196 results about "Short circuit ratio" patented technology

The invention discloses a power coupling-considered capacity ratio estimation method for a network-constructing / network-following multi-machine hybrid system, and the method comprises the steps: building a GFL-GFM hybrid system model, combining VSG power coupling small signal modeling and a dynamic relative gain matrix (DRGA), and quantifying the coupling strength of active / reactive power to output voltage; the frequency domain impedance characteristic of the GFM converter is simplified, and an ideal voltage source series equivalent reactance equivalent model is constructed; deriving an analytical relationship between a generalized short-circuit ratio (gSCR) and a capacity ratio based on the model, and generating a ratio formula in combination with engineering boundary sub-scenes to form a ratio range suitable for multiple scenes; for coupling time-varying characteristics, a closed-loop mechanism of'mixed mode-coupling sensing-correction calculation-execution feedback 'is constructed, and the ratio is dynamically adjusted. According to the method, coupling quantization and multi-machine coordination control are deeply fused, the problem that the external characteristic model precision and the multi-working-condition adaptability are difficult to consider under complex environment coupling is effectively solved, and the engineering applicability of the hybrid fan system is enhanced.

The invention discloses a stability evaluation and optimization method for a multi-infeed series-parallel new energy station based on equivalent external characteristics of a network construction type converter, and belongs to the technical field of electric power automation. Comprising the following steps: constructing a new energy multi-infeed hybrid system stability analysis closed-loop dynamic model, and simplifying a network construction type admittance transfer function; based on a stability analysis closed-loop dynamic model of the new energy multi-infeed series-parallel system, simplifying the new energy multi-infeed series-parallel system into an equivalent single-infeed system, and evaluating the stability of the equivalent single-infeed system through a generalized operation short-circuit ratio and a critical generalized operation short-circuit ratio; analyzing and quantifying the influence of key parameters of the network construction type equipment on the stability of the system through a parameter sensitivity analysis method; a node participation factor is used as an evaluation index, and control parameters are optimized based on a stability optimization method of key parameters of network construction type equipment of system weak nodes. The method provided by the invention has good effectiveness and reliability, and can realize gradual improvement and refined regulation and control of the system stability.

The invention relates to the technical field of stability analysis of a new energy grid-connected system, in particular to a new energy real-time short-circuit ratio margin evaluation method, system equipment and a medium, and the method comprises the steps: building an equivalent model based on power grid parameters, calculating equivalent capacity, and carrying out online correction in combination with multi-source data; calculating a new energy grid-connected short-circuit ratio according to the equivalent capacity ratio, calculating a short-circuit ratio index based on a constraint equation, refreshing a real-time index through measurement data of local voltage and current, and outputting a real-time short-circuit ratio; calculating the short-circuit ratio margin of the new energy station based on the short-circuit ratio difference value, quantitatively evaluating the stability, judging a stable state according to a positive value and a negative value of the margin, quantifying an instability risk level according to an absolute value of the margin, and generating a graded early warning signal and a control instruction; through dynamic fusion of multi-source data correction capacity, local measurement of millisecond-level refreshing indexes and margin positive and negative values, a control instruction is triggered, stable monitoring and active defense are realized, and the anti-disturbance capability and the safety level of a high-proportion new energy power grid are remarkably improved.

The invention relates to the technical field of power system planning, and discloses a new energy grid-connectable capacity margin evaluation method based on spatio-temporal distribution characteristics, which comprises the following steps: constructing a joint probability distribution model based on nonparametric kernel density estimation and a Copula function by using historical and meteorological data of a wind and light station, and generating a random output scene reflecting the spatio-temporal complementarity of wind and light resources; constructing a multi-dimensional stability constraint set containing a generalized short circuit ratio and broadband oscillation as a safety boundary of a random output scene; establishing a grid source interaction control strategy considering energy storage adjustment and direct current power modulation by taking grid-connected capacity maximization as a target, solving an optimal installed capacity scheme, and activating the grid source interaction control strategy to perform dynamic correction when a scene is out of limit; the maximum grid-connected capacity distribution meeting the constraint is counted, and the shadow price of the constraint is calculated to identify the bottleneck. According to the method, the wind and light resource complementary benefit and the system regulation potential can be quantified, and the new energy grid-connected capacity evaluation margin is improved on the premise of guaranteeing the safety.

The invention discloses a performance detection device for a network construction type converter suitable for new energy and energy storage, and relates to the field of power conversion equipment testing. The automatic test unit comprises a frequency adjustment test module, a phase jump test module, a short circuit ratio adjustment test module, a broadband harmonic injection test module, an island simulation test module, a source load switching test module and a damping test module. Compared with an existing test platform, the precision in the aspects of frequency, phase, short-circuit ratio adjustment and the like is improved, and the precision of a test result is ensured; testing of various complex working conditions such as isolated island operation, source load switching and broadband harmonic injection is supported, and all key working conditions possibly encountered by the power conversion system in practical application can be simulated; the system has an automatic testing function, various tests are automatically carried out through preset working conditions, a detailed analysis report is generated, and manual intervention is reduced.

The invention provides a smooth switching method of a converter network construction type control mode and a network following type control mode, and relates to the technical field of grid-connected control, and the method comprises the steps: obtaining a short-circuit ratio of a new energy grid-connected system; determining a current power grid type according to the short-circuit ratio of the new energy grid-connected system; under the condition that the current power grid type is determined to be a strong power grid and the converter operates in a network-building type control mode, a converter phase angle, a converter current reference value, an active power reference instruction value and a reactive power reference instruction value are respectively controlled to be switched into corresponding parameters in the network-building type control mode, and integral zero clearing operation is carried out on a converter current loop PI; and the converter is controlled to be switched to a network following type control mode. By means of the method, smooth switching between the network construction type control mode and the network following type control mode of the converter can be achieved.

The invention discloses a reactive compensation optimal configuration method and system of a new energy base, equipment and a medium, the method performs steady-state configuration of initial reactive capacity based on load flow calculation, can obtain effective steady-state reactive compensation configuration in a full output range, improves the robustness of steady-state reactive compensation, and improves the optimal configuration of the reactive compensation of the new energy base. A global coupling optimization architecture crossing steady state and transient state is constructed for the first time, closed-loop convergence of three optimization configuration stages is realized, so that global optimal configuration of reactive compensation is realized, and meanwhile, reasonable division and matching between two types of dynamic reactive compensation equipment, namely a phase modifier and an SVG / STATCOM, are realized; therefore, the new energy base not only can solve the transient voltage problem, but also has high power grid support strength, and the total configuration cost is greatly reduced while the requirements of standards, short-circuit ratio and transient voltage stability are met.

The invention discloses a mode switching method, device and equipment of an energy storage converter and a storage medium, and relates to the technical field of power grid control, and the method comprises the steps: obtaining a multi-mode control grid-connected model of the energy storage converter, and the grid-connected model comprises a grid-following type control model and a grid-constructing type control model; based on the grid-connected model, injecting a high-frequency small signal into a power grid through an energy storage converter, and processing the high-frequency small signal by adopting a discrete Fourier transform algorithm to obtain grid-connected point voltage and current response; obtaining a power grid impedance parameter according to the grid-connected point voltage and current response; calculating an operation short-circuit ratio according to the power grid impedance parameter in combination with the actual output power of the energy storage converter and the power grid voltage amplitude; according to the operation short-circuit ratio and the short-circuit ratio threshold value, mode switching is carried out on the following network type control and the construction network type control, and the method can improve the accuracy of mode switching of the energy storage converter.

The invention relates to the technical field of articles for old people, in particular to an adjusting method, system, equipment and medium for improving the short circuit ratio of a new energy station, and the method comprises the steps: calculating a first target index and a second target index of the new energy station, and switching a part of grid-connected converters into a virtual synchronous generator control mode; when the second target index does not meet the short-circuit ratio control requirement, changing the equivalent impedance of the grid-connected point by adjusting the virtual impedance of the virtual synchronous generator so as to reduce the second target index of the new energy station; and when the grid fault causes the voltage drop of the grid-connected point, reactive voltage control is carried out through the virtual exciter of the virtual synchronous generator, and voltage support is provided for the grid-connected point. The method has the beneficial effects that flexible and efficient dynamic adjustment is realized by using the virtual synchronous generator, the system operation efficiency is improved, and the short-circuit ratio of a new energy field station is improved by combining virtual impedance and a reactive power support function, so that the operation capability of the new energy field station in a weak power grid is enhanced.

The invention discloses a new energy openable capacity evaluation method, system, equipment and medium considering short-circuit ratio constraint, and belongs to the technical field of new energy openable capacity evaluation, and the method comprises the steps: calculating a new energy multi-station short-circuit ratio based on a ratio of an AC system equivalent short-circuit capacity to a new energy equivalent grid-connected capacity; calculating a new energy multi-station short-circuit ratio after the new station is accessed by considering the influence of adding the new energy station, and constructing a short-circuit ratio constraint by considering a critical short-circuit ratio limit value; considering constraint conditions, constructing a new energy openable capacity evaluation objective function, and forming an openable capacity evaluation model; and constructing a planning problem in combination with the constraint condition and the target function, and performing iterative solution on the planning problem based on a Benders decomposition algorithm to obtain a new energy openable capacity value under the corresponding condition. According to the method, starting from the influence of the access of the new energy station on the short-circuit ratio, the evaluation result of the new energy openable capacity of the power grid can be optimized, and an effective reference is provided for evaluation of the new energy openable capacity.

The invention provides a pure new energy large base network construction type equipment configuration method for direct current delivery through an island, and relates to the field of power grid planning, and the method comprises the steps: obtaining the multi-station short-circuit ratio condition of the boost transformer low-voltage side of a power generation unit of all new energy stations in a pure new energy large base, judging whether the short-circuit ratio condition meets a first preset condition or not, and according to a judgment result, determining whether the short-circuit ratio condition meets the first preset condition; selecting a corresponding new energy station to configure network energy storage, so as to enable the short-circuit ratio of multiple stations at the boost transformer low-voltage side of all power generation units to meet a first preset condition; obtaining an effective short-circuit ratio condition of the isolated island direct current, and configuring a network construction type SVG in the isolated island direct current, so that the effective short-circuit ratio of the isolated island direct current meets a second preset condition; and according to the configured networking type energy storage and the configured networking type SVG, forming a networking type equipment configuration scheme. According to the invention, the reasonable configuration of the network-forming type energy storage and the network-forming type SVG can be realized, and the power grid strength and the voltage supporting capability of the whole system are effectively improved.

The invention relates to the technical field of high-proportion new energy power systems, in particular to a method and system for calculating the short-circuit ratio of a network-following / network-constructing hybrid new energy power system, and the method comprises the steps: determining a network-constructing new energy access node, and deducing an impedance matrix of the network-following / network-constructing hybrid new energy power system; the system equivalent impedance calculation considering the virtual impedance control is used for considering the influence of the network construction type virtual impedance control on impedance characteristics; an improved new energy multi-station short-circuit ratio calculation model is given according to a traditional new energy multi-station short-circuit ratio simplification condition, the multi-station short-circuit ratio of any new energy node is calculated, and the influence rule of the access capacity, the connection reactance and the control characteristic of the network construction type new energy on the new energy multi-station short-circuit ratio of any node can be effectively evaluated; and the method can be further popularized and applied to strength calculation and influence law analysis of the power grid accessed by the converter with the network construction control characteristic.

The invention belongs to the technical field of grid-connected control of a power system, and discloses a method, equipment and medium for reducing a short-circuit ratio critical value of a new energy station, the method is applied to a grid-connected system, the grid-connected system comprises the new energy station and a grid-connected line for connecting the new energy station into a power grid, and the new energy station comprises a grid-following type converter. The method comprises the following steps: acquiring a rated capacity and a grid-connected voltage grade of a new energy station, and determining a pre-selected capacity of direct-current self-synchronization control networking type equipment; the method comprises the following steps of: deploying network construction type equipment in parallel at a main current collection bus side of a new energy station, configuring a direct current self-synchronization control ring on the network construction type equipment, and introducing equivalent inertia and damping characteristics into a direct current side voltage ring; and setting the parameters of the direct current self-synchronization control loop to reduce the short-circuit ratio critical value of the new energy station. The short-circuit ratio critical value of the new energy station is reduced on the premise of not transforming the infrastructure of the power grid side by introducing the network construction type equipment with the direct-current self-synchronization control function and setting the parameters of the network construction type equipment.

The invention discloses a low-voltage-crossing adaptive control method and device of a wind turbine generator, electronic equipment and a medium, and aims to solve the problems of slow system recovery, voltage overshoot and current out-of-limit in the current low-voltage-crossing control technology. The method comprises the following steps: acquiring running state data of a wind turbine generator at a grid-connected point in a low-voltage period in real time, and calculating a system short-circuit ratio according to the running state data; considering a power adjustment coefficient, and constructing a current feedback controller based on the operation state data; introducing an adaptive weighting strategy of a system short-circuit ratio, and combining a power adjustment coefficient to construct a multi-objective optimization function; the multi-objective optimization function is subjected to parameter optimization solution combined with system short-circuit ratio self-adaptive correction, and an optimized power adjustment coefficient is obtained; and substituting the optimized power adjustment coefficient into a current feedback controller, solving a control current value, and performing current control on the wind turbine generator based on the control current value.

The invention relates to a fault ride-through method based on hybrid synchronous control voltage / current source mode switching, aiming at fault ride-through (FRT) challenge in a novel power system, and breaking through the limitation of the existing solution from three key dimensions of overcurrent limitation, fault synchronization and reactive power support. On the basis of a hybrid synchronous control strategy, the damping characteristic of the system is remarkably improved, and the synchronous stability of the inverter during the fault period is effectively guaranteed; meanwhile, the intelligent control of smooth mode switching can be completed without complex switching logic or power grid information by utilizing simple detection of a saturation signal of a current limiter and combining with a mixed voltage / current source control architecture. Besides, the method has excellent short-circuit ratio (SCR) adaptive capacity, stable operation can be kept under different power grid strength conditions, and an innovative solution is provided for friendly improvement of new energy grid connection and transient performance optimization of a power system.

The invention discloses a direct-current transmission power evaluation method and device of a water-wind-light integrated base and a medium. The method comprises the steps that a direct-current transmission power evaluation model of the water-wind-light integrated base is established; the DC delivery power evaluation model takes DC power delivery maximization as an objective function and takes DC delivery power of each operation time period as a decision variable; according to the frequency response capability of the water-wind-light integrated base and the new energy multi-station short-circuit ratio, multiple safety constraints are constructed; the multiple security constraints comprise a frequency change rate security constraint, a maximum frequency deviation security constraint and a new energy multi-station short circuit ratio security constraint; adding multiple security constraints and multiple conventional constraints to the target function; and solving the target function to obtain the direct-current transmission power of the water-wind-light integrated base in each operation period. According to the invention, the problem of how to accurately evaluate the direct-current transmission power of the water-wind-light integrated base is solved.

The invention provides an optimal configuration method of a network construction type wind storage machine, a medium and computer equipment. The optimal configuration method comprises the steps that the machine end short-circuit ratio MRSCRG of each wind generating set connected to a power grid is calculated; calculating the grid-connected point short-circuit ratio MRSCRS of each wind power station accessed to the power grid; and according to the machine end short-circuit ratio MRSCRG of each wind generating set and the grid-connected point short-circuit ratio MRSCRS of each wind power plant station, determining the configuration mode of the grid-forming type wind storage machine.

The multi-inverter control mode self-adaptive switching method based on the operation short circuit ratio comprises the steps that an optical storage station grid-connected model is built, and inverter control modes are set to be a GFL mode and a GFM mode; acquiring operation data of a grid-connected point of the optical storage station, and calculating a numerical value of an operation short-circuit ratio (OSCR); when the operation short circuit ratio OSCR is smaller than C1 or larger than C2, the multi-inverter control mode switching optimization requirement is triggered; meanwhile, initializing a to-be-optimized variable; an MATD3 algorithm is adopted to determine an optimal switching combination of a multi-inverter control mode; issuing the output execution scheme of the optimal switching combination in the control period to a station inverter; when the operation short circuit ratio OSCR is between (C1 and C2), triggering the multi-inverter control mode switching optimization requirement again, outputting an optimal switching combination scheme by the MATD3 algorithm, and issuing the optimal switching combination scheme to the station inverter; wherein a part of the inverters are switched to GFL operation according to an optimization result, and the other part of the inverters are kept to control GFM operation in a network construction mode. According to the method, the collaborative minimization of dynamic voltage support and operation loss is realized.

The invention discloses a network construction type and network type energy storage combined control method, electronic equipment and a storage medium, and the method comprises the steps: firstly obtaining the inertia of a power grid and the short-circuit capacity of a grid-connected point of an energy storage power station, and calculating the short-circuit ratio of the grid-connected point of the power station; dynamically adjusting the basic operation proportion of the two types of energy storage according to the inertia and short-circuit ratio of the power grid; then determining the frequency deviation and the frequency change rate of the power grid, calculating the initial output of two types of energy storage in combination with the basic operation proportion, and executing hierarchical control: constructing network type energy storage dominated virtual inertia control based on the frequency change rate, and preferentially responding to the network type energy storage to primary frequency modulation control based on the frequency deviation of the power grid; and finally, dynamically distributing a real-time output weight by combining the power grid frequency deviation, the frequency change rate and the short-circuit ratio through the coordination controller, and carrying out weighted optimization on the initial output to realize collaborative adaptation of primary frequency modulation and virtual inertia control. According to the scheme, weak power grid stability improvement and fast frequency modulation active supporting capability are effectively considered, and the operation requirements of a high-proportion new energy power grid are met.

The invention discloses a flexible DC power transmission system grid following-grid construction hybrid control method, and the method comprises the following steps: obtaining the voltage and current of a receiving end MMC grid connection point, and carrying out the dq decomposition, thereby obtaining a d-axis component and a q-axis component under a dq rotating coordinate system; acquiring actual values and related reference values of direct-current voltage output by the receiving-end MMC, alternating-current voltage and frequency of a grid-connected point of the receiving-end MMC and average capacitance voltage of a sub-module; sequentially calculating a phase reference value of the receiving end MMC, a d-axis current reference value and a q-axis current reference value of the grid connection point, a d-axis voltage reference value and a q-axis voltage reference value of the differential mode voltage, a direct current reference value and a direct current modulation ratio reference value; and calculating the reference value of the modulation voltage of the receiving end MMC under the abc static coordinate system. The control method has the advantages of adapting to wide-range short-circuit ratio change of the receiving-end power grid, guaranteeing reliable transmission of power under the condition of wind speed change, and still maintaining synchronous operation when the receiving-end alternating-current power grid seriously breaks down.

The invention provides a new energy transmission system new energy-storage cooperative support control method under multiple constraints of a voltage stability domain, and relates to the technical field of power system voltage stabilization. According to the method, a model of reactive power, grid-connected voltage, active power and system parameters is established based on a power flow equation, and a required reactive reference is calculated by combining a set voltage expected value and real-time output power; and under the constraints of the voltage ride-through threshold, the converter capacity, the short-circuit ratio and the power margin, executing a new-storage cooperative voltage support strategy. Under the working conditions of new energy fault ride-through, output power out-of-limit and the like, the voltage stability can be remarkably improved, the output capacity of a new energy station is enhanced, and safe and stable operation of the system is ensured.

The invention is suitable for the technical field of converter configuration, and provides a capacity configuration optimization method and related equipment for a network tracking / constructing hybrid energy storage power station, and the method comprises the steps: constructing a capacity optimization objective function based on a short-circuit ratio; constructing a number constraint condition, an alternating current power flow constraint condition and a system stability constraint condition of the network tracking / constructing hybrid energy storage power station; and taking the capacity optimization objective function as a fitness function of a particle swarm optimization algorithm, and optimizing the capacity ratio of the tracking / networking hybrid energy storage power station by using the particle swarm optimization algorithm to obtain an optimal capacity ratio which has the minimum fitness function and meets a quantity constraint condition, an alternating current power flow constraint condition and a system stability constraint condition. According to the invention, an operable capacity ratio can be provided for the following / networking hybrid energy storage power station, so that the power station can meet engineering requirements.

The invention provides a new energy station voltage supporting capability evaluation method based on equivalent impedance. The method is suitable for a new energy power system with hybrid access of a constructed network type converter and a following network type converter. The method comprises the following steps: deducing an equivalent impedance model based on control parameters of the network-forming converter; constructing a new energy multi-station short-circuit ratio index considering the equivalent impedance characteristic; a hybrid new energy station model is constructed in a power system modeling platform, a voltage disturbance working condition is set, system dynamic response is simulated and analyzed, and the voltage supporting capacity is evaluated based on a short-circuit ratio index. The method can quantify the influence of the parameters of the network construction type converter on the system voltage support capability, supports the comparative analysis of the voltage support performance and the optimization of the control parameters, and provides a theoretical basis for the formulation of a multi-station coordination control strategy.

The invention discloses a matching analysis and solving method for a tracking-networking hybrid converter based on a grid-connected voltage short-circuit ratio. The method comprises the following steps: step 1, analyzing a flexible mechanism of a tracking and networking type converter; 2, analyzing the capacity ratio constraint of the hybrid system; step 3, connecting the following-networking single station into a large power grid for flexible deployment; and step 4, calculating to obtain the in-station tracking-networking unit proportion considering the multi-new energy station feed-in. The invention discloses a matching analysis and solving method for a tracking-networking hybrid converter based on a grid-connected voltage short-circuit ratio, and the method comprises the steps: analyzing the transient response characteristics of a system under large disturbance according to the working conditions of different short-circuit ratios; and the correctness of the provided capacity matching strategy is verified, and the stable operation of the system is ensured.

The invention discloses a self-adaptive regulation and control method, device and equipment for external characteristics of a new energy station in a network, and a medium, and the method comprises the steps: obtaining sensor parameters of the new energy station, an energy storage system and a flexible DC converter station, and constructing external characteristic parameters of the network; aiming at an alternating current side, performing outer-loop control and inner-loop control of the virtual synchronous machine based on a droop coefficient, a short-circuit ratio and voltage stiffness; for the energy storage system and the new energy field station, the output fluctuation condition of the new energy field station and the charge state of the energy storage system are determined according to sensor parameters, and in combination with the equivalent inertia and the droop coefficient, a combined frequency modulation strategy based on energy storage priority and a charge balance control strategy acting on an inner ring of an inverter are adopted for power distribution; through voltage fault detection, when a voltage fault occurs, an emergency control mode is entered and differential control is implemented according to a fault type; and parameter adaptive optimization is carried out according to the fault data of the historical record. According to the invention, the system control precision and the system stability are effectively improved.

The invention discloses a network following-construction flexible control converter and a self-adaptive ratio coefficient selection method thereof, a DNT-GCC comprises a control structure and a converter power circuit, and the control structure comprises a GFL control module, a GFM control module, a self-adaptive control module, a shared current loop and a stability analysis module; the control method comprises the following steps of: depicting a DNT-GCC stability domain which is a short-circuit ratio SCR coefficient and a GFM control coefficient, and correspondingly obtaining values of dynamic adjustment and GFL control coefficients corresponding to a stability domain boundary according to the strength of a power grid working condition so as to control a converter power circuit.

This invention provides an oscillation suppression method and system based on the D-segmentation method and considering the renewable energy transmission ratio and short-circuit ratio, relating to the field of power supply systems. The method includes: establishing an impedance model of the sending end of a wind farm-connected grid commutated HVDC transmission system; determining the first feasible region of the constant current controller's parameters based on the structure of the constant current controller at the sending end of the grid commutated HVDC transmission system; determining the second feasible region of the constant current controller's parameters corresponding to the renewable energy transmission ratio constraint based on the parameter stability control region of the constant current controller; and determining the third feasible region of the constant current controller's parameters corresponding to the short-circuit ratio constraint by combining the impedance model of the sending end of the wind farm-connected grid commutated HVDC transmission system and the short-circuit ratio constraint. This method controls the operation of the sending end of the grid commutated HVDC transmission system, achieving the advantage of oscillation suppression in systems with low short-circuit ratios and high renewable energy transmission ratios.

The invention relates to a power outer loop collaborative optimization virtual synchronous generator transient stability improvement method, and belongs to the technical field of virtual synchronous generator transient stability, and the method comprises the following steps: S1, building a virtual synchronous generator small signal power angle model; s2, performing active transient compensation and capacity constraint of power angle-frequency difference cooperative state feedback; s3, voltage deviation driven adaptive reactive power coefficient and active-reactive power combined current limiting are carried out; and S4, fault current impact suppression of the current-driven virtual impedance. The method can effectively reduce peak values and oscillation time of a power angle and a frequency difference, limit a fault current not to exceed a set upper limit, consider voltage support and active support capabilities, has good stability and robustness, and is suitable for controlling the grid-connected virtual synchronous generator under different short-circuit ratios and various fault working conditions.

This application relates to the field of power system stability control technology, specifically to a method and system for online stability assessment and control of hybrid systems based on an improved short-circuit ratio. The method includes: constructing an equivalent model of the integrated / grid-connected hybrid system; calculating the improved short-circuit ratio of multiple renewable energy power plants based on the voltage source characteristics of grid-connected equipment to quantify the grid strength at each grid connection point; constructing a characteristic polynomial based on the impedance matrix; and using the circular loop theorem to quickly search for the dominant eigenvalues, avoiding high-dimensional calculations, to obtain the critical short-circuit ratio. If the real-time short-circuit ratio is lower than the critical value, an instability risk is determined, triggering a control strategy that increases the capacity of grid-connected equipment or adjusts the grid connection point. This method, through the combination of the improved short-circuit ratio and the circular loop theorem, achieves online quantitative assessment and closed-loop control of the small-disturbance stability of integrated / grid-connected hybrid systems.

This application discloses a microgrid switching method, a coordination controller, and a power system, relating to the field of power system control technology. The method is applied to a coordination controller in a microgrid, which includes a master station and multiple substations. The microgrid also includes multiple power plants, which converge at a bus and connect to the grid through a grid connection point. The method includes: acquiring bus-side operating parameters and grid-side operating parameters at the grid connection point in real time through the master station; obtaining the real-time short-circuit ratio of the system using a power flow algorithm; determining the grid strength of the microgrid based on the real-time short-circuit ratio using a hysteresis strategy; determining the target mode based on the system operating conditions and / or grid strength; generating a mode switching command based on the target mode and issuing the mode switching command to each substation, so that each substation issues the mode switching command to the corresponding power plant according to the grid strength, thereby realizing the switching of the microgrid control mode. This application achieves the technical effect of improving the flexibility of coordinated control and realizing better intelligent control.