37results about How to "Improve harmonic performance" patented technology

A heating apparatus using an electromagnetic wave is disclosed, by which cut-of performance of an electromagnetic wave is enhanced by increasing an electromagnetic wave absorption bandwidth having cut-off performance below −70 dB. The present invention includes a door provided to an open front side of a body to be opened/closed and a choke filter having a panel type choke part arranged by at least one row each along an edge of the door and a filter part arranged by at least one row each along an edge of the choke part and having a plurality of slots, wherein a prescribed choke part is provided to a most inner side among rows of the choke and filter part.

The invention discloses a five-phase inverter random SVPWM modulation method, and belongs to the technical field of multi-phase inverter drive control. In every sampling cycle, the sampling cycle is kept constant, a PWM pulse is delayed randomly, to achieve random change of a switch cycle, at the same time, two vector action time obtained through an NFV-SVPWM algorithm are randomly allocated, and double-random of switch frequency and zero vector action time is achieved. According to the five-phase random SVPWM modulation method, on the condition of not influencing low frequency-band harmonic performance, the amplitude of higher harmonic is drastically lowered, harmonic originally concentrated on the switch frequency and around the integral multiple switch frequency is dispersed into a wider frequency spectrum range, thus a more consecutive and even frequency spectrum is obtained, electromagnetic interference and high frequency noise are effectively inhibited, and the electromagnetic compatibility of the system is improved.

The invention discloses a motor current harmonic and torque ripple suppression method based on order extraction. The method comprises the following steps of 1, collecting a motor rotation angle, a rotation speed and a quadrature axis current signal at equal angle intervals according to a rotor rotation angle; 2, constructing an angular domain single-point Fourier transform algorithm; 3, performingorder extraction of the rotating speed and current signals acquired in the step 1 by using an angular domain single-point Fourier transform algorithm in the step 2; 4, obtaining a quadrature axis voltage harmonic wave to be injected through a PI controller; 5, constructing an order single-point inverse Fourier transform algorithm; 6, performing angular domain reconstruction of the quadrature axisvoltage harmonic obtained in the step 4 by using an order single-point inverse Fourier transform algorithm in the step 5 to obtain an injection voltage signal; and 7, superposing the injection voltage signal into a driving voltage instruction value of the motor control strategy to carry out harmonic suppression.

The embodiment of the invention discloses a small dielectric dual-mode filter without a shell, and belongs to the technical field of communication. The filter comprises n resonant cavities connected in series through a metal rod, wherein a metal sheet is arranged between every two adjacent resonant cavities, the first resonant cavity and the last resonant cavity in the n resonant cavities are metal resonant cavities, the remaining n-2 resonant cavities in the n resonant cavities are dielectric dual-mode resonant cavities, the dielectric dual-mode resonant cavities are of a symmetrical polygonal structure, metallization of the surfaces of the dielectric dual-mode resonant cavities is achieved, and the n resonant cavities are coupled through coupling windows on the metal sheets. According tothe filter provided by the embodiment of the invention, a metal shell does not need to be arranged outside the dielectric dual-mode resonant cavity, so that the filter has the advantages of being compact in size, small in loss, large in power capacity, high in out-of-band rejection and good in harmonic performance so as to effectively improve the anti-interference capacity and the frequency spectrum utilization rate of a 5G communication system, reduce the power consumption of the 5G communication system and improve the coverage range of the 5G communication system.

The invention discloses an indirect matrix transformation type multi-phase multi-level permanent magnet motor system. The indirect matrix transformation type multi-phase multi-level permanent magnet motor system includes a double-stator multi-phase composite permanent magnet synchronous motor, wherein two independent five-phase three-level inverters supplies power for stator winding ports of the motor respectively; an independent controllable rectifier supplies power for each five-phase three-level inverter; the two controllable rectifiers can share one set of LC filter at the power grid side; the LC filter includes a three-phase grid-connected inductor and a three-phase filter capacitor which is connected with the three-phase grid-connected inductor in parallel; and the first five-phase three-level inverter and the second five-phase three-level inverter are respectively connected with the two stator winding ports of the double-stator multi-phase composite permanent magnet synchronous motor. The invention also discloses a control method of the indirect matrix transformation type multi-phase multi-level permanent magnet motor system. The indirect matrix transformation type multi-phase multi-level permanent magnet motor system and the control method thereof can significantly improve reliability, power density, torque smoothness and operation efficiency of the motor driving system, and can lay the foundation of solving the technical difficulty that a high capacity motor traction driving system requires compact designs, reliable operation and energy-efficient aspects.

A fast three-phase space vector modulation method based on a three-dimensional coordinate system belongs to the technical field of power electronics. At first, that vector is map from a two-dimensional coordinate system to a three-dimensional coordinate system by using a simple coordinate change, three modulation vectors are used to synthesize the reference voltage vector, Three modulation vectorsform a modulation triangle in the three-dimensional coordinate system, detect the closest modulation vector to the origin in the modulation triangle, calculate the three-phase switching state corresponding to the vector and map it to the three-dimensional coordinate system, and scale the reference voltage vector to simplify the multilevel vector space to the two-level vector space; Finally, the duty cycle of the three-phase switching state is calculated and compared with the triangular carrier of the converter to generate the switching driving signal. The invention can realize arbitrary leveloutput only through simple addition and subtraction operation, and has extremely strong expansibility; In addition, the present invention provides several controllable factors to improve the performance of various aspects of multilevel converters.

The embodiment of the invention discloses a small hybrid mode filter with two resonant cavities, and belongs to the technical field of communication. The filter comprises n resonant cavities which areconnected in series, a metal sheet is arranged between every two adjacent resonant cavities, and n is larger than or equal to 3. A first resonant cavity and a last resonant cavity in the n resonant cavities are metal resonant cavities, and the remaining n-2 resonant cavities are dielectric dual-mode resonant cavities. The n resonant cavities are coupled through coupling windows on the metal sheets. The filter provided by the embodiment of the invention has the characteristics of compact size, low loss, high power capacity, high out-of-band rejection and good harmonic performance, so that theanti-interference capability and the spectrum utilization rate of a 5G communication system can be effectively improved, the power consumption of the 5G communication system is reduced, and the coverage range of the 5G communication system is enlarged.

The invention relates to a harmonic suppression device based on epitaxy delta controllable reactor connection. The harmonic suppression device comprises a first group of magnetically controlled reactors using epitaxy delta connection and a second group of magnetically controlled reactors using epitaxy delta connection, wherein the first group of magnetically controlled reactors and the second group of magnetically controlled reactors have the same type and are connected in parallel; and a three-phase iron core column of the first group of magnetically controlled reactors and a three-phase iron core column of the second group of magnetically controlled reactors have flat five-core structures. The three-phase iron core column of the first group of magnetically controlled reactors and an alternating-current working winding of the second group of magnetically controlled reactors employ the epitaxy delta connection way; an alternating-current working winding of the first group of magnetically controlled reactors uses delta forward connection as the epitaxy delta connection way; and the alternating-current working winding of the second group of magnetically controlled reactors uses delta reverse connection as the epitaxy delta connection way. According to the invention, with the connection ways of the working windings of the reactors, the harmonic performance can be improved to the great extent.

The invention relates to the technical field of filters, in particular to a dielectric waveguide filter for improving the harmonic performance, a radio frequency module and a base station. The dielectric waveguide filter includes dielectric bodies and at least two resonance parts located on the different dielectric bodies. The resonance parts are coupled together through coupling windows, and thecoupling windows are arranged at the edges of the dielectric bodies. The coupling windows are main-path-coupling coupling windows or cross-coupling coupling windows. The coupling windows are strip-shaped, L-shaped or U-shaped (opened rightwards), and are symmetrically distributed along the central axes of the dielectric bodies. By adopting the dielectric waveguide filter for improving the harmonicperformance, the radio frequency module and the base station provided by the invention, harmonics can be kept away from the pass band of the filter, the loss of the filter and the complexity of the manufacturing process can be reduced, and the cost can be lowered.

The invention discloses a synchronous carrier modulation method for a three-level inverter, and the method comprises the steps: carrying out the negation of a three-phase sine wave, and injecting a specific offset, and obtaining three groups of three-phase initial modulation waves; respectively selecting specific initial modulation waves for three phases in different space angle regions to obtain three-phase actual modulation waves; obtaining two groups of carriers with opposite initial directions by setting the triangular carrier frequency to be the even number times of three of the fundamental wave frequency; selecting specific initial direction carriers in different space angle areas to obtain actual carriers; and formulating a comparison rule of the actual modulation wave and the actual carrier wave, and obtaining a control signal of the three-level inverter based on comparison of the actual modulation wave and the actual carrier wave, thereby realizing synchronous carrier wave modulation for reducing the common-mode voltage. According to the method, the amplitude of the common-mode voltage can be reduced by one half while harmonic waves of multiple of three and even harmonic waves in the line voltage are eliminated, the change frequency of the common-mode voltage can be reduced by two thirds, and the method has the advantages of being simple in calculation and convenient to implement.

The invention provides a space vector modulation method of a multi-source converter, and belongs to the technical field of pulse width modulation of the multi-source converter. The space vector modulation method comprises the steps of building a neutral point potential unbalance space vector model by combining a standard right-angle coordinate system; dividing a small vector into a first vector group and a second vector group, and determining a boundary equation of a small sector comprising small vectors in the first vector group and the second vector group; determining a reference voltage vector according to the boundary equation of the small sector; calculating an action time proportion of a basic vector of the small sector; and performing hybrid modulation on the first vector group andthe second vector group according to the action time proportion so as to achieve DC-side power allocation and acquire various energy circulation modes. The problem brought by neutral point voltage unbalance is solved by a coordinate operation-based method, and the operation quantity is reduced; and hybrid modulation of the first vector group and the second vector group is employed, power allocation of a DC side is achieved by controlling action time weights of the first vector group and the second vector group, and more energy circulation modes are obtained.

A heating apparatus using an electromagnetic wave is disclosed, by which a capacity of a cavity is increased and by which cut-off performance of the electromagnetic wave and facilitation of door cleaning can be enhanced. The present invention includes a door provided to an open front side of a body to be opened/closed, a choke filter having a panel type choke part arranged by at least one or more rows along an edge of the door and a filter part having a plurality of slots wherein a prescribed choke part is provided to a most outer side, and a glass panel attached to an inner lateral side of the door and the choke filter.