Multi-objective control of multi-functional grid-connected inverter for renewable energy integration and power quality service

摘要

Multi-functional grid-connected inverters (MFGCIs) not only interface renewable energy sources into the utility, but also provide ancillary power quality enhancement service. Therefore, extra installment of power quality conditioners can be partially avoided in a micro-grid including MFGCIs. Because the capacity of an MFGCI employed for power quality compensation is limited, how to balance the multiple functions and optimally utilise the limited capacity becomes a challenging for MFGCI application, and this is studied in details in this paper. First, to set up a benchmark for balancing the multiple functions of the MFGCI, a comprehensive power quality evaluation (CPQE) index is presented based on the catastrophe decision theory to quantify the power quality of a micro-grid. Then, for the strategic utilisation of the limited capacity, a multi-objective optimal compensation model is proposed in which the objectives are to optimise the CPQE index and minimise the occupied capacity of an MFGCI for power quality compensation. Finally, the solutions of the model are derived on the basis of Pareto approach. As a result, the MFGCI can flexibly customise the power quality of the micro-grid according to its available capacity margin and the users’ requirement. Finally, the experimental results performed on a 10 kVA MFGCI prototype have confirmed the validity of the proposed model.