323 results about "Three phase short circuit" patented technology

The invention belongs to the technical field of relay protection of distribution networks, relates to a protection method for a distribution network comprising inverse distributed power, and provides an improved self-adaptive current fast tripping protection proposal comprising an IIDG power distribution system on the basis of the prior self-adaptive current fast tripping protection. The protection method still performs online setting on protection according to the prior mode of a self-adaptive setting value expression under the condition of no consideration of the connection of an IIDG when the IIDG is connected to the rear side of the protection, utilizes a negative sequence component to solve for the actual equivalent impedance of the rear side of the protection and uses an equivalent electric potential under the current failure state to set the protection under the condition of two-phase short circuit, still adopts a calculation method under the condition of no connection of the IIDG to solve for the equivalent impedance under the current failure state, obtains a corresponding equivalent electric potential according to the equivalent impedance, and uses the equivalent electric potential to set the protection under the condition of three-phase short circuit. The method improves the prior current protection configuration and guarantees the reliable failure removal of a distribution system comprising an inverse DG.

The invention provides a method for determining commutation failure of a multi-infeed direct current power transmission system. The method is characterized by comprising the steps of calculating the extinction angle of an inverter station in the system in case of three-phase short-circuit grounding and single-phase short-circuit grounding of each node based on a nodal impedance matrix and by virtue of a node voltage interaction factor, and determining whether the direct current system fails in commutation with a critical extinction angle as the criterion. Besides, the calculation results of all the nodes are integrated, and a three-phase critical failure impedance boundary and a single-phase critical failure impedance boundary are delimited on a network topology, respectively. The minimum extinction angle is taken as the determination criterion of the method for the commutation failure, and an alternating current system area causing the commutation failure of the direct current system during a fault can be determined quickly and accurately through simple calculation by virtue of the critical failure impedance boundaries, and the accuracy of the determination method is improved while the determination process of the commutation failure is simplified. The influence, caused by a fault of an alternating current system, on the direct current system can be determined and analyzed clearly and visually.

The invention discloses a PMSM rotary transformer zero position initial angle calibration method and calibration system. The PMSM rotary transformer zero position initial angle calibration method comprises steps of connecting an PMSM, on which a rotary transformer is installed, to a driving motor, enabling a motor stator of the PMSM to perform three-phase short circuit, using the driving motor to drive the PMSM to rotate forward and maintain at a preset rotation speed, using an electronic control unit to perform sampling on three phase current Ia, Ib and I c and a rotary transformer reading phi read at a same moment, using the rotary transformer reading phi read to perform Park conversion on three phase current Ia, Ib and Ic to obtain current vectors Is,p, calculating a vector angle theta p corresponding the current vector Is,p, using the driving motor to drive the PMSM to rotate backwards and maintaining the rotation at a preset rotation speed, using the electronic control unit to record a vector angle theta n corresponding to a current vector Is,n when the motor is rotated backwards, and calculating that a practical electric rotation angle theta 0 corresponding to the rotary transformer reading zero point angle is a zero position initial angle according to a formula theta 0=(thetap+thetan)/2-180 degree.

The invention provides a d-q axis parameter identification method for a grid-connected inverter of a photovoltaic power generation system. The d-q axis parameter identification method includes: an inverter control reference value Udc-ref and Qref jump are arranged on the grid-connected inverter of the photovoltaic power generation system, or a three-phase short circuit fault is manufactured on the side of a power grid so as to collect disturbance data required by parameter identification; d axis parameters of the grid-connected converter are calculated according to the collected data, and the d axis parameters comprise filter inductance, d axis inner ring current control ring proportionality coefficients, inner ring current control ring integral coefficients, outer ring active power control ring proportionality coefficients and outer ring active power control ring integral coefficients; and a filter inductance parameter is fixed to be a d axis identification result, q axis parameters of the grid-connected inverter are calculated according to the collected data, and the q axis parameters comprise q axis inner ring current control ring proportionality coefficients, inner ring current control ring integral coefficients, outer ring reactive power control ring proportionality coefficients and outer ring active power control ring integral coefficients. The d-q axis parameter identification method for the grid-connected inverter of the photovoltaic power generation system reduces order and identification difficulty of a model to be recognized and improves identification accuracy.

The invention discloses a method for recognizing the fault type of a feed line of a power distribution line, and the method comprises the steps: obtaining waveform sampling data, and sequentially carrying out the Hilbert-Huang transformation and band-pass filtering of the waveform sampling data; reconfiguring a time frequency matrix according to the band-pass filtering data, solving the singular value of the time frequency matrix, and forming feature vector matrixes; carrying out the normalization processing of all feature vector matrixes, and enabling the feature vector matrixes to serve as the input samples of a multi-stage support vector machine after normalization processing, so as to recognize the fault type of the feed line of the power distribution line. The invention also provides a device for recognizing the fault type of the feed line of the power distribution line. The multi-stage support vector machine is good in performance, is clear in logic, is simple, and can recognize four types of power grid faults: single-phase grounding faults, two-phase grounding faults, two-phase short-circuit faults and three-phase short-circuit faults. The method provided by the invention is stronger in adaptive capability, and still has a high recognition rate of fault types under the impact of noise.

The invention discloses a method of optimal configuration of a plurality of superconducting fault current limiter based on a sensitivity technology, which comprises the steps of: calculating the three-phase short-circuit current of all nodes in a whole system, and finding b nodes with the short-circuit current exceeding the standard value; determining braches for installation and reliable startup of the SFCLs (superconducting fault current limiter) according to startup conditions of the SFCLs; calculating the sensitivity of self-impedance of each station with the short-circuit current exceeding the standard value, sequencing the stations in a sensitivity descending order, and taking the top a branches as candidate braches for installation of the SFCLs; and taking c candidate braches as optimal branches for a multi-objective optimization algorithm NSGA-II (non-dominated sorting genetic algorithm-II) in next step, determining a scheme with the optimal installation positions of the SFCLs, the number of SFCLs to be installed and the impedance, thereby realizing global optimum configuration. By adopting the method, the search space to be understood is reduced greatly, the speed of calculation is increased, and optimization results are more suitable for actual applications. Meanwhile, the problem of weight selection resulting from conversion of multi-objective optimization to single-objective optimization can be avoided, and a decision-maker can make final decisions according to actual engineering needs.

The invention discloses an electric power system wave-recoding file based fault detection method and system and relates to an electric power system fault detection technology. By using the method and system, the problem of non-real time feedback of electrical network states of a conventional dispatcher electrical network fault auxiliary system can be solved. The fault detection method comprises a wave-recoding file reading step, a fault type determining step and a fault situation analyzing step. The fault type determining step comprises: determining a fault according to the three-phase current information in a wave-recoding file and determining whether the fault is a grounding fault, if so, determining whether the grounding fault is a single-phase grounding fault or a two-phase grounding fault, otherwise, determining whether the grounding fault is a three-phase short circuit fault, and if the grounding fault is not the three-phase short circuit fault, determining which two phases are in a two-phase short circuit fault. The fault situation analyzing step involves determining fault situations according to fault states before and after a current abrupt change point and current change states. The method and system provided by the invention can be applied to the modernization operation management of a conventional electrical network.

In a first aspect, the invention is directed to a circuit for powering a gate drive for an electric motor for a vehicle with an electric motor. The circuit provides a primary power supply and a secondary power supply that powers the gate drive in the event the primary power supply fails. The primary power supply may draw power from the 12V battery on the vehicle. The secondary power supply may draw power from a high voltage battery pack on the vehicle that is normally used to provide power to the electric motor. By providing the secondary power supply to the gate drive, a 3-phase short can be applied to the motor in the event that it is needed as a safety measure even if there is a failure in the primary power supply.

The invention discloses a discharging method of a bus capacitor for an electric automobile, and belongs to the technical field of power electronics. According to the discharging method, by controlling switching on and switching off of a power module, charges stored in the bus capacitor are rapidly consumed on the power module. No additional parts are added, and on the premise that cost is reduced, discharging of the bus capacitor can be rapidly completed; meanwhile, three lower half bridge arms are in a switched on state in the discharging process, a motor is in a three-phase short-circuit state at the moment, and therefore reverse phase electromotive force can not be generated on a direct-current bus, and the problem that the bus capacitor is charged in the rotating process of a permanent magnetic synchronous motor of the new-energy automobile is solved.

The invention provides a method of checking an alternating current loop of a 500kV transformer substation through carrying out simulated through-type three-phase short circuit. According to the method, before the 500kV transformer substation is electrified and put into production, a simulated through-type three-phase short circuit system is carried out so as to check the correctness of the amplitude value, phase, polarity and wiring of the current loop of the whole substation. The method provided by the invention has the following advantages: (1), after problems are discovered, the time for searching and processing the problems is sufficient; (2), the check content for an alternating current secondary loop is more comprehensive and systematic; (3), the polarity wiring condition of a current transformer can be accurately judged; and (4) materials of equipment used in the method are simple and convenient, the workload is less, the current loop of the whole substation can be checked through simple operations, and the workload and test time can be reduced.

A switching control unit that ON/OFF-controls switching elements of a power conversion circuit includes a power supply side abnormality determination unit, and a regeneration abnormality response processing selection unit that selects either three-phase short circuit processing, in which all upper stage side switching elements or all lower stage side switching elements are switched ON, or six-switch opening processing, in which all of the switching elements of the power conversion circuit are switched OFF, as processing to be executed when the power supply side abnormality determination unit determines that a power supply side abnormality has occurred, the three-phase short circuit processing and the six-switch opening processing being selected in accordance with a motor operating condition of the AC motor at the time of the determination.

There is provided a fail-safe apparatus for an inverter that can suppress the voltage of a DC power source from rising when the voltage of the DC power source becomes excessive, due to an abnormality caused in an inverter that performs driving and electric-power generation by use of a synchronous motor in which a permanent magnet is utilized as a magnetic-field magnet. The fail-safe apparatus for the inverter includes an excessive voltage detection circuit for detecting a state of excessive voltage while monitoring the voltage of the DC power source of the inverter and a drive switching circuit for switching a driving method for a semiconductor switching device between three-phase PWM driving and three-phase short-circuiting driving in accordance with the state of an excessive voltage detection circuit.

The invention discloses a doubly-fed wind turbine generator parameter identification method. First, based on a simulation platform, a simulation system containing a doubly-fed wind turbine generator set is constructed; a three-phase short circuit fault is arranged at a doubly-fed wind turbine generator set port, active power and reactive power output by the doubly-fed wind turbine generator are used as outputs, track sensitivity of each parameter is calculated, and key parameters to be identified are determined; according to the shapes of track sensitivity curves, whether the key parameters to be identified can be distinguished and identified is judged; the doubly-fed wind turbine generator set port voltage amplitude and phase are used as inputs, the active power and reactive power output by the doubly-fed wind turbine generator set are used as outputs, an objective function of identification is established, and a particle swarm optimization algorithm is adopted to identify parameters of the doubly-fed wind turbine generator set; and finally, a final identification result of the parameters is obtained through a mean value method. The doubly-fed wind turbine generator parameter identification method provided by the invention comprehensively considers outlet voltage amplitude and phase angle change, and improves parameter identification precision.

The invention discloses a three-phase short circuit current calculating method for a double-fed motor. The method comprises calculating the stator side equivalent reactance after short circuit; calculating and obtaining the stator side linkage initial value and the rotor side linkage initial value before short circuit according to the stator side equivalent impedance after short circuit and the double-fed aerogenerator electromagnetic transient equation under the space rotating coordinates; calculating and obtaining the transient stator side linkage and the transient rotor side linkage according to the stator side linkage initial value and the rotor side linkage initial value before the short circuit; calculating and obtaining the stator side current according to the transient stator side linkage and the transient rotor side linkage; and obtaining the short circuit for A-phase, B-phase and C-phase, the short circuit current instantaneous maximum value and the short circuit current periodic component effective value by performing transformation of coordinates for the stator side current. The three-phase short circuit current calculating method for a double-fed motor is higher in calculating accuracy.

The present invention provides a calculation method of a back-open two-pole current parameter under an asymmetric fault condition, and a problem that the back-open two-pole current parameter can not be obtained through calculation is obtained. The method comprises the steps of (1) obtaining each phase current which passes a circuit breaker before first-open phase crossing zero time t0 when a three-phase short circuit fault happens, (2) carrying out independent vector operation of an AC component and a DC component of the back-open two-pole current after the first-open phase crossing zero time t0, and obtaining corresponding expressions. (3) stacking the estimated AC component and the DC component, and obtaining the back-open two-pole current parameter. According to the method, the obtained back-open two-pole current expressions are suitable for a neutral point effective grounding system and a neutral point non-effective grounding system, after the vector calculation of the AC component and the DC component, the AC component in the vector diagram obtained by a symmetrical component method and the DC component limited by a boundary condition can be stacked, and near-open pole and back-open pole current calculation formulas can be obtained.

The invention relates to a distribution line fault identification apparatus based on voltage monitoring. The distribution line fault identification apparatus based on voltage monitoring is characterized in that the distribution line fault identification apparatus based on voltage monitoring acquires the voltage of three-phase lines at the same time; when one phase or multi phases of the lines malfunction, the distribution line fault identification apparatus based on voltage monitoring automatically extracts the data of the forward and backward periods, analyzes the self voltage state of the three phases according to the synchronous period, and determines the practical corresponding different fault types of different combinations of the three-phase voltage state, so that the distribution line fault identification apparatus based on voltage monitoring can identify the following no less than 7 types of faults of the distribution line at the same time: single-phase grounding, single-phase disconnection, two-phase short circuit, two-phase short circuit grounding, three-phase short circuit, three-phase short circuit grounding and instantaneous interference fault.

Adopting second order RC lowpass filter and half wave difference Fourier algorithm, the invention combines phase module transformation to filter out and obtain negative sequence voltage and current component. Then, using formula obtains action angle of negative sequence direction component. The method possesses enough capability to filter out high-frequency component and attenuate DC component. The negative sequence direction component can capture asymmetry at three-phase short-circuit moment in time and correctly so that the invention shows asymmetric fault, and three phase fault developed from asymmetry. The invention executes correct action within milliseconds at moment fault occurs.

The invention provides a dynamic equivalence method for a double-fed type wind power plant based on active response and relates to the technical field of simulation modeling of an electric system. The invention aims to solve the problems of the present equivalence method for the wind power plant that the calculated amount and the equivalent precision cannot be considered and the fan clustering cannot be offline completed. The method comprises the following steps: establishing an electromagnetic transient model of a wind turbine generator and performing three-phase short-circuit simulation and on-site test experimental comparison; acquiring a transient active power response curve of the wind turbine generator in a full-wind-speed running area if the precision meets the standard; acquiring a clustering index according to the clustering characteristics of the curve; setting an active power error threshold according to the equivalence precision requirement, performing equivalent calculation on the typical wind speed distribution and adding the unit equivalent wind speed in the corresponding wind speed section as a supplementary cutting point if the precision does not meet the requirement; and causing the units in each cluster of the practical wind power plant be equivalent to one unit according to the offline acquired clustering indexes and calculating the equivalent parameters of the equivalent units and electric networks, thereby acquiring an equivalent model of the wind power plant.

The invention relates to a fault identification method for an isolated neutral system. According to the method, zero sequence voltage abrupt change amount detection is additional arranged in the initial phase of the algorithm and single-phase earth fault line selection is judged; then in order to reduce harmonic interference and accurately judge initial time of the fault, a negative sequence amount threshold value is set so that negative sequence amount of unbalance in normal operation is avoided; and non-earth fault line selection is judged according to the characteristics that zero sequence and negative sequence components do not exist in the system and high fault abrupt change current exists in the fault line when three-phase short circuit occurs. Group amplitude and phase comparison and zero sequence reactive power direction line selection methods are integrated in the aspect of algorithm, and variable threshold detection is additionally arranged so that interference of harmonic waves on the line selection process can be effectively reduced, and the complete fault identification method for the isolated neutral system is formed.

The invention provides a vehicle permanent magnet synchronous motor rotary transformer zero calibration method and system. The zero calibration method comprises the following steps of controlling a permanent magnet synchronous motor to operate according to the received given current vector amplitude and the given rotating speed value; after the permanent magnet synchronous motor stably operates atthe given rotating speed value, setting the inverter in a three-phase short circuit state, and recording a first included angle and a second included angle formed by a current vector at a specific rotation speed value and a d-axis negative half axis of a preset rotor coordinate system of the permanent magnet synchronous motor in the subsequent rotation speed reduction process, then calculating the average value of the first included angle and the second included angle, and obtaining the zero offset angle of the rotary transformer. The method has the beneficial effects that the rotation speedclosed-loop measurement is realized, the influences of the friction force, the cogging torque or other non-ideal factors to the zero calibration of the rotary transformer can be eliminated or suppressed, the measurement precision is high, and the calibration can be carried out under the condition that the calibrated motor is in a vehicle-mounted state.

The invention discloses a simplified calculating method of a double-fed motor three-phase short circuit current maximum. The method comprises the steps of firstly giving a double-feed motor three-phase short circuit current calculating formula which calculates a Crowbar resistor; then utilizing a sensitivity analyzing method to analyze the influencing degrees of various physical quantities on the sizes of the short circuit currents in the formula, and extracting a group of parameters which have greater influence degrees on the short circuit currents; finally utilizing the extracted parameters and multiple linear regression to analyze and deduce the simplified calculating formula of the double-feed motor three-phase short circuit current maximum. A simple method is provided for calculation of the double-fed motor three-phase short circuit current maximum, the calculating accuracy and practicability are achieved at the same time, and the simplified calculating method of the double-fed motor three-phase short circuit current maximum has great significance on economic security design of electrical equipment of a wind power plant.