Quasi-synchronous switching-on method and system for distributed power supply access

Abstract

The invention relates to the technical field of power system protection control, and provides a quasi-synchronous switching-on method and system for distributed power supply access, and the method comprises the steps: carrying out the non-voltage discrimination after a main supply line breaks down and meets a non-current condition: when the I bus voltage is higher than 0.3 p.u, executing a distributed power supply removal strategy based on power balance, and when the I bus voltage is lower than 0.3 p.u, carrying out the non-voltage discrimination; comprising the following steps: counting the capacities, inertia time constants and grid-connected conditions of all grid-connected conventional units and distributed power supplies in an island system during island operation, and calculating the inertia of the island system; calculating the unbalanced power of the island system according to the I mother frequency curve; calculating generator shedding capacity and combination or load shedding capacity and combination based on an approximate capacity matching algorithm according to the unbalanced power value; performing generator shedding or load shedding of the distributed power supply according to the capacity and the combination obtained by the approximate capacity matching algorithm; and step 3, performing quasi-synchronous closing after the generator tripping or the load shedding is completed. According to the invention, energy waste caused by splitting all distributed power supplies can be reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of power system protection and control, and in particular to a quasi-synchronous closing method and system for accessing a distributed power source. Background Art

[0002] With the increasing prominence of environmental issues and the advancement of power electronics technology, new energy generation, represented by distributed power generation, is on the rise. Distributed power generation, as a form of renewable energy, has been widely used in power grids. However, the integration of large-scale distributed power generation also poses challenges to the normal operation of the grid. The inherent distributed nature, low power, and low inertia of renewable energy sources complicates grid models, impacting the accuracy of closing criteria.

[0003] When a power grid failure occurs, the presence of distributed power sources (DGs) can cause substations to operate in isolated networks or experience a slow loss of voltage. For regions with a high proportion of renewable energy, existing backup and automatic switching devices often rely on a strategy of quickly disconnecting renewable energy before restoring power. This strategy relies on disconnecting renewable energy to ensure the backup and automatic switching device is de-energized. This can lead to wait times of tens of seconds or even minutes, impacting regional power supply reliability, harming user interests, and delaying grid restoration. Furthermore, during isolated network operation, voltage and frequency are extremely unstable, resulting in poor power quality and even damage to user equipment.

[0004] In areas with abundant new energy resources, if all distributed power sources are disconnected, it will result in a waste of resources and make it difficult to reconnect new energy to the grid. Therefore, it is necessary to find a strategy to maximize the efficiency of distributed power sources during island operation to achieve fast quasi-synchronous closing. Summary of the Invention

[0005] The purpose of the present invention is to solve at least one technical problem in the background technology and provide a quasi-synchronous closing method and system for accessing a distributed power source.

[0006] To achieve the above-mentioned object, the present invention provides a quasi-synchronous closing method for accessing a distributed power source, comprising:

[0007] Step 1: After the main supply line fails and meets the no-current condition, perform voltage no-voltage judgment:

[0008] When the I bus voltage is lower than or equal to 0.3pu, the distributed generation is disconnected until the voltage meets the no-voltage condition and then closed;

[0009] When the I bus voltage is higher than 0.3 pu, proceed to step 2;

[0010] Step 2: Distributed power generation removal strategy based on power balance, including:

[0011] 1) Count the capacity, inertia time constant and grid connection status of all grid-connected conventional units and distributed power sources in the island system during island operation, and calculate the inertia of the island system;

[0012] 2) Calculate the unbalanced power ΔP of the island system based on the I mother frequency curve d ;

[0013] 3) Calculate the generator shedding capacity and combination or load shedding capacity and combination based on the unbalanced power value and the approximate capacity matching algorithm;

[0014] 4) Distributed power generation is cut off or load is cut off according to the capacity and combination obtained by the approximate capacity matching algorithm;

[0015] Step 3: After the machine or load is cut off, perform quasi-synchronous closing:

[0016] Check whether the voltage and frequency on both sides of the busbar and backup power supply meet the requirements before closing the circuit breaker.

[0017] According to one aspect of the present invention, the capacity, inertia time constant and grid connection status of all grid-connected conventional units and distributed power sources in the island system during island operation are counted, and the inertia of the island system H is calculated based on the following formula: sys :

[0018]

[0019] And calculate the island system capacity S based on the following formula sys :

[0020]

[0021] Where H gen.i is the inertia time constant of the i-th conventional unit; S gen.i is the rated capacity of the i-th conventional unit; K gen.i is the grid-connected status of the i-th conventional unit; H VI.j is the inertia time constant of the jth distributed power supply, S VI.j is the rated capacity of the jth distributed power supply; K VI.j is the grid-connected status of the jth distributed generation;

[0022] Among them, the inertia time constant of the distributed power supply H VI It can be calculated by the power response characteristics of the distributed power supply. When the system frequency decreases, the distributed power supply increases the output power, and the inertia time constant H of the distributed power supply is VI It can be determined by the rate and duration of power change; assuming the output power change of the distributed power supply is △P and the frequency change is △f, the inertia time constant of the distributed power supply H is VI It can be expressed as:

[0023]

[0024] Where, P rated is the rated power of the distributed power supply.

[0025] According to one aspect of the present invention, based on the I mother frequency curve, the unbalanced power of the island system is calculated as:

[0026] Obtain the I mother frequency curve and calculate the unbalanced power ΔP of the island system based on the rotor motion equation d :

[0027]

[0028] Where, f I母 is the I mother frequency; f0 is the system rated frequency.

[0029] According to one aspect of the present invention, according to the unbalanced power value, the generator or load shedding capacity and combination are calculated based on an approximate capacity matching algorithm, including:

[0030] When the unbalanced power ΔP d > 0, it means that the power provided by the distributed power supply in the island system is greater than the load power, and the power cut operation based on the approximate capacity matching algorithm is performed; when the unbalanced power ΔP d When <0, it means that the power provided by the distributed generation in the island system is less than the load power, and the load shedding operation based on the approximate capacity matching algorithm is performed.

[0031] According to one aspect of the present invention, the capacity and combination of cutting machines are calculated based on an approximate capacity matching algorithm, including:

[0032] Sorting: First, the rated capacity S of the conventional units gen.1 、S gen.2 ,...,S gen.n Sort in order from largest to smallest;

[0033] Initialization: Set a variable current_sum to record the sum of the capacities of the currently selected power units, with an initial value of 0;

[0034] Traversal: From the sorted list of rated capacities of power units, starting from the largest capacity, consider each capacity one by one: if the current capacity plus the variable current_sum does not exceed the unbalanced power ΔP d , then add this capacity to the current switch combination and update the variable current_sum; if adding the current capacity will exceed the unbalanced power ΔP d , minus some smaller capacity that has been added to make the total as close as possible to the unbalanced power ΔP d ;

[0035] Adjustment: After adding a certain capacity, if the variable current_sum exceeds the unbalanced power ΔP d , adjustments need to be made: remove some smaller capacities from the current switch combination until the variable current_sum is less than or equal to the unbalanced power ΔP d , and record the current variable current_sum and the unbalanced power ΔP d The difference is used for subsequent comparison;

[0036] Record the best combination: include the generator sets whose capacity is included in the variable current_sum into the cutting combination. During the traversal process, if the cutting combination found is consistent with the unbalanced power ΔP d If the difference is less than the minimum difference recorded previously, update the optimal cutting machine combination and the minimum difference;

[0037] End condition: When all power unit capacities have been traversed, the algorithm ends;

[0038] Output result: Return the optimal machine switching combination and the corresponding total capacity.

[0039] According to one aspect of the present invention, the load shedding capacity and combination are calculated based on an approximate capacity matching algorithm, including:

[0040] Sorting: Get the load outgoing power P in real time L1 、P L2 ,...,P Ln , the load outgoing power P L1 、P L2 ,...,P Ln Sort in order from largest to smallest;

[0041] Initialization: Set a variable current_sum to record the sum of the capacities of the currently selected power units, with an initial value of 0;

[0042] Traversal: From the sorted list of outgoing power capacities, starting from the largest power, consider each power one by one: if the current power plus the variable current_sum does not exceed the unbalanced power ΔP d , then add this power to the current load shedding combination and update the variable current_sum; if adding the current power will exceed the unbalanced power ΔP d , minus some smaller power that has been added to make the total as close as possible to the unbalanced power ΔP d ;

[0043] Adjustment: After adding a certain power, if the variable current_sum exceeds the unbalanced power ΔP d, adjustments need to be made: remove some smaller powers from the current load shedding combination until the variable current_sum is less than or equal to the unbalanced power ΔP d , and record the current variable current_sum and the unbalanced power ΔP d The difference is used for subsequent comparison;

[0044] Record the best combination: include the generator sets whose power is recorded in the variable current_sum into the load shedding combination. During the traversal process, if the load shedding combination found is consistent with ΔP d If the difference is less than the previously recorded minimum difference, the optimal load shedding combination and the minimum difference are updated;

[0045] End condition: When all load outgoing power has been traversed, the algorithm ends;

[0046] Output result: Returns the optimal load shedding combination and the corresponding capacity sum.

[0047] To achieve the above-mentioned object, the present invention further provides a quasi-synchronous closing system for accessing a distributed power source, comprising:

[0048] Voltage no-voltage judgment module: When the main supply line fails and meets the no-current condition, voltage no-voltage judgment is performed:

[0049] When the I bus voltage is lower than or equal to 0.3pu, the distributed generation is disconnected until the voltage meets the no-voltage condition and then closed;

[0050] When the I bus voltage is higher than 0.3 pu, proceed to step 2;

[0051] Distributed power generation removal strategy module: Distributed power generation removal strategy based on power balance, including:

[0052] 1) Count the capacity, inertia time constant and grid connection status of all grid-connected conventional units and distributed power sources in the island system during island operation, and calculate the inertia of the island system;

[0053] 2) Calculate the unbalanced power ΔP of the island system based on the I mother frequency curve d ;

[0054] 3) Calculate the generator shedding capacity and combination or load shedding capacity and combination based on the unbalanced power value and the approximate capacity matching algorithm;

[0055] 4) Distributed power generation is cut off or load is cut off according to the capacity and combination obtained by the approximate capacity matching algorithm;

[0056] Synchronous closing module: quasi-synchronous closing is performed after the machine or load is cut off:

[0057] Check whether the voltage and frequency on both sides of the busbar and backup power supply meet the requirements before closing the circuit breaker.

[0058] To achieve the above-mentioned objectives, the present invention also provides an electronic device, comprising a processor, a memory, and a computer program stored in the memory and runnable on the processor, wherein when the computer program is executed by the processor, the quasi-synchronous closing method for distributed power supply access as described above is implemented.

[0059] To achieve the above-mentioned purpose, the present invention also provides a computer-readable storage medium, characterized in that a computer program is stored on the computer-readable storage medium, and when the computer program is executed by a processor, the quasi-synchronous closing method for distributed power supply access as described above is implemented.

[0060] According to the solution of the present invention, the present invention calculates the unbalanced power of the system based on the rotor motion equation, and performs machine or load shedding operations based on the cut-off capacity and combination obtained by the approximate capacity matching algorithm to achieve quasi-synchronous closing, thereby reducing the energy waste caused by decoupling all distributed power sources. The present invention effectively avoids the problem of large-scale disconnection of distributed power sources in traditional standby automatic switching schemes. In the event of a power grid failure, the method can quickly adjust the operating state of the isolated network, significantly reducing the power outage time for users, while maintaining the stability of the power grid by selectively retaining some distributed power sources. In the process of restoring power supply, the retained distributed power sources are used as a synchronization reference to achieve fast and smooth quasi-synchronous closing, which not only improves the power supply reliability, but also promotes the efficient absorption of distributed power sources, solving the problems of low utilization rate of new energy and difficulty in grid connection in traditional schemes. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 A flowchart schematically illustrates a quasi-synchronous closing method for distributed power supply access according to an embodiment of the present invention;

[0062] Figure 2 This is a schematic diagram of a system including a distributed photovoltaic power station according to Example 1. DETAILED DESCRIPTION

[0063] The present invention will now be discussed with reference to exemplary embodiments. It should be understood that the embodiments discussed are only intended to enable those skilled in the art to better understand and implement the present invention, rather than to imply any limitation on the scope of the present invention.

[0064] As used herein, the term "including" and variations thereof are to be interpreted as open-ended terms meaning "including, but not limited to." The term "based on" is to be interpreted as "based, at least in part, on." The terms "one embodiment" and "an embodiment" are to be interpreted as "at least one embodiment."

[0065] Figure 1The flowchart schematically shows a quasi-synchronous closing method for distributed power supply access according to an embodiment of the present invention. Figure 1 As shown, in this embodiment, the quasi-synchronous closing method for accessing a distributed power source includes:

[0066] Step 1: After the main supply line fails and meets the no-current condition, perform voltage no-voltage judgment:

[0067] When the I bus voltage is lower than or equal to 0.3pu, the distributed generation is disconnected until the voltage meets the no-voltage condition and then closed;

[0068] When the I bus voltage is higher than 0.3 pu, proceed to step 2;

[0069] Step 2: Distributed power generation removal strategy based on power balance, including:

[0070] 1) Count the capacity, inertia time constant and grid connection status of all grid-connected conventional units and distributed power sources in the island system during island operation, and calculate the inertia of the island system;

[0071] 2) Calculate the unbalanced power ΔP of the island system based on the I mother frequency curve d ;

[0072] 3) Calculate the generator shedding capacity and combination or load shedding capacity and combination based on the unbalanced power value and the approximate capacity matching algorithm;

[0073] 4) Distributed power generation is cut off or load is cut off according to the capacity and combination obtained by the approximate capacity matching algorithm;

[0074] Step 3: After the machine or load is cut off, perform quasi-synchronous closing:

[0075] Check whether the voltage and frequency on both sides of the busbar and the backup power supply meet the conditions (voltage difference, frequency difference threshold) before closing the circuit breaker.

[0076] Furthermore, according to one embodiment of the present invention, the capacity, inertia time constant and grid connection status of all grid-connected conventional units and distributed power sources in the island system during island operation are counted, and the inertia of the island system H is calculated based on the following formula: sys :

[0077]

[0078] And calculate the island system capacity S based on the following formula sys :

[0079]

[0080] Where H gen.i is the inertia time constant of the i-th conventional unit; S gen.iis the rated capacity of the i-th conventional unit; K gen.i is the grid-connected status of the i-th conventional unit; H VI.j is the inertia time constant of the jth distributed power supply, S VI.j is the rated capacity of the jth distributed power supply; K VI.j is the grid-connected status of the jth distributed generation;

[0081] Among them, the inertia time constant of the distributed power supply H VI It can be calculated by the power response characteristics of the distributed power supply. When the system frequency decreases, the distributed power supply increases the output power, and the inertia time constant H of the distributed power supply is VI It can be determined by the rate and duration of power change; assuming the output power change of the distributed power supply is △P and the frequency change is △f, the inertia time constant of the distributed power supply H is VI It can be expressed as:

[0082]

[0083] Where, P rated is the rated power of the distributed power supply.

[0084] Furthermore, according to an embodiment of the present invention, based on the I mother frequency curve, the unbalanced power of the island system is calculated as:

[0085] Obtain the I mother frequency curve and calculate the unbalanced power ΔP of the island system based on the rotor motion equation d :

[0086]

[0087] Where, f I母 is the I mother frequency; f0 is the system rated frequency.

[0088] Furthermore, according to an embodiment of the present invention, the generator or load shedding capacity and combination are calculated based on the unbalanced power value and an approximate capacity matching algorithm, including:

[0089] When the unbalanced power ΔP d > 0, it means that the power provided by the distributed power supply in the island system is greater than the load power, and the power cut operation based on the approximate capacity matching algorithm is performed; when the unbalanced power ΔP d When <0, it means that the power provided by the distributed generation in the island system is less than the load power, and the load shedding operation based on the approximate capacity matching algorithm is performed.

[0090] Furthermore, according to an embodiment of the present invention, the machine cutting capacity and combination are calculated based on the approximate capacity matching algorithm, including:

[0091] Sorting: First, the rated capacity of the conventional unit (power unit capacity) S gen.1 、S gen.2 ,...,S gen.n Sort in order from largest to smallest;

[0092] Initialization: Set a variable current_sum to record the sum of the capacities of the currently selected power units, with an initial value of 0;

[0093] Traversal: From the sorted list of power unit capacities, starting from the largest capacity, consider each capacity one by one: if the current capacity plus the variable current_sum does not exceed the unbalanced power ΔP d , then add this capacity to the current switch combination and update the variable current_sum; if adding the current capacity will exceed the unbalanced power ΔP d , minus some smaller capacity that has been added to make the total as close as possible to the unbalanced power ΔP d ;

[0094] Adjustment: After adding a certain capacity, if the variable current_sum exceeds the unbalanced power ΔP d , adjustments need to be made: remove some smaller capacities from the current switch combination until the variable current_sum is less than or equal to the unbalanced power ΔP d , and record the current variable current_sum and the unbalanced power ΔP d The difference is used for subsequent comparison;

[0095] Record the best combination: include the generator sets whose capacity is included in the variable current_sum into the cutting combination. During the traversal process, if the cutting combination found is consistent with the unbalanced power ΔP d If the difference is less than the minimum difference recorded previously, update the optimal cutting machine combination and the minimum difference;

[0096] End condition: When all power unit capacities have been traversed, the algorithm ends;

[0097] Output result: Return the optimal machine switching combination and the corresponding total capacity.

[0098] Furthermore, according to an embodiment of the present invention, the load shedding capacity and combination are calculated based on the approximate capacity matching algorithm, including:

[0099] Sorting: Get the load outgoing power P in real time L1 、P L2 ,...,P Ln , the load outgoing power P L1 、P L2 ,...,P LnSort in order from largest to smallest;

[0100] Initialization: Set a variable current_sum to record the sum of the capacities of the currently selected power units, with an initial value of 0;

[0101] Traversal: From the sorted list of outgoing power capacities, starting from the largest power, consider each power one by one: if the current power plus the variable current_sum does not exceed the unbalanced power ΔP d , then add this power to the current load shedding combination and update the variable current_sum; if adding the current power will exceed the unbalanced power ΔP d , minus some smaller power that has been added to make the total as close as possible to the unbalanced power ΔP d ;

[0102] Adjustment: After adding a certain power, if the variable current_sum exceeds the unbalanced power ΔP d , adjustments need to be made: remove some smaller powers from the current load shedding combination until the variable current_sum is less than or equal to the unbalanced power ΔP d , and record the current variable current_sum and the unbalanced power ΔP d The difference is used for subsequent comparison;

[0103] Record the best combination: include the generator sets whose power is recorded in the variable current_sum into the load shedding combination. During the traversal process, if the load shedding combination found is consistent with ΔP d If the difference is less than the previously recorded minimum difference, the optimal load shedding combination and the minimum difference are updated;

[0104] End condition: When all load outgoing power has been traversed, the algorithm ends;

[0105] Output result: Returns the optimal load shedding combination and the corresponding capacity sum.

[0106] According to the above solution of the present invention, the main impact of distributed power supply on the no-voltage detection of standby automatic switching is that the existence of distributed power supply makes the bus voltage have voltage after the fault occurs. Therefore, the no-voltage criterion of standby automatic switching is not applicable to the situation where a large number of distributed power sources are connected. Specifically, if the output power of the distributed power supply after the fault occurs is not equal to the load provided by the original power supply, it will cause power imbalance and cause the frequency of the island system to exceed the limit. The present invention can start the standby automatic switching device or the self-healing device (an intelligent protection and control device in the power system that can automatically detect faults, quickly isolate the fault area and restore power supply) by judging whether there is current in the main power supply line. At the same time, the I mother frequency is monitored, and when the I mother frequency exceeds the threshold, the machine cutting measure can be taken.

[0107] According to the above scheme of the present invention, the present invention calculates the system unbalanced power based on the rotor motion equation, and performs machine or load shedding operations based on the cut-off capacity and combination obtained based on the approximate capacity matching algorithm to achieve quasi-synchronous closing, thereby reducing the energy waste caused by decoupling all distributed power sources.

[0108] Furthermore, to achieve the above-mentioned object, the present invention also provides a quasi-synchronous closing system for accessing a distributed power source, comprising:

[0109] Voltage no-voltage judgment module: When the main supply line fails and meets the no-current condition, voltage no-voltage judgment is performed:

[0110] When the I bus voltage is lower than or equal to 0.3pu, the distributed generation is disconnected until the voltage meets the no-voltage condition and then closed;

[0111] When the I bus voltage is higher than 0.3 pu, proceed to step 2;

[0112] Distributed power generation removal strategy module: Distributed power generation removal strategy based on power balance, including:

[0113] 1) Count the capacity, inertia time constant and grid connection status of all grid-connected conventional units and distributed power sources in the island system during island operation, and calculate the inertia of the island system;

[0114] 2) Calculate the unbalanced power ΔP of the island system based on the I mother frequency curve d ;

[0115] 3) Calculate the generator shedding capacity and combination or load shedding capacity and combination based on the unbalanced power value and the approximate capacity matching algorithm;

[0116] 4) Distributed power generation is cut off or load is cut off according to the capacity and combination obtained by the approximate capacity matching algorithm;

[0117] Synchronous closing module: quasi-synchronous closing is performed after the machine or load is cut off:

[0118] Check whether the voltage and frequency on both sides of the busbar and backup power supply meet the requirements before closing the circuit breaker.

[0119] The quasi-synchronous closing system for distributed power access according to the present invention can implement the quasi-synchronous closing method for distributed power access. The specific process steps are as described above and will not be repeated here.

[0120] Furthermore, to achieve the above-mentioned purpose, the present invention also provides an electronic device, comprising a processor, a memory, and a computer program stored in the memory and executable on the processor. When the computer program is executed by the processor, the quasi-synchronous closing method for distributed power supply access as described above is implemented.

[0121] Furthermore, to achieve the above-mentioned purpose, the present invention also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the quasi-synchronous closing method for distributed power supply access as described above is implemented.

[0122] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiment described herein is only an optimal embodiment of the present invention and is only used to explain the present invention and does not limit the scope of protection of the present invention. All other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0123] Example 1

[0124] like Figure 1 As shown, this embodiment provides a quasi-synchronous closing method for accessing a distributed power supply, comprising the following steps:

[0125] When a fault occurs in the main supply line and the no-current condition is met, the voltage no-voltage judgment is performed:

[0126] When the voltage of bus I is lower than 0.3pu, the traditional automatic backup is activated; when the voltage of bus I is higher than 0.3pu, the capacity and combination of the generators are calculated based on the "approximate capacity matching algorithm";

[0127] Control the circuit breaker on the backup line to perform quasi-synchronous closing and activate the backup power supply.

[0128] The following takes a system including a distributed power supply as an example to further illustrate the above steps of this embodiment.

[0129] like Figure 2 As shown, backup lines are typically installed to prevent equipment downtime or production interruptions caused by power outages, and to prevent main power line failures from triggering relay protection devices and disconnecting them, thereby isolating the PV power source from the local load. When the main power line disconnects, the backup automatic switching device activates, closing the backup incoming line and restoring power to the islanded system.

[0130] Specifically, the method of this embodiment includes the following steps:

[0131] S1, circuit breaker operating status identification;

[0132] The status of incoming line 1 circuit breaker 1DL is checked. When the auxiliary contact position information of 1DL is tripped, if the current transformer on the main supply line detects that the current is lower than the preset "no current" threshold, the circuit breaker is determined to be in the open state and the backup automatic re-closing device is immediately activated.

[0133] S2, no pressure and frequency discrimination;

[0134] Monitor the voltage and frequency of I bus. When the voltage of I bus is lower than 0.3pu, the traditional automatic switching action will be performed; when the voltage of I bus is higher than 0.3pu, the frequency of I bus will be judged: when f I母 When <50.5Hz, start the traditional standby automatic switching; when f I母 When the frequency is ≥50.5Hz, calculate the inertia and unbalanced power of the island system.

[0135] S3. Calculation of inertia and unbalanced power of island system;

[0136] To achieve incomplete decoupling of distributed power sources for backup automatic re-closing, this embodiment first removes some distributed power sources to achieve source-load power balance before performing backup automatic re-closing. It should be emphasized that this example primarily targets scenarios where the "source is greater than the load" in an islanded system and requires generator removal. When the "source is less than the load," the distributed power sources cannot support the local load. To prevent further system collapse, some loads should be removed to achieve power balance.

[0137] Therefore, the specific value of the unbalanced power of the island system must be determined first. The capacity, inertia time constant and grid connection status of all conventional units and distributed power sources connected to the island system during island operation are counted, and the inertia of the island system H is calculated based on the following formula: sys :

[0138]

[0139] And calculate the island system capacity S based on the following formula sys :

[0140]

[0141] Where H gen.i is the inertia time constant of the i-th conventional unit; S gen.i is the rated capacity of the i-th conventional unit; K gen.i is the grid-connected status of the i-th conventional unit; H VI.j is the inertia time constant of the jth distributed power supply, S VI.j is the rated capacity of the jth distributed power supply; K VI.j is the grid-connected status of the jth distributed generation.

[0142] Among them, the inertia time constant of the distributed power supply H VI It can be calculated by the power response characteristics of the distributed power supply. Assuming that the output power change of the distributed power supply is △P and the frequency change is △f, the virtual inertia time constant H VI , which can be expressed as:

[0143]

[0144] Where, P rated is the rated power of the distributed power supply.

[0145] Obtain the I mother frequency curve, start timing from the fault occurrence, and calculate the unbalanced power ΔP of the island system within 100ms based on the following formula: d :

[0146]

[0147] Where H sys is the inertia of the island system calculated above; f I母 is the I mother frequency; f0 is the system rated frequency; S sys is the capacity of the island system.

[0148] S4. Calculate cutting machine capacity and combination;

[0149] To achieve accurate removal of distributed power sources, the capacity and combination of generators are calculated based on the "approximate capacity matching algorithm":

[0150] Sorting: First, the capacity S of the distributed power generation units G1, G2...Gn gen.1 、S gen.2 ...S gen.n Sort in order from largest to smallest;

[0151] Initialization: Set a variable current_sum to record the sum of the capacities of the currently selected power units, with an initial value of 0;

[0152] Traversal: From the sorted list of rated capacities of power units, starting from the largest capacity, consider each capacity one by one: if the current capacity plus current_sum does not exceed ΔP d , then add this capacity to the current switch combination and update current_sum; if adding the current capacity will exceed ΔP d , minus some smaller capacity that has been added to make the sum as close as possible to ΔP d ;

[0153] Adjustment: After adding a certain capacity, if current_sum exceeds ΔP d , adjustments need to be made: remove some smaller capacities from the current cutting machine combination until current_sum is less than or equal to ΔP d , and record the current difference, that is, current_sum and ΔP d The difference is used for subsequent comparison;

[0154] Record the best combination: include the generator sets whose capacity is included in the variable current_sum into the cutting combination. During the traversal process, if the cutting combination found is consistent with ΔP d If the difference is less than the minimum difference recorded previously, update the optimal cutting machine combination and the minimum difference;

[0155] End condition: When all power unit capacities have been traversed, the algorithm ends;

[0156] Output result: Return the optimal machine switching combination and the corresponding total capacity.

[0157] S5. Cut the generator according to the optimal cut-off (generator cutting) combination of the distributed power sources and the corresponding capacity.

[0158] According to the above steps, the optimal removal combination and corresponding capacity are calculated to perform distributed power generation cutting.

[0159] S6. The standby automatic transfer device starts and the standby circuit breaker closes.

[0160] After completing the above distributed power generation removal strategy, the circuit breaker on the backup line is generally closed quasi-synchronously after a 60ms delay.

[0161] S7. Complete the standby automatic investment.

[0162] After the backup power supply is put into operation, when the system is running normally and stably again, the backup power supply is completed.

[0163] Those skilled in the art will appreciate that the modules and algorithm steps described in conjunction with the embodiments disclosed herein can be implemented using electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present invention.

[0164] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described devices and equipment can refer to the corresponding processes in the aforementioned method implementation methods and will not be repeated here.

[0165] In the embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the modules is merely a logical function division. In actual implementation, there may be other division methods, such as multiple modules or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or modules, which can be electrical, mechanical or other forms.

[0166] The modules described as separate components may or may not be physically separate, and the components shown as modules may or may not be physical modules, that is, they may be located in one place or distributed across multiple network modules. Some or all of the modules may be selected according to actual needs to achieve the objectives of the embodiments of the present invention.

[0167] In addition, each functional module in the embodiment of the present invention may be integrated into one processing module, or each module may exist physically separately, or two or more modules may be integrated into one module.

[0168] If the functions are implemented as software modules and sold or used as standalone products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the portion that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the energy-saving signal transmission / reception method according to various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as a USB flash drive, a mobile hard drive, ROM, RAM, a magnetic disk, or an optical disk.

[0169] The above description is merely a preferred embodiment of the present application and an illustration of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to the technical solutions formed by the specific combination of the above-mentioned technical features, but also encompasses other technical solutions formed by any combination of the above-mentioned technical features or their equivalents without departing from the inventive concept. For example, a technical solution formed by replacing the above-mentioned features with (but not limited to) technical features with similar functions disclosed in this application.

[0170] It should be understood that the size of the serial numbers of each step in the content of the invention and the implementation methods of the present invention does not absolutely mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the implementation methods of the present invention.

Claims

1. A quasi-synchronous closing method for distributed power supply access is characterized in that: include: Step 1: After the main supply line fails and meets the no-current condition, perform voltage no-voltage judgment: When the I bus voltage is lower than or equal to 0.3pu, the distributed generation is disconnected until the voltage meets the no-voltage condition and then closed; When the I bus voltage is higher than 0.3 pu, proceed to step 2; Step 2: Distributed power generation removal strategy based on power balance, including: 1) Count the capacity, inertia time constant and grid connection status of all grid-connected conventional units and distributed power sources in the island system during island operation, and calculate the inertia of the island system; 2) Calculate the unbalanced power ΔP of the island system based on the I mother frequency curve d ; 3) Calculate the generator shedding capacity and combination or load shedding capacity and combination based on the unbalanced power value and the approximate capacity matching algorithm; 4) Distributed power generation is cut off or load is cut off according to the capacity and combination obtained by the approximate capacity matching algorithm; Step 3: After the machine or load is cut off, perform quasi-synchronous closing: Check whether the voltage and frequency on both sides of the busbar and backup power supply meet the requirements before closing the circuit breaker.

2. The quasi-synchronous closing method for distributed power supply access according to claim 1 is characterized in that: During the island operation period, the capacity, inertia time constant and grid connection status of all conventional units and distributed power sources in the island system are counted, and the inertia of the island system H is calculated based on the following formula: sys : And calculate the island system capacity S based on the following formula sys : Where H gen.i is the inertia time constant of the i-th conventional unit; S gen.i is the rated capacity of the i-th conventional unit; K gen.i is the grid-connected status of the i-th conventional unit; H VI.j is the inertia time constant of the jth distributed power supply, S VI.j is the rated capacity of the jth distributed power supply; K VI.j is the grid-connected status of the jth distributed generation; Among them, the inertia time constant of the distributed power supply H VI It can be calculated by the power response characteristics of the distributed power supply. When the system frequency decreases, the distributed power supply increases the output power, and the inertia time constant H of the distributed power supply is VI It can be determined by the rate and duration of power change; assuming the output power change of the distributed power supply is △P and the frequency change is △f, the inertia time constant of the distributed power supply H is VI It can be expressed as: Where, P rated is the rated power of the distributed power supply.

3. The quasi-synchronous closing method for distributed power supply access according to claim 2 is characterized in that: According to the I mother frequency curve, the unbalanced power of the island system is calculated as: Obtain the I mother frequency curve and calculate the unbalanced power ΔP of the island system based on the rotor motion equation d : Where, f I母 is the I mother frequency; f0 is the system rated frequency.

4. The quasi-synchronous closing method for distributed power access according to claim 2 is characterized in that: According to the unbalanced power value, the generator or load shedding capacity and combination are calculated based on the approximate capacity matching algorithm, including: When the unbalanced power ΔP d > 0, it means that the power provided by the distributed power supply in the island system is greater than the load power, and the power cut operation based on the approximate capacity matching algorithm is performed; when the unbalanced power ΔP d When <0, it means that the power provided by the distributed generation in the island system is less than the load power, and the load shedding operation based on the approximate capacity matching algorithm is performed.

5. The quasi-synchronous closing method for distributed power supply access according to claim 2, characterized in that: Calculate the cutting capacity and combination based on the approximate capacity matching algorithm, including: Sorting: First, the rated capacity S of the conventional units gen.1 、S gen.2 ,...,S gen.n Sort in order from largest to smallest; Initialization: Set a variable current_sum to record the sum of the capacities of the currently selected power units, with an initial value of 0; Traversal: From the sorted list of rated capacities of power units, starting from the largest capacity, consider each capacity one by one: if the current capacity plus the variable current_sum does not exceed the unbalanced power ΔP d , then add this capacity to the current switch combination and update the variable current_sum; if adding the current capacity will exceed the unbalanced power ΔP d , minus some smaller capacity that has been added to make the total as close as possible to the unbalanced power ΔP d ; Adjustment: After adding a certain capacity, if the variable current_sum exceeds the unbalanced power ΔP d , adjustments need to be made: remove some smaller capacities from the current switch combination until the variable current_sum is less than or equal to the unbalanced power ΔP d , and record the current variable current_sum and the unbalanced power ΔP d The difference is used for subsequent comparison; Record the best combination: include the generator sets whose capacity is included in the variable current_sum into the cutting combination. During the traversal process, if the cutting combination found is consistent with the unbalanced power ΔP d If the difference is less than the minimum difference recorded previously, update the optimal cutting machine combination and the minimum difference; End condition: When all power unit capacities have been traversed, the algorithm ends; Output result: Return the optimal machine switching combination and the corresponding total capacity.

6. The quasi-synchronous closing method for distributed power access according to any one of claims 1 to 5, characterized in that: Calculate load shedding capacity and combinations based on an approximate capacity matching algorithm, including: Sorting: Get the load outgoing power P in real time L1 、P L2 ,...,P Ln , the load outgoing power P L1 、P L2 ,...,P Ln Sort in order from largest to smallest; Initialization: Set a variable current_sum to record the sum of the capacities of the currently selected power units, with an initial value of 0; Traversal: From the sorted list of outgoing power capacities, starting from the largest power, consider each power one by one: if the current power plus the variable current_sum does not exceed the unbalanced power ΔP d , then add this power to the current load shedding combination and update the variable current_sum; if adding the current power will exceed the unbalanced power ΔP d , minus some smaller power that has been added to make the total as close as possible to the unbalanced power ΔP d ; Adjustment: After adding a certain power, if the variable current_sum exceeds the unbalanced power ΔP d , adjustments need to be made: remove some smaller powers from the current load shedding combination until the variable current_sum is less than or equal to the unbalanced power ΔP d , and record the current variable current_sum and the unbalanced power ΔP d The difference is used for subsequent comparison; Record the best combination: include the generator sets whose power is recorded in the variable current_sum into the load shedding combination. During the traversal process, if the load shedding combination found is consistent with ΔP d If the difference is less than the previously recorded minimum difference, the optimal load shedding combination and the minimum difference are updated; End condition: When all load outgoing power has been traversed, the algorithm ends; Output result: Returns the optimal load shedding combination and the corresponding capacity sum.

7. The quasi-synchronous closing system for distributed power access is characterized by: include: Voltage no-voltage judgment module: When the main supply line fails and meets the no-current condition, voltage no-voltage judgment is performed: When the I bus voltage is lower than or equal to 0.3pu, the distributed generation is disconnected until the voltage meets the no-voltage condition and then closed; When the I bus voltage is higher than 0.3 pu, proceed to step 2; Distributed power generation removal strategy module: Distributed power generation removal strategy based on power balance, including: 1) Count the capacity, inertia time constant and grid connection status of all grid-connected conventional units and distributed power sources in the island system during island operation, and calculate the inertia of the island system; 2) Calculate the unbalanced power ΔP of the island system based on the I mother frequency curve d ; 3) Calculate the generator shedding capacity and combination or load shedding capacity and combination based on the unbalanced power value and the approximate capacity matching algorithm; 4) Distributed power generation is cut off or load is cut off according to the capacity and combination obtained by the approximate capacity matching algorithm; Synchronous closing module: quasi-synchronous closing is performed after the machine or load is cut off: Check whether the voltage and frequency on both sides of the busbar and backup power supply meet the requirements before closing the circuit breaker.

8. An electronic device, characterized in that The invention comprises a processor, a memory and a computer program stored in the memory and executable on the processor, wherein when the computer program is executed by the processor, the method for quasi-synchronous closing of distributed power supply access as described in any one of claims 1 to 6 is implemented.

9. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, and when the computer program is executed by the processor, the quasi-synchronous closing method for accessing a distributed power source according to any one of claims 1 to 6 is implemented.

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