上机bug修复，命令修复添加

DeviceEditModule/ViewModels/IT7800EViewModel.cs

@@ -92,9 +92,9 @@ namespace DeviceEditModule.ViewModels
             set => SetProperty(ref _currentLimit, value);
         }
 
-        private string _selectedMode = "AC";
+        private PowerCouplingMode _selectedMode = PowerCouplingMode.AC;
         /// <summary>待设置的电源工作模式：AC / DC / ACDC。</summary>
-        public string SelectedMode
+        public PowerCouplingMode SelectedMode
         {
             get => _selectedMode;
             set => SetProperty(ref _selectedMode, value);