3.2 与现有协议的兼容性
区块链是一种信息化的技术架构,处于开放系统互联(open system interconnection,OSI)模型第7层,因此在具体实施过程中对底层的交互协议几乎没有影响。中关村区块链产业联盟在2016年2月正式成立后,将其层次划分为高级应用、中间层、底层技术3层架构。参与电力辅助服务市场交易的所有各方实体均可以作为全功能节点存在,也即支持区块链的完整功能,独立完成区块链信息记录(B)、支付(P)、挖矿(M)、路由(R)。然而,在系统实际实现过程中,要求所有节点均同时具有上述功能并不现实,特别是在需求侧参与的设备可能是仅具有简单控制逻辑的控制器,无法记录区块链上的完整交易。考虑到系统实现的复杂度,可以在满足区块链交易安全性的前提下,仅采用部分节点参与区块链完整信息维护,而性能较低的设备仅实现部分功能。
为了详细说明区块链对现有协议的影响,本文针对需求侧资源参与辅助服务市场业务为例进行说明。在OpenADR 1.0版本中详细的规定了与需求响应业务相关的交互逻辑及通信规约[29-30],由于该规范在国际化推广过程中遇到了较大的阻力,于是将该规范通过OASIS进行改版,依托于EI 1.0[31]、EMIX 1.0[32]、WS-Calendar 1.0[33]、oBIX 1.1[34],共同形成了OpenADR2.0规范[35-36]。为了与需求侧现有的控制协议兼容,参与实体可以采用OpenADR协议中定义的基本服务实现区块链的管理和维护,如图6所示。
图6 基于区块链的电力辅助服务交易节点组网
Fig. 6 Networking for blockchain based ancillary service transaction node
根据OpenADR目前的规范,其底层传输的方式可以采用XMPP[37-39]、HTTP[40-41]亦或者是由用户自行定义的传输规约。目前的安全性机制主要包括采用安全传输层协议(transport layer security,TLS)和可扩展标记语言(extensible markup language, XML)签名的方式。为了支撑区块链应用,可以在区块链OP_RETURN消息中进行OpenADR签名编码的扩展实现安全性校验。
3.3 交易信息快速安全处理
电力辅助服务市场中的服务类型包括两类：分别为基本辅助服务(一次调频、基本调峰、基本无功调节)、有偿辅助服务(AGC、AVC、有偿调峰、有偿无功调节、旋转备用、黑启动)等,其触发条件与补偿方式各不相同,在对基本辅助服务考核或者对有偿辅助服务补贴结算时,主要参照电力调度指令、能量管理系统(energy management system,EMS)、发电机组调节系统运行工况、WAMS实时数据、电能量采集计费系统的电量数据等。为了保障系统的稳定性,即使是目前最为成功的比特币应用,其交易速率也仅仅被限定在7 tps,相比VISA的2000 tps速率(峰值可达10 000 tps)还有很大提升空间。同时为确保更强的安全性,对于大额交易的计算时间代价更高,主要是为防止双花攻击[42-43]。信息的安全性与区块的规模密切相关,而且与处理速度是相互矛盾的[44]。虽然从理论上讲,在超过51%恶意的记账矿工时,区块链的技术可能会不安全,欺诈行为可能会发生。然而我国电网结构庞大,可将我国电力信息系统作为大型矿池,集中全国范围内的所有服务器,足以构建具有超强算力的电力专用服务器集群,如果破解如此规模区块链所构建的安全体系,攻击者需要掌握超过全国电力信息服务系统51%的算力,这几乎是毫无可能实现的。系统再结合地区能源金融中心的管理[45]、行政手段的监督,可以确保数据的绝对安全。而且,对于区块链技术的开发者而言,系统的安全问题也可以通过程序化控制解决,通过强大的网络效应与网络基础设施构建全新的电力区块链,通过智能合约手段,自动为参与电力辅助服务的用户、发电机组授权,自动匹配最恰当的辅助服务项目。
3.4 资源耗费问题
在区块链构建的体系中,资源浪费问题也是一个备受争议的话题,网络上众多机构的大部分操作除了挖矿外,并没有产生过多的益处。针对某些特定的应用场景,也可以设计计算力需求更低、速度更快的工作量证明机制,甚至可以采用无需挖矿的Hyperledger工作量证明方法[46]。根据微观经济学的技术原理,用户的电能消费与其他商品一样,电力用户的电力需求会持续增长,直到所实现的边际收益达到所需支付的市场价格为止[47-48]。通过公用总账的形式,在电力市场相关机制还不完善时,保障参与交易的各方利益及市场环境的公平性。对于零售商而言,其职能也不仅仅是买入卖出赚取差价利润,还可以通过掌控负荷群构建有效的能源缓冲池,减少需求侧电能价格波动对用户的影响。然而,为了保障零售商能够盈利,其必须通过技术手段获取准确的电力需求预测信息,在电力市场低价购买电能,再按照相对稳定的价格出售给零售用户,其盈利模式恰恰在于可以通过区块链的概率分析,在各类市场上购买所匹配的电能,从而形成电能差价利润。
4 结论
区块链技术的出现使得传统领域在互联网时代需要技术、管理上的革新。本文提出了区块链技术在电力辅助服务市场的应用设想,并对其前景进行了分析。通过区块链技术,传统的监管者可在无中心化的网络中发挥适当的监管职能,并且能很好地支撑未来的电力绿币交易或者碳税交易[49-53]。此外,区块链技术采用完全分布式的方法达到市场的均衡点,可有效支撑电力现货市场、远期市场的安全、高效交易与运营。
作者：
李彬 曹望璋 祁兵 孙毅 华北电力大学 电气与电子工程学院,北京市 昌平区 102206
郭乃网 苏运 国网上海市电力公司 电力科学研究院,上海市 虹口区 200437
崔高颖 国网江苏省电力公司 电力科学研究院,江苏省 南京市 210003
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