3744 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.

Circuitry and techniques designed to allow stable and continuous delivery of alternating power to a plasma with switch-mode power supply (16) include a variety of embodiments. Parallel, series, and other circuit elements connected across switching element (7) are tuned so that energy at other than the fundamental frequency is absorbed and dissipated. This energy may be only at the second harmonic or it may be across broad frequency ranges through selecting high impedance at the fundamental frequency and relatively low impedance at other frequencies. In overcoming instabilities, oscillations, and even changing class of operation of the switch-mode power supply, the stabilizing element absorbs the energy to avoid allowing it to affect switch (7) of power supply (16).

The invention discloses a green power converter which omits the pulse width modulation (PWM) technique in the traditional power converter, does not have high-frequency power device, does not generate EMI interference, simultaneously adopts the symmetry basic primitive (SBP) technique, the amplitude high modulate (AHM) technique and the dynamic rectification (DR) technique, and only needs to perform traditional power conversion on a small part of the input power so as to acquire the whole output power, namely that a large part of the output power neither need traditional power conversion nor need to pass through a magnetic core transformer. The input AC voltage neither needs to be rectified and filtered nor has large inductance and large capacitance, thus the power factor is 1, and the total harmonic distortion (THD) is 0. A transformer secondary side adopts dynamic rectification, can acquire a DC circuit, and can also acquire an AC voltage. The circuit complexity, the power consumption and the failure rate of the whole green power converter are greatly lowered, and the power converter can be applied in all the fields to replace the traditional power converter.

The invention discloses a serial arc-fault circuit interrupter, comprising a power circuit, a current sensor, a current sensing circuit, an amplifying and filtering circuit, a voltage zero-crossing comparison circuit, a microcontroller, a trip trigger circuit. A current transformer collects current signals in a circuit; the current signals are converted into voltage signals through the current sensing circuit, and are input into the microcontroller through the amplifying and filtering circuit; the voltage zero-crossing comparison circuit inputs a voltage zero-crossing pulse signal into the microcontroller; the microcontroller judges arc emergence through arc characteristics analysis and is disconnected with a load circuit by the trip trigger circuit. The protection method transforms a one-dimensional time signal into a two-dimensional time signal by utilizing short-time Fourier transform, analyzes changes of fundamental component, even-order harmonic and odd harmonic component of eachcyclic wave, extracts and judges the serial arc-fault characteristics. The method has the advantages that multiple characteristics are extracted to realize comprehensive judgment of fault arc, missedtrip and balk generated in serial arc detection in small load are prevented, and the reliability of judgment is improved effectively.

A method and system to detect and evaluate harmonic distortion in an electrical power system is disclosed. A plurality of monitoring devices is installed in the electrical power system. The hierarchy of the electrical power system is received. Data indicative of harmonic distortion on the electrical power system is received from at least two of said plurality of monitoring devices. The data indicative of harmonic distortion is automatically aligned in a temporal or pseudo-temporal context. An electrical characteristic of the harmonic distortion from the data indicative of harmonic distortion is determined.

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.

Exemplary embodiments of the invention provide a reference harmonic oscillator integrated circuit having three or more terminals, with systems and methods for calibrating the harmonic oscillator to a selected first frequency using a limited number of terminals. An exemplary apparatus comprises: a reference harmonic oscillator, a first terminal to receive a supply voltage, a second terminal to receive a ground potential, a third terminal to provide an output signal having an output frequency, and may also include a fourth terminal. One of the first, second, third or fourth terminals is further adapted for input of a calibration of the first frequency. The exemplary apparatus may enter calibration and testing modes in response to various commands such as a calibration mode signal, and may also be configured through one of the terminals for output frequency selection, spread-spectrum output, and output voltage levels.

The invention relates to a position sensor-free brushless direct-current motor rotor phase commutation error correction method and a position sensor-free brushless direct-current motor rotor phase commutation error correction control system. According to the position sensor-free brushless direct-current motor rotor phase commutation error correction method, opposite potential harmonic information of a motor is obtained through Fourier decomposition; an analytic relations between a motor-end voltage different value and a phase commutation point deviation phase when conduction begins and terminates and the phase of a phase commutation point deviates is analyzed; the phase commutation point deviation phase is obtained through backward reasoning based on the opposite potential harmonic information; and therefore, phase deviation which is calculated in real time is added to original signals, so that high-accuracy phase commutation signals can be obtained. According to the control system, based on the designed correction method, a closed-loop control mode is adopted, and therefore, the phase commutation error of the position sensor-free motor can be effectively reduced, and error convergence speed and the work efficiency of the position sensor-free motor can be greatly improved.

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 a high frequency heating apparatus that drives a magnetron such as a microwave, and provides a frequency modulation method of preventing harmonic current occurring due to a high frequency switching operation. When a driving signal is transmitted in order to drive a first semiconductor switching element (3) and a second semiconductor switching element (4), an inverter operating frequency in the every phase of a commercial power supply is provided as a frequency difference (inclination) of the phase range from 0° to 90° using a triangular wave-forming circuit in an oscillation circuit (16). A modulation waveform for a frequency modulation control is formed, configuring an upper limit clamp, a lower limit clamp, a lower limit value corresponding to the lowest frequency in a frequency modulation-forming circuit (15) on the basis of a commercial power rectifying voltage-dividing waveform after rectification. By combining these optimally, it is possible to prevent the harmonic current from occurring while forming the frequency modulation waveform handling several non-uniformities such as constants of major inverter circuit components or a power supply (Vcc) of a driving control IC unit (14).

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.

Method and apparatus for providing harmonic inductive power, and more particularly for delivering current pulses providing a desired amount of pulse energy in high frequency harmonics to a load circuit for inductive heating of an article. By controlling the shape and / or frequency of such current pulses, the apparatus and method can be used to enhance the rate, intensity and / or power of inductive heating delivered by the heater coil and / or to enhance the lifetime or reduce the cost and complexity of an inductive heating power supply. Of particular significance, the apparatus and method may be used to significantly increase the power inductively delivered to a ferromagnetic or other inductively heated load, without requiring an increase of current in the heater coil. This enables new heating applications, and in some known applications, decreases the energy consumption or cooling requirements and / or increase the lifetime of the heater coil.

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 relates to a multi-inverter module paralleling frequency conversion device for a transmission system and a control policy. The device comprises a rectifier, inverters, a braking device, a cooling system, a protection device, an interface and the like, and is characterized in that an inverter paralleling structure realizes a relatively high power factor; through the parallel connection of multiple rectifying modules and the parallel connection of multiple inversion units, the output capacity of the inverters is increased, and the input / output harmonic waves are reduced; a control box drives a motor to operate by controlling the work of a frequency converter; and a fuse group and control power supply perform fault protection on the system and provide power to each part. In the control policy, a motor driving mode that master and slave modules perform hierarchical control is adopted; as the master control module synchronizes the slave control module, the problem of difficult same-frequency and same-phase output of multiple inverters in the case of motor load is solved; by monitoring the current of each inversion module (multiple inversion modules) and dynamically adjusting the output of each inversion module, the key technology of realizing homogeneous flow of the outputs of multiple paralleling inversion modules is broken through, and an inverter paralleling frequency conversion and speed regulation control method with relatively high static and dynamic performance is realized; and high power of the frequency conversion device with multiple paralleling inversion modules for the transmission system is realized.

A high-voltage big-power frequency converter without harmonic wave pollution has an energy feedback device, a precharged circuit of bypass circuit and an easily changeable air filtering net added on the existing big-power and high-voltage frequency converter of power module unit in series connection. The said energy feedback device mainly consists of the feedback bridge control circuit and the feedback bridge connected in antiparallel at the side of rectifying bridge for each power module unit, the said bypass circuit includes the precharged circuit, silicon control and diode rectifying bridge which are connected in parallel at the said of each power module unit, the said air filtering net is mainly composed of the front panel and the filtering net supporting mechanism with the front panel having air ventilation holes on it.

An arrangement (900) and method (1000) for providing power line communication from an AC power source (910) to a circuit (900) for supplying power to a load (960), as well as electronic ballasts (20,30,40,70,80) that operate according to the method (1000). Method (1000) includes the steps of: providing (1010) an AC power source (910) that includes hot, neutral, and ground wires (10,12,14) and a control station (914) for generating a power line carrier control signal; providing (1020) a power supply circuit (920) having an EMI filter (930), power processing circuitry (940), and a power line communication (PLC) circuit (950); setting (1030) a fundamental frequency of the power line carrier control signal to be about equal to either an effective common-mode resonant frequency of the EMI filter (930) or a harmonic thereof; injecting (1040) a power line carrier control signal between the neutral and ground wires (12,14) of the AC power source (910); detecting (1050) the power line carrier control signal by monitoring a current flowing from the ground wire (14) to a circuit ground (90); and directing (1060) the power processing circuitry (940) to control load power in dependence on the detected power line carrier control signal. Specific preferred embodiments are directed to electronic ballasts (20,30,40,70,80) that include various PLC circuits (300,400,500,700).

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 relates to the technical field of power electronic current transformers, and provides a resonance-type power electronic current transformer and a current transformer device. The current transformer comprises an input-stage rectifying circuit and a rear-stage DC / DC circuit. The input-stage rectifying circuit comprises three bridge arms. Each bridge arm is composed of an upper half bridge arm body and a lower half bridge arm body. The midpoints of the bridge arms are connected with three phases of a high-voltage alternating-current power grid respectively. Each half bridge arm body comprises n module units. Ports of the module units are connected in a head-to-tail mode to form a bridge arm structure. Due to the high-frequency isolation of the input side and the output side, a heavy lower-frequency transformer is removed, and meanwhile efficient energy transmission and intelligent control are achieved. Harmonic wave transmission between different power grids and mutual influences caused by failures of the different power grids can be intercepted, meanwhile, the range of the output voltage is wide, continuous adjustment of the current and the voltage can be achieved, system operation information of the current transformer is easy and convenient to collect, mutual communication can be achieved among a plurality of current transformer systems, and the intelligent power grid is obtained.

A continuous grounding system for use in an alternating current system including a transformer is disclosed. The system includes a switch assembly connected between a transformer neutral of a transformer and a ground, the switch assembly having an open position and a closed position, the open position disrupting the path through the switch assembly between the electrical connection and the transformer neutral, and the closed position establishing a path connecting the electrical connection to the transformer neutral through the switch assembly, wherein in normal operation of the alternating current electrical device the switch assembly remains in a closed position. The system also includes a DC blocking component positioned in parallel with the switch assembly and connected between the transformer neutral and the ground. The system further includes a control circuit configured to control the switch assembly, the control circuit including a sensor configured to actuate the switch assembly to an open position upon detection of a predetermined harmonic signal threshold at one of the transformer phases or a predetermined threshold of DC current between the transformer neutral and ground.

An integrated multi-mode, large-scale electric power support system supplies on demand at least 2,500 kW to an electrical grid with low harmonic distortion either from co-located solar or wind renewable energy DC power sources or in combination with, or alternatively, from system stored energy DC power sources via a plurality of DC-to-AC inverters with phase-shifted outputs. The power support system can also inject on demand grid power factor correcting reactive power. An alternative high voltage power support system can supply on demand at least 50 megawatts to the grid.

The invention discloses a design method for a radio frequency ultra-wide band high-efficiency power amplifier and a circuit. The design method includes the steps of a multi-frequency point transistor input and output impedance test, design of a maximum power transmission output impedance matching network, design of a wide band input multi-section impedance matching network, design of an input harmonic suppression network and an output harmonic suppression network and design of a transistor offset network. The transistor input and output impedance test technology achieves precise calculation of transistor input and output impedance. The maximum power transmission output impedance matching network achieves transistor impedance matching and maximum power transmission. The wide band input multi-section impedance matching network achieves wide band transistor input impedance matching. The design of the input harmonic suppression network and the output harmonic suppression network eliminates higher harmonic influences at the input end and the output end of a transistor, reduce losses and improve power additional efficiency of the amplifier. The design of the offset network provides working voltage of the transistor. The power amplifier can acquire higher frequency bandwidth, output power and power additional efficiency.

A system and method for controlling a grid-connected inverter to provide negative sequence current during unbalanced grid operating conditions. The system uses a combination of feedforward and feedback controls to compute voltage signals which are used to control the inverter switches. The system includes both positive and negative sequence current controllers with voltage feedforward terms. The measured grid voltage is directly fed forward to the positive sequence control through a predictive algorithm, so that the instantaneous voltage information is kept, reducing the influence of grid voltage harmonics on the quality of the output current. The predictive voltages include positive, negative and harmonic component information of the grid voltage signals.

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.

A harmonic injection point a is set on a power line extending downstream from a harmonic measuring point b in an electric power system. The currents of interharmonics are injected to the harmonic injection point a by a current injection device. The frequencies of the interharmonics are located on both sides of the frequency of an n-th targeted harmonic in frequency spectrum and each of the frequencies is a nonintegral multiple of the frequency of a fundamental wave of an electric power transmitted by the electric power system. The current values and voltage values of the interharmonics at the harmonic measuring point are detected to thereby obtain admittance values of an equivalent circuit of a power line extending upstream from the harmonic measuring point b when the interharmonics flow therethrough. An admittance value of the equivalent circuit of the power line when the targeted harmonic flows therethrough is determined by interpolating the admittance values for the interharmonics. Measurement is made of a harmonic characteristic of the power line extending upstream from the harmonic measuring point b, which is set at a point located upstream from the harmonic injection point a.

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 principal reason that commercially available 10 gigabits per second electrical interconnect has not previously been available is that such interconnect structures possess too high a level of parasitic inductance, capacitance, resistance and conductance. These result in signal degradation as a result of attenuation, harmonic distortion and dispersion and so sufficiently error-free transmission of data has been virtually impossible for high data rates such as those around 5 gigabits per second and above. By providing compensation mechanisms, signal integrity is improved thus enabling reliable data transmission at data rates of 5 gigabits per second, 10 gigabits per second and above. Non-linear transmission lines are used to form these compensation mechanisms. The non-linear transmission line may take the form of a distributed diode, for example, formed from a layer of N-doped silicon covered on its top surface by a layer of platinum and on its bottom surface by a layer of silicon dioxide. Advantageously, voltage biased sections of NLTL are used to perform compensation for different regions of a signal pulse according to the particular voltage biasing used. A plurality of such voltage biased sections of NLTL may be connected in series in order to obtain improved signal compensation.

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.