Auxiliary power supply system and control method thereof

Abstract

The invention relates to a station service power supply system and a control method thereof, a station service branch reactor with multiple taps, a plurality of bypass switches, a voltage sampling end, a current sampling end and a controller are additionally arranged on the basis of an existing high-voltage bus, a step-up transformer, a generator and a station service bus, and the input end of the station service branch reactor is connected with the low-voltage side of the step-up transformer; the output end of the plant branch reactor is connected with a plant outlet circuit breaker through a plant inlet circuit breaker, and each tap is connected with a bypass switch in parallel; the controller is respectively connected with the high-voltage inlet wire circuit breaker, the high-voltage outlet wire circuit breaker, the outlet circuit breaker, the bypass switches, the auxiliary power inlet wire circuit breaker, the auxiliary power outlet wire 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 auxiliary branch reactors of the corresponding parts are switched on or switched off; the voltage level of the auxiliary power bus during full-voltage starting of the high-capacity motor is improved on the premise that the control target of the auxiliary power bus on the short-circuit current is met.

Description

Technical Field

[0001] The present invention relates to the field of auxiliary power supplies for industrial enterprises, and particularly to an auxiliary power supply system and a control method thereof. 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 provided 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, when the outlet voltage of the generator is the same as the auxiliary power bus voltage, a reactor is provided 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 provided 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 have a 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 as 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 auxiliary power supply system with an auxiliary power branch reactor with multiple taps and a bypass switch for the above-mentioned existing technology. This 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 plant power supply system.

[0007] The technical solution adopted by the present invention to solve the first technical problem is as follows: A plant power supply system includes 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. The plant power bus is connected to the corresponding plant power load through a plant power outgoing line circuit breaker. It is characterized in that it further includes:

[0008] A plant branch reactor, whose input end is connected to the low-voltage side of the step-up transformer. The output end of the plant branch reactor is connected to the plant power outgoing line circuit breaker through a plant power incoming line circuit breaker. A plurality of taps are arranged between the input end and the output end of the plant branch reactor;

[0009] A plurality of bypass switches, each bypass switch corresponding to one tap of the plant branch reactor, and each bypass switch is connected in parallel with its corresponding tap;

[0010] A voltage sampling terminal for collecting the output voltage of the plant branch circuit where the plant branch reactor is located;

[0011] A current sampling terminal for collecting the working current of the plant branch circuit where the plant branch reactor is located;

[0012] A 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 terminal, and the current sampling terminal for signal connection. The controller makes processing based on the switch states of the high-voltage incoming line circuit breaker, the high-voltage outgoing line circuit breaker, the outlet circuit breaker, the states of each bypass switch, the switch states of the plant power incoming line circuit breaker, 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 disconnected or closed to put into or withdraw from the corresponding part of the plant branch reactor.

[0013] Improved, in the plant 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] The technical solution adopted by the present invention to solve the second technical problem is as follows: A control method for a plant power supply system is applied to any one of the above-mentioned plant power supply systems. It is characterized in that the control method for the plant power supply system includes the following steps:

[0015] Step 1: Obtain in advance the high-voltage bus parameters, step-up transformer parameters, generator parameters, auxiliary power bus parameters, auxiliary power branch reactor parameters, and auxiliary power load parameters. Among them, the high-voltage bus parameters are the per-unit values of the maximum / minimum reactance of the high-voltage bus, the step-up transformer parameters are the per-unit value of the step-up transformer reactance, the generator parameters are the per-unit value of the generator reactance, the auxiliary power branch reactor parameters are the total per-unit value of the auxiliary power branch reactor and the positions of each tap, and the auxiliary power bus parameters are the base value of the short-circuit current of the auxiliary power bus, the starting current and starting capacity 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 current and starting capacity of all auxiliary power loads on the auxiliary power bus correspond one-to-one with the auxiliary power outgoing line circuit breakers.

[0016] 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.

[0017] 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.

[0018] 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 value of the short-circuit current of the auxiliary power bus of the auxiliary power supply system in the current state.

[0019] Step 5: Compare the obtained maximum value of the 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 value of the short-circuit current of the auxiliary power bus after adjusting the closing / opening state of the bypass switch.

[0020] Step 6: Based on the maximum value of the short-circuit current of the auxiliary 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 part of the auxiliary power branch reactor.

[0021] 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 voltage of the auxiliary power bus when the largest single-capacity motor that is not put into use on the auxiliary power bus of the auxiliary power supply system starts under full voltage in the current state.

[0022] Step 8: Compare the relative value of the auxiliary power bus voltage during the full-voltage starting of the single largest-capacity motor not in use on the obtained auxiliary power bus 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 during the full-voltage starting of the single largest-capacity motor not in use on the auxiliary power bus.

[0023] Step 9: Based on the predicted 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 during the full-voltage starting of the single largest-capacity motor not in use on the auxiliary power bus, make a treatment, control the corresponding bypass switch to perform the closing or opening operation, so as to withdraw or put into the corresponding part of the auxiliary power branch reactor.

[0024] Compared with the prior art, the advantages of the present invention are as follows: The 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 auxiliary power supply system in the invention 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 short-circuit current control target of the auxiliary power bus. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic diagram of an existing auxiliary power supply system;

[0026] Figure 2 is a schematic diagram of the auxiliary power supply system in the embodiment of the present invention;

[0027] Figure 3 is Figure 2 a schematic flow diagram of the control method of the shown auxiliary power supply system. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] The present invention will be further described in detail below with reference to the embodiments of the drawings.

[0029] This embodiment provides an auxiliary power supply system with an auxiliary power branch reactor with multiple taps and a bypass switch. Refer to Figure 2 As shown, the 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 circuit 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 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 bus L2 is connected to the corresponding auxiliary power load 6 through an auxiliary power outgoing circuit breaker 5. The auxiliary power load 6 is a motor. As an improvement, the auxiliary power supply system further includes:

[0030] The auxiliary power branch reactor 7 has its input end connected to the low-voltage side of the step-up transformer 1, and the output end of the auxiliary power branch reactor 7 is connected to the auxiliary power outgoing circuit breaker 5 through the auxiliary power incoming circuit breaker 8. A plurality of taps 7a are provided between the input end and the output end of the auxiliary power branch reactor 7;

[0031] A plurality of bypass switches 9, each bypass switch 9 corresponding to one tap 7a of the auxiliary power branch reactor 7, and each bypass switch 9 being connected in parallel with its corresponding tap 7a;

[0032] The voltage sampling terminal 10 samples the output voltage of the auxiliary power branch circuit where the auxiliary power branch reactor 7 is located;

[0033] The current sampling terminal 11 samples the working current of the auxiliary power branch circuit where the auxiliary power branch reactor 7 is located;

[0034] The controller 12 is respectively connected to the high-voltage incoming circuit breaker 13, the high-voltage outgoing circuit breaker 3, the outlet circuit breaker 4, each bypass switch 9, the auxiliary power incoming circuit breaker 8, the auxiliary power outgoing circuit 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 circuit breaker, the high-voltage outgoing circuit breaker, the outlet circuit breaker, the states of each bypass switch, the switch states of the auxiliary power incoming circuit breaker, the switch states of the auxiliary power outgoing circuit 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 so as to put into or withdraw from the corresponding part of the 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 required.

[0035] Specifically, in this embodiment, the basic data of the auxiliary power supply system is as follows:

[0036] (1) High-voltage incoming line and high-voltage bus

[0037] Nominal voltage: 110 kV

[0038] Short-circuit capacity of the first incoming line Q (located on the left): 2500 MVA (maximum value), 1500 MVA (minimum value). Short-circuit capacity of the second incoming line Q (located on the right): 2000 MVA (maximum value), 1000 MVA (minimum value)

[0039] The first incoming line Q and the second incoming 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 is: 0.022 (minimum value), 0.04 (maximum value); when the first incoming line Q is put into operation alone, the per-unit value of reactance of the high-voltage busbar is: 0.04 (minimum value), 0.067 (maximum value); when the second incoming line Q is put into operation alone, the per-unit value of reactance of the high-voltage busbar is: 0.05 (minimum value), 0.1 (maximum value).

[0040] (2) Generator

[0041] Rated power: 60 MW

[0042] Rated voltage: 6.3 kV

[0043] Power factor: 0.8

[0044] Percentage of subtransient reactance: 15%

[0045] Per-unit value of reactance: 0.20

[0046] (3) Step-up transformer

[0047] Rated capacity: 75 MVA

[0048] Percentage of impedance voltage: 10.5%

[0049] Per-unit value of reactance: 0.14

[0050] (4) Auxiliary power branch reactor

[0051] Rated voltage: 6 kV

[0052] Rated current: 2000 A

[0053] Total percentage of impedance voltage of the auxiliary power branch reactor: 12%

[0054] Total per-unit value of reactance of the auxiliary power branch reactor: 0.524

[0055] Two intermediate taps are provided to divide the auxiliary power branch reactor into three parts

[0056] The percentage of impedance voltage of the three parts of the auxiliary power branch reactor are: 3%, 4%, 5%

[0057] The per-unit value of reactance of the three parts of the auxiliary power branch reactor are: 0.131, 0.175, 0.218

[0058] (5) Auxiliary power busbar

[0059] Nominal voltage: 6 kV

[0060] Maximum sum of starting currents of high-voltage motors: 9.2 kA

[0061] Operating voltage before starting of large-capacity motor: 6.06 kV

[0062] Reactive power connected before starting of large-capacity motor: 5.63 MVar

[0063] Sum of starting currents of high-voltage motors already in operation before starting of large-capacity motor: 5.8 kA

[0064] (6) Single largest-capacity motor not in use

[0065] Rated voltage: 6 kV

[0066] Rated power: 4 MW

[0067] Rated starting capacity: 32.073 MVA

[0068] This embodiment also provides a control method applied to the above-mentioned station service power system. Specifically, refer to Figure 3 As shown, the control method of the station service power system in this embodiment includes the following steps:

[0069] Step 1, obtain high-voltage bus parameters, step-up transformer parameters, generator parameters, station service bus parameters, station service branch reactor parameters, and station service 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 value of the step-up transformer, the generator parameters are the per-unit reactance value of the generator, the station service branch reactor parameters are the total per-unit reactance value of the station service branch reactor and the positions of each tap, the station service bus parameters are the base value of the short-circuit current of the station service bus, the starting currents and starting capacities of all station service loads on the station service bus, the nominal voltage of the station service bus, the allowable value of the short-circuit current of the station service bus, and the allowable value of the relative voltage of the station service bus when a single station service load starts; the starting currents and starting capacities of all station service loads on the station service bus correspond one-to-one with the station service outgoing circuit breakers;

[0070] Step 2, obtain the switch states of the high-voltage incoming circuit breaker, high-voltage outgoing circuit breaker, outlet circuit breaker, each bypass switch, station service incoming circuit breaker, and station service outgoing circuit breaker;

[0071] Step 3, obtain the output voltage of the station service branch circuit collected by the voltage sampling terminal and the working current of the station service branch circuit collected by the current sampling terminal;

[0072] Step 4, based on all the obtained switch states, output voltage of the station service branch circuit, and working current of the station service branch circuit, process to obtain the maximum value of the short-circuit current of the station service bus in the current state of this station service power system;

[0073] Step 5: Compare the maximum short-circuit current of the obtained 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.

[0074] Step 6: Based on the predicted maximum short-circuit current of the auxiliary power bus after adjusting the closing / opening state of the obtained bypass switch, take corresponding actions, and control the corresponding bypass switch to perform closing or opening operations to withdraw or put into operation the corresponding part of the auxiliary branch reactor.

[0075] Step 7: Based on all the obtained switch states, the output voltage of the auxiliary branch circuit, and the working current of the auxiliary branch circuit, process to obtain the relative value of the auxiliary power bus voltage when the largest single-capacity motor not put into operation on the auxiliary power bus of the auxiliary power system starts with full voltage under the current state.

[0076] Step 8: Compare the relative value of the auxiliary power bus voltage when the largest single-capacity motor not put into operation on the obtained 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 put into operation on the auxiliary power bus starts with full voltage after adjusting the closing / opening state of the bypass switch.

[0077] 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 put into operation on the auxiliary power bus starts with full voltage after adjusting the closing / opening state of the obtained bypass switch, take corresponding actions, and control the corresponding bypass switch to perform closing or opening operations to withdraw or put into operation the corresponding part of the auxiliary branch reactor.

[0078] Specifically, the control method of the above auxiliary power system is elaborated with detailed examples as follows:

[0079] The control objectives for this auxiliary power system are as follows:

[0080] Short-circuit withstand capacity of electrical equipment on the auxiliary power bus: 31.5 kA

[0081] Allowable value of short-circuit current of the auxiliary power bus: ≤27 kA

[0082] Relative value of the auxiliary power bus voltage when the largest single-capacity motor starts: ≥85% of the nominal voltage.

[0083] The main control logic for the bypass switch is as follows:

[0084] Case 1: When the generator is put into operation and all auxiliary branch reactors are put into operation

[0085] A. Calculate the maximum short-circuit current of the auxiliary power bus under the current topology of the auxiliary power 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.

[0086] B. Predict the bus voltage when the largest single unoperated motor 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 some or all of the auxiliary power branch reactors, select the maximum value less than the allowable value from all the calculated values of the combinations, and select the corresponding bypass switch combination to issue a closing command; if all are greater than the allowable value, an alarm signal is issued.

[0087] C. After some or all of the auxiliary power branch reactors are withdrawn from operation, predict the bus voltage when the largest single unoperated motor 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.

[0088] Case 2: When the generator is out of operation and all auxiliary power branch reactors are in operation

[0089] A. Calculate the maximum short-circuit current of the auxiliary power bus under the current topology of the auxiliary power 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.

[0090] B. Predict the bus voltage when the largest single unoperated motor 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 some or all of the auxiliary power branch reactors, select the maximum value less than the allowable value from all the calculated values of the combinations, and select the corresponding bypass switch combination to issue a closing command; if all are greater than the allowable value, an alarm signal is issued.

[0091] C. After some or all of the auxiliary power branch reactors are withdrawn from operation, predict the bus voltage when the largest single unoperated motor 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.

[0092] Case 3: When the generator is in operation and all auxiliary power branch reactors are out of operation

[0093] 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 partially or fully inserting the auxiliary power branch reactors, select the maximum value less than the allowable value from all the calculated values of the combinations, and select the corresponding bypass switch combination to issue a trip command; if the maximum short-circuit current of the auxiliary power bus after fully inserting the auxiliary power branch reactors is still greater than the allowable value, select all of the bypass switches 1 to 3 to issue a trip command and simultaneously issue an alarm signal.

[0094] B. After all the auxiliary power branch reactors are withdrawn, partially or fully inserted, predict the bus voltage when the largest single-capacity motor not in operation 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.

[0095] Case 4: When the generator is out of operation and all the auxiliary power branch reactors are out of operation

[0096] 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 partially or fully inserting the auxiliary power branch reactors, select the maximum value less than the allowable value from all the calculated values of the combinations, and select the corresponding bypass switch combination to issue a trip command; if the maximum short-circuit current of the auxiliary power bus after fully inserting the auxiliary power branch reactors is still greater than the allowable value, select all of the bypass switches 1 to 3 to issue a trip command and simultaneously issue an alarm signal.

[0097] B. After all the auxiliary power branch reactors are withdrawn, partially or fully inserted, predict the bus voltage when the largest single-capacity motor not in operation 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.

[0098] I. Preliminary calculation in the engineering design stage

[0099] When the generator is in operation, all the auxiliary power branch reactors are in operation, the short-circuit capacity of the high-voltage bus is the largest (the first incoming line Q and the second incoming line Q are both inserted and are both the largest), and the starting current of the high-voltage motor is the largest, the short-circuit current of the auxiliary power bus is 24.14 kA;

[0100] When the generator is out of operation, the auxiliary power branch reactors are inserted at 4% + 5%, the short-circuit capacity of the high-voltage bus is the largest (the first incoming line Q and the second incoming line Q are both inserted and are both the largest), and the starting current of the high-voltage motor is the largest, the short-circuit current of the auxiliary power bus is 25.71 kA;

[0101] When the generator is put into operation, all the auxiliary branch reactors are put into operation, the short-circuit capacity of the high-voltage bus is the smallest (the second incoming line Q is the smallest), and the auxiliary power bus is loaded with the calculated load, the relative value of the bus voltage when the single largest-capacity motor on the auxiliary power bus starts with full voltage is 85.7%;

[0102] When the generator is taken out of operation, the 3% + 5% auxiliary branch reactors are put into operation, the short-circuit capacity of the high-voltage bus is the smallest (the second incoming line Q is the smallest), and the auxiliary power bus is loaded with the calculated load, the relative value of the bus voltage when the single largest-capacity motor on the auxiliary power bus starts with full voltage is 86.3%.

[0103] II. Control Scheme under Specific Operating Conditions

[0104] Before the device is put into operation, relevant parameters such as the per-unit value of the maximum / minimum reactance of the high-voltage bus, the per-unit value of the step-up transformer reactance, the per-unit value of the generator reactance, the total per-unit value of the auxiliary branch reactor and its tap positions, 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 by one to 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;

[0105] The controller will, according to the status signals of the high-voltage incoming line breaker, high-voltage outgoing line breaker, generator outlet breaker, bypass switch, auxiliary power incoming line breaker, and auxiliary power outgoing line 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 and the minimum value of the short-circuit capacity of the auxiliary power bus under the current topology of the auxiliary power supply system, predict the relative value of the bus voltage when the single largest-capacity motor not yet put into operation on the auxiliary power bus starts with full voltage under the current topology of the auxiliary power supply system, and at the same time predict the maximum value of the short-circuit current and the minimum value of the short-circuit capacity of the auxiliary power bus after adjusting the on / off state of the bypass switch, as well as the relative value of the bus voltage when the single largest-capacity motor not yet in operation starts with full voltage. According to the prediction results, an operation command for closing / opening the bypass switch is issued to withdraw / put into operation the corresponding part of the auxiliary branch reactor.

[0106] (2.1) The controller receives the closing signals of the high-voltage incoming line breakers 1 and 2, the high-voltage outgoing line breaker, the generator outlet breaker, and the opening signals of all bypass switches, as well as the closing signal of the auxiliary power incoming line breaker. At the same time, according to the corresponding closing states of the auxiliary power outgoing line breakers, the pre-input starting current values of these circuits are retrieved and summed. According to the basic data of the auxiliary power supply system in this embodiment and formula (1), the short-circuit current I of the auxiliary power bus can be calculated. ” max = 24.14 kA ≤ 27 kA, and at the same time, S is calculated. scBBased on 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 by retrieving the corresponding opening state of the auxiliary power outgoing circuit breaker, S can be calculated. st According to formula (2), u can be calculated. stB u = 85.9% ≥ 85%. The controller does not issue operation commands and alarm signals.

[0107] Formula (1): When the generator is put into operation and part or all of the auxiliary power branch reactors are put into operation

[0108]

[0109]

[0110] 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 * G represents the per-unit value of the generator reactance, X * R1～n represents the per-unit value of the reactance of part or all of the auxiliary power branch reactors with multiple intermediate taps (take 0 when all are withdrawn), ∑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).

[0111] Formula (2): Calculation method of the bus voltage during full-voltage starting of the motor

[0112]

[0113] u stB represents the relative value of the auxiliary power bus voltage during motor starting (unit: %), u s represents the relative value of the auxiliary power bus voltage before motor starting; S scB represents the minimum value of the short-circuit capacity of the auxiliary power bus before motor starting (unit: MVA); Q LRepresents the reactive power connected to the auxiliary power bus before the motor starts (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).

[0114] (2.2) When the controller receives the closing state signals of the high-voltage incoming circuit breakers 1 and 2, the high-voltage outgoing circuit breaker, the generator outlet circuit breaker is open, all bypass switches are open, and the auxiliary power incoming circuit breaker is closed, and at the same time, according to the corresponding closing states of the auxiliary power outgoing circuit breakers, the pre-input starting current values of these circuits are retrieved and summed. According to the basic data of the auxiliary power supply system in this embodiment and formula (3), the short-circuit current I of the auxiliary power bus can be calculated ” max = 22.56 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 . According to the maximum value of the starting capacity in these circuits pre-input according to the corresponding opening states of the auxiliary power outgoing circuit breakers, S can be calculated st . According to formula (2), u can be calculated stB = 84.7% < 85%. At this time, the controller will recalculate I in various combined states after some or all of the bypass switches are opened according to formula (3) ” max , and select the maximum value less than the allowable value of 25.71 kA (that is, the combination of reactors 4% and 5% is put into operation) among all the calculated values, and issue a command to close bypass switch 1. After bypass switch 1 is closed, u after closing bypass switch 1 is recalculated according to formula (2) stB = 88.1% ≥ 85%. The controller does not issue an alarm signal.

[0115] Formula (3): When the generator is out of operation and some or all of the auxiliary power branch reactors are put into operation

[0116]

[0117]

[0118] 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 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 * R1～n Represents the per-unit value of the reactance when part or all of the auxiliary power branch reactors with multiple intermediate taps are put into operation (take 0 when all are withdrawn), ∑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).

[0119] (2.3) The controller receives the closing signal of the high-voltage incoming circuit breaker 1 / opening signal of 2, the closing signal of the high-voltage outgoing circuit breaker, the closing signal of the generator outlet circuit breaker, the opening signals of all bypass switches, and the closing signal of the auxiliary power incoming circuit breaker. At the same time, according to the corresponding closing state of the auxiliary power outgoing circuit breaker, it retrieves the pre-input starting current values of these circuits and sums them up. According to the basic data of the auxiliary power supply system in this embodiment, the auxiliary power bus I ” max = 24.02 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 corresponding opening state of the auxiliary power outgoing circuit breaker, it retrieves the maximum value of the starting capacity in these circuits, and S st can be calculated. According to formula (2), u stB = 85.8% ≥ 85%. The controller does not issue operation commands and alarm signals.

[0120] (2.4) The controller receives the closing signal of the high-voltage incoming circuit breaker 1 / opening signal of 2, the closing signal of the high-voltage outgoing circuit breaker, the opening signal of the generator outlet circuit breaker, the opening signals of all bypass switches, and the closing signal of the auxiliary power incoming circuit breaker. At the same time, according to the corresponding closing state of the auxiliary power outgoing circuit breaker, it retrieves the pre-input starting current values of these circuits and sums them up. According to the basic data of the auxiliary power supply system in this embodiment, the auxiliary power bus I ” max = 22.22 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 corresponding opening state of the auxiliary power outgoing circuit breaker, it retrieves the maximum value of the starting capacity in these circuits, and S st can be calculated. According to formula (2), u stB= 84.3% < 85%. At this time, the controller will recalculate I for various combined states after the bypass switch is partially or fully opened according to formula (3). ” max , select the maximum value less than the allowable value of 26.52 kA (i.e., the combination of putting in reactors of 3% and 5%) among all the calculated values, and issue a command to close bypass switch 2. After bypass switch 2 is closed, recalculate u after closing bypass switch 2 according to formula (2). stB = 86.9% ≥ 85%. The controller does not issue an alarm signal.

[0121] (2.5) The controller receives the status signals of the high-voltage incoming circuit breaker 1 tripping / 2 closing, the high-voltage outgoing circuit breaker closing, the generator outlet circuit breaker closing, all bypass switches tripping, and the auxiliary power incoming circuit breaker closing. At the same time, according to the corresponding closing status of the auxiliary power outgoing circuit breaker, retrieve the pre-input starting current values of these circuits and sum them up. According to the basic data of the auxiliary power supply system in this embodiment, the auxiliary power bus I can be calculated according to formula (1). ” max = 23.95 kA ≤ 27 kA, and at the same time calculate S scB . According to the data collected by the current and voltage transformers of the auxiliary power branch circuits, u s and Q L can be calculated. According to the maximum value of the starting capacity pre-input in these circuits corresponding to the tripping status of the auxiliary power outgoing circuit breaker, S st can be calculated. According to formula (2), u stB = 85.8% ≥ 85%. The controller does not issue an operation command or an alarm signal.

[0122] (2.6) The controller receives the status signals of the high-voltage incoming circuit breaker 1 tripping / 2 closing, the high-voltage outgoing circuit breaker closing, the generator outlet circuit breaker tripping, all bypass switches tripping, and the auxiliary power incoming circuit breaker closing. At the same time, according to the corresponding closing status of the auxiliary power outgoing circuit breaker, retrieve the pre-input starting current values of these circuits and sum them up. According to the basic data of the auxiliary power supply system in this embodiment, the auxiliary power bus I can be calculated according to formula (3). ” max = 22.04 kA ≤ 27 kA, and at the same time calculate S scB . According to the data collected by the current and voltage transformers of the auxiliary power branch circuits, u s and Q L can be calculated. According to the maximum value of the starting capacity pre-input in these circuits corresponding to the tripping status of the auxiliary power outgoing circuit breaker, S st can be calculated. According to formula (2), u stB= 83.9% < 85%. At this time, the controller will recalculate I for various combined states after partially or fully opening the bypass switch according to formula (3). ” max , select the maximum value less than the allowable value, 26.20 kA (i.e., the combination of reactor 3% and 5% is put into operation), among all the calculated values, and issue a command to close bypass switch 2. After bypass switch 2 is closed, recalculate u after closing bypass switch 2 according to formula (2). stB = 86.3% ≥ 85%. The controller does not issue an alarm signal.

[0123] (2.7) The controller receives the closing state signals of high-voltage incoming circuit breakers 1 and 2, high-voltage outgoing circuit breaker, generator outlet circuit breaker, all bypass switches closed, and auxiliary power incoming circuit breaker. At the same time, it retrieves the pre-input starting current values of these circuits according to the corresponding closing states of the auxiliary power outgoing circuit breakers and sums them up. According to the basic data of the auxiliary power supply system in this embodiment, the auxiliary power bus I can be calculated according to formula (1). ” max = 111.52 kA > 27 kA. At this time, the controller will recalculate I for various combined states after partially or fully opening the bypass switch according to formula (1). ” max , select the maximum value less than the allowable value, 26.20 kA (i.e., all reactors are put into operation), among all the calculated values, and issue a command to open all bypass switches. After all bypass switches are fully opened, calculate u after opening all bypass switches according to formula (2). stB = 85.9% ≥ 85%. The controller does not issue an alarm signal.

[0124] (2.8) The controller receives the closing state signals of high-voltage incoming circuit breakers 1 and 2, high-voltage outgoing circuit breaker, generator outlet circuit breaker opened, all bypass switches closed, and auxiliary power incoming circuit breaker. At the same time, it retrieves the pre-input starting current values of these circuits according to the corresponding closing states of the auxiliary power outgoing circuit breakers and sums them up. According to the basic data of the auxiliary power supply system in this embodiment, the auxiliary power bus I can be calculated according to formula (3). ” max = 65.69 kA > 27 kA. At this time, the controller will recalculate I for various combined states after partially or fully opening the bypass switch according to formula (3). ” max , select the maximum value less than the allowable value, 25.71 kA (i.e., the combination of reactor 4% and 5% is put into operation), among all the calculated values, and issue a command to open bypass switches 2 and 3. After bypass switches 2 and 3 are opened, calculate u after opening bypass switches 2 and 3 according to formula (2). stB = 86.6% ≥ 85%. The controller does not issue an alarm signal.

[0125] (2.9) 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 closing signal of the generator outlet breaker, the closing signals of all bypass switches, and the closing state signal of the auxiliary power incoming breaker. At the same time, according to the corresponding closing states of the auxiliary power outgoing breakers, it retrieves the pre-input starting current values of these circuits and sums them up. Based on the basic data of the auxiliary power supply system in this embodiment, the auxiliary power bus I can be calculated according to formula (1) ” max = 105.94 kA > 27 kA. At this time, the controller will recalculate I for various combined states after partially or fully opening the bypass switches according to formula (1) ” max , and selects the maximum value less than the allowable value, which is 24.02 kA (i.e., all reactors are put into operation), among all the calculated values, and issues a command to open all bypass switches. After all bypass switches are opened, u after opening all bypass switches is calculated according to formula (2) stB = 85.8% ≥ 85%. The controller does not issue an alarm signal.

[0126] (2.10) 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 closing signals of all bypass switches, and the closing state signal of the auxiliary power incoming breaker. At the same time, according to the corresponding closing states of the auxiliary power outgoing breakers, it retrieves the pre-input starting current values of these circuits and sums them up. Based on the basic data of the auxiliary power supply system in this embodiment, the auxiliary power bus I can be calculated according to formula (3) ” max = 60.11 kA > 27 kA. At this time, the controller will recalculate I for various combined states after partially or fully opening the bypass switches according to formula (3) ” max , and selects the maximum value less than the allowable value, which is 26.52 kA (i.e., the combination of reactors 3% and 5% is put into operation), among all the calculated values, and issues a command to open bypass switch 2. After bypass switch 2 is opened, u after opening bypass switch 2 is calculated according to formula (2) stB = 86.9% ≥ 85%. The controller does not issue an alarm signal.

[0127] (2.11) 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 closing signals of all bypass switches, and the closing state signal of the auxiliary power incoming breaker. At the same time, according to the corresponding closing states of the auxiliary power outgoing breakers, it retrieves the pre-input starting current values of these circuits and sums them up. Based on the basic data of the auxiliary power supply system in this embodiment, the auxiliary power bus I can be calculated according to formula (1) ” max= 103.26 kA > 27 kA. At this time, the controller will recalculate the I of various combined states after some or all of the bypass switches are opened according to formula (1). ” max , select the maximum value less than the allowable value, which is 23.95 kA (i.e., all reactors are put into operation), among all the calculated values, and issue an order to open all the bypass switches. After all the bypass switches are tripped, calculate the u after all the bypass switches are opened according to formula (2). stB = 85.7% ≥ 85%. The controller does not issue an alarm signal.

[0128] (2.12) The controller receives the status signals of the high-voltage incoming circuit breaker 1 tripped / 2 closed, the high-voltage outgoing circuit breaker closed, the generator outlet circuit breaker tripped, all the bypass switches closed, and the auxiliary power incoming circuit breaker closed. At the same time, according to the corresponding closing status of the auxiliary power outgoing circuit breaker, retrieve the pre-input starting current values of these circuits and sum them up. According to the basic data of the auxiliary power supply system in this embodiment, the auxiliary power bus I can be calculated according to formula (3). ” max = 57.43 kA > 27 kA. At this time, the controller will recalculate the I of various combined states after some or all of the bypass switches are opened according to formula (3). ” max , select the maximum value less than the allowable value, which is 26.20 kA (i.e., the combination of reactors 3% and 5% is put into operation), among all the calculated values, and issue an order to open bypass switch 2. After bypass switch 2 is tripped, calculate the u after bypass switch 2 is opened according to formula (2). stB = 86.3% ≥ 85%. The controller does not issue an alarm signal.

[0129] 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 modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. The auxiliary power supply system includes 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 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 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 busbar (L2) is connected to a corresponding auxiliary power load (6) through an auxiliary power outgoing line breaker (5), and is characterized in that, It further includes: A station service branch reactor (7), whose input end is connected to the low-voltage side of the step-up transformer (1), and the output end of the station service branch reactor (7) is connected to the station service outgoing circuit breaker (5) through the station service incoming circuit breaker (8). A plurality of taps (7a) are arranged between the input end and the output end of the station service branch reactor (7); A plurality of bypass switches (9), each bypass switch (9) corresponding to one tap (7a) of the station service branch reactor (7), and each bypass switch (9) being connected in parallel with its corresponding tap (7a); A voltage sampling terminal (10) for collecting the output voltage of the station service branch circuit where the station service branch reactor (7) is located; A current sampling terminal (11) for collecting the operating current of the station service branch circuit where the station service branch reactor (7) is located; A controller (12) is respectively connected to the high-voltage incoming circuit breaker (13), the high-voltage outgoing circuit breaker (3), the outlet circuit breaker (4), each bypass switch (9), the station service incoming circuit breaker (8), the station service outgoing circuit 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 circuit breaker, the high-voltage outgoing circuit breaker, the outlet circuit breaker, the states of each bypass switch, the switch state of the station service incoming circuit breaker, the switch state of the station service outgoing circuit breaker, the output voltage of the station service branch circuit collected by the voltage sampling terminal, and the operating current of the station service branch circuit collected by the current sampling terminal, and controls the corresponding bypass switch to be disconnected or closed so as to put into or withdraw from the corresponding part of the station service branch reactor.

2. The auxiliary power supply system according to claim 1, wherein 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 control method of the auxiliary power supply system is applied to the auxiliary power supply system described in claim 1 or 2, and is characterized in that, The control method of this station service power system includes the following steps: Step 1, pre-obtain the high-voltage bus parameters, step-up transformer parameters, generator parameters, station service bus parameters, station service branch reactor parameters, and station service 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 value of the step-up transformer, the generator parameters are the per-unit reactance value of the generator, the station service branch reactor parameters are the total per-unit reactance value of the station service branch reactor and the positions of each tap, the station service bus parameters are the base short-circuit current value of the station service bus, the starting currents and starting capacities of all station service loads on the station service bus, the nominal voltage of the station service bus, the allowable value of the short-circuit current of the station service bus, and the allowable value of the relative voltage of the station service bus when a single station service load starts; the starting currents and starting capacities of all station service loads on the station service bus correspond to the station service outgoing circuit breakers one by one; Step 2, obtain the switch states of the high-voltage incoming circuit breaker, the high-voltage outgoing circuit breaker, the outlet circuit breaker, the states of each bypass switch, the switch state of the station service incoming circuit breaker, and the switch state of the station service outgoing circuit breaker; Step 3, obtain the output voltage of the station service branch circuit collected by the voltage sampling terminal and the operating current of the station service 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 the auxiliary power supply 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 on / off state of the bypass switch; Step 6, based on the maximum short-circuit current of the auxiliary power bus after predicting and adjusting the on / off 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 part of the 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 single largest-capacity motor not in use on the auxiliary power bus of the auxiliary power supply system starts with full voltage in the current state; Step 8, compare the obtained relative value of the auxiliary power bus voltage when the single largest-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 single largest-capacity motor not in use on the auxiliary power bus starts with full voltage after adjusting the on / off state of the bypass switch; Step 9, based on the maximum short-circuit current of the auxiliary power bus and the relative value of the auxiliary power bus voltage when the single largest-capacity motor not in use on the auxiliary power bus starts with full voltage after predicting and adjusting the on / off 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 part of the auxiliary power branch reactor.

Images