67results about How to "Modulation method is simple" patented technology

The invention discloses a transformer-free type low-leakage-current photovoltaic grid-connected inverter circuit with an active clamp and a modulation method thereof. The transformer-free type low-leakage-current photovoltaic grid-connected inverter circuit with the active clamp comprises two filter capacitors Cdc1, Cdc2, eight switch tubes S1, S2, S3, S4, S5, S6, S7, S8 and two filter inductors L1, L2, and is characterized in that an active switch tube is additionally arranged in the circuit so as to form a clamping unit, common-mode voltage in a grid-connected inductance follow current stage is clamped to the midpoint of a bus capacitor by being matched with an appropriate switching sequence, common-mode voltage disturbance of the system is removed, and thus a suspension problem of common-mode voltage of a decoupling inverter in zero level output is solved; and parasitic oscillation of a common-mode circuit is removed at the same time, and a phenomenon of common-mode resonance is suppressed. The photovoltaic grid-connected inverter circuit disclosed by the invention has the advantages of simple circuit structure, high efficiency, simple modulation method and the like. The photovoltaic grid-connected inverter circuit can ensure an inverter not to be affected by a current zero crossing point in unit power factor running, and can avoid current waveform distortion caused by influences of grid power fluctuations or operations at a non unit power factor.

The invention discloses a modulation method and product of a terahertz metamaterial and belongs to the field of metamaterials. The method comprises the steps that firstly, a periodic cylindrical air cavity is formed in a substrate of a PDMS material, then a flexible medium PDMS thin film is arranged above the air cavity, and the metamaterial is arranged on the PDMS thin film; then, outside pressure is added, so that the flexible medium PDMS thin film above the air cavity is protruding or sunken, then geometric parameters of the metamaterial on the PDMS thin film are changed, and finally the response to the incident terahertz wave is modulated. The invention further provides the product which achieves the modulation method. The product comprises a metamaterial structure and a PDMS substrate, the metamaterial structure is arranged on the PDMS substrate, the metamaterial comprises the PDMS thin film and a two-dimension periodic array which is arranged on the PDMS thin film, and the periodic cylindrical air cavity is formed in the PDMS substrate. The modulation method is simple and reliable, is easily controlled, and is relatively high in modulation performance of the linearly polarized beam and the circularly polarized light.

The invention discloses a three-level converter direct-current side neutral-point voltage balance control method based on SVPWM, and belongs to the technical field of electric system power electronics. According to the method, median vectors are eliminated, and small vectors and large vectors are combined to form a reference voltage vector. The method comprises the steps of analyzing the influence of an SVPWM control mechanism and the on-off state on the neutral-point potential, partition judgment is carried out on voltage space vectors, determining the action time of each space vector, and determining the vector sending sequence. By means of the method, change of the on-off state of a power device and loss of a converter are reduced, neither a voltage sharing circuit nor a hardware circuit is needed, and the dynamic balance performance of the direct-current side voltage of the three-level converter is improved. The control method is simple and has great reference value for engineering application.

The invention discloses a two-way wired / wireless hybrid optical access method and system based on homodyne / heterodyne detection. The two-way wired / wireless hybrid optical access method includes the steps of modulating a digital signal base band on an optical carrier through an I / Q modulator in a junction center, transmitting the digital signal base band to a mixed ONU through a downlink transmission link, providing coherent light vibration of homodyne reception and heterodyne reception by using a tunable laser in the mixed ONU, using the vibration source as the optical carriers of uplink wired / wireless data signals, carrying the wired access uplink signals and the wireless access uplink signals through a base band I / Q modulation method and a single side band modulation method respectively, using the laser as the vibration source in the junction center to carry out coherent reception, and finishing the full-duplex transmissions of the wired / wireless access signals between the junction center and the mixed ONU and the photovoltaic conversion of the wired / wireless access signals based on the homodyne / heterodyne detection. The two-way wired / wireless optical access method enables the flexible selection of mixed ONU access methods to be increased and achieves high-rate data transmission, sending and receiving, and the spectrum efficiency is high.

The invention discloses an H bridge cascaded multilevel inverter based on a phase shift space vector modulation method. The H bridge cascaded multilevel inverter comprises an inverter body and a controller. The controller is used for sending a PWM pulse to a power switch in the inverter body. The inverter body comprises 3n H bridge units, and n is a series stage number of H bridges of each phase. In A, B and C phases, each phase has n H bridges in series connection, and the series connection refers to the series connection of output sides of the n H bridges. One end of H bridge AC ends connected in series is connected to an A, B or C end, and the other end is connected an N point. An input side of each H bridge is connected to DC power supply, and the power switch of the H bridge is driven by PWM pulse. The controller forms a PWM signal based on the phase shift space vector modulation method. The inverter is simple to drive and easy to implement.

The invention discloses an RSSR-based LED indoor positioning method and a system thereof. The method comprises the following steps: 1, arranging at least three groups of LED lamps in different positions of an indoor ceiling, wherein every group of the LED lamps emits an optical signal with identification information; 2, using a photoelectric detector to receive the optical signal of every group of the LED lamps, and respectively recording to the received signal intensities of the three groups of the LED lamps; and 3, calculating the position of the photoelectric detector according to the position information of every group of the LED lamps and the received signal intensity information. The system comprises a receiving device and at least three emitting devices. A plurality of LED lamps are adopted to position, the optical signal intensities of the plurality of LED lamps are measured multiple times, and multi-time measurement can reduce the influence of a single measurement deviation and reduce the position estimation error, so the degree of dependence on environment is low, the complexity of the system is low, and the positioning precision and the stability of the positioning system are improved. The method can be widely applied to various LED indoor positioning systems.

The invention discloses a VIENNA rectifier modulation method, a VIENNA rectifier controller and a VIENNA rectifier control system for amending an injected zero-sequence component. The modulation method comprises the steps of amending instant polarity of a reference voltage according to an input current; computing the zero-sequence component of the amended reference voltage; injecting the zero-sequence component and computing a duty ratio corresponding to the reference voltage; and generating a PWM-driven VIENNA rectifier based on double carriers. The method, controller and system provided by the invention are simple, convenient, efficient and prone to be implemented in a numerical manner, so that the VIENNA rectifier has input and output with high quality, and is efficient, stable in operation, and greatly expanded in application occasions of the VIENNA rectifier.

The invention discloses a novel voltage type multi-level inverter. When the number of input power sources is expanded from n to n+1, the number of power switch tubes is increased from 2n+2 to 2n+4, wherein n is an integer not smaller than 1, similarly hereinafter; and when voltage of the input power sources is the same, the number of output levels changes from 2n+1 to 2n+3, namely when one power source is added, two power switch tubes and two levels are added. Compared with an existing classic multi-level inverter, the novel voltage type multi-level inverter enables the used power switch tubes and isolation driving to be less, a clamping diode and a flying capacitor and the like are not required, part of the power switch tubes are be in a low-frequency working state, on-off times is little, and switching loss is reduced. According to the novel voltage type multi-level inverter, one-dimensional space vector modulation is adopted, a modulation method is simple, the computing speed is quick, redundant vectors are reasonably utilized, quality of electric energy output by the inverter is improved, and the novel inverter meets the technical requirements of renewable energy and new energy power generation and is suitable for multi-input power source occasions.

The invention relates to a voltage switching instruction based decoupling-coupling SVM demodulation method of a matrix converter. A bidirectional controllable switch circuit is decomposed to a one-way controllable switch circuit by means of a decoupling-coupling idea, and thus, the matrix converter can be decomposed to a positive group of general voltage type converters and a negative group of general voltage type converters; and with the adoption of a voltage type six-section space vector method, appropriate coupling logic synthesis is performed on the obtained SVM signal and a voltage positive-negative switching instruction signal to obtain flexible and independent control on the bidirectional switch of the matrix converter, thus, a three-phase voltage type non-isolation matrix rectifier achieves functions of AC input and DC output by a simple control logic, and the matrix converter can have functions of positive DC output and negative DC output. The method has the advantages that the control method is simple, the positive DC output voltage polarity and the negative DC output voltage polarity of the matrix rectifier can be achieved, the adaptability to a load is high, the DC voltage utilization rate is improved, the bidirectional flow of switching frequency energy is reduced, and a compact structure and high efficiency are achieved.

The invention discloses a circulating current inhibition method of a parallel operation converter, and aims at solving the problem of high-frequency circulating current, caused by inconsistent modulated carrier waves, of a plurality of converter units. According to the method, grid-connected current of the converter units is detected in real time to obtain variable quantity of the high-frequency circulating current within a half switching period, thereby determining relative positions of the carrier waves of the converter units. The high-frequency circulating current of a parallel system is effectively inhibited by inserting a synchronization period, adjusting a carrier wave frequency and achieving resynchronization of the modulated carrier waves. The method disclosed by the invention has the advantages of being simple and practical, convenient to control, fast in dynamic response and the like.

The invention discloses a power electronic transformer control method based on hybrid pulse width modulation (HPWM). The method includes a CHB input-stage circuit control method and an IBDC output-stage circuit control method. According to the invention, HPWM is applied to cascaded power electronic transformers, and back-stage IBDC is used to control the intermediate DC voltage, an input-stage cascaded H-bridge rectifier only carries out simple power equalization, so as to simplify the control complexity. In order to solve the power equalization problem, the invention provides a switch-mode loop algorithm. With the algorithm, the opportunities of each module to participate in different switch modes are equal in the loop period, and the power is evenly distributed in a certain period of time; with the loop strategy, the HPWM modulation algorithm can be simplified, judging the current direction is not required, and the switch mode of each module can be determined only with the voltage instructions.

The invention discloses an Alpha'-Beta' coordinate-based space vector modulation method of a star-shaped cascaded inverter. The basic vector is greatly increased with increasing of cascaded units according to a space vector modulation algorithm, and the problems of a large amount of redundant switch state vectors, very complicated selection of switch state vectors and calculation of action time and the like exist. On the basis of an Alpha'-Beta' coordinate system, a horizontal coordinate, a vertical coordinate and the sum of the horizontal coordinate and the vertical coordinate of a basic vector of the star-connected cascaded multilevel inverter are respectively corresponding to three linear voltage vectors of a three-phase inverter, and phase voltages of 2n H-bridge cascaded inverters aredirectly controlled by employing linear voltage signals output from n H-bridge cascaded inverters according to a relation between a phase voltage and a linear voltage of the star-connected three-phase inverter. By the method, the switch state signal of each phase corresponding to the basic vector is not needed to be calculated, a large amount of redundant switch state vectors are not needed to becalculated, and the space vector modulation method of the cascaded multilevel inverter is greatly simplified.

The invention discloses a modulation method for spin waves in a self-bias magnetic oscillator waveguide, which is used for modulation a propagation behavior of the spin waves in the waveguide, wherein the propagation behavior comprises the maximum propagation frequency, the cut-off frequency and the propagation path of the spin waves. The modulation method comprises the steps of adjusting the maximum propagation frequency at which the spin waves can be constrained in a middle channel of the waveguide; adjusting the cut-off frequency of the spin waves in channels at two sides of the waveguide; and adjusting the propagation path of the spin waves. According to the invention, modulation can be performed on the propagation behavior of the spin waves on the switched elastic magnetic structure based magnetic oscillator waveguide.

The invention discloses a phase-shift space vector modulation method based on an H-bridge cascaded multi-level inverter. According to the space vector modulation algorithm, as the number of cascaded units increases, the basic vector greatly increases, a large number of redundant switch state vectors exist, selection of the switch state vector and calculation of the action time thereof are extremely complex, and the like. The method realizes the control of the H-bridge cascaded multi-level inverter based on the alpha'-beta 'coordinate system by using the phase-shift space vector modulation strategy, that is, the cascaded multi-level inverter control is achieved by using the two-level space vector modulation method to perform the appropriate phase shift, each H-bridge inverter unit of the cascaded multi-level inverter is divided into a left half-bridge arm and a right half-bridge arm, two-level space vector modulation is utilized to obtain the a half-bridge arm control signal, the signal is subjected to phase shift of 180 DEG as a right half-arm control signal, and the control signal phase difference between the corresponding bridge arms between the lever and the lever is [Pai] / kn. The modulation method is simple, easy to implement, and good in scalability.

The invention discloses an alpine-pastoral-area alfalfa spiral-type hay bundle processing technology in a severe cold pasturing area, which comprises the following steps of: (1) selection of variety; (2) harvesting; (3) forming the spiral type; (4) airing; and (5) storage. The alfalfa spiral-type hay bundle processing technology has the advantages of long pasture storage time, low requirement in water content, simplicity and easiness in operation and completeness in protein reservation.

The invention discloses a space vector modulation method for a delta connection cascaded H-bridge inverter. For the problems of a space vector modulation algorithm that as the number of cascading units increases, the basic vectors are greatly increased, a large number of redundant switch state vectors exist, and the selection of the switch state vectors and the calculation of the action time thereof are extremely complicated, the invention is based on alpha'-beta' coordinates, and uses the abscissa, the ordinate, and the sum of the abscissa and the ordinate of the basic vector of a star connection cascaded multilevel inverter and three line voltage vectors respectively corresponding to a three-phase inverter, and the relationship between the phase voltage of the star connection three-phaseinverter and the line voltage, to synthesize the basic vector of a phase voltage reference vector in a star connection mode as a control signal of the line voltage in a delta connection mode, the method requires neither calculation of the switch state signal of each phase corresponding to the basic vector, nor calculation of a large number of redundant switch state vectors, and the space vector modulation method for the cascaded multilevel inverter is greatly simplified.

The invention provides a speedily searching satellite tuner and a satellite television system, relates to the technical field of satellite television signal receiving devices, and particularly relates to the improvement of a structure of a satellite tuner. The technical problem that the dish antenna is inconveniently installed and adjusted in the traditional manner is solved. The speedily searching satellite tuner comprises a support platform shell, wherein a satellite tuner main body, a signal demodulator circuit and a signal indication device are arranged in the support platform shell. The required cost is low, the stability for installing the traditional dish antenna is high, the special external device is unnecessary, and the operation is simple. A signal of the satellite signal strength is fed back to the signal demodulator circuit by a satellite signal receiver; the signal demodulator circuit sends an indication signal according to the signal of the satellite signal strength, so as to drive the signal indication device; and the signal indication device sends a corresponding antenna status signal for reminding the installation personnel if the dish antenna is at optimum mounting position and angle at real time.

The invention discloses a space vector modulation method-based delta connection cascaded H-bridge inverter. The three phases of the delta connection cascade H-bridge inverter are in delta connection;2n H-bridges are cascaded so as to form each phase of the inverter; each H-bridge includes 4 IGBTs; a space vector modulation method is adopted to control the delta connection cascaded H-bridge inverter; and the space vector modulation method is formed on the basis of a triangular trajectory model. Since the unique space vector modulation method is adopted, the delta connection cascaded H-bridge inverter can operate more stably and is easy to control.

The invention discloses a three-level inverter carrier modulation method under the neutral-point potential deflection condition. The three-level inverter carrier modulation method includes the following steps: (1) collecting the upper capacitor voltage uC1 and the lower capacitor voltage uC2 on the direct current side through a voltage sensor; (2) giving the voltage ud and the voltage uq, converting the two-phase voltage ud and the two-phase voltage uq from a two-phase rotating coordinate system to a three-phase static coordinate system through Park inverse conversion and Clark inverse conversion, and obtaining the three-phase modulation voltage ua, ub and uc (please see the formula in the specification); (3) using the upper capacitor voltage uC1 and the lower capacitor voltage uC2 which are collected through the voltage sensor as peak values of carrier signals in carrier modulation, wherein the uC1 is the height of an upper carrier, and the uC2 is the height of a lower carrier; (4) using ux obtained through coordinate conversion as modulating signals in carrier modulation, wherein x is equal to a, b and c; (5) comparing the upper carrier and the lower carrier with a modulating wave, and outputting a three-phase switch sequence of a three-level inverter. By means of the three-level inverter carrier modulation method, the harmonic content of the voltage output by the inverter can be effectively reduced, and particularly the low-frequency even harmonic content of the voltage output by the inverter is restrained.

The invention discloses a single-phase current-type high-frequency chain matrix power electronic transformer topology and a modulation method thereof. The topology comprises a power network, a front-stage matrix converter, a high-frequency transformer, a post-stage matrix converter, an output filter and a load which are sequentially connected. The high-frequency transformer is used for magnetic coupling and power transferring, and the conversion of an output voltage and a frequency is achieved by the current-type circuit topology. In order that a bidirectional switch of the matrix converter reasonably works, a decoupling modulation strategy of which integral monopole frequency multiplication of the transformer front-stage circuit and the post-stage circuit are discretely combined is proposed; the front stage employs an integral control mode to achieve safety conversion of the matrix converter, and a voltage peak generated by leakage inductance of the transformer is effectively prevented; and the post stage employs a discrete control mode to reduce the switch action frequency, the switch loss of the device is reduced, the system efficiency is improved, and detail mode analysis is performed on a modulation principle and a working condition of a main circuit.

The invention provides a modulation method for improving the current stress of a quasi-Z-source inverter switching device, and the modulation method comprises the steps: subtracting the maximum valueof saddle waves from saddle waves of a conventional voltage space vector modulation SVPWM with the phase difference of 120 degrees to obtain three modulating waves, wherein the maximum value of three-phase saddle waves is a straight line according to the converted waveform, and translating the straight line upwards for M / 2, wherein M is the distance between the maximum value and the minimum valueof the modulated wave after the modulated wave and the triangular carrier wave are subjected to per-unit processing between 0 and 1. According to the modulation method, the gate-level signal generation process is simple, the switching loss is low, no low-frequency alternating-current component exists on the input direct-current side, the current stress of the switching device is greatly reduced, and the service life of the switching device is prolonged.

The invention provides an audio-frequency playback system of a parametric acoustic array, which comprises carrier waves for transferring signals and an ultrasonic transducer array for switching the signals, wherein the ultrasonic transducer array is provided with multiple ultrasonic transducers; the ultrasonic transducers are arranged in multiple groups; each group of ultrasonic transducers are provided with different central frequencies; and the central frequencies are larger than or equal to the frequency of the carrier waves or the central frequencies are less than or equal to the frequency of the carrier waves. The invention also provides a modulating method based on the audio-frequency playback system of a parametric acoustic array provided by the invention. Compared with the correlation art, the audio-frequency playback system of a parametric acoustic array provided by the invention is simple to modulate and implement and can obtain ultrasonic waves with low harmonic distortion.

The present invention discloses a non-isolated type three-phase three-level photovoltaic inverter modulation method. The modulation method can effectively inhibit leakage currents of two types of NPIC inverters provided by the present invention. The technical scheme adopted by the modulation method has the key points of: firstly, performing subtraction on any two of modulation signals (reference to the specification) of the NPIC inverters to obtain modulation signals (reference to the specification); then respectively multiplying the modulation signals by a coefficient K to obtain modulation signals (reference to the specification); performing zero-sequence component calculation by (reference to the specification) to obtain zero-sequence signals v0; respectively adding (reference to the specification) and the zero-sequence signals v0 to obtain modulation signals (reference to the specification); and comparing modulation signals (reference to the specification) with a triangular carrier wave VC by means of a comparator to obtain logical signals X,Y,Z; and performing a logical operation provided by the present invention on the X,Y,Z to obtain a logical expression of a switching signal. The modulation method provided by the present invention has the beneficial effects that the switching signal is generated by means of the logical operation, and the implementation manner is simple. The method solves the problem of excessive complexity for implementation of conventional multi-carrier wave modulation and spatial vector modulation, also ensures a constant common-mode voltage of a system, and effectively suppress the leakage currents.

The invention discloses a circulating current inhibition method of a parallel operation converter, and aims at solving the problem of high-frequency circulating current, caused by inconsistent modulated carrier waves, of a plurality of converter units. According to the method, grid-connected current of the converter units is detected in real time to obtain variable quantity of the high-frequency circulating current within a half switching period, thereby determining relative positions of the carrier waves of the converter units. The high-frequency circulating current of a parallel system is effectively inhibited by inserting a synchronization period, adjusting a carrier wave frequency and achieving resynchronization of the modulated carrier waves. The method disclosed by the invention has the advantages of being simple and practical, convenient to control, fast in dynamic response and the like.

The invention discloses three-phase single-phase high-frequency link matrix PET topology and modulation, which belong to the technical field of power electronic power converter topology and modulation. The topology is formed by connecting a three-phase alternating current power supply, an input L filter, a pre-stage matrix converter, a high-frequency transformer, a backward-stage matrix converter,an output LfCf filter and a load. Magnetic coupling and power transmission are performed by adopting a high-frequency transformer, conversion of output voltage and frequency is realized by using a voltage type circuit topology, and a decoupling modulation strategy of combining discrete SVPWM of a pre-stage circuit and discrete SPWM of a post-stage circuit of the transformer in a double-frequencyphase locking mode is adopted, so that a bidirectional switch of the matrix converter reasonably works. Safe current conversion of the matrix converter is realized by adopting a discrete control modeas a whole, and voltage spikes generated by existence of leakage inductance of the transformer are effectively suppressed.

The invention relates to a synchronization active type islanding detection system and a method based on M sequence modulation and variance estimation. The detection system comprises a synchronizationinverter, a synchronization switch, a voltage Hall sensor arranged on a synchronization communal join point, a digital signal processor connected with the synchronization inverter, the synchronizationswitch and the voltage Hall sensor. The detection method is to utilize the pseudo-random signal M sequence of the communication technique, modulate the modulation wave of the inverter according to the distribution law of the M sequence, so as to make the output have the characteristics of the M sequence, and thus the output signals also have the characteristics of random signals. During synchronizing, the voltage of the synchronization communal join point is controlled by a power network and the randomness is small; therefore the obtained variance value of the random sequence is very small; when islanding, the voltage of the synchronization communal join point is determined by the output of the inverter, the output of the inverter is modulated through the digital signal processor and havethe characteristics of the random signals, so the variance value is significantly increased. During detecting, a variance threshold value is set, and islanding can be determined when the detected variance is more than the threshold value. The synchronization active type islanding detection system and the method has the advantages of simple arithmetic, low cost, small effects to harmonic waves ofthe output power and small islanding detection blind zone.

The invention belongs to the technical field of absolute distance measurement, and relates to a virtual synthetic wavelength chain absolute distance interferometric method and a realization device. Two double-beam interferometers used in a straight line are modulated by piezoelectric ceramics and tunable lasers are used to measure the wavelength value and the phase of the single-wavelength interference signal while the wavelength is tuned, and calculate the virtual synthetic wave interference fringes. decimal order. A series of virtual synthetic wavelength chains from large to small are obtained by tuning the laser, and the rough and fine measurement of the absolute distance is completed. The invention has the characteristics of high measurement accuracy of fractional fringes and can complete the process from rough measurement to precise measurement at one time, is suitable for internal and external dimension measurement, and can be used for making micro-sized measuring heads.

The invention discloses an inverter topology circuit for suppressing leakage current in a photovoltaic grid-connected system and a control method thereof. The inverter topology circuit comprises a first controlled switch tube S1, a second controlled switch tube S2, a third controlled switch tube S3, a fourth controlled switch tube S4, a fifth controlled switch tube S5, a sixth controlled switch tube S6, a diode D, a power supply U, a capacitor C, a first inductor L1 and a second inductor L2. The inverter topology according to the invention can be seen as a combination of H5 topology and HERIC topology. The topology circuit has advantages of simple structure, high operation efficiency, high reliability and simple utilized modulating method. The inverter topology circuit has advantages of ensuring no influence by current zero-crossing distortion when an inverter operates in a unit power factor, preventing current waveform distortion caused by power grid power fluctuation or operation in a non-unit power factor, improving inverter safety factor and realizing output electric energy quality improvement.