Flight Crew Commercial; Flight Crew Multiengine
Flight Crew Last 90 Days 200; Flight Crew Total 1200; Flight Crew Type 1000
Aircraft Equipment Problem Critical
Flight Crew Landed As Precaution; Flight Crew Returned To Departure Airport; Flight Crew Inflight Shutdown
Aircraft
On departure the power on our #1 (left) engine stuck at max power.  We had not noticed any abnormalities during preflight or our run ups. We continued on our flight plan; notified ATC; and attempted some troubleshooting steps to fix the issue. After about 30 minutes of flying / troubleshooting; we opted to return to ZZZ. We planned the RNAV approach; and shut the engine down while descending to the initial approach fix; rather than try to land with 1 engine at max power. We [advised ATC] as we were now single engine; and proceeded to fly the approach and land without incident.
BE90 First Officer reported returning to departure airport after the left engine was shut down in flight because power could not be reduced below max.