Abstract
Single-stage utility-scale photovoltaic (PV) systems are usually interfaced with the host grid via a centralized voltage-source converter (VSC). Recently, and due to their reliability, the dc-link film capacitors are favored over electrolytic types in grid-connected applications. However, the capacitance per unit volume of film capacitors is significantly smaller than electrolytic capacitors. The overall system stability might be compromised by the reduction of the dc-link capacitance, particularly in PV systems that have a dynamic resistance that varies with operating conditions. Using a detailed small-signal model of the grid-connected PV system, it is shown in this paper that the reduction of the dc-link capacitance interferes with the dynamic resistance of the PV array, which eventually leads to instabilities. The minimum dc-link capacitance that preserves the overall system stability is determined. A simple and effective active compensator is developed to mitigate the instabilities with the reduced dc-link capacitance. Detailed time-domain simulations are presented to validate the analytical results and show the proposed compensator’s effectiveness in preserving the system stability.
Highlights
Due to the global climate change concerns and the continuous growth of energy demand, renewable energy is becoming increasingly popular all over the world
Even though MPPF capacitors are the best choice for reliability, their utilization is still challenging due to the high cost and the limited capacitance per unit volume
This study reported that the dynamic stability of the dc-link voltage control might be affected when the PV generator operates in the constant current region (CCR)
Summary
Due to the global climate change concerns and the continuous growth of energy demand, renewable energy is becoming increasingly popular all over the world. This study reported that the dynamic stability of the dc-link voltage control might be affected when the PV generator operates in the constant current region (CCR). To the best of the authors’ knowledge, the impact of the dynamic resistance of PV arrays on the single-stage grid-connected VSC with a reduced dc-link capacitance was briefly and solely addressed in [13], [14]. There is no proposed solution or mitigation technique to enhance the stability of the single-stage system and facilitate the integration of the PV generators with the reduced dc-link capacitance. 2) The characterization of the dynamic interactions between the interfacing VSC with the reduced dc-link capacitance at different operating points using time-domain simulations and small-signal analysis. The modeling and control details of the overall system are provided
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