Abstract：With the emergence of a large number of distributed power generations，various unbalanced and

nonlinear loads are connected to the power grid，resulting in the distortion of the grid current，which brings adverse effects to both the power grid and electrical equipment. A multifunctional energy storage converter was proposed，which is capable of simultaneously realizing the compensation of reactive current，harmonic current and unbalanced current of the load. This converter used a phase-locked loop based on double second-order generalized integrators to generate the required phase angle and frequency，and at the same time obtained the amplitude of the positive sequence component of the voltage.The converter obtained the command current by obtaining the positive sequence component of the load current and performing coordinate transformation，and then controled through the difference between the command current and the output current of the inverter to track the command signal. Proportional resonant control was used to obtain three-phase current，and pulses were generated through three-dimensional space vector control to control the conduction of the switch tube. By comparing with traditional energy storage converters，digital and analog hybrid experimental results have proven the effectiveness and reliability of this scheme.

      Key words：multifunctional；energy storage converter；unbalanced；harmonic；reactive power compensation