WO2018064929A1

WO2018064929A1 - Three-phase load balancing control method and system

Info

Publication number: WO2018064929A1
Application number: PCT/CN2017/102075
Authority: WO
Inventors: 陆惠斌; 车凯; 徐勇; 刘恒门; 高晓宁; 曹磊; 王宝安
Original assignee: 国网江苏省电力公司扬州供电公司; 国家电网公司
Priority date: 2016-10-09
Filing date: 2017-09-18
Publication date: 2018-04-12
Also published as: CN106374511A; CN106374511B

Abstract

A three-phase load balancing control method and a system. User loads in a power distribution station are divided into a first part and a second part. The first part is the user loads which are far away from the transformer in the power distribution station, and the second part is the user loads which are close to the transformer. Commutations are performed on the phases of the currents in the user loads so as to achieve three-phase load balance.

Description

Three-phase load balance control method and system

Technical field

The present disclosure relates to the field of power distribution technology, for example, to a three-phase load balancing control method and system.

Background technique

In the low-voltage distribution network system, there are a large number of single-phase, asymmetrical, non-linear, and impact loads. Due to the poor design of the power grid in the related technology, a large number of single-phase loads are concentrated in one or two phases. These unbalanced loads can cause a three-phase imbalance in the power distribution system, resulting in an imbalance in the three-phase voltage and current of the power supply system.

Three-phase load imbalance in low-voltage distribution networks is an objective problem in related technologies. The low-voltage distribution network usually adopts a three-phase four-wire power supply mode, and the users are mostly single-phase loads or single-phase and three-phase hybrid loads. A three-phase load imbalance in the low voltage distribution network will result in increased line losses and "low voltage" at the end of the line. Moreover, with the large-scale use of distributed new energy sources, especially the access of 220V single-phase new energy sources, the three-phase load imbalance problem of low-voltage distribution networks will become more prominent.

The three-phase unbalance problem is solved by installing a reactive power compensation device in the power distribution station area or manually commutating the user's load;

However, the installation of the reactive power compensation device can only ensure the current balance on the outlet side of the transformer, and can not effectively solve the problem of "low voltage" at the end of the distribution line, nor can it effectively reduce the line loss of the distribution network;

Manually commutating the user's load can only solve the above problems to a certain extent. However, due to the dynamic nature of the distribution network load, it is necessary to manually commutate the user's load frequently, which requires a lot of manpower and material resources and economic benefits. difference.

Summary of the invention

The present disclosure proposes a three-phase load balancing control method and system, which can determine an automatic phase selection switch installed at the user end for phase change, to achieve distributed load balancing of the low voltage distribution station line, and to solve the line end "low voltage" The problem is to minimize distribution line losses.

The present disclosure provides a three-phase load balancing control method, including:

11) dividing the user load in the power distribution station area into a first part and a second part, wherein the first part is a user load that exceeds a preset distance from a transformer in the power distribution station area, and the second part is a user load that is less than a preset distance from the transformer;

And dividing a user load in the first part according to a distance between the distribution network node and the transformer, and dividing all user loads in the second part into a last area;

And numbering the area according to the distance between the distribution network node and the transformer, wherein N is the number of the Nth area, and N is a natural number;

12), A phase total current I_a, B phase total current I_b and phase C total current I_c of all user loads in the detection area (N-1), summing and summing the currents of phase A in the region N, and B The phase currents are added and summed, and the currents of the C phases are added and summed, and the currents I_a, I_b, and I_c in the previous region are respectively added to obtain the region currents I_A_sum, I_B_sum, and I_C_sum, and regions. Current average I_sum_av=(I_A_sum+I_B_sum+I_C_sum)/3, and regional current imbalance s_area=(I_sum_max-I_sum_av)/3×100%, where I_sum_max is the largest current value among the regional currents I_A_sum, I_B_sum, and I_C_sum Current

13), determine whether the area N is the last area, in the case of yes, then perform step 15);

If not, when s_area is greater than or equal to the preset area current imbalance, step 14) is performed; when s_area is less than the preset area current imbalance, use N+1 to replace N, and perform step 12);

14), when the number of scheduled handovers to the area N is greater than or equal to the preset number of scheduled handovers, then replace N with N+1, and perform step 12);

When the number of scheduled handovers to the area N is less than the preset number of scheduled handovers, after performing the scheduling handover on the area N, step 12) is performed;

The scheduling switch is: searching for a user load in the region N that is identical to the I_sum_min and having the current value closest to (I_sum_max-I_sum_min)/2, and switching the current in the user load to the region N. I_sum_min is the same phase, where I_sum_min is the current with the smallest current value among the regional currents I_A_sum, I_B_sum, and I_C_sum;

15) detecting total current I_A of phase A at the outlet end of the transformer, total current I_B of phase B, and total current I_C of phase C to obtain an average value of current per phase I_av=(I_A+I_B+I_C)/3, and Current imbalance s=(I_max-I_av)/I_av×100%;

Where I_max is the current with the largest current value among I_A, I_B, and I_C;

16), when s is greater than or equal to the preset current imbalance, step 17); when s is less than the preset current imbalance, step 18);

17), searching for the user load in the last region that is in phase with I_max and having the current value closest to (I_max-I_min)/2, and switching the user load to be in phase with I_min; performing step 15); wherein, I_min Is the current with the smallest current value in I_A, I_B, and I_C;

18), cyclically execute according to a preset period, reset N to 0, and perform step 12) to step 18). A three-phase load balancing control system includes a transformer, a control center, and a plurality of automatic phase selection switches; the control center is coupled to the transformer, and the plurality of automatic phase selection switches are communicatively coupled to the control center;

The automatic phase selection switch is configured to: detect current information in a user load, and receive a control command of the control center to change a phase difference of currents in the user load;

The control center is configured to perform the method of any of the above.

DRAWINGS

1 is a schematic flow chart of a three-phase load balancing control method provided by this embodiment;

2 is a schematic structural diagram of a three-phase load balance control system provided by this embodiment;

3 is a schematic structural diagram of an automatic phase selection switch provided in this embodiment;

4 is a schematic structural diagram of a control center provided by this embodiment;

Figure 5 is a control flow chart provided by this embodiment;

6 is a schematic structural diagram of a smart commutation system provided by this embodiment;

7 is a schematic structural diagram of an automatic phase selection switch provided in this embodiment;

FIG. 8 is a schematic structural view of the switch module of the embodiment.

detailed description

The three-phase load balancing control method provided in this embodiment includes the following steps:

1) Establish a node model of the load in the distribution area; divide the load in the distribution area into two parts, the first part is 90% of the user load far from the transformer, and the second part is closer to the transformer. The remaining 10% of the user load;

According to the above method, the user load is divided into two parts, and the distance between the user load and the transformer is allocated by a distance of far and near, so that the balance of the entire distribution table area can be achieved. Taking the last 10% of the users as part of it is to prevent the imbalance of the entire distribution area from being difficult to meet the setting requirements after the following steps 2)-4), so 10% of the users are allowed to The imbalance of the distribution table area is adjusted.

Partition numbering the user load in the first part. The partition number is divided according to the distance between the distribution network node and the transformer of the distribution area, according to the order of far and near, for example, the area code starts from 01; Among them, one distribution network node is an area.

Number the user load included in each area, for example, the account number starts with 01;

Among them, the second part is taken as the last area;

You can create an array of corresponding structures:

{

Area code: N;

Account number: M;

User current: I_Load;

User distinct: Phase;

Instructions differ: Command

}

Wherein, the user current I_Load is the magnitude of the user current collected in real time, and the user phase is the phase determined by the current automatic phase selection switch, and the command phase is the target switching phase corresponding to the user load;

2) Real-time detection of the A, B, and C phase current values I_a, I_b, and I_c of the previous region (area code: N-1), and the regions (area number: N) are in the same phase (for example, A phase) The currents of the users are added, and the current values of the previous region (area number: N-1) are respectively added to obtain I_A_sum, I_B_sum, I_C_sum, and the regional current average value I_sum_av=(I_A_sum+I_B_sum+I_C_sum)/3 is calculated; Calculating the regional current imbalance s_area=(I_sum_max−I_sum_av)/3×100%; wherein I_sum_max is the current with the largest current value in I_A_sum, I_B_sum, I_C_sum;

Where I_a, I_b, and I_c are the current values of the A, B, and C phases of the region;

3), determine whether the area (area code: N) is the last area, and if so, proceed to step 5);

If not, determine the regional current imbalance s_area of the area (area code: N): if s_area>30%, perform step 4); if s_area<=30%, replace N with N+1, perform step 2);

4) If the scheduling switch has been performed twice for the area, and N is replaced by N+1, step 2) is performed;

If not, find the user load in the region N where the current maximum phase (same phase I_sum_max) and the current value is closest to (I_sum_max-I_sum_min)/2, switch it to the phase with the smallest regional current by the control center issuing the control command. Don't (same as I_sum_min), go to step 2). among them, I_sum_min is the current with the smallest current value in I_A_sum, I_B_sum, and I_C_sum.

Since there may be few users in some areas, in this case, it is possible that the current in the user load is commutated anyway, and the current imbalance in the area cannot be set. Since the previous area has been scheduled, the current imbalance is small and the load in this area generally does not exceed 10 households. Therefore, it is generally required to switch 1 or 2 times.

5) Real-time detection of the total current I_A, I_B, I_C of each phase, and calculate the average value of each phase current I_av = (I_A + I_B + I_C) / 3; calculate the current imbalance s = (I_max - I_av) /I_av×100%;

Where I_A, I_B, and I_C are the A, B, and C phase currents of the transformer outlet end detected by the control center;

I_max is the maximum value of current in I_A, I_B, I_C;

6), determine the current imbalance degree of the distribution area s: If s> 10%, go to step 7); if s <= 10%, go to step 8);

7) Find the user in the last region with the largest current phase (same phase as I_max) and the current closest to (I_max-I_min)/2, and switch it to the minimum phase current by the control center issuing the control command. (Same as I_min); Perform step 5); I_min is the current with the smallest current value in I_A, I_B, and I_C.

8), the area code is reset to 0, and steps 2) to 8) are executed every 15 minutes.

Although the power usage of each user changes in real time, in general, there is no large fluctuation in power usage in a short period of time. On the other hand, in order to protect the commutation switch, the scheduling period can be selected to be 15 minutes. Under the premise of as few switching times as possible, the load balance of the entire distribution area is reached.

Optionally, in step 3), the three-phase current of the previous region N-1 needs to be used to calculate the regional current imbalance of the region N.

Optionally, step 1) is to establish a node model of the user load of the distribution station area, and according to the distance from the transformer and the distribution network node, the user load is first divided into two parts, and then each user of each part is separately The load is zone numbered.

Optionally, in step 4) and step 7), searching for the user load to be commutated has the following characteristics: 1 the user load is in a current maximum phase; 2 the user load current is closest (I_sum_max-I_sum_min)/2 or (I_max-I_min)/2; 3 The user load needs to be commutated to the phase where the current is the smallest.

This embodiment provides another three-phase load balancing control method, including:

11) dividing the user load in the power distribution station area into a first part and a second part, wherein the first part is a user load that exceeds a preset distance from a transformer in the power distribution area, and the second part is a user load that is less than a preset distance from the transformer;

The scheduling switch is: searching for a user load in the region N that is identical to the I_sum_min and having the current value closest to (I_sum_max-I_sum_min)/2, and switching the current in the user load to the region N. I_sum_min is the same phase, where I_sum_min is the regional current I_A_sum, The current with the smallest current value in I_B_sum and I_C_sum;

18), cyclically execute according to a preset period, reset N to 0, and perform step 12) to step 18).

1 is a flowchart corresponding to the above method. Referring to FIG. 1, the above method includes:

Step 40: Divide the user load into two parts and perform the partition number. Corresponding to step 11) above.

Step 42: Detect the total three-phase currents I_a, I_b, and I_c of all user loads in the previous region N-1, and the current of the user load in the region N. Corresponding to step 12) above.

Step 44: Add the total three-phase current of the region N-1 and the three-phase current of the region N, respectively. Corresponding to step 12) above.

Step 46: Calculate the regional current imbalance s_area of the region N. Corresponding to step 12) above.

Step 48: It is determined whether the area N is the last area. If not, step 50 is performed; if yes, step 56 is performed. Corresponding to the above step 13).

Step 50: Determine whether the regional current imbalance s_area of the region N is less than a preset value. If the preset value is greater than or equal to the preset value, perform step 52; if less than, replace N with N+1, and perform steps. 42. Corresponding to the above step 13).

Step 52: Whether the phase change operation is performed on the area N for a preset number of times, in the case that the phase change operation of the preset number of times is not performed, step 54 is performed; in the case that the phase change operation of the preset number of times is performed, Replace N with N+1 and go to step 42. Corresponding to step 14) above.

Step 54: Find the user load in the region N whose current value is closest to (I_sum_max-I_sum_min)/2 and is at the maximum current value, and switch the user to the phase with the smallest current value through the phase selection switch. Don't go. Corresponding to step 14) above.

Step 56: Detect the total current value of each phase and calculate the total current imbalance. Corresponding to step 15) above.

Step 58: It is determined whether the current imbalance s is less than a preset value. In the case of YES, step 62 is performed; if not, step 60 is performed. Corresponding to the above step 16).

Step 60: Find the user load whose current value is closest to (I_max-I_min)/2 in the last region and is at the maximum value of the current value, and switch the user to the phase with the smallest current through the phase selection switch, and perform the steps. 56. Corresponding to the above step 17).

Step 62: Wait for the preset period duration. Corresponding to the above step 18).

Step 64: Reset N to 0 and perform step 42. Corresponding to the above step 18).

The three-phase load balance control method provided by the embodiment can realize the distributed load balance of the line of the low-voltage power distribution station by reversing the current in the user load, and solve the problem of “low voltage” at the end of the distribution line. The entire station is operated at a low imbalance, which reduces the line loss of the distribution station.

Optionally, the farther user load accounts for 90% of the total user load, and the closer user load accounts for 10% of the total user load.

Optionally, the preset area current imbalance is 30 percent.

Optionally, the preset scheduling switching number is 2 times.

Optionally, the preset current imbalance is 10 percent.

Optionally, the preset period is 15 minutes.

Referring to FIG. 2, the embodiment further provides a three-phase load balancing control system, including a transformer 220, a control center 210, and a plurality of automatic phase selection switches 230. The control center 210 is connected to the transformer 220, and the plurality of An automatic phase selection switch 230 is communicatively coupled to the control center 210; the automatic phase selection switch 230 is configured to: detect current information in a user load, and receive a control command from the control center 210 to change the user load The phase of the current is set; the control center 210 is configured to perform the method of any of the above.

The three-phase load balance control system provided in this embodiment can realize the distributed load balance of the line of the low-voltage distribution station area by commutating the current in the user load, and solve the end of the distribution network line. The "low voltage" problem allows the entire station to operate at low imbalances, reducing line losses in the distribution area.

Optionally, referring to FIG. 3, the automatic phase selection switch 230 includes a current sensor 231, a first communication module 232, a first processor 233, and three switch modules 234; the first processor 233 and the current respectively The sensor 231, the three switch modules 234, and the first communication module 232 are connected;

The first ends of the three switch modules 234 are respectively configured to be respectively connected to the A phase line, the B phase line and the C phase line in the power grid, and the second ends of the three switch modules 234 are set to be both The firewire connection in the user load;

The current sensor 231 is configured to: detect current information in a live line in the user load;

The first processor 233 is configured to: control the three switch modules 234 according to a control instruction to connect one of the A phase line, the B phase line, and the C phase line with a live line in the user load, and a processing center The current information is described, and the processed current information is transmitted through the first communication module 232.

Optionally, referring to FIG. 4, the control center 210 includes a second communication module 211, a second processor 212, and a current transformer 213; the second processor 212 and the second communication module 211, and the Current transformer connection 213;

The second communication module 211 is configured to: perform data transmission with the first communication module 232;

The second processor 212 is configured to process the current information processed by the first processor 233, and send the control instruction to the first processor 233 by using the second communication module 211.

Optionally, referring to FIG. 8 , the switch module 234 includes two insulated gate bipolar transistors IGBT 2341 connected in series.

The embodiment provides another intelligent commutation system, including a control center, an automatic phase selection switch installed on each user's incoming side, and a plurality of regional current sensors.

The control center sends a commutation command to each automatic phase selection switch according to the three-phase load balance control method, and the automatic phase selection switch communicates with the control center through General Packet Radio Service (GPRS).

The area current sensor is used to measure the three-phase current information of the area; in operation, the area current sensor can detect the total three-phase current of each area.

The control center is installed at the outlet side of the distribution transformer and can be connected to the three-phase of the transformer outlet side Voltage and current are detected;

The control center includes a GPRS communication module, a digital signal processing (DSP) control module, a Hall voltage sensor module, and a Hall current sensor module.

The GPRS communication module is used for data communication between the control center and the automatic phase selection switch.

The DSP control module is used for data processing, forming control commands, and processing the collected information.

The Hall voltage sensor module is used to detect voltage and the Hall current sensor module is used to detect current.

The automatic phase selection switch comprises a Hall current sensor module, a GPRS communication module, a DSP control module, an air switch of 4P (4 terminals) and three identical switch modules.

The Hall current sensor module is used to measure user current.

The GPRS communication module is used for automatic phase selection switch and control center for data communication.

The DSP control module is used for data processing and control switch modules.

The switch module is used to disconnect or close the line.

One end of the air switch is connected to the terminal of the power grid, the other end is connected to one end of the three switch modules and the user zero line, and the other end of the three switch modules is connected to the user fire line.

The switch module consists of two IGBTs connected in reverse series. The control signal output by the DSP control module controls the closing and opening operations of the switch module after being driven and amplified.

As shown in FIG. 8, the switch module 234 is connected in series by two IGBTs 2341. The control signal of the DSP control module can be controlled to be turned on and off after being driven and amplified. The response speed of the IGBT 2341 is on the us level. When the DSP control module sends out the open or closed control signal, the IGBT 2341 can open or close the circuit within a few microseconds.

As shown in Figure 7, the main circuit of the automatic phase selection switch is composed of three identical switch modules A, B and C. The terminals A, B, C and N of the watch grid are respectively connected to the three switches through the 4P air switch. The module and outgoing lines N, L and N are connected to the user's live and neutral lines, respectively. The current of the L line flows through the Hall current sensor, and the Hall current sensor detects the user current and transmits it to the DSP control module. The DSP control module processes the detected user current, and the current information of the user is different from the current user. Information, wirelessly transmitting data to the GPRS module of the control center through the GPRS communication module. The DSP control module can accept commutation commands from the control center via the GPRS communication module. After receiving the commutation command, perform the commutation operation. For example, if the current user is connected to phase A, the DSP control module accepts a commutation command that switches to phase B, and the DSP control module First, the switch module A is given a disconnection command, the switch module A disconnects the line, and after 5 us, the DSP control module issues a close command to the switch module B, and the switch module B is closed. At this point, the automatic phase selection switch completes the operation of switching the load from phase A to phase B. In order to prevent three-phase short circuit, at most one switch module A, B, C can be closed at most.

Figure 6 is a schematic diagram of the intelligent commutation system. The control center is installed on the exit side of the transformer. The current transformer N+1 is used to detect the three-phase current on the output side of the transformer and the current output from the transformer output side and the Hall of the control center. Current transformers are connected in series. The Hall current transformer transmits the detected information to the DSP module of the control center, and the Hall voltage sensor transmits the three-phase voltage information of the transformer output line to the DSP control module, and the GPRS module receives the real-time current of all users, and the current phase, etc. information. The DSP control module calculates the current user who needs to be commutated and the phase to be changed, and then sends a switching command to the corresponding user's automatic phase selection switch through the GPRS communication module, and the automatic phase selection switch receives the instruction, completes the commutation operation, and changes See the description of Figure 7 for the phase process.

Referring to FIG. 5, a node model of the load of the distribution area is established, and the user load is numbered. As shown in Figure 6, the user load is divided into two parts. The first part is divided into N areas (area number: 1-N), and one distribution network node is one area, in which the user load of each area is numbered (number :1-M). The second part consists of the user load close to the transformer (approximately 10% of the total user volume) and the user load for that part is numbered (number: 1-M). The current transformer 1 is mounted on the outer side of the region 2, and the current transformer N-1 is mounted on the outer side of the region N.

The scheduling starts from area 1, first detects the current level of the user of area 1, the number 1 - the number M, and the phase of the closing of the switch module, respectively sums the user currents of the phases A, B, and C, and finds the area. 1 current imbalance. If the current imbalance is less than 30%, then area 2 is scheduled. If the current imbalance is greater than 30%, find the user load in region 1 where the user current is closest (maximum phase current and - minimum phase current sum)/2 and is located on the largest phase, switching the user load to the current minimum phase . The current is detected again in the region 1, and a new current imbalance is obtained, and the current imbalance is judged again. If the current imbalance is still greater than 30%, the phase is again commutated as described above. After the commutation, the current imbalance is detected and calculated again. Here, if the same area does not satisfy the requirement that the current imbalance is less than 30% after having been switched twice, the handover is not continued but the next area is scheduled.

Scheduling the area 2, first detecting the area 2, the current in the user load of the household number 1 - the household number M is large The small and the switch modules are closed, respectively, and the user currents of the phases A, B, and C are summed, and the total currents of the A, B, and C phases detected by the current transformer 1 are respectively added to the respective regions of the aforementioned region 2 Current and medium in the load. And find the current imbalance of the region 2. The current imbalance is judged, and the operation steps in the area one are repeated until the scheduling of the area N is completed.

For the second part, the last region, the total three-phase current of the region is obtained by the current transformer N+1, and the total current imbalance is obtained. It is judged whether the current imbalance is less than 10%, and if it is less than 10%, the scheduling is completed for the entire distribution area. If the imbalance is greater than 10%, look for the user in the second part with the user current closest (maximum phase current and - minimum phase current sum)/2 and located on the largest phase, switching it to the current minimum phase. Then, the current is detected and the total current imbalance is obtained, and the determination is made, and the switching step of this part is repeated. Until the current imbalance is less than 10%. After completing the scheduling for the entire distribution area, the scheduling operation is started again from the area 1 after 15 minutes.

Industrial applicability

The present disclosure provides a three-phase load balance control method and system, which can realize distributed load balancing of low-voltage distribution station line, solves the problem of "low voltage" at the end of the distribution line, and makes the whole station low in imbalance. Running down, reducing the line loss of the distribution station area.

Claims

A three-phase load balancing control method includes:

11) dividing the user load in the power distribution station area into a first part and a second part, wherein the first part is a user load that exceeds a preset distance from a transformer in the power distribution station area, and the second part is a user load that is less than a preset distance from the transformer;

And dividing a user load in the first part according to a distance between the distribution network node and the transformer, and dividing all user loads in the second part into a last area;

And numbering the area according to the distance between the distribution network node and the transformer, wherein N is the number of the Nth area, and N is a natural number;

12), A phase total current I_a, B phase total current I_b and phase C total current I_c of all user loads in the detection area (N-1), summing and summing the currents of phase A in the region N, and B The phase currents are added and summed, and the currents of the C phases are added and summed, and the currents I_a, I_b, and I_c in the previous region are respectively added to obtain the region currents I_A_sum, I_B_sum, and I_C_sum, and regions. Current average I_sum_av=(I_A_sum+I_B_sum+I_C_sum)/3, and regional current imbalance s_area=(I_sum_max-I_sum_av)/3×100%, where I_sum_max is the largest current value among the regional currents I_A_sum, I_B_sum, and I_C_sum Current

13), determine whether the area N is the last area, in the case of yes, then perform step 15);

If not, when s_area is greater than or equal to the preset area current imbalance, step 14) is performed; when s_area is less than the preset area current imbalance, use N+1 to replace N, and perform step 12);

14), when the number of scheduled handovers to the area N is greater than or equal to the preset number of scheduled handovers, then replace N with N+1, and perform step 12);

When the number of scheduled handovers to the area N is less than the preset number of scheduled handovers, after performing the scheduling handover on the area N, step 12) is performed;

The scheduling switch is: searching for a user load in the region N that is identical to the I_sum_min and having the current value closest to (I_sum_max-I_sum_min)/2, and switching the current in the user load to the region N. I_sum_min is the same phase, where I_sum_min is the current with the smallest current value among the regional currents I_A_sum, I_B_sum, and I_C_sum;

15) detecting total current I_A of phase A at the outlet end of the transformer, total current I_B of phase B, and total current I_C of phase C to obtain an average value of current per phase I_av=(I_A+I_B+I_C)/3, and Current imbalance s=(I_max-I_av)/I_av×100%;

Where I_max is the current with the largest current value among I_A, I_B, and I_C;

16), when s is greater than or equal to the preset current imbalance, step 17); when s is less than the preset current imbalance, step 18);

17), searching for the user load in the last region that is in phase with I_max and having the current value closest to (I_max-I_min)/2, and switching the user load to be in phase with I_min; performing step 15); wherein, I_min Is the current with the smallest current value in I_A, I_B, and I_C;

18), cyclically execute according to a preset period, reset N to 0, and perform step 12) to step 18).
The method of claim 1 wherein said farther user load accounts for 90% of said total user load and said closer user load accounts for 10% of said total user load.
The method of claim 1, wherein the predetermined area current imbalance is 30 percent.
The method according to claim 1, wherein the preset scheduling switching number is two times.
The method of claim 1 wherein said predetermined current imbalance is 10 percent.
The method of claim 1 wherein the predetermined period is 15 minutes.
A three-phase load balancing control system includes a transformer, a control center and a plurality of automatic phase selection switches; the control center is connected to the transformer, and the plurality of automatic phase selection switches are communicatively connected with the control center;

The automatic phase selection switch is configured to: detect current information in a user load, and receive a control command of the control center to change a phase difference of currents in the user load;

The control center is arranged to perform the method of any of claims 1-6.
The system according to claim 7, wherein the automatic phase selection switch comprises a current sensor, a first communication module, a first processor and three switch modules; the first processor and the current sensor, respectively a switch module and the first communication module are connected;

The first ends of the three switch modules are respectively configured to be respectively connected to the A phase line, the B phase line and the C phase line in the power grid, and the second ends of the three switch modules are set to be both the user and the user. Firewire connection in the load;

The current sensor is configured to: detect current information in a live line in the user load;

The first processor is configured to: control the three switch modules according to a control command to connect one of an A phase line, a B phase line, and a C phase line with a live line in the user load, and process the current And transmitting the processed current information through the first communication module.
The system of claim 8, the control center comprising a second communication module, a second processor, and a current transformer; the second processor and the second communication module, and the current mutual Sensor connection

The second communication module is configured to: perform data transmission with the first communication module;

The second processor is configured to: process the current information processed by the first processor, and send the control instruction to the first processor by using the second communication module.
The system of claim 7 wherein said switching module comprises two series insulated gate bipolar transistor IGBTs.
A three-phase load balancing control method includes the following steps:

1) Establish a node model of the load in the distribution area; divide the user load of the above distribution area into two parts, the first part is 90% of the user load far from the transformer, and the second part is the distance transformer Nearly the remaining 10% of the user load; the user load is zone numbered, and the partition number is divided according to the distance from the distribution node to the distribution transformer, and the area code starts from 01;

Number the users in each zone, starting with 01;

Wherein, the second part as a whole is the last area;

Create a corresponding array of structures:

{

Area code: N;

Account number: M;

User current: I_Load;

User distinct: Phase;

Instructions differ: Command

}

The user current I_Load is the user current size used in real time, and the user phase is the phase corresponding to the current automatic phase selection switch, and the command phase is used for storing the target switching phase corresponding to the user M delivered by the control center; Natural number;

2), detecting the phase current values I_a, I_b, I_c of the previous region N-1 in real time, adding the user currents in the same phase in the region N, and adding respectively in the previous region N-1 Current values I_a, I_b, I_c, to obtain I_A_sum, I_B_sum, I_C_sum, and calculate the regional current average I_sum_av=(I_A_sum+I_B_sum+I_C_sum)/3, and calculate the regional current imbalance s_area=(I_sum_max-I_sum_av)/ 3×100%;

Where I_a, I_b, and I_c are the current values of the A, B, and C phases of the region, and I_sum_max is the current having the largest current value among the I_A_sum, I_B_sum, and I_C_sum;

3), determining whether the area N is the last area, and if so, performing step 5);

If not, determine the size of the regional current imbalance s_area of the region N: if s_area>30%, perform step 4); if s_area<=30%, replace N with N+1, perform step 2);

4) If the scheduling switch has been performed twice for the area, replace N with N+1 and perform step 2);

If not, find the user load in the region N where the current is the largest phase and the current value is closest to (I_sum_max-I_sum_min)/2, and the current in the user load is switched to the phase current minimum through the control center issuing the control command. ;

5) Real-time detection of the total current I_A, I_B, I_C of each phase, and calculate the average value of each phase current I_av = (I_A + I_B + I_C) / 3; calculate the current imbalance s = (I_max - I_av) /I_av×100%;

Wherein I_A, I_B, and I_C are the A, B, and C phase currents of the transformer outlet side detected by the control center;

I_max is the maximum value of current in I_A, I_B, I_C;

6) If the current imbalance degree s>10% of the power distribution station area, perform step 7); if s<=10%, perform step 8);

7), looking for the user in the last region where the current is the largest phase and the current is closest to (I_max-I_min)/2, and the control center issues a control command to switch it to the phase current minimum phase; step 5); Where I_min is the current with the smallest current value in I_A, I_B, and I_C;

8), the area code is reset to 0, and steps 2) to 8) are executed every 15 minutes.
A three-phase load balancing control system includes a control center, an automatic phase selection switch installed on each line side of the household, and a plurality of area current sensors.

The control center sends the commutation command to each of the automatic phase selection switches according to the three-phase load balance control method. The automatic phase selection switch communicates with the GPRS and the control center by using the packet radio service, and the area current sensor is used to measure the three-phase current information of the area.
The system according to claim 12, wherein the control center is installed on the outlet side of the distribution transformer, and detects three-phase voltage and current on the outlet side of the transformer; the control center includes a GPRS communication module, a digital signal processing DSP control module , Hall voltage sensor module and Hall current sensor module,

The GPRS communication module is set to control the center and the automatic phase selection switch for data communication;

The DSP control module is configured to perform data processing, control strategy calculation, and processing of collected information;

The Hall voltage sensor module is set to detect voltage, and the Hall current sensor module is set to detect electricity flow.
The system according to claim 12, wherein the automatic phase selection switch comprises a Hall current sensor module, a GPRS communication module, a DSP control module, a 4P air switch, and three identical switch modules;

The Hall current sensor module is configured to measure a user current;

The GPRS communication module is set to automatically select a phase switch and a control center for data communication;

The DSP control module is set to operate as a data processing and control switch module;

The switch module is configured to implement a line disconnection closing operation;

One end of the air switch is disposed to be connected to a terminal of the power grid, and the other end of the air switch is disposed to be connected to one end of the three switch modules and a user zero line, and the other end of the three switch modules is set to Connect to the user's FireWire.
The system of claim 14 wherein said switching module comprises two IGBTs connected in series.