Digital LQR steady-state optimal control with feedforward for nonminimum phase boost DC-DC converter

This paper presents a perfect optimal control for nonminimum phase boost DC-DC converters by adopting a combination of feedback and feedforward controller. A linear quadratic regulator (LQR) feedback controller is firstly designed and proposed to have the following improvements. Firstly, integral control by state augmentation is adopted in order to and eliminate the steady-state errors. Secondly, feedback gain and estimator gain are calculated offline based on LQR steady-state optimal control method and steady-state Kalman filter. Then, the problems of integral wind-up protection is also handled. A feedforward controller is then proposed to eliminate the phase error caused by right half phase zero (RHPZ) emerged in nonminimum phase of boost DC-DC converters. The feedforward controller is implemented by zero phase error tracking control (ZPETC) technique because the inverse of nonminimum phase system is unstable. Finally, the proposed controller has been implemented on NI CompactRio platform for boost converter voltage control. The experimental results clearly show the proposed controller offers better performance as compared to conventional digital compensation controller.