Control Strategy of Three-phase Inverter under Weak Grid Condition

With the rapid development of power electronics technology, renewable energy like wind and solar energy has become increasingly popular. However, high renewable penetration may cause mutual interactions and power grid instability, which is a main reason that Australian Electricity Market Operator (AEMO) curtailed the outputs of five solar farms in VIC by 50% in 2019. This means that power grid stability under weak grid condition cannot be maintained at a good level when using traditional control strategies. This paper illustrates the performance of the proposed LCL-filter based three-phase grid forming and grid feeding inverter by using quasi-proportional-resonant (QPR) controller and comparison with conventional double loop PI control strategy.