Improvements of reactive power and energy measurements insensitive to frequency variations

The paper describes the implementation of successive frequency-to-voltage and voltage-to-frequency conversion instead of phase locked loop (PLL) to achieve a wide band of frequency multiplication allowing reactive power and energy measurements in the range of 40-70 Hz of input signal frequency. A phase shifting which provides independence of the shifted signal on the capacitor value used in the phase shifter is described. This feature ensures better long term stability and wider temperature operating range of the meter with retention of high accuracy