Single-stage converters based on an impedance source (IS) network merged with a multilevel inverter remain a trending research topic, from both the topological and control perspectives, because of their potential in applications involving renewable energy. This paper presents a new, simplified space vector pulse-width modulation (SVPWM) for a three-phase three-level T-type quasi-impedance source inverter (3L-T-type qZSI). The benefits of the proposed modulation strategy include functionalities, such as boosting the input voltage and controlling the neutral-point (NP) voltage using the redundant small vectors, to mitigate the inner capacitors voltages imbalance. The proposed SVPWM guarantees a minimum common-mode voltage while preserving a very simple implementation, thus reducing the complex computations and cascaded proportional-integral (PI) control loops of the conventional SVPWM methods. The proposed algorithm can be applied to different multilevel inverter configurations combined with an IS network. A comprehensive simulation study and experimental results demonstrated the good performance of the proposed control method for dynamic response and imbalance conditions.

Distributed energy resources (DER) such as solar photovoltaics (PV) are required to achieve a high performance and an efficient use of generated renewable power in grid-integrated applications, both in normal and fault operating conditions. In this paper, a grid-following multi-functional control strategy for a three-phase three-level T-type quasi-impedance source inverter (3L-T-type qZSI) is studied through simulation and experimental tests. The grid-following functionality is achieved by a PI-based dq current controller for the active and the reactive power tracking. A PI-based dc controller is used for the dc-link voltage control by taking advantage of the quasi-impedance source network ability for input voltage boosting. The dc-ac power conversion is accomplished through a space vector pulse-width modulation (SVPWM) with inner capacitors voltages balancing capability and minimum common-mode voltage generation. Besides, a low voltage ride-through strategy was implemented to fulfill the fault requirements imposed by the Spanish standard. The simulation and experimental results demonstrate the above-mentioned functionalities and validate the stability and good dynamic response of the grid-connected 3L-T-type qZSI. Thus, this work supposes a novel contribution due to the few works previously reported in the literature concerning the performance of this relatively recent inverter topology in grid-tied applications.

This paper proposes an explicit predictive current control scheme implemented with a low carrier frequency PWM on an induction machine fed by a 3L-NPC inverter. The PWM carrier and the main current sampling frequency are both set to 1 kHz, resulting in a 500 [Hz] average switching frequency per device, which is very suitable for large drive applications. The explicit predictive control is introduced to optimise the available bandwidth provided by such a low sampling frequency, maximizing the dynamic performance. The strategy has been tested in a 2.2 kW induction motor experimental prototype.