CN110739860B - Transformer gear determination method and device and photovoltaic power generation system - Google Patents
Transformer gear determination method and device and photovoltaic power generation system Download PDFInfo
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- CN110739860B CN110739860B CN201911067073.1A CN201911067073A CN110739860B CN 110739860 B CN110739860 B CN 110739860B CN 201911067073 A CN201911067073 A CN 201911067073A CN 110739860 B CN110739860 B CN 110739860B
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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
- H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
- H02M5/02—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc
- H02M5/04—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters
- H02M5/10—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using transformers
- H02M5/12—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using transformers for conversion of voltage or current amplitude only
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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
Abstract
The embodiment of the invention discloses a transformer gear determining method, a transformer gear determining device and a photovoltaic power generation system, wherein the transformer gear determining method is applied to the photovoltaic power generation system, the photovoltaic power generation system comprises a photovoltaic component, an inverter and a transformer, and the transformer gear determining method comprises the following steps: acquiring historical direct-current voltage data of an inverter and historical voltage data of a high-voltage side of a transformer within preset time; calculating the voltage of the low-voltage side of the transformer under each gear according to the historical voltage data of the high-voltage side of the transformer; and determining the optimal gear of the transformer within the preset time based on the relation between the historical direct-current voltage of the inverter and the voltage of the low-voltage side of the transformer and the efficiency characteristic of the inverter. The method for determining the gear of the transformer can ensure that the inverter has higher operation efficiency in a normal working state.
Description
Technical Field
The embodiment of the invention relates to a transformer gear shifting technology, in particular to a transformer gear determining method and device and a photovoltaic power generation system.
Background
In a photovoltaic power station, in order to keep the alternating-current voltage output by an inverter at a rated grid-connected voltage, voltage regulation is realized by regulating the gear of a transformer, and the gear of the transformer determines the safety and stable operation of equipment related to a photovoltaic power generation system, which is an important research content.
At present, the existing transformer gear determining method only considers the influence of the voltage deviation of a power grid on the safety of power distribution system equipment, and can cause the problems of high loss and low working efficiency of an inverter.
Disclosure of Invention
The embodiment of the invention provides a method and a device for determining a gear of a transformer and a photovoltaic power generation system, and aims to achieve high operation efficiency of an inverter under a normal working state.
In a first aspect, an embodiment of the present invention provides a method for determining a gear of a transformer, where a photovoltaic power station includes a photovoltaic module, an inverter, and a transformer, and the method for determining the gear of the transformer includes:
acquiring historical direct-current voltage data of an inverter and historical voltage data of a high-voltage side of a transformer within preset time;
calculating the voltage of the low-voltage side of the transformer under each gear according to the historical voltage data of the high-voltage side of the transformer;
and determining the optimal gear of the transformer within the preset time based on the relation between the historical direct-current voltage of the inverter and the voltage of the low-voltage side of the transformer and the efficiency characteristic of the inverter.
Optionally, the preset time includes at least one preset time interval, and before calculating the voltage of the low-voltage side of the transformer at each gear according to the historical voltage data of the high-voltage side of the transformer, the method further includes:
determining the average direct current voltage of the inverter in each preset time interval according to historical direct current voltage data of the inverter;
determining the average voltage of the high-voltage side of the transformer in each preset time interval according to the historical voltage data of the high-voltage side of the transformer;
according to historical voltage data of the high-voltage side of the transformer, calculating the voltage of the low-voltage side of the transformer under each gear, wherein the calculation comprises the following steps:
calculating the transformation ratio of the transformer corresponding to each gear of the transformer;
and calculating the average voltage of the low-voltage side of the transformer in each preset time interval under each gear based on the average voltage of the high-voltage side of the transformer in each preset time interval and the transformation ratio of the transformer.
Optionally, the preset time interval is a month or a quarter.
Optionally, calculating a transformation ratio of the transformer corresponding to each gear of the transformer includes:
obtaining rated voltage corresponding to each gear in nameplate parameters of the transformer and rated voltage of a low-voltage side of the transformer;
and dividing the rated voltage corresponding to each gear by the rated voltage of the low-voltage side to obtain the transformation ratio corresponding to each gear of the transformer.
Optionally, determining an optimal gear of the transformer within a preset time based on a relationship between a historical dc voltage of the inverter and a voltage of a low-voltage side of the transformer and an efficiency characteristic of the inverter, includes:
and determining the highest voltage for the efficiency of the inverter from the low-voltage side voltage corresponding to each gear of the transformer in each preset time interval, wherein the gear corresponding to the voltage is the optimal gear.
Optionally, determining the maximum efficiency voltage of the inverter from the low-voltage side voltages corresponding to the respective gears of the transformer in each preset time interval, where the gear corresponding to the voltage is the optimal gear, includes:
based on
Obtaining a low-voltage side average voltage set meeting the conditions; wherein, U1For the AC output voltage of the inverter, U2For the low-side voltage of the transformer, UStraight barIs the DC input voltage of the inverter;
and taking the gear corresponding to the maximum value in the set as the optimal gear.
Optionally, after determining the optimal gear of the transformer within the preset time, the method further includes:
and verifying the determined optimal gear of the transformer according to whether the MPPT of the inverter can normally work and the temperature operation condition of the photovoltaic module.
Optionally, verifying the determined optimal gear of the transformer according to whether the MPPT of the inverter can work normally and the temperature operation condition of the photovoltaic module includes:
calculating the lowest direct current voltage of the photovoltaic module at the upper limit of the working temperature according to the operating parameters of the photovoltaic module; wherein, the maximum working temperature T corresponding to the upper limit of the working temperature of the photovoltaic modulecellIs calculated by the formula Tcell＝Tair+25·G/0.8，TairThe maximum temperature of the ambient temperature in a preset time interval is represented, G represents the real-time irradiance, and the lowest direct-current voltage V of the photovoltaic modulemp(min)Is calculated by the formula Vmp(min)＝VSTC·[1+(Tcell-25)·γ]Gamma is the voltage temperature coefficient of the illumination assembly, VSTCThe maximum power point voltage of the photovoltaic module measured under STC;
when the lowest direct current voltage is larger than the lower limit of the MPPT voltage range of the inverter, the gear of the transformer is determined to be adjusted correctly; wherein the lowest DC voltage is required to satisfy
n represents the number of photovoltaic modules connected in series.
In a second aspect, an embodiment of the present invention further provides a transformer gear determining device, which is applied to a photovoltaic power generation system, where the photovoltaic power generation system includes a photovoltaic module, an inverter, and a transformer, and the transformer gear determining device includes:
the acquisition module is used for acquiring historical direct current voltage data of the inverter and historical voltage data of the high-voltage side of the transformer within preset time;
the calculation module is used for calculating the voltage of the low-voltage side of the transformer under each gear according to the historical voltage data of the high-voltage side of the transformer;
the gear determining module is used for determining the optimal gear of the transformer within preset time based on the relation between the historical direct-current voltage of the inverter and the voltage of the low-voltage side of the transformer and the efficiency characteristic of the inverter.
In a third aspect, an embodiment of the present invention further provides a photovoltaic power generation system, which includes a photovoltaic module, an inverter, and a transformer, and further includes the transformer gear determination device described in the second aspect.
According to the transformer gear determining method, the transformer gear determining device and the photovoltaic power generation system, historical direct-current voltage data of the inverter and historical voltage data of the high-voltage side of the transformer in the preset time are obtained, and the voltage of the low-voltage side of the transformer under each gear is calculated according to the historical voltage data of the high-voltage side of the transformer, so that the optimal gear of the transformer in the preset time is determined based on the relation between the historical direct-current voltage of the inverter and the voltage of the low-voltage side of the transformer and the efficiency characteristic of the inverter. Compared with the existing method which only considers the influence of the power grid voltage deviation on the gear adjustment of the transformer, the method provided by the embodiment determines the optimal gear of the transformer within the preset time based on the relation between the historical direct-current voltage of the inverter and the voltage of the low-voltage side of the transformer and the efficiency characteristic of the inverter, and ensures that the inverter has higher operation efficiency in the normal working state.
Drawings
Fig. 1 is a flowchart of a method for determining a gear position of a transformer according to an embodiment of the present invention;
fig. 2 is a flowchart of a transformer gear determining method according to a second embodiment of the present invention;
fig. 3 is a flowchart of a method for determining a gear position of a transformer according to a third embodiment of the present invention;
fig. 4 is a block diagram of a transformer gear determining apparatus according to a fifth embodiment of the present invention;
fig. 5 is a block diagram of a photovoltaic power generation system according to a sixth embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.
Example one
Fig. 1 is a flowchart of a transformer gear determining method according to an embodiment of the present invention, where the method is applied to a photovoltaic power generation system, the photovoltaic power generation system includes a photovoltaic module, an inverter, and a transformer, an output end of the photovoltaic module is electrically connected to a dc side of the inverter, and an ac side of the inverter is electrically connected to a low-voltage side of the transformer, and referring to fig. 1, the transformer gear determining method specifically includes the following steps:
and 110, acquiring historical direct current voltage data of the inverter and historical voltage data of the high-voltage side of the transformer in preset time.
The preset time is a period of time in the past, and the range of the preset time can be determined according to actual needs, for example, historical dc voltage data of the inverter in the past year, a certain number of months and the like may include voltage data input by an input terminal of the inverter within the preset time, the voltage input by the input terminal of the inverter is a dc input voltage, the historical voltage data of a high-voltage side of the transformer may include voltage data of a high-voltage side of the transformer within the preset time, the voltage of the low-voltage side of the transformer is an output voltage of the inverter, and the output voltage of the inverter is an ac output voltage.
And step 120, calculating the voltage of the low-voltage side of the transformer under each gear according to the historical voltage data of the high-voltage side of the transformer.
For example, the transformer may include a plurality of gears, the name plate parameter of the transformer includes rated high voltage corresponding to each gear of the transformer, the rated high voltage corresponding to each gear is different, if the transformer includes five gears, the rated high voltage from 1 gear to 5 gears is decreased, the transformer transformation ratio may be determined according to the rated high voltage corresponding to each gear of the transformer and the rated voltage of the low voltage side of the transformer, the low voltage side voltage corresponding to each gear may be calculated according to the transformation ratio and the historical voltage data of the high voltage side of the transformer corresponding to each gear, if the rated high voltage corresponding to 1 gear of the transformer is 38850V and the rated voltage of the low voltage side is 315V, the transformation ratio corresponding to 1 gear of the transformer may be calculated to be 38850V/315V 123.3, if the average voltage of the high voltage side corresponding to 1 gear of the transformer in the last 1 month is 36876V, the average voltage of the low-voltage side month corresponding to the 1 st gear of the transformer in the month of last year 1 is 36876V/123.3-299V.
And step 130, determining the optimal gear of the transformer within the preset time based on the relation between the historical direct-current voltage of the inverter and the voltage of the low-voltage side of the transformer and the efficiency characteristic of the inverter.
Specifically, the ac voltage at the input end of the inverter and the dc voltage at the output end of the inverter need to satisfy a certain condition to ensure the normal operation of the inverter, and since the ac side of the inverter is electrically connected to the low-voltage side of the transformer, the ac voltage of the inverter, i.e., the voltage at the low-voltage side of the transformer, when the inverter normally operates, the larger the voltage value of the ac voltage within a certain range is, the higher the operation efficiency of the inverter is, so that, of the average voltages at the low-voltage side of the transformer at each gear that ensures the normal operation of the inverter, the gear with the largest voltage value is determined as the optimal gear, the preset time includes at least one preset time interval, the preset time interval is a month or a quarter, for example, the month is used as the preset time interval, and according to the monthly average voltages at the low-voltage side of the transformer at each gear in, the gear with the largest voltage value is the best gear of the month and can be used as the best gear of the corresponding month in the current year.
According to the method for determining the gear of the transformer, historical direct-current voltage data of the inverter and historical voltage data of the high-voltage side of the transformer in the preset time are obtained, and the voltage of the low-voltage side of the transformer in each gear is calculated according to the historical voltage data of the high-voltage side of the transformer, so that the optimal gear of the transformer in the preset time is determined based on the relation between the historical direct-current voltage of the inverter and the voltage of the low-voltage side of the transformer and the efficiency characteristic of the inverter. Compared with the existing method which only considers the influence of the power grid voltage deviation on the gear adjustment of the transformer, the method provided by the embodiment determines the optimal gear of the transformer within the preset time based on the relation between the historical direct-current voltage of the inverter and the voltage of the low-voltage side of the transformer and the efficiency characteristic of the inverter, and ensures that the inverter has higher operation efficiency in the normal working state.
Example two
Fig. 2 is a flowchart of a transformer gear determining method according to a second embodiment of the present invention, which may be based on the foregoing embodiments, and referring to fig. 2, the transformer gear determining method specifically includes the following steps:
and step 210, obtaining historical direct current voltage data of the inverter and historical voltage data of the high-voltage side of the transformer in preset time.
And step 220, determining the average direct current voltage of the inverter in each preset time interval according to the historical direct current voltage data of the inverter.
Specifically, the preset time comprises at least one preset time interval, the preset time interval is a month or a quarter, the preset time is a year, the preset time interval is a month, for example, the direct current voltage of the inverter at 9: 00-16: 00 a day in the last year can be obtained, data at other times need to be discarded due to low irradiance and large fluctuation, then the direct current voltage of the inverter is divided in a month unit, and the direct current voltage in each month is averaged to obtain the month average direct current voltage of the inverter in each month in the last year.
And step 230, determining the average voltage of the high-voltage side of the transformer in each preset time interval according to the historical voltage data of the high-voltage side of the transformer.
Illustratively, the preset time is year, the preset time interval is month, the high-voltage side voltage of the transformer at 9: 00-16: 00 per day in the last year can be obtained, then the high-voltage side voltage of the transformer is divided by taking month as a unit, and then the average number of the high-voltage side voltage of each month is taken to obtain the month average high-voltage side voltage of each month in the last year.
And 240, acquiring rated voltage corresponding to each gear in nameplate parameters of the transformer and rated voltage of the low-voltage side of the transformer.
The name plate parameters of the transformer comprise rated high-voltage voltages corresponding to all gears, high-voltage side rated voltages and low-voltage side rated voltages of the transformer, and data in the name plate parameters of the transformer can be directly acquired.
And step 250, dividing the rated voltage corresponding to each gear by the rated voltage of the low-voltage side to obtain the transformation ratio corresponding to each gear of the transformer.
Specifically, if the rated voltage of the low-voltage side of the transformer is 315V, and the rated high-voltage corresponding to the 1-gear of the transformer is 38850V, the transformation ratio corresponding to the 1-gear is 123.3(38850V/315V), and thus the transformation ratio corresponding to each gear of the transformer is obtained.
And step 260, calculating the average voltage of the low-voltage side of the transformer in each preset time interval under each gear based on the average voltage of the high-voltage side of the transformer in each preset time interval and the transformation ratio of the transformer.
For example, the preset time interval is a month, the high-voltage-side monthly average voltage corresponding to the 1-gear position of the transformer in the last 1 month is 37125V, the transformation ratio corresponding to the 1-gear position is 123.3, the low-voltage-side monthly average voltage of the 1-month transformer corresponding to the 1-gear position is 301.1V, and the low-voltage-side average voltage corresponding to each gear position of the transformer in each last month can be calculated. For example, five gear positions of the transformer are taken as an example, the calculated average voltage of the transformer on the low-voltage side of each month under each gear position can be represented by the matrix A
Wherein, U5-1Indicating the average voltage on the low side of the transformer for 1 month in the fifth gear, i.e. Ui-jRepresents the average voltage on the low-voltage side of the transformer in j months under i gear.
And step 270, determining the optimal gear of the transformer within the preset time based on the relation between the historical direct-current voltage of the inverter and the average voltage of the low-voltage side of the transformer and the efficiency characteristic of the inverter.
Specifically, the preset time interval is month as an example, and after the matrix a is obtained through calculation, it is determined that the normal operation condition of the inverter is satisfied
(U1For the AC output voltage of the inverter, U2For the low-side voltage of the transformer, UStraight barIs the dc input voltage of the inverter), i.e., a set B of voltage components selected in each column of the matrix a that satisfy the inequality condition described abovej，BjSet of average voltages on the low voltage side indicating that j month satisfies the condition, in set BjTo determine the maximum value Uj-k＝Max(Bj)，Uj-kAnd the average voltage of the low-voltage side of the transformer with the maximum voltage value of j months under the k gear is represented, and the gear k corresponding to the maximum voltage value is the best gear of the month. The optimal gear of the transformer in each month of the year can be determined according to the optimal gear of the transformer in each month of the last year, if the optimal gear determined in january of the last year is the fifth gear, the fifth gear can be used as the optimal gear of january of the present year, the optimal gears of the transformer in each month of the last year can be obtained correspondingly, the optimal gear of the transformer in each month of the last year can be determined at the beginning of the present year, and the optimal gear of each month of the present year can be determined according to the gear condition of the last year. Of course, the average voltage of the month in this year may also be determined according to the average voltage of the month in the last year, the previous year and the previous years, so as to determine the optimal gear of each month in this year, that is, the preset time is determined according to the actual situation, and is not limited herein.
In the method for determining the gear of the transformer provided by this embodiment, the historical dc voltage data of the inverter and the historical voltage data of the high-voltage side of the transformer in the preset time are obtained, and the average voltage of the low-voltage side of the transformer in each preset time interval under each gear is calculated according to the transformation ratio corresponding to each gear of the transformer, so that the optimal gear of the transformer in the preset time is determined based on the relationship between the historical dc voltage of the inverter and the voltage of the low-voltage side of the transformer and the efficiency characteristic of the inverter. Compared with the existing method which only considers the influence of the power grid voltage deviation on the gear adjustment of the transformer, the method provided by the embodiment determines the optimal gear of the transformer within the preset time based on the relation between the historical direct-current voltage of the inverter and the voltage of the low-voltage side of the transformer and the efficiency characteristic of the inverter, and ensures that the inverter has higher operation efficiency in the normal working state.
EXAMPLE III
Fig. 3 is a flowchart of a transformer gear determination method according to a third embodiment of the present invention, which may be based on the first embodiment, and referring to fig. 3, the transformer gear determination method specifically includes the following steps:
and 310, acquiring historical direct current voltage data of the inverter and historical voltage data of the high-voltage side of the transformer in preset time.
And 320, calculating the voltage of the low-voltage side of the transformer under each gear according to the historical voltage data of the high-voltage side of the transformer.
Step 330, based on
Obtaining a low-voltage side average voltage set meeting the conditions; wherein, U1For the AC output voltage of the inverter, U2For the low-side voltage of the transformer, UStraight barIs the dc input voltage of the inverter.
Specifically, the ac output voltage of the inverter, the low-voltage side voltage of the transformer, and the dc input voltage both need to satisfy the above inequality, the inverter can operate normally, and when the inequality is satisfied, the higher the ac output voltage of the inverter, the higher the efficiency of the inverter. And taking the preset time as the last year and the preset time interval as an example of a month, and determining a set of a plurality of voltage values meeting the inequality condition in the obtained low-voltage side voltage of the transformer in each gear in each month in the last year.
And step 340, taking the gear corresponding to the maximum value in the set as the optimal gear.
Specifically, in the set of low-voltage-side voltages of the transformer in each shift stage in the last month satisfying the inequality condition, the shift stage corresponding to the maximum voltage value is determined as the optimal shift stage in the current month, that is, the most efficient voltage for the inverter is determined from the low-voltage-side voltages of the transformer, and the shift stage corresponding to the voltage is the optimal shift stage.
And 350, calculating the lowest direct current voltage of the photovoltaic module at the upper limit of the working temperature according to the operating parameters of the photovoltaic module.
In particular, according to the maximum operating temperature T of the photovoltaic modulecellFormula Tcell＝Tair+ 25. G/0.8, wherein, TairThe maximum temperature of the corresponding month is shown, G represents the real-time irradiance, and 1kW/m can be taken2And calculating to obtain the highest working temperature T of the photovoltaic module when the ambient temperature of the month is highestcellAnd according to the calculation formula V of the lowest direct current voltage of the photovoltaic modulemp(min)＝VSTC·[1+(Tcell-25)·γ]Wherein the parameter gamma of the photovoltaic module is the voltage temperature coefficient of the module, VSTCMaximum power point voltage, gamma and V, measured for the module at STCSTCAll can be obtained by photovoltaic module data plate, can calculate from this and obtain Vmp(min)。
And step 360, when the lowest direct current voltage is larger than the lower limit of the MPPT voltage range of the inverter, determining that the gear adjustment of the transformer is correct.
Specifically, the condition that the minimum direct current voltage of the photovoltaic module needs to meet is that
Wherein n represents the serial number of the photovoltaic modules, n can be 22, when
After the gear of the transformer is determined, the inverter MPPT can normally work at the highest air temperature, namely, the gear can be determined to be the optimal gear of the transformer in the corresponding month.
Compared with the existing method in which only the influence of the grid voltage deviation on the adjustment of the gear of the transformer is considered, the method provided by the embodiment determines the optimal gear of the transformer within the preset time based on the relation between the historical direct-current voltage of the inverter and the voltage of the low-voltage side of the transformer and the efficiency characteristic of the inverter, ensures that the inverter has higher operating efficiency in a normal working state, and verifies the optimal gear after determining the optimal gear so as to improve the reliability of the determination of the optimal gear.
Example four
The present embodiment is an example of a month, and describes a method for determining a gear position of a transformer according to an embodiment of the present invention, where the method includes:
the method comprises the following steps: the method comprises the steps of collecting operating parameters of a certain power station.
Illustratively, table 1 illustrates the operating parameters of a certain photovoltaic power plant, and the operating parameters collected in the last month of february are as follows:
TABLE 1 operating parameters of a certain photovoltaic plant
According to the table, the collected direct current voltage and the collected high-voltage side voltage are respectively summed, and the sum result is averaged, so that the direct current monthly average voltage of the inverter in the month of May is 580V, and the high-voltage side monthly average voltage of the transformer is 36794V.
Step two: and calculating the transformation ratio corresponding to each gear of the transformer.
Illustratively, table 2 illustrates nameplate parameters of the transformer, which are as follows:
TABLE 2 Nameplate parameters of transformers
The ratio corresponding to the 1-gear is the rated high-voltage 38850V of the 1-gear divided by the rated voltage 315V of the low-voltage side, that is, the ratio corresponding to the 1-gear is 38850V/315V 123.3, and accordingly the ratio of each gear can be calculated, table 3 shows the ratio of the transformer in each gear, and the calculated ratio of each gear of the transformer is as follows:
TABLE 3 transformation ratio of transformers
| 1 st gear | 2-gear | 3 grade | 4-gear | 5-gear |
| 123.3 | 120.4 | 117.5 | 114.5 | 111.6 |
Step three: and determining the optimal gear of the transformer.
Specifically, according to the transformation ratio corresponding to each gear of the transformer and the voltage of the month of wu, the low-voltage side voltage matrix a of the box transformer in each gear in each month can be calculated as follows:
wherein, U5-1Represents the low-voltage side monthly average voltage, U, corresponding to the 1-gear of the transformer in May5-2The low-voltage side monthly average voltage corresponding to the 2-gear of the transformer in May is represented, the low-voltage side monthly average voltage of each gear in May is obtained by analogy, and the low-voltage side monthly average voltage of each gear in May is obtained according to the formula
B satisfying the condition set can be obtained5The following were used:
get B5Maximum value of U5-5Therefore, the optimal gear in the last month of May is determined to be 5 th gear, and 5 th gear can be used as the optimal gear in the month of May in this year.
Step four: and verifying the determined optimal gear of the transformer according to whether the MPPT of the inverter can normally work and the temperature operation condition of the photovoltaic module.
Specifically, the maximum air temperature in the last 5 months is 36 ℃ according to historical meteorological data, and the maximum working temperature T of the photovoltaic module is determinedcellFormula Tcell＝Tair+ 25. G/0.8, wherein, TairThe maximum temperature of the corresponding month is shown, G represents the real-time irradiance, and 1kW/m can be taken2And the maximum working temperature T of the photovoltaic module can be calculatedcell36+25 × 1/0.8 ═ 67.25 ℃, and according to the calculation formula V of the minimum operating voltage of the photovoltaic modulemp(min)＝VSTC·[1+(Tcell-25)·γ]Wherein the parameter gamma of the photovoltaic module is the voltage temperature coefficient of the module, and the parameter is obtained by a nameplate of the photovoltaic module, if the obtained gamma is-0.4%, and V isSTCObtaining the maximum power point voltage of the module measured at STC, the parameter being obtained from the photovoltaic module nameplate, e.g. obtainingV ofSTCIs 31.54V, V can be calculatedmp(min)＝31.54×[1+(67.25-25)×(-0.4％)]＝36.9V。
The inverter MPPT normally works under the condition that
Wherein n represents the serial number of the photovoltaic modules, and n can be 22, so that the photovoltaic module can be obtained
Therefore, when the transformer is shifted to the 5 th gear, the inverter MPPT can normally work at the highest air temperature, and the 5 th gear can be determined as the optimal gear of the transformer in May.
Compared with the existing method in which only the influence of the grid voltage deviation on the gear adjustment of the transformer is considered, the method provided by the embodiment determines the optimal gear of the transformer within the preset time based on the relation between the historical direct-current voltage of the inverter and the voltage of the low-voltage side of the transformer and the efficiency characteristic of the inverter, and ensures that the inverter has higher operating efficiency in the normal working state.
EXAMPLE five
Fig. 4 is a schematic structural diagram of a transformer gear determining device according to a fifth embodiment of the present invention, which is applied to a photovoltaic power generation system, where the photovoltaic power generation system includes a photovoltaic module, an inverter, and a transformer, and the transformer gear determining device includes: an acquisition module 410, a calculation module 420, and a gear determination module 430; wherein the content of the first and second substances,
the obtaining module 410 is configured to obtain historical dc voltage data of the inverter and historical voltage data of the high-voltage side of the transformer within a preset time; the calculation module 420 is configured to calculate voltages of low-voltage sides of the transformer at various gears according to historical voltage data of the high-voltage side of the transformer; the gear determination module 430 is configured to determine an optimal gear of the transformer within a preset time based on a relationship between a historical dc voltage of the inverter and a voltage of a low-voltage side of the transformer and an efficiency characteristic of the inverter.
On the basis of the above embodiment, the calculation module 420 may include a dc voltage determination submodule, a high-voltage side voltage determination submodule, a transformation ratio calculation submodule, and a low-voltage side voltage calculation submodule, where the dc voltage determination submodule is configured to determine an average dc voltage of the inverter within each preset time interval according to historical dc voltage data of the inverter; the high-voltage side voltage determining submodule is used for determining the average voltage of the high-voltage side of the transformer in each preset time interval according to the historical voltage data of the high-voltage side of the transformer; the transformation ratio calculation submodule is used for calculating the transformation ratio of the transformer corresponding to each gear of the transformer; and the low-voltage side voltage calculating submodule is used for calculating the low-voltage side average voltage of the transformer in each preset time interval under each gear based on the average voltage of the high-voltage side of the transformer in each preset time interval and the transformation ratio of the transformer.
Preferably, the transformation ratio calculation submodule comprises a voltage acquisition unit and a transformation ratio calculation unit, wherein the voltage acquisition unit is used for acquiring rated voltage corresponding to each gear in a nameplate parameter of the transformer and rated voltage of a low-voltage side of the transformer; and the transformation ratio calculation unit is used for comparing the rated voltage corresponding to each gear with the rated voltage on the low-voltage side to obtain the transformation ratio corresponding to each gear of the transformer.
In one embodiment, the gear determination module 430 may include a gear determination sub-module configured to determine a voltage that maximizes the efficiency of the inverter from the low side voltage of the transformer, the voltage corresponding to the gear being the optimal gear.
Preferably, the gear determination submodule includes a set determination unit for determining the gear to be used for the shift operation based on the gear information
Obtaining a low-voltage side average voltage set meeting the conditions; the gear determining unit is used for taking the gear corresponding to the maximum value in the set as the optimal gear.
In an embodiment, the transformer gear determination device may further include a verification module, and the verification module is configured to verify the determined optimal gear of the transformer according to whether the inverter MPPT can work normally and the temperature operation condition of the photovoltaic module.
Preferably, the check module comprises a voltage calculation submodule and a gear determination submodule, and the voltage calculation submodule is used for calculating the lowest working voltage of the photovoltaic module at the upper limit of the working temperature according to the operating parameters of the photovoltaic module; and the gear determining submodule is used for determining that the gear adjustment of the transformer is correct when the lowest working voltage is greater than the lowest direct-current voltage of the inverter MPPT in normal operation.
The transformer gear determining device provided by the embodiment has the corresponding beneficial effects of the transformer gear determining method.
EXAMPLE six
Fig. 5 is a block diagram of a photovoltaic power generation system according to a sixth embodiment of the present invention, where the photovoltaic power generation system includes a photovoltaic module 10, an inverter 20, and a transformer 30, and further includes a transformer position determination apparatus according to any embodiment of the present invention.
The photovoltaic power generation system provided by the embodiment has the corresponding beneficial effects of the transformer gear determination method.
It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.
Claims (10)
1. A transformer gear determination method is applied to a photovoltaic power generation system, the photovoltaic power generation system comprises a photovoltaic component, an inverter and a transformer, and the transformer gear determination method comprises the following steps:
acquiring historical direct-current voltage data of the inverter and historical voltage data of the high-voltage side of the transformer within preset time;
calculating the voltage of the low-voltage side of the transformer under each gear according to the historical voltage data of the high-voltage side of the transformer;
determining an optimal gear of the transformer within a preset time based on a relationship between a historical direct-current voltage of the inverter and a voltage on a low-voltage side of the transformer and an efficiency characteristic of the inverter.
2. The method according to claim 1, wherein the preset time includes at least one preset time interval, and before calculating the voltage of the low-voltage side of the transformer at each gear according to the historical voltage data of the high-voltage side of the transformer, the method further comprises:
determining the average direct current voltage of the inverter in each preset time interval according to historical direct current voltage data of the inverter;
determining the average voltage of the high-voltage side of the transformer in each preset time interval according to the historical voltage data of the high-voltage side of the transformer;
calculating the voltage of the low-voltage side of the transformer under each gear according to the historical voltage data of the high-voltage side of the transformer, wherein the calculation comprises the following steps:
calculating the transformation ratio of the transformer corresponding to each gear of the transformer;
and calculating the average voltage of the low-voltage side of the transformer in each preset time interval under each gear based on the average voltage of the high-voltage side of the transformer in each preset time interval and the transformation ratio of the transformer.
3. The method according to claim 2, wherein the preset time interval is a month or a quarter.
4. The method of claim 2, wherein calculating the transformer ratio for each gear of the transformer comprises:
obtaining rated voltage corresponding to each gear in nameplate parameters of the transformer and rated voltage of a low-voltage side of the transformer;
and dividing the rated voltage corresponding to each gear by the rated voltage of the low-voltage side to obtain the transformation ratio corresponding to each gear of the transformer.
5. The method of claim 1, wherein determining the optimal gear of the transformer for a preset time based on a relationship between a historical dc voltage of the inverter and a voltage of a low voltage side of the transformer and an efficiency characteristic of the inverter comprises:
and determining the voltage which enables the efficiency of the inverter to be the highest from the low-voltage side voltage corresponding to each gear of the transformer in each preset time interval, wherein the gear corresponding to the voltage is the optimal gear.
6. The method of claim 5, wherein determining a voltage for maximizing the efficiency of the inverter from the low-side voltage corresponding to each gear of the transformer in each of the preset time intervals, the gear corresponding to the voltage being an optimal gear, comprises:
based on
Obtaining a low-voltage side average voltage set meeting the conditions; wherein, U1Is the AC output voltage of the inverter, U2Is the low side voltage, U, of the transformerStraight barIs the DC input voltage of the inverter;
and taking the gear corresponding to the maximum value in the set as the optimal gear.
7. The method of claim 1, wherein after determining the optimal gear of the transformer for a preset time, the method further comprises:
and verifying the determined optimal gear of the transformer according to whether the MPPT of the inverter can normally work and the temperature operation condition of the photovoltaic module.
8. The method of claim 7, wherein the verifying the determined optimal tap position of the transformer according to whether the inverter MPPT is operating properly and the temperature operating condition of the photovoltaic module comprises:
calculating the lowest direct current voltage of the photovoltaic module at the upper limit of the working temperature according to the operating parameters of the photovoltaic module; wherein the maximum working temperature T corresponding to the upper limit of the working temperature of the photovoltaic modulecellIs calculated by the formula Tcell＝Tair+25·G/0.8，TairThe maximum temperature of the ambient temperature in the preset time interval is represented, G represents the real-time irradiance, and the lowest direct-current voltage V of the photovoltaic modulemp(min)Is calculated by the formula Vmp(min)＝VSTC·[1+(Tcell-25)·γ]Gamma is the voltage temperature coefficient of the photovoltaic module, VSTCThe maximum power point voltage measured by the photovoltaic module under STC;
when the lowest direct current voltage is larger than the lower limit of the MPPT voltage range of the inverter, the transformer gear is determined to be adjusted correctly; wherein the minimum DC voltage is required to satisfy
n represents the serial number of the photovoltaic modules, U1Is the AC output voltage of the inverter.
9. A transformer gear determining device is applied to a photovoltaic power generation system, the photovoltaic power generation system comprises a photovoltaic component, an inverter and a transformer, and the transformer gear determining device comprises:
the acquisition module is used for acquiring historical direct-current voltage data of the inverter and historical voltage data of the high-voltage side of the transformer within preset time;
the calculation module is used for calculating the voltage of the low-voltage side of the transformer under each gear according to the historical voltage data of the high-voltage side of the transformer;
a gear determination module to determine an optimal gear of the transformer within a preset time based on a relationship between a historical direct current voltage of the inverter and a voltage of a low voltage side of the transformer and an efficiency characteristic of the inverter.
10. A photovoltaic power generation system comprising a photovoltaic module, an inverter, and a transformer, further comprising the transformer gear determination apparatus of claim 9.
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| DE102011083720A1 (en) * | 2011-09-29 | 2013-04-04 | Siemens Aktiengesellschaft | Apparatus for connecting solar generator to electrical alternating current (AC) system of photovoltaic plant, has transformer with changeable transmission ratio, to transform AC voltages of different sizes to preset AC supply voltage |
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| DE102011083720A1 (en) * | 2011-09-29 | 2013-04-04 | Siemens Aktiengesellschaft | Apparatus for connecting solar generator to electrical alternating current (AC) system of photovoltaic plant, has transformer with changeable transmission ratio, to transform AC voltages of different sizes to preset AC supply voltage |
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