An optimal scheduling method considering source-load frequency modulation resources to achieve frequency security constraints

Abstract

The present invention relates to an optimization scheduling method for realizing frequency safety constraints by considering source-load frequency regulation resources, comprising the following steps: 1) constructing a system minimum inertia constraint according to the response principle of inertial resources on both sides of the source and load; 2) establishing a comprehensive evaluation index of inertial resources and primary frequency regulation resources according to the frequency regulation characteristics of each unit in the system; 3) determining the cost of inertial resources and primary frequency regulation resources respectively according to the quotation and the comprehensive evaluation index; 4) establishing a compensation mechanism adopted by the units participating in frequency regulation at peak time; 5) obtaining a frequency minimum point constraint according to a frequency dynamic response model including fire-water-wind-storage; 6) establishing a joint optimization model of source-load inertial resources and primary frequency regulation resources under frequency safety constraints, and obtaining the optimal solution of the model as a scheduling scheme for day-ahead scheduling of power system unit combinations. Compared with the prior art, the present invention can enhance the frequency regulation capability of the system and achieve frequency safety at a lower cost.

Description

Technical Field

[0001] The present invention relates to the field of power grid dispatching, and in particular to an optimization dispatching method for realizing frequency safety constraints by considering source-load frequency modulation resources. Background Art

[0002] In recent years, a large number of new energy sources have been integrated into the power system, and the characteristics of "double peaks" and "double highs" have become more prominent, causing the system's synchronous rotation inertia to decrease and the frequency deviation to increase. The current research mainly focuses on the joint optimization operation of primary and secondary frequency regulation in the frequency regulation market, and does not involve inertial response services. Inertial response services will become an important part of the future power frequency regulation market, so it is necessary to study the joint optimization of inertial resources and primary frequency regulation resources. When constructing a frequency response model, most people use the first-order inertial link to simulate the dynamic process of the unit speed regulator, only considering the time constants that have a greater impact on the frequency regulation, while ignoring some smaller time constants and the delay effect caused by the inverter, which may lead to optimistic calculation results of the lowest frequency point under disturbance.

[0003] Based on the differences in the inertial resources and primary frequency regulation responses on both sides of the source and load in the power system, comprehensive response evaluation indicators of inertial resources and primary frequency regulation resources are proposed respectively. Considering the impact of wind power and load fluctuations on inertial demand, a time-sharing incentive strategy is proposed to encourage inertial resources and primary frequency regulation resources to participate in the peak frequency regulation process. On the basis of the existing low-order frequency response model, the primary frequency regulation characteristics of wind turbines and energy storage are introduced to establish a frequency dynamic response model containing "fire-water-wind-storage". However, the existing model fails to comprehensively consider the impact of the joint frequency regulation of inertial resources and primary frequency regulation resources on the safety and stability of the system frequency. Therefore, an optimization scheduling method that considers the source-load frequency regulation resources to achieve frequency safety constraints is needed. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide an optimization scheduling method that takes into account source-load frequency modulation resources to achieve frequency safety constraints.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] An optimization scheduling method for realizing frequency safety constraints by considering source-load frequency modulation resources, the method comprising the following steps:

[0007] 1) According to the response principle of inertial resources on both sides of the source and load, the minimum inertia constraint of the system is established;

[0008] 2) Establish comprehensive evaluation indicators of inertial resources and primary frequency regulation resources based on the frequency regulation characteristics of each unit in the system;

[0009] 3) Determine the cost of inertial resources and primary frequency regulation resources respectively based on the quotation and comprehensive evaluation indicators;

[0010] 4) Considering the relevant factors of the system frequency response characteristics, establish a compensation mechanism for the units participating in frequency regulation during peak hours;

[0011] 5) According to the frequency dynamic response model including fire-water-wind-storage, the analytical expression of the system frequency response is obtained and linearized to obtain the frequency minimum point constraint;

[0012] 6) Establish a joint optimization model of source-load inertia resources and primary frequency regulation resources under frequency security constraints, and obtain the optimal solution of the model as the dispatching scheme for day-ahead dispatch of power system unit combinations.

[0013] In step 1), in order to maintain the system frequency stability, the total inertia of the system must be greater than the minimum inertia required when the system is disturbed, that is, the minimum inertia constraint, then:

[0014]

[0015]

[0016]

[0017] Among them, H Sy is the total system inertia, RoCoF max is the maximum frequency change rate, ΔP(t) is the power disturbance at time t, f N is the rated frequency, S Gg , S Hh , S W , S F , S SC are the rated capacities of thermal power units, hydropower units, wind power, flywheel energy storage, and supercapacitor energy storage, respectively. g , H h , H w , H f , H SC are the inertia time constants of thermal power units, hydropower units, wind power, flywheel energy storage, and supercapacitor energy storage, respectively, n is the rotor speed of the rotating unit, ω r is the rotor speed of the wind turbine, ω sc ,ω f are the rotation speeds of supercapacitor and flywheel respectively; G, H, W, F and SC are the number of thermal power units, hydropower units, wind power, flywheel energy storage and supercapacitor energy storage respectively.

[0018] In the step 2), the weights of the comprehensive evaluation indexes of the inertial resources and the primary frequency modulation resources are determined by using the hierarchical analysis method, and the comprehensive evaluation index values ​​are obtained accordingly, and then:

[0019]

[0020] Among them, D1 is the comprehensive evaluation index of the inertial response capability of the unit, D2 is the comprehensive evaluation index of the primary frequency regulation response capability of the unit, and x 11 、x 12 、x 13 are the rated capacity, inertia time constant, and stored kinetic energy of the unit, respectively. 21 、x 22 、x 23 They are the primary frequency regulation dead zone, speed inequality rate, and response lag time of the unit, and W1~W6 are weights;

[0021] By making a positive adjustment to the comprehensive evaluation index D2, we can obtain:

[0022] D3=A-(W4x 21 +W5x 22 +W6x 23 )

[0023] Where A is a constant.

[0024] In the step 3), the cost of the inertial resource and the cost of the primary frequency modulation resource are determined according to the quotation and the comprehensive evaluation index. The specific expression is:

[0025]

[0026] Among them, C IR is the corresponding cost of inertia, c1 is the quotation of inertia resources, h1 is the service time of inertia resources, C PFR is the cost of frequency modulation, c2 is the quotation of frequency modulation resources, and h2 is the service duration of frequency modulation resources.

[0027] In the step 4), the large and small sizes of the semi-trapezoidal membership function are used to describe the peak-valley membership, and the time division result is obtained according to the size of the membership function, and the compensation mechanism adopted by the frequency regulation units participating in the peak time is established accordingly, then:

[0028]

[0029] Among them, m1 and m2 are peak and valley membership respectively, f(x) is the real-time value on the wind-load curve, and f max 、f min are the maximum and minimum values ​​on the wind-load curve respectively.

[0030] In the step 5), the analytical expression of the system frequency response is specifically:

[0031]

[0032] Among them, ΔP is the power shortage, Δω is the system frequency deviation, ΔP Gg , ΔP Hydro,h , ΔP WT , ΔP F , ΔP SC are the primary frequency modulation outputs of thermal power units, hydropower units, fans, flywheel energy storage and supercapacitor energy storage, respectively. D is the system load active frequency regulation effect coefficient, C is a constant, K g , K h , K w , K f , K c are the mechanical power gain coefficients of thermal power units, hydropower units, fans, flywheels and supercapacitor energy storage, T RH is the reheat turbine time constant, T CH is the volume time constant, T S is the time constant of the oil motor, T G is the time constant of the thermal power unit speed regulator, F HP is the ratio of the steady-state output power of the high-pressure cylinder of the equivalent steam turbine to the total output power of the steam turbine, T w is the time constant of water hammer effect, T p is the time constant of the hydropower unit speed regulator, T y is the soft feedback time constant, D y is the soft feedback link coefficient, T IW , T c , T f are the inertia link time constants of the fan, supercapacitor energy storage and flywheel energy storage, T o , T e , T x is the delay time of the converter;

[0033] Taylor expansion is used to linearize the analytical expression, and the frequency minimum point constraint is obtained as follows:

[0034] f N -|Δω max |≥49.5

[0035] Among them, Δω max is the maximum frequency deviation, f N is the rated frequency of the system.

[0036] In the step 6), the objective function expression of the joint optimization model is:

[0037] min F1+F2

[0038]

[0039]

[0040] F2=C IR P IR +C PFR P PFR

[0041]

[0042]

[0043] Among them, F1 includes the electricity cost and start-up and shutdown cost of thermal power units, the start-up and shutdown cost of hydropower units and the wind power abandonment cost, F2 includes the purchase inertia and primary frequency regulation cost, C g,t (P g,t ) is the electricity cost of the thermal power unit, C op,g , C cl,g , C op,h , C cl,h are the startup and shutdown costs of thermal power units and hydropower units, respectively, u g,t 、v h,t are the operating state variables of thermal power unit g and hydropower unit h at time t, which are 0-1 variables, P g,t is the output of thermal power unit g at time t, P windc,t is the predicted output of the wind turbine, P wind,t is the actual output of the fan at time t, C wc is the wind curtailment cost, P IR is the inertial response output, P PFR is the primary frequency modulation output, C g IR , C h IR , C w IR , C f IR , C c IR Quote for inertial resources of thermal power units, hydropower units, fans, flywheels and supercapacitors, o g,t 、r h,t The state variable that provides a frequency modulation for thermal power unit g and hydropower unit h at time t is a 0-1 variable, C g PFR , C h PFR , C w PFR , C fPFR , C c PFR Provide quotation for primary frequency regulation resources of thermal power units, hydropower units, fans, flywheels and supercapacitors, They are the output of thermal power unit, hydropower unit, fan, flywheel and supercapacitor at time t, and T is the dispatching period.

[0044] In the step 6), the constraints of the joint optimization model include frequency safety constraints, unit conventional constraints, unit primary frequency regulation capacity constraints and day-ahead power balance constraints. The frequency safety constraints include frequency minimum point constraints, frequency change rate constraints and minimum inertia constraints. Then:

[0045]

[0046] Wherein, RoCoF(t) is the frequency change rate at time t.

[0047] The day-ahead power balance constraint is specifically:

[0048]

[0049] Among them, P g,t is the output of thermal power unit g at time t, P h,t is the output of hydropower unit h at time t, P wind,t is the actual output of the fan at time t, P load,t is the load output at time t, P t PFR is the primary frequency regulation demand of the system at time t.

[0050] The conventional constraints of the unit are specifically:

[0051]

[0052] Among them, P g,max , P g,min are the maximum and minimum output of thermal power units, R u,g , R d,g is the upward and downward ramp rate of the thermal power unit, MT g,t is the operating time of the thermal power unit, TMDT g,t 、TMUT g,t is the minimum start-up time and shutdown time of the thermal power unit, P h,max , P h,min are the maximum and minimum output of the hydropower unit, P h,t is the output of hydropower unit h at time t, q h,max ,q h,min is the maximum and minimum flow of hydropower unit h at time t, q h,tis the flow rate of hydropower unit h at time t, V h,t 、V h,(t+1) is the reservoir capacity of hydropower unit h at time t and t+1, V h,max 、V h,min are the maximum and minimum reservoir capacities of hydropower unit h at time t, W h,(t+1) is the net water volume of reservoir h at time t+1.

[0053] The primary frequency regulation capacity constraint of the unit is specifically:

[0054]

[0055] in, are the maximum output of primary frequency modulation of flywheel and supercapacitor energy storage, respectively. g,t 、r h,t The state variable that provides a frequency modulation for thermal power unit g and hydropower unit h at time t is a 0-1 variable, x i,t is the state of the units participating in primary frequency regulation, μ i,t The unit is powered on. They are the maximum frequency regulation outputs of thermal power unit g and hydropower unit h at time t respectively.

[0056] Compared with the prior art, the present invention has the following advantages:

[0057] This method takes inertial resources and primary frequency regulation resources as frequency regulation service products for market-oriented design. The units report the original performance indicators and quotations of inertial resources and primary frequency regulation resources respectively on the day before, and the unit quotations are corrected through comprehensive evaluation indicators. Finally, the units are optimized to provide inertial resources and primary frequency regulation. The inertial resources and primary frequency regulation resources on both sides of the source and load are synergistically enhanced to improve the system frequency safety at a lower cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 The figure is a flow chart of the method of the present invention.

[0059] Figure 2 It is the inertia quotation curve of the source side unit.

[0060] Figure 3 It is the inertia quotation curve of load side unit.

[0061] Figure 4 It is the primary frequency regulation quotation curve of the source side unit.

[0062] Figure 5 This is the primary frequency regulation quotation curve for the load-side units.

[0063] Figure 6 It is the daily load and wind power forecast value.

[0064] Figure 7 The results of the primary frequency regulation and system inertia of each scheme are shown in Figure (7a) for Scheme 1 and Figure (7b) for Scheme 2.

[0065] Figure 8 is the system frequency deviation of each scheme, among which Figure (8a) is scheme 1 and Figure (8b) is scheme 2.

[0066] Fig. 9 This is the primary frequency regulation output for the unit in Scheme 3. DETAILED DESCRIPTION

[0067] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0068] Example

[0069] like Figure 1 As shown, the present invention proposes an optimization scheduling method for realizing frequency safety constraints by considering source-load frequency regulation resources. First, the response principle of the inertia of the rotating unit on the power supply side and the virtual inertia of the wind turbine, as well as the flywheel inertia and the virtual inertia of the supercapacitor on the load side are analyzed; according to the differences in the response characteristics of each inertial resource and the primary frequency regulation resource, a comprehensive response evaluation considering the response characteristics of the inertial resource and the primary frequency regulation resource is proposed respectively; on the basis of the comprehensive evaluation, the influence of external factors on the inertial demand is considered, and a resource time-sharing incentive strategy is proposed; with the goal of optimizing the total cost of unit operation cost and the cost of purchasing frequency regulation service, a unit combination optimization scheduling model considering frequency safety constraints is established and solved to obtain the optimal scheduling plan. The method comprises the following steps:

[0070] 1) According to the response principle of inertial resources on both sides of the source and load, the minimum inertia constraint of the system is established;

[0071] 2) Based on the frequency regulation characteristics of each unit, the hierarchical analysis method is used to establish comprehensive evaluation indicators of inertial resources and primary frequency regulation resources;

[0072] 3) Determine the cost of inertial resources and primary frequency regulation resources based on the quotation and comprehensive evaluation indicators;

[0073] 4) Considering that the system frequency response characteristics are related to factors such as disturbance type and the proportion of renewable energy, a compensation mechanism should be established for units participating in frequency regulation during peak hours;

[0074] 5) Establish a frequency dynamic response model containing "fire-water-wind-storage" and derive the frequency minimum point constraint;

[0075] 6) Establish a joint optimization model of source-load inertia resources and primary frequency regulation resources under frequency security constraints, and obtain the optimal solution of the model as a dispatching scheme for day-ahead dispatch of power system unit combinations;

[0076] 7) Use cplex software programming to obtain the optimal solution and perform microgrid scheduling.

[0077] In the process of optimizing scheduling, the present invention divides the frequency regulation resources into the source side and the load side according to the differences in the response principles of each frequency regulation resource. The source side takes thermal power units, hydropower units and wind turbines using the virtual inertia control principle, and the load side takes supercapacitors and flywheel energy storage with strong response capabilities as examples. The inertial resources and primary frequency regulation resources on both sides of the source and load are coordinated and controlled to achieve frequency safety.

[0078] In step 1), when the power of each unit in the system is disturbed, its dynamic behavior is described by the swing equation:

[0079]

[0080] Among them, H g , H h , H w , H f , H SC are the inertia time constants of thermal power units, hydropower units, wind power, flywheel energy storage, and supercapacitor energy storage, respectively, n is the rotor speed of the rotating unit, ω r is the rotor speed of the wind turbine, ω sc ,ω f are the rotation speeds of the supercapacitor and the flywheel, respectively.

[0081] The inertial response expression of the entire system is:

[0082]

[0083] Among them, H Sy is the total inertia of the system, S Gg , S Hh , S W , S F , S SC They are the rated capacities of thermal power units, hydropower units, wind power, flywheel energy storage and supercapacitor energy storage respectively; G, H, W, F and SC are the numbers of thermal power units, hydropower units, wind power, flywheel energy storage and supercapacitor energy storage respectively.

[0084] In order to maintain the system frequency stability, the total inertia of the system must be greater than the minimum inertia required when the system is disturbed, that is, the minimum inertia constraint:

[0085]

[0086] Among them, RoCoF max is the maximum frequency change rate, ΔP(t) is the power disturbance at time t, f N is the rated frequency.

[0087] In step 2), according to the consideration of the unit response characteristics, the inertial resource response capability is related to the three indicators of the unit's inertial time constant, stored kinetic energy and rated capacity, and the primary frequency regulation is related to the three indicators of the unit's frequency regulation dead zone, speed inequality and response lag time. The analytic hierarchy process is used to determine the comprehensive evaluation index weights of inertial resources and primary frequency regulation resources, and the comprehensive evaluation is obtained as follows:

[0088]

[0089] Among them, D1 is the comprehensive evaluation of the inertial response capability of the unit, D2 is the comprehensive evaluation of the primary frequency regulation response capability of the unit, and x 11 、x 12 、x 13 are the rated capacity, inertia time constant, and stored kinetic energy of the unit, respectively. 21 、x 22 、x 23 They are the primary frequency regulation dead zone, speed inequality rate and response lag time of the unit respectively. W1~W6 are weights.

[0090] Since the smaller the primary frequency regulation index is, the better the primary frequency regulation performance of the unit is, the obtained comprehensive index is positively converted and the comprehensive index of primary frequency regulation resources is adjusted to:

[0091] D3=2-(0.3325x 21 +0.1396x 22 +0.5278x 23 ) (5)

[0092] Among them, D3 is the comprehensive evaluation of the primary frequency regulation response capability of the unit after correction.

[0093] In step 3), based on the frequency regulation performance differences of each unit, the units are required to report the performance indicators and quotations of inertia and primary frequency regulation respectively in advance, and the pricing of inertia resources and primary frequency regulation resources is corrected according to the comprehensive evaluation indicators, and the optimized units are selected to provide inertia and primary frequency regulation. The cost of inertia resources and primary frequency regulation resources is established according to the quotation and comprehensive evaluation indicators as follows:

[0094]

[0095] Among them, C IR is the cost of inertial resources, c1 is the quotation of inertial resources, h1 is the service time of inertial resources, C PFR is the cost of a frequency modulation resource, c2 is the quotation of a frequency modulation resource, and h2 is the service duration of a frequency modulation resource.

[0096] In step 4), from the perspective of inertia demand, the level of inertia is related to wind power output and the degree of disturbance of the system, so it is proposed to use time-sharing incentives for inertial resources and primary frequency regulation resources. The large and small semi-trapezoidal membership functions are used to describe the peak-valley membership, and the time-sharing division results are obtained according to the size of the membership function, and a compensation mechanism is established for the units participating in frequency regulation during peak hours:

[0097]

[0098] Among them, m1 and m2 are peak and valley membership respectively, f(x) is the real-time value on the wind-load curve, and f max 、f min are the maximum and minimum values ​​on the wind-load curve respectively.

[0099] In step 5), by performing equivalent aggregation on the prime movers, speed control systems and rotor motion equations of various units, a frequency dynamic response model containing "fire-water-wind-storage" is established, and the frequency response model of the system is constructed to obtain an analytical expression of the system frequency response, and the value of the lowest frequency point when the system is disturbed is calculated. The transfer function expression of the system is:

[0100]

[0101] Among them, ΔP is the power shortage, Δω is the system frequency deviation, K D is the system load active frequency regulation effect coefficient, ΔP Gg , ΔP Hydro,h , ΔP WT , ΔP F , ΔP SC They are the primary frequency modulation outputs of thermal power units, hydropower units, fans, flywheel energy storage, and supercapacitor energy storage.

[0102] From the frequency response model, we can get the output power of each prime mover when it is disturbed:

[0103]

[0104] Among them, K g , K h , K w , K f , K c are the mechanical power gain coefficients of thermal power units, hydropower units, fans, flywheels and supercapacitor energy storage, T RH is the reheat turbine time constant, T CH is the volume time constant, T S is the time constant of the oil motor, T G is the time constant of the thermal power unit speed regulator, F HPis the ratio of the steady-state output power of the high-pressure cylinder of the equivalent steam turbine to the total output power of the steam turbine, T w is the time constant of water hammer effect, T p is the time constant of the hydropower unit speed regulator, T y is the soft feedback time constant, D y is the soft feedback link coefficient, T IW , T c , T f are the inertia link time constants of the fan, supercapacitor energy storage and flywheel energy storage, T o , T e , T x is the delay time of the converter.

[0105] When the system is disturbed, the dynamic swing equation is:

[0106]

[0107] Among them, ΔP Gg , ΔP Hydro,h , ΔP WT , ΔP F , ΔP SC They are the primary frequency modulation outputs of thermal power units, hydropower units, fans, flywheel energy storage, and supercapacitor energy storage.

[0108] Solving equations (9) and (10) simultaneously, we can obtain the system frequency response expression when power is unbalanced:

[0109]

[0110] Among them, C is a constant, K g , K h , K w , K f , K c They are the mechanical power gain coefficients of thermal power units, hydropower units, fans, flywheels and supercapacitor energy storage respectively.

[0111] Using Taylor expansion, the above equation is linearized to obtain the frequency minimum point constraint:

[0112] f N -|Δω max |≥49.5 (12)

[0113] Among them, Δω max is the maximum frequency deviation, f N is the rated frequency of the system.

[0114] In step 6), the day-ahead power balance constraint is specifically:

[0115]

[0116] Where: P g,t is the output of thermal power unit g at time t, P h,t is the output of hydropower unit h at time t, P wind,t is the actual output of the fan at time t, P load,t is the load output at time t, They are the frequency modulation output of each unit at time t.

[0117] In step 6), according to the relevant parameters of the equipment, list the constraints of each equipment before the current day:

[0118]

[0119] Among them, P g,max , P g,min are the maximum and minimum output of thermal power units, u g,t 、v h,t are the operating state variables of thermal power unit g and hydropower unit h at time t, which are 0-1 variables, R u,g , R d,g is the upward and downward ramp rate of the thermal power unit, MT g,t is the operating time of the thermal power unit, TMDT g,t 、TMUT g,t is the minimum start-up time and shutdown time of the thermal power unit, P h,max , P h,min are the maximum and minimum output of the hydropower unit, P h,t is the output of hydropower unit h at time t, q h,max ,q h,min is the maximum and minimum flow of hydropower unit h at time t, q h,t is the flow rate of hydropower unit h at time t, V h,t is the reservoir capacity of hydropower unit h at time t, V h,max 、V h,min are the maximum and minimum reservoir capacities of hydropower unit h at time t, W h,(t+1) is the net water volume of reservoir h at time t+1.

[0120] In step 6), the primary frequency regulation capacity constraints of each unit are listed according to the frequency regulation capability of the unit:

[0121]

[0122] in: are the maximum output of primary frequency modulation of flywheel and supercapacitor energy storage, respectively. g,t 、r h,tThe state variable that provides a frequency modulation for thermal power unit g and hydropower unit h at time t is a 0-1 variable, x i,t is the state of the units participating in primary frequency regulation, μ i,t The unit is powered on. They are the maximum frequency regulation outputs of thermal power unit g and hydropower unit h at time t respectively.

[0123] In step 6), in order to ensure that the system frequency can be stable when disturbed, it is necessary to ensure that the system has a certain inertia and primary frequency modulation capacity when disturbed. The present invention uses one hour as the scheduling scale, and the frequency safety constraint for each period is specifically implemented as follows: Under the set power shortage, according to the second-level frequency response model calculation, the frequency minimum point constraint, frequency change rate constraint, and minimum inertia constraint are completed to ensure the frequency safety of the system under the set disturbance power.

[0124]

[0125] Wherein, RoCoF(t) is the frequency change rate at time t.

[0126] In step 6), the joint optimization model of source-load inertial resources and primary frequency regulation resources is constructed with the goal of optimizing the sum of unit operation cost, inertial response and primary frequency regulation cost. The objective function expression is:

[0127] min F1+F2 (17)

[0128] Among them, F1 includes the electricity cost and start-up and shutdown costs of thermal power units, the start-up and shutdown costs of hydropower units, and the wind power abandonment costs. For the quotation of generators, the operating cost of the generator units is used to approximately replace the electricity quotation. F2 includes the cost of purchasing inertia and primary frequency regulation.

[0129] min F1+F2

[0130]

[0131] F2=C IR P IR +C PFR P PFR

[0132]

[0133]

[0134] Among them, C g,t (P g,t ) is the electricity cost of the thermal power unit, C op,g , C cl,g , C op,h , C cl,hare the startup and shutdown costs of thermal power and hydropower units, respectively, g,t 、v h,t are the operating state variables of thermal power unit g and hydropower unit h at time t, which are 0-1 variables, P g,t is the output of thermal power unit g at time t, P windc,t is the predicted output of the wind turbine, P wind,t is the actual output of the fan at time t, C wc is the wind curtailment cost, C IR is the inertial response cost, P IR is the inertial response output, C PFR is the primary frequency regulation cost, P PFR is the primary frequency modulation output, C g IR , C h IR , C w IR , C f IR , C c IR Quote the inertia resource for each unit, o g,t 、r h,t The state variable that provides a frequency modulation for thermal power unit g and hydropower unit h at time t is a 0-1 variable, C g PFR , C h PFR , C w PFR , C f PFR , C c PFR Provide a quotation for each unit's primary frequency regulation resources, They are the frequency modulation output of each unit at time t.

[0135] Application Examples

[0136] The system of the present invention includes 10 conventional units, including 6 thermal power units, 4 hydropower units, a wind farm, and independent energy storage that only provides frequency regulation services to the system, including flywheel and super electrical energy storage. The parameters of each unit are shown in Table 1-3, and the inertial response of each unit and the price of a 24-hour frequency regulation service are shown in Table 1-3. Figure 2-5 As shown, the units participating in frequency regulation during peak hours will be compensated 20% of the quoted price.

[0137] Table 1 Thermal power unit parameters

[0138]

[0139] Table 2 Hydropower unit parameters

[0140] serial number Maximum power(MW) Minimum power (MW) Inertia time constant (s) 1 220 77 8.9 2 180 65 9.7 3 150 36 9.4 4 100 10 5.6

[0141] Table 3 Energy storage parameters

[0142]

[0143] According to the original performance indicators of inertia and primary frequency regulation reported by the units, a comprehensive evaluation was obtained using the hierarchical analysis method, as shown in Tables 4 and 5. The load and wind power forecast values ​​are shown in Figure 6 As shown, the time division results shown in Table 6 below are obtained according to the predicted values. The system rated frequency is set to 50Hz, the maximum frequency deviation is 0.5Hz, and the frequency change rate is 0.25Hz / s according to the linear relationship between the disturbance size and the minimum inertia set by the present invention. Assuming that the disturbance size at each moment is 10% of the load, in order to ensure that wind power and energy storage participate in primary frequency regulation, 12% and 10% of the rated power are reserved for primary frequency regulation respectively.

[0144] Table 4 Comprehensive evaluation of primary frequency regulation resources

[0145]

[0146] Table 5 Comprehensive evaluation of inertial resources

[0147]

[0148] Table 6 Time-sharing period

[0149] Division Time peak 11:00-15:00, 19:00-21:00 flat 9-10 o'clock, 16-18 o'clock valley 1-8 o'clock, 22-24 o'clock

[0150] In order to analyze the impact of load-side resource participation in frequency regulation and the use of comprehensive response evaluation based on response characteristics and time-sharing incentive strategies on dispatching, three comparative schemes are designed as follows:

[0151] Solution 1: Considering frequency safety constraints, only the inertial resources on the power supply side and the primary frequency regulation resources are involved in frequency regulation.

[0152] Option 2: Based on Option 1, load-side inertia resources and primary frequency regulation resources are added to participate in frequency regulation.

[0153] Plan 3: Based on Plan 2, a comprehensive response evaluation and time-sharing incentive strategy based on response characteristics is adopted.

[0154] When only the power supply side resources participate in frequency regulation and the source-load side resources participate in frequency regulation, the changes in system inertia and unit primary frequency regulation output are as follows: Figure 7As shown. When the system is disturbed, flywheels and supercapacitors are called upon at certain times to meet the frequency regulation requirements of the system, which can effectively alleviate the frequency regulation pressure of wind power and rotating units. At 13:00, the primary frequency regulation output of the rotating units and wind turbines in Scheme 1 is 129.3MW. At 13:00, the load-side resources in Scheme 2 participate in the frequency regulation, and the primary frequency regulation output of the rotating units and wind turbines is reduced to 114.7MW. The addition of load-side resources increases the total inertia of the system and reduces the primary frequency regulation demand. At 13:00, the system inertia of Scheme 1 is 23.7GW·s, and the total primary frequency regulation is 129.3MW; at 13:00, the system inertia of Scheme 2 is 29.3GW·s, and the total primary frequency regulation is 123.7MW. When a high-inertia system is disturbed, the primary frequency regulation demand is reduced compared to a low-inertia system.

[0155] The relationship between the lowest frequency point in each period, the disturbance magnitude of the system and the wind power output of Scheme 1 and Scheme 2 is as follows: Figure 7 As shown, the numbers on the sphere represent the time. In the wind power grid-connected environment, the more wind power output there is, the greater the disturbance it receives, resulting in a greater frequency deviation of the system. As can be seen from Figures (8a) and (8b), wind turbines with inertial response capabilities can provide a certain amount of inertial support, but compared to Scheme 1, Scheme 2 adds a flywheel and supercapacitor with fast response capabilities, and the frequency deviation during disturbance is reduced by about 1%, indicating that multiple resources participating in frequency regulation can effectively improve frequency fluctuations and improve the frequency response capability of the system. At moments of large disturbances and high wind power output, the system's frequency regulation demand increases. Therefore, in order to encourage units to participate in inertia and primary frequency regulation, time-sharing incentives should be adopted.

[0156] In order to meet the frequency safety constraint, from Figure (7b) and Fig. 9 It can be seen that Plan 2 and Plan 3 require greater frequency regulation during peak hours and when the system is subject to greater disturbances. At this time, multiple units with strong inertial support capabilities and strong primary frequency regulation capabilities are required to participate in frequency regulation. Compared with Plan 2, Plan 3 takes into account the response characteristics of resources while meeting the unit constraints, so it will give priority to units with strong frequency regulation capabilities.

[0157] From Table 7, we can see that compared with Scheme 2, Scheme 3 increases the inertia cost of the system by 17%, reduces the primary frequency regulation cost by 38%, and reduces the total cost by 2%. The combined frequency regulation of the inertia resources on both sides of the source and the load and the primary frequency regulation resources can meet the frequency security of the system at a lower cost.

[0158] Table 7 Costs of various schemes

[0159] plan Inertia cost (yuan) Frequency modulation cost (yuan) Other costs (yuan) Total cost (yuan) 2 329491 412683 3521503 4263677 3 386654 254757 3524609 4166020

[0160] The frequency response model of the present invention is used to obtain the value of the lowest frequency point when the system is disturbed. In order to verify the effectiveness of the frequency response model of the present invention, the lowest frequency value of the system after the disturbance is calculated using the traditional first-order equivalent model and the Digsilent Powerfactory simulation software, and compared with the frequency response model of the present invention. The comparison results are shown in Table 8. It can be seen from Table 8 that the value of the lowest frequency point calculated by the algorithm of the present invention is lower than the calculation result of the traditional first-order equivalent model, and is closer to the simulation value.

[0161] Table 8 Results of the lowest frequency obtained by the simplified model and Digsilent Powerfactory simulation

[0162]

Claims

1. An optimization scheduling method for realizing frequency security constraints by considering source-load frequency modulation resources, characterized in that: The method comprises the following steps: 1) According to the response principle of inertial resources on both sides of the source and load, the minimum inertia constraint of the system is established; 2) Establish comprehensive evaluation indicators of inertial resources and primary frequency regulation resources based on the frequency regulation characteristics of each unit in the system; 3) Determine the cost of inertial resources and primary frequency regulation resources respectively based on the quotation and comprehensive evaluation indicators; 4) Considering the relevant factors of the system frequency response characteristics, establish a compensation mechanism for the units participating in frequency regulation during peak hours; 5) According to the frequency dynamic response model including fire-water-wind-storage, the analytical expression of the system frequency response is obtained and linearized to obtain the frequency minimum point constraint; 6) Establish a joint optimization model of source-load inertia resources and primary frequency regulation resources under frequency security constraints, and obtain the optimal solution of the model as a dispatching scheme for day-ahead dispatch of power system unit combinations; In step 1), in order to maintain the system frequency stability, the total inertia of the system must be greater than the minimum inertia required when the system is disturbed, that is, the minimum inertia constraint, then: Among them, H Sy is the total system inertia, RoCoF max is the maximum frequency change rate, ΔP(t) is the power disturbance at time t, and f N is the rated frequency, S Gg , S Hh , S W , S F , S SC are the rated capacities of thermal power units, hydropower units, wind power, flywheel energy storage, and supercapacitor energy storage, respectively. g , H h , H w , H f , H c are the inertia time constants of thermal power units, hydropower units, wind power, flywheel energy storage, and supercapacitor energy storage, respectively, n is the rotor speed of the rotating unit, ω r is the rotor speed of the wind turbine, ω sc ,ω f are the rotation speeds of the supercapacitor and flywheel, respectively; G, H, W, F, and SC are the numbers of thermal power units, hydropower units, wind power, flywheel energy storage, and supercapacitor energy storage, respectively; In the step 2), the weights of the comprehensive evaluation indexes of the inertial resources and the primary frequency modulation resources are determined by using the hierarchical analysis method, and the comprehensive evaluation index values ​​are obtained accordingly, and then: Among them, D1 is the comprehensive evaluation index of the inertial response capability of the unit, D2 is the comprehensive evaluation index of the primary frequency regulation response capability of the unit, and x 11 、x 12 、x 13 are the rated capacity, inertia time constant, and stored kinetic energy of the unit, respectively. 21 、x 22 、x 23 They are the primary frequency regulation dead zone, speed inequality rate, and response lag time of the unit, and W1~W6 are weights; By making a positive adjustment to the comprehensive evaluation index D2, we can obtain: D3=A-(W4x 21 +W5x 22 +W6x 23 ) Where A is a constant; In the step 3), the cost of the inertial resource and the cost of the primary frequency modulation resource are determined according to the quotation and the comprehensive evaluation index. The specific expression is: Among them, C IR is the corresponding cost of inertia, c1 is the quotation of inertia resources, h1 is the service time of inertia resources, C PFR is the cost of a frequency modulation, c2 is the quotation of a frequency modulation resource, and h2 is the service duration of a frequency modulation resource; In the step 4), the large and small sizes of the semi-trapezoidal membership function are used to describe the peak-valley membership, and the time division result is obtained according to the size of the membership function, and the compensation mechanism adopted by the frequency regulation units participating in the peak time is established accordingly, then: Among them, m1 and m2 are peak and valley membership respectively, f(x) is the real-time value on the wind-load curve, and f max 、f min are the maximum and minimum values ​​on the wind-load curve respectively; In the step 5), the analytical expression of the system frequency response is specifically: Among them, ΔP is the power shortage, Δω is the system frequency deviation, ΔP Gg , ΔP Hydro,h , ΔP WT , ΔP F , ΔP SC are the primary frequency modulation outputs of thermal power units, hydropower units, fans, flywheel energy storage and supercapacitor energy storage, respectively. D is the system load active frequency regulation effect coefficient, C is a constant, K g , K h , K w , K f , K c are the mechanical power gain coefficients of thermal power units, hydropower units, fans, flywheels and supercapacitor energy storage, T RH is the reheat turbine time constant, T CH is the volume time constant, T S is the time constant of the oil motor, T G is the time constant of the thermal power unit speed regulator, F HP is the ratio of the steady-state output power of the high-pressure cylinder of the equivalent steam turbine to the total output power of the steam turbine, T w is the time constant of water hammer effect, T p is the time constant of the hydropower unit speed regulator, T y is the soft feedback time constant, D y is the soft feedback link coefficient, T IW , T c , T f are the inertia link time constants of the fan, supercapacitor energy storage and flywheel energy storage, T o , T e , T x is the delay time of the converter; Taylor expansion is used to linearize the analytical expression, and the frequency minimum point constraint is obtained as follows: f N -|Here max |≥49.5 Among them, Δω max is the maximum frequency deviation, f N is the system rated frequency; In the step 6), the objective function expression of the joint optimization model is: minF1+F2 F2=C IR P IR +C PFR P PFR Among them, F1 includes the electricity cost and start-up and shutdown cost of thermal power units, the start-up and shutdown cost of hydropower units and the wind power abandonment cost, F2 includes the purchase inertia and primary frequency regulation cost, C g,t (P g,t ) is the electricity cost of the thermal power unit, C op,g , C cl,g , C op,h , C cl,h are the startup and shutdown costs of thermal power units and hydropower units, respectively, u g,t 、v h,t are the operating state variables of thermal power unit g and hydropower unit h at time t, which are 0-1 variables, P g,t is the output of thermal power unit g at time t, P windc,t is the predicted output of the wind turbine, P wind,t is the actual output of the fan at time t, C wc is the wind curtailment cost, P IR is the inertial response output, P PFR is the primary frequency modulation output, C g IR , C h IR , C w IR , C f IR , C c IR Quote for inertial resources of thermal power units, hydropower units, fans, flywheels and supercapacitors, o g,t 、r h,t The state variable that provides a frequency modulation for thermal power unit g and hydropower unit h at time t is a 0-1 variable, C g PFR , C h PFR , C w PFR , C f PFR , C c PFR Provide quotation for primary frequency regulation resources of thermal power units, hydropower units, fans, flywheels and supercapacitors, are the output of thermal power unit, hydropower unit, fan, flywheel and supercapacitor at time t, respectively, and T is the dispatching period; In the step 6), the constraints of the joint optimization model include frequency safety constraints, unit conventional constraints, unit primary frequency regulation capacity constraints and day-ahead power balance constraints. The frequency safety constraints include frequency minimum point constraints, frequency change rate constraints and minimum inertia constraints. Then: Where, RoCoF(t) is the frequency change rate at time t; The day-ahead power balance constraint is specifically: Among them, P g,t is the output of thermal power unit g at time t, P h,t is the output of hydropower unit h at time t, P wind,t is the actual output of the fan at time t, P load,t is the load output at time t, P t PFR is the primary frequency regulation demand of the system at time t; the conventional constraints of the unit are specifically: Among them, P g,max , P g,min are the maximum and minimum output of thermal power units, R u,g , R d,g is the upward and downward ramp rate of the thermal power unit, MT g,t is the operating time of the thermal power unit, is the minimum start-up time and shutdown time of the thermal power unit, P h,max , P h,min are the maximum and minimum output of the hydropower unit, P h,t is the output of hydropower unit h at time t, q h,max ,q h,min is the maximum and minimum flow of hydropower unit h at time t, q h,t is the flow rate of hydropower unit h at time t, V h,t 、V h,(t+1) is the reservoir capacity of hydropower unit h at time t and t+1, V h,max 、V h,min are the maximum and minimum reservoir capacities of hydropower unit h at time t, W h,(t+1) is the net water volume of reservoir h at time t+1; The primary frequency regulation capacity constraint of the unit is specifically: in, are the maximum output of primary frequency modulation of flywheel and supercapacitor energy storage, respectively. g,t 、r h,t The state variable that provides a frequency modulation for thermal power unit g and hydropower unit h at time t is a 0-1 variable, x i,t is the state of the units participating in primary frequency regulation, μ i,t The unit is in the power-on state. They are the maximum frequency regulation outputs of thermal power unit g and hydropower unit h at time t respectively.

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