Generator one-key sequential control grid connection and disconnection shutdown method

Abstract

The invention relates to a one-key sequential control grid connection and disconnection shutdown method for a generator, which consists of two independent sequential control logics, the first logic is one-key sequential control grid connection operation of the generator, and the second logic is one-key sequential control disconnection shutdown operation of the generator. According to the technical scheme, electromechanical interlocking protection of the generator and the steam turbine is improved, and switching operation of a generator protection pressing plate before and after grid connection or disconnection is canceled; setting of a target value of generator voltage buildup and a target value of steam turbine rotating speed is optimized, and grid-connected time is shortened.

Description

Technical Field

[0001] The invention relates to a method for one-key sequential control grid connection and disconnection and shutdown of a generator, belonging to the technical field of automatic operation control of electric power systems. Background Art

[0002] The connection to the grid and the shutdown of the generator set are important operations in power plants. Traditional manual operation has high requirements on the experience, skills, and physical and mental state of the operators. Incorrect operation can easily cause accidents such as asynchronous connection to the grid of the generator and overspeed of the steam turbine. The manual operation of the grid connection takes a long time, and there has always been a problem of large energy loss during the grid connection process. The existing one-key operation technology still has problems such as too complicated and imprecise logical conditions and unreasonable and irregular electrical parameter settings. For example, the grid connection control method of the combined cycle double-pressure extraction condensing steam turbine generator with patent number CN115036980: there is no judgment on the voltage imbalance on both sides of the generator to be connected in the locking condition, and there is no judgment on the grounding fault of the DC system where the grid connection switch and the power supply of the synchronous circuit are located. If the voltage is seriously unbalanced and the DC is grounded at two points, it will cause an asynchronous grid connection accident; there is an automatic operation of the protection pressure plate during the generator grid connection process, which makes the operation that should be simple complicated and reduces reliability, especially the lack of the main protection of the generator may cause the expansion of the accident.

[0003] In view of the rapid development of intelligent manufacturing and the requirements for improving labor efficiency, in order to reduce the operation time of generator grid connection and reduce the energy loss during the grid connection process, and to avoid accidents caused by artificial electrical misoperation or equipment failure defects, the production safety is essentially improved. The present invention provides a method for one-key sequential control grid connection and disconnection shutdown of a generator. The switch quantity, analog quantity, and specific setting of analog quantity parameters collected in the present invention are selected and set to avoid asynchronous grid connection and illegal disconnection, so that the sequential control logic program is simple and reliable, and the grid connection or disconnection of the generator is not affected by unimportant signals, causing unnecessary economic losses. The present invention also improves the electromechanical interlocking protection of the generator and the steam turbine, with the purpose of avoiding the operation of the generator protection pressure plate before and after grid connection or disconnection, simplifying the operation process to realize remote centralized control and improve the safety of equipment operation. The present invention also optimizes the setting of the target value of the generator pressure and the target value of the steam turbine speed, with the purpose of not using the automatic synchronization device to adjust the voltage and frequency, thereby shortening the grid connection time. Summary of the invention

[0004] The present invention aims at the problems existing in the prior art and provides a method for one-key sequential control grid connection and decoupling shutdown of a generator. The technical solution improves the electromechanical interlocking protection of the generator and the steam turbine, cancels the operation of launching and withdrawing the generator protection pressure plate before and after grid connection or decoupling; optimizes the setting of the target value of the generator voltage build-up and the target value of the steam turbine speed, and shortens the grid connection time.

[0005] In order to achieve the above-mentioned purpose, the technical solution of the present invention is as follows: a method for one-key sequential control grid-connection and decoupling and shutdown of a generator, characterized in that the method consists of two independent sequential control logics, logic one is the one-key sequential control grid-connection operation of the generator, and logic two is the one-key sequential control decoupling and shutdown operation of the generator.

[0006] The electromechanical interlock protection includes two parts: machine tripping and electrical tripping. Machine tripping refers to the closing of the main steam valve of the steam turbine or the ETS action signal tripping the generator grid-connected switch and the demagnetizing switch; electrical tripping refers to the generator protection action signal tripping the steam turbine to close the main steam valve. Usually, the main steam valve closing signal, ETS action signal, main transformer light-watt signal, main transformer heavy-watt signal, etc. are connected to non-electrical protection devices. In addition, the demagnetizing switch tripping signal is also connected to the non-electrical protection device as a demagnetizing joint tripping protection. The conventional non-electrical protection device action output is a full stop, that is, the protection output mode is to close the main steam valve, trip the grid-connected switch, and trip the demagnetizing switch. Obviously, the main steam valve closing pressure plate and the demagnetizing joint tripping pressure plate must be operated before and after the generator is connected to the grid or decoupled, otherwise it will be unable to start due to the dead loop caused by the non-electrical protection output mode.

[0007] Furthermore, the role of the de-excitation protection in the electromechanical interlocking protection includes two aspects: on the one hand, it protects the tripping of the grid-connected switch to prevent the de-excitation switch from tripping, which causes the generator to absorb a large amount of reactive power from the system and affect the stability of the system, and the slip between the stator and the rotor causes the rotor to heat up; on the other hand, it closes the main steam valve after the protection is activated to prevent the generator from shedding load and causing the turbine to overspeed, which is a beneficial supplement to the turbine body overspeed protection. Obviously, from the perspective of electrical tripping, the de-excitation protection is not perfect. If the generator grid-connected switch trips and the de-excitation switch does not trip, the turbine body overspeed protection fails, and the turbine will have an overspeed accident.

[0008] In order to solve the above problems, the operation can be simplified and meet the requirements of remote centralized control and one-key sequential control, thereby improving the safety and stability of equipment operation.

[0009] The present invention makes the following improvements to the electromechanical interlocking protection:

[0010] (1) Cancel the de-excitation joint trip protection action to close the main steam valve, and set a grid-connected switch trip signal to close the main steam valve, which is defined as electrical overspeed protection:

[0011] Specifically, the DCS collects three generator grid-connected switch position signals, and the action logic issues a main steam valve closing command based on a 2-out-of-3 jump signal;

[0012] Specifically, when the generator active power P ≥ K × Pe, and after a delay of 10s, the DCS automatically switches on the protection. The setting of the coefficient K is calculated based on the turbine speed not exceeding 3300r / min, and the empirical value K = 8%. Pe is the rated active power of the generator;

[0013] Specifically, when the generator active power P < K × Pe, and after a delay of 10s, the DCS automatically exits the protection. The setting of the coefficient K is calculated based on the turbine speed not exceeding 3300r / min, and the empirical value K = 8%. Pe is the rated active power of the generator;

[0014] Specifically, if the protection has been put into operation, in order to avoid the generator active power P suddenly dropping to 0 after the grid-connected switch trips, causing the protection to exit, the active power participating in the protection is introduced into the Lag lag algorithm module, and the lag time is set to 3s, which is equivalent to the power signal value participating in the protection being the actual power value 3s ago.

[0015] (2) Select a new type of non-electrical protection device, whose protection tripping output mode can be arbitrarily combined by configuring the control word method;

[0016] (3) In order to break the endless loop and cancel the operation of the protection plate, the following settings are made for different non-electrical signals:

[0017] Specifically, the configuration control words of the main transformer body's light bearing, heavy bearing, pressure release and other signals are set to close the main steam valve, trip the grid-connected switch, and trip the demagnetization switch;

[0018] Specifically, the main steam valve closing signal, ETS action signal, and configuration control word are set to trip the grid-connected switch and trip the demagnetization switch;

[0019] Specifically, the demagnetization joint trip protection signal and the configuration control word are set to trip the grid-connected switch.

[0020] The target value of the optimized generator voltage build-up is intended to enable the excitation regulator to automatically track the system voltage and raise the generator voltage to be basically consistent with the system voltage (slightly higher than the system), so as to quickly meet one of the generator grid connection allowable conditions, the voltage difference ΔU set ≤5%Ue, Ue is the rated stator voltage of the generator:

[0021] Specifically, based on the historical data of the voltage waveform on the system side, the average of the maximum and minimum system voltages during normal operation is taken as the target final value of the generator voltage build-up;

[0022] Specifically, the system voltage tracking enable of the excitation regulator is put into operation, and the voltage at the generator excitation terminal is increased from 0 to the set target final value. At the same time, the regulator automatically tracks the system side voltage and quickly adjusts the generator terminal voltage to be slightly higher than the system side voltage.

[0023] Specifically, after the generator is connected to the grid, the excitation regulator receives the grid-connected switch closing signal and automatically withdraws from system voltage tracking. Because the regulator only takes one closing signal, if the contact is not good, the regulator will mistakenly enter the system voltage tracking. If the system PT fails, the regulator will continue to increase the magnetization and cause the generator to overexcite. In order to improve the reliability of the grid-connected switch closing signal connected to the excitation regulator, the aforementioned DCS collects three generator grid-connected switch position signals, and the logic is based on the closing signal of 2 out of 3 to open a contact for the regulator as the grid-connected switch closing signal.

[0024] The target value of the optimized steam turbine speed is to control the generator speed at 3005±2r / min by DEH, so as to quickly meet the second frequency difference Δf of the generator grid connection permission condition. set ≤0.15Hz:

[0025] Specifically, the speed control of the DEH control system is in automatic state, the target value of the speed controller is set at 3005r / min, and the allowable speed deviation is ±2r / min. Based on this target value, the turbine controls the speed at the speed required for the synchronous grid connection of the generator.

[0026] Among them, logic one is the one-key sequential control and grid-connected operation of the generator, including the following steps:

[0027] Step 1: Close the generator demagnetization switch;

[0028] 1.1.1 Generator one-button sequential control grid-connected start;

[0029] 1.1.2 Collect the generator stator current Ia, Ib, Ic. The three phases should be without current before the generator is connected to the grid. Specifically, the current I should be less than or equal to 1.5 times the no-load running current of the generator, or set to I≤0.75%Ie according to the empirical value, where Ie is the rated stator current of the generator;

[0030] 1.1.3 Collect the three-phase line voltages Uxab, Uxbc, and Uxca on the side of the system to be connected. The ratio of the maximum value to the average value should not be greater than 2%, that is, the three-phase voltage unbalance should be ε≤2%;

[0031] 1.1.4 Collect the generator speed n. The speed n satisfies the conditions according to the generator grid-connected allowable frequency difference Δf set =0.15Hz, specifically, according to the allowable frequency difference Δf set 1.5 times of the calculated speed n is 2987<n<3013r / min;

[0032] 1.1.5 Collect the alarm and fault output signals of the generator microcomputer protection device, generator excitation system, DC power supply system, etc. All of the above should operate normally without any alarm or fault signals;

[0033] 1.1.6 Collect the generator demagnetization switch position signal, the demagnetization switch should be in the open position;

[0034] 1.1.7 Collect the generator grid-connected switch position signal, the grid-connected switch should be in the open position;

[0035] 1.1.8 Collect the generator grid-connected switch trolley position signal. The grid-connected switch trolley position should be in the operating position.

[0036] 1.2 The DCS judges the conditions from 1.1.1 to 1.1.8 above. If any condition is not met, the DCS one-key sequential control grid connection operation is terminated, and an audible and visual alarm signal of the corresponding condition is issued; if all conditions are met, the DCS issues a demagnetization switch closing command with a command pulse width of 1s, and enters step 1.3;

[0037] 1.3 Determine the demagnetization switch position signal, and the DCS sets a 5s judgment time. If the demagnetization switch is in the open position, the DCS one-button sequential control grid connection operation is terminated, and an audible and visual alarm signal of the corresponding condition is issued; if the demagnetization switch is in the closed position, go to step 2;

[0038] Step 2: Generator voltage build-up;

[0039] 2.1.1 The three-phase currents Ia, Ib and Ic of the generator stator should be less than or equal to 1.5 times of the no-load running current of the generator, or according to the empirical value I≤0.75%Ie, where Ie is the rated stator current of the generator;

[0040] 2.1.2 The ratio of the maximum value to the average value of the three-phase line voltage Uxab, Uxbc, and Uxca on the side of the system to be connected should not be greater than 2%, that is, the three-phase voltage unbalance should be ε≤2%;

[0041] 2.1.3 The speed of the generator n should be 2987<n<3013r / min;

[0042] 2.1.4 The generator microcomputer protection device, generator excitation system, DC power supply system, etc. should all operate normally without any alarm or fault signal;

[0043] 2.1.5 The generator demagnetization switch position signal should be in the closed position;

[0044] 2.1.6 The generator grid-connected switch position signal should be in the open position;

[0045] 2.1.7 The generator grid-connected switch trolley position signal should be in the running position.

[0046] 2.2 The DCS judges the conditions from 2.1.1 to 2.1.7 above. If any condition is not met, the DCS one-key sequential control grid connection operation is terminated, and an audible and visual alarm signal of the corresponding condition is issued; if all conditions are met, the DCS issues a voltage build-up command to the excitation regulator, with a command pulse width of 2s, and enters step 2.3;

[0047] 2.3 Collect the generator output bus voltage Ufab, Ufbc, and Ufca, and DCS sets a judgment time of 20s. If the generator voltages Ufab, Ufbc, and Ufca all meet 0.925Ue<U<1.05Ue, and the three-phase voltage unbalance meets ε≤2%, then go to step 3;

[0048] Step 3: Start the automatic quasi-synchronous working circuit of the generator;

[0049] 3.1.1 The three-phase currents Ia, Ib and Ic of the generator stator should be less than or equal to 1.5 times of the no-load running current of the generator, or according to the empirical value I≤0.75%Ie, where Ie is the rated stator current of the generator;

[0050] 3.1.2 The ratio of the maximum value to the average value of the three-phase line voltage Uxab, Uxbc, and Uxca on the side of the system to be connected should not be greater than 2%, that is, the three-phase voltage unbalance should be ε≤2%;

[0051] 3.1.3 The speed of the generator n should be 2987<n<3013r / min;

[0052] 3.1.4 The generator microcomputer protection device, generator excitation system, DC power supply system, etc. should all operate normally without any alarm or fault signal;

[0053] 3.1.5 The generator grid-connected switch position signal should be in the open position;

[0054] 3.1.6 The generator grid-connected switch trolley position signal should be in the operating position;

[0055] 3.1.7 Collect the single / double-side no-pressure confirmation selection switch position signal on the generator microcomputer automatic quasi-synchronous screen. The selection switch should be in the quasi-synchronous position;

[0056] 3.1.8 Collect the manual / automatic selector switch position signal on the generator microcomputer automatic quasi-synchronous screen. The selector switch should be in the automatic position;

[0057] 3.1.9 Collect the three-phase line voltages of the generator Ufab, Ufbc, Ufca and the system side Uxab, Uxbc, Uxca, and the voltage difference ΔU between the same-phase lines on both sides to be connected shall meet the conditions according to the generator grid-connected allowable voltage difference ΔU set ≤5%Ue, specifically, according to the allowable pressure difference ΔU set1.5 times of the calculated value, the voltage difference between the generator and the system side ΔU≤7.5%Ue, Ue is the rated stator voltage of the generator;

[0058] 3.1.10 Collecting the generator voltage frequency f f With the system side voltage frequency f x The voltage frequency difference Δf between the two sides to be connected satisfies the condition according to the generator grid connection allowable frequency difference Δf set ≤0.15Hz, specifically, according to the allowable frequency difference Δf set ≤0.15Hz by 1.5 times, the frequency difference between the generator and the system side is calculated to be Δf≤0.225Hz,

[0059] 3.2 The DCS judges the conditions from 3.1.1 to 3.1.10 above. If any of the conditions is not met, the DCS one-key sequential control grid connection operation is terminated, and the corresponding sound and light alarm signal is issued; if all the conditions are met, the DCS issues an automatic quasi-synchronization command for the generator, with a command pulse width of 2s, and enters step 4;

[0060] Step 4: Start the automatic synchronization and close the generator grid-connected switch;

[0061] 4.1.1 Collect the ready signal of the generator microcomputer automatic quasi-synchronous device, the signal status should be ready;

[0062] 4.1.2 Collect the fault alarm signal of the generator microcomputer automatic quasi-synchronous screen, and it should run normally without alarm fault signal;

[0063] 4.1.3 The three-phase stator currents Ia, Ib and Ic of the generator should be less than or equal to 1.5 times the no-load running current of the generator, or according to the empirical value I≤0.75%Ie, where Ie is the rated stator current of the generator;

[0064] 4.1.4 The ratio of the maximum value to the average value of the three-phase line voltage Uxab, Uxbc, and Uxca on the side of the system to be connected should not be greater than 2%, that is, the three-phase voltage unbalance should be ε≤2%;

[0065] 4.1.5 The ratio of the maximum value to the average value of the three-phase line voltage Ufab, Ufbc and Ufca of the generator should not be greater than 2%, that is, the three-phase voltage unbalance should be ε≤2%;

[0066] 4.1.6 The speed of the generator n should be 2987<n<3013r / min;

[0067] 4.1.7 The generator microcomputer protection device, generator excitation system, DC power supply system, etc. should all operate normally without any alarm or fault signal;

[0068] 4.1.8 The voltage difference between the generators on both sides to be connected and the system side should satisfy ΔU≤7.5%Ue, where Ue is the rated stator voltage of the generator;

[0069] 4.1.9 The frequency difference between the generators on both sides to be connected and the system side should satisfy Δf≤0.225Hz.

[0070] 4.2 The DCS judges the conditions in 4.1.1 to 4.1.9 above, and the DCS sets a judgment time of 5s. If any condition is not met, the DCS one-key sequential control grid connection operation is terminated, and the sound and light alarm signal of the corresponding condition is issued; if all conditions are met, the DCS issues a command to start automatic quasi-synchronization, with a command pulse width of 2s, and enters step 4.3;

[0071] 4.3 The microcomputer automatic quasi-synchronization device automatically determines the voltage difference ΔU and frequency difference Δf on both sides of the grid to be connected. When the voltage difference and frequency difference are within the allowable value (≤ΔU set ,≤Δf set ) range to capture the first grid-connected opportunity, and the synchronization device issues a closing command to close the generator grid-connected switch;

[0072] 4.4 Determine the grid-connected switch position signal. Set a 60s judgment time after the DCS issues a start synchronization command. If the grid-connected switch is in the open position, the DCS one-button sequential control grid-connected operation is terminated, and an audible and visual alarm signal of the corresponding condition is issued; if the grid-connected switch is in the closed position, go to step 5.

[0073] Step 5: Exit the generator automatic quasi-synchronous working circuit,

[0074] 5.1 The generator has been connected to the grid, and the DCS issues a command to withdraw the automatic quasi-synchronous working circuit. The command pulse width is 2s, and then proceed to step 5.2;

[0075] 5.2 Collect the signal that the synchronization circuit of the generator microcomputer automatic quasi-synchronization screen has exited, and the DCS sets a judgment time of 5s. If the signal status is not exited, the DCS one-key sequential control grid connection operation is terminated, and the corresponding conditional sound and light alarm signal is issued; if the signal status is that the synchronization circuit has exited, the one-key sequential control grid connection is completed, and the DCS program is terminated.

[0076] In the logic 1,

[0077] The fault alarm signals of the generator microcomputer protection device include:

[0078] The line protection device is locked and alarmed; the system side PT voltage circuit is broken; the grid-connected switch control circuit is broken; the generator protection device is locked and alarmed; the generator main and backup protection action signals; the generator CT / PT is abnormal.

[0079] Generator excitation system fault alarm signals include:

[0080] Excitation regulator failure, alarm; power cabinet failure; excitation failure; PT failure;

[0081] DC system fault alarm signals include: DC charging device total fault; DC system grounding fault,

[0082] The fault alarm signals of the generator synchronization device include: synchronization device power failure; synchronization device general alarm; synchronization lockout.

[0083] The second logic: the generator one-key sequential control disconnection and shutdown operation includes the following steps:

[0084] Step 1. One-button sequential control of the generator to disconnect, stop and start;

[0085] Step 2. Collect the DEH decoupling permission signal; collect the generator active power signal, specifically, it should meet P≤1%Pe;

[0086] Step 3. The DCS judges the conditions of step 2 above. If any condition is not met, the DCS one-button sequential control decoupling and shutdown operation is terminated, and an audible and visual alarm signal of the corresponding condition is issued; if all conditions are met, go to step 4;

[0087] Step 4: Collect the generator excitation current signal. Specifically, it should meet I L ≤1.1I Lkz , I Lkz is the no-load excitation current of the generator;

[0088] 5.1 The DCS judges the conditions of step 4 above. If the conditions are met, the DCS issues a grid-connected switch opening command with a command pulse width of 1s, and then goes to step 6;

[0089] 5.2.1 The DCS judges the conditions of step 4 above. If the conditions are not met, the DCS issues a demagnetization command to the excitation regulator, with a command pulse width of 0.5s and a step length of 1s;

[0090] 5.2.2 Judge the excitation current DCS. If it satisfies I L ≤1.1I Lkz , then the DCS issues a grid-connected switch opening command with a command pulse width of 1s, and goes to step 6;

[0091] Step 6. Determine the grid-connected switch position signal, and the DCS sets a 5s determination time. If the grid-connected switch is in the closed position, the DCS one-button sequential control decoupling and shutdown operation is terminated, and an audible and visual alarm signal of the corresponding condition is issued; if the grid-connected switch is in the open position, proceed to step 7;

[0092] Step 7. The DCS sends an inverter command to the excitation regulator, with a command pulse width of 2s, and then goes to step 8;

[0093] Step 8. Collect the generator output bus voltage Ufab, Ufbc, Ufca. The three-phase voltage should satisfy U≤10%Ue. Collect the generator excitation current signal, which should satisfy I L ≤3%I Le , I Le is the rated excitation current of the generator;

[0094] Step 9. The DCS judges the conditions in step 8 above, and the DCS sets a judgment time of 5s. If none of the conditions are met, the DCS one-button sequential control decoupling and shutdown operation is terminated, and an audible and visual alarm signal of the corresponding condition is issued; if any condition is met, the DCS issues a demagnetization switch opening command with a command pulse width of 1s, and enters step 10;

[0095] Step 10. Determine the demagnetization switch position signal, and the DCS sets a 5s judgment time. If the demagnetization switch is in the closed position, the DCS one-button sequential control de-energizing and shutdown operation is terminated, and an audible and visual alarm signal of the corresponding condition is issued; if the demagnetization switch is in the open position, the one-button sequential control de-energizing and shutdown operation is completed, and the DCS program is terminated.

[0096] Compared with the prior art, the present invention has the following advantages. This technical solution was first applied to the sintering waste heat No. 1 generator set of Meishan Iron and Steel Company, and has been promoted and applied to the other 6 units after being improved. This technology integrates the excitation system, synchronization system, and DCS of the generator to form a one-button start system, and realizes one-button grid connection operation through logical judgment and automatic operation. Since the grid connection process is automatically controlled by the program, the possibility of operator error operation is reduced, and the startup realizes automatic grid connection successfully once, and the grid connection time only takes 60 seconds, which greatly saves the operation time compared with the previous manual operation and improves the quality of grid connection. This technology simplifies the generator grid connection operation steps through the improvement of electromechanical interlocking protection, reduces the harm caused by human error operation to the generator, and accumulates more experience for future intelligent transformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0097] Figure 1 This is one of the flow charts of one-key sequential control grid connection of a generator according to a preferred embodiment of the present invention;

[0098] Figure 2 This is the second flow chart of one-key sequential control grid connection of a generator according to a preferred embodiment of the present invention;

[0099] Figure 3 The present invention is a flowchart of a generator one-button sequential control disconnection and shutdown according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0100] In order to deepen the understanding of the present invention, the present embodiment is described in detail below with reference to the accompanying drawings.

[0101] Embodiment 1: A method for one-key sequential control of connecting to the grid and shutting down a generator by disconnecting the parallel connection, the method comprising the following three parts: 1. Improving the electromechanical interlocking protection of the generator and the steam turbine, and canceling the operation of the generator protection pressure plate before and after connecting to the grid or disconnecting the parallel connection; 2. Optimizing the setting of the target value of the generator voltage build-up and the target value of the steam turbine speed, and shortening the grid connection time; 3. Through the improvement and optimization of the aforementioned schemes 1 and 2, a method for one-key sequential control of connecting to the grid and shutting down a generator by disconnecting the parallel connection is provided.

[0102] The electromechanical interlock protection includes two parts: machine tripping and electrical tripping. Machine tripping refers to the closing of the main steam valve of the steam turbine or the ETS action signal tripping the generator grid-connected switch and the demagnetizing switch; electrical tripping refers to the generator protection action signal tripping the steam turbine to close the main steam valve. Usually, the main steam valve closing signal and the ETS action signal are connected to non-electrical protection devices. In addition, the demagnetizing switch tripping signal is also connected to the non-electrical protection device as a demagnetizing joint tripping protection. The conventional non-electrical protection device action output is a full stop, that is, the protection output mode is to close the main steam valve, trip the grid-connected switch, and trip the demagnetizing switch. Obviously, the main steam valve closing pressure plate and the demagnetizing joint tripping pressure plate must be operated before and after the generator is connected to the grid or decoupled, otherwise it will be unable to start due to the dead loop caused by the non-electrical protection output mode.

[0103] Furthermore, the role of the de-excitation protection in the electromechanical interlocking protection includes two aspects: on the one hand, it protects the tripping of the grid-connected switch to prevent the de-excitation switch from tripping, which causes the generator to absorb a large amount of reactive power from the system and affect the stability of the system, and the slip between the stator and the rotor causes the rotor to heat up; on the other hand, it closes the main steam valve after the protection is activated to prevent the generator from shedding load and causing the turbine to overspeed, which is a beneficial supplement to the turbine body overspeed protection. Obviously, from the perspective of electrical tripping, the de-excitation protection is not perfect. If the generator grid-connected switch trips and the de-excitation switch does not trip, the turbine body overspeed protection fails, and the turbine will have an overspeed accident.

[0104] In order to solve the above problems, thereby simplifying the operation and adapting to the requirements of remote centralized control and one-key sequential control, and further improving the safety and stability of equipment operation, the present invention makes the following improvements to the electromechanical interlocking protection:

[0105] 1. Cancel the de-excitation joint trip protection action to close the main steam valve, and set a grid-connected switch trip signal to close the main steam valve, which is defined as electrical overspeed protection:

[0106] Specifically, the DCS collects three generator grid-connected switch position signals, and the action logic issues a main steam valve closing command based on a 2-out-of-3 jump signal;

[0107] Specifically, when the generator active power P ≥ K × Pe = 8% × 20 = 1.6MW, and after a delay of 10s, the DCS automatically switches on the protection;

[0108] Specifically, when the generator active power P < K × Pe = 8% × 20 = 1.6MW, and after a delay of 10s, the DCS automatically exits the protection;

[0109] Specifically, if the protection has been put into operation, in order to avoid the generator active power P suddenly dropping to 0 after the grid-connected switch trips, causing the protection to exit, the active power participating in the protection is introduced into the Lag lag algorithm module, and the lag time is set to 3s, which is equivalent to the power signal value participating in the protection being the actual power value 3s ago.

[0110] 2. Choose PCS-985GS protection device of NARI Relay Protection, whose non-electrical protection tripping output mode can be arbitrarily combined by configuring control words;

[0111] 3. In order to break the endless cycle and cancel the operation of the protection plate, the following settings are made for different non-electrical signals:

[0112] Specifically, the main steam valve closing signal, ETS action signal, and configuration control word are set to trip the grid-connected switch and trip the demagnetization switch;

[0113] Specifically, the demagnetization joint trip protection signal and the configuration control word are set to trip the grid-connected switch.

[0114] The target value of the optimized generator voltage build-up is intended to enable the excitation regulator to automatically track the system voltage and raise the generator voltage to be basically consistent with the system voltage (slightly higher than the system), so as to quickly meet one of the generator grid connection allowable conditions, the voltage difference ΔU set ≤5%Ue, Ue is the rated stator voltage of the generator:

[0115] Specifically, according to the historical data of the voltage waveform on the system side, the maximum value of the system voltage during normal operation is 10.625KV, the minimum value is 9.68KV, and the target final value of the generator excitation regulator voltage building is taken as an average of 10.15KV;

[0116] Specifically, the system voltage tracking enable of the excitation regulator is put into operation, the generator voltage is built up and excitation is started, and the generator terminal voltage rises from 0V to the set target final value of 10.15KV. At the same time, the regulator automatically tracks the system side voltage and quickly adjusts the generator terminal voltage to slightly higher than the system side voltage.

[0117] Specifically, after the generator is connected to the grid, the excitation regulator receives the grid-connected switch closing signal and automatically withdraws from system voltage tracking. Because the regulator only takes one closing signal, if the contact is not good, the regulator will mistakenly enter the system voltage tracking. If the system PT fails, the regulator will continue to increase the magnetization and cause the generator to overexcite. In order to improve the reliability of the grid-connected switch closing signal connected to the excitation regulator, the aforementioned DCS collects three generator grid-connected switch position signals, and the logic is based on the closing signal of 2 out of 3 to open a contact for the regulator as the grid-connected switch closing signal.

[0118] The target value of the optimized steam turbine speed is to control the generator speed at 3005±2r / min by DEH, so as to quickly meet the second frequency difference Δf of the generator grid connection permission condition. set ≤0.15Hz:

[0119] Specifically, the speed control of the DEH control system is in automatic state, the target value of the speed controller is set at 3005r / min, and the allowable speed deviation is ±2r / min. Based on this target value, the turbine controls the speed at the speed required for the synchronous grid connection of the generator.

[0120] The method for one-key sequential control grid connection and disconnection and shutdown of a generator is composed of two independent sequential control logics, logic one is the one-key sequential control grid connection operation of the generator, and logic two is the one-key sequential control disconnection and shutdown operation of the generator.

[0121] like Figure 1 , Figure 2 As shown, it is the logic 1 of the present invention: the flow chart of one-key sequential control of generator and grid connection, the method comprises the following steps:

[0122] Step 1: Close the generator demagnetization switch;

[0123] 1.1.1 Generator one-button sequential control grid-connected start;

[0124] 1.1.2 Collect the generator stator current Ia, Ib, Ic. Before the generator is connected to the grid, the three phases have no current. Specifically, according to the empirical value, I is set to 0.75% Ie = 10.3A, and the stator rated current Ie = 1374.6A;

[0125] 1.1.3 Collect the three-phase line voltages Uxab, Uxbc, and Uxca on the side of the system to be connected. The ratio of the maximum value to the average value should not be greater than 2%, that is, the three-phase voltage unbalance should be ε≤2%;

[0126] 1.1.4 Collect the generator speed n. The speed n satisfies the conditions according to the generator grid-connected allowable frequency difference Δf set =0.15Hz, specifically, according to the allowable frequency difference Δf set 1.5 times of the calculated speed n is 2987<n<3013r / min;

[0127] 1.1.5 Collect the alarm and fault output signals of the generator microcomputer protection device, generator excitation system, DC power supply system, etc. All of the above should operate normally without any alarm or fault signals;

[0128] 1.1.6 Collect the generator demagnetization switch position signal, the demagnetization switch should be in the open position;

[0129] 1.1.7 Collect the generator grid-connected switch position signal, the grid-connected switch should be in the open position;

[0130] 1.1.8 Collect the generator grid-connected switch trolley position signal. The grid-connected switch trolley position should be in the operating position.

[0131] 1.2 The DCS judges the conditions from 1.1.1 to 1.1.8 above. If any condition is not met, the DCS one-key sequential control grid connection operation is terminated, and an audible and visual alarm signal of the corresponding condition is issued; if all conditions are met, the DCS issues a demagnetization switch closing command with a command pulse width of 1s, and enters step 1.3;

[0132] 1.3 Determine the demagnetization switch position signal, and the DCS sets a 5s judgment time. If the demagnetization switch is in the open position, the DCS one-button sequential control grid connection operation is terminated, and an audible and visual alarm signal of the corresponding condition is issued; if the demagnetization switch is in the closed position, go to step 2;

[0133] Step 2: Generator voltage build-up;

[0134] 2.1.1 Before the generator is connected to the grid, the three-phase stator currents Ia, Ib, and Ic should be zero. Specifically, they are set to I≤0.75%Ie=10.3A according to the empirical value;

[0135] 2.1.2 The ratio of the maximum value to the average value of the three-phase line voltage Uxab, Uxbc, and Uxca on the side of the system to be connected should not be greater than 2%, that is, the three-phase voltage unbalance should be ε≤2%;

[0136] 2.1.3 The speed of the generator n should be 2987<n<3013r / min;

[0137] 2.1.4 The generator microcomputer protection device, generator excitation system, DC power supply system, etc. should all operate normally without any alarm or fault signal;

[0138] 2.1.5 The generator demagnetization switch position signal should be in the closed position;

[0139] 2.1.6 The generator grid-connected switch position signal should be in the open position;

[0140] 2.1.7 The generator grid-connected switch trolley position signal should be in the operating position;

[0141] 2.2 The DCS judges the conditions from 2.1.1 to 2.1.7 above. If any condition is not met, the DCS one-key sequential control grid connection operation is terminated, and an audible and visual alarm signal of the corresponding condition is issued; if all conditions are met, the DCS issues a voltage build-up command to the excitation regulator, with a command pulse width of 2s, and enters step 2.3;

[0142] 2.3 Collect the generator outlet bus voltage Ufab, Ufbc, Ufca, and the generator rated stator voltage Ue=10.5KV. If the voltage U satisfies 9.71KV<U<11.03KV, and the three-phase voltage unbalance should be ε≤2%, then go to step 3;

[0143] Step 3: Start the automatic quasi-synchronous working circuit of the generator;

[0144] 3.1.1 Before the generator is connected to the grid, the three-phase stator currents Ia, Ib, and Ic should be zero. Specifically, they are set to I≤0.75%Ie=10.3A according to the empirical value;

[0145] 3.1.2 The ratio of the maximum value to the average value of the three-phase line voltage Uxab, Uxbc, and Uxca on the side of the system to be connected should not be greater than 2%, that is, the three-phase voltage unbalance should be ε≤2%;

[0146] 3.1.3 The speed of the generator n should be 2987<n<3013r / min;

[0147] 3.1.4 The generator microcomputer protection device, generator excitation system, DC power supply system, etc. should all operate normally without any alarm or fault signal;

[0148] 3.1.5 The generator grid-connected switch position signal should be in the open position;

[0149] 3.1.6 The generator grid-connected switch trolley position signal should be in the operating position;

[0150] 3.1.7 Collect the single / double-side no-pressure confirmation selection switch position signal on the generator microcomputer automatic quasi-synchronous screen. The selection switch should be in the quasi-synchronous position;

[0151] 3.1.8 Collect the manual / automatic selector switch position signal on the generator microcomputer automatic quasi-synchronous screen. The selector switch should be in the automatic position;

[0152] 3.1.9 Collect the three-phase line voltages of the generator Ufab, Ufbc, Ufca and the system side Uxab, Uxbc, Uxca, and the voltage difference ΔU between the same-phase lines on both sides to be connected shall meet the conditions according to the generator grid-connected allowable voltage difference ΔU set ≤5%Ue, specifically, according to the allowable pressure difference ΔU set Calculate 1.5 times of the voltage difference between the generator and the system side, ΔU≤0.79KV, Ue=10.5KV;

[0153] 3.1.10 Collecting the generator voltage frequency f f With the system side voltage frequency f x The voltage frequency difference Δf between the two sides to be connected satisfies the condition according to the generator grid connection allowable frequency difference Δf set≤0.15Hz, specifically, according to the allowable frequency difference Δf set ≤0.15Hz by 1.5 times, the frequency difference Δf between the generator and the system side is calculated to be ≤0.225Hz.

[0154] 3.2.1 The DCS judges the conditions in 3.1 above. If any condition is not met, the DCS one-key sequential control grid connection operation is terminated and an audible and visual alarm signal of the corresponding condition is issued;

[0155] 3.2.2 The DCS judges the conditions in 3.1 above. If all the conditions are met, the DCS issues an automatic quasi-synchronization command for the generator with a pulse width of 2s, and then goes to step 4.

[0156] Step 4: Start the automatic synchronization and close the generator grid-connected switch;

[0157] 4.1.1 Collect the ready signal of the generator microcomputer automatic quasi-synchronous device, the signal status should be ready;

[0158] 4.1.2 Collect the fault alarm signal of the generator microcomputer automatic quasi-synchronous screen, and it should run normally without alarm fault signal;

[0159] 4.1.3 Before the generator is connected to the grid, the three-phase stator currents Ia, Ib, and Ic should be zero. Specifically, they should be set to I≤0.75%Ie=10.3A according to the empirical value;

[0160] 4.1.4 The ratio of the maximum value to the average value of the three-phase line voltage Uxab, Uxbc, and Uxca on the side of the system to be connected should not be greater than 2%, that is, the three-phase voltage unbalance should be ε≤2%;

[0161] 4.1.5 The ratio of the maximum value to the average value of the three-phase line voltage Ufab, Ufbc and Ufca of the generator should not be greater than 2%, that is, the three-phase voltage unbalance should be ε≤2%;

[0162] 4.1.6 The speed of the generator n should be 2987<n<3013r / min;

[0163] 4.1.7 The generator microcomputer protection device, generator excitation system, DC power supply system, etc. should all operate normally without any alarm or fault signal;

[0164] 4.1.8 The voltage difference between the generators on both sides to be connected and the system side should meet ΔU≤7.5%Ue=0.79KV, Ue=10.5KV;

[0165] 4.1.9 The frequency difference between the generators on both sides to be connected and the system side should satisfy Δf≤0.225Hz;

[0166] 4.2 The DCS judges the conditions in 4.1.1 to 4.1.9 above, and the DCS sets a judgment time of 5s. If any condition is not met, the DCS one-key sequential control grid connection operation is terminated, and the sound and light alarm signal of the corresponding condition is issued; if all conditions are met, the DCS issues a command to start automatic quasi-synchronization, with a command pulse width of 2s, and enters step 4.3;

[0167] 4.3 The microcomputer automatic quasi-synchronization device automatically determines the voltage difference ΔU and frequency difference Δf on both sides of the grid to be connected. When the voltage difference and frequency difference are within the allowable value (ΔU set ≤5%Ue、0Hz<Δf set ≤0.15Hz) to capture the first grid-connected opportunity, and the synchronization device sends a closing command to close the generator grid-connected switch.

[0168] 4.4 Determine the grid-connected switch position signal. Set a 60s judgment time after the DCS issues a start synchronization command. If the grid-connected switch is in the open position, the DCS one-button sequential control grid-connected operation is terminated, and an audible and visual alarm signal of the corresponding condition is issued; if the grid-connected switch is in the closed position, go to step 5.

[0169] Step 5: Exit the generator automatic quasi-synchronous working circuit.

[0170] 5.1 The generator has been connected to the grid, and the DCS issues a command to withdraw the automatic quasi-synchronous working circuit. The command pulse width is 2s, and then proceed to step 5.2;

[0171] 5.2 Collect the signal that the synchronization circuit of the generator microcomputer automatic quasi-synchronization screen has exited, and the DCS sets a judgment time of 5s. If the signal status is not exited, the DCS one-key sequential control grid connection operation is terminated, and the corresponding conditional sound and light alarm signal is issued; if the signal status is that the synchronization circuit has exited, the one-key sequential control grid connection is completed, and the DCS program is terminated.

[0172] The logic 1: one-key sequential control and grid-connected operation of the generator, characterized by:

[0173] The fault alarm signal of the generator microcomputer protection device in steps 1, 2, 3 and 4 includes the following contents:

[0174] (1) Line protection device lockout and alarm;

[0175] (2) The PT voltage circuit on the system side is broken;

[0176] (3) The grid-connected switch control circuit is disconnected;

[0177] (4) The generator protection device is locked and alarmed;

[0178] (5) Generator main and backup protection action signals;

[0179] (6) Generator CT / PT abnormality.

[0180] The generator excitation system fault alarm signal in steps 1, 2, 3, and 4 includes the following contents:

[0181] (7) Excitation regulator failure and alarm;

[0182] (8) Power cabinet failure;

[0183] (9) Failure to start the incentive;

[0184] (10)PT failure.

[0185] The fault alarm signals of the DC system to which the generator synchronization device and the grid-connected switch belong in steps 1, 2, 3, and 4 include the following:

[0186] (11) Total failure of DC charging device;

[0187] (12) Ground fault in DC system.

[0188] The generator synchronization device fault alarm signal in step 4 includes the following contents:

[0189] (13) The synchronization device loses power;

[0190] (14) Synchronous device general alarm;

[0191] (15)Synchronous locking.

[0192] Figure 3 As shown, it is the logic 2 of the present invention: the flow chart of generator one-key sequential control disconnection and shutdown, and the method comprises the following steps:

[0193] Step 1. One-button sequential control of the generator to disconnect, stop and start;

[0194] Step 2. Collect the DEH decoupling permission signal; collect the generator active power signal, specifically, it should meet P≤1%Pe;

[0195] Step 3. The DCS judges the conditions of step 2 above. If any condition is not met, the DCS one-button sequential control decoupling and shutdown operation is terminated, and an audible and visual alarm signal of the corresponding condition is issued; if all conditions are met, go to step 4;

[0196] Step 4: Collect the generator excitation current signal. Specifically, it should meet I L ≤1.1I Lkz =164A,I Lkz is the generator no-load excitation current, I Lkz =149A;

[0197] 5.1 The DCS judges the conditions of step 4 above. If the conditions are met, the DCS issues a grid-connected switch opening command with a command pulse width of 1s, and then goes to step 6;

[0198] 5.2.1 The DCS judges the conditions of step 4 above. If the conditions are not met, the DCS issues a demagnetization command to the excitation regulator, with a command pulse width of 0.5s and a step length of 1s;

[0199] 5.2.2 Judge the excitation current DCS. If it satisfies I L ≤1.1I Lkz =164A, the DCS issues a grid-connected switch opening command with a command pulse width of 1s, and goes to step 6;

[0200] Step 6. Determine the grid-connected switch position signal, and the DCS sets a 5s determination time. If the grid-connected switch is in the closed position, the DCS one-button sequential control decoupling and shutdown operation is terminated, and an audible and visual alarm signal of the corresponding condition is issued; if the grid-connected switch is in the open position, proceed to step 7;

[0201] Step 7: DCS sends an inverter command to the excitation regulator, with a command pulse width of 2s, and then goes to step 8;

[0202] Step 8. Collect the generator output bus voltage Ufab, Ufbc, Ufca. The three-phase voltage should all satisfy U≤10%Ue=1.05KV; collect the generator excitation current signal, which should satisfy I L ≤3%I Le =13A,I Le is the rated excitation current of the generator, I Le =430A;

[0203] Step 9. The DCS judges the conditions in step 8 above, and the DCS sets a judgment time of 5s. If none of the conditions are met, the DCS one-button sequential control decoupling and shutdown operation is terminated, and an audible and visual alarm signal of the corresponding condition is issued; if any condition is met, the DCS issues a demagnetization switch opening command with a command pulse width of 1s, and enters step 10;

[0204] Step 10. Determine the demagnetization switch position signal, and the DCS sets a 5s judgment time. If the demagnetization switch is in the closed position, the DCS one-button sequential control de-energizing and shutdown operation is terminated, and an audible and visual alarm signal of the corresponding condition is issued; if the demagnetization switch is in the open position, the one-button sequential control de-energizing and shutdown operation is completed, and the DCS program is terminated.

[0205] It should be noted that the above embodiments are not intended to limit the protection scope of the present invention, and equivalent changes or substitutions made on the basis of the above technical solutions all fall within the protection scope of the claims of the present invention.

Claims

1. A method for one-key sequential control of generator grid connection and disconnection and shutdown, characterized in that: This method consists of two independent sequential control logics. Logic one is the generator one-key sequential control grid-connected operation, and logic two is the generator one-key sequential control de-coupling and shutdown operation.

2. The method for one-key sequential control of generator grid connection and disconnection and shutdown according to claim 1 is characterized in that: Logic 1 is the one-key sequential control and grid-connected operation of the generator, which includes the following steps: Step 1: Close the generator demagnetization switch; 1.1.1 Generator one-button sequential control grid-connected start; 1.1.2 Collect the generator stator current Ia, Ib, Ic. The three phases should be without current before the generator is connected to the grid. Specifically, the current I should be less than or equal to 1.5 times the no-load running current of the generator, or set to I≤0.75%Ie according to the empirical value, where Ie is the rated stator current of the generator; 1.1.3 Collect the three-phase line voltages Uxab, Uxbc, and Uxca on the side of the system to be connected. The ratio of the maximum value to the average value should not be greater than 2%, that is, the three-phase voltage unbalance should be ε≤2%; 1.1.4 Collect the generator speed n. The speed n satisfies the conditions according to the generator grid-connected allowable frequency difference Δf set =0.15Hz, specifically, according to the allowable frequency difference Δf set Calculate 1.5 times of the speed n, and the speed n is 2987<n<3013r / min; 1.1.5 Collect alarm and fault output signals of the generator microcomputer protection device, generator excitation system, DC power supply system, etc. All of the above should operate normally without alarm or fault signals; 1.1.6 Collect the generator demagnetization switch position signal, the demagnetization switch should be in the open position; 1.1.7 Collect the generator grid-connected switch position signal, the grid-connected switch should be in the open position; 1.1.8 Collect the generator grid-connected switch trolley position signal. The grid-connected switch trolley position should be in the operating position. 1.2 The DCS judges the conditions from 1.1.1 to 1.1.8 above. If any of the conditions is not met, the DCS one-key sequential control grid-connected operation is terminated and an audible and visual alarm signal of the corresponding condition is issued. If all the conditions are met, the DCS issues a demagnetization switch closing command with a command pulse width of 1s and proceeds to step 1.

3. 1.3 Determine the demagnetization switch position signal. The DCS sets a 5s judgment time. If the demagnetization switch is in the open position, the DCS one-button sequential control grid-connected operation is terminated, and an audible and visual alarm signal of the corresponding condition is issued; if the demagnetization switch is in the closed position, go to step 2; Step 2: Generator voltage build-up; 2.1.1 The three-phase currents Ia, Ib and Ic of the generator stator should be less than or equal to 1.5 times of the no-load running current of the generator, or according to the empirical value I≤0.75%Ie, where Ie is the rated stator current of the generator; 2.1.2 The ratio of the maximum value to the average value of the three-phase line voltage Uxab, Uxbc, and Uxca on the side of the system to be connected should not be greater than 2%, that is, the three-phase voltage unbalance should be ε≤2%; 2.1.3 The speed of the generator n should be 2987<n<3013r / min; 2.1.4 The generator microcomputer protection device, generator excitation system, DC power supply system, etc. should all operate normally without any alarm or fault signal; 2.1.5 The generator demagnetization switch position signal should be in the closed position; 2.1.6 The generator grid-connected switch position signal should be in the open position; 2.1.7 The generator grid-connected switch trolley position signal should be in the operating position; 2.2 The DCS judges the conditions from 2.1.1 to 2.1.7 above. If any of the conditions is not met, the DCS one-key sequential control grid-connected operation is terminated, and an audible and visual alarm signal of the corresponding condition is issued. If all the conditions are met, the DCS issues a voltage build-up command to the excitation regulator, with a command pulse width of 2s, and enters step 2.

3. 2.3 Collect the generator output bus voltage Ufab, Ufbc, and Ufca. The DCS sets a judgment time of 20s. If the generator voltages Ufab, Ufbc, and Ufca all satisfy 0.925Ue<U<1.05Ue, and the three-phase voltage unbalance satisfies ε≤2%, then go to step 3; Step 3: Start the automatic quasi-synchronous working circuit of the generator; 3.1.1 The three-phase currents Ia, Ib and Ic of the generator stator should be less than or equal to 1.5 times of the no-load running current of the generator, or according to the empirical value I≤0.75%Ie, where Ie is the rated stator current of the generator; 3.1.2 The ratio of the maximum value to the average value of the three-phase line voltage Uxab, Uxbc, and Uxca on the side of the system to be connected should not be greater than 2%, that is, the three-phase voltage unbalance should be ε≤2%; 3.1.3 The speed of the generator n should be 2987<n<3013r / min; 3.1.4 The generator microcomputer protection device, generator excitation system, DC power supply system, etc. should all operate normally without any alarm or fault signal; 3.1.5 The generator grid-connected switch position signal should be in the open position; 3.1.6 The generator grid-connected switch trolley position signal should be in the operating position; 3.1.7 Collect the single / double-side no-pressure confirmation selection switch position signal on the generator microcomputer automatic quasi-synchronous screen. The selection switch should be in the quasi-synchronous position; 3.1.8 Collect the manual / automatic selector switch position signal on the generator microcomputer automatic quasi-synchronous screen. The selector switch should be in the automatic position; 3.1.9 Collect the three-phase line voltages of the generator Ufab, Ufbc, Ufca and the system side Uxab, Uxbc, Uxca, and the voltage difference ΔU between the same-phase lines on both sides to be connected shall meet the conditions according to the generator grid-connected allowable voltage difference ΔU set ≤5%Ue, specifically, according to the allowable pressure difference ΔU set 1.5 times of the calculated value, the voltage difference between the generator and the system side ΔU≤7.5%Ue, Ue is the rated stator voltage of the generator; 3.1.10 Collecting the generator voltage frequency f f With the system side voltage frequency f x The voltage frequency difference Δf between the two sides to be connected satisfies the condition according to the generator grid connection allowable frequency difference Δf set ≤0.15Hz, specifically, according to the allowable frequency difference Δf set ≤0.15Hz by 1.5 times, the frequency difference between the generator and the system side is calculated to be Δf≤0.225Hz, 3.2 The DCS judges the conditions from 3.1.1 to 3.1.10 above. If any of the conditions is not met, the DCS one-key sequential control grid connection operation is terminated and an audible and visual alarm signal of the corresponding condition is issued. If all the conditions are met, the DCS issues an automatic quasi-synchronization command for the generator, with a command pulse width of 2s, and enters step 4. Step 4: Start the automatic synchronization and close the generator grid-connected switch; 4.1.1 Collect the ready signal of the generator microcomputer automatic quasi-synchronous device, the signal status should be ready; 4.1.2 Collect the fault alarm signal of the generator microcomputer automatic quasi-synchronous screen, and it should run normally without alarm fault signal; 4.1.3 The three-phase stator currents Ia, Ib and Ic of the generator should be less than or equal to 1.5 times the no-load running current of the generator, or according to the empirical value I≤0.75%Ie, where Ie is the rated stator current of the generator; 4.1.4 The ratio of the maximum value to the average value of the three-phase line voltage Uxab, Uxbc, and Uxca on the side of the system to be connected should not be greater than 2%, that is, the three-phase voltage unbalance should be ε≤2%; 4.1.5 The ratio of the maximum value to the average value of the three-phase line voltage Ufab, Ufbc and Ufca of the generator should not be greater than 2%, that is, the three-phase voltage unbalance should be ε≤2%; 4.1.6 The speed of the generator n should be 2987<n<3013r / min; 4.1.7 The generator microcomputer protection device, generator excitation system, DC power supply system, etc. should all operate normally without any alarm or fault signal; 4.1.8 The voltage difference between the generators on both sides to be connected and the system side should satisfy ΔU≤7.5%Ue, where Ue is the rated stator voltage of the generator; 4.1.9 The frequency difference between the generators to be connected and the system side should satisfy Δf≤0.225Hz. 4.2 The DCS judges the conditions in 4.1.1 to 4.1.9 above. The DCS sets a judgment time of 5s. If any condition is not met, the DCS one-key sequential control grid connection operation is terminated and an audible and visual alarm signal of the corresponding condition is issued. If all conditions are met, the DCS issues an automatic quasi-synchronization start command with a command pulse width of 2s and enters step 4.

3. 4.3 The microcomputer automatic quasi-synchronization device automatically determines the voltage difference ΔU and frequency difference Δf on both sides of the grid to be connected. When the voltage difference and frequency difference are within the allowable value (≤ΔU set ,≤Δf set ) range to capture the first grid-connected opportunity, and the synchronization device issues a closing command to close the generator grid-connected switch; 4.4 Determine the grid-connected switch position signal. After the DCS issues the start synchronization command, set a 60s judgment time. If the grid-connected switch is in the open position, the DCS one-key sequential control grid-connected operation is terminated, and an audible and visual alarm signal of the corresponding condition is issued; if the grid-connected switch is in the closed position, go to step 5. Step 5: Exit the generator automatic quasi-synchronous working circuit, 5.1 The generator has been connected to the grid, and the DCS issues a command to withdraw the automatic quasi-synchronous working circuit. The command pulse width is 2s, and then proceed to step 5.2; 5.2 Collect the signal that the synchronization circuit of the generator microcomputer automatic quasi-synchronization screen has exited. The DCS sets a judgment time of 5s. If the signal status is not exited, the DCS one-key sequential control grid-connected operation is terminated, and an audible and visual alarm signal of the corresponding condition is issued; if the signal status is that the synchronization circuit has exited, the one-key sequential control grid-connected operation is completed and the DCS program is terminated.

3. The method for one-key sequential control of generator grid connection and disconnection and shutdown according to claim 2 is characterized in that step 2.3 in logic 1: ① The generator outlet bus voltage Ufab, Ufbc, Ufca, the voltage U meets the conditions according to the generator grid-connected allowable voltage difference ΔU set =5%Ue, specifically, according to the allowable pressure difference ΔU set 1.5 times of the value, and the maximum voltage should meet the V / Hz limit setting 1.05, the voltage U is calculated to be 0.925Ue<U<1.05Ue, where Ue is the rated stator voltage of the generator. ②The ratio of the maximum value to the average value of Ufab, Ufbc, and Ufca should not be greater than 2%, that is, the unbalanced degree of the three-phase voltage of the generator should be ε≤2%.

4. The method for one-key sequential control of generator grid connection and disconnection and shutdown according to claim 2 is characterized in that: In the logic 1, The fault alarm signals of the generator microcomputer protection device include: Line protection device lockout, alarm; system side PT voltage circuit disconnection; grid-connected switch control circuit disconnection; generator protection device lockout, alarm; generator main and backup protection action signal; generator CT / PT abnormality, Generator excitation system fault alarm signals include: Excitation regulator failure, alarm; power cabinet failure; excitation failure; PT failure; DC system fault alarm signals include: DC charging device total fault; DC system grounding fault, The fault alarm signals of the generator synchronization device include: synchronization device power failure; synchronization device general alarm; synchronization lockout.

5. The method for one-key sequential control of generator grid connection and disconnection and shutdown according to claim 1, characterized in that: The second logic: the generator one-key sequential control disconnection and shutdown operation includes the following steps: Step 1. One-button sequential control of the generator to disconnect, stop and start; Step 2. Collect the DEH decoupling permission signal; collect the generator active power signal, specifically, it should meet P≤1%Pe; Step 3. The DCS judges the conditions of step 2 above. If any condition is not met, the DCS one-button sequential control decoupling and shutdown operation is terminated, and an audible and visual alarm signal of the corresponding condition is issued. If all conditions are met, go to step 4; Step 4: Collect the generator excitation current signal. Specifically, it should meet I L ≤1.1I Lkz , I Lkz is the no-load excitation current of the generator; 5.1 The DCS judges the conditions of step 4 above. If the conditions are met, the DCS issues a grid-connected switch opening command with a command pulse width of 1s, and then goes to step 6; 5.2.1 The DCS judges the conditions of step 4 above. If the conditions are not met, the DCS issues a demagnetization command to the excitation regulator, with a command pulse width of 0.5s and a step length of 1s; 5.2.2 Judge the excitation current DCS. If it satisfies I L ≤1.1I Lkz , then the DCS issues a grid-connected switch opening command with a command pulse width of 1s, and goes to step 6; Step 6. Determine the grid-connected switch position signal. The DCS sets a 5s judgment time. If the grid-connected switch is in the closed position, the DCS one-button sequential control decoupling and shutdown operation is terminated, and an audible and visual alarm signal of the corresponding condition is issued. If the grid-connected switch is in the open position, go to step 7. Step 7. The DCS sends an inverter command to the excitation regulator, with a command pulse width of 2s, and then goes to step 8; Step 8. Collect the generator output bus voltage Ufab, Ufbc, Ufca. The three-phase voltage should satisfy U≤10%Ue. Collect the generator excitation current signal, which should satisfy I L ≤3%I Le , I Le is the rated excitation current of the generator; Step 9. The DCS judges the conditions in step 8 above. The DCS sets a judgment time of 5s. If none of the conditions are met, the DCS one-button sequential control decoupling and shutdown operation is terminated, and an audible and visual alarm signal of the corresponding condition is issued. If any condition is met, the DCS issues a demagnetization switch opening command with a command pulse width of 1s, and enters step 10. Step 10. Determine the demagnetization switch position signal. The DCS sets a 5s judgment time. If the demagnetization switch is in the closed position, the DCS one-button sequential control de-energizing and shutdown operation is terminated, and an audible and visual alarm signal of the corresponding condition is issued; if the demagnetization switch is in the open position, the one-button sequential control de-energizing and shutdown operation is completed, and the DCS program is terminated.

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