Inert-speed synchronous grid-connected control method under dragging of pumped storage SFC and storage medium

Abstract

The invention discloses an idle-speed synchronous grid-connected control method under dragging of a pumped storage SFC and a storage medium. The method comprises the steps that S1, a pump turbine is dragged to the rotating speed of a set threshold value through a static frequency converter SFC; the set threshold value is higher than the rated rotating speed of the pump turbine; s2, starting to enter a synchronous grid connection stage; s3, the static frequency converter SFC is locked, an output circuit breaker of the static frequency converter SFC is opened, and inert speed reduction of the pump turbine is conducted to a set threshold value; s4, the direct-current excitation device is rapidly adjusted to increase the generator terminal voltage to be consistent with the grid-connected voltage; and S5, when the grid-connected parameters are met, the automatic quasi-synchronization device sends out a closing command, the grid-connected circuit breaker is closed, and grid connection is completed. A computer program for executing the method is stored in the storage medium. The method has the advantages that the principle is simple, operation is easy and convenient, cost can be reduced by changing the control mode, and safety is improved.

Description

Technical Field

[0001] The present invention mainly relates to the technical field of pumped storage control, and in particular to a pumped storage SFC dragging idle synchronous grid-connected control method and a storage medium. Background Art

[0002] Pumped storage plays a role in peak load reduction and valley filling in the construction of new power systems. As the construction scale of pumped storage power stations continues to expand, large-scale pumped storage power stations are used more and more frequently. In large-scale pumped storage power stations, when the motor is started under the working condition of the pump of the large-scale pumped storage power station, if the motor is directly connected to the grid to start, it will cause an impact on the unit and the grid.

[0003] At present, domestic pumped storage high-power variable current starting devices are mainly started by static frequency converters SFC. The static frequency converter (SFC) control system is used to reduce the impact load caused by motor starting and realize soft starting of the unit from static to grid connection.

[0004] When the pump turbine is operating as a pump, the SFC device needs to be started to drag the motor to the rated speed and rated voltage, so that the synchronization device can intervene and complete the grid connection. In this process, after the pumped storage SFC is started and synchronized with the grid, the SFC output voltage needs to match the grid voltage, resulting in excessive capacity demand.

[0005] That is to say, in the traditional technical solution, the static frequency converter SFC starts the unit, and generally when the speed rises to a frequency ≥49.5Hz, it begins to enter the synchronous grid-connected stage. The automatic quasi-synchronous device adjusts the voltage and frequency of the machine end according to the parameter requirements (for example, frequency difference ±0.2Hz, voltage difference 3%, phase angle difference = 0); when the various parameters meet the grid-connected requirements, the automatic quasi-synchronous device issues a closing command, the static frequency converter SFC is immediately locked, the static frequency converter SFC output circuit breaker is opened, and the grid-connected circuit breaker is immediately closed to complete the grid connection. However, in the above-mentioned synchronization method, the SFC output voltage during synchronous grid connection must be consistent with the grid side voltage. In order to meet this requirement, the SFC capacity configuration needs to be increased. That is, under this working condition, the required SFC capacity is large, which is not conducive to reducing costs and also poses a hidden danger to safety. Summary of the invention

[0006] The technical problem to be solved by the present invention is: in response to the technical problems existing in the prior art, the present invention provides a pumped storage SFC traction idling synchronous grid-connected control method and storage medium which has a simple principle, is easy to operate, and can reduce costs and improve safety by changing the control method.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions: A method for controlling synchronous grid connection under idling speed of pumped storage SFC drive, comprising: Step S1: driving the pump turbine to a speed of a set threshold through a static frequency converter SFC; the set threshold is higher than the rated speed of the pump turbine; Step S2: Start to enter the synchronous grid connection stage; Step S3: the static frequency converter SFC is locked, and the output circuit breaker of the static frequency converter SFC is opened to allow the pump turbine to inertialy decelerate to a set threshold; Step S4: quickly adjust the DC excitation device to raise the terminal voltage to the same level as the grid-connected voltage; Step S5: When the grid-connected parameters are met, the automatic quasi-synchronous device issues a closing command to close the grid-connected circuit breaker and complete the grid-connected connection.

[0008] As a further improvement of the method of the present invention: in the step S1, the speed for setting the threshold value is 101-110% of the rated speed.

[0009] As a further improvement of the method of the present invention: the rotation speed for setting the threshold value adopts 105% of the rated rotation speed.

[0010] As a further improvement of the method of the present invention: in step S3, the pump turbine is allowed to inertialy reduce its speed to 49.8-50.2 Hz.

[0011] As a further improvement of the method of the present invention: in step S4, the synchronization device quickly adjusts the DC excitation device to increase the machine terminal voltage from 12 kV to 18 kV.

[0012] As a further improvement of the method of the present invention: in step S2, the synchronous process satisfies the following three conditions: 1) △U =│Ug ─ Us│= 0; 2) △f =│fg ─ fs│= 0; 3) δ = 0° Among them, Ug is the voltage on the side to be connected; Us is the voltage on the system side; △U is the voltage difference between the two sides; fg is the frequency on the side to be connected; fs is the frequency on the system side; △f is the frequency difference between the two sides; δ is the phase angle difference between the two sides.

[0013] The present invention further provides a storage medium, which can be read by a computer or a processor, and stores a computer program for executing any one of the above methods.

[0014] Compared with the prior art, the advantages of the present invention are: The idle synchronous grid-connected control method and storage medium under pumped-storage SFC traction of the present invention have simple principles, easy operation, and can reduce costs and improve safety by changing the control method. The present invention solves the problem that the FC output voltage needs to match the grid-side voltage by using the idle synchronous grid-connected control method under pumped-storage SFC traction, which can reduce the SFC output voltage requirement, effectively reduce the capacity demand of the SFC device, and achieve safe grid connection; the present invention greatly saves the SFC system cost and can be promoted on a large scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0016] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0017] like Figure 1 As shown, a pumped storage SFC driven idle synchronous grid-connected control method of the present invention comprises: Step S1: driving the pump turbine to a speed of a set threshold through a static frequency converter SFC; the set threshold is higher than the rated speed of the pump turbine; Step S2: Start to enter the synchronous grid connection stage; Step S3: the static frequency converter SFC is locked, and the output circuit breaker of the static frequency converter SFC is opened to allow the pump turbine to inertialy decelerate to a set threshold; Step S4: quickly adjust the DC excitation device to raise the terminal voltage to the same level as the grid-connected voltage; Step S5: When the grid-connected parameters are met (such as: frequency difference ±0.2 Hz, voltage difference 3%, phase angle difference = 0), the automatic quasi-synchronous device issues a closing command to close the grid-connected circuit breaker and complete the grid connection.

[0018] From the above, it can be seen that the innovation of the control method for idling synchronous grid-connected under pumped-storage SFC drag of the present invention lies in the use of the control method for inertia speed reduction and synchronous grid-connected under pumped-storage SFC drag to solve the problem of the SFC output voltage matching the grid-side voltage and achieve safe grid connection.

[0019] The present invention innovatively allows the static frequency converter SFC to start the pump turbine to a speed above the rated speed, and then allows the synchronization and excitation device to adjust the pump turbine to idle and connect to the grid. The biggest advantage is that it reduces the capacity of the SFC and saves the cost of the static frequency converter SFC. For example, the original 18kV pumped storage generator grid-connected voltage needs to be matched with it. The process from starting to connecting to the grid is that the static frequency converter SFC starts the pump turbine to the rated speed, the synchronization device issues a grid-connected command, and the static frequency converter SFC exits after the grid connection is successful. Such a process requires the static frequency converter SFC to raise the voltage level to 18kV, so the static frequency converter SFC requires a larger capacity and a higher cost; the present invention reduces the capacity of the pumped storage SFC and saves costs. For example, the SFC that originally needed to be raised to 18kV output now only needs to output 12kV, and the cost is reduced by at least 33%.

[0020] When the pumped storage SFC is started, the maximum power of the system is directly related to the driving torque and driving speed required by the unit, and the determination of the driving torque is directly related to the unit starting time requirements, the unit rotational inertia and the resistance torque of the unit throughout the starting process.

[0021] In the process of calculating the system power at startup, it actually involves the selection of some key parameters, as follows: 1) According to the unit's sub-item loss values ​​under rated conditions and the relationship between each loss and speed, the "resistance torque-speed" curve of the unit under dragging conditions is calculated and drawn; 2) The moment of inertia of the unit directly selects the design value of the input parameter; 3) The unit speed is "rated speed*2π / 60".

[0022] According to the "torque-acceleration" formula: (1) It turns out that: (2) Further integration of the entire startup process: (3) in: (4) (5) Where J is the moment of inertia, is the angular acceleration, P SFC is the SFC output power, P 阻 is the resistance power, T SFC is the starting torque of SFC, T 阻is the resistance torque. From the above, it can be seen that in order to achieve the driving torque output by the static frequency converter SFC within the specified time, it is necessary to accelerate the water pump to the rated speed and then start the synchronous grid-connected device to complete and realize the grid connection.

[0023] In specific application examples, the synchronization process should meet the following three conditions: 1) △U =│Ug ─ Us│= 0; 2) △f =│fg ─ fs│= 0; 3) δ = 0° Among them, Ug is the voltage on the side to be connected; Us is the voltage on the system side; △U is the voltage difference between the two sides; fg is the frequency on the side to be connected; fs is the frequency on the system side; △f is the frequency difference between the two sides; δ is the phase angle difference between the two sides.

[0024] In a specific application example, in step S1, the speed for setting the threshold value is 101-110% of the rated speed; as a preferred embodiment, in this embodiment, the speed for setting the threshold value is 105% of the rated speed.

[0025] In a specific application example, in step S3, the pump turbine is allowed to inertialy reduce its speed to 49.8-50.2 Hz.

[0026] In a specific application example, in step S4, the synchronization device quickly adjusts the DC excitation device to increase the machine terminal voltage from 12 kV to 18 kV.

[0027] The present invention further provides a storage medium, which can be read by a computer or a processor and stores a computer program for executing the above method.

[0028] Those skilled in the art should understand that the above-mentioned embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application can take the form of a computer program product implemented on one or more computer-readable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the process Figure 1 A process or multiple processes and / or boxes Figure 1 These computer program instructions can also be stored in a computer-readable memory that can guide a computer or other programmable data processing device to work in a specific way, so that the instructions stored in the computer-readable memory produce a product including an instruction device, which implements the functions specified in the process. Figure 1 A process or multiple processes and / or boxes Figure 1 These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide for implementing the process in the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0029] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A pumped storage SFC driven idle synchronous grid-connected control method, characterized in that: include: Step S1: Driving the pump turbine to a speed of a set threshold through the static frequency converter SFC; The set threshold is higher than the rated speed of the pump turbine; Step S2: Start to enter the synchronous grid connection stage; Step S3: the static frequency converter SFC is locked, and the output circuit breaker of the static frequency converter SFC is opened to allow the pump turbine to inertialy decelerate to a set threshold; Step S4: quickly adjust the DC excitation device to raise the terminal voltage to the same level as the grid-connected voltage; Step S5: When the grid-connected parameters are met, the automatic quasi-synchronous device issues a closing command to close the grid-connected circuit breaker and complete the grid-connected connection.

2. The pumped storage SFC dragging idle synchronous grid-connected control method according to claim 1 is characterized in that: In step S1, the speed for setting the threshold is 101-110% of the rated speed.

3. The pumped storage SFC dragging idle synchronous grid-connected control method according to claim 1 is characterized in that: The speed of the set threshold is 105% of the rated speed.

4. The method for controlling synchronous grid connection under idle speed of pumped storage SFC drag according to any one of claims 1 to 3, characterized in that: In step S3, the pump turbine is decelerated to 49.8-50.2 Hz by inertia.

5. The method for controlling synchronous grid connection under idle speed of pumped storage SFC drag according to any one of claims 1 to 3, characterized in that: In step S4, the synchronization device quickly adjusts the DC excitation device to increase the machine end voltage from 12 kV to 18 kV.

6. The method for controlling synchronous grid connection under idle speed of pumped storage SFC drag according to any one of claims 1 to 3, characterized in that: In step S2, the synchronization process satisfies the following three conditions: 1) △U =│Ug ─ Us│= 0; 2) △f =│fg ─ fs│= 0; 3) δ = 0° Among them, Ug is the voltage on the side to be connected; Us is the voltage on the system side; △U is the voltage difference between the two sides; fg is the frequency on the side to be connected; fs is the frequency on the system side; △f is the frequency difference between the two sides; δ is the phase angle difference between the two sides.

7. The pumped storage SFC dragging idle synchronous grid-connected control method according to claim 6 is characterized in that: If this process fails to connect to the grid, the voltage at the DC excitation regulator terminal is consistent with the SFC output voltage, and the SFC device is re-started at high speed.

8. A storage medium, which can be read by a computer or a processor, characterized in that: The storage medium stores a computer program for executing any one of the methods in claims 1-6.

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