65results about How to "Reduce harmonic effects" patented technology

The invention discloses an optical fiber digitized remote phase-checking system and a phase-checking method thereof. A digital phase meter is respectively connected with two analog-to-digital conversion modules or two intelligent substation merging units through optical fibers. Checked voltage and reference voltage are respectively inputted into the two analog-to-digital conversion modules, and voltage analog quantities are converted into digital sampling values, which are transmitted to the digital phase meter via the optical fibers; the digital phase meter receives and filters the digital sampling values, calculates the fundamental wave quantities of the sampling values, and compares the amplitudes and phases of the two voltages in order to determine the amplitude and phase relation between the two voltages, and thereby the phase, phase sequence and polarity of the checked voltage are checked. Since the invention utilizes the analog-to-digital conversion modules to convert the voltage analog quantities into the form of digital quantities before transmission and the digital phase meter to synchronize, filter, calculate and process the voltage digital quantities in other ways, the phases of the voltages are checked, the potential safety hazards of conventional phase checking are eliminated, the accuracy and efficiency of phase checking are increased, and the invention is compatible with intelligent substation phase-checking tests.

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 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 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.

Invention is related to a method for controlling an alternating current electric machine with a frequency converter including a controllable machine bridge and a controllable line bridge, and a corresponding frequency converter. The method comprises calculating a line bridge control signal, controlling line current through the line bridge using the line bridge control signal, measuring or estimating rotor pole position of the electric machine, calculating a machine bridge control signal as a function of the rotor pole position, updating the machine bridge control signal when the rotor pole position changes, and controlling current of the electric machine through the machine bridge using the machine bridge control signal.