Presentation Details
| Voltage-Guided MPPT Curtailment for Active DC-Link Protection of Grid-Forming Inverters During Fault Arnab Acharya, Raja Ayyanar. Arizona State University, Tempe, AZ, USA |
Abstract
Solar PV grid-forming inverters must comply with stringent low-voltage ride-through (LVRT) requirements while safeguarding power semiconductor devices. During grid faults, current limiting constrains the inverter’s real-power transfer capability. If maximum power point tracking (MPPT) continues to extract the full available PV power, the resulting power mismatch charges the DC-link capacitor and can drive the DC-link voltage beyond safe operating limits, potentially triggering protective shutdown or stressing converter hardware. This work presents an active DC-link protection strategy that suspends MPPT and curtails PV power during LVRT to preserve DC-link energy balance. The central concept is to regulate the PV power reference using the inverter d-axis voltage as a fast, inverter-aware signal during the fault interval. Because the d-axis voltage directly reflects the converter’s available voltage and thus its power-transfer capability under current-limited operation, it enables inverter-aware PV power reduction to prevent DC-link overvoltage, without relying solely on slower outer-loop DC-link regulation. In contrast to passive approaches such as using braking choppers or resistors, the proposed method maintains DC-link stability without dissipative protection hardware, reducing cost and losses. Moreover, the strategy is agnostic to the underlying current-limiting scheme, facilitating integration across a broad range of PV grid-forming inverter controllers and limiter designs. The proposed approach is supported by controller-level insights and validated using PLECS simulations under LVRT conditions, demonstrating stable DC-link voltage throughout the fault period.
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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.