Grid-Tied Photovoltaic System under Non-ideal Source Voltage with Battery Energy Storage

Abstract

A Photo-Voltaic (PV) generator can be considered as a DC power supplier, AC source of power using a stand-alone inverter, or a grid-connected inverter. Unfortunately, the PV generator fails to produce power at its full capacity during low light condition or night, which force the whole system to be removed from the grid. Moreover, the frequent parallel operation and break-up actions make the control of the system more difficult. To overcome these difficulties multi-functional inverters along with Battery Energy System (BESS) can be used. Multi-function highlights the uninterrupted utilization of the inverter even when there is no light or at night. It can compensate for reactive power and harmonics of the connected load, ensuring unit power factor operation of the grid under distorted source voltage. Whereas, during strong sunlight, it can deliver active power to the grid and compensate for the reactive power of the load simultaneously. Grid integration of photovoltaic systems through various configurations is developed and performance is analyzed in this thesis to address the improvement using BESS. The photovoltaic inverter is a crucial element of a grid-connected DC system for the flow of power from the PV to a utility grid. There lies an opportunity to utilize the PV inverter for some other electrical issues such as load reactive power and harmonic compensation, apart from sending the power to the utility grid. This multi-functional application offers an opportunity as well as a challenge to utilize the PV inverter to achieve the above-cited objectives simultaneously in a coordinated manner. The coordinated regulation of active and reactive power, as well as harmonic compensation, can be successfully carried out using power theories such as Instantaneous Reactive Power (IRP) theory or using Instantaneous Active and Reactive Current Component (id−iq) methods. Under non-ideal source voltage, which includes distortion, voltage sag, and voltage swell phenomenon, the traditional methods do not yield the desired results. The variations in magnitude, unbalanced three-phase voltage waveform, and distorted source voltage waveform both for single-phase and three-phase are the frequently encountered conditions for which it can be termed as non-ideal source voltage. The proposed thesis work formulates the appropriate configurations to address these power quality issues under special circumstances with grid-connected solar PV and Battery Energy Storage Systems under non-ideal mains voltage.