440 results about "Short circuit ratio" patented technology

An LED driver circuit is provided for protecting one (or more) LEDs connected in series from over-current damages which may result from a short circuit condition. The driver circuit includes a current control circuit for receiving an input signal from a power source and providing a current output for powering the LED. A voltage sensor detects a voltage across the LED. An LED current restriction circuit such as a switching element restricts a current flow into the LED. A short circuit response circuit controls the LED current restriction circuit dependent on a comparison between the voltage detected by the voltage sensor and a predetermined threshold value. When the detected voltage is less than or equal to the threshold value, the response circuit determines a short circuit, and a signal is sent to the current restriction circuit to restrict current flow into the one or more LEDs.

The invention provides an alternating-current brushless generator fault detection method based on an exciter exciting current. The method comprises the following steps: firstly, measuring the direct-current component and each subharmonic amplitude value of the exciter exciting current of a generator set; and then, detecting whether the generator set generates electrical failures or not with a stator winding turn-to-turn short circuit diagnosis algorithm, a rotor winding turn-to-turn short circuit diagnosis algorithm, an exciter fault diagnosis algorithm and a rotary rectifier fault diagnosis algorithm, wherein the electrical failures comprise stator winding turn-to-turn short circuit, rotor winding turn-to-turn short circuit, exciter rotor winding turn-to-turn short circuit, exciter rotor winding interphase short circuit, open circuit of one diode of the rotary rectifier and short circuit of one diode of the rotary rectifier. According to the LabView development fault diagnosis algorithm, various electrical faults can be detected by measuring the exciter exciting current so as to save measurement points, and various invasive sensors do not need to be installed in the generator. The alternating-current brushless generator fault detection method has good instantaneity, and the on-line detection requirement can be satisfied.

The invention relates to the field of the electric system technology, in particular to a net rack optimization method for a multi-direct-current centralized fed receiving end power grid. According to the method, the network voltage supporting capacity of the receiving end power grid, the short-circuit current control effect of the receiving end power grid and the short-circuit current control measure cost of the receiving end power grid are all considered. The method includes the steps of taking the maximum multi-direct-current feeding comprehensive short-circuit ratio, the maximum short-circuit capacity comprehensive margin and the minimum total cost of investment of current limiting measures as three objective functions, building a multi-objective optimized mathematical model which includes the three objective functions and power grid constraint conditions, and utilizing an NSGA-II multi-objective genetic algorithm to carry out the multi-objective optimization method. A result provided through the method is a line unlocking or series reactor added combining scheme, and the power grid can have strong voltage supporting capacity and system stability on the basis of controlling of a short-circuit current through moderate cost. The method has strong adaptability to an existing receiving end power grid optimization scheme.

A 3-in-1 circuit for the protection of huge surge current, short circuit and overload features that the secondary winding of transformer in power supply is used as the secondary power supply for providing current to said protecting circuit when output circuit is shorted, a current detector installed at said secondary winding is used to detect the generation of overload current, and a timer is used to set up the time when the rated huge surge current can be generated to restrict its generation.

A rechargeable battery protection integrated circuit device, includes a short circuit detecting circuit configured to convert a discharge electric current of a rechargeable battery to a voltage value and detect a short circuit state of the rechargeable battery when the converted voltage value is equal to or greater than a designated short circuit detecting voltage; a discharge control terminal configured to output a control signal when the short circuit state is detected by the short circuit detecting circuit, the control signal being configured to stop a discharge of the rechargeable battery; and an overcharge detecting circuit configured to detect an overcharge of the rechargeable battery, wherein the short circuit detecting circuit includes a short circuit detecting voltage change part, the short circuit detecting voltage change part being configured to change the short circuit detecting voltage when the overcharge is detected by the overcharge detecting circuit.

The invention discloses a low voltage ride-through control method of a doubly fed induction aero-generator, which is used when a power network has short circuit faults. The control method is characterized in that a rotor exciting voltage positive-sequence control current and a rotor exciting voltage negative-sequence control signal are respectively formed through limiting a rotor slip frequency current and a rotor (2-s) rated frequency current when the power network has faults, and a generator is utilized for realizing the attenuation of stator flux transient DC components and reducing the rotor side influences of the stator flux transient components, positive-sequence components and negative-sequence components. The control method has the advantages that no hardware protecting device is required to be added; under the condition that the power network has symmetrical and asymmetrical faults, the overcurrent occurrence of the rotor can be effectively restrained, and the safe operations of the generator and a rotor exciting converter are protected; in the process that the power network has the faults, the transient generator impact to the power network and a mechanical system can be effectively reduced; the normal operation of the generator can be fast recovered after the faults are removed, and the timely support to the power network can be realized.

The invention provides a method that the system strength and the degree of impact on a system due to a fault are measured through the direct current multi-infeed short circuit ratio after the direct current receiving end grid is failed and a dynamic reactive power compensation configuration point can be ensured, namely, a selection method of the dynamic reactive power compensation configuration point. The selection method of the dynamic reactive power compensation configuration point comprises the following steps: building a mold; ensuring a contact line of a direct current receiving system, a direct current receiving inverter station and an alternating current system and enumerating and predicating system status collection after fault; calculating the direct current multi-infeed short circuit ratio; predicating the weak point of voltage stability; conducting simulation verification. When the result of the simulation verification is the weak point of the voltage stability, a dynamic reactive power compensation device is configured. By means of consideration of the state of the system after the fault and the influence of the fault on the system, the selection method of the dynamic reactive power compensation configuration point compensates the influence of the multi-infeed short circuit which is used as an index obtained through a static calculation on the fault transient state procedure and on the system and overcomes the defect that consideration of the status of the system after the fault is not enough, and the calculation is simple and convenient.

The invention provides a method for judging whether continuous phase changing of a direct-current system fails on basis of short-circuit ratio dynamic tracking. The method includes the following steps of calculating the ESCR and the MSCR i of an alternating-current system under the condition that the alternating-current system operates normally, calculating the ESCR and the MSCR i of the alternating-current system under the condition that line faults occur and power is cut off, sequencing the line faults, combining the poorest interlocking fault sets, calculating the ESCR 1 and MSCR 1 of the alternating-current system on the condition of interlocking faults, and judging whether phase changing fails. By means of the method, feature analysis is carried out on transient voltage instability accidents which probably exist in existing and planned alternating-current and direct-current hybrid power grids, fault screening and sequencing can be effectively carried out according to hazard degrees of alternating-current faults to stable operation of the direct-current system, by combination of the current transfer situation after the faults, the interlocking fault sets are reasonably built, and failures of continuous phase changing of the direct-current system and received-end power grid voltage instability risks after the faults can be quickly evaluated.

A method for controlling a wind turbine is proposed. The wind turbine is in a wind farm and connected to a point of common coupling that is connected to a utility grid. At least one quantity indicative of a short circuit ratio of the utility grid is measured. A control parameter of a control system controlling the wind turbine and the wind farm is adjusted. based on the measured value of the quantity.

The invention discloses a multi-infeed extra-high voltage power grid transverter wattless configuration method based on a short-circuit ratio. The extra-high voltage power grid transverter wattless configuration method comprises steps of 1) determining an object grid structure to be analyzed and related parameters, 2) arranging operation modes of an electric power system, 3) selecting a specific operation mode to calculate system load flows under different DC control modes, 4) calculating a multi-infeed short circuit ratio according to a load flow calculation result, 5) calculating a multi-infeed DC node voltage comprehensive improvement index, 6) determining a candidate node of the multi-infeed extra-high voltage DC power grid transverter wattless configuration n according to the multi-infeed DC node comprehensive improvement index, and 7) programming a single objective function optimization program according to an objective function to determine a wattless compensation capacity. The extra-high voltage power grid transverter wattless configuration method guarantees to reduce the operation cost of the power grid, guarantee the power grid to safely, reliably, economically, and efficiently operate, has significance and provides technical basis to planning design and operation control of the mmulti-infeed high voltage DC power grid.

The invention discloses a voltage stability assessment method for a multi-infeed AC/DC hybrid power system. On the basis of a multi-infeed effective short circuit ratio considering shunt capacitor compensation, a reactive power conversion factor is adopted for describing an influence degree on voltage of a DC system by a shunt capacitor compensation point in an AC system, a conversion method is adopted for acquiring reactive power influence quantity on the DC system by a shunt capacitor connected with each compensation point in the AC system, reactive power influence quantities on the DC system by all shunt capacitor compensation points in the system are accumulated, and bad influences on voltage stability of the DC system by whole system shunt compensation are acquired. According to the whole system reactive power influence quantities, the effective short circuit ratio is acquired, influences included in shunt capacitor compensation are further acquired, and stability of the power system is assessed according to the effective short circuit ratio. Compared with the current AC/DC hybrid power system voltage stability assessment method on the basis of the multi-infeed effective short circuit ratio, the method provided by the invention has high accuracy, and provides a basis for planning and operation of a multi-DC infeed power grid system.

The invention discloses an electric electronic multi-infeed power system low-interference stability evaluation method. An electric electronic equipment reference capacity diagonal matrix is obtained by electric electronic equipment parameters in an electric electronic multi-infeed power system, the matrix is converted into an inverse matrix, a receiving-end AC power grid obtains an equivalent admittance matrix through Thevenin equivalence, and an extended Jacobian matrix is obtained by multiplying the inverse matrix by the equivalent admittance matrix; according to a feature value of the extended Jacobian matrix, the electric electronic multi-infeed power system is equivalent to multiple electric electronic single-infeed power systems, and a generalized short circuit ratio of the electric electronic multi-infeed power system is obtained; and according to the generalized short circuit ratio of the electric electronic multi-infeed power system, low-interference stability is determined. According to the invention, a newly defined generalized short circuit ratio is brought forward, the physical mechanism is clear, and the method can be applied to low-interference stability evaluation of the electric electronic multi-infeed power system and enables the electric electronic multi-infeed power system to run stably.

The invention relates to a multiple-DC(direct current)-droppoint selection method based on multiple feed-in short circuit ratios, which comprises the following steps of: calculating the multiple feed-in short circuit ratio set M, determining a multiple-DC(direct current)-droppoint scheme, calculating integrated indexes of the scheme, calculating the balance indexes of the scheme, calculating interference indexes of the scheme, standardizing data results of an index matrix, formulating a multiple-DC-droppoint selection strategy, calculating assessed values, comparing the assessed values, selecting the optimal multiple-DC-droppoint scheme under the condition of an AC(alternating current) grid structure, adjusting the AC grid structure, returning to the first step, and comparing the optimal multiple-DC-droppoint schemes under the condition of the AC grid structure. The multiple-DC-droppoint selection method provides assessment indexes and technical basis for the planning and the design of a multiple-DC feed-in power grid, and has the characteristics of simpleness, practical use and strong operability.

The invention discloses a method for analyzing operation characteristics of a rectifying station connected with alternating current systems with different intensities in the technical field of high-voltage and direct-current transmission operation and control. The method comprises the first step of establishing a simplified model in which an alternating current system is interactive with a direct current system and introducing the short-circuit ratio concept to represent the intensities of the alternating current systems, the second step of establishing a mathematic model of the alternating current system and the direct current system and initializing variables in the mathematic model, the third step of solving an equation set obtained in the second step to obtain the operation characteristics of the rectifying station connected to the alternating current systems with different intensities. The simple equivalence is carried out on the alternating current systems through the Thevenin equivalent method, the relation between the short-circuit ratio representing the intensities of the alternating current systems and the equivalent impedance module value is established, the intensities of the alternating current systems can be conveniently modified, and an operation characteristic curve of the rectifying station connected to the alternating current systems with different intensities is obtained by solving the equation set describing the operation characteristics of the rectifying station. A new idea is provided for studying the transmission capability and the stability of a direct current power transmission system.

An output overcurrent short circuit protection device for a high power contravarient equipment relates to AC inverse power source protection field including output current real time detecting unit, analog signal digitalized unit, software judgement current step control and protection unit, transient excess-current impulse judgement unit, excess-current protection and automatic restoring unit after overshoot, continuous excess current or short protection unit. This invention can finish excess-current or output short protection for large power inverse output equipment.

The invention discloses a secondary startup control circuit and a switching power supply. The secondary startup control circuit comprises an under-voltage lock, a startup state register, an electrified restorer, an oscillator, a delay counter and a logic and gate. The circuit can reduce AC input power when secondary output of the switching power supply is in short circuit, enhance safety and reliability of the switching power supply, and save energy.

The invention discloses a power battery high voltage relay control circuit. The power battery high voltage relay control circuit is characterized by comprising a high side switch control circuit and alow side switch control circuit. The power battery high voltage relay control circuit comprises the high side switch control circuit and the low side switch control circuit, wherein the high side switch control circuit and the low side switch control circuit jointly control on or off of a high voltage relay, both the high side switch control circuit and the low side switch control circuit have adiagnosis circuit, so that fault diagnosis of a high side switch and a low side switch is realized according to a relationship between a fault diagnosis signal voltage and a diagnosis threshold voltage, faults like open circuit, short circuit to ground and short circuit to power supply can be determined and distinguished, and fault diagnosis coverage reaches up to 99%. Hardware architecture measurement and random hardware failure rate indexes meet security targets of security integrity level ASIL-C or ASIL-D.

A circuit and method is disclosed for measuring the resistance of a resistive sensor, such as a PTC or NTC temperature sensor used for monitoring the temperature of the windings of an electric motor. The measurement circuit is based on an electronic circuit in which conductors from a sensor located in the object to be monitored are connected to an amplifier circuit in a feedback configuration that reduces the DC level supplied to the voltage divider when the sensor resistance increases. The measured signal is amplified and, using a comparator to compare it with the output voltage of a sawtooth generator, a continuous PWM (Pulse Width Modulation) signal is generated and transmitted in digital format to a SELV electronic circuit, for example through an opto-isolator. The essentially logarithmic signal amplification makes it possible to reliably distinguish between a short circuit in the sensor circuit and low values of sensor resistance.

A wind turbine park (242) connected to a transmission system (234). The wind turbine park includes a component (230) for determining a short circuit ratio and based thereon for determining a parameter adjustment recipe, and a controller (238) for controlling an output of the wind turbine park, the controller (238) executing a control algorithm using a determined parameter adjustment recipe, the determined parameter adjustment recipe responsive to the short circuit ratio and determined within the component (230) or within the controller (238).

The invention discloses a BOOST circuit with a short circuit protection function, comprising a volt current condenser (VCC), an output end (OUT), a BOOST circuit module, a current or voltage sampling circuit module and a short circuit protection circuit module, wherein the input end of the BOOST circuit module is connected with the VCC, and the output end of the BOOST circuit module is connected with the negative pole of a second voltage regulator diode D2 and the short circuit protection circuit module; the positive pole of the second voltage regulator diode D2 is connected with one end of the current or voltage sampling circuit module; and the other end of the current or voltage sampling circuit module is connected with one end of a sixth resistance R6; and the other end of the sixth resistance R6 is connected with the VCC. By adopting the short circuit protection circuit in the BOOST circuit, the short circuit protection of an output port to a power supply and the earth can be realized under an open circuit state or a load state, and the normal work can be restored without electrification once again after fault removal.