Leonardo Comparatore

This paper presents a comparative analysis of three-level (3L-NPC) and five-level (5L-NPC) Neutral-Point-Clamped converters using Finite Control Set Model Predictive Control (FCS-MPC) for reactive power compensation. The research addresses a critical gap by providing a direct performance comparison under identical operating conditions, supported by simulation and experimental validation of a 3L-NPC prototype. The study evaluates harmonic performance, dynamic response, and DC-link balance. Results demonstrate that the 5L-NPC topology significantly outperforms the 3L-NPC, achieving a simulated grid current Total Harmonic Distortion (THD) of 3.36% compared to 7.84% for the 3L-NPC. This 57.1% reduction in THD allows the 5L-NPC to comply with the IEEE Std. 519-2022 limit (<5%), whereas the 3L-NPC experimental results (9.9% THD) highlight the impact of practical non-idealities such as dead time and sensor noise. While the 5L-NPC offers superior power quality, it entails higher hardware complexity, evaluating 125 switching states compared to 27 in the 3L-NPC. These findings provide quantitative guidelines for selecting NPC topologies in high-performance grid compensation systems.

This paper deals with the implementation and performance analysis of discrete-time sliding mode (DTSM) current control applied to a seven-level cascade H-bridge converter to track three-phase reference currents for a reactive load. The converter output voltages are synthesized using a modulation scheme based on phase-shifted carrier modulation. Simulation and experimental tests have been added to demonstrate the performance of the proposed controller. At the same time, the effectiveness of the DTSM is verified under transient and steady-state conditions, respectively, by measuring the total harmonic distortion and the mean square error.

Power converter technology has expanded into a wide range of low, medium, and high power applications due to the ability to manage electrical energy efficiently. In this regard, the modular multilevel converter has become a viable alternative to ensure an optimal harmonic profile with a sinusoidal voltage at the load side. Model predictive control (MPC) is a state-of-the-art technique that has been successfully used to control power electronic converters due to its ability to handle multiple control objectives. Nevertheless, in the classical MPC approach, the optimal vector is applied during the whole sampling period producing an output voltage. This solution causes an unbalanced switching frequency of the power semiconductor, which then causes unbalanced stress on the power devices. Modulation strategies have been combined with MPC to overcome these shortcomings. This paper introduces the experimental assessment of a 7-level converter combining a simple phase shift multicarrier pulse-width modulation approach with the MPC technique. A custom test-bed based on SiC-MOSFETs switches is used to validate the proposal.

This paper presents an active power filter based on a seven-level cascade H-bridge where the main contribution is a control strategy that combines model-based predictive control, the voltage vectors of the converter output levels, the phase shift PWM technique, and suboptimal DC-link voltage control. The proposed scheme greatly simplified the overall control system, making it well suited to compensate the current harmonics distortion at the grid side, generated by nonlinear loads connected to the point of common coupling. In addition, the proposed method achieved a balancing of the capacitor voltages of the seven-level cascade H-bridge converter by using the minimum DC-link voltage sensors. This feature significantly reduced the control system complexity and provided a low computational burden. Experimental results confirmed the feasibility and effectiveness of the proposed controller.

Due to problems caused by variable switching frequency a modulated model based predictive control was proposed for different topologies and their applications. However, for cascade H-bridge multilevel converters, there is another problem, the imbalance in the dc-link voltages. This paper proposes extend the modulated model based predictive control to a cascade H-bridge 7-level STATCOM, further including a switcher of redundant states to solve the imbalance voltage issue. Simulation results show improvements in terms of mean squared error, total harmonic distortion and balance voltages in the dc-links.

Model predictive control techniques are characterized by a variable switching frequency which cause noise as well as large voltage and current ripple. In this paper a predictive control strategy with a fixed switching frequency for a single-phase active power filter, namely modulated model predictive control, is proposed. This technique produces modulated waveform at the output of the converter. The feasibility of this strategy is evaluated using simulation results to demonstrate the advantages of predictive control, such as fast dynamic response and the easy inclusion of nonlinearities. The constraints of the system are maintained but the performance of the system in terms of power quality is improved compared to the traditional model predictive control strategy.

Classical model based predictive control for single-phase cascade H-bridge multilevel STATCOM generates a variable switching frequency that produces high frequency harmonics and high stress on the power semiconductor devices. To solve these issues, in this paper is proposed a predictive control strategy operating at fixed switching frequency. The method includes a modulation stage in the predictive controller. Simulation results show increased performance of the proposed control method in terms of current ripple and total harmonic distortion.

The absence of modulator in model based predictive control technique for different converter topologies generates a variable switching frequency that produces high frequency harmonics and higher stress on the power semiconductor devices. In this paper, a novel model based predictive control strategy with a fixed switching frequency applied to a three-phase cascade H-bridge multilevel STATCOM is introduced with the aim to increase the performance of classical model predictive control. Simulation results show increased performance of the proposed control method in terms of current waveform total harmonic distortion.

Conventional model based predictive control for cascade H-bridge multilevel STATCOM produces a different switching pattern for different cells. As a consequence, stresses, DC-link imbalance and active power losses are generated among the cells. To solve the aforementioned issues, this paper proposes to include a switcher of redundant vectors on the conventional model based predictive method. Additionally, improve the performance in terms of total harmonic distortion and remain focus the reactive power compensation. Simulation results are analyzed to verify the effectiveness of this proposal.