1086 results about "Phasor" patented technology

The present invention provides a digital (computational) branch calibrator which uses a feedback signal sensed from an RF transmit signal path following the combining stage of LINC circuitry of a transmitter to compensate for gain and phase imbalances occurring between branch fragment signals leading to the combiner. The calibrator feeds a quiet (zero) base band signal through the transmit path during the calibration sequence (i.e. a period when data is not transmitted) and adjusts the phase and gain of the phasor fragment signals input thereto by driving the sensed output power to zero. The calibration is performed by alternating phase and gain adjustments with predetermined (programmable) and multiple update parameters stages (speeds). A baseband modulation is preferably used to distinguish false leakage (e.g. due to local oscillator, LO, feed through and DC offset in the base band Tx) from imbalance leakage.

A device is provided for monitoring and controlling various power system device and elements. The device generally includes a communications channel for receiving phasor data associated with a location on the power system. The device further includes a logic engine which performs scalar, vector and/or other complex calculation based on the phasor data to provide control data or an output signal for effecting the various other power system devices or elements to provide local or wide area protection, control, and monitoring to maintain power system stability.

A phasor measurement system is provided for computing synchronized phasor measurements. The phasor measurement system includes acquisition circuitry for acquiring voltage or current values from a power line, sampling circuitry for sampling the voltage or current values, and processing circuitry for computing a phasor and at least one time derivative of the phasor based on the sampled voltage or current values and for computing a synchronized phasor value based on the phasor and the at least one time derivative of the phasor.

An apparatus and method estimates a plurality of synchronized phasors at predetermined times referenced to an absolute time standard in an electrical power system. The method includes acquiring and determining a frequency of a power system signal, sampling the power system signal at a sampling interval rate based on a frequency of the power system signal to form signal samples, and generating a plurality of acquisition time values based on an occurrence of each of the signal samples at a corresponding plurality of different times referenced to the absolute time standard. The method further includes adjusting a phasor of each of the signal samples based on a time difference between a corresponding selected acquisition time value and a predetermined time referenced to an absolute time standard to form the plurality of synchronized phasors.

A system for controlling a grid connected power generating system is provided. The system includes a wind turbine, a converter, a first controller and a second controller. The wind turbine supplies electrical power to a power grid and the converter couples the wind turbine to the power grid. The first controller calculates voltage commands to emulate a phasor back electromotive force behind an inductance. The controller further generates converter switching commands from the voltage commands. The voltage commands include a voltage magnitude reference and an internal frequency reference calculated from a power imbalance between an active power reference and the electrical power. The second controller is used to limit a converter current.

An apparatus and method compensate for the sensitivity of at least one line current differential element of a first current differential relay providing differential protection for a transmission line of a power system during a single-phase pole-open condition. The apparatus includes a first delta filter configured to remove a first pre-fault current from a first fault current of the transmission line to derive a compensated first current phasor. The apparatus also includes a second delta filter configured to remove a second pre-fault current from a second fault current of the transmission line to derive a compensated second current phasor. The compensated first and second current phasors are provided to the at least one line current differential element to compensate the sensitivity of the at least one line current differential element.

A means for improving the dynamic and voltage stability of utility transmission systems is provided by the coordinated control of windfarms. Electrical measurements of the system, which may include synchronized phasors, are supplied to one or more windfarm controllers, which in turn perform a regulation function improving the damping of electromechanical oscillations or voltage performance in the utility system. The control structure is of a decentralized nature, which maintains operation in case of communication failures. The benefits are improved damping to electromechanical oscillations and better voltage performance and ultimately increased utilization of assets, reducing the install additional network assets.

The disclosure relates to phasor-based monitoring, protection and control applications in electric power systems supervised and/or managed by a Supervisory Control And Data Acquisition/Energy Management System (SCADA/EMS). In order to enable the applications without incurring heavy infrastructural investments, a phasor measurement facility is integrated into a Remote Terminal Unit (RTU) that is part of the SCADA/EMS system and comprises Input/Output (I/O) interfaces hard-wired to a substation of an electric power system. By taking advantage of the fact that RTUs as indispensable building blocks for any SCADA/EMS are part of every substation of the power system, no extra housing, cabling and EMC shielding for the additional functionality needs to be provided.

The invention discloses a monitoring method of a power system, comprising the following steps of: acquiring a running state signal of the power system in real time by a sensor positioned in a power grid; sampling the running state signal by taking a second pulse signal of a satellite synchronous clock as a sampling reference signal and outputting the acquired data to a function application unit of a data application layer through an optical fiber communication interface by a data acquisition unit; and analyzing and processing the acquired data and transmitting the processed result to a main monitoring station through the function application unit. The invention integrates functions of phasor quantity monitoring, fault recording, traveling wave fault location and the like into a monitoring device, considers the expanding demand of a hardware platform on realizing an IEC61850 communication protocol system in the selection of the hardware platform and realizes the monitoring in the whole process of the running state of the power system. The functions realized by the three sets of traditional equipment are realized by one set of equipment, and the secondary wiring is reduced, so that the maintenance cost and the asset investment can be greatly reduced.

The high-accuracy synchronous phasor measurement method belongs to the field of automatic measurement technology of power system. On the basis of spaced sampling circulation DFT, when the system frequency is deviated from rated frequency, the influence of frequency deviation can be calculated to make the frequency and phasor measurement have higher accuracy. The field tests show that when the sampling frequency is 4800 Hz and phasor correction calculation frequency is 200 Hz, its static accuracy indexes are: phasor magnitude error is less than 0.5%, phasor phase angle error is less than 1 deg.C and frequency calculation error is less than 0.01 Hz, and its dynamic accuracy indexes are: phosar magnitude error is less than 1%, phasor phase angle error is less than 1 deg. and frequency calculation error is less than 0.01 Hz.

Methods and apparatus for reducing the coherence of an optical signal that is used to interrogate optical interferometric sensors are disclosed. The optical field phasor of the interrogation source is modulated in a controlled manner to produce a broadened optical source power spectrum at the output of the source unit. The output from the source unit is launched into an optical sensor network, comprising a multiple of optical pathways from its input to the detection unit, where pairs of optical pathways form sensor interferometers. A compensating interferometer with delay difference similar to the sensor delay difference may be arranged in a serially coupled manner with the optical sensor network, either before or after the network. The optical output power from the source unit may either be continuous or pulsed with a pulse duration similar to the sensor delay. The coherence modulation may be performed through direct modulation of the source or through external modulation of the light with piezoelectric ring modulator, a Lithium niobate phase or intensity modulator, or an acoustooptic modulator.

A measured phasor representing a sinusoidal power signal waveform is produced by orthogonal FIR filters, one of which produces the real part of the phasor and the other of which produces the imaginary part. The frequency difference between the rated frequency of the signal waveform in the power system and the actual frequency of the waveform at any selected point in time is determined and the elements (A, B, C, D) of a compensation matrix is determined. The compensation matrix is then used to perform a linear transformation to produce an exact phasor for the waveform.

Provided is an apparatus and method for determining a faulted phase resulting from a fault in a three-phase ungrounded power system. The method includes comparing a phase angle of an operating phasor to a phase angle of a fixed reference phasor. The operating phasor is derived from a digitized signal sample of a plurality of measured signals of the power system. The method also includes comparing a phase angle difference between the operating phasor and the fixed reference phasor to at least one threshold to determine the faulted phase. The fixed reference phasor may be a phase-to-phase voltage or a positive sequence voltage of the plurality of measured signals of the power system. The operating phasor may be a zero sequence current, a zero sequence voltage or a combination of a zero sequence current and a zero sequence voltage of the plurality of measured signals of the power system.

The present invention relates to the relay protection method in the field of a power system. The present invention discloses a method for realizing two-terminal fault location in the power system through two terminal synchronism sampling current and voltage according to the method of equal voltages at two ends of a fault point and using a phase current and a phase voltage without zero sequence current and zero sequence voltage. The method comprises main steps as follows: a line protection device samples to a line side current sensor secondary current and voltage sensor secondary voltage to obtain a corresponding instantaneous value of the current and the voltage. The Fourier form of a three phase current and a three phase voltage on the side is worked out using a Fourier algorithm. The phasor form of phase current and phase voltage obtained by filtering to compute of protecting synchronism sampling on the other side is received through optical fiber network of communication. The distance from the protection arranging place to the fault point is obtained using the situation that the phase voltages on two sides of the fault point is equal with each other. The method is not affected by the power supply impedance and the transition resistance in the line operation method. Theory and practice prove that the method greatly improves the accuracy of transmission line fault location.

A method for fault detection in a power transformer/autotransformer and/or interconnected power lines, which are within the zone protected by the differential protection, and particularly suitable for detecting turn-to-turn faults in power transformer/autotransformer windings. All individual instantaneous phase currents of the protected object are measured, individual phase currents as fundamental frequency phasors are calculated, the contributions of the individual protected object sides negative sequence currents to the total negative sequence differential current are calculated by compensating for the phase shift of an eventual power transformer within the protected zone, the relative positions of the compensated individual sides negative sequence currents in the complex plane are compared, in order to determine whether the source of the negative sequence currents, i.e. the fault position, is within the protected zone or outside of the protected zone, delimited with current transformer locations, the protected object is disconnected if determined that the source of the negative sequence currents is within the protected zone.

The invention provides a method for estimating a state of dynamic process of a power system. The method takes an estimated result of the static state before the electric grid disturbance as a basic section and introduces a load model and a motor model to perform the equivalent treatment to the electric grid; in the process of the electric grid disturbance, a synchronous phasor measuring unit(PMU) is used to measure and obtain data of a motor, and according to the active power and the reactive power zero injection pseudo-measurement equations of all nodes of the original electric grid, states of all nodes of the electric grid are estimated, and the state of dynamic process of the electric grid is acquired only by the PMU measurement of a power plant. Because the state of the electric grid before disturbance is taken as a basis and only the PMU distribution of the power plant is required, the method effectively resolves the problem of state monitoring under the condition of the electric grid disturbance; on the same disturbance, for continuous PMU measurement sections, PMU measurement data can be directly put in iterative computations, thereby the continuous sections in the process of electric grid disturbance are provided for stable control and analysis; moreover, the method is fast in speed, so that the method meets the requirement for monitoring the dynamic process in real time.

The inventive method assesses the stability of an electric power transmission network, where said network comprises a plurality of substations, buses and lines, and a system protection center (8). It comprises the steps of 1. measuring phasor data (9) for voltages and currents at a plurality of locations of the network, 2. transmitting said phasor data (9) to said system protection center (8), 3. transmitting information (5) regarding the state of switches of at least one substation to the system protection center (8), and 4. the system protection center (8) determining at least one stability margin value of the transmission network. In this way, detailed real-time information about the state of the network is collected at a system level of the network, allowing a corresponding global analysis of the information. In a preferred embodiment of the invention, the system protection center determines one or more control commands (6), based on the phasor data (9) and on the state of switches. The control commands (5) are transmitted to at least one substation and executed there.

The invention discloses an on-line positioning method of a section with low-current ground faults and a system based on the positioning method. The method and the system are suitable for a neutral ungrounded power grid of 3-60kV. Under the operation condition of a line with single-phase ground faults, the phasor information of a zero-sequence voltage and the amplitude and phasor information of a zero-sequence current of the line are measured, and the section position of a fault point is determined according to the amplitude and phase information. The accuracy and rapidity of positioning are fully ensured, and the on-line positioning problem of single-phase ground faults of the neutral ineffectively grounded power grid and the monitoring problem of short-circuit faults between lines are effectively solved.

An online insulation condition monitoring system for a rotating electric machine, includes a differential current sensor and a voltage sensor coupled to the machine, for measuring values for the instantaneous differential current and the instantaneous phase voltage respectively. A processing module is configured for converting the values for the instantaneous differential current and the instantaneous phase voltage to respective values for phasor current and phasor voltage. The processing module further calculates an angular relationship between phasor current and phasor voltage and generates an output based on the calculated angular relationship, as an indication of insulation condition.

The invention discloses a measuring method and measuring apparatus of subsynchronous and supersynchronous harmonic phasors. The method comprises the following steps: acquiring electrical signals so as to generate digital signals; performing filtering processing on the digital signals so as to obtain initial subsynchronous harmonic waves and/or supersynchronous harmonic waves; performing harmonic wave adaptive detection through DFT or FFT so as to obtain an initial frequency; according to the initial frequency, designing a filter so as to extract each subsynchronous harmonic wave and/or each supersynchronous harmonic wave; carrying out correction calculation by use of the phasor correction measuring algorithm so as to obtain the frequency, the amplitude and the phase of corresponding harmonic waves; and according to the gain and phase shift of the filter, performing amplitude compensation and phase compensation on the phasors so as to obtain a three-phase phasor of each subsynchronous harmonic wave and/or each supersynchronous harmonic wave. The measuring method provided by one embodiment of the invention can accurately measure the phasors of the subsynchronous and supersynchronous harmonic waves, thereby being applied to wide-area dynamic monitoring, analyzing, control and protection of subsynchrono resonance/oscillation of a power system.

“A label-free imaging method to monitor stem cell metabolism discriminates different states of stem cell as they differentiate in a living tissues. We use intrinsic fluorescence biomarkers and the phasor approach to Fluorescence Lifetime Imaging Microscopy (FLIM). We identify and map intrinsic fluorophores such as collagen, retinol, retinoic acid, flavins, nicotinamide adenine dinucleotide (NADH) and porphyrin. We measure the phasor values of germ cells in C. Elegans germ line. Their metabolic fingerprint cluster according to their differentiation state, reflecting changes in FAD concentration and NADH binding during the differentiation pathway. The phasor approach to lifetime imaging provides a label-free, fit-free and sensitive method to identify different metabolic state of cells during differentiation, to sense small changes in the redox state of cells and may identify symmetric and asymmetric divisions and predict cell fate.”

The invention discloses a clock synchronization device for measuring the synchronous phasor of an electric power system. Wherein, the local time synchronization module constitutes a synchronization time service network through connecting to the network protocol, an antenna and the GPS time receiver module receive the signal of the time information, the main module resolves the time information and resets the local real-time clock in the main module; the main module sends the time information to a second module through the network protocol and resets the local real-time clock in the second module, thus completes the time service of the local time synchronization modules in the main and second modules as the synchronization time service network. The clock synchronization device of the invention adopts a high-precision GPS time service mode and a low-cost main and second network time service mode, which satisfying the requirement of the high-precision clock synchronization in the measurement of the synchronous phasor in an electric power system, decreases the dependence on the GPS time receiving module when adopting the high-precision GPS time service mode in the entire network, and reduces the cost.

A system and method are provided for correction of parameters used in determination of stator turn faults of an induction motor. An embodiment may include determining a residual impedance and/or a residual voltage of the motor, and correcting a normalized cross-coupled impedance based on the residual impedance and residual voltage. Additional embodiments may include measuring an operating temperature of the motor and determining a negative sequence impedance of the motor based on the temperature. Another embodiment may include measuring voltages and currents of the motor and determining phasors for the voltages and currents using compensation for variations from a nominal frequency of the motor.