64results about How to "Reduce harmonic effects" patented technology

The invention provides a modularized H-bridge cascade multilevel mutual-balance power electronic transformer. Power electronic devices are formed on the basis of IGBTs, the power electronic transformer can achieve four-quadrant controlled operation through an effective control strategy, two-way power flow control can be performed, a H-bridge cascade multilevel modularized structure is adopted for a main circuit, large-scale modularized production is facilitated, actual high-voltage class application can be performed, the harmonic content of output voltage is lower, the switching frequency of the power electronic devices is low, loss is lower, and the voltage-sharing problem is avoided. The system structure of the modularized H-bridge cascade multilevel mutual-balance power electronic transformer is in an AC/DC/AC mode, the high-voltage stage, the isolation stage and the low-voltage stage are achieved, and while the voltage transformation function, the isolation function, the energy transmission function and the like of a conventional transformer are completed, the power flow control and the function of control over the quality of electric energy can be completed.

The invention discloses an island detection method of a photovoltaic grid connected system in the field of application of a photovoltaic grid connected system control technology. The island detection method is characterized in that a frequency deviation positive feedback coefficient k is self-adaptively regulated by sections through detecting a change time n of a voltage frequency fu at a point of common coupling (PCC) towards a certain direction, thus frequency deviation is accelerated; and if the absolute value of the change time n exceeds 12, the voltage frequency fu at the PCC does not exceed the limit, two continuous working frequency periods of negative pulse current amplitude interference are applied and low-voltage protection is triggered, thus an island is detected. The method has the advantages of little influence on power grid harmonic waves and active output of the photovoltaic grid connected system and high detection speed.

The invention discloses a SVPWM (Space Vector Pulse Width Modulation) method which comprises the following steps of: confirming an angle theta 0 corresponding to each PWM (Pulse Width Modulation) period within a single period of a fundamental wave according to a carrier-to-noise ratio; calculating a present angle theta n according to the theta 0; obtaining an amplitude value of a three-phase output at the present by a quantified SPWM (Sinusoidal Pulse Width Modulation) wave; injecting a higher harmonic on the basis of the quantified SPWM wave to enable the shape of the outputted SVPWM waveforms with different frequencies to be consistent with the shape of the waveform obtained according to a traditional SVPWM method and realize an over-modulation function; and meanwhile, setting the frequency, thereby enabling the flux linkage rotation of the space vector to be more approximate to a circular magnetic field. According to the SVPWM method provided by the invention, the dependence on mechanical parameters of system is weakened, the operation volume is reduced, the harmonic influence is reduced, the robustness of the system is enhanced, and the generality and timeliness are higher.

The invention discloses one triangle function limit micro variable flow method, which comprises the following steps: setting displacement transducer connection set to get needed basic voltage; using each base frequency and frequency function or different function to form triangle function limit micro variable equation with two sides as input and output signals; setting sine function transducer, power electron switch and outside circuit to get the analysis variable equation topological circuit and integrating the angle frequency and difference to form integral logic control.

The invention provides a specific harmonic wave eliminating system comprising a PWM (Pulse Width Modulation) inverter and a main control unit which controls the PWM inverter to convert direct current into alternating current and supply power to an alternating load; the main control unit comprises a obtaining sub-unit, an establishing sub-unit, a computing sub-unit and a control sub-unit; the obtaining sub-unit is used for obtaining a voltage output waveform of the PWM inverter; the establishing sub-unit is used for establishing a bipolar specific harmonic elimination mathematical model according to the voltage output waveform of the obtaining sub-unit; the computing sub-unit is used for computing out an exact solution of a switching angle by using a homotopy differential method and a Newton iteration method according to the bipolar specific harmonic elimination mathematical model in the establishing sub-unit; and the control sub-unit is used for controlling the on-off time of a switching tube in the PWM inverter according to the exact solution of the switching angle in the computing sub-unit. The system can effectively eliminate the influence of a harmonic wave.

The invention provides a method for separating positive and negative sequence components on basis of OVPR under a non-ideal micro-grid condition. The method comprises the following steps of: transforming micro-grid voltage from a three-phase a/b/c coordinate system to a two-phase static <alpha>/<beta> coordinate system through Clark transform; and obtaining a positive sequence component and a negative sequence component of the voltage through a signal separation subsystem: carrying out subtraction on the micro-grid voltage transformed to the two-phase static <alpha>/<beta> coordinate system and sum of components obtained through separation, forming negative feedback through a fundamental wave positive sequence detection unit and a negative sequence detection uniform formed by a first-order vector resonant controller, and taking output of each unit as the positive sequence component and negative sequence component of the voltage. The method has the characteristics of being relatively rapid in response, free of instant symmetric component separation and simple to realize, and is capable of rapidly, correctly and directly realizing positive sequence, negative sequence and harmonic wave separation. Simulation results and analysis prove the correctness and effectiveness of the method.

An autotuning method using an integral of a relay feedback response is disclosed, which obtains an ultimate data and frequency model of a process with greatly removing effects of harmonics by using integral of a relay feedback signal. The autotuning method using an integral of a relay feedback response comprises the first step for integrating a process data; and the second step for removing effects of harmonics after the first step and computing an ultimate gain, a frequency model and a parametric process model.

The invention discloses a railway traffic locomotive braking energy recovery device and method. The braking energy recovery device comprises a monitoring device, a battery management system (BMS) device, a storage battery pack and a DC chopper. The BMS device is connected with the storage battery pack and the monitoring device. The storage battery pack and the monitoring device are connected with the DC chopper. The monitoring device and the DC chopper are connected with an overhead line system. According to the railway traffic locomotive braking energy recovery device and method, the structural design is novel, and the advantages of fast, efficient and large-capacity electric energy storage and absorption and high antijamming capability are achieved; on the one hand, braking of a locomotive does not cause excessive voltage boosting of a power grid; and on the other hand, electric energy can be provided for an outbound locomotive, and discharging of energy storage batteries can keep the voltage balance of the overhead line system especially when the number of trains is increased in morning and evening rush hours.

The invention discloses a method for implementing a ship-navigation radar transmitting and receiving system. The method includes a transmitting aspect and a receiving aspect. An FPGA (field programmable gate array)-based process for controlling a ship-navigation radar transmitter is provided in the transmitting aspect, trigger pulses are generated via an FPGA, are transmitted through a buffer-stage circuit and a driving circuit and then are boosted to obtain pulsed high voltages by a pulse transformer, the pulsed high voltages are supplied for a magnetron, and radar electromagnetic waves are transmitted by the magnetron at corresponding frequencies. A ship-navigation radar intermediate-frequency digital module which can be directly connected with the FPGA is implemented in the receiving aspect, circuits of a logarithm amplifier, the buffer-stage circuit, an analog-to-digital conversion circuit and the like are integrated via reasonable circuit layout and shielding structures to obtain the module, analog intermediate-frequency signals of a radar radiofrequency receiver can be converted into digital signals by the module, and the digital signals can be outputted to the FPGA by the module. The method has the advantages of large dynamic range, high sensitivity, compact circuits, simplicity in debugging and the like. Besides, owing to the method for implementing the transmitting and receiving system, the ship-navigation radar transmitting and receiving system is compact in design and easy to implement, and the radar cost performance can be improved.

The principles described herein provide an electrical power supply system having circuitry that reduces the noise and interference of harmonic signals introduced by non-linear loads. In particular, one or more embodiments can include a power correction system that includes transformers and capacitors having parameters and configured to redirect harmonic energy in a power signal to deliver clean power to loads in a system. Additionally, the power correction system can mitigate negative effect of in-rush current passing through the electrical power supply system resulting in more efficient energy usage and reducing power failure of loads in the system. Moreover, the power correction system can include various additional features that facilitate convenient connection and/or disconnection of the power control system without disrupting the delivery of electrical power to loads in the system.

The invention discloses a three-phase load balancing control system for a low-voltage power distribution network. The power load of a user side is divided into a low-power load part directly connected into the power distribution network and a high-power load part connected into the power distribution network through a phase commutation device. The total power load of each user side and a multi-preset-cycle power average value of a to-be-connected phase commutation device are acquired, the phase with the low total phase power load of the low-voltage power distribution network or the phase commutation device needing trial phase switching on the phase with the low total phase power load is determined through calculation, the phase of the phase commutation device tries to be switched, the to-be-connected phase commutation device tries to be connected into the phase with the low total phase power load, if the loads of the three phases meet the balance requirement, the phase of the phase commutation device is switched to a target phase, and the to-be-connected phase commutation device is connected into the phase with the low total phase power load. The condition that the loads of the three phases are unbalanced is not likely to be caused by connection of the phase commutation devices, a little number of phase commutation devices need phase switching, harmonic interference on the power distribution network by phase switching can be reduced, and the load devices of the user sides can keep operating stably.

The invention discloses an industrial energy-saving high-frequency impulse electrolytic manganese device which comprises one or more phase-shifting transformers, one or more three-phase rectifier bridge assemblies, one or more power assemblies and a power master control unit, wherein the primary sides of the phase-shifting transformers are connected with the output end of a three-phase alternating-current supply and the secondary sides of the phase-shifting transformers are in one-to-one corresponding connection with the inputs of the three-phase rectifier bridge assemblies, respectively; the output ends of the three-phase rectifier bridge assemblies are correspondingly connected with the input ends of the power assemblies, and the output ends of the power units output high frequency impulse signals to electrolytic baths; the voltages output by the secondary sides of phase-shifting transforming units are determined according to the quantity of the electrolytic baths connected in series; when a plurality of the phase-shifting transformers are adopted, the phase-shifting transforming units are the phase-shifting transformers in multiple forms for reducing harmonic waves of an alternating current input current and harmonic amplitudes and current impulses of a direct current output voltage; the power master control unit is respectively connected with one or more power assemblies for current-sharing control of the power assemblies.

The invention belongs to the technical field of communication, and particularly relates to a broadband band-pass filter system and method, and the system comprises: a sampling unit which is used for collecting an original signal; ta band-pass filtering unit which is used for extracting fundamental wave signals of the signals; a zero-phase filtering unit which is used for receiving the output signal of the first band-pass filtering unit and carrying out secondary filtering on the output signal; and a first control unit which is used for fitting the amplitude-frequency characteristic curve of the fundamental wave filtering unit to obtain the relationship between the amplitude gain and the frequency, and carrying out amplitude compensation. After an original signal is collected, the originalsignal is preprocessed, when band-pass filtering is carried out on the preprocessed signal, a fundamental wave signal of the preprocessed signal is more easily extracted, and then signal amplitude compensation is carried out on the extracted fundamental wave signal, so that the accuracy of the finally band-pass signal is higher, and meanwhile, the band-pass filtering efficiency is higher.

The invention discloses a method for connecting a power load to a distribution network and a load balancing method. For the access method, before a power load of a user is connected to a distributionnetwork by a commutation device, calculation is carried out based on a commutation device trial access power estimation value and total power loads of all user terminals to determine the to-be-connected target phase, so that the three-phase loads of the distribution network are kept to be balanced. Therefore, the number of the commutation device of phase switching as well as the harmonic interference to the distribution network is reduced. In addition, according to the balancing method, the three-phase loads of the distribution network become unbalanced and a phase switching pair and an adjusting amount value are determined; commutation devices, not providing power for a built-in magnetic moving part load unit, of the source phase are marked; in terms of the source phase, the marked commutation device needing phase switching is selected; if the marked commutation devices are not enough, un-marked commutation devices are selected; and the phases of the selected commutation device are switched to the target phases, so that three-phase load balancing is realized. No commutation vibration is caused by the load device of the user terminal and thus the load device works stably.

The invention discloses a multi-segment linear LED drive circuit, device and method. The multi-segment linear LED drive circuit comprises a reference voltage input module, a current source module, a voltage control module, a current adjusting module, at least two LED lamp strings connected in series and at least two drive modules corresponding to the LED lamp strings. The reference voltage input module is used for providing reference voltage for each path of drive module; the current source module provides direct current for the voltage control module; the voltage control module controls the input voltage of the drive module according to the direct current; the drive module drives the corresponding LED lamp string to be turned on or turned off according to the reference voltage, the inputvoltage and the line voltage constant current; the current adjusting module adjusts the constant current; the constant current of the rear drive module is greater than the constant current of the front drive module, and when the current passes through the rear drive module, the front drive module stops driving, so that the harmonic influence is reduced, and meanwhile, the circuit implementation cost is reduced.

The invention provides an inverter topology decoupling method and an inverter topology decoupling device. The method comprises the following steps: making inverter topology decoupling equivalent to a parallel equivalent circuit of a first circuit, a second circuit, a third circuit and a fourth circuit; determining a coefficient relation according to a loop voltage equation of the parallel equivalent circuit; and making inverter topology decoupling equivalent to a parallel circuit of independent fifth, sixth and seventh circuits according to the coefficient relation. Thus, the output symmetry of three-phase output voltage is kept under three-phase imbalance or nonlinear load, balanced load operation is facilitated, and the harmonic effect of power equipment on the power system is reduced.