108 results about "Island state" patented technology

The invention discloses an island detection method of a high-power photovoltaic grid-connected converter. The method comprises the following steps of: determining whether a system operates at a grid-connected power generation state, and starting up an island detection algorithm instantly if the system is at the grid-connected power generation state; detecting whether the frequency of the voltage of a port power grid is within the normal range in real time, if the frequency is not within the normal range, considering that the system is at the island state, and carrying out automatic safety stop on the system; adding reactive current Iqdisturb with the duration of td periodically within the normal range; and superposing the reactive current Iqdisturb and reactive control Icqset of the converter, thus an axis q component reference Icqref of grid-connected current of the converter is formed finally. The contradiction between two aspects of reliability of detection and the quality after grid-connected electric energy reduction for the traditional island detection algorithm is effectively solved by the method provided by the invention, and the implementation method is simple and effective.

The invention discloses a method for detecting a piconet island state according to the self-characteristic of a piconet. The method comprises the following steps of: (1) detecting electrical characteristic value when the piconet runs; (2) judging whether the voltage at a load end is higher than the definite value or not, if yes, entering step (3), and if not, considering that the piconet is not in the island state; (3) judging whether the frequency changing rate is higher than the upper limit of the definite value or not, if yes, sending out a trip signal and then finishing, and if not, entering step (4); (4) detecting and judging whether the frequency changing rate is higher than the lower limit of the definite value or not, if yes, judging whether the phase difference is more than the phase difference setting valve or not, if yes, finishing the detection and sending out the trip signal, and if not entering step (5); and (5) after delaying for a period of time, judging whether the phase difference is more than the phase difference setting valve or not, if yes, sending out the trip signal, and if not, considering that the piconet is in the island state. Compared with the existing detection method, the method has the characteristics of rapid and reliable detection, and guarantees comparatively high anti-interference capability at the same time.

The invention relates to the field of protection and control of micro-grids of electric power systems and particularly relates to a micro-grid island fast detection method. The method is sued for an inverter-based distributed generation (IBDG) with a PQ (power quest) decoupling control strategy; a corresponding reactive power control strategy is adopted in the method on the basis of measuring a voltage effective value UPCC and the load reactive power of a common coupling point PCC in real time through comparing the voltage effective value UPCC with the voltage effective value under a normal condition; when island determination is performed, firstly, a voltage threshold value and a frequency threshold value are predetermined, the voltage effective value UPCC is compared with the voltage threshold value, if the voltage effective value UPCC exceeds the threshold value, the PCC is directly determined be in an island state and the island detection is finished, and if the voltage effective value UPCC does not exceed the threshold value, the voltage frequency f of the PCC is compared with the frequency threshold value, the PCC is determined to be in the island state if the voltage frequency f of the PCC exceeds the threshold value. With the adoption of the detection method, the micro-grid island detection can be realized fast, and the effectiveness of the island detection can be ensured even under the existence of a plurality of inverter-based distributed generations.

The invention discloses a grid-connected inverter island detection method based on wavelet transform and a neural network. The method is characterized in that the method comprises the following steps: firstly, gathering voltage values of a distributed grid-connected power generation system at a point of common coupling at island state and non-island state and the output current value of an inverter, then performing wavelet transform on the gathered voltage values and the output current value of the inverter and exacting high-frequency component wavelet coefficients to be processed, and finally taking processed signals as input signals of the neural network, and taking corresponding island state and non-island stage as output signals to train the neural network, so as to ensure that the system obtains recognition capability to the island state and the non-island state, and to adopt corresponding island protection measures when the distributed grid-connected power generation system is at the island state. The method can not only overcome the disadvantages of the existing passive island detection method that the detection blind area is large and the detection time is long, but also can solve the problem that the active island detection method affects the power supply quality of the distributed grid-connected power generation system, and rapidly accomplish island detection and island protection.

The invention relates to a transformer station domain island protection and backup automatic switching integrated method. The method is characterized by comprising the following steps: (1), acquiring the electrical amount information and switch state information at the high voltage side, the intermediate voltage side and the low voltage side of a transformer station in real time, and according to whether backup automatic switching upkeep pressure plates are thrown or retreat, identifying the current running states of elements at the high voltage side, the intermediate voltage side and the low voltage side of the transformer station; and (2), according to actual wiring conditions and onsite operation demands, through apparatus function pressure plates, selecting whether the backup automatic switching functions and island protection functions of the high voltage side, the intermediate voltage side and the low voltage side are open; and through apparatus software control words, setting backup switching modes of the high voltage side, the intermediate voltage side and the low voltage side for coupling to the previously identified operation states of the elements at the high voltage side, the intermediate voltage side and the low voltage side of the transformer station, and if coupling fails, sending alarm signals, locking an apparatus and discharging. The method firstly has an island protection function, can rapidly detect an island state and an island scope existing in the transformer station, and jumps away from photovoltaic power station grid connected switches in the corresponding scope.

A battery pack housing a plurality of battery cells in a case and respectively connecting the positive electrodes and the negative electrodes of the plurality of battery cells to conductive terminal boards to be led out to outside terminals is provided. The conductive terminal board has a structure in which a first member is joined with a second member such that the first member having excellent weldability is arrayed in a plurality-of-islands state in the second member having excellent conductivity, and the positive electrodes and the negative electrodes of the battery cell are welded to the first member of the conductive terminal board through resistance-welding, so that the battery pack capable of efficiently supplying a large amount of current is provided.

The invention relates to a photovoltaic microgrid system with a function of storing energy. The photovoltaic microgrid system comprises a solar cell plate, a storage cell, a bidirectional power converter, a local load and a grid-connection switch, wherein a first selector switch is arranged between the solar cell plate and the bidirectional power converter; and a second selector switch is arranged between the storage cell and the bidirectional power converter. In the photovoltaic microgrid system, functions of photovoltaic grid-connected power generation, storage cell grid-connected energy storage, storage cell grid-connected discharging and storage cell island discharging can be realized by adopting the same bidirectional power converter, so that the system structure is simplified and the cost is reduced; furthermore, as the bidirectional power converter is formed by combining three totally independent single-phase power conversion units, the balance of three phases of output voltage can be guaranteed through independent control of the single-phase power conversion unit in an island state when the storage cell supplies power to the local load, particularly when three phases of local loads are unbalanced severely.

The invention relates to a multiprocess island effect detection device and method and belongs to the field of fault detection of distributed power generation systems. Compared with the traditional island detection device, the multiprocess island effect detection device provided by the invention has the characteristics of small non-detection zone, high detection accuracy, strong applicability and the like; and island detection is carried out on a system by adopting a passive detection mode in which detection variables are mutually independent, and the island detection can be carried out on the system more comprehensively. Compared with the traditional island detection device which adopts single passive detection and active detection, the detection device provided by the invention has the characteristics that the advantages of less pollution to harmonic wave of a power grid and rapidity of passive detection are fully played, rapid judgement on the system is firstly realized, if the distributed power generation system is in an island state, the system is rapidly removed from the power grid. Besides, active detection is called to recheck the result of the passive detection, the advantage of high detection accuracy of the passive detection is fully played, and the defects that the detection time is long and the pollution level to the harmonic wave of the power grid is high can be overcome.

The invention pertains to the field of power system microgrid protection and control, and relates to a microgrid non-destructive island detection method based on adaptive reactive disturbance. The method comprises the following steps: periodic reactive disturbance is added on the reference value of IBDG reactive output, the peak value selection of a triangular wave reactive disturbance portion is related to the IBDG operating mode and the system frequency when the reactive disturbance value is zero in the last disturbance period; and if the absolute value of the frequency change rate is detected to be equal to a preset value, and the duration time reaches a time setting value, then the island state is judged. The method of the invention is simple and practicable, and can be used to minimize the total disturbance and the influences of the disturbance on the quality of electric energy.

The invention relates to photovoltaic power generation technology for direct-current microgrids and aims to provide a method and a system for power control of photovoltaic power generation in direct-current microgrids. The system comprises a photovoltaic power generation power controller which comprises a droop control module, a photovoltaic power-voltage curve fitting module, a rated point power control module and a voltage-current inner loop control module, and all of the modules of the photovoltaic power generation power controller are connected electrically to form a closed circuit. The photovoltaic power-voltage curve fitting module is further electrically connected with the voltage-current inner loop control module to transmit a photovoltaic direct-current bus voltage reference value, and the voltage-current inner loop control module outputs a pulse width modulation signal. The system is in a uniform control structure integrating various functions and can operate in a grid connection or an island state; when the system is in the grid connection state, photovoltaic power generation can be in a maximum power tracking mode or a fixed power tracking mode; when the system is in the island state, photovoltaic power generation can be in the maximum power tracking mode or a droop control mode, and participation in secondary voltage regulation of the direct-current microgrids can be realized.

The invention relates to the technical field of electric power system analysis and especially relates to an external centralized disturbance type impedance measurement island detection method suitable for a multimachine cluster. The method is characterized by, to begin with, generating a disturbance current signal iInj having a certain magnitude and waveform by utilizing an independent external centralized disturbance generation device; monitoring the voltage uPCC at the place of a system common coupling point, carrying out intermittent zero-crossing-point injection control at the place of the system common coupling point, and meanwhile, carrying out impedance measurement characteristic quantity calculation after data processing of the collected voltage uPCC at the place of the system common coupling point and the disturbance current signal iInj obtained in the injection process; and judging island state according to the change of characteristic quantity. The method is suitable for a distributed power supply system having a plurality of inverters, and meanwhile, is suitable for a power supply, having no inverter, of a synchronous generator and the like, thereby improving impedance measurement accuracy and reducing requirement for DC voltage grade of an injection device; and broad-frequency domain high-frequency reactance calculation enables island characteristic quantity difference to be enlarged, and the method has higher detection sensitivity and precision.

The invention relates to a method for stably controlling switchover from micro-grid connection into an island state. When switchover is planned, a micro-grid stability control system collects grid connection point power before the micro-grid is sectionalized from an electric system, a power source and a load are configured to be basically balanced, and meanwhile the grid connection point transmission power before sectionalization is sent to an inverter; a grid connection point breaker is stably cut off, the output power of the inverter is maintained as the grid connection point transmission power before the sectionalization, and power can reach the balance immediately after the micro-grid becomes off-grid. When the switchover is not planned, the micro-grid is sectionalized with the electric system suddenly to form an island, the load or the partial power branch circuit is cut within 10ms according to the difference between currents before the sectionalization of a grid connection point and the maximum output power of an energy storing inverter, and the stability of the system switchover moment is ensured; the energy storing inverter with the maximum capacity is immediately transferred into V/F control, and other power sources are set to be P/Q control. According to the method, the micro-grid connection can be smoothly switched over to the island state.

The invention relates to the technical field of power supply, and particularly relates to a two-stage power distribution network emergency island division method. The method comprises the steps: before a fault occurs, taking the guaranteeing of the stable transition of a system fault moment as a main target according to measurement information of a wide-area measurement system of a power distribution network, continuously solving a pre-fault island division optimization model at a certain time interval, and obtaining a pre-fault original island division scheme meeting the current state of thesystem; carrying out load increasing and load reducing correction of the original island scheme before the fault to obtain an island online division decision table, thereby facilitating real-time query at a fault moment to obtain a load shedding scheme meeting a system real-time state; after the system enters the initial island state through the execution decision table, dividing the whole power failure period into a plurality of time periods according to the estimated power failure time; taking the increase of the number of recovered loads as a target, solving the Look-ahead roll island division optimization model after the fault to obtain the latest island division scheme, and executing the latest island division scheme. According to the invention, the method guarantees the continuous power supply of a key load during the fault.

The invention discloses an island detection method based on harmonic distortion rate and frequency. The method herein includes the following steps: based on historical data, determining the maximum value (H<1>) of the harmonic distortion rate when a distributive photovoltaic power generation system joints a power grid and the minimum value (H<2>) of the harmonic distortion rate when the distributive photovoltaic power generation system is an island, if (H<1> is greater than H<2>) or the values of H<1> and H<2> can not be determined, and after it is detected that the harmonic distortion rate suddenly increases and lasts for a while, starting the harmonic distortion rate criterion and frequency varying amount to determine an island state; if (H<1> is smaller than H<2>), directly starting the harmonic distortion rate criterion and frequency varying amount to determine an island state. According to the invention, the method herein does not add a disturbing signal to the distributive photovoltaic power generation system, does not affect the quality of the electric energy of the distributive photovoltaic power generation system, and does not cause damage; uses the harmonic distortion rate and frequency, has small detection blind areas, increases the reliability of system island detection; and avoid sudden disturbance in the power grid by using a certain time delay, and prevents temporary change to the detected electric quantity from causing wrong determination of island detection.

The invention discloses an intelligent procedural remote control operation system. A topological fail-safe system of a D5000 automatic platform is arranged according to a topological relationship between an electrical island state and electrical equipment to realize fail-safe locking of equipment operation; the extraction of the topological fail-safe system is based on basic rules of operative locking between equipment as required by 'fail-safe', mutual operative locking equipment is found out through topological search so as to automatically adapt to the changes of the electrical equipment and a topological structure of a power grid. The intelligent procedural remote control operation system is a brand-new remote control technology researched and developed specific to a large operationalmode, has very strong innovativeness, safety and high efficiency, is quite beneficial to improving the working quality and efficiency of remote control operation, and can be wholly used for guaranteeing safe and stable operation of the power grid.

The invention relates to a mode self-adaptive improved droop control method based on composite virtual impedance. The control method comprises an improved droop control method in an isolated-island state, a dual-mode smooth switching control method and an improved droop control method in a networked state. The output power is quickly adjusted by changing a droop control strategy during isolated-island operation of a micro-grid, so that the frequency of the micro-grid is within an allowable range, the voltage almost does not fluctuate, and the stability of the isolated-island mode of the micro-grid is maintained; the PQ control is adopted during grid-connected operation, and the droop control is adopted during the isolated-island operation, so that the influence of voltage and frequency changes in an operation process of a system can be effectively reduced, and meanwhile, the smooth transition of the voltage and frequency of the micro-grid in a grid-connected to isolated-land process can be realized; and the method has the advantages of being stable in operation and smooth in isolated-land and grid-connected state switching.

The invention, which belongs to the technical field of photovoltaic generating and distributed generating inverter control, relates to an MPPT-based island detection method. A voltage amplitude value of a grid-connected point is affected by disturbance on MPPT; whether an island occurs is determined based on the voltage amplitude value of the grid-connected point; and disturbance on the MPPT is carried out by increasing a duty ratio D of a boost circuit, so that an objective of reduction of the photovoltaic output voltage and power can be achieved. In an off-grid state, with reduction of the photovoltaic output power, the voltage of the grid-connected point is reduced; and when the voltage of the grid-connected point deviates from a normal range, an island state is determined. According to the invention, with fully consideration of an active matching situation of a local load and a distributed photovoltaic generating system, the parameter setting becomes reasonable, the blind detection area is eliminated, the disturbance period setting becomes reasonable, the power loss is reduced, and the influence on the electric energy quality is affected.

The invention relates to a multi-inverter microgrid quick island detection method. The method, on the basis of real-time measurement of voltage effective value VPCC at the PCC place, and frequency and load reactive power, is characterized by comparing the voltage measurement value and a voltage rated value under normal condition, as well as the frequency and rated value 50Hz, and adopting a corresponding IBDG reactive power control strategy; when carrying out island judgment, presetting a voltage threshold value and a frequency threshold value in advance, and comparing the VPCC with the voltage threshold value; if the VPCC surpasses the voltage threshold value, directly judging the microgrid is in an island state, and terminating the current island detection; or otherwise, comparing the measured frequency f with the frequency threshold value, and if the measured frequency f surpasses the frequency threshold value, judging the microgrid is in the island state. The method does not have island detection dead zone, has universality, and is not only suitable for unity power factor operation IBDG but also suitable for non-unity power factor operation IBDG.

A household energy router includes a grid-connected module, a photovoltaic power generation module, a storage battery energy storage module, a diesel power generation module, and a household electrical AC load module. Respective modules are connected to a DC bus through a routing port. The routing port includes a power electronic converter that can interconnect electrical energy with other energysources (such as lighting illumination, oil and the like) and that can achieve rectification, inversion, isolation, and voltage boosting and reduction. The household energy router is oriented to household AC loads and achieves energy management and information interaction by using a grid-connected port as a master control via controllers and communication circuits of respective ports. The energy router has multiple ports, can get access to multiple power generation apparatuses, energy storage apparatuses, and household electric loads simultaneously, can flexibly control the magnitude and the flow direction of different energy according to the peaks and valleys of an AC grid and actual load requirements in a grid-connected state, can achieve energy flow between different apparatuses in an island state, and can achieve comprehensive energy use.

The invention discloses a flywheel energy-storing array coordinative control method and device for a micro-grid isolated island state. The method comprises: a flywheel energy-storing array topology formed by connecting a plurality of flywheels in parallel; a control strategy of single flywheel in an array; a coordinative control strategy of each flywheel in an energy-storing unit which is formed by connecting the plurality of flywheels in parallel in the same direct-current bus; a coordinative control strategy of each energy-storing unit in an energy-storing array which is formed by connectinga plurality of energy-storing units into a micro-grid alternating-current bus in parallel. According to the method, coordinative control of the flywheel energy-storing array can be realized, high-efficiency and stable operation of the flywheel energy-storing array is guaranteed, reasonable power distribution is realized, and voltage amplitude and frequency are guaranteed to be within the reasonable range.

The invention discloses a random sequence-dependent photovoltaic island state detection method and a random sequence-dependent photovoltaic island state detection device. According to the technical scheme, the method comprises the following steps of: detecting current output by a photovoltaic inverter and the variation of load voltage to obtain a dependency coefficient; comparing the dependency coefficient with a threshold value to obtain a logic value of the dependency coefficient; calculating the absolute value distribution of a difference between two adjacent code elements; performing not exclusive or calculation on the logic value of the dependency coefficient and an absolute value of the difference between the code elements, and adding 1 to the variable if the logic value is real; and counting the ratio of 1 according to a not exclusive or calculation result, and judging whether the photovoltaic inverter is in an island state or not. The device comprises a photovoltaic cell, a pulse signal generator, a power module, a filtering inductor, a current sensor, a voltage sensor, a current signal acquirer, a voltage signal acquirer, a random sequence-dependent island detector, a first circuit breaker, a power grid and a second circuit breaker. According to the method and the device, the photovoltaic island state can be detected without any dead zone, and the injection of power grid harmonics is effectively reduced.

The invention relates to a frequency feedback disturbance-based island detection method and apparatus. The method comprises the following steps: a preliminary determination step; to be specific, detecting a power grid parameter and determining whether an island state occurs preliminarily; a disturbance step; to be specific, if so, adjusting a frequency difference between a frequency of a phase-locked loop output and a power grid frequency by a PI controller, using the frequency difference as an reactive current input reference value iq*+ and outputting the value to an reactive current control link; and a secondary determination step; to be specific, detecting the power grid parameter again and determining whether an island effect occurs truly. According to the invention, the passive island detection and the active island detection are combined, thereby reducing the detection blind area of the inverter and detecting the island phenomenon occurrence accurately and rapidly. Moreover, manual disturbance of the frequency and phase and the like does not exist in the method and no harmonic waves are introduced in the power grid, thereby reducing the influence on the total harmonic wave content of the inverter output current by the island detection algorithm.

The invention relates to a method for simultaneously realizing low-voltage ride through and island detection. The method comprises the following steps in order: step one, sampling a network voltage at the outlet of a generation system to acquire an instant amplitude and instant frequency information of the network voltage; step two, determining whether the generation system is in a normal state; step three, judging that the generation system is in an abnormal state in the step two, the generation system emitting a certain amount of reactive current according to the voltage drop range of the network instant voltage so as to realize the low-voltage ride through; step four, disturbing the generation system through the reactive current produced in the step three so as to further determine whether the system is in an island state, if so, halting the system; step five, repeating above steps, guaranteeing the low-voltage ride through and the island detection when the electric network is in fault. Through the adoption of the detection method provided by the invention, the low-voltage ride through and the island detection can be simultaneously finished through a simple efficiency disturbance method, the method is good in real-time, and the structure based on the method is simple to realize.

The invention discloses a simple detection method for a micro-grid island. The simple detection method comprises the following steps: 1) detecting a voltage amplitude value and frequency on a PCC (Point of Common Coupling), if the voltage amplitude value and the frequency exceed a set threshold value, judging that the island happens, and otherwise, entering 2); 2) controlling an energy storage inverter in the micro-grid, injecting constant reactive power Qh with the smaller amplitude value into the micro-grid; 3) detecting current on a grid side, judging that the island happens if a detection result shows that the current is zero, and judging that the island does not happen if the detection result shows that the current is not zero. According to the simple detection method for the micro-grid island, the energy storage inverter in the micro-grid is controlled, the reactive power with the smaller amplitude value is injected into the grid, grid connected current is detected, and whether the island state happens or not can be quickly and accurately detected through the current detected by the grid side. The method has the advantages of simpleness, easiness in realization, high detection speed and no detection dead zone, and grid quality can not be affected.