49results about How to "Increase output level" patented technology

The invention discloses a frequency reduction control method of a modular multilevel converter containing auxiliary sub-modules. Each bridge arm of the modular multilevel converter topology is formedby connecting N half-bridge sub-modules, one auxiliary sub-module and one bridge arm inductor in series, the auxiliary sub-module adopts a full-bridge structure, and the capacitor voltage of the auxiliary sub-module is controlled to be 1 / 2 of that of the half-bridge sub-modules. A nearest level approximation modulation mode is adopted for the half-bridge sub-modules of each bridge arm, and the auxiliary sub-modules are input only when the input number of the bridge arm half-bridge sub-modules is smaller than or equal to a preset value; The forward input and the reverse input of the auxiliary sub-modules need to be determined according to the deviation between the actual values and the reference values of the capacitor voltages of the auxiliary sub-modules in the current state and the current directions of the bridge arms. According to the control method, the auxiliary sub-modules connected in series can only be input in part of time periods, the switching frequency of the auxiliary sub-modules is effectively reduced while the output level number of the MMC is increased and the output voltage harmonic distortion rate of the modular multilevel converter is reduced, and the loss of the system is reduced.

The invention discloses a parametric oscillator for enhancing terahertz waves. The parametric oscillator comprises a pumping source, a first beam splitter prism, a second beam splitter prism, a firstreflector, a second reflector, a third reflector, a fourth reflector, a fifth reflector, a sixth reflector, a seventh reflector and an eighth reflector. Pumping light emitted from a pumping source ischanged into transmission pumping light and reflection pumping light through the beam splitter prisms; the transmission pumping light is vertically incident to the LiNbO3 crystal; while phase matchingconditions are satisfied, the pumping light generates signal light in the LiNbO3 crystal through a parametric process; the signal light is oscillated and amplified in the two resonant cavities respectively, under the action of the beam splitter prisms and the reflectors, the pumping light forms oscillation around the crystal, and meanwhile, the pumping light and the signal light generate multiplebeams of terahertz waves in the crystal based on the action of optical parameters, so that the conversion efficiency from the pumping light to the terahertz waves is improved.