202 results about "Power imbalance" patented technology

The present invention relates to methods and apparatus for preventing power imbalance in a multiple input multiple output (MIMO) wireless precoding system. According to one aspect of the present invention, a codebook is constructed with a first subset of codewords that are constant modulus matrices, and a second subset of codewords that are non-constant modulus matrices. A mapping scheme is established between the first subset of codewords and the second subset of codewords. When a unit of user equipment feeds back a first codeword that is a non-constant modulus matrix, the Node-B may replace the first codewords with a second codeword that is selected from the first subset of codewords and that corresponds to the first codeword in accordance with the mapping scheme.

A system for controlling a grid connected power generating system is provided. The system includes a wind turbine, a converter, a first controller and a second controller. The wind turbine supplies electrical power to a power grid and the converter couples the wind turbine to the power grid. The first controller calculates voltage commands to emulate a phasor back electromotive force behind an inductance. The controller further generates converter switching commands from the voltage commands. The voltage commands include a voltage magnitude reference and an internal frequency reference calculated from a power imbalance between an active power reference and the electrical power. The second controller is used to limit a converter current.

An apparatus and method for preventing power imbalance between antennas in a closed-loop MIMO system are provided. In a transmitter in the MIMO system, a first calculator generates a vector by multiplying a transmission vector by a beamforming matrix and a second calculator generates a plurality of antenna signals by multiplying the vector by a predetermined phase rotation matrix.

A variable speed wind turbine is provided. The wind turbine comprises a generator, a power converter for converting at least a portion of electrical power generated by the generator, an energy management arrangement coupled to the power converter, the energy management arrangement comprises an energy storage unit, and a controller. The controller is adapted to detect a power imbalance event and to transfer at least a portion of excess electrical energy generated by the generator to the energy storage unit to be stored therein when the power imbalance event is detected.

The invention relates to a coordinative optimization unit combination method of energy. The energy comprises wind power, thermal power and pumped storage energy. The coordinative optimization unit combination method of the energy includes following steps: confirming a wind power output confidence interval; confirming running parameters and coal consumption characteristics of a thermal power generating unit and running parameters and running characteristics of a pumped energy storage unit; confirming combination object functions and constraint conditions of a wind power, thermal power and pumped storage energy joint optimization unit; confirming mixed integer nonlinear programming problems; confirming a starting and stopping plan of the wind power, thermal power and pumped storage energy joint optimization unit in future 24 hours. The coordinative optimization unit combination method of the energy improves unit combination reliability, guarantees that a system has enough regulation ability in real-time running so as to balance power imbalance caused by power fluctuation of wind, promotes consumption and absorption of the wind power, achieves coordinative optimization running of the multivariate energy, and thereby guarantees safety and economical efficiency of running of a power grid.

The invention provides a three-phase imbalance three-phase imbalance method for a power distribution network with distributed power supplies. The three-phase imbalance three-phase imbalance method for the power distribution network with distributed power supplies comprises: aiming at the complex power distribution network, on basis of the fundamental principle of the implicit Gaussian load flow calculation method.

The invention discloses a novel cascaded three-phase bridge converter and belongs to alternating current (AC) / direct current (DC) converters. The converter comprises three-phase AC power supplies, three input inductors and three cascaded three-phase voltage type bridge converters, wherein the three-phase AC power supplies are in star connection and do not have a neutral line. A voltage stress of a switching tube is reduced by using a connection mode of cascaded superposition of three-phase input line voltages, so the converter is applicable to high-voltage and high-power level occasions; and when three-phase input power supplies are unbalanced, inter-phase energy can be compensated for each other, so DC output voltages of each three-phase bridge are automatically equalized. By using cascade connection between bridge arms of the three-phase bridges, compared with a three-phase cascaded converter which is cascaded in same level (m level) and consists of single-phase H-bridge cascaded converters, the novel cascaded three-phase bridge converter has the advantage that: six active switching tubes and m+1 output capacitors are eliminated, so the cost and volume of the converter are reduced.

Engines that include different combustion strategies for different cylinders may create a power imbalance resulting in undesirable engine vibrations. The engine system of the present disclosure includes a first engine that is operable to produce a high NOx concentration exhaust and a second engine that is operable to produce a low NOx concentration exhaust. The first engine is fluidly connected to a first section of an exhaust passage and the second engine is fluidly connected to a second section of the exhaust passage. The exhaust from the first engine and the exhaust from the second engine are merged in a merged section of the exhaust passage downstream from both the first and second sections of the exhaust passages. The high NOx concentration exhaust may be converted to ammonia for reacting with the low NOx concentration exhaust to arrive at very low NOx concentration from the merged exhaust.

The present invention discloses a reactive compensation coordination control method during the DC emergency power support process and belongs to the technical field of power systems and automation. According to the technical scheme of the invention, according to a current running state and a to-be-lifted DC power, a reactive power, required to be consumed additionally for the DC system after the active power thereof is boosted, is estimated. Before the DC boosting process, filters or parallel capacitors of a corresponding number are put to use in the emergency manner. After the DC boosting process, reactive-load compensation equipment is put to use additionally according to the actual control manner of a convertor station. Meanwhile, the AC bus voltage of the convertor station is monitored. As a result, the condition that the AC voltage of the convertor station is out of limit due to the usage of the reactive-load compensation equipment can be avoided. The method can effectively improve the amount of the actual emergency power support in the DC large modulation mode. Meanwhile, the power imbalance problem of the power grid of a receiving end can be effectively relieved, and the safety and the stability of the power grid are improved.

The invention relates to an intelligent phase-changing switch system for adjusting three-phase imbalance and a method of the intelligent phase-changing switch system. The intelligent phase-changing switch system is characterized in that the system includes main controllers and phase-changing switches, wherein the main controllers are installed on branch line outgoing wires respectively, and the phase-changing switches are installed at the front ends of users. According to the method, load current effective values are collected in real time and are sent to the main controllers actively; the main controllers collect three-phase current values on branch lines at intervals of a fixed period and calculate the degree of three-phase current imbalance; the threshold of the degree of the three-phase imbalance and the threshold of the number of times of line crossing are set; and if the calculated degree of the three-phase imbalance exceeds the threshold, and at the same time, the cumulative number of the times of line crossing exceeds the threshold, a phase-changing adjustment optimization strategy is started. The system and method of the invention are reasonable in design. With the systemand method adopted, the steady three-phase load balance of branch lines and a transformer power supply zone can be achieved to the greatest extent, the degree of the three-phase imbalance can be low,the number of the action of the switches can be minimum, and therefore, the safety of equipment and the reliability of power supply can be improved.

The invention discloses a hybrid modulation strategy based power balance control method for a cascade H-bridge inverter and aims to solve a problem of incapability of stable operation of a system due to input power imbalance of a photovoltaic battery panel on a DC side of the photovoltaic inverter. The method includes steps of 1, master DC side voltage control used for realizing maximal power point voltage tracking by H-bridge unit DC side voltages and obtaining a system active current command value; 2, grid side current decoupling control capable realizing independent control of active current and reactive current and generating inverter total modulation wave voltage; 3, inter-unit power balance control including determining the correct switching states of each H-bridge unit so as to realize the power balance control among the H-bridge units and the maximal power tracking of the H-bridge units through DC side voltage error ranking of the H-bridge units. The method can be suitable for different kinds of working conditions. By adopting the method, stable operation of the cascade H-bridge photovoltaic inverter in a comparatively large range and system power generation capacity can be guaranteed.

The present invention discloses an apparatus, a method and a computer program for resolving a hidden node problem in relation to handshake message transferring e.g. in WLAN networks. In one embodiment of the invention, the apparatus receiving a Clear to Send (CTS) message repeats the message after a Short Interframe Space (SIFS) time period. Stations not directly hearing the original CTS due to a low power are able to receive the repeated CTS and defer their transmissions accordingly. In another embodiment, the apparatus receiving the CTS message indicates in its Ready to Send (RTS) message that the CTS sender station has a low transmitting power. With this knowledge, the other present stations can defer their transmissions until they are sure that the data transfer between the first two stations having the RTS-CTS messaging has not been initiated or is already completed.

The disclosure provides a power system vulnerability analysis method in consideration of information physical joint attack. When the primary equipment (generator, transformer, transmission line and the like) of the grip in a certain area is physically destroyed, stops operation, and causes changes in the topological structure of the grid, problems such as power flow transfer, branch out-of-limit power and power imbalance of the power system possibly occurs. If the information system suffers an information attack at this time, it is determined that a power dispatching center loses an optimization adjustment capability, the grid proportionally adjusts power generation and consumption power to ensure the power balance, and the out-of-limit branch is cut off by a relay protection device. If the information system does not suffer an information attack, after the destroyed equipment is shut down, the power dispatching center performs optimization with the minimum load loss as a goal, and performs adjustment and control from the power supply side and the load side to eliminate the branch out-of-limit power while ensuring the power balance of the grid.

The present invention discloses a three-phase cascade H bridge photovoltaic grid-connected inverter interphase power balance control method, and aims to solve a grid-connected current aberration problem caused by unbalanced input power of a direct current side photovoltaic cell panel. The method comprises the following steps: (1) controlling total power control to enable direct current side voltages of various H bridge units to track an MPPT instruction value and obtain a three-phase input active power actual value of a system and a total input active power actual value of an inverter; (2) controlling feedforward decoupling current so as to be capable of implementing independent control of active power and inactive power and simultaneously generating a three-phase original modulation signal of the inverter; and (3) controlling interphase power balance, obtaining an overlapped zero-sequence voltage by a ratio of the three-phase input active power actual value to a three-phase active power instruction value, and modifying a three-phase original modulation wave according to the zero-sequence voltage so as to implement balance control of interphase power. The control method is capable of providing an precise zero-sequence voltage value to suppress power imbalance so as to ensure grid-connected current symmetry, and the control method has the advantages of well-defined physical significance, excellent dynamic performance, easiness in engineering implementation and the like.

The invention relates to a system-control-requirement-oriented energy storage system optimum allocation method. The method is characterized by comprising the following steps: from the angle of power imbalance of wind power on the whole power grid, controlling the output power of a wind power plant group to not exceed the power balance target of the whole power grid, setting a discharge interval of the energy storage system in the residual power grid utilization space, performing optimal management on the energy of the energy storage system based on the SOC hierarchical control strategy, correcting the charge and discharge power of the energy storage system in real time, optimizing the working performance of the energy storage system, establishing a wind storage operating economy evaluation model, taking the maximum comprehensive income as a target, and determining the optimum discharge interval of the energy storage system. The capacity of the energy storage system is optimized, the service life of the energy storage system is prolonged, the grid-connected scale of new energy power is improved, and the acceptable wind-power space of the power grid is effectively utilized.

The invention relates to a bus voltage stability technology of an alternate current and direct current hybrid microgrid, in particular to a control method suitable for a bidirectional DC-AC converterof the alternate current and direct current hybrid microgrid. According to the method, partitioning control is conducted on voltage fluctuation aiming at the existing problem of power imbalance of thealternate current and direct current hybrid microgrid; the method is divided into an off-grid state and a grid-connected state, under the grid-connected state, partitioning is conducted according tothe voltage deviation value of a direct current bus, and different droop slopes are adopted in different partitions; under the off-grid state, working modes are chosen taking the energy supply and load consumption of an alternate current sub microgrid and a direct current sub microgrid into consideration, and meanwhile multi-slope droop control is adopted to achieve the partitioning curve dynamicdroop control of the alternate current and direct current hybrid microgrid; the control method of the bidirectional DC-AC converter of the alternate current and direct current hybrid microgrid under different states is provided, a multi-slope droop curve is adopted, the multi-slope droop curve is close to a real droop curve, and the control precision of the microgrid is ensured.

The invention researches the problem of controlling a voltage PWM rectifier when a power supply is unbalanced according to a principle that the change of a physical quantity depends on energy changes. On the basis of the passivity of a novel synchronous rotation transformation and a rectifier, a new passive energy control law is determined. The novel synchronous rotation transformation can transform an unbalanced system of the PWM rectifier supplied by an unbalanced power supply into a quasiequilibrium system. The passive energy control law determined by a novel damping injection method can decouple a system, transform a non-linear system into a linear system, and simultaneously converge the rectifier to an expected stable point quickly. A passivity-based control system for the voltage type PWM rectifier supplied by the unbalanced power supply (referring to an attached figure) established based on the novel synchronous rotation transformation and the new passive energy control law has excellent movable and still performances, and achieves unit power factors, current on-line side sine, and direct current voltage constant control.

Apparatus and methods are provided for receiving differential phase-shift keyed (DPSK) optical signals subjected to tight optical filtering, such as may be experienced by 40 Gb / s and 100 Gb / s channels in a dense wavelength division multiplexing (DWDM) communications system with 50 GHz channel spacing. An optical DPSK receiver is described which employs an optical delay interferometer (ODI) demodulator having a free spectral range (FSR) that is larger than the symbol rate (SR) of the DPSK signal to be demodulated. The receiver includes means for introducing an additional power imbalance between the outputs of the ODI demodulator, and the additional power imbalance may be related to the ratio of FSR to SR. The additional power imbalance increases the signal tolerance to tight optical filtering, thereby achieving high spectral efficiency in applications such as DWDM.

A method and apparatus for power imbalance correction comprising: a plurality of converters for converting a plurality of DC inputs to a multi-phase AC output, and coupling the multi-phase AC output to a multi-phase AC line, and a controller coupled to the plurality of converters. The controller determining whether phases of the multi-phase AC output are balanced, and controlling when all phases of the multi-phase AC output are not balanced, at least one converter of the plurality of converters to balance the multi-phase AC output.

The invention discloses a multi-infeed HVDC (high-voltage direct current) system partitioning method based on the mounting of fault current limiters. The fault current limiters are mounted on proper alternating current lines, so that a multi-infeed HVDC system is partitioned into a plurality of regional power grids which are isolated from one another by the fault current limiters; when the alternating current system in a certain regional power grid in the multi-infeed HVDC system is subjected to a short circuit fault, the impedance of the fault current limiter is increased to a rated value, so that an electrical distance among the regional power grids can be increased, and the short circuit fault can be prevented from being transmitted to other regional power grids from the faulted regional power grid; and the alternating current bus voltage in other regional power grids is increased, the phase change failure duration of each HVDC line in each of other regional power grids can be shortened, and the recovery speed of the transmission power of the direct current lines can be increased, so that the problems of power imbalance and flow transferring of the alternating current system caused by the simultaneous phase change failure of the HVDC lines in the multi-infeed HVDC system can be relieved, and the safety and stability of the multi-infeed HVDC system under the condition of the short circuit fault of the alternating current system are improved.

The invention relates to a method and system for adjusting the energy of a microgrid. The method includes obtaining power imbalance when the microgrid is switched to an island model from a grid-connected mode; determining whether stored energy available is greater than the power imbalance, adjusting the micro source output power if yes, and the microgrid entering into an island operation phase if the adjusted power imbalance is smaller than a set normal deviation value and the stored energy available is greater than a set proportion; otherwise, executing a preset first-level load control strategy; the microgrid entering into an island operation phase if the power imbalance is smaller than the set normal deviation value and the stored energy available is greater than a set proportion; otherwise, executing a preset second-level load control strategy until the power imbalance is smaller than the set normal deviation value. Power imbalance during a transition phase when the microgrid is switched from a grid-connected mode can be eliminated.

The invention discloses a resource mapping and code division multiplexing method and device, belonging to the communication field. The resource mapping method comprises the steps of: selecting one mapping scheme from at least two mapping schemes, mutually staggering a pilot frequency symbol with strongest transmitting power, corresponding to the selected mapping scheme, with a pilot frequency symbol with strongest transmitting power, corresponding to the mapping scheme selected by the least one adjacent cell; and carrying out resource mapping according to the selected mapping scheme. Through selecting one mapping scheme from the at least two mapping schemes by each cell, the invention realizes resource mapping, and effectively reduces the interferences of the pilot frequency symbols of the users at the boundary of the cell; and through carrying out vector exchange on an orthogonal matrix, a plurality of different codeword sequences are obtained, the codeword design is realized, and output power imbalance of the pilot frequency symbols can be effectively improved.

The invention relates to the technical field of distributed power supply and micro-grid, and relates to a layered energy storage micro-grid comprising a plurality of energy storage units. The layered energy storage micro-grid is composed of a central control system, a centralized energy storage system, a micro-grid sub-grid control system, a micro-grid sub-grid and a switching device. A micro-grid system uses the combination of centralized energy storage and decentralized energy storage. Decentralized energy storage is used as a main micro source in the micro-grid. The centralized energy storage is used for power grid peak regulation and auxiliary services. In the case that the micro-grid sub-grid operates reliably and has no fault, the micro-grids of the sub-grid independently operates. The sub-grid control system monitors the state of micro-grid in real time, and uploads data to a centralized layer central control system. If a certain micro-grid sub-grid faces unstability or power imbalance, the centralized layer central control system, based on real-time data and control strategies, rationally deploys other micro-grid power supplies to be switched to the centralized energy storage to protect the micro-grid sub-grid to continue to operate. The layered energy storage micro-grid can improve the safe and reliable operation of micro-grid and reduces power consumption and hardware loss.

A method for improving phase balance in a three-phase power system, such as a three-phase system feeding Single Wire Earth Return distribution networks. The inventive system can take power from a suitable source—including the three-phase distribution itself—and feed it to a “weaker” phase to improve balance. In addition, the system can store energy taken from the three-phase power system during off-peak periods and use this to boost a weaker phase during periods of phase imbalance. The inventive system preferably uses an organic Rankine cycle heat engine to extract stored thermal energy and use it to boost a weak phase or phases. The organic Rankine cycle heat engine may also take power from renewable sources such as solar collectors.

The invention discloses a multi-element energy storage integration method for increasing energy utilization rate of a regional power grid. The multi-element energy storage integration method integrates a lithium battery, a lead-acid storage battery, a supercapacitor and an all-vanadium redox flow battery energy storage unit to be applied to a regional power grid system, takes regional power grid power prediction, energy storage battery electricity quantity and energy storage battery charge-discharge times as constraint conditions, provides the optimal strategy for a multi-element energy storage system of the regional power grid system, and controls charge-discharge operating states according to the optimal strategy, so as to increase the energy utilization rate of the regional power grid system. By accessing the multi-element energy storage unit to the regional power grid system, the power fluctuations of the regional power grid system can be effectively inhibited, the solar curtailment and wind curtailment phenomena in regions with abundant renewable energy resources in the case of power imbalance are avoided, and the energy utilization rate of the regional power grid system can be effectively increased.

The invention belongs to the field of intelligent building access control systems, and specifically relates to an intelligent access control system for recognizing faces based on RGB image deep learning. The system includes a face recognition module, an ultrasonic module and an access control switch control module, the access control switch control module is electrically connected with the face recognition module, and the ultrasonic module is electrically connected with the face recognition module. The system solves the power imbalance problem in the face recognition 1:N scheme of access control systems, and improves the multi-view robustness in face recognition. The above scheme adopting the assistance of the ultrasonic module can carry out living body recognition, reduce the calculationamount of the access control system, improve the heat dissipation stability of the system and the heat aging resistance performance of a PCB, prolong the service life and greatly reduce the failure rate and the maintenance cost due to heat generation. A video streaming-based feature extraction scheme is used for various pose face models of faces, so an access control base library can be conveniently logged, and the recognition accuracy is high.