Testing the performance of battery energy storage in a wind energy conversion system

This paper examines the dynamic and transient performances of a battery energy storage system connected at the output of a wind energy conversion system to smoothen the short-term fluctuations in the output power. A low power experimental real-time test rig, using battery storage and representative power converters, is interfaced with a Real-Time Digital Simulator for reduced-scale power hardware-in-the-loop simulation. Different configurations, where the energy storage system is integrated on the ac side via STATCOM and directly at the dc link of the frequency converter using back-to-back converters, are examined under both constant- and variable- references. For each case, the resulting error in the net power flow; the operation of the battery, and the conduction losses in the power conversion stage are examined. The performances using constant and variable reference of storage device with full and reduced order hardware stage of storage element are demonstrated. The low-voltage transient performance of the battery energy storage system is also tested and results are presented. The novel approach of the real-time low power Battery Energy Storage System (BESS) test-bed opens the door for in-lab testing of energy storage devices for large wind or PV farms.