CN112737639B - Phase sequence identification method for power line carrier communication and photovoltaic system - Google Patents
Phase sequence identification method for power line carrier communication and photovoltaic system Download PDFInfo
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- CN112737639B CN112737639B CN202011572663.2A CN202011572663A CN112737639B CN 112737639 B CN112737639 B CN 112737639B CN 202011572663 A CN202011572663 A CN 202011572663A CN 112737639 B CN112737639 B CN 112737639B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B3/00—Line transmission systems
- H04B3/54—Systems for transmission via power distribution lines
- H04B3/542—Systems for transmission via power distribution lines the information being in digital form
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
- H02J13/00006—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment
- H02J13/00007—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment using the power network as support for the transmission
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
- Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
- Y04S40/00—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them
- Y04S40/12—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them characterised by data transport means between the monitoring, controlling or managing units and monitored, controlled or operated electrical equipment
- Y04S40/121—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them characterised by data transport means between the monitoring, controlling or managing units and monitored, controlled or operated electrical equipment using the power network as support for the transmission
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Abstract
The invention provides a phase sequence identification method for power line carrier communication and a photovoltaic system, and relates to the technical field of power. A phase sequence identification method of power line carrier communication is applied to the power line carrier communication of a photovoltaic system and comprises the following steps: after a photovoltaic system is electrified, starting a phase sequence identification mode; conducting a main node in a photovoltaic system with one phase sequence channel; the master node sends a plurality of rounds of test frames to the conducted phase sequence channel, receives response frames returned by the slave nodes, and counts the packet loss rate of each slave node according to the number of the response frames; traversing the other phase sequence channels under the three-phase three-wire system, and sequentially counting the packet loss rate of each slave node of different phase sequence channels; and taking the phase sequence channel with the minimum packet loss rate of each slave node as a transmitting and receiving phase sequence channel of the slave node. Therefore, the identification of each slave node phase sequence channel is realized, and the manpower is saved. In addition, the carrier communication under the correct phase sequence improves the communication quality of the main node and the slave node, and reduces the packet loss rate.
Description
Technical Field
The invention relates to the technical field of electric power, in particular to a phase sequence identification method for power carrier communication and a photovoltaic system.
Background
Power Line Communication (PLC) is a communication technology using Power lines as a transmission medium for high-frequency carrier signals, and has a major characteristic that data transmission can be performed as long as Power lines are available without newly setting up a network. At present, a power line carrier communication technology is widely used for power grid meter reading and photovoltaic inverter communication, a power line is used as a communication medium, a communication line does not need to be arranged independently, and a large amount of manpower and material resources are saved.
The PLC communication medium comprises a main node and a slave node, and when the main node and the slave node of the PLC communicate with each other, the main node needs to know what phase sequence channel the slave node is in at the beginning of communication so as to switch to the corresponding phase sequence channel for transceiving. Generally, on an initial grid-connected site, what phase sequence channel is used by a master node is specified according to a phase sequence channel of a slave node in a manual mode, but the situation that the master node and the slave node do not correspond to each other exists, and communication quality is affected.
Disclosure of Invention
The invention solves the problem that the communication quality is influenced by the condition that the master-slave phase sequence channel does not correspond to the slave-slave phase sequence channel when the master node uses the phase sequence channel which is appointed by the master node in a manual mode.
In order to solve the above problem, the present invention provides a phase sequence identification method for power line carrier communication, which is applied to power line carrier communication of a photovoltaic system, where the photovoltaic system includes a master node and a slave node for performing power line carrier communication, and includes:
after the photovoltaic system is powered on, starting a phase sequence identification mode;
conducting a main node in the photovoltaic system with one phase-sequence channel;
the master node sends a plurality of rounds of test frames to the conducted phase sequence channel, receives response frames returned by the slave nodes, and counts the packet loss rate of each slave node according to the number of the response frames;
traversing the other phase sequence channels under the three-phase three-wire system, and sequentially counting the packet loss rate of each slave node of different phase sequence channels;
and taking the phase sequence channel with the minimum packet loss rate of each slave node as a receiving and transmitting phase sequence channel of the slave node.
Therefore, the packet loss rate of each slave node in each phase sequence channel is counted, and the phase sequence channel with the minimum packet loss rate is used as the receiving and transmitting phase sequence channel of the slave node, so that the identification of the phase sequence channel of the slave node is realized, the wiring sequence of the slave node does not need to be specified manually, and the labor is saved. In addition, the situations of high communication packet loss rate and poor signals caused by cross-phase communication due to wrong wiring of the master node or the slave node can be prevented, so that the communication between the master node and the slave node is facilitated, and the problem of poor communication quality is solved. Namely, the carrier communication under the correct phase sequence improves the communication quality of the main node and the slave node and reduces the packet loss rate.
Optionally, after the photovoltaic system is powered on and before the phase sequence identification mode is started, the method further includes:
and switching the current network communication mode to a low-frequency mode.
Optionally, the master node sends multiple rounds of test frames to the conducted phase sequence channel, receives response frames returned by the slave nodes, and sends each round of test frame in a broadcast manner when sending multiple rounds of test frames to the conducted phase sequence channel in statistics of packet loss rates of each slave node according to the number of the response frames.
Optionally, the master node sends multiple rounds of test frames to the conducted phase sequence channel, receives response frames returned by the slave nodes, and sends each round of test frame in a point-to-point manner when sending multiple rounds of test frames to the conducted phase sequence channel in statistics of packet loss rates of each slave node according to the number of the response frames.
Optionally, the frame header information of the test frame includes a factory serial number of the inverter of the current square matrix.
Optionally, if the response frame returned by the slave node is not received in all of the three phase sequence channels, a preset phase sequence channel is selected as the phase sequence receiving and sending channel of the slave node.
Secondly, the invention provides a photovoltaic system, which comprises a master node, a plurality of slave nodes, three-phase power cables and a control unit, wherein any two power cables in the three-phase power cables are combined to form a phase sequence channel, the master node and the slave nodes are connected through the three-phase power cables to perform power carrier communication, and the control unit is used for combining the master node, the slave nodes and the three-phase power cables to enable the photovoltaic system to realize the phase sequence identification method of the power carrier communication. Therefore, the packet loss rate of each slave node in each phase sequence channel is counted, and the phase sequence channel with the minimum packet loss rate is used as the receiving and transmitting phase sequence channel of the slave node, so that the identification of the phase sequence channel of the slave node is realized, the wiring sequence of the slave node does not need to be specified manually, and the labor is saved. In addition, the situations of high communication packet loss rate and poor signals caused by cross-phase communication due to wrong wiring of the master node or the slave node can be prevented, so that the communication between the master node and the slave node is facilitated, and the problem of poor communication quality is solved. Namely, the carrier communication under the correct phase sequence improves the communication quality of the main node and the slave node and reduces the packet loss rate.
Optionally, the master node includes a modem module and a coupling transformer, where the modem module is connected to the three-phase power cable through the coupling transformer, and sends the test frame and receives the returned response frame.
Optionally, the number of the coupling transformers is three, primary sides of the three coupling transformers are respectively communicated with three phase sequence channels of the three-phase power cable, and secondary sides of the three coupling transformers are respectively connected with the modulation and demodulation module through electronic switches.
Optionally, the secondary side of the coupling transformer is connected to the modem module, two ports of the primary side of the coupling transformer are both communicated with three cables of the three-phase power cable, and an electronic switch is disposed on a connection line between the port and the cable.
Optionally, the number of the coupling transformers is two, wherein a primary side of a first coupling transformer is connected to one phase sequence channel in the three-phase power cable, and a secondary side of the first coupling transformer is connected to the modem module; the primary side of the second coupling transformer is connected with the remaining two phase-sequence channels, and the secondary side of the second coupling transformer is connected with the modulation and demodulation module; electronic switches are arranged on connecting lines of the first coupling transformer and the modulation and demodulation module, the second coupling transformer and the phase sequence channel, and the second coupling transformer and the modulation and demodulation module.
Optionally, the photovoltaic system further comprises a data collector comprising a master node and an inverter comprising a slave node, the master node and the slave node communicating over the three-phase power cable.
Drawings
Fig. 1 is a schematic flow chart illustrating a phase sequence identification method for power line carrier communication according to an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of a photovoltaic system according to an embodiment of the present invention;
FIG. 3 is a schematic view of a photovoltaic system according to another embodiment of the present invention;
fig. 4 is a schematic structural diagram of a photovoltaic system according to still another embodiment of the invention.
Description of reference numerals:
10-a master node; 20-a slave node; 30-a three-phase power cable; 40-a control unit; 50-a modem module; 60-coupled transformer.
Detailed Description
In a typical ground power station, the power station includes a plurality of square matrixes, each square matrix includes a data collector and an inverter, the data collector collects data of the inverter through a PLC communication medium, specifically, a PLC master node is installed on a data collector side, and a PLC slave node is installed on an inverter side, and communication is performed through the master node and the slave node. When the master node communicates with the slave node, the master node needs to know what phase sequence the slave node is in at the beginning of communication so as to switch to the corresponding phase sequence for transceiving. Generally, on an initial grid-connected site, what phase sequence channel is used by a master node is specified manually according to the phase sequence channel of a slave node, but the master node and the slave node do not correspond to each other in the phase sequence channel.
For a three-phase three-wire system, a PLC master node and a slave node are accessed in a general two-phase mode, namely an AB/BC/AC mode, and due to the mode of manual wiring, the situation of wrong wiring exists, the first situation is that three-phase wiring of an inverter is not corresponding to three-phase wiring of a low-voltage side of a box transformer, and the other situation is that PLC slave nodes in inverters of different models are possibly connected to AB, AC and BC phases. At this time, the phase sequence of the master node cannot be determined according to the phase sequence of the slave node, and cross-phase communication causes high communication packet loss rate, poor signals and the like.
In other words, the reason why the master-slave phase sequence does not correspond to the slave-slave phase sequence is that the lines of the master node or the slave node are connected in error during manual wiring, which causes phase crossing when the master node and the slave node communicate, and causes poor communication quality during master-slave communication. For the slave node, because of the problem of wiring, or because the wiring does not lead to the PLC slave node of the inverter connecting to AB or AC or BC, there is another case of wrong wiring, that is, the wiring of the master node is wrong, that is, the PLC master node is to induce three wires to the PLC master node through the box-type transformer, A, B, C may also be wrong, and it may be that a of the box-type transformer corresponds to B and C of the PLC master node, therefore, in the case that three wires on the master node are possibly wrong, two wires of the PLC on the slave side may also be possibly on AC or AB, and the wiring on both sides may be disordered. The condition of wrong wiring can lead to poor communication quality. Previously, under the condition that the technology is not good enough, the PLC slave nodes of all inverters on site are connected to the AB phase by default, then the PLC master node is also connected to the AB phase so as to correspond to each other in pairs, but the line of the slave node is found to be wrong at the site, the line is not connected to the AB phase and may be connected to the AC phase, then the line pulled from the box transformer on the host side may not be pulled from the AB phase but is pulled from the BC or AC phase, and the condition of phase crossing is caused, so that the phase sequence of the master node and the slave node does not correspond.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in other sequences than those illustrated or described herein.
As shown in fig. 1, fig. 1 is a schematic flow chart of a phase sequence identification method for power carrier communication according to an embodiment of the present invention. The application discloses phase sequence identification method of power line carrier communication, is applied to the power line carrier communication of photovoltaic system, photovoltaic system includes the main node and the slave node that are used for carrying out power line carrier communication, includes:
and S100, after the photovoltaic system is electrified, starting a phase sequence identification mode.
And after the power supply of the photovoltaic system is switched on, starting a phase sequence identification mode, so as to identify a phase sequence channel connected with the slave node. When the power of the photovoltaic system is switched on, the power of the photovoltaic system can be considered to be switched on when sunlight irradiates.
S200, conducting a main node in the photovoltaic system with one phase sequence channel.
The three phase sequence channels of the three-phase three-wire system photovoltaic system are respectively an AB phase sequence channel, a BC phase sequence channel and an AC phase sequence channel. When the communication is performed, the master node performs communication through one of the three phase-sequence channels, for example, the master node performs communication in an AB phase-sequence channel, a BC phase-sequence channel, or an AC phase-sequence channel, which facilitates the communication of the master node.
S300, the main node sends a plurality of test frames to the conducted phase sequence channel, receives response frames returned by the slave nodes, and counts the packet loss rate of each slave node according to the number of the response frames.
Wherein, for the communication between the master node and the slave node, the communication is carried out through a power line carrier.
Taking the conduction of the AB phase sequence channel as an example, when the AB phase sequence channel is conducted, a first round of test frame is sent, that is, the master node sends a test frame to the slave node through the AB phase sequence channel, and when the slave node receives the test frame sent by the master node side, the slave node may or may not respond, and at this time, it is recorded whether each slave node responds, that is, it is recorded whether a response frame returned by each slave node is received. After the number of response frames returned in the first round is recorded, the test frames in the second round are sent, and the number of response frames returned is also recorded. After a plurality of test frames are sent, the packet loss rate of each slave node is counted according to the times of sending the test frames and the times of receiving the returned response frames, and therefore the packet loss rate test of each slave node of one phase sequence channel is completed. It should be noted that, in the process of sending a round of test frames, the waiting response time of each round is the same for the sent test frames regardless of whether the slave node replies, for example, the waiting response time may be 10s-20 s.
S400, traversing the other phase sequence channels under the three-phase three-wire system, and sequentially counting the packet loss rate of each slave node of different phase sequence channels.
After the test frame statistics is sent to the AB phase sequence channel to obtain the packet loss rate, the action of sending the test frame statistics packet loss rate is repeatedly carried out on the BC phase sequence channel and the AC phase sequence channel in sequence, so that the packet loss rate statistics of each slave node in three different phase sequence channels is completed.
And S500, taking the phase sequence channel with the minimum packet loss rate of each slave node as a receiving and transmitting phase sequence channel of the slave node.
It should be noted that, because the number of the slave nodes is multiple, and each slave node has three packet loss rates corresponding to the three phase-sequence channels, the phase-sequence channel with the smallest packet loss rate among the three packet loss rates is used as the transceiving phase-sequence channel of the slave node, which means that the comparison of the packet loss rates is directed at the packet loss rate of the same slave node. Taking one slave node a1 as an example, packet loss rates of the slave node a1 in the AB phase sequence channel, the BC phase sequence channel, and the AC phase sequence channel are 0%, 20%, and 80%, respectively, and taking the phase sequence channel with the smallest packet loss rate of the slave node a1 as the transceiving phase sequence channel of the slave node means that the packet loss rate is the smallest, and for the phase sequence channel with the smallest packet loss rate of the slave node a1 being 0%, and corresponding to 0% being the AB phase sequence channel, it is finally determined that the AB phase sequence channel is taken as the phase sequence channel of the slave node a 1.
Therefore, the packet loss rate of each slave node in each phase sequence channel is counted, and the phase sequence channel with the minimum packet loss rate is used as the receiving and transmitting phase sequence channel of each slave node, so that the identification of the phase sequence channels of the slave nodes is realized, the wiring sequence of the slave nodes does not need to be manually specified, and the labor is saved. In addition, the situations of high communication packet loss rate and poor signals caused by cross-phase communication generated by wrong wiring of the master node or the slave node can be prevented, so that the communication between the master node and the slave node is facilitated, and the problem of poor communication quality is solved. Namely, the carrier communication under the correct phase sequence improves the communication quality of the main node and the slave node and reduces the packet loss rate.
For a three-phase three-wire system, the phase-sequence channels include an AB phase-sequence channel, a BC phase-sequence channel, and an AC phase-sequence channel. Because it is not clear to which phase sequence channel each slave node is connected to, and at this time, regardless of which phase sequence each slave node is connected to, after the photovoltaic system is powered on, phase sequence channel identification statistics can be performed according to the phase sequence channels, namely the AB phase sequence channel, the BC phase sequence channel, and the AC phase sequence channel, and according to statistics of the packet loss rate, the phase sequence channel corresponding to the slave node of each inverter is determined to be which phase sequence channel. Of course, the phase sequence channel for sending the test frame may also be counted according to the sequence of the arrangement of the AC phase sequence channel, the AB phase sequence channel, and the BC phase sequence channel, or according to the sequence of the arrangement of the BC phase sequence channel, the AB phase sequence channel, and the AC phase sequence channel. Here, the sequence of the phase sequence channel identification is not specifically limited, and the statistical sequence of the phase sequence identification may be selected according to actual needs in practical applications. Therefore, the phase sequence identification mode is started, so that the phase sequence channel to which each slave node is specifically connected is judged, the situations of high communication packet loss rate and poor signals caused by cross-phase communication due to the fact that the master node or the slave node is connected in a wrong mode can be prevented, communication between the master node and the slave node is facilitated, and the problem of poor communication quality is solved. In addition, by starting the phase sequence recognition mode, the phase sequence of the PLC slave node wiring at the inverter side does not need to be preset manually, so that the labor is saved, and the efficiency is improved.
Optionally, after the photovoltaic system is powered on and before the phase sequence identification mode is started, the method further includes:
and switching the current network communication mode to a low-frequency mode.
At a low frequency in the angle of communication, the electromagnetic wave with a low frequency is transmitted farther under the same condition. Taking the used mobile phone communication as an example, the mobile phone communication gradually develops from 2G, 3G and 4G to the current 5G communication, the coverage radius of the 2G base station is 5-10 km, the 3G base station covers 2-5 km, the 4G covers 1-3 km, the 5G coverage radius is 100-300 m, and the higher the frequency is, the greater the electromagnetic wave attenuation is. When the method is applied to the scheme, under the same condition, the lower the frequency is, the farther the signal is propagated. Considering that some inverters may be arranged far away in the field, the communication mode is switched to the low-frequency mode before the test frame is sent for reliable transmission of the signal, so that the signal can be propagated further, the robustness is stronger, and the application range is wider.
Optionally, the master node sends multiple rounds of test frames to the conducted phase sequence channel, receives response frames returned by the slave nodes, counts packet loss rates of each slave node according to the number of the response frames, and sends each round of test frames in a broadcast manner when sending multiple rounds of test frames to the conducted phase sequence channel.
The broadcasting mode is a one-to-many mode, when the master node sends multiple rounds of test frames, each round of test frames only needs to be sent once, the slave nodes in the square matrix can receive the test frames, and all the slave nodes can respond or do not respond according to actual conditions.
Therefore, the test frame is sent in a broadcasting mode to carry out multi-round statistics, and the test frame is only needed to be sent once in each round, so that the packet loss rate statistics time is reduced, and the packet loss rate statistics efficiency is improved.
In order to facilitate understanding of the case of transmitting each round of test frames in a broadcast manner, for example, taking the sequence of the AB phase-sequence channel, the BC phase-sequence channel, and the AC phase-sequence channel as an example, first transmitting a test frame to a data channel where the AB phase-sequence channel is located, taking the example of transmitting a round of test frames, when transmitting a test frame to the AB phase-sequence channel and only transmitting one test frame, all slave nodes may receive the test frame at this time, all slave nodes may or may not respond when receiving the test frame transmitted by the master node, and a response frame returned by the slave node for responding includes an address and a serial number of each inverter, and through the content of the returned response frame, the master node may identify which slave node has made a response.
For example, the number of inverters in the current square matrix is 15, and each inverter corresponds to one slave node, that is, there are 15 slave nodes. When the master node sends a test frame to the AB phase sequence channel, it is equivalent to first shouting a sentence in the phase sequence channel, and then it is counted which slave nodes in the 15 slave nodes responded and which slave nodes did not respond. After the first round of statistics is finished, the second round of statistics is carried out, the same test frame is sent in the second round, and the statistics of which slave nodes in the 15 slave nodes respond and which slave nodes do not respond is carried out again. After the test frames are sent in multiple rounds, for example, 10 rounds of test frames are sent, taking a slave node as an example, and the slave node responds 10 times in 10 shouts, the packet loss rate of the slave node in the AB phase-sequence channel is 0%. If the slave node does not respond every time in 10 shouting, for example, it may only respond 2 times, and the packet loss rate of the slave node in the AB phase-sequence channel is 80%. The packet loss rates of other slave nodes on the phase sequence channel are also obtained through statistics according to the number of times of sending the test frame and the number of times of receiving the response. The packet loss rate refers to the ratio of the number of lost packets in the test to the number of transmitted packets. Under the condition that the times of sending the test frames are the same, when the number of the received responses of the slave nodes is larger, the packet loss rate is smaller. And after the packet loss rate of each slave node in the AB phase sequence channel is counted, carrying out the same packet loss rate test on the BC phase sequence channel and the AC phase sequence channel. After the packet loss rates in the three phase sequence channels are counted, transversely comparing the packet loss rates of each slave node in the three phase sequence channels, and taking the phase sequence channel with the minimum packet loss rate in the three packet loss rates as a transceiving phase sequence channel of each slave node. Taking one of the 15 slave nodes as an example, if the packet loss rates of the slave node in the AB phase-sequence channel, the BC phase-sequence channel and the AC phase-sequence channel are 0%, 20% and 80%, respectively, the AB phase-sequence channel corresponding to the smallest 0% is selected as the phase-sequence channel of the slave node.
Optionally, the master node sends multiple rounds of test frames to the conducted phase sequence channel, receives response frames returned by the slave nodes, and sends each round of test frame in a point-to-point manner when sending multiple rounds of test frames to the conducted phase sequence channel in statistics of packet loss rates of each slave node according to the number of the response frames.
The main node sends test frames for many times in each round when sending test frames for many rounds, if the sequence number of the response frame is corresponding to the sequence number stored before, the response frame is returned, and if the sequence number is not corresponding, the response frame is silenced and not responded.
Therefore, the crosstalk of other matrixes is prevented by a point-to-point test frame sending mode, and the test result is prevented from being wrong.
Optionally, the frame header information of the test frame includes a factory serial number of the inverter of the current square matrix.
For the point-to-point test frame sending mode, the factory serial number of the current square matrix inverter is firstly obtained, all the inverter serial numbers which can be searched are firstly manually searched by the factory serial number of the current square matrix inverter, then the inverter serial numbers which are not in the current square matrix are manually removed, and a current square matrix serial number list is stored.
Because there are PLC crosstalk signals of square matrixes on site, a test frame may cause slave nodes of different square matrixes to respond, resulting in a test result error, and thus it is necessary to ensure that frame information of the test frame has uniqueness. The PLC master node obtains an SN (factory serial number) list of the current square matrix inverter from the data acquisition unit, because the SN code of each inverter is unique, the SN is added into the frame header information of the test frame to be sent, when the slave node corresponding to the inverter receives the test frame, the test frame conforming to the SN of the local machine is selected to respond, otherwise, silence is kept, so that response of the inverters which are not interfered by other square matrices can be avoided, and the accuracy of the test result is improved.
For the point-to-point sending mode, namely, the serial numbers of all inverters are obtained firstly, the serial number of each inverter is added into the frame header information of the test frame, when the first round of test frame is sent, the number of times of sending the test frame is the same as the number of the inverters, namely, how many inverters correspondingly send how many times of test frames in the first round, and then the number of returned response frames is counted. The way of obtaining the packet loss rate of the point-to-point statistical response frame is the same as the broadcast way, and is not described herein again.
Optionally, if the response frame returned by the slave node is not received in all of the three phase sequence channels, a preset phase sequence channel is selected as the phase sequence receiving and sending channel of the slave node.
In this way, by setting the preset phase sequence channel as the phase sequence receiving and sending channel of the slave node, when the master node is uncertain about which phase sequence channel to send for communication, the preset phase sequence channel can be directly selected as the default channel, and similarly, when the slave node is uncertain about which channel to return for communication, the default preset phase sequence channel can be selected. The preset phase sequence channel is selected as the default transceiving phase sequence channel, so that the guiding function is achieved, and the normal communication of the master node and the slave node is facilitated.
Optionally, the preset phase-sequence channel is an AB phase-sequence channel. The default phase sequence can be set, and the default phase sequence of the inverters of different manufacturers is different.
Therefore, when the response frame returned by the slave node is not received, the AB phase sequence channel is selected as the receiving and transmitting phase sequence channel of the slave node, so that the normal communication of the master node and the slave node can be ensured.
And after the phase sequence identification is completed, recording the phase sequence channel of the slave node, and entering a normal communication mode of the master and the slave machines. When the PLC slave node is polled, the PLC slave node is switched to a corresponding channel, so that the master-slave phase sequence can be ensured to correspond to the slave-slave phase sequence, the phenomenon of phase crossing is avoided, and the communication quality of the master-slave node and the slave node is ensured.
The application also discloses a photovoltaic system, which comprises a master node 10, a plurality of slave nodes 20, three-phase power cables 30 and a control unit 40, wherein any two power cables in the three-phase power cables 30 are combined to form a phase sequence channel, the master node 10 and the slave nodes 20 are connected through the three-phase power cables 30 to perform power carrier communication, and the control unit 40 is used for combining the master node 10, the slave nodes 20 and the three-phase power cables 30 to enable the photovoltaic system to realize the phase sequence identification method of the power carrier communication.
Therefore, the packet loss rate of each slave node in each phase sequence channel is counted, and the phase sequence channel with the minimum packet loss rate is used as the receiving and transmitting phase sequence channel of the slave node, so that the identification of the phase sequence channel of the slave node is realized, the wiring sequence of the slave node does not need to be specified manually, and the labor is saved. In addition, the situations of high communication packet loss rate and poor signals caused by cross-phase communication due to wrong wiring of the master node or the slave node can be prevented, so that the communication between the master node and the slave node is facilitated, and the problem of poor communication quality is solved. Namely, the carrier communication under the correct phase sequence improves the communication quality of the main node and the slave node and reduces the packet loss rate.
Optionally, the master node 10 includes a modem module 50 and a coupling transformer 60, and the modem module 50 is connected to the three-phase power cable 30 through the coupling transformer 60, and transmits the test frame and receives the response frame in return.
In this way, the signals of the test frame are coupled to the three-phase power cable through the coupling transformer, thereby facilitating transmission of the signals.
Alternatively, there are three coupling transformers 60, primary sides of the three coupling transformers 60 are respectively communicated with three phase-sequence channels of the three-phase power cable 30, and secondary sides of the three coupling transformers 60 are respectively connected with the modem module 50 through electronic switches.
As shown in fig. 2, fig. 2 is a schematic structural diagram of a photovoltaic system according to an embodiment of the invention. A. B, C correspond to three-phase power cables, T1-T3 are coupling transformers, A1-An are a plurality of PLC slave nodes in a plurality of inverters and are mounted on the AB phase, B1-Bn are a plurality of slave nodes and are mounted on the BC phase, and C1-Cn are a plurality of slave nodes and are mounted on the AC phase. The main node switches the PLC signal transceiving channels through S1-S6 electronic switches, wherein S1-S2 control the AB phase sequence channel to transmit and receive, S3-S4 control the BC phase sequence channel to transmit and receive, and S5-S6 control the AC phase sequence channel to transmit and receive.
Therefore, the primary sides of the three couplers are respectively communicated with the three phase sequence channels of the three-phase power cable, and different phase sequence channels are conducted through the switching of the electronic switch, so that the switching of the phase sequence channels is convenient to control. In addition, the electronic switch is arranged on the secondary side of the coupling transformer, so that the occupied volume of the device is reduced.
Optionally, as shown in fig. 3, fig. 3 is a schematic structural diagram of a photovoltaic system according to another embodiment of the present invention. A. B, C corresponds to three-phase power cables, T1 is a coupling transformer, A1-An are a plurality of PLC slave nodes in a plurality of inverters and are mounted on An AB phase, B1-Bn are a plurality of slave nodes and are mounted on a BC phase, and C1-Cn are a plurality of slave nodes and are mounted on An AC phase. The main node switches PLC signal transceiving channels through S1-S6 electronic switches, wherein S3-S5 control the AB phase sequence channel to receive and transmit, S2-S4 control the BC phase sequence channel to receive and transmit, and S1-S6 control the AC phase sequence channel to receive and transmit. The secondary side of the coupling transformer 60 is connected to the modem module 50, and two ports of the primary side of the coupling transformer 60 are both communicated with three cables of the three-phase power cable 30, and electronic switches are disposed on connection lines of the ports and the cables.
Therefore, only one coupling transformer is arranged, so that the use of the coupling transformer is reduced, the cost is saved to a certain extent, and the implementation mode is simpler.
Optionally, as shown in fig. 4, fig. 4 is a schematic structural diagram of a photovoltaic system according to still another embodiment of the present invention. A. B, C correspond to three-phase power cables, T1-T2 are coupling transformers, A1-An are a plurality of PLC slave nodes in a plurality of inverters and are mounted on the AB phase, B1-Bn are a plurality of slave nodes and are mounted on the BC phase, and C1-Cn are a plurality of slave nodes and are mounted on the AC phase. The main node switches PLC signal transceiving channels through S1-S6 electronic switches, wherein S3-S4 control the AB phase sequence channel to receive and transmit, S1, S2 and S5 control the BC phase sequence channel to receive and transmit, and S1, S2 and S6 control the AC phase sequence channel to receive and transmit. The number of the coupling transformers 60 is two, wherein the primary side of the first coupling transformer 60 is connected to one phase sequence channel in the three-phase power cable 30, and the secondary side of the first coupling transformer is connected to the modem module 50; the second coupling transformer 60 has a primary side connected to the remaining two phase-sequence channels and a secondary side connected to the modem module 50; electronic switches are arranged on connecting lines of the first coupling transformer 60 and the modulation and demodulation module 50, the second coupling transformer 60 and the phase sequence channel, and the second coupling transformer 60 and the modulation and demodulation module 50.
Therefore, the signals of the test frames are coupled to the three-phase power cable by arranging the two coupling transformers, so that the signals are conveniently transmitted, and the communication of the master node and the slave node is realized.
The modulation and demodulation module is connected with the three-phase power cable in three different modes. The person skilled in the art can select a suitable connection mode according to actual needs.
Optionally, the photovoltaic system further includes a data collector and an inverter, the data collector includes a master node 10, the inverter includes a slave node 20, and the master node 10 and the slave node 20 communicate through the three-phase power cable 30.
Thus, the data collector comprises a master node and the inverter comprises a slave node, and communication between the data collector and the inverter is realized through the master node and the slave node.
Although the present disclosure has been described above, the scope of the present disclosure is not limited thereto. Various changes and modifications may be effected therein by one of ordinary skill in the pertinent art without departing from the spirit and scope of the present disclosure, and these changes and modifications are intended to be within the scope of the present disclosure.
Claims (12)
1. A phase sequence identification method of power carrier communication is applied to power line carrier communication of a photovoltaic system, the photovoltaic system comprises a master node and a slave node which are used for carrying out power carrier communication, and the phase sequence identification method is characterized by comprising the following steps:
after the photovoltaic system is powered on, starting a phase sequence identification mode;
conducting a main node in the photovoltaic system with one phase-sequence channel;
the master node sends a plurality of rounds of test frames to the conducted phase sequence channel, receives response frames returned by the slave nodes, and counts the packet loss rate of each slave node according to the number of the response frames;
traversing the other phase sequence channels under the three-phase three-wire system, and sequentially counting the packet loss rate of each slave node of different phase sequence channels;
and taking the phase sequence channel with the minimum packet loss rate of each slave node as a receiving and transmitting phase sequence channel of the slave node.
2. The phase sequence identification method for power carrier communication according to claim 1, wherein after the photovoltaic system is powered on and before the phase sequence identification mode is started, the method further comprises:
and switching the current network communication mode to a low-frequency mode.
3. The phase sequence identification method for power carrier communication according to claim 1 or 2, wherein the master node sends multiple rounds of test frames to the turned-on phase sequence channel, receives response frames returned by the slave nodes, counts packet loss rates of each slave node according to the number of the response frames, and sends each round of test frames in a broadcast manner when sending multiple rounds of test frames to the turned-on phase sequence channel.
4. The method according to claim 1 or 2, wherein the master node sends multiple test frames to the turned-on phase sequence channel, receives response frames returned by the slave nodes, counts packet loss rates of each slave node according to the number of the response frames, and sends each test frame in a point-to-point manner when sending multiple test frames to the turned-on phase sequence channel.
5. The method according to claim 4, wherein the header information of the test frame includes a factory serial number of the inverter of the current matrix.
6. The phase sequence identification method for power carrier communication according to claim 1 or 2, wherein if the response frame returned from the slave node is not received in any of the three phase sequence channels, a preset phase sequence channel is selected as the receiving and transmitting phase sequence channel of the slave node.
7. A photovoltaic system, comprising a master node (10), a plurality of slave nodes (20), three-phase power cables (30), and a control unit (40), wherein any two of the three-phase power cables (30) are combined to form a phase sequence channel, the master node (10) and the slave nodes (20) are connected through the three-phase power cables (30) for power carrier communication, and the control unit (40) is configured to combine the master node (10), the slave nodes (20) and the three-phase power cables (30) to enable the photovoltaic system to implement the phase sequence identification method for power carrier communication according to any one of claims 1 to 6.
8. Photovoltaic system according to claim 7, characterized in that the master node (10) comprises a modem module (50) and a coupling transformer (60), the modem module (50) being connected to the three-phase power cable (30) through the coupling transformer (60), transmitting the test frames and receiving the response frames back.
9. The pv system according to claim 8, wherein the number of the coupling transformers (60) is three, the primary sides of the three coupling transformers (60) are respectively connected to the three phase-sequence channels of the three-phase power cable (30), and the secondary sides of the three coupling transformers (60) are respectively connected to the modem module (50) through electronic switches.
10. The pv system according to claim 8, wherein the secondary side of the coupling transformer (60) is connected to the modem module (50), and two ports of the primary side of the coupling transformer (60) are each connected to three cables of the three-phase power cable (30), and electronic switches are provided on the connection lines of the ports and the cables.
11. The photovoltaic system according to claim 8, wherein the coupling transformers (60) are two, wherein a first one of the coupling transformers (60) is connected with one phase-sequence channel in the three-phase power cable (30) on the primary side and with the modem module (50) on the secondary side; the primary side of the second coupling transformer (60) is connected with the remaining two phase-sequence channels, and the secondary side of the second coupling transformer is connected with the modulation and demodulation module (50); and electronic switches are arranged on connecting lines of the first coupling transformer (60) and the modulation and demodulation module (50), the second coupling transformer (60) and the phase sequence channel, and the second coupling transformer (60) and the modulation and demodulation module (50).
12. The photovoltaic system according to any one of claims 7-11, further comprising a data collector electrically connected to the master node (10) and an inverter electrically connected to the slave node (20), the master node (10) and the slave node (20) communicating via the three-phase power cable (30).
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