Design, Development and Analysis of a Voltage Sensor Based on Capacitive Voltage Divider for Smart Grid Applications
With the recent push for renewable energy several former consumers units now have energy generation capabilities. While this approach is beneficial in general, it also poses new challenges for cooperation and grid stability. The new smartgrid now needs bidirectional power flow, data communication, and intelligent controls in order to ensure reliable operation. Voltage sensing plays a key role, capacitive voltage transformers have been demonstrated useful for high- voltage (100kV+), but have not yet been discussed for low (220V) and medium (13kV) voltage. This paper proposes a simplified capacitive voltage divider circuit for low-voltage measurement. Mathematical modelling is used for steady-state operation, circuit design, and sensitivity to analysis. Monte-Carlo simulations are employed to verify the effect of component tolerances, indicating under 0.7dB gain, and 0.03° error at fundamental frequency. Experimental validation is performed at low-voltage levels (127V), indicating 0.5 dB magnitude and 0.3° phase deviation at fundamental frequency. Performance is also validated from 60Hz to the 50th harmonic, showing 20° phase deviation at the higher order harmonics (16th and up). From the obtained results it is expected that the sensor is sufficient for voltage quality measurements, but should be software-corrected if power measurement is required at the high-order harmonics.