7 results about "Zero crossing" patented technology

The invention relates to a series coupling inductance high-voltage direct current breaker and a control method thereof. The breaker comprises a change-over switch, a switching circuit and an energy consumption device which are connected in series. The change-over switch adopts a mechanical switch, the switching circuit adopts a coupling circuit, and the energy consumption device adopts a lightning arrester. The high-voltage direct current breaker is connected with a control circuit, when a failure happens, the mechanical switch detects failure current, and transfers the failure current to the coupling circuit. The failure current charges a capacitor in the coupling circuit, flows over current change of a conductance L1, generates change current which is opposite to the failure current in direction and flows through a conductance L2. The failure current and the change current are overlaid, and the overlaid current makes a zero crossing point on a main circuit of the mechanical switch to cut off the mechanical switch. Voltage on two ends of the capacitor reaches operation voltage of the lighting arrester so that the lightning arrester acts and energy is released from the lightning arrester. The series coupling inductance high-voltage direct current breaker can meet requirements of quick cutting off of the failure current, can realize non-arc cutting-off of the mechanical switch, and the control method is simple and easy to operate, and complete in function.

The invention discloses a resonance current suppression method based on synchronous detection of a current average value and an instantaneous value. A synchronous detection circuit is adopted to directly control an MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor); the synchronous detection circuit comprises a current zero crossing point detection module ZCD, a current average value detection module ACD, a signal detection module, a PWM module and a driver module. A current zero crossing point detection module ZCD is adopted to detect an inductive current instantaneous value, and a current average value detection module ACD is adopted to detect an inductive current average value; when the signal detection module receives the inductive current zero-crossing signal and the inductive current average value allowing signal at the same time, a turn-on allowing signal is sent to the PWM module; the PWM module controls the driver module to send out a driving signal, the MOSFET is turned on, and the influence of the resonance current on the input current is reduced by controlling the intermittent resonance time of the MOSFET; according to the invention, the parameter problem of the circuit does not need to be considered, the device type selection of the circuit is more flexible, the problem of input current distortion caused by resonance is fundamentally solved, and the power factor is improved.

The invention provides an eLORAN signal period identification method and device based on sky wave reconstruction, and the method comprises the steps: firstly judging whether a sky wave signal exists in an input signal, making a decision according to the sky wave intensity and position estimation, if the sky wave exists and is within a strong sky wave threshold, carrying out the sky wave and ground wave separation according to the signal and sky and ground wave parameter estimation values, otherwise, carrying out period identification directly according to the signal and the ground wave parameter estimation value; in the sky wave and ground wave separation, performing second-order variable step size search on the input signals to obtain optimal sky wave signal parameter estimation, then reconstructing and removing sky waves, and outputting optimal pseudo-ground wave signals; carrying out period identification according to the ground wave position estimation; or re-estimating the position of the ground wave signal by using a frequency spectrum division technology, calculating the zero crossing point position of the third cycle by using the ground wave signal position estimation value, and correcting in the cycle to obtain an accurate standard zero crossing point position, thereby realizing cycle identification. According to the invention, the recognition accuracy can be improved under severe conditions.

A method of performing a circuit-breaking and closing operation in a three-phase system having a first phase, a second phase lagging the first phase by 120 degrees, and a third phase lagging the firstphase by 240 degrees, wherein the method comprises: a) opening only one of the first phase, the second phase and the third phase before a zero crossing of a current of the corresponding phase, b) opening the remaining phases of the first phase, the second phase and the third phase after step a), and c) closing the first phase, the second phase and the third phase simultaneously or essentially simultaneously at a phase to ground voltage of the phase of the first phase, the second phase and the third phase which lagging the phase that was opened in step a) by 120 degrees in a time range from 60degrees before a peak of said phase to 90 degrees after the peak.