To tackle both thermal comfort and energy saving problems of HVAC systems and direct air-conditioning load control problem of power system, this dissertation presents a novel direct load control (DLC) method with a least-enthalpy estimation (LEE)-based thermal comfort control of air-conditioning units to manage loads efficiently.
First, a solution to least enthalpy estimation based on classic heat transfer theory is proposed and the LEE technique is applied to HVAC control for achieving both thermal comfort and energy saving. Second, in order to alleviate the constraints in direct air-conditioning load control such as outdoor temperature, thermal comfort level (TCL) of consumers and payback load effect, a new DLC plan with a LEE-based thermal comfort control for air-conditioning systems is proposed. Third, a novel group-DLC concept and a simplified DLC load model for a group of air-conditioning units are proposed.
The proposed DLC algorithm exploits the concept of pre-stored chilled-water heat-transfer capacity and the advantages of a LEE-based thermal comfort control, which effectively eliminates payback load and prolongs off-shift time of the DLC program, thereby increasing load-shedding time, while maintaining a TCL within an acceptable range. Hence, DLC constraints on air-conditioning loads are mitigated.
For applying DLC to a vast number of air-conditioning units, a novel group-DLC concept is developed. The g-DLC controller considers the least ON time constraint and produces an optimal DLC schedule for all units that are equipped with a LEE-based thermal comfort control. The g-DLC controller is the solution for problems between air-conditioning units and the load management program. An optimal load-shedding arrangement is adopted and the load profile is matched with load-shedding demand by the g-DLC controller. Accordingly, the group-DLC method can reduce the effects of DLC constraints on air-conditioning loads and optimize the schedule simultaneously. The proposed algorithm enables the load management program to treat the g-DLC controller directly as an aggregate load, which is a combination of a non-shedding load and a shedding load. Therefore, the load management program can tackle such loads easily.

為處理電力系統之空調負載直接卸載問題與空調系統本身之熱舒適及節能控制等問題，本研究提出全新直接負載控制（Direct Load Control, DLC）的方法，並結合空調系統最小焓值估測熱舒適控制以有效解決空調負載控制之相關問題。
首先以古典熱力學理論為基礎的焓值理論，提出最小焓值估測（Least Enthalpy Estimation, LEE）求解，以達成熱舒適及節能控制的目的，印證理論與實用的結果；其二針對相關文獻的研究結果所提空調負載進行直接卸載控制時所遭遇的空調空間舒適度不足、室外溫度影響及空調負載再次啟動時的熱積存負載(Payback Load)等三大限制及問題進行深入分析，並提出有效的解決對策；最後提出group-DLC的架構，並將群組的空調負載簡化為簡單之集總電力負載(Aggregate Load)。
基於空調系統最小焓值估測熱舒適控制可有效抑制室外溫度影響，本研究提出空調系統卸載前之預儲存冰水冷度之規劃，以防止再次啟動時的熱積存負載，同時延長可卸載時間又能維持室內熱舒適條件，因此空調系統之直接卸載控制之三大限制問題就可有效解決。
當進一步需處理大群組空調負載的直接卸載控制時，本研究提出group-DLC架構的原始概念，將大群組空調負載分成數個g-DLC控制器的小群組架構，由g-DLC控制器管理數個配有最小焓值估測熱舒適控制之空調負載。g-DLC控制器接受來自電力負載管理系統之卸載量，並基於本研究所提各空調機組卸載後最小運轉時間（least ON time）之考量，安排所轄之空調機組之最佳卸載排程，因此，空調負載因應直接負載法所需配合的卸載控制或排程規劃所導致的相關三大限制問題，均由g-DLC控制器與配有最小焓值估測熱舒適控制之空調機組處理，故電力負載管理就不必受到以往文獻所提的相關問題限制。因此電力負載管理可將g-DLC控制器視為一單純可調整的電力負載，此一電力負載模型可分為兩部份，其一為不卸載的固定負載，其二為可卸載的變動負載，而變動負載是在每一循環(per Cycle)就被決定的，因此此一負載就變成可預知的受控電力負載，這可大大簡化電力系統負載管理的複雜性。

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