A flywheel energy storage primary system for a two-on-one combined cycle unit

Abstract

The embodiment of the present disclosure provides a two-in-one combined cycle unit flywheel energy storage primary system, comprising: a flywheel energy storage system composed of single or multiple flywheel energy storage units in parallel, and configured with a battery management system and a converter control system; an access and switching system, comprising an energy storage transformer, an energy storage incoming line cabinet, a PT cabinet, an energy storage feeder cabinet, an energy storage grid-connected cabinet, a flywheel feeder cabinet, a fast protection device, a synchronization device and an island protection device; a coordinated control system for coordinated frequency regulation, peak regulation and load smoothing of the combined cycle unit and the flywheel energy storage system. Wherein, the grid-connected point of the flywheel energy storage system is arranged at the off-phase bus between the steam turbine generator unit and the steam turbine main transformer. The present disclosure realizes millisecond-level fast frequency regulation response by connecting the flywheel energy storage system to the off-phase bus on the steam turbine side, effectively compensates for the slow adjustment rate of the steam turbine, and improves the unit frequency regulation performance, load tracking accuracy and operation flexibility.

Description

Technical Field

[0001] The embodiments disclosed herein belong to the field of gas-steam combined cycle power generation and energy storage grid connection technology, specifically relating to a flywheel energy storage primary system for a two-to-one combined cycle unit. Background Technology

[0002] The "two-to-one" gas-steam combined cycle unit consists of two gas turbines, one steam turbine, and corresponding waste heat boilers and generators. It boasts advantages such as high efficiency, low carbon footprint, and rapid start-up and shutdown, and is widely used for grid peak shaving and combined heat and power (CHP). However, in scenarios involving deep peak shaving, rapid primary frequency regulation, AGC response, and renewable energy grid connection, existing combined cycle units exhibit the following problems: Gas turbine and steam turbine regulation suffers from inertia and delay, resulting in insufficient frequency regulation accuracy and limited ramp-up rate. Frequent load changes exacerbate unit fatigue losses, reducing equipment lifespan and operational economy. When grid frequency fluctuates significantly, the unit struggles to provide rapid support within milliseconds, impacting power supply quality and system stability. Typically, steam turbine generator sets do not have a 6kV auxiliary line, requiring a T-connection between the low-voltage side of the steam turbine main transformer and the phase busbar between the steam turbine generator set, necessitating the addition of an energy storage transformer and a substation.

[0003] Flywheel energy storage is a physical energy storage method, characterized by millisecond-level response, high power density, long cycle life, no power decay during charging and discharging, and environmental friendliness. It can rapidly absorb / release power, significantly improving the unit's frequency regulation capability, load tracking performance, and operational flexibility. Currently, most combined cycle units do not have flywheel energy storage, or only use simple parallel connections, lacking dedicated topologies, protection coordination, node access, and collaborative control structures that match the original primary system, making it difficult to achieve safe, efficient, and stable combined operation. Summary of the Invention

[0004] The embodiments of this disclosure aim to at least solve one of the technical problems existing in the prior art, and provide a flywheel energy storage primary system for a two-to-one combined cycle unit. The combined cycle unit includes two gas turbine generator sets, a gas turbine main transformer, a waste heat boiler, a high-voltage station service transformer, and one steam turbine generator set and a steam turbine main transformer. The flywheel energy storage primary system includes: The flywheel energy storage system consists of one or more flywheel energy storage units connected in parallel; the flywheel energy storage unit includes a flywheel rotor, a magnetic levitation bearing, a bidirectional electric motor / generator, a power electronic converter, a vacuum chamber and a cooling system, and is equipped with a battery management system and a converter control system; The access and switching system includes energy storage transformers, energy storage incoming line cabinets, PT cabinets, energy storage feeder cabinets, energy storage grid-connected cabinets, flywheel feeder cabinets, fast protection devices, synchronizing devices, and islanding protection devices. The coordinated control system is used for coordinated frequency regulation, peak shaving, and load smoothing of combined cycle units and flywheel energy storage systems. The grid connection point of the flywheel energy storage system is located on the phase-separated bus between the steam turbine generator set and the steam turbine main transformer.

[0005] Optionally, the rated power of the flywheel energy storage system is 5MW, and the capacity of the energy storage transformer is 6MW.

[0006] Furthermore, the access and switching system also includes an incoming line cabinet located in the booster compartment, the incoming line cabinet including a vacuum circuit breaker, a disconnecting switch, a surge arrester, and a grounding switch.

[0007] Furthermore, the cooperative control system is used for: When the grid frequency deviates from the rated value, the flywheel is triggered to rapidly absorb or generate additional power; and / or, Receive dispatch instructions to compensate for the unit's ramp rate; and / or, Smooth out power output fluctuations and reduce the operation of steam turbines and their valves.

[0008] Furthermore, the cooperative control system is used for: During periods of low grid load, the flywheel energy storage system is controlled to absorb excess power for charging. During peak grid load periods, the flywheel energy storage system is controlled to release power for discharge, thereby smoothing out fluctuations in generator output.

[0009] Furthermore, the flywheel energy storage system is equipped with an independent operation mode and a combined operation mode; In independent operation mode, the flywheel energy storage system is used to provide power balance support for the plant; In the combined operation mode, the flywheel energy storage system is used to cooperate with the combined cycle unit in frequency regulation, peak shaving and AGC regulation.

[0010] Furthermore, the flywheel energy storage system is equipped with a 380V low-voltage compartment and two 380V station power supplies.

[0011] Furthermore, the two gas turbine generator sets are connected to the power grid through the two gas turbine main transformers respectively; The steam turbine generator set is connected to the power grid through the steam turbine main transformer.

[0012] Furthermore, the rapid protection device, in conjunction with the synchronization device and the islanding protection device, performs protection linkage between the flywheel energy storage system and the combined cycle unit.

[0013] Furthermore, the collaborative control system is specifically used for: It collects grid frequency, unit output, energy storage SOC and dispatch commands, and outputs unit load commands, flywheel charging and discharging commands and protection linkage signals.

[0014] This disclosure discloses a flywheel energy storage primary system for a two-to-one combined cycle unit. By setting the grid connection point of the flywheel energy storage system at the phase bus between the steam turbine generator set and the steam turbine main transformer, and by setting up an access and switching system and a coordinated control system, it achieves close coupling and coordinated control between the flywheel energy storage and the combined cycle unit on the steam turbine side. This effectively solves the technical problem that the steam turbine cannot meet the requirements of primary frequency regulation and AGC commands due to its slow regulation rate and long response time. Because the flywheel energy storage system has millisecond-level response characteristics, it can quickly compensate for the insufficient regulation capability of the steam turbine, thereby significantly improving the overall frequency regulation performance and load tracking accuracy of the combined cycle unit. At the same time, by smoothing out output fluctuations, it reduces the frequent operation of the steam turbine and its valves, reduces equipment fatigue wear, and extends equipment life. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of a flywheel energy storage primary system of a two-to-one combined cycle power unit according to an embodiment of the present disclosure. Detailed Implementation

[0016] The technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. Based on the embodiments of this disclosure, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this disclosure.

[0017] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this disclosure. However, those skilled in the art will recognize that the technical solutions of this disclosure can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this disclosure.

[0018] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0019] It should be understood that although the terms first, second, third, etc., may be used in this disclosure to describe various components, these components should not be limited by these terms. These terms are used to distinguish one component from another. Therefore, the first component discussed below may be referred to as the second component without departing from the teachings of this disclosure. As used in this disclosure, the term "and / or" includes all combinations of any one and more of the associated listed items.

[0020] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of exemplary embodiments, and the modules or processes in the drawings are not necessarily necessary for implementing this disclosure, and therefore cannot be used to limit the scope of protection of this disclosure.

[0021] In the two-to-one combined cycle steam turbine unit, the two gas turbines can meet the requirements of the grid dispatching side in terms of regulation rate, accuracy, and response time for AGC frequency regulation commands and primary frequency regulation commands, so there is no need to install flywheel energy storage. However, the steam turbine, due to its slow regulation rate and long response time, cannot meet the grid dispatching side's AGC frequency regulation commands and primary frequency regulation commands. Therefore, a flywheel energy storage system is installed in this unit to meet the grid dispatching side's frequency regulation command requirements for each of the three units.

[0022] like Figure 1 As shown, embodiments of this disclosure provide a flywheel energy storage primary system for a two-to-one combined cycle power unit. The primary system includes a two-to-one combined cycle power unit 100, comprising two high-voltage plant service transformers T1 and T2, two gas turbine generator sets GT1 and GT2, two gas turbine main transformers T3 and T4, two waste heat boilers HRSG1 and HRSG2, one steam turbine generator set ST, and one steam turbine main transformer T5. Addressing the problems of insufficient primary frequency regulation capability, slow load regulation response, and high equipment losses in two-to-one gas-steam combined cycle power units, a flywheel energy storage system, an access and switching system, and a collaborative control system are added. The grid connection point of the flywheel energy storage system 200 is located on the phase-separated bus between the steam turbine generator set ST and the steam turbine main transformer T5, achieving seamless access, collaborative control, and protection linkage between the flywheel energy storage and the combined cycle power unit, thereby improving the unit's frequency regulation performance, peak shaving capability, and operational stability.

[0023] The flywheel energy storage system 200 consists of one or more flywheel energy storage units connected in parallel, with a rated power of 5MW, a response time ≤10ms, an efficiency ≥95%, and a cycle life ≥10. 6Each flywheel energy storage unit comprises a flywheel rotor, magnetic bearings, a bidirectional electric motor / generator, a power electronic converter, a vacuum chamber, and a cooling system, and is equipped with a Battery Management System (BMS) and a Power Conversion System (PCS). The flywheel energy storage system consists of multiple flywheel energy storage units connected in parallel. Power distribution and current sharing control are achieved through the power electronic converter, SOC (State of Charge) balancing management is achieved through the Battery Management System, and thermal management is achieved through the cooling system.

[0024] In the combined cycle unit 100, two gas turbine generator sets GT1 and GT2 are connected to the grid through two gas turbine main transformers T3 and T4, respectively, and the steam turbine generator set ST is connected to the grid through the steam turbine main transformer T5; the phase bus is set between the steam turbine generator set ST and the steam turbine main transformer T5, and the 5MW flywheel energy storage system 200 is connected to the grid through this phase bus.

[0025] The access and switching system includes: a 6MW energy storage transformer located in the plant's front area; energy storage incoming line cabinets, PT cabinets, and energy storage feeder cabinets located in the substation; energy storage grid-connected cabinets, PT cabinets, and a 5MW flywheel feeder cabinet located in the medium-voltage compartment; incoming line cabinets, step-up transformers, and protection and control devices located in the step-up compartment; fast protection devices, synchronizing devices, and islanding protection devices. The incoming line cabinets include vacuum circuit breakers, disconnect switches, surge arresters, and grounding switches to ensure safe operation and maintenance of the equipment.

[0026] The coordinated control system is used to collect grid frequency, generator output, energy storage SOC, and dispatch commands, and outputs generator load commands, flywheel charge / discharge commands, and protection linkage signals to achieve coordinated frequency regulation, peak shaving, and load smoothing between the combined cycle generator and the flywheel energy storage system. Specific functions are as follows: 1. Primary frequency regulation: When the grid frequency deviates from the rated value, the coordinated control system triggers the flywheel energy storage system in milliseconds to quickly absorb or generate additional power, thereby achieving short-term high-power support and reducing the unit's regulation pressure; 2. AGC Regulation: The collaborative control system receives dispatch AGC commands and uses the flywheel energy storage system to quickly compensate for the insufficient ramp rate of the combined cycle unit, achieving fast and accurate load tracking; the 5MW flywheel energy storage system can meet about 75% of the AGC frequency regulation command requirements, effectively compensating for the frequency regulation command requirements of each unit from the grid dispatch side. 3. Load smoothing: The collaborative control system quickly absorbs or releases power through the flywheel energy storage system, smooths out the output fluctuations of the unit, reduces the frequent operation of the steam turbine and its valves and actuators, thereby reducing equipment fatigue wear and extending equipment life; 4. Peak shaving operation: During periods of low grid load, the coordinated control system controls the flywheel energy storage system to absorb excess power for charging; during periods of high grid load, the system controls the flywheel energy storage system to release power for discharging, thereby smoothing out fluctuations in unit output and improving the peak shaving depth and economy of the combined cycle unit.

[0027] The flywheel energy storage system has two operating modes: independent operation and joint operation. In independent operation mode, the flywheel energy storage system is used to provide power balance support for the plant and ensure the stability of the plant power system. In joint operation mode, the flywheel energy storage system is used to cooperate with the combined cycle unit to participate in frequency regulation, peak shaving and AGC regulation to achieve overall performance optimization.

[0028] The flywheel energy storage system area also includes a 380V low-voltage compartment with two 380V station auxiliary power supplies. One supply is drawn from the 400V common PC A section of the generating units, and the other is drawn from the 400V common PC B section of the generating units. The station auxiliary low-voltage system uses a single busbar connection, and the incoming line is equipped with an ATS (Automatic Transfer Switch). When the main power supply fails, the backup power supply automatically switches on, ensuring the reliability of the flywheel energy storage system's auxiliary power supply.

[0029] The fast protection device works in conjunction with the synchronizing device and the islanding protection device to achieve protection linkage between the flywheel energy storage system and the combined cycle unit. Specifically, when a grid fault or unit abnormality is detected, the fast protection device quickly activates and disconnects the flywheel energy storage system from the off-phase bus; the synchronizing device ensures that voltage, frequency, and phase meet synchronization conditions when the flywheel energy storage system is reconnected to the grid to avoid impact; and the islanding protection device maintains system stability and ensures safety during islanded operation.

[0030] This disclosure discloses a primary flywheel energy storage system for a two-to-one combined cycle power unit. By connecting a 5MW flywheel energy storage system to the off-phase bus of the steam turbine, and designing a complete connection and switching system and a coordinated control system, the following beneficial effects are achieved: (1) Improved fast frequency regulation capability: The flywheel energy storage system has a millisecond-level response, which effectively compensates for the slow regulation rate of the steam turbine, so that the combined cycle unit as a whole can meet the requirements of the primary frequency regulation and AGC command of the power grid; (2) Improved load tracking performance: The flywheel compensates for the insufficient ramp rate of the unit, improves the tracking accuracy of AGC, and reduces the risk of scheduling assessment; (3) Reduced equipment fatigue wear: The flywheel quickly absorbs / releases power, smooths out power fluctuations, reduces the frequent operation of the steam turbine and its valves and actuators, and extends the equipment life; (4) Improved system safety: The configuration of fast protection, islanding protection, and synchronization device realizes the protection linkage between the flywheel system and the unit, ensuring safe grid connection and islanding operation; (5) Improved operational flexibility: Supports independent operation (for plant power balance) and joint operation (participation in frequency regulation and peak shaving), improving the overall economy and flexibility of the power plant.

[0031] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.

Claims

1. A flywheel energy storage primary system for a two-to-one combined cycle power unit, wherein the combined cycle power unit comprises two gas turbine generator sets, a gas turbine main transformer, a waste heat boiler, a high-voltage station service transformer, and one steam turbine generator set and a steam turbine main transformer, characterized in that, The flywheel energy storage primary system includes: The flywheel energy storage system consists of one or more flywheel energy storage units connected in parallel; the flywheel energy storage unit includes a flywheel rotor, a magnetic levitation bearing, a bidirectional electric motor / generator, a power electronic converter, a vacuum chamber and a cooling system, and is equipped with a battery management system and a converter control system; The access and switching system includes energy storage transformers, energy storage incoming line cabinets, PT cabinets, energy storage feeder cabinets, energy storage grid-connected cabinets, flywheel feeder cabinets, fast protection devices, synchronizing devices, and islanding protection devices. The coordinated control system is used for coordinated frequency regulation, peak shaving, and load smoothing of combined cycle units and flywheel energy storage systems. The grid connection point of the flywheel energy storage system is located on the phase-separated bus between the steam turbine generator set and the steam turbine main transformer.

2. The primary system according to claim 1, characterized in that, The rated power of the flywheel energy storage system is 5MW, and the capacity of the energy storage transformer is 6MW.

3. The primary system according to claim 1, characterized in that, The access and switching system also includes an incoming line cabinet located in the booster chamber, which includes a vacuum circuit breaker, a disconnecting switch, a surge arrester, and a grounding switch.

4. The primary system according to claim 1, characterized in that, The collaborative control system is used for: When the grid frequency deviates from the rated value, the flywheel is triggered to rapidly absorb or generate additional power; and / or, Receive dispatch instructions to compensate for the unit's ramp rate; and / or, Smooth out power output fluctuations and reduce the operation of steam turbines and their valves.

5. The primary system according to claim 4, characterized in that, The collaborative control system is used for: During periods of low grid load, the flywheel energy storage system is controlled to absorb excess power for charging. During peak grid load periods, the flywheel energy storage system is controlled to release power for discharge, thereby smoothing out fluctuations in generator output.

6. The primary system according to claim 1, characterized in that, The flywheel energy storage system is equipped with an independent operation mode and a combined operation mode; In independent operation mode, the flywheel energy storage system is used to provide power balance support for the plant; In the combined operation mode, the flywheel energy storage system is used to cooperate with the combined cycle unit in frequency regulation, peak shaving and AGC regulation.

7. The primary system according to claim 1, characterized in that, The flywheel energy storage system is equipped with a 380V low-voltage compartment and two 380V station power supplies.

8. The primary system according to claim 1, characterized in that, The two gas turbine generator sets are respectively connected to the power grid through the two gas turbine main transformers; The steam turbine generator set is connected to the power grid through the steam turbine main transformer.

9. The primary system according to claim 1, characterized in that, The rapid protection device works in conjunction with the synchronization device and the islanding protection device to perform protection linkage between the flywheel energy storage system and the combined cycle unit.

10. The primary system according to claim 1, characterized in that, The collaborative control system is specifically used for: It collects grid frequency, unit output, energy storage SOC and dispatch commands, and outputs unit load commands, flywheel charging and discharging commands and protection linkage signals.

Images