A novel harmonic control approach of distributed generation converters in a weak microgrid

This paper proposes a novel approach to compensate the voltage at the point of common coupling (PCC) and the grid line current harmonics through a distributed generation (DG) interfacing converter in a weak microgrid. In the proposed approach, the PCC voltage is indirectly derived from the measured converter output voltage, DG line current and line impedance. A voltage closed-loop controller and a current closed-loop controller are designed to achieve both functions of DG real power generation and PCC harmonics compensation. Therefore, the traditional harmonic measurement devices installed at the PCC as well as the long distance communication between the PCC and the converter are fully eliminated. In order to avoid overcompensation, a harmonic current limitation algorithm is implemented in the control loop. bBy properly dispatching the harmonic compensation capability, multiple DG unites can be connected to the same PCC in parallel with the same compensation function. Furthermore, the proposed control approach can be extended to a multi-bus microgrid, where the line impedance cannot be ignored. Matlab simulations and experimental results are presented to show the effectiveness of the proposed approach.