A photovoltaic power generation metering device based on hall effect and a metering monitoring method

Abstract

The present invention discloses a photovoltaic power generation metering device based on the Hall effect, which includes a main module for metering the power generation of the first photovoltaic string and one or more slave modules for monitoring the power generation of corresponding photovoltaic strings. The key lies in that open Hall components for data acquisition are provided on both the main module and the slave modules. The open Hall component includes a Hall seat connected to a circuit board matching the main module or the slave module, and a Hall plate connected to the Hall seat by means of a rotating shaft and a torsion spring. A hole for the current cable in the photovoltaic string to pass through is provided at the junction of the Hall plate and the Hall seat. In addition, the present invention also discloses a method for metering and monitoring the power generation of photovoltaic strings. The beneficial technical effects of the present invention are as follows: The real-time monitoring of the DC electric energy of photovoltaic strings is carried out by using one main module and multiple slave modules, with high isolation degree. The detection unit can be adjusted at any time according to the number of photovoltaic strings on site without power outage, and multiple modules can be flexibly increased or decreased, which is convenient for maintenance, fast and timely.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electric energy metering, in particular to a photovoltaic power generation metering device based on Hall effect and a metering monitoring method. BACKGROUND

[0002] Photovoltaic power is an important clean energy, and it is inevitable to build a new power system based on clean energy such as photovoltaic and wind power. Photovoltaic power metering and monitoring is an important support for building a new power system.

[0003] The centralized photovoltaic power generation system mainly consists of photovoltaic components, a direct current junction box, a direct current distribution cabinet, a grid-connected inverter, an alternating current distribution cabinet, an electric energy quality detection device, a data processing unit and a monitoring center. The monitoring unit for monitoring the power generation of photovoltaic strings is generally placed in the direct current junction box. However, the number of monitoring paths for monitoring photovoltaic strings is determined at the time of factory delivery, and the circuit is integrated in one device. On the one hand, for centralized photovoltaic systems with a large number of photovoltaic strings, such as desert photovoltaic power generation systems, the number of monitoring paths cannot be flexibly increased or decreased according to the needs of the site. When a certain path of the monitoring unit fails, the entire monitoring unit needs to be removed for maintenance or replacement, which brings many inconveniences to the maintenance of photovoltaic power generation. In addition, because high-voltage direct current is generated after the photovoltaic string, the power must be cut off during installation, and the safety performance is not high, which cannot meet the needs of the site. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a photovoltaic power generation metering device based on Hall effect and a metering monitoring method, which can adjust the slave module for power generation metering at any time according to the number of photovoltaic strings on site, without power cut, and flexibly increase or decrease the number of modules.

[0005] To solve the above technical problems, the technical scheme adopted by the present application is:

[0006] A photovoltaic power generation metering device based on Hall effect, comprising a master module for metering the power generation of a first photovoltaic string and one or more slave modules for monitoring the power generation of corresponding photovoltaic strings, characterized in that an open Hall component for collecting data is arranged on the master module and the slave module, the open Hall component comprises a Hall seat connected with a circuit board matched with the master module or the slave module, and a Hall plate connected with the Hall seat by means of a rotating shaft and a torsional spring, and a hole is arranged at the joint of the Hall plate and the Hall seat for the current cable in the photovoltaic string to pass through.

[0007] Based on the above-mentioned photovoltaic power generation metering device based on Hall effect, the present application further provides a metering monitoring method for the power generation of a photovoltaic string, comprising the following steps:

[0008] A, the master module and the slave module collect voltage analog values and current analog values of corresponding photovoltaic strings, and calculate power of the photovoltaic strings P m Then, it is judged whether the power of the photovoltaic strings is greater than a judgment threshold P m P 0 And the duration is greater than a delay time T 1 If yes, step B is executed, otherwise, it is judged that the corresponding photovoltaic string generates power abnormally, an alarm is given, and step E is executed, wherein, the value range of m is 1-X, and X is the number of photovoltaic strings corresponding to the master module and the slave module;

[0009] B, the master module and the slave module judge whether the power of the photovoltaic strings is less than a rated power of corresponding photovoltaic components P m P 额 And the duration is greater than a delay time T 2 If yes, step C is executed, otherwise, step A is returned;

[0010] C, the master module and the slave module obtain voltage of the photovoltaic strings U m And a photovoltaic component power generation PV curve stored in an EEPROM, and according to the PV curve, the corresponding power when the voltage is U m is calculated P m ’ It is judged whether the power of the photovoltaic strings is less than P m u 0 P m ’ If yes, it is judged that the photovoltaic string generates power abnormally, an alarm is given, and step E is executed, otherwise, step D is executed, wherein, u 0 The aging coefficient of the photovoltaic component;

[0011] D, the master module collects power of the remaining normal photovoltaic strings, and the centralized trend of the normal photovoltaic string power data is calculated through P 均 = P 均 The power of the normal photovoltaic strings is compared P m u 1 P 均 ​​​​​If yes, the main module determines that the photovoltaic string generates abnormally, alarms and executes step E, otherwise returns to step A, wherein, u 1 The i value range is 1-s, and s is the number of normal photovoltaic strings.

[0012] E. The main module obtains the alarm information and number of the alarm photovoltaic string, and then reports to the monitoring center.

[0013] The beneficial technical effects of the present application are: (1) the photovoltaic string direct current power is monitored in real time by using a master-slave module, the isolation degree is high, the detection unit can be adjusted at any time according to the number of on-site photovoltaic strings, power supply is not required, the number of modules can be flexibly increased or decreased, maintenance is convenient, fast and timely; (2) the fault of the photovoltaic string can be quickly found and reported in real time, which helps maintenance personnel to check and maintain in time and reduces power generation loss.

[0014] The present application will be described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 It is a control principle diagram of the photovoltaic string monitoring system;

[0016] Figure 2 It is a connection schematic diagram of the main module and the slave module and the installation guide rail;

[0017] Figure 3 It is a position schematic diagram between the current cable and the Hall plate and the Hall seat;

[0018] Figure 4 It is a photovoltaic module power generation PV curve diagram;

[0019] Figure 5 It is an access flowchart of the slave module processing new access slave module;

[0020] Figure 6 It is a new module access flowchart of the main module processing;

[0021] Figure 7 It is a flowchart of the metering and monitoring method.

[0022] In the drawings: 1 is an installation guide rail, 2 is a guide rail buckle, 3 is a circuit board, 4 is a hole, 5 is a Hall seat, 6 is a torsion spring, 7 is a Hall plate, and 8 is a current cable. DETAILED DESCRIPTION

[0023] The application provides a photovoltaic power generation metering device based on Hall effect, which comprises a master module for metering power generation of a first photovoltaic string and one or more slave modules for monitoring power generation of corresponding photovoltaic strings. The first slave module is electrically connected with the master module. When there are multiple slave modules, the multiple slave modules are sequentially electrically connected. In specific implementation, the first slave module and the master module and the adjacent slave module are electrically connected by means of the socket.

[0024] The master module is used for monitoring direct current operation of the first photovoltaic string and acquiring voltage, current, power and electric energy data; and the multiple slave modules are used for monitoring direct current operation of corresponding photovoltaic strings and acquiring voltage, current, power and electric energy data.

[0025] The master module comprises an isolation power supply, a master MCU, a master module metering unit, a module identification circuit, a next module power control switch, a communication unit and a master module interface. The communication unit comprises a network module or a micro-power wireless module for communication with a master station and an RS485 for communication with the slave modules. The slave module comprises a slave MCU, a slave module metering unit, a module identification circuit, a next module power control switch, an RS485 and a slave module interface. The master module interface and the slave module interface both comprise a power supply interface, a module identification circuit interface, a communication interface and a direct current voltage sampling interface.

[0026] Referring to the accompanying drawings, Figure 2 and 3 The master module and the slave module are both fixed on the installation rail 1. The master module and the slave module are both fixed on the installation rail 1 by means of the connecting assembly. The connecting assembly comprises a rail buckle 2 connected with the installation rail 1 and fixed on the circuit board 3. Specifically, the master module and the slave module are both provided with an open Hall assembly for collecting data. The open Hall assembly comprises a Hall seat 5 connected with the circuit board 3 matched with the master module or the slave module and a Hall plate 7 connected with the Hall seat 5 by means of a rotating shaft and a torsional spring 6. A hole 4 for the current cable 8 in the photovoltaic string to pass through is arranged at the joint of the Hall plate 7 and the Hall seat 5. The current cable 8 can be placed in the open Hall assembly by lifting the free end of the Hall plate 7. After being closed under the action of the torsional spring 6, the Hall plate 7 can be matched with the Hall seat 5 to form a Hall mutual inductor, so as to realize data collection.

[0027] When the first slave module is connected to the master module through the interface, the plug-in identification method of the master module for identifying the first slave module comprises the following steps: (1) the module identification circuit level of the master module is lowered and the low level duration is greater than 100 ms, and the master module determines that the first slave module is connected; (2) the master module automatically adds 1 to the total number of connected slave modules, and opens the power switch of the first slave module through the next module power control switch thereon, and the first slave module is powered on.

[0028] When the adjacent slave modules are connected in sequence by means of the sockets, the plug-in recognition method of the slave module comprises the following steps: (1) when the next slave module is inserted into the current slave module through the interface, if the module recognition circuit level of the current slave module becomes low and the low level duration is greater than 100 ms, the current slave module determines that the next slave module is connected and informs the master module through the RS485 bus communication mode; (2) the master module automatically adds 1 to the total number of connected slave modules, informs the current slave module to open the next module power supply control switch thereon, and the next slave module is powered on and started.

[0029] The master module communicates with the newly recognized slave module through the RS485 bus according to the default address of the slave module (the initial addresses of all slave modules are the same) and sets the communication address of the slave module as N (the address 1 is the address of the master module), and then performs data measurement on the Nth module, wherein N is the sum of the number of the current master module and the number of the slave module.

[0030] Referring to the accompanying drawings Figure 7 , based on the above device, the photovoltaic string power generation quantity measurement and monitoring method comprises the following steps.

[0031] A, the master module and the slave module collect the voltage analog value and the current analog value of the corresponding photovoltaic string, and calculate the power of the respective photovoltaic string P m , then determine whether the power of the respective photovoltaic string P m is greater than the determination threshold P 0 and the duration is greater than the delay time T 1 , if yes, step B is executed, otherwise, it is determined that the corresponding photovoltaic string generates abnormally, an alarm is given and step E is executed, wherein the value range of m is 1-X, X is the number of the photovoltaic string corresponding to the master module and the slave module. P1 is the power of the photovoltaic module corresponding to the master module, P2, P3, P4…P X are the power generation powers of the photovoltaic strings corresponding to the slave modules connected in sequence. T 1 The time of 10 seconds, 15 seconds, etc. can be set.

[0032] B, the master module and the slave module determine whether the power of the respective photovoltaic string P m is less than the rated power of the corresponding photovoltaic module P 额 and the duration is greater than the delay time T 2 , if yes, step C is executed, otherwise, step A is returned. T 2 The time of 10 seconds, 15 seconds, etc. can be set.

[0033] C. The main module and slave modules obtain the voltage of each photovoltaic string. U m And the PV curve of the photovoltaic module stored in the EEPROM, based on which the voltage is calculated. U m The power corresponding to time P m ’ Determine their respective power P m Is it less than u 0 P m ’ If so, the photovoltaic string power generation is determined to be abnormal, an alarm is triggered, and step E is executed; otherwise, step D is executed. Wherein, u 0 U1 represents the aging factor of the photovoltaic module, U2, U3, U4…U… x The voltage of the photovoltaic string corresponding to the modules connected in sequence.

[0034] The alarm process when the module detects an abnormal power generation of the corresponding photovoltaic string in steps A and C above is as follows: When the slave module detects an abnormal power generation alarm of the photovoltaic string, it will set the alarm flag bit to 1 and set the relevant alarm information bits. The master module polls the slave modules every 1ms through the RS485 bus. When it finds that the alarm flag of a slave module is set to 1, it immediately calls its address number and alarm information to obtain the alarm module number and alarm information. When the master module detects an abnormal power generation of its own corresponding photovoltaic string, it will directly obtain the module address number and alarm information through its CPU.

[0035] D. The main module calls upon the power of other normal photovoltaic strings from the slave modules, and then... P 均 = Calculate the central tendency of normal photovoltaic string power generation data P 均 Compare the power of a normal photovoltaic string P m Is it less than u 1 P 均 If so, the main module determines that the photovoltaic string power generation is abnormal, issues an alarm, and executes step E; otherwise, it returns to step A. u 1 The coefficient of variation represents the power generation characteristics of a batch of photovoltaic modules. The value of i ranges from 1 to s, where s is the number of normal photovoltaic strings and Pi is the power collected by the main module or slave module corresponding to the photovoltaic string in normal state.

[0036] E, the main module acquires alarm information and number of the alarm photovoltaic string, and then reports to the monitoring center.

[0037] The application will be described in detail below with reference to specific embodiments.

[0038] Referring to the accompanying drawings Figure 1 The photovoltaic component strings in the centralized solar photovoltaic power generation system are arranged in parallel, each string generally has 8-30 photovoltaic components, and each system has 2-32 strings. The number of photovoltaic components in series in the photovoltaic component strings in the same system is the same, so that the direct current high voltage value generated by the photovoltaic components in series in each string is equal under normal circumstances, and thus the photovoltaic components can be connected in parallel to the bus.

[0039] In the embodiment, the main module and the slave module have X (X≥2) corresponding to the X photovoltaic components arranged. When installed, the installation guide rail 1 is first fixed in the direct current bus box, the first module (the main module) is fixed on the guide rail, connected to the bus power supply, and then the first string cable is clamped into the hole 4 at the joint of the Hall plate 7 and the Hall seat 5. The first module provides the power required for the operation of the following modules (i.e. the slave modules) and the direct current voltage sampling of each module. When the mth (X≥m≥2) module is installed, it only needs to be installed on the guide rail, then the interface of the (m-1)th module and the mth module is connected by using the two-pin connector, then the mth string cable is clamped into the hole in the corresponding Hall component, and then it is fixed on the guide rail. The Hall has high isolation performance, can be operated under voltage, has high safety, and supports multiple slave modules to be connected, and then simultaneously connected to the main module (system), and the module order can still be identified and numbered.

[0040] Referring to the accompanying drawings Figure 5 and 6 When the second module is connected to the first module (i.e. the first slave module is connected to the main module through the interface), the plug-in identification method of the first module for identifying the second module includes the following steps: (1) the module identification circuit of the first module is low in level and the low level lasts for more than 100 ms, and the first module determines that the second module is connected; (2) the first module automatically adds 1 to the total number of connected modules, and the next module power supply control switch on the first module opens the power supply switch of the second module, and the second module is powered on and started.

[0041] When the adjacent modules are connected in sequence by means of the sockets, the module plug-in recognition method comprises the following steps: (1) when the mth module is plugged into the (m-1)th module through the interface, the module recognition circuit of the (m-1)th module becomes low in level and the low level lasts for more than 100 ms, and the (m-1)th module determines that the mth module is plugged in and informs the first module through the RS485 bus communication mode; at this time, m is a natural number greater than or equal to 3. (2) the first module automatically adds 1 to the total number of plugged-in modules, informs the next module on the (m-1)th module to open the power switch of the mth module, and the mth module is powered on and started.

[0042] The master module communicates with the mth module through the RS485 bus according to the default module address (the initial address of all modules is the same) and sets the communication address of the mth module as m, and then performs data measurement on the mth module.

[0043] When the mth (m≥2) module is unplugged from the (m-1)th module, the power of the mth module is immediately cut off, the level recognized by the MCU in the (m-1)th module changes from low to high, and the MCU in the (m-1)th module which has been in polling mode detects the high level. To exclude interference, when the low level lasts for more than 100 ms, the (m-1)th module determines that the mth module has been unplugged. When the (m-1)th module determines that the mth module is unplugged, the power control switch of the next module in the (m-1)th module closes the power switch of the mth module and informs the first module. The master module automatically reduces 1 from the total number of plugged-in modules, and the first module only performs data measurement on the modules with addresses from 1 to m-1, and no longer performs measurement on the module with address m.

[0044] When the photovoltaic string power generation is measured and monitored, the following steps are included.

[0045] Step A, each module samples the analog voltage and current of the photovoltaic string thereof, and then calculates the power P of each module 1、 P2, P3, P4…P X When the photovoltaic component is abnormal and disconnected (or close to disconnected), the power of the photovoltaic string thereof is about zero, and the threshold value is set in combination with the system date, the estimated sunshine, and the dark time P 0 and the delay time T 1 Each module determines whether the power of the photovoltaic string thereof is greater than the threshold value P 0 and the duration is greater than the delay time T 1 If yes, the next step is performed, otherwise, it is determined that the corresponding photovoltaic string generates power abnormally, an alarm is given, and step E is performed.

[0046] Step B, the rated power of each string of photovoltaic modules is P 额 When an abnormality occurs in a certain photovoltaic module, the power generated by the module will certainly decrease, and the power of the string in which the module is located will also decrease compared with the rated total power. However, the power generated by the photovoltaic string may also decrease due to external environmental reasons such as cloud cover. Therefore, it is necessary to determine the duration of the abnormality T 2 , T 2 The value can be determined according to the actual use environment and other factors. For the remaining photovoltaic modules, when each module determines that the power of the photovoltaic string is less than P 额 and the duration is T 2 , it is necessary to continue to determine whether an abnormality occurs in power generation through step C, otherwise, return to step A.

[0047] Step C, the PV curve of the power and voltage of the photovoltaic module is as shown in Figure 4 .

[0048] The above photovoltaic power PV curve is divided into three sections AB, BC and CD, and the relationship between power P and voltage U in each section is determined. In section AB, when a P = K 1 U ; in section BC, when b P = K 2 U + b 1 ; in section CD, when c P = -K 3 U 2 +b 2 The three sections of the curve are straight line, straight line and parabola in turn, wherein K 1 、K 2 、K 3 、b 1 、b 2 are all conventional coefficients.

[0049] The above segmented curve relationship is stored in the memory, and when the power is determined, the voltage U m of each photovoltaic string is obtained. First, the membership range of U m is determined from [a, b), [b, c) and [c, d), and then the PV curve relationship of the range is compared to calculate U mCorresponding power value in the curve P m ’ , considering the photovoltaic module in the process of use with the use of the date is long, aging and other factors, need to multiply the aging coefficient u 0 , to determine P m whether less than u 0 P m ’ , if so, the determination of the m photovoltaic string power generation abnormal and alarm, otherwise need to further determine by step D. In this step, the value range of m is 1-X.

[0050] Step D, because the photovoltaic power generation system used photovoltaic module power generation characteristics of the same or similar, its installation environment is the same, so the power generation of each photovoltaic string in the system is also similar, for the remaining photovoltaic string after step C, need to compare the power generation of other strings in the system, the present application adopts statistical method to screen and determine.

[0051] The main module calls the power of the remaining normal photovoltaic string, through P 均 = Calculate the central tendency of the normal photovoltaic string power generation data P 均 , compare the power of the normal photovoltaic string P m whether less than u 1 P 均 , if so, the main module determines that the photovoltaic string power generation is abnormal, alarm and execute step E, otherwise return to step A, wherein, u 1 represents the dispersion coefficient of the batch photovoltaic module, the value range of i is 1-s, s is the number of normal photovoltaic string. P 均 represents the central tendency of the normal photovoltaic string power generation data in the system, and it also covers the dispersion degree and fluctuation degree of different string power data. u 1 represents the dispersion coefficient of the batch photovoltaic module, compare the power of each normal photovoltaic string P m whether less than u 1 P 均 , if so, the determination of the m photovoltaic string power generation abnormal and alarm; if not, the photovoltaic string does not occur abnormal.

[0052] Step E, the main MCU of the first module acquires the above-mentioned alarm state information, acquires the number corresponding to all modules and photovoltaic strings of the power generation abnormal state, and reports the same to the monitoring center to prompt the fault and ask to go to check and maintain.

[0053] It should be noted that the above examples are used to illustrate the technical solutions of the present application, but not to limit them. Although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the specific embodiments of the present application can be modified or some technical features can be replaced by equivalent ones without departing from the spirit of the technical solutions of the present application, and all of them should be covered in the technical solution range of the present application.

Claims

1. A method for measuring and monitoring the power generation of a photovoltaic string, a photovoltaic power generation metering device based on the Hall effect. The photovoltaic power generation metering device includes a main module for measuring the power generation of the first photovoltaic string and one or more slave modules for monitoring the power generation of the corresponding photovoltaic strings. Open Hall components for collecting data are provided on both the main module and the slave modules. The open Hall component includes a Hall base (5) connected to a circuit board (3) supporting the main module or the slave module, and a Hall plate (7) connected to the Hall base (5) by means of a rotating shaft and a torsion spring (6). A hole (4) for the current cable (8) in the photovoltaic string to pass through is provided at the junction of the Hall plate (7) and the Hall base (5). It is characterized in that, Includes the following steps: A. The main module and slave modules collect the simulated voltage and current values ​​of the corresponding photovoltaic strings and calculate the power of each photovoltaic string. Then determine the power of each photovoltaic string. Is it greater than the judgment threshold? And the duration is greater than the delay time. If so, proceed to step B; otherwise, determine that the corresponding photovoltaic string is generating power abnormally, trigger an alarm, and proceed to step E. Here, the value of m ranges from 1 to X, where X is the number of photovoltaic strings corresponding to the master module and the slave module. B. The main module and slave module determine the power of their respective photovoltaic strings. Is it less than the rated power of the corresponding photovoltaic module? And the duration is greater than the delay time. If yes, proceed to step C; otherwise, return to step A. C. The main module and slave modules obtain the voltage of each photovoltaic string. And the PV curve of the photovoltaic module stored in the EEPROM, based on which the voltage is calculated. The power corresponding to time Determine their respective power Is it less than If so, the photovoltaic string power generation is determined to be abnormal, an alarm is triggered, and step E is executed; otherwise, step D is executed. The aging coefficient of the photovoltaic module; D. The main module calls upon the power of the remaining normal photovoltaic strings, through... = Calculate the central tendency of normal photovoltaic string power generation data Compare the power P of a normal photovoltaic string m Is it less than If so, the main module determines that the photovoltaic string power generation is abnormal, issues an alarm, and executes step E; otherwise, it returns to step A. The coefficient of variation represents the power generation characteristics of a batch of photovoltaic modules, where i ranges from 1 to s, and s is the number of normal photovoltaic strings. E. The main module obtains the alarm information and number of the alarm photovoltaic string and then reports it to the monitoring center.

2. The method for metering and monitoring the power generation of a photovoltaic string according to claim 1, characterized in that, When the first slave module connects to the master module, the insertion / removal identification method for the first slave module includes the following steps: (1) When the module identification circuit of the main module goes low and the low level lasts for more than 100ms, the main module determines that the first slave module is connected. (2) The main module will automatically increment the total number of connected slave modules by 1 and turn on the power switch of the first slave module, so that the first slave module is powered on and started.

3. The method for metering and monitoring the power generation of a photovoltaic string according to claim 1, characterized in that, When adjacent slave modules are connected via sockets, the slave module plug-in / plug-out identification method includes the following steps: (1) When the next slave module is inserted into the current slave module through the interface, if the module identification circuit level of the current slave module goes low and the low level lasts for more than 100ms, the current slave module determines that the next slave module is connected and notifies the master module through RS485 bus communication. (2) The master module will automatically increment the total number of connected slave modules by 1, and notify the current slave module to turn on the power switch of the next module, and the next slave module will be powered on and started.

4. The method for metering and monitoring the power generation of a photovoltaic string according to claim 2 or 3, characterized in that, The master module communicates with the newly identified slave module via RS485 bus according to the slave module's default address and sets its communication address to N. Then, it performs data recall on the Nth module, where N is the sum of the current number of all master and slave modules.

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