Design and Stability Analysis of a Fuzzy Adaptive SMC System for Three-Phase UPS Inverter

Abstract

This paper proposes a combined fuzzy adaptive sliding-mode voltage controller (FASVC) for a three-phase UPS inverter. The proposed FASVC encapsulates two control terms: a fuzzy adaptive compensation control term, which solves the problem of parameter uncertainties, and a sliding-mode feedback control term, which stabilizes the error dynamics of the system. To extract precise load current information, the proposed method uses a conventional load current observer instead of current sensors. In addition, the stability of the proposed control scheme is fully guaranteed by using the Lyapunov stability theory. It is shown that the proposed FASVC can attain excellent voltage regulation features such as a fast dynamic response, low total harmonic distortion (THD), and a small steady-state error under sudden load disturbances, nonlinear loads, and unbalanced loads in the existence of the parameter uncertainties. Finally, experimental results are obtained from a prototype 1 kVA three-phase UPS inverter system via a TMS320F28335 DSP. A comparison of these results with those obtained from a conventional sliding-mode controller (SMC) confirms the superior transient and steady-state performances of the proposed control technique.

Parallel Operation of Microgrid Inverters Based on Adaptive Sliding-Mode and Wireless Load-Sharing Controls

“…In microgrid dynamics, low-frequency oscillation modes generated by power-sharing controllers and power filters are dominant [25]. To enhance the performance of a conventional droop controller, transient droop terms can be added into Eq.…”

“…The output performance and robustness of microgrid inverters are mainly affected by the effectiveness of the control strategy [18]- [25]. In the past decade, various closed-loop control techniques were reported to achieve the dynamic characteristic and disturbance rejection performance under different types of loads, such as proportional-integral control [ 18], proportional-resonant control [19], [20], Lyapunov-function-based control [21], H∞ control [22], and fuzzy control [23].…”

“…However, the unbalanced condition is not considered in the study. In [25], a combined fuzzy adaptive sliding-mode voltage controller is used for three-phase uninterruptible power supply (UPS) inverter. Moreover, in [26], Mohamed et al present a direct-voltage control strategy for microgrid converters based on sliding-mode dynamic controller.…”