Publication: Low-Voltage-Ride-Through Control of a Modular Multilevel Single-Delta Bridge-Cell (SDBC) Inverter for Utility-Scale Photovoltaic Systems
Date
2018
Authors
Sochor P.
Tan N.M.L.
Akagi H.
Journal Title
Journal ISSN
Volume Title
Publisher
Institute of Electrical and Electronics Engineers Inc.
Abstract
This paper presents theoretical and experimental discussions on low-voltage-ride-through operation of a modular multilevel single-delta bridge-cell (SDBC) inverter intended for utility-scale photovoltaic (PV) systems. Modern grid codes require grid-tied inverters to provide dynamic grid support during grid-fault events by injecting reactive current. This paper discusses decoupled positive- and negative-sequence reactive-current control, focusing on asymmetric voltage sags with imbalanced magnitude and phase relationships. The main objective is to present a feedforward control method based on calculation of the zero-sequence current required for achieving power balance during normal and grid-fault conditions. Moreover, this paper demonstrates a practical method that minimizes overcurrent stress in the three inverter clusters by adjusting active power drawn from PV arrays. Experimental results on a three-phase 12.6-kVA system prove that the SDBC inverter is capable of seamlessly operating through asymmetric voltage sags. � 1972-2012 IEEE.
Description
Bridge circuits; Capacitors; Cascade control systems; Electric inverters; Feedforward control; Photovoltaic cells; Power quality; Quality control; Voltage control; Feedforward control methods; Grid fault conditions; Low voltage ride through (LVRT); Low-voltage ride-through; Medium voltage; Modular multilevel cascade inverters; Photovoltaic systems; Zero sequence current; Electric power system control