Detection method for remote disconnection of zero exchange power regional power grid

Abstract

A zero exchange power regional power grid remote network disconnection detection method comprises the steps that when a regional power grid is stable, the frequency change direction of the regional power grid is obtained, and the active power and frequency of a grid-connected tie line are collected; when the frequency deviation of the grid-connected tie line is smaller than a set frequency threshold value and the active power is smaller than zero power measurement precision, starting zero power grid disconnection monitoring when the time interval with the last load regulation exceeds a time threshold value; otherwise, starting non-zero power network disconnection monitoring. After the zero-power grid disconnection monitoring is started, when the active power variation of a generator in the regional power grid is smaller than a set power threshold within a set duration, load adjustment is carried out in the reverse frequency change direction; during load adjustment, if the frequency variation of the grid-connected tie line is greater than a frequency variation threshold and the active power variation of the grid-connected tie line is smaller than a power variation threshold, judging that the regional power grid is disconnected; otherwise, judging that the regional power grid is not disconnected. The problem of rapid judgment of the isolated network formed by remote network disconnection of the approximate zero exchange power regional power grid is solved.

Description

Technical Field

[0001] The present disclosure relates to the technical field of power system safety and stability control, and in particular to a method for judging the isolated grid operation state of a regional power grid under zero exchange power. Background Art

[0002] Regional power grids with distributed generation are at risk of being isolated from the external power grid due to transmission equipment failure. When the regional power grid is switched to an isolated grid operation state, it is necessary to promptly switch to the mode where the isolated grid controls the frequency by itself, that is, to establish a new fixed frequency control mechanism. Otherwise, due to the lack of frequency stabilization of the large power grid, the isolated grid system may quickly (from a few hundred milliseconds to a few seconds, depending on the size of the unbalanced power) exceed the upper or lower frequency limit, resulting in machine shedding and load. Since the load and power generation of the regional power grid are relatively small compared to the large power grid, its granularity is large, so it is often difficult to restore frequency stability. Therefore, it is necessary to switch to the operation mode where the isolated grid controls the frequency by itself as quickly as possible when the regional power grid is isolated. This requires determining the isolated grid operation state of the regional power grid as quickly as possible.

[0003] When the local side of the regional power grid's external interconnection line is disconnected, the regional power grid can determine the isolated grid area within tens of milliseconds because it has a monitoring device for the circuit breaker on this side. Because AC power grids below 500kV are usually ring-network construction and open-loop operation, if any one interconnection line is disconnected, an isolated grid will usually appear in some areas. When the circuit breaker on the local side of the regional power grid's external interconnection line refuses to operate during a fault or the circuit breaker on the opposite side trips without a fault, if the power of the interconnection line is relatively large before the fault, the isolated grid area will experience a sudden change in frequency or exceed the limit. At this time, the isolated grid can still be determined by combining the local measurement of the regional power grid. However, when the interconnection power between the regional power grid and the external grid is very small, and the disconnection of the opposite line cannot cause a significant change in frequency, there is currently no solution to promptly determine the isolated grid when the circuit breaker on this side is not disconnected.

[0004] In the case of near-zero power unbundling, the current technology is to wait until further large power imbalance occurs in the isolated grid area. When frequency anomalies occur, the isolated grid can be judged and frequency control measures can be taken. However, the measures taken at this time are not taken until a large power imbalance occurs for a long time, so the required recovery power and energy are large, and it is even possible that the generator group does not have such a large adjustment capacity, resulting in failure of frequency recovery in the isolated grid area. Therefore, it is necessary to study a method that can quickly judge the isolated grid when the power of the external interconnection line containing distributed power sources is close to zero and the remote end is disconnected. With the development of new energy, there are more working conditions for regional power grids containing distributed power sources to achieve local power balance. This method of timely detecting isolated grids under the condition of near-zero exchange power unbundling is even more necessary. Summary of the invention

[0005] In order to solve the deficiencies in the prior art, the present invention provides a method for detecting remote unblocking of a power grid in a zero exchange power area, so as to solve the problem of quickly determining an isolated grid formed by remote unblocking of a power grid in a region with approximately zero exchange power.

[0006] The present invention adopts the following technical solution.

[0007] The present invention proposes a method for detecting remote de-interconnection of a zero exchange power regional power grid, comprising:

[0008] When the regional power grid is in a stable state, the frequency change direction of the regional power grid is obtained, and the active power and frequency of the grid-connected interconnection line are collected;

[0009] When the frequency deviation of the grid-connected tie line is less than the set frequency threshold and the active power is less than the zero-power measurement accuracy, and the time interval with the last load adjustment exceeds the time threshold, the zero-power disconnection monitoring is started; otherwise, the non-zero-power disconnection monitoring is started;

[0010] After zero-power grid-breaking monitoring is started, within the set time, when the active power change of the generator in the regional power grid is less than the set power threshold, load adjustment is performed in the opposite direction of frequency change;

[0011] During load adjustment, if the frequency change of the grid-connected interconnection line is greater than the frequency change threshold and the active power change of the grid-connected interconnection line is less than the power change threshold, it is determined that the regional power grid has been disconnected to form an isolated grid, and the isolated grid control is started; otherwise, it is determined that the regional power grid has not been disconnected and has not formed an isolated grid.

[0012] Preferably, collecting the active power and frequency of the grid-connected tie line includes:

[0013] A measurement unit with a millisecond period is used to collect current data of the current transformer and voltage data of the voltage transformer of the grid-connected tie line, and the active power and frequency of the grid-connected tie line are calculated with a millisecond period;

[0014] The measurement results of the active power and frequency of the grid-connected tie line are obtained from the power frequency measurement unit.

[0015] Preferably, the frequency deviation is the absolute value of the difference between the actual frequency value and the rated frequency, and the frequency threshold is set to 1.0 Hz;

[0016] The zero power measurement accuracy is twice the measurement accuracy of the active power of the interconnection line.

[0017] Preferably, the time threshold is the time for the generator to complete 50% of the secondary frequency modulation power control amount, and the value range of the time threshold is greater than or equal to 10s and less than or equal to 30s.

[0018] Preferably, the set time length is the response time of the generator to the secondary frequency modulation power instruction, and the value range of the set time length is greater than or equal to 5s and less than or equal to 30s; the set power threshold is 1% of the total rated active power of the generators operating in the regional power grid.

[0019] Preferably, when the power generation in the regional power grid changes steadily, load regulation is performed in the opposite direction of frequency change, and the load regulation amount is 2% of the total rated active power of the generators operating in the regional power grid.

[0020] Preferably, the frequency change of the grid-connected interconnecting line within 1s is used as a criterion, and the frequency change threshold and the power change threshold are determined according to the total rated capacity of the thermal power and hydropower units in the regional power grid. For regional power grids with a total rated capacity of less than 1000MW, the frequency change threshold of the grid-connected interconnecting line within 1s is 0.2Hz, and the power change threshold is 0.4% of the total rated active power of the generators operating in the regional power grid.

[0021] Preferably, the load regulation flag Sta is set to 1 while starting the zero-power grid disconnection monitoring.

[0022] Preferably, one round of load regulation includes N consecutive active adjustments, and the time interval between each active adjustment is 1s; N is an integer greater than or equal to 3;

[0023] If after each active adjustment, the frequency change of the grid-connected tie line is greater than the frequency change threshold and the active power change of the grid-connected tie line is less than the power change threshold, it is determined that the regional power grid has been disconnected, and when it is determined that the regional power grid has been disconnected after the Nth active adjustment, the load adjustment flag Sta is set to 0, and the time when the disconnection flag is set to 0 is recorded as the time stamp t test-end ;

[0024] If after each active adjustment, the frequency change of the grid-connected tie line is not greater than the frequency change threshold and the active power change of the grid-connected tie line is not less than the power change threshold, it is determined that the regional power grid is not disconnected, and when it is determined that the regional power grid is not disconnected after the Nth active adjustment, the load adjustment flag Sta is set to 0, and the time when the disconnection flag is set to 0 is recorded as the time stamp t test-end .

[0025] Preferably, after the last load regulation obtains the regional power grid disconnection state test result, the load regulation flag Sta is set to 0, and the time when the load regulation flag is set to 0 is the time scale t test-end , the current time t and the time scale t test-end The difference between them is the time interval from the last load adjustment.

[0026] Preferably, if the load regulation flag Sta is not set to 0, it means that this round of load regulation cannot determine whether the regional power grid is disconnected, and another round of load regulation is needed.

[0027] The beneficial effect of the present invention is that, compared with the prior art, at least the method proposed by the present invention can detect the isolated network operation state by actively adjusting the load test when the interconnection line at the opposite end or farther away is disconnected to form a regional isolated network operation when the regional power grid is in a state of near zero power networking, and timely convert the frequency control mode to the fixed frequency control mode required for isolated network operation, thereby avoiding the frequency from losing safety and stability due to insufficient frequency control capability when a large disturbance occurs. The present invention solves the problem that the current isolated network operation judgment method fails in the state of zero power networking, and the frequency control mode cannot be converted in time when the isolated network state occurs, and the isolated network control can only be performed when a large disturbance occurs and the isolated network frequency exceeds the limit, resulting in the expansion of accident losses. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The present invention proposes a flow chart of a method for detecting remote de-interconnection of a zero exchange power regional power grid; DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only embodiments of a part of the present invention, rather than all embodiments. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0030] The present invention proposes a method for detecting remote unblocking of a zero exchange power regional power grid, such as Figure 1 As shown, the detection method comprises the following steps:

[0031] Step 1: When the regional power grid is in a stable state, the frequency change direction of the regional power grid is obtained, and the active power and frequency of the grid-connected interconnection line are collected.

[0032] In a non-limiting preferred embodiment, the frequency change direction of the regional power grid is the difference between the frequency at the current moment and the frequency at the moment 1 second ago.

[0033] In a non-limiting preferred embodiment, the power and frequency of the grid-connected interconnection line are continuously collected in a millisecond period. Those skilled in the art may adopt different sampling periods according to the requirements of grid operation and detection.

[0034] In a non-limiting preferred embodiment, the power and frequency of the grid-connected tie line include but are not limited to:

[0035] A measurement unit with a millisecond period is used to collect current data of the current transformer and voltage data of the voltage transformer of the grid-connected interconnection line, and the active power and frequency of the grid-connected interconnection line are calculated with a millisecond period; or, the measurement results of the active power and frequency of the grid-connected interconnection line are obtained from a power frequency measurement unit, and the measurement period of the measurement results is a sampling period of 10ms or 20ms. The power frequency measurement unit includes but is not limited to: a PMU device.

[0036] Step 2: When the frequency deviation of the grid-connected line is less than the set frequency threshold and the active power is less than the zero power measurement accuracy, and the time interval with the last load adjustment exceeds the time threshold, the zero power network release monitoring is started, and the load adjustment flag Sta is set to 1; otherwise, the non-zero power network release monitoring is started.

[0037] In a non-limiting preferred embodiment, the frequency deviation is the absolute value of the difference between the actual frequency value and the rated frequency, and the frequency threshold is set to 1.0Hz; the zero power measurement accuracy is set to be determined by twice the accuracy of the active power measuring device of the interconnection line. For example, for an interconnection line with a daily exchange power of 200MW, the range of the power measuring device is set to 1000MW, and the measurement accuracy of the power measuring device is level 0.5, i.e. 0.5%. Then, the active power measurement accuracy of the interconnection line power measuring device is 5MW, and the defined zero power measurement accuracy is 10MW.

[0038] The load regulation in the present invention is actually to artificially create a small load power disturbance, and to judge the regional power grid disconnection by observing the influence of the power fluctuation on the external network tie line power. After the regional power grid disconnection state test result is obtained in the last load regulation and the regional power grid is restored to a stable state, the load regulation flag Sta will be set to 0, and the time when the load regulation flag is set to 0 is the time scale t test-end , the current time t and the time scale t test-end The difference between them is the time interval from the last load adjustment.

[0039] Specifically, the time threshold is the time for the generator to complete 50% of the secondary frequency modulation power control amount. The value range of the time threshold is greater than or equal to 10s and less than or equal to 30s. In a non-limiting preferred embodiment, the time threshold is 10s.

[0040] In regional power grids that actually need to control the operation of isolated grids according to the disconnection status, there are usually special stabilization and control devices responsible for regional power grid disconnection or isolated grid judgment. However, existing stabilization and control devices usually do not have an adjustment interface for load increase or decrease. Therefore, the present invention proposes a detection method for remote disconnection of a zero exchange power regional power grid, which judges and processes the zero power disconnection of the interconnection line to realize zero power disconnection monitoring; as for the non-zero power disconnection monitoring of the interconnection line, it is realized by a conventional stabilization and control device with non-zero power disconnection monitoring capability.

[0041] Step 3: After the zero-power grid-breaking monitoring is started, within the set time, when the active power change of the generator in the regional power grid is less than the set power threshold, the load is adjusted in the opposite direction of the frequency change.

[0042] Specifically, the set time length is the response time of the generator to the secondary frequency modulation power instruction. The value range of the set time length is greater than or equal to 5s and less than or equal to 30s. In a non-limiting preferred embodiment, the set time length is 10s.

[0043] Specifically, the power threshold is set to be 1% of the total rated active power of the generators operating in the regional power grid.

[0044] In a non-limiting preferred embodiment, when the change in the total active power of the generators actually in operation within 10 seconds is less than 1% of the total rated active power of the generators in operation, it is determined that the power generation in the regional power grid changes smoothly and there is no active power increase or decrease, indicating that no secondary frequency modulation power instructions are being executed.

[0045] Specifically, in actual power grids, for regional power grids that need to perform isolated grid operation control according to the disconnection status, there is usually a dedicated stabilization and control device responsible for judging whether the regional power grid is disconnected or isolated. However, existing stabilization and control devices usually do not have an adjustment interface for load increase or decrease. Based on the existing disconnection or isolated grid judgment method of the stabilization and control device, it is impossible to judge whether the regional power grid has constituted an isolated grid when the interconnection line has zero exchange power and the interconnection circuit breaker on this side is not disconnected. Therefore, the present invention proposes to adjust the load slightly in the opposite direction of the frequency change when the regional power grid is in a stable state, to implement active disconnection testing on the actual power grid system, and obtain the impact of the power fluctuation on the interconnection line power during the active disconnection test, so as to make a judgment on the disconnection of the regional power grid.

[0046] In a non-limiting preferred embodiment, there is no strict limit on the amplitude of the short-term increase or decrease of the output of the regulated load within 1 minute, and the regulated load includes but is not limited to: electric boilers, condensing equipment, and small motor equipment.

[0047] Specifically, according to the power control interface of the load being adjusted, different control signals are selected, including: electrical analog control signals, state control signals or communication control signals. In a non-limiting preferred embodiment, electrical analog control signals include but are not limited to: 4-20mA current signals, ±5V voltage signals; state control signals include but are not limited to: 0-1 node signals, switch gear signals; communication control signals include but are not limited to: various communication protocols based on IP protocol.

[0048] Specifically, when the power generation in the regional power grid changes steadily, load regulation is performed in the opposite direction of the frequency change, and the load regulation amount is 2% of the total rated active power of the generators operating in the regional power grid.

[0049] It is worth noting that those skilled in the art can reasonably select the setting duration, power threshold and load adjustment amount according to multiple factors such as the stability requirements of the regional power grid. The preferred value given in the present invention is a non-restrictive and preferred choice.

[0050] Step 4, during load adjustment, if the frequency change of the grid-connected interconnection line is greater than the frequency change threshold and the active power change of the grid-connected interconnection line is less than the power change threshold, it is determined that the regional power grid has been disconnected to form an isolated grid; otherwise, it is determined that the regional power grid has not been disconnected and has not formed an isolated grid.

[0051] In a non-limiting preferred embodiment, the frequency change of the grid-connected interconnecting line within 1 second is used as a criterion, and the frequency change threshold and the power change threshold are determined according to the total rated capacity or moment of inertia of the thermal power and hydropower units in the regional power grid. For regional power grids with a total rated capacity of less than 1000MW, the frequency change threshold of the grid-connected interconnecting line within 1 second is 0.2Hz, and the power change threshold is 20% of the load regulation amount, that is, 0.4% of the total rated active power of the generators running in the regional power grid.

[0052] Specifically, one round of load regulation includes N consecutive active adjustments, and the time interval of each active adjustment is 1s; after each active adjustment, it is determined whether the frequency change of the grid-connected tie line is greater than the frequency change threshold and whether the active power change of the grid-connected tie line is less than the power change threshold;

[0053] Specifically, step 4 includes:

[0054] If after each active adjustment, the frequency change of the grid-connected tie line is greater than the frequency change threshold and the active power change of the grid-connected tie line is less than the power change threshold, it is determined that the regional power grid has been disconnected, and when it is determined that the regional power grid has been disconnected after the Nth active adjustment, the load adjustment flag Sta is set to 0, and the time when the disconnection flag is set to 0 is recorded as the time stamp t test-end .

[0055] If after each active adjustment, the frequency change of the grid-connected tie line is not greater than the frequency change threshold and the active power change of the grid-connected tie line is not less than the power change threshold, it is determined that the regional power grid is not disconnected, and when it is determined that the regional power grid is not disconnected after the Nth active adjustment, the load adjustment flag Sta is set to 0, and the time when the disconnection flag is set to 0 is recorded as the time stamp t test-end .

[0056] If the load regulation flag Sta is not set to 0, it means that this round of load regulation cannot determine whether the regional power grid is disconnected, and another round of load regulation is needed.

[0057] In a non-limiting preferred embodiment, N is an integer greater than or equal to 3.

[0058] Step 5: when it is determined that the regional power grid has been disconnected and an isolated grid has been formed, start the isolated grid control; if it is determined that the regional power grid has not been disconnected and an isolated grid has not been formed, return to step 1.

[0059] The existing method for judging whether the network is disconnected or isolated is unable to judge whether the area is isolated when the interconnection line has zero exchange power and the interconnection circuit breaker on this side is not disconnected. The present invention proposes to actively create a small amplitude load active power fluctuation in the regional power grid, and determine whether the network is disconnected by checking the influence of the load active power fluctuation on the grid frequency and the influence of the active power on the external interconnection line. Because in the case of grid connection, there are many generators in the power system, so the rotational inertia is large, and a small active power imbalance will hardly cause frequency changes; on the contrary, in the case of network disconnection, due to the small rotational inertia of the regional power grid, a small active power imbalance will cause obvious frequency changes. On the other hand, judging from the change of the active power of the interconnection line: in the case of network disconnection, the excess power will not be output to the external network, and the insufficient power will not be supplemented from the external network, and the power on the interconnection line will hardly change; on the contrary, in the case of grid connection, the excess power of the regional power grid will be output to the external power grid through the interconnection line, and the insufficient active power of the regional power grid will be supplemented from the external power grid through the interconnection line, and the power of the interconnection line will change significantly.

[0060] The present disclosure may be a system, a method and / or a computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0061] A computer-readable storage medium may be a tangible device that can hold and store instructions used by an instruction execution device. A computer-readable storage medium may be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. More specific examples of computer-readable storage media (a non-exhaustive list) include: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disk read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device, such as a punch card or a raised structure in a groove on which instructions are stored, and any suitable combination of the foregoing. As used herein, a computer-readable storage medium is not to be interpreted as a transient signal per se, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., a light pulse through a fiber optic cable), or an electrical signal transmitted through a wire.

[0062] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to each computing / processing device, or downloaded to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network can include copper transmission cables, optical fiber transmissions, wireless transmissions, routers, firewalls, switches, gateway computers, and / or edge servers. The network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in the computer-readable storage medium in each computing / processing device.

[0063] The computer program instructions for performing the operation of the present disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-related instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages, such as Smalltalk, C++, etc., and conventional procedural programming languages, such as "C" language or similar programming languages. Computer-readable program instructions may be executed completely on a user's computer, partially on a user's computer, as an independent software package, partially on a user's computer, partially on a remote computer, or completely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., using an Internet service provider to connect via the Internet). In some embodiments, an electronic circuit, such as a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA), may be customized by utilizing the state information of the computer-readable program instructions, and the electronic circuit may execute the computer-readable program instructions, thereby realizing various aspects of the present disclosure.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for detecting remote unblocking of a zero exchange power regional power grid, characterized in that: include: When the regional power grid is in a stable state, the frequency change direction of the regional power grid is obtained, and the active power and frequency of the grid-connected interconnection line are collected; When the frequency deviation of the grid-connected tie line is less than the set frequency threshold and the active power is less than the zero-power measurement accuracy, and the time interval with the last load adjustment exceeds the time threshold, the zero-power disconnection monitoring is started; otherwise, the non-zero-power disconnection monitoring is started; After zero-power grid-breaking monitoring is started, within the set time, when the active power change of the generator in the regional power grid is less than the set power threshold, load adjustment is performed in the opposite direction of frequency change; During load adjustment, if the frequency change of the grid-connected interconnection line is greater than the frequency change threshold and the active power change of the grid-connected interconnection line is less than the power change threshold, it is determined that the regional power grid has been disconnected to form an isolated grid, and the isolated grid control is started; otherwise, it is determined that the regional power grid has not been disconnected and has not formed an isolated grid.

2. The method for detecting remote unblocking of a zero exchange power regional power grid according to claim 1, characterized in that: Collect active power and frequency of grid-connected tie lines, including: A measurement unit with a millisecond period is used to collect current data of the current transformer and voltage data of the voltage transformer of the grid-connected tie line, and the active power and frequency of the grid-connected tie line are calculated with a millisecond period; The measurement results of the active power and frequency of the grid-connected tie line are obtained from the power frequency measurement unit.

3. The method for detecting remote unblocking of a zero exchange power regional power grid according to claim 1, characterized in that: Frequency deviation is the absolute value of the difference between the actual frequency and the rated frequency. The set frequency threshold is 1.0Hz; The zero power measurement accuracy is twice the measurement accuracy of the active power of the interconnection line.

4. The method for detecting remote unblocking of a zero exchange power regional power grid according to claim 1, characterized in that: The time threshold is the time for the generator to complete 50% of the secondary frequency modulation power control amount, and the value range of the time threshold is greater than or equal to 10s and less than or equal to 30s.

5. The method for detecting remote unblocking of a zero exchange power regional power grid according to claim 1, characterized in that: The set time is the response time of the generator to the secondary frequency modulation power instruction, and the value range of the set time is greater than or equal to 5s and less than or equal to 30s; the set power threshold is 1% of the total rated active power of the generators operating in the regional power grid.

6. The method for detecting remote unblocking of a zero exchange power regional power grid according to claim 1, characterized in that: When the power generation in the regional power grid changes steadily, load regulation is performed in the opposite direction of frequency change, and the load regulation amount is 2% of the total rated active power of the generators running in the regional power grid.

7. The method for detecting remote disconnection of a zero exchange power regional power grid according to claim 1, characterized in that: The frequency change of the grid-connected interconnection line within 1s is used as the criterion, and the frequency change threshold and power change threshold are determined according to the total rated capacity of thermal power and hydropower units in the regional power grid. For regional power grids with a total rated capacity of less than 1000MW, the frequency change threshold of the grid-connected interconnection line within 1s is 0.2Hz, and the power change threshold is 0.4% of the total rated active power of the generators operating in the regional power grid.

8. The method for detecting remote disconnection of a zero exchange power regional power grid according to claim 1, characterized in that: When zero-power grid disconnection monitoring is started, the load regulation flag Sta is set to 1.

9. The method for detecting remote disconnection of a zero exchange power regional power grid according to claim 1, characterized in that: One round of load regulation includes N consecutive active adjustments, and the time interval between each active adjustment is 1s; N is an integer greater than or equal to 3; If after each active adjustment, the frequency change of the grid-connected tie line is greater than the frequency change threshold and the active power change of the grid-connected tie line is less than the power change threshold, it is determined that the regional power grid has been disconnected, and when it is determined that the regional power grid has been disconnected after the Nth active adjustment, the load adjustment flag Sta is set to 0, and the time when the disconnection flag is set to 0 is recorded as the time stamp t test-end ; If after each active adjustment, the frequency change of the grid-connected tie line is not greater than the frequency change threshold and the active power change of the grid-connected tie line is not less than the power change threshold, it is determined that the regional power grid is not disconnected, and when it is determined that the regional power grid is not disconnected after the Nth active adjustment, the load adjustment flag Sta is set to 0, and the time when the disconnection flag is set to 0 is recorded as the time stamp t test-end .

10. The method for detecting remote disconnection of a zero exchange power regional power grid according to claim 9, characterized in that: After the last load regulation obtains the test result of the regional power grid disconnection status, the load regulation flag Sta will be set to 0, and the time when the load regulation flag is set to 0 is the time scale t test-end , the current time t and the time scale t test-end The difference between them is the time interval from the last load adjustment.

11. The method for detecting remote disconnection of a zero exchange power regional power grid according to claim 10, characterized in that: If the load regulation flag Sta is not set to 0, it means that this round of load regulation cannot determine whether the regional power grid is disconnected, and another round of load regulation is needed.

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