Use of solar PV inverters during night-time for voltage regulation and stability of the utility grid

Abstract

Photovoltaic (PV) inverters are vital components for future smart grids. Although the popularity of PV-generator installations is high, their effective performance remains low. Certain inverters are designed to operate in volt-ampere reactive (VAR) mode during the night. Yet, this approach is ineffective due to the consumption of active power from the grid (as internal losses) and the regulation necessity of the direct-current (DC) bus. This paper will demonstrate the operation of a PV inverter in reactive power-injection mode when solar energy is unavailable. The primary focus is on the design of the inverter controller with respect to the synchronous rotating frame control method. The proposed novel method enables an inverter to inject the required level of reactive power to regulate the voltage levels of the utility grid within specified limits. In the process, the inverter does not absorb active power from the grid for its internal operation. The presented model has the ability to inject ≤2 kVAR of reactive power at zero power factor without absorbing active power from the grid. Simulation and hardware models of the inverter were developed and tested for different reactive loads in which the hardware model represented the real-world application. The reactive power injection of the two models ran at zero power factor and produced the expected outcomes for their corresponding independent reactive loads. Henceforth, it was evident that the proposed method can enhance the efficiency of an inverter and ensure the stability of the utility grid to which it is connected.