A power grid phase sequence detection method and device

Abstract

The application discloses a kind of power grid phase sequence detection method, device, comprising the following steps: S1, the three-phase voltage signal of synchronous sampling power grid, and the three-phase voltage signal is converted into the alpha axis component and beta axis component under two-phase stationary coordinate system by Clarke transformation;S2, according to alpha axis component and beta axis component, the instantaneous phase angle of voltage space vector is calculated, and the instantaneous phase angle is handled with angle offset, and offset phase angle is obtained;S3, based on offset phase angle, instantaneous angular velocity is calculated;S4, set an effective angle interval away from the boundary of angle value domain;It is judged whether the offset phase angle corresponding to the current sampling point is located in the effective angle interval: if yes, then determine that the current sampling point is effective point, and execute step S5;If not, then discard the instantaneous angular velocity corresponding to the current sampling point, and return to step S1 and process next sampling point;S5, the sign of instantaneous angular velocity corresponding to continuous effective point is trend statistics.It realizes reliable and fast power grid phase sequence detection.

Description

Technical Field

[0001] This invention relates to the field of power grid detection technology, and in particular to a method and apparatus for power grid phase sequence detection. Background Technology

[0002] Accurate phase sequence detection in the power grid is a crucial guarantee for the safe and stable operation of the power system. In fields such as power quality monitoring, relay protection, grid synchronization, and motor drives, accurately and quickly determining the phase sequence (positive or negative) of the three-phase voltage is of great significance for preventing equipment reversal, avoiding malfunctions, and ensuring reliable system operation.

[0003] Currently, common power grid phase sequence detection methods mainly include phase sequence judgment based on zero-crossing detection and phase analysis based on Fourier transform (FFT / DFT).

[0004] The phase sequence determination method based on zero-crossing detection determines the phase sequence by detecting the zero-crossing moments of the three-phase voltage signals from negative to positive (or from positive to negative) and comparing the time sequence of the three zero-crossing moments. If the zero-crossing moments of phases A, B, and C lag by approximately 1 / 3 of a cycle (e.g., approximately 6.67 ms in a 50Hz power grid), it is determined to be in positive sequence; otherwise, it is in reverse sequence. However, this method has inherent drawbacks: First, harmonics in the power grid (especially even and subharmonics) can distort the voltage waveform, potentially generating multiple "false zero-crossing moments" or shifting the true zero-crossing moment, leading to misjudgments. Second, noise such as glitches and spikes in the voltage signal can severely interfere with the accurate capture of zero-crossing moments. Although this can be suppressed by setting a hysteresis comparator circuit, it increases the complexity and uncertainty of the algorithm. Third, this method requires a high sampling rate; a low sampling rate will introduce a large quantization error in the zero-crossing moment. Finally, when the power grid frequency fluctuates (deviating from the rated 50Hz or 60Hz), the fixed time delay threshold will no longer be applicable, potentially leading to incorrect judgments.

[0005] Phase analysis methods based on Fourier Transform (FFT / DFT) synchronously sample three-phase voltage signals, extract the phase angle of the fundamental voltage wave of each phase using Discrete Fourier Transform (DFT) or Fast Fourier Transform (FFT), and then calculate the phase difference to determine the phase sequence. The limitations of this method are as follows: First, when sampling is asynchronous (i.e., the sampling frequency is not an integer multiple of the signal's fundamental frequency), spectral leakage and the picket-fence effect occur, leading to distortion of the calculated phase angle and severely affecting the reliability of the judgment. Second, to obtain sufficient frequency resolution for accurate phase calculation, a data window of at least one power frequency cycle is usually required, resulting in a slow dynamic response of the algorithm and failing to meet the requirements for rapid phase sequence determination. Third, FFT computation is relatively large, placing a heavy burden on low-cost, low-power microcontrollers (MCUs). Fourth, FFT is inherently suitable for steady-state signal analysis; in transient processes such as phase sequence switching and voltage surges / dips, its analysis results are prone to severe distortion, resulting in poor adaptability.

[0006] It is evident that existing power grid phase sequence detection methods generally suffer from problems such as weak anti-interference capability (susceptible to harmonics and noise), slow dynamic response speed, poor adaptability to frequency fluctuations and non-steady-state signals, or high computational complexity.

[0007] Therefore, there is an urgent need for a new detection method that can still achieve rapid and reliable phase sequence determination even when there are distortions, frequency fluctuations, and transient processes in the power grid. Summary of the Invention

[0008] In a first aspect, to solve the above-mentioned technical problems, a power grid phase sequence detection method is provided, comprising the following steps: S1. Signal Acquisition and Transformation: Synchronously sample the three-phase voltage signal of the power grid, and convert the three-phase voltage signal into α-axis and β-axis components in a two-phase stationary coordinate system through Clarke transformation; S2. Phase Angle Calculation and Offset: The instantaneous phase angle of the voltage space vector is calculated based on the α-axis component and the β-axis component, and the instantaneous phase angle is subjected to angle offset processing to obtain the offset phase angle; wherein, the offset processing is configured to make the offset phase angle in the positive sequence monotonically increase with time, and the offset phase angle in the reverse sequence monotonically decrease with time. S3. Angular velocity calculation: Calculate the instantaneous angular velocity based on the offset phase angle; S4. Valid Data Filtering: Define a valid angle interval that is far from the boundary of the angle value range; determine whether the offset phase angle corresponding to the current sampling point is within the valid angle interval. If so, the current sampling point is determined to be a valid point, and step S5 is executed; If not, discard the instantaneous angular velocity corresponding to the current sampling point and return to step S1 to process the next sampling point; S5. Trend Judgment and Output: Perform trend statistics on the signs of the instantaneous angular velocities corresponding to consecutive valid points: When the instantaneous angular velocity signs of M consecutive valid points are all positive, the output power grid phase sequence is determined to be positive. When the instantaneous angular velocity signs of M consecutive valid points are all negative, the output power grid phase sequence is determined to be reversed; where M is a preset positive integer threshold.

[0009] Furthermore, in S1, the constant amplitude Clarke transform is used, and its transform formula is as follows:

[0010]

[0011] In the formula, Va, Vb, and Vc are the instantaneous values ​​of the three-phase voltages, and Vα and Vβ are the transformed α-axis and β-axis components.

[0012] Further, in S2, the instantaneous phase angle θ is calculated using the formula θ = atan2(Vβ, Vα), where atan2() is the arctangent function in the four quadrants, and the range of θ is [-π, π]; the angle offset processing is performed using the formula θ shift = θ + π to achieve, so that the offset phase angle θ shift The value range of is [0, 2π].

[0013] Furthermore, in S3, the instantaneous angular velocity ω is determined by the formula ω = (θ) shift (n) - θ shift Calculate (n-1) / ΔT, where θ shift (n) and θ shift (n-1) represents the offset phase angles of the current and previous sampling points, respectively, and ΔT is the sampling period.

[0014] Furthermore, the effective angle range is [π / 2, 3π / 2].

[0015] Furthermore, the step of performing trend statistics on the signs of the instantaneous angular velocities corresponding to consecutive effective points specifically includes: S51. Set the forward sequence counter and the reverse sequence counter; S52. For each sampling point that is determined to be a valid point: If the instantaneous angular velocity is greater than zero, then the forward-sequence counter is incremented by one, and the reverse-sequence counter is reset to zero; If the instantaneous angular velocity is less than zero, then the reverse-order counter is incremented by one, and the forward-order counter is reset to zero; When the positive order counter reaches the threshold M, the positive order decision result is output; When the reverse order counter reaches the threshold M, the reverse order decision result is output.

[0016] A second aspect of the present invention provides a power grid phase sequence detection device, comprising: The signal sampling module is used to synchronously acquire the three-phase voltage signals of the power grid; A signal processing module, connected to the signal sampling module, is used to execute the steps of the power grid phase sequence detection method. The result output module is connected to the signal processing module and is used to output the phase sequence decision result.

[0017] Furthermore, the signal processing module includes an embedded microprocessor or a digital signal processor.

[0018] Compared with the prior art, the embodiments of the present invention have the following beneficial effects: This invention converts three-phase voltage signals into offset phase angles with a clear monotonic direction of change through Clarke transform and angle offset processing, thereby calculating instantaneous angular velocity. By establishing an effective angle interval filtering mechanism, calculation errors caused by angle period jumps are effectively avoided. Finally, a fault-tolerant decision is made based on the consistency trend of the angular velocity sign across multiple consecutive effective sampling points. This improves the robustness and reliability of detection under voltage harmonics, noise interference, and frequency fluctuations, while achieving millisecond-level fast response. It also boasts advantages such as low computational complexity and ease of embedded implementation. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is the overall flowchart disclosed in this invention. Detailed Implementation

[0021] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] This invention aims to provide a novel and rapid power grid phase sequence detection method. Based on the detection mechanism of dynamic angular velocity sign and trend recognition, it achieves rapid and reliable phase sequence judgment under non-ideal power grid conditions through data processing. It overcomes the inherent defects of traditional zero-crossing detection methods, such as poor anti-interference ability and reliance on fixed frequency, as well as the slow dynamic response and computational complexity of Fourier transform methods.

[0023] Please see Figure 1 The following describes in detail each step of the method of the present invention.

[0024] S1. Signal Acquisition and Transformation: Synchronously sample the three-phase voltage signals of the power grid and convert them into α-axis and β-axis components in a two-phase stationary coordinate system using Clarke transformation.

[0025] In practice, a constant-amplitude Clarke transform is used to maintain the signal amplitude unchanged before and after the transform. The transform formula is as follows:

[0026]

[0027] In the formula, Va, Vb, and Vc are the instantaneous values ​​of the three-phase voltages, and Vα and Vβ are the transformed α-axis and β-axis components.

[0028] After this transformation, the information of the three-phase voltage is condensed into the orthogonal α-axis component Vα and β-axis component Vβ. Subsequently, the voltage space vector Vs(n) = Vα(n) + j The instantaneous phase angle θ(n) of Vβ(n). To ensure ambiguity-free calculation within a 360-degree range, the instantaneous phase angle θ is calculated using the formula θ = atan2(Vβ, Vα), where atan2() is the arctangent function in the four quadrants, and the value range of θ is [-π, π].

[0029] S2. Phase Angle Calculation and Offset: The instantaneous phase angle of the voltage space vector is calculated based on the α-axis and β-axis components, and the instantaneous phase angle is offset to obtain the offset phase angle. The offset process is configured such that the offset phase angle in the forward sequence monotonically increases with time, and the offset phase angle in the reverse sequence monotonically decreases with time.

[0030] This step is a key part of the invention, aiming to convert the phase angle into a variable that directly reflects the direction of rotation. First, the phase angle θ(n) is linearly shifted; the angle shift is processed using the formula θ... shift = θ + π to achieve, so that the offset phase angle θ shift The value range of is [0, 2π].

[0031] Those skilled in the art will understand that, under the ideal positive sequence (ABC) condition, the voltage space vector rotates counterclockwise, θ shift It will monotonically increase from 0 to 2π over time, then return to zero in the next cycle and continue increasing; conversely, in the reverse order (ACB) case, the vector rotates clockwise, θ shift It will monotonically decrease from 2π to 0 with time, and then continue to decrease. This monotonicity lays the foundation for determining the phase sequence by the sign of the angular velocity.

[0032] S3, Angular velocity calculation: Instantaneous angular velocity is calculated based on the offset phase angle.

[0033] In discrete systems, angular velocity can be approximated by the angular difference between adjacent sampling points. The instantaneous angular velocity ω is expressed by the formula ω = (θ / ω). shift (n) - θ shift Calculate (n-1) / ΔT, where θ shift (n) and θ shift (n-1) represent the offset phase angles of the current and previous sampling points, respectively, and ΔT is the sampling period. In actual programming, to simplify calculations, the angle difference Δθ(n) = θ (without dividing by ΔT) can be directly used. shift (n)-θ shift (n-1) is used as a relative quantity of angular velocity for sign determination. It has the same sign as the true angular velocity ω and is equivalent in effect.

[0034] S4. Valid Data Filtering: Define a valid angle interval that is far from the boundary of the angle value range; determine whether the offset phase angle corresponding to the current sampling point is within the valid angle interval. If so, the current sampling point is determined to be a valid point, and step S5 is executed.

[0035] If not, discard the instantaneous angular velocity corresponding to the current sampling point and return to step S1 to process the next sampling point.

[0036] When θ shift When (n) jumps to 0 (positive order) after approaching 2π or jumps from 0 to 2π (reverse order), the calculated Δθ(n) or ω(n) will have a huge negative or positive peak with an absolute value close to 2π. This is a non-physical jump error that will seriously interfere with the decision.

[0037] To address this issue, this invention introduces an effective angle interval filtering mechanism. Specifically, an effective interval located in the middle of the circumference and far from the boundaries of 0 and 2π is predefined. As a preferred embodiment, this effective angle interval is set to [π / 2, 3π / 2]. After calculating θ for each sampling point... shift After (n), immediately make a judgment: If θshift If ω(n) is not within the interval [π / 2, 3π / 2], then the current point is determined to be an "invalid point". In this case, the ω(n) calculated in this sampling period is directly discarded and not sent to the subsequent decision logic. The program waits for the next sampling point and returns to step S1.

[0038] If θ shift If ω(n) is located within the interval [π / 2, 3π / 2], then the current point is determined to be a "valid point". At this time, the calculated ω(n) is retained and allowed to proceed to the final decision step S5.

[0039] This screening effectively filters out all abnormal angular velocity values ​​caused by the abrupt change of the circumferential boundary, ensuring the cleanliness of the data on which subsequent decisions are based.

[0040] S5. Trend Judgment and Output: Perform trend statistics on the signs of the instantaneous angular velocities corresponding to consecutive valid points: When the instantaneous angular velocity signs of M consecutive valid points are all positive, the output power grid phase sequence is determined to be positive. When the instantaneous angular velocity signs of M consecutive valid points are all negative, the output power grid phase sequence is determined to be reversed; where M is a preset positive integer threshold.

[0041] This step uses statistical regularity to combat random interference and ensure the reliability of the decision. The decision-making process is based on the principle of confirming a continuous trend.

[0042] In this scheme, the sign of the instantaneous angular velocity corresponding to consecutive effective points is statistically analyzed to determine its trend, specifically including: S51. Set the forward sequence counter and the reverse sequence counter.

[0043] S52. For each sampling point that is determined to be a valid point: If the instantaneous angular velocity is greater than zero, the forward-sequence counter is incremented by one, and the reverse-sequence counter is reset to zero.

[0044] If the instantaneous angular velocity is less than zero, the reverse counter is incremented by one, and the forward counter is reset to zero.

[0045] When the positive sequence counter reaches the threshold M, the positive sequence decision result is output.

[0046] When the reverse order counter reaches the threshold M, the reverse order decision result is output.

[0047] During implementation, two software counters are set—the forward-order counter Count_Pos and the reverse-order counter Count_Neg—both initialized to 0, and a decision threshold M is set (M is a positive integer, such as 5, 8, or 10). For each valid point filtered through step S4 and its angular velocity ω(n), the following logic is executed: (a) If ω(n)>0, it indicates that the current instantaneous rotation direction is counterclockwise (potentially forward trend). At this time, execute Count_Pos = Count_Pos + 1, and reset Count_Neg to 0.

[0048] (b) If ω(n) < 0, it indicates that the current instantaneous rotation direction is clockwise (potentially reversed). In this case, execute Count_Neg = Count_Neg + 1, and reset Count_Pos to 0.

[0049] (c) If ω(n) = 0 (which rarely occurs in an ideal power grid), then both counters remain unchanged.

[0050] The reset mechanism ensures that the decisions for forward and reverse order are mutually exclusive, and only a continuous and stable trend can cause a certain counter to accumulate.

[0051] Perform a decision check immediately after each counter update: If Count_Pos>= M, then the final determination of the power grid phase sequence is positive sequence (ABC).

[0052] If Count_Neg>= M, then the final determination is that the power grid phase sequence is reversed (ACB).

[0053] If none of the above conditions are met, the previous valid decision result will be maintained, or the "phase order pending" state will be output.

[0054] This decision mechanism, which requires "consistent sign at M consecutive valid points," demands that the phase sequence determination be based on a continuous and stable trend in angular velocity signs. Errors caused by noise or interference at a single or a few sampling points cannot alter the output, thus endowing the algorithm with extremely strong anti-interference capabilities and fault tolerance.

[0055] In one specific embodiment, the sampling frequency is set to 6.4 kHz (i.e., 128 points are sampled per power frequency cycle), the effective angle range is set to [π / 2, 3π / 2], and the decision threshold M is set to 5.

[0056] When the power grid is in a pure positive sequence state, the calculated ω(n) of all sampling points within the effective interval is positive, and Count_Pos is quickly accumulated to 5. The algorithm outputs the positive sequence decision within a few milliseconds, with a rapid response.

[0057] When the power grid contains a large number of harmonics or noise, although the symbols of ω(n) at a few sampling points may be incorrect due to interference, these isolated erroneous points will only cause the counter to be reset or the accumulation to be paused due to the continuous trend decision mechanism, without triggering an erroneous decision. The result will only be output when the correct symbol trend appears continuously for M times, ensuring high reliability.

[0058] When the power grid frequency fluctuates between 45Hz and 65Hz, the algorithm can automatically adapt without any parameter adjustment because the criterion is only the sign of the angular velocity rather than its absolute value, thus exhibiting inherent frequency adaptability.

[0059] Furthermore, during transient processes where the phase sequence changes abruptly, the algorithm can quickly capture the continuous reverse trend of the angular velocity symbol and complete the decision update within tens of milliseconds, demonstrating better dynamic performance than spectrum analysis methods that require full-cycle data windows.

[0060] Furthermore, the present invention also provides a power grid phase sequence detection device, including a signal sampling module, a signal processing module, and a result output module. The signal sampling module is used to synchronously acquire the three-phase voltage signals of the power grid; the signal processing module is connected to the signal sampling module and is used to execute the aforementioned power grid phase sequence detection method; the result output module is connected to the signal processing module and is used to output the phase sequence decision result.

[0061] The signal processing module includes an embedded microprocessor or a digital signal processor.

[0062] Those skilled in the art will understand that the signal sampling module acquires the three-phase voltage signals of the power grid (A, B, and C) through a voltage transformer or a voltage divider resistor network. The signal processing module typically includes filtering and amplification circuits to suppress high-frequency noise and adjust the voltage signals to the input range of the ADC. The ADC synchronously samples the conditioned three-phase voltages, converting the analog quantities into discrete digital sequences Va(n), Vb(n), and Vc(n), where n is the sampling sequence number. The MCU / DSP, acting as the signal processing module, receives the digital sequence from the ADC and executes all the algorithm steps described above. The result output module can be a display screen, a communication interface, or a relay contact, used to output the final phase sequence decision result.

[0063] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for detecting phase sequence in a power grid, characterized in that, Includes the following steps: S1. Signal Acquisition and Transformation: Synchronously sample the three-phase voltage signal of the power grid, and convert the three-phase voltage signal into α-axis and β-axis components in a two-phase stationary coordinate system through Clarke transformation; S2. Phase Angle Calculation and Offset: Calculate the instantaneous phase angle of the voltage space vector based on the α-axis component and the β-axis component, and perform angle offset processing on the instantaneous phase angle to obtain the offset phase angle; wherein, the offset processing is configured to make the offset phase angle in the positive sequence monotonically increase with time, and the offset phase angle in the reverse sequence monotonically decrease with time. S3. Angular velocity calculation: Calculate the instantaneous angular velocity based on the offset phase angle; S4. Valid Data Filtering: Define a valid angle interval that is far from the boundary of the angle value range; determine whether the offset phase angle corresponding to the current sampling point is within the valid angle interval. If so, the current sampling point is determined to be a valid point, and step S5 is executed; If not, discard the instantaneous angular velocity corresponding to the current sampling point and return to step S1 to process the next sampling point; S5. Trend Judgment and Output: Perform trend statistics on the signs of the instantaneous angular velocities corresponding to consecutive valid points: When the instantaneous angular velocity signs of M consecutive valid points are all positive, the output power grid phase sequence is determined to be positive. When the instantaneous angular velocity signs of M consecutive valid points are all negative, the output power grid phase sequence is determined to be reversed; where M is a preset positive integer threshold.

2. The power grid phase sequence detection method according to claim 1, characterized in that, The constant-amplitude Clarke transform is used in S1, and its transform formula is as follows: In the formula, Va, Vb, and Vc are the instantaneous values ​​of the three-phase voltages, and Vα and Vβ are the transformed α-axis and β-axis components.

3. The power grid phase sequence detection method according to claim 2, characterized in that, In step S2, the instantaneous phase angle θ is calculated using the formula θ = atan2(Vβ, Vα), where atan2() is the arctangent function in the four quadrants, and the range of θ is [-π, π]. The angle offset processing is performed using the formula θ shift = θ + π to achieve, so that the offset phase angle θ shift The value range of is [0, 2π].

4. The power grid phase sequence detection method according to claim 1, characterized in that, In S3, the instantaneous angular velocity ω is obtained using the formula ω = (θ) shift (n) - θ shift Calculate (n-1) / ΔT, where θ shift (n) and θ shift (n-1) represents the offset phase angles of the current and previous sampling points, respectively, and ΔT is the sampling period.

5. The power grid phase sequence detection method according to claim 1, characterized in that, The effective angle range is [π / 2, 3π / 2].

6. The power grid phase sequence detection method according to claim 1, characterized in that, The trend analysis of the sign of the instantaneous angular velocity corresponding to consecutive effective points specifically includes: S51. Set the forward sequence counter and the reverse sequence counter; S52. For each sampling point that is determined to be a valid point: If the instantaneous angular velocity is greater than zero, then the forward-sequence counter is incremented by one, and the reverse-sequence counter is reset to zero; If the instantaneous angular velocity is less than zero, then the reverse-order counter is incremented by one, and the forward-order counter is reset to zero; When the positive order counter reaches the threshold M, the positive order decision result is output; When the reverse order counter reaches the threshold M, the reverse order decision result is output.

7. A power grid phase sequence detection device, characterized in that, include: The signal sampling module is used to synchronously acquire the three-phase voltage signals of the power grid; A signal processing module, connected to the signal sampling module, is used to perform the steps of the power grid phase sequence detection method as described in any one of claims 1-6; The result output module is connected to the signal processing module and is used to output the phase sequence decision result.

8. The power grid phase sequence detection device according to claim 7, characterized in that, The signal processing module includes an embedded microprocessor or a digital signal processor.

Images