Control protection system and method for direct current photovoltaic convergence system

Abstract

The invention belongs to the field of large-scale photovoltaic array grid-connected power generation, and discloses a control protection system and method for a direct-current photovoltaic convergence system.The system comprises a control protection master station and a control protection substation which are in communication connection with an AGC system, an MDC converter valve, a DCT converter and an MPPT combiner box. Comprehensive monitoring and protection of the whole direct-current photovoltaic convergence system are realized; through the arrangement of the fault recording module and the fault early warning module, sampling and recording can be carried out in time and an early warning signal can be sent out when the system has an abnormal working condition, so that the safety and the reliability of the system are effectively improved; the application of the power calculation module and the power modulation module not only realizes the accurate calculation and modulation of the system power, but also can feed the calculation result back to the related system in time, thereby ensuring the stable operation of the DC photovoltaic convergence system in the practical engineering, and having important practical application value.

Description

Technical Field

[0001] The present invention belongs to the technical field of large-scale photovoltaic array grid-connected power generation, and in particular relates to a control and protection system and method for a direct current photovoltaic convergence system. Background Art

[0002] With the construction and development of photovoltaic power stations, large-scale photovoltaic power station grid-connected power generation has become the main form of photovoltaic grid-connected power generation. Compared with traditional AC grid-connected power generation, large-scale photovoltaic array grid-connected power generation has become a new form of development because there are no frequency and synchronization problems. In addition, when photovoltaic power stations are connected to the system using DC boost collection, they have the advantages of stable power transmission and high transmission capacity. When connected to the AC power grid, they can improve the stability of the power grid.

[0003] As large-scale photovoltaic power stations are connected to the grid through DC step-up transformers and inverters, their topological structures become more and more complex, and the incidence of system failures is also increasing. The fault current when a fault occurs may exceed the maximum current of the components or transmission lines, leading to further expansion of the fault. Therefore, it is necessary to analyze the fault current components when the photovoltaic power station collection system fails, so as to formulate corresponding control and protection strategies to improve the stability of the system.

[0004] However, the current research on protection measures for large-scale photovoltaic arrays connected to the grid is relatively limited; and there are few cases of actual engineering implementation and application; the only protection measures now are based on control protection strategies and simulation, and cannot solve the application problems of DC photovoltaic aggregation systems in actual engineering. Summary of the invention

[0005] The present invention provides a control and protection system and method for a DC photovoltaic convergence system. The system and method can effectively solve the engineering realization and application problems of MW-level large-capacity DC photovoltaic convergence topology.

[0006] In order to achieve the above object, the present invention adopts the following technical contents: A control and protection system for a DC photovoltaic convergence system, comprising a control and protection master station and a control and protection substation; The control and protection master station is simultaneously connected to the AGC system and the MDC converter valve in communication; The control and protection substation is simultaneously connected to the DCT converter and the MPPT combiner box for communication; The control and protection master station is communicatively connected with the control and protection substation; The control and protection master station and the control and protection substation both include a fault recording module and a fault early warning module; The fault recording module is used to automatically sample and record when an abnormal working condition occurs in the DC photovoltaic convergence system; The fault warning module is used to send out a fault warning signal when it is determined that all the collected operating values ​​and status signals reach or exceed the corresponding threshold value; The control and protection master station also includes a power calculation module, which is used to receive the total active power instruction and the total reactive power instruction issued by the AGC system, send the target value obtained after calculating the total active power instruction to the control and protection substation, and send the target value obtained after calculating the total reactive power instruction to the MDC converter valve; and at the same time, feed back the upper and lower limits of active power and the upper and lower limits of reactive power to the AGC system; The control and protection substation also includes a power modulation module, which is used to receive all switch and knife switch position signals and all analog data signals of the primary circuit sent by the DCT converter and the MPPT combiner box, and simultaneously perform power modulation calculations on all switch and knife switch position signals and all analog data signals, and send the calculated target value to the corresponding DCT converter and MPPT combiner box.

[0007] Furthermore, the control and protection master station is connected to the AGC system through a GOOSE protocol optical fiber, and is connected to the MDC converter valve of the booster station through an IEC-60044-8 protocol optical fiber.

[0008] Furthermore, the control and protection substation is communicatively connected to the DCT converter of the new energy station via IEC-60044-8 protocol optical fiber, and is communicatively connected to the MPPT combiner box of the photovoltaic equipment via Modbus protocol optical fiber.

[0009] Furthermore, the control and protection master station is connected to the control and protection substation via high-speed Aurora optical fiber communication, and the high-speed Aurora optical fiber adopts single-mode optical fiber.

[0010] Furthermore, the control and protection main station and the control and protection substation adopt the same hardware platform; wherein, the hardware platform adopts a multi-main processor structure, and the backplane bus rate is at least 2.5Gbps, which is used to support the burst execution of multi-priority cyclic tasks and interrupt tasks; the minimum cyclic task period of the hardware platform is less than 50 microseconds.

[0011] Furthermore, the fault recording module is triggered by an automatic trigger signal, and the automatic trigger signal includes a lock / unlock signal of the converter, an AC control state signal, an active power control state signal, a DC voltage control state signal and a regulator operation state signal, a protection trip signal, a switch opening / closing signal and a system fault signal; All the operating values ​​and status signals include: action signals of AC / DC protection in the DC photovoltaic convergence system, self-test results of all connected devices, fault signals, and communication system fault signals.

[0012] Furthermore, it also includes an operation monitoring module, which is used to upload all operation control commands, control system instructions, control action processes, and changes in operation status to the local background when the DC photovoltaic convergence system is operating normally.

[0013] Furthermore, the DC photovoltaic convergence system is divided into a photovoltaic equipment protection zone, a DC transformer protection zone, a DC line protection zone and an MDC converter valve protection zone; The photovoltaic equipment protection area is a photovoltaic equipment collection area, and the protected equipment includes photovoltaic component strings, DC lines and DC combiner boxes; The DC transformer protection zone is the area between the DC busbar on the high-voltage side and the DC busbar on the low-voltage side. The protected equipment includes the equipment in the DC transformer prefabricated cabin. The equipment in the DC transformer prefabricated cabin includes an isolation transformer and a semiconductor switch device. The DC line protection zone is a DC transmission line zone, and the protected equipment includes multiple DC cables; The MDC converter valve protection zone is the area between the grid side of the AC connection transformer and the DC bus. The protected equipment includes the connection transformer, MDC converter valve, ±15kV medium voltage DC bus and DC collection switch cabinet.

[0014] A control and protection method for a DC photovoltaic convergence system, based on the control and protection system for the DC photovoltaic convergence system, comprises: The fault recording module is used to automatically sample and record when abnormal working conditions occur in the DC photovoltaic concentrator system; By using the fault warning module, when it is determined that all the collected operating values ​​and status signals reach or exceed the corresponding threshold value, a fault warning signal is issued; The power calculation module of the control and protection master station is used to receive the total active power command and total reactive power command issued by the AGC system, and the target value obtained after calculating the total active power command is sent to the control and protection substation, and the target value obtained after calculating the total reactive power command is sent to the MDC converter valve; at the same time, the upper and lower limits of active power and reactive power are fed back to the AGC system; The power modulation module of the control and protection substation is used to receive all switch and knife switch position signals and all analog data signals of the primary circuit sent by the DCT converter and MPPT combiner box, and all switch and knife switch position signals and all analog data signals are subjected to power modulation calculation at the same time, and the calculated target value is sent to the corresponding DCT converter and MPPT combiner box.

[0015] Furthermore, during the fault recording process, the recording length is not less than 5s, and the recording sampling rate is not less than 10ksps.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a control and protection system for a DC photovoltaic convergence system. The system comprises a control and protection main station and a control and protection substation, and is respectively connected to an AGC system, an MDC converter valve, a DCT converter and an MPPT junction box for communication, thereby realizing comprehensive monitoring and protection of the entire DC photovoltaic convergence system. By setting a fault recording module and a fault warning module, it is possible to timely sample and record and send out a warning signal when an abnormal working condition occurs in the system, thereby effectively improving the safety and reliability of the system. The application of a power calculation module and a power modulation module not only realizes the accurate calculation and modulation of the system power, but also can timely feed back the calculation result to a related system, thereby ensuring the stable operation of the DC photovoltaic convergence system in actual engineering. The system effectively solves the current technical problems such as limited research on protection measures for large-scale photovoltaic arrays connected to the power grid, few engineering implementation and application cases, and the inability of existing protection measures to solve actual engineering application problems, and has important practical application value.

[0017] Preferably, in the present invention, the GOOSE protocol and the IEC-60044-8 protocol are used for communication connection, which ensures the accuracy and real-time performance of data transmission between the master station and the AGC system, and between the master station and the MDC converter valve, and provides a guarantee for the stable operation of the system.

[0018] Preferably, in the present invention, communication connection is performed through IEC-60044-8 protocol and Modbus protocol, so that the substation can efficiently receive data sent by the DCT converter and the MPPT combiner box, ensuring the accuracy and integrity of the data and providing a reliable basis for power modulation.

[0019] Preferably, in the present invention, high-speed Aurora fiber optic communication is used for connection, and single-mode fiber is selected to ensure high-speed and stable data transmission between the control and protection main station and the control and protection substation, improve the response speed and reliability of the system, and can support a communication distance of 40 kilometers or even longer between the control and protection main station and the control and protection substation, thereby adapting to working conditions where the photovoltaic station and the booster station are far apart.

[0020] Preferably, in the present invention, the control and protection main station and the control and protection substation adopt the same hardware platform, and have a multi-main processor structure and a high backplane bus rate, support the burst execution of multi-priority cyclic tasks and interrupt tasks, ensure the high performance and real-time performance of the system, and meet the complex requirements of large-scale photovoltaic array access to the power grid.

[0021] Preferably, in the present invention, the fault recording module is triggered by an automatic trigger signal, covering a variety of key signals, ensuring that abnormal operating conditions can be recorded and analyzed in a timely manner; at the same time, comprehensive monitoring of operating values ​​and status signals improves the system's fault warning capability.

[0022] Preferably, in the present invention, the operation monitoring module can upload the system's operation control commands, instructions, action processes and status changes in real time, providing comprehensive monitoring information for operation and maintenance personnel, which helps to timely discover and deal with potential problems; dynamic monitoring during normal operation also helps to trace subsequent problems.

[0023] Preferably, in the present invention, the DC photovoltaic convergence system is divided into different protection zones, and the protected equipment and scope of each protection zone are clearly defined, which helps to implement targeted protection measures and improves the overall protection effect of the system.

[0024] The present invention also provides a working method of a control and protection system for a DC photovoltaic convergence system. Based on the above-mentioned control and protection system for the DC photovoltaic convergence system, the method realizes comprehensive and accurate protection of the DC photovoltaic convergence system by integrating multiple functional modules such as fault recording, fault warning, power calculation and power modulation. Compared with the prior art, the use of the present method not only enhances the response capability of the system under abnormal working conditions, improves the timeliness of fault processing through automatic sampling recording and warning signals, but also ensures the stable output and regulation of the system power through power calculation and modulation functions, effectively solving the shortcomings of current protection measures in actual engineering applications, and providing a more reliable and practical control and protection strategy for large-scale photovoltaic arrays to access the power grid.

[0025] Preferably, in the present invention, during the fault recording process, the recording length is not less than 5s and the recording sampling rate is not less than 10ksps, ensuring that the recording length and sampling rate meet the requirements, which helps to accurately record and analyze abnormal working conditions and provide strong support for system fault detection and repair. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A topological structure diagram of a large-capacity DC photovoltaic aggregation system provided by an embodiment of the present invention; Figure 2 A schematic diagram of a protection partition provided in an embodiment of the present invention; Figure 3 A schematic diagram of the control architecture of a DC photovoltaic convergence system provided by an embodiment of the present invention; Figure 4 A flow chart of starting from the maintenance state to running of the DC photovoltaic convergence system provided by an embodiment of the present invention; Figure 5 A schematic structural diagram of a control and protection system for a DC photovoltaic concentration system provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0027] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail in the following specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0028] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0029] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0031] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0032] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0033] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0034] As mentioned in the background technology, so far, there are few forms of large-scale photovoltaic arrays connected to the power grid abroad, and the domestic experience in related engineering is also limited. There have been many studies on large-capacity DC photovoltaic convergence topologies and fault theory studies on photovoltaic power station convergence systems, but there are few cases of actual engineering implementation and engineering application; and the only protection measures now are based on control protection strategies and simulations, which cannot solve the application problems of DC photovoltaic convergence systems in actual projects.

[0035] In order to solve the above problems, this embodiment provides a control and protection system for a DC photovoltaic convergence system, that is, it provides a detailed design of a practical large-capacity DC photovoltaic convergence control and protection system; this system adopts a safe and stable embedded hardware platform and a standard industrial data interface, as well as a layered architecture of a control and protection main station and a control and protection substation, so as to adapt to working conditions where the photovoltaic station and the booster station are far apart.

[0036] In order to facilitate further understanding of this technical solution, the following technical terms are explained: AGC (Automatic Generation Control): Automatic power generation control system; MDC (Modular DC-Link Converter): multi-level DC link converter; DCT (DC transformer): DC transformer; MPPT (Maximum Power Point Tracking): Maximum power point tracking solar controller.

[0037] like Figure 1As shown, this embodiment provides a topological structure of a large-capacity DC photovoltaic convergence system. This large-capacity DC photovoltaic convergence system adopts a 50MW photovoltaic DC convergence system; it relies on the output sides of 5 groups of 10MW photovoltaic DC convergence units to be connected in parallel to the ±15kV DC bus, and after aggregation, the DC-AC flexible DC converter valve inverter is connected to the AC 35kV power grid; for multi-channel DC convergence input scenarios, in order to prevent the entire system from being shut down due to a single-circuit line grounding fault, a line switch cabinet with a fault isolation function is designed to be configured at the convergence port location.

[0038] New energy photovoltaic station, with a total of 145 MPPTs divided into 15 groups, each group consists of 9 to 10 MPPTs connected in series to form a ring. The upper level of the MPPT is 5 DCTs, each DCT is connected to 3 groups of MPPTs, and the capacity of each DCT is 10MW.

[0039] like Figure 2 As shown in the figure, according to the principle of protection area division and the protected objects in the system, the entire architecture of the DC photovoltaic convergence system is divided into photovoltaic equipment protection area, DC transformer protection area, DC line protection area and MDC converter valve protection area (including connecting transformer), among which: The MDC converter valve protection area (including the connection transformer) is the area between the grid side of the AC connection transformer and the DC busbar. The protected equipment includes the connection transformer, MDC converter valve, ±15kV medium voltage DC busbar and DC collection switch cabinet; The DC line protection zone is the DC transmission line area, and the protected equipment includes multiple DC cables; The DC transformer protection zone is the area between the DC busbar on the high-voltage side and the DC busbar on the low-voltage side. The protected equipment includes the equipment in the DC transformer prefabricated cabin, mainly including isolation transformers, semiconductor switching devices, etc. The photovoltaic equipment protection zone is the photovoltaic equipment collection area, and the protected equipment includes photovoltaic module strings, DC lines and DC combiner boxes.

[0040] like Figure 3 As shown in the figure, the control architecture of the DC photovoltaic concentration system is as follows: Scheduling layer (VGC): Generates system operation mode instructions and their corresponding power reference value instructions based on scheduling requirements.

[0041] Control and protection layer: Determines whether the DC collection system accepts external dispatching operation modes and power instructions (active and reactive instruction reference values), and issues control instructions and control reference values ​​to each key device in the local equipment control layer. At the same time, the control system realizes smooth switching between operation modes and coordinated processing when the AC system fails.

[0042] On-site equipment control layer: Each key device such as MDC, DCT, MPPT, etc. is controlled according to its own principles and characteristics. The active power connected to the grid is controlled by the DC combiner boxes that are dispersed on-site according to the power instructions issued by the control and protection layer.

[0043] like Figure 4 As shown in the figure, the entire system starts from the maintenance state to the operation state. In the default state, all the switches are in the open state. The specific steps are as follows: First, the cooperative remote control MDC and DCT center knife are closed; then the cooperative remote control MDC one-key start is performed. If the start fails, the start steps are repeated; after the start is completed, the cooperative remote control 5 DCT start process is entered; finally, the system startup process is completed.

[0044] like Figure 5 As shown, this embodiment provides a control and protection system for a DC photovoltaic convergence system, including: a control and protection master station and a control and protection substation; The control and protection master station is equipped with a standard optical communication port, which communicates with the AGC via GOOSE protocol optical fiber and with the MDC converter of the booster station via IEC-60044-8 protocol optical fiber.

[0045] The control and protection substation is equipped with a standard optical communication port, which communicates with the DCT converter of the new energy station through IEC-60044-8 protocol optical fiber, and communicates with the MPPT combiner box of the photovoltaic through Modbus protocol optical fiber.

[0046] The control and protection master station and the control and protection substation communicate via high-speed Aurora optical fiber, which uses single-mode optical fiber and can support a communication distance of 40 kilometers or even longer between the master station and the substation.

[0047] In this embodiment, the control and protection main station also includes a power calculation module, which is used to receive the total active power instruction and the total reactive power instruction issued by the AGC system, send the target value obtained after calculating the total active power instruction to the control and protection substation, and send the target value obtained after calculating the total reactive power instruction to the MDC converter valve; at the same time, the upper and lower limits of active power and the upper and lower limits of reactive power are fed back to the AGC system.

[0048] In this embodiment, the control and protection substation also includes a power modulation module, which is used to receive all switch and knife switch position signals and all analog data signals of the primary circuit sent by the DCT converter and the MPPT combiner box, and perform power modulation calculations on all switch and knife switch position signals and all analog data signals, and send the calculated target value to the corresponding DCT converter and MPPT combiner box.

[0049] This protection system includes a control and protection main station and a control and protection substation, which are respectively connected to the AGC system, MDC converter valve, DCT converter and MPPT combiner box, realizing comprehensive monitoring and protection of the entire DC photovoltaic convergence system; through the setting of the fault recording module and the fault warning module, it can timely sample and record and issue a warning signal when the system has abnormal working conditions, effectively improving the safety and reliability of the system; the application of the power calculation module and the power modulation module not only realizes the accurate calculation and modulation of the system power, but also can timely feed back the calculation results to the relevant systems, thereby ensuring the stable operation of the DC photovoltaic convergence system in actual projects. The use of this system effectively solves the current technical problems such as limited research on protection measures for large-scale photovoltaic arrays connected to the power grid, few engineering implementation and application cases, and the inability of existing protection measures to solve actual engineering application problems.

[0050] The GOOSE protocol and IEC-60044-8 protocol are used for communication connection, ensuring the accuracy and real-time performance of data transmission between the master station and the AGC system, and between the master station and the MDC converter valve, providing a guarantee for the stable operation of the system; and the IEC-60044-8 protocol and Modbus protocol are used for communication connection, so that the substation can efficiently receive the data sent by the DCT converter and the MPPT junction box, ensuring the accuracy and integrity of the data, and providing a reliable basis for power modulation. The high-speed Aurora optical fiber communication is used for connection, and single-mode optical fiber is used to ensure the high speed and stability of data transmission between the control and protection master station and the control and protection substation, improving the response speed and reliability of the system, so as to adapt to the working conditions where the photovoltaic station and the booster station are far apart.

[0051] In this embodiment, the control and protection master station and the control and protection substation use the same hardware platform, the hardware platform uses a multi-master processor structure, the backplane bus rate is 2.5Gbps, the hardware platform supports the burst execution of multi-priority cyclic tasks and interrupt tasks, the minimum cyclic task period is less than 50 microseconds, and there are 3 main processor modules in the control and protection substation chassis for parallel processing. The control and protection master station and the control and protection substation use the same hardware platform, and have a multi-master processor structure and a high backplane bus rate, support the burst execution of multi-priority cyclic tasks and interrupt tasks, ensure the high performance and real-time performance of the system, and meet the complex needs of large-scale photovoltaic array access to the power grid.

[0052] In this embodiment, the control and protection master station and the control and protection substation both include a fault recording module and a fault warning module; that is, they have the function of fault recording and fault warning; during the fault recording process, the fault recording length is not less than 5s, and the recording sampling rate is not less than 10ksps; when the system has an abnormal working condition, the fault recording module automatically triggers the recording and saves it to the non-volatile memory, and the automatic trigger signal of the fault recording contains the main status information of the system: the lock / unlock signal of the converter, the AC control status signal, the active control status signal, the DC voltage control status signal and the regulator operation status, the protection trip signal, the switch opening / closing signal, the system fault signal and other signals of concern, etc. The fault recording module is triggered by the automatic trigger signal, covering a variety of key signals, ensuring that abnormal working conditions can be recorded and analyzed in time; at the same time, the comprehensive monitoring of the operating value and status signal improves the fault warning capability of the system.

[0053] In the fault warning module, the control and protection main station and the control and protection substation collect all operating values ​​and status signals in real time; when the design critical value or limit value is reached or exceeded, an alarm is displayed; specifically including: the action signals of all AC / DC protections; the self-test results and fault alarms of all connected equipment; it also has the display and alarm function of communication system faults.

[0054] In this embodiment, an operation monitoring module is also included, which is used to upload all operation control commands, control system instructions, control action processes, and changes in operation status to the local background when the DC photovoltaic convergence system is operating normally. The operation monitoring module can upload the system's operation control commands, instructions, action processes, and state changes in real time, providing comprehensive monitoring information for operation and maintenance personnel, which helps to timely discover and deal with potential problems; dynamic monitoring during normal operation is also helpful for subsequent problem tracing.

[0055] This embodiment also provides a control and protection method for a DC photovoltaic convergence system, based on the above protection system, including the following steps: The fault recording module is used to automatically sample and record when abnormal working conditions occur in the DC photovoltaic concentrator system; By using the fault warning module, when it is determined that all the collected operating values ​​and status signals reach or exceed the corresponding threshold value, a fault warning signal is issued; The power calculation module of the control and protection master station is used to receive the total active power command and total reactive power command issued by the AGC system, and the target value obtained after calculating the total active power command is sent to the control and protection substation, and the target value obtained after calculating the total reactive power command is sent to the MDC converter valve; at the same time, the upper and lower limits of active power and reactive power are fed back to the AGC system; The power modulation module of the control and protection substation is used to receive all switch and knife switch position signals and all analog data signals of the primary circuit sent by the DCT converter and MPPT combiner box, and all switch and knife switch position signals and all analog data signals are subjected to power modulation calculation at the same time, and the calculated target value is sent to the corresponding DCT converter and MPPT combiner box.

[0056] It can be seen that this method realizes comprehensive and accurate protection of the DC photovoltaic convergence system by integrating multiple functional modules such as fault recording, fault warning, power calculation and power modulation; compared with the existing technology, the adoption of this method not only enhances the system's response capability under abnormal conditions, improves the timeliness of fault processing through automatic sampling recording and warning signals, but also ensures the stable output and regulation of system power through power calculation and modulation functions, effectively solves the shortcomings of current protection measures in actual engineering applications, and provides a more reliable and practical protection strategy for large-scale photovoltaic arrays connected to the power grid.

[0057] In summary, the present invention provides a control and protection system for a DC photovoltaic concentration system, which has the following advantages over existing protection measures: The protection measures for large-scale photovoltaic arrays to be connected to the grid have been innovated, effectively solving the shortcomings of the existing technology in the actual engineering application of DC photovoltaic convergence system. By deploying the control and protection master station and the control and protection substation, the system can realize comprehensive monitoring and control of the DC photovoltaic convergence system, thereby improving the stability and reliability of the system. First, through the communication connection between the control and protection master station and the AGC system and the MDC converter valve, the macro-control of the entire system can be realized to ensure that the system operates in the best state. At the same time, the communication connection between the control and protection substation and the DCT converter and the MPPT combiner box can finely control the specific equipment in the system and improve the accuracy and flexibility of the control. Secondly, the introduction of the fault recording module and the fault warning module enables the system to respond quickly to abnormal working conditions, automatically sample and record, and issue a fault warning signal when reaching or exceeding the preset threshold, which not only helps to timely discover and handle faults, but also provides important data support for system maintenance, further improving the operation stability of the system. In addition, the power calculation module in the control and protection master station and the power modulation module in the substation work together to accurately control the power distribution and modulation of the system. By receiving and processing instructions from the AGC system, as well as data from the DCT converter and MPPT combiner box, the system can achieve precise control of the DC voltage and ensure that the system remains stable under various operating conditions. This method effectively solves the stability and reliability issues of large-scale DC photovoltaic systems in practical applications by integrating advanced control and protection strategies, combining high-speed communication technology and intelligent algorithms, and provides strong technical support for promoting the development and application of DC photovoltaic technology.

[0058] The above embodiment is only one of the implementation methods that can realize the technical solution of the present invention. The scope of protection claimed by the present invention is not limited only to this embodiment, but also includes changes, replacements and other implementation methods that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed by the present invention.

Claims

1. A control and protection system for a DC photovoltaic concentration system, characterized in that: Including control and protection main station and control and protection substation; The control and protection master station is simultaneously connected to the AGC system and the MDC converter valve in communication; The control and protection substation is simultaneously connected to the DCT converter and the MPPT combiner box for communication; The control and protection master station is communicatively connected with the control and protection substation; The control and protection master station and the control and protection substation both include a fault recording module and a fault early warning module; The fault recording module is used to automatically sample and record when an abnormal working condition occurs in the DC photovoltaic convergence system; The fault warning module is used to send out a fault warning signal when it is determined that all the collected operating values ​​and status signals reach or exceed the corresponding threshold value; The control and protection master station also includes a power calculation module, which is used to receive the total active power instruction and the total reactive power instruction issued by the AGC system, send the target value obtained after calculating the total active power instruction to the control and protection substation, and send the target value obtained after calculating the total reactive power instruction to the MDC converter valve; and at the same time, feed back the upper and lower limits of active power and the upper and lower limits of reactive power to the AGC system; The control and protection substation also includes a power modulation module, which is used to receive all switch and knife switch position signals and all analog data signals of the primary circuit sent by the DCT converter and the MPPT combiner box, and simultaneously perform power modulation calculations on all switch and knife switch position signals and all analog data signals, and send the calculated target value to the corresponding DCT converter and MPPT combiner box.

2. The control and protection system for a DC photovoltaic concentration system according to claim 1, characterized in that: The control and protection master station is connected to the AGC system through GOOSE protocol optical fiber, and is connected to the MDC converter valve of the booster station through IEC-60044-8 protocol optical fiber.

3. The control and protection system for a DC photovoltaic concentration system according to claim 1, characterized in that: The control and protection substation is connected to the DCT converter of the new energy station through IEC-60044-8 protocol optical fiber, and is connected to the MPPT combiner box of the photovoltaic equipment through Modbus protocol optical fiber.

4. The control and protection system for a DC photovoltaic concentration system according to claim 1, characterized in that: The control and protection master station is connected to the control and protection substation via high-speed Aurora optical fiber communication, and the high-speed Aurora optical fiber adopts single-mode optical fiber.

5. The control and protection system for a DC photovoltaic concentration system according to claim 1, characterized in that: The control and protection main station and the control and protection substation use the same hardware platform; wherein, the hardware platform adopts a multi-main processor structure, and the backplane bus rate is at least 2.5Gbps, which is used to support the burst execution of multi-priority cyclic tasks and interrupt tasks; the minimum cyclic task period of the hardware platform is less than 50 microseconds.

6. The control and protection system for a DC photovoltaic concentration system according to claim 1, characterized in that: The fault recording module is triggered by an automatic trigger signal, which includes a lock / unlock signal of the converter, an AC control state signal, an active power control state signal, a DC voltage control state signal, a regulator operation state signal, a protection trip signal, a switch opening / closing signal, and a system fault signal; All the operating values ​​and status signals include: action signals of AC / DC protection in the DC photovoltaic convergence system, self-test results of all connected devices, fault signals, and communication system fault signals.

7. The control and protection system for a DC photovoltaic concentration system according to claim 1, characterized in that: It also includes an operation monitoring module, which is used to upload all operation control commands, control system instructions, control action processes, and changes in operation status to the local background when the DC photovoltaic aggregation system is operating normally.

8. The control and protection system for a DC photovoltaic concentration system according to claim 1, characterized in that: The DC photovoltaic convergence system is divided into a photovoltaic equipment protection zone, a DC transformer protection zone, a DC line protection zone and an MDC converter valve protection zone; The photovoltaic equipment protection area is a photovoltaic equipment collection area, and the protected equipment includes photovoltaic component strings, DC lines and DC combiner boxes; The DC transformer protection zone is the area between the DC busbar on the high-voltage side and the DC busbar on the low-voltage side. The protected equipment includes the equipment in the DC transformer prefabricated cabin. The equipment in the DC transformer prefabricated cabin includes an isolation transformer and a semiconductor switch device. The DC line protection zone is a DC transmission line zone, and the protected equipment includes multiple DC cables; The MDC converter valve protection zone is the area between the grid side of the AC connection transformer and the DC bus. The protected equipment includes the connection transformer, MDC converter valve, ±15kV medium voltage DC bus and DC collection switch cabinet.

9. A control and protection method for a DC photovoltaic concentration system, based on the control and protection system for a DC photovoltaic concentration system according to any one of claims 1 to 8, characterized in that: include: The fault recording module is used to automatically sample and record when abnormal working conditions occur in the DC photovoltaic concentrator system; By using the fault warning module, when it is determined that all the collected operating values ​​and status signals reach or exceed the corresponding threshold value, a fault warning signal is issued; The power calculation module of the control and protection master station is used to receive the total active power command and total reactive power command issued by the AGC system, and the target value obtained after calculating the total active power command is sent to the control and protection substation, and the target value obtained after calculating the total reactive power command is sent to the MDC converter valve; at the same time, the upper and lower limits of active power and reactive power are fed back to the AGC system; The power modulation module of the control and protection substation is used to receive all switch and knife switch position signals and all analog data signals of the primary circuit sent by the DCT converter and MPPT combiner box, and all switch and knife switch position signals and all analog data signals are subjected to power modulation calculation at the same time, and the calculated target value is sent to the corresponding DCT converter and MPPT combiner box.

10. The control and protection method for a DC photovoltaic concentration system according to claim 9, characterized in that: During the fault recording process, the recording length shall not be less than 5s and the recording sampling rate shall not be less than 10ksps.

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