Subjects: Dynamic and Electric Engineering >> Electrical Engineering Subjects: Mathematics >> Control and Optimization. submitted time 2022-08-07
Xiaodong Zheng
Baorong Zhou
Xiuli Wang
Bo Zeng
Jizhong Zhu
Haoyong Chen
Peizheng Xuan
Waisheng Zheng
Abstract： Quick-start generation units are critical devices and flexible resources to ensure a high penetration level of renewable energy in power systems. By considering the wind uncertainty, and both binary and continuous decisions of quick-start units within the intraday dispatch, we develop a Wasserstein-metric-based distributionally robust optimization model for the day-ahead network-constrained unit commitment (NCUC) problem with mixed integer recourse. We propose two feasible frameworks for solving the optimization problem. One approximates the continuous support of random wind power with finitely many events, the other leverages the extremal distributions instead. Both solution frameworks rely on the classic nested column-and-constraint generation (C&CG) method. It is shown that due to the sparsity of L1-norm Wasserstein metric, the continuous support of wind power generation could be represented by a discrete one with a small number of events, and the extremal distributions rendered are sparse as well. With this reduction, the distributionally robust NCUC model with complicated mixed-integer recourse problems can be efficiently handled by both solution frameworks. Numerical studies are carried out, demonstrating that the model considering quick-start generation units ensures unit commitment (UC) schedules to be more robust and cost effective, and the distributionally robust optimization method captures the wind uncertainty well in terms of out-of-sample tests.
Subjects: Dynamic and Electric Engineering >> Electrical Engineering Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2022-04-10
Abstract：
Exergy is an index to measure energy quality, which reveals the essence of work capacity loss in the process of energy transfer. In order to study the dynamic evolution mechanism of exergy in time-varying energy networks, the constitutive relations between physical quantities in energy networks are listed based on the energy network theory, and the generalized expressions of exergy are given, including the generalized description and loss equation of exergy based on the second law of thermodynamics, and the energy level factor is introduced to evaluate the energy quality. The dynamic evolution process of different forms of exergy in the energy transfer tube (line) is analyzed, including electric exergy, thermal exergy and pressure exergy, and the output equation and efficiency calculation method of exergy are given. The dynamic evolution process of exergy in energy conversion equipment is analyzed, and the loss, storage and efficiency of exergy are calculated. Finally, the dynamic evolution process of exergy in an integrated energy system is simulated by a specific example. The study of this paper can fully tap the energy efficiency potential of the integrated energy system, and lay a solid theoretical foundation for better realization of energy cascade utilization.
Peer Review Status:
Awaiting Review
Subjects: Energy Science >> Engineering of Energy Sources System Subjects: Dynamic and Electric Engineering >> Electrical Engineering submitted time 2019-07-09
Abstract： The challenges of multi-area power system optimal dispatch exist on how to be in line with certain dispatching mode as well as on the modeling/solution. In this article, a multi-area system day-ahead scheduling, with a provincial systems-reducing method and a generation variances-minimizing objective, is proposed, based on the hierarchical dispatching organization and the long-term bilateral energy contract mode in China. Non-iteratively, the sub-optimal scheduling of ac/dc tie-lines and independent generation units can be derived from solving the model, which also considers some practical constraints like discrete constraints of dc power profiles and power flow limits of local ac interface, etc. Case study is carried out based on the realistic data from the multi-area hybrid ac/dc southern China power system, to verify the effectiveness and feasibility of the proposed model. It is demonstrated that with this method, the upper-level dispatching institution can generate an optimized and reliable transmission power plan with limited information, which decreases the peak-valley difference and standard variance of generation series, relieves the burden of peak regulation of its sub-systems, and hence improves the economic efficiency. The approach suits the dispatching mode of power systems in China well, handles various operation scenarios, and thus has been implemented in the system operator.
Peer Review Status:Awaiting Review
Subjects: Dynamic and Electric Engineering >> Electrical Engineering Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2017-08-28
Abstract： Different types of energy systems are coupled by energy conversion devices (e.g., induction motors, centrifugal pumps, etc.). It is of great practical significance to study the dynamic characteristics and simulation method of multi-type energy system for the optimization design and performance analysis of multi-energy complementary system. In order to model and analyze the time-varying energy network, from the point of view of the essence of energy, lumped parameter models of time-varying transfer line (pipe) and energy conversion equipment are established through in-depth study of the mechanism of energy transfer and conversion. On the basis of the time-varying energy network model, a method of modeling and simulating the dynamic characteristics of the multi-energy complementary system by constructing time-varying energy network equations (including state equations and output equations) is proposed, then the validity and practicability of which are verified by a practical example. The research of this paper lays the foundation for the modeling, analysis, optimization and planning of time-varying energy network.
Peer Review Status:Awaiting Review
Subjects: Dynamic and Electric Engineering >> Electrical Engineering submitted time 2017-08-27
Abstract： The theory of spot pricing is the basis of power market design in many countries, but there are many problems in the practice of spot electricity market. Spot electricity price has two major drawbacks: one is that it is still based on the traditional hourly scheduling/dispatch model, ignores the crucial time continuity in electric power production and consumption and does not handle the intertemporal constraints seriously; the second is that it assumes that the electricity products are homogeneous in the same dispatch period and cannot distinguish the base, shoulder and peak load power with obviously different technical and economic characteristics. To overcome the shortcomings, this paper presents a continuous time commodity model of electricity, including spot pricing model and the model priced according to load duration. The market optimization models under the two pricing methods are established with the Riemann and Lebesgue integrals respectively and the functional optimization problem are solved by the Euler-Lagrange equation to obtain the market equilibria. The feasibility of pricing according to load duration is proved by strict mathematical derivation. The theory and methods proposed in this paper will provide new ideas and theoretical foundation for the development of electric power markets in China and all over the world.
Peer Review Status:Awaiting Review
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