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467 results about "Capacitive current" patented technology
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Usually electrochemists are interested in the Faraday current that is the current caused by an electrochemical reaction; the capacitive current, caused by physics, is an unwanted side effect. The cause of this current is ions accumulating in front of the electrode. These ions and the electrode’s charged surface form a capacitor.
Probe station thermal chuck with shielding for capacitive current
InactiveUS20070030021A1Semiconductor/solid-state device testing/measurementThermoelectric device with peltier/seeback effectCapacitanceElectricity
To reduce noise in measurements obtained by probing a device supported on surface of a thermal chuck in a probe station, a conductive member is arranged to intercept current coupling the thermal unit of the chuck to the surface supporting the device. The conductive member is capacitively coupled to the thermal unit but free of direct electrical connection thereto.
Owner:FORMFACTOR BEAVERTON INC
Single-phase grounding fault detection and positioning method and system for low-current grounding power distribution network
Power distribution networks of countries such as China and the like mainly adopt a low-current grounding method. Most faults of the low-current grounding power distribution networks are single-phase high-resistance grounding faults and low amplitude of transient capacitive current signals, short duration, and high detection difficulty are generated in a fault process so that an effective fault detection and positioning system is lacked. The invention discloses a fault detection and positioning method and system for a low-current grounding power distribution network. The system includes feeder line monitoring units, a communication terminal and a system master station. A feeder line monitoring unit wirelessly and synchronously triggers the other two phases to transmit data after a suspected grounding fault is detected. The system master station and the communication terminal adopt GPS time service. The communication terminal and the feeder line monitoring units carry out time hack through a time division multiplexing wireless communication network. The system master station collects three-phase feeder line monitoring unit data at a plurality of points through the communication terminal and detects and positions a grounding fault according to calculated zero-sequence voltage and zero-sequence current and issues a fault signal to feeder line monitoring units in front of a fault point on a fault phase so as to carry out fault indication.
Owner:BEIJING INHAND NETWORKS TECH
Intelligent dynamic power distribution network neutral-point grounding method and complete device
ActiveCN103208788AReduce lightning strike arc establishment rateReduce trip rateEmergency protective arrangements for limiting excess voltage/currentCapacitanceTransformer
The invention discloses an intelligent dynamic power distribution network neutral-point grounding method and a complete device. The complete device comprises a grounding transformer (1), an arc suppression loop switch (2), a resistance loop switch (3), an adjustable reactor (4), a damping resistor (5), a damping resistor short-circuit switch (6), a resistor (7), a neutral-point voltage transformer (8) and a computer testing and control system (9). The intelligent dynamic power distribution network neutral-point grounding method and the complete device is technically characterized in that a power distribution network neutral-point grounding mode is dynamically converted from an arc suppression coil grounding mode into a small-resistance grounding mode. When the device is connected to a power grid or a power grid operation mode changes, the device firstly works in the arc suppression coil grounding mode. The device measures capacitive current, adjusts inductive current and enables IL-IC to be smaller than or equal to I delta, wherein the I delta is a preset residual current control value. When a single-phase grounding fault of the power grid occurs, the device outputs the inductive current to perform compensation and arc suppression to grounding fault current. If the fault is an instantaneous fault, the fault is eliminated through the compensation and the arc suppression. If the fault is a permanent fault and the grounding fault is still not eliminated after certain time T, the arc suppression coil grounding is converted into the resistance grounding mode, and a fault line is judged and disconnected by detecting zero-sequence current of feeder lines.
Owner:李景禄
Online monitoring method for DC-link capacitor of three-phase system
ActiveCN105717368AEnables non-intrusive online monitoringAccurate calculationCapacitance measurementsAviationControl signal
The invention provides an online monitoring method for a DC-link capacitor of a three-phase system. The method comprises that voltage of the DC-link capacitor is collected, and a voltage drop curve of the DC-link capacitor is obtained; three-phase output current is collected, and capacitive current is reconstructed according to the three-phase output current; and the capacitance (C) and equivalent serial resistance (ESR) of the DC-link capacitor are obtained according to the voltage drop curve and the capacitive current of the DC-link capacitor. The voltage drop curve and the three-phase output current of the DC-link capacitor as well as control signals of a semiconductor switch are monitored in the process that power equipment as a three-phase frequency converter is switched off, so that the C and ESR of the DC-link capacitor are calculated accurately, and non-invasive online monitoring for the DC-link capacitor of the AC / DC / AC system is realized. The method can be applied to online monitoring for an aluminum electrolytic capacitor, other capacitors as a film capacitor as well as other three-phase systems including a wind power converter, a photovoltaic AC / DC / AC system and a three-phase aviation power system.
Owner:CHONGQING UNIV
Miniaturised Biosensor with Optimized Amperometric Detection
InactiveUS20090178935A1Easy to detectWeather/light/corrosion resistanceMicrobiological testing/measurementCharacteristic lengthEngineering
A method to optimize the amperometric detection in a microsystem consists in limiting the detection to times when the diffusion layer (18-20) of the analyte to detect remains smaller than the microchannel (7) height. The charge detected during the second part of the amperometric measurement (which corresponds to the integral of the measured current over the corresponding time period) can also be considered so as to remove the contribution of the capacitive current and, when applicable, of the current resulting from the reduction or oxidation of the analyte molecules present in a recess above the electrode at the beginning of the detection. A microfluidic amperometric sensor for performing the method comprises at least one microchannel (7) having at least one electrode (15-17), integrated in one wall of the microchannel, and having a characteristic length or radius which is smaller than half the microchannel height.
Owner:BIOMERIEUX SA +1
Lighting power circuit with peak current limiter for EMI filter
Owner:GE LIGHTING SOLUTIONS LLC
Method for extracting resistive current of metal oxide arrester (MOA)
InactiveCN101986164AAvoid errorsGood application effectCurrent/voltage measurementElectrical testingCapacitanceAnti jamming
The invention provides a method for extracting the resistive current of a metal oxide arrester (MOA). The technical scheme comprises the following steps of: acquiring a voltage signal applied to the arrester and leakage current flowing through the MOA and performing fast Fourier transform on the voltage signal to acquire the amplitude and phase of each subharmonic; acquiring a capacitive current signal of which the waveform is the same as that of capacitive current of the arrester and the amplitude is in proportion to that of the capacitive current of the arrester according to a phase relationship between a voltage signal and a current signal on a capacitor and the acquired amplitude and phase of each subharmonic of voltage; and acquiring the resistive current of the arrester according to the principle that the resistive current is orthogonal to the capacitive current of the arrester. The method has a rigorous principle and is convenient to implement; a digital signal has high anti-jamming capability; phase shift is processed by the fast Fourier transform, so even if each subharmonic exists theoretically, errors cannot be generated; and the measurement accuracy of the resistive current can be effectively improved in practical application.
Owner:NORTH CHINA ELECTRIC POWER UNIV (BAODING)
Miniaturised biosensor with optimized amperometric detection
InactiveCN101421616AGood reproducibilityReduce the impact of noiseMaterial electrochemical variablesCapacitanceCharacteristic length
A method to optimize the amperometric detection in a microsystem consists in limiting the detection to times when the diffusion layer (18-20) of the analyte to detect remains smaller than the microchannel (7) height. The charge detected during the second part of the amperometric measurement (which corresponds to the integral of the measured current over the corresponding time period) can also be considered so as to remove the contribution of the capacitive current and, when applicable, of the current resulting from the reduction or oxidation of the analyte molecules present in a recess above the electrode at the beginning of the detection. A microfluidic amperometric sensor for performing the method comprises at least one microchannel (7) having at least one electrode (15-17), integrated in one wall of the microchannel, and having a characteristic length or radius which is smaller than half the microchannel height.
Owner:迪埃诺斯维斯股份有限公司 +1
Method for controlling grid-connected inverter of micro grid based on fuzzy PI algorithm
ActiveCN103956769AIncrease the damping ratioGuaranteed uptimeEfficient power electronics conversionAc-dc conversionControl signalFuzzy pi
The invention discloses a method for controlling a grid-connected inverter of a micro grid based on the fuzzy PI algorithm. The method comprises the steps that (1) the voltage of the current power grid, the output current of the current grid-connected inverter and the capacitive current of a current filter are sampled; (2) the command value of a grid-connected current is determined; (3) the proportionality coefficient and the integral coefficient of a PI controller are adjusted; (4) the command value of the capacitive current of the filter is acquired through the adjusted PI controller; (5) the command value of the output voltage of the grid-connected inverter is acquired through the PI controller; (6) a control signal is generated to control switch-on or switch-off of a switching tube of the grid-connected inverter, and an expected output voltage is generated at the power output end of the grid-connected inverter; (7) the step (1) to the step (6) are repeatedly executed to make the output current of the grid-connected inverter trace the command values all the time. According to the method, by adjusting the control parameter of the PI controller in an on-line mode through the fuzzy algorithm, the output current of the grid-connected inverter can trace a current command signal quickly and accurately.
Owner:HUAZHONG UNIV OF SCI & TECH
Transmission line single-phase grounding fault single-end ranging method
ActiveCN103630798AImprove ranging accuracyHigh utility valueFault locationCapacitanceCable fault location
A transmission line single-phase grounding fault single-end ranging method belongs to the field of power system protection and control. According to the method of the invention, positive, negative and zero sequence voltage and current phasors of a line during the time section between the occurrence of a single phase grounding fault and single phase tripping and the time section between single phase tripping and reclosing are measured at a substation protection installation site and are used as input. The initial value of fault distance is set from 0 to the overall length of the line with delta1 as the step length, and the initial value of transition resistance starts from 1 ohm and increases to 1000 ohms with 1 ohm as the step length. For each combination of the values of fault distance and transition resistance, the equivalent electromotive force values of a system at the opposite end of the line during the time section between the occurrence of the single phase grounding fault and single phase tripping and the time section after single phase tripping are respectively calculated, the sum of absolute errors of the equivalent electromotive force values is calculated, and the fault distance value corresponding to the minimum value of the sum of absolute errors is selected as the fault ranging distance. The method is high in precision, is not affected by distributed capacitive current, transition resistance, load and system impedance and has very high practical values.
Owner:TSINGHUA UNIV
Ground fault detection and localization in an ungrounded or floating DC electrical system
InactiveUS20090147415A1Short-circuit testingEmergency protective arrangements for automatic disconnectionDistribution power systemCapacitive current
An ungrounded or floating DC electrical power distribution system may experience a single line to ground fault. Such a fault may not disrupt operation of the system, but its presence may raise a risk of additional problems if left uncorrected. A system for progressively grounding the ungrounded system may be initiated when a line to ground fault is suspected based on the voltage difference measured to a common chassis point. As grounding through successively lower impedance proceeds, fault current may increase and detection of severity of the line to ground fault may be more readily achieved, thus facilitating localization of the fault. Localization may be achieved through an analysis of direction of capacitive currents in isolatable zones of the system.
Owner:HONEYWELL INT INC
Virtual-capacitor-based power sharing control method for micro-grid inverter parallel connection
ActiveCN105226727ANo need for additional communicationLow costSingle network parallel feeding arrangementsVoltage amplitudePower inverter
The invention discloses a virtual-capacitor-based power sharing control method for micro-grid inverter parallel connection. The method is characterized in that a voltage amplitude value and a phase angle value are obtained by using a power outer ring of a power outer ring control algorithm; and a virtual capacitor algorithm is added to obtain an output voltage amplitude value and a phase angle instruction, and dual-closed-ring control of the output voltage and the capacitive current is carried out. According to the virtual capacitor algorithm, parallel capacitor characteristics of output terminals of inverters are simulated by a control algorithm and the output voltages and reactive powers of the inverters are adjusted; and a virtual capacitance value is obtained by calculation based on outputted reactive powers of all inverters and a capacitance sagging formula. According to the invention, interconnection communication among inverters and connecting impedance detection are not required; the line impedance voltage drop can be compensated in a self-adaption mode; and reactive power sharing capabilities and output voltage precision of all inverters can be improved.
Owner:黄山科创中心有限责任公司
Current full compensation method and system based on single-phase earth fault
PendingCN108448562AEasy to measureNo complex calculations requiredCurrent measurements onlyEmergency protective arrangements for limiting excess voltage/currentHigh resistanceCompensation effect
The invention provides a current full compensation method and a system based on single-phase earth fault. When zero sequence voltage is not in a preset voltage value range, namely, the happened single-phase earth fault is instant ground connection, an arc extinction coil device with high flexibility in high-resistance ground connection can compensate ground connection capacitive current. When thezero sequence voltage is in the preset voltage value range, namely, the happened single-phase earth fault is not instant ground connection, a breaker in a fault phase transfer ground connection deviceconnected with a fault phase is turned off, fault current is converted into earth current, and a compensable compensation device is further utilized to output full compensation fault residual current. The fault current is converted into the earth current, the earth current can serve as tracking compensation signals of the compensable compensation device, and judgment reference is provided for a compensation effect of the compensable compensation device. In addition, the earth current can be determined by measurement; furthermore, measurement is convenient, and complex calculation is avoided;thus, compensation quickness and accuracy are ensured, compensation precision is improved, and fault points are shielded.
Owner:YUNNAN POWER GRID CO LTD ELECTRIC POWER RES INST
DC distribution system energy storage device adaptive virtual impedance droop control method
ActiveCN105305410ASuppress power oscillationsEliminate uneven distribution of powerLoad balancing in dc networkAc network load balancingCapacitanceClosed loop
The invention relates to a DC distribution system energy storage device adaptive virtual impedance droop control method, which is applied to multi-converter parallel control in a DC distribution system. The method comprises the steps of 1) acquiring electric power parameters of the DC distribution system, establishing a double closed-loop controller which consists a voltage outer loop and a capacitive current inner loop, and establishing a DC distribution system droop control model; 2) introducing virtual impedance ZD(s) into a part between converter output current and converter reference voltage signals of the double closed-loop controller in the DC distribution system droop control model so as to act as negative feedback, and acquiring equivalent output impedance Zov(s); and 3) enabling the equivalent output impedances Zov(s) corresponding to a plurality of lines to be equal through setting values of different virtual impedances ZD(s), and thus averaging output power and power distribution of the plurality of lines in the DC distribution system. Compared with the prior art, the method provided by the invention has the advantages of shock suppression, simple algorithm, low cost and the like.
Owner:SHANGHAI MUNICIPAL ELECTRIC POWER CO +1
Harmonic characteristic analytical method of MMC (Modular Multilevel Converter)
ActiveCN103427609AHigh precisionMeet the needs of practical engineeringPower conversion systemsHarmonic analysisEngineering
The invention discloses a harmonic characteristic analytical method of an MMC (Modular Multilevel Converter). The harmonic characteristic analytical method comprises utilizing operation conditions and system parameters of the MMC and considering a second harmonic component of the bridge arm current to calculate the bridge arm current of every bridge arm of the MMC; calculating the average capacitive current of sub-modules of the MMC through an average switching function model under the actual condition; calculating the average capacitive voltage of the sub-modules of the MMC according to the relationship between the voltage at two ends of a capacitor and the current which flows through the capacitor; calculating the total voltage of phase bridge arms of the MMC through the average switching function model under the actual condition; utilizing the fourier series harmonic analysis method and extracting second harmonics to perform analysis to calculate the double frequency circular current of the bridge arms. According to the harmonic characteristic analytical method of the MMC, a harmonic component of every electric parameter of the MMC can be calculated, so that the computation commonality is strong, the application range is wide, and the accuracy is greatly improved in comparison with the existing methods.
Owner:ZHEJIANG UNIV
Probe station thermal chuck with shielding for capacitive current
InactiveUS7138813B2Semiconductor/solid-state device testing/measurementThermoelectric device with peltier/seeback effectCapacitanceElectricity
To reduce noise in measurements obtained by probing a device supported on surface of a thermal chuck in a probe station, a conductive member is arranged to intercept current coupling the thermal unit of the chuck to the surface supporting the device. The conductive member is capacitively coupled to the thermal unit but free of direct electrical connection thereto.
Owner:CASCADE MICROTECH
Method and device for checking zinc oxide lightning arrester block property current tester
ActiveCN101299062AEasy to set upEasy to handleElectrical measurementsMathematical modelTotal current
A method for checking a resistive current tester of a zinc oxide lightning arrester is characterized in that a reference voltage signal v and a total current signal i are synthesized with a software technique according to a mathematical mode of the resistivity of zinc oxide lightning arrester established in the national standard DL / T987-2005 u=U Sin omega t (1); i=IR1Sin omega t+IR3Sin(3omega t+pi)+IC1Sin(omega t+pi / 2) (2). One set of high precision D / A converter is controlled by a computer. The digital signal of reference voltage and total current signal which are synchronized by software is converted to analogue signal. The analogue signal is modulated and amplified by a program controlled accurate power amplifying unit and is taken as a standard signal which checks the resistive current tester of the zinc oxide lightning arrester. The method adopts a computer intelligent control technique and has advantages of digital designing principle, high measuring accuracy, and convenient processing and storing of the measured data. The device can conveniently set various checking parameters such as reference voltage, total current, resistive current, capacitive current and the like, and can set the resistive current of third harmonic.
Owner:WUHAN HIGH VOLTAGE RESEARCH INSTITUTE OF STATE GRID
Ring generator for a wind power installation
InactiveUS6943462B2Improve efficiencyAvoid disadvantagesVector control systemsEmergency protective circuit arrangementsThree-phaseConductor Coil
Owner:WOBBEN ALOYS
Method for designing hybrid damping parameter of LCL filter in photovoltaic grid-connected inverter
InactiveCN102263417AImprove adaptabilityReduce lossSingle network parallel feeding arrangementsPhotovoltaic energy generationCapacitanceDamping factor
The invention discloses a method for designing a hybrid damping parameter of an LCL filter in a photovoltaic grid-connected inverter, and belongs to the technical fields of new energy sources and distributed grid-connected generation. The method is characterized in that: the resonance of the LCL filter is suppressed by adopting an active damping / passive damping cooperative working method, whereina filter capacitive current feedback control method is adopted for an active damping part and the method of connecting filtering capacitance in series with damping resistance is adopted for a passivedamping part. For the LCL filter, the damping resistance required by passive damping and a feedback coefficient of active damping are computed under the condition of ensuring a sufficient damping coefficient, and a designed cooperative damping control scheme is checked to make the loss of the damping resistance as low as possible, avoid the influence of system control delay on damping running; and the damping is adapted to strong power grid access and the weak power grid access of remote areas. The method is applied to photovoltaic grid-connected generation systems adopting the LCL filter, fuel cells and grid-connected wind power generation systems.
Owner:TSINGHUA UNIV
Power cable intersect cross connection grounding system grounding current monitoring and evaluating method
InactiveCN105004907AImprove effectivenessIncrease credibilityCurrent/voltage measurementElectrical testingCross connectionElectric cables
The present invention provides a power cable intersect cross connection grounding system grounding current monitoring and evaluating method which is implemented by a power cable grounding current monitoring system. The method comprises the steps of calculating a cable sheath self-impedance, calculating a sheath induction voltage caused by a to-be-tested cable wire core load current, calculating a cable sheath induction voltage caused by a to-be-tested cable sheath grounding current and a large ground leakage current, calculating an induction current of a to-be-tested cable, calculating a cable capacitive current, predicting a grounding current fluctuation value caused by the load change, predicting the grounding current fluctuation caused by the load change, analyzing and determining the current condition of a power cable intersect cross connection grounding system cable sheath, etc. The power cable intersect cross connection grounding system grounding current monitoring and evaluating method of the present invention is different from a method of analyzing and calculating a grounding current from a circuit model purely, introduces the ideas of prediction, analysis and cable parameter characteristic calculation, enables the grounding current monitoring and evaluating accuracy of a power cable intersect cross connection grounding system to be improved effectively, and provides a more effective analysis method for cable external insulation state evaluation.
Owner:CHANGZHOU POWER SUPPLY OF JIANGSU ELECTRIC POWER +2
Method for monitoring resistant current in leakage current of an arrester
InactiveCN1991395AImprove reliabilityAvoid accidentsCurrent/voltage measurementEngineeringUtility frequency
The invention discloses a method for monitoring the resistance current of leakage current in lightning arrester that includes following steps: collects the whole leakage current through the lightning arrester; the whole leakage current is divided into the resistance current and the capacitive current; and the two kinds of current are scaled to mA grade; decides the time that two current thorough the zero point, and measures the average value of the resistance current and the capacitive current at the same time, and the value is as the original standard value; measures the max value of two kinds of current at power frequency 20ms, and records the change of current, and compares the difference of change rate of current; when the current change of instantaneous max value is keep constant rising, and detects the value is reach the 10% of original standard value; If the said detection result is true, and then the resistance element is changed to make the average value of the capacitive current return to the original standard value, and detects the average value of the resistance current. The method can obtain the change trend of resistance current when the lightning arrester is degraded seriously.
Owner:SHANGHAI ELECTRICGROUP CORP
UHV DC transmission line protection method utilizing current abrupt change characteristic based on distributed parameter model
ActiveCN106505536AEliminate the effects of protectionThe principle is simpleEmergency protective circuit arrangementsCapacitanceTransformer
The invention discloses a UHV DC transmission line protection method utilizing current abrupt change characteristics based on a distributed parameter model. The UHV DC transmission line protection method comprises the steps of processing voltage and current signals measured by transformers at both ends of a DC line by means of an intelligent electronic device (IED), and identifying internal and external faults according to polarities of current abrupt variables. The UHV DC transmission line protection method adopts a distributed parameter model for carrying out distributed capacitive current compensation, eliminates the influence of asynchronization of the distributed capacitive current and data. A protection criterion selects components with the frequency band of [0,100] Hz in current information, avoids the electromagnetic coupling between DC side characteristic harmonics and a bipolar DC line and the influence of lightning interference. The polarities of current abrupt variables at both ends of the line are Boolean quantities, and the communication traffic of longitudinal channels is small. The UHV DC transmission line protection method utilizing the current abrupt change characteristics based on the distributed parameter model only utilizes polarities of the current abrupt variables for identifying the internal and external faults, is simple in principle and small in communication traffic, and is stable and reliable.
Owner:CHINA THREE GORGES UNIV
Bipolar parallel multi-terminal direct current power transmission system electric current modulus longitudinal differential protection method
ActiveCN106849029AStrong resistance to transition resistanceAdaptableEmergency protective arrangements for automatic disconnectionCapacitanceElectrical resistance and conductance
The invention discloses a bipolar parallel multi-terminal direct current power transmission system electric current modulus longitudinal differential protection method. The method comprises the steps that digital sampling and modulus decoupling are conducted in each converter station of the parallel system, and 1, 0-mode voltage and electric current are obtained; one point on the direct current main line is selected as the destination point of calculation, starting from each converter station, the line terminal voltage, the electric current up to the destination point are calculated segment-by-segment and the 1, 0-mode differential current is obtained through the overlay at the destination point. If the 1-mode differential current is greater than the fault threshold, the fault is an internal area fault, otherwise the fault is an external fault; if the 0-mode differential current is greater than the threshold, the fault is a positive pole grounding fault; if the 0-mode differential current is less than the threshold, the fault is a negative pole grounding fault; if the 0-mode differential current is between the positive and negative selection thresholds, the fault is an inter polar short-circuit fault. The differential protection method is fast in movement speed, high in transition resistance capability, and is not under the influence of capacitive current in distribution, and can be extended to arbitrary end parallel direct current systems, in principle can recognize the fault type and is strong in adaptability. According to the differential protection method, the required sampling rate is low, the method is easy to implement and has practical value.
Owner:菏泽福之源电气设备有限公司
Automatic tuning control method of post-set arc suppression coils
InactiveCN101626158AAccurately determine the sizeIncrease success rateEmergency protective arrangements for limiting excess voltage/currentCapacitanceActive component
The invention discloses an automatic tuning control method of post-set arc suppression coils, which works out the active component in network earth capacitive current and network grounded fault current by measuring variation of unbalanced voltage of a network. During normal operation of the network, the neutral point unbalanced voltage of the network and a thread of voltage value of the network are measured, the variation of relative unbalanced degree of the network is calculated and monitored so as to determine whether compensation operation exists in the network or not and to determine whether the active component in the network earth capacitive current and the network grounded fault current is remeasured or not. Measuring the active component in the network earth capacitive current and the network grounded fault current comprises the following steps: firstly measuring the unbalanced voltage of the network, then controlling the post-set arc suppression coil to increase to output a compensation current (susceptance) by a controller, and measuring the unbalanced voltage of the network again so as to calculate the active component in the network earth capacitive current and the network grounded fault current. The invention is simple and easy to operate without affecting the normal operation of the network, has high measuring precision and is particularly suitable for post-set control of arc suppression coils.
Owner:CHINA UNIV OF MINING & TECH
Method and apparatus for detecting deterioration of lightning arrester
InactiveUS20110057667A1Improve workabilityLow costElectrical testingAir-break switch detailsCapacitanceHigh frequency power
An apparatus for detecting deterioration of a lightning arrester includes: a high-frequency power supply; a pair of detecting terminals 12 connected to the high-frequency power supply via a resistance for measurement and touched to the terminals of the arrester; a voltage detecting circuit for obtaining a terminal voltage of the resistance for measurement when the detecting terminals touch the terminals of the arrester; and a determining circuit for comparing the detected voltage with a reference value to determine whether the detected voltage is good or bad. A voltage having a frequency sufficiently higher than the operation frequency of a power line is generated by the high-frequency power supply and applied to the arrester, and change in electrical characteristics due to deterioration of zinc oxide elements is detected as change in current including capacitive current, and then it is determined whether the detected change is good or bad.
Owner:NGK INSULATORS LTD
Drive device
InactiveUS20110285378A1Interference level can be optimizedImprove electromagnetic interferenceDc network circuit arrangementsDc-dc conversionDriving currentControl signal
Owner:PANASONIC CORP
Method for restraining voltage background harmonic wave of grid-connected inverter
InactiveCN102594106AImprove stabilityExpand the scope of workPower conversion systemsCapacitanceReference current
The invention discloses a method for restraining a voltage background harmonic wave of a grid-connected inverter. The method adopts a direct-current source, an IGBT (Insulated Gate Bipolar Transistor) intelligent power module and an LCL (Lower Control Limit) type filter, wherein the direct-current source is subjected to a single-phase inversion output through the IGBT intelligent power module; and the single-phase inversion output is accessed to a power grid after being accessed with the LCL type filter. The method disclosed by the invention is characterized by comprising the following steps of: multiplying a sampling voltage signal of the power grid with a reference current amplitude I* after carrying out PLL (Phase Locking Loop) phase locking, so as to obtain a reference current signal; carrying out closed-loop adjustment on the reference current signal and a feedback current iL2 so as to obtain a first path of signals; multiplying the sampling voltage signal of the power grid with a feed-forward function so as to obtain a second path of signals; multiplying a capacitive current signal led by a capacitive branch of the LCL type filter with a virtual resistance function so as to obtain a third path of signals; and combining the first path of the signals, the second path of the signals and the third paths of the signals and then sending the combined signals to Ginv(s) for modulation so as to generate a PWM (Pulse Width Modulation) gate pole drive signal; and triggering a switching tube of the IGBT intelligent power module to be switched on or off by the PWM gate pole drive signal. With the adoption of the method disclosed by the invention, the influence of the background harmonic wave of the power grid can be effectively removed.
Owner:JIANGSU UNIV
Characteristic-harmonic-based protection method and system for high-voltage direct current transmission line
ActiveCN102623968AOvercome the shortcomings of poor reliability and easy misoperationInhibition of protective effectsEmergency protective arrangements for automatic disconnectionCapacitanceDc current
The invention discloses a characteristic-harmonic-based protection method and a characteristic-harmonic-based protection system for a high-voltage direct current transmission line. The characteristic-harmonic-based protection method for the high-voltage direct current transmission line comprises the following steps of: synchronously sampling direct currents on the two sides of the high-voltage direct current transmission line to obtain real-time current data, and performing discrete Fourier transform to obtain current characteristic harmonics at the two ends of the line; and counting the number Nn.m of characteristic current harmonics, calculating a weighted index IH.M, and performing logic judgment on the weighted index IH.M, the number Nn.m of the characteristic current harmonics and set values IH.set and Nn.set to obtain a failure type. The influence of distributed capacitive current can be avoided, and the shortcomings of the conventional differential protection for the high-voltage direct current transmission line are overcome; and moreover, the method and the system are high in resistance to transition resistance, simple in operation, easy to implement and high in working speed and reliability, and special requirements on sampling frequency are avoided.
Owner:SHANGHAI JIAO TONG UNIV
Three phase converter fed motor having a shielding device to eliminate capacitive current in stator slots
InactiveUS6756712B1Windings insulation shape/form/constructionSupports/enclosures/casingsCapacitanceThree phase converter
A device for preventing bearing damage from currents through a three-phase motor is provided, including a shield for winding and copper wire within each stator slot of a motor. The shield includes an electrically conductive layer which is insulated from the winding and from the laminated stator core of the three-phase motor. The conductive layer is grounded or conductively connected to the laminated stator core of the three-phase motor on only that side on which the three-phase current is fed to the winding of the motor.
Owner:MANNESMANN AG
Control method for single-phase grid-connected inverter and control parameter obtaining method therefor
InactiveCN105870960ASimple design methodSmall steady state errorSingle network parallel feeding arrangementsHarmonic reduction arrangementCapacitanceReference current
The invention discloses a control method for a single-phase grid-connected inverter and a control parameter obtaining method therefor. The control method comprises the steps of collecting a power grid voltage value Ug, and inputting a phase-locked loop algorithm to obtain a phase angle <theta> of the power grid voltage; setting an amplitude value Im of a power grid reference current, and obtaining the power grid reference current Iref; enabling Iref and Ig to be subtracted obtain an error E, and enabling the obtained error E to pass through a proportional resonant controller and a harmonic compensation controller separately; enabling the output Upr of the proportional resonant controller to be added with the output Uhc of the harmonic compensation controller to obtain a sum Uab, and carrying out amplitude limiting on the obtained sum Uab to obtain a capacitive current reference value Icref of the filter; enabling the Ic and a feedback coefficient Kc to be multiplied to obtain a capacitive current feedback signal Ikc of the filter; enabling the difference value between the Ic and Ikc to be multiplied by a gain coefficient Kpwm of a PWM to form a modulation signal of a single-phase full-bridge inversion unit; and generating the driving pulse of the single-phase full-bridge inversion unit by the modulation signal. The control method is simple and feasible and capable of effectively restraining low-order harmonics.
Owner:GUANGDONG UNIV OF TECH
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