CN112751357A - Photovoltaic energy storage system and control method thereof - Google Patents
Photovoltaic energy storage system and control method thereof Download PDFInfo
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- CN112751357A CN112751357A CN201911053406.5A CN201911053406A CN112751357A CN 112751357 A CN112751357 A CN 112751357A CN 201911053406 A CN201911053406 A CN 201911053406A CN 112751357 A CN112751357 A CN 112751357A
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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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- 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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- 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
- Y02E70/00—Other energy conversion or management systems reducing GHG emissions
- Y02E70/30—Systems combining energy storage with energy generation of non-fossil origin
Abstract
The invention provides a photovoltaic energy storage system and a control method thereof, wherein the photovoltaic energy storage system comprises a bidirectional DC-DC converter, the bidirectional DC-DC converter comprises n bidirectional DC-DC conversion modules, and the high-voltage sides of the n bidirectional DC-DC conversion modules are respectively connected to the direct-current side of a photovoltaic inverter and the output end of a photovoltaic module through n corresponding direct-current buses; the energy storage device is connected with the low-voltage sides of the n bidirectional DC-DC conversion modules; and the controller is used for controlling the n bidirectional DC-DC conversion modules to constantly output corresponding target currents according to the rated power of the photovoltaic inverter and the input power of the direct current side. According to the system and the control method thereof, the output power of the photovoltaic inverter is smoothed and stabilized, and the utilization rate of the energy of the photovoltaic panel is improved.
Description
Technical Field
The invention relates to the field of new energy, in particular to photovoltaic energy storage and control thereof.
Background
Solar energy is used as a green energy source and is an inexhaustible clean energy source. However, photovoltaic power generation is affected by illumination and temperature, and when the external environment changes rapidly, the photovoltaic power generation power also changes rapidly, so that the power supply quality of an alternating current power grid is seriously affected, and grid-connected acceptance of a power grid company on photovoltaic power generation is low.
In order to make the output power of photovoltaic power generation smoother, an energy storage system can be added into the photovoltaic power generation system. The energy storage system in the prior art is generally located on the alternating current side of the photovoltaic inverter, and comprises an AC/DC converter and a battery; in the photovoltaic power generation period, the electric energy output by the photovoltaic inverter is rectified and stored in the battery through the AC/DC converter, and the energy stored in the battery is inverted into alternating current through the AC/DC converter when the photovoltaic power is insufficient and is transmitted to the alternating current power grid.
Therefore, in the prior art, because the energy storage system is connected to the alternating current side of the photovoltaic inverter, the output power of the system is limited to the rated power of the photovoltaic inverter, and the system cannot be applied to the condition that the power generation power of the photovoltaic panel is greater than the rated light rate of the photovoltaic inverter, so that the photovoltaic energy is wasted; meanwhile, when an energy storage system is connected to the alternating current side, alternating current harmonic waves of a power grid and a photovoltaic inverter can be obviously influenced, and the quality of the power grid is reduced; while affecting the MPPT efficiency of the photovoltaic inverter.
Disclosure of Invention
The present invention has been made in view of the above problems. The invention provides a photovoltaic energy storage system and a control method thereof to solve the problems.
According to a first aspect of the present invention, there is provided a photovoltaic energy storage system comprising:
the bidirectional DC-DC converter comprises n bidirectional DC-DC conversion modules, and the high-voltage sides of the n bidirectional DC-DC conversion modules are respectively connected to the direct-current side of the photovoltaic inverter and the output end of the photovoltaic module through n corresponding direct-current buses;
the energy storage device is connected with the low-voltage sides of the n bidirectional DC-DC conversion modules;
and the controller is used for controlling the n bidirectional DC-DC conversion modules to constantly output corresponding target currents according to the rated power of the photovoltaic inverter and the input power of the direct current side.
According to a second aspect of the invention, there is provided a control method for a photovoltaic energy storage system as described in the first aspect, the method comprising:
acquiring the total power of the photovoltaic module;
judging whether the photovoltaic module outputs power normally or not based on the total power of the photovoltaic module;
if the photovoltaic module normally outputs power, calculating a target output power Pdcobji, i of the ith bidirectional DC-DC conversion module to be 1,2,3, … …, n based on the rated power Pstd of the photovoltaic inverter and the input power of the direct current side;
and controlling the ith bidirectional DC-DC conversion module to constantly output corresponding target current according to the target output power Pdcobji of the ith bidirectional DC-DC conversion module.
According to the photovoltaic energy storage system and the control method, the energy storage system is arranged on the direct current side of the photovoltaic inverter as an independent unit, and the output power of the photovoltaic inverter is smoothed and stabilized, the utilization rate of the energy of a photovoltaic panel is improved, the generated energy and the quality of a power grid are improved, and the alternating current harmonic wave of the inverter is not influenced by respectively adjusting the power of each branch circuit on the direct current side of the photovoltaic inverter.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent by describing in more detail embodiments of the present invention with reference to the attached drawings. The accompanying drawings are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings, like reference numbers generally represent like parts or steps.
Fig. 1 is an example of a dc-side system of a photovoltaic inverter according to an embodiment of the invention;
FIG. 2 is a schematic block diagram of a photovoltaic energy storage system according to an embodiment of the present disclosure;
FIG. 3 is a schematic flow chart of a photovoltaic energy storage control method according to an embodiment of the present disclosure;
FIG. 4 is an example of a simulated photovoltaic characteristic of a control method of a photovoltaic energy storage system according to an embodiment of the present disclosure;
fig. 5 is a schematic block diagram of a control device of a photovoltaic energy storage system according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, exemplary embodiments according to the present invention will be described in detail below with reference to the accompanying drawings. It is to be understood that the described embodiments are merely a subset of embodiments of the invention and not all embodiments of the invention, with the understanding that the invention is not limited to the example embodiments described herein. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the invention described herein without inventive step, shall fall within the scope of protection of the invention.
Referring to fig. 1, fig. 1 illustrates an example of a dc-side system of a photovoltaic inverter according to an embodiment of the present invention. As shown in fig. 1, a dc-side system 100 of a photovoltaic inverter includes:
the photovoltaic module 110 is used for converting solar energy into electric energy and outputting the electric energy to the direct current bus 120;
a photovoltaic inverter 130, a direct current side of the photovoltaic inverter 120 is connected to the direct current bus 120, an alternating current side of the photovoltaic inverter 120 is connected to a power grid, and the photovoltaic inverter 130 converts a direct current voltage of the direct current bus 120 into an alternating current voltage and outputs the alternating current voltage to the power grid;
the photovoltaic energy storage system 140 comprises a bidirectional DC-DC converter 141 and an energy storage device 142, wherein a high-voltage side of the bidirectional DC-DC converter 141 is connected to the direct-current bus 120 and/or the direct-current side of the DC-AC inverter 130, and a low-voltage side of the bidirectional DC-DC converter 141 is connected to the energy storage device 142.
The photovoltaic energy storage system 140 may obtain at least a portion of the electric energy of each dc bus 120 to charge the energy storage device 142, or obtain at least a portion of the electric energy of the energy storage device 142 to discharge the photovoltaic inverter 130.
Referring to fig. 2, fig. 2 shows a schematic block diagram of a photovoltaic energy storage system according to an embodiment of the present invention. The photovoltaic energy storage system 200 may include:
the bidirectional DC-DC converter 210 comprises n bidirectional DC-DC conversion modules, and the high-voltage sides of the n bidirectional DC-DC conversion modules are respectively connected to the direct-current side of the photovoltaic inverter and the output end of the photovoltaic module through n corresponding direct-current buses;
an energy storage device 220 connected to the low-voltage side of the n bidirectional DC-DC conversion modules;
a controller 230 for controlling the output currents of the n bidirectional DC-DC conversion modules.
In some embodiments, the controller 230 may control the output currents of the n bidirectional DC-DC conversion modules to constantly output the corresponding target currents according to the rated power of the photovoltaic inverter and the input power of the DC side.
Optionally, the photovoltaic module 110 may include at least one photovoltaic panel group.
In some embodiments, the set of photovoltaic panels includes at least one photovoltaic panel.
Optionally, the photovoltaic inverter 130 may include at least one MPPT controller.
The MPPT (Maximum Power Point Tracking) controller adjusts the output Power of the photovoltaic panel group or the photovoltaic panel according to the characteristics of different external environment temperatures, illumination intensities and the like, so that the photovoltaic panel group or the photovoltaic panel always outputs the Maximum Power, and particularly, the Maximum voltage current Value (VI) can be tracked by detecting the output voltage of the photovoltaic panel group or the photovoltaic panel in real time, so that the photovoltaic panel group outputs the Maximum Power.
Optionally, the number of MPPT controllers in the photovoltaic inverter 130 matches the number of photovoltaic panels.
In some embodiments, the number of MPPT controllers is the same as the number of photovoltaic panels. At this time, each photovoltaic panel is connected to each MPPT controller through a corresponding dc bus.
In some embodiments, the MPPT controllers are the same number as the photovoltaic panel groups, wherein the photovoltaic panel groups include several photovoltaic panels in series and/or in parallel. At this time, each of the photovoltaic surface groups is connected to the dc side of each of the MPPT controllers, i.e., the photovoltaic inverters 130, through a corresponding dc bus.
Alternatively, the bidirectional DC-DC converter 141 may include at least one bidirectional DC-DC conversion module.
In some embodiments, each of the bidirectional DC-DC conversion modules in the bidirectional DC-DC converter 141 may be independently controlled.
Optionally, the number of the bidirectional DC-DC conversion modules is the same as the number of the direct current buses 120. That is, the number of the bidirectional DC-DC conversion modules, the number of the direct current buses, and the number of the MPPT controllers are the same. At this time, the high voltage side of each bidirectional DC-DC conversion module is connected to a corresponding DC bus, and is connected to a corresponding MPPT controller through the corresponding DC bus.
Alternatively, the energy storage device 142 may include several batteries connected in series and/or in parallel.
In some embodiments, the low-voltage side of each bidirectional DC-DC conversion module is connected in parallel to the energy storage device 142.
Optionally, the energy storage system 140 may further include:
the bidirectional DC-DC converter 141 and the energy storage device 142 communicate by wire or wirelessly.
In some embodiments, the bidirectional DC-DC converter 141 communicates with the energy storage device 142 by wire or wirelessly to obtain energy storage information of the energy storage device 142 and/or to control the on/off of the energy storage device 142.
In some embodiments, the energy storage information may include at least one of: voltage of the energy storage device 142, SOC (State of Charge), current limit value, and protection information (e.g., information of overcharge, overdischarge, overcurrent, short circuit, etc.).
Optionally, the dc-side system 100 of the photovoltaic inverter may further include:
at least one current sensor 150, each of which is disposed on the DC side of the DC-AC inverter 130, and is configured to collect an input current of each input of the photovoltaic inverter 130.
In some embodiments, the at least one current sensor 150 is also connected to the bidirectional DC-DC converter 141. Further, the at least one current sensor 150 collects an input current of each MPPT controller and transmits the input current to each bidirectional DC-DC conversion module correspondingly connected to each MPPT controller.
Optionally, the dc-side system 100 of the photovoltaic inverter may further include:
and at least one voltage sensor (not shown in the figure), wherein each voltage sensor is arranged on each direct current bus and used for collecting the voltage on each direct current bus.
According to the embodiment of the invention, when the illumination condition is good, that is, the sunlight is sufficient, the electric energy generated by the photovoltaic module 110 is sufficient, and when the electric energy generated by the photovoltaic module 110 is larger than the electric energy required by the power grid, the storage system 140 can store the surplus electric energy by charging the energy storage device 142; when the power generated by the photovoltaic module 110 is less than the power required by the grid, it cannot meet the demand of the grid, and the power in the storage system 140 needs to be discharged through the energy storage device 142 to be provided to the photovoltaic inverter 130 (e.g., DC-AC inverter). Therefore, no matter whether the electric energy generated by the photovoltaic module 110 can meet the power grid requirement or not, the output power of the energy storage system 140 can be actively adjusted to maintain the power of the direct-current input side of the photovoltaic inverter 130 to be stable and have small fluctuation, so that the output power of the photovoltaic inverter 130 is kept near the rated power of the photovoltaic inverter, the utilization rate of the energy of a photovoltaic panel is improved, the output power of the photovoltaic inverter is smooth and stable, the quality and the power generation amount of the electric energy input into the power grid are ensured, and the alternating current harmonic wave of the photovoltaic inverter is not influenced.
Referring now to fig. 3, fig. 3 shows a schematic flow chart of a control method of photovoltaic energy storage according to an embodiment of the present invention. As shown in fig. 3, a method 300 for controlling a photovoltaic energy storage system, the method 300 comprising:
step S310, acquiring the total power of the photovoltaic module;
step S320, judging whether the photovoltaic module outputs power normally or not based on the total power of the photovoltaic module;
step S330, if the photovoltaic module normally outputs power, calculating a target output power Pdcobji, i ═ 1,2,3, … …, n of the ith bidirectional DC-DC conversion module based on the rated power Pstd of the photovoltaic inverter and the input power on the direct current side;
and step S340, controlling the ith bidirectional DC-DC conversion module to constantly output corresponding target current according to the target output power Pdcobji of the ith bidirectional DC-DC conversion module.
According to the embodiment of the present invention, the step S310 may include:
detecting the power of an ith group of photovoltaic panel groups in the photovoltaic module, wherein i is 1,2,3, … …, n;
and calculating the sum of the power of the n groups of photovoltaic panel groups to obtain the total power Ppv.
According to the embodiment of the present invention, in step S320, determining whether the photovoltaic module normally outputs power based on the total power of the photovoltaic module may include:
respectively comparing the total power Ppv of the photovoltaic modules with a power threshold value Plow;
when the total power Ppv of the photovoltaic components is larger than or equal to the power threshold value Plow, determining the normal output power of the photovoltaic components; and/or the presence of a gas in the gas,
when the total power Ppv of the photovoltaic modules is smaller than the power threshold value Plow, determining that the photovoltaic modules do not have normal output power.
According to the embodiment of the present invention, the step S330 may include:
step S331, distributing a matching target power Pobji of the ith bidirectional DC-DC conversion module based on the rated power Pstd of the photovoltaic inverter;
step S332, acquiring the ith input power Pi corresponding to the ith bidirectional DC-DC conversion module in the direct current side of the photovoltaic inverter;
step S333, obtaining a target output power Pdcobji of the ith bidirectional DC-DC conversion module according to the matching target power Pobji of the ith bidirectional DC-DC conversion module and the corresponding ith input power Pi.
Optionally, in the step S331, the matching target power of each bidirectional DC-DC conversion module may be distributed equally or proportionally based on the rated power of the photovoltaic inverter.
In some embodiments, referring to fig. 3, when the power of each group of photovoltaic panels shown in fig. 3 is the same, the power rating of the photovoltaic inverter may be distributed in an evenly distributed manner. Then, allocating the matching target power of each of the bidirectional DC-DC conversion modules based on the rated power of the photovoltaic inverter may include:
the matching target power of each bidirectional DC-DC conversion module is as follows:
wherein Pstd is the rated power of the photovoltaic inverter, and i is 1,2,3, … …, n.
In some embodiments, referring to fig. 3, when the power of each group of photovoltaic panels shown in fig. 3 is different, the rated power of the photovoltaic inverter may be distributed in a proportional distribution manner according to the power of each group of photovoltaic modules. Then, allocating the matching target power of each of the bidirectional DC-DC conversion modules based on the rated power of the photovoltaic inverter may include:
the matching target power of the ith bidirectional DC-DC conversion module is as follows:
wherein Pstd is the rated power of the photovoltaic inverter, i is 1,2,3, … …, n; pvi is the output power of the ith group of photovoltaic panel groups corresponding to the ith bidirectional DC-DC conversion module, and Pv1+ Pv2+ … … + Pvn is the total output power of the photovoltaic module.
According to the embodiment of the present invention, the step S332 may include:
acquiring a voltage Uhighhi of an ith bidirectional DC-DC conversion module and an input current Idci of an ith input path corresponding to the ith bidirectional DC-DC conversion module in the photovoltaic inverter;
and obtaining the input power Pi (Uhighhi) and Idci of the ith input circuit based on the voltage Uhighhi and the input current Idci, wherein i (1, 2,3, … …, n).
According to an embodiment of the present invention, the step S333 may include:
calculating the variation power delta Pi of the ith bidirectional DC-DC conversion module to be Pobji-Pi, i to be 1,2,3, … …, n according to the matching target power Pobji of the ith bidirectional DC-DC conversion module and the corresponding ith direct current input power Pi;
and adjusting the current output power Pdcobji' of the ith bidirectional DC-DC conversion module according to the variable power delta Pi to obtain the target output power Pdcobji of the ith bidirectional DC-DC conversion module.
In some embodiments, the adjusting the previous output power Pdcobji' of the ith bidirectional DC-DC conversion module according to the variation power Δ Pi to obtain the target output power Pdcobji of the ith bidirectional DC-DC conversion module may include:
pdcobji ═ Pdcobji '+ Δ Pi ═ Pdcobji' + (Pobji-Pi), where i ═ 1,2,3, … …, n.
The initial value of Pdcobji' may be 0, and after continuously adjusting and accumulating, the target output power Pdcobji at the next time is the output power at the current time plus the variation power Δ Pi, so that the output power of the ith bidirectional DC-DC conversion module approaches the target power.
It should be noted that the output power of the ith bidirectional DC-DC conversion module should not exceed the rated power Pdcstd of the ith bidirectional DC-DC conversion module.
According to the embodiment of the present invention, the step S340 may include:
step S341, obtaining a target current Idcojbi of the ith bidirectional DC-DC conversion module according to the target output power Pdcobji of the ith bidirectional DC-DC conversion module and the low-voltage side voltage UdcLow of the bidirectional DC-DC converter;
step S342, controlling the output current of the ith bidirectional DC-DC conversion module to be constant at the target current Idcojbi of the ith bidirectional DC-DC conversion module.
In some embodiments, the step S341 may include:
idcojbi ═ pdcoji/UdcLow, where i ═ 1,2,3, … …, n.
In some embodiments, the step S341 may include: and adjusting the output current of the ith bidirectional DC-DC conversion module to be Idcojbi constantly by adopting a proportional-integral regulator.
By controlling the output current of each bidirectional DC-DC conversion module in the energy storage system to be constant according to the target current, the power on the DC input side of the DC-AC inverter 130 can be maintained to be stable and have small fluctuation, so that the total output power of the photovoltaic inverter is kept stable.
In order to ensure that the effects of smoothing the output power of the photovoltaic inverter and increasing the power generation capacity of the system are continuously and effectively achieved, the capacity of an energy storage device in an energy storage system of the photovoltaic inverter is generally configured to be large, otherwise the capacity of the energy storage device (such as a battery) is small, and the energy storage device can be quickly fully charged or emptied in the matching process and cannot meet the requirements.
Because the output power of the photovoltaic module is greatly influenced by the illumination condition, when the power generated by the photovoltaic module is greater than the rated power of the photovoltaic inverter, a part of the power generated by the photovoltaic module is used for being provided to the photovoltaic inverter, and the rest part of the power is used for charging the energy storage system; when the power generated by the photovoltaic module is smaller than the rated power of the photovoltaic inverter, for example, after 3 and 4 pm, the energy storage system starts to match and discharge to compensate the shortage power so as to maintain the rated power of the photovoltaic inverter; when the power generated by the photovoltaic module is close to 0, for example, after 6 or 7 pm in the evening, if the battery capacity allocation of the energy storage system is large, the battery capacity may not be completely discharged. At the moment, the energy of the photovoltaic inverter is almost completely provided by the battery of the energy storage system, and because the output characteristics of the bidirectional DC-DC converter in the energy storage system are different from those of the photovoltaic panel, the MPPT controller in the photovoltaic inverter can not track normally, so that overvoltage or overcurrent faults occur on the direct current side.
Based on the above consideration, when the power generated by the photovoltaic module is close to 0, the energy of the photovoltaic inverter is almost completely provided by the battery of the energy storage system, and the output characteristic exhibited by the energy storage system can be similar to or the same as the output characteristic of the photovoltaic module by controlling the output characteristic of the bidirectional DC-DC converter in the energy storage system, so that the MPPT controller in the photovoltaic inverter can continue to track the output characteristic, which is close to the photovoltaic characteristic, exhibited by the energy storage system, and further maintain the output of the photovoltaic inverter. Meanwhile, the energy storage system can also stably discharge under the condition that the output of the photovoltaic module is very weak or even 0, so that the system adaptability is improved, and the generated energy is remarkably increased.
According to an embodiment of the present invention, the method 300 may further include:
and step S350, if the photovoltaic module does not have normal output power, controlling the output power of each bidirectional DC-DC conversion module according to the high-voltage side voltage of each bidirectional DC-DC conversion module.
The method comprises the steps that power Ppv of a photovoltaic module is detected in real time, and when Ppv is reduced to be below a set power limit value Plow (approaching 0, such as 0.5kw), photovoltaic characteristics are simulated by controlling an energy storage system to maintain the output power of a photovoltaic inverter. Therefore, the optimum efficiency point voltage Ubest of the bidirectional DC-DC converter can be taken as the maximum power point voltage of the analog photovoltaic curve; if the photovoltaic voltage is equal to the optimal efficiency point voltage Ubest, enabling the output power of the energy storage system to meet the rated power operation of the photovoltaic inverter; when the voltage of the high-voltage side of the bidirectional DC-DC conversion module deviates from the optimum efficiency point voltage Ubest, the output power of the energy storage system is controlled to be reduced, so that the output characteristic presented by the energy storage system is as follows: when the optimum efficiency point voltage Ubest deviates from the optimum efficiency point voltage Ubest with respect to the maximum power point, the output power is reduced; this is similar to the output characteristics of the photovoltaic module, so that the photovoltaic inverter MPPT can track normally, and the high-voltage side voltage of the bidirectional DC-DC conversion module is finally stabilized near the optimum efficiency point voltage Ubest.
Referring to fig. 4, fig. 4 shows an example of a simulated photovoltaic characteristic of a control method of an energy storage system of a photovoltaic inverter according to an embodiment of the present invention. As shown in fig. 4, the upper limit value of the high-voltage side voltage of the ith bidirectional DC-DC conversion module is UdcHigh, the lower limit value is UdcLow, the best efficiency point voltage of the ith bidirectional DC-DC conversion module is Ubest, the highest power corresponding to the best efficiency point voltage Ubest is the target output power Pdcojbi of the ith bidirectional DC-DC conversion module, and UdcHigh > Ubest > UdcLow.
According to the embodiment of the present invention, step S350 may include:
when the high-voltage side voltage Uhighi of the ith bidirectional DC-DC conversion module is equal to the best efficiency point voltage Ubest of the ith bidirectional DC-DC conversion module, controlling the output power Pobji' of the ith bidirectional DC-DC conversion module to be the target output power Pdcojbi;
when the high-voltage side voltage Uhight of the ith bidirectional DC-DC conversion module is not equal to the optimal efficiency point voltage Ubest of the ith bidirectional DC-DC conversion module and meets UdcHigh > Uhight > UdcLow, controlling the ith bidirectional DC-DC conversion module to linearly reduce the output power;
and when the high-voltage side voltage Uhighi of the ith bidirectional DC-DC conversion module meets UdcHigh < Uhighi or Uhighi < UdcLow, controlling the output power Pobji' of the ith bidirectional DC-DC conversion module to be 0.
In some embodiments, the controlling the i-th bidirectional DC-DC conversion module to linearly reduce the output power may include:
when the high-voltage side voltage UdcHigh of the ith bidirectional DC-DC conversion module is greater than Uhighi which is greater than Ubest, controlling the output power Pobji' of the ith bidirectional DC-DC conversion module to be: pobji ═ Pdcojbi- [ Pdcojbi: (Uhighi-Ubest)/(UdcHigh-Ubest) ];
when the high-voltage side voltage Udcbest of the ith bidirectional DC-DC conversion module is more than Uhighhi and more than UdcLow, controlling the output power Pobji' of the ith bidirectional DC-DC conversion module to be: pobji ═ Pdcojbi- [ Pdcojbi: (Uhighi-Ubest)/(Ubest-UdcLow) ].
According to an embodiment of the present invention, there is also provided a control apparatus for an energy storage system of a photovoltaic inverter, the apparatus including: the embodiment of the invention provides the control method of the energy storage system of the photovoltaic inverter when the processor executes the computer program.
According to an embodiment of the present invention, a computer storage medium is further provided, on which a computer program is stored, and the computer program, when executed by a computer, implements the control method of the energy storage system of the photovoltaic inverter provided by the embodiment of the present invention.
Referring to fig. 5, fig. 5 shows a schematic block diagram of a control device of a photovoltaic energy storage system according to an embodiment of the present invention. The energy storage system includes a bidirectional DC-DC converter and an energy storage device, where the bidirectional DC-DC converter includes n bidirectional DC-DC conversion modules, high-voltage sides of the n bidirectional DC-DC conversion modules are respectively connected to a direct-current side of the photovoltaic inverter and an output end of the photovoltaic module through the n corresponding direct-current buses, and low-voltage sides of the n bidirectional DC-DC conversion modules are connected in parallel and then connected to the energy storage device, as shown in fig. 5, the control device 500 of the energy storage system of the photovoltaic inverter includes:
an obtaining module 510, configured to obtain a total power of the photovoltaic module;
a judging module 520, configured to judge whether the photovoltaic module outputs power normally based on the total power of the photovoltaic module;
a calculating module 530, configured to calculate, if the photovoltaic module normally outputs power, a target output power Pdcobji, i ═ 1,2,3, … …, n of the ith bidirectional DC-DC conversion module based on the rated power Pstd of the photovoltaic inverter and the input power on the direct current side;
and a control module 540, configured to control the ith bidirectional DC-DC conversion module to constantly output a corresponding target current according to the target output power Pdcobji of the ith bidirectional DC-DC conversion module.
The respective modules may perform the respective steps/functions of the control method of the photovoltaic energy storage system described above in connection with fig. 1-3, respectively. Only the main functions of the components of the control device 500 of the photovoltaic energy storage system are described above, and details that have been described above are omitted.
According to an embodiment of the invention, a photovoltaic energy storage system is provided, which is characterized by comprising a bidirectional DC-DC converter and an energy storage device, wherein the bidirectional DC-DC converter comprises n bidirectional DC-DC conversion modules, the high voltage sides of the n bidirectional DC-DC conversion modules are respectively connected to the direct current side of a photovoltaic inverter and the output end of a photovoltaic assembly through n corresponding direct current buses, and the low voltage sides of the n bidirectional DC-DC conversion modules are connected with the energy storage device after being connected in parallel;
the control device of the photovoltaic energy storage system is provided by the embodiment of the invention.
According to an embodiment of the present invention, there is provided a dc-side system of a photovoltaic inverter, the system including:
the photovoltaic module converts solar energy into electric energy and outputs the electric energy to the direct current bus;
the direct-current side of the photovoltaic inverter is connected to the direct-current bus, the alternating-current side of the photovoltaic inverter is connected to a power grid, and the photovoltaic inverter converts the direct-current voltage of the direct-current bus into alternating-current voltage and outputs the alternating-current voltage to the power grid;
and the energy storage system according to the embodiment of the invention.
According to the photovoltaic energy storage system and the control method and device thereof, the energy storage system is arranged on the direct current side of the photovoltaic inverter as an independent unit, and the output power of the photovoltaic inverter is smoothed and stabilized, the utilization rate of the energy of a photovoltaic panel is improved, the generated energy and the quality of a power grid are improved, and the alternating current harmonic wave of the inverter is not influenced by respectively adjusting the power of each branch circuit on the direct current side of the photovoltaic inverter.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
The above description is only for the specific embodiment of the present invention or the description thereof, and the protection scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and the changes or substitutions should be covered within the protection scope of the present invention. The protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (12)
1. A photovoltaic energy storage system, comprising:
the bidirectional DC-DC converter comprises n bidirectional DC-DC conversion modules, and the high-voltage sides of the n bidirectional DC-DC conversion modules are respectively connected to the direct-current side of the photovoltaic inverter and the output end of the photovoltaic module through n corresponding direct-current buses;
the energy storage device is connected with the low-voltage sides of the n bidirectional DC-DC conversion modules;
and the controller is used for controlling the n bidirectional DC-DC conversion modules to constantly output corresponding target currents according to the rated power of the photovoltaic inverter and the input power of the direct current side.
2. A control method for a photovoltaic energy storage system according to claim 1, characterized in that the method comprises:
acquiring the total power of the photovoltaic module;
judging whether the photovoltaic module outputs power normally or not based on the total power of the photovoltaic module;
if the photovoltaic module normally outputs power, calculating a target output power Pdcobji, i of the ith bidirectional DC-DC conversion module to be 1,2,3, … …, n based on the rated power Pstd of the photovoltaic inverter and the input power of the direct current side;
and controlling the ith bidirectional DC-DC conversion module to constantly output corresponding target current according to the target output power Pdcobji of the ith bidirectional DC-DC conversion module.
3. The method according to claim 2, wherein if the photovoltaic module outputs power normally, calculating a target output power of the ith bidirectional DC-DC conversion module based on the rated power of the photovoltaic inverter and the input power of the DC side, where i is 1,2,3, … …, n, comprises:
distributing the matched target power Pobji of the ith bidirectional DC-DC conversion module based on the rated power Pstd of the photovoltaic inverter;
acquiring ith input power Pi corresponding to the ith bidirectional DC-DC conversion module in the direct current side of the photovoltaic inverter;
and obtaining the target output power Pdcobji of the ith bidirectional DC-DC conversion module according to the matched target power Pobji of the ith bidirectional DC-DC conversion module and the corresponding ith input power Pi.
4. The method according to claim 3, wherein distributing the matching target power Pobji of the ith bidirectional DC-DC conversion module based on the rated power Pstd of the photovoltaic inverter comprises:
wherein Pstd is the rated power of the photovoltaic inverter, and i is 1,2,3, … …, n.
5. The method according to claim 3, wherein distributing the matching target power Pobji of the ith bidirectional DC-DC conversion module based on the rated power Pstd of the photovoltaic inverter comprises:
wherein Pstd is the rated power of the photovoltaic inverter, i is 1,2,3, … …, n; pvi is the output power of the ith group of photovoltaic panel groups corresponding to the ith bidirectional DC-DC conversion module, and Pv1+ Pv2+ … … + Pvn is the total output power of the photovoltaic module.
6. The method according to claim 3, wherein the obtaining the ith input power Pi corresponding to the ith bidirectional DC-DC conversion module in the DC side of the photovoltaic inverter comprises:
acquiring a voltage Uhighhi of an ith bidirectional DC-DC conversion module and an input current Idci of an ith input path corresponding to the ith bidirectional DC-DC conversion module in the photovoltaic inverter;
and obtaining the input power Pi (Uhighhi) and Idci of the ith input circuit based on the voltage Uhighhi and the input current Idci, wherein i (1, 2,3, … …, n).
7. The method as claimed in claim 6, wherein obtaining the target output power Pdcobji of the ith bidirectional DC-DC conversion module according to the matched target power Pobji of the ith bidirectional DC-DC conversion module and the corresponding ith input power Pi comprises:
calculating the variation power delta Pi of the ith bidirectional DC-DC conversion module to be Pobji-Pi, i to be 1,2,3, … …, n according to the matching target power Pobji of the ith bidirectional DC-DC conversion module and the corresponding ith direct current input power Pi;
and adjusting the current output power Pdcobji' of the ith bidirectional DC-DC conversion module according to the variable power delta Pi to obtain the target output power Pdcobji of the ith bidirectional DC-DC conversion module.
8. The method as claimed in any one of claims 2-7, wherein controlling the ith bidirectional DC-DC conversion module to constantly output a corresponding target current according to the target output power Pdcobji of the ith bidirectional DC-DC conversion module comprises:
obtaining a target current Idcojbi of the ith bidirectional DC-DC conversion module according to the target output power Pdcobji of the ith bidirectional DC-DC conversion module and the low-voltage side voltage UdcLow of the bidirectional DC-DC converter;
and controlling the output current of the ith bidirectional DC-DC conversion module to be constant as the target current Idcojbi of the ith bidirectional DC-DC conversion module.
9. The method according to any one of claims 2-7, further comprising:
and if the photovoltaic assembly does not have normal output power, controlling the output power Pobji' of the ith bidirectional DC-DC conversion module according to the high-voltage side voltage Uhighi of the ith bidirectional DC-DC conversion module.
10. The method of claim 9, wherein controlling the output power Pobji' of the ith bidirectional DC-DC conversion module according to the high side voltage Uhighi of the ith bidirectional DC-DC conversion module comprises:
when the high-voltage side voltage Uhighi of the ith bidirectional DC-DC conversion module is equal to the best efficiency point voltage Ubest of the ith bidirectional DC-DC conversion module, controlling the output power Pobji' of the ith bidirectional DC-DC conversion module to be the target output power Pdcojbi;
when the high-voltage side voltage Uhight of the ith bidirectional DC-DC conversion module is not equal to the optimal efficiency point voltage Ubest of the ith bidirectional DC-DC conversion module and meets UdcHigh > Uhight > UdcLow, controlling the ith bidirectional DC-DC conversion module to linearly reduce the output power;
when the high-voltage side voltage Uhighi of the ith bidirectional DC-DC conversion module meets UdcHigh < Uhighi or Uhighi < UdcLow, controlling the output power Pobji' of the ith bidirectional DC-DC conversion module to be 0;
wherein UdcHigh is an upper limit value of the high-voltage side voltage of the ith bidirectional DC-DC conversion module, UdcLow is a lower limit value of the high-voltage side voltage of the ith bidirectional DC-DC conversion module, and the maximum power corresponding to the optimum efficiency point voltage Ubest is the target output power Pdcojbi of the ith bidirectional DC-DC conversion module.
11. The method of claim 10, wherein the controlling the i-th bidirectional DC-DC conversion module to linearly reduce the output power comprises:
when the high-voltage side voltage UdcHigh of the ith bidirectional DC-DC conversion module is greater than Uhighi which is greater than Ubest, controlling the output power Pobji' of the ith bidirectional DC-DC conversion module to be: pobji ═ Pdcojbi- [ Pdcojbi: (Uhighi-Ubest)/(UdcHigh-Ubest) ];
when the high-voltage side voltage Udcbest of the ith bidirectional DC-DC conversion module is more than Uhighhi and more than UdcLow, controlling the output power Pobji' of the ith bidirectional DC-DC conversion module to be: pobji ═ Pdcojbi- [ Pdcojbi: (Uhighi-Ubest)/(Ubest-UdcLow) ].
12. The method of claim 2, wherein determining whether the photovoltaic module is outputting power normally based on the total power of the photovoltaic module comprises:
respectively comparing the total power of the photovoltaic modules with a power threshold value;
when the total power of the photovoltaic components is larger than or equal to the power threshold value, determining the normal output power of the photovoltaic components; and/or the presence of a gas in the gas,
when the total power of the photovoltaic modules is smaller than the power threshold value, determining that the photovoltaic modules do not have normal output power.
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