CN105958518B - A kind of working method of low-voltage network circuit Real-time Balancing device - Google Patents

Abstract

A kind of low-voltage network circuit Real-time Balancing device and its working method.It is related to a kind of current balancing device and its working method of mid ＆ low-voltage line.It can realize that the automatic Real-time Balancing of low-voltage network circuit solves the problems, such as three-phase current unbalance from the root cause.It is placed in step down side, including a host and several slaves, the host is electrically connected by triple line with the step down side, and current transformer is equipped in each phase of the triple line；The slave is placed between the step down side and several single-phase loads, and several single-phase loads are respectively connected on each slave.It can be with all the period of time to the three-phase current of low-voltage network busbar, each customer charge electric current is monitored under the electric current and each branch of each electricity consumption branch, reduce the loss of circuit, optimize the power quality of power grid, fundamentally solves the unbalanced state of threephase load, it is simple in structure, there is very high economy.

Description

A working method of a real-time balancing device for low-voltage distribution network lines

technical field

The invention relates to the field of power equipment, in particular to a current balance device for medium and low voltage lines and a working method thereof.

Background technique

With the development of my country's distribution network and changes in household appliances, there are a large number of single-phase loads in the distribution network. However, the unbalanced distribution of single-phase loads leads to unbalanced three-phase loads, which has become a prominent problem in the operation and maintenance of low-voltage distribution networks. The problem. The unbalanced three-phase load will increase the loss of the power grid, which will greatly reduce the quality of the power supply voltage of the heavy-duty phase in the distribution network, resulting in a decrease in the output of the distribution network transformer and a decrease in the efficiency of power conversion. Due to the poor design and planning of the early power grid, in the low-voltage distribution network system, there are a large number of single-phase, asymmetrical, nonlinear, and impact loads, and a large number of single-phase loads will be concentrated on one or two phases. Balanced load will cause three-phase unbalance in the power distribution system, resulting in unbalanced three-phase voltage and current in the power supply system.

At present, there are two solutions to the three-phase imbalance of the distribution network. One is to adjust the load through regular tests and experience by workers, and the balance point only focuses on the balance at a few test points such as the low-voltage side of the transformer, which requires a lot of work. Manpower and material resources are used to regulate, and the effect is not significant enough.

The second is to install a power electronic reactive power compensation device to adjust the unbalanced three-phase load through phase-to-phase reactive power compensation on the low-voltage side of the distribution transformer. For example, an application number 2015105417951 published by the State Intellectual Property Office on November 18, 2015, titled an invention patent application for a distribution transformer three-phase current dynamic balance device and its working method, mainly discloses a module unit, a current Acquisition unit, remote communication unit and human-computer interaction unit. The modular units are connected in parallel to the public connection point of the grid; the modular units include LCL filters, inverters, drive circuits and central controllers. The central controller, drive circuit, inverter and LCL filter are connected in sequence. Real-time monitoring, real-time and comprehensive reflection of load conditions, timely and accurate feedback of current conditions to the central controller, the central controller can adjust the three-phase load current in real time, dynamically and accurately, and improve the accuracy of dynamic current adjustment; flexibly increase or decrease the operation module, which reduces product power consumption and saves energy. However, this solution can only improve the problem of the distribution transformer itself to a certain extent, but cannot solve the unbalanced three-phase load of the low-voltage line in the distribution station area, and the cost is relatively high.

Therefore, in order to meet the large-scale, rapid, accurate and automatic three-phase current balance of the low-voltage distribution network, there is an urgent need for a working method of a device that can collect a large amount of user information and can control the three-phase current balance of the low-voltage distribution network in real time.

Contents of the invention

Aiming at the above problems, the present invention provides a low-voltage distribution network line real-time balancing device and a working method thereof capable of realizing automatic real-time balance of low-voltage distribution network lines and solving the problem of unbalanced three-phase current at the root.

The technical solution of the present invention is: a real-time balancing device for low-voltage distribution network lines, placed on the low-voltage side of the transformer, including a master and several slaves, the master is electrically connected to the low-voltage side of the transformer through a three-phase line, the Each phase of the three-phase line is provided with a current transformer; the slaves are placed between the low-voltage side of the transformer and several single-phase loads, and each of the slaves is connected to several single-phase loads.

The host includes a main control chip, a power carrier module, an interactive control panel and three current Hall sensors, the three current Hall sensors are respectively connected to the current transformers on the three-phase lines, and the three current Hall sensors are respectively connected to the current transformers on the three-phase lines. The sensors are respectively connected to the main control chip;

The main control chip is connected to the power carrier module, and realizes two-way communication with the power carrier module;

The interactive control screen is connected to the main control chip through the power carrier module.

The slave includes a slave chip, three bidirectional thyristors and three mechanical switches, and one mechanical switch is connected in parallel to each bidirectional thyristor;

Each phase of the three-phase line is respectively connected to an input terminal of a bidirectional thyristor, and the output terminals of the three bidirectional thyristors are connected in parallel and then connected to the load as the live wire of the single-phase load;

The slave chip is connected to the main control chip through a power carrier module;

The gate of the two-way thyristor and the mechanical switch are respectively connected to the slave chip.

It also includes a master station, which is connected to the power carrier module and receives information sent by the power carrier module.

The power carrier module is connected with the electric meter of each load, and reads the load current information.

A working method of a low-voltage distribution network line real-time balancing device, which works according to the following steps:

1) Pre-testing before work;

1.1) The main control chip sends a test signal to each part to test whether each part is normal, if it is normal, go to step 2), if it is not normal, go to step 1.2);

1.2) Display the fault point on the touch screen, notify the staff to overhaul, and lock the host at the same time,

1.3) Send the fault information to the master station, which will be archived by the master station;

2) Judgment of unbalance degree;

2.1) Write the range value of the unbalance degree through the touch screen;

2.2) The host scheduling part obtains the three-phase current value of the main circuit through the Hall sensor;

2.3) Compare the detected three-phase current value with the standard value to obtain the actual unbalance degree of each phase;

2.4) Calculate the switching current value that needs to be switched according to the actual unbalance degree;

2.5) Compare the actual unbalance degree with the set range value, if it is greater than the range value, go to step 3, if it is less than the range value, repeat step 2);

3) Eliminate three-phase imbalance;

3.1) The main control chip collects the current value of the load, and calculates the actual current value of each slave;

3.2) Compare the actual current value of each slave with the switching current value one by one, and select the slave that is closest to the switching current value;

3.3) Switch the closest slave machine selected in step 3.2), so that the three-phase current reaches a balance, complete.

In the present invention, the main control chip is used to monitor and adjust the load on the three-phase line in real time, so that the three-phase current can be balanced, so that the power supply quality in the power supply range of the entire distribution network can be optimized, and the three-phase unbalance in the distribution network can be solved to the greatest extent For the problem of too large, high-power bidirectional thyristors are selected to reduce the number of slaves used and the manpower and material resources required for installing slaves. Using the power carrier module as the communication module of the device does not need to build additional lines, saving costs. There is also an interactive control panel, which can display the current size of the branch where the slave machine is located, and the current size of each user load, and the switching time of each slave machine can be set by the user, as well as the automatic or manual switching working mode, so as to Adapt to different working environments and visualize the entire three-phase unbalanced process. At the same time, it can also visualize the fault point, which is convenient for the staff to find and repair and improve work efficiency.

The slave machine is composed of a triac and a mechanical switch. The mechanical switch and the triac are connected in parallel. arcing, extending the life of the mechanical switch and thus the life of the entire unit. Utilizing the bidirectional conduction function of the bidirectional thyristor, the AC current can pass through in time, and the biphase thyristor is a fully controlled device, the on-off can be controlled, and the sensitivity is high, and the energy consumption is low, so that the device responds quickly, takes a long time and safe and stable.

This device can monitor the three-phase current of the bus bar of the low-voltage distribution network, the current of each power consumption branch, and the load current of each user under each branch at all times, and switch and dispatch in units of branches to achieve large-scale The three-phase current balance of the distribution network bus greatly reduces the loss of the line, optimizes the power quality of the power grid, and through the integration of the user information collection system, the current of each user load is collected from the electric energy meter to reduce the use of current transformers , At the same time, a large number of hardware interfaces are reduced, thereby improving the reliability of the device, and also improving the scalability of the device, which has high popularization and application value and social and economic benefits. It avoids the defect that the existing technology can only improve the problem of the distribution transformer itself to a certain extent, but cannot solve the unbalanced three-phase load of the low-voltage line in the distribution area, and the cost is relatively high. The phase load is switched in the three-phase line, so as to realize the three-phase load balance, which fundamentally solves the unbalanced state of the three-phase load, and has a simple structure and high economical efficiency.

Description of drawings

Fig. 1 is a structural representation of the present invention,

Fig. 2 is a schematic block diagram of the structure of the device of the present invention,

Fig. 3 is the electrical schematic diagram of the slave machine in the present invention,

Fig. 4 is a flowchart of the working method of the present utility model;

In the figure, 1 is a transformer, 2 is a current transformer, 3 is a slave, 31 is a mechanical switch, and 32 is a bidirectional thyristor.

Detailed ways

As shown in Figures 1-4, the present invention is placed on the low-voltage side of the transformer and includes a master and several slaves. The master is electrically connected to the low-voltage side of the transformer through a three-phase line, and each phase of the three-phase line All are equipped with current transformers; the slaves are placed between the low-voltage side of the transformer and several single-phase loads, and each of the slaves is connected to several single-phase loads. The current situation in the three-phase line is collected by the host, and the unbalanced state of the power grid is monitored in real time, which is convenient for the host to deal with in time. The master controls the slaves to switch to eliminate the unbalanced state of the power grid as much as possible.

The host includes a main control chip, a power carrier module, an interactive control panel and three current Hall sensors, and the three current Hall sensors are respectively connected to the current transformers on the three-phase lines, that is, the current transformers connected to the A phase. The transformer is connected to one of the current Hall sensors, the current transformer connected on phase B is connected to the other current Hall sensor, the current transformer connected to phase C is connected to the third current Hall sensor, and the three described The current Hall sensors are respectively connected to the main control chip; the current transformer collects the current signal on the three-phase line, and transmits the collected continuously changing current signal to the corresponding current Hall sensor, and the current Hall sensor will continuously change The current signal is converted into a digital signal that the main control chip can recognize, and provides current data for the host control, which is convenient for the main control chip to process and judge.

The main control chip is connected with the power carrier module to realize two-way communication with the power carrier module; the interactive control panel is connected with the main control chip through the power carrier module. The main control chip transmits relevant information through the power carrier module to the interactive control screen for display, so that the staff can intuitively observe the status of the power grid and call relevant information in time. The staff can also manually control the switching of the slaves through the interactive control screen, so that the switching is subject to the needs of the staff. When one of the phases fails, the staff can switch the slaves on the faulty phase to the average through the interactive control screen. On the other two phases, the faulty one phase is unloaded, which is convenient for the staff to overhaul and does not affect the power supply during the overhaul.

As shown in Figure 3, the slave includes three bidirectional thyristors and three mechanical switches, each of which is connected in parallel with one of the mechanical switches; Its working method is the same as that of ordinary thyristors, and both have gate signals to trigger conduction. When the master sends a switching command to the slave, the internal controller of the slave will add a trigger signal to the gate of the bidirectional thyristor, so that the bidirectional thyristor can be turned on in both positive and negative directions.

The mechanical switch is connected in parallel with the bidirectional thyristor. When it is disconnected, the bidirectional thyristor is turned on first, so that the mechanical switch is not charged, and then the mechanical switch is disconnected, so that the mechanical switch will not generate an arc when it is disconnected, prolonging the service life of the mechanical switch. Thereby prolonging the service life of the whole device. Utilizing the bidirectional conduction function of the bidirectional thyristor, the AC current can pass through in time, and the biphase thyristor is a fully controlled device, the on-off can be controlled, and the sensitivity is high, and the energy consumption is low, so that the device responds quickly, takes a long time and safe and stable.

The slave chip is connected to the main control chip through a power carrier module; the gate of the bidirectional thyristor and the mechanical switch are respectively connected to the slave chip. The main control chip sends a switching command to the slave chip, and the slave chip sends a close or open command to the mechanical switch after receiving the command, and at the same time sends a gate trigger signal to turn on or off the corresponding mechanical switch, and at the same time controls the corresponding thyristor to turn on or off. to complete the switching instruction. In this way, the slave chip shares the functions of the main control chip, so that the main control chip only has the functions of calculation, judgment and sending switching instructions, thereby improving the response speed of the main control chip, making the switching action faster, and improving the work of the device. efficiency.

The switching principle of the slave machine is, taking the switching from phase A to phase B as an example, the essence of the switching is to turn off the mechanical switch of phase A and close the mechanical switch of phase B at the same time when the load is powered off. The on-off process of the mechanical switch is uncontrollable. If the interval between opening and closing is too long, the load will be cut off. Arcing affects the life of mechanical switches.

The bidirectional thyristor is connected in parallel with the mechanical switch. When switching is required, the host first gives a switching command. At this time, the slave receives the switching command, and the slave chip sends a gate trigger signal to the bidirectional thyristor on phase A. The bidirectional thyristor on phase A The thyristor is turned on, and at this time, the slave chip sends an instruction to turn off the mechanical switch on phase A. When phase A is disconnected, the current flows through the thyristor of phase A. At this time, the mechanical switch of phase A is disconnected, and no arc will be generated. When the gate trigger signal is removed, the thyristor of phase A will be disconnected to control the safe interval time. A trigger signal is given to the gate of the B-phase thyristor to make the B-phase thyristor turn on, and the mechanical switch of the B-phase is closed to complete the switching. The mutual switching between A and B phases is realized under the condition of electricity and no short circuit. Since the mechanical switch is not charged when the mechanical switch is closed and disconnected, since the triac cannot supply a large current for a long time, it is necessary to close the mechanical switch on the B phase after the bidirectional thyristor of the B phase is turned on, so as to avoid the triac being large for a long time. The current is turned on, causing damage to the biphase thyristor and prolonging the service life.

After the switching is completed, the switching status (the on-off status of each bidirectional thyristor and the on-off status of the mechanical switch) is transmitted to the host through the slave chip, so that the master can obtain the switching status through the host, and establish historical files, which is convenient for staff to review and analyze .

Each phase of the three-phase line is respectively connected to the input terminal of a bidirectional thyristor, and the output terminals of the three bidirectional thyristors are connected in parallel to the load; thus input four lines and output two lines, so that the load can be in the three-phase line Switching on any one of the phases achieves current balance and maintains the safety of the power grid. Through the switching of loads on the three-phase lines, the load on the three-phase lines is balanced, and the unbalanced state of the three phases is fundamentally resolved. It avoids the problem that the distribution transformer itself can only be improved to a certain extent, but the three-phase load imbalance of the low-voltage line in the distribution station area cannot be solved, and the cost is relatively high.

It also includes a master station, which is connected to the power carrier module and receives information sent by the power carrier module. The power carrier module of the master station is connected with the electric meter of each load, and reads the load current information. The master station is used to receive every action information of the main control chip (including fault information and switching information), establish a historical database to facilitate staff query and analysis, and realize the purpose of remote monitoring.

A working method of a low-voltage distribution network line real-time balancing device, as shown in Figure 4, works according to the following steps:

1) Pre-inspection before work; through pre-inspection, simple faults such as communication failures are found to reduce the probability of device failure during work.

1.1) The main control chip sends a test signal to each part to test whether each part is normal. If it is normal, go to step 2), if it is not normal, go to step 1.2); that is, to test whether the communication system is normal, test whether the mechanical switch and the two-phase thyristor are normal. It can be turned on and off normally, test whether the interactive control screen is displayed normally, etc.

1.2) Display the fault point on the interactive control screen, notify the staff for maintenance, and lock the host at the same time; the staff can directly understand the fault point from the interactive control screen, and carry out targeted troubleshooting to shorten the maintenance time and improve work efficiency .

1.3) Send the fault information to the master station, which will be archived by the master station; the establishment of the archive is convenient for the staff to analyze and improve the fault, and avoid the same fault from repeating.

2) Judgment of unbalance degree; the unbalance degree is judged by the real-time detected current value, which is used as the basis for switching.

2.1) Write the standard value of the unbalance degree through the touch screen; the unbalance degree is a positive value, and when one of the three-phase lines exceeds one phase, it is judged that the unbalance is too large and needs to be switched.

2.2) The host scheduling part obtains the three-phase current value of the main circuit through the Hall sensor; the actual unbalance degree is obtained by comparing the actual three-phase current value with the standard current value.

2.3) Compare the detected three-phase current value with the standard value to obtain the actual unbalance degree of each phase;

Taking the standard value of unbalance degree as 15% and the standard current value of each phase as 100A as an example, assuming that phase A is 120A and phase B is 80A, the actual current value of phase A is 120A minus the standard current value of 100A to get the difference The value is 20A, divided by the standard current value, the actual unbalance degree is 20%, if it exceeds the standard value by 15%, the actual unbalance degree of phase B is 20%, and switching is required at this time, otherwise no switching is required.

2.4) Calculate the switching current value that needs to be switched according to the actual unbalance degree; taking A phase 120A and B phase 80A as an example, subtracting the standard current value from the actual current value of A phase to get 20A, it means that A phase needs to cut out 20A. Able to achieve balance, the actual current value of phase B is 80A minus the standard current value of 100A to get -20A, indicating that phase B needs to be cut into 20A to achieve balance, and the obtained 20A at this time is the switching current value.

2.5) Compare the actual unbalance degree with the standard value of unbalance degree, if it is greater than the range value, go to step 3, if it is less than the range value, repeat step 2); compare the actual unbalance degree with the standard value of unbalance degree For comparison, if it exceeds the standard value, it means that switching is required, otherwise it is not necessary to switch, which makes the operation of the power grid more reasonable and economical, reduces the number of device actions, and prolongs the service life of the device.

3) Eliminate three-phase imbalance; make the power grid more secure and stable

3.1) The main control chip collects the current value of the load, and calculates the actual current value of each slave;

3.2) Compare the actual current value of each slave with the switching current value one by one, and select the slave that is closest to the switching current value;

3.3) Switch the closest slave machine selected in step 3.2), so that the three-phase current reaches a balance, complete.

Claims (5)

1. a kind of working method of low-voltage network circuit Real-time Balancing device, the Real-time Balancing device are placed in transformer low voltage Side, the Real-time Balancing device include a host and several slaves, and the host passes through triple line and the transformer low voltage Side is electrically connected, and current transformer is equipped in each phase of the triple line；The slave be placed in the step down side with Between several single-phase loads, several single-phase loads are respectively connected on each slave；

It is characterized in that, working as follows：

1）Pre-detection before work；

1.1）Main control chip sends test signal to each section, and whether test various pieces are normal, then go to step 2 if normal）If It is abnormal, go to step 1.2）；

1.2）By fault point in tactile screen display, staff is notified to overhaul, while by host lock,

1.3）Fault message is sent to main website, is achieved by main website；

2）Degree of unbalancedness judges；

2.1）The value range of degree of unbalancedness is written by touch screen；

2.2）Host schedules part obtains the three-phase electricity flow valuve of main circuit by Hall sensor；

2.3）The three-phase electricity flow valuve detected is compared with standard value, obtains the practical degree of unbalancedness of every phase；

2.4）The switching current values for needing to switch are calculated according to practical degree of unbalancedness；

2.5）Practical degree of unbalancedness is compared with the value range of setting, step 3 is then transferred to if more than value range）If being less than Value range then repeats step 2）；

3）Eliminate three-phase imbalance；

3.1）The current value of main control chip acquisition load, calculates the actual current value of each slave；

3.2）The actual current value of each slave is compared one by one with switching current values, is selected closest with switching current values Slave；

3.3）Switch step 3.2）In the immediate slave selected so that three-phase current reaches balance, finishes.

2. a kind of working method of low-voltage network circuit Real-time Balancing device according to claim 1, which is characterized in that The host includes main control chip, power line carrier module, interactive controlling screen and three current Hall sensors, three electric currents Hall sensor is connected respectively the current transformer in triple line, three current Hall sensors respectively with master control core Piece connects；

The main control chip is connect with power line carrier module, and both-way communication is realized with the power line carrier module；

The interactive controlling screen is connect by the power line carrier module with the main control chip.

3. a kind of working method of low-voltage network circuit Real-time Balancing device according to claim 2, which is characterized in that The slave includes slave chip, three bidirectional thyristors and three mechanical switch, distinguishes parallel connection one on each bidirectional thyristor A mechanical switch；

Each phase of triple line is separately connected the input terminal of a bidirectional thyristor, and the output end of three bidirectional thyristors is simultaneously It is connected with load after connection, the firewire as single-phase load；

The slave chip is connect with the main control chip by power line carrier module；

The gate pole and mechanical switch of the bidirectional thyristor are connect with the slave chip respectively.

4. a kind of working method of low-voltage network circuit Real-time Balancing device according to claim 3, which is characterized in that The balancing device further includes main website, and the main website is connect with the power line carrier module, receives what power line carrier module was sent Information.

5. a kind of working method of low-voltage network circuit Real-time Balancing device according to claim 4, which is characterized in that The power line carrier module is connect with the ammeter each loaded, reads load current information.