This paper proposes a high-power controllable current quality disturbance generator, which is composed of multiplex cascade H bridge modules, and simulates current quality problems, such as positive and negative current distrubance, current fluctuation, harmonic current and so on. The device adopts a topology with decoupling fundamental and harmonic current. A power module parallel-connected on the fundamental connection reactance outputs harmonic current, while cascade fundamental power modules generate fundamental and low order harmonic current, which realizes decoupling control of fundamental and harmonic current. This paper proposes the control strategies of all types of current disturbances, and the EtherCat-based controller. Finally, a 10kV/1MVA controllable current quality disturbance generator has been created. The experiment result proves that the proposed main circuit topology, control strategy and EtherCat-based controller are feasible and efficient. The emergence of this device creates a fundamental platform for measurement, analysis, evaluation and control of current quality in grid.