A variable speed constant frequency power generation system and control method for a hydroelectric generator set

Abstract

The invention discloses a variable speed constant frequency power generation system and control method of a hydroelectric generator set, wherein a power generation unit comprises a water turbine and a generator driven by the water turbine; the output end of the generator is connected to a power grid through a unit switch; an auxiliary conversion device comprises a rectifier and an inverter, the output end of the rectifier is electrically connected to the input end of the inverter, and the output end of the inverter is electrically connected to the power grid; a unit control module comprises a flow sensor, a flow controller and a guide vane controller; the flow controller is installed at a position where a water inlet channel supplies water to the water turbine, and the guide vane controller is used to control the guide vane opening of the water turbine; a total control device comprises a central controller and a data storage device for exchanging data with the central controller, and the central controller is used to electrically connect and control the auxiliary conversion device, the unit control module, the unit switch and the auxiliary switch; the problem that the current output by the generator of the hydroelectric generator set is difficult to synchronize with the current frequency and phase in the power grid is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydroelectric generators, and in particular relates to a variable speed constant frequency power generation system and a control method for a hydroelectric generator set. Technical Background

[0002] Hydropower generation is an important way to obtain clean energy. With the industrialization of my country, more and more hydropower units are beginning to operate on large and small rivers. In the process of hydropower generation, water will flow through the turbine to drive the turbine rotor to rotate, and then use the turbine rotor to drive the generator to generate electricity. However, hydropower units need to solve many problems in actual use. First, the reservoir used by small hydropower units is difficult to maintain stable water head due to the influence of rainfall in different seasons. At the same time, the power output of hydropower units to the outside is different in different seasons, so it is necessary to adjust the operating parameters of hydropower units in real time. Secondly, my country uses three-phase electricity for long-distance transmission of electricity. Due to various factors, the stability of the rotation speed of the turbine unit is easily affected, which makes it difficult for the current output of the generator to be synchronized with the current frequency and phase in the power grid, which causes a lot of waste of electricity. Summary of the invention

[0003] The technical problem to be solved by the present invention is: to provide a variable speed constant frequency power generation system and control method for a hydroelectric generator set, so as to solve the technical problem that when using three-phase electricity for long-distance transmission of electric power, the stability of the rotation speed of the turbine set is easily affected by various factors, which makes it difficult for the current output by the generator to be synchronized with the current frequency and phase in the power grid, thus causing a large amount of waste of electric energy.

[0004] Technical solution of the present invention:

[0005] A variable speed constant frequency power generation system of a hydroelectric generator set, the system comprising:

[0006] A power generation unit, the power generation unit includes a turbine and a generator driven by the turbine; the output end of the generator is connected to the power grid through a unit switch, and the frequency converter adjusts the frequency of the generator control winding current through the current change at the output end of the generator;

[0007] An auxiliary conversion device, the auxiliary conversion device includes a rectifier and an inverter, the output end of the rectifier is electrically connected to the input end of the inverter, the output end of the inverter is electrically connected to the power grid, and the output end of the generator is electrically connected to the rectifier through an auxiliary switch;

[0008] The unit control module includes a flow sensor, a flow controller and a guide vane controller; the flow sensor is installed on the tailwater pipe of the turbine, the water inlet end of the turbine is supplied with water through the water inlet channel, the flow controller is installed at the position where the water inlet channel supplies water to the turbine, and the guide vane controller is used to control the guide vane opening of the turbine;

[0009] The main control device includes a central controller and a data storage device for exchanging data with the central controller. The central controller is used to electrically connect and control the auxiliary conversion device, the unit control module, the unit switch and the auxiliary switch.

[0010] The generator is a brushless double-fed generator and the inverter is a sealed IP65 inverter.

[0011] The central controller is a PLC controller or an industrial computer, and the flow controller is a gate valve that adopts hydraulic drive to control opening and closing.

[0012] The data storage device inputs data through a keyboard or a human-computer interaction device. The reservoir is equipped with a reservoir monitoring module capable of monitoring the reservoir status and transmitting the detection data to the data storage device through a data line.

[0013] The control method comprises:

[0014] S1, initialization task; first, the operator turns off the unit switch corresponding to each turbine, and turns on the corresponding auxiliary switch, then stores the data required for turbine operation in the data storage, and sends the execution plan to the central controller;

[0015] S2, application parameter setting; when the central controller receives the plan to be executed, the central controller starts to retrieve the task data stored in the data storage, and then sets the operating parameters of each turbine according to the water head height of the reservoir, the total power required to be output by the power generation system, and the designated turbine to be turned on. At this time, the guide vane controller corresponding to each turbine that needs to work will adjust the guide vane opening of the corresponding turbine according to the data provided by the central controller, and then the central controller turns on the flow controller corresponding to the turbine that needs to work, so that the water starts to flow through the turbine that needs to work;

[0016] S3, achieve initial grid connection by adjusting parameters;

[0017] S4. Synchronous grid connection: The operator determines whether the frequency and phase between the current generated by the generator and the current in the grid are synchronized by installing a synchronization meter between the corresponding generator power winding and the grid. When synchronized, the operator first turns on the corresponding unit switch and then turns off the corresponding auxiliary switch. At this time, the power generation unit is in a synchronous grid-connected state.

[0018] The method for achieving initial grid connection by adjusting parameters described in S3 is: when the corresponding turbine starts working, the central controller uses the data transmitted by the speed sensor and flow sensor corresponding to each turbine as variables, and uses the PID algorithm to perform negative feedback control on the corresponding guide vane controller, so as to use the guide vane controller to adjust the guide vane opening of the corresponding turbine to maintain the output speed of the turbine at the rated speed. Subsequently, the frequency converter changes the frequency of the control winding in the generator according to the current frequency output by the generator so that the output current frequency of the generator is stabilized at the set frequency. During the generator adjustment process, the output current of the generator will be rectified and inverted by the rectifier and inverter inside the auxiliary conversion device and then connected to the power grid to achieve initial grid connection.

[0019] In the synchronous grid-connected state, the turbine still adjusts the turbine speed in real time through the guide vane controller, and adjusts the output frequency of the generator in real time through the inverter to maintain the synchronous grid-connected state.

[0020] The control method further comprises:

[0021] S5. When a power generation unit is in a synchronous grid-connected state, if the components in the system need to be shut down for maintenance or the operating parameters of different power generation units need to be changed, the power generation units involved need to be shut down first. At this time, the operator should turn off the unit switches corresponding to the various turbines involved, and turn on the corresponding auxiliary switches at the same time. At this time, the corresponding power generation unit is separated from the synchronous grid-connected state and connected to the grid through the auxiliary conversion device. Then the central controller turns off the corresponding flow controller according to the operating instructions to completely shut down the corresponding turbine. Then the operator sends the changed task to the central controller in the form of a to-be-executed plan, and re-executes steps S2 to S4.

[0022] Beneficial effects of the present invention:

[0023] The power generation system provided by the present invention groups different turbines into various power generation units controlled in parallel, so that the overall working state of the system can be steadily adjusted by changing the working state of different power generation units individually, and the maintenance operation is also convenient. At the same time, each power generation unit can effectively realize variable speed constant frequency power generation of the power generation unit through the unit control module and the frequency converter, and the power generation unit can also transmit electric energy to the power grid through the auxiliary conversion device when it cannot stably maintain the synchronous grid-connected state. Therefore, it can effectively improve the power generation efficiency and reduce the energy loss caused by the asynchronous output frequency of the power generation unit and the power grid, and has a high practical value. The technical problem of using three-phase electricity for long-distance transmission of electricity is solved, and the turbine unit is easily affected by various factors in the stability of its rotation speed, which makes it difficult for the current output by the generator to be synchronized with the current frequency and phase in the power grid, which causes a large amount of waste of electric energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of a hydroelectric generating set of the present invention;

[0025] Figure 2 This is a system block diagram of the present invention.

[0026] In the figure: 1. water inlet channel; 2. flow controller; 3. generator; 4. turbine; 5. flow sensor; 6. main control device; 7. auxiliary conversion device; 8. frequency converter; 9. inverter; 10. rectifier; 11. unit switch; 12. power generation unit; 13. auxiliary switch; 14. guide vane controller; 15. central controller; 16. unit control module; 17. speed sensor; 18. reservoir monitoring module; 19. data storage device. DETAILED DESCRIPTION

[0027] See also Figure 1 to Figure 2 The present invention provides a technical solution: a variable speed constant frequency power generation system of a hydroelectric generator set, the variable speed constant frequency power generation system comprising:

[0028] A power generation unit 12, the power generation unit 12 is composed of a turbine 4 and a generator 3 driven by the turbine 4, and the generator 3 is a brushless double-fed motor that uses a frequency converter 8 to adjust and control the winding current frequency, the generator 3 is a brushless double-fed generator, and the frequency converter 8 is a sealed IP65 type frequency converter, the output end of the generator 3 is connected to the power grid through a unit switch 11, and the frequency converter 8 adjusts the generator 3 to control the winding current frequency through the current change at the output end of the generator 3;

[0029] Auxiliary conversion device 7, the auxiliary conversion device 7 includes a rectifier 10 and an inverter 9, and the output end of the rectifier 10 is electrically connected to the input end of the inverter 9, the output end of the inverter 9 is electrically connected to the power grid, and the output end of the generator 3 is electrically connected to the rectifier 10 through an auxiliary switch 13;

[0030] The unit control module 16 includes a flow sensor 5, a flow controller 2 and a guide vane controller 14, and the flow sensor 5 is installed on the tailwater pipe of the turbine 4, the flow controller 2 is a gate valve that adopts hydraulic drive to control opening and closing, the progress end of the turbine 4 is supplied with water through the water inlet channel 1, and the flow controller 2 is installed at the position where the water inlet channel 1 supplies water to the turbine 4, and the guide vane controller 14 is used to control the guide vane opening of the turbine 4;

[0031] The main control device 6 includes a central controller 15 and a data storage device 19 for exchanging data with the central controller 15. The central controller 15 is used to electrically connect and control the auxiliary conversion device 7, the unit control module 16, the unit switch 11 and the auxiliary switch 13. The central controller 15 is a PLC controller or an industrial computer.

[0032] A control method for a variable speed constant frequency power generation system of a hydroelectric generator set comprises the following steps:

[0033] S1. Initialization: First, the operator turns off the unit switch 11 corresponding to each turbine 4 and turns on the corresponding auxiliary switch 13, then stores the data required for the operation of the turbine 4 in the data storage 19, and sends the execution plan to the central controller 15. The data to be stored in the data storage 19 for the central controller 15 to read include: the current water storage status and water head height of the reservoir, the specific composition data and working performance of each power generation unit 12, the total power required to be output by the power generation system, whether each power generation unit 12 is currently in maintenance or needs to change the operating parameter status, etc. The execution plan mainly includes various detailed execution parameters in the system pre-set by the operator;

[0034] S2. Application parameters: When the central controller 15 receives the plan to be executed, the central controller 15 starts to retrieve the task data stored in the data storage 19, and then sets the operating parameters of each turbine 4 according to the water head height of the reservoir, the total power required to be output by the power generation system, and the turbine 4 specified to be turned on or adjusted. At this time, the guide vane controller 14 corresponding to each turbine 4 that needs to work will adjust the guide vane opening of the corresponding turbine 4 according to the data provided by the central controller 15, and then the central controller 15 turns on the flow controller 2 corresponding to the turbine 4 that needs to work, so that the water starts to flow through the turbine 4 that needs to work, so that the turbine 4 can drive the corresponding generator 3 to generate electricity;

[0035] S3. Parameter adjustment: When the corresponding turbine 4 starts to work, the central controller 15 uses the data transmitted by the speed sensor 17 and the flow sensor 5 corresponding to each turbine 4 as variables, and uses the PID algorithm to perform negative feedback control on the corresponding guide vane controller 14, so as to use the guide vane controller 14 to adjust the guide vane opening of the corresponding turbine 4 to maintain the output speed of the turbine 4 near the rated speed. Then, the frequency converter 8 changes the frequency of the control winding in the generator 3 according to the current frequency output by the generator 3 so that the output current frequency of the generator 3 is stabilized near the set frequency. During the adjustment of the generator 3, the output current of the generator 3 will be rectified and inverted by the rectifier 10 and the inverter 9 inside the auxiliary conversion device 7 and then connected to the power grid to achieve initial grid connection. The rectifier 10 is used to convert the unstable frequency AC output of the generator 3 into DC, and the inverter 9 converts the DC output of the rectifier 10 into AC with the same frequency and phase as the AC in the power grid to achieve synchronous grid connection;

[0036] S4. Synchronous grid connection: The operator determines whether the frequency and phase between the current generated by the generator 3 and the current in the grid are synchronized by the synchronization meter installed between the power winding of the corresponding generator 3 and the grid. When the synchronization meter shows that it is not in a synchronous state for a long time, the operator can directly adjust the frequency conversion parameters of the inverter 8 through the central controller 15 to assist in completing the synchronization. When the synchronization meter shows that it is in a synchronous state, the operator first turns on the corresponding unit switch 11, and then turns off the corresponding auxiliary switch 13. At this time, the power generation unit 12 is in a synchronous grid-connected state. In the synchronous grid-connected state, the turbine 4 still needs to adjust the speed of the turbine 4 in real time through the guide vane controller 14, and adjust the output frequency of the generator 3 in real time through the inverter 8 to maintain the synchronous grid-connected state. Therefore, the auxiliary conversion device 7 in the power generation system is only used as a temporary grid-connected measure when the current frequency output of the generator 3 is unstable during normal use, thereby avoiding the overall power generation performance of the hydropower unit affected by the energy conversion efficiency problem of the auxiliary conversion device 7 itself;

[0037] S5. Task change: When the power generation unit 12 in the system needs to be shut down for maintenance or the operating parameters of different power generation units 12 need to be changed, for example, when the water inflow in the reservoir is insufficient to continue to maintain the water head and the turbine flow and speed need to be reduced, the power generation unit 12 involved needs to be shut down first. At this time, the operator should turn off the unit switch 11 corresponding to each turbine 4 involved, and turn on the corresponding auxiliary switch 13 at the same time. At this time, the corresponding power generation unit 12 is separated from the synchronous grid-connected state and is connected to the grid through the auxiliary conversion device 7. Then the central controller 15 turns off the corresponding flow controller 2 according to the operating instruction to completely shut down the corresponding turbine 4. Then the operator sends the changed task to the central controller 15 in the form of a to-be-executed plan. The central controller 15 re-executes steps S2 to S4 for the designed power generation unit 12 according to the plan to complete the task change process.

[0038] The power generation system provided by the present invention groups different turbines into parallel controlled power generation units 12, so that the overall working state of the system can be steadily adjusted by changing the working state of different power generation units 12 individually, and maintenance operations are also convenient. For example, in seasons with different precipitation, the water storage capacity of the reservoir can be maintained by adjusting the flow and speed of each turbine 4 and whether each power generation unit 12 works at the same time, or the real-time working state of each power generation unit 12 can be adjusted according to the electricity demand in different time periods. At the same time, each power generation unit can effectively realize variable speed constant frequency power generation of the power generation unit 12 through the unit control module 16 and the inverter 8, and the power generation unit 12 can also transmit electric energy to the power grid through the auxiliary conversion device 7 when it cannot stably maintain the synchronous grid-connected state. Therefore, the power generation efficiency can be effectively improved and the energy loss caused by the asynchronous output frequency of the power generation unit and the power grid can be reduced.

Claims

1. A variable speed constant frequency power generation system of a hydroelectric generator set, characterized in that: The system comprises: A power generation unit (12), the power generation unit (12) comprising a water turbine (4) and a generator (3) driven by the water turbine (4); the output end of the generator (3) is connected to the power grid via a unit switch (11), and the frequency converter (8) adjusts the frequency of the current of the control winding of the generator (3) through the current change at the output end of the generator (3); An auxiliary conversion device (7), the auxiliary conversion device (7) comprising a rectifier (10) and an inverter (9), the output end of the rectifier (10) being electrically connected to the input end of the inverter (9), the output end of the inverter (9) being electrically connected to a power grid, and the output end of the generator (4) being electrically connected to the rectifier (10) via an auxiliary switch (13); A unit control module (16), the unit control module (16) comprising a flow sensor (5), a flow controller (2) and a guide vane controller (14); the flow sensor (5) is mounted on the tailwater pipe of the water turbine (4); the water inlet end of the water turbine (4) is supplied with water through the water inlet channel (1); the flow controller (2) is mounted at a position where the water inlet channel (1) supplies water to the water turbine (4); and the guide vane controller (14) is used to control the guide vane opening of the water turbine (4); A total control device (6), the total control device (6) comprising a central controller (15) and a data storage device (19) for exchanging data with the central controller (15), the central controller (15) being used to electrically connect and control the auxiliary conversion device (7), the unit control module (16), the unit switch (11) and the auxiliary switch (13).

2. A variable speed constant frequency power generation system of a hydroelectric generator set according to claim 1, characterized in that: The generator (3) is a brushless double-fed generator, and the frequency converter (8) is a sealed IP65 frequency converter.

3. The variable speed constant frequency power generation system of a hydroelectric generator set according to claim 1, characterized in that: The central controller (15) is a PLC controller or an industrial computer, and the flow controller (2) is a gate valve that is hydraulically driven to control opening and closing.

4. The variable speed constant frequency power generation system of a hydroelectric generator set according to claim 1, characterized in that: The data storage device (19) inputs data via a keyboard or a human-computer interaction device, and a reservoir monitoring module (18) is installed in the reservoir, which is capable of monitoring the state of the reservoir and transmitting the detection data to the data storage device (19) via a data line.

5. The control method of a variable speed constant frequency power generation system of a hydroelectric generator set as claimed in claim 1, characterized in that: The control method comprises: S1, initialization task; first, the operator turns off the unit switch (11) corresponding to each turbine (4), and turns on the corresponding auxiliary switch (13), then stores the data required for the operation of the turbine (4) in the data storage (19), and sends the plan to be executed to the central controller (15); S2, application parameter setting; when the central controller (15) receives the plan to be executed, the central controller (15) starts to retrieve the task data stored in the data storage (19), and then sets the operating parameters of each turbine (4) according to the water head height of the reservoir, the total power required to be output by the power generation system, and the turbine (4) to be started. At this time, the guide vane controller (14) corresponding to each turbine (4) to be operated will adjust the guide vane opening of the corresponding turbine (4) according to the data provided by the central controller (15), and then the central controller (15) opens the flow controller (2) corresponding to the turbine (4) to be operated, so that water starts to flow through the turbine (4) to be operated; S3, achieve initial grid connection by adjusting parameters; S4, synchronous grid connection: the operator determines whether the frequency and phase between the current generated by the generator (3) and the current in the grid are synchronized by using a synchronization meter installed between the power winding of the corresponding generator (3) and the grid. When synchronized, the operator first turns on the corresponding unit switch (11), and then turns off the corresponding auxiliary switch (13). At this time, the power generation unit (12) is in a synchronous grid connection state; The method for achieving initial grid connection by adjusting parameters in S3 is as follows: when the corresponding turbine (4) starts to work, the central controller (15) uses the data transmitted by the speed sensor (17) and the flow sensor (5) corresponding to each turbine (4) as variables, and uses the PID algorithm to perform negative feedback control on the corresponding guide vane controller (14), so that the guide vane opening of the corresponding turbine (4) is adjusted by the guide vane controller (14) to maintain the output speed of the turbine (4) at the rated speed. Subsequently, the frequency converter (8) changes the frequency of the control winding in the generator (3) according to the current frequency output by the generator (3) so that the output current frequency of the generator (3) is stabilized at the set frequency. During the adjustment process of the generator (3), the output current of the generator (3) will be rectified and inverted by the rectifier (10) and the inverter (9) inside the auxiliary conversion device (7) and then connected to the grid, thereby achieving initial grid connection.

6. The control method of a variable speed constant frequency power generation system of a hydroelectric generator set according to claim 5, characterized in that: In the synchronous grid-connected state, the turbine (4) still adjusts the rotation speed of the turbine (4) in real time through the guide vane controller (14), and adjusts the output frequency of the generator (3) in real time through the frequency converter (8) to maintain the synchronous grid-connected state.

7. The control method of a variable speed constant frequency power generation system of a hydroelectric generator set according to claim 5, characterized in that: The control method further comprises: S5. When the power generation unit (12) is in a synchronous grid-connected state, if the components in the system need to be shut down for maintenance or the operating parameters of different power generation units (12) need to be changed, the power generation unit (12) involved needs to be shut down first. At this time, the operator should turn off the unit switch (11) corresponding to each turbine (4) involved, and turn on the corresponding auxiliary switch (13). At this time, the corresponding power generation unit (12) is separated from the synchronous grid-connected state and is connected to the grid through the auxiliary conversion device (7). Then, the central controller (15) turns off the corresponding flow controller (2) according to the operation instruction, so that the corresponding turbine (4) is completely shut down. Then, the operator sends the changed task to the central controller (15) in the form of a to-be-executed plan, and re-executes steps S2 to S4.

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