Self-starting synchronous grid-connected control method and system for variable-speed pumped storage unit

Abstract

The invention discloses a self-starting synchronous grid-connected control method and system for a variable-speed pumped storage unit, and the method comprises the steps: inputting an AC excitation system according to a pumping phase modulation or power generation phase modulation self-starting command of the unit, and controlling the AC excitation system to work in a self-starting mode corresponding to a target working condition; after the rotating speed of the unit reaches the preset rotating speed, exiting the alternating-current excitation system; controlling the alternating-current excitation system to work in an operation mode corresponding to the target working condition, and inputting the alternating-current excitation system to build voltage; after voltage building is completed, whether the synchronization condition is met or not is judged, if yes, a closing relay outlet is triggered, a synchronization checking relay carries out secondary checking on a synchronization checking device outlet at the same time, when the closing condition is met, a closing loop is conducted, and synchronization grid-connected control is completed. According to the method, the problem that the impact risk exists on the power grid and the unit due to the fact that synchronization check does not exist in grid connection in the self-starting process of an existing variable-speed unit can be solved, self-starting synchronization grid connection of the variable-speed unit can be safely and rapidly achieved, and impact during grid connection is avoided.

Description

Technical Field

[0001] The present invention belongs to the field of pumped storage industry control, and in particular relates to a variable speed pumped storage unit self-starting synchronous grid-connected control method and system. Background Art

[0002] Pumped storage is one of the important energy storage methods, which is characterized by large capacity and mature technology. With the construction of new power systems with new energy as the main body, pumped storage has entered a period of rapid development. Variable speed pumped storage technology is an important development direction of pumped storage in the future. Compared with fixed speed pumped storage units, variable speed pumped storage units have outstanding performance advantages, such as higher efficiency, faster power regulation speed, adjustable pump direction and power, etc., which can greatly improve the system's flexible adjustment ability and new energy absorption capacity, and provide better support for the construction of new power systems.

[0003] In addition to the characteristics of grid support, the units also have certain differences from fixed-speed units in terms of starting. For example, variable-speed units have the functions of self-starting for pumping phase adjustment and power generation phase adjustment, and do not require static inverter drag. At present, variable-speed units use direct grid-connected solutions in the grid-connected stage after startup, relying on the tracking function of the AC excitation system inverter on the grid voltage. There is no synchronous inspection link, which poses certain safety hazards. Summary of the invention

[0004] The purpose of the present invention is to provide a variable speed pumped storage unit self-starting synchronous grid-connected control method and system to solve the problem that there is no synchronous check during the self-starting process of the existing variable speed unit and the risk of impact on the power grid and the unit. The variable speed unit can be safely and quickly self-started and synchronized to the grid. Compared with the traditional variable speed unit without a synchronous device and direct closing scheme, the present invention can improve the safety during grid connection and avoid impact during grid connection.

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

[0006] A variable speed pumped storage unit self-starting synchronous grid-connected control method comprises the following steps:

[0007] Step 1: according to the self-starting command of the unit's pumping phase adjustment or power generation phase adjustment, the AC excitation system is put into operation and controlled to work in the self-starting mode corresponding to the target operating condition;

[0008] Step 2: After the unit speed reaches the preset speed, exit the AC excitation system;

[0009] Step 3, controlling the AC excitation system to operate in an operation mode corresponding to the target operating condition, and starting the AC excitation system to build up pressure;

[0010] Step 4: After the voltage is built up, the closing circuit is turned on when the synchronization conditions and closing conditions are met, completing the synchronization grid-connected control.

[0011] In the above step 4, the voltage amplitude deviation, voltage frequency deviation and voltage phase deviation on the unit side and the grid side are obtained. If each deviation is less than the first set value, it is considered that the synchronization condition is met; if each deviation is less than the second set value, it is considered that the closing condition is met.

[0012] In the above step 4, two relays are set between the unit and the grid to perform synchronization condition judgment. When the synchronization condition is met, the first relay output is triggered. Then, the closing condition is judged and the second relay output is triggered when the closing condition is met.

[0013] A variable speed pumped storage unit self-starting synchronous grid-connected control system, comprising:

[0014] The monitoring system unit is configured to control the AC excitation system to provide excitation current to the rotor of the generator motor according to the unit pumping phase adjustment or power generation phase adjustment self-starting command, so as to increase the speed and build up the pressure of the unit, and issue a start synchronization command after the pressure is built up;

[0015] The AC excitation system is configured to operate in a self-starting mode or a running mode under the control of the monitoring system unit;

[0016] A synchronization checking device is configured to perform synchronization condition discrimination according to the start synchronization command issued by the monitoring system unit, and trigger an internal closing relay output when the synchronization condition is met; and,

[0017] The synchronous check relay is configured to judge the closing condition when closing the relay output and trigger the output after the closing condition is met.

[0018] The synchronization checking device is connected in series with the synchronization checking relay.

[0019] After adopting the above scheme, the beneficial effect of the present invention is that it can realize the self-starting function of the variable speed unit in the pumping phase adjustment and power generation phase adjustment conditions. At the same time, through double synchronization checks, it avoids the impact problem existing in the existing variable speed unit when directly connected to the grid due to abnormal grid voltage tracking of the AC excitation system, and can more smoothly control the unit from static start-up to grid connection process. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a flow chart of the self-starting synchronous grid-connected control of the variable speed pumped storage unit of the present invention;

[0021] Figure 2 It is a schematic diagram of the composition of the variable speed pumped storage unit self-starting synchronous grid-connected control system of the present invention. DETAILED DESCRIPTION

[0022] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0023] like Figure 1 As shown, it is a flow chart of an embodiment of the control method for self-starting synchronous grid connection of a variable speed pumped storage unit of the present invention. When the variable speed unit switches from a stationary state to a pumping phase adjustment or a power generation phase adjustment, the following steps are included:

[0024] S1, the monitoring system unit LCU receives the unit pumping phase adjustment or power generation phase adjustment self-starting command;

[0025] S2. Set the AC excitation system to the corresponding self-starting mode (pumping phase adjustment self-starting mode or power generation phase adjustment self-starting mode) according to the target operating conditions, close the short-circuit switch at the machine end, put the AC excitation system into operation, and increase the speed of the unit;

[0026] S3, when the monitoring system unit LCU detects that the unit speed reaches the preset speed, it exits the AC excitation system and disconnects the short-circuit switch at the unit end;

[0027] S4. After the short-circuit switch at the machine end is separated, the AC excitation system is set to the target operating mode, the AC excitation system is re-activated to build voltage and track the grid voltage, frequency and phase to avoid impact at the moment of switch closing;

[0028] S5. After the pressure is built up, the monitoring system unit LCU issues a start synchronization command, and the synchronization check device determines the synchronization conditions. When the synchronization conditions are met, the internal closing relay output is triggered. The synchronization check device output is also checked by the synchronization check relay for a second time. When the synchronization conditions of the synchronization check device and the closing conditions of the synchronization check relay are met, the closing circuit is turned on and the synchronization grid-connected control is completed. If they are not met, the unit fails to start and is shut down.

[0029] In step S5, the synchronization condition involves the relationship between the system side voltage and the voltage on the side to be connected, and the difference between the tracked machine-side voltage data and the grid data is compared with a fixed value, specifically including: voltage amplitude deviation < first voltage difference fixed value, voltage frequency deviation < first frequency fixed value, voltage phase deviation < first phase difference fixed value. When all three conditions are met, it is considered that the synchronization condition is met;

[0030] In step S5, the closing conditions are synchronously checked, including: voltage amplitude deviation < second voltage difference constant, voltage frequency deviation < second frequency constant, voltage phase deviation < second phase difference constant. When all three conditions are met, the closing conditions are considered to be met; wherein, the second voltage difference constant may be appropriately higher than the first voltage difference constant, the second frequency constant may be appropriately higher than the first frequency constant, and the second phase difference constant may be appropriately higher than the first phase difference constant.

[0031] In order to realize the above-mentioned self-starting process, the present invention also provides an embodiment of a self-starting synchronous grid-connected control system for a variable speed pumped storage unit, such as Figure 2 As shown, it includes: a monitoring system unit LCU, an AC excitation system, a synchronization check device and a synchronization check relay; wherein, the monitoring system unit LCU receives external instructions, controls the AC excitation system to provide excitation current to the rotor of the generator motor, which is used for unit speed increase and voltage building, and at the same time, the monitoring system unit LCU receives the unit speed and machine-end voltage signals, starts the synchronization check device, and the synchronization check device and the synchronization check relay are serially connected in the closing circuit, and the synchronization check relay performs secondary verification of the synchronization grid-connected process, and finally completes the closing of the unit.

[0032] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes. The schemes in the embodiments of the present invention may be implemented in various computer languages, for example, object-oriented programming language Java and literal scripting language JavaScript, etc.

[0033] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks 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 flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0034] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0035] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0036] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0037] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A variable speed pumped storage unit self-starting synchronous grid-connected control method, characterized in that The steps include: Step 1: according to the self-starting command of the unit's pumping phase adjustment or power generation phase adjustment, the AC excitation system is put into operation and controlled to work in the self-starting mode corresponding to the target operating condition; Step 2: After the unit speed reaches the preset speed, exit the AC excitation system; Step 3, controlling the AC excitation system to operate in an operation mode corresponding to the target operating condition, and starting the AC excitation system to build up pressure; Step 4: After the voltage is built up, the closing circuit is turned on when the synchronization conditions and closing conditions are met, completing the synchronization grid-connected control.

2. The method according to claim 1, characterized in that: In step 4, the voltage amplitude deviation, voltage frequency deviation and voltage phase deviation on the unit side and the grid side are obtained. If each deviation is less than a first set value, it is considered that the synchronization condition is met; if each deviation is less than a second set value, it is considered that the closing condition is met.

3. The method according to claim 1, characterized in that: In step 4, two relays are set between the unit and the power grid to perform synchronization condition judgment. When the synchronization condition is met, the first relay output is triggered. Then, the closing condition is judged and the second relay output is triggered when the closing condition is met.

4. A variable speed pumped storage unit self-starting synchronous grid-connected control system, characterized in that: include, The monitoring system unit is configured to control the AC excitation system to provide excitation current to the rotor of the generator motor according to the unit pumping phase adjustment or power generation phase adjustment self-starting command, so as to increase the speed and build up the pressure of the unit, and issue a start synchronization command after the pressure is built up; The AC excitation system is configured to operate in a self-starting mode or a running mode under the control of the monitoring system unit; The synchronization checking device is configured to judge the synchronization conditions according to the start synchronization command issued by the monitoring system unit, and trigger the internal closing relay output when the synchronization conditions are met; as well as, The synchronous check relay is configured to judge the closing condition when closing the relay output and trigger the output after the closing condition is met.

5. The system according to claim 4, characterized in that: The synchronization checking device is connected in series with the synchronization checking relay.

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