Updated

controllers.application.js

import Ember from 'ember';
const { isBlank } = Ember;

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  
 	names: ['one', 'two', 'three', 'four'],
  actions: {
    toggleSelect() {
      let trigger = document.querySelector('.ember-power-select-trigger');
      let event = new MouseEvent('mousedown');
      trigger.dispatchEvent(event);
    }
  }
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
<div id="ember-basic-dropdown-wormhole"></div>

<button id="myButton" type="button" name="button" class="" style="padding: 10px; margin-bottom: 20px; cursor: pointer;" onclick={{action "toggleSelect"}}>My Button</button>

{{#power-select-multiple
  closeOnSelect=false
  options=names
  selected=name
  triggerComponent=testbutton
  placeholder="Select some values..."
  onchange=(action (mut name))
  dropdownClass="feedback-tags-power-select feedback-tags-power-select--core"
  as |name|}}
		{{name}}
{{/power-select-multiple}}
<br>
<br>

twiddle.json

{
  "version": "0.12.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.12.0",
    "ember-template-compiler": "2.12.0",
    "ember-testing": "2.12.0"
  },
  "addons": {
    "ember-data": "2.12.1",
    "ember-power-select": "1.9.5"
  }
}