A method of power transmission of hydro-photovoltaic system based on grid stability

Abstract

The present invention relates to a water-photovoltaic system power transmission method based on power grid stability, and belongs to the technical field of water conservancy and hydropower engineering. From the perspective of ensuring power grid stability, the principle of hydropower consumption and successive compensation of photovoltaics and transmission channels for hydropower compensation is adopted to formulate a hydro-photovoltaic intra-day complementary mechanism. In this process, capacity information is further extracted to guide the hydro-photovoltaic intra-year complementary scheduling. Through example analysis, it is found that the intra-day-annual step-by-step complementary mechanism can effectively improve the power consumption level and power grid stability. The example analysis calculation results are reliable and effective, and have reference and application value for the construction of large-scale clean energy bases.

Description

Technical Field

[0001] The invention relates to a water-photovoltaic system power transmission method based on power grid stability, belonging to the technical field of water conservancy and hydropower engineering. Background Art

[0002] Photovoltaic power, as an important component of renewable energy, will have an adverse impact on the safe and stable operation of the power system if it is directly connected to the grid, and will cause the phenomenon of abandoned photovoltaic power. In 2021, the abandonment rate of photovoltaic power in Tibet exceeded 25%, ranking first in the country. Under this circumstance, it is a key issue in the construction and operation of hydro-photovoltaic complementary power generation bases to establish large-scale hydro-photovoltaic complementary power generation bases, share the "West-to-East Power Transmission" transmission channel, and utilize the capacity and regulation capabilities of hydropower units in cascade reservoirs to smooth the fluctuation of power transmission in the hydro-photovoltaic system, alleviate the operating pressure of the power system, and optimize the power grid's ability to absorb hydro-photovoltaic power.

[0003] The existing intraday complementary methods of hydropower and photovoltaic systems are mostly: only considering electricity consumption or building multi-objective models for optimization calculations. The former is difficult to ensure the stability of the system's power transmission performance and does not take into account the power quality of "west-to-east power transmission". The latter is complex to calculate, especially for large reservoirs with annual regulation capabilities. It is difficult to extend the intraday complementary methods of hydropower and photovoltaic systems to the annual power generation plan arrangement and optimization scheduling process, and it is impossible to give full play to the regulation and storage complementary capabilities of large reservoirs in a complete scheduling cycle. Summary of the invention

[0004] In order to overcome the shortcomings of the prior art, the present invention provides a hydro-photovoltaic system power transmission method based on the stability of the power grid, so as to improve the power consumption efficiency of the hydro-photovoltaic system and ensure the stable performance of the hydro-photovoltaic system power transmission and grid connection.

[0005] The technical solution of the present invention:

[0006] The present invention provides a water-photovoltaic system power transmission method based on grid stability. The water-photovoltaic system is a joint power generation base that bundles the hydropower and photovoltaic power generated by the hydropower station and the photovoltaic power station and transmits them through a common transmission channel. The power transmission method includes the following steps:

[0007] Step A: The intraday power transmission mode of the hydro-photovoltaic system takes the day as the adjustment cycle and the hour as the calculation step length, predicts the photovoltaic 24-hour output process of the day, knows the daily average output of hydropower on the day, knows the upper limit and minimum output constraint of hydropower on the day, knows the maximum capacity of the transmission channel, formulates the intraday complementary mechanism of hydropower and photovoltaic, and obtains the output mode of the hydro-photovoltaic system after intraday complementary;

[0008] Step B: Introduce a mapping function relationship to represent the intraday complementary mechanism between water and photovoltaic, and further extend the intraday complementary mechanism between water and photovoltaic to the annual complementary scheduling process of the water and photovoltaic system. The annual power transmission mode of the water and photovoltaic system takes one year as the scheduling cycle and one month as the scheduling step. Predict the typical 24-hour photovoltaic output process of each month, predict the runoff information of each month, introduce the monthly hydro-photovoltaic power consumption information collected by the intraday complementary mechanism of the water and photovoltaic system, and use a dynamic programming optimization algorithm to perform the annual complementary optimization scheduling calculation of the water and photovoltaic system to obtain the output mode of the water and photovoltaic system after annual complementarity.

[0009] Furthermore, step A is specifically as follows:

[0010] Step A1: Calculate the hydropower and photovoltaic combined output before intraday complementarity by superimposing the daily average hydropower output and the 24-hour photovoltaic output process. The water-photovoltaic system's complementary front-end output mode during the day is obtained, including:

[0011]

[0012] Where N h The average daily output of hydropower The predicted output of photovoltaic power generation in the t period, t=1…T, T=24.

[0013] The amount of power wasted on the day W is obtained by using the intra-day complementary front output method of the hydro-photovoltaic system q , specifically:

[0014]

[0015]

[0016] In the formula, is the abandoned power output of the hydro-solar system in period t, representing the part of the output of the hydro-solar system that exceeds the maximum capacity of the transmission channel, t=1...T, T=24.

[0017] The "hydropower generation W" of the day is calculated by the average daily output of hydropower h ", calculate the photovoltaic power generation W of the day through the photovoltaic 24-hour output process p ”, specifically including:

[0018] W h =N h ·TΔt

[0019]

[0020] Where, T = 24, Δt is the intra-day complementary calculation step.

[0021] Step A2: Adjust the average daily output of hydropower to the lower limit of hydropower output, free up space in the transmission channel to absorb photovoltaic power, and compensate photovoltaic power once to obtain the output mode of the hydro-photovoltaic system after the hydropower is sunk.

[0022] Step A3: Guide the average daily output of hydropower to gradually increase from the lower limit of hydropower output, compensate for the decrease in the average daily output of hydropower through the transmission channel space, and perform secondary compensation for photovoltaic power to obtain the output mode of the hydro-photovoltaic system after the hydropower increases.

[0023] Furthermore, step A2 also includes calculating the maximum photovoltaic output that can be absorbed by the transmission channel in each time period and photovoltaic power consumption W pd , specifically including:

[0024]

[0025]

[0026] In the formula, The photovoltaic power output is predicted for the t period; It is the corrected photovoltaic output in the tth period, which means the maximum photovoltaic output that the transmission channel can absorb in the tth period, t=1…T.

[0027] Furthermore, step A2 also includes a primary compensation output of hydropower to photovoltaic power, wherein the primary compensation output mechanism is a process of reducing the fluctuation amplitude of photovoltaic sawtooth output, specifically including:

[0028]

[0029]

[0030] In the formula, is the PV output sawtooth depth in the t period, ΔS is the PV output sawtooth depth limit; The primary compensation output of hydropower in period t, t = 1...T;

[0031] Further, calculate the water-light superposition output The output mode of the hydropower system after sinking is obtained, including:

[0032]

[0033] In the formula, It is the lower limit of hydropower output; It is the corrected photovoltaic output in period t.

[0034] Furthermore, step A2 also includes the base capacity L of the hydropower c 、F c and capacity adjustment c ;

[0035] The base capacity is the minimum amount of hydropower that needs to be reserved to ensure the normal operation of hydropower and the primary compensation for photovoltaic power; the peak capacity is the maximum compensation amount of hydropower by the transmission channel under the constraints of photovoltaic power correction output and hydropower output; the regulating capacity is the amount of hydropower sinking, which specifically includes:

[0036]

[0037]

[0038]

[0039]

[0040] M c =W h -L c

[0041] In the formula, The upper limit of hydropower output; CT t The maximum output space of water and light in the t period; ST t It is the available space for hydropower output in period t, t=1…T.

[0042] Furthermore, step A2 also includes the hydropower consumption W hd , and get the system power consumption W T And system power loss ΔE, including:

[0043] W hd =min(W h 、F c )

[0044] W T =W hd +W pd

[0045] ΔE=W h +W p -W T

[0046] Where W h is the hydropower generation on that day; F c is the peak volume of the day; W hd W is the amount of electricity consumed by hydropower; pd is the amount of electricity consumed by photovoltaic power; when the peak capacity on that day is less than the hydropower generation, it means that the transmission channel cannot fully accommodate the hydropower generation on that day. The resulting system loss of electricity can be borne by photovoltaic power, hydropower, or hydropower at the same time according to the power transmission rules.

[0047] Furthermore, step A3 also includes introducing a horizontal output boundary Specifically include:

[0048]

[0049] Through the horizontal output boundary Guide the average daily output of hydropower to gradually increase from the lower limit of hydropower output, and provide secondary compensation output for photovoltaic power. The secondary compensation output mechanism is to reduce the overall fluctuation range of photovoltaic output. This process continues until the secondary compensation power of hydropower to photovoltaic power gradually approaches or is equal to the capacity adjustment, and the system power generation boundary is obtained. And secondary compensation output There are two specific situations:

[0050] Case ①: When ΔE>0, N S =N G

[0051] Case ②: When ΔE=0, there exists Make

[0052] In the above two cases, the secondary compensation output The calculations include:

[0053]

[0054]

[0055] In the formula, is the secondary compensation output of hydropower in period t; is the combined output of hydropower sinking and hydro-photovoltaic power in the t period, t=1…T;

[0056] In the above process, ΔE>0 means that the transmission channel can no longer fully accommodate the hydropower generation of the day, and the system power generation boundary is directly raised to the maximum capacity of the transmission channel; ΔE=0 means that the transmission channel can fully accommodate the hydropower generation of the day, and the system power generation boundary needs to be iteratively calculated in combination with the hydropower generation constraint and the maximum capacity constraint of the transmission channel.

[0057] Furthermore, step A3 also includes the following steps: Further obtain hydropower correction output Specifically include:

[0058]

[0059] In the formula, is the corrected hydropower output in period t, t=1…T;

[0060] Calculate the water-light superposition output The output mode of the water-light system after complementation during the day includes:

[0061]

[0062] In the formula, is the corrected hydropower output for period t; It is the corrected photovoltaic output in period t.

[0063] Furthermore, step B is specifically as follows:

[0064] Step B1: According to step A, the intraday complementary mode of the water-light system is obtained, and the mapping function relationship f1 and f2 are introduced to be expressed as:

[0065]

[0066]

[0067] Wherein, f1 represents the functional relationship of obtaining the system power consumption, base capacity and system power loss in the dispatching period through the average hydropower output, the upper limit of hydropower output, the lower limit of hydropower output, the 24-hour output of photovoltaic power and the maximum capacity of the transmission channel in the dispatching period; f2 represents the functional relationship of obtaining the hydropower corrected output and photovoltaic corrected output process in the dispatching period through the average hydropower output, the upper limit of hydropower output, the lower limit of hydropower output, the 24-hour output of photovoltaic power and the maximum capacity of the transmission channel in the dispatching period; t=1…T;

[0068] Step B2: Construct the annual complementary optimization scheduling objective function of the water-solar system, as follows:

[0069]

[0070]

[0071] Where: W is the amount of electricity consumed by the hydro-solar system in a year; The power consumption of the water-solar system in month m; is the system's base content for the mth month; The typical 24-hour photovoltaic output in month m; is the average monthly hydropower output of cascade power stations m; D m is the number of days in the mth month, m = 1...12; M is the number of months in the year, M = 12;

[0072] Construct the annual complementary optimization scheduling constraint function of the water-solar system and use dynamic programming and other optimization algorithms to solve it, including:

[0073]

[0074] Where: is the average output of the ith hydropower station in the mth month, L is the number of hydropower stations in the cascade; Vi,m+1 、V i,m RQ is the water storage capacity of the reservoir at the beginning and end of the mth day of the ith hydropower station; i,m , Q i,m 、qs i,m are the inflow, power generation and abandoned water flow of the i-th hydropower station in the m-th month; QJ i,m is the flow rate from the i-1th power station to the i-th power station; Z i,min , Z i,max are the lowest and highest operating water levels of the i-th hydropower station respectively; Q i,m,min , Q i,m,max are the lower and upper limits of the discharge flow of the i-th hydropower station in period t respectively; They are the minimum and maximum output of the i-th hydropower station in the mth month, m=1…12, i=1…L; is the system's base content for the mth month;

[0075] Step B3: The optimal average hydropower output for each month of the year obtained by solving steps B1 to B2 The hydropower and photovoltaic power transmission processes for each month of the year are further determined as follows:

[0076]

[0077] Where: This is the 24-hour hydropower transmission process in the mth month; The process of 24-hour photovoltaic power transmission in the mth month; The typical 24-hour photovoltaic output in month m; is the lower limit of hydropower output in month m; is the upper limit of hydropower output in month m; is the optimal average hydropower output of the cascade power station in month m; m = 1…12, t = 1…T.

[0078] Beneficial Effects

[0079] From the perspective of ensuring the stability of the power grid, the present invention adopts the principle of hydropower consumption and successive compensation of photovoltaic power, and the transmission channel compensates for hydropower to formulate a hydro-photovoltaic intra-day complementary mechanism. In the process, capacity information is further extracted to guide the hydro-photovoltaic intra-annual complementary scheduling. Through example analysis, it is found that the intra-day-annual step-by-step complementary mechanism can effectively improve the power consumption level and the stability of the power grid. The example analysis calculation results are reliable and effective, and have reference and application value for the construction of large-scale clean energy bases. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] Figure 1 It is the complementary front output mode of the water-light system during the day;

[0081] Figure 2 It is the way of outputting power after the hydropower of the water-light system sinks;

[0082] Figure 3 It is a schematic diagram of the hydropower compensation mechanism of the hydro-photovoltaic system;

[0083] Figure 4 It is the output mode after the water-light system complements each other during the day;

[0084] Figure 5 It is the output mode after the complementary and optimized scheduling of the hydropower and solar power systems within the year. DETAILED DESCRIPTION

[0085] The present application will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It should also be noted that, for ease of description, only the parts related to the relevant invention are shown in the accompanying drawings.

[0086] It should be noted that, in the absence of conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0087] Example

[0088] The scenario of a hydropower and photovoltaic energy base is analyzed, in which the hydropower installed capacity is 862WKW, the photovoltaic installed capacity is 500WKW, and the maximum capacity of the transmission channel is 1000WKW (the photovoltaic installed capacity and the transmission channel capacity are determined according to various installation selection methods in the engineering design process). The cascade hydropower system as a regulating medium consists of 6 reservoirs. The specific parameters are shown in Table 1:

[0089] Table 1 Scale parameters of cascade hydropower stations

[0090]

[0091] The hydropower and photovoltaic system is a joint power generation base that bundles the hydropower and photovoltaic power generated by the hydropower station and the photovoltaic power station and transmits them through a common transmission channel. The power transmission method includes the following steps:

[0092] 1. Daily complementary power transmission mode of water-solar system

[0093] The intraday power transmission mode of the hydro-photovoltaic system uses the day as the regulation cycle and the hour as the calculation step length to predict the 24-hour photovoltaic output of the day. The average daily hydropower output N is known. h , the upper limit of hydropower output for the day is known and hydropower output limit The maximum capacity of the transmission channel N is known. G , see the data in columns 2 to 6 of Table 2, and carry out complementary regulation of the water-light system during the day, specifically including:

[0094] like Figure 1 As shown in the figure, the average daily output of hydropower and the 24-hour output of photovoltaic power are superimposed to calculate the hydropower superposition output before intraday complementarity. The water-photovoltaic system's complementary front-end output mode during the day is obtained, including:

[0095]

[0096] Where N h The average daily output of hydropower The predicted output of photovoltaic power generation in the t period, t=1...T, T=24; the water-solar superposition output of the embodiment is shown in the example data in the 7th column of Table 2, and the total output is 20634WKW. The abandoned power of the day is obtained by the complementary front output of the water-solar system within the day, which is specifically:

[0097]

[0098]

[0099] In the formula, is the abandoned power output of the hydro-solar system in the t period, representing the output part of the hydro-solar superposition output exceeding the maximum capacity of the transmission channel, t=1...T, T=24; see the example data in the 7th column of Table 2 for the embodiment. It can be seen that the hydro-solar superposition output exceeded the maximum capacity of the transmission channel by 1000WKW from 9 to 15h on that day, resulting in abandoned power, totaling 1449WKW·h.

[0100] Furthermore, the “hydropower generation W” of the day is calculated by the average daily output of hydropower. h ", calculate the photovoltaic power generation W of the day through the photovoltaic 24-hour output process p ”, specifically including:

[0101] W h =N h ·TΔt

[0102]

[0103] Wherein, T=24, Δt is the intra-day complementary calculation step length; the hydropower generation of the embodiment is shown in the sum of the example data in the third column of Table 2, which is 15600WKW·h; the photovoltaic power generation of the embodiment W p See the sum of the sample data in the second column of Table 2, which is 5034 WKW·h.

[0104] like Figure 2 As shown in the figure, the average daily output of hydropower is adjusted to the lower limit of hydropower output, freeing up space for transmission channels to absorb photovoltaic power. The maximum photovoltaic output that can be absorbed by the transmission channel in each period is and photovoltaic power consumption W pd, specifically including:

[0105]

[0106]

[0107] In the formula, is the photovoltaic output in period t; It is the corrected photovoltaic output in the t-th period, which means the maximum photovoltaic output that can be absorbed by the transmission channel in the t-th period, t=1...T; the corrected photovoltaic output of the embodiment is shown in the example data in the 8th column of Table 2, and the photovoltaic power consumption is shown in the sum of the example data in the 8th column of Table 2, which is 5034WKW·h.

[0108] like Figures 2 to 3 As shown in the figure, when the average daily output of hydropower drops to the lower limit of hydropower output, hydropower implements a one-time compensation output for photovoltaic power. The one-time compensation output mechanism is to reduce the amplitude of the sawtooth output fluctuation of photovoltaic power, which specifically includes:

[0109]

[0110]

[0111] Where ΔS is the PV output sawtooth depth limit. If the PV output exceeds this limit at some time during the correction process, hydropower primary compensation output is required. is the PV output sawtooth depth in period t, It is the hydropower primary compensation output in the t period; t=1...T; the example data in the 9th column of the primary compensation output table 2 of the embodiment, in which primary compensation was carried out in the 9th and 13th periods, the fluctuation amplitude of the photovoltaic sawtooth output was significantly reduced.

[0112] According to the above process, the water-light superposition output of the water-light system after the hydropower sinks is calculated The output mode of the hydropower system after sinking is obtained, including:

[0113]

[0114] In the formula, It is the lower limit of hydropower output; It is the corrected photovoltaic output in the t period; the example data in the 10th column of Table 2 of the hydro-photovoltaic superimposed output after the hydropower of the hydro-photovoltaic system in the embodiment is sunk.

[0115] like Figure 2 As shown in the figure, when the average daily output of hydropower drops to the lower limit of hydropower output, the base capacity of hydropower L c 、F c and capacity adjustment c; Base capacity is the minimum amount of hydropower that needs to be reserved to ensure the normal operation of hydropower and the primary compensation for photovoltaic power; Peak capacity is the maximum compensation amount of hydropower by the transmission channel under the constraints of photovoltaic power correction output and hydropower output; Adjustment capacity is the amount of hydropower sinking, which specifically includes:

[0116]

[0117]

[0118]

[0119]

[0120] M c =W h -L c

[0121] In the formula, The upper limit of hydropower output; CT t is the maximum output space of water and light in the t period, indicating that the superimposed output of water and light is limited by the maximum capacity of the transmission channel; ST t It is the hydropower output space that can be increased in the t period, t=1...T; the base capacity, peak capacity and regulating capacity of the embodiment are shown in the 9th to 11th columns of example data in Table 2, and the maximum output space of hydro-photovoltaic power and the hydropower output space that can be increased are shown in the 11th to 12th columns of example data in Table 2.

[0122] This process can further calculate the hydropower consumption W hd , and get the system power consumption W T And system power loss ΔE, including:

[0123] W hd =min(W h 、F c )

[0124] W T =W hd +W pd

[0125] ΔE=W h +W p -W T

[0126] In the formula, if the peak capacity on that day is less than the hydropower generation, it means that the transmission channel cannot fully accommodate the hydropower generation on that day. The system loss of electricity generated can be borne by photovoltaic, hydropower, or hydropower at the same time according to the power transmission rules; the hydropower consumption in the embodiment is 15600WKW·h, which is consistent with the hydropower generation, indicating that it can be fully absorbed. The system consumption is 20634WKW·h, and the system loss is 0WKW·h. It can be seen that the example data in the 12th to 14th columns of Table 2.

[0127] like Figure 3 As shown, through the horizontal output boundary Guide the average daily output of hydropower to gradually increase from the lower limit of hydropower output, and provide secondary compensation output for photovoltaic power. The secondary compensation output mechanism is to reduce the overall fluctuation range of photovoltaic output. This process continues until the secondary compensation power of hydropower to photovoltaic power gradually approaches or is equal to the capacity adjustment, and the system power generation boundary is obtained. And secondary compensation output There are two specific situations:

[0128] Case ①: When ΔE>0, N S =N G

[0129] Case ②: When ΔE=0, there exists Make

[0130] in, is the horizontal output boundary, t=1……T;

[0131] In the above two cases, the secondary compensation output The calculations include:

[0132]

[0133]

[0134] In the formula, is the combined output of hydropower and photovoltaic power in the t period, t=1…T; in this process, ΔE>0 indicates that the transmission channel can no longer fully accommodate the hydropower and photovoltaic power generation of the day, and the system power generation boundary is directly raised to the maximum capacity of the transmission channel; ΔE=0 indicates that the transmission channel can fully accommodate the hydropower and photovoltaic power generation of the day, and the system power generation boundary needs to be iteratively calculated in combination with the hydropower and photovoltaic power generation constraints and the maximum capacity constraints of the transmission channel; the power loss of the system in the embodiment is 0WKW·h, which belongs to the second case. After iterative calculation, the system power generation boundary and secondary compensation output are obtained, as can be seen from the example data in the 13th to 14th columns of Table 2.

[0135] like Figure 4 As shown, through the secondary compensation output Further obtain hydropower correction output Specifically include:

[0136]

[0137] In the formula, is the corrected hydropower output in the tth period, t=1...T; the corrected hydropower output of the embodiment is shown in the 15th column of the example data in Table 2.

[0138] Further, calculate the water-light superposition output The output mode of the water-light system after complementation during the day includes:

[0139]

[0140] In the formula, is the corrected hydropower output for period t; is the corrected photovoltaic output in the t period; the water-photovoltaic superposition output after intraday complementarity of the water-photovoltaic system in the embodiment is shown in the example data in the 16th column of Table 2.

[0141] Through the intraday complementary process of the hydropower and photovoltaic systems, on the one hand, the amount of electricity absorbed by the hydropower and photovoltaic systems is improved, while at the same time avoiding the phenomenon of water or light abandonment due to power abandonment; on the other hand, hydropower is used to compensate photovoltaic power once to smooth the random fluctuation amplitude of photovoltaic power, and hydropower is used to compensate photovoltaic power twice to smooth the overall fluctuation amplitude of photovoltaic power, effectively ensuring the stability of the power grid.

[0142] Table 2 Calculation process of the water-light system intraday complementarity example

[0143]

[0144] 2. Complementary scheduling of water and solar systems within a year

[0145] According to the intraday complementary process of the water-light system, the mapping function relationship f1 and f2 are introduced as follows:

[0146]

[0147]

[0148] Wherein, f1 represents the functional relationship of obtaining the system power consumption, base capacity and system power loss in the dispatching period through the average hydropower output, the upper limit of hydropower output, the lower limit of hydropower output, the 24-hour output of photovoltaic power and the maximum capacity of the transmission channel in the dispatching period; f2 represents the functional relationship of obtaining the hydropower corrected output and photovoltaic corrected output process in the dispatching period through the average hydropower output, the upper limit of hydropower output, the lower limit of hydropower output, the 24-hour output of photovoltaic power and the maximum capacity of the transmission channel in the dispatching period; t=1…T;

[0149] Step B2: Construct the annual complementary optimization scheduling objective function of the water-solar system, as follows:

[0150]

[0151]

[0152] Where: W is the amount of electricity consumed by the hydro-solar system in a year; The power consumption of the water-solar system in month m; is the system's base content for the mth month; The typical 24-hour photovoltaic output in month m; is the average monthly hydropower output of cascade power stations m; D m is the number of days in the mth month, m=1...12; M is the number of months in the year, M=12.

[0153] Construct the annual complementary optimization scheduling constraint function of the water-solar system and use dynamic programming and other optimization algorithms to solve it, including:

[0154]

[0155] Where: is the average output of the ith hydropower station in the mth month, L is the number of hydropower stations in the cascade; V i,m+1 、V i,m RQ is the water storage capacity of the reservoir at the beginning and end of the mth day of the ith hydropower station; i,m , Q i,m 、qs i,m are the inflow, power generation and abandoned water flow of the i-th hydropower station in the m-th month; QJ i,m is the flow rate from the i-1th power station to the i-th power station; Z i,min , Z i,max are the lowest and highest operating water levels of the i-th hydropower station respectively; Q i,m,min , Q i,m,max are the lower and upper limits of the discharge flow of the i-th hydropower station in period t respectively; are the minimum and maximum output of the i-th hydropower station in the mth month, i=1…L; is the base capacity of the system in the mth month. Because the sawtooth output generated by photovoltaic output has a greater impact on the operation of the power system, the hydropower generation on that day needs to further meet the restriction requirements on the base capacity.

[0156] Step B3: The optimal average hydropower output for each month of the year obtained by solving steps B1 to B2 The hydropower and photovoltaic power transmission processes for each month of the year are further determined as follows:

[0157]

[0158] Where: This is the 24-hour hydropower transmission process in the mth month; The process of 24-hour photovoltaic power transmission in the mth month; The typical 24-hour photovoltaic output in month m; is the lower limit of hydropower output in month m; is the upper limit of hydropower output in month m; is the optimal average hydropower output of the cascade power station in month m; m = 1…12, t = 1…T; They all show the 24-hour hydro-solar power transmission process in each month, which retains the impact of the volatility of photovoltaic output on hydropower output during the day and can be used as the typical power transmission process in each month.

[0159] like Figure 5 As shown, according to the objective function and the constraint function, this embodiment adopts dynamic programming for calculation. It can be seen from the calculation results that there is no system power loss in each month, which ensures the power consumption level of the hydropower system; at the same time, the adjusted hydropower superimposed output in each month effectively smoothes the volatility of photovoltaic output. The smoothing effect in June and May is limited because the reservoir is at a low water level in June and May, the upper limit of hydropower output is limited, and the adjustment space of hydropower output is limited. In subsequent months, as the water level increases, the reservoir capacity regulation capacity increases, which can effectively enhance the system power transmission and grid connection quality and grid stability efficiency.

[0160] Through the step-by-step complementarity of water and solar power within the day and year, the photovoltaic absorption effect of large reservoirs in the long-term scheduling process can be effectively improved. On the one hand, the overall hydropower and photovoltaic power efficiency can be improved, and on the other hand, the power transmission stability of the hydropower system within each scheduling cycle can be taken into account.

[0161] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the embodiments of the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method of transmitting electricity through a hydro-photovoltaic system based on grid stability, characterized in that: The hydro-photovoltaic system is a combined power generation base that bundles the hydropower and photovoltaic power generated by the hydropower station and the photovoltaic power station and connects them to the grid, and transmits them through a common transmission channel. The power transmission method includes the following steps: Step A: The intraday power transmission mode of the hydro-photovoltaic system takes the day as the adjustment cycle and the hour as the calculation step length, predicts the photovoltaic 24-hour output process of the day, knows the daily average output of hydropower on the day, knows the upper limit and minimum output constraint of hydropower on the day, knows the maximum capacity of the transmission channel, formulates the intraday complementary mechanism of hydropower and photovoltaic, and obtains the output mode of the hydro-photovoltaic system after intraday complementary; Step A is specifically as follows: Step A1: Calculate the hydropower and photovoltaic combined output before intraday complementarity by superimposing the daily average hydropower output and the 24-hour photovoltaic output process. The water-photovoltaic system's complementary front-end output mode during the day is obtained, including: Where N h The average daily output of hydropower The predicted output of photovoltaic power generation in the t period, t = 1...T, T = 24; The amount of power wasted on the day W is obtained by using the intra-day complementary front output method of the hydro-photovoltaic system q , specifically: In the formula, is the abandoned power output of the hydro-solar system in period t, representing the output of the hydro-solar system that exceeds the maximum capacity of the transmission channel, t = 1...T, T = 24; N G For power transmission channels; The hydropower generation W of the day is calculated by the average daily output of hydropower h ", calculate the photovoltaic power generation W of the day through the photovoltaic 24-hour output process p ”, specifically including: W h =N h ·TΔt Where, T = 24, Δt is the intraday complementary calculation step length; Step A2: Adjust the average daily output of hydropower to the lower limit of hydropower output, free up space in the transmission channel to absorb photovoltaic power, and compensate photovoltaic power once to obtain the output mode of the hydro-photovoltaic system after the hydropower is sunk; Step A3: guide the average daily output of hydropower to gradually increase from the lower limit of hydropower output, compensate the amount of hydropower that decreases in the average daily output of hydropower through the transmission channel space, and perform secondary compensation on photovoltaic power to obtain the output mode of the hydro-photovoltaic system after the hydropower increases; Step B: Introduce a mapping function relationship to represent the intraday complementary mechanism of water and photovoltaic, further extend the intraday complementary mechanism of water and photovoltaic to the annual complementary scheduling process of the water and photovoltaic system, the annual power transmission mode of the water and photovoltaic system takes one year as the scheduling cycle and one month as the scheduling step, predict the typical 24-hour photovoltaic output process of each month, predict the runoff information of each month, introduce the monthly hydro-photovoltaic power consumption information collected by the intraday complementary mechanism of the water and photovoltaic system, use the dynamic programming optimization algorithm to perform the annual complementary optimization scheduling calculation of the water and photovoltaic system, and obtain the output mode of the water and photovoltaic system after annual complementarity; Step B is specifically as follows: Step B1: According to step A, the intraday complementary mode of the water-light system is obtained, and the mapping function relationship f1 and f2 are introduced to be expressed as: Wherein, f1 represents the functional relationship of obtaining the system power consumption, base capacity and system power loss in the dispatching period through the average hydropower output, the upper limit of hydropower output, the lower limit of hydropower output, the 24-hour output of photovoltaic power and the maximum capacity of the transmission channel in the dispatching period; f2 represents the functional relationship of obtaining the hydropower corrected output and photovoltaic corrected output process in the dispatching period through the average hydropower output, the upper limit of hydropower output, the lower limit of hydropower output, the 24-hour output of photovoltaic power and the maximum capacity of the transmission channel in the dispatching period; t=1…T; Step B2: Construct the annual complementary optimization scheduling objective function of the water-solar system, as follows: Where: W is the amount of electricity consumed by the hydro-solar system in a year; The power consumption of the water-solar system in month m; is the system's base content for the mth month; The typical 24-hour photovoltaic output in month m; is the average monthly hydropower output of cascade power stations m; D m is the number of days in the mth month, m = 1...12; M is the number of months in the year, M = 12; Construct the annual complementary optimization scheduling constraint function of the water-solar system and use dynamic programming and other optimization algorithms to solve it, including: Where: is the average output of the ith hydropower station in the mth month, L is the number of hydropower stations in the cascade; V i,m+1 、V i,m RQ is the water storage capacity of the reservoir at the beginning and end of the mth day of the ith hydropower station; i,m , Q i,m 、qs i,m are the inflow, power generation and abandoned water flow of the i-th hydropower station in the m-th month; QJ i,m is the flow rate from the i-1th power station to the i-th power station; Z i,min , Z i,max are the lowest and highest operating water levels of the i-th hydropower station respectively; Q i,m,min , Q i,m,max are the lower and upper limits of the discharge flow of the i-th hydropower station in period t respectively; They are the minimum and maximum output of the i-th hydropower station in the mth month, m=1…12, i=1…L; is the system's base content for the mth month; Step B3: The optimal average hydropower output for each month of the year obtained by solving steps B1 to B2 The hydropower and photovoltaic power transmission processes for each month of the year are further determined as follows: Where: This is the 24-hour hydropower transmission process in the mth month; The process of 24-hour photovoltaic power transmission in the mth month; The typical 24-hour photovoltaic output in month m; is the lower limit of hydropower output in month m; is the upper limit of hydropower output in month m; is the optimal average hydropower output of the cascade power station in month m; m = 1…12, t = 1…T.

2. According to claim 1, a water-solar system power transmission method based on grid stability is characterized in that: Step A2 also includes calculating the maximum photovoltaic output that can be absorbed by the transmission channel in each period and photovoltaic power consumption W pd , specifically including: In the formula, The photovoltaic power output is predicted for the t period; It is the corrected photovoltaic output in the t period, which means the maximum photovoltaic output absorbed by the transmission channel in the t period, t=1…T.

3. According to claim 2, a water-solar system power transmission method based on grid stability is characterized in that: Step A2 also includes a primary compensation output of hydropower to photovoltaic power. The primary compensation output mechanism is a process of reducing the amplitude of the photovoltaic sawtooth output fluctuation, which specifically includes: In the formula, is the PV output sawtooth depth in the t period, ΔS is the PV output sawtooth depth limit; The primary compensation output of hydropower in period t, t = 1...T; Further, calculate the water-light superposition output The output mode of the hydropower system after sinking is obtained, including: In the formula, It is the lower limit of hydropower output; It is the corrected photovoltaic output in period t.

4. According to claim 3, a water-solar system power transmission method based on grid stability is characterized in that: Step A2 also includes the base capacity L of the hydropower c 、F c and capacity adjustment M c ; The base capacity is the minimum amount of hydropower that needs to be reserved to ensure the normal operation of hydropower and the primary compensation for photovoltaic power; the peak capacity is the maximum compensation amount of hydropower by the transmission channel under the constraints of photovoltaic corrected output and hydropower output; The capacity adjustment is the amount of hydropower sinking, which specifically includes: M c =W h -L c In the formula, It is the upper limit of hydropower output; CT t The maximum output space of water and light in the t period; ST t It is the available space for hydropower output in period t, t=1…T.

5. According to claim 4, a water-solar system power transmission method based on grid stability is characterized in that: Step A2 also includes the hydropower consumption W hd , and get the system power consumption W T And system power loss ΔE, including: IN hd =min(W h 、F c ) IN T =In hd +W pd ΔE=W h +W p -W T Where W h is the hydropower generation on that day; F c is the peak volume of the day; W hd W is the amount of electricity consumed by hydropower; pd is the amount of electricity consumed by photovoltaic power; when the peak capacity on that day is less than the hydropower generation, it means that the transmission channel cannot fully accommodate the hydropower generation on that day. The resulting system loss of electricity can be borne by photovoltaic power, hydropower, or hydropower at the same time according to the power transmission rules.

6. A method of transmitting electricity through a hydro-photovoltaic system based on grid stability according to claim 5, characterized in that: Step A3 also includes introducing a horizontal output boundary Specifically include: Through the horizontal output boundary Guide the average daily output of hydropower to gradually increase from the lower limit of hydropower output, and provide secondary compensation output for photovoltaic power. The secondary compensation output mechanism is to reduce the overall fluctuation range of photovoltaic output. This process continues until the secondary compensation power of hydropower to photovoltaic power gradually approaches or is equal to the capacity adjustment, and the system power generation boundary is obtained. And secondary compensation output There are two specific situations: Case ①: When ΔE>0, N S =N G Case ②: When ΔE=0, there exists Make In the above two cases, the secondary compensation output The calculations include: In the formula, is the secondary compensation output of hydropower in period t; is the combined output of hydropower sinking and hydro-photovoltaic power in the t period, t=1…T; In the above process, ΔE>0 means that the transmission channel can no longer fully accommodate the hydropower generation of the day, and the system power generation boundary is directly raised to the maximum capacity of the transmission channel; ΔE=0 means that the transmission channel fully accommodates the hydropower generation of the day, and the system power generation boundary needs to be iteratively calculated in combination with the hydropower generation constraint and the transmission channel maximum capacity constraint.

7. A method of transmitting electricity through a hydro-photovoltaic system based on grid stability according to claim 6, characterized in that: Step A3 also includes the secondary compensation output Further obtain hydropower correction output Specifically include: In the formula, is the corrected hydropower output in period t, t=1…T; Calculate the water-light superposition output The output mode of the water-light system after complementation during the day includes: In the formula, is the corrected hydropower output for period t; It is the corrected photovoltaic output in period t.

Images