An Improved Hybrid Parallel Compensator for Enhancing PV Power Transfer Capability

This paper proposes an improved hybrid parallel compen-sator (IHPC) for enhancing the power transfer capability of a photovoltaic (PV) grid-connected inverter. A thyristor switched capacitor (TSC) module is used in series with a conventional inductive-coupling voltage source inverter (IVSI) to reduce the DC-link voltage. Under a low DC-link voltage, the voltage across the insulated gate bipolar tran-sistor (IGBT) will also be low, which will reduce the voltage stress of the IGBT, thereby improving the reliability and reducing the loss of the VSI. First, the mechanism of reac-tive compensation for improving the PV inverter power transmission capability is analyzed. Then, the circuit con-figuration and operating principle of the IHPC are intro-duced. After that, an optimal control strategy for the IHPC is proposed to address the resonance problem caused by the TSC connected in series with the L filter and to improve the compensation performance of the IHPC. Finally, the effec-tiveness of the proposed IHPC and the control method is validated by the simulation and experiments. The results show that the IHPC with optimal control strategy can achieve continuous reactive power compensation under a low DC-link voltage, thereby enhance PV power transfer capability.