Implementation of a Stable Solar-Powered Microgrid Testbed for Remote Applications

Abstract

An intrinsically stable microgrid, operated by inverter-interfaced distributed energy resources (I-DERs) is introduced in this paper. The microgrid is built upon a systematic design method, which is adapted from the operation of the synchronous machine (SM). The proposed method analogizes the dynamics of the dc-link in I-DERs to the rotor dynamics in synchronous generators (SGs) and utilizes the capacitor as energy storage. Thus, the proposed mechanism relaxes battery usage for frequency control, and by using the capacitive stored energy, provides a high fault ride-through capability, which is suitable for both on-grid and off-grid applications. Based on stability analysis of the SG and the dynamic state matrix eigenvalues for multimachine power system, the dc-link capacitor of I-DERs is characterized in the context of microgrid. The dc-link capacitor stores kinetic energy similar to the rotor of the SG and provides inertia in transients without the need of battery storage. The inverter angle responds to the change of the dc link voltage (energy). The dc-link voltage is then controlled similar to the field control pertaining to the SG. Finally, a governor-like mechanism is applied to maintain dc-link voltage stability. Simulation and experimental results are provided to show the effectiveness of the proposed design mechanisms.

Integration and Control of Distributed Renewable Energy Resources

“…In addition, the power fluctuations of DRER adversely affect the operation of power systems [6]. From the grid perspective, technical concerns associated with the high penetration of renewables with intermittent nature include energy management [7,8], forecasting [9,10], power quality (e.g., variations of voltage and harmonic issues) [5], grid stability [11], reliability, and protection issues.…”

On the Optimal Selection and Integration of Batteries in DC Grids through a Mixed-Integer Quadratic Convex Formulation

“…Electrical distribution networks have experienced important paradigm shifts associated with the large-scale insertion of renewable generation based on photovoltaic and wind sources in conjunction with energy storage technologies mainly focused on chemical storage [1][2][3][4]. All of these devices are interfaced with the distribution network through the implementation of power electronic converters with alternating current (AC) and direct current (DC) conversion stages as a function of the device interconnected and the technology of operation of the distribution grid, i.e., AC or DC network [5,6].…”