A quasi-Z-source active neutral point clamped inverter topology employingsymmetrical/unsymmetrical boost modulation control scheme for renewableenergy resources

Abstract

This paper proposes a bipolar quasi-Z-source active neutral point clamped inverter (QZS-ANPCI) topology. It acts as a buck/boost inverter (3-phase, 3-level) to integrate renewable energy resources under their fluctuating DC voltages. We propose a symmetrical/unsymmetrical boost modulation control technique to mitigate the DC-link unbalance voltage problem in an ANPC inverter. This worthwhile control technique exploits voltage-current closedloops on AC and DC sides to regulate the desired parameters. Moreover, the constant boost control (CBC) modulation has provided a switching sequence that generates a symmetrical/unsymmetrical full shoot-through (FST) state for boosting input DC voltage in the proposed inverter. Detailed loss and efficiency analysis is carried out to show its superior performance under the proposed scheme. Furthermore, the total harmonic distortion (THD) of the proposed QZS-ANPCI meets IEEE Standard-519. Simulink/MATLAB (MathWorks, USA) and PSIM (Powersim, USA) software programs are used to simulate the proposed topology. To verify the theoretical proposals and simulation results, we have developed an experimental prototype setup (1 kW). Both simulation results and experimental data show satisfactory agreement and support the theoretical postulates. Key words: Z-source inverter, quasi-z-source inverter, buck/boost inverter, neutral point clamped inverter, active neutral point clamped inverter 1. Introduction Renewable energy resources (RERs) are penetrating into electrical power systems. This trend is due to the rising inevitable problems of global warming. The main reason is the excessive consumption of fossil fuel for energy generation. Over the years, several RERs such as solar, wind, hybrid solar-gas, and biomass resources have been explored and developed for alternative power generation [1]. Power conditioning converters are mandatory to interface RERs with utility grid systems. Therefore, the voltage-fed inverter (VFI) and the current-fed inverter (CFI) are two main conventional power inverters that synchronize these resources with interconnected utility grids. These converters do not have the boost ability during low DC input voltage. Instead, they require separate DC-DC boost converters at their input stage. The Z-source inverter (ZSI) [2], developed in 2003, has a built-in buck/boost characteristic to overcome the above problems. The ZSI exploits unipolar X-shaped impedance (Z) * Correspondence: rehan_majeed2008@yahoo.com This work is licensed under a Creative Commons Attribution 4.0 International License.integrated with the conventional inverter. It contains capacitors (C) and inductors (L) as passive components.Due to its inherent characteristics, classical converters, such as DC-DC, AC-DC, DC-AC, and AC-AC, can have buck/boost ability working together with the same impedance [3].An improved form of the ZSI is the QZSI to overcome its problems. There are four distinct QZSI topologies for RERs. These topologies have various advantages, such as a continuous input current, lower componen...