42 results about "Transient energy function" patented technology

The invention discloses a method for quantitatively evaluating the transient stability of an electric power system based on network measuring information. The method is characterized by comprising the following steps of: constructing a transient energy function based on a structure preserving model of the electric power system; constructing a transient potential energy function of a branch circuit; and constructing an evaluation index of the transient stability of the electric power system by using the potential energy of the branch circuit. Due to the adoption of the method, the transient stability of the system can be analyzed quantitatively, the influence of the branch circuit in a network on the transient stability of the system is evaluated and weak links in the network can be found. Compared with the conventional method, the method has the advantages of capability of realizing quantitative evaluation of the transient stability of the electric power system by using the network measuring information independent of a generator model and information, simplicity in computation, accurate result, easiness for realization, high engineering application value and the like.

The invention provides a transient stabilization control method for an interconnection electrical network after impact disturbance. The method comprises: based on the transient energy function of the electrical network after the impact disturbance, establishing, according to the energy propagation characteristic of the power fluctuation of a junctor, a junctor cut set potential energy function; through a junctor cut set potential energy curve and the angular phase difference of the busbars at the two ends of the junctor, predicting the angular phase stability of the interconnection electrical network; and calculating the power for removing a unit when there is power angle instability. The method provided by the invention can be applied to the theoretically and simulation analysis of an electric power system. By using the method, the propagation characteristics of transient energy in the electrical network after the impact disturbance can be mastered, the stability of the interconnection electrical network can be predicted, and a controlled variable for maintaining stability can be calculated, thus effective measures can be taken by analysis personnel, and the safe and stable operation level of the electric power system can be improved.

The invention provides a transient energy function analysis method considering inverter current saturation. Based on an inverter virtual synchronous generator control strategy, by establishing a virtual synchronous generator rotor movement equation and considering the inverter current saturation factor, a transient energy function is established with the first integral method; approximation is conducted on non-integrable terms relevant to path in the transient energy function with the linear path method, then the critical energy value is obtained with the BCU method, and critical clearing time is obtained. According to the transient energy function analysis method considering virtual rotational inertia and inverter current saturation, the stability of an electric system containing a virtual synchronous generator can be evaluated quantitatively; the transient energy function is established considering the inverter saturation factor and is closer to reality, the problem that system instability can be caused when a traditional online evaluation method is adopted due to conservative property is solved, and the method is an important supplement to time-domain simulation methods.

The invention provides a transient energy function method in consideration of VSG inverter current limitation. The method comprises the steps that a current limitation model of an inverter is built; the power-angle characteristic under inverter current saturation is obtained; a system power-angle model in consideration of inverter saturation under a VSG strategy is built; an improved inverter current saturation element model is built, and a relation of an improved power angle and an unsaturated power angle is obtained; main parameters of electric parts are input; a Runge-Kutta method is used for solving a rotor motion equation to obtain delta(t) and dotted delta(t) of a VSG rotor, so that a fault trajectory is obtained, wherein delta(t) represents a relation of the system power angle and time, and dotted delta(t)=w(t) represents a relation of the system angular velocity and time; transient energy Vcl and critical energy Vcr of the system at the fault clearing time are obtained; the obtained transient energy Vcl and critical energy Vcr of the system at the fault clearing time are compared, if Vcl is smaller than or equal to Vcr, the system is stable, otherwise, the system is not stable; critical fault-clearing time is solved.

The present invention discloses an electric power system transient stability analysis method. The electric power system transient stability analysis method mainly comprises a time domain simulation method and a direct method. A transient energy function method belongs to the direct method. The transient energy function method model is simple, considers the non-linear problem, can avoid complex numerical integration operation, is fast in computing speed and can provide system stability margin indexes, and the restriction of the model precision, critical point selectivity and linearity path hypothesis allows a traditional transient energy function to always have the conservation problem. The improved transient energy function method based on the SMR (Squared Matrix Representation) technology introduces the SMR technology to improve the transient energy function analysis method, a superposition program is employed to obtain the optimal Lyapunov function so as to improve the problem of a traditional transient energy function conservation.

The invention provides a method for judging the transient state stability of an alternating-current and direct-current hybrid power system containing flexible direct current. The method comprises thefollowing steps: establishing an alternating-current and direct-current hybrid power system mathematical model considering the dynamic response of a direct-current circuit and the transient state response of a voltage source converter; based on the alternating-current and direct-current hybrid power system mathematical model, constructing an alternating current and direct current hybrid power system transient state energy function containing flexible direct current under a structure reservation model, and calculating the initial state energy value of the system after a fault according to the transient state energy function; calculating the critical energy value of the system by using an iterative potential energy boundary surface method; and judging the transient state stability of the alternating-current and direct-current hybrid power system containing the flexible direct current according to the initial state energy value of the system after the fault and the critical energy value of the system. According to the method, the stability of the system can be quantitatively judged in real time through the energy-function-based transient state stability analysis of the alternating-current and direct-current hybrid system containing flexible direct current power transmission.

The invention relates to a transient generator tripping control method considering wind power integration and wind-thermal coordination and belongs to the technical field of electric power system operation control. The method mainly comprises the step that generator tripping proportions of wind power to thermal power are calculated on the basis of a transient generator tripping model considering wind power integration and wind-thermal coordination based on an improved branch circuit transient energy function and PSASP software. By the adoption of the transient generator tripping control method considering wind power integration and wind-thermal coordination, transient stability calculation can be conducted on major failures of a wind-thermal power bundling transmitting system in different modes, and the optimal generator tripping proportion of a thermal power generator unit to a wind power generator unit is selected; on the premise of ensuring stability of system recovery, the characteristics of the system recovery process are improved, safety and stability of system operation are improved, a control basis is provided for transient stability control generator tripping measures of the wind-thermal power bundling transmitting system, convenience is provided for actual power grid dispatching and operating, and the method has practical significance.

The invention discloses a method for evaluating exchange capacity limit among large regional grids based on multiple restrictions. The method comprises the steps of: evaluating the capacity exchange ability among the large regional grids based on frequency response characteristic analysis, static voltage stability analysis, and transient energy function analysis; comparing exchange capacity limits meeting the restrictions of the frequency response characteristic, static voltage stability and a transient energy function to determine determinant factors restricting the capacity exchange ability of a power system; determining the exchange capacity limits among the large regional grids based on the multiple restrictions; and making and optimizing a regional capacity assignment plane based on the exchange capacity limits.

The invention discloses a reclosing time on-line capturing method of a power transmission line. The reclosing time on-line capturing method is characterized by comprising the following steps of: constructing a transient state energy function based on a power system structure keeping model, establishing a branch transient state potential energy function, analyzing transient characteristics of the power transmission line based on branch transient state potential energy, setting reclosing time and the like. According to the reclosing time on-line capturing method of the power transmission line, disclosed by the invention, the optimal reclosing time can be set exactly in real time by fully and effectively utilizing the measured branch information so that the transient state stability of a system is improved; in addition, the invention has the advantages of simple calculation, easiness for implementation, high application value and the like.

The invention relates to a positioning method of single-phase earth fault sections in a power distribution network based on extreme-point symmetric mode decomposition (ESMD). The positioning method comprises the steps that (1) whether a bus zero sequence voltage value exceeds the limit or not is determined, and if so, a step (2) is performed; and if not, the step (1) is repeated; (2)zero sequencecurrent signals in the 1 / 2 power frequency period after faults of all measuring points are collected; (3) the collected zero sequence current signals are subjected to ESMD decomposition, and a seriesof intrinsic mode functions IMF and a residual function R are obtained; (4) the intrinsic mode functions IMF and the residual function (R) obtained by the ESMD decomposition construct a fault transient energy function describing the oscillation intensity of transient zero sequence current waveforms; (5) based on the fault transient energy function, a fault section logic judgment function is constructed and subjected to normalizing processing; and (6) sections where faults are located are determined according to a power distribution network topological structure. According to the positioning method of the single-phase earth fault sections in the power distribution network based on the ESMD, the quite good adaptability to grounding faults under different grounding modes, different transitionresistances and different fault angles can be showed, and engineering is easy to realize.

The invention discloses an AC-DC hybrid system transient stability analysis method considering commutation failure, and the method comprises the steps: building a network structure maintenance model of an AC-DC hybrid system for the AC-DC hybrid system comprising a power grid commutation type high-voltage DC transmission line through enabling a DC converter station to be equivalent to a dynamic load on a corresponding commutation bus; constructing an energy function through first integration; secondly, approximately calculating a transient energy function of the system after the fault by adopting a trapezoidal integral path, proposing a transient stability criterion based on the energy function, and quickly calculating the limit clearing time of the system by utilizing a dichotomy; finally, building an improved IEEE-39 node alternating current and direct current hybrid system, and verifying the correctness of the theoretical analysis method through simulation. When an alternating current system of the alternating current and direct current series-parallel system breaks down and causes commutation failure on the inversion side of a direct current line, transient stability margin analysis can be rapidly carried out.

The invention discloses a method for calculating a transient energy function of a renewable energy power system, and belongs to the field of transient stability analysis of power systems. The method comprises the steps of firstly, establishing a mathematical model of a to-be-analyzed power system, eliminating intermediate nodes, and only reserving renewable energy equipment nodes, synchronous generator nodes and power load nodes; representing the transient process of the renewable energy equipment by a second-order phase-locked loop equation, representing the transient process of the synchronous generator equipment by a second-order swing equation, respectively listing and writing energy functions of all renewable energy equipment, the synchronous generator equipment, the power network andall power loads, and adding all the energy functions to obtain a transient energy function of the power system. Compared with the prior art, the method considers the transient energy function of thepower system when the renewable energy equipment and the synchronous generator are connected to the power grid at the same time, can analyze the transient stability of the system including the synchronous generator equipment and the renewable energy equipment, and expands the application range of the energy function direct method.

The invention relates to a transient-state function comprehensive index based intelligent control method for power system transient stability. The intelligent control method is characterized by comprising the following steps of calculating a stability index of each branch in the oscillation process at a current running state, and determining a weakest branch and a transient stability state of a power grid; identifying most advanced power generator set; giving out active limit power adjusted by a power generator; giving out a suggested adjustment range adjusted by the power generator; and verifying whether transient stability is achieved or not. By the intelligent control method, comprehensive estimation can be made on system transient stability from angles of network potential energy and power generator kinetic energy, transient stability estimation and vulnerable cutest selection are carried out by means of branch potential energy, a control object is distinguished according to kinetic energy slope of the power generator, the adjusted suggested adjustment range is determined according to a function relation of the branch potential index and the active power of the power generator, and an intelligent control strategy for transient stability taking an energy system as a main line is built. The intelligent control method has the advantages of scientificness, reasonableness, simple computation, an accurate result, high engineering application value and the like, and is easy to implement.

The invention relates to an analysis method for the influence of wind farm access on a fault limit cut-off time of a multi-machine system. Based on a transient energy function theory, starting from anoriginal multi-machine system, a first integral method is used to construct a transient state energy function of the multi-machine system including a wind farm. On the basis, a relationship between acritical energy value of the system and the transient output power of the wind farm is derived, the change of a critical energy borne by the system brought by the change generated by a network topology structure due to the access of a DFIG is quantitatively analyzed, and the influence of the wind farm access on system stability margin is reflected from the perspective of critical energy. According to the influence of the DFIG on the equivalent electromagnetic power of the system during a fault period, the change of a system state variable and an energy accumulation process are analyzed, and the influence mode of the wind farm access system on the speed of the system transient energy accumulation is given. The fault limit cut-off time is calculated by the accumulation time from the transient energy to the system critical energy.

The invention relates to a method and system for determining the transient stability margin of an alternating-current and direct-current hybrid system. The method comprises the steps of: firstly, building a network structure maintenance model of the alternating-current and direct-current hybrid system, employing a 6-order electromechanical model for a synchronous generator, employing a standard electromagnetic model for DC, and employing an electromagnetic model for direct current; secondly, according to an universal energy function model, rewriting a six-order electromechanical model of the synchronous generator and the network structure maintenance model of the alternating-current and direct-current hybrid system, and determining the transient energy function of the alternating-current and direct-current hybrid system; thirdly, calculating an energy function change curve of the alternating-current and direct-current hybrid system after a fault by adopting a trapezoidal integral path method, performing analysis by utilizing the energy function change curve to obtain a transient stability criterion of the alternating-current and direct-current hybrid system; and finally quickly calculating the limit clearing time of the system by adopting a dichotomy to realize transient stability margin evaluation of the alternating-current and direct-current hybrid system. According to the method, the transient stability margin of the alternating-current and direct-current hybrid system is accurately evaluated in the scene that the alternating-current fault causes the commutation failure of a direct-current inverter side.

The invention relates to a quantitative evaluation method for transient synchronous stability of a permanent magnet synchronous wind driven generator based on a Lyapunov direct method, and discloses a transient energy function method capable of quantitatively evaluating the transient stability of a wind power grid-connected system. The method comprises: based on the Lyapunov theory, constructing an energy function for a permanent magnet synchronous wind driven generator grid-connected system, used for quantitatively evaluating the transient synchronization stability of a fan; firstly, through reasonable order reduction of a grid-connected voltage source type converter control system, establishing a simplified fan grid side converter control model, and the model considering the influence of outer loop control on the dynamic characteristics of a phase-locked loop; then, deriving a fan synchronous motion equation similar to the synchronous machine rotor motion equation; on the basis of the synchronous motion equation, constructing a transient energy function of the fan by using a first integral method, and determining a critical energy value of the transient energy function by using a potential energy boundary surface method; and comparing the energy when the fault is removed with a critical energy value so as to judge the transient synchronization stability of the system. According to the method, the transient synchronous stability of the permanent magnet synchronous wind driven generator-infinite bus system is quantitatively evaluated.

The invention discloses an amplitude-phase control method for a power grid dominant voltage source converter. Firstly, a multi-type power supply dynamic differential and microgrid algebraic equation is established; a compensation control loop of a power grid dominant voltage source converter is provided. Secondly, an island alternating-current microgrid whole-system dynamic micro-increment rate model containing multiple types of power supplies and a converter compensation control loop is established, and compensation control loop parameters are designed and amplitude-phase variables are adjusted on the basis of a transient energy function of the micro-increment rate model so as to guarantee dynamic stability of the whole system, thereby suppressing a power oscillation phenomenon among themultiple types of power supplies.

The invention discloses a transient voltage instability and power angle instability identification method based on a transient energy function. The method comprises the following steps: firstly obtaining an admittance matrix of a system node, periodically collecting the operation parameters of a power system in an operation process, and if it is judged that the current power system is unstable according to the operation parameters, substituting the current operating parameters into a transient power angle relation function and a transient voltage relation function which are constructed based on the transient energy function, then calculating to obtain a sensitivity function, and then identifying a transient instability mode of the system in combination with the instability state of the system. The transient power angle relation function and the transient voltage relation function are provided based on a transient energy function method, and discrimination of different instability modesis realized by establishing sensitivity function indexes.

The invention provides a transient energy function method in consideration of VSG inverter current limitation. The method comprises the steps that a current limitation model of an inverter is built; the power-angle characteristic under inverter current saturation is obtained; a system power-angle model in consideration of inverter saturation under a VSG strategy is built; an improved inverter current saturation element model is built, and a relation of an improved power angle and an unsaturated power angle is obtained; main parameters of electric parts are input; a Runge-Kutta method is used for solving a rotor motion equation to obtain delta(t) and dotted delta(t) of a VSG rotor, so that a fault trajectory is obtained, wherein delta(t) represents a relation of the system power angle and time, and dotted delta(t)=w(t) represents a relation of the system angular velocity and time; transient energy Vcl and critical energy Vcr of the system at the fault clearing time are obtained; the obtained transient energy Vcl and critical energy Vcr of the system at the fault clearing time are compared, if Vcl is smaller than or equal to Vcr, the system is stable, otherwise, the system is not stable; critical fault-clearing time is solved.

The invention discloses an island transient stability determination method and system. The method comprises the steps of building a state vector analytic expression of each generator in an island based on a power system dynamic equation of the generators; converting the state vector analytic expression into a COI coordinate system to obtain a state vector analytic expression of each generator in the island under the COI coordinate system; based on the state vector analytic expression of each generator under the COI coordinate system, utilizing the transient energy function of the island to calculate the transient energy of the island; based on the state vector analytic expression of each generator and the state vector analytic expression under the COI coordinate system, calculating critical energy for stabilizing the island; calculating a difference value between the critical energy and the transient energy as an island stability margin; and determining the island transient stability according to the island stability margin. According to the method, the fault duration information which can be sensed by relay protection is combined, the energy function is applied to the split island, the constraint of time domain simulation is eliminated, and the calculation efficiency is improved on the premise that the precision is guaranteed.

A grid-dominated voltage source converter amplitude and phase control method, first establishes multi-type power supply dynamic differential and microgrid algebraic equations, proposes a grid-dominated voltage source converter compensation control loop, and then establishes multi-type power supply and commutation In order to ensure the dynamic stability of the whole system, based on the transient energy function of the micro-increase rate model, the parameters of the compensation control loop and the adjustment of the amplitude and phase variables are designed to suppress multiple Power oscillations between types of power supplies.

The invention provides a wind power-thermal power cutter strategy coordination optimization method. The method comprises the following steps that: step one, when a fault occurrence of the system is monitored, calculation is started to obtain a transient energy function of a wind power-thermal-power bundling system after the fault so as to determine whether the system is unstable; if so, the step two is executed; and if not, the cutter measure is not taken; step two, according to transient energy functions of thermal power generating units, whether any thermal power generating unit itself is unstable is determined; if so, the thermal power generating unit that is unstable is cut off and then the step one is executed; and if not, the step three is executed; step three, on the basis of the delivery power scale of the wind power-thermal-power bundling system before the fault and the delivery capacity limit of the power transmission channel after the fault, the thermal power generating unit capacity needing to be cut off is calculated; and after the cutter operation is completed and operation returns to the step one. According to the method provided by the invention, secure and stable operation of the wind power-thermal-power bundling delivery energy base station after the fault can be effectively guaranteed; the cutter capacities of the wind power and the thermal power are distributed reasonably; the effect of lost power generation capacity minimization is realized; the favorable conditions are created for system recovery after the fault; and the security and economy of the system are improved.

The invention relates to an analysis method for the influence of wind farm access on the fault limit removal time of a multi-machine system. Based on the transient energy function theory, starting from the original multi-machine system, the first integration method is used to construct a temporary multi-machine system including a wind farm. On this basis, the relationship between the critical energy value of the system and the transient output power of the wind farm is derived, and the changes in the critical energy that the system can withstand due to changes in the network topology due to the DFIG access are quantitatively analyzed. , from the perspective of critical energy, it reflects the influence of wind farm access on the system stability margin; according to the influence of DFIG on the system equivalent electromagnetic power during the fault period, the changes of system state variables and the energy accumulation process are analyzed, and the impact of wind farm access on the system is given. The influence mode of the transient energy accumulation speed; the fault limit clearing time is calculated by the accumulation time from the transient energy to the critical energy of the system.

The invention discloses an interconnected power grid electromechanical disturbance propagation control method based on thunder and lightning tracking, and the method comprises the steps: carrying out the thunder and lightning tracking and thunder and lightning prediction of two interconnected power grid regions based on thunder and lightning detection and thunder and lightning prediction technologies; control strategies of SMES controllers on the two sides of the interconnected power grid are adjusted in advance according to the prediction result; the SMES controller on the power grid side of the non-lightning-stroke area adopts a disturbance zero-transmission control strategy based on disturbance propagation characteristics to isolate disturbance propagation of the interconnected power grid, and disturbance propagation to the power grid of the non-lightning-stroke area is inhibited; the lightning stroke area power grid side SMES controller adopts a disturbance calming strategy based on a transient energy function method to accelerate attenuation of transient energy of a fault area power grid, and disturbance calming control is achieved. According to the method, disturbance can be inhibited from spreading to a non-lightning-stroke regional power grid, rapid smoothing of the disturbance is realized, and safe and stable operation of the whole interconnected power grid is ensured.

The invention discloses a method for identifying transient voltage instability and power angle instability based on a transient energy function. First, the admittance matrix of the system node is obtained, and its operating parameters are periodically collected during the operation of the power system. If according to If the operating parameters determine that the current power system is unstable, then the current operating parameters are substituted into the transient power angle relationship function and transient voltage relationship function constructed based on the transient energy function, and then the sensitivity function is calculated, and then combined with the system instability state , to identify the transient instability mode of the system. The invention proposes a transient power angle relation function and a transient voltage relation function based on a transient energy function method, and realizes discrimination of different instability modes by establishing a sensitivity function index.

The invention discloses a method and system for determining the transient stability of an isolated island. The method is: based on the power system dynamic equation of the generator, the state vector analytical formula of each generator in the isolated island is established; the state vector analytical formula is transformed into COI Coordinate system, obtain the state vector analytical formula in the COI coordinate system of each generator in the island; based on the state vector analytical formula in the COI coordinate system of each generator, use the transient energy function of the island to calculate the transient state of the island Energy; based on the state vector analytical formula of each generator and the state vector analytical formula under the COI coordinate system, calculate the critical energy to stabilize the island; calculate the difference between the critical energy and the transient energy as the island stability margin ; and the island transient stability is determined according to the island stability margin. The invention combines the fault duration information that can be sensed by the relay protection, applies the energy function to the isolated island after separation, gets rid of the constraints of time domain simulation, and improves the calculation efficiency under the premise of ensuring accuracy.

Embodiments of the present invention provide a method and device for predicting transient stability of a virtual synchronous generator connected to the grid. The method includes: obtaining the virtual speed and virtual power angle of the virtual synchronous generator VSG; The angle is input to the preset transient energy function model, and the transient energy value and critical cut-off time are output; the transient stability of VSG grid-connected is predicted according to the transient energy value and the critical cut-off time. The method and device for predicting transient stability of a virtual synchronous generator connected to the grid provided by the embodiment of the present invention constructs a transient energy function of a stand-alone infinite system connected to a VSG, and takes into account the influence of virtual damping to establish a transient energy function The accuracy is very high, and the transient stability of the virtual synchronous generator connected to the grid is predicted by calculating the transient energy function. The calculation amount is small, the use is convenient, and the prediction efficiency is high.

The present invention relates to a method and system for determining the transient stability margin of an AC / DC hybrid system. Firstly, a network structure maintenance model of the AC / DC hybrid system is established, wherein the synchronous generator adopts a 6-order electromechanical model, and the DC adopts a standard electromagnetic model. Secondly, according to the universal energy function model, the sixth-order electromechanical model of the synchronous generator and the network structure maintenance model of the AC / DC hybrid system are respectively rewritten to determine the transient energy function of the AC / DC hybrid system; again, the trapezoidal integral path method is used for calculation The energy function change curve of the AC-DC hybrid system after the fault is used to analyze and obtain the transient stability criterion of the AC-DC hybrid system. Finally, the limit cut-off time of the system is quickly calculated by using the dichotomy method, and the AC-DC hybrid system is realized. Evaluating the transient stability margin of the connected system. The present invention accurately realizes the evaluation of the transient stability margin of the AC-DC hybrid system under the scene of commutation failure on the DC inverter side caused by the AC fault.

The invention relates to a transient generator tripping control method considering wind power integration and wind-thermal coordination and belongs to the technical field of electric power system operation control. The method mainly comprises the step that generator tripping proportions of wind power to thermal power are calculated on the basis of a transient generator tripping model considering wind power integration and wind-thermal coordination based on an improved branch circuit transient energy function and PSASP software. By the adoption of the transient generator tripping control method considering wind power integration and wind-thermal coordination, transient stability calculation can be conducted on major failures of a wind-thermal power bundling transmitting system in different modes, and the optimal generator tripping proportion of a thermal power generator unit to a wind power generator unit is selected; on the premise of ensuring stability of system recovery, the characteristics of the system recovery process are improved, safety and stability of system operation are improved, a control basis is provided for transient stability control generator tripping measures of the wind-thermal power bundling transmitting system, convenience is provided for actual power grid dispatching and operating, and the method has practical significance.