Alternators will produce alternating current, which is converted to direct current by a diode pack "rectifier" which is inside the alternator. Thus, what you get out of an alternator will be DC electricity.
The alternator control unit is probably a "Voltage regulator", which senses the system voltage, and controls the alternator field power so as to control the output of the alternator to produce the required voltage. This is why most aircraft with alternators have over voltage protection systems, so if the voltage regulator quits, the alternators are taken offline, before they provide enough voltage to damage things.