Abstract:

In this paper, a novel method has been proposed and implemented to mitigate the loss of power from grid-connected solar PV systems during the grid outage condition. This loss during daytime grid outages usually occurs because of the built-in islanding feature of the commercially available grid-tied inverters. Unlike other existing grid outage mitigation methods such as; using the expensive hybrid inverters and other battery backup inverters, the proposed method introduces a battery-less topology which can avoid the significant cost of battery pack itself and associated auxiliary control circuits, its operation and maintenance. An optimized low capacity (around 5% of grid-tied inverter rating) DC-AC interface system in the form of a stand-alone inverter has been introduced to provide the reference AC bus for keeping the grid-tied solar inverter operational even during the daytime grid outage. The interface system is energized from a solar PV-powered DC bus instead of the commonly used high-capacity battery backup. The method also ensures the maximum available energy extraction from a grid-connected solar PV Plant without renovating the existing grid-tied solar inverters. The experimental validation has been done by a practical 2kWp grid-tied inverter and a 200VA stand-alone inverter interfaced solar PV system operation and control under sunny and cloudy day scenario. The proposed low-cost grid outage mitigation method is a generalized one and hence can be very useful for scalable grid-connected solar PV power plants also.

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