Research On The Electric Energy Measurement Algorithm Under Signal Distortion Condition

With the rapid development of industry, the makeup of power customer has changed greatly, which causes the nonlinear loads in power system increasing very quickly. And the nonlinear load will make the voltage and current signal distort very seriously, which leads to that the traditional electric energy measurement method cannot meet the real environment’s requirement any longer.This thesis studies the electric energy measurement methods when the power grid has voltage and current signal distortion, and proposes an effective algorithm which can calculate the basic frequency and the active power and apparent power of the basic and harmonic frequencies at the same time. Besides, this thesis also provides a software implementation solution for the proposed algorithm.The proposed algorithm uses CIC filter to get the voltage and current signals of dc and basic frequency and harmonic frequencies. The basic frequency’s instantaneous active power is the product of the basic frequency’s instantaneous voltage and current signal which are the output of the basic frequency’s CIC filter. And the basic frequency’s active power can be get by filtering the basic frequency’s instantaneous active power using a dc CIC filter. The basic frequency and its apparent power can be calculated based on Prony harmonic analysis method with the input of the result of basic frequency’s instantaneous active power minuses basic frequency’s active power. The basic frequency at time n can be used for the basic frequency’s CIC filter design at time n+1. The basic frequency is also used for the design of the mth harmonic frequency CIC filter. The mth harmonic frequency’s instantaneous active power is the product of the mth harmonic frequency’s instantaneous voltage and current signal which are the output of the mth harmonic frequency’s CIC filter. And the mth harmonic frequency’s active power can be get by filtering the mth harmonic frequency’s instantaneous active power using a dc CIC filter. The mth harmonic frequency and its apparent power can be calculated based on Prony harmonic analysis method with the input of the result of the mth harmonic frequency’s instantaneous active power minuses the mth harmonic frequency’s active power. The measurement accuracy for the active power and apparent power can be further improved after they are corrected by MLM method.This thesis uses Matlab for the algorithm performance simulation. The simulation results show that the proposed algorithm can track the basic frequency in real-time, and can accurately measure the active power and apparent power of basic frequency and harmonic frequencies.