EMB-170 First Officer reported an electrical malfunction when starting the descent which affected multiple display screens in the cockpit with associated EICAS messages. The flight landed and was towed to the gate by maintenance.

Narrative

Flying with Captain as the PF and myself as the PM. We had just gotten instructions to descend VIA the ZZZZZ arrival into ZZZ. We had gotten an arrival change off of the ZZZZZ1 and we were set up for ILS XXL. We were headed to ZZZZZ2 intersection in the turn back to ZZZZZ3. The arrival was already briefed; and we were about to build; bug and brief the ILS XXR approach. The power flickered in the flight deck and immediately the DU1 (Display Unit) and DU4 cut out and DU2 and DU5 reverted to the PFD (Primary Flight Display) screens. The EICAS Screen remained in EICAS Mode and was displaying a plethora of messages. CCD2 (Cursor Control Device) and MCDU1 (Multipurpose Control Display Unit) cut out and did not restart. The auto pilot and auto throttles disconnected and the MCDU2 unit displayed a series of messages to include GPS1 Fail; ACARS No comm; and other messages that were cleared so I could get back to the radio page. The captain immediately took control of the aircraft as we started a quick damage scan to see if anything else was wrong. After the initial Cautions were silenced; the captain noticed the VNAV and LNAV functions were unavailable and instructed me to tell the controller that we were unable to descend VIA due to an electrical issue and that we would get back to them with anything else after we evaluated the status of the aircraft. We then were assigned an altitude and heading. At this point the captain called for a start of the APU to get an additional source of electrical power to the aircraft; and I did such. The loss of power had caused the Emergency Lights to activate and that prompted the FA's (Flight Attendants) to call the front. They were instructed that there was an electrical issue and to go ahead and secure the cabin. After verifying that the captain had positive control still; I pulled out the QRH and started looking for the first messages that had chevrons next to them. The 3 that were chevroned and that were run to completion were AC BUS 1 OFF; DC BUS 1 OFF and AVNX MAU 1B FAIL (Modular Avionics Unit). As this was happening; we decided it would be best to go direct to the field as we only had a few extra lbs of fuel due to flow control and rerouting and did not want to add low fuel to the list of issues. Other than the initial though; no other worries of low fuel came up. During the exchange with ATC; and while we were trying to see if we were going to be able to get any of the systems back ATC [provided priority handling] for us and asked for fuel and souls. They were given the current fuel on the aircraft and that there were 76 souls. ATC then asked what runway we wanted. The decision was made to use runway XXL as that was the runway we were already set up for and we weren't sure if we could change aircraft configuration to assist with the reception of the ILS of the XXR runway and that it would be a quick response for the fire truck should they be needed. During the running of the checklists; reading out the inoperative items included nose wheel steering. The captain acknowledged the outage and was prepared to stop on the runway. The checklist also called for a Full flap landing and then immediately had me calculate a rough landing distance; new speeds; and a configuration change in the working FMS. After running the QRH for AVNX MAU 1B FAIL; I looked up as the captain was calling for assistance in configuring the aircraft for landing. We were probably about a 10-mile final; and the decision was made to hold further checklists and to configure the aircraft. After the aircraft was configured; I pushed the V/L button on my panel to check to see if the ILS would receive and it did. I used this; in conjunction with visual references as the field was VMC; to make appropriate speed and altitude callouts to the captain to assist in situational awareness about the aircraft's position. The captain landed the aircraft; and I made sure to remind that the thrust reverser 1 would beinoperative (per the QRH) so to be cautious if using them. There was an unusual vibration felt on roll out; like a nose wheel shimmy on a small GA aircraft. The captain was able to use the rudder pedals to steer the aircraft off the runway using the highspeed taxiway 1 and then was able to steer safely into the runway XYR runup block. We were then checked and cleared by ARFF (Airport Rescue and Firefighting) and Operations. We waited approximately 30 minutes for the Tug to be brought to us; then were towed to the gate where passengers were able to deplane safely. Maintenance had met the aircraft out at the runway and took the aircraft from us as we deplaned.