An energy-first reconfiguration of PV Array for Multi-MPPT systems considering inverter clipping under partial shading

Abstract

Impacts of partial shading and non-uniform irradiance in photovoltaic (PV) strings, and thus, arrays, can be mitigated by Array reconfiguration (ARC). On the other hand, the power clipping and the saturation of a PV inverter can lead to energy losses in grid-connected systems with limited maximum power point trackers (MPPTs) in their inverters. However, most ARC researchers focus on mismatched-oriented reconfiguration approaches that minimize the mismatch in each PV string to make them almost uniform. These conventional approaches aim to optimize the proxies, not the final alternating-current (AC) yield energy. Therefore, we proposed a string-level energy-first ARC method based on an Acceleration-Enhanced River Formation Dynamics (AE-RFD) algorithm. The proposed method directly maximized the delivered energy while maintaining current constraints and MPPT power limits. The proposed energy-first framework optimized the array configuration at the grid-tied inverter interface, maximizing delivered energy of multi-inputs and AC-side clipping constraints. A real grid-tied PV system of 15 kVA, 6 strings, and 3 MPPTs was utilized first to evaluate the proposed method with disturbed irradiance conditions for different MPPT architectures and a second benchmark PV system of 24 strings and 8 MPPTs. Our simulation results confirmed the effectiveness of the proposed method by demonstrating energy gains exceeding 5.5% with significant clipping reduction and enhancing the mismatch index. Comparisons with the ARC that is based on particle swarm optimization (PSO), Genetic Algorithm (GA), and Differential Evolution (DE) indicated that the proposed AE-RFD-based method exhibits improved robustness and stable convergence behavior.

Keywords

energy optimization / MPPT / array reconfiguration / partial shading / river formation dynamics

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