CN116526961B - Photovoltaic cell bypass circuit, photovoltaic junction box and photovoltaic module - Google Patents
Photovoltaic cell bypass circuit, photovoltaic junction box and photovoltaic module Download PDFInfo
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- CN116526961B CN116526961B CN202310806805.4A CN202310806805A CN116526961B CN 116526961 B CN116526961 B CN 116526961B CN 202310806805 A CN202310806805 A CN 202310806805A CN 116526961 B CN116526961 B CN 116526961B
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- 238000004146 energy storage Methods 0.000 claims abstract description 31
- 230000010355 oscillation Effects 0.000 claims abstract description 27
- 230000005669 field effect Effects 0.000 claims description 47
- 239000003990 capacitor Substances 0.000 claims description 20
- 230000003071 parasitic effect Effects 0.000 claims description 16
- 230000000694 effects Effects 0.000 abstract description 8
- 238000004804 winding Methods 0.000 description 7
- 238000010586 diagram Methods 0.000 description 5
- 230000005284 excitation Effects 0.000 description 3
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- 230000000737 periodic effect Effects 0.000 description 2
- 230000002441 reversible effect Effects 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 229910002601 GaN Inorganic materials 0.000 description 1
- JMASRVWKEDWRBT-UHFFFAOYSA-N Gallium nitride Chemical compound [Ga]#N JMASRVWKEDWRBT-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910052732 germanium Inorganic materials 0.000 description 1
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 230000002459 sustained effect Effects 0.000 description 1
Classifications
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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
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- 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
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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
- H02S40/36—Electrical components characterised by special electrical interconnection means between two or more PV modules, e.g. electrical module-to-module connection
-
- 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
- H02S50/00—Monitoring or testing of PV systems, e.g. load balancing or fault identification
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- 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
Abstract
The embodiment of the application provides a photovoltaic cell bypass circuit, which comprises a first connecting end and a second connecting end, wherein the first connecting end and the second connecting end are used for connecting the photovoltaic cell bypass circuit with at least one cell sub-string of a photovoltaic cell in parallel; the device also comprises an oscillation driving module which is used for controlling the intermittent conduction of the bypass switch module; the bypass switch module is used for bypassing at least one battery sub-string and is intermittently conducted under the control of the oscillation driving module so as to reduce power consumption; the oscillation driving module comprises a self-oscillation unit and an energy storage unit; the self-oscillation unit is used for generating an oscillation signal in a self-oscillation mode and charging the energy storage unit; the energy storage unit is used for outputting control voltage to the bypass switch module, and controlling the bypass switch module to be conducted under the condition that the control voltage reaches the conducting voltage of the bypass switch module; the self-oscillation unit comprises a transformer, a triode and a first resistor. The power loss is further reduced, the circuit structure is simplified, and the cost is further reduced while the hot spot effect is avoided.
Description
Technical Field
The application relates to the technical field of photovoltaics, in particular to a photovoltaic cell bypass circuit, a photovoltaic junction box and a photovoltaic module.
Background
The hot spot effect is a common phenomenon in solar cell modules, and means that under certain conditions, a solar cell module shielded in a series branch will become a load to generate heat, so as to damage the solar cell. The junction box of the existing solar photovoltaic module adopts a high-power bypass diode, when the module is shielded, the voltage of the junction box is reversely charged by other modules, the bypass diode becomes forward conduction, and the photovoltaic module is bypassed, so that the damage of a hot spot effect to the solar module is slowed down. However, the conduction voltage drop of the existing bypass diode is about 0.6V, which causes a larger power loss of the solar cell module.
At present, a bypass component for protecting a battery string by adopting an MOS tube is also available, but the bypass component needs to be combined with a charge pump, a comparator, a reference signal source and other components, the circuit is complex, the cost is high, and the bypass component can generate larger power loss.
How to further reduce the power loss of the bypass assembly while avoiding hot spots, simplify the bypass assembly, and further reduce the cost is an important technical problem which is constantly addressed in the field.
Disclosure of Invention
In view of the above, embodiments of the present application provide a photovoltaic cell bypass circuit, a photovoltaic junction box and a photovoltaic module for solving at least one problem existing in the background art.
In a first aspect, an embodiment of the present application provides a photovoltaic cell bypass circuit, including a first connection end and a second connection end, where the first connection end and the second connection end are used to connect the photovoltaic cell bypass circuit and at least one cell sub-string of a photovoltaic cell in parallel; the photovoltaic cell bypass circuit further comprises an oscillation driving module and a bypass switch module;
the oscillation driving module is used for controlling the bypass switch module to be intermittently conducted;
the bypass switch module is used for bypassing the at least one battery sub-string and is intermittently conducted under the control of the oscillation driving module so as to reduce power consumption;
the oscillation driving module comprises a self-oscillation unit and an energy storage unit;
the self-oscillation unit is used for generating an oscillation signal in a self-oscillation mode and charging the energy storage unit;
the energy storage unit is used for outputting control voltage to the bypass switch module; controlling the bypass switch module to be conducted under the condition that the energy storage unit is charged to enable the control voltage to reach the conducting voltage of the bypass switch module; controlling the bypass switch module not to be conducted under the condition that the energy storage unit discharges to enable the control voltage not to reach the conducting voltage of the bypass switch module;
the self-oscillation unit comprises a transformer, a triode and a first resistor; the collector electrode of the triode is connected with the first connecting end through the primary side of the transformer, and the base electrode of the triode is connected with the first connecting end through the first resistor and the secondary side of the transformer in sequence; and an emitter of the triode is connected with the second connecting end.
With reference to the first aspect of the present application, in an alternative embodiment, the primary side of the transformer includes a primary side first end and a primary side second end; the secondary side of the transformer comprises a secondary side third end and a secondary side fourth end; the first end of the primary side is connected with the first connecting end, and the second end of the primary side is connected with the triode collector; the third end of the secondary side is connected with the resistor, and the fourth end of the secondary side is connected with the first connecting end; the second end of the primary side and the fourth end of the secondary side are the same name ends.
With reference to the first aspect of the present application, in an alternative embodiment, the energy storage unit includes a first diode and a capacitor connected in series with each other; the anode of the first diode is connected with the first connecting end through the primary side of the transformer; the cathode of the first diode is connected with the first end of the capacitor; the second end of the capacitor is connected with the second connecting end.
With reference to the first aspect of the present application, in an alternative embodiment, the bypass switch module includes at least one field effect transistor; the source electrode of the field effect tube is connected with the first connecting end, and the drain electrode of the field effect tube is connected with the second connecting end; and the grid electrode of the field effect transistor is connected with the first end of the capacitor.
With reference to the first aspect of the present application, in an alternative embodiment, the field effect transistor includes: and the parasitic diode is used for forming an operating voltage drop between the source electrode and the drain electrode of the field effect transistor.
With reference to the first aspect of the present application, in an alternative embodiment, the bypass switch module includes at least one field effect transistor; the conduction voltage of the triode is lower than the working voltage drop of the bypass switch module.
With reference to the first aspect of the present application, in an optional implementation manner, the photovoltaic cell bypass circuit further includes a microcontroller connected to the bypass switch module, and the microcontroller is configured to control whether the bypass switch module is turned on or off.
With reference to the first aspect of the present application, in an alternative embodiment, the bypass switch module includes at least one field effect transistor; the microcontroller is connected with the grid electrode of the field effect tube.
In a second aspect, embodiments of the present application provide a photovoltaic junction box comprising a photovoltaic cell bypass circuit of any of the above aspects.
In a third aspect, an embodiment of the present application provides a photovoltaic module, including a photovoltaic cell bypass circuit according to any one of the above aspects.
According to the photovoltaic cell bypass circuit, the photovoltaic junction box and the photovoltaic module provided by the embodiment of the application, the photovoltaic cell bypass circuit with the intermittent conduction function is adopted to replace the traditional bypass module, so that the photovoltaic cell bypass circuit does not consume power under the condition that the bypass switch module in the photovoltaic cell bypass circuit is conducted, and the power consumption is greatly reduced while the hot spot effect is avoided. The intermittent conduction function is realized by adopting the self-oscillation unit comprising the transformer and the triode, expensive and complex digital circuits or chips are not needed, the circuits are greatly simplified, the cost is reduced, and the power consumption is further reduced.
Additional aspects and advantages of the application will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the application.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application and do not constitute a limitation on the application. In the drawings:
fig. 1 is a schematic diagram of a photovoltaic cell bypass circuit according to an embodiment of the present application;
FIG. 2 is a schematic diagram of a photovoltaic cell bypass circuit according to an embodiment of the present application;
FIG. 3 is a schematic diagram illustrating the operation of a photovoltaic cell bypass circuit according to an embodiment of the present application;
FIG. 4 is a second schematic diagram illustrating operation of a photovoltaic cell bypass circuit according to an embodiment of the present application;
FIG. 5 is a schematic diagram of a photovoltaic cell bypass circuit according to an embodiment of the present application;
FIG. 6 is a schematic view of a photovoltaic junction box according to an embodiment of the present application;
fig. 7 is a schematic view of a photovoltaic module according to an embodiment of the present application.
Detailed Description
In order to make the technical solution and the beneficial effects of the present application more obvious and understandable, the technical solution in the embodiments of the present application will be clearly and completely described by way of example only, and it is apparent that the described embodiments are only some embodiments of the present application, not all embodiments. 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.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.
It will be understood that the terms first, second, etc. as used herein may be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another element. For example, a first resistance may be referred to as a second resistance, and similarly, a second resistance may be referred to as a first resistance, without departing from the scope of the application. Both the first resistor and the second resistor are resistors, but they are not the same resistor. When "first" is described, it does not necessarily mean that "second" is present; and when "second" is discussed, it does not necessarily indicate that the application necessarily resides in a first element, component, region, layer or section. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The meaning of "a plurality of" is two or more, unless specifically defined otherwise. It will be further understood that the terms "comprises" and "comprising," when used in this specification, specify the presence of stated features, but do not preclude the presence or addition of one or more other features. As used herein, the term "and/or" includes any and all combinations of the associated listed items.
It is to be understood that in the context of the present application, "connected" means that the connected end and the connected end have electrical signals or data transferred therebetween, and may be understood as "electrically connected", "communicatively connected", etc. In the context of the present application, "a is directly connected to B" means that no other components than wires are included between a and B.
Referring to fig. 1, an embodiment of the present application provides a photovoltaic cell bypass circuit 100, which includes a first connection terminal P1 and a second connection terminal P2. The first connection terminal P1 and the second connection terminal P2 are used to connect the photovoltaic cell bypass circuit 100 and at least one cell sub-string of the photovoltaic cell assembly in parallel. The photovoltaic cell assembly includes a plurality of photovoltaic cell substrings connected in series with one another. Fig. 1 shows three battery sub-strings connected in series with each other, battery sub-string 01, battery sub-string 02, and battery sub-string 03. It will be appreciated that the number of battery sub-strings may also be two or more than three, as the application is not limited in this regard. The photovoltaic cell bypass circuit 100 is connected in series-parallel with at least one cell sub-string. Alternatively, the photovoltaic cell bypass circuit 100 is connected in parallel with one cell sub-string; or the bypass circuit of the photovoltaic battery assembly is connected with two batteries which are connected in series and in parallel at the same time. Optionally, each cell sub-string is connected in parallel with a photovoltaic cell bypass circuit 100; or select certain cell sub-strings to be connected in parallel with the photovoltaic cell bypass circuit 100 as desired. Fig. 1 only shows the photovoltaic cell bypass circuit 100 in parallel with the cell sub-string 02, it being understood that the cell sub-string 01 and the cell sub-string 03 may each also be connected in parallel with the corresponding photovoltaic cell bypass circuit 100.
The photovoltaic cell bypass circuit 100 is connected in parallel with the cell sub-string 02 through a first connection terminal P1 and a second connection terminal P2. The photovoltaic cell bypass circuit 100 is connected in series with both the cell substring 01 and the cell substring 03. As shown in fig. 1, the first connection terminal P1 is connected to the negative electrode of the battery sub-string 02, and the second connection terminal P2 is connected to the positive electrode of the battery sub-string 02. Meanwhile, the second connection terminal P2 is connected to the negative electrode of the battery sub-string 01, and the first connection terminal P1 is connected to the positive electrode of the battery sub-string 03. When the battery sub-string 02 is not blocked, the battery sub-string 02 is in a normal working state, the photovoltaic cell bypass circuit 100 does not work, and the battery sub-string 01, the battery sub-string 02 and the battery sub-string 03 are connected in series. When the battery sub-string 02 is blocked, the photovoltaic cell bypass circuit 100 bypasses the battery sub-string 02, the battery sub-string 02 does not work, and the battery sub-string 01, the photovoltaic cell bypass circuit 100 and the battery sub-string 03 work in series in sequence.
The photovoltaic cell bypass circuit 100 further includes a bypass switch module 10 and an oscillating drive module 20. The oscillation driving module 20 is used for controlling the bypass switch module 10 to conduct intermittently so as to reduce the power consumption of the bypass switch module 10. The bypass switch module 10 is used for bypassing at least one battery sub-string connected in parallel with the bypass switch module and is intermittently conducted under the control of the oscillation driving unit so as to reduce power consumption. When a hot spot effect occurs on a cell sub-string, the photovoltaic cell bypass circuit 100 in parallel with it begins to operate, the cell sub-string being bypassed. In the case where the photovoltaic cell bypass circuit 100 operates, by controlling the bypass switch module 10 to be intermittently turned on, the bypass switch module 10 does not generate power consumption during the on period, thus reducing the power consumption of the photovoltaic cell bypass circuit 100 in the operating state.
The bypass switch module 10 comprises a control terminal 103 and power supply connection terminals 101, 102. The oscillating drive module 20 comprises a control signal output 203 and power supply connections 201, 202. The control signal output terminal 203 of the oscillation driving module 20 is connected to the control terminal 103 of the bypass switch module 10 for outputting a control signal to the bypass switch module 10. The oscillation driving module 20 can output a periodic conduction signal to the bypass switch module 10 to control the bypass switch module 10 to conduct intermittently. When the bypass switch module 10 is turned on, the battery sub-string 02 connected in parallel thereto is bypassed, the battery sub-string 02 does not operate, and the battery sub-string 01, the photovoltaic cell bypass circuit 100, and the battery sub-string 03 operate in series in this order.
The oscillation driving module 20 includes an energy storage unit 21 and a self-oscillation unit 22. The self-oscillation unit 22 is configured to generate an oscillation signal in a self-oscillation manner and charge the energy storage unit 21. Self-oscillation refers to self-generating stable and sustained oscillations without the addition of an excitation signal. The oscillation driving module 20 is connected to the first connection terminal P1 and the second connection terminal P2 to obtain the operating voltage provided by the other battery sub-strings. In this way, the oscillation driving module 20 does not need additional power supply or an additional excitation signal source, which reduces power consumption and complexity of the circuit. The self-oscillation unit is connected with the first connection terminal P1 and the second connection terminal P2 to obtain an operating voltage required for self-oscillation.
The energy storage unit 21 is used for outputting control voltage to the bypass switch module 10; when the energy storage unit 21 is charged to enable the control voltage to reach the conducting voltage of the bypass switch module 10, the bypass switch module 10 is controlled to conduct; when the energy storage unit 21 is discharged and the control voltage does not reach the conduction voltage of the bypass switch module 10, the bypass switch module 10 is controlled to be not conducted. In this way, intermittent conduction of the bypass switch module 10 is achieved. When the bypass switch module 10 is turned on, the voltage drop across the bypass switch module is extremely low, and power is hardly consumed, so that the power consumption of the bypass switch module 10 during operation is further reduced.
The photovoltaic cell bypass circuit 100 of the embodiment of the present application operates as follows: in use, the photovoltaic cell bypass circuit 100 is connected in parallel with at least one cell sub-string, for example in parallel with the cell sub-string 02, via the first and second connection terminals P1 and P2. When the battery sub-string 02 is not blocked, the battery sub-string 02 is in a normal working state, the photovoltaic cell bypass circuit 100 does not work, and the battery sub-string 01, the battery sub-string 02 and the battery sub-string 03 are connected in series in sequence.
In the case where the battery sub-string 02 is blocked, the photovoltaic cell bypass circuit 100 bypasses the battery sub-string 02, the battery sub-string 02 does not operate, and the battery sub-string 01, the photovoltaic cell bypass circuit 100, and the battery sub-string 03 operate in series in this order. The first connection terminal P1 is connected to the positive electrode of the battery sub-string 03, and the voltage thereof is positive. The second connection terminal P2 is connected to the negative electrode of the battery string 01, and the voltage thereof is negative. The current flows from the positive electrode of the cell string 03, through the photovoltaic cell bypass circuit 100, and into the negative electrode of the cell string 01. Thus, the bypass function is realized, and the heat generated by the current flowing through the battery sub-string 02 is avoided, so that the battery sub-string 02 is damaged, and the hot spot effect is avoided.
At the same time, the oscillating drive module 20 operates on the voltage provided by the other battery sub-string, for example, the battery sub-string 03, and generates a periodic control signal to control the bypass switch module 10 to conduct intermittently. When the bypass switch module 10 is turned on, the voltage between the first connection terminal P1 and the second connection terminal P2 is very low, and little power is consumed. Because the bypass switch module 10 is intermittently conducted, the power loss of the bypass switch module 10 is greatly reduced, and the problem of high power loss of the traditional bypass diode is solved.
The self-oscillation unit 22 of the oscillation driving module 20 generates an oscillation signal by adopting the self-oscillation principle, and charges the energy storage unit 21. The energy storage unit 21 outputs a control signal to the bypass switch module 10 via the control signal output 203. As the energy storage unit 21 is continuously charged, the voltage of the control signal output from the energy storage unit 21 is continuously increased. After the oscillation signals are charged for a plurality of periods, the voltage of the control signal output by the energy storage unit 21 reaches the conducting voltage of the bypass switch module 10, and the bypass switch module 10 is conducted.
When the energy storage unit 21 continues to discharge and the voltage of the control signal outputted by the energy storage unit is lower than the conduction voltage of the bypass switch module 10, the bypass switch module 10 is in a non-conduction state, and the bypass switch module 10 corresponds to a bypass diode. The energy storage unit 21 enters the next charging cycle, and when the voltage of the control signal outputted by the energy storage unit reaches the conducting voltage of the bypass switch module 10, the bypass switch module 10 is conducted again. The bypass switch module 10 is intermittently conducted by circulating in this way.
The self-oscillation unit 22 adopts the self-oscillation principle to generate an oscillation signal, and does not need to be additionally connected with other power supplies and external excitation sources, so that the power consumption is not increased.
Referring to fig. 2, an embodiment of a photovoltaic cell bypass circuit 100 in accordance with the present application. The self-oscillation unit 22 includes a transformer T1, a transistor Q1, and a first resistor R1. The collector of the triode Q1 is connected to the first connection terminal P1 through the primary side of the transformer T1 via the power connection terminal 101. The base electrode of the triode Q1 is connected with the power supply connecting end 101 through the first resistor R1 and the secondary side of the transformer T1 in sequence. The power connection terminal 101 is connected to the first connection terminal P1. The emitter of transistor Q1 is connected to the second connection P2 via the power connection 102.
The primary side of the transformer T1 comprises a primary side first end 1 and a primary side second end 2. The secondary side of the transformer comprises a secondary side third end 3 and a secondary side fourth end 4. The primary side first end 1 is connected to the first connection end P1 through the power connection end 101. The second end 2 of the primary side is connected with the collector electrode of the triode Q1. The third terminal 3 of the secondary side is connected to the first resistor R1. The secondary side fourth terminal 4 is connected to the first connection terminal P1 through the power connection terminal 101. The primary side first end 1 and the secondary side fourth end 4 are the same name ends.
The energy storage unit 21 includes a first diode D1 and at least one capacitor C1 connected in series with each other. The anode of the first diode D1 is connected to the first connection terminal P1 through the primary side of the transformer T1. The anode of the first diode D1 is connected to the primary second terminal 2. The cathode of the first diode D1 is connected to the first terminal 5 of the capacitor C1. The second terminal 6 of the capacitor C1 is connected to the second connection terminal P2. Alternatively, the capacitor C1 may be replaced by more than two capacitors connected in parallel.
The bypass switch module 10 includes at least one field effect transistor Q2. The field-effect transistor Q2 is selected from a Junction FET (JFET) and a metal-oxide semiconductor FET (MOS transistor). The field effect transistor may be a PMOS (P-channel type) or NMOS (N-channel type) transistor. The source S of the fet Q2 is connected to the first connection P1 through the power connection 101. The drain D of the fet Q2 is connected to the second connection P2 through the power connection 102. The gate G of the fet Q2 is connected to the first terminal 5 and the control terminal 103 of the capacitor C1, respectively.
The field effect transistor Q2 includes a parasitic diode D2. The parasitic diode D2 is located between the source S and the drain D of the field effect transistor Q2. The parasitic diode D2 has an anode connected to the source S and a cathode connected to the drain D. Alternatively, the fet Q2 comprises a silicon-based fet, and the parasitic diode D2 has an operating voltage of about 0.6-V-0.7-V.
The photovoltaic cell bypass circuit 100 of this embodiment operates as follows: in use, the photovoltaic cell bypass circuit 100 is connected in parallel with the cell sub-string to be bypassed, for example with at least one photovoltaic cell sub-string 02. In the case where the battery sub-string 02 is not blocked, the battery sub-string 02 operates normally, and the voltages of the first connection terminal P1 and the second connection terminal P2 of the photovoltaic cell bypass circuit 100 are forward. The voltage at the first connection terminal P1 of the photovoltaic cell bypass circuit 100 is negative, the voltage at the second connection terminal P2 is positive, and the voltage direction is opposite to the direction of the parasitic diode inside the fet Q2, so that the fet Q2 does not work at all.
In the case where the cell sub-string 02 is blocked, the voltage of the access photovoltaic cell bypass circuit 100 is reversed, and the source S voltage of the field effect transistor Q2 is higher than the drain D voltage. That is, the voltage direction is the same as the direction of the parasitic diode D2 inside the fet Q2, the internal parasitic diode starts to operate, the diode PN junction voltage is generated at both ends of the source and drain of the fet Q2, and the photovoltaic cell bypass circuit 100 starts to operate.
The current is split three ways altogether from the source S to the drain D of the fet Q2, see fig. 3. Parasitic two of the first path of secondary field effect transistor Q2The anode of the polar tube D2 flows to the cathode. The second current flows from the source electrode S of the field effect transistor Q2 to the drain electrode D of the field effect transistor Q2 through the primary side of the transformer T1, the collector electrode and the emission set of the triode Q1. The third path passes through the secondary side of the transformer T1 from the source electrode S of the field effect transistor Q2, then passes through the first resistor R1, the base electrode of the triode Q1 and the emission set, and then flows to the drain electrode D of the field effect transistor Q2. At this time, the primary winding of the transformer T1 is positive, and the secondary winding is negative, i.e. the voltage at the primary first end 1 is positive, the voltage at the primary second end 2 is negative, the voltage at the secondary third end 3 is positive, and the voltage at the secondary fourth end 4 is negative. Voltage V between base and emitter of transistor Q1 be = V ds + V T1 ，V ds T1 is the secondary coil induced voltage, which is the voltage drop generated by the FET Q2. V (V) be And the conduction voltage is larger than that of the triode Q1, and the Q1 can be completely conducted, so that the self-excitation boost driving Q1 is conducted.
After the triode Q1 is driven to be fully conducted, the second current loop is fully conducted, and current flows from the source electrode S of the field effect tube Q2 to the drain electrode D of the field effect tube Q2 through the primary side of the transformer T1, the collector electrode and the emission set of the triode Q1. After the current flows through the T1 primary winding, the current of the T1 primary winding continues to increase and energy is stored in the inductance of the T1 primary winding. When the inductance of the primary coil T1 is full of energy, the current of the primary coil T1 is not increased any more, and the primary coil T1 forms reverse electromotive force. Referring to fig. 4, the primary winding of T1 is negative and positive from top to bottom, so that a positive voltage and a negative voltage are induced in the secondary winding of T1, that is, the primary first terminal 1 is negative, the primary second terminal 2 is positive, the secondary third terminal 3 is negative, and the secondary fourth terminal 4 is positive. Thus the voltage V between the base and the emitter of the triode Q1 be ’ = V ds - V T1 ’ ，V T1 ' is the T1 secondary coil induced voltage. V (V) T1 ' and V T1 May be the same or different. V (V) be ' is smaller than the turn-on voltage of transistor Q1, transistor Q1 is turned off. This achieves self-excited turn-off Q1. Since Q1 is turned off, the voltage V between the source S and the drain D ds After being overlapped with the primary side induction voltage of the T1, the capacitor C1 is charged through the first diode D1. The instantaneous current flow resulting from the charging is shown in fig. 4.
After charging for a plurality of periods, the source electrode S and the drain electrode D of the field effect transistor Q2 are conducted after the voltage on the capacitor C1 reaches the conducting voltage of the field effect transistor Q2. When the field effect transistor Q2 is turned on, the voltage drop between the Q2 source S and the drain D is extremely low, and a current flows from the Q2 source S to the drain D without passing through the parasitic diode D2. Since the conduction voltage drop of the source S and the drain D is small when Q2 is turned on, it is insufficient to drive the transformer T1 and the capacitor C1. So T1 and C1 stop working at this stage and no current flows. When the electric energy on the capacitor C1 is released, Q2 will enter the off state again, the parasitic diode D2 will restart to work, T1 and C1 will restart to work again, and the next self-excitation and step-up driving cycle is repeated, and the capacitor C1 restarts to charge.
As can be seen from the above working process, when the photovoltaic cell sub-string is blocked, the voltages of the first connection end P1 and the second connection end P2 of the photovoltaic cell bypass circuit 100 are reversed, the parasitic diode of the field effect transistor Q2 starts, and the photovoltaic cell bypass circuit 100 starts working, so as to realize the diode bypass function and the reverse automatic bypass function. The photovoltaic cell bypass circuit 100 can directly replace bypass diodes in the prior art, avoiding hot spot effects. In addition, the photovoltaic cell bypass circuit 100 is intermittently conducted when in operation, and the voltage drop between the source electrode and the drain electrode of the field effect transistor Q2 is extremely low when in conduction, so that power is hardly consumed, and compared with the bypass diode in the prior art, the power consumption is greatly reduced, and the power generation efficiency of the photovoltaic module is improved.
The embodiment of the application realizes self-oscillation by using the transformer, the triode and the resistor; a diode and at least one capacitor are adopted as an energy storage unit; at least one field effect transistor is used as a bypass switch module. Self-oscillation and boost driving of 0.3-0.7V low voltage of the parasitic diode in the field effect transistor are realized. And a complex chip or a digital circuit such as a digital amplifier, a comparator, a charge pump and the like is not needed, so that the circuit structure is simplified, and the cost is greatly reduced.
In one possible real-time mode, the bypass switch module 10 employs a fet, and the turn-on voltage of the transistor Q1 is lower than the turn-on voltage of the fet Q2. Normally, the on voltage of the fet Q2 is about 0.6V. Optionally, the triode Q1 comprises a germanium triode, and the conducting voltage is about 0.2-V-0.3V. The embodiment of the application has ingenious conception, and the bypass switch module 10 can realize the function of a photovoltaic cell bypass circuit by adopting at least one field effect transistor by adopting the triode Q1 with lower conducting voltage, thereby further reducing the starting voltage and the power consumption of the bypass circuit. The technical prejudice that the bypass circuit function of the photovoltaic cell cannot be realized by using the minimum devices due to the silicon-based triode commonly adopted in the traditional circuit design is overcome, and unexpected technical effects are obtained.
Referring to fig. 5, in an alternative embodiment of the present application, the photovoltaic cell bypass circuit 100 further includes a microcontroller 30 (MCU) coupled to the bypass switch module 10. The microcontroller 30 is connected to the control terminal 103 of the bypass switch module 10. The microcontroller 30 is used for controlling the conduction of the bypass switch module 30. Referring to fig. 2 to 4, the gate of the field effect transistor Q2 is connected to the control terminal 103. Microcontroller 30 outputs a control signal to field effect transistor Q2 via control terminal 103. When the voltage of the control signal is greater than the on voltage of the field effect transistor Q2, the field effect transistor Q2 is turned on.
When the photovoltaic cell bypass circuit 100 works normally, if the photovoltaic cell substring or the photovoltaic module needs to be actively turned off or the active bypass function is realized, the microcontroller 30 sends a conducting signal to the control end 103 of the bypass switch module 10 to control the bypass switch module 10 to conduct. At this time, the photovoltaic cell sub-string or the photovoltaic module connected in parallel with the photovoltaic cell bypass circuit 100 is bypassed, thereby realizing an active shutdown function. The situation that the photovoltaic cell sub-string or the photovoltaic module needs to be actively closed includes that when a fire disaster occurs or the potential safety hazard exists in the photovoltaic power station, for example, when an arc is detected, the photovoltaic cell sub-string or the photovoltaic module needs to be closed from the root.
The bypass diode in the prior art does not have an active bypass function and cannot actively close a photovoltaic cell substring or a photovoltaic module. The situation that the potential safety hazard occurs can not be dealt with, and the security is poor. By adopting the microcontroller 30 to actively send a control signal to the bypass switch module 10, the photovoltaic cell substring or the photovoltaic module is further actively turned off, and the safety performance is improved.
Alternatively, the parasitic diode D2 in the bypass switch module 10 may be replaced by a common diode to create an operating voltage drop between the source and drain of the field effect transistor. The field effect transistor does not include a parasitic diode, and the field effect transistor is, for example, a gallium nitride field effect transistor.
Optionally, a transformer is used instead of the transformer to achieve self-oscillation.
In a second aspect, embodiments of the present application provide a photovoltaic junction box 600, see fig. 6, comprising the photovoltaic cell bypass circuit 100 of any of the aspects described above.
In a third aspect, embodiments of the present application provide a photovoltaic module 700, see fig. 7, comprising the photovoltaic cell bypass circuit 100 of any of the aspects described above.
Optionally, the photovoltaic module 700 includes a plurality of cell sub-strings connected in series with each other, at least one cell sub-string being connected in parallel with the photovoltaic cell bypass circuit 100. Optionally, the cell substring is a photovoltaic cell stack. By way of example, fig. 7 shows a photovoltaic module 700 comprising three sub-strings of photovoltaic cells, each sub-string of photovoltaic cells being connected in parallel with a photovoltaic cell bypass circuit 100.Vout1 and Vout2 are two output voltage terminals of the photovoltaic module 700.
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.
Claims (9)
1. The photovoltaic cell bypass circuit is characterized by comprising a first connecting end and a second connecting end, wherein the first connecting end and the second connecting end are used for connecting the photovoltaic cell bypass circuit and at least one cell sub-string of a photovoltaic cell in parallel; the photovoltaic cell bypass circuit further comprises an oscillation driving module and a bypass switch module;
the oscillation driving module is used for controlling the bypass switch module to be intermittently conducted;
the bypass switch module is used for bypassing the at least one battery sub-string and is intermittently conducted under the control of the oscillation driving module so as to reduce power consumption;
the oscillation driving module comprises a self-oscillation unit and an energy storage unit;
the self-oscillation unit is used for generating an oscillation signal in a self-oscillation mode and charging the energy storage unit;
the energy storage unit is connected with the bypass switch module and is used for outputting control voltage to the bypass switch module; controlling the bypass switch module to be conducted under the condition that the energy storage unit is charged to enable the control voltage to reach the conducting voltage of the bypass switch module; controlling the bypass switch module not to be conducted under the condition that the energy storage unit discharges to enable the control voltage not to reach the conducting voltage of the bypass switch module;
the self-oscillation unit comprises a transformer, a triode and a first resistor; the collector electrode of the triode is connected with the first connecting end through the primary side of the transformer, and the base electrode of the triode is connected with the first connecting end through the first resistor and the secondary side of the transformer in sequence; the emitter of the triode is connected with the second connecting end;
the energy storage unit comprises a first diode and a capacitor which are connected in series; the anode of the first diode is connected with the first connecting end through the primary side of the transformer; the cathode of the first diode is connected with the first end of the capacitor; the second end of the capacitor is connected with the second connecting end.
2. The photovoltaic cell bypass circuit of claim 1, wherein the primary side of the transformer comprises a primary side first end and a primary side second end; the secondary side of the transformer comprises a secondary side third end and a secondary side fourth end; the first end of the primary side is connected with the first connecting end, and the second end of the primary side is connected with the triode collector; the third end of the secondary side is connected with the first resistor, and the fourth end of the secondary side is connected with the first connecting end; the second end of the primary side and the fourth end of the secondary side are the same name ends.
3. The photovoltaic cell bypass circuit of claim 1, wherein the bypass switch module comprises at least one field effect transistor; the source electrode of the field effect tube is connected with the first connecting end, and the drain electrode of the field effect tube is connected with the second connecting end; and the grid electrode of the field effect transistor is connected with the first end of the capacitor.
4. The photovoltaic cell bypass circuit of claim 3, wherein the field effect transistor comprises: and the parasitic diode is used for forming an operating voltage drop between the source electrode and the drain electrode of the field effect transistor.
5. The photovoltaic cell bypass circuit of claim 1, wherein the bypass switch module comprises at least one field effect transistor; the conduction voltage of the triode is lower than the working voltage drop of the bypass switch module.
6. The photovoltaic cell bypass circuit according to any one of claims 1 to 5, further comprising a microcontroller connected to the bypass switch module, the microcontroller being configured to control whether the bypass switch module is on or off.
7. The photovoltaic cell bypass circuit of claim 6, wherein the bypass switch module comprises at least one field effect transistor; the microcontroller is connected with the grid electrode of the field effect tube.
8. A photovoltaic junction box comprising the photovoltaic cell bypass circuit of any one of claims 1-7.
9. A photovoltaic module comprising the photovoltaic cell bypass circuit of any one of claims 1-7.
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