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

The invention discloses a coordination control method capable of improving hybrid direct-current system commutation failure resistance. The method is used for a rectifier station of a flexible direct-current transmission system of which an conventional direction current and a flexible direct-current operate in parallel, and commutation failure resistance of a conventional direct-current inverter station is improved by controlling a flexible direct-current rectifier. The method comprises the following steps that 1, a trigger angle coordination control component is additionally added on a reactive power outer-loop controller of a flexible direct-current unit; 2, a failure judgment module judges putting time of a delayed trigger angle coordination controller; 3, the size of amplitude limiting of a reactive current reference value and an active current reference value of an inner-loop current controller of the flexible direct-current unit is determined according to a judgment result of the failure judgment module. According to the coordination control method capable of improving the hybrid direct-current system commutation failure resistance, the commutation failure resistance of a conventional direct-current system inverter station in the parallel hybrid direct-current transmission system can be effectively improved.

The invention provides a resistor energy consumption-based high-voltage direct current system phase commutation failure defensive apparatus. The apparatus comprises N sub modules connected in series;and each sub module consists of a thyristor type H full bridge and a resistor connected in series, wherein the thyristor type H full bridge consists of four groups of thyristors, every two groups areconnected in series symmetrically left and right, and the central position is connected by a capacitor. The resistor energy consumption-based high-voltage direct current system phase commutation failure defensive apparatus provided by the invention is connected on the side, close to a converter, of a high-voltage direct current power transmission system; in case of a fault, the resistor is input to consume energy, so that the system phase commutation failure defensive capability can be improved; in addition, when a resistor branch works as normal, the capacitor is not input for use, so that alarge amount of harmonic is not generated; meanwhile, after the fault is finished, the thyristors can be switched off reliably to remove the resistor branch; and in addition, automatic charging of thecapacitor can be realized without needing an external power supply.

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.

The invention relates to a system and a method of analyzing the influence of AC transient voltage on a DC control protection system. The system comprises an AC system transient voltage acquisition module used for collecting an AC system transient process, a characteristic parameter extraction module used for extracting the characteristic parameters of AC transient voltage according to the acquired AC system transient process, a DC system influence function acquisition module used for acquiring a DC system influence function according to the characteristic parameters, and a DC system optimization module used for generating the control protection logic and parameters of an optimized DC control protection system according to the DC system influence function. Compared with the prior art, the system and the method have the advantages of convenience, reliable analysis result, and the like.

The invention provides an LCC-HVDC topological structure into which controllable sub-modules are connected in series. According to the topological structure, the controllable sub-modules are connected to six valve arms of a six-impulse current converter in series, the working states of the controllable sub-modules are changed to assist phase converting, and the capability for resisting phase converting failures of a direct current power transmission system is improved. The LCC-HVDC topological structure can improve the capability for resisting the phase converting failures of the direct current power transmission system and cannot give rise to harmonic problems under the normal operation situation.

The invention discloses a coordinated control method for improving a hybrid back-to-back DC system. The method is used for an inverter station of a hybrid back-to-back DC system in which a flexible DC unit and a conventional DC unit operate in parallel. The method includes the following steps: Step 1. In the flexible DC unit The reactive power outer loop controller of the unit and the AC voltage outer loop controller are additionally switched off angle coordination controller; step 2, according to the judgment result of the fault judgment module, the control mode of the flexible DC unit reactive power outer loop control is selected as reactive power A power outer loop controller or an AC voltage outer loop controller; Step 3. Determine the limit of the reactive current reference value and the active current reference value of the current inner loop control of the flexible DC unit according to the judgment result of the fault judgment module. The invention can effectively reduce the probability of phase commutation failure in the hybrid back-to-back DC system, and improve the ability of the system to ride through AC faults.