35results about How to "Meet the requirements of grid connection" patented technology

The invention provides a day-ahead wind speed multistep prediction method fused with numerical weather prediction, and belongs to the technical field of wind speed prediction. The problems that an existing method is directly fused with numerical weather prediction, the prediction error is large, and the prediction precision of wind electricity power is low are solved. According to the technical scheme, the method comprises the steps of analyzing the information effectiveness of an original wind velocity sequence, determining the predictability time duration of a statistic forecasting model, obtaining the wind speed prediction result within a predicable time duration, conducting information effectiveness analysis on a numerical weather prediction model, determining the predicable time duration of the numerical weather prediction model, obtaining the wind speed prediction result within the predicable time duration, establishing a day-ahead wind speed fusion prediction model according to the wind speed prediction result and predicting the actual wind speed. The day-ahead wind speed multistep prediction method fused with numerical weather prediction is suitable for predicting the wind speed within day-ahead 24 hours in the future.

The invention discloses a cascaded non-output transformer in-phase power supply system. The system is mainly composed of a power electronic conversion device cascaded with more than one three-phase-single-phase AC-DC-AC converter. The cascaded power electronic conversion device is directly connected to the traction catenary. Through the multi-module cascaded structure, the improvement The voltage level of the output converter is improved, so the output transformer can be eliminated. Since the output voltage amplitude, phase, and frequency can be controlled, the catenaries of adjacent substations can be directly connected to form a through traction power supply network. The present invention proposes a three-phase-single-phase converter structure suitable for arbitrary level diode clamping circuits. The structure includes a DC voltage stabilizing and equalizing auxiliary circuit, which can be realized under any power factor condition, especially when transmitting active current. The goal of voltage equalization and voltage regulation of each DC capacitor ensures that active power transfer or reactive power output can be achieved under any modulation depth.

The invention relates to a capacitor voltage feedforward control method of a grid-connected inverter under a weak power grid. The method belongs to the field of grid-connected inverter control, and comprises the following steps: S1, performing feedback control by using inverter side current i1, and performing phase locking, active damping and feedforward compensation by using capacitor voltage uCto obtain a capacitor voltage feedforward control system of a grid-connected inverter under a weak power grid; S2, performing active damping negative feedback design under a weak power grid on the capacitor voltage feedforward control system obtained in the step S1; and S3, on the basis of the step S2, designing a capacitor voltage feedforward compensation control strategy for the capacitor voltage feedforward control system. On the premise of ensuring the performance of the control system, the use of voltage and current sensors is reduced, and the hardware cost of the system is reduced; and the dynamic performance and stability of the control system are improved, so that the grid-connected inverter always has enough stability margin under the characteristic that the impedance of the powergrid changes in a relatively wide range.

The invention discloses a multi-gear transformer type voltage drop device which comprises a voltage drop device, a signal measuring module and a device protective module. The voltage drop device comprises a primary side controlled current source, a secondary side controlled current source, a primary side field winding, a secondary side field winding, a drop characteristic setting module, a three-phase impedance calculation module and a three-phase current calculation module. The primary side controlled current source is connected with voltage of power supply grid through a breaker, the secondary side controlled current source is connected with the input end of a tested device, the drop characteristic setting module is used for setting the voltage drop depth, a failure type, the drop speed and the drop time, the three-phase impedance calculation module is used for calculating impedance of a transformer three-phase winding, the three-phase current calculation module is used for calculating the current of the transformer three-phase winding, electrical parameters collected by the signal measuring module are sent to the device protective module, and the signal measuring module is used for protecting the device against the possibly-occuring faults. The multi-gear transformer type voltage drop device can simulate voltage drop experiments with different depths under various faults, and meet the penetrating testing requirements of low voltage of a wind motor set.

The invention discloses a cut-through type cophase power supply system for cascaded input-free and output-free transformers. The system is mainly composed of a power electronics conversion device with three phases connected in parallel after each being cascaded with one or more AC-DC-AC converters of single phase-single phase structures. The three phases of the cascaded power electronics conversion device are directly connected with a traction contact net after being connected in parallel. The single phase-single phase AC-DC-AC converters can bear high voltage levels through the multi-module cascaded structure; meanwhile, the voltage levels output by converters are improved; thus, input and output transformers can be omitted, power required for locomotive loads is borne by the three phases on average, and energy can flow in two directions. Due to the fact that amplitude values, phases and frequencies of the output voltage can be controlled, contact nets close to substations can be directly connected to form a cut-through traction power supply network. By means of the cut-through type cophase power supply system, the input and output transformers of the traction substations can be omitted, the defects that the transformers in the traction substations are large in size, heavy in weight, troublesome to overhaul and high in manufacturing cost are overcome, the capacity of the traction substations is easily improved, and the running cost of the substations is reduced.

The invention belongs to the wind electric power prediction technology field, and particularly relates to a short period wind power prediction system based on a covariance preferable combination model. The short period wind power prediction system based on a covariance preferable combination model comprises a data collection and storage model, a covariance preferable combination prediction module, a power prediction error analysis module and a real-time communication module. The data collection and storage module respectively transmits the collected data needed by wind power prediction and error analysis data to the covariance preferable combination prediction module and the power error analysis module to perform prediction on the wind power; the prediction result is transmitted to the power prediction error analysis module; the prediction data is transmitted to the real-time communication module; and the real-time communication module transmits the prediction data to a dispatching center in real time for service. The system and the method of the invention are simple and practical; the short period wind power prediction system is highly efficient and convenient and has function of real-time communication and self-regulation; the accuracy of the prediction algorithm is higher than that of the single physic model and the statistic model; and the development of wind power prediction is benefited.

The invention provides a grid-connected photovoltaic inverter MPPT control method capable of adjusting output power along with power grid frequency. The method comprises steps: power grid voltage and output current of an inverter are acquired, and the power grid frequency and the current output power of the inverter are calculated; the relationship between the current power grid frequency and limited frequency is judged, and a different adjusting method is adopted according to the current power grid frequency. The method has the advantages that the output power can be dynamically adjusted according to changes of the power grid frequency; if in a limited frequency range, the traditional MPPT control method is adopted; and if exceeding the limited frequency, the output power is linearly reduced according to the changes of the power grid frequency, and related requirements of a photovoltaic grid-connected power generation system can be met.

The invention belongs to the technical field of wind power forecast and specifically relates to a short-term wind power prediction method based on covariance. The method is characterized by obtaining data, comprising real-time wind power data, numerical weather prediction data, real-time network data and wind tower meteorological observatory data, of a wind power plant in real time; carrying out covariance calculation on the numerical weather prediction data, the real-time network data and the wind tower meteorological observatory data obtained in real time, wherein the covariance calculation prediction carries out wind power prediction based on an NWP space difference model, a BP neural network model and an LS-SVM model respectively; and carrying out error analysis on the real-time wind power data and covariance calculation prediction three-model data through weight distribution combination to obtain a final prediction result. The precision of the used prediction algorithm is higher than that of a single physical model and a statistical model, thereby facilitating development of wind power prediction. The method can solve the problem of large error of the single prediction model, is high in predication precision and meets grid-connection requirements of the wind power plant.

The invention discloses a wind-light power smoothing control method and system based on a hybrid energy storage system. The method includes the steps of acquiring the wind-light output power at a current moment, wherein the wind-light output power includes wind power output power and photovoltaic output power; according to the wind-light output power at the current moment, using a weighted movingaverage algorithm to calculate high-frequency power of the wind-light output power at the current moment; using a super capacitor for stabilizing the high-frequency power; according to the wind-lightoutput power at the current moment, using a low-pass filtering algorithm to calculate low-frequency power of the wind-light output power at the current moment; using a battery for stabilizing the low-frequency power. The method fully utilizes the advantages of large energy density of the battery and large power density of the super capacitor, so that power fluctuations in different frequency ranges are stabilized, and fluctuations of wind-light power are reduced to meet the requirements of grid connection.

The invention provides a through-type traction power supply system, relating to the technical field of traction power supply. A master transformer station CS<M> comprises a step-down transformer T0, the secondary side of which has more than one winding, and a super compensation system, the secondary side of which has more than one winding; the master transformer station CS<M> is used as a voltagesource, other transformer stations with a step-down transformer and a three phase-single phase cascaded converter N are used as system current sources, wherein the master transformer station CS<M> provides power through a three phase-single phase traction transformer TM, the structure of three phase input and single phase output is adopted, the primary side of the step-down transformer T0 is connected with a three phase power grid, the secondary side has more than one group of winding, three phases of output of the more than one group of winding are separately connected with a reactor in series and then are connected with an input end of corresponding super compensator SCN so as to form a parallel super compensation system SC; and the input end of a master controller MC is connected with athree phase network current, a three phase power grid voltage and a support capacitor voltage of the super compensator separately, and the output end of the master controller MC is connected with thecontrol end of the super compensation system SC.

A power decoupling circuit for alternating current side coupling comprises an inductor, main switching devices, parasitic diodes and a decoupling capacitor, wherein the main switching devices are seven switching tubes, and each switching tube is connected with one parasitic diode in inverse parallel. The power decoupling circuit comprises four work modes, including a PHC charging mode, a PHC discharging mode, an NHC charging mode and an NHC discharging mode. An input end of the power decoupling circuit is connected with an output side of an inverter in parallel, the voltage amplitude on the output side of the inverter is high and has positive and negative periodic variation, so that the decoupling capacitor in the decoupling circuit designed on the basis of boost and buck circuits can acquire higher average voltage and larger voltage variation range, the capacitance of the decoupling capacitor is greatly reduced, the polarity of the decoupling capacitor is fixed, the grid connection requirement of the inverter can be met without a large electrolytic capacitor, the system size and cost are greatly reduced, and thus the service life of a photovoltaic generation system is substantially prolonged.

The invention provides a three-level inverter modulation mode switching method and device, equipment and a storage medium. The method comprises the following steps: acquiring a three-phase sinusoidal modulation wave; determining a first zero-sequence voltage component according to the three-phase voltage of the three-phase sinusoidal modulation wave, and superposing the three-phase sinusoidal modulation wave with the first zero-sequence voltage component to obtain a three-phase saddle-type modulation wave; determining a second zero-sequence voltage component according to the three-phase voltage of the three-phase saddle-type modulation wave, superposing the three-phase saddle-type modulation wave with the second zero-sequence voltage component, and performing adjustment according to a preset zero-sequence voltage adjustment factor to obtain a hybrid modulation smooth switching modulation wave; comparing the hybrid modulation smooth switching modulation wave with a preset triangular wave stacked in an inverted manner to generate a pulse width modulation signal; according to the invention, smooth switching of continuous and intermittent modulation modes is realized, the common-mode voltage and the common-mode current change stably in the switching process, and the new energy grid connection requirement is met.

The present invention provides a harmonic current suppression method of a single phase inverter. The method analyzes the effect caused by dead zone(s) on the basis of analyzing basic vector control ofthe single phase inverter, and by adopting an improved repetitive controller algorithm, harmonic current(s) caused by the dead zone(s) or power grid harmonic(s) are effectively suppressed, so that the single phase inverter has a very high output current quality, and thus the grid-connection requirements are satisfied.

The invention discloses a wind power plant grid-connected power smoothing method for optimizing charging and discharging of a double-battery system. According to the method, on the basis of wind powerultra-short-term prediction, an average wind power prediction value in a control period T is used as basic reference output power of a wind power plant, and the basic reference output power of the wind power plant in each control period T is dynamically corrected according to the charging and discharging energy imbalance degree of the double-battery system; when the dischargeable energy of the double-battery system is greater than the chargeable energy, the double-battery system is enabled to be charged less and discharged more by adjusting the basic reference output power of the wind power plant; on the contrary, when the rechargeable energy is greater than the dischargeable energy, the double-battery system is made to be discharged less and charged more, and therefore the difference ofthe charging and discharging energy of the double-battery system is reduced. According to the method, the output power of the wind power plant can meet the scheduling and grid connection requirements,meanwhile, the charge-discharge energy imbalance of the double-battery system is improved, the charge-discharge depth of each battery pack is optimized, the long-term stable operation of the system is ensured, and the method is simple, effective and convenient for practical engineering application.

The invention relates to a grid-connected photovoltaic power generation system capable of stabilizing the quality of electric energy. The grid-connected photovoltaic power generation system comprises a power generation module and a grid-connected access box, wherein the power generation module comprises a fixed support and a solar cell panel arranged on the fixed support; the power generation module is connected with a direct-current motor for converting direct current generated by the power generation module into mechanical energy; the direct-current motor is connected with an alternating-current motor for converting the mechanical energy into alternating current; the alternating-current motor is connected with a transformer; and the transformer is connected with the grid-connected access box. The grid-connected photovoltaic power generation system has the advantages that the direct current generated by the power generation module is converted into the mechanical energy through the direct-current motor, then the mechanical energy is converted into the alternating current through the alternating-current motor, and the alternating current is converted into same-frequency and same-phase sinusoidal current with a power grid through the transformer, so that three-phase output balance for a three-phase alternating-current generator set is realized, the quality of the electric energy is stable, the system is free of harmonic generation, a synchronous connection requirement is met, and the operational safety performance of the grid-connected power generation system is improved.