A New Three-Level Three-Phase Boost PWM Inverter for PV Applications

Multilevel converters have seen an increasing popularity in the last decades, due to the increased power ratings, improved power quality, low switching losses, and reduced Electromagnetic Interference (EMI). Amongst, the most popular ones are the three-level Neutral Point Clamped (NPC) and the Flying Capacitor (FC) inverter topologies, alongside their derivatives. However, the main drawback of the NPC and FC topologies is the high DC-link voltage demand, which is more than twice of the peak grid voltage. Therefore, a front-end boost DC-DC converter is normally required before the inverter, which decreases the overall efficiency of the system. A Single-stage DC-AC power converter with boost capability offer an interesting alternative compared to the two-stage approach. Considering this aspect, a novel three-level three-phase boost type inverter is introduced in this paper for general-purpose applications (e.g. grid-connected renewable energy). Whilst reducing the DC-link voltage requirement, the number of active and passive components remains the same or even less than the conventional NPC and FC family topologies. The principle of operation and theoretical analysis are discussed in detail. The design methodology along with simulation and experimental waveforms for a 5 kVA inverter are presented to prove the concept of the proposed inverter topology for practical applications.