A Novel Direct Power Control Based on Switching Table for Four-Leg Voltage Source Inverter

Due to its fast dynamic response and simple implementation, direct power control (DPC) based on switching table (SWT) has been a popular control method for three-phase three-leg voltage-source inverters (3L-VSIs). It is extensively utilized in many applications, such as motor drives, power quality control, and renewable energy systems. Nevertheless, the SWT-based DPC strategy has not yet been developed for the four-leg VSI (4L-VSI) until now. Therefore, the main objective of this article is to introduce a novel SWT-based DPC strategy to control grid-connected 4L-VSI. Unlike the existing SWT-based control with three inputs (active power p, reactive power q, and grid voltage vector position), the proposed solution incorporates an additional input: reactive power q_αβ associated with the zero-sequence voltage and current. This additional input allows for the compensation of the neutral current. In the proposed approach, neither pulse width modulation (PWM) modulator nor a decoupling block for the active and reactive powers is needed. Additionally, there is no requirement for current regulation loops, as the switching states are selected directly from the proposed SWT. Experimental results are presented to illustrate the efficacy of the proposed DPC for 4L-VSI grid connected system.