Presentation Details
| Development of Grid-Forming and Grid-Following Control for Photovoltaic Systems Under Inverter Control Po-Yu Chen, Jian-Zhang Li, Che-Yu Huang, Kuo-Yuan Lo, Jiann-Fuh Chen. National Cheng Kung University, Tainan, Taiwan |
Abstract
With the increasing penetration of inverter-interfaced renewables such as photovoltaic (PV) systems, the equivalent inertia of modern power systems is reduced, making grid frequency dynamics more sensitive to disturbances. Using a two-stage PV system as an example, in the grid-connected Grid-Following (GFL) mode, the front-end DC-DC converter implements maximum power point tracking (MPPT). At the same time, the back-end inverter synchronizes to the grid voltage via a phase-locked loop (PLL). It regulates the grid-injected currents relative to the grid voltage phase, thereby satisfying grid-code requirements and power-quality constraints. In the Grid-Forming (GFM) mode, the front end primarily regulates the DC-link voltage and implements a power-curtailment strategy, shifting the PV operating point to the right of the MPP on the P–V curve; as a result, the delivered active power can be lower than the MPPT level. Meanwhile, the inverter behaves as a voltage source with internal voltage and frequency references. It can provide virtual inertia and damping via a virtual synchronous generator (VSG) or droop control, thereby supporting stand-alone (SA) and weak-grid operations. A two-stage PV conversion system is developed on a three-phase, three-level neutral-point-clamped (3L-NPC) inverter platform and validated in MATLAB/Simulink on a 100 kVA system with an 800 V DC input, a 220 Vrms AC output, a 50 kHz switching frequency, and a 60 Hz grid frequency. The results demonstrate the intended mode-dependent behavior and robust steady-state performance.
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No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the author.