Sliding Mode Control Applied To UPS Inverter Using Norm of the State Error

ABSTRACT: In dynamical system it is impossible to avoid dealing with uncertain conditions such as disturbances; that case is applicable on the UPS Inverter. There are many approaches to control inverters; here we are going to introduce a new approach of sliding mode control applied to UPS inverters. We reduce the sliding time of the state trajectory, by defining a function with respect to the error norm. This function gives the system a value of the sliding line at each instance, such that the performance is improved. The function is defined as the norm of both voltage error and its derivative multiplied by a factor. The norm value is saturated for small and large value of λ, which represents the slope of the sliding line. Another parameter (β) is also introduced, which is a gain multiplying the result of the saturated function. When the state is far from the origin, small value of λ is used in the reaching mode, while large value of λ is used when the state reaches the sliding line and start to “slide” on the sliding line. From the definition of the norm error, a function is derived which is used to minimize the reaching time. The results of simulation are compared to Three level hysteresis and rotating sliding mode approaches. The new approach shows a fast response with very small value of the voltage error. Keywords: uninterruptible power supply, inverters, sliding mode control, rotating sliding line. ……………………………………………………………………………………………………………………………………………………………………………………………………………………