1062 results about "Grid fault" patented technology

A protection system and a protection method are provided for protecting a double fed induction generator and a gearbox during a grid fault. The protection system includes a plurality of controlled impedance devices. Each of the controlled impedance devices is coupled between a respective phase of a stator winding of the double fed induction generator and a respective phase of a grid side converter. The protection system also includes a controller configured for coupling and decoupling impedance in one or more of the plurality of controlled impedance devices in response to changes in at least one of a utility grid voltage and a utility grid current.

The supercapacitor-based grid fault ride-through system provides a dynamic model of a wind generation system including a Voltage Source Converter (VSC), which functions as a Static Compensator (STATCOM). The power control capability of the STATCOM is extended by incorporating energy stored in a supercapacitor. The system implements a vector control technique based on the decoupling of real and reactive power. Simulation results show that a fixed speed induction generator is capable of withstanding a significant grid fault when aided by the supercapacitor-based grid fault ride-through system. Moreover, the induction generator regains its pre-fault status immediately after the fault is cleared.

This invention deals with an advanced Real-time Grid Monitoring System (RTGMS) suitable for both single-phase and three-phase electric power systems. This invention provides an essential signal processing block to be used as a part of complex systems either focused on supervising and diagnosing power systems or devoted to control power processors interacting with the grid. This invention is based on a new algorithm very suitable for real-time characterization of the grid variables under distorted and unbalanced grid conditions. The main characteristic of this invention is the usage of a frequency-locked loop, based on detecting the grid frequency, for synchronizing to the grid variables. It results in a very robust system response in relation to existing technique based on the phase-angle detection since grid frequency is much more stable variable than the grid voltage / current phase-angle, mainly during grid faults. Moreover, the algorithm supporting this invention is very efficient and can be implemented in regular industrial microprocessors. These features make the RTGMS object of this invention ideal to be applied in the control of distributed generation systems (DGS), flexible AC transmission systems (FACTS), power quality conditioners (PQC) and uninterruptible power supplies (UPS). In all these systems, the fast and precise real time detection of the voltage and / or current sequence components under grid fault conditions is a crucial matter.

The invention relates to a platform and a method for judging a fault of a match power grid and belongs to the technical field of power grid management. The platform comprises a fault information receiving module, a fault equipment positioning module, a fault information screening module, a line topological analysis module, an equipment operation information analysis module, a line switch analysis module and a fault analysis display module. The method comprises the following steps of: receiving fault information; acquiring source equipment information related to the fault information; screening the fault information to obtain a line topological structure and an equipment list; carrying out measurement analysis and judging whether equipment has a fault, executing the next step if yes, and finishing if no; detecting on-off information of a switch and judging whether a line fault exists; and determining the type, the position and the influence region of the fault and displaying the fault equipment and the information and the influence region thereof. According to the platform and the method, as soon as the reported fault information is received, the judgment can be automatically carried out in advance to obtain the accurate type, position and influence region of the fault so as to provide powerful basis for rush repair and management of the fault.

A dynamic layer diagnostic device for smart power grid fault comprises a data collection and monitoring unit, a data processing unit, a data base unit, a communication unit and a man-machine interaction unit. A dynamic layer diagnostic method includes: when a smart power grid breaks down, calculating fault diagnosis starting conditions to conform a diagnosis strategy, wherein the fault diagnosis strategy comprises switch layer diagnosis, feeder layer diagnosis and transformer substation layer diagnosis; starting the switch layer diagnosis when changes of switch motion information are remarkable before and after the fault; starting the transformer substation diagnosis when changes of electricity amount information are remarkable before and after the fault; stopping the diagnosis when a fault element is the only one element during the diagnosis of the switch layer; otherwise, retrieving the switch historical action recording, and starting the transformer substation diagnosis when recording matched with the current switch action exists; and otherwise, starting the feeder layer diagnosis. The dynamic layer diagnostic method performs layering analysis on the fault, fully utilizes various fault information and improves fault diagnosis accuracy according to different characteristics of multisource information after the power grid fault and difficulty layer in obtaining and processing of various information.

In one embodiment, a current-fed modular multilevel dual active-bridge DC-DC converter suitable for medium voltage direct current (MVDC) grid or high voltage direct current (HVDC) grid integration is described. The DAB modular converter and the current-fed DAB converter are soft-switched modular multilevel dual-active-bridge (DAB) converters having DC fault ride-through capability. In an additional embodiment a voltage-fed isolated modular dual active-bridge DC-DC converter for medium voltage direct current (MVDC) or high voltage direct current (HVDC) grids or systems is described. In specific embodiments, the converters may be coupled to a battery energy storage system (BESS), wherein the BESS comprises split-battery units and the interface of the isolated DC-DC converter connects the split-battery units to the MVDC or HVDC system. The converters can be implemented in single-phase or poly-phase configurations and can be controlled to maintain a desired DC output current under both normal and DC grid fault condition.

An uninterruptible power supply system has standby and backup modes and can change to backup mode upon detection of a grid fault. In both modes an alternator rotates at synchronous speed so that backup mode capability is ready. An energy storage unit through a DC-AC inverter remains coupled to the grid in standby mode so that it is charged, ready to supply power when changed to backup mode. In standby mode, first and third clutches are disengaged and engaged, transmitting alternator rotary motion to a flywheel but not therefrom to a heat engine. In backup mode, first and third clutch are engaged and disengaged to permit the alternator, via a second clutch, to overrun the flywheel and allow transmitting of flywheel torque to accelerate the heat engine to starting speed for driving the alternator to supply power to the grid after the engine is at operating speed and coupled to the alternator through a locked second clutch and an engaged third clutch.

The invention discloses a grid fault worksheet handling method, apparatus, and system. The grid fault worksheet handling method comprises the steps of obtaining a fault worksheet issued by a server, and displaying the fault worksheet on a terminal screen, wherein the fault worksheet comprises task information of fault equipment that is in fault and to be maintained; the task information at least comprises the recorded fault type; receiving a maintenance information confirmation instruction of the to-be-maintained fault equipment, wherein the maintenance information confirmation instruction is used for obtaining the fault information corresponding to the fault type of the to-be-maintained fault equipment; and displaying the maintenance information on the terminal screen. Through the grid fault worksheet handling method, the technical problem of low handling efficiency on the grid faults by operation and maintenance workers in the prior art is solved.

The invention discloses a low-voltage ride through control strategy for a grid-connected photovoltaic power generation system capable of providing the reactive support. The strategy comprises the steps of control over a preceding-stage DC / DC converter and control over a backward-stage grid side inverter. When grid faults occur, the backward-stage grid side inverter is controlled to provide needed reactive power for a power grid according to the voltage drop depth of the power grid; the feed-forward compensation dosage reflecting photovoltaic array output power and direct-current voltage fluctuation is added into a direct-current side voltage control ring of the inverter, and therefore over-voltage of the direct-current side of the inverter is reduced in the fault occurring process; a controller of the preceding-stage DC / DC converter controls a photovoltaic array to output active power according to the voltage drop depth and the rated capacity of the inverter, so that unbalanced energy in a photovoltaic system when the faults occur is reduced, and the purpose of reducing over-current and over-voltage in the photovoltaic system is achieved. According to the strategy, no hardware device is additionally arranged, the response speed is high, realizing is simple, the low-voltage ride through capacity of the photovoltaic system can be effectively improved, the reactive power can be provided for the power grid, and the voltage recovery of the power grid is supported.

A protection system and a protection method are provided for protecting a double fed induction generator and a gearbox during a grid fault. The protection system includes a plurality of controlled impedance devices. Each of the controlled impedance devices is coupled between a respective phase of a stator winding of the double fed induction generator and a respective phase of a grid side converter. The protection system also includes a controller configured for coupling and decoupling impedance in one or more of the plurality of controlled impedance devices in response to changes in at least one of a utility grid voltage and a utility grid current.

The invention provides an online detection and calibration method for a Hall current sensor. In power system application, the Hall current sensor is often impacted by grid fault current or thunder strike to cause bias magnet and damage of the Hall current sensor. In the method, a calibration coil, and auxiliary elements which assist calibrating the Hall current sensor and calibrate a current generator and the like are arranged in the Hall current sensor so as to realize the online detection and calibration of the Hall current sensor. The online detection and calibration method for the Hall current sensor has the advantages that: on the one hand, the measurement accuracy of the Hall current sensor can be improved and a bias magnet error problem can be solved; and on the other hand, a fault sensor can be discovered timely.

The invention relates to a rules-based intelligent system for grid fault diagnosis, comprising a real-time data acquisition module, a data receiver, a preprocessing module, a working database, a knowledge base, an inference engine and a command generator. The real-time data acquisition module acquires real-time data information of a grid and sends it to the data receiver; the data receiver performs reasonableness testing and encoding; the preprocessing module performs formatting and information fusing and sorting and stores the information in the working database; the working database sends a command to the inference engine; the inference engine sends an inference verification request to the knowledge base; the knowledge base acquires data from the working database and performs data matching on the basis of a grid CIM (common information model) according to knowledge rules in the knowledge base built; the inference engine performs inference analysis according to the data in the working database, system state and knowledge in the knowledge base. The system has the advantages that a self-learning function is achieved, checking and error correcting is facilitated and grid fault diagnosis is more efficient.

The present invention relates to a method and an apparatus for controlling a power-grid connected wind turbine generator during grid faults. During grid faults, the stator windings of the wind turbine generator are disconnected from the power grid and impedances for dissipating at least part of the power generated by the wind turbine during grid fault condition are connected to the stator windings. In this way, a certain magnetisation of the generator can be maintained and after removal of the grid fault condition, the generator is synchronised to the power grid and the impedances are disconnected and the stator windings are reconnected to the power grid. In this way, it is possible to keep the wind turbine generator at least partly magnetised during grid faults and thus ready for delivering power to the power grid, as soon as the grid voltage is re-established after the fault.

The invention discloses a nondelay control method for the current of the rotor of the variable speed constant frequency double feed nonsynchronous aerogenerator(DFIG). The switch of the rotational coordinate is finished by collecting three phase rotor current signal so as to obtain the rotor current feedback amount in the static frame of axes to compare with the rotor current command in the stator static frame of axes, the difference signal is input into the proportion-resonance regulator for comparison, the rotor voltage reference value in the stator static fame of axes is obtained after feedback compensation decoupling. The rotor voltage reference value is then transformed into reference signals for space vector pulse width regulation in the rotor frame axes to generate switch signals of the power components of the converter of the rotor to control the synchronize and close operation of the generator. The invention is needless of the break down of the positive and negative sequence of current of the EFIG rotor no matter the electric net voltage is balance or not without introducing break down delay. The invention can realize strengthened control of the generating system in imbalanced electric net, effectively improve non-stop operation of the aerogenerator.

The present invention relates to a method and an apparatus for controlling a power-grid connected wind turbine generator during grid faults. During grid faults, the stator windings of the wind turbine generator are disconnected from the power grid and impedances for dissipating at least part of the power generated by the wind turbine during grid fault condition are connected to the stator windings. In this way, a certain magnetisation of the generator can be maintained and after removal of the grid fault condition, the generator is synchronised to the power grid and the impedances are disconnected and the stator windings are reconnected to the power grid. In this way, it is possible to keep the wind turbine generator at least partly magnetised during grid faults and thus ready for delivering power to the power grid, as soon as the grid voltage is re-established after the fault.

A double fed induction generator (DFIG) system and controller are presented in which the rotor side converter is preloaded with one or more initial values for resuming regulated operation to counteract transients upon deactivation of the crowbar protection circuit to provide grid fault ride through.

The invention provides a transmission line monitoring method and a transmission line monitoring device. The transmission line monitoring method comprises the following steps: comparing acquisition information sent by multiple pieces of acquisition equipment with preset information thresholds respectively to get comparison results; if judging that the acquisition information is abnormal information according to the comparison results, sending an abnormality alarm to a monitoring platform; generating task planning information and a maintenance preparation list according to the historical fault information in a fault information base, the abnormal information, and the personnel information in a personnel information base; determining whether each of maintenance terminals corresponding to maintenance terminal identification numbers in the maintenance preparation list is online; determining a target maintenance terminal; sending the task planning information to the target maintenance terminal; receiving maintenance information returned by the target maintenance terminal; and updating the fault information base according to the maintenance information. The problem in the prior art that there is no good monitoring plan for transmission lines and a grid fault cannot be responded to in a timely manner when a transmission line is abnormal is alleviated.

The invention discloses a symmetrical fault ride-through control method of a double-fed wind generator set. Under a grid fault of the double-fed wind generator set, a rotor Crowbar circuit of the double-fed wind generator set starts operation, and a rotor converter is locked at the same time when the current flowing to the rotor converter exceeds the maximum allowable current of the rotor converter. During the occurrence of the fault, the rotor Crowbar circuit is cut off, and the rotor converter is restarted at the same time when the rotor current value is smaller than a Crowbar protection action threshold value after the rotor Crowbar circuit enters tauonr duration. After the fault is removed, the rotor converter is switched to be in an active power work mode by recovering the control strategy, and stops injecting the passive current to a grid. The method provided by the invention can overcome the disadvantages in the existing fault ride-through control strategy, thereby improving the fault ride-through capacity of the double-fed wind generator set.

The invention discloses a method for predicting power supply reliability of a power grid based on a BP neural network. According to the method in the invention, the BP neural network is adopted to perform modeling prediction, and then, the BP neural network is trained and a prediction model of the power grid reliability is established with power supply capacity of the power grid as well as natural disasters faced by the power grid and other factors acting as input variables of the model, and power grid fault outage time which affects the power supply reliability acting as output variables of the model; based on the previous steps, principal component analysis is adopted to perform reducing-dimension processing on inputted samples, and therefore, input structure of the artificial neural network is simplified, thereby improving learning speed and accuracy of the network.

The invention discloses a system and method for grid fault identification based on a random point distribution PMU and belongs to the technical field of power system fault identification. The system comprises a fault relative domain identification module, a fault locating module, a fault component identification module and a domain backup protection module. A grid structure changing characteristic is evolved to a branch current difference by the fault relative domain identification module, so that fault relative domain identification is achieved; overall traversal is conducted on a relative domain by the fault locating module, so that accurate location of a fault point is achieved based on a node voltage matching condition; based on virtual current differential, protecting criteria are constructed through an opposite terminal calculated current and a home terminal actually detected current by the fault component identification module, so that fault component identification is achieved; according to domain backup protection operation logic, the near backup tripping function and the far backup tripping function are achieved by the domain backup protection module. Complete domain backup protection under the environment of random PMU point distribution is achieved and the dependence degree on synchronous data of protection is reduced to a great extent.

In one aspect, a method for protecting one or more electrical machines during a grid fault on an electrical system connected with the one or more electrical machines is provided. The method includes detecting a grid fault on an electrical system; taking one or more first actions from a first set of actions based on detected grid fault on the electrical system; detecting at least one operating condition of the electrical system after taking one or more first actions from the first set of actions based on the detected grid fault on the electrical system; and taking one or more second actions from a second set of actions based on the detected at least one operating condition of the electrical system.

The invention provides a power grid fault diagnostic model and a diagnostic method thereof and belongs to the technical field of power grid fault diagnosis. A mathematical expression of the traditional fault diagnostic analytic model can be abstracted as the formula; analysis on the action state of protecting a switch is converted into description on the probability of protecting the switch; the description is information transmission uncertainty description based on an information theory; an objective function is established as an optimal solving function; mutual information between an information sink and an information source under every failure mode is calculated when multiple optimal solutions, namely multiple failure modes exist; corresponding failure modes are most likely to occur if the quantity of condition self-information is smallest; and a principle that the mutual information of the information sink and the information source is maximum is utilized to determine a fault sorting result when the plurality of condition self-information is similar. The power grid fault diagnostic model and the diagnostic method thereof have the advantages of enabling the uncertainty of fault diagnosis to be integrated in an analytic model, enabling the fault tolerance of the model to be improved and the dimension of the model to be greatly reduced, being high in diagnostic speed and diagnostic accuracy, being capable of being well applied to a scheduling terminal and playing a positive and important role in the field of the power grid fault diagnosis.

The invention, belonging to the field of dispatching and management of a distribution network, provides a method and system for switching a microgrid between an island mode and a grid connected mode. When an external electric network has a fault, distributed power in a microgrid system is cut off, a grid connected contact breaker of the microgrid system and the external electric network is opened, a voltage and a frequency of the microgrid system are regenerated by a main power switching control mode in the microgrid system, and the microgrid system works independently; and when the external electric network returns to normal, if the electric network side voltage of the grid connected contact breaker is monitored to be normal and is lasted for a certain time, operations of a fan, a photovoltaic power generation system and an energy storage system of a storage battery are stopped, the grid connected contact breaker of the microgrid system is closed, a load is powered with the external electric network, the devices such as the fan and the like are reconnected to the grid for operation, so that a stable operation of the microgrid system in a transient state process of switching between the island mode and the grid connected mode is satisfied, the transient time is shortened, and the requirements of the microgrid system in safety, reliability and quick response are satisfied. The method and system have the characteristics of quickness, stability and reliability.

The invention belongs to the technical field of electric system intelligent analysis and control, and particularly relates to an implementation method of a grid fault diagnosis system considering uncertain information. The implementation method of the grid fault diagnosis system considering the uncertain information is a grid fault diagnosis system practical method of an information theory and an expert system, is provided on the basis of a power system fault diagnosis method based on the information theory and the expert system, wherein the power system fault diagnosis method based on the information theory and the expert system is provided by a Chinese patent with a publication number of CN101661070A. The movement condition of reclosure and the movement condition of spare power automatic switching are added, and the practical requirement for applying the implementation method of the grid fault diagnosis system considering the uncertain information to an actual power system fault diagnosis system is met. The implementation method of the grid fault diagnosis system considering the uncertain information inherits an original method, and can further use movement information of the reclosure and movement information of the spare power automatic switching to give presentation of the movement condition of reclosure and presentation of the movement condition of the spare power automatic switching. Fault phase difference and fault types are used for reducing the scale of a protection set of possible movement, and complexity of a diagnosis process is reduced. The implementation method of the grid fault diagnosis system considering the uncertain information can serve as reference of a grid fault diagnosis system based on an algorithm of the same class.

The invention relates to a device and a method for testing pressure of an intelligent substation, and belongs to the technical field of intelligent substations. The device comprises an upper computer, a CPU (central processing unit), an FPGA (field programmable gate array) and an Ethernet physical layer circuit connected in sequence. A testing environment meeting requirements of an IEC (international electro-technical commission) 6185O specification system is provided, normal sampling values (SV) and GOOSE data can be output, normal system running or grid fault can be simulated, background interference flow data in an SV format and background interference flow data in a GOOSE format can also be output, and further, messages such as IP(internet protocol), ARP(address resolution protocol), ICMP(internet control message protocol) and SNMP(simple network management protocol) can be output to form a general background flow. By filtering and analyzing the SV message or the GOOSE message or the MMS message with the specific APPID, potential safety hazards existing in different load-pressure backgrounds of the specific IED device in the network or network switching devices of the whole process level are found, and safety running level of the intelligent substation is increased.

The invention discloses a method for detecting a reference signal controlled by a wind-powered electricity generation set in case of asymmetrical failure of an electric grid. The method separates a positive-sequence component and a negative-sequence component from the acquired three-phase asymmetrical voltage of a stator of a wind-driven generator by a'T / 16 delay' separation method, and realizes rapid detection on the positive-sequence component amplitude, the phase and the frequency of fundamental voltage. The method can rapidly separate the positive-sequence component and the negative-sequence component from the voltage in the electric grid with failure, has the advantages of high detection accuracy and good real-time property, and provides basis for the operation control of the wind-powered electricity generation set under various circumstances of failures in the electric grid.

The invention discloses a method for positioning a fault disturbance point in a power grid in the technical field of power system measurement and control. The method comprises the following steps of: preprocessing all PMU (Power Management Unit) devices with GPS (Global Position System) time marks; measuring a maximum value of phase voltage, a minimum value of phase voltage, a maximum value of phase current, a minimum value of phase current and corresponding moments corresponding to the maximum and minimal values of the phase voltage and the phase current in any one phase in each power frequency cycle of each node, and sending the measurement data to a power grid control center; judging if the fault disturbance is caused in the power grid by the power grid control center according to the received measurement data, and calculating active power and reactive power of each node when the fault disturbance is not generated in the power grid; otherwise, extracting a voltage disturbance quantity curve of each node, and judging the type of the fault disturbance, and determining the position of the fault disturbance point according to the type of the fault disturbance. The method solves theproblems on calculation of the active power and the reactive power in the stable running state of the power grid, judgment of the type of the fault disturbance in the power grid and positioning of the fault disturbance in the power grid.

The invention discloses a low voltage ride-through control method of a doubly fed induction aero-generator, which is used when a power network has short circuit faults. The control method is characterized in that a rotor exciting voltage positive-sequence control current and a rotor exciting voltage negative-sequence control signal are respectively formed through limiting a rotor slip frequency current and a rotor (2-s) rated frequency current when the power network has faults, and a generator is utilized for realizing the attenuation of stator flux transient DC components and reducing the rotor side influences of the stator flux transient components, positive-sequence components and negative-sequence components. The control method has the advantages that no hardware protecting device is required to be added; under the condition that the power network has symmetrical and asymmetrical faults, the overcurrent occurrence of the rotor can be effectively restrained, and the safe operations of the generator and a rotor exciting converter are protected; in the process that the power network has the faults, the transient generator impact to the power network and a mechanical system can be effectively reduced; the normal operation of the generator can be fast recovered after the faults are removed, and the timely support to the power network can be realized.

The invention provides a dynamic reactive current direct control method by a doubly-fed wind turbine generator set during a grid fault. The method includes the following steps: a, judging whether a doubly-fed wind turbine generator enters a low voltage ride through mode or not, b, in normal operation, adopting a double closed loop control mode with the power on the outer loop and the current on the inner loop for the wind turbine generator set, c, if a protective action is not triggered during the fault, performing direct current control by the wind turbine generator after the wind turbine generator enters the LVRT mode, and d, if the grid fault causes the overcurrent of a rotor current converter or the overvoltage of a direct current capacitor, after the current converter enters a lockout state, performing protective action by a crowbar to bypass the current converter until the set engaged time is over and a frequency converter is controlled again. The dynamic reactive current direct control technology by the doubly-fed wind turbine generator set during the grid fault can achieve that during the fault, the wind turbine generator set injects a reactive current into a power grid fast and provides voltage support, and helps the wind turbine generator set to achieve low-voltage riding through.