A method for removing three-phase unbalanced power oscillation components

Abstract

The application provides a three-phase unbalanced power oscillation component removal method, 100Hz power oscillation phasor caused by three-phase unbalance is obtained through power frequency synchronous phasor at second edge moment, 100Hz oscillation phasor is obtained through real-time power sweep calculation of wideband measurement device, 100Hz power oscillation phasor caused by three-phase unbalance is subtracted, and oscillation phasor after three-phase unbalance is removed is obtained, and the amplitude of the oscillation phasor after three-phase unbalance is removed is the oscillation component after three-phase unbalance is removed. The method solves the problem that three-phase unbalance causes 100Hz power oscillation, when the numerical value of the oscillation is larger than the oscillation threshold of the device, frequent alarm of the device is caused, and the normal oscillation monitoring function of the system is affected.

Description

Technical Field

[0001] This invention relates to the field of wide-area monitoring of power systems, and in particular to a method for removing three-phase unbalanced power oscillation components. Background Technology

[0002] With the continuous expansion of the power grid and the integration of renewable energy, the power grid structure and operating characteristics are becoming increasingly complex, placing higher demands on the real-time online monitoring of the power grid's operation. Currently, all levels of dispatch centers at the national, provincial, and municipal levels have built wide-area monitoring systems for online monitoring of real-time waveforms, frequencies, frequency change rates, oscillations, and other parameters of the power grid.

[0003] As a station acquisition terminal in a wide-area monitoring system, the broadband measurement device has the function of monitoring power oscillations from 0.1 to 300 Hz. However, due to the influence of power grid operation mode, load imbalance, or acquisition channel errors, three-phase imbalance often occurs in the voltage and current channels. Three-phase imbalance causes power oscillations of 100 Hz. When the value of such oscillations is large, it exceeds the device's oscillation threshold, causing the device to alarm frequently and affecting the normal power oscillation monitoring function of the system.

[0004] Currently, no method for eliminating three-phase unbalanced power oscillation components in broadband measurement devices for power plants has been provided. Therefore, considering the reasonable requirements of wide-area measurement systems for oscillation monitoring and alarms, and combining the computing power of secondary embedded devices, a method for removing three-phase unbalanced power oscillation components that is engineering-feasible and computationally efficient is proposed. Summary of the Invention

[0005] This invention provides a method for removing three-phase unbalanced power oscillation components, which solves the problem of 100Hz power oscillation caused by three-phase imbalance. Such oscillation values ​​are large and often exceed the device's oscillation threshold, causing frequent alarms and affecting the system's normal 100Hz oscillation monitoring function.

[0006] The present invention proposes the following technical solution.

[0007] This invention proposes a method for removing three-phase unbalanced power oscillation components. The method obtains the 100Hz power oscillation phasor caused by the three-phase imbalance by using the power frequency synchronous phasor at the second edge. The 100Hz oscillation phasor is obtained by real-time power sweep calculation using a broadband measurement device. The 100Hz power oscillation phasor caused by the three-phase imbalance is subtracted to obtain the power oscillation phasor after removing the three-phase imbalance.

[0008] Includes the following steps:

[0009] 1) Multiply the amplitudes of the phasor measurements of the single-phase voltage and current at the second edge of the broadband measuring device to obtain the amplitude of the single-phase power oscillation; add the phases of the phasor measurements of the single-phase voltage and current at the second edge of the broadband measuring device to obtain the phase of the single-phase power oscillation.

[0010] 2) Multiply the amplitude of the single-phase power oscillation by the cosine of the phase of the single-phase power oscillation to obtain the real part of the single-phase power oscillation; multiply the amplitude of the single-phase power oscillation by the sine of the phase of the single-phase power oscillation to obtain the imaginary part of the single-phase power oscillation.

[0011] 3) Summing the real parts of the single-phase power oscillations calculated for each of the three phases A, B, and C of the interval, we obtain the real part of the interval power; summing the imaginary parts of the single-phase power oscillations, we obtain the imaginary part of the interval power; and calculating the phasor of the 100Hz power oscillation caused by the three-phase imbalance from the real and imaginary parts of the interval power.

[0012] 4) Obtain the 100Hz oscillation phasor by instantaneous power sweep calculation using a broadband measuring device, and subtract the 100Hz power oscillation phasor caused by three-phase imbalance to obtain the power oscillation phasor after eliminating three-phase imbalance.

[0013] The amplitude of the power oscillation phasor after eliminating three-phase imbalance is the power oscillation component after eliminating three-phase imbalance.

[0014] The advantages and effects of this invention are: This invention provides a method for removing three-phase unbalanced power oscillation components, solving the problem that oscillation components caused by three-phase imbalance overwhelm the true oscillation components. This algorithm has a short CPU processing time, small storage footprint, and clear logic. The widespread application of this invention significantly improves the reliability and practicality of broadband oscillations. Attached Figure Description

[0015] Figure 1 The present invention provides a flowchart of a method for removing three-phase unbalanced power oscillation components;

[0016] Figure 2 This is a schematic diagram of the power polar coordinates of the power oscillation component after excluding three-phase imbalance in an embodiment of the present invention;

[0017] Figure 3 This is a schematic diagram illustrating the time lag in the calculation of the power oscillation component in an embodiment of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0019] This invention proposes a method for removing three-phase unbalanced power oscillation components. The method obtains the 100Hz power oscillation phasor caused by the three-phase imbalance by using the power frequency synchronous phasor at the second edge. The 100Hz oscillation phasor is obtained by real-time power sweep calculation using a broadband measurement device. The 100Hz power oscillation phasor caused by the three-phase imbalance is subtracted to obtain the power oscillation phasor after removing the three-phase imbalance.

[0020] In a non-limiting preferred embodiment, since the 100Hz power oscillation has a significant impact on the broadband measurement device, obtaining the 100Hz oscillation phasor by real-time power sweep calculation of the broadband measurement device is a non-limiting preferred choice in this embodiment of the invention.

[0021] Includes the following steps:

[0022] 1) Multiply the amplitudes of the phasor measurements of the single-phase voltage and current at the second edge of the broadband measuring device to obtain the amplitude of the single-phase power oscillation; add the phases of the phasor measurements of the single-phase voltage and current at the second edge of the broadband measuring device to obtain the phase of the single-phase power oscillation.

[0023] 2) Multiply the amplitude of the single-phase power oscillation by the cosine of the phase of the single-phase power oscillation to obtain the real part of the single-phase power oscillation; multiply the amplitude of the single-phase power oscillation by the sine of the phase of the single-phase power oscillation to obtain the imaginary part of the single-phase power oscillation.

[0024] 3) Summing the real parts of the single-phase power oscillations calculated for each of the three phases A, B, and C of the interval, we obtain the real part of the interval power; summing the imaginary parts of the single-phase power oscillations, we obtain the imaginary part of the interval power; and calculating the phasor of the 100Hz power oscillation caused by the three-phase imbalance from the real and imaginary parts of the interval power.

[0025] 4) Obtain the 100Hz oscillation phasor by instantaneous power sweep calculation using a broadband measuring device, and subtract the 100Hz power oscillation phasor caused by three-phase imbalance to obtain the power oscillation phasor after eliminating three-phase imbalance.

[0026] The amplitude of the power oscillation phasor after eliminating three-phase imbalance is the power oscillation component after eliminating three-phase imbalance.

[0027] Figure 1The flowchart of the algorithm for eliminating three-phase imbalance power oscillation components according to the present invention is shown. A broadband measurement device uploads broadband measurement data at 100 frames per second, with time stamps of 0ms, 10ms, 20ms…990ms. Power frequency phasors at the second edges are selected, including but not limited to acquiring power frequency single-phase voltage phasors and power frequency single-phase current phasors with a 0ms time stamp. The amplitudes of the single-phase voltage and current phasor measurements are multiplied to obtain the single-phase power oscillation amplitude; the phases are added to obtain the single-phase power oscillation phase. The single-phase power oscillation amplitude is multiplied by the cosine of the single-phase power oscillation phase to obtain the real part of the single-phase power oscillation; the amplitude is multiplied by the sine of the single-phase power oscillation phase to obtain the imaginary part of the single-phase power oscillation. The real parts of the single-phase power oscillations calculated for each of the three phases (A, B, and C) of the interval are summed to obtain the interval power real part; the imaginary parts of the single-phase power oscillations are summed to obtain the interval power imaginary part; the phasor of the 100Hz power oscillation caused by the three-phase imbalance is calculated from the real and imaginary power parts. The phasor of the 100Hz oscillation is obtained by real-time power sweep calculation using a broadband measurement device. Subtracting the phasor of the 100Hz power oscillation caused by the three-phase imbalance gives the oscillation phasor after eliminating the three-phase imbalance.

[0028] Figure 2 This diagram illustrates the power polar coordinates of the power oscillation component after eliminating three-phase imbalance. The phasor timestamp of the 100Hz power obtained through real-time power frequency sweeping is the start time of the frequency sweep data window, which is the second edge of the synchronous data acquisition. The phasor of the 100Hz power oscillation caused by the three-phase imbalance is the power frequency phasor selected at the second edge, i.e., the synchronous phasor selected with a 0ms timestamp; both are at the same second edge. Subtracting these two phasors yields the amplitude of the new phasor, which is the power oscillation component after eliminating the three-phase imbalance. The device uses the oscillation component after eliminating the three-phase imbalance for alarm judgment. The 100Hz oscillation component is obtained by instantaneous power frequency sweeping calculation using the device. If the master station needs to extract the power oscillation component after eliminating the three-phase imbalance, the method of this invention is used.

[0029] Since the acquisition time of the power frequency synchronous phasor is determined based on the timescale of the real-time power phasor, the real-time power phasor and the power frequency synchronous phasor are at the same second edge. Therefore, the present invention proposes to use the power frequency synchronous phasor to calculate the three-phase unbalanced power oscillation phasor. The difference between the real-time power phasor corresponding to the acquisition time of the power frequency synchronous phasor and the calculated three-phase unbalanced power oscillation phasor is used as the power oscillation phasor after removing the three-phase imbalance. This method is highly practical, simple to calculate, requires less computation, facilitates improved computational efficiency, and meets the needs of real-time online monitoring.

[0030] Figure 3This diagram illustrates the time lag in power oscillation component calculation. During the 1-second calculation time window, 0-1 second sampled data is used for Fast Fourier Transform frequency sweeping. Therefore, the actual timestamp of the currently transmitted power oscillation data lags behind the timestamp of the power frequency phasor data frame by 2 seconds. Simultaneously, the 100Hz oscillation component caused by three-phase imbalance is calculated using the 0-second power frequency phasor. Subtracting the two phasors yields the amplitude of the phasor at time 0 seconds, which is the power oscillation component after eliminating the three-phase imbalance. The device uses the oscillation component after eliminating the three-phase imbalance for alarm detection, with an alarm delay of 2 seconds and a timestamp of time 0 seconds.

[0031] This disclosure can be a system, method, and / or computer program product. A computer program product may include a computer-readable storage medium having computer-readable program instructions loaded thereon for causing a processor to implement various aspects of this disclosure.

Claims

1. A method for removing oscillating components of three-phase unbalanced power, characterized in that, The 100Hz power oscillation phasor caused by three-phase imbalance is obtained by the power frequency synchronous phasor at the second edge time. The 100Hz oscillation phasor is obtained by real-time power sweep frequency calculation by the broadband measurement device. The 100Hz power oscillation phasor caused by three-phase imbalance is subtracted to obtain the power oscillation phasor after eliminating three-phase imbalance. The method includes the following steps: 1) Multiply the amplitudes of the phasor measurements of the single-phase voltage and current at the second edge of the broadband measuring device to obtain the amplitude of the single-phase power oscillation; add the phases of the phasor measurements of the single-phase voltage and current at the second edge of the broadband measuring device to obtain the phase of the single-phase power oscillation. 2) Multiply the amplitude of the single-phase power oscillation by the cosine of the phase of the single-phase power oscillation to obtain the real part of the single-phase power oscillation; multiply the amplitude of the single-phase power oscillation by the sine of the phase of the single-phase power oscillation to obtain the imaginary part of the single-phase power oscillation. 3) Summing the real parts of the single-phase power oscillations calculated for each of the three phases A, B, and C of the interval, we obtain the real part of the interval power; summing the imaginary parts of the single-phase power oscillations, we obtain the imaginary part of the interval power; and calculating the phasor of the 100Hz power oscillation caused by the three-phase imbalance from the real and imaginary parts of the interval power. 4) Obtain the 100Hz oscillation phasor by instantaneous power sweep calculation using a broadband measuring device, and subtract the 100Hz power oscillation phasor caused by three-phase imbalance to obtain the power oscillation phasor after eliminating three-phase imbalance.

2. The method for removing three-phase unbalanced power oscillation components according to claim 1, characterized in that, The amplitude of the power oscillation phasor after eliminating three-phase imbalance is the power oscillation component after eliminating three-phase imbalance.

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