Power meter having complex quadrature output current and voltage filters

A method of measuring electrical power supplied to a load, comprising:

• first measuring a current through the load;
• first filtering a result of the first measuring with a bandpass filter response formed by two or more filter stages each having a single complex pole, wherein the poles of each of the stages have a frequency relationship in the complex plane other than a conjugate frequency relationship, to provide complex current output components having a substantially quadrature phase relationship throughout a pass-band of the first bandpass filter;
• second measuring a voltage across terminals of the load;
• second filtering a result of the second measuring with the bandpass filter response, to provide complex voltage output components having a substantially quadrature phase relationship throughout a pass-band of the second bandpass filter;
• and
• processing the complex current output components and the complex voltage output components to compute at least one indication of a power provided to the load.

A power measurement system comprising:

• a current measurement circuit for measuring a current through a load;
• a first analog-to-digital converter for converting an output of the current measurement circuit to a digital current value;
• a voltage measurement circuit for measuring a voltage across terminals of the load;
• a second analog-to-digital converter for converting an output of the voltage measurement circuit to a digital voltage value;
• and
• a digital signal processing system that receives the digital current value and the digital voltage values and filters each of the digital current value and the digital voltage value with a bandpass filter response formed by two or more filter stages each having a single complex pole, wherein the poles of each of the stages have a frequency relationship in the complex plane other than a conjugate frequency relationship, wherein the bandpass filter response rejects one of a positive or a negative half of a complex frequency spectrum, and generates complex output components having a substantially quadrature phase relationship throughout a pass-band of the filtering and wherein the digital signal processing system combines a result of the filtering of the digital current value and a result of the filtering of the digital voltage value to determine an indication of a power provided to the load.

A computer program product comprising computer readable storage media containing program instructions for execution by a digital signal processing core, the program instructions including program instructions for:

• first receiving a representation of a current through a load;
• first filtering a result of the first measuring with a a bandpass filter response formed by two or more filter stages each having a single complex pole, wherein the poles of each of the stages have a frequency relationship in the complex plane other than a conjugate frequency relationship, to provide complex current output components having a substantially quadrature phase relationship throughout a pass-band of the first filtering;
• second receiving a representation of a voltage across terminals of the load;
• second filtering a result of the second measuring with the bandpass filter response, to provide complex voltage output components having a substantially quadrature phase relationship throughout a pass-band of the second filtering;
• and
• processing the complex current output components and the complex voltage output components to compute at least one indication of a power provided to the load.