Variable Renewable Generation Contracting and Bidding Behaviour – A Case Study of Wind and Utility PV - Marshall et al.

Many electricity industries around the world have undergone a process of restructuring towards more market oriented arrangements over the past three decades. The past decade has also seen major growth in utility wind and PV generation. While early deployment was strongly supported by policy support mechanisms, variable renewables are now increasingly competitive market players. There are significant policy design questions that arise from observing the interaction of different longer-term contract arrangements intended to support renewables investment - policy or market driven - and wholesale electricity market outcomes. A particular issue here is how different contracting mechanisms may impact on the bidding strategies of renewable generator participants, and the implications of this for efficient electricity market dispatch. Our study investigates how different contracting arrangements, including over-the-counter and publicly traded derivatives, reverse auction-derived Power Purchase Agreements (PPAs), green certificate schemes, and direct market driven investment can influence renewable generator bidding strategies in wholesale electricity markets. We draw together game theoretic perspectives on possible bidding strategies with real-world market experience from the Australian National Electricity Market. The NEM provides a useful case study given its high transparency on participant market bidding and the range of both private and public contracting measures that have been implemented to support wind and utility PV investment over several decades of wholesale market operation. Building on existing knowledge of government incentive schemes and private contracting arrangements, a number of expected bidding strategies are developed from a game theoretic perspective with reference to wholesale risk mitigation strategies and offtake arrangements. A dataset containing ten years of half-hourly price and volume bids from renewable generators in the NEM is then used to investigate long-term patterns in the bidding behaviour of these market participants. Similar behaviours are grouped, classified and explained with reference to the previously developed bidding theory and knowledge of each generator’s underlying contractual arrangements. The analysis highlights a number of general patterns in renewable bidding behaviour and shows that bids are generally broken into three bands at or below $0/MWh, which seem to relate to various contract risk-mitigation and revenue-maximising principles. Additionally, a majority of generators are seen to infrequently attempt to exercise market power by submitting bids near the market ceiling. The research provides an overview of the behaviour of variable renewable generators in the context of Australia’s restructured electricity market, with consideration of the underlying contracting and offtake arrangements that determine investment in such projects.

过去三十年间，全球众多电力行业均朝着更具市场化导向的架构完成了重组进程。近十年间，公用事业级风电与光伏（PV）发电装机规模实现了大幅增长。早期部署阶段，这类可再生能源发电项目曾得到政策支持机制的强力扶持，而如今可变可再生能源（variable renewables）已逐步成长为具备竞争力的市场主体。针对旨在支持可再生能源投资的各类长期合同安排——无论其为政策驱动还是市场驱动——与电力批发市场运行结果之间的互动关系，学界提出了诸多关键的政策设计议题。其中一项核心问题是，不同合同机制会如何影响可再生能源发电商的报价策略，以及该策略对电力市场高效调度所带来的影响。本研究聚焦各类长期合同安排对电力批发市场中可再生能源发电商报价策略的影响，涵盖场外交易（over-the-counter）与公开交易衍生品、反向拍卖衍生购电协议（Power Purchase Agreements, PPAs）、绿色证书机制，以及纯市场驱动的投资模式。研究融合了博弈论视角下的潜在报价策略与澳大利亚国家电力市场（National Electricity Market, NEM）的真实市场实践经验。NEM因其发电商报价的高透明度，以及在数十年批发市场运营历程中为风电与公用事业级光伏投资推出的一系列私人与公共合同扶持措施，成为极具研究价值的案例样本。在现有政府激励方案与私人合同安排研究成果的基础之上，本研究结合批发市场风险缓释策略与购电安排，从博弈论视角推导出若干预期报价策略。随后，研究团队借助一份包含澳大利亚国家电力市场内可再生能源发电商十年间半小时频次的报价量价数据的数据集，对这类市场参与者的报价行为长期模式展开实证分析。研究将相似的报价行为进行归类与阐释，并结合此前构建的报价理论与各发电商的实际合同安排背景进行解读。分析结果揭示了可再生能源发电商报价行为的若干通用规律：发电商的报价通常可划分为三类区间，且均处于0美元/兆瓦时及以下价位，这一划分似乎与各类合同风险缓释与收益最大化原则相契合。此外，多数发电商极少尝试通过提交接近市场价格上限的报价来行使市场力。本研究概述了澳大利亚重组后的电力市场环境下可变可再生能源发电商的运行行为，并考量了决定此类项目投资的核心合同与购电安排。