A small high-speed turbine low-voltage generator set, grid-connected control system and method

Abstract

A small high-speed turbine low-voltage generator set, grid connection control system, and method are disclosed. The entire generator set includes a turbine expander, a reducer, and a synchronous generator. The turbine expander is connected to the synchronous generator after being reduced in speed by the reducer. The grid connection control system includes the generator set for power generation, a generator grid connection module for connecting the generator set to the power grid, and a generator protection module for detecting circuit faults, protecting equipment and personal safety, and ensuring the safe and reliable operation of the generator. The control method includes two synchronization grid connection modes: manual and automatic. Manual grid connection uses a manual synchronizing meter, while automatic grid connection uses an automatic quasi-synchronizing device. By controlling the closing of the generator grid connection circuit breaker, the synchronous generator is safely connected to the power grid. The system features low manufacturing difficulty of the synchronous generator, high mechanical equipment reliability, flexible grid connection mode, high grid connection success rate, and comprehensive protection functions with fast and reliable operation.

Description

Technical Field

[0001] This invention relates to the field of turbine generator set technology, specifically to a small high-speed turbine low-voltage generator set, grid-connected control system and method. Background Technology

[0002] Currently, turbine expanders with an installed capacity of several hundred kW mostly operate at very high speeds, some even reaching tens of thousands of rpm. There are many ways to connect small turbine low-voltage generator sets to the grid, with synchronous generator connection being one of the commonly used methods. The unit typically adopts a "turbine expander + synchronous generator" arrangement. Since the frequency used in my country's power grid is 50Hz, the frequency of the electricity generated by the generator must also be 50Hz for grid connection. The formula for generator speed and frequency is: n = 60f / p, where: n represents the generator speed; f represents the frequency; and p represents the number of generator pole pairs. Due to the limitation on the number of generator pole pairs, the range of generator selection is relatively small. If the turbine expander and synchronous generator are directly connected, the generator speed must be the same as the turbine expander speed. The higher the generator speed, the higher the corresponding output frequency, making it difficult to meet the requirements for direct grid connection. Furthermore, the generator is very difficult to manufacture, as its mechanical structure and other aspects cannot meet the requirements for high speeds.

[0003] Patent application CN 117220345 A discloses a rectifier-inverter system and its control method for a small turbine power generation. However, due to the use of a rectifier-inverter system, which is composed of power electronic switching devices, to convert the 666.7Hz high frequency of the synchronous generator into the 50Hz grid frequency consistent with the system for synchronous grid connection, the synchronous generator is difficult to manufacture, the entire system structure is complex, and the electronic components of the rectifier-inverter system have a high failure rate. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention aims to provide a small high-speed turbine low-voltage generator set, grid-connected control system and method. By adding a reducer 2B between the turbine expander 1A and the synchronous generator 3C, the turbine expander 1A is decelerated and then connected to the synchronous generator 3C. The frequency of the output of the synchronous generator 3C is consistent with the frequency of the system power grid. The mechanical reducer 2B has higher reliability than electronic components, and the synchronous generator 3C has a wide range of selection, low manufacturing difficulty and low output frequency, which can meet the characteristics of direct grid connection.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A small high-speed turbine low-voltage generator set includes a turbine expander 1A, the power output shaft of the turbine expander 1A is connected to the high-speed shaft of the reducer 2B, and the low-speed shaft of the reducer 2B is connected to the power input shaft of the synchronous generator 3C.

[0007] A grid-connected control system includes a small high-speed turbine low-voltage generator set, a generator grid-connection module, and a generator protection module;

[0008] The small high-speed turbine low-voltage generator set: the mechanical energy generated by the turbine expander 1A is converted into electrical energy by the synchronous generator 3C for the generator set to generate electricity;

[0009] The generator grid-connection module is used to transmit the electrical energy generated by the synchronous generator 3C to the power grid through synchronous grid-connection operation, so as to achieve a safe connection with the power grid.

[0010] The generator protection module is used to detect internal and external faults of the synchronous generator 3C, ensure the normal operation of the synchronous generator 3C, and can cut off the circuit in time when abnormal conditions occur in the system to protect equipment and personal safety.

[0011] The U, V, and W three-phase output terminals of the synchronous generator 3C are connected to the wiring input terminal of the generator grid-connected circuit breaker QF1 via cables. The wiring output terminal of the generator grid-connected circuit breaker QF1 is then connected to the wiring input terminal of the system interconnection circuit breaker QF2 via cables. The wiring output terminal of the system interconnection circuit breaker QF2 is connected to the system bus via cables.

[0012] The generator grid connection module includes generator-side fuses 1FU1 to 1FU6, generator-side voltage transformers 1TV1 to 1TV3, system-side fuses 2FU1 to 2FU4, system-side voltage transformers 2TV1 to 2TV2, grid connection selection switch SA1, manual synchronizing meter S, and automatic quasi-synchronizing device SYN.

[0013] The incoming terminal of the fuse 1FU1 is connected to the U-phase outgoing terminal of the synchronous generator 3C, the outgoing terminal of the fuse 1FU1 is connected to the primary terminal of the voltage transformer 1TV1, the secondary terminal of the voltage transformer 1TV1 is connected to the incoming terminal of the fuse 1FU4, and the outgoing terminal of the fuse 1FU4 is connected to the contacts 9 and 13 of the grid connection selection switch SA1.

[0014] The incoming terminal of the fuse 1FU2 is connected to the V-phase outgoing terminal of the synchronous generator 3C, the outgoing terminal of the fuse 1FU2 is connected to the primary terminal of the voltage transformer 1TV2, the secondary terminal of the voltage transformer 1TV2 is connected to the incoming terminal of the fuse 1FU5, and the outgoing terminal of the fuse 1FU5 is connected to the contacts 11 and 15 of the grid connection selection switch SA1.

[0015] The incoming terminal of the fuse 1FU3 is connected to the W-phase outgoing terminal of the synchronous generator 3C, the outgoing terminal of the fuse 1FU3 is connected to the primary terminal of the voltage transformer 1TV3, and the secondary terminal of the voltage transformer 1TV3 is connected to the incoming terminal of the fuse 1FU6.

[0016] The incoming terminal of the fuse 2FU1 is connected to the system bus U, the outgoing terminal of the fuse 2FU1 is connected to the primary terminal of the voltage transformer 2TV1, the secondary terminal of the voltage transformer 2TV1 is connected to the incoming terminal of the fuse 2FU3, and the outgoing terminal of the fuse 2FU3 is connected to contacts 1 and 5 of the grid connection selection switch SA1.

[0017] The incoming terminal of the fuse 2FU2 is connected to the system bus V, the outgoing terminal of the fuse 2FU2 is connected to the primary terminal of the voltage transformer 2TV2, the secondary terminal of the voltage transformer 2TV2 is connected to the incoming terminal of the fuse 2FU4, and the outgoing terminal of the fuse 2FU4 is connected to the contacts 3 and 7 of the grid connection selection switch SA1.

[0018] Contacts 2, 4, 10, and 12 of the grid-connected selection switch SA1 are all connected to the voltage input terminal of the manual synchronizing meter S, and contacts 6, 8, 14, and 16 are all connected to the voltage input terminal of the automatic synchronizing device SYN.

[0019] The generator protection module includes generator-side current transformers 1TA1~1TA3, 2TA1~2TA3, and generator protection device 1n;

[0020] The current input terminals of the current transformers 1TA1 and 2TA1 are sequentially connected to the U-phase output cable of the synchronous generator 3C.

[0021] The current input terminals of the current transformers 1TA2 and 2TA2 are sequentially connected to the V-phase output cable of the synchronous generator 3C.

[0022] The current input terminals of the current transformers 1TA3 and 2TA3 are sequentially connected to the W-phase output cable of the synchronous generator 3C.

[0023] The current output terminals of current transformers 1TA1, 1TA2, and 1TA3 are all connected to the current protection signal terminal of generator protection device 1n; the current output terminals of current transformers 2TA1, 2TA2, and 2TA3 are all connected to the current measurement signal terminal of generator protection device 1n.

[0024] The output terminals of the generator-side fuses 1FU4 to 1FU6 are simultaneously connected to the voltage signal terminal of the generator protection device 1n.

[0025] The generator protection device 1n includes a power supply module, an AC sampling module, a digital input module, a relay output module, and a communication module.

[0026] A grid connection control method includes two synchronous grid connection modes: manual and automatic.

[0027] When switching to the manual synchronization grid connection mode via the grid connection selection switch SA1, the specific steps include:

[0028] S1: After the unit meets the start-up conditions and the grid connection control system is successfully energized, first manually close the system tie circuit breaker QF2. The system bus is energized. Set the grid connection selection switch SA1 to the manual synchronization position. Contacts 1, 2, 3, and 4 of the grid connection selection switch SA1 are simultaneously connected. The system side voltage transformers 2TV1 and 2TV2 convert the system bus voltage into secondary AC voltage. The voltage signal on the system side is detected by the manual synchronization meter S.

[0029] S2: Turbine expander 1A starts to drive synchronous generator 3C to rotate. When the speed of synchronous generator 3C reaches or exceeds 1350rpm and is below 1500rpm, the excitation system is activated to increase or decrease the excitation signal and adjust the generator's output voltage. The speed of the generator is adjusted by increasing or decreasing the speed signal through the automatic control system. At the same time as contacts 1, 2, 3, and 4 of grid connection selection switch SA1 are closed, contacts 9, 10, 11, and 12 of grid connection selection switch SA1 are also closed. The generator-side voltage transformers 1TV1 to 1TV3 convert the generator-side voltage into secondary AC voltage. The voltage signal on the generator side is detected by the manual synchronizing meter S.

[0030] S3: Compare the voltage signals detected in step S1 and step S2 using the manual synchronizing table S. Manually observe the manual synchronizing table S. When the voltage, frequency, and phase of the generator and the system are consistent, the manual synchronizing table S points to the synchronization point, and the synchronization closing output contact is connected, manually close the generator grid-connected circuit breaker QF1 to connect the generator to the grid and ensure a safe connection between the generator and the grid.

[0031] When switching the automatic synchronization grid connection mode via the grid connection selection switch SA1, the specific steps include:

[0032] P1: After the unit meets the start-up conditions and the grid connection control system is successfully energized, first manually close the system tie circuit breaker QF2. The system bus is energized. Set the grid connection selection switch SA1 to the automatic synchronization position. The system side voltage transformers 2TV1 and 2TV2 convert the system bus voltage into secondary AC voltage. Contacts 5, 6, 7, and 8 of the grid connection selection switch SA1 are simultaneously connected. The voltage signal on the system side is detected by the automatic synchronizing device SYN.

[0033] P2: Turbine expander 1A starts driving synchronous generator 3C to rotate. When the speed of synchronous generator 3C reaches or exceeds 1350 rpm but is below 1500 rpm, the excitation system is activated to provide magnetization increase / decrease signals to adjust the generator voltage. The automatic control system provides speed increase / decrease signals to adjust the generator speed. At the same time as contacts 5, 6, 7, and 8 of grid connection selection switch SA1 are closed, contacts 13, 14, 15, and 16 of grid connection selection switch SA1 are also closed. The generator-side voltage transformers 1TV1 to 1TV3 convert the generator-side voltage into secondary AC voltage, and the voltage signal on the generator side is detected by the automatic synchronizing device SYN.

[0034] P3: The voltage signals detected in steps P1 and P2 are compared for synchronization by the automatic synchronizing device SYN. ​​When the automatic synchronizing device SYN detects that the voltage, frequency and phase of the generator and the system are consistent, the automatic synchronizing device SYN captures the grid connection point and the synchronizing device SYN's synchronizing closing output contact is closed, the generator grid connection circuit breaker QF1 automatically closes, so that the generator is connected to the grid and the generator is safely connected to the grid.

[0035] The specific start-up conditions are as follows: the turbine expander 1A process system is normal, the intake shut-off valve is closed, and the unit's major fault signal is reset; the lubricating oil pressure and lubricating oil temperature are normal; the reducer 2B turning device is normal, the turning motor is turned on, and the entire unit is turned, with the turning device gears engaged in place; the electrical system is normal, the system interconnection circuit breaker QF2 is in the closed state, and the grid connection circuit breaker QF1 is in the open state.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] 1. This invention adds a speed reducer 2B between the turbine expander 1A and the synchronous generator 3C to reduce the speed of the turbine expander 1A before connecting it to the synchronous generator 3C. This eliminates the need for a rectifier-inverter system and ensures that the frequency of the synchronous generator 3C output is consistent with the frequency of the power grid. It features high mechanical equipment reliability, a wide range of synchronous generators to choose from, low manufacturing difficulty, and low output frequency, thus meeting the requirements for direct grid connection.

[0038] 2. This invention achieves a safe connection between the synchronous generator and the system power grid through two synchronization methods: manual and automatic. It has the advantages of flexible grid connection and high grid connection success rate.

[0039] 3. By configuring the generator protection device 1n into the system, the present invention enables the protection device to cut off the circuit in a timely manner when an abnormal situation occurs in the system, thereby protecting the equipment and personal safety. It has comprehensive, fast and reliable protection functions.

[0040] In summary, the present invention has the advantages of easy manufacturing of synchronous generators, high reliability of mechanical equipment, flexible grid connection methods, high grid connection success rate, and complete protection functions with fast and reliable operation. Attached Figure Description

[0041] Figure 1 This is a layout diagram of the generator set according to the present invention.

[0042] Figure 2 This is the wiring diagram of the generator grid-connected control system of the present invention.

[0043] Figure 3 This is a table showing the contact closure of the grid-connected selection switch SA1 of the present invention.

[0044] Figure 4 This is the wiring diagram of the generator protection device 1n of the present invention. Detailed Implementation

[0045] The present invention will now be described in detail with reference to the accompanying drawings.

[0046] like Figure 1 As shown, a small high-speed turbine low-voltage generator set includes a turbine expander 1A. The power output shaft of the turbine expander 1A is connected to the high-speed shaft of the reducer 2B, and the low-speed shaft of the reducer 2B is connected to the power input shaft of the synchronous generator 3C. The medium enters the turbine expander 1A to do work. After being reduced in speed by the reducer 2B, it drives the synchronous generator 3C to rotate, converting mechanical energy into electrical energy. In this embodiment, the preset speed of the turbine expander 1A is 10,000 rpm. After being reduced in speed by the reducer 2B, the speed of the synchronous generator 3C is reduced to 1,500 rpm. This arrangement of "turbine expander + reducer + synchronous generator" connects the turbine expander 1A to the reducer 2B. After being reduced in speed by the reducer 2B, it is then connected to the synchronous generator 3C to ensure that the generator output frequency is 50Hz, which is consistent with the grid frequency and meets the requirements for direct grid connection.

[0047] In power systems, synchronous generators are the primary power supply equipment, transmitting electrical energy to the grid through grid-connected operation. Synchronous grid connection ensures the stability and reliability of electrical energy, while also enabling energy sharing and distribution. Synchronous grid connection is a crucial step in generator grid connection. Before a generator is connected to the grid, its voltage, frequency, phase, and other parameters need to be checked and adjusted to ensure they are basically consistent with the grid parameters. Only when these parameters meet the grid connection requirements can the grid connection operation proceed. Synchronous grid connection can be performed manually or automatically, with manual connection offering higher safety and reliability. Manual connection is simple to operate but has lower accuracy and relies heavily on the operator's professional skills and experience; it is suitable for generator grid connection testing. Automatic synchronizing devices automatically detect the connection, offering safe, reliable, fast, stable, and highly accurate grid connection with multiple functions; this method is commonly used for normal generator grid connection.

[0048] like Figure 2 As shown, a grid-connected control system includes a small high-speed turbine low-voltage generator set, a generator grid-connection module and a generator protection module. Through synchronization detection, a quasi-synchronous grid-connection method is adopted to send the electrical energy generated by the synchronous generator 3C to the system bus.

[0049] The small high-speed turbine low-voltage generator set: the mechanical energy generated by the turbine expander 1A is converted into electrical energy by the synchronous generator 3C for the generator set to generate electricity;

[0050] The generator grid-connection module is used to transmit the electrical energy generated by the synchronous generator 3C to the power grid through synchronous grid-connection operation, so as to achieve a safe connection with the power grid.

[0051] The generator protection module is used to detect internal and external faults of the synchronous generator 3C, ensure the normal operation of the synchronous generator 3C, and can cut off the circuit in time when abnormal conditions occur in the system to protect equipment and personal safety.

[0052] The U, V, and W three-phase outputs of the synchronous generator 3C are connected to the wiring input terminal of the generator grid-connected circuit breaker QF1 via cables. The wiring output terminal of the generator grid-connected circuit breaker QF1 is then connected to the wiring input terminal of the system interconnection circuit breaker QF2 via cables. The wiring output terminal of the system interconnection circuit breaker QF2 is connected to the system bus via cables.

[0053] The generator grid-connection module includes generator-side fuses 1FU1-1FU6, generator-side voltage transformers 1TV1-1TV3, system-side fuses 2FU1-2FU4, system-side voltage transformers 2TV1-2TV2, grid-connection selection switch SA1, manual synchronizing meter S, automatic quasi-synchronizing device SYN, and a reference table for the closing of the grid-connection selection switch SA1 contacts. Figure 3 As shown;

[0054] The incoming terminal of the fuse 1FU1 is connected to the U-phase outgoing terminal of the synchronous generator 3C, the outgoing terminal of the fuse 1FU1 is connected to the primary terminal of the voltage transformer 1TV1, the secondary terminal of the voltage transformer 1TV1 is connected to the incoming terminal of the fuse 1FU4, and the outgoing terminal of the fuse 1FU4 is connected to the contacts 9 and 13 of the grid connection selection switch SA1.

[0055] The incoming terminal of the fuse 1FU2 is connected to the V-phase outgoing terminal of the synchronous generator 3C, the outgoing terminal of the fuse 1FU2 is connected to the primary terminal of the voltage transformer 1TV2, the secondary terminal of the voltage transformer 1TV2 is connected to the incoming terminal of the fuse 1FU5, and the outgoing terminal of the fuse 1FU5 is connected to the contacts 11 and 15 of the grid connection selection switch SA1.

[0056] The incoming terminal of the fuse 1FU3 is connected to the W-phase outgoing terminal of the synchronous generator 3C, the outgoing terminal of the fuse 1FU3 is connected to the primary terminal of the voltage transformer 1TV3, and the secondary terminal of the voltage transformer 1TV3 is connected to the incoming terminal of the fuse 1FU6.

[0057] The incoming terminal of the fuse 2FU1 is connected to the system bus U, the outgoing terminal of the fuse 2FU1 is connected to the primary terminal of the voltage transformer 2TV1, the secondary terminal of the voltage transformer 2TV1 is connected to the incoming terminal of the fuse 2FU3, and the outgoing terminal of the fuse 2FU3 is connected to contacts 1 and 5 of the grid connection selection switch SA1.

[0058] The incoming terminal of the fuse 2FU2 is connected to the system bus V, the outgoing terminal of the fuse 2FU2 is connected to the primary terminal of the voltage transformer 2TV2, the secondary terminal of the voltage transformer 2TV2 is connected to the incoming terminal of the fuse 2FU4, and the outgoing terminal of the fuse 2FU4 is connected to the contacts 3 and 7 of the grid connection selection switch SA1.

[0059] Contacts 2, 4, 10, and 12 of the grid-connected selection switch SA1 are all connected to the voltage input terminal of the manual synchronizing meter S, and contacts 6, 8, 14, and 16 are all connected to the voltage input terminal of the automatic synchronizing device SYN.

[0060] The generator protection module includes generator-side current transformers 1TA1~1TA3, 2TA1~2TA3, and generator protection device 1n;

[0061] The current input terminals of the current transformers 1TA1 and 2TA1 are sequentially connected to the U-phase output cable of the synchronous generator 3C.

[0062] The current input terminals of the current transformers 1TA2 and 2TA2 are sequentially connected to the V-phase output cable of the synchronous generator 3C.

[0063] The current input terminals of the current transformers 1TA3 and 2TA3 are sequentially connected to the W-phase output cable of the synchronous generator 3C.

[0064] The current output terminals of current transformers 1TA1, 1TA2, and 1TA3 are all connected to the current protection signal terminal of generator protection device 1n; the current output terminals of current transformers 2TA1, 2TA2, and 2TA3 are all connected to the current measurement signal terminal of generator protection device 1n.

[0065] The current transformers 1TA1~1TA3 and 2TA1~2TA3 are connected to the three-phase output terminals of the synchronous generator 3C. When the generator grid-connected circuit breaker QF1 is closed, the synchronous generator 3C is safely connected to the power grid. The synchronous generator 3C is loaded, and the output current gradually increases, triggering the generator protection device 1n for current protection.

[0066] After the generator grid-connected circuit breaker QF1 is closed, the synchronous generator 3C is safely connected to the power grid. The voltage on the synchronous generator 3C side is the same as the voltage on the system side, and the generator protection device 1n provides voltage protection.

[0067] The generator protection device 1n detects the current and voltage signals of the synchronous generator 3C. When an internal or external fault of the synchronous generator 3C is detected, the generator protection device 1n will activate and trip the generator grid-connected circuit breaker QF1, thereby disconnecting the generator from the power grid, ensuring the normal operation of the generator, and protecting equipment and personal safety.

[0068] The output terminals of the generator-side fuses 1FU4 to 1FU6 are simultaneously connected to the voltage signal terminal of the generator protection device 1n.

[0069] See Figure 4In this embodiment, the generator protection device 1n used is SNP-6383, specifically including a power supply module, an AC sampling module, a switch input module, a relay output module, and a communication module. First, a DC 110V or 220V power supply is connected to the power supply module, and the generator protection device 1n operates under power. The current and voltage signals output by current transformers 1TA1-3, 2TA1-3, and voltage transformers 1TV1-3 are connected to the AC sampling module to monitor generator voltage, current, active power, reactive power, power factor, frequency, and other parameters in real time, completing generator overcurrent, overload, overvoltage, and loss-of-excitation protection functions. The auxiliary contacts of the generator grid-connected circuit breaker QF1 are connected to the switch input module to monitor the actual opening / closing status of the switch in real time. When a fault occurs in generator 3C, the relay output module trips, tripping the generator grid-connected circuit breaker QF1, disconnecting the generator from the power grid. The communication module has a reserved communication interface for remote communication.

[0070] A grid connection control method includes two synchronous grid connection modes: manual and automatic.

[0071] When switching to the manual synchronization grid connection mode via the grid connection selection switch SA1, the specific steps include:

[0072] S1: After the unit meets the start-up conditions and the grid connection control system is successfully energized, first manually close the system tie circuit breaker QF2. The system bus is energized. Set the grid connection selection switch SA1 to the manual synchronization position. Contacts 1, 2, 3, and 4 of the grid connection selection switch SA1 are simultaneously connected. The system side voltage transformers 2TV1 and 2TV2 convert the system bus voltage of 400V into 100V AC voltage. The voltage signal on the system side is detected by the manual synchronizing meter S.

[0073] S2: Turbine expander 1A starts to drive synchronous generator 3C to rotate. Manually open the intake shut-off valve to adjust the intake volume. The synchronous generator speed gradually increases. When the speed of synchronous generator 3C reaches or exceeds 1350rpm but is below 1500rpm, the automatic control system sends an excitation signal to the excitation system. Then, manually or automatically perform the increase or decrease of excitation on the excitation cabinet to adjust the generator's output voltage. The speed can be increased or decreased by pressing the soft button on the automatic control system screen to adjust the generator speed. At the same time, when the contacts 1, 2, 3, and 4 of the grid connection selection switch SA1 are closed, the contacts 9, 10, 11, and 12 of the grid connection selection switch SA1 are also closed. The generator-side voltage transformers 1TV1 to 1TV3 convert the generator-side voltage of 400V into 100V AC voltage. The voltage signal on the generator side is detected by the manual synchronizing meter S.

[0074] S3: Compare the voltage signals detected in step S1 and step S2 using the manual synchronizing table S. Manually observe the manual synchronizing table S. When the voltage, frequency, and phase of the generator and the system are consistent, the manual synchronizing table S points to the synchronization point, and the synchronization closing output contact is connected, manually close the generator grid-connected circuit breaker QF1 to connect the generator to the grid and ensure a safe connection between the generator and the grid.

[0075] When switching the automatic synchronization grid connection mode via the grid connection selection switch SA1, the specific steps include:

[0076] P1: After the unit meets the start-up conditions and the grid connection control system is successfully energized, first manually close the system tie circuit breaker QF2. The system bus is energized. Set the grid connection selection switch SA1 to the automatic synchronization position. The system side voltage transformers 2TV1 and 2TV2 convert the system bus voltage of 400V into 100V AC voltage. Contacts 5, 6, 7, and 8 of the grid connection selection switch SA1 are simultaneously connected. The voltage signal on the system side is detected by the automatic synchronizing device SYN.

[0077] P2: Turbine expander 1A starts to drive synchronous generator 3C to rotate. Manually open the intake shut-off valve to adjust the intake volume. The synchronous generator speed gradually increases. When the speed of synchronous generator 3C reaches or exceeds 1350rpm but is below 1500rpm, the automatic control system sends an excitation signal to the excitation system. Then, manually or automatically perform the increase or decrease of excitation on the excitation cabinet to adjust the generator's output voltage. The speed can be increased or decreased by pressing the soft button on the automatic control system screen to adjust the generator speed. At the same time as contacts 5, 6, 7, and 8 of the grid connection selection switch SA1 are closed, contacts 13, 14, 15, and 16 of the grid connection selection switch SA1 are also closed. The generator-side voltage transformers 1TV1 to 1TV3 convert the generator-side voltage of 400V into 100V AC voltage. The voltage signal on the generator side is detected by the automatic synchronizing device SYN.

[0078] P3: The voltage signals detected in steps P1 and P2 are compared for synchronization by the automatic synchronizing device SYN. ​​When the automatic synchronizing device SYN detects that the voltage, frequency and phase of the generator and the system are consistent, the automatic synchronizing device SYN captures the grid connection point and the synchronizing device SYN's synchronizing closing output contact is closed, the generator grid connection circuit breaker QF1 automatically closes, so that the generator is connected to the grid and the generator is safely connected to the grid.

[0079] The specific start-up conditions are as follows: the turbine expander 1A process system is normal, the air intake shut-off valve is closed, and the unit's major fault signal is reset; the lubricating oil pressure is normal; the lubricating oil temperature is normal; the reducer 2B turning device is normal, the turning motor is turned on, and the entire unit is turned, with the turning device gears engaged in place; the electrical system is normal, the system interconnection circuit breaker QF2 is in the closed state, and the grid connection circuit breaker QF1 is in the open state.

Claims

1. A grid-connected control method, characterized in that, Based on a grid-connected control system, the grid-connected control system includes a small high-speed turbine low-voltage generator set, as well as a generator grid-connection module and a generator protection module. The small high-speed turbine low-voltage generator set includes a turbine expander 1A, the power output shaft of the turbine expander 1A is connected to the high-speed shaft of the reducer 2B, and the low-speed shaft of the reducer 2B is connected to the power input shaft of the synchronous generator 3C. The small high-speed turbine low-voltage generator set: the mechanical energy generated by the turbine expander 1A is converted into electrical energy by the synchronous generator 3C for the generator set to generate electricity; The generator grid-connection module is used to transmit the electrical energy generated by the synchronous generator 3C to the power grid through synchronous grid-connection operation, so as to achieve a safe connection with the power grid. The generator protection module is used to detect internal and external faults of the synchronous generator 3C, ensure the normal operation of the synchronous generator 3C, and can cut off the circuit in time when abnormal conditions occur in the system to protect equipment and personal safety. The U, V, and W three-phase output terminals of the synchronous generator 3C are connected to the wiring input terminal of the generator grid-connected circuit breaker QF1 via cables. The wiring output terminal of the generator grid-connected circuit breaker QF1 is then connected to the wiring input terminal of the system interconnection circuit breaker QF2 via cables. The wiring output terminal of the system interconnection circuit breaker QF2 is connected to the system bus via cables. The generator grid connection module includes generator-side fuses 1FU1 to 1FU6, generator-side voltage transformers 1TV1 to 1TV3, system-side fuses 2FU1 to 2FU4, system-side voltage transformers 2TV1 to 2TV2, grid connection selection switch SA1, manual synchronizing meter S, and automatic quasi-synchronizing device SYN. The incoming terminal of the fuse 1FU1 is connected to the U-phase outgoing terminal of the synchronous generator 3C, the outgoing terminal of the fuse 1FU1 is connected to the primary terminal of the voltage transformer 1TV1, the secondary terminal of the voltage transformer 1TV1 is connected to the incoming terminal of the fuse 1FU4, and the outgoing terminal of the fuse 1FU4 is connected to the contacts 9 and 13 of the grid connection selection switch SA1. The incoming terminal of the fuse 1FU2 is connected to the V-phase outgoing terminal of the synchronous generator 3C, the outgoing terminal of the fuse 1FU2 is connected to the primary terminal of the voltage transformer 1TV2, the secondary terminal of the voltage transformer 1TV2 is connected to the incoming terminal of the fuse 1FU5, and the outgoing terminal of the fuse 1FU5 is connected to the contacts 11 and 15 of the grid connection selection switch SA1. The incoming terminal of the fuse 1FU3 is connected to the W-phase outgoing terminal of the synchronous generator 3C, the outgoing terminal of the fuse 1FU3 is connected to the primary terminal of the voltage transformer 1TV3, and the secondary terminal of the voltage transformer 1TV3 is connected to the incoming terminal of the fuse 1FU6. The incoming terminal of the fuse 2FU1 is connected to the system bus U, the outgoing terminal of the fuse 2FU1 is connected to the primary terminal of the voltage transformer 2TV1, the secondary terminal of the voltage transformer 2TV1 is connected to the incoming terminal of the fuse 2FU3, and the outgoing terminal of the fuse 2FU3 is connected to contacts 1 and 5 of the grid connection selection switch SA1. The incoming terminal of the fuse 2FU2 is connected to the system bus V, the outgoing terminal of the fuse 2FU2 is connected to the primary terminal of the voltage transformer 2TV2, the secondary terminal of the voltage transformer 2TV2 is connected to the incoming terminal of the fuse 2FU4, and the outgoing terminal of the fuse 2FU4 is connected to the contacts 3 and 7 of the grid connection selection switch SA1. Contacts 2, 4, 10 and 12 of the grid-connected selection changeover switch SA1 are all connected to the voltage input terminal of the manual synchronizing meter S, and contacts 6, 8, 14 and 16 are all connected to the voltage input terminal of the automatic quasi-synchronizing device SYN. The generator protection module includes generator-side current transformers 1TA1~1TA3, 2TA1~2TA3, and generator protection device 1n; The current input terminals of the current transformers 1TA1 and 2TA1 are sequentially connected to the U-phase output cable of the synchronous generator 3C. The current input terminals of the current transformers 1TA2 and 2TA2 are sequentially connected to the V-phase output cable of the synchronous generator 3C. The current input terminals of the current transformers 1TA3 and 2TA3 are sequentially connected to the W-phase output cable of the synchronous generator 3C. The current output terminals of current transformers 1TA1, 1TA2, and 1TA3 are all connected to the current protection signal terminal of generator protection device 1n. The current output terminals of current transformers 2TA1, 2TA2, and 2TA3 are all connected to the current measurement signal terminal of generator protection device 1n. The output terminals of the generator-side fuses 1FU4 to 1FU6 are simultaneously connected to the voltage signal terminal of the generator protection device 1n. The generator protection device 1n includes a power supply module, an AC sampling module, a digital input module, a relay output module, and a communication module; The grid-connected control method, based on the grid-connected control system including two synchronization grid-connection modes, manual and automatic, specifically includes the following steps when switching to the manual synchronization grid-connection mode via the grid-connection selection switch SA1: S1: When the unit is ready to start up and the grid connection control system is successfully energized, first manually close the system tie circuit breaker QF2. The system bus is energized. Then, switch the grid connection selection changeover switch SA1 to the manual synchronization position. Contacts 1, 2, 3, and 4 of the grid connection selection changeover switch SA1 are simultaneously connected. The system side voltage transformers 2TV1 and 2TV2 convert the system bus voltage into secondary AC voltage. The voltage signal on the system side is detected by the manual synchronization meter S. S2: Turbine expander 1A starts to drive synchronous generator 3C to rotate. When the speed of synchronous generator 3C reaches or exceeds 1350rpm and is below 1500rpm, the excitation system is activated to increase or decrease the excitation signal and adjust the generator's output voltage. The speed of the generator is adjusted by increasing or decreasing the speed signal through the automatic control system. At the same time as contacts 1, 2, 3, and 4 of grid connection selection switch SA1 are closed, contacts 9, 10, 11, and 12 of grid connection selection switch SA1 are also closed. The generator-side voltage transformers 1TV1 to 1TV3 convert the generator-side voltage into secondary AC voltage. The voltage signal on the generator side is detected by the manual synchronizing meter S. S3: Compare the voltage signals detected in step S1 and step S2 using the manual synchronizing table S. Manually observe the manual synchronizing table S. When the voltage, frequency, and phase of the generator and the system are consistent, the manual synchronizing table S points to the synchronization point, and the synchronization closing output contact is connected, manually close the generator grid-connected circuit breaker QF1 to connect the generator to the grid and ensure a safe connection between the generator and the grid.

2. The grid-connected control method according to claim 1, characterized in that, When switching the automatic synchronization grid connection mode via the grid connection selection switch SA1, the specific steps include: P1: After the unit meets the start-up conditions and the grid connection control system is successfully energized, first manually close the system tie circuit breaker QF2. The system bus is energized. Set the grid connection selection switch SA1 to the automatic synchronization position. The system side voltage transformers 2TV1 and 2TV2 convert the system bus voltage into secondary AC voltage. Contacts 5, 6, 7, and 8 of the grid connection selection switch SA1 are simultaneously connected. The voltage signal on the system side is detected by the automatic synchronizing device SYN. P2: Turbine expander 1A starts to drive synchronous generator 3C to rotate. When the speed of synchronous generator 3C reaches or exceeds 1350rpm and is below 1500rpm, the excitation system is activated to increase or decrease the excitation signal and adjust the generator voltage. The speed of the generator is adjusted by increasing or decreasing the speed signal through the automatic control system. At the same time as contacts 5, 6, 7 and 8 of grid connection selection switch SA1 are closed, contacts 13, 14, 15 and 16 of grid connection selection switch SA1 are also closed. The generator side voltage transformers 1TV1 to 1TV3 convert the generator side voltage into secondary AC voltage. The voltage signal of the generator side is detected by the automatic synchronizing device SYN. P3: The voltage signals detected in steps P1 and P2 are compared for synchronization by the automatic synchronizing device SYN. ​​When the automatic synchronizing device SYN detects that the voltage, frequency and phase of the generator and the system are consistent, the automatic synchronizing device SYN captures the grid connection point and the synchronizing device SYN's synchronizing closing output contact is closed, the generator grid connection circuit breaker QF1 automatically closes, so that the generator is connected to the grid and the generator is safely connected to the grid.

3. A grid-connected control method according to claim 1 or 2, characterized in that, The specific start-up conditions are as follows: the turbine expander 1A process system is normal, the air intake shut-off valve is closed, the unit's major fault signal is reset; the lubricating oil pressure is normal; the lubricating oil temperature is normal; the reducer 2B turning device is normal, the turning motor is turned on, the entire unit is turned, and the turning device gears are engaged in place. The electrical system is normal. The system interconnection circuit breaker QF2 is in the closed state, and the grid connection circuit breaker QF1 is in the open state.

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