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, 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 arranged by at least one or more rows along the choke and having a plurality of slots wherein a prescribed choke part is provided to a most inner side, a glass panel attached to an inner lateral side of the door and the choke filter, and a flange part provided to an external end portion of the door along the edge of the door to lie in a same level with an inner lateral side of the glass panel.

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. The present invention first utilizes the simple coordinate change to map the vector from the two-dimensional coordinate system to the three-dimensional coordinate system, and then uses three modulation vectors to synthesize the reference voltage vector, and the three modulation vectors form a modulation triangle in the three-dimensional coordinate system, and detect the modulation triangle Detect the modulation vector closest to the origin, calculate the three-phase switch state corresponding to the vector and map it to the three-dimensional coordinate system, scale the reference voltage vector to simplify the multi-level vector space into a two-level vector space; finally calculate the three-phase The duty cycle of the switch state is compared with the triangular carrier wave of the converter to generate the switch drive signal. The invention can realize arbitrary level output only through simple addition and subtraction operations, and has strong expansibility; in addition, the invention provides several controllable factors to improve the performance of various aspects of the multi-level converter.

The invention discloses a multi-parallel inverter motor speed regulating system and a control method of the multi-parallel inverter motor speed regulating system. The system is formed by connecting multiple inverter modules in parallel. The direct current sides of multiple inverter sub modules are directly connected with a direct current power supply with a direct current bus capacitor in parallel. The alternating current sides of the multiple inverter sub modules are connected with multiple sets of smoothing reactors respectively in series and then directly connected in parallel to drive an alternating current motor. By the adoption of the structure, modularization expansion of the motor speed regulating system is easily conducted, and the fault-tolerance performance of the motor speed regulating system is enhanced. By means of a random SVPWM method based on carrier phase shifting, switching frequency of parallel inverters is equivalently improved, switching subharmonic energy within narrow frequency bands is equalized, the harmonic performance of output currents of the parallel inverters is improved, and electromagnetic interference resistance of the motor speed regulating system is enhanced. By the adoption of a space vector synthetic technology for dynamically allocating SVPWM zero vectors, zero-sequence circulating currents between the parallel inverter modules are effectively eliminated, and normal operation of the system is guaranteed.

The invention provides a high power factor diode rectifier permanent magnet motor control method adopting a low capacity thin film capacitor. According to the method, a d-q axis specified is obtained via optimization algorithm-based off line calculation, and a PWM prediction controller is adopted for replacing a PI current controller based on conventional vector control. To compensate deviation between expected inverter output power and output power calculated based on a real time motor current and specific voltage, a voltage correction vector is added. A novel over-modulation algorithm is adopted; while voltage outputting capability of an inverter is increased, the specific voltage of a corrected inverter is enabled to be always in an inverter output voltage limiting scope. According to the control method, application of grid side high power factor control does not require any extra power factor correction circuit or input wave filter, and an input current harmonic wave component of a power grid can be suppressed. Compared with a conventional motor driver, a motor driving control solution put forward in the invention is markedly advantageous in terms of cost, size and reliability.

The invention discloses a multiple control method for a rectifier, belongs to the technical field of the rectifier, and solves the technical problems of non-ideal grid side harmonic performance and high probability of power grid resonance phenomenon of the rectifier in the existing control method. The multiple control method for the rectifier comprises the steps of obtaining set current and voltage control signals according to direct current voltages and set voltages of multiple rectifiers; performing harmonic suppression processing on input currents of the multiple rectifiers, and obtaining current control signals according to processed signals and set currents; generating modulation wave based on the voltage control signals, the current control signals and the power grid voltage; and performing carrier phase-shifting SPWM modulation according to the modulation wave to generate pulse signals so as to control the multiple rectifiers.

The invention provides a space vector modulation method of a multi-source converter and belongs to the technical field of pulse width modulation of a multi-source converter. Including combining the per unitized Cartesian coordinate system to construct the neutral point potential unbalanced space vector model; dividing the small vectors into vector group 1 and vector group 2, and determining the small sectors formed by the small vectors in vector group 1 and vector group 2 The boundary equation of the small sector; according to the boundary equation of the small sector, determine the reference voltage vector; calculate the action time ratio of the basic vector of the small sector; according to the action time ratio, the vector group 1 and the vector group 2 are mixed and modulated to realize DC Side power distribution to obtain multiple energy flow modes. The present invention adopts the method based on the coordinate operation to solve the problem caused by the unbalanced voltage of the midpoint, and reduces the calculation amount; adopts the mixed modulation of the vector group 1 and the vector group 2, and controls the action time weight of the vector group 1 and the vector group 2, The power distribution on the DC side is realized, and more energy flow modes are obtained.

The invention discloses an SVPWM synchronous over-modulation method. The method comprises: a to-be-modulated voltage vector is determined and a modulation ratio and an angle of the voltage vector arecalculated; according to the modulation ratio of the voltage vector, pre modulation of the voltage vector entering an over-modulation region is carried out; acting time of the voltage vector after premodulation is calculated; and the acting force of the voltage vector is compared with a carrier cycle to obtain an acting sequence of the voltage vector. According to the invention, transition from asynchronous SVPWM modulation to square wave modulation is realized. The SVPWM synchronous over-modulation method is suitable for the application fields like the low switching frequency.

The present invention provides a multi-level sine pulse width modulation method. The method comprises: (1) according to the level number N of a convertor, determining the waveform transformation of carrier waveform in a single-carrier period from isosceles triangle carrier waves to laminated multi-level triangle carrier waves; (2) according to the level number N of the convertor, performing phase shift of 360 degrees / (N-1) of each laminated carrier wave; (3) comparing the modulation waves with the laminated carrier waves: when the modulation waves are larger than or equal to the laminated carrier waves, outputting high levels, and when the modulation waves are smaller than the laminated carrier waves, outputting low levels; and (4) outputting one way of PWM waveform when the modulation waves are compared to each carrier wave according to the step (3), and finally obtaining each way of PWM waveform. The modulation method provided by the invention can be utilized in a single-phase circuit and a three-phase circuit, has good output voltage harmonic wave performance and can effectively improve the utilization of direct voltage.