72 results about "Infinite bus" patented technology

Disclosed herein are an intelligent system and method for monitoring a generator reactive power limit using machine model parameters. The intelligent system and method for monitoring a generator reactive power limit using machine model parameters can calculate a maximum reactive power limit corresponding to over-excitation and a generator terminal voltage corresponding to under-excitation, estimate a correct field current even when system variable are changed, and monitor the generator reactive power limit by using machine model parameters and a one-machine infinite bus, to thereby supply a maximum or minimum reactive power to a power system within an allowable generator reactive power limit and prevent a generator trip caused by the reactive power limit and a power failure over a wide area.

The invention discloses a Doubly-Fed Induction Generator (DFIG) parameter identification method, and belongs to the field of power system modeling. The DFIG parameter identification method comprises the following steps: firstly, determining an analytical expression of stator dq axis short circuit current under a condition of three-phase metal short circuit of a port of a doubly-fed induction generator, and determining parameters to be identified according to the analytical expression; building a single-machine infinite bus system of a doubly-fed wind turbine generator set based on a Matlab/Simulink platform, setting the three-phase metal short circuit at the port of the doubly-fed induction generator, and simulating to obtain a disturbed trajectory of the stator dq axis short circuit current; analyzing the identifiability of each parameter to be identified and the complexity for parameter identification by adopting a trace sensitivity method; and finally, identifying all the parameters to be identified by adopting a particle swarm optimization algorithm, and determining parameter identification values according to multiple identification results. Compared with a method based on active power and reactive power, the doubly-fed induction generator parameter identification method for DFIG parameter identification based on the stator dq axis short circuit current has the advantage that the influence caused by the current transformer control procedure is low; and the parameter identification values are determined according to the multiple parameter identification results, so that the problem of large errors possibly caused by single identification is avoided.

The invention provides an analysis method for subsynchronous oscillation generated by grid connection of wind driven generators. The analysis method comprises following steps: establishing a linearized system model formed in such a manner that wind driven generators are connected to an infinite-bus power system via series compensation capacitance; calculating static stable points of the linearized system model; obtaining characteristic roots of a coefficient matrix of the linearized system model and left and right feature vectors thereof; obtaining all oscillation frequencies of the linearized system model according to characteristic roots and obtaining state variables related to the oscillation modes of the all the oscillation frequencies in the linearized system model; and varying parameter values of the state variables in order to acquire states in which all the oscillation frequencies vary with the corresponding state variables.The analysis method for subsynchronous oscillation generated by grid connection of wind driven generators has following beneficial effects: a quantitative analysis on subsynchronous oscillation generated by grid connection of wind driven generators can be made so that subsynchronous oscillation generated by grid connection of wind driven generators can be effectively monitored and addressed.

The invention discloses a structure improvement and parameter configuration method for a power system stabilizer PSS4B, aims at solving the problem that the PSS4B is not easy to adjust since the structure is complicated and parameters are easily affected mutually, and provides the PSS4B with an improved structure. On the basis of classic parameters of IEEE, in order to avoid mutual influences of phase compensations between branches, the phase compensation links of all the branches set to be the same; on the basis of the improved structure, a phase compensation link parameter setting method for the improved PSS4B is provided; a state matrix comprising a single-machine infinite bus system of the PSS4B with the improved structure is listed; and the condition that the low-frequency oscillation suppression effect of the improved PSS4B is more excellent than that under classic parameters is shown through the damping ratio in an oscillation mode.

The invention provides a power grid equivalence method by which an exterior system of a generator set to be researched can be simplified and a remote complicated large power grid and a near bus set are equivalent to an infinite bus and a dynamic set respectively. The method is applicable to aspects such as modeling parameter time domain verification of an excitation system and parameter optimization of a power supply stabilizer (PSS), so that the characteristic of the exterior system can be represented better; and the simulation calculation of a power system is simplified and the simulation calculation precision is improved.

The invention discloses a method for evaluating the new energy acceptance capacity of a grid-connected point by comprehensively considering the stability characteristic, and belongs to the technical field of automation of power systems. The influences of wind power generation variability and instability on a power grid, an external load level and the change condition thereof are combined; a multi-machine system is equivalent to a single-machine infinite bus system through an EEAC method by employing a static stability constraint, reactive power control and a transient constraint of the power system as conditions; the stability margin and the sampling yield are calculated; and the capability of connecting a wind power station of considering a transient stability constraint to the power grid to the maximum extent is evaluated by employing the specified range of the sampling yield as an index. By the method, the safe and stable operation level of the wind power station can be improved; the generating capacity of the wind power station is effectively ensured; and the benefits of energy conservation and emission reduction are improved.

The invention discloses a method and a system for calculating the influence of excitation additional difference adjustment on the dynamic damping of a synchronous generator, wherein the method comprises the following steps: a single-machine infinite bus system Philips-Heiferon mathematical model represented by K1, K2, K3, K4, K5 and K6 is expanded to establish a difference adjustment model considering additional difference adjustment which is represented by K1, K2, K3, K4, K'5, K'6. According to the eigenvalues of the state equations of the single-machine infinite bus system without error adjustment, the oscillation frequency of the single machine infinite bus system without error adjustment is solved; according to the eigenvalues of the state equations of the single machine infinite bus system with additional deviation adjustment, the oscillation frequency of the single machine infinite bus system with additional deviation adjustment is solved; and the damping torque coefficient KD ofthe excitation system without additional adjustment Xc=0 and the damping torque coefficient KD of the excitation system after additional adjustment Xc is not equal to 0 are calculated. The differencebetween the damping torque coefficient KD of the excitation system without additional adjustment Xc = 0 and the damping torque coefficient KD of the excitation system with additional adjustment Xc not equal to 0 is compared. The results show that the damping torque coefficient KD of the excitation system with additional adjustment Xc not equal to 0 is higher than that of the excitation system with additional adjustment Xc = 0.

The invention discloses a method and system for calculating the influence of excitation additional difference adjustment on the synchronous torque of a synchronous generator. The method includes the following steps that: the Phillips-Heffron mathematical model of a single-machine infinite bus system is expanded, a difference adjustment model under additional difference adjustment is established; the oscillation frequency of the single-machine infinite bus system under no difference adjustment is solved according to the eigenvalue of the state equation set of the single-machine infinite bus system under no difference adjustment; the oscillation frequency of the single-machine infinite bus system under additional difference adjustment is solved according to the eigenvalue of the state equation set of the single-machine infinite bus system under additional difference adjustment; the synchronous torque coefficient KS of an excitation system under no additional difference adjustment ( a condition that Xc=0) is calculated according to the oscillation frequency of the single-machine infinite bus system under no difference adjustment; the value of the synchronous torque coefficient KS of the excitation system under additional difference adjustment (a condition that Xc is not equal to 0) is calculated according to the oscillation frequency of the single-machine infinite bus system underadditional difference adjustment; and the difference value of the synchronous torque coefficient KS of the excitation system under no additional difference adjustment (the condition that Xc is equalto 0) and the synchronous torque coefficient KS of the excitation system under additional difference adjustment (the condition that Xc is not equal to 0) is obtained by means of comparison.

The invention discloses a time-delayed stability criterion conservative assessment method based on Lyapunov function analysis, a numerical computation method is adopted to analyze a Lyapunov function, and conservative quantitative assessment is performed on time-delayed stability criterion. On the basis of a time-delayed power system mathematical model, constituent item difference of a corresponding Lyapunov function of an existing LMI time-delayed stability criterion is analyzed, system trajectory simulation and Lyapunov function normalization are performed on the difference, the derivative of the result is taken, a criterion conservative assessment index is further provided, and a time-delayed stability criterion conservative assessment method is constructed. Four existing typical time-delayed stability criterions are utilized to verify the provided method in a scene of a single-machine infinite bus time delay system. According to the invention, a Lyapunov function expression is utilized to directly analyze inherent differences of stability criterions and estimate conservatism of the criterions, and the method provides support for seeking more scientific time-delayed stability criterion.

The invention discloses a turbine control valve switch simulation modeling method based on turbine-grid coupling. Currently, no complete turbine-grid side system coupling model is studied and built to simulate the work characteristics of a steam admission control system of a turbo generator unit control valve when an electrical power system has transient failures. According to the technical scheme, the method mainly comprises the steps that a turbine power signal and a synchronous motor revolving speed signal serve as feedback signals, wherein the turbine power signal is transmitted to a synchronous motor on a grid side, and the revolving signal output by the synchronous motor is used for revolving speed feedback; a turbine DEH control system model and a grid side single machine infinite bus system model are strongly coupled, and a turbine-grid coupling control valve switch simulation model for the transient failures of the electrical power system is built; according to the turbine control valve switch logic, a control logic is built. The turbine control valve switch simulation modeling method is closer to the control valve fast closing action under the practical transient failures of the electrical power system, the simulation accuracy is improved, and the effect of the control valve fast closing technology on protecting the stable operation of a unit is verified.

The invention discloses a rapid assessment method for performance indexes of different emergency control measures in an electric power system, and belongs to the technical field of the electric power system and automation thereof. According to a transient calculation model of the electric power system, candidate emergency control information and time domain simulation data when no control is implemented, and the electromagnetic power of an emergency control moment synchronous machine is calculated directly after different candidate emergency control measures are implemented, thereby rapidly determining the variation in difference between the electromagnetic power and the mechanical power of a single machine infinite-bus equivalent machine under different emergency control measures at the emergency control moment. Furthermore, the increment of a retardation area under different emergency control measures is calculated based on an extended equal area criterion, thereby determining the performance indexes of the different emergency control measures. The rapid assessment method disclosed by the invention can be applied to offline emergency control strategy calculation or online pre-decision emergency control measure calculation, thereby being conducive to optimization and coordination among the different emergency control measures, improving the transient stability of the system, and improving the economy and the safety of operations of the electric power system.

The invention discloses a timing sequence optimization control method for a distributed power flow controller, and the controller, wherein a DPFC (deviation of power frequency component) device is connected into a single-machine infinite bus system, and the both ends of the single-machine infinite bus system are connected with a Y-Delta-type transformer; the DPFC device is used for switching current converters at the series side of the DPFC device in different time periods, and the number of the current converters switched in each time period is calculated according to a corresponding formula. According to the timing sequence optimization control method disclosed by the invention, the active power flow of an electric transmission line is adjusted in real time by controlling the switching time of the single-phase current converters at the series side of the DPFC device; simultaneously, the reduction of the active power of the electric transmission line during the charging energy storage process of direct-current capacitors at the series side of the DPFC device is prevented, the total harmonic distortion of a line current caused by the plurality of single-phase current converters is avoided, and the reactive compensation performance of the DPFC device is optimized.

The invention provides a use method for configuring a novel power system stabilizer PSS4B by using an improved PSO algorithm. According to the method, a random weight and hybrid operation-combined method is adopted to improve a basic PSO algorithm, and then, the transfer function of the PSS4B is partially simplified; the improved PSO algorithm is utilized to optimize parameters to be optimized inthe PSS4B; and a one-machine infinite bus system and a 3-machine 9-node system perform parameter optimization simulation on the PSS4B through using the improved PSO algorithm. With the method of the invention adopted, the problem of failure to achieve an optimal suppression effect which is caused by a condition that a three-branch phase compensation link is not applied provided that classical parameters are given by the IEEE can be solved; since the improved PSO algorithm is adopted to configure the novel power system stabilizer PSS4B, the suppression of low-frequency oscillation by the PSS4Bcan be quantitatively analyzed.

The invention discloses a parameter tuning method of a power system stabilizer and belongs to the technical field of stable control of a power system. The power system stabilizer is designed aiming at a classic small interference four-order single machine infinite bus system model. A lead link, a resetting link and an amplification link are selected as master variables and a certain effective range is set; the master variables are optimized by utilizing a particle swarm algorithm; meanwhile, an inertia weight linear change manner is adopted in order to increase the fast convergence of the algorithm. By adopting the method disclosed by the invention, damping is effectively increased and low-frequency oscillation of a system is inhibited; meanwhile, the defect that the effectiveness of the parameters of the stabilizer cannot be ensured is overcome.

The invention relates to a method for conducting multi-modal dynamic equivalence on complex electrical power systems except for generators. The method comprises the steps of S1 enabling an external system of a generator set to be studied to be equivalent to a parallel system of an infinite bus and N dynamic units, wherein the infinite bus is expressed as (a formula), and the N dynamic units are expressed as (a formula), S2 in a steady state condition, conducting load flow calculation or on-line measurement to obtain an initial steady-state value of a system, S3 exerting disturbance, recording obtained response quantity, S4 adopting spectral analysis or the prony method to analyze the number N of modals of significant variables at the end of the generator set to be studied, determining the total number N of dynamic equivalence units, S5 according to a multi-modal equivalent model, using data to select an appropriate identification method to identify parameters required to be equaled, and obtaining the dynamic equivalence result. The method better reflects dynamic characteristics of the external system of the generator set to be studied and improves accuracy of optimization design of an excitation controller.

The invention discloses a power grid regulation and control method and system for restraining low frequency oscillation. The method includes the steps that a state variable of a single-machine infinite bus system is acquired; the acquired state variable, a preset first weighting matrix, a preset second weighting matrix, a system state matrix and a system control matrix are converted into a transformation matrix through the following formula, wherein the system state matrix and the system control matrix correspond to the single-machine infinite bus system; the transformation matrix, the second weighting matrix and the state variable are converted into an optimum controlled variable; the optimum controlled variable is used as a feedback controlled variable to conduct feedback regulation and control over an infinite power grid. By the adoption of the method and system, the restraining efficiency of low frequency oscillation is improved, meanwhile, abrasion to power grid equipment can be lowered, so that optimum control is achieved, and the stability of an electric power system and the security of a generator set are effectively improved.

The invention provides an examination and evaluation system for torsional vibration of a shaft system of a nuclear power steam turbine generator unit. The nuclear power steam turbine generator unit is connected with a boosting transformer, the boosting transformer is connected with one end of a transmission line, and the other end of the transmission line is connected with an infinite bus system. The examination and evaluation system comprises three fault points which include the exit fault point located between the generator unit and the boosting transformer, the near fault point located at the end, close to the boosting transformer, of the transmission line, and the transmission line fault point located on the transmission line. The fatigue life losses of the examination section of the shaft system of the nuclear power steam turbine generator unit are calculated under the electrical disturbance working conditions of the three fault points and phase angle error parallelism, the calculated result is compared with the set standard, and therefore torsional vibration of the shaft system of the nuclear power steam turbine generator unit is evaluated. The invention further provides an examination and evaluation method for torsional vibration of the shaft system of the nuclear power steam turbine generator unit. The system and method have universality and practicality, and can be more comprehensive and closer to the practical situation.

The invention belongs to the technical field of wind power plant analysis and calculation, and particularly relates to an equivalent calculation method for a large-scale wind power plant of a parallelstructure. The method comprises the steps: establishing a wind power plant linearized state space model for the wind power plant of the parallel structure formed by M wind power generators; performing equivalent transformation on the state variables of the wind power plant, and similarly transforming a linearized state space matrix of the wind power plant into a block diagonal matrix; decouplingthe linearized state space model of the wind power plant in a manner: M-1 subsystems is formed by connecting a wind driven generator to an infinite bus via a line, and the M-th subsystem is formed byconnecting a wind driven generator into an external power system through a correction network; according to the linearization model of the M-th subsystem, reversely deducing a nonlinear model of the M-th subsystem to obtain a single-machine equivalent model of the wind power plant; dividing the M-th subsystem into two interconnection systems, namely a wind power plant part and an external power part, and solving the interface state variables of the interconnection systems and the dynamic process of the wind power plant.

The invention discloses a method and a system for identifying transient instability of a power system based on trajectory characteristics, and belongs to the technical field of transient stability analysis of the power system. The method comprises the following steps: acquiring real-time operating parameters of a target power system synchronously measured by a wide area measurement system WAMS, and performing digital filtering processing on the synchronously measured real-time operating parameters; enabling the target power system to be equivalent to a single-machine infinite bus system SMIB through stability-preserving transformation, and determining an extended phase trajectory of the target power system according to the equivalent real-time operation parameters of the SMIB; obtaining anintercept value of an extended phase trajectory tangent line on an angular acceleration axis, and extracting a transient stability feature of the target power system; and according to the transient stability criterion of the extended phase trajectory, in combination with transient stability features extracted in real time, it is determined whether the target power system is in transient instability or not. According to the method, the transient stability condition of the system can be correctly identified, the predictability is good, and the time margin is provided for the implementation of stability control measures.