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153results about How to "Suppression frequency" patented technology

Multi-wavelength locking method and apparatus for wavelength division multiplexing (WDM) optical communication system

Disclosed is a multi-wavelength locking method for a wavelength division multiplexing (WDM) optical communication network, and in particular, a multi-wavelength locking method and apparatus for a WDM optical communication system that can lock wavelengths of optical signals by producing pilot tones by applying a sine-wave current to a plurality of transmission lasers having different wavelengths, passing the optical signal through a Fabry-Perot etalon filter, and then Fourier-transforming the filtered optical signal. The multi-wavelength locking method includes frequency-modulating an optical signal by applying a small and specified sine-wave current to a bias current for driving WDM lasers, detecting pilot tones produced after filtering the optical signal through a filtering section and converting the detected signal into a digital signal by performing a sampling of the detected signal, detecting a magnitude and phase of the pilot tones by performing a fast Fourier transform, providing Fourier-transformed data as a first derivative signal of the filtering section, and locking an operation wavelength of WDM channels by controlling the temperature or current if resonance frequencies of the filtering section coincide with respective standard frequency.
Owner:KOREA ADVANCED INST OF SCI & TECH

Method for designing LCL (Logical Connection Layer) filter by uniformly controlling photovoltaic grid connection and active power filtering

The invention discloses a method for designing an LCL (Logical Connection Layer) filter by uniformly controlling photovoltaic grid connection and active power filtering. The method comprises the following steps of: (1) determining the total inductance value LT of the LCL filter; (2) determining the filtering capacitance value Cf of the LCL filter; and (3) determining the resonance frequency fres of the LCL filter. According to the method, the LCL filter is designed on the basis of uniform control over a photovoltaic grid-connected system and active power filtering by using power grid accessing current which is provided with fundamental waves and resonant waves under the comprehensive consideration of the restraint conditions of the control applications of the fundamental waves and the resonant waves; and as proved by verification, the LCL filter can be used for effectively restraining switching frequency and higher-order harmonics, a satisfied photovoltaic grid connection effect can be achieved in combination with modeling control, and idle work required by a power grid is compensated properly.
Owner:ELECTRIC POWER RES INST OF GUANGXI POWER GRID CO LTD +1

Independent micro-grid layered coordinated control method based on different time scales

The invention discloses an independent micro-grid layered coordinated control method based on different time scales. The method comprises the following steps of (1), according to the dynamic characteristics of voltage and frequency of an independent micro-grid system, dividing the fluctuation range of the voltage and frequency into three areas of A, B and C, wherein the area A represents that the deviation of the voltage and frequency is in a normal fluctuation range, the area B represents that the deviation of the voltage and frequency slightly exceeds the normal fluctuation range, and the area C represents that the deviation of the voltage and frequency seriously exceeds the normal fluctuation range; (2) monitoring and collecting the voltage U, the frequency f and the power P of the bus of the independent micro-grid, and determining the areas where the U and the f are located; (3) if the U and the f are located in the area A, keeping a storage battery energy storage system and a diesel generating set away from an adjustment process, if the U and the f are located in the area B, enabling the storage battery energy storage system in charge of primary control to participate in the adjustment process to achieve system power balance, and if the U and the f are located in the area C, enabling a secondary control diesel generator to participate in the adjustment process to achieve system power balance; (4) repeatedly collecting the U, the f and the P until the U and the f are determined to be located in the area A.
Owner:ELECTRIC POWER RESEARCH INSTITUTE, CHINA SOUTHERN POWER GRID CO LTD +1

TPS time synchronization improving algorithm based on IEEE1588 synchronization mechanism

The invention discloses a TPS time synchronization improving algorithm based on an IEEE1588 synchronization mechanism, and belongs to the technical field of accurate clock synchronization. The TPS time synchronization improving algorithm based the IEEE1588 synchronization mechanism includes following steps: step 1, statistically calculating clock frequency deviation, and completing frequency synchronization; step 2, statistically calculating synchronous time deviation, communication time delay and the minimum number of messages needed for achieving designated accurate time synchronization, and completing initial time synchronization based on symmetry time delay; step 3, completing the accurate time synchronization based on the symmetry time delay by using the minimum message number, building fuzzy control which uses transmission error and transmission error change rate as input in the subsequent process, and performing on-line time deviation and frequency change adjustment. The TPS time synchronization improving algorithm based the IEEE1588 synchronization mechanism is compatible with the IEEE1588 synchronization mechanism well, provides the time synchronization more accurate than time synchronization provided by the IEEE1588 synchronization mechanism, effectively restrains a frequency drift problem and a random fluctuation problem in the time synchronization, can adapt to abrupt change of network topology, and can save a large amount of synchronization message spending in long time running.
Owner:CHONGQING UNIV OF POSTS & TELECOMM

Space vector pulse width modulation method for suppressing common-mode voltage of multiphase motor

A space vector pulse width modulation (SVPWM) method for suppressing a common-mode voltage of a multiphase motor includes the following steps: (1) dividing all basic vectors of the multiphase motor into q types, and selecting therefrom x types having equal common-mode voltage magnitude of which an absolute value is smallest; (2) for each type in the x types of basic vectors, structuring y classes of auxiliary vectors according to an optimization model; (3) synthesizing reference vectors by virtue of the auxiliary vectors to obtain functioning time of basic vectors functioning in each switching period; and (4) obtaining an optimal functioning sequence of the basic vectors functioning in each switching period with fewest switching operations of a converter as a purpose. The present invention may effectively suppress a magnitude and frequency of the common-mode voltage of the multiphase motor without increasing calculation complexity or reducing other performance indexes, has a good harmonic suppression effect on a line voltage and a phase current and high steady state and dynamic performance of a torque and a rotating speed, and can be used for a high-performance multiphase power generation system, a multiphase excitation system and a multiphase driving system.
Owner:WUHAN UNIV
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