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 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 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 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 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 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 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.