Automatic balancing device and balancing method for double-alternating-current power supply load system of transformer substation

Abstract

The invention relates to an automatic balancing device and a balancing method for a double-alternating-current-power-supply load system of a transformer substation. The device comprises a current comparison unit, a signal receiving unit, a load balancing device processing unit, a state collector, a controller, a logic processing unit and a buffer. The balancing method comprises the following steps: collecting the states of two incoming lines of each sub-switch, when the load is unbalanced, disconnecting the first main incoming line sub-switch on the section of bus with large load, switching to the other section of incoming line, then comparing the load again, and if the load is not balanced, performing logic judgment from the beginning through the caching effect of the buffer, so as to achieve the purpose of balancing the load. When the load is balanced, judgment can be continued backwards from the current sub-switch, an adjusting signal is sent again for adjustment after the corresponding sub-switch is found, and judgment is carried out every time adjustment is carried out until the load is balanced. According to the invention, the load conditions of the two station transformers and related electrical equipment can be in a relatively balanced state, and the stability and the safety of an in-station alternating current system are facilitated.

Description

Technical Field

[0001] The invention belongs to the field of automatic control of AC and DC power supplies in transformer substations, and in particular relates to an automatic balancing device and a balancing method for a dual AC power supply load system in a transformer substation. Background Art

[0002] With the increasing safety, reliability and automation of substation operation, the safe and stable operation of the AC system in the station is of vital importance. The AC system in the station is composed of the transformer power supply, disconnector, fuse, ATS automatic switching switch, low-voltage AC bus, low-voltage AC load and measurement and control devices in the station, providing low-voltage AC power for DC, lighting, maintenance, power supply, etc.

[0003] At present, substations with voltage levels of 110kV and below generally use two station transformers or grounding transformers to provide two station AC power supplies, and adopt a double busbar wiring method, that is, two outgoing lines are drawn from the low-voltage side of the two station transformers, namely the main power supply and backup power supply of station transformer No. 1, and the main power supply and backup power supply of station transformer No. 2. They are connected to ATS No. 1 (ATS is an automatic transfer switch, which is a switching device that automatically switches the load power supply from one power supply (main) to another (backup) power supply, realizing rapid load switching of two power supplies to ensure continuous and reliable operation of important loads) and ATS No. 2, and the ATS automatic transfer switch is used to select, and each selects one outgoing line to connect to the I section AC bus and the II section AC bus with a voltage of 380V. See Figure 1 Under normal circumstances, the transformer for station No. 1 is connected to bus section I through ATS No. 1, and the transformer for station No. 2 is connected to bus section II through ATS No. 1. If the transformer for station No. 1 loses power, ATS No. 1 will automatically switch to the backup power supply of the transformer for station No. 2 after detecting that there is no power in the input, ensuring that the two 380V low-voltage AC busbars of the entire station operate without power outages.

[0004] The current problem is that the loads of the two AC power sources are different in type and importance, resulting in a large difference in loads between the two AC power sources. There is a common situation of unbalanced loads between the two power sources, which has an adverse effect on the operation of the two station transformers and related electrical equipment in the long run, causing the operation of heavy-load equipment to deteriorate, affecting the stability and safety of the AC system in the station. Therefore, it is necessary to design an automatic balancing system and balancing method for the load of dual AC power sources in substations to solve this problem. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide an automatic balancing device and a balancing method for a dual AC power supply load system of a transformer substation.

[0006] One of the above objects of the present invention is achieved by the following technical solution:

[0007] An automatic balancing device for a dual AC power supply load system of a substation, the dual AC power supply system of the substation includes a transformer for station No. 1 and a transformer for station No. 2, the transformer for station No. 1 is used as the main power supply to provide electric energy for section I AC bus, the transformer for station No. 2 is used as the main power supply to provide electric energy for section II AC bus, multiple air switches are connected to the two sections of AC bus to form multiple sub-switches, all sub-switches are combined into a switch group, each sub-switch of the switch group has two incoming lines, one main and one standby, and is connected by two incoming lines of AC bus I and AC bus II; the automatic balancing device includes a current comparison unit, a signal receiving unit, a load balancing device processing unit, a state collector, a controller, a logic processing unit, and a buffer:

[0008] The current comparison unit is connected to two AC bus sections, collects the current values ​​on the two bus sections, determines whether they are balanced by comparing the two, and sends the determination result to the signal receiver;

[0009] The signal receiver is used to retrieve the comparison result from the current comparison unit and send and receive signals to the load balancing device processing unit;

[0010] The status collector is used to collect the status of the two incoming lines of each sub-switch in the switch group, and send the main and backup status of each sub-switch to the load balancing device processing unit;

[0011] The logic processing unit is used to determine whether the difference between the two currents is positive or negative after receiving the load signal from the current comparison unit; call the sub-switch incoming line state information collected by the state collector to the load balancing device processing unit, and through logical operations, judge from low to high according to the sub-switch numbering sequence, and make a master and backup judgment on the two incoming lines of each sub-switch; when the current difference is positive, the load of the I-section AC bus is greater than that of the II-section AC bus, and the first sub-switch with a switch state of I main and II backup is selected; when the current difference is negative, the load of the II-section AC bus is greater than that of the I-section AC bus, and the first sub-switch with a switch state of II main and I backup is selected; then send an adjustment instruction to the load balancing device processing unit, and the load balancing device processing unit adjusts the switch through the controller; and at the same time, send the calculation result to the buffer to save the calculation data;

[0012] The controller is used to select the two incoming lines of the sub-switches in the switch group and send the line selection result to the load balancing device processing unit;

[0013] The buffer is used to cache the operation results processed by the logic operation unit, and the cached data is the sequence number of the sub-switch that the current sending controller needs to adjust and the main and standby status of the two incoming lines.

[0014] The second object of the present invention is achieved by the following technical solution:

[0015] A balancing method based on the automatic balancing device of the dual AC power supply load system of the substation, comprising the following steps:

[0016] Step 1: First, the electrical parameters of the output terminal of ATS No. 1 and the output terminal of ATS No. 2 are collected through the current comparison unit, and the electrical parameters include AC voltage, current and frequency;

[0017] Step 2: The current comparison unit makes a difference between the two current values ​​collected. When the difference is greater than the set value, it indicates that there is an obvious imbalance in the two loads.

[0018] Step 3, the current comparison unit sends a signal to the signal receiver to send an unbalanced current signal, and the signal receiver sends the signal to the load balancing system processing unit;

[0019] Step 4: After receiving the two-way current imbalance signal, the load balancing system processing unit calls the state collector to collect the current state of the switch group, and calls the logic processing unit to judge the signal of the current comparison unit. If the signal is positive, it indicates that the current load of the bus section I is greater than the current load of the bus section II; if the signal is negative, it indicates that the current load of the bus section II is greater than the current load of the bus section I;

[0020] Step 5: In case that the current load of bus section I is greater than that of bus section II, it is necessary to reduce the load on bus section I and increase the load on bus section II. At this time, the load balancing device processing unit sends an adjustment instruction to the controller to adjust the two incoming switch states of switch 1. In the current state where the incoming line of switch 1 is adjusted to supply power to bus section I and bus section II is standby, the incoming line of bus section I is switched from main to standby, and the incoming line of bus section II is switched from standby to main.

[0021] In case that the current load of bus section II is greater than that of bus section I, it is necessary to reduce the load on bus section II and increase the load on bus section I. At this time, the load balancing device processing unit sends an adjustment instruction to the controller to adjust the two incoming switch states of switch 1. In the current state where the incoming line of switch 1 is adjusted to supply power to bus section II and bus section I is standby, the incoming line of bus section II is switched from main to standby, and the incoming line of bus section I is switched from standby to main.

[0022] Step 6, the controller transmits the adjusted signal back to the load balancing device processing unit. After receiving the adjustment completion signal, the load balancing device processing unit sends it to the current comparison unit again through the signal receiver to perform load balancing and comparison. If it is balanced, the adjustment is ended; if it is unbalanced, steps 3 to 5 are repeated, and the controller adjusts switch 2, switch 3 and other switches in turn until balance is achieved.

[0023] Furthermore, in step 2, the setting value of the current difference is 5A.

[0024] The advantages and positive effects of the present invention are:

[0025] The present invention is a method for balancing the load on two AC low-voltage busbars. By selecting the main and standby relationship of the two incoming lines of each sub-switch, the load of the two busbars is adjusted to keep it relatively balanced. The balancing method is to collect the two incoming line status of each sub-switch. When the load is unbalanced, the first main incoming line sub-switch on the busbar with a large load is disconnected and switched to another incoming line. Then the load is compared again. If it is still unbalanced, the buffering effect of the buffer does not need to be logically judged from the beginning. It can continue to judge from the current sub-switch backwards, find the corresponding sub-switch and send the adjustment signal again for adjustment. A judgment is made every time the adjustment is made until the load is balanced. The present invention can make the load conditions of the two station transformers and related electrical equipment in a relatively balanced state, and the operating conditions of each equipment can be kept relatively consistent, avoiding the influence of the stability of the entire system due to the poor working condition of a certain equipment, which is beneficial to the stability and safety of the AC system in the station. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a connection diagram of a dual AC power supply load system of a substation involved in the present invention;

[0027] Figure 2 It is a schematic diagram of the structure of the automatic balancing device for the dual AC power supply load system of the substation of the present invention;

[0028] Figure 3 The present invention is a flow chart of a method for automatically balancing a dual AC power supply load system in a transformer substation. DETAILED DESCRIPTION

[0029] The structure of the present invention is further described below with reference to the accompanying drawings and by way of examples. It should be noted that the present examples are descriptive rather than restrictive.

[0030] Under normal circumstances, in the substation dual AC power supply system, the transformer used by station 1 is used as the main power supply to provide power for the AC bus section I, and the transformer used by station 2 is used as the main power supply to provide power for the AC bus section II. Multiple air switches will be connected to each AC bus section, and each air switch will be connected to different AC loads, such as lighting, DC power supply, maintenance power supply, power supply, etc., which are sub-switches for loads 1, 2, 3, 4, etc. Switch 1, switch 2, switch 3, switch 4, etc. are combined into a switch group. Each sub-switch of the switch group has two incoming lines, one main and one backup, and is connected by AC I bus and II bus. Under normal conditions, half of the I bus section is used as the power supply, and the other half is the II bus section as the power supply.

[0031] In view of the above-mentioned substation dual AC power supply load system, the present invention is a substation dual AC power supply load automatic balancing system, please refer to specific 1, and its invention points are: current comparison unit, signal receiving unit, load balancing device processing unit, state collector, controller, logic processing unit, buffer;

[0032] The current comparison unit is connected to two sections of AC bus, collects the current values ​​on the two sections of bus, determines whether they are balanced by comparing the two sections, and has the function of sending the comparison result to the signal receiver.

[0033] The low voltage AC mother I and II are 380V three-phase AC. For the sake of intuitiveness in the figure, one phase is used instead.

[0034] The signal receiver has the function of acquiring the comparison result from the current comparison unit and sending and receiving signals to the load balancing device processing unit;

[0035] The status collector is used to collect the status of the two incoming lines of each sub-switch in the switch group, and send the main and backup status of each sub-switch to the load balancing device processing unit;

[0036] The logic processing unit is used to determine whether the difference between the two currents is positive or negative after receiving the load signal from the current comparison unit; call the sub-switch incoming line status information collected by the status collector to the load balancing device processing unit, and through logical operations, judge from low to high according to the sub-switch numbering sequence, and make a main and backup judgment on the two incoming lines of each sub-switch; when the current difference is positive, the load of the I section AC bus is greater than that of the II section AC bus, and the first sub-switch with a switch status of I main and II backup is selected; when the current difference is negative, the load of the II section AC bus is greater than that of the I section AC bus, and the first sub-switch with a switch status of II main and I backup is selected; then send an adjustment instruction to the load balancing device processing unit, and the load balancing device processing unit adjusts the switch through the controller; at the same time, send the operation result to the buffer to save the operation data, so that the next operation can continue to call without restarting the operation.

[0037] The controller is used to select the two incoming lines of the sub-switches in the switch group and send the line selection result to the load balancing device processing unit.

[0038] The buffer is used to cache the calculation results processed by the logic operation unit. The cached data is the serial number of the sub-switch that needs to be adjusted by the current sending controller and the primary and standby conditions of the two incoming lines. The next time the logic operation unit calculates again, it can directly judge backward from the sub-switch serial number without having to judge the incoming line conditions of each sub-switch from the beginning, thereby improving efficiency.

[0039] Based on the above substation dual AC power supply load automatic balancing system balancing method, see Figure 3 , the invention point is that it comprises the following steps:

[0040] Step 1: First, the current comparison unit collects electrical parameters such as AC voltage, current and frequency at the output terminals of ATS No. 1 and ATS No. 2, with a focus on the difference between the two currents;

[0041] Step 2, the current comparison unit makes a difference between the two current values ​​collected. When the difference is greater than a set value, the set value in the present invention is preferably 5A, indicating that there is an obvious imbalance in the two loads;

[0042] Step 3, the current comparison unit sends a signal to the signal receiver to send an unbalanced current signal, and the signal receiver sends the signal to the load balancing system processing unit;

[0043] Step 4: After receiving the two-way current imbalance signal, the load balancing system processing unit calls the state collector to collect the current state of the switch group, and calls the logic processing unit to judge the signal of the current comparison unit. If the signal is positive, it indicates that the current load of the bus section I is greater than the current load of the bus section II; if the signal is negative, it indicates that the current load of the bus section II is greater than the current load of the bus section I;

[0044] Step 5: In case that the current load of bus section I is greater than that of bus section II, it is necessary to reduce the load on bus section I and increase the load on bus section II. At this time, the load balancing device processing unit sends an adjustment instruction to the controller to adjust the two incoming switch states of switch 1. In the current state where the incoming line of switch 1 is adjusted to supply power to bus section I and bus section II is standby, the incoming line of bus section I is switched from main to standby, and the incoming line of bus section II is switched from standby to main.

[0045] In case that the current load of bus section II is greater than that of bus section I, it is necessary to reduce the load on bus section II and increase the load on bus section I. At this time, the load balancing device processing unit sends an adjustment instruction to the controller to adjust the two incoming switch states of switch 1. In the current state where the incoming line of switch 1 is adjusted to supply power to bus section II and bus section I is standby, the incoming line of bus section II is switched from main to standby, and the incoming line of bus section I is switched from standby to main.

[0046] Step 6, the controller transmits the adjusted signal back to the load balancing device processing unit. After receiving the adjustment completion signal, the load balancing device processing unit sends it to the current comparison unit again through the signal receiver to perform load balancing and comparison. If it is balanced, the adjustment is ended; if it is unbalanced, steps 3 to 5 are repeated, and the controller adjusts switch 2, switch 3 and other switches in turn until balance is achieved.

[0047] Although the embodiments and drawings of the present invention are disclosed for illustrative purposes, those skilled in the art will appreciate that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments and drawings.

Claims

1. An automatic balancing device for a dual AC power supply load system of a substation, the dual AC power supply system of the substation includes a transformer for station No. 1 and a transformer for station No. 2, the transformer for station No. 1 is used as the main power supply to provide power for the I-section AC bus, the transformer for station No. 2 is used as the main power supply to provide power for the II-section AC bus, multiple air switches are connected to the two-section AC bus to form multiple sub-switches, all sub-switches are combined into a switch group, each sub-switch of the switch group has two incoming lines, one main and one standby, and is connected by two incoming lines of AC I bus and AC II bus; it is characterized in that: The automatic balancing device includes a current comparison unit, a signal receiving unit, a load balancing device processing unit, a state collector, a controller, a logic processing unit, and a buffer: The current comparison unit is connected to two AC bus sections, collects the current values ​​on the two bus sections, determines whether they are balanced by comparing the two, and sends the determination result to the signal receiver; The signal receiver is used to retrieve the comparison result from the current comparison unit and send and receive signals to the load balancing device processing unit; The status collector is used to collect the status of the two incoming lines of each sub-switch in the switch group, and send the main and backup status of each sub-switch to the load balancing device processing unit; The logic processing unit is used to determine whether the difference between the two currents is positive or negative after receiving the load signal from the current comparison unit; call the sub-switch incoming line state information collected by the state collector to the load balancing device processing unit, and through logical operations, judge from low to high according to the sub-switch numbering sequence, and make a master and backup judgment on the two incoming lines of each sub-switch; when the current difference is positive, the load of the I-section AC bus is greater than that of the II-section AC bus, and the first sub-switch with a switch state of I main and II backup is selected; when the current difference is negative, the load of the II-section AC bus is greater than that of the I-section AC bus, and the first sub-switch with a switch state of II main and I backup is selected; then send an adjustment instruction to the load balancing device processing unit, and the load balancing device processing unit adjusts the switch through the controller; and at the same time, send the calculation result to the buffer to save the calculation data; The controller is used to select the two incoming lines of the sub-switches in the switch group and send the line selection result to the load balancing device processing unit; The buffer is used to cache the operation results processed by the logic operation unit, and the cached data is the sequence number of the sub-switch that the current sending controller needs to adjust and the main and standby status of the two incoming lines.

2. A balancing method based on the automatic balancing device of the above-mentioned substation dual AC power supply load system, characterized in that: The steps include: Step 1: First, the electrical parameters of the output terminal of ATS No. 1 and the output terminal of ATS No. 2 are collected through the current comparison unit, and the electrical parameters include AC voltage, current and frequency; Step 2: The current comparison unit makes a difference between the two current values ​​collected. When the difference is greater than the set value, it indicates that there is an obvious imbalance in the two loads. Step 3, the current comparison unit sends a signal to the signal receiver to send an unbalanced current signal, and the signal receiver sends the signal to the load balancing system processing unit; Step 4: After receiving the two-way current imbalance signal, the load balancing system processing unit calls the state collector to collect the current state of the switch group, and calls the logic processing unit to judge the signal of the current comparison unit. If the signal is positive, it indicates that the current load of the bus section I is greater than the current load of the bus section II; if the signal is negative, it indicates that the current load of the bus section II is greater than the current load of the bus section I; Step 5: In case that the current load of bus section I is greater than that of bus section II, it is necessary to reduce the load on bus section I and increase the load on bus section II. At this time, the load balancing device processing unit sends an adjustment instruction to the controller to adjust the two incoming switch states of switch 1. In the current state where the incoming line of switch 1 is adjusted to supply power to bus section I and bus section II is standby, the incoming line of bus section I is switched from main to standby, and the incoming line of bus section II is switched from standby to main. In case that the current load of bus section II is greater than that of bus section I, it is necessary to reduce the load on bus section II and increase the load on bus section I. At this time, the load balancing device processing unit sends an adjustment instruction to the controller to adjust the two incoming switch states of switch 1. In the current state where the incoming line of switch 1 is adjusted to supply power to bus section II and bus section I is standby, the incoming line of bus section II is switched from main to standby, and the incoming line of bus section I is switched from standby to main. Step 6, the controller transmits the adjusted signal back to the load balancing device processing unit. After receiving the adjustment completion signal, the load balancing device processing unit sends it to the current comparison unit again through the signal receiver to perform load balancing and comparison. If it is balanced, the adjustment is ended; if it is unbalanced, steps 3 to 5 are repeated, and the controller adjusts switch 2, switch 3 and other switches in turn until balance is achieved.

3. The balancing method according to claim 2, characterized in that: The method comprises the following steps: in step 2, the setting value of the current difference is 5A.

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