31results about How to "Reduce the probability of commutation failure" patented technology

The invention discloses an LCC-HVDC topological structure internally provided with controllable sub-modules in series. The topological structure is characterized in that six valve arms of a six-pulse converter are connected with the controllable sub-modules in series. The invention further provides an optimal charging initial voltage determining method for the controllable sub-modules of the LCC-HVDC topological structure internally provided with the controllable sub-modules in series, the method is used for preventing the capacitor voltage of the controllable sub-modules from being out of control, ensuring normal work and operation of the controllable sub-modules and enhancing the function of preventing LCC-HVDC topology swapping phase failures.

The invention discloses a commutation failure suppression method and a system based on the current change rate. The method comprises the steps of subjecting the DC current obtained by the measurement of a conventional DC unit control system to derivation, and multiplying the DC current by an additional power coefficient to obtain the additional power of a flexible DC unit; subtracting the additional power of the flexible DC unit from an active power reference value originally input for the active power outer-loop control of the flexible DC unit so as to obtain a new active power reference value for the flexible DC unit; adopting the new active power reference value as an input for the active power outer-loop control of the flexible DC unit; and finally controlling the active power of the flexible DC unit. According to the technical scheme of the commutation failure suppression method and the system based on the current change rate, when the DC current of a conventional DC unit increases rapidly, the active power of the flexible DC transmission is reduced. Meanwhile, the short-circuit ratio of the system is increased, namely the strength of the AC system is enhanced. Therefore, the occurrence probability of conventional DC commutation failures is reduced.

The invention relates to a high-voltage DC constant reactive power AC fault recovery method and device. The high-voltage DC constant reactive power AC fault recovery method comprises the steps of differencing the reactive power consumed by a converter and the reactive power provided by a reactive power compensation device of a converter station according to converter bus voltage and direct current to obtain an exchange reactive power allowance range of an AC system and the converter station, selecting an exchange reactive power expected value from the exchange reactive power allowance range, and generating a direct current instruction value; and performing AC fault recovery on the converter station based on the direct current instruction value. In the AC fault recovery process, the exchange reactive power of the AC system and the converter station can be quantitatively controlled at the expected value, thereby improving the fault recovery performance of the system, and reducing the probability of commutation failure during the AC fault recovery process; and the high-voltage DC constant reactive power AC fault recovery method improves the voltage stability of a multi-infeed direct current system and the fault recovery performance of the system, and has importance significance for improving the stability of a direct current transmission system.