JP2015156091A - Power distribution circuit of solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power distribution circuit of solar cells which, when an output of a part of the solar cells of a photovoltaic power generation system is reduced by shading, etc., smooths steps observed in current-voltage characteristics of the system to improve a generation efficiency.

SOLUTION: The power distribution circuit periodically ON/OFF switches switching elements S1, S2 incorporated in each of charging paths X1, X2, thereby continuously distributing power via flyback transformers T1, T2 from a charging path X1(or X2) close to a solar cell M1(or M2) having a large power generation output across a discharging path Y2(or Y1) close to a solar cell M2(or M1) having a small power generation output, and equalizing the power generation output. Capacitors C1, C2 reduce noise generated by the switching elements S1, S2 and smooth variations of current flowing to an external load.

COPYRIGHT: (C)2015,JPO&INPIT

Description

  The present invention improves the power generation efficiency of the entire system even when the installation environment of solar cells used in a solar power generation system is bad and part of it is shaded or when the output characteristics between solar cells vary. The present invention relates to a power distribution circuit of a solar cell that can be increased.

  Here, the term “solar cell” means a cluster in which bypass diodes are connected in parallel to both ends of a string of solar cells (photovoltaic elements) connected in series, and such a cluster is a single or Both solar cell modules configured by connecting in series are meant.

  Currently, in order to increase the power generation efficiency of the solar power generation system, development of solar cells (modules) and power conditioners with high conversion efficiency is in progress. As described in Patent Document 1, the currently used photovoltaic power generation system is a centralized inverter system in which a plurality of solar cell modules are connected in series and parallel to increase the voltage and then converted into alternating current by an inverter. Has become the mainstream.

  However, in such a centralized inverter type solar power generation system, in actual use, some solar cell modules are placed in an installation environment such as a shade. In some cases, the power generation capacity cannot be fully demonstrated.

  FIG. 23 is a diagram schematically showing a solar power generation system composed of two solar cell modules M1 and M2 connected in series. These solar cell modules M1 and M2 have the same specifications. It has been.

  Further, a bypass diode D is connected between the positive electrode terminal P1 and the negative electrode terminal P2 of each of the solar cell modules M1 and M2, and the positive electrode terminal P1 of the solar cell module M1 and the negative electrode terminal P2 of the solar cell module M2 are Each is connected to an external load via an output line A.

  When these solar cell modules M1 and M2 are both installed in the sun and are sufficiently exposed to sunlight, the total external output is the maximum as shown by the thick solid line in FIG. The current / voltage characteristic with the output operating point as P is shown.

  However, for example, when one of the solar cell modules M2 enters the shade, these solar cell modules M1 and M2 have a stepped shape as shown in FIG. The current-voltage characteristics are shown.

  In FIG. 25, the sum of the areas of the region (1) and the region (3) represents the power generation output (maximum value) of the solar cell module M1, and the area of the region (2) is that of the solar cell module M2. It represents the power generation output (maximum value).

  In such current / voltage characteristics, the power generation output obtained when the maximum output operating point P is at the position shown in the figure is the sum of the areas of the area (1) and the area (2), and is indicated by hatching. The part (3) is a loss because it cannot contribute to the power generation output.

  On the other hand, as described in Patent Document 2, there is a solar power generation system using an AC solar cell module in which a microconverter is mounted on each solar cell module. This method is a solar cell module that performs maximum power follow-up (MPPT) control on each solar cell module and performs DC / AC conversion on the output, and is said to have little loss due to shade or the like.

JP 2000-347753 A JP 11-318042 A

  However, since the photovoltaic power generation system using the AC solar cell module as described above has a complicated conversion circuit, the manufacturing cost of each solar cell module is increased, and the conversion operation is always performed. There was a problem that conversion loss occurred even in the absence of shade.

  In addition, when the conversion circuit breaks down, the solar cell module itself on which the conversion circuit is mounted cannot be used, so there is a problem in reliability. For this reason, it is desired to develop a system that can maintain high system efficiency in any installation environment in the future.

  Therefore, the present invention solves the problems in the prior art as described above, and a step appearing in the current-voltage characteristics of the system when the output of a part of the solar cells of the photovoltaic power generation system is reduced by the shade or the like. An object of the present invention is to provide a power distribution circuit for a solar cell that can be smoothed to increase power generation efficiency.

  The power distribution circuit of the present invention provided for the above-described object includes a plurality of charging paths individually connecting between the positive terminals and the negative terminals of a plurality of solar cells connected in series to an external load. A plurality of discharge paths individually connecting between the positive electrode terminal and the negative electrode terminal of the solar cell, the charging path of the front-stage solar cell adjacent to the front and rear, the discharge path of the rear-stage solar cell, and the charging of the rear-end solar cell The discharge path of the solar cell at the front end of the road and the row, or the discharge path of the front solar cell and the charging path of the rear solar cell adjacent to each other, and the charging path of the solar cell at the front end of the row and the solar cell at the rear end of the row A plurality of flyback transformers that magnetically couple the respective discharge paths, a switching element incorporated in series with the primary side coil of the corresponding flyback transformer in each charge path, and each discharge A diode incorporated in series with the secondary side coil of the corresponding flyback transformer and in the direction of passing current from the negative terminal side to the positive terminal side of the corresponding solar cell, and the respective switching elements periodically A switching control circuit that is turned ON / OFF, and a smoothing circuit that includes at least one capacitor for smoothing current fluctuations in the corresponding charging path and discharging path for each solar cell.

  In the power distribution circuit of the present invention, it is desirable that the switching control circuit has a function of maintaining the OFF state of only arbitrarily selected switching elements during the periodic switching operation of each switching element.

  According to the first aspect of the present invention, when the power generation output varies between the solar cells used in the photovoltaic power generation system due to shade, dirt on the light receiving surface, aging deterioration, etc. Power can be distributed in a balanced manner between batteries.

As a result, the difference in the current-voltage characteristics of the entire photovoltaic power generation system is smoothed, and the power that was originally lost cannot be used and the lost power can be used. Can do.
In addition, since the step of the current-voltage characteristic is smoothed, the maximum output operating point of the power conditioner can be easily detected, and MPPT mismatch loss can be avoided.

  Further, the main part of the power distribution circuit of the present invention can have a very simple circuit configuration including switching elements such as relays and FETs (field effect transistors), diodes, flyback transformers, capacitors, and the like.

  In addition, a diode is used instead of the switching element so that the current flows at the timing when the switching element is turned off in the discharge path that is connected to the charging path and the flyback transformer by incorporating the switching element only in the charging path. Since the current flow is controlled, the number of necessary switching elements in the entire circuit can be reduced, and the generation of noise associated with the switching operation can be suppressed as much as possible.

  In addition, since the switching control circuit only needs to have a function of periodically turning on / off each switching element, the manufacturing cost can be reduced, and failure is unlikely to occur and high reliability is obtained. .

  In addition, in the system using the conventional AC solar cell module, even when there is no shade, circuit loss due to AC / DC conversion always occurs, whereas the power distribution circuit according to the present invention has no shade. Can stop the operation and eliminate the circuit loss, so that it is possible to prevent a decrease in power generation efficiency.

  Furthermore, in a photovoltaic power generation system using a conventional AC solar cell module, when a microconverter mounted on the solar cell module fails, the solar cell module itself becomes unusable, but in the power distribution circuit of the present invention, Even if a failure occurs and its function stops, there is no possibility that the function of the photovoltaic power generation system itself will be disturbed.

  According to the second aspect of the present invention, only the arbitrarily selected switching elements can be maintained in the OFF state during the periodic switching operation of each switching element. When the failure diagnosis is performed, the power generation output is reduced by stopping the power distribution to the solar cell connecting the charging path incorporating the switching element and the discharging path coupled by the flyback transformer. From the change in the current-voltage characteristics of the system caused by the stop of the power distribution to the solar cell, the solar cell in which a problem has occurred can be easily identified.

It is a schematic diagram of the photovoltaic power generation system which consists of two solar cell modules M1 and M2 connected in series which shows one Embodiment of the power distribution circuit of this invention. It is a block diagram of a switching control circuit in one embodiment of a power distribution circuit of the present invention. It is a figure which shows the waveform of the pulse signal output from the pulse oscillator of the switching control circuit shown in FIG. It is a figure which shows the electric power accumulation | storage process of the flyback transformer T1 in case the electric power generation output of the solar cell module M1 is larger than the electric power generation output of the solar cell module M2. It is a figure which shows the electric power discharge | release process from the flyback transformer T1 in case the electric power generation output of the solar cell module M1 is larger than the electric power generation output of the solar cell module M2. It is a figure which shows the current voltage characteristic of the system improved by the power distribution circuit. It is a figure which shows the electric power accumulation | storage process to the flyback transformer T2 in case the electric power generation output of the solar cell module M2 is larger than the electric power generation output of the solar cell module M1. It is a schematic diagram which shows the electric power discharge | release process from the flyback transformer T2 in case the electric power generation output of the solar cell module M2 is larger than the electric power generation output of the solar cell module M1. It is a schematic diagram of the photovoltaic power generation system which consists of two solar cell modules M1 and M2 connected in series which shows another embodiment of the power distribution circuit of this invention. It is a schematic diagram of the photovoltaic power generation system which consists of the three solar cell modules M1, M2, and M3 connected in series which shows another embodiment of the power distribution circuit of this invention. It is a figure which shows the current-voltage characteristic of a system in case the power generation output of two solar cell modules M1 and M2 is smaller than the power generation output of the solar cell module M3. It is a figure which shows the electric power accumulation | storage process from the solar cell module M3 to the flyback transformer T3. It is a figure which shows the process in which the electric power discharge | released from the flyback transformer T3 is accumulate | stored in the capacitor | condenser C1. It is a figure which shows the process in which the electric power discharge | released from the capacitor | condenser C1 is accumulate | stored in the flyback transformer T1. It is a figure which shows the process in which electric power is discharge | released from the flyback transformer T1 and the capacitor | condenser C1. It is a figure which shows the current-voltage characteristic of a system in case the electric power generation output of the solar cell module M3 is smaller than the electric power generation output of two solar cell modules M2 and M3. It is a figure which shows the electric power accumulation | storage process from the solar cell module M2 to the flyback transformer T2. It is a figure which shows the process in which electric power is discharge | released from the flyback transformer T2, is added to the solar cell module M3, and one part electric power is accumulate | stored in the capacitor | condenser C3. It is a figure which shows the electric power accumulation | storage process from the solar cell module M1 to the flyback transformer T1. It is a figure which shows the process in which electric power is discharge | released from the flyback transformer T1, and electric power is discharged | emitted from the capacitor | condenser C3 simultaneously. It is a figure showing typically cyclic power distribution operation at the time of steady operation of a power distribution circuit. It is a figure which compares and shows the current voltage characteristic of the system at the time of normal operation of a power distribution circuit, and the current voltage characteristic of a system when a power distribution operation | movement is stopped to the solar cell module in which the electric power generation output fell. It is a figure which shows typically the solar energy power generation system which consists of two solar cell modules M1 and M2. It is a figure which shows the current-voltage characteristic in case both solar cell modules are in the sun. It is a figure which shows the current-voltage characteristic when one solar cell module enters the shade.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiment shown in FIG. 1 shows an example in which the power distribution circuit 1 of the present invention is incorporated in a photovoltaic power generation system configured by two solar cell modules M1 and M2 connected in series to an external load. Yes.

  As shown in the figure, the positive terminal P1 of the solar cell module M1 and the negative terminal P2 of the solar cell module M2 are connected to an external load via the output line A, and the negative terminal P2 of the solar cell module M1. And a positive terminal P1 of the solar cell module M2 are connected by a connecting line B. Further, a bypass diode D is connected in parallel between the positive terminal P1 and the negative terminal P2 of these solar cell modules M1, M2.

  In the following description, the front and rear directions of these solar cell modules M1 and M2 are the positive electrode terminal P1 side as the front side, the negative electrode terminal P2 side as the rear side, the solar cell module M1 as the front side, and the solar cell module M2 as the solar cell module M2. The rear side.

  The power distribution circuit 1 of the present invention has charging paths X1 and X2 and discharging paths Y1 and Y2, and the charging path X1 and the discharging path Y1 are respectively between the positive terminal P1 and the negative terminal P2 of the solar cell module M1. Contact by bypassing. In addition, the charging path X2 and the discharging path Y2 communicate with each other by bypassing the positive electrode terminal P1 and the negative electrode terminal P2 of the solar cell module M2.

  That is, one end of each of the charging path X1 and the discharging path Y1 is connected to the output line A at the connection point J1, and is connected to the positive terminal P1 of the solar cell module M1 via the output line A. Moreover, each other end is connected to the connection line B at the connection point J2, and is connected to the negative terminal P2 of the solar cell module M1 via the connection line B.

  On the other hand, one end of each of the charging path X2 and the discharging path Y2 is connected to the connection line B at the connection point J3, and is connected to the positive terminal P1 of the solar cell module M2 via the connection line B. Each other end is connected to the output line A at the connection point J4, and is connected to the negative terminal P2 of the solar cell module M2 via the output line A.

  In addition, the power distribution circuit 1 includes a flyback transformer T1 that magnetically couples the charging path X1 on the front solar cell module M1 side and the discharge path Y2 on the rear solar cell module M2 side, and a rear stage (rear row) A charge path X2 on the solar cell module M2 side at the end) and a flyback transformer T2 that magnetically couples the discharge path Y1 on the solar cell module M1 side in the previous stage (row front end).

  In FIG. 1, the flyback transformer T1 is shown in both the charging path X1 and the discharging path Y2, and the flyback transformer T2 is shown in both the charging path X2 and the discharging path Y1, but they are the same. A flyback transformer is shown. Further, in the present embodiment, these flyback transformers T1 and T2 have the same specifications in which the winding ratio between the primary side and the secondary side is 1: 1.

  The power distribution circuit 1 is further connected in series with the primary coil L11 of the flyback transformer T1 in the charging path X1 and in series with the primary coil L21 of the flyback transformer T2 in the charging path X2. The switching element S2 incorporated in the.

  In practice, relays and transistors are used for these switching elements S1 and S2 in order to perform ON / OFF control quickly. In FIG. 1, for convenience of explanation, the switching operation of ON / OFF is understood. It is schematically illustrated with a mechanical switch.

  The power distribution circuit 1 includes a diode D1 incorporated in series with the secondary coil L22 of the flyback transformer T2 in the discharge path Y1, and a secondary coil L12 of the flyback transformer T1 in the discharge path Y2. And a diode D2 incorporated in series. These diodes D1 and D2 are incorporated in a direction in which current flows from the negative electrode terminal P2 side to the positive electrode terminal P1 side of the corresponding solar cell modules M1 and M2, respectively.

  Further, in the power distribution circuit 1 of the present embodiment, capacitors C1 and C2 as smoothing circuits are connected between the connection points J1 and J2 and between the connection points J3 and J4, respectively. Although not shown in FIG. 1, the power distribution circuit 1 further includes a switching control circuit 2 shown in FIG. 2 for periodically ON / OFF control of the two switching elements S1 and S2. ing.

  In the present embodiment, the switching control circuit 2 is individually provided for each of the switching elements S1 and S2, and includes a pulse oscillator and a driver circuit, respectively.

  The pulse oscillator outputs a rectangular wave pulse signal as shown in FIG. 3 to the driver circuit, and the driver circuit performs ON / OFF control of the switching elements S1 and S2 at the timing of the pulse signal.

  In the present embodiment, the ON / OFF timing is asynchronous between the two switching elements S1 and S2. The switching elements S1 and S2 have a duty ratio (Ton / (Ton + Toff) in FIG. 3: a value obtained by dividing the pulse width of the ON period by the pulse period) set to 50%.

Next, the operation of the power distribution circuit 1 configured as described above will be described.
In the system shown in FIG. 1, when the solar cell module M1 at the front stage has a power generation output larger than the power generation output at the solar cell module M2 at the rear stage, both the switching elements S1 and S2 are OFF (power distribution) as shown in FIG. When the circuit 1 is not functioning, the system exhibits a step-like current-voltage characteristic with the maximum output operating point as P, as shown in FIG.

  When the power distribution circuit 1 is started from this state and the switching element S1 is turned on as shown in FIG. 4, a part of the current I1 (indicated by a dotted line with an arrow) output from the solar cell module M1 is generated. From the positive electrode terminal P1 of the solar cell module M1, it returns to the negative electrode terminal P2 of the solar cell module M1 via the output line A, the connection point J1, the charging path X1, the connection point J2, and the connection line B.

  At this time, when the current I1 flows through the primary coil L11 of the flyback transformer T1, a part of the power generation output of the solar cell module M1 is accumulated as magnetic energy in the flyback transformer T1.

  Next, as shown in FIG. 5, when the switching element S1 is turned off, the magnetic energy stored in the flyback transformer T1 is released to the secondary coil L12 side, and as a result, the discharge path Y2 enters the discharge path Y2. Current I2 (indicated by a dotted line with an arrow) flows.

  At this time, since the secondary coil L12 is connected in parallel with the solar cell module M2 with respect to the preceding solar cell module M1, the current I2 is added to the current output from the solar cell module M2.

  In the process in which the switching element S1 is turned on and the current flowing through the primary coil L11 of the flyback transformer T1 increases, an induced electromotive force in the direction opposite to the direction of the current I2 is generated in the secondary coil L12. However, since the diode D2 is incorporated in the discharge path Y2, a current in the direction opposite to the current I2 does not flow.

  By periodically repeating the ON / OFF operation of the switching element S1, a part of the electric power generated by the solar cell module M1 is continuously distributed to the solar cell module M2 side via the flyback transformer T1. Is done. At this time, fluctuations in the current flowing through the charging path X1 and the discharging path Y2 are smoothed by the capacitors C1 and C2, respectively.

  When the power distribution circuit 1 is not used, the curve representing the current-voltage characteristics of the entire system is stepped with the maximum output operating point as P, as shown by the broken line in FIG. On the other hand, by operating the power distribution circuit 1, a part (3 ') of the generated power of the solar cell module M1 is added to the generated power (2) of the solar cell module M2.

  When the duty ratio of each of the switching elements S1 and S2 is set to 50%, the power that has been lost and cannot be used in the area (3) shown by hatching in FIG. 25 is hatched in FIG. As shown, approximately half (3 ') is distributed from the solar cell module M1 side to the solar cell module M2 side. As a result, the current-voltage characteristic of the system is improved to a smoothed characteristic in which the maximum output operating point is P ′ as shown by the solid line in FIG.

  On the other hand, when the power generation output of the subsequent solar cell module M2 is larger than the power generation output of the front solar cell module M1, the power distribution circuit 1 is activated and the switching element S2 is turned on as shown in FIG. When this happens, a part of the current I1 output by the solar cell module M2 (indicated by a dotted line with an arrow) passes from the positive terminal P1 of the solar cell module M2 via the connection line B, the charging path X2, and the output line A. To the negative electrode terminal P2 of the solar cell module M2.

  At this time, when the current I1 flows through the primary coil L21 of the flyback transformer T2, a part of the power generation output of the solar cell module M2 is accumulated as magnetic energy in the flyback transformer T2.

  Next, as shown in FIG. 8, when the switching element S2 is turned OFF, the magnetic energy stored in the flyback transformer T2 is released to the secondary coil L22 side, and as a result, enters the discharge path Y1. Current I2 (indicated by a dotted line with an arrow) flows.

  At this time, since the secondary coil L22 is connected to the external load in parallel with the solar cell module M1, the current I2 is added to the current output from the solar cell module M1.

  A part of the electric power generated by the solar cell module M2 is continuously distributed to the solar cell module M1 side by periodically repeating the ON / OFF operation of the switching element S2 as described above. At this time, fluctuations in the current flowing through the charging path X2 and the discharging path Y1 are smoothed by the capacitors C1 and C2, respectively.

  In the above description, in order to make the operation of the power distribution circuit 1 easier to understand, when the power generation output of the solar cell module M1 is larger than that of the solar cell module M2, paying attention to the ON / OFF operation of only the switching element S1, When the power generation output of the battery module M2 is larger than that of the solar battery module M1, the description is focused on the ON / OFF operation of only the switching element S2.

  However, in reality, these two switching elements S1 and S2 are individually controlled ON / OFF independently of each other, and therefore, both switching elements S1 and S2 may overlap in the ON state.

  For example, as shown in FIG. 5, when the switching element S2 is turned on while an electromotive force is generated in the secondary coil L12 of the flyback transformer T1 and the current I2 is flowing, the current I2 A part also flows to the primary side coil L21 of the flyback transformer T2, and electric power is temporarily stored as magnetic energy in the flyback transformer T2.

  The power stored in the flyback transformer T2 is then discharged from the secondary coil L22 to the discharge path Y1 on the solar cell module M1 side in the previous stage and flows to the external load when the switching element S2 is turned off.

As described above, the actual operation of the power distribution circuit 1 is such that power is simultaneously transferred between the charging path X1 and the discharging path Y1, and between the charging path X2 and the discharging path Y2, and the phenomenon is extremely complicated. However, irregular fluctuations in the current are absorbed by the two capacitors C1 and C2, and thus the temporal variation of the power distribution amount between the solar cell modules M1 and M2 within a very short time after the power distribution circuit 1 is started. Disappears and a steady power distribution operation is realized.
The capacitors C1 and C2 also have a role of reducing noise generated when the switching elements S1 and S2 are turned on / off.

  FIG. 9 is a schematic diagram of a photovoltaic power generation system including two solar cell modules M1 and M2 connected in series, showing another embodiment of the power distribution circuit of the present invention. The circuit 1A uses FETs (field effect transistors) Q1 and Q2 as the switching elements S1 and S2 in the power distribution circuit 1 shown in FIG. Has the same configuration as the power distribution circuit 1 described above.

  Each of these FETs Q1 and Q2 has a source terminal connected to the negative terminal P2 side of each solar cell M1 and M2, and a drain terminal connected to the primary side coils L11 and L22 side of the flyback transformers T1 and T2. In the figure, BD indicates a parasitic diode in these FETs Q1 and Q2.

  Although not shown, the power distribution circuit 1A shown in FIG. 9 performs the periodic ON / OFF control of the FETs Q1 and Q2, so that the switching control circuit 2 of the power distribution circuit 1 described above is used. Has the same switching control circuit.

  Next, FIG. 10 is a schematic diagram of a photovoltaic power generation system including three solar cell modules M1, M2, and M3 connected in series, showing still another embodiment of the power distribution circuit of the present invention. The power distribution circuit 1B in the system shown in the figure has three charging paths X1, X2, and X3 and discharging paths Y1, Y2, and Y3, respectively.

  As in the power distribution circuit 1 shown in FIG. 1 described above, one end of each of the charging path X1 and the discharging path Y1 is connected to the output line A at a connection point J1 near the positive terminal P1 of the solar cell module M1 at the front end of the column. The other end of each is connected to a connection line B1 connecting the front and rear solar cell modules M1 and M2 at a connection point J2.

  Also, one end of each of the charging path X2 and the discharging path Y2 is connected to the connection line 1 at a connection point J3 closer to the solar cell module M2 than the connection point 2, and each other end is connected to the front and rear at the connection point J4. The solar cell modules M2 and M3 are connected to a connection line B2 that connects the solar cell modules M2 and M3.

  Further, one end of each of the charging path X3 and the discharging path Y4 is connected to the connection line B2 at a connection point J5 closer to the solar cell module M3 than the connection point 4, and each other end is connected to the solar cell at the rear end of the column. The module M3 is connected to the output line A at a connection point J6 near the negative terminal P2.

  A flyback transformer T1 that magnetically couples the corresponding charging path and discharging path between the charging path X1 and discharging path Y2, between the charging path X2 and discharging path Y3, and between the charging path X3 and discharging path Y1, respectively. , T2 and T3 are incorporated.

  The primary coil L1 and switching element S1 of the flyback transformer T1 are incorporated in series in the charging path X1, and the primary coil L21 and switching element S2 of the flyback transformer T2 are incorporated in series in the charging path X2. Thus, the primary side coil L31 of the flyback transformer T3 and the switching element S3 are incorporated in the charging path X3 in series.

  Further, the secondary side coil L32 and the diode D1 of the flyback transformer T3 are incorporated in series in the discharge path Y1, and the secondary side coil L12 and the diode D2 of the flyback transformer T1 are incorporated in series in the discharge path Y2. Thus, the secondary side coil L22 of the flyback transformer T2 and the diode D3 are incorporated in series in the discharge path Y3. Each of these diodes D1, D2, and D3 is incorporated in a direction in which a current is passed from the negative terminal P2 side to the positive terminal P1 side of the corresponding solar cell module M1, M2, and M3.

  In the power distribution circuit 1B of the present embodiment, capacitors C1, C2, and C3 that function as smoothing circuits are connected between the connection points J1 and J2, between the connection points J3 and J4, and between the connection points J5 and J6, respectively. ing. Each switching element S1, S2, S3 is ON / OFF controlled by a switching control circuit (not shown).

The switching control circuit incorporates the same configuration of FIG. 2 used in the power distribution circuit 1 described above for each switching element S1, S2, S3, and these switching elements S1, S2, S3. Are turned on and off periodically.
Note that the ON / OFF control of these switching elements S1, S2, and S3 is performed asynchronously.

Next, the operation of the power distribution circuit 1B configured as described above will be described.
In the system shown in FIG. 10, among the three solar cell modules M1, M2, and M3 arranged in the front and rear directions, the two solar cell modules M1 at the front stage are compared with the power generation output of the solar cell module M3 at the rear end of the row. When the power generation output of M2 is small, when all the switching elements S1, S2, and S3 are OFF (the power distribution circuit 1B is not functioning) as shown in FIG. Current-voltage characteristics as shown are shown.

  Here, when the power distribution circuit 1B is activated and the switching element S3 of the charging path X3 is turned on as shown in FIG. 12, a part of the current I1 output by the solar cell module M3 (indicated by a dotted line with an arrow) Display) returns from the positive terminal P1 of the solar cell module M3 to the negative terminal P2 of the solar cell module M3 via the connection line B2, the connection point J5, the charging path X3, the connection point J6, and the output line A.

  At this time, when the current I1 flows through the primary coil L31 of the flyback transformer T3, a part of the power generation output of the solar cell module M3 is stored as magnetic energy in the flyback transformer T3.

  Next, as shown in FIG. 13, when the switching element S3 is turned off, the magnetic energy stored in the flyback transformer T3 is released to the secondary coil L32 side, and as a result, the current I2 flows into the discharge path Y1. (Indicated by a dotted line with an arrow) flows.

  At this time, since the magnitude of the current output from the solar cell module M1 side at the front end of the row to the external load through the output electric circuit A is limited by the magnitude of the current flowing through the subsequent solar cell module M2, The current I2 flows to the capacitor C1 and is stored here.

  Then, as shown in FIG. 14, when the switching element S1 of the charging path X1 is turned on, a part of the power stored in the capacitor C1 is discharged, and the discharge current I3 (indicated by a dotted line with an arrow) Flows through the primary coil L11 of the flyback transformer T1, so that a part of the electric power stored in the capacitor C1 is converted into magnetic energy and stored in the flyback transformer T1.

  Next, as shown in FIG. 15, when the switching element S1 is turned off, the magnetic energy stored in the flyback transformer T1 is released to the secondary coil L12 side, and as a result, is discharged to the discharge path Y2. A current I4 (indicated by a dotted line with an arrow) flows.

  At this time, since the secondary coil L12 is connected in parallel with the solar cell module M2, the current I4 is added to the output current of the solar cell module M2 and flows to the preceding solar cell module M1 side.

  Then, the remaining power stored in the capacitor C1 is discharged as a current I5 (indicated by a dotted line with an arrow), added to the output current of the solar cell module M1, and flows from the output electric circuit A to the external load.

  By repeating such an operation, a part of the electric power generated by the solar cell module M3 is evenly distributed to the solar cell module M1 and the solar cell module M2, and as a result, the current-voltage characteristics of the entire system are smoothed. Power generation efficiency is improved.

  Next, in the system shown in FIG. 10, among the three solar cell modules M1, M2, and M3 arranged in the front and rear, the power generation output of the solar cell module M3 at the rear end of the row is the two solar cell modules M1 at the front stage. When the power generation output is smaller than M2, when all the switching elements S1, S2, S3 are OFF (the power distribution circuit 1B is not functioning) as shown in FIG. 16, this system is shown in FIG. Such a current-voltage characteristic is shown.

  Here, as shown in FIG. 17, when the switching element S2 is turned on, a part of the current I1 (indicated by a dotted line with an arrow) output from the solar cell module M2 is the positive terminal P1 of the solar cell module M2. Then, it returns to the negative terminal P2 of the solar cell module M2 via the connection line B1, the connection point J3, the charging path X2, the connection point J4, and the connection line B2.

  At this time, when the current I1 flows through the primary coil L21 of the flyback transformer T2, a part of the power generation output of the solar cell module M2 is stored as magnetic energy in the flyback transformer T2.

  Next, as shown in FIG. 18, when the switching element S2 is turned OFF, the magnetic energy stored in the flyback transformer T2 is released to the secondary coil L22 side, and as a result, a current flows through the discharge path Y3. I2 (indicated by a dotted line with an arrow) flows, and a part of the current I3 is added to the output current of the solar cell module M2 and flows to the preceding solar cell module M2 side. At the same time, a difference current I4 between the currents I2 and I3 flows to the capacitor C3, and the capacitor C3 is charged.

  Next, as shown in FIG. 19, when the switching element S1 is turned on, a part of the current I5 (indicated by a dotted line with an arrow) output from the solar cell module M1 is generated from the positive terminal P1 of the solar cell module M1. It returns to the negative terminal P2 of the solar cell module M1 via the output line A, the connection point J1, the charging path X1, the connection point J2, and the connection line B1.

  At this time, when the current I5 flows through the primary coil L11 of the flyback transformer T1, a part of the power generation output of the solar cell module M1 is accumulated as magnetic energy in the flyback transformer T1.

  Next, as shown in FIG. 20, when the switching element S1 is turned OFF, the magnetic energy stored in the flyback transformer T1 is released to the secondary coil L12 side, and a current I6 (arrow) is supplied to the discharge path Y2. Discharged as a dotted line). The current I6 is added to the output current of the solar cell module M2 and flows to the solar cell module M1 side. At that time, a part of the current flows to the capacitor C2, and current fluctuation is suppressed.

  At this time, the current I6 is induced in the secondary coil L12, so that the power stored in the capacitor C3 is discharged as the current I7 (indicated by a dotted line with an arrow), and the output of the solar cell module M3 It is added to the current and flows to the preceding solar cell module 2.

  By repeating such an operation, a part of the electric power generated by the solar cell module M1 and the solar cell module M2 is distributed and equalized to the solar cell module M3, and the current-voltage characteristics of the entire system are smoothed. Power generation efficiency is improved.

  In the above description, in order to facilitate understanding of the power distribution operation between the solar cell modules M1, M2, and M3, focusing on the ON or OFF of a specific switching element, Although the current flow is schematically described, the actual circuit operation is such that the ON / OFF operations of all the switching elements S1, S2, and S3 are asynchronously and individually repeated. The current flow is complicated.

  However, in the state where the power distribution circuit 1B is continuously operating, as shown in FIG. 21, the operation of distributing the surplus power among the solar cell modules M1, M2, and M3 is indicated by a white arrow in the figure. In the power conditioner (external load), a current-voltage characteristic having no step is obtained with the maximum output operating point being Pa indicated by a black circle as shown by the solid line in FIG.

  On the other hand, when the power distribution to the solar cell module whose power generation output is reduced due to a failure or the like is cut off, the current output voltage characteristic changes to the stepped state where the maximum output operating point is Pb as shown by the broken line in FIG. To do.

  Therefore, during the operation of the power distribution circuit, a function is added to the switching control circuit that keeps only the arbitrarily selected switching element OFF during the periodic switching operation of each switching element ON / OFF. Only power distribution to any solar cell module can be cut off.

  Then, when the power generation output of the solar cell module whose power distribution has been cut off has decreased, the maximum output operating point changes from Pa to Pb on the power conditioner side as shown in FIG. Without stopping the operation of the photovoltaic power generation system, it is possible to identify a solar cell module in which a problem has occurred, and to efficiently perform failure diagnosis.

In the power distribution circuits 1, 1A, and 1B in the embodiments described above, the charging path X1 and the discharging path Y1, the charging path X2 and the discharging path Y2, and the charging path X3 and the discharging path Y3, respectively. Although one capacitor C1, C2, C3 is incorporated as a common smoothing circuit, the smoothing circuit is not limited to those of these embodiments, and is a capacitor that is individually incorporated in each charging path and discharging path. Also good.
Furthermore, each solar cell module may be a low-pass filter circuit including at least one capacitor for smoothing current fluctuations in the corresponding charging path and discharging path.

  Moreover, in each embodiment mentioned above, although the system which connected two solar cell modules M1 and M2 in series and the system which connected three solar cell modules M1, M2, and M3 in series were demonstrated, this invention is these. The present invention is not limited to this embodiment, and is also applied to a photovoltaic power generation system in which four or more solar cell modules are connected in series. Furthermore, the power distribution circuit for solar cells of the present invention includes a power distribution circuit between a plurality of clusters connected in series in the solar cell module.

The power distribution circuit for solar cells according to the present invention can be effectively used to improve the decrease in power generation efficiency of solar cell modules and clusters due to the shade of the solar power generation system.
In addition, solar power generation systems that combine different types of solar cell modules, solar power generation systems in which multiple solar cell modules including flexible solar cells are installed in different directions, and tracking concentrating type A system with different output characteristics of individual solar cells depending on the light collection characteristics of the condenser lens, such as a high-efficiency solar power generation system, a system with a double-sided solar cell module that also receives sunlight from the back surface, etc. In various cases, it can also be used as a means for increasing power generation efficiency.

  The solar cell power distribution circuit of the present invention is also used to improve the power generation efficiency when the output characteristics between solar cell modules vary due to deterioration over time or contamination of the light receiving surface in an existing solar power generation system. Is possible.

  In addition, when the switching control circuit of the power distribution circuit of the present invention has a function of individually stopping each switching element in the OFF state, it can be used as a failure diagnosis device for a solar cell module.

  Moreover, the present invention can be used not only in the field of photovoltaic power generation but also in a power supply system in which batteries, fuel cells, and the like are connected in series and parallel, which show current-voltage characteristics similar to those of a solar cell module.

1, 1A, 1B Power distribution circuit 2 Switching control circuit X1, X2, X3 Charging path Y1, Y2, Y3 Discharging path S1, S2, S3 Switching element Q1, Q2 FET (switching element)
BD Body diode T1, T2, T3 Flyback transformer L11, L21, L31 Primary coil L12, L22, L32 Secondary coil C1, C2, C3 Capacitor (smoothing circuit)
D1, D2, D3 Diode A Output line B, B1, B2 Connection line J1, J2, J3, J4, J5, J6 Connection point I1, I2, I3, I4, I5, I6, I7 Current

Claims (2)

A plurality of charging paths individually connecting between the positive terminal and the negative terminal of each of the solar cells connected in series to an external load;
A plurality of discharge paths individually communicating between the positive electrode terminal and the negative electrode terminal of each of the solar cells;
The front solar cell charging path and the rear solar cell discharge path adjacent to each other, the rear solar cell charging path and the front solar cell discharge path, or the front solar adjacent to the front and rear A plurality of flyback transformers that magnetically couple the discharge path of the battery and the charging path of the solar battery at the rear stage and the charging path of the solar battery at the front end of the line and the discharge path of the solar battery at the rear end of the line;
A switching element incorporated in series with the primary coil of the corresponding flyback transformer in each charging path;
A diode incorporated in each discharge path in series with the secondary coil of the corresponding flyback transformer and in a direction of passing current from the negative terminal side to the positive terminal side of the corresponding solar cell;
A switching control circuit for periodically turning on and off each of the switching elements;
A solar battery power distribution circuit comprising a smoothing circuit comprising at least one capacitor for smoothing current fluctuations in a corresponding charging path and discharging path for each solar battery.   2. The solar cell according to claim 1, wherein the switching control circuit has a function of holding only an arbitrarily selected switching element in an OFF state during a periodic switching operation of each switching element. Power distribution circuit.

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