Harmonic real-time state evaluation and data transmission method and system for power distribution network

Abstract

The present application relates to the technical field of data transmission system, and particularly relates to a distribution network harmonic real-time state evaluation and data transmission method and system, the distribution network harmonic real-time state evaluation and data transmission system comprises a harmonic monitoring device and a harmonic analysis platform; the harmonic monitoring device comprises a data acquisition module, a harmonic voltage evaluation module, a harmonic power evaluation module, a data fitting module and a data transmission module; the data acquisition module is used for acquiring harmonic data of a monitoring object; the harmonic voltage evaluation module is used for judging whether the harmonic voltage of the monitoring object is out of limit according to national standard requirements; the harmonic power evaluation module is used for judging whether the harmonic power of the monitoring object is the same as a predicted value; the data fitting module is used for polynomial fitting of the harmonic data, can perform real-time evaluation on the distribution network harmonic, and reduces harmonic data transmission amount.

Description

Technical Field

[0001] This invention relates to the field of data transmission system technology, and in particular to a method and system for real-time status assessment and data transmission of distribution network harmonics. Background Technology

[0002] The distribution network is the most complex and diverse part of the power system. It can be considered that any place where electricity is used belongs to the distribution network. In order for the normal operation of the distribution network, it is necessary to evaluate the harmonic characteristics of the distribution network. At present, in order to evaluate the harmonic characteristics of the distribution network, the 2nd to 25th harmonics are mainly obtained by installing harmonic monitoring devices in the distribution network, and then transmitted to the harmonic analysis platform on the grid side for analysis. This results in the analysis and evaluation not being real-time. Summary of the Invention

[0003] The purpose of this invention is to provide a method and system for real-time status assessment and data transmission of distribution network harmonics, which can assess distribution network harmonics in real time.

[0004] To achieve the above objectives, in a first aspect, the present invention provides a real-time status assessment and data transmission system for distribution network harmonics, including a harmonic monitoring device and a harmonic analysis platform;

[0005] The harmonic monitoring device includes a data acquisition module, a harmonic voltage assessment module, a harmonic power assessment module, a data fitting module, and a data transmission module; the harmonic voltage assessment module, the harmonic power assessment module, and the data fitting module are respectively connected to the data acquisition module; the data transmission module is respectively connected to the harmonic voltage assessment module, the harmonic power assessment module, and the data fitting module; the harmonic analysis platform is connected to the data transmission module;

[0006] The data acquisition module is used to acquire harmonic data of the monitored object;

[0007] The harmonic voltage assessment module is used to determine whether the harmonic voltage of the monitored object exceeds the limit according to the national standard requirements. If it exceeds the limit, a voltage harmonic over-limit event is generated.

[0008] The harmonic power assessment module is used to determine whether the harmonic power of the monitored object is the same as the predicted value. If they are different, a harmonic power change event is generated.

[0009] The data fitting module is used to perform polynomial fitting on the harmonic data to obtain fitted data.

[0010] The data transmission module is used to send the voltage harmonic exceedance event, the harmonic power change event, and the fitted data to the harmonic analysis platform.

[0011] The data acquisition module includes a voltage acquisition unit, a current acquisition unit, and a calculation unit; the voltage acquisition unit, the current acquisition unit, and the calculation unit are connected in sequence.

[0012] The voltage acquisition unit is used to acquire voltage data of the monitored object;

[0013] The current acquisition unit is used to acquire the current data of the monitored object;

[0014] The calculation unit is used to calculate harmonic data based on the voltage and current data of the monitored object.

[0015] The harmonic data includes harmonic voltage, harmonic current, and harmonic power.

[0016] The harmonic analysis platform can restore the fitted data into harmonic data.

[0017] Secondly, the present invention also provides a method for real-time status assessment and data transmission of distribution network harmonics, including: acquiring harmonic data of the monitored object;

[0018] According to national standards, it is determined whether the harmonic voltage of the monitored object exceeds the limit. If it does, a voltage harmonic over-limit event is generated.

[0019] Determine whether the harmonic power of the monitored object is the same as the predicted value. If they are different, generate a harmonic power change event.

[0020] The harmonic data are fitted using a polynomial to obtain the fitted data;

[0021] The voltage harmonic exceedance event, the harmonic power change event, and the fitted data are sent to the harmonic analysis platform.

[0022] The acquisition of harmonic data of the monitored object includes:

[0023] Acquire voltage data of the monitored object;

[0024] Acquire the current data of the monitored object;

[0025] Harmonic data are calculated based on the voltage and current data of the monitored object.

[0026] The step of performing polynomial fitting on the harmonic data to obtain the fitted data includes:

[0027] Let a certain harmonic data be the first dataset. Fit the first dataset with a polynomial fitting function. When the fitting function error is less than the threshold, the fitting ends. When the fitting error cannot reach the threshold, the fitting is done piecewise.

[0028] Obtain the starting value, maximum value, minimum value, and average value from the first dataset, and summarize them.

[0029] This invention discloses a method and system for real-time assessment and data transmission of distribution network harmonics. The method utilizes a data acquisition module to acquire harmonic data of the monitored object; a harmonic voltage assessment module determines whether the harmonic voltage of the monitored object exceeds limits according to national standards, generating a voltage harmonic exceedance event if limits are exceeded; a harmonic power assessment module determines whether the harmonic power of the monitored object is the same as the predicted value, generating a harmonic power change event if they are different; a data fitting module performs polynomial fitting on the harmonic data to obtain fitted data; and a data transmission module sends the voltage harmonic exceedance event, the harmonic power change event, and the fitted data to a harmonic analysis platform. This method enables real-time assessment of distribution network harmonics, reduces the amount of harmonic data transmission, ensures the timeliness of distribution network harmonic assessment, and significantly reduces data transmission volume. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the 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.

[0031] Figure 1 This is a schematic diagram of the distribution network harmonic real-time status assessment and data transmission system of the present invention.

[0032] Figure 2 This is a structural schematic diagram of the data acquisition module of the present invention.

[0033] Figure 3 This is a flowchart of the distribution network harmonic real-time status assessment and data transmission method of the present invention.

[0034] Figure 4 This is a flowchart of the present invention for acquiring harmonic data of the monitored object.

[0035] Figure 5 This is a flowchart of the present invention for performing polynomial fitting on the harmonic data to obtain the fitted data.

[0036] 1-Harmonic monitoring device, 2-Harmonic analysis platform, 11-Data acquisition module, 12-Harmonic voltage assessment module, 13-Harmonic power assessment module, 14-Data fitting module, 15-Data transmission module, 111-Voltage acquisition unit, 112-Current acquisition unit, 113-Calculation unit. Detailed Implementation

[0037] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0038] Please see Figures 1-5 In a first aspect, the present invention provides a real-time status assessment and data transmission system for distribution network harmonics: including a harmonic monitoring device 1 and a harmonic analysis platform 2;

[0039] The harmonic monitoring device 1 includes a data acquisition module 11, a harmonic voltage evaluation module 12, a harmonic power evaluation module 13, a data fitting module 14, and a data transmission module 15; the harmonic voltage evaluation module 12, the harmonic power evaluation module 13, and the data fitting module 14 are respectively connected to the data acquisition module 11; the data transmission module 15 is respectively connected to the harmonic voltage evaluation module 12, the harmonic power evaluation module 13, and the data fitting module 14; the harmonic analysis platform 2 is connected to the data transmission module 15;

[0040] The data acquisition module 11 is used to acquire harmonic data of the monitored object;

[0041] The harmonic voltage assessment module 12 is used to determine whether the harmonic voltage of the monitored object exceeds the limit according to the national standard requirements. If it exceeds the limit, a voltage harmonic over-limit event is generated.

[0042] The harmonic power assessment module 13 is used to determine whether the harmonic power of the monitored object is the same as the predicted value. If they are different, a harmonic power change event is generated.

[0043] The data fitting module 14 is used to perform polynomial fitting on the harmonic data to obtain fitted data;

[0044] The data transmission module 15 is used to send the voltage harmonic exceedance event, the harmonic power change event, and the fitted data to the harmonic analysis platform 2.

[0045] In this embodiment, the data acquisition module 11 is deployed on the distribution network line and user end to acquire harmonic data of the monitored object. The harmonic data includes harmonic voltage, harmonic current, and harmonic power. The harmonic voltage assessment module 12 assesses harmonic voltage based on the limits specified in the national standard for each harmonic voltage and harmonic distortion rate. Therefore, the harmonic voltage assessment is judged according to the limits specified in the national standard (GB / T 14549-93). If the limit is exceeded, an assessment event is triggered. For example, the national standard specifies that the limit for the 6th harmonic voltage content of 10kV is 1.6%. If the 6th harmonic voltage content is 1.7%, a voltage harmonic exceedance event is generated. The harmonic power evaluation module 13 is based on the evaluation of harmonic power. The harmonic power is calculated by harmonic voltage, harmonic current and harmonic phase angle. Therefore, it can comprehensively evaluate the standard harmonic characteristics. Its calculation is shown in Equation (1), where P is the harmonic power, U is the harmonic amplitude, I is the harmonic current and θ is the phase angle difference between the harmonic voltage and the harmonic current.

[0046] P=U*I*cos(θ) (1)

[0047] The implementation steps are as follows:

[0048] Step 1: Given that the harmonic power sequence is divided into i segments, i.e., Pi, Pi = [P1, P2...PN], and N is the sequence number, calculate the average value Pavg of the N harmonic powers, i.e., equation (2).

[0049]

[0050] Step 2: Calculate the difference between Pi and Pavg to obtain a new sequence P*i, P*i = [P*1, P*2...P*N], i.e., equation (3).

[0051] P i * =P i -P avg (3)

[0052] Step 3: Fit the power curve Pi using an exponential function, i.e., equation (4), with fitting coefficients of...

[0053]

[0054] Step 4: Similarly, use a sliding window to obtain the harmonic power of Pi+1 in the next segment, and use the method in Step 3 to obtain the fitting coefficients. Calculate the ratio of the two fitted coefficients respectively. For example, the ratio of the first coefficient is k, as shown in equation (5). For any coefficient ratio, when k≥1.01 or k≤0.9, it is considered abnormal and a harmonic power change event is generated.

[0055]

[0056] Through the above (1) and (2), the harmonic characteristics of each object in the distribution network can be evaluated and analyzed in real time. The evaluation object can be selected as a single harmonic or the total harmonics, which can greatly reduce the calculation requirements of the harmonic analysis platform 2.

[0057] The data fitting module 14, considering the large number of harmonic indicators in the distribution network, taking the transmission of harmonics from the 2nd to the 25th order as an example, can diffract 100 data items such as harmonic voltage, harmonic current, harmonic power, and harmonic phase angle. Taking a 10-minute interval as an example, a single monitoring object needs to transmit 100*6*24=14400 data points. If a provincial power grid needs to deploy 100,000 distribution network harmonic monitoring devices 1, the total number of data points that need to be transmitted per day is 144,000,000. Therefore, reducing the amount of data transmission is particularly important for distribution network harmonic analysis. To this end, this invention performs polynomial fitting on each data item for one day, and then transmits the coefficients, initial value, maximum value, minimum value, and average value of the fitting function, thereby greatly reducing the number of data points that need to be transmitted, while also ensuring that the distribution network harmonic platform has complete data. The implementation process is as follows:

[0058] Step 1: Let a certain harmonic data be HMi, such as the second harmonic voltage, HMi = [HMi1, HMi2...HMiL]. The polynomial fitting function is shown in equation (6). Specifically, the least squares method can be used to obtain the result. Of course, polynomial fitting is only one implementation method, and other techniques can also be used for fitting. When the fitting function error e HMi When the error is less than a certain threshold, the fitting ends; if the fitting error cannot reach the threshold requirement, the fitting can be performed in segments.

[0059] f(HMi)=b0+b1*HMi+b2*HMi 2 +...b r *HMi r (6)

[0060] Step 2: Obtain the initial value HMi from HMi int Maximum value HMi end Minimum value HMi min and average HMi avg The data to be transferred is summarized as [bo, b1...br, HMi]. int HMi end HMi min HMi avg e HMi Typically, a three-dimensional fit is sufficient, so the number of transmission terms needs to be compressed to nine. Compared to the existing 144 data points, this greatly reduces the amount of data transmitted, by 90%.

[0061] The data transmission module 15 sends the voltage harmonic exceedance event, the harmonic power change event, and the fitted data to the harmonic analysis platform 2. The harmonic analysis platform 2 can reconstruct the harmonic data at any time using the fitting coefficients. The original starting value, maximum value, minimum value, and average value can provide key information about the monitoring point object and can also be used to verify whether the reconstructed data is correct. The fitting error is used to correct the data when the harmonic analysis platform 2 reconstructs the data.

[0062] The present invention provides a real-time status assessment and data transmission system for distribution network harmonics, which can assess distribution network harmonics in real time and reduce the amount of harmonic data transmission. This not only ensures the timeliness of distribution network harmonic assessment but also greatly reduces the amount of data transmission.

[0063] Furthermore, the data acquisition module 11 includes a voltage acquisition unit 111, a current acquisition unit 112, and a calculation unit 113; the voltage acquisition unit 111, the current acquisition unit 112, and the calculation unit 113 are connected in sequence.

[0064] The voltage acquisition unit 111 is used to acquire voltage data of the monitored object;

[0065] The current acquisition unit 112 is used to acquire the current data of the monitored object;

[0066] The calculation unit 113 is used to calculate harmonic data based on the voltage and current data of the monitored object.

[0067] In this embodiment, the voltage data of the monitored object is acquired by the voltage acquisition unit 111; the current data of the monitored object is acquired by the current acquisition unit 112; and the harmonic data such as harmonic voltage, harmonic current, and harmonic power are calculated by the calculation unit 113 based on the voltage data and current data of the monitored object.

[0068] Furthermore, the harmonic data includes harmonic voltage, harmonic current, and harmonic power.

[0069] Furthermore, the harmonic analysis platform 2 can restore the fitted data into harmonic data.

[0070] Secondly, the present invention also provides a method for real-time status assessment and data transmission of distribution network harmonics, comprising:

[0071] S1 acquires harmonic data of the monitored object;

[0072] The specific steps are as follows:

[0073] S11 acquires the voltage data of the monitored object;

[0074] The voltage data of the monitored object is acquired through the voltage acquisition unit 111.

[0075] S12 acquires the current data of the monitored object;

[0076] The current data of the monitored object is acquired using the current acquisition unit 112.

[0077] S13 calculates harmonic data based on the voltage and current data of the monitored object;

[0078] The calculation unit 113 calculates harmonic data such as harmonic voltage, harmonic current, and harmonic power based on the voltage and current data of the monitored object.

[0079] S2 determines whether the harmonic voltage of the monitored object exceeds the limit according to the national standard requirements. If it exceeds the limit, a voltage harmonic over-limit event is generated.

[0080] Based on harmonic voltage assessment, since the national standard specifies the limits for each harmonic voltage and harmonic distortion rate, the assessment based on harmonic voltage is judged with reference to the limits of the national standard (GB / T 14549-93). If the limit is exceeded, an assessment event is triggered. For example, the national standard specifies that the limit for the 6th harmonic voltage content of 10kV is 1.6%. If the 6th harmonic voltage content is 1.7%, a voltage harmonic exceedance event is generated.

[0081] S3 determines whether the harmonic power of the monitored object is the same as the predicted value. If they are different, a harmonic power change event is generated.

[0082] Based on the evaluation of harmonic power, the harmonic power is calculated by harmonic voltage, harmonic current and harmonic phase angle. Therefore, it can comprehensively evaluate the standard harmonic characteristics. The calculation is shown in Equation (1), where P is the harmonic power, U is the harmonic amplitude, I is the harmonic current and θ is the phase angle difference between the harmonic voltage and the harmonic current.

[0083] P=U*I*cos(θ) (1)

[0084] The implementation steps are as follows:

[0085] Step 1: Given that the harmonic power sequence is divided into i segments, i.e., Pi, Pi = [P1, P2...PN], and N is the sequence number, calculate the average value Pavg of the N harmonic powers, i.e., equation (2).

[0086]

[0087] Step 2: Calculate the difference between Pi and Pavg to obtain a new sequence P*i, P*i = [P*1, P*2...P*N], i.e., equation (3).

[0088] P i* =P i -P avg (3)

[0089] Step 3: Fit the power curve Pi using an exponential function, i.e., equation (4), with fitting coefficients of...

[0090]

[0091] Step 4: Similarly, use a sliding window to obtain the harmonic power of Pi+1 in the next segment, and use the method in Step 3 to obtain the fitting coefficients. Calculate the ratio of the two fitted coefficients respectively. For example, the ratio of the first coefficient is k, as shown in equation (5). For any coefficient ratio, when k≥1.01 or k≤0.9, it is considered abnormal and a harmonic power change event is generated.

[0092]

[0093] Through the above (1) and (2), the harmonic characteristics of each object in the distribution network can be evaluated and analyzed in real time. The evaluation object can be selected as a single harmonic or the total harmonics, which can greatly reduce the calculation requirements of the harmonic analysis platform 2.

[0094] S4 performs polynomial fitting on the harmonic data to obtain the fitted data;

[0095] The specific steps are as follows:

[0096] S41 Let a certain harmonic data be the first dataset. Fit the first dataset with a polynomial fitting function. When the fitting function error is less than the threshold, the fitting ends. When the fitting error cannot reach the threshold, the fitting is done piecewise.

[0097] Let a certain harmonic data be HMi, such as the second harmonic voltage, HMi=[HMi1,HMi2...HMiL], the polynomial fitting function is as shown in equation (6), which can be obtained using the least squares method. Of course, polynomial fitting is only one implementation scheme, and other techniques can also be used for fitting; when the fitting function error e HMi When the error is less than a certain threshold, the fitting ends; if the fitting error cannot reach the threshold requirement, the fitting can be performed in segments.

[0098] f(HMi)=b0+b1*HMi+b2*HMi 2 +...b r *HMi r (6)

[0099] S42 obtains the starting value, maximum value, minimum value and average value from the first dataset and summarizes them;

[0100] Obtain the initial value HMi from HMi. int Maximum value HMi end Minimum value HMi min and average HMi avg The data to be transferred is summarized as [bo, b1...br, HMi]. int HMi end HMi min HMi avg e HMi Typically, a three-dimensional fit is sufficient, so the number of transmission terms needs to be compressed to nine. Compared to the existing 144 data points, this greatly reduces the amount of data transmitted, by 90%.

[0101] S5 sends the voltage harmonic exceedance event, the harmonic power change event, and the fitted data to the harmonic analysis platform 2;

[0102] By sending the voltage harmonic exceedance event, the harmonic power change event, and the fitted data to the harmonic analysis platform 2, the harmonic analysis platform 2 can reconstruct the harmonic data at any time using the fitting coefficients. The original starting value, maximum value, minimum value, and average value can provide key information about the monitoring point object and can also be used to verify whether the reconstructed data is correct. The fitting error is used to correct the data when the harmonic analysis platform 2 reconstructs the data.

[0103] The present invention provides a method for real-time status assessment and data transmission of distribution network harmonics, which can assess distribution network harmonics in real time and reduce the amount of harmonic data transmission. This not only ensures the timeliness of distribution network harmonic assessment but also greatly reduces the amount of data transmission.

[0104] The above description discloses only one preferred embodiment of the present invention, and should not be construed as limiting the scope of the present invention. Those skilled in the art will understand that all or part of the processes of the above embodiments can be implemented, and equivalent changes made in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1.A system for real-time harmonic state evaluation and data transmission in distribution network, comprising a harmonic monitoring device and a harmonic analysis platform, wherein the harmonic monitoring device comprises a data acquisition module, a harmonic voltage evaluation module, a harmonic power evaluation module, a data fitting module and a data transmission module, the harmonic voltage evaluation module, the harmonic power evaluation module and the data fitting module are connected with the data acquisition module, the data transmission module is connected with the harmonic voltage evaluation module, the harmonic power evaluation module and the data fitting module, and the harmonic analysis platform is connected with the data transmission module. 2.The system of claim 1, wherein the harmonic data comprises harmonic voltage, harmonic current and harmonic power. 3.The system of claim 2, wherein the harmonic analysis platform can restore the fitting data into harmonic data. 4.A method for real-time harmonic state evaluation and data transmission in distribution network, comprising: acquiring harmonic data of a monitoring object; judging whether harmonic voltage of the monitoring object is out of limit according to national standard, and generating a voltage harmonic over-limit event if the harmonic voltage is out of limit; judging whether harmonic power of the monitoring object is the same as a predicted value, and generating a harmonic power change event if the harmonic power is different from the predicted value; performing polynomial fitting on the harmonic data to obtain fitting data; and transmitting the voltage harmonic over-limit event, the harmonic power change event and the fitting data to the harmonic analysis platform. 5.The method of claim 4, wherein the acquiring harmonic data of a monitoring object comprises: acquiring voltage data of the monitoring object; acquiring current data of the monitoring object; and calculating harmonic data according to the voltage data and the current data of the monitoring object. The harmonic power evaluation module is used to judge whether the harmonic power of the monitoring object is the same as the predicted value, and if not, a harmonic power change event is generated; the specific implementation steps are: the harmonic power is calculated through harmonic voltage, harmonic current and harmonic phase angle, and the calculation formula is: , wherein P is the harmonic power, U is the harmonic amplitude, I is the harmonic current, is the phase angle difference between the harmonic voltage and the harmonic current; the harmonic power sequence is divided into i sections, i.e. i , P i =[P1, P2...P N ], N is the sequence number, the average value P avg of the N harmonic powers is calculated, and the formula is: ; the difference between P i and P avg is obtained to obtain a new sequence , , i.e. the formula is: ; the power curve is fitted using the exponential function, and the fitting coefficients are =[ , ... ]; the harmonic power of the next section is obtained using the sliding window, and the fitting coefficients =[ , ... ] obtained by fitting are used to calculate the ratio k of the two fitting coefficients, and the formula is: , for any coefficient ratio, when k≥1.01 or k≤0.9, it is considered abnormal, and a harmonic power change event is generated; 6.The method of claim 5, wherein the performing polynomial fitting on the harmonic data to obtain fitting data comprises: ​ ​ ​ ​ ​ ​ ​ ​ ​ 4. A method for real-time state evaluation and data transmission of power distribution network harmonics, applied to the system for real-time state evaluation and data transmission of power distribution network harmonics according to any one of claims 1-3, characterized in that, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ If a certain harmonic data is a first data set, fitting is performed on the first data set with a polynomial fitting function, and when the fitting function error is less than a threshold value, the fitting is ended, and when the fitting error cannot reach the threshold value, then piecewise fitting is performed; The starting value, maximum value, minimum value and average value are obtained from the first data set, which are summarized.

Images