CN116207788A - Bus control method of photovoltaic energy storage system - Google Patents
Bus control method of photovoltaic energy storage system Download PDFInfo
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- CN116207788A CN116207788A CN202310479223.XA CN202310479223A CN116207788A CN 116207788 A CN116207788 A CN 116207788A CN 202310479223 A CN202310479223 A CN 202310479223A CN 116207788 A CN116207788 A CN 116207788A
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- 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
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/381—Dispersed generators
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- 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
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
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- 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
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
- H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
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- 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
- H02J7/0068—Battery or charger load switching, e.g. concurrent charging and load supply
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
- H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
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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
- H02M3/01—Resonant DC/DC converters
- H02M3/015—Resonant DC/DC converters with means for adaptation of resonance frequency, e.g. by modification of capacitance or inductance of resonance circuit
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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
- H02M3/33573—Full-bridge at primary side of an isolation transformer
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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
- H02M3/33576—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 having at least one active switching element at the secondary side of an isolation transformer
- H02M3/33584—Bidirectional converters
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- 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
- H02J2207/00—Indexing scheme relating to details of circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J2207/20—Charging or discharging characterised by the power electronics converter
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- 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
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/20—The dispersed energy generation being of renewable origin
- H02J2300/22—The renewable source being solar energy
- H02J2300/24—The renewable source being solar energy of photovoltaic origin
- H02J2300/26—The renewable source being solar energy of photovoltaic origin involving maximum power point tracking control for photovoltaic sources
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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
- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Direct Current Feeding And Distribution (AREA)
Abstract
The application discloses a bus control method of a photovoltaic energy storage system, which comprises the following steps: detecting MPPT voltage v corresponding to photovoltaic panel pv_mppt And bus voltage v bus The method comprises the steps of carrying out a first treatment on the surface of the When the battery is discharged, if v pv_mppt ＞v bus The full-bridge delay control of the bidirectional DC/DC unit is performed; otherwise, maintaining constant frequency f r Working; if v when the battery is charged pv_mppt ＞v bus The bidirectional DC/DC unit performs frequency modulation control; otherwise, maintaining constant frequency f r Work is performed.The beneficial effects of this application: the bus voltage of the photovoltaic energy storage system can be lifted by carrying out full-bridge delay control on the bidirectional DC/DC unit, so that the photovoltaic system can maintain maximum power for output, and further the working efficiency of the photovoltaic system is effectively improved.
Description
Technical Field
The application relates to the technical field of photovoltaic power generation, in particular to a bus control method of a photovoltaic energy storage system.
Background
As shown in fig. 1, a structure of a common dc bus is adopted for a photovoltaic energy storage system 100 commonly used in the prior art. The specific structure is as follows: photovoltaic panel 110 is connected to the bus via DC/DC unit 120, battery 130 is connected to the bus via bi-directional DC/DC unit 140, and grid 200 and load 300 are connected to the bus via DC/AC unit 150. As shown in fig. 2, in the prior art, the bidirectional DC/DC unit 140 at the connection side of the battery 130 usually adopts a single-stage LLC topology or a topology of LLC plus Buck/Boost, which makes the bus voltage of the system determined by the voltage of the battery 130, and does not consider the voltage of the photovoltaic panel 110, and further uses the voltage v of the MPPT corresponding to the photovoltaic panel 110 pv_mppt Higher than the bus voltage v bus When the photovoltaic panel 110 has to be de-rated, which results in the photovoltaic system not being able to perform maximum power output.
Disclosure of Invention
One of the purposes of the application is to provide a bus control method of a photovoltaic energy storage system, which can ensure that the photovoltaic system always outputs the maximum power.
In order to achieve the above purpose, the technical scheme adopted in the application is as follows: a bus control method of a photovoltaic energy storage system comprises the following specific steps of bus control by utilizing a bidirectional DC/DC unit with a single-stage LLC structure:
s100: detecting MPPT voltage v corresponding to photovoltaic panel pv_mppt And bus voltage v bus ；
S200: judging the working state of the battery, and if the battery discharges, performing step S300; if the battery is charged, go to step S400;
s300: if v pv_mppt ＞v bus Performing full-bridge delay control on the bidirectional DC/DC unit; otherwise the bidirectional DC/DC unit maintains constant frequency f r Working;
s400: if v pv_mppt ＞v bus Performing frequency modulation control on the bidirectional DC/DC unit; otherwise the bidirectional DC/DC unit maintains constant frequency f r Work is performed.
Preferably, the bidirectional DC/DC unit includes four semiconductor switching devices connected in a bridge manner through the secondary sides to form a full-bridge circuit, which pulses at a 50% duty cycle.
Preferably, in step S300, the secondary side driving of the bidirectional DC/DC unit is set to a delay of Φ time, so that the bidirectional DC/DC unit performs full-bridge delay control.
Preferably, the semiconductor switching devices of the two secondary sides of the bidirectional DC/DC unit may be defined as S1, S2, S3 and S4 and S5, S6, S7 and S8, respectively; wherein the driving of S1 and S4 are the same, the driving of S2 and S3 are the same, the driving of S5 and S8 are the same, and the driving of S6 and S7 are the same; when the bidirectional DC/DC unit performs full-bridge delay control, the driving of S7 and S8 is respectively the same as the driving of S3 and S4; and, the driving of S5 and S6 has a delay of Φ time compared with S1 and S2.
Preferably, the photovoltaic energy storage system is adapted to identify the current working state of the bus through the control loop system, and send corresponding driving signals to each semiconductor switching device of the bidirectional DC/DC unit according to the identification result, so as to realize different operation modes of the bidirectional DC/DC unit in steps S300 and S400.
Preferably, the control loop system comprises a comparison control module and a driving signal generation module; the comparison control module is suitable for identifying the current working state of the bus and sending different operation signals to the driving signal generating module according to the current working state of the bus, and then the driving signal generating module sends corresponding driving signals to each semiconductor switching device according to the received operation signals.
Preferably, when the comparison control module recognizes that the bidirectional DC/DC unit needs to perform constant frequency f r In operation, the comparison control module is adapted to output a constant frequency directly to the drive signal generation module, so that the drive signal generation module generates a corresponding drive signal.
Preferably, when the comparison control module recognizes that the bidirectional DC/DC unit needs to perform full-bridge delay operation, the comparison control module is suitable for sending a delay control signal with phi time to the driving signal generating module according to comparison between the bus voltage and the MPPT voltage corresponding to the photovoltaic panel, and then the driving signal generating module generates a corresponding driving signal according to the received delay control signal.
Preferably, when the comparison control module recognizes that the bidirectional DC/DC unit needs to perform frequency modulation operation, the comparison control module is adapted to send a frequency modulation control signal to the driving signal generating module according to comparison between the bus voltage and the MPPT voltage corresponding to the photovoltaic panel, so that the driving signal generating module generates a corresponding driving signal according to the received frequency modulation control signal.
Preferably, in step S200, the working state of the battery is adapted to be determined according to the power flow direction of the photovoltaic energy storage system; in steps S300 and S400, the constant frequency f r The resonance frequency is suitably used.
Compared with the prior art, the beneficial effect of this application lies in:
the application discloses a photovoltaic panel corresponding MPPT voltage v pv_mppt Higher than the bus voltage v bus And when the bidirectional DC/DC unit is in full-bridge delay control, the bus voltage of the photovoltaic energy storage system can be raised, so that the photovoltaic system can maintain maximum power for output, and the working efficiency of the photovoltaic system is effectively improved. In addition, the bus control direction disclosed by the application is simpler in implementation, and redundancy caused by complex circuits can be effectively avoided.
Drawings
Fig. 1 is a schematic circuit architecture diagram of a photovoltaic energy storage system in the prior art.
Fig. 2 is a schematic circuit diagram of a conventional bidirectional DC/DC unit.
Fig. 3 is a schematic diagram of the relationship between the bus voltage and the battery voltage in the prior art.
Fig. 4 is a logic control table of the bidirectional DC/DC unit in which the present invention operates.
Fig. 5 is a schematic diagram of a control flow of the bidirectional DC/DC unit when the battery is in a discharging state in the present invention.
Fig. 6 is a schematic diagram of a control flow of the bidirectional DC/DC unit when the battery is in a charged state in the present invention.
Fig. 7 is a schematic diagram of a control flow when the bidirectional DC/DC unit of the present invention is operated at constant frequency.
Fig. 8 is a schematic diagram of a control flow when the bidirectional DC/DC unit of the present invention is operated with full-bridge delay.
Fig. 9 is a schematic diagram of a control flow when the bidirectional DC/DC unit of the present invention adopts frequency modulation operation.
Fig. 10 is a schematic diagram showing the generation of driving signals when the bidirectional DC/DC unit of the invention is operated with full bridge delay.
In the figure: photovoltaic energy storage system 100, photovoltaic panel 110, DC/DC unit 120, battery 130, bi-directional DC/DC unit 140, DC/DA unit 150, grid 200, load 300.
Detailed Description
The present application will be further described with reference to the specific embodiments, and it should be noted that, on the premise of no conflict, new embodiments may be formed by any combination of the embodiments or technical features described below.
In the description of the present application, it should be noted that, for the azimuth terms such as terms "center", "lateral", "longitudinal", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., the azimuth and positional relationships are based on the azimuth or positional relationships shown in the drawings, it is merely for convenience of describing the present application and simplifying the description, and it is not to be construed as limiting the specific protection scope of the present application that the device or element referred to must have a specific azimuth configuration and operation, as indicated or implied.
It should be noted that the terms "first," "second," and the like in the description and in the claims of the present application are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order.
Fig. 2 is a schematic circuit diagram of a bidirectional DC/DC unit 140 commonly used in the conventional photovoltaic energy storage system 100. To simplify the control of the existing photovoltaic energy storage system 100, the bidirectional DC/DC unit 140 generally adopts a single-stage LLC structure, and circuits corresponding to the LLC structure are turned onThe loop controls and operates with a fixed switching frequency. For the bus of the existing photovoltaic energy storage system 100, the battery 130 is equivalent to a voltage source, and the bus voltage v of the photovoltaic energy storage system 100 bus Is determined by the output voltage of the battery 130.
As shown in fig. 3, the control method is adopted for the bidirectional DC/DC unit 140 in the conventional photovoltaic energy storage system 100, and the bus voltage v bus And the output side voltage of the battery 130. Since the bidirectional DC/DC unit 140 operates at constant frequency with constant gain, the battery 130 outputs a side voltage and a bus voltage v bus The ratio of (2) may be considered as a straight line.
The output side voltage of the battery 130 typically ranges from 43.6V to 60V, the bus voltage V bus Typically in the range of 400V to 550V. When the MPPT voltage v corresponding to the photovoltaic panel 110 pv_mppt To the left of this line, i.e., the MPPT voltage v corresponding to the photovoltaic panel 110 pv_mppt Less than the bus voltage v bus When the photovoltaic system is capable of performing maximum power output on the photovoltaic panel 110 through MPPT control, the DC/DC unit 120 located at the photovoltaic panel 110 side is operated in Boost mode. When the MPPT voltage v corresponding to the photovoltaic panel 110 pv_mppt On the right side of the straight line, i.e., in the diagonally shaded area of the figure, the MPPT voltage v corresponding to the photovoltaic panel 110 pv_mppt Greater than the bus voltage v bus Maximum power output of the photovoltaic system to the photovoltaic panel 110 through MPPT control is not achievable because the DC/DC unit 120 located at the side of the photovoltaic panel 110 generally operates as Boost, and cannot step down. Thus, the photovoltaic system has to operate de-rated for the output power of the photovoltaic panel 110, i.e. the MPPT function of the photovoltaic system cannot be guaranteed. It should be appreciated that the specific values of the voltages described above may vary from scene to scene, and are for illustration only.
To avoid derating the output power of the photovoltaic panel 110 by the photovoltaic system, to ensure that the photovoltaic system is always able to output at the maximum power of the photovoltaic panel 110. In one preferred embodiment of the present application, as shown in fig. 4 to 10, a bus control method of a photovoltaic energy storage system is provided, which specifically includes the following working steps:
s100: detecting MPPT voltage v corresponding to photovoltaic panel 110 pv_mppt And bus voltage v bus 。
S200: judging the working state of the battery 130, and if the battery 130 discharges, proceeding to step S300; if the battery 130 is charged, the process proceeds to step S400.
S300: if v pv_mppt ＞v bus The full-bridge delay control is performed on the bidirectional DC/DC unit 140; otherwise the bi-directional DC/DC unit 140 maintains a constant frequency f r Work is performed.
S400: if v pv_mppt ＞v bus The bi-directional DC/DC unit 140 is subjected to frequency modulation control; otherwise the bi-directional DC/DC unit 140 maintains a constant frequency f r Work is performed.
It can be appreciated that when the MPPT voltage v corresponding to the photovoltaic panel 110 pv_mppt Bus voltage v less than or equal to bus In this case, the photovoltaic system can perform maximum power output of the photovoltaic panel 110 through MPPT control. Then the photovoltaic energy storage system 100 does not need to perform the bus voltage v bus Thereby only ensuring that the bi-directional DC/DC unit 140 of the photovoltaic energy storage system 100 maintains a constant frequency f r And (5) working. In general, the bi-directional DC/DC unit 140 may employ a resonant frequency f s Operates at the most constant frequency, i.e. f r =f s The method comprises the steps of carrying out a first treatment on the surface of the Selecting the resonant frequency may effectively improve the control efficiency of the bidirectional DC/DC unit 140.
It should be noted that the resonant frequency f s Also referred to as the natural frequency of the circuit, the specific value may be determined by the own parameters of the capacitance and inductance employed in the bi-directional DC/DC unit 140.
While when the photovoltaic panel 110 corresponds to the MPPT voltage v pv_mppt Bus voltage v bus When the photovoltaic system cannot output the maximum power of the photovoltaic panel 110 through the MPPT control, the photovoltaic energy storage system 100 needs to output the bus voltage v bus Lifting is performed. Bus voltage v of on-going photovoltaic energy storage system 100 bus The specific manner of control of the bi-directional DC/DC unit 140 during lifting also depends on the operating state of the battery 130.
When the battery 130 is in chargeIn the state, the power of the photovoltaic energy storage system 100 can be transmitted from the bus to the battery 130, and the bidirectional DC/DC unit 140 can realize the bus voltage v by frequency modulation bus Is a lifting force of the lift. It should be noted that the essence of frequency modulation boosting is to use reactance (impedance, inductance, capacitance, etc.) to divide voltage, and since the magnitudes of inductance and capacitance are all functions of frequency f, as the frequency changes, the magnitudes of inductance and capacitance will follow the changes, the ac voltage division on the exciting inductance can be adjusted by the driving frequency, i.e. by adjusting the driving frequency, the bus voltage v can be made bus Is a lifting force of the lift. The specific tuning scheme is conventional in LLC structure and is well known to those skilled in the art and will not be described in detail herein.
When the battery 130 discharges, the power of the photovoltaic energy storage system 100 is transferred from the battery 130 to the bus, and the bidirectional DC/DC unit 140 can realize the bus voltage v by full-bridge delay control bus Is a lifting force of the lift.
It will be appreciated that when the battery 130 is being charged, the photovoltaic energy storage system 100 may not need to supply power to the load 300, or the photovoltaic panel 110 may still be able to meet the power demand of the load 300 with a derated power output, and output a portion of the excess electrical energy to the battery 130 for storage. Then the bus voltage v of the photovoltaic energy storage system 100 at this time bus Is not urgent or bus voltage v bus The lifting requirement is not high, and only a frequency modulation boosting mode corresponding to the traditional LLC structure is needed; of course, the bus voltage v can also be realized rapidly by a full-bridge delay control mode bus Is a lifting force of the lift.
It is further understood that in step S200, the operation state of the battery 130 may be determined by the flow direction of the power in the photovoltaic energy storage system 100.
In order to facilitate understanding of the full-bridge delay control of the bidirectional DC/DC unit 140, the specific structure of the bidirectional DC/DC unit 140 may be known first.
As shown in fig. 2, the bidirectional DC/DC unit 140 may form a full-bridge circuit by four semiconductor switching devices, each of which includes a bridge connection, and the full-bridge circuit pulses at a 50% duty ratio. Thus, when the full-bridge delay control is performed on the bidirectional DC/DC unit 140 in step S300, the delay setting of Φ time can be performed by driving the secondary sides on both sides of the bidirectional DC/DC unit 140.
Specifically, as shown in fig. 2, the semiconductor switching devices of the bidirectional DC/DC unit 140 connected in full-bridge fashion near the secondary side of the battery 130 are defined as S1, S2, S3, and S4, respectively, and the semiconductor switching devices of the bidirectional DC/DC unit 140 connected in full-bridge fashion near the secondary side of the bus are defined as S5, S6, S7, and S8, respectively. Wherein the driving of S1 and S4 are the same, the driving of S2 and S3 are the same, S1 and S2 are complementary, and S3 and S4 are complementary; s5 and S8 drive the same, S6 and S7 drive the same. When the bidirectional DC/DC unit 140 performs full-bridge delay control, unlike conventional secondary uncontrolled rectification or synchronous rectification, it is: the driving of S7 and S8 is the same as the driving of S3 and S4, respectively; and, the driving of S5 and S6 has a delay of Φ time compared with S1 and S2.
At this time, as shown in fig. 10, the two secondary sides of the bidirectional DC/DC unit 140 have the bus side secondary side bridge arm voltage v due to the existence of the delay stage bus_ac There are three levels, high, zero and low. Compared with the traditional mode, the bus voltage v is caused by the insertion of the zero level bus Lifting is achieved; and the larger the value of the delay time phi is, the greater the bus voltage v bus The higher the lift of (c).
In one embodiment of the present application, the bi-directional DC/DC unit 140 may be controlled by a control loop system for bus control. Specifically, the photovoltaic energy storage system 100 may identify the current working state of the bus through the control loop system, and send corresponding driving signals to each semiconductor switching device of the bidirectional DC/DC unit 140 according to the identification result, so as to implement different operation modes required by the bidirectional DC/DC unit 140 in steps S300 and S400.
In this embodiment, the control loop system includes a comparison control module and a driving signal generating module; the comparison control module can identify the current working state of the bus and send different operation signals to the driving signal generating module according to the current working state of the bus, and then the driving signal generating module sends corresponding driving signals to each semiconductor switching device according to the received operation signals.
It is understood that the comparison control module may first detect the power flow direction of the photovoltaic energy storage system 100. Then the busbar voltage v of the photovoltaic energy storage system 100 bus MPPT voltage v corresponding to photovoltaic panel 110 pv_mppt And (5) detecting. Then according to the bus voltage v bus MPPT voltage v corresponding to photovoltaic panel 110 pv_mppt The current operating state of the bus can be determined by combining the comparison results of the photovoltaic energy storage system 100 and the power flow direction. Finally, the operation mode required by the bidirectional DC/DC unit 140 is obtained according to the judging result.
Specifically, as shown in fig. 5, when the comparison control module recognizes that the power of the photovoltaic energy storage system 100 is transmitted from the battery 130 to the bus, and the bus voltage v bus MPPT voltage v corresponding to photovoltaic panel 110 pv_mppt When the comparison control module determines that the bidirectional DC/DC unit 140 needs to perform constant frequency operation.
Meanwhile, when the comparison control module recognizes that the power of the photovoltaic energy storage system 100 is transmitted from the battery 130 to the bus, and the bus voltage v bus < MPPT voltage v for photovoltaic panel 110 pv_mppt When the comparison control module determines that the bidirectional DC/DC unit 140 on the bus side needs to perform full-bridge delay operation.
As shown in fig. 6, when the comparison control module recognizes that power of the photovoltaic energy storage system 100 is transferred from the bus to the battery 130, and the bus voltage v bus MPPT voltage v corresponding to photovoltaic panel 110 pv_mppt When the comparison control module determines that the bidirectional DC/DC unit 140 needs to perform constant frequency operation.
Meanwhile, when the comparison control module recognizes that the power of the photovoltaic energy storage system 100 is transmitted from the bus to the battery 130, and the bus voltage v bus < MPPT voltage v for photovoltaic panel 110 pv_mppt When the comparison control module determines that the bidirectional DC/DC unit 140 needs to perform the frequency modulation operation.
In this embodiment, as shown in FIG. 7, when the comparison control module identifies the bidirectional DC/DC unit140 need to perform constant frequency f r In operation, the comparison control module can directly output constant frequency f to the driving signal generation module according to the resonant frequency r So that the driving signal generating module generates corresponding driving signals and sends the driving signals to the corresponding semiconductor switching devices respectively.
In this embodiment, as shown in fig. 8, when the comparison control module recognizes that the bidirectional DC/DC unit 140 needs to perform the full-bridge delay operation, the comparison control module may determine that the bus voltage v is equal to or higher than the threshold voltage v bus MPPT voltage v corresponding to photovoltaic panel 110 pv_mppt And sending a delayed control signal of phi time to the driving signal generating module, so that the driving signal generating module generates corresponding driving signals according to the received delayed control signals and sends the corresponding driving signals to the corresponding semiconductor switching devices respectively.
Specifically, as shown in fig. 8, the comparison control module includes a comparator and a controller. Command value v of bus voltage dc_ref Set to MPPT voltage v corresponding to photovoltaic panel 110 pv_mppt The comparator may command the bus voltage value v dc_ref And output voltage v of photovoltaic panel 110 dc And comparing, and then sending the comparison result to a controller by the comparator to obtain the delay time phi, and sending a delay control signal to the driving signal generating module by the controller according to the obtained delay time phi.
In this embodiment, as shown in fig. 9, when the comparison control module recognizes that the bidirectional DC/DC unit 140 needs to perform the frequency modulation operation, the comparison control module may determine that the bidirectional DC/DC unit is required to perform the frequency modulation operation according to the bus voltage v bus MPPT voltage v corresponding to photovoltaic panel 110 pv_mppt And sending the frequency modulation control signals to the driving signal generating module, and further generating corresponding driving signals according to the received frequency modulation control signals by the driving signal generating module and respectively sending the driving signals to the corresponding semiconductor switching devices.
Specifically, as shown in fig. 9, the comparison control module includes a comparator and a controller. Command value v of bus voltage dc_ref Set to MPPT voltage v corresponding to photovoltaic panel 110 pv_mppt The comparator may command the bus voltage value v dc_ref And output voltage v of photovoltaic panel 110 dc Comparison is performedThe comparator then sends the result of the comparison to the controller to obtain the switching frequency, i.e., the resonant frequency f s And the controller sends a frequency modulation control signal to the driving signal generating module according to the obtained switching frequency.
The foregoing has outlined the basic principles, main features and advantages of the present application. It will be appreciated by persons skilled in the art that the present application is not limited to the embodiments described above, and that the embodiments and descriptions described herein are merely illustrative of the principles of the present application, and that various changes and modifications may be made therein without departing from the spirit and scope of the application, which is defined by the appended claims. The scope of protection of the present application is defined by the appended claims and equivalents thereof.
Claims (10)
1. The bus control method of the photovoltaic energy storage system is characterized by comprising the following specific steps of performing bus control by utilizing a bidirectional DC/DC unit with a single-stage LLC structure:
s100: detecting MPPT voltage v corresponding to photovoltaic panel pv_mppt And bus voltage v bus ；
S200: judging the working state of the battery, and if the battery discharges, performing step S300; if the battery is charged, go to step S400;
s300: if v pv_mppt ＞v bus Performing full-bridge delay control on the bidirectional DC/DC unit; otherwise the bidirectional DC/DC unit maintains constant frequency f r Working;
s400: if v pv_mppt ＞v bus Performing frequency modulation control on the bidirectional DC/DC unit; otherwise the bidirectional DC/DC unit maintains constant frequency f r Work is performed.
2. The bus bar control method of a photovoltaic energy storage system of claim 1, wherein: the bi-directional DC/DC unit includes four semiconductor switching devices connected in a bridge manner through both sides to form a full-bridge circuit, which pulses at a 50% duty cycle.
3. The bus bar control method of a photovoltaic energy storage system of claim 2, wherein: in step S300, the secondary side driving of the bidirectional DC/DC unit is set to a delay of Φ time, so that the bidirectional DC/DC unit performs full-bridge delay control.
4. The bus bar control method of a photovoltaic energy storage system of claim 3, wherein: the semiconductor switching devices of the two secondary sides of the bidirectional DC/DC unit are respectively defined as S1, S2, S3 and S4, and S5, S6, S7 and S8; wherein the driving of S1 and S4 are the same, the driving of S2 and S3 are the same, the driving of S5 and S8 are the same, and the driving of S6 and S7 are the same; when the bidirectional DC/DC unit performs full-bridge delay control, the driving of S7 and S8 is respectively the same as the driving of S3 and S4; and, the driving of S5 and S6 has a delay of Φ time compared with S1 and S2.
5. The bus bar control method of a photovoltaic energy storage system of claim 3, wherein: the photovoltaic energy storage system is suitable for identifying the current working state of the bus through the control loop system, and sending corresponding driving signals to each semiconductor switching device of the bidirectional DC/DC unit according to the identification result, so that different operation modes of the bidirectional DC/DC unit in the steps S300 and S400 are realized.
6. The bus bar control method of a photovoltaic energy storage system of claim 5, wherein: the control loop system comprises a comparison control module and a driving signal generation module; the comparison control module is suitable for identifying the current working state of the bus and sending different operation signals to the driving signal generating module according to the current working state of the bus, and then the driving signal generating module sends corresponding driving signals to each semiconductor switching device according to the received operation signals.
7. The bus bar control method of a photovoltaic energy storage system of claim 6, wherein: when the comparison control module recognizes that the bidirectional DC/DC unit needs to perform constant frequency f r In operation, the comparison control module is adapted to output a constant frequency directly to the drive signal generation module,so that the driving signal generating module generates a corresponding driving signal.
8. The bus bar control method of a photovoltaic energy storage system of claim 6, wherein: when the comparison control module recognizes that the bidirectional DC/DC unit needs to perform full-bridge delay operation, the comparison control module is suitable for sending a delay control signal with phi time to the driving signal generating module according to comparison of bus voltage and MPPT voltage corresponding to the photovoltaic panel, and the driving signal generating module generates a corresponding driving signal according to the received delay control signal.
9. The bus bar control method of a photovoltaic energy storage system of claim 6, wherein: when the comparison control module recognizes that the bidirectional DC/DC unit needs to perform frequency modulation operation, the comparison control module is suitable for sending a frequency modulation control signal to the driving signal generation module according to comparison of bus voltage and MPPT voltage corresponding to the photovoltaic panel, and the driving signal generation module generates a corresponding driving signal according to the received frequency modulation control signal.
10. The bus bar control method of a photovoltaic energy storage system of any of claims 1-9, wherein: in step S200, the working state of the battery is adapted to be determined according to the power flow direction of the photovoltaic energy storage system; in steps S300 and S400, the constant frequency f r The resonance frequency is suitably used.
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