Photovoltaic system and black start method based on photovoltaic power plant equipment

Abstract

The application discloses a photovoltaic system and a black start method based on a photovoltaic power station device. The photovoltaic system comprises a plurality of inverters and a subarray controller; a target inverter is used for receiving a first message sent by the subarray controller, the target inverter is part or all of the plurality of inverters, and the first message is used for instructing the target inverter to perform the black start; a preamble of the first message is used for assisting the target inverter in identifying a starting moment of a signal frame of the first message; a frame control field and a payload of the first message are used for assisting the target inverter in determining a reference moment of the black start; the target inverter is used for determining the starting moment according to the preamble, obtaining the reference moment of the black start according to the starting moment, an analysis time of the frame control field or an analysis time of the payload, obtaining a starting moment of the black start according to the reference moment of the black start and a specified delay time, and performing the black start when the starting moment is reached. In this way, the target inverter unifies the starting moment, and effectively ensures that the plurality of inverters simultaneously perform the black start.

Description

Technical Field

[0001] This application relates to the field of photovoltaic technology, and in particular to a photovoltaic system and a black-start method based on photovoltaic power plant equipment. Background Technology

[0002] A photovoltaic (PV) power plant is an infrastructure that converts sunlight into electrical electricity through the photovoltaic effect of photovoltaic panels. In a PV power plant, the PV system generates electricity during the day and consumes electricity at night. A PV system consists of multiple PV modules, subarray controllers, multiple inverters, and a box-type transformer. The power output of the PV modules determines the input power of the inverters. Among these, the inverters are the main power consumers due to their large number. To reduce the power consumption of multiple inverters, they are typically powered off at night when there is no sunlight to save energy. The next day, when there is sunlight, the multiple inverters synchronously start up. Since multiple inverters are connected to the same copper busbar of the box-type transformer, if the inverters start asynchronously, the inverter that starts first will cause reverse current, flowing back to the inverter that starts later, potentially causing prolonged startup time or startup failure. Therefore, synchronous black start of multiple inverters is crucial for the successful startup of PV modules. Ensuring that multiple inverters perform black start simultaneously is a technical problem that needs to be solved in this field. Summary of the Invention

[0003] This application provides a black-start method for a photovoltaic system and photovoltaic power station equipment, which ensures that multiple inverters can perform black-start simultaneously. The technical solution is as follows.

[0004] In a first aspect, a photovoltaic system is provided, comprising a subarray controller and multiple inverters connected in parallel, and the multiple inverters are communicatively connected to the subarray controller via a power line carrier communication PLC; the clocks of the multiple inverters are kept in sync with the clock of the subarray controller; the subarray controller is used to send a first message to a target inverter, which may be some or all of the multiple inverters, the first message being used to instruct the target inverter to perform a black start; the first message includes a preamble, a frame control field, and a payload; the preamble is used to assist the target inverter in identifying the start time of the signal frame of the first message; the frame control field and the payload are used to assist the target inverter in determining a reference time for the black start; the target inverter is used to receive the first message, determine the start time based on the preamble, and obtain the reference time for the black start based on the start time and a resolution time, the resolution time being the resolution time of the frame control field or the resolution time of the payload; the target inverter is also used to obtain the start time of the black start based on the reference time and a specified delay time, and perform the black start when the start time arrives.

[0005] In this application, the first message includes a preamble, a frame control field, and a payload. The preamble assists the inverter in identifying the start time of the signal frame of the first message; the frame control field and the payload assist the inverter in determining the reference time for black start. Therefore, when multiple inverters are time-synchronized with the subarray controller, the target inverter can determine the start time based on the preamble, the reference time for black start based on the parsing time of the frame control field or the parsing time of the payload, and then determine the start time of black start based on the reference time and a specified delay time. In this way, the target inverter can determine a unified start time and immediately execute black start upon arrival, effectively ensuring that multiple inverters execute black start simultaneously and reducing the time difference between multiple inverters executing black start.

[0006] In one possible implementation, the subarray controller is further configured to determine the target number of inverters participating in black start based on the load of the box-type transformer, the rated power reported by each inverter among the multiple inverters, and the solar irradiance value; the subarray controller is further configured to select the target inverter from among the multiple inverters according to the target number; the subarray controller is further configured to carry the first identifier of the target inverter in the payload; the target inverter is configured to perform black start when the start time arrives if, after receiving the first message, the identifier corresponding to the target inverter matches the first identifier obtained by parsing the payload.

[0007] In this way, the subarray controller determines the target number of inverters to participate in black start based on the load of the box-type transformer, the rated power reported by each inverter in the multiple inverters, and the solar irradiance value. Then, the subarray controller selects the target inverter from among the multiple inverters according to the target number, and then sends the first identifier of the target inverter along with the payload of the first message to the target inverter. After receiving the first message, the target inverter matches its own identifier with the first identifier carried in the payload. If a match is found, black start is performed when the start-up time arrives. Therefore, by selecting the target inverter from multiple inverters for black start based on the actual situation, inverters can be rationally selected and controlled to perform black start, providing flexibility and practicality.

[0008] In one possible implementation, the subarray controller is further configured to configure a first identifier for each of the multiple inverters in the order in which the multiple inverters communicate with the subarray controller; or, the subarray controller is further configured to configure a first identifier for each of the multiple inverters in the order of the physical address MAC or product serial number SN of the multiple inverters.

[0009] In one possible implementation, the first message includes a controller SOF service signal for secure forwarding; the subarray controller is used to assign a first identifier to each of the multiple inverters via the SOF service signal. Therefore, when the subarray controller and the multiple inverters are connected via a power line carrier communication PLC, the subarray controller can assign a first identifier to each of the multiple inverters using the SOF service signal.

[0010] In one possible implementation, the first message is a broadcast signal, and the reserved field of the broadcast signal is a frame control field. The threshold corresponding to the reserved field is used to characterize the broadcast signal as a black-start broadcast signal. The subarray controller is also used to configure a first value or a second value in the payload of the black-start broadcast signal according to the arrangement order of the first identifiers of the multiple inverters, and generate a string. The string is used to indicate whether each inverter in the multiple inverters participates in black-start. The string includes a first value and a second value, where the first value indicates participation in black-start and the second value indicates non-participation in black-start. Therefore, when the subarray controller and the multiple inverters are connected via a power line carrier communication PLC, the subarray controller can configure a first value or a second value in the payload of the broadcast signal according to the arrangement order of the first identifiers of the multiple inverters. The first value indicates participation in black-start, and the second value indicates non-participation in black-start. In this way, the first message can indicate whether each inverter in the multiple inverters participates in black-start.

[0011] Secondly, a black-start method based on photovoltaic power plant equipment is provided. This method is applied to a photovoltaic system, which includes a subarray controller and multiple inverters connected in parallel. The multiple inverters are connected to the subarray controller via a power line carrier communication PLC. The clocks of the multiple inverters are synchronized with the clock of the subarray controller. The method includes: the subarray controller sending a first message to a target inverter, where the target inverter may be some or all of the multiple inverters. The first message instructs the target inverter to perform a black start. The first message includes a preamble, a frame control field, and a payload. The preamble assists the target inverter in identifying the start time of the signal frame of the first message. The frame control field and the payload can be used to assist the target inverter in determining a reference time for the black start. The target inverter receives the first message and determines the start time based on the preamble, and obtains the reference time for the black start based on the start time and a resolution time, where the resolution time is the resolution time of the frame control field or the resolution time of the payload. The target inverter obtains the start time for the black start based on the reference time and a specified delay time, and performs the black start when the start time arrives.

[0012] In one possible implementation, before the multiple inverters receive the first message, the method further includes: the subarray controller determining the target number of inverters participating in black start based on the load of the box-type transformer, the rated power reported by each inverter in the multiple inverters, and the solar irradiance value; the subarray controller selecting the target inverter from the multiple inverters according to the target number; the subarray controller carrying the first identifier of the target inverter in the payload; and the target inverter performing black start when the start time arrives, including: after receiving the first message, if the identifier corresponding to the target inverter matches the first identifier obtained by parsing the payload, the target inverter performs black start when the start time arrives.

[0013] In one possible implementation, before the subarray controller carries the first identifier of the target inverter in the payload, the method further includes: configuring the first identifier for each of the multiple inverters in the order in which the multiple inverters establish communication connections with the subarray controller; or, configuring the first identifier for each of the multiple inverters in the order of the size of the physical address MAC or product serial number SN of the multiple inverters.

[0014] In one possible implementation, the first message includes a controller SOF service signal for secure forwarding; the subarray controller sends the first message to multiple inverters, including: the subarray controller assigns a first identifier to each of the multiple inverters using the SOF service signal.

[0015] In one possible implementation, the first message is a broadcast signal, the reserved field of the broadcast signal is a frame control field, and the threshold corresponding to the reserved field is used to characterize the broadcast signal as a black start broadcast signal; the subarray controller carries the first identifier of the target inverter in the payload, including: the subarray controller configures a first value or a second value in the payload of the black start broadcast signal according to the arrangement order of the first identifiers of multiple inverters, and generates a string, the string is used to indicate whether each inverter in the multiple inverters participates in black start, the string includes a first value and a second value, the first value is used to indicate participation in black start, and the second value is used to indicate non-participation in black start.

[0016] It should be understood that the beneficial effects of the technical solution of the second aspect of this application and the corresponding possible implementation can be found in the above description of the technical effects of the first aspect and its corresponding possible implementation, and will not be repeated here. Attached Figure Description

[0017] Figure 1 A schematic diagram of a photovoltaic system provided for related technologies;

[0018] Figure 2A schematic diagram of inverter reverse current in a photovoltaic system, provided for related technologies;

[0019] Figure 3 This is a schematic diagram of the structure of a photovoltaic system provided in an embodiment of this application;

[0020] Figure 4 A flowchart illustrating a black start method based on photovoltaic power station equipment provided in this application embodiment;

[0021] Figure 5 This is a schematic diagram of a frame structure in a wireless communication protocol provided in an embodiment of this application;

[0022] Figure 6 This is a schematic diagram of a frame structure in another wireless communication protocol provided in an embodiment of this application;

[0023] Figure 7 This is a flowchart illustrating another black-start method based on photovoltaic power station equipment provided in an embodiment of this application. Detailed Implementation

[0024] The terminology used in the implementation section of this application is for the purpose of explaining specific embodiments of this application only, and is not intended to limit this application.

[0025] A photovoltaic (PV) system is a power generation system that uses the photovoltaic effect of semiconductor materials to convert solar energy into electrical energy. Figure 1 A schematic diagram of a photovoltaic system provided for related technologies, such as Figure 1 As shown, a photovoltaic system may include multiple photovoltaic modules, a subarray controller, multiple inverters, and a box-type transformer (referred to as a box-type transformer). The subarray controller is electrically connected to multiple photovoltaic modules and multiple inverters, and the multiple inverters are all electrically connected to the box-type transformer. The photovoltaic modules are used to directly absorb sunlight and convert it into electric current. The subarray controller is used to collect and process the current output from the multiple photovoltaic modules. The inverters are used to convert the DC current collected by the subarray controller into AC current to match the standard frequency and voltage of the power grid. The box-type transformer is used to step up or step down the AC current output from the inverters to adapt to transmission lines of different voltage levels.

[0026] Photovoltaic systems generate electricity during the day and consume it at night. Due to the large number of inverters, multiple inverters are the main power consumers. To reduce the power consumption of these multiple inverters, they are typically powered off at night when there is no sunlight to save energy. The next day, when sunlight returns, the multiple inverters synchronously start up again. For example... Figure 2As shown, since multiple inverters (such as inverter 1, inverter 2, ... inverter n) are connected to the same copper busbar of the box-type transformer, if the inverters start asynchronously, the inverter that starts first will cause reverse current, which will flow back to the inverter that starts later, potentially causing prolonged startup time or startup failure. Therefore, synchronous black start of multiple inverters is crucial for the successful startup of photovoltaic modules. How to ensure that multiple inverters perform black start simultaneously is a technical problem that needs to be solved in this field.

[0027] To solve the above technical problems, Figure 3 This is a schematic diagram of the structure of a photovoltaic system provided in an embodiment of this application, such as... Figure 3 As shown, in the photovoltaic system of this embodiment, multiple inverters are connected in parallel, and these inverters are connected to a subarray controller via power line communication (PLC). The clocks of the multiple inverters are synchronized with the clock of the subarray controller. The subarray controller sends a first message to a target inverter, which may be some or all of the multiple inverters. The first message instructs the target inverter to perform a black start. The first message includes a preamble, a frame control field, and a payload. The preamble assists the target inverter in identifying the start time of the signal frame of the first message. The frame control field and the payload assist the target inverter in determining the reference time for the black start. The target inverter receives the first message, determines the start time based on the preamble, and obtains the reference time for the black start based on the start time and a resolution time, where the resolution time is the resolution time of the frame control field or the resolution time of the payload. The target inverter also obtains the start time for the black start based on the reference time and a specified delay time, and performs a black start when the start time arrives.

[0028] The first message includes a preamble, a frame control field, and a payload. The preamble helps the inverter identify the start time of the signal frame in the first message; the frame control field and the payload help the inverter determine the reference time for black start. Therefore, when multiple inverters are time-synchronized with the subarray controller, the target inverter can determine the start time based on the preamble, the reference time for black start based on the parsing time of the frame control field or the payload, and then determine the black start time based on the reference time and a specified delay. In this way, the target inverter can determine a unified start time and immediately execute black start upon its arrival, effectively ensuring that multiple inverters execute black start simultaneously and reducing the time difference between black start executions.

[0029] based on Figure 3The photovoltaic system shown in this application also provides a black-start method. The following describes in detail, with reference to examples, a black-start method based on photovoltaic power station equipment provided by this application embodiment. Figure 4 This application provides a schematic flowchart of a black start method based on photovoltaic power station equipment, as shown in the embodiments. Figure 4 As shown, the method may include: S401-S403.

[0030] S401, the subarray controller sends a first message to the target inverter, which instructs the target inverter to perform a black start. Correspondingly, the target inverter receives the first message.

[0031] The first message may include a preamble, a frame control field, and a payload. The preamble helps the target inverter identify the start time of the signal frame of the first message. The frame control field and the payload can be used to help the target inverter determine the reference time for black start.

[0032] The first message mentioned above can be at least one of a broadcast message (beacon), a security-oriented forwarding controller (SOF) service message, or an acknowledgment (ACK) message. For example, as shown... Figure 5 The image shows a frame structure in a wireless communication protocol provided in this application embodiment, which is typically used as a beacon frame in a wireless local area network (WLAN). Figure 5 As shown, the first message can be an SOF service message, an ACK message, or a broadcast beacon message. All three—SOF service messages, ACK messages, and broadcast beacon messages—include Preamble and FC (Frame Control) fields. SOF service messages and broadcast messages also include a Payload. RIFS (Short Interframe Space) is a short interval between consecutive transmissions to avoid signal collisions. CIFS (Beacon Interframe Space) is the interval between beacon frames, used to periodically send beacon frames so that devices can synchronize and maintain communication connections. Time indicates the temporal order of frame transmission.

[0033] The Preamble is the start of the frame, used for synchronization and signal detection, helping the target inverter identify the start time of the message. The FC (Frame Control) field contains information such as the frame type, subtype, and protocol version, helping the target inverter understand the frame's purpose and format. Since the parsing time of the FC field and the start time indicated by the Preamble are known, the parsing time of the FC field can be determined, which is the reference time for black start. Therefore, the FC field also helps the target inverter determine the reference time for black start. The Payload is the main data part of the frame, containing the actual transmitted information. Similar to the FC field, since the parsing time of the Payload and the start time indicated by the Preamble are known, the parsing time of the Payload can be determined, which is the reference time for black start. Therefore, the Payload also helps the target inverter determine the reference time for black start.

[0034] For example, such as Figure 6 As shown, the FC field of the broadcast message `beacon` carries information for controlling black start. When the target inverter receives the broadcast message `beacon`, it can determine the start time of the broadcast message `beacon`, i.e., interrupt 1, based on the preamble of the broadcast message `beacon`. When the target inverter parses the FC field, the parsing time of the FC field is known, i.e., the first parsing duration. The target inverter can determine the reference time for black start based on the start time and the first parsing duration, i.e. Figure 6 Interrupt 2 is shown. Alternatively, the payload of the broadcast message beacon carries a list of target inverters participating in the black start. When a target inverter parses the payload, the parsing time is known, i.e., the second parsing duration. The target inverter can determine the reference time for black start based on the start time, the first parsing duration, and the second parsing duration. Figure 6 Interruption 3 is shown.

[0035] The subarray controller sending the first message to the target inverter can be understood in two scenarios: First, the subarray controller can send the first message to the target inverter in a one-to-many manner. For example, the subarray controller can broadcast the first message to all target inverters. Second, the subarray controller can send the first message to the target inverter in a one-to-one manner. For example, the subarray controller sends the first message to each target inverter individually. Both scenarios are acceptable and are not specifically limited in the embodiments of this application.

[0036] To ensure consistent black-start timing for the target inverters, time synchronization can be performed on the subarray controller and multiple inverters before executing S401. For example, the subarray controller performs time synchronization on multiple inverters based on time synchronization rules. These time synchronization rules can include any of the following: a time synchronization protocol, a network time base (NTB) rule (or NTB time reference rule), or a satellite clock reference rule. The time synchronization protocol can include the Coordinated Universal Time (UTC) synchronization protocol, the PLC's NTB (zero cross-detection) count time, the Network Time Protocol (NTP), the Precision Time Protocol (PTP), or the 1588 time protocol. The satellite clock reference rule can include the BeiDou satellite clock reference rule, the Global Positioning System (GPS) time reference, or the Global Navigation Satellite System (GNSS) time reference. In this way, by synchronizing the subarray controller with multiple inverters, it is ensured that the subarray controller and multiple inverters are on the same time base, effectively ensuring that multiple inverters can subsequently perform black-start simultaneously.

[0037] The target inverter can be some or all of a plurality of inverters. For example, the target inverter can be some of a plurality of inverters. Before executing S401, the subarray controller can select some inverters as the target inverters from the plurality of inverters. In one possible implementation, such as... Figure 7 As shown, after the subarray controller establishes communication connections with multiple inverters via power line carrier communication (PLC), it can obtain the physical address (MAC) or product serial number (SN) of the inverters. For example, the subarray controller can obtain the inverter's SN based on its MAC address and the relationship between the MAC and SN. Alternatively, it can obtain the inverter's MAC based on the SN and the relationship between the MAC and SN. The subarray controller configures a first identifier for each inverter according to the order in which they establish communication connections; or, it configures a first identifier for each inverter according to the order of their MAC addresses or SNs. Then, the subarray controller can carry each inverter's identifier in the SOF (Service-on-Flight) service signal and send the SOF service signal to each inverter. In this way, each inverter can obtain its own first identifier.

[0038] Subsequently, each inverter in the multiple inverters reports its rated power and solar irradiance value to the subarray controller. The subarray controller can then determine the target number of inverters to participate in black start based on the load of the box-type transformer, the rated power reported by each inverter, and the solar irradiance value. For example, the subarray controller can obtain the average rated power based on the rated power of the multiple inverters, which can be expressed as:

[0039]

[0040] The subarray controller obtains the average solar irradiance value based on the solar irradiance values ​​of multiple inverters, which can be expressed as:

[0041]

[0042] Therefore, the subarray controller can determine the target number of inverters participating in black start based on the average rated power and average solar irradiance, as expressed by:

[0043]

[0044] Where M is the number of inverters participating in black start, i.e., the target number of units; α is the proportional coefficient; and L is the load of the box-type transformer.

[0045] In practical applications, the target number of inverters can be one or more. This means that the number of inverters participating in the black start is one or more. After obtaining the target number of inverters, the subarray controller can select the target inverters from among multiple inverters. The selection strategy for the subarray controller to select the target inverters can be based on the inverters' order, their operating capacity, or random selection. Thus, the subarray controller determines the target number of inverters participating in the black start based on the load of the box-type transformer, the rated power reported by each inverter, and the solar irradiance value. Then, the subarray controller selects the target inverters from among the multiple inverters according to the target number of inverters, and then sends the first identifier of the target inverter, along with the payload of the first message, to the target inverter. After receiving the first message, the target inverter matches its own identifier with the first identifier carried in the payload. If a match is found, black start is performed when the start-up time arrives. It is evident that by selecting a target inverter from multiple inverters for black start based on actual conditions, the inverter can be rationally selected and controlled to perform black start, demonstrating flexibility and practicality.

[0046] In this way, the subarray controller determines the target number of inverters to participate in black start based on the load of the box-type transformer, the rated power reported by each inverter in the multiple inverters, and the solar irradiance value. Then, the subarray controller selects the target inverter from among the multiple inverters according to the target number, and then sends the first identifier of the target inverter along with the payload of the first message to the target inverter. After receiving the first message, the target inverter matches its own identifier with the first identifier carried in the payload. If a match is found, black start is performed when the start-up time arrives. Therefore, by selecting the target inverter from multiple inverters for black start based on the actual situation, inverters can be rationally selected and controlled to perform black start, providing flexibility and practicality.

[0047] After the subarray controller selects the target inverters, it edits the list of target inverters into the first message. The first message is a broadcast signal, and the reserved field for the broadcast signal is a frame control field. The threshold corresponding to the reserved field is used to characterize the broadcast signal as a black-start broadcast signal. The list of target inverters can be the identifiers of the target inverters. For example, the list of target inverters can be carried in the payload of the black-start broadcast signal. For instance, the payload of the black-start broadcast signal can be configured with a first value or a second value according to the order of the first identifiers of multiple inverters, and a string can be generated. This string indicates whether each inverter participates in the black-start process. The string includes a first value and a second value; the first value indicates participation in the black-start process, and the second value indicates non-participation.

[0048] For example, multiple inverters may include eight inverters. The subarray controller assigns numbers to these eight inverters, numbered sequentially from 0 to 7. The subarray controller then sends a notification to each of these eight inverters, carrying the inverter's identifier, number, and the correspondence between the identifier and number. Upon receiving the notification, each inverter knows its number on the subarray controller's side. In the Beacon protocol, the subarray controller sets a one-byte (8-bit) field called `bs_mask`, the target field. This byte corresponds to the numbers of the eight inverters. For example, if the 8 bits of this byte are 01010101, it means that numbers 0-7 correspond to 0, 1, 0, 1, 0, 1, 0, 1 respectively. If 0 represents not participating in synchronous black start and 1 represents participating in synchronous black start, then 01010101 means that inverters numbered 2, 4, 6, and 8 do not participate in synchronous black start, while inverters numbered 1, 3, 5, and 7 participate in synchronous black start. For example, an 8-bit byte like 10101010 represents inverters numbered 0-7 as 1, 0, 1, 0, 1, 0, 1, 0 respectively. If 0 represents participation in synchronous black start and 1 represents non-participation, then 10101010 means that inverters numbered 1, 3, 5, and 7 do not participate in synchronous black start, while inverters numbered 2, 4, 6, and 8 participate. The subarray controller will generate a broadcast signal and carry it in the broadcast signal's payload, sending it to multiple inverters, including the target inverter.

[0049] As can be seen, when the subarray controller and the multiple inverters are connected via a power line carrier communication PLC, the subarray controller can configure a first value or a second value in the payload of the broadcast signal according to the arrangement order of the first identifiers of the multiple inverters. The first value is used to indicate participation in black start, and the second value is used to indicate non-participation in black start. In this way, the first message can indicate whether each inverter in the multiple inverters participates in black start.

[0050] S402. The target inverter determines the start time based on the preamble, and obtains the reference time for black start based on the start time and the resolution time. The resolution time is the resolution time of the frame control field or the resolution time of the payload.

[0051] After receiving the first message, the target inverter determines the start time based on the preamble of the first message. The FC field of the first message can carry information controlling the black start; therefore, after parsing this information, the target inverter can execute the black start. Since the parsing duration and start time of the FC field of the first message are known, the parsing time of the FC field can be determined, which is the reference time for the black start. The payload of the first message can carry a list of target inverters. The target inverter can check if it is on the list. If it is, it participates in the black start; otherwise, it does not. Since the parsing duration and start time indicated by the preamble are known, the parsing time of the payload can be determined, which is the reference time for the black start. Of course, to simplify the parsing process, it can also be configured that the target inverter can determine to participate in the synchronous black start as soon as it receives a message of a specified type carrying preamble information.

[0052] S403. The target inverter obtains the start time of black start based on the reference time and the specified delay time, and performs black start when the start time arrives.

[0053] As described above, the target inverter determines that it needs to participate in the black start process. Based on this, the target inverter performs a black start when the start time arrives. The start time is determined based on a reference time and a specified delay time. The specified delay time can be any set duration. For example, the specified delay time T can be 0, meaning that the target inverter can perform a black start when the reference time arrives. As another example, the specified delay time T can be 10 minutes, meaning that the target inverter performs a black start when the reference time is extended by 10 minutes. Of course, in this embodiment, the specified delay time T is not limited to the durations listed above; it can also be other durations, such as 10 seconds or 0.5 hours, which will not be listed here.

[0054] Example 1: If the specified delay time T can be 0, then S403 can be implemented as follows: After the target inverter receives the first message, it can determine the start time based on the Preamble of the broadcast information in the first message. Furthermore, the target inverter parses the FC field of the broadcast information to obtain the information on black start control and the first parsing duration carried in the FC. Additionally, the target inverter parses the Payload of the broadcast information to obtain the list of inverters participating in black start and the second parsing duration carried in the Payload. Based on the start time, the first parsing duration, and the second parsing duration, the target inverter determines the reference time t1 for black start. Based on the reference time t1 and the specified delay time T, the target inverter determines the start time of black start. Since the specified delay time T is 0, the start time is the reference time t1. Additionally, the target inverter checks its identifier in the list. If the identifier is in the list, the target inverter participates in the black start when reference time t1 arrives; if the identifier is not in the list, the target inverter does not participate in the black start. Assuming the above example continues, with a total of 8 inverters, the list of inverters participating in the black start carried in the payload can be represented as 01010101, where 0 represents not participating in the black start and 1 represents participating. The target inverter compares its own number with the value in "01010101". Therefore, it can be determined that inverters numbered 2, 4, 6, and 8 participate in the synchronous black start. Inverters numbered 2, 4, 6, and 8 are the target inverters, and these target inverters immediately perform the black start when the start time (i.e., reference time t1) arrives. In this way, when the subarray controller is synchronized with multiple inverters, the target inverter will immediately perform a black start when the start-up time arrives after receiving the first message, effectively ensuring that all target inverters perform black starts at the same time and effectively reducing the time difference between the target inverters performing black starts.

[0055] Example 2: If the specified delay time T is not 0, then S403 can be implemented as follows: After the target inverter receives the first message, it can determine the start time based on the Preamble of the broadcast information in the first message. Furthermore, the target inverter parses the FC field of the broadcast information to obtain the information on black start control and the first parsing duration carried in the FC. Additionally, the target inverter parses the Payload of the broadcast information to obtain the list of inverters participating in black start and the second parsing duration carried in the Payload. The target inverter determines the reference time t1 for black start based on the start time, the first parsing duration, and the second parsing duration. The target inverter determines the start time of black start based on the reference time t1 and the specified delay time T. Since the specified delay time T is not 0, the start time is the reference time t1 + the specified delay time T. Additionally, the target inverter checks its identifier in the list. If the identifier is present, the target inverter participates in the black start when the start time (reference time t1 + specified delay time T) arrives. If the identifier is not present, the target inverter does not participate in the black start. Assuming the above example continues, with 8 inverters, the list of inverters participating in the black start carried in the payload can be represented as 10101010, where 0 represents participation and 1 represents non-participation. The target inverter compares its own number with the value in "10101010". Therefore, inverters numbered 2, 4, 6, and 8 participate in the synchronous black start, and these inverters are the target inverters. These target inverters immediately perform the black start when the start time (reference time t1 + specified delay time T) arrives. In this way, when the subarray controller is synchronized with multiple inverters, multiple inverters will immediately perform black start when the delay time T arrives after receiving the first message, effectively ensuring that all target inverters perform black start at the same time and effectively reducing the time difference of target inverters performing black start.

[0056] The two examples above are merely examples and are not intended to limit the scope of this application.

[0057] In this application, the first message includes a preamble, a frame control field, and a payload. The preamble assists the inverter in identifying the start time of the signal frame of the first message; the frame control field and the payload assist the inverter in determining the reference time for black start. Therefore, when multiple inverters are time-synchronized with the subarray controller, the target inverter can determine the start time based on the preamble, the reference time for black start based on the parsing time of the frame control field or the parsing time of the payload, and then determine the start time of black start based on the reference time and a specified delay time. In this way, the target inverter can determine a unified start time and immediately execute black start upon arrival, effectively ensuring that multiple inverters execute black start simultaneously and reducing the time difference between multiple inverters executing black start.

[0058] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0059] In the description of the embodiments of this application, unless otherwise stated, " / " means "or". For example, A / B can mean A or B. "And / or" in this document is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone.

[0060] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of this application, unless otherwise stated, "a plurality of" means two or more.

[0061] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0062] It is understood that the aforementioned communication devices, etc., include hardware structures and / or software modules corresponding to the execution of each function in order to achieve the above-mentioned functions. Those skilled in the art should readily recognize that, based on the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein, the embodiments of this application can be implemented in hardware or a combination of hardware and computer software. Whether a function is executed in a hardware-driven or software-driven manner depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the embodiments of this application.

[0063] This application embodiment can divide the above-mentioned communication equipment into functional modules according to the above method examples. For example, each function can be divided into its own functional module, or two or more functions can be integrated into one processing module. The integrated module can be implemented in hardware or as a software functional module. It should be noted that the module division in this application embodiment is illustrative and only represents one logical functional division. In actual implementation, there may be other division methods.

[0064] Through the above description of the embodiments, those skilled in the art will clearly understand that, for the sake of convenience and brevity, only the division of the above functional modules is used as an example. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above. The specific working process of the system, device, and unit described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

Claims

1. A photovoltaic system, characterized in that, The photovoltaic system includes a subarray controller and multiple inverters connected in parallel. The multiple inverters are connected to the subarray controller via a power line carrier communication PLC. The clocks of the multiple inverters are kept in sync with the clock of the subarray controller. The subarray controller is used to send a first message to a target inverter, which may be some or all of the plurality of inverters. The first message is used to instruct the target inverter to perform a black start. The first message includes a preamble, a frame control field, and a payload. The preamble is used to assist the target inverter in identifying the start time of the signal frame of the first message. The frame control field and the payload are used to assist the target inverter in determining the reference time for the black start. The target inverter is used to receive the first message, determine the start time according to the preamble, and obtain the reference time of the black start according to the start time and the parsing time, wherein the parsing time is the parsing time of the frame control field or the parsing time of the payload; The target inverter is also used to obtain the start time of the black start based on the reference time and the specified delay time, and to perform the black start when the start time is reached.

2. The photovoltaic system according to claim 1, characterized in that, The subarray controller is also used to determine the target number of inverters participating in black start based on the load of the box transformer, the rated power reported by each inverter in the plurality of inverters, and the solar irradiance value. The subarray controller is also configured to select the target inverter from the plurality of inverters according to the target number of inverters; The subarray controller is also configured to carry the first identifier of the target inverter in the payload; The target inverter is configured to perform the black start when the start time arrives, provided that the identifier corresponding to the target inverter matches the first identifier obtained by parsing the payload after receiving the first message.

3. The photovoltaic system according to claim 2, characterized in that, The subarray controller is further configured to configure the first identifier for each of the plurality of inverters according to the order in which the plurality of inverters establish communication connections with the subarray controller; or... The subarray controller is further configured to configure the first identifier for each of the plurality of inverters according to the order of their physical address MAC or product serial number SN.

4. The photovoltaic system according to claim 3, characterized in that, The first message includes a controller SOF service signal for secure forwarding; The subarray controller is used to assign the first identifier to each of the plurality of inverters via the SOF service signal.

5. The photovoltaic system according to any one of claims 2-4, characterized in that, The first message is a broadcast signal, and the reserved field of the broadcast signal is the frame control field. The threshold corresponding to the reserved field is used to characterize the broadcast signal as a black-start broadcast signal. The subarray controller is further configured to configure a first value or a second value in the payload of the black start broadcast signal according to the arrangement order of the first identifiers of the plurality of inverters, and generate a string, the string being used to indicate whether each of the plurality of inverters participates in black start, the string including the first value and the second value, the first value being used to indicate participation in black start, and the second value being used to indicate non-participation in black start.

6. A black-start method based on photovoltaic power station equipment, characterized in that, The method is applied to a photovoltaic system, which includes a subarray controller and multiple inverters connected in parallel. The multiple inverters are communicatively connected to the subarray controller via a power line carrier communication PLC. The clocks of the multiple inverters are kept consistent with the clock of the subarray controller. The method includes: The subarray controller sends a first message to the target inverter, which may be some or all of the plurality of inverters. The first message instructs the target inverter to perform a black start. The first message includes a preamble, a frame control field, and a payload. The preamble helps the target inverter identify the start time of the signal frame of the first message. The frame control field and the payload can be used to help the target inverter determine the reference time for the black start. The target inverter receives the first message, determines the start time based on the preamble, and obtains the reference time for the black start based on the start time and the parsing time, wherein the parsing time is the parsing time of the frame control field or the parsing time of the payload. The target inverter obtains the start time of the black start based on the reference time and the specified delay time, and performs the black start when the start time arrives.

7. The method according to claim 6, characterized in that, Before the plurality of inverters receive the first message, the method further includes: The subarray controller determines the target number of inverters to participate in black start based on the load of the box transformer, the rated power reported by each inverter in the plurality of inverters, and the solar irradiance value. The subarray controller selects the target inverter from the plurality of inverters according to the target number of inverters; The subarray controller carries the first identifier of the target inverter in the payload; The target inverter performs the black start when the start-up time arrives, including: After receiving the first message, if the target inverter matches the identifier corresponding to the target inverter with the first identifier obtained by parsing the payload, it will perform the black start when the start time arrives.

8. The method according to claim 7, characterized in that, Before the subarray controller carries the first identifier of the target inverter in the payload, the method further includes: The subarray controller configures the first identifier for each of the plurality of inverters according to the order in which the inverters establish communication connections with the subarray controller; or... The subarray controller configures the first identifier for each of the plurality of inverters according to the order of their physical address MAC or product serial number SN.

9. The method according to claim 8, characterized in that, The first message includes a controller SOF service signal for secure forwarding; the subarray controller sends the first message to the plurality of inverters, including: The subarray controller assigns the first identifier to each of the plurality of inverters using the SOF service signal.

10. The method according to any one of claims 7-9, characterized in that, The first message is a broadcast signal, and the reserved field of the broadcast signal is the frame control field. The threshold corresponding to the reserved field is used to characterize the broadcast signal as a black-start broadcast signal. The subarray controller carries the first identifier of the target inverter in the payload, including: The subarray controller configures a first value or a second value in the payload of the black start broadcast signal according to the arrangement order of the first identifiers of the plurality of inverters, and generates a string. The string is used to indicate whether each inverter in the plurality of inverters participates in black start. The string includes the first value and the second value, the first value is used to indicate participation in black start, and the second value is used to indicate non-participation in black start.

Images