Current Harmonic Distortion Suppression Method Considering the Power Interaction of Source and Load Under High Photovoltaic Penetration

With the increasing penetration of the photovoltaic (PV) in the distribution network, the harmonic pollution becomes more serious and threatening. Many control strategies are applied into PV converters or other devices to suppress the harmonic pollution caused by increased PV integration. However, an abnormal variation of the total harmonic distortion (THD) is disclosed that THD does not continuously increase with increasing PV penetration. The true current THD trend behaves as an inverted 'U' shape while PV output is increasing. This strange phenomenon changes the control logic for harmonic mitigation strategies and conventional pollution suppression methods may lose efficacy or even bring negative influence. To clarify this new phenomenon of the THD trend, the relationship between harmonic and PV penetration is clarified through mathematical derivation. Then, a novel harmonic current feedback strategy is proposed to enhance the double loop control of the inverter, in which the harmonic current is fed back to the inner loop of the inverter to reduce the harmonic content of the inverter output. As a result, the power quality is improved. Finally, a modified IEEE 33-bus distribution network model and a hardware experiment platform are established to verify the performance of the proposed control strategy.