Low inertia of distributed energy resources (DERs), high penetration levels of renewable energy sources (RESs) and load demand variations put the islanded microgrids (MGs) security at risk of instability. This paper proposes a twostage stochastic model for coordination of DERs and responsive loads in islanded MGs with regard to voltage and frequency security constraints. Based on the proposed model, scheduling of the controllable units in both supply and demand sides is done in a way not only to maximize the expected profit of MG operator (MGO), but also to minimize the energy payments of customers under the premise of security and stability of MG. An AC optimal power flow (AC-OPF) procedure is also used to study operating condition of the system under uncertainties and to guarantee acceptable nodal voltages and system frequency during different scenarios. The proposed stochastic optimization model is then applied to a typical autonomous MG and its effectiveness is demonstrated through different scenarios under uncertainties in load consumption and renewable energy resources (RESs) productions. Simulation results demonstrate that customers' participation in DR programs have significant effect on the system's performance in terms of voltage and frequency stability. Moreover, optimal coordination of DERs and responsive loads can increase the expected profit of MGO significantly. The effectiveness of the proposed scheduling approach is verified on an islanded MG test system over a 24-h period.Index Terms-Demand response (DR), microgrid (MG), distributed energy resource (DER), voltage and frequency security, renewable energy sources (RESs).
DR t j D BIncome of group j of customer at period t after implementing DR programs.
,t j BIncome of group j of customer at period t when the demand is at nominal value. Energy bid submitted by wind unit w (PV v) in period t (cents/kWh).Bid of the up (down)-spinning reserve submitted by DG i in period t (cents/kWh).Bid of the non-spinning reserve submitted by DG i in period t (cents/kWh).Bid of the up (down)-spinning reserve submitted by load j in period t (cents/kWh).Demand of load j in period t (and scenario s) (kW).Demand of load group j after implementing DR programs in period t (kW).Self-elasticity (Cross-elasticity) of load group j.
LFMaximum power flow from node n to r (kW).
2I. Introduction Recently, microgrid (MG) idea has been introduced to transform the conventional power systems to a more reliable, economic and environmentally friendly system. The diversified load consumption pattern and availability of power from green distributed energy resources (DERs) cause supply-demand mismatch in MGs. Optimal operation of MGs both technically and economically mainly relies on the coordination between different components including DERs, energy storage systems (ESSs), and responsive loads [1]- [2]. In grid-connected MGs, normally the economic operation is the main objective as there is a stiff-grid on upstream to support the system frequency and voltage at the point of ...