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Aiming at the issue of zero-sequence current (ZSC) in the dual-inverter fed open-end winding transformer (OEWT-DI) based photovoltaic (PV) grid-tied system with common DC bus, a carrier-based pulse width modulation (CBPWM) strategy with steerable zero-sequence is proposed. The modulation wave of the dual-inverter is decomposed into two modulation waves with same amplitude and 120° phase difference, and each of the modulation waves is modified through adding steerable zero-sequence component. The zero-sequence component is regulated by the ZSC control loop based on a quasi-proportional resonant regulator, which is designed to suppress the ZSC caused by the dead-time effect and other nonlinear factors. Meanwhile, the effective modulation range is also analyzed. The proposed strategy is an alternative approach to the conventional zero-sequence steerable phase shift based space vector pulse width modulation (SVPWM) strategy, but has the advantage of easy implementing and low computation cost. With the proposed strategy, both the high-frequency and low-frequency ZSC in the system can be effectively suppressed. Effectiveness of the proposed strategy is validated by experimental results on a 30-kW OEWT-DI experimental platform.

Vehicle-to-everything (V2X) communications are regarded as the key technology in future vehicular networks due to its ability in providing efficient and reliable massive connections, improving traffic efficiency and safety, and supporting in-vehicle entertainment and working. Recently, non-orthogonal multiple access (NOMA), as a promising solution in the fifth-generation (5G) mobile communication systems, has drawn much attention because it can significantly improve the network throughput and lower the accessing and transmission latency to meet the quality-of-service (QoS) requirements of many 5G-enabled applications. Noticing these, in this paper, we consider a device-to-device (D2D)-enhanced V2X network, in which NOMA is introduced to increase the capacity. In our studied NOMA-V2X system, except for the NOMA-based intra-group resource reuse, the D2D-enabled resource sharing based on spatial reuse among all the V2X communication groups is also permitted through centralized resource management, leading to a significantly improved network performance but a more complicated and challenging interference scenario. In order to efficiently manage the interference and allocate the resource in the NOMA-V2X network, we create a weighted 3-partite interference hypergraph (IHG) to imitate the complex interference environment in our studied scenario. Then, with the help of this hypergraph, we make another step to put forward an IHG-based 3-dimensional matching (IHG-3DM) resource allocation protocol with a greedy 3DM algorithm and an iterative 3DM algorithm. As a consequence, the network throughput is significantly improved with the help of our proposed IHG-3DM resource allocation protocol for the investigated NOMA-integrated V2X communications, which is verified by the simulation results.

Owing to the necessity of the transformer for the multi-parallel inverters connected to the medium-voltage (MV) grid, the conventional multi-parallel inverter topology can be reconfigured to the dual-inverter fed open-end winding transformer (DI-OEWT) topology to obtain lower output voltage harmonics, which can reduce the requirement of the filter inductance. However, due to the special structure of the DI-OEWT topology, the arrangement scheme of the filter can be more than one kind, and different schemes may affect the filter performance. In this paper, research on the existing two kinds of filters, as well as a proposed one, for the DI-OEWT topology used in photovoltaic grid-tied applications is presented. The equivalent circuits of these filters are derived, and based on this, the harmonic suppression capability of these filters is analyzed and compared. Furthermore, a brief parameter design method of these filters is also introduced, and based on the design examples, the inductance and capacitance requirements of these filters are compared. In addition, these filters are also evaluated in terms of the applicability for fault tolerance. At last, the analysis is verified through an experiment on a 30 kW dual-three-level inverter prototype.