Small high-speed turbine low-voltage generator set and grid-connected control system and method

Abstract

The invention discloses a small high-speed turbine low-voltage generator set and a grid-connected control system and method, the whole generator set comprises a turbo expander, a speed reducer and a synchronous generator, and the turbo expander is connected with the synchronous generator after being decelerated by the speed reducer; the grid-connected control system comprises a generator set used for generating power, a generator grid-connected module used for realizing connection of the generator set and a power grid, and a generator protection module used for detecting circuit faults and protecting equipment and personal safety, and safe and reliable operation of a generator is ensured. The control method comprises a manual synchronous grid connection mode and an automatic synchronous grid connection mode, manual grid connection adopts a manual synchronization table, automatic grid connection adopts an automatic quasi-synchronization device, and a synchronous generator is safely connected with a power grid by controlling a generator grid connection circuit breaker to be switched on; the device has the effects of low manufacturing difficulty of the synchronous generator, high reliability of mechanical equipment, flexible grid connection mode, high grid connection success rate, complete protection functions and quick and reliable action.

Description

Technical Field

[0001] The present invention relates to the technical field of turbine generator sets, and in particular to a small-sized high-speed turbine low-voltage generator set, a grid-connected control system and a method. Background Art

[0002] At present, the speed of turboexpanders with installed capacity of several hundred kW is mostly very high, and some even reach tens of thousands of rpm. There are many ways to connect a small turbine low-voltage generator set to the grid, and synchronous generator synchronous grid connection is one of the commonly used grid connection methods. The unit usually adopts the layout of "turbine expander + synchronous generator". Since the frequency of my country's power grid is 50Hz, this requires the frequency of the electric energy generated by the generator to be 50Hz to be connected to the grid. The formula of generator speed and frequency: n = 60f / p, where: n represents the generator speed; f represents the frequency; p represents the number of generator pole pairs. Due to the limitation of the number of generator pole pairs, the range of generator selection is relatively small. If the turboexpander and the synchronous generator are directly connected, the generator speed must be the same as the turboexpander speed. The higher the generator speed, the higher the corresponding output frequency will be, which makes it difficult to meet the needs of direct grid connection; it is also very difficult to manufacture the generator, and the mechanical structure of the generator is difficult to meet the requirements of high speed.

[0003] The patent application with publication number CN 117220345 A discloses a rectifier-inverter system for small turbine power generation and its control method. However, due to the use of a rectifier-inverter system, which is composed of power electronic switching devices, the 666.7Hz high frequency of the synchronous generator is converted into a 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] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a small high-speed turbine low-pressure generator set, a 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 connected to the synchronous generator 3C after being decelerated, and the frequency output by the synchronous generator 3C is consistent with the frequency of the system power grid. The mechanical equipment reducer 2B has higher reliability than electronic components, and the synchronous generator 3C has a wide selection range, low manufacturing difficulty, and low output frequency, which can meet the characteristics of direct grid connection.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

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

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

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

[0009] The generator grid-connected module is used to transmit the electric energy generated by the synchronous generator 3C to the power grid through synchronous grid-connected operation to achieve safe connection with the power grid;

[0010] The generator protection module is used to detect internal and external faults of the synchronous generator 3C to ensure the normal operation of the synchronous generator 3C and to cut off the circuit in time when an abnormal situation occurs 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 through cables, and the wiring output terminal of the generator grid-connected circuit breaker QF1 is connected to the wiring input terminal of the system interconnection circuit breaker QF2 through cables, and the wiring output terminal of the system interconnection circuit breaker QF2 is connected to the system bus through cables;

[0012] The generator grid-connected module includes generator-side fuses 1FU1-1FU6, generator-side voltage transformers 1TV1-1TV3, system-side fuses 2FU1-2FU4, system-side voltage transformers 2TV1-2TV2, a grid-connected selection switch SA1, a manual synchronization meter S, and an automatic quasi-synchronization device SYN;

[0013] The inlet terminal of the fuse 1FU1 is connected to the U-phase outlet terminal of the synchronous generator 3C, the outlet 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 inlet terminal of the fuse 1FU4, and the outlet terminal of the fuse 1FU4 is connected to the contact 9 and the contact 13 of the grid-connected selection switch SA1;

[0014] The inlet terminal of the fuse 1FU2 is connected to the V-phase outlet terminal of the synchronous generator 3C, the outlet 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 inlet terminal of the fuse 1FU5, and the outlet terminal of the fuse 1FU5 is connected to the contact 11 and the contact 15 of the grid-connected selection switch SA1;

[0015] The inlet terminal of the fuse 1FU3 is connected to the W-phase outlet terminal of the synchronous generator 3C, the outlet 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 inlet 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 the contact 1 and the contact 5 of the grid-connected selection switch SA1;

[0017] The inlet terminal of the fuse 2FU2 is connected to the system bus V, the outlet 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 inlet terminal of the fuse 2FU4, and the outlet terminal of the fuse 2FU4 is connected to the contact 3 and the contact 7 of the grid-connected 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 synchronization meter S, and contacts 6, 8, 14 and 16 are all connected to the voltage input terminal of the automatic quasi-synchronization device SYN.

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

[0020] The current input ends of the current transformers 1TA1 and 2TA1 are sequentially sleeved on the U-phase output end cable of the synchronous generator 3C;

[0021] The current input ends of the current transformers 1TA2 and 2TA2 are sequentially sleeved on the V-phase output end cable of the synchronous generator 3C;

[0022] The current input ends of the current transformers 1TA3 and 2TA3 are sequentially sleeved on the W-phase output end cable of the synchronous generator 3C;

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

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

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

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

[0027] When the manual synchronous grid-connection mode is selected by switching the grid-connection selection switch SA1, the following steps are specifically included:

[0028] S1: After the unit is ready for start-up and the grid-connected control system successfully supplies power, first manually close the system interconnection circuit breaker QF2, the system bus is energized, and the grid-connected selection switch SA1 is turned to the manual synchronization position. Contacts 1, 2, 3, and 4 of the grid-connected selection switch SA1 are connected at the same time. The voltage transformers 2TV1 and 2TV2 on the system side convert the system bus voltage into a secondary AC voltage, and the voltage signal on the system side is detected by the manual synchronization meter S;

[0029] S2: The turbine expander 1A starts to drive the synchronous generator 3C to rotate. When the speed of the synchronous generator 3C reaches or exceeds 1350rpm and is lower than 1500rpm, the excitation system is put into operation to increase or decrease the magnetic field signal to adjust the output voltage of the generator; the automatic control system is used to increase or decrease the speed signal to adjust the speed of the generator. When the contact 1, contact 2, contact 3, and contact 4 of the grid-connected selection conversion switch SA1 are connected, the contact 9, contact 10, contact 11, and contact 12 of the grid-connected selection conversion switch SA1 are also connected. The voltage transformers 1TV1 to 1TV3 on the generator side convert the voltage on the generator side into a secondary AC voltage, and the voltage signal on the generator side is detected by the manual synchronous meter S;

[0030] S3: The voltage signals detected in step S1 and step S2 are compared synchronously through the manual synchronization meter S. The manual synchronization meter S is manually observed. When it is observed that the voltage, frequency and phase of the generator are consistent with those of the system, the manual synchronization meter S points to the synchronization point, and the synchronization closing output contact is connected, the generator grid-connected circuit breaker QF1 is manually closed to connect the generator to the grid. The generator is safely connected to the grid.

[0031] When the automatic synchronous grid-connection mode is selected by switching the grid-connection selection switch SA1, the following steps are specifically included:

[0032] P1: When the unit is ready for start-up and the grid-connected control system successfully supplies power, first manually close the system interconnection circuit breaker QF2, the system bus is energized, and the grid-connected selection switch SA1 is turned to the automatic synchronization position. The voltage transformers 2TV1 and 2TV2 on the system side convert the system bus voltage into a secondary AC voltage. Contacts 5, 6, 7, and 8 of the grid-connected selection switch SA1 are connected at the same time, and the voltage signal on the system side is detected by the automatic quasi-synchronization device SYN.

[0033] 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 lower than 1500rpm, the excitation system is put into operation to increase or decrease the magnetic field signal to adjust the voltage of the generator; the automatic control system is used to increase or decrease the speed signal to adjust the speed of the generator. When contacts 5, 6, 7, and 8 of the grid-connected selection switch SA1 are connected, contacts 13, 14, 15, and 16 of the grid-connected selection switch SA1 are also connected. The voltage transformers 1TV1 to 1TV3 on the generator side convert the voltage on the generator side into a secondary AC voltage, and the voltage signal on the generator side is detected by the automatic quasi-synchronous device SYN.

[0034] P3: The voltage signals detected in step P1 and step P2 are synchronously compared through the automatic quasi-synchronizing device SYN. ​​When the automatic quasi-synchronizing device SYN detects that the voltage, frequency and phase of the generator are consistent with those of the system, the automatic quasi-synchronizing device SYN captures the grid connection point, and the synchronous closing output contact of the automatic quasi-synchronizing device SYN is connected, the generator grid-connected circuit breaker QF1 is automatically closed, so that the generator is connected to the grid, and the generator is safely connected to the grid.

[0035] The starting conditions are specifically as follows: the process system of the turbine expander 1A is normal, the air intake shut-off valve is closed, and the unit's serious fault signal is reset; the lubricating oil pressure is normal, and the lubricating oil temperature is normal; the cranking device of the reducer 2B is normal, the cranking motor is turned on, the entire unit is cranked, and the cranking device gears are engaged; the electrical system is normal, the system interconnection circuit breaker QF2 is in the closed state, and the grid-connected circuit breaker QF1 is in the open state.

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

[0037] 1. The present invention adds a speed reducer 2B between the turbine expander 1A and the synchronous generator 3C, and connects the turbine expander 1A to the synchronous generator 3C after speed reduction. There is no need to configure a rectifier inverter system, so that the output frequency of the synchronous generator 3C is consistent with the frequency of the system power grid. The present invention has the advantages of high mechanical equipment reliability, wide selection range of synchronous generators, low manufacturing difficulty, and low output frequency, which can meet the effect of direct grid connection.

[0038] 2. The present invention realizes the safe connection between the synchronous generator and the system power grid through two synchronous grid-connected modes, manual and automatic, and has the effects of flexible grid-connected mode and high grid-connected success rate.

[0039] 3. The present invention configures the generator protection device 1n in the system, so that when an abnormal situation occurs in the system, the protection device can act in time to cut off the circuit to protect equipment and personal safety, and has a comprehensive, fast and reliable protection function.

[0040] In summary, the present invention has the advantages of low difficulty in manufacturing the synchronous generator, high reliability of mechanical equipment, flexible grid connection mode, high grid connection success rate, complete protection functions, and fast and reliable operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a layout diagram of the generator set of 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 The contact closure table of the transfer switch SA1 is selected for the grid connection of the present invention.

[0044] Figure 4 FIG. 1 is a wiring diagram of the generator protection device 1n of the present invention. DETAILED DESCRIPTION

[0045] The present invention will be described in detail below in conjunction with the accompanying drawings.

[0046] like Figure 1 As shown, a small high-speed turbine low-pressure generator set includes a turbine expander 1A, wherein 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, and after being decelerated by the reducer 2B, it drives the synchronous generator 3C to rotate, and converts mechanical energy into electrical energy. In this embodiment, the speed of the turbine expander 1A is preset to 10000rpm, and after being decelerated by the reducer 2B, the speed of the synchronous generator 3C is 1500rpm. This "turbine expander + reducer + synchronous generator" arrangement connects the turbine expander 1A to the reducer 2B, and after being decelerated by the reducer 2B, it is 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 needs of direct grid connection.

[0047] In the power system, synchronous generators are the main power supply equipment, which transmit electric energy to the power grid through grid-connected operation. Synchronous grid connection can ensure the stability and reliability of electric energy, and can also realize the sharing and distribution of electric energy. Synchronous grid connection is a key step in the generator grid connection. Before the generator is ready to be connected to the grid, its voltage, frequency, phase and other parameters need to be checked and adjusted to ensure that they are basically consistent with the parameters of the grid. Only when these parameters meet the grid connection requirements can the grid connection operation be carried out. Synchronous grid connection can be done in two ways: manual and automatic. Synchronous grid connection is safer and more reliable. The manual grid connection method is simple to operate, but the grid connection accuracy is not high. It is highly dependent on the professional quality and operating experience of the operator. This grid connection method can be used for the generator grid connection test; automatic quasi-synchronous detection is automatically detected by the device. The grid connection is safe, reliable, fast, stable, accurate, and multi-functional. This grid connection method is often used when the generator is normally connected to the grid.

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

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

[0050] The generator grid-connected module is used to transmit the electric energy generated by the synchronous generator 3C to the power grid through synchronous grid-connected operation to achieve safe connection with the power grid;

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

[0052] The U, V, and W three-phase outgoing lines of the synchronous generator 3C are connected to the wiring input terminal of the generator grid-connected circuit breaker QF1 through a cable, and the wiring output terminal of the generator grid-connected circuit breaker QF1 is connected to the wiring input terminal of the system interconnection circuit breaker QF2 through a cable, and the wiring output terminal of the system interconnection circuit breaker QF2 is connected to the system bus through a cable;

[0053] The generator grid-connected 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-connected selection switch SA1, manual synchronization table S, automatic quasi-synchronization device SYN, grid-connected selection switch SA1 contact closure table reference Figure 3 As shown;

[0054] The inlet terminal of the fuse 1FU1 is connected to the U-phase outlet terminal of the synchronous generator 3C, the outlet 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 inlet terminal of the fuse 1FU4, and the outlet terminal of the fuse 1FU4 is connected to the contact 9 and the contact 13 of the grid-connected selection switch SA1;

[0055] The inlet terminal of the fuse 1FU2 is connected to the V-phase outlet terminal of the synchronous generator 3C, the outlet 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 inlet terminal of the fuse 1FU5, and the outlet terminal of the fuse 1FU5 is connected to the contact 11 and the contact 15 of the grid-connected selection switch SA1;

[0056] The inlet terminal of the fuse 1FU3 is connected to the W-phase outlet terminal of the synchronous generator 3C, the outlet 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 inlet 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 the contact 1 and the contact 5 of the grid-connected selection switch SA1;

[0058] The inlet terminal of the fuse 2FU2 is connected to the system bus V, the outlet 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 inlet terminal of the fuse 2FU4, and the outlet terminal of the fuse 2FU4 is connected to the contact 3 and the contact 7 of the grid-connected 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 synchronization meter S, and contacts 6, 8, 14 and 16 are all connected to the voltage input terminal of the automatic quasi-synchronization device SYN.

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

[0061] The current input ends of the current transformers 1TA1 and 2TA1 are sequentially sleeved on the U-phase output end cable of the synchronous generator 3C;

[0062] The current input ends of the current transformers 1TA2 and 2TA2 are sequentially sleeved on the V-phase output end cable of the synchronous generator 3C;

[0063] The current input ends of the current transformers 1TA3 and 2TA3 are sequentially sleeved on the W-phase output end cable of the synchronous generator 3C;

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

[0065] The current transformers 1TA1-1TA3, 2TA1-2TA3 are connected to the three-phase outgoing 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 grid. The synchronous generator 3C is loaded, the output current gradually increases, and the generator protection device 1n performs current protection;

[0066] After the generator grid-connected circuit breaker QF1 is closed, the synchronous generator 3C is safely connected to the 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 performs voltage protection;

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

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

[0069] See also Figure 4The generator protection device 1n used in this embodiment is SNP-6383, which specifically includes a power module, an AC sampling module, a switch input module, a relay output module, and a communication module. First, connect the DC 110V or 220V power supply to the power module, and the generator protection device 1n works with power on; the current and voltage signals output by the current transformers 1TA1~3, 2TA1~3 and the voltage transformers 1TV1~3 are connected to the AC sampling module to monitor the generator voltage, current, active power, reactive power, power factor, frequency and other parameters in real time, and complete the protection functions of the generator overcurrent, overload, overvoltage, demagnetization, etc.; the auxiliary contacts of the generator grid-connected circuit breaker QF1 are connected to the switch input module to monitor the actual state of the switch opening / closing in real time; when the generator 3C fails, the tripping contact of the relay output module is actuated, tripping the generator grid-connected circuit breaker QF1, so that the generator is disconnected from the power grid; the communication module reserves a communication interface to realize the remote communication function.

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

[0071] When the manual synchronous grid-connection mode is selected by switching the grid-connection selection switch SA1, the following steps are specifically included:

[0072] S1: After the unit has the conditions to start and the grid-connected control system has successfully supplied power, first manually close the system interconnection circuit breaker QF2, the system bus is energized, turn the grid-connected selection switch SA1 to the manual synchronization position, and the contact 1, contact 2, contact 3, and contact 4 of the grid-connected selection switch SA1 are connected at the same time. The voltage transformer 2TV1 and the voltage transformer 2TV2 on the system side convert the system bus voltage 400V into an AC voltage of 100V, and the voltage signal on the system side is detected by the manual synchronization meter S;

[0073] S2: The turbine expander 1A starts to drive the synchronous generator 3C to rotate. The air intake cut-off valve is opened manually to adjust the air intake. The speed of the synchronous generator gradually increases. When the speed of the synchronous generator 3C reaches or exceeds 1350rpm and is lower than 1500rpm, the automatic control system sends an excitation signal to the excitation system. Then, the excitation cabinet is manually or automatically increased or decreased to adjust the output voltage of the generator. The speed increase or decrease is performed by clicking the soft button on the automatic control system screen to adjust the speed of the generator. When the contact 1, contact 2, contact 3, and contact 4 of the grid-connected selection switch SA1 are connected, the contact 9, contact 10, contact 11, and contact 12 of the grid-connected selection switch SA1 are also connected. The voltage transformers 1TV1 to 1TV3 on the generator side convert the voltage of 400V on the generator side into an AC voltage of 100V. The voltage signal on the generator side is detected by the manual synchronous meter S.

[0074] S3: The voltage signals detected in step S1 and step S2 are compared synchronously through the manual synchronization meter S. The manual synchronization meter S is manually observed. When it is observed that the voltage, frequency and phase of the generator are consistent with those of the system, the manual synchronization meter S points to the synchronization point, and the synchronization closing output contact is connected, the generator grid-connected circuit breaker QF1 is manually closed to connect the generator to the grid. The generator is safely connected to the grid.

[0075] When the automatic synchronous grid-connection mode is selected by switching the grid-connection selection switch SA1, the following steps are specifically included:

[0076] P1: After the unit has the conditions to start and the grid-connected control system has successfully supplied power, first manually close the system interconnection circuit breaker QF2, the system bus is energized, and the grid-connected selection switch SA1 is turned to the automatic synchronization position. The voltage transformers 2TV1 and 2TV2 on the system side convert the system bus voltage of 400V into an AC voltage of 100V. Contacts 5, 6, 7, and 8 of the grid-connected selection switch SA1 are connected at the same time, and the voltage signal on the system side is detected by the automatic quasi-synchronization device SYN.

[0077] P2: Turbine expander 1A starts to drive synchronous generator 3C to rotate, manually open the air intake cut-off valve, adjust the air intake, and the speed of the synchronous generator gradually increases. When the speed of synchronous generator 3C reaches or exceeds 1350rpm and is lower than 1500rpm, the automatic control system sends an excitation signal to the excitation system, and then manually or automatically increase or decrease the magnetization on the excitation cabinet to adjust the output voltage of the generator; the speed increase or decrease is performed by jogging the soft button on the automatic control system screen to adjust the speed of the generator. When the contacts 5, 6, 7, and 8 of the grid-connected selection switch SA1 are connected, the contacts 13, 14, 15, and 16 of the grid-connected selection switch SA1 are also connected, and the voltage transformers 1TV1 to 1TV3 on the generator side convert the voltage of 400V on the generator side into an AC voltage of 100V. The voltage signal on the generator side is detected by the automatic quasi-synchronous device SYN.

[0078] P3: The voltage signals detected in step P1 and step P2 are synchronously compared through the automatic quasi-synchronizing device SYN. ​​When the automatic quasi-synchronizing device SYN detects that the voltage, frequency and phase of the generator are consistent with those of the system, the automatic quasi-synchronizing device SYN captures the grid connection point, and the synchronous closing output contact of the automatic quasi-synchronizing device SYN is connected, the generator grid-connected circuit breaker QF1 is automatically closed, so that the generator is connected to the grid, and the generator is safely connected to the grid.

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

Claims

1. A small high-speed turbine low-voltage generator set, characterized in that: It comprises a turbo expander 1A, the power output shaft of the turbo 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.

2. A grid-connected control system, characterized in that: It comprises the small-sized high-speed turbine low-voltage generator set as claimed in claim 1, as well as a generator grid connection module and a generator protection module; The small high-speed turbine low-pressure generator set: the mechanical energy generated by the work of the turbine expander 1A is converted into electrical energy through the synchronous generator 3C and used for the unit to generate electricity; The generator grid-connected module is used to transmit the electric energy generated by the synchronous generator 3C to the power grid through synchronous grid-connected operation to achieve safe connection with the power grid; The generator protection module is used to detect internal and external faults of the synchronous generator 3C to ensure the normal operation of the synchronous generator 3C and to cut off the circuit in time when an abnormal situation occurs in the system to protect equipment and personal safety.

3. A grid-connected control system according to claim 2, characterized in that: 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 through cables, and the wiring output terminal of the generator grid-connected circuit breaker QF1 is connected to the wiring input terminal of the system interconnection circuit breaker QF2 through cables, and the wiring output terminal of the system interconnection circuit breaker QF2 is connected to the system bus through cables; The generator grid-connected module includes generator-side fuses 1FU1-1FU6, generator-side voltage transformers 1TV1-1TV3, system-side fuses 2FU1-2FU4, system-side voltage transformers 2TV1-2TV2, a grid-connected selection switch SA1, a manual synchronization meter S, and an automatic quasi-synchronization device SYN; The inlet terminal of the fuse 1FU1 is connected to the U-phase outlet terminal of the synchronous generator 3C, the outlet 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 inlet terminal of the fuse 1FU4, and the outlet terminal of the fuse 1FU4 is connected to the contact 9 and the contact 13 of the grid-connected selection switch SA1; The inlet terminal of the fuse 1FU2 is connected to the V-phase outlet terminal of the synchronous generator 3C, the outlet 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 inlet terminal of the fuse 1FU5, and the outlet terminal of the fuse 1FU5 is connected to the contact 11 and the contact 15 of the grid-connected selection switch SA1; The inlet terminal of the fuse 1FU3 is connected to the W-phase outlet terminal of the synchronous generator 3C, the outlet 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 inlet 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 the contact 1 and the contact 5 of the grid-connected selection switch SA1; The inlet terminal of the fuse 2FU2 is connected to the system bus V, the outlet 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 inlet terminal of the fuse 2FU4, and the outlet terminal of the fuse 2FU4 is connected to the contact 3 and the contact 7 of the grid-connected selection switch SA1; Contacts 2, 4, 10 and 12 of the grid-connected selection switch SA1 are all connected to the voltage input terminal of the manual synchronization meter S, and contacts 6, 8, 14 and 16 are all connected to the voltage input terminal of the automatic quasi-synchronization device SYN.

4. A grid-connected control system according to claim 2, characterized in that: The generator protection module includes generator-side current transformers 1TA1-1TA3, 2TA1-2TA3, and a generator protection device 1n; The current input ends of the current transformers 1TA1 and 2TA1 are sequentially sleeved on the U-phase output end cable of the synchronous generator 3C; The current input ends of the current transformers 1TA2 and 2TA2 are sequentially sleeved on the V-phase output end cable of the synchronous generator 3C; The current input ends of the current transformers 1TA3 and 2TA3 are sequentially sleeved on the W-phase output end cable of the synchronous generator 3C; The current output terminals of the current transformer 1TA1, the current transformer 1TA2 and the current transformer 1TA3 are all connected to the current protection signal terminal of the generator protection device 1n; The current output terminals of the current transformer 2TA1 , the current transformer 2TA2 , and the current transformer 2TA3 are all connected to the current measurement signal terminal of the generator protection device 1 n .

5. A grid-connected control system according to claim 3 or 4, characterized in that: The outgoing terminals of the generator-side fuses 1FU4 to 1FU6 are simultaneously connected to the voltage signal terminals of the generator protection device 1n.

6. A grid-connected control system according to claim 5, characterized in that: The generator protection device 1n includes a power supply module, an AC sampling module, a switch input module, a relay output module, and a communication module.

7. A grid-connected control method, characterized in that: The grid-connected control system according to claim 6 includes two synchronous grid-connected modes: manual and automatic.

8. A grid connection control method according to claim 7, characterized in that: When the manual synchronous grid-connection mode is selected by switching the grid-connection selection switch SA1, the following steps are specifically included: S1: After the unit is ready for start-up and the grid-connected control system successfully supplies power, first manually close the system interconnection circuit breaker QF2, the system bus is energized, turn the grid-connected selection switch SA1 to the manual synchronization position, and the contact 1, contact 2, contact 3, and contact 4 of the grid-connected selection switch SA1 are connected at the same time. The voltage transformers 2TV1 and 2TV2 on the system side convert the system bus voltage into a secondary AC voltage, and the voltage signal on the system side is detected by the manual synchronization meter S; S2: The turbine expander 1A starts to drive the synchronous generator 3C to rotate. When the speed of the synchronous generator 3C reaches or exceeds 1350rpm and is lower than 1500rpm, the excitation system is put into operation to increase or decrease the magnetic field signal to adjust the output voltage of the generator; the automatic control system is used to increase or decrease the speed signal to adjust the speed of the generator. When the contact 1, contact 2, contact 3, and contact 4 of the grid-connected selection conversion switch SA1 are connected, the contact 9, contact 10, contact 11, and contact 12 of the grid-connected selection conversion switch SA1 are also connected. The voltage transformers 1TV1 to 1TV3 on the generator side convert the voltage on the generator side into a secondary AC voltage, and the voltage signal on the generator side is detected by the manual synchronous meter S; S3: The voltage signals detected in step S1 and step S2 are compared synchronously through the manual synchronization meter S. The manual synchronization meter S is manually observed. When it is observed that the voltage, frequency and phase of the generator are consistent with those of the system, the manual synchronization meter S points to the synchronization point, and the synchronization closing output contact is connected, the generator grid-connected circuit breaker QF1 is manually closed to connect the generator to the grid. The generator is safely connected to the grid.

9. A grid connection control method according to claim 7, characterized in that: When the automatic synchronous grid-connection mode is selected by switching the grid-connection selection switch SA1, the following steps are specifically included: P1: When the unit is ready for start-up and the grid-connected control system successfully supplies power, first manually close the system interconnection circuit breaker QF2, the system bus is energized, and the grid-connected selection switch SA1 is turned to the automatic synchronization position. The voltage transformers 2TV1 and 2TV2 on the system side convert the system bus voltage into a secondary AC voltage. Contacts 5, 6, 7, and 8 of the grid-connected selection switch SA1 are connected at the same time, and the voltage signal on the system side is detected by the automatic quasi-synchronization 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 lower than 1500rpm, the excitation system is put into operation to increase or decrease the magnetic field signal to adjust the voltage of the generator; the automatic control system is used to increase or decrease the speed signal to adjust the speed of the generator. When contact 5, contact 6, contact 7, and contact 8 of grid-connected selection switch SA1 are connected, contact 13, contact 14, contact 15, and contact 16 of grid-connected selection switch SA1 are also connected. The voltage transformers 1TV1 to 1TV3 on the generator side convert the voltage on the generator side into a secondary AC voltage, and the voltage signal on the generator side is detected by the automatic quasi-synchronization device SYN. P3: The voltage signals detected in step P1 and step P2 are synchronously compared through the automatic quasi-synchronizing device SYN. ​​When the automatic quasi-synchronizing device SYN detects that the voltage, frequency and phase of the generator are consistent with those of the system, the automatic quasi-synchronizing device SYN captures the grid connection point, and the synchronous closing output contact of the automatic quasi-synchronizing device SYN is connected, the generator grid-connected circuit breaker QF1 is automatically closed, so that the generator is connected to the grid, and the generator is safely connected to the grid.

10. A grid connection control method according to claim 8 or 9, characterized in that: The startup conditions are as follows: the process system of the turbine expander 1A is normal, the air intake shut-off valve is closed, and the unit serious fault signal is reset; the lubricating oil pressure is normal; the lubricating oil temperature is normal; the cranking device of the reducer 2B is normal, the cranking motor is turned on, the entire unit is cranked, and the cranking device gears are engaged; The electrical system is normal, the system interconnection circuit breaker QF2 is in the closed state, and the grid-connected circuit breaker QF1 is in the open state.

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