Smart voltage-source inverter with a novel approach to enhance neutral current compensation

The presence of neutral current is quite common in three-phase four-wire distribution systems due to unequal distribution of linear and nonlinear single-phase loads. However, high neutral current can overload the neutral conductor, which can cause electrical safety concerns at the installation terminals. Among neutral current compensators, the three-phase four-leg voltage source inverter (VSI) provides better control flexibility and efficient performance than the passive compensators, but requires a higher VSI capacity. To provide a solution to the aforementioned problem, this paper presents a novel control method to utilize the available capacity of a three-phase four-leg (3P-4L) VSI after active and reactive power regulation to enhance the neutral current compensation. A smart (S) VSI is designed to operate with renewable energy sources and minimize the neutral current. Case studies are conducted using commercial building actual load data in PSCAD/EMTDC software environment. The system with the proposed control method can provide improvement in the neutral current compensation, phase balancing and unbalance factor compared to a fixed capacity 3P-4L SVSI. Experimental results using a TMS320F28335 DSP microcontroller and modified Semiteach 3P-4L inverter are presented to verify the robustness of the controllers and enhancement in the neutral current compensation using the proposed capacity control method.