Abstract: Star-connected cascaded H-bridge STATCOM is widely used in the high-voltage power distribution and transmission systems. But the negative-sequence current compensation region is limited, which would result in imbalance of DC voltage among three phases. In order to achieve any imbalance degree of negative sequence current compensation, a new static synchronous compensator (STATCOM) topology based on dual-frequency power loop is proposed. Compared with the traditional topology, the novel topology only adds two groups of RLC resonator. A resonant current is used to transfer power between phases and the extra resonant current would not affect the output of the fundamental current. On the basis of analyzing working principles of the proposed topology, the control strategy based on dual-frequency power is further proposed. The control strategy could redistribute the unbalanced power among three phases to guarantee the equivalence of three phase DC voltages and realize the negative sequence current compensation of arbitrary unbalance degree. Finally, the proposed topology and control strategy are verified by simulation and experiments, and the effectiveness and advantages of the proposed methods are proved.