A unit startup method considering comprehensive indicators of recovery time and success rate

Abstract

The present invention relates to power system restoration technology, and specifically to a unit starting method that considers comprehensive indicators of restoration time and success rate, including abstracting the topology of a power grid to be restored, establishing a mathematical model of the output of black start units and non-black start units, and constructing a weighted topological map of the power grid based on line charging time, transformer operation time, and line capacitance value; searching for the optimal restoration path of all non-black start units to be started in the power grid based on the Dijkstra shortest path algorithm; constructing a comprehensive index of the unit start sequence in combination with the unit capacity, climbing rate, starting power and other characteristics, and deciding the start sequence of the non-black start units according to the index value; and starting each non-black start unit in turn through the optimal restoration path. The method takes into account the coupling relationship between the unit start sequence and the restoration path, and can quickly provide power generation power to the power outage system in the early stage of power system restoration, while improving the success rate of unit restoration.

Description

Technical Field

[0001] The invention belongs to the technical field of power system restoration, and in particular relates to a unit starting method taking into account comprehensive indicators of restoration time and success rate. Background Art

[0002] In recent years, due to the influence of human operation factors, power equipment failures and extreme weather disasters, large-scale power outages in power systems at home and abroad still occur from time to time. With the expansion and development of the current power system, the interconnection between different subsystems in the large power grid has gradually strengthened, and the connection between local regional power grids has become closer; on the other hand, the hybrid connection of AC and DC power grids, the mixing of multiple voltage levels, and the continuous penetration of new energy have become the general trend of today's development, making the power system structure increasingly complex and bringing more uncertainties to the operation of the system. In the context of modern power systems, minor faults in local power grids can easily trigger a domino chain effect, resulting in large-scale power outages. Therefore, ensuring that the power system can recover quickly and reliably after a large-scale power outage, shortening the power grid recovery time, and reducing the losses caused by the accident are important issues facing modern power systems.

[0003] The recovery control after a large-scale power outage in the power system is a large and complicated process. Existing research usually divides it into three stages: black start, grid reconstruction and load recovery. The unit start-up described in the present invention refers to the black start power supply providing starting power to the generator sets that cannot start by themselves after a large power outage, helping them to start and restore their power generation capacity, laying the foundation for network recovery and load recovery. The formulation of the unit start-up method includes the selection of the unit start-up sequence and the recovery path. The decision-making of the two is not separated and single, and there is often an internal connection. Current research usually ignores the mutual coupling relationship between the recovery sequence of the units to be started and the optimal start-up path when formulating the unit start-up method, and considers the two independently in the solution process. Therefore, it is easy to cause the unit start-up sequence and the recovery path to be not optimal after combination, affecting the speed and reliability of power system recovery. Summary of the invention

[0004] In view of the problems existing in the background technology, the present invention provides a method for formulating a unit startup strategy taking into account comprehensive indicators of recovery time and success rate.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solution: a unit startup method considering the comprehensive index of recovery time and success rate, comprising the following steps:

[0006] Step 1: Abstract the topology of the power grid to be restored, establish the output mathematical model of the black start unit and the non-black start unit, and construct the weighted topology map of the power grid according to the line charging time, transformer operation time and line capacitance value;

[0007] Step 2: Based on the Dijkstra shortest path algorithm, search for the optimal restoration path of all non-black start units to be started in the power grid;

[0008] Step 3: Based on the optimal recovery path obtained in step 2, combined with the unit capacity, ramp rate, starting power characteristics, and the recovery speed and recovery success rate of the black start unit to restore the waiting unit, a comprehensive index of the unit start sequence is constructed, and the start sequence of the non-black start units is determined according to the index value;

[0009] Step 4: Check the constraints of the units to be started, including the starting time limit constraint, starting power constraint, generator power constraint and voltage constraint, and start each non-black start unit in turn through the optimal recovery path.

[0010] In the above-mentioned unit startup method considering the comprehensive index of recovery time and success rate, the implementation of step 1 includes the following steps:

[0011] Step 1.1, establish the output mathematical model of the black start unit and the non-black start unit;

[0012] 1) Ignore the starting power of the black start unit and give priority to self-start recovery after a power outage. At the same time, the unit responds quickly and is considered to have reached the maximum climbing capacity throughout the process;

[0013] During the black start process, the relationship between the black start unit's external output power and time is as follows:

[0014]

[0015] In the formula, t s is the start time of the black start unit, here t is set s =0; t c It is the moment when the black start unit is connected to the grid and ramps up to transmit power; K represents the ramp rate of the black start unit; P max is the maximum active power of the black start unit; t max is the full power operation time of the black start unit, and the calculation formula is:

[0016]

[0017] The power ramp-up after the unit is connected to the grid is divided into two stages with the minimum technical output as the boundary: K NA Represents the ramp rate of the non-black start unit under the minimum technical output; K NB Represents the ramp rate of the unit above the minimum technical output, where K NA <K NB ; Define the average ramp rate K of the unit N ;

[0018] 2) Non-black start units Considering conventional thermal power units, a mathematical model of non-black start units in the process of power grid recovery is established, and the expression of the external output power of non-black start units is obtained:

[0019]

[0020] In the formula, t s is the starting time of the non-black start unit; t c It is the moment when the unit is started and connected to the grid and begins to ramp up and transmit power to the outside; t max P is the moment when the unit outputs maximum power m The minimum technical output of the unit; P st P is the starting power that needs to be supplied by an external power supply; max is the maximum active power of the unit; t max is the full power operation time of the black start unit, and the calculation formula is as follows:

[0021]

[0022] Step 1.2, construct a weighted topological map of the power grid;

[0023] The generators and loads in the power grid are extracted as undifferentiated nodes, the lines and transformers are regarded as branches, and the power grid is abstracted into a topological graph G = (V, E), where V represents the vertex set of the graph and E represents the branch set of the graph;

[0024] Taking into account the charging time of the line, the operating time of the transformer and the capacitance value of the line, weights are assigned to the branches to obtain a weighted topology diagram:

[0025] w ij =t ij +c ij

[0026] In the formula, w ij represents the branch weight between node i and node j, t ij represents the recovery speed of the branch between node i and node j, specifically the normalized recovery time of the branch, including the line charging time and the transformer recovery time, c ij represents the recovery success rate of the branch between node i and node j, which is represented by the normalized capacitance value;

[0027] The adjacency matrix A is used to describe the connection relationship of the power grid topology graph:

[0028]

[0029]

[0030] In the above-mentioned unit startup method considering the comprehensive index of recovery time and success rate, the optimal recovery path of searching for all non-black start units to be started in the power grid in step 2 includes:

[0031] 1) Store the nodes with the shortest path found in the set V S , other nodes are stored in the set V o , the set D stores the distance between the black start power node and each node, the matrix S stores the shortest path of each node, and the set V S Initially, it only contained black start power nodes;

[0032] 2) According to the adjacency matrix, in V o Select the node k with the shortest distance to the black start power source and include it in the set V S , record the shortest path to the S matrix, and remove the node from the set V o Removed;

[0033] 3) Compare the path length obtained with node k as the intermediate node with the original path length, take the minimum value between the two, and update the distance from each node in the adjustment set D to the starting point;

[0034] 4) Repeat the above steps until all nodes are traversed and the shortest paths and shortest distances from all nodes to the black start power supply node are obtained.

[0035] In the above-mentioned unit startup method considering the comprehensive index of recovery time and success rate, the step 3 of constructing the comprehensive index of unit startup sequence is specifically:

[0036] 1) Comprehensively consider the unit starting power, ramp rate and unit capacity, and calculate the unit characteristic indicators, specifically:

[0037] O(k)=P * (k)-S * (k)-C * (k)

[0038] Where O(k) is the characteristic index of the kth unit, P * (k) is the normalized value of the starting power of the kth unit, S * (k) is the normalized value of the capacity of the kth unit, C * (k) is the normalized value of the ramp rate of the kth unit;

[0039] 2) The specific normalization method is:

[0040]

[0041] In the formula, x * represents the normalized value of x, x min represents the minimum value of x, xmax represents the maximum value of x;

[0042] 3) Based on the recovery path of the node of the unit to be started, calculate and normalize the sum of the branch weights contained in the recovery path as the unit distance index D(k);

[0043] 4) Taking into account the unit's own characteristic indicators and distance indicators, establish the unit startup comprehensive indicators, specifically:

[0044] Z(k)=O(k)+D(k)

[0045] Where Z(k) is the comprehensive startup index of the kth unit, O(k) is the characteristic index of the kth unit, and D(k) is the distance index of the kth unit.

[0046] In the above-mentioned unit startup method considering the comprehensive index of recovery time and success rate, the constraint conditions of the unit to be started described in step 4 are specifically as follows:

[0047] 1) The unit is set to remain in operation after startup and will not shut down again;

[0048] s k (t)≤s k (t+1) k=1,2,…,N

[0049] In the formula, s k (t) represents the start / stop status of unit k at time t. When the unit is started, the value is 1, otherwise it is 0;

[0050] 2) The start time of the generator set is within the hot start time limit of the unit, and the unit is quickly restored by hot start, specifically:

[0051]

[0052] In the formula, t s is the starting time of the non-black start unit, t s max The maximum hot start time limit for non-black start units refers to the maximum power outage time during which the unit can be hot started;

[0053] 3) When the start time of the unit is greater than the minimum hot start time limit, the unit will be delayed for a certain period of time to complete a series of preparations before cold start. The start time of the unit meets the minimum cold start time limit, specifically:

[0054]

[0055] In the formula, t s is the starting time of the non-black start unit, t s minThe minimum cold start time limit for non-black start units;

[0056] 4) Non-black start units rely on external power to start. When the power generation provided by the system meets the starting power requirement of the next unit to be started, the unit starts. Specifically:

[0057]

[0058] In the formula, p represents the number of black start units in the system, represents the active power output of the i-th black start unit at time t, q represents the number of non-black start units that have been restored in the system, P represents the active power output of the jth non-black start unit at time t. st Indicates the starting power required by the next unit to be started;

[0059] 5) The start-up time of the unit to be started needs to meet the charging time constraint of the recovery path, specifically:

[0060] t i,st ≥t j,st +t ij

[0061] In the formula, t i,st represents the starting time of the unit i to be started, t j,st represents the startup time of the restored unit j, t ij Indicates the charging time of the recovery path from the restored system to the unit i to be started;

[0062] 6) When starting each non-black start unit through the recovery path, the power output of the generator set should be within the upper and lower power limits, specifically:

[0063]

[0064] Where P Gi represents the active power generated by the i-th generator, represents the minimum active power allowed to be output by the i-th generator, represents the maximum active power allowed to be output by the i-th generator; Q Gi is the reactive power generated by the i-th generator set, is the minimum reactive power allowed to be output by the i-th generator set, is the maximum reactive power allowed to be output by the i-th generator set;

[0065] 7) The active power transmitted by the line should meet the power upper limit requirements, specifically:

[0066]

[0067] Where P Li is the power flowing through the i-th line, The power upper limit of the transmission of the i-th line; the active power transmitted by the line should meet the power upper limit requirements.

[0068] Compared with the prior art, the present invention has the following beneficial effects:

[0069] In the unit starting method, weights are assigned to branches according to the recovery time and capacitance value, and the sum of the weights on the recovery path of each unit is considered to construct a comprehensive index for the unit starting sequence. In the early stage of power system recovery, non-black start units can be started in a shorter time, providing power generation power to the power outage system more quickly, while improving the reliability of unit recovery.

[0070] This unit starting method takes into account the coupling relationship between the unit starting order and the recovery path. The shortest recovery path of the unit is considered when deciding the unit starting order. At the same time, the starting order will in turn affect the optimal recovery path of each unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 : is a flow chart of the method according to the embodiment of the present invention;

[0072] Figure 2 : is the mathematical model of the black start unit in the embodiment of the present invention;

[0073] Figure 3 : is the mathematical model of the non-black start unit in the embodiment of the present invention;

[0074] Figure 4 : is a flow chart of the unit recovery path search according to an embodiment of the present invention;

[0075] Figure 5 : is a result diagram of the unit recovery path according to an embodiment of the present invention;

[0076] Figure 6 : It is a result diagram of the unit recovery path of the comparative method of the embodiment of the present invention. DETAILED DESCRIPTION

[0077] The technical solutions in the embodiments of the present invention will be described clearly and completely below in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0078] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0079] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited thereto.

[0080] This embodiment proposes a unit starting method that takes into account the recovery time and success rate. This method takes into account the line charging time, transformer recovery time, and branch capacitance, constructs a weighted topology diagram for the power grid to be restored, and searches for the recovery path of the unit to be started based on the Dijkstra algorithm; combines the unit capacity, climbing rate, starting power and other characteristics and the distance index on the recovery path to construct a comprehensive index for the unit start-up sequence; takes into account various constraints, considers the relationship between the start-up sequence and the recovery path, and formulates a unit start-up method. This method takes into account the coupling relationship between the unit start-up sequence and the recovery path, and can quickly provide power generation power to the power outage system in the early stage of power system recovery, while improving the success rate of unit recovery.

[0081] A flow chart of a unit startup method considering the comprehensive index of recovery time and success rate in this embodiment is as follows: Figure 1 As shown, the following steps are included:

[0082] 1. Abstract the topology of the power grid to be restored, establish the output mathematical model of the black start unit and the non-black start unit, and construct the weighted topology map of the power grid according to the line charging time, transformer operation time and line capacitance value;

[0083] 1) Establish the output mathematical model of black start and non-black start units, specifically:

[0084] The starting power of the black start unit can be ignored, and it will be restarted and restored automatically after a power outage. At the same time, the unit responds quickly, and it can be considered that it has reached the maximum climbing capacity throughout the whole process.

[0085] Therefore, during the black start process, the relationship between the black start unit's external output power and time is as follows:

[0086]

[0087] In the formula, t s is the start time of the black start unit, here t is set s =0; t c It is the moment when the black start unit is connected to the grid and ramps up to transmit power; K represents the ramp rate of the black start unit; P max is the maximum active power of the black start unit; t max is the full power operation time of the black start unit, and the calculation method is as follows:

[0088]

[0089] Non-black start units do not have the ability to start automatically. After a major power outage, they must be shut down by an external power supply to restore their output. The power ramp-up after the unit is connected to the grid is divided into two stages, with the minimum technical output as the boundary. NA Represents the ramp rate of the non-black start unit under the minimum technical output; K NB Represents the ramp rate of the unit above the minimum technical output, where K NA <K NB In order to simplify the unit ramping process, the unit average ramping rate K is defined as N Common non-black start units mainly include conventional thermal power units and nuclear power units. Here we mainly consider conventional thermal power units, establish a mathematical model of non-black start units during power grid recovery, and obtain the expression of the output power of non-black start units:

[0090]

[0091] In the formula, t s is the starting time of the non-black start unit; t c It is the moment when the unit is started and connected to the grid and begins to ramp up and transmit power to the outside; t max P is the moment when the unit outputs maximum power m The minimum technical output of the unit; P st P is the starting power that needs to be supplied by an external power supply; max is the maximum active power of the unit; t max is the full power operation time of the black start unit, and the calculation method is as follows:

[0092]

[0093] The characteristic parameters of each generator set are shown in Table 1;

[0094] Table 1 Generator set characteristic parameters

[0095]

[0096] 2) Construct the power grid topology diagram. The specific steps are as follows: Figure 4 As shown:

[0097] The generators and loads in the power grid are extracted as undifferentiated nodes, the lines and transformers are regarded as branches, and the power grid is abstracted as a topological graph G = (V, E), where V represents the vertex set of the graph and E represents the branch set of the graph.

[0098] Considering the overvoltage problem of line no-load charging, the capacitance value is used to measure the success rate of branch recovery. The larger the capacitance value, the greater the reactive power generated by line no-load charging, which can easily lead to excess reactive power and cause overvoltage at the end node of the line, causing line recovery failure and affecting the recovery of the units to be started.

[0099] Taking into account the charging time of the line, the operating time of the transformer and the capacitance value of the line, weights are assigned to the branches to obtain a weighted topology diagram:

[0100] w ij =t ij +c ij

[0101] In the formula, w ij represents the branch weight between node i and node j, t ij represents the recovery speed of the branch between node i and node j, specifically the normalized recovery time of the branch, including the line charging time and the transformer recovery time, c ij Represents the recovery success rate of the branch between node i and node j, which is represented by the normalized capacitance value.

[0102] The adjacency matrix A is used to describe the connection relationship of the power grid topology graph:

[0103]

[0104]

[0105] 2. Based on the Dijkstra shortest path algorithm, search for the optimal recovery path for all non-black start units to be started in the power grid, ensuring that the time required for the units to recover via this path is as short as possible and has a high success rate;

[0106] The optimal recovery path for searching non-black start units is as follows:

[0107] Store the nodes with the shortest path found in the set V S , other nodes are stored in the set V o , the set D stores the distance between the black start power node and each node, the matrix S stores the shortest path of each node, and the set V S Initially, it only contained black start power nodes;

[0108] According to the adjacency matrix, in V o Select the node k with the shortest distance to the black start power source and include it in the set V S , record the shortest path to the S matrix, and remove the node from the set V o Removed;

[0109] Compare the path length obtained with node k as the intermediate node with the original path length, take the minimum value between the two, and update the distance from each node in the adjustment set D to the starting point;

[0110] Repeat the above steps until all nodes are traversed to obtain the shortest path and shortest distance from all nodes to the black start power supply node; the sum of the branch weights on the obtained shortest path is the smallest, which can ensure that the time required for the unit to recover via this path is as short as possible and the recovery success rate is high. Therefore, it is used as the optimal recovery path for non-black start unit nodes.

[0111] 3. Based on the optimal recovery path result obtained in step 2, combined with the unit's own characteristics such as capacity, ramp rate, and starting power, a comprehensive index for the unit's starting sequence is constructed, and the starting sequence of non-black start units is determined based on the index value;

[0112] The specific comprehensive indicators for constructing the unit startup sequence are:

[0113] Taking into account the unit starting power, ramp rate and unit capacity, the unit characteristic indicators are calculated, specifically:

[0114] O(k)=P * (k)-S * (k)-C * (k)

[0115] Where O(k) is the characteristic index of the kth unit, P * (k) is the normalized value of the starting power of the kth unit, S * (k) is the normalized value of the capacity of the kth unit, C * (k) is the normalized value of the ramp rate of the kth unit.

[0116] The specific normalization method is:

[0117]

[0118] In the formula, x * represents the normalized value of x, x min represents the minimum value of x, x max Represents the maximum value of x.

[0119] Based on the restoration path of the node of the unit to be started, the sum of the branch weights contained in the restoration path is calculated and normalized as the unit distance index D(k);

[0120] Taking into account the unit's own characteristic indicators and distance indicators, the unit startup comprehensive indicators are established, specifically:

[0121] Z(k)=O(k)+D(k)

[0122] Where Z(k) is the comprehensive startup index of the kth unit, O(k) is the characteristic index of the kth unit, and D(k) is the distance index of the kth unit.

[0123] 4. Verify the constraints of the units to be started, including the starting time limit constraint, starting power constraint, generator power constraint and voltage constraint, and start each non-black start unit in turn through the optimal recovery path;

[0124] The specific constraints for checking the units to be started are as follows:

[0125] It is assumed that once the unit is started, it will remain in operation and will not be shut down again.

[0126] s k (t)≤s k (t+1) k=1,2,…,N

[0127] In the formula, s k (t) represents the start / stop status of unit k at time t. When the unit is started, the value is 1, otherwise it is 0.

[0128] The start time of the generator set must be within the hot start time limit of the unit, so that the unit can be quickly restored by hot start, specifically:

[0129]

[0130] In the formula, t s is the starting time of the non-black start unit, t s max The maximum hot start time limit for non-black start units refers to the maximum power outage time during which the unit can be hot started;

[0131] When the unit's startup time is greater than the minimum hot start time limit, the unit can only be cold started after a certain delay to complete a series of preparations. At this time, the unit's startup time needs to meet the minimum cold start time limit, specifically:

[0132]

[0133] In the formula, t s is the starting time of the non-black start unit, t s min The minimum cold start time limit for non-black start units;

[0134] The non-black start unit relies on external power to start. The unit can only start smoothly when the power generation power provided by the system can meet the starting power requirements of the next unit to be started. Specifically:

[0135]

[0136] In the formula, p represents the number of black start units in the system, represents the active power output of the i-th black start unit at time t, q represents the number of non-black start units that have been restored in the system, P represents the active power output of the jth non-black start unit at time t. st Indicates the starting power required by the next unit to be started;

[0137] The start-up time of the unit to be started needs to meet the charging time constraint of the recovery path, which is:

[0138] t i,st ≥t j,st +t ij

[0139] In the formula, t i,st represents the starting time of the unit i to be started, t j,st represents the startup time of the restored unit j, t ij Indicates the charging time of the recovery path from the restored system to the unit i to be started;

[0140] When starting each non-black start unit through the recovery path, the power output of the generator set should be within the upper and lower power limits, specifically:

[0141]

[0142] Where P Gi represents the active power generated by the i-th generator, represents the minimum active power allowed to be output by the i-th generator, represents the maximum active power allowed to be output by the i-th generator; Q Gi is the reactive power generated by the i-th generator set, is the minimum reactive power allowed to be output by the i-th generator set, is the maximum reactive power allowed to be output by the i-th generator set;

[0143] The active power transmitted by the line should meet the power upper limit requirements, specifically:

[0144]

[0145] Where P Li is the power flowing through the i-th line, The power upper limit of the i-th line transmission. The active power transmitted by the line should meet the power upper limit requirements;

[0146] In order to verify the effectiveness of the unit startup strategy proposed in this embodiment, the following two unit startup methods are used to start each unit in turn until all non-black start units in the grid are traversed, and the unit startup results obtained by the two methods are compared and analyzed:

[0147] Method 1: The unit startup method that only considers the unit characteristic indicators;

[0148] Method 2: The present invention adopts a unit startup method based on comprehensive indicators of unit startup sequence;

[0149] The unit startup conditions obtained by method 1 are shown in Table 2, and the unit startup conditions obtained by method 2 are shown in Table 3;

[0150] Table 2 Unit startup status of method 1

[0151]

[0152] Table 3 Unit startup status of method 2

[0153]

[0154]

[0155] Method 2 introduces the unit distance index when formulating the unit start-up strategy, taking into account the unit location distribution. The unit start-up strategy obtained gives priority to starting the non-black start units that are closer to the black start units. The unit at node 37 is started at 9 minutes, and the unit at node 39 is started at 11 minutes. These two non-black start units climb to positive output at 11.13 minutes and 16.31 minutes respectively, and can output power to the outside. Comparative analysis shows that method 2 can start non-black start units in a shorter time at the initial stage of power system recovery, thereby providing power generation power to the power outage system more quickly;

[0156] From the perspective of successful unit recovery, method 1 first recovers the unit at node 34, whose shortest recovery path capacitance weight is 3.31×10-3p.u., while method 2 considers the branch capacitance value when deciding the unit start sequence, and prioritizes the start of the unit at node 37, whose shortest recovery path capacitance weight is 0.46×10-3p.u. The smaller the capacitance value, the smaller the reactive power generated by line no-load charging, which reduces the possibility of overvoltage at the node, and is conducive to the successful recovery of the unit in the early stage of power outage recovery, outputting reliable power generation capacity for the power system;

[0157] Taking the non-black start units located at nodes 35 and 36 as an example, the recovery path diagram is as follows: Figure 5 , Figure 6 The red line represents the restored system, the blue line represents the shortest restoration path of the unit to be started at node 35, and the yellow line represents the shortest restoration path of the unit at node 36;

[0158] From Table 2 and Table 3, it can be seen that method 1 uses unit characteristic index to decide the unit startup sequence, first starting unit node 35, then starting unit node 36; while method 2 uses unit comprehensive index to decide the unit startup sequence, first starting the 36-node unit that is closer to the black start unit, and then starting the 35-node unit;

[0159] Depend on Figure 5 , Figure 6 It can be seen that the optimal recovery paths of unit nodes 35 and 36 have changed due to the change in the start-up order of the units under the two methods, which further illustrates that the start-up order and recovery path of the units are interrelated. Method 2 considers the shortest recovery path of the units when deciding the start-up order of the units, and the start-up order will also affect the recovery path of each unit;

[0160] In summary, the unit startup strategy proposed in this embodiment takes into account the coupling relationship between the unit startup sequence and the unit recovery path, which can accelerate the unit recovery speed in the early stage of system power outage recovery and improve the reliability of unit recovery.

[0161] The above are only preferred embodiments of the present invention, and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the contents of the specification of the present invention should be included in the protection scope of the present invention.

Claims

1. A unit startup method considering comprehensive indicators of recovery time and success rate, characterized in that: The following steps are involved: Step 1: Abstract the topology of the power grid to be restored, establish the output mathematical model of the black start unit and the non-black start unit, and construct the weighted topology map of the power grid according to the line charging time, transformer operation time and line capacitance value; Step 2: Based on the Dijkstra shortest path algorithm, the optimal recovery path of all non-black start units to be started in the power grid is searched, including: 1) Store the nodes with the shortest path found in the collection VS , other nodes are stored in the collection V ,gather D Store the distance between the black start power node and each node, matrix S Store the shortest path of each node, set VS Initially, it only contained black start power nodes; 2) According to the adjacency matrix, V Select the node with the shortest distance to the black start power supply k , include it in the collection VS , record the shortest path to S matrix, and remove the node from the collection V Removed; 3) Node k Compare the path length obtained as the intermediate node with the original path length, take the minimum value between the two, and update the adjustment set D The distance from each node to the starting point; 4) Repeat the above steps until all nodes are traversed and the shortest path and shortest distance from all nodes to the black start power supply node are obtained; Step 3: Based on the optimal recovery path obtained in step 2, combined with the unit capacity, ramp rate, starting power characteristics, and the recovery speed and recovery success rate of the black start unit to the unit to be started, a comprehensive index of the unit start sequence is constructed, and the start sequence of the non-black start units is determined according to the index value; the construction of the comprehensive index of the unit start sequence specifically includes: 1) Comprehensively consider the unit starting power, ramp rate and unit capacity, and calculate the unit characteristic indicators, specifically: In the formula, is the characteristic index of the kth unit, is the normalized value of the starting power of the kth unit, is the normalized value of the kth unit capacity, is the normalized value of the ramp rate of the kth unit; 2) The specific normalization method is: In the formula, represent x The normalized value of represents the minimum value of x, represents the maximum value of x; 3) Based on the recovery path of the node of the unit to be started, calculate and normalize the sum of the branch weights contained in the recovery path as the unit distance index ; 4) Taking into account the unit's own characteristic indicators and distance indicators, establish the unit startup comprehensive indicators, specifically: In the formula, For the k The comprehensive startup index of each unit, For the k The characteristic index of the unit, For the k Distance index of each unit; Step 4: Check the constraints of the units to be started, including the starting time limit constraint, starting power constraint, generator power constraint and voltage constraint, and start each non-black start unit in turn through the optimal recovery path.

2. The unit startup method considering the comprehensive index of recovery time and success rate according to claim 1 is characterized in that: The implementation of step 1 includes the following steps: Step 1.1, establish the output mathematical model of the black start unit and the non-black start unit; 1) Ignore the starting power of the black start unit and give priority to self-start recovery after a power outage. At the same time, the unit responds quickly and is considered to have reached the maximum climbing capacity throughout the process; During the black start process, the relationship between the black start unit's external output power and time is as follows: In the formula, The start time of the black start unit is set here. ; It is the moment when the black start unit is connected to the grid and ramps up to deliver power; Represents the ramp rate of the black start unit; is the maximum active power of the black start unit; is the full power operation time of the black start unit, and the calculation formula is: The power ramp-up after the unit is connected to the grid is divided into two stages, with the minimum technical output as the boundary; KN Represents the ramp rate of non-black start units at minimum technical output; KNB Represents the ramp rate of the unit above the minimum technical output, where KNA< KNB ; Define the average ramp rate of the unit KN ; 2) Non-black start units Considering conventional thermal power units, a mathematical model of non-black start units during power grid recovery is established, and the expression of the external output power of non-black start units is obtained: In the formula, It is the starting time of the non-black start unit; It is the moment when the unit is started and connected to the grid and begins to ramp up and transmit power outward; The moment when the unit outputs maximum power P m Minimum technical contribution for the crew; The starting power needs to be supplied by an external power supply; is the maximum active power of the unit; is the full power operation time of the black start unit, and the calculation formula is as follows: ； Step 1.2, construct a weighted topological map of the power grid; The generators and loads in the power grid are extracted as undifferentiated nodes, the lines and transformers are regarded as branches, and the power grid is abstracted into a topological diagram , where V represents the vertex set of the graph, and E represents the branch set of the graph; Taking into account the charging time of the line, the operating time of the transformer and the capacitance value of the line, weights are assigned to the branches to obtain a weighted topology diagram: In the formula, wij Representative Node i With Node j The branch weight between tij Representative Node i With Node j The recovery speed of the intermediate branch is the normalized recovery time of the branch, including the line charging time and the transformer recovery time. cij Representative Node i With Node j The recovery success rate of the intermediate branch is represented by the normalized capacitance value; The adjacency matrix A is used to describe the connection relationship of the power grid topology graph: 。 3. The unit startup method considering the comprehensive index of recovery time and success rate according to claim 1 is characterized in that: The specific verification constraints of the units to be started described in step 4 are as follows: 1) The unit is set to remain in operation after startup and will not shut down again; In the formula, Indicates the start / stop status of unit k at time t. When the unit is started, the value is 1, otherwise it is 0; 2) The start time of the generator set is within the hot start time limit of the unit, and the unit is quickly restored by hot start, specifically: In the formula, ts is the starting time of the non-black start unit, tsmax The maximum hot start time limit for non-black start units refers to the maximum power outage time during which the unit can be hot started; 3) When the start time of the unit is greater than the minimum hot start time limit, the unit will be delayed for a certain period of time to complete a series of preparations before cold start. The start time of the unit meets the minimum cold start time limit, specifically: In the formula, ts is the starting time of the non-black start unit, tsmin The minimum cold start time limit for non-black start units; 4) Non-black start units rely on external power to start. When the power generation provided by the system meets the starting power requirement of the next unit to be started, the unit starts. Specifically: In the formula, p Indicates the number of black start units in the system. express t Moment i The active power output of the Taihei starter unit is as follows: q Indicates the number of non-black start units that have recovered in the system. express t Moment j The amount of active power output by non-black start units. Indicates the starting power required by the next unit to be started; 5) The start-up time of the unit to be started needs to meet the recovery path charging time constraint, specifically: In the formula, Indicates the unit is ready to start i The start time, Indicates that the unit has been restored j The start time, Indicates that the system is restored to the unit to be started. i Charging time of the recovery path for power transmission; 6) When starting each non-black start unit through the recovery path, the power output of the generator set should be within the upper and lower power limits, specifically: In the formula, Representative The active power generated by the generator is Representative The minimum active power allowed to be output by a generator, Representative The maximum active power allowed to be output by a generator; For the The reactive power generated by the generator sets, For the The minimum reactive power allowed to be output by each generator set, For the The maximum reactive power allowed to be output by each generator set; 7) The active power transmitted by the line should meet the power upper limit requirements, specifically: In the formula, P Li For the i The power flowing through the line, No. i The upper limit of the power transmitted by the line; The active power transmitted by the line should meet the power upper limit requirements.

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