A Novel Method for the Measurement of Active and Reactive Power by Sample-and-Hold

The measurement of active and reactive power plays a significant role in electrical power systems as continuous monitoring and control of power are required. In this work a novel technique based on sample-hold of a bilateral analog switch is proposed for the measurement of both active and reactive power. The proposed measurement scheme is capable to provide an average (dc) voltage signal proportional to active and reactive power of the system, separately and independently. It has been shown that the proposed technique is equally valid for lagging and leading power factors. In the proposed method, both $V cos\phi$ and $Vsin\phi$ are found directly without any computation and without finding $cos \phi, sin\phi$ and their multiplication with voltage. Here only one multiplication with current, suffices for active and reactive power measurement. The output signals can further be used in feedback control loop where a dc voltage signal proportional to reactive power is required for compensation through SVC. The proposed method is proved mathematically and the simulated results on MATLAB/Simulink tools verify the proposed technique. The main advantages of the proposed method are linearity of the output, frequency invariant, simple working, least component count, fast response (within a power cycle) and on line measurement capability.