CN112858844A - Method and system for detecting direct current arc fault in photovoltaic system - Google Patents
Method and system for detecting direct current arc fault in photovoltaic system Download PDFInfo
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Abstract
The invention provides a method and a system for detecting direct current arc faults in a photovoltaic system. By adopting the technical scheme of the invention, high-frequency signal data does not need to be extracted, the problems that high-frequency signals are easy to interfere and attenuate in the prior art are solved, the accuracy of a fault detection result is effectively improved, the defects of complex operation and redundant sampling data are avoided, the equipment cost in the detection process is reduced, faults can be quickly found and can be timely stopped, and the safety and the stability of the operation of a photovoltaic system are ensured to a considerable extent.
Description
Technical Field
The invention relates to the technical field of power grid system detection and maintenance, in particular to a method and a system for detecting a direct current arc fault in a photovoltaic system.
Background
In recent years, with the rapid development of the photovoltaic industry, the photovoltaic power generation technology is also continuously promoted. One important direction is the rise of the dc input voltage, which has reached 1500V at the highest dc input. The improvement of the direct current input can bring many advantages such as the improvement of the generating efficiency, the reduction of the system cost and the like, but some hidden dangers can be generated or amplified at the same time, and a direct current arc fault is one of the more typical potential safety dangers.
In the process of long-time operation of the whole photovoltaic system, the phenomena of poor conductor contact, insulation material damage, insulation impedance reduction and the like can be caused due to the inevitable occurrence of conditions of random failure, insulation aging, electrical connection looseness and the like of devices, and further the frequent occurrence of direct-current arc faults can be caused. Importantly, because the temperature of peripheral devices and materials is easily and rapidly increased due to the direct current arc fault, the probability of fire is high, and data statistics shows that 40% of fire accidents in the existing photovoltaic power station are caused by the direct current arc fault. Therefore, it is necessary to provide a technical solution for efficiently and accurately detecting a dc arc fault in a photovoltaic system.
At present, domestic and foreign researchers detect the direct current arc fault of the photovoltaic system mainly based on a frequency characteristic detection method, and the principle is that when the arc fault occurs, a certain specific high-frequency signal is always accompanied, the high-frequency signal does not occur under the normal working condition, and once the signal occurs, the arc fault exists. This detection is susceptible to interference from inverter or other device noise. Furthermore, most detection devices are not located at the site of the fault, and arc fault signals, particularly frequency signals, may be attenuated during transmission from the site of the photovoltaic system to the detection device, causing the detection device to malfunction. When the method is adopted for detection, the sampling frequency must be more than twice of the frequency of the arc fault signal, so that a large amount of data must be acquired, information redundancy is caused, and the requirement on a processor is high, so that the protection cannot be upgraded for a plurality of products put into operation on site.
Disclosure of Invention
To solve the above problem, the present invention provides a method of detecting a dc arc fault in a photovoltaic system, which in one embodiment comprises:
s1, collecting fault detection characteristic data according to the real-time running state of the circuit to be detected in the photovoltaic system;
step S2, processing the collected fault detection characteristic data to determine the fault detection value of the circuit to be detected;
and step S3, determining the fault detection result corresponding to the circuit to be detected based on the fault detection value.
In a preferred embodiment, in step S1, the process of collecting the fault detection characteristic data of the photovoltaic system according to the real-time operation state of the photovoltaic system includes:
and collecting real-time direct current data, real-time voltage data, real-time temperature data and shutdown real-time direct current data in a set time period of the circuit to be detected as fault detection characteristic data.
In one embodiment, in the step S2, the process of determining the fault detection value of the circuit to be detected includes:
for the circuit to be detected with the real-time operation state as operation:
selecting a current maximum value Imax and a current minimum value Imin from the collected real-time direct current data, and calculating a difference value delta I between the current maximum value Imax and the current minimum value Imin to be used as a current fault detection value of the circuit to be detected;
selecting a maximum voltage value Vmax and a minimum voltage value Vmin from the collected real-time voltage data, and calculating a difference value delta V of the maximum voltage value Vmax and the minimum voltage value Vmin as a voltage fault detection value of the circuit to be detected;
calculating the temperature change rate v of the circuit to be tested according to the collected real-time temperature dataTAs a first temperature fault detection value of the circuit to be detected;
and acquiring a real-time temperature T change amplitude value in a set time period of the circuit to be detected as a second fault judgment temperature index value.
In one embodiment, in the step S2, the process of determining the fault detection value of the circuit to be detected further includes:
for the circuit to be detected with the real-time running state of shutdown:
calculating the current integral value I of the circuit to be detected in the corresponding time period delta t according to the collected shutdown real-time direct current datatAs a shutdown fault detection value for the circuit to be detected.
In one embodiment, in the step S3, the process of determining the fault detection result corresponding to the circuit to be detected includes:
for a circuit to be detected in a real-time operation state, if any one of the following requirements is met, determining that the corresponding circuit to be detected has a direct current arc fault:
the current fault detection value is more than or equal to a set fault current protection value PI；
The voltage fault detection value is more than or equal to a set fault voltage protection value PV；
The first temperature fault detection value is greater than or equal to a set first fault temperature protection value PT1；
The second temperature fault detection value is greater than or equal to a set second fault temperature protection value PT2。
In one embodiment, the step S3 of determining the fault detection result corresponding to the circuit to be detected further includes
If the shutdown fault detection value of the circuit to be detected in the real-time running state is shutdown and is greater than or equal to the set shutdown fault current protection value PIsAnd judging that the circuit to be detected has the direct current arc fault.
Further, in one embodiment, the method comprisesThe fault current protection value PIIs set according to the power change rate of the circuit corresponding to the inverter, wherein PIThe current change value corresponding to the maximum power change rate when the circuit normally operates needs to be larger than;
the fault voltage protection value PVIs set according to the supporting capacitance and discharge resistance of the circuit corresponding to the inverter configuration, wherein PVThe discharge speed of the voltage is larger than that of the direct current when the direct current is cut off;
said first fault temperature protection value PT1The current power of the circuit to be detected, the environment temperature in a set range and the configuration parameters of the heat dissipation device are set;
said second fault temperature protection value PT2Is set according to the current power required by the configuration of the circuit to be detected, the ambient temperature in a set range and the configuration parameters of the heat dissipation device, wherein P isT2The temperature of the circuit to be detected after full-load operation is stable at the maximum ambient temperature of normal operation of the system.
In one embodiment, the shutdown fault current protection value PIsIs set according to the sampling precision of the current sensor corresponding to the circuit, wherein PIsIt must be greater than the maximum sample zero drift value during normal operation.
Based on other aspects of the present invention, there is also provided a system for detecting a dc arc fault in a photovoltaic system, the system comprising:
the characteristic data acquisition module is used for acquiring fault detection characteristic data of the circuit to be detected in the photovoltaic system according to the real-time running state of the circuit to be detected;
the detection value determining module is used for processing the collected fault detection characteristic data and determining the fault detection value of the circuit to be detected;
and the detection result determining module is arranged to determine a fault detection result corresponding to the circuit to be detected based on the fault detection value.
In a preferred embodiment, the detection result determining module determines the fault detection result of the circuit to be detected by:
if the circuit to be detected is in operation, each fault detection value of the circuit to be detected is compared and analyzed, and if any fault detection value meets the set condition, the circuit to be detected is judged to have a direct current arc fault;
if the circuit to be detected is in a shutdown state, comparing and analyzing the fault detection value of the circuit to be detected, and if the fault detection value meets the set condition, judging that the circuit to be detected has the direct current arc fault.
Compared with the closest prior art, the invention also has the following beneficial effects:
according to the method for detecting the direct current arc fault in the photovoltaic system, provided by the invention, the fault detection characteristic data related to the direct current arc fault in the photovoltaic system under different operation states are firstly obtained, the fault detection characteristic data obtained in the step are necessary data in the operation process of the photovoltaic system, the fault detection work is carried out based on the data without changing the hardware structure of the system, and the hardware cost is not increased. And then, performing calculation processing according to the acquired fault detection data to determine corresponding fault detection values, further respectively comparing the determined fault detection values with set protection values, and determining a final fault detection result according to the comparison result. Compared with the traditional fault detection method, the technical scheme does not need to extract high-frequency signal data, reduces the operation complexity, simultaneously solves the problems that the fault detection method through current frequency in the prior art is easy to interfere and the high-frequency signal is easy to attenuate, effectively improves the accuracy of the fault detection result, avoids the defect of sampling data redundancy, can quickly find the fault, further cuts off a fault source and timely stops damage, and is favorable for promoting the stable operation and development of a photovoltaic system.
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The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
FIG. 1 is a schematic flow diagram of a method for detecting a DC arc fault in a photovoltaic system in an embodiment of the present invention;
FIG. 2 is a schematic diagram of the state of current flow in the event of a DC arc fault in a photovoltaic system circuit in accordance with an embodiment of the present invention;
FIG. 3 is a schematic diagram of the voltage conditions in the event of a DC arc fault in a photovoltaic system circuit in accordance with an embodiment of the present invention;
fig. 4 is a schematic structural diagram of a system for detecting a dc arc fault in a photovoltaic system according to an embodiment of the present invention.
Detailed Description
The following detailed description will be provided for the embodiments of the present invention with reference to the accompanying drawings and examples, so that the practitioner of the present invention can fully understand how to apply the technical means to solve the technical problems, achieve the technical effects, and implement the present invention according to the implementation procedures. It should be noted that, unless otherwise conflicting, the embodiments and features of the embodiments of the present invention may be combined with each other, and the technical solutions formed are all within the scope of the present invention.
With the rapid development of the photovoltaic industry, the photovoltaic power generation technology is continuously improved, the direct current input voltage is greatly improved, and the highest direct current input reaches 1500V at present. The improvement of the direct current input can bring many advantages such as the improvement of the generating efficiency, the reduction of the system cost and the like, but some hidden dangers can be generated or amplified at the same time, and a direct current arc fault is one of the more typical potential safety dangers. In the process of long-time operation of a photovoltaic system, the conditions of random failure, insulation aging, electrical connection looseness and the like inevitably occur to devices, so that the phenomena of poor conductor contact, insulation material damage, insulation impedance reduction and the like can be caused, and further, the direct-current arc fault is caused to occur frequently. Importantly, because the temperature of peripheral devices and materials is easily and rapidly increased due to the direct current arc fault, the probability of fire is high, and data statistics shows that 40% of fire accidents in the existing photovoltaic power station are caused by the direct current arc fault. Direct current arc protection is used as an important index and function when photovoltaic systems are designed in all parts of the world. Among them, north america clearly requires that a photovoltaic system having a photovoltaic input voltage exceeding 80V or more must have dc arc detection and protection capabilities. Therefore, it is necessary to provide a technical solution for efficiently and accurately detecting a dc arc fault in a photovoltaic system, and a perfect fault detection mechanism needs to be established to detect whether a dc fault arc that may cause a fire hazard is generated during the operation of the photovoltaic system, so as to block the fault arc in time and ensure the safe operation of the photovoltaic system.
The method for detecting the direct current arc fault of the photovoltaic system in the prior art is mainly a detection method based on frequency characteristics, when the arc fault occurs, a certain specific high-frequency signal is always accompanied, the high-frequency signal does not appear under the normal working condition, once the signal appears, the arc fault is indicated, and the method can realize the detection of the direct current arc fault of the photovoltaic system to a certain extent, but has the following problems:
(1) the detection mode is easily interfered by noise of an inverter or other devices, the error probability is high, and the accuracy is insufficient;
(2) arc fault signals, particularly frequency signals, may be attenuated during field transmission from the photovoltaic system to the detection device to cause malfunction of the detection device;
(3) when the method is adopted for detection, the sampling frequency is more than twice of the frequency of the arc fault signal, so that a large amount of data is necessarily acquired, and information redundancy is caused;
(4) the detection method has high requirements on the processor, so that a plurality of products put into operation on site cannot be upgraded and protected, the universality is insufficient, and comprehensive and systematic protection cannot be provided for the photovoltaic system.
In order to solve the problems, the invention provides a method and a system for detecting a direct current arc fault in a photovoltaic system. And (3) analyzing the collected information such as direct current, direct voltage, temperature and the like to formulate a detection strategy. Various embodiments of the present invention will be described below with reference to the accompanying drawings.
Example one
Fig. 1 is a schematic flow chart illustrating a method for detecting a dc arc fault in a photovoltaic system according to an embodiment of the present invention, and as can be seen from fig. 1, the method includes the following steps:
and S110, acquiring fault detection characteristic data according to the real-time running state of the circuit to be detected in the photovoltaic system.
In the step, through comprehensive analysis of characteristics of the direct current arc and secondary phenomena caused by the arc fault, a plurality of characteristic data related to the direct current arc fault are determined and can be used for fault detection.
In practical application, the fault detection characteristic data required to be collected are different for a photovoltaic system in operation and a photovoltaic system in a shutdown state. For example, in an operating photovoltaic system, in an arc combustion process, due to the fact that a click material burns and evaporates, when a click current is large, a magnetic field is generated, and the like, an arc current and an arc impedance waveform can continuously change, fig. 2 shows a state diagram of a current when a direct current arc fault occurs in a photovoltaic system circuit according to an embodiment of the present invention, and as shown in fig. 2, a result of continuous change of the arc current due to chaos of an arc is a pulse characteristic of the arc current waveform, that is, a current amplitude value can be changed drastically even in a short time. Therefore, the change data of the current in the set period of time can be collected as one of the fault detection characteristic data.
On the other hand, the arc discharge phenomenon in the photovoltaic system is generated with a sharp drop in voltage. Fig. 3 is a schematic diagram showing a state of voltage when a dc arc fault occurs in a photovoltaic system circuit according to an embodiment of the present invention, and as shown in fig. 3, in a time period of the occurrence of the arc fault, the voltage of the photovoltaic system is abruptly decreased compared with a voltage in normal operation, and thus, voltage change data in a set time period is also one of scientific fault detection characteristic data.
When a direct current arc fault occurs, if an available temperature acquisition point is near a fault occurrence point, a remarkable temperature rise must be detected in the arc combustion process, and particularly after combustible devices around the fault diffusion burn, the temperature can rise extremely rapidly. Based on the temperature change data of the photovoltaic system to be detected within the set time can be used as fault detection characteristic data. If the fault occurrence point is far from the temperature collection point, the temperature change is not severe, but if the arc discharge phenomenon continues or spreads, the temperature continuously rises. In this case, it is necessary to acquire real-time temperature data of the circuit to be detected as fault detection characteristic data, and then analyze the data to obtain a fault detection result.
For the photovoltaic system in the shutdown state, if a direct current arc fault occurs in a certain circuit, continuous low current exists in the initial stage of arc discharge fault generation, so that the continuous low current can be detected to identify the fault in the early stage. Based on the technical analysis, the process for collecting the fault detection characteristic data of the photovoltaic system comprises the following steps:
and collecting real-time direct current data, real-time voltage data, real-time temperature data and shutdown real-time direct current data in a set time period of the circuit to be detected as fault detection characteristic data. Specifically, in the step, if the real-time operation state of the circuit to be detected is in operation, the real-time direct current data, the real-time voltage data and the real-time temperature data in the set time period of the circuit to be detected are collected as the fault detection characteristic data. If the real-time running state of the circuit to be detected is shutdown, the shutdown real-time direct current data of the circuit to be detected within a set time period is collected and used as fault detection characteristic data.
After the fault detection characteristic data is acquired, corresponding processing needs to be carried out on the fault detection characteristic data, and the acquired data is converted into data which directly reflects whether a direct current arc fault occurs, so that the following steps are carried out:
and step S120, processing the collected fault detection characteristic data and determining the fault detection value of the circuit to be detected.
In this step, the process of determining a fault detection value of the circuit to be tested includes:
for the circuit to be detected with the real-time operation state as operation:
and selecting a current maximum value Imax and a current minimum value Imin from the collected real-time direct current data, and calculating a difference value delta I between the current maximum value Imax and the current minimum value Imin to be used as a current fault detection value of the circuit to be detected.
And selecting a maximum voltage value Vmax and a minimum voltage value Vmin from the collected real-time voltage data, and calculating a difference value delta V between the maximum voltage value Vmax and the minimum voltage value Vmin to be used as a voltage fault detection value of the circuit to be detected.
Calculating the temperature change rate v of the circuit to be tested according to the collected real-time temperature dataTAs a first temperature fault detection value for the circuit to be tested.
And acquiring a real-time temperature T change amplitude value in a set time period of the circuit to be detected as a second fault judgment temperature index value.
For the circuit to be detected with the real-time running state of shutdown:
calculating the current integral value I of the circuit to be detected in the corresponding time period delta t according to the collected shutdown real-time direct current datatAs a shutdown fault detection value for the circuit to be detected.
Based on the above operation, the above fault detection values of the circuit to be detected of the photovoltaic system are compared with the corresponding protection threshold values to determine the fault detection result of the circuit to be detected, so the present invention has the step S130 of determining the fault detection result of the corresponding circuit to be detected based on the fault detection values.
In this step, the process of determining the fault detection result of the circuit to be tested includes:
for a circuit to be detected in a real-time operation state, if any one of the following requirements is met, determining that the corresponding circuit to be detected has a direct current arc fault:
the current fault detection value is more than or equal to a set fault current protection value PI；
The voltage fault detection value is more than or equal to a set fault voltage protection value PV；
The first temperature fault detection value is greater than or equal to a set first fault temperature protection value PT1；
The second temperature fault detection value is greater than or equal to a set second fault temperature protection value PT2。
If the shutdown fault detection value of the circuit to be detected in the real-time running state is shutdown and is greater than or equal to the set shutdown fault current protection value PIsAnd judging that the circuit to be detected has the direct current arc fault. And once the direct current arc fault of a certain circuit is determined, immediately carrying out fault early warning, disconnecting a corresponding switch and controlling the circuit to stop running so as to avoid the fault continuation or diffusion.
The setting of the above protection values has a great influence on the accuracy of the detection result. In particular, the fault current protection value PIIs set according to the power change rate of the circuit corresponding to the inverter, wherein PIThe current change value corresponding to the maximum power change rate when the circuit is in normal operation needs to be larger than.
The fault voltage protection value PVIs set according to the supporting capacitance and discharge resistance of the circuit corresponding to the inverter configuration, wherein PVThe discharge rate of the voltage must be greater than the discharge rate of the dc off voltage.
Said first fault temperature protection value PT1The method is set according to the current power of the circuit to be detected, the ambient temperature in a set range and the configuration parameters of the heat dissipation device.
Said second fault temperature protection value PT2Is set according to the current power required by the configuration of the circuit to be detected, the ambient temperature in a set range and the configuration parameters of the heat dissipation device, wherein P isT2The temperature of the circuit to be detected after full-load operation is stable at the maximum ambient temperature of normal operation of the system.
The shutdown fault current protection value PIsIs set according to the sampling precision of the current sensor corresponding to the circuit, wherein PIsIt must be greater than the maximum sample zero drift value during normal operation.
According to the technical scheme of the embodiment of the invention, the change state of each data in a specific time period is comprehensively analyzed by analyzing the fault detection characteristic data of the photovoltaic system in different running states, including current data, voltage data, temperature data and the like, starting from various characteristic data, so that the fault detection result of the photovoltaic system is determined, and the arcing fault can be more effectively identified. In addition, the data used in the detection process of the embodiment of the invention are all necessary data in the operation of the photovoltaic system, acquisition hardware does not need to be increased or decreased, the problem of data redundancy does not occur, meanwhile, the high accuracy of the fault detection result is ensured, the fault position can be quickly and timely found, the fault source can be cut off, the fault influence expansion is prevented, the loss caused by the fault is effectively reduced, and the stable operation of the photovoltaic system is facilitated.
Based on the above embodiment, an embodiment of the present invention further provides a system for detecting a dc arc fault of a photovoltaic system, and fig. 4 shows a schematic structural diagram of the system for detecting a dc arc fault of a photovoltaic system to be detected in the embodiment of the present invention, where each module in the system respectively executes corresponding steps in the embodiment.
As shown in fig. 4, the system for detecting a dc arc fault of a photovoltaic system according to an embodiment of the present invention includes: a characteristic data acquisition module 401, a detection value determination module 403, and a detection result determination module 405, which respectively execute the steps and methods in the above embodiments, and respectively execute steps S110, S120, and S130.
Specifically, the characteristic data acquisition module 401 is configured to acquire fault detection characteristic data of the circuit to be detected in the photovoltaic system according to a real-time operation state of the circuit to be detected.
A detection value determining module 403, configured to process the collected fault detection characteristic data to determine a fault detection value of the circuit to be detected.
A detection result determination module 405 arranged to determine a fault detection result for the circuit to be tested based on the fault detection value.
Specifically, the characteristic data acquisition module, its process according to photovoltaic system's real-time running state collection photovoltaic system's fault detection characteristic data includes:
and collecting real-time direct current data, real-time voltage data, real-time temperature data and shutdown real-time direct current data in a set time period of the circuit to be detected as fault detection characteristic data. Specifically, if the real-time operation state of the circuit to be detected is in operation, the real-time direct current data, the real-time voltage data and the real-time temperature data in the set time period of the circuit to be detected are collected as the fault detection characteristic data. If the real-time running state of the circuit to be detected is shutdown, the shutdown real-time direct current data of the circuit to be detected within a set time period is collected and used as fault detection characteristic data.
The detection value determining module determines the fault detection value of the circuit to be detected by the process of:
for the circuit to be detected with the real-time operation state as operation:
and selecting a current maximum value Imax and a current minimum value Imin from the collected real-time direct current data, and calculating a difference value delta I between the current maximum value Imax and the current minimum value Imin to be used as a current fault detection value of the circuit to be detected.
And selecting a maximum voltage value Vmax and a minimum voltage value Vmin from the collected real-time voltage data, and calculating a difference value delta V between the maximum voltage value Vmax and the minimum voltage value Vmin to be used as a voltage fault detection value of the circuit to be detected.
Calculating the temperature change rate v of the circuit to be tested according to the collected real-time temperature dataTAs a first temperature fault detection value for the circuit to be tested.
And acquiring a real-time temperature T change amplitude value in a set time period of the circuit to be detected as a second fault judgment temperature index value.
For the circuit to be detected with the real-time running state of shutdown:
calculating the current integral value I of the circuit to be detected in the corresponding time period delta t according to the collected shutdown real-time direct current datatAs a shutdown fault detection value for the circuit to be detected.
The detection result determining module determines the fault detection result of the circuit to be detected by the following steps:
if the circuit to be detected is in operation, each fault detection value of the circuit to be detected is compared and analyzed, and if any fault detection value meets the set condition, the circuit to be detected is judged to have a direct current arc fault;
if the circuit to be detected is in a shutdown state, comparing and analyzing the fault detection value of the circuit to be detected, and if the fault detection value meets the set condition, judging that the circuit to be detected has the direct current arc fault.
Specifically, the process of determining the fault detection result corresponding to the circuit to be detected by the detection result determining module includes:
for a circuit to be detected in a real-time operation state, if any one of the following requirements is met, determining that the corresponding circuit to be detected has a direct current arc fault:
the current fault detection value is more than or equal to a set fault current protection value PI；
The voltage fault detection value is more than or equal to a set fault voltage protection value PV；
The first temperature fault detection value is greater than or equal to a set first fault temperature protection value PT1；
The second temperature fault detection value is greater than or equal to a set second fault temperature protection value PT2。
If the shutdown fault detection value of the circuit to be detected in the real-time running state is shutdown and is greater than or equal to the set shutdown fault current protection value PIsAnd judging that the circuit to be detected has the direct current arc fault.
Wherein the fault current protection value PIIs set according to the power change rate of the circuit corresponding to the inverter, wherein PIThe current change value corresponding to the maximum power change rate when the circuit normally operates needs to be larger than;
the fault voltage protection value PVIs set according to the supporting capacitance and discharge resistance of the circuit corresponding to the inverter configuration, wherein PVThe discharge speed of the voltage is larger than that of the direct current when the direct current is cut off;
said first fault temperature protection value PT1The current power of the circuit to be detected, the environment temperature in a set range and the configuration parameters of the heat dissipation device are set;
said second fault temperature protection value PT2Is set according to the current power required by the configuration of the circuit to be detected, the ambient temperature in a set range and the configuration parameters of the heat dissipation device, wherein P isT2The temperature of the circuit to be detected after full-load operation is stable at the maximum ambient temperature of normal operation of the system.
The shutdown fault current protection value PIsIs set according to the sampling precision of the current sensor corresponding to the circuit, wherein PIsIt must be greater than the maximum sample zero drift value during normal operation.
In the system for detecting the direct current arc fault of the photovoltaic system, provided by the embodiment of the invention, each module or unit structure can be independently operated or operated in a combined mode according to test requirements, so that a corresponding technical effect is realized.
It is to be understood that the disclosed embodiments of the invention are not limited to the particular structures, process steps, or materials disclosed herein but are extended to equivalents thereof as would be understood by those ordinarily skilled in the relevant arts. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.
Reference in the specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, appearances of the phrase "an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment.
Although the embodiments of the present invention have been described above, the above descriptions are only for the convenience of understanding the present invention, and are not intended to limit the present invention. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. A method of detecting a dc arc fault in a photovoltaic system, the method comprising:
s1, collecting fault detection characteristic data according to the real-time running state of the circuit to be detected in the photovoltaic system;
step S2, processing the collected fault detection characteristic data to determine the fault detection value of the circuit to be detected;
and step S3, determining the fault detection result corresponding to the circuit to be detected based on the fault detection value.
2. The method according to claim 1, wherein in step S1, the step of collecting the fault detection characteristic data of the photovoltaic system according to the real-time operation state of the photovoltaic system comprises:
and collecting real-time direct current data, real-time voltage data, real-time temperature data and shutdown real-time direct current data in a set time period of the circuit to be detected as fault detection characteristic data.
3. The method according to claim 1 or 2, wherein in step S2, the process of determining the fault detection value of the circuit under test comprises:
for the circuit to be detected with the real-time operation state as operation:
selecting a current maximum value Imax and a current minimum value Imin from the collected real-time direct current data, and calculating a difference value delta I between the current maximum value Imax and the current minimum value Imin to be used as a current fault detection value of the circuit to be detected;
selecting a maximum voltage value Vmax and a minimum voltage value Vmin from the collected real-time voltage data, and calculating a difference value delta V of the maximum voltage value Vmax and the minimum voltage value Vmin as a voltage fault detection value of the circuit to be detected;
calculating the temperature change rate v of the circuit to be tested according to the collected real-time temperature dataTAs a first temperature fault detection value of the circuit to be detected;
and acquiring a real-time temperature T change amplitude value in a set time period of the circuit to be detected as a second fault judgment temperature index value.
4. The method according to any one of claims 1 to 3, wherein in step S2, the process of determining the fault detection value of the circuit to be tested further comprises:
for the circuit to be detected with the real-time running state of shutdown:
calculating the current integral value I of the circuit to be detected in the corresponding time period delta t according to the collected shutdown real-time direct current datatAs a shutdown fault detection value for the circuit to be detected.
5. The method according to claim 2 or 3, wherein in step S3, the process of determining the fault detection result corresponding to the circuit under test comprises:
for a circuit to be detected in a real-time operation state, if any one of the following requirements is met, determining that the corresponding circuit to be detected has a direct current arc fault:
the current fault detection value is more than or equal to a set fault current protection value PI；
The voltage fault detection value is more than or equal to a set fault voltage protection value PV；
The first temperature fault detection value is greater than or equal to a set first fault temperature protection value PT1；
The second temperature fault detection value is greater than or equal to a set second fault temperature protection value PT2。
6. The method according to claim 2 or 4, wherein in step S3, the process of determining the fault detection result corresponding to the circuit under test further comprises
If the shutdown fault detection value of the circuit to be detected in the real-time running state is shutdown and is greater than or equal to the set shutdown fault current protection value PIsAnd judging that the circuit to be detected has the direct current arc fault.
7. The method of claim 5, wherein the fault current protection value PIAccording to the power change set by the circuit corresponding to the inverterRate is set, wherein PIThe current change value corresponding to the maximum power change rate when the circuit normally operates needs to be larger than;
the fault voltage protection value PVIs set according to the supporting capacitance and discharge resistance of the circuit corresponding to the inverter configuration, wherein PVThe discharge speed of the voltage is larger than that of the direct current when the direct current is cut off;
said first fault temperature protection value PT1The current power of the circuit to be detected, the environment temperature in a set range and the configuration parameters of the heat dissipation device are set;
said second fault temperature protection value PT2Is set according to the current power required by the configuration of the circuit to be detected, the ambient temperature in a set range and the configuration parameters of the heat dissipation device, wherein P isT2The temperature of the circuit to be detected after full-load operation is stable at the maximum ambient temperature of normal operation of the system.
8. The method of claim 6, wherein the shutdown fault current protection value PIsIs set according to the sampling precision of the current sensor corresponding to the circuit, wherein PIsIt must be greater than the maximum sample zero drift value during normal operation.
9. A system for detecting a dc arc fault in a photovoltaic system, the system comprising:
the characteristic data acquisition module is used for acquiring fault detection characteristic data of the circuit to be detected in the photovoltaic system according to the real-time running state of the circuit to be detected;
the detection value determining module is used for processing the collected fault detection characteristic data and determining the fault detection value of the circuit to be detected;
and the detection result determining module is arranged to determine a fault detection result corresponding to the circuit to be detected based on the fault detection value.
10. The system of claim 9, wherein the detection result determination module determines the fault detection result of the circuit under test by:
if the circuit to be detected is in operation, each fault detection value of the circuit to be detected is compared and analyzed, and if any fault detection value meets the set condition, the circuit to be detected is judged to have a direct current arc fault;
if the circuit to be detected is in a shutdown state, comparing and analyzing the fault detection value of the circuit to be detected, and if the fault detection value meets the set condition, judging that the circuit to be detected has the direct current arc fault.
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