Optimization Model for the Short-Term Operation of Hydropower Plants Transmitting Power to Multiple Power Grids via HVDC Transmission Lines

Abstract

Long-distance and large-capacity hydropower transmission from large hydropower plants in southwestern China to load centers is an important and effective measure for the accommodation of largescale hydropower in China. However, the load demands of the receiving-end power grids are not fully considered in the conventional power transmission mode, which has greatly affected their enthusiasm for the absorption of trans-regional hydro energy. In order to make full use of the peak shaving capability of the hydropower plants, this paper develops an optimization model for determining the hourly generation scheduling of the hydropower plants transmitting electric power to several power grids via high voltage direct current (HVDC) transmission lines. A large-capacity and highly complex multi-unit hydropower system, the Xiluodu plant in China, is taken as the case study. In the proposed model, minimizing the peak-valley differences of multiple receiving-end power grids is adopted as the objective to alleviate the peak shaving pressure of the receiving-end power grids. In addition to the traditional hydraulic constraints, the operation constraints of individual units and HVDC power transmission limits are well considered. The study focuses mainly on modeling the stair-like power transmission curve constraint which is discrete and nonlinear and has been rarely considered in previous studies. This constraint is then linearized through limiting the logical relations between multiple binary integer variables. Case studies demonstrate that the proposed model has high computational efficiency, and the peak-valley differences of the two receiving-end power grids, i.e., Zhejiang Power Grid and Guangdong Power Grid, are decreased by 15.2% and 7.33%, respectively. Moreover, frequent conversion of HVDC converter equipment can also be avoided, which makes the obtained generation schedule more executable.INDEX TERMS Hydropower plants, high voltage direct current, power transmission limits, peak shaving, Xiluodu plant. NOMENCLATURE A. SETS AND INDICES China, in 1965. He received the Ph.D. degree in hydraulic engineering from the

Peak Shaving Model for Coordinated Hydro-Wind-Solar System Serving Local and Multiple Receiving Power Grids via HVDC Transmission Lines

“…Moreover, HVDC systems are environmentally superior and have lower investment cost for bulk and long-distance power transmission compared to HVAC, enhance power system controllability and reduce carbon emissions and power loss [12]. Thus, China has built extensive HVDC and ultra-high-voltage direct current (UHVDC) transmission projects to facilitate bulk power transfers [13], [14]. Currently, China has commissioned fourteen UHVDC transmission projects, include thirteen ±800kV lines, and the left one is the world's highest voltage level, longest distance and largest capacity Changji -Guquan transmission project, with voltage of ±1100 kV over 3324 km with a capacity of 12 GW.…”

Optimization Model for the Long-Term Operation of an Interprovincial Hydropower Plant Incorporating Peak Shaving Demands

“…In Section 2.1, a simple NLP model, which has a general nonlinear programming structure, was used to solve the approximate problem. With Equation ( 12) as the objective and Equations ( 7)-( 9) and ( 13)-( 15) as constraints, the complex short-term simulation model in Section 2.2 was reformulated as an MILP model that could be easily solved by efficient solvers such as LINGO and CPLEX [12,32,33]. The mathematical model in Section 2.3 was converted into its discretized deterministic equivalents based on the considered inflow scenarios [34].…”

“…The algorithm of the MILP model was developed using a branch and bound (B-and-B) solver (LINGO 18.0, http://www.lindo.com) that showed good stability and global convergence [12,35]. The nonlinear global search method based on the B-and-B algorithm was detailed in the literature of Gau et al [36].…”

“…At present, the load centers in China are generally dominated by thermal power; notably, the peak shaving cost is high, and the flexible power sources are insufficient [9,10]. Moreover, external hydropower is usually considered non-dispatchable generation because the transmission schedules are usually made by the generation side with little attention given to the load demand of the receiving power grid [11,12]. As a result, the load centers often receive large amounts of power during valley hours, and these increase the peak shaving burden.…”

Real-Time Dispatch for Multi-Unit Hydroelectric Plants With AC Optimal Power Flow: The Case of the Santo Antonio System

“…Although dependent on simplifications in PF modeling, practical works have considered commercial solver-based solution strategies that approximate transmission grid operational features. In [17], for example, the HUC of a plant with 18 GUs is studied, where a high voltage direct current (HDVC) system is considered. The HUC is formulated as a mixed-integer linear programming (MILP) problem, and the transmission load targets of HVDC lines are achieved via specific constraints.…”