A method for optimizing the calculation of compensation capacity of multi-energy frequency division and complementary new energy

Abstract

The present invention relates to the technical field of conventional unit capacity configuration calculation after the access of new energy, specifically a compensation capacity optimization calculation method for multi-energy frequency division and complementary new energy. The method first starts with calculating the power spectrum of the compensation capacity, divides the compensation interval according to the output characteristics of multiple compensation units, and then considers multiple constraints with the goal of economy to introduce the fluctuation penalty coefficient to perform optimization calculation modeling to optimize the boundary frequency and calculate each compensation capacity. The beneficial effect of the present invention is that the results obtained by adopting this method can not only fully tap the ability of various types of units to compensate and suppress the fluctuation of new energy, but also optimize the scheduling economy under the conditions of meeting multiple constraints of the system, and calculate the capacity of each unit on this basis, thereby improving the consumption of new energy.

Description

Technical Field

[0001] The present invention relates to the technical field of conventional unit capacity configuration calculation after new energy is connected, and specifically to a compensation capacity optimization calculation method for multi-energy frequency division and complementary new energy. Background Art

[0002] The dwindling supply of fossil fuels and their associated pollution have led to an urgent need for renewable energy. Clean, environmentally friendly energy sources have long been a focus of attention. However, the integration of large-scale renewable energy into the grid has led to a decline in power system stability, with wind and solar curtailment and power rationing becoming the primary means of improving stability. Due to the uncertain power fluctuations of large-scale, high-proportion renewable energy, one of the key impacts on traditional power systems during grid integration is the difficulty in power dispatching, ultimately leading to widespread wind and solar curtailment and power rationing. The output characteristics of various types of generators vary significantly under different power generation methods, particularly in frequency, even between units of the same generation method. Identifying and leveraging these differences can fully tap the potential of each generator to mitigate renewable energy fluctuations. A multi-energy complementary optimization calculation method based on power spectrum analysis can both divide the output ranges of each generator based on its own characteristics and determine the appropriate unit capacity configuration for each divided range. Frequency differentiation can improve the grid's ability to respond to faults, shorten emergency response times, and effectively mitigate grid fluctuations caused by large-scale photovoltaic and wind power generation, thereby enhancing the absorption of renewable energy. Summary of the Invention

[0003] The purpose of the present invention is to overcome the above-mentioned technical deficiencies and provide a method for optimizing the calculation of the compensation capacity of multi-energy frequency division and complementary new energy. The results obtained by this method can not only fully tap the ability of various types of units to compensate and suppress the fluctuation of new energy, but also optimize the scheduling economy while meeting various constraints of the system, and calculate the capacity of each unit on this basis, thereby improving the consumption of new energy.

[0004] In order to achieve the above object, the specific scheme adopted by the present invention is as follows:

[0005] A method for optimizing the calculation of compensation capacity of multi-energy frequency division complementary new energy sources comprises the following steps:

[0006] 1) For the renewable energy power generation output in the region, calculate the output curve of non-renewable energy units based on the total power generation plan, and use discrete Fourier transform to calculate the compensation power spectrum;

[0007] 2) Divide the compensation intervals of various compensation units according to the types of units that can be dispatched;

[0008] 3) Carry out optimization calculation modeling for each unit;

[0009] 4) Optimize the boundary frequency and calculate the compensation capacity.

[0010] Furthermore, the principle of division in step 2) is to classify units operating in the same frequency range into one category, and the output of the compensation unit is:

[0011] P b =P1+P2+...+P N (1)

[0012] Furthermore, the unit optimization model in step 3) is:

[0013]

[0014] Where L(P) is the output value of the load forecasting model, ΔP d,i and ΔP u,i are the maximum downlink and uplink step lengths of generator i, S(f) is the output curve of the power spectrum model, H(P t,i , P t,j )≤0 are other safety constraints, where:

[0015]

[0016] Furthermore, the optimization calculation of the capacity of each unit in step 3) is based on an economic dispatch model with minimum new energy grid-connected fluctuations, as shown in the following formula:

[0017]

[0018] Where α is the annual depreciation rate of the equipment; N i 、C i are the service life (years) and initial investment cost of each frequency band unit; P t,i is the output power of each unit at time t; K mi , K pi is the maintenance cost and fuel cost per kilowatt-hour of power generated by unit i; ρ is the fluctuation penalty coefficient and is always positive; P t is the total active power generated by the generator set at time t; P t,D is the total load demand at time t for output regulation; P t,C is the transmission power of the interconnection line; η is the network loss rate.

[0019] Furthermore, in step 4), in order to obtain the frequency demarcation point, multiple factors of the unit and the power grid need to be considered. When solving the optimal solution of the model, the following constraints should be considered:

[0020] a. Unit balance constraints

[0021] The basic characteristics of the power system require that the real-time supply and demand balance between the generation side and the load side be maintained during the dispatch process. Therefore, the output of conventional units plus the output of renewable energy should be equal to the power generation plan.

[0022]

[0023] Where, P t,i is the active power generated by generator set i at time t; P t,D is the total load demand at time t for output regulation; P t,C is the transmission power of the tie line;

[0024] b. Upper and lower limit constraints for unit operation

[0025] During the dispatching process, the output of each frequency band unit during operation shall not be less than the base load nor higher than the capacity limit, so:

[0026] P i min ≤P i ≤P i max (6)

[0027] Where, P i min With P i max They are the upper and lower operating boundaries of the unit respectively;

[0028] c. Unit ramp rate constraint

[0029] The key is the ramp rate constraint of the unit, which determines the frequency range of the corresponding unit. A unit with a high frequency, i.e., a fast ramp rate, can theoretically complete the tasks of a unit with a low frequency. However, the general limitation is that the frequency is inversely proportional to the capacity. The ramp rate constraint is described as:

[0030]

[0031] Where, and are the upper and lower limits of the unit output change of unit i within the unit time step respectively;

[0032] d.Boundary frequency constraints

[0033] To ensure that each unit operates within its own frequency band, a boundary frequency constraint is essential. It is a constraint on the range of the compensation interval, specifically described as:

[0034]

[0035] Where, f iis the boundary frequency between unit i and unit i+1, S(f) is the power spectrum function, and T is the sampling time.

[0036] The beneficial effects of the present invention lie in: first, calculating the power spectrum of compensation capacity, dividing the compensation interval according to the output characteristics of various compensating units, and then considering various constraints and introducing a fluctuation penalty coefficient to optimize the calculation model to optimize the cutoff frequency and calculate the compensation capacity. The results obtained by this method not only fully exploit the ability of various types of units to compensate and suppress new energy fluctuations, but also optimize the dispatch economy while meeting various system constraints. Based on this, the capacity of each unit is calculated, thereby improving the absorption of new energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is the compensated power generation power spectrum diagram of the present invention.

[0038] Figure 2 This is the curve of the total cost of the present invention changing with the f1 value.

[0039] Figure 3 This is the curve of the total cost of the present invention changing with the f2 value.

[0040] Figure 4 This is the curve of the total cost of the present invention changing with the ρ value.

[0041] Figure 5 This is a flow chart for calculating the capacity of each frequency division according to the present invention. DETAILED DESCRIPTION

[0042] The structure and beneficial effects of the present invention are further described below with reference to the accompanying drawings.

[0043] As shown in the attached figure, a method for optimizing the calculation of compensation capacity for multi-energy frequency division and complementary new energy is a conventional unit capacity calculation method for joint scheduling with new energy units, calculated from the frequency domain scale. For the renewable energy power generation output in the region, the output curve of non-new energy units is calculated based on the total power generation plan, and the compensation power spectrum is calculated using discrete Fourier transform. Furthermore, the types of units that can be scheduled are divided into unit type 1, unit type 2, ..., unit type N. The principle of division is that units operating within the same frequency range are divided into one category, and the compensation unit output is:

[0044] P b =P1+P2+...+P N (9)

[0045] Multiple compensation intervals are divided according to the upper capacity limit and climbing rate upper limit of each type of unit. Higher frequency band units can also switch unit modes to assist lower frequency band units to achieve interactive coordination.

[0046] Taking the annual operating cost as the objective function, similar units are regarded as a single aggregate unit. By introducing a fluctuation penalty coefficient to ensure that the grid-connected fluctuation after power compensation is within a reliable range, the frequency cutoff point is used as a decision variable and the frequency limit is put into the optimization model as a constraint condition. The frequency cutoff point is optimized with the optimization cost function as the goal to achieve the most economically efficient frequency cutoff point. The optimization model is described in detail as follows:

[0047]

[0048] Where L(P) is the output value of the load forecasting model, ΔP d,i and ΔP u,i are the maximum downlink and uplink step lengths of generator i, S(f) is the output curve of the power spectrum model, H(P t,i , P t,j )≤0 are other safety constraints.

[0049] in:

[0050]

[0051] The optimal calculation of the capacity of each unit is based on the economic dispatch model with the minimum fluctuation of renewable energy grid connection, as shown in the following formula:

[0052]

[0053] Where α is the annual depreciation rate of the equipment; N i 、C i are the service life (years) and initial investment cost of each frequency band unit; P t,i is the output power of each unit at time t; K mi , K pi is the maintenance cost and fuel cost per kilowatt-hour of power generated by unit i; ρ is the fluctuation penalty coefficient and is always positive; P t is the total active power generated by the generator set at time t; P t,D is the total load demand at time t for output regulation; P t,C is the transmission power of the interconnection line; η is the network loss rate.

[0054] In order to obtain the frequency demarcation point, it is necessary to consider various factors of the unit and the power grid. When solving the optimal solution of the model, the following constraints should be considered:

[0055] a. Unit balance constraints

[0056] The basic characteristics of the power system require that the real-time supply and demand balance between the generation side and the load side be maintained during the dispatch process. Therefore, the output of conventional units plus the output of renewable energy should be equal to the power generation plan.

[0057]

[0058] Where, P t,i is the active power generated by generator set i at time t; P t,D is the total load demand at output regulation time t; P t,C is the transmission power of the tie line.

[0059] b. Upper and lower limit constraints for unit operation

[0060] During the dispatching process, the output of each frequency band unit during operation shall not be less than the base load nor higher than the capacity limit, so:

[0061] P i min ≤P i ≤P i max (14)

[0062] Where, P i min With P i max They are the upper and lower operating boundaries of the unit respectively.

[0063] c. Unit ramp rate constraint

[0064] The key is the ramp rate constraint of the unit, which determines the frequency range of the corresponding unit. A unit with a high frequency, i.e., a fast ramp rate, can theoretically complete the tasks of a unit with a low frequency. However, the general limitation is that the frequency is inversely proportional to the capacity. The ramp rate constraint is described as:

[0065]

[0066] Where, and are the upper and lower limits of the unit output change of unit i within a unit time step.

[0067] d.Boundary frequency constraints

[0068] To ensure that each unit operates within its own frequency band, a boundary frequency constraint is essential. It is a constraint on the range of the compensation interval, specifically described as:

[0069]

[0070] Where, f i is the boundary frequency between unit i and unit i+1, S(f) is the power spectrum function, and T is the sampling time.

[0071] The calculated optimal boundary frequencies f1, f2, ..., f of each frequency band are NOn the basis of the power spectrum function, the configuration capacity of the corresponding unit type is obtained through the inverse Fourier transform. This configuration capacity is the most economical capacity configuration scheme under the frequency division scheduling method.

[0072] Example 1

[0073] The compensation units are divided into three categories: unit 1, unit 2, and unit 3. The sampling interval of the analysis data is 5 minutes, the total number of sampling points is 288, the system operating reference frequency is 50Hz, its rated power is 4000MW, the network loss rate η is 5%, and the penalty coefficient ρ is 1.1. The power spectrum density of the compensation power is calculated by discrete Fourier transform (DFT) and its fitting curve is shown as follows: Figure 1 shown.

[0074] Depend on Figure 1 The fitted curve shows a linear relationship between compensation power and frequency, with lower frequencies resulting in higher power ratios. The power spectrum amplitude decreases rapidly at high frequencies due to the motor's inertia acting as a low-pass filter. The essence of using the Fourier transform lies in the choice of coordinate system, without changing the total energy.

[0075] The frequency ranges that divide the three types of machines need to be pre-determined before optimization calculations. The ranges are related to two points: capacity limitation and ramp rate limitation. The details are as follows:

[0076] 1)

[0077] 1.2 Class unit boundary frequency f1 range limit: upper limit f 1max It is the minimum of the upper frequency limit of the Class 1 unit and the frequency corresponding to the maximum installed capacity; the maximum capacity of Class 2 and Class 3 units determines the lower limit of f1. 1min ;

[0078] 2)

[0079] 2.3 Class unit boundary frequency f2 range limit: upper limit f 2min The lower limit f is the minimum of the upper frequency limit of the Class 2 unit and the frequency corresponding to the maximum installed capacity; 2min The maximum configurable capacity of the 3 units will be determined;

[0080] The optimized model parameters are shown in Table 1:

[0081] Table 1 Model parameters

[0082]

[0083] It can be calculated that the boundary frequencies f1 are 0.0024 Hz and f2 are 0.0726 Hz.

[0084] 1) Impact of cutoff frequencies f1 and f2 on total power generation cost

[0085] like Figure 2 、 Figure 3 As shown in the figure, the points (0.0024, 1.0) and (0.0726, 1.0) are the minimum points. The changes in the cutoff frequencies f1 and f2 have a direct impact on the control of the total cost. That is, under the set conditions, the total cost is optimized at 0.0024Hz and 0.0726Hz respectively.

[0086] 2) The impact of penalty coefficient ρ on total power generation cost and system security.

[0087] from Figure 4 It can be seen that changes in the penalty coefficient ρ represent the degree of fluctuation risk that the designer can accept. Increasing ρ increases costs, but also improves system safety and reliability. When the penalty coefficient is too high, the cost increase is more gradual, and even small fluctuations can result in significant cost losses. Furthermore, when ρ exceeds 1.0, the improvement in system reliability is not significant. Therefore, investing in the construction of individual units to reduce fluctuations is a better option.

[0088] The patent calculation flow chart is summarized as follows Figure 5 The specific steps are as follows:

[0089] (1) Calculate the power spectrum of the new energy compensation capacity;

[0090] (2) Divide the compensation intervals of various compensation units;

[0091] (3) Optimize the calculation model of each unit, including various constraints;

[0092] (4) Optimize the boundary frequency and calculate the compensation capacity.

[0093] Compared with the prior art, the present invention has the following advantages:

[0094] 1. Not limited to a specific power generation method, frequency is used as the only distinguishing indicator to analyze the frequency range that needs to be compensated or adjusted, thereby providing targeted scheduling;

[0095] 2. When higher-frequency units have sufficient capacity, they can switch to lower-frequency units when their capacity is insufficient, enabling interactive coordination and improving the grid's ability to respond to faults.

[0096] 3. For the new energy grid connection in the region, it can effectively calculate the optimal configuration of the unit capacity in each frequency band, and improve the economic efficiency on the basis of effectively suppressing the fluctuation of new energy grid connection.

[0097] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for optimizing the calculation of compensation capacity of multi-energy frequency division complementary new energy, characterized in that: The following steps are involved: 1) For the renewable energy power generation output in the region, calculate the output curve of non-renewable energy units based on the total power generation plan, and use discrete Fourier transform to calculate the compensation power spectrum; 2) Divide the compensation intervals of various compensation units according to the types of units that can be dispatched; 3) Carry out optimization calculation modeling for each unit; 4) Optimize the demarcation frequency and calculate the compensation capacity; The unit optimization model in step 3) is: Where L(P) is the output value of the load forecasting model, ΔP d,i and ΔP u,i are the maximum downlink and uplink step lengths of generator i, S(f) is the output curve of the power spectrum model, H(P t,i , P t,j )≤0 are other safety constraints, and are the upper and lower operating boundaries of the unit respectively; P t,i 、P tj is the output power of each unit at time t; in: Where α is the annual depreciation rate of the equipment; N i 、C i are the service life and initial investment cost of each frequency band unit respectively; K mi , K pi is the maintenance cost and fuel cost per kilowatt-hour of power generated by unit i; ρ is the fluctuation penalty coefficient and is always positive; P t is the total active power generated by the generator set at time t; P t,D is the total load demand at output regulation time t; P t,C is the transmission power of the interconnection line; η is the network loss rate. The optimization calculation of the capacity of each unit in step 3) is based on the economic dispatch model with minimum new energy grid-connected fluctuation, as shown in the following formula:

2. The method for optimizing the calculation of compensation capacity of multi-energy frequency division complementary new energy according to claim 1 is characterized by: The principle of division in step 2) is to classify units operating in the same frequency range into one category, and the output of the compensation unit is: P b =P1+P2+…+P N (1)。 3. The method for optimizing the calculation of compensation capacity of multi-energy frequency division complementary new energy according to claim 1 is characterized by: In step 4), in order to obtain the frequency demarcation point, it is necessary to consider various factors of the unit and the power grid. When solving the optimal solution of the model, the following constraints should be considered: a. Unit balance constraints The basic characteristics of the power system require that the real-time supply and demand balance between the generation side and the load side be maintained during the dispatch process. Therefore, the output of conventional units plus the output of renewable energy should be equal to the power generation plan. Where, P t,i is the active power generated by generator set i at time t; P t,D is the total load demand at output regulation time t; P t,C is the transmission power of the tie line; b. Upper and lower limit constraints for unit operation During the dispatching process, the output of each frequency band unit during operation shall not be less than the base load nor higher than the capacity limit, so: Where, and They are the upper and lower operating boundaries of the unit respectively; c. Unit ramp rate constraint The ramp rate constraint of the unit determines the frequency range in which the corresponding unit operates. A unit with a high frequency, i.e., a fast ramp rate, can theoretically complete the tasks of a unit with a low frequency. However, the common limitation is that the frequency is inversely proportional to the capacity. The ramp rate constraint is described as: Where, and are the upper and lower limits of the unit output change of unit i within the unit time step respectively; d.Boundary frequency constraints To ensure that each unit operates within its own frequency band, a boundary frequency constraint is essential. It is a constraint on the range of the compensation interval, specifically described as: Where, f i is the boundary frequency between unit i and unit i+1, S(f) is the power spectrum function, and T is the sampling time.

Images