153results about How to "Reduce distortion rate" patented technology

The utility model relates to a voltage type source rectifier stable control system and method based on LCL filter wave, belonging to the source rectifying technical range of electronic technology. The system comprises a DC voltage control cell, a current control cell, an active damp control cell and a voltage space vector generating cell. the utility model produces six PWM signals to gain the current signal of the filter wave capacitor branch directly or indirectly, outputs the reference value of the damp voltage and achieves the stable control on the system. The method provides an adjustable sine control on the DC voltage output and input current through the active damp vector control of the voltage type source rectifier stable control system, the damp voltage reference value outputted by the active damp vector control cell, and the network voltage to execute summation operation. The utility model has the advantages of controllable DC voltage, low aberrance rate of the network input current, high power factor, satisfying the requirement of energy double-redirection flowing, and achieving the stability of the system without increasing the quantity of hardware damp resistance.

The invention discloses a super-low-speed high-torque motor and a crane with the motor. The motor comprises an outer rotor and a stator. The stator is provided with a stator temperature sensor for collecting a temperature signal within the stator. The outer cylinder inner side of the outer rotor is fixedly equipped with a plurality of permanent magnets which are the same tile-shaped hexahedral structures and are regularly arranged along a circumferential direction and an axial direction. A plurality of permanent magnets are arranged in any circumferential and any axial direction. Two circumferential side faces of the permanent magnets are inclined plane shapes with inside cutting angle shapes, and the angle of a cutting angle is 5 degrees to 35 degrees. According to the crane with the motor, the outer cylinder of the motor is used as the winding drum of a lifting mechanism. The motor can normally run in the condition of low speed (super low speed) and large torque, the operation is stable, the vibration is small, the noise is small, the temperature rise is small, and the motor is mainly used for a crane, a port machine, a tower crane, an elevator, a winding machine and other similar occasion.

The invention discloses a middle point voltage control device and method based on modulation wave interval division. The device comprises a three-level inverter, a digital processing control module and a driving circuit, wherein the digital processing control module comprises a sampling unit, a closed-loop control unit, a sine pulse width modulation unit, a modulation wave interval division unit and a zero-sequence component calculation unit. The method comprises steps that an offset angle of a zero-crossing point after adding a zero-sequence component to a three-phase modulation signal is calculated; the modulation wave interval is divided, and the zero-sequence component required to suppress the midpoint voltage fluctuation is calculated; the sign of the zero sequence component is determined through comparing instantaneous voltages of upper and lower capacitors of the DC side; the zero-sequence component is added to the three-phase modulation signal and is then processed by the sinepulse width modulation unit to acquire a pulse width modulation control signal, and a switch tube of the three-level inverter is controlled by the driving circuit for operation. The device is advantaged in that hardware cost is low, accurate control is realized, the application scope is wide, the midpoint voltage fluctuation can be effectively inhibited, and the distortion rate of the network current is reduced.

The present invention discloses a current prediction control method for two-level three-phase grid-connected inverter. The method comprises the steps of collecting the voltage of a three-phase grid and a grid-connected current signal in real time, using the voltage of the three-phase grid and the grid-connected current signal collected in real time and a two-level three-phase grid-connected inverter model in a three-phase static coordinate to carry out two-phase static alpha beta coordinate conversion and obtaining the output voltage vector needed by the two-level three-phase grid-connected inverter, selecting the optimal effective voltage vector of the two-level three-phase grid-connected inverter according to the obtained output voltage vector needed by the two-level three-phase grid-connected inverter and obtaining the optimal action time of the optimal effective voltage vector, and using the optimal action time of the effective voltage vector to obtain the switch-on and switch-off times of an inverter switch element, and thus realizing the control of the output current of the two-level three-phase grid-connected inverter. According to the prediction control method of the invention, the current tracking effect can be improved, the distortion rate is reduced, and thus the switch change becomes regular.

The invention belongs to the technical field of electricity and relates to a single-stage photovoltaic grid-connected micro inverter and a control method thereof. The primary side of an isolation transformer achieves bidirectional excitation only through one switch tube, and the switch tube can achieve zero-voltage connection and disconnection and at the meantime transmit energy to the secondary side of the isolation transformer; the secondary side of the isolation transformer comprises two sets of high-frequency full-wave rectification circuits, which are controlled to output at a power frequency and then connected in parallel back to back, and is combined with modulation of a high-frequency switch tube of the primary side of the isolation transformer to form a pulse sequence changing by sinusoidal modulation rules and then filtered into grid-connectable power-frequency alternate current. The single-stage photovoltaic grid-connected micro inverter is simple in structure, small in size, low in cost and high in efficiency and reliability, and can be applied to other small grid-connected inverters besides photovoltaic grid-connected micro inverters; after island detection and phase lock programs are eliminated, the single-stage photovoltaic grid-connected micro inverter can be applied in a generalized mode to vehicle-mounted inverters, USB (universal serial bus) power sources, frequency converters and isolated boost DC-AC (direct current-alternate current) converters.

The invention discloses a special diet edible food formula for improving sperm quality of males and a preparation method of the formula and belongs to the field of special diet edible food. Whey protein, sea cucumber polypeptide, oyster polypeptide, bone collagen peptide, soybean peptide, corn oligopeptide, wheat oligopeptide and casein phosphopeptides are used as basic raw materials, edible and medicinal raw materials including raspberries, fructus lycii, cortex cinnamomi and the like are added, wall-broken piney flower powder, spirulina platensis powder, a roxburgh rose extract, a maca extract, cordyceps militaris and fructooligosaccharide are matched, so that the special diet edible food is formed. The formula product is formed through steps of raw material pretreatment (cleaning, enzymolysis, extraction and the like), crushing, sieving, mixing and the like. The formula components are all food materials, and the prepared product has functions of increasing sperm density, increasingsperm motility rate, reducing sperm aberration rate and improving immunity and fatigue resistance. The product has high safety, has no toxic or side effects, has low fishy smell and bitterness and canbe eaten for a long term.

The invention discloses a micro-current measuring circuit for dielectric response tests; the micro-current measuring circuit comprises a logarithm operation unit, a linear optical coupler unit, an index operation unit, and a signal secondary amplification unit connected in sequence; the logarithm operation unit comprises an ultra low bias current amplifier and a negative feedback element; the linear optical coupler unit comprises a linear optical coupler chip and a negative feedback circuit; the index operation unit comprises a high speed operation amplifier and a photosensitive diode; the micro-current measuring circuit has no feedback resistor, so the measuring result cannot be affected by a resistance temperature coefficient, thus providing high temperature drift influence inhibition ability, and the temperature coefficient can reach 100ppm/C.

The invention discloses a low-frequency offset three-phase multi-inverter parallel operation control method under a micro-grid island. Each inverter and an LC filter thereof under the micro-grid island are controlled to be voltage-controlled current sources; a reference frequency of fundamental current output by each inverter is a rated value; a reference phase can be obtained through a disturbance observation-based maximum output voltage tracking method; a reference amplitude of the fundamental current output by each inverter is obtained through common bus-based feedback proportional control; distribution of output current of each inverter according to the capacity proportion can be achieved by reasonably setting a proportion coefficient and a voltage amplitude on a micro-grid bus is controlled to be close to the rated value; a harmonic current reference output by each inverter is obtained through bus harmonic voltage feedback control; and quasi proportional resonant control in a static coordinate system is adopted as current tracking control of each inverter. According to the low-frequency offset three-phase multi-inverter parallel operation control method under the micro-grid island, the influence of the difference between line parameters on equal division of output current of each inverter is overcome, the frequency of the voltage in the micro-grid operation process is relatively stable and the influence of voltage frequency fluctuation on a load is reduced.

The invention relates to an offshore wind power grid connection system based on full-bridge MMC DC-side serial connection and a control method thereof, and belongs to the technical field of offshore wind power grid connection. The grid connection system comprises a plurality of prime motors, a gear case, a wind power generator, an isolation transformer, a plurality of offshore platform devices composed of full bridge MMC, DC cables and a grid connection converter arranged on the land. The control method includes controlling amplitude of voltage at the full-bridge MMC AC side, controlling voltage at the full-bridge MMC DC side and controlling current at the DC side of the grid connection converter. High voltage is obtained through DC side serial connection, and the system and method are applicable to offshore wind power transmission. Converters and transformers are not needed in the system, the output power of the wind power generator can be controlled by adjusting the output voltage at the DC side of the full bridge MMC, and the current of a DC loop is controlled by the grid connection converter. The grid connection system and control method are simple for controlling, and easy to realize. The performance and extendibility are good.

The invention relates to a three-level NPC inverter zero-sequence circulation suppression method based on model prediction virtual voltage vector control. Through analyzing a space vector of a three-level inverter, seven voltage vectors contributing zero to zero-sequence circulating current are selected as basic vectors, and 12 virtual voltage vectors are synthesized through the basic vectors, sothat the distortion rate of output current of the parallel system can be remarkably reduced while the zero-sequence circulating current of the parallel system is effectively suppressed, the quality ofgrid-connected current is improved, and the method is very suitable for a three-level inverter system operating in parallel.

The invention relates to an external rotor motor. A rotor shell is internally and fixedly provided with a plurality of permanent magnets which are the same tile-shaped hexahedral structures and are regularly arranged along a circumferential direction and an axial direction. A plurality of permanent magnets are arranged in any circumferential and any axial direction. Two circumferential side faces of the permanent magnets are inclined plane shapes with inside cutting angle shapes, and the angle of a cutting angle is 5 degrees to 35 degrees. The outer edge of a permanent magnet cross section in a radial direction is a circular arc line shape whose center is at the axis of the rotor shell. The inner edge of the permanent magnet cross section in a radial direction is a single arc shape or a curved line formed by connecting a plurality of arc shapes mutually. The permanent magnets are made of high performance NdFeB materials, the lengths of the permanent magnets are between 30mm and 95mm, and the thicknesses of the permanent magnets are between 8mm and 18mm. The external rotor motor has the advantages of good stability, small vibration, low noise and high power in low-speed operation and is especially suitable for a drum direct drive crane lifting mechanism and the like.

The invention discloses an LCL type inverter grid-connected device based on parameter joint design and a control method. The device comprises a three-level inverter, a digital processing control module and a driving circuit, wherein the digital processing control module comprises a sampling unit, a closed-loop control unit, an active damping unit and a sine pulse width modulation unit. The methodcomprises the following steps: selecting the capacitance value of an LCL filter capacitor, a network side inductor and an inverter side inductor inductance value; determining a feasible range of a PRcontroller proportion parameter and an active damping feedback coefficient through Nyquist stability analysis in combination with a resonance suppression condition; and in the determined feasible region, using a Lagrange multiplier method to select a proper PR controller proportion parameter and an active damping feedback coefficient so that the control system obtains a large bandwidth and good dynamic performance. The device and the method have the advantages of being low in hardware cost, accurate in control and wide in application range, the harmonic component of the resonant frequency of the LCL filter can be effectively restrained, and the distortion rate of the network access current is reduced.

The invention discloses an active filter control method based on harmonic voltage selection compensation. According to the method, by introducing a base wave and step factors in sub-harmonic wave self-adaption filtering link, the weight coefficient of sub-voltage component is rapidly and accurately calculated through recursive iteration, and the defects that according to traditional sliding Fourier transform, the calculated amount is large and the resource consumption is large are overcome. The method includes the steps of achieving sub-harmonic voltage selection compensation by reconstituting sub-harmonic components, and adjusting sub-harmonic wave conductance gains through the self-adaption algorithm according to the magnitude of the sub-harmonic wave containing ratio. The method is not influenced by the route parameter uncertainty or the time-varying characteristics, and the defect of fixed gains is overcome. According to the active filter control method, when distortion of the system voltage is serious and the system runs in an asymmetrical mode, sub-harmonic wave voltage components can be accurately extracted, self-adaption adjustment of the conductance gains can be accurately conducted, the stability is high, and the tracing speed is high.

The invention mainly relates to a stator punching structure of a permanent magnet motor, and belongs to the technical field of permanent magnet motors. The air-gap magnetic flux density waveforms are optimized by cutting angles from two ends of a stator tooth; the ratio of a distance between two start points of each cut angle at a tooth part to the angle and the ratio of each stator tooth to the angle are set within a range of 0.4-0.6; the angle theta of each cut angle is set within a range of 5-15 degrees. According to the structure, the harmonic content of the air-gap magnetic flux density is reduced, loss and vibration noise of the motor are reduced, and the performance of the motor is improved. The punching structure is simple, is convenient to manufacture, is lower in cost and is suitable for popularization and application.