124 results about "Quasi steady" patented technology

The invention provides a multistage and multidirectional electromagnetic forming method comprising the following steps of: establishing a stable magnetic field area by adopting quasi-steady state current; generating induced eddy current in a workpiece by using pulse current; driving the part of the workpiece, which is positioned outside a female die, to be deformed away from the direction of the female die by using an electromagnetic force between the induced eddy current and the pulse current and driving the part of the workpiece, which is positioned inside the female die, to be deformed towards the direction close to the female die; and when the part inside the female die is deformed to an area of a stable magnetic field area, driving the workpiece to do accelerated motion to be attached to the female die under the action of induced eddy current in the stable magnetic field and the woprkpiece to finish the forming. The invention also provides a device for realizing the method, mainly comprising an edge pressing ring and coils arranged at different positions of the female die. According to the method and device disclosed by the invention, the workpiece is accelerated in a multistage and multidirectional electromagnetic forming manner, the forming, the processing and the manufacturing in a longer time and larger space range are realized and the forming depth of the workpiece is effectively increased.

The invention belongs to the technical field of mineral resources, and particularly relates to a method for computing unsteady state output of a shale gas reservoir complex fracture network. The method comprises the following steps that S1, basic parameters of shale gas reservoir strata and shale gas are collected, and a shale substrate porous media capillary tube permeability model is established; S2, shale gas reservoir microseism fracture imaging data is collected, a box method is applied to acquire fractal dimensions, a two-dimensional discrete fracture network model is established, and animproved cubic law is adopted to calculate the complex fracture network permeability; S3, it is considered that a shale gas reservoir fracturing horizontal well outer region is a substrate area infiltration area and a shale gas reservoir fracturing horizontal well inner region is a complex fracture network area flow area, and a shale gas reservoir fracturing horizontal well steady-state productivity model is established; according to a shale gas pressure propagation radius equation and a shale gas reservoir material balance equation, a continuous quasi-steady method is applied to establish ashale gas reservoir fracturing horizontal well unsteady state model. The method for the computing unsteady state output of the shale gas reservoir complex fracture network has the advantages that theconsideration factors are close to the actual conditions of strata, and computed results are more accurate.

The embodiment of the invention discloses a minimum life cycle net cost-based microgrid system optimal design method, which is used for confirming the optimum capacity configuration of each distributed power source and accumulation energy in the microgrid system in accordance with an operating strategy of a microgrid system and according to the conditions of the renewable energy sources resources, the load demands and the like in the microgrid system to guarantee the net cost to be within the life cycle, i.e. the cost is minimum. The method disclosed by the embodiment of the invention comprises the steps of: building a life cycle net cost-based target function of the microgrid system; confirming the optimal variable quantity of the target function according to the operating strategy of the microgrid system; confirming a constraint condition of the target function according to the operating strategy of the microgrid system; performing the quasi-steady-state emulation on the target function according to the constraint condition, and generating an optimal variable quantity combination to obtain an optimal computation result by means of the intersection and variation operations of a standard genetic algorithm; and confirming system parameters of the microgrid system according to the optimal computation result.

The invention discloses a method for establishing a dynamic and static aero-engine onboard model and belongs to the technical field of aero-engine control. Firstly, sample data compression is conducted through a similarity criterion and a taylor expansion principle so that the sample data size can be greatly reduced and time can be greatly shortened; then, a dynamic onboard model based on a sparse autocoder and a static onboard model based on a BP neural network are trained through dynamic data and static data in compressed sample data respectively; finally, corresponding quasi-steady-state judgment logic is set, the sparse autocoder dynamic model is used in the dynamic process, and the BP network static model is used in the static process. Compared with the prior art, the established aero-engine onboard model has higher precision under the dynamic condition and the static condition and is better in instantaneity and lower in requirement for data storage space.

The invention discloses a method for calculating a non-steady state yield of a volume fractured horizontal well of a shale gas reservoir. The method comprises the following steps of dividing the reservoir into a volume fractured region and a non-transformed matrix region, and collecting basic parameters of the volume fractured region, the non-transformed matrix region and the horizontal well, wherein the volume fractured region is Darcy flow, and the non-transformed matrix region is Knudson flow; according to a mass conservation law, establishing a steady-state yield formula of the volume fractured horizontal well of the shale gas reservoir; based on a pressure propagation formula, the steady-state yield formula and a matter balance equation, calculating the non-steady state yield of the volume fractured horizontal well of the shale gas reservoir by applying a continuous quasi-steady method; and repeating the previous step, and performing calculation to obtain the non-steady state yield of the volume fractured horizontal well of the shale gas reservoir. The method fully considers a process that a pressure is propagated to a boundary gradually in a production process of the volume fractured horizontal well of the shale gas reservoir, different seepage laws of shale gas in a volume transformation region and the non-transformed matrix region, and adsorption and desorption effects of the shale gas, so that actual conditions are better met.

The invention discloses a self-adaptive constant-on-time control circuit, which comprises a first transistor, a second transistor, a third transistor, a fourth transistor, a first operational amplifier, a first comparator, a first capacitive reactance unit, a first resistance unit and a switch unit. Due to the adoption of the self-adaptive constant-on-time control circuit, the problem of a traditional constant-on-time (Cot) control circuit that the working frequency is changed along with the input voltage can be solved, the quasi-steady working frequency under continuous conduction mode (CCM) status is realized, the on-off action of a power tube is reduced by reducing the working frequency under the discontinuous conduction mode (DCM) status, the on-off loss is reduced, the efficiency of a converter under a light load is improved, and the high efficiency of a full load section can be realized.

The invention discloses a hypersonic flight vehicle wing flutter damage estimation method based on dynamic flight. The method comprises the following steps: establishing a flutter model of a hypersonic flight vehicle wing according to a lagrange equation, and solving unsteady aerodynamics and a torque thereof of the wing according to a piston theory; by combining the established wing flutter model, and on the basis of a considering longitudinal short-period dynamatic model of the elastically-fluttered hypersonic flight vehicle, establishing a more accurate wing flutter model and analyzing quasi-steady aerodynamics and a torque thereof; and analyzing the influence of a wing flutter stress on the flutter damage of the wing according to a stress-strain model and a strain-fatigue service lifemodel, establishing a damage dynamic model, and acquiring damage information of the hypersonic flight vehicle when the wing flutters in a flight task process in real time. By adopting the method, thedefects that the existing flutter model is not dynamically associated with the flight of the whole airplane and only the local wing flutter damage is considered can be overcome, the wing flutter can be more accurately predicted, and the real-time wing flutter damage can be estimated.

The invention discloses a fast calculation method for dynamic plasma sheath radio wave propagation. The method comprises the following steps of establishing a mathematical model of a dynamic plasma sheath electron density based on a physical mechanism of the change speed of the electron density; then adopting a quasi-steady-state monte carlo method and a classical electromagnetic computing method on this basis to acquire a time-varying field intensity result of radio wave propagation of this complex random change medium. The invention is a simple, effective and fast radio wave calculation method, and can solve the radio wave propagation calculation of the dynamic plasma and avoid the high difficulty and high complexity by directly using a random medium modeling method to calculate.

The invention discloses a horizontal well gas-water two-phase numerical simulation method based on non-structural grids. The horizontal well gas-water two-phase numerical simulation method comprises the following steps of S1 carrying out the three-dimensional geologic body generation and grid dispersion of a low-permeability fractured reservoir horizontal well; S2 establishing a fractured tight reservoir multiphase flow seepage model; S3 carrying out the non-structural grid unit feature analysis and integral numerical calculation format establishment; S4 considering a horizontal well point grid quasi-steady-state well model of the flow characteristics in the horizontal well shaft; and S5 solving the established stratum seepage and wellbore internal flow coupling model, and analyzing the water saturation, stress sensitivity and other parameter sensitivities. According to the method, the horizontal well shaft flowing condition and the low-permeability reservoir micro-crack development characteristics are considered; a finite volume control method is adopted, a gas-water two-phase flow numerical solution of the low-permeability fractured reservoir is obtained on the basis of non-structural grids, and the problems that a traditional structural grid simulator is high in grid orientation, neglects stress sensitivity, ignores flow characteristics in a horizontal shaft and the like aresolved.

The invention relates to the field of information recognition, in particular to a voice information recognition method and terminal equipment. The voice information recognition method and the terminal equipment resolve the problem in the prior art that when a sound source of voice information to be recognized is not stable or sound transmission equipment generates interference, determined feature information has deviation easily. Voiced sound information is extracted from the voice information to be recognized, fundamental tone frequency parameters and an MFCC are extracted from the voiced sound information, the fundamental tone frequency parameters are processed to obtain a fundamental tone frequency parameter matching value, the MFCC is processed to obtain an MFCC parameter matching value, and the feature information of the voice information to be recognized is determined according to the fundamental tone frequency parameter matching value and the MFCC parameter matching value. Due to the facts that voiced sound in the voice information has the periodicity of a voice fundamental tone, the voiced sound information has a relatively fixed frequency in general, the characteristic of the voiced sound information can be treated as a quasi-steady-state process, and the probability that the feature information of the voice information determined according to the voiced sound information has mistakes is low.

The invention provides an experimental device for testing a heat conductivity coefficient of a building material based on quasi steady state and unsteady state methods, relates to the field of a testing technology of thermophysical parameters of a building material, and solves the problems that an existing thermophysical parameter experimental device can not simultaneously load the measurement processes by using three methods including a quasi steady state method, a normal power method and a heat pulse method, and one-time testing time is long and a measurement maximum relative error is large. An anode and a cathode of a low-potential potentiometer are correspondingly connected with a switch control interface of an oil immersed key conversion switch; thermoelectromotive force signals output by thermocouples are respectively connected into a thermoelectromotive force signal output end of the oil immersed key conversion switch; cold ends of the thermocouples are respectively inserted into an ice bottle containing an ice-water mixture; measuring ends of the thermocouples are respectively contacted with a testing piece to be tested; a heating resistor is used for heating the testing piece to be tested. The theoretical error analysis and the actual measurement prove that the measurement maximum relative errors are as follows: the heat conductivity coefficient is less than or equal to 5.1%, the thermal diffusivity is less than or equal to 9.2% and the specific heat value is less than or equal to 7.7%; the requirement on precision by engineering is met.

The invention discloses a variable temperature sample platform, belonging to the field of measuring a thermoelectric material. The variable temperature sample platform comprises a sample base, a sample rod and a connecting piece arranged between the sample base and the sample rod, wherein the sample base comprises a main heater, two temperature difference heaters, a substrate, an insulating padding plate, a sample padding block and a sample pressing block; a main heater pressing block is used for fixing the main heater; temperature difference heater pressing blocks are used for fixing the temperature difference heaters; the sample padding block is fixed on the substrate by virtue of a first fastener; the insulating padding plate is located between the sample padding block and the substrate; and the sample pressing block is fixedly connected to the sample padding block by virtue of second fasteners at two ends of the sample pressing block. The variable temperature sample platform disclosed by the invention is suitable for detection of thermoelectric potential under two modes, namely a steady-state mode and a quasi-steady-state mode, and can be used for simultaneously measuring a specific resistance.

The invention discloses a turbocharging system capable of changing charging modes when a turbine is placed centrally, and belongs to the technical field of internal-combustion engines. The turbocharging system comprises an air cylinder, an exhaust branch, exhaust pipes, a turbine, a connecting pipe and a valve, wherein one end of the connecting pipe is connected with a tail end of a first exhaust pipe, while the other end is connected with a second exhaust pipe at a position close to turbine. A first valve is arranged at a connection part of the first exhaust pipe and the connecting pipe, and a second valve is arranged in the connecting pipe close to the second exhaust pipe. When the two valves both close, the charging mode of the engine is pulse pressure-charging which has good performance during lowlaod and transient operating conditions of the engine; and when the both of the two valves open, the charging mode of the engine is quasi-steady pressure charging. Therefore, the high-load performance of the engine can be improved. The turbocharging system is reasonable in design, simple in structure, free from limitation of the number of cylinders and suitable for turbocharging device with two centrally placed turbines at a turbine inlet.

The invention discloses a safe and stable online comprehensive defense method for an electric power system, and belongs to the safe and stable control technical field of the electric power system. When the electric power system is in a quasi-steady-state operational state, a safe and stable prevention control online strategic decision specific to a preconceiving fault set, a safe and stable emergency control online pre-strategic decision specific to each preconceiving fault, and a safe and stable emergency control real-time strategic decision specific to the actual operational state of the electric power system are calculated separately; whether the duration between the operational moment and the current moment of the electric power system under the three kinds of control strategic decisions exceeds a corresponding constant value or not is taken as the effective criterion for each type of the control strategic decision; a to-be-executed control measure is determined by combination with the control strategic decision selection principle that the safe and stable emergency control real-time strategic decision is adopted firstly, the safe and stable emergency control online pre-strategic decision is adopted secondly, and the safe and stable prevention control online strategic decision is adopted finally in sequence; and therefore, a practical and effective method is supplied to the safe and stable online comprehensive defense of the electric power system.

The invention relates to a method for acquiring coordinated constraint upper and lower limits of provincial-regional coordinated busbar voltage, and belongs to the technical field of power system automatic voltage control. The method comprises that: based on quasi-steady-state sensitivity, a second time programming model is constructed to calculate the upper limit of the coordinated busbar voltage which can increase reactive power output of a provincial dispatching generator as possible under the conditions of meeting a generator busbar voltage constraint limit, a coordinated busbar voltage operating constraint limit, a monitoring busbar voltage constraint limit and a generator reactive power constraint limit, and the lower limit of the coordinated busbar voltage which can decrease reactive power output of the provincial dispatching generator as possible under the conditions of meeting the generator busbar voltage constraint limit, the coordinated busbar voltage operating constraint limit, the monitoring busbar voltage constraint limit and the generator reactive power constraint limit. The method can effectively reduce grid loss and improve voltage safety level of power grids.

The invention relates to a method for determinating semi-volatile organic compound emission parameters of indoor and in-vehicle materials, and belongs to the field of indoor and in-vehicle environmentinspection. The method comprises the following steps: building a physical model; placing the indoor and in-vehicle materials to be tested in an environmental chamber capable of strictly controlling the temperature and the humidity, inflating a certain flow to enable the materials to freely emit semi-volatile organic compounds till a quasi-steady state, and measuring the quasi-steady-state SVOC concentration value under the flow; changing the flow inflated into the environmental chamber for several times, and working out a series of quasi-steady-state concentration values corresponding to different flows; then, according to the physical model, calculating emission parameters such as the gas-phase SVOC concentration at a material interface and the convective mass transfer coefficient on thematerial surface in the emission process of the indoor and in-vehicle materials. By the method, operation is convenient, the test cycle is short and the precision is relatively high; the method is suitable for laboratory detection and engineering application.

The invention discloses a method for optimizing a PI parameter of a high-voltage direct-current transmission constant-current controller. The method includes the following steps of firstly, using a high-voltage direct-current transmission quasi-steady-state model as a calculation model for parameter optimization; secondly, calculating a target function; thirdly, initiating an algorithm parameter; fourthly, calculating the feasible region of the PI parameter; fifthly, optimizing a genetic algorithm; sixthly, embedding a simplex method to judge the condition; seventhly, optimizing a mixed algorithm. The method relies mainly on the genetic algorithm while the simplex method subsidiary, the simplex method is embedded after optimization of the genetic algorithm tends to stop, and the advantages of local optimization of the simplex method are utilized while the individual variation and the global optimization capacity of population of a traditional genetic algorithm are kept. The simplified mode, namely, the quasi-steady-state model which is widely adopted during direct-current power transmission engineering calculation, is adopted, and therefore the calculation speed is high, the calculation accuracy meets the engineering requirements, the method is suitable for optimizing the parameter of the direct-current transmission system controller, and the degree of combination between the method and practical engineering is high.

The invention discloses an online voltage stabilization assessment method for an alternating current and direct current system based on wide-area measurement. The method comprises the following steps:obtaining state quantity information under the current alternating current and direct current system based on real-time measurement; through the real-time measurement information of a direct currentsystem converter station, based on a direct current system quasi-steady-state mathematic model, establishing the online equivalent models of rectification side and inverter side converters respectively; based on wide-area measurement information and a direct current system converter equivalent model, establishing a load node Thevenin's equivalent circuit; expanding the voltage stabilization L index of an alternating current system into a voltage stability index applicable for the alternating current and direct current systems, and proposing the expanded L index to assess the voltage stabilityof the alternating current and direct current system. According to the method, the operation mode and control system actions of a direct current system can be taken into account accurately, and the voltage stability level of an alternating current and direct current power grid is assessed comprehensively by the system.

The invention provides a power system frequency situation prediction method based on deep learning. By taking unit regulation power of a unit, an active power disturbance quantity, a unit inertia level, a unit switch state, a rotating reserve level and a damping coefficient as input variables, and taking a frequency extreme value, a maximum frequency change rate and a quasi-steady-state frequencyas output variables, the frequency stability after a disturbance event is comprehensively judged. According to a deep learning method based on a stack extreme learning machine, a nonlinear mapping relation between input and output is built through a deep framework; in the process of layer-by-layer unsupervised training from bottom to top, an automatic encoder algorithm and a regularization coefficient are introduced; and a weight matrix between an input layer and a hidden layer is optimized layer by layer, so that a deep learning network can effectively represent a complex function, and the prediction precision and the generalization ability are improved. The method is used for online prediction of a frequency situation of a power system; and corresponding emergency control measures can beformulated according to prediction conditions, so that the system frequency collapse is prevented.

The invention discloses a method for predicting a membrane pollution tendency in a membrane distilled water processing system on the basis of a GA-LSSVM (Genetic Algorithm- Least Squares Support Vector Machine) model. The method comprises the following steps: firstly, utilizing an LSSVM algorithm to establish a prediction model in a membrane distilled sewage processing process; secondly, utilizing a GA to optimize the parameter of the prediction model independently under a quasi-steady state and an unsteady state; thirdly, utilizing the optimized prediction model to predict the change tendency of membrane flux and membrane pollution resistance independently under a quasi-steady state and an unsteady state, and analyzing an influence on the membrane flux and the membrane pollution resistance by the basic operation parameter of membrane distilling; and finally, carrying out sensitivity analysis and calculation on a prediction result, and determining a leading factor which affects the membrane flux and the membrane pollution resistance. The method utilizes GA-LSSVM to predict a change situation of the membrane flux and the membrane pollution resistance in real time, and the influence on membrane pollution by the basic operation parameter of the membrane distilling is clarified and quantized.

The invention relates to a creep deformation test method and platform of full-dimension pipeline bend. The invention is suitable for researching creep deformation mechanical behavior of non-standard sample with heavy gauge. A loading which is more than 200 kN is realized by servo motor, leading screw and guide rail slide block. A force transducer senses stress relaxation, and controls running of the motor, thereby realizing quasi-steady stress loading. A ceramic heater is used for heating and thermostatic control of the pipeline bend. Data acquisition is completed by a high temperature strain gauge, which is used for dynamic acquisition of strains at different directions. The invention can be used for full-dimension high temperature creep deformation test of high temperature part, and research of creep deformation damage mechanism of high temperature part under the state of multiaxial stress, thereby overcoming uncertainty of result brought by using creep deformation experiment result of miniaturization sample to evaluate a real member.

The invention discloses a construction method of a quasi-steady-state model of a direct-current system under an asymmetric fault. In a direct-current convertor station with extra-high voltage and extreme-high voltage, when an asymmetric fault happens on an alternating-current system, a control center in the station is used for obtaining the waveform information of triple-phase line voltage half cyclic wave of an inversion side alternating-current system, a zero-crossing moment of phase change line voltage is predicted through the practical waveform of asymmetric phase change voltage, a triggering moment of the trigger pulse of each thyristor valve block is improved so as to obtain the numerical values of direct-current average voltage and a phase change angle caused by the consideration of the change of the phase change voltage to obtain an improved quasi-steady-state model of the direct-current system under the asymmetric fault, and therefore, an alternating current / direct current hybrid power system can be quickly and accurately subjected to electromechanical transient simulation.

The invention discloses an airplane aerodynamic parameter partition multi-step identification method adopting an acceleration observer, and the problem in aerodynamic parameter identification performed according to the flight data in the prior art is partly solved. A aircraft angular acceleration observer, flight data multiple partition and information matrix singular value decomposition are as a core of the method. The characteristics and the advantages of the method comprises: the angular acceleration is accurately estimated by adopting a prediction observer of uniform acceleration model, an accurate aerodynamic moment coefficient is calculated by adopting a kinetic equation of the aircraft, so that the problem of the inaccurate estimation of the angular acceleration is effectively solved; the flight data collinearity question is detected and estimated through the singular value decomposition, so that the identifiable part of the aerodynamic parameter item can be accurately obtained; under the quasi-steady assumption, a linear model of aerodynamic parameter in each section is established through the flight data multiple partition, each aerodynamic parameter can be effectively identified by adopting the least square method, and the method is suitable for the large maneuvering flight data.

A method for correcting an actuator characteristic 32 of a clutch actuator 16 for a friction clutch 14 of a vehicle transmission 12 after the commissioning thereof. The actuator characteristic 32 relates a first desired variable, such as a desired clutch pressure, to a second desired variable, such as an desired actuator current. The method comprises the steps: approaching a quasi-steady-state operating point (KP; VB) of the friction clutch 14; detecting a deviation between the first desired variable and an actual variable of the friction clutch 14; and setting up a correction function 34 for the actuator characteristic 32 according to the deviation.

The invention discloses an online optimization decision method and system for manual emergency load reduction and a storage medium. The method includes the following steps of: carrying out safety evaluation on the current operation state of a power grid to obtain a safety margin; for the situation that the safety margin does not meet the requirements of safe operation of the power grid, calculating a real-time manual emergency load reduction strategy meeting the safety constraint; for the situation that the safety margin meets the requirements of safe operation of the power grid, simulating the expected faults defended by an automatic safety device, and carrying out safety evaluation on the quasi-steady-state operation mode of the power grid after the expected faults; and for the situationthat the requirements of safe operation of the power grid are not met after the expected faults, calculating an expected fault manual emergency load reduction strategy meeting the safety constraint.According to the scheme of the invention, the risk that the power grid does not meet the requirements of safe and stable operation due to offline load reduction strategy mismatch or insufficient control amount of the automatic safety device can be eliminated, and the risk cost of manual emergency load reduction accidents can be reduced.

The invention relates to a method for analyzing the structure of a power system, and belongs to the technical field of power system evaluation and control. The method comprises the steps that a reactive source space control method is adopted to carry out modeling on a power system network, and partition is carried out on a motor in the power system according to the model through a principal component analysis method; then, a load bus is added to the partition of a corresponding generator, and finally all the generators and the load buses in the power system are divided into p partitions. The method has the advantages that modeling is carried out on the power system through quasi-steady-state sensitivity, and the modeling method is more accurate than a traditional method. According to the power system self-adaption partition method based on the principal component analysis method, a more accurate and scientific partition number determining method is provided, and compared with a traditional partition number determining method, the partition scheme of the power system can be determined in a self-adaption mode.

The invention discloses a technical scheme and a high-precision measuring method of a measuring device for measuring low-heat-conduction thermal insulation materials, provides a device and a method for measuring the heat conductivity of an active heat-protection type calorimeter by virtue of a quasi-steady-state method as well as a calorimeter correction method and technical scheme based on ASTME2584. Aiming at the shapes and types of different testing materials, an active heat-protection type structural design of a measuring device including a single panel sample, a dual-panel sample and a cylindrical sample is provided. According to the technical scheme, the lateral heat loss can be effectively eliminated, one-dimensional heat flow can be effectively guaranteed, the low heat conductivity measurement and the ultralow heat conductivity measurement on the thermal insulation materials can be realized under high-temperature and ultrahigh-temperature conditions, the continuous dynamic measurement on the heat conductivity in the whole temperature range can be realized, and meanwhile, the measurement accuracy is relatively high.

The invention discloses a precise measuring method of crystalline silicon body lifetime. The precise measuring method of the crystalline silicon body lifetime comprise the steps that minority carrier lifetime is measured through a quasi-steady-state photoelectric conduction method, a true value of the silicon wafer minority carrier lifetime can be obtained accurately and quickly through a quasi-steady-state minority carrier lifetime measuring method, the effective minority carrier lifetime comprises a body lifetime and a surface recombination lifetime, on the precise of the same silicon wafer recombination conditions, the true body lifetime of the silicon wafer is obtained by calculating through formulas, and the calculated true body lifetime of the silicon wafer is similar to the body lifetime measured through the photoconductive decay method. The method for measuring the minority carrier lifetime through the quasi-steady-state photoelectric conduction method and obtaining the true body lifetime through calculation has the advantages of being simple, fast, free of contamination and the like.

The invention provides a method for controlling reverse penetration into the back of an aluminium alloy pipeline during welding. In the method, inert gas is continuously inflated into a pipeline to be welded by using an adjustable pressure control device to ensure that the inflating flow is mutually coordinated with the deflating flow of an unwelded connector, so that the pressure in the pipeline reaches a macroscopic quasi-steady state, a steady and outward force is applied to a weld pool to prevent the back of the weld pool from collapsing to cause deformation, and thus the reverse penetration into the back of a weld joint can be effectively controlled. The method is not limited by complexity of the shape of the pipeline; the inert gas in the pipeline can play a role of a protective gas, so that the weld joint can be formed easily and the welding quality is ensured; therefore, by the method, the thin-wall, complex and multi-elbow pipeline with the wall thickness of 1.0-3.0mm and the external diameter of 22-40mm can be welded.