Fault ride through capability for grid interfacing large scale PV power plants

Integration of dynamic grid support is required for distributed power systems that are interconnected with medium voltage grids. This study proposes a comprehensive control solution to enhance fault ride through (FRT) capability for utility-scale photovoltaic (PV) power plants. Based on positive and negative sequence control schemes and PV characteristics, the approach alleviates dc-bus double-line-frequency ripples, reduces voltage stress on inverter power switches and DC-link capacitors, and minimises undesirable low-order voltage and current harmonics that are presented on the ac side. The study proposes a new feature to achieve superior FRT performance by using the overload capability of grid-tied inverters. A weak electric grid is used for the test case including a wind turbine induction generator, diesel engine driven synchronous generators and various loads. A comprehensive simulation verified the capability of the proposed control schemes for mitigating the voltage dip, enhancing the voltage response and further improving the stability of interconnected distributed generation in reaction to severe unbalanced voltage conditions because of asymmetrical grid faults.