A multi-time scale connected thermal power energy storage and frequency modulation method

Abstract

The application provides a thermal power energy storage coordinated frequency modulation method with multi-time scale connection. The method judges a disturbance stage according to a frequency deviation and a change rate, divides a frequency modulation process into a disturbance initial stage, a disturbance middle stage and a steady-state recovery stage in sequence, and divides the work of flywheel energy storage and super capacitor energy storage according to respective response characteristics. On this basis, an equivalent inertia constant of a system is determined according to the number of different unit combinations, and an energy storage charging and discharging adjustment margin is calculated based on the minimum technical output constraint of each unit, and the excess power is absorbed by the energy storage when the downward adjustment space of the thermal power is insufficient. The simulation results show that the method can effectively improve the lowest point of the system frequency, suppress the frequency change rate, expand the downward adjustment space when the unit output is limited, and improve the frequency stability of the power grid.

Description

Technical Field

[0001] This invention relates to the field of power system frequency control, and specifically to a multi-timescale coordinated frequency regulation method for thermal power plants with energy storage configuration. Background Technology

[0002] In new power systems with a high proportion of renewable energy integration, renewable energy sources are connected to the grid through power electronic devices, exhibiting volatility and uncontrollability. This leads to increasing pressure on the power grid to regulate peak loads and maintain frequency stability when facing power supply and demand imbalances. Currently, the frequency regulation of the power grid still heavily relies on traditional thermal power. However, the thermodynamic and physical inertia of boilers and turbines causes a delay in the power response of thermal power units, which limits their peak load regulation depth and inertial response capability.

[0003] The frequency regulation process of traditional thermal power units is divided into multiple time scales: In the initial stage of disturbance, the synchronous generator rotor releases its rotational inertia to suppress the rate of frequency change, but the mechanical power of the prime mover cannot change abruptly due to the mechanical delay of the speed control system and the frequency regulation dead zone; subsequently, the governor gradually increases the valve opening according to the frequency deviation, and the mechanical power slowly increases with a gentle slope characteristic, and the frequency drops to the lowest point and then slowly recovers; in the steady-state stage, the automatic generator control eliminates the steady-state frequency difference. In this process, when the thermal power unit regulates the frequency alone, the power curve exhibits a gentle slope characteristic, the ramp rate is limited, and when facing a large power deficit, the transient frequency drops deeply and the rate of frequency change is large.

[0004] To improve the frequency regulation performance of thermal power units, existing technologies propose a thermal power-energy storage coordinated frequency regulation scheme, which uses the millisecond-level response speed of energy storage to compensate for the defects of large mechanical inertia and slow response of thermal power.

[0005] In the prior art, the patent "A Coordinated Frequency Regulation Method for Pumped Storage and Battery Energy Storage Based on Virtual Inertia and Virtual Droop" (patent application number: CN113824156A) discloses a coordinated frequency regulation method for pumped storage and battery energy storage based on virtual inertia and virtual droop. This scheme uses a combination of virtual inertial control and virtual droop control to control electrochemical energy storage to participate in grid frequency regulation, and switches the control mode according to the frequency deterioration stage and the frequency recovery stage. The patent "A Method for Controlling a Combined Thermal Power-Energy Storage System to Participate in Grid Frequency Regulation" (patent application number: CN111555371A) discloses a method for controlling a combined thermal power-energy storage system to participate in grid frequency regulation. This scheme establishes an optimization model that considers the operating constraints of thermal power units and energy storage systems, and allocates control commands for thermal power and energy storage through an optimization solution. Both of the above schemes have the following shortcomings: First, neither explicitly defines the multi-timescale coordination process between the steep-slope output of energy storage and the gradual-slope output of thermal power. The former only treats energy storage as an additional frequency regulation means, while the latter relies on the optimization model to iteratively solve the problem in each control cycle, and the power allocation relationship is implicitly completed. Both lack an explicit strategy for energy storage to decrease as thermal power climbs the slope to complete the handover of regulation responsibilities. Second, neither incorporates the reverse charging and absorption of energy storage under the minimum technical output constraint of thermal power units into the coordinated control strategy. When thermal power reaches the minimum technical output and the load decreases, it is impossible to expand the downward regulation space through energy storage charging.

[0006] Existing thermal power-energy storage coordinated frequency regulation schemes mostly employ filtering decomposition or simple command allocation to divide the frequency regulation power into high-frequency and low-frequency components. The high-frequency component is handled by energy storage, and the low-frequency component by thermal power, with the power allocation relationship implicitly completed in the simulation model. Furthermore, existing schemes generally lack an access judgment step before energy storage participates in frequency regulation, failing to consider the limited participation capability of energy storage when its state of charge is insufficient or excessive, and failing to determine the energy storage participation mode based on the minimum technical output state of thermal power and the direction of load disturbance. Regarding frequency regulation performance optimization, existing schemes do not use curve shape indicators such as response time and ramp rate as quantitative targets for coordinated control, and the improvement effect of energy storage on the shape of the frequency regulation curve is not explicitly characterized.

[0007] Therefore, a thermal power-energy storage coordinated frequency regulation method is needed that can explicitly reflect the connection and coordination of multiple time scales, have the ability to judge the participation of energy storage in frequency regulation access, and take the curve shape index as the optimization target. At the control strategy level, the power handover logic of fast and slow time scales should be clearly defined to give full play to the advantages of energy storage in rapid ramping and inertia support. Summary of the Invention

[0008] The technical problem this invention aims to solve is that existing thermal power-energy storage coordinated frequency regulation schemes rely on simulation to implicitly process power allocation, lack explicit multi-timescale coordination mechanisms, and the technical value of rapid ramp-up and inertia support for energy storage has not been fully explored; there is a lack of access judgment before energy storage participates in frequency regulation, and the selection of participation mode under the constraints of limited state of charge and minimum technical output of thermal power is not considered; at the same time, there is a lack of coordinated optimization with curve shape indicators such as response time and ramp-up rate as quantitative targets.

[0009] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0010] A method for coordinated frequency regulation of thermal power and energy storage across multiple time scales includes the following steps:

[0011] Step S1: Collect the frequency signal of the power system, calculate the frequency deviation and the frequency change rate. The frequency deviation is the difference between the real-time frequency of the system and the rated frequency. The frequency change rate is output after filtering out high-frequency noise through a low-pass filter.

[0012] Step S2: Obtain the state of charge (SOC) of the energy storage device, the relationship between the current active power output and the minimum technical output of the thermal power unit, and the direction of load disturbance. Based on the SOC, the relationship between the current active power output and the minimum technical output of the thermal power unit, and the direction of load disturbance, determine whether the energy storage should participate in frequency regulation and the mode of participation. The SOC threshold includes a warning threshold and an upper threshold. When the SOC is between the lower threshold and the warning threshold, the energy storage has full-power charging and discharging bidirectional frequency regulation capability. When the SOC is between the warning threshold and the upper threshold, the energy storage charges at reduced power and triggers the thermal power unit to pre-reduce its output. When the SOC reaches the upper threshold, the energy storage participates in frequency regulation in an emergency power-limited charging mode.

[0013] Step S3: When the judgment result is that the energy storage participates in frequency regulation, the energy storage device generates a fast power component through virtual inertia control based on the frequency change rate, and generates a continuous power component through droop control based on the frequency deviation. The fast power component and the continuous power component are combined into an energy storage composite control power command.

[0014] Step S4: The thermal power unit generates a thermal power mechanical power command based on the frequency deviation through the governor and the turbine primary frequency regulation;

[0015] Step S5: Allocate the output of energy storage devices and thermal power units according to a multi-timescale coordination strategy. In the initial rapid timescale of the disturbance, the energy storage devices prioritize outputting rapid power. In the medium-slow timescale as the mechanical power of the thermal power units gradually builds up, the thermal power units gradually assume continuous frequency regulation power. The output of the energy storage devices decreases accordingly as the mechanical power of the thermal power units increases. The actual output power of the energy storage devices and the mechanical power of the thermal power units are superimposed on the system side. The total support power is the sum of the actual output power of the energy storage devices and the mechanical power of the thermal power units, jointly compensating for the active power imbalance caused by load disturbances. When the system experiences a load reduction disturbance and the thermal power units have reached their minimum technical output and the state of charge of the energy storage devices has reached the upper limit threshold, the extreme condition fallback absorption strategy is activated. The remaining excess power is absorbed through the DC-side energy-consuming resistor of the power conversion device, providing a final power absorption means before the high-frequency tripping action.

[0016] Step S6: Optimize the curve shape using frequency regulation response time and equivalent ramp rate as the target, and output the energy storage power and thermal power. The frequency regulation response time is the difference between the moment when the energy storage output power reaches 10% of the rated power and the moment when the load disturbance occurs. The equivalent ramp rate is the average power change rate during the period when the frequency regulation power increases from 10% to 90% of the rated power. The frequency regulation response time is not greater than the preset response time threshold, and the equivalent ramp rate is not less than the preset ramp rate threshold. Both indicators are stricter than the corresponding performance when the thermal power unit regulates the frequency alone.

[0017] Furthermore, the state of charge threshold mentioned in step S2 includes a warning threshold and an upper limit threshold. When the state of charge reaches the warning threshold but not the upper limit threshold, the energy storage device participates in charging with derated power, and at the same time, the coordinated control link issues a pre-reduction output command to the thermal power unit. The derated power decreases linearly as the state of charge increases, and the pre-reduction output command causes the output of the thermal power unit to decrease towards the minimum technical output direction, freeing up power absorption space for the system.

[0018] Furthermore, when the state of charge reaches the upper limit threshold, the energy storage device is still allowed to participate in frequency regulation in an emergency power-limited charging mode. The emergency power limit is no more than 10% of the rated power of the energy storage, which is used to provide a buffer when the system frequency rises sharply, so as to avoid the power excess that cannot be consumed due to the complete withdrawal of energy storage.

[0019] Furthermore, the power conversion device is equipped with a power-consuming resistor on the DC side. When the system frequency exceeds the high-frequency warning threshold and the charging power of the energy storage device has reached the upper limit, the power-consuming resistor is activated to absorb the excess power of the system. The power of the power-consuming resistor increases with the frequency, providing a final power absorption method before the high-frequency switching action.

[0020] This invention also provides a multi-timescale integrated thermal power and energy storage coordinated frequency regulation system, including a thermal power unit, an energy storage device, a power conversion device, a frequency measurement link, and a coordinated control link. The frequency measurement link is used to collect the system frequency and calculate the frequency deviation and frequency change rate. The frequency change rate is output after filtering out high-frequency noise by a low-pass filter. The coordinated control link is used to execute the above-mentioned multi-timescale integrated thermal power and energy storage coordinated frequency regulation method, outputting energy storage power commands to the energy storage device and thermal power regulation commands to the thermal power unit. The energy storage device is connected to the power grid through the power conversion device and releases or absorbs active power according to the energy storage power commands. The thermal power unit changes its mechanical power output according to the thermal power regulation commands.

[0021] The present invention also provides a computer-readable storage medium storing instructions that, when executed, enable the aforementioned multi-timescale coordinated frequency regulation method for thermal power and energy storage.

[0022] The beneficial effects of this invention are as follows:

[0023] First, this invention explicitly defines a multi-timescale coordination strategy, in which energy storage prioritizes outputting rapid power with steep slope characteristics in the early stage of disturbance. As thermal power gradually builds up mechanical power with gentle slope characteristics, thermal power gradually assumes continuous frequency regulation power, and energy storage decreases accordingly. At the control strategy level, the power handover logic of fast and slow time scales is clearly defined, rather than relying on implicit processing by simulation models. This can give full play to the rapid ramp-up advantage of energy storage and improve the transient frequency drop depth of the system.

[0024] Secondly, the energy storage device of the present invention adopts virtual inertia and droop composite control. The virtual inertia component responds to the frequency change rate and suppresses the maximum frequency change rate in the early stage of disturbance, while the droop component responds to the frequency deviation and provides continuous active power support. The combination of the two enables the energy storage to have both inertia support and frequency regulation capability, highlighting the technical value of energy storage in terms of frequency regulation speed and inertia adjustment.

[0025] Third, this invention sets up an access judgment step before energy storage participates in frequency regulation. It comprehensively considers the energy storage's state of charge, the minimum technical output of thermal power, and the direction of load disturbance. It determines whether energy storage participates and how it participates through threshold judgment and priority ranking. This avoids equipment damage caused by forced discharge when the state of charge is insufficient or forced charging when the state of charge is too high. At the same time, when thermal power reaches the minimum technical output and the load decreases, it prioritizes energy storage charging to absorb excess power, so that the net on-grid power at the thermal power plant's grid connection point can be lower than the sum of the minimum technical output, thus expanding the downward adjustment space of thermal power plants.

[0026] Fourth, this invention uses frequency regulation response time and equivalent ramp rate as the curve shape optimization targets. After the intervention of energy storage, the system frequency regulation response time can be shortened and the equivalent ramp rate can be increased. Both indicators are stricter than the corresponding performance when thermal power alone regulates the frequency, so that the shape of the frequency regulation curve is significantly improved in both the response speed and ramp slope dimensions.

[0027] Fifth, the present invention sets a low-pass filter in the frequency change rate calculation stage to effectively suppress high-frequency noise in the frequency differential signal, avoid high-frequency noise causing frequent operation or even resonance of the energy storage converter, and improve the engineering practicality and operational stability of the control strategy.

[0028] Sixth, this invention expands the energy storage state of charge threshold to two levels: a warning threshold and an upper limit threshold. When the state of charge approaches the upper limit, it initiates derating charging and coordinated control with thermal power output reduction in advance. This avoids the power handover gap caused by the sudden and complete withdrawal of energy storage in the traditional binary access judgment, enabling a smooth transition of energy storage from full power participation to limited power participation, and improving the continuity and stability of coordinated frequency regulation.

[0029] Seventh, this invention configures an energy-consuming resistor on the DC side of the power conversion device and designs a fallback strategy for extreme operating conditions. When the thermal power unit has reached its minimum technical output and the energy storage charge state has reached its limit, and the system still has excess power, the remaining excess power is absorbed through the energy-consuming resistor, providing a last line of defense before high-frequency tripping, and completely eliminating the frequency spike and high-frequency tripping risk caused by the bidirectional non-adjustable nature of the load drop disturbance. Attached Figure Description

[0030] Figure 1 A complete flowchart of a multi-timescale integrated frequency regulation method for thermal power and energy storage;

[0031] Figure 2 Comparison of system frequency curves under different energy storage access conditions (no energy storage, flywheel energy storage, supercapacitor energy storage).

[0032] Figure 3 Comparison of system frequency curves under different unit combinations for flywheel energy storage (single unit, dual units, and triple units).

[0033] Figure 4 Comparison of system frequency curves under different unit combinations (single unit, dual unit, and triple unit) for supercapacitor energy storage.

[0034] Figure 5 The system frequency curve under load decrease disturbance under minimum technical output constraint. Detailed Implementation

[0035] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. It should be noted that the terms "front," "rear," "left," "right," "up," and "down" used in the following description refer to directions in the accompanying drawings, and the terms "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0036] like Figure 1 As shown, the multi-time-scale coordinated frequency regulation method in this embodiment is executed sequentially from steps S1 to S6: frequency signal acquisition and deviation calculation (step S1) → energy storage participation in frequency regulation access judgment (step S2) → energy storage composite control (step S3) → primary frequency regulation of thermal power (step S4) → multi-time-scale connection and coordination (step S5) → curve shape optimization output (step S6). Each link works in concert to compensate for active power imbalance and support grid frequency. Details are as follows.

[0037] Step S1: Collect the frequency signal of the power system, calculate the frequency deviation and the frequency change rate, wherein the frequency deviation is the difference between the real-time frequency of the system and the rated frequency;

[0038] Step S2: Obtain the state of charge (SOC) of the energy storage device, the relationship between the current active power output and the minimum technical output of the thermal power unit, and the direction of load disturbance. Based on the SOC, the relationship between the current active power output and the minimum technical output of the thermal power unit, and the direction of load disturbance, determine whether the energy storage should participate in frequency regulation and the mode of participation. The SOC threshold includes a warning threshold and an upper threshold. When the SOC is between the lower threshold and the warning threshold, the energy storage has full-power charging and discharging bidirectional frequency regulation capability. When the SOC is between the warning threshold and the upper threshold, the energy storage charges at reduced power and triggers the thermal power unit to pre-reduce its output. When the SOC reaches the upper threshold, the energy storage participates in frequency regulation in an emergency power-limited charging mode.

[0039] Step S3: When the judgment result is that the energy storage participates in frequency regulation, the energy storage device generates a fast power component through virtual inertia control based on the frequency change rate, and generates a continuous power component through droop control based on the frequency deviation. The fast power component and the continuous power component are combined into an energy storage composite control power command.

[0040] Step S4: The thermal power unit generates a thermal power mechanical power command based on the frequency deviation through the governor and the turbine primary frequency regulation;

[0041] Step S5: Allocate the output of energy storage devices and thermal power units according to a multi-timescale coordination strategy. In the initial rapid timescale of the disturbance, the energy storage devices prioritize outputting rapid power. In the medium-slow timescale as the mechanical power of the thermal power units gradually builds up, the thermal power units gradually take on the continuous frequency regulation power. The output of the energy storage devices decreases accordingly as the mechanical power of the thermal power units increases. The actual output power of the energy storage devices and the mechanical power of the thermal power units are superimposed on the system side. The total support power is the sum of the actual output power of the energy storage devices and the mechanical power of the thermal power units, which jointly compensate for the active power imbalance caused by the load disturbance. When the system experiences a load drop disturbance and the thermal power units have reached their minimum technical output and the state of charge of the energy storage devices has reached the upper limit threshold, the extreme condition fallback absorption strategy is activated. The remaining excess power is absorbed through the DC side energy-consuming resistor of the power conversion device, providing a last means of power absorption before the high-frequency tripping action.

[0042] Step S6: Optimize the curve shape using frequency regulation response time and equivalent ramp rate as the target, and output the energy storage power and thermal power. The frequency regulation response time is the difference between the moment when the energy storage output power reaches 10% of the rated power and the moment when the load disturbance occurs. The equivalent ramp rate is the average power change rate during the period when the frequency regulation power increases from 10% to 90% of the rated power. The frequency regulation response time is not greater than the preset response time threshold, and the equivalent ramp rate is not less than the preset ramp rate threshold. Both indicators are stricter than the corresponding performance when the thermal power unit regulates the frequency alone.

[0043] The specific implementation process is as follows:

[0044] In step S1, the frequency measurement stage acquires the system frequency. The frequency deviation was then calculated.

[0045]

[0046] and the rate of change of frequency ,in For the system's real-time frequency, The system's rated frequency, For frequency deviation, It is a differential operator.

[0047] Considering that frequency differentiation easily amplifies high-frequency noise in practical engineering, leading to frequent converter operation or even resonance, this invention incorporates a first-order inertial low-pass filter after the frequency differentiation stage. The frequency change rate after filtering is:

[0048]

[0049] in The original frequency differential signal, The rate of change of the filtered frequency. The time constant of the low-pass filter. The Laplace operator. Low-pass filter time constant. The value ranges from 0.01s to 0.1s, representing a trade-off between suppressing high-frequency noise and ensuring fast response. The larger the value, the better the high-frequency noise suppression effect, but the greater the phase lag. A smaller value results in a faster response but weaker noise suppression. In typical engineering applications, T... f Setting the time to 0.05s effectively filters out high-frequency noise components above 10Hz while ensuring millisecond-level response. The filtered frequency change rate is input to the virtual inertia control loop in step S3 to prevent high-frequency noise from directly affecting the power control loop and causing frequent converter operation or even resonance.

[0050] In step S2, the admission judgment comprehensively considers the energy storage state of charge. The relationship between the current active power output PG of the thermal power unit and the minimum technical output PGmin, as well as the direction of load disturbance, are the three factors.

[0051] This invention divides the state of charge threshold into three levels to achieve a smooth transition in the degree of energy storage participation, rather than a binary switching. The three threshold levels include: a lower threshold... Warning threshold and upper limit threshold .when < At that time, the remaining energy of the energy storage device is too low to continue discharging; when ≤ <SOC warn At this time, the energy storage device is in its normal operating range and has bidirectional frequency regulation capability for full-power charging and discharging; when ≤ < When the energy storage device enters the warning zone, it participates in charging at derated power. The upper limit of charging power decreases linearly with the increase of state of charge. At the same time, the coordination control loop issues a pre-reduction output command to the thermal power unit. ≥ When the energy storage device enters the restricted area, regular charging is prohibited, but emergency power limiting (P) is still permitted. emerg Short-term charging (not exceeding 10% of rated power) is used to suppress sharp increases in frequency. It should be noted that the power limits in the aforementioned warning and restricted zones only apply to charging conditions; the power limits for discharging conditions are determined by the discharging-side threshold (…). and Independently determined, not limited by charging-side thresholds. Typical values ​​are: = 10%, = 80%, = 95%, =20%.

[0052] The admission criteria are based on priority ranking according to the direction of load disturbance, specifically including steps 21 and 22:

[0053] Step 21: When the system frequency decreases and the corresponding load disturbance increases, the discharge side participates in frequency regulation according to the state of charge: If < The energy storage device does not have discharge capability and will not participate in this frequency regulation; the frequency regulation task will be undertaken solely by the thermal power unit. ≤ < Energy storage devices discharge at derating power to avoid deep discharge damage caused by excessively low state of charge; if ≥ The energy storage device discharges at full power to quickly fill the power gap before the mechanical power of the thermal power unit is established.

[0054] Step 22:

[0055] (a) Charging access conditions: When the system frequency increases and the corresponding load disturbance is in the downward direction, if the current active power output of the thermal power unit is... Achieve minimum technical output and The energy storage device has charging capabilities and prioritizes absorbing excess power through charging, thereby increasing the net on-grid power at the thermal power plant's grid connection point. Below This allows for a breakthrough in the downward adjustment boundary when thermal power plants operate alone; among which, when ≤ < At this time, the energy storage device participates in charging at dated power, and the upper limit of charging power decreases linearly with the increase of state of charge. At the same time, the coordinated control loop issues a pre-reduction output command to the thermal power unit; when ≥ When the emergency power-limited charging fails to meet the frequency regulation requirements, the energy storage device will withdraw from regular charging and activate the backup consumption strategy.

[0056] (II) Definition of relevant parameters: where Net on-grid power at the thermal power plant's grid connection point They always contribute to thermal power plants. The charging power of the energy storage device, with a positive value indicating the absorbed power, is under charging conditions. ;

[0057] (iii) This breaks through the downward regulation boundary of thermal power plants operating alone; when the state of charge does not meet the participation conditions in the corresponding direction, the energy storage device does not participate in this frequency regulation. The energy storage device is in its state of charge. This is the upper limit threshold for the charged state. The state of charge charging warning threshold, This is the state-of-charge discharge warning threshold. This is the upper limit threshold for the state of charge.

[0058] The minimum technical output constraint of thermal power units is incorporated into the collaborative control strategy; for each thermal power unit operating online, its actual active power output is... satisfy:

[0059]

[0060] in To achieve the minimum technical output for a single generating unit, This represents the maximum output of a single generating unit. The total output of the thermal power plant is:

[0061]

[0062] in The total active power output and the minimum technical output for a thermal power plant are:

[0063]

[0064] in The minimum technical output of the thermal power plant is given by u, where u is the unit's operating state variable. This indicates that the unit has been put into operation. This indicates that the generator unit is out of service.

[0065] As a further preferred embodiment, the admission determination in step S2 can be based on a quantitative index. The discharge admission index is:

[0066]

[0067] in As a discharge access indicator, when Right now Energy storage has the capability to participate in discharge; charging access criteria are:

[0068]

[0069] in As a charging access indicator, when Right now And the current active power output of thermal power units has reached Energy storage systems have the capability to participate in charging; the charging access criteria comprehensively consider the difference between the state of charge (SOC) and the upper limit threshold. When the SOC is close to the upper limit threshold... max When the access criteria are lowered, a reduced charging rate mode is adopted accordingly.

[0070] As a further preferred embodiment, the energy storage composite control power command undergoes state-of-charge (SOC) feedback limiting after the power limiting stage. Under charging conditions, the upper limit of the charging power after SOC feedback is:

[0071]

[0072] in This is the upper limit of charging power. For the rated power of the energy storage device, when ≤ < When; when ≥ hour, ,in This is the upper limit of charging power under emergency power limiting conditions. Under discharge conditions, the upper limit of discharge power after state-of-charge feedback is:

[0073]

[0074] in This is the upper limit of discharge power. The discharge warning threshold is typically set at 20%. Through state-of-charge feedback limiting, the charging and discharging power of the energy storage device changes smoothly with the state of charge, avoiding sudden power changes at the threshold boundary.

[0075] In step S3, the energy storage device employs a combined control of virtual inertia and droop. The virtual inertia control power is:

[0076]

[0077] in This is the virtual inertia control coefficient. The frequency change rate is used to quickly release or absorb power when the frequency changes rapidly in the early stage of a disturbance, thus suppressing the maximum frequency change rate.

[0078] The droop control power is:

[0079]

[0080] in This is the droop control coefficient. To compensate for frequency deviation, active power support will continue to be provided while the frequency deviation persists. The composite control power command is as follows:

[0081]

[0082] in The power command for energy storage composite control is output after power limiting. The power limiting is as follows:

[0083]

[0084] in This represents the actual output power of the energy storage device. This represents the maximum charging and discharging power of the energy storage device. To find the maximum value function, To find the minimum value function, Indicates energy storage and discharge. This indicates energy storage charging.

[0085] In step S4, the primary frequency regulation process of the thermal power unit is as follows: when the system frequency drops, the generator speed is lower than the reference speed. The governor generates a primary frequency regulation power command based on the droop coefficient. The valve opening is adjusted through the speed relay and the servo motor dynamic link to change the steam flow rate entering the turbine. The turbine converts the steam volume energy into mechanical power through the high-pressure cylinder, intermediate-pressure cylinder and low-pressure cylinder. Due to the steam volume effect of the intermediate reheater, the establishment of mechanical power is delayed and exhibits a gradual slope characteristic.

[0086] The primary frequency regulation power command for thermal power units is:

[0087]

[0088] in For the primary frequency regulation power command (per unit value) of thermal power units, δ The droop factor for thermal power units (per unit value, usually taken as...) ,Right now ), This represents the frequency deviation (per unit value). The negative sign indicates that the active power output of the motor increases when the frequency decreases and decreases when the frequency increases.

[0089] After passing through multiple inertial stages in the governor and turbine, the command is converted into an actual increase in mechanical power. Its dynamic response time constant is much larger than that of the energy storage device.

[0090] The frequency dynamics of a thermal power unit system containing energy storage devices can be described by an incremental equivalent rotor motion equation:

[0091]

[0092] in For the increase in mechanical power of thermal power units, For the frequency regulation output power increment of the energy storage device, This represents the increase in system load disturbance power. The system's equivalent inertial time constant. For frequency deviation, The rate of change of frequency deviation The equivalent load damping coefficient of the system.

[0093] Energy storage device output power As an additional active power support term, it directly acts on the rotor motion equation, and in the initial stage of disturbance, the increase in thermal power mechanical power... Before it was established, It can quickly compensate for power deficit.

[0094] In step S5, the power response time constant of the energy storage device is smaller than that of the thermal power unit; after the disturbance occurs, the energy storage device quickly reaches its peak output with a steep slope characteristic, while the thermal power unit gradually increases its mechanical power with a gentle slope characteristic. The peak output of the energy storage device occurs earlier than the steady-state establishment time of the thermal power unit's mechanical power. Step S5 specifically includes steps 51, 52, 53, and 54:

[0095] Step 51: Within a rapid timescale following a load disturbance, the energy storage device, with its millisecond-level response speed, quickly reaches its peak output with a steep ramp characteristic, prioritizing rapid power support. Simultaneously, the thermal power unit, limited by the mechanical delay of the speed control system and the steam volume effect of the turbine, gradually increases its mechanical power with a gentle ramp characteristic. The power response time constant of the energy storage device is smaller than that of the thermal power unit, and the peak output of the energy storage device occurs earlier than the steady-state establishment time of the thermal power unit's mechanical power. Therefore, when the power deficit is greatest in the initial stage of the disturbance, the energy storage provides timely power support, effectively reducing the frequency drop depth and frequency change rate.

[0096] Step 52: On a medium-to-slow time scale, as the mechanical power of thermal power units gradually builds up and approaches steady state, the units gradually assume continuous frequency regulation power, and the output of energy storage devices decreases accordingly, completing the handover of regulation responsibility from the rapid time scale of energy storage to the medium-to-slow time scale of thermal power. The total supported power is:

[0097]

[0098] in For the total frequency modulation support power of the system, This represents the actual output power of the energy storage device. This represents the increase in mechanical power of thermal power units.

[0099] The multi-timescale coordination is achieved through a weighted allocation where energy storage output decreases as thermal power machinery power is established: before thermal power machinery power begins to build up, energy storage maintains peak output; as thermal power machinery power gradually builds up, energy storage output decreases as thermal power output increases. One implementation uses a linearly decreasing weighting:

[0100]

[0101] in This represents the peak output of the energy storage device at the initial stage of the disturbance. This represents the steady-state power increment of the primary frequency regulation of thermal power units. For thermal power units The increase in mechanical power at any given moment.

[0102] when When the disturbance occurs , Energy storage, with its steep slope characteristics, fully undertakes rapid power support; with Increase The slope gradually increases in size due to its gentle slope characteristics. The corresponding linear decrease;

[0103] when hour The responsibility for regulation is completely transferred to the thermal power units. In the initial stages of the disturbance, Rapid ascent due to steep slope characteristics It rises slowly due to its gentle slope characteristics. Mainly composed of Contribution; over time, Gradually increase Decrease accordingly The two will work together to maintain and smoothly transition to continuous frequency regulation of thermal power.

[0104] The load disturbance power increment is At that time, the steady-state power increment of primary frequency regulation of thermal power and Phase balance, peak energy storage output Not less than To fully compensate for the power deficit in the early stages of the disturbance, thereby ensuring the total supporting power during the handover process. Keep it constant.

[0105] Step 53: When a load reduction disturbance occurs in the system and the thermal power units are constrained by the minimum technical output and cannot further reduce their output, the energy storage device absorbs the excess power of the system through charging. The charging power of the energy storage device and the downward adjustment capacity of the thermal power units jointly absorb the load reduction. The minimum technical output constraint of the thermal power units is expressed as the actual active power output of each online unit. satisfy:

[0106]

[0107] in This refers to the actual active power output of a single thermal power unit. To achieve the minimum technical output for a single generating unit, Maximum output of a single generating unit; minimum technical output of the entire thermal power plant. Based on the sum of the minimum technical outputs of all online generating units, the downward adjustment range for thermal power plants is:

[0108]

[0109] in This provides downward adjustment space for thermal power plants. Contribute to the minimum technical requirements of thermal power plants. To determine the total output of the thermal power plant before the disturbance.

[0110] If the load decrease Greater than Thermal power units, limited by minimum technical output, cannot fully absorb power fluctuations, resulting in the following excess power:

[0111]

[0112] in For surplus or excess power, This is the amount of load reduction. The charging power for the energy storage device, when The system still has excess power, causing frequency increase. Excess power can be absorbed by both thermal power plant power reduction and energy storage charging. When the energy storage device reaches its State of Charge (SOC)... max When charging cannot continue in the normal way, the above-mentioned excess power cannot be absorbed by energy storage charging. At this time, the extreme condition fallback absorption control in step 54 needs to be activated.

[0113] Step 54: Emergency control for waste disposal under extreme conditions.

[0114] When the system experiences a load reduction disturbance and the thermal power unit is constrained by the minimum technical output and cannot further reduce its output, while the energy storage device's state of charge has reached its upper limit threshold and cannot continue charging in the conventional way, if the remaining excess power If the value remains greater than zero, the system frequency will continue to rise, triggering high-frequency switching if no additional measures are taken. To completely eliminate this bidirectional unadjustable dead zone, this invention designs a three-level fallback strategy:

[0115] Level 1: Emergency power-limited charging for energy storage. When ≥ At that time, energy storage devices are still allowed to use emergency power limiting. (Typical value is 5%–10% of rated power) for short-term charging. Emergency charging power command is:

[0116]

[0117] in Emergency charging power command for energy storage. For emergency charging coefficient, For the system's real-time frequency, This is the rated frequency. Emergency power-limiting charging provides a buffer in the early stages of frequency increase, buying time for subsequent backup measures to be implemented.

[0118] Level Two: Energy-consuming resistors are used for absorption. A braking resistor (energy-consuming resistor) is installed on the DC side of the energy storage power conversion device. When the system frequency exceeds the high-frequency warning threshold... (Typical value 50.5Hz) When the emergency charging power of the energy storage has reached its limit, the energy-dissipating resistor is activated to convert excess electrical energy into heat energy. The activated power of the energy-dissipating resistor is:

[0119]

[0120] when ≤ < hour; ,when ≥ At that time. This represents the actual power input of the energy-consuming resistor. The power control coefficient is set for the energy-consuming resistor. The threshold for full-power operation of the energy-consuming resistor (typical value 51.0Hz). The rated power of the energy-dissipating resistor is typically 20%–50% of the rated power of the energy storage. The input ratio of the energy-dissipating resistor is controlled by a DC-side chopper circuit with a response time in the millisecond range, enabling it to quickly absorb excess power in the system.

[0121] Level 3: Plant power load increase and external transmission via tie lines. If the system frequency continues to rise after the energy-consuming resistors are put into full power operation, plant power load increase will be initiated to absorb the excess power, sequentially activating standby plant equipment (such as standby circulating water pumps, electric boilers, etc.) to increase plant power consumption. If the thermal power plant is connected to the adjacent regional power grid via tie lines, the external transmission power will be increased through tie line control to transfer excess power to the adjacent region. High-frequency generator tripping protection is only permitted to be triggered if all three levels of fallback measures are implemented and the frequency rise still cannot be suppressed.

[0122] The aforementioned three-tiered backup power absorption measures are implemented sequentially according to the degree of frequency increase, with time delays and frequency hysteresis between each tier to prevent over-adjustment caused by simultaneous operation of multiple tiers. Through this three-tiered backup power absorption strategy, the system still possesses power absorption capacity under the dual constraints of the minimum technical output of thermal power units and the upper limit of the state of charge of energy storage, fundamentally avoiding the risk of sharp frequency spikes and high-frequency unit tripping under load reduction disturbances.

[0123] In step S6, the frequency modulation response time is:

[0124]

[0125] in This refers to the moment when the energy storage output power reaches 10% of the rated power. The time when the load disturbance occurs.

[0126] When a thermal power unit adjusts its frequency independently, the process from the occurrence of a frequency deviation to the start of a change in mechanical power involves multiple stages, including frequency dead zone detection, governor proportional amplification, speed relay and servo motor operation, valve opening changes, and steam volume energy transfer. The response time is typically in the second range (generally no more than 3 seconds). Energy storage devices, connected to the grid via power electronic converters, have a response time in the millisecond range. When thermal power and energy storage units coordinate frequency regulation, the response time of the total system frequency regulation output is determined by the response time of the energy storage devices, which is reduced from the second range to the hundreds of milliseconds range, meeting the requirements. The equivalent climbing rate is

[0127]

[0128] in For frequency modulation rated power, The moment when the frequency modulation power reaches 10% of the rated power. This refers to the moment when the frequency-regulated power reaches 90% of the rated power. The rate of change of active power output of thermal power units is constrained by boiler thermal inertia and steam volume effect, and is typically [missing information]. The output power of the energy storage device is directly controlled by a power electronic converter, enabling it to quickly reach peak output with a steep ramp characteristic. In multi-timescale coordination, the energy storage device handles the rapid ramp-up during the initial stage of disturbances, with an equivalent ramp rate of no less than 20%. / min, which is significantly higher than the ramp rate when thermal power plants regulate frequency alone.

[0129] When a thermal power unit is frequency regulated alone, the power curve is a flat, gently sloping line with a large response delay and slow ramp-up. After adding energy storage, the power curve becomes a steep sloping line in the early stage of disturbance, with a very small response delay, fast ramp-up, and rapid attainment of peak output. The maximum frequency drop and the maximum frequency change rate of the system are significantly reduced.

[0130] Regarding meeting primary frequency regulation standards, the active power lag time for primary frequency regulation of an energy storage power station should not exceed 1 second, and the rise time should not exceed 3 seconds; the primary frequency regulation response lag time of a thermal power unit is typically not greater than 3 seconds. This invention, through the intervention of energy storage, ensures that the system's frequency regulation response time is no greater than 1 second, and the equivalent ramp rate is no less than 20%. / min, both indicators are more stringent than the performance of thermal power plants when frequency regulation is performed alone, while meeting the standard requirements.

[0131] Energy storage device and system composition

[0132] The thermal power-energy storage coordinated frequency regulation system consists of thermal power units, energy storage devices, power conversion devices, frequency measurement links, and coordinated control links.

[0133] A thermal power unit consists of a governor, a steam turbine, and a synchronous generator. It changes the mechanical power output and connects to the power grid through primary frequency regulation.

[0134] The energy storage device is connected to the power grid via a power conversion device, which includes a generator-side converter, a DC-side capacitor, and a grid-side converter. It employs a dual closed-loop control structure (voltage outer loop, current inner loop) to achieve rapid and precise power control. The DC side of the power conversion device is also equipped with a power-consuming resistor and a chopper control circuit. Under extreme operating conditions, the chopper circuit controls the proportion of the power-consuming resistor in operation, converting excess DC-side electrical energy into heat energy for consumption. The power command of the energy storage device uses the active power command output by the energy storage controller as input. A power limiting circuit and a first-order inertial circuit characterize the dynamic lag from receiving the command to the actual output.

[0135]

[0136] in The actual output power of the energy storage equivalent model. This is the energy storage power command after power limiting. The equivalent response time constant for energy storage For the Laplace operator.

[0137] The energy storage device employs either a flywheel energy storage device or a supercapacitor energy storage device. The flywheel energy storage system stores energy in the form of mechanical kinetic energy, and charging and discharging are achieved by the motor switching between generating and motoring states. It possesses physical inertia, and its power response exhibits a lag of approximately 0.1 seconds (corresponding to...). Larger capacity), suitable for short- to medium-term continuous power support; supercapacitor energy storage systems rely on the double electric layer to achieve rapid charge storage and release, with high power density and near-instantaneous response (corresponding to...). (Smaller in size), suitable for instantaneous power compensation during the initial stage of disturbances. When the system frequency drops, the energy storage device releases active power to the grid; when the system frequency rises or the thermal power unit is limited by the minimum technical output and cannot continue to reduce its output, the energy storage device absorbs the excess power of the system through charging.

[0138] To prevent the energy storage device from maintaining a high state of charge (SOC) for extended periods during operation, thus reducing its charging and absorption capacity under extreme conditions, this invention incorporates dynamic SOC recovery control. When the system frequency is normal (|Δf| < frequency dead zone), if the SOC is higher than the upper limit of the optimal range (SOCopt,max, typically 60%), the coordinated control loop slightly discharges or reduces charging to bring the SOC back to the optimal range [SOCopt,min, SOCopt,max]. If the SOC is lower than the lower limit of the optimal range (SOCopt,min, typically 40%), it actively charges to the optimal range when the system has surplus power. The power command for dynamic SOC recovery control does not exceed 5% of the energy storage's rated power to avoid disturbances to the system frequency. Through dynamic SOC management, the energy storage device maintains a moderate SOC level for most of the time, always possessing sufficient bidirectional charging and discharging regulation capabilities.

[0139] Thermal power units include at least one online operating thermal power generating unit. The system's equivalent inertia constant and total minimum technical output vary with the number of units in operation. The unit combination method of thermal power units affects the coordinated frequency regulation effect: as the number of online thermal power units increases, the overall physical inertia of the system increases, the minimum frequency increases significantly, and the maximum frequency drop and maximum frequency change rate both decrease, enhancing the ability to resist load disturbances. Under the same unit combination, flywheel energy storage has an advantage in reducing the maximum frequency drop, while supercapacitor energy storage performs better in suppressing the maximum frequency change rate.

[0140] To verify the effectiveness of the multi-timescale integrated thermal power-storage frequency regulation method proposed in this invention, two types of thermal power-storage joint frequency regulation models were built based on the MATLAB / Simulink simulation platform: a single-grid thermal power-storage distribution model and a modified IEEE_9-node thermal power-storage distribution system model. Simulation comparison and analysis were carried out from three dimensions: energy storage type, unit combination, and minimum technical output constraint.

[0141] (1) Comparison between single-network model and energy storage type

[0142] In a single-grid thermal power-storage model, the rated power of the thermal power unit is 200MW, with 5MW flywheel energy storage and 5MW supercapacitor energy storage respectively. The system rated frequency is 50Hz, and the initial load is set to 50MW. A 5MW step load disturbance (accounting for 2.5% of the rated power) is applied at the 10th second. The system frequency curves are measured under three conditions: no energy storage, flywheel energy storage, and supercapacitor energy storage (e.g., ...). Figure 2 The table shows the frequency dynamic index (as shown in Table 1), where RoCoF is the frequency change rate.

[0143] Table 1. Dynamic Indicators of System Frequency under Different Energy Storage Access Conditions

[0144] Operating conditions Lowest frequency (Hz) Lowest frequency moment (s) Maximum frequency drop (Hz) Maximum RoCoF (Hz / s) No energy storage 49.8475 11.8988 0.1525 0.1554 Connect to flywheel energy storage 49.9018 11.4844 0.0982 0.1552 Connecting to supercapacitor energy storage 49.8873 12.8509 0.1127 0.1251

[0145] As can be seen from Table 1 and the comparison of frequency curves:

[0146] ① Compared to the case without energy storage, the minimum frequency was significantly improved after the system was connected to flywheel energy storage or supercapacitors, and the maximum frequency drop decreased from 0.1525Hz to 0.0982Hz and 0.1127Hz, respectively. This verifies that the connection of energy storage systems can effectively improve the frequency support capability of thermal power plants to the power grid and mitigate the impact of load disturbances.

[0147] ② Comparing different energy storage types, it can be seen that flywheel energy storage performs better in improving the maximum frequency drop and takes less time to reach the lowest frequency (11.4844s less than 12.8509s), with a faster frequency response speed. This is consistent with the characteristics of flywheel energy storage, which has physical inertia and is suitable for supporting short- to medium-term continuous power.

[0148] ③ The effect of supercapacitors in improving the maximum frequency change rate is more significant than that of flywheels (0.1251Hz / s < 0.1552Hz / s), which verifies that supercapacitors are more advantageous than flywheels in smoothing out drastic frequency changes. This is consistent with the characteristics of supercapacitors, such as high power density, near-instantaneous response, and suitability for instantaneous power compensation in the early stages of disturbances.

[0149] The above results are consistent with the technical features of the division of labor between flywheel energy storage and supercapacitor energy storage in the claims of this invention.

[0150] (2) Comparison of the modified IEEE_9 system with the unit combination

[0151] To further verify the effectiveness of the thermal power-storage coordinated frequency regulation strategy in multi-unit systems, the standard IEEE_9 node system was modified, with three 200MW thermal power units equivalently connected to the same thermal power plant node to simulate different unit combinations within a thermal power plant. The minimum technical output of each thermal power unit was set to 25% of its rated power (i.e., 50MW), and the initial total load of the system was 150MW, with a +10MW step load disturbance applied. Three unit combinations were set up: single unit (G1), dual unit (G1 / G2), and triple unit (G1 / G2 / G3). Each combination was equipped with 10MW flywheel energy storage and 10MW supercapacitor energy storage. The measured frequency dynamic indicators are shown in Table 2, and the frequency curves are compared. Figure 3 , Figure 4 As shown.

[0152] Table 2 System dynamic frequency indices under different unit combinations

[0153] Operating conditions Lowest frequency (Hz) Lowest frequency moment (s) Maximum frequency drop (Hz) Maximum RoCoF (Hz / s) Case A1 (Single G1 unit + flywheel) 49.8198 6.2740 0.1802 0.2667 Case A2 (Dual G1 / G2 + Flywheel) 49.8778 6.5407 0.1222 0.1408 CaseA3 (Three units G1 / G2 / G3 + flywheel) 49.9145 6.8015 0.0855 0.0970 Case A4 (Single G1 unit + supercapacitor) 49.7771 6.0197 0.2229 0.2203 CaseA5 (Dual G1 / G2 + Supercapacitor) 49.8661 6.3229 0.1339 0.1264 Case A6 (Three units G1 / G2 / G3 + supercapacitor) 49.9110 7.2407 0.0890 0.0900

[0154] From Table 2 and Figure 3 , Figure 4 It can be seen that: ① As the number of thermal power units put into operation increases, the minimum frequency of the system increases significantly, while the maximum frequency drop and the maximum RoCoF both show a trend of significant decrease. Taking flywheel energy storage as an example, the maximum frequency drop is 0.1802Hz and the maximum RoCoF is 0.2667Hz / s in Case A1 (single unit G1), while in Case A3 (three units G1 / G2 / G3), they drop to 0.0855Hz and 0.0970Hz / s respectively. This is because the increase in the number of online units directly increases the overall physical inertia of the system, thereby enhancing the system's ability to resist load disturbances. This verifies the technical feature of "the system's equivalent inertia constant and total minimum technical output change with the number of units put into operation" in this invention. ② Comparing different energy storage types under the same unit combination, Case A3 (flywheel) has an advantage in reducing the maximum frequency drop (0.0855Hz, less than Case A6's 0.0890Hz), while Case A6 (supercapacitor) performs better in suppressing the maximum RoCoF (0.0900Hz / s, less than Case A3's 0.0970Hz / s), which is consistent with the conclusion of the single-grid model.

[0155] (3) Comparison of load reduction disturbances under minimum technical output constraints

[0156] To address the minimum technical output constraint scenario for thermal power units, which is a key focus of this invention, the modified IEEE_9 system was configured to have three thermal power units operating at a minimum technical output of 50MW (total output 150MW), with a -10MW step load reduction disturbance applied. Under this constraint, the thermal power units could not further reduce their output. Tests were conducted under three operating conditions: no energy storage, flywheel energy storage, and supercapacitor energy storage. The measured frequency dynamic indicators are shown in Table 3, and the frequency curves are as follows. Figure 5 As shown.

[0157] Table 3 System frequency dynamic indicators under minimum technical output constraint

[0158] Operating conditions Maximum frequency (Hz) Maximum frequency time (s) Deviation from rated frequency (Hz) Maximum RoCoF (Hz / s) Case C1 (No energy storage, minimum output is limited) 50.1000 6.8168 0.1000 0.1002 Case C2 (connected flywheel, minimum output is limited) 50.0945 6.7281 0.0945 0.1001 Case C3 (connected to a supercapacitor, minimum output is limited) 50.0874 6.6268 0.0874 0.1000

[0159] From Table 3 and Figure 5It can be seen that: ① When the system experiences a load reduction disturbance and the thermal power units are constrained by the minimum technical output and cannot further reduce their output, the system frequency rises to 50.1000Hz in Case C1 (without energy storage), which is 0.1000Hz higher than the rated frequency. This verifies the technical problem of thermal power plants being constrained by the minimum technical output and having limited downward adjustment space when operating alone. ② After connecting energy storage, the energy storage absorbs the excess power of the system through charging, effectively reducing the maximum frequency value. After Case C2 (connecting the flywheel), the maximum frequency is 0.0945Hz higher than the rated frequency, and after Case C3 (connecting the supercapacitor), the maximum frequency is 0.0874Hz higher than the rated frequency, both below 0.1Hz. This operating condition verifies the effectiveness of the energy storage charging to absorb excess power. When the output of the thermal power units cannot be further reduced, the energy storage charging makes the net on-grid power at the grid connection point lower than the sum of the minimum technical outputs of each unit, thereby expanding the downward adjustment space of the thermal power plant.

[0160] ③ Under this low-load limited operating condition, CaseC3 (supercapacitor) is slightly better than CaseC2 (flywheel) in suppressing frequency rise (maximum frequency rise 0.0874Hz less than 0.0945Hz), which is consistent with the characteristics of supercapacitors that have faster response speed and are more suitable for instantaneous power absorption.

[0161] In summary, the three sets of simulation examples verified the effectiveness of the proposed multi-timescale integrated thermal power and energy storage coordinated frequency regulation method from three dimensions: energy storage type, unit combination, and minimum technical output constraint. Simulation results show that: energy storage integration can significantly improve system frequency dynamics; flywheel energy storage is superior in reducing the maximum frequency drop; and supercapacitors perform better in suppressing the maximum frequency change rate. Multi-unit combination further enhances frequency regulation capability by increasing system inertia. Under the minimum technical output constraint scenario, energy storage charging to absorb excess power can effectively expand the downward adjustment space of thermal power plants. All of the above results are consistent with the technical features and beneficial effects of this invention.

[0162] The technical means disclosed in this invention are not limited to those disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features.

Claims

1. A method for coordinated frequency regulation of thermal power and energy storage across multiple time scales, characterized in that, Includes the following steps: Step S1: Acquire the frequency signal of the power system, calculate the frequency deviation and the frequency change rate, wherein the frequency deviation is the difference between the real-time frequency of the system and the rated frequency; the frequency change rate is output after filtering out high-frequency noise through a low-pass filter. Step S2: Obtain the state of charge (SOC) of the energy storage device, the relationship between the current active power output and the minimum technical output of the thermal power unit, and the direction of load disturbance. Based on the SOC, the relationship between the current active power output and the minimum technical output of the thermal power unit, and the direction of load disturbance, determine whether the energy storage should participate in frequency regulation and the mode of participation. The SOC threshold includes a warning threshold and an upper threshold. When the SOC is between the lower threshold and the warning threshold, the energy storage has bidirectional frequency regulation capability with full power charging and discharging. When the SOC is between the warning threshold and the upper threshold, the energy storage charges at reduced power and triggers the thermal power unit to pre-reduce its output. When the SOC reaches the upper threshold, the energy storage participates in frequency regulation in an emergency power-limited charging mode. Step S3: When the judgment result is that energy storage participates in frequency regulation, the energy storage device generates a fast power component through virtual inertia control according to the frequency change rate, and generates a continuous power component through droop control according to the frequency deviation. The fast power component and the continuous power component are combined into an energy storage composite control power command. Step S4: The thermal power unit generates a thermal power mechanical power command based on the frequency deviation through the governor and the turbine primary frequency regulation; Step S5: Allocate the output of energy storage devices and thermal power units according to a multi-timescale coordination strategy: In the initial stage of disturbance, energy storage devices prioritize power output; as the mechanical power of thermal power units gradually builds up, the thermal power units gradually assume frequency regulation power, and the output of energy storage devices decreases accordingly; the output of energy storage devices and the output of thermal power units are superimposed on the system side to jointly compensate for the imbalance of active power; when the system experiences a load reduction disturbance and the thermal power units have reached their minimum technical output and the state of charge of the energy storage devices has reached the upper limit threshold, the extreme condition fallback absorption strategy is activated, and the remaining excess power is absorbed through the DC side energy-consuming resistor of the power conversion device, providing a last means of power absorption before the high-frequency tripping action; Step S6: Using frequency regulation response time and equivalent ramp rate as the curve shape optimization targets, output energy storage power and thermal power; the frequency regulation response time and the equivalent ramp rate both meet the preset indicators and are better than the corresponding performance when the thermal power unit regulates the frequency alone.

2. The multi-timescale coordinated frequency regulation method for thermal power and energy storage as described in claim 1, characterized in that, Step S2 specifically includes the following steps: Step 21: The energy storage participation in frequency regulation access judgment combines the state of charge, the relationship between the current active power output and minimum technical output of the thermal power unit, and the direction of load disturbance to prioritize: when the system frequency decreases and the corresponding load disturbance is in the increasing direction, the discharge side participates in frequency regulation in stages according to the state of charge: if The energy storage device does not have discharge capability and will not participate in this frequency regulation; the frequency regulation task will be undertaken solely by the thermal power unit. ≤ < The energy storage device discharges at derating power to avoid deep discharge damage to the equipment caused by excessively low state of charge. If SOC ≥ The energy storage device discharges at full power to quickly fill the power deficit before the mechanical power of the thermal power unit is established; Step 22: When the load disturbance is in a decreasing direction and the current active power output of the thermal power unit reaches the minimum technical output and At that time, the energy storage device prioritizes absorbing excess power through charging, ensuring that the net on-grid power at the thermal power plant's grid connection point is lower than the sum of the minimum technical outputs of the thermal power units; among which, when ≤ < At this time, the energy storage device participates in charging at dated power, and the upper limit of charging power decreases linearly with the increase of state of charge. At the same time, the coordinated control loop issues a pre-reduction output command to the thermal power unit; when ≥ When the emergency power limiting charging fails to meet the frequency regulation requirements, the energy storage device will withdraw from regular charging and activate the backup consumption strategy. Step 23: When the state of charge does not meet the participation conditions in the corresponding direction, the energy storage device will not participate in this frequency regulation; in The energy storage device is in its state of charge. This is the lower limit threshold for the charged state. The state of charge charging warning threshold, This is the state-of-charge discharge warning threshold. This is the upper limit threshold for the state of charge.

3. The multi-timescale coordinated frequency regulation method for thermal power and energy storage as described in claim 1, characterized in that, In step S3, the energy storage composite control power command is output after being constrained by the power limiting circuit to limit the maximum charging and discharging power. The actual power after limiting is: ； in This represents the actual output power of the energy storage device. For energy storage composite control power commands, This represents the maximum charging and discharging power of the energy storage device. To find the maximum value function, To find the minimum value function, Indicates energy storage and discharge. This indicates energy storage charging.

4. The multi-timescale coordinated frequency regulation method for thermal power and energy storage as described in claim 1, characterized in that, The energy storage device is connected to the power grid through a power conversion device, which includes a generator-side converter, a DC-side capacitor, and a grid-side converter. The power command of the energy storage device is characterized by a first-order inertial element to represent the dynamic lag from receiving the command to the actual output. ； in The actual output power of the energy storage equivalent model. This is the energy storage power command after power limiting. The equivalent response time constant for energy storage For the Laplace operator.

5. The multi-timescale coordinated frequency regulation method for thermal power and energy storage as described in claim 1, characterized in that, Step S5 specifically includes the following steps: Step 51: The power response time constant of the energy storage device is less than the power response time constant of the thermal power unit; after the disturbance occurs, the energy storage device quickly reaches the peak output with a steep slope characteristic, while the thermal power unit gradually increases its mechanical power with a gentle slope characteristic; the peak output of the energy storage device occurs earlier than the steady-state establishment time of the mechanical power of the thermal power unit. Step 52: The coordination method in which the output of the energy storage device decreases as the mechanical power of the thermal power unit increases is expressed as follows: ； in This represents the peak output of the energy storage device at the initial stage of the disturbance. This represents the steady-state power increment of the primary frequency regulation of thermal power units. For thermal power units Increment of mechanical power at any moment; Step 53: When a load reduction disturbance occurs in the system and the thermal power unit cannot further reduce its output due to the minimum technical output constraint, the energy storage device absorbs the excess power of the system by charging. The charging power of the energy storage device and the thermal power unit's output reduction capacity jointly absorb the load reduction. The minimum technical output constraint of the thermal power unit is expressed as the actual active power output of each online unit meeting the following requirements: ； in This refers to the actual active power output of a single thermal power unit. To achieve the minimum technical output for a single generating unit, Maximum output of a single generating unit; minimum technical output of the entire thermal power plant. Based on the sum of the minimum technical outputs of all online generating units, the downward adjustment range for thermal power plants is: ； in This provides downward adjustment space for thermal power plants. Contribute to the minimum technical requirements of thermal power plants. To affect the total output of the thermal power plant before the disturbance; Step 54: When the system experiences a load reduction disturbance and the thermal power unit has reached its minimum technical output and the energy storage device has reached its upper limit threshold of charge, the extreme operating condition fallback absorption strategy is activated. The remaining excess power is absorbed through the DC side energy-consuming resistor of the power conversion device, providing a final power absorption means before the high-frequency tripping action.

6. The multi-timescale coordinated frequency regulation method for thermal power and energy storage according to claim 1, characterized in that, The low-pass filtering stage for the frequency change rate mentioned in step S1 uses a first-order inertial low-pass filter, and the filtered frequency change rate is: ； in The original frequency differential signal, The rate of change of the filtered frequency. The time constant of the low-pass filter. The Laplace operator; the time constant of the low-pass filter The value range is from 0.01s to 0.1s, which is a trade-off between suppressing high-frequency noise and ensuring fast response. The filtered frequency change rate is input to the virtual inertia control loop in step S3 to avoid frequent operation or even resonance of the converter caused by high-frequency noise.

7. The multi-timescale coordinated frequency regulation method for thermal power and energy storage according to claim 1, characterized in that, The energy storage device is a flywheel energy storage device or a supercapacitor energy storage device; the flywheel energy storage device provides continuous power support for short and medium time, and the supercapacitor energy storage device provides instantaneous power compensation in the early stage of disturbance; the thermal power unit includes at least one online thermal power generating unit, and the system equivalent inertia constant and total minimum technical output change with the number of units put into operation.

8. The multi-timescale coordinated frequency regulation method for thermal power and energy storage according to claim 1, characterized in that, In step S6, the frequency regulation response time is the difference between the moment when the energy storage output power reaches 10% of the rated power and the moment when the load disturbance occurs. The equivalent ramp rate is the average power change rate during the period when the frequency regulation power increases from 10% to 90% of the rated power. The frequency regulation response time is not greater than a preset response time threshold, and the equivalent ramp rate is not less than a preset ramp rate threshold. Both indicators are stricter than the corresponding performance when the thermal power unit regulates the frequency alone.

9. The multi-timescale coordinated frequency regulation method for thermal power and energy storage according to claim 1, characterized in that, The frequency dynamics of a thermal power unit system containing energy storage devices are described by an incremental equivalent rotor motion equation: ； in For the increase in mechanical power of thermal power units, For the frequency regulation output power increment of the energy storage device, This represents the increase in system load disturbance power. The system's equivalent inertial time constant. For frequency deviation, The rate of change of frequency deviation The equivalent load damping coefficient of the system.

10. A multi-timescale integrated thermal power and energy storage coordinated frequency regulation system, characterized in that, It includes a thermal power unit, an energy storage device, a power conversion device, a frequency measurement link, and a coordinated control link; the frequency measurement link is used to collect the system frequency and calculate the frequency deviation and frequency change rate, and the frequency change rate is output after being filtered by a low-pass filter to remove high-frequency noise; The coordinated control unit is used to execute the multi-timescale coordinated frequency regulation method of thermal power and energy storage as described in any one of claims 1 to 9, outputting energy storage power commands to the energy storage device and outputting thermal power regulation commands to the thermal power unit; the energy storage device is connected to the power grid through the power conversion device, and releases or absorbs active power according to the energy storage power commands; the thermal power unit changes its mechanical power output according to the thermal power regulation commands.

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