Improved cascaded h‐bridge multilevel inverters with voltage‐boosting capability

This paper proposes two improved cascaded H‐bridge (ICHB) multilevel inverters that feature voltage‐boosting capability. The conventional H‐bridge with a front‐end dc–dc boost converter was restructured for single‐stage operation. The developed three‐level topology not only saves one power switch but also exhibits lower voltage stress across its capacitor. Extension to five-level generation was also introduced by merely adding two power switches and one capacitor. The final five‐level topology outperforms the classical cascaded H‐bridge (CHB) multilevel inverter with a significant reduction in the power switch count, with a 42% and 50% reduction in both the isolated dc source and inductor counts. The power efficiency was also improved without compromising the modularity feature of the classical CHB multilevel inverter. The operation and theoretical analysis of the proposed topologies were validated via simulations and experimental tests

A Compact Design Using GaN Semiconductor Devices for a Flying Capacitor Five-Level Inverter

Multilevel inverters (MLIs) based on the flying capacitor (FC) concept are beneficial in many renewable energy-based applications due to their compactness, low current stress on semiconductor devices, and reasonable thermal behavior for high-power applications. However, the recently developed FC-based topologies suffer from half dc-link voltage utilization and a variable high-frequency common-mode voltage (HF-CMV). The aim of this paper is to propose an FC-based family of MLIs with a five-level (5L) output voltage, full dc-link voltage utilization, and low HF-CMV. Using redundant states and the phase-shifted sinusoidal PWM technique, the value of the flying capacitor has been reduced significantly. The performance of the converter has been verified using Gallium Nitride (GaN) power switches. Circuit description and a brief comparative study with existing MLIs are given to justify the suitability of the topology

A New Common-Ground Switched-Boost Five-Level Inverter Suitable for both Single and Three-Phase Grid-Tied Applications

Common-Ground (CG)-type multilevel inverters exhibit some interesting features in removing the concern of ground leakage current and improving the overall efficiency of the system within a single power processing stage. In this paper, a new reduced-switch count five-level (5L)-CG-based inverter is proposed, which offers a step-up voltage boosting property and can be extended to the three-phase systems whilst maintaining its CG-feature. The circuit descriptions, comparative study and the relevant measurement results for both the single and three-phase systems are presented to verify the feasibility of the proposed topology

Model Predictive Control of a Five-level Active Boost Neutral Point Clamped (5L-ABNPC) Inverter for Transformerless Grid-Connected PV Applications

Recently, an improved version of active boost neural point clamped (ABNPC) inverter with the capability to produce five output voltage levels using only six power switches has been presented in the literature. The presented modulation strategy of such inverter is based on an open-loop voltage-oriented control approach. The major advantage lies in its inherent voltage balancing of the integrated flying capacitor with the leakage current elimination capability for transformerless grid-tied photovoltaic applications. Using a fast and robust current controller-based technique, the injected grid current of the 5L-ABNPC can be tightly controlled under various dynamic conditions of the local grid. The aim of this paper is to apply two improved versions of the Finite Control Set (FCS) and Continues Control Set (CCS)-Model Predictive Control (MPC) strategies to control different operations of the discussed 5L-ABNPC inverter. The proposed solutions present an optimal switching state scheme with less computational burden for FCS-MPC and also a fixed switching frequency spectrum for the CCS-MPC. To verify the correctness of the inverter operation and its control platform, simulation and experimental results are also presented

A Dual Mode 5-Level Inverter with Wide Input Voltage Range

This paper presents a novel dual mode six- switch five-level boost-ANPC inverter (5L-DM-ABNPC) topology with wide input voltage range (400 V - 800 V). It consists of one flying-capacitor and six semiconductor switches forming a similar structure to that of conventional 5L-ANPC or 5L-ABNPC inverter. Depending on the magnitude of the input voltage, the converter can operate in buck or boost mode to produce the same ac voltage out. Further, the number and the size of the active and passive components are also reduced with simple PWM control. Consequently, this make the overall system appealing for various industrial applications. The analysis shows that the proposed topology is suitable for wide range of power conversion applications (for example, rolling mills, fans, pumps, marine appliances, mining, tractions, and most prominently grid-connected renewable energy systems). Simulation and experimental prove the concept of the proposed inverter. The principle of operation and theoretical analysis supported by key simulation and preliminary experimental waveforms are presented

Improved cascaded h‐bridge multilevel inverters with voltage‐boosting capability

This paper proposes two improved cascaded H-bridge (ICHB) multilevel inverters that feature voltage-boosting capability. The conventional H-bridge with a front-end dc–dc boost converter was restructured for single-stage operation. The developed three-level topology not only saves one power switch but also exhibits lower voltage stress across its capacitor. Extension to five-level generation was also introduced by merely adding two power switches and one capacitor. The final five-level topology outperforms the classical cascaded H-bridge (CHB) multilevel inverter with a significant reduction in the power switch count, with a 42% and 50% reduction in both the isolated dc source and inductor counts. The power efficiency was also improved without compromising the modularity feature of the classical CHB multilevel inverter. The operation and theoretical analysis of the proposed topologies were validated via simulations and experimental tests

Five-Level Grid-Tied Inverter Employing Switched-Capacitor Cell with Common-Grounded Feature

An advanced topology of single-phase five-level transformerless grid-connected inverter is presented in this paper, which offers a common ground between the input source and the null of the grid. This alleviated the concern of variable common-mode voltage and the leakage current problem, which makes the inverter suitable for grid-tied photovoltaic (PV)-based applications. The proposed topology is operated by a series-parallel switching conversion of a switched-capacitor (SC) cell. It consists of a single dc source, two power diodes/capacitors alongside six power switches. Using the SC technique, a single-stage two times voltage boosting inverter with a self-voltage balancing of the capacitors is achieved. By employing the SC cell, five distinct voltage levels are also made at the inverter's output, so a small L-Type filter can be utilized. The control/modulation of the proposed inverter is also on the basis of a new peak current controller (PCC) technique. The circuit description along with the proposed PCC operation is discussed and a brief comparative study besides the experimental results are given at the end to demonstrate the feasibility of the proposed topology