Review, analysis and improving the utilization factor of a PV-grid connected system via HERIC transformerless approach

This paper proposed an improved Highly Efficient and Reliable Inverter Concept (HERIC) inverter with photovoltaic (PV)-grid connected power system. However, transformerless inverter based on HERIC topology is considered as one of the most reliable, efficient, and approximately leakage free inverters with the PV-grid connected systems. The main drawback of this inverter is drawing a discontinuous current from the photovoltaic generating unit. Also, continuous photovoltaic current is needed to guarantee the maximum power point tracking (MPPT) operation. Subsequently, the operation of the HERIC inverter at maximum power point tracking condition is not a clear issue. Therefore, the PV utilization factor (Kuf) value falls down to about 50%, which leads to increasing in the cost and size of the photovoltaic generator unit. In this study, derivation of the utilization factor based on the PV-grid connected through HERIC inverter analyses are presented. Also, an improved version of the HERIC inverter is introduced to remove the previous drawbacks. To validate the analysis and idea, digital simulation results are carried out for both the proposed and classical PV-grid via HERIC inverter system. The transient response of the proposed grid current controller, proportion resonance (PR) controller, is tested. The effects of parameters uncertainties on the system performance factors are also studied to validate the robustness of the control approach.