JP2015079833A - State estimation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To estimate more detailed state of a solar battery as compared with a conventional state on the basis of action of an operation point of the solar battery.SOLUTION: A state estimation apparatus 300 is an apparatus for estimating a state concerned with a change in a power generation amount of a solar battery string 110 including a plurality of solar cells connected in series and bypass diodes each of which is connected to the plurality of solar cells in parallel. When MPPT control for allowing an operation point of the solar battery string 110 to follow a maximum power point is performed for instance, the state estimation apparatus 300 detects switching of the bypass diodes from OFF to ON. A controller 350 in the state estimation apparatus 300 analyzes history data 352 including frequencies, generation time bands, duration time, and secular change of switching e.g. as history of switching from OFF to ON of the bypass diodes, collates the history data with a state estimation database 351, estimates a state of the solar battery string 110, and outputs data indicating the estimated result.

Description

  The present invention relates to a technique for estimating a state related to a change in power generation amount of a solar cell.

  In the solar power generation system, each of a plurality of solar cells constituting the solar battery receives sunlight to generate power. Since a solar power generation system is a power generation system using natural energy, it is known that the amount of power generation is likely to change over time. For this reason, the technique which detects the cause by which the electric power generation amount of the solar power generation system fell has been proposed conventionally. In Patent Document 1, the generated power of one solar cell module and the generated power of another solar cell module in a solar power generation system are compared with each other. It is disclosed to detect whether an abnormality (failure) occurs. Patent Document 2 describes whether or not there is a failure in a solar cell module based on on / off control of a switch element that short-circuits or opens both ends of the solar cell module constituting the solar cell string, and a measured value of the generated power of the solar cell string. It is disclosed that the presence or absence of output decrease due to shade is determined.

JP 2013-168535 A JP 2012-89562 A

In the technology disclosed in Patent Document 1, when the power generated by both of the solar cell modules to be compared decreases, whether both solar cell modules are shaded or whether both solar cell modules have failed. It cannot be determined accurately. In the technique disclosed in Patent Document 2, on / off control of the switch element and measurement of the generated power must be performed on occasions other than the opportunity to obtain the generated power from the solar cell string, and the generated power from the solar cell string Will interfere with the supply.
On the other hand, an object of the present invention is to estimate a more detailed state than the conventional solar cell based on the behavior of the operating point of the solar cell.

  In order to solve the above-described problem, a state estimation device according to the present invention is a photovoltaic power generation system including a solar cell including a plurality of solar cells connected in series and a bypass diode connected in parallel to the plurality of solar cells. A state estimation device for estimating the state of the solar cell when the amount of power generation changes, and detecting means for detecting switching of the bypass diode from OFF to ON, and the switching detected by the detection means History specifying means for specifying a history, and estimation means for estimating the state of the solar cell based on the history specified by the history specifying means and outputting data indicating the estimation result.

In the state estimation device of the present invention, the detection means may detect the switching by detecting that the output voltage of the solar cell has changed at a preset speed or more.
In the state estimation device according to the present invention, the estimation unit is configured to control the solar cell based on the history when the operation of the solar cell is controlled to follow the maximum power point in the solar power generation system. May be estimated.

In the state estimation device of the present invention, the history specifying unit specifies at least the frequency at which the switching is detected as the history, and the estimation unit is any one of the plurality of candidates for the state according to the frequency. May be the estimation result.
In the state estimation device, the history specifying unit further specifies a period in which the switching is detected as the history, and the estimation unit selects any one of the plurality of candidates for the state according to the frequency and the period. It is good also as said estimation result.

  The state estimation apparatus according to the present invention further includes a measurement unit that measures a power generation amount of the solar cell, the estimation unit according to the history and the power generation amount measured by the measurement unit among a plurality of candidates of the state. Any of the above may be used as the estimation result.

  According to the present invention, based on the behavior of the operating point of a solar cell, it is possible to estimate a more detailed state than the conventional solar cell.

The figure which shows the whole structure of the solar energy power generation system which is one Embodiment of this invention. Explanatory drawing of the electrical connection of a solar cell string and a state estimation apparatus. Explanatory drawing of the electrical property of a photovoltaic cell. Explanatory drawing of the relationship between MPPT control and the behavior of an operating point. Explanatory drawing of the relationship between a minute electric current fluctuation | variation and the ease of the movement of the high resistance area | region of an operating point. The figure which shows the relationship between the weather and time, and the magnitude | size of an electric current margin. Explanatory drawing of the electrical property in case a photovoltaic cell has failed and is hardly generating electric power. Explanatory drawing of an electrical characteristic when the electric power generation amount of a photovoltaic cell falls. Explanatory drawing of the relationship between the state of a solar cell string, a weather, and time, and the frequency which a bypass diode turns on. The block diagram which shows the hardware constitutions of a state estimation apparatus. The circuit diagram of a level shift circuit, a voltage change detection circuit, and an edge detection circuit. The flowchart which shows the flow of the process which a controller performs. The figure which shows the output voltage and output current of a solar cell string, and an edge detection result. The figure which shows an example of the information described in a state estimation database. The figure which shows the other structural example of a state estimation apparatus. The figure which shows an example of the information described in a state estimation database. The figure which shows an example of the information described in a state estimation database. The figure which shows an example of the information described in a state estimation database. The figure which shows an example of the information described in a state estimation database.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing an overall configuration of a photovoltaic power generation system 1 according to an embodiment of the present invention.
As shown in FIG. 1, the photovoltaic power generation system 1 includes a solar cell array 100, a power conditioner 200, and a plurality of state estimation devices 300. The solar cell array 100 is installed, for example, on the rooftop of a building such as a house or a building or in the vicinity thereof. The solar cell array 100 has a configuration in which a plurality of solar cell strings 110 are arranged in an array. Each of the plurality of solar cell strings 110 is connected in parallel to the power conditioner 200. The solar cell string 110 has a configuration in which a plurality of solar cell modules 120 are connected in series. In this embodiment, the connection means an electrical connection.
Note that the number of solar cell strings 110 included in the solar cell array 100 and the number of solar cell modules 120 included in the solar cell string 110 may be any number.

  The power conditioner 200 is a voltage converter connected to each of the plurality of solar cell strings 110 included in the solar cell array 100 via a blocking diode 400. The blocking diode 400 has an anode connected to the solar cell string 110 and a cathode connected to the power conditioner 200. The power conditioner 200 takes in the output voltage (DC voltage) of the solar cell array 100 and controls the operation of the solar cell array 100.

  The power conditioner 200 includes a DC-DC converter and an inverter. The DC-DC converter boosts the DC voltage (for example, 200 to 300 V) taken from each of the solar cell arrays 100 to a higher DC voltage (for example, 300 to 400 V) by controlling to turn on or off the switch element. The inverter converts the DC voltage input from the DC-DC converter into an AC voltage, and sends the AC current to the grid power network. The inverter adjusts the transmission amount of the alternating current by performing PWM (Pulse Width Modulation) control of the switch element. Maximum power point tracking control (hereinafter referred to as “MPPT control”) is realized by PWM control performed by the inverter. “MPPT” is an abbreviation for Maximum Power Point Tracking. MPPT control is control that causes the operating point of the solar cell to follow the maximum power point. The solar cell here is a concept including a solar cell array 100, a solar cell string 110, a solar cell module 120, and a solar cell block 130 described later.

  The state estimation device 300 is a device that estimates the state of the solar cell included in the solar power generation system 1 when the power generation amount of the solar power generation system 1 changes. Here, one state estimation device 300 is provided corresponding to each of the solar cell strings 110. For this reason, the state estimation apparatus 300 estimates the state of the solar cell string 110. For example, the state estimation device 300 estimates the cause of the change in the power generation amount of the solar power generation system 1.

FIG. 2 is a diagram for explaining electrical connection between the solar cell string 110 and the state estimation device 300. As shown in FIG. 2, each of the plurality of solar cell modules 120 connected in series in the solar cell string 110 has a configuration in which a plurality of solar cell blocks 130 are connected in series. The solar cell module 120 has a configuration in which, for example, a plurality of solar cell blocks 130 are connected to each other and formed into a panel shape, or formed from a flexible material (that is, a flexible material). It may become. Each of the plurality of solar cell blocks 130 includes a plurality of solar cells 131 connected in series and a bypass diode 132 connected in parallel to the plurality of solar cells 131. The solar cell block 130 may be called a solar cell cluster.
Note that the number of the solar battery blocks 130 included in the solar battery module 120 and the number of the solar battery cells 131 included in the solar battery block 130 may be any number.

  The solar cells 131 of the solar cell block 130 receive sunlight to generate electric power and output a direct current. The solar cell 131 is the minimum power generation unit. An equivalent circuit of the solar battery 131 can be represented by a current source, a diode, and a resistor. The bypass diode 132 of the solar cell block 130 is in a state where all the solar cells 131 constituting the solar cell block 130 generate power with a power generation amount equal to or greater than a certain amount (hereinafter referred to as “steady state”). Is off. For this reason, when the solar cell block 130 is in a steady state, a direct current flows through a path passing through the solar cells 131 of the solar cell block 130 as indicated by an arrow A1 in FIG. However, when the power generation amount of at least some of the solar cells 131 of the solar cell block 130 is reduced (including the case of zero), the bypass diode 132 of the solar cell block 130 may be turned on. Bypass diode 132 bypasses (that is, bypasses) the output current of other solar cell blocks 130 by electrically disconnecting solar cell block 130 including solar cells 131 whose power generation amount has decreased. This is a diode. For this reason, when the power generation amount of at least some of the solar cells 131 constituting the solar cell block 130 decreases, a direct current flows through a path passing through the bypass diode 132 as indicated by an arrow A2 in FIG.

  The reason why the power generation amount of the solar cell 131 is reduced and the bypass diode 132 is switched from OFF to ON is, for example, a decrease in the amount of solar radiation with respect to the solar cell 131. The decrease in the amount of solar radiation occurs, for example, due to weather or time. A decrease in the amount of power generated due to a decrease in the amount of solar radiation occurs almost uniformly throughout the solar cell array 100. Other than the decrease in the amount of solar radiation, the power generation amount of the solar cell 131 may be reduced by, for example, a failure or deterioration with time, partial shade, dirt attached to the surface of the solar cell 131, or the like. is there. The partial shade means that some of the solar cells 131 among the plurality of solar cells 131 included in one solar cell block 130 are shaded. The decrease in the amount of power generation due to a cause other than the decrease in the amount of solar radiation often occurs in a part of the solar cell array 100 (for example, locally).

  FIG. 3 is a diagram for explaining electrical characteristics of the solar battery 131 in a steady state. In the upper part of FIG. 3, a current (I) -voltage (V) characteristic curve (hereinafter referred to as “the output current of the solar battery cell 131 corresponding to the vertical axis and the output voltage of the solar battery cell 131 corresponding to the horizontal axis” "IV curve"). In the lower part of FIG. 3, the output power (P) of the solar battery cell 131 corresponds to the vertical axis and the output voltage (V) of the solar battery cell 131 corresponds to the horizontal axis (P) −voltage (V). A characteristic curve (hereinafter referred to as “PV curve”) is shown. When the IV curve is determined, the PV curve is also uniquely determined. The voltage at which the output voltage V is maximum and the output current I is zero on the IV curve is referred to as “open voltage”. On the IV curve, the current at the point where the output voltage V is zero and the output current I is maximum is referred to as “short circuit current”.

As shown in the upper part of FIG. 3, the region on the IV curve is divided into a “low resistance region” and a “high resistance region” according to the change in the output voltage V with respect to the change in the output current I. . The low resistance region is a region where the amount of change in the output voltage V relative to the change in the output current I is relatively small. The high resistance region is a region where the amount of change in the output voltage V relative to the change in the output current I is relatively large.
The current (I) -voltage (V) characteristic curve of the solar battery block 131 including the solar battery cell 131, the solar battery module 120, the solar battery string 110, and the solar battery array 100 is not limited to the solar battery 131. A curve having the same shape as the IV curve and the PV curve of the battery cell 131 is drawn. The regions on the IV curve of the solar cell block 130, the solar cell module 120, the solar cell string 110, and the solar cell array 100 are also divided into a “low resistance region” and a “high resistance region”.

Here, the MPPT control performed by the power conditioner 200 will be described with reference to FIG. 4A and 4B show the IV curve and the PV curve of the solar cell array 100. FIG. That is, in FIG. 4 and the description thereof, the output current I is the output current of the solar cell array 100, the output voltage V is the output voltage of the solar cell array 100, and the output power P is the output voltage of the solar cell array 100. It is the output power.
As shown in FIG. 4A, the power conditioner 200 causes the operating point Pc (shown by a white circle) on the IV curve of the solar cell array 100 to follow the maximum power point Pm (shown by a black circle). MPPT control is performed. The maximum power point Pm is a point at which the output power P on the PV curve is maximized. If the maximum power point Pm on the PV curve is determined, the maximum power point Pm on the IV curve is uniquely determined. The maximum power point Pm is located in the low resistance region on the IV curve. In this embodiment, the power conditioner 200 performs MPPT control according to a known Hill Climbing Method, but may perform MPPT control according to other methods.

  By the way, the IV curve and the PV curve are not always constant, and change according to the amount of solar radiation with respect to the solar cell array 100, for example. In general, the amount of solar radiation in the morning and evening is smaller than the amount of solar radiation at other times such as daytime. In addition, the amount of solar radiation in cloudy weather such as cloudy or rainy weather is less than the amount of solar radiation in fine weather. Even in fine weather, the amount of solar radiation may decrease due to temporary shade. When the amount of solar radiation with respect to the solar cell array 100 decreases, the IV curve changes from the state shown in FIG. 4A to the state shown in FIG.

  The IV curve shown in FIG. 4B draws a curve that changes in the direction in which the output current I decreases compared to the IV curve shown in FIG. Due to the change in the IV curve, the maximum power point Pm moves to the low potential side, that is, in a direction approaching the high resistance region, as compared with the case of the IV curve shown in FIG. The smaller the amount of solar radiation, the more prominent the tendency of this change in the IV curve. For this reason, when the amount of solar radiation slightly decreases, the output current I only needs to decrease slightly, and the maximum power point Pm also needs to move slightly to the low potential side. However, as the amount of solar radiation is greatly reduced, the output current I is greatly reduced, and the maximum power point Pm is also greatly moved toward the low potential side, that is, in a direction approaching the high resistance region.

  In the MPPT control, when the operating point Pc is on the higher potential side than the maximum power point Pm, when the output current I slightly increases or decreases, the output voltage V also slightly changes. For this reason, it can be said that the low resistance region is a region where the fluctuation of the output voltage V is small and the control for stably obtaining the generated power is easily performed. On the other hand, when the operating point Pc is in the high resistance region on the lower potential side than the maximum power point Pm, even if the output current I is slightly increased or decreased, the output voltage V is from near zero to near the maximum voltage in the high resistance region. Can vary greatly between. For this reason, it can be said that the high resistance region is a region in which the fluctuation of the output voltage V is large and it is difficult to perform control for stably obtaining the generated power. Therefore, the power conditioner 200 generally performs MPPT control so as not to move the operating point Pc to the high resistance region.

  However, when the power conditioner 200 is performing MPPT control, the operating point Pc may move to the high resistance region. In particular, as the amount of solar radiation is smaller, the maximum power point Pm is closer to the high resistance region, so that the operating point Pc is more likely to move to the high resistance region. For example, when the output power P of the solar cell array 100 changes suddenly, the control of the operating point Pc by the power conditioner 200 may not be in time, and the operating point Pc may move to the high resistance region. When the operating point Pc moves to the high resistance region, when the electrical characteristics of the solar cells 131 in the solar cell module 120 are the same, the output voltage V of the solar cell module 120 drops very greatly instantaneously. . When there is a variation in the electrical characteristics of the solar cell 131, the output voltage of the solar cell block 130 including the solar cell 131 having the worst electrical characteristics is greatly reduced, and the bypass diode 132 of the solar cell block 130 is May switch from off to on.

As a cause of the movement of the operating point Pc to the high resistance region, there is a minute current fluctuation included in the output current I of the solar cell array 100. The output current I of the solar cell array 100 is not a complete DC current but a current with a slight fluctuation. This minute current fluctuation is caused by the operation of the power conditioner 200, and includes the following two causes (I) and (II).
(I) Small current fluctuation caused by a ripple component generated in the DC-DC converter of the power conditioner 200. (Specifically, a ripple component having a shape close to a triangular wave synchronized with the switching frequency of the switch element.)
(II) Small current fluctuation generated when the power conditioner 200 performs the hill-climbing MPPT control. (In many cases, the power conditioner 200 is a step change due to a current change periodically fluctuated.)

  The two minute current fluctuations (I) and (II) are caused by the operation of the power conditioner 200 and are independent of, for example, the amount of solar radiation and the presence or absence of shade. The switching frequency (for example, several tens to several hundreds kHz) of the DC-DC converter is higher than the frequency of current change (for example, several to several tens Hz) that the power conditioner 200 periodically varies. For this reason, the frequency of the minute current fluctuation of (I) is often higher than the frequency of the minute current fluctuation of (II). However, since the two minute current fluctuations (I) and (II) are generated independently, the actual minute current fluctuation is the sum of these two fluctuations. The ease of movement of the operating point Pc to the high resistance region due to the minute current fluctuation also changes according to the amount of solar radiation with respect to the solar cell array 100.

FIG. 5 is a diagram for explaining the relationship between the minute current fluctuation and the ease of movement of the operating point Pc to the high resistance region. 5A is an explanatory diagram for the case of the IV curve shown in FIG. 4A, and FIG. 5B is an explanatory diagram for the case of the IV curve shown in FIG. 4B. is there.
As shown in FIG. 5A, when the amount of solar radiation is relatively large, the operating point Pc is hardly moved to the high resistance region due to the minute current fluctuation. As shown in FIG. 5A, the reference value for the control of the operating point Pc is the average value of the output current I of the solar cell array 100 (average current shown in FIG. 5A). The operating point Pc moves to the high resistance region when the peak of the minute current fluctuation becomes equal to or higher than the output current of the high resistance region. On the other hand, when the amount of solar radiation is relatively large and the maximum power point Pm is at a position relatively distant from the high resistance region on the IV curve, the peak of the current due to minute current fluctuation (FIG. 5 (a The current margin IM, which is the difference between the peak current shown in (2)) and the minimum output current in the high resistance region, is sufficiently secured. For this reason, it is difficult for the operating point Pc to move to the high resistance region due to the minute current fluctuation of the output current I. For example, the current margin IM is about 10% of the short-circuit current of the solar cell array 100, and the operating point Pc adjusted to the maximum power point Pm usually enters the high resistance region due to fluctuations in the amount of solar radiation. Absent.

  On the other hand, as shown in FIG. 5B, when the amount of solar radiation is relatively small, the operating point Pc is likely to move to the high resistance region due to minute current fluctuations. This is because when the amount of solar radiation is relatively small and the maximum power point Pm is located relatively close to the high resistance region on the IV curve, the current margin IM disappears or is extremely small. That is, when the amount of solar radiation is relatively small and the output current I of the solar cell array 100 is small, the operating point Pc enters the high resistance region due to a minute current fluctuation, and as a result, the bypass diode 132 in the solar cell array 100 is obtained. May switch from off to on. As shown in FIG. 5B, when the bypass diode 132 is repeatedly turned on and off due to the minute current fluctuation of the output current I of the solar cell array 100, the frequency corresponds to the frequency of the minute current fluctuation.

  FIG. 6 is a diagram showing the relationship between the weather and time (time zone) and the size of the current margin IM. As shown in FIG. 6, the current margin IM is sufficiently secured as the amount of solar radiation increases. Therefore, the current margin IM is larger as the weather or time is higher. On the contrary, the current margin IM is smaller as the weather or time is lower.

When the power generation amount of the solar cell array 100 decreases due to a cause other than the decrease in the amount of solar radiation, the curve changes to an IV curve different from the IV curve described with reference to FIGS. Hereinafter, the relationship between the cause of the decrease in the amount of power generation and the IV curve will be described by taking as an example the IV curve of the solar cell string 110 provided one by one corresponding to the state estimation device 300. In FIGS. 7 and 8 and the description of each of these figures, the output current I is the output current of the solar cell string 110, the output voltage V is the output voltage of the solar cell string 110, and the output power P is It is the output power of the solar cell string 110.
FIG. 7 is a diagram illustrating an IV curve and a PV curve of the solar cell string 110 when a specific solar cell 131 hardly generates power due to a failure. As shown in FIG. 7, when a specific solar cell 131 hardly generates power due to a failure, as shown in FIG. 7, a step in a region A close to the open voltage of the IV curve, that is, a high resistance region Will occur. As a result, a similar step is also generated in the PV curve. However, in the vicinity of the maximum power point Pm, the curve is almost the same as when the amount of solar radiation is large.
It should be noted that the IV curve and the PV curve having the shapes shown in FIG. 7 are obtained not only when the solar battery cell 131 fails but also when the solar battery cell 131 is heavily shaded. Moreover, when there are many failure | damaging photovoltaic cells 131, the number of the level | step differences on an IV curve and a PV curve will increase according to the number.

  FIG. 8 is a diagram illustrating an IV curve and a PV curve of the solar cell string 110 when the power generation amount of the specific solar cell 131 is decreased. This decrease in the amount of power generation is caused by, for example, contamination of the solar cells 131, deterioration with time, or thin partial shade. As shown in FIG. 8A, when the power generation amount of a specific solar cell 131 is reduced, two steps, that is, two high resistance regions are generated in the IV curve. For this reason, two peaks of output power P appear on both sides of the maximum power point Pm in the PV curve. When the step portion of the IV curve is enlarged, it becomes as shown in FIG. As shown in FIG. 8B, a high resistance region appears slightly on the low potential side of the maximum power point Pm. For this reason, the frequency at which the operating point Pc moves to the high resistance region is likely to increase due to the influence of the minute current fluctuation described above, and the MPPT control tends to become unstable. In this case, the bypass diode 132 may be repeatedly turned on and off frequently.

  The MPPT control in this case will be described. The power conditioner 200 tries to make the operating point Pc follow the maximum power point Pm. However, it is difficult to stably hold the operating point Pc at the maximum power point Pm on the high potential side of the high resistance region because the high resistance region and the maximum power point Pm are close to each other. As described above, since the output current of the solar cell array 100 includes a minute current fluctuation, there is almost always a moment when the operating point Pc enters the high resistance region. Once the operating point Pc enters the high resistance region, the output voltage V continues to fluctuate for a while. Finally, as shown in FIG. 8B, the operating point Pc1, which is one voltage peak, Or, it often moves to one of the operating points Pc2 on the higher potential side than the maximum power point Pm. For example, if the current margin IM at the operating point Pc1 is larger than the minute current fluctuation, the operating point Pc1 is set, and if not, the operating point Pc2 is set. However, even if the operating point Pc changes with time at the position of the operating point Pc1, if the amount of power generation is larger than the position of the operating point Pc2, control that remains at the position of the operating point Pc1 may be performed.

From the above, the relationship between the cause of the decrease in the amount of power generated by the solar cell array 100, the combination of weather and time, and the frequency with which the bypass diode 132 is switched from OFF to ON (hereinafter referred to as “switching frequency”). Is as shown in FIG. In FIG. 9, it means that the switching frequency is high in the order of “Yes”, “Sometimes”, “No”, and “Stop”. Of these, “stop” means that the solar cell array 100 is in a state where power generation is stopped or considered to be stopped.
As described above, the cause of the decrease in the power generation amount of the solar cell array 100 and the switching frequency of the bypass diode 132 are related to the IV curve and the cause of the decrease in the power generation amount of the solar cell array 100. This is because the way of changing the PV curve is different, and as a result, the behavior of the operating point Pc by the MPPT control is also different.

  As described above, when the power generation amount of the solar battery cell 131 is reduced, the bypass diode 132 of the solar battery block 130 including the solar battery cell 131 is switched from OFF to ON. This switching is, for example, several tens of nanoseconds. It is relatively fast to complete with. On the other hand, the speed at which the operating point Pc moves due to a change in the amount of solar radiation or the like is relatively low because it is completed in units of seconds, for example. Therefore, if a high-speed voltage change is detected based on the behavior of the operating point Pc of the solar battery cell 131, it should be possible to detect the moment when the bypass diode 132 is turned on. Furthermore, the switching frequency of the bypass diode 132 may be different due to a decrease in the power generation amount of the solar cell array 100. Further, the weather and time at which the bypass diode 132 is switched from OFF to ON may vary depending on the cause of the decrease in the amount of power generated by the solar cell array 100. Therefore, by analyzing the history of switching of the bypass diode 132 from OFF to ON, the state of the solar cell array 100 when the power generation amount of the solar cell array 100 decreases (for example, the cause of the decrease in power generation amount) is estimated. The inventors thought that this could be done. A device for estimating the state of the solar cell string 110 (that is, the solar cell array 100 including the solar cell string 110) by analyzing the history of switching of the bypass diode 132 from OFF to ON is the state estimation device 300. .

FIG. 10 is a block diagram illustrating a hardware configuration of the state estimation device 300.
As illustrated in FIG. 10, the state estimation device 300 includes a level shift circuit 310, a voltage change detection circuit 320a, an edge detection circuit 330a, a voltage change detection circuit 320b, an edge detection circuit 330b, and a power generation amount measurement unit 340. A controller 350, a communication circuit 360, and a display device 370.
The level shift circuit 310 is a circuit that converts the voltage level of the output voltage V of the solar cell string 110.

  The voltage change detection circuits 320 a and 320 b are circuits that detect a voltage change in the output voltage of the level shift circuit 310. The voltage change detection circuit 320a detects a voltage change equal to or higher than a preset speed so as to detect that the bypass diode 132 is switched from OFF to ON. The voltage change detection circuit 320a detects, for example, that a voltage of about several percent of the output voltage V has changed rapidly (for example, at a speed of at least several tens of nanoseconds), and conversely, a voltage slower than that. It does not detect changes. The voltage change detection circuit 320b is a circuit that detects a voltage change at a slower speed (eg, several tens of nanoseconds or more) than the voltage change detection circuit 320a. The voltage change detection circuit 320b detects not a voltage change when the bypass diode 132 is switched from OFF to ON, but a low-speed voltage change that may occur due to other reasons.

  The edge detection circuit 330a is a circuit that detects an edge of a voltage change detected by the voltage change detection circuit 320a, here, a rising edge and a falling edge. The edge detection circuit 330b is a circuit that detects edges (rising edge and falling edge) of the voltage change detected by the voltage change detection circuit 320b.

  The power generation amount measuring unit 340 (measuring means) is a circuit that measures the power generation amount of the solar cell string 110. The power generation amount measurement unit 340 measures each of the output voltage V and the output current I of the solar cell string 110, for example. Then, the power generation amount measurement unit 340 multiplies the measured output voltage V and output current I to calculate the generated power. The power generation amount measuring unit 340 notifies the controller 350 of the calculated generated power as the power generation amount.

The controller 350 is a microcomputer including, for example, a CPU (Central Processing Unit) and a memory, and is a control device that controls each part of the state estimation device 300. The controller 350 stores a state estimation database 351 and history data 352 in a memory. The state estimation database 351 is a database that is referred to in order to estimate the state of the solar cell string 110. In the state estimation database 351, the state of the solar cell string 110 is associated with a phenomenon related to the bypass diode 132 that occurs in that state. The history data 352 is data indicating the switching history of the bypass diode 132. In addition, the controller 350 acquires the detection result of the amount of solar radiation from the sunshine meter 101 provided in the solar cell array 100. The controller 350 determines the weather at the installation location of the solar cell array 100 based on the detection result of the illuminance by the sunshine meter 101. However, the controller 350 may determine the weather by another method, or may acquire and determine data for specifying the weather via the communication circuit 360. An estimation algorithm for the controller 350 to estimate the state of the solar cell string 110 will be described later.
The contents, data format, and data output destination of the estimation result data output from the controller 350 are not limited to this example, and various modifications are possible.

  When controller 350 estimates the state of solar cell string 110, controller 350 outputs data indicating the estimation result to communication circuit 360 and display device 370. For example, the controller 350 outputs notification data for reporting the estimation result to the external device to the communication circuit 360. Further, the controller 350 outputs display data for displaying the estimation result to the display device 370. The communication circuit 360 includes a modem, for example, and transmits data to an external device (a device such as a maintenance company) via a communication line such as the Internet (not shown). The display device 370 is a liquid crystal display, for example, and displays an image (screen) according to display data supplied from the controller 350.

FIG. 11 is a diagram illustrating a circuit configuration of the level shift circuit 310, the voltage change detection circuit 320a, and the edge detection circuit 330a (detection means). In FIG. 11, the solar cell string 110 is represented by a circuit symbol of a DC power source.
In the level shift circuit 310, a series circuit of resistors 3101, 3102 and 3103 and a series circuit of resistors 3104 and 3105 are connected in parallel to the solar cell string 110. For example, the resistance values of the resistors 3101 and 3104 are the same, and the resistance values of the resistors 3103 and 3105 are the same. The level shift circuit 310 divides and outputs the output voltage V of the solar cell string 110 from each of the node N1 that is a contact point between the resistor 3102 and the resistor 3103 and the node N2 that is a contact point between the resistor 3104 and the resistor 3105. To do. In the level shift circuit 310, the voltage division ratio is set by the resistance values of the resistors 3101 to 3105. Here, the voltage of the node N1 is lower than the voltage of the node N2.

In the voltage change detection circuit 320a, the node N1 of the level shift circuit 310 is connected to the negative terminal of the differential amplifier 3208 through a diode 3201 and a resistor 3202 connected in the forward direction. One end of a parallel circuit (RC parallel circuit) of a capacitor 3203 and a resistor 3204 is connected between the resistor 3202 and the negative terminal of the differential amplifier 3208. The other end of the RC parallel circuit is connected to the ground point GND. The node N2 of the level shift circuit 310 is connected to the positive terminal of the differential amplifier 3208 via a diode 3205 and a resistor 3206 that are forward-connected. One end of a resistor 3207 is connected between the resistor 3206 and the positive terminal of the differential amplifier 3208. The other end of the resistor 3207 is connected to the ground point GND. The differential amplifier 3208 is a comparator (comparator) that amplifies and outputs the voltage difference between the input voltage from the node N1 and the input voltage from the node N2. For example, the resistance values of the resistor 3202 and the resistor 3206 are the same, and the resistance values of the resistor 3204 and the resistor 3207 are the same. For this reason, when the output voltage V of the solar cell string 110 does not change more than the set speed, the input voltage at the negative terminal of the differential amplifier 3208 is lower than the input voltage at the positive terminal. In this case, the output level of the differential amplifier 3208 is a high (H) level. On the other hand, when the output voltage V of the solar cell string 110 changes more than the set speed, the voltage applied to the capacitor 3203 changes more slowly than the resistor 3207 in the RC parallel circuit. For this reason, when the voltage change more than a setting speed arises in the solar cell string 110, the input voltage of the negative terminal of the differential amplifier 3208 changes later than the input voltage of the positive terminal. Therefore, when the output voltage V of the solar cell string 110 decreases at a set speed or higher, the input voltage at the negative terminal of the differential amplifier 3208 becomes higher than the input voltage at the positive terminal, and the output level of the differential amplifier 3208 is changed from the H level. Change to low (L) level. The speed of voltage change at which the voltage change detection circuit 320a outputs an L level signal is set by, for example, the time constant of the RC parallel circuit.
Note that the output voltage of the differential amplifier 3208 is a voltage corresponding to the power supply voltage VDD of the differential amplifier 3208 and the resistance value of the resistor 3209.

  In the edge detection circuit 330a, a resistor 3301, an N-type MOSFET 3302 and a resistor 3303 are sequentially connected between the power supply line of the power supply voltage VDD and the ground point GND. The gate of the N-type MOSFET 3302 is connected to the output terminal of the differential amplifier 3208, the drain is connected to one end of the resistor 3301, and the source is connected to one end of the resistor 3303. The output voltage of the N-type MOSFET 3302 is input to the inverter 3304. When the output voltage of the N-type MOSFET 3302 is logically inverted by the inverter 3304, the inverted voltage is input to the XNOR element 3311 via two signal line paths having different response speeds in the edge detection circuit 330a. One of the signal line paths includes a series circuit of inverters 3305 and 3306. The other of the signal line paths includes an inverter 3307, a resistor 3308 and an inverter 3309 series circuit, and a capacitor 3310 having one end connected to the contact point between the resistor 3308 and the inverter 3309 and the other end connected to the ground point GND. In other words, the resistor 3308 and the capacitor 3310 constitute an integrating circuit.

The XNOR element 3311 performs negative exclusive OR using these response speed differences based on input voltages from two signal line paths having different response speeds, thereby rising and falling of the input signal. A one-shot pulse is generated in response to. The inverter 3312 outputs the output signal of the XNOR element 3311 as a logical inversion. As a result, the edge detection circuit 330a outputs a pulse signal having an H level corresponding to a voltage change equal to or higher than the set speed of the solar cell string 110, and an L level in other cases.
The edge time of the edge detected by the edge detection circuit 330a is set by, for example, the time constant of the integration circuit composed of the resistor 3308 and the capacitor 3310.
Although the configuration of the voltage change detection circuit 320a and the edge detection circuit 330a has been described here, the voltage change detection circuit 320b and the edge detection circuit 330b may have the same circuit configuration. However, the voltage change detection circuit 320b and the edge detection circuit 330b are set to have different time constants from the voltage change detection circuit 320a and the edge detection circuit 330a in order to detect a low-speed voltage change.

Under the above configuration, the controller 350 executes processing according to the procedure shown in the flowchart of FIG.
When the controller 350 detects that the bypass diode 132 has been switched from off to on based on the edge detection result of the edge detection circuit 330a (step S1), the controller 350 records the history data 352 in the memory (step S2). The history data 352 includes, for example, the time (date and time) when the bypass diode 132 is switched from OFF to ON. The history data 352 includes information in which the power generation amount measured by the power generation amount measuring unit 340 is associated with the measurement time. In addition to this, the history data 352 includes information that can specify the switching frequency of the bypass diode 132 (for example, the frequency at which the bypass diode 132 is turned on), and the period during which the bypass diode 132 is turned on and off (for example, the generation time zone). Or one or more data such as duration).

Next, the controller 350 (history specifying means), based on the history data 352 stored in the memory, the history of the switching of the bypass diode 132 from off to on and the amount of power generation measured by the power generation amount measurement unit 340. A history is specified (step S3). For example, the controller 350 may change the switching frequency of the bypass diode 132 (for example, the frequency at which the bypass diode 132 is turned on), the period during which the bypass diode 132 is turned on / off (for example, the generation time period or duration), And the change with time of the power generation amount is specified as the history of the power generation amount. Then, the controller 350 (estimating means) estimates the state of the solar cell string 110 based on the history specified in the process of step S3 and the state estimation database 351, and outputs data indicating the estimation result (step S4). ).
In controller 350, an opportunity to perform processing for recording history data 352 and an opportunity to estimate the state of solar cell string 110 based on history data 352 may be provided separately.

Here, an estimation algorithm of the state of the solar cell string 110 in the controller 350 will be described.
For example, when the switching frequency of the bypass diode 132 is relatively low, partial shade may occur. FIG. 13A shows an output voltage V of the solar cell string 110, an output current I of the solar cell string 110, and an edge detection result of the edge detection circuit 330a when partial shade occurs. When the bypass diode 132 is turned on due to partial shade, the partial shade is affected by a few seconds at a minimum, usually longer. For this reason, when the bypass diode 132 switches from OFF to ON, if the switching frequency is relatively low, such as a period of several seconds, a change in power generation amount due to partial shade (here, a decrease) is a candidate for the cause.

  FIG. 13B shows the output voltage V of the solar cell string 110, the output current I of the solar cell string 110, and the edge detection result of the edge detection circuit 330a when the bypass diode 132 is turned on by a minute current fluctuation. It is shown. The bypass diode 132 is turned on when the current peak due to the minute current fluctuation becomes the output current in the high resistance region, and therefore the bypass diode 132 is repeatedly turned on and off frequently. At this time, the frequency at which the bypass diode 132 is turned on corresponds to the frequency of the minute current fluctuation. Specifically, the frequency at which the bypass diode 132 is repeatedly turned on and off depends on the switching frequency of the DC-DC converter when it is caused by the ripple component of the DC-DC converter of the power conditioner 200, and the frequency associated with MPPT control is very small. When it originates in an electric current fluctuation | variation, it depends on the frequency of the electric current change which the power conditioner 200 fluctuates periodically. That is, when ON / OFF of the bypass diode 132 is detected at a high switching frequency due to a minute current fluctuation, for example, a change in the power generation amount due to contamination, deterioration, or thin partial shade of the solar cell 131 is a candidate. .

  FIG. 13C shows the output voltage V of the solar cell string 110 and the output current I of the solar cell string 110 when a specific solar cell 131 fails in power generation due to a failure and the bypass diode 132 is turned on. The edge detection result of the edge detection circuit 330a is shown. When a failure occurs in a specific solar cell 131, the bypass diode 132 is not turned off for the time being (for example, a longer period than in the case of partial shade) after the bypass diode 132 is switched from off to on. For example, the bypass diode 132 is not turned off until the power generation failure is resolved. However, when the conditions such as when the amount of solar radiation is small, the bypass diode 132 may be turned off even if the failure remains. In any case, when a failure occurs in the solar cell 131, for example, it can be said that the switching frequency of the bypass diode 132 is lower than that in the case where partial shade occurs. For this reason, when the on / off state of the bypass diode 132 is detected at a relatively low switching frequency, for example, a change in the amount of power generated due to a failure of the solar battery cell 131 is a candidate.

  For the reasons described above, based on the switching frequency of the bypass diode 132, a candidate for a cause of a decrease in the amount of power generated by the solar cell array 100 (solar cell string 110) can be specified. In addition to the frequency of this switching, further referring to the period (occurrence time zone and duration) when switching from OFF to ON of the bypass diode 132, the time-dependent change in the switching frequency, and the time-dependent change in power generation amount, A more detailed cause of the decrease in power generation amount can be estimated. Therefore, the controller 350 describes in the state estimation database 351 the history of switching from OFF to ON of the bypass diode 132 specified in the process of step S4 and the history of the power generation amount measured by the power generation amount measurement unit 340. The more detailed state of the solar cell string 110 is estimated by collating with the information.

FIG. 14 is a diagram illustrating an example of information described in the state estimation database 351.
As shown in FIG. 14, in the state estimation database 351, a phenomenon related to the switching frequency of the bypass diode 132, an occurrence time zone of switching of the bypass diode 132 from OFF to ON, a duration of the switching, and the switching occur. Each condition of the change over time of the duration or time zone and the change over time of the power generation amount is associated with the state of the solar cell string 110. The controller 350 compares the switching history obtained from the history data 352 and the power generation amount history with the conditions described in the state estimation database 351, and the solar cell string 110 associated with a condition that matches or is close to the condition. Extract the state. The controller 350 uses the state of the solar cell string 110 extracted from the state estimation database 351 as an estimation result. In this case, the controller 350 may narrow down to any one state and obtain an estimation result, or a plurality of states may be generated in a composite manner. Therefore, a plurality of states may be obtained as an estimation result.

The information described in the state estimation database 351 shown in FIG. 14 is determined based on the matters described in FIG. 9 and the inventors' knowledge about the phenomenon that can occur according to the state of the solar cell string 110. . As shown in FIG. 14, it can be seen that there is a close relationship between the behavior of the operating point of the solar cell string 110 when the bypass diode 132 is turned on and off and the state of the solar cell string 110.
Although not shown in FIG. 14, the controller 350 detects a relatively slow voltage change by the voltage change detection circuit 320 b and the edge detection circuit 330 b, and when there is a decrease in the amount of power generation, the solar radiation by the cloud is detected. It may be estimated that the amount has changed (decreased).
The manager of the external device that has received the notification data transmitted by the communication circuit 360 or the person who has seen the display on the display device 370 can know the cause of the decrease in the power generation amount of the solar cell array 100. This can be utilized in measures for recovering the power generation amount of the solar power generation system 1.

By the way, the state estimation device 300 further estimates the state of the solar cell string 110 by changing constants of one or more circuits of the level shift circuit 310, the voltage change detection circuits 320a and 320b, and the edge detection circuits 330a and 330b. It may have the function to do. FIG. 15 is a diagram illustrating the configuration of the state estimation device 300 in this case. In FIG. 15 and the description thereof, the voltage change detection circuits 320a and 320b are collectively referred to as “voltage change detection circuit 320”, and the edge detection circuits 330a and 330b are collectively referred to as “edge detection circuit 330”.
For example, the controller 350 of the state estimation device 300 uses the resistance (that is, the voltage division ratio) in the level shift circuit 310 and the constant of the voltage change detection circuit 320 according to an instruction (for example, remote operation of the external device) received from the external device by the communication circuit 360. And one or more of the constants of the edge detection circuit 330 are changed. Note that the controller 350 may change the constant of any element included in the circuit in order to change the constant of a certain circuit. In FIG. 15, in order to prevent the drawing from becoming complicated, circuit symbols of elements whose constants can be changed are also represented by the same circuit symbols as in FIG.

The constant of the element that can be changed by the voltage change detection circuit 320 is, for example, the resistance value of the resistor 3204 constituting the RC parallel circuit. In this case, the controller 350 changes the resistance of the resistor 3204, which is a variable resistor, by electrical control such as using an electronic volume. Due to this change in resistance, the time constant of the RC parallel circuit changes, so the speed of voltage change detected by the voltage change detection circuit 320 changes. Then, the controller 350 estimates the state of the solar cell string 110 for each speed while changing the speed of the voltage change detected by the voltage change detection circuit 320. For example, the controller 350 estimates the state of the solar cell string 110 one by one while changing the speed of the voltage change to be detected, which can help to estimate the degree of contamination of the solar cell string 110 in more detail. The controller 350 may change the capacitance of the capacitor 3203 constituting the RC parallel circuit instead of or in combination with the resistor 3204. The controller 350 may change each resistance (voltage division ratio) in the level shift circuit 310 so that the condition of the solar cell string 110 is suitable for estimation. Further, the controller 350 changes the time constant of the integration circuit of the edge detection circuit 330 and adjusts the response speed of the signal line path, thereby changing the edge time of the rising edge and the falling edge to be detected. Also good.
As described above, the controller 350 changes the constant of the circuit (element) and estimates the state of the solar cell string 110 when each constant is set, so that the constant is more detailed than when the constant is fixed. The state may be estimated.
The controller 350 may change the constant of each circuit under conditions other than the instruction received by the communication circuit 360. For example, the controller 350 may change the constant of each circuit according to a program executed by the controller 350.

The present invention may be implemented in a form different from the above-described embodiment. Moreover, you may combine each of the modification shown below.
(Modification 1)
The state of the solar cell string 110 estimated by the state estimation device 300 described in the above-described embodiment is merely an example. For example, based on the relationship illustrated in FIG. 16, the controller 350 may estimate a state (that is, an operation state) related to the operation of the solar cell string 110. As shown in FIG. 16, depending on the cause of the bypass diode 132 being turned on / off, this on / off switching may occur continuously (intermittently) or intermittently. Therefore, the controller 350 specifies the continuity of the occurrence period of the on / off switching of the bypass diode 132 and the duration of the occurrence period as a history from the off-state of the bypass diode 132 to the relation shown in FIG. Based on this, the operating state of the solar cell string 110 is estimated. The operating state shown in FIG. 16 corresponds to the behavior of the operating point on the IV curve.

  Further, the state estimation device 300 may estimate the operation state of the solar cell string 110 based on the power generation amount of the solar cell string 110 (for example, temporal change in the power generation amount). As shown in FIG. 17, the controller 350 estimates that there is a possibility of failure of a plurality of solar cell blocks when the amount of power generation is greatly reduced. Furthermore, when there is a time dependency (for example, time zone dependency or season dependency) in the decrease in the power generation amount, the controller 350 estimates that the plurality of solar cell blocks 130 are darkly shaded.

  Moreover, the state estimation apparatus 300 may estimate the operation state of the solar cell string 110 according to the frequency at which the bypass diode 132 is turned on due to a minute current fluctuation. As shown in FIG. 18, the controller 350 estimates that there is a high possibility of generation of a ripple component due to the operation of the DC-DC converter if the frequency is, for example, several tens to several hundreds kHz. For example, if the frequency is several Hz to several tens Hz, the controller 350 estimates that the adjustment current of the MPPT control is the cause. In addition, the controller 350 estimates that the possibility of partial shading is high when the on-off state of the bypass diode 132 occurs from time to time or occurs instantaneously and continuously.

Moreover, the state estimation apparatus 300 may estimate the operation state of the solar cell string 110 according to the output voltage V or the output current I of the solar cell string 110 based on the relationship shown in FIG. In this case, the controller 350 may use the measured value of the output voltage V or the output current I by the power generation amount measuring unit 340. For example, the controller 350 estimates the operating state of the solar cell string 110 based on the measured value of the output voltage V or the output current I of the solar cell string 110 or the temporal change of the measured value.
The information shown in FIGS. 16 to 19 described above may be described in the state estimation database 351.

As described above, there are various relationships between the state estimated by the state estimation device 300 and the phenomenon that occurs in the solar cell string 110 in that state. For this reason, the state estimation apparatus 300 may estimate the state of the solar cell string 110 (solar cell array 100) based on still another phenomenon that occurs in the solar cell string 110. For example, when the power generation amount recovers (that is, increases), the state estimation device 300 is based on the history of switching of the bypass diode 132 from OFF to ON and the power generation amount history measured by the power generation amount measurement unit 340. The state of the solar cell string 110 (for example, elimination of dirt adhesion) may be estimated.
On the contrary, the state estimation apparatus 300 may not estimate all the states described in the above-described embodiments and modifications, and may estimate only a part of the states. In this case, the state estimation apparatus 300 does not specify a part of the history of the switching from the off-state of the bypass diode 132 or the history of the power generation amount measured by the power generation amount measurement unit 340. Also good. For example, the state of the solar cell string 110 is omitted based on the switching history of the bypass diode 132 from off to on without omitting the power generation amount measurement unit 340 of the state estimation device 300 and the controller 350 specifying the power generation amount history. May be estimated.

(Modification 2)
The circuit configurations of the voltage change detection circuits 320a and 320 and the edge detection circuits 330a and 330b of the above-described embodiments are merely examples, and may be realized by other circuit configurations. For example, the state estimation apparatus 300 may detect that the output voltage V decreases (falling edge) at a set speed or higher and does not detect that the output voltage V increases (rising edge). Further, the edge detection circuit may not be a one-shot circuit, and may be realized using a counter, a latch, and an integration circuit that count pulses.
Moreover, the state estimation apparatus 300 may include a reset circuit that can be used at the time of startup or abnormality.

  Moreover, the state estimation apparatus 300 may include one set or three or more sets of voltage change detection circuits and edge detection circuits instead of two sets. In the former case, the state estimation device 300 includes a detection circuit corresponding to the voltage change detection circuit 320a and the edge detection circuit 330a for detecting the switching of the bypass diode 132 from OFF to ON. In the latter case, the speed of the detected voltage change may be different for each set of the voltage change detection circuit and the edge detection circuit. In this case, the state estimation device 300 may be useful for estimating a more detailed state of the solar cell string 110.

  Further, the means for detecting the switching of the bypass diode 132 from OFF to ON may not be detection of a voltage change at a speed higher than a preset speed. For example, instead of the voltage change detection circuits 320a and 320, a circuit that detects a current change (in this case, an increase in current) at a set speed or higher may be provided. When the bypass diode 132 is switched from OFF to ON, an instantaneously large output current I such as an inrush current flows through the solar cell string 110. Therefore, the switching from the OFF state to the ON state of the bypass diode 132 may be detected by detecting a change in the current that is equal to or higher than the set speed. Further, the state estimation device 300 may detect the switching of the bypass diode 132 from off to on by another method.

(Modification 3)
In the solar power generation system 1, an environmental sensor that detects environmental information indicating an environment where the solar cell array 100 is placed may be used in combination. The environmental sensor is, for example, a sensor that detects temperature, humidity, or wind power. However, environmental information other than these may be detected. In this case, the controller 350 acquires the environment information detected from the environment sensor, and estimates the state of the solar cell string 110 based on the acquired environment information and the history data 352 described in the above-described embodiment. Good.

(Modification 4)
In the solar power generation system 1 of the above-described embodiment, the state estimation device 300 is provided in units of solar cell strings 110, but is provided in units of solar cell arrays 100, units of solar cell modules 120, or units of solar cell blocks 130. Also good. In the solar power generation system 1, two or more state estimation devices 300 provided in units of 100 solar cell arrays, 110 units of solar cell strings, 120 units of solar cell modules, or 130 units of solar cell blocks may be combined. If it carries out like this, in the photovoltaic power generation system 1, based on the estimation result of the state by the several state estimation apparatus 300, it may be useful for estimating the more detailed state of the solar cell array 100. FIG.
Moreover, the solar cell of this invention should just contain at least 1 set of the several solar cell connected in series, and the bypass diode connected in parallel with these several solar cell. For this reason, the solar cell of this invention may be considered by any of a solar cell block, a solar cell module, a solar cell string, and a solar cell array. And the scale and specific structure of the solar cell of this invention are not limited to the example demonstrated by embodiment mentioned above.

  One power conditioner 200 may be provided for each solar cell string 110 instead of one for each solar cell array 100. That is, the number and operation | movement of the power conditioners 200 with which the solar power generation system 1 is provided are not limited to the example demonstrated by embodiment mentioned above.

(Modification 5)
The solar power generation system of the present invention may be a solar power generation system in which control for causing the operating point to follow the maximum power point by MPPT control is not performed. Even in this solar power generation system, the state estimation device of the present invention detects the state of the solar cell by detecting the switching of the bypass diode of the solar cell included in the solar power generation system from OFF to ON. Can be estimated. As a specific example of the solar power generation system in which MPPT control is not performed, there is a solar power generation system in which a solar battery is directly connected to a storage battery without providing a power conditioner. In this solar power generation system, for example, the output voltage of the solar cell may be monitored to control charging of the storage battery, but the control of the output voltage of the solar cell (control of the operating point) may not be performed. is there.

(Modification 6)
In addition, the function realized by the state estimation device of the present invention can be realized by either hardware resources or software resources or by their cooperation. For example, the present invention can be provided as a program executed by a computer.
When the function of the state estimation apparatus according to the present invention is implemented using a program, the program can be a magnetic recording medium (magnetic tape, magnetic disk (HDD (Hard Disk Drive), FD (Flexible Disk), etc.)), optical recording. It may be provided in a state stored in a computer-readable recording medium such as a medium (such as an optical disk), a magneto-optical recording medium, or a semiconductor memory, or may be distributed via a network. Further, the present invention can be grasped as a state estimation method performed by a computer.

DESCRIPTION OF SYMBOLS 1 ... Solar power generation system, 100 ... Solar cell array, 101 ... Solar meter, 110 ... Solar cell string, 120 ... Solar cell module, 130 ... Solar cell block, 131 ... Solar cell, 132 ... Bypass diode, 200 ... Power Conditioner, 300 ... State estimation device, 310 ... Level shift circuit, 320a, 320b ... Voltage change detection circuit, 330a, 330b ... Edge detection circuit, 340 ... Power generation amount measuring unit, 350 ... Controller, 351 ... State estimation database, 352 ... History data, 360 ... communication circuit, 370 ... display device, 400 ... blocking diode.

Claims (6)

Estimating the state of the solar cell when the amount of power generated by a solar power generation system including a plurality of solar cells connected in series and a bypass diode connected in parallel to the plurality of solar cells is changed. A state estimation device that performs
Detecting means for detecting switching of the bypass diode from off to on;
History specifying means for specifying the switching history detected by the detecting means;
A state estimation device comprising: estimation means for estimating a state of the solar cell based on the history specified by the history specifying means and outputting data indicating an estimation result. The detection means includes
The state estimation device according to claim 1, wherein the switching is detected by detecting that the output voltage of the solar cell has changed at a preset speed or higher. The estimation means includes
2. The solar cell state is estimated based on the history when the control of making the operating point of the solar cell follow the maximum power point is performed. Or the state estimation apparatus of Claim 2. The history specifying means includes
As the history, specify at least the frequency of detecting the switching,
The estimation means includes
The state estimation device according to any one of claims 1 to 3, wherein one of the plurality of candidates for the state according to the frequency is used as the estimation result. The history specifying means includes
As the history, further specify the period of detecting the switching,
The estimation means includes
The state estimation apparatus according to claim 4, wherein any one of the plurality of candidates for the state according to the frequency and the period is used as the estimation result. Comprising measuring means for measuring the power generation amount of the solar cell,
The estimation means includes
6. The method according to claim 1, wherein among the plurality of candidates for the state, any one of the history and the power generation amount measured by the measurement unit is used as the estimation result. The state estimation apparatus described.

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