High-precision voltage sag detection method based on unit Hartley joint matrix decomposition

Abstract

The invention belongs to the technical field of electric power, and discloses a high-precision voltage sag detection method based on unit Hartley joint matrix decomposition. Firstly, a voltage sag data model is established, and secondly, a joint matrix capable of completely and accurately expressing voltage sag characteristics is designed. And solving an expression coefficient of the voltage sag in the joint matrix by using orthogonal matching pursuit, and finally solving voltage sag characteristics according to a joint matrix coefficient, including starting and ending time and amplitude of the voltage sag. According to the method, the voltage sag amplitude and the sag starting and ending time can be accurately detected at the same time, and the real-time and accurate detection effect is achieved. And a unit Hartley matrix is utilized, so that complex operation required by a traditional frequency method is omitted, and the calculation complexity is reduced.

Description

Technical Field

[0001] The invention belongs to the field of electric power technology, and in particular relates to a high-precision voltage sag detection method based on unit Hartley joint matrix decomposition. Background Art

[0002] In actual smart grids, the complexity and unknown nature of power quality disturbances make accurate detection difficult. Voltage sags contain both steady-state disturbance characteristics (sag amplitude) and transient disturbance characteristics (sag start and end time). Due to the limitations of the Heisenberg uncertainty principle, the time and frequency resolution cannot be optimized at the same time, that is, the two characteristics cannot be accurately detected at the same time. Therefore, in practical applications, traditional methods cannot accurately detect all the characteristics of voltage sags at the same time, which makes it difficult to accurately detect voltage sags. Summary of the invention

[0003] To solve the above problems, the purpose of the present invention is to propose a high-precision voltage sag detection method based on unit Hartley joint matrix decomposition, and the present invention is implemented by adopting the following technical solutions.

[0004] A high-precision voltage sag detection method based on unit Hartley joint matrix decomposition, characterized by comprising the following steps: S1. Use voltage transformer and current transformer to collect voltage and current signals of distribution network; S2. Establishing a power quality disturbance data model; S3. Design a joint basis and establish an expression equation for power quality disturbance data in the joint basis; S4. Use OMP to express the components of power quality disturbance data with optimal resolution in the joint basis; S5. Extract the power quality disturbance characteristics, including the start and end time and amplitude of the voltage sag.

[0005] The high-precision voltage sag detection method based on unit Hartley joint matrix decomposition described above is characterized in that step S1 specifically includes: S1, using a voltage transformer to collect the voltage signal of the distribution network, and connecting the voltage transformer in parallel at the voltage sag detection point to obtain the voltage signal.

[0006] The high-precision voltage sag detection method based on unit Hartley joint matrix decomposition described above is characterized in that step S2 specifically includes: establishing a voltage sag mathematical model such as formula Where u(t) is the voltage signal detected by the transformer, U sag is the voltage amplitude after the temporary drop, U N is the rated voltage, ω nis the system power frequency, θ1 is the voltage phase angle before the sag, θ2 is the voltage phase angle before the sag, t1 is the start time of the sag, and t2 is the end time of the sag.

[0007] The high-precision voltage sag detection method based on unit Hartley joint matrix decomposition described above is characterized in that step S3 specifically includes: designing a joint matrix consistent with the voltage sag characteristics. According to the power quality measurement standard, the voltage sag characteristics include the sag amplitude U sag And the sag start and end time t1, t2. The sag start and end time is a transient characteristic, which is an instantaneous change in voltage, and the sag amplitude is a steady-state characteristic, which is the voltage value maintained after the voltage sag. Therefore, the present invention constructs a joint matrix based on the unit matrix and the Hartley matrix, using the unit matrix to express the transient characteristics and the Hartley matrix to express the steady-state characteristics. In formula (2), n is the number of sample points of discrete voltage, I is the unit matrix, whose dimension is n×n, and H is the Hartley matrix, whose dimension is n×n. Function cas(.)=sin(.)+cos(.). The unit Hartley joint matrix A is obtained as follows: A=[Ι,H] n×2n (3).

[0008] The high-precision voltage sag detection method based on unit Hartley joint matrix decomposition described above is characterized in that step S4 specifically comprises: performing joint matrix decomposition on the voltage vector u containing n sampling points to express it as: u=Ac=[Ι,H][c I ,c H ] T (4) Where c is the coefficient vector after the voltage is decomposed, c I The coefficients corresponding to the decomposition of the unit matrix, c H Corresponding to the coefficients after Hartley matrix decomposition, T is the matrix transpose. Using orthogonal matching pursuit to solve equation (4) to obtain c I With c H .

[0009] The high-precision voltage sag detection method based on unit Hartley joint matrix decomposition is characterized in that step S5 specifically comprises: I The voltage sag start and end time are obtained by processing. Voltage sag is defined as a voltage drop of 0.2 pu, that is, a sudden change of voltage to 0.2 pu. I The first point in the vector that is greater than or equal to 0.2pu is at time t1, and the second point that is greater than or equal to 0.2pu is at time t2. HThe voltage sag amplitude is obtained by processing. The voltage sag part is restored according to t1 and t2 and equation (5), and U is obtained by the effective value method. sag . RMS(u(t))=RMS(U sag cos(ω n t+θ2))t1≤t≤t2 (5) In formula (5), RMS(.) is the effective value function.

[0010] The present invention has the following main beneficial technical effects: the present invention uses the unit Hartley joint matrix analysis method to accurately detect the voltage sag amplitude (steady-state characteristics) and the sag start and end time (transient characteristics) at the same time. At the same time, the method only uses real number operation, avoids complex complex number operation, and improves algorithm efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 Block diagram of a high-precision voltage sag detection method based on unit Hartley joint matrix decomposition.

[0012] Figure 2 Schematic diagram of the measurement of the start and end time and amplitude of the disturbance without phase angle displacement.

[0013] Figure 3 Schematic diagram of the measurement of the start and end time and amplitude of a disturbance with phase angle shift. DETAILED DESCRIPTION

[0014] In order to enable those skilled in the art to better understand and implement this patent, the specific implementation methods of this application are now described in detail in conjunction with the drawings in the specification.

[0015] Implementation Example 1: Please see Figures 1 to 3 , a high-precision voltage sag detection method based on unit Hartley joint matrix decomposition, comprising the following steps: S1, using voltage transformer to collect distribution network voltage signal; S2. Establishing voltage sag disturbance data model; S3, design a joint matrix consistent with the voltage sag characteristics; S4, using orthogonal matching pursuit to obtain the optimal resolution expression of the voltage sag in the joint matrix; S5. Calculate the voltage sag amplitude and the voltage sag start and end time using the coefficients obtained by decomposing the voltage sag in the joint matrix.

[0016] The above-mentioned step S1 specifically includes: connecting a voltage transformer in parallel at a voltage sag detection point to obtain a voltage signal. The above-mentioned step S2 specifically includes: establishing a voltage sag mathematical model as shown in the formula Where u(t) is the voltage signal detected by the transformer, U sag is the voltage amplitude after the temporary drop, U N is the rated voltage, ω n is the system power frequency, θ1 is the voltage phase angle before the sag, θ2 is the voltage phase angle before the sag, t1 is the start time of the sag, and t2 is the end time of the sag.

[0017] The above-mentioned step S3 specifically includes: designing a joint matrix consistent with the voltage sag characteristics. According to the power quality measurement standard, the voltage sag characteristics include the sag amplitude U sag And the sag start and end time t1, t2. The sag start and end time is a transient characteristic, which is an instantaneous change in voltage, and the sag amplitude is a steady-state characteristic, which is the voltage value maintained after the voltage sag. Therefore, the present invention constructs a joint matrix based on the unit matrix and the Hartley matrix, using the unit matrix to express the transient characteristics and the Hartley matrix to express the steady-state characteristics. In formula (2), n is the number of sample points of the discrete voltage, I is the unit matrix, whose dimension is n×n, and H is the Hartley matrix, whose dimension is n×n. Function cas(.)=sin(.)+cos(.). The unit Hartley joint matrix A is obtained as follows: A=[Ι,H] n×2n (3)

[0018] The above-mentioned step S4 specifically includes: performing a joint matrix decomposition on the voltage vector u containing n sampling points to express it as: u=Ac=[Ι,H][c I ,c H ] T (4) Where c is the coefficient vector after the voltage is decomposed, c I The coefficients corresponding to the decomposition of the unit matrix, c H Corresponding to the coefficients after Hartley matrix decomposition, T is the matrix transpose. Using orthogonal matching pursuit to solve equation (4) to obtain c I With c H .

[0019] The above-mentioned step S5 specifically includes: I The voltage sag start and end time are obtained by processing. Voltage sag is defined as a voltage drop of 0.2 pu, that is, a sudden change of voltage to 0.2 pu. I The time at which the first point in the vector is greater than or equal to 0.2pu is t1, and the time at which the second point in the vector is greater than or equal to 0.2pu is t2. C HThe voltage sag amplitude is obtained by processing. The voltage sag part is restored according to t1 and t2 and equation (5), and U is obtained by the effective value method. sag . RMS(u(t))=RMS(U sag cos(ω n t+θ2))t1≤t≤t2 (5) In formula (5), RMS(.) is the effective value function.

[0020] Specific implementation verification: Because the voltage sag is defined as below 0.8pu, that is, the voltage drops by 0.2pu, the non-zero coefficients of the time domain coefficients less than 0.2pu are ignored. Fundamental frequency f n =50Hz,ω n =2πf n , sampling frequency is 6400Hz, and voltage signal duration is 0.2s.

[0021] (1) Generate a time domain signal x, which starts with a cosine wave with a frequency of 50 Hz and an amplitude of 1. At 0.05 s, the signal amplitude changes to 0.4, and at 0.15 s, the signal amplitude changes back to 1. This signal has no phase shift, and random noise is added to the signal to simulate the disturbance in the actual measurement. This signal simulates the actual voltage sag. The joint basis decomposition is applied to the disturbance signal to extract the time domain and frequency domain data. The start and end time of the voltage sag is obtained using the time domain data. The signal is reconstructed using the frequency domain data, and then the amplitude of the voltage sag is obtained by processing. The measurement of the start and end time and amplitude of the disturbance without phase shift is as follows: Figure 2 It can be seen that the sag amplitude detection is accurate and the start and end times are error-free.

[0022] (2) Generate another time domain signal x, which starts with a cosine wave with a frequency of 50 Hz and an amplitude of 1. At 0.05 s, the signal amplitude changes to 0.4 and the phase shifts by 60 degrees. At 0.15 s, the signal amplitude returns to 1 and the phase also returns to the original phase. Add random noise to the signal to simulate the disturbance in the actual measurement. This signal simulates the actual voltage sag. The joint basis decomposition is applied to the disturbance signal to extract the time domain and frequency domain data. The start and end time of the voltage sag is obtained using the time domain data. The signal is reconstructed using the frequency domain data, and then the amplitude of the voltage sag is obtained by processing. The measurement of the start and end time and amplitude of the disturbance with phase angle shift is as follows: Figure 3 It can be seen that the sag amplitude detection is accurate and the start and end times are error-free.

[0023] The above embodiments are only preferred technical solutions of the present invention and should not be regarded as limiting the present invention. The protection scope of the present invention shall be the technical solutions recorded in the claims, including the equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A high-precision voltage sag detection method based on unit Hartley joint matrix decomposition, characterized in that The steps include: S1. Use voltage transformer and current transformer to collect voltage and current signals of distribution network; S2. Establishing a power quality disturbance data model; S3. Design a joint basis and establish an expression equation for power quality disturbance data in the joint basis; S4. Use OMP to express the components of power quality disturbance data with optimal resolution in the joint basis; S5. Extract the power quality disturbance characteristics, including the start and end time and amplitude of the voltage sag.

2. A high-precision voltage sag detection method based on unit Hartley joint matrix decomposition according to claim 1, characterized in that Step S1 specifically includes: S1, using a voltage transformer to collect a voltage signal of the distribution network, and connecting the voltage transformer in parallel at a voltage sag detection point to obtain a voltage signal.

3. The high-precision voltage sag detection method based on unit Hartley joint matrix decomposition according to claim 2 is characterized in that Step S2 specifically includes: establishing a voltage sag mathematical model such as: Where u(t) is the voltage signal detected by the transformer, U sag is the voltage amplitude after the temporary drop, U N is the rated voltage, ω n is the system power frequency, θ1 is the voltage phase angle before the sag, θ2 is the voltage phase angle before the sag, t1 is the start time of the sag, and t2 is the end time of the sag.

4. The high-precision voltage sag detection method based on unit Hartley joint matrix decomposition according to claim 1 is characterized in that Step S3 specifically includes: designing a joint matrix consistent with the voltage sag characteristics. According to the power quality measurement standard, the voltage sag characteristics include the sag amplitude U sag And the sag start and end time t1, t2, where the sag start and end time is the transient characteristic, which is the instantaneous change of voltage, and the sag amplitude is the steady-state characteristic, which is the voltage value maintained after the voltage sag. Therefore, a joint matrix based on the unit matrix and the Hartley matrix is ​​constructed, and the unit matrix is ​​used to express the transient characteristics, and the Hartley matrix is ​​used to express the steady-state characteristics: In formula (2), n is the number of sample points of discrete voltage, I is the unit matrix, whose dimension is n×n, H is the Hartley matrix, whose dimension is n×n; function cas(.)=sin(.)+cos(.); The unit Hartley joint matrix A is obtained as follows: A=[I,H] n×2n (3)。 5. The high-precision voltage sag detection method based on unit Hartley joint matrix decomposition according to claim 1 is characterized in that Step S4 specifically includes: performing a joint matrix decomposition on the voltage vector u containing n sampling points to express it as: u=Ac=[Ι,H][c I ,c H ] T (4) Where c is the coefficient vector after the voltage is decomposed, c I The coefficients corresponding to the decomposition of the unit matrix, c H Corresponding to the coefficients after Hartley matrix decomposition, T is the matrix transpose; using orthogonal matching pursuit to solve equation (4) to obtain c I With c H .

6. The high-precision voltage sag detection method based on unit Hartley joint matrix decomposition according to claim 1 is characterized in that Step S5 specifically includes: I The voltage sag start and end time are obtained by processing; the voltage sag is defined as a voltage drop of 0.2 pu, that is, the voltage suddenly changes to 0.2 pu; at c I The time at which the first point in the vector is greater than or equal to 0.2 pu is t1, and the time at which the second point is greater than or equal to 0.2 pu is t2; for c H The voltage sag amplitude is obtained by processing; the voltage sag part is restored according to t1 and t2 and formula (5), and U is obtained by the effective value method. sag : RMS(u(t))=RMS(U sag cos(ω n t+θ2))t1≤t≤t2 (5) In formula (5), RMS(.) is the effective value function.

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