Abstract
In making short-term optimal operation schemes of cascade reservoirs, water flow hysteresis between the upper reservoir and the lower reservoir is often considered as constant, which cannot really reflect the hysteresis variation between different water flows and will lead to losses of the optimal operation scheme’s benefit. To depict the water flow hysteresis, a Dynamic Water Flow Hysteresis Method (DWFHM) is proposed, based on the space mapping principle. With the mapping operator in the DWFHM, the lower reservoir inflow can be directly obtained. Besides, the DWFHM is used to deal with the hydraulic relation constraint in the short-term optimal operation model of cascade reservoirs. Then, the improved model is applied to the Jinguan cascade reservoirs in the Yalong River basin and solved by an Improved Progressive Optimal Algorithm (IPOA). The results are as follows. (1) Compared with the traditional Fixed Water Flow Hysteresis Method (FWFHM), the inflow processes of the lower reservoir obtained by the DWFHM are more in line with the actual values, due to full consideration of the attenuation effect. (2) The optimal operation with the DWFHM can effectively increase the generated energy (2827 MW·h and 504 MW·h in the non-flood season and the flood season, respectively). Through the analysis of this case, the DWFHM developed in this study can effectively improve the practicability of the optimal operation scheme and reduce the risk in the operation of cascade reservoirs.
Highlights
In the process of the short-term optimal operation of cascade reservoirs, water balance between reservoirs is the most important constraint to be considered [1], and water flow hysteresis is a key factor related to the water balance constraint
Different from the short-term optimal operation model of cascade reservoirs that couples with the Fixed Water Flow Hysteresis Method (FWFHM), the cascade hydraulic relation constraint shown in Equation (12) is adopted in the dynamic scheme instead of the hydraulic relation constraint shown in Equation (1), in order to transform the dynamic water flow hysteresis into the dynamic mapping relationship between upper reservoir outflow, interval outflow, and lower reservoir inflow
In the non-flood season, compared with the FWFHM, the Nash-Sutcliffe efficiency coefficient (NSE) of the Dynamic Water Flow Hysteresis Method (DWFHM) increased by 1.88%, the average relative error (ARE) decreased by 2.32%, and the qualification rate (QR) increased by 3.02%, 6.36 0.66
Summary
In the process of the short-term optimal operation of cascade reservoirs, water balance between reservoirs is the most important constraint to be considered [1], and water flow hysteresis is a key factor related to the water balance constraint. Hysteresis Method (FWFHM) to the short-term optimal operation study [13,14], in which the lower reservoir inflow in a calculation period was the same as the upper reservoir outflow in the previous calculation period. To further quantify the influence of water flow hysteresis on the optimal operation of cascade reservoirs, a Dynamic Water Flow Hysteresis Method (DWFHM) is proposed, based on the space mapping principle. When the existence of water flow hysteresis is taken into account, the Dynamic Programming (DP) algorithm, traditionally used in solving the short-term optimal operation model, is not suitable, because the non-after-effect condition is not satisfied [16]. The short-term optimal operation model of cascade reservoirs considering water flow hysteresis is coupled with the DWFHM and the FWFHM separately, and the optimal operation schemes are obtained by solving the two different models. The Jinguan cascade reservoirs in Yalong River are taken as an example to verify the validity and rationality of the new method
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