自來水事業之目標是確保自來水供應的穩定與安全，滿足用戶進行各種活動時所需的用水。自來水屬於公用事業，成本原則上由所有用戶負擔，必需提高營運效率。在一個具有多淨水場的供水系統，操作人員常依照經驗調整出水量，一般均優先利用最小成本之水源，或由較高地形高程之淨水場出水，但今日在配水系統日趨複雜後，如僅賴經驗選用各類低成本的可用水源，水壓可能無法滿足最小要求的水頭，如何在滿足水頭要求下選擇最小的水源成本以提高營運效率，為值得探討的課題。
　　自來水單位成本中，因加壓所需的動力成本往往佔有相當的比重，故前人對於尋找最低供水成本策略的研究，往往著重於尋找幫浦最佳的調度方式，將自來水系統之耗電量減至最低，依此求出最低成本的供水策略，較少同時整合考慮水源成本及系統水壓要求對自來水營運成本的影響。
由於自來水成本受到動力成本影響甚鉅，若部分淨水場有足夠高程，可以不需要加壓，則在適當配置出水下，或可得到系統不需額外加壓的低水源成本供水策略，而僅考慮水源成本，對於降低營運成本有莫大助益。因此在淨水場不需額外加壓的前提下，本研究使用序列二次規劃法(Sequential Quadratic Programming, SQP)優選最小水源成本之淨水場供水策略，並經由管網水力分析檢核用戶端水壓是否滿足需求、淨水場水頭是否小於可用水頭，以優選出最低總水源成本且水力可行之供水策略。
　　計算成果發現，若任何淨水場自身高程可以提供管網所需水頭或忽略加壓成本，則最低成本供水策略直接由水源成本較低的淨水場優先出水，水源成本較高的淨水場減少出水；在淨水場可用水頭有限且不加壓時，則非僅依照淨水場水源成本的高低決定出水優先順序，反而水源成本高但可用水頭較大的淨水場有可能優先出水。
　　多淨水場的自來水供水系統有許多營運條件，為期獲致實務可行的最佳供水策略，對操作成果有顯著影響的重要營運條件均須納入分析，本研究運用SQP法優選一日兩個時段的供水策略，運用有限的水源水量，設定各淨水場固定速率產水，以配水池調蓄淨水場不同時段的不同出水量，以提供用戶不同的時段需求水量，並假設淨水場僅能以自身地形高程重力送水，且達成滿足用戶的最小需求水壓，相較於優選單一時段的供水策略，問題尺度較大且較複雜；本法可於二十秒內得到四座淨水場及十二個需求點的最低成本供水策略，計算效率高，可於現場使用。

The operation policy of purification stations in water distribution system is to provide satisfactory water quality to customers at required flow and pressure.
In a water distribution system with multiple purification stations, the operator often adjusts the amount of aquifer yield of purification stations by experience. In the complex water systems, based on experience to operate the system may not be able to meet customer needs.
Among the total operational cost, considerable portion is related to pumps are often the greatest energy consumer in water distribution systems. Many researchers were dedicated to minimize electricity consumption by optimizing the working schedule of these pumps in water distribution system, but raw water cost has been seldom discussed.
Because of pumping water in water distribution systems accounts for a large part of the operational cost, this paper assumes part of purification stations has sufficient elevation which can supply water without additional pumping to users, has the potential to significantly decrease operational cost.
This study use a method called sequential quadratic programming, SQP, to optimize raw water cost in a hypothetical water distribution system. Hydraulic simulations performed by using Newton-Raphson method, assuring the water pressure level fulfilment for users and activities. If water pressure doesn’t meet user needs, then using the penalty function to enlarge the value of the objective function, induce the SQP method converge to the operation policy with lowest raw water cost without violating all constraints.
The results showed that if any purification stations itself could supply required water head in pipe-network system via its elevation or by extra pumping, then the optimization algorithm used to making the purification station which has the lowest raw water cost provide water first priority. If the purification stations can only supply water by its elevation, then the purification stations with higher raw water cost may provide water prior to the lower.
Water distribution system has many operating conditions; all the conditions should be taken into account before optimizing the operation cost. The purpose of this paper is to optimize raw water cost that combines the objective function and constraints into a merit function. It outperforms every other optimization method in terms of accuracy and computational efficiency.

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