Three-phase voltage state estimation method and system based on virtual coordinates

Abstract

The invention relates to the technical field of three-phase systems, and provides a three-phase voltage state estimation method and system based on virtual coordinates, and the method comprises the steps: calculating the voltage peak value of each phase for three-phase voltages, and determining that a phase is open if the peak voltage of a certain phase is lower than a threshold value in the three peak voltages; for three-phase voltage, virtual beta-axis voltage is generated through an all-pass filter, actual beta-axis voltage is obtained through Clark transformation, the product of the virtual beta-axis voltage and the actual beta-axis voltage serves as an evaluation function, and a positive sequence and a negative sequence are distinguished according to the positive and negative of the evaluation function. The system state can be accurately and effectively judged under the conditions of three-phase imbalance and voltage distortion, the anti-noise capability and the anti-harmonic interference capability are high, and safe and stable operation of equipment under the abnormal condition is ensured.

Description

Technical Field

[0001] This invention belongs to the field of three-phase systems, and particularly relates to a method and system for estimating the three-phase voltage state based on virtual coordinates. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] In a three-phase system, ideally, the three-phase voltage amplitudes are equal, the phase difference is 120 degrees, and they rotate in RST sequence. However, in actual operation, due to load fluctuations, equipment failures, or line problems, voltage imbalance, phase sequence reversal, or phase loss often occur in three-phase systems, seriously affecting the operational safety of equipment. In particular, for induction equipment such as motors, voltage imbalance or incorrect phase sequence can lead to torque imbalance, thermal overload, and even equipment damage. For parallel generator sets, phase sequence reversal or phase mismatch may cause synchronization failure, resulting in a three-phase system malfunction.

[0004] Currently, various methods exist for anomaly detection in three-phase systems, such as those based on zero-crossing, dual-synchronous reference systems, and phase-locked loops (PLLs), which can identify problems like voltage imbalance and phase sequence reversal. However, these methods often experience performance degradation when faced with extreme voltage imbalances or harmonic distortions, making it difficult to achieve real-time and efficient detection. Summary of the Invention

[0005] To address the technical problems mentioned above, this invention provides a three-phase voltage state estimation method and system based on virtual coordinates. It generates a virtual β-axis voltage that lags the R-phase voltage by 90°, multiplies it by the actual β-axis voltage obtained through Clarke transform, and uses the sign of the evaluation function to determine abnormal states such as positive sequence and negative sequence. Furthermore, it designs an all-pass filter for each phase voltage to calculate the peak value of each phase, thereby determining phase loss. This method achieves accurate and effective system state determination under three-phase imbalance and voltage distortion conditions, exhibits strong noise and harmonic interference resistance, and ensures the safe and stable operation of equipment under abnormal conditions.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of the present invention provides a three-phase voltage state estimation method based on virtual coordinates, comprising: Obtain the three-phase voltage; For three-phase voltage, calculate the peak voltage of each phase. If the peak voltage of a certain phase is lower than the threshold among the three peak voltages, it is determined to be a phase loss. For three-phase voltage, a virtual β-axis voltage is generated through an all-pass filter, and the actual β-axis voltage is obtained through Clarke transform. The product of the virtual β-axis voltage and the actual β-axis voltage is used as the evaluation function, and the positive and negative sequences are distinguished by the sign of the evaluation function.

[0007] Furthermore, the voltage peak is the square root of the sum of the squares of the phase voltage and its 90° phase delay signal.

[0008] Furthermore, the 90° phase delay signal is obtained by inputting each phase voltage into an all-pass filter.

[0009] Furthermore, the all-pass filter is designed to cause the output signal to lag the input signal by 90° at the corresponding three-phase voltage frequency.

[0010] Furthermore, under voltage balance conditions, the actual β-axis voltage is ;in, The peak value of each phase voltage is given. Let t be the voltage angular frequency, and t be the time variable.

[0011] Furthermore, under voltage imbalance conditions, the actual β-axis voltage is ;in, For amplitude terms, For phase terms, Let t be the voltage angular frequency, and t be the time variable.

[0012] Furthermore, the virtual β-axis voltage is ;in, The peak value of each phase voltage is given. Let t be the voltage angular frequency, and t be the time variable.

[0013] A second aspect of the present invention provides a three-phase voltage state estimation system based on virtual coordinates, comprising: The data acquisition module is configured to acquire three-phase voltage. The phase loss detection module is configured to: calculate the peak voltage of each phase for three-phase voltage; if the peak voltage of a certain phase is lower than the threshold among the three peak voltages, it is determined to be a phase loss. The positive and negative sequence determination module is configured as follows: for three-phase voltage, a virtual β-axis voltage is generated through an all-pass filter, and the actual β-axis voltage is obtained through Clarke transformation. The product of the virtual β-axis voltage and the actual β-axis voltage is used as the evaluation function, and the positive and negative sequences are distinguished by the sign of the evaluation function.

[0014] A third aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the three-phase voltage state estimation method based on virtual coordinates as described above.

[0015] A fourth aspect of the present invention provides a computer device including a computer-readable storage medium, a processor, and a computer program stored on the computer-readable storage medium and executable on the processor, wherein the processor executes the program to implement the steps in the three-phase voltage state estimation method based on virtual coordinates as described above.

[0016] Compared with the prior art, the beneficial effects of the present invention are: This invention generates a virtual β-axis voltage that lags the R-phase voltage by 90°. After multiplying this virtual voltage with the actual β-axis voltage obtained through Clarke transformation, it uses the sign of the evaluation function to determine abnormal states such as positive sequence and negative sequence. Furthermore, it designs an all-pass filter for each phase voltage to calculate the peak value of each phase, thereby determining the phase loss situation. This invention achieves accurate and effective judgment of the system state under three-phase imbalance and voltage distortion conditions, and has strong anti-noise and anti-harmonic interference capabilities, ensuring the safe and stable operation of the equipment under abnormal conditions. Attached Figure Description

[0017] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0018] Figure 1 This is a flowchart of a three-phase voltage state estimation method based on virtual coordinates according to Embodiment 1 of the present invention; Figure 2 This is a conceptual diagram of the Clarke transform according to Embodiment 1 of the present invention; Figure 3 This is the Bode plot of the all-pass filter that generates a 90° phase delay at the three-phase voltage frequency according to Embodiment 1 of the present invention. Figure 4 This is a control block diagram of phase sequence detection according to Embodiment 1 of the present invention; Figure 5 This is a graph of the evaluation function curve as a function of voltage amplitude under voltage imbalance conditions according to Embodiment 1 of the present invention. Figure 6 This is a schematic diagram of the voltage waveform and detection results under the forward phase sequence in Embodiment 1 of the present invention; Figure 7 This is a schematic diagram of the voltage waveform and detection results under reverse phase sequence according to Embodiment 1 of the present invention; Figure 8 This is a schematic diagram of the voltage waveform and detection results under forward and reverse phase sequence transient conditions in Embodiment 1 of the present invention; Figure 9 This is a schematic diagram of the voltage waveform and detection results under the forward phase sequence of the present invention when the three-phase voltage is distorted; Figure 10This is a schematic diagram of the voltage waveform and detection results under reverse phase sequence three-phase voltage distortion in Embodiment 1 of the present invention; Figure 11 This is a schematic diagram of the voltage waveform and detection results under the condition of three-phase voltage imbalance in the case of phase sequence transients in Embodiment 1 of the present invention. Figure 12 This is a schematic diagram of the structure of a computer device according to Embodiment 4 of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0020] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0021] Example 1 This embodiment provides a three-phase voltage state estimation method based on virtual coordinates.

[0022] How to detect the three-phase voltage status in a complex three-phase system in real time and effectively identify abnormal situations has become a key issue in ensuring the safe operation of equipment.

[0023] This embodiment provides a three-phase voltage state estimation method based on virtual coordinates, which has low computational complexity and high real-time performance, and can better adapt to complex three-phase system environments, ensuring the safe operation of equipment.

[0024] To address the problem of equipment failure or three-phase system accidents caused by abnormal conditions such as incorrect phase sequence, phase loss, and voltage imbalance in three-phase systems, this embodiment provides a three-phase voltage state estimation method based on virtual coordinates. By generating a virtual voltage that lags the R-phase voltage by 90°, and comparing it with the actual β-axis voltage obtained by the three-phase voltage through the Clark Transform, the system abnormal states such as positive sequence, reverse sequence, and open phase can be distinguished.

[0025] This embodiment provides a three-phase voltage state estimation method based on virtual coordinates, which does not rely on complex phase-locked loops or differential calculations, greatly reducing the computational burden and improving the noise immunity of the three-phase system. It can also effectively determine the state of the three-phase system under complex conditions such as three-phase imbalance and voltage distortion, effectively improving the monitoring accuracy and real-time performance of the three-phase system, and ensuring the safe and stable operation of the equipment under abnormal conditions of the three-phase system.

[0026] This embodiment provides a three-phase voltage state estimation method based on virtual coordinates, comprising two main parts: phase loss detection and phase sequence determination.

[0027] This embodiment provides a three-phase voltage state estimation method based on virtual coordinates, such as... Figure 1 As shown, it includes the following steps: Step 1, Phase Loss Detection: Measure the three-phase voltage v R , v S , v T Each phase voltage is processed by an all-pass filter to generate a 90° phase delay signal, which can be used to calculate the peak phase voltage (the square root of the sum of the squares of the phase voltage and its 90° phase delay signal is the peak value of each phase voltage). If the peak voltage of one of the three calculated peak voltages is lower than a set threshold, it is determined to be a phase loss.

[0028] Step 2: Determine the positive and negative order.

[0029] The three-phase stationary coordinate system voltage signal is converted into the α-axis and β-axis voltage signals in the two-phase stationary coordinate system by the Clarke transform. Figure 2 This shows the α-β axis plane obtained through the Clarke transform. Under ideal equilibrium conditions, the mathematical relationship in the α-β coordinate system can be defined as follows: ; in, and Three-phase voltage v R , v S , v T The α-β axis voltages obtained through the Clarke transform.

[0030] (1) Under voltage balance conditions, the peak values ​​of the phase voltages are the same, and this common value is denoted as . The three-phase voltage is defined by the following formula: ; in, Let t be the voltage angular frequency, and t be the time variable.

[0031] By analyzing the R-phase voltage signal v R Adding an all-pass filter can generate a virtual β-axis voltage. . Figure 3The Bode plot of an all-pass filter is given. It does not change the amplitude of the signal, but only its phase. This shows that an all-pass filter can be designed to lag the output signal by 90° at the corresponding three-phase voltage frequencies, thereby generating a virtual β-axis voltage. The resulting signal with a phase shift of 90° is shown in equation (3); furthermore, under positive and negative sequence conditions, the actual β-axis voltage obtained by the Clarke transform conforms to equation (4): ; ; Generate a virtual β-axis voltage that lags the R-phase voltage by 90°. Then, it is compared with the actual β-axis voltage obtained by the Clarke transform. Comparison. Under positive sequence conditions (three-phase voltages in RST order), the β-axis voltage... It will lag the R-phase voltage by 90°. and They appear to be in phase. Under negative sequence conditions (the phases of the three-phase voltages are in RTS order), It will lead the R-phase voltage by 90°. and This exhibits a 180° phase difference. Therefore, in the positive sequence case, the virtual voltage... With actual β-axis voltage The product is positive; in the negative sequence case, the virtual voltage... With actual β-axis voltage The product of is negative.

[0032] The evaluation function is defined as the product of the virtual β-axis voltage obtained from equation (3) and equation (4), and its expression is: ; Therefore, the sign of equation (5) can be used to determine whether the three-phase system is in positive or negative sequence.

[0033] Figure 4 The control block diagram for phase sequence detection is given, and the three-phase voltage is converted into phase sequence using the Clarke transform. and All-pass filters introduce a 90° phase delay at the three-phase voltage frequency (50Hz or 60Hz, etc.), thereby producing ;Will and The product is multiplied, and the result is passed through a low-pass filter and compared with 0 to generate a phase sequence indicator signal DIR to determine the positive and negative sequence of the three-phase system.

[0034] (2) Under voltage imbalance, the actual three-phase β-axis voltage described in equation (4) will vary with the degree of voltage imbalance. Equation (4) can be restated as: ; The amplitude term in equation (6) and phase term The definition is as follows: ; ; Under voltage imbalance, the evaluation function can be reformulated as: ; in, , and These represent the voltage amplitudes of phases a, b, and c under unbalanced conditions, respectively.

[0035] Figure 5 This indicates that, as the amplitude of a certain phase voltage changes, the minimum value of the evaluation function is always greater than 0.4 under voltage imbalance conditions. This shows that even if there is noise of up to 50% in the phase voltage amplitude, the evaluation function can still distinguish between positive and negative sequence cases.

[0036] In summary, the judgment criteria can be summarized as follows: (10).

[0037] This embodiment provides a three-phase voltage state estimation method based on virtual coordinates. It generates a virtual voltage β-axis voltage that lags the R-phase voltage by 90°, multiplies it with the actual β-axis voltage obtained by Clarke transformation, and then judges the abnormal state of the three-phase system, such as positive sequence and negative sequence, by the positive or negative sign of the evaluation function.

[0038] Since it is difficult to extract specific information for each phase after the Clarke transform, this embodiment provides a three-phase voltage state estimation method based on virtual coordinates, which designs an all-pass filter for each phase voltage to calculate the peak value of each phase, thereby determining the phase loss situation.

[0039] This embodiment provides a three-phase voltage state estimation method based on virtual coordinates, which can accurately and effectively determine the state of the three-phase system even under three-phase imbalance and voltage distortion conditions. It has strong anti-noise and anti-harmonic interference capabilities, ensuring the safe and stable operation of the equipment under abnormal three-phase system conditions.

[0040] like Figure 6 , Figure 7 , Figure 8 , Figure 9 , Figure 10 , Figure 11As shown, the simulation results confirm that the three-phase voltage state estimation method based on virtual coordinates provided in this embodiment can accurately and effectively determine the positive and negative sequence conditions, and the phase sequence detection can be achieved in 6ms; it can accurately and effectively determine the positive and negative sequence conditions, and can effectively determine the state of the three-phase system under conditions such as phase sequence transients, voltage distortion, and voltage imbalance.

[0041] This embodiment provides a three-phase voltage state estimation method based on virtual coordinates, which is simple, easy to implement, and has a fast response. It does not rely on complex algorithms and circuits and is suitable for implementation on embedded systems such as digital signal processors.

[0042] Example 2 This embodiment provides a three-phase voltage state estimation system based on virtual coordinates, including: The data acquisition module is configured to acquire three-phase voltage. The phase loss detection module is configured to: calculate the peak voltage of each phase for three-phase voltage; if the peak voltage of a certain phase is lower than the threshold among the three peak voltages, it is determined to be a phase loss. The positive and negative sequence determination module is configured as follows: for three-phase voltage, a virtual β-axis voltage is generated through an all-pass filter, and the actual β-axis voltage is obtained through Clarke transformation. The product of the virtual β-axis voltage and the actual β-axis voltage is used as the evaluation function, and the positive and negative sequences are distinguished by the sign of the evaluation function.

[0043] It should be noted that each module in this embodiment corresponds one-to-one with each step in Embodiment 1, and their specific implementation processes are the same, so they will not be repeated here.

[0044] Example 3 This embodiment provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps in the three-phase voltage state estimation method based on virtual coordinates as described in Embodiment 1 above.

[0045] Example 4 This embodiment provides a computer device, such as... Figure 12 As shown, the system includes a computer-readable storage medium 1003, a processor 1001, a communication interface 1002, and a computer program stored on the computer-readable storage medium 1003 and executable on the processor 1001. The processor 1001, communication interface 1002, and computer-readable storage medium 1003 can be connected via a bus or other means. The communication interface 1002 is used to receive and transmit data. When the processor 1001 executes the program, it implements the steps in the three-phase voltage state estimation method based on virtual coordinates as described in Embodiment 1 above.

[0046] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A virtual coordinate-based three-phase voltage state estimation method, characterized by, The method comprises: acquiring three-phase voltages; for the three-phase voltages, calculating a voltage peak value of each phase, and determining a phase loss if a peak value of a certain phase is lower than a threshold value among the three peak voltage values; for the three-phase voltages, generating a virtual β-axis voltage through a all-pass filter, obtaining an actual β-axis voltage through a Clarke transformation, taking a product of the virtual β-axis voltage and the actual β-axis voltage as an evaluation function, and distinguishing a positive sequence and a negative sequence through a positive and negative of the evaluation function.

2. A virtual coordinate based three-phase voltage state estimation method as claimed in claim 1, wherein, The voltage peak value is a square root of a sum of a phase voltage and a 90° phase delay signal of the phase voltage.

3. A virtual coordinate based three-phase voltage state estimation method as claimed in claim 2, wherein, The 90° phase delay signal is obtained by inputting each phase voltage into a all-pass filter.

4. The virtual coordinate based three-phase voltage state estimation method of claim 1, wherein, The all-pass filter is designed to make an output signal lag an input signal by 90° at a frequency corresponding to the three-phase voltage.

5. The virtual coordinate based three-phase voltage state estimation method of claim 1, wherein, Under the voltage balance condition, the actual β-axis voltage is ; wherein, is the peak value of each phase voltage, is the voltage angular frequency, and t is the time variable.

6. A virtual coordinate based three-phase voltage state estimation method as claimed in claim 1, wherein, Under voltage unbalance conditions, the actual β-axis voltage is ; where, is the amplitude term, is the phase term, is the voltage angular frequency, and t is the time variable.

7. A virtual coordinate based three-phase voltage state estimation method as claimed in claim 1, wherein, The virtual β-axis voltage is ; wherein is the peak value of the phase voltage, is the voltage angular frequency, and t is the time variable.

8. A virtual coordinate based three-phase voltage state estimation system, characterized by, The method comprises: a data acquisition module configured to acquire three-phase voltages; a phase loss judgment module configured to, for the three-phase voltages, calculate a voltage peak value of each phase, and determine a phase loss if a peak value of a certain phase is lower than a threshold value among the three peak voltage values; a positive and negative sequence judgment module configured to, for the three-phase voltages, generate a virtual β-axis voltage through a all-pass filter, obtain an actual β-axis voltage through a Clarke transformation, take a product of the virtual β-axis voltage and the actual β-axis voltage as an evaluation function, and distinguish a positive sequence and a negative sequence through a positive and negative of the evaluation function.

9. A computer readable storage medium having stored thereon a computer program, characterized in that, The program is executed by the processor to implement the steps in the three-phase voltage state estimation method based on virtual coordinates according to any one of claims 1-7.

10. A computer device, comprising a computer readable storage medium, a processor, and a computer program stored on the computer readable storage medium and executable on the processor, wherein, The processor executes the program to implement the steps in the three-phase voltage state estimation method based on virtual coordinates according to any one of claims 1-7.

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