70results about How to "Improve current waveform" patented technology

The invention discloses a surface-mounted permanent magnet synchronous motor sensorless direct torque control method. The method comprises a direct torque control method based on SVPWM and a flux linkage self-adaptive method, a novel method for estimating the positions and the rotating speed of rotors by a sliding mode observer and a novel compound control method which is suitable for self-detecting the positions of the rotors within a full speed range. According to the surface-mounted permanent magnet synchronous motor sensorless direct torque control method, the problem that in traditional SVPWM direct torque control, straight-axis currents are large when a motor is operated in a no-load state or under the condition that the heavy load is suddenly applied is fundamentally solved, the buffeting problem of a traditional sliding mode observer is solved, the phase delay problem of the traditional sliding mode observer caused by a low pass filter is solved, and estimation accuracy of the positions of the rotors when the motor is operated is improved. In addition, the problem that the positions of the rotors are inaccurately estimated when the motor is operated in a low speed and standstill mode is further solved, and the sensorless self-starting function can be achieved.

The invention discloses a distributed power quality conditioner and a method for controlling the same. The distributed power quality conditioner comprises one or more series compensation devices and parallel compensation devices, wherein each of the series compensation devices and the parallel compensation devices comprises a central controller; the series compensation devices and the parallel compensation devices do not share a direct current bus; and when the series compensation devices and the parallel compensation devices are used together, a management center is configured for acquiring the voltage of an electric network and load current information to determine the failure type of the electric network, and coordinately operating all series compensation devices and all parallel compensation devices.

The invention relates to a method for suppressing harmonics of power network current of a variable-speed constant-frequency doubly-fed wind power generator system, comprising the following steps of: collecting d q axis components in a synchronous rotating coordinate system oriented by a stator flux linkage; collecting reference values of the d q axis components in the synchronous rotating coordinate system oriented by the stator flux linkage during the steady state of the system,; extracting alternating-current harmonic current components in a power network; obtaining harmonic current reference values of a network-side inverter, which are required adding for suppressing each harmonic current; and summing all harmonic current reference values of the network-side inverter, and adding the result in the current d q axis component reference values of the alternating-current side of the network-side inverter to generate reverse current harmonics to eliminate existed harmonic currents in the power network current. The invention can effectively suppress low-order harmonics which have great damages in the power network current of the doubly-fed wind power generator system, improves the current waveform of the power network, is simple in realization method and convenient for control, and can be widely applicable to harmonic suppression of power network current of the wind power generator systems.

The invention discloses a dual-three-phase bisymmetric winding permanent-magnet brushless direct-current motor. In the dual-three-phase bisymmetric winding permanent-magnet brushless direct-current motor, two permanent-magnet brushless direct-current motors are designed to share a rotor and a stator: 1, the two permanent-magnet brushless direct-current motors are designed as a special structure which shares the rotor and the stator; and 2, a self-charging function is realized by using the double winding permanent-magnet brushless direct-current motors which drive an electric vehicle. Namely, one motor winding is operated with no load by utilizing a motor winding when a vehicle parks; and the other motor winding forms a generator to realize a charging function, so that the charging function is singly realized when the motor is not operated.

The invention discloses a scattered type power quality regulation system. The scattered type power quality regulation system comprises one or more series-wound type compensation apparatus and shunt-wound type compensation apparatus, wherein each of the series-wound type compensation apparatuses and shunt-wound type compensation apparatuses comprises a central control unit; and direct current buses are not shared between the series-wound type compensation apparatuses and shunt-wound type compensation apparatuses. When the multiple series-wound type compensation apparatuses and shunt-wound type compensation apparatuses are jointly used, a management center is provided, wherein the management center judges power grid fault types by sampling power grid voltages and load current information so as to realize coordinated operation of the respective series-wound type compensation apparatuses and the shunt-wound type compensation apparatuses.

It is a current transformer excitation test system in electric power test technique field, wherein the power system comprises bridge rectification module, filter capacitor and start protection circuit; the data collection system comprises current sensor, voltage sensor, isolation module, temperature sensor, temperature transducer and analog channel of data collection card; the control sub-system comprises digit output channel of data collection card, three solid relays, three electromagnetic relays, and three contactors; the central processor is connected with data collection system and control sub-system through data collection card.

The invention discloses a control method of a high-speed permanent magnet brushless DC motor based on a variable conduction period, The method realizes stepless speed regulation by adjusting the conduction period of control signal, obtains the required conduction period by speed-current double closed-loop control, divides the conduction period into one pulse, two symmetrical pulses or two asymmetrical pulses according to the principle of minimum current ripple, and then applies the conduction period to each power transistor according to three-phase six-state conduction law. As that optimal commutation angle is dynamically adjusted, the high-speed running current waveform of the motor system can be completely symmetrical and the ripple is minimum, the stator current waveform of the high-speed permanent magnet brushless DC motor can be effectively improved, and the eddy current loss of the rotor can be reduced.

A method for self-adaptive harmonic elimination current control of a single-phase photovoltaic inverter is provided. The invention is suitable for a two-stage single-phase photovoltaic grid-connectedinverter system connected with a photovoltaic array, a boost converter, an inverter and an inverter controller in turn. For the inverter, the control method comprises the steps of converting the output current of the inverter and the voltage on the grid side in static coordinates to dq rotational coordinates; The state equation of the system in dq coordinate system is listed and the two-loop PI control model of the inverter controller is established. The characteristic harmonic components of the inverter output current are extracted by the harmonic detection module and input to the adaptive neural network control module. The compensation gain is adjusted to compensate the output signal of the double-loop PI control, and the PWM is injected into the inverter to realize the grid-connected control. Grid-connected current distortion of two-stage single-phase photovoltaic grid-connected inverter due to dead-time, DC side fluctuation and other reasons can be overcome, the grid-connected current waveform can be optimized, and the current tracking performance can be improved.

The invention discloses an isolated double-full-bridge ANPC three-level DC/DC converter which comprises two full-bridge ANPCs, a transformer and an inductor. Each full-bridge ANPC is composed of two voltage dividing capacitors and two half-bridge ANPCs. The voltage dividing capacitors are connected to Vdc in series, the voltage of each voltage dividing capacitor is Vdc/2, and the half-bridge ANPCsconnect the midpoint of bridge arms of series-connected switching tubes to the series midpoint of the two DC voltage dividing capacitors, so that the voltage stress borne by the switching tube in each half-bridge ANPC is Vdc/2. Each half-bridge ANPC can output three levels, namely, Vdc/2, 0 and -Vdc/2. The output level of each full-bridge ANPC is determined by the difference value of the output levels of the two half-bridge ANPCs, and five levels of Vdc, Vdc/2, 0, -Vdc/2 and -Vdc can be output. The two full-bridge ANPC active bridges can output five levels to enable the voltage at the two ends of the inductor to have nine levels. According to the invention, the AC voltage series is increased, and a higher degree of control freedom is obtained.

The invention relates to an implementation method of a high-efficiency Doherty power amplifier based on a switching resonant structure. The switching resonant structure for inhibiting the higher harmonic component of an auxiliary power amplifier is arranged behind the auxiliary power amplifier so that the auxiliary power amplifier realizes class E work; the switching resonant structure comprises a switch, and a resistor, a capacitor and an inductor, the three of which are connected with the switch; an inductance value is optimized to enable a signal to resonate under a fundamental frequency, and therefore, a high impedance characteristic is presented to harmonics and an orthogonal relation between the time domain voltage and the current waveform of an ideal class E amplifier is realized. As a result, the efficiency of the Doherty power amplifier is greatly improved under a high linearity condition. The inductance value of the novel switching resonant structure decides the working frequency thereof; the inductance value in the switching resonant structure is reasonably calculated, and meanwhile, the implementation of a zero-current switch of the class E power amplifier is considered to guarantee the implementation of high efficiency performance of the power amplifier within a working frequency range.

The invention provides a common-anode half-bridge power factor correction circuit which comprises a first chopping unit and a second chopping unit. The first chopping unit is used for achieving unity power factor single-phase AC-DC conversion in a network voltage positive half cycle and outputting stable direct-current voltages. The second chopping unit is used for achieving unity power factor single-phase AC-DC conversion in a network voltage negative half cycle and outputting stable direct-current voltages. The first chopping unit and the second chopping unit work in a time division mode according to the complete network voltage negative half cycle or network voltage positive half cycle and are used for cooling in the standby process. The common-anode half-bridge power factor correction circuit can achieve single-phase power factor correction, and has the advantages of being simple in structure, supporting large power output, saving total cost and the like.

The present invention discloses a non-harmonic intelligent frequency conversion controller and a control method thereof, and relates to the frequency conversion technology field. The controller mainlycomprises an isolation transformer, a silicon controlled soft starter, an alternating current inductor, a power conversion bridge circuit, a direct current filter capacitor and a control system. Thecontrol system comprises a DSP processor, a single-chip microcomputer processor, a phase-loss detection circuit, a soft-start circuit, a driving protection circuit, an alternating current sampling circuit and a direct current sampling circuit. A mathematical model of a three-phase voltage-type PWM rectifier is established in a three-phase stationary coordinate system, and mathematical models in atwo-phase stationary coordinate system and a two-phase synchronous rotating coordinate system are deduced through coordinate transformation. Through PI regulation current control in the two-phase synchronous rotating coordinate system, a difference between an actual current and a given current is taken as an input of a PI regulator, and an instruction voltage vectors of an alternating current sideof a rectifier is obtained through the PI regulator, thereby controlling the conduction of a power tube, realizing stable operation of a system and improving operation efficiency of the system.

The invention relates to the air-conditioning control technique, and discloses a control method for improving the compensation control accuracy of a motor dead zone, which solves the acquisition problem of an arc tangent angle while improving the acquiring accuracy of the arc tangent angle so as to improve the compensation accuracy of the dead zone. The method comprises the steps of establishing a high-accuracy arc tangent data look-up table for a single-chip microcomputer to acquire the compensation data of the dead zone and compensate the dead zone, wherein the high-accuracy arc tangent data look-up table is subdivided into 2n parts based on 0-45 degree tangent function values and tangent values in each part are set apart; determining an angle value corresponding to each tangent function value and amplifying the angle value; rounding the amplified angle value and storing the rounded value in the ROM of the single-chip microcomputer for the single-chip microcomputer to inquire and use. According to the invention, generally, n is larger than or equal to 8, and m is larger than or equal to 16. The above method is used for controlling the permanent-magnet brushless direct current motor of an air conditioner.

The invention discloses a harmonic suppression method and system for a generator-side converter of an eighteen-phase direct drive permanent magnet wind generator, and a medium. The harmonic suppression method for the generator-side converter provided by the invention has the steps of inputting a deviation of a rotation speed omega, a d shaft command current and 1/6 of the sum of d shaft response currents, and a deviation of a q shaft command current and the 1/6 of the sum of d shaft response currents into a proportional-integral resonant controller to acquire a d shaft voltage Udref and a q shaft voltage Uqref; and controlling the working condition of the generator-side converter of the eighteen-phase direct drive permanent magnet wind generator through adjusting and generating a switchingsignal. According to the method and system provided by the invention, the specified times of harmonic suppression are performed on the generator-side converter of the eighteen-phase direct drive permanent magnet wind generator, so that the purposes of eliminating stator current harmonics and improving current waveform are achieved, and thus the problem that iron consumption and copper consumptionof the generator are increased and the torque pulse is caused by the harmonics can be avoided, the generating efficiency of the wind generator unit can be effectively enhanced, and the service life of the generator can be prolonged.

The present invention discloses a three-level optimization PWM method based on a PSO algorithm, relating to the field of optimizing a pulse width modulation method. According to the three-level optimization PWM method based on the PSO algorithm, the harmonic optimization is carried out for a three-level traction inverter, through comparing the inverter output current waveforms obtained by two PWM methods in different frequency-division sections, the current THD obtained by PSO-PWM is much lower than the SPWM, and the current waveform sine degree is better. The current waveform of four working points of different sub frequency bands are optimized for a certain degree, and the good harmonic optimization effect of the PSO-PWM method is verified.

The invention discloses a 20kW three-level photovoltaic grid-connected inverter. The inverter comprises three portions including a 20kW three-level photovoltaic grid-connected inverter main circuit, aBoost control system, and an NPC inverter control system. The system employs a design without a step-up transformer, the Boost portion employs an interleaved parallel structure, the inversion portionemploys an I-type NPC three-level structure, and parameters of a system layer are designed. Aiming at the problem of neutral-point voltage balance of the NPC topology structure, the neutral-point voltage is adjusted through change of the charging and discharging time of upper and lower capacitors in a Boost circuit, a neural-point potential balance control algorithm based on a bus capacitance neural-point charge is combined, and test verification is performed. The control of the inverter employs power grid voltage orientation vector control, and the reliability of the apparatus is verified through the test.

The invention discloses a three-level power unit main circuit which comprises the components of two wire inlet end circuits; two rectifying circuits, wherein each rectifying circuit is parallelly connected with one wire inlet end circuit; two filtering capacitors, wherein each filtering capacitor is connected with one rectifying circuit and the two filtering capacitors are serially connected; an inverter circuit which is a three-level H bridge, wherein the two filtering capacitors are parallelly connected with the DC input side of the three-level H bridge; and a wire outlet end circuit which is parallelly connected with the AC output side of the three-level H bridge. The three-level power unit main circuit is advantageous in that the two rectifying circuits are used for rectifying, thereby effectively settling midpoint voltage fluctuation and eliminating harmonic pollution of a variable-frequency speed regulating device to a power grid; smaller number of power units, more compact power unit structure, easier power unit realization, effective output level number increase and low output harmonic wave of the power unit are realized, thereby obtaining better user-friendly performance to motor insulation.