A method for solving the water storage and discharge sequence of parallel hydropower stations considering water abandonment risk

Abstract

The present invention belongs to the field of hydropower dispatching, and discloses a method for solving the water storage and discharge order of parallel hydropower stations considering the risk of water abandonment. First, the target period for solving the water storage and discharge order is determined on a daily scale, and the relevant initial conditions of the power station are input; then, the abandoned water power and non-storage loss index values ​​of each hydropower station in the parallel system are calculated according to the initial water level, forecast water inflow data, historical power generation flow data and power grid load data of the target period, and the storage and discharge order is sorted in real time with the minimum abandoned water power as the main goal and the minimum non-storage loss as the secondary goal; finally, the sorting result is used to distribute the system load in this period, and the daily load distribution process of the hydropower system is obtained.

Description

Technical Field

[0001] The present invention belongs to the field of hydropower dispatching, and relates to a method for solving the water storage and discharge sequence of parallel hydropower stations considering the risk of water abandonment. When there is a need to adjust the load of the power grid, the method solves the real-time optimal water storage and discharge sequence of the hydropower station group based on the characteristics of hydropower stations with abundant water supply and limited regulation capacity, which have a prominent risk of water abandonment, and considers the factors of water abandonment and non-energy storage loss. Background Art

[0002] The joint dispatching and operation of a group of hydropower stations needs to rely on reasonable dispatching rules. Among them, the order of water storage and release, as a summary of the dispatching rules, is related to the coordination between the hydropower stations and affects the overall operation of the entire hydropower system. For areas with high pressure of water abandonment, the risk of water abandonment should be paid attention to when studying the order of water storage and release. This is because there are two common characteristics in these areas: one is that the water inflow is abundant, especially the concentrated water inflow during the flood season, coupled with the uncertainty of runoff, which makes hydropower stations prone to greater water abandonment risks during the flood season; the other is that the regulation performance of hydropower stations is weak. When facing concentrated water inflow, it may be difficult to absorb this part of hydropower due to insufficient reservoir regulation capacity, thus generating water abandonment risks. Therefore, how to master a reasonable order of water storage and release on the basis of reducing water abandonment and ensuring flood control safety in the reservoir area is one of the key issues to promote short-term orderly dispatching in areas with large water inflow and weak regulation performance of power stations.

[0003] At present, the solution methods for the water storage and release sequence of a group of reservoirs mainly consider power generation and energy storage, and few of them provide appropriate solution strategies based on the risk of water abandonment. In terms of solution methods and results, the results obtained are mostly qualitative analyses of the general laws of water storage and release of a group of reservoirs. It is difficult to quantitatively determine the real-time storage and release sequence and load distribution, which is insufficient to provide sufficient guidance for real-time scheduling. Summary of the invention

[0004] In view of the above problems, the present invention proposes a method for sorting the order of water storage and discharge with the goal of minimizing the amount of abandoned water and minimizing the loss of non-storage energy for a parallel reservoir group with regulating capabilities. The method uses a day as the calculation scale, and by inputting the initial water level of each hydropower station in the parallel system in the current period, the forecast water inflow data and the total load demand of the system, the order of water storage and discharge and the load distribution results of each hydropower station in the parallel hydropower system in the next period (one day) starting from the current period can be obtained.

[0005] The technical solution of the present invention:

[0006] A method for solving the water storage and discharge sequence of parallel hydropower stations considering the risk of water abandonment, the method mainly includes four parts: a method for calculating the amount of abandoned water, a method for calculating the loss of non-storage, a method for sorting the water storage and discharge sequence, and a method for applying the water storage and discharge sequence, and specifically includes the following steps (the following steps and formulas are applicable to any power station in the parallel system, so the power station number is not distinguished in the formula):

[0007] Step (1) Calculation of abandoned hydropower. In order to balance the goals of reducing abandoned hydropower and improving power generation efficiency, the maximum abandoned hydropower situation that may occur in the next M days starting from the current period is considered. In principle, power stations with large abandoned hydropower within the forecast period of M days are given priority to increase output and reduce abandoned hydropower, while other hydropower stations are given priority to store water.

[0008] Step 1.1 According to the current water level, the power generation capacity of the hydropower station and related constraints, the maximum water storage capacity of each hydropower station in the current period (day 1) is determined by taking the boundary conditions from the water balance equation. The calculation formula is as follows:

[0009] V in,max =V max +V out,max -V start (1)

[0010] Where V in,max V is the maximum total inflow, that is, the maximum amount of water that can be stored without water abandonment; max is the upper limit of storage capacity; V out,max is the maximum total outflow of water; V start is the water storage at the beginning of the period.

[0011] According to formula (1), the maximum amount of water that can be stored in the current period can be obtained. out,max The total amount of water generated during the current period when the hydropower station is at full capacity.

[0012] Step 1.2 Determine the maximum amount of water and electricity that may be abandoned in the current period (Day 1). Calculate the total amount of water entering the reservoir in the current period based on the forecast water inflow data and compare it with the maximum amount of water that can be stored. If the total amount of water entering the reservoir is greater than the maximum amount of water that can be stored, water will be abandoned in the current period. The amount of water abandoned in the hydropower station in the current period is calculated using the following formula.

[0013]

[0014] Where V spill V is the amount of discarded water; in To forecast the total amount of water.

[0015] If the abandoned water volume calculated by formula (2) is used for power generation, the abandoned water volume that can be generated by the abandoned water volume in the current period can be obtained. The calculation formula is as follows:

[0016] Espill =AHV spill (3)

[0017] In the formula, E spill is the amount of abandoned hydropower; A is the output coefficient; H is the generating head in the current period.

[0018] Step 1.3 Calculate the total amount of abandoned water in the forecast period M days. If water was abandoned in the previous period, the initial water storage capacity V in this period is start is the storage capacity corresponding to the upper limit of the water level of the hydropower station; if there is no water abandonment in the previous period, the initial water storage capacity of this period is calculated by adding the initial water storage capacity of the previous period to the forecast water inflow of the previous period, minus the maximum total outflow of the previous period, that is, the total power generation water of the power station at full power. Repeat Step 1.1 and 1.2 to calculate the daily water abandonment and abandoned water power within the forecast period M days, and sum them up to get the total abandoned water power.

[0019] For all power stations in the parallel system, the corresponding abandoned hydropower index values ​​are calculated according to step (1).

[0020] Step (2) Calculation of non-storage loss. When a hydropower station increases its output, it will lose a portion of the generating head. The impact of this portion of generating head on the power generation efficiency in the subsequent period is called non-storage loss. In principle, the power stations with small non-storage loss are given priority to increase their output, and the hydropower stations with large non-storage loss are given priority to store water.

[0021] Step 2.1 Calculate the water level change of the hydropower station after increasing the unit output in the current period, and obtain the change in the generating head Δz that affects the power generation. The calculation formula is as follows:

[0022]

[0023] Wherein, Δp is the output change of the hydropower station in the current period; Δq is the change in the power generation flow of the hydropower station under the output change Δp; A is the output coefficient; H is the power generation head in the current period; V and V′ are the reservoir capacity at the end of the current period before and after the output change, respectively; Δz is the head change value after the output change in the current period; f(*) is the water level storage capacity function relationship.

[0024] Step 2.2 Calculate the power generation loss value caused by the change in water head, that is, the loss without energy storage. This indicator value (loss without energy storage) represents the power generation loss value caused by the loss of power generation head in the subsequent period starting from the current period. The subsequent impact period of water head change on power generation is calculated until the reservoir is full to the highest water level or emptied to the lowest water level. The calculation formula is as follows:

[0025] ΔE=AΔzW (5)

[0026] In the formula, ΔE is the non-storage energy loss value caused by increasing the output in the current period; W is the total water volume for power generation in the subsequent period. Q n is the average value of the power generation flow in the n period, t is the number of the current period, and T is the maximum value of the period number that increases or decreases the output on the subsequent power generation, which is determined by the supply and demand status of the reservoir.

[0027] In formula (5), the total amount of water for power generation W is obtained from the historical power generation flow data. The specific method is: starting from the period of each year in the historical data, calculate the total amount of water consumed for power generation when the water level reaches the highest or lowest period, and take the average value to obtain the total amount of water for power generation in the subsequent impact period.

[0028] For all power stations in the parallel system, the corresponding non-energy storage loss index values ​​are calculated according to step (2).

[0029] Step (3) sorts the order of water storage and release according to the two indicators of abandoned water volume and non-storage loss in the current period obtained by solving the parallel system.

[0030] Step 3.1 Generate a priority output increase ranking table. Give priority to abandoned hydropower, and hydropower stations with large abandoned hydropower will be given priority to increase output. When the abandoned hydropower is the same, hydropower stations with less energy storage loss and less energy storage loss will be given priority to increase output. Generate a priority output increase ranking table based on this rule.

[0031] Step 3.2 Generate a priority output reduction ranking table. Similar to the priority output increase ranking table, give priority to abandoned hydropower, and hydropower stations with small abandoned hydropower will be given priority to reduce output. When the abandoned hydropower is the same, hydropower stations with less energy storage loss and larger energy storage loss will be given priority to reduce output. Based on this rule, a priority output reduction ranking table is generated.

[0032] Step (4) uses the storage and release water sorting results to distribute output. After generating a priority increase and decrease output sorting table, output is distributed to the system load that needs to be adjusted according to the sorting results.

[0033] Step 4.1: To improve the accuracy of output optimization allocation, the total system load that needs to be adjusted in the current period is divided into N parts, and one part of the output is allocated each time.

[0034] Step 4.2 Calculate the abandoned water power and non-storage loss value of each hydropower station in the current period from steps (1) to (3), and generate the corresponding storage and release order ranking table. If it is necessary to increase the output, according to the priority increase output ranking table, increase one of the N outputs of the first-ranked hydropower station. If the hydropower station cannot increase the output due to constraints such as water level and reservoir capacity, or can only increase part of the output, increase the remaining output of the next-ranked hydropower station until the output is fully allocated. If it is necessary to reduce the output, according to the priority reduction output ranking table, allocate the first part of the output in the same way as above.

[0035] Step 4.3 repeats steps (1) to (3), recalculates the abandoned hydropower and non-storage loss index values ​​of each power station in the system, and distributes the second output according to the method in Step 4.2. After N output distributions, the water storage and discharge sequence table is updated before each distribution to obtain the load adjustment result guided by the water storage and discharge sequence.

[0036] Beneficial effects of the invention: The present invention aims at the problem of competitive water storage in parallel reservoir groups, and combines the characteristics of seasonal regulation reservoirs that have the risk of water abandonment during the flood season and the flood-dry season to propose a water storage and discharge order determination model that simultaneously considers the minimum amount of abandoned water and the minimum loss of non-storage. The water storage and discharge order generated by the model is affected by the real-time changes in water levels and guides the daily load distribution of the hydropower system. At the same time, the model method also has a good performance in controlling the risk of water abandonment, which is conducive to the parallel reservoir group to give full play to the compensation and regulation capabilities between river basins, can effectively improve the comprehensive benefits of hydropower stations, and help dispatchers make more reasonable decisions. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is the overall framework of the method for solving the water storage and release sequence of the present invention;

[0038] Figure 2 This is a schematic diagram of the division of the supply and storage periods of a hydropower station;

[0039] Figure 3 It is a simulation of the water level dispatching process of a power station in Chongqing; wherein, model 1 represents the dispatching result using the conventional method, and model 2 represents the dispatching result using the method for solving the water storage and discharge sequence of the present invention. DETAILED DESCRIPTION

[0040] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0041] The objective function adopted by the method for solving the water storage and discharge order involved in the present invention is to minimize the amount of abandoned water and minimize the loss of non-storage. Currently, the common existing methods for determining water storage and discharge mainly focus on power generation and energy storage, and rarely consider the risk of water abandonment. Since the water abandonment index has received much attention in the economic operation of hydropower, many power generation companies have relevant standards and restrictions on water abandonment, and most of the existing domestic methods are limited to deriving the water storage and discharge discriminant formula from the loss of non-storage. Therefore, it is necessary to further consider the impact of water abandonment risk on water storage and discharge, and obtain a water storage and discharge determination method that focuses on the risk of water abandonment.

[0042] For the parallel system, since there is no relevant hydraulic connection between the hydropower stations, the calculation of abandoned hydropower and non-storage loss can be carried out independently. Therefore, the following specific implementation methods are only for a single hydropower station, and other power stations in the parallel system can be solved using the same method.

[0043] When considering the risk of water abandonment, the present invention uses the amount of water abandoned to quantify the impact of the water abandonment factor on the power generation of the hydropower station. The amount of water abandoned in a certain period of time is the amount of power that can be generated by this part of the abandoned water if water abandonment occurs from the beginning of this period to a period in the future. The larger the amount of water abandoned, the higher the risk of water abandonment, and the smaller the amount of water abandoned, the lower the risk of water abandonment. In the face of areas with obvious water abandonment risks, it is necessary to focus on the impact of water abandonment on reservoir safety and hydropower station power generation when determining a reasonable water storage and discharge sequence. In order to improve the long-term scheduling benefits of hydropower stations and reduce the risk of water abandonment, the present invention considers the maximum water abandonment that may occur in the next M days starting from the current period when formulating the water storage and discharge sequence. When the output of the target period is adjusted using the water storage and discharge sequence determination method involved in the present invention, water abandonment can be minimized in the future period and better power generation benefits can be obtained.

[0044] Solving the possible amount of abandoned water from the current period to the forecast period of M days requires the daily scale inflow forecast data of the hydropower station. If the forecast inflow data for the next M days is known, the total inflow water volume for each day in the forecast period can be directly calculated. If the forecast inflow data is missing, the historical water inflow data can be used to describe the forecast inflow process. It is assumed that the inflow flows of two consecutive days are independent random variables. The flow of any day in the 30 days before and after the same period of the historical water inflow data is used instead. The historical multi-year flow data is subjected to hydrological frequency analysis to obtain the multi-scenario water inflow process as the forecast inflow flow data involved in the calculation.

[0045] When a hydropower station has a risk of abandoning water in the foreseeable period, the power generation flow can be increased to use this abandoned water for power generation as much as possible to reduce the loss of abandoned water. If the hydropower station is in full power generation state and still produces abandoned water, the amount of power generated by this abandoned water is the abandoned water power. The calculation in this process adopts the water balance equation: V in,max =V max +V out,max -Vstart , V in,max V is the maximum total inflow, that is, the maximum amount of water that can be stored without water abandonment; max is the upper limit of storage capacity; V out,max is the maximum total outflow, i.e. the water consumption of the hydropower station under full power generation. The maximum storable water capacity in a single period is obtained from this, and then compared with the maximum inflow water obtained from the forecast inflow flow data in that period. V spill is the calculated amount of discarded water, V in V is the total amount of water forecast. in,max is the maximum amount of water that can be stored. According to the above expression, the amount of water abandoned in the current period is obtained. If water abandonment occurs in the current period, the water level at the end of the period reaches the upper limit. If water abandonment does not occur, the water level at the end of the period is obtained by the water balance equation. In order to obtain the total amount of water abandoned in the forecast period of M days, the amount of water abandoned in the next period is calculated in the same way until the total amount of water abandoned in M ​​days is calculated.

[0046] When all power stations do not abandon water, the non-energy storage loss index is used to determine the order of water storage and release of the reservoir group. If the amount of water used for power generation is certain, the amount of power generated depends on the power generation head in the current period, and is approximately proportional. When the system load increases and the total output generated by the current reservoir group does not meet the requirements and the output needs to be adjusted, the hydropower station can consume less water for power generation under high head. If the output is increased, the power generation head will be reduced, and this reduced part of the power generation head affects the power generation in all subsequent periods. The corresponding power loss is the non-energy storage loss.

[0047] The impact of the non-energy storage loss caused by the loss of this part of the water head due to the increased output continues until the time point when the reservoir's water supply period and water storage period alternate, that is, when the reservoir reaches a full or empty state. In actual operation, due to the influence of water inflow uncertainty, the time nodes of the supply and storage alternation period in different years may be different and difficult to accurately judge. In order to reduce the calculation complexity while ensuring that the accuracy requirements are met, the present invention sets two time nodes for supply and storage alternation in a year, from dry to flood and from flood to dry. This node is the boundary of the time period for calculating the impact of non-energy storage loss. Figure 2 As shown, assuming that the end of April is the end of the water supply period, the reservoir water level drops to the lowest water level, and the end of September is the end of the water storage period, and the reservoir water is stored to the highest water level, then when the calculation period is between October 1 and May 1 of the following year, the non-storage loss is calculated to the end of April, at which time the reservoir water level has dropped to the lowest value, after which the reservoir begins to store water, and the power generation is not affected by the previous head changes; when the calculation period is between May 1 and October 1 of the same year, the non-storage loss is calculated to the end of September, at which time the reservoir water level has reached the highest water storage level, after which the reservoir begins to release water, and the power generation is not affected by the previous head changes.

[0048] In the process of calculating the non-storage loss index, for any power station in the parallel system, assuming that the unit output of the hydropower station is increased, the required increase in power generation flow can be obtained through the power generation head in the current period: Δp is the output change of the hydropower station in the current period, Δq is the change in the power generation flow of the hydropower station under the output change Δp in the current period, A is the output coefficient, and H is the average power generation head in the current period. The power generation flow change value can be obtained from the reservoir capacity at the end of the period after the output is increased V′=V-3600ΔqΔt, V and V′ are the reservoir capacities at the end of the period before and after the output changes in the current period, respectively. The head change value Δz=f(V′)-f(V) for the increased output is calculated through the water level capacity function relationship, Δz is the head change value at the end of the current period after the output changes; f(*) is the water level capacity function relationship. The non-energy storage loss caused by the head change is calculated by the formula ΔE=AΔzW, ΔE is the non-energy storage loss value caused by increasing the output in the current period, W is the total water volume for power generation in the subsequent period, and Q n is the average value of the power generation flow in the n period, t is the number of the current period, and T is the maximum value of the period number that increases or decreases the output on the subsequent power generation, which is determined by the supply and demand status of the reservoir.

[0049] The above method can be used to calculate the abandoned hydropower and non-storage index values ​​of each power station in the parallel system in the current period, and the storage and release order can be sorted according to the two indicators. When sorting, the abandoned hydropower is given priority, and the hydropower stations with large abandoned hydropower are given priority to increase their output. When the abandoned hydropower is the same, the non-storage loss is considered, and the hydropower stations with small non-storage losses are given priority to increase their output.

[0050] In the actual dispatching process of a group of parallel hydropower stations, it is often necessary to adjust the real-time output of each power station according to the load requirements of the power grid. At this time, it is necessary to use the order of water storage and discharge to distribute the output. First, compare the real-time total output of each hydropower station in the current period with the load of the power grid demand to obtain the total system load that needs to be adjusted. If the actual output is less than the demand, the system needs to increase the output. If the actual output is greater than the demand, the system needs to reduce the output. Since the index values ​​of abandoned hydropower and non-storage loss will change after the output of the hydropower station is adjusted, that is, the order of water storage and discharge of the hydropower station will change in real time with the output adjustment. In order to improve the accuracy of output optimization distribution, this method divides the total system load that needs to be adjusted into several parts, and distributes the output multiple times, distributing a small part of the output each time, and regenerates the real-time order of water storage and discharge before distribution.

[0051] The specific implementation method is as follows: first, determine the output that needs to be adjusted in the current period according to the load requirements, and divide the total output that needs to be adjusted into multiple parts. The more parts are divided, the more accurate the calculation result is. Perform the first output distribution, calculate the abandoned hydropower and non-storage loss index values ​​of each power station in the system, and use the water storage and discharge order sorting method to sort them. According to the sorted results, adjust the output. If it is necessary to increase the output, increase this part of the output of the hydropower station with the highest priority in the water discharge order. If the hydropower station reaches the upper limit of the output or the lower limit of the water level, adjust the next hydropower station according to the sorting priority result until this part of the output is allocated; if it is necessary to reduce the output, reduce this part of the output of the hydropower station with the highest priority in the water storage order. At the same time, it is also necessary to check whether the reduction of the output of the power station violates the relevant constraints. If it violates, adjust the next hydropower station. After the first output adjustment, recalculate the abandoned hydropower and non-storage loss of each power station and sort them. Perform the next output distribution according to the same method. After multiple adjustments, the total system load that needs to be adjusted will be fully allocated, and the load adjustment result guided by the water storage and discharge order is obtained.

[0052] Application examples:

[0053] Taking the Chongqing power grid coordinated power station as an example, the method involved in the present invention is verified. There are 32 coordinated hydropower stations in the Chongqing power grid, distributed in 19 different river basins. Since the regulation performance of hydropower stations in the Chongqing power grid is generally weak, the power generation capacity of hydropower stations with better regulation performance is not strong, and the water level of the reservoir varies greatly due to the water inflow, it is easy to have insufficient hydropower consumption space during the flood and dry season and the flood season. Therefore, the study of the water storage and release rules of the Chongqing power grid reservoir group is of great importance to the optimization of Chongqing hydropower joint dispatching.

[0054] The present invention selects 10 seasonally regulated hydropower stations connected in parallel as the research object, and uses the actual inflow data and power generation flow data from 2014 to 2019 as historical data. Since each hydropower station is connected in parallel and there is no upstream and downstream hydraulic connection, the 10 hydropower stations are regarded as a system in the calculation. In general, the invention is applied to real-time load adjustment, and only the water storage and discharge order of the current period is calculated. In the example, in order to show the results of the water storage and discharge order during the difficult period of alternating flood and dry seasons, a certain day (May 20) from dry season to flood season in a certain year in history was selected as the target period for load adjustment, and 7 days was used as the forecast period. In order to show the output distribution process in a continuous period, the storage and discharge order and output distribution process for 5 consecutive days are calculated. Given the initial water level of each power station in the starting period and the total daily load of the entire system in the next 5 days, the actual water storage and discharge order is calculated time period by time, and the load distribution of the hydropower station in each period is gradually completed according to the water storage and discharge order.

[0055] The application process of the present invention is as follows:

[0056] (1) Calculation of abandoned hydropower

[0057] Due to the lack of forecast inflow data, the actual inflow data from 2014 to 2019 were selected in this example to extract the historical inflow process of each hydropower station from May 5 to June 5 each year for the next 7 days, that is, 180 consecutive 7-day water inflow processes. For each water inflow process, given the initial water level, the abandoned water volume and abandoned water power volume calculation method were used to calculate the abandoned water volume and abandoned water power volume generated every day in the 7-day forecast period, as shown in formulas (1) to (3), and the total abandoned water volume and total abandoned water power volume were obtained, and the maximum abandoned water power volume of each hydropower station was taken as the abandoned water power volume index value of the current period of the power station.

[0058] (2) Calculation of energy loss without storage

[0059] For any hydropower station, if the unit output is increased in the current period, the water level change value at the end of the period is obtained by the change of its power generation flow, as shown in formula (4). When determining the number of subsequent periods affected by head loss, the water supply period and water storage period are divided into two time nodes, May 1 and October 1, that is, it is assumed that the power station stores water from May 1 to October 1, and releases water from October 1 to May 1 of the following year. Since the target period selected is May 20, which is after May 1 and before October 1, when calculating the non-storage loss, the data from May 20 to October 1 of each year in the historical power generation flow from 2014 to 2019 are selected for calculation to obtain the total power generation water volume. The impact of the head change caused by the increase in unit output on the power generation in the subsequent period is calculated according to formula (5), and the average value of the calculation results for 6 years is taken as the non-storage loss value of the power station.

[0060] (3) Order of water storage and release

[0061] After calculating the abandoned hydropower and non-storage loss index values ​​of each hydropower station, the initial ranking results of the water storage and release order of each power station are obtained by considering the minimum abandoned hydropower as the main goal and the minimum non-storage loss as the secondary goal, as shown in Table 1.

[0062] Table 1 Priority sorting results of the first water release in the initial period

[0063]

[0064] The table shows the water release priority sorting results when no output adjustment was made during the target period (May 20), and the water storage priority sorting results are in reverse order of the water release priority sorting results.

[0065] (4) Application of water storage and release sequence

[0066] Compare the total output of each power station in the current period with the load demand of the power grid. The system needs to increase the output in this period. The output that needs to be increased is divided into 20 equal parts. The first output distribution is based on the results in Table 1. One of the outputs is first allocated to the Pengshui Power Station ranked first. At this time, the water level and output of the Pengshui Power Station change. If the output continues to be allocated to Pengshui, it may not be the best choice. Therefore, it is necessary to recalculate the non-storage loss and abandoned water power of Pengshui, and re-rank it with the new calculation results. Then allocate the output to the power station ranked first. If the power station cannot allocate output, the output is allocated to the next power station in the ranking. If Pengshui cannot increase its output, the remaining unallocated output is allocated to the Youchou Power Station, and so on. According to this method, 20 output allocations are performed. The storage and discharge order ranking table is regenerated before each allocation, and all loads that need to be adjusted are allocated. In actual operation, the number of output allocations can be determined according to the accuracy requirements.

[0067] After the load distribution of the first period is completed, the distribution result is used as the initial condition, and the next period is used as the target period. The above method is repeated to distribute the load of the next period. Therefore, the system load distribution results of the five periods are shown in Table 2;

[0068] Table 2 System load distribution results Unit: MW

[0069]

[0070] Compared with the conventional method that does not consider the risk of water abandonment, the output allocation result in the example of the present invention reduces the amount of water abandoned by 1.658 million m 3 , reducing the amount of wasted electricity by 848,000 kWh. Taking the Youchou Power Station as an example, the water level process after 5 consecutive days of load distribution during the target period is as follows Figure 3 As shown, model 1 represents the dispatching result of the conventional method, and model 2 represents the dispatching result of the method for solving the water storage and discharge order of the present invention. The method of the present invention gives priority to power generation in order to reduce the risk of water abandonment, reserves a certain amount of water storage space, and significantly reduces the loss of water abandonment. The water storage and discharge order generated by the present invention is affected by the real-time change of water level, guides the daily load distribution of the hydropower system, and can better reduce the abandonment of water and power during the alternating period of flood and dry seasons compared with the conventional method that does not consider the risk of water abandonment, which is conducive to the parallel reservoir group to give full play to the compensation and regulation capacity between river basins.

Claims

1. A method for solving the water storage and discharge sequence of parallel hydropower stations considering the risk of water abandonment, characterized in that: The steps include: Step (1) Calculation of abandoned hydroelectricity: In order to balance the goals of reducing abandoned hydroelectricity and improving power generation efficiency, the maximum abandoned hydroelectricity situation that may occur in the next M days starting from the current period is considered. In principle, power stations with large abandoned hydroelectricity within the forecast period M days are given priority to increase output and reduce abandoned hydroelectricity, while other hydroelectric stations are given priority to store water; Step 1.1 According to the current water level, the power generation capacity of the hydropower station and related constraints, the maximum water storage capacity of each hydropower station in the current period is determined by taking the boundary conditions from the water balance equation. The calculation formula is as follows: V in,max =V max +V out,max -V start (1) Where V in,max V is the maximum total inflow, that is, the maximum amount of water that can be stored without water abandonment; max is the upper limit of storage capacity; V out,max is the maximum total outflow of water; V start is the water storage at the beginning of the period; According to formula (1), the maximum water storage capacity in the current period is obtained; the maximum total outflow water volume V out,max The total amount of water generated during the current period when the hydropower station is fully powered; Step 1.2 Determine the maximum amount of water and electricity that may be abandoned in the current period: Calculate the total amount of water entering the reservoir in the current period based on the forecast water inflow data and compare it with the maximum storable water volume. If the total amount of water entering the reservoir is greater than the maximum storable water volume, water abandonment will occur in the current period. The amount of water abandoned by the hydropower station in the current period is calculated by the following formula; Where V spill V is the amount of discarded water; in To forecast the total amount of water inflow; If the abandoned water volume calculated by formula (2) is used for power generation, the abandoned water volume that can be generated by the abandoned water volume in the current period can be calculated as follows: E spill =AHV spill (3) In the formula, E spill is the abandoned hydropower; A is the output coefficient; H is the generating head in the current period; Step 1.3 Calculate the total abandoned water power within the forecast period M days: If abandoned water occurs in the previous period, the initial water storage capacity V in this period is start is the storage capacity corresponding to the upper limit of the water level of the hydropower station; if there is no water abandonment in the previous period, the initial water storage capacity of this period is calculated by adding the initial water storage capacity of the previous period to the forecast water inflow of the previous period, minus the maximum total outflow of the previous period, that is, the total power generation water of the power station at full power; repeat Step 1.1 and 1.2 to calculate the daily water abandonment and water abandonment power within the forecast period M days, and sum them up to get the total water abandonment power; For all power stations in the parallel system, the corresponding abandoned hydropower index values ​​are calculated according to step (1); Step (2) Calculation of non-storage loss: When a hydropower station increases its output, it will correspondingly lose a portion of the generating head. The impact of this portion of generating head on the power generation efficiency in the subsequent period is called non-storage loss. In principle, the power stations with small non-storage loss are given priority to increase their output, and the hydropower stations with large non-storage loss are given priority to store water. Step 2.1 Calculate the water level change per unit time after the hydropower station increases the unit output in the current period, and obtain the head change per unit time Δz after the output changes in the current period that affects the power generation. The calculation formula is as follows: Wherein, Δp is the output change of the hydropower station in the current period; Δq is the change of the power generation flow under the output change Δp of the hydropower station in the current period; A is the output coefficient; H is the power generation head in the current period; V and V′ are the reservoir capacities at the beginning and end of the unit period after the output changes in the current period; Δz is the head change per unit time after the output changes in the current period; f(*) is the water level storage capacity function relationship; Step 2.2 Calculate the power generation loss value caused by the change in water head, that is, the non-energy storage loss: the non-energy storage loss represents the power generation loss value caused by the loss of power generation head in the subsequent period starting from the current period; the subsequent impact period of water head change on power generation is calculated until the reservoir is full to the highest water level or emptied to the lowest water level; the calculation formula is as follows: ΔE=AΔzW (5) Where ΔE is the non-storage energy loss value caused by increasing output in the current period; W is the total water volume for power generation in the subsequent period; Q n is the average value of the power generation flow in the n period, t is the number of the current period, and T is the maximum number of periods that increase or decrease the output will affect the subsequent power generation, which is determined by the supply and demand status of the reservoir; In formula (5), the total amount of water for power generation W is obtained from the historical power generation flow data. The specific method is as follows: starting from the period of each year in the historical data, the total amount of water consumed for power generation is calculated until the water level reaches the highest or lowest period, and the average value is taken to obtain the total amount of water for power generation in the subsequent impact period; For all power stations in the parallel system, the corresponding non-storage energy loss index values ​​are calculated according to step (2); Step (3) sorting the order of water storage and release according to the two indicators of abandoned water power and non-storage loss in the current period obtained by solving the parallel system: Step 3.1 Generate a priority output increase ranking table: give priority to abandoned hydropower, and hydropower stations with large abandoned hydropower will be given priority to increase output. When the abandoned hydropower is the same, hydropower stations with less energy storage loss and less energy storage loss will be given priority to increase output. Generate a priority output increase ranking table based on this rule; Step 3.2 Generate a priority reduction output ranking table: Similar to the priority increase output ranking table, give priority to abandoned hydropower, and hydropower stations with small abandoned hydropower should give priority to reducing output. When the abandoned hydropower is the same, hydropower stations with large energy storage losses should give priority to reducing output. Based on this rule, a priority reduction output ranking table is generated; Step (4) using the water storage and release sorting results to distribute output; after generating a priority increase and decrease output sorting table, distribute output to the system load that needs to be adjusted according to the sorting results; Step 4.1 To improve the accuracy of output optimization allocation, the total system load that needs to be adjusted in the current period is divided into N parts, and one part of the output is allocated each time; Step 4.2 Calculate the abandoned water power and non-storage loss value of each hydropower station in the current period from steps (1) to (3), and generate a corresponding storage and release order ranking table; if it is necessary to increase the output, increase the output of the first hydropower station in N parts according to the priority increase output ranking table; if the hydropower station cannot increase the output due to constraints, or can only increase part of the output, increase the remaining output of the next hydropower station until the output is completely allocated; if it is necessary to reduce the output, allocate the first part of the output according to the priority reduction output ranking table and the method in this step; Step 4.3 repeats steps (1) to (3), recalculates the abandoned hydropower and non-storage loss index values ​​of each power station in the system, and distributes the second output according to the method in Step 4.

2. After N output distributions, the water storage and discharge sequence table is updated before each distribution to obtain the load adjustment result guided by the water storage and discharge sequence.

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