Fault Ride-Through Capability for Grid-Supporting Inverters

Voltage control strategy has been observed as being more advantageous than current control strategy for microgrid applications where grid-connected and standalone operation of grid-supporting inverters are desired. Voltage control, however, limits the ability to directly control the inverter current. As a result, the fault ride-through or the low-voltage ride-through (LVRT) capability becomes more challenging to address. This paper develops a method for addressing this challenge by adding an auxiliary controller to the main voltage control system to enable the inverter to ride through the grid faults and inject a balanced current with controlled real and reactive components. Moreover, soft transition into the fault and out from the fault is achieved by the proposed controller. Derivations, partial stability analysis and detailed simulation results are presented.