阅读说明：本技术 变压器档位确定方法、装置及光伏发电系统 (Transformer gear determination method and device and photovoltaic power generation system ) 是由 方俊峰 杨宗军 于 2019-11-04 设计创作，主要内容包括：本发明实施例公开了一种变压器档位确定方法、装置及光伏发电系统,变压器档位确定方法应用于光伏发电系统,光伏发电系统包括光伏组件、逆变器和变压器,变压器档位确定方法包括：获取预设时间内的逆变器的历史直流电压数据和变压器高压侧的历史电压数据；根据变压器高压侧的历史电压数据,计算变压器各个档位下的低压侧的电压；基于逆变器的历史直流电压和变压器的低压侧的电压的关系以及逆变器的效率特性,确定预设时间内的变压器的最佳档位。本发明实施例提供的变压器档位确定方法,能够保证逆变器在正常工作状态下有较高的运行效率。(The embodiment of the invention discloses transformer gear determining methods and devices 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, the transformer gear determining method comprises the steps of obtaining historical direct current voltage data of the inverter and historical voltage data of a high-voltage side of the transformer in preset time, calculating voltage of a 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 an optimal gear of the transformer in 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 transformers is applied to a photovoltaic power generation system, the photovoltaic power generation system comprises a photovoltaic assembly, an inverter and a transformer, and the method for determining the gear of the transformers 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 of claim 1, wherein the preset time includes at least preset time intervals, and before calculating the voltage of the low-voltage side of the transformer in 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

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 module_cellIs calculated by the formula T_cell＝T_air+25·G/0.8，T_airThe 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 module_mp(min)Is calculated by the formula V_mp(min)＝V_STC·[1+(T_cell-25)·γ]Gamma is the voltage temperature coefficient of the illumination assembly, V_STCThe 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

The gear determining device of kinds of transformers, characterized by, apply to the photovoltaic power generation system, the photovoltaic power generation system includes photovoltaic module, inverter and transformer, the gear determining device of said transformer 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;

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, which comprises a photovoltaic module, an inverter and a transformer, and further comprises the transformer gear position determination device of claim 9.

Technical Field

The embodiment of the invention relates to a transformer gear shifting technology, in particular to a method and a device for determining transformer gears 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 transformer gear determining methods and devices and a photovoltaic power generation system, so that an inverter has higher operation efficiency in a normal working state.

, the embodiment of the invention provides transformer gear determination methods, a photovoltaic power station 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 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 preset time intervals, 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, U_{Straight bar}Is 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:

according to the operating parameters of the photovoltaic module, calculating the maximum working temperature upper limit of the photovoltaic moduleA low DC voltage; wherein, the maximum working temperature T corresponding to the upper limit of the working temperature of the photovoltaic module_cellIs calculated by the formula T_cell＝T_air+25·G/0.8，T_airThe 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 module_mp(min)Is calculated by the formula V_mp(min)＝V_STC·[1+(T_cell-25)·γ]Gamma is the voltage temperature coefficient of the illumination assembly, V_STCThe 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 transformer gear determination devices, which are 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 determination 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, the embodiment of the present invention further provides photovoltaic power generation systems, which include a photovoltaic module, an inverter, and a transformer, and further include the transformer gear determination apparatus 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 flow chart of a transformer tap position determination method provided by embodiment of the present invention;

FIG. 2 is a flowchart illustrating a method for determining the gear positions of transformers according to a second embodiment of the present invention;

FIG. 3 is a flowchart illustrating a gear determination method for transformers according to a third embodiment of the present invention;

fig. 4 is a block diagram of kinds of transformer gear position determination devices according to a fifth embodiment of the present invention;

fig. 5 is a block diagram of photovoltaic power generation systems according to a sixth embodiment of the present invention.

Detailed Description

The present invention will now be described in further detail with reference to the drawings and examples, it being understood that the specific embodiments herein described are merely illustrative of and not restrictive on the broad invention, and it should be further noted that for the purposes of description, only some, but not all, of the structures associated with the present invention are shown in the drawings.