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

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 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 provides a coordinated control method and device for a synchronous phase modifier and LCC-HVDC (line-commutated-converter high voltage direct current). According to the coordinated control method and device, a fault judgment module is used to judge whether a fault occurs in an alternating current system, if the fault occurs in the alternating current system, turn-off angle deviationis calculated according to the turn-off angle of the LCC-HVDC; voltage deviation is determined according to the turn-off angle deviation, and the control input quantity of the synchronous phase modifier is calculated according to the voltage deviation; the excitation voltage of the synchronous phase modifier is determined according to the control input quantity of the synchronous phase modifier; and the coordinated control of the synchronous phase modifier and the LCC-HVDC is realized according to the excitation voltage of the synchronous phase modifier; and the capacity of the LCC-HVDC to resist commutation failures can be improved through the coordinated control of the synchronous phase modifier and LCC-HVDC. With the coordinated control method and device of the invention adopted, the capacity of the LCC-HVDC to resist commutation failures can be improved by means of the capability of the reactive power of the synchronous phase modifier to stabilize the voltage of a bus-bar, and theprobability of the commutation failure of the LCC HVDC can be decreased.

The invention discloses an inverter-side control method and system based on an extra high voltage direct-current transmission project. The method comprises the steps of additionally adding an extinction angle modulation module at the inverter-side control system of a direct-current transmission system, increasing a reactive compensation capacity of an inverter station and setting an extinction angle given value when the direct-current transmission system is in a steady state; respectively obtaining second alternating current bus voltage values V0 and Vac at an inverter side when the system isin the steady state and goes wrong; judging whether the extinction angle given value is changed or not, and starting the extinction angle modulation module when a deviation between V0 and Vac is not in the range of +/-5%; and stopping modulation until the second bus voltage level restores to the given range, and restoring the original extinction angle set value. According to the method, the probability of commutation failures of a direct current can be reduced by additionally adding the extinction angle modulation module, the fluctuation range of the alternating current bus voltage is inhibited, the recovery speed of a direct current power is accelerated and the stability of the alternating current power grid voltage is improved.

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 discloses a series voltage injection-based current-type high voltage direct current transmission (LCC-HVDC) system commutation failure suppression method. The core of the method is thatthree-phase voltage series injection is carried out between the inverter of the LCC-HVDC and a receiving-end AC system to compensate dynamic fall of the voltage of the receiving-end AC system, seriesvoltage injection is realized through a unified power flow controller, a parallel transformer of the unified power flow controller is parallelly connected at the AC system side, and a series transformer is serially connected at the inverter side of the LCC-HVDC. A dynamic voltage series injection control algorithm is designed for the series converter of the unified power flow controller, so as toenable the three-phase voltage generated by the series converter of the unified power flow controller to dynamically compensate the dynamic fall of the voltage at the AC system side through the seriestransformer. Voltage distortion and voltage fall at the LCC-HVDC inverter side can be further reduced, and finally, the LCC-HVDC inverter commutation failure possibility is reduced.

The invention provides a thyristor full-bridge energy consumption module for inhibiting LCC-HVDC (Low Voltage Current Converter-High Voltage Direct Current) commutation failure. Each module consists of four groups of thyristors, capacitors and energy-consuming resistors, every two groups of thyristors are connected in series and are bilaterally symmetrical, the centers of the thyristors are connected by the capacitors, and the resistors are connected with one group of thyristors in series. The thyristor full-bridge energy consumption module for suppressing the LCC-HVDC commutation failure is connected in series in an inverter side converter valve bridge arm of a high-voltage direct-current power transmission system; when a system breaks down, resistance energy consumption is input, attenuation of fault current is accelerated, the commutation failure resisting capacity of the system is improved, a resistance energy consumption branch is bypassed when the system operates normally, and active loss cannot be generated.

The invention discloses a method for inhibiting simultaneous phase change failure of two layers of inverters, and a controller; the method comprises the following steps of acquiring a difference valuebetween a turn-off angle preset value and a turn-off angle operation value of a first-layer inverter; obtaining a turn-off angle additional value according to the difference value; and under a condition that a compensation condition is met, enabling the turn-off angle additional value to be compensated to a second-layer inverter. According to the technical scheme provided by the invention, the turn-off angle operation value of the other layer of inverter can be dynamically compensated according to the situation of the turn-off angle of the inverter which suffers from phase change failure caused by fault of a connected alternating current system, so that the possibility that the two-layer inverters connected with the alternating-current system in a direct-current power transmission systemare subjected to phase change failure simultaneously is lowered.

The invention discloses a multi-feed-in direct-current power transmission system control optimization method and device and a storage medium, and the method comprises the following steps: calculatinga direct-current voltage correction coefficient of a feed-in system according to a voltage measurement value of a direct-current side of each feed-in system and a voltage rated value of the direct-current side of each feed-in system; calculating a multi-feed-in mutual influence factor according to the voltage value of each DC system current conversion bus, judging whether each multi-feed-in mutualinfluence factor meets a preset interaction intensity condition or not, and obtaining a DC voltage setting value of each feed-in system low-voltage current limiting link according to a judgment result; switching the voltage value of the direct-current side of each feed-in system into a direct-current voltage setting value when any one of the feed-in systems is in an alternating current fault state; detecting the feed-in system is in a normal operation state, and enabling the direct current sides of the feed-in systems to operate according to the corresponding voltage rated values, so that theprobability of commutation failure of non-fault systems at the same time can be effectively reduced, and the commutation capability and the fault recovery capability of the multi-feed-in direct current power transmission system are improved on the whole.