31results about How to "Shorten protection time" patented technology

The invention discloses an overcurrent protection circuit of an electric drive controller for an electric vehicle. The overcurrent protection circuit is characterized in that six paths of drive signals of an insulated gate bipolar transistor (IGBT) can be immediately switched off when bus or phase wire overcurrent exists in the electric drive controller for the electric vehicle; and when one path of the IGBT has an overcurrent failure, one path of failed drive signal is switched off, and the IGBT operates in a limping home manner. According to the invention, not only is the overcurrent protection of the electric drive controller for the electric vehicle realized, but also a motor can be ensured and maintained to operate continuously when the IGBT has the overcurrent failure, thus the safety of the electric vehicle is ensured.

The invention relates to the communication field. The embodiment of the invention discloses a protection method of a WDM optical network ring, which is based on resources and considers protecting time control. The method mainly comprises the processing procedures under three states of preconfigured state, normal working state and fault state. The proposal also provides a heuristic ring search configuration method and a protection switch process matched with the configuration method.

A system for selectively grounding each of a plurality of short-haul buried utility conveyances coupled to a common long-haul buried utility conveyance to enable a conveyance locating signal transmitted through the long-haul conveyance to travel from the long-haul utility conveyance to a selected short-haul utility conveyance. The system includes a first optical switch for selecting each of the plurality of short-haul utility conveyances to be grounded, where the first optical switch is adapted to receive an optical signal and selectively output the optical signal on one of a plurality of optical fibers; and a second optical switch coupled to each of the plurality of optical fibers for grounding each short-haul utility conveyance in response to the optical signal on a corresponding optical fiber.

The invention relates to a DC transmission line protection method and system, belonging to the technical field of electric power system relay protection. Collect the single-ended traveling wave signal of the line to obtain the variation of the traveling wave signal, and use it to construct the start signal; calculate the short window energy of the start signal within the set short window; judge whether the short window energy is greater than the set start threshold, If not, then return to continue to calculate the short window energy, if so, calculate the maximum value of the rate of change in the set short window after the power transformation of the short window energy, and construct the fault section identification signal; judge whether the fault section identification signal is greater than If the section threshold is set, if it is not, then it is not the fault of the own line, if it is, then it is the fault of the own line, and a protection action command is issued. The invention only utilizes single-ended quantity, does not need synchronous time adjustment, can realize fast and reliable detection and identification of faults, and takes into account the selectivity, quickness, sensitivity and reliability of protection.

The invention discloses a signal acquisition controller, which quickly judges the overcurrent state of a three-phase alternating current. The signal acquisition controller comprises an input / output board and a central processing unit board, wherein the input / output board is used for receiving an alternating-current signal acquired by peripheral equipment on the three-phase alternating current, and conditioning the alternating-current signal to acquire an alternating-current conditioning signal, and is also used for executing the circuit protection action according to a protective signal sent by the central processing unit board; the central processing unit board is used for receiving a judging threshold value inputted by a user and judging whether the three-phase alternating current is inthe overcurrent state or not according to the judging threshold value and the alternating-current conditioning signal; if the three-phase alternating current is in the overcurrent state, the central processing unit board generates the protective signal and judges the protective signal is a quick protective signal or not; and if the protective signal is the quick protective signal, the protective signal is sent to the input / output board, otherwise the protective signal is sent to the peripheral equipment. The method and the device acquire and judge the alternating current directly, shorten thesignal acquisition time and the protective time during overcurrent.

The invention discloses a segmentation control method for low-voltage ride-through of a doubly-fed motor during symmetric drop of network voltage. The method comprises the following steps: respectively detecting the current of a rotor and the voltage of a DC bus; comparing the instantaneous values of real-timely detected current of the rotor and voltage of the DC bus with the respective upper limit values, determining the logic control signal of a crowbar circuit according to the comparison result, outputting the logic control signal as high level if either the current of the rotor or the voltage of the DC bus exceeds the limit value, and starting up the first-stage control; and after starting crowbar protection, continuing to detect the current of the rotor and the voltage of the DC bus, comparing the values with the respective lower limit values, outputting the logic control signal as low level if the current of the rotor and the voltage of the DC bus are smaller than the respective lower limit values, stopping operation of the crowbar circuit, recovering excitation control, and conducting the second-stage control. The segmentation control method can effectively realize fault ride-through of the doubly-fed motor, and simultaneously injects demagnetization current and reactive current into a power grid to shorten the crowbar protection time.

The present invention provides a method and device for rapid protection of DC line faults in an overhead line flexible DC power grid. Multiple protection criteria are formed by introducing protections such as DC undervoltage protection, DC voltage traveling wave protection, and DC current traveling wave protection, and the rapid protection algorithm is improved. Reliability; and wavelet transform is used to enhance the transition resistance tolerance and noise anti-interference ability of the protection algorithm. In addition, in order to further compress the protection time, the parallel processing method of lightning strike interference and fault protection discrimination is adopted, which is suitable for DC grids with any number of terminals, and will not be affected by the complexity of the DC grid line structure, the change of the converter type, and the DC voltage level. change to reduce its applicability.

The present invention discloses a combined on-off control system. The system comprises a programmable logic controller (PLC), a signal acquisition controller and an advance electricity leakage detector. The signal acquisition controller and the advance electricity leakage detector are respectively connected with the PLC. The signal acquisition controller is used for acquiring three phase AC current, comparing the three phase AC current with a preset current threshold value and judging whether overcurrent occurs or not. When overcurrent occurs, whether quick protection is to be carried out or not is judged. If quick protection is to be carried out, output first on-off control signals. Otherwise, send protection signals to the PLC. The advance electricity leakage detector is used for measuring the resistance of an electricity leakage resistor and sending the resistance to the PLC. The PLC is used for judging whether the resistance of an electricity leakage resistor is smaller than a preset resistance threshold value or not. If the resistance is smaller than the preset resistance threshold value, output second on-off control signals. The second on-off control signals are output according to the protection signals. The system can acquire data in environments and carry out quick overcurrent protection and advance electricity leakage protection.