CN113644876B - Photovoltaic power generation system and protection circuit of photovoltaic module - Google Patents

Photovoltaic power generation system and protection circuit of photovoltaic module Download PDF

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Publication number
CN113644876B
CN113644876B CN202110924479.8A CN202110924479A CN113644876B CN 113644876 B CN113644876 B CN 113644876B CN 202110924479 A CN202110924479 A CN 202110924479A CN 113644876 B CN113644876 B CN 113644876B
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photovoltaic module
resistor
bypass diode
photovoltaic
protection circuit
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CN113644876A (en
Inventor
李运生
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Sungrow Renewables Development Co Ltd
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Sungrow Renewables Development Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02S—GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
    • H02S40/00—Components or accessories in combination with PV modules, not provided for in groups H02S10/00 - H02S30/00
    • H02S40/30—Electrical components
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/20—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for electronic equipment
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
    • H02H9/02—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess current
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
    • H02H9/04—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage
    • H02H9/045—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage adapted to a particular application and not provided for elsewhere
    • H02H9/047—Free-wheeling circuits
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Photovoltaic Devices (AREA)
  • Protection Of Static Devices (AREA)

Abstract

The invention provides a photovoltaic power generation system and a protection circuit of a photovoltaic module; the protection circuit includes: a reverse overvoltage detection unit and a protection branch unit; the reverse overvoltage detection unit, the current branch and the bypass diode are connected in parallel; the reverse overvoltage detection unit is used for detecting whether the photovoltaic module has a reverse overvoltage fault or not; when detecting that the reverse overvoltage fault exists, triggering the protection branch unit to shunt the bypass diode; the reverse overvoltage fault is that the photovoltaic module generates reverse overvoltage; when the photovoltaic module is subjected to reverse overvoltage, the protection branch unit is triggered to shunt the bypass diode so as to protect the bypass diode from damaging the photovoltaic module; meanwhile, the protection mode is shunt, the bypass diode is not directly disconnected, the function of the bypass diode is kept, and the safety of a circuit where the bypass diode is located is improved.

Description

Photovoltaic power generation system and protection circuit of photovoltaic module
Technical Field
The invention belongs to the technical field of protection of photovoltaic modules, and particularly relates to a photovoltaic power generation system and a protection circuit of a photovoltaic module.
Background
At present, a photovoltaic module is formed by serially connecting dozens of silicon wafers, and then the serially connected silicon wafers are divided into three photovoltaic cell sub-strings, namely, a plurality of photovoltaic cell sub-strings are connected in parallel, and if one photovoltaic cell sub-string fails, other photovoltaic cell sub-strings can be influenced.
As shown in fig. 1, in the prior art, each photovoltaic cell sub-string is connected in parallel with a bypass diode, but when the bypass diode fails, particularly when the photovoltaic module is reversely overvoltage, the bypass diode cannot work normally, and further the bypass diode cannot bypass the fault photovoltaic cell sub-string blocked by shadow, and the stability of other photovoltaic cell sub-strings and systems still can be affected by the fault photovoltaic cell sub-string.
Disclosure of Invention
In view of the above, the present invention is directed to a photovoltaic power generation system and a protection circuit for a photovoltaic module, which are used for maintaining the function of a bypass diode and improving the safety and stability of the photovoltaic module and the system thereof.
The invention discloses a protection circuit of a photovoltaic module, which comprises N photovoltaic cell substrings, wherein the N photovoltaic cell substrings are sequentially connected in series; two ends of each photovoltaic cell substring are reversely connected with a bypass diode in parallel; the protection circuit includes: a reverse overvoltage detection unit and a protection branch unit;
The protection branch unit and the bypass diode are directly or indirectly connected in parallel;
the reverse overvoltage detection unit is connected with the bypass diode in series or in parallel;
the reverse overvoltage detection unit is used for detecting whether the photovoltaic module has a reverse overvoltage fault or not; triggering the protection branch unit to shunt the bypass diode when the reverse overvoltage fault is detected; the reverse overvoltage fault is that the photovoltaic module generates reverse overvoltage.
Optionally, the reverse overvoltage detection unit includes: a first resistor and a voltage stabilizing switch connected in series;
the connection point between the first resistor and the voltage stabilizing switch is used as an output end of the reverse detection unit.
Optionally, the voltage stabilizing switch is a voltage stabilizing diode.
Optionally, the zener diode is the bypass diode, or is a zener diode independent of the bypass diode.
Optionally, the first resistor and the voltage stabilizing switch are sequentially connected in series between the positive electrode and the negative electrode of the photovoltaic module; or,
the first resistor and the voltage stabilizing switch are sequentially connected in series between the negative electrode and the positive electrode of the photovoltaic module.
Optionally, the protection branching unit includes: a first controllable switch;
two ends of the first controllable switch are used as two ends of the protection branch unit;
the control end of the first controllable switch is used as the control end of the protection branch unit.
Optionally, the first controllable switch includes at least one of a relay and a switching tube.
Optionally, if the first controllable switch is the relay, the reverse overvoltage detection unit is a coil secondary side of the relay.
Optionally, the protection branching unit further comprises a second resistor connected in series with the first controllable switch.
The invention discloses a protection circuit of a photovoltaic module, which comprises N photovoltaic cell substrings, wherein the N photovoltaic cell substrings are sequentially connected in series; the output ends of the photovoltaic cell substrings are reversely connected with a bypass diode in parallel; the protection circuit includes: a forward overcurrent detection unit and a bypass shunt unit;
the forward overcurrent detection unit is connected with the bypass diode in series;
the bypass shunt unit is connected with the bypass diode in parallel;
the forward overcurrent detection unit is used for detecting whether the photovoltaic module has a forward overcurrent fault or not; when the forward overcurrent fault is detected to exist, triggering the bypass shunt unit to shunt the bypass diode; the positive overcurrent fault is that the photovoltaic module has positive overcurrent.
Optionally, the forward overcurrent detection unit includes: the second resistor and the third resistor;
the second resistor and the third resistor are connected in series and then connected in series with the bypass diode;
and the connection point between the second resistor and the third resistor is connected with the output end of the forward overcurrent detection unit.
Optionally, the forward overcurrent detection unit further includes: a first switching tube;
the control end of the first switching tube is connected with a connection point between the second resistor and the third resistor;
the first end of the first switch tube is connected with one end of the second resistor far away from the third resistor;
the second end of the first switching tube is connected with the output end of the forward overcurrent detection unit.
Optionally, the third resistor is a thermistor;
the thermistor is disposed proximate the bypass diode.
Optionally, the first switching tube is a low-impedance switching tube driven by voltage.
Optionally, the bypass flow dividing unit includes: a second controllable switch and a fourth resistor;
the second controllable switch is indirectly connected with the bypass diode in parallel;
the control end of the second controllable switch is connected with one end of the fourth resistor;
The first end of the second controllable switch is connected with the other end of the fourth resistor, and the connection point is used as the control end of the bypass shunt unit.
Optionally, when the forward overcurrent detection unit includes a first switching tube:
the connection point between the third resistor and the fourth resistor is connected with the second end of the first switching tube;
the second end of the second controllable switch is connected with the cathode of the bypass diode.
Optionally, the second controllable switch is an NPN triode.
A third aspect of the present invention discloses a photovoltaic power generation system comprising: the photovoltaic module comprises an inversion unit, at least one photovoltaic module and at least one protection circuit of the photovoltaic module according to any one of the first aspect of the invention or the protection circuit of the photovoltaic module according to any one of the second aspect of the invention; wherein:
the photovoltaic modules are connected in series to form a photovoltaic group string, and the output ends of the photovoltaic group strings are connected in parallel and then connected to the direct current side of the inversion unit;
and the alternating current side of the inversion unit is connected to a power grid.
Optionally, the protection circuit in the photovoltaic module is arranged in a junction box of the photovoltaic module.
As can be seen from the above technical solution, the protection circuit of a photovoltaic module provided by the present invention includes: a reverse overvoltage detection unit and a protection branch unit; the reverse overvoltage detection unit, the current branch and the bypass diode are connected in parallel; the reverse overvoltage detection unit is used for detecting whether the photovoltaic module has a reverse overvoltage fault or not; when detecting that the reverse overvoltage fault exists, triggering the protection branch unit to shunt the bypass diode; the reverse overvoltage fault is that the photovoltaic module generates reverse overvoltage; when the photovoltaic module is subjected to reverse overvoltage, the protection branch unit is triggered to shunt the bypass diode so as to protect the bypass diode from damaging the photovoltaic module; meanwhile, the protection mode is shunt, the bypass diode is not directly disconnected, the function of the bypass diode is kept, and the safety of a circuit where the bypass diode is located is improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a photovoltaic module provided by the prior art;
fig. 2 is a schematic diagram of a protection circuit of a photovoltaic module according to an embodiment of the present invention;
fig. 3 is a schematic diagram of a protection circuit of another photovoltaic module according to an embodiment of the present invention;
fig. 4 is a schematic diagram of a protection circuit of another photovoltaic module according to an embodiment of the present invention;
fig. 5 is a schematic diagram of another photovoltaic module and a protection circuit thereof according to an embodiment of the present invention;
fig. 6 is a current timing diagram of a photovoltaic module according to an embodiment of the present invention;
fig. 7 is a schematic diagram of a protection circuit of another photovoltaic module according to an embodiment of the present invention;
fig. 8 is a schematic diagram of a protection circuit of another photovoltaic module according to an embodiment of the present invention;
Fig. 9 is a schematic diagram of another photovoltaic module and a protection circuit thereof according to an embodiment of the present application;
FIG. 10 is a current timing diagram of another photovoltaic module according to an embodiment of the present application;
fig. 11 is a schematic diagram of a protection circuit of another photovoltaic module according to an embodiment of the present application;
fig. 12 is a schematic diagram of another photovoltaic module and a protection circuit thereof according to an embodiment of the present application.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments of the present application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
In the present disclosure, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The embodiment of the application provides a protection circuit of a photovoltaic module, which is used for solving the problems that in the prior art, each photovoltaic cell sub-string is connected with a bypass diode in parallel, but once the bypass diode fails, particularly when the photovoltaic module is reversely overvoltage, the bypass diode cannot work normally, and further the bypass diode cannot bypass the fault photovoltaic cell sub-string shielded by shadow, and the stability of other photovoltaic cell sub-strings and systems is still affected by the fault photovoltaic cell sub-string.
Referring to fig. 2, the photovoltaic module includes N photovoltaic cell sub-strings, and in particular, N photovoltaic cell sub-strings are sequentially connected in series. The output ends of the photovoltaic cell substrings are connected in reverse parallel with a bypass diode.
This photovoltaic module's protection circuit includes: a reverse overvoltage detection unit 10 and a protection bypass unit 20.
The protection branching unit 20 and the bypass diode DP are connected directly or indirectly in parallel.
The reverse overvoltage detection unit 10 is connected in series with the bypass diode DP, or the reverse overvoltage detection unit 10 is connected in parallel with the bypass diode DP; the specific structures are not described in detail herein, and are all within the scope of the present application.
A reverse overvoltage detection unit 10 for detecting whether a reverse overvoltage fault exists in the photovoltaic module; and when detecting that a reverse overvoltage fault exists, triggering the protection bypass unit 20 to shunt the bypass diode DP; the reverse overvoltage fault is that the photovoltaic module generates reverse overvoltage.
That is, if the photovoltaic module has a reverse overvoltage, the reverse overvoltage detection unit 10 can detect the reverse overvoltage, and trigger the protection bypass unit 20 to protect the photovoltaic module when a reverse overvoltage fault is detected. Specifically, the protection bypass unit 20 shunts the bypass diode DP to protect the photovoltaic module.
That is, the protection branching unit 20 is used for protecting the photovoltaic module in such a way that the bypass diode DP is branched, and is not directly cut out, so that the bypass diode DP can still continue to operate.
Specifically, the protection branching unit 20 branches the bypass diode DP, so that the current flowing through the bypass diode DP originally is reduced, the problem that the photovoltaic module cannot be protected due to failure of the bypass diode DP when reverse overvoltage occurs in the photovoltaic module is avoided, and the safety and stability of the photovoltaic module are improved.
In this embodiment, when reverse overvoltage occurs in the photovoltaic module, the protection branching unit 20 is triggered to shunt the bypass diode DP so as to maintain the protection of the bypass diode DP on the photovoltaic module, thereby protecting the bypass diode DP from being damaged; meanwhile, the protection mode is shunt, the bypass diode DP is not directly disconnected, the function of the bypass diode DP is kept, and the safety of a circuit where the bypass diode DP is located is improved.
In practical use, as shown in fig. 3, the reverse overvoltage detection unit 10 includes: a first resistor R1 and a voltage stabilizing switch (D1 shown in fig. 3) connected in series.
The connection point between the first resistor R1 and the voltage stabilizing switch is used as the output end of the reverse overvoltage detection unit 10; that is, the voltage at the connection point between the first resistor R1 and the voltage stabilizing switch is used as the output signal of the reverse overvoltage detection unit 10 to control the protection branching unit 200, and the specific control procedure thereof may be: when the voltage at the junction between the first resistor R1 and the voltage stabilizing switch is higher than the threshold value, the protection branching unit 20 is triggered to shunt the bypass diode DP. Of course, other modes are also possible, and are not described in detail herein, and are all within the scope of the present application.
The first resistor R1 and the voltage stabilizing switch are sequentially connected in series between the positive electrode and the negative electrode of the photovoltaic module; or the first resistor R1 and the voltage stabilizing switch are sequentially connected in series between the cathode and the anode of the photovoltaic module.
Specifically, one end of the first resistor R1 is connected with the battery anode of the photovoltaic battery sub-string, the other end of the first resistor R1 is connected with one end of the voltage stabilizing switch, and the other end of the voltage stabilizing switch is connected with the cathode of the photovoltaic battery sub-string. Or one end of the first resistor R1 is connected with the battery cathode of the photovoltaic battery substring, the other end of the first resistor R1 is connected with one end of the voltage stabilizing switch, and the other end of the voltage stabilizing switch is connected with the anode of the photovoltaic battery substring. The connection position between the first resistor R1 and the voltage stabilizing switch is not specifically limited herein, and may be any connection position as appropriate, and is within the scope of the present application.
The first resistor R1 may be a thermistor or a common resistor, and is not specifically limited herein, and may be any resistor as appropriate, and is within the scope of the present application.
In practical applications, the voltage stabilizing switch is a voltage stabilizing diode D1.
Specifically, the direction of the anode of the zener diode D1 pointing to the cathode is opposite to the direction from the positive electrode to the negative electrode of the cells of the photovoltaic cell substring; that is, the pass of zener diode D1 is antiparallel to the output of the photovoltaic cell substring.
Note that, the zener diode D1 may be a zener diode D1 independent of the bypass diode DP; that is, at this point, there are two diodes in the photovoltaic cell substring (as shown in FIG. 3). The zener diode D1 may be a bypass diode DP in the photovoltaic module; that is, there is only one diode in the photovoltaic cell substring (as shown in fig. 4).
In practical application, the protection branching unit 20 includes: a first controllable switch S1.
Both ends of the first controllable switch S1 serve as both ends of the protection branching unit 20; the control terminal of the first controllable switch S1 serves as the control terminal of the protection branching unit 20.
Specifically, as shown in fig. 3, the control end of the first controllable switch S1 is connected to the anode of the zener diode D1 and one end of the first resistor R1 respectively; one end of the first controllable switch S1 is respectively connected with the other end of the first resistor R1 and the battery cathode of the photovoltaic battery substring; the other end of the first controllable switch S1 is respectively connected with the cathode of the zener diode D1 and the battery anode of the photovoltaic battery substring.
It should be noted that, when the positions of the first resistor R1 and the zener diode D1 are exchanged, the connection relationship of the first controllable switch S1 is similar to that shown in fig. 3, and will not be described in detail herein, and is within the protection scope of the present application.
When the photovoltaic cell sub-string is subjected to reverse overvoltage, the voltage difference between two ends of the first resistor R1 reaches a threshold value, and then the first controllable switch S1 is triggered to be conducted, so that the bypass diode DP is shunted by the first controllable switch S1, and the protection of the photovoltaic cell sub-string is realized.
In this embodiment, the protection circuit can realize protection of the photovoltaic module by adding the first resistor R1 and the first controllable switch S1.
The first controllable switch S1 includes at least one of a relay and a switching tube.
If the first controllable switch S1 is a relay, the reverse overvoltage detection unit 10 is the coil secondary side of the relay. The structures are not described in detail herein, and can be determined according to practical situations, and are all within the protection scope of the application.
In practice, the protection branching unit 20 further comprises a second resistor R2 connected in series with the first controllable switch S1.
The second resistor R2 is used to limit the current flowing through the first controllable switch S1. The purpose of limiting the first controllable switch S1 is to avoid the first controllable switch S1 from being damaged by overcurrent.
As shown in fig. 5, taking the number of photovoltaic cell sub-strings equal to 3 as an example, a photovoltaic module is formed by connecting several tens of silicon wafers in series, and then dividing the silicon wafers connected in series into three photovoltaic cell sub-strings, and reversely connecting a bypass diode DP in parallel to each photovoltaic cell sub-string; three protection circuits and three bypass diodes DP (DP, DP2 and DP2 as shown in fig. 5) are provided accordingly.
Wherein, in the first protection circuit: r11, S11 are reverse overvoltage conditions for protecting the bypass diode DP 1. In the second protection circuit: r12, S12 are reverse overvoltage conditions for protecting the bypass diode DP 2. In the third protection circuit: r13, S13 are reverse overvoltage conditions for protecting the bypass diode DP 3.
The source electrode S of the switch tube S11 is respectively connected with the first resistor R11 and the battery cathode of the corresponding photovoltaic battery substring; the grid G of the switch tube S11 is connected with the anode of the bypass diode DP 1; the drain D of the switching tube S11 is connected to the cell anode of the corresponding photovoltaic cell substring. The source electrode S of the switch tube S12 is respectively connected with the first resistor R12 and the battery cathode of the corresponding photovoltaic battery substring; the grid G of the switching tube S12 is connected with the anode of the bypass diode DP 2; the drain D of the switching tube S12 is connected to the cell anode of the corresponding photovoltaic cell substring. The source electrode S of the switching tube S13 is connected with the battery cathode of the corresponding photovoltaic battery substring through a first resistor R13 respectively; the grid G of the switch tube S13 is connected with the anode of the bypass diode DP 3; the drain D of the switching tube S13 is connected to the cell anode of the corresponding photovoltaic cell substring.
And then, analyzing the working principle process of the protection circuit of one group of independent photovoltaic modules, and analyzing the normal illumination working condition of the photovoltaic modules, the shadow shielding working condition of the photovoltaic cell substrings of the photovoltaic modules and the reverse overvoltage short-circuit working condition of the bypass diode DP.
Firstly, when the illumination of a photovoltaic module is normal, a photovoltaic cell sub-string is used as output to generate power, the direction of the power generation voltage U1 at an output end is consistent with the voltage direction of the photovoltaic cell sub-string, and at the moment, a bypass diode DP1 is disconnected, namely i2=0; at this time, VT > vsg=0, and the switching tube S11 is in an off state, wherein the voltage u_s1=u1 <0 across the switching tube S11. At this time, the bypass diode DP1 is turned off, the switching tube S11 is turned off, and the photovoltaic module is in normal power generation.
Secondly, when the shading working condition occurs in the battery sub-string of the photovoltaic module and the internal resistance formed by shading is larger than the external load resistance, the direction of the power generation voltage U1 at the output end is inconsistent with the voltage direction of the battery sub-string, a specific value is as shown in formula (1), the bypass diode DP1 is conducted to shunt, and the second resistance R2 generates voltage drop; wherein the shunt current i2>0, the voltage drop at the source S and gate G of the switching tube S11 at this time is formula (2).
U1＝i2×(R1+R2+R4)+V D1 Formula (1)
0＜V SG ＝i2×R2＝-V GS Formula (2)
Wherein V is DP To bypass the voltage across diode DP1, V SG Is the source gate voltage of the corresponding switching tube.
When the driving voltage VGS <0 of the switching tube S11 is obtained by the formula (1), the switching tube S11 is in the off state. At this time, the bypass diode DP1 is in a normal on state, and the switching tube S11 is turned off to exert no protection effect.
When the reverse voltage of the bypass diode DP1 born by the photovoltaic module exceeds the tolerated reverse voltage, the bypass diode DP1 will be reverse overvoltage causing a short circuit.
The reverse overvoltage can be divided into two types, one type is electric breakdown, i.e. recoverable breakdown, and the other type is thermal breakdown, i.e. unrecoverable breakdown. The breakdown process can be divided into two phases, one is a dynamic phase in which the diode breaks down due to external reverse voltage; the second stage is a steady-state stage after breakdown, and the steady-state stage has two states, namely, the state is that the short circuit cannot be recovered after the breakdown of the diode, and the state is that the diode is recovered to be normal after the breakdown of the diode.
Stage one: a dynamic process.
Since the reverse overvoltage voltage is externally applied, that is, the direction of the voltage U1 is inconsistent with the direction of the photovoltaic cell substring, the bypass diode DP1 breaks down and conducts when receiving the reverse withstand voltage, the current i2 flows from bottom to top, the voltages VGS at the two ends of the gate G and the source S of the switching tube S11 are generated by the second resistor R2, and the first resistor R1 increases with the heating resistance of the bypass diode DP1 if the first resistor R1 is a thermistor due to the heat generated by the reverse overvoltage of the bypass diode DP 1. As shown in equation (3), when VGS is greater than the threshold voltage VT of the switching tube S11, the switching tube S11 is turned on. At this time, the switching tube S11 will shunt the bypass diode DP1 to reduce the heat loss of the bypass diode DP1, so as to protect the bypass diode DP1 from thermal breakdown.
V T ＜V GS =i2×r2 formula (3)
After the temperature of the bypass diode DP1 decreases or after the current decreases, the voltage across the second resistor R2 decreases. As shown in formula (4), when the voltage drop of the second resistor R2 is lower than the on voltage of the switching tube S11, the switching tube S11 is turned off; the bypass diode DP1 continues to take full current at this time. When the temperature or current of the bypass diode DP1 rises to a certain extent, the voltage at two ends of the second resistor R2 increases to enable the switch tube S11 to be turned on, so that the switch tube S11 is turned on to shunt the bypass diode DP1, the current on the switch tube S1 is i3, and the current of the bypass diode DP is i4. The formula adopted for each current is formula (5).
V T ＞V GS =i2×r2 formula (4)
i2 =i3+i4 formula (5)
Stage two: steady state process.
Taking the recoverable steady state as an example, the following description will be given:
when the bypass diode DP1 returns to normal after reverse overvoltage, the bypass diode DP1 returns to off under the normal condition of illumination, and at this time, the current i2=0 of the branch where the bypass diode DP1 is located, vgs=0 of the switching tube S11, and the switching tube S1 is turned off.
When the photovoltaic cell substring is shaded, the bypass diode DP1 is turned on forward after shading to a certain extent, and specific analysis is described above, which is not repeated herein, and the current timings in the protection circuit and the bypass diode DP1 are shown in fig. 6, that is, the values of the currents in the above description are repeated.
In this embodiment, when the bypass diode DP is in a reverse overvoltage condition, the protection circuit protects the photovoltaic module by using an automatic shunt mechanism, so as to avoid the occurrence of unrecoverable thermal breakdown of the bypass diode DP. Meanwhile, when the photovoltaic module and the inverter are connected to normally generate electricity, a single photovoltaic cell sub-string which is reversely overvoltage is automatically protected, namely, other photovoltaic modules are not influenced, the modules with reverse overvoltage voltage are also protected, and the whole process does not influence the generation of the photovoltaic system.
The invention further provides a protection circuit of the photovoltaic module; the photovoltaic module comprises N photovoltaic cell substrings, and the N photovoltaic cell substrings are sequentially connected in series; the output ends of the photovoltaic cell substrings are connected in reverse parallel with a bypass diode DP.
As shown in fig. 7, the protection circuit of the photovoltaic module includes: a forward overcurrent detection unit 30 and a bypass shunt unit 40.
The forward overcurrent detection unit 30 is connected in series with the bypass diode DP. That is, the forward overcurrent detecting unit 30 serves to detect the current flowing through the bypass diode DP. When the current of the bypass diode DP is larger than a preset current value, indicating that the bypass diode DP has a forward overcurrent fault; when the current of the bypass diode DP is smaller than a preset current value, the bypass diode DP is indicated to have no forward flowing fault; the current of the bypass diode DP may be detected by detecting a temperature condition or by detecting a voltage across a series resistor with the bypass diode DP.
The bypass shunt unit 40 is connected in parallel with the bypass diode DP; therefore, the bypass shunt unit 40 can shunt the bypass diode DP, thereby protecting the photovoltaic module.
A forward overcurrent detection unit 30 for detecting whether a forward overcurrent fault exists in the photovoltaic module; and triggers the bypass shunt unit 40 to shunt the bypass diode DP upon detecting the presence of a forward overcurrent fault.
The positive overcurrent fault is that the photovoltaic module has positive overcurrent.
That is, if the photovoltaic module has a forward overcurrent, the forward overcurrent detecting unit 30 can detect the forward overcurrent, and when detecting the forward overcurrent fault, the bypass shunt unit 40 is triggered to protect the photovoltaic module. Specifically, the bypass shunt unit 40 shunts the bypass diode DP to realize protection of the photovoltaic module.
That is, the bypass shunt unit 40 is used for shunting the bypass diode DP, and not directly cutting the bypass diode DP, so that the bypass diode DP can still operate continuously.
Specifically, the bypass shunt unit 40 shunts the bypass diode DP, so that the current flowing through the bypass diode DP originally is reduced, the problem that the photovoltaic module cannot be protected due to failure of the bypass diode DP when the photovoltaic module is in forward overcurrent is avoided, and the safety and stability of the photovoltaic module are improved.
In this embodiment, when the photovoltaic module has forward overcurrent, the bypass shunt unit 40 is triggered to shunt the bypass diode DP to maintain the protection of the bypass diode DP on the photovoltaic module, so as to protect the bypass diode DP from being damaged; meanwhile, the protection mode is shunt, the bypass diode DP is not directly disconnected, the function of the bypass diode DP is kept, and the safety of a circuit where the bypass diode DP is located is improved.
In practical application, as shown in fig. 8, the forward overcurrent detecting unit 30 includes: a second resistor R2 and a third resistor R3.
The second resistor R2 and the third resistor R3 are connected in series and then connected in series with the bypass diode DP. The connection point between the second resistor R2 and the third resistor R3 is connected to the output end of the forward overcurrent detecting unit 30.
In practical applications, the third resistor R3 may be a thermistor, or may be a common resistor, where when the third resistor R3 is a thermistor, the third resistor R3 is disposed close to the bypass diode DP, so that the third resistor R3 can detect the temperature of the bypass diode DP more sharply.
That is, the third resistor R3 is mounted closely to the side of the bypass diode DP, and the resistance of the third resistor R3 increases as the temperature of the bypass diode DP increases.
Specifically, one end of the second resistor R2 is used as an input end of the branch where the bypass diode DP is located; the other end of the second resistor R2 is connected with one end of the third resistor R3, and the connection point is used as the output end of the forward overcurrent detection unit 30; the other end of the third resistor R3 is connected with the anode of the bypass diode DP; the cathode of the bypass diode DP serves as the output of the branch in which the bypass diode DP is located.
In practical applications, as shown in fig. 3, the forward overcurrent detecting unit 30 may further include: and a first switching tube Q1 disposed between a connection point between the second resistor R2 and the third resistor R3 and an output terminal of the forward overcurrent detection unit 30.
The control end of the first switching tube Q1 is connected with a connection point between the second resistor R2 and the third resistor R3; the first end of the first switching tube Q1 is connected with one end of the second resistor R2 far away from the third resistor R3; the second end of the first switching tube Q1 is connected to the output end of the forward overcurrent detecting unit 30.
Specifically, one end of the second resistor R2 is connected to the first end of the first switching tube Q1, and the connection point is used as the input end of the branch where the bypass diode DP is located; the other end of the second resistor R2 is respectively connected with one end of the third resistor R3 and the control end of the first switching tube Q1; the second end of the first switching tube Q1 is connected with the output end of the forward overcurrent detection unit 30; the other end of the third resistor R3 is connected with the anode of the bypass diode DP; the cathode of the bypass diode DP serves as the output of the branch in which the bypass diode DP is located.
Specifically, the first switching tube Q1 is a low-impedance switching tube driven by voltage; for example, the control end of the first switch tube Q1 is the gate of the N-type MOS tube, the first end of the first switch tube Q1 is the drain of the N-type MOS tube, and the second end of the first switch tube Q1 is the source of the N-type MOS tube.
In practical use, as shown in fig. 8, the bypass flow dividing unit 40 includes: a second controllable switch S2 and a fourth resistor R4.
The second controllable switch S2 is indirectly connected in parallel with the bypass diode DP; the control end of the second controllable switch S2 is connected with one end of a fourth resistor R4; the first end of the second controllable switch S2 is connected with the other end of the fourth resistor R4, and the connection point is used as the control end of the bypass shunt unit 40; the connection point also serves as an input to the bypass flow splitting unit 40; i.e. the connection point is connected to the output of the forward overcurrent detection unit 30; a second terminal of the second controllable switch S2 is connected to the cathode of the bypass diode DP.
In practical application, when the forward overcurrent detecting unit 30 includes the first switching tube Q1:
the connection point between the second resistor R2 and the third resistor R3 is connected with the control end of the first switching tube Q1; the first end of the second controllable switch S2 is connected to one end of the first switching tube Q1, and the second end of the second controllable switch S2 is connected to the cathode of the bypass diode DP.
The second controllable switch S2 may be an NPN transistor; the control end of the second controllable switch S2 is the base electrode of an NPN triode, the first end of the second controllable switch S2 is the collector electrode of the NPN triode, and the second end of the second controllable switch S2 is the emitter electrode of the NPN triode.
Specifically, as shown in fig. 8, the operation of the forward overcurrent detecting unit 30 and the bypass shunt unit 40 in the protection circuit will be described:
first, when the bypass diode DP is off, i.e., the current i2=0 flowing through the bypass diode DP; the gate-source voltage vgs=0 of the switching transistor Q1. The switching tube Q1 is in an off state. At this time, the base current ib=0 of the transistor S2 turns off the transistor S2; the diode between the BE terminal of the triode S2 and the reverse diode of the switching tube Q1 are reverse, and the switching tube Q1 and the triode S2 in the protection circuit are in a disconnected and non-working state.
Secondly, the bypass diode DP is turned on with a current i2>0; when i2 is smaller or the bypass diode DP temperature is lower, VGS of the switching tube Q1 is smaller than the threshold voltage VT of the switching tube Q1, the switching tube Q1 is in an off state, i.e. 0< VGS < VT. When the temperature of the bypass diode DP is too high or i2 is large, the resistance of the third resistor R3 increases rapidly along with the temperature rise of the bypass diode DP, wherein vbe=0.7v of the transistor S2, and when VGS of the switching tube Q1 is larger than the turn-on voltage VT thereof, the switching tube Q1 is turned on. After the switch Q1 is turned on, ib of the transistor S2 is >0, so that the transistor S2 is in a saturated conduction state, and at this time, both the switch Q1 and the transistor S2 are in conduction states.
When the switching tube Q1 and the triode S2 are conducted, the current i2 of the bypass diode DP is shunted, the shunt current is i3, and the current of the bypass diode DP is reduced to be i4, so that the switching tube Q1 shares some power on the bypass diode DP, heat energy on the bypass diode DP is reduced, and further the bypass diode DP is protected.
As the temperature or current of the bypass diode DP decreases, the resistance of the third resistor R3 decreases; wherein, the rate of increase of the resistance value of the third resistor R3 along with the temperature rise is larger than the rate of decrease along with the temperature drop; as the resistance of the third resistor R3 decreases, the gate VGS <0 of the switching transistor Q1 is turned off. At this time, i3=0, the base current ib=0 of the transistor, and the transistor S2 is turned off.
In this embodiment, the third resistor R3 automatically senses the on-off state of the trigger switch Q1, and the shunt protection of the bypass diode DP is achieved by accurately driving the on-off state of the switch Q1 under different working conditions. Through the series connection of the switching tube Q1 and the triode S2, the forward conduction problem of the anti-parallel diode of the switching tube Q1 is effectively solved, and the forward conduction overheat protection of the bypass diode DP is realized.
That is, according to the working state of the bypass diode DP, the on-off of the switching tube is automatically triggered to increase one branch of the shunt branch, and the heating power of the bypass diode DP is reduced by reducing the current of the bypass diode DP, so as to realize the protection of the abnormal working state of the bypass diode DP. Meanwhile, the automatic triggering circuit of the protection circuit is simple and reliable, and is effectively triggered through the high-precision third resistor R3.
Specifically, as shown in fig. 9, the operation of the reverse overvoltage detection unit 10 and the bypass shunt unit 40 in the protection circuit will be described:
it should be noted that, as shown in fig. 9, taking N equal to 3 and the third resistor as a thermistor as an example, a photovoltaic module is formed by connecting several tens of silicon wafers in series, and dividing the silicon wafers connected in series into three photovoltaic cell sub-strings, each of which is connected in reverse parallel with a bypass diode DP (such as DP1, DP2 and DP3 shown in fig. 9); three protection circuits are provided correspondingly to protect the respective bypass diodes DP (DP 1, DP2 and DP3 as shown in fig. 9).
That is, in the first protection circuit: r21, R31, R41, S21 and Q11 are bypass diodes DP1 used for protecting the shading working condition, and a triode S21 is connected in series with a source S of the switch tube Q11. The drain D of the switching tube Q11 is connected to the upper end of R21, the gate G is connected to the middle of resistors R21 and R31, and the source S is connected to the cathode of the bypass diode DP 1.
In the second protection circuit: r22, R32, R42, S22 and Q12 are bypass diodes DP2 used for protecting the shading working condition, and a triode S22 is connected in series with a source S of the switch tube Q12. The drain D of the switching tube Q12 is connected to the upper end of the resistor R22, the gate G is connected to the middle of the resistors R22, R32, and the source S is connected to the cathode of the bypass diode DP 2.
In the third protection circuit: r23, R33, R43, S23 and Q13 are bypass diodes DP3 used for protecting the shading working condition, and a triode S23 is connected in series with a source S of the switch tube Q13. The drain D of the switching tube Q13 is connected to the upper end of the resistor R23, the gate G is connected to the middle of the resistors R23, R33, and the source S is connected to the cathode of the bypass diode DP 3.
In practical use the respective protection circuits and bypass diodes DP (DP 1, DP2 and DP3 as shown in fig. 9) are arranged in the junction box. Specifically, the negative terminal output line of the junction box is led out from the connection point between the resistor R21 and the switching tube Q11, and the positive terminal of the junction box is led out from the cathode of the bypass diode DP 3.
The working process analysis is carried out on the protection circuit of the photovoltaic module of one group of sub-strings, and the working condition that the photovoltaic module is in normal illumination and the shadow shielding working condition of the photovoltaic cell sub-strings of the photovoltaic module is analyzed.
Firstly, when the photovoltaic module is in normal illumination, the photovoltaic cell substring is used as output to generate power, the direction of the power generation voltage U1 at the output end is consistent with the voltage direction of the photovoltaic cell substring, and at the moment, the bypass diode DP1 is disconnected, namely the current i2=0 flowing through the bypass diode DP; the gate-source voltage vgs=0 of the switching transistor Q11, and the switching transistor Q11 is in an off state. At this time, the base current ib=0 of the transistor S21 turns off the transistor S21; the diode between the BE ends of the triode S21 is opposite to the reverse diode of the switching tube Q11, and photovoltaic power generation cannot BE affected due to the parasitic diode of the switching tube, so that the switching tube Q11 and the triode S21 in the protection circuit are in a disconnected and non-working state under the condition that the photovoltaic module is used as a power supply system when no shading exists. The formula adopted for the gate-source voltage of the switching transistor Q11 is formula (6).
V GS Formula =i2×r2=0 (6)
Secondly, a shadow shielding working condition appears in a photovoltaic cell sub-string in the photovoltaic module, when the internal resistance formed by shielding is larger than the external load resistance, the direction of the power generation voltage U1 at the output end is inconsistent with the voltage direction of the photovoltaic cell sub-string, so that the bypass diode DP1 is conducted to shunt i2>0; when i2 is smaller or the bypass diode DP1 is at a lower temperature, VGS of the switching tube Q11 is smaller than the threshold voltage VT thereof, the switching tube Q11 is in an off state, i.e., 0< VGS < VT. When the temperature of the bypass diode DP1 is too high, the resistance of the third resistor R31 increases rapidly with the temperature rise of the bypass diode DP1, wherein vbe=0.7v of the transistor S2, and according to formula (7), when VGS of the switching transistor Q11 is greater than the turn-on voltage VT thereof, the switching transistor Q11 is turned on. After the switch Q11 is turned on, ib >0 of the transistor makes the transistor S21 in a saturated on state, and at this time, both the switch Q11 and the transistor S21 are in an on state.
When the switching tube Q11 and the triode S21 are turned on, the current i2 of the bypass diode DP1 is split, the split current is i3, and the current of the bypass diode DP1 is reduced to i4, so that the switching tube Q11 shares some power on the bypass diode DP1 to reduce the heat energy on the bypass diode DP1, and further the bypass diode DP1 is protected. Wherein the formula adopted by each current is formula (8).
V T ＜V GS ＝i2×R2-V BE Formula (7)
i2＝imp-i1
i2 =i3+i4 formula (8)
i3＝imp-i1-i4
Wherein V is T For the threshold voltage of the corresponding switching tube, V GS For the gate-source voltage of the corresponding switching tube, V BE Is the voltage between the B terminal and the E terminal of the corresponding switching tube.
As the temperature of the bypass diode DP1 decreases, the resistance of the third resistor R3 decreases; wherein, the rate of the increase of the resistance value of the third resistor R31 along with the temperature rise is larger than the rate of the decrease of the resistance value along with the temperature drop; the gate VGS <0 of the switching transistor Q11 is turned off as in equation (9). At this time, i3=0, the base current ib=0 of the transistor S21, and the transistor S21 is turned off.
0 > VGS=i2×R2-VBE equation (9)
With the switching tube Q11 turned off, if the shadow is blocked, the bypass diode DP1 is heated due to the current of i2 again, so that the resistance value of the third resistor R31 is increased, the switching tube Q11 and the triode S21 are turned on to shunt i3, and the switching tube Q11 is turned on and off to shunt the bypass diode DP1, and meanwhile, the switching tube Q11 is not turned on for a long time. Wherein fig. 10 is a current curve of the bypass diode DP1 and the protection circuit under the shadow masking condition.
In this embodiment, the protection circuit does not influence the normal power generation of the photovoltaic module, and can automatically sense and trigger protection according to the third resistor R31, so that the photovoltaic module is effectively protected under the reverse overvoltage breakdown condition caused by the shadow shielding of the photovoltaic module.
It should be noted that, the protection circuits of the photovoltaic modules provided in the above two embodiments may be integrated together, and the specific structure thereof is shown in fig. 11, and at this time, the two protection circuits may also share a resistor. Specifically, R1, DP1 and S1 together form one protection circuit, and R1, R2, R4, Q1 and S2 together form another protection circuit. Referring to fig. 12, a block diagram of a photovoltaic module is shown, in which the number of photovoltaic cell substrings in the photovoltaic module is equal to 3, and specific working principles and working processes thereof are shown, and details refer to two protection circuits provided in the foregoing embodiments, which are not described in detail herein, and are all within the protection scope of the present application.
Another embodiment of the present application also provides a photovoltaic power generation system, including: the photovoltaic module comprises an inversion unit, at least one photovoltaic module and a protection circuit of the at least one photovoltaic module; wherein:
each photovoltaic module is connected in series to form a photovoltaic group string, and the output ends of each photovoltaic group string are connected in parallel and then connected to the direct current side of the inversion unit.
The protection circuit is used for protecting each photovoltaic cell substring in the photovoltaic module; the protection circuit can realize protection of the photovoltaic cell sub-strings by maintaining the functions of the bypass diodes of the opposite parallel connection of the corresponding photovoltaic cell sub-strings.
The alternating current side of the inversion unit is connected to the power grid.
In practical application, the protection circuit is arranged in a junction box of the photovoltaic module.
The junction box can be arranged on the back surface of the photovoltaic module, is not particularly limited herein, and can be used according to actual conditions, and is within the protection scope of the application.
The specific structure and the working principle of the protection circuit are just described in detail in the above embodiments, and are not described in detail herein, and are all within the protection scope of the present application.
It should be noted that, the protection circuits in the prior art are embedded in the components, and the maintainability is poor.
In this embodiment, the protection circuit of the photovoltaic module is placed in the junction box, so that maintenance is facilitated.
Features described in the embodiments in this specification may be replaced or combined, and identical and similar parts of the embodiments may be referred to each other, where each embodiment focuses on differences from other embodiments. In particular, for a system or system embodiment, since it is substantially similar to a method embodiment, the description is relatively simple, with reference to the description of the method embodiment being made in part. The systems and system embodiments described above are merely illustrative, wherein the elements illustrated as separate elements may or may not be physically separate, and the elements shown as elements may or may not be physical elements, may be located in one place, or may be distributed over a plurality of network elements. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art will understand and implement the present application without undue burden.
Those of skill would further appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative elements and steps are described above generally in terms of functionality in order to clearly illustrate the interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (14)

1. The protection circuit of the photovoltaic module is characterized in that the photovoltaic module comprises N photovoltaic cell substrings, and the N photovoltaic cell substrings are sequentially connected in series; two ends of each photovoltaic cell substring are reversely connected with a bypass diode in parallel; the protection circuit includes: a reverse overvoltage detection unit and a protection branch unit; the protection branch comprises a first controllable switch; the reverse overvoltage detection unit includes: a first resistor and a voltage stabilizing switch connected in series; the connection point between the first resistor and the voltage stabilizing switch is used as the output end of the reverse overvoltage detection unit; two ends of the first controllable switch are used as two ends of the protection branch unit; the control end of the first controllable switch is used as the control end of the protection branch unit;
the protection branch unit and the bypass diode are directly or indirectly connected in parallel;
the reverse overvoltage detection unit is connected with the bypass diode in series or in parallel;
the reverse overvoltage detection unit is used for detecting whether the photovoltaic module has a reverse overvoltage fault or not; when the reverse overvoltage fault is detected, triggering the protection branch unit to shunt the bypass diode so as to keep the bypass diode to protect the photovoltaic module; the reverse overvoltage fault is that the photovoltaic module generates reverse overvoltage.
2. The protection circuit of a photovoltaic module according to claim 1, wherein the voltage stabilizing switch is a voltage stabilizing diode.
3. The protection circuit of a photovoltaic module according to claim 2, wherein the zener diode is the bypass diode or is a zener diode independent of the bypass diode.
4. The protection circuit of the photovoltaic module according to claim 2, wherein the first resistor and the voltage stabilizing switch are sequentially connected in series between a positive electrode and a negative electrode of the photovoltaic module; or,
the first resistor and the voltage stabilizing switch are sequentially connected in series between the negative electrode and the positive electrode of the photovoltaic module.
5. The protection circuit of a photovoltaic module according to claim 1, wherein the first controllable switch comprises at least one of a relay and a switching tube.
6. The protection circuit of a photovoltaic module according to claim 5, wherein if the first controllable switch is the relay, the reverse overvoltage detection unit is a coil secondary of the relay.
7. The protection circuit of a photovoltaic module according to claim 1, wherein the protection branching unit further comprises a second resistor connected in series with the first controllable switch.
8. The protection circuit of the photovoltaic module is characterized in that the photovoltaic module comprises N photovoltaic cell substrings, and the N photovoltaic cell substrings are sequentially connected in series; the output ends of the photovoltaic cell substrings are reversely connected with a bypass diode in parallel; the protection circuit includes: a forward overcurrent detection unit and a bypass shunt unit; the forward overcurrent detection unit is connected with the bypass diode in series;
the bypass shunt unit is connected with the bypass diode in parallel;
the forward overcurrent detection unit is used for detecting whether the photovoltaic module has a forward overcurrent fault or not; when the forward overcurrent fault is detected, triggering the bypass shunt unit to shunt the bypass diode so as to keep the bypass diode to protect the photovoltaic module; the positive overcurrent fault is that the photovoltaic module has positive overcurrent;
wherein, forward overcurrent detection unit includes: the second resistor, the third resistor and the first switch tube; the second resistor and the third resistor are connected in series and then connected in series with the bypass diode; the connection point between the second resistor and the third resistor is connected with the output end of the forward overcurrent detection unit; the control end of the first switching tube is connected with a connection point between the second resistor and the third resistor; the first end of the first switch tube is connected with one end of the second resistor far away from the third resistor; the second end of the first switching tube is connected with the output end of the forward overcurrent detection unit;
The bypass flow splitting unit includes: a second controllable switch and a fourth resistor;
the second controllable switch is indirectly connected with the bypass diode in parallel;
the control end of the second controllable switch is connected with one end of the fourth resistor;
the first end of the second controllable switch is connected with the other end of the fourth resistor, and the connection point is used as the control end of the bypass shunt unit.
9. The protection circuit of a photovoltaic module according to claim 8, wherein the third resistor is a thermistor;
the thermistor is disposed proximate the bypass diode.
10. The protection circuit of a photovoltaic module according to claim 8, wherein the first switching tube is a voltage-driven low-impedance switching tube.
11. The protection circuit of a photovoltaic module according to claim 8, wherein when the forward overcurrent detection unit includes a first switching tube:
the connection point between the third resistor and the fourth resistor is connected with the second end of the first switching tube;
the second end of the second controllable switch is connected with the cathode of the bypass diode.
12. The protection circuit of a photovoltaic module according to claim 8, wherein the second controllable switch is an NPN transistor.
13. A photovoltaic power generation system, comprising: an inverter unit, at least one photovoltaic module, and at least one protection circuit of a photovoltaic module according to any one of claims 1 to 7 or a protection circuit of a photovoltaic module according to any one of claims 8 to 12; wherein:
the photovoltaic modules are connected in series to form a photovoltaic group string, and the output ends of the photovoltaic group strings are connected in parallel and then connected to the direct current side of the inversion unit;
and the alternating current side of the inversion unit is connected to a power grid.
14. The photovoltaic power generation system of claim 13, wherein the protection circuit in the photovoltaic module is disposed in a junction box of the photovoltaic module.
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Address after: High tech Zone of Hefei city of Anhui Province in 230088 Lake Road No. 2

Applicant after: Sunshine New Energy Development Co.,Ltd.

Address before: High tech Zone of Hefei city of Anhui Province in 230088 Lake Road No. 2

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