A method and device for regulating three-phase unbalance of single-phase load

Abstract

The present invention belongs to the field of three-phase unbalanced regulation of single-phase load, and specifically relates to a method and device for regulating three-phase unbalanced single-phase load. The method comprises the following steps: S1: online monitoring of the load on the power consumption side is performed through an online monitoring module, and the information obtained from the online monitoring is uploaded to a cloud processing center in real time; S2: when the cloud recognizes that a three-phase unbalanced condition occurs, the cloud formulates a load shedding strategy for the phase-changing mechanism through the information obtained by the online monitoring module; S3: the cloud controls the phase-changing mechanism to perform a load shedding operation according to the load shedding strategy; S4: after the load shedding operation is completed, the cloud continues to perform online monitoring through the online monitoring module, and detects whether the three-phase unbalance is eliminated or controlled within an acceptable range. If not, step S2 is repeated until the three-phase unbalance is controlled. The three-phase unbalanced fault caused by the unbalanced single-phase load can be eliminated, the power quality is improved, and the safety of electricity use is guaranteed at the same time.

Description

Technical Field

[0001] The invention belongs to the field of three-phase unbalanced regulation of single-phase load, and in particular relates to a method and a device for regulating three-phase unbalanced regulation of single-phase load. Background Art

[0002] Three-phase load balance is the basis of safe power supply, while unbalanced three-phase load will reduce the power supply efficiency of the line and distribution transformer at the least, and may cause serious consequences such as burning of a phase conductor, burning of switches, or even burning of a single phase of the distribution transformer due to excessive overload of the heavy load phase. Therefore, only when the three-phase impedance is balanced can the low-voltage leakage protection operate well and prevent personal electric shock casualties. Only when the three-phase load is balanced can the power quality of users be guaranteed. Keeping the three-phase load balanced is also the basis for saving energy, reducing losses and reducing prices. Summary of the invention

[0003] The technical problem to be solved by the present invention is that in the low-voltage distribution network of the power system, a single-phase fault or a sudden increase in single-phase load often causes a three-phase unbalanced fault in the power system, which will endanger the power quality or cause serious accidents.

[0004] The technical solution provided by the present invention is: a method for regulating three-phase unbalance of a single-phase load, comprising the following steps:

[0005] S1: Monitor the load on the power consumption side online through the online monitoring module, and upload the information obtained from the online monitoring to the cloud processing center in real time;

[0006] S2: When the cloud recognizes that a three-phase imbalance occurs, the cloud formulates a load shedding strategy for the commutation mechanism based on the information obtained by the online monitoring module;

[0007] S3: The cloud controls the commutation mechanism to perform load shedding operations according to the load shedding strategy;

[0008] S4: After the load shedding operation is completed, the cloud continues to perform online monitoring through the online monitoring module and detects whether the three-phase imbalance is eliminated or controlled within an acceptable range. If not, repeat step S2 until the three-phase imbalance is effectively controlled;

[0009] The cloud uses the load balancing method to judge different commutation modes based on the voltage and current waveforms when three-phase imbalance occurs and the circuit information to which the single-phase load increases, and thus makes a commutation strategy.

[0010] The load balancing method is as follows: Assume that there are 3m commutation mechanisms at the location where a single-phase load mutation occurs, and each commutation mechanism is connected to one load. Then the A, B, and C three-phase load matrix d formed by the 3m loads before commutation is m×3 for:

[0011]

[0012] Among them, dia, dib, and dic represent the current three-phase load values ​​respectively;

[0013]

[0014]

[0015]

[0016] Where L A is the total load of phase A, L B is the total load of phase B, L C is the total load of phase C; let the average value of the total load of the three phases be L avg By exchanging the positions of the three values ​​in each row of the matrix, the difference between the single-phase total load and is minimized, that is, Min(|L A -L avg |+|L B -L avg |+|L C -L avg |);

[0017] K=(|L A -L avg |+|L B -L avg |+|L C -L avg |); K is the three-phase load unbalance coefficient.

[0018] -ΔL A =L A -L avg ;

[0019] -ΔL B =L B -L avg ;

[0020] -ΔL C =L C -L avg ;

[0021] ΔL A , ΔL B and ΔL C are the required adjustment values ​​for the three-phase loads respectively; A , ΔL B and ΔL C Arrange from large to small, find the phase where the load in the middle position needs to be adjusted, and calculate the d in each row of the other two phases. iPerform exhaustive exchange; there are 2 n permutations; and find out K after each permutation, select K i The minimum commutation scheme obtains the corresponding commutation strategy.

[0022] Furthermore, the cloud can also filter the voltage and current data monitored by the online monitoring module, and perform harmonic analysis on the filtered third and above harmonics to analyze the hidden dangers of the load.

[0023] Furthermore, the cloud can also record the time when the load that causes three-phase imbalance occurs, the circuit information to which it belongs, and the current and voltage waveforms; and identify whether it is a valid load or an unexpected load through the waveform; if it is a valid load, it will be recorded, and machine learning will be performed through the large amount of recorded data to provide a control strategy for the power generation side.

[0024] Furthermore, the filtering process may be a wavelet threshold filtering process.

[0025] Furthermore, the threshold selection method of the wavelet threshold filtering process may be: a fixed threshold, an extreme value threshold, an unbiased likelihood estimation threshold and a heuristic estimation threshold.

[0026] Furthermore, the wavelet basis of the wavelet threshold filtering process may be Haar wavelet, db wavelet or sym wavelet.

[0027] On the other hand, the present invention also provides a single-phase load three-phase unbalanced regulation device, comprising: an online monitoring module, a cloud and a phase-changing mechanism; the input end of the phase-changing mechanism is connected to the mains, and the output end is connected to the load;

[0028] The online monitoring module includes: a current transformer, a voltage transformer and a communication device; the current transformer and the voltage transformer are respectively connected to the communication device; the communication device establishes a data connection with the cloud; the current transformer and the voltage transformer are both mounted on the wire;

[0029] The commutation mechanism includes: a processor and a contact commutator; the processor is connected to the contact commutator; and the processor establishes a data connection with the cloud.

[0030] Furthermore, the phase switching mechanism may also include a contactless phase switch, and the contactless phase switch is connected to the processor.

[0031] The beneficial effects of the present invention are: reasonable phase-changing decisions are made through the cloud, and the phase-changing mechanism executes the decision, thereby effectively eliminating the three-phase unbalanced fault caused by single-phase load imbalance, improving the quality of electric energy, and ensuring the safety of electricity use. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A flow chart of a method for regulating three-phase unbalance of a single-phase load according to the present invention;

[0033] Figure 2 A flow chart of a load balancing method of a single-phase load three-phase unbalanced regulation method of the present invention;

[0034] Figure 3 The present invention is a system structure diagram of a phase-changing mechanism of a three-phase unbalanced regulating device for a single-phase load.

[0035] Marks in the figure: K1, K2 and K3 are all contact commutators, and CT is an online monitoring module. DETAILED DESCRIPTION

[0036] In order for those skilled in the art to better understand the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0037] Example 1

[0038] See also Figure 1 and Figure 2 The present invention provides a method for regulating three-phase unbalance of a single-phase load, comprising the following steps:

[0039] S1: The load on the power consumption side is monitored online through the online monitoring module, and the information obtained from the online monitoring is uploaded to the cloud processing center in real time;

[0040] S2: When the cloud recognizes that a three-phase unbalanced state occurs, the cloud formulates a load shedding strategy for the phase-changing mechanism through the information obtained by the online monitoring module;

[0041] S3: The cloud controls the commutation mechanism to perform load shedding operations according to the load shedding strategy;

[0042] S4: After the load shedding operation is completed, the cloud continues to perform online monitoring through the online monitoring module and detects whether the status is eliminated or controlled within an acceptable range. If not, repeat step S2 until the three-phase imbalance is effectively controlled;

[0043] The cloud uses the voltage and current waveforms when the fault occurs and the circuit information to which the fault belongs to, and uses the load balancing method to judge different commutation methods, thereby making the optimal commutation strategy;

[0044] The load balancing method is as follows: Assume that there are 3m commutation mechanisms at the location where a single-phase load mutation occurs, and each commutation mechanism is connected to one load. Then the A, B, and C three-phase load matrix d formed by the 3m loads before commutation is m×3 for:

[0045]

[0046] Among them, dia, dib, and dic represent the current three-phase load values ​​respectively;

[0047]

[0048]

[0049]

[0050] Among them, L A is the total load of phase A, L B is the total load of phase B, L C is the total load of phase C; let the average value of the total load of the three phases be L avg By exchanging the positions of the three values ​​in each row of the matrix, the difference between the single-phase total load and is minimized, that is, Min(|L A -L avg |+|L B -L avg |+|L C -L avg |);

[0051] K=(|L A -L avg |+|L B -L avg |+|L C -L avg |); K is the three-phase load unbalance coefficient.

[0052] -ΔL A =L A -L avg ;

[0053] -ΔL B =L B -L avg ;

[0054] -ΔL C =L C -L avg ;

[0055] ΔL A , ΔL B and ΔL C are the required adjustment values ​​for the three-phase loads respectively; A , ΔL B and ΔL C Arrange from large to small, find the phase where the load in the middle position needs to be adjusted, and calculate the d in each row of the other two phases. i Perform exhaustive exchange; there are 2 n permutations; and find out K after each permutation, select K i The minimum commutation scheme obtains the corresponding commutation strategy.

[0056] The cloud monitors the current and voltage data in real time through the online monitoring module to obtain the load data; when three-phase imbalance occurs, the cloud makes a load shedding strategy and executes the strategy through the phase switching mechanism; the single-phase excessive load is reduced to eliminate the three-phase imbalance fault, thereby improving the power quality and ensuring the user's power safety.

[0057] Example 2

[0058] Based on Example 1, the cloud can also filter the voltage and current data monitored by the online monitoring module; and perform harmonic analysis on the filtered third and above harmonics to analyze the potential fault hazards of the load.

[0059] Harmonics are a major hazard to the quality of power in distribution systems. When a sinusoidal voltage is applied to a nonlinear load, harmonics are generated when the fundamental current is distorted. Therefore, the cloud needs to analyze the harmonics in the distribution system and give timely safety warnings.

[0060] It should be pointed out that the cloud can also record the time when the load that causes three-phase imbalance occurs, the circuit information to which it belongs, and the current and voltage waveforms; and identify whether it is a valid load or an unexpected load through the waveform; if it is a valid load, it will be recorded, and machine learning will be performed through the large amount of recorded data to provide a control strategy for the power generation side.

[0061] When a new community is being renovated collectively, or the temperature changes suddenly, the cooling or heating equipment is frequently started and stopped. This is the main reason for the imbalance of the three-phase load in the low-voltage civil distribution network. The cloud can learn from a large amount of historical data to predict the occurrence of three-phase load imbalance. Therefore, the cloud can also make predictions based on historical data to provide power generation control strategies to the power generation side.

[0062] It should be noted that the cloud can perform wavelet threshold filtering on the data obtained from online monitoring. Wavelet threshold filtering can retain harmonic information to the greatest extent, and the information processed by wavelet threshold filtering has a higher signal-to-noise ratio, and obtains true and reliable signals to the greatest extent.

[0063] Among them, the threshold selection methods for wavelet threshold filtering can be: fixed threshold, extreme value threshold, unbiased likelihood estimation threshold and heuristic estimation threshold. These four threshold selection methods can be flexibly selected according to the different loads and interference types, which can optimize the filtering results and make the information obtained by the cloud more accurate.

[0064] In addition, the wavelet basis of the wavelet threshold filtering process can be Haar wavelet, db wavelet or sym wavelet. Different wavelets are suitable for different load conditions, which can optimize the filtering effect and make the information obtained by the cloud more accurate.

[0065] Example 3

[0066] like Figure 3 As shown, a single-phase load three-phase unbalanced regulation device includes: an online monitoring module CT, a cloud and a phase-changing mechanism;

[0067] The online monitoring module CT includes: a current transformer, a voltage transformer and a communication device; the current transformer and the voltage transformer are respectively connected to the communication device; the communication device establishes a data connection with the cloud; the current transformer and the voltage transformer are both sleeved on the wire; the phase-changing mechanism includes: a processor and a contact phase-changing device; the processor is connected to the contact phase-changing device; the processor establishes a data connection with the cloud. The incoming line end of the phase-changing mechanism is connected to the mains, and the output end is connected to the load.

[0068] The online monitoring module CT collects load information in the circuit through current transformers and voltage transformers, and uploads it to the cloud in real time; the commutation mechanism, as the commutation actuator, completes the commutation operation, and the processor controls the contact commutator to complete the commutation operation according to the commutation decision made by the cloud.

[0069] Preferably, the commutation mechanism may further include a contactless commutator, which is respectively connected in parallel with the contact commutator K1, the contact commutator K2 and the contact commutator K3; the contactless commutator is connected to the processor.

[0070] In order to reduce the risk of operating overvoltage and other hazards during the phase change process, the device can also be equipped with a contactless phase changer; during the phase change operation, the contactless phase changer is first connected, then the contact phase changer is connected, and the contactless phase changer is disconnected to complete the phase change operation. The contactless phase changer participates in the phase change process, which can suppress the generation of operating overvoltage, improve the stability of the power supply system, improve the power quality, and increase the safety of the system.

[0071] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of equivalent changes by using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for regulating three-phase unbalance of a single-phase load, characterized in that: The steps include: S1: The load on the power consumption side is monitored online through the online monitoring module, and the information obtained from the online monitoring is uploaded to the cloud processing center in real time; S2: When the cloud recognizes that a three-phase imbalance occurs, the cloud formulates a load shedding strategy for the commutation mechanism based on the information obtained by the online monitoring module; S3: The cloud controls the commutation mechanism to perform load shedding operations according to the load shedding strategy; S4: After the load shedding operation is completed, the cloud continues to perform online monitoring through the online monitoring module and detects whether the three-phase imbalance is eliminated and suppressed. If not, repeat step S2 until the three-phase imbalance is controlled; The cloud uses a load balancing method to judge different commutation modes based on the voltage and current waveforms when three-phase imbalance occurs and the circuit information to which the single-phase load increases, thereby making a commutation strategy; The load balancing method is as follows: assuming that there are 3m commutation mechanisms at the location where a single-phase load mutation occurs, and each commutation mechanism is connected to one load, then the A, B, and C three-phase load matrix formed by the 3m loads before commutation is for: in, , , Respectively represent the current three-phase load values; is the total load of phase A, is the total load of phase B, is the total load of phase C; Assume that the average value of the total three-phase load is , ; K is the three-phase load unbalance coefficient; ； ； ； , and are the required adjustment values ​​for the three-phase loads respectively; , and Arrange from large to small, find the phase where the load in the middle position needs to be adjusted, and Perform exhaustive exchange; permutations; and find out K after each permutation, select The minimum commutation scheme, and the corresponding commutation strategy; The cloud performs filtering processing on the voltage and current data monitored by the online monitoring module; and performs harmonic analysis on the filtered third and above harmonics to analyze the potential fault hazards of the load; The cloud records the time when the load that causes three-phase imbalance occurs, the circuit information to which it belongs, and the current and voltage waveforms; and identifies whether it is a valid load or an unexpected load through the waveform; if it is a valid load, it is recorded, and machine learning is performed through the recorded data to provide a control strategy for the power generation side.

2. A method for regulating three-phase unbalance of a single-phase load as claimed in claim 1, characterized in that: The filtering process is a wavelet threshold filtering process.

3. A method for regulating three-phase unbalance of a single-phase load as claimed in claim 2, characterized in that: The threshold selection methods of the wavelet threshold filtering process are: fixed threshold, extreme value threshold, unbiased likelihood estimation threshold and heuristic estimation threshold.

4. A method for regulating three-phase unbalance of a single-phase load as claimed in claim 2, characterized in that: The wavelet basis of the wavelet threshold filtering process is Haar wavelet, db wavelet or sym wavelet.

5. A three-phase unbalanced regulating device for a single-phase load, characterized in that: A method for regulating three-phase unbalanced single-phase load according to any one of claims 1 to 4, comprising: an online monitoring module, a cloud and a phase-changing mechanism, wherein the input end of the phase-changing mechanism is connected to the mains, and the output end is connected to the load; The online monitoring module includes: a current transformer, a voltage transformer and a communication device. The current transformer and the voltage transformer are respectively connected to the communication device. The communication device establishes a data connection with the cloud. The current transformer and the voltage transformer are both mounted on the wire. The commutation mechanism includes: a processor and a contact commutator, the processor is connected to the contact commutator, and the processor establishes a data connection with the cloud.

6. A three-phase unbalanced regulating device for a single-phase load as claimed in claim 5, characterized in that: The phase-changing mechanism also includes a contactless phase-changing device, and the contactless phase-changing device is connected to the processor.

Images