SFC and flexible excitation integrated system for pumped storage unit and control method of SFC and flexible excitation integrated system
By designing an integrated SFC and flexible excitation system, and adopting fully controlled switching devices and a parallel architecture, the pumped storage unit has achieved efficient and reliable operation under multiple operating conditions, solving the problems of limited speed regulation range and non-reusability of hardware resources, and improving the system's integration and grid adaptability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- THREE GORGES INTELLIGENT CONTROL TECHNOLOGY CO LTD
- Filing Date
- 2026-04-20
- Publication Date
- 2026-05-19
AI Technical Summary
Existing pumped storage units have limited SFC speed regulation range, slow dynamic response speed, and cannot reuse hardware resources. The control signal interaction is delayed and interfered with, resulting in low system integration, high cost, and complex operation and maintenance, making it difficult to meet the unit's high-efficiency operation under multiple operating conditions.
Design an integrated SFC and flexible excitation system, adopting a parallel architecture of isolation module, grid-side rectifier module, smoothing module and machine-side converter module. Utilize fully controllable switching devices and disconnect switches to realize dual-function multiplexing of SFC inverter and flexible excitation, and adapt to different operating conditions by switching through control logic.
It improves the hardware integration and reliability of the system, reduces equipment costs and maintenance difficulty, optimizes startup performance and excitation regulation accuracy, and enhances the adaptability of the unit under multiple operating conditions and its grid compatibility.
Smart Images
Figure CN122068804A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of pumped storage unit control technology, and specifically relates to an integrated SFC and flexible excitation system and its control method for pumped storage units. Background Technology
[0002] Pumped storage units, as crucial peak-shaving and frequency-regulating equipment in power systems, directly impact grid stability and energy efficiency through their startup and control performance. Currently, pumped storage units commonly employ static frequency converters (SFCs) for speed control during startup, coupled with independent flexible excitation systems to provide precise excitation regulation. However, existing technologies still have several shortcomings in system architecture, component selection, and functional coordination. Regarding SFC power conversion, most current pumped storage units utilize thyristors (SCRs) as the core switching device, with a topology primarily based on a thyristor-based three-phase bridge rectifier-inverter circuit. As semi-controlled power electronic devices, thyristors can only achieve on-state control and cannot actively turn off, resulting in limited SFC speed range and slow dynamic response, making it difficult to meet the smooth startup requirements of the unit across a wide speed range. Furthermore, thyristor topologies rely on complex commutation circuits to maintain power flow switching, which not only increases system hardware complexity but also easily introduces higher harmonic interference, adversely affecting the power quality of the grid and the unit. In terms of system integration, existing pumped storage units with flexible excitation typically employ a hardware architecture where the SFC (Self-Fueling Controller) and flexible excitation system are independent. The SFC handles the unit's startup speed regulation function alone, while the flexible excitation system has independent excitation converters, regulating units, and other hardware. This separate architecture results in the inability to reuse hardware resources between the two systems, low equipment integration, and large installation space requirements. Simultaneously, control signals between the SFC and the flexible excitation system need to interact across devices, posing risks of transmission delays and signal interference. This reduces the accuracy of coordinated control during the switching between startup and excitation conditions, and also increases the complexity and cost of system design and maintenance. Therefore, there is an urgent need for an integrated system that can combine the SFC start-up function and the flexible excitation function to overcome the shortcomings of existing technologies in terms of speed regulation performance, system integration, control coordination and harmonic suppression, and improve the operating efficiency and reliability of pumped storage units under multiple operating conditions. Summary of the Invention
[0003] To address the aforementioned issues, this invention provides an integrated SFC and flexible excitation system and its control method for pumped-storage units. This system solves the problems of limited speed regulation range, slow dynamic response, difficulty in adapting to the wide-speed start-up requirements of units using traditional thyristor-type SFCs, separate hardware structure, inability to reuse hardware resources, and transmission delay and interference issues caused by cross-device interaction of control signals between the SFC and flexible excitation systems.
[0004] An integrated SFC and flexible excitation system for pumped-storage units includes: The isolation module has its input end connected to the power grid to achieve electrical isolation and voltage adaptation between the power grid and the power conversion unit. The grid-side rectifier module has its AC input terminal connected to the output terminal of the isolation module, and its DC output terminal connected to the DC bus, which is used to convert the AC power from the grid side into DC power. The input terminal of the smoothing module is connected to the DC output terminal of the grid-side rectifier module, and the output terminal of the smoothing module is connected to the machine-side converter module and the excitation converter module respectively, for stabilizing DC power transmission. The generator-side converter module has its DC input terminal connected to the smoothing module and its AC output terminal connected to the generator stator. It is used to achieve dual-function multiplexing of SFC inverter and flexible excitation chopper through control logic.
[0005] According to a specific embodiment of the present invention, the isolation module includes three sets of harmonic suppression circuits and an isolation transformer. The three sets of harmonic suppression circuits are connected to the isolation transformer through an isolation switch K1.
[0006] According to a specific embodiment of the present invention, the harmonic suppression circuit includes a grid-side reactor and a resistor, wherein the grid-side reactor and the resistor are connected in series.
[0007] According to a specific embodiment of the present invention, the isolation transformer is a Δ / Y type isolation transformer.
[0008] According to a specific embodiment of the present invention, the grid-side rectifier module includes multiple sets of three-phase full-bridge rectifier circuits, which are connected in parallel.
[0009] According to a specific embodiment of the present invention, the three-phase full-bridge rectifier circuit includes six fully controlled switching devices.
[0010] According to a specific embodiment of the present invention, the smoothing module includes a smoothing reactor and a DC support capacitor.
[0011] According to a specific embodiment of the present invention, the generator-side converter module includes two sets of parallel three-phase full-bridge inverter circuits. Each set of three-phase full-bridge inverter circuits includes an upper bridge arm and a lower bridge arm. The AC sides of the two sets of bridge arms are connected in parallel and connected to the generator stator. The DC sides of the two sets of bridge arms are connected to the DC bus.
[0012] According to a specific embodiment of the present invention, the switching devices in the three-phase full-bridge inverter circuit are fully controlled power electronic devices.
[0013] A control method for an integrated SFC and flexible excitation system for pumped-storage units includes: When the unit is in pumping mode, the disconnect switch K1 is closed, the generator-side converter module switches to SFC inverter mode, and provides starting power to the unit stator. When the unit speed reaches the rated value and is synchronized with the grid, the control disconnect switch K1 is opened, and the generator-side converter module switches to DC chopper mode to provide excitation current to the unit rotor. When the unit is in power generation mode, it is directly started through the grid or synchronizing device. The generator-side converter module switches to flexible excitation mode and runs continuously, providing excitation current to the unit rotor.
[0014] Compared with the prior art, the integrated SFC and flexible excitation system and its control method for pumped-storage units provided by the present invention have the following advantages: 1. Hardware integration optimization, simplified topology and reduced overall cost: This invention achieves dual-function multiplexing of SFC inverter start-up and flexible excitation chopper through the parallel architecture of switching devices and the collaborative design of disconnecting switches. It eliminates the need for independent excitation converter modules and dedicated hardware for operating condition switching in traditional solutions, greatly simplifying the system hardware topology and reducing equipment manufacturing costs, installation space occupation and subsequent operation and maintenance difficulty.
[0015] 2. Enhanced power carrying capacity and redundancy fault tolerance to ensure reliable system operation: The two sets of three-phase full-bridge parallel architectures designed in this invention enhance the module's power carrying capacity, adapting to the high-power start-up and excitation requirements of large pumped storage units. At the same time, it forms hardware redundancy, so that when a single switching device or a single bridge arm fails, the remaining units can maintain the core function output, significantly improving the reliability and fault tolerance of the system operation.
[0016] 3. Optimize startup performance, reduce impact and improve speed regulation smoothness: This invention uses fully controlled switching devices to replace traditional thyristors, and with PWM precise control, it realizes continuous adjustment of frequency / voltage during the unit startup phase, solving the problems of narrow speed regulation range and slow response of thyristors. This makes the unit's acceleration process from standstill to rated speed smoother, significantly reduces startup inrush current, and reduces the impact on the unit's mechanical structure and the power grid.
[0017] 4. Enhance excitation regulation accuracy and improve unit adaptability to the grid: When the generator-side converter module switches to DC chopper mode, the excitation current amplitude and direction are dynamically adjusted through the four-quadrant control of the switching devices. The flexible excitation has a fast response speed and high regulation accuracy, effectively maintaining the stability of the generator terminal voltage and improving the unit's reactive power regulation capability and grid adaptability under power generation / pumping conditions.
[0018] 5. Adapting to multiple operating conditions and expanding the application scenarios of the technical solution: The integrated design of SFC and flexible excitation of this invention is adapted to the multi-condition switching requirements of pumped storage units, namely "start-up-power generation-pumping". No additional hardware is required. The functional requirements under different operating conditions can be met by simply switching the control logic. This enhances the versatility and scenario adaptability of the technical solution and can be widely used in pumped storage units of different capacities and voltage levels. Attached Figure Description
[0019] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0020] Figure 1 This is a circuit diagram of an integrated SFC and flexible excitation system for pumped storage units according to an embodiment of the present invention. Detailed Implementation
[0021] To enable those skilled in the art to more clearly understand the concepts and ideas of the present invention, the present invention is described in detail below with reference to specific embodiments. It should be understood that the embodiments given herein are only a part of all possible embodiments of the present invention. Those skilled in the art, after reading this specification, are capable of making improvements, modifications, or substitutions to parts or the entirety of the following embodiments, and such improvements, modifications, or substitutions are also included within the scope of protection claimed by the present invention.
[0022] In this document, the terms “announcement,” “arrival,” and other similar words are not intended to imply any order, quantity, or importance, but are merely used to distinguish different elements. The terms “one,” “a,” and other similar words are not intended to indicate the existence of only one thing, but rather that the description pertains to only one of the things, which may have one or more. The terms “contains,” “includes,” and other similar words are intended to indicate a logical relationship, not a spatial relationship. For example, “A includes B” means that logically B belongs to A, not that spatially B is located inside A. Furthermore, the meanings of the terms “contains,” “includes,” and other similar words should be considered open-ended, not closed. For example, “A includes B” means that B belongs to A, but B does not necessarily constitute all of A; A may also include other elements such as C, D, and E.
[0023] In this document, the terms "embodiment," "this embodiment," "an embodiment," and "one embodiment" do not imply that the description applies only to one specific embodiment, but rather that such description may also be applicable to one or more other embodiments. Those skilled in the art will understand that any description made herein with respect to one embodiment can be substituted, combined, or otherwise combined with the descriptions in one or more other embodiments. New embodiments resulting from such substitutions, combinations, or other combinations are readily conceived by those skilled in the art and fall within the scope of protection of this invention.
[0024] Example 1 Additional aspects and advantages of embodiments of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of embodiments of the invention. Figure 1 This invention provides an integrated SFC and flexible excitation system for pumped-storage units, comprising: The isolation module has its input connected to the power grid to achieve electrical isolation and voltage adaptation between the power grid and the power conversion unit.
[0025] The grid-side rectifier module has its AC input terminal connected to the output terminal of the isolation module, and its DC output terminal connected to the DC bus, which is used to convert AC power from the grid side into DC power.
[0026] The smoothing module has its input terminal connected to the DC output terminal of the grid-side rectifier module, and its output terminal connected to the machine-side converter module and the excitation converter module, respectively, for stabilizing DC power transmission.
[0027] The generator-side converter module has its DC input terminal connected to the smoothing module and its AC output terminal connected to the generator stator. It is used to achieve dual-function multiplexing of SFC inverter and flexible excitation chopper through control logic.
[0028] Specifically, the isolation module includes three sets of harmonic suppression circuits and an isolation transformer. The three sets of harmonic suppression circuits are connected to the isolation transformer through the disconnect switch K1. The harmonic suppression circuit includes a grid-side reactor and a resistor, with the grid-side reactor and the resistor connected in series.
[0029] In one specific embodiment of the present invention, the isolation module serves as the electrical interface between the system and the power grid, undertaking the functions of grid-side power access, isolation, and adaptation. It is a fundamental unit ensuring stable interaction between the system and the power grid. This module employs three sets of series circuits composed of grid-side reactors and resistors, working in conjunction with an isolation transformer to achieve electrical isolation between the power grid and the power conversion unit. In this embodiment, the isolation transformer is a Δ / Y type isolation transformer. This module design effectively suppresses grid-side harmonic injection, buffers inrush currents between the power grid and the system, and adapts to the voltage levels of the power grid and the power conversion unit through commutation of the isolation transformer.
[0030] Specifically, the grid-side rectifier module includes multiple sets of three-phase full-bridge rectifier circuits connected in parallel. Each three-phase full-bridge rectifier circuit includes six fully controlled switching devices.
[0031] In one specific embodiment of the present invention, the grid-side rectifier module is the core unit for the system to convert AC power to DC power. This module is responsible for converting the AC power from the grid side into stable DC power required by the DC bus, that is, rectifying the AC power output from the isolation transformer into stable DC power, which is the energy input terminal for subsequent power conversion. This module consists of multiple sets of parallel three-phase full-bridge rectifier circuits. The present invention adopts a multi-module parallel architecture to improve the power capacity of the system, and at the same time, it can realize hardware redundancy. When a single module fails, other modules can be activated, thus not affecting the operation of the system.
[0032] Specifically, the smoothing module includes a smoothing reactor and a DC support capacitor.
[0033] In one specific embodiment of the present invention, the smoothing module, serving as a common carrier for power transmission and buffering within the system, connects the grid-side rectifier module, the machine-side inverter module, and the excitation converter module, and is the core hub for realizing power sharing among multiple modules. This module connects between the grid-side rectifier module and the machine-side inverter module. By configuring a large-capacity smoothing reactor and a DC support capacitor, it can suppress voltage ripple and current fluctuations on the DC bus, stabilize DC power transmission, and simultaneously provide common DC power to the grid-side rectifier module, the machine-side inverter module, and the excitation converter module.
[0034] Specifically, the generator-side converter module includes two sets of parallel three-phase full-bridge inverter circuits. Each set of three-phase full-bridge inverter circuits includes an upper bridge arm and a lower bridge arm. The AC sides of the two bridge arms are connected in parallel to the generator stator, and the DC sides of the two bridge arms are connected to the DC bus. The switching devices in the three-phase full-bridge inverter circuit are fully controlled power electronic devices.
[0035] In a specific embodiment of the present invention, the generator-side converter module is the core power unit for realizing the dual-function multiplexing of SFC start-up and flexible excitation in this system. This module adapts to the parallel topology of switching devices and control logic, and simultaneously carries the inverter speed regulation and DC chopping functions for excitation regulation during unit start-up. It is a key carrier for the hardware integration of this system. The module adopts a two-set parallel three-phase full-bridge inverter circuit architecture, which not only improves the power carrying capacity of the module and can adapt to the high power demand of pumped storage units, but also realizes hardware redundancy. When a single module fails, the remaining circuit modules can continue to maintain functional output. At the same time, the module has dual-function multiplexing of inverter and DC chopping. With the exit mechanism design of the isolating switch, the traditional independent excitation converter module and additional operating condition switching hardware are eliminated, which greatly improves the integration of the device and the reliability of operating condition switching.
[0036] In one specific embodiment of the present invention, the generator-side converter module can also be replaced with a single multilevel converter module. The multilevel converter module is a multilevel three-phase full-bridge topology composed of several switching devices. The AC side of this module is connected to the generator stator via an isolating switch, and the DC side is connected to a common DC bus. It is also connected to the generator rotor via a branch switching switch. Through multilevel switching device control logic optimization, this module achieves dual-function multiplexing of inverter speed regulation (SFC function) and DC chopping (excitation function) within the same module. There is no need to add an independent module. The integration of SFC and flexible excitation can be completed simply by optimizing the level of the topology and branch switching, thus meeting the dual-function requirements of generator start-up speed regulation and excitation regulation.
[0037] In a specific embodiment of the present invention, the generator-side converter module can be further optimized into a high-frequency optimized parallel topology. This structure adopts the core architecture of two sets of three-phase full-bridge inverter circuits connected in parallel, and optimizes the topology adaptation design for the high-frequency characteristics of the switching devices. Specifically, a miniaturized smoothing buffer module is configured on the DC side to reduce the buffer unit capacity by utilizing the high-frequency characteristics of the switching devices. The connection logic between its AC side and the generator stator and excitation branch remains integrated. Through high-frequency control strategy optimization, the power conversion efficiency and operating condition switching response speed are improved. Without changing the core logic of "parallel architecture + dual-function multiplexing", the efficient integration of SFC and flexible excitation is achieved by adapting the topology to high-frequency operation requirements, while simplifying the DC side hardware configuration and further improving the system integration.
[0038] Example 2 Based on the above system, embodiments of the present invention also provide a control method for an integrated SFC and flexible excitation system for pumped-storage units, comprising: When the unit is in pumping mode, the disconnect switch K1 is closed, the generator-side converter module switches to SFC inverter mode, and provides starting power to the unit stator. When the unit speed reaches the rated value and is synchronized with the grid, the control disconnect switch K1 is opened, and the generator-side converter module switches to DC chopper mode to provide excitation current to the unit rotor. When the unit is in power generation mode, it is directly started through the grid or synchronizing device. The generator-side converter module switches to flexible excitation mode and runs continuously, providing excitation current to the unit rotor.
[0039] In a specific embodiment of the present invention, when the unit is in pumping operation, the isolating switch K1 is closed, and the generator-side converter module operates in inverter mode. Through PWM (pulse width modulation) control of the switching devices, the power from the DC bus is inverted into three-phase AC power with continuously adjustable frequency and voltage. Two sets of parallel three-phase full-bridge inverter circuits output synchronously, jointly providing the driving power required for startup to the generator stator, realizing a smooth speed-up of the unit from standstill to synchronous speed. When the unit speed reaches the rated value and is synchronized with the grid, the isolating switch K1 is opened, cutting off the electrical connection between the generator-side converter module and the generator stator. At this time, the inverter function of the SFC stops, the generator-side converter module exits the pumping operation state, and the functional closed loop of the pumping operation is completed. After the SFC (Sequencing Factor Control) is deactivated, the generator-side converter module switches to DC chopper mode. By controlling the on / off timing of the switching devices, it converts the electrical energy from the DC bus into a dynamically adjustable DC excitation current with variable amplitude and direction. At this time, the two parallel three-phase full-bridge inverter circuits are equivalent to a four-quadrant DC chopper, utilizing the characteristics of the switching devices to achieve rapid regulation of the excitation current, providing flexible excitation support for the generator rotor. When the generator is in generating mode, it is started directly by the grid or synchronizing device without the need for SFC. Simultaneously, the generator-side converter module seamlessly switches to flexible excitation mode and continues to operate, ensuring stable power supply under generating conditions. In this state, the module acts as an independent, full-performance excitation regulator, providing excitation current to the generator rotor in generating mode. Leveraging the full control characteristics and rapid response capabilities of the switching devices, this module can efficiently perform advanced auxiliary functions such as voltage regulation, reactive power support, and power system stabilizer, ensuring stable and efficient operation of the generator and the grid.
[0040] In summary, the integrated SFC and flexible excitation system and its control method for pumped-storage units described in this invention have the following advantages: 1. Hardware integration optimization, simplified topology and reduced overall cost: This invention achieves dual-function multiplexing of SFC inverter start-up and flexible excitation chopper through the parallel architecture of switching devices and the collaborative design of disconnecting switches. It eliminates the need for independent excitation converter modules and dedicated hardware for operating condition switching in traditional solutions, greatly simplifying the system hardware topology and reducing equipment manufacturing costs, installation space occupation and subsequent operation and maintenance difficulty.
[0041] 2. Enhanced power carrying capacity and redundancy fault tolerance to ensure reliable system operation: The two sets of three-phase full-bridge parallel architectures designed in this invention enhance the module's power carrying capacity, adapting to the high-power start-up and excitation requirements of large pumped storage units. At the same time, it forms hardware redundancy, so that when a single switching device or a single bridge arm fails, the remaining units can maintain the core function output, significantly improving the reliability and fault tolerance of the system operation.
[0042] 3. Optimize startup performance, reduce impact and improve speed regulation smoothness: This invention uses fully controlled switching devices to replace traditional thyristors, and with PWM precise control, it realizes continuous adjustment of frequency / voltage during the unit startup phase, solving the problems of narrow speed regulation range and slow response of thyristors. This makes the unit's acceleration process from standstill to rated speed smoother, significantly reduces startup inrush current, and reduces the impact on the unit's mechanical structure and the power grid.
[0043] 4. Enhance excitation regulation accuracy and improve unit adaptability to the grid: When the generator-side converter module switches to DC chopper mode, the excitation current amplitude and direction are dynamically adjusted through the four-quadrant control of the switching devices. The flexible excitation has a fast response speed and high regulation accuracy, effectively maintaining the stability of the generator terminal voltage and improving the unit's reactive power regulation capability and grid adaptability under power generation / pumping conditions.
[0044] 5. Adapting to multiple operating conditions and expanding the application scenarios of the technical solution: The integrated design of SFC and flexible excitation of this invention is adapted to the multi-condition switching requirements of pumped storage units, namely "start-up-power generation-pumping". No additional hardware is required. The functional requirements under different operating conditions can be met by simply switching the control logic. This enhances the versatility and scenario adaptability of the technical solution and can be widely used in pumped storage units of different capacities and voltage levels.
[0045] The concepts, principles, and ideas of the present invention have been described in detail above with reference to specific embodiments (including examples and instances). Those skilled in the art should understand that the embodiments of the present invention are not limited to those given above. After reading this application, those skilled in the art can make any possible improvements, substitutions, and equivalents to the steps, methods, systems, and components in the above embodiments. These improvements, substitutions, and equivalents should be considered to fall within the scope of the present invention, and the scope of protection of the present invention is limited to the claims.
Claims
1. An integrated SFC and flexible excitation system for pumped-storage units, characterized in that, include: An isolation module, the input of which is connected to the power grid, is used to achieve electrical isolation and voltage adaptation between the power grid and the power conversion unit; A grid-side rectifier module, wherein the AC input terminal of the grid-side rectifier module is connected to the output terminal of the isolation module, and the DC output terminal of the grid-side rectifier module is connected to the DC bus, for converting AC power from the grid side into DC power; The smoothing module has its input terminal connected to the DC output terminal of the grid-side rectifier module, and its output terminal connected to the machine-side converter module and the excitation converter module, respectively, for stabilizing DC power transmission. The generator-side converter module has its DC input terminal connected to the smoothing module and its AC output terminal connected to the generator stator. It is used to realize the dual-function multiplexing of SFC inverter and flexible excitation chopper through control logic.
2. The integrated SFC and flexible excitation system for pumped-storage units according to claim 1, characterized in that, The isolation module includes three sets of harmonic suppression circuits and an isolation transformer. The three sets of harmonic suppression circuits are connected to the isolation transformer through an isolation switch K1.
3. The integrated SFC and flexible excitation system for pumped-storage units according to claim 2, characterized in that, The harmonic suppression circuit includes a grid-side reactor and a resistor, with the grid-side reactor connected in series with the resistor.
4. The integrated SFC and flexible excitation system for pumped-storage units according to claim 2, characterized in that, The isolation transformer is a Δ / Y type isolation transformer.
5. The integrated SFC and flexible excitation system for pumped-storage units according to claim 1, characterized in that, The grid-side rectifier module includes multiple sets of three-phase full-bridge rectifier circuits, which are connected in parallel.
6. The integrated SFC and flexible excitation system for pumped-storage units according to claim 5, characterized in that, The three-phase full-bridge rectifier circuit includes six fully controlled switching devices.
7. The integrated SFC and flexible excitation system for pumped-storage units according to claim 1, characterized in that, The smoothing module includes a smoothing reactor and a DC support capacitor.
8. The integrated SFC and flexible excitation system for pumped-storage units according to claim 1, characterized in that, The generator-side converter module includes two sets of parallel three-phase full-bridge inverter circuits. Each set of three-phase full-bridge inverter circuits includes an upper bridge arm and a lower bridge arm. The AC sides of the two sets of bridge arms are connected in parallel to the generator stator, and the DC sides of the two sets of bridge arms are connected to the DC bus.
9. The integrated SFC and flexible excitation system for pumped-storage units according to claim 8, characterized in that, The switching devices in the three-phase full-bridge inverter circuit are fully controlled power electronic devices.
10. A control method for an integrated SFC and flexible excitation system for pumped-storage units, the method being based on the integrated SFC and flexible excitation system for pumped-storage units as described in claim 1, characterized in that... include: When the unit is in pumping mode, the disconnect switch K1 is closed, the generator-side converter module switches to SFC inverter mode, and provides starting power to the unit stator. When the unit speed reaches the rated value and is synchronized with the grid, the control disconnect switch K1 is opened, and the generator-side converter module switches to DC chopper mode to provide excitation current to the unit rotor. When the unit is in power generation mode, it is directly started through the grid or synchronizing device. The generator-side converter module switches to flexible excitation mode and runs continuously, providing excitation current to the unit rotor.