CN104796082A - System and method for diagnosing faults of photovoltaic power generation systems in online manner - Google Patents

Abstract

The invention provides an online fault diagnosis system for a photovoltaic power generation system, which includes a host computer with analysis and processing functions, an environmental monitor connected to the host computer, a photovoltaic monitoring terminal, and combiner box monitors respectively arranged on each combiner box. Modules, component monitoring modules installed on each photovoltaic module, etc., have a simple and reasonable structure. By installing a component monitoring module on each photovoltaic module and a combiner box monitoring module on each combiner box, it can detect each The voltage, current and power of photovoltaic modules, each photovoltaic string and combiner box are organized into a network by multiple monitoring modules, and cooperate with environmental monitors and photovoltaic monitoring terminals to make the monitoring and collection of each equipment of the photovoltaic power generation system The data and other reference data can be gradually uploaded to the host computer along the network nodes, so as to comprehensively analyze the operating status of the photovoltaic power generation system and realize the function of online fault diagnosis.

Description

An online fault diagnosis system and method for a photovoltaic power generation system

technical field

The invention relates to the field of solar power generation, in particular to an integrated, efficient and intelligent online fault diagnosis system for a photovoltaic power generation system and an online fault diagnosis method for a photovoltaic power generation system.

Background technique

After more than ten years of rapid development, my country's photovoltaic industry has entered the stage of large-scale development. As of 2013, the cumulative installed capacity of photovoltaics in my country was 17.16GW, and the target for newly installed photovoltaic capacity in 2014 is 14GW. In 2020, the total capacity of photovoltaic power generation will reach 180GW. The operation level of the photovoltaic power generation system is the core element that affects the system benefits. It will directly affect the operation and maintenance cost, power generation efficiency, and power generation reliability of the photovoltaic power generation system. How to ensure the high-level operation of the system is a common concern of all parties.

However, such a large-scale photovoltaic power generation system requires a huge number of equipment. When a certain equipment fails, it is very heavy to check all the equipment one by one. Taking a 50,000-kilowatt photovoltaic power station as an example, there are more than 100 inverters, more than 800 combiner boxes, more than 190,000 battery components, and a large number of DC confluence branches. In addition, the current distribution of photovoltaic power generation systems or geographical The location is remote, the transportation is inconvenient, or it is built on the roof of the building, so it is very difficult to inspect and manage the equipment.

At present, there are also data acquisition and monitoring systems for photovoltaic power generation systems, but the existing problems are as follows: 1) The monitoring data is unacceptable and unreliable. There is no string monitoring or only simple string data collection, the monitoring measurement accuracy is not high, and the measurement data is inaccurate; 2) It is difficult to report the monitoring data. The monitoring data is uploaded through the RS-485 bus, the transmission rate is low, there are many communication failures, false alarms and false alarms are serious; 3) fault location is difficult. The number of photovoltaic modules and nodes is huge, and there is a lack of effective fault location methods. Fault detection mainly relies on manual inspection and manual measurement and comparison through multimeters. The fault processing cycle is long, affecting power generation output, low maintenance efficiency, and large investment in manpower; 4) system Management lacks digital means. Simple collection and presentation of monitoring information, manual processing of a large number of data reports through Excel, poor comprehensive data analysis capabilities, lack of quantitative means for power generation operation analysis and improvement, and unified management of multiple systems cannot be realized.

It can be seen that it is necessary to improve the existing systems and methods for fault detection and diagnosis of photovoltaic power generation systems.

Contents of the invention

In view of the above problems, the object of the present invention is to propose an integrated, efficient and intelligent photovoltaic power generation system online fault diagnosis system and method, so as to realize the online fault diagnosis of the photovoltaic power generation system.

In order to solve the problems of the technologies described above, the technical solution of the present invention is as follows:

An online fault diagnosis system for a photovoltaic power generation system. The photovoltaic power generation system used includes an AC cabinet and several photovoltaic inverters. Each photovoltaic inverter is connected to several combiner boxes, and each combiner box is connected to several photovoltaic groups. Each photovoltaic string is composed of several photovoltaic modules in series. The online fault diagnosis system of the photovoltaic power generation system includes a host computer with analysis and processing functions, an environmental monitor connected to the host computer, a photovoltaic monitoring terminal, and A combiner box monitoring module installed on each combiner box, and a component monitoring module respectively installed on each photovoltaic module;

in,

The component monitoring module is used to monitor the voltage, current and power of the photovoltaic module, and upload it to the upper combiner box detection module;

The combiner box monitoring module is used to collect the voltage, current and power of each photovoltaic string in the combiner box, and collect the data uploaded by the lower-level component detection module, and upload them to the photovoltaic monitoring terminal;

Photovoltaic monitoring terminal, used to collect the data uploaded by each combiner box detection module, collect the operating parameters of the AC cabinet, monitor the switch status signal and analog signal of each device in the photovoltaic power generation system, and store the collected, collected and monitored data , and then upload to the host computer.

Correspondingly, the present invention also proposes an online fault diagnosis method for a photovoltaic power generation system, comprising the following steps:

Step A. Determine the equipment to be diagnosed according to the type of photovoltaic power generation system;

Step B, determining the characteristic parameters representing the operating state of the equipment to be diagnosed, and reading the real-time values of the characteristic parameters;

Step C, reading or calculating thresholds of characteristic parameters according to the evaluation model of the device to be diagnosed;

Step D, making a difference between the real-time value of the corresponding characteristic parameter and the threshold value;

Step E. When the difference exceeds the preset range, it is determined that there is a fault in the corresponding device to be diagnosed, and the fault is recorded, and an alarm is sent to the operation and maintenance personnel;

Step F, read the fault handling method from the knowledge base preset in the host computer with read-write and storage functions and guide the operation and maintenance personnel to repair the fault;

Step G, update the knowledge base after the fault is repaired.

In the present invention, a component monitoring module is arranged on each photovoltaic module, and a combiner box monitoring module is arranged on each combiner box, which can detect the voltage, current and power of each photovoltaic module, each photovoltaic string and the combiner box, And it is organized into a network by multiple monitoring modules, and cooperates with environmental monitors and photovoltaic monitoring terminals, so that the data and other reference data of various equipment in the photovoltaic power generation system that are monitored and collected can be gradually uploaded to the host computer along the network nodes. The operating status of the photovoltaic power generation system is comprehensively analyzed to realize the function of online fault diagnosis.

The present invention has the following advantages: 1. It is possible to use relatively easy-to-obtain, low-cost, and low-power components as component monitoring modules to realize the monitoring of a large number of photovoltaic components and provide feasibility for its fault detection and location; 2. Divide the photovoltaic power generation system into square array level, string level, and component level to realize hierarchical monitoring and location of faults, making fault monitoring and positioning faster and more accurate; 3. Monitoring and collecting data are more accurate and reported step by step Simple and reliable, high transmission rate, less false positives and false negatives.

Description of drawings

Figure 1 is a schematic diagram of a medium and high voltage grid-connected non-energy storage photovoltaic power generation system and its monitoring system;

Fig. 2 is a flowchart of an online fault handling method for a photovoltaic power generation system;

Figure 3 is a schematic diagram of a low-voltage grid-connected non-energy storage photovoltaic power generation system and its monitoring system;

Figure 4 is a schematic diagram of a low-voltage grid-connected energy storage photovoltaic power generation system and its monitoring system;

Figure 5 is a schematic diagram of a low-voltage off-grid energy storage photovoltaic power generation system and its monitoring system;

Explanation of reference signs: 1. Component monitoring module; 2. Combiner box monitoring module; 3. Photovoltaic monitoring terminal; 4. Environmental monitoring instrument; 5. Host computer.

Detailed ways

Photovoltaic power generation systems are divided into grid-connected and off-grid photovoltaic power generation systems according to whether they are connected to the grid, divided into high-voltage, medium-voltage and low-voltage photovoltaic power generation systems according to voltage levels, and divided into energy storage and non-grid photovoltaic power generation systems according to whether they include energy storage. Energy storage photovoltaic power generation system. Generally speaking, the off-grid type is a low-voltage type, and it should be equipped with an energy storage system. Furthermore, for medium and high voltage grid-connected types, energy storage systems are generally not configured. As for the structure of medium and high voltage grid-connected photovoltaic power generation systems, they are almost the same except for the different voltage levels of grid-connected transformers. Therefore, the actual photovoltaic power generation system mainly includes four types: low-voltage off-grid energy storage type, low-voltage grid-connected energy storage type, low-voltage grid-connected non-energy storage type, and medium-high voltage grid-connected non-energy storage type.

In order to make the above objects, features and advantages of the present invention more comprehensible, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Example 1

Figure 1 is a schematic diagram of a medium-high voltage grid-connected non-energy storage photovoltaic power generation system and its monitoring system. The photovoltaic system includes step-up transformers, AC power distribution cabinets, photovoltaic inverters and other equipment. Each photovoltaic inverter is connected to several combiner boxes, and each combiner box is connected to several photovoltaic strings. The string is composed of multiple photovoltaic modules in series; the specific number of the above-mentioned devices depends on the scale of the system. The configuration scheme of its online fault diagnosis system is: a host computer 5, a photovoltaic monitoring terminal 3, an environmental monitor 4, several combiner box monitoring modules 2, and several component monitoring modules 1. When performing online fault diagnosis on a photovoltaic power generation system, the data acquisition and communication process is as follows: first, a component monitoring module 1 is connected to each photovoltaic module, and the component monitoring module 1 monitors the voltage, current, and power of the photovoltaic module, and communicates with the superior The combiner box monitoring module 2 communicates and reports the voltage, current, and power data of the photovoltaic modules in real time; and then a combiner box monitoring module 2 is connected to each combiner box to collect the total voltage and current of each photovoltaic string in the combiner box on the one hand. , power data, on the other hand communicate with the component monitoring module 1 installed on the photovoltaic module through the wireless communication port, obtain the voltage, current and power data of the photovoltaic module, and send them to the photovoltaic monitoring terminal 3 through the wireless communication port; The monitoring terminal 3 plays an important role in this system, and its functions include: (1) wireless communication function, communicate with the combiner box, and collect voltage, current, and power data of the photovoltaic strings and photovoltaic modules of the combiner box; Position signal monitoring function, monitoring switch status signals in transformers, AC cabinets, and DC cabinets of photovoltaic power generation systems; (3) With analog monitoring functions, monitoring analog signals in step-up transformers, AC cabinets, and DC cabinets; (4 ) has the RS485/RS232 communication function, communicates with the photovoltaic inverter, and collects relevant data of the photovoltaic inverter; (5) has the data storage function, and stores the above-mentioned collected data; (6) Ethernet communication function, communicates with the upper Computer 5 communicates and uploads the above data to the host computer 5. In the figure, thin solid lines represent wired communication links, dashed lines represent wireless communication links, and thick solid lines represent power lines.

Correspondingly, the present invention also proposes an online fault diagnosis method for a photovoltaic power generation system, which can be run in a host computer as a software program, including the following steps:

Step A. Determine the equipment to be diagnosed according to the type of photovoltaic power generation system;

Step B, determining the characteristic parameters representing the operating state of the equipment to be diagnosed, and reading the real-time values of the characteristic parameters;

Step C, reading or calculating thresholds of characteristic parameters according to the evaluation model of the device to be diagnosed;

Step D, making a difference between the real-time value of the corresponding characteristic parameter and the threshold value;

Step E. When the difference exceeds the preset range, it is determined that there is a fault in the corresponding device to be diagnosed, and the fault is recorded, and an alarm is sent to the operation and maintenance personnel;

Step F, read the fault handling method from the knowledge base preset in the host computer with read-write and storage functions and guide the operation and maintenance personnel to repair the fault;

Step G, update the knowledge base after the fault is repaired.

FIG. 2 is a fault diagnosis and treatment process of the host computer 5 . This method regards the entire photovoltaic power generation system as a whole, sets corresponding characteristic parameters for each device in the system, and directly reads the threshold value of the characteristic parameters from the device by collecting the real-time values of these characteristic parameters, or according to the failure of each device The evaluation model calculates the threshold value of the characteristic parameter, compares the real-time value of the characteristic parameter with the threshold value, thereby identifying the equipment fault, and alarms the operation and maintenance personnel through sound, light, image, SMS, etc., and the fault handling is provided by the knowledge base Suggestion; among them, the knowledge base can learn independently and improve continuously according to the results of each fault handling.

First, according to the type of photovoltaic power generation system, determine the system equipment that needs fault diagnosis, that is, the equipment to be diagnosed. The equipment of the photovoltaic power generation system mainly includes grid-connected transformers, AC grid-connected cabinets, photovoltaic inverters, DC cabinets, controllers, batteries, combiner boxes, photovoltaic modules, etc. Among them, photovoltaic modules have the largest number and the most difficult to identify faults. But not all photovoltaic power generation systems include the above-mentioned equipment. For example, island-type photovoltaic power generation systems do not have grid-connected transformers and grid-connected cabinets, and non-energy storage photovoltaic power generation systems do not have batteries and controllers. For this embodiment, the equipment of the photovoltaic power generation system mainly includes transformers, grid-connected cabinets, photovoltaic inverters, combiner boxes, photovoltaic modules, etc., and these equipments are used as the equipment to be diagnosed.

Secondly, according to different equipment types, determine the characteristic parameters that can represent the normal operation of the equipment to be diagnosed, and then determine whether the equipment to be diagnosed is faulty by collecting and judging whether these operating parameters are in the normal range.

The characteristic parameters of the grid-connected transformer include high and low voltage side voltage, current, power, transformer oil temperature, pressure, etc. The monitoring method is to collect through the photovoltaic monitoring terminal 3, and upload to the monitoring system through the Ethernet communication interface of the photovoltaic monitoring terminal 3. center.

The characteristic parameters of the AC grid-connected cabinet are the position signal of the grid-connected switch and the meter. The characteristic parameter of the DC cabinet is the position signal of the DC switch. Its monitoring method is the same as that of grid-connected transformers, collecting and uploading through the photovoltaic monitoring terminal 3 .

The characteristic parameters of the photovoltaic inverter include DC side voltage, current, power, AC side voltage, current, power, frequency, power factor, module temperature, etc. In addition, many photovoltaic inverters also have a fault monitoring function, forming an alarm status word. These are sent to the upper computer 5 through the monitoring interface (generally RS232 or RS485) of the photovoltaic inverter itself.

Controllers and batteries are usually used in photovoltaic power generation systems that require energy storage, and they must be used at the same time. The monitoring of batteries is mostly realized through controllers. Complex controllers need to monitor the status of each battery. Simple control The controller only monitors the status of the battery strings. Its characteristic parameters include voltage, current, temperature and so on. The controller judges the charging and discharging status of the battery according to the real-time values of these characteristic parameters, and sends it to the upper computer 5 through its own monitoring interface.

The characteristic parameters of the photovoltaic module are the voltage, current and power of the module. The fault monitoring of photovoltaic modules is the most difficult. In order to accurately monitor and locate the faults of photovoltaic modules, the present invention can monitor through three levels: square array level, string level, and component level. The basic principle is: combine the technical index parameters of the photovoltaic module, such as volt-ampere characteristics, conversion efficiency, open circuit voltage, current, etc., with the solar radiation (including total radiation, scattering, direct sunlight), ambient temperature, humidity, etc. monitored by the environmental monitor 4. Atmospheric pressure and other parameters are input into the output power calculation model of the photovoltaic power generation system together, and the theoretical values of the power generation output power of the square array level, the string level, and the component level are calculated respectively, and then monitored with the inverter, combiner box, and components Compare the actual power generation output values of the corresponding stages monitored by module 1 to see if the difference is within a reasonable range. If the difference is within a reasonable range, it is considered that there is no fault. Otherwise, it is considered that there is a fault in the component of this level.

Among them, the output power calculation model of the photovoltaic power generation system is: first, according to the environmental parameters (mainly solar radiation and temperature), compare the VI characteristic curve of the module to obtain the theoretical output power of the module (denoted as P). For the calculation formula of string power: _Ptotal =P×N×η ₁ , where N is the number of components, and η ₁ is the series efficiency. The calculation formula for the power of the square array is as follows: _Ptotal = P×N×η ₂ , where η ₂ is the efficiency of the square array. For the same photovoltaic power generation system, the number of series modules and parallel modules are basically fixed, so η ₁ and η ₂ can be selected as certain constants in the system.

The component-level monitoring method is to embed a low-cost, low-power component monitoring module 1 on each photovoltaic component. The component monitoring module 1 can not only detect the voltage, current and power of the photovoltaic component, but also has a wireless Wifi communication function. Can automatically detect adjacent Wifi nodes, self-organizing network. The control commands and collected data of each component monitoring module 1 are transmitted along other sensor nodes one by one, and then go through multiple routes to the aggregation node—the gateway (relay receiving transmitter), and finally through wired Ethernet, WiFi, 3G Wait for the wireless communication method to deliver to the upper computer 5.

If there is a fault in the equipment to be diagnosed, an alarm will be generated, and the operation and maintenance personnel will be notified through sound, light, image, SMS, etc., and then the troubleshooting method will be queried from the fault diagnosis knowledge base to guide the operation and maintenance personnel to repair the fault; or operation and maintenance Personnel repair faults based on their own skills, experience and actual conditions. Finally, according to the fault repair plan of the operation and maintenance personnel, the knowledge base is updated to provide better guidance for the next fault handling; so repeated, the knowledge base is continuously improved.

Example 2

Figure 3 is a schematic diagram of a low-voltage grid-connected non-energy storage photovoltaic power generation system and its monitoring system. Compared with Example 1, the structure of the photovoltaic power generation system is almost identical, except that there is no step-up transformer. Therefore, the online fault diagnosis system for the photovoltaic power generation system is the same as that of Embodiment 1, and when performing online fault diagnosis for the photovoltaic power generation system, only the step-up transformer needs to be excluded when determining the equipment to be diagnosed.

Other technical features are the same as those in Embodiment 1, and will not be repeated here.

Example 3

Fig. 4 is a schematic diagram of a low-voltage grid-connected energy storage photovoltaic power generation system and its monitoring system. Compared with Embodiment 2, the photovoltaic power generation system adds a charging and discharging controller and a storage battery. Its online fault diagnosis method is as follows: the charging and discharging controller collects and monitors the voltage, current, power of its AC and DC terminals and the working temperature of the storage battery, stores and uploads these data to the host computer 5; establishes fault diagnosis of these devices in the host computer 5 Model, determine the characteristic parameters that can characterize the normal operation of these devices, judge whether these operating parameters are in the normal range, and then judge whether the device is faulty.

For other technical features, refer to Embodiments 1 and 2, which will not be repeated here.

Example 4

Figure 5 is a schematic diagram of a low-voltage off-grid energy storage photovoltaic power generation system and its monitoring system. Compared with Embodiment 3, the photovoltaic power generation system is not connected to the distribution network only when the AC flows into the AC cabinet, but is directly connected to the load connected, but this does not affect the construction of the online fault diagnosis system and the diagnosis and treatment of faults, so the online fault diagnosis method is the same as that of Embodiment 3.

The above-mentioned embodiments refer to each other.

In the present invention, a component monitoring module is arranged on each photovoltaic module, and a combiner box monitoring module is arranged on each combiner box, which can detect the voltage, current and power of each photovoltaic module, each photovoltaic string and the combiner box, And it is organized into a network by multiple monitoring modules, and cooperates with environmental monitors and photovoltaic monitoring terminals, so that the data and other reference data of various equipment in the photovoltaic power generation system that are monitored and collected can be gradually uploaded to the host computer along the network nodes. The operating status of the photovoltaic power generation system is comprehensively analyzed to realize the function of online fault diagnosis. It uses components that are relatively easy to obtain, low-cost, and low-power consumption as component monitoring modules to monitor a large number of photovoltaic components and provide feasibility for fault detection and location; the photovoltaic power generation system is divided into square array, String level, component level, realize hierarchical monitoring and location of faults, make fault monitoring and location faster and more accurate; monitoring and collected data are more accurate, and report step by step is simple and reliable, high transmission rate, false positives and false negatives few.

The above-mentioned embodiments only express several implementation modes of the present invention, and the description thereof is relatively specific and detailed, but should not be construed as limiting the patent scope of the present invention. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention should be based on the appended claims.

Claims (2)

1. An online fault diagnosis system for a photovoltaic power generation system, the applied photovoltaic power generation system includes an AC cabinet and several photovoltaic inverters, each photovoltaic inverter is connected to several road combiner boxes, and each road combiner box is connected to several road Photovoltaic strings, each photovoltaic string is composed of several photovoltaic modules connected in series, which is characterized by: The online fault diagnosis system of the photovoltaic power generation system includes a host computer with analysis and processing functions, an environmental monitor connected to the host computer, a photovoltaic monitoring terminal, and combiner box monitoring modules respectively arranged on the combiner boxes of each road. Component monitoring modules on each photovoltaic module; in, The component monitoring module is used to monitor the voltage, current and power of the photovoltaic module, and upload it to the upper combiner box detection module; The combiner box monitoring module is used to collect the voltage, current and power of each photovoltaic string in the combiner box, and collect the data uploaded by the lower-level component detection module, and upload them to the photovoltaic monitoring terminal; Photovoltaic monitoring terminal, used to collect the data uploaded by each combiner box detection module, collect the operating parameters of the AC cabinet, monitor the switch status signal and analog signal of each device in the photovoltaic power generation system, and store the collected, collected and monitored data , and then upload to the host computer. 2. An online fault diagnosis method using the photovoltaic power generation system online fault diagnosis system as claimed in claim 1, characterized in that, comprising the following steps: Step A. Determine the equipment to be diagnosed according to the type of photovoltaic power generation system; Step B, determining the characteristic parameters representing the operating state of the equipment to be diagnosed, and reading the real-time values of the characteristic parameters; Step C, reading or calculating thresholds of characteristic parameters according to the evaluation model of the device to be diagnosed; Step D, making a difference between the real-time value of the corresponding characteristic parameter and the threshold value; Step E. When the difference exceeds the preset range, it is determined that there is a fault in the corresponding device to be diagnosed, and the fault is recorded, and an alarm is sent to the operation and maintenance personnel; Step F, read the fault handling method from the knowledge base preset in the host computer with read-write and storage functions and guide the operation and maintenance personnel to repair the fault; Step G, update the knowledge base after the fault is repaired.