3646 results about "Harmonics" patented technology

A method for reducing the harmonics contents of an input current drawn from a power line into an electrical system without sensing an input voltage, the method comprising providing an active power factor correction controller with a switch module having a main switch and a timing device, wherein the main switch has an on-time correlated with an on-duty cycle duration, and an off-time correlated with an off-duty cycle duration, and maintaining a linear relationship between the off-duty cycle duration and the input current by using the timing device; and an apparatus for active power factor correction with minimum input current distortion, comprising an active power factor correction assembly that includes a main switch and a timing device, wherein the main switch has associated therewith an on-time correlated with an on-duty cycle duration, and an off-time correlated with an off-duty cycle duration, and wherein the timing device generates the mentioned on-time and off-time, and linearization means for maintaining a linear relation between the off-duty cycle duration and the input current.

The invention discloses a fundamental voltage synchronous signal detection method during harmonic distortion and unbalance of network voltage. A novel resonant phase locked loop (PLL) can quickly compensate phase tracking errors caused by various network faults, effectively inhibit frequency fluctuation and phase jitter caused by a negative sequence and a harmonic component in the network voltage, and realize accurate detection of fundamental voltage synchronous signals in a distorted network. The method can meet the detection requirements on voltage frequency, amplitude and phase under the ideal network conditions, is particularly suitable for capturing the fundamental voltage synchronous signals under severe transient state and stable state network faults such as network voltage drop, unbalance, harmonic pollution and the like, and can realize quick extraction of the positive and negative sequences and the harmonic component in the voltage. The method has the characteristics of highdetection accuracy and good real-time property, can provide an accurate control basis for operating control of grid-connected power equipment such as various wind generating sets, solar photovoltaic grid-connected devices, reversible speed control transmission systems, dynamic reactive compensators and the like.

A low-voltage arc fault detection method comprises collecting current signals in a loop through a current sensor, obtaining fundamental frequency analog signals and high frequency analog signals, achieving accumulating calculation of the fundamental frequency analog signals and high frequency analog signals of power frequency cycle through an integrating circuit, an interrupt trigger and a timer, and further obtaining higher harmonic occupancy. According to the method, whether arc faults occur is judged by real-time monitoring of change characteristics of the line current higher harmonic occupancy and calculation of over-limit times of the higher harmonic occupancy, normal arc and fault arc which are generated by some special electric appliance loads and normal on-off action are distinguished by judging whether higher harmonic occupancy changes caused by the arc faults are periodic and judging occurring frequency, occurrence of the arc faults can be detected in real time, the method is not limited by an installing position, malfunction caused by disturbance of operating arc generated by normal circuit opening and closing and loads such as a switch power and a dust collector can be avoided well, and the reliability is high.

The invention relates to an active damping method of an LCL grid-connected inverter system. The active damping method is realized through the following steps of: setting conjugated zero points or independent zero points to set off conjugated resonance limit points generated by an LCL filter in the grid-connected inverter system or to draw the conjugated resonance limit points to a stable area, and adopting grid-side inductive current to feed back and introduce a state variable in the LCL filter to conduct feedback compensation. By conducting feedback compensation on grid-side inductive voltage, the resonance damping of the LCL filter is controlled, the waveform and the amplitude of grid current of the grid-connected inverter system are controlled and the influence of grid voltage harmonic wave on the grid current can be effectively suppressed. The active damping method is a simple and effective realization method. A realization circuit comprises parallel and series active damping circuits.

A motor control apparatus comprises a fundamental wave current control system that controls a fundamental wave component of a motor current in an orthogonal coordinate system which rotates in synchronization with a rotation of a 3-phase AC motor, a higher harmonic current control system that controls a higher harmonic component contained in the motor current in an orthogonal coordinate system rotating with a frequency which is an integral multiple of the frequency of the fundamental wave component of the motor current, a voltage command value generating device that generates 3-phase AC voltage command values by adding an output from the fundamental wave current control system and an output from the higher harmonic current control system, a power conversion device that converts a DC source voltage to a 3-phase AC voltage corresponding to the 3-phase AC voltage command values and outputs the 3-phase AC voltage to the 3-phase AC motor, a voltage saturation detection device which detects that an output voltage from the power conversion device is in a saturated state and a gain adjustment device that reduces a current control gain for the higher harmonic current control system if the voltage saturation detection device detects that an output voltage is in a saturated state.

The invention discloses a method for measuring electric energy of impact load, including the following five aspects: (1) electrical power system produces harmonic and flicker induced by the impact load, electric energy metering of the impact load relates to fundamental wave metering, harmonic electric energy metering and flicker electric energy metering; (2) voltage, current signal of the electrical power system pass through high-pass filter, and perform multi-channel synchronous frequency-change sample by a high-speed ADC(analog/digital converter), realizing harmonic electric energy metering by FFT or wavelet transform, determining harmonic source direction according to positive negative signs of harmonic active power; (3) voltage, current signal of the electrical power system which passing through low-pass filter are performed multi-channel synchronous frequency-change sample by a high-speed ADC, realizing flicker electric energy metering by FFT or wavelet transform, determining flicker source direction according to positive negative signs of harmonic active power; (4) voltage, current signal of the electrical power system which passing through low-pass filter are performed multi-channel synchronous frequency-change sample by a high-speed ADC, abstracting fundamental wave signal by FFT or wavelet transform, realizing fundamental wave electric energy metering; (5) the sampling of high-speed ADC is frequency-change sampling with sampling frequency determined by the fundamental wave frequency.

The present invention relates to the technical field of electrical engineering and discloses a PRBS disturbance injection-based power grid impedance online identification device. The device is mainly composed of a grid-connected inverter, a current loop controller, a sampling device and an impedance identification unit. The device is characterized in that the grid-connected inverter is connected with the current loop controller. When the grid-connected state is stable, the grid-connected inverter injects the PRBS disturbance into the power grid. During the injection process of a PRBS signal, a built-in output voltage THD is fed back to the controller, so that the THD value of the output voltage of the inverter is ensured to be smaller than 5%. The sampling device is connected with the PCC part of the power grid and is used for sampling and recording the voltage and the current at the PCC part of the power grid. The impedance identification unit is used for subjecting the sampled data of the sampling device to DFT analysis, and taking the average value of the amplitude and the average value of the phase of each harmonic component of the voltage and the current during the current sampling period. The method of the invention is high in precision, high in speed, strong in real-time property, wide in frequency range, lower in measuring cost and difficulty, and better in stability.

The invention discloses a polyphase permanent magnet synchronous motor current waveform optimal control method, comprising the following steps of A, current reference value coordinate transformation; B, current multiple proportion resonance regulation; and C, coupling compensation. In the control method, based on polyphase permanent magnet synchronous motor vector control, a polyphase synchronous rotating coordinate system current reference value is transformed to a current reference value of each phase in a polyphase static coordinate system through polyphase coordinate transformation, the current reference value of each phase and a current feedback value of each phase of a motor are respectively subjected to improved multiple superposition proportion resonance regulation, and a resonance separation method is introduced, decoupling is realized by feed-forward compensation, and floating tracking and harmful subharmonic restraining for highly dynamic property fundamental waves and usable subharmonic are realized. The method can restrain the adverse impacts, such as motor loss, torque ripple and vibration noise, caused by a harmful harmonic current of the polyphase motor, can explore the positive effects of the usable harmonic current, gives full play to the advantages of the polyphase motor and improves the system performance.

The invention relates to an in-slot self-cooling high-speed permanent magnetic motor system for a compressor and belongs to the technical field of motors. The megawatt high-speed variable-frequency motor comprises a cooling water jacket, a stator core, a stator winding, a stator radial air channel, an inner stator air channel, a permanent magnet rotor, two sliding bearings and two compressor impellers. The system has the advantages that the problems of severe heat and uneven temperatures of a high-speed motor rotor can be solved effectively; the problems of the over-temperature and overlarge axial temperature gradient of the stator core are solved; and not only the strength problem of a permanent magnet under a condition of high-speed rotation of the rotor can be solved mechanically, but also higher harmonics can be effectively prevented from entering the permanent magnet and generating added losses electromagnetically.

The invention relates to a power quality comprehensive control method and a power quality comprehensive control device for an electric railway traction power supply system, which belong to the field of electric railway power supply. The power quality comprehensive control device comprises a passive filter consisting of a trinary filter and a second-order high-pass filter and a set of voltage source converter with an energy-storage battery, wherein the voltage source converter with energy storage is connected with a 10kV bus in parallel through a phase reactor and the passive filter and then connected with a 110kV power network through a power transformer. The method and the device can compensate for power factors of the electric railway power supply system and solve the power quality problems of three-phase imbalance, harmonic wave, voltage fluctuation, flickering and the like at the same time. Moreover, the method and the device give full play to the advantages of simple configuration and low cost of the passive filter and the advantages of small occupied area and low loss of the voltage source converter, so that the whole device has the optimal technology index and economic performance.

The invention discloses a voltage source type direct-current deicing and static synchronous compensation device and a control method thereof. The voltage source type direct-current deicing and static synchronous compensation device comprises at least one basic current convertor unit. The basic current convertor unit comprises a connection electric reactor Ls, a modular multi-level current convertor MMC adopting a full-bridge sub-module, disconnecting links (K1, K2, K3 and K4), and smoothing electric reactors (Ld1 and Ld2). The voltage source type direct-current deicing and static reactive generation device can meet the requirements for deicing of power transmission lines of various voltage classes. The method for switching the voltage source type direct-current deicing and static synchronous compensation device among different function modes and the control method of the voltage source type direct-current deicing device can meet the requirement for safe and rapid deicing of the lines, no harmonic pollution at an access point is caused, and dynamic reactive power compensation can be provided for the access point. The voltage source type direct-current deicing and static synchronous compensation device can be used for a newly-constructed direct-current deicing project, can also be used for upgrading and reconstruction of the direct-current deicing device in the constructed direct-current deicing project, and has the wide application prospect.

Vibrations at harmonic frequencies are reduced by injecting harmonic balancing signals into the armature of a linear motor/alternator coupled to a Stirling machine. The vibrations are sensed to provide a signal representing the mechanical vibrations. A harmonic balancing signal is generated for selected harmonics of the operating frequency by processing the sensed vibration signal with adaptive filter algorithms of adaptive filters for each harmonic. Reference inputs for each harmonic are applied to the adaptive filter algorithms at the frequency of the selected harmonic. The harmonic balancing signals for all of the harmonics are summed with a principal control signal. The harmonic balancing signals modify the principal electrical drive voltage and drive the motor/alternator with a drive voltage component in opposition to the vibration at each harmonic.

The invention relates to a broadband multifrequency electric capacity unified measurement analysis system and implementation method. The system includes at least one electric capacity measuring device and a data storage and analysis host, the electric capacity measuring device acquires the power grid data at high frequency, and the data storage and analysis host receives the power grid data transmitted by the electric capacity measuring device for storage and meanwhile analyses, displays and forwards the received power grid data and transmits the data analysis result; the data storage and analysis host includes a network module for data storage and information exchange of multiple electric capacity measuring devices in the substation; and the electric capacity measuring device is arranged in the substation spacing layer, and the data storage and analysis host is arranged in the substation control layer. The system solves the problem that the measurement technology in the prior art cannot carry out the comprehensive and accurate measurement for the new characteristics of increasingly frequent harmonic interference and subsynchronous oscillation of a conventional power grid due to high-voltage DC power transmission technology, FACTS technology, and new energy large-scale access.

This invention provides a power supply device capable of widening a conduction period of an input current by a simple control to improve a power factor, and reducing a harmonic distortion of the input current The power supply device comprises a rectifier circuit, a reactor, a power factor correction circuit having switching elements, capacitors and a reverse-current blocking rectifier elements, a smoothing capacitor for smoothing an output voltage of the power factor correction circuit to obtain a DC voltage, a pulse signal controller generating and outputting a pulse signal for turning on and off the switching elements, and a driver for receiving the pulse signal to drive a switching elements of the power factor correction circuit.

The invention provides a model prediction three-level direct torque control method based on state trajectory extrapolation. According to the method, a traditional hysteresis controller with direct torque control is replaced by a model prediction controller. The method includes the following steps: aiming at allowable switching vectors, determining a step-length prediction range for output trajectory extrapolation by using an internal state prediction model, and with average switching frequency of an inverter as a value function, solving an optimal switching vector in real time to act on the inverter directly according to limited time zone rolling optimization strategies of model prediction control. According to the model prediction three-level direct torque control method based on the state trajectory extrapolation, the switching frequency of an NPC three-level inverter can be reduced to about 300Hz, quick dynamic response capability and ideal current harmonic distortion characteristics can be obtained, and the method has broad application prospects in middle-high voltage and high power fields.

The invention relates to a capacitor voltage transformer suitable for high-voltage harmonic measurement and a measurement method. The capacitor voltage transformer is characterized in that a current transformer is respectively connected into a low-voltage capacitance branch and an intermediate transformer branch of a capacitive voltage divider of the capacitor voltage transformer in series, two conventional current transformers are additionally arranged in a conventional capacitor voltage transformer, and the size and the phase position of harmonic voltage of a high-voltage system can be worked out by using electric currents measured by the two current transformers. Therefore, the capacitor voltage transformer has the advantages of being simple in structure and convenient to realize, having high measurement accuracy of voltage harmonics, being free of influence of the size of a load of the capacitor voltage transformer and having very high application value and market promotion prospect in occasions where high-voltage harmonics are measured.

A harmonic gear drive includes a flexspline and a rigid spline which are meshed with each other, and a wave generator which deforms the flexspline to displace meshing points between the flexspline and the rigid spline. The length of each contact part between the flexspline and the wave generator always becomes shorter as viewed in a sectional plane containing a rotation axis of the wave generator than the width of the wave generator.

The invention comprises a high frequency inductor filter apparatus coupled with an inverter yielding high frequency harmonics and/or non-sixty Hertz output. For example, an inductor/converter apparatus is provided that uses a silicon carbide transistor to output power having a carrier frequency, modulated by a fundamental frequency, and a set of harmonic frequencies. A filter, comprising an inductor having a distributed gap core material and optional magnet wires, receives power output from the inverter/converter and processes the power by passing the fundamental frequency while reducing amplitude of the harmonic frequencies.