Abstract
The presented system is a three-phase three-wire (3P-3W), seamless, capable, dual-stage PV power generation system without battery storage for rural residential loads to ensure a continuous power supply during the daytime. This system effortlessly shifts from the grid-connected (GC) mode to the standalone (SA) mode when the grid utility is unavailable. During the GC mode, a voltage source converter (VSC) is regulated by the polynomial zero-attracting least mean square (PZA-LMS) algorithm-based current control scheme. During the GC mode, the power balance is achieved at the point of common coupling (PCC) by exchanging active power with the grid, whereas the VSC delivers reactive power. Considering the low efficiency of PV power generation systems, an incremental conductance (InC)-based maximum power point tracking (MPPT) algorithm is necessary for the maximum power extraction out of a PV array. During the unavailability of the grid, the presented system operates in the SA mode, when the load is delivered with PV power only via VSC. Considering the high cost of the battery storage system (BSS), bi-directional converter, and charge control circuitry incurred by rural consumers, they were omitted from the system. Without a BSS, the InC-based MPPT is executed in the derated mode, extracting the PV power to exactly match the load demand. Without derated PV power generation operation, the load may be damaged due to excess PV power flow to the load end or the load may remain underpowered, leading to load shedding or complete disconnection. A synchronous reference frame (SRF)-based voltage control scheme is responsible for the VSC control during the SA operation of the system. The presented system performance was observed and found satisfactory during the irradiation variation, load balancing, islanding, and re-synchronization of the grid. The presented system was found to carry out harmonics suppression and active and reactive power balance at the PCC during both the GC and SA modes. The grid's total harmonics distortion (THD) levels were shown to be kept below 5% as per the IEEE 519 standard in the GC mode.