Evaluation method for influence of wind power access scale on operation of Francis hydroelectric generating unit

Abstract

The application provides a kind of wind and light access scale influence evaluation method on operation of mixed flow hydroelectric generating set, including the following steps: three models are established, including from power generation to transmission, determine the objective function of each model, understand the optimization target, while the constraint condition of objective function is clear;Flexibility evaluation analysis standard is constructed, and evaluation indexes are divided into three categories: power supply side, load side and power network;According to the specific analysis of the evaluation index, the influence of wind and light access scale on the medium and long term operation flexibility of mixed flow hydroelectric generating set is analyzed.Compared with the modern technology, the influence of wind and light access on the flexibility of hydroelectric generating set is quantified by more indexes, so as to obtain the best proportion of wind and light power access, the influence is quantified, and the conclusion is more accurate.

Description

Technical Field

[0001] This invention relates to the field of power technology, specifically to a method for assessing the impact of wind and solar grid connection scale on the operation of mixed-flow hydropower units. Background Technology

[0002] Large-scale wind and solar power plants are about to be connected to the grid. However, wind and solar power generation is characterized by randomness, volatility, and unpredictability, which will affect the safe and stable operation of the power grid. Hydropower, as a good regulating power source, can effectively eliminate the impact of wind and solar power plants on grid stability when operating in conjunction with them. Utilizing the excellent regulating performance of hydropower and the storage and release of energy storage devices can regulate fluctuations in the grid in time and space, reducing the impact of grid connection on grid stability. Therefore, considering the impact on hydropower flexibility under the condition of large-scale wind and solar grid connection has become an urgent issue. How to quantify the hydropower flexibility after large-scale wind and solar grid connection is a key factor in promoting the coordinated development and large-scale consumption of hydropower, wind, and solar power. At the same time, in multi-energy complementary power generation systems of hydropower, wind, and solar power, electricity production is related to the development of enterprises, and the safe transmission and minimum loss transmission of electricity are matters of concern to power generation enterprises.

[0003] Power system flexibility is not a new or isolated concept; it is an essential requirement for power systems to cope with various random factors and uncertain conditions and maintain power and energy balance at different time scales. It runs through every stage and process of power system development and operation. The introduction of large-scale intermittent power sources increases the randomness of system operation, and the corresponding flexibility requirements directly affect the power balance of the entire system.

[0004] Therefore, how to provide a comprehensive evaluation method for the impact of wind and solar grid connection scale on the long-term operational flexibility of mixed-flow hydropower units is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention is mainly applied to the optimization of hydro-wind-solar hybrid power generation systems from production to transmission and the evaluation of technical flexibility. Three evaluation indicators are set, including power source evaluation indicators, load side evaluation indicators and power system evaluation indicators. Based on the indicators, the impact of wind and solar integration with hydropower on its flexibility is specifically analyzed.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention discloses a method for evaluating the impact of wind and solar power grid integration on the operation of mixed-flow hydropower units, comprising the following steps:

[0008] S1. Construct an optimization model for a hydro-wind-solar multi-energy complementary power generation system, namely, an optimization model for each stage of power generation in the hydro-wind-solar multi-energy complementary power generation system, including:

[0009] With the objective functions of maximizing system benefits and minimizing volatility, a power generation optimization model under the multi-energy complementarity of hydro, wind and solar is constructed.

[0010] An optimization model for AC to DC conversion is constructed with the objective function of maximizing DC output power.

[0011] A DC transmission optimization model is constructed with the objectives of minimizing DC distribution network losses and maximizing the initial power transmission margin of converters.

[0012] S2. A flexibility assessment index was constructed, which is divided into three categories: power supply side, load side and power network.

[0013] S3. Analyze the optimization model of the hydro-wind-solar multi-energy complementary power generation system based on the aforementioned flexibility evaluation index, determine the parameter values ​​of the constraint conditions of the optimization model of the hydro-wind-solar multi-energy complementary power generation system, and obtain the optimal model for the hydro-wind-solar complementary power generation system to achieve stable operation.

[0014] Preferably, the constraints of the power generation optimization model under the multi-energy complementarity of hydropower, wind power, and solar power include:

[0015] Wind turbine and photovoltaic installed capacity constraints:

[0016]

[0017] Where, N w.max and N pv.max These are the maximum number of wind turbines and photovoltaic panels to be installed, respectively.

[0018] Power constraints:

[0019]

[0020] in, The power generation capacity of wind farms and photovoltaic power plants; Power directly transmitted to loads from wind farms, photovoltaic power stations, and pumped storage power stations; P is the pumping power of the pumps in a pumped storage power station. gmin P gmax The lower and upper limits of transmission power; This refers to the total power generation capacity of a pumped storage power station. As backup power;

[0021] Hydropower station constraints:

[0022] 0≤V i ≤V max ;

[0023]

[0024]

[0025]

[0026] Among them, V i V represents the reservoir's capacity. max E represents the maximum storage capacity of the reservoir. i The energy of the pumped storage power station in the i-th time period; Power constraints for pumping units; Power constraints for hydroelectric generator sets; H i P(V) is the head or pumping head of a pumped storage unit. i H i () represents the output value of the pumped storage power station;

[0027] Network constraints, including generator output constraints and voltage over-limit constraints:

[0028]

[0029] Among them, P Gi Q Gi P represents the active and reactive power of the generator. Gmin P Gimax Q represents the upper and lower limits of active power. Gimin Q Gimax These are the upper and lower limits of reactive power. The first and second inequalities together represent the upper and lower limits of the output power of the PV node; U i The third inequality represents the upper and lower limits of the voltage amplitude at node PQ.

[0030] Preferably, the constraints of the AC-to-DC conversion optimization model include:

[0031] Maximum rectified current constraint:

[0032] I d ≤I Md

[0033] Among them, I Md This is the maximum rectified current of the diode in the rectifier circuit; the maximum rectified current refers to the maximum average forward current that the diode is allowed to pass through.

[0034] Preferably, the constraints of the DC transmission optimization model include:

[0035] System power flow constraints:

[0036] f(P,U)=0

[0037]

[0038] Where P and U are the node active power and node voltage, respectively; P dc To inject active power; P dcref The active power reference value is taken as the rated power of the connected load; k is the traditional droop factor; U dc The node voltage;

[0039] Topological constraints:

[0040] A radial topology is adopted, meaning the network operates radially with no isolated nodes;

[0041] Upper limit constraints on converter capacity and current:

[0042]

[0043] Among them, P i and I i P represents the actual active power and current passing through converter i, respectively; imax and I imax These are the rated capacity and rated current corresponding to converter i, respectively;

[0044] Node voltage upper and lower limit constraints:

[0045] U imin ≤U i ≤U imax

[0046] Among them, U imin and U imax This represents the upper and lower voltage limits of node i.

[0047] Preferably, the evaluation indicators on the power supply side include: volatility, ramp rate, ramp duration, shortest start-up and shutdown time, start-up time, response time, maximum fluctuation amplitude, rated capacity of the unit, upper and lower operating limits, and equivalent forced outage rate.

[0048] Preferably, the evaluation indicators for the power network include: upward adjustment of flexibility deficit expectation, downward adjustment of flexibility deficit expectation, static safety margin, power flow distribution factor, flexibility supply range, minimum flexibility supply level, flexibility ramp rate, fluctuation complementarity rate, ramp complementarity rate, and combined and independent generation fluctuation difference.

[0049] Preferably, the evaluation metrics on the load side include: net load ramp rate and ramp acceleration.

[0050] As can be seen from the above technical solution, compared with the prior art, this invention analyzes the impact of wind power generation and photovoltaic power generation on the flexibility of hydropower generation by establishing a basic mathematical model of a wind-solar-hydro complementary power generation system, as well as a power generation optimization model, an AC-to-DC conversion optimization model, and a DC transmission optimization model under multi-energy complementarity of wind, water, and solar power. The beneficial effects of this invention include:

[0051] 1) This invention establishes various optimization models for the power generation and transmission process, which saves energy to a certain extent;

[0052] 2) The diversification of indicators makes the assessment of the impact of wind and solar grid connection scale on the medium- and long-term operational flexibility of mixed-flow hydropower units more accurate;

[0053] 3) Study the impact of changes in indicators in various models on the stable operation of the complementary power generation system, and analyze the optimal model power generation system that enables the stable operation of the hydro-wind-solar complementary system;

[0054] 4) It provides a research method for the volatility and mutual influence of operation of renewable energy complementary systems, which is of great significance for reducing the adverse effects of new energy volatility and fully leveraging the scheduling advantages of complementary systems. Attached Figure Description

[0055] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0056] Figure 1 A flowchart illustrating the method for assessing the impact of wind and solar grid connection scale on the operation of mixed-flow hydropower units, as provided in an embodiment of the present invention.

[0057] Figure 2 The conventional reservoir operation rules provided for embodiments of the present invention. Detailed Implementation

[0058] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and 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.

[0059] This invention discloses a method for assessing the impact of wind and solar grid connection scale on the operation of mixed-flow hydropower units. See [link to relevant documentation]. Figure 1 This is achieved through the following technical steps:

[0060] Based on a multi-energy complementary power system of hydropower, wind power, and solar power, three models are established, covering everything from power generation to transmission. The objective functions for each model are determined, the optimization objectives are understood, and conventional reservoir operation rules are considered. Figure 2 As shown, the constraints of the objective function are clearly defined. First, for the power generation stage, the power plant's power generation optimization model is developed, taking into account the impact of frequency in hybrid power generation, and paying attention to frequency regulation and volatility issues among the three types of power generation.

[0061] Then, in order to reduce energy loss during transmission, the generated AC power needs to be converted into DC power. Therefore, it is necessary to establish an optimization model for AC power to DC power conversion, and at the same time, based on the constraints, understand the range of values ​​of various indicators when the conversion efficiency is optimal.

[0062] Subsequently, the study investigated energy loss during transmission, established a DC transmission optimization model, and developed a model that minimizes energy loss during transmission.

[0063] Secondly, to more clearly understand the impact of wind and solar grid integration on the medium- and long-term operational flexibility of mixed-flow hydropower units, three categories of indicators were defined to quantify the specific impact: power supply side, load side, and power grid. The power supply side includes volatility, ramp rate, ramp duration, minimum start-up / shutdown time, start-up time, response time, maximum fluctuation amplitude, unit rated capacity, upper and lower operating limits, and forced outage rate. The load side includes net load ramp rate and ramp acceleration. The power grid includes: probability and expectation of insufficient flexibility upwards, probability and expectation of insufficient flexibility downwards, static safety margin, power flow distribution factor, flexibility supply range, minimum flexibility supply level, flexibility ramp rate, ramp complementarity rate, volatility complementarity rate, and fluctuation difference between combined and independent generation.

[0064] Finally, based on specific evaluation indicators, various models were analyzed to derive the optimal model for the stable operation of the hydro-wind-solar hybrid power generation system, thus providing a reference for the development of the hydro-wind-solar hybrid system and the energy structure allocation of the power system.

[0065] The specific execution steps are as follows:

[0066] Optimization models for various states in a hydro-wind-solar multi-energy complementary power generation system:

[0067] Model 1: Power Generation Optimization Model under Multi-Energy Complementarity of Hydropower, Wind Power, and Solar Power

[0068] Objective function:

[0069] (1) Maximizing system benefits

[0070]

[0071] In the formula, Power directly transmitted to loads from wind farms, photovoltaic power stations, and pumped storage power stations; C is the pumping power of the pumps in a pumped storage power station; i This is for implementing feed-in tariffs. It describes a joint system benefit maximization model, seeking how to optimize the scheduling of wind turbines, solar panels, pumps, and turbines in wind farms and photovoltaic power plants at different times, given certain wind and solar energy resources, in order to obtain the greatest economic benefits.

[0072] (2) Volatility Minimization

[0073]

[0074] In the formula: V σ This represents the relative standard deviation. The average output power through the tie line; N is the calculation period. Relative standard deviation V. σ Used to reflect the dispersion of individual samples, obviously, the smaller the relative standard deviation, the higher the instantaneous power P of the connection line output. gs (t) is closer to the average value within a period The smaller the volatility, the better.

[0075] Constraints:

[0076] (1) Constraints on installed capacity of wind turbines and photovoltaics. The number of wind turbines and photovoltaic panels is constrained by the land area required.

[0077]

[0078] (2) Power constraint.

[0079]

[0080] in, P represents the power generation capacity of wind farms and photovoltaic power plants. gmin P gmax The lower and upper limits of transmission power; This refers to the total power generation capacity of a pumped storage power station. The reserve power is related to the installed capacity of wind farms and photovoltaic power plants and the accuracy of forecasts.

[0081] (3) Constraints of hydropower stations:

[0082] 0≤V i ≤V max ;

[0083]

[0084]

[0085]

[0086] Among them, V i V represents the reservoir's capacity. max E represents the maximum storage capacity of the reservoir. i The energy of the pumped storage power station in the i-th time period; Power constraints for pumping units; Power constraints for hydroelectric generator sets; H i P(V) is the head or pumping head of a pumped storage unit. i H i () represents the output value of the pumped storage power station.

[0087] Network constraints. These mainly include generator output constraints and voltage over-limit constraints.

[0088]

[0089] Where P Gi Q Gi Representing the active and reactive power of the generator, the first two inequalities mainly constrain the upper and lower limits of the output power of the PV nodes, U i The third inequality represents the voltage amplitude at the node. It mainly represents the upper and lower limits of the voltage amplitude at the PQ node.

[0090] Model 2: Optimization Model for AC to DC Conversion

[0091] Objective function:

[0092] Maximize DC output power.

[0093] maxP out =U dR I d

[0094]

[0095] Among them: U dR The DC voltage of the six-pulse rectifier; α R U is the rectifier firing angle; dioR U is the ideal no-load DC voltage on the rectifier side; dioNR U is the rated no-load DC voltage on the rectifier side; T For the forward pressure drop of the converter valve; d xR The relative inductive voltage drop on the rectifier side; d rR The relative resistive voltage drop on the rectifier side; I d This is the actual DC current; I dN E is the rated DC current; E is the effective value of the AC line voltage on the valve side.

[0096] Constraints:

[0097] (1) Maximum rectified current constraint.

[0098] I d ≤I Md

[0099] Among them: I Md This refers to the minimum maximum rectified current for all diodes used in rectifier circuits. The diode parameters include "maximum rectified current," which refers to the maximum average forward current that the diode is allowed to pass during long-term operation. It describes the maximum average current that the diode can handle without damage, and its value is related to the PN junction area and external heat dissipation conditions. Under specified heat dissipation conditions, if the average forward current of the diode exceeds this value, it will burn out due to excessive junction temperature rise.

[0100] Model 3: DC Transmission Optimization Model

[0101] Objective function:

[0102] (1) DC distribution network has the lowest network loss.

[0103] DC system power loss mainly includes line power loss P line Converter VSC power loss P VSC DC-DC converter power loss P DC-DC

[0104] minP loss =P line +P VSC +P DC-DC

[0105] (2) The converter has the largest initial power transfer margin.

[0106] The optimization of the DC distribution network structure should maximize the initial power margin of the optimized converter stations to ensure better regulation capabilities in the event of potential power imbalances. Adjusting the converter power transmission margin requires the use of adaptive droop control coefficients.

[0107]

[0108]

[0109]

[0110] In the formula: α is the adjustment coefficient, taken as 3; k is the traditional droop coefficient; β is the adjustment constant, taken as 0.75; I dcmax I represents the maximum value of the converter current. dc Converter current; I dcref The reference current of the converter is determined by the reference power and reference voltage of each converter; Udcmax U represents the maximum converter voltage. dcref This is the reference voltage on the DC side of the converter, with a base value of 1 pu.

[0111] To maximize the converter's ability to share unbalanced power, i.e., to maximize the power margin of the converter station, the adaptive droop coefficient should be as large as possible while satisfying the upper and lower bounds.

[0112] Constraints:

[0113] System power flow constraints.

[0114] f(P,U)=0

[0115] f(*) represents the constraint relationship between active power and nodal voltage, which must satisfy the following formula:

[0116]

[0117] In the formula: P and U are the node active power and node voltage, respectively.

[0118] P dc To inject active power; P dcref For meritorious service

[0119] The reference value is taken as the rated power of the connected load; k is the traditional droop factor; U dc This represents the node voltage.

[0120] (2) Topological constraints.

[0121] Although DC distribution networks can operate in a closed loop, radial network relay protection settings are convenient. Therefore, this paper still adopts a radial topology, that is, the network maintains radial operation and has no isolated nodes.

[0122] (3) Upper limit constraints on converter capacity and current.

[0123]

[0124] In the formula: P i and I i P represents the actual active power and current passing through converter i, respectively; imax and I imax These are the rated capacity and rated current corresponding to converter i, respectively.

[0125] (4) Node voltage upper and lower limit constraints.

[0126] U imin ≤U i ≤U imax

[0127] In the formula: U imin and Uimax This represents the upper and lower voltage limits specified for node i.

[0128] The evaluation indicators for the impact of wind and solar grid connection scale on hydropower flexibility include:

[0129] Power supply side: volatility, ramp rate, ramp duration, minimum start / stop time, start-up time, response time, minimum stable output, maximum fluctuation amplitude, unit rated capacity, upper and lower operating limits, forced outage rate; Load side: net load ramp rate, ramp acceleration.

[0130] Power Grid: Upward adjustment of the probability and expectation of insufficient flexibility, downward adjustment of the probability and expectation of insufficient flexibility, static safety margin, power flow distribution factor, flexibility supply range, minimum flexibility supply level, flexibility ramp rate, ramp complementarity rate, fluctuation complementarity rate, and fluctuation differences between joint and independent generation.

[0131] Load side: Net load ramp rate and ramp acceleration.

[0132] In this embodiment, the specific evaluation indicators are as follows:

[0133] Regarding the power supply side:

[0134] (1) Volatility represents the fluctuation and change of variables within a certain device.

[0135]

[0136] γ i =P i+1 -P i ,i=1n-1

[0137] In the formula, γ i It is t i The change corresponding to each time point, where n is the discrete time series {t} i The number of time points, FR represents volatility. The magnitude of FR reflects the degree of instantaneous volatility of the time series under examination; the smaller its absolute value, the smaller the oscillation and the better the stability.

[0138] for and If R(i-1,j) = 0 and R(i.j+1) = 0, then R(i,j) represents a climbing event, where i and j are the start and end points of the climbing event, respectively. The mathematical expression for R(i,j) is shown below:

[0139]

[0140]

[0141]

[0142] (2) The ramp rate RR over a period of time is the increase or decrease in output per unit time for each unit.

[0143]

[0144] Number of climbs N:

[0145]

[0146] A certain uphill climb ρ within a certain period of time m Climbing rate:

[0147]

[0148] In the formula, Δt=t j -t i and P j -P i Let m be the duration and magnitude of the m-th climb.

[0149] (3) The shortest start-up and shutdown time refers to the shortest time that the unit experiences during the restart process.

[0150] t min =t sj +t si

[0151] t sj and t si These represent the shutdown and startup times during unit restart, respectively. si In other words, startup time refers to the time spent by the unit during the startup phase.

[0152] (4) Response time refers to the time consumed by the application system from the time the request is sent until the client receives all the data.

[0153] t R =t Rj -t Ri

[0154] t Rj With t Ri This indicates the time point at which the system transmits the signal and the corresponding time point.

[0155] (5) Maximum fluctuation amplitude indicates the maximum amplitude when the unit experiences fluctuations.

[0156] The maximum range of fluctuation of a physical quantity over a period of time is called the maximum fluctuation amplitude A, which is defined as follows:

[0157] A = P max -P min

[0158] In the formula, Pmin and P max These represent the minimum and maximum values ​​of the independent variable within the time period.

[0159] (6) The rated capacity of the unit indicates the maximum capacity that the unit can carry; the upper and lower operating limits indicate the maximum and minimum operating power of the unit when it is running.

[0160]

[0161] in

[0162] In the formula: These represent the confidence interval boundaries for the maximum, minimum, and extreme values ​​of output fluctuation, or the maximum positive deviation, maximum negative deviation, and extreme values ​​of deviation fluctuation, respectively; Ph i,t Let i be the output of hydropower station i during time period t; These represent the upper and lower limits of the output of hydropower station i during time period t, respectively. t represents the installed capacity of the wind and solar power convergence target during time period t; n and N are the number and total number of hydropower stations, respectively.

[0163] (7) The equivalent forced outage rate represents the time probability of a forced outage of a power generation device.

[0164]

[0165] In the formula: EFOR is the equivalent forced outage rate; EUDH is the equivalent outage hours due to unplanned reduced output; ERUDH is the equivalent standby outage hours due to unplanned reduced output; FOH is the forced outage hours; and SH is the outage hours.

[0166] Regarding the power grid:

[0167] (1) The expectation of upward adjustment of insufficient flexibility represents the expected difference between the demand for upward adjustment of flexibility and the capacity for upward adjustment of flexibility at time t due to insufficient upward adjustment capacity. The expectation of downward adjustment of insufficient flexibility represents the expected difference between the demand for downward adjustment of flexibility and the capacity for downward adjustment of flexibility at time t due to insufficient downward adjustment capacity.

[0168]

[0169]

[0170]

[0171] In the formula: The expectation of insufficient flexibility adjustment refers to the expected difference between the flexibility adjustment demand and the flexibility adjustment capability at time t due to insufficient adjustment capability. The expectation of insufficient flexibility reduction refers to the expected difference between the flexibility reduction demand and the flexibility reduction capability at time t due to insufficient reduction capability. These respectively represent the need for flexibility adjustment; These represent the ability to increase flexibility and the ability to decrease flexibility, respectively.

[0172] (2) Static safety margin represents the safety index of the unit during operation; power flow distribution factor represents the assessment of the steady-state distribution of voltage at each node, active power on the line, and reactive power in the power grid.

[0173]

[0174]

[0175]

[0176] In the formula: Static safety margin is an indicator for evaluating the flexibility of power transmission networks; N b is the number of nodes in the network; i and j are the node numbers at both ends of a branch in the network; The current margin of branch ij (the difference between the maximum operating current and the actual operating current); It is the sum of the absolute values ​​of the power flow distribution factors of the branch relative to all generator nodes; N is the power flow distribution factor of branch ij relative to node k; gb y represents the number of generator nodes; ij For the series admittance of the branch; Z ik Let be the mutual impedance between nodes i and k in the node impedance matrix.

[0177] (3) Flexibility supply range refers to the range of flexibility that can be supplied under normal operating conditions.

[0178]

[0179] In the formula: L FSR Indicates the range of power system flexibility supply; n represents the nth generator of a certain type, N represents the total number of generators of that type, and P n,max and P n,min These represent the maximum output power and minimum stable operating power of the nth unit of this type, respectively. FSR The larger the value, the greater the range of flexibility provided by that type of unit; conversely, the smaller the value, the smaller the range of flexibility provided.

[0180] (4) The minimum level of flexibility supply represents the minimum level of total supply that flexibility can provide under normal operating conditions.

[0181]

[0182] In the formula: L FMSL L represents the minimum supply level of power system flexibility. FMSL The larger the value, the less flexibility this type of generator set can provide when there is a need for flexibility in the power system, and vice versa.

[0183] (5) Flexibility ramp rate represents the total ramp rate of flexibility supply.

[0184]

[0185] In the formula: L FRR R represents the power system flexibility ramp rate. n L represents the ramp rate of the nth unit of this type. FRR The larger the value, the faster the type of unit provides flexibility, and vice versa.

[0186] (6) The fluctuation complementarity rate represents the ratio of the difference between the power generation fluctuation rate and the combined power generation fluctuation rate to the independent power generation fluctuation rate; the ramp complementarity rate represents the ramp complementarity of independent and combined power generation; the fluctuation difference between combined and independent power generation represents the fluctuation difference between the output curves of complementary power generation and isolated power generation.

[0187]

[0188]

[0189] In the formula, FROC is the volatility of a combined power generation system with k energy sources; Let be the power output fluctuation of the k-th energy source generated independently at time i; α represents the fluctuation in the output of the combined power generation system at time i; k The proportion of electricity generated from energy sources.

[0190] Based on this, there is the volatility complementarity ratio (CROF):

[0191]

[0192]

[0193] FROI represents the sum of the volatility of the islanded power generation system with specific weights, while CROF represents the difference in volatility between the output curves of complementary power generation and islanded power generation. Its value ranges from 0 to 1, and the closer it is to 1, the better the performance of complementary power generation.

[0194] The Climbing Complementarity Ratio (CROR) represents the climbing complementarity of joint power generation, and its expression is:

[0195]

[0196]

[0197] The CROR value ranges from 0 to 1, with a value closer to 1 indicating better complementarity.

[0198] Regarding the load side (defined according to user requirements):

[0199] (1) Net load ramp rate represents the increase or decrease in output per unit time of the load obtained by subtracting the output of new energy sources from the electricity load.

[0200]

[0201] In the formula: ρ Qm Net load ramp-up rate; P Qj P Qi For t j t i The output power at any given moment.

[0202] (2) Climbing acceleration represents the rate of change of climbing speed over time.

[0203]

[0204] In the formula: C na R is the acceleration due to climbing. nti For the nth unit at t i The rate of ascent.

[0205] This study investigates the relationships between various indicators and quantifies the impact of wind and solar grid integration on hydropower flexibility, providing a reference for the development of wind-solar-hydro complementary systems and the energy structure allocation of the power system. Based on the above indicators, an optimization model for a multi-energy complementary hydro-wind-solar power generation system is analyzed. Combining the constraints of the optimization model, the values ​​of each parameter in the constraints are determined. When the optimization model reaches its optimum in all three stages, satisfying the indicator requirements, the hydro-wind-solar complementary power generation system reaches stable operation. These three optimal models constitute the optimal model for the power generation system.

[0206] The above provides a detailed description of the method for evaluating the impact of wind and solar grid connection scale on the operation of mixed-flow hydropower units. Specific examples are used in this embodiment to illustrate the principle and implementation of the invention. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of the invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the ideas of the invention. Therefore, the content of this specification should not be construed as a limitation of the invention.

[0207] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined in these embodiments may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for assessing the impact of wind and solar power integration scale on the operation of mixed-flow hydropower units, characterized in that, Includes the following steps: S1. Construct an optimization model for a hydro-wind-solar multi-energy complementary power generation system, namely, an optimization model for each stage of power generation in the hydro-wind-solar multi-energy complementary power generation system, including: With the objective functions of maximizing system benefits and minimizing volatility, a power generation optimization model under the multi-energy complementarity of hydro, wind and solar is constructed. An optimization model for AC to DC conversion is constructed with the objective function of maximizing DC output power. A DC transmission optimization model is constructed with the objectives of minimizing DC distribution network losses and maximizing the initial power transmission margin of converters. S2. A flexibility assessment index was constructed, which is divided into three categories: power supply side, load side and power network. S3. Analyze the optimization model of the hydro-wind-solar multi-energy complementary power generation system based on the aforementioned flexibility evaluation index, determine the parameter values ​​of the constraint conditions of the optimization model of the hydro-wind-solar multi-energy complementary power generation system, and obtain the optimal model for the hydro-wind-solar complementary power generation system to achieve stable operation.

2. The method for assessing the impact of wind and solar grid integration scale on the operation of mixed-flow hydropower units according to claim 1, characterized in that, The constraints of the power generation optimization model under the multi-energy complementarity of hydropower, wind power, and solar power include: Wind turbine and photovoltaic installed capacity constraints: in, and These are the maximum number of wind turbines and photovoltaic panels to be installed, respectively. Power constraints: in, , The power generation capacity of wind farms and photovoltaic power plants; , , Power directly transmitted to loads from wind farms, photovoltaic power stations, and pumped storage power stations; The pumping power of the pumps in a pumped storage power station; , The lower and upper limits of transmission power; This refers to the total power generation capacity of a pumped storage power station. As backup power; Hydropower station constraints: ； ； ； ； in, For the reservoir capacity; This is the maximum storage capacity of the reservoir; The energy of the pumped storage power station in the i-th time period; , Power constraints for pumping units; , Power constraints for hydroelectric generator sets; The head or lift of a pumped storage unit; This refers to the output value of the pumped storage power station; Network constraints, including generator output constraints and voltage over-limit constraints: in, , Represents the active and reactive power of the generator. , These are the upper and lower limits of active power; , These are the upper and lower limits of reactive power. The first and second inequalities together represent the upper and lower limits of the output power of the PV node. The third inequality represents the upper and lower limits of the voltage amplitude at node PQ.

3. The method for assessing the impact of wind and solar grid integration scale on the operation of mixed-flow hydropower units according to claim 1, characterized in that, The constraints of the AC-to-DC conversion optimization model include: Maximum rectified current constraint: in, This is the actual DC current; This refers to the maximum rectified current of the diode in the rectifier circuit; the maximum rectified current refers to... diode The maximum permissible average forward current.

4. The method for assessing the impact of wind and solar grid integration scale on the operation of mixed-flow hydropower units according to claim 1, characterized in that, The constraints of the DC transmission optimization model include: System power flow constraints: Where f(*) represents the constraint relationship between active power and node voltage; P and U are the node active power and node voltage, respectively; To inject active power; The active power reference value is taken as the rated power of the connected load; The reference voltage on the DC side of the converter; k is the traditional droop factor; The node voltage; Topological constraints: A radial topology is adopted, meaning the network operates radially with no isolated nodes; Upper limit constraints on converter capacity and current: in, and These represent the actual active power and current passing through converter i, respectively; and These are the rated capacity and rated current corresponding to converter i, respectively; Node voltage upper and lower limit constraints: in, and This represents the upper and lower voltage limits of node i.

5. The method for assessing the impact of wind and solar grid connection scale on the operation of mixed-flow hydropower units according to claim 1, characterized in that, The evaluation metrics for the power supply side include: volatility, ramp rate, ramp duration, minimum start-up / shutdown time, start-up time, response time, maximum fluctuation range, rated capacity of the unit, upper and lower operating limits, and equivalent forced outage rate.

6. The method for assessing the impact of wind and solar grid integration scale on the operation of mixed-flow hydropower units according to claim 1, characterized in that, The evaluation metrics for the power network include: upward adjustment of flexibility deficit expectation, downward adjustment of flexibility deficit expectation, static safety margin, power flow distribution factor, flexibility supply range, minimum flexibility supply level, flexibility ramp rate, fluctuation complementarity rate, ramp complementarity rate, and combined and independent generation fluctuation difference.

7. The method for assessing the impact of wind and solar grid integration scale on the operation of mixed-flow hydropower units according to claim 1, characterized in that, The load-side evaluation metrics include: net load ramp rate and ramp acceleration.

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