This paper presents a transformerless single-phase inverter topology based on a modified H-bridge based multilevel converter. The topology comprises two legs, namely, a usual twolevel leg, and a T-type leg. The latter is based on a usual two-level leg, which has been modified to gain access the mid-point of the split DC-link by means of a bidirectional switch. The topology is referred as asymmetrical T-type five-level (5L-T-AHB) inverter. An ad-hoc modulation strategy based on sinusoidal pulse width modulation (PWM) is also presented to control the 5L-T-AHB inverter, where the two-level leg is commuted at fundamental frequency. Numerical and experimental results show that the proposed 5L-T-AHB inverter achieves high efficiency, exhibits reduced leakage currents, and complies with the transformerless norms and regulations, which makes it suitable for the transformerless PV inverters market¹.

In this paper, a model-based control scheme for a DC-DC power converter as a battery charger is presented. The proposed DC-DC converter for this task is a high-gain step-down converter based on the switched inductor concept. Thus, the considered topology is able to considerably reduce the output voltage on a single stage compared to traditional step-down converters. The proposed control strategy is aimed at fulfilling the requirements of the constant current and constant voltage algorithm widely used for battery charging purposes. Given the structure of the system model, the proposed control scheme results in a multi-loop control scheme, which is structured by a PI current control loop and a PI voltage control loop. During the constant current stage, the system is required to inject constant current into the battery while the voltage freely increases. Thus, the current control loop maintains the input battery current at a constant reference value. On the other hand, in the constant voltage stage, the battery is regulated to a desired constant value. Hence, in the end, both control loops act on the system to fulfill the objective. An external battery management system is aimed at controlling the transition between both modes, considering the physical thresholds of current and voltage required by the battery to guarantee the successful charging process. Finally, the performance of the proposed control strategy for battery charging is assessed on an experimental setup.

This work presents the design of a control law based on the average model of a shunt active power filter considering an H-bridge neutral point clamped topology and its experimental validation. Therefore, the proposed controller is formed by three control loops, namely current (inner), regulation (outer), and balance control loops. The current loop aims to compensate both the displacement power factor and the harmonic distortion produced by nonlinear loads connected to the point of common coupling. To deal with harmonic current distortion, the current loop involves an adaptive mechanism based on a bank of resonant filters tuned at odd harmonics of the fundamental grid frequency. The regulation and balance loops are aimed to maintain the voltage of the capacitors forming the DC-link at a desired constant level. For this, proportional-integral controllers are designed. The design of all three loops considers the average model of the system. The performance of the proposed multi-loop control law is evaluated through numerical results and real-time experimental implementation, both considering a 2 kW academic benchmark with a constant switching frequency of 7 kHz. In order to provide harmonic distortion, a nonlinear load based on an uncontrolled diode bridge rectifier is considered. Additionally, step-load changes from 0.5 kW to 1 kW are considered for the nonlinear load. As a result, a suitable current tracking, voltage regulation, and balance are observed despite parametric uncertainties, load variations, and harmonic distortion. As a consequence, in steady state, simulation results indicate that the compensated grid current THD is 1.75%; meanwhile, the nonlinear load current THD is 52.5%. Experimental results indicate that the compensated grid current THD is 2.32%; meanwhile, the nonlinear load current THD is 53.8%.

In this paper, a solution to mitigate the leakage-ground currents in a grid-tied H-bridge neutral-point clamped inverter is presented. This solution consists in splitting the LC filter capacitor and connecting each capacitor to a DC-link terminal. The proposal is referred to as the DC-link-tied LC output filter. Out of this hardware modification, it is not necessary to increase the number of switches nor design a new modulation scheme. Furthermore, a formal analysis is provided based on the common-mode model describing the role of this particular connection of the output LC filter on the minimization of the leakage-ground current. In addition, a closed loop control strategy has been implemented to allow testing the prototype connected to the electrical grid. The mitigation of the leakage-ground currents has been evaluated under this condition as well. To validate the proposed circuit modification, numerical simulations and experimental tests have been performed in a 1 kW laboratory prototype of the H-bridge neutral-point clamped inverter with the DC-link-tied LC filter solution.

In this paper, a multistage DC-DC buck converter with a high reduction ratio is presented, based on the concept of switched inductance. The proposed converter offers significantly a higher reduction ratios compared to the conventional step-down converters. The analysis and design of the proposed multistage converter are considered for three operating regions, i.e., continuous conduction mode, boundary conduction mode, and discontinuous conduction mode. Besides, an averaged model is obtained, based on the analysis of the conduction modes. Also, a model-based control strategy is proposed to meet the proposed control objectives. Thus, a control law is designed that results in a two control loop controller, i.e., a current control loop and a voltage control loop. To highlight the advantages and disadvantages of the proposed converter, a comparison is carried out in terms of efficiency, number of components, and type of control. Finally, an experimental prototype is built to evaluate the performance of the system reducing from an input voltage of 200 V to an output voltage of 12 V. The closed-loop converter is evaluated in an experimental setup under steady-state and transient conditions.