CN113612393B - Power supply circuit, direct current power supply and photovoltaic system - Google Patents

Power supply circuit, direct current power supply and photovoltaic system Download PDF

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Publication number
CN113612393B
CN113612393B CN202111002516.6A CN202111002516A CN113612393B CN 113612393 B CN113612393 B CN 113612393B CN 202111002516 A CN202111002516 A CN 202111002516A CN 113612393 B CN113612393 B CN 113612393B
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circuit
voltage
power supply
bus
direct current
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CN113612393A (en
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李随军
胡方
张骕骦
王富
黄瑞
郭红强
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Sungrow Power Supply Co Ltd
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Sungrow Power Supply Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/34—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering
    • H02J7/35—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering with light sensitive cells
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • 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
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
    • 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
    • Y02E10/56—Power conversion systems, e.g. maximum power point trackers

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The invention provides a power supply circuit, a direct current power supply and a photovoltaic system, which are applied to the technical field of power electronics, wherein the power supply circuit comprises a voltage equalizing circuit and a power supply conversion circuit which are respectively connected with a direct current bus, the voltage equalizing circuit is provided with a voltage equalizing connection end, the power supply conversion circuit comprises a flyback transformer, a switching circuit, a clamping circuit and an output circuit, wherein a primary winding of the flyback transformer is connected with the switching circuit in series, and meanwhile, the primary winding of the flyback transformer is connected with a voltage equalizing connection end of the voltage equalizing circuit through the clamping circuit, and the output circuit is connected with a secondary winding of the flyback transformer.

Description

Power supply circuit, direct current power supply and photovoltaic system
Technical Field
The invention relates to the technical field of power electronics, in particular to a power supply circuit, a direct current power supply and a photovoltaic system.
Background
Referring to fig. 1, fig. 1 is a circuit topology diagram of a flyback power supply circuit commonly used in a photovoltaic system, the power supply circuit comprises switching tubes Q1 and Q2, clamping diodes D1 and D2, a flyback transformer, a corresponding output circuit and other components, and when the turn-off voltage of the switching tubes is greater than the bus voltage U of a direct current bus BUS At this time, the clamp diode D1 or the clamp diode D2 is in an on state, and accordingly, the off voltage of the switching tube Q1 or the switching tube Q2 is clamped to the bus voltage.
However, as the bus voltage in the photovoltaic system is higher and higher, the turn-off voltage born by each switching tube in the flyback power supply circuit of the dual switching tubes shown in fig. 1 is also increased, which makes the type selection of the switching tube difficult and affects the overall cost of the power supply circuit.
Disclosure of Invention
The invention provides a power supply circuit, a direct current power supply and a photovoltaic system, wherein a voltage equalizing circuit and a clamping circuit are arranged, so that the turn-off voltage born by a switching circuit in the power supply circuit can be clamped to the voltage equalizing voltage output by the voltage equalizing circuit, and the voltage equalizing voltage is smaller than the bus voltage, so that the requirement on the type selection of the switching circuit can be reduced, the overall cost of the power supply circuit is reduced, and the overall reliability is improved.
In order to achieve the above purpose, the technical scheme provided by the invention is as follows:
in a first aspect, the present invention provides a power supply circuit comprising: the voltage equalizing circuit and the power supply converting circuit, wherein,
the voltage equalizing circuit and the power supply conversion circuit are respectively connected with a direct current bus;
the voltage equalizing circuit is provided with a voltage equalizing connecting end, and the voltage equalizing voltage of the voltage equalizing connecting end is lower than the bus voltage of the direct current bus;
the power supply conversion circuit comprises a flyback transformer, a switching circuit, a clamping circuit and an output circuit;
the primary winding of the flyback transformer is connected in series with the switching circuit;
the primary winding is connected with the voltage equalizing connecting end through the clamping circuit;
the output circuit is connected with a secondary winding of the flyback transformer.
Optionally, the voltage equalizing circuit comprises n+2 paths of voltage equalizing sub-circuits with equal capacitance, wherein N is the total number of primary windings of the flyback transformer in the power supply conversion circuit, and N is more than or equal to 1;
each voltage equalizing sub-circuit is connected in series to form a first series branch;
the first series branch is connected between a positive DC bus and a negative DC bus of the DC bus;
and the connection point of any two adjacent voltage equalizing sub-circuits is used as the voltage equalizing connection end.
Optionally, the voltage equalizing sub-circuit includes at least one voltage equalizing capacitor.
Optionally, the power conversion circuit includes at least one flyback transformer, n+1 switching circuits and 2N clamping circuits;
wherein N is the total number of primary windings of the flyback transformer in the power conversion circuit;
the switching circuits and the primary windings of the flyback transformers are sequentially connected in series to form a second series branch, and the switching circuits and the primary windings of the flyback transformers are arranged at intervals;
the second series branch is connected between a positive DC bus and a negative DC bus of the DC bus;
any one end of any primary winding is connected with one voltage equalizing connecting end through one clamping circuit.
Optionally, the voltage equalizing circuit comprises n+2 voltage equalizing sub-circuits connected in series, and a connection point of any two adjacent voltage equalizing sub-circuits is used as the voltage equalizing connection end;
one end, close to the positive DC bus, of an ith primary winding in the second series branch is connected with a voltage-sharing connecting end, close to the negative DC bus, corresponding to an (i+1) th voltage-sharing sub-circuit in the voltage-sharing circuit through one path of clamping circuit;
one end, close to the negative electrode direct current bus, of an ith primary winding in the second series branch is connected with a voltage-sharing connecting end, close to the positive electrode direct current bus, corresponding to an (i+1) th voltage-sharing sub-circuit in the voltage-sharing circuit through one path of clamping circuit;
wherein i is [1, N ], and the 1 st primary winding is the primary winding near the positive DC bus in the second series branch;
the 1 st voltage equalizing sub-circuit is a voltage equalizing sub-circuit which is close to the positive DC bus in the voltage equalizing circuit.
Optionally, the power conversion circuit includes at least one flyback transformer;
the flyback transformer comprises at least one primary winding and at least one secondary winding;
the turns ratio of any primary winding to any secondary winding is a preset ratio.
Optionally, the turns ratio of the flyback transformer is set based on the ratio of the bus voltage to the preset output voltage of the power supply circuit and the total number of primary windings and the total number of secondary windings connected in series in the power conversion circuit.
Optionally, the switching circuit includes at least one switching tube;
in the case of a plurality of switching tubes, the switching tubes are connected in series and parallel in a preset manner.
Optionally, the clamping circuit includes at least one of a controllable switching circuit and a unidirectional conducting circuit.
Optionally, the controllable switch circuit includes at least one of a relay, a contactor and a controllable switch tube;
the unidirectional conduction circuit includes a diode.
Optionally, the output circuit comprises a rectifier diode and a filter circuit, wherein,
the rectifier diode and the filter circuit are connected in series to form an output series branch;
the output serial branch is connected with a secondary winding of the flyback transformer;
the two ends of the filter circuit are used as the output ends of the output circuit.
Optionally, for any one of the power conversion circuits:
when the switch circuit is conducted, the primary winding of the flyback transformer stores energy, and the filter circuit of the output circuit provides energy for an electric load;
when the switch circuit is turned off, the flyback transformer releases energy, and the rectifier diode of the output circuit is turned on to provide energy for the electric load;
when the turn-off voltage of the switch circuit is larger than the voltage equalizing voltage, the clamping circuit is conducted, and the turn-off voltage of the switch circuit is clamped at the voltage equalizing voltage.
Optionally, each of the switch circuits adopts an isolated driving circuit, and timing sequences of driving signals of each of the isolated driving circuits are synchronous.
In a second aspect, the present invention provides a dc power supply comprising: at least one power supply circuit according to any one of the first aspects of the invention, wherein,
the input ends of the power supply circuits are sequentially connected in series to form a third series branch;
the third serial branch is connected with a direct current bus;
the output ends of the power supply circuits are connected in parallel.
Optionally, the turns ratio of the flyback transformer in the power supply circuit is determined based on the following parameters:
the ratio of the bus voltage of the direct current bus to the preset output voltage of the power supply circuit;
the total number of primary windings included in a power conversion circuit in the power circuit;
the total number of secondary windings in series included in the power conversion circuit in the power circuit;
the number of said power circuits in the dc power supply.
In a third aspect, the present invention provides a photovoltaic system comprising: a photovoltaic host system, a controller and a direct current power supply according to any one of the second aspects of the present invention, wherein,
the input end of the direct current power supply is connected with a direct current bus of the photovoltaic main system;
the output end of the direct current power supply is connected with an electric load of the photovoltaic main system;
the controller is connected with the direct current power supply and controls the direct current power supply to work.
The invention provides a power supply circuit, which comprises a voltage equalizing circuit and a power supply conversion circuit which are respectively connected with a direct current bus, wherein the voltage equalizing circuit is provided with a voltage equalizing connecting end, the power supply conversion circuit comprises a flyback transformer, a switching circuit, a clamping circuit and an output circuit, wherein a primary winding of the flyback transformer is connected with the switching circuit in series, meanwhile, the primary winding of the flyback transformer is connected with a voltage equalizing connecting end of the voltage equalizing circuit through the clamping circuit, and the output circuit is connected with a secondary winding of the flyback transformer.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are necessary for the description of the embodiments or the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention and that other drawings may be obtained from them without inventive effort for a person skilled in the art.
FIG. 1 is a circuit topology of a flyback power supply circuit of the prior art;
FIG. 2 is a block diagram of a power circuit according to an embodiment of the present invention;
FIG. 3 is a circuit topology of a power supply circuit according to an embodiment of the present invention;
FIG. 4 is a circuit topology of another power supply circuit provided by an embodiment of the present invention;
FIG. 5 is a circuit topology of yet another power supply circuit provided by an embodiment of the present invention;
fig. 6 is a block diagram of a dc power supply according to an embodiment of the present invention;
fig. 7 is a circuit topology diagram of a dc power supply according to an embodiment of the present invention;
fig. 8 is a circuit topology diagram of another dc power supply according to an embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present application will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all, of the embodiments of the present application. All other embodiments, which can be made by one of ordinary skill in the art based on the embodiments herein without making any inventive effort, are intended to be within the scope of the present application.
Referring to fig. 2, fig. 2 is a block diagram of a power supply circuit according to an embodiment of the present invention, where the power supply circuit includes a voltage equalizing circuit and a power conversion circuit,
the voltage equalizing circuit and the power supply conversion circuit are respectively connected with the direct current bus, and specifically, the direct current bus comprises an anode direct current bus and a cathode direct current bus, the anode connecting end of the voltage equalizing circuit and the anode connecting end of the power supply conversion circuit are respectively connected with the anode direct current bus, and the cathode connecting end of the voltage equalizing circuit and the cathode connecting end of the power supply conversion circuit are respectively connected with the cathode direct current bus. In practical applications, the positive dc bus or the negative dc bus may be directly grounded.
Further, the voltage equalizing circuit is provided with voltage equalizing connection ends, and the total voltage born by the two ends of the voltage equalizing circuit, namely between the positive electrode connection end and the negative electrode connection end, is the bus voltage U of the direct current bus BUS Therefore, the voltage-sharing voltage output by the voltage-sharing connection end in the voltage-sharing circuit is necessarily lower than the bus voltage of the direct current bus.
As shown in fig. 2, the power conversion circuit in this embodiment includes a flyback transformer, a switching circuit, a clamping circuit, and an output circuit. It should be noted that, in the power supply circuit provided in the present application, the flyback transformer, the switching circuit, the clamping circuit, and the output circuit are basic modules forming the power conversion circuit, and the number of the four basic modules may be different according to the different capacities of the power supply circuit, but the connection manner between the modules is similar to that shown in fig. 2. Of course, the power conversion circuit configuration shown in fig. 2 is only an alternative implementation, and for other implementations will be developed in the subsequent embodiments.
In this embodiment, the primary winding of the flyback transformer is connected in series with the switching circuit, specifically, the switching circuit includes two switching tubes, namely, a switching tube Q1 and a switching tube Q2, one connection end of the switching tube Q1 is used as an anode connection end of the power conversion circuit and is connected with an anode direct current bus, the other connection end of the switching tube Q1 is connected with one end of the primary winding of the flyback transformer, and the other end of the primary winding of the flyback transformer is connected with a cathode direct current bus through the switching tube Q2.
Meanwhile, the primary winding of the flyback transformer is also connected with the voltage equalizing connecting end through a clamping circuit. Optionally, the clamping circuit comprises a controllable switching circuit and a unidirectional conduction circuit, which in the embodiment shown in fig. 2 is implemented based on a diode D1 and a diode D2. When the clamping circuit is realized based on the controllable switching circuit, the controllable switching circuit can be realized by at least one of a relay, a contactor and a controllable switching tube.
The secondary winding of the flyback transformer is connected with an output circuit, the output end of the output circuit is connected with an electric load (not shown in the figure), and the output circuit is mainly used for converting the output voltage of the power supply conversion circuit into a preset output voltage corresponding to the power supply circuit and supplying the preset output voltage to the electric load connected with the subsequent stage.
In practical application, no matter what mode the clamping circuit is specifically realized, the clamping circuit is in a conducting state under the condition that the turn-off voltage of the switching circuit is larger than the voltage-sharing voltage output by the voltage-sharing connecting end of the voltage-sharing circuit, so that the voltage clamp born by the switching circuit in the power supply conversion circuit is positioned at the voltage-sharing voltage.
In summary, in the power supply circuit provided by the embodiment of the invention, the voltage-sharing circuit and the power supply conversion circuit are provided, the voltage-sharing voltage output by the voltage-sharing circuit is smaller than the bus voltage of the direct current bus, and the clamping circuit in the power supply conversion circuit is in a conducting state and is communicated with the voltage-sharing circuit and the switching circuit in the power supply conversion circuit when the switching circuit in the power supply conversion circuit is in a switching-on state under the condition that the switching-off voltage is larger than the voltage-sharing voltage, so that the switching-off voltage born by the switching circuit can be clamped to the voltage-sharing voltage output by the voltage-sharing circuit. Furthermore, the switching loss of the circuit is reduced, and the efficiency of the power circuit is improved.
Optionally, referring to fig. 3, fig. 3 is a circuit topology diagram of a power supply circuit according to an embodiment of the present invention, and this embodiment further provides an alternative implementation manner of the voltage equalizing circuit and the output circuit based on the embodiment shown in fig. 2.
The voltage-sharing circuit comprises 3 paths of voltage-sharing sub-circuits with equal capacitance values, and optionally, any path of voltage-sharing sub-circuit comprises at least one voltage-sharing capacitor, in this embodiment, the voltage-sharing sub-circuits are all shown by one voltage-sharing capacitor, in practical application, the voltage-sharing sub-circuits can be realized by adopting a mode of combining a plurality of capacitors, so long as the capacitance values of all the voltage-sharing sub-circuits can be ensured to be equal, and the voltage-sharing sub-circuits also belong to the protection scope of the invention on the premise of not exceeding the core idea scope of the invention.
Further, the voltage equalizing sub-circuits are connected in series to form a first series branch connected between the positive dc bus and the negative dc bus, and it is conceivable that the voltages borne by the two ends of the voltage equalizing sub-circuits are equal due to the equal capacitance values of the voltage equalizing sub-circuits. Taking fig. 3 as an example, the voltage is 1/3 of the bus voltage, the connection point of any two adjacent voltage-sharing subcircuits is the voltage-sharing connection end described in the foregoing, and the voltage-sharing voltage output by the voltage-sharing connection end is 2/3 of the bus voltage.
Based on the above, the voltage equalizing connection end between the capacitor C1 and the capacitor C2 is connected with the cathode of the clamping diode D2, and the anode of the clamping diode D2 is connected with one end of the primary winding of the flyback transformer; correspondingly, the voltage equalizing connection end between the capacitor C2 and the capacitor C3 is connected with the anode of the clamping diode D1, and the cathode of the clamping diode D1 is connected with the other end of the primary winding of the flyback transformer, as shown in fig. 3, and the flyback transformer in this embodiment includes a primary winding and a secondary winding in total.
The output circuit comprises a rectifying diode Df and a filter circuit (shown as a filter capacitor Cb in this embodiment), wherein the rectifying diode Df is connected in series with the filter circuit Cb to form an output series branch, and the resulting output series branch is connected to the secondary winding of the flyback transformer. Specifically, the anode of the rectifying diode Df is connected to one end of the secondary winding, and the cathode of the rectifying diode Df is connected to the other end of the secondary winding through a filter circuit, and at the same time, two ends of the filter circuit, namely two ends of the filter capacitor Cb in this embodiment, are used as output ends of the output circuit and are connected to the electric load of the subsequent stage. It should be noted that other forms of filter circuit in the prior art are also optional, and the specific configuration of the filter circuit is not limited in the present invention. Moreover, in the case of flyback converters of other configurations, the connection of the secondary winding to the output circuit will vary, as will be seen in the following, only one of the alternative connections being shown.
Optionally, in the power supply circuit provided in this embodiment, the turns ratio of the flyback transformer may be reasonably set based on the ratio of the bus voltage of the dc bus to the preset output voltage of the power supply circuit and the total number of primary windings and serially connected secondary windings in the power supply conversion circuit.
Based on the connection relation, when the switching tubes Q1 and Q2 in the power conversion circuit are conducted, the primary winding of the flyback transformer stores energy, the rectifying diode Df is cut off, and meanwhile, the filter capacitor Cb supplies energy to the power utilization load; correspondingly, when the switching tubes Q1 and Q2 are turned off, the flyback transformer releases energy, the rectifying diode Df is turned on to output energy, and meanwhile, when the turn-off voltage of the switching tubes Q1 and Q2 is larger than that of the switching tubes
Figure BDA0003236083010000081
At this time, the clamp diodes D1 and D2 are turned on to clamp the off voltage of the switching transistor to +.>
Figure BDA0003236083010000082
The purpose of reducing the turn-off voltage of the switching tube is achieved. For example, when the bus voltage is 1500V, if a conventional double-tube flyback circuit is employed, the maximum off voltage of the switching tube can only be clamped to 1500V, but with the power supply circuit shown in fig. 3, the off voltages of the switching tubes Q1 and Q2 can be clamped to 1000V.
In addition, in the present embodiment, the turn-off voltage of the switching transistors Q1 and Q2 can be reduced to 1000V or less by further reasonably adjusting the turn ratio of the flyback transformer.
In summary, compared with the prior art, the power supply circuit provided by the embodiment increases 2 voltage-sharing capacitors on the basis of the original dual-switch flyback circuit, and can clamp the maximum turn-off voltage of each switch circuit to 2/3 bus voltage, in addition, the turn-off voltage of the switch circuit can be reduced below 2/3 bus voltage by further reasonably adjusting the turn ratio of the flyback transformer, the turn-off voltage of the switch device can be greatly reduced under the condition of increasing a small number of devices, the switching loss is reduced, the device selection is facilitated, and the reliability of the circuit is improved while the circuit cost is reduced.
Further, referring to fig. 4, fig. 4 is a circuit topology diagram of another power supply circuit provided in the embodiment of the present invention, in which, based on the embodiment shown in fig. 3, a flyback transformer in a power supply conversion circuit includes two primary windings in total, namely, primary windings Np1 and Np2, and the primary windings Np1 and Np2 share a secondary winding Ns; also included are 3 switching circuits, namely Q1, Q2 and Q3. The switch circuits and the primary windings are sequentially connected in series to form a second series branch, the switch circuits and the primary windings of the flyback transformer are arranged at intervals, and the second series branch is connected between the positive DC bus and the negative DC bus.
Meanwhile, the clamping circuit in the power conversion circuit comprises four clamping diodes, namely D1-D4. The voltage equalizing circuit comprises four voltage equalizing capacitors C1-C4, each of which is connected in series as described above, the resulting series branch being connected between the positive and the negative dc bus. As for the connection between the clamping circuit and the voltage equalizing circuit, this can be achieved in connection with the embodiment shown in fig. 4 and described above with reference to fig. 3, which is not developed here.
In practical application, when the switching circuits Q1-Q3 in the power conversion circuit are turned on, the primary winding of the flyback transformer stores energy, the rectifier diode Df in the output circuit is turned off, and the filter capacitor Cb supplies energy to the power load; correspondingly, when the switching circuits Q1-Q3 are turned off, the flyback transformer releases energy, and the rectifying diode Df is turned on to output stored energy.
Compared with the embodiment shown in fig. 3, the flyback transformer of the power supply circuit provided by the embodiment adopts two primary windings, simultaneously sets three switching circuits, totally sets four voltage-sharing capacitors of C1-C4, correspondingly sets four clamping diodes, and can clamp the maximum turn-off voltage of each switching circuit to 1/2 busbar voltage through the voltage-sharing capacitors and the clamping diodes. On the basis of the 2/3 bus voltage of the embodiment shown in fig. 3, the maximum turn-off voltage of each switch circuit is further reduced to 1/2 bus voltage, the turn-off voltage of a switch device is further reduced, the switching loss is reduced, the device selection is facilitated, the circuit cost is reduced, and meanwhile, the reliability of the circuit is improved.
It should be emphasized that, as can be seen from the embodiment shown in fig. 3 and the embodiment shown in fig. 4, the number of the voltage equalizing sub-circuits in the voltage equalizing circuit and the number of the switch circuits and the clamp circuits in the power converting circuit have direct corresponding relation with the total number of primary windings of the flyback transformer in the power converting circuit, and specifically, see table 1.
TABLE 1
Figure BDA0003236083010000091
With reference to table 1, in the case where the power conversion circuit includes N primary windings, the voltage equalizing circuit includes n+2 voltage equalizing sub-circuits having equal capacitance values, and the power conversion circuit includes n+1 switching circuits and 2N clamping circuits.
On a specific connection relation, each switch circuit and each primary winding in the power conversion circuit are sequentially connected in series to form a second series branch, the switch circuits and the primary windings of the flyback transformer are arranged at intervals, meanwhile, the second series branch is connected between the positive DC bus and the negative DC bus of the DC bus, any one end of any primary winding is connected with one voltage-equalizing connecting end through one clamping circuit, and the clamping circuits connected with the connecting ends of the primary windings are different from each other.
Further, the voltage equalizing circuit comprises n+2 voltage equalizing sub-circuits which are connected in series, and the connection point of any two adjacent voltage equalizing sub-circuits can be used as a voltage equalizing connection end. One end, close to the positive DC bus, of the ith primary winding in the second series branch is connected with a voltage-sharing connecting end, close to the negative DC bus, corresponding to the (i+1) th voltage-sharing sub-circuit in the voltage-sharing circuit; one end, close to the negative direct current bus, of the ith primary winding in the second series branch is connected with a voltage-sharing connection end, close to the positive direct current bus, corresponding to the (i+1) th voltage-sharing sub-circuit in the voltage-sharing circuit, wherein the ith primary winding is the primary winding, close to the positive direct current bus, in the second series branch, and the 1 st voltage-sharing sub-circuit is the voltage-sharing sub-circuit, close to the positive direct current bus, in the voltage-sharing circuit, and the specific connection mode can be seen from the embodiments shown in the foregoing fig. 3 and 4.
It should be noted that, in the embodiments shown in fig. 3 and fig. 4, the power conversion circuit includes only one flyback transformer, where the flyback transformer in the embodiment of fig. 3 includes one primary winding and one secondary winding in total, the flyback transformer in the embodiment of fig. 4 includes two primary windings and one secondary winding, for the flyback transformer provided in the embodiment of fig. 4, the turns ratio of any one primary winding to the secondary winding is a preset ratio, that is, the turns ratio of each primary winding to the secondary winding is equal, and for the flyback transformer including more than one primary winding and one secondary winding, the turns ratio setting should be set according to the requirements of the embodiment of fig. 4.
In this case, the secondary windings may be connected in series, or may be connected in parallel, with the difference that the number of windings of the secondary windings connected in parallel is calculated as 1, and the number of windings of the secondary windings connected in series is directly calculated as the actual number of secondary windings, that is, the number of series, when determining the off-voltage of each switching circuit.
Accordingly, in yet another embodiment, a power conversion circuit may include a plurality of flyback transformers, referring to fig. 5, and fig. 5 is a circuit topology diagram of another power circuit provided in an embodiment of the present invention, where the power conversion circuit includes two flyback transformers, i.e., T1 and T2, and the flyback transformer T1 includes a primary winding Np1 and a secondary winding Ns1, and the flyback transformer T2 includes a primary winding Np2 and a secondary winding Ns2. Each flyback transformer comprises a primary winding, and each primary winding is connected in series with a switching circuit in the power conversion circuit. The connection manner of the other components may be implemented with reference to the embodiment shown in fig. 4, and will not be described herein.
It is emphasized that in some cases the implementation shown in the previous embodiments may be combined with the implementation shown in fig. 5. For example, the power conversion circuit includes 2 flyback transformers, each flyback transformer may include 2 primary windings and 1 secondary winding, or each flyback transformer may include 2 primary windings and 2 secondary windings, which are also possible in combination, and are also within the scope of the present invention without exceeding the scope of the core concept of the present invention.
Referring to the foregoing, for the embodiment shown in fig. 5, the voltage equalizing circuit includes 4 voltage equalizing capacitors, four clamping diodes are correspondingly arranged, the maximum turn-off voltage of each switching circuit can be clamped to 1/2 bus voltage through the voltage equalizing capacitors and the clamping diodes, on the basis, the maximum turn-off voltage of each switching circuit can be further reduced on the basis of 1/2 bus voltage through reasonably selecting the turns ratio of the transformer, the switching loss is reduced, the device selection is facilitated, and the reliability of the circuit is improved while the circuit cost is reduced.
It can be seen from the power supply circuit provided by the above embodiments that, for a power supply circuit including N primary windings, the voltage-equalizing voltage output by the voltage-equalizing connection terminal is
Figure BDA0003236083010000111
When the turn-off voltage of the switch circuit is greater than +.>
Figure BDA0003236083010000112
At the time, the clamp circuitOn, clamping the off-voltage of the switching circuit +.>
Figure BDA0003236083010000113
The purpose of reducing the turn-off voltage of the switch circuit is achieved. In addition, by further rationally adjusting the turns ratio of the flyback transformer, the turn-off voltage of the switching circuit can also be reduced to +.>
Figure BDA0003236083010000114
The following is given.
Further, based on the comparison between the embodiment shown in fig. 4 and the embodiment shown in fig. 3, and the comparison between the embodiment shown in fig. 5 and the embodiment shown in fig. 3, it can be seen that, in the case of using the same voltage equalizing circuit, the turn-off voltage of each switch circuit in the power supply circuit and the number of primary windings of the flyback transformer in the power supply circuit have a negative correlation, that is, as N increases, the turn-off voltage of the switch circuit further decreases. Of course, as N increases, the setting and connection of the flyback transformer in the power supply circuit will become more complex correspondingly, so in practical application, the specific value of N should be determined in combination with the actual requirement.
Optionally, for the power supply circuit provided in any one of the foregoing embodiments, the power supply circuit further includes at least one path of isolation driving circuit, where any path of isolation driving circuit is connected to a control end of at least one switching tube in the power supply conversion circuit, and the switching tubes connected to each isolation driving circuit are different from each other, and each isolation driving circuit synchronously outputs a driving signal to control a conducting state of a corresponding switching tube.
In practical application, the isolation type driving circuit can be realized based on any one of an integrated isolation chip, an optical coupling isolation circuit and an isolation circuit realized based on a transformer, and the specific selection of the driving circuit is not limited.
Optionally, the present invention further provides a dc power supply, which includes at least one power circuit provided in any one of the above embodiments, wherein,
the input ends of the power supply circuits are sequentially connected in series to form a third series branch;
the third serial branch is connected with the direct current bus;
the output ends of the power supply circuits are connected in parallel.
For the case where the direct current power supply includes one power supply circuit, no specific illustration will be given. For the case of including multiple power circuits, as shown in fig. 6, the input ends of the power circuits are sequentially connected in series to form a third serial branch, and the obtained third serial branch is connected between the positive dc bus and the negative dc bus, and the output ends of the power circuits are connected in parallel and commonly connected to the electric load.
It is emphasized that the turns ratio of the flyback transformer in the power supply circuit is determined based on the following parameters: the ratio of the bus voltage of the direct current bus to the preset output voltage of the power supply circuit, the total number of primary windings included in the power supply conversion circuit in the power supply circuit, the total number of secondary windings connected in series included in the power supply conversion circuit in the power supply circuit, and the number of power supply circuits in the direct current power supply.
Fig. 7 and fig. 8 are specific connection cases of the dc power supply implemented based on the power supply circuit provided in the foregoing embodiments, where M is the number of power supply circuits included in the dc power supply. For the specific connection relationships of the embodiments shown in fig. 7 and fig. 8, reference may be made to the foregoing embodiments, and details are not repeated here.
In the embodiment shown in fig. 7, each power circuit has the same topology, the voltage equalizing circuit comprises 3 capacitors C1-M, C2-M and C3-M with equal capacitance, the capacitors are connected in series, 2 switching tubes Q1-M and Q2-M are connected in series with the primary winding of the flyback transformer, and the driving of the 2 switching tubes is synchronous.
Based on the above, it can be seen that the maximum off voltage of 2M switching tubes can be clamped to by the voltage equalizing circuit and the clamping circuit
Figure BDA0003236083010000131
Further, the maximum turn-off voltage of the 2M switching tubes can be smaller than +.>
Figure BDA0003236083010000132
Correspondingly, in the embodiment shown in fig. 8, in each power supply circuit, the voltage equalizing circuit comprises 4 capacitors C1-M, C2-M, C-M and C4-M with equal capacitance, and three switching tubes Q1-M, Q2-M and Q3-M are connected in series with two primary windings of a flyback transformer, and the driving of the three switching tubes is synchronized.
Based on the above, it can be seen that the maximum turn-off voltage of 3M switching tubes can be clamped to by the voltage equalizing circuit and the clamping circuit
Figure BDA0003236083010000133
Furthermore, the maximum turn-off voltage of the 3M switching tubes can be smaller than +.>
Figure BDA0003236083010000134
As can be seen from the embodiment shown in fig. 7 and 8, in the case that the dc power supply includes a plurality of power supply circuits, one filter circuit may be shared between the output circuits in the power conversion circuits of the power supply circuits, so that the number of filter circuits is reduced, and the overall cost of the dc power supply is further reduced.
Further, when a plurality of identical power supply circuits constitute a dc power supply, the off-voltage of the switching circuit in the dc power supply is also reduced relative to the off-voltage of the switching circuit in the single power supply circuit, and the input voltage range of the dc power supply can be widened as compared with the dc power supply employing the single power supply circuit, thereby being applied to a higher-voltage power supply system.
Optionally, an embodiment of the present invention further provides a photovoltaic system, including: the photovoltaic host system, the controller, and the dc power supply provided by any of the above embodiments, wherein,
the input end of the direct current power supply is connected with a direct current bus of the photovoltaic main system;
the output end of the direct current power supply is connected with an electric load of the photovoltaic main system;
the controller is connected with the direct current power supply and controls the direct current power supply to work.
In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant points refer to the description of the method section.
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 steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. The software modules may be disposed in Random Access Memory (RAM), memory, read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.
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. A power supply circuit, comprising: the voltage equalizing circuit and the power supply converting circuit, wherein,
the voltage equalizing circuit and the power supply conversion circuit are respectively connected with a direct current bus;
the voltage equalizing circuit is provided with a voltage equalizing connecting end, and the voltage equalizing voltage of the voltage equalizing connecting end is lower than the bus voltage of the direct current bus;
the power supply conversion circuit comprises a flyback transformer, a switching circuit, a clamping circuit and an output circuit;
the primary winding of the flyback transformer is connected in series with the switching circuit;
the primary winding is connected with the voltage equalizing connecting end through the clamping circuit;
the output circuit is connected with a secondary winding of the flyback transformer;
the voltage equalizing circuit comprises voltage equalizing sub-circuits with the same N+2 paths of capacitance values, wherein N is the total number of primary windings of the flyback transformer in the power supply conversion circuit, and N is more than 1;
each voltage equalizing sub-circuit is connected in series to form a first series branch;
the first series branch is connected between a positive DC bus and a negative DC bus of the DC bus;
the connection point of any two adjacent voltage equalizing sub-circuits is used as the voltage equalizing connection end;
the voltage equalizing sub-circuit comprises at least one voltage equalizing capacitor.
2. The power supply circuit of claim 1, wherein said power conversion circuit comprises at least one of said flyback transformer, n+1 of said switching circuits, and 2N of said clamping circuits;
wherein N is the total number of primary windings of the flyback transformer in the power conversion circuit;
the switching circuits and the primary windings of the flyback transformers are sequentially connected in series to form a second series branch, and the switching circuits and the primary windings of the flyback transformers are arranged at intervals;
the second series branch is connected between a positive DC bus and a negative DC bus of the DC bus;
any one end of any primary winding is connected with one voltage equalizing connecting end through one clamping circuit.
3. The power supply circuit according to claim 2, wherein the voltage equalizing circuit includes n+2 voltage equalizing sub-circuits connected in series, and a connection point of any adjacent two voltage equalizing sub-circuits serves as the voltage equalizing connection terminal;
one end, close to the positive DC bus, of an ith primary winding in the second series branch is connected with a voltage-sharing connecting end, close to the negative DC bus, corresponding to an (i+1) th voltage-sharing sub-circuit in the voltage-sharing circuit through one path of clamping circuit;
one end, close to the negative electrode direct current bus, of an ith primary winding in the second series branch is connected with a voltage-sharing connecting end, close to the positive electrode direct current bus, corresponding to an (i+1) th voltage-sharing sub-circuit in the voltage-sharing circuit through one path of clamping circuit;
wherein i is [1, N ], and the 1 st primary winding is the primary winding near the positive DC bus in the second series branch;
the 1 st voltage equalizing sub-circuit is a voltage equalizing sub-circuit which is close to the positive DC bus in the voltage equalizing circuit.
4. The power supply circuit of claim 1, wherein the power conversion circuit comprises at least one of the flyback transformers;
the flyback transformer comprises at least one primary winding and at least one secondary winding;
the turns ratio of any primary winding to any secondary winding is a preset ratio.
5. The power circuit of claim 1, wherein the turn ratio of the flyback transformer is set based on a ratio of the bus voltage to a preset output voltage of the power circuit and a total number of primary windings and a total number of secondary windings in series in the power conversion circuit.
6. The power supply circuit of claim 1, wherein the switching circuit comprises at least one switching tube;
in the case of a plurality of switching tubes, the switching tubes are connected in series and parallel in a preset manner.
7. The power supply circuit of claim 1, wherein the clamp circuit comprises at least one of a controllable switch circuit and a unidirectional conductive circuit.
8. The power supply circuit of claim 7, wherein the controllable switching circuit comprises at least one of a relay, a contactor, and a controllable switching tube;
the unidirectional conduction circuit includes a diode.
9. The power supply circuit of claim 1, wherein the output circuit comprises a rectifier diode and a filter circuit, wherein,
the rectifier diode and the filter circuit are connected in series to form an output series branch;
the output serial branch is connected with a secondary winding of the flyback transformer;
the two ends of the filter circuit are used as the output ends of the output circuit.
10. The power supply circuit of claim 9, wherein for any one of the power conversion circuits:
when the switch circuit is conducted, the primary winding of the flyback transformer stores energy, and the filter circuit of the output circuit provides energy for an electric load;
when the switch circuit is turned off, the flyback transformer releases energy, and the rectifier diode of the output circuit is turned on to provide energy for the electric load;
when the turn-off voltage of the switch circuit is larger than the voltage equalizing voltage, the clamping circuit is conducted, and the turn-off voltage of the switch circuit is clamped at the voltage equalizing voltage.
11. The power supply circuit according to any one of claims 1 to 10, wherein each of the switch circuits employs an isolated drive circuit, and timing of drive signals of each of the isolated drive circuits is synchronized.
12. A direct current power supply, comprising: at least one power supply circuit according to any one of claims 1 to 11, wherein,
the input ends of the power supply circuits are sequentially connected in series to form a third series branch;
the third serial branch is connected with a direct current bus;
the output ends of the power supply circuits are connected in parallel.
13. The direct current power supply of claim 12, wherein the turns ratio of the flyback transformer in the power supply circuit is determined based on the following parameters:
the ratio of the bus voltage of the direct current bus to the preset output voltage of the power supply circuit;
the total number of primary windings included in a power conversion circuit in the power circuit;
the total number of secondary windings in series included in the power conversion circuit in the power circuit;
the number of said power circuits in the dc power supply.
14. A photovoltaic system, comprising: the photovoltaic host system, the controller and the direct current power supply of any one of claims 12-13, wherein,
the input end of the direct current power supply is connected with a direct current bus of the photovoltaic main system;
the output end of the direct current power supply is connected with an electric load of the photovoltaic main system;
the controller is connected with the direct current power supply and controls the direct current power supply to work.
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