2116 results about "Islanding" patented technology

A method and apparatus for anti-islanding of distributed power generation systems having an inverter comprising a phase locked loop (PLL), a phase shift generator for injecting a phase shift into the PLL during at least one sample period, and a phase error signature monitor for monitoring at least one phase error response of the PLL during the at least one sample period.

A system and method for detecting islanding in a Distributed Generation utility grid is described. In some examples, the system, via an inverter, injects a frequency disturbance to a location of the utility grid associated with a DG generator, measures both the frequency error due to the disturbance and the frequency drift of the location of the utility grid, and determines islanding based on a maximum value of the frequencies. In some cases, the system is able to reduce or minimize the Non-Detection Zone of the inverter by detecting islanding without always relying on a detectable frequency error due to an injected waveform.

A control strategy for distributed power generation modules in a power system that varies the line frequency or voltage according to a predetermined pattern to cause a PV inverter to modify its power output and thereby avoid overcharging a battery. When the power system operates in islanded mode, the AC load demand can be lower than the available energy from the PV array, causing the battery to become overcharged. To avoid this scenario, a hybrid inverter executes a pattern generator algorithm that varies the line frequency or voltage linearly, exponentially or any mathematical function or look-up tables. The PV inverter executes a pattern detection algorithm that detects the linear, exponential, or any mathematical function or look-up table change in the line frequency. In response, the PV inverter modifies its power output until an overcharging condition of the battery is removed. The line frequency/voltage can be varied within the anti-islanding limits to avoid premature disruption of the power system, and no additional settings are required at the device level in order to operate in any mode of operation: islanded, grid-connected or genset-connected.

A cluster recovery and maintenance system, method and computer program product for use in a server cluster having plural nodes implementing a server tier in a client-server computing architecture. A first group of N active nodes each run a software stack comprising a cluster management tier and a cluster application tier that actively provides services on behalf of one or more client applications running in a client application tier on the clients. A second group of M spare nodes each run a software stack comprising a cluster management tier and a cluster application tier that does not actively provide services on behalf of client applications. First and second zones in the cluster are determined in response to an active node membership change involving one or more active nodes departing from or being added to the first group as a result of an active node failing or becoming unreachable or as a result of a maintenance operation involving an active node. The first zone is a fault tolerant zone comprising all active nodes that remain operational. The second zone is a fault containment zone comprising all active nodes participating in the membership change and at least a corresponding number of spare nodes to the extent that the membership change involves a node departure. During recovery and maintenance, fast recovery/maintenance and high application availability are implemented in the fault containment zone, while continuous application availability is maintained in the fault tolerant zone.

An area electric power system includes a number of direct current power sources, and a number of inverters operatively associated with the number of direct current power sources. Each of the number of inverters is structured to provide real power and controlled reactive power injection to detect islanding. An output is powered by the number of inverters. A number of electrical switching apparatus are structured to electrically connect the number of inverters to and electrically disconnect the number of inverters from a utility grid. A number of devices are structured to detect islanding with respect to the utility grid responsive to a number of changes of alternating current frequency or voltage of the output.

The present invention provides an improved control methodology for maximum power point tracking (MPPT), anti-islanding, and output current regulation for distributed generation sources connected to a utility grid. The control includes enhancements for MPPT and regulating the inverter output-current that is sourced into the utility grid. In addition, the functions associated with MPPT, anti-islanding detection and output current regulation are integrated together; the MPPT algorithm operates in conjunction with the anti-islanding detection, and the output current regulation operates in conjunction with the MPPT algorithm.

The invention discloses a medical data security cooperation system based on a block chain, which realizes unified management of medical big data and solves the problem of medical data islands. According to the system, a set of stable, authentic and decentralized medical record data storage system is designed by combining a block chain technology and a cryptography technology; reliable storage of personal electronic health records is ensured by using the decentralized, traceable and tamper-proof core application capability of the block chain; a ciphertext access control strategy for sensitive data is designed by applying cryptography hybrid encryption, attribute encryption and other technologies while reliable storage of personal electronic health records is guaranteed, and personal privacyand data security are fully protected through data desensitization and encryption in the processes of information authentication, broadcasting and transmission. An effective excitation mechanism is also designed, and interconnection and intercommunication and security cooperation of medical big data are realized under the action of the excitation mechanism.

The invention discloses a method for islanding microgrid control and optimization based on rotating coordinate virtual impedance. Aiming to a fact that the actual microgrids have complicated impedance characteristics, the method for islanding microgrid control and optimization based on the rotating coordinate virtual impedance includes utilizing the coordinate rotation orthogonal transformation to design the coordinate rotation virtual impedance, improving the impedance characteristics of the microgrid, compensating errors of power distribution and improving power decoupling performance; establishing a complete small-signal dynamic model of the microgrid, wherein the small-signal dynamic model comprises distributed energy sources, power converters, loads and power grids, and guiding the selection of an optimal value on the basis of the small-signal dynamic analytical method; and simultaneously, providing a theoretical basis for the optimization selection of islanding microgrid control parameters by using the small-signal dynamic analytical method, wherein the islanding microgrid control parameters comprise droop control coefficients of the power distribution, process identifier (PI) parameters of a voltage current feedback controller, feedforward control coefficients and the like. The microgrid after being subjected to optimization design in an islanded operational mode is capable of effectively achieving power decoupling and improving the accuracy of the power distribution, the stability of the system and the dynamic performances.

The invention relates to a microgrid smooth switch control method and strategy based on composite energy storage. According to the invention, a low voltage microgrid containing a plurality kinds of distributed power supplies is arranged, a public connecting point PCC in the low voltage microgrid, the distributed power supplies and the switches of all branches are monitored by a microgrid energy management system EMS, and the microgrid energy management system EMS detects the on/off state of the public connecting point PCC of the microgrid to judge whether the low voltage microgrid is located at an isolated island operation state or a grid-connected operation state. The microgrid smooth switch control method is characterized in that a composite energy storage unit composed of a supercapacitor and a storage battery is arranged in the low voltage microgrid containing the plurality kinds of distributed power supplies, and the composite energy storage unit is used for performing microgrid smooth switch control on the basis of the monitoring of the microgrid energy management system EMS on the low voltage microgrid. According to the invention, the composite energy storage characteristics are fully utilized to greatly improve the power supply reliability and power supply quality of the microgrid under a switch emergency state to facilitate the generalization and application of the microgrid.

A method of controlling a generator system connected to an electric power system in which the output frequency characteristic of the generator system is measured, a first phase angle and frequency of the measured frequency characteristic is estimated using a first phase locked loop having a first bandwidth, and a second phase angle and frequency of the measured frequency characteristic is estimated using a second phase locked loop having a second bandwidth greater than the first bandwidth. Further, the method calculates a frequency difference between the first and second estimated frequencies, and an angle variation that is proportional to the calculated frequency difference. The estimated second phase angle is then added to the calculated angle variation so as to form an output current phase angle reference, and an output current phase angle of the generator system is controlled to be aligned with the output current phase angle reference. The method also determines whether or not the generator system is within a generation island based on the measured frequency characteristic.

An electrical power supply system connected to an electrical grid, includes at least one source of electrical power, an inverter which receives power from the electrical source and delivers power to a local load, and a connection to the electrical grid. The system also includes a control unit for controlling the inverter, which interrupts the delivery of power by the inverter when at least one electrical parameter of the system exceeds a threshold value. The system also includes anti-islanding logic which detects at least one symptom of an islanding condition of the system and, when the symptom is detected, to cause a variation in the power level delivered by the inverter.

Disclosed is a comprehensive coordination control method of a wind-solar direct current micro-grid. The wind-solar direct current micro-grid comprises wind driven generator and alternating current (AC)/direct current (DC)/DC converters, photovoltaic array and DC/DC converters, a circuit interrupter, AC/DC load and DC/AC and DC/DC converters, a DC bus, a supercapacitor energy storage system and bi-directional DC/DC module, a storage battery energy storage system and bi-directional DC/DC module, a bi-directional AC/DC converter, a coordination controller, a control network for connecting the coordination controller and the converters and a communication network for connecting the coordination controller and a large power grid power scheduling center, and an operational mode of the wind-solar direct current micro-grid is divided into two categories of a grid-connected mode and an island mode. Stable operation of the wind-solar direct current micro-grid under the grid-connected mode and the island mode is achieved by comprehensively using power scheduling, load scheduling and energy storage device scheduling.

The invention discloses an alternating current and direct current hybrid micro-grid system and a control strategy of the micro-grid system. The micro-grid system comprises multiple generation units, load, a distribution line for connecting the generation units and the loads, and a monitoring protection unit; each generation unit comprises a large power grid, grid-connected AC/DC (alternating current/direct current) of the large power grid, an energy storage system, a DC/DC (direct current/direct current) converter of the energy storage system, a wind power generation system, an AC/DC converter of the wind power generation system, a photovoltaic power generation system, a DC/DC converter of the photovoltaic power generation system, and a diesel generator; said load includes AC non-significant load, AC significant load, AC/DC load, DC significant load and DC non-significant load; the distribution line comprises a DC distribution line and an AC distribution line; the operating status of each energy conversion device can be monitored in real time by the monitoring protection unit, two operating ways such as grid connection and isolation of the system can be realized by different control strategies, the distributive generation unit and the energy storage unit realize coordination and cooperation by controlling energy storage DC/DC, photovoltaic DC/DC, and wind power AC/DC, so that the power supply reliability is improved and the significant load can continuously operate.

The invention provides an isolated island operation detection method of photovoltaic grid-connected generation system which includes: a control device detects voltage frequency of grid-connected point, judges voltage frequency of grid-connected point whether reaching frequency protection threshold, if yes, a start anti-isolated island protection signal is outputted; if not, frequency signal of grid-connected current instruction is calculated by using double positive feedback active frequency deflection method, and the frequency signal is outputted; the double positive feedback active frequency deflection method is that obtained grid-connected point voltage frequency deflection relative to average frequency is used as first positive feedback, and change trend of frequency deflection is used as second positive feedback, feedback magnification factor of first positive feedback is adjusted. The method realizes isolated island detection rapidly, simulation and experimental result, isolated island detection time is shorten in 0.10s, 0.13s, grid-connected current harmonic distortion THD are 2.06%, 2.97% respectively, and has advantage over traditional method in isolated island detection speed and reducing interference to power network.

The invention discloses a DG (distributed generation)-containing power distribution network distributed protection and control method, and provides a protection and control technical method based on an AFTU (advanced feeder terminal unit) for the phenomenon that the high-permeability distributed power access power distribution network causes great difficulties in traditional power distribution protection and control. The method disclosed by the invention divides the DG-containing power distribution network into multiple areas capable of running as islands in advance according to the DG capacity and load. Circuit breakers and AFTUs are arranged at the feeder outlet, the DG access position and the area boundary, and the AFTUs are connected through an optical network. Each AFTU detects local electric quantity information in real time and performs information interaction with other AFTUs. The method disclosed by the invention quickly positions the fault section according to the local and neighbor electric quantity information, and realizes the fault isolation and island running. A reclosing and island network re-connection control strategy is designed by use of the related AFTU information.

The invention relates to a dual-network routing method. The method comprises the following steps: nodes are initialized to establish routing registry connection and generate a routing list; a first communication link is adopted for transmitting data, and the first communication link is preferentially switched to a second communication link to continue to transmit data in the case of communication link interrupt. The first communication link is a wireless communication link, the second communication link is a power line communication link, and vice versa. The method has the advantages that higher communication reliability and carrier class reliability are realized, communication real-time property is guaranteed, and the technical problem of signal island in the prior art is solved.

The invention provides a control method of a grid friendly type distributed power source based on hybrid energy storage. The method comprises the steps of optimally designing a topology structure of the distributed power source, controlling a direct current power supply system in a coordinating mode through a direct current (DC)/DC converter controlling a model normalization model, and self-adaptively controlling a grid of an alternating current (AC) side DC /AC converter. The distributed power source not only can be connected in a large grid to operate so as to reduce the influence of intermittent renewable energy power generation grid connection on the grid and provide support of voltage and frequency for the grid, but also can be connected into a micro-grid to operate as a network unit of the off-network type micro-grid to maintain stability of voltage and frequency of the off-network type micro-grid. When an outer grid breaks down, the distributed power source can realize switch between a grid mode and an island mode so as to improve power supply reliability of important loads in the system. The distributed power source improves technical performance and economic performance of the whole system through matching utilization of an energy type system and a power type energy storage system.

The invention discloses an optimization method of a network variable structure with a distributed type power supply distribution system. The optimization method includes that basic static data of electric power network structure parameters, distributed type power supply distribution, load capacity, faulty lines and the like are extracted, under the condition of present line fault, the basic static data are utilized to perform islanding scheme calculation and correction, survivability indexes constructed by the method are combined to perform an online evaluation for islanding network safe operation performances and implement immediate control measures, finally, on account of residual network structure data after final islanding electric power network division is performed, by means of an ant colony algorithm, a reconfiguration optimal computation is performed for residual network with minimum network loss as a target, and finally the electric power network structure with high safe operation level is obtained. On the basis of the developed algorism and function modules, the invention further provides a large-scale power distribution network intelligent optimization decision system based on multi-stage computation correction and survivability evaluation, according to the technical scheme, the division and reconstruction of the network with the generalized model distributed type power supply distribution system are achieved, and accurate reference of network structure adjustment, schedule and operation can be excellently provided for regional electric power network schedule staffs.

A method and system fulfills ad requests for delivery of ads to mobile clients in a mobile network. Ad data silos for ad requesters are maintained. The ad data silos are organized according to selected characteristics of the mobile clients of the ad requesters. In response to an incoming request for delivery of an ad, an attempt to fill the incoming request includes at least one of (1) retrieving an ad from a corresponding ad data silo to fulfill the incoming request, and (2) retrieving an ad according to a first priority policy from ad source among the plurality of ad sources to fulfill the incoming request. Also, in response to the incoming request, or other signals that may indicate current activity by the ad requester, an ad is retrieved according to a second priority policy for filling the corresponding ad data silo.

The invention discloses a mixed bipolar DC transmission system. The system comprises a rectification converter station and an inversion converter station which are connected through a DC transmission line, wherein the rectification converter station is formed by two thyristor converters through serial connection, and the serial connection node is grounded; and the inversion converter station is formed by two modular multilevel converters (MMCs) through serial connection, the serial connection node is grounded, and positive and negative ends after serial connection are connected with one-way connection power devices. The system has the advantages of low cost and loss, high reliability and the like of the existing thyristor converter, flexible control of the MMCs, low harmonic, active-reactive power decoupling control, low dependence on an alternating current system and the like; and the system is divided into positive and negative poles, so that operating reliability is strengthened, and the power devices provided with the one-way connection capacity and additionally arranged at outlets of inverters can effectively handle DC faults. The system is suitable for occasions such as high-power long-distance high-voltage DC transmission and island current delivery, provided with broad development space, and worthy of being popularized vigorously.