A Novel Family of Four-Port Three-Phase DCAC Converter and Its Carrier-Based PWM Strategy

A novel family of four-port three-phase DC-AC converter (FPTPC) topology is proposed in this paper, which has two DC ports and two three-phase AC ports. It can be combined with DC-DC to form the quasi-single-stage FPTPC whose low voltage dc port voltage can be varied over a wide range. The proposed four-port three-phase DC-AC converter topology is firstly described. Then its differences with T-type three-level dual output converter are analyzed, and the constraints that should be satisfied for the normal operation of FPTPC, the various operating modes available for the FPTPC, and the key issues such as the DC bias, modulation index range, and displacement angle constraints of the two three-phase AC outputs under different operating modes are discussed. In order to increase the output power of the low voltage (LV) DC port, a sinusoidal carrier-based pulse width modulation (CBPWM) strategy for increasing the output power of the LV DC port is proposed by analyzing the effects of the upper bias as well as the lower bias on the output power of the LV DC port, and on the basis of the above mentioned increase of the output power of the LV DC port, three non-sinusoidal CBPWM modulation strategies are also proposed to increase the utilization of the DC bus voltage. Finally, the effectiveness of the proposed topologies and their corresponding modulation schemes are verified through experimental results.