10results about How to "Eliminate harmonics" patented technology

The invention provides a network construction type unbalanced fault low-voltage ride-through method and device, and the method comprises the steps: collecting unbalanced three-phase voltage and three-phase current at a grid connection point of a power grid; the grid-connected point is connected in parallel with a grid-following type converter and a grid-constructing type converter; converting the three-phase voltage and the three-phase current into three groups of balance components by using a positive and negative sequence separation method; eliminating harmonic waves in the three-phase current based on the three-phase balance component; based on the three groups of balance components, generating a reference voltage by using a network-forming converter; performing virtual impedance on the reference voltage by using a virtual impedance current limiting algorithm to obtain an actual expected output voltage; based on the actual expected output voltage, overcurrent caused by a short-circuit fault is suppressed; based on the grid following type converter and the grid constructing type converter, when low-voltage ride-through occurs in the power grid, the grid following type converter is used for reactive compensation, and low-voltage ride-through suppression of the power grid is completed. A grid-connected system can be controlled to generate overcurrent and low-voltage ride-through caused by current harmonics and short-circuit faults.

The invention provides a robot control method and device, a robot, a computer program product and a computer readable storage medium. The method comprises the steps that the energy conversion state of a motor is determined according to the rotation direction and the current direction of the motor in the joint steering engine; determining a target torque current mapping relation from a plurality of torque current mapping relations based on the energy conversion state; according to the real-time rotating speed of the motor and a torque instruction received by the joint steering engine, determining conversion current from the target torque current mapping relation; determining a first compensation current used for eliminating harmonic waves brought by the conversion current, and compensating the conversion current by using the first compensation current to obtain a current instruction; and based on the current instruction, a motor in the joint steering engine is controlled to generate target torque. According to the invention, the precision degree of the action of the robot can be improved.

The utility model relates to the technical field of loudspeakers, and discloses a low-distortion loudspeaker, which comprises a fixed cylinder, an annular cone is fixedly connected inside the fixed cylinder, one side of the annular cone is fixedly connected with a core fixing frame, the outer side of the core fixing frame is sleeved and fixedly connected with a magnet, the outer side of the core fixing frame is sleeved and fixedly connected with a voice coil, and the voice coil is sleeved and fixedly connected with a loudspeaker. Sound-absorbing cotton is fixedly connected to one side, close to the fixed core frame, of the inner wall of the fixed cylinder, and the sound-absorbing cotton is attached to the fixed core frame. According to the utility model, the external data line is electrically connected with the voice coil, so that the annular cone can vibrate, the core fixing frame can be driven to vibrate in the vibration process of the annular cone, and through the sound absorption cotton, the sound density can be enhanced, harmonic waves caused by vibration can be eliminated, and the sound background is quiet and has more details.

The utility model provides a high-impedance rectification phase-shifting transformer, which relates to the technical field of transformers and comprises a main body, a coil winding and a magnetic leakage sheet. The main body comprises an iron core, and the iron core comprises three core columns which are arranged in parallel; the coil winding is divided into three coil groups, the three coil groups are respectively wound on the three core columns, each coil group comprises a primary winding and a secondary winding, the primary winding is wound on the core column, and the secondary winding is wound on the primary winding; and the magnetic leakage sheet is arranged between the primary winding and the secondary winding. By arranging the magnetic leakage sheets between the primary winding and the secondary winding, high-impedance rectification phase-shift transformation is realized. The impedance of the transformer can be effectively improved by arranging the magnetic leakage sheet, the harmonic wave of the input current of the rectification circuit can be better eliminated through the higher impedance, and the pollution of the harmonic current to a power grid is reduced.

The present application relates to the technical field of flat wire motor, and discloses a flat wire motor suitable for different parallel branch windings. In the present application, Y / 2+1 kinds of hairpins are needed to realize the design of motor windings, the kinds of hairpins are less, and the mold opening cost and equipment cost are reduced; in the motor production, the production efficiency is increased. In the single unit of the present application, two kinds of same-layer hairpins and one kind of cross-layer hairpin group are adopted, so that different branch numbers can be obtained through simple series connection or parallel connection of the unit, and the unit is suitable for 1 branch, 2 branches and 4 branches, thereby improving the universality of the unit of the present application, facilitating product serialization, and achieving the purpose of reducing the manufacturing cycle. In addition, the unit composed of the three kinds of hairpin combinations forms a "short distance" arrangement form, which is beneficial to eliminate harmonics.

The present invention provides a low harmonic flat wire stator and motor, including a stator core and a flat wire winding; the inner wall of the stator core is evenly provided with 12m stator slots along the circumferential direction, the stator slots are divided into 2n layers along the radial direction of the core, and the flat wire winding is wound in the stator slots; the flat wire winding includes two sets of three-phase windings, which are 30 degrees electrical angle apart in space, and the flat wire windings are arranged symmetrically in double short distances in the stator slots; each phase winding includes at least one parallel branch, each parallel branch includes a plurality of flat wire coils connected in series, each of the flat wire coils includes a forming end and two welding ends, and the two welding ends are respectively inserted into the 2i and 2i-1 layers of the stator slots, 1≤i≤n. While maintaining a small number of line types, the electrical balance of the motor, the balance of the number of winding layers, the low harmonic content, the high torque density, the small span of the cross-line end and the welding end, the high efficiency, the strong fault tolerance, and the connection scheme of the flat wire winding that is universal for different voltage platforms are achieved.

An unbalance control method giving consideration to harmonic compensation and three-phase active power regulation functions comprises the following steps that 1, a three-phase four-wire system is decomposed into three independent single-phase power supply systems, and A-phase, B-phase and C-phase fundamental wave active currents are distributed again through a single-phase harmonic detection method; 2, calculating A-phase current ia (t); and step 3, obtaining a sinusoidal signal which has the same frequency and phase as the A-phase power grid voltage and has a peak value of 1 through phase locking, and multiplying the voltage ua (t) by the current ia (t). The method is used for solving the problems that existing electric equipment basically uses uncontrolled bridge rectification, carries a large amount of harmonic waves and is limited in improvement of electric energy quality.

The invention discloses a transformer fault identification method and system based on fitting weight and equivalent inductance, and the method comprises the steps: selecting voltages at two ends of a primary winding and currents of primary and secondary double-end windings in a transformer as sampling points, and generating a matrix of the voltages at the two ends of the primary winding and the currents at the two ends of the primary winding in each unit data window; carrying out equivalent inductance normalization calculation to obtain unweighted equivalent inductance; accumulatively calculating equivalent inductance in the weighted data window to obtain weighted equivalent inductance; and designing a fault protection criterion according to the weighted equivalent inductance, performing transformer fault identification by using the fault protection criterion, designing a protection criterion, and if the value of the equivalent inductance always meets the protection criterion within the time window length, determining that the transformer has an internal fault. Compared with the prior art, the method overcomes the defect that traditional time domain calculation is large in volatility, and the stability and reliability of protection are improved.

The invention provides an electric energy quality treatment method of a coal mine power grid and an electric energy treatment system of the coal mine power grid. The method comprises the steps that current information of a coal mine power grid is acquired, the current information is information of current generated by load operation in the coal mine power grid, and the current corresponding to the current information at least comprises harmonic current; switching pulse frequencies are obtained, the switching pulse frequencies are switching frequencies of a switch of the STATCOM between on and off, and the current information and the switching pulse frequencies are in one-to-one correspondence; and controlling the STATCOM to emit compensation current according to the switching pulse frequency so as to counteract harmonic current in current corresponding to the current information. According to the scheme, the problem of potential safety hazards of other equipment in a power grid caused by a large amount of current harmonics in the coal mine power grid in the prior art is solved.

The application discloses a modulation method for suppressing common-mode voltage high-frequency harmonics. The method re-synthesizes a virtual voltage vector, adopts a virtual voltage vector to synthesize a reference vector, and adopts effective vectors with opposite phases to synthesize a zero vector, so that common-mode voltage waveforms between carrier periods are completely identical and positive and negative polarity acting time is equally divided. According to the characteristics of the common-mode voltage waveform, the modulation strategy can completely eliminate harmonics at even multiple carrier frequencies and sideband harmonics near each carrier frequency while reducing the common-mode voltage amplitude, and effectively reduces the adverse effects caused by the common-mode voltage amplitude and high-frequency harmonics. The modulation method greatly reduces the content of common-mode voltage high-frequency harmonics, reduces harmonic loss and the adverse effects of the common-mode voltage on a motor system, and has high research value and application value.