A New Step-Up Switched-Capacitor Voltage Balancing Converter for NPC Multilevel Inverter-Based Solar PV System

Amir Taghvaie,Md. Enamul Haque,Sajeeb Saha,Md. Apel Mahmud

doi:10.1109/access.2020.2992093

Amir Taghvaie, Md. Enamul Haque + Show 2 more

Open Access

https://doi.org/10.1109/access.2020.2992093

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Abstract

This paper proposed a grid connected solar Photovoltaic (PV) Systems with a new voltage balancing converter suitable for Neutral-Point-Clamped (NPC) Multilevel Inverter (MLI). The switched-capacitors used in the proposed converter is able to balance the DC link capacitor voltage effectively by using proper switching states. The proposed balancing converter can be extended to any higher levels and it can boost the DC input voltage to a higher voltage levels without using any magnetic components. This feature allows the converter to operate with the boosting capability of the input voltage to the desired output voltage while ensuring the self-balancing. In this paper the proposed converter is used for a grid connected solar PV system with NPC multilevel inverter, which is controlled using vector control scheme. The proposed grid connected solar PV system with associated controllers and maximum power point tracking (MPPT) is implemented in Matlab/SimPowerSystem and experimentally validated using dSPACE system and designed converters. The simulation and experimental results show that the proposed topology can effectively balance the DC link voltage, extract maximum power from PV module and inject power to the grid under varying solar irradiances with very good steady state and dynamic performances.

Highlights

Multilevel inverters (MLIs) are broadly used for the grid integration of solar photovoltaic (PV) systems due to several advantages such as lower harmonic distortions, less electromagnetic interference (EMI), less standing voltage on semiconductors, high output waveform quality and smaller filter size [1], [2]
The main drawback of this type of converter is capacitor voltage balancing at the input of Multilevel Inverter (MLI) in solar PV system which causes problems with the grid connected solar PV system [13]
Several methods have been suggested to solve the problem of capacitor voltage balancing of Neutral-Point-Clamped Multilevel Inverter (NPC-MLI) [14]

Summary

INTRODUCTION

Multilevel inverters (MLIs) are broadly used for the grid integration of solar photovoltaic (PV) systems due to several advantages such as lower harmonic distortions, less electromagnetic interference (EMI), less standing voltage on semiconductors, high output waveform quality and smaller filter size [1], [2]. A. Taghvaie et al.: New Step-Up Switched-Capacitor Voltage Balancing Converter balancing capability is achieved where NPC-MLIs are connected in parallel. Taghvaie et al.: New Step-Up Switched-Capacitor Voltage Balancing Converter balancing capability is achieved where NPC-MLIs are connected in parallel In this system, at least one of the inverters generates opposite voltage which limits the output voltage levels and increases the number of power semiconductors in higher voltage levels. It is worth mentioning that in NPC-MLIs, the series connection of the DC-link capacitors is used to charge the capacitors through the PV unit in order to produce high voltage levels at the output These converters with series capacitors are more vulnerable to capacitors unbalancing and voltage dynamics instability as compared to the converters using capacitors in parallel.

SYSTEM STRUCTURE

MODULATION TECHNIQUE

CALCULATION OF POWER LOSS AND CAPACITANCE

CALCULATION OF CAPACITANCE

CONCLUSION