How to programmatically save a value in a long text with summary field?
You forget the # in the #format, use this:

$form['field_name'][LANGUAGE_NONE][0]['#format'] = 'full_html';
$form['field_name'][LANGUAGE_NONE][0]['#format'] = 'filtered_html';


Read this: How to set the default format per content type at Drupal 7?