Abstract
For enhancing the stability of the microgrid operation, this paper proposes an optimization model considering the small-signal stability constraint. Due to the nonsmooth property of the spectral abscissa function, the droop controller parameters’ optimization is a nonsmooth optimization problem. The Sequential Quadratic Programming with Gradient Sampling (SQP-GS) is implemented to optimize the droop controller parameters for solving the nonsmooth problem. The SQP-GS method can guarantee the solution of the optimization problem globally and efficiently converges to stationary points with probability of one. In the current iteration, the gradient of the nonsmooth function can be evaluated on a set of randomly generated nearby points by computing closed-form sensitivities. A test on the microgrid system shows that the optimality and the efficiency of the SQP-GS are better than those of the heuristic algorithms.
Highlights
Microgrid is an alternative solution to integrate distributed energy resources (DERs)
Due to the negligible physical inertia of power-electronic converters, the microgrid operation is susceptible to random disturbances, such as variability of distributed generation (DG) and random load fluctuations [3], like charging for electric vehicles [4], especially in an islanded mode. e small-signal stability of an islanded microgrid is critical for its reliable operation
Droop control, following a predefined droop coefficient, is widely used to maintain the proportional load sharing between DERs [5]. e small-signal stability of the microgrid in islanded mode is strongly affected by the droop controller parameters. erefore, it is essential to optimize the controller parameters to enhance the small-signal stability of an islanded microgrid
Summary
Microgrid is an alternative solution to integrate distributed energy resources (DERs). E small-signal stability of the microgrid in islanded mode is strongly affected by the droop controller parameters. Erefore, it is essential to optimize the controller parameters to enhance the small-signal stability of an islanded microgrid. E study in [7] proposed a method for optimizing the controller parameters of dynamic droop control for a microgrid in islanded mode and used a spectral abscissa objective function to consider small-signal stability. E study in [8] tried to optimize proportional-integral (PI) current controller parameters considering three design criteria and multiple operating conditions which include grid-connected mode and different islanded modes by a weighted sum of multiple objective functions. Erefore, droop controllers with optimized parameters can enhance the small-signal stability of the microgrid in islanded mode. E LC filter and coupling inductance can remove the harmonic wave near the switch frequency; and the smallsignal stability model of the LC filter and coupling inductance are given by
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