拒绝服务攻击下直流微电网的事件触发控制

本文研究受拒绝服务攻击下直流微电网的事件触发控制问题. 考虑到直流微电网的状态并不总是可获得, 设计了一个观测器来估计直流微电网的状态. 基于观测器的估计状态, 对于受拒绝服务攻击的直流微电网设计了一种新颖的弹性攻击的事件触发控制器. 所提出的控制器设计方法可以通过分离方法转化成一个凸问题. 此外, 在所设计的事件触发机制中, Zeno行为也被讨论并且通过矛盾法被排除. 最后, 一个实际的电网例子被用来验证所提出的控制方案的有效性.     

采用非线性无源理论的MMC–MG并网电流控制

针对MMC半桥串联结构微电网(modular multilevel converter microgrids, MMC–MG)并网电流控制中, 采用 传统PI控制方法时其动态性能较差的问题, 提出一种利用无源控制理论的电流控制策略. 首先, 阐述了系统的拓扑 结构, 并建立了其欧拉–拉格朗日数学模型. 然后, 通过选取系统的状态变量, 设置误差能量函数及需注入的阻尼项, 以得到无源控制律; 并依据该控制律设计无源电流控制器. 此外, 通过观察采用不同阻尼值时控制器的稳定性、电 流谐波特性、幅频和相频特性曲线, 进而得到最佳的阻尼参数; 最后, 由系统的并网仿真模型验证所提无源电流控 制的有效性. 结果表明, 与传统PI控制相比, 阻尼注入无源控制方法能在不同运行工况下实现对电流和功率参考值 的快速跟踪. 同时, 具有良好的谐波特性和稳定性.     

Backstepping and Sliding‐Mode Techniques Applied to Distributed Secondary Control of Islanded Microgrids

In this paper, secondary voltage control scheme for a droop‐controlled inverter‐based islanded microgrid is addressed. Motivated by the cooperative control theory of multi‐agent systems, the proposed secondary voltage control is a distributed scheme which uses a simple communication network. Two nonlinear control algorithms are applied to restore the voltage of each distribution generation (DG) to the reference value. The simulation results verify the effectiveness of the proposed secondary voltage control for a prototype microgrid system.     

Sectionalized microgrids: The key to regulatory assistance for unbundling reliability?

Are telecom precedents involving the development of premium reliability services transferable to electric utilities? Can electric utilities offer customers premium reliability services through microgrids? We believe sectionalization, a new network design, can preserve customer choice and ensure that incremental costs for premium services are not shifted to customers taking standard service – key objectives necessary to gain regulatory approval. We present three case studies to illustrate how sectionalization can be used.     

基于改进下垂控制的微网孤岛运行研究

针对传统下垂控制不能稳定微网频率的缺陷,在有功-频率(P-f)下垂方程中引入Sigmoid函数,使微网的频率能自主限制在一定范围内,保证微网的频率稳定性。在多微源并联微网系统中,由于线路阻抗差异引起的无功功率分配问题,采用修正无功-电压(QV)下垂系数来补偿线路阻抗的压降,从而提高功率分配精度,并限定了电压的范围,使负荷点电压得到了保证。在PSCAD仿真软件中搭建了模型,仿真结果验证了引入Sigmoid函数和修正系数法的下垂控制,能使微网频率和负荷点电压自动保持在一定的范围内。改进的下垂控制策略适用于多微源微网在孤岛模式下的控制系统,可以提高微网运行的稳定性。     

Blockchain for decentralized transactive energy management system in networked microgrids

The proliferation of distributed energy resources is reshaping the landscape of power distribution systems, including a network of autonomous microgrids. Networked microgrids transact energy for managing the efficiency, reliability, resilience, security, and sustainability of electric power services. This article offers a vision and analyzes a scheme developed for networked microgrids that utilizes blockchain technologies to optimize the financial and physical operations of power distribution systems. Blockchain provides a powerful and trustworthy path for launching distributed data storage and management, the article explores the possibility of customizing blockchain technologies to meet socioeconomic requirements of transactive energy management at the power distribution level. Then, a set of interoperable blockchains embedded with self-enforcing smart contracts is proposed to manage energy and financial flows among transacting microgrids in a credible manner. The article presents additional smart contract measures for securing optimal energy transactions between networked microgrids and the local distribution grid. It is concluded that blockchain technologies embedded in transactive energy will play a significant role in the evolution of traditional power distribution systems to active distribution networks.     

Optimal Resource Management of Microgrids in a Competitive Market Environment Using Dual Layer Control Approach

Abstract

Renewable integrated microgrids effectively contribute in reducing GHG emissions substantially, at a global level. A multi-agent control system to facilitate information exchange for a microgrid participating in the deregulated framework of the electricity market is proposed. A novel energy management system, aimed at the effective utilization of RES and stored energy in PHESS in order to ensure maximum priority based social benefit to the microgrid controller is presented. The intermittent nature of RES which might cause uncertainties in availability during real-time dispatch, is effectively dealt in the proposed dual layer control approach, through optimal usage of PHESS and employment of load prioritization technique in the proposed renewable microgrid. Thus, the research carried out in this work not only ensures the committed power exchange is maintained constant in both DASL and RTDL, but also contributes significantly in PBSB maximization of the microgrid, while managing real-time uncertainties in RES availability. The importance of pre-prioritizing the loads is put forth, in order to ensure that, if load curtailing needs to be done during peak demand intervals, the critical loads must not suffer. The developed algorithm has been successfully implemented on a 16 bus microgrid interconnected with a 30 bus main grid.     

微电网中并列运行逆变器控制策略研究

考虑到微网内分布式电源的多样化和分散性,提出一种PQ控制与基于下垂特性的电压电流控制相结合的控制策略。PO控制可以实现间歇性微源的最大能源利用率,基于下垂特性的电压电流控制在微网运行模式或结构发生变化时,可以很好地实现负荷功率共享,以维持微网频率和电压的稳定。此控制策略既可以在并网模式下运行,也可以在孤岛模式下运行。并在PSCAD／EMTDC仿真平台上搭建了微电网仿真模型,验证了此控制策略的正确性和有效性。     

A techno-economic comparison of rural electrification based on solar home systems and PV microgrids

Solar home systems are typically used for providing basic electricity services to rural households that are not connected to electric grid. Off-grid PV power plants with their own distribution network (micro/minigrids) are also being considered for rural electrification. A techno-economic comparison of the two options to facilitate a choice between them is presented in this study on the basis of annualised life cycle costs (ALCC) for same type of loads and load patterns for varying number of households and varying length and costs of distribution network. The results highlight that microgrid is generally a more economic option for a village having a flat geographic terrain and more than 500 densely located households using 3–4 low power appliances (e.g. 9 W CFLs) for an average of 4 h daily. The study analyses the viability of the two options from the perspectives of the user, an energy service company and the society.     

Dynamic State Estimation for Microgrid Structures

Abstract

In this article, the dynamic state estimation of the islanded microgrids problem is addressed. The electrical network and energy sources are represented as a set of Nonlinear Differential Algebraic Equations, with the aim to capture the nonlinear phenomena and a novel solution, by using a variation of the Kalman Filter ad hoc for differential algebraic systems, is presented. In this representation, the state is given by the voltage phasors at each bus and the variables related to the energy sources. The proposed algorithm permits not only to effectively obtain an estimate of the state variables but also it allows to recover these variables during the microgrid transient behavior. Moreover, the estimation may be carried out using fewer measurements than those needed by conventional static estimators. The performance of the proposed dynamic state estimator is evaluated via numerical experiments using two practical microgrids containing wind power and hydroelectric generators. This novel method has been tested for load variations and wind speed changes demonstrating its capabilities and efficiency.