Design and Implementation of a High Accuracy Sampling Wattmeter under Non-sinusoidal and Time Varying Environments

Errors may creep in when measuring active power under non-sinusoidal and time varying conditions by conventional regularly spaced sampling digital wattmeter (RSSDW) due to the existence of higher order voltage and current harmonics, and asynchrony between the signal fundamental frequency and the sampling rate. This paper presents design and implementation of a modified regularly spaced sampling digital wattmeter, called M-RSSDW, immune to above mentioned drawbacks of RSSDW. The proposed method utilizes a novel first degree digital integrator design technique to diminish the effects of higher order harmonics. The truncation error during asynchrony has also been reduced using numerical compensation method. M-RSSDW has been implemented in real time by means of a TMS320VC5416 digital signal processor. The laboratory test results confirm the accuracy of M-RSSDW under both static and dynamic conditions.