175results about How to "Reduce harmonic components" patented technology

A system and method are provided to isolate outputs of parallel converter threads of a power system converter on a generator side of a wind turbine generator by utilizing isolated power windings on the wind turbine generator. Such isolation eliminates the circulating common mode current between the parallel converters of the wind turbine system and eliminates the need for a common mode inductor. System reliability is enhanced and total system cost is reduced.

The invention provides a low-voltage ride through (LVRT) control system of a photovoltaic inverter and a method thereof. The system comprises a solar cell panel, a photovoltaic inverter, a power grid and a controller, wherein the solar cell panel, the photovoltaic inverter and the power grid are sequentially connected; and the controller is respectively connected with the photovoltaic inverter and the power grid. The system and the method have the advantages that 1) when the power grid breaks down to cause power grid voltage balance sag, good dynamic response is provided, and grid-connected current can be steadily outputted by three phases of current sharing of the photovoltaic inverter; and 2) in unbalanced voltage sag, the positive and negative sequence voltage influence of the power grid can be eliminated by the control system, only the positive sequence current component is outputted, and the three-phase current sharing is ensured and has a lower harmonic component, so that the loss caused by the faults of the power grid is reduced, and the power supply reliability of the power grid is improved. The special situation of the unbalanced power grid is supported by the system, and the stable operation of the normal three-phase current sharing is guaranteed.

The invention discloses a resonance enhanced wireless power transmission structure with high resonance frequency stability, and relates to the technical field of wireless power transmission. According to the wireless power transmission structure provided by the invention, the change of a coupling coefficient and a load cannot influence the resonance frequency, the primary side works at a constant frequency, the voltage and the current are same in phase, and the design of an absorption circuit and a soft switch is easily realized; due to a secondary-side impedance adjusting circuit, on one hand, the whole back-stage omega 0 frequency component of a rectifier bridge is purely resistive and the load change is guaranteed not to influence the resonance frequency, and on the other hand, the output voltage is stable and the power supply demand of the back-stage load is met; meanwhile, compared with an existing secondary-side wireless power transmission structure, the secondary-side structure proposed by the invention has relatively high resonance value Q, so that the resonance is enhanced, the transmission power under the weak coupling condition is increased, and the transmission efficiency under the weak coupling condition is improved. The resonance enhanced wireless power transmission structure is suitable for wireless power transmission occasions.

A linear power amplifier system using pulse area modulation includes: an envelop/phase decomposer for decomposing an input signal into an envelop signal and a phase signal; a pulse area modulator for modulating the envelop signal such that an area of the modulated envelop signal is proportional to an amplitude of the envelop signal; a control signal generator for converting the modulated envelop signal into a control signal; an automatic gain adjuster for equalizing pulse height of the modulated envelop signal; a mixer for mixing the phase signal with the output of the automatic gain adjustor to produce a RF pulse train; a power amplifier for amplifying the RF pulse train, to generate an amplified RF pulse train; and a band pass filter for restoring the original input signal from the amplified RF pulse train. The output level of the power amplifier is controlled by the control signal.

The invention discloses a Halbach-structure-based iron-core-free axial magnetic field brushless direct-current electromotor which comprises a stator iron-core-free armature disc, a permanent magnet, a rotor disc, a shaft, a bearing and a rotor outer shell, wherein two symmetrical rotor discs are arranged at two sides of the stator iron-core-free armature disc; the stator iron-core-free armature disc and the rotor disc are installed on the shaft; the shaft is installed in the rotor outer shell through the bearing; the permanent magnet is pasted on the rotor disc, and is pasted on the inner surface of the rotor outer shell; a Halbach magnet structure with axial magnetizing and tangential magnetizing is adopted for the permanent magnet, and an enclosed magnetic circuit is formed automatically; and a soft magnetic material is placed at the middle of the permanent magnet with tangential magnetizing. According to the invention, on the basis that more permanent magnets are not used, flux density with great air clearance can be obtained, and are is in sine distribution; the output torque is high; the torque density is large; the efficiency is high; the structure is simple; the assembly is simple; and the Halbach-structure-based iron-core-free axial magnetic field brushless direct-current electromotor is suitable for relevant driving occasions with compact structures for electric automobile hub motors and the like.

The invention relates to a reactive power compensation method and a reactive power compensation system for a micro power grid. The system comprises a distributed measuring unit, a reactive power compensation control unit, a reactive power compensation unit and a communication unit. The micro power grid comprises a distributed power supply with reactive regulation output. For the micro power grid operated in an isolated network mode, the overall reactive power balance condition of the micro power grid is obtained by measuring the active and reactive power distribution conditions of each branchcircuit of the micro power grid, and a reactive power compensation device or the reactive power compensation device and the distributed power supply are subjected to reactive regulation in the micro power grid according to a specific isolated network reactive control strategy to realize the reactive power compensation of the micro power grid. The power factor of the micro power grid can be measured and corresponding reactive power compensation is performed according to the power factor when the micro power grid is operated in a grid-connected mode and in the isolated network mode.

The invention discloses a switch power supply and a controlling circuit and a controlling method thereof. Through regulating a first multiplying input signal, waveform-following input voltage of an average current is inputted by the switch power supply, so that a harmonic component of an input electric current of the switch power supply is reduced, the THD (Total Harmonic Distortion) is lowered and then the power factor of the switch power supply is increased.

The present invention relates to a large-scale dual-rotor direct-drive permanent magnet wind power generator and a generating set thereof. The generator includes a stator and a rotor. The rotor is a dual-rotor structure including an outer rotor and an inner rotor; the stator is mainly composed of stator iron Core, outer ring group and inner ring group, the inner and outer ring groups correspond to the in-phase windings in anti-phase series; the stator is located between the outer rotor and the inner rotor, the outer rotor and the stator form the first working air gap, and the inner rotor and the stator form the second Two working air gaps, the first working air gap is connected in series with the second working air gap magnetic circuit. The generator set also includes a hub, a main shaft, a rotor turntable, a casing and a frame, and the stator is fixed inside the casing; the inner and outer rotors are connected and synchronized with the main shaft and the hub through the rotor turntable. The invention adopts a double-rotor ring winding structure, which greatly improves the torque power density of the motor, makes full use of the internal space of the motor, reduces the volume and weight of the motor, reduces the production cost, and facilitates transportation.

The invention discloses a linear permanent-magnet generator, which comprises a primary iron core, a primary coil, a secondary iron core and a non-magnetic material shaft. The primary iron core, the primary coil, the secondary iron core and the non-magnetic material shaft are arranged in turn from the outside to inside; the primary coil is wound on the interior of the primary iron core; the non-magnetic material shaft is embedded in the secondary iron core; and a permanent magnet of a Halbach array is also sleeved outside the secondary iron core, and the permanent magnet enhances the magnetic field outside the permanent magnet and weakens the magnetic field inside the permanent magnet. The Halbach permanent-magnet array is applied to the linear generator and has the advantages of improving the power density of the generator, improving the utilization rate of the permanent magnet and simultaneously reducing eddy-current loss in the secondary iron core; therefore, the structure of an electric motor is simplified, the electric motor runs more stably, and the volume and weight of the generator are reduced.

The invention discloses a high-dynamic-response pulse width modulation method at a low switching frequency. The method comprises the steps that (1) in the offline state, an optimization algorithm is adopted for calculation with the modulation ratio as a variable for the purpose of eliminating specific secondary current harmonics, so that switching angles corresponding to all frequency division numbers are calculated; (2) judgment and rejection principles are put forward for the calculated switching angles, wherein if the shape of an obtained stator flux link is a regular hexagon or a regular octadecagon or a regular shape with 30 edges, namely the difference of the numbers of the edges is 12, the switching angles are adopted, and the switching angles are abandoned otherwise; (3) the switching angles corresponding to the modulation ratio are sequentially stored at fixed positions in hardware, or curve fitting is conducted on the switching angles, so that the corresponding relation between the modulation ratio and the switching angles is obtained; (4) in the actual operation process of a system, table look-up or calculation is conducted according to the modulation ratio and the frequency division numbers, so that all the switching angles are obtained. The high-dynamic-response pulse width modulation method at the low switching frequency has the advantages that the specific subharmonics can be effectively eliminated, so that system noise and torque pulsation are lowered, and the dynamic responsiveness of the system can be greatly improved at the same time.

The invention discloses a high-efficiency power regulating device based on power factor correction, which comprises a front-end power factor correction circuit, a back-end power regulating circuit and a microcontroller. A phase trapping module is used for trapping the zero crossing point (ZCP) of sine voltage Uac acquired from an electric network, and a sampling module is used for acquiring rectified DC voltage Ui, current Ii, voltage Uc at two ends of an energy storage capacitor and output current Ic when insulated gate bipolar transistors Q1 and Q4 or Q2 and Q3 are conducted; then, a pulse triggering signal J is output to control the on-off of a metal oxide semiconductor field effect transistor (MOSFET) in the front-end power factor correction circuit, pulse triggering signals J1 and J4 are respectively output to the insulated gate bipolar transistors Q1 and Q4, and pulse triggering signals J2 and J3 of which the time sequence is 1/2Tc delayed than the time sequence of the pulse triggering signals J1 and J4 and the duty ratio is the same as the duty ratio of the pulse triggering signals J1 and J4 are respectively output to the insulated gate bipolar transistors Q2 and Q3 to control the on-off of the insulated gate bipolar transistors Q1, Q2, Q3 and Q4; and finally, the high-efficiency power regulating device outputs larger power required by the load and simultaneously ensures that the power factor is approximate to 1 and the harmonic component is very low.

The invention discloses a power collection and transmission system for a wind power plant. The system comprises an alternating current generatrix, a wind generating set, a rectifier station and an inverter station, wherein the rectifier station comprises a rectifier and a converter transformer; the direct current side of the rectifier is connected with the direct current side of the inverter station, and the alternating current side of the rectifier is connected with one side of the converter transformer through a converter inductor; and the other side of the converter transformer is connected with the alternating current generatrix, and is grounded through a capacitor. The invention also discloses a voltage control method for the alternating current generatrix of the system. The voltage comprising the amplitude and frequency of the voltage of the alternating current generatrix of the system is integrally controlled by two control dimensions of the rectifier on a wind power plant side, so that the stability of the alternating current voltage of the power collection and transmission system of the wind power plant is ensured, and harmonic components of an alternating current system of the wind power plant are reduced.

The invention relates to a high-frequency multiphase interleaved conversion device and a control method, and belongs to the field of power electronics and electric drive. The device comprises a drive and power amplification unit, an EV (Electric Vehicle) manager module, an AD (Analog-Digital) sampling module, a DSP (Digital Signal Processor) processor, a serial port communication module, an HCI (Human-Computer Interaction) module, a DC (Direct Current) voltage detection circuit, a DC voltage conditioning circuit, a current detection circuit, a current conditioning circuit and a main circuit. The system adopts a double closed-loop control technology and a new topological structure to realize system stability and broad stability margin; three inductors at the front end of the topological structure work alternately, and the equivalent switching frequency is 6 times of the traditional switching frequency, so that the whole converter has high frequency, and the output voltage and the ripple amplitude and harmonic component of current are reduced; and the equal-time work of the three front-end inductors per unit time reduces the power requirements on power components IGBT (Insulated Gate Bipolar Transistor) and diodes, reduces the manufacturing cost of the whole device, and improves the application value of the DC converter.

The invention relates to a frequency synthesis source applied by a DDS short-wave transmitter based on a CPLD design. The frequency synthesis source mainly comprises a direct digital synthesis circuit, a high-speed DAC transformation circuit, a tracking filter circuit and a gain control circuit, a controller and a phase locked crystal oscillator. According to the invention, the high-speed DAC transformation circuit converts frequency data output by direct digital synthesis circuit to a sine frequency signal; and the tracking filter circuit filters components of stray and harmonic wave in the high-speed DAC transformation circuit, and the gain control circuit enables the output of the direct digital synthesis circuit to be stable in amplitude within a frequency range. In addition, the controller comprises a microprocessor and a microcomputer, wherein the microprocessor is connected with the microcomputer through an interface circuit of the microcomputer, and frequency arrangement and transition of working mode are realized by an upper computer. The phase locked crystal oscillator generates a clock source signal with ultrahigh frequency and high stability, and the clock source signal is used as a clock signal of the frequency synthesis source. The frequency synthesis source applied by a DDS short-wave transmitter based on a CPLD design provided in the invention has advantages of high frequency accuracy and high distinguishability, short switching time of frequency signals, constant output amplitude, and simple and high-reliable circuit.

Arrangement at an electric machine, particularly motor, generator, or actuator, with a stator with teeth (11, 12) carrying coils (15), particularly one layer, for concentrated windings. A permanent magnetic rotor is movable relatively to the stator (11, 12). The teeth of the stator are arranged for receiving coils (15) with generally rectangular opening. Advantages are achieved if the stator teeth (11, 12) are provided to receive generally identical coils (15) closing the grooves (14, 16). The teeth (11, 12) may be alternating rectangular and converging/diverging toward the top, to provide grooves (14, 16), with parallel sides to enter the coils (15). The converging teeth (22) have preferably a shortened top (23). The grooves are preferably provided to make room for a semi magnetic groove wedge (17, 18) between adjacent teeth.

A permanent magnetic type electric rotating machine includes: a stator having armature winding arranged in several slots formed in a stator core; and a rotor having permanent magnets held in several permanent magnetic insertion holes formed in a rotor core, in which a peripheral surface of the rotor core is configured to be a combination of arcs around two points different from a center of the rotor core for each magnetic pole in such a manner that when an axis extending in a central direction of a magnetic pole of the rotor is a d axis, and an axis extending in a direction between magnetic poles that is offset from the central direction of the magnetic pole by 90 electrical degrees is a q axis, a radial distance from a center of the rotor core to a periphery of the rotor is reduced gradually from the d axis to the q axis.

The invention discloses a two-section Halbach permanent magnet motor with an optimal magnetization angle, which is characterized in that the optimal magnetization angle of a first permanent magnet section of the N-pole is an included angle of a magnetization direction and a clockwise circumference tangential direction; the optimal magnetization angle of a second permanent magnet section of the N-pole is an included angle between the magnetization direction and an anticlockwise circumference tangential direction; the optimal magnetization angle of a first permanent magnet section of the S-poleis an included angle between the magnetization direction and the anticlockwise circumference tangential direction; and the optimal magnetization angle of a second permanent magnet section of the S-pole is an included angle between the magnetization direction and the clockwise circumference tangential direction, and a rotor is matched with a corresponding stator to form a two-section Halbach permanent magnet motor with an optimal magnetization angle. The two-section Halbach permanent magnet motor can improve the radial air gap flux density fundamental wave amplitude and reduce a harmonic component of the air gap flux density, thereby being capable of outputting the torque at the same volume and cost. Therefore, the torque density and the power density of the kind of motors can be improved,and the scheme is also applicable to motor without a rotor core and external rotor motors.

The invention discloses a folding type three-dimensional triangular transformer open reel iron core having a hexagonal cross section. The folding type three-dimensional triangular transformer open reel iron core comprises an iron core group; the iron core group is of a three-dimensional triangular structure seamlessly spliced by three single-phase open reel iron cores, which are independent and are the same both in a size and a structure, at central angles of 120 DEG; a middle hollow place of the single-phase open reel iron cores is a window; an upper end of the window is provided with an upper yoke, and a lower end of the window is provided with a lower yoke; core columns are arranged between the upper yoke and the lower yoke; each group of silicon steel sheet material straps laminated into the single-phase open reel iron cores is composed of two parts, namely a first rectangular material strap and a second right-angled triangular material strap; widths of the second material straps are gradually reduced along extension directions of the first material straps; the cross sections of the core columns of the single-phase open reel iron cores laminated by each group of the silicon steel sheet material straps after being folded and sheared are of an isosceles trapezoid; and the cross sections of three columns of the spliced iron core group are of a regular hexagon. According to the folding type three-dimensional triangular transformer open reel iron core having the hexagonal cross section, the material utilization rate is high, the production cost is low, the production efficiency is high and the manufacturing process is simple.

The invention relates to a multi-channel multi-target satellite-borne AIS (Automatic Identification System) reconnaissance signal simulation system, and is a system for simulating a multi-target aliasing dynamic AIS signal received when a satellite-borne AIS multi-channel reconnaissance system carries out in-orbit operation. All filtering and frequency conversion of four channels of AIS signals and two paths of signals generated by the system can be subjected to all-digital calculation, interchannel consistency is good, signal straying is small, and a harmonic component is good; a clock sampling rate is high, the time resolution of the generated AIS signal is high, and the control accuracy of time delay can achieve about a 8us order of magnitude; a quantity of AIS targets which can be generated is large, continuous simulation time is long (which is longer than five minutes), and any scene of 0-10000 ships in the same field of view can be simulated. By use of the system, a purpose that the dynamic-change multi-target aliasing AIS radio frequency signal which receives Doppler frequency shift, amplitude fluctuation and the like caused by relative movement during satellite-borne reconnaissance can be vividly generated is realized.

The invention discloses a multiple symmetrical winding magnetic flux switching motor and a winding design method thereof. The method is based on exertion of complementarity of windings of the magnetic flux switching motor with maximization of induced electric potential of each phase as the principle, and coil compositions of a phase winding, coil compositions of a set of symmetrical windings and coil connection types of all phase windings are obtained in sequence through optimizing the phase difference between two sets of adjacent symmetrical windings. The winding design method is clear in thinking and easy to operate. The multiple symmetrical winding magnetic flux switching motor has the advantages of being high in no-load induced electric potential sine degree and winding utilization rate, large in torque output and small in electromagnetic torque pulsation, and superior motor performance is embodied.

An apparatus for controlling a switched reluctance motor with use of a power conversion circuit. In the apparatus, a command voltage setter sets a command voltage for a coil of the motor, where the command voltage is set to change gradually during either or both of a ramp-up period and a ramp-down period of the command voltage. A voltage controller controls an applied voltage to the coil to the command voltage set by the command voltage setter by operating the power conversion circuit.

The present invention relates to a linearisation method and signal processing device for reducing intermodulation distortions by extracting harmonic components generated from first and second carrier signals with different carrier frequencies, which are input into two first non-linear stages (11, 12). The harmonic components may be generated by the two first non-linear stages (11, 12) or by two additional harmonic generating elements (NE1, NE2). The extracted harmonic components are phase and/or amplitude adjusted and mixed with harmonic components generated in a second non-linear stage (4) to thereby reduce harmonic components so as to achieve a linear output waveform. Thus, an intermodulation distortion suppression can be achieved over the entire operating bandwidth, wherein no phase coherency of the two carrier signals is required.