Determination of optimal reserve contribution of thermal units to afford the wind power uncertainty

Due to unforeseen variations in wind speed profiles, wind farm integrations are recognized as intermittent and uncertain energy contributors. More specifically, integration of such renewable energy resources aligned with the conventional thermal units although reduces the emissions and brings about a clean environment, it introduces serious problems in assigning optimal and reliable level of these units in load supplying and spinning reserve provision. This situation is more intensified considering the uncertainties arisen by the power system loading demand. To facilitate such operational hurdles, the ongoing study puts forward an efficient model for assigning the optimal spinning reserve which accommodates the uncertainties in both the wind speed and load profiles. Stochastic behavior of these parameters is simulated by generating a proper number of scenarios through the Monte Carlo simulation (MCS) approach. Then, each of these scenarios is evaluated based on the established linear mixed integer approach in a deterministic fashion. Accordingly, a computationally efficient approach is obtained paving the way for real-world implementations and assuring the global optimum results. The proposed approach is applied to a 12-unit test system including 10 thermal units and 2 wind farms. Results are reflected in terms of the commitment status, energy dispatches, and reserve contributions of each committed unit. A comprehensive discussion is conducted to disclose the possible improvements

A multi-stage linearized interactive operation model of smart distribution grid with residential microgrids

This paper addresses an interactive energy scheduling model developed between distribution system and residential microgrids (RMGs). To make such concepts, a three-stage mathematical programming framework is proposed. Residential energy management (REM) approach which is in interaction with residential microgrid operator (RMGO) is developed which contains two stages, sequentially. The main goal of these stages is to modify RMGs day-ahead load profile by considering the minimized total daily energy expenses of each home at each RMG. Moreover, in these stages, in addition to existing fixed-loads at each evaluated residential homes, in-home energy management (iHEM) systems are responsible for adjusting the shiftable appliances and small scale distributed energy resources (DERs) commitment. In third stage, besides the interactions between distribution system operator (DSO) and RMG operators (RMGOs), optimal operation cost of the distribution system is determined as well. In this way, optimal scheduling of distribution system active elements namely large scale DERs are considered and the changing trends in energy exchanges, power losses, and voltage profile are addressed. To lower the computational burden of the proposed model, linearization techniques are applied in the proposed model. Simulation studies are reported on modified IEEE 33-bus distribution test system to assess the performance of the proposed model. Results are discussed in depth

An optimal procedure for sizing and siting of DGs and smart meters in active distribution networks considering loss reduction

The presence of responsive loads in the promising active distribution networks (ADNs) would definitely affect the power system problems such as distributed generations (DGs) studies. Hence, an optimal procedure is proposed herein which takes into account the simultaneous placement of DGs and smart meters (SMs) in ADNs. SMs are taken into consideration for the sake of successful implementing of demand response programs (DRPs) such as direct load control (DLC) with end-side consumers. Seeking to power loss minimization, the optimization procedure is tackled with genetic algorithm (GA) and tested thoroughly on 69-bus distribution test system. Different scenarios including variations in the number of DG units, adaptive power factor (APF) mode for DGs to support reactive power, and individual or simultaneous placing of DGs and SMs have been established and interrogated in depth. The obtained results certify the considerable effect of DRPs and APF mode in determining the optimal size and site of DGs to be connected in ADN resulting to the lowest value of power losses as well

Investigating the impacts of feeder reforming and distributed generation on reactive power demand of distribution networks

The rapid integration of the distributed generations (DGs) in distribution grids could result in voltage control issues. These issues are more noticeable in grids, which are reformed from overhead wires to underground cables. Different values of line characteristics, particularly the charging capacitance, differently influence the power flow results. The higher capacitance value of underground cables leads to increased reactive power generation of lines and a lower amount of imported reactive power from the transmission network. However, it is not an issue of distribution grids with overhead lines. The augmented effect of the cable-generated reactive power coincident with the active power of renewable generation units such as photovoltaics (PVs) may deteriorate the voltage control procedures. Accordingly, investigating the impacts of feeder reforming strategies with different cable structures and of DGs penetration seems to be of great importance in power system planning and operation studies. Different scenarios are defined for the undergrounding of overhead wires and PVs’ penetration levels to assess the changing trend of the reactive power demand of distribution networks. The Danish network is used as a test system for investigating these scenarios. In each scenario, the imported reactive power from the transmission network and the voltage profile of the test system are investigated. The obtained results are discussed in depth