232 results about "Power coefficient" patented technology

Wind turbine with a rotor blade relatively insensitive to turbulence because it is more slender than prior blades and is nevertheless able to generate sufficient lift by virtue of the fact that flow enhancing elements such as vortex generators combat flow separation. The slenderness is defined by the chord numbers C and D of which C is defined as C=Nc_rc_lrλ²/R², in which N is the number of blades, c_r is the local chord, c_l the lift coefficient, r the radial position, λ the tip speed ratio and R the rotor radius. Subsequently, the chord should be less than what follows from the equation C=M in which M=−1.19+9.74C_p−21.01C_p²+17.50C_p³ and C_p is the power coefficient. This wind turbine is subject to about 2-12% less operational loads and to about 5-40% reduced survival wind speed loads compared to classical designs.

A windpark includes at least two wind energy installations, each of which installations comprises a rotor, a generator driven by the rotor and a control device, and which are connected via connecting lines to a main line. The windpark also includes a linking point which connects the main line to a power transmission network, a parkmaster which is configured for power factor control and has communication lines for transmission of control signals to the wind energy installations, and a power-factor control section including a distributed regulator having a higher-level regulator located at the parkmaster which is configured to determine a nominal voltage in order to set a global power coefficient for the power which is emitted to the power transmission network and to emit the global power coefficient as a signal via the communication lines and lower-level regulators at the wind energy installations.

The invention relates to a control method of three-phase voltage type PWM rectifier under unbalance voltage of a power grid, relates to the technical field of power electrons. The method comprises the following steps: detecting three-phase power grid voltage value, and transforming to be under a two-phase static coordinate system; carrying out digital filtering on an Alpha-axis voltage component and a Beta-axis voltage component under the two-phase static coordinate system by a positive-negative sequence filter, and obtaining the Alpha-axis positive-negative sequence component and Beta-axis positive-negative sequence component; calculating and obtaining the Alpha-axis and Beta-axis current instruction according to the Alpha-axis and Beta-axis positive-negative sequence voltage component under the given active and reactive power and two-phase static coordinate system; detecting three-phase alternating current, transforming to be under the two-phase static coordinate system, adopting a predicting current control method, calculating and obtaining Alpha-axis input voltage instruction and Beta-axis input voltage instruction of the alternating side under the two-phase static coordinate system. SVPWM modulation is adopted to obtain driving pulse. The control method eliminates direct current voltage harmonic component of three-phase PWM rectifier under the unbalance voltage of the power grid and realizes the operation of controlled power coefficient.

The invention provides an LED (Light Emitting Diode) driving circuit and a constant-current control circuit thereof. The constant-current control circuit comprises an error amplifier, a turn-on time control module and a driving signal generation module, wherein the first input end of the error amplifier receives load current through a sampling port and the second input end of the error amplifier receives preset first reference voltage; the input end of the turn-on time control module is connected with the output end of the error amplifier; and the driving signal generation module generates a driving signal for turning off a switching tube in the LED driving circuit according to the output signal of the turn-on time control module, the driving signal is output through a driving port, a ground port is configured to receive floating ground voltage and the floating ground voltage is different from the reference ground voltage of the input voltage of the LED driving circuit. The constant-current control circuit has the advantages that the precise constant-current control can be realized, the power coefficient is high, the input harmonic is low, the working safety is high and the conversion efficiency is high.

Methods, controllers and computer program products for controlling a wind turbine. Under de-rated operating conditions in which the power requested from a wind turbine is less than the available power, a controller adjusts blade pitch of the wind turbine to reduce the rotor power coefficient. The captured wind power is thereby reduced to be approximately equal to the requested electrical power, which is less than either the available power or the rated power of the wind turbine generator. This reduction in captured power provides the controller with an additional degree of freedom that allows the controller to increase the electrical power output of the wind turbine in response to wind fluctuations without damaging the wind turbine. By allowing increases in power under de-rated conditions, the controller may reduce the amount of pitching necessary to prevent the turbine from exceeding its rated power output level.

A method includes calculating, using a processor, an impedance or forward and reflected power coefficients of a phased system including a plurality of actuators disposed on a structure; and activating the plurality of actuators disposed on the structure to produce shear stress via ultrasonic continuous wave activation to at least one of delaminate or weaken an adhesion strength of a contamination on the structure.

An optical device includes an optical reflector based on a coupled-loopback optical waveguide. In particular, an input port, an output port and an optical loop in arms of the optical reflector are optically coupled to a directional coupler. The directional coupler evanescently couples an optical signal between the arms. For example, the directional coupler may include: a multimode interference coupler and/or a Mach-Zehnder Interferometer (MZI). Moreover, destructive interference during the evanescent coupling determines the reflection and transmission power coefficients of the optical reflector.

The present invention provides a battery remaining electrical charge/remaining capacity estimating method which makes it possible to obtain a convergence value of a battery open circuit voltage with high accuracy and in a short time.

The method includes a voltage estimating step of obtaining a stable open circuit voltage estimated value after a lapse of desired time, the step including: a step of using an approximate function including a plurality of exponential function terms of time and a plurality of coefficients, stopping charge or discharge operation for a predetermined time, measuring a battery voltage over time during the time and using an obtained relation between the battery voltage and the time as a basis to determine the coefficients; and a step of determining at least one power coefficient of inferior logarithm of the exponential function terms based on temperature by expressing the coefficient as a previously obtained function of temperature.

The invention discloses a line selection method for a single-phase earth fault of a power distribution network. The method comprises the steps of measuring zero sequence voltage of a power distribution network bus, switching a parallel resistor, connected in parallel with an arc suppression coil, of an electric structure if the amplitude of the zero sequence voltage of the power distribution network bus is greater than 15% of that of A phase voltage of the power distribution network during normal operation, measuring sampling values of the zero sequence voltage of the power distribution network bus and sampling values of zero sequence currents of power distribution network feeder lines at sampling times, selecting any cycle of sampling values of the zero sequence voltage of the power distribution network bus and sampling values of the zero sequence currents of the power distribution network feeder lines, sequentially calculating line selection power coefficients of the power distribution network feeder lines, and selecting the power distribution network feeder line of which the line selection power coefficient is less than zero and the absolute value of the line selection power coefficient is maximum as a fault feeder line. A fault line selection result of the method is not influenced by factors such as a feeder line type, a fault location, line parameters, transition resistance, an earth fault type and line length, is adapted to a complicated power distribution network operating environment, and is good in practicability.

The invention discloses a multi-wing collecting vane capable of utilizing wind power efficiently, comprising at least two wings and at least one zone formed between the adjacent wings. By designing the shape of each wing and the shape of the zone, the adjacent wings is enabled to generate a collecting effect on the fluid flowing through the zone between the adjacent wings, the zone is the space formed by the rear concave surface of front adjacent wings and the front convex surface of rear adjacent wings, and the rear concave surface and the front adjacent wings and the front convex surface of the rear adjacent wings are upward and front-biased; the relative direction of the adjacent wings is arranged for enhancing the collecting effect, the kinetic energy of the fluid flowing through the zone is increased, so the lifting force of the adjacent rings in the rear of the zone is improved, and the rotor power coefficient of the whole multi-wing collecting vane formed by the wings and the zones is accordingly improved. The multi-wing collecting vane capable of utilizing wind power efficiently makes full use of the Bernoulli effect and is more reasonable in design.

Wind turbines and methods for controlling wind turbine loading are provided. In one embodiment, a method includes the steps of determining a current wind speed. The method further includes determining a tip speed ratio and a pitch angle that maximize a power coefficient under at least one of the following conditions: a thrust value is less than or equal to a pre-established maximum thrust, a generator speed value is less than or equal to a pre-established maximum generator speed, or a generator torque is less than or equal to a pre-established maximum generator torque. The method further includes calculating a desired generator speed value based on the current wind speed and a tip speed ratio. The method further includes calculating a desired generator power value based on the desired generator speed value.

Systems and methods are provided that can be utilized to estimate power associated with a circuit design. The estimated power is determined by evaluating a functional relationship of estimated power based on calculated transistor gate area. One or more power coefficients can be employed with transistor gate area calculations of a circuit design to compute relative power estimates of one or more circuit design sizing instances.

The invention relates to a wind generating set control method. The wind generating set control method comprises the following steps: step 1, acquiring an estimated wind regime characteristic value and a wind generator running state initial value via a local or remote communication system; step 2, according to the estimated wind regime characteristic value, the wind generator running state initial value and a wind generating set control parameter, calculating a running state value of a wind generating set at each time point; step 3, comparing the running state values, obtained in step 2, of the wind generating set with a designed safety threshold value of the wind generating set; step 4, adopting an absorption power coefficient reduction and power output improvement method to obtain a corrected wind generating set control parameter; and step 5, using the wind generating set control parameter meeting the designed safety threshold value as a final execution parameter of a wind generator control system. With the adoption of the wind generating set control method, the response speed of the wind generating set is increased, and energy loss and mechanical load brought by shutdown are avoided.

The invention discloses an intelligent optimization design method for a low-wind-speed wind turbine generator wind wheel, which comprises the following steps: selecting blade aerodynamic configurationparameters as optimization variables, calculating a blade power coefficient and a thrust coefficient according to variable values, and constraining Cpmax and Ctr; selecting the structural layer design parameters as optimization variables, calculating the mass center, the rigidity distribution and the inertia structural performance of each section of the blade, and forming a blade model by combining the aerodynamic configuration data; Adding the blade model into the complete machine model, and calculating the annual generating capacity of the complete machine; calculating and counting the dynamic load to obtain the maximum limit load of the blade root, the fatigue load and the blade clearance, and constraining the blade clearance; and finally, selecting a reasonable range of each optimization variable, and searching a blade design optimal solution by taking the maximum annual generating capacity and the minimum blade root load as optimization objectives. The optimized blade can ensurethe structural strength, the annual generating capacity is increased, the blade root load is reduced, the blade efficiency is improved, the cost is reduced, and the competitiveness is higher.

The invention belongs to the technical field of communication, and particularly relates to an NOMA physical layer security transmission method of a heterogeneous network. The implementation process isas follows: for each legitimate user of the heterogeneous network using the non-orthogonal multiple access NOMA technology, the NOMA is configured to serve a signal power coefficient of each legitimate user, a zero-space artificial noise distribution coefficient is configured according to the position distribution of the legitimate user, and NOMA physical layer security transmission of the heterogeneous network based on the configured signal power coefficient and the zero-space artificial noise distribution coefficient is performed. According to the NOMA physical layer security transmission method provided by the invention, by reasonably configuring the artificial noise and enhancing the resistance to passive eavesdropping when the eavesdropping channel quality of the system is better than the legal user channel quality, the physical layer security performance of NOMA wireless transmission in the heterogeneous network is improved, the ability of the NOMA system to resist potential silent eavesdropping is enhanced, particular when the eavesdropping channel quality is better than the channel quality of the legitimate user, the physical layer security performance of the system is improved, and the NOMA physical layer security transmission method can be used for the security transmission in mobile communication systems with high user density, such as heterogeneous cellular networks.

The invention discloses a direct current tractive power supply system based on flexible direct current power transmission. The direct current tractive power supply system comprises a step-down transformer, a double-end active high-voltage direct current power transmission system and a buck chopper. The double-end active high-voltage direct current power transmission system is based on the modularized multi-level converter technology and comprises two converters which are completely symmetric and connected through a direct current power transmission cable. Each converter is connected with the three-phase alternating current through the step-down transformer. The input end of the buck chopper is connected with the direct current side of the double-end active high-voltage direct current power transmission system through a first switch assembly, and the output end of the buck chopper is connected with a traction system through a second switch assembly. The second switch assembly is interlocked with a third switch assembly, when a metro or a light rail operates, the second switch assembly is switched on, the third switch assembly is switched off, and when an electric locomotive operates, the third switch assembly is switched on, and the second switch assembly is switched off. The direct current tractive power supply system has the advantages of being low in cost, little in traction network voltage and electric energy loss, low in harmonic content, high in system power coefficient, wide in application range and the like.

The invention discloses a non-contact inductive electricity-getting device for an electric tunnel cable, which has the advantages of simple structure, convenient use, non-contact electricity getting, and the like. The non-contact inductive electricity-getting device for the electric tunnel cable comprises at least one electricity-getting loop, each electricity-getting loop comprises a mutual-induction electricity-getting device which is connected with a rectifying circuit, the rectifying circuit is connected with a protection circuit and a power coefficient correcting circuit which is connected with a voltage stabilizing circuit; and the voltage stabilizing circuit in each electricity-getting loop is connected with an electricity-getting balance control circuit.

The invention relates to a method for optimizing power generation performance of a wind turbine generator under low air density. The method comprises: calculating an induced velocity flow field by utilizing a dynamic inflow model, and establishing a dynamic stall model of the blade airfoil; generating a grid of an airfoil flow field computational domain by adopting CFD software; carrying out dynamic stall model simulation analysis on changes of shape parameters and position parameters of the vortex generator by the blade airfoil; and carrying out optimal design on the aerodynamic characteristics of the blade airfoil according to the shape parameters and the position parameters of the vortex generator through an optimal algorithm from the two aspects of the maximum power coefficient and themaximum lift-drag ratio of the designed attack angle alpha, and obtaining the optimal parameters of the vortex generator. The method has the advantages that the vortex generators are reasonably arranged on the wind generating set, so that the problems of blade stall and wind power blade flow separation easily caused by the large-thickness airfoil blade under the conditions of large attack angle,high altitude, low air density and the like are solved.

The invention provides a self-adaption maximum power tracing control method of a power generating set. First, the reference tip speed ratio and reference power coefficient of the to-be-tested power generating set are set, so that a reference rotate speed torque tracking curve and a deformation curve can be obtained according to the reference tip speed ratio and reference power coefficient. Then a section between a cut-in wind speed and a rated wind speed is divided into small sections. The power generating set runs according to the deformation curve corresponding to a deformation coefficient in a tracing manner. After each operation period, result data such as output power in the period are measured and subjected to statistical averaging. Therefore, during constant operation, the deformation coefficient is an optimization variable and the output power is an optimization object, the optimal deformation coefficient is sought through a method of optimization, so that the output power of the power generating set becomes the maximum. Finally, after long term operation of the power generating set, the optimal rotate speed torque tracking curve in the whole operation wind speed range can be obtained by connecting segments of the deformation curves determined according to deformation coefficients of each wind speed section.