  This paper presents a P-Q coordination based high voltage ride through (HVRT)
control strategy for double fed induction generators (DFIGs) based on a
combined Q-V control and P-V de-loading control. The active/reactive power
injection effect of DFIG on transient overvoltage is firstly analyzed and the
reactive power capacity evaluation of DFIG considering its de-loading operation
is then conducted. In the proposed strategy, the reactive power limit of DFIG
can be flexibly extended during the transient process in coordination with its
active power adjustment, as a result the transient overvoltage caused by DC
bipolar block can be effectively suppressed. Moreover, key outer loop
parameters such as Q-V control coefficient and de-loading coefficient can be
determined based on the point of common coupling (PCC) voltage level and the
available DFIG power capacity. Finally, case studies based on MATLAB/Simulink
simulation are used to verify the effectiveness of the proposed control
strategy
