A Center Controller reported an aircraft approaching their destination became disoriented when Tower turned the runway lights off. The aircraft descended from their assigned altitude and flew below the Minimum Vectoring Altitude.

Narrative

On the date and time identified; Aircraft X was inbound to ZZZ for landing. I noticed an unidentified track which appeared inbound to ZZZ as well. I called the Tower Controller and asked if they were talking to the aircraft. Which they said no. I asked if they do because it appeared the aircraft was inbound to let me know. I then began to plan with Aircraft X what he would like to do to avoid the aircraft. I then began to vector the aircraft with a XXL turn to begin the plan. Then the Tower called to inform me it was an Aircraft Y inbound. I told Tower the plan then was to give Aircraft X a box pattern vector and come in behind the Aircraft Y. After Aircraft X was boxed and back toward the airport I told the aircraft to report the field in sight 14 miles ahead. They continued. I then asked again if they got it at around 9 to 10 miles. This is when they informed me 'No; it seems like they are messing with the lights'.I called the Tower at ZZZ and was informed that they did turn the lights off and were conducting an Night Vision Goggle (NVG) arrival procedure with the Aircraft Y. Aircraft X was then unable to get the airfield or runway in sight as they became confused from the Tower turning the lights back on and the other lights around the airfield. I noticed the aircraft begin descending below 3000 ft. and issued a Low Altitude Alert and for them to climb and maintain 3000 ft. The aircraft was able to on an adjusted base vector at 4.5 miles get the runway for landing in sight and was able to land without incident. NVG operations should not be allowed to be conducted if there is more than one aircraft inbound to an airport of intended landing.