How to do PDOI for a foreign currency supplier

Hi All,
R: 12.1.3

Question : Through PDOI, How to create a CNY PO for a  USD supplier ?

Foreign Currency = USD
Base currency = CNY

I have tried several times, all failed with different error message In table po_interface_errors

Case 1 : leave rate filed as null in po_headers_interface, error is
COLUMN_NAME     ERROR_MESSAGE
RATE                          Error: Column RATE should not be NULL. (VALUE=)

Case 2 : set rate filed = gl_daily_rate.conversion_rate, error is
COLUMN_NAME     ERROR_MESSAGE
RATE                          Error: The rate value(VALUE=.159195109526235) specified is invalid.


Regards.& Thanks