradiated with the color bias light in the color bias light irradiation step;
    a modulated light irradiation step of irradiating the multi-junction solar cell, which is in operation by irradiation with sunlight, with a monochromatic modulated light having a weak intensity when estimating the operating voltage of each of the plurality of sub-cells;
    a wavelength selection step of selecting a wavelength of the monochromatic modulated light irradiated in the modulated light irradiation step;
    When the monochromatic modulated light is irradiated in the modulated light irradiation step, the monochromatic light is irradiated according to a reference signal indicating the phase of the monochromatic modulated light and the operating voltage of each of the plurality of subcells of the multijunction solar cell. A signal indicating the output current of the multi-junction solar cell mixed with the synchronous component with the modulated light is input, and the synchronous component with the monochromatic modulated light mixed in the output current of the multi-junction solar cell is extracted. a phase detection step to be output;
    a differential resistance calculation step of calculating a differential resistance corresponding to an operating voltage of each of the plurality of sub-cells based on a synchronous component with the monochromatic modulated light output in the phase detection step when the monochromatic modulated light is irradiated;
    an operating voltage calculating step of calculating an operating voltage of each of the plurality of sub-cells based on the differential resistance calculated in the differential resistance calculating step;
    Operating voltage estimation method.

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