CN109901003B - Inverter power fault detection method and system - Google Patents

Abstract

The invention provides an inverter power fault detection method and system, including: collecting the DC bus voltage, the input power and output power of the inverter; determining the power partition where the input power of the inverter is located; normalize the input power of the inverter according to the power partition where the input power of the inverter is located; according to the normalized DC bus voltage and the input power of the inverter and the Enter the power partition where the power is located, and obtain the power loss value; determine the power fault according to the output power and power loss value of the inverter. The technical scheme provided by the present invention improves the accuracy of fault judgment.

Description

Inverter power fault detection method and system

technical field

The invention belongs to the field of photovoltaic power generation fault detection, and in particular relates to an inverter power fault detection method and system.

Background technique

In the photovoltaic power generation system, the price of the inverter accounts for only about 5%-8%, but it is the decisive factor for the power generation efficiency. The fault of the inverter will directly affect the output power, and the timely detection of the inverter status will improve the The key to power generation. Studies have shown that in the case of stable bus voltage, the losses of photovoltaic inverters are related to semiconductor switching parameters, switching frequency and passing current. Under the current trend of market modularization and low cost, the mainstream inverter topologies, control algorithms, and semiconductor switching parameters are close, so the output power is closely related to the current.

At the same time, with the increase in the application of string inverters, the traditional centralized inverter monitoring system compares the output power to judge the fault, and there are certain missed judgments and misjudgments. It is likely to cause a large area of the photovoltaic inverter to trip out of the working state or false alarms, resulting in large power grid fluctuations.

According to the manufacturer's power-efficiency curve, it is impossible to accurately analyze the output power of the power between the power partitions, such as the power under the load rate of 35% and 63%, so when a power failure occurs, it cannot be accurately judged.

SUMMARY OF THE INVENTION

In order to solve the problem of missed judgment and misjudgment in the way that the traditional centralized inverter monitoring system compares the output power to judge the fault, the present invention provides an inverter power fault detection method, including:

Collect DC bus voltage, inverter input power and output power;

Determine the power partition where the input power of the inverter is located;

Normalize the DC bus voltage, and normalize the input power of the inverter according to the power partition where the input power of the inverter is located;

The power loss value is obtained according to the normalized DC bus voltage, the input power of the inverter, and the power partition where the input power is located;

The power failure is determined based on the output power and power loss values of the inverter.

Before determining the power partition where the input power of the inverter is located, it also includes: detecting whether the DC bus voltage is within the preset working range of the inverter, and if so, retaining the DC bus voltage information, otherwise deleting the DC bus voltage information , and end the detection after the alarm is an unknown fault.

The determining of the power partition where the output power of the inverter is located includes:

Compare the input power of the inverter with the rated power of the inverter to determine the power partition where the input power of the inverter is located.

The DC bus voltage is normalized as follows:

为归一化后的直流母线电压。where V _in is the DC bus voltage, V _n is the rated voltage of the inverter,

is the normalized DC bus voltage.

The input power of the inverter is normalized as follows:

为归一化的功率，P_in为逆变器的输入功率，P_n×k％为逆变器输入功率所在功率分区对应的功率值，其中P_n为逆变器的额定功率值，k％为功率分区的值，P_in在第1至n-1个功率分区时，k％取对应功率分区的最大值，P_in在第n个功率分区时，k％取100％，n为功率分区总数。In the formula,

is the normalized power, P _in is the input power of the inverter, P _n ×k% is the power value corresponding to the power partition where the input power of the inverter is located, where P _n is the rated power value of the inverter, k% is the value of the power partition, when Pin is _in the 1st to n-1th power partition, k% takes the maximum value of the corresponding power partition, and when Pin is _in the nth power partition, k% takes 100%, and n is the power partition total.

According to the normalized DC bus voltage and the input power of the inverter, and the power partition where the input power is located, the power loss value is calculated as follows:

的拟合值；b_i0、b_i1均为归一化功率

的拟合值；c_i0、c_i1均为归一化功率平方

的拟合值；i为功率分区号。In the formula, P _{loss_i} is the power loss value, a _i0 and a _i1 are the normalized DC bus voltage

The fitted value of ; b _i0 and b _i1 are normalized power

The fitted value of ; c _i0 , c _i1 are normalized power square

The fitted value of ; i is the power partition number.

Power failures based on inverter output power and power loss values, including:

The theoretical output power value is obtained by subtracting the power loss value from the input power of the inverter;

Calculate the absolute value of the difference between the theoretical output power value and the output power of the inverter;

It is judged whether the absolute value is greater than a preset threshold, and if it is greater than the threshold, it is judged that a power failure has occurred; if it is less than or equal to the threshold, it is judged that there is no power failure.

An inverter power fault detection system provided by the present invention includes:

The acquisition module is used to collect the DC bus voltage, the input power and output power of the inverter;

The partition module is used to determine the power partition where the input power of the inverter is located;

The normalization module is used for normalizing the DC bus voltage, and normalizing the input power of the inverter according to the power partition where the input power of the inverter is located;

The loss calculation module obtains the power loss value according to the normalized DC bus voltage, the input power of the inverter and the power partition where the input power is located;

The fault judgment module is used to determine the power fault according to the power loss value and the output power of the inverter.

The inverter power fault detection system further includes a pre-check module for detecting whether the DC bus voltage is within the preset inverter working range, if so, the DC bus voltage information is retained, otherwise the DC bus is deleted. The voltage information, and the alarm is an unknown fault, and the detection is ended.

The partition module includes:

a first comparison sub-module for comparing the input power of the inverter with the rated power of the inverter;

The determination sub-module is used for determining the power partition where the input power of the inverter is located according to the comparison result of the comparison unit.

The fault judging module includes:

a first calculation sub-module for obtaining a theoretical output power value by subtracting the power loss value from the input power of the inverter;

The second calculation submodule is used to calculate the absolute value of the difference between the theoretical output power value and the inverter output power;

The fault determination sub-module judges whether the absolute value is greater than a preset threshold value, and if it is greater than the threshold value, it is determined that a power failure occurs; if it is less than or equal to the threshold value, it is determined that there is no power failure.

Compared with the closest prior art, the technical solution provided by the present invention has the following beneficial effects:

The technical solution provided by the present invention is to perform power partition judgment on power, normalize data based on the power partition, calculate the power loss value according to the normalized data and the power partition number, and perform fault judgment according to the power loss value, so that The fault judgment is more accurate, the calculation is faster, the accuracy of fault judgment is improved, and the problem of missed judgment and misjudgment is solved;

The technical solution provided by the present invention is to judge the power by division, each division can realize a relatively accurate fitting amount, and calculate the power loss according to the fitting quantity, so as to more accurately judge whether a power failure occurs, which is suitable for large-scale Online monitoring of string photovoltaic inverters in parallel power stations.

Description of drawings

FIG. 1 is a flowchart of a method for detecting a power fault of an inverter according to the present invention;

FIG. 2 is a flowchart of an inverter power fault detection method according to an embodiment of the present invention;

FIG. 3 is a flowchart of an inverter power fault detection method according to an embodiment of the present invention.

Detailed ways

Below in conjunction with accompanying drawing, the present invention is described in further detail:

Embodiment 1.

FIG. 1 is a flowchart of an inverter power fault detection method according to the present invention. As shown in FIG. 1 , an inverter power fault detection method provided by the present invention includes:

Collect DC bus voltage, inverter input power and output power;

Determine the power partition where the input power of the inverter is located;

Normalize the DC bus voltage, and normalize the input power of the inverter according to the power partition where the input power of the inverter is located;

The power loss value is obtained according to the normalized DC bus voltage, the input power of the inverter, and the power partition where the input power is located;

The power failure is determined based on the output power and power loss values of the inverter.

Before determining the power partition where the input power of the inverter is located, it also includes: detecting whether the DC bus voltage is within the preset working range of the inverter, and if so, retaining the DC bus voltage information, otherwise deleting the DC bus voltage information , and end the detection after the alarm is an unknown fault.

The determining of the power partition where the output power of the inverter is located includes:

Compare the input power of the inverter with the rated power of the inverter to determine the power partition where the input power of the inverter is located.

The DC bus voltage is normalized as follows:

为归一化后的直流母线电压。where V _in is the DC bus voltage, V _n is the rated voltage of the inverter,

is the normalized DC bus voltage.

The input power of the inverter is normalized as follows:

为归一化的功率，P_in为逆变器的输入功率，P_n×k％为逆变器输入功率所在功率分区对应的功率值，其中P_n为逆变器的额定功率值，k％为功率分区的值，P_in在第1至n-1个功率分区时，k％取对应功率分区的最大值，P_in在第n个功率分区时，k％取100％，n为功率分区总数。In the formula,

is the normalized power, P _in is the input power of the inverter, P _n ×k% is the power value corresponding to the power partition where the input power of the inverter is located, where P _n is the rated power value of the inverter, k% is the value of the power partition, when Pin is _in the 1st to n-1th power partition, k% takes the maximum value of the corresponding power partition, and when Pin is _in the nth power partition, k% takes 100%, and n is the power partition total.

According to the normalized DC bus voltage and the input power of the inverter, and the power partition where the input power is located, the power loss value is calculated as follows:

的拟合值；b_i0、b_i1均为归一化功率

的拟合值；c_i0、c_i1均为归一化功率平方

的拟合值；i为功率分区号。In the formula, P _{loss_i} is the power loss value, a _i0 and a _i1 are the normalized DC bus voltage

The fitted value of ; b _i0 and b _i1 are normalized power

The fitted value of ; c _i0 , c _i1 are normalized power square

The fitted value of ; i is the power partition number.

Power failures based on inverter output power and power loss values, including:

The theoretical output power value is obtained by subtracting the power loss value from the input power of the inverter;

Calculate the absolute value of the difference between the theoretical output power value and the output power of the inverter;

It is judged whether the absolute value is greater than a preset threshold, and if it is greater than the threshold, it is judged that a power failure has occurred; if it is less than or equal to the threshold, it is judged that there is no power failure.

Embodiment two,

Based on the same inventive concept, the present invention provides an inverter power fault detection system, which may include:

The acquisition module is used to collect the DC bus voltage, the input power and output power of the inverter;

The partition module is used to determine the power partition where the input power of the inverter is located;

The normalization module is used for normalizing the DC bus voltage, and normalizing the input power of the inverter according to the power partition where the input power of the inverter is located;

The loss calculation module obtains the power loss value according to the normalized DC bus voltage, the input power of the inverter and the power partition where the input power is located;

The fault judgment module is used to determine the power fault according to the power loss value and the output power of the inverter.

The inverter power fault detection system may further include a pre-check module for detecting whether the DC bus voltage is within the preset inverter working range, if so, keep the DC bus voltage information, otherwise delete the DC bus voltage The bus voltage information, and the alarm is an unknown fault, and the detection is ended.

The partition module may include:

a first comparison sub-module for comparing the input power of the inverter with the rated power of the inverter;

The determination sub-module is used for determining the power partition where the input power of the inverter is located according to the comparison result of the comparison unit.

The fault judging module may include:

a first calculation sub-module for obtaining a theoretical output power value by subtracting the power loss value from the input power of the inverter;

The second calculation submodule is used to calculate the absolute value of the difference between the theoretical output power value and the inverter output power;

The fault determination sub-module judges whether the absolute value is greater than a preset threshold value, and if it is greater than the threshold value, it is determined that a power failure occurs; if it is less than or equal to the threshold value, it is determined that there is no power failure.

The normalization module can normalize the reserved DC bus voltage as follows:

为归一化后的直流母线电压电压。where V _in is the DC bus voltage, V _n is the rated voltage of the inverter,

is the normalized DC bus voltage.

The normalization module can normalize the input power of the inverter as follows:

为归一化的功率，P_in为逆变器的输入功率，P_n×k％为逆变器输入功率所在功率分区对应的功率值，其中P_n为逆变器的额定功率值，k％为功率分区的值，P_in在第1至n-1个功率分区时，k％取对应功率分区的最大值，P_in在第n个功率分区时，k％取100％，n为功率分区总数。In the formula,

is the normalized power, P _in is the input power of the inverter, P _n ×k% is the power value corresponding to the power partition where the input power of the inverter is located, where P _n is the rated power value of the inverter, k% is the value of the power partition, when Pin is _in the 1st to n-1th power partition, k% takes the maximum value of the corresponding power partition, and when Pin is _in the nth power partition, k% takes 100%, and n is the power partition total.

The loss calculation module can calculate the power loss value as follows:

的拟合值；b_i0、b_i1均为归一化功率

的拟合值；c_i0、c_i1均为归一化功率平方

的拟合值；i为功率分区号。In the formula, P _{loss_i} is the power loss value, a _i0 and a _i1 are the normalized DC bus voltage

The fitted value of ; b _i0 and b _i1 are normalized power

The fitted value of ; c _i0 , c _i1 are normalized power square

The fitted value of ; i is the power partition number.

Embodiment three,

Figure 2 is a schematic diagram of an inverter power fault detection system. As shown in Figure 2, the system is composed of a pre-check module, a normalization module, a loss calculation module, a power comparison module and a fault judgment module;

The inverter power fault detection system is located in the host computer system, and judges the power fault according to the DC bus voltage, the input power and the output power of the inverter collected in real time by the host computer.

The DC bus voltage and input power are transmitted to the pre-check module and the normalization module, the output power is transmitted to the power comparison module, and the results are successively transmitted from the pre-check module to the normalization module, loss calculation module, power comparison module, and fault judgment module. Finally, the fault judgment module outputs a conclusion, indicating whether the power is faulty.

Fig. 3 is a flow chart of a method for detecting power failure of an inverter. As shown in Fig. 3, in the pre-check module, when the DC bus voltage is within the working range of the inverter, data is retained, and when the DC bus voltage is within the working range of the inverter Remove the data and alarm "unknown fault". The input power is compared with the rated power of the inverter, for example, it can be divided into 0%-5%, 5%-10%, 10%-20%, 20%-30%, 30 according to the load rate in the efficiency weighting table %-50%, 50%-75%, 75%-100%, 100% above these 8 partitions. The pre-check module will output whether it is other faults and the zone i where the output power is located.

其中额定电压值V_n由厂家提供，或通过采集逆变器正常运行时3个以上直流电压数据的平均值。输入功率P_in除以所在功率段对应值P_n×k％得到归一化功率比

其中额定功率值P_n由厂家提供，k在1-7分区按最大值，第8分区按100％计算。In the normalization module, the DC bus voltage V _in is divided by the rated voltage value V _n to obtain the normalized DC bus voltage.

The rated voltage value V _n is provided by the manufacturer, or the average value of three or more DC voltage data collected during normal operation of the inverter. The normalized power ratio is obtained by dividing the input power P _in by the corresponding value of the power section P _n ×k%

Among them, the rated power value P _n is provided by the manufacturer, k is calculated according to the maximum value in the 1-7 division, and 100% in the 8 division.

归一化功率

传递至损耗计算模块，损耗计算模块根据公式计算损耗。公式如下：The partition number where the input power is located, and the normalized DC bus voltage

normalized power

It is passed to the loss calculation module, and the loss calculation module calculates the loss according to the formula. The formula is as follows:

in,

的拟合值；a _i0 and a _i1 are the normalized DC bus voltage

the fitted value;

的拟合值；b _i0 and b _i1 are the normalized power

the fitted value;

的拟合值；i为功率分区号。c _i0 , c _i1 are the power squares after normalization

The fitted value of ; i is the power partition number.

The power comparison module determines whether the difference between the detected power output P _out and the calculated power output P _in -P _{loss_i} , that is, |P _out -P _in -P _{loss_i} | is greater than the threshold, and outputs a conclusion to the fault judgment module. The initial value of the threshold is set to |P _in -P _{loss_i} |×5%, which can be changed manually.

Fault judgment module, when the conclusion output from the power comparison module is that |P _out -P _in -P _{loss_i} | is less than or equal to the threshold, it is judged as no power fault; |P _out -P _in -P _{loss_i} | is greater than the threshold, it is judged as occurrence Power failure.

As will be appreciated by those skilled in the art, the embodiments of the present application may be provided as a method, a system, or a computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) having computer-usable program code embodied therein.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present application. It will be understood that each flow and/or block in the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to the processor of a general purpose computer, special purpose computer, embedded processor or other programmable data processing device to produce a machine such that the instructions executed by the processor of the computer or other programmable data processing device produce Means for implementing the functions specified in a flow or flow of a flowchart and/or a block or blocks of a block diagram.

These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory result in an article of manufacture comprising instruction means, the instructions The apparatus implements the functions specified in the flow or flow of the flowcharts and/or the block or blocks of the block diagrams.

These computer program instructions can also be loaded on a computer or other programmable data processing device to cause a series of operational steps to be performed on the computer or other programmable device to produce a computer-implemented process such that The instructions provide steps for implementing the functions specified in the flow or blocks of the flowcharts and/or the block or blocks of the block diagrams.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit its protection scope. Although the application has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: After reading this application, those skilled in the art can still make various changes, modifications or equivalent replacements to the specific embodiments of the application, but these changes, modifications or equivalent replacements are all within the protection scope of the pending claims.

Claims (8)

1. An inverter power failure detection method, comprising:

collecting direct current bus voltage, input power and output power of an inverter;

determining a power partition where the input power of the inverter is located;

normalizing the direct current bus voltage, and normalizing the input power of the inverter according to the power partition where the input power of the inverter is located;

obtaining a power loss value according to the direct-current bus voltage after normalization processing, the input power of the inverter and a power partition where the input power is located;

determining a power fault according to the output power and the power loss value of the inverter;

normalizing the DC bus voltage according to the following formula:

in the formula, V _in Is a DC bus voltage, V _n Is the rated voltage value of the inverter,

the normalized direct current bus voltage is obtained;

normalizing the input power of the inverter according to the following formula:

in the formula,

for normalized power, P _in Is the input power of the inverter, P _n Xk% is the power value corresponding to the power partition where the input power of the inverter is located, wherein P _n Is the inverse ofRated power value of the converter, k% being the value of the power division, P _in In the 1 st to n-1 st power partitions, k% is the maximum value of the corresponding power partition, P _in When the nth power partition is used, k% is 100%, and n is the total number of the power partitions;

according to the direct-current bus voltage after normalization processing, the input power of the inverter and the power partition where the input power is located, calculating a power loss value according to the following formula:

in the formula, P _{loss_i} Is a power loss value, a _i0 、a _i1 Are all normalized DC bus voltage

The fitting value of (a); b _i0 、b _i1 Are all normalized power

The fitting value of (a); c. C _i0 、c _i1 Are all normalized power squared

The fitting value of (a); i is the power partition number.

2. The inverter power failure detection method of claim 1, wherein determining the power partition in which the input power of the inverter is located further comprises: and detecting whether the voltage of the direct current bus is in a preset inverter working range, if so, retaining the voltage information of the direct current bus, otherwise, deleting the voltage information of the direct current bus, and alarming to be an unknown fault and then finishing the detection.

3. The inverter power failure detection method of claim 1, wherein the determining the power partition in which the output power of the inverter is located comprises:

and comparing the input power of the inverter with the rated power of the inverter, and determining the power partition where the input power of the inverter is located.

4. The inverter power failure detection method of claim 1, wherein the power failure based on the output power of the inverter and the power loss value comprises:

subtracting the power loss value from the input power of the inverter to obtain a theoretical output power value;

calculating the absolute value of the difference between the theoretical output power value and the output power of the inverter;

judging whether the absolute value is greater than a preset threshold value, and if so, judging that a power failure occurs; and if the power failure is less than or equal to the threshold value, determining that no power failure exists.

5. An inverter power failure detection system for use in the inverter power failure detection method of claim 1, comprising:

the acquisition module is used for acquiring the voltage of the direct-current bus, and the input power and the output power of the inverter;

the partitioning module is used for determining a power partition where the input power of the inverter is located;

the normalization module is used for performing normalization processing on the direct current bus voltage and performing normalization processing on the input power of the inverter according to the power partition where the input power of the inverter is located;

the loss calculation module is used for obtaining a power loss value according to the direct-current bus voltage after normalization processing, the input power of the inverter and the power partition where the input power is located;

and the fault judgment module is used for determining power faults according to the power loss value and the output power of the inverter.

6. The inverter power failure detection system of claim 5, further comprising a pre-check module for detecting whether the DC bus voltage is within a preset inverter operating range, if so, retaining the DC bus voltage information, otherwise, deleting the DC bus voltage information, and ending the detection after an alarm is given as an unknown failure.

7. The inverter power failure detection system of claim 5, wherein the partition module comprises:

the first comparison submodule is used for comparing the input power of the inverter with the rated power of the inverter;

and the determining submodule is used for determining the power partition where the input power of the inverter is located according to the comparison result of the comparison unit.

8. The inverter power failure detection system of claim 5, wherein the failure determination module comprises:

the first calculation submodule is used for subtracting a power loss value from the input power of the inverter to obtain a theoretical output power value;

the second calculation submodule is used for calculating the absolute value of the difference between the theoretical output power value and the output power of the inverter; the fault determining submodule judges whether the absolute value is larger than a preset threshold value or not, and if the absolute value is larger than the preset threshold value, the power fault is judged to occur; and if the power failure is less than or equal to the threshold value, determining that no power failure exists.

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