Low-voltage ride-thorough capability of photovoltaic grid-connected neutral-point-clamped inverters with active/reactive power injection

• Published in: IET renewable power generation 2017-06, Vol.11 (8), p.1182-1190
• Main Authors: Dehghani Tafti, Hossein, Maswood, Ali Iftekhar, Konstantinou, Georgios, Pou, Josep, Kandasamy, Karthik, Lim, Ziyou, Ooi, Gabriel H.P
• Format: Article
• Language: English
• Subjects: active power injection; apparent power 150 kVA; apparent power 3.3 kVA; current references; dc‐dc converter; DC‐DC power convertors; dq‐frame; fault conditions; fault diagnosis; grid code requirements; grid voltage enhancement; inverter current limitation; invertors; large‐scale grid‐connected PVPP; low‐voltage ride‐thorough capability; medium‐scale grid‐connected photovoltaic power plants; medium‐voltage test‐case system simulation model; network voltage; photovoltaic grid‐connected neutral‐point‐clamped inverters; photovoltaic power systems; photovoltaic strings; point of common coupling; power grids; power supply quality; power system operators; reactive power; reactive power injection; reference circuits; Special Issue: Active Power Control of Renewable Energy Generation Systems; three‐level inverter; voltage 12.47 kV; voltage sags
• ISSN: 1752-1416; 1752-1424; 1752-1424
• DOI: 10.1049/iet-rpg.2016.0544

Low-voltage ride-thorough capability is among the challenges in the operation of medium- and large-scale grid-connected photovoltaic power plants (PVPPs). In addition, reactive power injection during voltage sags is required by power system operators in order to enhance the voltage of the point of common coupling. The performance of medium- and large-scale grid-connected PVPPs during these events is studied. An algorithm for the calculation of current references, in the dq-frame, during voltage sags is introduced, which considers the inverter current limitation, grid code requirements and the amount of extracted power from photovoltaic strings. The proposed algorithm uses the full current capacity of the inverter in injecting active or reactive powers to the grid during voltage sags, which leads in a better grid voltage enhancement. The performance of proposed control strategies is investigated on a 150-kVA PVPP connected to the 12.47-kV medium-voltage test-case system simulation model during different fault conditions. An experimental setup of the 3.3-kVA grid-connected three-level neutral-point-clamped inverter with a dc/dc converter illustrates and validates the performance of the controller in injecting required active/reactive power and supporting the network voltage.