Primary frequency modulation method based on deep coupling of energy storage system and coal power unit

Abstract

The invention belongs to the technical field of primary frequency modulation of a power system, and relates to a primary frequency modulation method based on deep coupling of an energy storage system and a coal power unit. Comprising the following steps: acquiring historical primary frequency modulation assessment action data of a coal power unit, determining power and capacity configuration of an energy storage system according to the historical primary frequency modulation assessment action data, and enabling the power and capacity configuration to cover effective frequency modulation actions in a preset proportion; the energy storage system is connected to the station service bus of the coal power unit through a boosting transformer; a PMU of the coal power unit is transformed, voltage and current signals of the energy storage system and the coal power unit are coupled to form a synthetic total power signal, and the synthetic total power signal is uploaded to a scheduling end; when the frequency of the power grid fluctuates, the valve adjusting function of the DEH / CCS of the coal power unit is locked, the energy storage system directly responds to a frequency modulation instruction and outputs compensation power, the frequency of the power grid is pulled back to a dead zone, and efficient, rapid and accurate response of primary frequency modulation is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of primary frequency regulation of power systems, and relates to a primary frequency regulation method based on deep coupling of an energy storage system and a coal-fired power unit. Background Art

[0002] Currently, coal-fired power units play a crucial role in the primary frequency regulation of the power grid. However, traditional frequency regulation relies primarily on the coal-fired unit's DEH (Digital Electro-Hydraulic Control System) and CCS (Coordinated Control System) to adjust the turbine valve opening to change the unit's power load. However, this approach suffers from slow response, low regulation accuracy, and severe unit wear.

[0003] In recent years, energy storage systems have been introduced into the primary frequency regulation of coal-fired power units to assist them in completing frequency regulation tasks. However, existing energy storage-assisted frequency regulation technologies mostly use a passive tracking mode, with weak coupling between the energy storage system and the coal-fired unit. Energy storage does not interfere with the operation of the coal-fired unit or change its operating status. In this mode, the energy storage system performs logical judgment and power response only after the coal-fired unit's DEH system responds, resulting in high latency. This also risks the coal-fired unit's primary frequency regulation being reversed, further increasing the charging and discharging pressure on the energy storage system.

[0004] Currently, the main methods for implementing energy storage-assisted primary frequency regulation of coal-fired power units include: (1) Passive tracking mode: After the DEH system of the coal-fired power unit responds, the energy storage system adjusts power according to the frequency regulation command. However, the coupling between the energy storage system and the coal-fired power unit is weak and cannot intervene in the operation of the unit in real time.

[0005] (2) Independent frequency regulation mode: The energy storage system independently participates in the grid frequency regulation and is completely separated from the frequency regulation function of the coal-fired power units. Although this mode reduces the frequency regulation pressure of the coal-fired power units, it cannot fully utilize the frequency regulation capabilities of the coal-fired power units, resulting in limited overall frequency regulation performance.

[0006] In summary, the limitations of existing technologies mainly include: (1) High response delay: The energy storage system performs logical judgment and power regulation only after the DEH system of the coal-fired power unit responds, resulting in a long frequency regulation response time and an inability to quickly respond to grid frequency fluctuations.

[0007] (2) Serious reverse regulation: Coal-fired power units may experience reverse regulation during a frequency regulation process, that is, the frequency regulation direction is opposite to the direction of grid frequency change. This not only reduces the frequency regulation effect, but also increases the charging and discharging pressure of the energy storage system.

[0008] (3) Severe wear of the units: Frequent adjustment of valve openings in coal-fired power units leads to increased wear of the units, shortening the life of the equipment and increasing maintenance costs.

[0009] (4) Poor economic efficiency: The existing energy storage-assisted frequency regulation mode cannot fully utilize the frequency regulation capability of coal-fired power units, resulting in a large capacity demand for the energy storage system and increasing the system construction cost. Summary of the Invention

[0010] In order to solve the problems of high response delay, serious back-regulation phenomenon, severe unit wear and poor economy existing in the energy storage-assisted primary frequency regulation technology of coal-fired power units in the existing technology, the present invention provides a primary frequency regulation method based on deep coupling of energy storage system and coal-fired power units, so as to achieve efficient, fast and accurate response of primary frequency regulation.

[0011] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention provides a primary frequency modulation method based on deep coupling of an energy storage system and a coal-fired power unit, comprising the following steps: Obtain historical primary frequency regulation assessment action data for coal-fired power units and, based on this data, determine the power and capacity configuration of the energy storage system to cover a preset proportion of effective frequency regulation actions. Connect the energy storage system to the coal-fired power plant busbar through a step-up transformer; The PMUs of coal-fired power units were modified to couple the energy storage system with the voltage and current signals of the coal-fired power units to form a synthetic total power signal and upload it to the dispatching end. When the grid frequency fluctuates, the valve adjustment function of the DEH / CCS of the coal-fired power unit is locked, and the energy storage system directly responds to the frequency regulation command and outputs compensation power to pull the grid frequency back within the dead zone.

[0012] Preferably, the preset ratio is 95%.

[0013] Preferably, the historical frequency regulation assessment action data includes the power shortage, theoretical integrated power and response time of each effective action.

[0014] Preferably, the energy storage system uses lithium iron phosphate batteries, whose power configuration meets the power shortage covering ≥95% of effective actions, and whose capacity configuration meets the theoretical integral power demand of the corresponding actions.

[0015] Preferably, the response delay of the energy storage system is ≤50ms, and the frequency modulation power output accuracy error is ≤1% of the rated power.

[0016] Preferably, the specific method for transforming the PMU of the coal-fired power unit is: The voltage signal of the energy storage system is connected in parallel to the PMU input, and the current signal of the energy storage system is superimposed in series on the current sampling loop, so that the power data received by the dispatching end is the real-time algebraic sum of the power of the coal-fired power unit and the energy storage system.

[0017] Preferably, the specific method for blocking the valve adjustment function of the DEH / CCS of the coal-fired power unit when the grid frequency fluctuates is: When the frequency fluctuation exceeds the dead zone, a locking command is sent to the DEH / CCS system to force the valve opening to remain unchanged until the energy storage system completes the frequency modulation response and the frequency returns to the dead zone.

[0018] Preferably, the voltage level of the step-up transformer matches the plant bus voltage of the coal-fired power unit, and its capacity is not less than 120% of the rated power of the energy storage system.

[0019] Preferably, before the synthesized total power signal is uploaded to the dispatching end, it needs to be verified by the plant AGC system to ensure that it is consistent with the actual grid-connected power.

[0020] Preferably, the method further includes establishing frequency modulation instruction allocation logic: When the power shortage is less than the rated power of the energy storage system, the energy storage system will respond independently; When the power shortage exceeds the rated power of the energy storage system, the energy storage system outputs at full power, and the remaining shortage is supplemented by the coal-fired power unit through valve adjustment.

[0021] Compared with the prior art, the present invention has the following beneficial effects: Through the deep coupling of the energy storage system and coal-fired power units, an efficient and rapid response to grid frequency fluctuations is achieved, completely avoiding the mechanical wear caused by valve adjustment during the frequency regulation of traditional coal-fired power units, and significantly extending the service life of the unit's key equipment; PMU transformation and power synthesis ensure the accuracy and consistency of monitoring data on the dispatching end, fundamentally solving the common reverse regulation phenomenon in traditional solutions; the direct response of the energy storage system has significantly improved the frequency regulation speed, and can pull the grid frequency back to the dead zone range at a speed of milliseconds, effectively shortening the frequency limit time and achieving efficient, fast and accurate response of primary frequency regulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 Flow chart of the method of the present invention; Figure 2 This is the electrical coupling topology diagram of the energy storage system and coal-fired power unit in the present invention.

[0024] Among them: 1. Primary frequency modulation frequency transmitter; 2. DCS control system; 3. Steam turbine; 4. Generator; 5. Energy storage control system; 6. Dispatching system. DETAILED DESCRIPTION

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0026] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0027] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0028] In the description of the embodiments of the present invention, it should be noted that if the terms "upper," "lower," "horizontal," "inner," etc. appear, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the inventive product is typically placed when in use. These terms are merely for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first," "second," etc. are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0029] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0030] In the description of the embodiments of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0031] The present invention is described in further detail below with reference to the accompanying drawings: The present invention provides a primary frequency regulation method based on deep coupling of energy storage system and coal-fired power unit. Through deep coupling of energy storage system and coal-fired power unit, the valve regulation of the unit is directly replaced by energy storage power response, the frequency is pulled back to within the dead zone, and the full replacement of primary frequency regulation is achieved, mechanical loss and response delay are eliminated, and the data consistency of the dispatching end is ensured through the power synthesis of the electrical secondary system. Figure 1 As shown, the specific steps include: Obtain historical primary frequency regulation assessment action data for coal-fired power units (including the power shortfall, theoretical integrated power, and response time for each effective action). Based on this historical primary frequency regulation assessment action data, determine the power and capacity configuration of the energy storage system to cover a preset proportion (95%) of effective frequency regulation actions. Connect the energy storage system to the coal-fired power plant busbar through a step-up transformer; Modify the phasor measurement units (PMUs) of coal-fired power units to couple the voltage and current signals of the energy storage system with those of the coal-fired power units, generating a composite total power signal that is uploaded to the dispatching end. When the grid frequency fluctuates, the valve adjustment function of the DEH / CCS of the coal-fired power unit is locked, and the energy storage system directly responds to the frequency regulation command and outputs compensation power to pull the grid frequency back within the dead zone.

[0032] The primary frequency regulation method based on deep coupling of energy storage systems and coal-fired power units, provided by this invention, achieves efficient and rapid response to grid frequency fluctuations through deep coupling of the energy storage system and coal-fired power units. This method completely avoids the mechanical wear caused by valve adjustment during the frequency regulation process of traditional coal-fired power units, significantly extending the service life of the unit's key equipment. The direct response of the energy storage system significantly improves frequency regulation speed, enabling the grid frequency to be brought back within the dead zone within milliseconds, effectively shortening the time it takes for the frequency to exceed the limit. PMU modification and power synthesis ensure the accuracy and consistency of monitoring data at the dispatch end, fundamentally resolving the back-regulation phenomenon common in traditional solutions. This method not only significantly improves frequency regulation performance, but also enables additional ancillary service revenue from energy storage participation in frequency regulation, while reducing assessment costs incurred due to substandard frequency regulation. Furthermore, an intelligent capacity configuration method based on historical data enables the energy storage system to accurately match actual frequency regulation needs, improving resource utilization efficiency. This invention achieves the deep integration of coal-fired power units and energy storage, providing an innovative solution for the coordinated control of traditional power sources and energy storage in the context of new power systems, effectively enhancing the safe and stable operation of the power grid.

[0033] The energy storage system utilizes lithium iron phosphate batteries, whose power configuration meets the power shortfall required to cover ≥95% of effective operations and whose capacity configuration meets the theoretical integrated power requirements of the corresponding operations. The high rate capability of the lithium iron phosphate batteries provides the system with instantaneous power support, while their advantageous cycle life ensures long-term economical operation. Its power and capacity configurations are optimized based on analysis of historical frequency regulation data, ensuring coverage for the vast majority of frequency regulation scenarios. This ensures that the energy storage system has both sufficient power output to cope with grid frequency fluctuations and adequate energy reserves to meet continuous regulation needs, thereby optimizing the utilization of frequency regulation resources. Furthermore, the energy storage system boasts a response delay of ≤50ms and a frequency regulation power output accuracy error of ≤1% of rated power, enabling near-real-time and precise compensation for grid frequency fluctuations. This ultra-fast response enables the system to promptly detect and eliminate subtle deviations in grid frequency, effectively suppressing secondary frequency fluctuations caused by mechanical delays in traditional frequency regulation methods. High-precision power output control not only ensures the accuracy of frequency regulation but also avoids common issues such as over- and under-regulation, making the frequency recovery process smoother and more reliable.

[0034] The specific method for transforming the PMU of the coal-fired power unit is as follows: The voltage signal of the energy storage system is connected in parallel to the PMU input, and the current signal of the energy storage system is superimposed in series on the current sampling loop, so that the power data received by the dispatching end is the real-time algebraic sum of the power of the coal-fired power unit and the energy storage system.

[0035] By modifying the PMU measurement circuit and adopting a voltage-parallel, current-series signal coupling method, this invention achieves a deep integration of coal-fired power units and energy storage systems at the electrical measurement level. This non-invasive modification solution allows the power data received by the dispatcher to naturally present the real-time power superposition value of the unit and energy storage. It not only fully retains the measurement function of the original PMU, but also accurately reflects the actual output of the joint frequency modulation. It effectively solves the problem of inconsistent monitoring data in traditional parallel systems and fundamentally avoids the misjudgment of reverse modulation caused by signal asynchrony. At the same time, it does not require changing the operating logic and data processing methods of the existing dispatch system 6.

[0036] The specific method for blocking the valve adjustment function of the DEH / CCS of the coal-fired power unit when the grid frequency fluctuates is as follows: When the frequency fluctuation exceeds the dead zone, a locking command is sent to the DEH / CCS system to force the valve opening to remain unchanged until the energy storage system completes the frequency modulation response and the frequency returns to the dead zone.

[0037] The present invention uses the DEH / CCS locking control strategy to actively cut off the valve regulation loop of the DEH / CCS system when the grid frequency fluctuates, forcing the valve opening of turbine 3 to remain constant, so that the frequency regulation task is completely undertaken by the energy storage system with a faster response speed. This method not only completely avoids the regulation lag and reverse regulation caused by valve mechanical delay in traditional frequency regulation methods, but also significantly reduces the mechanical wear of key equipment of the unit. Secondly, when the frequency returns to the normal range, the locking state is released, realizing the timing optimization coordination between the thermal power unit and the energy storage system in the frequency regulation process, which not only retains the operating stability of the unit itself, but also gives full play to the rapid regulation advantage of energy storage. The voltage level of the step-up transformer matches the plant bus voltage of the coal-fired power units, and its capacity is no less than 120% of the energy storage system's rated power. This proper voltage matching reduces energy conversion losses, while the capacity redundancy design provides a reliable guarantee for the system to cope with sudden high power demands, enabling the energy storage system to fully utilize its rapid frequency regulation capabilities.

[0038] Before being uploaded to the dispatching end, the synthesized total power signal must be verified by the plant's AGC system to ensure consistency with the actual grid-connected power. This not only maintains the dispatching system's precise control of the power plant's output, but also ensures data transparency when the energy storage system participates in frequency regulation, ensuring that grid dispatch instructions and actual execution results remain synchronized. This data consistency assurance mechanism not only improves the reliability of frequency regulation control but also avoids misadjustments or assessment disputes caused by data errors, providing reliable data support for grid dispatch operations under the new source-storage collaborative model.

[0039] The method of the present invention further includes establishing frequency modulation instruction allocation logic: When the power shortage is less than the rated power of the energy storage system, the energy storage system will respond independently; When the power shortage exceeds the rated power of the energy storage system, the energy storage system outputs at full power, and the remaining shortage is supplemented by the coal-fired power unit through valve adjustment.

[0040] This approach not only ensures that the unit's valves do not need to be activated in most frequency regulation scenarios, effectively reducing equipment wear, but also provides reliable protection in extreme situations, ensuring that the system can always meet the grid's frequency regulation requirements. By rationally dividing the regulation responsibilities between energy storage and the units, this technical solution maximizes the life of the energy storage system while maintaining frequency regulation performance and reduces the unit's operating and maintenance costs. This creates an optimized operating mode that balances economy and reliability, providing a flexible and efficient solution for traditional thermal power units to participate in grid frequency regulation.

[0041] The working process of the present invention is as follows: like Figure 2 As shown, the primary frequency regulation control of the power system is a dynamic process in which multiple links work together. The dispatching system 6, as the core control center, obtains grid frequency information in real time by connecting to the primary frequency regulation frequency transmitter 1, and issues dispatching instructions accordingly. The frequency transmitter continuously monitors changes in grid frequency and transmits frequency signals to the dispatching system 6 and the unit PMU. The unit PMU accurately measures key electrical parameters such as voltage and current of the generator 4, providing data support for subsequent power regulation. These measurement data are transmitted to the unit + energy storage output synthesis unit, which comprehensively analyzes the unit output and energy storage system output through an intelligent algorithm, calculates the optimal power adjustment plan based on the frequency deviation value, and realizes the coordinated control of power generation and energy storage.

[0042] On the power generation side, DCS control system 2 receives control signals from the primary frequency regulator and adjusts parameters such as the steam inlet to steam turbine 3 to alter the unit's output. As the prime mover, adjustments to steam turbine 3's output power directly affect the power generation of generator 4. Generator 4 converts mechanical energy into electrical energy, which is then boosted to grid transmission voltage levels by the main transformer, enabling efficient long-distance transmission of electrical energy. Simultaneously, a high-voltage plant transformer draws power from the main transformer and provides reliable power to the power plant's internal equipment via the 6kV plant busbar.

[0043] The energy storage control system 5 adjusts output in real time based on the unit's primary frequency regulation parameters. By continuously monitoring the voltage and current parameters of sections A and B of the energy storage system, it ensures that the system operates within a safe range. The power storage converter (PCS), as the core power regulation device, precisely controls the charging and discharging processes of the energy storage system, enabling efficient energy exchange with the grid. The power output of the energy storage system is boosted by a dedicated step-up transformer and then fed into the grid, complementing the output of generator 4.

[0044] The entire frequency regulation process forms a closed-loop control loop: when the grid frequency fluctuates, the frequency transmitter immediately detects the deviation and transmits the signal to each control system. Dispatch system 6 integrates global information and issues optimization instructions. Generator 4 adjusts power via the DCS, while the energy storage system rapidly responds via the PCS. This deep synergy between power generation and energy storage not only optimizes the allocation of frequency regulation resources but also establishes a complete control chain from frequency monitoring to power regulation, ensuring that the grid frequency remains stable and significantly improving the dynamic response and operational reliability of the power system.

[0045] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A primary frequency modulation method based on deep coupling of energy storage system and coal-fired power unit, characterized in that: The following steps are involved: Obtain historical primary frequency regulation assessment action data for coal-fired power units and, based on this data, determine the power and capacity configuration of the energy storage system to cover a preset proportion of effective frequency regulation actions. Connect the energy storage system to the coal-fired power plant busbar through a step-up transformer; The PMUs of coal-fired power units were modified to couple the energy storage system with the voltage and current signals of the coal-fired power units to form a synthetic total power signal and upload it to the dispatching end. When the grid frequency fluctuates, the valve adjustment function of the DEH / CCS of the coal-fired power unit is locked, and the energy storage system directly responds to the frequency regulation command and outputs compensation power to pull the grid frequency back within the dead zone.

2. A primary frequency modulation method based on deep coupling of energy storage system and coal-fired power unit according to claim 1, characterized in that: The preset ratio is 95%.

3. The primary frequency modulation method based on deep coupling of energy storage system and coal-fired power unit according to claim 1, characterized in that: The historical frequency regulation assessment action data includes the power shortage, theoretical integrated power and response time of each effective action.

4. A primary frequency modulation method based on deep coupling of energy storage system and coal-fired power unit according to claim 3, characterized in that: The energy storage system uses lithium iron phosphate batteries, whose power configuration meets the power shortage covering ≥95% of effective actions, and whose capacity configuration meets the theoretical integral power demand of the corresponding actions.

5. The primary frequency modulation method based on deep coupling of energy storage system and coal-fired power unit according to claim 1, characterized in that: The response delay of the energy storage system is ≤50ms, and the frequency modulation power output accuracy error is ≤1% of the rated power.

6. A primary frequency modulation method based on deep coupling of energy storage system and coal-fired power unit according to claim 1, characterized in that: The specific method for transforming the PMU of the coal-fired power unit is as follows: The voltage signal of the energy storage system is connected in parallel to the PMU input, and the current signal of the energy storage system is superimposed in series on the current sampling loop, so that the power data received by the dispatching end is the real-time algebraic sum of the power of the coal-fired power unit and the energy storage system.

7. The primary frequency modulation method based on deep coupling of energy storage system and coal-fired power generation unit according to claim 1, characterized in that: The specific method for blocking the valve adjustment function of the DEH / CCS of the coal-fired power unit when the grid frequency fluctuates is as follows: When the frequency fluctuation exceeds the dead zone, a locking command is sent to the DEH / CCS system to force the valve opening to remain unchanged until the energy storage system completes the frequency modulation response and the frequency returns to the dead zone.

8. The primary frequency modulation method based on deep coupling of energy storage system and coal-fired power generation unit according to claim 1, characterized in that: The voltage level of the step-up transformer matches the bus voltage of the coal-fired power unit, and its capacity is not less than 120% of the rated power of the energy storage system.

9. The primary frequency modulation method based on deep coupling of energy storage system and coal-fired power unit according to claim 1, characterized in that: Before the synthesized total power signal is uploaded to the dispatching end, it must be verified by the plant AGC system to ensure that it is consistent with the actual grid-connected power.

10. The primary frequency modulation method based on deep coupling of energy storage system and coal-fired power unit according to claim 1, characterized in that: It also includes establishing the frequency modulation instruction distribution logic: When the power shortage is less than the rated power of the energy storage system, the energy storage system will respond independently; When the power shortage exceeds the rated power of the energy storage system, the energy storage system outputs at full power, and the remaining shortage is supplemented by the coal-fired power unit through valve adjustment.

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