Low-cost Power Analyser Design & Implementation

This work presents the design and implementation of a low-cost power analyzer. The design is based on a sound card used as the signal acquisition device. This offers the advantage of internal synchronizing circuits for all channels which means that no external synchronizer circuit is needed. The hardware part of the system includes a current clamp to measure load current and a simple resistive voltage divider circuit to measure load voltage. The software of the power analyzer processes the voltage and current signals received by the sound card and computes the RMS values of the load voltage and current, the apparent, real and reactive power values. It carries out harmonic analysis of the voltage and current signals in order to determine the Total Harmonic Distortion (THD) value and the true power factor. The power analyzer has been designed to operate with the autonomous renewable energy sources microgrid of the Energy Systems Laboratory. Its performance is demonstrated for a variety of loads such as different lighting technologies, switching devices and motors which constitute the controllable load of the microgrid. The results are compared against those of a commercial power analyzer.