1353 results about "Islanding" patented technology

The present disclosure relates to the technical field of power systems. Disclosed are a distributed fault self-healing method and system for an active distribution network, and a device and a medium. In the present disclosure, using a two-terminal waveform difference as a faulty section locating principle is applicable to an active distribution network, which contains various types of DGs and different DG permeabilities. The present disclosure has a relatively low requirement for data computation and storage regarding an STU, and topology identification and update can be automatically completed during operation by simply configuring basic static network topology information for the STU, thereby adapting to a change in the operation mode of the network. By means of the present disclosure, a rational fault recovery rule is set, and important load nodes can be recovered as much as possible while meeting a network power constraint. In a recovery solution, the presence of distributed generation is taken into consideration, and different processing methods are designed according to whether the distributed generation can operate in an island manner for a long period of time.

The invention discloses a micro-grid dynamic coordination control method and system for distributed energy, and relates to the technical field of micro-grid energy management. The method comprises the steps of 1, collecting multi-source micro-grid data in real time, performing edge calculation and data preprocessing operation, and performing early judgment of an island mode; 2, converging the structure and state of each micro-grid, dynamically constructing and updating a micro-grid topological graph, analyzing the structure change and health condition of the micro-grid topological graph, and evaluating the comprehensive risk of micro-grid nodes; 3, calculating the actual distributable power of each type of loads, and carrying out autonomous control and elastic mode switching; and step 4, on the basis of the actual distributable power of each type of loads, evaluating the collaborative energy scheduling capability of the micro-grid in real time, performing role identification and implementing an optimization strategy. The problem of island emergency scheduling response lag caused by sudden failure of a main network due to some extreme events along with continuous expansion of the access scale of distributed energy and a micro-grid is solved.

The invention discloses a non-impact grid-connected recovery method, system and device for a coal mine isolated network power supply system and a medium, and belongs to the technical field of non-impact grid-connected recovery of power supply systems, and the method comprises the steps: monitoring the operation state of an isolated network, and obtaining voltage, frequency and phase parameters; preparation before grid connection is executed, and main network parameter confirmation and equipment verification are completed; performing parameter synchronous adjustment based on the controller to complete dynamic matching of voltage, frequency and phase; pre-synchronization control is implemented to realize phase prediction and power pre-balance; executing closing operation and performing impact suppression; carrying out stability regulation and control after grid connection, wherein the stability regulation and control comprise oscillation suppression and smooth load loading; and when grid connection is abnormal or fails, an emergency processing branch is entered, and standby power supply switching or island splitting control is triggered. Through multi-dimensional synchronous control, impedance reconstruction and hierarchical coordination mechanisms, high-precision and low-impact grid connection of multiple energy units under extreme working conditions is realized, and the grid connection stability and success rate of a coal mine isolated network power supply system are remarkably improved.

The invention provides an anti-islanding protection method based on cloud edge collaboration, and the method comprises the steps: obtaining historical fault data, carrying out the data processing of the historical fault data, obtaining a fault mode discrimination result, judging whether a micro-grid has an islanding operation risk or not through combining the topological structure information of a power grid, real-time operation data, and load demand prediction data, and obtaining an islanding protection result. If so, acquiring power output fluctuation data; the output power of the power supply and the load demand power are monitored in real time, if the output fluctuation of the power supply exceeds a voltage protection constant value or the load demand power exceeds a frequency protection constant value, the edge computing gateway starts a local anti-islanding control strategy, and meanwhile, the charging and discharging power of the power distribution network is adjusted; in the anti-islanding control strategy execution process, the edge computing gateway continuously collects real-time operation state data of the micro-grid, the power supply duration, the electric energy quality and the standby capacity of the micro-grid under islanding operation are evaluated according to the operation state data, and the multi-target optimization model and the operation constraint condition of the micro-grid are dynamically adjusted.

The invention relates to the technical field of hydrogen production, in particular to a micro-grid hydrogen production system based on dynamic optimization control and a multi-mode energy scheduling method. Comprising a renewable energy power generation unit which comprises at least two distributed power supplies with different power generation characteristics; the multi-stage hydrogen production device is configured to receive the electric energy output of the renewable energy power generation unit and perform proton exchange membrane water electrolysis hydrogen production; the hybrid energy storage system comprises a super capacitor bank and a lithium ion battery pack which are connected in parallel to the direct current bus through a bidirectional DC / DC converter; the dynamic optimization controller is internally provided with a multi-time-scale coordination algorithm and is used for acquiring meteorological prediction data, load demand data and an energy storage SOC state in real time; the multi-mode scheduling module comprises three working modes including an island operation mode, a grid-connected operation mode and an emergency standby mode; according to the scheme, hydrogen production economy, equipment durability and power supply reliability can be considered at the same time.

The invention discloses a mobile energy storage pre-layout and dynamic scheduling system and method oriented to toughness improvement of a power distribution network, and belongs to the technical field of power systems and intelligent power grids. In the pre-disaster stage, a two-stage robust optimization model fusing photovoltaic output uncertainty is constructed, and the configuration cost of mobile energy storage, the load reduction risk and the traffic accessibility of key nodes are comprehensively considered to generate an optimal deployment scheme; in a post-disaster stage, based on a traffic network state and a multi-source output characteristic, a multi-source collaborative dynamic scheduling model is constructed, a migration path, a charging and discharging strategy and charge state control of mobile energy storage are optimized in real time, and power supply loss of a key load is minimized. The system realizes rapid power supply recovery and safe operation in the island power grid by cooperatively controlling distributed resources such as mobile energy storage, electric vehicles, photovoltaic and diesel generators and the like. According to the invention, the quick response capability and recovery efficiency of the power distribution network under extreme disasters are significantly improved.

The invention discloses an active power distribution network two-stage island division method and system considering flexible resource support. The method comprises the following steps: establishing a first resource allocation model considering energy storage and controllable load, the first resource allocation model comprises energy storage battery charging and discharging upper and lower limit constraints, an energy storage battery degradation cost model, a controllable load model and a controllable load related user protocol; obtaining parameter data of a target power distribution system, wherein the parameter data comprises a line parameter, a load level, a load level, a network topology connection relationship, a system operation voltage level and branch current limitation, a system fault position, a reference voltage and a reference power initial value; and according to the parameter data, establishing a mathematical model for two-stage island power supply recovery based on a first resource allocation model. The method for solving the island is simple and convenient, the island recovery amount can achieve the optimal recovery effect, meanwhile, the search time is greatly shortened, the solving efficiency is higher, and the rapid power supply recovery capacity of the power distribution network is improved.

The invention relates to an active splitting and isolated island operation method based on load importance under a disaster condition, and belongs to the technical field of power systems and automation thereof. On the basis of disaster types and power supply area characteristics, constructing a load importance dynamic grading system, optimizing the weight through an analytic hierarchy process-index weight optimization collaborative algorithm, and combining with real-time updating to generate a grading result; the method comprises the following steps: deploying wide-area and local monitoring devices to collect power grid data, setting a safety threshold, triggering a splitting decision when the safety threshold exceeds the limit and the trend deteriorates, calculating an instability rate by using a multi-parameter collaborative instability pre-judgment algorithm, and starting pre-splitting preparation; and the main control center calls a target splitting section optimization algorithm to determine a section in combination with the grading result and the power grid data, generates a splitting instruction after verifying the stability of the island through load flow calculation, and performs classified stability control on the split island. The method can realize accurate load grading, early instability pre-judgment, guarantee of important load power supply such as medical treatment and the like, reduces catastrophe loss, and is suitable for power grid management and control under various disasters.

The invention provides a self-adaptive constraint model active mismatch prediction control method based on voltage and current ripple resistance of a power converter in a hybrid energy storage system, and the method comprises the steps: building an island DC micro-grid system model, collecting the voltage and current information of a system, and designing a model prediction control frame of a power loop and a cost function of the model prediction control frame; designing a model predictive control framework of the current loop and a cost function of the model predictive control framework; designing an active model mismatch mechanism to enhance the response capability to dynamic change; determining an optimization problem with a normal value, and designing an adaptive constraint optimization algorithm to dynamically adjust constraint parameters and optimize control performance; and designing a steady-state and dynamic-mode trigger for adapting to the running state of the system. According to the invention, the trajectory tracking precision of the system under dynamic and steady-state working conditions can be significantly improved, current ripples caused by control delay can be effectively eliminated, damage to electrical equipment due to overlarge ripples can be avoided, and the service life of the equipment can be prolonged.

The invention discloses an island detection method based on harmonic dynamic characteristics and reactive slip collaborative identification and a detection system thereof, and relates to the field of new energy island detection. In order to solve the defects of low feature extraction precision, threshold stiffness and insufficient response speed of existing island detection, an operation data set of a micro-grid system is acquired according to a topological structure of the micro-grid system; dynamic characteristic data fusion processing is implemented, and harmonic voltage is calculated; a harmonic voltage break variable is used as a starting criterion of island detection; sequentially judging whether the harmonic voltage break variable, the fundamental voltage amplitude and the offset of each harmonic voltage are out of limit or not so as to judge whether the micro-grid is in an island state or not; and constructing a virtual orthogonal signal to calculate a three-phase reactive slip ratio, judging whether the three-phase reactive slip ratio is out of limit, if not, determining that the microgrid is in a non-islanding state, and if yes, determining that the microgrid is in an islanding state. The method is mainly used for judging whether the microgrid is in the island state or not.

The invention relates to the technical field of distributed energy storage and intelligent power grid control, in particular to an intelligent distributed energy storage cluster collaborative management system. Comprising a state acquisition module used for acquiring local power grid state parameters of an edge computing node in real time; the power grid state parameters comprise power grid frequency, power grid voltage and a heartbeat communication state with the cloud management platform; the risk calculation module is used for calculating quantified island risk indexes; the mode judgment module is used for determining a current operation mode decision; the mode switching module is used for switching the system from a vertical cooperative mode to a horizontal autonomous mode when the island risk index is greater than an island switching threshold value; and when the island risk index is smaller than or equal to the island switching threshold value, the system is maintained to operate in the vertical cooperation mode. According to the system, misjudgment and missed judgment of a traditional single threshold value mode are overcome, it is ensured that the mode switching module can be switched to the horizontal autonomous mode from the vertical cooperative mode in time under the real risk, and decision making is accurate and reliable.

The invention discloses a high-proportion new energy power grid island division method considering frequency constraint, and belongs to the technical field of power system stability analysis and control, and the method comprises the steps: calculating a coherence coupling matrix of a generator and a new energy station through point voltage phase angle information; constructing a homology information undirected graph and calculating a normalized Laplacian matrix; performing characteristic value analysis, and determining the number of coherent generator groups and the coordinates of the generator and the new energy station; determining the composition of a coherent generator group through inverse mapping, and obtaining a multi-type power supply grouping result; establishing a coherence grouping constraint and a frequency security constraint according to a multi-type power supply grouping result; and constructing an island division optimal section search model and solving to obtain an optimal splitting section. By the adoption of the method, coherence grouping of multiple types of power supplies is achieved, and the optimal island division scheme is obtained by constructing and solving the island division optimal section search model considering the new energy supporting capacity and the frequency constraint.

The invention relates to the technical field of new energy intelligent decentralized control, and discloses a distributed photovoltaic power station intelligent monitoring method and system, and the method comprises the steps: collecting electrical state parameters, and carrying out the normalization processing; performing anomaly detection and island detection based on a multi-dimensional deviation fusion mechanism; generating a power support parameter through a self-adaptive reactive power injection mechanism; under the island mode, loading voltage frequency double-droop combined control; and after the main network is recovered, grid-connected reconnection is realized based on a phase progressive phase locking mechanism. Compared with the prior art that multi-dependence centralized master station judgment and scheduling cannot realize fault isolation and independent operation in time especially under the condition that main network communication is abnormal or frequency fluctuation occurs in a far-end island edge node, the technical problem that fault isolation and independent operation cannot be realized in time in the prior art is solved. Autonomous monitoring of an individual power station level and stable operation of an island are realized, and the stability of the system in a weak network or island operation scene is improved.

A meter socket adapter may include an integrated whole-building disconnect switch configured to disconnect a building associated with the meter socket adapter from a utility grid, a distributed energy resource (DER) interface to connect a distributed energy resource (DER), and an energy management system (EMS) configured to monitor electrical current passing through the meter socket adapter and, based on the monitored current, actuate the whole-building disconnect switch.

The invention discloses an island micro-grid operation scheduling method and device. According to the scheme, the method comprises the steps that power generation characteristic modeling is conducted on a distributed power source and an energy storage system of a diesel storage island micro-grid; constructing a function taking the minimum daily total operation cost as a target, wherein the function covers the operation cost of a diesel generator and an energy storage system and the pollutant treatment cost; establishing a power impact type load mathematical model including power characteristics, system dynamic frequency response characteristics, micro-grid dynamic frequency safety constraints and diesel generator frequency control constraints; establishing a micro-grid operation constraint model which has constraints such as power balance, Distflow power flow, energy storage, charging, discharging and capacity, diesel generator output and climbing rate; and solving the model by using a particle swarm optimization algorithm, generating a diesel generator output, energy storage system charging and discharging and frequency modulation reserve capacity distribution strategy, and obtaining an island microgrid optimal operation scheduling decision.

The invention discloses a power distribution network photovoltaic and energy storage configuration method considering island division and network reconstruction. The method comprises the following steps: collecting basic information of a power distribution network; monitoring output change and load fluctuation of a photovoltaic power supply in real time, constructing a photovoltaic power supply output model and a load time-varying model, and predicting photovoltaic output data and load demand data in the fault duration; determining an island range by using a breadth-first search algorithm by taking a load node directly supplied with power by the photovoltaic power supply as a starting point; based on an island division result, identifying residual load nodes of which the power supply is not recovered and network lines connected with the load nodes; the lowest comprehensive cost is determined as an optimization target, an electrical constraint condition is converted into a second-order cone constraint form, the optimization target and the electrical constraint condition are used for solving a network reconstruction problem for the fault duration, and a switch operation strategy is determined; power supply of the fault area is recovered; and performing configuration optimization on the photovoltaic power supply according to the load operation state in the island during the fault period of the power distribution network.

A transient stability control method for an islanding system with parallel heterogeneous networking inverters comprises the following steps: when a symmetric short-circuit fault occurs in a common line, collecting a grid-connected point voltage effective value of a droop control inverter and a frequency output value of a droop control and virtual synchronous generator; calculating a fault degree based on the voltage effective value, and determining a relative frequency by combining droop control and a VSG frequency difference value; generating a transient stability improvement coefficient according to the fault degree; the lifting coefficient and the relative frequency are fused through an integrator, and adjusting power is generated; injecting the adjusting power into the droop control equation to obtain an improved droop control equation; and combining the improved droop control equation and the VSG control equation to obtain an equivalent synchronous motion equation of the heterogeneous network-building type inverter parallel system during the fault period. According to the method, the power distribution is dynamically adjusted, the power transmission limit of the system during the fault period is improved, the transient stability under the serious fault is ensured, and an effective control scheme is provided for the micro-grid containing the heterogeneous inverter.

The invention relates to the technical field of micro-grid control, and discloses a micro-grid adaptive switching control method and system based on multi-source information fusion, and the method comprises the steps: obtaining the internal operation parameters of a micro-grid, and the state parameters of an external large power grid connected with the micro-grid; the internal operation parameters and the external large power grid state parameters are fused, and a real-time comprehensive operation state model of the micro-grid is constructed; based on the real-time comprehensive operation state model, adaptively determining a target operation mode of the micro-grid; and according to the target operation mode, generating and executing a smooth switching control instruction of the micro-grid. According to the method, the multi-source operation information of the large power grid inside and outside the microgrid is fused, the comprehensive operation state model is constructed in real time, the target operation mode is adaptively selected, and switching control is smoothly executed, so that efficient and stable switching of the microgrid between multiple modes such as grid connection and island can be realized, and the power supply reliability, the system stability and the electric energy quality are improved.

The invention discloses a power operation mode intelligent arrangement and risk prevention and control method under mass new energy access, and relates to the technical field of power system operation control, and the method comprises the steps: constructing a main distribution network architecture data model, carrying out the fusion processing of dynamic data of different voltage levels and professional attributes, and generating a system operation state model; based on the system operation state model, topological structure analysis is executed, and a network connection relation model is established; and calculating a new energy access optimization scheme according to the network connection relation model, and generating an operation mode arrangement result and a risk prevention and control strategy. According to the method, the problems of data islands and inaccurate topology identification in the prior art are effectively solved. By constructing the multi-objective optimization model, the new energy access capacity can be scientifically evaluated, the optimal operation scheme can be generated, and the operation efficiency, safety and reliability of a power system under the condition of massive new energy access are remarkably improved.

The invention discloses an optical storage grid-connected and off-grid operation method, which relates to the field of optical storage grid-connected and off-grid operation, and comprises a photovoltaic power generation unit, an energy storage unit, an intelligent switching unit, an energy management system (EMS), and grid-connected operation and off-grid operation controlled by the system, the grid-connected operation comprises the following steps: system connection: uniquely connecting a photovoltaic system with a power grid through an intelligent switch to realize second-level automatic grid connection; in the operation mode, the daily operation mode is grid-connected operation, and the energy storage system and the power grid jointly supply power to the load; and the system automatically or manually switches back to the grid-connected mode after detecting that the power grid recovers normal power supply. Through a current type control method, the voltage of the power grid is tracked, the magnitude of the output current is set, stable grid-connected operation is achieved, the islanding effect is avoided, it is ensured that the photovoltaic power generation system is automatically powered off when the power grid is powered off, the power grid safety is protected, and the charging and discharging process of the energy storage system is reasonably scheduled according to the load requirement and the photovoltaic power generation condition; the energy utilization efficiency is improved.

The invention provides a photovoltaic power station anti-islanding protection method, device and equipment and a storage medium, and relates to the technical field of power system protection. The method comprises the following steps: controlling an inverter of a photovoltaic power station to continuously inject a disturbance signal into a photovoltaic grid-connected system, and monitoring power measurement data of a grid-connected point after the disturbance signal is injected; when the electric power measurement data exceed a preset threshold range, determining that the electric power measurement data is abnormal; determining an abnormal duration in combination with historical power measurement data; and if the abnormal duration is greater than the abnormal duration threshold, the grid-connected switch is controlled to be switched off, and anti-islanding protection of the photovoltaic power station is realized. According to the method, the disturbance signal is actively injected, the detection sensitivity is remarkably improved, the abnormal duration is analyzed in combination with historical data, the islanding effect and instantaneous fluctuation are effectively distinguished, misjudgment is reduced, the islanding detection precision is remarkably improved, it is ensured that the islanding effect can be recognized and processed timely and accurately, and the islanding detection efficiency is improved. And the safety and the reliability of the operation of the photovoltaic power station are further enhanced.

The invention discloses a multi-mode hybrid energy storage cooperative control method and system for a megawatt-level network-building type energy storage power station, and the method comprises the steps: S1, collecting the frequency, voltage amplitude and phase of a power grid, and the charge state and temperature of each energy storage branch, and generating real-time monitoring data; s2, determining an operation mode of the energy storage power station based on a comparison result between the frequency deviation and the voltage deviation in the real-time monitoring data and a preset threshold value; s3, based on the operation mode of the energy storage power station, performing double-layer decomposition on the power instruction through a high-pass filter and a low-pass filter to generate a super-capacitor power instruction and a lithium battery power instruction; s4, generating an internal potential amplitude and a phase angle by adopting a virtual synchronous machine algorithm; and S5, on the basis of the amplitude and the phase angle of the internal potential and the detection result of the power grid connection state, executing switching control of a network construction type control mode or a network following type control mode. The millisecond-second level multi-time scale power optimal distribution is realized; self-adaptive inertia and voltage support is carried out; and island / grid-connected seamless switching is realized.

The invention relates to the technical field of energy storage systems, and provides a self-adaptive power distribution method and system for multiple energy storage units of an island microgrid. According to the invention, a discrete consistency algorithm is adopted to realize coordination control of multiple units, each unit only exchanges information with adjacent units, and power distribution targets of all the units are converged to a consistent value through iterative computation, so that the communication bottleneck and the single-point fault risk of centralized control are avoided; according to the invention, a complete fault-tolerant processing mechanism is designed, the operation state of each energy storage unit is monitored in real time, topology updating and power redistribution are automatically carried out when a unit fault is detected, and the self-healing operation of the system is realized. Experiments show that compared with a traditional method, the method has remarkable advantages in key performance indexes such as capacity balance among energy storage units, system operation efficiency, communication overhead and fault recovery time, and the operation efficiency and reliability of the island microgrid system are remarkably improved.

The invention relates to the field of clean energy, and provides a distributed secondary control method for an island micro-grid system based on event triggering, which comprises the following steps: S1, connecting adjacent distributed units in an island micro-grid through a local communication link, and constructing a distributed control architecture to eliminate dependence on a central controller; s2, triggering communication of the local communication link based on a preset threshold value, and transmitting a secondary control signal when the system state deviation exceeds the threshold value; s3, performing cooperative calculation on the secondary control signal by using the distributed control architecture, adjusting frequency and voltage deviation, and shielding original power data; and S4, connecting a newly added distributed unit to the distributed control architecture through the local communication link, thereby reducing high communication burden and single-point fault of centralized control of the island microgrid.

A meter socket adapter may include an integrated whole-building disconnect switch configured to disconnect a building associated with the meter socket adapter from a utility grid, a distributed energy resource (DER) interface to connect a distributed energy resource (DER), and an energy management system (EMS) configured to monitor electrical current passing through the meter socket adapter and, based on the monitored current, actuate the whole-building disconnect switch.

The invention provides a coordinated control method and device for flexible interaction of an optical storage and charging micro-grid and a power distribution network, and belongs to the technical field of intelligent power grids and distributed energy management. According to the method, through a day-ahead, intra-day and real-time three-layer coordination control architecture, the system operation cost is optimized, and the power grid stability is improved. The day-ahead layer generates a 24-hour scheduling plan based on photovoltaic output prediction, electric vehicle charging requirements and time-of-use electricity price; the intra-day layer performs rolling optimization in combination with real-time photovoltaic / load fluctuation, and dynamically allocates V2G and energy storage adjustment tasks; the real-time layer adopts adaptive droop control, monitors power grid abnormity and triggers cross-layer cooperation, and also sets photovoltaic fluctuation compensation and island mode switching conditions. Collaborative optimization is realized among the layers through bidirectional data channels. According to the method, the defect of interactive control of the optical storage and charging micro-grid and the power distribution network in the prior art is overcome, the adaptability of the system to distributed energy fluctuation is enhanced, the V2G resource potential is fully played, and the coping capacity under the abnormal condition of the power grid is improved.

The invention discloses a bidirectional self-adaptive inertia control method and device for an interconnected converter, and the method comprises a voltage source converter structure, a bidirectional inertia control method and self-adaptive inertia coefficient set.The bidirectional self-adaptive inertia control method and device are suitable for an AC-DC hybrid micro-grid so as to balance AC micro-grid frequency and DC micro-grid voltage dynamic response. Virtual synchronous motor control is adopted as a control outer ring to realize power adjustment and emergency control mode switching, an additional virtual capacitor control ring is designed to suppress the influence of high-frequency interference on a differential element, and the method can enable an IC to adjust a working mode to operate in a rectification or inversion state under a self-adaptive operation condition, so that the reliability of the IC is improved. The strategy enables the interconnection converter to smoothly adapt to three operation modes of grid connection, island power adjustment and island emergency control, thereby balancing the dynamic response characteristics of the two modes after disturbance, and achieving the improvement of the overall performance of the AC / DC micro-grid.

The invention discloses an island micro-grid reliability evaluation method and device considering a hybrid energy storage system, and the method comprises the steps: obtaining the operation parameters of an island micro-grid energy storage system, considering the uncertainty of load output, and the charge and discharge and capacity constraints of the energy storage system, building a load output model and an energy storage charge and discharge model, state parameters of the hybrid energy storage system are obtained, a multi-state model of the hybrid energy storage system is established, the state probability is solved, and a reliability index of the hybrid energy storage system is obtained; establishing a minimum load reduction strategy model on the basis of considering the load importance; and according to the hybrid energy storage system multi-state model, the energy storage charging and discharging model, the load output model and the minimum load reduction strategy model, constructing an island photovoltaic micro-grid reliability evaluation program containing the hybrid energy storage system, and outputting a reliability index of the hybrid energy storage system. And reliability evaluation can be carried out on the island photovoltaic micro-grid system containing the wind and light storage.

A device, method, and non-transitory computer readable medium for controlling a power distribution system includes an islanded microgrid and a control system. The islanded microgrid includes battery energy storage systems (BESSs) that operate as a primary energy source, and a decentralized consensus-based virtual synchronous generator (VSG). The control system simultaneously, emulates inertial response of a synchronous generator by the virtual synchronous generator during grid disruptions to regulate and stabilizes frequency of the islanded microgrid, and maintain consensus among the plurality of battery energy storage systems (BESSs).

The invention discloses an active island detection method and system based on harmonic impedance characteristic identification, and the method comprises the steps: analyzing the harmonic impedance difference of grid-connected points in a grid-connected state and an island state, and building a state criterion based on resonant frequency deviation and impedance amplitude through the comparison of the frequency response characteristics of island impedance and grid-connected impedance; fitting the grid impedance into an RLC parallel model in a selected frequency band, and mapping the topological difference of the power grid into a parameter difference; embedding a low-voltage ride-through strategy in the control of the voltage source converter, and adjusting reactive current in a grading manner according to the voltage drop degree of a grid-connected point; fundamental waves and harmonic waves are separated through a cascade notch filter, two synchronous harmonic waves are injected into the system through constant current control, and it is ensured that injection signals of a multi-voltage source converter are in the same phase in a phase locking link; and solving an overdetermined equation set based on the double-frequency response data to identify RLC parameters, setting an island criterion, and synchronously completing island judgment in a low-voltage ride-through time window. Detection precision is improved, dynamic response is optimized, and power generation efficiency is improved.