Cascade hydropower-to-hybrid variable-speed pumping energy storage broadband virtual inertia coordination control method

Abstract

The invention discloses a cascade hydropower-to-hybrid variable-speed pumping energy storage broadband virtual inertia coordination control method. The method comprises the following steps: S1, acquiring required parameters; s2, decomposing the frequency signal through Fourier transform, judging a dominant frequency band, and calculating the total virtual inertia Jreq required by the power grid; s3, calculating a comprehensive weight Wi; s4, instruction distribution is carried out; s5, step variable-speed water pumping and energy storage cooperative correction is carried out; s6, synchronously issuing the power regulation instruction of each device to the corresponding device; and S7, monitoring the regulation and control effect in real time, dynamically correcting the parameters, and returning to the step S1 for circulation. According to the invention, wide-frequency-domain full coverage is realized, and the frequency stabilization precision is improved; water-light-wind storage multi-energy collaborative synchronization is achieved, and the response efficiency is improved; small and medium-sized variable-speed water pumping energy storage units are high in adaptability, and the service life of equipment is prolonged.

Description

Technical Field

[0001] This invention belongs to the field of novel energy storage and power generation technology, specifically relating to a broadband virtual inertia co-control method for converting cascade hydropower into hybrid variable-speed pumped water storage. Background Technology

[0002] Currently, the installed capacity of photovoltaic and wind power has exceeded that of coal-fired power. The rapid increase in new energy sources has led to the following problems: (1) New energy sources cannot be absorbed: wind and solar power fluctuate greatly, with daily fluctuations reaching 50% to 80%, and the curtailment rate of wind and solar power reaching 5% to 8% or more; (2) Conflicts in the utilization of cascade hydropower: Most of the existing small and medium-sized cascade hydropower plants are run-of-river type, which waste water during the wet season and lack power during the dry season, with equipment utilization rate of only 60% to 70%.

[0003] Transforming existing small and medium-sized cascade hydropower into variable-speed pumped storage, and then combining it with photovoltaic, wind power, and existing hydropower to form a multi-energy complementary system of hydro-solar-wind-storage, can achieve the following: (1) No new dams, reservoirs, or water pipelines are built, and the renovation cost is 50% to 70% lower than that of building new pumped storage facilities; (2) Variable speed pumped hydro storage can smooth out wind and solar power fluctuations, and the wind and solar curtailment rate can be reduced to below 2%; (3) Existing hydropower provides base load power, while variable speed pumped storage provides peak shaving and inertia support, improving system flexibility.

[0004] Grid frequency stability relies on the physical inertia of synchronous generators in traditional thermal and hydropower plants, which suppress frequency abrupt changes through rotor kinetic energy. However, with the integration of wind and solar power at a high proportion, the grid's equivalent inertia drops to 2-3 seconds, leading to reduced frequency stability. (1) Low frequency band of 0.1~1Hz: The slow fluctuation of wind and solar power causes the frequency to drift slowly. If the inertia compensation is not timely, it will trigger frequent malfunctions of the low frequency load shedding device. (2) Mid-frequency band of 1-10Hz: Sudden increase in load and sudden drop in wind and solar power cause the frequency to drop rapidly, resulting in lag in inertial response and threatening the safety of the power grid.

[0005] Small and medium-sized variable-speed pumped hydro storage is an ideal choice for providing distributed virtual inertia due to its small capacity and large quantity. However, the multi-device coordination and wide-frequency domain adaptation of hydro-solar-wind-storage hybrid systems are challenges that cannot be solved by existing technologies.

[0006] Current virtual inertia control technology has shortcomings and cannot be adapted to multi-energy complementarity of hydro, solar, wind, and storage: (1) Existing technologies are mostly aimed at the mid-frequency band (1-5Hz) and do not take into account the low-frequency band (0.1-1Hz) dominated by wind and solar power, which leads to low-frequency drift problem; (2) Existing hybrid energy storage regulation mainly considers "conventional pumped storage + battery", without considering the original cascade hydropower, and the command allocation does not consider the cascade hydraulic coupling, resulting in asynchronous coordinated response; (3) Existing technologies are mostly designed for large-scale conventional pumped storage, and the control algorithm does not set capacity threshold constraints. Small and medium-sized variable speed pumped storage units may be damaged due to "overload control". Summary of the Invention

[0007] This invention aims to solve the problems of multi-energy complementary systems consisting of variable-speed pumped storage, photovoltaic, wind power, and existing small and medium-sized cascade hydropower in the wide frequency range (0.1-10Hz) frequency regulation of the power grid when converting small and medium-sized cascade hydropower into hybrid variable-speed pumped storage systems. It achieves virtual inertia control with "wide frequency range full coverage, synchronous multi-energy complementarity of water, photovoltaic, wind and storage, and capacity adaptation of small and medium-sized variable-speed pumped storage", ensuring grid frequency stability when a high proportion of photovoltaic and wind power are connected.

[0008] According to the technical solution of this invention, this invention provides a method for broadband virtual inertia co-control of cascade hydropower conversion into hybrid variable-speed pumped storage energy, comprising the following steps: Step S1: Collect the required parameters; Step S2: Decompose the frequency signal using Fourier transform, determine the dominant frequency band, and calculate the total virtual inertia J required by the power grid according to the following formula. req : , , , In the formula, J low For the total virtual inertia requirement in the low-frequency band; K low The inertia coefficient is the low-frequency inertia coefficient; Δf low For low-frequency band frequency deviation; ΔP renew,pred For short-term predicted power deviation of wind and solar power; K H This is the correction factor for the cascade head. ΔH is the actual head difference. max For design head difference; J mid For the total virtual inertia requirement in the mid-frequency band; K mid This is the mid-frequency inertia coefficient; S is the rate of change of frequency. total S represents the total capacity of the hybrid system. rated This is the system's rated capacity; Step S3: Calculate the overall weight W according to the following formula. i : , In the formula, W S,i S represents the capacity weight of the i-th device;i S represents the actual available capacity of the i-th device. i,rated Let i be the rated capacity of the i-th device; , In the formula, W V,i The response speed weight for the i-th device; t i Let be the device response time of the i-th device; , In the formula, W E,i C is the economic weight of the i-th device. i The equipment control cost for the i-th device; , In the formula, α is the first weighting coefficient, β is the second weighting coefficient, and γ is the third weighting coefficient; Step S4: Assign instructions according to the following formula: , In the formula, ΔP i For the power adjustment command of the i-th device; K J,i Let be the virtual inertia coefficient of the i-th device; Δf is the real-time power grid frequency deviation; Step S5: Perform coordinated correction of cascade variable-speed pumped storage energy storage according to the following formula: , , In the formula, ΔP down To correct the downstream pumped storage unit command; ΔP down,0 For initial allocation instructions; Q up Q represents the pumping capacity of the upstream pumped storage unit; rated To design the pumping capacity; Step S6: Simultaneously send the power adjustment commands of each device to the corresponding device; Step S7: Monitor the control effect in real time, dynamically adjust the parameters, and return to step S1 to repeat the process.

[0009] In some implementations, in step S2, the low-frequency inertia coefficient K low The value ranges from 0.9 to 1.1. The higher the wind and solar penetration rate, the higher the low-frequency inertia coefficient K. low The larger the value; the higher the mid-frequency inertia coefficient K mid The value ranges from 1.2 to 1.4. The larger the load change amplitude, the greater the mid-frequency inertia coefficient K. mid The larger.

[0010] In some implementations, in step S3, S i ≤1.1S i,rated In the formula, Si,rated Let be the rated capacity of the i-th device; the first weighting coefficient α = 0.4, the second weighting coefficient β = 0.3, and the third weighting coefficient γ = 0.3.

[0011] In some implementations, in step S4, the virtual inertia coefficient of the variable speed pumped storage unit is 0.8 to 1.0, the virtual inertia coefficient of the original hydropower unit is 0.6 to 0.8, and the virtual inertia coefficient of the wind and solar power station is 0.5 to 0.7.

[0012] In some implementations, in step S6, the equipment includes a variable speed pumped storage converter for a variable speed pumped storage unit, a wind and solar inverter for a wind and solar power station, and a guide vane control system for an existing hydropower unit.

[0013] In some implementations, step S6 further includes: For variable speed pumped storage units, power tracking is achieved by adjusting the IGBT switching frequency through a variable speed pumped storage converter. For wind and solar power plants, reactive power compensation is adjusted through wind and solar inverters. When wind and solar power are curtailed, the power regulation command is set to negative to reduce power output and provide inertia. For existing hydropower units, the guide vane opening is adjusted through the guide vane control system to regulate the current power. The guide vane adjustment delay time is controlled in advance to ensure that the guide vane opening adjustment is synchronized with the adjustment of other equipment.

[0014] In some implementations, step S7 specifically includes: real-time monitoring of the frequency deviation Δf and the inertia response deviation ΔJ; if the control effect is not satisfactory, then correcting the control parameters; the control parameters include the low-frequency inertia coefficient K. low Intermediate frequency inertia coefficient K mid Comprehensive weight W i .

[0015] In some implementations, the control parameters are updated every 500ms to adapt to changes in the environment and equipment status; the control parameters include the low-frequency inertia coefficient K. low Intermediate frequency inertia coefficient K mid Comprehensive weight W i .

[0016] Compared with the prior art, the beneficial technical effects of the present invention are as follows: 1. This invention achieves full coverage across a wide frequency range and improves frequency stability accuracy. This invention establishes inertia demand models for low-frequency bands (0.1-1Hz) and mid-frequency bands (1-10Hz), and introduces frequency change rate and wind and solar prediction corrections to solve the problem of "incomplete frequency band coverage" in existing technologies. With the solution of this invention, the power grid frequency deviation can be controlled within ±0.2Hz, and the number of malfunctions of low-frequency load shedding devices is reduced to 0 times / year.

[0017] 2. This invention achieves multi-energy synergy and synchronization of hydropower, solar power, wind power, and energy storage, thereby improving response efficiency. This invention solves the problem of "synchronous coordination" in existing technologies by using "three-dimensional weighted allocation + cascade collaborative correction + synchronous command issuance". With the solution of this invention, the response time difference of multiple devices is ≤50ms, the overall inertial response efficiency is increased from 60% to 100%, and the grid frequency recovery time is shortened from 5s to 2s.

[0018] 3. The small and medium-sized variable speed pumped storage unit of the present invention has strong adaptability and extends the equipment life; the present invention introduces "capacity threshold constraint + overload monitoring and weight correction" to solve the problem of "poor adaptability of small and medium-sized variable speed pumped storage" in the prior art; with the solution of the present invention, the overload rate of small and medium-sized variable speed pumped storage unit is ≤1.1, and the MTBF of IGBT module is extended from 3000h to 8000h, significantly extending the service life of the equipment. Attached Figure Description

[0019] Figure 1 This is a flowchart of the method provided by the present invention. Detailed Implementation

[0020] This invention provides a broadband virtual inertia collaborative control method for converting cascade hydropower into hybrid variable-speed pumped storage. Specifically, it is a broadband virtual inertia collaborative control method for small and medium-sized cascade hydropower conversion into hybrid variable-speed pumped storage. The main purpose is to solve the problems existing in the broadband frequency regulation (0.1-10Hz) of the power grid when converting small and medium-sized cascade hydropower into hybrid variable-speed pumped storage systems. This method achieves virtual inertia control with "wideband coverage, synchronous multi-energy complementarity of hydropower, photovoltaic, wind power, and existing small and medium-sized cascade hydropower," ensuring grid frequency stability when a high proportion of photovoltaic and wind power are connected.

[0021] First, the technical terms involved in this invention are explained as follows.

[0022] (1) Small and medium-sized cascade hydropower station transformation into mixed variable speed pumped storage: transforming the original small and medium-sized cascade hydropower stations into variable speed pumped storage without building new dams, upper reservoirs, lower reservoirs, or water conveyance facilities, including "the transformed variable speed pumped storage + the original cascade hydropower station"; small cascade hydropower stations generally refer to those with a total installed capacity of less than or equal to 50MW, and medium cascade hydropower stations generally refer to those with a total installed capacity of less than or equal to 300MW.

[0023] (2) Wideband Virtual Inertia: Virtual inertia is the function of "inertia suppressing frequency change" of traditional synchronous generators through power electronic equipment. Wideband refers to 0.1 to 10 Hz.

[0024] (3) Coordinated regulation: In a multi-energy complementary system of water, solar, wind and storage, variable speed pumped storage, photovoltaic, wind power and existing hydropower are allocated regulation commands according to the grid inertia demand and preset rules to ensure that the response time difference of multiple devices is ≤50ms and avoid “some devices are over-compensated and some are under-compensated”.

[0025] (4) Virtual inertia coefficient (K) J ): A parameter characterizing the ability of a device to provide virtual inertia, measured in kW•s / Hz, and calculated using the formula K. J =ΔP / Δf (ΔP is the power regulation of the equipment, and Δf is the frequency deviation of the power grid).

[0026] (5) Cascaded Synergistic Gain (K) c ): Considering the correction coefficient for hydraulic coupling between upstream and downstream of the cascade power station, the value ranges from 0.8 to 1.0 and is determined by the difference in head between the cascade stations.

[0027] Existing technologies have failed to solve the complex problems of "hybrid cascade retrofitting + wide frequency domain subdivision + adaptation to small and medium-sized variable speed pumped storage". Specifically, existing technologies have the following shortcomings.

[0028] Disadvantage 1: Incomplete wideband coverage, and the low-frequency drift problem remains unresolved; Reasons: Some existing technologies only target the mid-frequency band (1-5Hz), while others do not divide the frequency band, and none of them consider the low-frequency band (0.1-1Hz) dominated by the slow fluctuation of wind and solar power; moreover, none of the existing technologies consider the "frequency change rate (dΔf / dt)" as a correction for inertia requirements, and cannot distinguish between "slow drift" and "rapid change". Conclusion: When the power grid experiences frequency drift in the low-frequency band, the lack of inertia compensation leads to malfunction of the low-frequency load shedding device.

[0029] Disadvantage 2: Failure to consider multi-energy coordination and cascade hydraulic coupling leads to asynchronous response; Reasons: Some existing technologies do not consider the multi-energy complementarity between new energy sources such as photovoltaics and wind power and existing cascade hydropower; some existing technologies do not consider cascade hydropower; all existing technologies do not consider the hydraulic coupling effect of cascade hydropower, and the cascade synergistic gain K is not considered when allocating commands. c ; Conclusion: The response time of multiple devices in the hydro-solar-wind-storage hybrid system is different. Pumped storage has responded, while the original hydropower is delayed. The actual power of the downstream units of the cascade hydropower is ≥15% lower than the design due to the reduction of water head. The overall inertial response efficiency decreases by 40%, and the grid frequency deviation cannot be controlled within ±0.2Hz.

[0030] Disadvantage 3: Poor adaptability of small and medium-sized hydropower units, leading to overload damage; Reasons: Some existing technologies are designed for large hydropower units, and some do not set capacity threshold constraints; none of the existing technologies consider the "unit rated capacity factor (K)". S = P i / S i S i "(Rated capacity)," the control command exceeded the carrying capacity of small and medium-sized hydropower units; Conclusion: In small and medium-sized hydropower units, the IGBT module overheats and is damaged due to "overload control", resulting in a shortened MTBF (Mean Time Between Failures) of 3000h.

[0031] Disadvantage 4: It does not utilize existing cascade hydropower resources, resulting in poor economic efficiency; Reasons: Some existing technologies only have conventional pumped storage, and some use lithium batteries. Neither of them takes into account the original cascade hydropower retained in the hydro-solar-wind-storage hybrid system. The original hydropower can provide base load inertia and reduce the regulation pressure of pumped storage and batteries. Conclusion: Conventional pumped storage units experience increased start-up and shutdown frequency and shortened battery cycle life.

[0032] To address the aforementioned issues, this invention employs a five-layer architecture—"data acquisition, wideband inertia demand calculation, multi-energy collaborative allocation, machine-network collaborative execution, and closed-loop feedback optimization"—and establishes five modules to construct a wideband virtual inertia collaborative control system for converting cascade hydropower into hybrid variable-speed pumped storage. This system achieves "wideband coverage, multi-energy collaboration, and adaptation to small and medium-sized variable-speed pumped storage." The five modules are detailed below.

[0033] (1) Multi-source data acquisition module: Real-time acquisition of required parameters and transmission and storage as needed for calculation, feedback, optimization, etc.; (2) Wideband Inertia Demand Algorithm Module: Divide the low-frequency band (0.1-1Hz) and the mid-frequency band (1-10Hz) to establish an inertia demand model and calculate the total virtual inertia J required by the power grid. req ; (3) Multi-energy complementary and coordinated allocation module of hydropower, solar power, wind power and storage (hereinafter referred to as multi-energy coordinated allocation module): Based on the weighted principle of "capacity-response speed-economy", the module will allocate J req Distributed to variable speed pumped storage units (ΔP) pump ), wind and solar power stations (ΔP) renew ), existing hydropower units (ΔP) hydro ); (4) Machine-Network Coordination Execution Module: Synchronously sends control commands to the variable speed pumped storage converter, wind and solar inverter, and the existing hydropower guide vane control system to ensure synchronous response of multiple devices; (5) Closed-loop feedback optimization module: Real-time monitoring of frequency deviation Δf and inertia response deviation ΔJ, dynamic correction of weight allocation and inertia parameters, forming closed-loop control.

[0034] The multi-source data acquisition module (Module 1) collects parameters categorized as follows: grid parameters, parameters of the hydro-solar-wind-storage multi-energy complementary system (referred to as hybrid system parameters), cascade hydraulic parameters, and equipment status parameters. Further, environmental parameters may also be included. Grid parameters specifically include frequency f, frequency change rate dΔf / dt, and voltage U. Corresponding acquisition equipment includes, for example, a high-precision frequency analyzer with a sampling frequency of, for example, 100Hz. The sampling accuracy requirement for frequency f is, for example, ±0.001Hz, and the sampling accuracy requirement for frequency change rate dΔf / dt is, for example, ±0.01Hz / s. Hydro-solar-wind-storage multi-energy complementary system parameters specifically include wind power P. wind Photovoltaic power P solar Variable speed pumped storage unit power P pump State S pump (Take 1 in power generation mode, and 0 in pumped storage mode) Original hydropower P hydro The guide vane opening θ, and the corresponding data acquisition equipment, such as power sensors, operating condition switches, and angle sensors, with a sampling frequency of, for example, 10Hz, and sampling accuracy requirements for each power level, such as ±0.5%, and sampling accuracy requirements for the guide vane opening θ, such as ±1°. The specific hydraulic parameters of the cascade include the upstream water level H. up Downstream water level H down The head difference ΔH, and the corresponding data acquisition equipment, such as a water level sensor, with a sampling frequency of, for example, 1Hz and a sampling accuracy requirement of, for example, ±0.01m. Specific equipment status parameters include the temperature T of the variable-speed pumped storage converter. conv The original hydroelectric generator unit speed n hydro The corresponding data acquisition equipment includes thermocouples and speed sensors, with a sampling frequency of, for example, 5Hz, and the temperature T of the variable speed pumped water storage converter. conv The sampling accuracy requirement is, for example, ±0.5℃, and the original hydropower unit speed n hydro The sampling accuracy requirement is, for example, ±1 r / min. Specific environmental parameters include wind speed (v) and light intensity (G). Data transmission and storage methods include, for example, using industrial Ethernet for data transmission, deploying a local edge server to store one month's worth of historical data for parameter optimization.

[0035] The wideband inertia requirement algorithm module (Module 2) is based on "frequency band subdivision + multi-factor correction" to calculate the required inertia for the low-frequency and mid-frequency bands respectively. Specifically, it includes the following inertia requirement models: low-frequency band (0.1-1Hz), mid-frequency band (1-10Hz), and wideband total inertia requirement model: Considering that the low-frequency band is dominated by the slow fluctuation of wind and solar power, the predicted wind and solar power and the frequency drift need to be combined to form the following low-frequency inertia demand model (model formula 1): , In the formula, J low The total virtual inertia requirement for the low-frequency band (unit: kW·s / Hz). K low The inertia coefficient is a low-frequency inertia factor (determined by experimental fitting, with values ​​ranging from 0.9 to 1.1; the higher the wind and solar permeability, the higher K). low The larger); Δf low This refers to the frequency deviation in the low-frequency band (unit: Hz, e.g., 50Hz-49.8Hz=0.2Hz). ΔP renew,pred The short-term predicted power deviation for wind and solar power (unit: kW, for example, using the ARIMA model to predict power changes within 10 minutes; for example, if the predicted power is 50MW and the actual power is 40MW, then the deviation is 10MW). K H This is the correction factor for the cascade head. ΔH is the actual head difference. max For design head difference (e.g., ΔH=80m, ΔH max =100m, then K H =0.96).

[0036] Considering that the mid-frequency band is dominated by sudden load changes and a sharp drop in wind and solar power, the frequency change rate dΔf / dt is introduced to form the following mid-frequency inertia demand model (model formula 2): , In the formula, J mid The total virtual inertia requirement for the mid-frequency band (unit: kW·s / Hz). K mid K is the mid-frequency inertia coefficient (values ​​range from 1.2 to 1.4; the larger the load change amplitude, the greater the inertia coefficient). mid The larger); The frequency change rate (unit: Hz / s, for example, if the frequency changes from 50Hz to 49.5Hz in 0.5s, then...) =1Hz / s); S total The total capacity of the hybrid system (unit: kW, total capacity includes pumped storage, wind and solar power, and existing hydropower). S rated The rated capacity of the system (unit: kW, which is the design value).

[0037] By decomposing the frequency signal using Fourier transform, the dominant frequency band is determined, and the total inertia requirement is calculated. Specifically, the following wideband total inertia requirement model (model formula 3) is adopted: , In the formula, J req This represents the total virtual inertia required by the power grid. If the dominant frequency band is in the range of 0.1Hz to 1Hz (i.e., low frequency band), then the total virtual inertia required by the power grid is J. req That is, the total virtual inertia requirement J in the low-frequency band. low If the dominant frequency band is in the range of 1Hz to 10Hz (i.e., the mid-frequency band), then the total virtual inertia required by the power grid is J. req This is the total virtual inertia requirement J in the mid-frequency band. mid If the frequency bands overlap, the total virtual inertia J required by the power grid will be... req =0.6 J low +0.4J mid .

[0038] The dominant frequency band refers to the frequency band containing the dominant frequency. The dominant frequency is the frequency value corresponding to the peak power spectral density after the real-time frequency signal is decomposed by Fourier transform. Frequency band overlap refers to the frequency range in which both low-frequency (0.1-1Hz) and mid-frequency (1-10Hz) frequency components exist simultaneously, and the energy proportion of both components is relatively high (without a clear single dominant frequency). In this invention, it specifically refers to the transition range of 0.8-1.2Hz, which spans the low-frequency and mid-frequency bands, to improve the accuracy of calculations.

[0039] The hydro-solar-wind-storage multi-energy complementary and coordinated allocation module (Module 3) is based on the three-dimensional weighted principle of "capacity-response speed-economy" to ensure that small and medium-sized variable speed pumped storage units are not overloaded and that multiple devices respond synchronously. Specifically, it includes the following: Three types of weights are set: capacity weight, response speed weight, and cost-effectiveness weight. Capacity weight W S Positively correlated with the rated capacity of the equipment, to avoid overloading of small and medium-sized units: S i ≤1.1S i,rated , In the formula, W S,i S represents the capacity weight (of the i-th device); i S represents the actual available capacity of the i-th device. i,rated To further limit S to the rated capacity of the (i-th) device. i ≤1.1S i,rated To prevent overload.

[0040] Response speed weight W V The response time of the equipment is negatively correlated with its speed: wind and solar inverters are the fastest (e.g., ≤30ms), followed by pumped storage inverters (e.g., ≤50ms), and existing hydropower is the slowest (e.g., ≤80ms). , In the formula, W V,iThe response speed weight (for the i-th device); t i Let be the device response time (of the i-th device). For example, if the device response time t of a wind-solar inverter is 30ms, then 1 / t = 0.033ms. -1 ).

[0041] Economic weight W E The cost of hydropower is negatively correlated with equipment control costs. Existing hydropower has the lowest cost (e.g., 0.1 yuan / kWh), followed by pumped storage (e.g., 0.3 yuan / kWh), while wind and solar power (when curtailment occurs) have a cost of 0. , In the formula, W E,i C is the economic weight (for the i-th device). i Let C be the equipment control cost (for example, if the original hydropower equipment control cost C is 0.1 yuan / kWh, then 1 / C = 10kWh / yuan).

[0042] Then, comprehensive weight calculation and instruction allocation are performed.

[0043] Overall weight W i The weighted sum of the three weights (Model Formula 4): ; The weighting coefficients are determined through particle swarm optimization. For example, the first weighting coefficient α = 0.4, the second weighting coefficient β = 0.3, and the third weighting coefficient γ = 0.3.

[0044] The instruction allocation model (model formula 5) is as follows: , In the formula, ΔP i This is the power adjustment command for the i-th device (unit: kW, positive for power generation mode, negative for pumping mode). K J,i The virtual inertia coefficient of the i-th device (e.g., 0.8–1.0 for variable speed pumped storage units, 0.6–0.8 for existing hydropower units, and 0.5–0.7 for wind and solar power stations). Δf is the real-time power grid frequency deviation (unit: Hz).

[0045] Next, a coordinated correction for cascade variable-speed pumped hydro storage is performed. For small and medium-sized cascade variable-speed pumped hydro storage, a cascade coordinated gain K is established. c Correct downstream unit commands to avoid deviations caused by hydraulic coupling.

[0046] The command correction model for the cascade variable speed pumped storage unit (model formula 6) is as follows: , , In the formula, ΔP down The revised downstream pumped storage unit instruction (unit: kW); ΔP down,0 For the initial allocation instruction (unit: kW, which is a given data, usually the rated power). Q up Pumping capacity of upstream pumped storage unit (unit: m³) 3 / s); Q rated Design pumping capacity (unit: m³) 3 / s).

[0047] The machine-network collaborative execution module (Module 4) adopts "synchronous command issuance + device characteristic adaptation" to ensure synchronous response from multiple devices, specifically including: (1) Synchronous instruction issuance: ΔP is transmitted via the network. i Simultaneously, the data was distributed to the controllers of each device (variable speed pumped storage converter, wind and solar inverter, and existing hydropower guide vane control system (PLC control system)). (2) Equipment characteristic adaptation: For variable speed pumped storage units: power tracking is achieved by adjusting the IGBT switching frequency through a variable speed pumped storage converter; For wind and solar power plants: Reactive power compensation is adjusted via wind and solar inverters. When wind and solar power are curtailed, priority is given to adjusting ΔP. i Setting it to negative reduces output and effectively provides inertia. For existing hydropower units: the guide vane opening is adjusted through the guide vane control system to adjust the current power. The guide vane adjustment delay is initiated 50ms in advance through "predictive control" (based on the guide vane adjustment delay time to ensure that the guide vane opening adjustment is synchronized with the adjustment of other equipment).

[0048] As a supplementary explanation, ΔP i The power regulation command for the i-th device is calculated using model formula 5, and includes downstream pumped storage units, wind and solar power, and existing hydropower; ΔP down The corrected downstream pumped storage unit command is ΔP. i One of the instructions.

[0049] The closed-loop feedback optimization module (module 5) monitors the control effect in real time and dynamically corrects the parameters. Preferably, it monitors the frequency deviation Δf and the inertial response deviation ΔJ in real time (more preferably, it also includes the overload rate K). over If the control effect is not satisfactory, the control parameters will be adjusted; the control parameters include the low-frequency inertia coefficient K. low Intermediate frequency inertia coefficient K mid Comprehensive weight W i Preferably, K is updated every 500ms.low K mid W i This ensures long-term adaptability to changes in environment and equipment condition. Overload rate K over The overload rate is used to quantify whether a hydropower unit is operating under overload conditions. It is the ratio of the actual output power to the rated power and is a commonly used monitoring indicator to ensure the safety of hydropower units.

[0050] The overall system control flow is as follows Figure 1 As shown, in summary: Start → Multi-source data acquisition (Module 1) → Fourier transform frequency band identification → Determine the dominant frequency band (low frequency / mid frequency / overlapping) → Calculate J req (Model Formula 1 / 2 / 3) → Calculate Equipment Weights (Model Formula 4) → Allocate ΔP i (Model Formula 5) → Downstream correction (Model Formula 6) → Synchronous instruction issuance (Module 4) → Execution control → Monitoring Δf / ΔJ / K over (Module 5) → Determine if the standard is met (Yes → Loop through data collection, No → Loop through data collection after parameter correction) → End.

[0051] Specifically, the present invention provides a broadband virtual inertia co-control method for converting cascade hydropower into hybrid variable-speed pumped storage, comprising the following steps: Step S1: Collect the required parameters, specifically, for example, through the aforementioned module 1.

[0052] Step S2: Decompose the frequency signal using Fourier transform, determine the dominant frequency band, and calculate the total virtual inertia J required by the power grid according to the following formulas (Model Formula 3, Model Formula 1 and / or Model Formula 2). req : , , .

[0053] Step S3: Calculate the overall weight W according to the following formulas (model formula 4 and the calculation formulas for capacity weight, response speed weight, and economy weight). i : , , , .

[0054] Step S4: Assign instructions according to the following formula (Model Formula 5): .

[0055] Step S5: Perform coordinated correction of cascade variable-speed pumped storage energy storage according to the following formula (model formula 6): , .

[0056] Step S6: The power adjustment commands of each device are synchronously sent to the corresponding device, for example, through the aforementioned module 4.

[0057] Step S7 involves real-time monitoring of the control effect and dynamic adjustment of parameters, specifically through module 5 mentioned above; then returning to step S1 and repeating the process to form a closed-loop control, specifically through module 5 mentioned above.

[0058] This invention breaks through the technical bottleneck of "hybrid variable speed pumped storage + wide frequency domain virtual inertia" by "wide frequency domain subdivision modeling + multi-energy collaborative weighting + closed-loop feedback protection". It achieves "multi-objective balance" and balances the contradiction between "accuracy-cost-adaptability", taking into account stability, safety and economy. The key points are as follows:

[0059] Key Point 1: Wideband Subdivision Modeling and Multi-Factor Correction; Existing technologies do not segment frequency bands and only cover a single frequency band. This invention is the first to subdivide the power grid frequency regulation band into "low-frequency band dominated by wind and solar fluctuations - mid-frequency band dominated by load mutations", and introduces differentiated correction factors for each frequency band: (1) Low frequency band: Combine short-term wind and solar forecasts with cascade head to solve the problem of insufficient compensation for "slow drift"; (2) Mid-frequency band: Introduce frequency change rate to solve the response lag of "rapid change"; Real-time frequency band identification is achieved through Fourier transform, ensuring that the inertia requirement calculation is "accurately adapted to the frequency band characteristics".

[0060] Key Point 2: A three-dimensional weighted allocation strategy for multi-energy synergy of hydropower, solar power, wind power, and energy storage; Existing technologies allocate commands only based on capacity and response speed. This invention proposes a three-dimensional weighted strategy of "capacity-response speed-economy," and introduces a synergistic gain K for cascade hydropower. c : (1) Capacity weighting avoids overload of small and medium-sized variable speed pumped storage systems; (2) Response speed weighting ensures synchronization; (3) The economic weighting adopts the existing hydropower to reduce costs; (4) Step correction to resolve hydraulic coupling deviation.

[0061] Key Point 3: Closed-loop feedback protection mechanism for small and medium-sized variable speed pumped storage; Existing technologies lack overload protection and dynamic optimization. This invention constructs full life-cycle protection for small and medium-sized variable-speed pumped hydro storage through "overload rate monitoring + real-time parameter correction." (1) Avoid overload risks in real time and extend equipment life; (2) Dynamically adapt to environmental changes such as wind speed and water head fluctuations to avoid the decrease in accuracy caused by parameter fixation; This mechanism addresses the inherent shortcomings of small and medium-sized variable speed pumped storage units, namely "small capacity and weak anti-interference capability," and is an important guarantee for the practical application of the technology.

[0062] Based on the comparison between the technical solution of this invention and the prior art, the following advantages are found.

[0063] Advantage 1: Wide frequency range coverage, improving frequency stability accuracy; Reason: This invention establishes inertia demand models for low-frequency bands (0.1-1Hz) and mid-frequency bands (1-10Hz), and introduces frequency change rate and wind and solar prediction corrections to solve the problem of "incomplete frequency band coverage" in existing technologies; Conclusion: The power grid frequency deviation can be controlled within ±0.2Hz, and the number of malfunctions of the low-frequency load shedding device is reduced to 0 times / year.

[0064] Advantage 2: Synergistic and simultaneous operation of hydropower, solar power, wind power, and energy storage improves response efficiency; Reason: This invention solves the problem of "unsynchronized collaboration" in existing technologies by using "three-dimensional weighted allocation + tiered collaborative correction + synchronous instruction issuance"; Conclusion: The response time difference between multiple devices is ≤50ms, the overall inertia response efficiency is improved from 60% to 100%, and the power grid frequency recovery time is shortened from 5s to 2s.

[0065] Advantage 3: Small and medium-sized variable speed pumped storage units have strong adaptability and extend equipment life; Reason: This invention introduces "capacity threshold constraint + overload monitoring and weight correction" to solve the problem of "poor adaptability to small and medium-sized variable speed pumped storage" in existing technologies; Conclusion: The overload rate of small and medium-sized variable speed pumped storage units is ≤1.1, and the MTBF of IGBT modules is extended from 3000h to 8000h, thus extending the service life of the equipment.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; obviously, the described embodiments are some embodiments of the present invention, but not all embodiments; based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention; in the absence of conflict, the embodiments and features in the embodiments of the present invention can be combined with each other; modifications to the technical solutions described in the foregoing embodiments, or equivalent substitutions for some of the technical features, do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for broadband virtual inertia co-control of cascade hydropower converted into hybrid variable-speed pumped storage energy, characterized in that, Includes the following steps: Step S1: Collect the required parameters; Step S2: Decompose the frequency signal using Fourier transform, determine the dominant frequency band, and calculate the total virtual inertia J required by the power grid according to the following formula. req : ， ， ， In the formula, J low For the total virtual inertia requirement in the low-frequency band; K low The inertia coefficient is the low-frequency inertia coefficient; Δf low For low-frequency band frequency deviation; ΔP renew,pred For short-term predicted power deviation of wind and solar power; K H This is the correction factor for the cascade head. ΔH is the actual head difference. max For design head difference; J mid For the total virtual inertia requirement in the mid-frequency band; K mid This is the mid-frequency inertia coefficient; S is the rate of change of frequency; total S represents the total capacity of the hybrid system. rated This is the system's rated capacity; Step S3: Calculate the overall weight W according to the following formula. i : ， In the formula, W S,i S represents the capacity weight of the i-th device; i S represents the actual available capacity of the i-th device. i,rated Let i be the rated capacity of the i-th device; ， In the formula, W V,i The response speed weight for the i-th device; t i Let be the device response time of the i-th device; ， In the formula, W E,i C is the economic weight of the i-th device. i The equipment control cost for the i-th device; ， In the formula, α is the first weighting coefficient, β is the second weighting coefficient, and γ is the third weighting coefficient; Step S4: Assign instructions according to the following formula: ， In the formula, ΔP i For the power adjustment command of the i-th device; K J,i Let be the virtual inertia coefficient of the i-th device; Δf is the real-time power grid frequency deviation; Step S5: Perform coordinated correction of cascade variable-speed pumped storage energy storage according to the following formula: ， ， In the formula, ΔP down To correct the downstream pumped storage unit command; ΔP down,0 For initial allocation instructions; Q up Q represents the pumping capacity of the upstream pumped storage unit; rated To design the pumping capacity; Step S6: Simultaneously send the power adjustment commands of each device to the corresponding device; Step S7: Monitor the control effect in real time, dynamically adjust the parameters, and return to step S1 to repeat the process.

2. The method for broadband virtual inertia co-control of cascade hydropower conversion to hybrid variable-speed pumped storage energy storage according to claim 1, characterized in that, In step S2, the low-frequency inertia coefficient K low The value ranges from 0.9 to 1.

1. The higher the wind and solar penetration rate, the higher the low-frequency inertia coefficient K. low The larger the value; the higher the mid-frequency inertia coefficient K mid The value ranges from 1.2 to 1.

4. The larger the load change amplitude, the greater the mid-frequency inertia coefficient K. mid The larger.

3. The method for broadband virtual inertia co-control of cascade hydropower conversion to hybrid variable-speed pumped storage energy storage according to claim 1, characterized in that, In step S3, S i ≤1.1S i,rated In the formula, S i,rated Let be the rated capacity of the i-th device; the first weighting coefficient α = 0.4, the second weighting coefficient β = 0.3, and the third weighting coefficient γ = 0.

3.

4. The method for broadband virtual inertia co-control of cascade hydropower conversion to hybrid variable-speed pumped storage energy storage according to claim 1, characterized in that, In step S4, the virtual inertia coefficient of the variable speed pumped storage unit is 0.8 to 1.0, the virtual inertia coefficient of the original hydropower unit is 0.6 to 0.8, and the virtual inertia coefficient of the wind and solar power station is 0.5 to 0.

7.

5. The method for broadband virtual inertia co-control of cascade hydropower conversion to hybrid variable-speed pumped storage energy storage according to claim 1, characterized in that, In step S6, the equipment includes the variable speed pumped storage converter of the variable speed pumped storage unit, the wind and solar inverter of the wind and solar power station, and the guide vane control system of the original hydropower unit.

6. The method for broadband virtual inertia co-control of cascade hydropower conversion to hybrid variable-speed pumped storage energy storage according to claim 5, is characterized in that, Step S6 also includes: For variable speed pumped storage units, power tracking is achieved by adjusting the IGBT switching frequency through a variable speed pumped storage converter. For wind and solar power plants, reactive power compensation is adjusted through wind and solar inverters. When wind and solar power are curtailed, the power regulation command is set to negative to reduce power output and provide inertia. For existing hydropower units, the guide vane opening is adjusted through the guide vane control system to regulate the current power. The guide vane adjustment delay time is controlled in advance to ensure that the guide vane opening adjustment is synchronized with the adjustment of other equipment.

7. The method for broadband virtual inertia co-control of cascade hydropower conversion to hybrid variable-speed pumped storage energy storage according to claim 1, characterized in that, Step S7 specifically includes: real-time monitoring of frequency deviation Δf and inertia response deviation ΔJ; if the control effect is not satisfactory, the control parameters are corrected; the control parameters include the low-frequency inertia coefficient K. low Intermediate frequency inertia coefficient K mid Comprehensive weight W i .

8. The method for broadband virtual inertia co-control of cascade hydropower conversion to hybrid variable-speed pumped storage energy storage according to claim 1, characterized in that, The control parameters are updated every 500ms to adapt to changes in the environment and equipment status; the control parameters include the low-frequency inertia coefficient K. low Intermediate frequency inertia coefficient K mid Comprehensive weight W i .

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