The working principle of active magnetic bearing is introduced, the mathematic model of active magnetic bearing is inferred, and the two approaches of unbalance compensation are given.

In this paper, compensation techniques of seismic simulation system are introduced primarily, including geometric cross coupling compensation, overturning movement compensation, off center load compensation and force balance compensation.

For D-STATCOM used for large unbalanced load compensation, the criteria for selection are proposed, such as fitness for high voltage large capacities, capability of phase by phase compensation and convenience in redundancy design.