This paper proposes a grid-connected single-stage multilevel inverter topology as a proof of concept, which is based on the five-level packed U-cell (PUC5) and the split-source inverter (SSI) topologies. The distinctive feature of the proposed topology is that it can boost the input voltage without requiring a separate DC-DC converter, only by adding three passive components to the original PUC5: a capacitor, an inductor, and a diode. Moreover, despite the added passive components, the proposed topology can still benefit from the sensor-less voltage balancing technique originally introduced for PUC5 to balance the voltage of its flying capacitor without the need for an external controller. The voltage gain is affected by different system parameters due to discontinuous conduction mode operation. The simulation results obtained using MATLAB/Simulink verified the functionality and potential of the single-stage topology introduced.

This study presents a comprehensive analysis of the aging behavior and cycle performance of commercial lithium-ion (Li-ion) cells, with the objective of developing accurate State of Health (SoH) estimation models. Empirical data were collected through a series of cycling experiments at varied current, depth of discharge (DoD) ratings, and cycle targets, thereby creating a robust data pool. Utilizing this data, two distinct SoH estimation models were generated. The first model is a detailed analysis incorporating parameters such as cycle count, depth of discharge, and charge current. The second model is based on direct current internal resistance (DCIR) and the number of cycles. Comparative analysis demonstrates that the detailed model, developed using fine mesh tree modeling, significantly outperforms the basic linear regression model in terms of accuracy. Nevertheless, both models are viable for SoH estimation, with the simpler model offering ease of control and implementation. These models are intended to assess the SoH levels of cells collected from customers and field applications for second-life usage.

In this study, a finite control set-sliding mode controller (FCS-SMC) is applied to a grid-connected 9-level Crossover Switches Cell (CSC9) inverter. The proposed control technique is model-independent, as it selects the control actions based on the current state variables' errors rather than the past values. The control algorithm optimizes the control inputs to fulfill the reaching requirements of two designed cost functions that were derived based on the sliding mode (SM) theory. Moreover, a small permissible capacitor voltage error (hysteresis width h) is introduced to add an extra degree of freedom to the system, which allows the reduction of the average switching frequency without compromising the design requirements. The main advantages of the proposed method lie in its simplicity, absence of gain adjustment requirements, and straightforward design process. Simulation results are presented to demonstrate the effectiveness of the proposed SMC in achieving excellent dynamic performance and robustness against disturbances while controlling the capacitor voltage and grid current.

This study proposes the application of a Lyapunov-based Model Predictive Control (L-MPC) approach to a 9-level Crossover Switches Cell (CSC9) converter operating in grid connection mode. The proposed method utilizes the structure of the classical finite-control-set MPC (FCS-MPC) technique while integrating a cost function that requires no tuning. By deriving the cost function based on Lyapunov theory, the system stability is ensured. Notably, the suggested approach offers several advantages over traditional MPC controllers. Firstly, it eliminates the need for gain tuning, thereby simplifying the implementation process. Secondly, the proposed controller prioritizes stability as a key design aspect. The presented simulation results prove that the proposed controller effectively regulates the voltage of the DC capacitor around its desired value and feed a smooth sinusoidal current to the grid with low total harmonic distortion (THD) while operating at a unity power factor.

In this paper, a novel and simple controller for seven-level packed U-cell (PUC) grid-connected inverter is presented. The control method is derived based on sliding mode control theory. Making use of the measured grid voltage and computed reference grid current, the reference value of the inverter output voltage is determined. According to the calculated voltage value, the suitable control set is selected (offline) in order to satisfy the reaching conditions of two separate sliding lines. The sliding lines are defined based on the grid current and the auxiliary capacitor voltage errors. Simulation results are presented to show the effectiveness of the proposed simple controller in tracking the desired values.