A multilevel threshold detection method for single-sensor multiple DC appliance states sensing

Detecting state change processes of appliances is very useful when optimizing a system's energy management. The term “state change” implies an appliance shifts operation from one state to another; the simplest example is the process in which the appliance switches between an “on” and “off” state. This paper proposes a multilevel threshold detection method that can provide a way to detect state changes of multiple appliances along a DC power line by using a single sensor. The method starts detecting during the transient state by setting multiple threshold levels in the gradient waveform obtained from the filtered power waveform. Compared to a steady-state detection algorithm, the method has shown to be faster in detection. This paper describes the method in detail and its successful application in detecting multiple appliances' state change processes on a low voltage DC office grid using only one sensor.