A multi-machine high-power motor auxiliary control system optimal control method

Abstract

The application discloses an optimal control method for an auxiliary control system of multiple high-power motors, which comprises the following steps: step one, adding a conventional self-starting loop, a conventional standby starting loop and a conventional emergency starting loop in the whole system; step two, dividing the multiple high-power motors into three groups; step three, connecting the three groups of high-power motors into the conventional self-starting loop, the conventional standby starting loop and the conventional emergency starting loop respectively; and step four, connecting the conventional self-starting loop, the conventional standby starting loop and the conventional emergency starting loop into a PLC, and setting the PLC to be locked for a certain time when the signals reach the PLC to output a starting motor logic. The application solves the technical problem of providing an optimal control method for an auxiliary control system of multiple high-power motors, which improves the control method from two aspects, i.e., optimizing a conventional control system control loop and optimizing a PLC software control logic, so as to realize the control optimization by combining the hardware control loop and the software control program.

Description

Technical Field

[0001] This invention relates to the field of motor control technology, and in particular to an optimal control method for an auxiliary control system for multiple high-power motors. Background Technology

[0002] Hydropower stations have numerous important auxiliary equipment systems, such as maintenance drainage systems, leakage drainage systems, medium-pressure gas systems, and low-pressure gas systems, which are crucial to the normal operation of the entire power station. Due to their functional requirements, these auxiliary systems control multiple high-power motors. Ensuring that these high-power motors respond correctly and quickly under both normal and abnormal operating conditions, reaching the control objectives without affecting the safe operation of the plant's power supply system, is critical to the safe and stable operation of the entire power station. Currently, the control systems for high-power motor auxiliary equipment mainly face the following problems:

[0003] (1) Under normal operating conditions, it is impossible to guarantee that multiple high-power motors can start and stop correctly, sequentially, and in order according to a certain pattern.

[0004] (2) Multiple motors require manual intervention to operate, and cannot achieve automatic balanced start and stop, which can easily damage the motors in the long run;

[0005] (3) In abnormal circumstances, when multiple high-power motors start at the same time, the starting current is too large, causing the plant power supply to trip.

[0006] This invention aims to address the problems existing in the current control systems of multiple high-power auxiliary equipment in power plants by simultaneously addressing both hardware loops and software programs, seeking solutions, and researching optimal control schemes to ensure the correct, safe, and stable operation of the system, thereby providing a guarantee for the safe and stable operation of the power plant. Summary of the Invention

[0007] The technical problem to be solved by this invention is to provide an optimal control method for an auxiliary control system for multiple high-power motors. The method is improved in two ways: first, by optimizing the control loop of the conventional control system, and second, by optimizing the PLC software control logic. The optimal control is achieved by combining the hardware control loop and the software control program.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: an optimal control method for an auxiliary control system for multiple high-power motors, comprising the following steps:

[0009] Step 1: Add a standard self-starting circuit, a standard backup starting circuit, and a standard emergency starting circuit to the entire system;

[0010] Step 2: Divide the multiple high-power motors into three groups;

[0011] Step 3: Connect the three groups of high-power motors to the conventional self-starting circuit, the conventional standby starting circuit, and the conventional emergency starting circuit respectively;

[0012] Step 4: Connect the conventional self-starting circuit, the conventional standby starting circuit, and the conventional emergency starting circuit to the PLC, and set the logic for the PLC to start the motor within a certain time when such signals are reached.

[0013] Preferably, four water level detection points are set in the pump control system for maintenance, namely low water level L1, high water level H1, excessive high water level H2, and ultra-high water level H3. When the water level is at the low water level point L1, all motors are stopped. At the other water level points, when the water level reaches each detection point, one motor is started, and when it exceeds the detection point, another motor is started.

[0014] Preferably, after one motor is started, a certain period of time elapses before starting the next motor.

[0015] Preferably, when the PLC starts the motor, it preferentially outputs the start signal for the motor with fewer historical cumulative start times.

[0016] Preferably, when the analog water level value A1 reaches H1, the PLC outputs the start signal for one motor for pump drainage during maintenance;

[0017] When the analog water level value H1 < A1 < H2, the PLC starts another motor for pump drainage during maintenance after an interval of t5;

[0018] When the analog water level value A1 rises from H1 to H2, the PLC starts another motor for pump drainage during maintenance after an interval of t8;

[0019] When the analog water level value H2 < A1 < H3, the PLC starts another motor for pump drainage during maintenance after an interval of t6;

[0020] When the analog water level value A1 rises from H2 to H3, the PLC starts another motor for pump drainage during maintenance after an interval of t9;

[0021] When the analog water level value A1 > H3, the PLC starts another motor for pump drainage during maintenance after an interval of t7.

[0022] Preferably, the three groups of motors are respectively connected to different section buses of the plant service power.

[0023] Preferably, the motor starting sequence is to start the motors in the conventional self-starting circuit, the conventional standby starting circuit, and the conventional emergency starting circuit in sequence. <00,00050>The present invention provides an optimal control method for the auxiliary control system for multiple high-power motors, having the following advantages:

[0025] (1) This invention patent achieves optimal control of the auxiliary control system for high-power motors by combining hardware control loop optimization and software control program optimization. It takes multiple approaches and fully considers various situations, thereby improving the reliability and feasibility of control optimization.

[0026] (2) This invention patent can realize the automatic start and stop of the controlled objects in the system according to the rules, which improves the safety, stability and reliability of the control system.

[0027] (3) The rotating start logic in this invention enables each high-power motor in the system to be in a balanced state of starting and stopping, effectively avoiding the situation where some motors are in service for a long time while others are not started for a long time, thus achieving the effect of protecting the motor and extending its life.

[0028] (4) By rationally arranging conventional control loops, interlocking hardware loops and software loops, and delaying the start of pump start and pump increase orders, the simultaneous start of multiple high-power motors on the same section of plant power is avoided, which greatly improves the stability of plant power.

[0029] (5) This invention patent only requires minor modifications to the existing control loop and software control program, resulting in low engineering application costs, reliable performance, and strong feasibility.

[0030] (6) This invention patent has strong applicability and can be used as a reference template for control systems of various high-power motor-type equipment in industry. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the conventional loop control principle of the present invention;

[0032] Figure 2 This is a flowchart of the PLC start-up process for the conventional circuit start-up interlock of this invention.

[0033] Figure 3 This is a flowchart of the process for determining the validity of analog quantities reaching a set value in this invention.

[0034] Figure 4 This is a flowchart illustrating the basic logic of PLC analog pump start / stop control in this invention.

[0035] Figure 5 This is a flowchart of the PLC pump start-up logic of the present invention;

[0036] Figure 6 This is a flowchart of the PLC rotating pump starting logic of the present invention;

[0037] Figure 7 This is a flowchart of the PLC pump start-up interlock conventional circuit pump start-up logic of the present invention. Detailed Implementation

[0038] This invention improves the control method in two ways: first, by optimizing the control loop of a conventional control system; and second, by optimizing the PLC software control logic. It achieves optimal control by combining hardware control loops and software control programs.

[0039] Taking the maintenance drainage pump control system of a power station as an example, its controlled objects are 7 high-power motors of 225KW.

[0040] 1. For example Figure 1 As shown, the pump start-up and stop control principle of a conventional control loop is as follows:

[0041] (1) Install a water level sensor and a water level measuring device in the maintenance pump control system of a power station. Connect the current or voltage signal output by the sensor to the water level measuring device. Set the output contacts of the water level measuring device according to the maintenance drainage setting sheet of a power station. Open four pairs of empty contacts: low water level 1, high water level 1, excessively high water level 1, and extremely high water level 1, as the first set of switch quantity start and stop pump control signals.

[0042] (2) Four water level floats are installed in the maintenance pump control system of a power station. According to the maintenance drainage setting sheet of a power station, the floats are fixed at the corresponding elevation of the maintenance well and output low water level 2, high water level 2, excessively high water level 2, and ultra-high water level 2 signals respectively, as the second set of switch quantity start and stop pump control signals.

[0043] (3) After connecting the corresponding start and stop pump control signals of the first and second sets of switch quantities in parallel, output four sets of repeating relays for conventional control: low water level stop pump 3ZJ, automatic water level start pump 1ZJ, standby water level start pump 2ZJ, high water level start pump and alarm 4ZJ.

[0044] (4) The control system of a power station’s maintenance pumps controls pumps 1 to 7, and their power supply is taken from the power station’s plant power supply section I (pumps 1 and 2), section II (pumps 3 and 4), and section III (pumps 5, 6, and 7).

[0045] (5) The low water level pump stop relay 3ZJ is applicable to all pumps. Its normally closed contact is connected to the self-holding circuit of pump 1 to 7. When the low water level pump stop signal arrives, all pumps under maintenance will stop.

[0046] (6) To avoid starting multiple maintenance pumps powered by the same section of plant power supply when the automatic water level or standby water level signal arrives, causing excessive instantaneous starting current and posing a risk to the safety and stability of plant power supply, the normally open contact of the automatic water level pump start relay 1ZJ is connected to the starting circuit of maintenance pumps 1#, 3#, and 7#, the normally open contact of the standby water level pump start relay 2ZJ is connected to the starting circuit of maintenance pumps 2#, 4#, and 6#, and the normally open contact of the high water level start and alarm relay 4ZJ is connected to the starting circuit of maintenance pump 5#.

[0047] 2. Control principle of starting pump lockout of PLC starting pump command for conventional control loop:

[0048] (1) Connect the open contact signals D2, D3, and D4 of the relays of conventional automatic water level starting pump 1ZJ, standby water level starting pump 2ZJ, high water level starting pump and alarm 4ZJ into the PLC.

[0049] (2) To prevent multiple maintenance pumps from starting simultaneously due to the starting of the conventional loop and the PLC output at the same time, add the starting pump lockout logic of the conventional loop in the PLC control program. When any digital quantity starting pump signal D2, D3, or D4 of the PLC arrives, the parallel output of the conventional loop lockout PLC starting pump signal D5 is generated, and the lockout duration is t2, as Figure 2 shown.

[0050] 3. Basic logic of PLC analog quantity starting and stopping pump control:

[0051] According to the analog quantity water level value A1 collected by the PLC and the maintenance drainage fixed value list of a certain power station, set four groups of different water level fixed values of analog quantity low water level L1, high water level H1, high water level H2, and ultra-high water level H3, and judge whether the fixed value is reached, as Figure 3 shown. When the analog quantity water level reaches L1, stop all maintenance pumps; when the water level reaches H1, H2, or H3, issue the starting pump command for one pump each time, as Figure 4 shown. When the PLC starts the pump, it preferentially issues the command to start the pump with the least cumulative starting times in history. When the starting times are the same, start in the order of pump No. 1 to No. 7. When the water level does not drop or continues to rise, use the pump addition logic to start the subsequent maintenance pumps.

[0052] 4. As Figure 5 [[ID=2​​​​​​​​​​​​​​​​​(6) When the simulated water level value A1>H3, the PLC will start another maintenance drainage pump at interval t7.

[0059] (7) Each time the PLC starts the pump, it will prioritize starting the maintenance pump with the fewest historical cumulative starts.

[0060] 5. For example Figure 6 As shown, the PLC pump rotation start-up logic is as follows:

[0061] To ensure balanced startup of each maintenance pump, a rotating startup control logic is adopted. A maintenance pump enters the rotating startup judgment stage when there is no fault signal, the handle is in the automatic position, and it is not running. The number of runs of all maintenance pumps entering the rotating startup judgment stage is compared, and the pump with the fewest runs is marked as "pump allowed". If two pumps have the same number of starts, they are marked as "pump allowed" in the order of pumps 1#, 2#, 3#, 4#, 5#, 6#, and 7#. When a pump start command or pump addition command is issued, the maintenance pump marked as "pump allowed" is started.

[0062] 6. For example Figure 7 As shown, the PLC pump start-up interlock logic for the conventional circuit pump start-up is as follows:

[0063] When the PLC issues a pump start command or a pump increase command, it sends a PLC lockout signal D6 for the normal circuit pump start and opens the normal circuit pump start relay. Its contacts are connected in series in the control circuit of maintenance pumps #1 to #7. The lockout time for the normal circuit pump start is t1, to prevent the PLC from issuing the command and the normal circuit from starting the pump at the same time.

[0064] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A method for optimal control of a multi-machine auxiliary control system for high-power electric machines, characterized in that, It comprises the following steps: Step one, add a conventional self-starting circuit, a conventional standby starting circuit and a conventional emergency starting circuit in the whole system; Step two, divide the multiple high-power motors into three groups; Step three, connect the three groups of high-power motors to the conventional self-starting circuit, the conventional standby starting circuit and the conventional emergency starting circuit respectively; Step four, connect the conventional self-starting circuit, the conventional standby starting circuit and the conventional emergency starting circuit to the PLC, and set the PLC to lock the starting motor logic for a certain time when such signals are reached; PLC pump rotation starting logic: when the maintenance pump has no fault signal, the handle is in the automatic position and is not running, enter the rotation judgment, compare the running times of all the maintenance pumps that enter the rotation judgment, and mark the pump with the least running time as "pump allowed". If two pumps have the same starting times, mark the pump with the lowest number as "pump allowed" in priority. When there is a pump starting order or a pump adding order, start the maintenance pump marked as "pump allowed".

2. The optimal control method for the auxiliary control system of the multi-machine high-power motor according to claim 1, characterized in that, In the maintenance pump control system, four water level detection points are set, namely low water level L1, high water level H1, high water level H2 and super high water level H3. When the water level reaches each detection point, one motor is started.

3. The optimal control method for the auxiliary control system of the multi-machine high-power motor according to claim 2, characterized in that, One motor is started, and the next motor is started after a period of time.

4. The optimal control method for the auxiliary control system of the multi-machine high-power motor according to claim 3, characterized in that, When the PLC starts the motor, it gives priority to the motor with the least cumulative starting times in history.

5. The optimal control method of the auxiliary control system for multiple high-power motors according to claim 3, characterized in that: (1) When the analog water level value A1 reaches H1, the PLC starts one maintenance drainage pump motor; (2) When the analog water level value H1 < A1 < H2, the PLC starts another maintenance drainage pump motor after a period of t5; (3) When the analog water level value A1 rises from H1 to H2, the PLC starts one maintenance drainage pump motor after a period of t8; (4) When the analog water level value H2 < A1 < H3, the PLC starts another maintenance drainage pump motor after a period of t6; (5) When the analog water level value A1 rises from H2 to H3, the PLC starts one maintenance drainage pump motor after a period of t9; (6) When the analog water level value A1 > H3, the PLC starts another maintenance drainage pump motor after a period of t7.

6. The optimal control method for the auxiliary control system of the multi-machine high-power motor according to claim 1, characterized in that, The three groups of motors are connected to different segmented buses of the plant power supply.

7. The optimal control method for the auxiliary control system of the multi-machine high-power motor according to claim 1, characterized in that, The motor starting sequence is to start the motors in the conventional self-starting circuit, the conventional standby starting circuit and the conventional emergency starting circuit in turn.

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