Harmonic Resonance Analysis and Suppression Method for Transmission Cables Between Renewable Energy Sources and Power Grid

As the siting of photovoltaic or wind power is generally far from the traditional power distribution network, long transmission cables are often needed to transport electric energy. But the cable parasitic capacitance is big, the harmonic voltage in the power distribution network is apt to propagate along the transmission cable. Incorporating a resistor in the cable line terminal can effectively damp harmonic resonance, and the most optimal resistance value is equal to the characteristic impedance of the cable. Except for the fundamental power output, the grid-connected inverter of distributed generator can also be controlled as the pure resistor in continuous harmonic frequency to damp the harmonic resonance in a wide frequency domain. This paper develops the distribution parameter model of transmission cable, and analyzes the cable harmonic resonance caused by the voltage harmonics at the access point of renewable energy. Based on the active harmonic resistor, a new generation method of harmonic current reference is proposed. With the new strategy, the grid-connected inverter can serve as a pure resistor in a continuous harmonic frequency. Finally, the correctness of the theoretical analysis and the effectiveness of the proposed harmonic current control method are verified by simulation and experiment.