A method and device for improving power grid benefit and stable operation of a power system

Abstract

The application discloses a method and device for improving power grid benefit and stable operation of a power system, and the method comprises input parameters, a unit commitment target function, and cascade hydropower and thermal power and system constraints; a unit commitment model of the cascade hydropower and thermal power considering complex vibration zones is established, and the model is solved; and the solving result is applied to the power system to reduce output fluctuation and start-stop times of the thermal power unit. The unit commitment model of the cascade hydropower and thermal power system considering complex vibration zone characteristics is established, effectively avoiding problems such as poor power system safety and low operation benefit caused by the hydropower running in the vibration zone for flexible peak regulation, and has important significance for guaranteeing safe, stable and economic operation of the power grid.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power technology, in particular to a method and device for improving power grid benefit and stable operation of power system. BACKGROUND

[0002] In recent years, hydropower has been widely concerned in the research of power system optimal scheduling due to its good regulation ability, rapid start and stop, strong load tracking ability and other characteristics. In particular, in the water-fire power system with high proportion of hydropower, hydropower often adjusts the system load with its excellent peak shaving ability, reduces the output fluctuation and start-stop times of thermal power units, and reduces the fuel consumption and start-stop costs of the system, which has a significant effect on the optimization goal of overall consideration of power grid operation benefit and energy saving and consumption reduction. However, in this process, the risk of hydropower operation in the vibration zone is increased. The vibration zone refers to the cavitation and vibration phenomenon of the hydropower unit at certain water head or output, which can cause low efficiency and unstable output of the unit, threaten the safe operation and service life of the unit, and even damage the power grid in severe cases. At present, many large-scale cascade hydropower stations have been built in southwest China and other regions. These power stations are often accompanied by complex large water head, large installed capacity, and large-scale units, and complex multi-vibration zones. In the development of power grid scheduling plan, the unit commitment problem of cascade hydropower-thermal power system cannot be avoided. How to fully consider the influence of the characteristics of the complex vibration zone of the cascade hydropower and actively play the peak shaving benefit of the cascade hydropower is a key link to improve the benefit of the power grid and ensure the stable operation of the power system. However, there is no related research in the prior art. SUMMARY

[0003] In order to solve at least one technical problem existing in the prior art, the present application provides a method and device for improving the benefit of the power grid and the stable operation of the power system.

[0004] To achieve the above purpose, the technical scheme of the present application is:

[0005] In a first aspect, the present application provides a method for improving the benefit of the power grid and the stable operation of the power system, comprising:

[0006] input parameters to construct a unit commitment objective function and cascade hydropower-thermal power system constraints;

[0007] establishing a cascade hydropower-thermal power unit commitment model considering the complex vibration zone, and solving the model;

[0008] applying the solving result to the power system to reduce the output fluctuation and start-stop times of the thermal power unit.

[0009] In a second aspect, the present application provides a device for improving the benefit of the power grid and the stable operation of the power system, comprising:

[0010] An input module is configured to input parameters to construct a unit commitment objective function and cascade hydropower and thermal power system constraints;

[0011] A model module is configured to establish a unit commitment model of cascade hydropower and thermal power considering complex vibration zones and solve the model;

[0012] An application module is configured to receive a solution result and apply the solution result to a power system to reduce output fluctuation and start-stop times of thermal power units.

[0013] The unit commitment objective function is as follows:

[0014]

[0015] wherein N is the total number of thermal power units, T is the total number of scheduling time periods of the system, is the active power output of the thermal power unit i at the time period t, ai, bi, and ci are consumption characteristic parameters of the unit i, represents a variable of the operation state of the unit i at the time period t, represents shutdown, represents startup, is the startup cost of the unit i at the time period t.

[0016] Further, the cascade hydropower and thermal power system constraints include thermal power unit characteristic constraints, cascade hydropower characteristic constraints, and system power balance constraints.

[0017] The thermal power unit characteristic constraints include upper and lower limits of unit output, unit ramping / slope constraints, and minimum start-stop time constraints of units.

[0018] The cascade hydropower characteristic constraints include hydropower station output constraints, relationship constraints between hydropower station output and unit output, hydropower station storage capacity constraints, hydropower station power generation flow constraints, hydropower station output constraints, water abandonment constraints, storage capacity balance constraints, and hydropower station vibration zone constraints.

[0019] Further, the system constraints include:

[0020] System power balance constraints: the sum of active power outputs of all units at each time period of the system is equal to the load to ensure stable operation of the power system;

[0021] System reserve constraints: the reserve provided by all units at any optimization time period should meet the reserve demand of the system;

[0022] Line power flow constraints: the active power flowing through the line at each time period of the system cannot exceed the set upper and lower limits.

[0023] Further, the solving of the model comprises: using multiple sets of class step functions to approximate the high-dimensional nonlinear condensation function constraint, converting the cascade hydropower-thermal power unit combination problem considering complex vibration region characteristics into a mixed integer linear programming problem.

[0024] Compared with the prior art, the present application has the beneficial effects that:

[0025] The present application establishes a cascade hydropower-thermal power system unit combination model considering complex vibration region characteristics, effectively avoids the problems of poor power system safety and low operation efficiency caused by the flexible peak shaving operation of hydropower in the vibration region, and has important significance for guaranteeing the safe, stable and economic operation of the power grid; meanwhile, multiple sets of class step functions are used to approximate the high-dimensional nonlinear condensation function constraint, the cascade hydropower-thermal power unit combination problem considering complex vibration region characteristics is converted into a mixed integer linear programming problem, the solving efficiency is improved, and the computer operation power consumption is reduced. In the model solving process, the information of the stable operation region and the vibration region is considered, and the dimension disaster problem is avoided. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 A method flowchart for improving power grid efficiency and stable operation of a power system is provided for the embodiment 1 of the present application;

[0027] Figure 2 A power station data indication diagram;

[0028] Figure 3 A multiple set class step function approximation condensation function constraint diagram;

[0029] Figure 4 A composition schematic diagram of a device for improving power grid efficiency and stable operation of a power system is provided for the embodiment 2 of the present application. DETAILED DESCRIPTION

[0030] The technical solutions of the present application will be further described below in combination with the drawings and embodiments.

[0031] Embodiment 1:

[0032] Referring to Figure 1 The method for improving power grid efficiency and stable operation of a power system provided by the present embodiment mainly comprises the following steps:

[0033] 101, input parameters to construct a unit combination objective function and cascade hydropower-thermal power system constraints;

[0034] 102, establish a cascade hydropower-thermal power unit combination model considering complex vibration region, and solve the model;

[0035] Thus, the two steps are used to establish a cascade hydroelectricity-thermal power system unit combination model (model for objective function + constraint) considering the characteristics of complex vibration area, effectively avoiding the problems of poor power system safety and low operation efficiency caused by the flexible peak shaving operation of hydroelectricity in the vibration area.

[0036] 103. According to the solving result, the output fluctuation and start-stop times of the thermal power unit are reduced by applying to the power system, which is more significant for the optimization target of energy saving and consumption reduction than the pure thermal power unit combination for overall guarantee of power grid operation efficiency.

[0037] Specifically, the unit combination objective function described above uses the sum of the coal consumption cost and start-stop cost of the thermal power unit as the target for minimization, and is specifically expressed as follows:

[0038]

[0039] In the formula, N is the total number of thermal power units, T is the total number of scheduling periods of the system, is the active power output of the thermal power unit i at period t, ai, bi, and ci are the consumption characteristic parameters of the unit i, is the variable representing the operating state of the unit i at period t, represents shutdown, represents start-up, is the start-up cost of the unit i at period t.

[0040] The cascade hydroelectricity-thermal power system constraints described above include thermal power unit and cascade hydroelectricity characteristic constraints, power balance, reserve and network power flow system constraints, and reasonable arrangement of unit start-stop and output planning in the scheduling period.

[0041] Specifically, the thermal power unit characteristic constraints include:

[0042] 1) Unit output upper and lower limit constraint. When the unit operating state , the thermal power unit output at this period is also 0; when , the output of the thermal power unit at each period should be between the maximum and minimum output range.

[0043]

[0044] In the formula, and are the minimum and maximum values of the active power output of the unit i.

[0045] 2) Unit ramping / slope constraint. The unit output has certain restrictions in adjacent periods and cannot be changed at will. The unit should meet the ramping / slope rate requirement when ramping up or down.

[0046]

[0047] respectively represent the maximum ramping / de-ramping capability of thermal unit i.

[0048] 3) Minimum start-up / shut-down time constraint. A unit needs to be on for a certain period of time before it can be shut down, corresponding to the minimum continuous operation time; a unit needs to be off for a certain period of time before it can be started up again, corresponding to the minimum continuous shut-down time.

[0049]

[0050]

[0051] T i is the minimum continuous operation time and is the minimum continuous shut-down time of unit i, and τ represents the time period. Take the minimum continuous operation time constraint as an example. When t = 6, and that is, unit i switches from the off state to the on state at time period 6, if its minimum on time is 5 time periods, then according to the minimum continuous operation time constraint, the unit must be kept in the on state for at least time periods 6, 7, 8, 9 and 10. From equation (4), we know that τ∈[7,10), and because is a 0-1 integer variable, it can only take the value 1, plus satisfies the minimum continuous operation time requirement of the unit. Similarly, the minimum continuous shut-down time constraint can be explained.

[0052] The cascade hydropower characteristics constraint includes:

[0053] 1) Hydropower station output constraint. The output of a cascade hydropower station should be between its maximum and minimum output.

[0054]

[0055] is the active output of hydropower station j at time period t, and

[0056] 2) Relationship between hydropower station output and unit output. The output of hydropower station j is equal to the sum of the outputs of all hydropower units in the station.

[0057]

[0058] is the active output of hydropower unit h of hydropower station j at time period t.

[0059] ​​​​​​​​3) Reservoir capacity constraints. The volume of cascade hydropower stations should be within the safe interval at any time period to ensure the normal operation of upstream and downstream hydropower stations in the basin. It can be expressed as follows:

[0060]

[0061] wherein, are the upper and lower limits of the volume of power station j, represents the reservoir capacity value of power station j at time period t.

[0062] 4) Hydropower station generation flow constraints.

[0063]

[0064] wherein, are the upper and lower limits of the generation flow of power station j, is the generation flow of power station j at time period t.

[0065] 5) Hydropower station output expression.

[0066]

[0067] wherein, aj represents the flow-power conversion coefficient of hydropower station j, which represents the ability to convert flow into output. This value can be fitted using historical output data and historical generation flow data of hydropower stations.

[0068] 6) Spillage constraints. When the reservoir capacity of a cascade hydropower station exceeds its upper limit at a certain time, spillage occurs. This water quantity cannot be used for power generation and is called spillage.

[0069]

[0070] wherein, represents the spillage flow of cascade hydropower plant j at time period t, represents the spillage flow of cascade hydropower plant j at time period t.

[0071] 7) Reservoir capacity balance constraints. There is a complex coupling characteristic between upstream and downstream cascade power stations, which can be described as follows:

[0072]

[0073] wherein, is the natural inflow of power station j at time period t.

[0074] 8) Hydropower station vibration zone constraints. In the process of power generation, if the output is unreasonable, it will cause excessive vibration of the water turbine set, affecting the safe operation and service life of the hydropower unit.

[0075]

[0076] Pj,kminand Pj,kmaxdenote the lower and upper limits of the power output of the power station j in the stable operation region k, respectively. and Pj,kminand Pj,kmaxdenote the lower and upper limits of the power output of the power station j in the stable operation region k, respectively.

[0077] The system constraints include:

[0078] 1) System power balance constraint. The sum of the active power outputs of all units in each time period of the system is equal to the load, so as to ensure the stable operation of the power system.

[0079]

[0080] Pj,kminand Pj,kmaxdenote the lower and upper limits of the power output of the power station j in the stable operation region k, respectively. Pj,kminand Pj,kmaxdenote the lower and upper limits of the power output of the power station j in the stable operation region k, respectively.

[0081] 2) System reserve constraint. The reserve capacity of the system is provided by the units that are started, so as to suppress the fluctuations of the system supply-demand imbalance caused by uncertain factors such as load prediction deviation. The reserve provided by all units in any optimization time period should meet the reserve demand of the system.

[0082]

[0083] Pj,kminand Pj,kmaxdenote the lower and upper limits of the power output of the power station j in the stable operation region k, respectively.

[0084] 3) Line power flow constraint. The active power flowing through the line in each time period of the system is limited and cannot exceed the set upper and lower limits.

[0085]

[0086] Pj,kminand Pj,kmaxdenote the lower and upper limits of the power output of the power station j in the stable operation region k, respectively. t m,n Pj,kminand Pj,kmaxdenote the lower and upper limits of the power output of the power station j in the stable operation region k, respectively. Pj,kminand Pj,kmaxdenote the lower and upper limits of the power output of the power station j in the stable operation region k, respectively.

[0087] The unit commitment problem shown in equations (1)-(16) can be converted into a mixed integer linear programming problem for solving by processing the thermal power operation cost function in equation (1) through piecewise linearization and introducing integer variables to linearize the unit commitment vibration region constraint (13). However, the vibration region information is stripped off in the direct linearization process of the stable operation region constraint (13), and the vibration region information is lost in the optimization process, which may lead to a biased result and cause deviation in the solution. In addition, when the model cannot converge, long-time manual intervention is required to adjust the hydropower output plan. Therefore, the embodiment proposes a vibration region constraint representation method that takes into account the stable operation region and vibration region information of the hydropower, so as to ensure the completeness of the vibration region constraint in the problem solving process and improve the solution accuracy.

[0088] The vibration zone of a cascade hydropower station is essentially a nonlinear constraint. By constructing a polynomial function of the station output, and using the root axis method to determine the positive and negative of the value interval function with adjacent roots as endpoints, the complex vibration zone characteristics of the hydropower station can be simulated. Assuming that the number of vibration zones of a certain cascade hydropower station j is s, and are the upper and lower limits of the output of the station, and are the upper and lower limits of the output of the station j, and

[0089] 1) Data labeling and value interval generation

[0090] The output of the station j and the upper and lower limit values of each vibration zone are sequentially labeled on the number axis, and the number of value intervals is determined with the adjacent two numbers as endpoints to generate a value interval table. For example, if the output of the station j and the upper and lower limit values of each vibration zone are all inconsistent, the number axis labeling diagram and the value interval table can be as shown in Figure 2 .

[0091] Table 1 Value interval table

[0092]

[0093]

[0094] 2) Positive and negative judgment of polynomial function in value interval

[0095] After generating the value interval table, a polynomial function of the output of the hydropower station is constructed according to the endpoints of the value interval, and then the root axis method is used to judge the positive and negative of the polynomial function in the value interval, based on which the vibration zone constraint of the hydropower station is simulated. The value of the root axis method to judge the function can be divided into the following 4 scenarios.

[0096] Scenario 1: When the output of the station j and the upper and lower limit values of each vibration zone are all inconsistent, then

[0097]

[0098] When the output of the station is in , the first term is positive, and the remaining 2s+1 terms are all negative, i.e. the polynomial function takes a negative value in interval 1; when the output of the station is in , the first two terms are positive, and the remaining 2s terms are all negative, i.e. the polynomial function takes a positive value in interval 2.

[0099]

[0100] ​​

[0101] Thus, the positive and negative of the polynomial function in the remaining value interval of the hydropower station output function can be determined, and the positive and negative of the final function in each value interval can be shown in Table 2.

[0102] Table 2 Positive and negative of polynomial function in scenario 1

[0103]

[0104] Scenario 2: when the lower limit value of the output of the power station j is consistent with the lower limit value of the vibration area 1, then

[0105]

[0106] When the output of the power station is in , the first term factor is positive, and the remaining 2s term factors are negative, that is, the polynomial function takes a positive number in interval 1; when the output of the power station is in , the first two term factors are positive, and the remaining 2s-1 term factors are negative, that is, the polynomial function takes a negative number in interval 2.

[0107]

[0108] Similarly, the positive and negative of the polynomial function in the remaining value interval of the hydropower station output function can be determined, and the positive and negative of the final function in each value interval can be shown in Table 3.

[0109] Table 3 Positive and negative of polynomial function in scenario 2

[0110]

[0111] Scenario 3: when the upper limit value of the output of the power station j is consistent with the upper limit value of the vibration area s, then

[0112]

[0113] When the output of the power station is in , the first term factor is positive, and the remaining 2s term factors are negative, that is, the polynomial function takes a positive number in interval 1; when the output of the power station is in

[0114] , the first two term factors are positive, and the remaining 2s-1 term factors are negative, that is, the polynomial function takes a negative number in interval 2.

[0115]

[0116] ​​​​

[0117] Similarly, the positive and negative of the hydropower station output function in the remaining value interval can be determined, and the positive and negative of the final function in each value interval can be shown in Table 4.

[0118] Table 4 Positive and negative of polynomial function in scenario 3

[0119]

[0120] Scenario 4: When the upper and lower limit values of the power station j output are consistent with the lower limit value of the vibration zone 1 and the upper limit value of the vibration zone s respectively, then

[0121]

[0122] When the power station output is in , the first term factor is positive, and the remaining 2s-1 term factors are negative, that is, the polynomial function takes negative values in interval 1; when the power station output is in , the first two term factors are positive, and the remaining 2s-2 term factors are negative, that is, the polynomial function takes positive values in interval 2.

[0123]

[0124]

[0125] Similarly, the positive and negative of the hydropower station output function in the remaining value interval can be determined, and the positive and negative of the final function in each value interval can be shown in Table 5.

[0126] Table 5 Positive and negative of polynomial function in scenario 4

[0127]

[0128] 3) Vibration zone constraint representation

[0129] As can be seen from 2), the polynomial function of the power station output is always positive or always negative in the value interval with the upper and lower limit values of the vibration zone as endpoints. Therefore, the vibration zone constraint of the power station j can be represented as:

[0130]

[0131] In summary, the vibration zone constraint of any hydropower station can be simulated by the polynomial function of the power station output , and the construction of the polynomial function and the positive and negative of the vibration zone constraint are closely related to the upper and lower limits of the power station output, the number of vibration zones and the upper and lower limit values.

[0132] After the above processing, the vibration zone constraint of the power station can be represented by the polynomial function The value, i.e. nonlinear inequality constraint to simulate. In the calculation of the cascade hydropower-thermal power unit combination problem containing large-scale complex vibration area, there are a large number of nonlinear inequality constraints of cascade power station vibration area in the optimization model, the expression form is complex, and a large amount of time will be occupied in solving, even leading to problem not converging. Therefore, improving the calculation efficiency of the treatment of nonlinear inequality constraints can greatly speed up the convergence speed and time of problem solving.

[0133] The condensation function method proposed by scholars such as Li Xingsheng can integrate the nonlinear inequality constraints in the optimization problem and speed up the calculation speed of the optimization problem, providing a new solution to the problem. In addition, the condensation function is also widely used in structural optimization problems, which has reference significance for subsequent processing of unit combination problems containing irregular vibration areas.

[0134] The basic idea of condensation function method is to derive a differentiable function containing parameter β by using maximum entropy principle, and to convert multiple inequality constraints into one inequality constraint. When the parameter β is large enough, the new optimization problem can be considered equivalent to the original optimization problem. Assuming that the number of nonlinear inequality constraints of optimization problem is r, any constraint can be expressed as a quadratic differentiable function g u (x), u = 1, 2, …, r, define the augmented entropy surrogate function:

[0135]

[0136] In the formula, μ u The effect of nonlinear inequality constraint g u (x) in the calculation is determined by the maximum entropy criterion. The second term on the right side of the equation is the additional entropy term, and β is a positive constant to control the precision. When β is large, the value of the additional entropy term is small; The first term on the right side of the equation determines the size of the surrogate function. When β is large enough, take a set of optimal values μ* to maximize the surrogate function, then the maximum value of the surrogate function F e (x) is close to all the original nonlinear constraints G(x). At this time, F e (x) can be regarded as the approximation of G(x). The optimal value μ* and the approximate surrogate constraint of nonlinear inequality constraint G(x) are as follows:

[0137]

[0138]

[0139] Derivation process:

[0140] The derivation and proof of the optimal solution and the approximate surrogate constraint are shown in equations (33)-(38) and equations (39)-(42).

[0141]

[0142]

[0143] g u (x)β=lnμ u +1 (35)

[0144]

[0145]

[0146]

[0147] g u (x)β=lnμ u +1 (39)

[0148] μ u g u (x)β=μ u lnμ u +μ u (40)

[0149]

[0150]

[0151] Water power vibration zone constraint unified agent:

[0152] The vibration zone constraint of power station is unified as When the number of power stations increases, the vibration zone constraint of multiple power stations can be further represented based on the condensation function theory. At this time, the original unit combination problem is converted into the problem represented by formula (1)-(12), (14)-(16) and (43), and formula (43) contains the information of the stable operation zone and the vibration zone of multiple power stations.

[0153]

[0154] Water power vibration zone "0-1-∞-1-0" change characteristics

[0155] By observing formula (43), when the power output of the power station is within the operable zone, the corresponding condensation function index component tends to 0; when the power output of the power station is at the boundary of the operable zone, the corresponding condensation function index component tends to 1, and in these two cases, the power output of each power station can satisfy formula (43) when β is large enough. When the power output of the power station is within the vibration zone, the corresponding condensation function index component tends to infinity, which cannot satisfy formula (43).

[0156]

[0157]

[0158]

[0159] "0-1-∞-1-0" change characteristics prove

[0160] From the above, the power station vibration zone constraint is unified as is a polynomial function of the power station output, which is closely related to the upper and lower limits of the power station output, the number of vibration zones and the upper and lower limit values. The proof of the change characteristics of the hydropower vibration zone can also be divided into four scenarios. This section takes scenario 1 as an example for detailed description. When the output of power station j and the upper and lower limit values of each vibration zone are all inconsistent, then

[0161]

[0162]

[0163]

[0164]

[0165] Equations (47)-(50) are the proof process of the change characteristics of the hydropower vibration zone in scenario 1, and the remaining three scenarios can be proved in the same way.

[0166] Based on the above step change characteristics of the hydropower vibration zone, a group of step-like functions is introduced to approximate the corresponding condensation function components of the hydropower station. The expression of the step-like function is as follows:

[0167]

[0168]

[0169] In the formula, is the output of power station j, Ω j represents the stable operation zone of power station j, including the interior and boundary of the operable zone. For the condensation function components of each power station, a group of step-like functions is used for approximation, so that the original high-order nonlinear condensation function coupled with the exponential logarithm can be replaced by a group of step-like functions as shown in Figure 3 , thereby realizing the simplification of the condensation function.

[0170] In this way, equation (43) can be transformed into equation (53).

[0171]

[0172] After processing the condensation function constraint, the original optimization problem with the condensation function can be transformed into the equivalent optimization problem (54). The objective function f(x) of problem (54) and the original linear constraint condition G yuan(x) is unchanged, the condensing function constraint G(x) is replaced by a multi-section step function Φ(x).

[0173]

[0174] An adaptive factor ε is introduced in the objective function when solving the problem (54), and the original constraint G yuan Under the premise that (x) is unchanged, a plurality of step function constraints are placed in the objective function, and a new unconstrained problem (55) is regenerated. The solving process of the problem (55) takes into account the stable operation area and the vibration area information of the vibration area constraint. When the adaptive factor ε is large enough, in order to ensure the minimum of the objective, each type of step function is equal to 0 in each optimization period, that is, the power plant output is ensured to run in the stable operation area in the optimization process, and the new problem (55) is equivalent to the problem (54).

[0175]

[0176]

[0177] Compared with the prior art, the present application has the following technical advantages:

[0178] (1) A cascade hydropower-thermal power system unit combination model considering the characteristics of the complex vibration area is established, which effectively avoids the problems of poor power system safety and low operation efficiency caused by the flexible peak shaving operation of hydropower in the vibration area, and has important significance for ensuring the safe, stable and economic operation of the power grid.

[0179] (2) A new vibration area representation method is proposed, which takes into account the stable operation area and the vibration area information of the hydropower, prevents the deviation of the solving result caused by the loss of the vibration area information in the optimization process, and improves the solving accuracy.

[0180] (3) Based on the step change rule of "0-1-∞-1-0" of hydropower in the algorithm implementation process, a plurality of step function approximation functions are used to approximate the high-dimensional nonlinear condensing function, the condensing function is simplified, a new solution idea for solving the condensing function problem is provided, the dimension disaster problem caused by the introduction of a large number of relaxation variables and multiplier coefficients in the traditional numerical method is avoided, the solving efficiency is improved, and the computer operation power consumption is reduced.

[0181] (4) In the solving process, the adaptive factor ε is introduced in the objective function, and a plurality of step function approximation functions are relaxed, so that the original complex nonlinear problem is converted into a mixed integer linear programming problem, the problem solving efficiency is improved. In addition, when the model cannot converge, a set of relaxed solutions can be obtained by adjusting the adaptive factor ε.

[0182] Example 2:

[0183] Referring to Figure 4As shown, the embodiment provides a device for improving power grid benefit and stable operation of power system, comprising:

[0184] The input module 401 is configured to input parameters to construct a unit commitment target function and a cascade hydropower thermal power and system constraint;

[0185] The model module 402 is configured to establish a unit commitment model of cascade hydropower thermal power considering a complex vibration area, and solve the model;

[0186] The application module 403 is configured to receive a solution result, and apply the solution result to a power system to reduce output fluctuation and start-stop times of thermal power units.

[0187] The functions of the above modules and the steps 101-103 of the embodiment 1 correspond to each other, and thus will not be described herein.

[0188] The above embodiments are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made according to the essence of the present application should be covered within the protection scope of the present application.

Claims

1. A method for improving grid benefits and stable operation of power system, characterized in that, The application relates to a method for solving a unit commitment problem of a power system. The method comprises the following steps: inputting parameters to build a unit commitment objective function and cascade hydropower thermal power and system constraints; establishing a unit commitment model of cascade hydropower thermal power considering complex vibration zones and solving the model; applying the solving result to a power system to reduce output fluctuation and start-stop times of thermal power units; wherein N is the total number of thermal power units, T is the total number of dispatch periods of the system, is the active power output of the thermal power unit i in the period t, ai, bi, and ci are the consumption characteristic parameters of the unit i, is a variable representing the operating state of the unit i in the period t, represents shutdown, represents startup, is the startup cost of the unit i in the period t; the unit commitment objective function is: the cascade hydropower thermal power and system constraints comprise thermal power unit characteristic constraints, cascade hydropower characteristic constraints and system power balance constraints; the thermal power unit characteristic constraints comprise upper and lower limits of unit output, unit climbing / slide constraints and minimum start-stop time constraints of units; the cascade hydropower characteristic constraints comprise hydropower station output constraints, relationship constraints between hydropower station output and unit output, hydropower station storage capacity constraints, hydropower station power generation flow constraints, hydropower station output constraints, water abandonment quantity constraints, storage capacity balance constraints and hydropower station vibration zone constraints; the hydropower station vibration zone constraints are specifically represented as 1) data marking and value interval generation marking the output of a hydropower station j and upper and lower limit values of each vibration zone on a number axis in sequence, determining the number of value interval and generating a value interval table by taking two adjacent numbers as endpoints; 2) positive and negative judgment of a polynomial function in a value interval after generating the value interval table, a polynomial function of the output of the hydropower station is constructed according to the endpoints of the value interval, then the root axis method is used to judge the positive and negative of the polynomial function in the value interval, and the vibration zone constraints of the hydropower station are simulated based on this; 3) vibration zone constraint representation 2. The method of claim 1, wherein the method is performed by a power system stabilizer. the polynomial function of the output of the hydropower station is always positive or negative in the value interval with the upper and lower limit values of the vibration zone as the endpoints. the system constraints comprise: system power balance constraints: the sum of active power outputs of all units in each period of the system is equal to the load, so as to ensure stable operation of the power system; system reserve constraints: the reserve provided by all units in any optimization period should meet the reserve demand of the system; 3. The method of claim 1, wherein the method is performed by a power system stabilizer (PSS) of the power system. line power flow constraints: the active power flowing through the line in each period of the system cannot exceed the set upper and lower limits. the model solving comprises the following steps: a plurality of groups of step functions are used to approximate high-dimensional nonlinear condensed function constraints, and the cascade hydropower thermal power unit commitment problem considering complex vibration zone characteristics is converted into a mixed integer linear programming problem.

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