Optimal operation method of pumped storage power station considering speed change characteristics

Abstract

The invention relates to an optimal operation method of a pumped storage power station considering speed change characteristics, and belongs to the technical field of electric power system operation. The method comprises the following steps: constructing a constant-variable speed coupled pumped storage power station model based on the operation conditions of a constant speed unit and a variable speed unit in the pumped storage power station; constructing an operation cost model of the power grid based on the operation condition of each unit in the power grid system; based on node power balance constraint, line power flow constraint, thermal power generating unit operation constraint, pumping and storage operation constraint, system load reserve constraint, carbon emission constraint and an operation cost model, constructing a wind-solar-thermal-constant-variable-speed coupling pumping and storage optimization scheduling model; taking the operation cost minimization of a power grid system as a target, solving an optimal solution for the wind-solar-thermal-constant-variable-speed coupling pumping and storage optimization scheduling model based on a pumped storage power station model, obtaining an optimal operation scheme of the pumped storage power station, improving the utilization rate of the pumped storage power station, and reducing the operation cost of the power grid system.

Description

Technical Field

[0001] The present invention belongs to the technical field of power system operation, and in particular relates to an optimal operation method of a pumped storage power station taking into account variable speed characteristics. Background Art

[0002] Due to the randomness, volatility and uncertainty of renewable energy power generation, the power system will be affected in many aspects such as power supply security, new energy consumption and safe and stable operation. As a typical regulating power source, pumped storage has unique advantages over new energy storage in terms of technology development, economy and construction scale.

[0003] The pumped storage power stations in the current power grid system are mainly fixed-speed pumped storage units using synchronous motors. As the proportion of new energy grid-connected power systems in new power systems gradually increases, the scale of pumped storage power stations continues to expand. Their role and functional positioning in the power grid will not only be energy storage devices, but also adjustable power sources with fast system response speed, wide load power regulation capability, and high efficiency. Fixed-speed pumped storage units are affected by the control method, and the speed of pumping conditions is constant and cannot be adjusted, which is insufficient in flexibility. Variable-speed pumped storage units have advantages such as higher operating flexibility and lower mechanical wear, and are a new choice for solving uncertainties in new power systems. Therefore, how to effectively play the regulatory role of pumped storage power stations in the power system, improve the utilization rate of pumped storage power stations, and reduce the operating costs of the power grid system are issues that need to be studied. Summary of the invention

[0004] In view of the above analysis, the present invention aims to provide an optimal operation method of a pumped-storage power station taking into account the variable speed characteristics, by modeling a fixed-variable speed coupled pumped-storage power station, and then constructing a wind-solar-fire-fixed variable speed coupled pumped-storage optimization dispatching model, with the goal of minimizing the operating cost of the power grid system, giving play to the supplementary and regulatory role of the pumped-storage power station on the uncertainty of wind and solar output, and improving the utilization rate of the pumped-storage power station. Specifically, it includes the following steps:

[0005] A fixed-variable speed coupled pumped storage power station model is constructed based on the power generation power, pumping power, power generation status, and pumping status of the fixed-speed units and variable-speed units in the pumped storage power station; an operation cost model is constructed based on the output of thermal power units, carbon emissions of thermal power units, system load loss, wind abandonment, and solar abandonment;

[0006] Based on the node power balance constraints, line flow constraints, thermal power unit operation constraints, pumped storage operation constraints, system load reserve constraints, carbon emission constraints and the operation cost model, a wind-solar-thermal-fixed-speed-variable-speed coupled pumped storage optimization scheduling model is constructed;

[0007] With the goal of minimizing the operating cost of the power grid system, the optimal solution of the wind-solar-fired-fixed-speed and variable-speed coupled pumped-storage optimization scheduling model is sought based on the pumped-storage power station model, and the optimal operation plan of the pumped-storage power station is obtained, including the generating power, pumping power, generating status and pumping status of the fixed-speed units and variable-speed units in the pumped-storage power station.

[0008] Furthermore, the fixed-variable speed coupled pumped storage power station model constructed based on the power generation power, pumping power, power generation state, and pumping state of the fixed-speed units and variable-speed units in the pumped storage power station includes:

[0009] Construct the extraction power constraint based on the generating power and pumping power of the fixed-speed units and variable-speed units;

[0010] Construct pumped storage operation constraints based on the power generation status and pumping status of fixed-speed units and variable-speed units;

[0011] The startup variables and shutdown variables of fixed-speed units, the startup and shutdown variables of variable-speed units, and the maximum number of startup units and the number of startup pumps in a pumped-storage power station at the same time are used to construct constraints on the number of startup pumps.

[0012] Pumped storage ramp constraints are constructed based on the continuous operating variables of fixed-speed units and variable-speed units, power generation / pumping power, and maximum power generation / pumping ramp values;

[0013] Constructing storage capacity constraints based on the pumping / generation efficiency of fixed-speed units and variable-speed units;

[0014] The minimum continuous pump-on time constraint is constructed based on the minimum continuous pump-on time constant of the fixed-speed unit and the variable-speed unit;

[0015] The minimum continuous start-stop time constraint is constructed based on the minimum continuous start-up time constant and the minimum continuous stop time constant of the fixed-speed unit and the variable-speed unit;

[0016] Establish the start-stop number constraint based on the maximum start-stop number of fixed-speed units and variable-speed units;

[0017] Construct pumping / generation efficiency constraints based on the electricity-water conversion efficiency, water transmission efficiency, and unit operation efficiency of fixed-speed units and variable-speed units;

[0018] Based on the above constraints, a fixed-variable speed coupled pumped storage power station model is obtained.

[0019] Furthermore, the pumped storage ramp constraint includes a pumping ramp constraint and a power generation ramp constraint. The power generation ramp constraint is expressed as:

[0020]

[0021] in, is the power generated by the pumped storage power station to the grid during period t; The maximum value of the power generation ramp during period t; and are the power generated by the fixed speed unit and the variable speed unit to the grid in period t; N cp and N vp are the number of fixed speed units and variable speed units respectively; and are the startup variables of the fixed speed unit and the variable speed unit in period t respectively; and are the maximum power generation of fixed-speed units and variable-speed units respectively; UTS represents the maximum number of units that can be started simultaneously in a pumped-storage power station; and are the continuous operating variables of the variable speed unit and the fixed speed unit in period t respectively.

[0022] Furthermore, the reservoir capacity constraint constructed based on the pumping / generating efficiency of the fixed speed unit and the variable speed unit includes:

[0023] Based on the pumping / generation efficiency of the fixed-speed units and the variable-speed units, the water balance relationship and water level constraint of the upper reservoir and the water balance relationship and water level constraint of the lower reservoir are constructed, respectively expressed as:

[0024]

[0025] in, and are the storage capacities of the upper and lower reservoirs in period t; N cp and N vp are the number of fixed speed units and variable speed units respectively; and are the pumping operation states of the variable speed unit and the fixed speed unit in period t respectively; and are the pumping power purchased from the power grid by the variable speed unit and the fixed speed unit during period t respectively; and are the pumping efficiencies of the variable speed unit and the fixed speed unit respectively; and are the power generation operation states of the variable speed unit and the fixed speed unit in period t respectively; and are the power generated by the variable speed unit and the fixed speed unit to the grid in period t respectively; and are the power generation efficiencies of variable speed units and fixed speed units respectively; and They are the safe storage capacity of the upper and lower reservoirs respectively; and are the upper and lower reservoir water levels respectively; and are the dead water levels of the upper and lower reservoirs respectively; and are the normal water levels of the upper and lower reservoirs respectively; T is the total number of time periods.

[0026] Furthermore, the pumping / power generation efficiency constraint is expressed as:

[0027]

[0028] in, and are the power generation efficiencies of variable speed units and fixed speed units respectively; and are the pumping efficiencies of the variable speed unit and the fixed speed unit respectively; The water-to-electricity conversion efficiency of each unit under power generation conditions; is the electricity-water conversion efficiency of each unit under pumping conditions; η hyd is the water transmission efficiency of each unit; and are the unit operating efficiencies of the fixed-speed units under power generation conditions and pumping conditions, respectively; and are the unit operating efficiencies of the variable speed unit under power generation conditions and pumping conditions during period t, respectively.

[0029] Furthermore, the operation cost model is constructed based on the output of thermal power units, carbon emissions of thermal power units, system load loss, wind abandonment and solar abandonment, including:

[0030] Calculate the operating cost of thermal power units based on the output of thermal power units;

[0031] Calculate the start-stop cost based on the start-stop variables of thermal power units;

[0032] Calculate carbon emission costs based on carbon emissions from thermal power units;

[0033] Calculate the load loss cost based on the system load loss amount;

[0034] Calculate the cost of wind and solar power abandonment based on the amount of wind and solar power abandoned;

[0035] An operating cost model is constructed based on the operating cost, start-up and shutdown cost, carbon emission cost, load loss cost and wind and solar power abandonment cost of thermal power units.

[0036] Furthermore, the operating cost model is expressed as:

[0037]

[0038] Where C is the operating cost of the power grid system; C g,ope , C g,stu , Cg,co2 , C voll , C volr are respectively the operation cost, start-up and shutdown cost, carbon emission cost, load loss cost and wind and solar power abandonment cost of thermal power units; N g 、N w 、N s 、N b are the number of thermal power units, wind power stations, photovoltaic power stations, and system nodes respectively; T is the total number of time periods; P is the number of ng,t Output for thermal power units; a ng , b ng 、c ng are the cost coefficients of thermal power units; α ng,t , β ng,t is the start and stop variable of the thermal power unit; C ng,sta , C ng,shu , C co2 , C cul , C cuw , C cus They are respectively the startup cost, shutdown cost, unit carbon emission cost, unit load loss cost, unit wind abandonment cost, and unit solar abandonment cost of thermal power units; cco2 is the carbon emission intensity; They are the system load loss, wind abandonment and solar abandonment respectively.

[0039] Furthermore, the system load reserve constraint includes a thermal power unit reserve capacity constraint, a fixed speed unit reserve capacity constraint and a variable speed unit reserve capacity constraint.

[0040] Furthermore, the system load reserve constraint includes a positive load reserve constraint and a negative load reserve constraint, which are expressed as:

[0041]

[0042] in, and They are the upper and lower reserve capacities of thermal power units respectively; and They are the upper and lower reserve capacities of the variable speed unit respectively; and They are upper and lower reserve capacities of fixed-speed units respectively; are the load forecast error fuzzy number, wind power output forecast error fuzzy number and photovoltaic output forecast error fuzzy number respectively; δ is the confidence level of satisfying the system reserve constraint; Cr{·} is the confidence expression.

[0043] Furthermore, based on the relaxation model, the wind-solar-fire-fixed-speed-variable-speed coupled pumped-storage optimization scheduling model is solved to obtain the optimal operation plan of the pumped-storage power station, including the generating power, pumping power, generating status and pumping status of the fixed-speed units and variable-speed units in the pumped-storage power station.

[0044] The present invention can achieve at least one of the following beneficial effects:

[0045] By considering the operating constraints of fixed-speed and variable-speed pumped-storage units, a fixed-variable speed coupled pumped-storage power station model is constructed; by considering the output characteristics of various energy sources in the power grid system, including the output characteristics of thermal power, wind power, and photovoltaics, a wind-solar-thermal-fixed-variable speed coupled pumped-storage optimization scheduling model is constructed to give full play to the flexible adjustment role of pumped-storage power stations, supplement the uncertainty of the power grid system due to wind power and photovoltaics, and take the minimum total operating cost of the system as the goal, which can reduce the system load loss rate and wind and solar abandonment rate, and improve the utilization rate of pumped-storage power stations.

[0046] By finding the optimal solution for the wind-solar-thermal-constant-speed-variable-speed coupled pumped-storage optimization scheduling model based on the relaxation model and branch-and-bound, the solution efficiency is improved, the search space is reduced, and the global optimal solution is ensured to be found in the integer solution space.

[0047] Other features and advantages of the present invention will be described in the following description, and some advantages may become apparent from the description, or may be understood by practicing the present invention. The purpose and other advantages of the present invention may be realized and obtained through the contents particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The accompanying drawings are only used for the purpose of illustrating specific embodiments and are not to be considered as limiting the present invention. In the entire drawings, the same reference symbols represent the same components;

[0049] Figure 1 is a flow chart of the method of the present invention;

[0050] Figure 2 This is a flow chart of the solution process of the wind-solar-thermal-constant-speed coupled pumped storage optimal dispatching model based on the relaxation model. DETAILED DESCRIPTION

[0051] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0052] A specific embodiment of the present invention discloses an optimal operation method of a pumped storage power station taking into account variable speed characteristics, which specifically includes steps S01 to S03.

[0053] Step S01, construct a fixed-variable speed coupled pumped storage power station model based on the power generation power, pumping power, power generation status, and pumping status of the fixed-speed units and variable-speed units in the pumped storage power station; and construct an operation cost model based on the output of the thermal power units, the carbon emissions of the thermal power units, the system load loss, the wind abandonment, and the solar abandonment.

[0054] Specifically, the extraction power constraint is constructed based on the generating power and pumping power of the fixed-speed units and the variable-speed units;

[0055] Construct pumped storage operation constraints based on the power generation status and pumping status of fixed-speed units and variable-speed units;

[0056] The startup variables and shutdown variables of fixed-speed units, the startup and shutdown variables of variable-speed units, and the maximum number of startup units and the number of startup pumps in a pumped-storage power station at the same time are used to construct constraints on the number of startup pumps.

[0057] Pumped storage ramp constraints are constructed based on the continuous operating variables of fixed-speed units and variable-speed units, power generation / pumping power, and maximum power generation / pumping ramp values;

[0058] Constructing storage capacity constraints based on the pumping / generation efficiency of fixed-speed units and variable-speed units;

[0059] The minimum continuous pump-on time constraint is constructed based on the minimum continuous pump-on time constant of the fixed-speed unit and the variable-speed unit;

[0060] The minimum continuous start-stop time constraint is constructed based on the minimum continuous start-up time constant and the minimum continuous stop time constant of the fixed-speed unit and the variable-speed unit;

[0061] Establish the start-stop number constraint based on the maximum start-stop number of fixed-speed units and variable-speed units;

[0062] Construct pumping / generation efficiency constraints based on the electricity-water conversion efficiency, water transmission efficiency, and unit operation efficiency of fixed-speed units and variable-speed units;

[0063] Based on the above constraints, a fixed-variable speed coupled pumped storage power station model is obtained.

[0064] Furthermore, the extraction power constraint includes the output constraint of the power generation condition and the output constraint of the pumping condition;

[0065] Among them, the output constraint of power generation condition is expressed as:

[0066]

[0067] in, and are the power generated by the variable speed unit and the fixed speed unit to the grid in period t respectively; and are the minimum and maximum power generation of the variable speed unit respectively; and are the minimum and maximum power generation of the fixed speed unit respectively; and They are the power generation operation status of the variable speed unit and the fixed speed unit in period t respectively.

[0068] The output constraint of the pumping condition is expressed as:

[0069]

[0070] in, and are the pumping power purchased from the power grid by the variable speed unit and the fixed speed unit during period t respectively; and are the minimum and maximum pumping power of the variable speed unit respectively; is the maximum pumping power of the fixed speed unit; and They are the pumping operation status of the variable speed unit and the fixed speed unit in period t respectively.

[0071] Furthermore, the pumped storage operation constraints are expressed as:

[0072]

[0073] in, and They are the shutdown operation status of the variable speed unit and the fixed speed unit in period t respectively.

[0074] Furthermore, for a single pumped-storage power station, adding multiple pumps at the same time will cause a greater load and stress on the power station's electrical equipment, increasing the risk of equipment failure; for the power grid, restricting the number of additional pumps can also avoid larger power shocks to ensure the stable operation of the power grid.

[0075] The constraint on the number of additional pumps is expressed as:

[0076]

[0077] Among them, N cp and N vp are the number of fixed-speed units and variable-speed units, respectively; T is the total number of time periods; UTS and PTS are the maximum number of units and pumps that can be started at the same time in a pumped-storage power station, respectively; and They are the starting variables of the fixed speed unit and the variable speed unit respectively; and They are the pump start variables for the fixed speed unit and the variable speed unit respectively;

[0078] Among them, the startup variables and pump startup variables of the variable speed unit meet the following constraints:

[0079]

[0080]

[0081] in, and They are the shutdown variables and pump stop variables of the variable speed unit respectively.

[0082] Furthermore, the pumped storage ramp constraint includes the pumping ramp constraint and the power generation ramp constraint. The power generation ramp constraint is expressed as:

[0083]

[0084] in, is the power generated by the pumped storage power station to the grid during period t; The maximum value of the power generation ramp during period t; and are the power generated by the fixed speed unit and the variable speed unit to the grid in period t; N cp and N vp are the number of fixed speed units and variable speed units respectively; and are the startup variables of the fixed speed unit and the variable speed unit in period t respectively; and are the maximum power generation of fixed-speed units and variable-speed units respectively; UTS represents the maximum number of units that can be started simultaneously in a pumped-storage power station; and are the continuous operating variables of the variable speed unit and the fixed speed unit in the power generation condition in period t respectively;

[0085] The pumping uphill constraint is expressed as:

[0086]

[0087] in, is the pumping power purchased by the pumped storage power station from the power grid during period t; is the maximum value of the pumping uphill slope during period t; and are the pumping power purchased from the power grid by the fixed-speed unit and the variable-speed unit during period t; N cp and N vp are the number of fixed speed units and variable speed units respectively; and are the pump start variables of the fixed speed unit and the variable speed unit in period t respectively; and They are the maximum pumping power of fixed-speed units and variable-speed units respectively; PTS represents the maximum number of pumps that can be operated simultaneously in a pumped-storage power station; and are the continuous operation variables of the variable speed unit and the fixed speed unit in the pumping condition in period t respectively;

[0088] Furthermore, the reservoir capacity constraints include the upper reservoir water balance relationship and water level constraints, and the lower reservoir water balance relationship and water level constraints. The reservoir capacity constraints constructed based on the pumping / generation efficiency of the fixed speed unit and the variable speed unit include:

[0089] Based on the pumping / generation efficiency of the fixed-speed units and the variable-speed units, the water balance relationship and water level constraint of the upper reservoir and the water balance relationship and water level constraint of the lower reservoir are constructed, respectively expressed as:

[0090]

[0091]

[0092] in, and are the storage capacities of the upper and lower reservoirs in period t; N cp and N vp are the number of fixed speed units and variable speed units respectively; and are the pumping operation states of the variable speed unit and the fixed speed unit in period t respectively; and are the pumping power purchased from the power grid by the variable speed unit and the fixed speed unit during period t respectively; and are the pumping efficiencies of the variable speed unit and the fixed speed unit respectively; and are the power generation operation states of the variable speed unit and the fixed speed unit in period t respectively; and are the power generated by the variable speed unit and the fixed speed unit to the grid in period t respectively; and are the power generation efficiencies of variable speed units and fixed speed units respectively; and They are the safe storage capacity of the upper and lower reservoirs respectively; and are the upper and lower reservoir water levels respectively; and are the dead water levels of the upper and lower reservoirs respectively; and are the normal water levels of the upper and lower reservoirs respectively; T is the total number of time periods.

[0093] Furthermore, the minimum continuous pump-on time constraint includes the minimum continuous pump-on time constraints of the fixed-speed unit and the variable-speed unit. The minimum pump-on time constraint of the variable-speed unit is expressed as:

[0094]

[0095] in, It is the minimum continuous pump-on time constant of the variable speed unit.

[0096] The minimum pump-on time constraint of a fixed-speed unit is similar to that of a variable-speed unit and will not be described in detail here.

[0097] Furthermore, the minimum continuous start-stop time constraint includes the minimum continuous start-stop time constraint of the fixed speed unit and the variable speed unit. The minimum continuous start-stop time constraint of the variable speed unit is expressed as:

[0098]

[0099] in, and They are respectively the minimum continuous start-up time constant and the minimum continuous stop time constant of the variable speed unit.

[0100] The minimum continuous on / off time constraint of a fixed-speed unit is similar to that of a variable-speed unit and will not be described in detail here.

[0101] Furthermore, the start-stop number constraint is expressed as:

[0102]

[0103] Among them, UDTS is the maximum number of starts and stops of variable speed units and fixed speed units.

[0104] Furthermore, the pumping / generation efficiency constraint is expressed as:

[0105]

[0106] in, and are the power generation efficiencies of variable speed units and fixed speed units respectively; and are the pumping efficiencies of the variable speed unit and the fixed speed unit respectively; The water-to-electricity conversion efficiency of each unit under power generation conditions; is the electricity-water conversion efficiency of each unit under pumping conditions; η hyd is the water transmission efficiency of each unit; and are the unit operating efficiencies of the fixed-speed units under power generation conditions and pumping conditions, respectively; and are the unit operating efficiencies of the variable speed unit under power generation and pumping conditions during period t, respectively;

[0107] The derivation process is as follows:

[0108]

[0109] Among them, E p is the gravitational potential energy; m is the mass of water; g is the gravitational acceleration; H set is the gross water head; ρ is the density of water; V is the volume of water.

[0110] Combining the above constraints, a fixed-variable speed coupled pumped storage power station model is obtained.

[0111] Specifically, the operation cost model is constructed based on the output of thermal power units, carbon emissions of thermal power units, system load loss, wind abandonment and solar abandonment, including:

[0112] Calculate the operating cost of thermal power units based on the output of thermal power units;

[0113] Calculate the start-stop cost based on the start-stop variables of thermal power units;

[0114] Calculate carbon emission costs based on carbon emissions from thermal power units;

[0115] Calculate the load loss cost based on the system load loss amount;

[0116] Calculate the cost of wind and solar power abandonment based on the amount of wind and solar power abandoned;

[0117] An operating cost model is constructed based on the operating cost, start-up and shutdown cost, carbon emission cost, load loss cost and wind and solar power abandonment cost of thermal power units.

[0118] Specifically, the operating cost model is expressed as:

[0119]

[0120] Where C is the operating cost of the power grid system; C g,ope , C g,stu , C g,co2 , C voll , C volr are respectively the operation cost, start-up and shutdown cost, carbon emission cost, load loss cost and wind and solar power abandonment cost of thermal power units; N g 、N w 、N s 、N b are the number of thermal power units, wind power stations, photovoltaic power stations, and system nodes respectively; T is the total number of time periods; P is the number of ng,t Output for thermal power units; a ng 、b ng 、cng are the cost coefficients of thermal power units; α ng,t , β ng,t is the start and stop variable of the thermal power unit; C ng,sta , C ng,shu , C co2 , C cul , C cuw , C cus They are respectively the startup cost, shutdown cost, unit carbon emission cost, unit load loss cost, unit wind abandonment cost, and unit solar abandonment cost of thermal power units; co2 is the carbon emission intensity; They are the system load loss, wind abandonment and solar abandonment respectively.

[0121] Step S02: construct a wind-solar-thermal-fixed-speed-variable-speed coupled pumped-storage optimization scheduling model based on node power balance constraints, line flow constraints, thermal power unit operation constraints, pumped-storage operation constraints, system load reserve constraints, carbon emission constraints and the operation cost model.

[0122] Specifically, the node power balance constraint is expressed as:

[0123]

[0124] Among them, P ng,t , P nw,t , P ns,t , P nl,t , D nb,t , They are the output of thermal power units, wind power station output, photovoltaic power station output, line transmission power, system load, and load loss; G, W, S, SP, VP, L, and D are the associated sets of thermal power units, wind power stations, photovoltaic power stations, fixed-speed units, variable-speed units, lines, system loads, and nodes.

[0125] Specifically, the line flow constraint is expressed as:

[0126]

[0127] Among them, P l,max is the maximum transmission capacity of the line; G l-ng , G l-ncp , G l-nw , G l-ns , G l-nvp , G l-nb They are the transfer distribution factors of the nodes where the thermal power units, fixed speed units, wind power stations, photovoltaic power stations, variable speed units and loads are located on line l.

[0128] Specifically, the operating constraints of thermal power units include upper and lower output limits, ramp constraints, and minimum start and stop time constraints.

[0129] The output upper and lower limit constraints are expressed as:

[0130]

[0131] Among them, x ng,t is the operating status of the thermal power unit; and It is the minimum and maximum output of thermal power.

[0132] The hill climbing constraint is expressed as:

[0133] in, and It is the maximum up and down climbing limit of thermal power.

[0134] The minimum start-stop constraint is expressed as:

[0135]

[0136]

[0137] Among them, α ng,t and β ng,t are the startup variables and shutdown variables of the thermal power unit respectively; x ng,t is the operating status of the thermal power unit; and They are the shortest startup time and the shortest shutdown time of thermal power units respectively.

[0138] Specifically, load reserve refers to the upward active power regulation range and the downward active power regulation range within the response time (5 minutes). Due to the different flexibility of different units, the reserve capacity within the response time is also different, so the reserve capacity of the three types of reserve units, thermal power, fixed speed pumped storage, and variable speed pumped storage, is described separately.

[0139] Specifically, the system load reserve constraints include the reserve capacity constraints of thermal power units, the reserve capacity constraints of fixed-speed units, and the reserve capacity constraints of variable-speed units.

[0140] Furthermore, the reserve capacity constraint of thermal power units is expressed as:

[0141]

[0142] in, and is the upper and lower reserve capacity of the thermal power unit, Δt 5 is the load backup response time.

[0143] Furthermore, for the fixed-speed unit, it can only be at rated power under pumping conditions, so it has no backup capacity under pumping conditions, and its startup time exceeds the load backup response time, so it has no backup capacity under shutdown conditions. The backup constraint of the fixed-speed unit under power generation conditions is expressed as:

[0144]

[0145] in, For the upper and lower spare capacities of the fixed speed units, It is the up and down climbing rate of the fixed speed pumped storage unit.

[0146] Furthermore, for variable-speed units, they have backup capacity under both pumping and power generation conditions. Due to their rapid response capability, their climbing capability basically cannot limit their backup capacity. Instead, the output upper and lower limits caused by the inverter capacity constrain their backup capacity. Variable-speed pumped storage has a faster start-up and still has backup capacity under shutdown conditions. Therefore, the backup capacity of variable-speed units includes the backup capacity under shutdown conditions, pumping conditions, and power generation conditions. The backup capacity constraint of variable-speed units is expressed as:

[0147]

[0148] in, and They are the upper and lower reserve capacities of the variable speed unit respectively; and They are the upper and lower reserve capacities under the variable speed unit shutdown condition; and They are the upper reserve and lower reserve capacities under the variable speed unit power generation condition; and They are the upper and lower reserve capacities under the variable speed unit pumping condition.

[0149] Furthermore, under shutdown conditions:

[0150]

[0151] in, The upper and lower reserve capacities under the variable speed unit shutdown condition. is the up and down climbing rate of the variable speed unit, T s-t , T s-p They are the start-up time from the shutdown condition of the variable speed unit to the power generation condition and the pumping condition respectively.

[0152] Furthermore, the upper reserve capacity of the variable speed unit under power generation conditions is related to the difference between its output upper limit and the current output. However, when its operating condition is converted to pumping conditions, it must go through the process of power generation-no load-idling-rotation-transfer shutdown-pumping phase adjustment-pumping. Therefore, the lower reserve capacity under power generation conditions only considers its power generation to shutdown and down-climbing capacity:

[0153]

[0154]

[0155] in, is the upper and lower reserve capacity of the variable speed unit under power generation conditions, T t-s It is the shortest downtime time from the variable speed unit generating condition to the shutdown condition.

[0156] Furthermore, the lower reserve capacity of the variable speed pumped storage unit under pumping conditions is related to the difference between its output upper limit and current output. However, unlike the power generation condition, the pumping condition can be directly converted into the power generation condition. Therefore, the upper reserve capacity under pumping conditions takes into account its lower ramping capacity, pumping to shutdown and pumping-power generation conditions:

[0157]

[0158]

[0159] in, is the upper and lower reserve capacity of the variable speed pumped storage unit under pumping conditions, T p-s , T p-t They are the shutdown time from the generating condition to the shutdown condition and the switching time from the generating condition to the pumping condition of the variable-speed pumped storage unit.

[0160] Furthermore, this application considers the uncertainty of source and load, and adopts trapezoidal fuzzy variables to represent the prediction errors of load, wind power and photovoltaic output. The fuzzy parameters of the three are as follows:

[0161]

[0162] in, are the load forecast error fuzzy number, wind power output forecast error fuzzy number and photovoltaic output forecast error fuzzy number respectively; k d , k w , k s They are load forecast error membership parameter, wind power output forecast error membership parameter and photovoltaic output forecast error membership parameter respectively.

[0163] The membership function of the forecast error of load, wind power and photovoltaic output is described as:

[0164]

[0165] Among them, kP is the function parameter, which is used to determine the variation range of the membership function; μ A (x) describes the degree to which the input variable x belongs to set A, and its value range is between 0 and 1.

[0166] Then, the positive load reserve constraint and negative load reserve constraint of the system load reserve constraint are expressed as:

[0167]

[0168] Where Cr{·} is the confidence expression; δ is the confidence level that satisfies the system backup constraint.

[0169] Specifically, the carbon emission constraint is expressed as:

[0170]

[0171] Where Q g,co2 For carbon emissions.

[0172] In step S02, a wind-solar-fire-fixed-speed coupled pumped storage optimization scheduling model is constructed based on the above-mentioned node power balance constraints, line flow constraints, thermal power unit operation constraints, system load reserve constraints, carbon emission constraints, the pumped storage operation constraints mentioned in step SO1, and the operation cost model.

[0173] Step S03, with the goal of minimizing the operating cost of the power grid system, the optimal solution of the wind-solar-fire-fixed-speed coupled pumped-storage optimization scheduling model is sought based on the pumped-storage power station model to obtain the optimal operation plan of the pumped-storage power station, including the generating power, pumping power, generating status and pumping status of the fixed-speed units and variable-speed units in the pumped-storage power station.

[0174] Furthermore, the goal of minimizing the operating cost of the power grid system is expressed as:

[0175] minC=C g,ope +C g,stu +C g,co2 +C voll +C volr .

[0176] Specifically, the problem of finding the optimal solution to the wind-solar-thermal-constant-speed coupled pumped storage optimization scheduling model is a mixed integer linear programming problem. This application solves the scheduling model based on a relaxation model.

[0177] When solving, the integer variables in the mixed integer linear programming problem are relaxed into continuous variables (hereinafter referred to as relaxation variables). Exemplary integer variables include: the start and stop variables α of the thermal power unit ng,t , βng,t , the operating status of the thermal power unit x ng,t , the startup variables of the fixed speed unit and the variable speed unit in period t and Pump start variables for fixed speed units and variable speed units and Stop variables and pump stop variables of variable speed units and Stop variables and pump stop variables for fixed speed units and Pumping operation status of variable speed unit and fixed speed unit in period t and The power generation status of the variable speed unit and the fixed speed unit in period t and wait.

[0178] Furthermore, the relaxed wind-solar-thermal-constant-speed-variable-coupled pumped-storage optimization dispatch model is solved to obtain the optimal solution (in the optimal solution, the relaxation variable is a non-integer) and the corresponding first minimum grid system operation cost. Optionally, the solution process can be implemented using the solver gurobi or cplex.

[0179] Further, such as Figure 2 As shown, the process of solving the dispatch model based on the relaxation model and the branch and bound method is shown. When the non-integer optimal solution and the corresponding minimum grid system operating cost are obtained by solving the relaxed wind-solar-fire-fixed variable speed coupled pumped storage optimization dispatch model, the minimum grid system operating cost is determined as the current cost lower bound, and then branch and bound are performed.

[0180] In each branch iteration, a non-integer solution relaxation variable in the feasible domain is selected, and the variable is rounded down or up to obtain the sub-problem after branching, and the integer of the variable in each branch is used as the new constraint condition of each branch, and the optimal solution is continued to be sought based on the relaxation model; the corresponding power grid system operation cost is determined based on the optimal solution of each branch, and compared with the current cost lower bound, and the larger value is taken as the new cost lower bound.

[0181] If in a certain branch iteration, the relaxation variables in the optimal solution obtained are all integers, the power grid system operating cost corresponding to the optimal solution is set as the cost upper bound, and the corresponding optimal solution is recorded; in the subsequent branch process, if the relaxation variables in a new optimal solution are all integers, the corresponding operating cost is compared with the cost upper bound determined last time, and the lower value is taken as the new cost upper bound.

[0182] It should be noted that in the process of branch iterative solution, in order to improve the solution efficiency, it is necessary to prune the branch. If the following situations occur during the branch iteration process, the current branch will be pruned and the current branch will no longer continue to branch iterate:

[0183] 1. The relaxation variables in the optimal solution obtained in the current branch are all integers;

[0184] 2. The current branch has no feasible region, that is, the optimal solution cannot be obtained;

[0185] 3. The running cost corresponding to the optimal solution obtained by the current branch has exceeded the current cost upper bound.

[0186] When all branches are iteratively calculated or pruned, the optimal solution corresponding to the current cost upper bound is the optimal solution of the wind-solar-fire-fixed-speed coupled pumped-storage optimization scheduling model, and the slack variables are all integer solutions in the optimal solution. The optimal solution includes the optimal operation plan of the pumped-storage power station, and the optimal operation plan includes the power generation power, pumping power, power generation status and pumping status of the fixed-speed units and variable-speed units in the pumped-storage power station in each time period.

[0187] This embodiment discloses an optimal operation method of a pumped-storage power station taking into account variable speed characteristics. By considering the operation constraints of fixed-speed and variable-speed pumped-storage units, a fixed-variable speed coupled pumped-storage power station model is constructed; by considering the output characteristics of various energy sources in the power grid system, including the output characteristics of thermal power, wind power, and photovoltaic power, a wind-solar-fire-fixed variable speed coupled pumped-storage optimization scheduling model is constructed to give play to the flexible adjustment role of the pumped-storage power station, supplement the uncertainty of the power grid system due to wind power and photovoltaic power, and take the minimum total system operating cost as the goal, which can reduce the system load loss rate, wind and photovoltaic abandonment rate, and improve the utilization rate of the pumped-storage power station. By finding the optimal solution for the wind-solar-fire-fixed variable speed coupled pumped-storage optimization scheduling model based on a relaxation model and branch and bound, the solution efficiency is improved, the search space is reduced, and it is guaranteed to find the global optimal solution in the integer solution space.

[0188] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. An optimal operation method of a pumped storage power station taking into account variable speed characteristics, characterized in that: The steps include: A fixed-variable speed coupled pumped storage power station model is constructed based on the power generation power, pumping power, power generation status, and pumping status of the fixed-speed units and variable-speed units in the pumped storage power station; an operation cost model is constructed based on the output of thermal power units, carbon emissions of thermal power units, system load loss, wind abandonment, and solar abandonment; Based on the node power balance constraints, line flow constraints, thermal power unit operation constraints, pumped storage operation constraints, system load reserve constraints, carbon emission constraints and the operation cost model, a wind-solar-thermal-fixed-speed-variable-speed coupled pumped storage optimization scheduling model is constructed; With the goal of minimizing the operating cost of the power grid system, the optimal solution of the wind-solar-fired-fixed-speed and variable-speed coupled pumped-storage optimization scheduling model is sought based on the pumped-storage power station model, and the optimal operation plan of the pumped-storage power station is obtained, including the generating power, pumping power, generating status and pumping status of the fixed-speed units and variable-speed units in the pumped-storage power station.

2. The optimal operation method according to claim 1, characterized in that: The fixed-variable speed coupled pumped storage power station model constructed based on the power generation power, pumping power, power generation state, and pumping state of the fixed-speed units and variable-speed units in the pumped storage power station includes: Construct the extraction power constraint based on the generating power and pumping power of the fixed-speed units and variable-speed units; Construct pumped storage operation constraints based on the power generation status and pumping status of fixed-speed units and variable-speed units; The startup variables and shutdown variables of fixed-speed units, the startup and shutdown variables of variable-speed units, and the maximum number of startup units and the number of startup pumps in a pumped-storage power station at the same time are used to construct constraints on the number of startup pumps. Pumped storage ramp constraints are constructed based on the continuous operating variables of fixed-speed units and variable-speed units, power generation / pumping power, and maximum power generation / pumping ramp values; Constructing storage capacity constraints based on the pumping / generation efficiency of fixed-speed units and variable-speed units; The minimum continuous pump-on time constraint is constructed based on the minimum continuous pump-on time constant of the fixed-speed unit and the variable-speed unit; The minimum continuous start-stop time constraint is constructed based on the minimum continuous start-up time constant and the minimum continuous stop time constant of the fixed-speed unit and the variable-speed unit; Establish the start-stop number constraint based on the maximum start-stop number of fixed-speed units and variable-speed units; Construct pumping / generation efficiency constraints based on the electricity-water conversion efficiency, water transmission efficiency, and unit operation efficiency of fixed-speed units and variable-speed units; Based on the above constraints, a fixed-variable speed coupled pumped storage power station model is obtained.

3. The optimal operation method according to claim 2, characterized in that: The pumped storage ramp constraint includes the pumping ramp constraint and the power generation ramp constraint. The power generation ramp constraint is expressed as: in, is the power generated by the pumped storage power station to the grid during period t; The maximum value of the power generation ramp during period t; and are the power generated by the fixed speed unit and the variable speed unit to the grid in period t; N cp and N vp are the number of fixed speed units and variable speed units respectively; and are the startup variables of the fixed speed unit and the variable speed unit in period t respectively; and are the maximum power generation of fixed-speed units and variable-speed units respectively; UTS represents the maximum number of units that can be started simultaneously in a pumped-storage power station; and are the continuous operating variables of the variable speed unit and the fixed speed unit in period t respectively.

4. The optimal operation method according to claim 2, characterized in that: The reservoir capacity constraint constructed based on the pumping / generation efficiency of the fixed-speed unit and the variable-speed unit includes: Based on the pumping / generation efficiency of the fixed-speed units and the variable-speed units, the water balance relationship and water level constraint of the upper reservoir and the water balance relationship and water level constraint of the lower reservoir are constructed, respectively expressed as: in, and V t low are the storage capacities of the upper and lower reservoirs in period t; N cp and N vp are the number of fixed speed units and variable speed units respectively; and are the pumping operation states of the variable speed unit and the fixed speed unit in period t respectively; and are the pumping power purchased from the power grid by the variable speed unit and the fixed speed unit during period t respectively; and are the pumping efficiencies of the variable speed unit and the fixed speed unit respectively; and are the power generation operation states of the variable speed unit and the fixed speed unit in period t respectively; and are the power generated by the variable speed unit and the fixed speed unit to the grid in period t respectively; and are the power generation efficiencies of variable speed units and fixed speed units respectively; and They are the safe storage capacity of the upper and lower reservoirs respectively; and are the upper and lower reservoir water levels respectively; and are the dead water levels of the upper and lower reservoirs respectively; and are the normal water levels of the upper and lower reservoirs respectively; T is the total number of time periods.

5. The optimal operation method according to claim 2, characterized in that: The pumping / generation efficiency constraint is expressed as: in, and are the power generation efficiencies of variable speed units and fixed speed units respectively; and are the pumping efficiencies of the variable speed unit and the fixed speed unit respectively; The water-to-electricity conversion efficiency of each unit under power generation conditions; is the electricity-water conversion efficiency of each unit under pumping conditions; η hyd is the water transmission efficiency of each unit; and are the unit operating efficiencies of the fixed-speed units under power generation conditions and pumping conditions, respectively; and are the unit operating efficiencies of the variable speed unit under power generation conditions and pumping conditions during period t, respectively.

6. The optimal operation method according to any one of claims 1 to 5, characterized in that: The operation cost model is constructed based on the output of thermal power units, carbon emissions of thermal power units, system load loss, wind abandonment and solar abandonment, including: Calculate the operating cost of thermal power units based on the output of thermal power units; Calculate the start-stop cost based on the start-stop variables of thermal power units; Calculate carbon emission costs based on carbon emissions from thermal power units; Calculate the load loss cost based on the system load loss amount; Calculate the cost of wind and solar power abandonment based on the amount of wind and solar power abandoned; An operating cost model is constructed based on the operating cost, start-up and shutdown cost, carbon emission cost, load loss cost and wind and solar power abandonment cost of thermal power units.

7. The optimal operation method according to claim 6, characterized in that: The operating cost model is expressed as: Where C is the operating cost of the power grid system; C g,ope , C g,stu , C g,co2 , C voll , C volr are respectively the operation cost, start-up and shutdown cost, carbon emission cost, load loss cost and wind and solar power abandonment cost of thermal power units; N g 、N w 、N s 、N b are the number of thermal power units, wind power stations, photovoltaic power stations, and system nodes respectively; T is the total number of time periods; P is the number of ng,t Output for thermal power units; a ng , b ng 、c ng are the cost coefficients of thermal power units; α ng,t , β ng,t is the start and stop variable of the thermal power unit; C ng,sta , C ng,shu , C co2 , C cul , C cuw , C cus They are respectively the startup cost, shutdown cost, unit carbon emission cost, unit load loss cost, unit wind abandonment cost, and unit solar abandonment cost of thermal power units; co2 is the carbon emission intensity; They are the system load loss, wind abandonment and solar abandonment respectively.

8. The optimal operation method according to claim 7, characterized in that: The system load reserve constraints include reserve capacity constraints for thermal power units, reserve capacity constraints for fixed-speed units, and reserve capacity constraints for variable-speed units.

9. The optimal operation method according to claim 8, characterized in that: The system load reserve constraint includes a positive load reserve constraint and a negative load reserve constraint, which can be expressed as: in, and They are the upper and lower reserve capacities of thermal power units respectively; and They are the upper and lower reserve capacities of the variable speed unit respectively; and They are upper and lower reserve capacities of fixed-speed units respectively; are the load forecast error fuzzy number, wind power output forecast error fuzzy number and photovoltaic output forecast error fuzzy number respectively; δ is the confidence level of satisfying the system reserve constraint; Cr{·} is the confidence expression.

10. The optimal operation method according to claim 1, characterized in that: Based on the relaxation model, the wind-solar-fired-fixed-speed-variable-speed coupled pumped-storage optimization scheduling model is solved to obtain the optimal operation plan of the pumped-storage power station, including the generating power, pumping power, generating status and pumping status of the fixed-speed units and variable-speed units in the pumped-storage power station.

Images