Improved auxiliary power supply system and control method thereof

Abstract

The invention relates to an improved auxiliary power supply system and a control method thereof, and the system is additionally provided with a plurality of auxiliary branch reactors, a plurality of bypass switches, a voltage sampling end, a current sampling end and a controller which are sequentially connected in series from front to back on the basis of a high-voltage bus, a boost transformer, a generator and an auxiliary power bus. The input end of the first station-service branch reactor is connected with the low-voltage side of the boost transformer, the output end of the last station-service branch reactor is connected with a station-service outlet circuit breaker through a station-service inlet circuit breaker, and each station-service branch reactor is connected with a bypass switch in parallel; the controller is connected with the high-voltage incoming / outgoing line circuit breaker, the outlet circuit breaker, the bypass switches, the station service incoming / outgoing line circuit breaker, the voltage sampling end and the current sampling end so as to control the corresponding bypass switches to be switched off or switched on, and the corresponding station service branch reactors are switched on or switched off. And the voltage level of the auxiliary power bus during full-voltage starting of the high-capacity motor is improved.

Description

Technical Field

[0001] The present invention relates to the field of auxiliary power supplies for industrial enterprises, and particularly to an improved auxiliary power supply system and its control method. Background Art

[0002] Due to insulation capacity, the rated voltage of large generators does not exceed 28 kV at most, and the working current is very large. Usually, a transformer is used to step up the voltage and then connect it to the high-voltage bus. A large number of mechanical devices are set as power sources for the boilers, steam turbines and their auxiliary equipment of the enterprise's cogeneration device. Its power supply is called auxiliary power, and its distribution bus is called auxiliary power bus. Generally speaking, when the outlet voltage of the generator is the same as the auxiliary power bus voltage, a reactor is set in the auxiliary power branch circuit at the outlet of the generator, such as Figure 1 shown, so that the short-circuit current of the auxiliary power bus is within an acceptable range, and the auxiliary power can obtain the working power supply from the high-voltage bus. In addition, the auxiliary power generally also needs to obtain the standby power supply from other high-voltage power sources.

[0003] The design principle of the enterprise's cogeneration device is usually "steam determines electricity". The stable operation of the cogeneration device is the basis for the continuous and safe production of the enterprise. Therefore, the power supply reliability of the auxiliary power must be guaranteed. In order to improve the power supply reliability of the auxiliary power, an outlet circuit breaker is generally set at the outlet of the generator to ensure that after the generator is shut down, the auxiliary power can obtain the working power supply from the high-voltage bus through the step-up transformer and the auxiliary power branch reactor, without having to switch to the standby power supply. The small and medium-sized units of the existing enterprise cogeneration devices usually adopt the unit wiring of generator-step-up transformer-auxiliary power branch reactor-auxiliary power, and its typical auxiliary power supply system topology is as Figure 1 shown. However, during the operation of the auxiliary power supply system shown in Figure 1 shown, if there is a large deviation in any link, it is possible that the short-circuit current or bus voltage of the auxiliary power bus exceeds the control target. Even if there is no large deviation, the topology of this auxiliary power supply system also limits the starting ability of the auxiliary power bus for large-capacity motors.

[0004] Therefore, how to avoid the situation that the short-circuit current or bus voltage of the auxiliary power bus exceeds the control target and improve the starting ability of the auxiliary power bus for large-capacity motors has become a technical problem to be solved currently. Summary of the Invention

[0005] The first technical problem to be solved by the present invention is to provide an improved auxiliary power supply system with multiple auxiliary power branch reactors and bypass switches for the above-mentioned existing technology. This improved auxiliary power supply system can improve the voltage level of the auxiliary power bus during the full-voltage starting of large-capacity motors on the premise of meeting the control target of the short-circuit current of the auxiliary power bus.

[0006] The second technical problem to be solved by the present invention is to provide a control method for the above-mentioned improved factory power supply system.

[0007] The technical solution adopted by the present invention to solve the first technical problem is: an improved plant power supply system, including a high-voltage bus, a step-up transformer, a generator, a plant power bus and at least one incoming line for supplying power to the high-voltage bus, the high-voltage bus is connected to the incoming line through a corresponding high-voltage incoming line circuit breaker, the high-voltage bus is connected to the high-voltage side of the step-up transformer through a high-voltage outgoing line circuit breaker, the low-voltage side of the step-up transformer is connected to the output end of the generator through an outlet circuit breaker, and the plant power bus is connected to the corresponding plant power load through the plant power outgoing line circuit breaker, characterized in that it also includes:

[0008] A plurality of plant branch reactors connected in series, wherein the input end of the first plant branch reactor among the plurality of plant branch reactors is connected to the low voltage side of the step-up transformer, and the output end of the last plant branch reactor among the plurality of plant branch reactors is connected to the plant power outgoing line circuit breaker through the plant power incoming line circuit breaker;

[0009] Multiple bypass switches, each bypass switch corresponds to a plant branch reactor, and each bypass switch is connected in parallel with its corresponding plant branch reactor;

[0010] The voltage sampling terminal collects the output voltage of the plant branch circuit where the plant branch reactor is located;

[0011] The current sampling terminal collects the working current of the plant branch circuit where the plant branch reactor is located;

[0012] The controller is respectively connected to the high-voltage incoming line circuit breaker, the high-voltage outgoing line circuit breaker, the outlet circuit breaker, each bypass switch, the plant power incoming line circuit breaker, the plant power outgoing line circuit breaker, the voltage sampling end and the current sampling end for signal connection. The controller processes based on the switch state of the high-voltage incoming line circuit breaker, the switch state of the high-voltage outgoing line circuit breaker, the switch state of the outlet circuit breaker, the state of each bypass switch, the switch state of the plant power incoming line circuit breaker, the switch state of the plant power outgoing line circuit breaker, the output voltage of the plant branch circuit collected by the voltage sampling end and the working current of the plant branch circuit collected by the current sampling end, and controls the corresponding bypass switch to open or close, so as to put into or exit the corresponding plant branch inductor.

[0013] Improved, in the improved factory power supply system, the controller is a device with data processing and logic programming functions, and the bypass switch is a high-voltage contactor or a high-voltage circuit breaker.

[0014] Optionally, in the improved plant power supply system, the plurality of plant branch reactors are reactors with parameters that are not completely the same; or, the plurality of plant branch reactors are reactors with parameters that are completely the same.

[0015] The technical solution adopted by the present invention to solve the second technical problem is: a control method for the plant power supply system, which is applied to any of the improved plant power supply systems described above, and is characterized in that the control method for the plant power supply system includes the following steps:

[0016] Step 1, pre-obtain high-voltage bus parameters, step-up transformer parameters, generator parameters, plant power bus parameters, plant power branch reactor parameters, and plant power load parameters; among them, the high-voltage bus parameters are the maximum / minimum per-unit reactance values of the high-voltage bus, the step-up transformer parameters are the per-unit reactance values of the step-up transformer, the generator parameters are the per-unit reactance values of the generator, the plant power branch reactor parameters are the per-unit reactance values of each plant power branch reactor, and the plant power bus parameters are the base value of the short-circuit current of the plant power bus, the starting current and starting capacity of all plant power loads on the plant power bus, the nominal voltage of the plant power bus, the allowable value of the short-circuit current of the plant power bus, and the allowable value of the relative voltage of the plant power bus when a single plant power load starts; the starting current and starting capacity of all plant power loads on the plant power bus correspond one-to-one with the plant power outgoing line circuit breakers;

[0017] Step 2, obtain the switch states of the high-voltage incoming line circuit breaker, the high-voltage outgoing line circuit breaker, the outlet circuit breaker, each bypass switch, the plant power incoming line circuit breaker, and the plant power outgoing line circuit breaker;

[0018] Step 3, obtain the output voltage of the plant power branch circuit collected by the voltage sampling terminal and the working current of the plant power branch circuit collected by the current sampling terminal;

[0019] Step 4, based on all the obtained switch states, the output voltage of the plant power branch circuit, and the working current of the plant power branch circuit, process to obtain the maximum value of the short-circuit current of the plant power bus in the current state of the plant power supply system;

[0020] Step 5, compare the obtained maximum value of the short-circuit current of the plant power bus with the allowable value of the short-circuit current of the plant power bus, and based on the comparison result, predict the maximum value of the short-circuit current of the plant power bus after adjusting the closing / opening state of the bypass switch;

[0021] Step 6, based on the maximum value of the short-circuit current of the plant power bus predicted and adjusted after the closing / opening state of the bypass switch, make a process, and control the corresponding bypass switch to perform a closing or opening operation to withdraw or put into the corresponding plant power branch reactor;

[0022] Step 7, based on all the obtained switch states, the output voltage of the plant power branch circuit, and the working current of the plant power branch circuit, process to obtain the relative value of the voltage of the plant power bus when the single largest-capacity motor on the plant power bus that is not put into use starts with full voltage in the current state of the plant power supply system;

[0023] Step 8: Compare the relative value of the auxiliary power bus voltage when the single largest-capacity motor not in use on the obtained auxiliary power bus is started at full voltage with the allowable value of the relative value of the auxiliary power bus voltage. According to the comparison result, predict the maximum short-circuit current of the auxiliary power bus after adjusting the closing / opening state of the bypass switch and the relative value of the auxiliary power bus voltage when the single largest-capacity motor not in use on the auxiliary power bus is started at full voltage.

[0024] Step 9: Based on the predicted maximum short-circuit current of the auxiliary power bus after adjusting the closing / opening state of the obtained bypass switch and the relative value of the auxiliary power bus voltage when the single largest-capacity motor not in use on the auxiliary power bus is started at full voltage, make a treatment, and control the corresponding bypass switch to perform a closing or opening operation to withdraw or put into the corresponding auxiliary power branch reactor.

[0025] Compared with the prior art, the advantages of the present invention are as follows: The improved auxiliary power supply system in the invention has the advantages of low investment, small floor area, simple wiring, small operation and maintenance workload, high automation level, and can provide data prediction and operation guidance for operators; The improved auxiliary power supply system in the invention can improve the voltage level of the auxiliary power bus when a large-capacity motor is started at full voltage on the premise of meeting the short-circuit current control target of the auxiliary power bus. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of an existing auxiliary power supply system;

[0027] Figure 2 It is a schematic diagram of the improved auxiliary power supply system in the embodiment of the present invention;

[0028] Figure 3 For Figure 2 A schematic flow chart of the control method of the improved auxiliary power supply system shown. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The present invention will be further described in detail below in conjunction with the embodiments of the drawings.

[0030] This embodiment provides an improved auxiliary power supply system with multiple auxiliary power branch reactors and bypass switches. Refer to Figure 2As shown, the improved auxiliary power supply system of this embodiment includes a high-voltage bus L1, a step-up transformer 1, a generator 2, an auxiliary power bus L2, and two incoming lines Q for supplying power to the high-voltage bus L1. Each incoming line Q is connected to the high-voltage bus L1 through a corresponding high-voltage incoming line breaker 13. The high-voltage bus L1 is connected to the high-voltage side of the step-up transformer 1 through a high-voltage outgoing line breaker 3. The low-voltage side of the step-up transformer 1 is connected to the output terminal of the generator 2 through an outlet breaker 4. The auxiliary power bus L2 is connected to the corresponding auxiliary power load 6 through an auxiliary power outgoing line breaker 5. The auxiliary power load 6 is a motor. As an improvement, the improved auxiliary power supply system further includes:

[0031] A plurality of auxiliary power branch reactors 7 connected in series in sequence before and after. The input end of the first auxiliary power branch reactor among the plurality of auxiliary power branch reactors 7 is connected to the low-voltage side of the step-up transformer 1. The output end of the last auxiliary power branch reactor among the plurality of auxiliary power branch reactors 7 is connected to the auxiliary power outgoing line breaker 5 through an auxiliary power incoming line breaker 8. In this embodiment, according to the series connection order before and after, they are respectively called auxiliary power branch reactor 1, auxiliary power branch reactor 2,..., auxiliary power branch reactor n, where n≥2;

[0032] A plurality of bypass switches 9. Each bypass switch 9 corresponds to an auxiliary power branch reactor 7, and each bypass switch 9 is connected in parallel with its corresponding auxiliary power branch reactor 7. Among them, in this embodiment, according to the parallel relationship with each auxiliary power branch reactor, the bypass switch corresponding to the auxiliary power branch reactor n is called bypass switch n;

[0033] A voltage sampling terminal 10 for collecting the output voltage of the auxiliary power branch circuit where the auxiliary power branch reactor 7 is located;

[0034] A current sampling terminal 11 for collecting the working current of the auxiliary power branch circuit where the auxiliary power branch reactor 7 is located;

[0035] A controller 12 is respectively connected to the high-voltage incoming line breaker 13, the high-voltage outgoing line breaker 3, the outlet breaker 4, each bypass switch 9, the auxiliary power incoming line breaker 8, the auxiliary power outgoing line breaker 5, the voltage sampling terminal 10, and the current sampling terminal 11 for signal connection. The controller makes processing based on the switch states of the high-voltage incoming line breaker, the high-voltage outgoing line breaker, the outlet breaker, the states of each bypass switch, the switch states of the auxiliary power incoming line breaker, the switch states of the auxiliary power outgoing line breaker, the output voltage of the auxiliary power branch circuit collected by the voltage sampling terminal, and the working current of the auxiliary power branch circuit collected by the current sampling terminal, and controls the corresponding bypass switch to be disconnected or closed to put into or withdraw the corresponding auxiliary power branch reactor. Among them, the controller 12 is a device with data processing and logic programming functions, and the bypass switch 9 adopts a high-voltage contactor or a high-voltage circuit breaker as needed.

[0036] Specifically, in this embodiment, the basic data of the improved auxiliary power supply system is as follows:

[0037] (1) High-voltage infeed lines and high-voltage busbars

[0038] Nominal voltage: 110 kV

[0039] Short-circuit capacity of the 1st infeed line Q (located on the left): 2500 MVA (maximum value), 1500 MVA (minimum value); Short-circuit capacity of the 2nd infeed line Q (located on the right): 2000 MVA (maximum value), 1000 MVA (minimum value)

[0040] The 1st infeed line Q and the 2nd infeed line Q may be put into operation simultaneously or separately; When put into operation simultaneously, the per-unit value of reactance of the high-voltage busbar: 0.022 (minimum value), 0.04 (maximum value); When the 1st infeed line Q is put into operation alone, the per-unit value of reactance of the high-voltage busbar: 0.04 (minimum value), 0.067 (maximum value); When the 2nd infeed line Q is put into operation alone, the per-unit value of reactance of the high-voltage busbar: 0.05 (minimum value), 0.1 (maximum value);

[0041] (2) Generator

[0042] Rated power: 40 MW

[0043] Rated voltage: 6.3 kV

[0044] Power factor: 0.8

[0045] Percentage of subtransient reactance: 14.5%

[0046] Per-unit value of reactance: 0.29

[0047] (3) Step-up transformer

[0048] Rated capacity: 50 MVA

[0049] Percentage of impedance voltage: 10.5%

[0050] Per-unit value of reactance: 0.21

[0051] (4) Auxiliary power branch reactor

[0052] Two auxiliary power branch reactors are provided, with series connection

[0053] Rated voltage: 6 kV

[0054] Rated current: 2000 A

[0055] Percentage of impedance voltage of auxiliary power branch reactor 1: 5%

[0056] Per-unit value of reactance of auxiliary power branch reactor 1: 0.218

[0057] Percentage impedance voltage of auxiliary branch reactor 2: 6%

[0058] Per-unit reactance value of auxiliary branch reactor 2: 0.262

[0059] (5) Auxiliary power bus

[0060] Nominal voltage: 6 kV

[0061] Maximum value of the sum of starting currents of high-voltage motors: 7.1 kA

[0062] Operating voltage before starting of large-capacity motors: 6.12 kV

[0063] Reactive power connected before starting of large-capacity motors: 3.38 MVar

[0064] Sum of starting currents of high-voltage motors already in operation before starting of large-capacity motors: 3.7 kA

[0065] (6) Largest single non-operating motor

[0066] Rated voltage: 6 kV

[0067] Rated power: 4 MW

[0068] Rated starting capacity: 32.073 MVA

[0069] This embodiment also provides a control method applied to the above improved auxiliary power system. Specifically, as shown in Figure 3 The control method of the auxiliary power system in this embodiment includes the following steps:

[0070] Step 1, obtain high-voltage bus parameters, step-up transformer parameters, generator parameters, auxiliary power bus parameters, auxiliary branch reactor parameters, and auxiliary power load parameters in advance; among them, the high-voltage bus parameters are the maximum / minimum per-unit reactance values of the high-voltage bus, the step-up transformer parameters are the per-unit reactance values of the step-up transformer, the generator parameters are the per-unit reactance values of the generator, the auxiliary branch reactor parameters are the per-unit reactance values of each auxiliary branch reactor, and the auxiliary power bus parameters are the short-circuit current reference value of the auxiliary power bus, the starting currents and starting capacities of all auxiliary power loads on the auxiliary power bus, the nominal voltage of the auxiliary power bus, the allowable value of the short-circuit current of the auxiliary power bus, and the allowable value of the relative voltage of the auxiliary power bus when a single auxiliary power load starts; the starting currents and starting capacities of all auxiliary power loads on the auxiliary power bus correspond one by one to the auxiliary power outgoing line circuit breakers;

[0071] Step 2, obtain the switch states of the high-voltage incoming line circuit breaker, high-voltage outgoing line circuit breaker, outlet circuit breaker, each bypass switch, auxiliary power incoming line circuit breaker, and auxiliary power outgoing line circuit breaker;

[0072] Step 3: Obtain the output voltage of the auxiliary power branch circuit collected by the voltage sampling terminal and the working current of the auxiliary power branch circuit collected by the current sampling terminal.

[0073] Step 4: Based on all the obtained switch states, the output voltage of the auxiliary power branch circuit, and the working current of the auxiliary power branch circuit, process to obtain the maximum short-circuit current of the auxiliary power bus of this auxiliary power system in the current state.

[0074] Step 5: Compare the obtained maximum short-circuit current of the auxiliary power bus with the allowable value of the short-circuit current of the auxiliary power bus. According to the comparison result, predict the maximum short-circuit current of the auxiliary power bus after adjusting the closing / opening state of the bypass switch.

[0075] Step 6: Based on the predicted maximum short-circuit current of the auxiliary power bus after adjusting the closing / opening state of the bypass switch, make a treatment, and control the corresponding bypass switch to perform a closing or opening operation to withdraw or put into the corresponding auxiliary power branch reactor.

[0076] Step 7: Based on all the obtained switch states, the output voltage of the auxiliary power branch circuit, and the working current of the auxiliary power branch circuit, process to obtain the relative value of the auxiliary power bus voltage when the largest single-capacity motor that is not put into use on the auxiliary power bus of this auxiliary power system starts with full voltage.

[0077] Step 8: Compare the obtained relative value of the auxiliary power bus voltage when the largest single-capacity motor that is not put into use on the auxiliary power bus starts with full voltage with the allowable value of the relative value of the auxiliary power bus voltage. According to the comparison result, predict the maximum short-circuit current of the auxiliary power bus and the relative value of the auxiliary power bus voltage when the largest single-capacity motor that is not put into use on the auxiliary power bus starts with full voltage after adjusting the closing / opening state of the bypass switch.

[0078] Step 9: Based on the predicted maximum short-circuit current of the auxiliary power bus and the relative value of the auxiliary power bus voltage when the largest single-capacity motor that is not put into use on the auxiliary power bus starts with full voltage after adjusting the closing / opening state of the bypass switch, make a treatment, and control the corresponding bypass switch to perform a closing or opening operation to withdraw or put into the corresponding auxiliary power branch reactor.

[0079] Specifically, the control method of the above auxiliary power system is elaborated in detail with examples as follows:

[0080] The control objectives for this auxiliary power system are as follows:

[0081] Short-circuit withstand capacity of electrical equipment on the auxiliary power bus: 31.5 kA

[0082] Allowable value of short-circuit current of the auxiliary power bus: ≤27 kA

[0083] Relative value of the auxiliary power bus voltage when the largest single-capacity motor starts: ≥ 85% of the nominal voltage.

[0084] The main control logic for the bypass switch is as follows:

[0085] Case 1: When the generator is put into operation and auxiliary branch reactors 1 and 2 are all put into operation

[0086] A. Calculate the maximum short-circuit current of the auxiliary power bus under the current topology of the auxiliary power supply system. If it is less than the allowable value, the controller does not issue an operation command; if it is greater than the allowable value, an alarm signal is issued.

[0087] B. Predict the bus voltage when the largest single-capacity motor not in use on the auxiliary power bus starts with full voltage. If the requirement is met, the controller does not issue an operation command. If the requirement is not met, the controller will calculate the maximum short-circuit current of the auxiliary power bus after withdrawing auxiliary branch reactors 1 and 2. If it is less than the allowable value, select bypass switches 1 and 2 to issue closing commands. If it is greater than the allowable value, calculate the maximum short-circuit current of the auxiliary power bus after withdrawing either auxiliary branch reactor 1 or 2. If both are less than the allowable value, select the bypass switch with the larger value to issue a closing command; if only one is less than the allowable value, select that bypass switch to issue a closing command; if both are greater than the allowable value, an alarm signal is issued.

[0088] C. After all or one of the auxiliary branch reactors are withdrawn from operation, predict the bus voltage when the largest single-capacity motor not in use on the auxiliary power bus starts with full voltage. If the requirement is met, the controller does not issue an operation command; if the requirement is not met, an alarm signal is issued.

[0089] Case 2: When the generator is withdrawn from operation and auxiliary branch reactors 1 and 2 are all put into operation

[0090] A. Calculate the maximum short-circuit current of the auxiliary power bus under the current topology of the auxiliary power supply system. If it is less than the allowable value, the controller does not issue an operation command; if it is greater than the allowable value, an alarm signal is issued.

[0091] B. Predict the bus voltage when the largest single-capacity motor not in use on the auxiliary power bus starts with full voltage. If the requirement is met, the controller does not issue an operation command. If the requirement is not met, the controller will calculate the maximum short-circuit current of the auxiliary power bus after withdrawing auxiliary branch reactors 1 and 2. If it is less than the allowable value, select bypass switches 1 and 2 to issue closing commands. If it is greater than the allowable value, calculate the maximum short-circuit current of the auxiliary power bus after withdrawing either auxiliary branch reactor 1 or 2. If both are less than the allowable value, select the bypass switch with the larger value to issue a closing command; if only one is less than the allowable value, select that bypass switch to issue a closing command; if both are greater than the allowable value, an alarm signal is issued.

[0092] C. After all or one of the auxiliary branch reactors is taken out of service, predict the bus voltage during the full-voltage starting of the single largest-capacity motor not in use on the auxiliary power bus. If the requirement is met, the controller does not issue an operation command; if the requirement is not met, an alarm signal is issued.

[0093] Case 3: When the generator is put into operation and both auxiliary branch reactors 1 and 2 are taken out of service

[0094] A. Calculate the maximum short-circuit current of the auxiliary power bus under the current topology of the auxiliary power supply system. If it is less than the allowable value, the controller does not issue an operation command; if it is greater than the allowable value, the controller will calculate the maximum short-circuit current of the auxiliary power bus after putting in auxiliary branch reactor 1 or 2. If both are greater than the allowable value, trip commands for both bypass switches are issued simultaneously; if one is less than the allowable value, select this bypass switch to issue a trip command; if both are less than the allowable value, select the bypass switch with the larger value to issue a trip command; if the calculated maximum short-circuit current of the auxiliary power bus after all auxiliary branch reactors are put in is still greater than the allowable value, select all bypass switches to issue trip commands and an alarm signal is issued simultaneously.

[0095] B. After all auxiliary branch reactors are taken out of service and all or one of them is put into operation, predict the bus voltage during the full-voltage starting of the single largest-capacity motor not in operation on the auxiliary power bus. If the requirement is met, the controller does not issue an operation command; if the requirement is not met, an alarm signal is issued.

[0096] Case 4: When the generator is taken out of service and both auxiliary branch reactors 1 and 2 are taken out of service

[0097] A. Calculate the maximum short-circuit current of the auxiliary power bus under the current topology of the auxiliary power supply system. If it is less than the allowable value, the controller does not issue an operation command; if it is greater than the allowable value, the controller will calculate the maximum short-circuit current of the auxiliary power bus after putting in auxiliary branch reactor 1 or 2. If both are greater than the allowable value, trip commands for both bypass switches are issued simultaneously; if one is less than the allowable value, select this bypass switch to issue a trip command; if both are less than the allowable value, select the bypass switch with the larger value to issue a trip command; if the calculated maximum short-circuit current of the auxiliary power bus after all auxiliary branch reactors are put in is still greater than the allowable value, select all bypass switches to issue trip commands and an alarm signal is issued simultaneously.

[0098] B. After all auxiliary branch reactors are taken out of service and all or one of them is put into operation, predict the bus voltage during the full-voltage starting of the single largest-capacity motor not in use on the auxiliary power bus. If the requirement is met, the controller does not issue an operation command; if the requirement is not met, an alarm signal is issued.

[0099] I. Preliminary calculation in the engineering design stage

[0100] When the generator is put into operation, all of the auxiliary branch reactors 1 and 2 are put into operation, the short-circuit capacity of the high-voltage bus is at its maximum (the first incoming line Q and the second incoming line Q are both put into operation and are at their maximum), and the starting current of the high-voltage motor is at its maximum, the short-circuit current of the auxiliary power bus is 22.15 kA;

[0101] When the generator is taken out of operation, auxiliary branch reactor 1 is taken out and reactor 2 is put into operation, the short-circuit capacity of the high-voltage bus is at its maximum (the first incoming line Q and the second incoming line Q are both put into operation and are at their maximum), and the starting current of the high-voltage motor is at its maximum, the short-circuit current of the auxiliary power bus is 25.65 kA.

[0102] When the generator is put into operation, all of the auxiliary branch reactors 1 and 2 are put into operation, the short-circuit capacity of the high-voltage bus is at its minimum (the second incoming line Q is at its minimum), and the auxiliary power bus is carrying the calculated load, the relative value of the bus voltage when the largest single-capacity motor on the auxiliary power bus starts with full voltage is 85.9%.

[0103] When the generator is taken out of operation, auxiliary branch reactor 1 is put into operation and reactor 2 is taken out of operation, the short-circuit capacity of the high-voltage bus is at its minimum (the second incoming line Q is taken as the minimum), and the auxiliary power bus is carrying the calculated load, the relative value of the bus voltage when the largest single-capacity motor on the auxiliary power bus starts with full voltage is 87.8%.

[0104] II. Control Scheme under Specific Operating Conditions

[0105] Before the device is put into operation, relevant parameters such as the maximum / minimum per-unit value of the reactance of the high-voltage bus, the per-unit value of the reactance of the step-up transformer, the per-unit value of the reactance of the generator, the per-unit value of the reactance of auxiliary branch reactor 1, the per-unit value of the reactance of auxiliary branch reactor 2, the reference value of the short-circuit current of the auxiliary power bus, the starting current and starting capacity of all high-voltage motors on the auxiliary power bus (corresponding one-to-one with the auxiliary power outgoing line switches), the nominal voltage of the auxiliary power bus, the allowable value of the short-circuit current of the auxiliary power bus, and the allowable value of the relative value of the bus voltage when a single motor starts are input into the controller.

[0106] The controller will, based on the status signals of the high-voltage incoming circuit breaker, high-voltage outgoing circuit breaker, generator outlet circuit breaker, bypass switch, auxiliary power incoming circuit breaker, and auxiliary power outgoing circuit breaker received, as well as the current and voltage data of the auxiliary branch circuit collected in real time, calculate in real time the maximum value of the short-circuit current of the auxiliary power bus and the minimum value of the short-circuit capacity under the current topological structure of the auxiliary power supply system, predict the relative value of the bus voltage when the largest single-capacity motor not yet put into operation on the auxiliary power bus starts with full voltage under the current topological structure of the auxiliary power supply system, and at the same time predict the maximum value of the short-circuit current of the auxiliary power bus and the minimum value of the short-circuit capacity after adjusting the on / off state of the bypass switch, as well as the relative value of the bus voltage when the largest single-capacity motor not yet put into operation starts with full voltage, and issue an operation command for closing / opening the bypass switch according to the prediction results, and take out / put into operation the corresponding auxiliary branch reactor.

[0107] (2.1) The controller receives the closing status signals of the high-voltage incoming circuit breakers 1 and 2, the high-voltage outgoing circuit breaker, the generator outlet circuit breaker, the opening of bypass switches 1 and 2, and the closing of the auxiliary power incoming circuit breaker. At the same time, according to the corresponding closing status of the auxiliary power outgoing circuit breaker, the pre-input starting current values of these circuits are retrieved and summed up. According to the basic data of the improved auxiliary power supply system in this embodiment, the auxiliary power bus I can be calculated according to formula (1). ” max = 22.15 kA ≤ 27 kA, and at the same time, S is calculated scB . According to the data collected by the current and voltage transformers of the auxiliary power branch circuit, u s and Q L can be calculated. According to the maximum value of the starting capacity in these circuits retrieved in advance according to the corresponding opening status of the auxiliary power outgoing circuit breaker, S st can be calculated. According to formula (2), u stB = 86.2% ≥ 85%. The controller does not issue operation commands and alarm signals.

[0108] Formula (1): When the generator is put into operation and all of the auxiliary power branch reactors 1 and 2 are put into operation

[0109]

[0110]

[0111] I ” max represents the maximum value of the short-circuit current of the auxiliary power bus (unit: kA), S scB represents the minimum value of the short-circuit capacity of the auxiliary power bus before the motor starts (unit: MVA), I b represents the reference value of the short-circuit current of the auxiliary power bus (unit: kA), X * S represents the per-unit value of the high-voltage bus reactance (min is the minimum value, max is the maximum value), X * T represents the per-unit value of the step-up transformer reactance, X * G represents the per-unit value of the generator reactance, X * R1 and X * R2 represent the per-unit values of the auxiliary power branch reactors 1 and 2, ∑I Mstmax represents the maximum value of the sum of the starting currents of the high-voltage motors (unit: kA), ∑I Mst represents the actual value of the starting current of the high-voltage motors (unit: kA), and U represents the voltage value of the auxiliary power bus (unit: kV).

[0112] Formula (2): Calculation method of the bus voltage during the full-voltage starting of the motor

[0113]

[0114] u stB represents the relative value of the auxiliary power bus voltage during motor starting (%) ; u s represents the relative value of the auxiliary power bus voltage before motor starting; S scB represents the minimum short-circuit capacity of the auxiliary power bus before motor starting (unit: MVA); Q L represents the reactive power connected to the auxiliary power bus before motor starting (unit: MVar); S st represents the starting capacity of the motor starting circuit (which can be approximately taken as the rated starting capacity of the motor) (unit: MVA).

[0115] (2.2) When the controller receives the closing state signals of the high-voltage incoming line breakers 1 and 2, the high-voltage outgoing line breaker, the generator outlet breaker opening, the bypass switches 1 and 2 opening, and the auxiliary power incoming line breaker closing, at the same time, according to the corresponding closing states of the auxiliary power outgoing line breakers, it retrieves the pre-input starting current values of these circuits and sums them up. According to the basic data of the improved auxiliary power system in this embodiment, the auxiliary power bus I can be calculated according to formula (3) ” max = 19.97 kA ≤ 27 kA, and at the same time, S is calculated scB . According to the data collected by the current and voltage transformers of the auxiliary power branch circuit, u s and Q L can be calculated. According to the corresponding opening states of the auxiliary power outgoing line breakers, the maximum starting capacity value among these circuits pre-input is retrieved, and S st can be calculated. According to formula (2), u stB = 84.3% < 85%. At this time, the controller will recalculate I stB ” max = 46.56 kA > 27 kA after all bypass switches are closed according to formula (4), and then recalculate I max ” max1 = 27.45 kA > 27 kA and I ” max2 stB = 25.65 kA ≤ 27 kA after bypass switch 2 is closed or bypass switch 1 is closed according to formula (5), and issue a command to close bypass switch 1. After bypass switch 1 is closed, recalculate u stB stB = 88.1% ≥ 85% after closing the bypass switch according to formula (2), and the controller does not issue an alarm signal.

[0116] Formula (3): When the generator is out of service and both auxiliary bus reactors 1 and 2 are in service

[0117]

[0118]

[0119] I ” max represents the maximum short - circuit current of the auxiliary power bus (unit: kA), S scB represents the minimum short - circuit capacity of the auxiliary power bus before motor starting (unit: MVA), I b represents the reference value of the short - circuit current of the auxiliary power bus (unit: kA), X * S represents the per - unit value of the high - voltage bus reactance (min for minimum value, max for maximum value), X * T represents the per - unit value of the step - up transformer reactance, X * R1 and X * R2 represent the per - unit values of the reactances of auxiliary bus reactors 1 and 2, ∑I Mstmax represents the maximum sum of the starting currents of high - voltage motors (unit: kA), ∑I Mst represents the actual value of the starting current of high - voltage motors (unit: kA), U represents the voltage value of the auxiliary power bus (unit: kV).

[0120] Formula (4): When the generator is out of service and both auxiliary bus reactors 1 and 2 are out of service

[0121]

[0122]

[0123] I ” max represents the maximum short - circuit current of the auxiliary power bus (unit: kA), S scB represents the minimum short - circuit capacity of the auxiliary power bus before motor starting (unit: MVA), I b represents the reference value of the short - circuit current of the auxiliary power bus (unit: kA), X * S represents the per - unit value of the high - voltage bus reactance (min for minimum value, max for maximum value), X * T represents the per - unit value of the step - up transformer reactance, ∑I Mstmax represents the maximum sum of the starting currents of high - voltage motors (unit: kA), ∑I MstI represents the actual value of the starting current of the high-voltage motor (unit: kA), and U represents the voltage value of the auxiliary power bus (unit: kV).

[0124] Formula (5): When the generator is out of service and one of the auxiliary power branch reactors 1 or 2 is put into operation

[0125]

[0126]

[0127] I ” max represents the maximum value of the short-circuit current of the auxiliary power bus (unit: kA), S scB represents the minimum value of the short-circuit capacity of the auxiliary power bus before motor starting (unit: MVA), I b represents the reference value of the short-circuit current of the auxiliary power bus (unit: kA), X * S represents the per-unit value of the high-voltage bus reactance (min is the minimum value, max is the maximum value), X * T represents the per-unit value of the step-up transformer reactance, X * R1 / 2 represents the per-unit value of the reactance of auxiliary power branch reactor 1 or 2, ∑I Mstmax represents the maximum value of the sum of the starting currents of high-voltage motors (unit: kA), ∑I Mst I represents the actual value of the starting current of the high-voltage motor (unit: kA), and U represents the voltage value of the auxiliary power bus (unit: kV).

[0128] (2.3) When the controller receives the closing signal of the high-voltage incoming breaker 1 / opening signal of breaker 2, closing signal of the high-voltage outgoing breaker, closing signal of the generator outlet breaker, opening signals of bypass switches 1 and 2, and closing signal of the auxiliary power incoming breaker, at the same time, according to the corresponding closing state of the auxiliary power outgoing breaker, it retrieves the pre-input starting current values of these circuits and sums them up. According to the basic data of the improved auxiliary power system in this embodiment, the auxiliary power bus I can be calculated according to formula (1) ” max = 22.02 kA ≤ 27 kA, and at the same time, S is calculated scB . According to the data collected by the current and voltage transformers of the auxiliary power branch circuit, u s and Q L can be calculated. According to the maximum value of the starting capacity pre-input in these circuits retrieved according to the corresponding opening state of the auxiliary power outgoing breaker, S st can be calculated. According to formula (2), u stB = 86.1% ≥ 85%. The controller does not issue operation commands and alarm signals.

[0129] (2.4) The controller receives the closing signal of the high-voltage incoming breaker 1 / opening signal of breaker 2, the closing signal of the high-voltage outgoing breaker, the opening signal of the generator outlet breaker, the opening signals of bypass switches 1 and 2, and the closing signal of the auxiliary power incoming breaker. At the same time, according to the corresponding closing state of the auxiliary power outgoing breaker, it retrieves the pre-input starting current values of these circuits and sums them up. According to the basic data of the improved auxiliary power system in this embodiment, the auxiliary power bus I can be calculated according to formula (3) ” max = 19.65 kA ≤ 27 kA, and at the same time, S is calculated scB . According to the data collected by the current and voltage transformers of the auxiliary power branch circuit, u s and Q L can be calculated. According to the maximum starting capacity in these circuits pre-input according to the corresponding opening state of the auxiliary power outgoing breaker, S st can be calculated. According to formula (2), u stB = 83.9% < 85%. At this time, the controller will recalculate I after all bypass switches are closed according to formula (4) ” max = 43.76 kA > 27 kA, and then recalculate I after bypass switch 2 is closed or bypass switch 1 is closed according to formula (5) ” max1 = 26.67 kA ≤ 27 kA and I ” max2 = 25.00 kA ≤ 27 kA, and issue a command to close bypass switch 2. After bypass switch 2 is closed, recalculate u after the bypass switch is closed according to formula (2) stB = 88.4% ≥ 85%. The controller does not issue an alarm signal.

[0130] (2.5) The controller receives the opening signal of the high-voltage incoming breaker 1 / closing signal of breaker 2, the closing signal of the high-voltage outgoing breaker, the closing signal of the generator outlet breaker, the opening signals of bypass switches 1 and 2, and the closing signal of the auxiliary power incoming breaker. At the same time, according to the corresponding closing state of the auxiliary power outgoing breaker, it retrieves the pre-input starting current values of these circuits and sums them up. According to the basic data of the improved auxiliary power system in this embodiment, the auxiliary power bus I can be calculated according to formula (1) ” max = 21.95 kA ≤ 27 kA, and at the same time, S is calculated scB . According to the data collected by the current and voltage transformers of the auxiliary power branch circuit, u s and Q L can be calculated. According to the maximum starting capacity in these circuits pre-input according to the corresponding opening state of the auxiliary power outgoing breaker, S st can be calculated. According to formula (2), u stB= 85.9% ≥ 85%. The controller does not issue an operation command or an alarm signal.

[0131] (2.6) The controller receives the opening signal of the high-voltage incoming breaker 1 / closing signal of the high-voltage outgoing breaker, closing signal of the generator outlet breaker, opening signals of the bypass switches 1 and 2, and closing signal of the auxiliary power incoming breaker. At the same time, according to the corresponding closing states of the auxiliary power outgoing breakers, the starting current values of these circuits pre-input are retrieved and summed up. According to the basic data of the improved auxiliary power supply system in this embodiment, the auxiliary power bus I can be calculated according to formula (3) ” max = 19.48 kA ≤ 27 kA. At the same time, S is calculated scB . According to the data collected by the current and voltage transformers of the auxiliary power branch circuits, u can be calculated s and Q L . According to the maximum starting capacity in these circuits pre-input retrieved according to the corresponding opening states of the auxiliary power outgoing breakers, S can be calculated st . According to formula (2), u can be calculated stB = 83.4% < 85%. At this time, the controller will recalculate I after all bypass switches are closed according to formula (4) ” max = 42.35 kA > 27 kA. Then, according to formula (5), I after bypass switch 2 is closed or bypass switch 1 is closed is recalculated ” max1 = 26.26 kA ≤ 27 kA and I ” max2 = 24.66 kA ≤ 27 kA. A command to close bypass switch 2 is issued. After bypass switch 2 is closed, u after the bypass switch is closed is recalculated according to the formula in 4.2.3 stB = 87.8% ≥ 85%. The controller does not issue an alarm signal.

[0132] (2.7) The controller receives the closing signals of the high-voltage incoming breakers 1 and 2, closing signal of the high-voltage outgoing breaker, closing signal of the generator outlet breaker, closing signals of the bypass switches 1 and 2, and closing signal of the auxiliary power incoming breaker. At the same time, according to the corresponding closing states of the auxiliary power outgoing breakers, the starting current values of these circuits pre-input are retrieved and summed up. According to the basic data of the improved auxiliary power supply system in this embodiment, the auxiliary power bus I can be calculated according to formula (6) ” max = 78.17 kA > 27 kA. At this time, the controller will recalculate I after bypass switch 1 is opened or bypass switch 2 is opened according to formula (7) ” max1 = 33.50 kA > 27 kA and I ” max2= 30.55 kA > 27 kA, and at the same time, commands to open bypass switches 1 and 2 are issued. After the bypass switches 1 and 2 are tripped, the controller will recalculate I after opening bypass switches 1 and 2 according to formula (1). ” max = 22.15 kA ≤ 27 kA, and at the same time, S is calculated. scB . According to the data collected by the current and voltage transformers of the auxiliary power branch circuit, u can be calculated. s and Q L . By retrieving the maximum value of the starting capacity in these circuits pre-entered according to the corresponding tripped state of the auxiliary power outgoing circuit breaker, S can be calculated. st . Calculate u after opening the bypass switch according to formula (2). stB = 86.2% ≥ 85%. The controller does not issue an alarm signal.

[0133] Formula (6): When the generator is put into operation and auxiliary power branch reactors 1 and 2 are all taken out of operation

[0134]

[0135]

[0136] I ” max represents the maximum value of the short-circuit current of the auxiliary power bus (unit: kA), S scB represents the minimum value of the short-circuit capacity of the auxiliary power bus before the motor starts (unit: MVA), I b represents the reference value of the short-circuit current of the auxiliary power bus (unit: kA), X * S represents the per-unit value of the high-voltage bus reactance (min is the minimum value, max is the maximum value), X * T represents the per-unit value of the step-up transformer reactance, X * G represents the per-unit value of the generator reactance, ∑I Mstmax represents the maximum value of the sum of the starting currents of high-voltage motors (unit: kA), ∑I Mst represents the actual value of the starting current of high-voltage motors (unit: kA), U represents the voltage value of the auxiliary power bus (unit: kV).

[0137] Formula (7): When the generator is put into operation and one of the auxiliary power branch reactors 1 or 2 is put into operation

[0138]

[0139]

[0140] I ” maxRepresents the maximum short-circuit current of the auxiliary power bus (unit: kA), S scB Represents the minimum short-circuit capacity of the auxiliary power bus before motor starting (unit: MVA), I b Represents the reference value of the short-circuit current of the auxiliary power bus (unit: kA), X * S Represents the per-unit value of the reactance of the high-voltage bus (min is the minimum value, max is the maximum value), X * T Represents the per-unit value of the reactance of the step-up transformer, X * G Represents the per-unit value of the reactance of the generator, X * R1 / 2 Represents the per-unit value of the reactance of the auxiliary branch reactor 1 or 2, ∑I Mstmax Represents the maximum value of the sum of the starting currents of high-voltage motors (unit: kA), ∑I Mst Represents the actual value of the starting current of high-voltage motors (unit: kA), U represents the voltage value of the auxiliary power bus (unit: kV).

[0141] (2.8) The controller receives the closing state signals of the high-voltage incoming line breakers 1 and 2, the high-voltage outgoing line breaker, the generator outlet breaker, the bypass switches 1 and 2, and the auxiliary power incoming line breaker. At the same time, according to the corresponding closing state of the auxiliary power outgoing line breaker, it retrieves the pre-input starting current values of these circuits and sums them up. According to the basic data of the improved auxiliary power system in this embodiment, the auxiliary power bus I can be calculated according to formula (4) ” max = 46.56 kA > 27 kA. At this time, the controller will recalculate I after opening bypass switch 1 or bypass switch 2 according to formula (5) ” max1 = 27.45 kA > 27 kA and I ” max2 = 25.65 kA ≤ 27 kA, and issues a command to open bypass switch 2. After bypass switch 2 is opened, the controller calculates S scB . According to the data collected by the current and voltage transformers of the auxiliary branch circuit, u s and Q L can be calculated. According to the maximum value of the starting capacity in these circuits retrieved according to the corresponding opening state of the auxiliary power outgoing line breaker, S st can be calculated. According to formula (2), u after opening the bypass switch stB = 88.1% ≥ 85%. The controller does not issue an alarm signal.

[0142] (2.9) The controller receives the closing signal of the high-voltage incoming line breaker 1 / opening signal of breaker 2, the closing signal of the high-voltage outgoing line breaker, the closing signal of the generator outlet breaker, the closing signals of bypass switches 1 and 2, and the closing signal of the auxiliary power incoming line breaker. At the same time, according to the corresponding closing state of the auxiliary power outgoing line breaker, it retrieves the pre-input starting current values of these circuits and sums them up. According to the basic data of the improved auxiliary power supply system in this embodiment, the auxiliary power bus I can be calculated according to formula (6) ” max = 75.36 kA > 27 kA. At this time, the controller will recalculate I after opening bypass switch 1 or bypass switch 2 according to formula (7) ” max1 = 33.10 kA > 27 kA and I ” max2 = 30.24 kA > 27 kA, and at the same time issues commands to open bypass switches 1 and 2. After bypass switches 1 and 2 open, the controller will recalculate I after opening bypass switches 1 and 2 according to formula (1) ” max = 22.02 kA ≤ 27 kA, and at the same time calculates S scB . According to the data collected by the current and voltage transformers of the auxiliary power branch circuit, u s and Q L can be calculated. According to the maximum value of the starting capacity in these circuits retrieved according to the corresponding opening state of the auxiliary power outgoing line breaker, S st can be calculated. According to formula (2), calculate u after opening the bypass switch stB = 86.1% ≥ 85%. The controller does not issue an alarm signal.

[0143] (2.10) The controller receives the closing signal of the high-voltage incoming line breaker 1 / opening signal of breaker 2, the closing signal of the high-voltage outgoing line breaker, the opening signal of the generator outlet breaker, the closing signals of bypass switches 1 and 2, and the closing signal of the auxiliary power incoming line breaker. At the same time, according to the corresponding closing state of the auxiliary power outgoing line breaker, it retrieves the pre-input starting current values of these circuits and sums them up. According to the basic data of the improved auxiliary power supply system in this embodiment, the auxiliary power bus I can be calculated according to formula (4) ” max = 43.76 kA > 27 kA. At this time, the controller will recalculate I after opening bypass switch 1 or bypass switch 2 according to formula (5) ” max1 = 26.67 kA ≤ 27 kA and I ” max2 = 25.00 kA ≤ 27 kA, issues a command to open bypass switch 1, and at the same time calculates S scB . According to the data collected by the current and voltage transformers of the auxiliary power branch circuit, u sand Q L Retrieve the maximum value of the starting capacity in these circuits pre - input according to the corresponding opening state of the auxiliary power outgoing circuit breaker, and S can be calculated. st Calculate u after opening the bypass switch according to formula (2). stB = 88.4% ≥ 85%. The controller does not issue an alarm signal.

[0144] (2.11) The controller receives the opening signal of the high - voltage incoming circuit breaker 1 / closing signal of the high - voltage incoming circuit breaker 2, closing signals of the high - voltage outgoing circuit breaker, generator outlet circuit breaker, bypass switches 1 and 2, and closing signal of the auxiliary power incoming circuit breaker. At the same time, retrieve the starting current values of these circuits pre - input according to the corresponding closing state of the auxiliary power outgoing circuit breaker and sum them up. According to the basic data of the improved auxiliary power supply system in this embodiment, the auxiliary power bus I can be calculated according to formula (6). ” max = 73.95kA > 27kA. At this time, the controller will recalculate I after opening bypass switch 1 or bypass switch 2 according to formula (7). ” max1 = 30.07kA > 27kA and I ” max2 = 29.36kA > 27kA. At the same time, issue commands to open bypass switches 1 and 2. After bypass switches 1 and 2 open, the controller will recalculate I after opening bypass switches 1 and 2 according to formula (1). ” max = 21.95kA ≤ 27kA. At the same time, calculate S scB According to the data collected by the current and voltage transformers of the auxiliary power branch circuit, u can be calculated. s and Q L Retrieve the maximum value of the starting capacity in these circuits pre - input according to the corresponding opening state of the auxiliary power outgoing circuit breaker, and S can be calculated. st Calculate u after opening the bypass switch according to formula (2). stB = 85.9% ≥ 85%. The controller does not issue an alarm signal.

[0145] (2.12) The controller receives the opening signal of the high - voltage incoming circuit breaker 1 / closing signal of the high - voltage incoming circuit breaker 2, closing signal of the high - voltage outgoing circuit breaker, opening signal of the generator outlet circuit breaker, closing signals of bypass switches 1 and 2, and closing signal of the auxiliary power incoming circuit breaker. At the same time, retrieve the starting current values of these circuits pre - input according to the corresponding closing state of the auxiliary power outgoing circuit breaker and sum them up. According to the basic data of the improved auxiliary power supply system in this embodiment, the auxiliary power bus I can be calculated according to formula (4). ” max = 42.35kA > 27kA. At this time, the controller will recalculate I after opening bypass switch 1 or bypass switch 2 according to formula (5).” max1 = 26.26 kA ≤ 27 kA and I ” max2 = 24.66 kA ≤ 27 kA, issue the command to open bypass switch 1, and simultaneously calculate to obtain S scB . Based on the data collected by the current and voltage transformers of the auxiliary power branch circuit, u can be calculated s and Q L . According to the maximum starting capacity in these circuits pre-inputted by retrieving the corresponding opening states of the auxiliary power outgoing circuit breakers, S can be calculated st . Calculate u after opening the bypass switch according to formula (2) stB = 87.8% ≥ 85%. The controller does not issue an alarm signal

[0146] Although the preferred embodiments of the present invention have been described in detail above, it should be clearly understood that various changes and modifications can be made to the present invention for those skilled in the art. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention

Claims

1. An improved auxiliary power supply system, comprising a high-voltage busbar (L1), a step-up transformer (1), a generator (2), an auxiliary power busbar (L2), and at least one incoming line (Q) for supplying power to the high-voltage busbar (L1). The high-voltage busbar (L1) is connected to the incoming line (Q) through a corresponding high-voltage incoming line circuit breaker (13). The high-voltage busbar (L1) is connected to the high-voltage side of the step-up transformer (1) through a high-voltage outgoing line circuit breaker (3). The low-voltage side of the step-up transformer (1) is connected to the output terminal of the generator (2) through an outlet circuit breaker (4). The auxiliary power busbar (L2) is connected to a corresponding auxiliary power load (6) through an auxiliary power outgoing line circuit breaker (5), characterized in that Also includes: A plurality of plant branch reactors (7) connected in series in sequence, wherein the input end of the first plant branch reactor among the plurality of plant branch reactors (7) is connected to the low voltage side of the step-up transformer (1), and the output end of the last plant branch reactor among the plurality of plant branch reactors (7) is connected to the plant power outgoing line circuit breaker (5) via the plant power incoming line circuit breaker (8); A plurality of bypass switches (9), each bypass switch (9) corresponds to a plant branch reactor (7), and each bypass switch (9) is connected in parallel with its corresponding plant branch reactor (7); A voltage sampling terminal (10) collects the output voltage of the plant branch circuit where the plant branch reactor (7) is located; A current sampling terminal (11) collects the working current of the plant branch circuit where the plant branch reactor (7) is located; The controller (12) is respectively connected to the high-voltage incoming line circuit breaker (13), the high-voltage outgoing line circuit breaker (3), the outlet circuit breaker (4), each bypass switch (9), the plant power incoming line circuit breaker (8), the plant power outgoing line circuit breaker (5), the voltage sampling terminal (10) and the current sampling terminal (11) for signal transmission. The controller processes based on the switch state of the high-voltage incoming line circuit breaker, the switch state of the high-voltage outgoing line circuit breaker, the switch state of the outlet circuit breaker, the state of each bypass switch, the switch state of the plant power incoming line circuit breaker, the switch state of the plant power outgoing line circuit breaker, the output voltage of the plant branch circuit collected by the voltage sampling terminal and the working current of the plant branch circuit collected by the current sampling terminal, and controls the corresponding bypass switch to be opened or closed, so as to put into operation or withdraw the corresponding plant branch reactor.

2. The improved auxiliary power supply system according to claim 1, characterized in that, The controller (12) is a device with data processing and logic programming functions, and the bypass switch (9) is a high-voltage contactor or a high-voltage circuit breaker.

3. The improved auxiliary power supply system according to claim 1 or 2, characterized in that, The plurality of plant branch reactors (7) are reactors with parameters that are not completely the same; or, the plurality of plant branch reactors (7) are reactors with parameters that are completely the same.

4. The control method of the auxiliary power supply system is applied to the improved auxiliary power supply system described in any one of claims 1 to 3, and is characterized in that, The control method of the plant power supply system includes the following steps: Step 1, pre-acquire high-voltage bus parameters, step-up transformer parameters, generator parameters, plant power bus parameters, plant branch reactor parameters and plant power load parameters; wherein, the high-voltage bus parameters are the maximum / minimum per unit reactance of the high-voltage bus, the step-up transformer parameters are the per unit reactance of the step-up transformer, the generator parameters are the per unit reactance of the generator, the plant branch reactor parameters are the per unit reactance of each plant branch reactor, the plant power bus parameters are the plant power bus short-circuit current reference value, the starting current and starting capacity of all plant power loads on the plant power bus, the plant power bus nominal voltage, the plant power bus short-circuit current allowable value, and the allowable value of the relative value of the plant power bus voltage when a single plant power load is started; the starting current and starting capacity of all plant power loads on the plant power bus correspond to the plant power outgoing line circuit breaker one by one; Step 2, obtaining the switch status of the high-voltage incoming line circuit breaker, the switch status of the high-voltage outgoing line circuit breaker, the switch status of the outlet circuit breaker, the status of each bypass switch, the switch status of the plant power incoming line circuit breaker, and the switch status of the plant power outgoing line circuit breaker; Step 3: Obtain the output voltage of the auxiliary power branch circuit collected by the voltage sampling terminal and the working current of the auxiliary power branch circuit collected by the current sampling terminal; Step 4: Based on all the obtained switch states, the output voltage of the auxiliary power branch circuit, and the working current of the auxiliary power branch circuit, process to obtain the maximum short-circuit current of the auxiliary power bus of this auxiliary power system in the current state; Step 5: Compare the obtained maximum short-circuit current of the auxiliary power bus with the allowable value of the short-circuit current of the auxiliary power bus. According to the comparison result, predict the maximum short-circuit current of the auxiliary power bus after adjusting the closing / opening state of the bypass switch; Step 6: Based on the predicted maximum short-circuit current of the auxiliary power bus after adjusting the closing / opening state of the bypass switch, make a decision, and control the corresponding bypass switch to perform a closing or opening operation to withdraw or put into the corresponding auxiliary power branch reactor; Step 7: Based on all the obtained switch states, the output voltage of the auxiliary power branch circuit, and the working current of the auxiliary power branch circuit, process to obtain the relative value of the auxiliary power bus voltage when the largest single-capacity motor not in use on the auxiliary power bus of this auxiliary power system starts with full voltage; Step 8: Compare the obtained relative value of the auxiliary power bus voltage when the largest single-capacity motor not in use on the auxiliary power bus starts with full voltage with the allowable value of the relative value of the auxiliary power bus voltage. According to the comparison result, predict the maximum short-circuit current of the auxiliary power bus and the relative value of the auxiliary power bus voltage when the largest single-capacity motor not in use on the auxiliary power bus starts with full voltage after adjusting the closing / opening state of the bypass switch; Step 9: Based on the predicted maximum short-circuit current of the auxiliary power bus and the relative value of the auxiliary power bus voltage when the largest single-capacity motor not in use on the auxiliary power bus starts with full voltage after adjusting the closing / opening state of the bypass switch, make a decision, and control the corresponding bypass switch to perform a closing or opening operation to withdraw or put into the corresponding auxiliary power branch reactor.

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