Direct current micro-grid protection method and system based on local information

Abstract

The invention relates to a DC micro-grid protection method and system based on local information. The method comprises the following steps: S1, acquiring a line voltage and a line current in real time through a local protection terminal; s2, calculating the first-order difference of the positive voltage of the line, judging whether the absolute value of the first-order difference of the positive voltage is greater than a first set value or not, if so, meeting a protection starting criterion, namely starting protection, and executing a step S3, and if not, returning to the step S2; s3, calculating the positive current square first-order difference of the circuit, judging whether the absolute value of the positive current square first-order difference is greater than a second set value or not, if so, meeting the action criterion of protection, namely starting the protection action, and if not, returning to the step S2; and S4, starting a corresponding circuit breaker to execute a protection action according to the fault type. Compared with the prior art, the method has the advantages that the response is quick, the dependence on a complex communication network is not needed, and the reliability and robustness of the direct-current micro-grid are improved.

Description

Technical Field

[0001] The present invention relates to a DC microgrid protection mechanism, and more particularly to a DC microgrid protection method and system based on local information. Background Art

[0002] In recent years, the implementation of DC microgrids has shown an exponential growth trend, which benefits from its high efficiency, high power density, high flexibility, and simple control characteristics. Although DC microgrids have significant advantages in terms of flexibility and survivability, their protection mechanisms face many challenges, which hinder the further development of DC microgrids. Existing DC microgrid protection technologies have their own deficiencies in different specific protection methods. For example, differential protection may generate false alarms due to unbalanced currents and is not fast enough to respond in the case of rapid current changes. Traveling wave protection can quickly detect faults, but it may be difficult to accurately determine the fault location in the case of low-impedance faults or complex network structures. Protection methods based on the rate of change of voltage and current may be affected by load changes or other non-fault factors, resulting in false alarms or delayed protection actions. Although protection methods based on control and protection coordination provide more intelligent protection strategies, their implementation usually requires complex control systems and algorithms, increasing the complexity and cost of the system.

[0003] After retrieving the prior art, it is found that Chinese patent application CN111276950A discloses a microgrid protection method and system based on current polarity comparison. The method includes: configuring unit protection modules at the access points of the branch lines and distributed power sources of the microgrid; calculating the phase difference between the pre-fault current and the fault component current of each unit protection module, and calculating the polarity of each unit protection module according to a preset phase difference range; calculating the product of the polarities of adjacent unit protection modules, and when the product of the polarities is a preset value, it is determined that there is a fault between the adjacent unit protection modules; cutting off the control circuit breakers of the adjacent unit protection modules with the product of the polarities being the preset value to isolate the fault interval and complete the protection of the microgrid. However, this prior art does not consider the voltage characteristics of the DC microgrid and has problems such as slow response in the case of rapid current changes and inaccurate fault location. Summary of the Invention

[0004] The object of the present invention is to address the problems existing in the current DC microgrid protection technology, such as insufficient consideration of voltage characteristics, slow response speed, and inability to effectively locate faults. A DC microgrid protection method and system based on local information are provided. By fusing local information such as voltage and current, rapid response is achieved, and it does not rely on a complex communication network, thereby reducing the complexity and cost of the system, operating independently to a certain extent, and improving the reliability and robustness of the system.

[0005] The object of the present invention can be achieved by the following technical solutions:

[0006] A DC microgrid protection method based on local information, comprising the following steps:

[0007] S1. Obtain the line voltage and line current in real time through a local protection terminal;

[0008] S2. Calculate the first-order difference of the positive-pole voltage of the line, and determine whether the absolute value of the first-order difference of the positive-pole voltage is greater than a first set value. If so, the starting criterion for protection is satisfied, that is, start the protection and execute step S3. If not, return to step S2;

[0009] S3. Calculate the first-order difference of the square of the positive-pole current of the line, and determine whether the absolute value of the first-order difference of the square of the positive-pole current is greater than a second set value. If so, the action criterion for protection is satisfied, that is, start the protection action. If not, return to step S2;

[0010] S4. Start the corresponding circuit breaker to execute the protection action according to the fault type.

[0011] Further, the first-order difference of the positive-pole voltage is the difference between the positive-pole voltages in two consecutive sampling periods.

[0012] Further, the first-order difference of the square of the positive-pole current is the difference between the squares of the positive-pole currents in two consecutive sampling periods.

[0013] Further, in step S4, determine the fault type according to the states of the positive-pole voltage and the negative-pole voltage.

[0014] Further, the fault type includes a bipolar short-circuit fault, a positive-pole short-circuit fault or a negative-pole short-circuit fault.

[0015] Further, in step S4, determine whether the absolute value of the difference between the absolute value of the positive-pole voltage and the absolute value of the negative-pole voltage is less than a third set value. If so, it is determined as a bipolar short-circuit fault. If not, determine whether the absolute value of the positive-pole voltage is less than a fourth set value u set , if so, it is determined as a positive-pole grounding fault. If not, it is determined as a negative-pole grounding fault.

[0016] Further, the DC microgrid includes a renewable energy-dominated microgrid or a hybrid energy microgrid.

[0017] The present invention also provides a DC microgrid protection system based on local information, comprising:

[0018] A local information sampling module, configured to obtain the line voltage and line current in real time through a local protection terminal;

[0019] The startup criterion module is used to calculate the first-order difference of the positive-pole voltage of the line based on the data of the local information sampling module, and determine whether the absolute value of the first-order difference of the positive-pole voltage is greater than a first set value. If so, the startup criterion of the protection is satisfied, that is, the protection is started. If not, the data of the local information sampling module is continuously acquired;

[0020] The action criterion module responds when the startup criterion module obtains a result that satisfies the startup criterion of the protection. It is used to calculate the first-order difference of the square of the positive-pole current of the line based on the data of the local information sampling module, and determine whether the absolute value of the first-order difference of the square of the positive-pole current is greater than a second set value. If so, the action criterion of the protection is satisfied, that is, the protection action is started. If not, the data of the local information sampling module is continuously acquired;

[0021] The action execution module responds when the action criterion module obtains a result that satisfies the action criterion of the protection, and is used to start the corresponding circuit breaker to execute the protection action according to the fault type.

[0022] The present invention also provides a computer-readable storage medium, including one or more programs for execution by one or more processors of an electronic device, and the one or more programs include instructions for executing the above-mentioned DC microgrid protection method based on local information.

[0023] The present invention also provides an electronic device, including one or more processors, a memory, and one or more programs stored in the memory, and the one or more programs include instructions for executing the above-mentioned DC microgrid protection method based on local information.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. Comprehensive consideration of local information: The data and signals directly obtained from the location where the protection device is located in the present invention can detect and isolate faults faster by using the data available on a single terminal than the method relying on communication between multiple terminals. This is particularly important for sensitive power electronic devices because they cannot withstand high fault currents for a long time. The present invention reduces the dependence on the communication link, thereby improving the reliability of the protection system and avoiding the delay and fault problems that are prone to occur in the communication link. This independence helps to ensure consistent protection performance, even under adverse conditions. By focusing on local information, the method of the present invention simplifies the overall system design and reduces the complexity and cost of the extensive communication network required for fault detection and protection coordination. The present invention not only pays attention to the change of current, but also fully considers the voltage characteristics. By real-time monitoring the changes of voltage and current, and making protection judgments based on information such as the first-order difference of the positive-pole voltage and the first-order difference of the square of the positive-pole current, the accuracy and reliability of protection are improved. This method can more comprehensively evaluate the state of the microgrid and avoid misjudgment and missed judgment that may be caused by relying only on a single variable.

[0026] 2. Quick response: By adopting high-speed data acquisition and processing technology, it can quickly respond under the condition of rapid current change, greatly shortening the time for fault detection and isolation. This is crucial for protecting the microgrid from serious damage, especially in the case of high load or sudden fault.

[0027] 3. Precise fault location: Through the pole selection criterion, it can more accurately identify the fault type, thereby taking targeted protection measures, reducing the false alarm rate and missed alarm rate. This can not only reduce unnecessary switching operations, but also ensure power supply restoration as soon as possible when a fault occurs, reducing the impact on users.

[0028] 4. High efficiency and energy saving: Through the quick response and precise location of faults, unnecessary switching operations are reduced, energy consumption is lowered, which is beneficial to improving the overall efficiency of the microgrid. This not only saves power resources, but also helps to extend the equipment life and reduce the maintenance cost.

[0029] 5. Easy to implement: The protection method proposed in the present invention is simple and easy to implement, facilitating application and promotion in actual projects, and helping to improve the safety and stability of the DC microgrid. Whether it is a new project or the transformation of existing facilities, this protection system can be easily integrated without complex hardware upgrades or large-scale rewiring.

[0030] 6. The fault threshold is easy to set: The fault threshold of the protection method of the present invention is easy to set and adjust, improving the adjustability of the protection system.

[0031] 7. Adapt to different working conditions: This protection method can reliably identify faults and select poles under different fault scenarios and operating modes, and has strong adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a flowchart of the present invention;

[0033] Figure 2 is a schematic diagram of a DC microgrid structure applicable to the present invention;

[0034] Figure 3 are the positive - pole voltage waveforms in various situations of the DC microgrid in the embodiments of the present invention;

[0035] Figure 4 are the positive - pole current waveforms in various situations of the DC microgrid in the embodiments of the present invention;

[0036] Figure 5 are the first - order difference waveforms of the positive - pole voltage in various situations of the DC microgrid in the embodiments of the present invention;

[0037] Figure 6 are the first - order difference waveforms of the square of the positive - pole current in various situations of the DC microgrid in the embodiments of the present invention;

[0038] Figure 7 is the waveform of the pole - selection criterion change in the embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] The present invention will be described in detail below with reference to the drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and gives detailed implementation manners and specific operation processes, but the protection scope of the present invention is not limited to the following embodiments.

[0040] Embodiment 1

[0041] This embodiment provides a DC microgrid protection method based on local information, as Figure 1 shown, including the following steps:

[0042] S1. Continuously obtain the line voltage and line current through the local protection terminal. By continuously collecting the current and voltage data of each node in the microgrid, the latest line - state information can be obtained, providing a basis for subsequent fault judgment.

[0043] The local information in this embodiment refers to the data and signals directly obtained from the location where the protection device is located. By utilizing the data available on a single terminal, faults can be detected and isolated more quickly than methods relying on communication between multiple terminals, which is particularly important for sensitive power electronic devices as they cannot withstand high fault currents for a long time. In addition, the dependence on communication links is reduced, thereby improving the reliability of the protection system and avoiding the latency and fault problems that communication links are prone to. This independence helps to ensure consistent protection performance, even under adverse conditions. By focusing on local information, this embodiment simplifies the overall system design and reduces the complexity and cost of the extensive communication network required for fault detection and protection coordination.

[0044] S2. Calculate the first-order difference of the positive-pole voltage of the line, and determine whether the absolute value of the first-order difference of the positive-pole voltage is greater than a first set value. If it is, the starting criterion for protection is met, that is, start the protection and execute step S3. If not, return to step S2 and continue to monitor.

[0045] The first-order difference refers to the operation of calculating the difference between each element in a sequence and its previous element. In the application of relay protection, the first-order difference is often used to detect the rate of change of a signal. For example, when monitoring the current or voltage waveform, if the current or voltage value suddenly changes significantly at a certain moment, the first-order difference can help quickly identify this change. By calculating the difference between adjacent sampling points, the occurrence of a fault can be effectively detected. This method is particularly suitable for protection scenarios that require rapid response because it can quickly capture the current or voltage mutation caused by a fault.

[0046] In this embodiment, the first-order difference of the positive-pole voltage refers to the difference in the positive-pole voltage within two consecutive sampling periods, and its mathematical expression is: Δu P =u P_k -u P_k-1 , where k represents the current sampling period, k - 1 represents the previous sampling period, Δu P represents the first-order difference of the positive-pole voltage, and u P represents the positive-pole voltage. By calculating this first-order difference, the changing trend of the positive-pole voltage over time can be reflected, and it has high sensitivity to rapidly changing voltage fluctuations.

[0047] The starting criterion in this embodiment means that when the absolute value of the first-order difference Δu P of the positive-pole voltage is greater than the first set value Δu set , it indicates that an abnormal change has occurred in the positive-pole voltage, and there may be a fault risk. At this time, the protection system starts to enter the working state and prepares to further analyze and determine whether there is an actual fault situation. The design of the starting criterion aims to screen out scenarios that may have problems, avoid misoperation caused by normal fluctuations, and ensure timely response when a real fault occurs.

[0048] S3. Calculate the first-order difference of the square of the positive-pole current of the line, and determine whether the absolute value of the first-order difference of the square of the positive-pole current is greater than a second set value. If it is, the operating criterion for protection is satisfied, that is, start the protection action. If not, return to step S2 and continue monitoring.

[0049] In this embodiment, the first-order difference of the square of the positive-pole current refers to the difference between the squares of the positive-pole currents in two consecutive sampling periods, and its mathematical expression is: where k represents the current sampling period, and k - 1 represents the previous sampling period. represents the first-order difference of the square of the positive-pole current, and i P represents the positive-pole current. By calculating this first-order difference, the transient change degree of the positive-pole current can be reflected, especially having a better response ability for situations such as large current impacts or short circuits.

[0050] The operating criterion of this embodiment means that when the absolute value of the first-order difference of the square of the positive-pole current is greater than the second set value it indicates that the positive-pole current has changed sharply, and there may be a fault risk. At this time, the protection system needs to further confirm the fault type and decide whether to perform corresponding protection actions, such as disconnecting relevant switching equipment to isolate the fault area. The design of the operating criterion aims to ensure that the protection action is triggered only when the current change reaches a certain degree, prevent unnecessary switching operations caused by small current fluctuations, and at the same time ensure that actions can be taken in a timely manner in the case of a real fault.

[0051] S4. Start the corresponding circuit breaker to perform the protection action according to the fault type.

[0052] In step S4 of this embodiment, determine the fault type according to the states of the positive-pole voltage u P and the negative-pole voltage u N , which is called the pole selection criterion. The fault types include bipolar short-circuit faults, positive-pole short-circuit faults, negative-pole short-circuit faults, etc. The pole selection criterion is executed on the basis of satisfying the start criterion and the operating criterion. Specifically, judge whether there is an absolute value of the difference between the absolute value of the positive-pole voltage and the absolute value of the negative-pole voltage less than a third set value, that is, judge whether there is ||u P |-|u N ||<Du set (pole selection criterion 1). If so, determine it as a bipolar short-circuit fault. If not, judge whether the absolute value of the positive-pole voltage is less than a fourth set value u set , that is, judge whether there is |u P |<u set (pole selection criterion 2). If so, determine it as a positive-pole grounding fault. If not, determine it as a negative-pole grounding fault.

[0053] The design of the pole selection criterion is to more accurately identify the fault type, help the protection system make correct decisions, and thus take corresponding measures targeted, such as disconnecting the switching equipment of the corresponding branch to minimize the scope of the fault impact.

[0054] The DC microgrid applicable to the above protection includes a renewable energy-dominated microgrid (mainly powered by renewable energy such as solar energy and wind energy, usually equipped with an energy storage system, such as a solar photovoltaic DC microgrid, etc.), a hybrid energy microgrid, etc., with a wide range of applications.

[0055] Figure 2 Figure 8 shows a common microgrid structure applicable to the above method - a radial DC microgrid. The characteristic of this structure is that it consists of multiple units connected to a central node through DC lines, forming a layout similar to a radial shape. Different from a loop network, there are no loops in the radial network, so loop faults will not occur. This central node is usually a high-voltage DC collection point, and other nodes are connected to it through DC lines, jointly forming a distributed energy network. The advantage of the radial network lies in its flexibility. Each node can be either a power generation unit, an energy storage unit, or a load unit, and energy can be directly exchanged between units, supporting the access and flexible configuration of distributed energy, and being able to adapt to diverse electricity demands and power generation scenarios. In addition, since each unit is directly connected to the central node, power can be obtained from it at any time, and even if some units fail, it will not affect the operation of the overall system. The Simulink simulation parameters are shown in Table 1.

[0056] Table 1 Simulink simulation parameters of the DC microgrid

[0057] Parameter Value Voltage level 1000V Resistance of the outgoing line of the distributed power source 0.05 Ohms Inductance of the outgoing line of the distributed power source 5e-2 H Number of poles of the permanent magnet synchronous motor PMSMJ in the wind power system 4 Moment of inertia J <![CDATA[60kg.m 2 > <![CDATA[Stator phase resistance R s > 0.025 Ω <![CDATA[Stator phase inductance L s > 8.5 mH <![CDATA[d-axis inductance L d > 8.5 mH <![CDATA[q-axis inductance L q > 8.5 mH Rated capacity of the battery 400 Ah Cut-off voltage of the battery 450V Full charge voltage of the battery 698V Nominal voltage of the battery 400V Nominal discharge current of the battery 174A Initial state SOC of the battery 60％ Maximum output power of the battery photovoltaic cell 230W <![CDATA[Standard light intensity S of the storage battery ref > <![CDATA[1000W / m 2 > <![CDATA[Standard ambient temperature T of the storage battery ref > 25℃ <![CDATA[Short-circuit current I of the storage battery and the photovoltaic cell sc > 8.1A <![CDATA[Open-circuit voltage V of the storage battery oc > 36.42V <![CDATA[Maximum power point current I m > 7.58A <![CDATA[Maximum power point voltage V m > 30.36V

[0058] Table 2 Data processing parameters of the protection method

[0059]

[0060]

[0061] When applying the above protection method, the data processing parameters are shown in Table 2. In the simulation experiment, the first-order difference of the positive-pole voltage corresponding to the 0.50001 s of the positive-pole grounded fault line satisfies the protection startup criterion; the first-order difference of the positive-pole voltage corresponding to the 0.50001 s of the negative-pole grounded fault line satisfies the protection startup criterion; the first-order difference of the positive-pole voltage corresponding to the 0.50001 s of the bipolar short-circuit fault satisfies the protection startup criterion; the first-order difference of the voltage does not satisfy the startup criterion during no-fault. The first-order difference of the square of the line current corresponding to the 0.5005 s of the positive-pole grounded fault satisfies the protection action criterion; the first-order difference of the square of the line current corresponding to the 0.5005 s of the negative-pole grounded fault satisfies the protection action criterion; the first-order difference of the square of the line current corresponding to the 0.5005 s of the bipolar grounded fault satisfies the protection action criterion. The waveforms of the positive-pole voltage, positive-pole current, first-order difference of the positive-pole voltage, and first-order difference of the square of the positive-pole current under various conditions of the DC microgrid obtained in the simulation of this embodiment are as Figure 3 - Figure 7 shown.

[0062] The voltage sampling value corresponding to the 0.50003 s satisfies ||u P |-|u N ||<Du set , and the pole selection for the fault is completed; similarly, in the case of positive-ground fault, the voltage sampling value corresponding to the 0.50003 s satisfies ||u P |-|u N ||> and |u P |<u set , and the pole selection for the fault is completed; in the case of negative-ground fault, the voltage sampling value corresponding to the 0.50003 s satisfies ||u P |-|u N ||> and |u P |>u set , and the pole selection for the fault is completed.

[0063] Set an out-of-zone fault, and the remaining data processing parameters are set exactly the same, and the data processing process is also very similar to the above. Compare the protection action situations of no-fault, in-zone fault, and out-of-zone fault, as shown in Table 3.

[0064] Table 3 Comparison of protection actions under various fault conditions

[0065]

[0066] As shown in Table 3, the protection scheme can effectively respond to different fault conditions. For the case of no fault, the protection device will not take any action; for the bipolar short-circuit fault within the zone, the protection device will start within 0.50001 seconds, then meet the protection action criterion within 0.5005 seconds, and then meet the pole selection criterion 1 within 0.50003 seconds. Similarly, for the positive pole grounding fault within the zone and the negative pole grounding fault within the zone, the protection device will also start and meet the corresponding protection conditions within the same time range, only the pole selection criterion is different. For the external fault, the protection device will not take any action. The simulation results prove the selectivity and reliability of the protection scheme of the present invention.

[0067] If the above method is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in various embodiments of the present invention. The foregoing storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memories (ROM, Read-Only Memory), random access memories (RAM, Random Access Memory), magnetic disks, or optical discs that can store program codes.

[0068] In another embodiment, the present invention further provides an electronic device, including one or more processors, a memory, and one or more programs stored in the memory. The one or more programs include instructions for executing the DC microgrid protection method based on local information as described above.

[0069] Embodiment 2

[0070] This embodiment provides a DC microgrid protection system based on local information, including a local information sampling module, a startup criterion module, an action criterion module, and an action execution module, where:

[0071] The local information sampling module is used to obtain the line voltage and line current in real time through the local protection terminal;

[0072] The startup criterion module is used to calculate the first-order difference of the positive pole voltage of the line according to the data of the local information sampling module, and determine whether the absolute value of the first-order difference of the positive pole voltage is greater than a first set value. If so, the startup criterion of the protection is met, that is, the protection is started. If not, continue to obtain the data of the local information sampling module;

[0073] The action criterion module responds when the startup criterion module obtains the startup criterion result that meets the protection, and is used to calculate the first-order difference of the square of the positive-pole current of the line according to the data of the local information sampling module, and determine whether the absolute value of the first-order difference of the square of the positive-pole current is greater than the second set value. If it is, the action criterion for protection is met, that is, the protection action is started. If not, the data of the local information sampling module is continuously obtained;

[0074] The action execution module responds when the action criterion module obtains the action criterion result that meets the protection, and is used to start the corresponding circuit breaker to execute the protection action according to the fault type.

[0075] The rest is the same as in Embodiment 1.

[0076] Compared with the prior art, the performance indicators of the present invention are improved as follows: First, thanks to the application of high-speed data acquisition and processing technology, the present invention can quickly respond under the condition of rapid current change, greatly shortening the time for fault detection and isolation, thereby improving the timeliness of protection. At the same time, by using the data of the positive-pole voltage and current and combining with the pole selection criterion, the present invention can more accurately identify the fault type, reducing the false alarm rate and missed alarm rate, thereby improving the accuracy of protection. On the other hand, through the rapid response and accurate positioning of faults, unnecessary switching operations are reduced, energy consumption is reduced, which is beneficial to improving the overall efficiency of the microgrid. More importantly, the present invention is applicable to various types of DC microgrids, including but not limited to solar power generation, wind power generation, energy storage systems, etc., and has wide applicability. Although the initial investment may be slightly higher than the traditional protection method, in the long run, considering its high protection effect and long-term energy-saving benefits, the present invention is more economically beneficial. Finally, by reducing the losses caused by faults and improving the energy utilization rate, the present invention indirectly promotes the development of green energy, conforms to the concept of sustainable development, and helps to build a cleaner and safer energy supply system.

[0077] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations according to the concept of the present invention without creative labor. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field of the present invention based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art should be within the protection scope determined by the claims.

Claims

1. A DC microgrid protection method based on local information, characterized in that: The following steps are involved: S1, obtain line voltage and line current in real time through the local protection terminal; S2, calculating the first-order difference of the positive voltage of the circuit, and determining whether the absolute value of the first-order difference of the positive voltage is greater than the first set value. If so, the protection start criterion is met, that is, the protection is started, and step S3 is executed. If not, returning to step S2; S3, calculating the first-order difference of the square of the positive current of the line, and judging whether the absolute value of the first-order difference of the square of the positive current is greater than the second set value, then the action criterion of the protection is met, that is, the protection action is started; if not, returning to step S2; S4. Start the corresponding circuit breaker to perform protection action according to the fault type.

2. The DC microgrid protection method based on local information according to claim 1, characterized in that: The first-order difference of the positive electrode voltage is the difference between the positive electrode voltages in two consecutive sampling periods.

3. The DC microgrid protection method based on local information according to claim 1, characterized in that: The first-order difference of the square of the positive electrode current is the difference between the squares of the positive electrode current in two consecutive sampling periods.

4. The DC microgrid protection method based on local information according to claim 1, characterized in that: In step S4, the fault type is determined according to the states of the positive electrode voltage and the negative electrode voltage.

5. The DC microgrid protection method based on local information according to claim 4 is characterized in that: The fault type includes a bipolar short circuit fault, a positive short circuit fault or a negative short circuit fault.

6. The DC microgrid protection method based on local information according to claim 5, characterized in that: In step S4, it is determined whether the absolute value of the difference between the absolute value of the positive electrode voltage and the absolute value of the negative electrode voltage is less than the third set value. If so, it is determined to be a bipolar short circuit fault. If not, it is determined whether the absolute value of the positive electrode voltage is less than the fourth set value u set If yes, it is determined to be a positive ground fault, if no, it is determined to be a negative ground fault.

7. The DC microgrid protection method based on local information according to claim 1, characterized in that: The DC microgrid includes a renewable energy-dominated microgrid or a hybrid energy microgrid.

8. A DC microgrid protection system based on local information, characterized in that: include: A local information sampling module is used to obtain line voltage and line current in real time through a local protection terminal; A start criterion module, used to calculate the first-order difference of the positive voltage of the line according to the data of the local information sampling module, and determine whether the absolute value of the first-order difference of the positive voltage is greater than a first set value. If so, the start criterion of the protection is met, that is, the protection is started; if not, the data of the local information sampling module is continued to be obtained; an action criterion module, which responds when the start criterion module obtains a start criterion result that satisfies the protection, and is used to calculate the square first-order difference of the positive current of the line according to the data of the local information sampling module, and judge whether the absolute value of the square first-order difference of the positive current is greater than a second set value, then the action criterion of the protection is met, that is, the protection action is started; if not, the data of the local information sampling module is continued to be obtained; The action execution module responds when the action criterion module obtains an action criterion result that satisfies the protection, and is used to start the corresponding circuit breaker to execute the protection action according to the fault type.

9. A computer-readable storage medium, characterized in that: It includes one or more programs for execution by one or more processors of an electronic device, and the one or more programs include instructions for executing the DC microgrid protection method based on local information as described in any one of claims 1-7.

10. An electronic device, characterized in that: It includes one or more processors, a memory and one or more programs stored in the memory, wherein the one or more programs include instructions for executing the DC microgrid protection method based on local information as described in any one of claims 1-7.

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