Power quality improvement by grid-connected inverters driven by the three-phase damping control strategy operated in different modes

The increased demand for renewable energy and electrification of transportation such as electric vehicles can lead to power quality problems in the low voltage distribution grids. Overvoltages and voltage unbalance are among the most prominent power quality challenges in these grids. Typically, three-phase distributed generation units and electric vehicle chargers are interfaced to the grid via an inverter that is driven by the three-phase positive-sequence control strategy. This control strategy cannot mitigate the voltage unbalance and perform power quality improvement. Although this control can be implemented to be bidirectional, it cannot impact the negative- and zero-sequence voltage components. In contrast to the positive-sequence control strategy, the three-phase damping control strategy reacts resistively towards the negative- and, zero-sequence components and it is able to mitigate the voltage unbalance at the point of common coupling. In this article, the three-phase damping control strategy is examined in three operating modes namely: injection mode, power draw mode and zero-input power mode. The experimental results show that the three-phase damping control strategy is able to mitigate the negative-sequence and zero-sequence voltage unbalance factors by about 1 % and 3%, respectively, within the nominal voltage range in all operating voltages. • Zero- and negative-sequence component voltage unbalance mitigation. • Voltage unbalance mitigation is achieved when the control strategy injects power. • Voltage unbalance mitigation is achieved when the control strategy consumes power. • Voltage unbalance mitigation is achieved there is no power from the primary source. • Suitable for various applications that are inverter interfaced to the grid or microgrid.