2420 results about "Utility frequency" patented technology

There is provided an inductive power line data coupler. The coupler includes (a) a magnetic core having a high magnetic permeability at a data communication frequency and being configured to allow a power line of a power distribution system to be routed through the magnetic core to serve as a primary winding, (b) a data signaling circuit that provides a secondary winding through the magnetic core for coupling a data signal between the power line and a communication device, and (c) a choke coil coupled to the data signaling circuit for creating a flux-canceling power frequency current opposite in direction and comparable in magnitude to a power frequency current. The coupler may also include a circuit for sensing a level of current in the power line.

The invention discloses a control circuit for a voltage dropping type power factor corrector, which is used for controlling a voltage dropping converter to realize the power factor correction function. Inductance current critical intermittent control of changed on-time is performed on a Buck circuit through the control circuit to ensure that the on-time of a switching tube rises in the power frequency period along with increase of input voltage; and the critical intermittent working mode of inductance current in the Buck circuit is controlled, and when the inductance current is greater than zero, the junction capacitance of the switching tube and inductance are resonated, and the switching tube is connected when the voltage resonance of the junction capacitance reaches the volley bottom. The control circuit for the voltage dropping type power factor corrector has the characteristics of ensuring high power factors in the whole input voltage range, and meeting the harmonic requirements of IEC 61000-3-2 Class C, Class D, along with high efficiency.

The invention relates to a distributed single-phase earth fault ranging system that is used for realizing ranging of a fault on a high tension transmission line between two transformer substations. The system comprises: at least two sets of fault current detection device sets, which are installed at preset test points of a high tension transmission line; a remote wireless communication module; and a remote monitoring master station. The remote monitoring master station is respectively connected with the fault current detection device sets by the remote wireless communication module as well as receives fault currents collected by the fault current detection device sets by the remote wireless communication module; and the remote monitoring master station carries out comparison and an analysis according to positional data of the preset test points and length data of the high tension transmission line, so that a final fault position is obtained. In addition, a ranging method of the distributed single-phase earth fault ranging system is also provided. Power frequency fault current information and fault current travelling wave energy information are utilized to determine fault intervals; and different positioning equations are selected according to different fault intervals as well as fault point positions are determined; therefore, a dead zone problem can be solved, wherein the problem occurs when there are faults at a head and an end of a line, that is, when a fault point approaches a bus.

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 discloses a control method of an alternating voltage sensorless high voltage direct current transmission converter, belonging to the technical field of electrical equipment and comprising the following steps: establishing a stator resistor and an inductor for a virtual motor; building relative position relationships among a current vector, a voltage vector and a flux linkage vector, and analyzing a vectorgram; establishing a converter and flux linkage mathematic model, and calculating a virtual flux linkage vector of a system to obtain a power feedback quantity of the system; acquiring an active control signal and a reactive control signal of the system through a direct power control algorithm, and generating a PWM trigger converter for respectively and independently controlling the active power and reactive power of the system; and utilizing MATLAB simulation software to set up a system model for verifying, and obtaining a systematic selection device when the verification is successful. By utilizing Matlab / Simulink to set up a corresponding simulation model, the designed method is verified to have rapid response speed, the voltage and power after startup can still reach stable values after about 2 power frequency periods and have high steady state precision.

The invention belongs to the field of on-line monitoring technology of insulative condition of SF6 (sulfur hexafluoride) gas insulated electric equipment, and in particular relates to a gas insulated electric equipment partial discharge multi-source joint detection method. The detection method mainly comprises the steps of preparing a test, cleaning a stainless steel cylinder, filling with SF6 gas, performing an industrial frequency AC SF6 gas PD test, pulse current detection, ultrahigh frequency sensor detection, fluorescent optical fiber sensor detection, discharge gas collection and component detection and the like. The detection method provided by the invention is simple in operation, liable to promote, and provides references for multi-dimensional information joint detection method. The detection method is widely applied to SF6 gas insulated electric equipment partial discharge multi-sensor joint detection under the condition of power frequency, and provides a simple test scheme for multi-dimensional information extraction of PD (Potential Difference) decomposition characteristics and a decomposition theory.

The invention discloses audible noise measuring circuit and method of a power capacitor. The audible noise measuring method comprises the following steps of: selecting a noise-eliminating test area; mounting a power capacitor to be measured in the noise-eliminating test area; setting a power capacitor to be measured in accompany; building the power capacitor to be measured and the power capacitorto be measured in accompany into a bridge-type power capacitor loading circuit; respectively loading an external high-voltage alternating current power source and an external harmonic power source attwo ends of the bridge-type power capacitor loading circuit, wherein the whole bridge-type circuit achieves resonance state under the common action of power frequency voltage generated by the high-voltage alternating current power source and various time harmonic voltage generated by the harmonic power source; and obtaining various noise values generated by the power capacitor to be measured in an actual work state according to data which are measured by a noise sensor arranged around the power capacitor to be measured and are related to the noise. The invention reduces the random of the noise measuring operation of the power capacitor, so that a measuring result has more comparability and a set of noise measuring method of the power capacitor with systematicness, completeness, science and reasonability is formed.

An inverter controlling method is applied in a system comprising a single-phase rectification circuitry and three-phase inverter. The method determines a capacitance of a capacitor connected between output terminals of the single-phase rectification circuitry for allowing an output voltage of the single-phase rectification circuitry to pulsate at twice frequency with respect to a power frequency; controls the three-phase inverter for supplying output voltages or output currents from the three-phase inverter to a motor; and suppresses a current flowing into the capacitor from a power source via the single-phase rectification circuitry.

The invention discloses a pulse width modulation (PWM) control method for a single-phase grid-connected inverter, which is implemented according to the steps of: calculating to obtain single-polarity PWM wave; comparing network voltage detection with a zero crossing comparator to obtain a synchronous square wave signal, and then performing two divided-frequency on the synchronous square wave signal to obtain a synchronous square wave two divided-frequency signal; keeping only one of four power switch tubes of a single-phase full-bridge inverter in a high-frequency PWM action state, the power switch tube, which is on the diagonal of the power switch tube, of another bridge arm in a power frequency action state, and the other two power switch tubes in a shutoff state; making the four power switch tubes alternately act in a high-frequency PWM mode according to certain phase sequence; and adopting a principle that the power switch tube which conducts shuts off in advance to add dead zone time only during the zero crossing of network voltage at the same time. The method is applicable to single-phase grid-connected power generation systems, and has the characteristics of reducing the loss of switches, eliminating dead zone effect and optimizing heat dissipation.

The invention discloses a method for detecting an island of a photovoltaic grid-connected inverter. The method comprises the following steps of: 1), detecting a voltage frequency at a common coupling point of the inverter and a power grid, wherein when the voltage frequency is between f11 and f12, a phase position of output current of the inverter is the same to that of voltage at the coupling point; and, by modifying the phase position between the output current of the inverter and the voltage at the coupling point, compared with the voltage at the coupling point, the output current is ahead of time in theta degrees (when fgrid is more than f12 and less than f22) or lags in theta degrees (when fgrid is more than f21 and less than f11); and 2), to compensate a dead zone appeared in frequency detection, judging whether an island effect exists by modifying an amplitude value of the output current of the inverter within one power frequency period after every four power frequency periods and recovering the amplitude value of the output current into an original value after the period. According to the method, harmonic waves output by the inverter to the power grid can be effectively reduced; the detection time is short; the calculation method is simple; and the computing resource of a control chip can be saved.

The invention relates to a control method of restraining the output DC component of a grid-connected photovoltaic inverter, which pertains to the technical field of inverting grid-connected control. The invention is proposed for solving the problems of high cost of the adoption of a high-capacity blocking capacitor system and the large volume, high power consumption and high price of the adoption of a power frequency transformer during the restraining of the output DC component of a grid-connected photovoltaic inverter. The method of the invention adopts the grid-connected current, attains the DC component thereof and carries out restraining by two steps: 1. DC component due to sampling errors is introduced into the given grid-connected current in a manner of inverse feedback; 2. the average DC component of the modulating signals of each switch cycle in the previous power frequency period is obtained and then the DC component due to unbalanced impulse width is formed after PI regulation and introduced into the primary modulating signals in a manner of inverse feedback. With the two steps, modulating signals of restraining DC component are finally formed and PWM driving signals are obtained for driving the four switching tubes of the grid-connected photovoltaic inverter.

The invention relates to a low-voltage power line carrier communication circuit. The circuit comprises a carrier control circuit, a zero-cross detection circuit and a signal coupling circuit. A signal amplifying filter circuit and a receiving filter circuit are arranged between the carrier control circuit and the signal coupling circuit. The signal amplifying filter circuit amplifies and filters analog signals output by the carrier control circuit, and then the analog signals enters into a power line information channel to be transmitted through the signal coupling circuit. The signals transmitted in the power line information channel is converted by the signal coupling circuit, then high-frequency interference is eliminated by the receiving filter circuit, and last the signals are transmitted to the carrier control circuit. The signal amplifying filter circuit is connected with a current-limiting circuit which is used for controlling the output current of the carrier control circuit. The zero-cross detection circuit is connected between the carrier control circuit and a power line, and is used for detecting power network power frequency signal zero passage. The low-voltage power line carrier communication circuit is simple in circuit, and is low in power dissipation, high in fidelity and high in carrier communication property due to the fact that the signal amplifying filter circuit and the current-limiting circuit are added.

The invention provides a capacitance measurement method for a power distribution network with a neutral point grounded through an arc suppression coil and a measurement device based on the method. The measurement method comprises the following steps of: (1) applying an excitation source, and injecting an excitation signal with the frequency between f0 and 2f0 (assuming the working frequency of the power distribution network as f0) into the power network through a secondary coil of the arc suppression coil, and assuming the frequency of the excitation signal as fc; (2) measuring the current, and measuring an output signal of a zero sequence current mutual inductor to obtain current magnitude; (3) measuring the voltage, and measuring voltage magnitude through a bus voltage transformer; and (4) calculating the capacitive reactance over the ground. The measuring device comprises a signal injecting module, and a bus voltage acquisition and processing module and a zero sequence current acquisition and processing module; the zero sequence current acquisition and processing module comprises a signal processing module electrically connected with an output end of the zero sequence current transformer. The measuring method can be used for conveniently and accurately measuring the capacitive reactance over the ground and the current, and the operations of an operator to the primary side of the power network are avoided.

This invention belongs to power measuring technique region, relates to a line frequency parameter measurement and device of electric transmission line. The trait is: measuring electric transmission line by frequency sweeping at intermediate frqquency range of 100 to 2000hz, base on Signal-to-Noise Ratio of measuring signal to set frequency of supply oscillator used for measuring. Base on length of electric transmission line to set voltage of supply oscillator for measuring. picking up fundamental circuit parameter of electric transmission line, then calculate and obtain line frequency equivalent parameter of electric transmission line; line frequency parameter measurement device of electric transmission line includes control system that takes singlechip as controlling center, brainpower numerical control frequency conversion transform power that operated by singlechip, voltage and electric current sensing circuit, digital filter and signal acquisition circuit. Power supply of brainpower numerical controlling, frequency conversion and variable voltage supply signal source to electric transmission line. Electric transmission line detects the signal and then sends to digital filter and signal acquisition circuit. Digital filter and signal acquisition circuit would turn circuit signal to fundamental circuit parameter, and send into singlechip.

The invention discloses a converter valve thyristor level damping loop parameter testing device and method. The device comprises a measurement and control system used for applying an excitation source to a tested thyristor level, and a signal collection unit connected with the measurement and control system. The signal collection unit comprises a voltage sensor used for measuring voltage signals at the two ends of a damping loop in the testing process, a current sensor used for measuring current signals flowing through the damping loop, and an alternating-current power supply used for being applied to a measurement and control system of a thyristor level test object, wherein the frequency of an excitation source of the alternating-current power supply is 50 Hz. According to the method, the alternating-current power supply with the 50 Hz working frequency is applied to the two ends of the thyristor level test object, and meanwhile the damping resistance and the damping capacitance are calculated through the phase difference of the voltage and the current of the thyristor level test object. The testing device is simple in structure, convenient to operate and accurate in measurement. Due to the fact that the testing work condition of the device is completely the same with the actual running work condition of the converter valve thyristor level, the accuracy and reliability of the testing result of the testing device is determined by the characteristic.

The invention provides a frequency sweeping test method for measuring the power frequency ground resistance of a grounding device and a test instrument for the frequency sweeping test method, which are used for solving the problems that in the conventional measurement, wires are inconveniently laid, measurement is interfered and the like. The measuring method comprises the following steps of: arranging a voltage electrode, a current electrode and a lead according to a preset ground resistance test way; selecting a frequency with a small interference signal as a test frequency; measuring ground impedance at the selected test frequency; and computing the power frequency ground resistance according to the measured ground impedance. The adopted test instrument comprises a variable-frequency alternating current power supply, a current sensor, a voltage divider, an isolating transformer, a signal acquisition device, an analog / digital (A / D) convertor and a portable personal computer (PC). The frequency sweeping test method for measuring the power frequency ground resistance of the grounding device and the test instrument for the frequency sweeping test method can effectively avoid each interference frequency and acquire a reliable test result.

The invention relates to an ultra-low frequency alternating-current (AC) constant-current demagnetization device of a large transformer or mutual inductor, comprising a display (1) and a CPU control unit (2), wherein the CPU control unit (2) is connected with a power-frequency signal generator (3); the power-frequency signal generator (3) is connected with a voltage power amplifier (4); the voltage power amplifier (4) is connected with a voltage booster (5); the CPU control unit (2) is also connected with an ultra-low frequency signal generator (6); a switch is arranged between a transformer or a mutual inductor (8) to be tested and the voltage booster (5); and a switch is arranged between the transformer or the mutual inductor (8) to be tested and a current power amplifier (7). The invention overcomes the defects of long demagnetization time, easy transformer coil deformation, and the like of the traditional method and has the advantages of short demagnetization time, light equipment weight, and the like. The invention also discloses a demagnetization detection method adopting the demagnetization device.

The invention relates to an online calibration method for error characteristics of a voltage transformer for a power system, which is an online calibration method for the error characteristics of the voltage transformer working in an energized state in a power network under the condition that the power network is not powered off. Particularly, a special power frequency voltage proportion standardized device of which the insulation level is not lower than that of the voltage transformer to be calibrated is adopted as a standard and is connected with the power network for online calibration of the error characteristics of the running voltage transformer; or a voltage transformer, which is offline in a short term, is calibrated by a normal detection method to acquire error detection data, and then is connected with the power network to serve as a reference voltage transformer for the online calibrate of other inphase voltage transformers and the necessary processing of measured data errors. By means of the calibration method, the error characteristics of the running voltage transformer can be calibrated in the power-on state, so the problem that the power network can be hardly powered off for calibration is solved, the cost for running and maintaining the power network is reduced and the running reliability of the power network is improved.

The invention discloses a high voltage overhead transmission line power frequency electric field shielding analysis method, which comprises building a physical model for a high voltage overhead transmission line according to the arc sag lowest point, considering the high voltage overhead transmission line at the lowest point as a round transmission line parallel with ground, adopting the physical model as a two-dimension physical model formed by the section of the round transmission line, and utilizing charge simulation method to calculate the electric field intensity at any point of the shielded high voltage overhead transmission line. The invention adopts a simple method to confirm the maximum value of the electromagnetic field distribution of a transmission line in a controllable range of the calculated result, thereby completely considering the safety of the electromagnetic condition around the transmission line in the analysis of the invention, the invention can process the comparative analysis of the line at various condition, can realize the research about the field distribution change of the line under various shielding devices, and can quickly provide an optimization scheme of the shield on the power frequency electric field of a prior overhead high voltage transmission line, to find an ideal overhead line scheme.

The over-voltage monitor sensor for 110KV-50KV ac power system comprises: a shell, a disk, a voltage-division capacitor / resistance, a matching resistance, a protective unit, and the co-axial cable. This invention can bear large impact voltage, can respond the signal fast, and has wide application for high precision and stability.

The invention discloses a photovoltaic grid-connected inverter of Boost and Buck cascade and a control method thereof; the inverter comprises a main circuit composed of four branch circuits and a switch control circuit composed of four branch circuits. The pre-stage DC / DC converter in the method works in an SPWM way and provides sine half-wave current for the post stage, the post-stage DC / AC converter switches at power frequency, and the conversion efficiency of the whole machine is high; a control strategy adopts a uniform compensation circuit at a Boost-Buck mode; and the duty cycle of a Boost switch tube is formed by subtracting a fixed amount on the basis of the duty cycle of a Buck switch tube. In the converter, only one switch tube works at high frequency at any time and the efficiency of the converter is high; the work mode of the pre-stage DC / DC converter achieves smooth switch; and the converter needs no electrolytic capacitor and has long life.

The invention discloses a field dynamic balance measuring device and method for a utility boiler side fan. The method comprises the following steps of: I, reading a vibration value by using an axis vibration probe and a key phase value, wherein the vibration value comprises a power frequency amplitude and a phase angle; II, determining a weighting testing position: directly calculating a position required to be weighted by using a read-out phase angle, and calculating a weighting position angle theta according to a formula (1), wherein a position on a key phase groove where a disk rotor is reversely rotated by the angle theta serves as the position required to be weighted; and III, determining a weighting testing magnitude: inquiring needed parameters in a formula (2) from fan specifications to calculate the weighing testing magnitude. Due to the adoption of the device and the method, the successful rate of one-time weighing is greatly increased, a calculating formula is simplified, and complex steps for attaching cursors by halting are reduced on the aspect of process.

The invention provides an application method for a travelling wave positioning system of a distributed high-precision electric transmission line. The method comprises the following steps: receiving power frequency failure current transmitted in an electric transmission line wire by an on-site testing device, performing analog-to-digital conversion to the power frequency failure current to obtain digital waveform signals, uplinking the digital waveform signals to an upper computer, and determining the accurate position of trouble spot by a supervisory system installed in the upper computer via calculation. The method remarkably reduces the travelling wave positioning error and improves the positioning accuracy.

The invention provides a calibrating test device of an electronic type transformer checking instrument, comprising a power-frequency proportion power supply, a standard A / D converter, a synchronous-pulse generating device, a packet software processing device and a checked electronic type transformer checking instrument, wherein the power-frequency proportion power supply comprises an error display unit, a standard small-signal output unit, a standard current or voltage signal output unit and an output control unit; and the checked electronic type transformer checking instrument comprises a standard signal input unit of the checked electronic type transformer checking instrument, a synchronous clock input unit of the checked electronic type transformer checking instrument, a measured analog quantity input unit of the checked electronic type transformer checking instrument and a measured digital quantity input unit of the checked electronic type transformer checking instrument. The device not only can conduct a global error calibrating test on the calibrating function of the analog quantity of the electronic type transformer checking instrument, but also can conduct a global error calibrating test on the calibrating function of the digital quantity of the electronic type transformer checking instrument, and fill the blank of the field.

The invention provides a novel high-frequency and high-voltage power supply for electrostatic precipitation, which comprises a rectifier module, a load module, a plurality of parallel power conversion circuit modules and a control loop module, wherein the parallel power conversion circuit modules and the control loop module are arranged between the rectifier module and the load module. The new high-frequency and high-voltage power supply for the electrostatic precipitation can overcome the defects of the traditional power-frequency power supply and the existing high-frequency power supply, and has good reliability and large power.

The invention discloses an on-line positioning method of small current earth fault and a positioner based on the positioning method. The method is suitable for a 3 to 60 kV neutral non-effective grounding electrical network. When a line is in operation with single phase earth fault, a 130 to 230 Hz (excluding power frequency of integer times of 50 Hz) AC signal is filled into a transformer station PT (potential transformer), voltage phasor of the filled signal is measured in a transformer station, current phasor of the filled signal is measured in a line, thus the section position of a fault point is determined according to the phase relationship of the filled signal voltage phasor and the filled signal current phasor. The positioner in the present invention comprises a host computer and a lower computer. The host computer is installed in the transformer station, and is used for filling 130 to 230 Hz (excluding power frequency of integer times of 50 Hz) AC signal into the transformer station PT and measuring the voltage phasor of bus filling signal. The lower computer is installed on the line, and is used for measuring current phasor of the filled signal. The lower computer uploads a measuring result to the host computer, and the host computer carries out phasor analysis and completes positioning calculation. The on-line positioning method of small current earth fault and the positioner based on the positioning method provided in the invention have the advantages of mature technology and high reliability.

The invention discloses a holographic dynamic balance method based on empirical modal breakdown flexible rotor, which is characterized by the following: resolving the data of rotor in the whole speed raising course through empirical modal breakdown advantage based on holographic spectrum information integral elementary and system theory; extracting the industrial frequency component; drawing the holographic baud graph; calculating the weight quality and orientation of different rotary speeds, especially near the weight information of critical rotary speed. The invention breaks through the limitation of traditional stable data and reduces the risk, which can reach the better balancing effect.

A method is disclosed for arranging and exciting the stator, rotor and various windings of a multi-stage brushless high frequency alternator so that the resulting multiple high frequency sub-phase armature winding outputs can be rectified and commutated into desired phases of power-frequency alternating current (AC) electrical output, including single-phase, split-phase, three-phase and other multiple phase output. Power frequency currents in field windings control output amplitude, output frequency, and output phase. If desired, DC power output can be accommodated as zero power-frequency operation. Devices incorporating this arrangement are suitable of generating fixed frequency electrical power while accommodating variable speed rotation of a generator shaft and offer multiple advantages over existing techniques. The capability to generate speed independent electric power allows natural power sources such as windmills and hydro-power stations to be efficiently coupled to fixed frequency power grids.