The condition for flow to be constant is to have the pressure constant.
but since it is a storage tank, that might not be possible. if the tank has an input feed from the compressor and the delivery flow matches the inlet flow for a given period of time. then the ripples in the pressure can be filtered out with the storage tank and the pressure and flow will be more or less constant.
If the output flow stops a pressure sensor can trip the input compressor feed to the storage tank to keep the pressure constant.
If the flow required is greater that that what the compressor can deliver, the system would be unstable and would stabilize at the flow rate the compressor can deliver.
If the flow from the compressor is much higher than what is required at the delivery, then the compressor could be tripped intermittently to maintain pressure within set points to ensure the flow is constant (pressure controlled).
Or use a VFD (variable frequency drive) to operate the compressor motor at the flow required.