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In this study, a multi-stage planning model of the distribution network with high photovoltaic (PV) penetration considering operational reliability is presented. The operation reliability cost consisting of three modified reliability indices is imposed in the objective function in the proposed distribution systems planning model. Additionally, the distribution network reconfiguration including microgrid is considered at the operation level to improve system operation reliability. Nonlinear expressions of modified reliability indices aggravate the complexity of the proposed planning model. To address the computational burden, the planning model is simplified as a mixed integer linear programming (MILP) model, which have an efficient computational behavior with exiting MILP solvers. The benefits of imposing operation reliability cost in the objective function and network reconfiguration including microgrid as operation strategies, are discussed. The effectiveness of the proposed model is tested by numerical results.

This article presents a novel power injection priority optimization-based control strategy for a PMSG-based wind farm. The proposed strategy seeks to provide voltage support while mitigating the frequency excursion resulting from voltage dip during the fault. To achieve this objective, the conventional fixed reactive power injection priority plan is replaced by an adaptive power injection priority plan in the proposed method. The control problem is formulated as a multi-objective function optimization problem, where the power injection priority plan is calculated by minimizing the shortfall of WF active power and maximizing the reactive power injection of WF. During the fault period, the optimized result is directly applied to the outer control of machine-side converter and grid-side converter to regulate the active/reactive power generation. The simulation system model and proposed optimal model are built in EMTDC/PSCAD and MATLAB, respectively, to verify the effectiveness of the proposed strategy. Test results demonstrate that the proposed control strategy is applicable to mitigate frequency excursion while complying with the voltage support requirement during the fault.