This paper proposes a H7 current source inverter (CSI) with a single shunt-connected silicon carbide (SiC) switch and traditional H6 CSI circuitry, which could employ the superior characteristics of SiC switch to significantly increase the whole switching frequency with expected low losses simultaneously. A novel modulation scheme for H7 current source inverter is then proposed, which can significantly reduce the switching counts and meanwhile realize the zero current switching (ZCS) for the rear-end CSI circuitry. The proposed H7 current source inverter can guarantee the high performance and high efficiency with a smaller DC inductor. To some extent, the H7 current source inverter circuitry could be a universal solution for all CSI systems. Matlab simulations and experimental verifications have been presented to show the performance of proposed inverter. Index Terms--H7 current source inverter, SiC switch, zero current switching, shoot-through insertion

The current source inverter (CSI) is essentially a converter with inherent boost capability and has been preliminarily applied in the field of renewable energy generation systems. However, conventional CSIs are mostly operated independently. Several existing multilevel CSI topologies entirely rely on parallel combinations, which seems to be not very suitable for capacity expansion. To solve this issue, this paper proposes a concept of three-phase boost-stage coupled current source inverter (BSC-CSI) through the duality principle, which can output multi-level currents with a reduced number of switches as well as hardware costs. Compared with the state-of-the-art CSIs, the proposed BSC-CSI can notably simplify the implementation of the multi-level modulation scheme and meanwhile ensure the power devices switch under lower current stress. To further take full advantage of the modularity and scalability, the BSC-CSI can be constructed by hybrid using silicon-carbide (SiC) and silicon (Si) based semiconductor switches for improving efficiency. The experimental results have verified the theoretical findings.

High-power current source inverters (CSI) usually operate at a low switching frequency to reduce switching loss. To suppress low-order harmonics and simplify filter design, the selective harmonic elimination pulse width modulation (SHEPWM) technique is a feasible common modulation strategy in industrial applications. This paper proposes an operational strategy that uses an H7 current source inverter (H7-CSI) with hybrid switches to perform the SHEPWM technique. On the basis of retaining the conventional H6 inverter bridge, the commutation speed of the CSI is improved by an additional shunt-connected high-performance power switch. The proposed scheme solves the problem that the CSIs built with low-speed switches (such as GTOs) may have difficulty for implementing the setting pulse widths of null states, while further reducing the switching losses at an acceptable cost. In addition, mitigating the influence of overlap-time by optimizing the driving signal of the H6 converter bridge. Finally, simulation and experiments have verified the effectiveness of the proposed CSI scheme.