Optimal Power Scheduling for a Medium Voltage AC/DC Hybrid Distribution Network

Abstract

Abstract:With the great increase of renewable generation as well as the DC loads in the distribution network; DC distribution technology is receiving more attention; since the DC distribution network can improve operating efficiency and power quality by reducing the energy conversion stages. This paper presents a new architecture for the medium voltage AC/DC hybrid distribution network; where the AC and DC subgrids are looped by normally closed AC soft open point (ACSOP) and DC soft open point (DCSOP); respectively. The proposed AC/DC hybrid distribution systems contain renewable generation (i.e., wind power and photovoltaic (PV) generation); energy storage systems (ESSs); soft open points (SOPs); and both AC and DC flexible demands. An energy management strategy for the hybrid system is presented based on the dynamic optimal power flow (DOPF) method. The main objective of the proposed power scheduling strategy is to minimize the operating cost and reduce the curtailment of renewable generation while meeting operational and technical constraints. The proposed approach is verified in five scenarios. The five scenarios are classified as pure AC system; hybrid AC/DC system; hybrid system with interlinking converter; hybrid system with DC flexible demand; and hybrid system with SOPs. Results show that the proposed scheduling method can successfully dispatch the controllable elements; and that the presented architecture for the AC/DC hybrid distribution system is beneficial for reducing operating cost and renewable generation curtailment.

Security-Constrained Unit Commitment Considering Differentiated Regional Air Pollutant Intensity

“…Hourly SCUC constraints include system power balance constraints (Equation (16)), wind power limit (Equation 17), unit minimum on/off limits (Equations (18) and (19)), unit ramping up/down limits (Equations (20) and (21)), unit generation limits (Equation (22)), system regulation up/down limits (Equations (23) and (24)), system spinning/operating reserve limits (Equations (25) and 26), and generalized DC power flow constraints (Equation 27):…”

“…Traditional environmental economic dispatch (ED) or unit commitment (UC) constrains the total emissions of the power sector [17], and various environment-aware technologies and policies are considered [18,19]. Wei et al [20] proposed a bi-objective ED considering carbon capture plants and wind power uncertainty.…”

Security-Constrained Day-Ahead Operational Planning for Flexible Hybrid AC/DC Distribution Networks

“…Since the application of SOPs provides operational flexibility to distribution networks, it has been considered as one of the factors to determine an optimal placement for distributed energy storage in [11]. A dynamic energy management framework considering renewable generations, energy storage systems, flexible demands, and the SOP application was proposed in [12]. In a recent study, [13] introduced a decentralised control of VSC stations to address the issue of communication failure.…”

“…In a recent study, [13] introduced a decentralised control of VSC stations to address the issue of communication failure. Like the demonstration project in [6], these studies [7][8][9][10][11][12][13] only considered the interconnection between any two feeders which would limit control (e.g., load transfer capability) to the two feeders. In recent years, the multi-terminal high voltage direct current (HVDC) configurations have been investigated extensively at the transmission level [14][15][16][17][18][19].…”

“…Our contributions in this paper are three-fold: (1) A day-ahead distribution network management framework with flexible demand and DG curtailment to uphold the secure operation during contingencies, (2) an extended security constrained, which covers three stages, pre-contingency, short-term, and long-term post-contingencies, is used to highlight the different remedial action capabilities between slow response (i.e., load tap changer) and fast response (i.e., VSCs) control devices, and (3) a multi-terminal configuration of MVDC is introduced to alleviate the limitations of back-to-back (BTB) or point-to-point (P2P) configurations used in [7][8][9][10][11][12][13] and thus a more flexible network operation can be achieved. The MVDC interface works as a platform for renewable energy integrations at the end of distribution feeders that uses the same number of VSCs as in P2P configuration.…”