Sliding mode control strategy of voltage source inverter based on load current sliding mode observer

Abstract

In order to overcome too large switching gain problem in the traditional sliding mode control in the inverter, a sliding mode control strategy based on load current sliding mode observer for single phase voltage inverter is proposed. Combined with inverter dual-loop system idea, the inverter system is decomposed into the voltage outer-loop and the current inner-loop, while the output of voltage outer-loop controller is set as the reference of the current inner-loop controller. The sliding mode control is adapted as the control strategy for the voltage outer-loop and observed load current is used for feed-forward compensation. According to the proposed method, the load current disturbance and chattering problem caused by large switch gain are weakened. In order to reduce system chattering further, switching function sgn(s) is replaced by tanh(λs). It has been shown by experimental results that the response of observer is fast and observation error is small; the steady error of output voltage is almost zero and total harmonic distortion is extremely low. Meanwhile, the system is robust to the disturbance of loads.