Identify the key legislative tools and policy initiatives introduced by the EU to strengthen its security of electricity supply.

“One of the Energy Union’s (EU) policy priorities is to strengthen the security of the EU’s electricity supply. Identify the key legislative tools and policy initiatives introduced by the EU to strengthen its security of electricity supply. Try to summarise and give your assessment of the efficiency of such EU action since 2009 and by more specifically considering the EU’s more recent policy initiatives.”