Abstract
The three-phase four-leg inverter (TPFLI) provides unbalanced voltage to a load or injects unbalanced current to a grid to compensate unbalanced current. However, it has a high switching loss because of the fourth leg. This paper presents a discontinuous pulse-width modulation (DPWM) method that minimizes the per-phase switching loss of the TPFLI. The discontinuous three-dimensional space-vector pulse-width modulation (3D SVPWM) can be implemented in the TPFLI by injecting the same offset voltage as the conventional DPWM of three-phase three-leg inverter (TPTLI). However, the conventional DPWM is unsuitable for TPFLI because of its unbalanced current. We demonstrate that the discontinuous phase can be chosen according to the offset direction when a voltage reference vector is specified. Based on this result, a new per-phase minimum-loss discontinuous PWM strategy is developed and compared with the conventional DPWM. This method can also be applied to the TPTLI and implemented by injecting an offset voltage generated using the inverter phase voltage reference and phase current. Furthermore, the lifespan of a TPFLI can be extended by preventing deterioration of a specific leg. The validity of the proposed method is verified through simulation and experiments.
Highlights
The three-phase three-leg inverter (TPTLI) is a power converter that connects dispersed generations (DGs), such as photovoltaic (PV) and energy storage system (ESS), to the grid
We show that the discontinuous 3D SVPWM can be implemented to the three-phase four-leg inverter (TPFLI) by injecting the same offset voltage as that of the conventional discontinuous pulse-width modulation (DPWM) of the TPTLI
The generated offset voltage is the same as the conventional MLDPWM, so the MLDPWM-PP can be applied to the TPTLI
Summary
The three-phase three-leg inverter (TPTLI) is a power converter that connects dispersed generations (DGs), such as photovoltaic (PV) and energy storage system (ESS), to the grid. We demonstrate how to select a discontinuous phase according to the offset direction when a voltage reference vector is specified To this end, we propose a carrier-based discontinuous PWM method suitable for a TPFLI, which minimizes the switching loss. As shown in (7), CBPWM generates the offset voltage by changing the phase voltage reference to its maximum, medium, and minimum values This process is the same as finding the adjacent active voltage vector by identifying the prism and tetrahedron of the 3D SVPWM. In order to implement the symmetrically aligned-class I 3D SVPWM using CBPWM, the gating time must be equalized by injecting the offset voltage This equation can be written as (7), and the switching state is shown in Fig 6(b) [26], [27]. The validity of the proposed method is verified through experimental result and numerical analysis based on (24) and (28)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
