49results about How to "Avoid commutation failure" patented technology

The invention discloses a commutation failure detection method based on a commutating current time area index. The commutation failure detection method is characterized in that a conception of the commutating current time area is provided for a commutation process of an inversion side of a convertor station for a direct current system according to an area defined by commutating current and a timeaxis; the physical significance of the commutation process is disclosed in terms of energy by a commutating current time area method; corresponding criteria are provided according to the magnitude ofthe commutating current time area; and the criteria can be used as a new index for correctly judging whether the inversion side of the convertor station has commutation failure or not.

The invention discloses a hybrid direct-current transmission converter. The hybrid direct-current transmission converter is provided with four topological structures which are series connection circuits formed by combining anodes and cathodes of current source type valve group units and positive electrodes and negative electrodes of voltage source type valve group units in different modes. Each current source type valve group unit only comprises a current source type valve group or comprises a current source type valve group and a bypass switch or comprises a current source type valve group, a bypass switch and a disconnecting link assembly. Each voltage source type valve group unit only comprises a voltage source type valve group or comprises a voltage source type valve group and a bypass circuit or comprises a voltage source type valve group, a bypass circuit and a disconnecting link assembly. A direct-current transmission device composed of the hybrid direct-current transmission converter effectively solves the problem of commutation failures of a direct-current transmission system based on thyristors and the problem of direct-current faults of a direct-current transmission system based on a voltage source converter, and has the advantages that loss is low, a reactive compensation device is not needed or a small number of reactive compensation devices are needed, and the direct-current transmission device can be connected into a passive alternating-current system and has the inverse power output function.

The invention provides a method for high-voltage direct-current transmission commutation failure prevention. The method comprises the following steps that: whether commutation failure caused by alternating current-side faults occurs or not is judged; a commutation failure prevention system outputs rectangular wave commands to a control protection system; and rectangular waves are subtracted from trigger angle commands in the control protection system, and a thyristor is triggered in advance. With the method adopted, commutation failure can be prevented when grounding faults or interphase short-circuit faults occur on an alternating current system, and the reduction amplitude of direct-current voltage and power transmission can be lowered after the faults occur.

The invention provides a dual feed-in DC transmission method, belonging to the distribution technical field. The invention is used for solving the operation reliability of the high-voltage DC transmission. The technical proposal is that an HVDC subsystem and a VSC-HVDC subsystem are connected on the same generatrix of a transmission AC system in parallel or respectively connected with two substations which are very closely connected with each other electrically; the HVDC subsystem consists of an AC system S1 at a sending end, a system resistance Zs1, a converter transformer Ts1, an HVDC converter and a transmission line DC1, and a converter transformer (Tr1); the VSC-HVDC subsystem consists of an AC system S2 at the sending end, a system resistance Zs2, a converter transformer Ts, a VSC-HVDC converter and a transmission line DC2, and a converter transformer (Tr2). Compared with the existing HVDC system, the invention can effectively reduce the possibility that steering failure occurs to the HVDC sub-system inverter, and improves the operation reliability of the HVDC subsystem.

Disclosed is a multi-degree-of-freedom dynamic control method of an inverter bridge advance commutation angle of a static frequency converter starter, comprising the steps of: the detection of motor operating frequency, main circuit direct current of a static frequency converter, terminal voltage, and the calculation of the inverter bridge advance commutation angle, Beta=cos<-1>(cos(360f(t(off)+t0))-(square root 2X(C)I(d)/U))+Xi. The control method enables the inverter bridge advance commutation angle to carry on the dynamic control with the change of motor operating frequency, of main circuit direct current of the static frequency converter and of terminal voltage in the process of frequency conversion start, and causes a considerable reduction in the inverter bridge advance commutation angle while ensuring the constant of the arc extinguishing time of the inverter bridge commutation, so as to reduce the main circuit output direct current of the frequency converter and increase the power factor of the inverter bridge and the start efficiency of the static frequency converter starter.

The invention discloses a control and monitor method of a silicon controlled rectifier converter valve for extreme high voltage direct current power transmission. The control and monitor method of the silicon controlled rectifier converter valve for the extreme high voltage direct current power transmission includes: monitoring work status of the silicon controlled rectifier converter valve through a silicon controlled rectifier high potential electronic unit TEU; reporting the work status back to a valve base electronic equipment cabinet VBE through a high voltage optical fiber; for triggering a control signal, sending light trigger pulse signals through the valve base electronic equipment cabinet VBE so as to control the silicon controlled rectifier converter valve; for performing monitor protection, initiatively generating trigger protection through the silicon controlled rectifier high potential electronic unit TEU. Single pulses are adopted in the light trigger pulse signals, and coding standard design of all the pulses adopts the single pulse mode, and therefore pulse coding is simple, the problems that a silicon controlled rectifier is always in a conducting state due to recognition incorrectness of a pulse sequence formed by a plurality of continuous pulses, and then inverting failure, protection failure in a reverse recovery period and the like are caused by the silicon controlled rectifier are solved, and the control and monitor method of the silicon controlled rectifier converter valve for the extreme high voltage direct current power transmission is high in timeliness and reliability.

The invention provides a method for prejudging phase change failure of a converter valve. The method includes the steps of calculating an inverter side alternating current voltage amplitude per unit value and a direct current per unit value, calculating a fire angle upper limit of the converter valve on the inverter side and prejudging whether phase change is failed. According to the method for prejudging the phase change failure of the converter valve, phase change failure caused by inverter side alternating current system failure or direct current system overloading and other common reasons can be accurately judged, and information is provided for preventing the phase change failure. Judgment can be carried out quickly, phase change failure judgment information can be obtained in 1ms after the failure occurs, and measures can be quickly taken to prevent the phase change failure. Judgment is accurate, the calculation method of the fire angle upper limit is obtained through theoretical deduction, and the phase change failure can be accurately judged through the method.

The invention provides a control method and device of a multi-split air conditioning system. The control method of the multi-split air conditioning system comprises the steps that four-way valve reversing requirements of the multi-split air conditioning system are obtained; high pressure and low pressure of the multi-split air conditioning system are obtained, wherein the high pressure is the pressure between an air outlet of a compressor and the air outlet ends of four-way valves of the multi-split air conditioning system, and the low pressure is the pressure between the air suction ends of the four-way valves and an air suction opening of the compressor; the pressure difference between the high pressure and the low pressure of the multi-split air conditioning system is calculated; and the running frequency of the compressor and the opening of throttling devices of the multi-split air conditioning system are subjected to a first-time adjustment and a second-time adjustment. Thus, through the first-time adjustment and the second-time adjustment to the running frequency of the compressor and the opening of throttling devices of the multi-split air conditioning system, the pressure difference between the high pressure and the low pressure of the multi-split air conditioning system is improved, and the reversing failure of the four-way valve in the multi-split air conditioning system is avoided.

The invention discloses an energy storage type static synchronous compensation device and a direct-current transmission commutation failure suppression method, The large-capacity energy-storage type static synchronous compensation device is composed of a plurality of energy-storage type static synchronous compensators which are connected in parallel. The energy-storage type static synchronous compensator (1) comprises an energy storage unit, a DC/DC converter, a capacitor and a voltage source converter. The energy storage static synchronous compensator is connected to the AC bus of the receiving end converter station of the UHVDC transmission system through a transformer. The inductor is serially connected to the AC bus bar of the energy storage type static synchronous compensation deviceand the receiving end converter station, The large-capacity energy storage type static synchronous compensation device operates in a voltage source mode, and can provide sufficient voltage support forthe receiving end AC bus bar of the receiving end converter station to ensure normal commutation, thereby restraining commutation failure caused by fault of the receiving end AC power network and preventing cascading failure caused by commutation failure to the UHVDC transmission system.

The invention discloses a secondary commutation failure determination method and system; the method comprises the following steps: using an equivalent fault method to obtain an extinction angle of each inversion station after the fault occurs; determining the minimum extinction angle according to the extinction angle of each inversion station, the inversion station with the minimum extinction angle, and a commutation bus on which the inversion station with the minimum extinction angle is located; determining whether the minimum extinction angle is smaller than or equal to a critical extinctionangle or not; if yes, determining the inversion station with the minimum extinction angle has a commutation failure, and obtaining the voltage of the commutation bus on which the inversion station with the minimum extinction angle is located; determining whether the voltage of the commutation bus on which the inversion station with the minimum extinction angle is located is smaller than or equalto a commutation bus voltage critical value or not; if not, determining the commutation failure type of the inversion station with the minimum extinction angle is the secondary commutation failure. The method and system can determine the commutation failure type as the secondary commutation failure, thus improving the commutation failure prevention effect.

The invention provides a current source type phase modulator variable frequency starting commutation lead angle piecewise control method which comprises the concrete steps that a commutation lead angle of 30 degrees is used when a current source type phase modulator is started; commutation failure is judged through a detection system, the commutation lead angle of 30 degrees is maintained if the commutation failure is not detected, and the closest thyristor seamless switching time point t0 is found when the commutation failure is detected; and the commutation lead angle is switched to 60 degrees. The method is simple and convenient in practical application without redundant algorithm control; the problem of thyristor commutation failure can be effectively avoided, the starting efficiency of the phase modulator can be improved, the starting time can be shortened, the whole control process only needs one time of switching of the commutation lead angle and the redundancy of thyristor operation times can be avoided; and commutation lead angle piecewise control is used so as to have high practical engineering application value.

The invention discloses a commutation failure prediction control method and device based on a direct-current (DC) electric quantity, which is used to prevent the phenomenon that in a high-voltage or ultrahigh-voltage DC system, failure of a DC side of some pole causes commutation failure of a healthy pole through mutual inductance between the two poles. The method is characterized in that a suddenincrement (or sudden increments) of an absolute value (or absolute values) of the DC voltage and/or the DC current of a current pole in some time window is/are detected in a real-time manner; and when the sudden increment(s) of the absolute value(s) of the DC voltage and/or the DC current exceeds/exceed a preset threshold (or preset thresholds), an extinction angle of an inversion side converterof the current pole is enlarged through a DC control system, so that the commutation failure of the current pole is prevented. The method provided by the invention is applicable for prediction and prevention of the commutation failure of the healthy pole caused by the failure of the DC side of the other pole, and has the advantages of high response speed and high action accuracy.

The invention relates to a high-voltage direct-current commutation failure control method, device and equipment for quickly detecting an alternating-current fault, which are applied to a high-voltage direct-current power transmission system. According to the invention, a single-phase fault occurrence phase, namely a fault phase, is determined according to a three-phase voltage of an alternating-current side bus of a high-voltage direct-current power transmission system, the maximum phase offset between a phase voltage and a phase positive sequence voltage at the moment is solved according to the fault phase, a commutation angle with the maximum offset and a synchronous phase angle output by the phase-locked loop of the high-voltage direct-current power transmission system are added to obtain a corrected synchronous phase angle, and the trigger angle of the fault phase is adjusted or corrected by correcting the synchronous phase angle to achieve the effect of correcting the actual trigger angle; and compared with the prior art, the high-voltage direct-current commutation failure control method for quickly detecting the alternating-current fault has the advantages that the fault phase can be quickly judged, a commutation failure result caused by an output error of a phase-locked loop of the high-voltage direct-current power transmission system in an alternating-current fault period is effectively avoided, and the problem of commutation failure of an existing high-voltage direct-current power transmission system is solved.

The invention relates to a method for controlling at least three power converters (2), which can be controlled by a rectifier (6) or an inverter (8) and are connected together by a direct current network (7), in the region of power distribution and power transmission. The aim of the invention is to provide a method which has a simple structure and also works in a reliable manner. As a result, a measuring direct current voltage (Udc_l, ... Udc_rr; Udc_il ... Udc_ii) and a measuring direct current (Idc__rl, ... Idc_rr; Idc__il, ... Idc_ii) are measured on each power converter and respectively, transmitted to the respective rectifier control (11) and/or inverter control (12), and a rectifier desired direct power and/or inverter desired direct power (Pdco_rl, ... Pdco-rr,- Pdco_il, ... Pdco_ii) is determined for each power converter. The total of all desired direct powers (Pdco_rl, ...; Pdco_rr; Pdco-il, ... Pdco_ii) is equal to zero, and a desired direct voltage (¿˜dco_rl, ... Udco_rr; Udco__il, ... Udco_ii) is determined from each desired direct power, the smallest inverter desired direct voltage (Udco_il, ... Udco_ii) of all connected inverters (8) is fixed as minimal direct voltage (Udco) by means of a minimal direct voltage and the desired direct voltage, a desired direct current (Idco_rl; ... Idco_rr; Idco_il, ... Idco_ii) is formed from the minimal voltage (Udco) and the measuring direct voltage, a differential direct voltage (du_rl, ... du_rr, du_il, ... du_ii) is formed from the minimal voltage (Udco) and the differential direct current (di_rl; ... di_rr; di_il, ... di_ii) is formed from the desired direct current and the measuring direct current.

It provides a control system for LCC of an HVDC system and a control method therefor. The control system includes: a first measurement unit (20) being configured to provide a current magnitude measurement indicative of a magnitude of DC current of the HVDC system; and a controller (21) being configured to increase a first extinction angle at which the controlled LCC operates to a second extinctionangle in response to that the current magnitude measurement exceeds a current reference level in order to avoid commutation failure of the controlled LCC. By using the solutions according to the HVDCsystem with increase of the extinction angle of the LCC, it is possible to decrease the probability of commutation failures caused by a rapid rise of the DC current of the HVDC system. The overall ACand DC power system reliability and stability are improved.

The invention discloses a commutation failure prevention and control optimization method and system based on SVM-PSO, and the method comprises: taking the minimum reactive control quantity and the minimum number of fault nodes triggering commutation failure as a target function, considering the steady-state safety constraint, and building a multi-target optimization function for optimizing the reactive output and reactive compensation capacity of a generator; and solving the multi-objective optimization function by adopting an improved particle swarm algorithm with parameter adaptability to obtain optimal reactive output and reactive compensation capacity of the generator. The method has the beneficial effects that the support vector machine agent model is constructed to evaluate the commutation result, so that the particle adaptation value is quickly solved.

The invention discloses an active commutation hybrid converter topological structure and a control method thereof. The active commutation hybrid converter topological structure comprises a three-phase six-bridge arm circuit, an upper bridge arm auxiliary valve, a lower bridge arm auxiliary valve, a controllable switch module and a selection unit, wherein each phase of bridge arm circuit of the three-phase six-bridge arm circuit comprises an upper bridge arm and a lower bridge arm, and the upper bridge arm or the lower bridge arm is provided with a thyristor valve; the first end of the upper bridge arm auxiliary valve is connected with the cathode end of the thyristor valve of each phase of each upper bridge arm; the first end of the lower bridge arm auxiliary valve is connected with the anode end of the thyristor valve of each phase of each lower bridge arm; the first end of the controllable switch module is connected with the second end of the upper bridge arm auxiliary valve and the second end of the lower bridge arm auxiliary valve; the selection unit comprises two connecting ends and at least two selection ends, and the connecting ends are connected with the second end of the controllable switch module; and the first selection end is connected with the anode end of the thyristor valve of each upper bridge arm, and the second selection end is connected with the cathode end of the thyristor valve of each lower bridge arm. By implementing the active commutation hybrid converter topological structure and the control method, the occurrence of commutation failure is avoided, and the stability and safety of power grid operation are ensured.

The invention provides an extra-high-voltage converter transformer with a filtering function. A making method of the extra-high-voltage converter transformer with the filtering function comprises thefollowing steps that S1, the converter transformer of an extra-high-voltage direct-current power transmission system serves as an object, and the magnetic circuit saturation condition and the harmoniccirculation condition of the converter transformer are taken into consideration, wherein a circuit magnetic circuit analysis structure of a single iron core column is included; and S2, the magnetic circuit distribution and a circuit structure of the converter transformer are taken into consideration, and a four-winding type converter transformer electromagnetic coupling circuit and an electromagnetic coupling circuit equivalent circuit model according to an extra-high voltage direct current power transmission operation scene. The extra-high-voltage converter transformer with the filtering function is suitable for an extra-high-voltage direct-current power transmission system, and has a harmonic filtering function while having voltage matching and electrical isolation functions of a commonconverter transformer, so the grid-side harmonic and reactive burdens of an existing extra-high-voltage direct-current power transmission project converter transformer are reduced, and the reliability of the extra-high-voltage direct-current power transmission project is improved; and thus, the investment of a grid-side alternating-current filter is reduced.

The invention discloses a hybrid converter topological structure and a control method thereof. The hybrid converter topological structure comprises at least one phase of main branch circuit and at least one phase of auxiliary branch circuit, wherein each phase of the main branch circuit comprises an upper bridge arm main branch circuit and a lower bridge arm main branch circuit, each upper bridge arm main branch circuit is provided with a first thyristor valve, and each lower bridge arm main branch circuit is provided with a second thyristor valve; each phase of the auxiliary branch circuit comprises an upper bridge arm auxiliary branch circuit and a lower bridge arm auxiliary branch circuit, each upper bridge arm auxiliary branch circuit is provided with a first auxiliary reversing valve, and each lower bridge arm auxiliary branch circuit is provided with a second auxiliary reversing valve; the auxiliary branch circuit is connected in parallel with the main branch circuit and is used for assisting the main branch circuit to perform forced commutation when the commutation of the main branch circuit fails; and a switchable valve is arranged on the main branch circuit or the auxiliary branch circuit and is used for transferring the current of the main branch circuit to the auxiliary branch circuit during forced commutation. By implementing the hybrid converter topological structure and the control method thereof, the reliable turn-off of the main branch circuit and the active commutation of each phase of bridge arm are realized, the commutation failure is avoided, and the stable and safe operation of a power grid is ensured.

The invention relates to the technical field of power electronics, in particular to a HVDC converter and a control method thereof, aiming at solving the technical problem of how to overcome the commutation failure and fault crossing failure of the converter. For this purpose, the invention provides a high-voltage direct-current transmission converter and a control method thereof. Specifically, theHVDC converter mainly comprises a first converter circuit formed by cascading a plurality of power sub-modules, The first converter circuit can output a multi-level AC pulse voltage, thereby drivingthe half-controlled power electronic device in the second converter circuit to be turned on or off actively or passively, and realizing fault crossing when a fault occurs on the high-voltage AC voltage source side. In this process, the commutation failure of HVDC converter can be effectively avoided without considering the voltage phase of HVAC voltage source side.

The invention discloses a four-way reversing valve and a heat exchange system comprising the same. The four-way reversing valve comprises a valve body; a valve element is arranged inside the valve body; an air suction pipe opening, an air exhaust pipe opening, a first connecting pipe opening and a second connecting pipe opening are formed in the valve body; the valve element can move along an inner cavity of the valve body; a first cavity is formed by the left side of the valve body and the valve element; a second cavity is formed by the right side of the valve body and the valve element; a connecting rod is horizontally arranged on one side, connected with the first cavity, of the valve element; one end of the connecting rod is rotationally connected with an inner crank; one end of the inner crank is rotationally connected with a control shaft; a linear actuator is arranged in the position, close to the first connecting pipe opening, of the outer side of the valve body; an outer crankis rotationally connected to a front-end extending shaft of the linear actuator; and the control shaft penetrates through the valve body outwards to be rotationally connected with the outer crank. Bythe aid of the four-way reversing valve and the heat exchange system comprising the same, the problem of ineffective reversing caused by the fact that valve elements are relatively heavy and are relatively difficult to push and high-pressure gas colludes in the prior art is solved.

The invention relates to a starting control method and device of a power transmission system, a flexible inverter station, the power transmission system and a storage medium. The method comprises the steps that after the flexible inverter station is controlled to be unlocked, the output electrical parameter of the flexible inverter station is controlled to be a target parameter smaller than a rated electrical parameter; then, the conventional inverter station is controlled to be unlocked, the conventional inverter station is indicated to send an unlocking signal to the conventional rectifier station after being unlocked, the conventional inverter station normally executes phase commutation operating under the target parameters, and the unlocking signal is used for unlocking the conventional rectifier station; that is to say, the method can control the output electrical parameters of the flexible inverter station after the flexible inverter station is unlocked so as to avoid that the power of the flexible inverter station flows to the conventional inverter station too much after the conventional inverter station is unlocked due to the fact that the output electrical parameters of the flexible inverter station are too large. Therefore, by the adoption of the method, the starting efficiency of the power transmission system can be greatly improved.