A Single-Stage Switched-Boost Grid-Connected Five-Level Converter With Integrated Active Power Decoupling Under Polluted Grid Voltage Condition

Abstract

Grid-connected inverters with a multilevel output voltage and an integrated dynamic voltage boosting feature are promising to achieve higher overall efficiency/power density, reduced output filter size, and better power quality. However, the input current of such a single-stage system might be pulsating with low- and high-frequency ripple contents in a single-phase grid-connected application. To tackle this challenge, active power decoupling (APD) can be used to keep the input current flat and reduce the current stress of the devices with an efficient performance. On the other hand, the grid voltage is usually nonideal in practice, polluted with the harmonics. This causes additional complexity in the closed-loop control system to maintain the injected power quality. The aim of this article is to apply a tailored closed-loop APD control on a recently proposed single-source single-stage switched-boost (SB) five-level converter leading to further enhancing its overall efficiency without adding any extra circuit components. A distinctive feature of the proposed solution is using a single proportional–resonant controller with a filtered feedforward term to achieve APD, even under a distorted grid voltage condition. This solution can also be applied to other single-stage SB-based converters as long as their input current before integration of the APD control contains a low-frequency ripple content. A 2-kW SiC-based prototype is built to validate the feasibility and accurate performance of the proposed method via experiments when connected to a grid with harmonic pollution.

Keywords

• Active power decoupling (APD)
• grid voltage disturbance
• single-stage multilevel inverter
• switched-boost (SB) technique