Vref value goes low

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I am performing LVRT lag test . regulated bus voltage 0.99, inverter at maximum absorbing power. after run dynamic using REPCA1 model , Vref=0.9 after LVRT analysis , voltage is set at 0.86 as result active power is reduce by 20% . and inverter is not able to supplyring reactive power. REPCA1 paramter - reference of voltage control ( vref) L= 0.5215 as result plant controller now able to give command to machine , can some one help to get how can i increase REPCA1 paramter - reference of voltage control ( vref) L