36results about How to "Reduce current harmonic content" patented technology

The invention discloses a co-rectifier transformer medium voltage type regenerative braking energy feedback device and a control method thereof; the feedback device comprises a rectifier transformer,an energy feedback unit, and a rectifier unit; a grid connected switch and an isolation transformer are respectively connected in series between the energy feedback unit and a rectifier transformer valve side winding; the energy feedback unit comprises two inverters; DC sides of the two inverters are provided with a single-knife-double-end isolation switch block; the DC sides of the two invertersare connected with a DC traction network through the single-knife-double-end isolation switch block; the feedback device control method comprises the following steps: starting, running and stopping the energy feedback unit according to a first startup threshold value, a second startup threshold value, an overvoltage protection value, a stop threshold value and a current gradient determination value. The feedback device can eliminate the circulation between the energy feedback unit and the rectifier unit, has a larger feedback capacity than a low voltage feedback device, has a simplified structure when compared with a conventional medium voltage feedback device, and uses less general assembly dimensions and land occupation areas, thus reducing cost, and providing good versatility.

The invention relates to a grid-connected photovoltaic power generation system which consists of a phase-locked loop, a current transformator, a repetitive controller and a PWM generator. The invention also relates to a working method of the grid-connected photovoltaic power generation system, comprising the steps of: (1) acquiring network voltage phase position and grid-connected current; (2) designing the repetitive controller; (3) setting the modulation ratio, switch frequency and sampling times within unit cycle of an inverter; and (4) sending the output of the repetitive controller into the PWM generator, completing the switch operation for the inverter, and finally finishing grid-connected control for solar photovoltaic power generation. The invention has the advantages that the output waveform is greatly improved, the grid-connected current harmonic content is low, the total harmonic distortion is less than 1%, dc component is not contained, the power factor of the inverter is high, all indexes such as electrical energy quality and the like is in accordance with the requirement of grid-connected engineering technology, and the invention has application prospect.

The invention provides a steady-state testing device and a steady-state testing method for modularized multi-level converter valves. The device comprises a load electric reactor, a sample valve, an auxiliary valve, a water cooler, a direct-current power supply, a controller and a protection device. Current alternating components and current direct components of the electric reactor can be controlled individually. The structure of a steady-state testing circuit is simple. The steady-state testing device and the steady-state testing method have the advantages that the auxiliary valve and the sample valve are controlled to be unlocked and locked in a charging phase and a testing phase, support capacitors in the auxiliary valve and the sample valve are charged in different phases, and steady-state testing of the modularized multi-level converter valves is realized; charging and energy supplement of the support capacitors in the auxiliary valve are performed only through N output interfacesin the direct-current power supply, and additional direct-current power supplies are not needed for charging of the support capacitors in the sample valve, so that the cost of the whole test circuitis low; the actual working conditions of the modularized multi-level converter valves can be represented completely.

A PWM rectification type energy feedback device, based on improved phase amplitude control and PWM method thereof, estimates optimal value of feedback grid energy according to DC bus voltage and pumpascending rate thereof to be as reference input of an inverter; based on rotary coordinate change and model reference self-adaptive software lock phase ring technology and DSP and DC bus co-groundinginversion output voltage direct detection technology, the output end of the inverter can be precisely detected and avoid from DC component injection into the grid due to member feature drift or parameter change or current leakage. The optimization of feedback grid power causes the current to be in a continuous and relatively constant state, thus reducing current harmonic content injected into thegrid; fixed PWM ensures harmonic component to be fixed and to be high frequency, thus reducing the volume of the output end serial connected inducer and the switch noise; the software lock phase reduces hardware complexity and ensures the detection such as voltage fall, frequency drift and other grid faults to be more reliable.

The invention provides a double-rotor motor and an air conditioning unit. The double-rotor motor comprises a stator, an outer rotor and an inner rotor, the stator is fixedly arranged, the stator formsan outer stator section and an inner stator section which are connected along the height direction of the stator, the outer rotor is arranged on the outer side of the outer stator section, and the inner rotor is arranged on the inner side of the inner stator section. By means of the technical scheme, only the stacking height of the outer rotor with the large radius can be increased, the increasedcost is small, and the brought rotational inertia is obviously increased. The moment of inertia of the motor is increased, the torque fluctuation of low-frequency operation of a compressor is reduced, the low-frequency operation current fluctuation is reduced, the current harmonic content is reduced, the compression low-frequency operation rotating speed is more stable, and the efficiency of thecompressor in low frequency operation is enhanced.

The invention relates to a six-level circuit topology for a power conversion system, the circuit comprises a left circuit composed of first to fifth busbar capacitors connected in series in the same direction in turn, A first switching device A1, second switching device A2, third switching device A3, fourth switching device A4, fifth switching device A5, the sixth switching device A6 is sequentially connected in series on the right side, a first intermediate circuit composed of a ninth switching device A9, a second intermediate circuit composed of a seventh switching device A7 and a tenth switching device A10 in series, a third intermediate circuit composed of an eighth switching device A8 and an eleventh switching device A11 in series, a fourth intermediate circuit composed of a twelfth switching device A12, and three clamping capacitors. The invention can effectively reduce switching loss and voltage harmonics in the circuit, and can also control flexibly in controlling the switchingtransistor, and can be applied to power conversion devices such as inverters.

The invention relates to a double-cylinder variable-capacity compressor and an air conditioner. The double-cylinder variable-capacity compressor comprises a motor and a pump body assembly, the motor comprises a stator and a rotor, the rotor is arranged in the stator, the rotor can drive the pump body assembly to work when rotating relative to the stator, the displacement of the pump body assemblyis V, the induction voltage constant between stator wires is E, and when the rotating speed of the motor is 1000 RPM, and E and V meet the following formula: E=kV, wherein the value range of k is 0.9-1. According to the double-cylinder variable-capacity compressor and the air conditioner, when the rotating speed of the motor is 1000 RPM, E and V meet the formula that E=(0.9-1) V, when the double-cylinder variable-capacity compressor is low in load, the operating frequency of the motor is lower, the current harmonic content of a motor winding is greatly reduced, meanwhile, the voltage harmoniccontent of the motor end is greatly reduced, the motor iron core loss is obviously reduced, and the motor winding loss is basically unchanged; and the motor efficiency is improved, and the energy efficiency of the double-cylinder variable-capacity compressor is improved.

The present invention discloses a harmonic current compensation device used for a rectifier. The harmonic current compensation device comprises a harmonic injection circuit, and the harmonic injectioncircuit comprises a first filtering capacitor, a second filtering capacitor, a third filtering capacitor, a compensation filtering inductor, a first switching tube and a second switching tube. A first current detection module is used to detect a current flowing through the compensation filtering inductor, a second current detection module is used to detect a load current of the rectifier, a voltage detection module is used to detect the voltage of a three-phase power grid, and a control module is connected with the current detection modules, the voltage detection module, the control end of the first switching tube and the control end of the second switching tube separately and is used to generate a switch control signal according to the voltage of the three-phase power grid, the load current and the current flowing through the compensation filtering inductor and control the first and second switching tubes according to the switch control signal, thereby distributing a harmonic compensation current generated by the harmonic injection circuit to the three-phase power grid.

The invention relates to the technical field of motors, and discloses a motor starting control method, device and equipment and a storage medium. The motor starting control method comprises the steps of: judging whether a motor enters a preset rotating speed interval or not according to a current rotating speed value of the motor when the motor is started; when the motor enters the preset rotating speed interval, determining the frequency amplification of the switching frequency according to the switching error time of the motor and the current rotating speed value of the motor; and updating the first switching frequency according to the frequency amplification to obtain an updated switching frequency, and controlling the motor to start according to the updated switching frequency. When the motor enters the preset rotating speed interval, the first switching frequency is updated according to the rotating speed value of the motor and the switching error time, and the motor is controlled to be started according to the updated switching frequency, so that the current harmonic content of the motor in the low-speed starting stage can be effectively reduced, the noise in the starting stage is reduced, and the operation burden of a micro-control unit of the controller is not increased.

The invention provides an opening-winding permanent-magnet synchronous motor driving system for mine traction and a working method thereof. The driving system is composed of a first power supply circuit connected with a three-phase voltage, a second power supply circuit connected with the three-phase voltage, a permanent-magnet motor connected with the first power supply circuit and the second power supply circuit, a sampling module connected with the permanent-magnet motor, a main control module connected with the sampling module, and a driving module connected with the main control module, the first power supply circuit and the second power supply circuit. The driving system has the following beneficial effects: the neutral point of the permanent-magnet synchronous motor is opened to form a winding opening structure with dual ports; the opening-winding permanent-magnet synchronous motor is used as a driving motor of the mining electric locomotive, so that the requirement of the largestarting torque is met and the starting characteristic of the driving system is improved; and two converters are connected to the two ends of the opening-winding permanent-magnet synchronous motor, so that the system stability is improved and the fault rate is reduced.