Optical storage power station multi-mode frequency support control method considering time-of-use electricity price

Abstract

The invention discloses an optical storage power station multi-mode frequency support control method considering time-of-use electricity price, and the method integrates multi-source information, constructs a joint criterion of time-of-use electricity price-supply and demand relation-power grid demand, and achieves the multi-mode adaptive cooperative control and active support of an optical storage power station. The photovoltaic side is switched between a maximum power point tracking mode and an active standby mode to provide a controllable power margin; the energy storage side realizes reasonable power distribution and rapid frequency support among multiple energy storage units by introducing state-of-charge balance and frequency droop control; and the energy storage charge state threshold value is dynamically adjusted according to the electricity price level and the power grid operation state, so that the frequency adjustment capability is reserved while economic operation is ensured. According to the invention, economy and power grid frequency active support requirements can be considered in different electricity price periods and operation conditions, the frequency response speed of the optical storage power station, the available active support margin and the system operation stability are improved, and the method has good engineering application value.

Description

Technical Field

[0001] This invention belongs to the field of new energy grid connection and power electronic control, specifically involving a multi-mode frequency support control method for photovoltaic-storage power stations that considers time-of-use pricing, applicable to the grid-connected operation of centralized / string photovoltaic-storage power stations with multiple energy storage units. Background Technology

[0002] Modern power grids are shifting their requirements for renewable energy power plants from "passive grid connection" to "active support," especially in rapidly providing active power support during frequency disturbances. Under time-of-use (TOU) pricing mechanisms, photovoltaic (PV) and energy storage power plants can increase their operating revenue by purchasing electricity during periods of local electricity price and selling it during periods of high electricity price. However, existing multi-mode operating strategies that consider TOU pricing often prioritize economic efficiency and are difficult to proactively buffer frequency fluctuations during grid disturbances. On the other hand, control based solely on frequency support may lead to a decrease in electricity price arbitrage capabilities and an increase in the imbalance of energy storage SOC, thereby weakening sustainable support capabilities. Furthermore, existing multi-mode control methods that consider TOU pricing are mostly "passive adaptations," making it difficult to buffer frequency fluctuations "naturally and proactively." A shift from passive to active support is needed.

[0003] Therefore, a control scheme is needed that can simultaneously take into account economic operation under time-of-use pricing and active grid frequency support, and can maintain SOC balance and improve available support margin under multiple energy storage units.

[0004] A search revealed Chinese invention patent CN104065095A, which discloses a method for optimizing primary frequency regulation control of a battery energy storage system. The method includes the following steps: obtaining the power deficit and grid frequency deviation rate of the primary frequency regulation; determining the regulation ratio coefficient of the battery energy storage system; calculating the output power value of the battery energy storage system; determining the timing and degree of correction for the battery's state of charge (SOC), and performing the correction. This invention overcomes the shortcomings of insufficient generator power variation, and due to the fast response speed of the energy storage system, it facilitates faster grid frequency recovery. After frequency regulation, without causing the grid frequency to exceed the dead zone, the battery's SOC is corrected to ensure the smooth progress of the next frequency regulation process. Furthermore, considering time-of-use pricing, the charging cost of energy storage is reduced, and the reverse discharge benefit is increased.

[0005] The technical comparison between this application and the aforementioned patent is as follows:

[0006] The patent "A Method for Assisted Primary Frequency Regulation Optimization Control of a Battery Energy Storage System" provides a method for assisting primary frequency regulation optimization control of a battery energy storage system. This method collects grid frequency deviation and its rate of change, uses fuzzy inference to obtain the frequency regulation ratio coefficient, and then calculates the frequency regulation output power of the energy storage system. Furthermore, when frequency regulation ends or the system is not participating in regulation, the system's state of charge (SOC) is corrected in conjunction with time-of-use pricing. The control object of this scheme is primarily the battery energy storage system, and time-of-use pricing is mainly used for SOC correction and operational economic optimization after frequency regulation. It does not address the issues of photovoltaic power mode switching or the collaborative participation of photovoltaic and energy storage systems in frequency support.

[0007] The "Multi-mode Frequency Support Control Scheme for Photovoltaic-Storage Power Stations Considering Time-of-Use Pricing" proposed in this invention not only performs frequency regulation control on the energy storage system, but also introduces the switching between the photovoltaic side's MPPT mode and active power reserve mode, enabling the photovoltaic system to participate in frequency support with controllable power margin. At the same time, time-of-use pricing, power station supply and demand relationship, and grid frequency demand are used as operating mode criteria. During operation, the energy storage SOC threshold is dynamically adjusted and a balanced distribution of multiple energy storage SOCs is achieved. This ensures that both the economic operation of the power station and the grid's active frequency support capability are taken into account during different electricity price periods. This control concept and technical means are different from the aforementioned existing technologies.

[0008] A search revealed that Chinese invention patent CN120955807A discloses a coordinated optimization control method and system for a grid-connected photovoltaic-storage-charging integrated power station. If the DC bus voltage exceeds the limit and the actual output power of the grid-connected converter is greater than the grid-connected power reference value, and the State of Charge (SOC) is less than or equal to the lower limit of the grid support zone, the system controls the output power reference value of the charging pile and the grid-connected power reference value of the grid-connected converter. If the SOC is greater than the lower limit of the grid support zone, the system controls the discharge power reference value of the energy storage system, the output power reference value of the charging pile, and the grid-connected power reference value of the grid-connected converter. If the DC bus voltage exceeds the limit and the actual output power of the grid-connected converter is not greater than the grid-connected power reference value, and the SOC is greater than or equal to the upper limit of the grid support zone, the system controls the output power reference value of the photovoltaic system and the grid-connected power reference value of the grid-connected converter. If the SOC is less than the upper limit of the grid support zone, the system controls the charging power reference value of the energy storage system, the photovoltaic output power, and the grid-connected power reference value of the grid-connected converter, thus achieving switching of operating modes under different application scenarios.

[0009] The technical comparison between this application and the aforementioned patent is as follows:

[0010] The patent "Coordinated Optimization Control Method and System for Grid-Based Photovoltaic-Storage-Charging Integrated Power Station" discloses a coordinated optimization control method and system for a grid-based photovoltaic-storage-charging integrated power station. This method uses DC bus voltage and grid-connected power deviation as primary triggering conditions. By dividing the SOC of the energy storage system into different intervals, it coordinates the power reference values ​​of photovoltaic, energy storage, charging piles, and grid-connected converters when the bus voltage exceeds limits or power is unbalanced, achieving multi-mode switching and stable operation within the station. This solution focuses on the coordination of multiple devices within the grid-based power station and DC-side stability, with SOC thresholds often using a fixed ratio for partitioning.

[0011] The "Multi-mode Frequency Support Control Scheme for Photovoltaic and Energy Storage Power Stations Considering Time-of-Use Pricing" proposed in this invention focuses on constructing a joint criterion based on time-of-use pricing, power station supply and demand, and grid frequency status to drive multi-mode coordinated control of photovoltaic and energy storage. This invention proposes to dynamically adjust the energy storage SOC threshold based on electricity price level and grid frequency demand, and introduces a frequency support mechanism that combines photovoltaic active power reserve with energy storage droop control, thereby realizing the active support of the photovoltaic and energy storage system for grid frequency under different operating conditions. Its control objectives, criterion construction methods, and SOC management strategies are all different from the above-mentioned integrated grid-connected power station control methods.

[0012] A search revealed that Chinese invention patent CN111224414A discloses a method and apparatus for configuring energy storage capacity in a photovoltaic-storage power station. The method involves obtaining the output power of the photovoltaic system and the actual load of the power system; inputting the output power of the photovoltaic system and the actual load of the power system into a pre-constructed energy storage capacity configuration model; and using linear programming to solve the energy storage capacity configuration model to obtain the configured capacity of the energy storage system. The energy storage capacity configuration model is constructed based on the expected amount of curtailed solar power during ramp-up and the confidence capacity of the photovoltaic-storage power station. This invention helps improve the efficient utilization of energy storage in photovoltaic-storage power stations during automatic generation control frequency regulation. Considering the dynamic ramp-up reliability of photovoltaic-storage power stations, it helps reduce the amount of curtailed solar power caused by ramp-up events through the energy storage system, improves the effective load capacity of photovoltaic-storage power stations through energy storage, and helps provide energy storage capacity configuration that adapts to the different energy storage configuration requirements of various photovoltaic-storage power stations, thus providing a foundation for energy storage configuration in photovoltaic-storage power stations.

[0013] The technical comparison between this application and the aforementioned patent is as follows:

[0014] The patent "A Method and Device for Configuring Energy Storage Capacity in a Photovoltaic-Storage Power Station" discloses a method and device for configuring energy storage capacity in a photovoltaic-storage power station. This method optimizes the configuration of energy storage system capacity by establishing an objective function and constraints that include indicators such as curtailment, confidence capacity, and AGC demand. This belongs to the capacity configuration method in the planning and design phase of a photovoltaic-storage power station. However, this scheme focuses on determining the scale and configuration ratio of energy storage capacity and does not address how the photovoltaic-storage system performs multi-mode control based on time-of-use pricing and grid frequency conditions during actual operation.

[0015] The "Multi-mode Frequency Support Control Scheme for Photovoltaic-Energy Storage Power Stations Considering Time-of-Use Pricing" proposed in this invention addresses the operation and control phase after the photovoltaic-energy storage power station is put into operation. This scheme considers time-of-use pricing and, by constructing a joint criterion of "electricity price—supply and demand—frequency," enables adaptive mode switching between photovoltaic and energy storage systems under different operating conditions. Furthermore, it enhances the real-time frequency support capability of the photovoltaic-energy storage system through SOC equalization and dynamic threshold adjustment. This invention focuses on the coordinated control and frequency support effect at the operational level, and differs fundamentally from the aforementioned capacity configuration technologies in terms of technical stage, control object, and technical effect. Summary of the Invention

[0016] To address the aforementioned issues, this invention proposes a multi-mode frequency support control method for photovoltaic-storage power stations that considers time-of-use pricing: economic operation is achieved through multi-mode adaptive switching under varying time-of-use pricing and operating conditions, while active support for grid frequency is achieved through energy storage SOC balancing and photovoltaic active power reserve / charge-discharge regulation.

[0017] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0018] A multi-mode frequency support control method for photovoltaic-storage power plants considering time-of-use pricing includes the following steps:

[0019] S1. Multi-source information acquisition and state quantity calculation;

[0020] S2, Photovoltaic operating mode design, including MPPT control mode and active power reserve control mode;

[0021] S3, Energy storage side DC-DC control;

[0022] S4, Photovoltaic-Storage Integrated Unit Converter Control;

[0023] S5. Adjustment of SOC threshold based on grid demand;

[0024] S6. Determination of the model based on the joint criterion of "time-of-use electricity price - supply and demand relationship".

[0025] As a preferred technical solution of the present invention, step S1 is specifically as follows:

[0026] Collect and update the following multi-source information:

[0027] Time-of-use pricing level λ(t);

[0028] Photovoltaic power generation output P pv ;

[0029] Near-end load demand P L

[0030] Grid connection point frequency f and rated frequency f n Calculate frequency ;

[0031] The state of charge (SOC) of the i-th energy storage unit i .

[0032] As a preferred technical solution of the present invention, step S2 is specifically as follows:

[0033] The photovoltaic (PV) operating mode adopts dual-mode control, namely MPPT control mode and active power reserve control mode, as described below:

[0034] (1);

[0035] Among them, V pv_ref V is the voltage setpoint for PV control. mppt This is the maximum power output of PV obtained by the MPPT algorithm at this moment, k vp With k vi These are the proportional and integral coefficients of the PI control, respectively, where s is the Laplace operator, and V... dc_ref The given value for the DC capacitor voltage, V dc EN represents the DC capacitor voltage, and EN is the mode switching logic signal.

[0036] As a preferred technical solution of the present invention, step S3 is as follows:

[0037] The specific implementation of DC-DC control on the energy storage side is as follows:

[0038] (2);

[0039] Among them, i ess_ref The setpoint for the energy storage output current; k pp With k pi These are the PI proportional and integral coefficients of the energy storage PI power loop, respectively; P ess_ref P is the power setpoint for the energy storage output; ess For energy storage output; m is the active power droop coefficient, ω n ω is the reference value for the frequency, sgn(·) is the output frequency, and n is the sign function; n is used to balance the SOC among multiple ESUs.i This represents the SOC state of the i-th ESU.

[0040] As a preferred technical solution of the present invention, step S4 is specifically as follows:

[0041] The inverter control of the photovoltaic-storage integrated unit adopts adaptive droop control, as detailed below:

[0042] (3);

[0043] Where ω is the output frequency, ω n k is the reference value for frequency. acp With k aci These are the PI proportionality and integral coefficients, respectively, where s is the Laplace operator; V dc_ref The given value for the DC capacitor voltage, V dc EN is the DC capacitor voltage; EN is the mode switching logic signal, P ref P and P represent the active power setpoint and calculated active power, respectively. The voltage control of the photovoltaic-storage integrated unit converter is E. n .

[0044] As a preferred technical solution of the present invention, step S5 is as follows:

[0045] The specific adjustments to the SOC threshold are as follows:

[0046] During periods of low electricity prices:

[0047] Energy storage devices actively charge to reduce electricity costs, adjust the charging threshold of the energy storage device's State of Charge (SOC) to avoid excessive grid frequency fluctuations, and provide active grid support by reserving power margins. This can be described as follows:

[0048] (4);

[0049] Among them, SOC th Here, A is the power reserve factor between frequency and state of charge (SOC), and f is the grid connection frequency. n The rated frequency;

[0050] During peak electricity price periods:

[0051] In scenarios where supply exceeds demand, when the grid frequency is too low, the SOC of the energy storage device can be increased. th Energy storage devices can release more electricity to support grid operation, as stated in the following statement:

[0052] (5);

[0053] In scenarios where supply falls short of demand, energy storage discharges to reduce electricity purchase costs while adjusting the State of Charge (SOC).th To support the power grid, even when the grid frequency drops, it is stated as follows:

[0054] (6);

[0055] During the flat electricity price period:

[0056] Similar to the above, based on the standard grid frequency, and on the basis of energy storage charging and discharging, the SOC is... th Adjusting power reserves to enhance the grid's proactive support capabilities.

[0057] As a preferred technical solution of the present invention, step S6 is specifically as follows:

[0058] Based on the relationship between λ(t) and power balance And the frequency difference Δf, to determine the system operating mode.

[0059] Beneficial effects:

[0060] In time-of-use pricing scenarios, this invention achieves multi-mode operation through a joint criterion of "electricity price-supply-demand-frequency difference," balancing economic efficiency with grid-side frequency support requirements. State of Charge (SOC) equalization allocation enables multiple energy storage units to have greater instantaneous available active power support capacity, preventing premature depletion of support capacity due to individual unit overcharging and over-discharging. The dual-mode photovoltaic MPPT / active power reserve provides the power plant with controllable power margins, enabling rapid upsampling during frequency drops and rapid absorption during frequency rises. Adaptive droop control of the grid-connected converter improves frequency support response speed and system grid deployment capability. Attached Figure Description

[0061] Figure 1 This is a flowchart of the present invention;

[0062] Figure 2 This is the circuit topology diagram of the present invention;

[0063] Figure 3 This is a block diagram of the control algorithm of the present invention;

[0064] Figure 4 This is a schematic diagram of the SOC equalization principle of the present invention;

[0065] Figure 5 This is the hardware-in-the-loop experimental platform of the present invention;

[0066] Figure 6 The output waveform (valley electricity price) of the grid-connected experimental platform of this invention.

[0067] Figure 7 The output waveform (peak electricity price) of the grid-connected experimental platform of this invention.

[0068] Figure 8This is the output waveform (electricity price level) of the grid-connected experimental platform of the present invention. Detailed Implementation

[0069] 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.

[0070] This invention proposes a multi-mode frequency support control method for photovoltaic-storage power stations that considers time-of-use pricing. It achieves economical operation by adaptively switching between multiple modes under changes in time-of-use pricing and operating conditions, while actively supporting the grid frequency through energy storage SOC balancing and photovoltaic active power reserve / charge and discharge regulation.

[0071] like Figure 1-8 As shown, the present invention proposes a multi-mode frequency support control method for photovoltaic-storage power stations considering time-of-use pricing, comprising the following steps:

[0072] S1. Multi-source information acquisition and state quantity calculation:

[0073] Collect and update the following multi-source information:

[0074] 1. Time-of-use electricity pricing level λ(t) (peak / flat / valley electricity price);

[0075] 2. Photovoltaic power generation output P pv ;

[0076] 3. Near-end load demand P L ;

[0077] 4. Grid connection point frequency f and rated frequency f n Calculate frequency ;

[0078] 5. State of charge (SOC) of the i-th energy storage unit i .

[0079] S2. Photovoltaic operating mode design, including MPPT control mode and active power reserve control mode:

[0080] Photovoltaic systems based on the traditional maximum power point tracking (MPPT) control mode can only passively adapt to large power grids by improving power generation efficiency, and cannot actively respond to the frequency support requirements of the power grid.

[0081] Based on the active power reserve mode, PV can flexibly absorb excess power or limit output power by stabilizing DC capacitor voltage and participate in grid frequency regulation.

[0082] To meet the frequency support requirements under the dual fluctuations of irradiance and local load, the photovoltaic operating mode is PV dual-mode control, which is described as follows:

[0083] (1);

[0084] Among them, V pv_ref V is the voltage setpoint for PV control. mppt This is the maximum power output of PV obtained by the MPPT algorithm at this moment, k vp With k vi It is divided into proportional and integral coefficients for PI control, where s is the Laplace operator, and V dc_ref The given value for the DC capacitor voltage, V dc EN represents the DC capacitor voltage, and EN is the mode switching logic signal.

[0085] The switching between the two modes is triggered by the logic signal EN, which automatically switches based on the state of charge (SOC) of the energy storage unit (ESU) and the system frequency. When the ESU can no longer absorb power to suppress the rise in grid frequency, EN will switch from 1 to 0, at which point the MPPT algorithm will stop updating. In this mode, the DC link voltage V... dc The photovoltaic output power is kept constant within the maximum power range through PI control.

[0086] S3, Energy storage side DC-DC control:

[0087] Energy storage control based on state of charge balance: regulating the charging and discharging process of the energy storage device by maximizing the total available power.

[0088] By monitoring grid frequency changes in real time, energy storage devices can flexibly and quickly absorb and release power, thereby optimizing the overall system's operating efficiency and frequency support capabilities. The specific control implementation is as follows:

[0089] (2);

[0090] Among them, i ess_ref The setpoint for the energy storage output current; k pp With k pi These are the PI proportional and integral coefficients of the energy storage PI power loop, respectively; P ess_ref P is the power setpoint for the energy storage output; ess For energy storage output; m is the active power droop coefficient, ω n ω is the reference value for the frequency, sgn(·) is the output frequency, and n is the sign function; n is used to balance the SOC among multiple ESUs. i This represents the SOC state of the i-th ESU.

[0091] The state-of-charge balance of an energy storage system is essentially a dynamic adjustment of its output power, and its principle is as follows: Figure 4As shown, in discharge mode, energy storage units with a higher state of charge (SOC) output more power, while those with a lower SOC output less power. Similarly, in charging mode, units with a lower SOC inject more power, while those with a higher SOC inject less. Based on this principle, the SOC difference gradually decreases, eventually achieving SOC balance. When the SOC of all energy storage units tends to be balanced, the system can participate more effectively in active grid support. This energy storage system can seamlessly adjust its output power—whether maintaining grid stability during frequency fluctuations through discharge or absorbing excess energy under high-frequency conditions—without causing any individual energy storage unit to overload.

[0092] S4, Photovoltaic-Storage Integrated Unit Converter Control:

[0093] Since energy storage no longer controls the DC capacitor voltage, the inverter control strategy of the photovoltaic-energy storage integrated unit adopts adaptive droop control, as described in detail below:

[0094] (3);

[0095] Where ω is the output frequency, ω n k is the reference value for frequency. acp With k aci These are the PI proportionality and integral coefficients, respectively, where s is the Laplace operator; V dc_ref The given value for the DC capacitor voltage, V dc EN is the DC capacitor voltage; EN is the mode switching logic signal, P ref P and P are the given value and calculated value of active power, respectively.

[0096] In addition, the voltage control of the photovoltaic-storage integrated unit converter is E n .

[0097] S5. SOC threshold adjustment based on grid demand:

[0098] During periods of low electricity prices:

[0099] Energy storage reduces electricity costs through active charging. However, to avoid excessive grid frequency fluctuations, the state of charge (SOC) charging threshold of the energy storage device needs to be adjusted. By reserving a certain power margin, the energy storage device can provide active grid support. This control strategy can be expressed as:

[0100] (4);

[0101] Among them, SOC th Here, A is the state-of-charge threshold, A is the power reserve factor between frequency and SOC, and f is the grid connection point frequency. n This is the rated frequency.

[0102] During peak electricity price periods:

[0103] In scenarios where supply exceeds demand, by increasing the state-of-charge threshold of the energy storage system, the energy storage device can release more electricity to support grid operation when the grid frequency is too low.

[0104] (5);

[0105] In scenarios where supply falls short of demand, energy storage discharges to reduce electricity purchase costs, while simultaneously adjusting the SOC threshold to support the grid, even when grid frequency decreases.

[0106] (6);

[0107] During the flat electricity price period:

[0108] Similar to the above idea, based on the standard frequency of the power grid, the SOC threshold is adjusted for power reserve on the basis of energy storage charging and discharging, so as to improve the active support capability for the power grid.

[0109] S6. Determination of the joint criterion of "time-of-use pricing - supply and demand relationship":

[0110] Based on the relationship between λ(t) and power balance And the frequency difference Δf, to determine the system operating mode.

[0111] As shown in Table 1, electricity prices are at their lowest point during off-peak hours:

[0112]

[0113] Table 1. Electricity Price Low Points

[0114] As shown in Table 2, electricity prices are at their peak:

[0115]

[0116] Table 2 Peak Electricity Prices

[0117] As shown in Table 3 when electricity prices are at parity:

[0118]

[0119] Table 3 Electricity Price Parity

[0120] Experimental verification:

[0121] To verify the adaptive switching and proactive support capabilities of the proposed control method under complex operating conditions, three operating condition cases were designed for different electricity price periods in this section. The experiments were conducted on a hardware-in-the-loop (CHIL) platform. Figure 5The CHIL platform configuration based on OPAL-RT 4510 and RT-BOX is demonstrated. The RT-BOX implements the controller functions, while the hardware circuitry is simulated in the OPAL-RT 4510 at a sampling frequency of 10 kHz.

[0122] Case 1: This case aims to evaluate the performance of a photovoltaic (PV) and energy storage (ESS) power station during off-peak electricity price periods. At this time, PV output is zero, while load demand exceeds available power. For economic reasons, the ESS will charge to meet peak demand (Phase 1). Charging will stop when the ESS reaches its State of Charge (SOC) threshold (Phase 2). During periods of rapid grid frequency increases (Phase 3), the ESS will raise its SOC threshold to absorb additional grid power and actively support the grid, while the converter output power remains fixed at -3kW.

[0123] Case 2: This case validated a multi-mode operation mechanism during peak electricity price periods, characterized by an 8kW surplus of photovoltaic (PV) output. The energy storage system absorbed the excess PV power, ensuring the PV-storage power station's output matched load demand (Phase 1). When PV output suddenly dropped (Phase 2), the energy storage system began discharging to maintain load supply, thereby reducing electricity costs during peak periods. Charging ceased when the energy storage system's state of charge (SOC) fell to the lower threshold (Phase 3). When the grid frequency suddenly decreased (Phase 4), the energy storage system further reduced the SOC threshold, continuously discharging to support stable grid operation.

[0124] Case 3: Analysis of the system operation mechanism during grid parity. Initially, the photovoltaic system outputs 7kW, and the energy storage device absorbs excess power through charging (Phase 1). When the grid frequency drops sharply (Phase 2), the energy storage device switches to discharge mode to support the grid. After the grid frequency recovers (Phase 3), the energy storage device resumes charging. If the photovoltaic output suddenly drops significantly (Phase 4), the energy storage device meets local electricity demand through discharge. Faced with a sudden drop in grid frequency (Phase 5), the energy storage device switches back to charging mode to absorb excess grid power. When the energy storage device is close to full charge (Phase 6), the photovoltaic system switches from MPPT mode to active power storage mode, maintaining grid stability by reducing power generation.

[0125] It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any modifications or equivalent changes made based on the technical essence of the present invention shall still fall within the scope of protection claimed by the present invention.

Claims

1. A multi-mode frequency support control method for photovoltaic-storage power stations considering time-of-use pricing, characterized in that, Includes the following steps: S1. Multi-source information acquisition and state quantity calculation; S2, Photovoltaic operating mode design, including MPPT control mode and active power reserve control mode; S3, Energy storage side DC-DC control; S4, Photovoltaic-Storage Integrated Unit Converter Control; S5. Adjustment of SOC threshold based on grid demand; S6. Determination of the model based on the joint criterion of "time-of-use electricity price - supply and demand relationship".

2. The multi-mode frequency support control method for photovoltaic-storage power stations considering time-of-use pricing as described in claim 1, characterized in that, Step S1 is as follows: Collect and update the following multi-source information: Time-of-use pricing level λ(t); Photovoltaic power output P pv ; Proximal load demand P L Grid connection point frequency f and rated frequency f n Calculate frequency ; The state of charge (SOC) of the i-th energy storage unit i .

3. The multi-mode frequency support control method for photovoltaic-storage power stations considering time-of-use pricing as described in claim 1, characterized in that, Step S2 is as follows: The photovoltaic (PV) operating mode adopts dual-mode control, namely MPPT control mode and active power reserve control mode, as described below: （1）； Among them, V pv_ref V is the voltage setpoint for PV control. mppt This is the maximum power output of PV obtained by the MPPT algorithm at this moment, k vp With k vi These are the proportional and integral coefficients of the PI control, respectively, where s is the Laplace operator, and V... dc_ref The given value for the DC capacitor voltage, V dc EN represents the DC capacitor voltage, and EN is the mode switching logic signal.

4. The multi-mode frequency support control method for photovoltaic-storage power stations considering time-of-use pricing as described in claim 1, characterized in that, Step S3 is as follows: The specific implementation of DC-DC control on the energy storage side is as follows: （2）； Among them, i ess_ref The setpoint for the energy storage output current; k pp With k pi These are the PI proportional and integral coefficients of the energy storage PI power loop, respectively; P ess_ref P is the power setpoint for the energy storage output; ess For energy storage output; m is the active power droop coefficient, ω n ω is the reference value for the frequency, sgn(·) is the output frequency, and n is the sign function; n is used to balance the SOC among multiple ESUs. i This represents the SOC state of the i-th ESU.

5. The multi-mode frequency support control method for a photovoltaic-storage power station considering time-of-use pricing as described in claim 1, characterized in that, Step S4 is as follows: The inverter control of the photovoltaic-storage integrated unit adopts adaptive droop control, as detailed below: （3）； Where ω is the output frequency, ω n k is the reference value for frequency. acp With k aci These are the PI proportionality and integral coefficients, respectively, where s is the Laplace operator; V dc_ref The given value for the DC capacitor voltage, V dc EN is the DC capacitor voltage; EN is the mode switching logic signal, P ref P and P represent the active power setpoint and calculated active power, respectively. The voltage control of the photovoltaic-storage integrated unit converter is E. n .

6. The multi-mode frequency support control method for photovoltaic-storage power stations considering time-of-use pricing as described in claim 1, characterized in that, Step S5 is as follows: The specific adjustments to the SOC threshold are as follows: During periods of low electricity prices: Energy storage devices actively charge to reduce electricity costs, adjust the charging threshold of the energy storage device's State of Charge (SOC) to avoid excessive grid frequency fluctuations, and provide active grid support by reserving power margins. This can be described as follows: （4）； Among them, SOC th Here, A is the power reserve factor between frequency and state of charge (SOC), and f is the grid connection frequency. n The rated frequency; During peak electricity price periods: In scenarios where supply exceeds demand, when the grid frequency is too low, the SOC of the energy storage device can be increased. th Energy storage devices can release more electricity to support grid operation, as stated in the following statement: （5）； In scenarios where supply falls short of demand, energy storage discharges to reduce electricity purchase costs while adjusting the State of Charge (SOC). th To support the power grid, even when the grid frequency drops, it is stated as follows: （6）； During the flat electricity price period: Similar to the above, based on the standard grid frequency, and on the basis of energy storage charging and discharging, the SOC is... th Adjusting power reserves to enhance the grid's proactive support capabilities.

7. The multi-mode frequency support control method for photovoltaic-storage power stations considering time-of-use pricing as described in claim 1, characterized in that, Step S6 is as follows: Based on the relationship between λ(t) and power balance And the frequency difference Δf, to determine the system operating mode.

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