позднее статическое связывание

Active.php

<?php

namespace app\modules\admin\models;

use yii\db\ActiveRecord;

class Active extends ActiveRecord
{
    public static function getDb()
    {
        return \Yii::$app->db2;
    }
}

db2.php

<?php
/**  app/config */
return [
    'class' => 'yii\db\Connection',
    'dsn' => 'mysql:host=localhost;dbname=active',
    'username' => 'root',
    'password' => 'password',
    'charset' => 'utf8',
];

Type.php

<?php
/** MODEL TYPE */
namespace app\modules\admin\models;

class Type extends Active
{
  ...
}

TypeController.php

<?php

namespace app\modules\admin\controllers;

use app\modules\admin\models\Type;

public function actionCreate()
    {
        $model = new Type();

        if ($model->load(Yii::$app->request->post()) && $model->save()) {
            return $this->redirect(['view', 'id' => $model->id]);
        }

        return $this->render('create', [
            'model' => $model,
        ]);
    }

web.php

<?php
/**  app/web */
$db = require __DIR__ . '/db.php';
$db2 = require __DIR__ . '/db2.php';
'components' => [
       'db' => $db,
       'db2' => $db2,
  ];
...