In this work, a methodology for implementation of an automated transition of a solar PV array and battery integrated unified power quality conditioner (PV-BUPQC) between standalone and grid connected modes of operation is presented and analyzed. This system consists of a shunt and series active filters connected back to back with a common DC-link. The system addresses the issue of the integrating power quality improvement along with the generation of clean energy. Moreover, due to the automated transition, the critical loads have continuous power supply irrespective of grid availability. The key challenges addressed are implementation of automated transition in a PV-B-UPQC system with minimal disturbance to the local loads. The system operation is validated through experimentation under a number of dynamic conditions such as automated transition, supply voltage variations, unavailability of the grid, variation in solar power generation, load variation, etc., which are typically encountered in a modern distribution network.
- Power quality
- Unified power quality conditioner
- Solar PV Generation
- Battery energy storage
- Automated transition
- Constant power generation
The design and performance of solar PV and battery integrated UPQC have been presented in this work. Due to the presence of energy storage in form of battery bank, the system operates in standalone mode of operation whenever grid is not available thus maintaining continuity of power supply to critical loads. Moreover, the system mitigates power fluctuations occurring in PV power generation due to weather conditions, thus enabling smooth power generation. This leads to increased stability of the overall system. The behavior of the system under steady state has been found satisfactory and the PCC currents meet the THD limits prescribed in the IEEE-519 standard.
The response of the PV-B-UPQC has been extensively evaluated under both standalone and grid connected modes of operation. The response of PV-B UPQC is found satisfactory under various conditions of irradiation variation, load unbalance and sags/swells in PCC voltage. Under all these disturbance conditions, the PV-B-UPQC is able to feed constant power into distribution network. The system automatically changes from the grid-tied operation to islanded operation and vice versa with minimal disturbance to the sensitive and critical load. The three wire PV-B-UPQC is suitable for the systems with operating with sensitive and critical load such as in data centers, hospitals, factories where uninterrupted power supply is of prime importance. The integration of battery and renewable energy, enables minimum dependence on the grid for power demand while the surplus PV power can support the grid by giving power to nearby loads at PCC.
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