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A Power System Phasor Calculation Method Applicable to Frequency Offset
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A technology of power system and calculation method, which is applied in the direction of frequency measurement device, measurement of electrical variables, frequency to amplitude conversion, etc., can solve the problems of large amount of calculation, troublesome correction, sacrifice of measurement accuracy, etc., achieve small memory occupation, simple method, The effect of fast calculation speed
Inactive Publication Date: 2016-06-01
SHANDONG UNIV
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Problems solved by technology
However, the current phasor algorithm either makes the correction after Fourier transform very troublesome and requires a lot of calculation in order to meet the accuracy; or sacrifices the measurement accuracy in order to meet the calculation speed
At present, there is still no suitable algorithm that can meet the actual phasor measurement accuracy on the basis of taking into account the calculation cost, and is suitable for severe frequency offset and various system operation modes
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Embodiment 1
[0050] Assume that the sequence of single-phase sampled values after low-pass filtering is expressed as X(i)=1.34*cos(2*f*π*i*0.00025), i=0, 1, 2, 3, . . . . N is taken as 80, that is, 80 sampling points per cycle, and the sampling interval is T S =0.00025 seconds. Unless otherwise specified, the calculation variable is of double type, the unit of phase is angle, the unit of frequency is Hz, and decimal truncation is rounded off.
[0051] Assume that the current system is in a three-phase balanced state, the system frequency is 47Hz, and the current sampling time is (100×T S ), then when f=47Hz, the nearest integral frequency range to this frequency is: M=85, 47Hz is out of the whole point frequency range. According to the algorithm rules, choose step three.
[0052] X(i) A =1.34*cos(2*f*π*i*0.00025)
[0053] X ( i ) B = 1.34 * cos ...
Embodiment 2
[0059] Assume that the sequence of single-phase sampled values after low-pass filtering is expressed as X(i)=1.34*cos(2*f*π*i*0.00025), i=0, 1, 2, 3, . . . . N is taken as 80, that is, 80 sampling points per cycle, and the sampling interval is T S =0.00025 seconds. Unless otherwise specified, the calculation variable is of double type, the unit of phase is angle, the unit of frequency is Hz, and decimal truncation is rounded off.
[0060] Assuming that the current system is in a three-phase unbalanced state, there is a 5% negative sequence component, and the negative sequence leads the positive sequence by 30°. The system frequency is 47Hz, and the current sampling moment is (100×T S ).
[0061] Then when f=47Hz, the whole point frequency range closest to this frequency is: M=85, 47Hz is out of the whole point frequency range. According to the algorithm rules, choose step five.
[0062] X ( i ) ...
Embodiment 3
[0070] Assume that the sequence of single-phase sampled values after low-pass filtering is expressed as X(i)=1.34*cos(2*f*π*i*0.00025), i=0, 1, 2, 3, . . . . N is taken as 80, that is, 80 sampling points per cycle, and the sampling interval is T S =0.00025 seconds. Unless otherwise specified, the calculation variable is of double type, the unit of phase is angle, the unit of frequency is Hz, and decimal truncation is rounded off.
[0071] Suppose the current system frequency is 50.01Hz, and the sampling time is (100×T S ), then when f=50.01Hz, according to the algorithm rules, choose step 2. Select the sampling window length as the default power frequency sampling points per cycle N=80.
[0072] X 100 = 2 80 Σ k = - 79 0 x 100 + ...
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Abstract
The invention discloses an electric systemphasor calculating method suitable for frequency deviation. The method comprises the step of carrying out synchronization fixed time interval discrete sampling is carried out on a three-phase signal, carrying out lowpass filtering on a sampling value sequence and carrying out real-time and accurate measurement on the system frequency to obtain the system frequency f, and the step of respectively selecting a fixed wavelengthFourier transformalgorithm or a variable window length Fourier transformalgorithm or a phaser correction positive sequence compensation algorithm or a variable window length positive sequence compensation algorithm according to different system states and different system frequency ranges to calculate the amplitude and the phase angle of the phasor. The electric system phasor calculating method has the advantages that only a period of sampling data need to be selected, the occupied internal storage is small, the three-phase data can be operated at the same time, the computing speed is high, precision is very high, the phase angle error is controlled within 0.1 degree, and the amplitude error is controlled within 0.1 percent. The electric system phasor calculating method is suitable for occasions on which the accurate frequency value can be obtained and the requirement for the phasor measuring precision and the computing speed are high, and the method meets the current measuring requirement for the phasor of a current smart power grid.
Description
technical field [0001] The invention belongs to the technical field of phasor measurement in electric power systems, and in particular relates to a high-precision phasor calculation method suitable for frequency deviation in electric power systems. Background technique [0002] Phasor in power system is an important observation quantity, which includes magnitude and phase. The power system safety automatic device should measure its value in real time, and make corresponding control measures according to the phasor changes of voltage and current. At present, PMUs are widely used in intelligent substations to measure the voltage and current phasors of the power system, and the calculation methods are almost all based on Fourier transform to calculate the amplitude and phase. Since the actual frequency of the power system fluctuates and cannot be kept at a power frequency of 50Hz continuously, the traditional phase-locking processing technology is no longer applicable to an A / ...
Claims
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Application Information
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