隨著淨零排放與企業永續的國際趨勢加劇，綠色電力需求快速升高。然而，台灣綠電市場目前仍高度仰賴分散的小型發電業者（Power Generators, PG），使得企業用戶（Enterprises, EP）難以穩定採購。為解決此問題，聚合商（Aggregators, AG）成為關鍵中介角色，透過契約設計整合多個PG，並將綠電提供給企業。本研究建立一套單期雙層隨機決策模型，以台灣北部與南部兩位具區域異質性的PG為對象，探討AG如何透過包含門檻分位（α）、基本購價（"w" ）與誘因強度（κ）的門檻導向合約，引導PG進行最佳投資決策。模型亦納入PG的心理誘因感知（β）、空間限制("A" ^*)、保留利潤與FiT外部選項等真實參與條件。
模擬結果顯示，AG利潤與PG投資行為具顯著非線性門檻效應，契約參數稍有調整即可能觸發PG行為跳躍。其中，門檻過高將導致誘因折損，反而抑制投資；而適度提升基本購價可激勵供應，但若超出區間則將提高AG成本。敏感度分析進一步指出，外部收購價的提升將壓縮AG誘因空間，而投資成本上升與空間限制惡化將直接衝擊PG參與動機。上述結果顯示契約績效對心理與政策參數高度敏感。
本研究提出的門檻式合約設計，能有效誘導小型發電業者投資綠能，並協助聚合商在不確定環境下整合分散電源。後續研究可延伸為多期規劃、內生化 AG 投資決策，並納入多家具異質偏好的企業用戶，以貼近真實綠電供應鏈之制度挑戰。

關鍵字：綠色電力、聚合商、投資誘因、門檻導向合約設計、心理誘因感知、
雙層隨機決策模型

With the increasing global momentum toward net-zero carbon goals and corporate sustainability, the demand for green electricity has risen sharply. In Taiwan, the green power supply remains heavily reliant on decentralized small-scale power generators (PGs), posing challenges for enterprises (EPs) to secure reliable procurement. Aggregators (AGs) have emerged as key intermediaries by consolidating PGs and delivering electricity through tailored contracts. This study develops a single-period bi-level stochastic decision model to examine how AGs can induce optimal PG investments under uncertainty by offering threshold-based contracts defined by a quantile threshold (α), baseline purchase price (α), and incentive intensity (κ). The model incorporates critical real-world constraints such as psychological perception of incentives (β), spatial limitations ("A" ^*), reservation profit, and alternative income from Feed-in Tariff ("FiT" ).
Simulations reveal nonlinear threshold effects, where small changes in contract terms can trigger sharp shifts in PG investment. High thresholds reduce participation due to psychological discounting of bonuses, while moderate increases in baseline prices can encourage investment, but excessive increases raise AG costs. Sensitivity analysis shows that higher external purchase prices levels compress AG's incentive space, while rising investment costs and spatial constraints diminish PG willingness to participate. These results underscore the model's sensitivity to behavioral and policy parameters.
The proposed contract mechanism encourages PG investment in green generation and supports AGs in coordinating decentralized supply under uncertainty. Future research may extend this model to multi-period settings, endogenous AG investment decisions, and multiple heterogeneous EPs to reflect the complexity of real-world green electricity systems.
Keywords: Green electricity, Aggregator, Investment incentive, Threshold-based contract design, Psychological incentive perception, Bi-level stochastic decision model

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