You can use ngInit for default:
<body ng-app="demoApp">
<div ng-controller="DemoController">
<div ng-repeat="data in selected">
<select ng-model="data.sel" ng-init="data.sel = options[$index]"
ng-options="opt.value as opt.label for opt in options">
options" ng-init="data.sel = data.sel || options[$index].value">
</select>
selected must be : {{data.sel}}
</div>
</div>
</body>