The present disclosure relates to a system for controlling power walk-in for an uninterruptible power supply (UPS) being switched to receive AC power from an AC generator. The system may have a control system and a power walk-in (PWI) subsystem. The PWI subsystem may be controlled in part by the control system. The PWI subsystem may be configured to control at least one of an input current or an input power of an AC signal being provided by an AC generator during a power walk-in operation to attempt to maintain a minimum frequency of the AC signal from the AC generator during the power walk-in operation.