To extend the working bandwidth for piezoelectric vibration energy harvesting, autoparametric internal resonant system is proposed. Unstable quasiperiodic motion and chaos, however, are accompanied by broadband characteristic in nonlinear energy conversion. In order to control unwanted irregular motions for power management, we presented a new autoparametric vibration energy harvester coupled by nonlinear energy sink. Mathematical model considering the electromechanical coupling and modal coupling for the high-order nonlinear energy harvesting system is established. Nonlinear analyses via power spectrum, phase portrait and Poincaré map illustrate the effectiveness of chaos control using nonlinear energy sink. In addition, average power of the lower boundary of the harvesting band is enhanced by increasing the stiffness and damping of nonlinear energy sink. Average power of the upper boundary of the harvesting band is improved by increase of the nonlinear energy sink mass and substructural natural frequency ratio. The maximum average power of the proposed piezoelectric autoparametric vibration energy harvester is enhanced 200%, compared to the power harvested by the system without the nonlinear energy sink. This study provides a chaos control method for stable broadband vibration energy harvesting. With simultaneous energy harvesting and chaos control, such system can fit in with more applications.