74 results about "Transient analysis" patented technology

The invention discloses a fire fighting system intelligent management method and device based on intelligent property management, and relates to the technical field of data management. The intelligent management method and device for the fire fighting system based on the intelligent property management comprises the following steps: S1, dynamically triggering and collecting a multi-source fire fighting data set through multiple protocols, and temporarily storing the multi-source fire fighting data set at the edge in a normalized manner; s2, constructing an event full-period window and a ternary association index of the event, the time sequence data and the original message; s3, performing double-track storage of the semantic analysis data and the original message, and constructing multi-dimensional index association; s4, reconstructing a visual playback alarm process through edge cloud increment synchronization and a multi-dimensional time sequence chain; and S5, performing transient analysis, protocol upgrading and responsibility evidence obtaining based on the cloud data collaborative link and the original message data set. According to the method, the complete acquisition of the fire-fighting data and the reproducibility of the event process are effectively improved, and the problem that in the prior art, only polling recording of single-point alarm is carried out, and an original message is discarded, so that the transient process and message-level evidence is lost is solved.

The invention discloses a series-parallel system transient stability analysis and fault ride-through control method considering current limiting, and belongs to the field of power fault analysis. In order to reveal an action mechanism of a current amplitude limiting and converter coupling effect on the transient synchronization stability of the hybrid system, the method comprises the following steps: firstly, considering the influence of control mode switching of a constructed network type converter, and establishing a transient analysis model of the hybrid system considering a current amplitude limiting link; then, based on a phase plane method, analyzing an action rule of converter control parameters on system transient stability, determining an optimal active power reference value and a saturation current phase angle of the grid-forming converter during a fault period, and proposing a fault ride-through control strategy according to the optimal active power reference value and the saturation current phase angle; and finally, verifying the correctness of theoretical analysis and the effectiveness of the proposed control strategy through multi-working-condition simulation.

The application provides a floor grinding machine gear box guide plate structure parameter optimization design method, which is used for determining the optimal values of three radial clearances between the guide plate and the gear tooth top. Firstly, a parameterized gear box model containing clearance as a variable is constructed, and a gear oil stirring loss theoretical model is established based on the boundary layer theory and the fluid resistance theory; taking the maximum lubrication efficiency as the target and the oil stirring power loss not exceeding the set threshold as the constraint condition, a central composite design method is used to select representative sample points in the design space; through computational fluid dynamics simulation, a moving particle semi-implicit method is used for splash lubrication transient analysis to obtain performance data of each point; based on the simulation data, a high-precision proxy model is constructed; finally, under the condition of meeting the oil stirring power loss constraint condition, the maximum lubrication efficiency is taken as the target for optimization solving to obtain the optimal clearance combination. The method realizes the quantitative design from parameters to performance, and effectively replaces the traditional trial and error method.

The application provides an electromigration reliability non-uniform discrete equivalent circuit modeling method and system, adopts an equivalent circuit-based method to analyze electromigration stress evolution of a general complex interconnection structure, fully considers a thermal field effect in a model, realizes stress analysis equivalent circuit modeling under multi-physical field coupling, and solves the problem of waste of computing resources in processing large-span interconnection structures by using a traditional uniform discrete method, avoids unnecessary transient simulation on an immortal interconnection tree, reduces the computing load of full-chip-level analysis, and realizes efficient and high-precision transient analysis of electromigration reliability of a large-scale interconnection network under multi-physical field coupling effects.

The invention relates to the technical field of industrial data analysis, and discloses an original data feature analysis system in water meter detection, comprising: a pulse data aggregation unit for acquiring an original pulse time sequence; the time sequence difference processing unit is used for receiving the original pulse time sequence and executing first-order difference operation to generate a first-order time sequence difference value sequence; the feature decoupling shunting unit is used for executing logic locking by using a monitoring carrier environment baseline scalar, and dividing a first-order time sequence difference value sequence into a steady state processing channel and a transient analysis channel; the intrinsic mode mapping unit is used for pre-storing intrinsic mode feature vectors; the transient distortion judgment unit is used for extracting the frequency domain feature vector, executing orthogonal projection mapping with the intrinsic mode feature vector and outputting an effective transient distortion tensor, the problem of feature information entropy collapse of the high-frequency pulse sequential sequence in the dimensionality reduction aggregation process is solved, and a semantic gap between an information processing domain and a physical design domain is eliminated.

The invention belongs to the technical field of transient analysis of a new energy grid-connected system, and particularly relates to a transient overvoltage analysis method of a direct-driven wind power grid-connected system under an asymmetric fault, which comprises the following steps: acquiring three-phase asymmetric voltage and current, and constructing a positive and negative sequence dq control model of positive and negative sequence bisynchronization of a direct-driven wind power plant station; establishing a mapping relation with a symmetric component method, and determining a positive-sequence dynamic reactive current increment and a negative-sequence current suppression coefficient according to a converter control strategy; establishing sequence network boundary conditions under various asymmetric faults; enabling the direct-driven wind power plant to be equivalent to a frequency-related controlled sequence impedance source, and obtaining equivalent sequence impedance of the wind power plant; establishing a sequence network equation considering wind power dynamic support; calculating the current and sequence voltage of the fault point, and obtaining a three-phase voltage through symmetric component inverse transformation; and an overvoltage coefficient is calculated, and a quantitative relational expression between the overvoltage coefficient and the negative-sequence current suppression coefficient is established and applied. The method provides theoretical support for parameter setting and capacity planning of the wind power integration system.

The invention provides a mechanical arm event trigger control transient analysis and trigger controller design method based on response characteristics. The mechanical arm event trigger control transient analysis and trigger controller design method comprises the following steps that 1, a mechanical arm input and output response model is constructed; 2, system input serves as a piecewise function, and a trigger control transient relation is analyzed; and step 3, proposing a new time constraint event triggering strategy to avoid a sesame phenomenon. According to the method, the transient process is combined, the time constraint condition is introduced, the mechanical arm event triggering control strategy is established, the false triggering frequency is reduced, the sesame phenomenon is avoided, and the communication overhead is reduced.

The invention relates to the field of photovoltaic grid-connected management and control, in particular to an intelligent grid-connected management and control method and platform for a photovoltaic power station, and the method comprises the following steps: collecting the operation information of a target photovoltaic power station, carrying out the transient analysis, and constructing a transient operation state set; performing continuous time tracking on the transient operation state set to generate a photovoltaic evolution track; performing comprehensive change frequency analysis on the photovoltaic evolution track to obtain a change frequency matrix; synchronously acquiring operation parameters of a power grid side; performing grid-connected risk assessment on a change frequency matrix according to the power grid side operation parameters, and generating a grid-connected risk assessment value; grid-connected risk assessment is carried out based on the grid-connected risk assessment value, and when it is judged that the target photovoltaic power station meets the direct grid-connected condition, synchronous grid-connected processing is executed; when it is judged that the target photovoltaic power station does not meet the direct grid connection condition, grid connection power modulation is carried out, and intelligent grid connection management and control processing is completed. According to the invention, the safety and stability of photovoltaic power station grid connection are effectively improved.

The invention provides a transient lubrication analysis method and system for a floating bush of a high-pressure fuel pump under the synergistic effect of cam shaft bending-torsional vibration and multiple friction pairs in order to solve the problems that the reliability, the efficiency and the service life of an engine are reduced due to the fact that a coupling mechanism of cam shaft vibration and floating bush lubrication in a marine diesel engine oil supply mechanism is not clear. Belongs to the technical field of high-pressure fuel pump camshafts. According to the method, a cam shaft bending-torsional vibration model integrating bending-torsional deformation is constructed, the synergistic effect of multiple friction pairs of a cam-roller and a floating bush is combined, a parallel transient lubrication analysis strategy is adopted, iterative solution including mechanical and thermal balance is carried out on each friction pair, oil film characteristic parameters are fed back to the bending-torsional vibration model to update boundary conditions, and the bending-torsional vibration of the cam shaft is obtained. And dynamic coupling convergence of system vibration and lubrication states is realized through time-marching iteration, and complete transient analysis of the cam-roller-roller pin system is completed. The method is suitable for designing a camshaft system of a marine diesel engine oil supply mechanism, and the operation stability of equipment can be effectively improved.

The invention discloses a full-power offshore wind turbine generator modular full-electromagnetic transient test method, which comprises the following steps: constructing a full-power fan monomer model, performing equivalent amplification on a fan internally adopting a multi-module parallel structure through a multiplication unit module based on the monomer model, obtaining an equivalent fan model, and establishing a working condition test module, by adjusting an input signal of an external power grid voltage source, the voltage amplitude, frequency and phase are controlled, and steady-state and fault working conditions under different power grid conditions are simulated; and finally, a control signal input and output relation is specified between the equivalent fan model and the working condition test module, so that modularized and extensible full-electromagnetic transient test is realized. According to the method, integrated, rapid and high-precision simulation of the single fan and multi-airport station-level modeling is realized, the modeling efficiency and example reusability are improved, and a standardized and modularized engineering technical scheme is provided for electromagnetic transient analysis of the wind turbine generator.

The invention relates to the technical field of product design and simulation, in particular to a sealing rubber strip abrasion state simulation evaluation method, device and equipment and a medium, and the method comprises the steps that geometric data of the section of a sealing rubber strip and the section of a corresponding metal plate are acquired, and a corresponding finite element analysis model is established based on the geometric data; applying a displacement amount corresponding to the target direction to the finite element analysis model to generate a corresponding pre-pressing analysis result, and adjusting the finite element analysis model according to the pre-pressing analysis result; and on the basis of the adjusted finite element analysis model, applying a movement speed to a sheet metal section rigid body to generate a corresponding dynamic transient analysis result, and evaluating the wear state of the sealing rubber strip according to the transient analysis result. Therefore, the problems that in the prior art, temporary remedial measures are generally adopted only after abrasion occurs, and the abrasion resistance cannot be fundamentally improved are solved.

The invention discloses an electric vertical take-off and landing aircraft demisting one-dimensional and three-dimensional coupling transient simulation analysis method, and belongs to the technical field of CFD simulation analysis, and the method specifically comprises the steps: firstly, building a one-dimensional simulation model S1 and a three-dimensional CFD simulation model S2; thirdly, coupling simulation is established for the one-dimensional simulation model S1 and the three-dimensional CFD simulation model S2, real-time circulation interaction of simulation data of the one-dimensional simulation model S1 and the three-dimensional CFD simulation model S2 is formed, demisting transient analysis is carried out, and the evaporation condensation flow process of a water mist layer on the surface of the windscreen of the aircraft is simulated; and then, whether the demisting performance of the air conditioning system meets the design requirement or not is evaluated according to the demisting transient analysis result. According to the method, the simulation requirement of the vertical take-off and landing aircraft in the internal and external circulation demisting function can be met, the actual demisting process is simulated, and the accuracy of demisting transient simulation analysis is improved.

This invention discloses a power grid risk early warning method based on digital twins, belonging to the field of power grid risk early warning technology. The method includes: firstly, integrating data from the power grid energy management system, production management system, and information security system to construct a digital twin base for the primary system physical model, the secondary system mechanism model, and associated operating modes; then, considering the virtual automatic voltage control constraint calculation baseline situation; subsequently, injecting hypothetical equipment faults, and linking the execution of electromechanical transient analysis, relay protection action prediction, standby automatic transfer action prediction, and power flow recalculation to form a predictive topology; further, combining power source backtracking and dynamic voltage difference calculation at both ends after virtual disconnection of tie switches, identifying single-source risks, risks from the same upstream power source, and risks of double circuits on the same pole. This method achieves unified extrapolation of power grid operating status, secondary device actions, and structural risks, improving the completeness, foresight, and targeted level of risk identification and response.

This invention discloses an efficient transient analysis method for electromagnetic-thermal-fluid multiphysics fields on integrated chips. Focusing on electromagnetic, thermal, and fluid fields as core research objects, and centering on typical scenarios of full electromagnetic-thermal-fluid coupling, it systematically integrates the governing equations, boundary conditions, and constitutive relations of each physical field to construct a unified set of coupled partial differential equations. Under the premise of verifying and satisfying the stability conditions of all physical field discretization schemes, simultaneous numerical solutions for the multiphysics fields are achieved through FDTD. This invention, through multi-faceted synergistic optimization, achieves comprehensive adaptation to complex structures, providing reliable technical support for solving various complex engineering multiphysics coupling problems.

This application relates to a strategy for improving the transient synchronization stability of a heterogeneous parallel system of VSG and GFL-ESS, including: obtaining the main circuit of the heterogeneous parallel system of VSG and GFL-ESS; determining the equivalent circuit structure of the heterogeneous parallel system of VSG and GFL-ESS based on the main circuit of the heterogeneous parallel system of VSG and GFL-ESS; constructing a transient analysis model of the heterogeneous parallel system of VSG and GFL-ESS based on the equivalent circuit structure of the heterogeneous parallel system of VSG and GFL-ESS; and determining the stable operation feasible region of the heterogeneous parallel system of VSG and GFL-ESS based on the transient analysis model. This application can, after a voltage drop in the distribution network, control the GFL-ESS to absorb active and reactive currents, thereby achieving transient power angle stability of the VSG while limiting its output current amplitude, ensuring stable grid-connected operation of the VSG during fault periods.

This invention provides a non-uniform discrete equivalent circuit modeling method and system for electromigration reliability. It employs an equivalent circuit-based approach to analyze the electromigration stress evolution of general complex interconnect structures, fully considering thermal field effects in the model. This achieves equivalent circuit modeling for stress analysis under multi-physics coupling. Furthermore, by using an adaptive mesh method with non-uniform spatial discretization and a steady-state / quasi-steady-state filtering mechanism, it solves the problem of wasted computational resources in traditional uniform discretization methods when dealing with large-span interconnect structures, and avoids unnecessary transient simulations of immortal interconnect trees, reducing the computational load of full-chip-level analysis. This enables efficient and high-precision transient analysis of the electromigration reliability of large-scale interconnect networks under multi-physics coupling effects.

The application provides a myocardial microsphere transient analysis method and device. The method comprises the following steps: obtaining a myocardial microsphere video, using a segmentation method to obtain a myocardial microsphere region of each frame in the myocardial microsphere video, determining the position of all myocardial microspheres of each frame according to the myocardial microsphere region obtained by each frame, finding corresponding myocardial microspheres between frames according to the nearest distance of myocardial microspheres between frames, selecting a reference frame and calculating a jumping strength and a jumping speed by using a frame difference method and a maximum value projection method, and generating a jumping strength curve and a jumping speed curve respectively, determining each wave peak according to the jumping curve, calculating a frequency according to the wave peak, and performing transient analysis on each wave peak. The myocardial microsphere region in the video is extracted by using the segmentation method to be analyzed separately, and the effect of simultaneously analyzing multiple myocardial microsphere videos can be achieved. The maximum value projection of the frame difference method result is obtained first, then the reference frame is automatically selected, and then the frame difference method result is multiplied by the maximum value projection, so that the noise can be suppressed.

This invention discloses a method and system for transient analysis of helium leakage in a nuclear fusion device, relating to the field of nuclear fusion safety analysis technology. The method includes the following steps: obtaining the structural parameters and operating parameters of the Dewar radiator of the nuclear fusion device; dividing the internal space of the Dewar radiator into multiple interconnected control volumes based on the structural parameters; establishing a set of transient analysis equations containing target physical quantities for each control volume based on the operating parameters; solving the transient analysis equations using a variable step-size integration method to obtain the transient time histories of the target physical quantities in each control volume; and converting the transient time histories of the target physical quantities into load data files recognizable by the target engineering analysis platform. This method, by dividing the internal space of the Dewar radiator into control volumes and solving the helium leakage transient process based on the divided structures, can accurately predict the pressure and temperature evolution under leakage accidents and generate load files that can be directly used for structural safety assessment, thus improving the efficiency of safety analysis and design optimization capabilities.

The invention relates to the technical field of automobile electronic manufacturing, in particular to an automobile oxygen sensor production line automatic test and inspection system based on a cloud platform. The system comprises a data acquisition module, a phase-space reconstruction module, a manifold analysis module and a feedback control module. The system collects parameters such as sensor voltage and heating rod current, and constructs a dimensionless phase space state vector; the core of the method is to calculate a difference integral between a vector actual evolution speed and a good product manifold field, and generate an accumulated trajectory deviation score to judge quality. According to the method, transient high-frequency data which does not reach heat balance is utilized, judgment depending on a long-time steady state is converted into short-time transient analysis, the problem that the production takt is slow due to the fact that heat balance needs to be waited is solved, and the detection efficiency is greatly improved.

The invention belongs to the technical field of electromagnetic transient characteristics, and particularly relates to a GIL partial discharge electromagnetic transient time domain finite element analysis method, which comprises the following steps: constructing a three-dimensional electromagnetic field simulation model according to actual structure parameters of a gas insulated metal closed transmission line; setting boundary conditions of electromagnetic wave propagation according to the three-dimensional electromagnetic field simulation model; respectively setting an oscillation type excitation source and a non-oscillation type excitation source in the three-dimensional electromagnetic field simulation model according to the physical characteristics of partial discharge; according to the three-dimensional electromagnetic field simulation model, the boundary condition and the excitation source, performing electromagnetic transient simulation calculation by adopting a time domain finite element method to obtain electromagnetic field time domain response data of each detection point in the space; according to the electromagnetic field time domain response data, electromagnetic field peak intensity and spatial distribution characteristics under different excitation sources are extracted, and electromagnetic transient characteristics of the two excitation sources are analyzed.

This invention discloses a modeling and current limiting method for grid-type energy storage that considers the short-circuit impedance phase angle. Addressing the issue of existing transient analyses neglecting the short-circuit impedance phase angle, this method establishes a fault transient model under non-metallic short-circuit grounding scenarios, correcting the analysis error caused by traditional transient analyses that only consider voltage drops. Based on this, this invention constructs an adaptive virtual impedance based on voltage and current deviations and proposes a hybrid current limiting strategy for actual fault scenarios, combined with a ring current limiter. This improves the transient modeling theory of grid-type energy storage and provides a reference for enhancing overcurrent limiting capabilities under large disturbances. Hardware-in-the-loop simulation results show that this hybrid current limiting strategy can achieve effective current suppression throughout the entire fault process, laying a solid foundation for the safe operation of power electronic equipment.

This invention discloses a reinforcement learning simulation step size control method based on closed-loop adaptive noise injection and entropy increase optimization strategy, belonging to integrated circuit computer-aided design technology. Specifically, the method involves: first, inputting the circuit netlist and interacting with the simulator using file read / write; next, establishing two new network output layers to convert the deterministic actions of the policy network's output into a probability distribution; then, obtaining the entropy regularization term based on the probability density function and weight coefficients, and adding it to the policy loss function; next, generating Gaussian-distributed exploration noise and adjusting the standard deviation of the noise at each step using a PID controller; finally, adjusting the policy network parameters using a gradient update method and injecting the exploration noise into the output actions to obtain the final time step. Using this invention helps enhance the simulation stability of pseudo-transient analysis, improves simulation efficiency, and provides a new method for DC analysis.

This invention relates to the field of geological engineering, specifically to a method and system for quantitatively analyzing the diffusion effect of synergistic grouting in water-rich soft rock fracturing and seepage. The method includes: conducting parameter tests and obtaining time-varying characteristic parameters through orthogonal experiments; establishing a coupled dynamic model including the grout volumetric flow rate equation, seepage motion equation, and flow continuity equation to obtain the spatiotemporal distribution of the grout field, the flow distribution coefficient of the dual-domain coupling, and the grouting parameters at different grouting times; constructing an index system with synergistic effects and obtaining quantitative values ​​of the diffusion effect. This invention constructs a dual-domain coupled dynamic model that couples the grout volumetric flow rate equation, seepage motion equation, flow continuity equation, and stress continuity equation, modifies the classical flow law to adapt to the grout yield stress characteristics, and achieves transient analysis through finite element numerical solution. It can output the spatiotemporal distribution of the grout field, the flow distribution coefficient, and the grouting parameters, and determine the micro-zone division boundary threshold based on experimental data.

The invention relates to the technical field of ships, and provides a vibration noise simulation analysis method and device, and the method comprises the steps: constructing a fluid domain model, a structural domain model and an acoustic model corresponding to an emptying valve; performing bidirectional fluid-solid coupling transient analysis on the fluid domain model and the structural domain model to obtain time domain vibration response data; according to the time domain vibration response data, acoustic simulation calculation is carried out through an acoustic model, and noise characteristics are obtained; and performing noise source contribution analysis according to the noise characteristics to determine a target noise source. According to the method, the fluid domain model, the structural domain model and the acoustic multi-domain model of the air exhaust valve are constructed, the time domain vibration response is accurately captured in combination with bidirectional fluid-solid coupling transient analysis, then noise characteristics are restored through acoustic simulation calculation, and finally accurate positioning of a core noise source is achieved through noise source contribution analysis. The authenticity of the vibration and noise association relationship is ensured, and the key noise source can be identified.

This invention belongs to the technical field of high-field magnet structure design, specifically involving an adaptive selection method for simulation type in pulse magnet structure design. The method includes: establishing a model of the pulse magnet; using a circuit model to calculate the actual current waveform of the magnet at the required power supply voltage; importing this waveform into an electromagnetic finite element model to calculate the peak electromagnetic load of the magnet; applying this load as a single step load to the structural finite element model; extracting the stress-time curve of each target component; and extracting the fundamental component of this curve using Fourier transform to determine the natural vibration frequency of the component. ω m Perform a Fourier transform on the actual current waveform to determine its fundamental component. ω i If all target components ω m All are greater than N × ω i If a steady-state simulation evaluation is selected, then this invention can solve the problem of the lack of a standardized operating system in the existing pulse magnet structure design that can reasonably use static analysis results to approximate transient analysis results.

The invention provides a lightning stroke transient analysis method and system for a high-voltage power transmission line. The method comprises the following steps: acquiring power transmission line parameters, material electromagnetic parameters and atmosphere lightning stroke channel parameters; acquiring a three-dimensional electromagnetic field partial differential model and performing space-time discretization based on the three-dimensional electromagnetic field partial differential model and a plurality of preset data to acquire electric field intensity, current density and magnetic field intensity; obtaining structural material parameters; acquiring simulation voltage data and simulation current data based on the data and a plurality of preset data; acquiring actually measured data, and calculating a rise time error, a wave crest amplitude error and a high-frequency component amplitude-frequency response error based on the three data; and if the preset convergence condition is met, realizing accurate simulation of the lightning stroke transient process of the high-voltage transmission line. According to the lightning stroke transient analysis method for the high-voltage transmission line, high-precision global simulation can be carried out on the lightning stroke transient process of the high-voltage transmission line, and reliable data support is provided for lightning protection design optimization.

The invention relates to a tracking-networking type hybrid system transient stability analysis method considering the influence of power coupling and current amplitude limiting, and belongs to the field of grid-connected control technology and system stability analysis. The method comprises the following steps: establishing a tracking-constructing network type converter hybrid system transient analysis model considering current amplitude limiting, introducing a global sensitivity analysis method, quantifying the contribution rate of each variable to the system response variance under the action of multi-parameter coupling, and realizing sensitivity identification of key parameters; based on a power angle characteristic curve and an expansion phase diagram theory, performing qualitative and quantitative analysis on transient response characteristics of the GFM converter in the whole fault process, and revealing a dynamic mechanism of the GFM converter; on the basis of an equal area rule, reasonable approximation is carried out on a damping effect, transient stability calculation is carried out on an established switching system, and a limit cut-off angle of the GFM under the influence of damping and power coupling is obtained through derivation. The method has accuracy and effectiveness under the conditions of different parameter settings and different faults.

The application discloses a pantograph-catenary arc electrical characteristic and transient overvoltage analysis method considering the influence of time-varying parameters, in which, in the transient analysis of pantograph-catenary off-line arc, time-varying impedance and capacitive impedance parameters of a traction network are introduced into the pantograph-catenary arc electrical characteristic formation process for the first time, and an improved arc model considering the influence of train speed and a fine train-track grounding system model are combined to realize the unified analysis of the overvoltage of a train roof and a train body, avoid the overvoltage evaluation deviation caused by the static traction network parameters and the simplified grounding model, and improve the accuracy and engineering applicability of the pantograph-catenary off-line arc transient overvoltage analysis.

The invention relates to the technical field of transient analysis of a power system, in particular to a zero-sequence equivalent model analysis method and system for a step-down self-coupling phase shifter, and the method comprises the steps: applying the same zero-sequence voltage condition to a self-coupling branch port of the step-down self-coupling phase shifter, building a zero-sequence current loop model of a self-coupling branch and a phase-shifting branch, and building a zero-sequence equivalent model of the self-coupling branch and a zero-sequence equivalent model of the phase-shifting branch; listing a port current relational expression; solving a current relation between the primary winding and the secondary winding of the phase-shifting transformer based on a magnetomotive force balance principle, and substituting the current relation between the primary winding and the secondary winding into a port current relational expression; deducing an equivalent zero-sequence reactance expression between a self-coupling branch and a phase-shifting branch in the step-down self-coupling phase shifter; establishing a zero-sequence equivalent model of the step-down self-coupling phase shifter based on the equivalent zero-sequence reactance, and calculating and simulating the zero-sequence current of the power grid under the conditions of single-phase grounding, two-phase inter-phase grounding or asymmetric grounding faults by using the equivalent model; and the influence on the zero-sequence current protection sensitivity of the corresponding line after the step-down self-coupling phase shifter is connected is evaluated.

The embodiment of the application discloses a dynamic phasor representation DC power system random transient analysis method, relates to the power electronic field of the DC power system, and can reflect system characteristics caused by source-load random excitation conditions and multi-rate simulation, and balance the contradiction between precision and efficiency. The application comprises the following steps: obtaining DC power system parameters and setting initial parameters; obtaining circuit models of two types of lumped elements in the DC power system; establishing a dynamic phasor model of a converter station in the DC power system and obtaining a dynamic companion circuit of the converter station; using the circuit models of the two types of lumped elements and the dynamic companion circuit of the converter station, establishing a model of the DC power system; obtaining node voltage equations of the DC power system; updating a node admittance matrix and an injected current vector according to changes in a switching function of the converter station; and converting dynamic phasors output by the model of the DC power system into instantaneous values.