A power grid safety-oriented energy storage system energy scheduling optimization method

Abstract

The application discloses a kind of energy storage system energy scheduling optimization methods for power grid safety, it is related to power grid safety technical field, the application includes the following steps: wide-area measurement data synchronization and initial fault feature extraction;Based on the dynamic identification of chain failure propagation path of electrical distance;Based on the search and definition of virtual isolation section of power flow transfer impact;Energy storage system energy island at receiving end transient construction and synchronous control;Based on energy balance, reactive power-active power collaborative impact suppression in island;Island stable state detection and smooth grid recovery control;The application is not carried out after identifying branch overload impact Whole network optimization calculation, but directly disconnects the boundary breaker of preset virtual electrical isolation section, and limits the fault energy in the minimum topological range;Energy storage system switches to network type control mode in island instantaneously, establishes voltage and frequency reference autonomously, and can complete control mode conversion without relying on master station communication.

Description

Technical Field

[0001] This invention belongs to the field of power grid security technology, and in particular relates to an energy dispatch optimization method for energy storage systems oriented towards power grid security. Background Technology

[0002] With the continuous increase in the penetration rate of new energy sources in new power systems, the safe operation of the terminal distribution network under extreme weather disasters faces severe challenges. When disasters such as typhoons and thunderstorms cause critical transmission channels to trip due to faults, the power flow will be transferred to adjacent backup lines on a large scale, which can easily trigger a chain of faults in which multiple lines trip due to overload. To address the above problems, the existing mainstream technical solutions usually adopt a correction control method based on unified optimization of the entire network. That is, after the initial fault occurs, the dispatch center master station uses the optimal power flow algorithm to solve the power regulation commands of each controllable resource based on the global power grid topology and power flow model and issues them for execution.

[0003] However, when the aforementioned unified optimization method for the entire network is applied to cascading fault blocking scenarios, it faces the problem of blocking failure caused by the time scale mismatch between computation time and fault propagation speed. In cascading faults, the time window from power flow influx to overload tripping of backup lines is only a few hundred milliseconds, while the convergence time of optimal power flow calculation far exceeds this time scale, resulting in the fault spreading further when the correction control command is issued. At the same time, fault energy is directionally propagated along the path of least impedance in the grid topology. If only global power balance calculation is performed without considering the spatial propagation direction of fault energy, it is impossible to implement precise blocking locally on overloaded lines. Furthermore, in existing methods, energy storage systems rely on master station dispatch commands and grid voltage references for power regulation. During the period of severe voltage and frequency fluctuations caused by the fault, the energy storage system is limited by communication delays and grid-connected control modes, making it difficult to independently complete transient energy absorption and blocking actions in the early stages of fault propagation. Therefore, the following solutions are proposed to address the above problems. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution: This invention provides an energy dispatch optimization method for energy storage systems aimed at grid security, comprising the following steps: Step S1: Wide-area measurement data synchronization and initial fault feature extraction. The voltage phasor of the grid node and the power of the branch are obtained in real time through the phasor measurement unit. After the branch tripping is detected, the cross-sectional power flow data before the tripping branch fault is extracted as the reference value for energy impact calculation. Step S2: Dynamic identification of cascading fault propagation paths based on electrical distance. Starting from the end node of the tripped branch, the path vulnerability transmission factor is calculated using the branch reactance and load rate to screen the set of high-risk transmission paths. Step S3: Search and define virtual isolation sections based on power flow transfer impact, monitor the active power change rate in the high-risk transmission path set, and when the change rate exceeds the impact ramp-up threshold, search for the minimum electrical distance area containing energy storage nodes as the virtual electrical isolation section, centered on the overload branch receiving node, and determine the set of circuit breakers at the section boundary. Step S4: Transient construction and synchronous control of energy island at the receiving end of the energy storage system. Send the island defense mode command to the energy storage system within the virtual electrical isolation section, disconnect the boundary circuit breaker set to make the section separate from the main grid to form an energy island at the receiving end, and switch the energy storage converter from the grid-following mode to the grid-building mode to establish island voltage and frequency reference. Step S5: Based on the energy balance, the local controller of the energy storage system dynamically adjusts the virtual resistance and virtual inductance based on the virtual impedance adaptive adjustment strategy, corrects the converter reference voltage, absorbs transient energy and suppresses voltage frequency fluctuations. Step S6: Island stability detection and smooth grid-connection recovery control. When the frequency and voltage amplitude in the island meet the stability judgment conditions, the energy storage system adjusts the output voltage phase to track the main grid phase. When the synchronous grid connection conditions are met, the boundary circuit breaker is closed in sequence, and the energy storage converter switches back to the grid-following mode.

[0005] Further, step S1 includes the following steps: Step S11: The dispatch center master station uses the phasor measurement unit to... The sampling period is used to obtain the voltage phasor amplitude of each node in the power grid in real time. and phase angle and the active power of each branch. With reactive power ; Step S12: Capture the initial fault occurrence time using the switch quantity change information of the data acquisition and monitoring control system. When a branch is detected After the relay protection trips, the topology location of the tripped branch is locked and the cross-sectional power flow data of the previous cycle before the fault is extracted. This serves as the baseline value for subsequent energy impact calculations.

[0006] Furthermore, step S2 includes the following steps: Step S21: Connect the end node of the trip branch downstream first-order adjacent nodes per-unit reactance of the branch As electrical distance weight; Step S22: Define the vulnerability transmission factor Evaluation from the end node The vulnerability of any downstream path to fault energy conduction is calculated using the vulnerability conduction factor formula:

[0007] In the formula, Branches in the path The per-unit value of reactance, branch road The real-time load factor, i.e., the ratio of apparent power to thermal stability limit; Step S23: Filter out The three paths with the highest values ​​constitute the set of high-risk transmission paths. .

[0008] Furthermore, step S3 includes the following steps: Step S31: In the set of high-risk transmission paths Real-time monitoring of the active power change rate of each branch. When one branch road of Exceeding the preset impact climb threshold At that time, it is determined that an overloaded branch is about to experience a cascading trip; Step S32: Overload branch The receiving node Centered on the target area, search outwards for the closest electricalally accessible location equipped with an energy storage system. nodes Among them, the electrical distance is closest to that of the receiving end node. The sum of path reactances to each candidate energy storage node is minimized; Step S33: Define the node containing the receiving node Energy storage nodes and the receiving node With energy storage nodes The minimum spanning tree region of the connected paths is the virtual electrical isolation section. The boundary of the virtual electrical isolation section is defined by a set of circuit breakers connected to the external network. constitute.

[0009] Furthermore, step S4 includes the following steps: Step S41: The main station sends data to the virtual electrical isolation section. Internal energy storage system Issue the island defense mode activation command and simultaneously send a command to the boundary circuit breaker. Issue a simultaneous disconnection command; Step S42: In The disconnection action is executed continuously to create a virtual electrical isolation section. Decoupled from the main grid, forming an energy storage system Supported energy islands at the receiving end can be disconnected without waiting for the power balance calculation results of the entire network; Step S43: At the moment the island is formed, the energy storage system The converter control mode is switched from grid-based to grid-connected, and the voltage reference of the islanded system is established using the virtual synchronous machine parameters preset in the energy storage system. and frequency reference .

[0010] Furthermore, step S5 includes the following steps: Step S51: After the island is formed, the overload branch... Transient energy flowing in from the main grid is confined to the virtual electrical isolation section. Internal energy storage system The local controller utilizes the energy storage terminal voltage and output current Real-time calculation of instantaneous active power upon entering the island and no merit ; Step S52: Introduce a power absorption strategy based on adaptive adjustment of virtual impedance, and define a dynamic virtual resistance. and dynamic virtual inductance Dynamic virtual resistance is used to increase damping, absorb active power, and suppress frequency surges during the initial stage of active power surges, and gradually return to its base value during the steady-state recovery period to reduce losses; dynamic virtual inductance is used to adjust reactive power support according to the rate of frequency change and suppress voltage fluctuations. and dynamic virtual inductance The calculation formula is:

[0011]

[0012] In the formula, , Based on virtual impedance, , For adaptive gain coefficients, For voltage deviation, The rate of change of frequency, The decay time constant; Step S53: The energy storage converter corrects the output reference voltage based on the dynamic virtual impedance. The reference voltage correction formula is:

[0013] In the formula, This is the base value of the rated voltage. ω is the angular frequency.

[0014] Furthermore, step S5 includes the following steps: Step S61: When the energy storage system The local controller detected the frequency within the island. and voltage amplitude In continuous When the fluctuation range within a power frequency cycle meets the stability criterion, it is determined that the impact energy has been completely absorbed and the island has reached a quasi-steady state. The stability criterion is:

[0015] In the formula, For the rated frequency, This is the rated voltage amplitude. For frequency tolerance, This refers to the allowable voltage deviation. Step S62: Energy Storage System Actively adjust the output voltage phase The voltage phase measured by the residual voltage transformer at the disconnection point of the main grid is tracked. ; Step S63: When the conditions for simultaneous grid connection are met At this time, the islanded controller sends a reconnection permission signal to the master station, and the master station sequentially closes the boundary circuit breakers. Each circuit breaker in the circuit creates a virtual electrical isolation section. Seamless connection back to the mainnet; Step S64: Energy Storage System Switch back from the network configuration mode to the follower network mode and re-accept the global optimization scheduling instructions from the master station.

[0016] The present invention has the following beneficial effects: 1. Upon detecting a branch overload impact, this invention does not perform full-network optimization calculations but directly disconnects the preset virtual electrical isolation section boundary circuit breaker, limiting the fault energy to the minimum topology range. The energy storage system instantly switches to a network-based control mode in the islanded state, autonomously establishing voltage and frequency references, and can complete the control mode conversion without relying on master station communication. The above mechanism compresses the response delay to the execution time of the disconnection action, completing spatial blocking in the early stage of cascading fault propagation, avoiding control failure caused by calculation delays, and improving the timeliness of power grid security defense under extreme conditions.

[0017] 2. This invention uses the direction of fault impact energy transmission as a basis to dynamically search for the minimum spanning tree region containing the overloaded branch receiving node and energy storage node, constructing a virtual electrical isolation section that precisely corresponds to each fault event. By disconnecting the boundary circuit breaker of the section, the transient energy of the fault is guided into a controlled, finite topology space, rather than allowing the energy to spread freely throughout the network. This approach enables the energy storage system to act as an energy absorption terminal, spatially cutting off the physical path of fault energy transmission to the next level of lines, and energyally consuming and storing transient energy through virtual impedance adaptive adjustment, achieving cascading fault interruption in both spatiotemporal dimensions.

[0018] 3. This invention introduces a virtual impedance adaptive adjustment strategy based on voltage deviation and frequency change rate. In the initial stage of an impact, the virtual resistance is automatically increased to enhance damping and power absorption, while the virtual inductance is adjusted to suppress voltage fluctuations. After the impact energy decays, the virtual resistance gradually returns to its base value through an exponential decay term. The energy storage converter corrects the output reference voltage based on the dynamic virtual impedance. The entire process is completed in a closed loop by the local controller, without relying on external communication. Even in an information-constrained environment like an isolated system, it can quickly smooth out transient impacts, improving the robustness of the energy storage system in independently coping with cascading fault energy impacts.

[0019] 4. This invention incorporates a stability detection mechanism within the isolated system, requiring that the frequency and voltage amplitude meet allowable deviations for multiple consecutive power frequency cycles before initiating the grid connection process. The energy storage system actively adjusts its output voltage phase to track the main grid phase, and after meeting the synchronous grid connection conditions, the master station sequentially closes the boundary circuit breakers. This process ensures that the isolated system and the main grid are synchronized at the moment of grid connection, eliminating the risk of transient impacts caused by asynchronous grid connection. After grid connection, the energy storage system smoothly switches from grid-connected mode back to grid-following mode, restoring its responsiveness to master station dispatch, achieving a seamless transition from proactive defense to normal operation.

[0020] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a flowchart illustrating an energy dispatch optimization method for energy storage systems aimed at grid security, according to the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Please see Figure 1 As shown, this invention provides an energy dispatch optimization method for energy storage systems aimed at grid security, comprising the following steps: Step S1: Wide-area measurement data synchronization and initial fault feature extraction. The voltage phasor of the grid node and the power of the branch are obtained in real time through the phasor measurement unit. After the branch tripping is detected, the cross-sectional power flow data before the tripping branch fault is extracted as the reference value for energy impact calculation. Step S2: Dynamic identification of cascading fault propagation paths based on electrical distance. Starting from the end node of the tripped branch, the path vulnerability transmission factor is calculated using the branch reactance and load rate to screen the set of high-risk transmission paths. Step S3: Search and define virtual isolation sections based on power flow transfer impact, monitor the active power change rate in the high-risk transmission path set, and when the change rate exceeds the impact ramp-up threshold, search for the minimum electrical distance area containing energy storage nodes as the virtual electrical isolation section, centered on the overload branch receiving node, and determine the set of circuit breakers at the section boundary. Step S4: Transient construction and synchronous control of energy island at the receiving end of the energy storage system. Send the island defense mode command to the energy storage system within the virtual electrical isolation section, disconnect the boundary circuit breaker set to make the section separate from the main grid to form an energy island at the receiving end, and switch the energy storage converter from the grid-following mode to the grid-building mode to establish island voltage and frequency reference. Step S5: Based on the energy balance, the local controller of the energy storage system dynamically adjusts the virtual resistance and virtual inductance based on the virtual impedance adaptive adjustment strategy, corrects the converter reference voltage, absorbs transient energy and suppresses voltage frequency fluctuations. Step S6: Island stability detection and smooth grid-connection recovery control. When the frequency and voltage amplitude in the island meet the stability judgment conditions, the energy storage system adjusts the output voltage phase to track the main grid phase. When the synchronous grid connection conditions are met, the boundary circuit breaker is closed in sequence, and the energy storage converter switches back to the grid-following mode.

[0025] Step S1 includes the following steps: Step S11: The dispatch center master station uses the phasor measurement unit to... The sampling period is used to obtain the voltage phasor amplitude of each node in the power grid in real time. and phase angle and the active power of each branch. With reactive power ; Step S12: Capture the initial fault occurrence time using the switch quantity change information of the data acquisition and monitoring control system. When a branch is detected After the relay protection trips, the topology location of the tripped branch is locked and the cross-sectional power flow data of the previous cycle before the fault is extracted. This serves as the baseline value for subsequent energy impact calculations.

[0026] Step S2 includes the following steps: Step S21: Connect the end node of the trip branch downstream first-order adjacent nodes per-unit reactance of the branch As electrical distance weight; Step S22: Define the vulnerability transmission factor Evaluation from the end node The vulnerability of any downstream path to fault energy conduction is calculated using the vulnerability conduction factor formula:

[0027] In the formula, Branches in the path The per-unit value of reactance, branch road The real-time load factor, i.e., the ratio of apparent power to thermal stability limit; Step S23: Filter out The three paths with the highest values ​​constitute the set of high-risk transmission paths. .

[0028] Step S3 includes the following steps: Step S31: In the set of high-risk transmission paths Real-time monitoring of the active power change rate of each branch. When one branch road of Exceeding the preset impact climb threshold At that time, it is determined that an overloaded branch is about to experience a cascading trip; Step S32: Overload branch The receiving node Centered on the target area, search outwards for the closest electricalally accessible location equipped with an energy storage system. nodes Among them, the electrical distance is closest to that of the receiving end node. The sum of path reactances to each candidate energy storage node is minimized; Step S33: Define the node containing the receiving node Energy storage nodes and the receiving node With energy storage nodes The minimum spanning tree region of the connected paths is the virtual electrical isolation section. The boundary of the virtual electrical isolation section is defined by a set of circuit breakers connected to the external network. constitute.

[0029] Step S4 includes the following steps: Step S41: The main station sends data to the virtual electrical isolation section. Internal energy storage system Issue the island defense mode activation command and simultaneously send a command to the boundary circuit breaker. Issue a simultaneous disconnection command; Step S42: In The disconnection action is executed continuously to create a virtual electrical isolation section. Decoupled from the main grid, forming an energy storage system Supported energy islands at the receiving end can be disconnected without waiting for the power balance calculation results of the entire network; Step S43: At the moment the island is formed, the energy storage system The converter control mode is switched from grid-based to grid-connected, and the voltage reference of the islanded system is established using the virtual synchronous machine parameters preset in the energy storage system. and frequency reference .

[0030] Step S5 includes the following steps: Step S51: After the island is formed, the overload branch... Transient energy flowing in from the main grid is confined to the virtual electrical isolation section. Internal energy storage system The local controller utilizes the energy storage terminal voltage and output current Real-time calculation of instantaneous active power upon entering the island and no merit ; Step S52: Introduce a power absorption strategy based on adaptive adjustment of virtual impedance, and define a dynamic virtual resistance. and dynamic virtual inductance Dynamic virtual resistance is used to increase damping, absorb active power, and suppress frequency surges during the initial stage of active power surges, and gradually return to its base value during the steady-state recovery period to reduce losses; dynamic virtual inductance is used to adjust reactive power support according to the rate of frequency change and suppress voltage fluctuations. and dynamic virtual inductance The calculation formula is:

[0031]

[0032] In the formula, , Based on virtual impedance, , For adaptive gain coefficients, For voltage deviation, The rate of change of frequency, The decay time constant; Step S53: The energy storage converter corrects the output reference voltage based on the dynamic virtual impedance. The reference voltage correction formula is:

[0033] In the formula, This is the base value of the rated voltage. ω is the angular frequency.

[0034] Step S5 includes the following steps: Step S61: When the energy storage system The local controller detected the frequency within the island. and voltage amplitude In continuous When the fluctuation range within a power frequency cycle meets the stability criterion, it is determined that the impact energy has been completely absorbed and the island has reached a quasi-steady state. The stability criterion is:

[0035] In the formula, For the rated frequency, This is the rated voltage amplitude. For frequency tolerance, This refers to the allowable voltage deviation. Step S62: Energy Storage System Actively adjust the output voltage phase The voltage phase measured by the residual voltage transformer at the disconnection point of the main grid is tracked. ; Step S63: When the conditions for simultaneous grid connection are met At this time, the islanded controller sends a reconnection permission signal to the master station, and the master station sequentially closes the boundary circuit breakers. Each circuit breaker in the circuit creates a virtual electrical isolation section. Seamless connection back to the mainnet; Step S64: Energy Storage System Switch back from the network configuration mode to the follower network mode and re-accept the global optimization scheduling instructions from the master station.

[0036] One specific application of this embodiment is: This embodiment is applied to a 10kV urban power distribution network scenario, which includes 12 nodes and 15 distribution branches. Node 7 is equipped with a 2MW / 2MWh lithium iron phosphate electrochemical energy storage system; the system's rated frequency... Rated voltage amplitude The base power is set at 10 MVA. The specific execution process of the energy dispatch optimization method for energy storage systems oriented towards grid security described in this embodiment is as follows: Step S1: Wide-area measurement data synchronization and initial fault feature extraction Step S11: The dispatch center master station uses the phasor measurement unit (PMU) to... A fixed sampling period (single power frequency cycle) is used to collect the voltage phasor amplitude of each node in the power grid in real time. With phase angle and the active power of each branch. With reactive power All measurement data are synchronized at the microsecond level via fiber optic communication.

[0037] Step S12: Capture the initial fault moment using the switch change signal from the Supervisory Control and Data Acquisition System (SCADA). In this embodiment, the branch The system immediately located the branch topology and extracted the cross-sectional power flow data of the previous cycle before the fault due to the lightning strike causing the relay protection to trip. , This serves as the benchmark value for subsequent energy impact calculations.

[0038] Step S2: Dynamic identification of cascading fault propagation paths based on electrical distance Step S21: Using the tripped branch Starting from the terminal node 5, the per-unit reactance values ​​of the branches between node 5 and its downstream first-order adjacent nodes 6 and 8 are used as the electrical distance weights. , .

[0039] Step S22: Define the vulnerability transmission factor The vulnerability of any path extending downstream from node 5 to fault energy conduction is assessed using the following formula:

[0040] In the formula, Branches in the path The per-unit value of reactance, branch road The real-time load factor is the ratio of apparent power to thermal stability limit.

[0041] In this embodiment, the three candidate paths are calculated as follows: Path 5-6-9: , ; , Substituting into Path 5-8-11: , ; , Substituting into Path 5-8-10: , ; , Substituting into Step S23: Press The values ​​are sorted from largest to smallest, and the top three paths are selected to form a set of high-risk transmission paths. .

[0042] Step S3: Search and definition of virtual isolation sections based on power flow transfer impact Step S31: Monitor the rate of change of active power in real time for all branches within the set of high-risk transmission paths. Preset impact climb threshold After the fault occurred At that time, the branch road was monitored. of If the threshold is exceeded, it is determined that the branch is about to experience a cascading trip.

[0043] Step S32: Overload branch Centered on receiving node 9, the search extends outwards to the node with the closest electrical distance and equipped with an energy storage system; the calculated sum of the path reactance from node 9 to energy storage node 7 is... Since the value is the minimum among all candidate energy storage nodes, node 7 is selected as the energy storage node for this defense. .

[0044] Step S33: Define the minimum spanning tree region containing receiving node 9, energy storage node 7, and the connecting branch between them as the virtual electrical isolation section. The boundary of this section is formed by three circuit breakers connecting to the external network, i.e., the boundary circuit breaker set. .

[0045] Step S4: Transient construction and synchronization control of energy islands at the receiving end of the energy storage system Step S41: The dispatch master station immediately sends a signal to the virtual electrical isolation section. Internal energy storage system Issue the island defense mode activation command and simultaneously send a command to the boundary circuit breaker. Issue a simultaneous disconnection command.

[0046] Step S42: In The disconnection action is executed at all times, disconnecting all boundary circuit breakers, so that the virtual electrical isolation section is separated from the main grid, forming an energy island at the receiving end independently supported by the energy storage system. This disconnection action does not need to wait for the power balance calculation results of the whole grid, and is executed directly after being triggered, so as to reduce the response delay.

[0047] Step S43: At the same moment the island is formed, the converter control mode of the energy storage system seamlessly switches from grid-following to grid-building mode, and the voltage and frequency references of the island system are established using preset virtual synchronous machine parameters.

[0048] The virtual inertia is set to The damping coefficient is set to .

[0049] Step S5: Reactive-Active Coordination Impact Suppression within an Island Based on Energy Balance Step S51: After island formation, the transient energy generated by power flow transfer is confined within the virtual electrical isolation section; the local controller of the energy storage system collects the voltage at the energy storage terminal. With output current Real-time calculation of instantaneous active power entering the island With reactive power In this embodiment, the peak impact time , .

[0050] Step S52: Employ a power absorption strategy based on adaptive adjustment of virtual impedance to define a dynamic virtual resistance. With dynamic virtual inductance The dynamic virtual resistance increases damping in the initial stage of an impact to absorb active power and suppress frequency surges, and gradually returns to its base value in the steady-state stage to reduce losses; the dynamic virtual inductance dynamically adjusts the reactive power support strength according to the rate of frequency change to suppress voltage fluctuations. The calculation formulas for both are as follows:

[0051]

[0052] In the formula: Basic virtual impedance , ; Adaptive gain coefficient , ; Voltage deviation ; decay time constant .

[0053] At the peak of the impact, the voltage deviation was measured. Rate of change of frequency Substituting, we get:

[0054]

[0055] As the impact energy decays, the virtual resistance gradually returns to its base value along with the exponential term.

[0056] Step S53: The energy storage converter corrects the output reference voltage in real time based on the dynamic virtual impedance. The correction formula is as follows:

[0057] In the formula, This is the base value of the rated voltage phasor. This is the system angular frequency. Through this correction, the energy storage converter can actively absorb transient energy and smooth out voltage and frequency fluctuations within the island.

[0058] Step S6: Islanding Stability Detection and Smooth Grid-Connected Recovery Control Step S61: The local controller of the energy storage system continuously monitors the islanded operation status, when the frequency... and voltage amplitude In continuous When the stability criterion is met for all power frequency cycles, the impact energy is considered to have been completely absorbed, and the islanding system enters a quasi-steady state. The stability criterion is:

[0059] In this embodiment, the allowable frequency deviation Voltage tolerance Approximately after the fault occurred If the indicators within the isolated system continuously meet the above conditions, the system is considered stable.

[0060] Step S62: The energy storage system actively adjusts the phase of the output voltage. The voltage phase measured by the residual voltage transformer at the disconnection point of the main grid is tracked. The phase difference is gradually reduced.

[0061] Step S63: When the phase difference meets the conditions for synchronous grid connection (This embodiment) When the islanded controller sends a grid connection permission signal to the master station, the master station closes the three circuit breakers in the boundary circuit breaker set in a preset order, so that the virtual electrical isolation section can be seamlessly connected back to the main grid and the grid connection process is not significantly impacted.

[0062] Step S64: After grid connection is completed, the converter of the energy storage system smoothly switches back from grid-connected mode to grid-following mode, reconnects to the master station's global optimization and scheduling system, and resumes normal operation.

[0063] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0064] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. An energy dispatch optimization method for energy storage systems oriented towards grid security, characterized in that, Includes the following steps: Step S1: The voltage phasors of the grid nodes and the power of the branches are acquired in real time through the phasor measurement unit. After the branch tripping is detected, the cross-sectional power flow data before the tripping branch fault is extracted as the reference value for energy impact calculation. Step S2: Starting from the terminal node of the tripped branch, calculate the path vulnerability transmission factor using the branch reactance and load rate, and screen the set of high-risk transmission paths; Step S3: Monitor the active power change rate in the high-risk transmission path set. When the change rate exceeds the impact ramp-up threshold, take the overload branch receiving end node as the center, search for the minimum electrical distance area containing the energy storage node as the virtual electrical isolation section, and determine the set of circuit breakers at the section boundary. Step S4: Issue an island defense mode command to the energy storage system within the virtual electrical isolation section, disconnect the boundary circuit breaker set to make the section separate from the main grid and form a receiving-end energy island, and switch the energy storage converter from the grid-following mode to the grid-building mode to establish island voltage and frequency references; Step S5: The local controller of the energy storage system dynamically adjusts the virtual resistance and virtual inductance based on the virtual impedance adaptive adjustment strategy, corrects the converter reference voltage, absorbs transient energy and suppresses voltage frequency fluctuations; Step S6: When the frequency and voltage amplitude in the island meet the stability judgment conditions, the energy storage system adjusts the output voltage phase to track the main grid phase. When the synchronous grid connection conditions are met, the boundary circuit breaker is closed in sequence, and the energy storage converter switches back to the grid-following mode.

2. The energy dispatch optimization method for an energy storage system oriented towards grid security according to claim 1, characterized in that, Step S1 includes the following steps: Step S11: The dispatch center master station uses the phasor measurement unit to... The sampling period is used to obtain the voltage phasor amplitude of each node in the power grid in real time. and phase angle and the active power of each branch. With reactive power ; Step S12: Capture the initial fault occurrence time using the switch quantity change information of the data acquisition and monitoring control system. When a branch is detected After the relay protection trips, the topology location of the tripped branch is locked and the cross-sectional power flow data of the previous cycle before the fault is extracted. This serves as the baseline value for subsequent energy impact calculations.

3. The energy dispatch optimization method for an energy storage system oriented towards grid security according to claim 1, characterized in that, Step S2 includes the following steps: Step S21: Connect the end node of the trip branch downstream first-order adjacent nodes per-unit reactance of the branch As electrical distance weight; Step S22: Define the vulnerability transmission factor Evaluation from the end node The vulnerability of any downstream path to fault energy conduction is calculated using the vulnerability conduction factor formula: In the formula, Branches in the path The per-unit value of reactance, branch road The real-time load factor, i.e., the ratio of apparent power to thermal stability limit; Step S23: Filter out The three paths with the highest values ​​constitute the set of high-risk transmission paths. .

4. The energy dispatch optimization method for an energy storage system oriented towards grid security according to claim 1, characterized in that, Step S3 includes the following steps: Step S31: In the set of high-risk transmission paths Real-time monitoring of the active power change rate of each branch. When one branch road of Exceeding the preset impact climb threshold At that time, it is determined that an overloaded branch is about to experience a cascading trip. Step S32: Overload branch The receiving node Centered on the target area, search outwards for the closest electricalally accessible location equipped with an energy storage system. nodes Among them, the electrical distance is closest to that of the receiving end node. The sum of path reactances to each candidate energy storage node is minimized; Step S33: Define the node containing the receiving node Energy storage nodes and the receiving node With energy storage nodes The minimum spanning tree region of the connected paths is the virtual electrical isolation section. The boundary of the virtual electrical isolation section is defined by a set of circuit breakers connected to the external network. constitute.

5. The energy dispatch optimization method for an energy storage system oriented towards grid security according to claim 1, characterized in that, Step S4 includes the following steps: Step S41: The main station sends data to the virtual electrical isolation section. Internal energy storage system Issue the island defense mode activation command and simultaneously send a command to the boundary circuit breaker. Issue a simultaneous disconnection command; Step S42: In The disconnection action is executed continuously to create a virtual electrical isolation section. Decoupled from the main grid, forming an energy storage system Supported energy islands at the receiving end can be disconnected without waiting for the power balance calculation results of the entire network; Step S43: At the moment the island is formed, the energy storage system The converter control mode is switched from grid-based to grid-connected, and the voltage reference of the islanded system is established using the virtual synchronous machine parameters preset in the energy storage system. and frequency reference .

6. The energy dispatch optimization method for an energy storage system oriented towards grid security according to claim 1, characterized in that, Step S5 includes the following steps: Step S51: After the island is formed, the overload branch... Transient energy flowing in from the main grid is confined to the virtual electrical isolation section. Internal energy storage system The local controller utilizes the energy storage terminal voltage and output current Real-time calculation of instantaneous active power upon entering the island and no merit ; Step S52: Introduce a power absorption strategy based on adaptive adjustment of virtual impedance, and define a dynamic virtual resistance. and dynamic virtual inductance Dynamic virtual resistance is used to increase damping, absorb active power, and suppress frequency surges during the initial stage of active power surges, and gradually return to its base value during the steady-state recovery period to reduce losses; dynamic virtual inductance is used to adjust reactive power support according to the rate of frequency change and suppress voltage fluctuations. and dynamic virtual inductance The calculation formula is: In the formula, , Based on virtual impedance, , For adaptive gain coefficients, For voltage deviation, The rate of change of frequency, The decay time constant; Step S53: The energy storage converter corrects the output reference voltage based on the dynamic virtual impedance. The reference voltage correction formula is: In the formula, This is the base value of the rated voltage. ω is the angular frequency.

7. The energy dispatch optimization method for an energy storage system oriented towards grid security according to claim 1, characterized in that, Step S5 includes the following steps: Step S61: When the energy storage system The local controller detected the frequency within the island. and voltage amplitude In continuous When the fluctuation range within a power frequency cycle meets the stability criterion, it is determined that the impact energy has been completely absorbed and the island has reached a quasi-steady state. The stability criterion is: In the formula, For the rated frequency, This is the rated voltage amplitude. For frequency tolerance, For voltage tolerance; Step S62: Energy Storage System Actively adjust the output voltage phase The voltage phase measured by the residual voltage transformer at the disconnection point of the main grid is tracked. ; Step S63: When the conditions for simultaneous grid connection are met At this time, the islanded controller sends a reconnection permission signal to the master station, and the master station sequentially closes the boundary circuit breakers. Each circuit breaker in the circuit creates a virtual electrical isolation section. Seamless connection back to the mainnet; Step S64: Energy Storage System Switch back from the network structure mode to the follower network mode and re-accept the global optimization scheduling instructions from the master station.

Images