Get Product By Product Type Id

1. Get your products in 3 different collections using addAttributeToFilter where attribute name is type_id. For the condition you can use

Mage_Catalog_Model_Product_Type::TYPE_SIMPLE, Mage_Catalog_Model_Product_Type::TYPE_CONFIGURABLE and Mage_Catalog_Model_Product_Type::TYPE_GROUPED.

 

Example:

$simple_products = $model->getCollection()
        ->addAttributeToSelect('*')
        ->addAttributeToFilter('type_id', Mage_Catalog_Model_Product_Type::TYPE_SIMPLE);