Power measurement device
AssigneeSmart Energy Instruments Inc.
InventorDONALD JEFFREY DIONNE
Life of this patent
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Abstract
A power measurement device for sampling current or voltage signals of a power system to produce a 1-bit delta-sigma bitstream. The power measurement device includes a frequency locked loop for determining the power system frequency directly from the 1-bit delta-sigma bitstream. The frequency locked loop includes a 1-bit rotate CORDIC that is configured to produce difference signals having a multi-bit word for each bit of the 1-bit delta-sigma bitstream, and a phase error calculator that determines the difference between the phase of the power system frequency and a phase ramp generated from a frequency measurement value in a frequency register. The phase error calculator feeds back a phase correction signal to the frequency register to lock the frequency measurement value to the power system frequency.
Claims20
A method of measuring power system characteristics, the power system having a system frequency and one or more phases, the method comprising:
- sampling one of voltage or current of the power system to produce a 1-bit delta-sigma modulated bitstream;
- generating in-phase and quadrature difference signals from the 1-bit delta-sigma bitstream using a 1-bit rotate CORDIC receiving a phase ramp signal, the difference signals each having a multi-bit word for each bit of the 1-bit delta-sigma signal, wherein the phase ramp signal has a periodicity based upon a frequency value;
- and
- generating a phase error signal based upon a difference between the difference signals, wherein the difference indicates an error between a phase of the phase ramp signal and the phase of the system frequency contained within the 1-bit delta-sigma signal;
- and
- adjusting the frequency value to lock it to the system frequency based upon the phase error signal.
A power measurement device for measuring phase and frequency in multi-phase power system, the power system having a system frequency, the device comprising:
- a plurality of delta-sigma modulators each measuring one of voltage or current on one of the phases in the multi-phase power system and outputting a 1-bit delta-sigma signal;
- a phase accumulator configured to produce a phase ramp signal having a periodicity determined by a frequency value;
- a 1-bit rotate CORDIC for each delta-sigma modulator, wherein each 1-bit rotate CORDIC receives the phase ramp signal and a respective one of the 1-bit delta-sigma signals and outputs an in-phase difference signal and a quadrature-phase difference signal, the difference signals each having a multi-bit word for each bit of the 1-bit delta-sigma signal;
- and
- a phase error calculator for each 1-bit rotate CORDIC to receive the difference signals from that 1-bit rotate CORDIC and to output a phase error signal based upon the difference between a phase of the phase ramp signal and the phase of the respective one of the 1-bit delta-sigma signals,
- wherein one of the phase error calculators corrects the frequency value using its phase error signal to lock it to the system frequency, and wherein the other of the phase error calculators corrects a respective phase offset value measured for its respective one of the 1-bit delta-sigma signals using its respective phase error signal.
A method of measuring phase and frequency in multi-phase power system, the power system having a system frequency, the method comprising:
- measuring one of voltage or current on each one of the phases in the multi-phase power system and delta-sigma modulating each of the measurements to output 1-bit delta-sigma signals;
- generating a phase ramp signal using a phase accumulator, the phase ramp signal having a periodicity determined by a frequency value;
- for each of the 1-bit delta-sigma signals, producing an in-phase difference signal and a quadrature-phase difference signal using a respective 1-bit rotate CORDIC, wherein each 1-bit rotate CORDIC receives the phase ramp signal and its respective one of the 1-bit delta-sigma signals, the difference signals each having a multi-bit word for each bit of the 1-bit delta-sigma signal;
- for each pair of difference signals, generating a phase error signal based upon the difference between a phase of the phase ramp signal and the phase of the respective one of the 1-bit delta-sigma signals;
- correcting the frequency value to lock it to the system frequency using one of the phase error signals;
- and
- for each of the other phase error signals, correcting a respective phase offset value measured for its respective one of the 1-bit delta-sigma signals.
Dependencies are inferred from the claim text.