Study on the Control Mode of Storage Balance of Multi-channel Pools in Series Channel Systems

Abstract

【Background】 Open channels have been widely used to transfer water in many projects. Automatically controlling them is a prerequisite in realizing intelligent management, optimizing water distribution, and achieving flexible water supply in emergency. Traditional automatic control systems normally use water level, flow rate, or storage pool as objective to control the channel operation based on some logic analysis. Existing control operation modes include keeping the upstream and downstream water levels constant, equal-volume method and control-volume method, with the control-volume method being most flexible and able to quickly respond to any changes. The disadvantage of the control-volume method is that it only uses the volume of a single channel section as its control objective. Therefore, its storage capacity is limited, and it cannot complement adjacent channels. 【Objective】 The objective of this paper is to resolve the inferiorities of the control-volume method, including limited storage capacity, inability to adjust the changes in the storage capacity between adjacent channels when using the storage capacity of a single section as the control objective. 【Method】 The proposed method was based on the balanced operation mode of multi-channel pool storage capacity with equal downstream water depth. We established a robust and easy-to-implement model to calculate the gate target flow based on the change in storage capacity, which not only keeps the total storage capacity of the channel unchanged, but also makes the downstream target water depth in each channel pool consistent. As a validation and verification, we applied the model to Jiping main canal on the east route of the south-north water transfer project. 【Result】 In the multi-canal pool storage balance mode, multiplying the storage difference by a weight coefficient can effectively reduce the gate flow overshoot and shorten the time it takes the system to stabilize. Under normal operating conditions, the regulation pressure on the head reservoir in the canal calculated by the proposed method was lower than that calculated by the conventional downstream constant water level control mode. Overall, the proposed method improved all dimensionless performance indexes, with the system stabilization time reduced by up to 10 hours. Considering that the difference in pool lengths in a canal could be more than 10 times, it is found that when there are large flow changes, adding a control gate to reduce the length of a single pool can further reduce the overall stabilization time and improve all dimensionless performance indexes. 【Conclusion】 Multi-channel pool storage control works better than the single channel pool storage control system, and the method we proposed lays a foundation for its further study and improvement.

Keywords

• canal control
• operation mode
• water volume control
• variable control water depth
• the jiping canal of the east route of the south-to-north water transfer project