Level Doubling Network and Ripple Correlation Control MPPT Algorithm for Grid-Connected Photovoltaic Systems

The implementation of ripple correlation control (RCC) algorithms for maximum power point tracking (MPPT) schemes in PV generation systems is presented and discussed in this PhD thesis in order to improve static and dynamic performances. Improvements in RCC are introduced first, considering fast irradiance transients and a hybrid RCC scheme is proposed. Power quality of the PV generation system is improved by multilevel inverter implemented by level doubling network (LDN), reducing output voltage and current harmonics. Reference is made to single-phase single-stage multilevel PV generation systems, when the inverter input variables, actually PV voltage and PV current, have multiple low-frequency (ripple) harmonics. The harmonic analysis is carried out with reference to a multilevel configuration consisting in H-bridge inverter and level doubling network (LDN) cell, leading to a multilevel inverter having the double of output voltage levels compared to the basic H-bridge inverter topology (i.e., five levels vs. three levels). The LDN cell is basically a half-bridge fed by a floating capacitor, with self-balancing voltage capability. The multilevel configuration introduces additional PV voltage and current low-frequency harmonics, perturbing the basic implementation of the RCC scheme (based on the 100 Hz component in case of 50 Hz fundamental), leading to malfunctioning. The proposed RCC algorithm employs the PV current and voltage harmonics at a specific frequency for the estimation of the voltage derivative of the power dP/dV (or dI/dV), driving the PV operating point toward the MPP in a more precise and faster manner. The steady-state and transient performances of the proposed RCC-MPPT schemes have been tested and compared by MATLAB/ Simulink. Results have been verified by experimental tests considering the whole single-phase multilevel PV generation system, including real PV modules, multilevel IBGTs inverter, and utility grid

Common-Ground-Type Single-Source High Step-Up Cascaded Multilevel Inverter for Transformerless PV Applications

The cascaded multilevel inverter (CMI) is one type of common inverter in industrial applications. This type of inverter can be synthesized either as a symmetric configuration with several identical H-bridge (HB) cells or as an asymmetric configuration with non-identical HB cells. In photovoltaic (PV) applications with the CMI, the PV modules can be used to replace the isolated dc sources; however, this brings inter-module leakage currents. To tackle the issue, the single-source CMI is preferred. Furthermore, in a grid-tied PV system, the main constraint is the capacitive leakage current. This problem can be addressed by providing a common ground, which is shared by PV modules and the ac grid. This paper thus proposes a topology that fulfills the mentioned requirements and thus, CMI is a promising inverter with wide-ranging industrial uses, such as PV applications. The proposed CMI topology also features high boosting capability, fault current limiting, and a transformerless configuration. To demonstrate the capabilities of this CMI, simulations and experimental results are provided

Power Converters in Power Electronics

In recent years, power converters have played an important role in power electronics technology for different applications, such as renewable energy systems, electric vehicles, pulsed power generation, and biomedical sciences. Power converters, in the realm of power electronics, are becoming essential for generating electrical power energy in various ways. This Special Issue focuses on the development of novel power converter topologies in power electronics. The topics of interest include, but are not limited to: Z-source converters; multilevel power converter topologies; switched-capacitor-based power converters; power converters for battery management systems; power converters in wireless power transfer techniques; the reliability of power conversion systems; and modulation techniques for advanced power converters

A New Topology of Cross-Switched Multilevel Inverter

This study proposed a Multilevel Inverter (MLI) topology that generates a high number of output voltage levels with a reduced number of components. The proposed topology was configured with symmetrical, asymmetrical, and hybrid configurations. Each configuration generates a different level of output voltage. In parallel to the increased output level, the output voltage has a better output quality (i.e., a lower percentage of total harmonic distortion), simple design and less demanding operation

Advanced Modeling and Research in Hybrid Microgrid Control and Optimization

This book presents the latest solutions in fuel cell (FC) and renewable energy implementation in mobile and stationary applications. The implementation of advanced energy management and optimization strategies are detailed for fuel cell and renewable microgrids, and for the multi-FC stack architecture of FC/electric vehicles to enhance the reliability of these systems and to reduce the costs related to energy production and maintenance. Cyber-security methods based on blockchain technology to increase the resilience of FC renewable hybrid microgrids are also presented. Therefore, this book is for all readers interested in these challenging directions of research

A modular interleaved converter for output current ripple minimization in dc fast chargers for electric vehicles

In this work, a DC off-board fast battery charger topology is presented, designed, and tested. It is expected to be able to fight the range anxiety by significantly diminish the EVs' charging times up to 15-20 minutes, meanwhile keeping low manufacturing, Operation and Maintenance (O&M) costs. The charger is made out of two main power stages the AC/DC and DC/DC converters. In order to keep the costs lower as possible, both parts are designed using interleaved topologies organized by using the same two-level three-phase modules coupled through reactors. This architecture allows to use the already well-known industrial three-phase modules taking advantage of the benefits guaranteed by mass production and at the same time permitting an effortless expansion thanks to its modularity. Thanks to the interleaved connections, it is possible to reach a high efficiency by distributing current and power evenly among the legs. Furthermore, this topology can handle bidirectional power flows, and it might be used for operating in both Grid to Vehicle (G2V) and Vehicle to Grid (V2G) modalities. In order to reduce the dimensions, and the costs of the filters, a control strategy able to keep a zero current ripple at any operative condition is developed. The proposed charger architecture uses an AC input BUS followed by an active rectifier stage. A ripple-free strategy acts on the variable DC BUS voltage according to the chopper duty cycle keeping the current ripple null. Meanwhile, DC/DC provides the requested output current. This strategy involves the AC/DC with the tasks to regulate the DC BUS voltage level and correcting the input power factor. A model-based control system ensures that every leg’s current follows an average current reference signal. Legs’ currents are actively rebalanced throughout a current rebalancing network. Finally, the simulation results are carried out trough MATLAB Simulink and validated with laboratory measurements on an adequately scaled prototype

Hughes electrical and electronic technology

10th edition, 200

Input current and voltage ripple analysis in ldn cells for h-bridge multilevel inverters

This paper deals with the analysis of the input dc-link voltage ripple in multilevel inverter based on H-bridge and level doubling network (LDN). The LDN is basically a half-bridge fed by a floating capacitor, with voltage self-balancing capability, recalling the concept of a flying capacitor configuration. The amplitude of the LDN voltage ripple is analytically determined considering both the low-order and the switching harmonic components. In particular, peak-To-peak distributions of voltage ripples over the fundamental period are analytically determined, making possible the design of dc-link capacitor relying only on the dc-voltage ripple requirements. The case study makes reference to negligible switching ripple in the output current. It well represents either grid connection or passive load having almost sinusoidal currents. Numerical simulations carried out by MATLAB/Simulink and a complete set of experimental verifications are given to confirm the theoretical developments