阅读说明：本技术 光伏i-v曲线测试系统、测试方法及光伏设备 (Photovoltaic I-V curve test system, test method and photovoltaic equipment ) 是由 隋馨 赵龙 张林江 葛鹏霄 徐亮辉 杨青斌 于 2021-09-13 设计创作，主要内容包括：本发明适用于光伏技术领域,提供一种光伏I-V曲线测试系统、测试方法及光伏设备,该光伏I-V曲线测试系统包括：光伏组件,汇流装置,逆变器,可调负载,检测单元,控制单元。通过在测试时控制逆变器处于离网状态,将逆变器调整为电压源模式,并接入可调负载,然后调节逆变器的工作电压,使其在0至额定电压范围变动,并获取各光伏组串的电压和电流,以此得到全电压下的光伏I-V曲线,根据该光伏曲线可准确的判断光伏组件是否存在故障或电流失配等问题。相对于现有的光伏I-V曲线测试装置,本实施例的光伏I-V测试系统可测试全电压范围内的光伏I-V曲线,因此可对光伏组件的运行状态进行精准的监控,并进行精细化的管理。(The invention is suitable for the technical field of photovoltaics, and provides a photovoltaic I-V curve test system, a test method and photovoltaic equipment, wherein the photovoltaic I-V curve test system comprises: the photovoltaic module, the device that converges, the dc-to-ac converter, adjustable load, detecting element, the control unit. The inverter is controlled to be in an off-grid state during testing, the inverter is adjusted to be in a voltage source mode, an adjustable load is connected, then the working voltage of the inverter is adjusted to be changed within the range from 0 to a rated voltage, the voltage and the current of each photovoltaic group string are obtained, a photovoltaic I-V curve under the full voltage is obtained, and whether a photovoltaic module has a fault or current mismatch and other problems can be accurately judged according to the photovoltaic curve. Compared with the existing photovoltaic I-V curve testing device, the photovoltaic I-V testing system can test the photovoltaic I-V curve in the full voltage range, so that the running state of the photovoltaic assembly can be accurately monitored, and fine management can be performed.)

1. A photovoltaic I-V curve test system is characterized in that,

the photovoltaic I-V curve test system comprises:

the photovoltaic module consists of a plurality of photovoltaic string;

the confluence device is connected with the photovoltaic assembly and is used for converging the photovoltaic strings;

an inverter connected to the bus device;

the adjustable load is arranged in the inverter and is used for accessing the inverter when the inverter is in an off-grid state;

the detection unit is arranged in the confluence device, is connected with each photovoltaic group string and is used for detecting the current and the voltage of each photovoltaic group string;

a control unit connected with the confluence device, the inverter, the adjustable load and the detection unit,

the control unit is used for sending control signals to the inverter and the adjustable load during testing; the photovoltaic I-V curve acquisition unit is used for receiving data of the detection unit in an inversion voltage adjustment range of the inverter and acquiring a photovoltaic I-V curve in a full voltage range according to the data of the detection unit;

the adjustable load is used for accessing the inverter according to the control signal;

the inverter is used for controlling the inverter to be in an off-grid state according to the control signal and adjusting the inverter to be in a voltage source mode; and adjusting the inversion voltage of the inverter to enable the inversion voltage to be changed within the range from 0 to the rated voltage.

2. The photovoltaic I-V curve test system of claim 1,

the inverter also comprises a transformer connected with the inverter, and the low-voltage side of the transformer is connected with the inverter.

3. The photovoltaic I-V curve test system of claim 1,

and a first switch connected with the low-voltage side of the transformer is arranged in the inverter and used for disconnecting when a photovoltaic I-V curve is measured so as to enable the inverter to be in an off-grid state.

4. The photovoltaic I-V curve test system of claim 1,

and a second switch is arranged between the adjustable load and the inverter and is used for closing when the inverter is in an off-grid state.

5. The photovoltaic I-V curve test system of claim 1,

the transformer is characterized by further comprising a power grid connected with the transformer, the high-voltage side of the transformer is connected with the power grid, and the power grid is connected with the control unit.

6. The photovoltaic I-V curve test system of claim 5,

the inverter is centralized, distributed or in a group string mode.

7. A photovoltaic I-V curve testing method is characterized by comprising the following steps:

controlling an inverter to be in an off-grid state, adjusting the inverter to a voltage source mode, and connecting an adjustable load to the inverter;

adjusting the working voltage of the inverter to change within the range from 0 to the rated voltage;

acquiring the voltage and current of each photovoltaic group string when the working voltage of the inverter is changed within the range from 0 to the rated voltage;

and obtaining a photovoltaic I-V curve according to the voltage and the current of each photovoltaic group string.

8. The method for photovoltaic I-V curve testing according to claim 7, wherein controlling the inverter in an off-grid state and engaging an adjustable load comprises:

when the inverter is in an off-grid state, acquiring the opening voltage of the photovoltaic module;

adjusting the adjustable load to adapt to the open circuit voltage.

9. The method for testing a photovoltaic I-V curve according to claim 7, wherein the step of obtaining a photovoltaic curve according to the voltage and current of each photovoltaic string further comprises:

and analyzing the photovoltaic curve and judging whether the photovoltaic module has a fault or not.

10. A photovoltaic device comprising the test system of any one of the above 1 to 6 and a processor, wherein the processor is capable of operating the test method of any one of the above 7 to 9.

Technical Field

The invention belongs to the technical field of photovoltaics, and particularly relates to a photovoltaic I-V curve test system, a photovoltaic I-V curve test method and photovoltaic equipment.

Background

With the continuous expansion of the installed capacity of a photovoltaic power generation system, the aim of ensuring the high-efficiency and reliable operation of the photovoltaic power generation system becomes the pursuit of the whole industry. Since the photovoltaic system is installed outdoors and is continuously exposed to a relatively harsh environment, monitoring of the working state of the photovoltaic system is particularly important. The method for judging the working state of the photovoltaic system through the photovoltaic I-V curve is a method which is currently generally adopted.

In the existing photovoltaic system, a group-string inverter has a relatively wide range of I-V curve detection due to a two-pole conversion structure of the group-string inverter, but is limited by a DC-DC boosting range, and can still not detect an I-V curve in a full voltage range; the centralized and decentralized inverters are not provided with a DC-DC boosting mechanism, so that the detection range of the I-V curve is more limited, and theoretically, the I-V curve above the voltage of a starting point can only be detected. The detection of the I-V curves in the two specific voltage ranges is very disadvantageous to the state monitoring and fine management of the system.

Disclosure of Invention

The embodiment of the invention provides a photovoltaic I-V curve testing system, and aims to solve the problems that the existing I-V curve in a full voltage range cannot be detected, so that the running state of a photovoltaic system cannot be accurately monitored, and the current mismatch fault of the photovoltaic system cannot be quickly identified.

The embodiment of the invention is realized in such a way, and provides a stone photovoltaic I-V curve test system, which comprises: the photovoltaic module consists of a plurality of photovoltaic string; the confluence device is connected with the photovoltaic assembly and is used for converging the photovoltaic strings; an inverter connected to the bus device; the adjustable load is arranged in the inverter and is used for accessing the inverter when the inverter is in an off-grid state; the detection unit is arranged in the confluence device, is connected with each photovoltaic group string and is used for detecting the current and the voltage of each photovoltaic group string; the control unit is connected with the confluence device, the inverter, the adjustable load and the detection unit, and is used for sending control signals to the inverter and the adjustable load during testing; the photovoltaic I-V curve acquisition unit is used for receiving data of the detection unit in an inversion voltage adjustment range of the inverter and acquiring a photovoltaic I-V curve in a full voltage range according to the data of the detection unit; the adjustable load is used for accessing the inverter according to the control signal; the inverter is used for controlling the inverter to be in an off-grid state according to the control signal and adjusting the inverter to be in a voltage source mode; and adjusting the inversion voltage of the inverter to enable the inversion voltage to be changed within the range from 0 to the rated voltage.

Further, the inverter further comprises a transformer connected with the inverter, and the low-voltage side of the transformer is connected with the inverter.

Furthermore, a first switch connected with the low-voltage side of the transformer is arranged in the inverter and used for being disconnected when a photovoltaic I-V curve is measured, so that the inverter is in an off-grid state.

Further, a second switch is arranged between the adjustable load and the inverter and used for being closed when the inverter is in an off-grid state.

Furthermore, the transformer also comprises a power grid connected with the transformer, the high-voltage side of the transformer is connected with the power grid, and the power grid is connected with the control unit.

Further, the inverter is centralized, distributed or in a group string mode.

The embodiment of the invention also provides a photovoltaic I-V curve testing method, which comprises the following steps:

controlling an inverter to be in an off-grid state, adjusting the inverter to a voltage source mode, and connecting an adjustable load to the inverter;

adjusting the working voltage of the inverter to change within the range from 0 to the rated voltage;

acquiring the voltage and current of each photovoltaic group string when the working voltage of the inverter is changed within the range from 0 to the rated voltage;

and obtaining a photovoltaic I-V curve according to the voltage and the current of each photovoltaic group string.

Further, the controlling the inverter to be in an off-grid state and to be connected to the adjustable load comprises:

when the inverter is in an off-grid state, acquiring the opening voltage of the photovoltaic module;

adjusting the adjustable load to adapt to the open circuit voltage.

Further, the step of obtaining a photovoltaic curve according to the voltage and the current of each photovoltaic string further includes:

and analyzing the photovoltaic curve and judging whether the photovoltaic module has a fault or not.

The embodiment of the invention also provides photovoltaic equipment which comprises the photovoltaic I-V curve testing system and a processor, wherein the processor can operate the photovoltaic I-V curve testing method.

The photovoltaic I-V curve test system of the embodiment of the invention comprises: the photovoltaic module consists of a plurality of photovoltaic string; the confluence device is connected with the photovoltaic assembly and is used for converging the photovoltaic strings; an inverter connected to the bus device; the adjustable load is arranged in the inverter and is used for accessing the inverter when the inverter is in an off-grid state; the detection unit is arranged in the confluence device, is connected with each photovoltaic group string and is used for detecting the current and the voltage of each photovoltaic group string; the control unit is connected with the confluence device, the inverter, the adjustable load and the detection unit, and is used for sending control signals to the inverter and the adjustable load during testing; the photovoltaic I-V curve acquisition unit is used for receiving data of the detection unit in an inversion voltage adjustment range of the inverter and acquiring a photovoltaic I-V curve in a full voltage range according to the data of the detection unit; the adjustable load is used for accessing the inverter according to the control signal; the inverter is used for controlling the inverter to be in an off-grid state according to the control signal and adjusting the inverter to be in a voltage source mode; and adjusting the inversion voltage of the inverter to enable the inversion voltage to be changed within the range from 0 to the rated voltage. According to the testing system, when the inverter is in an off-grid state, the adjustable load is connected, then the working voltage of the inverter is adjusted to enable the inverter to change from 0 to a rated voltage, the voltage and the current of each photovoltaic group string are obtained, a photovoltaic I-V curve under the full voltage is obtained, and whether faults or current mismatch and other problems exist in the photovoltaic module can be accurately judged according to the photovoltaic I-V curve.

Drawings

FIG. 1 is a schematic structural diagram of a photovoltaic I-V curve test system according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a corresponding relationship between test points of photovoltaic I-V curves in the embodiment of the invention;

FIG. 3 is a schematic of a photovoltaic I-V curve for a photovoltaic string in accordance with an embodiment of the present invention;

fig. 4 is a schematic of a photovoltaic I-V curve for a plurality of photovoltaic strings in accordance with an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

The invention provides a photovoltaic I-V curve testing system, which is characterized in that when an inverter is in an off-grid state, the inverter is adjusted to a voltage source mode, an adjustable load is connected, then the working voltage of the inverter is adjusted to change from 0 to a rated voltage, then the voltage and the current of each photovoltaic group string are obtained when the inverter voltage changes from 0 to the rated voltage, so that a photovoltaic I-V curve under the full voltage is obtained, and whether a photovoltaic module has faults or current mismatch and other problems can be accurately judged according to the photovoltaic I-V curve. Through the test system, the working state of the photovoltaic assembly can be accurately monitored and refined management can be performed.

Example one

As shown in fig. 1, the present embodiment provides a photovoltaic I-V curve testing system, which includes: the photovoltaic module consists of a plurality of photovoltaic string; the confluence device is connected with the photovoltaic module and is used for converging the photovoltaic group strings; an inverter connected to the bus device; the adjustable load is arranged in the inverter and is used for accessing the inverter when the inverter is in an off-grid state; the detection unit is arranged in the confluence device, is connected with each photovoltaic group string and is used for detecting the current and the voltage of each photovoltaic group string; the control unit is connected with the confluence device, the inverter, the adjustable load and the detection unit, and is used for sending control signals to the inverter and the adjustable load during testing; the photovoltaic I-V curve acquisition unit is used for receiving data of the detection unit in an inversion voltage adjustment range of the inverter and acquiring a photovoltaic I-V curve in a full voltage range according to the data of the detection unit; the adjustable load is used for accessing the inverter according to the control signal; the inverter is used for controlling the inverter to be in an off-grid state according to the control signal and adjusting the inverter to be in a voltage source mode; and adjusting the inversion voltage of the inverter to enable the inversion voltage to be changed within the range from 0 to the rated voltage.

In this embodiment, the detection unit is a current sensor and a voltage sensor, and is connected to each photovoltaic string for measuring the voltage and the current of each photovoltaic string. Wherein, the test system comprises a plurality of confluence devices; a plurality of photovoltaic group strings are converged at one converging device, and each inverter corresponds to a plurality of converging devices.

In the photovoltaic power generation process, when the voltage of the photovoltaic module reaches the lowest starting voltage of the inverter, the inverter is in a grid-connected state, so that the full-voltage photovoltaic I-V curve of the photovoltaic module cannot be detected in the grid-connected state. When the photovoltaic I-V curve testing system is used for testing, the inverter is controlled to be in an off-grid state, and the inverter is adjusted from a current source mode to a voltage source mode.

Specifically, when the inverter is in an off-grid state, the open-circuit voltage of the photovoltaic module is obtained, the inverter is not connected to an adjustable load at the moment, and the open-circuit voltage at the moment is the maximum voltage of the photovoltaic module. And adjusting the adjustable load according to the obtained opening voltage of the photovoltaic module to enable the adjustable load to be matched with the opening voltage, and then connecting the adjustable load to the inverter to ensure that the adjustment range of the inverter voltage of the inverter is changed within the range from 0 to the rated voltage.

Further, the test system further comprises a transformer T1 connected with the inverter, and the low-voltage side of the transformer T1 is connected with the inverter.

In the embodiment, a first switch Q1 connected with the low-voltage side of the transformer T1 is arranged inside the inverter and used for being switched off when a photovoltaic I-V curve is measured, so that the inverter is in an off-grid state. And after the test is finished, the first switch Q1 is closed, so that the inverter is in a grid-connected state.

Further, a second switch Q2 is provided between the adjustable load and the inverter for closing when the inverter is in an off-grid state.

In this embodiment, the second switch Q2 is closed to switch the adjustable load into the inverter when testing the photovoltaic I-V curve. Before switching in the inverter, the switched-in load needs to be determined. And adjusting the adjustable load connected into the inverter according to the opening voltage of the photovoltaic module.

Specifically, the adjustable load is an adjustable electronic load, when the inverter is off-grid, the second switch Q2 is closed, the opening voltage of the photovoltaic module is obtained at this time, and the opening voltage at this time is the maximum opening voltage of the photovoltaic module. And the control unit calculates to obtain the optimal load according to the obtained maximum opening voltage. The adjustable electronic load comprises a first control module, the first control module receives a control signal of the control unit, the first control module adjusts the adjustable electronic load to the optimal load position according to the control signal, and then closes a second switch Q2 to connect the adjusted optimal load to the inverter. The optimal load is used for ensuring that the inversion voltage of the inverter can be adjusted to 0 volt, and if the load is smaller than the calculated optimal load, the adjustment range of the inversion voltage cannot reach 0. Therefore, the adjustment range of the inverter voltage of the inverter is influenced, the range of the opening voltage of the photovoltaic module is further influenced, and a photovoltaic I-V curve in the full voltage range cannot be obtained.

Further, the test system further comprises a power grid connected with the transformer T1, the high-voltage side of the transformer T1 is connected with the power grid, and the power grid is connected with the control unit.

In this embodiment, a second control module at the power grid end is connected with the control unit, and the second control module acquires the photovoltaic I-V curve obtained by the control unit, monitors the operating state of the photovoltaic module according to the photovoltaic I-V curve, and further determines whether the photovoltaic module is abnormal or whether a current mismatch condition exists.

In another embodiment, the control unit may be provided at the grid side, and the detection unit is connected to the grid side to transmit the detection data to the control unit at the grid side. Specifically, the control unit can be arranged at a power grid end, the junction device and the inverter are both connected with the power grid end, the control unit at the power grid end sends a test signal, the first switch Q1 is controlled to be switched off at the moment, meanwhile, the second switch Q2 is switched on, the inverter is controlled to adjust the inversion voltage, the inversion voltage is enabled to be changed within the range from 0 to the rated voltage, and therefore the photovoltaic I-V curve within the full voltage range is obtained.

It is understood that in other embodiments, the control unit may be disposed at the inverter side, and the detection unit directly transmits the detection data to the inverter.

Furthermore, the inverter comprises an inverter bridge, control logic and a filter circuit, wherein the control logic comprises a controller, and the controller is connected with the control unit and is used for controlling the inverter to regulate the inverter voltage.

In this embodiment, the control unit may be integrated on a controller of the inverter, and in an off-grid state, the inverter is adjusted to a voltage source mode, and the adjustable load is adjusted and connected to the inverter; controlling an inverter to adjust the inversion voltage, so that the inversion voltage ranges from 0 to the rated voltage; and receiving data of the detection unit in the inversion voltage adjustment range, and obtaining a photovoltaic I-V curve in the full voltage range according to the data of the detection unit.

Further, the control unit and the detection unit are connected through an RS485 communication interface or through an optical fiber.

In the embodiment, the control unit and the detection unit are connected through RS485 communication interfaces on the bus device and the inverter. In other embodiments, the connection may also be through an optical fiber, and this embodiment is not particularly limited.

Referring to fig. 2, in the present embodiment, the rated voltage of the inverter voltage is U₀Maximum power of adjustable load is P₀The open voltage of the photovoltaic string is V_CS. In the process of changing the inversion voltage, the lowest value of the inversion voltage is 0.01 percent U₀And the maximum value of the current of the photovoltaic string at the moment is I_CS. The regulation range of the inverter voltage can be regarded as 0 to U₀The specific adjustment ratio can be set as required. For example, in a proportion of 1%, until U is reached₀. Or gradually increased according to the trend of 0.01 percent until U is reached₀. And testing according to the change rate of the regulated voltage to sequentially obtain the voltage and the current of each photovoltaic group string.

Specifically, in the process of regulating the inversion voltage from low to high, the initial lowest value is 0.01 percent U₀To make the current of the photovoltaic string close to 0 wirelessly, and the current of the photovoltaic string is maximum I_CS. In the case of fixed loadIn this case, the load current decreases as the inverter voltage increases. Under the condition that the solar irradiance is stable, the voltage of the photovoltaic string can be increased along with the increase of the inverter inversion voltage, and the current of the photovoltaic string can be gradually reduced. When the inverter voltage rises to the rated voltage U₀And the working voltage of the photovoltaic string also reaches the maximum opening voltage V_CSAt this point, the I-V curve point of the full voltage range is tested.

It can be understood that, in the present embodiment, the variation trend of the inversion voltage can be adjusted from the highest value to the lowest value. During the process of regulating the inversion voltage from high to low, the maximum value is U₀At this time, the open voltage of the photovoltaic string is maximum V_CSAt this time, the current of the photovoltaic string is 0. With a fixed load, the load current increases with decreasing inverter voltage. Under the condition that the solar irradiance is stable, the voltage of the photovoltaic string can be reduced along with the reduction of the inverter inversion voltage, and the current of the photovoltaic string can be gradually increased. When the inversion voltage is reduced to 0.01% U₀When the inverter voltage is infinitely close to 0, the maximum value of the current of the photovoltaic string is I_CSAt this point, the I-V curve point of the full voltage range is tested. The voltage and current relationships corresponding to the test points at this time are shown in fig. 2.

Referring to fig. 3 and 4, in the present embodiment, a schematic diagram of a photovoltaic I-V curve can be drawn according to the corresponding diagram of fig. 2. The corresponding photovoltaic I-V curve of each photovoltaic string is shown in fig. 3. Photovoltaic I-V curves for multiple strings of photovoltaic groups can also be derived, as shown in fig. 4.

Referring to fig. 4, in an actual application process, a photovoltaic I-V curve is affected by conditions such as open voltage, irradiance, temperature, deputy, or actual internal damage. For example, the curves a and b in fig. 4 are curves for normal operation, with only one knee bend. And the curve c has a plurality of knee bends, which indicates that the curve c is an abnormal curve. Thus, the photovoltaic string corresponding to the c is abnormal.

In general, the weak deviation of the opening voltage and the short-circuit current of the photovoltaic module is influenced by the factors such as irradiance and temperature, but the problem of the photovoltaic module is judged if the opening voltage and the short-circuit current are too low, such as a d curve or a c curve with a plurality of knee bends. Therefore, the abnormity of the photovoltaic string and the reason of the abnormity can be diagnosed by analyzing the photovoltaic I-V curve.

Further, the inverters include, but are not limited to, centralized inverters, distributed inverters, and string-type inverters. The photovoltaic I-V curve test system of the embodiment can be suitable for various inverters and can test photovoltaic I-V curves of various inversion types.

Further, the voltage of the photovoltaic module includes photovoltaic systems of various voltage classes, such as: the photovoltaic system is suitable for photovoltaic systems with 1000V, 1500V, 2000V, 3000V and higher voltage levels.

The photovoltaic I-V test system is suitable for photovoltaic modules with large, medium and small voltage grades, and can test photovoltaic I-V curves of the photovoltaic modules with various voltage grades, so that the operating states of the photovoltaic modules with various voltage grades can be monitored and refined management can be performed.

According to the photovoltaic I-V curve testing system, the inverter is controlled to be in an off-grid state during testing, the inverter is adjusted to be in a voltage source mode, an adjustable load is connected, the working voltage of the inverter is adjusted to enable the inverter to range from 0 to a rated voltage, then the voltage and the current of each photovoltaic group string are obtained when the inverter voltage ranges from 0 to the rated voltage, a photovoltaic I-V curve under the full voltage is obtained, and whether faults or current mismatch and other problems exist in a photovoltaic module can be accurately judged according to the photovoltaic curve. Compared with the existing photovoltaic I-V curve, the photovoltaic I-V test system can test the photovoltaic I-V curve in a full voltage range, so that the running state of the photovoltaic module can be accurately monitored and refined management can be performed.

Example two

The embodiment provides a method for testing a photovoltaic I-V curve, which comprises the following steps:

controlling the inverter to be in an off-grid state, adjusting the inverter to a voltage source mode, and connecting an adjustable load to the inverter;

adjusting the working voltage of the inverter to change within the range from 0 to the rated voltage;

acquiring the voltage and current of each photovoltaic group string when the working voltage of the inverter is changed within the range from 0 to the rated voltage;

and obtaining a photovoltaic I-V curve according to the voltage and the current of each photovoltaic group string.

In this embodiment, after receiving the test signal, the control unit turns off the first switch Q1 between the inverter and the transformer T1, controls the inverter to be in an off-grid state, and adjusts the inverter from a current source mode to a voltage source mode. And then closing a switch between the adjustable load and the inverter to enable the adjustable load to be connected into the inverter so as to adjust the inversion voltage of the inverter, and enable the inversion voltage to be variable within the range from 0 to the rated voltage. And receiving the voltage and the current of each group of strings of the photovoltaic module when the inverter voltage is changed from 0 to the rated voltage, and obtaining a photovoltaic curve according to the voltage and the current of each group of strings of the photovoltaic module.

Further, controlling the inverter to be in an off-grid state and to access the adjustable load further comprises:

when the inverter is in an off-grid state, acquiring the opening voltage of the photovoltaic module;

the adjustable load is adjusted to adapt to the open circuit voltage.

In this embodiment, when the inverter is in an off-grid state, the open-circuit voltage of the photovoltaic module is obtained, at this time, the inverter is not connected to an adjustable load, and the open-circuit voltage at this time is the maximum voltage of the photovoltaic module. And adjusting the adjustable load according to the obtained opening voltage of the photovoltaic module, enabling the adjustable load to be matched with the opening voltage, and connecting the adjustable load into the inverter to ensure that the adjustment range of the inverter voltage of the inverter is changed within the range from 0 to the rated voltage. If the load is small, the lowest value of the inversion voltage is less than 0, and a photovoltaic curve in a full voltage range cannot be obtained.

In this embodiment, the rated voltage of the inverter voltage is U₀Maximum power of adjustable load is P₀The open voltage of the photovoltaic string is V_CS. In the process of changing the inversion voltage, the lowest value of the inversion voltage is 0.01 percent U₀Infinitely close to 0, can be identifiedThe lowest value of the regulating range of the inversion voltage is 0, and the maximum value of the current of the photovoltaic group at the moment is I_CS. The regulation range of the inverter voltage can be regarded as 0 to U₀The specific adjustment ratio can be set as required. For example, in a proportion of 1%, until U is reached₀. Or gradually increased according to the trend of 0.01 percent until U is reached₀. And sequentially obtaining the voltage and the current of each photovoltaic group string according to the change rate of the inversion voltage.

Specifically, in the process of regulating the inversion voltage from low to high, the initial lowest value is 0.01 percent U₀To make the current of the photovoltaic string close to 0 wirelessly, and the current of the photovoltaic string is maximum I_CS. With a fixed load, the load current decreases with increasing inverter voltage. Under the condition that the solar irradiance is stable, the voltage of the photovoltaic string can be increased along with the increase of the inverter inversion voltage, and the current of the photovoltaic string can be gradually reduced. When the inverter voltage rises to the rated voltage U₀And the working voltage of the photovoltaic string also reaches the maximum opening voltage V_CSAt this point, the I-V curve point of the full voltage range is tested.

It can be understood that, in the present embodiment, the variation trend of the inversion voltage can be adjusted from the highest value to the lowest value. During the process of regulating the inversion voltage from high to low, the maximum value is U₀At this time, the open voltage of the photovoltaic string is maximum V_CSAt this time, the current of the photovoltaic string is 0. With a fixed load, the load current increases with decreasing inverter voltage. Under the condition that the solar irradiance is stable, the voltage of the photovoltaic string can be reduced along with the reduction of the inverter inversion voltage, and the current of the photovoltaic string can be gradually increased. When the inversion voltage is reduced to 0.01% U₀When the inverter voltage is infinitely close to 0, the maximum value of the current of the photovoltaic string is I_CSAt this point, the I-V curve point of the full voltage range is tested. The voltage and current relationships corresponding to the test points at this time are shown in fig. 2.

Referring to fig. 3 and 4, in the present embodiment, a schematic diagram of a photovoltaic I-V curve can be drawn according to the corresponding diagram of fig. 2. The corresponding photovoltaic I-V curve of each photovoltaic string is shown in fig. 3. It is also possible to derive a photovoltaic I-V plot for a plurality of strings of photovoltaic groups as shown in fig. 4.

Further, the step of obtaining a photovoltaic curve according to the voltage and the current of each photovoltaic string further includes:

and analyzing the photovoltaic curve and judging whether the photovoltaic module has a fault.

Referring to fig. 4, in an actual application process, a photovoltaic I-V curve is affected by conditions such as open voltage, irradiance, temperature, deputy, or actual internal damage. For example, the curves a and b in fig. 4 are curves for normal operation, with only one knee bend. And the curve c has a plurality of knee bends, which indicates that the curve c is an abnormal curve. Thus, the photovoltaic string corresponding to the c is abnormal.

In general, the weak deviation of the opening voltage and the short-circuit current of the photovoltaic module is influenced by the factors such as irradiance and temperature, but the problem of the photovoltaic module is judged if the opening voltage and the short-circuit current are too low, such as a d curve or a c curve with a plurality of knee bends. Therefore, the abnormity of the photovoltaic string and the reason of the abnormity can be diagnosed by analyzing the photovoltaic I-V curve.

Further, the step of obtaining a photovoltaic I-V curve according to the voltage and current of each photovoltaic string further includes:

after the test is finished, the inverter is controlled to be in a grid-connected state, and the controller is adjusted to be in a current source mode, so that the photovoltaic system works normally.

In this embodiment, after the test is completed, if the operating state of the photovoltaic module is normal, the first switch Q1 between the inverter and the transformer T1 is closed, and the adjustable load is disconnected, so that the photovoltaic system operates normally.

If an abnormality occurs after the analysis, the photovoltaic string with the problem needs to be checked or replaced.

The photovoltaic I-V curve testing method of the embodiment comprises the following steps: the method comprises the steps of controlling an inverter to be in an off-grid state, adjusting the inverter to a voltage source mode, connecting an adjustable load, adjusting the working voltage of the inverter to enable the inverter to change from 0 to a rated voltage, obtaining the voltage and current of each photovoltaic group string when the inverter voltage changes from 0 to the rated voltage, obtaining a photovoltaic I-V curve under the full voltage, and accurately judging whether a photovoltaic module has faults or current mismatch and other problems according to the photovoltaic curve. Compared with the existing photovoltaic I-V curve, the photovoltaic I-V test system can test the photovoltaic I-V curve in a full voltage range, so that the working state of the photovoltaic module can be accurately monitored and refined management can be performed.

EXAMPLE III

The embodiment also provides a photovoltaic device, which comprises the test system and a processor, wherein the processor can run the steps of the photovoltaic I-V curve test method. The photovoltaic I-V curve testing method is as above, and the description of this embodiment is omitted.

According to the photovoltaic equipment, when a photovoltaic I-V curve is tested, the inverter is controlled to be in an off-grid state, the inverter is adjusted to be in a voltage source mode, an adjustable load is connected, the working voltage of the inverter is adjusted to enable the inverter to change from 0 to a rated voltage, the voltage and the current of each photovoltaic group string are obtained when the inverter voltage changes from 0 to the rated voltage, the photovoltaic I-V curve under the full voltage is obtained, the working state of a photovoltaic module can be monitored according to the photovoltaic curve, and whether the photovoltaic module has faults or current mismatch and other problems is judged. Compared with the existing photovoltaic equipment, the photovoltaic equipment of the embodiment can monitor the working state of the photovoltaic assembly within a full voltage range, and fine management is carried out on the working state.

According to the photovoltaic I-V curve testing system, the inverter is controlled to be in an off-grid state during testing, the inverter is adjusted to be in a voltage source mode, an adjustable load is connected, the working voltage of the inverter is adjusted to enable the inverter to change from 0 to a rated voltage, then the voltage and the current of each photovoltaic group string are obtained when the inverter voltage changes from 0 to the rated voltage, a photovoltaic I-V curve under the full voltage is obtained, and whether a photovoltaic module has a fault or current mismatch or not can be accurately judged according to the photovoltaic curve. Compared with the existing photovoltaic I-V curve test system, the photovoltaic I-V test system can test the photovoltaic I-V curve in a full voltage range, so that the running state of the photovoltaic assembly can be accurately monitored, and fine management can be performed.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.